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Biomedical subjects

N Banerjee

Publications and source records attributed to N Banerjee.

10 recordsLinked to original sources
PubMed1992

Leishmania donovani: isolation of a concanavalin-A specific antigen and its evaluation for serodiagnosis of visceral leishmaniasis.

A glycoconjugate antigen of 27-39 kDa was isolated from a cell-free extract of Leishmania donovani by affinity chromatography using a Concanavalin-A sepharose-4B column and eluted with 0.5 M alpha-methylmannoside. The antigen was recognized specifically by sera from kala-azar (visceral leishmaniasis) patients and did not react with sera from tuberculosis, leprosy or malaria patients. The antigen may therefore be useful in developing a serodiagnostic assay for visceral leishmaniasis.

Animals↗
PubMed1990

Lipid A mutants of Vibrio cholerae: isolation and partial characterization.

Vibrio cholerae mutants resistant to common antibiotics and neutral and anionic detergents were isolated. Analysis of isolated outer membranes revealed a significant deficiency in the acylation of lipid A in the resistant strains. The content of amide-linked and ester-bound fatty acids in the lipid A of the mutant strains compared to that of the wild type was about 50-56% and 29-37% respectively. This defect was specific for lipid A as there was no change in the acylation of phospholipids. The reduction in fatty acid content of lipid A was reflected in the altered endotoxic properties in the mutant strains.

Drug Resistance, Microbial↗
PubMed1990

Ustilago maydis KP6 killer toxin: structure, expression in Saccharomyces cerevisiae, and relationship to other cellular toxins.

There are a number of yeasts that secrete killer toxins, i.e., proteins lethal to sensitive cells of the same or related species. Ustilago maydis, a fungal pathogen of maize, also secretes killer toxins. The best characterized of the U. maydis killer toxins is the KP6 toxin, which consists of two small polypeptides that are not covalently linked. In this work, we show that both are encoded by one segment of the genome of a double-stranded RNA virus. They are synthesized as a preprotoxin that is processed in a manner very similar to that of the Saccharomyces cerevisiae k1 killer toxin, also encoded by a double-strand RNA virus. Active U. maydis KP6 toxin was secreted from S. cerevisiae transformants expressing the KP6 preprotoxin. The two secreted polypeptides were not glycosylated in U. maydis, but one was glycosylated in S. cerevisiae. Comparison of known and predicted cleavage sites among the five killer toxins of known sequence established a three-amino-acid specificity for a KEX2-like enzyme and predicted a new, undescribed processing enzyme in the secretory pathway in the fungi. The mature KP6 toxin polypeptides had hydrophobicity profiles similar to those of other known cellular toxins.

Amino Acid Sequence↗
PubMed1989

A very small viral double-stranded RNA.

UmV is a double-stranded RNA (dsRNA) virus of the corn fungal pathogen Ustilago maydis. UmV has no infectious cycle. Some UmV subtypes have viral dsRNAs encoding secreted toxins that kill sensitive cells of the same species and related species. There are three viral subtypes, P1, P4 and P6, which differ in the specificity of their secreted killer toxins. Each has three size classes of dsRNA: H (heavy), M (medium) and L (light). The L segments of UmV are unique in being derived from one end of the larger M segments. We have sequenced P1 L and placed it at the 3' end of the P1 M1 plus strand. In their overlapping regions, these dsRNAs are identical in sequence. In vitro translation of P1 M1 results in a peptide whose size is consistent with its being encoded by the non-L region of M1. P1 L is a very small dsRNA of 355 bp. It has no long open reading frames and produces no detectable in vitro translation product. The sequence of P1 L suggests that it is derived by a process unique among dsRNA viruses: replication and packaging of the 3' end fragment of a processed mRNA.

Base Sequence↗
PubMed1986

Elongation of C20 polyunsaturated fatty acids by human skin fibroblasts.

Human skin fibroblasts actively elongate a portion of incorporated C20 polyunsaturated fatty acids to their respective C22 derivatives. As much as 40% of incorporated [14C]eicosapentaenoate is elongated within 8 h and 85% by 48 h. Elongation of [14C]arachidonate is initially less than half that of [14C]eicosapentaenoate and plateaus at 20-30% of incorporated 14C-labeled fatty acid. The elongation of 5,8,11-[14C]eicosatrienoate is intermediate between that of 20:4(n-6) and 20:5(n-3). Docosatetraenoate is not an effective inhibitor of the elongation of arachidonate, thus suggesting that the observed plateau is not due to product inhibition. When concentrations of exogenous fatty acids are increased, these cells elongate substantial quantities of C20 polyunsaturated fatty acids; elongation of eicosapentaenoate is consistently more extensive than that of arachidonate. Eicosapentaenoate is also an effective inhibitor of the elongation of [14C]arachidonate. Increases in exogenous arachidonate up to 10 microM result in an increase in elongation of [14C]arachidonate both in absolute quantities and as a percentage of that incorporated; the arachidonate thus acts as a positive modulator of its own elongation. Increased eicosapentaenoate also enhances the elongation of [14C]eicosapentaenoate, but only at lower concentrations (0.02-0.15 microM). The factors which regulate the elongation of C20 polyunsaturated fatty acids in human skin fibroblasts serve to permit extensive elongation of eicosapentaenoate while retaining incorporated arachidonate primarily in its C20 form.

8,11,14-Eicosatrienoic Acid↗
PubMed1985

High-affinity incorporation of 20-carbon polyunsaturated fatty acids by human skin fibroblasts.

This study has examined the acyl specificity of incorporation of polyunsaturated fatty acids into cellular glycerolipids of human skin fibroblasts. At low exogenous fatty acid concentrations (0.2-1.2 microM) the extent of incorporation of arachidonate, eicosapentaenoate, 8,11,14-eicosatrienoate and 5,8,11-eicosatrienoate is 60-150% greater than that of oleate or linoleate. As the concentration of exogenous free fatty acid is increased to 25 microM, there is little decrease in the percentage of exogenous oleate incorporated into cellular glycerolipids. Under these conditions, the percentage incorporation of arachidonate and eicosapentaenoate drops 2-3-fold and approaches that of oleate. In contrast, the percentage incorporation of 8,11,14-eicosatrienoate remains high as exogenous fatty acid concentrations are increased. Incorporation of arachidonate, eicosapentaenoate, 8,11,14-eicosatrienoate and 5,8,11-eicosatrienoate is inhibited by addition of any of the other C20 polyunsaturated fatty acids but not by palmitate or oleate. C20 polyunsaturated fatty acids other than the eicosanoid precursors are also not effective inhibitors of arachidonate incorporation. The high affinity incorporation of C20 polyunsaturated fatty acids does not appear to be due to their selective esterification in any one class of cellular phospholipids. These results are compatible with a model of two pathways of fatty acids incorporation into mammalian cells. One pathway utilizes all exogenous long-chain fatty acids and, at least in fibroblasts, is not readily saturable. The second is a high-affinity, low-capacity uptake mechanism specific for arachidonate and other precursors of eicosanoids. The acyl specificity of this latter pathway appears to be similar to that of platelet arachidonyl- CoA synthetase. Results obtained with 8,11,14-eicosatrienoate would indicate, however, that at high concentrations, additional mechanisms influence the acyl specificity of fatty acid incorporation in these cells.

8,11,14-Eicosatrienoic Acid↗