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Biomedical subjects

H Wakimoto

Publications and source records attributed to H Wakimoto.

61 records · Page 4Linked to original sources
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↗
PubMed1984

Specific antibodies to porcine zona pellucida detected by quantitative radioimmunoassay in both fertile and infertile women.

The specific radioimmunoassay system was developed for the titration of the antibodies to porcine zona pellucida (ZP) in human sera by using 125I-labeled purified porcine ZP as antigen, which is known to have cross-reactivity with human ZP. The antibodies in human sera were detected in 3 of 11 (27%) women with unexplained infertility, in 16 of 48 (33%) amenorrheic patients, in 4 of 12 (33%) fertile women, and in 3 of 10 (30%) men. Moreover, antibody titers in infertile women were no higher than those in fertile women and in men. These results seem to suggest that the antibodies in human sera that cross-react with porcine ZP may not be an important factor in causing infertility in women.

Animals↗
PubMed1983

Involvement of collagen formation in the hormonally induced functional differentiation of mouse mammary gland in organ culture.

In mammary gland organ culture from midpregnant mice, synergistic actions of insulin, cortisol, and prolactin stimulate differentiation of mammary epithelium and induce the synthesis of the milk proteins casein and alpha-lactalbumin. In the present study we examined the production of collagen and its function in the hormone-dependent development of mammary gland in vitro. The measurement of collagen production by the hydroxyproline assay and by sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed that the accumulation of collagen type I and type III in cultured mammary explants increased with the addition of insulin, cortisol, and prolactin to a chemically defined medium. When an analog of proline, L-azetidine-2-carboxylic acid (LACA), was added at a concentration of 80 microgram/ml with insulin, cortisol, and prolactin at the beginning of culture, collagen production in cultured tissue was inhibited by 75% during a 3-day incubation period. This agent also inhibited the synthesis of casein and alpha-lactalbumin by about 77 and 70%, respectively. The inhibitory effect of LACA could be prevented by L-proline; concomitant addition of L-proline (80 microgram/ml) with LACA (80 microgram/ml) resulted in complete restoration of milk protein synthesis to normal levels. Measurement of the amount of milk protein mRNAs in mammary explants by a cell-free translation assay demonstrated that LACA reduced the hormone-stimulated accumulation of casein mRNA and alpha-lactalbumin mRNA by 79 and 76%, respectively. LACA, however, produced little inhibition of DNA synthesis in cultured tissue. These results suggest that collagen production may be involved in the phenotypic expression of milk protein genes during hormonal induction of mammary epithelial differentiation in vitro.

Animals↗
PubMed1980

Activity of testosterone 5 alpha-reductase in various tissues of human skin.

In order to know the distribution of testosterone 5 alpha-reductase activity in human skin, we developed a micro-method, in which we used 20-50 micrograms of various tissues microdissected from freeze-dried sections. The characteristics of this enzyme in the sebaceous gland are briefly described, as follows: the identified 5 alpha-reduced metabolites are 5 alpha-dihydrotestosterone, 5 alpha-androstane-3 beta, 17 beta-diol and 5 alpha-androstanedione; the optimal pH is about 7.5; and the apparent Km is approximately 2.4 x 10(-5) M. The measurement of 5 alpha-reductase activity of various components of the skin obtained from 7 men and 5 women revealed that the sweat gland (probably apocrine) in the axillary skin possessed the highest activity of 5 alpha-reductase: the value was nearly 400 pmoles/mg dry weight/hr in the standardized condition. The sebaceous gland also showed a high activity of 85-261 pmoles/mg/hr. The hair follicles exhibited a significantly lower activity than the sebaceous gland. The enzyme activity was negligible in the epidermis, while it was detected in the dermis though the values determined were variable probably because of contamination with other components such as sweat glands and hair follicles. Thus, the present study demonstrates that the 5 alpha-reductase activity is mainly located in the apocrine sweat gland and sebaceous gland. This suggests that 5 alpha-reduction of testosterone is an important step in mediating the action of androgens in these tissues.

3-Oxo-5-alpha-Steroid 4-Dehydrogenase↗
PubMed1980

Androgen receptor in serially subcultured human endometrial fibroblasts.

Specific dihydrotestosterone (DHT) binding was demonstrated in the whole cell sonicates obtained from serially subcultured human endometrial fibroblasts. This binding showed a high affinity and specificity for DHT (Kd=3.3 X 10(-10) M). Various kinds of excess nonradioactive steroids were arranged, as a result of competition among them, in the following decreasing order of binding affinity: DHT, testosterone, cyproterone acetate, 17 beta-estradiol, progesterone, and 5 alpha-androstane-3 alpha, 17 beta-diol. Androsterone, 5 alpha-androstanedione, cortisol, androstenedione and estrone hardly affected the binding even at 200 fold excess. Saturation analysis indicated that cultured endometrial and genital skin fibroblasts have a similar number of binding sites for DHT (14.3 +/- 8.5 vs 11.5 +/- 8.6 fmoles/mg cell protein). Sucrose density gradient centrifugation brought about a sharp peak of 3H-DHT in the 4S region in high ionic strength buffer. This binding was abolished by heating sonicates at 37 degrees C for 1 hr, treating them with pronase or adding to them excess nonradioactive DHT. Endometrial fibroblasts also contained testosterone binding components which formed a peak in the 4S region and showed a similar binding affinity to that for DHT.

Adult↗
PubMedDate not supplied

Electrophysiological characterization of murine myocardial ischemia and infarction.

BACKGROUND: Genetically altered mice will provide important insights into a wide variety of processes in cardiovascular physiology underlying myocardial infarction (MI). Comprehensive and accurate analyses of cardiac function in murine models require implementation of the most appropriate techniques and experimental protocols. OBJECTIVE: In this study we present in vivo, whole-animal techniques and experimental protocols for detailed electrophysiological characterization in a mouse model of myocardial ischemia and infarction. METHODS: FVB mice underwent open-chest surgery for ligation of the left anterior descending coronary artery or sham-operation. By means of echocardiographic imaging, electrocardiography, intracardiac electrophysiology study, and conscious telemetric ECG recording for heart rate variability (HRV) analysis, we evaluated ischemic and post-infarct cardiovascular morphology and function in mice. RESULTS: Coronary artery ligation resulted in antero-apical infarction of the left ventricular wall. MI mice showed decreased cardiac function by echocardiography, infarct-typical pattern on ECG, and increased arrhythmia vulnerability during electrophysiological study. Electrophysiological properties were determined comprehensively, but were not altered significantly as a consequence of MI. Autonomic nervous system function, measured by indices of HRV, did not appear altered in mice during ischemia or infarction. CONCLUSIONS: Cardiac conduction, refractoriness, and heart rate variability appear to remain preserved in a murine model of myocardial ischemia and infarction. Myocardial infarction may increase vulnerability to inducible ventricular tachycardia and atrial fibrillation, similarly to EPS findings in humans. These data may be of value as a reference for comparison with mutant murine models necessitating ischemia or scar to elicit an identifiable phenotype. The limitations of directly extrapolating murine cardiac electrophysiology data to conditions in humans need to be considered.

Animals↗