In vivo 31P-NMR studies of myocardial high energy phosphate metabolism during anoxia and recovery

31P NMR spectra of heart in-situ in live guinea pigs were obtained continuously in 20.5 s time blocks during 3 min of anoxia, during subsequent reoxygenation and, in separate animals, during terminal anoxia. Reversible anoxia resulted in rapid degradation of phosphocreatine (t 1/2 = 54.5 +/- 2.5 s) which recovered fully during reoxygenation. Heart Pi increased during anoxia and returned to basal levels after oxygen was restored. During 3 min of anoxia, no significant changes in ATP levels or pH were detected. The results demonstrate that it is feasible to measure rapid fluxes of high energy phosphates by 31P NMR in intact animals during and after anoxic stress to the myocardium.

In vivo carbon-13 nuclear magnetic resonance studies of heart metabolism

Guinea pig heart metabolism was studied in vivo by 13C NMR at 20.18 MHz. High-quality proton-decoupled 13C NMR spectra with excellent signal-to-noise ratios and resolution could be obtained in 6 min. Natural-abundance spectra showed resonances that could be assigned to fatty acids, but glycogen was not seen. During intravenous infusion of D-[1-13C]glucose and insulin, the time course of myocardial glycogen synthesis was followed serially for up to 4 hr. Anoxia resulted in degradation of the labeled glycogen within 6 min and appearance of 13C label in lactic acid. Infusion of sodium [2-13C]acetate resulted in incorporation of label into the C-4, C-2, and C-3 positions of glutamate and glutamine, reflecting "scrambling" of the label expected from tricarboxylic acid cycle activity. Examination of the 31P NMR spectrum of the guinea pig heart in vivo demonstrated no change in the high-energy phosphates during the time periods of the 13C NMR experiments. Our studies indicate that 13C NMR is a unique non-destructive tool for the study of heart metabolism in vivo.

Gastrointestinal manifestations of diabetic ketoacidosis

The evaluation of gastrointestinal symptoms in patients with diabetic acidosis frequently challenges the physician's clinical acumen. Faced with a seriously ill patient, he must judge whether the abdominal pain, nausea, or vomiting are a consequence of the metabolic decompensation, and hence likely to resolve with correction of the ketoacidosis, or if these symptoms signal a serious underlying intra-abdominal process (e.g., cholecystitis, appendicitis, etc.) which may have precipitated the development of ketoacidosis. The pathogenesis of the reversible gastrointestinal symptoms which frequently accompany diabetic acidosis has not been rigorously defined and may be multifactorial, involving metabolic, humoral, and neural processes. Careful attention to the medical history and abdominal examination greatly facilitates distinguishing patients with intra-abdominal pathology from those with reversible symptoms secondary to ketoacidosis. Similarly, the judicious use of laboratory tests (electrocardiography, blood counts, urinalysis, serum enzyme profile, and abdominal roentgenograms) materially aids in differential diagnosis. Finally, clinical suspicion of an acute abdominal process should prompt early surgical consultation and, if required, surgical intervention as the acidosis is being brought under control.

Insulin resistance in diabetic ketoacidosis

The effect of "low-dose" (6--10 U/h) insulin treatment on the rate of decline of plasma glucose concentration was determined in 15 diabetic subjects admitted in ketoacidosis (plasma glucose = 948 79 mg/dl) and in six normal volunteers rendered hyperglycemic by a combined infusion of somatostatin and glucose (plasma glucose = 653 28 mg/dl). The fractional glucose turnover and the half-time of the fall in plasma glucose during insulin treatment were both 10-fold reduced (P less than 0.001) in the diabetics as compared with the controls. In the ketoacidotic subjects, the mean glucose clearance during insulin treatment was only 8% of that in the controls (P less than 0.001). In the normal subjects, tissue glucose clearance during insulin treatment of the hyperglycemia (5.8 0.7 ml/min . kg) was similar to that measured in the same subjects using a standard technique to quantitate insulin sensitivity (euglycemic insulin clamp). In the ketoacidotic patients, a history of prior insulin therapy, but not the degree of hyperglycemia at the time of admission, was associated with a more rapid rate of decline of plasma glucose in response to insulin treatment. We conclude that marked insulin resistance is present in virtually all diabetics in ketoacidosis.

The differential release of basal ATPase, Ca2+-dependent ATPase, 5'-nucleotidase and cholesterol during homogenization of skeletal muscle

The influence of homogenization times on the presence of constituents in the microsomal fraction of skeletal muscle was investigated. Membranes having Ca2+-activated ATPase activity have a fragmentation pattern distinct from that of membranes displaying Ca2+-independent or basal ATPase activity. These latter membranes were found in highest specific concentration in the microsomal fraction prepared from homogenates subjected to short periods of homogenization. 5'-Nucleotidase (EC 3.1.3.5) activity paralleled that of basal ATPase on short periods of homogenization, as also did the specific concentration of cholesterol. Longer periods of homogenization led to a decrease in the specific activity of basal atpase, which reached its lowest value at 120s of homogenization, whereas the specific activity of 5'-nucleotidase and the specific concentration of cholesterol decreased initially in a similar manner to basal ATPase, but both increased substantially after the longest period of homogenization.

Cholesterol in muscle membranes

The composition of skeletal muscle microsomes is reviewed. Evidence for the involvement of cholesterol in the transport of calcium by vesicles derived from the sarcoplasmic reticulum is considered. Results obtained by non aqueous extractions of skeletal muscle microsomes, and by use of the cholesterol analogue 20, 25 diazacholesterol indicate that cholesterol is not involved in calcium transport by vesicles of sarcoplasmic reticulum origin. Use of density perturbation procedures indicating that cholesterol is present in muscle membranes other than those of the sarcoplasmic reticulum involved in calcium transport is discussed. The distribution of membranal cholesterol in muscle is compared to that in other tissues.

Hepatitis B in Australian Aborigines and Torres Strait Islanders: georgraphical, age and familial distribution of antigen subtypes and antibody

Hepatitis B antigen of subtype ay is prevalent in Australian Aboriginal populations, but only subtype ad was found in Torres Strait Islanders. Both subtypes were found in Caucasion hepatitis patients and blood donors from Brisbane. Antigenaemia in Aborigines was more prevalent in Northern Territory than in Queensland, and in males in all areas, but different age distributions were found in Queensland (maximal over 30 years) and Northern Territory (maximal under 30 years). Family clustering was striking in all populations where genealogies were known. In a limited survey antibody was found to be more common than antigen in all Aboriginal groups, the prevalence increasing with age with a peak at 11 to 30 years. Hepatitis B virus infection was equally common in some areas of high and low arbovirus activity providing some evidence against arthropod transmission of hepatitis B virus in these areas.

Association of basal ATPase activity and cholesterol with a distinct group of rabbit skeletal muscle microsomal particles

Basal ATPase is readily separated from the Ca2+-ATPase of the sarcoplasmic reticulum. The median density distributions of cholesterol and basal ATPase activities are almost identical. Digitonin has been successfully employed in determining the association of cholesterol with specific vesicles in rat liver microsomal preparations. Treatment of rabbit skeletal muscle microsomal preparations with digitonin alters the density distribution patterns of basal ATPase activity and cholesterol in an identical fashion. Protein distribution displays a less marked change in median density. Enzymic activity associated with calcium transport, measured under differing conditions, is largely unaffected. It is concluded that cholesterol and basal ATPase activity are associated with a distinct group of rabbit skeletal muscle microsomal particles.