Interstitium: site of steroid synthesis in the ovary of the long term hypophysectomized hamster

The ovaries of hamsters hypophysectomized (H̅) on the afternoon of proestrus synthesize in vitro substantial amounts of progesterone for as long as 20 days post-H̅ (Taya and Greenwald, 1979b). The purpose of the present study was to identify by histochemistry and ultrastructure the ovarian cell type which still possessed the enzymes capable of steroidogenesis despite the long term absence of gonadotropins. After Day 6 post-H̅, the ovaries contained interstitium and viable and atretic small preantral follicles. The viable preantral follicles were histochemically devoid of Δ 5-3β -hydroxysteroid dehydrogenase (3β -HSDH). Histochemically, there were no appreciable changes in lipids in the interstitial gland cells (IGC) until Day 20 post-H̅, followed by a slight decrease by Day 30. The 3β -HSDH activity in the IGC showed no appreciable changes until Day 6 and thereafter decreased gradually until Day 30. Trace amounts of glucose-6-phosphate dehydrogenase were found in the IGC until Day 6 and thereafter the enzyme was undetectable. The IGC contained only trace amounts of acid phosphatase until Day 10, followed by a gradual increase by Day 30. A single i.p. injection of 5 μg ovine LH on Day 10, 20 or 30 resulted 3 h later in dramatic increases in the concentration of serum progesterone and ovarian progesterone and testosterone but not estradiol-17β . Concomitantly, the depletion of lipid droplets in viable interstitial cells was observed by histochemical and ultrastructural criteria. However, lipid accumulations in degenerating interstitial cells and atretic granulosa cells were unaffected by LH treatment. These data indicate that the interstitium is an active steroidogenic tissue for at least 30 days post-H̅ and that LH can rapidly stimulate synthesis and secretion of progesterone and testosterone by the interstitium in long term hypophysectomized hamsters

Circulating inhibin and testosterone during sexual maturation and reproductive seasonality of captive male killer whales (Orcinus orca)

The present study aimed to investigate the reproductive biology of male killer whales. Changes in the concentrations of two circulating testicular hormones, inhibin and testosterone, were monitored during sexual maturation of two male Type 1 Eastern Northern Atlantic killer whales over a period of 20 years. The two killer whales grew rapidly at the pubertal stage and reached a plateau at the age of 23 and 20 years, respectively, after which growth slowed down. In the younger male, circulating inhibin was higher in the juvenile than in the pubertal and mature stages; whereas circulating testosterone exhibited the opposite trend. The pubertal period was estimated to last approximately 5 years, from 12 to 17 years of age. In the elder male, circulating testosterone was high from the onset of this study (12 years of age), when the animal also sired successfully for the first time. This finding shows that the male killer whale is possible to sire even if it is not socially matured, if there is opportunity for copulation. During the mature stage, both animals exhibited significantly higher circulating testosterone concentrations in spring compared to autumn and winter; whereas no seasonal change was observed for circulating inhibin. These results clearly demonstrate that the male killer whale is a seasonal breeder, even though it is fertile throughout the year. This is the first study to elucidate the inhibin concentration and secretory source in the male killer whale

Expression of P450arom and Estrogen Receptor Alpha in the Oviduct of Chinese Brown Frog ( Rana dybowskii

One specific physiological phenomenon of Chinese brown frog (Rana dybowskii) is that its oviduct expands prior to hibernation instead of expanding during the breeding period. In this study, we investigated the expression of P450arom and estrogen receptors α and β (ERα and ERβ) in the oviduct of Rana dybowskii during the breeding period and prehibernation. The results of the present study showed that there were significant differences in both oviductal weight and size with values markedly higher in prehibernation than in the breeding period. P450arom was observed in stromal tissue in both the breeding period and prehibernation. ERα was expressed in stromal tissue and epithelial cells in both periods, whereas ERβ could not be detected. The mean protein and mRNA levels of P450arom and ERα were significantly higher in prehibernation as compared to the breeding period. Besides, oviductal content of 17β-estradiol was also higher in prehibernation than in the breeding period. These results suggested that estrogen may play autocrine/paracrine roles mediated by ERα in regulating the oviductal hypertrophy during prehibernation

Acute testicular atrophy in an active Thoroughbred stallion

A Thoroughbred stallion was used as an active stallion for ten years, however, the number and motility of sperm dramatically decreased and azoospermia occurred at 16 years of age. Circulating luteinizing hormone (LH) was high at 16 years of age compared to the levels before the occurrence of these symptoms. Testicular endocrine function was examined by human chorionic gonadotropin (hCG) administration. No increase in circulating testosterone was detected at 16 years of age, whereas two peaks of testosterone were observed with hCG treatment at 12 years of age. The number of Leydig cells in the testes increased, but the LH receptor was not detected in Leydig cells. These results demonstrated that acute testicular atrophy occurred within one year

Epithelial cell differentiation regulated by MicroRNA-200a in mammary glands.

Mammary gland epithelial cells undergo periodic cycles of proliferation, differentiation, and involution. Many studies have reported that miRNAs, which are small, non-coding RNAs, influence a variety of biological processes during posttranscriptional regulation. Here, we found that one miRNA, miR-200a, was relatively highly expressed in epithelial cell-rich organs such as mammary glands, lung, and kidney in mice. In mammary glands, miR-200a expression increased during mid-pregnancy through lactation; its expression was stimulated by lactogenic hormone treatment of mammary epithelial cells. Lactogenic hormone also induced the expression of milk protein ß-casein mRNA (a marker of cell differentiation) and E-cadherin mRNA (a marker of epithelial cells). However, knockdown of miR-200a prevented increases in ß-casein and E-cadherin mRNA expression. Protein analysis revealed that E-cadherin signal was decreased and ZEB1 (a marker of EMT) was increased following miR-200a knockdown. Finally, in a three-dimensional culture system modeling lumen-containing mammary ducts, miR-200a knockdown decreased the cavity formation rate and suppressed claudin-3 and par-6b expression, indicating reduced epithelial cell polarity. These observations suggest that miR-200a is important for maintaining the epithelial cell phenotype, which contributes to lactogenic hormone induction of cellular differentiation in mammary glands

仓鼠妊娠期瘦素分泌及其调节机制

对妊娠期瘦素的分泌及其调节机制进行探讨.将100只3月龄雌性金黄仓鼠分成16组,每组6-7只,每天采血样用于测定其妊娠期的瘦素分泌.实验结果表明,瘦素于妊娠第9天开始显著升高,于妊娠第12天达到高峰.为验证不同生殖阶段的血清是否对瘦素分泌有不同影响,将不同生殖阶段抽提与未抽提类固醇激素的血清加入培养液中进行培养,发现动情期及妊娠期的血清均可刺激体外培养的脂肪细胞瘦素分泌,动情期抽提与未抽提类固醇激素的血清对脂肪细胞瘦素分泌的刺激作用没有显著差异(P>0.05).与动情期血清相比,妊娠中后期未抽提类固醇激素的血清显著刺激脂肪细胞瘦素分泌(P0.05).妊娠不同阶段未抽提类固醇激素的血清对瘦素分泌的刺激作用有很大差异,妊娠第15天的血清对瘦素分泌的刺激作用显著高于妊娠第8天(P<0.0001)和妊娠第12天(P<0.001)的血清.体外研究进一步表明,肾上腺皮质素、孕酮以及胰岛素均能刺激瘦素分泌,而雌激素却能抑制体外瘦素分泌.研究结果提示,妊娠期血液类固醇激素水平的上升是引起妊娠期瘦素峰出现的重要因素.国家自然科学基金(批准号:30070555);; STEP计划(日本)资助项

Roles of Sex Hormones on the Regulation of Leptin Secretion in Pregnant Golden Hamster

目的 :验证性腺激素对瘦素分泌的影响 ,寻找妊娠期瘦素峰出现的原因。方法 :用 3月龄的金黄仓鼠作为实验动物。制备雌激素及孕激素硅胶埋植管、检验其释放剂量以用于提供后续实验中持续性的高水平雌激素及孕酮 ;制备雌激素以及抑制素的抗血清、检验其生物活性 ,用于后续实验中消减体内这两种激素的生物学作用 ,观察这两种激素缺失对于瘦素分泌活动的影响 ;通过妊娠期间卵巢切除来观察该期间内性腺对于瘦素分泌活动的影响。通过对于切除性腺的动物激素埋植的方法来观察不同激素对在体时瘦素分泌的作用。结果 :金黄仓鼠于妊娠第 11天去除卵巢后瘦素水平显著下降 ,妊娠第 12天的瘦素峰消失 ;妊娠第 11天注射雌激素及抑制素抗血清对瘦素的分泌没有产生显著影响 ;与正常对照相比 ,未孕的金黄仓鼠切除卵巢后瘦素水平显著下降 (p <0 0 5 ) ,切除卵巢后单独埋植雌激素、孕酮不能阻止瘦素水平的下降 ,但是当埋植孕酮和雌激素复合物时瘦素的水平得到恢复。这些结果说明性腺激素对于瘦素的分泌有重要的调节作用。单独的雌激素或孕激素对瘦素分泌没有影响 ,但雌激素与孕激素复合物却对于瘦素的分泌有重要的调节作用。结论 :妊娠后期高水平的雌激素、孕激素等性腺激素的综合作用可能促成了该期瘦素水平的上升。Objective To investigate the effect of sex hormones on the secretion of leptin and the causative factor of the gestational leptin spike in the golden hamster. Methods Three months old female golden hamster were used as animal model. As a source of high level estradiol and progesterone, silicane rabber tubes impregnates with estradiol and progesterone were prepared and their bioactivity were determined. Antisera against estradiol and progesterone were prepared and activity tested to be used? for the elimination of the effects of endogenous hormones on leptin secretion in the subsequent experiments. Biological activity of the antiserum was determined by evaluating effects of these antisera on the weight of uterus or ovary. Groups of pregnant animals were ovariectomied during day 11 of pregnancy to explore the effect of the gonad on the secretion of leptin. Groups of virgin animals were ovariectomied and the silicone rubber tubes containing estradiol and progesterone were implanted to determine the effect of high level estradiol and progesterone on the secretion of leptin in vivo. Results Plasma concentration of leptin decreased and the gestational leptin profile disappeared with absence of the secrection spike on day 12 after ovarectomy on the day 11 of pregnancy. Injections of antiserum against estradiol or progesterone had no significant effect on the plasma concentration of leptin. Leptin level significantly decreased after ovarectomy in the virgin golden hamsters ( p <0 05). Implantation of silicone rubber tubes of estradiol or progesterone after overectomy could not restore leptin levels, but implantation of tubes containing both estradiol and progesterone could prevent the decrease of leptin levels. Conclusion Our results suggested that sex hormones had important regulatory effect on the secretion of leptin. Estradiol plus progesterone had stimulatory effects on the secretion of leptin in vivo. High estradiol and progesterone levels during pregnancy was at least one of the most important causative factors of the appearance of leptin profile with a secretion spike in the golden hamster.国家自然科学基金 (3 0 0 70 5 5 5 );; STEPprogram(Japan)资