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10×gおよび3×gの過重力下で栽培したヒメツリガネゴケの、光合成速度測定、CO₂コンダクタンス測定および形態変化の観察を行った。

Although it was confirmed that nucleation density and crystal growth rate in the diamond thin films by means of DC-plasma CVD were increased with increasing gravity, the reasons of these effects have not clearly been explained. To this end, an OES (optical emission spectroscopy) apparatus was installed in the high gravity equipment. In-situ plasma diagnostics enabled identification of the active species in the plasma, and a series of experiments were conducted for various experimental conditions with gravity, substrate temperatures, and methane concentration as the parameters., 資料番号: AA0046917068

It has been reported that Paramecium proliferates slower when cultured under hypergravity. In order to gain an insight into the mechanism underlying the sensitivity to hypergravity, the proliferation under hypergravity was compared with that under lowering temperature or reduced nourishment, where cell proliferation rate is known to be reduced. Proliferation experiments was conducted under different conditions with three variables; gravity, temperature, and nourishment. In each experiment, control cells were grown under 1 G at 24 C with 100 percent nourishment through three experiments. In order to assess the proliferation under different conditions, the kinetic parameters of proliferation were obtained through a numerical analysis based the least squares fitting of the logistic growth equation. Maximum proliferation rate was reduced under hypergravity, lowering temperature and reduced nourishment. Saturation density was maintained under lowering temperature, while those were lower under hypergravity and reduced nourishment. Logistic parameter which was maintained under hypergravity became smaller under lowering temperature, and larger under reduced nourishment. It was also reported that hypergravity reduced the cell size of Paramecium. The maximum cell volume significantly decreased under hypergravity, while it tended to increase under lowering temperature and decrease under reduced nourishment. These results indicate that the mechanism of reduced proliferation rate under hypergravity is different from those under lowering temperature and reduced nourishment., 資料番号: AA0046917013

In response to hypergravity treatment at 300 g for 12 h, the gene expression of CesA1, 6, 7 and 9 decreased in 3-day old seedlings, but did not change in the floral stem in 20 day-old plants. On the other hand, hypergravity treatment at 300 g for 1 h decreased the gene expression of XTH15, and increased that of XTH22. The effect of hypergravity on the gene expression of two XTHs was partially alleviated by 0.1 mM La(3+), suggesting the possible involvement of mechanosensor in hypergravity-induced changes in XTH gene expression. In addition, the morphology of the secondary cell wall was influenced by hypergravity. Xylem vessels showed intense staining with phloroglucinol-HC1 and autofluorescence under UV light at the basal region of floral stem 3 day after hypergravity treatment. The cross section area of the metaxylem element increased after hypergravity treatment, suggesting that lignification and the development of the secondary wall of xylem vessels are positively regulated under hypergravity., 資料番号: AA0046917040

Three weeks old male ICR mice were bred under 3 G hyper gravity and feed restricted condition. The weight of testis compared with the body weight in both of them became larger than that of ground control when measured about two weeks after the breeding. On the other hand, seminal vesicle and body fat became smaller. Sperm appearance in vas deference of them was also a little earlier than the control. It was likely that the food restriction provided similar effect on the mice under the hyper gravity, except the mice were of starvation, while not in the mice under the hyper gravity. Corticosterone increased at the beginning of exposure of hyper gravity, however, decreased down to the level of the control three weeks after breeding under the hyper gravity. Secretion of FSH was a little suppressed by hyper gravity. The present results suggested that effects of hyper gravity appeared via hormonal regulation., 資料番号: AA0046917016

Modifications of cell wall structure of wheat coleoptiles in response to continuous hypergravity (300 g) treatment were investigated. Growth of coleoptiles exposed to hypergravity for 2 to 4 days from germination stage was substantially reduced. The net amounts of cell wall polysaccharides of hypergravity-treated coleoptiles increased as much as those of 1 g control coleoptiles during the incubation period. As a result, the levels of cell wall polysaccharides per unit length of coleoptile, which mean the thickness of cell walls, largely increased under hypergravity conditions. In the hemicellulose fraction, a polysaccharide fraction extracted from cell walls with strong alkali, glucose (Glc), arabinose (Ara) and xylose (Xyl) were the major sugar components, and the ratios of Ara and Xyl to Glc were higher in hypergravity-treated coleoptiles than in control coleoptiles. Furthermore, the fractionation of hemicellulosic polymers into the neutral and acidic polymers by the anion-exchange column showed that the levels of acidic polymers (mainly composed of arabinoxylans) in cell walls of hypergravity-treated coleoptiles were higher than those of control coleoptiles. In addition to wall polysaccharides, the amounts of cell wall-bound phenolics, such as ferulic acid and diferulic acid, increased at the same extent in both hypergravity-treated and control coleoptiles. These results suggest that hypergravity stimuli from the germination stage do not restrict the net synthesis of cell wall constituents in wheat coleoptiles, although they bias the type of synthesized hemicellulosic polysaccharides. The stimulation of the synthesis of arabinoxylans may be involved in the structural changes, such as thickening of cell walls, under hypergravity conditions. These structural changes in cell walls may contribute to plant resistance to gravity stimuli., 資料番号: AA0046917039

In order to clarify the possible effects of high gravity environments on eggs and developing embryos, Rana rugosa unfertilized eggs, fertilized eggs and embryos at cell stages 2, 4, 8, 16, 32 and 64, the blastula, gastrula, neurula and tail- bud stages were raised in 2 G, 5 G, 7 G and 10 G up to premetamorphic Taylor and Kollros' stage 1. The results showed that: 1) High gravity strikingly retarded the development of eggs and embryos beginning treatment before the blastula stage and induce microcephally and multiple malformation, suggesting that high gravity is apt to disrupt the animal-vegetal axis. On the other hand, embryos beginning treatment after the gastrula stage showed a striking increase in the number of normal stage 1 tadpoles. 2) Autopsy revealed that brains, notochords and muscles were reduced in development and differentiation for embryos and tadpoles developed in high gravity., 資料番号: AA0045438015

The International Space Station (ISS) under construction is useful to see the effect of microgravity on plant life cycle in that JEM plant experiment units in ISS has a centrifuge to assess the effect of 1 g on plants in space. In the present report, it will be shown that two ecotypes of Arabidopsis, Landsberg erecta and Columbia, complete their seed to seed life cycle in JEM plant experiment units. In addition, RT-PCR analysis revealed that hypergravity of 300 g changes the expression of xyloglucan transferase genes, which are involved in the construction and reconstruction of the cell wall, being essential for plant growth and development., 資料番号: AA0045438032

Behavior of fine bubbles in front of solidifying interface of C8H17SO3Na water solution was directly observed under the gravity condition from micro G to 2 G by combining Mach-Zehnder interferometer. Fine bubbles inside the concentration boundary layer of C8H17SO3Na formed in front of the interface move quickly toward the interface and are engulfed by the interface. On the other hand, the bubbles outside the boundary layer, just float up under 1.5 G and 2 G or don't move under micro G in the solution. The above motion of fine bubbles toward the interface can be explained reasonably based on the driving force, acting on the bubble, caused by the surface tension gradient along the bubble surface due to the concentration gradient of C8H17SO3Na in front of the interface., 資料番号: AA0045438041

Article, 信州医学雑誌 47(4): 279-286(1999)

我々がこれまでに明らかにした、ラット過重力負荷時に前庭神経系で発現増加する遺伝子:CREB(Cyclic AMP-responsive element binding protein)、syntaxinについて、線虫ではどのような変化を起こしているかを検討したところ、哺乳類であるラットの結果とは相違を見せた。哺乳類と線虫の重力感知機構の違い(遺伝子発現の相違)や、異なる重力下にさらした期間の長さの違いが原因ではないかと考えられた。, In this study, we compared the gene expression differences of CREB and syntaxin, which we found that were overexpressed under hypergravity in the rat vestibular end organs, in the Caenorhabditis elegans. The expression patterns of CREB and syntaxin were different from rat. It was thought that these results came from the differences of gravity perception mechanism and/or the differences of the period exposing to the hypergravity., 資料番号: AA0049801002, レポート番号: JAXA-SP-05-040

メダカ(ヒメダカ:成魚)およびイモリ(アカハライモリ:成体および幼生)の行動並びに姿勢を、パラボリックフライト中の微小重力下で観察した。結果および考察は以下の通りであった。メダカ:純系5系統および雑系(オレンジ・赤、閉鎖群体)1種の成魚について実験を行った。試験したすべての純系の内で、3系統(HO5、HO4C、HB12A)は微小重力および明視条件下でひねりと共に回転行動を示した。HNI-2系統はまったく回転行動を示さなかった。HB32C系統のメダカの大半は、回転行動を示したものもあったにも拘らず、どちらの条件でも回転しなかった。雑系はどちらの条件にも回転の気配を示さなかった。このように、微小重力および明視条件下でのメダカの行動反応には明らかに系統別の差が存在した。しかし、微小重力および暗視条件下では試験したすべてのメダカ、すなわち純系5系統と雑系が回転行動を示した。これらのパラボリックフライトデータから、現在のところ、宇宙実験に最適な候補はHNI-2系統のメダカである。イモリ:水中のイモリ成体はゆっくりとした回転、うねりを示しながら泳いだ。発生段階にある幼生の幾つかは舞い上がった。後期段階(54-57)の幼生は微小重力の開始時および微小重力期間中活発に上向きまたは横向きに遊泳して反応を示す傾向があった。過重力に対する反応は顕著でも活発でもなかった。初期段階(42-48)の幼生の約1/3は微小重力の開始時に上向きに泳ぐ反応を示した。これらの反応は暗視条件よりも明視条件においてより活発で長く続いた。過重力への反応は、微小重力に入る前あるいはその後のいずれの場合でも、明視条件および暗視条件の両方で活発に見られた。暗視条件で、最も共通した反応は微小重力期間中をじっとして動かないか、あるいは短い距離だけ、上向きあるいは横向きに動き、その後はじっとして動かないというものであった。パラボリックフライト中に行った観察結果は行動の違いが半規管の発生状態に関係している可能性を示唆した。両生類に動揺病がおこる可能性があるか調べるために、数種の両生類にパラボリックフライトを行った。ニホンアマガエルは1990年12月に宇宙ステーションミールへと飛行し、軌道上で8日間過ごした。ミール上で、表面に張り付いたカエルはしばしば首を後方に反らし後退りした。この行動を今回のパラボリックフライトで観察し、動揺病の徴候でありうる陸上で具合の悪くなったカエルの吐き気行動に似ている。これらの結果は、カエルは動揺病になることを示し、ミール上でのカエルの異常な姿勢は動揺病を表していたのかもしれないことを示唆した。, Behaviors and postures of the fish medaka (Oryzias latipes) (adult) and the newt (Cynops pyrrhogaster) (adult and larvae) were observed under microgravity during the parabolic flight. Results and discussions were as follows. Medaka: the experiments were done on the adult fish of five different inbred strains and one variety of the species. Among all the inbred strains tested, three strains (HO5, HO4C, HB12A) showed looping (together with twisting) behavior under microgravity and light conditions. The strain HNI-2 did not show any looping behavior at all. Most fish of the strain HB32C did not loop either, though some of them did. The variety showed no sign of looping either. Thus, there existed a clear strain-difference in the behavioral response of the fish under microgravity and light conditions. However, under microgravity and dark conditions, all the fish tested, i.e., all the fish of the five inbred strains and the variety did loop. At present, from these parabolic flight data, the best fish candidates for the space experiments are those of HNI-2 strain. Newt: an adult newt in water swam with gentle rolling and twisting. Several developmental stage of larvae were flown. Later-stage (54-57) larvae tend to respond both at the onset and during periods of microgravity with vigorous upward or sideways swimming. Responses to hypergravity are not frequent or vigorous. Approximately 1/3 of early-stage larvae (42-48) respond to the onset of microgravity with upward swimming. These responses are more vigorous and long-lasting in light than in dark. Vigorous responses to hypergravity, either before or after microgravity, were seen in both light and dark. In dark, the most common response was to either freeze throughout the period of microgravity or to make a short movement, either upward or sideways, and then to freeze. The observations made during these parabolic flights suggest that the differences in behavior might be related to the development of the semicircular canals. Several species of amphibians were exposed to the parabolic flight to test the possibility of getting motion sickness in amphibians. Japanese tree frogs (Hyla japonica) were flown to the space station MIR. On the MIR, frogs on a surface often bent their neck backward and walked backwards. This behavior was observed on present parabolic flights and resembles the retching behavior of sick frogs on land a possible indicator of motion sickness. These results indicate that frogs can get motion sickness and suggest that the unusual posture of the frogs on the MIR may have represented motion sickness., 資料番号: AA0000741001, レポート番号: NASDA-TMR-960024

Autonomic nerve responses of human subjects were evaluated by frequency analysis of heart rate and pulse plethysmogram under linear acceleration applied to parallel (Z) and perpendicular (Y) to the body axis in supine posture. The acceleration applied were 0.25 G with sinusoidal frequencies, 0.1 to 0.17 Hz. The acceleration loading to Z-axis only induced additional frequency component in the power spectra obtained from heart rate and pulse plethysmogram at the foot finger skin, while no additional response was observed in Y-axis loading. The frequency dependency of the acceleration induced heart rate and pulse plethysmogram components suggested a resonance characteristic at higher frequency than 0.17 Hz. Iris diameter change during the acceleration loading measured by infrared light indicated a correlation to the acceleration. The results suggested that an autonomic hemodynamic modulation may arise from a feedback of low pressure receptors when the slow sinusoidal acceleration is loaded to the body axis., 資料番号: AA0046917003

The embryonic development of the nematode Caenorhabditis elegans was examined under different gravitational conditions. The early embryos after fertilization dissected from adult hermaphrodites normally hatched under hypergravity (200 G) or 3 D-clinorotation. On the other hand, the number of eggs laid by each hermaphrodite decreased and their hatching rate was reduced under hypergravity condition (100 G). The frequency of mitosis in the gonadal tips was also reduced. These indicate that the meiotic process and/or fertilization step and germline mitosis are more sensitive to hypergravity. It was also found that the first cleavage plane in the 1-cell embryo was slid to some extent by re-orientation of liquid culture vessel, but the pattern and timing of cleavages were not affected., 資料番号: AA0046917021

It was previously reported that 2G hypergravity exposure modulated the nociceptive response of rats, being mediated through induction of beta-endorphin in the arcuate, paraventricular, suprachiasmatic and supraoptic nuclei of the hypothalamus. However, it is unclear whether these hypothalamic areas are the primarily sensitive sites of gravity change or the secondarily affected areas via neurons that are projected from the higher CNS, including limbic system. In the present study, the effects of 2G hypergravity on the synaptic plasticity, change in the amplitude of the negative deflection of field potential around the CAI region were examined, by stimulating the Schaffer Collateral in rat hippocampus slice., 資料番号: AA0045438006

Mechanical stimuli play key roles in osteoblast proliferation and differentiation. Adhesion receptors like integrins are among candidates for transducers of mechanical stimuli. As a mediator of mechanical stimuli via integrins, ERK (extracellular signal-regulated kinase) which has an essential role in osteoblast proliferation and differentiation is focused on. However, it has not been fully understood how ERK activation relates to either osteoblast differentiation or mechanical stimulus perception. The transitions in ERK activation and cell surface integrin expression during in vitro differentiation of osteoblast-like MC3T3-E1 cells were investigated. Alkaline phosphatase (ALP) activity, an osteoblastic marker, increased after confluence. Phosphorylation of ERK detected by Western blot analysis was observed throughout 15 days culture. The degree of ERK activation in 15-day culture was about 40 percent of that in 3-day culture. EGF treatment increased ERK activation but suppressed ALP increase. U0126, an inhibitor of ERK activation, suppressed both ERK activation and ALP increase. These results indicate that basal sustained ERK activation is essential to proper osteoblast differentiation. The increase in ALP activity was suppressed by treating with DGEA peptide, which interferes collagen-alpha2beta1 integrin interaction. Cell surface expressions of integrin alpha2 and beta1 decreased as culture days extended. These findings suggest that sustained ERK activation may be regulated by signals from cell surface integrins., 資料番号: AA0046917009

Spermiogenesis is the final step of spermatogenesis that takes place in a differentiating spermatid. Some events orderly progress in the spermatid as a result of having contact with Sertoli cells in the testis of vertebrates. Each event in spermiogenesis is controlled by the combined effect of an intrinsic control of the spermatid and the germ-somatic cell interaction in vertebrates. A culture system of spermatogenic cells has been established in the medaka fish, Oryzias latipes. In the culture, primary spermatocytes differentiate into fertilizable sperm, through meiosis and spermiogenesis. These processes proceed without contacting Sertoli cells. On the other hand, the timing of these events in the cultured spermatids, agree with that in vivo, suggesting that it is intrinsically controlled in the cultured spermatids. This control mechanism is suggested to be similar to that acts in vivo. It has been demonstrated that this culture system is available to estimate the influences of hypergravity in the mechanism controlling spermiogenesis in vertebrates. In the present study, the cell culture of primary spermatocytes of the medaka fish was centrifuged at 10 G and the influences of hypergravity were estimated in the spermiogenic events, especially in the cytoplasmic lobe formation. When the primary spermatocytes were cultured at 10 G, the timing for meiotic division completion agreed with that observed in the culture at 1 G, as the control. The cytoplasmic lobe formation was suggested to take place in the spermatids after completing the organelle replacement, thus the shapes of the cultured spermatids were observed using scanning electron microscopy. In Day 4, protrusions were observed in many spermatids and the elongated protrusions were typically observed in the spermatids in Day 5. Using transmission electron microscopy, the protrusion was sited near the flagellum and many organelles, such as mitochondria and vacuoles, were observed in its cytoplasm. Thus, the protrusion corresponded to the cytoplasmic lobe. In Day 4, four types of spermatids were observed: the spermatids with a large round head (stage 1), with small protrusions (stage 2), with elongated protrusions (stage 3) and with a small round head (stage 4). Every type of spermatid was also observed in the culture at 10 G. However, the percentages of spermatids at stage 1 and at stage 2 were larger than those in the control. This result suggests that hypergravity suppressed the cytoplasmic lobe formation in the cultured spermatids. This cell culture system can be used for estimating the influences of gamete production in vertebrates against a specialized environment in space., 資料番号: AA0046917014