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Biomedical subjects

N Srivastava

Publications and source records attributed to N Srivastava.

17 recordsLinked to original sources
PubMed1992

Piperine, a plant alkaloid of the piper species, enhances the bioavailability of aflatoxin B1 in rat tissues.

Piperine is known to modify the biotransformation of drugs. The effect of piperine on the metabolic activation and distribution of [3H]-aflatoxin B1 (AFB1) in rats has been described. Piperine markedly inhibited liver microsome-catalysed [3H]AFB1 binding to calf thymus DNA in vitro, in a dose dependent manner. Rats pretreated with piperine accumulated considerable [3H]AFB1 radioactivity in plasma and in the tissues examined as compared to the controls. However, piperine had no influence on hepatic [3H]AFB1-DNA binding in vivo, which could possibly be due to the null effect of piperine on liver cytosolic glutathione (GSH) 5-transferase activity. Piperine-treated rat liver microsomes demonstrated a tendency to enhance [3H]AFB1 binding to calf thymus DNA in vivo. The effect of piperine on AFB1 metabolism thus closely resembles the mode of action of SKF 525-A on biotransformation of foreign compounds.

Aflatoxin B1↗
PubMed1992

Characterization of the RNA processing enzyme RNase III from wild type and overexpressing Escherichia coli cells in processing natural RNA substrates.

1. A precursor to small stable RNA, 10Sa RNA, accumulates in large amounts in a temperature sensitive RNase E mutant at non-permissive temperatures, and somewhat in an rnc (RNase III-) mutant, but not in an RNase P- mutant (rnp) or wild type E. coli cells. 2. Since p10Sa RNA was not processed by purified RNase E and III in customary assay conditions, we purified p10Sa RNA processing activity about 700-fold from wild type E. coli cells. 3. Processing of p10Sa RNA by this enzyme shows an absolute requirement for a divalent cation with a strong preference for Mn2+ over Mg2+. Other divalent cations could not replace Mn2+. 4. Monovalent cations (NH+4, Na+, K+) at a concentration of 20 mM stimulated the processing of p10Sa RNA and a temperature of 37 degrees C and pH range of 6.8-8.2 were found to be optimal. 5. The enzyme retained half of its p10Sa RNA processing activity after 30 min incubation at 50 degrees C. 6. Further characterization of this activity indicated that it is RNase III. 7. To further confirm that the p10Sa RNA processing activity is RNase III, we overexpressed the RNase III gene in an E. coli cells that lacks RNase III activity (rnc mutant) and RNase III was purified using one affinity column, agarose.poly(I).poly(C). 8. This RNase III preparation processed p10Sa RNA in a similar way as observed using the p10Sa RNA processing activity purified from wild type E. coli cells, confirming that the first step of p10Sa RNA processing is carried out by RNase III.

Chromatography, Liquid↗
PubMed1992

Expression of low density lipoprotein receptor, apolipoprotein AI, AII and AIV in various rat organs utilizing an efficient and rapid method for RNA isolation.

Intact RNA from various rat organs was isolated by an efficient and rapid method. This method of RNA isolation is a modification of an earlier method that uses guanidinium isothiocynate followed by extraction in the presence of sarcosyl, acetate and phenol. The RNA obtained by the method reported here was comparable with the RNA prepared by the CsCl2 ultracentrifugation method and the commercially available kit based on published methods. The quality of RNA was found suitable for Northern blotting analysis, RNase protection assays and reverse transcriptase-polymerase chain reaction (RT-PCR). Since reverse transcriptase is active in the buffer used for Taq DNA polymerase, only one reaction needs to be set up. We also found that the use of aurintricarboxylic acid in the RNA preparation prevents the degradation of RNA during storage. Expression of low density lipoprotein (LDL) receptor, apolipoprotein (apo) AI, AII and AIV mRNAs were quantified in various rat organs. Our results indicated that rat LDL receptor mRNA is expressed in several organs whereas apoAI and AIV mRNAs were expressed mainly in the liver and intestine. However, apo AII mRNA is expressed mainly in the liver. Unlike mice and some species of monkeys, in the rat apoAI mRNA is expressed at 5-6 times higher levels in the intestine compared to liver. Apo AIV mRNA abundance was also found to be several fold higher in intestine compared to hepatic tissues. We present here, for the first time, data on the absolute amounts of LDL receptor, apoAI, AII and AIV mRNA in various rat organs which were quantified by a novel RNase protection/solution hybridization assay.

Animals↗
PubMed1991

Phosphoinositides of sheep platelets plasma membranes.

Phospholipid composition of sheep blood platelets and its various plasma membrane fractions have been analyzed. Based on their flotation rates in discontinuous sucrose density gradient centrifugation, three membrane fractions were isolated. 5'-Nucelotidase and alkaline phosphatase were distributed nearly equally in all the three membrane fractions. However these membrane fractions showed differences in the distribution of phosphatidyl ethanolamine, phosphatidyl choline and phosphoinositides. Phosphatidyl ethanolamine was predominant in fraction I (11.05 micrograms PLP/mg protein) while phosphatidyl choline was predominant in fractions II and III (110.10 and 68.30 micrograms PLP/mg protein respectively). Phosphatidyl inositol (Ptd-InsP) was equally distributed in all three membrane fractions. However, both Ptd-InsP and phosphatidyl inositol 4,5-bisphosphate were about 4-fold higher in fraction II (73.55 and 89.89 micrograms PLP/mg protein respectively).

Animals↗
PubMed1991

RNA processing enzymes RNase III, E and P in Escherichia coli are not ribosomal enzymes.

We recently showed that RNase III can process a small stable RNA, precursor 10Sa RNA, that accumulates in an rne (RNase E) strain at non-permissive temperatures. Precursor 10Sa (p10Sa) RNA is processed to 10Sa RNA in two steps, the first step is catalyzed by RNase III in the presence of Mn2+ but not Mg2+. It was shown that RNase III cosediments with membrane preparation from wild type as well as RNase III overexpressing cells. However, the possibility of membrane preparation contamination with ribosomes could not be ruled out. Here we show that RNase III, E and P are not associated with ribosomes. E. coli cells were opened either by alumina grinding or by sonication and fractionated into cytosolic and pellet fractions. The characterization of membrane preparations was done by assaying NADH oxidase, a bona fide membrane enzyme. Ribosomes prepared by alumina grinding were found to be contaminated with small fragments of membrane which contained RNase III activity. RNase III and NADH oxidase activities were present in the ribosomal preparations which could be solubilized by reagents that dissolve the inner membrane. Isopycnic sucrose gradient centrifugation of the membrane and ribosomal preparations also confirmed that RNase III fractionated with the inner membrane. Similarly RNase P activity was found in the corresponding fractions when isopycnic centrifugation of membrane and ribosome preparations was carried out. RNase E activity was also found to be present mostly in the post-ribosomal supernatant. These findings show that RNase III, E and P are not ribosomal enzymes.

Cell Membrane↗
PubMed1991

Role of oesophageal electrocardiograms in differentiation of old anteroseptal myocardial infarction from emphysema in cases with poor R wave progression in precordial leads.

R wave height, S wave depth and the R/S ratio on electrocardiograms obtained with unipolar oesophageal lead recorded at various levels were studied in 54 cases with emphysema without myocardial infarction and 46 cases with healeeed anteroseptal myocardial infarction. All patients had poor R wave progression in anterior precordial leads. The criterion of R wave height of greater than or equal to 7.5 mm at the ventricular level oesophageal electrocardiogram was most sensitive (85.7%), specific (80%) and accurate (82.4%) for the diagnosis of healed anteroseptal myocardial infarction.

Electrocardiography↗
PubMed1990

Interaction of ethanol, cholesterol and vitamin A on phospholipid methylation in hepatic microsomes of rats.

Effect of ethanol, cholesterol and vitamin A either alone or in combination has been studied on cyt P450 and phospholipid methylation in hepatic microsomes of rats. Ethanol increased cyt P450 activity and decreased phospholipid methylation. Cholesterol effects were opposite to ethanol. Combination of cholesterol and ethanol decreased cyt P450 activity and increased phospholipid methylation. Vitamin A, which alone did not affect cyt P450 activity and phospholipid methylation behaved like cholesterol when given along with ethanol.

Animals↗
PubMed1987

Interaction of ethanol and acute hypoxia (7620 m) on vitamin A distribution in rat organs.

The effect of a moderate dose of ethanol (3 g/kg body weight) and acute hypoxia (282 mmHg pressure) for 6 h on vitamin A content of rat tissue has been investigated. In addition, to find the effect of ethanol administration and hypoxic exposure on freshly absorbed vitamin A, a tracer dose of 3H-retinyl acetate was administered prior to hypoxic exposure. The results indicate that ethanol and hypoxia interfere in the transfer of vitamin A stored as well as freshly absorbed, from intestine to liver. When ethanol administered rats were exposed to hypoxia, the secretion of vitamin A from liver is also disturbed. The vitamin A metabolism in the tissues like kidney and lung are affected adversely on ethanol administration and/or hypoxic exposure. This could be due to interference in the transfer of vitamin A from intestine to liver and secretion of vitamin A from liver into plasma.

Absorption↗
PubMed1978

Distribution of C3 phenotypes in North India: a pilot study.

The commonly occurring phenotypes and some rare variants of C3 were studied in a North Indian population. Based on known gene frequencies, the Indian population seemed more akin to Mongol, African, and Afghan populations than to Caucasians.

Complement C3↗
PubMed1977

Clinically silent pericardial effusions in patients on long-term hemodialysis. Pericardial effusions in hemodialysis.

The danger of cardiac tamponade occurring when pericarditis is accompanied by pericardial effusion, as opposed merely to the presence of a friction rub without effusion, has been unclear. Forty patients on hemodialysis were studied by physical examination, chest x-ray film, and echocardiography for evidence of pericarditis and pericardial effusion. Only two patients developed a friction rub during the study and were placed on regional heparin. Ten of 11 patients who were positive on echocardiogram for pericardial effusion had unremarkable physical examinations. These 11 patients had cardiomegaly as noted on chest x-ray examination. Eighteen of 25 patients without effusion also had cardiomegaly on chest x-ray film. No patient remaining on systemic heparin and having a pericardial effusion developed cardiovascular complications during hemodialysis. This study suggests that while many patients on longterm hemodialysis have pericardial effusion undiagnosed on the basis of physical examination, but noted on echocardiogram, special precautions to prevent tamponade during hemodialysis are not necessary. Also, posterior-anterior chest x-ray film showing a normal-sized heart will usually exclude significant pericardial effusion.

Cardiac Tamponade↗
PubMed1977

New indolic cysticidal agents.

From a series of compounds having amino acid esters linked into the 3 position of substituted indole 3-acetic acids only the compounds 2 and 6 have shown promizing biological activity where as compound 2 process excystment property only, compound 6 has shown both excystment and cysticidal properties. All other compounds are inactive.

Amebicides↗