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Biomedical subjects

T Asai

Publications and source records attributed to T Asai.

At least 595 records · Page 33Linked to original sources
PubMed1977

Transmission and scanning electron microscopy of host cell entry by Toxoplasma gondii.

Entry by tachyzoites of Toxoplasma gondii, the causative agent of toxoplasmosis, into peritoneal cells was investigated with transmission and scanning electron microscopy. The process of entry is initiated by the parasite contacting the host cell with its anterior end, creating a small depression in the plasmalemma of the host cell. Occasionally, a small portion of the host cell cytoplasm protrudes and contaccts the anterior end of the parasite. A cylindrical structure (35 nm in diameter) extends from the pellicle of the parasite to the host cell. Such structures appear to assist host cell entry by T. gondii. As the entry process progresses, pseudopods of the host cell surround theparasite and finally T gondii becomes intracellular, being located in a vacuole separated from the host cell cytoplasm by a unit membrane. (Am J. Pathol 87:285-296, 1977).

Animals↗
PubMed1976

Immunohistochemical localization of LH-producing cells in the adenohypophysis of the Japanese quail, Coturnix coturnix japonica.

The cells that produce luteinizing hormone (LH) in the adenohypophysis of the Japanese quail were identified immunohistochemically using anti-chicken LH serum and horseradish peroxidase-labeled goat anti-rabbit gamma globulin serum. The LH cells are localized in the caudal lobe of the pars distalis. They are elongate in shape shape and are polarized toward the sinusoids, especially in their active states. Alterations in size of LH cells are directly related to changes in circulating LH levels as induced by castration or photostimulation. The LH cells identified immunohistochemically were only stained by alcian blue with periodic acid-Schiff (PAS), alcian blue and orange G. PAS-positive gonadotropic cells in the cephalic lobe were stained immunohistochemically only slightly if at all using anti-chicken LH serum and consequently may be FSH producing cells. In the cephalic lobe another type of basophilic cell was stained with alcian blue. These cells were also stained immunohistochemically with anti-chicken LH serum. These cells may possibly be identified as TSH cells due to the characteristics of the anti-chicken LH serum used in this study which cross react with LH and TSH but only slightly with FSH, and also on the basis of previous light and electron microscopic studies.

Alcian Blue↗
PubMed1975

Ependymal absorption of luteinizing hormone-releasing hormone injected into the third ventricle of the rat.

LRH injected into the third ventricle induced increases of serum LH and FSH in the rat. Following injection of LRH-125I into the third ventricle, autoradiographic grains were concentrated in the ependymal cell bodies and ependymal processes in the median eminence. Aggregations of grains were also found in the capillaries of the portal vessels, and in both sinusoids and parenchymal cells of the adenohypophysis. These findings show that the ependymal cells represent a link between the cerebrospinal fluid and the portal blood.

Animals↗
PubMed1975

Changes in LH-releasing hormone content of the hypothalamus and electron microscopy of the anterior pituitary after prostaglandin E2 injection in rats.

The purpose of this study is to present evidence that prostaglandin (PG) E2 stimulates a release of luteinizing hormone-releasing hormone (LH-RH) from the hypothalmus. In experiment 1, 72 hours after estrogen and progesterone treatment, a solution of 700 mug of PGE2 was injected into the jugular vein. Blood samples for plasma LH and the hypothalamus for LH-RH assay were collected before and 5, 10, and 30 minutes after PGE2 injection and subjected to radioimmunoassay. The total LH-RH content of the hypothalamus decreased from 20.4 to 15.3 ng. at 5 minutes after PGE2 and had returned to the pretreatment level by 30 minutes after PGE2 administration. On the other hand, plasma LH levels increased at 5 minutes, reached a peak at 10 minutes, followed by a decline at 30 minutes after PGE2 injection. In Experiment 2, 10 and 30 minutes after a single injection of PGE2 or synthetic LH-RH, the anterior pituitary were excised for an electromicroscopic study. Ten minute after PGE2, an enlarged Golgi apparatus, well-developed rough endoplasmic reticulum, and decreased secretory granules were observed in pituitary gonadotropins as compared with the control group. These changes were more conspicuous in the pituitaries obtained 30 minutes after PGE2. In Experiment 3, plasma LH levels were determined serially before and 10, 30, 60, and 90 minutes after a single injection of PGE2, LH-RH, or saline. There is a striking resemblance between the PGE2- and LH-RH-treated groups. Plasma LH levels in both these groups reached a peak at 10 minutes and started to decline 30 minutes after PGE2 or LH-RH administration. Our findings would indicate that PGE2 stimulates LH-RH secretion from the hypothalamus.

Animals↗
PubMed1975

Bulk flow in the cerebrospinal fluid system of the dog.

Ventriculo-cisternal, intracranial subarachnoid-to-subarachnoid space and spinal subarachnoid space perfusions were carried out on dogs. The perfusate contained inulin as a tracer and the design of these experiments was based upon the concept that inulin leaves cerebrospinal fluid (CSF) compartments only by means of bulk absorption, and that actual diffusion and active transport of inulin is negligibly small. Inulin was removed from different CSF spaces by bulk absorption at rates which varied linearly with hydrostatic pressure. The rate of formation of CSF is equal to inulin clearance plus the difference between outflow and inflow rates. The total CSF formation in dogs weighing 12 to 17 kg was measured as 0.065 ml/min, and 58.5 per cent of this amount was found to come from extraventricular CSF space. The rates are independent of hydrostatic pressure in the range studied.

Animals↗
PubMed1975

Neural control of LH release in anterior periventriculo-median eminence-pituitary system.

Separate regions of the anterior periventricular area (PVA), median eminence (ME) and frontal cortex from brains of hypophysectomized female and intact male rats were extracted and homogenized. The LH-RH content of these homogenates was determined by a specific double antibody radioimmunoassay. LH-RH was found in the PVA as well as in the ME of both hypophysectomized female and intact male rats; it was not detected in the frontal cortex. Extracellular recordings were made from neurons in the PVA and 55 neurons were activated antidromically by stimulating the ME. This suggests that PVA neurons exist with axons terminating in the ME. It is assumed that these axons are unmyelinated since their conduction velocity was approximately 0.3-0.8 m/sec. In addition to the antidromically-activated neurons, 26 neurons with characteristics of transsynaptic activation were recorded in the PVA following stimulation of the ME. Some of the units recorded from the ME-arcuate (ARC) region were also activated either antidromically or transsynaptically by stimulating the PVA. The effect of PVA stimulation on LH release was tested in ovariectomized, estrogen-treated rats with or without anterior deafferentation of the hypothalamus. Increased LH concentration in serum was elicited by PVA stimulation of rats in which deafferentation was either not performed or not completed; no increase in serum LH level was observed following PVA stimulation in rats with complete deafferentation. These data suggest that PVA neurons synthesize LH-RH, which is released at the ME.

Afferent Pathways↗
PubMed1975

Effects of x-ray irradiation on the subsequent gonadotropin secretion in normal and neonatally estrogenized female rats.

Female rats were irradiated with 190R of X-rays at 10 days of age and sacrificed 4, 7 or 12 months later. Their ovaries were histologically examined and serum levels and pituitary contents of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) were determined by radioimmunoassay. Both serum levels and pituitary contents of LH and FSH rose significantly 4 and 7 months after irradiation, although the ovaries were markedly reduced in weight. On the contrary, 12 months after irradiation, the ovaries increased in weight and consisted mostly of polyhedral, hyperplastic interstitial cell masses, and both LH and FSH in the serum and pituitary were reduced to normal levels. These characteristic changes in the ovarian weight and histological appearance could not be observed in the similarly irradiated animals which were received daily injections of estrone for the first 30 days of postnatal life, i.e., daily injections of 50 mug for the first 10 days, 100 mug for the middle 10 days and 200 mug for the last 10 days. Serum LH levels of the estrogenized irradiated rats at 7 or 12 months of age did not elevate although those of FSH were significantly higher than the non-irradiated intact levels. From these results, a rise in the blood levels of LH and the FSH may be attributed to the increase in weight and the histological changes in the ovaries of the irradiated female rats, and the elevation of only FSh level may not result in the abnormal growth of the irradiated ovaries.

Adrenal Glands↗
PubMed1975

Changes of hypothalamic LH-RF content during the rat estrous cycle.

Anti-LH-RF serum was produced in rabbits by synthetic LH-RF-BSA conjugate prepard with bis-diazotized benzidine. Employing this antiserum, a radioimmunoassay for LH-RF was established with the assay range from 0.8 to 10 ng/ml. Acid extracts of hypothalami from 4 day cycling rats through various stages of the estrous cycle particularly in the afternoon of proestrus were measured for their LH-RF contents. The hypothalamic LH-RF content was high at 10:00 on the day of proestrus and declined until 17:00 and thereafter, the content gradually increased to reach the basal level. Serum LH showed the highest level at 17:00 on the day of proestrus and fell at 21:00 on the same day. Accompaning this change of serum LH level, pituitary LH content began to decrease at 17:00 of proestrus. These results indicate that LH-RF released in the afternoon of proestrus may participiate to stimulate the preovulatory discharge of LH in the rat.

Animals↗