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D Andre

Publications and source records attributed to D Andre.

5 recordsLinked to original sources
PubMed1992

Problems associated with the use of exclusion-diffusion chromatography for identification of zinc ligands in human milk.

The effect of operating conditions used in gel filtration, i.e. the type of gel and elution buffer, on the qualitative and quantitative distribution of zinc in human milk was studied. The gels used were Sephadex G10 and G15, Biogel P2 and Trisacryl GF05. The three elution buffers used were 0.05 M Tris-HCl, pH = 7.4, 0.05 M Tris-acetate, pH = 7.4 and 0.1 M ammonium acetate, pH = 6.5. Ultrafiltration was used as an additional technique for the verification of a number of the results obtained. Zinc ligands in human milk are, possibly, serum albumin and citric acid. The results showed a gel effect, which was greater on the identification and quantitation of the low molecular-weight ligand (the percentage of zinc associated with citric acid was lower with Biogel P2). The elution buffer had a considerable effect, particularly when quantifying the protein-bound fraction. The percentage of zinc coeluted with proteins decreased when the elution buffer contained acetate ions. The combination of Sephadex G15 and 0.05 M Tris-HCl, pH = 7.4 was found to be the best compromise. Zinc distribution with this system was 35-44% of zinc coeluted with proteins and 18-22% with citric acid.

Chromatography, Gel↗
PubMed1988

Physicochemical, pharmacological and pharmacokinetic study of a new GABAergic compound, calcium acetylhomotaurinate.

It has been shown that calcium acetylhomotaurinate (Ca AOTA; Meram Patent, France) decreased voluntary ethanol intake in rats (1); this was antagonized by bicuculline. Homotaurine did not have this effect. We thought this was due to a different blood-brain barrier crossing ability for the two drugs. The present study was, therefore, planned to confirm blood-barrier crossing by Ca AOTA and to study the drug's physicochemical and pharmacokinetic characteristics. Both in vitro and in vivo (i.p.) administration of Ca AOTA increased the accumulation of [3H] GABA in rat striatal synaptosomal preparations. The chemical study confirmed Ca AOTA's great stability in biological and hydrophilic media, excluding a "homotaurine-dispensing" effect. The molecule was totally dissociated in such media, but the absence of any detectable acid form at any pH indicates that ion pairs are formed to cross barriers, and/or that a carrier system is used. The pharmacokinetic study showed short half-lives (5 and 30 min for the distribution and elimination phases) and small distribution volumes. However, the elimination phase distribution volume was dose-dependent, a further argument for a carrier transport system. From the present study it appears that Ca AOTA is an extremely stable drug, totally dissociated in hydrophilic media, which acts centrally as a GABA agonist after crossing the blood-brain barrier. It is not a precursor of homotaurine and presumably crosses barriers with the help of a transporter.

Acamprosate↗
PubMed1978

Hypothermic decrease in microtubule density and birefringence in unimyelinated axons.

The density of microtubules, T.D. (number of tubules/unit area) is highest in small crab nerve axons. After cooling of the nerve at 0 degrees C, the tubule density tends to zero (T.D. 2% of the normothermic value). Once the cooled nerves are returned in normothermia, the reconstitution of the microtubules is evidenced (T.D. = 90% of the initial normothermic value). Therefore cooling "depolymerizes" the tubules, whereas rewarming leads to their "repolymerization." These results definitely improve the interpretation of the birefringence decrease by cooling: as tubules and filaments contribute to the positive fraction of the total positive birefringence, their depolymerization by cooling explains to a large extent the decrease in total birefringence.

Animals↗