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Dive into the research topics where Kunio Shiota is active.

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Featured researches published by Kunio Shiota.


Molecular and Cellular Endocrinology | 1990

Activin A increases the number of follicle-stimulating hormone cells in anterior pituitary cultures.

Tetsuro Katayama; Kunio Shiota; Michio Takahashi

The mode of action of activin A on the anterior pituitary gland (AP) was investigated using primary cultured cells. The AP cells were cultured with activin A (1 ng/ml) at various cell densities for 24-96 h, and further incubated for 3 h with activin A-free medium. When the cells were pretreated with activin A for 48 h, follicle-stimulating hormone (FSH) secretion during the following 3-h incubation was increased only at a density of 1 x 10(5) cells/200 mm2, but not at 2 x 10(5) or 4 x 10(5) cells/200 mm2. A longer pretreatment (96 h) was required in order to induce this response at a density of 2 x 10(5) cells/200 mm2. Luteinizing hormone (LH) secretion was not affected by activin A. Thus, the FSH secretory activity of the primary culture of AP was stimulated by activin A in a cell density-dependent manner. Furthermore, it was found that treatment with activin A (10 ng/ml) for 72 h increased the number of immunoreactive FSH cells by 25-41%, and that these newly induced FSH cells were low responders to gonadotropin-releasing hormone stimulation. The proportions of immunoreactive LH, thyroid-stimulating hormone, prolactin or growth hormone cells were not affected. From these results, we conclude that activin A increases FSH secretion by changing the cell population of pituitary gonadotropes.


Biochimica et Biophysica Acta | 1991

Purification and characterization of rat ovarian 20α-hydroxysteroid dehydrogenase

Ken Noda; Kunio Shiota; Michio Takahashi

To investigate the regulatory mechanism of 20 alpha-hydroxysteroid dehydrogenase (20 alpha-HSD) (EC 1.1.1.149) activity in ovarian tissue, the enzyme was purified from ovaries of normal mature female rats. Column chromatography of the cytosolic fraction from ovaries on DEAE-Toyopearl 650M revealed two peaks of the 20 alpha-HSD activity at different ionic strengths. These peaks were designated HSD1 and HSD2, respectively. Each of the active fractions was further purified to homogeneity by dye-affinity chromatography using Matrex Green A and AF Red-Toyopearl. Both the fractions appeared as a single band on sodium dodecyl sulfate-polyacrylamide gel electrophoresis (at Mr = 33,000 under reducing conditions). Under non-reducing conditions, similar values were obtained on gel-exclusion HPLC, indicating that the enzyme fractions were single-stranded, monomeric polypeptides. Homogeneous HSD1 and HSD2 were purified 361-fold and 509-fold, respectively, and differed in their substrate preference. The two enzyme fractions had Km values of 4.75 microM and 5.16 microM for 20 alpha-dihydroprogesterone, respectively, and showed almost the same RF values on reverse-phase HPLC and free-zone capillary electrophoresis. However, amino acid composition was slightly different, i.e. lysin content was higher in HSD1 than HSD2. Thus, it was clarified that two types of 20 alpha-HSD with very similar molecular structures are present in the rat ovary.


Experimental Biology and Medicine | 1991

Basic Fibroblast Growth Factor-Like Substance in Nuclei of Male Germ Cells Undergoing Meiosis

Katsushi Suzuki; Takayuki Kamei; Yoji Hakamata; Keiichiro Kikukawa; Kunio Shiota; Michio Takahashi

Abstract The presence of a basic fibroblast growth factor-like immunoreactive substance was demonstrated in the nuclei of germ cells at stages from spermatocyte to spermatid in adult rat testis by using immunohistochemistry with an antibody raised against a synthetic peptide corresponding to residues 1–10 of bovine basic fibroblast growth factor [1–146]. The fluorescence was very weak in the nuclei and cytoplasm of spermatogonia, Sertoli cells, and most of the interstitial compartments, except for capillary endothelial cells. This is the first study to demonstrate the presence of basic fibroblast growth factor-like immunoreactive material in the nuclei of haploid cells in vivo.


Molecular and Cellular Endocrinology | 1991

Effects of activin A on anterior pituitary cells fractionated by centrifugal elutriation

Tetsuro Katayama; Kunio Shiota; Michio Takahashi

We have shown previously that activin A increases the number of immunoreactive follicle-stimulating hormone (FSH) cells. To further investigate the action of activin A, we examined its effects on anterior pituitary cells fractionated by centrifugal elutriation. Before activin A treatment, FSH cells were widely distributed among various fractions; a higher proportion of FSH cells was found in larger cell fractions (fractions 5-9), and a lower proportion in smaller cell fractions (fractions 2-4). After culture of the cells in each fraction with activin A (10 ng/ml) for 72 h, the number of FSH cells in fraction 4 only was significantly (P less than 0.05) higher by 225% than that in cells cultured without activin A. The amount of FSH secreted into the medium was minimal or undetectable in fractions 1-4. However, FSH secretion tended to be, or was significantly (P less than 0.01 in fraction 9), stimulated by activin A in fractions 5-9, in which the numbers of FSH cells were not significantly affected. These results suggest a dual mode of action of activin A on FSH: activin A increases the number of FSH cells in a specific type(s) of middle-sized cell fraction, and stimulates FSH secretion at least from larger cells without affecting the number of FSH cells.


Endocrine Journal | 1994

A cDNA encoding a new member of the rat placental lactogen family, PL-I mosaic (PL-Im).

Mitsuko Hirosawa; Ryuichi Miura; Kwan-Sik Min; Naka Hattori; Kunio Shiota; Tomoya Ogawa


Endocrine Journal | 1993

20α-hydroxysteroid dehydrogenase activity in rat placenta

Kunio Shiota; Hwan-Hoo Seong; Ken Noda; Naka Hattori; Akihiko Ikeda; Atsuo Ogura; S.-I. Itagaki; Michio Takahashi; Toshihisa Ogawa


Biology of Reproduction | 1992

Splenic macrophages enhance prolactin-induced progestin secretion from mature rat granulosa cells in vitro.

Keitaro Yamanouchi; Shigemi Matsuyama; Masugi Nishihara; Kunio Shiota; Chikashi Tachi; Michio Takahashi


Endocrinologia Japonica | 1991

Two Distinct Placental Lactogen-like Substances in Serum during Mid-Pregnancy in the Rat

Naoki Furuyama; Kunio Shiota; Michio Takahashi


Journal of Veterinary Medical Science | 1991

Histochemical localization of inhibin and activin .ALPHA., .BETA.A and .BETA.B subunits in rat gonads.

Kenji Ogawa; Masamichi Kurohmaru; Kunio Shiota; Michio Takahashi; Takao Nishida; Yoshihiro Hayashi


Endocrinologia Japonica | 1991

Characterization of antisera directed against follistatin/activin-binding protein peptides

Sachiko Saito; Kishiko Sugino; Keitaro Yamanouchi; Kyoko Kogawa; Koiti Titani; Kunio Shiota; Michio Takahashi; Hiromu Sugino

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