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Biomedical subjects

H Lal

Publications and source records attributed to H Lal.

At least 145 records · Page 8Linked to original sources
PubMed1982

Effect of dietary restriction with and without excess leucine on hepatic tryptophan oxygenase, 3-hydroxyanthranilate oxygenase and leucine aminotransferase in rats.

Tryptophan oxygenase (EC 1.13.1.12), 3-hydroxyanthranilate oxygenase (EC 1.13.1.6) and leucine aminotransferase (EC 2.6.1.6) activities were determined in livers of rats subjected to different dietary restrictions, with and without excess leucine. The activities of all three enzymes were significantly increased with undernutrition in animals not receiving excess leucine. Excess leucine with moderate undernutrition (50% ad libitum intake) further induced this effect while excess leucine with severe restriction (25% ad libitum intake) acted in the opposite direction.

3-Hydroxyanthranilate 3,4-Dioxygenase↗
PubMed1982

Effect of excess leucine on tryptophan oxygenase, 3-hydroxyanthranilate oxygenase and leucine aminotransferase in livers of young rats.

Hepatic tryptophan oxygenase (EC 1.13.1.12) 3-hydroxyanthranilate oxygenase (EC 1.13.1.6) and leucine aminotransferase (EC 2.6.1.6) activities were determined in livers of rat pups of various ages whose mothers were fed on diets with or without excess leucine. Tryptophan oxygenase activity was detectable on the 20th day in both the groups and thereafter increased with age. Low activity of 3-hydroxyanthranilate oxygenase was observed at birth, the levels increased on the 10th day and thereafter remained unaltered on both diets. Leucine aminotransferase activity was highest at birth and thereafter decreased with age. Tryptophan oxygenase and leucine aminotransferase activities were significantly higher at all ages in livers of pups born to mothers given excess leucine in their diet.

Age Factors↗
PubMed1982

A comparative trial of oral chloroquine and oral co-trimoxazole in vivax malaria in children.

Responses of parasitemia and fever in vivax malaria to standard doses of chloroquine and different dosage schedules of co-trimoxazole were compared in 165 children. Though both the drugs were effective, chloroquine was significantly faster in clearing parasitemia than all the dosage schedules of co-trimoxazole. No statistically significant difference was observed in rapidity of defervescence between chloroquine and the two high daily dosage regimens of co-trimoxazole. Gastrointestinal intolerance was persistently higher with chloroquine. Asymptomatic sulphonamide crystalluria was seen in a large number of cases receiving the two high daily dosage schedules of co-trimoxazole.

Administration, Oral↗
PubMed1982

Diazepam-induced changes in tardive dyskinesia: suggestions for a new conceptual model.

Using an ABA' research design, the effects of a benzodiazepine gamma-aminobutyric acid (GABA)-ergic agent, diazepam, on various aspects of tardive dyskinesia (TD) were investigated in 21 patients. Videotaped recordings of the examinations were rated blind on the Abnormal Involuntary Movements Scale. In nonsedating amounts, diazepam had a significant anti-TD effect, especially in terms of limb dyskinesia. A significant portion of the therapeutic effect persisted after the medication was withdrawn. The results suggest that diazepam has a specific anti-TD action and that in some cases it may be able to produce a somewhat lasting correction of the deranged neurobiological mechanisms in TD. Since the main sites of action of benzodiazepines and the highest concentrations of benzodiazepine-linked GABA receptors are in the limbic and cortical structures that provide principal sources of inputs to the basal ganglia, it is suggested that the supra-striato-pallidal mechanisms of voluntary movement control should be considered in understanding the pathogenesis and treatment of TD.

Adult↗
PubMed1982

Discriminative stimuli produced by clonidine: an investigation of the possible relationship to adrenoceptor stimulation and hypotension.

In a leverpressing operant procedure, male rats were trained to respond for food reinforcement on one lever after an injection of clonidine (0.04 mg/kg) and to respond on an alternate lever for food reinforcement after an injection of saline. All 36 rats learned to discriminate the drug reliably from saline, thereby indicating that clonidine produces discriminative interoceptive stimuli. The discriminative stimulus was both dose- and time-dependent, with an ED50 of 0.018 mg/kg and an optimum time of action occurring from 15 to 60 min after injection. Although clonidine produced a reduction in response rate, this was not the basis of the discriminative stimulus as other drugs with similar depressant action did not generalize. The clonidine stimulus was dose-dependently antagonized by the alpha-2 adrenergic antagonist, yohimbine, whereas receptor antagonists of alpha-1 adrenergic, beta adrenergic, dopaminergic, serotonergic, cholinergic or opioid systems were ineffective in blocking the interoceptive stimulus produced by clonidine Lofexidine, guanabenz and methyldopa, all centrally acting hypotensive drugs that act through alpha-2 adrenoceptor mechanisms dose-dependently generalized to the clonidine cue, whereas hydralazine, minoxidil, propranolol and prazosin, hypotensive drugs acting through other mechanisms, did not generalize. These results suggest that clonidine produces interoceptive stimuli that are discriminable by rats and mediated through central alpha-2 adrenoceptor stimulation.

Animals↗
PubMed1982

Senescence related changes in brain diazepam binding and motor performance.

Senescent mice showed attenuation of habituation in locomotor activity and marked deficit in the motor performance requiring limb coordination. Also, the binding of 3H-diazepam to the crude synaptosomal fraction prepared from cerebral cortex of the senescent mice was significantly altered. The binding maximum (Bmax) was significantly greater in the aged (23-26 months) mice, but no change was found in the apparent dissociation constant (Kd). Senescent related changes appear to include neurochemical alteration of the endogenous benzodiazepine system (increased receptor sites without any change in receptor affinity) and, perhaps, related physiological deficits in the limb coordination and/or strength.

Aging↗
PubMed1982

Discrimination of sucrose-taste by the rat as a potential bioassay for sweeteners.

Male hooded rats were trained to discriminate the taste of a sucrose solution from that of water by responding with a lever on one side of a food cup after 20 licks (500 microliter) a 0. M sucrose solution and responding with a lever on the alternating side after 20 licks of water for food reinforcement. All of the rats learned this discrimination reliably. The gustatory stimulus produced by sucrose was concentration dependent (EC50 = 1.3 X 10(-2) M). Saccharin (0.0002-0.002 M), dextrose (0.05-0.25 M), and glycine (0.002-0.2 M) produced a concentration-dependent generalization to the sucrose taste. The EC50 values were 1 X 10(-3), 2.7 X 10(-2), and 1.3 X 10(-1) M, respectively. Solutions of sodium chloride (0.15 M), citric acid (0.01 M), caffeine citrate (0.01 M), quinine hydrochloride (0.001 M), or l-amphetamine sulfate (0.05 M) did not produce sucrose-like taste. Generalization of sweet compounds and lack of generalization of other tastes to the sucrose taste suggest that the procedure of sucrose-water discrimination by the rat has potential in the detection and quantitation of the sweetening properties of new chemicals.

Animals↗
PubMed1981

Effect of acute and chronic pentylenetetrazol treatment on benzodiazepine and cholinergic receptor binding in rat brain.

The binding of [3H] diazepam and [3H] flunitrazepam in rat cerebral cortex was not altered by either acute or chronic administration of pentylenetetrazol except in rats made to convulse 30 min before sacrifice. Rats treated for up to 6 months with doses of pentylenetetrazol which are below seizure threshold in naive rats, became increasingly sensitive to the CNS stimulant effect of pentylenetetrazol as demonstrated by the development of myoclonus and convulsions during treatment periods. These effects were not correlated with any changes in benzodiazepine binding in cerebral cortex or cerebellum and [3H] quinuclidinyl benzilate binding in cerebral cortex. Acute convulsant doses of pentylenetetrazol increased benzodiazepine binding in cerebral cortex, but only in those rats which actively convulsed. Benzodiazepine and cholinergic receptors of the cortex, and benzodiazepine receptors of the cerebellum, therefore, do not appear to change with either the acute or chronic subconvulsive administration of pentylenetetrazol.

Animals↗
PubMed1981

Nonnarcotic antidiarrheal action of clonidine and lofexidine in the rat.

Clonidine (0.01 to 0.16 mg/kg) and lofexidine (0.01 to 0.64 mg/kg) produced a dose-dependent inhibition of diarrhea induced by castor oil treatment in the rat. Both drugs were more potent and longer acting than diphenoxylate. Pre- and posttreatment with naloxone (5 mg/kg) failed to prevent or antagonize the antidiarrheal effect of clonidine and lofexidine. These data suggest that clonidine and lofexidine may provide potent antidiarrheal activity of a nonnarcotic nature.

Animals↗
PubMed1981

Discriminative response control by naloxone in morphine pretreated rats.

In an operant procedure using a lever press response 12 male, hooded rats were trained to discriminate 1.25 mg/kg naloxone from a saline injection. On certain days, according to a counterbalanced training schedule, naloxone was administered 8 h after 40 mg/kg morphine and 10 min prior to a trail in which food was available on an FR10 schedule from one of two levers in a dual lever operant chamber. On other days saline was administered 10 min prior to a trial in which food was made available by pressing the other lever. After criterion performance for acquisition of the discrimination had been reached, tests were carried out to determine its nature. Discrimination of naloxone was dose-dependent and was significantly diminished when naloxone was administered 36 h after morphine. Partial generalization of cyclazocine with naloxone was observed. Spontaneous withdrawal from morphine, tested during trials preceeded by an injection of saline instead of naloxone at various time intervals after morphine, did not generalize with the naloxone discriminative stimulus.

Animals↗