In experimental animals dietary restriction reduces the body weight increase due to aging, increases longevity and delays the onset of age-related physiological deterioration, including age-related changes in serum lipids. Little is known about the influence of food restriction on brain lipids, whose concentration and composition have been shown to change with age. We studied whether some biochemical and biophysical parameters of rat brain membranes, known to be modified with age, were affected by a diet low in calories, in which 50% of lipids and 35% of carbohydrates have been replaced by fibers. The diet was started at weaning and maintained throughout the animal's entire life span. Animals fed the low calorie diet survived longer and gained less body weight than standard diet fed rats. Age-related increases in microviscosity, cholesterol/phospholipid and sphingomyelin/phosphatidylcholine ratios were reduced or restored to the levels of young animals in cortex membranes of 32 old rats fed the low calorie diet, while the age-related increase in mono- to polyunsaturated fatty acid ratios in phospholipids was further raised. In conclusion we have shown that a diet low in calories and high in fibers affects lipid composition in the rat brain, in a direction opposite to that normally believed to reduce age-related deterioration of brain functions.

Aging↗

PubMedDate not supplied

Fluorescence polarization changes with gestational age in amniotic fluid of rabbit and guinea pig.

The variation of amniotic fluid microviscosity with gestational age was measured in rat, rabbit, and guinea pig. In rat, the changes followed the same pattern as known for women, microviscosity being high during early and mid-gestation and markedly lowering 12 h before delivery. Surprisingly, an opposite trend was observed in rabbit and guinea pig amniotic fluid. Moreover, the lecithin to sphingomyelin ratio markedly rose in late gestation in all species considered. Qualitative and quantitative analysis of lipids and phospholipids were performed in woman and rabbit amniotic fluids at early and late gestational ages. Among all the parameters measured, the most important differences that can influence the amniotic fluid microviscosity are the presence of very high levels of lysophosphatidylcholine both in early and late gestation in rabbit (much higher than in woman) and the cholesterol to total phospholipid ratio which decreased with gestational age in woman but remained stable in rabbit. The Arrhenius plot of the logarithm of microviscosity against the reciprocal of absolute temperature of mature and immature amniotic fluids from woman and rabbit was also determined. The temperature profiles confirmed the differences in lipid profile between woman and rabbit in early and late gestation which could be quantified on a physicochemical basis by determining the activation energy (delta E) at 25 degrees and 37 degrees C for each curve. This confirmed the opposite patterns in woman and rabbit and showed that amniotic fluid from the immature rabbit was the most fluid.

Amniotic Fluid↗