Biomedical subjects

R Yokote

Publications and source records attributed to R Yokote.

7 recordsLinked to original sources

PubMed1992

Light stimulation of the hypothalamic neuroendocrine system.

This paper demonstrates that, in the mediation of light, the suprachiasmatic nucleus (SCN) functionally associates with the anterior periventricular and parvocellular paraventricular neuron systems in rats. Intact rats (group 1) and rats undergoing a hemicomplete cutting of the SCN (group 2) were housed in a dark room (2-3 weeks) and killed after an exposure to light for 10, 30 or 60 min. Other intact animals (group 3) kept in a dark room (2 weeks) were exposed to light for 10 min, then stored 60 min in the dark room, and killed in darkness. The SCN, anterior periventricular nucleus, and parvocellular paraventricular nucleus were examined immunohistochemically using antisera for vasoactive intestinal polypeptide (VIP), arginine vasopressin, somatostatin, rat corticotropin releasing factor (rCRF), and c-fos protein. In comparison with animals kept in darkness, animals exposed for 10 and 30 min to light indicated a remarkable reduction of VIP immunoreactivity in the SCN and some increase of CRF immunoreactivity in the parvocellular paraventricular nucleus. The diminution of VIP immunoreactivity did not occur in the isolated SCN of group 2 animals. In group 3, a 10 min-light exposure induced a remarkable enhancement of nuclear c-fos immunoreactivity in neurons in the ventrolateral region of the SCN, in the anterior periventricular nucleus, and in the parvocellular paraventricular nucleus, most strongly in the SCN. Double immunolabeling methods have shown that VIP, somatostatin, and CRF neurons in the respective nuclei were c-fos positive.

Animals↗

PubMed1991

Further evidence of the presence of rat embryonic hypothalamic factors that induce the differentiation of gonadotrophic hormone-releasing hormone-containing secretory neurons.

We examined the presence of factor(s) in the embryonic medial basal hypothalamus (MBH) that may influence nasal placode (NAP)-derived luteinizing hormone-releasing hormone (LHRH) neurons in determining their secretory phenotype. In this study, we performed organotypic culture and transplantation of the NAP from 12.5-day-old embryos of rats and vomeronasal organ (VNO) from 14.5-day-old embryos. Surgical operations, however, were performed on 16.5-day-old embryos. The NAP and VNO were cultured singly or with the MBH obtained from the embryos of the same age and, further, in a medium with a nerve growth factor or fibroblast growth factors. Although LHRH neurons were derived from the NAP and VNO in all the cultures, judging from numbers and cellular morphologies, the MBH was most effective. The VNO was transplanted into the third ventricle of adult female rats singly or with the cerebral cortex, the mesencephalon-myelencephalon complex, or the MBH from 14.5-day-old embryos. All the grafts gave rise to LHRH neurons, but the number of the neurons was far greater in the grafts cotransplanted with the MBH, in which the neurons projected long processes to blood capillaries and formed neurovascular complexes, the feature of which may suggest the occurrence of the secretory activity in the fibers. The animals were examined 5 days after the surgical operations. In rhinoectomized embryos, LHRH neurons were distributed throughout the brain in the same pattern as found in intact rats, showing normal cellular morphology. In the encephalectomized rats, immunoreactive LHRH cells were present only in the terminal ganglia. These findings indicate that the embryonal MBH has a factor (s) that is essential to the development of secretory LHRH neurons.

Animals↗

PubMed1991

Immunohistochemical localization of glucocorticoid receptors in anterior pituitary cells of rats.

Adenohypophysial cells having a glucocorticoid receptor were immunohistochemically determined in rats. For detecting the presence of the glucocorticoid receptor, we used the monoclonal antibody for a glucocorticoid receptor (BuGR-2), and immunohistochemically examined the phenotypes of the cells that exhibited BuGR-2-immunoreactivity. The immunoreaction for the glucocorticoid receptor was confined to the nuclei of the majority of corticotrophs (70%) and of some somatotrophs in intact animals. Following adrenalectomy, all corticotrophs became significantly hypertrophic, losing their immunoreactivity for the glucocorticoid receptor. In contrast, somatotrophs that had also lost the immunoreactivity for the glucocorticoid receptor in the nuclei greatly diminished in size. Intraperitoneal administration of corticosterone was performed in adrenalectomized animals to supplement glucocorticoids. This treatment restored BuGR-2-immunoreactivity in the nuclei of some corticotrophs. In intact rats, immunolabeled corticotrophs were classified into two types, stellate and polyhedral. However, the immunoreaction for the glucocorticoid receptor was equally evident in the cell nuclei of these different types of cells. It is concluded that, in rats, both corticotrophs and somatotrophs are target cells of glucocorticoids, although these cell types display opposite growth responses to the removal of glucocorticoids.

Adrenalectomy↗

PubMed1990

Development of the dorsal pancreatic primordium transplanted into the third ventricle of rats.

The dorsal pancreatic primordia of 12.5-day-old rat embryos transplanted into the third ventricle of adult female rats were immunohistochemically examined 10, 20 and 40 days after transplantation. On day 10, the grafts grew into an epithelial sacculus (S) with a thick subepithelial tissue (ST). Tubular and vesicular structures with a single cuboidal epithelium were found within the wall of the S, but they underwent thereafter a regression without allowing the primordia to differentiate into the exocrine acinar tissues. In contrast with this, pancreatic hormone-containing cells existed in the ST, and were arranged like the islands of a mature animal. The tissue also has smooth muscle fibers and neurons. When the primordium was grafted along with its root connected to the duodenum, gut-like tubular structures differentiated, showing mucosa with villi and crypts, submucous mesenchymal tissue and muscle layers. The mucosa possesses epithelial cells immunoreactive for the pancreatic hormones, and the muscle layers have the myenteric plexuses. These findings seem to provide further evidence that in the rat pancreas, pancreatic-hormone-containing cells differ from the acinar cells in origin.

Animals↗

PubMed1990

Appearance of neurons with glucocorticoid receptors and neurovascular links in the embryonal rat hypothalamus grafted in the third ventricle.

We have investigated the appearance of the transmitter phenotypes of hypothalamic neurons in grafts transplanted into the third ventricle of adult female rats. The grafts were the mediobasal hypothalamus and the preoptic area of 12.5-day-old rat embryos, and were examined 40-100 days later. Wheat germ agglutinin (WGA) was injected into the jugular vein of several animals for the examination of the existence of neurovascular associations. Three days after the injection, WGA appeared to have been incorporated into the neurons in the paraventricular, periventricular, and arcuate nuclei of the host animals. In the grafts, WGA was also seen incorporated in certain neurons which were found immunoreactive for tyrosine hydroxylase (TH), rat corticotropin-releasing factor (rCRF), substance P (SP), or somatostatin (SRIH). Neurons immunoreactive for neuropeptide Y (NPY) and ACTH did not seem to incorporate WGA. These findings suggest that the neurons containing TH, rCRF, SP, or SRIH link with fenestrated capillaries developed in the grafts. The immunoreactivity for glucocorticoid receptor (GR) was detected mainly in the nucleus of certain neurons and glial cells in the grafts as well as in the host hypothalamic neurons. In the grafts, strong GR immunoreactivity was detected in the cells immunoreactive for TH, NPY, and rCRF as in the host animals. It is concluded that the undifferentiated hypothalamic neurons differentiate to synthesize GR as well as definitive peptides and TH in the grafts.

Animals↗

PubMed1990

The familial occurrence of bullous mastocytosis (diffuse cutaneous mastocytosis).

We studied four patients (a mother, her two daughters, and her son) with bullous mastocytosis, or diffuse cutaneous mastocytosis, whose genetic inheritance suggested an autosomal dominant pattern. The clinical characteristics included extensive bullae, numerous urticaria, pruritus, flushing, and pseudolichenified skin over all body surfaces without systemic organ involvement. The histopathologic findings disclosed a pronounced accumulation of mast cells in the dermis. Electron microscopic studies of lesional skin obtained in infancy showed round or spindle-shaped mast cells with numerous fingerlike villous protrusions. The cytoplasmic granules varied in size and shape, and the appearance of degranulation was markedly noted. In the adult, most mast cells had markedly decreased numbers of granules and cytoplasmic villi. Some cells displayed degenerative or necrotic appearances. These findings correlated well with the clinical course of these cases, which improved spontaneously over time.

Adult↗

PubMed1989

Hypothalamic neurons from a developmental aspect.

The development of hypothalamic neurons was examined in vivo and in transplanted grafts in rats. The neurons appeared in vivo in distinctive chronotopical schedules showing such morphological characteristics as synaptocrine or hemocrine neurons. These phenotypical properties seemed to be primed already by day 12.5 of gestation in rats, because the grafted hypothalamic primordia from 12.5-day-old embryonal rats differentiated neurons, which express these neuronal properties in the third ventricle of adult female rats. The synaptocrine neurons projected to other neurons, suggesting the establishment of synaptic contacts, and the hemocrine neurons projected to vasculatures developed in the grafts, suggesting the accomplishment of neurovascular associations.

Animals↗