Search PubMed⌕ Search

Biomedical subjects

R Srivastava

Publications and source records attributed to R Srivastava.

At least 163 records · Page 9Linked to original sources
PubMed1985

Molecular organization of the class I genes of human major histocompatibility complex.

In this brief review, our main emphasis has been on the analysis of the sequence diversity among various class I genes and their functional implications. The availability of complete nucleotide sequences of 7 different genes representing different loci allowed us to derive a consensus sequence. One mouse MHC Class I gene was included in these comparisons as a representative of H2 genes Evolutionary patterns can be seen on the basis of divergence of various genes from the derived consensus sequence. At least 1 human gene which has a promoter similar to that of H2 genes and which contains a single initiation codon following this promoter (unlike all other human genes and like all the H2 genes) has been identified. Both variable and homology regions can be identified in the entire length of the gene. While exons show relatively strong conservation of sequences, the introns have many variable regions, introns 6 and 7 being the most heterogeneous. Stretches of conserved nucleotide sequences are noticed at the 3' regions of most introns. Estimation of total number of class I genes is presented on the basis of cloning experiments, and the abundance of 1 particular pseudogene is discussed.

Alleles↗
PubMed1983

Effect of organo-tellurium compounds on the enzymatic alterations in rats.

An attempt has been made to correlate early toxicity of organo-tellurium (Te) compounds with enzymic alterations in liver, kidney, brain and serum at 1 and 3 days following single i.p. injections of bis-(tetraphenyl phosphonium) tetracyanato-bis-p-methoxy p-phenyl tellurate(IV) (TTMT) and bis-(tetraheptyl ammonium) tetraiodocyclopentane tellurate(IV) (TACT). These compounds, at 2 and 1 mg Te/kg body weight as TTMT and TACT, respectively, produced cholinergic signs and caused death within 3 days. Administration at maximum tolerable doses of 0.5 mg and 0.1 mg Te/kg body weight as TTMT and TACT, respectively, resulted in significant reduction of acetylcholine esterase (AChE) and monoamine oxidase (MAO) in serum and brain and by a significant decrease in hepatic glutathione and in glutathione-S-transferase (GST) and alkaline phosphatase in liver and kidney.

Acetylcholinesterase↗
PubMed1982

The effect of cadmium and manganese on the distribution of iron-59 in partially-hepatectomized rats.

The distribution of iron-59 in blood at various time intervals was studied in sham and partially-hepatectomized rats after a single intravenous injection of 59Fe (III) citrate. A significant difference was observed in the rate of disappearance and reappearance of iron-59 in circulation. Administration of cadmium and manganese at a concentration of 0.5 and 2 mg/kg b.wt., respectively, did not cause any significant change in this pattern. A significant decrease in iron-59 incorporation in the liver of hepatectomized rat was produced by cadmium while manganese had no effect.

Animals↗
PubMed1982

Haem and drug-metabolizing enzymes in regenerating rat liver.

Various parameters of haem and drug metabolism were measured during the course of liver regeneration after two-thirds hepatectomy. Partial hepatectomy produced a significant depression in delta-ALA synthetase and delta-ALA dehydratase, and induction in haem oxygenase at an early stage of regeneration. The values returned to normal within 7-14 days. These changes were also accompanied by a marked decline in benzo(a)pyrene hydroxylase and aminopyrene demethylase. The level of glutathione and the activity of glutathione reductase also increased during the early stage of proliferation. The increased level of glutathione with concomitant decrease in drug-metabolizing enzymes and induction in haem oxygenase could be considered as a protective mechanism for the detoxication process, although a contribution from other biotransforming mechanisms cannot be excluded.

5-Aminolevulinate Synthetase↗
PubMed1981

Deoxyribonucleic acid methylation in mycobacteria.

Deoxyribonucleic acid modification in six strains of mycobacteria was investigated. The presence of 5-methylcytosine in the virulent strain Mycobacterium tuberculosis H37Rv and its absence in the avirulent strain M. tuberculosis H37Ra and other saprophytic, fast-growing mycobacteria appear to be the salient features. However, deoxyribonucleic acid from M. smegmatis SN2 lysogenized with the temperature phage I3 showed the presence of 5-methylcytosine. All of the strains had N6-methyladenine.

5-Methylcytosine↗
PubMed1980

Isolation of a non-adhesive mutant of Vibrio cholerae and chromosomal localization of the gene controlling mannose-sensitive adherence.

A mutant (CD11) of Vibrio cholerae was isolated after exposure of a wild-type pathogenic strain (KB207) to N-methyl-N'-nitro-N-nitrosoguanidine. Although the mutant was motile and chemotactic, it adhered poorly to rabbit intestinal mucosa. Pretreatment of vibrios with 10 mg D-mannose ml-1 and of intestinal mucosa with 100 mmol sodium metaperiodate inhibited adherence of KB207 but not of CD11. The gene (ams) controlling mannose-sensitive adherence was mapped on the bacterial chromosome closely linked to the pur locus.

Adhesiveness↗
PubMed1980

Events in the pathogenesis of experimental cholera: role of bacterial adherence and multiplication.

Pathogenic, and laboratory-derived non-adherent, non-motile, streptomycin-dependent and attenuated strains of Vibrio cholerae, were injected into the ileal loops of adult rabbits. The pattern of bacterial adherence and multiplication was studied. It was shown that all the strains multiplied to the same extent in the intestine; multiplication per se had no role in pathogenesis except when the infecting dose was low. Vibrio strains differed in their capacity to adhere to the intestine. A good correlation was found between adherence and pathogenesis. While adhesive strains were pathogenic, the poorly adhesive strains proved to be poor pathogens. There was no trace of toxin the ileal loops inoculated with poorly adhesive strains and very little in the diarrhoeal fluid produced by pathogenic strains. Adhesive strains adhered poorly to the intestine of immunised animals. It is suggested that adherence is concerned in the release of toxin and thus plays an important role in the pathogenesis of cholera.

Animals↗
PubMed1979

Attenuated recombinant strains of Vibrio cholerae for oral immunization.

Two attenuated strains of Vibrio cholerae, CD1 and CD3, have been isolated that have remained stable since 1976. These strains are motile, adhere to and multiply in rabbit intestine, and colonize the gut of infant mice for 6-7 days. Both strains are antigenic and provide protection to challenge in the mouse protection test and in the rabbit ileal loop model. Because of their ability to adhere to and colonize the gut, and since they are antigenic, strains CD1 and CD3 have the potentiality of oral vaccines.

Administration, Oral↗
PubMedDate not supplied

Role of protozoa as risk factors for persistent diarrhea.

A case control study including 175 children aged 0-36 months suffering from diarrhea of > or = 14 days duration was undertaken to determine whether there is an association between Giardia lamblia, Entamoeba histolytica or Cryptosporidium infection and persistent diarrhea (PD). Subjects were identified by ongoing household surveillance and enrolled as cases. For each case two controls were selected by survey of neighbouring households--a child with acute diarrhea and one without diarrhea. Both the controls were matched with the case for age and nutritional status. Two fresh stool samples were collected from all cases and controls at enrollment and examined for trophozoites of Giardia lamblia, Entamoeba histolytica and Cryptosporidium. Giardia lamblia trophozoites were detected in a significantly higher proportion of PD cases (20.0%) than acute diarrheal and non diarrheal controls (4.6% each, p < 0.0001). There were no significant differences in the proportion of cases and controls who passed E. histolytica trophozoites or cryptosporidium in their stools. There was a consistent trend towards poorer weight gain in PD cases who passed Giardia trophozoites in stool; the differences were statistically significant at days 14 and 21, after enrollment. Giardia lamblia infection is more prevalent in PD cases than in acute diarrhea or non-diarrheal controls. This prevalence is not high enough to warrant routine anti-giardia therapy in patients with PD. However, as giardiasis was observed to have adverse growth impact in PD cases, stool microscopy for detection and subsequent treatment of Giardia lamblia seems to be justified.

Animals↗