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Biomedical subjects

K S Venkateswaran

Publications and source records attributed to K S Venkateswaran.

12 recordsLinked to original sources
PubMed1997

Transmission of HIV-1 in infants born to seropositive mothers: PCR-amplified proviral DNA detected by flow cytometric analysis of immunoreactive beads.

The diagnosis of HIV infection in newborns is established by amplification of proviral DNA using the polymerase chain reaction (PCR). We developed a nonisotopic method for heminested PCR using a biotinylated primer among sets of three oligonucleotides, each selected from the HIV long terminal repeat (LTR) and gag sequences. An internal probe incorporating digoxigenin-dUTP was also synthesized by PCR. The PCR products, hybridized with LTR region or gag region probes, were captured with streptavidin-coated magnetic beads and detected by fluorescein isothiocyanate-labeled antidigoxigenin in flow cytometric analysis. This immunoreactive bead assay (PCR-IRB) detected about three copies of HIV proviral DNA. A panel of 50 coded DNA specimens of infants previously assayed by conventional PCR and with known clinical results revealed that the PCR-IRB findings using LTR, but not gag, were in agreement. A double-blind prospective study of blood samples from 14 mother-infant pairs using the PCR-IRB amplification of LTR gave results similar to the commercial Amplicor HIV-1 PCR test and were consistent with the clinical outcomes. PCR-IRB results were positive for 11 mothers and three infants, one at birth, one at 2 weeks after birth, and one at 8 weeks after birth. PCR-IRB is a simple, reliable, specific, and automatable assay useful in the early diagnosis of perinatal HIV infection in clinical practice and regional screening programs.

Acquired Immunodeficiency Syndrome↗
PubMed1996

Editorial summary of the Pre-symposium workshop on the Contemporary Assessment of Technologies.

The following is the editor's summary of the Pre-symposium workshop on Contemporary Assessment of Technologies presented at the Symposium on Molecular Approaches to Laboratory Diagnosis at San Francisco in February 1995. This workshop was moderated by Dr Joel M. Palefsky, and Dr Michael P. Busch. We have briefly summarized the presentations by: (1) Dr Indira Hewlett of the Center for Biologics Evaluation and Research, Food and Drug Administration entitled 'Technology overview'; (2) Dr John J. Sninsky of Roche Molecular Systems Inc. entitled "Polymerase Chain Reaction'; (3) Dr Terrance Walker of Becton Dickinson Research Center entitled 'Strand Displacement Amplification'; (4) Dr Mickey Urdea of Chiron Corporation entitled 'bDNA assay' and (5) Dr Robert H. Singer of University of Massachussetts Medical Center entitled 'Image analysis of in situ hybridization'. Although it was not possible to list all the references to the primary literature, we have attempted to provide the key references as far as possible.

DNA↗
PubMed1994

Potency of partially purified malleo-proteins for mallein test in the diagnosis of glanders in equines.

Malleo-proteins from synthetic broth mallein of six strains of Pseudomonas mallei were separated by trichloroacetic acid precipitation, ammonium sulfate precipitation and Ultrogel AcA 34 gel filtration chromatography. When tested comparatively with Dutch PPD mallein as standard on P. mallei-sensitized and normal horses all the strains were found to be malleinogenic, trichloroacetic acid precipitated proteins were comparable to Dutch PPD mallein in potency and innocuity whereas ammonium sulfate-precipitated proteins elicited non-specific reactions. Ultrogel AcA 34 chromatographed high molecular weight proteins (MW range > 350,000) were having equal or higher potency and without adverse reactions and low molecular weight proteins (MW range 120,000-170,000) nearly inactive. Ultrogel AcA 34 column fractionation studies revealed that mallein activity was associated with high molecular weight proteins and represented a purer sensitin than PPD mallein for the purpose of mallein test.

Animals↗
PubMed1994

Dose dependent effects on lymphoid organs following a single dermal application of sulphur mustard in mice.

The effects of a single dermal application of sublethal doses [15.5, 7.75 and 3.88 mg kg-1] of bis(2-chloroethyl)sulphide [sulphur mustard, SM] on body weight, organ/body weight ratio, haematology, histology and cellularity of spleen and thymus were studied after 7 days, in Balb/c mice. A progressive fall in body weight was noticed from the fifth day onwards after SM treatment. A dose-dependent decrease in the relative weights of spleen, liver and peripheral lymph nodes, and an increase in adrenal weight were also seen. An increase in red blood cell count, packed cell volume and haemoglobin concentration following SM intoxication were also dose dependent. These changes, together with a significant reduction in the cellularity of the spleen and thymus and degenerative histological changes, show that a single sublethal dermal dose of SM can cause considerable dose dependent systemic effects in Balb/c mice.

Administration, Cutaneous↗
PubMed1994

Degradation of bacteriophage lambda deoxyribonucleic acid in vitro by sulfur mustard.

The degradation of bacteriophage lambda (lambda) deoxyribonucleic acid (DNA) by interaction with 0.1, 0.5 and 1 mM concentrations of sulfur mustard (SM) was investigated using agarose gel electrophoresis. Alkaline agarose gel electrophoresis also revealed single strand breaks at 0.5 and 0.1 mM concentrations of SM. The presence of magnesium ions in the reaction mixture prevented DNA degradation. It is proposed that the degradation of lambda DNA by its interaction with an excess of SM may be caused by the breakage of phosphodiester backbone of DNA via the formation of an intermediate phosphotriester bond.

Bacteriophage lambda↗
PubMed1992

Indirect haemagglutination test for the serodiagnosis of brucellosis using stabilised sheep red blood cells.

Sheep red blood cells (SRBCs) stabilised with formaldehyde, glutaraldehyde, pyruvic aldehyde and double aldehyde were evaluated, in the indirect haemagglutination (IHA) test, for their suitability for the serodiagnosis of brucellosis in bovines. Serum samples from 23 standard tube agglutination test (STAT)-positive and 12 clinically suspected but STAT-negative cows were titrated by the IHA test. Double aldehyde and glutaraldehyde-stabilised SRBCs were found to be more sensitive in the IHA than the formaldehyde or pyruvic aldehyde-stabilised SRBCs. Double aldehyde and glutaraldehyde treatments enabled the IHA to clearly differentiate between the normal and the diseased cows. Double aldehyde-stabilised cells have an edge over the glutaraldehyde-stabilised SRBCs because the former treatment makes the SRBCs readily available for antigen coating without tannic acid activation.

Aldehydes↗
PubMed1992

Modified spot hybridization test using biotinylated DNA probe.

A modification that simplifies the spot hybridization technique is described for using biotinylated DNA probes. Plasmid EWD299 having LT gene insert, labelled with biotin either by nick translation or using photobiotin was used as DNA probe for the specific detection of enterotoxigenic Escherichia coli. A simple protocol has been described for easy lysis of test samples by boiling in distilled water followed by detergent treatment and was found to be as efficient as the lysis using lysozyme and protease. Three different solid supports namely DEAE-cellulose paper, nitrocellulose paper and nylon membrane were also compared for their suitability in this spot hybridization test. Nitrocellulose paper was found to give better colour signal with the photobiotinylated DNA probe.

Biotin↗
PubMed1992

Monitoring of haemoglobin-methyl isocyanate adduct by high-performance liquid chromatography with diode array detector.

Carbamylation of haemoglobin by methyl isocyanate (MIC) was detected by high-performance liquid chromatography (HPLC) using a photodiode array detector following cyclisation of the N-terminal valine into methyl isopropyl hydantoin (MIH). MIH was also synthesised by reaction of MIC with valine, the chromatographic conditions standardised and the spectrum derived by a photodiode array detector recorded for confirmation of the identity of MIH. This HPLC method is specific, sensitive and suitable for the detection of exposure of blood samples to methyl isocyanate.

Accidents↗
PubMed1990

Development of an avidin-biotin dot enzyme-linked immunosorbent assay and its comparison with other serological tests for diagnosis of glanders in equines.

A dot enzyme-linked immunosorbent assay (dot ELISA) was developed for diagnosis of glanders in equines. The test was based on the detection of IgG antibodies to Pseudomonas mallei antigens bound to nitrocellulose coated on plastic strips (dipsticks), the reaction being amplified by an avidin-biotin system with biotinylated anti-horse IgG and horseradish peroxidase-avidin D. Sera from 810 normal, six naturally infected and 48 sensitized equines were tested by this assay, and results were compared with complement fixation, indirect haemagglutination and counter-immunoelectrophoresis tests. Dot ELISA had the highest sensitivity, and was superior to other tests in that it was rapid and easy to perform, the results were easy to interpret, the assay was not influenced by anti-complement activity, and it was able to detect antibodies at an early stage. Testing of serum at 1:200 dilution is proposed for epidemiological screening.

Animals↗
PubMed1989

Influence of arecoline on immune system: I. Short term effects on general parameters and on the adrenal and lymphoid organs.

Arecoline, a suspected carcinogenic/cocarcinogenic alkaloid was screened to explore in detail its immunomodulatory influence in murine model system. The oral LD50 value for male mice was 371 mg/kg bw whereas it was 309 mg/kg bw for female mice. The subcutaneous LD50 value for both sexes was 97 mg/kg bw. Only a marginal difference was observed in intraperitoneal LD50 values between male (120 mg/kg bw) and female (109 mg/kg bw) mice. Arecoline was administered subcutaneously to male mice at subtoxic dose levels (5, 10, and 20 mg/kg bw) for 1, 2 and 3 weeks on a daily basis. In groups where significant decreases in body weight were present (at 20 mg/kg bw for both sexes), reductions in thymus weight were also noted. Spleen, mesenteric lymph nodes (MLN), liver, and kidney showed moderate reductions in their weights. Histopathological effects at 20 mg/kg bw included lymphocyte depletion of the thymic cortex, and the B and T lymphocyte areas in spleen and MLN. In concordance with the zona fasciculata hypertrophy of adrenals, corticosterone concentration in serum increased depending on the dose with a significant elevation at 20 mg/kg bw. While total protein, albumin, glucose, acid phosphatase and hemoglobin concentrations were not altered, increases in SGOT and SGPT levels were observed at the high dose. The white and red blood cell counts decreased in a dose-dependent manner. Marked reduction in cell number of thymus, and moderate effect on cellularity of spleen and MLN, were observed at 20 mg/kg bw. In vitro exposure of rat thymocytes to arecoline resulted in a biphasic oxygen consumption response with progressive increase in oxygen consumption, reaching a maximum value at 10(-5) M and decreasing sharply at 10(-3) M. Exogenously added substrates such as glucose, pyruvic acid and lactic acid retarded the fall in the oxygen consumption induced at 10(-3) M arecoline. These observations demonstrate the effects of arecoline on lymphoid organs, which may be due to its direct action or through the elevation of corticosterone.

Administration, Oral↗
PubMed1988

Gas chromatographic studies of the carbamylation of haemoglobin by methyl isocyanate in rats and rabbits.

Carbamylation of the N-terminal valine of haemoglobin with methyl isocyanate in rats and rabbits has been demonstrated in vitro and in vivo by gas chromatography. N-Methylcarbamylated haemoglobin, converted by cyclization into 3-methyl-5-isopropylhydantoin, has been quantified by gas chromatography. Standard hydantoin was synthesized, chemically characterized and used for calibration. The method is simple and reliable in the concentration range 0.06-2 nmol. Carbamylation of haemoglobin by methyl isocyanate in vivo in rats can be identified only above a dose of 1.05 mg/l in inhalation exposures. It is inferred that methyl isocyanate in the "active" form crosses the alveolar and erythrocyte membranes and carbamylates the haemoglobin.

Animals↗