Biomedical subjects
Publications and source records attributed to A Kumar.
This is the first report of Pneumocystis carinii infection seen in patients with AIDS in India. Two of the three patients were of Indian origin while the third was an American tourist. This report indicates that the technical problem of demonstrating P carinii may be an important factor underlying the diagnosis of PCP.
BACKGROUND: The acid suppressive abilities of H2 receptor antagonists and anticholinergics have been claimed to be additive. METHODS: A multicenter, double-blind, randomized trial comparing ranitidine (150 mg) plus propantheline bromide 15 mg at bedtime to ranitidine 300 mg alone at bedtime was conducted in 161 patients with endoscopically confirmed uncomplicated duodenal ulcer. RESULTS: After six weeks of therapy, ulcer healing rates in the two groups were comparable ie 80% in the combination group (ranitidine + propantheline) and 79.4% in the ranitidine group. Pain relief after one, two and four weeks of treatment was also comparable in the two groups. Side effects to drugs were minor and comparable in both the groups. CONCLUSION: A combination of 150 mg ranitidine and 15 mg propantheline bromide is as efficacious as 300 mg ranitidine in inducing healing of uncomplicated duodenal ulcers, with similar side-effects but at greatly reduced cost.
A case of macular infarction after intravitreal amikacin was observed in a patient with postoperative endophthalmitis. A review of the literature revealed no previously documented case occurring after intravitreal amikacin. Suggestions to avoid such a complication in an otherwise recovered patient are discussed. Also, better alternatives to intravitreal aminoglycosides should be sought.
We report a new single-reagent colorimetric assay for the determination of calcium in serum. The assay is based on a novel chromogenic tetracarboxylic acid chelating agent. The method has several advantages over the o-cresolphthalein complexone (CPC) method, including improved linearity, better accuracy, increased stability, and lower working pH (9.0). The calibration curve for the assay is linear up to 4 mmol/L. The results for 47 patients' samples correlated well with results obtained with an Instrumentation Laboratory atomic absorption spectrophotometer. The mean (+/- SD) calcium values for the new method were 2.27 +/- 0.06 mmol/L and 2.26 +/- 0.05 mmol/L for the comparison method. The on-system stability of the reagents is 1 week vs 8 h for the CPC method.
Genomic and cDNA clones of the anther-specific APG gene from Arabidopsis thaliana and Brassica napus, which encodes a novel proline-rich protein, were isolated and characterized. Southern blotting and Northern analysis of male fertile and cytoplasmic male sterile varieties of B. napus showed that the APG gene is present as a single copy in the Arabidopsis genome, and that the B. napus APG gene is a member of a small anther-specific gene family. Analysis of developmentally staged B. napus flower buds indicated that APG transcript is confined to the anther during the period of microspore development. Reporter gene fusions established that the APG promoter directs expression in a number of cell types in anthers of transformed plants. This expression is consistent with the temporal pattern of mRNA accumulation in B. napus buds and follows a complex developmental pattern. Most significantly, the promoter is active in both sporophytic and gametophytic cell types, with activity of the transgene in each cell type being delineated by various cytological markers.
Adult and larval insecticidal tests conducted in Panaji, Goa, revealed that adults of An. stephensi were resistant to DDT (4.0%), dieldrin (0.4%) and malathion (5.0%). The larvae of An. stephensi were also resistant to DDT (2.5 mg/l) and malathion (3.125 mg/l). Cx. quinquefasciatus adults were resistant to DDT, dieldrin, malathion and fenitrothion (1.0%), and larvae were highly resistant to DDT but showed low resistance to malathion and fenitrothion (0.125 mg/I). Adults of Ae. aegypti were resistant to DDT and dieldrin and the larvae showed resistance to DDT but good susceptibility to fenitrothion and complete susceptibility to malathion. The triple resistance of An. stephensi to DDT, dieldrin and malathion is intriguing as malathion has never been used in the health sector in Goa. A very limited use of malathion was done in the agricultural sector in Chandor area, which is 50 km away from the study area.
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A hybridoma secreting immunoglobulin G1 antibody was produced against Aspergillus fumigatus. In this study we used interleukin-4 as a growth factor to augment the survival and multiplication of immunoglobulin G1-secreting hybridomas. The antigen recognized by this monoclonal antibody is a low-molecular weight concanavalin A-nonbinding component of A. fumigatus. The monoclonal antibody affinity-purified antigen showed specific reactivity with serum from patients with allergic bronchopulmonary aspergillosis, whereas all allergic asthmatic patients with skin-test reactivity to A. fumigatus demonstrated only low levels of antibodies similar to those in normal control subjects. This antigen failed to show cross-reactivity with other fungal antigens. These results indicate that this monoclonal antibody can be used for the purification of specific antigens useful in the immunodiagnosis of allergic bronchopulmonary aspergillosis.
Ultrasonography (US) plays a crucial role in the evaluation of scrotal masses and is highly accurate in distinguishing extratesticular from intratesticular lesions. Occasionally, however, it may be difficult to distinguish an extratesticular process adherent to the testis from an intratesticular mass on the basis of US findings. The authors present one such unusual case, in which an epididymal sperm granuloma mimicked a testicular mass.
Delayed onset ocular ethambutol toxicity is usually considered to be reversible following prompt withdrawal of the drug. However, in a series of seven consecutive patients with severe visual deficit due to ethambutol toxicity, only 42.2% (3 of the 7 patients) achieved a visual recovery of better than 20/200 after an average follow-up of 8.3 +/- 2.1 months after stoppage of the drug. On fluorescein angiography, three cases (42.2%) progressed to optic atrophy during the follow-up with permanent visual damage. There were no predisposing or risk factors to contribute toward the poor visual gain. In this background, we recommend discontinuation of ethambutol from the antituberculous regimen. As an additional sidelight, the value of visually evoked potential in the monitoring of patients on ethambutol, especially in cases with early periaxial neuritis, has been emphasised.
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Ethanol is the major metabolic product of glucose fermentation by the protozoan parasite Entamoeba histolytica under the anaerobic conditions found in the lumen of the colon. Here an internal peptide sequence determined from a major 39-kDa amoeba protein isolated by isoelectric focusing followed by SDS/PAGE was used to clone the gene for the E. histolytica NADP(+)-dependent alcohol dehydrogenase (EhADH1; EC 1.1.1.2). The EhADH1 clone had an open reading frame that was 360 amino acids long and encoded a protein of approximately 39 kDa (calculated size). EhADH1 showed a 62% amino acid identity with the tetrameric NADP(+)-dependent alcohol dehydrogenase of Thermoanaerobium brockii. In contrast, EhADH1 showed a 15% amino acid identity with the closest human alcohol dehydrogenase. EhADH1 contained 18 of the 22 amino acids conserved in other alcohol dehydrogenases, including glycines involved in binding NAD(P)+ as well as histidine and cysteine residues involved in binding the catalytic zinc ion. Like the T. brockii alcohol dehydrogenase, EhADH1 lacked a 23-amino acid stretch present in other alcohol dehydrogenases that includes four cysteines that bind a second noncatalytic zinc ion. An EhADH1-glutathione-S-transferase fusion protein showed the expected NADP(+)-dependent alcohol dehydrogenase and NADPH-dependent acetaldehyde reductase activities. The enzymatic activities of the EhADH1 fusion protein were inhibited by pyrazole and 4-methylpyrazole.
The 39-kDa DNA polymerase beta (beta-Pol) molecule can be readily converted into two constituent domains by mild proteolysis; these domains are represented in an 8-kDa N-terminal fragment and a 31-kDa C-terminal fragment [Kumar et al. (1990a) J. Biol. Chem. 265, 2124-2131]. Intact beta-Pol is a sequence-nonspecific nucleic acid-interactive protein that binds both double-stranded (ds) and single-stranded (ss) polynucleotides. These two activities appear to be contributed by separate portions of the enzyme, since the 31-kDa domain binds ds DNA but not ss DNA, and conversely, the 8-kDa domain binds ss DNA but not ds DNA [Casas-Finet et al. (1991) J. Biol. Chem. 266, 19618-19625]. Truncation of the 31-kDa domain at the N-terminus with chymotrypsin, to produce a 27-kDa fragment (residues 140-334), eliminated all DNA-binding activity. This suggested that the ds DNA-binding capacity of the 31-kDa domain may be carried in the N-terminal segment of the 31-kDa domain. We used CNBr to prepare a 16-kDa fragment (residues 18-154) that spans the ss DNA-binding region of the 8-kDa domain along with the N-terminal portion of the 31-kDa domain. The purified 16-kDa fragment was found to have both ss and ds polynucleotide-binding capacity. Thermodynamic binding properties for these activities are similar to those of the intact enzyme.(ABSTRACT TRUNCATED AT 250 WORDS)
The identities of the DNA polymerases required for conversion of single-strand (ss) M13 DNA to double-strand (ds) M13 DNA were examined both in injected Xenopus laevis oocytes and in an oocyte nuclear extract. Inhibitors and antibodies specific to DNA polymerases alpha and beta were used. In nuclear extracts, inhibition by the antibody to polymerase beta could be reversed by purified polymerase beta. The polymerase beta inhibitors, dideoxythymidine triphosphate (ddTTP) and dideoxycytidine triphosphate (ddCTP), also blocked DNA synthesis and indicated that polymerase beta is involved in the conversion of ssDNA to dsDNA. These results also may have particular significance for emerging evidence of an ssDNA replication mode in eukaryotic cells.
Following an ill-defined activation event, the Arg-Gly-Asp (RGD) recognition site of the platelet integrin, glycoprotein IIb-IIIa (alpha IIb beta 3), can bind to fluid-phase, RGD-containing protein ligands, such as fibrinogen, or to the murine monoclonal IgM, PAC-1, which contains the sequence Arg-Tyr-Asp (RYD) within the third complementarity-determining region of its heavy chain (H3). PAC-1 has thus become a widely exploited marker of platelet alpha IIb beta 3 activation. In this report, we compare PAC-1 with two murine IgG, OP-G2 (IgG1 kappa) and LJ-CP3 (IgG1 kappa), that also contain the sequence RYD in H3 but bind to alpha IIb beta 3 without prior activation. Each antibody can inhibit the binding of the other two to intact platelets or to purified IIb-IIIa, the binding of each antibody is completely inhibited by peptides containing RGD, and H3 of each antibody uses the germline D-gene DSP 2.10 (CTATAGGTACGAC) which includes the sequence RYD. Two other murine IgG, HP20 and PCG1-1, cloned and sequenced by other laboratories, also utilize the DSP 2.10 sequence, but neither antibody binds to alpha IIb beta 3. From a comparison of the H3 sequences of these antibodies, we have developed a molecular model of the H3 loop region which can explain these differences in specificity. This model predicts that both the ability to bind to alpha IIb beta 3 and the activation dependence of that binding are a function of the orientation and, therefore, accessibility of the RYD sequence. This model and refinements thereof can be exploited to study the molecular basis for specificity and affinity of RGD-containing ligands for integrins.
We have used the polymerase chain reaction to isolate fragments of Ty1-copia group retrotransposons from a wide variety of members of the higher plant kingdom. 56 out of 57 species tested generate an amplified fragment of the size expected for reverse transcriptase fragments of Ty1-copia group retrotransposons. Sequence analysis of subclones shows that the PCR fragments display varying degrees of sequence heterogeneity. Sequence heterogeneity therefore seems a general property of Ty1-copia group retrotransposons of higher plants, in contrast to the limited diversity seen in retrotransposons of Saccharomyces cerevisiae and Drosophila melanogaster. Phylogenetic analysis of all these sequences shows, with some significant exceptions, that the degree of sequence divergence in the retrotransposon populations between any pair of species is proportional to the evolutionary distance between those species. This implies that sequence divergence during vertical transmission of Ty1-copia group retrotransposons within plant lineages has been a major factor in the evolution of Ty1-copia group retrotransposons in higher plants. Additionally, we suggest that horizontal transmission of this transposon group between different species has also played a role in this process.
The double-stranded RNA (dsRNA)-binding domain of the human p68 kinase has been localized to the N-terminal half of the enzyme by using progressive deletion analysis and in vitro binding assays. To further define the domains responsible for binding to dsRNA, we cloned the mouse dsRNA-activated p65 kinase and used sequence alignment to identify conserved domains in the N-terminal region. Deletions in either of two 12-amino-acid-long and arginine- or lysine-rich regions abrogated binding to dsRNA. Moreover, in an in vivo growth inhibition assay in the yeast Saccharomyces cerevisiae, these mutants failed to exhibit a slow-growth phenotype.