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Biomedical subjects

Akira Higashibata

Publications and source records attributed to Akira Higashibata.

9 recordsLinked to original sources
PubMed2006

Influence of simulated microgravity on the activation of the small GTPase Rho involved in cytoskeletal formation--molecular cloning and sequencing of bovine leukemia-associated guanine nucleotide exchange factor.

BACKGROUND: The irregular formation of cytoskeletal fibers in spaceflown experimental cells has been observed, but the disorganization process of fibers is still poorly understood. It is well known that the activation of the small GTPase Rho leads to actin stress fibers assembly. This study was performed to evaluate the effect of simulated microgravity on the activation of Rho that is involved in actin fiber remodeling in cells. RESULTS: Clinorotation influences actin fiber remodeling and its related signaling pathways that involve the small GTPase Rho. Actin stress fiber remodeling was significantly inhibited to a greater extent in cells cultured under clinorotation than in static cultured cells. From the gene and protein expression analyses, we found that the expression level of leukemia-associated Rho guanine nucleotide exchange factor (LARG), which activates Rho, was downregulated under clinorotation. Moreover, we identified the full-length LARG cDNA. The amount of GTP-bound RhoA, that is, the active form of RhoA, decreased under this condition. CONCLUSION: The activation of the small GTPase Rho was influenced by simulated microgravity generated by a three-dimensional (3D) clinostat. Furthermore, the full-length cDNA of bovine LARG, a member of the Rho guanine nucleotide exchange factor (GEF) family, was identified, and its gene expression was observed to be downregulated under clinorotation. This downregulation subsequently resulted in the repression of RhoA activation. These results indicated that the disorganization of the actin fibers was caused by the inhibition of Rho activation by 3D clinorotation.

Animals↗
PubMed2006

Decreased expression of myogenic transcription factors and myosin heavy chains in Caenorhabditis elegans muscles developed during spaceflight.

The molecular mechanisms underlying muscle atrophy during spaceflight are not well understood. We have analyzed the effects of a 10-day spaceflight on Caenorhabditis elegans muscle development. DNA microarray, real-time quantitative PCR, and quantitative western blot analyses revealed that the amount of MHC in both body-wall and pharyngeal muscle decrease in response to spaceflight. Decreased transcription of the body-wall myogenic transcription factor HLH-1 (CeMyoD) and of the three pharyngeal myogenic transcription factors, PEB-1, CEH-22 and PHA-4 were also observed. Upon return to Earth animals displayed reduced rates of movement, indicating a functional defect. These results demonstrate that C. elegans muscle development is altered in response to spaceflight. This altered development occurs at the level of gene transcription and was observed in the presence of innervation, not simply in isolated cells. This important finding coupled with past observations of decreased levels of the same myogenic transcription factions in vertebrates after spaceflight raises the possibility that altered muscle development is a contributing factor to spaceflight-induced muscle atrophy in vertebrates.

Animals↗
PubMed2005

Clinorotation prevents differentiation of rat myoblastic L6 cells in association with reduced NF-kappa B signaling.

In this study, we examined effects of the three-dimensional (3D)-clinorotation, a simulated-model of microgravity, on proliferation/differentiation of rat myoblastic L6 cells. Differentiation of L6 cells into myotubes was significantly disturbed in the 3D-clinorotation culture system, although the 3D-clinorotation had no effect on the proliferation. The 3D-clinorotation also suppressed the expression of myogenesis marker proteins, such as myogenin and myosin heavy chain (MHC), at the mRNA level. In association with this reduced differentiation, we found that the 3D-clinorotation prevented accumulation of ubiquitinated proteins, compared with non-rotation control cells. Based on these findings, we focused on the ubiquitin-dependent degradation of I kappa B, a myogenesis inhibitory protein, to clarify the mechanism of this impaired differentiation. A decline in the amount of I kappa B protein in L6 cells was significantly prevented by the rotation, while the amount of the protein in the non-rotated cells decreased along with the differentiation. Furthermore, the 3D-clinorotation reduced the NF-kappaB-binding activity in L6 cells and prevented the ubiquitination of I kappa B proteins in the I kappa B- and ubiquitin-expressing Cos7 cells. Other myogenic regulatory factors, such as deubiquitinases, cyclin E and oxygen, were not associated with the differentiation impaired by the clinorotation. Our present results suggest that simulated microgravity such as the 3D-clinorotation may disturb skeletal muscle cell differentiation, at least in part, by inhibiting the NF-kappa B pathway.

Animals↗
PubMed2004

Effects of running exercise during recovery from hindlimb unloading on soleus muscle fibers and their spinal motoneurons in rats.

The effects of hindlimb unloading and recovery with or without running exercise on morphological and metabolic properties of soleus muscle fibers and their spinal motoneurons in rats were investigated. Ten-week-old rats were hindlimb suspended for 2 weeks and thereafter were rehabilitated with or without voluntary running exercise for 2 weeks. A decreased percentage of type I fibers and atrophy of all types of fibers were observed after hindlimb unloading. In addition, decreased oxidative enzyme activity of all types of fibers was observed after hindlimb unloading. In contrast, an improvement in the decreased percentage of type I fibers, decreased fiber cross-sectional area, and decreased fiber oxidative enzyme activity was observed after recovery with running exercise, but not without running exercise. There were no changes in the number, cell body size, or oxidative enzyme activity of motoneurons innervating the soleus muscle after hindlimb unloading or recovery with or without running exercise. These results indicate that running exercise is beneficial for the recovery of the decreased percentage of type I fibers and the atrophy and decreased oxidative enzyme activity of all types of fibers in the soleus muscle induced by hindlimb unloading and that there are no changes in morphological or metabolic properties of spinal motoneurons innervating the soleus muscle following decreased or increased neuromuscular activity.

Animals↗
PubMed2004

Development and verification of hardware for life science experiments in the Japanese Experiment Module "Kibo" on the International Space Station.

Japan Aerospace Exploration Agency (JAXA) has developed a cell biology experiment facility (CBEF) and a clean bench (CB) as a common hardware in which life science experiments in the Japanese Experiment Module (JEM known as "Kibo") of the International Space Station (ISS) can be performed. The CBEF, a CO2 incubator with a turntable that provides variable gravity levels, is the basic hardware required to carry out the biological experiments using microorganisms, cells, tissues, small animals, plants, etc. The CB provides a closed aseptic operation area for life science and biotechnology experiments in Kibo. A phase contrast and fluorescence microscope is installed inside CB. The biological experiment units (BEU) are designed to run individual experiments using the CBEF and the CB. A plant experiment unit (PEU) and two cell experiment units (CEU type1 and type2) for the BEU have been developed.

Animals↗
PubMed2003

Growth-related changes in cell body size and succinate dehydrogenase activity of spinal motoneurons innervating the rat soleus muscle.

Cell body sizes and oxidative enzyme (succinate dehydrogenase) activities of spinal motoneurons innervating the soleus muscle were determined in rats ranging in postnatal age from 3 to 13 weeks. The soleus motoneurons were labeled by a retrograde neuronal tracer, nuclear yellow. The mean cell body sizes of motoneurons increased from 3 to 7 weeks of age, while the mean succinate dehydrogenase activities of motoneurons decreased from 3 to 7 weeks of age. There were no changes in mean cell body size or mean succinate dehydrogenase activity of motoneurons from 7 to 13 weeks of age. An inverse relationship between cell body size and succinate dehydrogenase activity of motoneurons was observed, irrespective of age. These results indicate that motoneurons innervating the rat soleus muscle show the adult pattern of cell body size and succinate dehydrogenase activity at an earlier stage of postnatal growth, 7 weeks of age.

Aging↗
PubMed2003

Point of a space experiment proposal.

JAXA will solicit research proposals for space flight experiments that would be conducted for less than three years after the selection. In principle, available samples will be limited to Arabidopsis and C. elegans and flight hardware and protocol of space flight experiment will be pre-fixed. Proposals using different combinations of species and flight hardware will not be acceptable. Besides scientific issues, it is very important for proposer to write an impressive proposal. Hypothesis basis research proposal is the accepted standard. Reviewers will dislike a descriptive and unfocused research proposal without hypothesis. Ground preparation experiments, which are not related directly to space experiments, should not be included in the solicitation.

Animals↗
PubMed2002

[Change of the gene expression related to a cytoskeleton cultured under gravity-vector changing].

Many researches to elucidate the mechanism of gravity sense and its response in the living cells have been advanced. But it has not yet identified that key molecule or signal transduction pathway related to gravity sense and its response. Our goal is to clarify the mechanism of gravity sense, especially the point of gravity sense. First, we have investigated about differences of gene expression level (mRNA) of the endothelial cells cultivated under vector-averaged gravity condition (Clinorotation). The Differential Display pattern showed that expression level of several genes had changed between clinorotated condition and control. The homologues of these fragments were searched on the BLAST database. From BLAST database searching results, GEF and cell adhesion protein effected by clinorotaion. Moreover, morphological and immunological techniques data showed that the cytoskeletal formation of actin, tubulin, etc. or localization in cell of Rho protein were changed. These results suggested that signal transduction pathway through Rho played an important role in the gravity sense mechanism of endothelial cells. Furthermore, we are going to investigate relation between gene expression and morphological data.

Cells, Cultured↗