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Biomedical subjects

S Ohtsuka

Publications and source records attributed to S Ohtsuka.

At least 127 records · Page 7Linked to original sources
PubMed1988

[Control of glycogen metabolism in the rat fetal brain].

Rat fetal brain glycogen content, and glycogen synthase and phosphorylase activities were measured both in control and in hypoxia on 17th, 19th and 21st days of gestation. Glycogen distribution in the brain was also observed with an optical microscope. The results obtained were as follows: 1. Glycogen content was highest in the choroid plexus, and there tended to be located more in the periventricular areas and hemispheric surface layers of the cerebrum than in other areas. 2. Glycogen content increased from the 17th day, reaching a peak on the 19th day; it decreased with age thereafter and had decreased significantly by the 21st day. 3. Glycogen synthase a-type activity showed no change with fetal age. 4. Glycogen phosphorylase activity was lowest on the 17th day, and it increased thereafter with age. 5. When an ischemic load was applied, brain glycogen content decreased and glycogen phosphorylase a-type activity increased on the 17th and 19th days. The abovementioned findings suggest that glycogen in the rat fetal brain is distributed in the most likely sites of intracranial hemorrhage. The amount of glycogen in the rat fetal brain may depend on glycogen phosphorylase activities. Glycogen may be used as an energy source to maintain brain tissue function during hypoxia. It is also possible that glycogen plays a role in brain maturation.

Animals↗
PubMed1987

Aneurysm of patent ductus arteriosus in an adult case: findings of cardiac catheterization, angiography, and pathology.

A 42-year-old male was admitted to our hospital for evaluation of a left precordial continuous murmur. Results of catheterization revealed a step-up of oxygen content in the pulmonary arteries and the calculated left-to-right shunt flow was 40% of the pulmonary arterial flow. Furthermore, aortography unexpectedly revealed an aneurysm of the patent ductus arteriosus. During surgery, the aneurysm was discovered to arise from the frontal wall of the ductus arteriosus, and histological observation showed focal necrosis and mucoid degeneration of the media of the aneurysmal wall in contrast to a thickened intimal fibroelastosis of the adjacent ductal wall. This is presumed to be the first adult case of patent ductal aneurysm ever reported in which antemortem diagnosis and surgical treatment were successfully conducted. Our case may suggest that the fragility of the ductal wall following the structural change in an incomplete closing process is considered as a potential pathogenesis of ductal aneurysm formation.

Adult↗
PubMed1987

Involvement of H1 histamine receptor in basal and estrogen-stimulated luteinizing hormone-releasing hormone secretion in rats in vitro.

For determination of the roles of histamine and its receptors, H1 and H2, in the control of basal and estrogen-induced LH-RH secretion, the mediobasal hypothalamus (MBH) and/or pituitary was excised from normally cycling female rats and perifused in an in vitro sequential double chamber perifusion system. Administration of 10(-7) M histamine caused significant release (90-170% increase, p less than 0.05) of LH from the pituitary in sequence with the MBH, whereas 10(-7) M histamine had no effect on LH release from the pituitary perifused alone; administration of 10(-5) M 2-methylhistamine, an H1 agonist, induced significant release (50-120% increase, p less than 0.05) of LH-RH from the MBH, and addition of 10(-5) M mepyramine, and H1 antagonist, abolished this LH-RH release. The LH concentrations in the efflux were not affected by the administration of the H2 agonist 4-methylhistamine. Estradiol caused significant release of LH-RH from the MBH and LH from the pituitary in sequence with the MBH. The estradiol-induced release of LH-RH and LH were completely abolished by perifusion with medium containing 10(-5) M mepyramine. The H2 receptor antagonist ranitidine did not affect estradiol-induced LH release. Histamine did not change the LH release induced by 20 ng LH-RH. These findings suggest that histamine induces release of hypothalamic LH-RH, and that histamine H1 receptors in the hypothalamus are involved in the basal and estradiol-induced LH-RH release.

Animals↗
PubMed1987

Absence of effect of estrogen on dopamine, norepinephrine and beta-endorphin-like immunoreactivity in human plasma.

The plasma concentrations of immunoreactive norepinephrine (NE), dopamine (DA), beta-endorphin (beta-E), luteinizing hormone (LH) and follicle stimulating hormone (FSH) were determined by RIA and HPLC every 6 h until 72 h after iv administration of conjugated estrogens during the midfollicular phase. The LH level showed a biphasic pattern after the injection of conjugated estrogens, i.e. significant suppression (-50%) for 6-42 h after the injection, followed by a rebound increase with a peak (+85%) at 72 h. The plasma levels of immunoreactive beta-E, NE and DA did not change significantly for 72 h after the injection.

Adult↗
PubMed1987

Substance P stimulates gonadotropin-releasing hormone release from rat hypothalamus in vitro with involvement of oestrogen.

The effects of substance P on the release of LH and GnRH were examined in a sequential double-chamber perifusion system by perfusing the medio-basal hypothalamus and/or pituitary excised from normal female rats in dioestrus or ovariectomized rats. When the medio-basal hypothalamus and pituitary from normal rats were perifused in series with substance P (10(-6) mol/l), the concentration of LH in the efflux was significantly (P less than 0.05) increased by 70-120% compared with that before the injection, but substance P had no effect on LH release from the pituitary perifused alone. This LH release by substance P increased in a dose-dependent manner and was blocked by substance P antagonist. Administration of 10(-6) mol/l substance P induced a significant release (40-80% increase, P less than 0.05) of GnRH from the medio-basal hypothalamus. Infusion of 10(-6) mol/l substance P induced significant release (50-100% increase, P less than 0.05) of LH and GnRH in ovariectomized rats with an implanted oestradiol capsule, but caused no significant increase in LH release in ovariectomized rats without an oestradiol capsule. Progesterone injection to both ovariectomized rats and ovariectomized rats with an implanted oestradiol capsule had no significant effect on the response of LH to substance P. These findings suggest that substance P induces GnRH release from the medio-basal hypothalamus, resulting in LH release from the pituitary, and that oestrogen may be involved in these processes.

Animals↗
PubMed1987

Effects of coronary collaterals on regional myocardial function during temporary coronary occlusion and hypoxic coronary perfusion.

The effects of coronary collaterals on regional myocardial function during temporary ischemia and hypoxia were studied in 12 open-chest dogs. Using an ultrasonic dimension gauge, systolic segment shortening in the left anterior descending coronary artery (LAD) area was measured at 1 min after the following three experimental conditions: LAD occlusion and LAD hypoxic perfusion with nonoxygenated solutions at two different pressures (60 mmHg and 120 mmHg). Collateral function was assessed by both LAD diastolic retrograde pressure and the percentage of increase in left circumflex coronary flow at 1 min after LAD occlusion. Systolic segment shortening decreased less with hypoxic perfusion than with occlusion, however, this beneficial effect on regional contraction was greater at a perfusion pressure of 60 mmHg than at one of 120 mmHg. The magnitude of decrease of systolic shortening was variable among individual dogs but correlated linearly with each of the two collateral function indexes, not only during occlusion but also during hypoxic perfusion. In conclusion, the preventive effect of hypoxic coronary perfusion on the early decline of regional myocardial function, in comparison to the changes seen during ischemia, may depend on coronary collaterals in addition to its washout effect on metabolites. In order to maintain myocardial function, perfusion pressure should be at an optimal level.

Animals↗
PubMed1987

Effects of the rise in aortic pressure on coronary flow reserve in dogs. Comparison between constriction of the descending thoracic aorta and injection of methoxamine.

In order to investigate the effect of a rise in aortic pressure on coronary flow reserve and also on the difference of its effect according to the methods used to raise aortic pressure, this experiment was performed. Using 7 anesthetized dogs with heart rate held constant by a pacemaker, both the resting and the peak reactive hyperemic left circumflex coronary flow were measured following raising of the aortic pressure by either descending thoracic aorta constriction or methoxamine injection. The resting and peak reactive hyperemic coronary flows both increased linearly following the rise in aortic pressure. The magnitude of the resting flow increment and the resting coronary vascular resistance following raising aortic pressure did not differ significantly between the two different methods. However, the magnitude of the peak hyperemic flow increment and the peak hyperemic coronary vascular resistance following raising aortic pressure were significantly smaller with methoxamine injection than with aortic constriction. These data indicate that coronary flow reserve increases proportionally with a rise in aortic pressure. However, the magnitude of the increment of coronary flow reserve is smaller following an alpha-adrenoceptor-mediated rise in aortic pressure, because the maximal coronary vasodilation was reduced by alpha-stimulated coronary vasoconstriction.

Animals↗
PubMed1986

Wen-jing-tang, a traditional Chinese herbal medicine increases luteinizing hormone release in vitro.

For examination of the effect on luteinizing hormone (LH) release of Wen-Jing-Tang, a traditional Chinese herbal medicine, the pituitary from normal female rats in diestrus was perifused alone or in sequence with the mediobasal hypothalamus (MBH) in a sequential double-chamber perifusion system. Wen-Jing-Tang at 5 or 500 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. These data suggest that Wen-Jing-Tang induces LH release from the pituitary through hypothalamic LH-RH.

Animals↗
PubMed1985

Significant role of alpha 2-adrenoceptors in coronary artery spasm.

Ergonovine, methoxamine and clonidine were administered intravenously in order to clarify the mechanism of coronary artery spasm in canine experiments. After these administrations, 27.5% of the dogs treated with ergonovine, 59.5% of the dogs treated with methoxamine and 72.7% of the dogs treated with clonidine showed ST segment elevation. The combined application of propranolol with ergonovine or methoxamine could more easily induce ST segment elevation than a single application of ergonovine or methoxamine. Most cases of elevated ST segment returned to the normal after the administration of nitroglycerin and phentolamine. Yohimbine was completely effective for the restoration of normal ST segment. Plasma norepinephrine decreased to 20 +/- 8.0% of the control when ST segment elevation was induced. This is a significantly greater decrease than that seen without ST segment elevation (p less than 0.001). Concomitant with the restoration of normal ST segment, plasma norepinephrine increased after the administration of yohimbine. Methoxamine and clonidine increased (p less than 0.01) and yohimbine decreased (p less than 0.01) coronary vascular resistance. Coronary spasm was visualized on coronary arteriogram after the application of clonidine; also coronary vasodilation was visualized after the administration of yohimbine. These results confirm the hypothesis that coronary artery spasm is mediated by pre- and postsynaptic alpha 2-adrenoceptors.

Animals↗
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

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↗