Metabolism of C14-labeled acetone, acetate and palmitate in fasted pregnant and nonpregnant guinea pigs

Metabolism of acetone-2-C14, Na acetate-2-C14, and Na palmitate-1-C14 was compared in normal and pregnant ketotic guinea pigs. Expired CO2, lipids, urine, liver tissue and acetone bodies were quantitated and assayed for radioactivity. After acetone-C14 injections, pregnant ketotic, as well as nonpregnant guinea pigs injected with carrier acetone, metabolized markedly less C14 as the blood concentration of acetone was progressively elevated. The data showed that the actual milligrams of free acetone utilized remained fairly constant regardless of the size of the body acetone pool. After acetate-C14 injections, pregnant fasted guinea pigs utilized less C14 for CO2 excretion and more C14 for biosynthesis than the nonpregnant fasted group. The difference in CO2 specific activity with regard to size of the body acetate pool is discussed. After palmitate-C14 injections, the mean specific activity of the CO2 was greater in the pregnant fasted than in the nonpregnant fasted animals. Since the liver fat content of the former was lower, the data indicate a faster turnover rate of a smaller fatty acid pool.

ADVENTITIOUS FACTORS AFFECTING THE CONCENTRATON OF FREE FATTY ACIDS IN THE PLASMA OF RATS

The concentration of free fatty acids in the plasma of rats has been shown to be affected by the sex and body weight of the animals, their external environment, the availability of food and water, and the time of day and season of the year.

CHRONIC ELECTRICAL ACTIVITY OF GASTRODUODENAL AREA: EFFECTS OF FOOD AND CERTAIN CATECHOLAMINES

A method of implanting electrodes for long-term chronic studies in the gastrointestinal tract of dogs was developed. The electrodes are placed without disrupting bowel continuity, content flow, nerve, or blood supply. They record the two waveforms of electric activity of the gastrointestinal tract (basic electric rhythm (BER) and spike potentials), conduction patterns, and display interrelationships between various segments of the tract. The electrodes were used to evaluate the action of epinephrine, levarterenol, and feeding on the antral-duodenal region. Spike potentials which are associated with contractions were eliminated by the drugs in both antrum and duodenum. The catecholamines initially on infusion, produced arrhythmias in the antral BER and some distortion of the duodenal BER. With continued drug infusion, the frequency of the antral BER was either unchanged or slightly reduced, while the two drugs increased duodenal BER frequency. These differences in response to the drugs suggest that the basic mechanisms which control the electrical rhythms differ in the two organs.

EFFECTS OF HYPERTHYROIDISM, EPINEPHRINE, AND DIET ON HEART LIPOPROTEIN LIPASE ACTIVITY

Rats were fasted for several days, placed on diets high in carbohydrate, fat, or containing iodinated casein so as to produce hyperthyroidism, or were chronically injected with epinephrine. Lipoprotein lipase (LPL) activities of homogenates of the hearts of these animals were determined. Significant increases in LPL activity occurred in thyrotoxic animals, in rats receiving epinephrine injections chronically, or after prolonged fasting, while significant lowering of cardiac LPL activity was observed in rats on the high-carbohydrate or high-fat diets. Single doses of fat or single injections of epinephrine had no effect. Addition of epinephrine or of triiodothyronine to heart slices or homogenates in vitro caused no LPL increases. It is postulated that adaptive changes in cardiac LPL activity may occur in response to altered needs for utilization of fatty acids by the heart. Microsomal fractions of heart cells had the highest specific LPL activities, suggesting synthesis of the enzyme by these cellular components, or activity of the enzyme at the endoplasmic reticulum.

ACETOACETATE TURNOVER AND OXIDATION RATES IN OVINE PREGNANCY KETOSIS

Labeled acetoacetic acid (AcAc) was administered as a tracer dose and as a continuous infusion to 24 twin-pregnant ewes with varying degrees of spontaneous or fasting hypoglycemic ketosis. The mean AcAc turnover rate of five normal twin-pregnant sheep (plasma AcAc < 1 mg/100 ml) was only 0.04 g/hr kg3/4 or 1.0 g/sheep hr. During ketosis the turnover rate of AcAc was directly proportional to the plasma AcAc concentration until a maximal concentration of about 10 mg/100 ml was attained (total ketone bodies, expressed as acetone, would be about 20 mg/100 ml). At higher plasma concentrations, the AcAc turnover rates remained constant at nearly 0.4 g/hr kg3/4 (9 g/sheep hr). About one-half of this AcAc was oxidized to CO2 regardless of the actual amount utilized. The mean percentage of the total exhaled CO2 derived from AcAc metabolism increased from 2% in normal ewes to a maximum of about 20% during pregnancy ketosis. Comparisons of these data to values obtained in previous experiments on artificially ketotic nonpregnant sheep indicate that an overproduction of ketone bodies, rather than an underutilization, is the major cause of ruminant ketosis.

ABORTIVE INTESTINAL INFECTION WITH AN ESCHERICHIA COLI-SHIGELLA FLEXNERI HYBRID STRAIN

Formal, Samuel B., (Walter Reed Army Institute of Research, Washington, D.C.), E. H. LaBrec, T. H. Kent, and S. Falkow. Abortive intestinal infection with an Escherichia coli-Shigella flexneri hybrid strain. J. Bacteriol. 89:1374-1382. 1965.-The mechanism of the apparent loss of virulence of an Escherichia coli-Shigella flexneri hybrid strain was studied. The parent Shigella strain caused a fatal enteric infection when fed to starved guinea pigs, and signs of dysentery followed its oral administration to monkeys. The hybrid strain failed to produce any apparent symptoms when fed to either of these species. The parent strain was shown to invade the intestinal mucosa of starved guinea pigs. This caused a severe inflammatory reaction in the lamina propria, which progressed to ulceration of the intestinal epithelium and resulted in death of the animal. The hybrid strain also invaded the intestinal mucosa and produced an inflammatory reaction. In this case, the inflammatory reaction subsided, the intestine returned to normal within 4 days after challenge, and the animal survived. Both fluorescent-antibody techniques and in vivo growth studies have shown that the hybrid strain can not maintain itself in the intestinal mucosa. Preliminary studies have indicated that a similar situation also exists in the monkey. It is concluded that the virulence of dysentery bacilli rests not only in the capacity to reach the lamina propria, but also in the ability to multiply in this region.

THE EFFECT OF FASTING ON THE HYPERGLYCAEMIC RESPONSES TO CATECHOL AMINES IN RATS

The relative activities of adrenaline, noradrenaline and isoprenaline in producing hyperglycaemia and glycogenolysis in skeletal muscle have been studied in both fed and fasted rats, 1 hr after subcutaneous injection of the catechol amines. The relative hyperglycaemic activities of the three catechol amines depended greatly upon the prandial state of the rats and on the dose range used. In fed rats the relative potencies were in the descending order of potency, adrenaline-noradrenaline-isoprenaline, irrespective of the dose range. Isoprenaline had no hyperglycaemic activity in fed rats even at doses as high as 2 mg/kg. In fasted rats the order of potency depended on the dose. At low doses (0.005 to 0.02 mg/kg) the descending order was isoprenaline-adrenaline-noradrenaline. At higher doses (0.1 to 1 mg/kg) the descending order was adrenaline-isoprenaline-noradrenaline. The relative activities of the three catechol amines in causing glycogenolysis in muscle was independent of the dose range or the prandial state of the rats. Under all conditions the descending order of potency was isoprenaline-adrenaline-noradrenaline. The results are discussed with reference to Ahlquist's (1948) hypothesis of alpha- and beta- receptors and were consistent with the concept that, in the rat, liver glycogenolysis is mediated predominantly by alpha-receptors and muscle glycogenolysis mainly by beta-receptors. In general the hyperglycaemic response in the fed rat is mediated predominantly by alpha-receptors and in the fasted rat the response is mainly due to the activation of beta-receptors. A drug possessing both alpha- and beta-receptor activity elicits an exception to this rule in the fasted rat. Several perturbing problems in the literature, particularly with regard to the hyperglycaemic activity of isoprenaline and to the difficulty in blocking the hyperglycaemic response, can now be explained in the light of these findings.

AUTONOMIC MEDIATION OF THE EFFECT OF RAISED ARTERIAL GLUCOSE UPON FREE FATTY ACIDS

The intravenous infusion of 600 milligrams of glucose over 30 minutes caused a 17 percent fall in the concentration of free fatty acids in arterial blood of subjects who had fasted overnight. This response to glucose was abolished in subjects treated previously with ganglionic or adrenergic blocking agents. Small amounts of insulin were secreted in response to these glucose infusions, but in insulin-dependent diabetics incapable of altering plasma insulin to any great extent, the effect of glucose upon free fatty acids could be obtained provided the subjects were primed with long-acting insulin before the infusions were begun. The response of free fatty acids to doses of glucose which elevated the concentration of glucose in arterial blood by only 3 mg percent and the blockade of this response by autonomic and adrenergic blocking agents suggest that centers in the central nervous system exist which are capable of responding to elevations of arterial glucose by inhibiting the sympathetic tone partially responsible for sustaining lipolysis in fasting.

STIMULATION OF PEPTIDE SYNTHESIS IN ADIPOSE TISSUE BY INSULIN WITHOUT GLUCOSE

The ability of insulin to stimulate incorporation of histidine-2(ring)-C14 into rat epididymal adipose tissue protein in absence of added glucose was investigated. Insulin alone was without effect, but a significant insulin stimulation was obtained when 10, 20, or 40 mm sodium pyruvate was added to the Krebs-bicarbonate incubation medium. This stimulation was not dependent on traces of glucose, since the pyruvate contained no detectable glucose; moreover, the concentration of glucose required to support the insulin stimulation was found to be not markedly different from that for pyruvate. The conclusion is that the effect of insulin on protein synthesis in adipose tissue is not dependent on any effect it may have on glucose entry.

PYRUVATE METABOLISM AND CONTROL: FACTORS AFFECTING PYRUVIC CARBOXYLASE ACTIVITY

Pyruvic carboxylase activated by acetyl coenzyme A is highly active in the mitochondria of rodent liver, and its activity is increased in fasting and alloxan diabetes. In conjunction with acyl carboxylase activated by di- and tricarboxylic acid, it forms a reciprocating control network. Analog models of similar networks tend to correct for perturbations, stabilizing the overall system.