Adenohypophysial cell-types in the pituitary gland of the soft-shelled turtle, Trionyx sinensis. I. Seasonal cycles.

By using various staining techniques, two acidophilic and three basophilic cell-types have been distinguished in the pars distalis of Trionyx sinensis. Seasonal fluctuations in their cytoplasmic granulation, cell and nuclear size have been compared with seasonal patterns of activity in the gonads, adrenals and thyroid. On the basis of the results, specific functions have been ascribed to each cell-type. Basophils 1 activity closely parallels the seasonal thyroid cycle. Basophils 2 are probably FSH-secreting gonadotropes and their activity correlates with the seasonal cycle of spermatogenesis in the seminiferous tubules. The functional activity of the testicular interstitial cells correlates with the secretory pattern of the basophils 3. That these are LH-secreting cells is also suggested by the epididymidal cycle, which indicates a high level of androgen secretion coincident with the rapid degranulation of these cells, at a time of no spermatogenetic activity. Adrenal activity shows no relationship with the basophils 3 cycle, and chromophobic cells may be the locus of ACTH secretion. Acidophils 2 remain stable throughout the year and are probably somatotropes, but acidophils 1 increase their activity in autumn and are likely to be lactotropes.

PIP: 2 acidophilic and 3 basophilic cell types were identified in the pars distalis of the soft-shelled turtle (Trionyx sinensis) and their function was interpreted. Comparison of seasonal fluctuations in cytoplasmic granulation and cell and nuclear size with seasonal patterns of gonadal, adrenal, and thyroid activities indicated specific functions for each of the cell types. The activity of basophils 1 closely paralleled the seasonal pattern of the thyroid cycle, while basophils 2 are most likely follicle-stimulating-hormone-secreting gonadotropes whose activity correlated with the seasonal pattern of spermatogenesis in the seminiferous tubules. The secretory pattern of the basophils 3 was correlated with the functional activity of the testicular interstitial cells, which suggests that these are luteinizing-hormone-secreting cells. This is supported by a high degree of androgen secretion during the epididymal cycle which coincided with rapid degranulation of these cells at a time when spermatogenesis was in arrest. No apparent correlation between adrenal activity and the basophils 3 cycle was observed. It is suggested that the chromophobic cells may be the site of ACTH secretion. Acidophils 1 increased their activity in the autumn and are probably lactotropic in function, while acidophils 2 activity was stable throughout the year, which suggests that they are likely to be somatotropes.

Arbovirus infections in reptiles: studies on the presence of Japanese encephalitis virus antibody in the plasma of the turtle, Trionyx sinensis.

This study was undertaken to examine further the natural infection of poikilothermic animals e.g. turtles, to Japanese encephalitis (JE) virus. Plasma samples from 75 soft-shelled fresh water turtles (Trionyx sinensis Wiegman) from China were examined in virus neutralization (VN) and hemagglutination inhibition (HAI) tests for the presence of specific antibody. The total incidence of antibody detected by either test to a titer of 10 or greater was 89% while 77% and 60% were positive by VN and HAI tests, respectively. Forty-one per cent were jointly positive by both tests. Mean HAI and VN titers were similar and showed no obvious differences between spring/summer and autumn/winter seasons. The HAI reactivity was associated with a 7S component for both seasons. The significance of this inhibition in the serology of poikilothermic hosts and the possible behaviour of T. sinensis in the natural history of JE virus is briefly considered.