Guanylin-immunoreactive cells in the female and male rat adenohypophysis and their changes under various physiological and experimental conditions

The peptide guanylin, first isolated from rat small intestine, is involved in the regulation of water–electrolyte transport between the intracellular and extracellular compartments of the epithelia. The main sites of guanylin expression are the intestinal, airway, or exocrine gland ductal epithelia where guanylin acts in a paracrine/luminocrine fashion. Because guanylin also circulates in the blood, sources of this peptide were sought in endocrine glands. Our group has already demonstrated the presence of guanylin-immunoreactive cells in the pars tuberalis of male rat adenohypophysis. In this study, we investigated whether guanylin-immunoreactive cells exist also in the adenohypophysial pars distalis and whether their appearance or distribution correlates with various physiological conditions in female rats or alters after gonadectomy in both sexes. These studies revealed that the rat pars distalis contains two guanylin-immunoreactive cell types, gonadotrophic cells, whose number varied notably during the estrous cycle, reached a peak in the proestrous phase, and increased consistently during pregnancy, in lactating animals, and after gonadectomy, and folliculo-stellate cells, a discrete number of which were found only in female rats at the estrous phase. These findings suggest that guanylin is involved in regulating gonadotrophic cell function. They also add important information on the controversially discussed functions of folliculo-stellate cells.     

Effect of castration on hypothalamic testosterone metabolism in the male rat

In vitro studies were performed of hypothalamic testosterone (T) metabolism 30 days after castration of adult male rats. No changes were seen in T conversion into dihydrotesterone and estrogens in the castrated rats. Plasma T levels were decreased while plasma estradiol concentrations did not differ from those of intact controls. It was suggested that the hypothalamic T metabolism probably is not androgen dependent.     

Effects of brain and mesenchyme upon the cytogenesis of rat adenohypophysis in vitro

Summary The objective of this in-vitro study was to examine whether the diencephalic floor or the mesenchyme is involved in differentiation of LH cells in the developing rat adenohypophysis. Overall growth of the adenohypophysial tissue was retarded when the adenohypophysial primordium was cultivated after enzymatic removal of the diencephalic floor on days 11.5 and 12.5 of gestation. This malgrowth was more marked when the brain was separated on day 11.5; most expiants retained a simple cystiform structure that consisted of a few layers of undifferentiated cells. Removal of the brain also caused a highly significant decrease (P < 0.001) in the number of immunoreactive LH cells, if it was performed on day 11.5 but not day 12.5. Mesenchyme had little effect on the adenohypophysial growth or the number of immunopositive cells. Cultivation of the adenohypophysial primordium with the diencephalic floor resulted in the appearance of many immunoreactive LH cells. The number of LH cells significantly decreased, however, when the co-cultivated brain completely surrounded the adenohypophysial tissue.These results indicate that in 11.5-day-old fetal rats the diencephalic floor is indispensable for the initial proliferation of adenohypophysial primordial cells and for the early determinating process of LH cells. Once determined, the development of LH cells may proceed without the surrounding tissues. The cytodifferentiation seems to be rather inhibited when in contact with the brain. The significance of the intimate spatial relationship between developing LH cells and the surrounding mesenchyme is also discussed.     

Changes in rat brain opiate receptor content upon castration and testosterone replacement.

The saturable binding of naltrexone-³H in the brains of castrated male rats exceeds that found in intact animals by a factor of two. This increase is androgen dependent since testosterone replacement reduced the binding to control levels. Scatchard analysis of the saturation curves revealed that the change in binding reflects increased available binding sites and is not due to increased binding affinity. This relationship between testosterone and brain opiate receptors provides for the participation of endorphins in the regulation of pituitary gonadotropins by gonadal hormones. The increased content of opiate receptors in the brains of castrated rats correlates with the greater brain N-demethylation of morphine establishing a further link between this biotransformation and agonist action.     

Castration cells in rat adenohypophysis after long-term alcohol consumption

Histological and ultrastructural changes of hypophyseal gonadotropic cells of rats which received a 15% solution of ethyl alcohol for 6 months were studied. Light microscopy revealed hyperplasia and hypertrophy of these cells; some contained a vacuole of varying size. Ultrastructural analysis showed that this vacuole originated from, and anastomosed with, dilated cisternae of the granulated endoplasmic reticulum. Vacuolated cells in the pituitary of alcoholized rats were identical with cells observed after surgical or chemical castration. The development of these alcohol-induced castration cells is achieved in four stages. The first stage was characterized by beginning hydropic degeneration and other still reversible alterations. Cells in the second and third stages seemed already irreversibly on their way to decay. The fourth stage was represented by typical signet-ring cells. Our results offer a morphological basis to the adoption of a biphasic effect of alcohol on gonadotropic secretion.     

The ultrastructural characteristics of the corticotropic cells of the rat adenohypophysis

Ultrastructural characteristics of corticotropic cells have been studied on serial semithin and ultrathin sections of the hypophysis from intact rats by the immunofluorescence and electron microscopic methods. It is shown that the population of corticotropic cells is heterogeneous and consists of degranulated, moderate granulated, hypergranulated cells and transitional forms among them. Ultrastructurally corticotropic cells correspond to Siperstein-Nakayama's ACTH cells. Kurosumi-Kobayashi "corticotrophs" fail to react with the antiserum to ACTH, so they have not regard for its production.     

Estrogens and cell multiplication in the adenohypophysis of the male rat: in vivo and in vitro studies

A single dose (1 microgram) of oestradiol sub-cutaneously injected to an immature male rat promotes a transitory increase of the pituitary mitotic activity, the maximum of which is reached between 32 and 48 hours ; the observed fluctuations are similar to those previously described for the thymidine kinase activity. In these conditions, the concentration of blood prolactin remains unaltered, as were those of LH and FSH. It follows that hyperplasy of the pituitary can be quickly induced by doses of oestrogen that do not affect significantly the hormone release. Using Moxestrol, a synthetic oestrogen not bound by the oestradiol plasma binding protein, we show that in the very young rat, the in vivo responsiveness of the pituitary increases and reaches its maximum by day 17. This results can be tentatively related to the ontogeny of the oestradiol receptors in the pituitary described by others ; all our attempts to induce the thymidine kinase in cultured glands remained unsuccessful.     

Time-dependent changes in brain biogenic amine dynamics following castration in male rats

—Alterations in whole-brain and hypothalamic levels of serotonin (5-HT), 5-hydroxyindoleacetic acid (5-HIAA), norepinephrine (NE), dopamine (DA) as well as the turnover rates of NE and DA of adult male rats were analysed fluorometrically at either 3 weeks or 6 weeks following castration. Significant increases were observed in whole-brain (minus hypothalamus) 5-HIAA levels and hypothalamic DA levels, fractional rate constants and utilization rates at the 3 but not the 6 week intervals. Elevated levels of 5-HT were observed at both time intervals while an increase in whole-brain DA was seen only at the 6 week interval. Whole brain NE turnover rates of castrated animals did not differ significantly from those of sham-castrate control animals at either test interval. However, a tendency toward increased hypothalamic NE turnover rates was seen in the castrated animals. These biochemical changes resulted in decreased NE/5-HT and DA/5-HT ratios for the castrate rats as compared to controls. The results are discussed in relation to emotional and aggressive behavior and are interpreted as being consistent with the hypothesis purporting an inhibitory role for 5-HT and excitatory role for NE and DA in sex-specific behavior patterns including aggression.     

Immunocytological study of the gonadotrophic and thyrotrophic cells of the rat adenohypophysis]

On paraffin or semi-thin sections various anti-LH or anti-TSH sera stain indifferently all the thyrotrophs and the gonadotrophs. Inversely anti-beta-TSH, anti-beta-LH or anti-beta-FSH purified sera permit the discrimination of these two cell populations. The constancy of fixation of the anti-beta-LH and anti-beta-FSH sera on all the gonadotrophs gives evidence of their ability to produce both FSH and LH. However in a few female rats the central gonadotrophs are stained more weakly by anti-beta-FSH serum than by anti-beta-LH serum. The purification of the antisera by adjunction of hormonal antigens (alpha subunits or heterologous hormone) does not enable, with the PAP technique on thin sections, a selective staining of the secretory granules of the thyrotrophs or of the gonadotrophs.     

人骨髓间充质干细胞在成年大鼠脑内的迁移及分化

骨髓间充质干细胞 (mesenchymalstemcells,MSCs)是目前备受关注的一类具有多向分化潜能的组织干细胞 ,体外可以分化为骨、软骨、脂肪等多种细胞。因此 ,MSCs是细胞治疗和基因治疗的种子细胞之一。为了探索MSCs的迁移和分化趋势 ,为帕金森病 (Parkinsondisease,PD)的干细胞治疗提供理论和实验依据 ,本实验将体外扩增并转染增强型绿色荧光蛋白 (enhancedgreenfluorescentprotein ,EGFP)的人骨髓MSCs注入PD大鼠脑内纹状体 ,观察了人骨髓MSCs在大鼠脑内的存活、迁移、分化以及注射MSCs前后大鼠的行为变化。结果表明 ,人骨髓MSCs在大鼠脑内可存活较长时间 ( 10周以上 ) ;随着时间的延长 ,MSCs迁移范围扩大 ,分布于纹状体、胼胝体、皮质以及脑内血管壁 ;免疫组化法检测证实MSCs在大鼠脑内表达人神经丝蛋白 (neurofilament,NF)、神经元特异性烯醇化酶 (neuron specificeno lase,NSE)以及胶质原纤维酸性蛋白 ( glialfibrillaryacidprotein ,GFAP) ;PD大鼠的异常行为有所缓解 ,转圈数由 8 86±2 0 9r/min下降到 4 87± 2 0 6r/min ,统计学分析P <0 0 5为差异显著。以上观察结果表明 ,骨髓MSCs有望成为治疗PD的种子细胞     

Semi-automatic morphometric analysis of secretory granules in the cells of the rat adenohypophysis

The authors carried out a morphometric analysis--using a semi-automatic system for image analysis--of the secretory granules in the cells of the Wistar rat adenohypophysis. They evaluated the mean diameter (CIRCLE D), maximum diameter (MAX D), the factor of circular form (PE FORM) and the harmonic factor of form (HAR FORM). They also computed the coefficient of correlation between CIRCLE D and PE FORM and the percentual distribution of the values according to mean diameter.     

Neural stem cells in the brain

Stem cells in the central nervous system were usually considered as relevant for evaluation only in embryonic time. Recent advances in molecular cloning and immunological identification of the different cell types prove the presence of neurogenesis of the new neurons in adult mammals brains. New neurons are born in two areas of the mammal and human brain--sybventricular zone and subgranular zone of dentate gyrus. New born granular neurons of dentate gyrus have a great importance for memory and learning. New neurons originate from precursors which in culture and in situ could also transform into astrocytes and oligodendrocytes, thus fulfill criteria of neural stem cells. In culture, mitotic activity of these stem sells depends on fibroblast growth factor 2 and epidermal growth factor. Depletion of cultural medium of these factors and addition of serum, other growth factors (Platelet-derived growth factor and ciliary neurotrophic factor) leads to generation of neurons and astrocytes. Isolation and clonal analysis of stem cells is based on immunological markers such as nestin, beta-tubulin III, some types of membrane glicoproteids. Identification and visualization of stem cells in brain revealed two populations of cells which have properties of stem cells. In embryonic time, radial glia cells could give origin to neurons, in mature brain cells expressing glial fibrillar acidic protein typical marker of astrocytes fulfill criteria for stem cells. Neural stem cells could transform not only into mature neurons and glial cells but also into blood cells, thus revealing broad spectrum of progenitors from different embryonic tissues. Further progress in this field of neurobiology could give prosperity in the cell therapy of many brain diseases.     

A paradoxical castration effect on LH-RH levels in male rat hypothalamus and serum

Serum and hypothalamic luteinizing hormone releasing hormone (LH-RH) was lowered in young mature male rats after castration. Testosterone injections raised the hypothalamic LH-RH content significantly. The mean value of serum LH level was elevated by testosterone, but not significantly. Hypothalamic LH-RH content was also lowered by hypophysectomy. In this circumstance, testosterone injections significantly increased LH-RH content. These results suggest that there may be a positive feedback of testosterone upon the hypothalamic LH-RH release and synthesis mechanisms.