Peer reviewed papers of various Dutch gravity, spaceflight and astrobiology related studies.

Peer reviewed Papers

This page provides a list of peer reviewed papers in the field of gravitational life sciences (biology / physiology), astrobiology (exobiology), physical sciences or closely related disciplines that were published by or in collaboration with Dutch investigators.
Please note that this page is updated regularly to provide a complete overview of research undertaken from within Dutch universities and other research institutes. Input from you as a scientist / participant in the various studies is very much appreciated.
Some of the papers presented here are in PDF format and may be downloaded and printed. When you do not have a PDF reader please click PDF icon

2005

• V. Bouet, F. Dijk, J. IJkema-Paassen, R.J. Wubbels, J.J. van der Want, A. Gramsbergen. Early hypergravity exposure effects calbindin-D28k and inositol-3-phosphate expression in Purkinje cells. Neuroscience Letters 382 (2005) 10–15.

Abstract:
In this study the effects of hypergravity were analyzed on cerebellar Purkinje cells during early development in rats. The cerebellum is a key structure in the control and the adaptation of posture and anti-gravity activities. This holds particularly when external conditions are modified. Three groups of rats were conceived, born and reared in hypergravity (2 g). At postnatal day 5 (P5), P10 or P15, they were exposed to normal gravity and at P40, the cerebella were investigated on the expression of calbindin-D28k and inositol-3-phosphate (IP3) in Purkinje cells. Control animals were bred in the same conditions but at 1 g. Immunoreactivity of Purkinje cells was studied in lobules III and IX of the vermis. Lobule IX of the vermis is one of the targets of primary otolithic vestibular projections, and lobule III served as a control, being much less related with vestibular inputs. The results show that hypergravity induces a decrease in calbindin and IP3 labeling in 20% of Purkinje cells of lobule IX without any change in lobule III. Animals transferred from 2 g to 1 g at P5 or P10 showed the most pronounced effects and much less at P15. This study demonstrates that early development of the cerebellum is highly sensitive to changes in gravity. Ages until P10 are critical for the development of vestibulo-cerebellar connections, and in particularly the calcium signaling in Purkinje cells. Download full pdf version (412 kb).

• Steven J. Pardo, Mamta J. Patel, Michelle C. Sykes, Manu O. Platt, Nolan L. Boyd, George P. Sorescu, Min Xu, Jack J. W. A. van Loon, May D. Wang and Hanjoong Jo. Simulated microgravity using the Random Positioning Machine inhibits differentiation and alters gene expression profiles of 2T3 preosteoblasts. Am J Physiol Cell Physiol. 288:1211-1221, 2005.

Abstract:
Exposure to microgravity causes bone loss in humans, and the underlying mechanism is thought to be at least partially due to a decrease in bone formation by osteoblasts. In the present study, we examined the hypothesis that microgravity changes osteoblast gene expression profiles, resulting in bone loss. For this study, we developed an in vitro system that simulates microgravity using the Random Positioning Machine (RPM) to study the effects of microgravity on 2T3 preosteoblast cells grown in gas-permeable culture disks. Exposure of 2T3 cells to simulated microgravity using the RPM for up to 9 days significantly inhibited alkaline phosphatase activity, recapitulating a bone loss response that occurs in real microgravity conditions without altering cell proliferation and shape. Next, we performed DNA microarray analysis to determine the gene expression profile of 2T3 cells exposed to 3 days of simulated microgravity. Among 10,000 genes examined using the microarray, 88 were downregulated and 52 were upregulated significantly more than twofold using simulated microgravity com-pared with the static 1-g condition. We then verified the microarray data for some of the genes relevant in bone biology using real-time PCR assays and immunoblotting. We confirmed that microgravity downregulated levels of alkaline phosphatase, runt-related transcrip-tion factor 2, osteomodulin, and parathyroid hormone receptor 1 mRNA; upregulated cathepsin K mRNA; and did not significantly affect bone morphogenic protein 4 and cystatin C protein levels. The identification of gravisensitive genes provides useful insight that may lead to further hypotheses regarding their roles in not only micrograv-ity- induced bone loss but also the general patient population with similar pathological conditions, such as osteoporosis.

• Auke Verhaar, Kausilia K. Krishnadath and Maikel P. Peppelenbosch. Using Microgravity for Defining Novel Anti-Atherosclerotic Therapy. Current Genomics, Volume 6, Number 6, 2005.

Abstract:
Among the most important insights into coronary and inflammatory disease is that the formation of vessel occluding placques is its essence an inflammatory process, that is counteracted by anti-inflammatory drugs Current therapeutical options of dealing with the increased challenge to public health posed by increased vessel disease are limited and unsatisfactory. Disturbingly, an increasing cohort of patients does not react to the immunosuppressive drugs available. Importantly, however, space travel is associated with well-tolerated immunosuppression and thus identification of the molecular mechanisms underlying this space travel-associated immunosuppression may have significant benefit for directing clinical research on earth. Devising an experimental set up for investigating the molecular details of space flight-induced immunosuppression is, however, fraught with difficulties. Two recent ESA-sponsored space missions (the Delta Taxi flight to ISS and Maser 10 sounding rocket mission) have now shown that these technical hurdles can be successfully tackled.

2004

• V. Bouet, R.J. Wubbels, H.A.A. de Jong, A. Gramsbergen. Behavioural consequences of hypergravity in developing rats. Developmental Brain Research 153, 69– 78, 2004.

Abstract:
Gravity represents a stable reference for the nervous system. When the individual is increasing in size and weight, gravity may influence several aspects of the sensory and motor developments. To clarify this role, we studied age-dependent modifications of several exteroceptive and proprioceptive reflexes in five groups of rats conceived, born and reared in hypergravity (2 g). Rats were transferred to normal gravity (1 g) at P5 (post-natal day 5), P10, P15, P21, and P27. Aspects of neural development and adaptation to 1 g were assessed until P40. Hypergravity induced a delay in growth and a retardation in the development of contact-righting, air-righting, and negative geotaxis. However, we found an advance in eye opening by about 2–3 days in HG-P5 and HG-P10 rats and an increase in grip-time. No differences were found in tail and grasp reflexes. Our results show that hypergravity leads to a retarded development of motor aspects which are mainly dependent upon the vestibular system. Download full pdf version (458 kb).

In this study the effects of hypergravity were analyzed on cerebellar Purkinje cells during early development in rats. The cerebellum is a key structure in the control and the adaptation of posture and anti-gravity activities. This holds particularly when external conditions are modified. Three groups of rats were conceived, born and reared in hypergravity (2 g). At postnatal day 5 (P5), P10 or P15, they were exposed to normal gravity and at P40, the cerebella were investigated on the expression of calbindin-D28k and inositol-3-phosphate (IP3) in Purkinje cells. Control animals were bred in the same conditions but at 1 g. Immunoreactivity of Purkinje cells was studied in lobules III and IX of the vermis. Lobule IX of the vermis is one of the targets of primary otolithic vestibular projections, and lobule III served as a control, being much less related with vestibular inputs. The results show that hypergravity induces a decrease in calbindin and IP3 labeling in 20% of Purkinje cells of lobule IX without any change in lobule III. Animals transferred from 2 g to 1 g at P5 or P10 showed the most pronounced effects and much less at P15. This study demonstrates that early development of the cerebellum is highly sensitive to changes in gravity. Ages until P10 are critical for the development of vestibulo-cerebellar connections, and in particularly the calcium signaling in Purkinje cells.

• V. Bouet, IJkema-Paassen, R.J. Wubbels, A. Gramsbergen. Journal of Gravitational Physiology • P165-166, Vol 11(2) • 2004.

Abstract:
Several studies have shown the detrimental effect of microgravity exposure on the locomotor development in young rats. The opposite situation, i.e. hypergravity, which strongly stimulates several sensory systems and in particular the vestibular system, has unknown effects on the development of locomotion. This study reports 1) the temporal course of walking development of rats which were conceived and born in 2 g, and subsequently transferred to 1 g at different postnatal ages, and 2) the correlated modifications of soleus and tibialis anterior muscles. Download full version.

• René Wubbels, Valentine Bouët, Herman de Jong, Albert Gramsbergen. Journal of Gravitational Physiology • P21-22, Vol 11(2) • 2004.

Abstract:
During gestation and early postnatal development, the animal’s size and weight rapidly increase. Within that period, gravity affects sensory and motor development. We studied age-dependent modifications of several types of motor reflexes in 5 groups of rats conceived, born and reared in hypergravity (HG; 2 g). These rats were transferred to normal gravity (NG; 1 g) at various post-natal days, and their behavioral reflexes were compared with a control group which was constantly kept under NG. HG induced a retarded development of vestibular dependent reflexes. Other types of motor behavior were not delayed. Download full version.

2003

• van Loon Jack J.W.A., Erik H.T.E. Folgering, Carlijn V.C. Bouten, J. Paul Veldhuijzen, Theo H. Smit. ASME J. Biomechan. Eng. vol. 125, 342-46, June 2003.

Abstract:
Centrifuges are used for 1×g controls in space flight microgravity experiments and in ground based research. Using centrifugation as a tool to generate an Earth like acceleration introduces unwanted inertial shear forces to the sample. Depending on the centrifuge and the geometry of the experiment hardware used these shear forces contribute significantly to the total force acting on the cells or tissues. The inertial shear force artifact should be dealt with for future experiment hardware development for Shuttle and the International Space Station (ISS) as well as for the interpretation of previous space-flight and on-ground research data. Download full pdf version (444 kb).

• Wubbels Rene J. The influence of 2.5 G exposure on the morphology of rat vestibular epithelia. Proc. 'Life in Space for Life on Earth", 8th Eur. Symp. Life Sciences in Space, 23rd Annual Internat. Gravit. Physiol. Meeting. Karolinska Inst., Stockholm, Sweden, 2-7 June 2002: (ESA SP-501, Sept. 2002)

Abstract:
Several studies have shown that altered gravity causes changes in vestibular induced reflexes and behaviour (2,5-7), and in vestibular morphology (1,3,4). How the level of gravity affects the morphology of vestibular epithelia, however, is largely unknown. Vestibular epithelia of hypergravity (HG) exposed animals and control animals were histochemically labeled for actin and tubulin (two characteristic proteins for specific cytoskeletal structures in hair cells and supporting cells). Cellular organization, cytoskeletal structure and apical cross-sectional area were investigated. Download full pdf version (117 kb).

2002

• Bos JE, Bles W. Theoretical considerations on canal-otolith interaction and an observer model. Biological Cybernetics 86:191-207, 2002.

• Bos JE, Bles W, Graaf B de. Eye movements to yaw, pitch, and roll about vertical and horizontal axes: adaptation and motion sickness. Aviation Space and Environmental Medicine 73:436-444, 2002.

• Kraeger A.M. (Alwin), van Paassen M.M. (René). Micro- and partial gravity atmospheric flight. Congres of the American Institute for Aeronautics and Astronautics (AIAA) in Monterey, 2002.

Abstract:
This paper presents a study on a possible control concept for micro- or partial gravity flight of conventional aircraft that can be implemented in any aircraft with a minimum in effort. The method makes use of a conventional pitch rate controller to track the continuously changing pitch rate along the desired micro- or partial gravity trajectory. As a first step towards automatic flight this principle is used to design a micro- and partial gravity flight director. The flight director has been experimentally evaluated in a fixed base manned simulation and its performance checked against other flight director principles. Pilots unanimously pointed out this flight director as their favorite one and it also showed the best performance. A baseline version will be implemented and flight-tested in the Delft University Cessna Citation research aircraft in the near future. Download full pdf version (1.9 Mb).

• Wieling W, Halliwill JR, Karemaker JM. Orthostatic intolerance after space flight. Journal of Physiology (2002),538.1 ,p.1

Abstract:
Physiologists have always been challenged by the adjustments of the human body to hostile environments. The set of papers in this issue of The Journal of Physiology (Cox et al. 2002; Ertl et al. 2002; Levine et al. 2002) fits into the tradition of the study of human responses to extreme physical circumstances. The Neurolab project represents a huge undertaking that required major contributions from many different collaborators, and the coordination of efforts at different institutions. The studies succeeded because of the dedication and years of work of the astronauts involved. The manuscripts present the fundamental findings from the first direct recordings of sympathetic vasoconstrictor nerves and noradrenaline kinetics in humans during microgravity. Despite the difficulties of performing such measurements on the space shuttle and the small numbers of astronauts involved, unique data are set forth that represent a major advance in our understanding of the physiology of space flight. Download full pdf version (36 kb).

• Wubbels R. J. , H. N. P. M. Sondag, J. van Marle, H. A. A. de Jong. Effects of hypergravity on the morphological properties of the vestibular sensory epithelium. I. Long-term exposure of rats after full maturation of the labyrinths. Brain Research Bulletin, Vol. 57, No. 5, pp. 677–682, 2002.

Abstract:
The effect of prolonged exposure to hypergravity on the morphology of vestibular epithelia of rats was investi-gated. At the age of 1 month, i.e., when vestibular end organs are fully maturated, three rats were transferred to a hypergrav-ity environment of 2.5 g inside a large radius centrifuge. After 9 months, vestibular epithelia of these animals and of three con-trol animals were immunohistochemically labeled for actin and tubulin. The apical cross-sectional area of epithelial cells of hypergravity exposed rats appeared to be smaller in all end organs. Area reduction was 1.9% in the saccule (not signifi-cant), 5.0% in the utricle (p < 0.005), and 11.6% in the crista (p <<0.001). No indications for a deterioration of vestibular functioning were observed. KEY WORDS: Gravity, Vestibular system, Hair cell, Actin, Tubulin. Download full pdf version (498 kb).

• Wubbels R.J., J.van Marle, H.N.P.M.Sondag, H.A.A.de Jong. Effects of hypergravity on the morphological properties of the vestibular sensory epithelium.II.Life-long exposure of rats including embryogenesis. Brain Research Bulletin, Vol. 58, No. 6, pp. 575–580, 2002.

Abstract:
Rats were exposed to a hypergravity (HG) level of 2 .5 × g from conception until the age of 14 weeks.The vestibular epithelia of four of these animals and four control animals were immunohistochemically labeled for actin and tubulin.The apical cross-sectional area of epithelial cells of HG exposed rats appeared to be larger in all end organs. Area increase was 7.0% in the utricle (p<0 .005)and 8.2% in the crista (p<<0 .001). Hair cells and supporting cells appeared to be intact.The cellular arrangement and the proportion of different cell types within the epithelia was normal. Download full pdf version (277 kb).

2001

• Muñoz Caro, G.M., Ruiterkamp, R., Schutte, W.A., Greenberg, J.M., Mennella, V.: "UV photodestruction of CH bonds and the evolution of the 3.4 mum feature carrier. I. The case of aliphatic and aromatic molecular species", Astronomy and Astrophysics 367, 347-354, 2001.

• Mennella, V., Muñoz Caro, G.M., Ruiterkamp, R., Schutte, W.A., Greenberg, J.M., Brucato, J.R., Colangeli, L.: "UV photodestruction of CH bonds and the evolution of the 3.4 mu m feature carrier. II. The case of hydrogenated carbon grains", Astronomy and Astrophysics 367, 355-361, 2001.

• Stokroos I, Litinetsky L, van Der Want JJ, Ishay JS. Magnetic minerals Keystone-like crystals in cells of hornet combs. Nature Jun 7;411(6838):654, 2001.

Abstract:
The hexagonal brood-rearing cells inside the nest combs of the hornet Vespa orientalis are uniform in both their architecture and orientation. We have discovered that each cell contains a minute crystal that projects down from the centre of its domed roof and has a composition typical of the magnetic mineral ilmenite. These tiny crystals form a network that may act like a surveyor's spirit-level, helping the hornets to assess the symmetry and balance of the cells and the direction of gravity while they are building the comb. Download full pdf version (1.3 Mb).

• van Loon Jack J.W.A. Hypergravity studies in the Netherlands. Journal of Gravitational Physiology, 8(1): 139-142, July 2001.

Abstract:
It looks like that with the utilization phase of the International Space Station (ISS) scientists will have the possibility to perform long duration and more sophisticated microgravity experiments than could be performed previously. In preparation for these spaceflight studies, ground based experiment tools for simulated (or real) microgravity and hypergravity are important. To provide the infrastructure and user support necessary to perform these ground based studies we have setup the Dutch Experiment Support Center, DESC (1). This paper will focus on the three centrifuge facilities. It is shown that these hypergravity facilities can be used to show sounding rocket launch effects, identify alterations in body mass, bone parameters and matrix composition in rodents as well as to derive a test protocol for the Space Adaptation Syndrome in humans. DESC coordinates the use of these centrifuge facilities. Download full pdf version (105 kb).

• Veldman A.E.P., Gerrits J. "Transient dynamics of containers partially filled with liquid". In: Moving Boundaries VI, Sarler, B. and Brebbia C.A. (eds), WIT Press, Southampton, 63-72, 2001.

• Wubbels R.J., H.A.A. de Jong. The horizontal vestibulo-ocular reflex of hypergravity rat at different gravity levels. Neuroscience Letters 303, 5-8, 2001.

Abstract:
The horizontal vestibulo-ocular relfex (VOR) of two groups of rats was measured. One group was bred and kept under hypergravity (HG; 2.5 g) conditions, the other group lived under normal gravity (NG; 1 g). Eye position was recorded in response to horizontal rotatory stimuli. Measurements were made under NG (1 g), and during parabolic flight (0.0 and 1.8 g). For both groups, the response to a rotatory stimulus during parabolic flight is similar to the response that was observed under 1 g conditions. In general, however, the VOR of HG rats is reduced by 20±50% relative to the response of NG rats and the phase is shifted by 2408. We conjecture that this amplitude reduction and phase shift are the consequence of living in a rotating system.
Keywords: Long±Evans rat; Vestibulo-ocular reflex; Gravity; Vestibular adaptation; Parabolic fight
Download full pdf version (156 kb).

• Wubbels R.J., H.A.A. de Jong. The vestibulo-ocular reflex of hypergravity rats. Journal of Gravitational Physiology. Vol 8(1), 2001, 113-114.

Introduction:
The vertebrate vestibular system detects linear (otolith organs) and angular (semicircular canals) acceleration. The function of the otolith system is twofold, 1: perception of linear acceleration of the head, and 2: assessment of the spatial orientation of the head relative to the vector of gravity. Because of the latter function, a change of gravity will affect the vestibular input which, in turn, may have a wide range of serious physiological effects, for instance on ocular reflexes. The function of the vestibulo-ocular reflex (VOR) is to stabilize the visual image on the retina. Measurement of this VOR provides a method to investigate the (processing within the) vestibular system. Discrimination between gravity and linear acceleration, caused by movement of the head, is not possible. Therefore, information from the otolith system must be constantly compared with additional information from other sensory systems in order to solve the inherent ambiguity between tilt and translation. In this processing, cues from the semicircular canals also play a role. During parabolic flight, experiments can be performed at altered gravity levels for brief periods of time. On earth, the only effective possibility to manipulate gravity for longer periods of time is a centrifuge. Together with experiments in weightlessness during orbital flight, these methods form useful tools to investigate the influence of gravity on physiology. In our laboratory, rats have been kept inside a centrifuge at 2.5g during their entire life-span (i.e. including gestation). Download full pdf version (26 kb).

• Wubbels René, Herman de Jong, Eric Sondag. The effects of hypergravity on vestibular epithelia and behaviour of the rat. Journal of Gravitational Physiology, Vol 8(1), 2001, 105-108.

Introduction:
In order to assess the effects of gravity, miscellaneous physiological systems of several species have been investigated. The main reason for this research has been the wide-scale consequences of weightlessness in space for human physiology. Available methods to manipulate the level of gravity for physiological research are 1: parabolic flight, 2: orbital flight, and 3: a centrifuge. The only possibility to breed (mammalian) species successfully at an altered level of gravity is inside a centrifuge at hypergravity (HG). The duration of this HG period can be adjusted to the investigator's design. For rodents, it has been shown that this HG period can start at conception and can be extended to the animal's entire life-span. In our laboratory, hamsters and rats have been bred inside our centrifuge (Fig. 1) at 2.5g (6,7,9,10). Gravity conditions that deviate from the normal level on earth (i.e. both weightlessness and hypergravity) may have a significant impact on growth, body composition, metabolism and sensory functioning. One obvious cause for these physiological changes is the altered mechanical load (and/or energy requirements) of a particular system (bone, cardiovascular, renal/fluid, muscle, blood). For instance, adult rats living at 2.5g have a lower body mass than normal gravity (NG) animals (9). When NG animals are transferred to HG conditions they lose weight (10-15%) and remain relatively inactive during a period of approximately 1 week. After that period they appear to be adapted to the new situation: animals start growing again (although when compared to NG animals, their weight remains reduced) and they resume their normal life including procreation. There appears to be no acute distress among centrifuge-bred or centrifuge-adapted rats when the centrifuge is stopped. Immediately when the centrifuge is being decelerated all animals become very active (they start running, romping, climbing, and stand on their hind legs). A change of gravity will affect the vestibular input which, in turn, may have a wide range of serious effects (on posture, locomotion, ocular reflexes, righting reflexes) and which can cause motion sickness. The entire scope of effects of a prolonged change of gravity level is far from clear yet. It is to be expected, however, that possible effects will depend on the developmental stage during which the animal is subjected to altered gravity, and that the nature of these effects will probably be diverse. For these reasons, our research has been focussed on different topics that are directly related to the vestibular system: 1: the histology of the peripheral sensory system, 2: vestibular induced ocular reflexes, and 3: vestibular-controlled behaviour. Elsewhere in this volume results from a study on vestibulo-ocular reflexes are presented. Here, we will show some results of the histological and behavioural studies. Download full pdf version (216 kb).

2000

• Alpatov AM, Chernyshov VB, Zotov VA, Rietveld WJ. Sand-desert tenebrionid beetle Trigonoscelis gigas reitter: a promising biological model for space chronobiology. [Article in Russian] Aviakosm Ekolog Med, 34(1):58-6, 2000.

Abstract:
The beetle proposed for studying has a unique feature: unusually precise and reliable circadian clock that evolved as an advanced adaptation to extreme arid environment. Consequently this clock became functionally similar to that of vertebrates, i.e. it has a narrow range of entrainment, stable free-running period, strong endogenous component of rhythm. This beetle is also using due to its high viability, good tolerance to housing and handling, small size and safety in use. Space flight experiments with beetles on BION, PHOTON satellites and on MIR orbital station proved that parameters of circadian rhythms are dependent upon gravity. Future studies will focus on electrophysiology and comparative ecology of these beetles. This biological species together with developed methods represent a new promising technology of research in gravitational chronobiology.

• Greenberg JM, Gillette JS, Munoz Caro GM, Mahajan TB, Zare RN, Li A, Schutte WA, de Groot M, Mendoza-Gomez C. Ultraviolet Photoprocessing of Interstellar Dust Mantles as a Source of Polycyclic Aromatic Hydrocarbons and Other Conjugated Molecules. Astrophys J. 2000 Mar 1;531(1):L71-L73.

By co-depositing a gas mixture of simple carbon- and nitrogen-containing molecules with water on a 10 K surface and exposing it to ultraviolet radiation, we were able to form a residue. This residue was then placed aboard the EURECA satellite behind a magnesium fluoride window and exposed to solar radiation for 4 months before it was returned and analyzed. The resulting residue is believed to simulate the photoprocessing of organic dust mantles in the interstellar medium. Mass spectrometry indicated that the photoprocessing created a rich mixture of polycyclic aromatic hydrocarbons (PAHs) and other conjugated organic molecules, which may explain how PAHs are replenished in space.

• Kraft Tristan F. B. , Jack J. W. A. van Loon, John Z. Kiss. Plastid position in Arabidopsis columella cells is similar in microgravity and on a random-positioning machine. Planta. 211(3), 415-422, 2000.

Abstract:
In order to study gravity effects on plant structure and function, it may become necessary to remove the g-stimulus. On Earth, various instruments such as clinostats have been used by biologists in an attempt to neutralize the effects of gravity. In this study, the position of amyloplasts was assayed in columella cells in the roots of Arabidopsisthaliana (L.) Heynh. seedlings grown in the following conditions: on Earth, on a two-dimensional clinostat at 1 rpm, on a three-dimensional clinostat (also called a random-positioning machine, or an RPM), and in space (true microgravity). In addition, the effects of these gravity treatments on columella cell area and plastid area also were measured. In terms of the parameters measured, only amyloplast position was affected by the gravity treatments. Plastid position was not significantly different between spaceflight and RPM conditions but was significantly different between spaceflight and the classical two-dimensional clinostat treatments. Flanking columella cells showed a greater susceptibility to changes in gravity compared to the central columella cells. In addition, columella cells of seedlings that were grown on the RPM did not exhibit deleterious effects in terms of their ultrastructure as has been reported previously for seedlings grown on a two-dimensional clinostat. This study supports the hypothesis that the RPM provides a useful simulation of weightlessness. Key words: Amyloplast · Arabidopsis · Simulated microgravity · Spaceflight experiments · Weightlessness. Download full pdf version (314 kb).

• Vreeburg, J.P.B., Veldman, A.E.P.: "Transient and sloshing motions in an unsupported container", in: Physics of Fluids in Microgravity, Monti, R. (ed.), Gordon and Breach Academic Publishers, 2000.

• Wubbels RJ, de Jong, HAA. Vestibular induced behaviour of rats born and raised in hypergravity. Brain Research Bulletin, Vol. 52, No. 5, pp. 349–356, 2000.

Abstract:
One group of rats were bred and kept under hypergravity (HG) conditions (2.5 g) in a centrifuge. Another group were bred and kept under normal gravity conditions (1 g). Rats from both groups were dropped from a supine position into a water basin under infrared illumination leaving only gravity (1 g for both groups) for orientation. The airrighting reflex and reappearance at the water surface were examined. The success rate for airrighting of HG rats is 47% versus 45% for controls, and is performed about equally fast by both groups. The success rate of HG and control hamsters is <= 25% and >= 80%, respectively [Sondag et al. 1997]. This interspecific difference does not appear to support the conjecture that altered behaviour is caused by a structural change of vestibular end organs during ontogenetic development under HG. The success rate for surfacing of control rats is 100%. Surfacing of young HG rats is less successful (36% at age 6 weeks) and requires more time. On average, surfacing of adult rats of both groups is about the same. Apparently, the repeated stay of centrifuge-bred rats at 1 g for experiments and daily care suffices to recalibrate and improve their orientation, which is essential for surfacing. Download complete paper (PDF 308 kb)

1999

• Boonstra J. Growthfactor induced signal transduction in adherend mammalian cells in sensitive to gravity. FASEB J., 13, S35, 1999.

Abstract:
Epidermal growth factor (EGF) activates a well-characterized signal transduction cascade in a wide variety of cells. This activation leads to increased cell proliferation in most cell types. Among the early effects evoked by EGF are receptor clustering, cell rounding, and early gene expression. The influence of gravity on EGF-induced EGF receptor clustering and gene expression as well as on actin polymerization and cell rounding have been investigated in adherent A431 epithelial cells with the use of sounding rockets to create microgravity conditions. EGF-induced c-fos and c-jun expression decreased in microgravity. This was caused by alteration of the EGF receptor and protein kinase C-mediated signal transduction pathways. In contrast, neither the binding of EGF to the receptor nor the receptor clustering were changed under microgravity conditions. Because cell morphology was also modulated under microgravity conditions, and the growth factor-induced signal transduction cascades have been demonstrated to be linked to the actin microfilament system, it is tempting to suggest that the actin microfilament system constitutes the gravity-sensitive cell component. Download complete paper in P DF format: 186 kb.

• Burger E.H., Klein-Nulend J. Mechanotransduction in bone - role of the lacunocanalicular network. FASEB J., 13, S101, 1999.

Abstract:
The capacity of bone tissue to alter its mass and structure in response to mechanical demands has long been recognized but the cellular mechanisms involved remained poorly understood. Over the last several years significant progress has been made in this field, which we will try to summarize. These studies emphasize the role of osteocytes as the professional mechanosensory cells of bone, and the lacuno-canalicular porosity as the structure that mediates mechanosensing. Strain-derived flow of interstitial fluid through this porosity seems to mechanically activate the osteocytes, as well as ensuring transport of cell signaling molecules and nutrients and waste products. This concept allows an explanation of local bone gain and loss, as well as remodeling in response to fatigue damage, as processes supervised by mechanosensitive osteocytes. Download complete paper in P DF format: 497kb.

• Fermin, C.D., Lychakov, D., Campos, A., Hara, H., Sondag, E., Jones, T., Jones, S., Taylor, M., Meza-Ruiz, G., Martin, D.S.: "Otoconia biogenesis, phylogeny, composition and functional attributes", Histol. Histopathol. 13, 1103-1154, 1999.

• Folkersma, R., Diemen, A.J.G. van, Stein, H.N.: "Understanding the influence of gravity on perikinetic coagulation on the basis of the DLVO theory", Advances in Colloid and Interface Science 83, Issues 1-3, pp. 71-84, 1999.

• Gerrits, J., Loots, G.E., Fekken, G., Veldman, A.E.P.: "Liquid sloshing on earth and in space", in: Moving Boundaries V (B. Sarler, C.A. Brebbia and H. Power eds.), WIT Press, Southampton, 111-120, 1999.

• Greenberg J.M., Schutte W.A., Li A. Space irradiation of the interstellar dust analogs at cryogenic temperatures. Advances in Space Research, 23(1-6), 289-292, 1999.

• Greenberg, J.M.: "Tracking the organic refractory component of interstellar dust", in: Formation and evolution of solids in space, Greenberg, J.M., Li, A. (eds.). Kluwer, 53-76, 1999.

• Greenberg, J.M., Li, A.: "All comets are born equal: infrared emission by dust as a key to comet nucleus composition", Planet. Space Sci. 47, 787-795, 1999.

• Greenberg, J.M., Li, A.: "Tracking the organic refractory component from interstellar dust to comets", Adv. Space Res. 24, 497-504, 1999.

• Greenberg, J.M., Li, A.: "Morphological structure and chemical composition of cometary nuclei and dust", in: Composition and origin of cometary materials, Altwegg, K., Ehrenfreund, P., Geiss, J., Huebner, W., eds., Space Sci. Rev. 90, 149-161, 1999.

• Jongebloed Willem L., Eyal Rosenzweig, Dharamdajal Kalicharan, Johannes J.L. van der Want and Jacob S. Ishay. Ciliary hair cells and cuticular photorecepters of the hornet Vespa orientalis as components of a gravity detecting system: a SEM/TEM investigation. Journal of Electron Microscopy 48 (1): 63- 75, 1999.

Abstract:
This paper describes three types of hair cell configurations with stereo- and kinocilia in the head of the hornet; these were encountered at the vertex and frons regions adjacent to the three ocelli and are assumed to be part of the hornet's gravity detecting system together with cuticular photoreceptors. The first and most common type of hair cell configuration (type A) was a cell surrounded by a septurn, having a diameter of 30-50 µm. Aggregates of over 20 such hair cell groups together formed a larger unit, 130-300 µm in diameter, which was also enclosed by a septum. Many of these larger round units were, in turn, arranged in either angular or leaf-like clusters. The hair cells bore numerous cilia of 45-6.0 µm long, and were themselves composed of smaller sub-units of about 7-8 µm in diameter, which were not enclosed by a septum. The second type of hair cell configuration (type B) was of discrete cells with a diameter of appr. 12.5-14 µm, located in the vicinity of the pore canal outlet of the peripheral photoreceptor. These single hair cells were either devoid of or only partially enclosed by a septum. Their cilia were 45-6.0 µm long as well, but with a diameter of only 150-160 nm. On the exterior of each cilium a tubular system could be detected. Furthermore, the tips of adjacent cilia were interconnected by a kind of fibre bearing a spherical body in its middle. The third type of hair cell (type C), present in the neighbourhood of the second type of hair cell (type B), was chalice-shaped and had interconnecting fibrils comparable to those found at type B. We believe that these three types of hair cell configuration along with the ganglion cells inter-connecting their bases are all components of the gravity organ of the hornet (the Ishay Organ) and together with the cuticular photoreceptors function in the navigation system of the hornet. We further conjecture that the described structures are engulfed by endolymph; produced signals by each unit are conducted by neural fibrils to the hornet's central nervous system.

• Kingma, I.,Toussaint, H.M., Commissaris, D.A.C.M. and Savelsbergh, G.J.P. Adaptation of center of mass control under microgravity in a whole body lifting task. Exp. Brain Res. 125, 35-42, 1999.

Abstract:
Human balance in stance is usually defined as the preservation of the vertical projection of the center of mass (COM) on the support area formed by the feet. Under microgravity conditions, the control of equilibrium seems to be no longer required. However, several reports indicate preservation of COM control in tasks such as arm or leg raising, tiptoe standing, or trunk bending. It is still unclear whether COM control is also maintained in complex multijoint movements during short term exposure to microgravity. In the current study, the dynamics of equilibrium control were studied in four subjects performing two series of seven whole-body lifting movements under microgravity during parabolic flights. The aims of the study were to examine whether the trajectory of horizontal COM motion during lifting movements changes in short-term exposure to microgravity and whether there is any sign of recovery after several lifting movements. It was found that, compared with control movements under normal gravity, the horizontal position of the COM was shifted backward during the entire lifting movement in all subjects. In the second series of lifting movements under microgravity, a partial recovery of the COM trajectory toward the normal gravity situation was found. Under microgravity, angles of the ankle, knee, hip, and lumbar joints differed significantly from the angles found under normal gravity. Recovery of joint angular trajectories in the second series of lifting movements mainly occurred for those angles that could contribute to a reduction of the backward COM shift. It is to be pointed out that COM control under microgravity is not redundant but functional. Persisting COM control under microgravity may be required for pure mechanical reasons, since rotational movements of the body are dependent on adequate control of the COM position with respect to external forces. It is shown that, from a mechanical perspective, subjects can benefit from a backward displacement of the COM in the downward as well as the upward phase of the lifting movement under microgravity.

• Kingma, I., Savelsbergh, G.J.P. and Toussaint, H.M. Object size effects on initial lifting forces under microgravity conditions. Exp. Brain Res. 124, 422-428, 1999.

Abstract:
Individuals usually report for two objects of equal mass but different volume that the larger object feels lighter. This so-called size-weight illusion has been investigated for more than a century. The illusion is accompanied by increased forces, used to lift the larger object, resulting in a higher initial lifting speed and acceleration. The illusion holds when subjects know that the mass of the two objects is equal and it is likely that this also counts for the enlarged initial effort in lifting a larger box. Why should this happen? Under microgravity, subjects might be able to eliminate largely the weight-related component of the lifting force. Then, if persistent upward scaling of the weight-related force component had been the main cause of the elevated initial lifting force under normal gravity, this elevated force might disappear under microgravity. On the other hand, the elevated initial lifting effort in the large box would be preserved if it had been caused mainly by a persistent upward scaling of the force component, necessary to accelerate the object. To test whether the elevated initial lifting effort either persists or disappears under microgravity, a lifting experiment was carried out during brief periods of microgravity in parabolic flights. Subjects performed whole-body lifting movements with their feet strapped to the floor of the aircraft, using two 8-kg boxes of different volume. The subjects were aware of the equality of the box masses. The peak lifting forces declined almost instantaneously with approx. a factor 9 in the first lifting movements under microgravity compared with normal gravity, suggesting a rapid adaptation to the loss of weight. Though the overall speed of the lifting movement decreased under microgravity, the mean initial acceleration of the box over the first 200 ms of the lifting movement remained higher (P=0.030) in the large box (1.87±0.127 m/s2) compared with the small box (1.47±0.122 m/s2). Under normal gravity these accelerations were 3.30±0.159 m/s2 and 2.67±0.159 m/s2, respectively (P=0.008). A comparable trend was found in the initial lifting forces, being significant in the pooled gravity conditions (P=0.036) but not in separate tests on the normal gravity (P=0.109) and microgravity (P=0.169) condition. It is concluded that the elevated initial lifting effort with larger objects holds during short-term exposure to microgravity. This suggests that upward scaling of the force component, required to accelerate the larger box, is an important factor in the elevated initial lifting effort (and the associated size-weight illusion) under normal gravity.

• Rosenzweig Eyal, Arieh Sorin Solomon, Jacob S. Ishay, Shira Kirshboim, Han van der Want, Dharam-dajal Kalicharan and Willem L.Jongebloed. Micromorphology of the dorsal ocelli of the oriental hornet and its possible function in navigation. Physiol. Chem. Phys. & Med. NMR 30: 241-269, 1999.

Abstract:
The subject of our study is the morphology and functional physiology of the three dorsal ocelli in the adult worker of the Oriental hornet (Vespa orientalis: Hymenoptera, Vespinac). The components of the ocelli are as follows: The rhabdont which is located in the deeper, more basal part of the retinularcells with a lengthof about 30 µm. The length of the retinular cell itself is about 30 µm and its width is 3-4 µm. Around the rhabdom there is a high concentration of mitochondria. The retinular cells contain pigment granules. The greatest concentration of pigment gramules is located distal to the rhabdont and generally pigment granule enwrap the rhabdorn along its entire length. On the upper part of the retinula there are comeogenic cells. The retinular cells are somewhat separated above the region where the common rhabdorn is formed and between every two cells there is a gap into which penetrates an extension of a comeogenic cell that serves as a sort of focal lens, directing and concentrating light toward the rhabdom. The latter structure thus corresponds to a scotopic eye. Each rhabdom, together with the two retinular cells and the cormeogenic cell, constitutes a unit for light processing (equivalent to the ommatidium in a compound eye) for which we propose the name " ocelion ". From the outside, a homogeneous comea covers the entire ocellus. Beneath the comea is one lens and around each ocellus there is an envelope composed of connective tissue and containing both numerous melanocytes as well as glia cells. This envelope is generally of a dark color. The envelope attaches upon a convex, reticulate substrate through which pass dendrites of the ocellar nerve, The reticular nature of the structure enables considerable flow of hervolymph both for the provision of nutrients as well as for themoregulatory purposes. The base of the ocellus is likewise perforated by pores through which dendrites pass, the hornet cuticle here is of a typically areolar structure. Around the base of the ocellus there is a canal observable. This canal is filled with a fluid, while around it there is a cuticular fold which enwraps all of the ocellus. On this cuticle appear kinocilia.The structure of the canal, coupled with the surrounding cristae and cilia, enables the hornet to sense radial acceleration similar to the function of the semicircular canals in vertebrate ear. Each of the ocelli is situated on a separate plane, with the three planes forming a 90o angle with each other and so panaoramical-ly encircling the dome at the tip of the vertex. Apparantly the ocelli figure importantly in navigation, because covering or masking of the ocelli causes, in a significant percentage of hornets, loss of orientation even at short distances from the nest. A connection between the wings and the ocelli was mentioned by Kirshfeld (1977). In our opinion, the location of the ocelli on the head is connected to sunlight and the suns position and orientation in navigation.

• Sondag, H. N. P. M.; de Jong, H. A. A.; Oosterveld, W. J., Behaviour of adult hamsters subjected to hypergravity. J. Vestib. Res. 9: 13-18; 1999.

• Stok W.J., Stringer R.C.O., Karemaker J.M. Non-invasive cardiac output measurement in orthostasis: pulse contour analysis compared with acetylene rebreathing. J. Appl. Physiol. 87,(6), 2266-2273, 1999.

1998

• Alpatov, A.M., Lazarev, A.O., Rietveld, W.J.: "Entrainment of circadian rhythms of Trogonocelis Gigas Reitter (Coleoptera: Tenebrionidae) by various skeleton Photoperiods", Biological Rhythm Res. 1998, suppl. 112-113.

• Alpatov AM, Hoban-Higgins TM, Fuller CA, Lazarev AO, Rietveld WJ, Tschernyshev VB, Tumurova EG, Wassmer G, Zotov VA. Effects of microgravity on circadian rhythms in insects. J Gravit Physiol. 1998 Jul;5(1):P1-4.

• Burger E.H.; Klein-Nulend J. Microgravity and bone cell mechanosensitivity, Bone, Volume 22, Issue 5 SUPPL., Pages 127S-130S, 1998.

Abstract
B one cells, in particular osteocytes, are extremely sensitive to mechanical stress, a quality that is probably linked to the process of mechanical adaptation (Wolff's law). The in vivo operating cell stress derived from bone loading is likely a flow of an interstitial fluid along the surface of the osteocytes and lining cells. The response of bone cells in culture to fluid flow includes prostaglandin synthesis and expression of inducible prostaglandin G/H synthase (PGHS-2 or inducible cyclooxygenase, COX-2), an enzyme that mediates the induction of bone formation by mechanical loading in vivo. Disruption of the actin-cytoskeleton abolishes the response to stress, suggesting that the cytoskeleton is involved in cellular mechanotransduction. Microgravity has catabolic effects on the skeleton of astronauts, as well as on mineral metabolism in bone organ cultures. This might be explained simply as resulting from an exceptional form of disuse under weightlessness conditions. However, under microgravity conditions, the assembly of cytoskeletal elements may be altered, as gravity has been shown to determine the pattern of microtubular orientation assembled in vitro. Therefore, it is possible that the mechanosensitivity of bone cells is altered under microgravity conditions, and that this abnormal mechanosensation contributes to the disturbed bone metabolism observed in astronauts. In vitro experiments on the International Space Station should test this hypothesis experimentally.
Keywords: Microgravity; Mechanosensitivity; Bone cell; Prostaglandin; Fluid shear stress; Cytoskeleton
Download complete paper in P DF format: 137 kb.

• Coker, Eric N.; Jansen, Jacobus C.; Martens, Johan A.; Jacobs, Pierre A.; DiRenzo, Francesco; Fajula, Francois; Sacco, Albert Jr. Synthesis of zeolites under micro-gravity conditions: A review. Microporous and Mesoporous Materials. Volume 23, Issue 1-2, p119-136, July 1998.

Abstract
The crystallization of zeolites and other microporous materials in space has attracted some attention in recent years, in the search for larger or more `pure' and perfect crystals. Hydrodynamics and hydrostatics of zeolite synthesis solutions are strongly influenced by gravitational force, and the growth of zeolites in solutions which are effectively free from convection and sedimentation in micro-gravity may produce crystals of different character to those grown on Earth. The exact nature of the changes which occur on synthesizing zeolites in micro-gravity depends upon the chemical and physical properties of the solutions as well as the `quality' of micro-gravity. The results from several experiments performed in space are summarized and discussed, and a few suggestions are made concerning possible improvements in experimental design and strategy. (Index Terms: Zeolites; Synthesis (chemical); Crystallization; Crystal growth; Microgravity processing; Gravitational effects; Gravitational force).

• Fermin CD, Lychakov D, Campos A, Hara H, Sondag E, Jones T, Jones S, Taylor M, Meza-Ruiz G, Martin DS. Otoconia genesis, phylogeny, composition and functional attributes. Histol Histopathol 13: 1103-54, 1998.

• Folkersma R.; Van Diemen A.J.G.; Stein H.N. Influence of gravity on perikinetic coagulation. Part I: Experimental. Journal of Colloid and Interface Science, Volume 206, Issue 2, 15 October, 482-493, 1998.

Abstract
Perikinetic coagulation experiments are reported which were performed under 1g and g conditions during a flight in a sounding rocket, for dispersions of polystyrene, quartz, and amorphous silica particles. Coagulation rates for dispersions of polystyrene, quartz, and amorphous silica are found to increase significantly under g conditions compared to 1g conditions. Another set of experiments was performed at 1g, 2g, 4g, and 7g, with different densities of the continuous phase; also a mixture of two different polystyrene latices was used. The most pronounced effect of gravity on coagulation rate is found for dispersions with a small density difference, on going from 1g to 2g. In this regime a significant decrease in coagulation rates is observed. For the latex mixture at pronounced density differences, gravity-induced coagulation was observed; however, the aggregates formed did not have a lasting contact. The rate constant calculated under g conditions approaches the theoretical value of yon Smoluchowski. By means of a video analysis of the perikinetic coagulation process, the formation of doublets was studied. The 'interaction time' for two particles was found to be longer for the density-matched dispersion. Doublets of particles are easily disrupted, and at 1g, free convection currents were observed even at small temperature differences in the system. Drug Index Terms: polystyrene; silicon dioxide; latex; sucrose; methanol; deuterium oxide.

• Geim A.K. Everyone's Magnetism, Physics Today, 51, 36, 1998.

• Gielen C.C.A.M.; Van Bolhuis B.M. Task-dependent reduction of the number of degrees of freedom in sensorimotor systems, Brain Research Reviews, Volume 28, Issue 1-2, Pages 136-142, 1998

Abstract
In this paper we present a concise review of experiments on sensorimotor performance in man from the perspective of new opportunities provided by research in microgravity, which will contribute to our basic understanding of sensorimotor processes. In particular, we will discuss some new results on strategies for dealing with the large number of degrees of freedom in biological limbs with special emphasis on human motor control and on the specific role for mono- and bi-articular muscles. Finally, we propose some ideas for future experiments on motor function in microgravity, which will reveal new basic knowledge about the role of the CNS in motor control and which will contribute to a better performance of man in sensorimotor tasks in microgravity conditions. Download complete paper in P DF format: 125 kb.

• Greenberg, J.M.: "Making a comet nucleus", Astron. Astrophys. 330, 375-380, 1998.

• Greenberg, J.M., Li, A.: "From interstellar dust to comets: the extended CO source in comet Halley", A&A 332, 374-384, 1998.

• Greenberg, J.M., Li, A.: "From interstellar dust to comets: distributed CO in comet Halley", in: Solar System Ices (Schmitt, B., De Bergh, C., Festou, M., eds.), Kluwer, 337-351, 1998.

• Greenberg, J.M., Li, A.: "Evolution of interstellar dust and its relevance in life's origin: laboratory and space experiments", Biological Sciences in Space 12, 96-101, 1998.

• Greenberg, J.M., Li, A.: "Comets as a source of life's origins", in: Exobiology: matter, energy, and evolution of life in the Universe (J. Chela-Flores, F. Raulin, eds.), Kluwer, 275-285, 1998.

• Hashimoto, H., Greenberg, M., Brack, A., Colangeli, L., Horneck, G., Navarro-Gonzalez, R., Raulin, F., Kouchi, A., Saito, T., Yamashita, M., Kobayashi, K.: "A conceptual design for cosmo-biology experiments in earth's orbit", Biol. Sci. Space 12, 106-111, 1998.

• Jongebloed W.L., E.Rosenzweig, D.Kalicharan and J.S.Ishay. Are ciliary hair cells and photoreceptors components of a gravitic system of the hornet vespa orientalis ? Journal of gravitational Physiology (1998) 5 (1): 135-136, 1998.

Abstract:
Social wasps, including the sub-family Vespinae, are social insects that build combs beneath the grond which are directed towards the gravitic pull of the earth, and this at dim light or complete darkness. On the inner side of the frons plate located in the head - as part of the multi-layererd cuticle - there is a gravity sensing apparatus, which is called the "Ishay organ". It is composed of three different types of hair cell structures with cilia of various length, shape and diameter and of static and dynamic fibres, some of which connect between the frons plate and the brain. It is highly probable that that the interaction between the fibres and the various structures in the head is responsible for the proprioceptive ability of hornets including gravity detection. Additionally there are throughout the cuticle, at intervals of several micrometers apart, distinct pores which are the outlets of peripheral photoreceptors, which probably also play a role in the orientation and navigation system of the hornet. In this study we will discuss the fine structure of the three types of hair cell structures.

• Li, A., Greenberg, J.M.: "The dust properties of a short-period comet: comet P/Borrelly", A&A 338, 364-370, 1998.

• Li, A., Greenberg, J.M.: "A comet dust model for the ß Pictoris disk", A&A 331, 291-313, 1998.

• Li, A., Greenberg, J.M.: "The dust extinction, polarization and emission in the high-latitude cloud toward HD 210121", Astron. Astrophys. 339, 591-600, 1998.

• Oostra, W., Marijnissen, J.C.M., Scarlett, B.: "The measurement of thermophoresis under gravity conditions and the influence of charge", J. Aerosol Sci. 29, S1109-S1110, 1998.

• Oostra, W., Marijnissen, J.C.M., Scarlett, B.: "Thermophoretic velocities under microgravity conditions", Space Forum 3, 251-260, 1998.

• Rosenzweig Eyal, Arieh Sorin Solomon, Shira Kirshboim, Jacob S. Ishay, Han van der Want, Dharam-dajal Kalicharan and Willem L. Jongebloed. Micromorphology of the dorsal ocelli of the oriental hornet. Journal of gravitational Physiology, 5 (1): 113-114, 1998.

Abstract:
The hornets of the sub-family Vespinae have three ocelli organized on the dorsal side of the head, receiving their innervation from the optical lobes that are located in the protocerebrum within the head. An ocellus is an intracuticular organ built in the shape of an upside-down cone whose base faces out and contains a convex corneal lens, while its truncated apex faces inwards and from it extends the ocellar nerve. The diameter of the cornea is about 400 µm, that of the blunt apex about 250 µm. Each ocellus consist of a group of visual cells beneath the common lens, which possibly accentuate the response to light stimuli, that are perceived by compound eyes. Recently the the ocelli have been ascribed a role in orientation and navigation. In honeybees the sensitivity of the ocelli to light at various wavelenghts was compared with that of the compound eyes and was found different. In the ocelli there were two peaks at a wavelength of 335-340 nm (UV-light) and of 490 nm (green light) respectively, while at compound eyes the peaks were found at 350 nm and 540 nm respectively. In this study we will describe the fine structure of the ocelli of the Oriental hornet, as visualized by LM, SEM and TEM and discuss their possible role in orientation and navigation.

• Sondag H.N.P.M., de Jong H.A.A., van Marle J., Oosterveld W.J. Behavioural changes in hamsters with otoconial malformations. Acta Otolaryngol (Stockh), 118(1): 86-89, 1998.

Abstract:
For a period of 10 months, the perceptive-motor skills of golden hamsters were tested as part of an experiment to investigate vestibular controlled behaviour. We found that four out of 40 hamsters had more difficulties with swimming and equilibrium maintenance than the rest of the group. These disturbances either were apparent during the first months of testing or developed at a later period. In three hamsters the disturbances persisted over time while in one hamster performance in perceptive-motor skills increased. Histological examination with scanning electron microscopy revealed otoconial abnormalities in the saccule and/or the utricle. The otoconia were either malformed or replaced by spherulites. We conclude that the observed behavioural disturbances were caused by a defective peripheral vestibular organ. The results show similarities with data from pathology in other animals as well as in the human inner ear. Download full pdf version (240 kb).

• Vermeer C, Wolf J, Craciun AM and Knapen MH. Bone markers during a 6-month space flight: effects of vitamin K supplementation. J Gravit Physiol 5: 65-69, 1998.

1997

• Berry M.V., Geim A.K. Of flying frogs and levitation. Eur. J. Phys. 18, 307-313, 1997.

Abstract.
Diamagnetic objects are repelled by magnetic fields. If the fields are strong enough, this repulsion can balance gravity, and objects levitated in this way can be held in stable equilibrium, apparently violating Earnshaw’s theorem. In fact Earnshaw’s theorem does not apply to induced magnetism, and it is possible for the total energy (gravitational C magnetic) to possess a minimum. General stability conditions are derived, and it is shown that stable zones always exist on the axis of a field with rotational symmetry, and include the in ection point of the magnitude of the field. For the field inside a solenoid, the zone is calculated in detail; if the solenoid is long, the zone is centred on the top end, and its vertical extent is about half the radius of the solenoid. The theory explains recent experiments by Geim et al, in which a variety of objects (one of which was a living frog) was levitated in a field of about 16 T. Similar ideas explain the stability of a spinning magnet (Levitron TM ) above a magnetized base plate. Stable levitation of paramagnets is impossible. Download full pdf version (228 kb).

Samenvatting. Magnetische velden stoten diamagnetische voorwerpen af. Zulke velden kunnen zo sterk zijn dat zij de zwaartekracht opheffen. Het is op deze wijze mogelijk zulke voorwerpen te laten zweven. Dit vormt een stabiel evenwicht, wat in tegenspraak schijnt te zijn met Earnshaw’s Theorema. Echter Earnshaw’s Theorema is niet langer geldig als het magnetisme veld geinduceerd is. De totale energie (bevattende bijdragen van het magnetisme en de zwaartekracht) kan toch een lokaal minimum vertonen. Algemene criteria voor zo’n minimum zullen worden opgesteld. Verder zal worden aangetoond dat voor een cilindrisch symmetrisch veld, langs zijn symmetrie as altijd een zone gevonden kan worden waarin een stabiel evenwicht bestaat. Voor het veld binnen een soleno¨ýde zal deze zone in detail bepaald worden. Als deze spoel voldoende land is bevindt deze zone zich aan het uiteinde van de spoel. De lengte van deze zone langs de symmetrie as van het veld is ongeveer de helft van de straal van de spoel. Deze theorie geeft een goede verklaring voor de experimenten van Geim et al. In deze experimenten werden een grote verscheidenheid aan verschillende voorwerpen (waaronder een levende kikker) tot zweven gebracht in velden van ongeveer 16 T. Analoge theori¨ en verklaren de stabiliteit van een roterend permanent magneetje (Levitron TM ) boven een magneetische grondplaat. Het is onmogelijk om paramagnetische voorwerpen stabiel te doen zweven. Download het volledige artikel in pdf formaat (228 kb).

• Bles W., de Graaf B., Bos J.E., Groen E., Krol J.R. A sustained hyper-g load as a tool to simulate space sickness. J. Gravitational Physiol., 4(2), P1-P4, 1997.

• Boonstra, J., Rijken, P.J., Groot, R.P. de, Verkley, A.J., Saag, P.T. van der, Laat, S.W. de: "Growth factor-induced signal transduction in mammalian cells is sensitive to gravity", in: Frontiers of Biological Science in Space, Sato, A. (ed.), Taiyo Printings Sales Co., Ltd. Tokyo, Japan, 2-18, 1997.

• de Bruijn, R.; van Diest, R.J.J.; Karapantsios, T.D.; Michels, A.C.; Wakeham, W.A.; Trusler, J.P.M. Heat transfer in pure critical fluids surrounded by finitely conducting boundaries in microgravity, Physica A: Statistical and Theoretical Physics, Volume 242, Issue 1-2, 1, Pages 119-140, August 1997.

Abstract
The behaviour of a near-critical sample of SF6, bounded by container walls with finite thermal properties, was studied in space during the 1994 IML-2 mission. Experiments were performed in the range 2500 to 1 mK above the critical point in which simultaneous density and temperature measurements are conducted during a number of transient heating runs. The results of these measurements show clearly that a fast isentropic thermalization takes place uniformly throughout the sample, with essentially no effect on existing temperature and density gradients. The temperature rise caused by the isentropic thermalization is described quantitatively by a theoretical expression which takes into account the finite thermal impedance of the cell walls. It has been possible to do so in a manner that satisfactorily represents the observations. The success of this description enables the separation of isentropic thermalization from true heat transport effects, thereby opening the way to a determination of the thermal diffusivity of the fluid at temperatures as close as 1 mK to the critical temperature. In addition, the observed isentropic compressive heating mechanism suggests a new way for assessing specific important thermodynamic properties in the critical region, based on the experimental determination of the isentropic thermal expansion coefficient.
Index Terms: Sulfur compounds; Heat transfer; Gravitational effects; Density measurement (specific gravity); Temperature measurement; Thermal gradients; Thermal diffusion in solids; Thermal expansion; Critical fluids; Isentropic thermalization; Thermal impedance; Thermal expansion coefficient; Critical region; Adiabatic effect.
Download complete paper in P DF format: 956 kb.

• Grainger, R.M., Ubbels, G.A.: "Early amphibian development: genes and signals involved in embryonic induction and pattern formation", Cell. mol. life sci. 53, 303-304, 1997.

• Greenberg, J.M., Li, A.: "Silicate core organic refractory mantle particles as interstellar dust and as aggregated in comets and stellar disks", Adv. Space Res. 19, 981-990, 1997.

• Greenberg, J.M., Li, A.: "From interstellar dust to comets: The extended CO source in comet Halley", A&A 332, 374-384, 1997.

• Hoba-Higgins T.M., Alpatov A.M., Wassmer G.T., Rietveld W.J., Fuller C.A. Response of insect activity rhythms to altered gravitational environments. J. Grav. Physiology, vol4(2), p109-110, 1997.

• Li, A., Greenberg, J.M.: "A unified model of interstellar dust", A&A 323, 566-584, 1997.

• Michels, A.C.; de Bruijn, R.; Karapantsios, T.D.; van Diest, R.J.J.; van den Berg, H.R.; van Deenen, B.; Sakonidou, E.P.; Wakeham, W.A.; Trusler, J.P.M.; Louis, A.; Papadaki, M.; Straub, J. Adiabatic compressive heating of critical fluids under microgravity conditions, Heat Transfer in Microgravity Systems; American Society of Mechanical Engineers, Heat Transfer Division, (Publication) HTD, Volume 305, Pages 137-145, 1997.

Abstract
In this paper we report initial results from space experiments in which heat transport in near-critical SF6 was studied. The experiment utilized the Critical Point Facility (CPF) which was flown aboard ESA's Spacelab in the cargo bay of the Space Shuttle Columbia during the 1994 IML-2 mission. We report temperature and density measurements made during a number of transient heating runs in which energy was supplied by a plane heater immersed in the sample. Temperature measurements were made with a resolution of 10 K by means of a set of five thermistors while density changes in the sample were monitored interferometrically. The results of these measurements show clearly that diffusive heat transfer slows dramatically as one approaches the critical point and that only a thin boundary layer adjacent to the heater is influenced directly by thermal conduction. We also observe clear evidence of the so-called adiabatic or piston-effect which results in a spatially-uniform temperature and density rise in the bulk of the fluid. The adiabatic temperature rise is shown to be essentially linear in time, synchronous with the heating and proportional to the heater power. The magnitude of the temperature rise is found to be consistent with theory, only when heat losses are taken into account. [Author abstract; 13 Refs; In English] Conference Information:
Index Terms: Heat transfer; Gravitational effects; Sulfur compounds; Temperature measurement; Density measurement (specific gravity); Thermistors; Interferometry; Boundary layers; Thermal conductivity; Adiabatic compressive heating; Liquid vapor critical point; Microgravity; Diffusive heat transfer; Piston effect.

• Oostra, W., Romedahl, L.A., Marijnissen, J.C.M., Scarlett, B.: "The measurement of thermophoretic velocities under gravity and micro-gravity conditions in a Millikan cell", J. Aerosol Sci. 28, S321-S322, 1997.

• Sondag H.N.P.M., de Jong H.A.A., Oosterveld W.J. Altered behaviour in hamsters conceived and born in hypergravity. Brain Res Bul,43(3): 289-94, 1997.

Abstract:
We studied vestibular function in 37 hamsters (1 month old) conceived and born in either hypergravity (n = 21) or normal gravity (n = 16). Four groups were made: (1) HL group: 20 weeks in 2.5 G and 14 weeks in 1 G; (2) HS group: 4 weeks in 2.5 G and 30 weeks in 1 G; (3) CON group: 34 weeks in 1 G; and (4) ROT group: 4 weeks in 1 G, 16 weeks in rotation in 1 G, at the centre of the centrifuge and 14 weeks 1 G. When the hamsters were 4 weeks old, their locomotor activity, swimming ability, and air-righting was assessed. We found that HL and HS hamsters had no disturbances during locomotion in 1 G but their swimming ability was disturbed (swimming underwater, circling, and decreased speed of swimming). The HL hamsters showed less activity during 2.5 G and showed fewer correct air-rightings than the other groups. Differences between groups in swimming ability and the number of correct air-righting responses remained even after 3 months of normal gravity. Based on these findings, we suggest that the persistent behavioural disturbances are caused by the embryonal development of the hamsters in a hypergravity environment. Furthermore, hypergravity and rotation each have a different effect on behaviour. Download full pdf version (490 kb).

• Ubbels G.A. Establishment of polarities in the oocyte of Xenopus laevis: the provisional axial symmetry of the full-grown oocyte of Xenopus laevis [published erratum appears in Cell Mol Life Sci 1997 Jul;53(7):620] Cell Mol Life Sci. 53(4):382-409, Apr. 1997.

Abstract:
We aimed at understanding of formation and function of the "Nieuwkoop Centre" in embryonic pattern formation. Discussed are data on genesis of cytoplasmic localizations in ovarian oocytes, transient modifications of cytoskeletal structures creating cytoplasmic asymmetries in fertilized eggs, the axis determining "vegetal cortical rotation" and fate of distinct cells, as shown by injection of specific molecular markers into particular blastomeres at specific times. Egg rotation and centrifugation suggested that sperm that gravity cooperate in symmetrization of the axially symmetrical anuran egg. After fertilization in space or in a fast rotating clinostate, axis formation and embryonic development were normal although the blastocoel was transiently abnormal. Normal tadpoles came back on Earth after ovulation, fertilization and culture in space. They metamorphosed normally and got healthy Earth-born F1 offspring. We conclude that neither sperm nor gravity are required for determination of the bilateral symmetry in the embryo of Xenopus laevis. In normal development sperm and gravity, either alone or in collaboration, may overrule an initial bilaterality inherent to, the full-grown oocyte, residing in some still unidentified component(s)/or mechanisms. Download full pdf version (2.28 Mb).

• Voogel AJ; Stok WJ; Pretorius PJ; Van Montfrans GA; Langewouters GJ; Karemaker JM. Circadian blood pressure and systemic haemodynamics during 42 days of 6 degrees head-down tilt. Acta Physiol Scand. 161(1):71-80, Sep. 1997.

Abstract:
Head-down tilted bedrest is a ground-based microgravity simulation model. Since in this position the influence of chief external determinants of circadian blood pressure variation, i.e. activity and posture, are reduced, it may reveal endogenous oscillatory factors. The effects of 42 days of 6 degrees head-down tilt on the circadian profiles of continuous finger blood pressure, heart rate, stroke volume, cardiac output and total peripheral resistance were analysed. In seven healthy volunteers (25-31 years) twelve 22 h Portapres registrations were performed: two in an ambulatory baseline period, eight during 42 days of head-down tilt, and two during recovery. Stroke volume was estimated by a pulse contour method ('Modelflow') from the finger arterial blood pressure tracing. Head-down tilt rapidly reduced circadian BP variation, especially for diastolic blood pressure. No effect of long-term head-down tilt on blood pressure level was observed. The day-night difference in heart rate was essentially unaffected. Cardiac output was maintained through an increase of heart rate and simultaneous decline of stroke volume. Our observations confirm the overriding importance of physical activity and orthostatic load on the diurnal variation of BP. The time-frame of the changes in stroke volume and heart rate during head-down tilt might point to a contribution of other factors besides a reduction of circulating blood volume affecting cardiovascular performance under these conditions.

1996

• de Graaf B., Bos, J.E., Groen, E.: "Saccular impact on Ocular Torsion", Brain Research Bulletin 40, 321-326, 1996.

• de Graaf B., Roo A.J. Effects of long duration centrifugation on head movements and psycomotor task. J. Vest. Res. 1, 23-29, 1996.

• De Maziere A; Gonzalez-Jurado J; Reijnen M; Narraway J; Ubbels GA. Transient effects of microgravity on early embryos of Xenopus laevis. Adv Space Res. 17(6-7):219-23, 1996.

Abstract:
In order to study the role of gravity on the early development of the clawed toad Xenopus laevis, we performed an experiment on the Maser-6 sounding rocket launched from Kiruna (Sweden) on 4 Nov 1993. The aim was to find out whether a short period of microgravity during fertilization and the first few minutes of development does indeed result in abnormal axis formation as was suggested by a pilot experiment on the Maser 3 in 1989. On the Maser 6 we used two new technical additions in the Fokker CIS unit, viz. a 1-g control centrifuge and a video recording unit which both worked successfully. The 1-g control centrifuge was used to discriminate between the influences of flight perturbations and microgravity. After fertilization shortly before launch, one of the first indications of successful egg activation, the cortical contraction, was registered in microgravity and on earth. Analysis of the video tapes revealed that the cortical contraction in microgravity starts earlier than at 1 g on earth. After recovery of the eggs fertilized in microgravity and culture of the embryos on earth, the morphology of the blastocoel has some consistent differences from blastulae from eggs fertilized in the 1-g centrifuge of the rocket. However from the gastrula stage onward, the microgravity embryos apparently recover and resume normal development: the XBra gene is normally expressed, and histological examination shows normal axis formation.

• De Jong HAA, Sondag ENPM, Kuipers A, Oosterveld WJ. Swimming behavior of fish during short periods of weightlessness. Aviat Space Envirn Med, 67:463-466, 1996.

BACKGROUND: Birds and fish show tumbling and spinning movements when subjected to short periods of weightlessness during parabolic flight. The reason for this behavior is not clear.HYPOTHESIS: The semicircular canal system is a rotation-detecting device; however, it seems that linear accelerations have an influence, too. Microgravity induces rotatory sensations which leads to a compensatory behavior (e.g., rotatory movements). METHODS: The swimming behavior of goldfish was studied with the fish in four different conditions: normal fish (group I); fish with one eye recently removed (group II); fish with both eyes recently removed (group III); and fish with both eyes removed 10 months previously (group IV). Further, a group of naturally blind (e.g., not surgically treated) cavefish (group V) were involved in the study also. All procedures conformed to the guiding principles as required in the Dutch Law on Care and Use of Animals. RESULTS: Three main different patterns of abnormal swimming behavior could be observed: tumbling (pitch), corkscrew movements (pitch and roll), and spinning movements (roll). NF did not shown any special swimming pattern. One-eyed fish (group II): mostly corkscrew movements (62%). Blind fish (group III): a mixture of the three movements (17, 22 and 25%). Blind fish (group IV): mostly spinning movements (20%). Cavefish (group V): tumbling (21%), corkscrew movements (12%) and spinning movements (58%). CONCLUSION: Vision is the dominant cue, explaining the behavior of normal goldfish. When vision is absent, the fish relies on vestibular information with respect to orientation. The swimming behavior is presumably caused by an attempt to compensate rotatory illusions. As all movements were shown in the planes of the vertical canals, we conclude that these canals play a dominant role when fish are deprived from proper otolith information.

• Groen E., de Graaf B., Bles W., Bos J.E. Ocular torsion before and after 1 hour centrifugation. Brain Res. Bull. 40, 5/6, 331-335, 1996.

Abstract:
To assess a possible otolith contribution to effects observed following prolonged exposure to hypergravity, we used video oculography to measure ocular torsion during static and dynamic conditions of lateral body tilt (roll) before and after 1 h of centrifugation with a Gx-load of 3 G. Static tilt (from 0 to 57° to either side) showed a 10% decrease in otolith-induced ocular torsion after centrifugation. This implies a reduced gain of the otolith function. The dynamic condition consisted of sinusoidal body roll (frequency 0.25 Hz, amplitude 45°) about an earth horizontal and about an earth vertical axis (respectively, "with" and "without" otolith stimulation). Before centrifugation the gain of the slow component velocity (SCV) was significantly lower "with" otolith stimulation than "without" otolith stimulation. Apparently, the contribution of the otoliths counteracts the ocular torsion response generated by the semicircular canals. Therefore, the observed increase in SCV gain in the condition "with" otolith stimulation after centrifugation, seems in correspondence with the decreased otolith gain in the static condition. Author Keywords: Hypergravity; Otoliths; Adaptation; Vestibulo-ocular reflex. Download full pdf version (417 kb).

• Linnarsson D, Sundberg CJ, Tedner B, Haruna Y, Karemaker JM, Antonutto G, Di Prampero PE. Blood pressure and heart rate responses to sudden changes of gravity during exercise. Am J Physiol 1996 Jun;270(6 Pt 2):H2132-42.

Abstract:
Heart rate (HR) and blood pressure responses to sudden changes of gravity during 80- to 100-W leg exercise were studied. One group was exposed to sudden changes between 1.0 and 0 g in the head-to-foot direction (Gz+), starting upright and with repeated 30-s tilts to the supine position. Another group was exposed to sudden Gz+ changes between 1.8 and 0 g in an aircraft performing parabolic flight. Arterial blood pressure at the level of the carotid (carotid distending pressure, CDP) showed a large transient increase by 27-47 mmHg when Gz+ was suddenly decreased and a similar drop when Gz+ was suddenly increased. HR displayed a reverse pattern with larger transients (-22 to -26 min-1) in response to Gz+ decreases and more sluggish changes of lower amplitude in the other direction. Central blood volume, as estimated from the inverse of transthoracic impedance (1/TTI), varied in concert with Gz+. A model is proposed in which HR responses are described as a function of CDP and 1/TTI after a time delay of 2.3-3.0 s and including a low-pass filter function with time constants of 0.34-0.35 s for decreasing HR and time constants of 2.9-4.6 s for increasing HR. The sensitivity of the carotid component was around -0.8 to -1.0 min-1 . mmHg-1 (4-7 ms/mmHg). The cardiopulmonary baroreceptor component was an additive input but was of modest relative importance during the initial HR responses. For steady-state HR responses, however, our model suggests that inputs from carotid and cardiopulmonary receptors are of equal importance.

• Mesland B.S., Finlay A.L., Wertheim A.H., Barnes G.R., Morland A.B., Bronstein A.M., Gresty M.A. Object motion perception during ego-motion: patients with a complete loss of vestibular function vs. normals. Brain Res. Bull. 40(5/6), 459-465, 1996.

• Mesland B.S., Wertheim A.H. A puzzling percept of stimulus stabilisation (Short Comm in Vision Res. 36(20), 3325-28, 1996.

• Mesland, D.A.M., Anton, A.H., Willemsen, H., Ende, H. van den: "The free fall machine - a ground-based facility for microgravity research in life sciences", Microgravity Sci. Technol. 9, pp. 10-14, 1996.

• Oostra, W., Bryant, D., Marijnissen, J.C.M., Scarlett, B., Wissenburg, J.: "Measurement of soot production of a candle under microgravity conditions", J. Aerosol Sci. 27, S715-S716, 1996.

• Oostra, W., Bryant, D., Marijnissen, J.C.M., Scarlett, B., Stratmann, J.: "A comparison of thermophoresis in a laminar flow under gravity and microgravity conditions", J. Aerosol Sci. 27, S407-S408, 1996.

• Sondag HNPM, de Jong HAA, Oosterveld WJ. Altered behaviour of hamsters by prolonged hypergravity; adaptation and re-adaptation to increased gravity forces. Acta Otolaryngol (Stockh), 116:192-197, 1996.

Abstract:
We studied the functional adaptation process in 40 hamsters subjected to either prolonged hypergravity to normal gravity. Subadult golden hamsters (n = 20) exposed to a hypergravity condition of 2.5 G for 6 months were tested to investigate the effect of hyper gravity on the perceptive motor skills and compared with control hamsters (n = 20). The motor coordination of the hypergravity hamsters hardly changed; locomotion was normal and swimming was possible. Equilibrium maintenance was disturbed during the first 3 months as was shown by the higher crossing time (p < 0.001) and higher fall frequency (p Ä 0.001) for the hypergravity group. Significant differences were also found in orientation during swimming (p = 0.007) and turning behaviour in the rotation task (p < 0.001) and in the no-rotation task (p = 0.029). After 6 months, 10 hamsters of both groups were tested for another 4 months, also the hypergravity hamsters were living at 1 G. Differences in orientation in the two groups did not change during swimming and turning behaviour during the rotation task (p = 0.026). Based on our findings, we conclude that the hamsters functionally adapted to hypergravity, which led to an altered performance of several tasks. The condition continued after 4 months of normal gravity.

• Sondag HNPM, de Jong HAA, van Marle J, Willekens B, Oosterveld WJ (1996). Otoconial alterations after embryonal development in hypergravity. Brain Res Bul, 40:353-357. 1995

• van Loon JJ; Veldhuijzen JP; Burger EH. Bone and space flight: an overview. In: Moore D, Bie P, Oser H, eds. Biological and medical research in space: an overview of life sciences research in microgravity. Berlin : Springer-Verlag, 1996. :p. 259-99.

Abstract:
The authors developed two extensive tables of bone physiology data gathered from 63 studies conducted during space flight. Data contained in the first table include author, flight, experimental organism, number of samples, bone site and/or cells examined, and remarks. The second table contains author, experimental organism, technique, and results and discussion. Data were gathered from studies conducted in Gemini, Skylab, Cosmos, Salyut-7 and Mir, and Space Shuttle programs.

• Wolf J., Vermeer C. Potential Effect of Vitamin K on microgravity - induced bone loss. J. Grav. Physiol. 3(2), 29-32, 1996.

1995

• Demaria Pesce, V.H., Visser, G.H., Daan, S.: "Evolution de la température corporelle au cours des vols paraboliques", Rev. Méd. Aéron. et Spat. 34, 93-97, 1995.

• Giegé, R., Drenth, J., Ducruix, A., McPherson, A., Saenger, W.: "Crystallogenesis of biological macromolecules; biological, microgravity, and other physico-chemical aspects", Prog. Crystal Growth and Charact. 30, 237-281, 1995.

• Hoefsloot H. C. J., L. P. B. M. Janssen, and H. W. Hoogstraten. Marangoni convection around a ventilated air bubble under microgravity conditions. Chemical Engineering Science Volume 49, Issue 1, 1994, Pages 29-39.

Abstract:
Under microgravity conditions in both parabolic and sounding rocket flights, the mass-transfer-induced Marangoni convection around an air bubble was studied. To prevent the bubble from becoming saturated, the bubble was ventilated. It turned out that the flow rate of the air through the bubble determined the flow pattern in the liquid. A mathematical model is presented which can adequately describe the observed phenomena.

• Karemaker, J.M.: "Blood pressure measurement under extreme circumstances: Finapres in actual and simulated weightlessness", Homeostasis 36, 275-280, 1995.

• Kingma, I., Toussaint, H.M., Commissaris, D.A.C.M., Hoozemans, M.J.M. and Ober, M.J. Optimizing the determination of the body center of gravity. J. Biomechanics 28, 1137-1142, 1995.

• Konings H. Gravitropism of roots: an evaluation of progress during the last three decades. Acta Bot. Neerl. 44(3), 195-223, Sept. 1995.

• Mesland B.S., Wertheim A.H. Visual and non-visual contributions to perceive ego-motion studied with a new phychophysical method. J. Vest. Res. 5(4), 277-288, 1995.

• Mazière, A. de, Gozales-Jurado, J., Reijnen, M., Narraway, J., Ubbels, G.A.: "Transient effects of microgravity on early embryos of Xenopus laevis", Adv. Space Res. 17, 219-223, 1995.

• Oostra, W., Marijnissen, J.C.M., Scarlett, B., Bryant, D.: "A comparison of thermophoresis in a laminar under gravity and microgravity conditions", J. Aerosol Sci. 26, S317-318, 1995.

• Sondag H.N.P.M., de Jong H.A.A., van Marle J., Oosterveld W.J. Effects of sustained acceleration on the morphological properties of otoconia in hamsters. Acta Otolaryngol (Stockh), 115:227-230, 1995.

• Sondag H.N.P.M., de Jong H.A.A., Oosterveld W.J. The effect of prolonged hypergravity on the vestibular system; a behavioural study. ORL, 57:189-193, 1995.

• Loon, J.J.W.A. van, Bierkens, J., Maes, J., Schoeters, G.E.R., Ooms, D., Zandieh Doulabi, B., Veldhuijzen, J.P.: "Polysulphone inhibits final steps of osteogenesis in vitro", J. Biomedical Materials Res. 29, 1155-1163, 1995.

• Loon, J.J.W.A. van, Bervoets, T.J.M., Burger, E.H., Diedonné, S.C., Hagen, J.W., Semeins, C.M., Veldhuijzen, J.P.: "Decreased mineralization and increased calcium release in isolated fetal mouse long bones under near-weightlessness", J. Bone and Mineral Res. 10, 550-557, 1995.

1994

• Alpatov, A.M., Rietveld, W.J., Oryntaeva, L.B.: "Impact of microgravity and hypergravity on free-running circadian rhythm of the desert beetle Trigonoscelis gigas Reitt.", Biological Rhythm Res. 25, 168-177, 1994.

• Gasset, G., Tixador, R., Eche, B., Lapchine, L., Moatti, N., Toorop, P., Woldring, C.: "Growth and division of Escherichia coli under microgravity conditions", J. Gen. Microbiology 145, 111-120, 1994.

•Johns JP, Vernalis MN, Karemaker JM, Latham RD. Doppler evaluation of cardiac filling and ejection properties in humans during parabolic flight. J Appl Physiol 1994 Jun;76(6):2621-6.

Abstract:
The cardiac filling and ejection properties of seven normal human subjects were examined during microgravity created on a National Aeronautics and Space Administration aircraft during parabolic flight. Doppler echocardiography was used to measure intracardiac velocities in sitting and supine subjects during three phases of flight: hypergravity (phase I), early microgravity (phase III), and late microgravity (phase IV). Heart rate declined 6% (P < 0.001) and right ventricular inflow velocities rose (46%, early; 26%, mean; P < 0.01) between phase I and phases III or IV in the sitting position only. Peak left ventricular outflow velocities rose 12% and inflow velocities rose (13%, early; 20%, mean) between phases I and IV while subjects were in the supine position (P < 0.05). A 14% rise in early velocities alone was seen between phases I and IV while subjects were in the sitting position (P < 0.05). In subjects entering microgravity while sitting, right heart chambers can accept additional venous return. When microgravity was entered while subjects were supine, however, venous augmentation was not observed. Left heart filling was more prominently enhanced when microgravity was entered while subjects were supine, suggesting a shift of fluid within the pulmonary vasculature.

• Karemaker J.M., Stok W.J., Latham R.D. G-suit inflation to 50 mmHg alters the cardiovascular transients when entering micro-G in parabolic flight. J Gravit Physiol. 1994 May;1(1):P33-4.

Abstract:
In the present experiments it was decided to have each test-subject serve as his own control by fitting the test-subjects with a G-suit and comparing the condition of inflated G-suit to the normal situation. G-suit inflation was intended to only displace blood on the venous side of the circulation, not to increase total peripheral resistance. Therefore, a very modest inflation of 50 mmHg was applied. This was considered sufficient to expel most of the blood from the venous pool in abdomen and legs, even under the condition of increased G-loading in the pull-up phase. The parabolas were to be undergone in three body positions: standing upright, sitting and supine. The prediction of the experimental outcome was that we would find no difference between transients with and without G-suit inflation in the supine position, that an initial overshoot in pressure and stroke volume in the upright position would be very much damped by the G-suit, even more in the standing than in the sitting position. Studies were performed in 5 flights of NASA's KC-135, in January 1993. Per flight 40 parabolas were flown in an adapted 'roller coaster profile', i.e. 0-G phases were followed by a 2-G pull-out phase, after a very brief 1-G phase again followed by the next 2-G pull-up phase. This sequence was flown for 10 parabolas, then a 1-G horizontal flight period was inserted. The first 3 parabolas of each set of 10 the subjects were sitting upright, seat belt fastened. The next three they were standing, feet stuck under a load strap on the floor, stabilizing themselves by a grip on the ceiling. Then three parabolas were flown with the test-subject supine, loosely attached to the floor by a load strap and further aided by a grip to another strap on the floor. The last parabola of a set was used as 'spare' to repeat any failed maneuver.

• Loon, J.J.W.A, van, Veldhuijzen, J.P., Windgassen, E.J., Brouwer, T., Wattel, K., Vilsteren, M van, Maas. P.: "Development of tissue culture techniques and hardware to study mineralization under microgravity conditions.", Adv. Space Res., 14:289-298, 1994.

• Rijken P.J., Boonstra J., Verkleij A.J., de Laat S.W. Effects of gravity on the cellular response to epidermal growth factor. Adv Space Biol Med. 1994;4:159-88.

Abstract:
EGF and related polypeptides are involved in the regulation of cell growth and differentiation of continuously regenerating tissues, in tissue repair processes and in placental and fetal development. Their initial mode of action generally constitutes binding to specific plasma membrane localized receptors, transduction of the signal across the plasma membrane, subsequent activation of signalling pathways in the cell, and the induction of early nuclear gene expression. EGF-induced signal transmission from the plasma membrane to the nucleus has been studied in microgravity in order to gain insight in the molecular mechanisms that constitute the effects of gravity on cell growth. Exposure of human A431 cells to microgravity strongly suppresses EGF- and PMA-induced c-fos and c-jun expression. In contrast, forskolin- and A23187-induced c-fos expression and constitutive beta-2 microglobulin expression remain unaffected. This suggests that microgravity differentially modulates EGF-induced signal transduction pathways. Since both EGF and PMA are known to be activators of PKC, which is not the case for forskolin and A23187, PKC-mediated signal transduction may be a cellular target for microgravity. Inhibition of EGF-induced c-fos expression by microgravity occurs downstream of the initiation of EGF-induced signal transduction, i.e., EGF binding and EGFR redistribution. In addition to PKC signaling, actin microfilament organization appears to be sensitive to microgravity. Therefore, the inhibition of signal transduction by microgravity may be related to alterations in actin microfilament organization. The fact that early gene expression is affected by agents that alter the organization of the actin microfilament system supports this hypothesis. The decrease in c-fos and c-jun expression in microgravity may result in the decreased formation of the FOS and JUN proteins. Consequently, a short-term reduction in gene expression in microgravity may have a more dramatic effect over the long term, since both the JUN and FOS protein families are required for normal cell cycle progression. However, since more than 20 years of manned spaceflight have shown that humans can survive in microgravity for prolonged periods, it appears that cells in the human body can partly or completely overcome gravitational stress. Although some insight in the molecular basis on human cells has been obtained, future studies will be needed for a better understanding of the grounds for alterations in the cellular biochemistry due to altered gravity conditions.

• Ubbels G.A., Reijnen M., Meijerink J., Narraway J. Xenopus laevis embryos can establish their spatial bilateral symmetrical body pattern without gravity. Adv Space Res. 1994;14(8):257-69.

Abstract:
One assumes that gravity cooperates with the sperm in the establishment of bilateral symmetry in the embryo, particularly in species with yolky eggs. However, only experiments under genuine microgravity can prove this. May 2nd 1988 on the TEXUS-17 Sounding Rocket, eggs of Xenopus laevis became the first vertebrate eggs ever successfully fertilized in Space. Fertilization was done in fully automated hardware; the experiment was successfully repeated and extended in 1989. Here we report a "Space First" from the IML-1 Space Shuttle mission (January 1992): In similar hardware and under microgravity, artificially fertilized Xenopus eggs started embryonic development. Histological fixation was pre-programmed at the time gastrulation would occur on Earth and indeed, gastrulae were fixed. Thus after fertilization in near weightlessness Xenopus embryos do develop bilaterally symmetrically, very probably cued by the sperm alone.

• Tixador, R., Gasset, G., Eche, B., Moatti, N., Lapchine, L., Woldringh, C., Toorop, P., Moatti, J.P., Delmotte, F., Tap, G.: "Behaviour of bacteria and antibiotic under space conditions", J. Aviation, Space & Environ. Med. 65, 551-556, 1994.

1993

• Bles W., de Graaf B. Postural consequences of long duration centrifugation. J. Vest. Res. 3, 87-95, 1993.

• Karemaker JM, Stok WJ, Latham RD. Body position and volume status as determinants of cardiovascular responses to transition into microgravity in parabolic flight. Physiologist 1993;36(1 Suppl):S56-7

Abstract:
The condition of microgravity during spaceflight imposes a new challenge to the cardiovascular system and to its homeostatic mechanisms. Initial fluids shifts from the dependent parts to the upper parts of the body are supposed to induce a plethora of effects which eventually lead to the well-known puffy faces and chicken legs' of astronauts. At the same time some 2-3 kgs. in fluid is lost in urine and by diminished uptake. For research into these longer-term effects of spaceflight extensive physiologic experiments are required in space. In view of the high cost and the logistic problems related to space-research much work is done in simulation experiments like bedrest or head down tilt studies. For the very initial effects of micro-G parabolic flight can be used. In parabolic flights we have addressed the question of immediate cardiovascular effects of the transition into microgravity. Since a parabola will last for not more than some 25 seconds, one may expect to observe mainly changes in the outflow of the autonomic nervous system, reflecting in blood pressure and heart rate as easily measurable parameters. Such changes can be expected to be caused by the sudden disappearance of hydrostatic effects and the shifts of fluid from pools where it is kept under the influence of gravity. Hydrostatic effects will play a role in the position of the baroreceptors with respect to the heart: in the upright position the carotid sinuses are some 25 cm above heart level, consequently they observe a lower pressure than that at the heart. When this effect disappears in micro-G a suddenly increased pressure will be observed and the baroreflex is called into action. On the venous side blood will rush to the right atrium when it is no longer pulled down in the compliant vessels of the abdomen and legs. This may be expected to lead to increased pressures on the low-pressure side of the heart. Apart from changes in filling of the left heart this may lead to autonomic nervous effects on systemic blood pressure and heart rate as well.

• Marcus, J.T., Kuipers, A., Smoorenburg, G.F.: "Otolith responses in man during parabolic flight", Exp. Brain Res. 93, 328-334, 1993.

• Rijken P.J., de Groot R.P., van Belzen N., de Laat S.W., Boonstra J., Verkleij A.J. Inhibition of EGF-induced signal transduction by microgravity is independent of EGF receptor redistribution in the plasma membrane of human A431 cells. Exp Cell Res. 1993 Feb;204(2):373-7.

Abstract:
Epidermal growth factor (EGF)-induced c-fos and c-jun expression is strongly suppressed in microgravity. We investigate here whether this is due to inhibition of processes occurring during the initiation of EGF-induced signal transduction. For this purpose, EGF-induced receptor clustering is used as a marker. The lateral distribution of EGF receptors is directly visualized at an ultrastructural level by the label-fracture method. Quantification of the receptor distributions shows that EGF-induced receptor redistribution is similar under normal and microgravity conditions. This suggests that microgravity influences EGF-induced signal transduction downstream of EGF binding and EGF receptor redistribution, but upstream of early gene expression in human A431 cells.

1992

• Baisch F., Beck L., Karemaker J.M., Arbeille P., Gaffney F.A., Blomqvist C.G. Head-down tilt bedrest. HDT'88--an international collaborative effort in integrated systems physiology. Acta Physiol Scand Suppl. 1992;604:1-12.

Abstract:
An international collaborative project, initiated by the DLR-NASA Life Sciences Working Group, led to the performance of a head-down tilt bedrest (HDT) study at the DLR Institute for Aerospace Medicine. Scientific and operational questions were addressed in preparation for the D-2 Spacelab mission. Principal areas of interest were cardiovascular regulation and fluid/electrolyte metabolism. The results are detailed in a series of 13 reports to which the present paper serves as an introduction.

• Beck L., Baisch F., Gaffney F.A., Buckey J.C., Arbeille P., Patat F., ten Harkel A.D., Hillebrecht A., Schulz H., Karemaker J.M., et al. Cardiovascular response to lower body negative pressure before, during, and after ten days head-down tilt bedrest. Acta Physiol Scand Suppl. 1992;604:43-52.

Abstract:
The haemodynamic response to lower body negative pressure (LBNP) was studied in 6 test subjects before (baseline), during, and after (recovery) ten days of 6 degrees head-down bedrest. The LBNP protocol consisted of a 35 min control period, application of a staircase differential pressure profile (15 min at -15 mmHg; 5 min at -30 mmHg; 15 min at -40 mmHg), and a 10 min post-stress observation period. Cardiac output was measured by a foreign gas rebreathing technique. Finger plethysmographic arterial blood pressure (BP), ECG, and heart rate (HR), lower limb crossectional area, and the electrical impedance of three body segments were recorded continuously. As expected, HDT caused a decrease in plasma volume and total body fluid volume. Resting CO at the end of HDT was 16% below the baseline level and similar to CO in the upright position before HDT. Stroke volume (SV) was also reduced, but there were no significant changes in control HR or BP. Absolute changes in CO and SV during LBNP were similar at baseline and during HDT, but the relative changes were larger during HDT. HR and vasoconstriction responses were enhanced, but presyncope occurred in two subjects. Reduced cardiac filling with decreased stroke volume at rest is the apparent primary cause of the altered LBNP response during HDT.

• ten Harkel AD; Beck L; Karemaker JM. Influence of posture and prolonged head-down tilt on cardiovascular reflexes. Acta Physiol Scand Suppl. 1992;604:77-87.

Abstract:
We investigated the influence of ten days 6 degrees head-down tilt (HDT) on short-term cardiovascular control. To help differentiate between the effects of HDT-induced fluid redistribution and changed autonomic cardiovascular modulation under prolonged HDT, the effect of acute posture changes was investigated as well. Six healthy male volunteers were studied. Continuous finger blood pressure was measured non-invasively by means of Finapres. Heart rate (HR) was derived from the electrocardiogram. Responses to forced breathing (FRSA), Valsalva's manoeuvre (VM), Mental Stress (MS) and Sustained Handgrip (SHG) were measured. Changing posture from HDT to standing enhanced the BP and HR responses to VM, both during straining and after release. During prolonged HDT, responses to VM changed toward the pattern seen in the upright posture before HDT, suggesting a strong influence of fluid redistribution. Neither posture nor prolonged HDT influenced HR variation during FRSA and responses to MS and SHG. BP variation during FRSA was influenced by posture but not by prolonged HDT. Thus, cardiovascular reflex tests which reflect the parasympathetic (FRSA) or the sympathetic (MS and SHG) efferents to the heart were not influenced by posture or prolonged HDT. Only the responses to VM were affected by both posture and prolonged HDT. These results are probably due to a decrease in blood volume and stroke volume under prolonged HDT, an increase in venous distensibility and, to a lesser extent, to inadequate cardiovascular regulatory responses.

• ten Harkel AD, Baisch F, Karemaker JM. Increased orthostatic blood pressure variability after prolonged head-down tilt. Acta Physiol Scand Suppl 1992;604:89-99.

Abstract:
The effect of simulated weightlessness on orthostatic blood pressure regulation was evaluated with passive 70 degrees head-up tilt (HUT) after 10 days 6 degrees head-down tilt (HDT). Six healthy male volunteers were studied. Continuous recording of finger blood pressure (BP) was obtained non-invasively with a FinapresTM device. Instantaneous heart rate (HR) was derived from the electrocardiogram. To quantify orthostatic BP variability, a fast fourier transform (FFT) of the beat-by-beat BP- and RR-interval values was performed. Control HR before HUT after the 10-day HDT period was increased, probably due to an arousal state of the test subjects. The change in BP induced by HUT was not influenced by 10 days' HDT, in contrast to the HR rise which increased from 24 +/- 2 beats/min to 41 +/- 7 beats/min (P less than 0.05). After HDT the total variance in orthostatic BP almost doubled. FFT indicated that this increase in variance can be ascribed to BP oscillations with a frequency of around 0.1 Hz. In three subjects transient HR decelerations during HUT after HDT were observed. Analysis of the relationship between BP and HR in the transients showed that each HR decrease was preceded by a BP increase above normal. These HR decelerations seemed, therefore, to be an effect of the vagal part of the arterial baroreflex and did not necessary signal an impending vasovagal syncope. The present study indicates that although 10 days' HDT do not influence absolute BP responses to 70 degrees HUT BP was maintained by an increased sympathetic activity, reflected by an increased HR response and an augmented variance in BP around 0.1 Hz.

• Hoefsloot HCJ, Hoogstraten HW, Janssen LPBM, Knobbe JW. GROWTH-FACTORS FOR MARANGONI INSTABILITY IN A SPHERICAL LIQUID LAYER UNDER ZERO-GRAVITY CONDITIONS. APPL SCI RES 49 (2): 161-173 APR 1992

Abstract:
The neutral-stability analysis presented by Hoefsloot et al. [3] is completed by computing the growth factors-beta for the normal modes and by showing that the neutral states (Re(beta) = 0) are stationary (Im(beta) = 0) rather than oscillatory (Im(beta) not-equal 0).

• HOOGSTRATEN HW, HOEFSLOOT HCJ, JANSSEN LPBM. MARANGONI CONVECTION IN V-SHAPED CONTAINERS. JOURNAL OF ENGINEERING MATHEMATICS 26 (1): 21-37 FEB 1992.

Abstract:
This paper presents a numerical study of the time evolution of Marangoni convection in two V-shaped containers involved in the microgravity experiments reported in Hoefsloot et al.[7]. First the case of the triangular container with a plane gas/liquid interface is considered, next the container having the shape of a circular sector with a curved interface is dealt with. The numerical results show the same behaviour as observed experimentally: convection caused by macroscale effects in the former, and microconvection in the latter case.

• Karemaker J.M., Akkerman E.M. Computer modelling the effects of gravity on the cardiovascular system. Physiologist. 1992 Feb;35(1 Suppl):S162-4.

• de Laat, S.W., de Groot, R.P., den Hertog, J., Rijken, P.J., Verkleij, A.J., Kruijer, W., and Boonstra, J. (1992) Epidermal growth factor induced signal transduction in A431 cells is influenced by altered gravity conditions. The Physiologist 35, S19-21.

• van Lieshout EJ, van Lieshout JJ, Krol J, Simons M, Karemaker JM. Assessment of cardiovascular reflexes is of limited value in predicting maximal +Gz-tolerance. Aviat Space Environ Med 1992 Jan;63(1):21-6.

Abstract:
The importance of +Gz-induced loss of consciousness as a major cause of inflight incapacitation emphasizes the need for predicting +Gz-tolerance and investigating its possible determinants. The cardiovascular changes from +Gz-stress are initially counteracted reflexly by the cardiovascular autonomic system. The integrity of neural cardiovascular reflex control can be assessed by analysing the blood pressure (BP) and heart rate (HR) responses to different maneuvers, such as the Valsalva maneuver, standing and forced respiratory sinus arrhythmia. The aim of the present study was to investigate a possible relation between the cardiovascular responses to these tests and +Gz-tolerance. In 10 healthy subjects continuous Finapres BP and HR responses to the tests have been determined and correlated with their G-levels of peripheral light loss (PLL) during centrifuge-runs (0.1 G/s). Only mean BP recovery during Valsalva maneuver correlated marginally significantly with PLL (r = 0.63, p = 0.049). Cardiovascular findings were within normal range revealing no cardiovascular autonomic dysfunction. These results indicate that intact neural cardiovascular control seems to be a condition for tolerating +Gz-stress without determining maximal +Gz-tolerance. We conclude that assessment of cardiovascular reflexes may only confirm baroreflex integrity. However, they have limited value in predicting +Gz-tolerance.

• Rijken, P.J., de Groot, R.P., Kruijer, W., de Laat, S.W., Verkleij, A.J. and Boonstra, J. (1992) Identification of specific gravity sensitive signal transduction pathways in human A431 carcinoma calls. Adv. Space Res. 1, 145-152.

• Rijken, P.J., Groot, R.P. de, Kruijer, W., Verkleij, A.J., Boonstra, J., Laat, S.W. de: "Altered gravity conditions affect early EGF-induced signal transduction in human epidermal A431 cells", ASGSB Bulletin 5, 77-82, 1992.

• Schulz H, Hillebrecht A, Karemaker JM, ten Harkel AD, Beck L, Baisch F, Meyer M. Cardiopulmonary function during 10 days of head-down tilt bedrest. Acta Physiol Scand Suppl 1992;604:23-32.

Abstract:
Pulmonary and cardiovascular responses to simulated weightlessness, i. e. 6 degrees head-down tilt bedrest (HDT) were investigated in six healthy male volunteers (mean age 26 yrs). Pulmonary diffusing capacity, functional residual capacity, pulmonary capillary blood flow, and lung tissue volume were measured by inert gas rebreathing. Heart rate and mean arterial blood pressure were obtained from finger blood pressure readings using a plethysmographic technique (Finapres). The short-term (20 min) response to HDT consisted of a 22% increase in pulmonary blood flow, and 13% and 31% falls in blood pressure and heart rate relative to standing. Functional residual capacity fell by 33%, while lung tissue volume increased insignificantly. Subsequent measurements during 10 days of HDT and 5 days of recovery revealed no further changes in lung volume, lung tissue volume, or blood pressure. However, diffusing capacity fell gradually and remained 4%-5% below baseline values after the 7th day of bedrest and during recovery (p less than 0.05). Pulmonary blood flow decreased by 16% during head-down bedrest and recovered partially within the following 5 days (p less than 0.05). We conclude that during and after simulated weightlessness marked alterations in cardiovascular function and marginal affections of gas exchange can be demonstrated already at rest. They may be considered as contributing factors to orthostatic and exercise intolerance observed after space flight.

• Ubbels G.A. Developmental biology on unmanned space craft. Adv Space Res. 1992;12(1):117-22.

Abstract:
Even the short period (6-7 min) of real microgravity during Sounding Rocket (SR) flights has provided important basic new information about the influence of the lack of gravity on particular developmental processes. However some of the reports also clearly revealed the need of an increased number of larger samples per experiment. The SR provides a very appropriate way for testing of specific flight hardware designed for experiments on long-duration missions. It was stated that the number of flight opportunities should be extended, in order to keep scientists interested in the performance of Space experiments. To this end ESA and USSR have started to collaborate in the BIOKOSMOS-9 Mission with the aim of continuing that collaboration in the future, to provide additional unmanned flight opportunities with a duration of 10-14 days. The reports on experiments performed on Biokosmos-9 showed that such missions can be a very useful extension of flight opportunities, although several of the experimental conditions should be improved. In comparison with the 1988 COSPAR meeting, the material presented at the 1990 COSPAR Session on Developmental Biology showed considerable progress in methodology: the more descriptive phase is over, the period of the actual microgravity-experiments has started, and cell- and molecular biological approaches are increasingly applied. It also became clear that in experiments with relatively small cells (plant cells, human A431 epidermoid carcinoma cells and lymphocytes) the experimental results from flight experiments were often identical to those obtained in simulated microgravity. When applicable to the biological systems involved, users should more often consider the application of such Earth-based methods, that is not only in preparation of a real Space experiment. Finally, it was emphasized that some of the results from earlier experiments, which were assumed to demonstrate real microgravity effects, might have only seemingly been due to the microgravity conditions. Instead, they could have been caused secondarily by factors such as the lack of convection in surrounding media. It is important to test this possibility in future experiments.

• Ubbels GA; Berendsen W; Kerkvliet S; Narraway J. Fertilization and development of eggs of the South African clawed toad, Xenopus laevis, on sounding rockets in space. Adv Space Res. 1992;12(1):181-94.

Abstract:
Egg rotation and centrifugation experiments strongly suggest a role for gravity in the determination of the spatial structure of amphibian embryos. Decisive experiments can only be made in Space. Eggs of Xenopus laevis, the South African clawed toad, were the first vertebrate eggs which were successfully fertilized on Sounding Rockets in Space. Unfixed, newly fertilized eggs survived reentry, and a reasonable number showed a seemingly normal gastrulation but died between gastrulation and neurulation. Only a few reached the larval stage, but these developed abnormally. In the future, we intend to test whether this abnormal morphogenesis is due to reentry perturbations, or due to a real microgravity effect, through perturbation of the reinitiation of meiosis and other processes, or started by later sperm penetration.

1991

• de Groot RP, Rijken PJ, den Hertog J, Boonstra J, Verkleij AJ, de Laat SW, Kruijer W. Nuclear responses to protein kinase C signal transduction are sensitive to gravity changes. Exp Cell Res. 1991 Nov;197(1):87-90.

Abstract:
A number of studies have suggested that gravity changes may influence mammalian cell growth and differentiation. To obtain insight in the molecular mechanisms underlying these effects, we have studied immediate early gene expression in response to activation of cytoplasmic signal transduction under microgravity conditions. In this paper we show that epidermal growth factor (EGF)- and 12-O-tetradecanoyl-phorbol-13-acetate (TPA)-induced expression of the c-fos and c-jun protooncogenes is decreased in microgravity, while no effect of gravity changes was observed on A23187- and forskolin-induced expression of these genes. These decrease in c-fos expression was not due to delayed kinetics under microgravity. These results demonstrate that gravity differentially modulates distinctive signal transduction pathways.

• de Groot RP, Rijken PJ, Boonstra J, Verkleij AJ, de Laat SW, Kruijer W. Epidermal growth factor-induced expression of c-fos is influenced by altered gravity conditions. Aviat Space Environ Med. 1991 Jan;62(1):37-40.

Abstract:
Epidermal growth factor (EGF) activates a well characterized signal transduction system in human A431 epidermoid carcinoma cells, which leads to rapid and transient expression of the c-fos proto-oncogene. In order to investigate the influence of altered gravity on EGF-induced signal transduction, we have studied the EGF-induced c-fos expression under simulated hypo- and hypergravity conditions. In this report we show that EGF-induced fos expression is decreased under simulated hypogravity conditions, while hypergravity has a stimulatory effect on EGF-induced fos expression. These results show that the EGF-activated signal transduction system is influenced by gravity, and that gravity exerts its effects already in the early phases of the signal transduction cascade.

• Rijken PJ, de Groot RP, Briegleb W, Kruijer W, Verkleij AJ, Boonstra J, de Laat SW. Epidermal growth factor-induced cell rounding is sensitive to simulated microgravity. Aviat Space Environ Med. 1991 Jan;62(1):32-6.

Abstract:
Epidermal growth factor (EGF) induces rapid rounding of A431 human epidermoid carcinoma cells. This process is dependent upon temperature and EGF concentration. To investigate the possible influence of gravity variations on EGF-induced cell rounding of A431 cells, experiments were performed using a fast-rotating clinostat and centrifuge, thereby simulating microgravity and higher gravity values, respectively. We demonstrated that simulated microgravity conditions enhance EGF-induced cell rounding significantly, whereas hypergravity values do not show significant effects on this process. These results suggest that simulated microgravity modulates growth factor-induced signal transduction.

1990

• Beck L, Blomqvist G, Arbeille P, Baisch F, Buckey J, Gaffney A, Hillebrecht A, Karemaker J, Patat F, Schulz H, et al. Effect of a 10-day HDT on the hemodynamic response to LBNP. Physiologist 1990 Feb;33(1 Suppl):S173-4

• de Groot RP, Rijken PJ, den Hertog J, Boonstra J, Verkleij AJ, de Laat SW, Kruijer W. Microgravity decreases c-fos induction and serum response element activity. J Cell Sci. 1990 Sep;97 ( Pt 1):33-8.

Abstract:
Several studies have shown that altered gravity conditions influence mammalian cell growth and differentiation. The molecular mechanisms underlying these effects, however, remain relatively obscure. In this paper we show that microgravity reached in a sounding rocket strongly decreases epidermal growth factor (EGF)-induced expression of the proto-oncogenes c-fos and c-jun, which are both implicated in the regulation of proliferation and differentiation. Decreased activity of the serum response element (SRE), present in the c-fos promoter-enhancer region, is probably responsible for the decrease in EGF-induced c-fos expression. In addition, we show that gravity alterations differentially modulate distinctive signal transduction pathways, indicating that gravity-dependent modulations of mammalian cell proliferation are unlikely to be caused by a nonspecific stress response of the cell.

• de Jong HAA, Kortschot HW, Oosterveld WJ. Caloric nystagmus decay during parabolic flight. Acta Otolaryngol (Stockh) 109:1-7, 1990.

• Ockels W.J., Furrer R., Messerschmid E. Simulation of space adaptation syndrome on earth. Exp. Brain Res., 79/3, 661-663, 1990.

• Rijken, P.J., Groot, R.P. de, Briegleb, W., Kruijer, W., Verkleij, A.J., Boonstra, J., Laat, S.W. de: "Epidermal growth factor induced cell rounding is sensitive to simulated weightlessness", Aviat. Space Environ. Med. 62, 32-36, 1990.

• ten Harkel AD, Baisch F, Beck L, Karemaker JM. The autonomic nervous system in blood pressure regulation during 10 days 6 degrees head down tilt. Physiologist 1990 Feb;33(1 Suppl):S178-9

1989

• Ubbels, G.A., W. Berendsen, J. Narraway. Fertilization of frog eggs on the sounding rocket in space. Adv. Space Res. Vol 9(11), -. (11)187-(11)197, 1989.

• Ubbels, G.A. Developmental biology in space. Why and how. Adv. Space Res. Vol 9(11), -. (11)131-(11)134, 1989.

1988

• Bles W., van Raay J.L. Pre- ans Postflight (D-1) posturl control in tilting environments. Adv. Oto-Rhino-Laryngol. 42: 13-17, 1988.

• Greenberg, J.M. The interstellar dust model of comets: post Halley. In: Dust in the Universe, eds. Baily, M.E. & Williams, D.A., 121-143, Cambridge University Press. 1988.

1987

• de Jong HAA, Oosterveld WJ. Rotation test in the weightless phase of parabolic flight. Aviat Space Environ Med 58(Suppl):A253-A256, 1987.

• Oosterveld, W. J.; de Jong, H. A. A., The effect of weightlessness on the flight behavior of pigeons with canal lesions. Aviat. Space Environ. Med. 58 (suppl.): A250-A252, 1987.

1985

• Oosterveld W.J., Greven A.J., Gürsel A.O., de Jong H.A.A. Caloric vestibular test in the weightless phase of parabolic flight. Acta Otolaryngol., 99: 571-576, 1985.

1984

• Ubbels G.A., T.G. Brom. Cytoskeleton and gravity at the work in the establishment of dorso/ventral polarity in the egg of Xenopus laevis. Adv. Space Res., 4, 9-18, 1984.

1982

• Greenberg, J.M. What are comets made of? A model based on interstellar dust, Comets, Edt. Wilkening, L., IAU Coll. No. 61, 131-163. University of Arizona Press, Tuscon, 1982.

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