A species comparison of liver slice synthesis and secretion of triacylglycerol from nonesterified fatty acids in media.

The ability of liver slices from eight species to synthesize and secrete triacylglycerol from nonesterified fatty acids contained in media was investigated. Species were grouped according to the relative proportion of lipogenesis occurring in the liver. The rate of liver triacylglycerol synthesis from nonesterified fatty acids in media was similar among species studied. Liver slices from species in which the liver contribution to lipogenesis is minor (sheep, cattle, pig and guinea pig) secreted less triacylglycerol synthesized from nonesterified fatty acids than did liver slices from species in which lipogenesis occurs predominantly in the liver (chicken and fish) or in liver and adipose tissue (rat and rabbit). The results suggest that the ability of liver to secrete triacylglycerol in very low density lipoproteins is proportional to the liver's lipogenic capacity.

The chemical, physical and biological properties of a neat cutting oil during prolonged use in a large manufacturing facility.

A 5-year study was conducted to investigate changes in the chemical, physical and biological properties of a neat cutting oil during prolonged use in a large manufacturing facility. Samples of cutting oil and other materials as appropriate, were collected at regular intervals. They were analysed for individual and total 4-6 ring polycyclic aromatic hydrocarbons (PCAs), additive and wear elements, boiling range, viscosity and particulates and in addition they were tested biologically to determine irritancy, sensitization and carcinogenic potential. Records were kept of plant utilization data and all oil additions, including the headstock lubricant and hydraulic oil which entered the cutting oil as contaminants on a regular basis. The cutting oil was 'laundered' each year. This involved removal of water and particulates, the lowering of viscosity by addition of mineral seal oil and the adjustment of the additive balance. The total amount of new oil entering the system during the study period amounted to an oil renewal rate averaging 38% by volume per annum. The generation of individual PCAs during the use of the cutting oil was slow and the dilution effect of oil additions prevented their excessive build-up. An equilibrium was reached after 2-3 years. The low level of build-up of individual PCAs was sufficient to produce a measurable increase in total PCAs determined by a gravimetric method. Laundering had no effect on individual PCA content or on the presence of wear elements but was useful in maintaining the physical properties and additive content. No evidence of any increase in irritancy, sensitizing or carcinogenic potential was found in the course of the study. These findings may also be applicable to other cutting oil systems, if the manner of use, the solvent-refined quality of all oils used, rate of oil losses and additions and the volume of the systems, are comparable with those described in the study.

Effect on days of lactation and methionine hydroxy analog on incorporation of plasma fatty acids into plasma triglycerides.

Methionine hydroxy analog has been proposed to stimulate hepatic lipoprotein synthesis and incorporation of plasma fatty acids into plasma triglyceride. Seven cows were fed diets containing 0 or 30 g analog/d starting 14 d prepartum. At approximately 30 and 60 d postpartum, cows were continuously infused intravenously with 1-[14C] palmitic acid for 160 min to achieve steady-state labeling of plasma fatty acid and triglyceride. Turnover of fatty acid and transfer quotients for triglyceride and CO2 were 3.3 and 2.7 mmol min-1; 13.0 and 10.0%; and 8.0 and 5.0%, for control and analog, respectively. Proportion of fatty acid turnover incorporated into triglyceride and CO2 were 14.0 and 15.0%; and 21.0 and 18.0, respectively, for control and analog. Analog increased 14C recovered in milk fat (52 vs. 36%). Plasma concentration of fatty acids, percent oxidized to CO2, and percent of CO2 from fatty acids decreased with increasing lactation days. Milk fat percent and yield, fatty acid turnover, and oxidation were positively correlated with concentration of plasma fatty acids, whereas fatty acid incorporated into plasma triglyceride was negatively correlated with fatty acid concentration. The data suggest that hepatic triglyceride secretion is not increased in early lactation; further, no effects of analog on lipid metabolism were detected.

Turnover of hepatic and plasma triacylglycerol in sheep.

Contributions of the intestine and liver to triacylglycerol (TG) formation from endogenous fatty acids were investigated in sheep. Cannulation and sampling of the intestinal lymph ducts and portal veins of two mature, nonpregnant ewes followed by an i.v. dose of 100 microCi of [14C]palmitate into a mesenteric cannula suggested intestinal contribution to endogenous TG production to be of no consequence. Turnover rates of TG within the plasma, hepatic microsomal and hepatic fat droplet compartments of four wethers averaged 20 +/- 8, 7.8 +/- 1.5 and 2.3 +/- .8 mg.h-1.kg body weight-1, respectively. A large, relatively inert pool of fat droplets with a slow turnover contained between 80 and 90% of the total hepatic TG. Hepatic TG concentration and turnover rates within the hepatic microsomal and fat droplet pools were inversely (r = -.86) and positively (r = .99) correlated, respectively, indicating that hepatic secretion of TG as lipoprotein was decreased as hepatic TG concentration increased. The model developed from these figures suggest that 40% of the plasma TG turnover is of endogenous origin and that this percentage value decreases when hepatic TG content is increased.

Effect of bile acids and diet composition on lipid absorption in chickens with cannulated bile ducts.

The effect of bile acids on lipid research was examined in meat-type chicks, 8 weeks of age, with cannulated cystic and hepatic ducts. The procedure allowed for biliary collection in free-roving birds. Shams retained 90 to 92% dietary fat and those with cannulated ducts retained 43 to 72%. Addition of .04, .08, or .16% cholic acid or .08% freeze-dried chicken bile did not improve lipid retention significantly. The percentage retained for tallow and corn oil was 57 and 64%, respectively, far less then the 75 and 90% values, respectively, obtained in normal chickens. Neither practical-type nor purified-type diets, saturated (tallow) nor unsaturated (corn oil) fats at 8% of the diet significantly influenced lipid retention in chickens with cannulated ducts. In these chickens, percent dry matter retained of the purified diet was 81%, a significantly higher value than the 62% retained of the practical-type diet.