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Biomedical subjects

Y Yoshimoto

Publications and source records attributed to Y Yoshimoto.

At least 145 records · Page 8Linked to original sources
PubMed1987

Free calcium wave upon activation in Xenopus eggs.

Eggs of Xenopus laevis were preloaded with aequorin and the spatial and temporal pattern of free calcium release in the egg cortex on artificial activation was determined by the aequorin luminescence emitted from the thin cortical layer of naturally opaque eggs. The aequorin luminescence was detected with a photonic microscope system consisting of a light microscope and a two-dimensional photon-counting system with an image processor. A free calcium increase was initiated around the point of prick activation. The state of increased Ca2+ propagated in the cortical cytoplasm of the egg as a wave with a velocity of about 8 micron/sec at 22 degrees C. This wave reached the antipode by 5 to 6 min of prick activation. The spatial pattern of the Ca2+ wave was similar to that of changes in brightness of the egg surface on activation, termed the "activation wave" by K. Hara and P. Tydeman (1979, Wilhelm Roux's Arch. Dev. Biol. 186, 91-94). To examine the temporal correlation between the Ca2+ wave and the activation wave, images of aequorin luminescence and those of the egg cortex taken by incident light illumination were recorded alternately in the same egg. The zone of free calcium increase corresponded to the light (relaxation) zone of the activation wave, where exocytosis of cortical granules and elongation of microvilli were taking place.

Aequorin↗
PubMed1987

Effect of clomiphene citrate administration during the early luteal phase on the luteal function and pregnancy rate of women.

To study the effect of clomiphene citrate (clomiphene) administration during the early luteal phase of the menstrual cycle on the luteal function and the pregnancy rate in women, 75 infertile women who ovulated but did not conceive after clomiphene treatment during the early follicular phase and 6 normal cycling women were chosen. Clomiphene was administered orally to 35 of the 75 infertile women at a dose of 50 mg per day for 5 days from the second day of the rise in the basal body temperature (BBT) as well as during the follicular phase, while 40 control patients received clomiphene only during the follicular phase. In the test patients, the rate of pregnancy (25.7%) was significantly (p less than 0.05) higher than that of control patients (10.0%). On the 7th of the rise of BBT, the mean serum progesterone levels of the test patients and normal cycling women treated with clomiphene were significantly (p less than 0.05) higher than those of the control patients. However, the levels of serum estradiol, LH and FSH, the gonadotropin pulsatilities, and the pituitary responses to LH-RH in the test women were not significantly different from those of the control. These data suggest that, when administered during the early luteal phase, clomiphene may act directly on the ovary, enhancing the secretion of progesterone from the corpus luteum, and thereby increasing the rate of pregnancy in infertile women with clomiphene-induced ovulation.

Adult↗
PubMed1987

Neuro-otological findings in a case of Marinesco-Sjögren syndrome with nystagmus.

Marinesco-Sjögren syndrome is a very rare disease that develops in childhood with main symptoms of cataract, ataxia, mental deficiency and microsomia, and is regarded as a type of spinocerebellar degeneration. The author performed the neuro-otological tests on a case of suspected Marinesco-Sjögren syndrome. The patient exhibited bilateral congenital cataract, mild cerebellar symptoms, bilateral gaze nystagmus with rebound nystagmus, mental retardation, deformity and muscular atrophy of the limbs. Though cerebellar symptoms of the limb were mild, the findings of bilateral gaze nystagmus that appeared most notably immediately after lateral gaze and diminished gradually thereafter with rebound nystagmus suggested cerebellar disturbances. Marked atrophy of the cerebellar hemisphere in CT scans supported the neurootological findings. The author agrees to the opinion of Skre and Löcken who included Marinesco-Sjögren syndrome in the cerebellar form of spinocerebellar degeneration.

Adult↗
PubMed1987

A case of lithium intoxication with downbeat vertical nystagmus.

Lithium carbonate has recently been used in the treatment of manic diseases. However, since the marginal range between therapeutic and toxic doses is very narrow, close attention should be paid to the development of adverse reactions in its application. Lithium intoxication is manifested by neurological symptoms. Neurotological tests were performed on a patient with lithium intoxication that occurred in the course of psychiatric treatment of mania. The observed sequelae included marked downbeat vertical nystagmus and truncal ataxia. The main lesions in the present case were considered to be located in the cerebellum. Close observation, including neurotological tests, is of greatest importance because in cases of lithium intoxication the development of cerebellar as well as brainstem disorders must not be overlooked.

Cerebellar Ataxia↗
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

Damaging effect of peripheral mononuclear cells of dermatomyositis on cultured human skin fibroblasts.

When human skin fibroblasts were incubated with mononuclear cells (MNC) from 6 patients with dermatomyositis (DM), striking attachment of MNC around fibroblasts was observed. Simultaneously, cell number and 3H-thymidine incorporation of fibroblasts after 4 days of incubation were significantly decreased. MNC of normal subjects, of patients with systemic lupus erythematosus, myasthenia gravis, rheumatoid arthritis, and other miscellaneous diseases with skin manifestations did not show this effect. MNC of patients with DM did not adhere to KYM-1 cells (human rhabdomyosarcoma cell-line) and did not inhibit cell proliferation of these cells. Our study strongly suggests that cell mediated injury of fibroblasts might play an important role in the pathogenesis of DM.

Adult↗
PubMed1987

Serum TSH, thyroglobulin, and thyroidal disorders in atomic bomb survivors exposed in youth: 30-year follow-up study.

Follow-up examinations to determine the frequency of thyroidal disorders were conducted by the Radiation Effects Research Foundation (RERF) on individuals in Hiroshima and Nagasaki who were less than 20 yr of age at the time of exposure to the atomic bomb. Concentrations of serum thyroid stimulating hormone (TSH), thyroglobulin (TG), and anti-TG antibody 30 yr after exposure were also determined. Nontoxic uninodular goiter was found in 13 cases of the 100 + rad exposed group (n = 477) and in three cases of the nonexposed group (n = 501). The prevalence in the 100+ rad exposed group was significantly higher (chi-squared = 6.584, p less than 0.01). Thyroid cancer was found in eight exposed cases, all of whom were in the 100+ rad group, and the prevalence was significantly greater (chi-squared = 7.919, p less than 0.01). Regardless of the presence or absence of thyroid disorders, serum TSH and TG levels were not statistically different between the 100 rad + exposed and nonexposed groups. Although hypothyroidism was found in 23 of the total cases, there was no correlation between its development and exposure to ionizing irradiation.

Adolescent↗
PubMed1986

Temporal and spatial dynamics of the periodic increase in intracellular free calcium at fertilization of golden hamster eggs.

A series of periodic increases in intracellular free calcium concentration ([Ca2+]i) occurred upon fertilization in golden hamster eggs. The spatial distribution of the Ca2+ transients was investigated in single zona-free, aequorin-injected eggs, inseminated by single sperm. A supersensitive TV camera system for recording Ca2+-aequorin luminescence enabled us to observe the spatial distribution of the Ca2+ rise. In the first response, which usually occurred 10-30 sec after the sperm attachment, the increase in [Ca2+]i began near the sperm attachment site, and the Ca2+ rise spread over the entire egg within 4-7 sec. The Ca2+ rise attained its peak in 5-8 sec, declined with almost even distribution, and ceased in 12-17 sec. The spreading Ca2+ rise was repeated in the second and sometimes the third response, starting from the same focus, but spreading more rapidly (approximately 2 sec). In succeeding responses [Ca2+]i increased synchronously in the whole cytoplasm within 1 sec. When additional sperm attached to the egg after the occurrence of the first response by the first sperm, the spread of the Ca2+ rise could take place from near the site of additional sperm attachment but only in the second or third response.

Aequorin↗
PubMed1986

Biological activity of vitamin D metabolites and analogs: dose-response study of 45Ca transport in an isolated chick duodenum perfusion system.

We have previously reported that vascular perfusion of the normal vitamin D3-replete chick duodenum with physiological amounts of 1,25-dihydroxyvitamin D3 [1,25(OH)2D3] increases the unidirectional movement of 45Ca from the lumen to the venous effluent under conditions of normal (0.9 mM) Ca2+ concentrations in both the lumen and vascular perfusate [Endocrinology 115: 1476 1984)]. The purpose of the present study was to determine the dose responsivity of this perfused intestinal calcium transport system for 1,25(OH)2D3 and some structurally related congeners. The dose-response curve was biphasic for all compounds studied; for 1,25(OH)2D3 initial stimulation of transport was detected at only 30 pM [the plasma concentration of 1,25(OH)2D3 is normally 125 pM] while maximal stimulation was 154% above control at a concentration of 650 pM. Above 650 pM 1,25(OH)2D3 the stimulation fell off sharply and transport had returned to basal levels by 1.3 nM. The relative potency of the D homologs tested was respectively 1,25(OH)2D3: 10,000; 1-alpha-hydroxyvitamin D3: 400; 25-hydroxyvitamin D3: 200; 24R,25-dihydroxy-vitamin D3: 137; vitamin D3: 34; 5,6-trans-25-hydroxyvitamin D3: 3. These results establish the usefulness of the perfused intestinal calcium transport system to study the nongenomic actions of 1,25(OH)2D3 on intestinal calcium transport.

24,25-Dihydroxyvitamin D 3↗
PubMed1986

Impaired parathyroid hormone-stimulated adenosine 3',5'-monophosphate release by isolated perfused bones obtained from vitamin D-deficient rats.

The present studies were designed to explore the mechanism underlying skeletal refractoriness to PTH in a vitamin D-deficient animal by assessment of PTH-stimulated cAMP release from isolated perfused bone. In vitamin D-deficient (-D) rats both basal and PTH-stimulated cAMP release were markedly diminished, compared with that in vitamin D-replete (+D) rats. Isolated perfused bones from -D rats that had undergone parathyroidectomy 2 days before death still showed reduced cAMP release in response to PTH, compared with +D bones. To investigate which factors in terms of Ca, endogenous PTH, or vitamin D might primarily be responsible for the impaired PTH-stimulated cAMP release from -D bones, some -D rats were switched to a diet identical to the vitamin D-deficient diet but with high Ca content (4%) for 2 or 5 weeks before death. This schedule maintained normocalcemia despite vitamin D deficiency. PTH-stimulated cAMP release in these rats was increased to a level intermediate between that in -D rats and +D rats, indicating partial restoration of the impaired response to PTH in -D rats. These data indicate that skeletal refractoriness to PTH in vitamin D-deficient animals might, in part, be due to the impaired activation of adenylate cyclase, which cannot be explained entirely by hypocalcemia or associated secondary hyperparathyroidism. Vitamin D deficiency per se, therefore, may play a key role in the impaired cAMP response to PTH.

Animals↗
PubMed1986

Hypercalcemia inhibits the rapid stimulatory effect on calcium transport in perfused duodena from normal chicks mediated in vitro by 1,25-dihydroxyvitamin D3.

We have previously reported that vascular perfusion of normal vitamin D3-replete chick duodena with physiological amounts of 1,25-dihydroxyvitamin D3 [1,25-(OH)2D3] increases the movement of 45Ca2+ from the lumen to the venous effluent within 14 min under conditions of normal Ca2+ (0.9 mM) concentration in both the lumen and vascular perfusate. The present studies were designed to further explore details of this rapid 1,25-(OH)2D3 effect as a function of seco-steroid concentration and under conditions where the free Ca2+ concentrations in the perfusate were varied from 0.54-1.26 mM. Concentrations of 1,25-(OH)2D3 in the vascular perfusate ranging from 30-650 pM elicited an increasing stimulation of Ca transport, as judged by 45Ca levels in the venous effluent. At 0.98-6.5 nM 1,25-(OH)2D3, progressive inhibition of Ca transport was observed, yielding a biphasic dose-response curve. The optimal concentration of 650 pM 1,25-(OH)2D3 was used in subsequent experiments designed to study the effects of vascular Ca2+ levels on 45Ca transport mediated by the seco-steroid. The basal Ca2+ transport ratio, in the absence of 1,25-(OH)2D3, did not change when the divalent cation of the vascular perfusate was varied over the range 0.54-1.26 mM free calcium. However, the effect of 1,25-(OH)2D3 on 45Ca2+ transport was completely abolished in the group treated with 1.21 mM Ca2+ in the perfusate, but not in the groups treated with concentrations less than 1.17 mM Ca2+. These results suggest that the rapid intestinal calcium transport response to 1,25-(OH)2D3 may be modulated locally in part by the prevailing ionized Ca concentration of the vascular perfusate.

Animals↗
PubMed1986

Monoamine oxidase in rat ovary during the estrous cycle. A histochemical study by a new coupled peroxidatic oxidation method.

A new coupled peroxidatic oxidation method for histochemical detection of monoamine oxidase (MAO) was applied to rat ovary. With this new method, fixed tissues could be used, and two forms of MAO could be identified by use of selective inhibitors. MAO activity was observed in the corpora lutea, interstitial gland cells, and blood vessels. In the corpora lutea, no activity was detected during the first estrous cycle, but strong activity was observed in the next two cycles. MAO in blood vessels showed characteristic changes of activity during the estrous cycle. The results suggest that MAO activity might possibly be involved in ovulation and progesterone metabolism in the ovary. Like other organs, rat ovary was found to contain two types of MAO; type A MAO was predominant in the corpora lutea. On the other hand, only one type of MAO, type B, was found in the blood vessels.

Animals↗
PubMed1986

Histochemical studies on human placental and chorionic monoamine oxidase.

A new coupled peroxidation method for detection of monoamine oxidase was applied to human chorionic and placental tissues of various weeks of gestation. With this new method, the precise localization of monoamine oxidase activity could be determined and the two isotypes of the enzyme could be identified using selective inhibitors. Significant monoamine oxidase activity was observed in syncytiotrophoblasts of fine villi and budding villi. Monoamine oxidase activity in chorionic and placental tissues remained similar in intensity and localization throughout pregnancy. Only one type of monoamine oxidase, type A, was found in the placenta. The functional role of monoamine oxidase is discussed.

Chorion↗