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Biomedical subjects

A Miyake

Publications and source records attributed to A Miyake.

At least 271 records · Page 15Linked to original sources
PubMed1985

Suppressive effect of prolactin on oestrogen-induced secretion of LH by sequentially perifused rat hypothalamus-pituitary.

The effect of prolactin (Prl) on oestrogen-induced gonadotrophin secretion was examined in vitro in a sequential double chamber perfusion system. As control groups, mediobasal hypothalamus (MBH)-pituitary pairs or pituitaries without the MBHs were perifused with Medium 199. As an experimental group, MBH-pituitary pairs were perifused with Medium 199 containing 1 micrograms/ml of rat Prl. These groups were stimulated with 10(-7) M oestradiol-17 beta (E2) for 30 min, and luteinizing hormone (LH) in the serial fractions of effluent was measured. In the control group of MBH-pituitary pairs perifused with medium without Prl, secretion of LH began to rise within 30 min after the beginning of stimulation, reached a peak 30 min after the end of stimulation and then remained at a plateau for the rest of the experimental period, whereas in the control group of pituitaries alone no significant response was observed. In the experimental group perifused with medium containing Prl, LH-secretion showed peaks 20 and 80 min after the end of E2-stimulation, respectively, and the first peak was significantly (P less than 0.01) less than the level in the control group. These data demonstrate that Prl at this concentration suppressed the rapid LH release induced by E2. Its site of action is suggested to be at the hypothalamic level, and its possible mechanism of action is discussed.

Animals↗
PubMed1985

Epidermal growth factor stimulates secretion of rat pituitary luteinizing hormone in vitro.

The effects of epidermal growth factor (EGF) on pituitary luteinizing hormone (LH) release and on the releases induced by oestradiol (E2) and LH-releasing hormone (LRH) were examined in a sequential double chamber perifusion system. In this system the mediobasal hypothalami (MBH) and/or pituitaries excised from normally cycling female rats in dioestrus were perifused with test media. Perifusion with EGF at 1 ng/ml for 30 min induced significant release (80-100% increase, P less than 0.05) of LH from hypothalamo-pituitary pairs, but not from the pituitary alone. Perifusion of the pituitary alone with medium containing 1 ng/ml EGF, resulted in significant release of LH (70-140% increase, P less than 0.05) after administration of 10(-7) M E2, but did not significantly influence LH release in response to 20 ng/ml LRH. These findings suggest that EGF may be involved in the regulation of pituitary gonadotrophin secretion by a direct effect on the hypothalamus and indirectly by increasing the pituitary responsiveness to E2.

Animals↗
PubMed1985

Possible site of negative and positive feedback action of oestrogen on gonadotrophin secretion in normal women.

For determination of the site of action of oestrogen (E) during the negative and positive feedback phases of gonadotrophin secretions, studies were made on the pituitary response to a small amount of LRH and the pulsatility of gonadotrophins after E administration in normal cycling women in the mid-follicular phase. The pituitary responses to an iv bolus of 2.5 micrograms of synthetic LRH were evaluated by measuring serum LH and FSH 2 h before and 8 h after administration of 20 mg of conjugated E (Premarin). In the next cycle, the pituitary responses to a same dose of LHRH were also observed 2 h before and 56 h after E injection. The mean levels of serum LH and FSH and the peak responses to LRH were significantly (P less than 0.05) decreased 8 h after E injection, but were significantly (P less than 0.05) increased 56 h after E administration. In the third cycle, the pulsatility of gonadotrophins was evaluated by measuring serum LH and FSH every 15 min for 180 min before and 8 h and 56 h after E injection. The pulse frequencies of gonadotrophins were not significantly different before and 8 h and 56 h after E injection. The amplitudes of pulses 56 h after Premarin injection were significantly higher than those before the injection. These findings suggest that the negative and positive feedback effects of E on gonadotrophin secretion may be caused, in part, by its direct action on the pituitary response to LRH.

Adult↗
PubMed1985

Prolactin inhibits oestradiol-induced luteinizing hormone release at the pituitary level.

The direct action of prolactin (Prl) on pituitary LH secretion was studied by examining its effect on oestradiol (E2)-induced luteinizing hormone (LH) release from the rat pituitary in a perifusion system and determining the oestrogen receptor (ER) content of the pituitary in hyperprolactinaemic female rats. When the pituitary from rats in pro-oestrus was perifused with medium alone, 10(-7) M E2 significantly (P less than 0.05) increased the LH concentration in the effluent by 60-130% of the basal level, but in medium containing 1 microgram/ml Prl it did not cause LH release. In hyperprolactinaemic rats produced by implanting 2 anterior pituitary glands under the kidney capsule, the ER content of the cytosol of the pituitary (53.2 +/- 2.9 fmol/pituitary) was significantly increased (P less than 0.05), but that of the nuclei (6.8 +/- 0.2 fmol/pituitary) was significantly decreased (P less than 0.05) compared with the contents in rats in pro-oestrus. These data suggest that Prl has a direct suppressive effect on LH secretion from the pituitary in the rat, and that decreased translocation of ER into the nucleus might relate to impaired LH release by E2 from the pituitary of hyperprolactinaemic rats.

Animals↗
PubMed1985

Decrease of LRH receptors in the pituitary gland in streptozotocin-induced diabetic rats.

In studies into the mechanism of anovulation in the diabetic condition, the LRH receptor content of the pituitary gland of rats with diabetes mellitus was determined. Normal female rats weighing 180-200 g were injected iv with either streptozotocin (6 mg/100 g body weight) or vehicle in dioestrus of the oestrous cycle. The rats were sacrificed by decapitation 9 days after treatment, and serum LH concentrations and the LRH content of the medial basal hypothalamus (MBH) were measured by radioimmunoassay (RIA), and the LRH receptor content of the pituitary gland was determined. The serum concentration of LH and the LRH content of the MBH in diabetic rats were 34.4 +/- 4.8 ng/ml (mean +/- SEM) and 2.05 +/- 0.04 ng/MBH, respectively, which were similar to the respective values of normal rats in dioestrus. However, the LRH receptor content of diabetic rats (13.2 +/- 3.9 fmol/pituitary) was significantly (P less than 0.05) lower than that of normal rats in dioestrus (68.0 +/- 7.1 fmol/pituitary) and pro-oestrus (59.4 +/- 13.6 fmol/pituitary). These results suggest that anovulation in diabetic rats is at least partly attributable to a low content of LRH receptors in the pituitary gland.

Animals↗
PubMed1985

[Stimulatory effect of a traditional herbal medicine, Unkeito on LH-RH release].

In order to study the effect of Unkeito (Chinese name, Wen-Jan-Tang), a traditional Chinese herbal medicine and its components on luteinizing hormone-releasing hormone (LH-RH) and LH release, the mediobasal hypothalamus (MBH) alone or the pituitary alone or the pituitary in sequence with the MBH from normal female rats in diestrus was perifused in a sequential double-chamber perifusion system. LH-RH release from MBH increased significantly (p less than 0.05) by 50-100% of the basal level 30-90 min after the beginning of Unkeito administration. Unkeito at 5 micrograms/ml induced significant LH release (60-95% increase) from the pituitary in series with the MBH, but had no effect on LH release from the pituitary perifused alone. One of Unkeito's components Botanpi induced significant LH release, although other five components had no effect on LH release. These data suggest that Unkeito induces LH release from the pituitary through hypothalamic LH-RH, and can be used for the treatment of patients with hypothalamic amenorrhea.

Animals↗
PubMed1984

Effect of pituitary transplants on the LH-RH concentrations in the medial basal hypothalamus and hypophyseal portal blood.

The effects of hyperprolactinemia on catecholamine turnover in the medial basal hypothalamus (MBH) and on the luteinizing hormone-releasing hormone (LH-RH) concentrations in MBH and hypophyseal portal blood were investigated in female Wistar rats. Chronic endogenous hyperprolactinemia was produced by implantation of anterior pituitary glands under the kidney capsule. Catecholamine turnover in the MBH was studied by inhibiting monoamine oxidase and then measuring the accumulation of catecholamines by high-performance liquid chromatography with electrochemical detection. Rats bearing pituitary transplants exhibited: (1) persistent vaginal diestrus within 3-6 days of the implantation; (2) increased serum concentrations of prolactin (PRL); (3) decreased serum concentrations of luteinizing hormone (LH); (4) increased pituitary concentrations of LH and follicle-stimulating hormone (FSH); (5) increased turnovers of dopamine in the MBH; and (6) decreased concentrations of LH-RH in the MBH and in plasma of hypophyseal portal blood. These findings suggest that chronic hyperprolactinemia may increase dopaminergic tone in the MBH that may inhibit LH-RH secretion from the MBH, and LH release from the pituitary. These processes may be responsible for disturbances of cyclic pituitary-ovarian activity.

Animals↗
PubMed1984

Organization and properties of visually responsive neurones in the suprageniculate nucleus of the cat.

Visually responsive neurones of the cat's suprageniculate nucleus were categorized according to their responses to a variety of different types of light stimuli. Their velocity preferences were assessed quantitatively and have been found to predominate in the high range. The positions and dimensions of their receptive fields were determined and these tended to be found within a zone between the vertical meridian and 30-35 degrees. Receptive fields had mean diameters smaller than those reported by others for the pulvinar-LP complex. From these and other electrophysiological data, inferences have been made of the likely sources of afferents providing visual driving. A proposal is offered for SGn visuotopic organization based on correlations of receptive field location with cell position, as determined through electrode track reconstructions.

Animals↗
PubMed1984

Site of negative feedback action of estrogen on gonadotropin secretion in normal women.

We have reported that iv administration of conjugated estrogens results in no significant change in the plasma LH-RH level during the negative feedback phase of LH, suggesting that estrogen does not suppress LH by decreasing hypothalamic LH-RH. To determine the site of estrogen action during the negative feedback phase, we studied the pituitary response to a small amount of LH-RH after estrogen administration in normal cyclic women in the mid-follicular phase. The pituitary responses to an iv bolus of 2.5 micrograms of synthetic LH-RH were evaluated by measuring serum LH and FSH 2 h before and 8 h after administration of 20 mg of conjugated estrogens (Premarin). The mean levels of serum LH and FSH were significantly (p less than 0.05) decreased 8 h after the injection. The peak responses of LH and FSH to LH-RH were also significantly (p less than 0.05) reduced after Premarin administration. These findings suggest that the negative feedback effect of estrogen on gonadotropin secretion is caused by its direct suppression on the pituitary response to LH-RH.

Adult↗
PubMed1984

Impaired LH-RH release by estrogen in women with sulpiride-induced hyperprolactinemia.

The effects of hyperprolactinemia on the release of immunoreactive luteinizing hormone-releasing hormone (LH-RH) and luteinizing hormone (LH) in response to iv injection of 20 mg conjugated estrogens (Premarin) were studied. Five normal cycling women were injected with Premarin on the morning of the 7th day of the first cycle (control cycle), and then the plasma levels of LH-RH, LH, and prolactin (PRL) were determined every 8 to 16 hours for 72 h. Two months later, the same women received 200 mg of oral sulpiride daily for 8 days from the 3rd day of the cycle (sulpiride treated cycle), and then the same protocol as in the control cycle was applied. Mean (+/- SE) plasma levels of PRL on day 7 in the sulpiride treated cycle were significantly higher than those in the control cycle (118 +/- 24 ng/ml vs. 14 +/- 4 ng/ml, p less than 0.001). After estrogen injection, the mean percent increases in immunoreactive LH-RH at 32 h (control: 71 +/- 38% vs. sulpiride: 6 +/- 36%) and 40 h (154 +/- 38% vs. -5 +/- 21%) and in LH at the 48 h (175 +/- 89% vs. 57 +/- 57%) and 56 h (99 +/- 32% vs. 7 +/- 21%) were significantly (p less than 0.01 or p less than 0.05) suppressed in the sulpiride cycle. These data suggest that the impaired positive feedback effect of estrogen on LH-release in hyperprolactinemic anovulatory women may be caused, at least in part, by disturbed LH-RH release.

Adult↗
PubMed1984

Absence of effect of the peptide PHI-27 on LH release in vitro.

The effects of PHI-27, a peptide of the glucagon-secretion family, on luteinizing hormone (LH) release and on LH-releasing hormone (LH-RH)- or estradiol-induced LH release were examined in a sequential double chamber perifusion system by perifusing the pituitary alone or in sequence with the mediobasal hypothalamus (MBH) from normal female rats in diestrus. PHI at 10(-7) M had no significant effect on LH release from the pituitary in series with the MBH. Moreover, on perifusion of the pituitary alone with medium containing 10(-7) M PHI, LH release induced by 20 ng/ml LH-RH from the pituitary was not significantly different from that without PHI. Furthermore, PHI had no effect on estradiol-induced LH release from the pituitary in sequence with the MBH. These data indicate that PHI has no effect on LH release in vitro.

Animals↗
PubMed1984

Abnormality of testicular FSH receptors in infertile men.

To ascertain whether abnormalities in testicular binding of follicle stimulating hormone (FSH) are related with spermatogenic impairment found in idiopathic male infertility, we measured FSH receptors in testicular tissues obtained by biopsy from 37 infertile men. Since there had been few reports on the characterization of human testicular FSH receptor, we first established conditions for FSH receptor assay in small amounts of human testicular tissues taken by biopsy. Thirty-seven infertile men were divided into 3 groups by histological grading using Johnsen's score count, and testicular FSH receptors among these groups were compared. Although 6 of 12 infertile men with low Johnsen's score count and 3 of 9 men with middle score count had no obvious FSH binding sites with high affinity, all 16 men with high score count had high affinity FSH binding sites. The present findings demonstrate that the decrease in testicular high affinity binding sites for FSH is related with the degree of spermatogenic impairment found in idiopathic male infertility.

Adult↗
PubMed1984

Hydrocortisone elicits the effect of clomiphene citrate on luteinizing hormone-releasing hormone release in vitro.

The effect of hydrocortisone on the release of luteinizing hormone (LH) and LH-releasing hormone (LRH) in response to clomiphene citrate (clomiphene) were examined in a sequential double chamber perifusion system by perifusing the mediobasal hypothalami (MBH) and/or pituitaries excised from normal female rats in dioestrus. When the MBH and the pituitary were perifused in sequence with medium containing 5 X 10(-6) M hydrocortisone, a significant release in LH (100- 150% increase, P less than 0.01-P less than 0.05) was observed 40 min after the administration of 3 X 10(-8) mol clomiphene. Clomiphene had no effect on LH release from the pituitary when perifused in series with the MBH without basal hydrocortisone infusion. Administration of clomiphene did not cause a significant increase in LH from the pituitary perifused alone, with or without medium containing hydrocortisone. The concentration of LRH in the efflux was significantly increased 40 min after clomiphene administration when MBH was perifused with medium containing hydrocortisone, whereas clomiphene had no effect when perifused with medium only. These data indicate that hydrocortisone stimulates the effect of clomiphene on LRH release from the hypothalamus, which in turn induces LH release from the pituitary.

Animals↗
PubMed1984

Involvement of norepinephrine in pituitary LH release induced by oestradiol in vitro.

The direct effects of oestradiol-17 beta (E2) on pituitary luteinizing hormone (LH) release and the role of norepinephrine (NE) in E2-induced gonadotrophin release were examined in a sequential double chamber perifusion system by perifusing the mediobasal hypothalami (MBH) and/or pituitaries excised from normally cycling female rats. Administration of E2 induced significant release (70-160% increase, P less than 0.05) of LH from the pituitary of rats in pro-oestrus, but not in other stages of the oestrous cycle. When the MBH and the pituitary were perifused in sequence, E2 induced significant release of LH in all stages of the oestrous cycle except oestrus. When the pituitary from rats in dioestrus II was perifused alone with medium containing 200 ng/ml NE, significant release of LH (80-170% increase, P less than 0.05) was observed after the administration of E2. The E2-induced LH release in pro-oestrus was completely abolished by perifusion with medium containing diethyldithiocarbamate, an inhibitor of NE synthesis. These findings suggest that NE may be involved in changes of pituitary responsiveness in LH secretion to oestrogen during the rat oestrous cycle.

Animals↗
PubMed1983

Requirement of successive protein syntheses for the progress of meiosis in Blepharisma.

Germ nuclei of Blepharisma japonicum begin meiosis within a few hours when cells of complementary mating types conjugate. We synchronized the onset of conjugation and treated cells in different stages of meiosis with 10 micrograms/ml cycloheximide which strongly inhibits protein synthesis in this ciliate. Cycloheximide arrested meiosis at six stages: I, between pairing of cells and swelling of germ nuclei; II, leptotene; III, zygotene; IV, pachytene; XI, interkinesis; XII, prometaphase II. Five of these arrests were reversible. Puromycin (250-500 micrograms/ml) also inhibited the progress of meiosis, though to lesser extents. We propose that the progression of meiosis of B. japonicum requires at least six proteins which are synthesized sequentially during meiosis.

Animals↗
PubMed1983

Absence of effect of danazol on estrogen-induced luteinizing hormone release from rat hypothalamo-pituitary axis in vitro.

The effects of danazol on luteinizing hormone (LH) release by estradiol (E2) were examined in a sequential double chamber superfusion system by superfusing the mediobasal hypothalamus (MBH) and pituitary excised from normal female rats in diestrus. Administration of 3x10(-13) mole E2 caused a significant (p less than 0.05) increase of LH (80-220% above the pre-injection level) from the pituitary in series with MBH superfused with Medium 199 alone or Medium 199 containing 10(-4)M danazol. These data indicate that acute administration of danazol does not affect estrogen-induced LH release in rats.

Animals↗
PubMed1983

Congenital malformations of newborn infants after clomiphene-induced ovulation.

The effect of clomiphene citrate (CC) on the incidence of congenital malformations in newborn infants was assessed from the outcome of 1034 pregnancies after CC-induced ovulation recorded at nine university hospitals in a 5-year period. Of these pregnancies, 14.2% ended in abortion, 0.5% in ectopic pregnancy, 0.1% in molar pregnancy, and 1.6% in stillbirth. In all, 935 infants were born, and 21 (2.3%) showed visible malformations. This incidence of malformations was not significantly different from that in 30,033 infants (1.7%) after spontaneous ovulation (spontaneous ovulation group), and the types of malformations after CC treatment were similar to e those in the spontaneous ovulation group. These data indicate that CC has no teratogenic effect.

Abnormalities, Drug-Induced↗