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Biomedical subjects

H V Nguyen

Publications and source records attributed to H V Nguyen.

63 records · Page 4Linked to original sources
PubMed1982

Characterization of human placental neuraminidases. Stability, substrate specificity and molecular weight.

1. At least two components of neuraminidase can be distinguished on the basis of thermolability and sedimentability by using the artificial fluorogenic substrate 4-methylumbelliferyl N-acetyl-alpha-D-neuraminate. 2. In crude homogenates, thermodenaturation at 25 degrees C showed a biphasic curve corresponding to component A (half-life, 21 min) and B (half-life, 85 min). The two components were partially resolved by centrifugation. A being soluble and B sedimentable. Both had similar pH-activity curves (pH optimum, 4.4), Km values (A, 0.10 mM; B, 0.06 mM) and molecular weight as determined by radiation inactivation (A, 67000; B, 63000). 3. The soluble A form was still aggregated or bound to membranous debris since almost all neuraminidase activity was eluted near or at the void volume of a Sephacryl S-300 column. 4. Both soluble and sedimentable fractions of placenta hydrolysed the GD1A ganglioside and N-acetyl-neuraminyl-D-lactose linearly for 12 h but no fetuin hydrolysis was detected. 5. The neuraminidase activity with the artificial fluorogenic substrate was inhibited by N-acetylneuraminyl-D-lactose but not by the GD1A ganglioside. These preliminary results suggest that there exist two closely related enzymes hydrolysing both the artificial substrate and N-acetylneuraminyl-D-lactose and a third one hydrolysing the GD1A ganglioside exclusively.

Chromatography, Gel↗
PubMed1982

[The muscular atrioventricular septum].

On the left ventricle septal wall, the tricuspid valve ring attachment is displaced forward, towards the cardiac apex. To this trapezoïdal area between the two atrio-ventricular annuli, the medial wall of the right atrium is attached (laminar attachment), resulting in a atrio-ventricular septum which is: --membranous at its superior extremity (membranous atrio-ventricular septum well described in all classical anatomy textbooks); --and muscular at its inferior extremity. Located in the inferior anterior portion of the Koch triangle, the muscular atrio-ventricular septum is roughly triangular in shape. Its superior and anterior borders are well delineated and represented by: --the pars muscularis crest, at its junction with the membranous atrio-ventricular septum; --and the insertion of the tricuspid septal leaflet on this pars muscularis of the inter-ventricular septum. On the contrary, its third border, the posterior inferior left, is not well defined and varies greatly with the amount of fat filling the crux of the heart. The atrio-ventricular septum separates the right atrium from the base of the left ventricle outflow tract. It shares the important relationship of the "carrefour" of the four cardiac chambers (7 - 8) and first of all the conduction system and its vascular supply. The concept of an atrio-ventricular septum, both muscular and membranous, is to be kept in mind for the good understanding and the surgical correction of different types of "common atrio-ventricular canal" (2 - 10).

Heart Septum↗
PubMedDate not supplied

Chromosomal polymorphism of the yeast Yarrowia lipolytica and related species: electrophoretic karyotyping and hybridization with cloned genes.

Significant differences in electrophoretic karyotyping patterns were found among 27 strains of Y. lipolytica. Twenty-one of these strains were classified into four groups of similar karyotypes while six strains showed unique karyotypes. Chromosomal DNAs of different strains were hybridized with cloned genes of Y. lipolytica (URA3, LEU2, ARS18 and ARS68), which revealed four different bands in most strains. We conclude that the haploid chromosome number of Y. lipolytica is at least four, and possibly five or six. Electrophoretic karyotyping and hybridization with cloned genes of Y. lipolytica provided evidence of a large divergence between Y. lipolytica and related species of Saccharomycopsis, Endomycopsella and Endomyces.

Blotting, Southern↗
PubMedDate not supplied

Rapid removal of Chernobyl fallout from Mediterranean surface waters by biological activity.

The sinking of particulate organic matter from the euphotic zone is an important pathway for the vertical transport of many elements and organic compounds in the sea. Many natural and artificial radionuclides in surface waters are readily adsorbed onto suspended particles and are presumably scavenged and removed to depth on time scales commensurate with both particle sinking rate and retention time of the radionuclide on the particle. Previously, abyssal benthic organisms from the northeast Pacific were found to contain short-lived fission products which entered the sea surface as fallout from nuclear testing. The presence of these radionuclides at great depth could not be explained by Stokesian settling of small fallout particles and it was hypothesized that zooplankton grazing in the surface layers packaged these particle-reactive radionuclides into large, relatively dense faecal pellets which rapidly sank to depth. We report here data from a time-series sediment trap experiment and concomitant zooplankton collections which show conclusively that Chernobyl radioactivity, in particular the rare earth nuclides 141Ce and 144Ce, entering the Mediterranean as a single pulse, was rapidly removed from surface waters and transported to 200 m in a few days primarily by zooplankton grazing.

Accidents↗
PubMedDate not supplied

[Absorbable synthetic clips and pulmonary excision].

From the beginning of this decade, two new, 2nd generation, resorbable synthetic materials--polydioxanone and lactomer--have been able to be molded into clips which, in contrast to metallic clips, are fitted with an original locking system preventing any slipping, either transversal or longitudinal, on the vessels. An experimental study was conducted to confirm their great reliability and perfect safety on large vessels (up to 8-9 mm) of large laboratory animals--both pulmonary and systemic vessels. Positive results justified their application to pulmonary vessels in humans during surgery, the pulmonary vessel being at a much lower pressure than in the main circulatory system. These new clips possess the advantages of metallic clips and resorbable synthetic threads without their inconveniences: rapidity, simplicity and ease of application, radio-transparency and complete inertia in magnetic fields enabling radiotherapy and modern postoperative investigations (scanner, NMR...) to be carried out.

Absorption↗