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Biomedical subjects

C Wagner

Publications and source records attributed to C Wagner.

At least 307 records · Page 17Linked to original sources
PubMed1978

The determination of thiamin pyrophosphate in blood and other tissues, and its correlation with erythrocyte transketolase activity.

A sensitive method for the specific measurement of thiamin pyrophosphate (TPP) has been developed using the apoenzyme recombination concept. Yeast pyruvic decarboxylase apoenzyme can be reconstituted by the addition of TPP or samples containing TPP, yielding the holoenzyme with activity proportionate to the amount of TPP added. Using this technique, reaction mixtures containing 0.2 to 1.5 ng TPP can be assayed. Normal human erythrocyte TPP ranges from 50 to 150 ng per ml packed cells. When rats are fed a thiamin deficient diet, the erythrocyte TPP level falls more rapidly than the erythrocyte transketolase activity. After 8 days, the level of TPP in the erythrocytes of deficient animals was 10% of the level in pair-fed controls. At this time, however, there was no appreciable decrease in their respective transketolase activities. The level of TPP in the liver also is decreased drastically after 8 days. Therefore it appears that erytyrocyte and liver TPP stores have begun to be depleted and suggest that erythrocyte TPP levels are a more sensitive indicator of thiamin status.

Animals↗
PubMed1977

Identification of folate binding proteins in rat liver.

Intraperitoneal injection of tritiated folic acid (PteGlu) into rats has revealed the presence of three separate protein fractions in the cytosol fraction of the liver and one in the mitochondria which bind folate derivatives. The proteins in the cytosol (cytosol I, II and III) have approximate molecular weights of 350,000, 150,000, and 25,000 and the protein in the mitochondria has an approximate molecular weight of 90,000 as estimated by gel filtration. The bound folate derivatives are primarily polyglutamate forms while cytosol II contains primarily bound 5-methyltetrahydrofolate polyglutamate derivatives. Little binding of radioactively labeled folic acid or 5-methyltetrahydrofolate to these fractions was observed when binding was carried out in vitro. Significant binding in vitro was observed, however, when a mixture of biosynthetically labeled natural folate derivatives was used. These proteins have not been purified, but cytosol III partially consists of the enzyme, tetrahydrofolate dehydrogenase (EC 1.5.1.3). Studies on the time course of folic acid incorporation into the liver showed that soon after injection nonmetabolized folic acid was bound to the plasma membrane fraction of the liver cell. It is suggested that at least one of the binding proteins in the cytosol may be involved in storage of the vitamin while the binding of nonmetabolized folic acid to the plasma membrane may reflect the existence of a carrier for folic acid transport into the cell.

Animals↗
PubMed1977

Effect of folacin deficiency on folacin-binding proteins in the rat.

The effect of experimental folacin deficiency on the uptake and distribution of radioactive folic acid in the rat was investigated. Less radioactivity was taken up by livers of deficient rats than controls 24 hours after intraperitoneal injection of [3H]-folic acid, although more radioactivity was incorporated by the brain and kidneys of deficient rats. The distribution of radioactivity among the three folacin-binding proteins of rat liver cytosol and the binding protein of mitochondria was also studied. In deficiency, very little radioactivity was incorporated into cytosol binding proteins I and II, while more radioactivity was incorporated into cytosol binding protein II and the mitochondrial binding protein. A decrease in the endogenous folacin associated with all protein-bound and free forms was seen in deficiency with the major decrease coming at the expense of unbound folacin, and cytosol binding protein I. This latter protein may have a primary storage role in the liver.

Animals↗
PubMed1976

Abnormal regulation of plasma pyridoxal 5'-phosphate in patients with liver disease.

UNLABELLED: Pyridoxal 5'-phosphate (PLP), the coenzyme form of vitamin B6, is essential for many biochemical reactions in the body. Studies in experimental animals have suggested that the liver is a primary site for the formation of PLP circulating in the plasma, and that it may also participate in its degradation. This study evaluates, for the first time, the effects of liver disease in man on the regulation of plasma PLP. The plasma PLP level was measured before and sequentially after the rapid intravenous administration of 50 mg of pyridoxine to patients with alcoholic cirrhosis, acute hepatitis, and extrahepatic obstruction, and to normal control subjects. The base line plasma PLP concentration was significantly lower in cirrhotic patients than in normal persons (P less than 0.025), and there was a tendency for it to be reduced in patients with extrahepatic obstruction. After administration of pyridoxine there was a significant increase in the plasma PLP level over a 2- to 12-hr period, after which the concentration returned gradually toward the initial value. The area under the concentration/time curve was from 2 to 8 times smaller (P less than 0.002) in the patients with liver disease. To assess possible mechanisms of this change, 5 mg of PLP were intravenously administered to the various patient groups and the pharmacokinetics of the disposition were assessed. The initial and steady state volumes of distribution of PLP were comparable in cirrhotics and controls (P greater than 0.05), but the clearance of plasma PLP in cirrhotics was much faster (63.0 +/- 7.4 versus 31.7 +/- 2.7 ml per min, P less than 0.004). Similar findings were obtained in the other liver disease subjects. The in vitro plasma binding of PLP at supracirculatory concentrations was comparable in cirrhotics and controls (99.4 versus 99.5%, P greater than 0.05). IN CONCLUSION: (1) plasma PLP regulation in patients with liver disease is abnormal, (2) a significant factor in the decrease in plasma PLP after intravenous pyridoxine administration in these patients appears to be an increase in the total plasma clearance of the coenzyme, and (3) it is postulated that this may be due to increased degradation of PLP by the diseased liver.

Acute Disease↗
PubMed1975

Purification and characterization of N-methylalanine dehydrogenase.

Cell free extracts of Pseudomonas MS previously have been shown to carry out the synthesis of a novel amino acid, N-methylalanine (Kung, H.F., and Wagner, C. (1970) Biochim. Biophys. Acta 201, 513-516). An enzyme has been isolated from this organism which is responsible for the synthesis of N-methylalanine. The stoichiometry of the reaction catalyzed by this enzyme leads to the following formulation: Methylamine + pyruvate + NADPH + H-+ yields N-methylalanine + NADP-+ + H2O. This enzyme has been physically separated from alanine dehydrogenase, which is also present in these extracts. This new enzyme has been named N-methylalanine dehydrogenase. It has been purified to near homogeneity as judged by disc gel electrophoresis. Gel filtration chromatography showed that N-methylalanine dehydrogenase has an apparent molecular weight of 77,000, while electrophoresis in sodium dodecyl sulfate gave rise to a single band with a molecular weight of approximately 36,500. The enzyme is optimally active in the pH range between 8.2 and 8.6. The apparent K-m values for pyruvate, NADPH, and methylamine, respectively, are 1-5 times 10 minus 2 M, 3-5 times 10 minus 5 M, and 7.5 times 10 minus 2 M.

Alanine↗
PubMed1975

Vitamin B6 deficiency in uremia.

Significant decreases in plasma pyridoxal-5-phosphate (PLP), plasma glutamic-oxaloacetic transaminase (PGOT) and erythrocyte glutamic-oxaloacetic transaminase (EGOT) were found in 29 uremic patients including 14 who had been on hemodialysis an average of 15.8 months. The mean PLP values of the uremic patients (5.39 +/- 0.37 ng/ml) were clearly lower than the values obtained for the normal group (9.30 +/- 0.80 mg/ml). The mean PGOT values of the uremic patients (dialyzed 4.07 +/- 0.29 U/liter, undialyzed 5.31 +/- 0.49 U/liter) were significantly lower than the normal group (6.57 +/- 0.39 U/liter). The mean EGOT value of the uremic patients (325 +/- 17 U/liter) was also lower than normal subjects (416 +/-21 U/liter). Stimulation of the EGOT by exogenous PLP (EGOT index) was less in dialyzed patients (1.60) than normal subjects (1.80) while the undialyzed uremic subjects had a greater than normal stimulation (2.12). All of these results indicate that uremic patients are vitamin B6 deficient and that those undergoing hemodialysis may have decreased amounts of the EGOT apoenzyme.

Adult↗
PubMed1975

Enzymes involved in the assimilation of one-carbon units by Pseudomonas MS.

Pseudomonas MS can grow on methylamine and a number of other compounds containing C1 units as a sole source of carbon and energy. Assimilation of carbon into cell material occurs via the "serine pathway" since enzymes of this pathway are induced after growth on methylamine, but not malate or acetate. A mutant has been isolated which is unable to grow on methylamine or any other related substrate providing C1 units. This mutant is also unable to grow on acetate. Measurment of enzyme activities in cell-free extracts of wild-type cells showed that growth on methylamine caused induction of isocitrate lyase, a key enzyme in the glyoxylate cycle. The mutant organism lacks malate lyase, a key enzyme of the serine pathway, and isocitrate lyase as well. These results suggest that utilization of C1 units by Pseudomonas MS results in the net accumulation of acetate which is then assimilated into cell material via the glyoxylate cycle.

Acetates↗