Biomedical subjects

J Canal

Publications and source records attributed to J Canal.

At least 19 recordsLinked to original sources

PubMed1995

Age-related increased 14C-arachidonic acid uptake by platelets in normal subjects.

Arachidonic acid uptake activity (pmol/10(8) platelets min) measured in platelets obtained from normal subjects was significantly higher in over-forty year old (3.53 +/- 0.38) than in under-forty year old subjects (2.33 +/- 0.12). No significant correlations were found between the arachidonic acid uptake activity and fasting plasma glucose, total cholesterol, HDL-cholesterol or triglyceride levels. The arachidonic acid uptake activity was significantly reduced by the presence of indomethacin in platelets obtained from both under and over-forty year old subjects, and by the presence of nordihydroguaiaretic acid in platelets obtained from over-forty year old subjects. In conclusion, these data show that arachidonate uptake activity by platelets increased with age. This increase was abolished when platelets were incubated in the presence of inhibitors of the arachidonic acid metabolism.

Adolescent↗

PubMed1982

Total automated method for determination of cholesterol concentration in high density lipoprotein by heparin-magnesium-albumin precipitation.

We describe an automated procedure for determination of high-density-lipoprotein cholesterol in serum by use of heparin-MgCl2-albumin reagent. 'AutoAnalyzer' II equipment was used in which high-density lipoprotein was separated from precipitate containing very-low and low-density lipoproteins by filtering on-line across a cellulose acetate membrane. Cholesterol concentration was measured by the enzymic method of Allain. Good correlation was obtained using the automated method compared to the heparin-MgCl2-albumin (r=0.99) or sodium phosphotungstate-MgCl2 procedure (r=0.97). Contamination was minimal with a contamination coefficient lower than 2.5%. The method presented was linear (0 to 2.50 mmol/1) and could be applied to lipemic samples with a coefficient of variation better than 3%. This study showed thus that this new procedure was suitable for routine work with a good rate (60 samples/h) in almost any laboratory.

Autoanalysis↗

PubMed1980

[Critical aspects of actual methods for high-density-lipoprotein cholesterol quantitation].

In this study we compare various methods for h;igh-density-lipoprotein cholesterol quantitation: ultracentrifugation; electrophoresis either on cellulose acetate or on agarose gel; precipitation methods with polyanions-bivalent cations; adsorption procedure using concanavalin A (Con A). quantification by electrophoresis is slow and not precise. Except heparin-Mn++ and dextran (MM 5 X 10(5) and 2 X 10(6)) - CaCl2 procedures, precipitation and Con A methods own a good repeatability (VC 2%) and give a linear response after VLDL or LDL-VLDL addition to tested sera. Regression analysis of the data obtained using these methods in pairs demonstrate a correct accuracy (r > 0.95). The Student t-test shows that the usual values must be evaluated for each method. We suggest to use either phosphotungstate - Mg++ or Con A procedure as method for HDL cholesterol quantitation.

Adsorption↗

PubMed1980

Heparin--magnesium chloride--albumin method for enzymic measurement of cholesterol in high-density lipoprotein.

We describe a new method for measuring high-density-lipoprotein cholesterol in sera, with use of heparin, MgCl2, and albumin to precipitate very-low- and low-density lipoproteins, Lipoprotein electrophoresis and immunochemical methods show that high-density lipoprotein is completely and specifically isolated in the supernate, the cholesterol concentration of which is estimated by the enzymic method of Allain et al. (Clin. Chem. 20, 470, 1974). The precision of the method is excellent (CV = 1%) and the response is linear. Values so obtained correlate well with those obtained with the heparin-Mn2+ (r = 0.98) or the phosphotungstate-Mg2+ (r = 0.98) procedures. The technique is appropriate for routine clinical laboratory use.

Adult↗

PubMed1980

[Serum phospholipids determination by an automatic enzymatic method (author's transl)].

The serum phospholipids determination by an automatic enzymatic method (AEM) is suggested in this study. A comparison was made between the classical chemical method, the manual enzymatic method (MEM) and the AEM one. 100 serum samples were tested in this experiment and the correlation coefficient between these methods was found to be acceptable. The result indicates a good precision and a negligible contamination. The calibration curve is linear to 5 mmol/l. Triglyceride and cholesterol concentrations, glucose and high concentrated uric acid presence do not interfere on the value measured. However, the haemolysis and a large quantity of bilirubin in sera tend to induce a variation in the phospholipids determination.

Autoanalysis↗

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

[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↗

PubMed1974