Search PubMed⌕ Search

Biomedical subjects

S Daikoku

Publications and source records attributed to S Daikoku.

At least 145 records · Page 8Linked to original sources
PubMed1983

Location of thyrotropin-releasing hormone-like immunoreactivity in rat pancreas.

The location of TRH-like immunoreactivity (TRH-LI) was determined in developing rat pancreas (20.5 and 22.5 days of gestation, 1, 3, and 8 days, and 3 months after birth). The pancreatic tissue was freeze-dried and fixed in acrolein or paraformaldehyde vapor, and paraffin sections (2 microns) were prepared for immunostaining. TRH-LI was detected only in the islets. On day 20.5 of gestation, a few cells contained TRH-LI. During development, cells bearing TRH-LI increased in number and were most numerous in the early neonatal period (1-3 days). Then their number decreased again from 8 days after birth; in adult rats the immunoreactivity was too weak to allow identification of TRH-LI-positive cells. The topographical relation of TRH-LI with other islet hormones was studied in serial sections from perinatal rats stained with different antisera. TRH-LI was found in almost all cells containing insulin and in some containing glucagon, but not in those containing somatostatin.

Aging↗
PubMed1983

Topography and ultrastructure of LHRH- and somatostatin-containing axonal terminals in the median eminence of rats.

The topography and ultrastructure of LHRH and somatostatin nerve fibers in the median eminence in male rats were investigated with special reference to the relation between the fiber terminals and the perivascular space of the portal capillaries. Vibratome sections taken from the rostral and preinfundibular portions of the median eminence were immunostained with anti-LHRH or anti-somatostatin serum before plastic embedding for electron microscopy. In the external layer of the median eminence, the LHRH fibers did not directly contact the perivascular space, although they were in close proximity to the external surface of the median eminence. On the contrary, somatostatin fibers divided into branches in the external layer of the median eminence and terminated in direct contact with the perivascular space in the median eminence. LHRH fiber terminals contain immunoreactive granules, whereas somatostatin fibers are characterized by the presence of synaptic vesicle-like structures, vesicle ghosts and immunoreactive granules in their terminals. These topographical and ultrastructural differences might be regarded as a morphological manifestation of different mechanisms in the release of neurohormones.

Animals↗
PubMed1982

Immunohistochemical studies of intrahypothalamic somatostatin-containing neurons in rat.

Intrahypothalamic somatostatin-containing neurons were investigated immunohistochemically. In intact rats, immunoreactive cell bodies appeared in the rostral periventricular area, and immunoreactive beaded fibers were observed to terminate in the median eminence and to form delicate networks surrounding immunonegative cell bodies within the medial preoptic, suprachiasmatic, arcuate, ventromedial and premammillary nuclei. Intraventricular colchicine infusion resulted in the appearance of immunoreactive cell bodies in the arcuate, ventromedial and suprachiasmatic nuclei, and an increase in the number of cell bodies seen in the periventricular area. Complete deafferentation of the medial-basal hypothalamus excluding the rostral periventricular area caused the immunoreactive structures in the median eminence to disappear and enhanced the staining of periventricular cell bodies. In the arcuate and ventromedial nuclei, the immunoreactive fiber networks were left intact and the immunoreactive cell bodies were occasionally recognized. Horizontal knife cut between the arcuate nuclei and median eminence did not alter immunoreactivity in either region. Neonatal administration of MSG caused only the disappearance of arcuate nuclei. The results indicate that two kinds of somatostatin neuronal systems exist in rat hypothalamus: one is involved in the production of hormonal somatostatin and the other serves for the regulation of neuronal activities in restricted hypothalamic nuclei.

Animals↗
PubMed1982

Immunoreactive ACTH/beta-endorphin neurons in the tubero-infundibular hypothalamus of rats.

In the preinfundibular portion of male rat hypothalamus, the arcuate-median eminence region was examined after staining with anti-porcine ACTH 1-39 serum. In several cases, anti-beta-endorphin serum was also employed. Both sera stain the same cell bodies. The cell bodies of the immunoreactive neurons are scattered in the subependymal layer, arcuate nucleus and lateral tuberal region. Fibers originating from these cell bodies are distributed extensively throughout these regions. They make synaptic contacts on immunonegative fibers in the arcuate nuclei, or terminate directly in the perivascular space in the internal layer of the median eminence. The findings suggest that the ACTH/beta-endorphin neuronal system may serve neuronally and humorally as an intrahypothalamic constituent of the hypothalamic pituitary regulation system.

Adrenocorticotropic Hormone↗
PubMed1982

Ontogenetic appearance of immunoreactive endocrine cells in rat pancreatic islets.

Chronological development of immunoreactive, pancreatic endocrine cells was immunohistochemically studied in rats. The first immunoreaction occurs for glucagon on day 11.5 and for insulin on day 12.5 of gestation, respectively, in the cells located within the cap-like or tubular pancreatic primordium derived from the gut wall. Immunoreactive somatostatin cells appear first at the periphery of primitive islets on day 15.5. On day 18.5, the cells of the primitive islets obtain their definite arrangement and the islets are now separated from the tissue of the exocrine pancreas. Decapitation or encephalectomy performed on day 16.5 embryos fails to influence the ensuing further development of endocrine pancreas. This suggests that the hypothalamus or pituitary does not play an essential role in the histogenesis of the pancreatic islets.

Animals↗
PubMed1982

Immunohistochemical demonstration of LHRH-neurons in young rat hypothalamus: light and electron microscopy.

Localization and ultrastructural appearance of immunoreactive LHRH neurons were studied in 2-, 8- and 21-day-old rats. The lower half of the diencephalon including the septo-preoptic area was serially cut at 10 microns in the frontal plane, and all sections stained with an anti-LHRH serum were examined light microscopically. Although the antiserum could not demonstrate LHRH-immunoreactive perikarya in adult rats, they were stained in these young rats. The immunoreactive perikarya were scattered in the following regions: nucleus tractus diagonalis, medial septum, medial preoptic area, lateral septum, lateral preoptic area, tuberculum olfactorium, suprachiasmatic area, supraoptic area, pericommisural area, anterior commissure, vascular organ of the lamina terminalis (OVLT), lateral hypothalamic region and lateral tuberal region. The first three regions contained many cells but others showed only sporadical cells. The cells were most frequently observed in 8-day-old rats. Most of the cells appeared to be bipolar showing two immunoreactive processes. Electron microscopy observation was made using the section prepared by a pre-embedding technique. In the immunoreactive perikarya, secretory granules, ribosomal particles, and the particles on the outer surface of endoplasmic reticulum appeared to be immunoreactive, but the Golgi area was immunonegative. The secretory granules appeared along the cytoplasmic membrane but were surprisingly few in number. By contrast, the immunoreactive nerve terminals in the median eminence and in the OVLT contained many granules. These findings suggest that LHRH produced in the perikarya is prompted to be transported and stored in the axonal terminals.

Aging↗
PubMed1981

Development of the hypothalamic-hypophysial-gonadotrophic activities in fetal rats.

Pituitary responsiveness to LHRH and anti-LHRH serum was investigated in fetal rats aged 18.5-22.5 days. Synthetic LHRH injection in utero into fetuses brought about a remarkable depletion of pituitary-LH with a corresponding increase of serum-LH on day 18.5. On the contrary, anit-LHRH serum administration to day-20.5 fetuses caused a significant augmentation of pituitary-LH 1 day later. These data indicate that LH-gonadotrophs respond to LHRH even on day 18.5, and that endogenous LHRH begins to affect LH gonadotrophs on day 20.5.

Animals↗
PubMed1981

Electron microscopic study of immunoreactive LHRH perikarya with special reference to neuronal regulation.

In early postnatal rats, immunoreactive LHRH perikarya in the preoptic area were studied by light and electron microscopy. Synaptic junctions were found between the immunoreactive perikaryon or its process, and the immunonegative nerve fibers. The significance of these synapses is discussed in relation to possible mechanisms by which the activities of LHRH neurons are regulated.

Animals↗
PubMed1981

Immunohistochemical demonstration of LHRH neurons and their pathways in the rat hypothalamus.

LRHR neurons and fiber tracts have been studied immunohistochemically in rats. After the intraventricular infusion of colchicine, a number of immunoreactive LHRH neurons were consistently evident in the preoptico-septal area and in the diagonal band of Broca. The immunoreactive fiber tracts originating in those areas were classified into two groups: preoptico-terminal and preoptico-infundibular tracts. The former terminated in the OVLT. The latter was further divided into the mediobasal and laterobasal tracts; both were found to terminate in the median eminence. The mediobasal tract ran posteriorly through the ventral portion of the lateral periventricular area. The laterobasal tract ran posteriorly in the medial forebrain bundle and was accompanied by several immunoreactive neurons. The immunoreactive cell bodies were further scattered in the base of the tuberal hypothalamic area. An anterior bilateral Halász cut in the retrochiasmatic region was followed by a great reduction of the immunoreactive materials in the median eminence and by the appearance of the immunoreactive perikarya and in the preoptico-septal area and in the diagonal band of Broca. A horizontal hypothalamic cut, on the other hand, which disconnected the tubero-infundibular tract between the median eminence and the arcuate nuclei, caused neither reduction of the immunoreactive materials in the median eminence nor appearance of the immunoreactive perikarya in the arcuate nuclei. Those results indicate that the bulk of the immunoreactive LHRH is synthesized in the anterior hypothalamic area and transported by the preoptico-terminal and -infundibular tracts but a minor part is produced in the cell bodies located in the basal tuberal hypothalamus and transported to the median eminence.

Afferent Pathways↗
PubMed1981

Topographical appearance of adenohypophysial cells with special reference to the development of the portal system.

To determine whether or not the portal vessels play any essential role on the cytogenesis of adenohypophysis through the mediation of hypothalamic neurohormones, chronological and topographical relations between the portal system and adenohypophysial cells have been studied in fetal rats aged from 14.5 to 18.5, by vascular infusion with India ink and by immunohistochemistry. On day 14.5 the intraglandular fossa (Atwell's recess) receives several blood vessels (primitive portal vessels) from the subtuberal capillary plexus and a pair of fine branches from the internal carotid arteries: those blood vessels anastomose within the recess. On day 15.5 the recess becomes narrow but the vasculature extends posteriorly into the growing anterior wall of the rathke's pouch, in which they sprout short branches showing terminal dilations. Immunoreactive ACTH cells first appear in the ventral-middle portion of the pars distalis, where the vascular sproutings are not evident. On day 16.5 the intraglandular blood vessels spread through the pars distalis and connect occasionally with extraglandular venous system suggesting the initiation of the hypophysial portal circulation. TSH cells first appear sporadically in the posterior part of the pars distalis, where blood vessels are still scarce and very occasional cells abut on te sinusoids. On day 17.5, the recess becomes indistinct and pituitary acquires the mature shape. The intraglandular vasculature of the portal system makes a dense meshwork in the adenohypophysis except the pars intermedia. LH cells appear first in the ventral region of the anterior half of the adenohypophysis, where occasional cells appear abutting on the sinusoids. The conclusion is that the portal blood supply, which might convey hypothalamic neurohormones, is not essential or initial cytogenesis of the adenohypophysial cells studied here.

Animals↗
PubMed1980

Light and electron microscopic observation on the appearance of immunoreactive LHRH in perinatal rat hypothalamus.

The appearance and localization of LHRH were studied in the developing hypothalamus of perinatal rats using the unlabelled antibody method. By light microscopy, immunoreactive LHRH was first detected as brown dots on day 18.5 of gestation in the OVLT and on day 19.5 in the median eminence, respectively. When the median eminence was examined by the preembedding immunohistochemistry technique for electron microscopy, the occurrence of immunoreactive LHRH fibers could be demonstrated on day 18.5. These fibers were thin and very occasionally encountered near the surface of the lateral regions of the median eminence. The axoplasm contained a few immunopositive secretory granules and also extragranular immunoreactive products. With development, a gradual increase was noted both in number and size of nerve fibers with a concomitant accumulation of secretory granules within the axoplasm. A possible physiological significance of LHRH is discussed in relation to the onset of hypothalamo-hypophysial system in fetal life.

Animals↗
PubMed1980

Studies on the development of hypothalamic regulation of the hypophysial gonadotropic activity in rats.

Development of the hypothalamic regulation of gonadotrophs has been studied in rats. Pituitaries of rat fetuses were cut serially at 4 micrometer in the coronal plane, and every 5th section was mounted and stained immunohistochemically with anti-HCG serum. Sum total of the numbers of the immunoreactive cells in each section was used as an index of the number of gonadotrophs of the pituitary. Anti-rLH, anti-rLH beta, anti-rFSH, anti-rTSH and anti-rTSH beta sera were also applied additionally for staining. The anti-HCG serum-positive cells were first evident on day 17.5 of gestation, and the cells reacting for anti-rLH and anti-rLH beta sera started also to appear. On day 19.5, very few cells appeared to react for anti-rFSH serum. Intraperitoneal injection of LHRH to the fetuses induced a remarkable disappearance of the immunoreactive materials, and as a result a numerical reduction occurred in the immunoreactive cells. These phenomena were noted even on day 18.5 of gestation. Encephalectomy of day 16.5 fetuses and daily i.p injection of anti-LHRH serum to 17.5 to 19.5 day old fetuses were carried out with the purpose of blocking the effect of endogenous LHRH to fetal pituitary. Dense staining of the cytoplasm and remarkable reduction in size and in number of gonadotrophs were obtained after day 20.5 of gestation in both animal groups. These findings suggest that the hypothalamus may start to govern virtually the hypophysial gonadotrophs on day 20.5 of gestation in rat.

Animals↗
PubMed1978

In vivo and in vitro studies on the appearance of LHRH neurons in the hypothalamus of perinatal rats.

Ontogenetic development of LHRH-containing neurons was studied by fluorescence and enzyme immunohistochemistry in rats. In in vitro studies, the tissues of the septal-chiasmatic and mediobasal hypothalamic areas of fetal rats on day 16.5 or 18.5 of gestation were trypsinized separately for dissociation of the neural cells, and cultured for several days. Immunopositive reaction against LHRH was first detected in nerve cells derived from both areas of the hypothalamus of the fetuses on days 16.5 and 18.5 of gestation, after 8 and 6 days culture, respectively. The cells were small, and seemed to be bipolar in morphology indicating an axon and arborized dendrites. Immunopositive material occurred in the cell soma as well as in the cellular processes. In in vivo studies, immunopositive material, possibly deposited in nerve fibers, appeared first in OVLT and simultaneously in the external layer of the median eminence of fetuses on day 20.5 of gestation. The immunoreactive fibers increased in number of both parts with development, especially after birth in the median eminence. No immunopositive material was detected within any neural cell bodies nor in the cytoplasm of any ependymal cells.

Animals↗