Measurement of lactate and pyruvate in whole blood is valuable in critical-care medicine and exercise physiology. However, information on the biological variability of lactate and pyruvate is lacking, a fact that may seem surprising when one considers the many reports on lactate and pyruvate as indicators of the state of tissue oxidation. To investigate the analytical and biological variation o...

Gluconeogenesis in thyrotoxicosis was studied by oral glycerol-loading test and alanine-loading test performed on 5 normal subjects and 5 cases of thyrotoxicosis. The blood glucose levels in thyrotoxicosis rose after the administration of glycerol deposit elevation of the plasma levels of insulin. After the administration of alanine, the levels of IRI, pyruvate and lactate elevated in thyrotoxi...

Interest in brain glucose-sensing mechanisms is motivated by two distinct neuronal responses to changes in glucose concentrations. One mechanism is global and ubiquitous in response to profound hypoglycemia, whereas the other mechanism is largely confined to specific hypothalamic neurons that respond to changes in glucose concentrations in the physiological range. Although both mechanisms use i...

1. Brain tissue infected with the virus of Western equine encephalomyelitis shows specific differences in metabolism from brain tissue infected with the virus of poliomyelitis. 2. With added glucose concentration of 121 mg. per cent, oxygen utilization of poliomyelitic brain is significantly below normal and that of encephalitic brain is not. 3. With added glucose concentration of 217 mg. per c...

Leptin is a hormone that is secreted by fat cells and has roles in body weight regulation, glucose metabolism, reproduction, and other neuroendocrine functions. The purpose of this study was to determine whether the secretagogues, insulin, glucose, and pyruvate, enhance leptin secretion by increasing leptin synthesis, or whether these secretagogues stimulate the quantal release of a stored cyto...

Stopped-flow kinetics indicate that human and chicken heart-type(4) lactate dehydrogenases (LDH) become inhibited as DPNH is oxidized in the presence of high concentrations of pyruvate. This inhibition is much less marked with the human and chicken muscle-type(4) enzymes. The initial rates and the difference in inhibition between the two types of enzyme have made it possible to determine the am...

Rainbow trout ( Oncorhynchus rnykiss ) retain the majority of lactate produced during exhaustive exercise within the white muscle. Previous studies have suggested that this retention is partiaiiy via a reuptake of released lactate. The purpose of this work was to study lactate uptake using trout white muscle sarcolemmai vesicles. Through modifications to the original mammalian giant vesicle tec...

The activation level of ribulosebisphosphate carboxylase following preincubation with ribulose 1,5-bisphosphate was increased by ATP and ribulosebisphosphate carboxylase activase in the absence of thylakoids or illumination. Maximal activation was obtained with 0.5 millimolar ATP in the presence of an ATP regenerating system (phosphoenolpyruvate and pyruvate kinase). Without the ATP regeneratin...

Neither fasting nor pyruvate supplementation affects the oxidation of octanoic acid by liver slices (l-3). Similarly, neither fasting nor glucose supplementation affects the oxidation of this acid by the intact rat (4). On the other hand, the oxidation in vivo of palmitic acid and tripalmitin is increased by prior fasting of the animal and decreased by prior glucose administration (4). The diff...

A method has been developed for the positional 13C isotope analysis of pyruvate and acetate by stepwise quantitative degradation. On its base, the kinetic isotope effects on the pyruvate dehydrogenase reaction (enzymes from Escherichia coli and Saccharomyces cerevisiae) for both of the carbon atoms involved in the bond scission (double isotope effect determination) and on C-3 of pyruvate have b...