Ultrastructural and hormonal modulations of the thyroid gland following arecoline treatment in albino mice.

Arecoline is a plant alkaloid of betel nut Areca catechu. Arecoline has immunosuppressive, hepatotoxic, mutagenic and teratogenic effects, and disturbs some endocrine organs in rats. The objective is to investigate the untoward effects of arecoline on the thyroid gland in mice. Intraperitoneal injection of arecoline (10 mg/kg body weight only once) increased the serum T(3) and T(4) levels and decreased the serum TSH 20, 40 or 60 min after the treatment, with maximum effect at 40 min. Chronic arecoline treatment (10 mg/kg body weight daily for 15 days) caused light microscopic and ultrastructural degenerations of thyro-follicular cells with depletion of T(3) and T(4) levels followed by the elevation of the TSH level. Atropine (arecoline antagonist) injection prevented the changes (hyperactivity) induced by acute (40 min) arecline treatment. Arecoline initially stimulates thyroid activity, and eventually inhibits the activity; atropine prevents thyroid dysfunction induced by arecoline. Arecoline action is mediated probably via muscarinic cholinergic receptor-hypothalamic-pituitary-thyroid axis in mice.

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.

Thyroidal inhibition following diverse stress in soft-shelled turtle, Lissemys punctata punctata bonnoterre.

The current study was undertaken to ascertain the effects of diverse stress on thyroid activity in soft-shelled turtles, Lissemys punctata punctata. The findings revealed that starvation (10 days), dehydration (10 days) or exposure to electric shock (12 volts for 15 seconds at an interval of 30 min for 3 h) caused significant decrease in the body weight (except in electric shock), relative weight, peripheral and central epithelial heights of the follicles and peroxidase activity of the thyroid gland of turtles. The degree of change in the values of these parameters was nearly same in all the stress experiments, indicating that there is not much difference in the degree of thyroid responses to diverse stress in turtles. It is suggested that these stressors might have exerted their actions on thyroid activity presumably indirectly via adrenal medulla and/or substance in metabolic stress (starvation and dehydration) and via hypothalamo-hypophysial-adrenocortical axis in non-metabolic stress (electric shock) in Lissemys turtles.

Ultrastructural and hormonal changes in the pineal-testicular axis following arecoline administration in rats.

Arecoline is an alkaloid of betel nut of Areca catechu. Betel nut is chewed by millions of people in the world and it causes oral and hepatic cancers in human. It has therapeutic value for the treatment of Alzheimer and schizophrenia. Arecoline has immunosuppressive, mutagenic and genotoxic effects in laboratory animals. It also affects endocrine functions. The objective of this study was to investigate the effects of arecoline on pineal-testicular axis in rats. Since pineal activity is different between day and night, the current study is undertaken in both the photophase and scotophase. The findings were evaluated by ultrastructural and hormonal studies of pineal and testicular Leydig cells, with quantitations of fructose and sialic acid of sex accessories. Arecoline treatment (10 mg/kg body weight daily for 10 days) caused suppression of pineal activity at ultrastructural level by showing dilatation of the cisternae of the rough endoplasmic reticulum (RER), large autophagosome-like bodies with swollen mitochondrial cristae, numerous lysosomes, degenerated synaptic ribbons and reduced number of synaptic-like microvesicles. Moreover, pineal and serum N-acetylserotonin and melatonin levels were decreased with increased serotonin levels in both the gland and serum. In contrast, testicular Leydig cell activity was stimulated with abundance of smooth endoplasmic reticulum (SER), electron-dense core vesicles and vacuolated secretory vesicles, and increased testosterone level in the arecoline recipients. Consequently, the testosterone target, like prostate, was ultrastructurally stimulated with abundance of RER and accumulation of secretory vesicles. Fructose and sialic acid concentrations were also significantly increased respectively in the coagulating gland and seminal vesicle. These results were more significant in the scotophase than the photophase. The findings suggest that arecoline inhibits pineal activity, but stimulates testicular function (testosterone level) and its target organs presumably via muscarinic cholinergic receptor in rats.

Thyroid responses to altered photoperiod in the soft-shelled turtle Lissemys punctata punctata bonnoterre.

The aim of the current investigation was to investigate the effect of photoperiod on thyroid activity in soft-shelled turtles (Lissemys punctata punctata). Thirty days exposure of short photoperiod with 2L:22D increased relative weight, follicular epithelial height and peroxidase activity of the thyroid gland; whereas exposure of long photoperiod with 22L:2D for 30 days showed reversed changes to those of the short photoperiod in adult female turtles. These findings indicate that short photoperiod stimulates thyroid activity and long photoperiod inhibits its activity in soft-shelled turtles. It is suggested that photoperiod exerts its action on thyroid activity presumably via gonads and/or pineal-gonadal axis in 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.

Adrenocortical involvement during diverse stress in soft-shelled turtle Lissemys p. punctata Bonnoterre.

Adrenocortical responses to diverse stressful situations (dehydration, formaldehyde treatment and salt loading) were studied in the adult female soft-shelled turtle, Lissenmys p. punctata. Dehydration, formaldehyde treatment (formalin, 1%: 0.1 ml/100 g body weight daily) or salt loading (NaCl, 1%: 0.1 ml/100 g body weight daily) treatments consecutively for 7 days caused hypertrophy of the adrenocortical cells with their nuclear diameter increased, and depletions of adrenal cholesterol and ascorbic acid concentrations followed by decreased acid phosphatase and alkaline phosphatase activities in turtles. Corticosterone levels were elevated in both the adrenal gland and serum of turtles after dehydration and formalin stress, but the hormone level remained unaltered after salt loading in turtles. The results suggest active involvement of adrenal cortex in stress for homeostasis in Lissemys turtles.

Thyroidal modulation following hypo- and hyper-thermia in the soft-shelled turtle Lissemys punctata punctata Bonnoterre.

The aim of the current study was to investigate the effects of ambient temperature on thyroid activity of the soft-shelled turtle (Lissemys punctata pucntata). Turtles exposed to low ambient temperature (10 degrees C for 15 days) showed a significant decrease in relative thyroid weight, follicular cell size (cell became squamous from cuboidal type) and epithelial height in both the peripheral and central follicles of the gland, with the appearance of homogeneous colloid materials in the follicular lumen. Thyroid peroxidase activity declined significantly. In contrast, high ambient temperatures (32/34 degrees C for 15 days) caused reverse changes to those observed after exposure with low ambient temperature. No significant difference was marked in thyroid activity between 32 and 34 degrees C temperature treatments. The findings provide evidence that low ambient temperature inhibits thyroid activity and high ambient temperature stimulates the gland activity in soft-shelled turtles. Ambient temperature acts presumably via the hypothalamo-hypophysial (TRF-TSH) axis which in turn alters thyroid function in turtles.