PubMed Health⌕ Search

Biomedical subjects

S Ray

Publications and source records attributed to S Ray.

At least 163 records · Page 9Linked to original sources
PubMed1996

HIV seroincidence and correlates of seroconversion in a cohort of male factory workers in Harare, Zimbabwe.

OBJECTIVES: Given that health promotion messages on transmission of HIV and other sexually transmitted diseases (STD) have been widely publicized in Zimbabwe and elsewhere in the late 1980s, it is vital to analyse which risk events still expose individuals to infection. A cohort was established with the objectives of estimating HIV seroincidence, behavioural and biological determinants of infection, and ultimately, evaluating the impact of AIDS prevention interventions in the workplace. METHODS: HIV seroincidence was estimated in a prospectively followed cohort of male factory workers recruited in Harare, Zimbabwe during the period prior to a workplace AIDS prevention intervention. Correlates of HIV seroconversion were identified using Cox regression analysis. RESULTS: There were 51 seroconversions among 1607 HIV-negative participants following 1738 person-years (PY) of observation [seroincidence, 2.93 per 100 PY; 95% confidence interval (CI), 2.18-3.86]. The prevalence of HIV in the cohort was 19.1%. HIV seroincidence was significantly increased among men who were younger [hazard ratio (HR) per year, 0.96; 95% CI, 0.93-0.99], were single (HR, 3.29; 95% CI, 1.56-6.96), were married but resided separately from their wives (HR, 2.18; 95% CI, 0.99-4.80), reported having any STD (HR, 3.00; 95% CI, 1.53-5.86), reported having a genital ulcer (HR, 4.87; 95% CI, 2.18-10.91), and reported paying for sex (HR, 2.01; 95% CI, 1.06-3.77). Seroincidence also increased with the number of sex partners reported in the year preceding enrolment (HR per partner, 1.10; 95% CI, 1.01-1.21). In multiple Cox regression analysis, three independent associations with HIV seroconversion were reporting a genital ulcer (adjusted HR, 3.55; 95% CI, 1.52-8.29), number of sex partners (adjusted HR, 1.10; 95% CI, 1.01-1.21), and being married but residing separately from one's wife (adjusted HR, 2.21; 95% CI, 1.00-4.89). CONCLUSIONS: Innovative and sustained workplace-based interventions are needed to address the high risk of HIV infection in this economically productive population. The predictors of HIV seroconversion described in this study underscore the need for public health efforts to simultaneously address the biological, socioeconomic and behavioural factors that continue to place individuals at risk of HIV in general populations of Africa.

Acquired Immunodeficiency Syndrome↗
PubMed1996

Peri-operative hypoxaemia in children undergoing application of a plaster jacket for scoliosis.

Twenty children (six female), median age 24 months (range 12-156) who presented for application of a plaster jacket for scoliosis were studied pre-operatively with pulse oximetry overnight and on the first postoperative night. Pre-operatively the median (range) arterial oxygen saturation was 97 (95-98)%, although eight children had short episodes of desaturation to < 90%. Postoperatively the median saturation was unchanged, and nine children had short episodes of desaturation. Neither the presence of episodes of desaturation pre-operatively, nor the median or lowest saturation recorded were predictors of postoperative median saturation or the presence of episodes of desaturation. Despite the presumed reduction in chest wall compliance, the application of a plaster jacket for scoliosis in these young children was not associated with a significant change in their oxygenation.

Adolescent↗
PubMed1996

A review of 560 Hickman catheter insertions.

Indwelling, cuffed, tunnelled, central venous (Hickman) catheters are increasingly being used for venous access and the administration of chemotherapy for oncological patients. This paper reviews the technical problems associated with the percutaneous insertion of these catheters and the complications arising from their use. Five hundred and sixty catheters were inserted; 31.3% had complications at insertion, most commonly precipitation of an arrhythmia (13.9%). Arterial puncture occurred in 3.8% and pneumothorax in 1.6%. Catheters remained in place for a median period of 91 days. Forty percent of catheters were removed electively on completion of treatment; 30.2% required removal because of complications, which included sepsis, migration, thrombosis and blockage. Twenty percent of patients died with their catheter in place, 8.5% were still in situ and 1.6% were removed because of patient non compliance. Sepsis remains the commonest, long term complication, with staphylococcus epidermidis being the organism isolated most frequently. There were no catheter-related deaths.

Adolescent↗
PubMed1996

Differential interaction of temperature-sensitive simian virus 40 T antigens with tumor suppressors pRb and p53.

Previous studies have shown that simian virus 40 large T antigen transforms cells by binding and inactivating suppressors of cell cycle progression and tumor formation. Here, we characterize the interactions of five temperature-sensitive T antigens with the tumor suppressor proteins pRb and p53. All five mutant T antigens bind pRb at the nonpermissive temperature with efficiencies similar to that of wild-type T antigen. A single transformation-competent mutant, with a substitution of amino acid 186, binds p53 at the nonpermissive temperature. Four transformation-defective mutants, with a substitution at T antigen position 357, 422, 427, or 438, are temperature sensitive for the binding and inactivation of p53. Our findings provide a basis for understanding the behavior of cells transformed by temperature-sensitive T antigens.

Animals↗
PubMed1996

SHORT INTEGUMENT (SIN1), a gene required for ovule development in Arabidopsis, also controls flowering time.

The short integument (sin1) mutation causes a female-specific infertility, and a defect in the control of time to flowering in Arabidopsis. Female sterility of Sin- plants is due to abnormal ovule integument development and aberrant differentiation of the megagametophyte in a subset of ovules. An additional defect of sin1 mutants is the production of an increased number of vegetative leaf and inflorescence primordia leading to delayed flowering. The delayed flowering phenotype of sin1-1 is not due to a defect in the perception of day length periodicity or in gibberellic acid metabolism. Phenotypes of double mutant combinations of sin1 with terminalflower (tfl1) indicate that SIN1 activity is required for precocious floral induction typical in a tfl1 mutant. Unexpectedly, sin1-1 tfl1-1 plants do not make pollen, thus revealing a novel role for TFL1 in the anther. Early flowers of sin1-1 ap1-1 double mutants are transformed to long inflorescence-like shoots. A genetic model for the role of SIN1 in flowering time control is proposed.

Adaptor Protein Complex 1↗
PubMed1996

Isolation of high-molecular-length DNA from human skin.

An agarose plug method for isolating high-molecular-length DNA from mammalian tissues has been developed, including from those that are difficult, such as skin. It gives high yields of DNA that contain a minimum of single-strand breaks and is readily digested by restriction and other nucleases. The method requires only simple equipment and is readily adaptable to field or clinical studies.

Adult↗
PubMed1996

Intracellular metabolism of Ara-C and resulting DNA fragmentation and apoptosis of human AML HL-60 cells possessing disparate levels of Bcl-2 protein.

We examined the effects of high intracellular levels of Bcl-2 on the metabolism and DNA incorporation of high-dose Ara-C (HIDAC) as well as on Ara-C-induced DNA strand breaks and apoptosis of human AML HL-60 cells. HL-60/Bcl-2 and HL-60/neo cells were created by retrovirally transfecting the human AML HL-60 cells with the pZip-bcl-2 and pZip-neo plasmids, respectively. As compared to HL-60/neo, HL-60/Bcl-2 cells contained significantly higher (approximately 10-fold) p26Bcl-2, but equivalent levels of Bax and undetectable levels of Bcl-xL. HIDAC (10 or 100 microM for 4 h) produced the kilobase size and internucleosomal DNA fragmentation associated with apoptosis in HL-60/neo but not in HL-60/Bcl-2 cells. Significantly greater loss of survival (by MTT assay) and flowcytometric and morphologically recognizable apoptosis were observed in HL-60/neo cells. HIDAC did not affect Bcl-2 levels in either cell type. The intracellular accumulation of Ara-CTP relative to dCTP, Ara-C DNA incorporation and Ara-C-induced early DNA damage in the form of strand breaks (detected by alkaline elution assay) were not significantly different between HL-60/Bcl-2 and HL-60/neo cells. In addition, HIDAC treatment caused similar DNA synthesis inhibition in the two cell types. These results indicate that high intracellular levels of Bcl-2 operate distally to inhibit the final apototic cell death pathway by preventing the conversion of HIDAC-induced early DNA damage into lethal DNA fragmentation associated with apoptosis.

Antimetabolites, Antineoplastic↗
PubMed1996

Enforced expression of Bcl-XS induces differentiation and sensitizes chronic myelogenous leukemia-blast crisis K562 cells to 1-beta-D-arabinofuranosylcytosine-mediated differentiation and apoptosis.

Human chronic myelogenous leukemia-blast crisis K562 cells have been demonstrated to be relatively resistant to antileukemic drug-induced apoptosis. This has been attributed to the activity of p210bcr-abl tyrosine kinase present in the K562 cells, which is known to suppress drug-induced apoptosis. Recently, K562 cells have been shown to express the antiapoptosis Bcl-xL but not Bcl-2 proteins. To investigate the contribution of Bcl-xL toward resistance to drug-induced apoptosis, we created K562/Bcl-xS and K562/neo cells by electroporating the expression plasmids pSFFVneo-Bcl-xS and pSFFVneo, containing the bcl-xS and neomycin resistance genes, respectively, into K562 cells. K562/Bcl-xS but not K562/neo cells expressed the bcl-xS mRNA and p19Bcl-xS protein. In contrast, both cell types expressed equivalent levels of Bcl-xL, Bax, Bcl-2, Myc, retinoblastoma, p21cbor-abl, and p145abl proteins. A significant increase in the hemoglobin levels was observed in the K562/Bcl-xS compared with the K562/neo cells (P < 0.05). In addition, K562/Bcl-xS cells were significantly more sensitive than K562/neo cells to undergoing erythroid differentiation induced by low-dose 1-beta-D-arabinofuranosylcytosine (ara-C) and hexamethyl bisacetamide (P < 0.05), but not by all-trans-retinoic acid. Low-dose ara-C- or hexamethyl bisacetamide-induced differentiation was not associated with apoptosis of K562/Bcl-xS or K562/neo cells. Low-dose ara-C-induced erythroid differentiation was accompanied by conversion of the retinoblastoma protein to predominantly its underphosphorylated isoform as well as by down-regulation of Myc levels in K562/Bcl-xS and K562/neo cells. Importantly, exposure to high-dose ara-C (HIDAC; 100 microM ara-C for 4 h) caused internucleosomal DNA fragmentation and the morphological features of apoptosis in K562/Bcl-xS cells. These effects were modestly enhanced by cotreatment with HIDAC plus herbimycin A. In contrast, K562/neo cells were completely resistant to HIDAC- and herbimycin A-induced apoptosis. These results indicate that the expression of Bcl-xS induces erythroid differentiation and partially sensitizes chronic myelogenous leukemia-blast crisis-derived K562 cells to ara-C-induced differentiation and apoptosis.

Antimetabolites, Antineoplastic↗
PubMed1995

Cross-reactive antibodies have both protective and pathogenic potential.

We report the characteristics of five IgM anti-phosphorylcholine (PC) Abs derived from nonautoimmune BALB/c mice. These Abs were chosen on the basis of their unique ability to cross-react with dsDNA. Three Abs protect mice from a lethal pneumococcal infection, and all five Abs deposit in glomeruli and cause renal dysfunction. Analysis of V region gene usage shows that none of the Abs is encoded by the V1 gene segment used to encode the dominant T15+ anti-PC response typically expressed in serum of PC-immunized BALB/c mice. The demonstration of the existence of noncanonical protective anti-PC Abs that also display pathogenic autoreactivity suggests that idiotypically restricted responses may serve to prevent the expression of Abs that react with both foreign and self Ags and so help maintain self-tolerance.

Amino Acid Sequence↗
PubMed1995

Two tryptophans at the active site of UDP-glucose 4-epimerase from Kluyveromyces fragilis.

Efficient fluorescence energy transfer from aromatic residues to the pyridine moiety of the bound coenzyme (NAD) of UDP-glucose 4-epimerase from Kluyveromyces fragilis had been reported earlier (Mukherji, S., and Bhaduri, A. (1992) J. Biol. Chem. 267, 11709-11713). We have employed N-bromosuccinimide (NBS) to identify tryptophan as the exclusive aromatic donor in the energy transfer. The characteristic UV absorption spectrum associated with Trp oxidation is observed during NBS modification of two of the four Trp residues of native epimerase along with concomitant inactivation of the enzyme. Excellent correlation between the observed inactivation and abolition of fluorescence energy transfer to coenzyme from Trp in epimerase upon treatment with NBS implicates the involvement of the same two tryptophans in both catalytic activity and fluorescence energy transfer. SDS-polyacrylamide gel electrophoresis and fluorescence data preclude gross structural/conformational changes in epimerase due to NBS oxidation. The susceptible tryptophans do not reside at the substrate binding site as substrates and UMP fail to protect against NBS modification. However, failure of sodium borohydride to reduce the bound NAD in the NBS-inactivated epimerase suggests that the reactive tryptophans are close to the coenzyme. Tryptophan fluorescence lifetime values of 1.9 and 3.9 ns for the native and 3.5 ns for the NBS-modified epimerase, complemented by a linear Stern-Volmer plot (effective Stern-Volmer constant = 2.85 M-1) of acrylamide quenching, suggest that the two key tryptophans are buried close to an intrinsic quencher, presumably NAD.

Binding Sites↗
PubMed1995

The structure of unliganded reverse transcriptase from the human immunodeficiency virus type 1.

The crystal structure of the reverse transcriptase (RT) from the type 1 human immunodeficiency virus has been determined at 3.2-A resolution. Comparison with complexes between RT and the polymerase inhibitor Nevirapine [Kohlstaedt, L.A., Wang, J., Friedman, J.M., Rice, P.A. & Steitz, T.A. (1992) Science 256, 1783-1790] and between RT and an oligonucleotide [Jacobo-Molina, A., Ding, J., Nanni, R., Clark, A. D., Lu, X., Tantillo, C., Williams, R. L., Kamer, G., Ferris, A. L., Clark, P., Hizi, A., Hughes, S. H. & Arnold, E. (1993) Proc. Natl. Acad. Sci. USA 90, 6320-6324] reveals changes associated with ligand binding. The enzyme is a heterodimer (p66/p51), with domains labeled "fingers," "thumb," "palm," and "connection" in both subunits, and a ribonuclease H domain in the larger subunit only. The most striking difference between RT and both complex structures is the change in orientation of the p66 thumb (approximately 33 degrees rotation). Smaller shifts relative to the core of the molecule were also found in other domains, including the p66 fingers and palm, which contain the polymerase active site. Within the polymerase catalytic region itself, there are no rearrangements between RT and the RT/DNA complex. In RT/Nevirapine, the drug binds in the p66 palm near the polymerase active site, a region that is well-packed hydrophobic core in the unliganded enzyme. Room for the drug is provided by movement of a small beta-sheet within the palm domain of the Nevirapine complex. The rearrangement within the palm and thumb, as well as domain shifts relative to the enzyme core, may prevent correct placement of the oligonucleotide substrate when the drug is bound.

Binding Sites↗
PubMed1995

Glyoxalase III from Escherichia coli: a single novel enzyme for the conversion of methylglyoxal into D-lactate without reduced glutathione.

A single novel enzyme, glyoxalase III, which catalyses the conversion of methylglyoxal into D-lactate without involvement of GSH, has been detected in and purified from Escherichia coli. Of several carbonyl compounds tested, only the alpha-ketoaldehydes methylglyoxal and phenylglyoxal were found to be substrates for this enzyme. Glyoxalase III is active over a wide range of pH with no sharp pH optimum. In its native form it has an M(r) of 82000 +/- 2000, and it is composed of two subunits of equal M(r). Glutathione analogues, which are inhibitors of glyoxalase I, do not inhibit glyoxalase III. Glyoxalase III is found to be sensitive to thiol-blocking reagents. The p-hydroxymercuribenzoate-inactivated enzyme could be almost completely re-activated by dithiothreitol and other thiol-group-containing compounds, indicating the possible involvement of thiol group(s) at or near the active site of the enzyme.

Aldehyde Oxidoreductases↗
PubMed1995

Kinesin does not support the motility of zinc-macrotubes.

Moving along a microtubule, kinesin follows a course parallel to the protofilaments; but it is not known whether kinesin binds exclusively on a single protofilament. The presence of zinc during tubulin polymerization induces sheets where neighboring protofilaments are antiparallel. If kinesin could support the motility of these zinc-sheets, then the binding site for a kinesin molecule would be limited to a single protofilament. Kamimura and Mandelkow [1992: J. Cell Biol. 118:865-75] reported that kinesin moves along zinc-sheets. We found that zinc-sheets grown under their conditions often had a microtubule-like structure along one edge. We confirmed the possibility that the motility observed by Kamimura and Mandelkow [1992: J. Cell Biol. 118:865-75] is attributed to the microtubule-like structure rather than the zinc-sheet. To resolve the question of whether kinesin can recognize an antiparallel protofilament lattice, we investigated the kinesin-mediated motility of zinc-macrotubes. At higher free zinc concentrations, zinc-sheets roll up as macrotubes, free of edges. In the presence of 10 microM taxol and 100 nM free Zn2+ at pH 6.8, the samples were shown by electron microscopy to contain only macrotubes. Under these buffer conditions, kinesin could bind strongly to axonemal doublets in the presence of AMP-PNP, and generate motility in the presence of ATP, but kinesin did not bind to nor move the macrotubes. This shows that kinesin cannot bind efficiently to nor move on the anti-parallel lattice; it is possible (though not necessary) that the groove between two parallel protofilaments is required for kinesin's motility.

Animals↗
PubMed1995

Metabolism of 3H-1 alpha,25-dihydroxyvitamin D3 in cultured human keratinocytes.

In the present investigation we studied the metabolism of 1 alpha,25-dihydroxy-[1 beta-3H]vitamin D3 (3H-1,25(OH)2D3) in culture-grown human keratinocytes (CHK). Our results showed that the cellular uptake of 3H-1,25(OH)2D3, upon incubation with CHK, occurred very rapidly; and it paralleled a decrease in the concentration of 3H-1,25(OH)2D3 in the medium. The amount of 3H-calcitroic acid, on the other hand, increased slowly in the medium, while the concentration of 3H-calcitroic acid in the cell remained undetectable during the whole period of incubation. When the cells were preincubated with 1,25(OH)2D3 (10(-8)M), conversion of 3H-1,25(OH)2D3 to 3H-calcitroic acid increased almost twofold, indicating that 1,25(OH)2D3 catalyzed its own catabolism.

Calcitriol↗
PubMed1995

Comparative in vitro cytotoxic effects of taxol and its major human metabolite 6 alpha-hydroxytaxol.

Taxol is metabolized by the liver microsomal cytochrome P450 enzyme system into its principal metabolite 6 alpha-hydroxytaxol (6HT). In the present in vitro studies 6HT was compared to taxol with respect to its effects on tubulin depolymerization, mitotic arrest, clonogenic survival and apoptosis in HL-60 cells. 6HT was generated by incubating taxol with human liver microsomes in a NADPH-generating system. HL-60 cells were incubated for 24 h with either taxol or 6HT, washed and placed in drug-free suspension or cultured for colony growth in agarose. For the suspension and colony culture growth of the cells, the IC50 concentrations of 6HT were 500 +/- 46 and 350 +/- 37 nM, while those of taxol were 3.2 +/- 0.2 and 2.8 +/- 0.5 nM, respectively. Immediately after a 24-h exposure of HL-60 cells to 50 nM taxol, electrophoresis of genomic DNA from HL-60 cells revealed an internucleosomal DNA fragmentation 'ladder'. In addition, 39% of the cells were arrested in mitosis and 16% showed the morphologic features of apoptosis. In contrast, an identical treatment with 6HT resulted in the mitotic arrest of only 2.8% of the cells, with 4.0% displaying apoptosis (P < 0.01); internucleosomal DNA fragmentation was not observed. 6HT was also significantly less effective than taxol in inhibiting the temperature-induced depolymerization of microtubules in a cell-free system. However, at equipotent concentrations, the effect of 6HT on tubulin depolymerization, mitotic arrest or apoptosis was similar to that of taxol. In addition, at concentrations of taxol or 6HT at or below their IC50, there was little tubulin depolymerization, mitotic arrest or apoptosis. The results presented here show that the biotransformation of taxol to 6HT substantially detoxifies taxol.

Apoptosis↗