Morphologic alterations in somatotrophs of the rat adenohypophysis following administration of hypothalamic extracts

Correlation of behavior with brain damage after in utero exposure to toxic agents

Early postnatal behaviors involving sensorimotor integration were measured along with thickness of the sensorimotor cortex in rats irradiated with 1.0 Gy on gestational day 11 or 17. Body weight and morphology of anterior pituitary cells were recorded. Irradiation on day 17 was more effective in reducing cortical thickness and body weight and performance on behavioral tests and less effective in altering pituitary cells than irradiation on day 11. Prediction of behavioral effects, using cortical layers, body weight and pituitary morphology as predictors in stepwise multiple regression, was measured in both irradiated and control rats. Cortical Layer V more than I more than IV and VI as significant predictors of behavior. The best predictions accounted for about half of the variance in the data. When behavioral data were used to predict brain damage, the best predictor was negative geotaxis. Significant association of behavior with Layers V and VI was found. These experiments show the difficulties in correlating complex behaviors with specific brain areas and, at the same time, implicate especially Layer V of the sensorimotor cortex in these behaviors.

Intracisternal granules in the somatotrophs in the anterior pituitary of the mouse

A detailed study of the anterior pituitaries of pregnant and lactating mice revealed changes occurring in the ultrastructure of the somatotrophs. The rough endoplasmic reticulum cisternae become greatly dilated forming channels that are continuous with the perivascular space. This occurrence expands the membrane surface available for the release of hormone. Individual granules and cytoplasmic islands containing numerous granules appear in these channels. This suggests an alternative mechanism for granule release which would facilitate a rapid response to increased hormone requirement.

A quantitative electron microscopic study on the frequency of exocytosis in the anterior pituitary of perinatal rats

Granule exocytosis was quantitatively investigated in the perinatal rat anterior pituitary at the electron microscopic level. Both the number of cells in the process of exocytosis and the number of extruded granules per cell profile found in a standardized area of section were counted. The first distinct figure of exocytosis was detected in the anterior pituitary of fetal rats on day 18.5 of gestation, although occasional cells on day 17.5 had structures resembling granule extrusion. The frequency of cells showing granule discharge was very low on day 18.5 of gestation, but it sharply increased on day 19.5; a similar level was maintained up to day 21.5 of gestation. While the number of exocytosed granules per cell profile was almost unchanged during the fetal and neonatal period up to day 3 after birth. The frequency of cells undergoing exocytosis decreased near the time of birth, after which it transiently increased and dropped again to a minimum at 12 h after delivery. During days 1 to 3 of postnatal life, cells in the process of exocytosis were less frequent compared to fetuses between day 19.5 and 21.5. Both the number of cells undergoing exocytosis and the number of discharged granules per cell profile first exceeded the fetal values on the 6th postnatal day and were remarkably augmented between days 9-20 of the neonatal period. These data are discussed in relation to the hormone secreting activity of the anterior pituitary gland of perinatal rats.

Ultrastructure of pituitary somatotrophs of male rats during liver carcinogenesis by 3'-methyl-4-dimethylaminoazobenzene

Somatotrophs of male Wistar rats fed a carcinogenic dose of the potent hepatocarcinogen 3'methyl-4-dimethylaminoazobenzene-(3'MeDAB) in a complete diet for up to 21 weeks, showed ultrastructural changes within one week of the start of the experiment. Morphometric analysis showed that the area of the somatotrophs occupied by hormone storage granules was reduced significantly at all stages up to 21 weeks, when the experiment was terminated. The cell area occupied by rough endoplasmic reticulum (RER) was significantly increased after three weeks and RER surface density increased after eight weeks, whilst granule size was reduced after four weeks. Pituitary content of radioimmunoassayable growth hormone (RIA-GH) was also lower in treated rats than in controls, from one week after the start of the experiment, but only significantly so at eight and twelve weeks, owing to large standard errors. Serum levels of RIA-GH were similarly lower in 3'MeDAB treated rats than in controls. Withdrawal of 3'MeDAB diet after twelve weeks treatment permitted partial recovery of some cell organelles, in that the content of hormone storage granules increased and the area of the RER decreased compared to rats fed 3'MeDAB continuously. There was also a partial, but non-significant, increase in pituitary RIA-GH. The pituitaries of rats pair-fed 3'MeDAB diet for 15 weeks contained significantly less RIA-GH than matched controls. These results suggest that 3'MeDAB, or its metabolites, may react with pituitary somatotrophs and impair their ability to synthesise and secrete hormone.

Lysosomes in anterior pituitary corticotrophs of the rat. A combined immunocytochemical and enzyme cytochemical study

E600 resistant non-specific esterase activity or acid phosphatase activity were localized in corticotrophic cells identified by postembedding immunocytochemistry (PAP of protein A-immunogold techniques). The lysosomal system of this cell type consists of dense bodies, of a population of small lysosomes mostly situated at the cell periphery in the vicinity of secretory granules as well as of tubular structures. These latter were located either in the central part of the cytoplasm and probably belonged to the Golgi apparatus or at the cell periphery, partly in the extensions. Small lysosomes occurred to be in continuity with enzyme-containing tubules. In a few structures lysosomal enzyme activity and ACTH immunoreactivity overlapped. Some autophagic vacuoles seemed to contain secretory granule matrix. It is suggested that the concept of crinophagy can be extended to the corticotrophs, though the lysosomal system may be involved in the specific function of this cell type by other mechanisms as well.

Immunohistochemical study of the responsiveness of LH cells of fetal rats to synthetic LHRH in vitro

Fetal rat pituitaries on days 17-19 of gestation were maintained in serum-free Medium 199 for 24 h in the presence of 1, 10 and 100 ng/ml of synthetic LHRH. Immunohistochemical examination of such stimulated tissue reveals a complete depletion of immunoreactive material in most of the LH cells, irrespective of the LHRH concentrations tested, though some cells remain weakly immunopositive in the pituitaries of later developmental stages. Once discharge has occurred, there is little reaccumulation of secretory material in LH cells during prolonged incubation for 48 h in LHRH-free medium containing 10% calf serum. The LHRH treatment causes no immunohistochemical change in TSH cells. It is concluded that in fetal rats recently differentiated LH cells can release the secretory product if they are stimulated by hypothalamic LHRH.

Ultrastructural study of somatotroph cells from mice bearing a fast growing transplanted hepatoma, in different periods of the tumor development

The presence of a transplanted, fast-growing hepatoma (SS1-K) produces conspicuous ultrastructural changes in pituitary STH cells of C3H-S male mice. These changes are suggestive of an increased secretion of growth hormone only during the first stages of the tumor development. The hepatoma influence does not seem to be clearly related to the illumination regimen or time of killing.

Immunochemical staining of the rat adenohypophysis in organ culture

Rat anterior pituitaries were cytologically studied following cultivation in organ culture, with and without the addition of hypothalamic and cortical extracts. Although five distinct cell types could be identified with classical stains in the uncultivated glands, the peroxidase-labeled antibody technique (using antibodies against STH, LTH, FSH, LH and TSH) showed that not all of the immune-specific cell types were being identified with the classical stains. This discrepancy was magnified following culture as chromophilic cells seen with classic stains decreased in number with an increase in culture time. The peroxidase technique, however, revealed that all cells remained constant in type and number regardless of time in culture. While the addition of either hypothalamic or cortical extract to the culture medium produced cytological alterations demonstrated by the classical dyes, the antibody technique showed no such alterations. Such a comparison of staining techniques emphasizes the hazards of relying solely on histological procedures to reveal the hormonal activity of the pituitary gland.