Comparative study of endralazine and hydralazine for the treatment of hypertension uncontrolled by a beta-blocker and diuretic.

Endralazine and hydralazine were compared in a randomized double-blind, parallel group study lasting 1 year in 30 patients with essential hypertension inadequately controlled by a beta-blocker and a diuretic. Dosage ranged from 10 mg to 30 mg endralazine per day and from 75 mg to 200 mg hydralazine per day according to patient response. The results showed that endralazine was at least as effective as hydralazine in reducing blood pressure. Patients' tolerance, assessed by drop-out rate, was significantly better (p less than 0.05) in the endralazine group. No cases were found of drug-induced lupus-like syndrome on endralazine as opposed to 2 cases with hydralazine. The dose of endralazine required much less adjustment than that of hydralazine.

Some neurobiological applications of the BBC Model B microcomputer and Unilab 8-bit interface.

Four computer programs written for the BBC Model B microcomputer (coupled to a Unilab 8-bit interface) are discussed. These programs enable the system to be used as (1) a transient recorder, (2) a rapid signal averager, (3) a spike-train analyser and (4) an instrument for measuring the amplitude of single channel currents. Flow-charts illustrating the operation of each program are given along with a detailed discussion of how the programs may be used in the laboratory. The discussion is illustrated using recordings taken from experiments conducted on a range of neurobiological preparations.

Branched-chain amino acid metabolism and alanine formation in rat muscles in vitro. Mitochondrial-cytosolic interrelationships.

Muscle branched-chain amino acid metabolism is coupled to alanine formation via branched-chain amino acid aminotransferase and alanine aminotransferase, but the subcellular distributions of these and other associated enzymes are uncertain. Recovery of branched-chain aminotransferase in the cytosol fraction after differential centrifugation was shown to be accompanied by leakage of mitochondrial-matrix marker enzymes. By using a differential fractional extraction procedure, most of the branched-chain aminotransferase activity in rat muscle was located in the mitochondrial compartment, whereas alanine aminotransferase was predominantly in the cytosolic compartment. Phosphoenolpyruvate carboxykinase, like aspartate aminotransferase, was approximately equally distributed between these subcellular compartments. This arrangement necessitates a transfer of branched-chain amino nitrogen and carbon from the mitochondria to the cytosol for alanine synthesis de novo to occur. In incubations of hemidiaphragms from 48 h-starved rats with 3mM-valine or 3mM-glutamate, the stimulation of alanine release was inhibited by 69% by 1 mM-aminomethoxybut-3-enoate, a selective inhibitor of aspartate aminotransferase. Leucine-stimulated alanine release was unaffected. These data implicate aspartate aminotransferase in the transfer of amino acid carbon and nitrogen from the mitochondria to the cytosol, and suggest that oxaloacetate, via phosphoenolpyruvate carboxykinase, can serve as an intermediate on the route of pyruvate formation for muscle alanine synthesis.

Branched-chain amino acid metabolism and alanine formation in rat diaphragm muscle in vitro. Effects of dichloroacetate.

Dichloroacetate (which activates pyruvate dehydrogenase) decreases the release of alanine, pyruvate and lactate in hemidiaphragm incubations with valine. Dichloroacetate interferes with alanine formation by diverting pyruvate into oxidative pathways, which not only limits pyruvate availability for direct transamination to form alanine but also indirectly affects branched-chain amino acid transamination by limiting 2-oxoglutarate regeneration from glutamate.

An inexpensive microcomputer system for analysis of single channel currents.

A description is given of a system for rapidly measuring the durations of open times and closed times of single channel currents obtained by patch clamp techniques. The apparatus required, a BBC microcomputer and a Unilab interface, is inexpensive and easy to use. An outline of the software is given and measurements of the accuracy of timings presented. Examples of analyses of single channel currents obtained from spinal neurones in cultures are also presented.

Limitations of commonly used spectrophotometric assay methods for phosphoenolypyruvate carboxykinase activity in crude extracts of muscle.

Phosphoenolpyruvate carboxykinase activity in crude extracts of muscle has frequently been determined by using a continuous spectrophotometric method, which is shown to grossly overestimate enzyme activity. NADH oxidation attributed to phosphoenolpyruvate carboxykinase activity in the assay is due to lactate production. Under the normal assay conditions. Na+ ions stimulate pyruvate kinase, providing pyruvate for lactate formation by lactate dehydrogenase and sufficiently to account for most of the observed NADH oxidation.

Effect of altered neonatal nutrition on the development of enzymes of lipid and carbohydrate metabolism in the rat.

Rats were overnourished during suckling by litter-size manipulation in order to investigate the possible association of overfeeding in infancy with the development of obesity in later life. Rats were raised in litters of 4, 10 and 16 corresponding to overfeeding, normal feeding and underfeeding during the suckling period. From 6-19 days post partum, growth rates of pups from different litter sizes were significantly different (4 greater than 10 greater than 16). Differences in mean body weights between the groups continued to increase after weaning when all groups were allowed access to diet ad libitum and the significant weight difference between overfed and normally fed rats persisted into adult life in both males and females. Overfed animals showed modifications in the development of activities of a number of hepatic enzymes involved in lipid and carbohydrate metabolism. In later life (20 weeks) neonatally overnourished rats exhibited alterations in hepatic enzyme activities that reflected an increased capacity for lipid synthesis by the liver. "Supernourishment" of neonatal rats (by intubation with glucose of animals in small litters), accelerated the appearance of some of these alterations. These studies show that the pattern of early infant nutrition can profoundly influence the activities of liver enzymes in later, adult life.

The hepato-muscular metabolic axis and gluconeogenesis.

During starvation alanine synthesised de novo by muscle is an important precursor for hepatic gluconeogenesis. The alanine carbon derives in part from branched-chain amino acids such as valine. In vitro incubations of muscle with [1-14 C]- or [U14C]-valine have shown that sufficient valine carbon passes beyond decarboxylation by branched-chain dehydrogenase, but escapes total oxidation, to account for the observed rate of de novo alanine synthesis. Experiments using hydroxymalonate (an inhibitor of malic enzyme) and mercaptopicolinate (an inhibitor of PEP carboxykinase) have shown that muscle alanine synthesis occurs via the latter route. Ketone bodies suppress muscle alanine formation suggesting a role in the conservation of glucogenic precursors in long-term starvation. Conversely alanine diminishes ketogenesis by isolated hepatocytes. It appears that there is an hepato-muscular metabolic axis operating by which liver and muscle metabolism is co-ordinately controlled by alanine and ketone bodies.

The release of alanine by rat diaphragm muscle in vitro.

Alanine release by rat diaphragm muscle in vitro is stimulated by glutamate, valine, leucine and glucose. The stimulation by glutamate and valine (but not leucine) is inhibited by 3-mercaptopicolinate. These results suggest a metabolic route involving phosphoenolpyruvate carboxykinase which directs amino acid carbon skeletons towards pyruvate synthesis for alanine formation.