Comparative studies on NADP(+)-linked malic enzyme in the central nervous system of ectothermic and endothermic animals.

The maximum activity and intracellular distribution of NADP(+)-linked malic enzyme in brain of Mammalia, Aves, Reptilia, Amphibia and Pisces are reported. Malic enzyme activity was present in all animals brains investigated. Most of the enzyme activity was located in the mitochondrial fraction.

Purification and properties of cytosolic and mitochondrial malic enzyme isolated from human brain.

Three isoforms of malic enzyme have been described in mammalian tissues: a cytosolic NADP(+)-dependent enzyme, a NADP(+)-dependent mitochondrial isoform and a mitochondrial isozyme which can use both NAD+ and NADP+ but is more effective with NAD+. We purified mitochondrial and cytosolic malic enzyme from human brain extract to apparent homogeneity in order to compare properties of these isozymes and to verify whether mitochondria contain one or two malic enzyme. Specific activities of both isoforms are approx.

Effect of methyl methacrylate on mitochondrial function and structure.

1. Treatment of isolated rat liver mitochondria with methyl methacrylate (MM) produced membrane disruption as evidenced by the release of citrate synthase, and changes in the ultrastructure of mitochondria. 2.

Subregional and intracellular distribution of NADP-linked malic enzyme in human brain.

High total activity (expressed as mumol/min/g of wet tissue or per milligram of DNA) and differential subregional distribution of NADP-linked malic enzyme was found in autopsy specimens of human brain. Striatum showed the highest activity of malic enzyme, which was two- to five-fold higher than that in other human organs tested. High activity was also found in frontal cortex, while the lowest activity of the enzyme in the central nervous system was found in cerebellum, substantia alba, and corpus callosum.

High performance liquid chromatographic determination of methacrylate in blood serum.

Methacrylic acid is a hydrolytic breakdown product of methylmethacrylate which is widely used in orthopaedic surgery, dentistry and in the chemical industry for fabrication of acrylic resins. Information on the toxicity of methacrylic acid and its metabolism is limited. To facilitate studies in this field we developed a liquid chromatographic procedure allowing determination of methacrylate in blood serum.

Inhibition of lipogenesis in rat brown adipose tissue by clofibrate.

The effect of clofibrate (Atromid S, ethyl-2-(4-chlorophenoxy)-2-methylpropionate) administration for 7 days to rats on lipogenesis and on some lipogenic enzyme activities in brown adipose tissue (BAT), liver and white adipose tissue (WAT) was examined. As compared to control rats the rate of lipogenesis in BAT in the clofibrate-treated animals was significantly decreased. The rate of liver lipogenesis increased slightly, whereas lipogenesis in the WAT was not affected by clofibrate.

AMP-deaminase from human uterine smooth muscle: the effect of DTNB treatment on kinetic and regulatory properties of the enzyme.

Reactivity of sulfhydryl groups of human uterine smooth muscle AMP-deaminase with DTNB, and the effect of their chemical modification on kinetic and regulatory properties of the enzyme were investigated. (1), Approx. 7 and 5 sulfhydryl groups per mol of the enzyme have been shown to be accessible for DTNB (5,5'-dithiobis(2-nitrobenzoic acid)) titration in denaturated and native AMP-deaminase, respectively.

Acetate-induced changes of adenine nucleotide levels in rat liver.

The changes in adenine nucleotide concentration induced by acetate were investigated in rat liver in situ and in isolated rat hepatocytes. Adenosine monophosphate (AMP) concentration increased approximately threefold within 15 minutes after intraperitoneal injection of sodium acetate. A small but significant decrease in adenosine triphosphate (ATP) concentration also occurred.

Formation and breakdown of uridine in ischemic hearts of rats and humans.

In contrast to cardiac purine metabolism, little is known about pyrimidine catabolism in heart. We therefore investigated uridine and uracil formation in ischemic rat and human hearts. Human donor hearts accumulated uridine 3 x (P < 0.

Changes of nucleotide content in human and rat heart during cardiac surgery and ischemia.

The influence of ischemia on purine nucleotide and their catabolite concentration in human myocardium was investigated during surgery of acquired and congenital heart defects. This was compared with the influence of ischemia on rat heart. Concentrations of adenine and guanine nucleotides and their catabolites were measured in the extracts of heart biopsies taken at the onset of ischemia and at the time of reperfusion.

The influence of NADPH-dependent lipid peroxidation on the progesterone biosynthesis in human placental mitochondria.

In an in vitro system consisting of human term placental mitochondria and an NADPH-generating system plus Fe2+, significant lipid peroxidation was observed along with a concomitant inhibition of progesterone biosynthesis. This inhibition could be markedly blocked by Mn2+, superoxide dismutase and dimethylfuran, inhibitors of NADPH-dependent lipid peroxidation. In addition, it has been found that malondialdehyde formation is accompanied by a corresponding decrease in placental mitochondrial cytochrome P-450 content.

Purification and properties of AMP-deaminase from human kidney.

AMP-deaminase from human kidney (cortex and medulla) was purified and the physicochemical properties were characterized. The enzyme from both portions of the kidney exhibited identical kinetics and regulatory properties. At optimal pH (6.

Terminal vessels of dentate gyrus in chronically alcohol-intoxicated rats.

Quantitative changes in the microvasculature of the central nervous system of the rat following chronic ethanol intoxication were studied. For 6 months, 12 rats drank only 25% ethanol and eight control rats only water. After fixation by perfusion, semithin sections of dentate gyrus were obtained.

Changes of malic enzyme activity in the developing rat brain are due to both the increase of mitochondrial protein content and the increase of specific activity.

1. The pattern of NADP-linked malic enzyme activity estimated in the whole brain homogenate did not parallel that found in liver of developing rat. 2.

Adenine nucleotide catabolism in human myocardium during heart and heart-lung transplantation.

The influence of ischemia and reperfusion on nucleotide concentration in human myocardium was investigated during heart and heart-lung transplantation. Myocardial preservation during heart transplantation was achieved by infusion of cold St. Thomas' Hospital cardioplegic solution followed by storage in Ringer's solution at 4 degrees C during transport.

Developmental changes of lipogenic enzyme activities and lipogenesis in brown adipose tissue and liver of the rat.

1. Brown adipose tissue (BAT) and liver lipogenesis in vivo estimated by using 3H2O as tracer was very low and did not change significantly between 10 and 20 days after birth. Lipogenesis increased dramatically in both tissues by weaning at 20 days, peaking between 25 and 30 days of age.

Malic enzyme in human liver. Intracellular distribution, purification and properties of cytosolic isozyme.

In human liver, almost 90% of malic enzyme activity is located within the extramitochondrial compartment, and only approximately 10% in the mitochondrial fraction. Extramitochondrial malic enzyme has been isolated from the post-mitochondrial supernatant of human liver by (NH4)2SO4 fractionation, chromatography on DEAE-cellulose, ADP-Sepharose-4B and Sephacryl S-300 to apparent homogeneity, as judged from polyacrylamide gel electrophoresis. The specific activity of the purified enzyme was 56 mumol.

Molecular forms of human heart muscle AMP deaminase.

Chromatography on phosphocellulose revealed the presence of two, kinetically different forms of human heart AMP deaminase. The main portion of the activity eluted from the column at about 1.1 M KCl, and the enzyme present in this eluate manifested a sigmoidal type of substrate saturation kinetics.