Supriti Sarkar

Histological and functional changes of oviductal endometrium during seasonal reproductive cycle of the soft‐shelled turtle, Lissemys punctata punctata

Scanning electron and light microscopic studies reveal significant changes in the endometrial histophysiology of the soft‐shelled turtle Lissemys punctata punctata during its seasonal reproductive cycle. Scanning electron microscopy shows the entire oviductal mucosa to be only slightly folded throughout the non‐breeding period (regressive, quiescent, preparatory and recrudescent phases). With the onset of the breeding phase, the mucosa shows extensive foldings and convolutions. The adluminal mucosal lining of the non‐breeding oviduct is covered by a tall, dense ciliary bed, interrupted by a few fissures and pits. Microvilli‐bordered secretory cells only appear amongst the ciliated cells during the breeding phase.

PHOTOTHERMAL EFFECTS ON OVARIAN GROWTH AND FUNCTION IN THE SOFT-SHELLED TURTLE LISSEMYS PUNCTATA PUNCTATA

Investigations were carried out to find out the role of higher and lower ambient temperatures together with short and long photoperiods on ovarian growth and secretion of steroids (estradiol-17 beta and progesterone) in the adult female soft-shelled turtle Lissemys punctata punctata during the preparatory, recrudescent, and quiescent phases of its seasonal reproductive cycle. In each phase, females were treated with 3 degrees C higher and 3 degrees C lower than the mean highest and lowest ambient temperatures in association with short and long photoperiods for short-term (4 week) and long-term (8 weeks or more) durations. Short-term high-temperature treatment significantly stimulated ovarian growth and secretion of estradiol-17 beta during the preparatory phase. Eight-week treatment failed to exercise further stimulation over 4-week treatment, whereas 10-week treatment caused regressive changes of ovary (atresia of follicles). Both short- and long-term high-temperature treatments caused degeneration of ovarian follicles during the recrudescent phase. Low-temperature treatment slowed down ovarian growth and secretion in both the preparatory and recrudescent phases. In the quiescent phase, low- as well as high-temperature treatments exercised little influence over the refractory ovarian growth and secretion. Photoperiod appeared to have no effect on female reproduction in any phase. Thus, high temperature is suggested to have a triggering role on ovarian growth and secretion of estrogen at the early preparatory phase, but once the ovarian function sets in, high temperature seems to have a regressive rather than stimulatory effect on ovarian growth and function.

Seasonal Thyroid Cycle of the Soft-shelled Turtle, Lissemys p. punctata (Bonnoterre)

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.

Roles of thyroid, adrenal and pancreatic hormones on thyroid activity of the soft-shelled turtles Lissemys punctata punctata Bonnoterre.

The effects of some exogenous peripheral hormones (thyroxine, corticosterone, epinephrine, norepinephrine and insulin) on thyroid activity were investigated in juvenile female soft-shelled turtles, Lissemys punctata punctata. Each hormone was injected in three different doses (25 microg, 50 microg or 100 microg each per 100 g body weight, once daily at 9 AM) for 10 consecutive days. Thyroid activity was evaluated by gravimetry, histology (epithelial height) and thyroperoxidase assay. The findings revealed that thyroxine in low dose (25 microg) stimulated thyroid activity by increasing the relative thyroid weight, epithelial height and thyroperoxidase activity, but inhibited gland activity at a high dose (100 microg) by decreasing the values of all these parameters. The medium dose (50 microg) had no significant effect. All other hormones, in all doses, significantly decreased thyroid activity by decreasing the values of all the parameters. Thyroid responses to exogenous hormones are generally dose-dependent in turtles. The mechanisms of actions of the hormones administered are suggested.

Arecoline aggravates hypothyroidism in metabolic stress in mice.

Abstract Millions of people consume betel nut for increased capacity of work. It contains arecoline which is highly toxic and has several untoward side effects on endocrine functions. In this article, the role of arecoline on thyroid function under metabolic stress was investigated in mice. Water or food-deprivation, each for 5 days, caused ultrastructural degeneration of thyro-follicular cells, evident from pycnotic nuclei, scanty rough endoplasmic reticulum and mitochondria followed by depletion of blood serum T3 and T4 levels with alteration of TSH level as compared with control. Thyroid activity was also suppressed ultrastructurally as well as at hormonal level after arecoline administration. Further, arecoline treatment in water deprivation or food deprivation stress also caused thyroid dysfunction beyond that of metabolic stress, as evident from further ultrastructural degeneration of thyrocytes and depletion of thyroid hormones in mice. The findings suggest that arecoline aggravates hypothyroid condition in metabolic stress in mice.

Modulations of thyroid activity following reproductive hormonal manipulations in soft-shelled turtles, Lissemys punctata punctata

Prolactin and sex hormones are known to modulate thyroid activity in vertebrate animals, but their findings are different in different vertebrates. Prolactin inhibits thyroid activity in higher dose by decreasing 131I uptake, serum PBI and T4 levels, follicular size and epithelial height in mammals, birds, red efts Triturus viridiscens, prometamorphic tadpoles of Rana pipiens and Rana catesbeiana, but stimulates in low dose by increasing values of these parameters in mammals, birds, crested newts and eels (Decuypere and Kühn, 1985). Estradiol, estriol, estrone and progesterone also inhibit thyroid activity in intact/gonadectomized/ hypophysectomized rats, rabbits and rhesus monkeys (Boado et al., 1983), intact juvenile ducks or ovariectomized Japanese quail (Maiti and Sahu, 1982; Pethes and Peczely, 1983) and in rainbow trout Salmo gairdneri, Anabus testudineus and Chana punctatus (Leatherland, 1985; Cyr et al., 1988), but stimulate in intact/gonadectomized/hypophysectomized rats and other mammals (Bisaria and Kapoor, 1976). Thyroid activity is not altered after progesterone treatment in rabbit, or estradiol or TSH treatment in adult male rats (Kannan et al., 1980). Whereas combined treatments of progesterone and estradiol, or progesterone, estradiol and testosterone inhibit thyroid activity in adult male rats, female ducklings and ovariectomized Japanese quail, but stimulates in adult male and female rats (Maiti and Sahu, 1982; Pethes and Péczely, 1983).

Alterations of circadian rhythms of thyroid-stimulating hormone, thyroid, adrenal and insulin hormones, and blood glucose profiles following lithium treatment in alternate Light–Dark, constant Light and constant Dark regimens in rats

Lithium, widely used for the treatment of mania, has adverse side effects on circadian rhythms of pineal and testicular hormones. Objective was to examine the role of lithium on circadian rhythms of other hormones and glucose profiles in light–dark (12L:12D), constant light (12L:12L) and constant dark (12D:12D) regimens in rats. Intraperitoneal injection of lithium (2 mEq/kg body wt daily for 15 days) sustained circadian rhythms of T3, T4, thyroid-stimulating hormone (TSH), corticosterone, norepinephrine and epinephrine in light–dark and constant dark but not in constant light. But it abolished circadian rhythms of insulin and blood glucose in all the photoperiodic regimens, except insulin, without changing their pattern in constant dark. Patterns of circadian rhythms of thyroid and TSH, and adrenal hormones remained unchanged after lithium treatment in L–D or D–D, except TSH in L–D. The probable role of photoperiodic cue and lithium on circadian and/or nycthemeral (daily) rhythms of hormones and blood glucose profiles is discussed.

Adrenomedullary and glycemic alterations following diverse stress in soft-shelled turtles Lissemys punctata punctata Bonnoterre.

The objective of the current investigation was to study adrenomedullary and glycemic responses to stress in soft-shelled turtles, Lissemys p. punctata. Dehydration (7 days) and formalin (formaldehyde 1%, 0.1 mL/100 g body wt. daily for 7 days) stress-stimulated adrenomedullary activity at histological (by increasing the nuclear diameter and degranulation of chromaffin cells) and hormonal levels (by elevations of norepinephrine and epinephrine concentrations) with hyperglycemia in turtles. But salt loading (NaCl: 1%, 1 mL/100 g body wt. daily for 7 days) had no significant effect on adrenomedullary activity or glycemia presumably owing to the nonresponsiveness of adrenocortical activity to salt stress in turtles. It is suggested that dehydration and formalin stresses might have exerted their actions through the hypothalamo (CRF)–hypophysial (ACTH)–adrenocortical axis in turtles.

Fenugreek, A Potent Hypoglycaemic Herb Can Cause Central Hypothyroidism Via Leptin – A Threat To Diabetes Phytotherapy

Fenugreek (Trigonella foenum graecum), a medicinal herb with potent antihyperglycaemic and hypoglycaemic effects, is used to treat diabetes. This study is aimed to explore the interaction of fenugreek seed extract (FSE) and HPT (hypothalamic-pituitary-thyroid) axis in context of leptin secretion which have important role in normal and type-1 diabetic subjects. FSE (confirmed to contain trigonelline, diosgenin, 4 hydroxyisoleucine) was gavaged (0.25 gm/kg body weight/day) to normal and alloxan-induced type-1 diabetic rats for 4 weeks. Expression of hypothalamic prepro-TRH (Thyrotropin releasing hormone) mRNA, serum levels of TRH, TSH (Thyroid stimulating hormone), fT3, fT4, insulin, leptin, glucose; thyroperoxidase activity and growth of thyroid gland, food intake, adiposity index were also studied FSE significantly down regulated prepro-TRH mRNA expression; decreased serum TRH, TSH, fT3, fT4 levels, and regressed thyroid gland in FSE-fed normal and diabetic rats than those observed in normal diet-fed control and diabetic rats. FSE decreased (p<0.005-0.001) adiposity index and leptin secretion, increased food intake and body weight in all FSE-fed rats. FSE improved insulin secretion, decreased glucose level but impaired HPT axis in diabetic rats, indicating insulin-independent central hypothyroidism. Results suggested that the dominant signal to hypothalamus suppressing HPT axis is the fall in leptin level which i resulted from decreased adiposity index following FSE feeding. Fenugreek simultaneously having hypoglycaemic and hypothyroidal actions raises questions whether it can be safely used to treat diabetes and/or hyperthyroidism as was suggested by many workers.