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Biomedical subjects

E Montalvo

Publications and source records attributed to E Montalvo.

9 recordsLinked to original sources
PubMed2001

Seroprevalence of Kaposi's sarcoma-associated herpesvirus infection among blood donors from Texas.

PURPOSE: Kaposi's sarcoma-associated herpesvirus (KSHV), a gammaherpesvirus recently discovered among AIDS patients with Kaposi's sarcoma, is a potential candidate for screening in blood and plasma donors. While a number of studies have assessed KSHV infection among U.S. blood donors, larger-scale population-based studies would be necessary to develop more refined estimates of the magnitude and variation of KSHV infection across different geographic regions of the U.S. blood supply. The goal of the present study, therefore, was to determine the seroprevalence of KSHV infection and to assess demographic correlates of KSHV infection among south Texas blood donors. METHODS: KSHV infection was determined using specific serologic assays that measure antibodies to KSHV latent and lytic antigens. RESULTS: The overall seroprevalence of KSHV in Texas blood donors (15.0%) is substantially higher than previously reported among blood donor and general population samples in the United States. This high rate of KSHV infection persisted across most of the sociodemographic subgroups under study but was particularly elevated among participants with less than a high school education. The infection rate also increased linearly with age. CONCLUSIONS: The elevated infection rate reported in the present study suggests that screening methods to detect KSHV infection in blood donors should be considered. In view of the etiologic role of KSHV for several malignancies, it would be important for future studies to directly assess the risk of KSHV transmission via blood transfusion.

Adolescent↗
PubMed2000

OAZ uses distinct DNA- and protein-binding zinc fingers in separate BMP-Smad and Olf signaling pathways.

We have identified the 30-zinc finger protein OAZ as a DNA-binding factor that associates with Smads in response to BMP2, forming a complex that transcriptionally activates the homeobox regulator of Xenopus mesoderm and neural development, Xvent-2. OAZ contains a BMP signaling module formed by two clusters of fingers that bind Smads and the Xvent-2 BMP response element, respectively. Previously implicated as a transcriptional partner of Olf-1/EBF in olfactory epithelium and lymphocyte development in the rat, OAZ fulfills this role through clusters of fingers that are separate from the BMP signaling module. The mutually exclusive use of OAZ by the BMP-Smad and Olf pathways illustrates the dual role of a multi-zinc finger protein in signal transduction during development.

Amino Acid Sequence↗
PubMed1997

Infectivity of hepatic allografts with antibodies to hepatitis B virus.

BACKGROUND: Since suitable recipients for hepatic allografts from donors with antibodies to hepatitis B virus (HBV) have not been determined, a review of our 7-year experience with donors positive for hepatitis B surface antibody (anti-HBs), hepatitis B core antibody (anti-HBc), or both was undertaken. METHODS: Recipients of hepatic allografts from donors with antibodies to HBV were identified by a retrospective review of procurement records and screened for HBV infection. RESULTS: From January 1, 1990, to January 1, 1997, 2578 liver transplants were performed and 140 (5.4%) recipients received an allograft from a donor with antibodies to HBV. Twenty-five of 48 recipients of a hepatic allograft from a donor positive only for anti-HBs were screened and none developed HBV infection. Twenty-five of 41 naive recipients of a hepatic allograft from an anti-HBc positive donor were screened and 18/25 (72%) developed HBV infection. Four of these 18 naive recipients with HBV infection received an allograft from a donor positive for both anti-HBc and anti-HBs. Seven of 13 anti-HBs-positive recipients of an allograft from an anti-HBc-positive donor were screened and none developed HBV infection. Fifteen of 16 recipients positive only for anti-HBc who received a hepatic allograft from an anti-HBc-positive donor were screened and 2/15 (13%) developed HBV infection. CONCLUSIONS: Hepatic allografts from donors positive only for anti-HBs do not transmit HBV infection. Hepatic allografts from anti-HBc-positive donors frequently transmit HBV infection to naive recipients regardless of the donor anti-HBs status, and antiviral prophylaxis may be indicated. Anti-HBs-positive recipients appear resistant to HBV infection after orthotopic liver transplantation with an allograft from an anti-HBc-positive donor. Recipients positive only for anti-HBc infrequently develop HBV infection when transplanted with an allograft from an anti-HBc-positive donor; however, HBV prophylaxis may be justified.

Hepatitis B↗
PubMed1997

Differential interaction of the cyclin-dependent kinase (Cdk) inhibitor p27Kip1 with cyclin A-Cdk2 and cyclin D2-Cdk4.

Although p27(Kip1) has been considered a general inhibitor of G1 and S phase cyclin-dependent kinases, we report that the interaction of p27 with two such kinases, cyclin A-Cdk2 and cyclin D-Cdk4, is different. In Mv1Lu cells containing a p27 inducible system, a 6-fold increase over the basal p27 level completely inhibited Cdk2 and cell cycle progression. In contrast, the same or a larger increase in p27 levels did not inhibit Cdk4 or its homologue Cdk6, despite extensive binding to these kinases. A p27-cyclin A-Cdk2 complex formed in vitro was essentially inactive, whereas a p27-cyclin D2-Cdk4 complex was active as a retinoblastoma kinase and served as a substrate for the Cdk-activating kinase Cak. High concentrations of p27 inhibited cyclin D2-Cdk4, apparently by conversion of active complexes into inactive ones by the binding of additional p27 molecules. In contrast to their differential interaction, cyclin A-Cdk2 and cyclin D2-Cdk4 were similarly inhibited by bound p21(Cip1/Waf1). Roles of cyclin A-Cdk2 as a p27 target and cyclin D2-Cdk4 as a p27 reservoir may result from the differential ability of bound p27 to inhibit the kinase subunit in these complexes.

Animals↗
PubMed1996

Activation of signalling by the activin receptor complex.

Activin exerts its effects by simultaneously binding to two types of p rotein serine/threonine kinase receptors, each type existing in various isoforms. Using the ActR-IB and ActR-IIB receptor isoforms, we have investigated the mechanism of activin receptor activation. ActR-IIB are phosphoproteins with demonstrable affinity for each other. However, activin addition strongly promotes an interaction between these two proteins. Activin binds directly to ActR-IIB, and this complex associates with ActR-IB, which does not bind ligand on its own. In the resulting complex, ActR-IB becomes hyperphosphorylated, and this requires the kinase activity of ActR-IIB. Mutation of conserved serines and threonines in the GS domain, a region just upstream of the kinase domain in ActR-IB, abrogates both phosphorylation and signal propagation, suggesting that this domain contains phosphorylation sites required for signalling. ActR-IB activation can be mimicked by mutation of Thr-206 to aspartic acid, which yields a construct, ActR-IB(T206D), that signals in the absence of ligand. Furthermore, the signalling activity of this mutant construct is undisturbed by overexpression of a dominant negative kinase-defective ActR-IIB construct, indicating that ActR-IB(T206D) can signal independently of ActR-IIB. The evidence suggests that ActR-IIB acts as a primary activin receptor and ActR-IB acts as a downstream transducer of activin signals.

Activin Receptors↗
PubMed1995

Sodium orthovanadate-resistant mutants of Saccharomyces cerevisiae show defects in Golgi-mediated protein glycosylation, sporulation and detergent resistance.

Orthovanadate is a small toxic molecule that competes with the biologically important oxyanion orthophosphate. Orthovanadate resistance arises spontaneously in Saccharomyces cerevisiae haploid cells by mutation in a number of genes. Mutations selected at 3 nM sodium orthovanadate have different degrees of vanadate resistance, hygromycin sensitivity, detergent sensitivity and sporulation defects. Recessive vanadate-resistant mutants belong to at least six genetic loci. Most mutants are defective in outer chain glycosylation of secreted invertase (van1, van2, van4, van5, van6, VAN7-116 and others), a phenotype found in some MNN or VRG mutants. The phenotypes of these vanadate-resistant mutants are consistent with an alteration in the permeability or specificity of the Golgi apparatus. The previously published VAN1 gene product has a 200 amino acid domain with 40% identity with the MNN9 gene product and 70% identity with the ANP1 gene product. Cells containing the van1-18, mnn9 (vrg6) or anp1 mutations have some phenotypic similarities. The VAN2 gene was isolated and its coding region is identified and reported. It is an essential gene on chromosome XV and its translated amino acid sequence predicts a unique 337 amino acid protein with multiple transmembrane domains.

Amino Acid Sequence↗
PubMed1990

Expression of a proteolipid gene from a high-copy-number plasmid confers trifluoperazine resistance to Saccharomyces cerevisiae.

A wild-type haploid yeast strain was transformed with a library of wild-type yeast DNA fragments ligated into a high-copy-number plasmid vector (YEp24). The pooled URA+ transformants were plated on rich medium containing a lethal concentration of trifluoperazine (TFP). Plasmids rescued into Escherichia coli from TFP-resistant yeast colonies contained overlapping DNA fragments from a unique region of yeast chromosome XVI. Deletion and disruption experiments, mini-Tn10 LUK hop analysis, and DNA sequencing defined a novel gene with significant amino acid identity to bovine and yeast vacuoletype proteolipid subunits. This is the second locus identified that can be altered to confer TFP resistance to Saccharomyces cerevisiae and that has significant amino acid identity to a vacuolar ATPase subunit. This suggests that a target for TFP in S. cerevisiae is the electrogenic membranes of the vacuolar network and that alteration of expression or activity of vacuolar proton ATPase subunits is a general mechanism for TFP resistance in this yeast.

Amino Acid Sequence↗