The “Frog in Space” (FRIS) experiment marked a major step for Japanese space life science, on the occasion of the first space flight of a Japanese cosmonaut. At the core of FRIS were six Japanese tree frogs, Hyla japonica, flown on Space Station Mir for 8 days in 1990. The behavior of these frogs was observed and recorded under microgravity. The frogs took up a “parachuting” posture when drifting in a free volume on Mir. When perched on surfaces, they typically sat with their heads bent backward. Such a peculiar posture, after long exposure to microgravity, is discussed in light of motion sickness in amphibians. Histological examinations and other studies were made on the specimens upon recovery. Some organs, such as the liver and the vertebra, showed changes as a result of space flight; others were unaffected. Studies that followed FRIS have been conducted to prepare for a second FRIS on the International Space Station. Interspecific diversity in the behavioral reactions of anurans to changes in acceleration is the major focus of these investigations. The ultimate goal of this research is to better understand how organisms have adapted to gravity through their evolution on earth.

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In SLJ⁄L-1 we proposed to study three major objectives. They were; 1. hormonal changes associated with fluid and electrolyte metabolism, 2. the effect of space flight on the circadian rhythms of endocrine and metabolic systems, 3. the changes in the indices of the bone and muscle metabolism during space flight. In this report, the changes in the bone metabolism during Spacelab-J will be presented with a special emphasis on urinary excretion of pyridinium cross-links. Timed urine samples from three Japanese payload specialists were obtained for 3 days from May 19 to 21, 1991 (one year before the launch = L-1 year). Immediately before the launch (L-3 to L-0), urine samples were obtained from a payload specialist who was on board the Space Shuttle Endeavor (PS). During the inflight period (flight from September 3 to 10 in 1992), urine samples from the PS were collected by using Urine Monitoring System (UMS). After the landing, they were obtained from the PS for three days (R+0 - R+2). Various parameters related to bone metabolism such as hydroxyproline, pyridinium cross-links and calcium were determined. It was noted that excretion of hydroxyproline decreased during the preflight periods when compared with that in the control L-1 year period. The average excretory rate during control period was 846.2 ±198.7 μg⁄hour (mean ± SD), while those in the preflight 474.6 ± 171.1 μg⁄hour, suggesting the diminished collagen intake during the preflight period. Average excretion rate of pyridinium cross-links during the first 4 mission days (MD0 - MD3) was similar to that of preflight and control L-1 year period. However, it was significantly increased during the last 4 mission days (MD4 - MD7). It returned to the preflight level during postflight days (R+0 - R+2). Increased urinary excretion of calcium during the last 4 mission days were also observed. These results suggest that increase in bone resorption could occur during relatively short stay in microgravity.

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: In the 8-d flight mission of Spacelab-J (STS-47) conducted in 1992, behavior of the dorsal light response (DLR) and EEG activity of the cerebellum were intermittently examined for two carp, normal and otolith-removed. The latter carp had immobilization trouble caused by twisting of the EEG cable on day 2 inflight. The problem continued for the remainder of the experiment. Analyses made on the normal carp provided additional evidence in fish for sensory-motor disorder and readjustment during early phase of microgravity, thus supporting the sensory conflict hypothesis for space motion sickness. In the present report, why and how this space experiment was conducted were reviewed with a brief summary of the results.

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Three theories have been suggested as to the cause of space motion sickness: 1)eye and vestibular sensory mismatch, 2)abnormal shift of body fluids producing increased intracranial pressure and 3)prewarning signals for unpleasant physical situations by self-produced neurotoxic substances released in the body. We are interested in the possible functional disabilities⁄incongruities of eye, head and body movements in 0-G. Space motion sickness might be explained from the viewpoint of lack of coordination of the movements of the eye and head. It is important to ascertain the significance of gravity in the maintenance of human visual stability. We will examine the coordination of Japanese Payload Specialist (JPS) eye and head movement by electrooculogram and neck muscle electromyogram recordings, as well as obtaining a subjective evaluation of visual stability from the PS during space flight. We hypothesize that 1)poor performance of the eye movement will be observed, 2)unusual neck muscle activity will be observed and 3)there will be decreased visual stability in micro gravity. We obtained all digital data and VCR taped image data in

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A space experiment involving protein crystallization was conducted in a microgravity environment using the space shuttle “Endeavour”of STS-47, on a 9-day mission from September 12th to 20th in 1992. The crystallization was carried out according to a batch method, and 5 proteins were selected as flight samples for crystallization. Two of these proteins : hen egg-white lysozyme and co-amino acid: pyruvate aminotransferase from Pseudomonas sp. F-126, were obtained as single crystals of good diffraction quality. Since 1992 we have carried out several space experiments for protein crystallization aboard space shuttles and the space station MIR. Our experimental results obtained mainly from hen egg-white lysozyme are described below, focusing on the effects of microgravity on protein crystal growth.

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To examine the possible effects of space radiation on living organisms, fruit flies Drosophila melanogaster were loaded on the US Space Shuttle Endeavour, and after the flight we have analyzed two types of mutations, sex-linked recessive lethal mutations induced in male reproductive cells and somatic mutations which give rise to morphological changes in hairs growing on the surface of wing epidermal cells. Wild type strains and a radiation-sensitive strain mei-41 were used. The frequencies of sex-linked recessive lethal mutations in flight groups were 2 and 3 times higher for wild type Canton-S and mei-41 strains, respectively, than those in ground control groups. By contrast, the frequencies of wing-hair somatic mutations differed little between flight and control groups. The possibility that the space environment causes mutations in certain types of cells such as male reproductive cells, is discussed.

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In a space experiment, the adaptation of goldfish behavior during flight and readaptation after landing were investigated. Six goldfish (1 normal, 1 with otoliths removed on both sides, 4 with otoliths removed on one side) were flown in a fish package (F⁄P) of Aquatic Animal Experiment Unit (AAEU). The dorsal light responses (DLRs) of fish with otoliths removed were recorded after operation until launch and after landing. The behaviors of the fish were recorded with a video camera on Mission Elapsed Time (MET) Day-00, 02, 05, 08, 12. On MET Day-00, two fish with otoliths removed on one side showed flexion of body toward the operated side. These fish also showed rolling behavior toward the operated side. However, the body flexion disappeared on MET Day-05 or MET Day-08. No rolling behaviors were observed after that time. Five fish showed backward looping behaviors during the mission. Although the frequency of looping episodes decreased after MET Day-08, five fish still showed looping behavior on MET Day-12, that was the last day of video recording on orbit. In microgravity, visual system of fish did not seem to provide sufficient cues to prevent them from looping or rolling. After landing, no looping and rolling behavior was observed. However, the tilt angle of the DLR increased in the fish with otolith removed 5 month before launch but not in normal fish and those with otoliths removed 2 weeks before launch. These results suggest that the behavioral dysfunction and the adaptational process in space are dependent on vestibular inputs.

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Space radiation dosimetry measurements have been made onboard the Space Shuttle STS-65 in the Second International Microgravity Laboratory (IML-2: 28.5° x 300 km: 14.68 days) and the STS-79 in the 4th Shuttle MIR mission (S⁄MM#4: 51.6° x 300-400 km: 10.2 days). In these measurements, three kinds of detectors were used; one is a newly developed active detector telescope called “Real-time Radiation Monitoring Device (RRMD-I for IML-2 and RRMD-II with improved triggering system for S⁄MM#4)“ utilizing silicon semi-conductor detectors and the other detectors are conventional passive detectors of thermoluminescence dosimeters (TLDs) and CR-39 plastic track detectors. The main contribution to dose equivalent for particles with LET > 5.0 keV⁄μm(IML-2) and LET>3.5. keV⁄μm (S⁄MM#4) is seen to be due to galactic cosmic rays (GCRs) and the contribution of the South Atlantic Anomaly (SAA) is less than 5%(IML-2: 28.5° x 300 km) and 15% (S⁄MM#4: 51.6° x 400 km) in the above RRMD LET detection conditions. For the whole LET range (> 0.2 keV⁄μm) obtained by TLDs and CR-39 in these two typical orbits (a small inclination x low altitude and a large inclination x high altitude), absorbed dose rates range from 94 to 114 μGy⁄day, dose equivalent rates from 186 to 207μSv⁄day and average quality factors from 1.82 to 2.00 depending on the locations and directions of detectors inside the Spacelab at the highly protected IML-2 orbit (28.5°x 300 km) , and also, absorbed dose rates range from 290 to 367 μGy⁄day, dose equivalent rates from 582 to 651 μSv⁄day and average quality factors from l.78 to 2.01 depending on the dosimeter packages around the RRMD-II “Detector Unit” at the S⁄MM#4 orbit (51.6° x 400 km). In general, it is seen that absorbed doses depend on the orbit altitude (SAA trapped particles contribution dominant) and dose equivalents on the orbit inclination (GCR contribution dominant). The LET distributions obtained by two different types of active and passive detectors, RRMDs and CR-39, are in good agreement for LET of 15 - 200 keV⁄μm and difference of these distributions in the regions of LET<15 keV/μm and LET >200 keV⁄μm can be explained by considering characteristics of CR-39 etched track formation especially for the low LET tracks and chemical etching conditions.

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Space radiation dosimetry measurements have been made on board the Space Shuttle. A newly developed active detector called “Real-time Radiation Monitoring Device (RRMD)” was used (Doke et al., 1995; Hayashi et al., 1995). The RRMD results indicate that low Linear Energy Transfer (LET) particles steadily penetrate around the South Atlantic Anomaly (SAA) without clear enhancement of dose equivalent and some daily periodic enhancements of dose equivalent due to high LET particles are seen at the lower geomagnetic cutoff regions (Doke et al., 1996). We also have been analyzing the space weather during the experiment, and found that the anomalous high-energy particle enhancement was linked to geomagnetic disturbance due to the high speed solar wind from a coronal hole. Additional analysis and other experiments are necessary for clarification of these phenomena. If a penetration of high-energy particles into the low altitude occurs by common geomagnetic disturbances, the prediction of geomagnetic activity becomes more important in the next Space Station's era.

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