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Biomedical subjects

R Lal

Publications and source records attributed to R Lal.

At least 127 records · Page 7Linked to original sources
PubMed1989

The effects of dieldrin, dimethoate and permethrin on Tetrahymena pyriformis.

The effects of three insecticides, dieldrin, dimethoate and permethrin, on the growth of a holotrichous ciliate, Tetrahymena pyriformis, were studied for 5 days. The ciliate was very sensitive to dieldrin and dimethoate. Both these insecticides produced approximately 81% and 84% inhibition of growth within two days. Dieldrin caused rounding of cells, while dimethoate induced cell lysis. Dimethoate also triggered a general mucocyst discharge. Of the three insecticides, permethrin was the least toxic and induced no morphological alterations.

Journal Article↗
PubMed1989

The 43-kD polypeptide of heart gap junctions: immunolocalization, topology, and functional domains.

Analysis by SDS-PAGE of gap junction fractions isolated from heart suggests that the junctions are comprised of a protein with an Mr 43,000. Antibodies against the electroeluted protein and a peptide representing the 20 amino terminal residues bind specifically on immunoblots to the 43-kD protein and to the major products arising from proteolysis during isolation. By immunocytochemistry, the protein is found in ventricle and atrium in patterns consistent with the known distribution of gap junctions. Both antibodies bind exclusively to gap junctions in fractions from heart examined by EM after gold labeling. Since only domains of the protein exposed at the cytoplasmic surface should be accessible to antibody, we conclude that the 43-kD protein is assembled in gap junctions with the amino terminus of the molecule exposed on the cytoplasmic side of the bilayer, that is, on the same side as the carboxy terminus as determined previously. By combining proteolysis experiments with data from immunoblotting, we can identify a third cytoplasmic region, a loop of some 4 kD between membrane protected domains. This loop carries an antibody binding site. The protein, if transmembrane, is therefore likely to cross the membrane four times. We have used the same antisera to ascertain if the 43-kD protein is involved in cell-cell communication. The antiserum against the amino terminus blocked dye coupling in 90% of cell pairs tested; the antiserum recognizing epitopes in the cytoplasmic loop and cytoplasmic tail blocked coupling in 75% of cell pairs tested. Preimmune serum and control antibodies (one against MIP and another binding to a cardiac G protein) had no or little effect on dye transfer. Our experimental evidence thus indicates that, in spite of the differences in amino acid sequence, the gap junction proteins in heart and liver share a general organizational plan and that there may be several domains (including the amino terminus) of the molecule that are involved in the control of junctional permeability.

Animals↗
PubMed1989

Theophylline pharmacokinetics in well-nourished and malnourished asthmatic children.

The influence of age, sex and nutritional status on theophylline pharmacokinetics was studied in stable asthmatic children. Theophylline was given at a dose of 6 mg/kg orally on an empty stomach and the pharmacokinetic parameters were calculated from the estimated plasma concentration of theophylline. No significant difference in the elimination half-life (t1/2), volume of distribution (Vd), clearance (cl) and area under the time plasma curve (AUC) could be observed between the three pediatric age groups. Also, there was no influence of sex and nutritional status on the pharmacokinetic parameters. The notable observation was a 5-fold interindividual difference in the peak plasma concentration (Cmax) after a single dose.

Adolescent↗
PubMed1988

Interaction of Endosulfan and malathion with blue-green algae Anabaena and Aulosira fertilissima.

The growth of Anabaena and Aulosira fertilissima was adversely affected by endosulfan even at 1 microg ml(-1). The inhibition was significantly above 50% at 20 microg ml(-1) throughout the incubation. Anabaena survived up to 500 microg ml(-1) of malathion, but was completely bleached in the presence of 50 microg ml(-1) of endosulfan. Aulosira was more sensitive to malathion than Anabaena and recovered to control levels only at 10 microg ml(-1). The morphology and hetercyst frequency were not altered in Anabaena. Aulosira cultures were dull brown in colour at 20 microg ml(-1) of endosulfan with the filaments clumping, instead of the usual mat formation. Both malathion and endosulfan considerably lowered (14)C uptake and nitrogenase activities in Aulosira. Nitrogen fixation was unaffected in Anabaena as the amounts of ethylene produced were equal to, or above, control levels. The impact of these insecticides on photosynthesis in Anabaena was only slight.

Journal Article↗
PubMed1988

Uptake of dieldrin, dimethoate and permethrin by cyanobacteria, Anabaena sp. and Aulosira fertilissima.

Blue-green algae showed a poor ability to pick up and concentrate dieldrin and dimethoate. However, the uptake and bioconcentration factor for permethrin was very high. The uptake of dieldrin by Anabaena and Aulosira ranged from 5.1 to 73.2 and 5.5 to 17.4 microg g(-1) (ppm), respectively. The uptake of permethrin was from 9.0 to 249.7 and 4.6 to 1422.5 microg g(-1) by Anabaena and Aulosira, respectively. The highest bioconcentration factors for permethrin in Anabaena and Aulosira were 813 and 2373, respectively. This was followed by the bioconcentration factor of dieldrin (620) and dimethoate (119) in Aulosira fertilissima.

Journal Article↗
PubMed1988

An epidemic of hepatitis D in the foothills of the Himalayas in south Kashmir.

We have identified hepatitis D as an etiologic cause of an outbreak of 'hepatitis' in an endemic area for hepatitis B in South Kashmir, India. Thirty-five of the 51 patients with jaundice were hepatitis B virus carriers. Twenty-two of the 24 such patients tested had hepatitis D (hepatitis D virus superinfection). Two of the 3 patients with acute hepatitis B were coinfected with hepatitis D virus (HDV). Thirty-six asymptomatic household contacts of hepatitis D patients were assessed. Six were hepatitis B virus carriers, 3 of whom had HDV superinfection. Two contacts had acute hepatitis B, one with HDV coinfection. The disease occurred in adults with a mean age of 28.2 +/- 10.5 years (range 10-56 years) and was equally distributed between the sexes. Three patients with HDV superinfection presented with fulminant hepatic failure with a fatal outcome. All the patients with non-fulminant hepatitis D showed apparent clinical recovery. However, in the subsequent follow-up at 4 years, 7 patients with HDV superinfection had evidence of chronic hepatitis. One of these 7 patients died due to progressive chronic liver disease.

Adolescent↗
PubMed1988

Pharmacokinetic study of a new sustained release preparation of propranolol in normal healthy volunteers.

The pharmacokinetics of a sustained release (SR) propranolol (Betalong) were compared with conventional propranolol (Inderal) after single and multiple dosing in 8 normal healthy volunteers. The study was designed in a crossover fashion. SR propranolol 80 mg in a single dose maintained the plasma concentration of propranolol above the minimum therapeutic concentration up to 25 h. The steady-state propranolol concentration after 80 mg conventional propranolol twice daily and SR propranolol 80 mg daily was almost similar. The results indicate that Betalong (SR propranolol) satisfies the pharmacokinetic criteria expected of a sustained release preparation of propranolol and may be useful in single daily dose.

Adult↗
PubMed1988

Single dose kinetics of rifampicin and isoniazid in well-nourished and malnourished patients of tuberculosis.

A single dose kinetics of isoniazid and rifampicin alone, and combination was studied in well-nourished and malnourished patients of tuberculosis. The elimination half-life of isoniazid was significantly increased when administered in combination with rifampicin in well-nourished and malnourished patients, while no significant difference was observed in any of the pharmacokinetic parameters of rifampicin in combination with isoniazid or alone in both groups of patients. Results are discussed on the basis of pharmacokinetic drug interaction.

Acetylation↗
PubMed1988

Plasma dapsone and its metabolite monoacetyldapsone levels in leprotic patients.

Dapsone (DDS) is a drug of choice in the treatment of leprosy. The DDS and MADDS levels and different pharmacokinetic parameters after a single dose of dapsone and at steady state in leprotic patients have been studied. At steady state, all the patients showed plasma DDS and MADDS levels above 0.5 micrograms/ml throughout the 24-h duration. There was no significant difference in the elimination half-lives of DDS and MADDS after a single dose as compared to at steady state, but AUC0-alpha for both DDS and MADDS were significantly increased at steady state. From these results, it could be concluded that 100 mg daily dose is sufficient to maintain plasma therapeutic concentration in leprotic patients in Indian population.

Adult↗
PubMed1988

Pharmacokinetics of aspirin and chloramphenicol in normal and leprotic patients before and after dapsone therapy.

Pharmacokinetics of aspirin and chloramphenicol was studied in 16 normal and 16 patients suffering from leprosy. A significant increase (p less than 0.05) in the elimination half-life of chloramphenicol was observed before and after dapsone treatment in leprotic patients as compared with the normal volunteers, while no significant difference was observed in any of the pharmacokinetic parameters with aspirin.

Adult↗
PubMed1987

Bioconcentration and metabolism of DDT, fenitrothion and chlorpyrifos by the blue-green algae Anabaena sp. and Aulosira fertilissima.

Anabaena and Aulosira fertilissima showed a marked ability to accumulate DDT, fenitrothion and chlorpyrifos. Although the maximum accumulation of DDT was almost the same in both organisms, there were significant differences in their abilities to accumulate fenitrothion and chlorpyrifos. Patterns of uptake of DDT under different treatments were also similar in both Anabaena and Aulosira, but there were significant differences in the patterns of accumulation of fenitrothion between these two organisms. In Aulosira the maximum accumulation of fenitrothion was observed on the second day, whereas, in Anabaena, maximum accumulation was noticed on the first day. A completely different pattern of accumulation of chlorpyrifos was observed in Aulosira, which continued to accumulate chlorpyrifos throughout the experimental period. Bioconcentration of DDT in Anabaena and Aulosira ranged from 3 to 1568 ppm (microg g(-1)) and 6 to 1429 ppm, respectively. Bioconcentration of fenitrothion and chlorpyrifos in Anabaena varied from 53 to 3467 ppm and 7 to 6779 ppm, respectively. In Aulosira the bioconcentration varied from 100 to 6651 ppm and 53 to 3971 ppm for fenitrothion and chlorpyrifos, respectively. Anabaena and Aulosira metabolised DDT to DDD and DDE. Amounts of these DDT metabolites detected in the organisms were dependent on the concentration of treatment. DDD was the major, and DDE the minor, metabolite. These organisms were not able to metabolise the organophosphorus insecticides, fenitrothion and chlorpyrifos.

Journal Article↗
PubMed1987

Paroxysmal nonreentrant supraventricular tachycardia due to simultaneous fast and slow pathway conduction in dual atrioventricular node pathways.

Electrophysiologic studies were performed on a 49 year old woman who had paroxysmal nonreentrant supraventricular tachycardia due to simultaneous anterograde conduction through dual atrioventricular (AV) node pathways. Slow pathway conduction was inversely related to the preceding sinus cycle length and fast pathway conduction was determined by the Hs-A interval (measured from the His potential due to slow pathway conduction to the onset of the subsequent atrial electrogram). Major determinants of sustained simultaneous anterograde fast and slow pathway conduction during sinus rhythm were 1) a retrograde unidirectional block in both fast and slow pathways, and 2) a critical conduction delay in the slow pathway and a long enough Hs-A interval to allow sequential conduction of impulse from both pathways. Flecainide was successful in preventing recurrences of the tachycardia by eliminating slow pathway conduction during long-term follow-up.

Atrioventricular Node↗
PubMed1987

Oral habits.

Explore the source record for details and available documents.

Child↗
PubMed1987

Differential effect of some antiarrhythmic drugs in right- or left-sided aconitine-induced experimental atrial arrhythmias.

The differential effect of different antiarrhythmic agents, quinidine, propranolol, verapamil and sotalol was studied on right- and left-sided aconitine-induced atrial arrhythmias in dogs. In control experiments the time required for the reversion of right aconitine-induced atrial arrhythmias to normal sinus rhythm was higher as compared to left-sided aconitine-induced atrial arrhythmias. All the drugs studied were effective in reverting atrial arrhythmias to normal sinus rhythm, and doses required for suppression of the right atrial arrhythmias as compared to the left atrial arrhythmias were significantly higher in the case of quinidine, sotalol and verapamil, but not in the case of propranolol. The differential antiarrhythmic effect of these drugs in atrial arrhythmias is discussed.

Aconitine↗
PubMed1986

Treatment of paroxysmal reentrant supraventricular tachycardia with flecainide acetate.

The electrophysiologic effects and therapeutic efficacy of intravenous and oral flecainide were studied in 15 patients with spontaneous and inducible sustained paroxysmal supraventricular tachycardia (SVT). Twelve patients had atrioventricular (AV) reentrance using an accessory pathway for retrograde conduction and 3 had AV nodal reentrance. Fourteen patients received intravenous flecainide (2 mg/kg body weight over 15 minutes) during an initial electrophysiologic study. Nine patients were restudied during oral flecainide administration (200 to 400 mg/day). After intravenous or oral flecainide therapy, reentrant SVT was noninducible in 6 patients with AV reentrance and in the 3 with AV nodal reentrance. In these 9 patients, intravenous flecainide prevented induction of reentrant SVT by depressing conduction over the retrograde limb of the reentry circuits. In the 6 patients with inducible sustained AV reentrant SVT before and after flecainide therapy, the cycle length of tachycardia increased significantly, mainly as the result of an increase in ventriculoatrial conduction time. There was concordance between the intravenous and the oral effects of flecainide on the mechanism of the SVT. Twelve patients continued oral flecainide treatment for a mean of 16 months (range 5 to 28). Tachycardia recurred in 3 of 4 patients whose arrhythmia remained inducible after flecainide therapy and in 1 of 8 patients whose SVT was suppressed. It is concluded that flecainide is an effective and convenient antiarrhythmic agent to treat patients who have AV nodal or AV reentrant SVT.

Administration, Oral↗
PubMed1986

Flecainide and amiodarone interaction.

Oral amiodarone therapy was given to seven patients already taking oral flecainide regularly. In one additional patient, administration of flecainide was temporarily discontinued when amiodarone therapy was begun, and then resumed. Amiodarone produced a rise in mean dose-adjusted flecainide plasma level (trough plasma level at steady state/daily dose) from 2.3 +/- 0.8 to 3.4 +/- 0.9 (ng/ml)(mg/day) (p less than 0.01). Accordingly, the mean dose of flecainide required to maintain similar plasma levels of the drug was one-third lower during combined treatment than during therapy with flecainide alone. This drug interaction must be accounted for when amiodarone and flecainide are used concomitantly.

Adult↗