F.D. Sauer

Relationship between erucic acid and myocardial changes in male rats.

The back and belly fat of pigs fed a diet containing 20% by wt rapeseed oil (22% erucic acid) for 16 weeks was rendered into oil. This rendered pig fat, which contained 5.6% erucic acid, was fed to male rats in three separate experiments at 20% by wt of the diet for 16 weeks. In experiment I rendered pig fat was compared only toBrassica campestris var. Span rapeseed oil containing 4.8% erucic acid. In experiments II and III, rendered pig fat was compared to commerical lard containing 0.2% docosenoic acid, commercial lard to which 5.4% free erucic acid was added, and Span rapessed oil. There was no significant (P<0.01) differences observed in the level of erucic acid in the hearts of rats fed diets of rendered pig fat, Span rapeseed oil, or commercial lard plus erucic acid. However, the incidence (P<0.001) and severity (P<0.01) of cardiac lesions were significantly higher in Span rapeseed oil fed rats compared to rats fed control diets. The number of rats affected or the severity of lesions in the rendered pig fat fed group was not significantly different from controls. The results of this study indicate that the myocardial lesions associated with feeding 20% rapeseed oil diets are not related to the content of erucic acid per se. The possible reasons why rapeseed oil causes cardiac lesions in rats are discussed. It is suggested that a triglyceride imbalance in the oil might play an important role in causing these lesions in rats.

Brassica campestris var. Span: II. Cardiopathogenicity of fractions isolated from span rapeseed oil when fed to male rats

Rapeseed oils low in erucic acid caused myocardial lesions when fed to weanling male rats for 16 weeks. The cardiopathogenic properties appear to be associated with the triglycerides of the oil, and not to nontriglyceride components present in fully refined rapeseed oil. Cardiac lipid analysis confirmed that erucic acid accumulation was proportional to the concentration of this acid in the diet.

Failure of dietary erucic acid to impair oxidative capacity or ATP production of rat heart mitochondria isolated under controlled conditions

1. Male, 8-week old rats were fed Purina Rat Chow for semisynthetic diets containing 20% by weight of rapeseed oil or corn oil for 3 days. 2. The hearts from the animals fed the three diets were analyzed for total lipid, phospholipid, free fatty acids, cholesterol esters, tri-, di- and monoacylglyerols. There was a seven-fold increase in the levels of triacylglycerols in the hearts of rats fed rapeseed oil diet compared to the levels in the hearts of animals fed the other two diets. Smaller increases in the content of other neutral lipid fractions were also observed. 3. Heart mitochondria from the three groups of animals were isolated under controlled conditions in the presence or absence of heparin. The rats of oxidation of different substrates and of ATP synthesis by these mitochondria were compared. 4. Mitochondria isolated in the absence of heparin from rapeseed oil-fed rats had much lower rates of oxidation and ATP synthesis than mitochondria isolated similarly from rats fed the other two diets. 5. With mitochondria freshly isolated in the presence of heparin, no significant differences in rates of oxidation or ATP synthesis were found among the three groups of animals. 6. It is concluded that, when properly isolated, mitochondria from rapeseed oil-fed rats are functionally intact with respect to oxidation and energy-coupling capacity.

Valinomycin inhibited methane synthesis in Methanobacteriumthermoautotrophicum

Abstract Methanobacterium thermoautotrophicum cells, incubated anaerobically under H2 in 0.1 M KCl or 0.1 M NaCl, above pH 7.5, are interior acid with respect to the incubation medium. The pH gradient thus established can be discharged by either carbonyl cyanide m-chlorophenylhydrazone or valinomycin at high concentration (17μM). In these cells, which actively synthesize CH4 from CO2 and H2, methanogenesis is strongly inhibited when the pH gradient is discharged.

Brassica campestris var. Span: I. Fractionation of Rapeseed oil by molecular distillation and adsorption chromatography

Procedures for the large scale isolation of pure triglycerides and fractions rich in nontriglyceride components from Span rapeseed oil are described. Fractionation ofBrassica campestris var. Span rapeseed oil by molecular distillation yielded 4 triglyceride fractions, all of which contained traces of sterol esters. An additional triglyceride fraction rich in free and esterified sterols and other volatile components was obtained from the oil. Separation by adsorption chromatography of Span rapeseed oil yielded three fractions: A) a pure triglyceride fraction; B) a triglyceride fraction rich in sterol esters; and C) another fraction containing free sterols and other polar components.

The accumulation of citrate cycle intermediates in rat liver cells oxidizing palmitate

Abstract 1. 1. Rat liver cells oxidizing [1- 14 C]palmitate or [1- 14 C]palmitoyl-carnitine show linear rates of 14 CO 2 output after an initial 10-min lag period. 2. 2. During this interval, there was considerable accumulation of 14 C in water soluble organic acids, acetyl-CoA, and acetyl-carnitine, but much less radioactivity accumulated in palmitoyl-CoA, phospholipid or neutral lipid fractions. 3. 3. It was concluded that the lag period in 14 CO 2 output was not the result of rate limiting reactions involving palmitate uptake, transport or activation to the CoA or carnitine ester, but resulted from an initial accumulation of 14 C in acetyl-CoA, acetyl-carnitine, and water-soluble organic acids which subsequently were oxidized to 14 CO 2 .

Structure of purified cytoplasmic cofactor from methanobacterium thermoautotrophicum

The reduction of methylcoenzyme M to methane is known to require a heat stable and oxygen sensitive cofactor. Recently it has been shown that the active site of this cofactor is 7-mercaptoheptanoylthreonine phosphate. The present study shows that in the complete structure of this cofactor 7-mercaptoheptanoylthreonine phosphate is linked by pyrophosphate to two N-acetyl-glucosamine residues and an unidentified terminal group R with m/z 214. By fast-atom-bombardment mass spectrometry the intact cofactor, isolated as the mixed disulfide with 2-mercaptoethanol, was shown to have a molecular weight of 1084.5. The pyrophosphate bond is quite labile and undergoes hydrolysis or prolonged storage. This lability of the pyrophosphate bond may explain why the intact cofactor has not been isolated until now.

Methane production by cell-free particulate fraction of rumen bacteria.

Rumen bacteria retained methanogenic activity when stored at −60° under H2. This activity, which resides in Methanobacterium ruminantium and Methanobacterium mobilis, is not lost when the cells are broken, as has been suggested. Unlike in Methanosarcina barkerii and Methanobacterium M.o.H., in rumen bacteria methanogenic enzymes are not soluble but readily precipitated at 15,000 g. Methane was synthesized from tetrahydrofolate derivatives but at slower rates than from CO2. From the data, it was not possible to determine if methyl- and methylene tetrahydrofolate were oxidized to CO2 prior to reduction to CH4. In room light, CH3-B12 was reduced to CH4 non-enzymatically in the presence of protein. When the reactions were carried out in the dark, very little CH4 was formed from CH3-B12 by rumen bacterial enzymes. The cell-free particulate fraction did not require added ATP for methanogenesis but showed an absolute requirement for H2.

Effect of cold stress on rapeseed oil fed rats

No mortality was observed in 6 week old male Sprague-Dawley rats subjected to cold at 4 C for 3 weeks and fed either a control diet (Chow) or a semisynthetic diet containing 20% by wt rapeseed oil high in erucic acid (23.6%). All rats fed the Chow diet and 17 of 20 rats fed the rapeseed oil-containing diet survived 4 weeks in the same environment. Three rats on the latter diet died of self-mutilation. Marked myocardial lipidosis as well as a large accumulation of 20∶1 and 22∶1 was observed in the hearts of rats fed the rapeseed oil-containing diet. Five of 20 rats on the Chow diet and 2 of 20 rats on the rapeseed oil-containing diet had focal necrotic areas in the myocardium.

The separation of pyruvate-ferredoxin oxidoreductase from Clostridium pasteurianum into two enzymes catalysing different reactions

The ferredoxin requiring cleavage of pyruvate to acetyl-CoA and CO2 is catalyzed by pyruvate ferredoxin oxidoreductase (pyruvate:ferredoxin oxidoreductase (CoA-acetylating):, EC 1.2.7.1). The same enzyme is thought to catalyze the reversal of this reaction, i.e. the synthesis of pyruvate from acetyl-CoA and CO2 in the presence of reduced ferredoxin. Evidence is presented that the forward and reverse reactions are catalyzed not by one, but by two proteins that are clearly separable by Sephadex G-200 gel filtration.