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Biomedical subjects

D Guha

Publications and source records attributed to D Guha.

29 records · Page 2Linked to original sources
PubMed1992

Effect of certain toxicants on gonadotropin-induced ovarian non-esterified cholesterol depletion and steroidogenic enzyme stimulation of the common carp Cyprinus carpio in vitro.

Isolated ovarian tissues from the common carp, Cyprinus carpio were incubated in vitro to obtain a discrete effect of four common toxicants of industrial origin, namely phenol, sulfide, mercuric chloride and cadmium chloride, on gonadotropin-induced alteration of nonesterified and esterified cholesterol and steroidogenic enzymes, delta 5-3 beta-HSD and 17 beta-HSD activity. Stage II ovarian tissue containing 30-40% mature oocytes were shown to be most responsive to gonadotropins in depleting only nonesterified cholesterol moiety and stimulating the activity of both. Safe doses of above mentioned toxicants when added separately to stage II ovarian tissue with oLH (1 microgram/incubation) gonadotropin-induced depletion of nonesterified cholesterol and gonadotropin-induced stimulation of the activity of both enzymes was significantly inhibited. Esterified cholesterol remained almost unaltered. Findings clearly indicate the impairment of gonadotropin induced fish ovarian steroidogenesis by the four toxicants separately.

17-Hydroxysteroid Dehydrogenases↗
PubMed1989

Influences of vestibulo-cerebellum on kindling in the cat.

The development of amygdaloid kindling was assessed under conditions of pharmacological depression of the nodular areas of vestibulocerebellum and also following vestibular stimulation in chronically prepared cats. The results demonstrated that a single intra-nodular micro-injection of procaine hydrochlorides could significantly facilitate such epileptogenesis for at least several days. The number of kindling trials required to reach the first generalized convulsions was significantly increased by natural vestibular stimulation in comparison with control kindled animals. The intensity of fit, development of amygdaloid seizures and the convulsions were reduced markedly within a week by pre-conditioning the kindled animals with daily vestibular stimulation for 15-30 min. In addition, analysis of the behaviour of sleep-wake cycle indicated a significant increase in total sleep time and in the percentage of rapid eye movement (REM) sleep. These findings suggest that the natural rotational vestibular stimulation may result in a durable modification of brain function through development of enduring focal sensitization of catecholamine-mediated inhibitory mechanisms, reflecting the tonic inhibitory influences of the vestibulo-cerebellum in regulating the development and attenuation of epileptic states.

Animals↗
PubMed1979

Stimulation of gastric secretion by prostaglandin F2 alpha in rats.

In rats with chronic gastric fistulas, prostaglandin F2 alpha stimulated the gastric acid secretion in graded doses of 50, 100, 200 and 400 microgram/kg b.wt, while higher doses above 1 mg/kg b.wt tended to inhibit significantly. The gastric antisecretory effect of prostaglandin E1 could not be altered or modified by subsequent treatment of prostaglandin F2 alpha, while the latter alone without any prior treatment of the former, stimulated output of gastric juice, HCl and pepsin without significantly affecting the concentration of these components.

Animals↗
PubMed1979

Electrophysiological correlates of the behavioral effects of tubocurarine in conscious cats.

The effects of tubocurarine on behavior, electrical activity, and auditory evoked potentials were studied in restrained conscious cats. Tubocurarine hydrochloride (doses of 0.05--1 micrograms intraventricularly) produced various central stimulatory effects characterized by EEG desynchronization, decrease in both low (7--9 Hz) and high (10--14 Hz) alpha waves, and decrease in the amplitude and area of the surface positive (P1) wave of auditory evoked potentials. Concomitant with the alterations in brain electrical activity tubocurarine hydrochloride produced generalized behavioral arousal phenomena and the cats became restless and exhibited miaowing and increased movement of the head and ears. Almost all parameters except behavior showed a distinct dose-response relationship. A correlation between the behavioral effects and the EEG analog was thus demonstrated.

Alpha Rhythm↗
PubMed1976

Effects of sound stimulus on gastric secretion and plasma corticosterone level in rats.

The effects of sound stimulus were studied on the gastric secretion in rats with chronically implanted cannulas. Attempts were made to correlate the changes in the secretion with those of the plasma corticosterone level. Exposure of the animals to sound stimulus (1 hr or 2 hr) produced a marked decrease in gastric secretion and a concomitant increase in plasma corticosterone. It appears that in producing these effects sound stimulus acted as a stressor. Furthermore, a paradoxical increase in secretion was noted in the first hour collection prior to the sound stimulus. This initial increase in secretion may be due to an adaptive compensatory mechanism in anticipation of its marked inhibition.

Acoustic Stimulation↗
PubMed1975

Cardiovascular effects of central microinjections of apomorphin in cats.

Microinjections of apomorphine (25-300 mug) were made into the lateral ventricle, dorsal nucleus of the vagus and ventromedial nucleus of the hypothalamus of cats through a stereotaxically implanted cannula-electrode. Apomorphine caused depressor and bradycardic effects without any dose-response relationship. At the above doses of apomorphine the efferent vagal discharges werr markedly increased concurrent with cardiovascular changes. Respiration was not affected except at higher doses causing depression in some experiments. Pretreatment with atropine, scopolamine or haloperidol abolished those responses. Similar results were observed with bivagotomy and midcollicular transection. Dopamine (125-100 mug), acetylcholine (10-100 mug) and norepinephrine (25-100 mug) caused similar cardiovascular changes, as in the case of apomorphine, and such effects were blocked by both specific and non-specific autonomic blackers. Thus the hypothalamus and the dorsal nucleus of the vagus appear to be inbolved in the central cardiovascular effects of apomorphine and such effects may be mediated through more than one neurotransmitter mechanisms.

Acetylcholine↗