THERE have been only a few reports in the literature concerning the oxidative metabolism of arterial tissue." Maier and Haimovici were the first to compare the oxidative capacity of different segments of normal rabbit aorta, using succinate and pphenylenediamine as substrates. Their results were reported as c. mm. O2 consumed per mg. dry weight of tissue per hour. They demonstrated no significa...

During the course of feeding experiments with nn-phenylalanine, labeled in the ring with deuterium, it was found that the liver and carcass cholesterol of the rats contained deuterium. Further, liver slice studies with ring-labeled phenylalanine showed that the deuterium content of the cholesterol was not proportionately lowered by the presence of large excesses of non-isotopic acetate.’ It has...

Several compounds were evaluated in vitro as alternative electron sinks to ruminal methanogenesis. They were incubated with ruminal fluid, buffer mixture, and finely ground alfalfa hay for 24 h, at 0, 6, 12, and 18 mM initial concentrations. The propionate enhancer oxaloacetic acid, the butyrate enhancer beta-hydroxybutyrate, and the butyrate unsaturated analog 3-butenoic acid were ineffective ...

Recently considerable work has been reported on the enzyme system in mammalian liver which metabolizes tyrosine to fumarate and acetoacetate. This conversion has been shown to consist of several steps, involving first a transamination of tyrosine to p-hydroxyphenylpyruvic acid, and subsequent oxidation of this intermediate to 2,5-dihydroxyphenylpyruvic acid, then to homogentisic acid, and final...

In this sensitive, reproducible method for determination of D-3-hydroxybutyrate (3-OHB) in plasma, it is converted to acetone by use of 3-hydroxybutyrate dehydrogenase (EC 1.1.1.30)/lactate dehydrogenase (EC 1.1.1.27) coupled with acetoacetate decarboxylase (EC 4.1.1.4). The resulting acetone is detected by head-space gas chromatography. The lowest concentration of 3-OHB detectable in plasma wa...

The regulation of the pyruvate dehydrogenase multienzyme complex was studied in the isolated perfused rat heart. Because 95% of the “CO2 produced as a result of the decarboxylation of [l-‘4C]pyruvate occurs via pyruvate dehydrogenase in the heart, the rate of 14COz production from infused [l-‘4C]pyruvate was utilized as the monitor of the metabolic flux through this enzyme complex. In contrast ...

A sensitive and specific procedure is described for the determination of serum creatinine by reverse phase high performance liquid chromatography. The method involves sample pretreatment with a cation exchange resin followed by the isocratic separation of creatinine and an external standard which are detected by their absorbances at 254 nm. The analytical recovery of creatinine from serum was 9...

Despite decades of study, it is still unclear whether regional brain glucose uptake is lower in the cognitively healthy elderly. Whether regional brain uptake of ketones (β-hydroxybutyrate and acetoacetate [AcAc]), the main alternative brain fuel to glucose, changes with age is unknown. We used a sequential, dual tracer positron emission tomography (PET) protocol to quantify brain (18)F-fluorod...

The structure of the mixed, enzyme-cofactor disulfide intermediate of ketopropyl-coenzyme M oxidoreductase/carboxylase has been determined by X-ray diffraction methods. Ketopropyl-coenzyme M oxidoreductase/carboxylase belongs to a family of pyridine nucleotide-containing flavin-dependent disulfide oxidoreductases, which couple the transfer of hydride derived from the NADPH to the reduction of p...

Twenty Karakul rams were allotted to four groups, subjected first to starvation and then allowed restricted amounts (approximately 1/3 of ad l ib i tum intake) of a high fiber, low energy diet containing no additive (control), 5% 1,3-butanediol (BD), 10% BD, and 5% 1,2-propanediol (PD) for 6 weeks. Starvation elevated (P<.O01) serum ketones (3-hydroxybutyrate and acetoacetate) and decreased (P<...