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Your search keyword '"Ohsawa, Motoyasu"' showing total 93 results
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93 results on '"Ohsawa, Motoyasu"'

5. Energization of amino acid transport in energy-depleted Ehrlich cells and plasma membrane vesicles

Author

Department of Biological Chemistry, The University of Michigan, Ann Arbor, MI 48109, U.S.A., Ohsawa, Motoyasu, Kilberg, Michael S., Kimmel, Gene, Christensen, Halvor N., Department of Biological Chemistry, The University of Michigan, Ann Arbor, MI 48109, U.S.A., Ohsawa, Motoyasu, Kilberg, Michael S., Kimmel, Gene, and Christensen, Halvor N.

Abstract

We redirect attention to contributions to the energization of the active transport of amino acids in the Ehrlich cell, beyond the known energization by down-gradient comigration of Na+, beyond possible direct energization by coupling to ATP breakdown, and beyond known energization by exchange with prior accumulations of amino acids. We re-emphasize the uphill operation of System L, and by prior depletion of cellular amino acids show that this system must receive energy beyond that made available by their coupled exodus. After this depletion the Na+-independent accumulation of the norbornane amino acid, 2-aminobicycloheptane-2-carboxylic acid becomes strongly subject to stimulation by incubation with glucose. Energy transfer between Systems A and L through the mutual substrate action of ordinary amino acids was minimized although not entirely avoided by the use of amino acid analogs specific to each system. When 2,4-dinitrophenol was included in the depleting treatment, and pyruvate, phenazine methosulfate, or glucose used for restoration, recovery of uptake of the norbornane amino acid was independent of external Na+ or K+ levels. Restoration of the uptake of 2-(methylamino)isobutyric acid was, however, decreased by omission of external K+. Contrary to an earlier finding, restoration of uptake of each of these amino acids was associated with distinct and usually correlated rises in cellular ATP levels. ATP addition failed to stimulate exodus of the norbornane amino acid from plasma membrane vesicles, although either NADH or phenazine methosulfate did stimulate exodus. ATP production and use is thus associated with transport energization, although evidence for a direct role failed to appear.

Published
2006

25. Cadmium-induced dna single-strand scissions and their repair in cultured chinese hamster cells

Author

Takayanagi Masashi, Ohsawa Motoyasu, and Ochi Takafumi

Subjects
inorganic chemicals, Xeroderma pigmentosum, DNA Repair, DNA, Single-Stranded, chemistry.chemical_element, Biology, Cadmium chloride, Toxicology, chemistry.chemical_compound, Cricetulus, Cricetinae, medicine, Animals, Cells, Cultured, Cadmium, DNA synthesis, Elution, DNA replication, General Medicine, medicine.disease, Molecular biology, chemistry, Biochemistry, DNA, Nucleotide excision repair
Abstract

DNA lesions induced by cadmium chloride (CdCl2) were characterized using the technique of alkaline or neutral elution for cell-DNA in cultured V79 cells. A marked increase in elution of the DNA was observed on elution of the proteinase-K-digested cell lysates with alkaline eluting solution (pH 12.2) after treatment with 5 X 10(-5) M CdCl2 for 2 h. In contrast, no increase in elution of the DNA was observed when the same cell lysates were eluted with an eluting solution of pH 9.6. These findings indicate that the DNA lesions induced by cadmium were DNA single-strand but not double-strand scissions. The DNA single-strand scissions by cadmium were partly rejoined after 4 h of repair incubation. However, the DNA lesions were not rejoined up to the control level in the technique of alkaline elution, even after 20 h of repair incubation. On the other hand, an apparent increase in elution of the DNA was observed by combined treatment with cadmium and inhibitors of repair DNA synthesis, hydroxyurea (HU) and 1-beta-D-arabinofuranosylcytosine (ara-C), for 4 h when compared to elution of the DNA from the cells treated with cadmium alone or HU and ara-C. These results indicate that cadmium-induced DNA single-strand scissions accumulated as a result of inhibition of repair DNA replication by HU and ara-C. Thus, it is concluded that cadmium-induced DNA single-strand scissions were repairable and their repair might be dependent upon the excision repair mechanism.

Published
1983
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26. Diesel Exhaust Particles Block Induction of Oral Tolerance in Mice

Author

Yoshino, Shin, Ohsawa, Motoyasu, and Sagai, Masaru

Abstract

We investigated the effect of diesel exhaust particles (DEP) on oral tolerance. Oral tolerance was induced by feeding mice with 10 mg of hen egg lysozyme (HEL) daily over a period of 5 days before immunization with the antigen. Varying doses of DEP were orally administered immediately before each feeding of HEL. The results showed that oral administration of HEL significantly suppressed production of anti-HEL IgG, IgG1 and IgG2a antibodies, delayed-type hypersensitivity and proliferative responses of lymph node cells to the antigen. The suppression of these immune responses to HEL by the oral antigen was associated with a marked decrease in secretion of interferon-γ and interleukin-4 from the lymphoid cells. Administration of DEP dose-dependently blocked suppression by oral HEL of antigen-specific IgG, IgG1 and IgG2a antibody production, delayed-type hypersensitivity and lymphoid cell proliferation. The suppression by the fed antigen of secretion of interferon-γ and interleukin-4 was also markedly diminished by the particles. Thus, DEP appear to be effective in blocking induction of oral tolerance.

Published
1998
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27. Suppression of the proliferative response of human lymphocytes to cultured allogeneic HeLa cells by zinc

Author

Ochi Takafumi, Ohsawa Motoyasu, and Sato Kazue

Subjects
Immunosuppression Therapy, Macrophages, chemistry.chemical_element, General Medicine, Zinc, T lymphocyte, Biology, Toxicology, biology.organism_classification, Lymphocyte Activation, Molecular biology, Proliferative response, HeLa, chemistry, Concanavalin A, Immunology, biology.protein, Humans, Lymphocyte Culture Test, Mixed, Mitogens, HeLa Cells, Thymidine
Abstract

Zinc added to the culture medium caused a dose-related suppression of the proliferative response of human lymphocytes to cultured allogeneic HeLa cells without any significant decrease in cell viability. In contrast to the response to HeLa cells, this metal ion moderately enhanced T lymphocyte response to mitogens such as phytohemagglutinin (PHA), concanavalin A (ConA) and 12-O-tetradecanoylphor-bol-13-acetate (TPA). These findings seem to indicate that zinc may be a crucial factor for the modulation of the T lymphocyte function. It can also be considered that the different effect of zinc on the proliferative responses of lymphocytes to allogeneic HeLa cells and to some soluble mitogens might reflect a difference in mechanisms between the two proliferative responses.

Published
1983

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