Follicle-stimulating hormone regulates both Sertoli cell and spermatogonial populations in the adult photoinhibited Djungarian hamster testis

The hormones that regulate spermatogonial development are ill defined, in part due to lack of appropriate experimental models. The photoinhibited hamster model provides a rich source of spermatogonia, thus making it an ideal model to study their control. This study aimed to assess the effects of FSH, in the absence of testosterone, on the reinitiation of Sertoli cell and spermatogonial development in the photosensitive adult Djungarian hamster. Hamsters raised under long photoperiods (LD, 16L:8D) were exposed to short photoperiods (SD, 8L:16D) for 11 wk, leading to suppression of gonadotropins and regression of testicular function. Groups of 10 animals then received FSH alone or in combination with the antiandrogen, flutamide, for 7 days. Two control groups maintained either under long or short photoperiods were treated with vehicle. Sertoli and germ cell number were then determined using the optical disector (sic) stereological technique. The number of Sertoli cells, type A spermatogonia, type B spermatogonia/preleptotene spermatocytes, and leptotene/zygotene spermatocytes were suppressed in SD controls to 66%, 34%, 19%, and 10% (all P < 0.01) of long-day control values, respectively. Later germ cell types were not detected. FSH treatment, with or without flutamide, increased Sertoli cell number (P < 0.01) to normal long-day values. Similarly, FSH treatment in the absence/presence of flutamide increased type A spermatogonia, type B spermatogonia/preleptotene spermatocytes, and leptotene/zygotene spermatocytes to approximately 85%, 69%, and 80% (all P < 0.01) of long-day controls, respectively. Our data demonstrate that the reinitiation of spermatogonial maturation in this model is dependent on FSH in the presence of an antiandrogen. Surprisingly, the adult Sertoli cell population in this model is also hormone dependent. This naturally occurring model provides a unique opportunity to understand the mechanisms (apoptotic and/or proliferative) by which FSH regulates Sertoli and germ cell development in the adult animal.     

Optimalized transient transfection of chondrogenic primary cell cultures

We aimed to find a transfection method which provides high efficiency with minimal cytotoxic and/or apoptotic effects for gene transfer into multilayer primary chondrogenic cell cultures. The pEGFP-C1 plasmid was introduced into the cell culture and the efficiency of transformation quantified by GFP fluorescence; the resulting nucleofection was effective but resulted in severe apoptosis. Two liposomal reagents designed to allow transfection into adherent cells did not deliver the plasmids sufficiently and cartilage formation did not occur. In addition, a third liposomal compound, recommended for transfection into either adherent or suspension cell cultures, lead to acceptable transfection efficiency but no cartilage formation. When an amphiphilic reagent was used however, there was acceptable transfection efficiency as well as cartilage formation. The viability of the cells which were transfected using the amphiphilic reagent remained unaffected but proliferation was severely diminished, particularly in the presence of GFP. In addition, the amount of cartilage decreased when GFP was expressed, despite unchanged levels of mRNAs of sox9 and aggrecan core protein, factors reflecting on the efficiency of chondrogenesis. Overexpression of both the constitutively active delta and gamma isoforms of catalytic subunit of calcineurin, a protein phosphatase described as a positive regulator of chondrogenesis, decreased protein level of Sox9 and subsequent cartilage formation. In conclusion, we found that amphiphilic reagent applied prior to the adhesion of cells provides a useful means to transfer plasmids to primary differentiating chondrogenic cells.     

Structural specificity of steroids in stimulating DNA synthesis and protooncogene expression in primary rat hepatocyte cultures

Among the chemical compounds of varied structure which possess liver tumour-promoting are steroids, such as estrogens, pregnenolone derivatives and anabolic steroids. Although the mechanism(s) of tumour promotion in liver by these xenobiotics is not well understood, it is clear that growth stimulation is one important element in their action. As a basis for better defining whether steroids stimulate growth by a common mechanism or fall into sub-groups with differing actions, the effects of 46 steroids on DNA synthesis and the expression of protooncogenes c-fos and c-myc were examined in primary cultures of normal rat hepatocytes. Tentative groupings of steroids have been identified based on apparent structural requirements for stimulation of DNA synthesis, and effects of auxiliary factors in modulating this growth stimulus. For a "progestin" group, insulin appeared to be permissive for stimulation of DNA synthesis, and presence of an ester or hydroxyl group at 17alpha-position in combination with a non-polar group at C(6) appeared to be required for stimulation. For the pregnenes, dexamethasone was stimulatory. Structural requirements include a non-polar substitution at 16alpha-position and presence of a 6alpha-methyl group. Androgens were weak or ineffective stimulators of DNA synthesis. Anabolic steroids were weak to strong stimulators and alteration to A ring structure in combination with non-polar substitution at 17alpha-position appeared to be required for the activity. With the exception of the anabolic steroid, dianabol, there do not appear to be strong correlation between ability to stimulate DNA synthesis and ability to induce protooncogene expression among the steroids. This study provides a starting point for future more detailed examination of growth-stimulatory mechanism(s) of action of steroids in the liver.     

Effects of neonatal diethylstilbestrol exposure on c-fos and c-jun protooncogene expression in the mouse uterus

Quantitative and cell-type-specific expression of c-fos and c-jun genes after 17beta-estradiol (E2) stimulation, was investigated in the uteri of neonatally diethylstilbestrol (DES)-exposed and ovariectomized adult mice (neoDES-mice), employing Northern blot analysis, immunohistochemistry and in situ hybridization. The c-fos mRNA level before E2 injection (at baseline) was about 2.2-fold higher in neoDES-mice than in vehicle-treated control mice. In controls, E2 treatment transiently increased c-fos mRNA levels, showing a peak value (15.8-fold relative to the baseline) after 2 hours. In neoDES-mice, c-fos mRNA level reached a peak showing a 2.1-fold increase compared with its baseline value 1 hour after E2 injection. Immunohistochemistry and in situ hybridization revealed that c-fos protein (Fos) and mRNA are induced in the epithelium and vascular endothelium in both groups. Most uterine epithelia of neoDES-mice revealed low sensitivity to the c-fos expression after E2 administration compared with those of vehicle-treated controls, whereas few epithelia showed high c-fos mRNA expression even at baseline. The c-jun mRNA concentration in the neoDES-mice uteri at baseline was 70% of that in vehicle-treated controls. At 1 hour after E2 injection, c-jun mRNA levels increased 1.8-fold in controls and 1.3-fold in the neoDES-mice relative to each baseline value. There were no significant differences in the distribution pattern of c-jun protein (Jun) and mRNA in the uteri of either groups; E2 stimulated c-jun mRNA expression in the stromal and myometrial cells but suppressed it in the epithelial cells, whereas intensity of c-jun immunostaining increased in the three cell types. The permanent changes in the expression of estrogen-regulated protooncogenes, c-fos and c-jun genes, by neonatal DES exposure may be responsible for the wide range of abnormalities in the genital tract of mature animals.     

Kinetics of inhibin secretion in static and superfused Sertoli cell cultures in response to follicle-stimulating hormone

It is generally accepted that inhibin secretion in the testis is regulated by FSH; however, the kinetics of inhibin secretion have not been well defined in vivo and in vitro. We investigated the kinetics of inhibin secretion in response to FSH stimulation in static and superfused Sertoli cell cultures. Sertoli cells from 18-day-old rats were cultured in chemically defined medium for 3 days and were then stimulated for different time periods with FSH (0.1 microgram/ml). In static cultures, media were changed every 2, 4, or 8 h, and the superfusion was carried out at a steady rate of 3 ml/h. Inhibin in the culture media was measured by RIA, using antiserum against synthetic replicate [30Tyr]inhibin alpha-chain-(1-30) and, in some experiments, also by bioassay. The dynamics of inhibin secretion were similar in static and superfused Sertoli cell cultures. A significant increase (p less than 0.01) of inhibin secretion was noted after 5-6 h of FSH exposure. After 8-12 h of continuous FSH presence, the secretion of inhibin reached a maximal level, 5-10-fold higher than basal secretion (no FSH). In the continuous presence of FSH, inhibin secretion remained stable at the high level for up to 54 h. FSH removal caused a delayed (8-h) decrease (p less than 0.01) of inhibin secretion, with return to control basal values after approximately 30 h. When FSH was removed 4 h after its addition, inhibin secretion again increased 5-10-fold between 4 and 12 h, then returned to basal values within 30 h.(ABSTRACT TRUNCATED AT 250 WORDS)     

Regulation of hormone secretion in primary cell cultures of human somatotropinomas]

The effects of somatostatin and thyroliberin (thyrotropin-releasing hormone; TRH) on growth hormone (GH) and prolactin (PRL) secretion were studied in short-term (0.5-3h) or long-term (21-24h) incubations using monolayer cell cultures of somatotropin obtained from surgical material of patients with acromegaly. High sensitivity of both GH and PRL release to inhibitory action of somatostatin (10(-11) M) was established. We could not reveal the unambiguous influence of TRH on somatotropic function in the in vivo and in vitro conditions, as compared to the action of this tripeptide on PRL secretion. The results obtained permit us to propose that cell cultures of pituitary adenomata represent adequate and convenient models for studying the pathogenesis of tumor processes in the pituitary gland and for the development of new procedures of pharmacotherapy.     

Novel approach for transient protein expression in primary cultures of human dental pulp-derived cells

Transfection is a powerful method for investigating variable biological functions of desired genes. However, the efficiency of transfection into primary cultures of dental pulp-derived cells (DPDC) is low. Therefore, using a recombinant vaccinia virus (vTF7-3), which contains T7 RNA polymerase, we have established a transient protein expression system in DPDCs. In this study, we used the human polymeric immunoglobulin receptor (pIgR) cDNA as a model gene. pIgR expression by the vTF7-3 expression system was confirmed by flow cytometry analysis and Western blotting. Furthermore, exogenous pIgR protein localized at the cell surface in DPDCs and formed a secretory component (SC). This suggests that exogenous pIgR protein expressed by the vTF7-3 expression system acts like endogenous pIgR protein. These results indicate the applicability of the method for cells outgrown from dental pulp tissue. In addition, as protein expression could be detected shortly after transfection (approximately 5h), this experimental system has been used intensely for experiments examining very early steps in protein exocytosis.     

冷应激诱导的脾脏NK细胞活性下降和脑内c-fos表达

目的 :观察单一冷应激对大鼠脾脏NK细胞活性的影响以及脑内Fos表达。方法 :大鼠置于 4℃的冷室 4h。采用YAC 1细胞51Cr释放法测定脾脏NK细胞的活性。用免疫细胞化学观察脑内有关核团的Fos表达 ,以及PVN和LC中Fos表达阳性的神经元的性质。结果 :单一冷应激能使脾脏NK细胞活性明显下降 ,下丘脑室旁核 (PVN)和脑干蓝斑 (LC)出现明显的Fos表达。双染实验表明 ,PVN中有部分神经元同时表达精氨酸加压素 (AVP) ,LC中大多数神经元同时表达酪氨酸羟化酶 (TH)。结论 :PVN中的AVP能神经元和LC中的儿茶酚胺能神经元很可能参与冷应激诱发的脾脏NK细胞活性的下降     

Follicle-stimulating hormone induces spermatogenesis mediated by androgen production in Japanese eel, Anguilla japonica

Follicle-stimulating hormone (FSH) plays important roles in spermatogenesis. However, the biologic activity of FSH can vary in different vertebrate classes, and the definitive function of FSH has not been established. In this study, we investigated the functions of FSH on spermatogenesis using an in vitro culture system for Japanese eel testis. The eel Fsh receptor was expressed in testis tissue during the whole process of spermatogenesis, mainly by Leydig cells that produce steroid hormones and by Sertoli cells surrounding type A spermatogonia and early type B spermatogonia. In an in vitro organ culture, recombinant eel Fsh (r-eFsh) induced complete spermatogenesis from the proliferation of spermatogonia to spermiogenesis during 36 days of culture; also, spermatozoa were observed in the testicular fragments. Spermatogenesis induced by r-eFsh was inhibited by trilostane, a specific inhibitor of 3beta-hydroxysteroid dehydrogenase. However, trilostane did not inhibit spermatogenesis induced by 11-ketotestosterone. These results clearly show that the main function of FSH in eel is to induce spermatogenesis via stimulating androgen production.     

Follicle-stimulating hormone and estradiol regulate antrum-like reorganization of granulosa cells in rat preantral follicle cultures

Formation of a fluid-filled antrum results from the actions of FSH and estrogen on preantral ovarian follicles in most mammalian species. To investigate the novel proposal that hormone-regulated cell-cell interactions mediate antrum formation, we isolated preantral follicles from infant (10- or 11-day-old) Wistar rats and cultured them in a substratum-adherent manner in Minimum Essential Medium supplemented with 2 mM hypoxanthine, 3 mg/ml bovine serum albumin, 5 micrograms/ml insulin, 5 micrograms/ml transferrin, and 5 ng/ml selenium. Similar cultures were previously shown to support oocyte growth and acquisition of meiotic competence. In the absence of FSH, follicles attached to the plastic surface and granulosa cells spread-out uniformly around granulosa cell-enclosed oocytes. FSH treatment caused certain follicles to show an increase between culture days 3 and 7 in appearance of conspicuous antrum-like reorganization of the granulosa cells, but without forming a completely enclosed fluid-filled cavity. This response was biphasic over 10-500 ng/ml FSH, with an optimal concentration of 50 ng/ml resulting in a mean of 37.8 +/- 4.7% of follicles showing antrum-like reorganization for 3 similar experiments. Estradiol-17 beta alone at 10(-10)-10(-8) M was without effect on this response, but at 10(-10) and 10(-9) M, it significantly augmented the action of an optimal concentration of FSH by about 2-fold in 4 experiments. In these experiments, the effect of 10(-8) M estradiol was not significantly different from FSH alone, indicating that the response to estradiol was also biphasic.(ABSTRACT TRUNCATED AT 250 WORDS)     

Microinjection of transforming ras protein induces c-fos expression.

Microinjection of p21ras induced c-fos protein accumulation in three types of 3T3 cells. The induction was rapid and efficient and persisted for many hours. In addition, anti-ras antibody dramatically reduced c-fos accumulation after serum stimulation of injected cells. However, cells which expressed p21ras continuously did not maintain a high level of c-fos expression.     

Transglutaminase activity in testicular homogenates and serum-free Sertoli cell cultures

Transglutaminase (EC 2.3.2.13) (TGase) activity has been localized in homogenates of rat Leydig cells and seminiferous tubules and is present in cytosol and membrane fractions. The enzyme has a requirement for Ca2+ and when the acceptor substrate casein was deleted from the assay mixture, incorporation of [14C]putrescine into cytosolic and membrane fractions occurred. Transglutaminase was also detected in Sertoli cells cultured in serum-free medium. Sertoli cells reside within the seminiferous tubule and are involved in normal spermatogenesis. Sertoli cell TGase has a strict requirement for Ca2+ and is not activated by Mg2+. Activation of the enzyme occurs with as little as 0.3 microM Ca2+; however, consistent with intracellular calcium levels, maximum stimulation occurred at 1.9 mM Ca2+. Sertoli cell TGase activity is markedly stimulated if the cells are cultured in 10% fetal bovine serum rather than in serum-free medium. Inhibition of Sertoli cell TGase by monodansylcadaverine concomitantly decreased the response of the cells to follicle-stimulating hormone (FSH)-induced secretion of cAMP but did not change basal cAMP levels. These data suggest that TGase may play a facilitative rather than an absolute role in activation of Sertoli cells by FSH and the resultant secretion of cellular products. This may occur through modulation of activities of membrane and cytosolic components by TGase.