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V Shanmugam

Publications and source records attributed to V Shanmugam.

12 recordsLinked to original sources
PubMed1994

Osteopontin: its transglutaminase-catalyzed posttranslational modifications and cross-linking to fibronectin.

Osteopontin (OP) is a component of extracellular, bone, and urinary stone matrices, but the mechanism by which it is stably incorporated into such matrices remains unknown. By SDS-PAGE analysis of [125I]OP, treated with a catalytic amount of TG, we first demonstrate both intra- and intermolecular covalent cross-linking of OP. Most importantly, the analysis of the products generated from reactions containing OP, Fn, and TG by SDS-PAGE, autoradiography, and Western blotting using either OP or Fn antibody, and quantitation of TG-catalyzed epsilon-(gamma-glutamyl)lysine isopeptide formation between OP and Fn demonstrate, for the first time, covalent cross-linking between these two proteins. Similar reactions in the presence of polyamine substrates of TG show OP-Fn intermolecular cross-linking via N,N-bis-(gamma-glutamyl)polyamine formation. Finally, immunoprecipitation of 125I-labeled NRK cell surface proteins with anti-OP and anti-Fn antibodies, SDS-PAGE analysis, and autoradiography provides critical evidence for nonreducible OP-Fn cross-linking in vivo. These results clearly suggest that TG-mediated cross-linking between OP and Fn represents one of the most likely mechanisms by which OP becomes covalently linked to bone matrix, urinary stone matrix, and to ECM.

Amino Acid Sequence↗
PubMed1993

Calcium-binding properties of osteopontin derived from non-osteogenic sources.

Osteopontin (OP), purified from rat bone, binds Ca2+ but whether different molecular forms of OPs derived from non-osteogenic sources and non-phosphorylated OP also possess this property remains to be determined. Furthermore, it is not known which specific site or sites of the molecule bind Ca2+. In the present study, following an established procedure, total proteins in the conditioned media from OP-synthesizing cell cultures were separated by SDS-PAGE, transferred to Immobilon-P membranes, and incubated with 45CaCl2, then Ca2+ ions bound to protein bands were analyzed by autoradiography. Purified OPs, and synthetic oligopeptides representing specific domains of the OP molecule were adsorbed on the membrane and processed as described above. Our results show that OPs synthesized by normal rat kidney cells, oncogenically transformed Rat-1 cells, OP purified from human milk, and non-phosphorylated OP secreted by 1 alpha, 25-dihydroxyvitamin D3-treated mouse epidermal JB6 cells all bind detectable levels of Ca2+ with specificity. We also show that a synthetic peptide representing the domain of OP which contains nine consecutive aspartic acid residues binds Ca2+ with specificity. It is probable, therefore, that a Ca(2+)-binding site resides in this region of the OP molecule. We conclude that Ca(2+)-binding is a general property of OP, irrespective of its molecular mass and origin, and the phosphate moieties of OP may not influence the conformation or accessibility of the Ca2+ affinity sites of the molecule.

Amino Acid Sequence↗
PubMed1993

CD4-independent infection of human peripheral blood dendritic cells with isolates of human immunodeficiency virus type 1.

Dendritic cells (DC) are members of a distinct family of bone marrow-derived leukocytes. DC are potent accessory cells for a number of T cell-mediated immune responses, including autologous and allogeneic mixed leukocyte reactions, and mitogen- and antigen-stimulated lymphocyte proliferation. In the present study, DC purified from human peripheral blood were inoculated with various strains (IIIB, SF2, WMJ1, SF162, 89.6 and clone HXB2) of human immunodeficiency virus type 1 (HIV-1) displaying different patterns of cellular tropism. Viral replication was demonstrated by detection of p24 antigen (Ag) intracellularly and in culture supernatants, and by Southern and Northern blot analyses for the presence of HIV DNA and RNA, respectively, within infected cells. Cell-free and cell-associated p24 Ag levels rose substantially when DC were inoculated with strains SF162, 89.6 and clone HXB2. In contrast, p24 Ag levels rose only marginally after inoculation of DC with strains IIIB, SF2 and WMJ1. Purified DC did not express detectable membrane CD4, although CD4 mRNA was detected by reverse transcriptase PCR. The presence of anti-CD4 monoclonal antibodies failed to block infection of DC by any of the HIV strains tested, suggesting the existence of a CD4-independent alternative pathway of viral entry. The possibility that DC serve as a reservoir for HIV-1 must be considered.

Adult↗
PubMed1992

Evaluation of sialic acid in lipoprotein fractions in fibrosarcoma bearing rats by 14C-glucose chase.

The changes in sialoglycoconjugates synthesis after administration of 14C-glucose to fibrosarcoma bearing rats were studied. After 1 hr treatment 14C-glucose tumor bearing rat synthesized hexosamine which contained more radioactivity when compared to sialic acid. On fractionation of lipoproteins, low density lipoproteins (LDL) contained more sialic acid. This was further confirmed by separating the lipoproteins, as more radioactivity incorporation was observed in the LDL fraction. It is noteworthy that inspite of the tumor, high density lipoproteins (HDL) did not show any change.

Animals↗
PubMed1989

Multi-infarct dementia: a computed tomographic study.

CT Scan of 30 patients with multi-infarct dementia (MID) were compared with age- and sex-matched controls. Infarcts were seen in 93% of MID cases and 10% of controls. A marked difference in the occurrence of white matter low attenuation was seen between the groups. All the parameters of cerebral atrophy studied showed a statistically significant correlation with the presence of dementia.

Brain↗
PubMed1987

Controlled study of alexithymic characteristics in patients with psychogenic pain disorder.

Alexithymic characteristics were examined in a sample of 30 patients fulfilling the DSM-III criteria for psychogenic pain disorder using an interviewer-rated scale (Beth Israel Hospital Psychosomatic Questionnaire), a self-rated scale (Toronto Alexithymia Scale) and a projective technique (Thematic Apperception Test). The findings were compared with a control group of healthy subjects matched on sociodemographic variables. Pain patients were found to be more alexithymic in contrast to the control group as evidenced by the interviewer-rated and self-rated scales. The correlations among the three measures were in the expected direction.

Adolescent↗
PubMed1987

A rapid prognostic electrophoretic assay for serum lipid conjugates in carcinoma uterine cervix and breast.

The levels of cholesterol and lipid associated sialic acid in sera of patients with carcinoma uterine cervix and breast cancer were determined using agarose electrophoresis and precipitation method. Elevated level of lipid associated sialic acid was found, that was specifically reflected only in LDL and VLDL fractions. In carcinoma uterine cervix patients, cholesterol in low density lipoprotein increased with corresponding decrease in high density lipoprotein and there was no change in total as well as VLDL cholesterol content. But breast cancer patients were found to have higher concentrations of both total and high density lipoprotein cholesterol. A good positive correlation was found between electrophoresis and precipitation methods for the lipoprotein analysis. We recommend electrophoretic method for rapid routine analysis.

Breast Neoplasms↗