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Biomedical subjects

V P Nguyen

Publications and source records attributed to V P Nguyen.

8 recordsLinked to original sources
PubMed2001

Results of up to 9 years of high-temperature-fixed valvular bioprostheses in a young population.

BACKGROUND: Bioprosthetic valve replacement in young patients remains a controversial issue due to a high rate of early calcification. Previous studies in our laboratory have shown that high-temperature fixation of glutaraldehyde preserved bioprosthesis (HTF) mitigates calcification. The first clinical application of this technique was started in 1991. METHODS: From January 1991 to September 1998, 50 patients in whom anticoagulants were contraindicated underwent single aortic valve replacement (n = 33) or mitral valve replacement (n = 17) using HTF bioprostheses. The age of the patients ranged from 7 months to 35 years (mean 22.7+/-6.8 years). The mean New York Heart Association status was 2.4. Mean follow-up 4 years +/- 1.8 for a total follow-up of 196 patient-years. RESULTS: There were no operative deaths and but there were two late deaths, one valve related. Structural failure occured in 4 patients (2%/patient-year) requiring a reoperation in 3 patients (1.5%/patient-year). No endocarditis or thromboembolic episodes were observed. At late examination (June 2000), 46 patients (92%) were in New York Heart Association class I or II, with a well functioning valve. CONCLUSIONS: Replacement with HTF bioprostheses in young patients has demonstrated encouraging midterm results with a low incidence of structural failure

Adolescent↗
PubMed1998

Coronavirus envelope glycoprotein assembly complexes.

Protein:protein interactions, and their subcellular localization, play important roles in coronavirus assembly. In this study, we have identified similar envelope glycoprotein complexes that are present in mouse hepatitis coronavirus A59 (MHV-A59) and bovine coronavirus (BCV) infected cells. Complexes consisting of the spike (S) and membrane (M) proteins were identified in cells infected with MHV-A59 or BCV. Kinetic analyses demonstrated that S and M quickly associated after translation, and suggested that both initially interacted in a pre-Golgi site. In addition, the hemagglutinin esterase (HE) was identified as part of a complex with M and S in BCV infected cells. Taken together, our data indicate that similar glycoprotein complexes are present in cells infected with two different coronaviruses, and thus likely represent important prerequisite complexes involved in virus assembly.

Animals↗
PubMed1998

Variation in the immune status of two Australian pig breeds.

OBJECTIVE: To investigate the variation in immune competence of two Australian pig breeds. DESIGN: A panel of immune tests were used to assess breed and sire differences in weaner piglets of Large White and Duroc breeds. PROCEDURE: All piglets were immunised against porcine leptospirosis. Blood samples were taken for studies on lymphocyte phenotypes, mitogenic responses of blood cells and serological analysis. RESULTS: Significantly larger blood leucocyte numbers were found in Large White piglets compared with Duroc piglets after vaccinations. No significant difference in concanavalin A induced blood cell proliferation was found between these two breeds before or after vaccinations. Some significant breed variation in blood lymphocyte phenotypes was found. While the age-related changes of lymphocyte phenotypes were similar for the two breeds, the Large White breed had significantly larger numbers of CD2+ and CD4+ cells than the Duroc breed after the two vaccinations. There were also significant sire effects on CD8+ cells within the Large White breed after the first vaccination. No significant breed difference was detectable in serum IgG concentrations but sire differences within each breed before the primary vaccination were found. The serum antibody response to vaccination against leptospirosis was generally small, and showed no variations due to either breed or sire. No gender effects were found during the entire study. CONCLUSION: The study demonstrated significant differences in some important immune components of the pig breeds studied. This may in turn indicate the variation in their immune competence or disease resistance. However, further investigation into the heritability and correlation with specific immune responses is required.

Agglutination Tests↗
PubMed1997

Protein interactions during coronavirus assembly.

Coronaviruses assemble and obtain their envelope at membranes of the intermediate compartment between the endoplasmic reticulum and Golgi complex. Like other enveloped viruses, coronavirus assembly is presumably dependent on protein localization and protein-protein as well as protein-RNA interactions. We have used the bovine coronavirus (BCV) as a model to study interactions between the viral proteins in virus-infected cells that are important for coronavirus assembly. BCV is a prototype for the coronaviruses that express an additional major structural protein, the hemagglutinin esterase (HE), in addition to the spike (S) glycoprotein, membrane (M) glycoprotein, and nucleocapsid (N) protein. Complexes consisting of the M, S, and HE proteins were detected in virus-infected cells by coimmunoprecipitations. Kinetic analyses demonstrated that S protein and HE each quickly formed a complex with M protein after synthesis, whereas heterocomplexes consisting of all three proteins formed more slowly. The kinetics of HE biosynthesis revealed that the half-life of oligomerization was approximately 30 min, which correlated with the appearance of complexes consisting of M, HE, and S proteins, suggesting that oligomerization and/or conformational changes may be important for the S-M-HE protein complexes to form. Only HE dimers were found associated with the heterocomplexes consisting of all three proteins. S-M-HE protein complexes were detected prior to processing of the oligosaccharide chains on HE, indicating that these protein complexes formed in a premedial Golgi compartment before trimming of sugar chains. Transient coexpressions and double-labeling immunofluorescence demonstrated that HE and S proteins colocalized with M protein. This was further supported by coimmunoprecipitation of specific HE-M and S-M protein complexes from transfected cells, indicating that these proteins can form complexes in the absence of other viral proteins.

Animals↗
PubMed1995

Repression of glucocorticoid receptor-mediated transcriptional activation by unliganded thyroid hormone receptor (TR) is TR isoform-specific.

Two genes, c-ErbA alpha and c-ErbA beta, generate at least three functional T3 receptor (TR) isoforms in the rat: TR alpha-1, TR beta-1, and TR beta-2. The latter is an N-terminal splice variant of TR beta-1 whose expression is high in the pituitary gland, whereas the other isoforms are more widely expressed. It is believed that TR beta-2 might play an important role in the pituitary, but no specific biological activities have been defined. Using in vitro translated receptors, we were unable to detect striking isoform-specific differences in T3 binding, DNA binding, homodimerization and heterodimerization activities with retinoid X receptor in the electrophoretic mobility assay, or T3-dependent repression and activation of basal transcription in transfection assays. The N-terminus of TR beta is completely dispensible for these activities. However, we found that unliganded TR alpha-1 and TR beta-1, but not TR beta-2, can repress glucocorticoid receptor-mediated transcriptional activation if the reporter gene promoter contains binding sites for both receptor species. TR beta-2 also synergizes most efficiently with the glucocorticoid receptor in the presence for the of T3. The TR beta-2-specific N-terminus is required for these effects. This result indicates that the relative abundance of specific TR isoforms may determine the with the glucocorticoid receptor in the presence of T3. The TR beta-2 specific N-terminus is required for these effects. This result indicates that the relative abundance of specific TR isoforms may determine the quantitative response of a gene that is regulated by T3 and glucocorticoids. In particular, pituitary TR beta-2 may be an important mediator of GH gene expression, which is regulated by both of these hormones.

Animals↗
PubMed1994

Rat Rev-erbA alpha, an orphan receptor related to thyroid hormone receptor, binds to specific thyroid hormone response elements.

Rat Rev-erbA alpha (rRev), which is related to thyroid hormone receptor (TR), is a conserved member of the nuclear hormone receptor superfamily whose physiological roles are unknown ("orphan" receptor). We studied DNA binding of rRev in vitro by electrophoretic mobility shift assay. A fusion protein was constructed, called NGR.Rev, containing part of the N terminus of the glucocorticoid receptor fused to nearly full-length rRev. Inasmuch as rRev and TR share homology in their DNA-binding domains, we tested binding to three different thyroid hormone response elements (TREs) in which the half-sites are arranged in different orientations. NGR.Rev bound direct repeats (DR4), but not palindromic (TREpal) or inverted palindromic (F2H) repeats. Also, transfection of CV1 cells with a reporter gene containing the luciferase gene under control of the inducible thymidine kinase promoter resulted in an increase in luciferase activity when NGR.Rev was cotransfected and when the thymidine kinase promoter contained DR4. In addition, a series of deletions in the ligand-binding domain of NGR.Rev revealed regions that can modulate DNA binding. Finally, we studied DNA binding of bacterially produced fusion proteins that contain the DNA-binding domains of rRev or rTR alpha fused to glutathione S-transferase, to a panel of natural TREs. Our results indicate that Rev binds DNA with a different specificity than TR alpha-1 and might be involved in the regulation of a subset of thyroid hormone-regulated genes.

Amino Acid Sequence↗
PubMedDate not supplied

Fertility and family planning in Vietnam: evidence from the 1994 Inter-censal Demographic Survey.

Results from the 1994 Vietnam Inter-censal Demographic Survey reveal substantial change over recent years in reproductive behavior and attitudes. Fertility has continued to decline to a level not far above a total fertility rate of three children per woman. Compared with the late 1980s, contraceptive knowledge has broadened and contraceptive prevalence has increased, reaching a level of 65 percent of currently married women of reproductive age. The dominance of the IUD among modern methods has been reduced somewhat. Stated family-size preferences have shifted noticeably downward. Recently married women indicate that they want only 2.3 children, on average, suggesting that fertility will continue to fall in coming years. These findings suggest that Vietnam is in the midst of a transition that will lead to low levels of fertility in the near future.

Abortion, Induced↗