Search Results

You are looking at 1 - 4 of 4 items for

  • Author: T Sakai x
  • Refine by Access: All content x
Clear All Modify Search
Restricted access

K. Inoue, T. Sakai, and M. Hattori


Both native and recombinant basic fibroblast growth factor (FGF) exerted a marked effect on the morphology of a pituitary clonal somatotroph-like cell line (MtT/S) in vitro. Addition of 10 pg–20 ng bovine basic FGF/ml caused the cells to flatten and spread out over the culture dish, the cells showing strong surface contact. Those in contact with the culture dish were epithelial in appearance, being polygonal, closely apposed and forming a pavement-like monolayer. Basic FGF inhibited cell proliferation in a dose-dependent manner at the higher concentrations tested (0·5–20 ng/ml). This cell-adhesive effect of basic FGF was also observed in normal dispersed pituitary cells. The observed stimulation of pituitary cell adhesion is the first report of a morphological effect of basic FGF on pituitary cells and could explain the physiological significance of basic FGF and its high concentration in the pituitary gland.

Journal of Endocrinology (1991) 130, 381–386

Restricted access

T. Harigaya, S. Sakai, K. Kohmoto, and Y. Shoda

Regulation of mammary prolactin receptors by steroid hormones was investigated in ovariectomized mid-pregnant mice. Ovariectomy increased the number of mammary prolactin receptors per cell with no effect or a slight decrease in dissociation constant (K d). The simultaneous removal of adrenals prevented this increase in numbers. A single injection of glucocorticoid (corticosterone or cortisol) in ovariectomized–adrenalectomized mice restored the number of prolactin receptors in mammary glands to the same level as that in ovariectomized controls without changing the K d. Aldosterone, deoxycorticosterone and oestradiol did not affect the number of mammary prolactin receptors after ovariectomy–adrenalectomy. Serum concentration of prolactin was not influenced by the hormone manipulation except with injections of oestradiol or cortisol and apparently did not correlate with the number of prolactin receptors. These results indicated that glucocorticoids are required for the increase in the number of mammary prolactin receptors induced by ovariectomy in mid-pregnant mice.

Restricted access

N. Koibuchi, S. Matsuzaki, H.-T. Ma, M. Sakai, and S. Yamaoka


The effect of testosterone on the activity of ornithine decarboxylase (ODC), its protein level and immunocytochemical distribution were examined in the mouse kidney. Male BALB C mice at 8 weeks of age were used throughout. Fourteen hours before death, they received a subcutaneous injection of testosterone (1 mg/animal) or solvent to measure renal ODC activity or to detect the distribution of ODC immunoreactivity in the kidney. Renal ODC activity and the content of the enzyme were markedly increased after testosterone treatment. Histologically, few cells that were obviously immunoreactive to ODC were observed in the control animals and in the testosterone-treated animals a marked increase in ODC immunoreactivity was observed only in the cortex. ODC immunoreactive cells were located diffusely in the proximal tubule. In the pars recta, cells were stained weakly and homogeneously, while in the pars convoluta, the luminal surface of the cells showed stronger immunoreactivity. Moreover, many granule-like particles that were strongly ODC immunoreactive were observed inside the lumen of the pars convoluta. These results show that testosterone treatment induces an increase in ODC content in certain cells located in the proximal tubule of the cortex.

Journal of Endocrinology (1993) 136, 85–89

Free access

I Sakata, T Tanaka, M Matsubara, M Yamazaki, S Tani, Y Hayashi, K Kangawa, and T Sakai

Ghrelin was recently isolated from the rat stomach as an endogenous ligand for the GH secretagogue receptor. Although it is well known that a large amount of ghrelin is produced in the gastrointestinal tract, developmental changes in ghrelin mRNA expression and differentiation of ghrelin-immunopositive (ghrelin-ip) and mRNA-expressing (ghrelin-ex) cells in the stomach have not been elucidated. In this study, we therefore investigated the changes in ghrelin mRNA expression levels and in the numbers of ghrelin-ip and -ex cells in the stomachs of 1- to 8-week-old male and female rats by Northern blot analysis, immunohistochemistry and in situ hybridization. Northern blot analysis showed that the level of weak ghrelin mRNA expression was low in the postnatal period but then increased in a dimorphic pattern, i.e. transient stagnation at 4 weeks in the male rats and at 5 weeks in the female rats. The number of ghrelin-ip and ghrelin-ex cells also increased after birth, and more numerous ghrelin cells were found in female rats than in male rats, and this finding was confirmed by Northern blot analysis. Ghrelin-ip and -ex cells first appeared in the glandular base of the fundic gland and then they were found in the glandular base and the glandular neck at 3 weeks of age, suggesting that the distribution of ghrelin cells is extended from the glandular base to the glandular neck during the postneonatal development period. This is the first report on detailed changes in postneonatal ghrelin expression level and in the number of ghrelin cells in the rat stomach. The sexual dimorphism of ghrelin expression and ghrelin cell differentiation suggest that ghrelin plays an important physiological role in the stomach.