Effect of a linseed diet on lipogenesis, fatty acid composition and stearoyl-CoA-desaturase in rabbits.

The aim of the study was to examine the effect of a linseed diet on meat quality and on lipogenesis in rabbits. Twelve rabbits were fed a control or a linseed diet. There was no diet effect on growth, food consumption, carcass characteristics and meat ultimate pH and colour. Feeding the linseed diet increased the n-3 polyunsaturated fatty acids (PUFA) levels in perirenal and interscapular fats, in the Longissimus dorsi muscle and in the liver. The linseed diet produced lower linoleic acid/α-linolenic acid ratios in adipose tissues and in the Longissimus dorsi muscle, but not in the liver. Diet did not affect lipogenic enzyme activities in the Longissimus dorsi muscle, whereas the linseed diet decreased the lipogenic potential in perirenal and interscapular fats, and in the liver. Feeding rabbits with a high n-3 PUFA diet led to a decrease in the oxidative stability of perirenal fat and the Longissimus dorsi muscle, and to an inhibition of stearoyl-CoA-desaturase activity in liver and in adipose tissues, but not in muscle.

Effects of dietary crude palm oil, fish oil and their association on cholesterol and lipoprotein constants in rats which could be beneficial in humans.

The aim was first to examine the differential effects of crude and refined palm oil (CPO and RPO) on the lipid and lipoprotein constants of plasma in rats and to compare the effect of crude palm oil to that of fish oil. Secondarily, it was to know whether one can take advantage from the association of CPO with FO. Twenty-four-day-old weaning rats were divided into five experimental groups, each receiving a purified diet containing 10% oil as either a single oil or an equal amount of two oils. After a feeding period of 36 days, the main results were as follows. As compared to the rats fed the RPO diet, those fed the CPO diet had lower total cholesterol, LDL-C, VLDL-C and apoB and higher HDL-C/LDL-C and apoA1/apoB ratios. Those fed the FO diet had only lower VLDL-C and triglycerides and higher HDL-C and HDL-C/LDL-C ratio. Whereas FO associated with RPO in the same diet had the same effect as FO alone, FO associated with CPO tends to reinforce the effect of CPO. This is particularly true for the effects on apoB and apoA1 which were found to be synergistically depressed and enhanced, respectively. Given the role played by these biological constants as predictors of CVD in humans, and in spite of the fact that these predictors are not relevant in rats, these results would suggest the potential interest of CPO or the association of CPO with FO in human nutrition.

The extracellular xylan degradative system in Clostridium cellulolyticum cultivated on xylan: evidence for cell-free cellulosome production.

In this study, we demonstrate that the cellulosome of Clostridium cellulolyticum grown on xylan is not associated with the bacterial cell. Indeed, the large majority of the activity (about 90%) is localized in the cell-free fraction when the bacterium is grown on xylan. Furthermore, about 70% of the detected xylanase activity is associated with cell-free high-molecular-weight complexes containing avicelase activity and the cellulosomal scaffolding protein CipC. The same repartition is observed with carboxymethyl cellulase activity. The cellulose adhesion of xylan-grown cells is sharply reduced in comparison with cellulose-grown cells. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis revealed that cellulosomes derived from xylan- and cellulose-grown cells have different compositions. In both cases, the scaffolding protein CipC is present, but the relative proportions of the other components is dramatically changed depending on the growth substrate. We propose that, depending on the growth substrate, C. cellulolyticum is able to regulate the cell association and cellulose adhesion of cellulosomes and regulate cellulosomal composition.

Rate of alteration of hepatic mixed-function oxidase system in rats fed different dietary fats.

Studies were carried out to evaluate and relate the rate of alteration in mixed-function oxidase system with the changes of the fatty acid composition of rat microsomes induced by different dietary lipids. Male weanling rats were fed from day 21 to 120 with a commercial rat diet or a semisynthetic diet containing no fat or 10% fat consisting of peanut-rapeseed oil, sunflower oil, or salmon oil. In rats fed a fat-free diet, the cytochrome P-450 concentration and aniline hydroxylase, aminopyrine N-demethylase, and NADPH-cytochrome-c reductase activities of liver microsomes at 120 days were, respectively, 26, 16, 10, and 24% lesser than those of rats fed the control diet. However, cytochrome b5 concentration and NADH-cytochrome-b5 reductase activity were, respectively, 33 and 43% higher than those of the control group at the same time. When rats were fed the sunflower oil diet, the cytochrome P-450 concentration and NADH-cytochrome-b5 reductase activity at 120 days were, respectively, 11 and 23% lesser than those of control group. But the cytochrome b5 concentration was 10% higher than that of the control group. In rats fed the fish oil diet, the cytochrome P-450 concentration and NADPH-cytochrome-c reductase, aniline hydroxylase, and aminopyrine N-demethylase activities at 120 days were, respectively, 30, 48, 41, and 31% higher than those of rats fed the control diet. These enzymes were correlated very well (0.84 < r < 0.93), P < 0.05 with dietary sigma polyunsaturated fatty acids (n-3).(ABSTRACT TRUNCATED AT 250 WORDS)

The effects of dietary alpha-linolenic acid on the composition of nerve membranes, enzymatic activity, amplitude of electrophysiological parameters, resistance to poisons and performance of learning tasks in rats.

Feeding rats diets containing oils that have a low alpha-linolenic acid [18:3(n-3)] content, such as sunflower oil, results in reduced amounts of docosahexaenoic acid [22:6(n-3)] in all brain cells and organelles compared to rats fed a diet containing soybean oil or rapeseed oil. During the period of cerebral development there is a linear relationship between the n-3 fatty acid content of the brain and that of food until alpha-linolenic acid represents approximately 200 mg/100 g food [0.4% of the total dietary energy for 18:3(n-3)]. Beyond that point brain levels reach a plateau. Similar values are also found for other organs. The level of 22:6(n-3) in membranes is little affected by the dietary quantity of linoleic acid [18:2(n-6)] if 18:3(n-3) represents approximately 0.4% of energy. In membranes from rats fed diets containing sunflower oil, Na+, K(+)-ATPase activity in nerve terminals was 60%, 5'-nucleotidase in whole brain homogenate was 80%, and 2',3'-cyclic nucleotide 3'-phosphodiesterase was 88% of that in membranes from rats fed diets containing soybean oil. A diet low in alpha-linolenic acid leads to anomalies in the electroretinogram, which partially disappear with age. It has little effect on motor activity, but it seriously affects learning tasks as measured with the shuttle box test. Rats fed a diet low in alpha-linolenic acid showed an earlier mortality in response to an intraperitoneal injection of a neurotoxin, triethyltin, than did rats fed a normal soybean oil diet.

Brain cell and tissue recovery in rats made deficient in n-3 fatty acids by alteration of dietary fat.

Rats were fed a purified diet containing either 1.5% sunflower oil [940 mg linoleic acid [18:2(n-6)]/100 g diet; 6 mg alpha-linolenic acid [18:3(n-3)]/300 g diet] or 1.9% soybean oil [940 mg 18:2(n-6)/100 g diet; 130 mg 18:3(n-3)/100 g diet]. In all cases and tissues examined 22:6(n-3) was lower and 22:5(n-6) was higher in rats fed sunflower oil than in rats fed soybean oil. Levels of 22:4(n-6) and 20:4(n-6) were largely unaffected. Expressed as a percentage of that in soybean oil-fed rats, 22:6(n-3) in sunflower oil-fed rats was as follows: neurons, 49; astrocytes, 47; oligodendrocytes, 10; lung, 27; testes, 32; retina, 36; liver, 35 and kidneys, 45. Ten wk after the change in diet of 60-d-old rats from one containing sunflower oil to one containing soybean oil, the fatty acid composition of the brain cells had not reached control values, e.g., that obtained in animals continuously fed soybean oil; 22:6(n-3) was 77, 65 and 80% of control levels for astrocytes, oligodendrocytes and neurons, respectively. In contrast, the recovery measured by the decay of 22:5(n-6) was complete within 10 wk. For 22:6(n-3), it took approximately 2 wk for liver and kidney to recover to the control value, 3 wk for lung, 6 wk for retina and 10 wk for testes. The decrease of 22:5(n-6) was rapid: the control values were reached within 2 wk for kidney, liver and lung and within 6 wk for retina.(ABSTRACT TRUNCATED AT 250 WORDS)

Slow recovery of the fatty acid composition of sciatic nerve in rats fed a diet initially low in n-3 fatty acids.

The sciatic nerve of rats fed sunflower oil (6 mg 18:3-n-3/100 g of diet) presented dramatic alterations in the long chain polyunsaturated fatty acids in comparison with those fed soy oil (130 mg 18:3n-3/100 g of diet). In both 15-day-old and 60-day-old animals fed sunflower oil, 22:6n-3 (cervonic acid) was four-fold less, 22:5n-6 was 10-fold greater; adrenic acid (22:4n-6) was slightly greater and arachidonic acid (20:4n-6) was close to that in rats fed soy oil. The percentage distribution of total polyunsaturated fatty acids as well as the individual saturated and monounsaturated fatty acids were the same in both groups. When the sunflower oil-fed animals were switched to a soy oil-containing diet for either 15 or 60 days, the percentage distribution of 22:6n-3 increased slowly to reach the control value 2.5 months later. Conversely 22:5n-6 decreased slowly. The decay of 22:5n-6 was more rapid than the increase of 22:6n-3.

Recovery of altered fatty acid composition induced by a diet devoid of n-3 fatty acids in myelin, synaptosomes, mitochondria, and microsomes of developing rat brain.

Rats were fed a semisynthetic diet containing either sunflower oil or soya oil. Half the litter fed with sunflower oil diet was changed to a soya oil diet when the pups were 15 days old (during active myelination). Fatty acid analysis was then performed on subcellular fractions of the animals fed (a) soya oil, (b) sunflower oil, and (c) soya oil replacing sunflower oil from the 15th day, to determine the speed of the recovery. All material from animals fed sunflower oil showed an important reduction in docosahexaenoic acid (22:6 n-3), compensated by an increase in docosapentaenoic acid (22:5 n-6), whereas arachidonic acid (20:4 n-6) was not affected. In all fractions examined, when sunflower oil was replaced by soya oil in 15-day-old pups the recovery started from the very first day but lasted more than 2 months (this recovery was determined by the increase of 22:6 n-3 up to the normal value and decrease of the 22:5 n-6). In addition a delay was found for myelin recovery, starting only from the 25th day.

[Study of cyclic AMP in rat tissue during the phase of hypocalcemic activity of parathyroid hormone]. / Etude de l'AMPc tissulaire chez le rat pendant la phase d'action hypocalcémiante de l'hormone parathyroïdienne.

As soon as two minutes after PTH i.v. injection the blood and kidney AMPc level is maximally increased but the lowering blood calcium effect remained till to ten minutes. At this time the calvaria AMPc level reached its maximum just at the onset of hypercalcemic effect of PTH. Thus AMPc increase in tissues is consistent with the two opposite effects of PTH.