Search PubMed⌕ Search

Biomedical subjects

A Sanson

Publications and source records attributed to A Sanson.

66 records · Page 4Linked to original sources
PubMed1980

A NMR study of the ionization of fatty acids, fatty amines and N-acylamino acids incorporated in phosphatidylcholine vesicles.

The ionization of fatty acids, fatty amines and N-acylamino acids incorporated in phosphatidylcholine single-walled vesicles has been measured. The guest molecules have been specifically enriched with 13C and titrated by using NMR spectroscopy. The apparent pKa of fatty acids in phosphatidylcholine bilayers if 7.2-7.4 and those of fatty amines are approx. 9.5. These pKa values depend on many different parameters related to the structure of the lipid/solution interface, to the composition of the aqueous medium and to the localization of the ionizable groups. A special sensitivity to the ionic strength and to the surface charge has been found. A positive surface charge decreases the pKa value whereas a negative one increases it, the total range of variation being 2.5-3 units. In a qualitative macroscopic interpretation, it is proposed that pKa is essentially determined by the low polarity of the lipidic matrix.

Amines↗
PubMed1978

Variations in apolipoproteins B and A1 during the course of myocardial infarction.

The plasma apolipoproteins B and A1, and plasma lipids and lipoproteins, were studied in fifteen patients with acute myocardial infarction. In the days immediately after acute infarction there was a decrease in total cholesterol, low density lipoprotein-cholesterol, total apolipoprotein-B, low density lipoprotein apolipoprotein-B and high density lipoprotein apolipoprotein A1. High density lipoprotein-cholesterol remained unchanged. In the same period the total triglycerides, very low density lipoprotein-protein, very low density lipoprotein-cholesterol, very low density lipoprotein apolipoprotein-B and very low density lipoprotein apolipoprotein A1 were increased. A reduction of the apolipoprotein ratio CII/CIII occurred after the acute phase. After 25--30 days all these values regained their baseline values.

Aged↗
PubMed1977

Fatty acids diffusion in lecithin multilayers: hydration and PH effects.

The diffusion of the sodium salt of monocarboxylic fatty acids, from formate to stearate, has been studied as a function of water content and pH in lecithin--water lamellar phases. Evolution of the diffusion coefficients with increasing chain length reflects the different localizations of fatty acids in the system. From formate to butyrate, which are mainly restricted to the hydrophilic layer of the phase, diffusion rates decrease rapidly. From butyrate to stearate, fatty acids (anchored at the hydrophilic--lipophilic interface) undergo lateral diffusion and then the decrease of D with increasing chain length is much slower. The diffusion of stereate is already comparable to the diffusion of the lecithin molecule itself. The diffusion rates strongly depend upon phase hydration and pH: it is shown that both parameters control the fatty acid ionization. The variations in diffusion rates observed may be ascribed to the fact that, depending upon their state of ionization, fatty acids assume a different localization and therefore experience different interactions in the lamellar system.

Biological Transport↗
PubMed1976

An ESR study of the anchoring of spin-labeled stearic acid in lecithin multilayers.

In egg lecithin-water lamellar phases, spin-labeled stearic acid gives two superimposed ESR spectra which are only well resolved when the temperature is greater than 30 degrees C. These two spectral components are attributed to the dissociated and non-dissociated forms of the fatty acid carboxylic group, anchored at two different positions in the polar interface constituted by the hydrated lipid polar heads. Results on such interactions of other functional groups (spin-labeled fatty ester and fatty alcohol) are also presented.

Binding Sites↗
PubMed1976

An ESR study of the hydration steps of lecithin multilayers.

A spin-labeled stearic acid and other spin-labeled molecules have been used for an ESR study of the hydration process of the egg lecithin lamellar phase for water concentrations, CW greater than 10%. Two hydration steps are found for CW approximately 20% and CW congruent to 30%, in good agreement with results of the literature. To explain discontinuities in the behavior of three spin-labeled molecules at CW congruent to 20%, a conformational change of the phosphatidylcholine polar head and a phase transition in the polar interface are proposed.

Binding Sites↗
PubMedDate not supplied

1H- and 2H-NMR studies of a fragment of PMP1, a regulatory subunit associated with the yeast plasma membrane H(+)-ATPase. Conformational properties and lipid-peptide interactions.

PMP1 is a 38-residue polypeptide associated with the yeast plasma membrane H(+)-ATPase, found to regulate the enzyme activity. To investigate the molecular basis of the PMP1 biological function, the conformational properties of a synthetic PMP1 fragment, A18-F38, comprising the predicted C-terminal cytoplasmic domain and a part of the transmembrane anchor have been studied by 1H- and 2H-NMR spectroscopies. High resolution 1H-NMR experiments showed that, in deuterated DPC micelles, the A18-G34 segment adopts a well defined helix conformation. Our data suggest that the whole PMP1 molecule forms a unique helix whose axis might be slightly tilted with respect to the bilayer normal. Protonated DPC, DMPC and DMPS were incorporated in deuterated micelles containing the PMP1 fragment for studying lipid-peptide interactions. Unusually strong and selective intermolecular NOEs between lipid chain and peptide side chain protons, especially those of the unique Trp residue, were observed. Solid state 2H-NMR experiments performed on pure deuterated POPC and mixed deuterated POPC:POPS (5:1) bilayers revealed that the PMP1 fragment specifically interacts with negatively charged PS lipids.

Amino Acid Sequence↗
PubMedDate not supplied

[Treatment of unstable angina with dipyridamole combined with low doses of aspirin. A multicenter pilot double-blind controlled study].

In order to assess the usefulness of a combination of low-dose aspirin (25 mg b.i.d.) with dipyridamole (200 mg b.i.d.) in the prevention of major coronary events in patients with acute unstable angina, we performed a prospective, double-blind, placebo-controlled study involving 88 consecutive patients admitted to three Hospital Departments of Cardiology. The patients entered the study as soon as possible after hospital admission, and were treated and followed up to one year. There was no appreciable difference in side effects and adverse reactions between the treatment and control group. The incidence of cardiac death and/or nonfatal myocardial infarction during the whole period of observation was 14% (6/44) in the treatment group and 25% (11/44) in the placebo group by "intention-to-treat" analysis; 16% (4/25) and 32% (10/31), respectively, by "drug-efficacy" analysis (p = 0.21 by Fisher's exact test, non significant difference). However, when considering the only events occurred in the first month (2/44 in the treatment group and 9/44 in the placebo group, amounting to 4.5 and 20 percent, respectively), the combination of dipyridamole with low-dose aspirin reached a statistically significant protective effect (p = 0.04). The results of this pilot study provide strong evidence for a beneficial effect of the regimen tested in patients with acute unstable angina, at least in the first weeks of treatment, while at the same time suggesting a safe alternative for patients with contraindications to higher doses of aspirin.

Adult↗