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Biomedical subjects

T B Nguyen

Publications and source records attributed to T B Nguyen.

31 records · Page 2Linked to original sources
PubMed1996

Use of 2,6-dihydroxyacetophenone for analysis of fragile peptides, disulphide bonding and small proteins by matrix-assisted laser desorption/ionization.

Several peptides were shown to undergo fragmentation during matrix-assisted laser desorption/ionization time-of-flight mass spectrometry to a degree which complicated their analysis using alpha-cyano-4-hydroxycinnamic acid (CHCA) as a matrix, even at threshold laser irradiance. These peptides included synthetic peptides, peptides isolated from viral proteins and a phosphopeptide from beta-casein (residues 33-48). The excessive fragmentation occurred usually as a post-source phenomenon; however, in-source fragmentation was also observed. The combined effects of in-source and post-source fragmentation of one peptide studied led to a failure to observe the protonated molecule of this peptide in reflector mode analysis. The phosphopeptide studied exhibited a high degree of beta-elimination of phosphate. It was demonstrated that the fragility exhibited by these peptides in CHCA, including beta-elimination of phosphate from serine, was not evident with a matrix comprising 2,6-dihydroxyacetophenone (DHAP) and di-ammonium hydrogen citrate (DAHC). The DHAP/DAHC matrix was also adapted for direct analysis of peptides from an acidic reducing milieu containing tris(2-carboxyethyl)phosphine. The molecular weight of equine cytochrome c was determined with a relatively high degree of accuracy (experimental M(r) = 12360.2 +/- 1.4 Da compared to the theoretical M(r) = 12360.09 Da) using DHAP/DAHC as a matrix for reflector mode analysis.

Acetophenones↗
PubMed1996

[Intrapulmonary hemorrhages associated with Basedow disease].

We report the second case of intraalveolar haemorrhage associated with an autoimmune thyrotoxicosis. While intraalveolar haemorrhage was not recurrent since 7 years with corticosteroid therapy, a relapse occurred when we began the treatment for an autoimmune thyrotoxicosis. We discuss the link between intraalveolar haemorrhage and autoimmune thyrotoxicosis or its treatment.

Adult↗
PubMed1995

[Pneumocystis carinii infection disclosing untreated systemic lupus erythematosus].

Pneumocystis carinii pneumonia (PCP) is a well known opportunistic infection in Systemic Lupus Erythematosus (SLE) patients with lymphopenia and treated with corticosteroid or cytotoxics agents. We report a new case of PCP in an untreated SLE with severe lymphopenia. We discuss the origin of lymphopenia in SLE, lymphopenia as a risk factor of Pneumocystis carinii infection, and safety precautions to take.

Female↗
PubMed1993

Modeling the complexation of substituted benzenes by a cyclophane host in water.

Monte Carlo statistical mechanics simulations have been used to study the complexation of disubstituted benzenes by Diederich's octamethoxy tetraoxaparacyclophane host. Relative free energies of binding were obtained in water at 25 degrees C for benzene, p-xylene, p-cresol, p-dicyanobenzene, and hydroquinone from statistical perturbation theory. The computed results agree well with experimental data, including the binding affinity of benzene, which was determined after the calculations were completed. The computed structures for the complexes reveal details that are important for understanding the order of binding affinities. It is found that hydroquinone protrudes from one side of the complex and participates in hydrogen bonds between one hydroxyl group and two water molecules and in an intracomplex hydrogen bond between the other hydroxyl group and ether oxygens. The calculations also show a clear preference for binding p-cresol with the hydroxyl group hydrated rather than inside the host's cavity.

Journal Article↗
PubMed1987

Effects of different monoamine oxidase inhibitors on the metabolism of L-dopa in the rat brain.

The influence of monoamine oxidases A and B on the metabolism of dopamine or the expanded dopamine pool following L-dopa administration remains unclear. This study found that treatment of Sprague-Dawley rats with monoamine oxidase inhibitors strongly affected L-dopa metabolism in the brain, but the influence varied with each individual inhibitor. In animals pretreated with pargyline or clorgyline, L-dopa administration led to huge accumulations of dopamine and significantly raised central norepinephrine concentrations. In contrast, similar L-dopa injections in deprenyl-pretreated rats caused only a moderate rise in dopamine and no change in norepinephrine. There seems to be little relationship between the degree of monoamine oxidase inhibition and the accumulation of catecholamines and their metabolites in the rat brain. The effects of monoamine oxidase inhibitors on dopamine accumulation appeared to occur outside the catecholaminergic neurons since in the animals pretreated with 6-hydroxydopamine, which decreased significantly the content of brain catecholamines, dopamine accumulation following L-dopa administration still remained considerable. On the other hand, the influence of monoamine oxidase inhibitors on brain norepinephrine concentrations seemed to originate in the noradrenergic neurons because norepinephrine increase was greatly reduced in rats treated with 6-hydroxydopamine but was restored when the treatment with 6-hydroxydopamine was accompanied by desimipramine which specifically protects noradrenergic stores.

Animals↗
PubMed1986

Atrial natriuretic factor inhibits the sympathetic nervous activity in one-kidney, one-clip hypertension in the rat.

The one-kidney, one-clip model of rat hypertension was found to have an increased natriuresis following chronic infusion of atrial natriuretic factor (ANF). We have now found that this natriuretic effect of ANF is associated with a suppression of the initially elevated urinary excretion of norepinephrine and epinephrine and increase of the excretion of the main dopamine metabolite-dihydroxyphenylacetic acid as well as of the urinary dopamine to norepinephrine ratio. These data are compatible with the hypothesis that ANF suppresses the increased sympathetic activity in this model of hypertension and this action combined with opposite changes of dopamine may contribute to the natriuretic effect of ANF.

Animals↗