Xenopus embryos raised under conditions of hypergravity develop various abnormalities, including head defects such as microcephaly and cyclopis. However, it is unknown which region of the head is most sensitive to hypergravity, and whether regions behind the midbrain are affected by hypergravity. In this study, we investigated the effects of hypergravity on Xag, Xotx2, En2, Krox20, and HoxB9 expression by whole-mount in situ hybridization. Double staining with Xag and Xotx2 revealed that Xotx2 expression was dramatically suppressed in embryos exposed to 5G; Xag expression was also affected, but to a lesser extent. Furthermore, En2 expression was also affected by hypergravity. A detailed examination by double staining with Xotx2 and En2 showed that although Xotx2 expression was strongly suppressed in embryos exposed to 5G, the region expressing En2 was only slightly smaller. Lastly, Krox20 or HoxB9 expression was unaffected by hypergravity. These results suggest that formation of the anterior head region, including the eyes, forebrain, and midbrain, in Xenopus embryos is sensitive to hypergravity, while the posterior regions (i.e., behind the hindbrain) are unaffected by hypergravity.

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We aimed to investigate the effects of dynamic mechanical loading on the expression of osteoblast- and osteoclast-specific genes in regenerating goldfish scales. Fourteen days after the removal of scales from goldfish, the regenerating scales were found to contain calcified tissue, with osteoblasts, osteoclasts, and a newly synthesized calcified bone matrix plate. Recently, we found that goldfish scale regeneration shows similar gene expression to intramembranous mammalian bone osteogenesis. Using such regenerating scales on day 14, we analyzed the effects of dynamic 3G acceleration, via application of a vibration stimulus, on the mRNA expression in osteoblasts and osteoclasts. In osteoblasts, vibration increased distal-less homeobox 5 (an osteoblastic transcriptional gene) mRNA expression at 3 h after stimulation and type I collagen (an osteoblastic functional gene) mRNA expression at 6 h and 12 h after stimulation. Moreover, vibration decreased the mRNA expression of the receptor activator of the NF-κB ligand, which binds to the osteoclast surface receptor and facilitates bone resorption, at 12 h and 24 h after stimulation in osteoblasts. Further, vibration decreased cathepsin K (an osteoclastic functional gene) mRNA expression at 12 h after stimulation. Thus, our results indicate that vibration drives osteoblastic and osteoclastic control of antiresorptive and bone-formative effects through mRNA expression.

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cDNAs containing the open reading frames of a putative auxin influx carrier and/or facilitator, PsAUX1 (Accession No. AB488680), and putative auxin efflux carriers and/or facilitators, PsPIN1, PsPIN2 and PsPIN3 (Accession No. AB488679, AB488681 and AB488678, respectively) from etiolated epicotyls of an agravitropic pea mutant, ageotropum, have been isolated. In PsPIN1 and PsPIN2, a few deduced amino acids were different between ageotropum and Alaska showing a normal gravitropic response. No insertion and deletion were observed in PsPIN1 and PsPIN2 of ageotropum compared with those of Alaska. However, PsAUX1 of ageotropum had additional amino acids at the C-terminus compared to that of Alaska. Phylogenetic analyses based on deduced amino acid sequences revealed that PsPIN1 of ageotropum and Alaska belonged to the same clade as MtPIN4, while PsPIN2 of ageotropum and Alaska belonged to a subclade including MtPIN3, BjPIN2, BjPIN3, SlPIN3 and SlPIN4. PsAUX1 of ageotropum with additional amino acids at C-terminus belonged to the same subclade as MiAUX1 and PtAUX1. PsPIN1, PsPIN2, PsPIN3 mRNAs in 3.5-day-old etiolated ageotropum pea seedlings were significantly expressed in the proximal and the distal sides of the first internode of epicotyls to cotyledon. Judging from the results of the structure and the expression of genes related to auxin polar transport, an abnormal gravitropic response of etiolated ageotropum pea seedlings might be related to post transcriptional regulation and translocation of PsAUX1, PsPIN1, PsPIN2 and PsPIN3 as well as the perturbation of auxin transport due to additional amino acids at C-terminus of PsAUX1.

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It is known that the teleost scale regenerates after being removed. We previously reported that the osteogenesis in regenerating scales was very similar to that in calvarial bone, which suggests that regenerating scale can be used as a model for osteogenesis. In the present study, we determine calcium sensing receptor (CaSR) cDNA from the regenerating scales of goldfish. The determined partial sequence was coded as a 258-amino acid protein. The amino acid identity of this receptor to teteost CaSRs is 89 to 96%, lizard CaSR is 82%, and mammalian CaSR is 83 to 84%. These results indicate that CaSR is highly conserved in fish, lizard and mammals. Then, to examine the role of CaSR in bone metabolism, effect of acceleration loading (3 G) by vibration on the expression of CaSR mRNA in the regenerating scales of goldfish was investigated. We found that CaSR mRNA expression increased after acceleration loading by vibration in the regenerating scales. Significant difference between control and treatment group was observed at 6 and 24 h of incubation. Our cloned CaSR appears to act for the metabolism of bone in the regenerating scales. This is the first demonstration, to our knowledge, of an effect of hyper-loading on the induction of CaSR mRNA expression of hard tissues.

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High linear energy transfer (LET) radiation is important components of cosmic rays that has neurobiological effects: it is known to induce conditioned taste aversion, and suppress neurogenesis that may underlie cognitive impairment. However, the impact of high-LET radiation on other learning effects remains largely unknown. Here, we focus on kinetics of the radiation response for the salt chemotaxis learning (SCL) behavior in the nameatode, Caenorhabditis elegans, because the SCL during the learning conditioning was modulated after low-LET γ-irradiation. Firstly, the SCL ability was examined following high-LET irradiation (¹²C, 18.3 MeV/u, LET = 113 keV/μm), revealing its dose-dependent decrease after high- and low-LET exposure. Next, we demonstrate that the SCL at the early phase of the learning conditioning is greatly affected by high- and low-LET irradiation, and interestingly, the magnitude of these effects by high-LET radiation was significantly smaller than that by low-LET one. Moreover, the analysis of gpc-1 mutant showed that the G-protein γ subunit, GPC-1 is responsible for such early phase response. This study is the first to provide the evidence for the kinetics of changes in SCL after high-LET irradiation of C. elegans.

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The Japan Aerospace Exploration Agency (JAXA) has been developing several life science hardware components for the Japanese experiment module ‘Kibo’ in the International Space Station (ISS). The Cell Biology Experiment Facility (CBEF) is one of these. It contains an environmental control system to regulate variables such as the temperature and humidity. It is also equipped with a centrifuge and has the ability to culture bio-specimens in a temperature range of 15 to 40°C. In biological experiments that include in vitro cell culture, temperature control is a key factor in the success of the experiment. Thus, we first examined the temperature data in the CBEF on the ground while changing the room temperature and cooling water temperature to investigate the ability of the CBEF. Based on the ground experiment data, we carried out life science experiments onboard Kibo. Judging from the temperature data in the CBEF under microgravity, 12 life science experiments were successfully conducted up until 2011. Considering our present data, we strongly believe that the CBEF is a functional incubator in the ISS and will contribute to future experiments.

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Effects of high linear energy transfer (LET) radiation on the functions of the nervous system is a potential risk in interplanetary manned space missions. However, little is known about how the nervous system is protected against high-LET radiation exposure. The analysis of high-LET radiation resistant animals would be therefore important for space missions. Here, we investigated the resistance to high-LET radiation exposure for two behaviors of the nematode, Caenorhabditis elegans, which is known as a model organism for the nervous system. Tested behaviors were locomotion and chemotaxis to NaCl. In addition, egg hatchability was examined as an indicator of high-LET radiation sensitivity. Relative biological effectiveness (RBE) of high-LET radiation (¹²C, 18.3 MeV/u, LET = 113 keV/μm) relative to low-LET radiation for hatchability was 4.5, whereas RBEs for locomotion and chemotaxis were 1.4 and 1.1, respectively. This study shows that the behavioral system for locomotion and chemotaxis of C. elegans is highly resistant to high-LET radiation exposure.

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Xenopus embryos raised under hypergravity conditions develop a variety of abnormalities. Among them, head defects such as microcephaly and cyclopia are the most common phenotypes. Higher hypergravity (i.e., 5G) has been shown to cause more head defects in embryos than a lower one (i.e., 2G). However, the degree of head defects in embryos has not been studied quantitatively. In this study, we applied the Dorsoanterior Index (DAI) to quantitatively evaluate the degree of head defects caused by hypergravity. Moreover, we investigated the molecular mechanisms of head defects. Because Wnt signaling plays a crucial role in dorsal specification of embryos required for proper head formation, we examined the activity of endogenous Wnt signaling by monitoring direct Wnt target gene expression and found that the expression of these genes was reduced in hypergravity-treated embryos. This suggests that inhibition of Wnt signaling may be one of the mechanisms of hypergravity-derived head defects in early Xenopus embryos.

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