Choliparambil K. Pushpendran

Differences in lipid peroxidation of rat liver rough and smooth microsomes.

The rough and smooth microsomes of rat liver show significant differences in lipid peroxidation induced by both NADPH and ascorbate. The parameters studied include kinetics, response towards cofactors and sensitivity to inhibitors. Smooth microsomes are more prone to lipid peroxidation with increasing concentrations of NADPH, Fe3+, ascorbate and Fe2+, and are more susceptible to inhibitors than rough microsomes. Smooth microsomes also contain higher amounts of ascorbic acid, NADPH cytochrome c reductase and total lipids, besides possessing a higher degree of unsaturation in lipids, all of which promote lipid peroxidation. Our results suggest that, although smooth microsomes are more sensitive to lipid peroxidation, they are compensated for by being more sensitive to inhibitors of lipid peroxidation.

Changes in ascorbate-induced lipid peroxidation of hepatic rough and smooth microsomes during postnatal development and ageing of rats

In female Wistar rats, sensitivity to ascorbate-induced lipid peroxidation in rough and smooth microsomes increases with age, reaching a maximum in 1-year-old rats and decreases during ageing. Time course of lipid peroxidation, and lipid peroxidation with optimum concentrations of ascorbic acid, Fe2+ and protein in rough microsomes show that 1-year-old rats are the most susceptible followed by 75-day-old, 15-day-old, 2-year-old and 1-day-old rats. However, smooth microsomes show a slightly different trend with maximum sensitivity in 1-year-old rats followed by 15-day-old, 75-day-old, 2-year-old and 1-day-old rats. Smooth microsomes are more susceptible to lipid peroxidation than the rough in all age groups except 75-day-old rats. Smooth microsomes are also more sensitive to inhibitors of lipid peroxidation. Microsomal content of phospholipid increases during postnatal development and decreases during ageing, whereas that of ascorbic acid and alpha-tocopherol do not show any particular trend.

Study on lipid peroxidation potential in different tissues induced by ascorbate-Fe2+: possible factors involved in their differential susceptibility.

Susceptibility of four major rat tissues to oxidative damage in terms of lipid peroxidation induced by in vitro by ascorbate-Fe2+ in homogenates and mitochondria has been examined. Lipid peroxidation, as assessed by thiobarbituric acid reactive substances (TBARS) and conjugated dienes was maximum in brain followed by liver, kidney and heart. However, the time course of lipid peroxidation showed different patterns in tissues examined. The higher susceptibilities of brain and liver can be explained by substrate availability and to a lesser extent the level of antioxidants. The differences observed in the tissues studied may reflect their susceptibility to degenerative diseases and xenobiotic toxicity which are considered as a result of oxidative damage to membranes.

Changes in enzymes of hepatic rough and smooth microsomes during postnatal development and ageing of rats

Significant changes are observed in wet weight, microsomal protein content and enzymes of purified rough and smooth microsomes of liver during postnatal development and ageing of female Wistar rats. Protein content of total microsomes increases up to 15 days of age and remains steady during subsequent development, unlike that of rough and smooth microsomes which shows changes throughout the same period. Activities of cytochrome P-450, cytochrome b5 and NADPH-cytochrome c reductase increase during the period of maturation and decline during senescence. The decrease during senescence is at different rates in the two microsomal fractions. Microsomal glucose-6-phosphatase, but not adenosine triphosphatase, shows a similar increase during development and decrease during senescence.

Studies on Lipids of Brain, Kidneys and Liver of Mice during Postnatal Development

The postnatal changes in distribution and synthesis of lipids of mice liver, kidneys and brain have been studied. The hepatic lipids show greater variation in females than in males during postnatal de

Induction of rat liver microsomal enzymes by cycloheximide

Abstract Administration of cycloheximide into rats induced certain enzymes of rough and smooth microsomes. NADPH cytochrome c reductase of smooth microsomes and glucose-6-phosphatase of rough and smooth microsomes attained peak activities 2 hr after cycloheximide treatment. Cytochrome P-450 and cytochrome b 5 of the rough microsomes were highest 6 hr after the antibiotic injection. On the other hand, cycloheximide reduced ATPase activity in the smooth microsomes. All the components studied except NADPH cytochrome c reductase of the smooth microsomes approached control values 24 hr after the treatment. The responses of rough and smooth microsomes toward cycloheximide were different.

Effect of temperature acclimation, X-irradiation and tail amputation on incorporation of leucine-14C into hepatic proteins of the house lizard (Hemidactylus leschenaulti)

Abstract 1. 1. Synthesis as well as the turnover of proteins is higher in the liver of animals acclimated to 37°C than in that of animals acclimated to 24°C. 2. 2. X-irradiation and tail amputation enhanced the incorporation of labelled leucine into proteins. The effect on the rate of incorporation is highest during the first hour after irradiation or amputation. 3. 3. The treatments did not seem to affect the total protein content during the course (150 min) of the experiments.

Studies in Lipogeiiesis by Red Cells of Mice

Summary. The incorporation of[1‐14C]acetate,[U‐14C]glucose and [1‐14C]palmitate into lipids of red cells from 5‐, 30‐ and 180‐day‐old mice has been studied. The results show that the cells from 5‐ and 180‐day‐old mice have greater capacity for lipid synthesis than those from 30‐day‐old animals. Ghost preparations exhibit a similar pattern of incorporation but the levels of incorporation are higher than those of intact cells. There arc age‐dependent differences in the incorporation of the precursors into various types of lipids. The results show that there are changes in the levels of free fatty acids and triglycerides of red cells as a function of animal age. No quantitative changes were observed in phospholipids and cholesterol.