Eldon G. Hill

The thiobarbituric acid reaction and the autoxidations of polyunsaturated fatty acid methyl esters.

Abstract The TBA reaction of autoxidized single methylene-interrupted diene, triene, tetraene, pentaene, and hexaene fatty acid esters has been measured at various stages of autoxidation. Linoleate free of higher polyunsaturates gave no TBA color at early stages of oxidation. At early stages of oxidation TBA values of triene, tetraene, pentaene, and hexaene were found to vary linearly with diene conjugation, peroxide value, and oxygen uptake. TBA values of triene, tetraene, pentaene, and hexaene were found to vary linearly with diene conjugation throughout the course of the oxidation. A mechanism is proposed for TBA reactant formation from methylene-interrupted polyunsaturated compounds with cyclic peroxide as an intermediate in the formation of malonaldehyde. The existence of a cyclic five-membered ring peroxide in the oxidation products of polyunsaturated acids is postulated. The mechanism of oxidation of methylene-interrupted trienes, tetraenes, pentaenes, and hexaenes postulates an additional step in chain propagation involving intramolecular rearrangement of the hydroperoxy free radical to a free radical bearing a closed five-membered ring peroxide. The scope of usefulness and the limitations of the TBA test are discussed.

Effects of essential fatty acid deficiency in young swine.

Summary Rigid exclusion of essential fatty acids from the diet of young swine leads to a deficiency disease not characterized by consistent or early skin lesions. The severity of the dietary regime imposed caused high mortality, but of the 8 pigs that survived beyond the normal weanling age, skin lesions were observed in one and aortic lesions in 5, at or before 98 days on experiment. The data suggest that essential fatty acids are required by swine and that deficiency of essential fatty acids may lead to impairment of the arterial wall.

Dietary fats containing concentrates ofcis ortrans octadecenoates and the patterns of polyunsaturated fatty acids of liver phosphatidylcholine and phosphatidylethanolamine

The effects of the mixedcis- 18∶1 isomers and mixedtrans-18∶1 isomers present in partially hydrogenated soybean oil (PHSO) upon the patterns of polyunsaturated fatty acids (PUFA) in liver phosphatidylcholine (PC) and phosphatidylethanolamine (PE) were studied in rats fed concentrates ofcis- 18∶1 ortrans- 18∶1 isomers isolated as triacylglycerides from PHSO. Thecis- 18∶1 andtrans- 18∶1 concentrates were fed at levels equal to those present in PHSO fed at 17.9% of the diet. All diets contained the required amounts of both linoleic and linolenic acids. Thetrans- 18∶1 concentrate was found to suppress the levels of 20∶4ω6 and 20∶3ω9, and to increase the levels of 18∶2ω6 and 20∶5ω3 in PC and PE. Thecis- 18∶1 concentrate suppressed 20∶4ω6 in PC, 20∶5ω3 in PC and PE, and 18∶2ω6 was more effective than thetrans concentrate in suppressing 22∶6ω3. Thetrans- 18∶1 concentrate was more effective in suppressing 20∶4ω6. Thetrans-18∶ isomers appear to modify PUFA metabolism by inhibition of PUFA synthesis, whereas thecis- 18∶1isomers appear to compete with 2-position fatty acyl transfer and to inhibit ω3 PUFA acylation.

Development of hyperbetalipoproteinemia in pigs fed atherogenic diet

Hormel miniature pigs were studied over a period of 24 weeks to observe the changes in serum lipoprotein pattern, cholesteryl ester, free cholesterol, and triglyceride in the atherogenic-fed pigs. These pigs were compared to age-related control animals in our breeding herd. Pigs fed the atherogenic diet (20% tallow, 3% cholesterol, and a bile supplement) exhibited a heterogeneous response but showed mean increases in cholesteryl ester (571 mg/dl) and free cholesterol (226 mg/dl), a slight increase in triglyceride (58 mg/dl), and a severe hyperbetalipo proteinemia. Three animals with the highest cholesteryl ester (all above 600 mg/dl) had resolvable β components in their 1.006 g/ml very low density lipoprotein fraction (type III), as well as huge increases in the Sf 12–20 low density lipoprotein fraction. The other four animals had substantial increases in Sf 0–20, and the three highest had much of their low density lipoprotein in the Sf 12–20, or “remnant” fraction. The test pigs all showed gross lesions in the aorta with an increase in cholesteryl ester and free cholesterol in the tissue as compared with control animals.

Accumulation and depletion of trans octadecenoic acid in rat peripheral nerve phospholipid

The accumulation and depletion of trans 18:1 acids in the sciatic nerve phospholipids was studied in rats fed a diet containing 18% partially hydrogenated soybean oil of which 45% was trans 18:1. The nerve phospholipid of rats fed partially hydrogenated soybean oil beginning at weaning age reached a maximum incorporation of trans 18:1 or 0.8% in 4 weeks; whereas the nerve phospholipid of 18-day-old pre-weanling pups of mothers fed the partially hydrogenated soybean oil diet since their weaning contained 3.3% trans 18:1. The trans content decreased rapidly after the weaning of these second-generation rats to a steady-state level 50% higher than the maximum level reached in the first generation. Upon removal of partially hydrogenated soybean oil from the diet, the trans 18:1 of nerve phospholipid decreased much more slowly than from liver or heart phospholipid. Essential fatty acid deficiency had no influence on incorporation or removal of trans 18:1 in nerve phospholipid. The accumulation and depletion of trans 18:1 in nerve phospholipid of second-generation partially hydrogenated soybean oil-fed rats paralleled the changes of polyunsaturated fatty acids and was quite different from the changes observed in 18:0 and cis 18:1. Polyunsaturated fatty acids increased in nerve phospholipid from second but not first-generation rats fed partially hydrogenated soybean oil and declined rapidly when partially hydrogenated soybean oil was removed from the diet.

Replacement of Pteroylglutamic Acid by Folinic Acid for the Chick.

Summary Studies on the biological activity of synthetic folinic acid show that it may replace pteroylglutamic acid in the diet of the chick.

HYPERCHOLESTEROLEMIC EFFECT OF MENHADEN OIL IN THE PRESENCE OF DIETARY CHOLESTEROL IN SWINE.

Summary Thirty male miniature swine were fed a beef tallow basal ration supplemented with crude soybean phosphatides and menhaden oil with and without 0.5% cholesterol for a period of 48 weeks. The animals that received no cholesterol supplement all maintained normal plasma cholesterol values (75–85 mg %). The swine fed soybean phosphatides plus cholesterol showed no change in plasma cholesterol values. The swine fed beef tallow showed on cholesterol supplementation a rise in plasma cholesterol, but returned to normal in 12 weeks. The swine fed menhaden oil showed a 100% increase in plasma cholesterol when supplemented with 0.5% cholesterol and, although this level decreased, it remained substantially above the remaining groups throughout the experiment. Fecal analyses of cholesterol showed much less cholesterol in the feces of fish oil-fed pigs supplemented with cholesterol, indicating that the fish oil (or the highly unsaturated fatty acids in fish oil) may have facilitated the absorption of the dietary cholesterol. The heart and liver analyses showed much lower levels of cholesterol than the other groups, suggesting that the polyunsaturated fatty acids of the fish oil may have aided in transport of the cholesterol to prevent an accumulation in these tissue sites.

Influence of sex and dietary phosphatides on cholesterol levels in blood plasma of swine.

Summary 1) Body weights and blood plasma cholesterol values were observed periodically in male and female miniature swine fed high-tallow diets supplemented with dietary soybean phosphatides, for 17 weeks. Body weight changes were uniform throughout and were not related to sex or dietary treatment. The plasma cholesterol values of females as a whole after 3 weeks on the test, were significantly higher than for males (P < .05) and remained so after 6 weeks on test diets (P < .01), when gilts were pregnant. 2) While differences in plasma cholesterol values of several groups, due to dietary treatment, were not statistically significant at the 5% level, definite trends were observed. Plasma cholesterol values of all pigs fed the low-fat diet were reduced during test period, while those fed the high-tallow diet increased slightly. All 3 of the dietary soybean phosphatide supplements, when added to the high-tallow diets, reduced plasma cholesterol values of males. The alcohol-insoluble fraction supplement (2/3 inositol phosphatides) also slightly reduced plasma cholesterol values of females. 3) Thus, under conditions employed, soybean phosphatides incorporated in the diet appeared to counteract the hypercholesteremic effect of the diet containing a relatively high proportion of a saturated fat. 4) The tetraenoic acid concentration of plasma tended to be higher in females than in males fed comparable diets. The feeding of phosphatide supplements, while having little effect on plasma lipides of pregnant miniature pigs, promoted a marked drop in plasma cholesterol, phospholipides, and phospholipide-cholesterol ratios in male miniature pigs. There was no apparent correlation between changes in plasma polyunsaturated acids and changes in other plasma lipides during this study.

L-lyxoflavin in the starting diets of turkeys and chickens.

Summary In trials with turkey poults highly significant growth responses were obtained with male poults fed a corn-soybean diet supplemented with L-lyxoflavin. Chicks fed purified diets failed to show a growth response when the diet was supplemented with L-lyxoflavin.