The anatomy, histology and androgen receptor immunohistochemistry of the prostate (P), seminal vesicles (SV), bulbourethral and coagulant gland (CG) were studied in male viscacha, a seasonally reproductive wild rodent. Two histologically well-defined zones, peripheral and central, were identified in the prostate, according to their relationship with the urethra. The epithelial cells were periodic acid-Schiff (PAS)-positive in the central zone and alcian blue negative in the two zones. The SV are a paired gland, tubular, of tortuous aspect and formed by radial layers. The bulbourethral glands were paired, formed by tubuloalveolar acini and surrounded by a thick layer of skeletal muscle. The CG was multilobulated. The large adenomers showed PAS-positive epithelium and were negative to alcian blue. Androgen receptors in the P, SV and coagulating gland showed variations in their distribution with immunohistochemistry heterogeneous pattern. Finally, the reproductive system accessory glands of male viscacha may be considered as a novel and interesting model for the study of seasonal reproduction in photoperiod-dependent animals.
The gonadotropes, LH and FSH cells, were immunohistochemically identified in the pituitary pars distalis of the adult male viscacha (Lagostomus maximus maximus) using specific antibodies against hLH‚ and hFSH‚ with the streptavidinbiotin- peroxidase complex. The distribution, size and percentage immunopositive area of these cells were analyzed by image analysis in viscachas captured during the annual reproductive cycle and after the chronic administration of melatonin. The LH‚ and FSHb cells showed seasonal changes in the distribution, size and percentage immunopositive area. The LHb cells were found widely distributed throughout the pars distalis during the reproductive period, and they were found in the ventro-medial region in the pars distalis during the gonadal regression and gonadal recovery periods. The LHb cells reached the largest size and immunopositive area during the reproductive period and the smallest size and immunopositive area during the gonadal regression period. The FSHb cells were found in the ventro-medial region during reproductive and gonadal regression periods. The FSHb cells were found widely distributed throughout the pars distalis during the gonadal recovery period when they showed the maximum percentage immunopositive area. A decrease in the size of LH‚ and FSHb cells was observed after the chronic administration of melatonin. Moreover, it produces a decrease in the immunopositive area occupied by the LH‚ cells but not in the immunopositive area occupied by the FSHb cells. Our results show great activity of LHb and FSHb cells in different moments of the annual reproductive cycle demonstrating that these cells are not secrete in parallel. Moreover, melatonin acts differentially on the activity of the gonadotrope cells
Somatotrophs were identified and quantified in pituitary pars distalis of male viscachas (Lagostomus maximus maximus) during the annual reproductive cycle, after the administration of melatonin, after castration and in different growth stages by immunohistochemistry and morphometric analysis. In adult male viscachas, the somatotrophs were distributed throughout the pars distalis during the reproductive cycle. They were oval, pyramidal or round in shape with a large round nucleus. The percentage immunopositive area, the major cellular diameter and the number of cells decreased during the gonadal regression period in relation to the values found in the reproductive period. The administration of melatonin did not provoke any variations of the morphometric parameters studied. On the contrary, a significant decrease in the percentage immunopositive area, in the major cellular diameter and in the number of somatotrophs in castrated viscachas was observed. The study of different growth stages showed that these morphometric parameters increased from immature to adult animals in the reproductive period. The results obtained suggested that the variations of the morphometric parameters of somatotrophs are more related to the gonadal development and activity than to a direct effect of melatonin.
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