Mikio Shikita
University of Tokyo
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Featured researches published by Mikio Shikita.
Radiation Research | 1993
Hiroshi Ishihara; Kazuko Tsuneoka; Alexander Borrisov Dimchev; Mikio Shikita
Spleen cells freshly isolated from normal mice were irradiated with 20 Gy X rays in culture. Northern blot hybridizations revealed that expression of the interleukin-1 beta (IL-1 beta) gene was induced immediately after irradiation and was increased for 2 h thereafter. Dibutyryl cyclic AMP also caused a persistent expression of the IL-1 beta gene, although it differed from X rays in that it coincidentally induced expression of the c-fos gene, which was not induced by X rays. Activation of either protein kinase C or calmodulin also induced early expression of both IL-1 beta and c-fos. Myeloid cells collected from the spleen of mice with granulocytic leukemia were X-irradiated in culture as above. The leukemia cells responded to X rays as well as to other stimuli in the same manner as the spleen cells, except that IL-1 beta mRNA was no longer detected 30 min after irradiation while c-fos was detectable for 2 h. When the leukemia cells were irradiated twice with a 3-h interval between irradiations, the second irradiation led to prolonged expression of IL-1 beta without inducing c-fos expression. These results suggest that ionizing radiation elicits early expression of the IL-1 beta gene through a mechanism that does not involve protein kinase C or A, or the transcription factor, c-fos. Whole-body irradiation of mice with 50 Gy 137Cs gamma rays also induced IL-1 beta expression in spleen but not in bone marrow or liver, although there was a delay of several hours before it was amply expressed. Furthermore, a delay as long as 24 or 72 h was observed when the radiation dose was reduced to 8.5 or 4 Gy. The results of this in vivo study suggest that the rapidity of expression of the IL-1 beta gene is dependent on the dose of radiation, and that the cells in the body cannot respond to radiation as rapidly as cells in culture.
Radiation Research | 1974
Yoshinari Takagi; Mikio Shikita; Toyozo Terasima; Sanya Akaboshi
Cysteamine at 0.5-5 mM effectively kills
General and Comparative Endocrinology | 1964
Ryoichi Arai; Mikio Shikita; Bun-Ichi Tamaoki
{\rm HeLa}\ {\rm S}_{3}
Radiation Research | 1991
Koji Nomoto; Teruo Yokokura; Kazuko Tsuneoka; Mikio Shikita
cells, while it is much less toxic in higher concentration (30 mM). The toxicity develops gradually with time as peroxide generates in the medium. Addition of catalase and peroxidase to the culture inhibits the toxic effect of cysteamine. The results suggest that the paradoxical cell-killing action of cysteamine can be ascribed to the generation of the peroxide by the compound (
Radiation Research | 1988
Koichi Ando; Sachiko Koike; Mikio Shikita; Hiroshi Otsu; Shinichiro Satoh
2{\rm RSH}+{\rm O}_{2}={\rm RSSR}+{\rm H}_{2}{\rm O}_{2}
Radiation Research | 1993
Hiroshi Ishihara; Kazuko Yoshida; Kumie Nemoto; Kazuko Tsuneoka; Mikio Shikita
). In higher concentrations, cysteamine protects the cells by decomposing the produced peroxide (
Radiation Research | 1992
Hisashi Kobayashi; Hayao Abe; Tsutomu Ueyama; Akira Awaya; Mikio Shikita
{\rm H}_{2}{\rm O}_{2}+2{\rm RSH}={\rm RSSR}+2{\rm H}_{2}{\rm O}
Radiation Research | 1970
Yoshinari Takagi; Fumiko Sato; Mikio Shikita; Masato Shinoda; Toyozo Terasima; Sanya Akaboshi
). Radioprotective effect of cysteamine is not directly related to the cytotoxic action of the compound. The magnitude of dose reduction factor (Y) is a linear function of logarithms of the concentration (X) of the compound (Y = 1.4 log X + 1.2). It is to be noted that the minimum effective concentration is about 0.7 mM and that the protective pow...
Journal of Biological Chemistry | 1973
Mikio Shikita; Peter F. Hall
Minced testes of the Japanese dace, Tribolodon hakonensis Gunther, were incubated in vitro with progesterone-4-C14. At least eleven transformation products were isolated by paper chromatography, two of which were identified as 17α-hydroxyprogesterone and androst-4-ene-3,17-dione by their chromatographic behavior and chemical characteristics, as well as on the basis of repeated crystallizations of the substances. The results seem to indicate that there are present the enzymes which catalyze 17α-hydroxylation and side-chain cleavage of progesterone in testicular tissue of the fish. These transformation products suggest that the biochemical pathway from progesterone to androst-4-ene-3,17-dione through 17α-hydroxyprogesterone is the same in fish as it is in mammals.
Proceedings of the National Academy of Sciences of the United States of America | 1974
Mikio Shikita; Peter F. Hall
Treatment of whole-body gamma-irradiated mice with a preparation of Lactobacillus casei (LC 9018) immediately after irradiation caused a sustained increase in serum colony-stimulating activity which was followed by an enhanced repopulation of granulocyte-macrophage colony-forming cells in the femoral marrow and spleen. Numbers of blood leukocytes, erythrocytes, and platelets were increased earlier in the treated mice than in the controls, and the survival rate was elevated significantly. The radioprotective effect was dependent on the dose of LC 9018 as well as on the dose of radiation. These results demonstrate the value of LC 9018 for the treatment of myelosuppression after radiotherapy or radiation accidents.