B. R. Maiti

Pineal activity during the seasonal gonadal cycle in a wild avian species, the tree pie (Dendrocitta vagabunda)

The aim of the present investigation was to study the pineal activity during the seasonal gonadal cycle in both sexes of the Indian tree pie (Dendrocitta vagabunda). The findings revealed that the nuclear diameter of the pineal parenchymal cells moderately decreased and was followed by a moderate increase in the cell population density (per microscopic field of the pineal sections) and serotonin content of the gland during the progressive phase. The values of these parameters were further altered (decreased nuclear diameter with increased cell population density and serotonin level) during breeding but were reversibly altered to some extent during the regression phase, and further altered during the nonbreeding phase in both sexes of the birds. It is suggested that the pineal activity distinctly varies with the seasonal gonadal cycle, being minimum during breeding and maximum during nonbreeding in both sexes of the tree pie.

Influence of age on diurnal rhythms of adrenal norepinephrine, epinephrine, and corticosterone levels in soft-shelled turtles (Lissemys punctata punctata)

An investigation was made of what role aging plays on diurnal rhythms of norepinephrine, epinephrine, and corticosterone contents in the adrenal gland of soft-shelled turtles. To resolve this problem, juvenile and adult soft-shelled turtles were sacrificed at four different time intervals (0600, 1200, 1800, and 2400 hr) and adrenal hormonal levels were measured by spectrofluorometer. The findings revealed that peak norepinephrine, epinephrine, and corticosterone values were observed at 2400, 0600, and 2400 hr, respectively, and trough values for all the hormones were found at 1200 hr in both juvenile and adult animals. Thus, diurnal rhythms for all the hormones studied exist in both juvenile and adult animals. It is suggested that aging apparently has no influence on diurnal variations of adrenal hormones in turtles.

Circadian rhythms in serotonin, norepinephrine, and epinephrine contents of the pineal-paraphyseal complex of the soft-shelled turtle (Lissemys punctata punctata)

Diurnal variations in pineal serotonin, norepinephrine, and epinephrine levels were measured at four different time intervals (06:00, 12:00, 18:00, and 24:00 hr) in adult male soft-shelled turtles. The serotonin level increased during day and decreased during night. But the norepinephrine and epinephrine levels showed reverse changes. The findings reveal that there is a distinct circadian rhythm in serotonin, norepinephrine, and epinephrine contents of the pineal-paraphyseal complex in adult male soft-shelled turtles.

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.

Circadian rhythms and influence of light on serotonin, norepinephrine, and epinephrine contents in the pineal-paraphyseal complex of soft-shelled turtles (Lissemys punctata punctata)

The aims of the current investigation were to examine the circadian rhythms in the pineal-paraphyseal amines and indoleamine in juvenile turtles. An attempt was also made to study the influence of photoperiod on pineal activities in adult turtles. Serotonin, norepinephrine, and epinephrine levels were studied at four different time intervals (0600, 1200, 1800, and 2400 hr) of a 24-hr period. Increased serotonin level was observed during day and trough values during night, but the norepinephrine and epinephrine levels showed reverse changes. Continuous light (24L:0D) or long photoperiod (22L:2D) resulted in an elevation of serotonin level and diminution of norepinephrine level, but continuous darkness (0L:24D) or short photoperiod (2L:22D) showed reverse changes. Epinephrine level altered in parallel to that of norepinephrine with long (22L:2D) or short (2L:22D) photoperiod, but remained unaltered with continuous light (24L:0D) or continuous darkness (0L:24D). It is suggested that circadian rhythms exist in pineal-paraphyseal amines and indoleamine in juvenile turtles like that of adult turtles. It is also suggested that light greatly modulates serotonin, norepinephrine, and epinephrine contents in the pineal-paraphyseal complex of the soft-shelled turtle.

Effect of ambient temperature on serotonin, norepinephrine, and epinephrine contents in the pineal−paraphyseal complex of the soft-shelled turtle (Lissemys punctata punctata)

The aim of the present investigation was to ascertain the influence of ambient temperature on serotonin, norepinephrine, and epinephrine contents in the pineal-paraphyseal complex of soft-shelled turtles. Turtles were exposed to low (10 degrees) and high (32 degrees) temperatures for 7 days in an incubator with the same photoperiod (12L:12D). Control animals were also kept in the same incubator at 25 degrees for similar duration with the same photoperiod. The findings revealed that ambient temperatures significantly altered serotonin, norepinephrine, and epinephrine content in the pineal-paraphyseal complex of turtles. The results thus indicate that ambient temperature has some influence on pineal serotonin, norepinephrine, and epinephrine contents in soft-shelled turtles.

EFFECT OF STRESS ON SEROTONIN, NOREPINEPHRINE, EPINEPHRINE AND CORTICOSTERONE CONTENTS IN THE SOFT-SHELLED TURTLE

1. Adult soft‐shelled turtles were exposed to hyperosmotic and dehydration stresses.

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.