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The objective of this study was to investigate the circannual ovarian cycle month-wise round the year at morphological, ultrastructural and hormonal levels in an estuarine teleost, the grey mullet Mugil cephalus L. The gonadosomatic index and follicular population per ovary began to rise from September to October (pre-breeding), reached peak during November and December (breeding) and declined from January to August (post-breeding phase). Oocyte diameter increased during pre-breeding, attained maximum size in breeding and drastically reduced in post-breeding phase. But the follicular populations per milligram of ovary per microscopic field were moderately high in pre-breeding, least in breeding and highest in post-breeding. Histologically, the ovarian lobules were moderately large and contained small and large follicles in pre-breeding, maximally enlarged with mostly large follicles in breeding and became narrow with very small follicles in post-breeding. Ultrastructurally, three types of oocytes (1) smal...

Circadian rhythms of ovarian activity during the breeding phase of the circannual ovarian cycle were poorly known in estuarine teleosts. This topic was resolved in an Indian estuarine teleost, the grey mullet, Mugil cephalus. Several hormones and blood glucose profiles were investigated at four different time intervals (06.00, 12.00, 18.00 and 24.00 h) of a 24-h period. Sex hormones [estradiol-17β, testosterone and 17α,20β-dihydroxy-4-pregnen-3-one (DHP)] were quantitated by RIA, FSH, LH, prolactin, T3, T4 and TSH and insulin by ELISA and cortisol, catecholamines and indoleamines by fluorometric analysis. Estradiol-17β, testosterone and DHP profiles were higher in the photophase (06.00–18.00 h) than the scotophase (18.00–06.00 h), with a peak at 12.00 h, whereas, FSH, LH and prolactin concentrations were higher in the scotophase than the photophase with a peak at 24.00 h. But cortisol, epinephrine, norepinephrine, and insulin levels were higher in the photophase than the scotophase, with peaks at 06.00 h ...

The aim of the current investigation was to study the effect of lithium on circadian rhythms of pineal – testicular hormones by quantitations of pineal and serum serotonin, N-acetylserotonin and melatonin, and serum testosterone at four time points (06.00, 12.00, 18.00 and 24.00) of a 24-hr period under normal photoperiod (L:D), reversed photoperiod (D:L), constant light (L:L) and constant dark phase (D:D) in rats. Circadian rhythms were observed in pineal hormones in all the combinations of photoperiodic regimens, except in constant light, and in testosterone levels in all the photoperiodic combinations. Pineal and serum N-acetylserotonin and melatonin levels were higher than serotonin at night (24.00 hr), in natural L:D cycle, in reversed L:D cycle or similar to normal L:D cycle in constant dark phase, without any change in constant light. In contrast, testosterone level was higher in light phase (12.00 hr through 18.00 hr) than in the dark phase (24.00 hr through 06.00 hr) in normal L:D cycle,...

The current study was undertaken to ascertain the seasonal influence of thyroid activity in female soft-shelled turtles, Lissemys p. punctata. Thyroid gland was studied month-wise throughout the year from relative gland weight, histology, epithelial height, glandular peroxidase activity, and RIA of T3 and T4 levels from blood serum and the thyroid gland. The values of all the parameters, except those of T3 and T4, were higher during March through May, decreased from June through August and began to rise thereafter (September through February). Whereas T3 and T4 levels were highest in May, lower during June to November and began to rise thereafter. The difference in the peaks between T3 and T4 levels and other parameters have been explained. The findings suggest that thyroid activity of Lissemys turtles varies seasonally and that seasonal factors like temperature play an important role in influencing thyroid activity in soft-shelled turtles.

The seasonal adrenocortical cycle in the female soft-shelled turtle Lissemys p. punctata was investigated by examining the adrenal gland once a month throughout the year from gravimetric, histological, histochemical and biochemical standpoints. The adrenal gland weight, nuclear diameter, histochemically detected 3s-hydroxysteroid dehydrogenase activity, corticosterone and RNA concentrations, and acid phosphatase and alkaline phosphatase activities began to increase from early summer (March-June), reached a peak in late summer (July-August) and declined subsequently (September-February), but adrenal cholesterol and ascorbic acid levels together with histochemically demonstrated sudanophilic lipids were altered reversely to those of other parameters. The results indicate that adrenocortical activity varies seasonally, being higher in early summer, highest in late summer and low in winter, that coincides with the seasonal ovarian cycle in Lissemys. It is suggested that there is a correlation between ovarian ...

The aim of the present study was to acertain the seasonal pattern of adrenomedullary hormones and of glycemia in Lissemys turtles. Both the norepinephrine and epinephrine concentrations as well as blood glucose levels varied seasonally which began to rise from February, became maximum during April–May (early summer), declined during June–September (late summer) and were extremely low subsequently (October–January). The seasonal adrenomedullary hormonal and glycemic cycles however do not coincide with the annual ovarian cycle, thereby indicating that the adrenomedullary and glycemic cycles are out of phase with the ovarian cycle in turtles. The possible mechanisms of seasonality of the adrenal medulla and glycemia are discussed.

The present investigation was carried out on oviductal activity during the annual ovarian cycle of the Indian tree pie (Dendrocitta vagabunda). The oviductal activity was evaluated by weight, length, histology (gross and quantitative) and peroxidase, acid phosphatase, alkaline phosphatase, sialic acid, glycogen, RNA and protein concentrations of different regions of the oviduct. All these values w ere low during the nonbreeding phase (August to January), increased during the progressive phase (February to March), became maximum during breeding (April to May) and decreased in the regression phase (June to July). The functional change of the oviduct is suggested to be due to fluctuation of ovarian steroid activity in this avian species.