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Biomedical subjects

J P Thapliyal

Publications and source records attributed to J P Thapliyal.

At least 19 recordsLinked to original sources
PubMed1992

The effects of daily injections of L-dihydroxyphenylalanine and 5-hydroxytryptophan in different temporal relationships on thyroid-gonadal interaction in an Indian finch, spotted munia, Lonchura punctulata.

Daily injection of L-dihydroxyphenylalanine (L-DOPA, a dopamine precursor) given 12 hr after 5-hydroxytryptophan (5-HTP, a serotonin precursor) stimulated testicular growth and body weight increase in the spotted munia Lonchura punctulata. Daily injections of the same drugs given 8 hr apart had the opposite effect, inhibiting both testicular growth and body weight gain. These responses were not observed when either of the drugs were given alone, indicating that the effect was due to temporal synergism between serotonergic and dopaminergic functions. The inhibitory effect of daily injections of thyroxine on testicular and body growth were negated by injections of 5-HTP and L-DOPA separated by 12 hr. Conversely, the stimulatory effects of thyroidectomy in maintaining full testicular size and body weight after the breeding seasons were negated by daily injections of 5-HTP and L-DOPA separated by 8 hr. It is concluded that the inverse relationship between seasonal changes in thyroidal and reproductive functions may involve seasonal changes in phase relationships between daily rhythm in serotonergic and dopaminergic activity in the central nervous system.

5-Hydroxytryptophan↗
PubMed1992

Thyroid in intermediary metabolism of the migratory redheaded bunting, Emberiza bruniceps (Brandt).

Effect of thyroidectomy and replacement therapy with L-T4, on liver and plasma biochemical constituents of E. bruniceps, was studied during January (recovery phase). Thyroidectomy elevated significantly the levels of plasma glucose, protein, cholesterol, diglyceride, hepatic cholesterol and depressed significantly hepatic free fatty acid without affecting liver and body weights. Treatment of thyroidectomized birds with L-T4 restored liver and plasma constituents, but had significantly depressed plasma phospholipid. These findings suggest that thyroid hormones are critically involved in lipo-regulatory mechanism(s) in E. bruniceps.

Animals↗
PubMed1987

Effect of melatonin on gonads, body weight, and luteinizing hormone (LH) dependent coloration of the Indian finch, Lal munia (Estrilda amandava).

Four doses of melatonin were administered intramuscularly over 30 days in separate groups of intact adult male Lal munia, Estrilda amandava, during mid-day (1300 hr) and mid-night (0100 hr) in separate sets during the month of August (late progressive phase), and their effects were studied on the body weight, gonadal and thyroidal activities, and luteinizing hormone (LH)-dependent plumage and beak pigmentation. Melatonin, irrespective of its dose and the time of administration, invariably induced complete inhibition of seasonal gonadal growth and activity, and also the LH-dependent plumage pigmentation. Melatonin had no effect on LH-dependent beak coloration. The inhibitory effect of melatonin on the body weight growth was found to be dependent on the time of administration and the dose of the hormone. Melatonin inhibited the thyroid activity in all the groups. These findings seem to suggest that while melatonin influences gonadal activity, body weight growth, and thyroid activity by acting directly at the hypothalamo-hypophyseal complex, it counteracts the effect of LH at the feather papillae level. Further, synthesis and/or release of FSH seems to be more sensitive to melatonin than that of LH. However, the metabolic action of melatonin might be species specific.

Animals↗
PubMed1985

Role of thyroid and testicular hormones in the oxidative metabolism of the Indian garden lizard, Calotes versicolor.

L-Thyroxine (L-T4) and testosterone were administered separately to intact, thyroidectomized, and castrated male Indian garden lizards, Calotes versicolor (maintained under natural climatic conditions) throughout the year to study their effects on the whole-body oxygen consumption and on tissue (liver, muscle, kidney, and brain) respiration. The findings indicate that the calorigenic actions of L-T4 and testosterone are independent of ambient temperature, and different tissues have different, temperature-independent, annual rhythms of sensitivity to L-T4 and testosterone. Internal factors seem to play a major role in the determination of these annual tissue sensitivity rhythms. Effects of thyroidectomy and castration are brought about by decreased levels of both thyroidal and testicular hormones. It is suggested that gonadal hormones are directly involved in the oxidative metabolism of Calotes which is regulated jointly by thyroid and gonadal steroids, and the degree of involvement of the glands depends upon the energy demand and sensitivity of tissues during different months of the year.

Animals↗
PubMed1984

Light, thyroid, gonad, and photorefractory state in the migratory redheaded bunting, Emberiza bruniceps.

When exposed to constant long photoperiods the redheaded bunting, Emberiza bruniceps, was shown to become absolutely photorefractory and the condition was observed to be accelerated by thyroidectomy. Photoinduced gonadal growth was inhibited partially and the photoinduced increase in body weight was inhibited completely by thyroidectomy. Injection of thyroxine reversed the effects of thyroidectomy if administered during the nonbreeding photosensitive or breeding states, but had no effect in birds which had entered the photorefractory state. Gonadal growth was stimulated by pregnant mare serum gonadotrophin in intact and thyroidectomized photorefractory birds, suggesting that thyroidectomy does not lead to loss of response of the gonads to gonadotrophins but directly affects the secretion of gonadotrophins. Injection of prolactin increased the body weight of intact but not of thyroidectomized photorefractory birds, suggesting that metabolic photorefractoriness is due to a decreased secretion of prolactin and that the effects of T4 on body weight depend on its synergism with prolactin. It is suggested that thyroid hormone(s) may be part of the coupling mechanism(s) for body weight and gonad development cycles and that the beneficial role of thyroid hormones may consist in an increased threshold of the central nervous system control of neuroendocrine functions towards the negative feedback regulation of increased sex steroid levels.

Animals↗
PubMed1984

Role of thyroid and testicular hormones in the regulation of basal metabolic rate, gonad development, and body weight of spotted munia, Lonchura punctulata.

Normal saline, L-thyroxine (L-T4, 0.5 micrograms/bird/day), and testosterone (100 micrograms/bird/day) were administered separately to intact, thyroidectomized, and castrated spotted munia over a 30-day period and the effects on basal metabolic rate (BMR), gonads, and body weight were recorded. Thyroidectomy and castration decreased the BMR. L-Thyroxine increased the BMR of intact and thyroidectomized but not of the castrated birds. Testosterone had no effect on BMR of either the intact or of the operated birds. L-Thyroxine and testosterone both had no effect on regressing gonads but inhibited thyroidectomy-induced testicular development. Body weight increased in intact, testosterone-treated birds, and in thyroidectomized and castrated spotted munia. L-Thyroxine inhibited body weight gain only in thyroidectomized birds. It is suggested that the physiological actions of L-T4 and testosterone depend on the gonadal status, thyroid activity, and nature of the thyroid-gonad relationship.

Animals↗
PubMed1984

Thyroid and annual gonad development, body weight, plumage pigmentation, and bill color cycles of lal munia, Estrilda amandava.

Long-term administration of L-thyroxine (T4) in the wax bill (lal munia) inhibited the current gonad development cycle, and the increase in gonadal volume in the second cycle was suppressed only by higher concentrations. Gonadal inhibition by high but not by low doses of L-T4 was associated with a failure in the development of LH-dependent pigmented nuptial plumage. This suggests that L-T4 depresses FSH secretion more readily than LH secretion. The results indicate that the effects of L-T4 administration on the body weight cycle depends upon the physiological and/or gonadal status of the bird at the start of the experiment and that the juvenile hypothalamo-hypophysial-gonadal axis is more sensitive to L-T4 than that of the adult birds. The bill color, like plumage pigmentation, appears to be LH controlled. It is suggested that while thyroid hormone, acting by way of the hypothalamo-hypophysial complex and/or by direct action on the feather papillae, modulates the annual cycles of plumage pigmentation, bill color, gonad development, and body weight of lal munia, the finch has an endogenous mechanism which enables it to adapt to chronic hyperthyroidism in such a way that breeding occurs at the normal time of the year.

Animals↗
PubMed1984

Erythropoietin, testosterone, and thyroxine in the erythropoietic response of the snake, Xenochrophis piscator.

The erythropoietic response of snakes was examined after injecting human urinary erythropoietin (Ep), testosterone propionate (TP), and L-thyroxine (T4), separately and in combinations, into starved ophids. The effect of starvation was reflected by a decrease in the number of erythrocytes, a fall in hemoglobin concentration, and a decline in hematocrit. Statistically significant elevation of erythrocyte number, hemoglobin concentration, and hematocrit was observed at 24 hr following the administration of Ep + T4, and Ep + TP + T4 into starved ophids. The erythrocyte number was also increased by T4 treatment at 24 hr. Furthermore, while T4 and Ep individually increased the red blood cell number at 168 hr, T4, TP + T4, and Ep + TP + T4 elevated the hemoglobin concentration and Ep + T4 and Ep + TP + T4 increased the hematocrit value. It is suggested that the influence of any one of the hormones utilized in the present study on blood morphology of fasted snakes depends to a greater extent on the presence or absence of the other hormone(s).

Animals↗
PubMed1983

Thyroid and gonad in the oxidative metabolism, erythropoiesis, and light response of the migratory redheaded bunting, Emberiza bruniceps.

In the thyroidectomized, adult male redheaded bunting exposed to a L/D cycle of 15/09, there were no significant changes in body weight, gonad size, respiratory rates of whole body, liver, muscle, red blood cell number, hemoglobin concentration, or hematocrit, unlike in intact birds. Further, while testosterone appeared as effective as L-T4 in determining body weight, gonadal size, and activity and oxygen uptake by skeletal muscle, it was of greater significance for kidney respiration and of secondary importance in its influence on blood morphology and respiratory rates of the liver and of the whole body of the bird.

Animals↗
PubMed1983

Thyroid photoperiod and gonadal regression in the common myna Acridotheres tristis.

In the common myna, extirpation of the thyroid glands inhibited seasonal development of the testes of birds maintained under normal length days, but full development, similar to sham-operated birds, resulted when maintained under 15L:9D. Further, thyroidectomy delayed and reduced the rate of gonadal regression when performed in 15L:9D exposed birds having fully developed testes. The thyroid-gonad relationship exhibited in the common myna is of great adaptive value to the bird, especially in the subtropics, where sudden fluctuations in environmental temperature (due to heat wave/hail storm) may lead to sharp alterations in thyroid activity.

Animals↗
PubMed1983

Role of thyroid in tissue respiration of birds.

Thyroidectomy after 1 week, 1 month, and 13 months significantly depressed and low level of L-T4 significantly elevated the oxygen uptake of the liver and skeletal muscle of spotted munia and common myna. A higher dose of L-T4 had no effect on the rate of respiration. A reexamination of the published results on submammalian vertebrates together with those presented here suggests that an uniform pattern of response of skeletal muscle emerges if the values from thyroidectomized animals are compared not only with the final controls but also with the initial controls. It is, therefore, suggested that all the earlier works be reexamined and reinterpreted.

Animals↗
PubMed1983

Adrenal hormones and oxidative metabolism of the garden lizard (Calotes versicolor).

Daily administration of adrenaline over a 10-day period invariably induced significant increases in the metabolic rate of the whole body and of specific tissue (liver, muscle, kidney and brain) of both intact and thyroidectomized lizards except during June (breeding season) when the presence of thyroid hormones was a prerequisite for the stimulation of oxygen consumption by the whole body, muscle, kidney and brain but not by the liver. Corticosterone had no effect on whole body oxygen consumption but stimulated, inhibited or was without influence on the oxygen consumption of individual tissues, depending on the season and the presence or absence of thyroid hormones. It is suggested that adrenaline, due to its temperature-independent calorigenic effect, acts as the emergency hormone for energy release and helps the animal to survive during hibernation (winter months) when almost all the endocrine glands are inactive.

Animals↗