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Age-related changes in Δ6 desaturation of [1-C]α-linolenic acid and [1-C]linoleic acid and in Δ5 desaturation of [2-C]dihomo-γ-linolenic acid were studied in liver microsomes from Wistar male rats at various ages ranging from 1.5 to 24 mon. Desaturase activities were expressed both as specific activity of liver microsomes and as the capacity of whole liver to desaturate by taking into account the total amount of liver microsomal protein. Δ6 Desaturation of α-linolenic acid increased from 1.5 to 3 mon and then decreased linearly up to 24 mon to reach the same desaturation capacity of liver measured at 1.5 mon. The capacity of liver to desaturate linoleic acid increased up to 6 mon and then remained constant, whereas microsomal specific activity was equal at 1.5 and 24 mon of age. The capacity of liver to convert dihomo-γ-linolenic acid to arachidonic acid by Δ5 desaturation decreased markedly from 1.5 to 3 mon. It then increased to reach, at 24 mon, the same level as that observed at 1.5 mon. Age-related changes in the fatty acid composition of liver microsomal phospholipids at the seven time points studied and of erythrocyte lipids at 1.5 and 24 mon were consistent with the variations in desaturation capacity of liver. In particular, arachidonic acid content in old rats was slightly higher than in young rats whereas contents in linoleic and docosahexaenoic acids varied little throughout the life span. The results suggest that, in liver, the activity of desaturases may be regulated in the course of aging to maintain a constant level of polyunsaturated fatty acids in cellular membranes. [ABSTRACT FROM AUTHOR]

The combined effects of age and dietary n−6 and n−3 fatty acids were studied in 3-, 6- and 9-month-old rats. At each age, two groups were fed diets containing 5% (w/w) of vegetable oils rich in either 18∶3n−6 (borage group) or 18∶3n−6 plus 18∶4n−3 (black currant group), for a period increasing with age. A control group was fed the essential fatty acids 18∶2n−6 and 18∶3n−3 only. For each group, Δ6, Δ5 and δ9 desaturase activities were measured in liver microsomes, and fatty acid composition was determined in microsomal phospholipids. Desaturase activity varied as a function of age and dietary lipids. Δ6 Desaturation of 18∶3n−3 was more sensitive to these factors while Δ6 desaturation of 18∶2n−6 and Δ9 desaturation were more dependent on season than the other two. Desaturase activity was influenced more by the black currant than by the borage diet, especially at 6 and 9 months of age. A large proportion of arachidonic acid was maintained in the microsomes independent of the diet. Changes in the fatty acid composition did not strictly reflect the differences in desaturase activities. The effects of the two factors (age and diet) on the activities of the desaturases are complex, suggesting that the enzymes are susceptible to other factors as well. [ABSTRACT FROM AUTHOR]

A method is described for the determination of molecular species of oil triacylglycerols. The method is based on the analytical separation of the enantiomeric sn-1,2-and sn-2,3-diacylglycerols, derived from triacylglycerols, by high-performance liquid-chromatography (HPLC) on a chiral column containing N-(R)-1-(α-naphthyl)ethylaminocarbonyl-(S)-valinecarbonyl-(S)-valine as stationary phase. Model triacyl-glycerol molecules comprising three known fatty acids were isolated from peanut oil and cottonseed oil by a combination of argentation-TLC and reversed-phase HPLC and submitted to partial chemical deacylation. The derived sn-1,2(2,3)-diacylglycerols were analyzed and fractionated as 3,5-dinitrophenyl urethane derivatives by reversed-phase HPLC according to chainlength and unsaturation. From the sn-1,2(2,3)-diacylglycerol composition and the diacylglycerol sn-1,2-and sn-2,3-enantiomer composition, the individual molecular species of four peanut oil triacylglycerols and one cottonseed oil triacylglycerol were identified and quantitated. The method can be applied to triacylglycerols of any other oil or fat. [ABSTRACT FROM AUTHOR]

The relationship between the presence of linolenic acid and the ability to form respirationdeficient mutants induced by acriflavin has been established. The metabolic coefficients and the composition of fatty acids in samples metabolizing lactose are presented. [ABSTRACT FROM AUTHOR]

The effect of simvastatin, a hypocholesterolemic drug, on the biosynthesis of arachidonic acid was studied in obese and lean Zucker rats. After administration of 2 mg/kg body weight/d for 13 d, Δ6 and Δ5 desaturase activities were measured in liver microsomes at two substrate concentrations. In untreated rats, the Δ6 desaturation rate was similar in the obese and lean rats when measured at saturating substrate levels, whereas Δ5 desaturation was lower in the obese animals. Treatment with simvastatin did not change Δ6 desaturation in either phenotype but increased Δ5 desaturation in obese rats to reach the unchanged rate observed in lean animals. The changes were not reflected in the fatty acid composition of liver microsomal phospholipids when expressed as μg fatty acid/g of liver. [ABSTRACT FROM AUTHOR]

Evaluates the oocyte competence for in-vitro maturation and the expression of maturation-promoting factor components and mitogen-activated protein kinase (MAPK). Influence of the culture medium and the physiological stage of the mare on maturation rate at the time of oocyte recovery; Presence of MAPK and its subunits in equine oocytes.