Effects of pyrophosphate, triphosphate, and potassium chloride on adenylate deaminase from rat muscle.

Inorganic pyrophosphate and triphosphate inhibit adenylate deaminase from rat skeletal muscle with K1 values of 10 and 1.5 microM, respectively, in the presence of 150 mM KCl at pH 7. They act by reducing the apparent affinity of the enzyme for AMP, with relatively small effects on Vmax.

Mammoth albumin.

Serum albumin was detected immunologically in muscle from a mammoth that died about 40,000 years ago. Rabbits injected with ground mammoth muscle produced antibodies that react strongly with elephant albumin, weakly with sea cow albumin, and still more weakly or not at all with other mammalian albumins. Since elephant albumin elicited antibodies with the same specificity, some of the surviving mammoth albumin molecules evidently have antigenic sites identical to those on native elephant albumin.

Species-specific proteins in fossils.

With a solid-phase radioimmunoassay it has been possible to detect species-specific collagen and albumin fossils as old as 1.9 million years. This technique may provide new data on the genetic relations of fossil species to each other and to living forms.

Propranolol: an unrecognized cause of central nervous system dysfunction in patients undergoing cardiopulmonary bypass.

An organic mental syndrome developed in a patient soon after he underwent repair of a dissecting thoracic aortic aneurysm. The operation was accomplished with cardiopulmonary bypass. Initially, the mental changes were thought to be related to the operation.

Rebound hypertension after sodium nitroprusside-induced hypotension.

Patients undergoing surgical procedures using sodium nitroprusside-induced hypotension were studied to determine the role of the renin-angiotensin system in the pathogenesis of rebound hypertension (RH) after discontinuing sodium nitroprusside (SNP) infusion. Retrospective observations documented RH in 9 of 12 patients (group I) with a systolic blood pressure (SBP) increase from 112 +/- 3.92 before SNP to 144 +/- 5.

Effect of a heptapeptide angiotensin analog on aldosterone secretion in the rabbit.

We examined the effects of an angiotensin III (AIII) analog, isoleucine-7 AIII (Ile7-AIII), on the steroidogenic and pressor responses to angiotensin II (AII) and AIII. AII or AIII (25 ng/kg/min) were infused alone or superimposed on an infusion of Ile7-AIII (100 ng/kg/min) in conscious male New Zealand rabbits. AII and AIII induced comparable increases in plasma aldosterone concentration, but AII exhibited significantly greater pressor effect.

Drugs five years later: clonidine.

Clonidine represents the prototype of a new class of centrally acting antihypertensive agents, classed as partial alpha-adrenergic antagonists. Blood pressure reduction is characterized, hemodynamically, by reduced cardiac output with unchanged peripheral vascular resistance at rest. Reflex control of blood pressure during orthostasis and exercise appears to be unimpaired, and orthostatic hypotension is uncommon.

Creatine phosphate inhibition of heart lactate dehydrogenase and muscle pyruvate kinase is due to a contaminant.

Previously reported inhibitions of heart lactate dehydrogenase (Guppy, M., and Hochachka, P.W.

Unimpaired beta adrenergic responses during prazosin administration.

We have examined insulin-induced hypoglycemia to determine whether prazosin inhibits the response to sympathetic stimulation, either centrally or at beta adrenergic receptors. Nine patients with essential hypertension were studied during administration of prazosin, hydralazine or placebo. Plasma renin activity increased significantly with hydralazine and was unchanged during prazosin administration.

Adenylate deaminase from rat muscle. Regulation by purine nucleotides and orthophosphate in the presence of 150 mM KCl.

Adenylate deaminase from rat skeletal muscle has been studied with the objective of understanding how the activity of the enzyme is regulated in vivo. ATP and GTP inhibit the enzyme at low concentrations in the presence of 150 mM KCl. The ATP inhibition is reversed as the ATP concentration is raised to physiological levels.

Inhibition of fatty acid oxidation by 2-bromooctanoate. Evidence for the enzymatic formation of 2-bromo-3-ketooctanoyl coenzyme A and the inhibition of 3-ketothiolase.

Incubation of rat liver mitochondria with 10 microM DL-2-bromooctanoate causes complete and irreversible inactivation of 3-ketothiolase I (acyl-CoA:acetyl-CoA C-acyltransferase). Evidence is presented that mitochondria convert bromooctanoate to 2-bromo-3-ketooctanoyl-CoA, an alpha-haloketone which is probably the active form of the inhibitor. The inactivation is accompanied by incorporation of radioactivity from [1-14C]bromooctanoate into the enzyme.

Measurements of fatty acid synthesis by incorporation of deuterium from deuterated water.

Fatty acid synthesis by perfused livers of rat is measured by using D2O as tracer. The newly synthesized, deuterium-labeled fatty acids are separated from unlabeled fatty acids by gas chromatography using glass capillary columns. The areas of the deuterium-labeled peaks are proportional to the amounts of fatty acids synthesized.

Creatine phosphate inhibition of adenylate deaminase is mainly due to pyrophosphate.

Inhibition of rat skeletal muscle adenylate deaminase by creatine phosphate reported previously is due to inorganic pyrophosphate present as a contaminant in commercial preparations of creatine phosphate. This conclusion is based on the following evidence: a compound that inhibits adenylate deaminase can be separated from commercially prepared creatine phosphate by ion exchange chromatography; the inhibition by "creatine phosphate" and by the separated inhibitory compound is relieved by treatment with inorganic pyrophosphatase; inhibition by inorganic pyrophosphate is similar to that produced by unpurified creatine phosphate; and pyrophosphate is present in commercially available creatine phosphate in amounts sufficient to account for the inhibition. Some commercial preparations of creatine phosphate contain much less pyrophosphate than others; these preparations are only weakly inhibitory.

Metabolic control of the circulation. Effects of acetate and pyruvate.

Chloralose-anesthetized dogs were infused intravenously with either Tris-acetate or Tris-pyruvate at 0.0375, 0.075, and 0.

Effect of diet on adenylosuccinase activity in various organs of rat and chicken.

Adenylosuccinase activity of rat liver is depressed by prolonged starvation, cortisol administration, high protein diets, and alloxan diabetes. The loss of activity is not due to the accumulation of a dissociable inhibitor or loss of a cofactor. Starvation produces no loss in activity for 1 day; thereafter the activities of the liver and spleen enzyme decay with a half-life of about 0.

The purine nucleotide cycle in skeletal muscle.

The following evidence demonstrates that ammonia production in muscle occurs via the reactions of the purine nucleotide cycle: i) Extracts of cytosol which lack glutamine dehydrogenase produce ammonia under conditions that mimic muscle doing work. In such extracts a member of the purine nucleotide cycle (AMP, IMP, or adenylosuccinate) must be present in order that ammonia production can take place, ii) Perfused hindleg of rat or hindleg in situ produces ammonia during exercise, and there is a concomitant production of IMP and adenylosuccinate. Exercise causes a decrease in the contents of glutamate, aspartate, and glutamine and an increase in the content of alanine of perfused hindleg of rat.

Plasma renin and serum dopamine-beta-hydroxylase during orthostatic hypotension in quadriplegic man.

To determine whether orthostatic hypotension in patients with cervical spinal cord lesions is the result of impaired sympathetic nerve response and/or impaired renin release, serum dopamine-beta-hydroxylase (DbetaH) activity and plasma renin activity (PRA) were examined during passive tilting in 6 quadriplegic patients and in 6 able-bodied control subjects. Serum DbetaH was measured by an isotopic enzymatic method and PRA by radioimmunoassay. Following head-up tilting, quadriplegic subjects demonstrated a prompt, significant decrease in mean arterial pressure (MAP) and increase in heart rate (HR).

Inhibition of adenylosuccinase by adenylophosphonopropionate and related compounds.

Adenylosuccinase from muscle, liver and yeast is strongly inhibited by the substrate analogue adenylophosphonopropionate (N6-(DL-1-carboxy-2-phosphonoethyl)-adenosine 5'-monophosphate). The inhibition is freely reversible and of the competitive type, with apparent K1 values between 5.4 and 86 nM depending on the source of enzyme.