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Biomedical subjects

U K Sharma

Publications and source records attributed to U K Sharma.

At least 19 recordsLinked to original sources
PubMed2005

First year donation patterns predict long-term commitment for first-time donors.

BACKGROUND AND OBJECTIVES: Converting first-time donors to become regular donors continues to be a challenge facing blood centres. We examined whether first-time donors with frequent return in the first 12 months were more likely to become regular donors. SUBJECTS AND METHODS: The donation histories of 179 409 community whole-blood donors, whose first-time donation in 1991 was negative on donor screening tests, were evaluated. Donors were categorized by the number of donations made in the 12 months after (and including) their first donation. The donor return pattern in the subsequent 6 years, and its association with first-year donation frequency and demographics, was evaluated by using logistic regression analysis. A 'regular donor' was defined as one who returned to donate in at least 4 of the 6 years of follow-up. RESULTS: First-year donation frequency was significantly correlated with long-term donor return (P < 0.0001). Among those giving 1, 2, 3, 4 and > or = 5 donations in the first year, 4%, 11%, 21%, 32% and 42%, respectively, became regular donors (P < 0.0001). Similar associations between donation pattern and donor return behaviour were observed after adjusting for demographic variables (P < 0.0001). CONCLUSIONS: Strategies aimed at encouraging current donors to donate more frequently during the first year may help to establish a regular donation behaviour.

Age Factors↗
PubMed2001

Incidence rates of viral infections among repeat donors:are frequent donors safer?

BACKGROUND: Incidence rates (IRs) for viral infections may vary with the frequency of donation among repeat, community, whole-blood (WB) donors, with IRs thought to be lower among donors with higher frequency of donation. STUDY DESIGN AND METHODS: IRs for HIV, HTLV, HCV, and HBV infection were stratified by frequency of donation among 868,403 repeat WB donors who gave approximately 4 million donations at five United States blood centers from 1991 through 96. All donors had given at least 2 donations during those years, with the first donation being nonreactive on confirmatory testing. Frequency of donation was measured in three ways: by the number of donations per year; at the time of donation, by the number of donations given within the preceding 2-year period; and by the number of donations given from 1991 through 1993. RESULTS: The IRs for HIV, HCV, and HBV infection did not appear to differ among donors with lower or higher numbers of donation per year. However, the IR for HTLV infection decreased as the number of donations per year increased (p = 0.0004). IRs for all viral markers remained stable, regardless of the number of donations given within the 2-year period before the donation. Although IRs for HIV, HTLV, and HCV infection did not vary by the number of donations given in 1991 through 1993, the IR for HBV infection appeared to be lower in donors who gave more donations in that period (p = 0.01). CONCLUSION: These findings do not provide evidence of a lower IR for transfusion-transmissible viral infections among repeat WB donors who give more frequently. Abbreviated screening histories for frequent repeat donors might not be advisable.

Adult↗
PubMed2001

Knowledge of HIV/AIDS transmission and screening in United States blood donors.

BACKGROUND: Increased knowledge of HIV transmission and behavioral and test screening may encourage high-risk blood donors to self-defer. STUDY DESIGN AND METHODS: Knowledge of HIV transmission and screening and the association with demographics, screening test reactivity, and unreported deferrable risks (UDRs) was assessed by a 1998 anonymous mail survey sent to 92,581 blood donors, of whom 57 percent responded. Groups were compared by using weighted chi-square tests and logistic regression analysis. RESULTS: Four percent of the donors thought that it was very likely or somewhat likely for a person to contract HIV from donating blood, and 20 percent perceived a similar risk from blood transfusion. Only 60 percent of the donors knew that the available screening tests may not detect a recent infection. Thirty-seven percent either did not know or felt it was acceptable to donate blood to obtain HIV testing. Those most likely to answer knowledge questions incorrectly were more likely to have a higher prevalence of test reactivity or UDRs and to be <or=25 years old, members of a minority, less educated, non-US-born, or first-time donors. CONCLUSION: Innovative ways to increase donor understanding of the implications of risk behaviors and the limitations of current screening procedures should be developed. They might prevent high-risk individuals from donating blood.

Acquired Immunodeficiency Syndrome↗
PubMed1999

Study of the interaction between bacteriophage T4 asiA and Escherichia coli sigma(70), using the yeast two-hybrid system: neutralization of asiA toxicity to E. coli cells by coexpression of a truncated sigma(70) fragment.

The interaction of T4 phage-encoded anti-sigma factor, asiA, and Escherichia coli sigma(70) was studied by using the yeast two-hybrid system. Truncation of sigma(70) to identify the minimum region involved in the interaction showed that the fragment containing amino acid residues proximal to the C terminus (residues 547 to 603) was sufficient for complexing to asiA. Studies also indicated that some of the truncated C-terminal fragments (residues 493 to 613) had higher affinity for asiA as judged by the increased beta-galactosidase activity. It is proposed that the observed higher affinity may be due to the unmasking of the binding region of asiA on the sigma protein. Advantage was taken of the increased affinity of truncated sigma(70) fragments to asiA in designing a coexpression system wherein the toxicity of asiA expression in E. coli could be neutralized and the complex of truncated sigma(70) and asiA could be expressed in large quantities and purified.

Bacterial Proteins↗
PubMed1998

A novel factor produced by placental cells with activity against HIV-1.

The factors controlling the dynamics of HIV-1 transmission from mother to infant are not clearly known. Previous studies have suggested the existence of maternal and placental protective mechanisms that inhibit viral replication in utero. Preliminary studies from our laboratory revealed that supernatant from placental stromal cells protected HIV-1-infected PBMC from virus-induced apoptosis and suppressed virus production. We have attempted to characterize the antiviral activity of this placental factor (PF) and delineate the stages of HIV-1 replication affected. This activity was not due to the presence of any known cytokine reported to have anti-HIV effect. Direct exposure to PF had no suppressive effect on the infectivity of cell-free HIV-1, and envelope-mediated membrane fusion appeared to be unaffected. Western blot analysis of HIV-1 from infected PBMC treated with PF revealed that expression of all viral proteins was reduced proportionately, both intracellularly and in released virions. However, exposure of HIV-1-infected cells to PF resulted in production of virions with 10-100-fold-reduced infectivity. PF-treated virions contained two- to threefold reduced ratios of cyclophilin A:Gag protein as compared with untreated virus. Reduced cyclophilin A content resulting in decreased binding of cyclophilin A to Gag could account, in part, for the observed reduction in infectivity. Our results suggest that placental cells produce an antiviral factor that protects the fetus during gestation and may have therapeutic potential.

Anti-HIV Agents↗
PubMed1997

Failure of insulin-like growth factor type I to suppress HIV type 1 in adult or umbilical cord mononuclear blood cells.

Insulin-like growth factor type I (IGF-I) has been used as a treatment for cachexia in adults with AIDS and has been reported to show inhibitory activity against HIV-1IIIB in cord blood mononuclear cells (CBMCs) in vitro at low-concentration (1%) fetal bovine serum (FCS). We evaluated the effect of IGF-I on MN, IIIB, and BaL strains, as well as on a patient isolate of HIV-1 in CBMCs and adult peripheral blood mononuclear cells (PBMCs). IGF-I failed to show any inhibitory effect on HIV replication in CBMCs or adult PBMCs under various culture conditions. In contrast to an earlier report of an antiviral effect, IGF-I augmented HIV-1 replication in PHA-stimulated PBMCs maintained in a low concentration of FCS.

Adult↗
PubMed1997

Chemokine-independent in vitro resistance to human immunodeficiency virus (HIV-1) correlating with low viremia in long-term and recently infected HIV-1-positive persons.

Chemokines have been implicated as protective factors against human immunodeficiency virus (HIV) infection, competing for binding to receptors that also function as coreceptors for HIV. In this study of HIV-positive donors, peripheral blood mononuclear cell (PBMC) culture resistance to endogenous and exogenous HIV correlated with low plasma viremia and high in vitro RANTES production. However, resistant cells were not rendered susceptible by neutralization of C-C chemokines, and addition of C-C chemokines did not consistently suppress endogenous virus or exogenous HIV-1MN. In contrast, CD8 T cell depletion markedly decreased the frequency of resistant cultures without reducing C-C chemokine production. Among newly infected persons, half exhibited phenotype switching from preinfection susceptibility to postinfection resistance, suggesting that genetically predetermined constitutive cytokine production or allelic receptor expression are not generally responsible for in vitro resistance and nonprogression.

Acquired Immunodeficiency Syndrome↗
PubMed1997

Diagnosis of human immunodeficiency virus infection using citrated whole blood.

Standard isolation of human immunodeficiency virus type 1 (HIV-1) from peripheral blood mononuclear cells (PBMC) requires 5 to 20 ml of blood, and the centrifugal separation of PBMC is expensive and time-consuming. Whole-blood coculture techniques use small sample volumes, do not require centrifugation, and allow measurement of the total viral burden in peripheral circulation. We compared the results of citrated whole-blood coculture with those obtained by the standard AIDS Clinical Trials Group PBMC semiquantitative culture method and reverse transcription-PCR quantitation of plasma HIV-1 RNA levels. PBMC cocultures were also set up with added erythrocytes (RBCs) to determine if the presence of RBCs affects the replication of HIV-1 in vitro. The mean number of cells required for a p24-positive PBMC coculture was approximately seven times greater than that required for a positive citrated whole-blood coculture (P < 0.01). At volumes of 100, 50, and 25 microl, the sensitivities of the whole-blood coculture were 94.5, 93.6, and 87.3%, respectively. The PBMC culture in the presence of added RBCs was more sensitive than PBMC coculture alone. The citrated whole-blood coculture was simple to perform, produced a reliable diagnosis of HIV infection in adult volunteers, was more sensitive than previously reported techniques even in half the culture time, and showed less variability than the PBMC coculture. Citrated whole-blood coculture may be a useful and efficient tool for diagnosing infection with HIV-1.

Adult↗
PubMed1995

Adherence of human immunodeficiency virus-infected lymphocytes to fetal placental cells: a model of maternal --> fetal transmission.

The precise timing and mechanism of in utero human immunodeficiency virus (HIV) infection are unknown, but transplacental transmission is likely. Term placentas from HIV+ pregnancies contain only rare HIV-infected cells whose origins and phenotypes remain controversial, and no correlation has been found between the presence of HIV in term placentas and transmission to offspring. Reports of trophoblast infectibility have not been reproducible and do not address the question of infection in the placental stroma, the cells in direct contact with fetal circulation. We report that primary cultures of fetal placental chorionic villus stromal cells, while not infectable in vitro, do support lethally irradiated HIV-infected peripheral blood mononuclear cells (PBMCs) in a form that permits rescue of HIV by activated PBMCs weeks later. Infected PBMCs adhere and become intimately associated with placental cells by a mechanism that is LFA-1 and CD4 independent but can be blocked by antibodies or soluble CD4 binding to cell surface-expressed HIV envelope. The ability to sustain infected irradiated cells was not shared by several trophoblast, fibroblast, or epithelial cell lines. This model has several features that are compatible with in utero transmission and allow testing of various agents proposed as interventions to block maternal-->fetal transmission. Placental stromal cells appear to inhibit apoptosis of HIV-infected, irradiated lymphocytes.

Antibodies, Monoclonal↗
PubMed1995

Expression and characterization of the ponA (ORF I) gene of Haemophilus influenzae: functional complementation in a heterologous system.

The coding sequence of the Haemophilus influenzae ORF I gene was amplified by PCR and cloned into different Escherichia coli expression vectors. The ORF I-encoded protein was approximately 90 kDa and bound 3H-benzyl-penicillin and 125I-cephradine. This high-molecular-weight penicillin-binding protein (PBP) was also shown to possess transglycosylase activity, indicating that the ORF I product is a bifunctional PBP. The ORF I protein was capable of maintaining the viability of E. coli delta ponA ponB::spcr cells in transcomplementation experiments, establishing the functional relevance of the significant amino acid homology seen between E. coli PBP 1A and 1B and the H. influenzae ORF I product. In addition, the physiological functioning of the H. influenzae ORF I (PBP 1A) product in a heterologous species established the ability of the enzyme not only to recognize the E. coli substrate but also to interact with heterologous cell division proteins. The affinity of the ORF I product for 3H-benzylpenicillin and 125I-cephradine, the MIC of beta-lactams for E. coli delta ponA ponB::spcr expressing the ORF I gene, and the amino acid alignment of the PBP 1 family of high-molecular-weight PBPs group the ORF I protein into the PBP 1A family of high-molecular-weight PBPs.

Bacterial Proteins↗
PubMed1995

A case of non-Hodgkin's lymphoma presenting with polyuria and acute renal insufficiency.

A case of non-Hodgkin's lymphoma presenting with polyuria, enlarged kidneys, and renal insufficiency is reported. The diagnosis was made by percutaneous needle biopsy of the kidney. Renal failure reversed and the kidneys regressed in size on exhibition of the first cycle of chemotherapy. The rarity of polyuria at presentation, the role of renal biopsy in the diagnosis, and the response of renal failure to specific chemotherapy are discussed.

Acute Kidney Injury↗
PubMed1994

De novo diabetic glomerulosclerosis in a renal allograft recipient.

Posttransplant diabetes mellitus is a well-recognized complication of renal transplantation. Although such patients are at risk for the development of de novo diabetic glomerulosclerosis with increasing graft survival, this has rarely been reported. We describe a patient with posttransplant diabetes mellitus who developed end-stage renal failure due to diabetic glomerulosclerosis 12 years after renal transplantation.

Diabetic Nephropathies↗
PubMed1993

Deletion analysis of the essentiality of penicillin-binding proteins 1A, 2B and 2X of Streptococcus pneumoniae.

An internal fragment from each of the penicillin-binding protein (PBP) 1A, 2B and 2X genes of Streptococcus pneumoniae, which included the region encoding the active-site serine residue, was replaced by a fragment encoding spectinomycin resistance. The resulting constructs were tested for their ability to transform S. pneumoniae strain R6 to spectinomycin resistance. Spectinomycin-resistant transformants could not be obtained using either the inactivated PBP 2X or 2B genes, suggesting that deletion of either of these genes was a lethal event, but they were readily obtained using the inactivated PBP 1A gene. Analysis using the polymerase chain reaction confirmed that the latter transformants had replaced their chromosomal copy of the PBP 1A gene with the inactivated copy of the gene. Deletion of the PBP 1A gene was therefore tolerated under laboratory conditions and appeared to have little effect on growth or susceptibility to benzylpenicillin.

Bacterial Proteins↗
PubMed1991

Identification of carbohydrate structures as receptors for localised adherent enteropathogenic Escherichia coli.

Enteropathogenic Escherichia coli strains of diffused adherent (DA) and localised adherent (LA) phenotypes were tested for their ability to bind to glycolipids. DA strains did not bind to the glycolipids tested, while LA strains bound to asialo GM1, asialo GM2, globoside and lacto-N-neotetraose in decreasing order of avidity. The minimum common sequence among the four glycolipids could be delineated as GalNac beta 1-4 Gal as the binding epitope with GalNac beta 1-3 Gal and GlcNac beta 1-3 Gal serving as relatively weaker binders. The binding was not inhibited by a variety of free oligosaccharides or by the neoglycoproteins tested. Adhesion-negative mutants of an enteropathogenic LA strain showed a markedly reduced binding to asialo GM1 indicating that the recognition of GalNac beta 1-4 Gal was correlated with the ability to adhere to HeLa cells. Thus recognition and binding to glycolipids could play an important role in colonisation through adherence to intestinal surfaces.

Binding Sites↗