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154 results on '"Nimura, Noriyuki"'

16. Occurrence of -Amino Acids and a Pyridoxal 5′-Phosphate-Dependent Aspartate Racemase in the Acidothermophilic Archaeon, Thermoplasma acidophilum

Author

Long, Zhiqun, primary, Lee, Jen-Ai, additional, Okamoto, Taizo, additional, Sekine, Masae, additional, Nimura, Noriyuki, additional, Imai, Kazuhiro, additional, Yohda, Masafumi, additional, Maruyama, Tadashi, additional, Sumi, Masato, additional, Kamo, Naoki, additional, Yamagishi, Akihiko, additional, Oshima, Tairo, additional, and Homma, Hiroshi, additional

Published
2001
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48. Occurrence of d-Amino Acids and a Pyridoxal 5′-Phosphate-Dependent Aspartate Racemase in the Acidothermophilic Archaeon, Thermoplasma acidophilum

Author

Long, Zhiqun, Lee, Jen-Ai, Okamoto, Taizo, Sekine, Masae, Nimura, Noriyuki, Imai, Kazuhiro, Yohda, Masafumi, Maruyama, Tadashi, Sumi, Masato, Kamo, Naoki, Yamagishi, Akihiko, Oshima, Tairo, and Homma, Hiroshi

Abstract

Free d-amino acid content in some archaea was investigated and D-forms of several amino acids were found in them. In the acidothermophilic archaeon, Thermoplasma acidophilum, the proportion of d-aspartate (d-Asp) to total Asp was as high as 39.7%. Crude extracts of Thermoplasma acidophilum had Asp-specific racemase activity that was pyridoxal 5′-phosphate (PLP)-dependent. The relative insensitivity to a SH-modifying reagent distinguished this activity from those of the PLP-independent Asp racemases found in other hyperthermophilic archaea (Matsumoto, M., et al., J. Bacteriol. 181, 6560–6563 1999). Thus, high levels of d-Asp should be produced by a new type(s) of Asp-specific racemase in Thermoplasma acidophilum, although the function of d-Asp in this archaeon remains unknown.

Published
2001
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49. Localization, Transport, and Uptake of d-Aspartate in the Rat Adrenal and Pituitary Glands

Author

Lee, Jen-Ai, Long, Zhiqun, Nimura, Noriyuki, Iwatsubo, Takeshi, Imai, Kazuhiro, and Homma, Hiroshi

Abstract

Large amounts of d-aspartate (d-Asp) are present in the rat adrenal and pituitary glands. d-Asp is thought to be synthesized in the mammalian body and also accumulates in various tissues following intraperitoneal or intravenous administration. This report examines the origins of d-Asp in the adrenal and pituitary glands. We administered d-Asp to male rats intraperitoneally and immunolocalized this exogenous d-Asp in adrenal and pituitary tissue, using an anti-d-Asp antiserum which was previously developed in our laboratory. d-Asp levels in the rat adrenal gland have been shown to undergo a transient increase at 3 weeks of age and to decrease rapidly thereafter. We found that in the adrenal gland, exogenous d-Asp administered intraperitoneally was incorporated into the same region of the adrenal cortex in which endogenous d-Asp was present. By Northern and Western blot analysis and immunohistochemistry of glutamate (Glu) transporter, we also found that expression of the Glu transporter (GLAST), which has an affinity for d-Asp, transiently increased at 3 weeks of age and that localization patterns of the Glu transporter within the tissue were almost coincident with those of endogenous d-Asp. These observations suggest that d-Asp in the adrenal cortex of 3-week-old male rats is primarily acquired by uptake from the vascular system. We have previously shown that d-Asp is specifically localized in prolactin (PRL)-containing cells in the anterior lobe of the adult rat pituitary gland. Here we report that in the pituitary gland, exogenous d-Asp accumulated in endothelial cells, but not in PRL-containing cells. Northern and Western blot analysis and immunohistochemistry of Glu transporter revealed that developmental changes in the Glu transporter (GLAST) expression did not correlate with tissue levels of d-Asp and that the Glu transporter was not expressed in PRL-containing cells. These observations suggest that, in contrast to the adrenal gland, most of the d-Asp in the pituitary gland of adult male rats originates inside the gland itself.

Published
2001
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50. d-Aspartate in a Prolactin-Secreting Clonal Strain of Rat Pituitary Tumor Cells (GH3)

Author

Long, Zhiqung, Lee, Jen-Ai, Okamoto, Taizo, Nimura, Noriyuki, Imai, Kazuhiro, and Homma, Hiroshi

Abstract

d-Aspartate (d-Asp) is found in prolactin (PRL)-containing cells of the rat anterior pituitary gland [Lee et al., Brain Res. 838, 193–199, 1999]. In order to determine whether d-Asp is actually produced by the anterior pituitary gland and whether it plays a physiological role in PRL function, a PRL-secreting clonal strain of rat pituitary tumor cells (GH3) was employed in this study. HPLC analysis and immunocytochemical staining detected the presence and synthesis of d-Asp inthe cytoplasm of these cells. In addition, thyrotropin-releasing hormone-stimulated PRL secretion was increased in a dose-dependent fashion by d-Asp from these cells. These results suggest that the anterior pituitary gland synthesizes d-Asp and that d-Asp acts as a messenger in this gland.

Published
2000
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