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Biomedical subjects

K Shirama

Publications and source records attributed to K Shirama.

At least 19 recordsLinked to original sources
PubMed1997

Enhancement of apoptosis in developing chick neural retina cells by basic fibroblast growth factor.

To evaluate the role of various growth factors in naturally occurring cell death during development of the neural retina, we examined the effects of such factors on the nuclear morphology and the size of DNA in cultured chick embryonic neural retina cells. Basic fibroblast growth factor (bFGF) increased internucleosomal cleavage of DNA and nuclear fragmentation in a time- and dose-dependent manner. The effect was inhibited by anti-bFGF antibody, suramin, and cycloheximide. Epidermal growth factor, platelet-derived growth factor, nerve growth factor, tumor necrosis factor-alpha, and dexamethasone had no effect. These results provide evidence that bFGF may eventually act as a lethal factor inducing apoptotic cell death during the development of the neural retina in chick embryo.

Animals↗
PubMed1996

Ultrastructural study on the harderian gland of the rabbit (Oryctolagus cuniculus).

The ultrastructure of the Harderian gland of the rabbit has been studied. The gland can be divided into two lobes (pink and white) by the naked eye. At the microscopic level, their epithelial cells differ morphologically, the vacuoles in the cells of the pink lobe being large, while those of the white lobe, small. In addition to the pink and white lobes, an intermediate area can be distinguished around the boundary between the two lobes on the basis of epithelial cell compositions. The acini on this area consist of two epithelial cell types, one is similar to that found in the white lobe, the second consists of the same cells as the pink lobe Myoepithelial cells are located between the secretory epithelium and its basal lamina. Mast cells, macrophages and plasma cells are found in the interstitial connective tissue of the Harderian gland.

Animals↗
PubMed1996

Influence of serotonergic neurons and of pineal gland on the development of the neonatal androgen sterilization syndrome in the rat.

The effect of the removal of pineal gland, performed in adult age or during perinatal life, was investigated in the neonatal androgen sterility (NA-CEA) syndrome, in combination with drugs acting on serotonergic neurons. Perinatal pinealectomy (Px) was more potent in preventing the development of NA-CEA state than Px performed in the adult age. These data indicate that the masculinized hypothalamus becomes less sensitive to pineal influences during the lifespan. Effect of Px was potentiated by drugs increasing the central serotonergic tone. The results lead to the assumption that pineal hormones are influential on the maturation of serotonergic neurons, which might interfere with the sterilizing property of neonatal androgen treatment during the "critical" period of sexual differentiation.

Animals↗
PubMed1992

Ultrastructural study on experimentally induced ovarian tumors in the rat.

Ovarian tumors induced by intrasplenic ovarian grafting were studied ultrastructurally to obtain the details with particular references to cytoplasmic organelles associated with steroid synthesis. The grafted cells were transformed ultrastructurally at around 7 months following intrasplenic ovarian grafting, in fact, intermediate type of cells were also seen in the grafts at this period. The grafted cells before the transformation showed fine structural evidence of steroid hormone secretions, as indicated by the presence of abundant smooth endoplasmic reticulum, lipid droplets and mitochondria with tubular or vesicular criste. After transformation, the cells, however, had no fine structural features associated with the production of steroid hormones.

Animals↗
PubMed1992

Effect of Harderian gland-derived growth factor on the growth of cornea stromal cells.

To investigate the physiological role of Harderian gland-derived growth factor (HGDGF), the effects of HGDGF and various other growth factors on the growth of cultured guinea pig cornea stromal cells were examined. HGDGF increased the incorporation of [3H]thymidine to 150% of the control (5% fetal calf serum). The combination of HGDGF with fibroblast growth factors (FGFs) or platelet-derived growth factor enhanced the cell growth over that of either growth factor alone, increasing the incorporation of [3H]thymidine to 180 and 190% of the control, respectively. The combination of HGDGF with transforming growth factor (TGF-beta) decreased the growth to 60% of the control, and epidermal growth factor had no effect on the activity of HGDGF. The growth-stimulating activity of HGDGF was inhibited by suramin in a different manner from that of FGFs. These findings suggest that HGDGF binds a specific cell-surface receptor and plays a role in the repair of injured parts of the cornea and in the maintenance of the cornea stromal cells.

Animals↗
PubMed1991

Electron-microscopic studies on the maturation of secretory cells in the mouse Harderian gland.

The porphyrins in the Harderian glands of mice are first detectable at 7-8 days of age in both sexes. Thereafter, the levels show a marked rise during the closed-eye period, reaching a peak around the time of eyelid disjunction and then decrease gradually until day 25. At onset of puberty, the level rises again and exhibits a sexual dimorphism. The development of the Harderian gland was examined by light and electron microscopy in the mouse. Although two types of secretory cells, designated as type A and type B, comprise the glandular epithelium in fully developed glands, the time of neonatal appearance is different between the two. Type A cells first appear on the 5th day of age, while type B cells appear around the 7th day corresponding to the time at which porphyrins are first detected. Results of the investigations suggest that the porphyrins in the Harderian gland of mice may be synthesized mainly by type B cells.

Aging↗
PubMed1988

Fine structure of melanocytes and macrophages in the Harderian gland of the mouse.

The presence of dendritic cells containing melanin granules has been demonstrated employing silver impregnation and electron microscopy in the interstitial tissue of the Harderian gland of the mouse. Two types of melanocytes, either with or without the various developmental stages of melanin granules, were found in the gland. Cells with developing granules were more dendritic and contained a large number of cytoplasmic organelles. The other cells were ellipsoidal or slender in shape and contained few cytoplasmic organelles and a large number of fully melanized granules, but no developing granules. In general, the granules of the Harderian gland melanocytes resembled granules from other organs (particularly the skin of the eyelids). The general size range of the granules was 0.2-0.9 micron. Each granule was enclosed by a membrane. The Harderian gland macrophages contained fully pigmented melanin granules of various sizes. The granules were enclosed by a membrane either singly or in groups. Some of the melanin granules within the phagosomes showed signs of degradation, revealing the underlying matrix.

Animals↗
PubMed1988

Effects of endocrine glands and hormone replacement on the mast cell count of the Harderian gland of mice.

There are marked sex differences in the Harderian gland of the C3H/He mouse strain, the females having a larger number of mast cells than the males as one of the major differences. Mast cell counts of the Harderian gland were made on male mice subjected to combinations of adrenalectomy, gonadectomy and administration of sex steroid hormones. Castration alone caused a significant increase in the count resulting in about three times the number found in intact males. Castration plus adrenalectomy increased the count over 6-fold, to levels close to those found in female mice. Administration of testosterone or estrone to the mice which had been castrated and adrenalectomized prevented the increase, while progesterone treatment had no effect on the count. Although the number of mast cells in the male Harderian gland was necessarily small compared to either the female gland or that of castrated and adrenalectomized males, no obvious dimorphism could be found microscopically.

Administration, Cutaneous↗
PubMed1987

Effects of lighting conditions and of hormone replacement on the level of porphyrins in the rat Harderian gland.

The effects of lighting conditions and/or gonadal secretions on the porphyrins of rat Harderian glands were studied. In female rats, exposure to constant light (= LL) induced a 50% decrease of porphyrin in the Harderian gland. Ovariectomy in these animals caused an increase to levels comparable to those found in intact controls. In males, exposure to constant darkness (= DD) produced a marked increase in the glandular porphyrins together with greatly decreased weights of accessory sexual organs. Further, orchidectomy remarkably increased porphyrin levels in rats kept under conditions of LL or DD. Administration of testosterone propionate to castrated male rats significantly decreased the porphyrin contents in the gland, although estradiol benzoate and progesterone treatments had no effect on the levels. Similar results were obtained in female rats.

Animals↗
PubMed1984

Plasma progesterone concentrations during the estrous cycle, pregnancy, and lactation in the Chinese hamster, Cricetulus griceus.

From vaginal smear and histological observations, Chinese hamster (Cricetulus griseus) exhibited four day estrous cycles and had a gestation period of 20 days. The concentrations of progesterone fluctuated in a biphasic pattern during the estrous cycle with peak values at diestrus and proestrus. The levels of the hormone increased approximately threefold from day five to day eight of gestation, remained elevated until parturition, and then fell precipitously during lactation to levels on day zero of gestation.

Animals↗
PubMed1983

Dissociation of estrous cycle and activity rhythm in rats.

When rats were kept in continuous light there was a time-lag between the onset of activity arrhythmia and that of persistent estrus. When animals showing both arrhythmias in continuous light were kept under a LD 21:3 photoperiod, the activity rhythm returned to normal but the estrous cycle did not.

Activity Cycles↗
PubMed1983

Clearance of materials from breakdown of uterine collagen in mice during postpartum involution.

The collagen content of the mouse uterus increases during pregnancy and rapidly decreases to the level of nulliparous mice within a few days post partum. Most of the hydroxyproline in the uterine collagen had disappeared by day 3 post partum. During postpartum involution the hydroxyproline concentration in both the serum and blood clot was not higher than in nulliparous mice. The total hydroxyproline content in the liver, spleen and thymus was significantly increased during postpartum involution. These results indicate that materials derived from the breakdown of uterine collagen are rapidly removed from the blood stream by reticuloendothelial clearance.

Animals↗
PubMed1982

Development of Harderian gland during metamorphosis in anurans.

Development of Harderian gland of larvae of Rana japonica, Bufo bufo japonicus, and Xenopus laevis was studied. In the adult animals, well-developed Harderian glands were invariably present in the orbit. In Rana and Bufo, the gland first appeared at late prometamorphic stage and in Xenopus it appeared around climax stage. In thyroidectomized tadpoles of Bufo and Rana, the Harderian gland was induced by thyroxine. In hypophysectomized tadpoles of Bufo the gland developed when they were treated with thyroxine or TSH.

Animals↗
PubMed1982

Direct effect of melatonin on the accessory sexual organs in pinealectomized male rats kept in constant darkness.

Pinealectomized and sham-pinealectomized male rats were subcutaneously implanted with 2 cm silicone elastomer capsules filled with testosterone or dihydrotestosterone (DHT) and placed in constant darkness (DD) for 50 days. The data revealed that the sham-pinealectomized group treated with testosterone differed from the pinealectomized group, having lower weights of accessory sexual organs and levator ani muscle. Pinealectomy had no effect on organ and muscle weights of DHT-treated animals. Exposure of male rats to DD resulted in a marked decrease in weights of ventral prostate, seminal vesicle, coagulating gland and levator ani muscle and a decrease in plasma DHT levels. However there was no significant reduction in plasma LH, FSH or testosterone. Pinealectomy of the rats exposed to DD resulted in restoration of both DHT levels and accessory sex organ weights. Melatonin implants in pinealectomized males led to an increase in both testosterone and DHT levels, accompanied by a decrease in sexual organ weights. The data indicate that the anti-gonadal effect of the pineal gland cannot be completely mediated by melatonin and that melatonin and some unknown factors can act at the tissue level to reduce the size and function of the affected sexual organs.

Animals↗
PubMed1981

Influences of some endocrine glands and of hormone replacement on the porphyrins of the Harderian glands of mice.

There are marked sex differences in the Harderian gland of the C3H/He strain of mice. Female (but not male) glands contain large amounts of porphyrin, which are readily visible as solid depositions within the lumina. The histology and porphyrin content of the Harderian gland were examined in intact and in pregnant mice and in mice subjected to combinations of adrenalectomy, gonadectomy and administration of sex steroid hormones. In male mice, castration approximately doubled the amount of porphyrin in the Harderian gland. Castration plus adrenalectomy increased the levels over 30-fold, to levels similar to those found in female mice, although adrenalectomy alone produced no significant effect. Administration of testosterone to the male mice which had been castrated and adrenalectomized prevented the increases while progesterone treatment produced further increases in porphyrins. In intact females, the amount of porphyrin varied with the phase of the oestrous cycle; being lowest during metoestrus and highest during dioestrus. In ovariectomized-adrenalectomized females, the effects of administered sex hormones on the amount of porphyrin in the gland were the same as in males. In pregnant mice, the level was no significantly different from that in intact oestrous animals.

Adrenalectomy↗
PubMed1978

Induction of persistent estrus by constant light: effects of neonatal constant light and Harderian gland function.

The effect of constant light on the age at onset of persistent estrus was compared in rats exposed to constant light since birth (LL-0) and those exposed beginning at 70 days of age (LL-70). Persistent estrus occurred about 27 days later in the LL-0 rats than in the LL-70 rats. Exposure to LL for just the 1st 15 days of life (LL-0-15) and then subsequent exposure to LL at 71 days also delayed the induction of persistent estrus. Neonatal injection of a Harderian gland (HG) homogenate to LL-0-15 rats reduced the age of vaginal opening and 1st estrus and reduced the delayed onset of persistent estrus caused by the neonatal LL. Harderianectomy of LL-0 or hematoporphyrin injections in LL-0-15 rats had no effect on the onset of LL-induced persistent estrus.

Animals↗