The mode of secretion in the anterior pituitary gland of the cow and the ewe.

In the present study of the bovine and ovine pars distalis adenohypophysis another secretion mechanism besides the well established exocytosis is described. Within cellular accumulations surrounded by a sparse connective tissue the process of secretion seems to be induced by fusion of the glandular cells. The direct passage of glandular cell material out of these syncytia into the adjacent sinusoidal capillaries is demonstrated in light and electron microscopic photographs. This secretion mechanism must be considered to be holocrine in nature, because the nuclei of the glandular cells are also found to pass directly into the blood vessels. The question concerning the replacement of the glandular cells, however, could not be finally clarified. The significance of the holocrine secretion in the adenohypophysis might be seen in the maintenance of a certain base-line secretion, while the fine hormonal regulation presumably is controlled by exocytosis, with the release of individual hormones being receptor mediated.

The morphogenesis of the vasculature in swine fetal skin.

The morphogenesis of the vascular elements in the skin of 45 swine fetuses (German landrace), from 50 to 330 mm crown-to-rump (C-R) length, was described. A simple pattern for the cutaneous vascular networks could be recognized in fetuses ranging from 90 to 100 mm C-R length. In 150 to 170 mm length-fetuses, the cutaneous blood vessel networks were differentiated into a definite pattern of construction. The venous blood drained regionally through the Plexus venosus subpapillaris profundus into the Plexus venosus dermis profundus. Each region ("Unit Vascular Zone") was supplied by more than one R. arteriosus cutaneus . The large branches of R. arteriosus cutaneus were accompanied by 2 satellite veins. At the end of gestation, the vessels of the Plexus venosus dermis profundus exhibited a beaded appearance which indicated the presence of valves.

The effect of long-term HCG or TP administration on reproductive functions in adult male rabbits. I. Histomorphological changes in the scrotum.

The effect of long-term treatment with various doses of HCG or TP on the scrotum was studied in 36 adult rabbits of pure Bouscat breed. The epidermis of the scrotum exhibited a more significant dose-related increase in thickness in animals injected with TP than those treated with HCG. The hair follicles in animals injected with higher doses of HCG or TP were thicker in diameter and extended deeper within the dermis where they curved to grow parallel to the surface of the skin. The high dose of HCG was more effective in demonstrating higher glandular activity than that seen in rabbits treated with high doses of TP. The vascularization in the scrotum was more prominent in rabbits treated with higher doses of HCG. The fibers of the Tunica dartos were much thicker in animals treated with high doses of HCG or TP.

Effect of cyproterone acetate, d-norgestrel and progesterone on cells of the pars distalis of the adenohypophysis in the beagle bitch.

The effects of short-term (8 weeks) treatment with different doses of cyproterone acetate (CPA), d-norgestrel (d-N) and progesterone on cells of the pars distalis, as revealed by the immunoperoxidase technique, were studied in cycle-synchronized beagle bitches (first anoestrus). Pituitary glands from non-treated primiparous beagle bitches at the 6th and 9th week of pregnancy were also included. For immunochemical staining specific antisera to the following hormones were used: canine GH, canine PRI, porcine ACTH, bovine TSHbeta, bovine LHbeta and human FSHbeta. Morphological features of high secretory activity in GH cells were evident even after the human oral contraceptive does of CPA and d-N, and after a dose as low as 0.1 mg/kg/day subcutaneously (s.c.) of progesterone. In contrast, PRL cells did not show any significant treatment-related effects except in those animals which received the highest dose of d-N (0.5 mg/kg/day per os). In this group, as well as in all pregnant bitches, hyperplasia and hypertrophy of PRL cells were found. In the animals treated with the highest doses of CPA (4.0 mg/kg/day per os) and progesterone (42.5 mg/kg/day s.c.) as well as in pregnant bitches, ACTH/MSH and TSH cells showed marked atrophy and regressive changes. Similar morphological signs of depressed secretory activity were also observed in the cells shown to contain FSHbeta and/or LHbeta as a result of treatment with the highest dose of progesterone and at the 9th week of pregnancy. These structural responses indicate that quantitiative and/or qualitative differences may exist between progesterone, the synthetic progesterone derivative CPA and the nortestosterone type progestagen d-N with regard to their effect on pituitary hormone secretion in the beagle bitch.

Localization of gonadotrophic hormones in the dog pituitary gland. A study using immunoenzyme histochemistry and chemical staining.

Using the immunoperoxidase technique and antisera to the specific beta (beta) subunits of FSH and LH1, selective immunochemical staining was localized mostly in the same cell type in the pars distalis and pars tuberalis of the dog pituitary gland. However, some cells were consistently shown to react solely with antisera to either LH beta of FSH beta. The cells stained for FSH beta were at least 1.5 times less numerous than those shown to contain LH beta. In the pars distalis of adult male dogs the immunoreactive gonadotrophs varied greatly in their relative proportion and were mostly shown to be much less numerous than in bitches in the anestrus phase of the sexual cycle. These cells were found to be positive to aldehyde fuchsin, alcian blue, periodic acid-Schiff (PAS) and aniline blue. The performic acid-alcian blue (pH 0.2)-PAS-orange G procedure stained the FSH/LH cells blue or turquoise, demonstrating TSH cells (blue-purple), ACTH/MSH cells (red-purple) and PRL cells (orange-red). The FSH/LH cells were further differentiated from other functional cell types of the pars distalis on the basis of their typical cytological features, intraglandular distribution and by immunochemical double staining. These observations support the concept that the one cell-one hormone theory may not apply to gonadotrophic hormones, although some cells seem to be the source of either FSH or LH.

Effect of cyproterone acetate on cells of the pars distalis of the adenohypophysis in the beagle bitch.

The effects of oral administration of 100 mg per kg per day cyproterone acetate (CPA) for four weeks on cells of the pars distalis, as revealed by the immunoperoxidase technique and chemical staining, were studied in the ovariectomized beagle bitch. For immunochemical staining antisera to the following hormones were used: canine GH, canine PRL, procine ACHT, bovine TSH beta, bovine LH beta and human FSH beta1. The most striking effects of the treatment were an overall increase in the relative proportion of GH cells and a marked morphological indication of high secretory activity in these cells. In contrast, PRL cells were not affected significantly. In all ovariectomized control bitches a marked atrophy of the cells stained for FSH beta (FSH cells) and hypertrophy of the cells shown to contain LH beta (LH cells) were observed. FSH cells became enlarged, while LH cells appeared reduced in size by administration of CPA. In some treated bitches ACTH/MSH cells showed atrophy and regressive changes, whereas TSH cells seemed to become enlarged and were more densely arranged. These structural responses indicate that, in addition to its partial antigonadotropic properties, CPA as a synthetic progesterone derivative may stimulate GH secretion and possibly suppress CRH-ACTH activity in the ovariectomized beagle bitch.