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Biomedical subjects

P Lal

Publications and source records attributed to P Lal.

At least 73 records · Page 4Linked to original sources
PubMed1990

Absence of an effect of naloxone, an opioid antagonist, on luteinizing hormone release in vivo and luteinizing hormone-releasing hormone I release in vitro in intact, castrated, and food restricted cockerels.

The possibility that the tonic secretion of luteinizing hormone (LH) and chicken luteinizing hormone-releasing hormone I (LHRH-I) is regulated by an inhibitory action of endogenous opioid peptides was investigated in cockerels using the opiate receptor antagonist, naloxone. Baseline concentrations of plasma LH in the experimental cockerels were increased by surgical castration or reduced by limiting food intake. Baseline and K(+)-induced releases of LHRH-I from perifused mediobasal-preoptic hypothalami from castrated cockerels were higher than those from hypothalami from intact cockerels. Similarly, baseline and K(+)-induced releases of LHRH-I from perifused mediobasal hypothalami from fully fed cockerels were higher than those from the hypothalami from fasting cockerels. Intravenous injections of 0.1, 1, or 10 mg naloxone/kg body weight failed to increase the concentration of plasma LH in castrated, intact, fully fed, or fasted cockerels. Perifusion of mediobasal-preoptic hypothalami from castrated or intact cockerels with 200 microM naloxone or mediobasal hypothalami from fully fed or fasted cockerels with 10 microM naloxone failed to stimulate the release of LHRH-I. These observations suggest in the cockerel that endogenous opioid peptides may not play an obligatory role in the inhibitory control of the tonic secretion of luteinizing hormone.

Animals↗
PubMed1988

Role of thyroid in sexual and body weight cycles of the migratory redheaded bunting, Emberiza bruniceps.

In the male redheaded bunting, Emberiza bruniceps, kept under natural lighting in northern India (Lat 25 degrees 18'N, Long 83 degrees 01'E), testicular growth began during March/April and full spermatogenesis was achieved in May/June; thereafter, the testes regressed and remained regressed for the rest of the year. Thyroidectomy between November and April partially suppressed photoinduced testicular growth in May/June, but did not prevent testicular regression in July. The extent to which thyroidectomy suppressed photoinduced testicular growth was directly related to the time elapsed between thyroidectomy and photostimulation. Thyroidectomy in mid-late May induced testicular regression, an effect which was reversed by daily im injection of 500-2000 ng thyroxine/bird/day/30 days. Thyroidectomy or treatment of intact or thyroidectomized birds between July and March when the testes were regressed had no immediate effect on testicular growth. Body weight which was about 24 g between December and March, increased to about 28 g during the breeding season. Thereafter, it decreased to 21-22 g between August and October. Thyroidectomy between November and May caused an immediate fall in body weight, an effect which was reversed by daily im injection of 500-2000 ng thyroxine/bird/day/30 days. Neither thyroidectomy nor thyroxine treatment prevented the seasonal fall in body weight in June and July nor affected body weight between August and October. It is suggested that in the male redheaded bunting, under natural lighting, thyroid hormones are necessary for the full development of the testes and an increase in body weight during the breeding season. However, thyroid hormones do not appear to be necessary for the development of photorefractoriness or for the seasonal decrease in body weight.

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↗
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

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↗
PubMed1976

Study of an epidemic of venoocclusive disease in India.

Twenty-five cases of rapidly developing ascites occurring in an epidemic form were observed in a tribal district in Central India during August 1972-May 1973. Eleven of the patients died. Six patients were brought to hospital and studied for periods of two to 17 months. Necropsy was performed on one patient who died. The clinical features suggested an outflow tract obstruction such as a Budd-Chiari-like syndrome or venoocclusive disease. Radiographic and haemodynamic studies demonstrated a combination of post and perisinusoidal blocks. Liver dysfunction was indicated by the presence of a marked bromsulphthalein retention and mild to moderate hypoalbuminaemia. Histological examination of the liver biopsies showed changes that ranged from centrizonal haemorrhagic necrosis to an extensive centrilobular fibrosis associated with central vein occlusion. The disease was apparently caused by a food toxin, and the possible nature of this is discussed.

Adolescent↗
PubMed1975

Epidemic dropsy in New Delhi.

Forty-five cases of epidemic dropsy were studied from an epidemic in New Delhi. Argemone oil contamination was found in the mustard oil used for cooking. Sanguinarine was detected in the eight urine samples collected within 2-3 weeks of onset of dropsy and its concentration ranged from 0.4 to 3.6 mug/100 ml. Three of the 18 sera were positive for sanguinarine, the concentration being 1.2, 1.6 and 3.6 mug/100 ml. The clinical manifestations and epidemiological factors were studied. Edema of the legs was the most consistent clinical finding, and was present in all the patients. In contrast to the earlier epidemics, three striking features were pigmentation in 33%, hair loss in 77.7% and nontender hepatomegaly in 24.4% of cases. A follow-up of 10 months showed almost complete recovery in all.

Adolescent↗