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Mechanisms of interference of nonesterified fatty acids in radioimmunoassays of steroids.

Addition of nonesterified fatty acids caused an apparent increase in unbound steroid present in supernatants in radioimmunoassays for steroids utilizing dextran-coated charcoal. Nonesterified fatty acid interference occurred at the initial binding interaction between steroid and its antiserum, and also at the step separating bound from unbound steroid. It was determined that nonesterified fatty acids, which had been added to radioimmunoassays, formed micelles and trapped steroids. The extent of the entrapment was inversely related to the number of polar groups in the steroid molecule, that is, hydrophobic steroids more easily interacted with the nonesterified fatty acid micelles. However, if the charcoal concentration were increased, the nonesterified fatty acid effect was eliminated for assays of polar steroids and greatly reduced for non-polar steroid assays.

Binding Sites

The determination of nonesterified fatty acids in blood serum using a stable cupric reagent.

A modification of the method for the determination of nonesterified fatty acids in blood serum using a stable cupric reagent stabilized with sodium citrate, has been developed. 33 g of NaCl are dissolved in 100 ml of the described reagent, and its pH should not be additionally adjusted. The reagent is stable for at least one year if kept in the refrigerator at 5 degrees C. The determination may be done in 0.1--0.2 ml of blood serum. The relationship between the absorbance and concentration of palmitic acid is still linear at a concentration of 2500 mumol/l. Error of the method is +/- 3%.

Citrates

[Variation in serum nonesterified fatty acids during glucose tolerance test in undernourished patients with anorexia nervosa and in obese patients].

Intravenous glucose tolerance tests (0,33 g glucose per kg body weight) are performed in 11 self starved women suffering from anorexia nervosa, 10 obese and 8 normal women. They have no genetic or chemical diabetes and belong to the same age group. Plasma concentrations of immuno-reactive insuline (IRI) and non esterified fatty acids (NEFA) are determined during these tests. The basal concentrations of NEFA are very high in the obese patients. In the starved women the elevation of the basal plasma NEFA concentration is less striking and statistically not significant. The plasma level of NEFA is reduced in all subjects by hyperinsulinism secondary to hyperglycemia. This drop in NEFA concentration is significantly reduced in the obese patients and markedly inhibited in the starved women. This observation points toward an increased resistance to the antilipolytic action of insulin in anorexia nervosa because, in these patients, the glucose load determines a normal increase in plasma IRI but the fall in plasma NEFA concentration is severely impaired.

Adolescent

[Studies of the spectrum of nonesterified fatty acids in blood and muscle tissue of swine. 1. Effect of genotype (muscular substance)].

The percentual composition of unesterified fatty acids in M. longissimus dorsi was determined by means of gas chromatography, and its correlations with the given genotype and pork condition were studied. Polyene fatty acids recorded from the Piétrain race deviated (C-18:2, C-18:3, C-20:4) from values recorded from large white and improved land race pigs. Animals of PSE nature were like Piétrain probands, in that their monoene acids were higher and diene acids lower by percentage than the comparable values in animals of normal pork condition.

Animals

Comparison of lipid status in the hearts of piglets and rats on short term feeding of marine oils and rapeseed oils.

A series of 4 experiments with piglets and one experiment with rats has been conducted to establish the cardiac lipid status of weanling (3 weeks old) male animals fed fats with different contents of docosenoic fatty acids. Experimental fats were rapeseed oil (RSO) (48.0% 22:1), refined fish oil (RFO) (14.6% 22:1), partially hydrogenated fish oil (PHFO) (14.3% 22:1) and lard (0% 22:1) combined with sunflower seed oil (SFO) in different proportions in diets with 21% total fat. Lipidosis could not be detected in piglets as increased heart weights, by chemical assay for myocardial contents of triglycerides, or by accumulation of docosenoic fatty acids or nonesterified fatty acids (NEFA). In rats, diets with RSO at a level of 16% increased myocardial triglyceride and docosenoic fatty acid contents about 7 times while the effect on cardiac NEFA was inconsistent. Histological examinations of the hearts revealed stainable intracellular fat droplets in some piglets fed 16% RSO for 8 to 13 days, but not after 2, 4 and 6 and 16, 19 and 22 days of feeding. After 10 days of feeding, mild to moderate histological lipidosis was found in piglets fed diets containing 2% or more of 22:1 fatty acids, with no significant difference between RSO, RFO and PHFO in this respect. The same diets in rats gave about 5 times more histological lipidosis than in piglets. This is attributed to a difference in species response, the rat reacting in a more pronounced manner than the piglet. The cardiac lipidosis no-effect level in piglets corresponded to a daily intake of docosenoic fatty acids of 0.4 g per kg body weight. Mild lipidosis was also found in a few animals on docosenoic acid-free diets.

Animal Feed

Endocrine control of energy metabolism in the cow: correlations of hormones and metabolites in high and low yielding cows for stages of lactation.

Measures of hormones and metabolites in blood plasma of high and low yielding cattle matched for diet and stage of lactation were investigated for relationships between milk yield, body weight, and concentrations of hormones (prolactin, growth hormone, insulin, and thyroxine) and metabolites (glucose, nonesterified fatty acids, beta-hydroxybutyric acid, and L-lactic acid) for stages of lactation. A first approach correlated total milk yields of 15 cows with average constituents during the four 24-h blood samplings through the first 27 wk of lactation. The second examined associations of changes with sampling periods in milk yield or body weight with changes in hormones and metabolites. Total milk yield of the high yielding group was correlated positively with ratios of growth hormone/thyroxine and glucose/thyroxine and correlated negatively with thyroxine. Changes in growth hormone and its ratio to insulin, and changes in yield were correlated positively for groups combined. Changes in thyroxine were correlated negatively with changes in yield. Changes in liveweight gain were related positively to insulin and lactic acid and negatively with changes in growth hormone. Changes in growth hormone were related positively to changes in nonesterified fatty acids.

Animals