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Biomedical subjects

M A Grillo

Publications and source records attributed to M A Grillo.

At least 91 records · Page 5Linked to original sources
PubMedDate not supplied

Effect of caffeine on ornithine metabolism in rat brain, liver and kidney.

Prolonged treatment with caffeine promotes in rats an increase of liver ornithine carbamyltransferase activity (14-day treatment). In contrast, arginase activity is already reduced in brain and kidney after 10 days, and in the liver much later (17 days). Ornithine transaminase activity was increased in both liver and kidney, while in the brain it was reduced (17 days). Ornithine decarboxylase activity showed only minor modifications in kidney, while it was unchanged in brain. Of the polyamines, only spermidine was significantly modified, being increased in brain, decreased in liver and kidney. Although these results do not explain the mechanism of the modification of brain arginine and ornithine concentration promoted by caffeine, they point to further marked effects, i.e. on OAT activity and on spermidine concentration, which could have a relevant metabolic role.

Adenosylmethionine Decarboxylase↗
PubMedDate not supplied

Catabolism of ornithine in chicken liver.

It is shown that most ornithine in a chicken liver homogenate is decarboxylated in the particulate fraction. This fraction, however, requires the cytosol for complete activity. The dialyzed supernatant does not activate decarboxylation of ornithine, while the supernatant is more effective when previously inactivated at 100 degrees C. The supernatant can be substituted by the intermediates of the citric acid cycle (oxaloacetate, citrate, succinate, malate), by pyruvate, and partially by ADP as well. Rotenone blocks decarboxylation suggesting that this occurs through the pathway ornithine leads to glutamic semialdehyde leads to glutamate leads to alpha-ketoglutarate, which in turn is decarboxylated. The activating metabolites would thus have a role in reoxidizing NADH, and the ketoacids also in supplying the acceptor for transamination of glutamate, and indirectly for ornithine transamination. Pyruvate and oxaloacetate do not transaminate with ornithine. Insulin promotes a marked increase of cytosol ornithine decarboxylase activity, but has little effect on decarboxylation by the particulate cellular fraction.

Adenine Nucleotides↗
PubMedDate not supplied

S-Adenosylmethionine decarboxylase in liver, heart and pancreas of pyridoxine-deficient chickens.

S-adenosylmethionine decarboxylase activity has been measured in liver, heart and pancreas of pyridoxine-deficient chickens: in liver and heart muscle it is increased, while in pancreas the activity is unchanged with respect to control animals. Insulin induced activity in liver and in heart muscle of normal as well as of pyridoxine-deficient chickens, while in the pancreas an induction was observed in the control animals and a decrease in the deficient ones. These data appear to rule out any involvement of pyridoxal phosphate in the reaction catalyzed by S-adenosylmethionine decarboxylase.

Adenosylmethionine Decarboxylase↗
PubMedDate not supplied

Regulation of spermidine acetyltransferase activity by phosphorylation and dephosphorylation.

Spermidine acetyltransferase activity is more than 10-fold higher in the pancreas of a 20-hr-fasted than in that of a fed chicken. The preparation of the fed bird inactivates the other. The effect is due to a thermolabile component of microsomes, and is also obtained with alkaline phosphatase. The inactivated preparation partially recovers its activity through phosphorylation catalyzed by a cAMP-dependent protein kinase. The results presented strongly suggest that spermidine acetyltransferase activity is regulated by phosphorylation and dephosphorylation.

Acetyltransferases↗
PubMedDate not supplied

Carbamylphosphate hydrolysis in donkey liver.

Mitochondria, microsomes, and cytosol all hydrolyze carbamylphosphate. Microsomes show the greatest specific activity. The mitochondrial enzyme is localized in the inner membranes, has optimum pH 5.5 and is heat-stable; the cytosol enzyme has optimum pH 5.0 and is heat-labile. Km for carbamylphosphate is 1.1 to 1.2 X 10(-2 M for both the cytosol and the mitochondrial enzyme. Both enzymes are inhibited by high substrate concentrations.

Animals↗