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Biomedical subjects

B B Gupta

Publications and source records attributed to B B Gupta.

At least 19 recordsLinked to original sources
PubMed1992

Involvement of cyclic guanosine monophosphate (cGMP) and cytosolic guanylate cyclase in the regulation of synaptic ribbon numbers in rat pineal gland.

In the rat pineal gland N-acetyltransferase (NAT) activity and synaptic ribbon (SR) numbers display a circadian rhythm. It is well-known that NAT activity is regulated by adrenergic mechanisms involving cyclic adenosine monophosphate (cAMP) as a second messenger. However, the mechanism involved in the regulation of SR numbers has not been established so far. In the present in vitro study, we have investigated the effects of 8-bromo-cyclic guanosine monophosphate (8-bromo-cGMP), a cyclic guanosine monophosphate (cGMP) analog, and stimulation of guanylate cyclase on SR numbers. Incubation with 8-bromo-cGMP increased SR numbers in a dose- and time-dependent manner. Further, stimulation of the cytosolic guanylate cyclase also resulted in increased SR numbers. Adrenergic agonists stimulated cGMP but did not alter SR numbers. These findings suggest that cGMP is involved as a second messenger in the regulation of SR numbers. Since the adrenergically stimulated increase in cGMP did not influence SR numbers, a non-adrenergic cGMP metabolic pathway seems to be involved in the regulation of SR numbers in the rat pineal gland.

Animals↗
PubMed1992

In vitro effects of putative neurotransmitters on synaptic ribbon numbers and N-acetyltransferase activity in the rat pineal gland.

The pineal contains a large number of classical transmitters and neuropeptides. Some of these neurochemicals are involved in the regulation of serotonin N-acetyltransferase (NAT) activity and hence in melatonin synthesis. Synaptic ribbons present in the pineal gland also exhibit a numerical day/night rhythm parallel to that of NAT activity. There is scarcity of information regarding the regulation of synaptic ribbon (SR) numbers. In the present study, we have investigated in vitro effects of a number of classical neurotransmitters and neuropeptides. NAT activity was used to monitor melatonin synthesis under the experimental conditions used. Norepinephrine (NE), Delta sleep-inducing peptide (DSIP), vasoactive intestinal polypeptide (VIP), adenosine and N-acetyl-asp-glu (NAAG) significantly increased NAT activity in rat pineal. DSIP and VIP also increase the stimulatory effect of NE on NAT activity. These neurochemicals had no effect on SR numbers. Gamma aminobutyric acid (GABA), serotonin and taurine affected neither NAT activity nor SR. Somatostatin increased SR numbers significantly, without having any effect on NAT activity. The effect of somatostatin is regarded to be pharmacologic, since rather high dosages (10(-4) M) were required to obtain a significant effect. Although somatostatin is present in the pineal and may change rhythmically, the inconsistency of the day/night rhythmicity and the lack of such a rhythm in female rats and male gerbils speaks against an important physiological role of somatostatin in regulating SR numbers.

Animals↗
PubMed1992

Biphasic 24-hour variations in cyclic GMP accumulation in the rat pineal gland are due to corresponding changes in the activity of cytosolic and particulate guanylate cyclase.

Various parameters of the rat pineal gland display a 24-h rhythm. However, nothing is known about possible 24-h variations in cyclic GMP (cGMP) metabolism. In the present study, 24-h variations in pineal gland cGMP accumulation were investigated by determining the increase in cGMP level with and without inhibitors of phosphodiesterase at different time points over a light/dark cycle (12/12 h). Furthermore, the activity of guanylate cyclase (GC) was determined under substrate-saturated conditions regarding the cytosolic and particulate forms of the enzyme. It has been found that cGMP accumulation and GC activity display biphasic 24-h variations with two peaks--one approximately 7 h after lights "on" and the other approximately 7 h after lights "off." The activity of cytosolic GC remains unchanged in the presence of the nitric oxide (NO) synthesis inhibitor N-monomethyl-L-arginine, indicating that 24-h variations in the activity do not reflect changes in the synthesis of the GC stimulator NO.

Animals↗
PubMed1991

Acetylcholine and muscarinic agonists increase synaptic ribbon numbers in the rat pineal.

Mammalian pinealocytes possess synaptic ribbons (SR) which are commonly present in photoreceptor cells at synaptic junctions. Pineal SR numbers undergo a diurnal rhythm parallel to that of pineal N-acetyltransferase (NAT) activity and melatonin levels. Recent findings suggest that SR numbers, unlike NAT activity and melatonin synthesis and release, do not seem to be regulated by adrenergic mechanisms or neuropeptides in adult rats. Since the pineal gland also receives cholinergic nerve fibres, we have investigated in vitro effects of acetylcholine (ACh) and carbamyl-beta-methylcholine (CBMC; a specific muscarinic agonist) in the presence and absence of pirenzipine (a specific inhibitor of muscarinic M1 receptors). ACh and CBMC increased SR numbers significantly. Pirenzipine inhibited the CBMC-induced increase in SR numbers. On the basis of these findings, it is suggested that cholinergic agonists increase pineal SR numbers by acting through muscarinic M1 receptors. Hence muscarinic mechanisms may have a functional role in pineal physiology.

Acetylcholine↗
PubMed1991

Comparison of polyamide and polypropylene membranes for plasma separation.

Plasma separation experiments were made with polyamide experimental prototype hollow-fiber plasma filters with surface areas between 0.025 m2 and 0.1090 m2 using bovine blood collected in acid citrate dextrose (ACD). The maximum filtration velocity rose with the wall shear rate gamma w as gamma w 0.72 +/- 0.02 and decreased with the length of fiber L as L-0.41 with a correlation coefficient of 0.97 +/- 0.02. The results were similar to those with polypropylene fibers. We also investigated the occurrence of hemolysis as a function of shear rate and transmembrane pressure. The free hemoglobin concentration of filtered plasma was checked using a U.V. spectrophotometer. It was concluded that polyamide membrane filters can be safely used for plasma separation from blood.

Animals↗
PubMed1990

Controlled trial of twice a day versus once a day cimetidine therapy for duodenal ulcer.

A randomized controlled trial was carried out to compare the efficacy of conventional 400 mg twice daily dose of cimetidine with single bedtime 800 mg dose, in 40 patients with endoscopically proven duodenal ulcer. At repeat endoscopy after four weeks of therapy, complete ulcer healing was achieved in 78% of patients on twice daily dosage and 79% of patients on single daily dosage. A more convenient single nocturnal dosage of cimetidine is as effective in the treatment of duodenal ulcer as a twice daily dosage in the Indian population.

Adult↗
PubMed1990

Effects of thyroidal, gonadal and adrenal hormones on tissue respiration of streaked frog, Rana limnocharis, at low temperature.

In vivo and in vitro effects of thyroidal, gonadal and adrenal hormones were studied on the rate of liver and skeletal muscle respiration in both the sexes of R. limnocharis during active and inactive phases of the annual activity cycle. Triiodothyronine (L-T3) and thyroxine (L-T4) did not stimulate tissue (liver and muscle) respiration in any of the experiments irrespective of season, sex and temperature. Testosterone, estradiol and corticosterone stimulated O2 uptake significantly irrespective of season, sex and temperature. Adrenaline and nor-adrenaline also stimulated tissue respiration significantly during the winter month. Since the ambient temperature was low even during the active phase (max. temperature 21 degrees C), it seems that the frog might have developed tissue sensitivity for gonadal and adrenal hormones at low temperatures when thyroid hormones are calorigenically ineffective.

Animals↗
PubMed1989

High shear rate hemofiltration: influence of fiber dimensions and shear rates.

The variation of ultrafiltration flow rate (QF) at high transmembrane pressure with inlet wall shear rate (gamma w) was found to be proportional to gamma wn, with n ranging from 0.45 to 0.55, when gamma w increases up to 4,500 s-1. To test whether long filters operated at high shear rates were more efficient than shorter ones for the same inlet blood flow, we made experiments with 10- and 20-cm filters with same number of fibers (550) at various shear rates from 700 to 3,000 s-1. The filtration rates provided by the 20-cm filter were found to be 5-15% larger than those provided by two 10-cm filters arranged in parallel and 10-20% smaller than those provided by two 10-cm filters arranged in a series. The explanation lies in the rapid decay of QF with distance from the inlet due to the developing concentration boundary layer. When pulsations are imposed on the inlet blood flow, the filtration rate was seen to increase by 10-20%, and the effect of plugging was seen to decrease in small-area hemofilters.

Animals↗
PubMed1989

Ultrasonography in non-cirrhotic portal hypertension: correlation with splenoportography.

Real time sonography followed by splenoportography was performed in 38 cases with non-cirrhotic portal hypertension. Eleven of these cases, in whom porto-systemic shunt surgery was done, were also evaluated by real time sonography post-operatively. The ultrasound findings correlated well in 37 cases (98%) with splenoportography. All the post-operative cases also revealed a patent portosystemic shunt on sonography. Ultrasonography, a valuable, non-invasive, initial investigation of portal hypertension, may thus be used as the only investigation to distinguish intra- from extra-hepatic obstruction and to evaluate patency of surgically created porto-systemic shunts. Invasive portography may be performed only if surgical treatment is anticipated.

Adolescent↗
PubMed1989

Modelling of plasma-separation through microporous membranes.

Available mathematical models of ultrafiltration have been used to predict changes in maximum plasma filtration rate with wall shear rate for given filters and blood properties. We have done many plasmapheresis experiments in vitro, using hollow-fiber filters (500-1000 cm2) and fresh bovine blood collected on ACD or heparin. The comparison between predicted and experimentally obtained filtration rates was good for models based on the concentration polarization theory and lift velocity theory. In other experiments with pulsatile inlet flow we found that plasma filtration rate increased by 20 to 50% compared to non-pulsatile conditions. These results are in good agreement with the modified model of ultrafiltration incorporating pulsating flow. This paper presents relationships between plasma filtration velocity (steady and pulsating flow) and hemolysis limit as a function of wall shear rate and filter size.

Blood Flow Velocity↗
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↗
PubMed1986

Membrane plasma separation through small-area, hollow-fiber filters.

The filtration capabilities of small polypropylene hollow-fiber plasma filters with membrane areas ranging from 100 to 1,000 cm2 have been investigated. It is found that the filtration flux per unit membrane area is approximately proportional to the wall shear rate gamma w at least up to gamma w = 7,500 s-1. As a result, the total filtration flow rate increases very little when the number of fibers is increased as the increase in membrane area is offset by the decrease in shear rate, but it increases with the fiber length L as L 2/3. Hemolysis occurs when the transmembrane pressure exceeds a certain threshold, but this threshold is itself an increasing function of shear rate. As a result, it is possible to circulate high blood flow rates even in very small filters (100 cm2) without hemolysis, provided the fiber length is below a critical value.

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↗