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Biomedical subjects

J Delattre

Publications and source records attributed to J Delattre.

At least 91 records · Page 5Linked to original sources
PubMed1987

Liposomally-entrapped ATP: improved efficiency against experimental brain ischemia in the rat.

ATP was entrapped inside negatively charged liposomes composed of sulfatide, in order to improve its penetration into the brain and to reduce its degradation into other tissues. These liposomes were prepared according to an original method allowing a satisfying stability of the formulation. Liposomally entrapped ATP was administered intracerebroventricularly to rats submitted to brain ischemic episodes by both carotid artery clamping and systemic blood pressure lowering (during 3 minutes every 15 minutes). Such treatment importantly increases the number of ischemic episodes before brain silence appeared. So, this paper allows new perspectives in the administration of drugs into the brain.

Adenosine Triphosphate↗
PubMed1987

[Serum zinc and copper in hypercholesterolemia].

For some authors, absolute or relative copper deficiency, with an elevated plasmatic zinc/copper ratio, could be a risk factor in the etiology of cardiovascular diseases by altering lipid metabolism. Animal or human studies carried out with zinc and/or copper supplemented or deficient diets on biochemical lipid parameters, led to inconsistent results. Nevertheless, no study was already done in hypercholesterolemic patients, concerning possible correlation between serum levels of these trace elements and cholesterol, HDL cholesterol and apolipoprotein B blood levels. 67 patients were distributed in three groups according to their hypercholesterolemia. The serum copper concentration was elevated, serum zinc concentration and zinc/copper ratio were decreased in the hypercholesterolemic group (cholesterol greater than 7.7 mmol/l). Serum zinc, copper and zinc/copper ratio were significantly correlated with HDL cholesterol (respectively r = + 0.56 p less than 0.05, r = - 0.68 p less than 0.01, r = + 0.76 p less than 0.001).

Adult↗
PubMed1986

[Contribution of Jacques Canal in the field of lipoproteins].

The scientific works of J. Canal have essentially related to low density lipoproteins (L.D.L.), between 1.025 and 1.050. By using proteolytic enzymes and phospholipases, he is able to obtain informations on the accessibility of apolipoprotein B and phospholipids. So, as early as 1975, he expresses the hypothesis that only 30 p. cent of Apo B occupy a superficial position. In addition, he proposes the fact that Apo B has at least four antigenic determinants; this hypothesis formulated by J. Canal, almost 10 years ago, was recently confirmed by using monoclonal antibodies. At the same time, using phospholipases, J. Canal reaches the conclusion that phospholipids are localized on the surface of L.D.L. He demonstrates that phospholipids play a major role in the precipitation of L.D.L. by sulfate polysaccharides in the presence of L.D.L. by sulfated polysaccharides in the presence of divalent cations (Reaction of Burnstein). He proposes a mechanism for this reaction. This research on the mechanism of Burnstein's reaction will receive in clinical biochemistry an important application with the development of a completely original technique of dosage of total lipids in the serum.

France↗
PubMed1984

Radiopaque liposomes: effect of formulation conditions on encapsulation efficiency.

Liposomes containing sodium ioxitalamate were prepared by sonication. Suitable amounts of purified soybean phosphatidylcholine and cholesterol were used at various molar ratios. Stearylamine or dicetylphosphate were added to this lipid composition when charged liposomes were required. After sonication and removal of unencapsulated solute, this manufacturing process yielded small multilamellar vesicles as confirmed by electron microscopy. These liposomes did not exhibit a narrow range of size distribution; the mean particle size varied from 135 to 145 nm. With respect to the efficiency of encapsulation, two parameters were distinguishable: the volume of encapsulated aqueous space per unit of lipid weight and the percentage of the contrast agent added that became encapsulated in the liposomes. Investigation of the preparative parameters revealed that increased molar ratios of cholesterol yielded higher aqueous volume and iodine contents in the liposomes, which were attributed to a reduction of the liposome permeability to the contrast agent. However, the inclusion of cholesterol into the bilayer liposomal membrane was limited, probably by solubility restrictions. Negatively and positively charged liposomes had higher rates of encapsulation than did neutral liposomes. This result was expected since efficient encapsulation of polar compounds requires formation of large aqueous spaces within the vesicles per mole of lipids. Increase of the lipid fractions at a constant, reduced the aqueous volume entrapped per millimole of lipid and, consequently, the iodine content in the liposomes. However, an increase in the initial sodium ioxitalamate concentration diminished the aqueous volume entrapped in the liposomes but increased the iodine content.

Chemistry, Pharmaceutical↗
PubMed1980

A rapid and sensitive fluorometric assay of serum phospholipid.

A fluorometric assay of phospholipid in serum is presented. The reaction is based upon the binding of phospholipids with a fluorescent probe: 1-6-Diphenyl-1-3-5 hexatriene (DPH). The method is in very good agreement with other techniques for phospholipid estimation: phosphorus assay phospholipid extraction (Fiske and Subarrow), and enzymatic assay of phospholipid containing choline (Takayama). The correlation coefficient obtained was 0.81, when the proposed method was compared with the two other ones. Parameters influencing the reaction: DPH concentration, time and temperature of incubation are described. The normal range for human serum lies between 2.1 and 3.4 mmol/l. The sensitivity of the fluorometric assay is also sufficient for the determination of phospholipid in amniotic fluid and broncho-alveolar washings.

Amniotic Fluid↗
PubMed1979

[Influence of phosphatidylcholine/cholesterol molar ratios in liposomes on cholesterol reactivity with cholesterol:oxygen oxidoreductase].

The reactivity of sonicated phosphatidylcholine-cholesterol liposomes with cholesterol : oxygene oxydoreductase, an enzyme which catalyses the oxidation of the 3 beta hydroxyl group of cholesterol to a ketone group, is compared with that of ternary system phosphatidylcholine-cholesterol-Thesit. Regardless to the phosphatidylcholines nature and the phosphatidylcholine/cholesterol molar ratio (R), the enzymatic oxidation rate of liposomal cholesterol is slower than when the reaction is developed in the present of Thesit, a surfactif agent which destroyes the lamellar particles. This is true whether Thesit is added during preparation of dispersions or during incubation with cholesterol oxydase. The enzymatic oxydation rate of cholesterol of ternary systems phosphatidylcholine-cholesterol-Thesit is independent of the (R) value and the phosphatidylcholine fatty acid unsaturation, whereas that of phosphatidylcholine-cholesterol dispersions depends on these two parameters. The reaction rate increases in the order: dipalmitoylphosphatidylcholine to yolk egg phosphatidylcholines, and dioleylphosphatidylcholine. The optimal conditions for cholesterol oxidation were found to be R = 0.5. This result is not affected by the phosphatidylcholines nature. In order to explain these data, various hypotheses are considered. In particular, the weak liposomal cholesterol reactivity with cholesterol oxidase could result from an inhibitory effect on the enzyme-substrate combination due to the polar phosphorylcholine groups.

3-Hydroxysteroid Dehydrogenases↗
PubMed1976

[A simple method for evaluation of the lecithin/sphingomyelin ratio in amniotic fluid. Variation in normal and abnormal pregnancies (138 cases) (author's transl)].

The determination of the lecithin/sphingomyelin ratio in amniotic fluid is a useful index for assessing fetal pulmonary maturity. The authors propose a simple and specific method : the amniotic lipids are extracted and thin layer chromatography is carried out in an acetic acid containing medium. The L/S ratio was studied and discussed in 138 normal and pathological cases.

Amniotic Fluid↗
PubMed1976

[Study of the specificity of action of cholesterol oxygen oxidoreductase on various sterols and related substances].

The authors studied the action of oxygen cholesterol oxidoreductase (E.C. 1.1.3.6) extracted from Nocardia erythropolis on different sterols following simultaneously:--the disappearance of the substrate by chromatography on thin layers of silic acid, the formation of hydrogen peroxide by Röschlau's reaction, changes in the absorption spectrum between 220 and 320 nm. The results obtained show that sterol oxidase presents a broad spectrum of activity. It catalyses the transformation into ketone of the secondary alcohol group at the 3 beta position of sterols which possess in the C17 position a lateral chain of at least two carbon atoms. In the other hand, the reaction does not take place if there exists in the C5 position, an H in the cis position or if two hydrogen atoms linked to carbon 4 are substituted. Finally, only oxidation products derived from sterols possess a double bond situated in the 4-5 or 5-6 position presenting an absorption band between 240 and 250 nm.

Chromatography, Thin Layer↗
PubMed1975

[Role of phosphorylcholine group on inhibiting capacity of lecithin-cholesterol liposomes on streptolysin O].

Cholesterol inhibition of the hemolytic activity of streptolysin O was used for testing the presence of cholesterol on the surface of lecithin-cholesterol liposomes. Cholesterol as a liposome component is not available for streptolysin inhibition when the molar ratio lecithin-cholesterol greater than 1,25. Incubation of such liposomes with phospholipase C, which converts the phosphadylcholine group into neutral diglycerides, restores an inhibiting activity of cholesterol parallel to the phosphatid degradation. Incubation of the liposomes with phospholipase D, which converts the phosphatidylcholine group into phosphatidic acid, also restores the inhibiting capacity of cholesterol on the hemolysin. The accessibility of liposome cholesterol to streptolysin O appears to mainly depend upon the cholin group of lecithin.

Cholesterol↗