Showing papers on "Lipid biosynthesis published in 1968"

Inhibition of lipid biosynthesis.

Abstract: FIGURE 1. Pathways of enzymic cholesterol synthesis involving naturally occurring 3P-hydroxysteroids containing 27 carbon atoms. This scheme depicts the known cofactors and catalytic steps consistent with the results of tkjs paper and previous findi n g ~ . ' ~ Reaction steps 4, 5, 9, and 10 are catalyzed by a A -reductase apd inhibited by triparanol and o-chlorobenzylamine; steps 3 and 8 are catalyzed by a A -reductase and inhibited by AY-9944, phenformin, triparanol, and o-chlorobenzylamine; steps 2 and 7 are catalyzed by a A5-dehydrogenase and inhibited by tolbutamide, chloropropamide, potassium cyanide (KCN), ethylenediaminetetraacetic acid tetrasodium salt (EDTA), and cysteine; steps 1 and 6 are catalyzed by AsA7-isomerase.

Control of mitochondrial lipid biosynthesis by testosterone in male sex accessory gland tissue and liver of castrate rats.

Abstract: Incorporation of 14C-acetate in vivo into total mitochondrial lipid was used as an index of mitochondrial biosynthesis in seminal vesicle, coagulating gland, ventral prostate and liver mitochondria of castrate rats receiving testosterone or equivalent amounts of vehicle. In target tissues, incorporation values were greater in mitochondria prepared from seminal vesicles and prostates after 18 hr of stimulation and in mitochondria from coagulating glands after 24 hr of stimulation. No significant differences in target organ weights or incorporation values were noted between experimental and control animals after 12 hr of androgen treatment. Incorporation of label into lipids of liver mitochondria was high but was unaffected by 3 days of androgen treatment. Comparison of incorporation values obtained from whole mitochondria and mitochondrial fragments suggests that lipids of mitochondria labeled in vivo with 14C-acetate are entirely membrane bound. (Endocrinology 82: 535, 1968)

The effect of ionizing irradiation on the lipid biosynthesis by thymus and liver.

Abstract: New Zealand rabbits, fasted for 12 hours, were subjected to 500 rads of whole-body irradiation. Analysis of thymus lipids, at various time intervals following irradiation, showed a threefold increase of triglycerides at 24 hours. Fatty acid composition of the 600 × g supernatant was not affected at 24 hours after irradiation. Lipid biosynthesis from $\text{acetate-}1\text{-}{}^{14}{\rm C}$ by the thymus homogenates was increased to a small extent at 4 hours following irradiation, while the radioactivity distribution into fatty acids was not considerably affected. Contrary to the above findings, fatty acid synthesis from $\text{acetate-}1\text{-}{}^{14}{\rm C}$ by the liver preparations showed a decreased incorporation between the fourth and twelfth hour following irradiation. Counting of the radioactivity of the separated fatty acids suggested that the system for synthesis of short-chain fatty acids was impaired as early as 4 hours following irradiation.

The control of lipid biosynthesis in liver particles

Abstract: When lipid synthesis is studied with isolated enzyme systems fortified by the necessary cofactors, it becomes apparent that the system is self-limiting ; synthesis slows clown drastically after certain amounts of products have been f0rmed.l In the following, some of the factors involved in this self-limitation are described and their possible importance for the regulation of lipid and lipoprotein synthesis is discussed. Lipid synthesis from 1 -14C-DL-cu glycerophosphate by rat liver microsome in the presence of adenosine triposphate ( A T P ) , Mg\", Coenzyme A, and palinitic acid follows a kinetics shown in FIGURE 1. The initial rate of the reaction is rapid, but then falls very low after a short time. Synthesis continues when more microsomes are added, indicating that the necessary cofactors are still available. The amount of lipid formed during this rapid synthesis is a function of the amount of microsomes employed, and it rises sharply and disproportionally with this amount. Synthesis could be raised not only by increasing the microsome concentration, but also by adding serum lipoproteins or serum albumin to the microsomes. These two activating proteins acted somewhat differently. The addition of lipoprotein converts the microsome-lipid synthesis line into a nearly straight one, thus supplying a necessary constituent of the reaction or abolishing some inhibitory factor. This effect is especially potent with low concentrations; it is less so with the higher concentrations

Lipid Biosynthesis by Bovine Mammary Cells in Vitro

Abstract: Dispersed alveolar cells from lactating bovine mammary glands actively secreted lipids both morphologically and eompositionally similar to those isolated from normal milk. Using various radioactively labeled lipid substrates, it was demonstrated that the cells possess the same biochemical capacity as the intact tissue for about three days in fresh culture. Lipogenesis markedly decreased after 48 hours in vitro. Whereas, fresh cells incorporated acetate preponderantly into triglycerides, the established proliferating cells markedly incorporated acetate into phospholipids. There is a paucity of precise information coneerning the control and regulation of milk lipid production in the bovine mammary gland, though such knowledge should have widespread interest and importance biomedieally. Milk fat, normally produced, is assembled in the mammary alveolar cells from fatty acids derived partly by de novo synthesis from acetate within these specialized cells, and partly by absorption from the blood (13). Fatty acids anabolized within these cells are predominantly saturated and contain from four to sixteen carbon atoms per molecule. Fortunately, the lipids produced by the lactating bovine mammary cell are unique, which facilitates the assessment of the biochemical fidelity of these cells when used in vitro. This report summarizes preliminary studies concerning the lipogenic properties of cultured bovine mammary cells. Methods