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Biomedical subjects

R E McCallum

Publications and source records attributed to R E McCallum.

32 records · Page 2Linked to original sources
PubMed1979

Growth yields and fermentation balance of Bacteroides fragilis cultured in glucose-enriched medium.

Bacteroides fragilis is an obligate anaerobic bacterium classified with the gram-negative, non-sporeforming bacilli and is the Bacteroides species most frequently isolated from human infections. In the present study, experiments were designed to investigate growth characteristics of B. fragilis in a complex medium. In a minimal defined medium, which was employed for comparison purposes, B. fragilis grew with a generation time of 2 h. Growth of the organism in glucose-enriched medium used in the present study was superior. Maximum generation time was 60 min. Total and viable cells (colony-forming units) were 8.9 x 10(9) and 2.1 x 10(9), respectively, at maximum measurable growth. The molar growth yield (Ym) was 51.5. Growth yields were found to reach a maximum 2 to 3 h before maximum growth and to vary with respect to the phase of growth. Estimates of the fermentation products indicated that glucose was the sole energy substrate. Major products included acetic acid, propionic acid, lactic acid, and succinic acid. Other products included ethyl alcohol, pyruvic acid, and fumaric acid. No attempt was made to recover CO2 or formic acid. The OR balances from two experiments were 0.013 and -0.093 and the respective carbon recoveries were 6.268 and 6.241. The results of the present study show that B. fragilis is capable of rapid rates of growth in vitro by using glucose as the sole energy source.

Bacteroides fragilis↗
PubMed1979

The removal of 14C labeled endotoxin by activated charcoal.

Endotoxin shock due to Gram-negative enteric bacteria is of major medical concern with an estimated 100,000 fatalities in the United States per year. An effective therapy for endotoxin shock, particularly in combination with significant liver damage, has not been available to date. Since activated charcoal is known as a universal sorbent, the use of activated charcoal in a hemoperfusion apparatus to remove endotoxin has interesting possibilities. Current assays for endotoxin are inadequate. The Limulus Amoebocyte Lysate (LAL) assay was found to give nonreproducible results within our range of requirements for accuracy. We, therefore, grew Salmonella typhimurium in 14C-labeled glucose to obtain 14C labeled endotoxin. Radiolabeled endotoxin was used to measure the rate of adsorption on activated charcoal. The rates of removal of endotoxin from normal saline, plasma, and whole blood will be presented in graphical form for use in design calculations. This work provides a foundation for encouraging in vivo hemoperfusion experimentation now underway at the University of Oklahoma and the Veteran's Administration Hospital in Oklahoma City.

Adsorption↗
PubMed1979

Carbohydrate metabolism in C3H/HeJ (nonresponder) mice during endotoxic shock.

This study was undertaken to evaluate the hypoglycemic effects of endotoxin in C3H/HeJ (nonresponder) mice. Endotoxin from Salmonella enteritidis ser Typhimurium strain SR-11 was used and the median lethal dosed (LD50) for random-outbred Swiss-Webster mice and C3H/HeJ mice were 450 microgram and 3,000 microgram, respectively. At intervals after intraperitoneal injection of endotoxin (1 LD50) animals were killed, and blood glucose, liver glucose, and liver glycogen levels were killed, and blood glucose, liver glucose, and liver glycogen levels were measured. The time course of carbohydrate depletion in both strains of mice was almost identical. Little change from controls was noted, however, in nonresponder mice given the LD50 dose for normal responder mice. Passive transfer of plasma from C3H/HeJ mice appeared to protect conventional responder mice from the carbohydrate-depleting effects of endotoxin; whereas, passive transfer of peritoneal cells from C3HeB/FeJ responder mice to nonresponders appeared to sensitize C3H/HeJ mice to this effect. In order to evaluate clearance and detoxification of endotoxin in non-responder mice, 14 C-labeled lipopolysaccharide was prepared from bacteria grown in broth containing D-glucose-14 C(U). Mice were injected intravenously with labeled endotoxin, and blood, liver, spleen, kidney, heart, lung, and brain were counted for radioactivity at intervals after injection. Results from these tracer studies indicate that the clearance of lipopolysaccharide in nonresponder mice is slower than that seen in conventional animals. The results of this study further support the suggestion that endotoxin exerts its effects on carbohydrate metabolism via mediators resulting from endotoxin-cell surface interactions.

Animals↗
PubMed1976

Response of mouse liver glycogen cycle enzymes to endotoxin treatment.

The present study was undertaken to characterize endotoxin-induced changes in carbohydrate metabolism and more specifically, to determine the contribution of glycogenolysis to the loss of liver glycogen. Female ICR mice, fasted overnight, were injected with a median lethal dose (LD50, 9 mg/kg) of endotoxin extracted from Salmonella typhimurium strain SR-11. Glycogen synthase and glycogen phosphorylase activities were measured at 0.5 and 6 h after treatment. Endotoxin treatment did not alter total glycogen synthase activity, but the amount of enzyme present in the active form was significantly lower in endotoxic mice. There was no significant increase in glycogen phosphorylase activity in endotoxin-treated mice. Glycogen phosphorylase was activated to the same extent in control and endotoxic mice by decapitation or intravenous epinephrine (25 or 1 mug/kg). The results of this study indicate no significant increase in glycogen phosphorylase activity in endotoxic mice, contraindicating enhanced glycogenolysis as a mechanism for depletion of carbohydrate following endotoxin injection. Altered activation of glycogen synthase, however, may contribute to the loss of glycogen during endotoxemia.

Animals↗
PubMed1973

Effects of endotoxin on gluconeogenesis, glycogen synthesis, and liver glycogen synthase in mice.

This study was undertaken to characterize the nature of carbohydrate loss due to endotoxin poisoning in mice and to elucidate mechanisms responsible for the changes. Female ICR mice, fasted overnight, were injected intraperitoneally with a mean lethal dose of endotoxin extracted from Salmonella typhimurium strain SR-11. Liver glycogen levels, alanine-U-(14)C and pyruvate-2-(14)C incorporation into blood glucose and liver glycogen, glucose-U-(14)C incorporation into liver glycogen, and liver glycogen synthase activities were measured at intervals after treatment. Liver glycogen in fasted mice given endotoxin was diminished significantly as early as 1 h after treatment. Liver glycogen synthase was significantly decreased in poisoned mice at 17 h. The use of actinomycin D showed that the induction of this enzyme due to fasting or hydrocortisone, or both, was inhibited by endotoxin. The incorporation of the (14)C-label from alanine-U-(14)C, pyruvate-2-(14)C, or glucose-U-(14)C into blood glucose and liver glycogen was substantially impaired in endotoxemic animals at 12 h. Decreases in incorporation occurred as early as 4 h after treatment. The progressive increase in glycogen synthase activity observed in fasted controls was not seen in endotoxin-poisoned mice. The administration of a glucose or pyruvate load to endotoxin-treated mice did not restore gluconeogenesis, glycogen synthesis, or liver glycogen synthase activity to normal levels. The in vivo activation of glycogen synthase by glucose was significantly reduced in endotoxemic animals. These changes indicate reduced carbohydrate synthesis as a probable cause for rapid sugar loss during endotoxemia in mice.

Alanine↗
PubMed1972

Mechanisms of pathogenesis in Listeria monocytogenes infection. V. Early imbalance in host energy metabolism during experimental listeriosis.

Early changes in hepatic carbohydrate metabolism without apparent hepatocyte dysfunction were reported previously in mice infected with Listeria monocytogenes. This study was undertaken to examine possible imbalance in host regulatory mechanisms which might be responsible for these changes. Female CD-1 mice fasted 12 hr prior to the experiments were injected intraperitoneally with 10(5), 10(6), or 10(7)Listeria. Control mice received either 10(9) heat-killed Listeria or 150 mug of Salmonella typhimurium lipopolysaccharide. Hepatic glycogen, adenosine triphosphate (ATP), adenosine diphosphate (ADP), and nicotinamide adenine dinucleotide (NAD) (NAD(+), NADH, NADP(+), and NADPH) levels were assayed periodically. Activities of ATP hydrolyzing enzyme and NAD glycohydrolase were measured at various intervals after infection. Decreases in glycogen occurred as early as 10 hr after infection. Responses in the controls differed from those in infected mice. Hepatic ATP levels decreased as early as 10 hr after infection, with concomitant increases noted in ADP. Hepatic ATP hydrolyzing enzyme activity increased as the infection progressed. Decreases were noted in hepatic NAD levels, with the greatest reduction in the reduced form of NAD. Slight changes were observed after 10 hr, and greater differences were noted 20 hr after infection. The magnitude of these biochemical changes appeared to be dose-dependent. Significant increases in hepatic NAD glycohydrolase activity were noted as the infection progressed. Small but significant increases in serum inorganic phosphate were noted 10 and 20 hr after infection, with a larger increase observed 30 hr after infection. The results indicate impairment of host energy metabolism early in the course of experimental listeriosis.

Adenosine Diphosphate↗
PubMed1972

Mechanisms of pathogenesis in Listeria monocytogenes infection. VI. Oxidative phosphorylation in mouse liver mitochondria during experimental listeriosis.

Previous reports have demonstrated early changes in hepatic carbohydrate and energy metabolism in mice infected with Listeria monocytogenes. This study was undertaken to further elucidate mechanisms of damage involved in these changes. Female CD-1 mice were injected intraperitoneally with 10(6)L. monocytogenes A4413. At 0, 10, and 20 hr after infection, groups of mice were sacrificed and the livers were removed and pooled. Oxidative phosphorylation was assayed immediately upon isolation of mitochondria from pooled liver homogenates. Appropriate metabolic inhibitors were employed to examine each of the three phosphorylation sites in mitochondrial electron transport. When pyruvate-malate (equimolar concentrations) and alpha-ketoglutarate were used as substrates, decreases in both phosphorylation and oxidation were noted as early as 10 hr after infection. With beta-hydroxybutyrate and citrate as substrates, alterations were not noted until 20 hr after infection, whereas no changes were seen when glutamate, succinate, or ascorbate were employed. These results suggest possible derangement of the first site in oxidative phosphorylation as well as lowered activity of nicotinamide adenine dinucleotide-linked dehydrogenases during experimental listeriosis in mice.

Animals↗
PubMed1970

Mechanisms of Pathogenesis in Listeria monocytogenes Infection IV. Hepatic Carbohydrate Metabolism and Function in Experimental Listeriosis.

Previous reports have shown alterations in carbohydrate metabolism in mice infected with Listeria monocytogenes. This study was undertaken to elucidate mechanisms involved in these changes. Female CD-1 mice were injected intraperitoneally with 10(6)L. monocytogenes strain A4413. Animals were fasted 12 hr prior to infection, and pooled tissue from several mice was observed at intervals after infection. Blood glucose, liver glucose, and liver glycogen decreased within 10 hr after infection. Sustained treatment with gluconeogenic precursors, including glucose-6-phosphate, fructose-1, 6-biphosphate, phosphoenolpyruvate, alpha-glycerophosphate, pyruvate, and amino acids, did not restore and maintain glucose and glycogen at normal levels and did not affect survival. Administration of hydrocortisone induced restoration of liver glycogen early in the infection but did not maintain normal levels as the infection progressed. Activities of succinic dehydrogenase and cytochrome oxidase in liver homogenates from infected mice were elevated as early as 10 hr after infection. Liver function tests using rose bengal sodium-(131)I showed no significant differences in plasma clearance or liver uptake between normal and infected mice except in terminal infections (60 hr after infection).

Journal Article↗