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Biomedical subjects

R L Veech

Publications and source records attributed to R L Veech.

At least 91 records · Page 5Linked to original sources
PubMed1980

The presence of 2,3-butanediol in the blood of chronic alcoholics admitted to an alcohol treatment center.

Fifty-one of sixty-three unselected alcoholic subjects had 2,3-butanediol in their blood in concentrations ranging from 0.011 to 0.775 mM upon admission to an alcohol detoxification center. The concentration of 2,3-butanediol was below the detection limit of 0.01 mM in twelve non-alcoholic controls. Eighteen hours after admission, second blood samples showed no ethanol in all eleven subjects tested. 2,3-Butanediol levels declined in all of the patients and became undetectable in eight.

Adolescent↗
PubMed1980

Changes in liver inorganic pyrophosphate content during ethanol metabolism.

The injection of ethanol (70 mmol/kg body weight) into male Wistar rats fed ad libitum caused an increase within 15 min in the liver inorganic pyrophosphate (PPi) content from 0.012 +/- 0.001 mumol/g (wet weight) to 0.029 +/- 0.001 mumol/g. The injection of acetate (20 mmol/kg body weight) increased the liver PPi to 0.157 +/- 0.075 mumol/g in 15 min. The alcohol dehydrogenase inhibitor 4-methylpyrazole blocked the accumulation of acetate and the increase in PPi was prevented. Disulfiram, an inhibitor of aldehyde dehydrogenase, did not prevent changes in redox state, but the accumulation of acetate in the liver was decreased and the increase in liver PPi content was diminished (0.019 +/- 0.003 mumol/g). These data suggest that the increase in PPi observed after injection of ethanol may be due to the activation of the acetate produced during ethanol and acetaldehyde oxidation.

Animals↗
PubMed1980

Isolation of a lipocyte-rich fraction from rat liver nonparenchymal cells.

A modified pronase digestion procedure is described for isolating nonparenchymal liver cells from vitamin A treated rats, which yielded a 15-23% population of lipocytes in the total cell suspension. The criteria for defining a lipocyte was the appearance of vitamin A containing cells as determined by fluorescent microscopy. Measurement of alcohol dehydrogenase and retinol dehydrogenase activities indicated that these enzyme activities were not present in the isolated nonparenchymal cells. A lipocyte-rich fraction of nonparenchymal cells was obtained by centrifugation of purified nonparenchymal cells in a linear Metrizamide gradient. Vitamin A fluorescence and chemical assay of vitamin A in the cell fractions indicated a four-fold enrichment of lipocytes in the cell fraction with d = 1.043 g/ml. Fractions high in vitamin A also had numerous cells with fat droplets as shown by transmission electron microscopy.

Adipose Tissue↗
PubMed1980

Alcohol dehydrogenase in cultured human skin fibroblasts. Human fibroblast alcohol dehydrogenase.

Studies of ethanol oxidation and other metabolic pathways in humans are often limited by the availability of a reproducible test material. Because of this we have tested human fibroblasts for ethanol metabolism and alcohol dehydrogenase content. Seven different cell lines have been studied and found to contain an enzymatic activity identified as alcohol dehydrogenase by the following criteria: it is NAD+-dependent, the Km for ethanol is like human liver, it is completely inhibited by 25 microM 4-pentylpyrazole. The fibroblast activity was analyzed by isoelectric focusing and found to contain several isozymes also present in the human liver sample. In addition, fibroblasts contain 2 major isozymes which migrate anodally to any isozymes previously reported in human liver. Thus, fibroblasts appear to be useful material for comparing enzymatic aspects of ethanol metabolism in alcoholics and nonalcoholics.

Acetaldehyde↗
PubMed1980

Alcohol and very low density lipoprotein synthesis and secretion by isolated hepatocytes.

Labeled leucine can be used to measure accurately the rate of both total and secretory protein synthesis by isolated hepatocytes if at least 1 mM leucine is added to the incubation medium, even in the presence of 50 mM ethanol. Using this technique it was found that ethanol caused a significant inhibition of very low density lipoprotein (VLDL) as well as total protein synthetic rates in hepatocytes from both fed and fasted rats. In contrast, a single acute oral dose of ethanol to fasted rats caused within 4 hr a threefold stimulation in the rate of VLDL synthesis without affecting the total protein synthetic rate in the hepatocyte system.

Animals↗
PubMed1979

Phosphorylation of ATP citrate lyase in response to glucagon.

Incubation of hepatocytes with [32P]orthophosphate resulted in the incorporation of 32P into material that is precipitated by reaction with antibodies to ATP citrate lyase. The amount of radioactivity precipitated was decreased when unlabeled, purified ATP citrate lyase was added to extracts of hepatocytes that had been incubated with [32P]orthophosphate. Addition of glucagon to hepatocytes that had been preincubated with [32P]orthophosphate resulted in a 56% increase in acid-stable 32P in the trichloroacetic acid-insoluble portion of immunoprecipitates. Catalytic phosphate bound to ATP citrate lyase reaction with ATP and Mg2+ is acid-labile; thus, glucagon-dependent phosphorylation is distinguished from the catalytic phosphate. When hepatocytes were incubated in the absence of [32P]orthophosphate and extracted in a medium containing [gamma-32P]ATP, no acid-stable 32P was present in immunoprecipitates. This indicates that the incorporation into ATP citrate lyase of acid-stable phosphate occurs prior to extraction of the enzyme. Preliminary studies, using a procedure that allows for measurement of enzyme activity starting 1 min after beginning the extraction of lyase from hepatocytes, have shown no difference in lyase activity when hepatocytes are treated with or without glucagon.

ATP Citrate (pro-S)-Lyase↗
PubMed1979

Effects of pH and free Mg2+ on the Keq of the creatine kinase reaction and other phosphate hydrolyses and phosphate transfer reactions.

The observed equilibrium constants (Kobs) of the creatine kinase (EC 2.7.3.2), myokinase (EC 2.7.4.3), glucose-6-phosphatase (EC 3.1.3.9), and fructose-1,6-diphosphatase (EC 3.1.3.11) reactions have been determined at 38 degrees C, pH 7.0, ionic strength 0.25, and varying free magnesium concentrations. The equilibrium constant (KCK) for the creatine kinase reaction defined as: KCK = [sigma ATP] [sigma creatine] divided by ([sigma ADP] [sigma creatine-P] [H+]) was measured at 0.25 ionic strength and 38 degrees C and was shown to vary with free [Mg2+]. The value was found to be 3.78 x 10(8) M-1 at free [Mg2+] = 0 and 1.66 x 10(9) M-1 at free [Mg2+] = 10(-3) M. Therefore, at pH 7.0, the value of Kobs, defined as Kobs = KCK[H+] = [sigma ATP] [sigma creatine] divided by ([sigma ADP] [sigma creatine-P] was 37.8 at free [Mg2+] = 0 and 166 at free [Mg2+] = 10(-3) M. The Kobs value for the myokinase reaction, 2 sigma ADP equilibrium sigma AMP + sigma ATP, was found to vary with free [Mg2+], being 0.391 at free [Mg2+] = 0 and 1.05 at free [Mg2+] = 10(-3) M. Taking the standard state of water to have activity equal to 1, the Kobs of glucose-6-P hydrolysis, sigma glucose-6-P + H2O equilibrium sigma glucose + sigma Pi, was found not to vary with free [Mg2+], being 110 M at both free [Mg2+] = 0 and free [Mg2+] = 10(-3) M. The Kobs of fructose-1,6-P2 hydrolysis, sigma fructose-1,6-P2 equilibrium sigma fructose-6-P + sigma Pi, was found to vary with free [Mg2+], being 272 M at free [Mg2+] = 0 and 174 M at free [Mg2+] = 0.89 x 10(-3) M.

Adenosine Diphosphate↗
PubMed1979

Cytosolic phosphorylation potential.

The tissue contents of the reactants of the myokinase (EC 2.7.4.3) and the combined glyceraldehyde-3-phophate dehydrogenase (EC 1.1.1.29)-3-phosphoglycerate kinase (EC 2.7.2.3) reactions were measured in rapidly inactivated samples of human blood and rat brain, muscle, and liver. The tissue contents of the reactants of the creatine kinase (EC 2.7.3.2) reaction were measured in rat brain and muscle. In vitro the value of the expression: KG+G = [sigma3PG] . [sigmaATP] . [sigmalactate] KLDH = [sigmaHAP]/22] . [sigmaADP][sigmaPi] . [sigmaRUVATE] (1) was found to be 0.725 x 10(7) M-1 at I = 0.25, T = 38 degrees C, and free [Mg2+] = 0.15 mM and the value measured in vivo in red cell was 0.699 x 10(7) M-1. The value of the expression KMYK = ([sigma ATP] [sigma AMP]/[ADP2]) measured under the above conditions and at pH 7.2 was found to be 0.744 while the value found in red cell was 0.784 +/- 0.037. These reactions, therefore, appear to be in a state of near-equilibrium in the red cell and the measured tissue contents of ATP and ADP, which are common reactants in both reactions, approximate closely the activity of these reactants in vivo. In brain and muscle, the value of KG + G/KLDH calculated from the measured tissue contents of the reactants was a factor of 20 or more lower than that expected at equilibrium as was the measured value of the expression: KCK = [sigma ATP] [sigma creatine] divided by [sigma ADP] [sigma creatine-P] [H+] (2) Substitution of calculated free [sigma ADP] values in the expression of KG + G/KLDH gave values of 0.83 +/- 0.19 x 10(7) M-1 for brain and muscle, respectively, which agreed well with the value of 1.65 x 10(7) M-1 measured in vitro at I = 0.25, free [Mg2+] = 1 mM, T = 38 degrees C. This agreement between two highly active enzyme systems in the same compartment is taken as evidence of the existence of near-equilibrium in both these systems and suggests that free cytosolic [sigma ADP] is probably 20-fold lower than measured cell ADP content in mitochondrial-containing tissues.

Adenine Nucleotides↗
PubMed1978

Ketogenesis and malonyl coenzyme A content of isolated rat hepatocytes.

We have measured rates of ketogenesis and malonyl-CoA contents of hepatocytes isolated from meal-fed rats under a variety of incubation conditions in order to determine the relationship between the intracellular malonyl-CoA level and the rate of ketogenesis. Evidence obtained from rat liver homogenates suggested that malonyl-CoA, which is a major determinant of fatty acid synthesis in vivo, also inhibits carnitine acyltransferase I (EC 2.3.1.21) and thereby decreases the rate of ketogenesis (McGarry, J.D., Mannaerts, G.P., and Foster, D.W. (1977) J. Clin. Invest. 60, 265-270). In hepatocytes from meal-fed rats, malonyl-CoA could be increased by glucose or lactate plus pyruvate and decreased by glucagon, oleic acid and the fatty acid synthesis inhibitor 5-(tetradecyloxy)-2-furoic acid. Malonyl-CoA varied from 14.8 +/- 1.2 to 1.4 +/- 0.1 nmol/g wet weight of cells. Rates of ketone body production varied from 0.10 +/- 0.01 to 0.96 +/- 0.06 mumol/min/g wet weight of cells and varied inversely with the malonyl-CoA content. Dixon plots and Cornish-Bowden plots of data suggest that malonyl-CoA is a competitive inhibitor of ketogenesis with a Ki of 2 nmol/g wet weight of cells. We conclude that in hepatocytes from meal-fed rats the cellular content of malonyl-CoA and the concentration of long chain fatty acid available to the cells are major determinants of the rate of ketogenesis.

Acyl Coenzyme A↗