Cytology of the pituitary gland of the Plains viscacha (Lagostomus maximu)

Histopathological and biochemical effects of gossypol acetate on pituitary-gonadal axis of male albino rats

Histopathological and biochemical effects of gossypol acetate (GA) on pituitary-gonadal axis were investigated. 10 and 25 mg GA/kg were administered orally to sexually mature adult male Wistar rats for 4 and 5 weeks, respectively. STH and LTH/PRL cells showed no significant changes as compared to those of controls while TSH cells showed hypertrophy, hyperplasia and degranulation in both experimental groups. Pituitary FSH, LH/ICSH cells showed progressive regression. Gonosomatic indices of sex accessory glands at 25 mg showed significant reduction in the experimental animals as compared to those of controls. The diameter of seminiferous tubules reduced and azoospermia developed. Sertoli and Leydig cells also regressed. At 10 and 25 mg GA treatment, spermatogenesis ceased at secondary spermatocytes and spermatogonia stages, respectively. Epididymis and prostate regressed. Seminal vesicle showed no significant histological variations as compared to that of control except reduction in secretion. Biochemical observations revealed increased levels of acid phosphatase, fructose and citric acid and significant reduction in glycerylphosphoryl choline in reproductive glands of both experimental groups as compared to those of controls. Possible mechanism of antifertility action of GA is discussed.

Effects of gossypol acetate on pituitary-adrenal axis in male albino rats

Histopathological effects of gossypol acetate (GA) on pituitary-adrenal axis in male Wistar rats were investigated. Sexually mature rats of proven fertility were administered orally with 10 and 25 mg/kg for 4 and 5 weeks, respectively. In both experimental groups, corticotrophs (ACTH cells) of anterior pituitary showed progressive regression. At the 10 mg low-dose treatment for 4 weeks, no significant changes were observed in all the zones of the adrenal gland, while at the same dose for 5 weeks of treatment, cells of zona glomerulosa showed hypertrophy and degranulation as compared to that of control. Cells of zona fasciculata and reticularis showed no significant changes. In the medulla, the thickly granulated cells were degranulated and reduced in number. At the 25 mg treatment, the cells of the zona fasciculata showed hypertrophy and degranulation. The possible mechanism of action of GA is discussed.

Presence of alpha-melanocyte-stimulating hormone in bovine pituitary intraglandular colloid of intermediate lobe origin

Alpha-melanocyte-stimulating hormone (alpha-MSH), one of several peptide hormones originating in the intermediate lobe of the pituitary as proopiomelanocortin, was discovered in bovine pituitary intraglandular colloid by using radioimmunoassay. The quantity of alpha-MSH varied from 5 to 368 micrograms/mg protein in the three pools. The importance of this finding is discussed in light of the possibility that the colloid is a transport medium for alpha-MSH and other intermediate lobe hormones.

Seasonal variations in pituitary thyrotropes of the hibernating bat Myotis lucifugus lucifugus: an immunohistochemical study

Pituitary thyrotropes were identified throughout the year in the hibernating bat Myotis lucifugus lucifugus by means of light microscopic immunohistochemistry. These cells occupied a small proportion of the volume of the pars distalis (mean = 1.36% in males; mean = 1.52% in females) and exhibited a limited distribution pattern that was characteristic of all animals examined. Cells that were immunoreactive with an antiserum directed against the beta subunit of thyroid-stimulating hormone were most numerous in the median rostral and ventral regions; they were scarce or absent in the dorsal portion of the gland and in the extreme lateral wings. No significant seasonal variations were observed in this cell population in females. In males, however, immunoreactive thyrotropes occupied a significantly larger proportion of the pars distalis in June (following arousal from hibernation than at other times of year. No evidence of involution was observed in these anterior pituitary cells in either males or females during hibernation.

A quantitative study of pituitary colloid in the bat Myotis lucifugus lucifugus in relation to age, sex, and season

Extracellular colloid accumulations were examined in pituitary glands of adult and juvenile, male and female, little brown bats, Myotis lucifugus lucifugus (Chiroptera: Vespertilionidae), collected at various times during the annual reproductive cycle. Round or ovoid periodic acid-Schiff-reactive accumulations of colloid were scattered throughout the pars distalis, pars intermedia, and pars tuberalis. These accumulations were surrounded by processes of agranular "follicular" cells. The proportion of the volume of the pars distalis occupied by colloid (volume fraction) exhibited considerable variation among animals, ranging from 0.00 to 3.18% in the total sample of bats. Pituitaries of juvenile males, yearling males, and nonparous females contained significantly less colloid than those of parous females and adult males. The mean volume fraction for each of these groups suggested that colloid content increased progressively from birth through sexual maturity in this animal. In addition, the frequency distribution of colloid content measurements made in parous females and adult males provided indirect evidence that colloid continues to accumulate throughout life. No sexual dimorphism in colloid content was observed before or after sexual maturity, and colloid content did not fluctuate in relation to the annual reproductive cycle of either males or females.

Induction of labour in sheep after fetal hypophysectomy: an investigation of the possible involvement of a fetal pituitary secretion in the activation of placental enzymes by fetal cortisol

Activities of 17 alpha-hydroxylase, C-17, 20 lyase and aromatase were measured in placentae of intact and hypophysectomized fetuses after premature induction of parturition by fetal administration of Synacthen. Activities of these enzymes were compared with concentrations of steroids produced by the placenta, which were measured in maternal plasma before and during parturition. Hypophysectomy was assessed by determining fetal plasma concentrations of LH before and after administering LH-RH, and histologically post partum. Concentrations of progesterone, which decreased before parturition, and of 17 alpha, 20 alpha-dihydroxypregn-4-en-3-one and oestradiol-17 beta, which increased, were not affected by fetal hypophysectomy. However, fetal hypophysectomy reduced the normal rise in oestrone sulphate which precedes parturition and abolished the normal rise in androstenedione. Although placental activities of C-17, 20 lyase and aromatase (but not 17 alpha-hydroxylase) tended to be reduced by fetal hypophysectomy, these effects were not statistically significant. The data support an earlier suggestion that an unidentified product of the fetal pituitary may be involved in the activation of C-17, 20 lyase by fetal cortisol before parturition. However, the results of the present study show that the action of such a factor is more likely to be permissive than obligatory.