Conference Abstracts

This page provides a list of abstracts in the field of gravitational life sciences (biology / physiology), astrobiology, 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

2004

• Andreescu CE*, De Zeeuw CI, De Jeu MTG. Department of Neuroscience, Erasmus MC, Rotterdam. Keeping balanced in space. 3rd Endo-Neuro-Phycho meeting and 8th Endo-Neuro meeting, June 1-4, 2004, Doorwerth, The Netherlands

Abstract:
On earth the sensory information from the vestibular system, the optokinetic system and the proprioceptors is necessary to maintain balance and a stable retinal image. In space the sensory information provided by the otolith organs is absent or very small due to the lack of gravity (microgravity). Here, on earth, we studied the influence of gravity and the consequences of gravity perception loss on eye movements using a mutant mouse lacking the otoconia, which serve as the gravito-inertial loading of the otolith organs (the tilted mouse, tlt). The horizontal and vertical vestibulo-ocular reflex (VOR), optokinetic reflex (OKR) and visually enhanced vestibulo-ocular reflex (VVOR) were recorded in tlt and control littermate mice, using a video eye-tracking technique. Furthermore, otolith sensitivity was studied by positioning the mouse in different roll angles. The otolith-ocular responsiveness to various gravitational forces was significantly attenuated in the mutant mice, indicating that these mice do not have functional otolith organs. VOR gains were lower and VOR phases were higher in tlt mice compared to littermates, regardless of the head position with respect to gravity. In all tested conditions the OKR gain in tlt mice was significantly higher than in the control mice, with no phase difference between the two groups. Despite the higher OKR gain in the tlt mice, the mutant mice couldn’t reach the VVOR gain of the control mice. The increased OKR gain is a frequency dependent compensatory mechanism, which is not influenced either by the position of the mouse or by the eye movement plane. This study clearly reveals that there is a functional synergy in the processing of otolith and optokinetic signals regarding the gravito-inertial acceleration. This mechanism might also be important for maintaining balance and stable retinal images in space.
*Corina E Andreescu, Department of Neuroscience, Erasmus MC, 3000 DR Rotterdam, PO Box 1738, The Netherlands, t 0630003170, e-mail c.andreescu@erasmusmc.nl. See also the poster for this abstract.

• Bouët Valentine, Jos Ijkema-Paassen, Wubbels René, Gramsbergen Albert. Locomotor system development in hypergravity. University of Groningen, Groningen NL & Academic Medical Center, Amsterdam NL. Abstract from 25th Annual International Gravitational Physiology Meeting 6 - 11 June, 2004 Russian Academy of Sciences Moscow, Russia.

Abstract:
When the essential sensory cues are modified during development, locomotion could be permanently affected. That is the case with exposure to microgravity which induces long lasting alterations in locomotor parameters. 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 in rats conceived, born and reared in hypergravity (HG: 2 g) and then transferred to 1 g, and 2) the correlated modifications of soleus and tibialis anterior muscles. Pups born in a centrifuge (2 g) were transferred to 1 g at the ages of: P5 (5-days postnatal), P10, P15, P21 and P27. Behavioral observations started at this time and carried on until the age of P40. A control group was tested from P5 to P40. Locomotor development was video recorded and analyzed during free walking in a runway and in an open-field enclosure. Also, adaptations in muscles were studied. To this, muscles were removed at P40, and on P9 and P16, for immunohistological analysis Rats transferred to normal gravity at P5 and P10 were able to walk belly and head free from the floor and to perform rearing and grooming before control rats. On the other hand HG-P15 seemed delayed in several aspects of their walking performances. The older rats (HG-P21 and HG-P27) did not display drastic locomotor alterations. We found slight changes in muscular composition. These results suggest that some locomotor parameters are accelerated by a hypergravity exposure followed by a transfer to a relative microgravity, notably those linked with the vertical component (belly and head lifting up, rearing). This may be due to an advanced development of postural control and increased muscular force. On the other hand, our results demonstrate that, apart from an adaptational period, no long lasting effects occur after a period of hypergravity during early development. (Sponsored by the European Space Agency.)

• Jack J.W.A. van Loon(1*), M.C. van Laar(1), J.P. Korterik(2), F.B. Segerink(2), R. J. Wubbels(3), H. A. A. de Jong(3), NF. Van Hulst(2). DEMONSTRATE ON LINE CELL SHAPE CHANGES DUE TO GRAVITY 1: DESC-ACTA-VU, van der Boechorststraat7, Amsterdam. 2: Applied Optics group, Fact. Appl. Physics, Univ. Twente, Enschede, NL. 3:Vestibular Department ENT, AMC, UvA, Amsterdam, NL.

Abstract:
Cell shape and integrity depend, at least partially, on the equilibrium of intracellular and extracellular mechanical forces applied to that cell. In contract to a complete organism under near weightlessness conditions where e.g. bones and muscles are highly unloaded, gravity is a nearly insignificant force at the scale of a single cell. Past spaceflight and ground based cell biological studies in hypogravity or hypergravity environments showed changes in e.g. cell behavior (signal transduction) cell shape (cytoskeleton) or proliferation. From these studies it is not clear whether these result emerged from direct of indirect effects of (micro-) gravity. In the current pilot study we measured changes of cell shape under various hypergravity conditions. Cell shape was measured both in cells fixed after rotation in a small diameter tissue culture centrufuge (MidiCAR) as well as on line using an atomic force microscope (AFM) mounted onto the large diameter centrifuge at the AMC in Amsterdam. We have shown that cells do change shape under hypergravity conditions and that it is feasible to investigate these changes on line using AFM. Supported by NWO-SRON grant MG-053/057

• Wubbels René, Bouët Valentine, Gramsbergen Albert. Sensory motor reflex developed in hypergravity. Academic Medical Center, Amsterdam NL & University of Groningen, Groningen NL. Abstract from 25th Annual International Gravitational Physiology Meeting 6 - 11 June, 2004 Russian Academy of Sciences Moscow, Russia.

Abstract:
Functional postural control and effective execution of behavioral motor patterns depend on the existence of a previously established consistent frame of reference, together with instantaneous input from various sensory systems. Adaptation to a new frame of reference after a change of environmental conditions, e.g. in weightless-ness during space flight, is possible, and probably relies on a recalibration of sensory input and an update of motor commands. A gravity change during the interdependent differentiation and growth processes of an animal's development has even more severe consequences. In this study, gestation and early postnatal development of rats occurred under hypergravity (HG; 2g) inside a centrifuge. Development of a control group occurred under normal gravity (NG). Five groups of HG exposed rats were transfered to NG on different postnatal days (P5, P10, P15, P21, P27). Behavioral tests started on the day HG rats were removed from the centrifuge; NG rats were tested from P5. Six types of motor behavior were studied: 1 Contact-righting: how long takes a pup to turn from a supine to prone position on the floor, 2 Air-righting: time needed to turn from a supine to prone position during fall, 3 Negative geotaxis: time taken to turn from nose-down position on a tilted plane (45°) to nose-up, 4 Grasp reflex: flexion of fore- and hindpaw digits at touch of a thin rod, 5 Forepaw grip time: suspension time when grasping a rod, 6 Postural tail reflex: when held by the tail, do pups extend neck and limbs? The results show that HG exposure delays development of reflexes and motor patterns which depend on vestibular input (1, 2 & 3); other reflexes (4, 5 & 6) are not delayed. It appeared that some developmental processes are accelerated: HG exposed pups (P5) initially displayed increased muscle strength (5), and eye opening of HG pups (P5 & P10) was advanced by about 2-3 days. We conclude that (a change of) the magnitude of the gravitational field plays a role during gestation and postnatal development of the rat, and can alter the chronological order of these processes and the relative predominance of separate sensory systems for motor activity. (Sponsored by the European Space Agency.)

2001

Several abstracts are available from the 3rd 'NL-Gravity & Astrobiology Symposium' which was held on Tuesday 15th and Wednesday 16th May 2001 at the Free University in Amsterdam. See also left hand index (NL-Symposium) for the 1998 and 1999 programs or go directly to the 2001 abstracts.

• Poovaiah B.W.1, T. Yang1 and J.J.W.A. van Loon2. Effects of Simulated Microgravity and Hypergravity on the Expression of Arabidopsis Genes Encoding Calmodulins and Calmodulin-Binding Proteins. 1 Department of Horticulture, Washington State University, Pullman, WA. 2 DESC, OCB-ACTA-VU, Amsterdam, Netherlands. Proceedings of 17th ASGSB Annual Meeting, Alexandria, Virginia, USA, 7-11 November 2001. abstract 67, p. 31.

Abstract:
Calcium and calmodulin (CaM) play an important role in plant gravity signal transduction. However, the molecular and biochemical mechanisms involved are not clearly understood. To study the effects of gravity-induced changes on the expression of genes involved in Ca2+/CaM-mediated signaling, two week old Arabidopsis seedlings were subjected to simulated microgravity using the Random Positioning Machine, and hypergravity (10 g) using the MidiCAR centrifuge (ranging from 5 hrs to 5 days). The changes in mRNA levels of 11 CaM /CaM-like genes, and 20 genes encoding CaM-binding proteins were studied by RT-PCR using gene-specific primers. Actin 8 was used as a positive internal control. Selective and significant differences were observed between controls and simulated microgravity and hypergravity treated samples. Three CaM genes were induced by simulated microgravity and one was induced by both hypergravity and simulated microgravity. Similarly, we have identified several genes encoding CaM-binding proteins that are differentially expressed in response to gravi-stimulation. Our results suggest that these genes may play an important role in gravity signal transduction.

• van Loon J. J.W.A. 1, E. Folgering 2, J. P. Veldhuijzen 3, C. V.C. Bouten 2. INERTIAL SHEAR FORCES IN GRAVITATIONAL BIOLOGY. 1 Dutch Experiment Support Center (DESC), VU, Amsterdam, Netherlands. 2 Eindhoven University Technology, MATE, Eindhoven, Netherlands. 3 ACTA-VU, Oral Biology, Gr. Oral Cell Biology, Amsterdam. ELGRA-News 22, Proceedings of the Biennal meeting, Banyuls sur Mer, France, 25-28 September 2001.

Abstract:
Based on Einstein's equivalent principal, a 1g condition is "generated" in a sample that remains on Earth or that is put into a centrifuge running at an angular velocity of 1g on-board a free falling spacecraft. In gravitational biology it was with facilities like Biorack that one could use an on-board 1g control. The on-board centrifuge was regarded as the best control for an actual microgravity experiment. However, one of the never addressed differences between ground 1g and in-flight 1g is the inertial shear force generated in on-board centrifuges while this shear force could be one of the main artefacts in spaceflight and on-ground studies using centrifuges. Shear forces are generated in two ways. Static shear and fluid shear. Fluid shear is best known from the circulatory system where the endothelium is exposed blood flows. Static shear forces are generated in materials exposed to e.g. accelerations. The latter being the main issue of this numerical study. Although differently shear forces have, in vitro, an impact on both attached and free-floating cells. They may even have a significant effect in animal centrifuge studies.
We calculated that for some experiment set-ups in the past as well as for some future ISS facilities the level of shear force in on-board centrifuges could be as much as 95% of the total force. Some of the differences reported between ground 1g and in-flight 1g centrifuge could have been caused by this phenomenon.
The inertial shear force artefact should be dealt with for future missions and hardware designs as well as for the interpretation of previous data.
This work is supported by SRON and the NIVR combined grant # MG-051

• Veldhuijzen, J.P., Blieck-Hogervorst, J.M.A. de, Loon, J.J.W.A. van: "Effectiveness of the random positioning machine (RPM) to provide simulated microgravity for cultured fetal mouse long bones", ELGRA-News 22, 96-97, Proceedings of the Biennal meeting, Banyuls sur Mer, France, 25-28 September 2001.

Abstract:
Having the possibility to perform experiments in the laboratory under simulated microgravity conditions would be a great advantage in microgravity research. Recently a Random Positioning Machine has been developed (Fokker Space, The Netherlands) which should offer simulated microgravity conditions. Previous experiments with cultured fetal mouse long bones under space flight conditions (IML-1, IML2 and BION-10) revealed that 4 days of real microgravity did not change overall growth but reduced the mineralization of the diaphysis. Effectiveness of the RPM to duplicate the results of our flight experiments was tested in 4-day cultures of 17-day old fetal mouse long bones in real flight hardware. The long bones were individually cultured in double-layered culture bags with 0.7 ml medium (alfa-MEM including 5% FCS and 2-3 mM Na-ß-glycerophosphate). Experiments were performed in Biorack type I/0 containers, each with 8 culture bags. The content of the container was flushed with air/5% CO₂ at the beginning of the experiment and, in a number of experiments, again after 2 days. Prior to the experiment and at the end, photomicrographs were taken of each individual long bone. These photographs were used for measurements to calculate the increase in overall length and length of the mineralized diaphysis.
In space flight experiments the isolated long bones are not attached inside the culture bag but in the RPM this resulted in movements of the long bones that should be avoided in true random positioning. Experiments with these "mobile" long bones did not show any difference in growth and mineralization between the RPM and control cultures. We were able to prevent these movements by immobilizing the long bones in a small piece of agarose gel. Overall growth was never changed under RPM-conditions. In most of the experiments also no differences in the mean values for mineralization on the RPM and under control conditions were found. However in the RPM-groups in many cases the standard deviation was higher then in the controls. In some experiments comparable results were found as under real microgravity conditions (decreased mineralization), whereas in another experiment the mineralization seemed to have increased on the RPM.
The inability to reproduce the results of our flight experiment on the RPM leads to the conclusion that the RPM did not provide simulated microgravity to our fetal mouse long bones. However during the introduction of the agarose-immobilized long bones into the culture bags it was in most cases impossible to avoid also the inclusion of air bubbles. These air bubbles do not affect culture conditions under real microgravity or in the controls of the RPM-experiments. In the culture bags on the RPM however, these bubbles are very motile during RPM-operation and may have mixed the medium, resulting in different culture conditions, which may have obscured possible differences between the RPM-groups and the controls. Further experiments are needed to clarify this issue.
This project was supported by the Space Research Organization of the Netherlands (SRON grant MG-045)

• Veldhuijzen, J.P., Blieck-Hogervorst, J.M.A. de, Loon, J.J.W.A. van: "Response of cultured fetal mouse long bones to random positioning", Gravitational and Space Biology Bulletin, abstract 116, p. 49, Proceedings of 17th Annual Meeting, Alexandria, Virginia, USA, 7-11 November 2001.

Abstract:
Recently a Random Positioning Machine (RPM) has been developed (Fokker Space, The Netherlands) which should provide simulated microgravity conditions. Effectiveness of the RPM to duplicate the results of our real microgravity experiments where bones showed a clear reduction in mineralization, was tested in cultures of 17-day old fetal mouse bones. The bones were cultured “free floating” in double layered polyethylene culture bags (0.7 ml medium); 8 of these bags were placed in standard flight hardware in Biorack type I containers. Containers with control cultures were placed on the non-moving frame of the RPM. Initially no effects of the RPM were found. However, the “free floating “ bones went through uncontrolled movements during RPM-operation. Immobilizing the bones in small pieces of agarose gel prevented these movements of the bones and agarose did only marginally affected growth and mineralization of these bones. Experiments with these immobili-zed bones showed that overall growth of the bones on the RPM did not change. In most experiments again no differences were found in the mineralization. However in the RPM-groups in many cases the standard deviation was higher then in the controls. In some experiments we found indeed a decrease in mineralization; in another experiment we found an increase. This leads to the conclusion that the RPM did not provide simulated microgravity to the cultured long bones. However in the culture bags always air bubbles were present. Under real microgravity these bubbles do not move and do not affect the culture but on the RPM these bubbles revealed to be very mobile. This will have changed culture conditions on the RPM, which could have obscured possible effect of the RPM. Further experiments are needed to clarify this issue. (Supported by the Space Organization of the Netherlands (SRON): MG-045/3).

• Vreeburg J. P.B. MEASUREMENT OF INERTIAL PROPERTIES OF FREE-FLOATING BODIES ON ISS. National Aerospace Laboratory, Space Department, PB 90502, NL-1006 BM Amsterdam, The Netherlands. ELGRA-News 22, 96-97, Proceedings of the Biennal meeting, Banyuls sur Mer, France, 25-28 September 2001.

Abstract:
A body is characterized by ten inertial properties, namely mass (1), center of mass location (3) and inertia tensor (6). The mass property, or weight on earth, is a useful measurement data with many applications. The remaining properties depend on the mass distribution, including shape, and measurement data can be used to diagnose such distribution. A relevant application would be the determination of liquid shift in an astronaut. A necessary condition is to take the data in a reference posture in order to determine the difference measurement.
Instruments to measure mass and scales are available in great variety. For the other inertial properties, only few designs exist and the market is small. Space vehicles customarily have the center of mass and inertia tensor determined because these properties are necessary input for attitude control systems. Need for data exists also in the biodynamics field.
Knowledge of the motion of a free-floating body can be processed in order to determine its inertial properties. The appropriate equations will be discussed, and various options for the construction of a viable instrument will be assessed. Applicable sensors are accelerometers and gyroscopes. Results of simulations will be given to illustrate the achievable accuracies.

2000

• Bravenboer N., H. de Jong, R. Wubbels, AM. Tromp, HW. van Essen, JWA. van Loon, A. van Lingen, P. Lips. Hypergravity modulates body composition. 22^nd Annual Meeting of the American Sociaty for Bone and Mineral Research (ASBMR). Toronto, Ontario, Canada, Sept. 22-26 2000. Abstract SA086 page S249 (See also 'Posters' for more info)

Abstract:
Introduction: Subjecting animals to sustained acceleration in a centrifuge, leading to an increased gravity force (hypergravity or HG) results in changes of various parts of the organism. HG decreases body weight on the long term while food intake is only decreased in the first few days of the HG condition. Anatomical examination of HG animals showed a pronounced decrease in body fat, particularly in the abdominal fat depots and the lipid content of internal organs. Concerning bone mass the literature is equivocal. Some studies show longer femur length. In other studies femur length is shorter, indicating that hypergravity inhibits the longitudinal growth. Some studies showed a higher density resulting in a better capability to withstand mechanical stress. The aim of this study was to study the body composition by dual x-ray absorptiometry ( DXA) after long-term acceleration in a centrifuge, inducing HG conditions. Methods: 28 Long Evans rats with an average of 9.9 months centrifugation at 2.5 G. All animals were sacrificed and frozen at -20 until scanning. Bone mineral content (BMC), and bone mineral density (BMD), lean body mass (LBM) and Fat mass was determined at room temperature by DXA (Hologic QDR 2000). The Mann Whitney signed rank test was used to test for differences between HG and control conditions for males and females separately. Results: Body weight was 441.3 ± 31.9g in HG males and 551.5 ± 28.0g in control males (p< 0.002) In females body weight was not significantly lower (4%). In males LBM was 12 % lower (371.5 ± 20.4g v.s. 420.9 ± 13.5g, p< 0.004). BMC was 20.8 % lower in male rats (9.9 ± 0.9g v.s. 12.5 ± 0.7g, p< 0.002), but when BMD was calculated, this difference disappeared. Fat mass measured in grams was 54% lower in males (42.5 ± 9.7g v.s. 91.8 ± 14.4g, p< 0.002) and 46% in females (18.3 ± 5.1 v.s. 33.9 ± 6.4, p<0.0004) and as percentage of body weight it was 43% (p<0.002) lower in males and females respectively. Discussion: In male rats long-term HG conditions decreased the body weight, this was reflected in all the body compartments: bone mass, lean body mass and fat mass. When bone mass is corrected for size, as in BMD no differences could be observed. In female rats HG conditions only induced a decreased fat mass.

• Jack J.W.A. van Loon, Erik Folgering, J. Paul Veldhuijzen, Carlijn V.C. Bouten. Shear forces and the proper control. Combined ASGSB / CSA / ELGRA Annual meeting. Montreal, Canada, 25-28 October 2000.

Abstract:
To draw any conclusions from microgravity, experiments it is important to have a proper control. To define the this we have to understand the artifacts involved in such studies. Based on Einstein's equivalent principal, a 1×g control can either be a sample that remains on Earth or that is put into an on-board centrifuge. It was with facilities like Biorack that one could use an on-board 1×g control. One of the never addressed differences between ground 1g and in-flight 1g is the shear force generated in on-board centrifuges while this shear force might be one of the main artifacts in spaceflight and on-ground studies involving centrifuges. Shear forces are generated in two ways. Static shear and fluid shear. Fluid shear is best known from the circulatory system where the endothelium is exposed blood flows. Static shear forces are generated in materials exposed to e.g. accelerations. The latter being the main issue of this numerical study. Although differently shear forces have, in vitro, an impact on both attached and free-floating cells. They may even have a significant effect in animal centrifuge studies. We calculated that for some experiment set-ups in the past as well as for some future ISS facilities the level of shear force in on-board centrifuges could be as much as 95% of the total force. Some of the differences reported between ground 1×g and in-flight 1×g centrifuge could have been caused by this phenomenon. The artifact should be dealt with for future missions and hardware designs as well as for the interpretation of previous data. Supported by SRON and the NIVR combined grant # MG-051

• F.A. Van Nieuwenhoven, V.V. Heijnen, H.A. De Jong and L.H. SnoeckxChronic hypergrvaity increases the HSP70 content in skeletal muscles of rats. Experimental Biology, San Diego, 15-18 april 2000, Faseb J. vol 14 nr 4 (2000) pag A622

Abstract:
Environmental stresses cause tissues to enhance the transcription of a special set of genes, leading to increased levels of so-called heat shock proteins (HSPs). Increased tissue levels of HSPs can protect them against a subsequent stressful event. One of the strongest induced HSPs in mammalian tissues is HSP70. Since it is essentially unknown whether chronic hypergravity (HG) exerts stress upon tissues, the HSP70 synthesis was studied in several tissues of adult HG-rats. Three male Long Evans rats were conceived, born and raised in a large radius centrifuge under 2.5 times g force, while three age-matched controls were kept under 1 times g force. At the age of 7 months the rats were sacrificed and the following tissues harvested: heart, brain, lung, liver, kidney, testes, and the soleus and gastrocnemius muscle. After SDS-PAGE and Western blotting, HSP70 was identified using a specific polyclonal AB and quantified using chemiluminescence. In all examined tissues of control rats, basal HSP70 levels could be detected, indicating that this protein is constitutively present in various body tissues. None of the investigated HG-tissues showed elevated HSP70 levels, except for the soleus and gastrocnemius muscles. In these tissues the HSP70 content was significantly higher than in the controls. Thus, chronic hypergravity in rats leads to enhanced HSP70 levels in skeletal muscles. At present, the function of this phenomenon remains elusive. This research project was facilitated by the Dutch Experiment Support Center (DESC).

• E. Tanck, G.H. Van Lenthe, R.J. Wubbels, T. Hara, R. Huiskes. Trabecular bone architecture in the rat, normally and after long-term exposure to 2.5g. 10^th European Research Society Meeting in Wiesbaden, 2000. Oral presentation Session name: Bone-Osteogenesis and tissue engineering.

Abstract:
Mechanical loading is important for the maintenance of the skeleton. In this study we addressed the following question. What is the influence of long-term exposure to 2.5 g on bone architecture in male rats? We expect that bone density will increase. For the experiments we used a total of 14 Long Evans rats. Two experiments were performed in which the rats were exposed to 2.5 g for a period between 33 and 44 weeks. In the first experiment we analyzed the 3D trabecular structure in the femoral head, and in the second one the structure in the proximal tibia (metaphysis) was analyzed using micro-computer-tomography. Rats exposed to 2.5 g had between 6% and 29% less total body weight than controls. Changes in anisotropy, which is a measure for trabecular alignment, were negligible. In the femoral head, the bone volume fraction (BV/TV) was similar for rats exposed to 2.5 g and controls. The diameters of the femoral head and neck in rats exposed to hypergravity were smaller than in controls, but not significantly. In the tibia, the BV/TV was lower for rats exposed to 2.5 g than for control rats (p<0.05), whereas the size of the tibial plateau was larger in the exposed rats (p<0.05). These preliminary results were in contrast to our expectation. When exposed to 2.5 g, the trabecular architecture in the femoral head hardly changed, and in the tibia the BV/TV decreased. The tibial plateau was however larger. Adaptation to hypergravity conditions might be more at the global, cortical level than at the trabecular level. Alternatively, it is possible that the activity of rats exposed to hypergravity was less compared to controls. This would result in decreased dynamic stimulation of the bone so that the BV/TV still may satisfy the mechanical demands of rats exposed to hypergravity. Download one page abstract.

1999

Several abstracts are available from the 2nd 'NL-Gravity Symposium which was held on Friday 10th of December at the Free University in Amsterdam. See index on the left hand site for the 1998 and 1999 program or go directly to the 1999 abstracts.

• Boonstra J. Growth Factor-Induced Signal Transduction in Mammalian Cells is Sensitive to Gravity. In: Cells in Spaceflight: Past, Present & Future. Center for Advanced Studies in the Space Life Sciences, Marine Biological Laboratory, Woods Hole, MA. March 6 - 9, 1999.

Abstract:
Polypeptide growth factors, amongst them epidermal growth factor (EGF), have been demonstrated to play an essential role in the regulation of mammalian cell proliferation and differentiation. These growth factors activate well-characterised signal transduction cascades, and this activation leads usually 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 has been investigated in A431 epithelial cells using sounding rockets to perform microgravity conditions. EGF-activated signal transduction in A431 cells results within five minutes in the rapid induction of the proto-oncogenes c-fos and c-jun. Experiments performed during sounding rocket flights demonstrated clearly the EGF-induced expression of c-fos and c-jun decreased under microgravity conditions. 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, indicating that the observed effects are due to a gravity-sensitive cellular component.. Since 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. Preliminary experiments indeed suggest that the actin microfilament system is modulated under microgravity conditions. Furthermore we have demonstrated that the actin microfilament system plays a prominent role in protein kinase C-mediated feed-back regulation of EGF-induced signal transduction. In combination, we suggest that the effects of microgravity on EGF-induced signal transduction are due to modulations in actin-mediated regul;ation of protein kinase C activity.

• Greenberg, J.M., Schutte, W.A., Li, A.: "Space irradiation at cryogenic temperatures", Proc. 2nd European symp. on the Utilisation of the International Space Station, ESTEC, Noordwijk, 16-18 Nov. 1998. ESA SP-433, 517-519, 1999.

• Hosman, Ruud J.A.W.; Kunen, Robert C. A.M.S. Consult, Delft, Netherlands. Flight director guidance throughout the parabolic maneuver. Proceedings of the IEEE International Conference on Systems, 'Human Communication and Cybernetics'; Oct 12-Oct 15 1999; Tokyo, Japan; Man and Cybernetics, Volume 5, Pages V-1076 - V-1081, 1999.

Abstract
The high precision required to maintain constant accelerations during the parabolic micro-gravity condition makes the pilot's control task difficult: The optimization of the duration requires an accurate entry into the parabola at the right moment, while the aircraft limitations may not be exceeded. To resolve this problem, flight director control laws incorporating a gain scheduler, a predictor, and a sequencer have been developed to improve the quality and duration of the parabolic maneuver and to increase the safety by monitoring the progress of the maneuver. A flight simulation program was then used to evaluate the flight director system in a fixed-based simulation, and to train the test pilot. Finally the flight director was evaluated during flight tests with the laboratory aircraft. A considerable improvement to maintaining the precision of micro-gravity conditions was obtained. The development and design of the flight director system, as well as its experimental evaluation, are discussed in the paper. [Author abstract; 2 Refs; In English] Conference Information: 1999 IEEE International Conference on Systems, Man, and Cybernetics 'Human Communication and Cybernetics'; Oct 12-Oct 15 1999; Tokyo, Japan; Sponsored by IEEE (SMC); SCJ; SICE; RSJ; JSME

• Kingma, I. , Toussaint, H.M., Commissaris, D.A.C.M. , Savelsbergh, G.J.P. and Dieën, J.H. van (1999) Motor control during lifting under microgravity conditions. International Society of Biomechanics, XVIIth Congress, Calgery, Canada.

• Kramer, B.M.R., Jenks, B.G., Roubos, E.W.: "Effects of microgravity in space on brain development of Xenopus laevis", 7th European Symposium on Life Sciences Research in Space, Maastricht, May 30-June 2, 1999.

• van Loon J.J.W.A, Mastenbroek O., Lemcke C. The Biopack Facility. 'Life Odyssey' 7th European Symposium on Life Sciences Research in Space, 29 May to 2 June 1999. Maastricht, The Netherlands. ESA-SRON publication. (download full text PDF file, 185 kB)

Introduction:
The coming years for microgravity research will be dominated by the assembly of the International Space Station (ISS). During these assembly flights of the US Space Shuttle, Russian launchers and at a later stage the European Ariane, only limited flight opportunities are available for microgravity researchers, especially biologists. Therefore there is a need for small sophisticated payloads, requiring limited resources, that provide scientists with experiment platforms to conduct science during the ISS assembly phase. Space Shuttle Middeck Locker-based payloads are the most suitable in this respect. The Biopack is such a locker-based facility that builds on already existing experiment hardware and facility infrastructure. The Biopack provides scientists with a research facility for biological experiments under varying gravity conditions. Although the Biopack builds on ESA's very successful facilities Biorack (flown already three times in Spacelab and three times in Spacehab) and Biobox (flown three times in the Russian retrievable capsules and once in Spacehab), its design and operations scheme overcomes some of the disadvantages of the previous facilities. Biopack is aiming for flights in the Space Shuttle middeck, in Spacehab, and at the long-term in the European Drawer Rack (EDR) in COF, the Columbus Orbiting Facility.

• van Loon J..J.W.A, van Hulst N.F. Atomic Force Microscopy as Tool in Cell Biological research for Ground Based and In-Flight Studies. 'Life Odyssey' 7th European Symposium on Life Sciences Research in Space, 29 May to 2 June 1999. Maastricht, The Netherlands. ESA-SRON publication (PDF file, 705 kB)

Introduction:
From previous investigations it has become clear that cells behave differently under conditions of hypergravity (centrifuges), simulated hypogravity (clinostats, Random Positioning Machine, Free Fall Machine)(1) and spaceflight compared to their appropriate 1×g controls. Changes in gene expression, signal transduction, energy consumption or general cell differentiation are measured using (bio-) chemical assays. Morphological or (bio-) mechanical changes in cells such as general cell shape, intracellular architecture (cytoskeleton, location / shape of cell organelles), cell-cell interactions, or cell motility require imaging techniques such as light microscopic or transmission electron microscopy (TEM). Since gravity acts on mass, it might be expected that changes in cells due to (micro-) gravity are due to intracellular mass displacements and / or changes in general cell shape. Both processes involve the cytoskeleton and this might be a focal point for future gravity studies both on ground as well as for the international space station. For light microscopic observations the more advanced Confocal Laser Scanning Microscope (CLSM) has been used to study intracellular static or dynamic processes. Most of these studies still require some way of chemical fixation. For the CLSM a sample has to be stained with a fluorescent probe and may then be studied in a three-dimensional way by reconstructing a series of optical sections. In recent years the Atomic Force Microscope (AFM) has become available to study biological samples. Although both systems have their particularities, the AFM has some advantages over a CLSM. The AFM is a very compact system and provides high spatial resolutions as well as the possibility to visualize living cells in vitro.

• van Loon J.J.W.A.¹, J.P. Veldhuijzen², J. Kiss³, C. Wood³, H. vd Ende⁴, A. Guntemann⁵, D. Jones⁵, H. de Jong⁶, R. Wubbels⁶. Microgravity research starts on the ground ! Apparatusses for long term ground based hypo- and hypergravity studies. Proceedings of the 2nd European Symposium on the Utilisation of the International Space Station, ESTEC, Noordwijk, The Netherlands. 16-18 November 1998. ESA SP-433, Edt. A. Wilson, ESTEC Noordwijk, The Netherlands, page 415-419, February 1999. (PDF file, 91kB)

Abstract:
In the last decades many experiments using different biological systems are performed during space flight to study the effects of microgravity and to find the cellular mechanisms leading to the various biological responses. Unfortunately many experiments could not be repeated due to limited flight opportunities and associated high costs for actual space experiments. Prior to the utilization the International Space Station (ISS), flight opportunities for biological experiments will become even almost extinct. Therefore the development and utilization of cheap and readily available ground based experiment tools for simulated (or real) microgravity and hypergravity (centrifuges) will be necessary to keep microgravity research productive and attractive. Recently a new Random Positioning Machine (RPM), which provides for a 3D volume of simulated microgravity for experiments with small plants and isolated cells and tissues, became available. The temperature and gas phase (air/CO2) in the RPM can be controlled; video observations during the experiment are possible. Preliminary experiments with developing Arabidopsis on the RPM showed comparable effects as during a recent Space Shuttle flight (Kiss & Wood, USA). Verification experiments with isolated fetal mice long bones to study bone mineralization and demineralization (previously also performed during Space Shuttle and BION flights) are just started (Veldhuijzen, The Netherlands). In the future the software of the RPM will be prepared to allow threshold studies between µg and 1xg. The Free Fall Machine (FFM), which generates short but constantly repeated periods of real microgravity, is in use for some time already. The latest version of the FFM has its own dedicated 1xg control. Experiments with Chlamydomonas showed comparable results in cell cycle changes and cell morphology as found during two Russian BION missions (vd Ende, The Nether-lands). To broaden the scope for acceleration studies, a small Tissue Culture Centrifuge (Midi-CAR) is available which can generate static and dynamic accelerations up to 100xg. It allows the use of standard tissue culture plates (multiwells) as well as standard flight hardware (like Biorack type I/O & I/E containers) under various temperature conditions. Recently the Midi-CAR was successfully used to study launch effects (g-profiles) on cultures of bone forming osteoblasts in preparation for a Texus sounding rocket flight (Guntemann, Germany). Finally, a Large Radius Centrifuge may be used to study the long-term effects of hypergravity on e.g. small animals like rodents or fish. The use of ground based microgravity simulators as well as the extention of the acceleration gamma from hypogravity to hypergravity, will greatly attribute to the growing understanding of the effects of weight on living systems and the mechanisms involved. More detailed hypotheses on the effects of microgravity may be generated using ground based facilities. However, these hypotheses have to be verified under real microgravity conditions.
¹Dutch Experiment Support Center (DESC) & ²Dept. Oral Biology, ACTA / Vrije Universiteit, Amsterdam, The Netherlands ³Dept. Botany, Miami Univ. Oxford, OH, USA, ⁴Dept. Moleclar Plant Physiology, Univ. of Amsterdam, ⁵Dept. Exp. Orthopedics & Biome-chanics, Phillipps University, Marburg, Germany. ⁶Vestibular Dept. of the Academic Medical Center (AMC), Amsterdam, The Netherlands.

• Wubbels R. J., H. A. A. de Jong, H. W. Kortschot and W. J. Oosterveld. No Gravity, No Balance. Parabolic Flights, 4th International Symposium, June 14th-15th 1999, Salon International de l'aeronautique et de l'espace, Paris - Le Bourget - France, p 16-17.

Abstract:
During the hundreds of millions of years in which life evolved on our planet, the circumstances have often changed. Transformations happened either all of a sudden or very gradually. Whatever the time scale, some changes had very dramatic effects on the life forms on earth. Photosynthesis of green plants increased the oxygen concentration in the atmosphere. Erosion made the oceans more saline. Global climate changes and tectonic activity in the earth’s crust had an impact on temperature, humidity, seasonal variability and gulf streams. A collision with a meteoroid wiped out an unknown number of species. Etcetera. Because the local circumstances vary we see a diversity of anatomical and physiological adaptations. Among all the physical constraints with which animals (and plants) had to cope, however, one has remained constant all the time: the earth’s gravitational field.
When man decided to leave the earth, it turned out that weightlessness can have serious physiological consequences for the crew and also for animals on a space flight mission. Difficulties may occur with the cardiovascular, renal or neurological system or with blood chemistry or the psychological condition. Locomotion becomes unpredictable because motor control has not been adjusted to this situation, and the vestibular system is deprived of its usual input (the gravitational force). This is thought to be the cause of motion sickness from which more than 30% of the crew of space flight missions suffer. However, the exact relationship between the absence of gravity and motion sickness is still not understood. (full paper)

• Wubbels R.J. and H. A. A. de Jong. Vestibular induced behaviour of rats born and raised under hypergravity conditions. 'Life Odyssey' 7th European Symposium on Life Sciences Research in Space, 29 May to 2 June 1999. Maastricht, The Netherlands. ESA-SRON publication

Introduction:
A gravity level change from 1 G to prolonged weightlessness or from prolonged hypergravity (HG) to normal gravity (NG) can cause symptoms of motion sickness.1,2 Therefore, it is thought that ground-based experiments, in which humans or animals are exposed to sustained HG conditions, can bring about symptoms of the Space Adaptation Syndrome.1 It has been shown that vestibular induced behaviour of hamsters born and raised at 2.5 G is less appropriate than that of control animals.3 In the present study, rats are bred in a centrifuge in order to investigate how the vestibular system is affected by long-term HG conditions. Two types of vestibular induced behaviour are studied, i.e. the airrighting reflex (turning from a supine to prone position during fall) and the reappearance at the water surface after a fall. Both types of behaviour require orientation relative to the direction of gravity. And the question is whether this behaviour at 1 G is affected by the ontogenetic development of the vestibular system under HG conditions. (full paper)

1998

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

• J.P. Veldhuijzen¹, J.J.W.A. van Loon², J. Kiss³, C. Wood³, H.vd Ende⁴, A. Guntermann⁵. Ground based facilities for long term microgravity research. AGSGB annual meeting, 28-31 October 1998. Houston, TX, USA.

Abstract:
In the last decades many experiments using different biological systems were performed to study effects of microgravity and find the cellular mechanisms leading to the biological response. Un-fortunately many experiments could not be repeated due to lim-ited flight opportunities and associated high costs for the actual space experiment. Also in view of reduced flight opportunities prior to the ISS-utilization, the development and utilization of cheap and readily to use ground based experiment tools for simulated (or real) microgravity and hypergravity will be neces-sary. Recently a new Random Positioning Machine (RPM), which generates simulated microgravity, became available. Preliminary experiments with developing Arabidopsis showed comparable effects as under space flight conditions (3). Experiments with isolated fetal mouse long bones are just started (1). In the future the RPM will be prepared for threshold studies between µg and 1xg. The Free Fall Machine (FFM), which generates short but constantly repeated periods of real microgravity, is in use for some time already. Experiments with Chlamydomonas showed comparable results in cell cycle changes and cell morphology as found during BION-missions (4). To broaden the scope for accel-eration studies a Tissue Culture Centrifuge (Midi-CAR) is avail-able which can generate accelerations up to 100xg and allows culture in tissue culture plates and standard flight HW. The cen-trifuge was successfully used to study launch effects (TEXUS g-profiles) on cultures of bone forming osteoblasts (5). These ground based facilities may help efficiently to clarify the cellular mechanisms leading to the biological response to microgravity.
¹Dept. Oral Bio- logy & ²Dutch Experiment Support Center (DESC), ACTA / Vrije Univ., Amsterdam, The Netherlands; ³Dept. Botany, Miami Univ., Oxford OH, USA; ⁴Dept. Molec. Plant Physiology. Univ. of Amsterdam, Amsterdam,The Netherlands; ⁵Dept. Exp. Orthop.& Biomechan., Phillipps Univ., Marburg, Germany.

• Geim A.K. , H.A. Carmona, J.C. Maan and P.C. Main. Molecular Magnetism and Levitation in: Proceedings of European Low Gravity Association (ELGRA) Biannual Meeting, ed., p. 378, 1997.

1996

• Demaria-Pesce V; Visser GH; Daan S. Measurement of human energy metabolism in spaceflight. In: Kaldeich-Schurmann B, comp. Sixth European Symposium on Life Sciences Research in Space. Noordwijk, The Netherlands : ESA Publ. Div., 1996. :p. 375-7. (European Space Agency SP ; 390). European Symposium on Life Sciences Research in Space (6th : 1996 Jun 16-20 : Trondheim, Norway).

Abstract:
There are very few fragmentary records of energy utilization in spaceflight, and interpretation of results is difficult because discrepancies of data of different missions. This study was aimed to evaluate the average level of Daily Energy Expenditure (DEE) in man during prolonged spaceflight using the doubly labeled water (DLW) method. DLW (2H2 18O) was orally administered to two crew members of the Euromir '94 mission. A saliva sample was taken every other day during a 30-day flight. Water efflux rate was, for the first subject, low in the first four days of the flight reaching the preflight values by the flight day eight. The second subject had a very high water efflux during the first four days of flight to later decreased to the preflight values. For the two subjects, DEE levels in space were consistently 8-21% lower than their levels observed during ground experiments. We conclude that reduced DEE in space may result from the effect of microgravity itself as well as the influence of the space station environment on the energy metabolism.

• Veldhuijzen, J.P.: "Isolated skeletal tissues cultured under microgravity., "Proc. of COSPAR 31th Scientific Assembly, July 14-18, 1996, Birmingham, England. F1.2-0003, 1996.

1995

• de Graaf B., Bles W., Bos J.E., Groen E. Otolith function under hypo- and hypergravity conditions. Workshop Proc. Experiment results of the ESA and CNES parabolic flights campaigns. Tenth aniversary of the first ESA parabolic flight campaign. Toulouse (F) 28-29 Nov. 1994. ESA WPP-90 CNES ED/MV-95-039. Febr. 1995.

• Mazičre, A. de, et al.: "Early cleavage of Xenopus laevis is perturbed in microgravity", Proceedings European Developmental Biology Congress, Toulouse, France, 9-13 July 1995, p. 62, 1995.

• Montufar-Solis D; Duke PJ; Veldhuijzen JP. Ultrastructure of chondrocytes of fetal metatarsals flown on IML-2, a preliminary report. ASGSB Bull. 1995 Oct;9(1):89.

Abstract:
Development of mammalian long bones occurs through the process of endochondral ossification, which has been shown to be altered in growth plates of young adult rats exposed to microgravity. Developing mouse metatarsals flown on IML-1 had decreased calcification and increased osteoclastic resorption. Since the experiment (BONES) used cartilaginous anlage undergoing endochondral ossification, the results could reflect changes in cartilage differentiation and/or the production or aggregation of cartilage matrix molecules. The BONES experiment was reflown on IML-2 using ED17 cultured fetal metatarsals which were fixed in space after 4 days of microgravity exposure, stored at 5 degrees C, decalcified, and prepared for electron microscopy. Cells showed good fixation as evidenced by membrane and mitochondrial preservation, and had the high nuclear/cytoplasmic ratio typical of chondrocytes. Intracellularly, numerous mitochondria were associated with the RER which usually consisted of greatly expanded cisternae. Large vacuolar areas within the cells may represent extracted vesicles, and some inclusions (possibly lipids) are also present. The ECM/cell ratio was higher in early stages of differentiation, where cells within lacunae showed less of the typical shrinkage associated with fixation. Cell division was observed in both horizontal and vertical axes throughout the developing metatarsal, and less organized fibrils were apparent in the more actively proliferating areas. Numerous vesicles were observed in the ECM which is much less organized--having smaller fibrils with less orientation--than in adult growth plates previously studied. No ultrastructural differences were observed between these metatarsals and 1g ground controls, but comparisons with 1g inflight controls and studies of matrix morphology are not complete.

• Veldhuijzen JP; van Loon JJ; Haaijman A; Semeins CM; Bervoets TJ. Short-term exposure to 1-g conditions counteracts micro-g effects on mineralization in isolated fetal mouse long bones. ASGSB Bull. 1995 Oct;9(1):89.

Abstract:
Previous experiments with isolated fetal mouse long bones have shown that microgravity significantly reduced mineralization, increased mineral resorption while no effect was found on growth. The present experiment, which was performed during the IML-2 mission of the Space Shuttle (STS-65), was designed to verify previous finding and to study the existence of a minimal 1-g exposure period which could prevent the micro-g related reduction in mineralization. Mouse metatarsal long bones with a mineralized diaphysis (17-day old embryos) were cultured (alfa-MEM, 0.2% BSA, 2mM Na-beta-glycerophosphate) during 4 days. One group was exposed continuously to micro-g. The flight control was placed continuously on the 1-g centrifuge. Three groups were exposed daily to micro-g for 21,18 and 12 hours, the remaining daily period these groups were placed on the on-board reference 1-g centrifuge (3, 6 and 12 hours). Samples were fixed and stored at 4 degrees C for further histological evaluation. Before and after the experiment photomicrographs were made from each long bone individually to determine overall length and i the length of the mineralized diaphysis. No differences were found in the percentage overall length increase. Mineralization was significantly reduced under micro-g compared to both flight and ground control. A daily 12 hr exposure to 1-g completely counteracted the micro-g induced reduction in mineralization. In contrast, 3 and 6 hr exposure to 1-g was not effective. These data confirm results of previous microgravity experiments. It is suggested that there is at least a 12 hr memory period for loading dependent in vitro mineralization.

• Veldhuijzen, J.P., Loon, J.J.W.A. van, Haaijman, A., Semeins, C.M., Bervoets, T.J.M.: "Reduced mineralization under microgravity is counteracted by short term exposure to 1xg conditions.", Calcif. Tissue Int. 56: 458, 1995.

1994

• Veldhuijzen, J.P., Loon, J.J.W.A. van,: "Microgravity decreases mineralization and increases mineral resorption in cultured embryonic mouse long bones.", 10th Annual meeting of the American Society for Gravitational and Space Biology, October 19 -23 1994, San Francisco, CA, USA, ASBSG Bulletin 8(1): 51, 1994.

1993

• Burger, E.H., Klein Nulend, J., Veldhuijzen, J.P., Loon, J.J.W.A. van, Huiskes, R., Goldstein, S., Jepsen, K.: "The effect of mechanical forces on bone development.", Proc. Experimental Biology, Canterbury, England, March 29 - April 2 1993, C1.12, 78, 1993.

• Loon, J.J.W.A., Berg, L.C. van den, Schelling, R., Veldhuijzen, J.P., Huijzer, R.H.: "Development of a centrifuge for acceleration research in cell and development biology." IAF/IAA-93-G.4.166, 1993.

• Veldhuijzen, J.P., Loon, J.J.W.A van.: "Mineral metabolism in isolated mouse long bones: opposite effects of microgravity on mineralization and resorption.: "Proc. of the 5th European Symposium on Life Sciences Research in Space. Arcachon, France, September 26 - October 1 1993, ESA SP-366, 19-24, 1993.

• Veldhuijzen, J.P., Loon, J.J.W.A. van, Burger, E.H.: "Microgravity changes matrix mineralization and mineral resorption in cultured fetal mouse long bones".", Calcif. Tissue Int., 52 (suppl. 1):S54, 1993.

1992

• Veldhuijzen, J.P., Loon, J.J.W.A. van: "Microgravity effects on cultured mouse long bone rudiments: bone cell differentiation and functioning.", Proc. of COSPAR 29th Scientific Assembly, Washington DC, USA, August 28 - September 5, 1992, F1.1-S.6.11, 534, 1992.

• Veldhuijzen, J.P., Loon, J.J.W.A., Hagen, J.W., Dieudonné, Bervoets, T.J.M., Semeins, C.M., Zandieh-Doulabi, B., Burger, E.H.: "Cellular responses in cultured fetal mouse long bones to microgravity: preliminary results of the IML-1 mission.", Proc. 5th International Congress on Cell Biology, July 26-31, 1992, Madrid, Spain, P-16.6, 316, 478, 1992.

1990

• Groot, R.P. de, Rijken, P.J., Hertog, J. den, Boonstra, J., Verkleij, A.J., Laat, S.W. de, Kruijer, W.: "Epidermal growth factor induced signal transduction in A431 cells is influenced by altered gravity conditions", in: Proceedings of the 4th European Symposium on Life Science Research in Space, Trieste, Italy, May 28- June 1 1990, ESA SP-307, 243-248, 1990.

• Tomson A; Demets R; van den Briel W; van den Ende H. Unicellular algae in space. I. Preparatory tests. In: David V, ed. Fourth European Symposium on Life Sciences Research in Space. Noordwijk, The Netherlands : ESA Publ. Div., 1990. :p. 329-37. (European Space Agency SP ; 307). European Symposium on Life Sciences Research in Space (4th : 1990 May 28-Jun 1 : Trieste, Italy).

Abstract:
To investigate the mating process of the unicellular green alga Chlamydomonas in a sounding rocket, new instrumentation was developed: the flexible tube-unit, including a miniature illumination device. For gravity-independent performance of the tube-unit it was necessary to equalize the buoyant density of all liquids used. Special attention had to be paid to the set-up of the 1g-control, because mating algae tend to sink down at 1g which appeared to affect the rate of the mating process. Further research was aimed at obtaining a proper launch window. Also launch simulation tests (vibration, acceleration) were performed.

• Ubbels GA; Berendsen W; Kerkvliet S; Narraway J. Fertilization of Xenopus eggs in space. In: David V, ed. Fourth European Symposium on Life Sciences Research in Space. Noordwijk, The Netherlands : ESA Publ. Div., 1990. :p. 249-54. (European Space Agency SP ; 307) European Symposium on Life Sciences Research in Space (4th : 1990 May 28-Jun 1 : Trieste, Italy).

Abstract:
Egg rotation and centrifugation experiments strongly suggest that gravity functions 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 became larvae, but these developed similarly abnormal. In the future, we intend to test whether this is due to reentry perturbations, a real microgravity effect, or due to other causes.

• van Loon JJ; Veldhuijzen JP; Burger EH. Hypergravity and bone mineralization. In: David V, ed. Fourth European Symposium on Life Sciences Research in Space. Noordwijk, The Netherlands : ESA Publ. Div., 1990. :p. 393-6. (European Space Agency SP ; 307). European Symposium on Life Sciences Research in Space (4th : 1990 May 28-Jun 1 : Trieste, Italy)

Abstract:
16 Days old fetal mouse long bone rudiments were cultured under hypergravity conditions (1.0, 2.2, 2.5, and 3.1x gravity) to study growth and mineralization of the tissue. Longitudinal growth of the rudiments proceeded normally during the four days culture period. At the same time calcification of the growth plate cartilage and bone determined by the length of the diaphyses and radioactive calcium incorporation was strongly increased, by 87% and 620%, respectively. This in vitro model allows the study of fetal bone growth, mineralization and metabolism under increased acceleration conditions.

1988

• de Jong HA, Goossens HP, Oosterveld WJ. Eye movements induced by calorization of the vertical semicircular canals. A study in pigeon. Adv Otorhinolaryngol. 1988;42:36-8. No abstract available.

• Wit HP, Segenhout JM. Caloric stimulation of the vestibular system of the pigeon under minimal influence of gravity. Acta Otolaryngol. 1988 Mar-Apr;105(3-4):338-42.

Abstract:
Vestibular microphonics in response to acoustical stimulation were recorded in cochlea-deprived pigeons. Endolymph flow in the semicircular canals alters this response. A caloric stimulus was applied to the horizontal canal or the posterior vertical canal close to the ampulla. To minimize the influence of gravity, the canal being studied was positioned in the horizontal plane. Local temperature changes were generated with an electrically heated miniature copper probe, producing an approximately trapezoidal temperature profile. Because of the opposite hair cell polarization in the horizontal and the vertical ampulla, we could prove that the observed effects were of (hydro-)mechanical origin and were not caused by a direct effect of sensory epithelium temperature change. The first effect of temperature increase was an utriculopetal endolymph flow, as predicted by the 'expansion theory'.

1987

• Veldhuijzen, J.P., Klein Nulend J., Burger, E.H.: "An in vitro model system to study the effect of microgravity and loading conditions on the mineralization and resorption of skeletel tissues.", Proc. Of the 3th European Symposium on Life Sciences Research in Space, Graz, Austria, September 14-18, 1987, ESA SP-271, 173-178,1987.

• Oosterveld WJ, de Jong HA. The effect of weightlessness on the flight behavior of pigeons with canal lesions. Aviat Space Environ Med. 1987 Sep;58(9 Pt 2):A250-2.

Abstract:
The flight behavior of birds in parabolic flight was studied. Pigeons with labyrinthine lesions were released in weightlessness. Birds with one obstructed labyrinth showed a barbecue spin rotation, with movement directed toward the obstructed labyrinth. The birds with vertical canal blocks showed rotatory movements in the plane of the blocked canals. In weightlessness, the head was in retroflexion and bent over the shoulder, on the side of the obstructed anterior canal. They made tumbling movements backwards around the Y-axis through the skull, and this resulted in a spiral flight pattern. In birds with both the labyrinths obstructed three different phases can be distinguished. The first phase, in which a barbecue spin rotation directed towards the most recently obstructed labyrinth was clear, lasted 1 week. In the second phase this spin behavior is superimposed on a forward tumbling movement: an "outside loop." In the third phase this tumbling phenomenon is the only pattern that remains. The experiments offer not only a model to use in the explanation of the causes of particular vertiginous complaints in human patients, but, furthermore, give an answer to the question of what specific illusions belong to specific vestibular end-organ lesions.