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Biomedical subjects

S Narasimhan

Publications and source records attributed to S Narasimhan.

68 records · Page 4Linked to original sources
PubMed1982

Cardamom--production, technology, chemistry, and quality.

Cardamom, Elettaria cardamomum Maton var. Miniscula Burkill (Fam. Zingiberaceae) known as true or lesser cardamom is the widely cultivated variety and important in the world trade. It occupies a high second or third place in world trade, being a high priced spice. It belongs to the sweet spices group and is used predominantly to flavor sweets, baked goods, and coffee, particularly in the Arab countries. This monograph critically reviews the post-harvest handling and processing and the chemistry of the volatiles. The components contributing to the characteristic aroma for which the spice is valued are specifically considered. Gas chromatographic analysis for quality control and attempts are evaluating the aroma quality by sensory profile are discussed in relation to regional varieties, and processing variables. The areas in which further research is required are indicated. The botanical and cultivation aspects and production and trade of the different growing and consuming regions are briefly considered. Available information on other "cardamoms" from related species and genera are summarized.

Agriculture↗
PubMed1982

Structure of the glycopeptides of a human gamma 1-immunoglobulin G (Tem) myeloma protein as determined by 360-megahertz nuclear magnetic resonance spectroscopy.

High field magnetic resonance spectroscopy has been utilized to deduce the primary structure of the glycopeptides from a human myeloma gamma 1-immunoglobulin G (Tem). The major structures found belong to the biantennary complex class of glycopeptides, with a minor (5%) fraction belonging to the bisected biantennary complex class. In the biantennary class, three structures were present with different residues at the termini of the alpha Man(1-6) and alpha Man(1-3) arms: (i) with beta Gal(1-4) and alpha NeuNAc(2-6), respectively (33%); (ii) with beta Gal(1-4) and beta Gal(1-4), respectively (45%); and (iii) beta Gal(1-4) and beta GlcNAc(1-2), respectively (17%). In the bisected biantennary class only the latter termini were found for the two arms. These results suggest that the galactosyl transferase in these cells has a preference for the beta GlcNAc(1-2) of the alpha Man(1-6) arm and that the sialyltransferase has a preference for the beta Gal(1-4) of the alpha Man(1-3) arm.

Chemical Phenomena↗
PubMed1980

Control of glycoprotein synthesis. The purification by preparative high voltage paper electrophoresis in borate of glycopeptides containing high mannose and complex oligosaccharide chains linked to asparagine.

The heterogeneity of glycopeptides prepared from pronase digests of various glycoproteins has previously been demonstrated primarily by lengthy paper chromatography of oligosaccharides released from the glycopeptides by enzymatic or chemical means. We describe the use of high voltage paper electrophoresis in borate for the resolution of seven glycopeptides from ovalbumin and seven glycopeptides from human immunoglobulin G. This technique has been used in the preparation of glycopeptide substrates required for the study of certain glycosyltransferases and glycosidases.

Asparagine↗
PubMed1979

A structural basis for four distinct elution profiles on concanavalin A--Sepharose affinity chromatography of glycopeptides.

Twelve 14C-acetylated glycopeptides have been subjected to affinity chromatography on concanvalin A (Con A)--Sepharose at pH 7.5. The elution profiles could be classified into four distinct patterns. The first pattern showed no retardation of glycopeptide on the column and was elicited with a glycopeptide having three peripheral oligosaccharide chains: (abstract:see text). Such glycopeptides have only a single mannose residue capable of interacting with Con A--Sepharose; an interacting mannose residue is either an alpha-linked nonreducing terminal residue or an alpha-linked 2-O-substituted residue. The second type of profile showed a retarded elution of glycopeptide with buffer lacking methyl alpha-D-glucopyranoside (indicative of weak interaction with the column) and was given by glycopeptides with the structures: (abstract: see text) where R1 is either H or a sialyl residue. The third profile type showed tight binding of glycopeptide to Con A--Sepharose and elution as a sharp peak with 0.1 M methyl alpha-D-glucopyranoside; glycopeptides giving this pattern had the structures: (abstract: see text) where R2 is either H, glcNAc, Gal-beta 1,4-GlcNAc, or sialyl-Gal-beta 1,4-GlcNAc. These glycopeptides all have two interacting mannose residues, the mimimum required for binding to the column; one of these mannose residues must, however, be a terminal residue to obtain tight binding and sharp elution. The fourth profile type showed tight binding of glycopeptide to the column but elution with 0.1 M methyl alpha-D-glucopyranoside resulted in a broad peak indicating very tight binding; glycopeptides showing this behaviour had the structures: (abstract: see text) where R3 is either GlcNAc,Gal-beta 1,4-GlcNAc, or sialyl-Gal-beta 1,4-GlcNAc. Therefore it can be concluded that although a minimum of two interacting mannose residues is required for binding to Con A--Sepharose, the residues linked to these mannoses can either strengthen or weaken binding to the column.

Carbohydrates↗
PubMed1979

Pseudomonas infection and the anaesthetist.

Cultures of specimens taken from anaesthetic equipment after routine cleaning and chemical decontamination revealed contamination with Pseudomonas Aeruginosa. Attention is drawn to the widely practised but unsatisfactory methods of decontaminating equipment. Consideration of the subject of decontamination of anaesthetic equipment led to the re-evaluation of our current practice, with surprising results. At the end of our brief look, we had changed our methods of decontamination dramatically and heightened awareness of a large section of theatre staff with regard to aseptic technique. We had also found a possible method of eliminating Pseudomonas Aeruginosa from the sinks in the operating theatre. Recommendations as to future practice are included.

Anesthesia Department, Hospital↗
PubMed1978

Syntheses of DNA and chromosomal proteins in the rat thymus following whole-body X-irradiation.

Syntheses of chromosomal proteins was studied in relation to DNA syntheses in the rat thymus following whole-body X-irradiation (600 rad). There was a considerable depression of the syntheses of DNA and histones during the first 4--48 hours after irradiation. The syntheses of histones H3 and H4 plus H2A were affected to a much greater degree than those of histones H1 and H2B, suggesting a tight coupling between the syntheses of DNA and histones H3 and H4 plus H2A. A part of the lysine-rich histones H1 and H2B, however, seems to be synthesized, even in the absence of DNA synthesis. Biosynthesis of non-histone proteins was also depressed in the thymus after irradiation. The degree of inhibition, however, was very low, except for the syntheses of a few non-histone protein components which were depressed to a considerable extent. This implies that the synthesis of the majority of non-histone proteins is independent of DNA synthesis.

Animals↗
PubMed1977

Sickle cell anemia and trait in a population of southern India.

In an ethnic group in southern India, the Irula, seven individuals with sickle cell anemia were found to manifest only mild illness. Although a relatively high level of fetal hemoglobin was present in one, none of the factors thought to ameliorate the course of sickling disorders could be identified in the remaining six. In a random population survey, sickle hemoglobin was found in 90 of 292 Irula (31%). In those with sickle cell trait, the proportion of sickle hemoglobin in hemolysates (mean = 26%, range 19-32%) was substantially lower than that reported for any other population.

Anemia, Sickle Cell↗
PubMed1975

Chinese hamster ovary cells selected for resistance to the cytotoxicity of phytohemagglutinin are deficient in a UDP-N-acetylglucosamine--glycoprotein N-acetylglucosaminyltransferase activity.

Several clones of Chinese hamster ovary cells resistant to the cytotoxicity of the phytohemagglutinin from Phaseolus vulgaris show decreased binding of 125I-labeled phytohemagglutinin and contain decreased levels of a UDP-N-acetylglucosamine--glycoprotein N-acetylglucosaminyltransferase (EC 2.4.1.51; UDP-2-acetamido-2-deoxy-D-glucose:glycoprotein 2-acetamido-2-deoxy-D-glucosyltransferase) activity when compared to wild-type cells. The decrease in transferase activity varies from 45% to 96%, depending on the exogenous acceptor used in the enzyme assay. No differences between lectin-resistant and wild-type cells were noted for several other glycosyltransferases. The absence of a particular N-acetylglucosaminyltransferase in the lectin-resistant cells apparently results in defective glycosylation of lectin-binding glycoproteins on the cell surface. A phytohemagglutinin-resistant clone which shows decreased binding of 125I-labeled phytohemagglutinin but does not exhibit the enzyme deficiency has also been isolated.

Binding Sites↗
PubMedDate not supplied

Nimbolide and isonimbolide.

Nimbolide 1, a potent molecule of biological significance, was isolated. Attempts were made to cleave the ether linkage in nimbolide using boron trifluoride etherate in the presence of tetrabutyl ammonium bromide so as to generate a ring-opened structure akin to azadirachtins, which are known to possess excellent antifeedant properties. However, a novel rearranged product was envisaged during the course of the reaction, which was determined as isonimbolide 2-a structural isomer of nimbolide through spectroscopic methods.

Humans↗