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Biomedical subjects

S Daikoku

Publications and source records attributed to S Daikoku.

At least 163 records · Page 9Linked to original sources
PubMed1978

Quantitative observations of the effect of sex-steroids on the postnatal development of LH-cells. An immunohistochemical study.

The effects of sex-steroids on the LH-cell development in neonatal rats were studied. The cells were stained immunohistochemically by applying anti-HCG serum. On the second day after birth some of the animals of both sexes were gonadectomized and simultaneously injected with testosterone or estradiol (50 or 200 microgram). The remaining animals were either gonadectomized or injected with either one of the sex-steroids. The LH-cell numbers in each group were determined on the 12th day of age from serially cut histological sections of the pituitary. In castrated males the number of LH-cells was about twice that of the intact animals. In the so-called sex-zone, LH-cells tended to be hypertrophied in castrates. These alterations in the appearance of LH-cells did not occur after ovariectomy. In gonadectomized animals injected with sex-steroids (200 microgram), the cells were markedly reduced in number and size, both in males and females. Testosterone injection (50 microgram) into intact newborn animals also suppressed the numerical development of LH-cells, especially in females. These alterations were particularly evident in the sex-zone in both sexes. Thus the present findings show that sex-steroids may be involved in sexual differences in morphological development of LH-cells in newborn rats.

Animals↗
PubMed1978

Effects of testosterone and orchiectomy on the development of gonadotrophs in neonatal rats with hypophysial stalk section.

The development of gonadotrophs in newborn Sprague-Dawley rats subjected to a hypophysial stalk section (SS) by an electrical cauterization of the infundibulum of the hypothalamus was examined throughout the first 12 postnatal days. The electrical cauterization of the infundibulum was performed during 24 to 30 h after birth, and the pituitaries were studied by immunohistochemical procedures 11 days later. In several animals orchiectomy or an administration of testosterone propionate (TP) was performed simultaneously with the cauterization. The SS animals showed remarkable retardation in body growth and in pituitary development. In males the development of gonadotrophs was strongly suppressed in number and in size after the cauterization, whereas in females the suppression was less prominent. Orchiectomy promoted the development of gonadotrophs in the SS males, while TP administration suppressed it in the SS females. These findings indicate that there is sexual difference in the neonatal development of gonadotrophs even in the pituitary isolated from the hypothalamus and that testosterone inhibits the development of gonadotrophs at the level of the hypophysis during the neonatal period in rats.

Animals↗
PubMed1977

Sexual difference in LH-cells of the neonatal rats as revealed by immunocytochemistry.

Localization and number of pituitary LH-cells were studied in neonatal male and female rats (from the birth to 12th day) applying anti-HCG serum in immunoenzymological procedures. The cells increased in number with developing age after birth. The cells in males and females were equal in number until 4 days of age, wheres thereafter the increase of the cell number in females exceeded that in males. After birth, the cells are mainly concentrated ventrally, being ventro-lateral in the anterior region but converging into the medial-ventral area in the posterior part of the gland. Some dispersion in a dorsal direction is also noted in the latter region. At birth the cells begin to appear in the dorsal area in the anterior portion, as well as in the posterior portion, particularly in the area close to the intermediate lobe and in the zone adjacent ot the residual lumen. This was particularly evident in females after 4 days of age. Thus it is concluded that in rats the sexual differences in the pituitary become apparent after the 4th day of postnatal life.

Aging↗
PubMed1977

Development of the adrenal medullary cells in rats with reference to synaptogenesis.

The adrenal medullae of rats were studied electron microscopically from day 13.5 of gestation. Synapses with thickening of pre-and post-synaptic membranes were first evidenced on the medullary cells of 15.5-day-old fetuses. They increased gradually in number with advancing age. In the medullary cells, a few membrane-limited granules were recognized on day 13.5 of gestation, and thereafter they increased in number. The appearance of the granules was not uniform; some of the granular contents consisted of fine or coarse particles and others contained homogeneous material of varying electron-densities. The population of these granules in the cytoplasm was different from cell to cell. Thus, the discrimination of cell types (NA-and A-cells) was not possible in the prenatal period. Granular discharge of the cells was totally absent in the normal untreated fetuses. However upon the intraperitoneal administration of insulin to the fetus on day 16.5, 18.5, or 21.5 of gestation, discharge by reverse pinocytosis was first evidenced in the medullary cells of the 21.5-day-old fetus.

Adrenal Medulla↗
PubMed1976

Ultrastructural study on the hypothalamic-hypophysial-adrenal axis in fetal rats.

The adrenal glands of decapitated and encephalectomized fetal rats were investigated electron microscopically and compared to those of normal intact fetal rats. Although the adrenal cortices did not show three zones (zona glomerulosa, fasciculata, and reticularis) on the 16.5th day of gestation when the decapitation or encephalectomy was carried out in utero, the zonation was recognized in fetuses operated on the 21.5th day of gestation. The same was true for normal control fetuses. However, cytoplasmic characteristics suggesting steroidogenesis in the cortical cells were reduced to various degrees in the encephalectomized or decapitated fetuses, especially in the latter ones. The change in cytoplasmic appearance was more conspicuous in the inner portion of the cortex. This result suggests that for the maintenance of normal adrenocortical function the hypothalamus may be indispensable even during the prenatal life of rats.

Adrenal Cortex↗
PubMed1976

Immunohistochemical study on adenohypophysial primordia in organ culture.

Rathke's pouches isolated from rat fetuses on day 12 were maintained in organ culture for 9 days and investigated immunohistochemically to test whether or not the hypothalamus is involved in the cytodifferentiation of the adenohypophysis. The unlabeled antibody enzyme method demonstrated that the cultured tissue contains different types of glandular cells, i.e., adrenocorticotropin (ACTH)-, growth hormone (GH)-, luteinizing hormone (LH)-, thyrotropin (TSH)-, and prolactin-producing cells. Indirect evidence was also obtained to indicate the presence of melanocyte stimulating hormone (MSH)-cells. These findings suggest that adenohypophysial primordial cells of rats start to synthesize their respective hormones without stimuli from the neurosecretory substances of the brain which are known to be essential for the maintenance of the secretory activity of the adult gland.

Adrenocorticotropic Hormone↗
PubMed1976

Efferent projection of the nucleus praeopticus medialis to the median eminence in rats.

Efferent projection from the medial preoptic nucleus, especially to the median eminence, was studied in the rat by light and electron microscopy, in combination with 3H-leucine labelling and electrical coagulation of the nucleus. In the light microscopy autoradiographs of the brain, an ipsilateral distribution of silver grains was followed caudally and dorsally in the periventricular area, into the triangular area between the ventromedial nucleus and the arcuate nucleus, and, further, into the paraventricular and supraoptic nuclei and median eminence. After electrical coagulation of the medial preoptic area, electron microscopy showed numerous degenerated nerve terminals in the external layer of the median eminence. Occasionally, cored vesicles (90 nm mean diameter with a core of 70 nm mean diameter) and clear vesicles (40-50 nm diameter) were encountered in the axoplasm of the degenerated nerve terminals. These findings indicate that the axons of the nerve cells of the medial preoptic nucleus extend caudally, terminating in the external layer of the median eminence.

Animals↗
PubMed1975

Electron-microscopic studies on developing intramural ganglia of the small intestine in human and rabbit fetuses.

Electron-microscopic studies were made on the appearance of synapses in the intramural ganglion (Auerbach) and findings were correlated with the onset and development of intestinal peristalsis in 6- to 30-week-old human and rabbit fetuses from the 12th day after conception until birth. At stage I, in which the small intestine shows no indication of a muscle layer or spontaneous peristalsis, primitive synapses containing several clear vesicles and a few cored vesicles are seen on neuroblasts and their processes (dendrites). At stage II, in which the circular muscle is developed and bidirectional peristalsis occurs, synaptic profiles can be classified into 3 types. Type 1 is the most numerous but seldom shows membrane specificity on the synaptic portion. Types 2 and 3 have small flattened vesicles and small round vesicles, respectively. They are further characterized by thickening of snyaptic membranes and aggregation of small clear vesicles associated with the presynaptic membrane. At stage III, the longitudinal muscle layer develops in the small intestine. At this stage, nerve terminals containing mainly cored vesicles have been observed and classified into types 4 and 5, according to their morphology. At stage IV, antiperistalsis no longer occurs and type 6 nerve terminals in the intramural ganglia can be recognized by their densely packed, large-cored vesicles. The possible physiological significance of the nerve terminals has been discussed.

Animals↗