Variation in testosterone production among boards and its relationship to sexual interest and breeding performance

Variation in ability to produce testosterone in response to both GnRH and ACTH administration and quatitative relationships between GnRH-stimulated testosterone levels, ACTH-stimulated testosterone levels, sexual interest and breeding performance were assessed in a group of 31 Duroc boars (115.4 +/- 2.5 kg body weight and 212.2 +/- 3.0 days of age). Mean area beneath the testosterone response curve increased (P<0.01) after GnRH and ACTH but the magnitude of response was variable among boars. Post-GnRH testosterone area varied from 7.44 to 50.86 ng/ml X h with a CV = 52.41% while post-ACTH testosterone area varied from 4.99 to 28.78 ng/ml X h with a CV = 45.46%. Mean sexual interest and mean breeding performance scores were correlated (r = 0.67, P<0.01); however, correlations of either variable with testosterone areas were low and nonsignificant. These results indicate that the testosterone-producing ability of boars of similar age and breeding is highly variable and suggest that peripheral testosterone concentrations may not be good indicators of either libido or breeding performance.     

Autoregulation of testicular luteinizing hormone receptors in hypogonadal (hpg/hpg) mice

The autoregulation of testicular luteinizing hormone (LH) receptors was studied in hypogonadal (hpg/hpg) and normal mice. The basal concentration of LH receptors was more than three-fold higher in hpg/hpg than in normal mice. After injection of hCG, hpg/hpg mice showed a decrease in LH receptor levels which was not observed in normal mice. Plasma testosterone was undetectable in hpg/hpg mice, even after treatment with a single dose of hCG. Plasma prolactin levels were higher in hpg/hpg than in normal mice. The increase in basal LH receptor levels is thought to be due to a compensatory mechanism in which elevated prolactin could play a role. The differences between hpg/hpg and normal mice in the autoregulation of LH receptors observed could be due to the hypersensitivity of the physiologically immature testis in hpg/hpg mice to the action of hCG, to gonadotropin deficiency, particularly during the earlier stages of development, or to a direct effect of the hpg locus on the metabolism of LH receptors.These studies were supported by NIH Grants HD 12642 and HD 12671 (AB) and Grant CA-24145 (WGB).     

Gonads ofCarassius auratus (teleosts) in organ culture: A new technique and the effects of testosterone

Summary The use of a semi-natural medium (Eagle’s MEM supplemented with chicken embryo extract) appears to be satisfactory for ovarian and testicular fragment cultures ofCarassius auratus. The male germ cells show a normal degeneration which might be attributed to a lack of pituitary hormones: gonadotropic and, possibly, somatotropic hormone. The ovarian fragments maintain a normal organization during 21 days of culture. Only the occytes in late vitellogenesis massively atresiate at the beginning of culture. The addition of fetal bovine serum to this medium produces surprising effects on the testicular explants, particularly on the spermatogonial mitoses. This might be attributed to the presence of STH and androgen in the serum. The modifications of ovarian explants, on the other hand, are identical to those observed with Eagle’s MEM supplemented with chicken embryo extract. M 199 has been tested as a synthetic medium; the preliminary results are encouraging. Testosterone, when added to the semi-natural medium, permits complete spermatogenesis in the testicular fragments during the 21 days of culture, but does not produce any effect on the ovarian explants.     

催乳素对培养的绵羊睾丸间质细胞睾酮分泌的影响

在绵羊睾丸间质细胞体外无血清长期培养的条件下,研究了催乳素对睾丸间质细胞睾酮分泌的调节作用。实验结果表明,催乳素可增强细胞对人绒毛膜促性腺激素(hCG)刺激的反应。催乳素的这种作用呈双相调节。睾酮分泌量显著高于hCG和催乳素单独作用时的总和。在hCG存在下,不同的底物转化为睾酮的量不同。其中雄烯二酮和孕酮转化为睾酮的方式存在着双相性。脱氢表雄酮转为睾酮的量少,不存在双相性,而与其剂量成正比。催乳素在hCG存在下可调节底物转化为睾酮。低剂量的催乳素(1ng/ml)可使一定剂量的孕酮(10～30ng/ml)转化为睾酮的量明显增加,而高剂量的催乳素(>10ng/ml)却明显地抑制孕酮转化为睾酮。催乳素可明显地抑制雄烯二酮转化为睾酮,与剂量无关。可见催乳素对于孕酮和雄烯二酮这两个关键底物转化为睾酮的调节是不同的。催乳素增强hCG刺激睾酮分泌的作用可能部分是通过其促进孕酮转化为睾酮来实现的。     

Steroid hormone effects on growth and apical dominance of sunflower

External application of estradiol-17β increased shoot growth but decreased root growth of sunflower seedlings. It completely inhibited cotyledonary axillary bud development in decapitated plants at the concentration of 1 μg/plant. Concentrations lower than this promoted cotyledonary axillary bud formation. Testosterone on the other hand inhibited both shoot and root growth and promoted cotyledonary axillary bud formation at all the concentrations used. Progesterone at high (0.25,μg/plant) concentration promoted shoot growth but inhibited root growth. A low concentration (0.1 μg/plant) of progesterone produced the opposite effect.     

Failure to detect delta 5-3 beta-hydroxysteroid oxidoreductase activity in the preimplantation rabbit embryo

Preimplantation rabbit embryos were incubated with pregnenolone and dehydroisoandrosterone under conditions which gave formazan precipitation by the histochemical technique. The metabolic fate of the labeled steroids was assessed simultaneously. There was no concomitant transformation of pregnenolone to progesterone and dehydroisoandrosterone was not transformed to androstenedione. It is concluded that the formazan precipitation is coupled with an "activity" other than delta 5-3 beta-hydroxysteroid oxidoreductase.     

Induced sex reversal in Tilapia nilotica (Cichlidae) with methyl testosterone

Gonadally undifferentiated Tilapia nilotica fry were fed with methyl testosterone at the dosage of 50 mg/kg of dry diet. The fry used in the investigation belonged to two age groups with a mean total length of 10 mm and 13.5 mm. Treatment lasted for a minimum of four weeks and a maximum of six weeks. 100% males were obtained in all the various groups under androgen treatment.     

The conversion of testosterone to 7α-hydroxy-testosterone by incubated rat testes

Incubations of testes of adult rats with testosterone yield rather important amounts of a very polar metabolite which is identified as 7α-hydroxytestosterone. The identification of the metabolite is based on chromatography, spectrophotometry, fluorimetry, counter current distribution and NMR spectrometry.     

The Effect of Testosterone Upon the Urate Reabsorptive Transport System in Mouse Kidney

It is hypothesized that hyperuricemia in males is caused by androgen-induced urate reabsorptive transport system in the kidney. The expression of urate transporter 1 (Urat1), sodium-coupled monocarboxylate transporter 1 (Smct1) and glucose transporter 9 (Glut9) were investigated in orchiectomized mice with or without testosterone replacement. Testosterone enhanced mRNA and protein levels of Smct1 while those of Glut9 were attenuated. Although the mRNA level of Urat1 was enhanced by testosterone, the corresponding levels of Urat1 protein remained unaffected. Thus, the induction of Smct1 by testosterone is a candidate mechanism underlying hyperuricemia in males.     

睾酮对鸟类繁殖影响研究进展

类固醇激素睾酮是影响鸟类繁殖最重要的性激素之一,与鸟类的繁殖行为的各个方面息息相关。睾酮通过影响鸟类的羽色、鸣声等来影响鸟类的配偶选择,同时睾酮可以调节配偶选择和繁殖投入之间的平衡。睾酮水平影响出雏数、出飞数、孵化率成功率等繁殖成效。睾酮还对个体的免疫活性和个体的存活率等产生影响。目前关于睾酮对鸟类繁殖影响的研究大多是通过外源性植入睾酮的方式来改变个体睾酮的浓度,其研究结果也常出现相互矛盾之处,对于自然状态下影响睾酮水平变化的因素尚缺乏了解,睾酮对雌雄鸟在繁殖过程中的影响也不尽相同,有必要继续深入研究。