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Selenocysteine insertion during selenoprotein biosynthesis begins with the aminoacylation of selenocysteine tRNA[ser]sec with serine, the conversion of the serine moiety to selenocysteine, and the recognition of specific UGA codons within the mRNA. Selenocysteine tRNA[ser]sec exists as two major forms, differing by methylation of the ribose portion of the nucleotide at the wobble position of the anticodon. The levels and relative distribution of these two forms of the tRNA are influenced by selenium in mammalian cells and tissues. We have generated Chinese hamster ovary cells that exhibit increased levels of tRNA[ser]sec following transfection of the mouse tRNA[ser]sec gene. The levels of selenocysteine tRNA[ser]sec in transfectants increased proportionally to the number of stably integrated copies of the tRNA[ser]sec gene. Although we were able to generate transfectants overproducing tRNA[ser]sec by as much as tenfold, the additional tRNA was principally retained in the unmethylated form. Selenium supplementation could not significantly affect the relative distributions of the two major selenocysteine tRNA[ser]sec isoacceptors. In addition, increased levels of tRNA[ser]sec did not result in measurable alterations in the levels of selenoproteins, including glutathione peroxidase.

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Seasonal variations of total lipids, free fatty acids, triglycerides, phospholipids and cholesterol content of the freshwater fish Tilapia nilotica and the marine fish Sparus auratus were investigated. Male fish of S. auratus showed higher muscular and hepatic total lipids and hepatic free fatty acids than those of T. nilotica (P less than 0.05). The mean differences in gonadal male lipids of the two species were not significant. Tilapia nilotica female fish showed a significantly higher content of hepatic free fatty acids, phospholipids and cholesterol (P less than 0.01, 0.01, 0.05 respectively) and gonadal total lipids, triglycerides, and cholesterol (P less than 0.05) than those of S. auratus females. In contrast S. auratus females exhibited higher muscular total lipids, triglycerides, phospholipids and cholesterol content (P less than 0.01, 0.05, 0.02, 0.05, respectively) and gonadal phospholipids (P less than 0.05) than those of the T. nilotica females. In general hepatic and gonadal lipids of freshwater fish T. nilotica were higher than those of the marine fish S. auratus, and in contrast the marine fish contained higher muscular lipids than the freshwater fish.

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The effect of long acting progestational contraceptive injection, norethisterone-oenanthate was studied in twenty six women. The post injection results showed a significant decrease in total lipids, free cholesterol, total cholesterol, triglycerides, phospholipids and free fatty acids.

PIP: 26 healthy Egyptian women, aged 20-35 years, were studied to determine the effects of norethindrone-enanthate in injectable form on lipid metabolism. The dose was 200 mg, with the 1st injection being given on Day 5 of the menstrual cycle. Blood samples were taken before injection, while the subjects were in a fasting state, and 2 months after the last injection, a total of 6 months later. Injections were repeated every 2 months in the interim. Levels of total lipids, free cholesterol, total cholesterol, triglycerides, phospholipids, and free fatty acids were compared. Total serum lipids decreased significantly after 2, 4, and 6 months of injection (significantly different from pretreatment values at the level of 1%). Total and free serum cholesterol both decreased significantly after 2, 4, and 6 months of injection. Serum triglycerides and serum phospholipids were likewise significantly decreased after 2, 4, and 6 months of injection. however, plasma free fatty acids were significantly lower after 2 months but not after 4 and 6 months of injection. The decrease in free fatty acids may be attributed to suppression of lipolysis due to decreased cyclic adenosine monophosphate or to epinephrine suppression; triglyceride suppression may have resulted from a possible effect on estrogen receptors decreased transport of lowered fatty acids to adipose tissues or increased lipoprotein lipase; phospholipid reduction may be related to the lessening of fatty acids being transported to the adipose tissues or to impaired liver function; and total lipid suppresson was thought to be the result of the significant decrease in blodd lipid fractions observd. it is concluded that this injectable preparation is more satisfactory, in terms of lipid metabolic effects, than combined contraceptive preparatios.

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Pancreatic cancer was induced in male Sprague-Dawley rats by 7,12-dimethylbenz(a)anthracene. Pancreatic amylase has been purified from normal as well as treated rats after 2, 3 and 4 months of exposure to the carcinogen. The level of pancreatic amylase in rats with pancreatic carcinoma was significantly decreased (L.S.D.-5.25). Purified enzyme was then subjected to disc gel electrophoresis. Both normal and treated rats gave the same electrophoretic pattern (three bands: two major, and one minor). Therefore, there was no isoenzyme component in pancreatic extracts of rats bearing pancreatic cancer that could be held to be peculiar for pancreatic cancer. Histological findings showed a decrease in zymogen content together with its total absence in some areas of malignant cells. The data obtained suggested that the original carcinogenic events were associated with a decrease in amylase initial activity, and did not involve alteration in gene expression related to amylase biosynthesis.

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