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Biomedical subjects

A Rigo

Publications and source records attributed to A Rigo.

At least 109 records · Page 6Linked to original sources
PubMed1977

Determination of red blood cell superoxide dismutase and glutathione peroxidase in newborns in relation to neonatal hemolysis.

Superoxide dismutase and glutathione peroxidase activities have been determined in newborns. Their mean values are approximately the same as in normal adults. In some cases a low content of superoxide dismutase and/or a high (superoxide dismutase/glutathione peroxidase) ratio are associated with hematological symptoms. In addition, a low superoxide dismutase activity is associated with hyperbilirubinemia and is present in two of the three cases showing maximal acetylphenylhdrazine-induced hemoloysis.

Adult↗
PubMed1977

The binding of copper ions to copper-free bovine superoxide dismutase. Copper distribution in protein samples recombined with less than stoicheiometric copper ion/protein ratios.

Samples of superoxide dismutase containing less than stoicheiometric amounts of Cu2+ were obtained by either partial re-addition of Cu2+ to the Cu2+-free protein or partial removal of Cu2+ by controlled CN-treatment. In these samples the distribution of the metal between the two identical sites on the two subunits was studied by quantitative gel electrophoresis and found to be statistical only in the process of copper removal by CN-. In the other case the distribution fits a model of co-operative interaction between the two sites, where the sites are equivalent for the binding of the first Cu2+ ion, but the occupation of the first site lowers the activation energy of the binding of the second Cu2+ ion. This indicates that binding of Cu2+ ion at its site on one subunit brings about conformational changes that facilitate Cu2+ binding on the other subunit. These results may relate to possible intersubunit interactions during the catalytic activity.

Animals↗
PubMed1977

The binding of copper ions to copper-free bovine superoxide dismutase. Properties of the protein recombined with increasing amounts of copper ions.

1. E.p.r. (electron-paramagnetic-resonance), proton-relaxation and u.v.-absorption parameters, and enzyme activity of samples of Cu2+-free bovine superoxide dismutase recombined with different amounts of Cu2+ up to the stoicheiometric [Cu2+]/protein] ratio were investigated after attainment of equilibrium in the recovery process. 2. The e.p.r. spectra were identical with the spectrum of the native protein at all [Cu2+]/[protein] ratios. The relaxation rate of the water protons (T1) and the u.v. absorption increase as linear functions of the added Cu2+. 3. On the other hand, in recombination experiments in the range pH 7.6-10.5 the enzyme activity shows a non-linear increase as the [Cu2+]/[protein] ratio rises. The experimental curves can be interpreted in terms of the model of co-operative binding of Cu2+ to the two sites proposed on the basis of the electrophoretic analyses of the samples, and show that the specific activity of the molecules containing only one Cu2+ ion is twice as high as that of the molecules with two Cu2+ ions. 4. These results support the hypothesis of an anti-co-operative interaction between the two sites during the activity, which allows only one Cu2+ ion to function in catalysis.

Animals↗
PubMed1976

Dosage effect of SOD-A gene in 21-trisomic cells.

SOD-A activity was measured by the polarographic method of catalytic currents in 30 subjects 10-24 years of age with a karyotype 47, + 21, and 30 age matched normal subjects. The ratio of the average amount of SOD-A in 21-trisomic cells to the average amount in normal cells is 1.4495. Statistical analysis confirms that this ratio does not differ significantly from the ratio 1.5 expected in the case of a simple gene dosage effect.

Adolescent↗
PubMedDate not supplied

Selenium enhances glutathione peroxidase activity and prostacyclin release in cultured human endothelial cells. Concurrent effects on mRNA levels.

Selenium (Se) is an essential component of glutathione peroxidase (GSH-Px), an enzyme that protects cells by reducing intracellular peroxides. Impaired Se status and GSH-Px activity seem associated with increased risk of atherosclerotic vascular diseases. This study reports the effects of Se supplementation on GSH-Px activity, on prostacyclin (PGI2) production, on 12-hydroxy-eicosatetraenoic acid (12-HETE) levels, and on GSH-Px mRNA expression in cultured human umbilical vein endothelial cells (HUVEC). Se-enriched HUVEC showed significant increase of both GSH-Px activity and thrombin-stimulated production of PGI2 in the presence of stable concentrations of 12-HETE. On the other hand, an inverse correlation between Se concentrations in culture media and GSH-Px mRNA levels in Northern blot analysis was shown; this suggests that a major degree of regulation for GSH-Px expression by Se is most likely exerted at the posttranscriptional level. These observations may help to explain the increased incidence of atherosclerosis described in Se-deficient individuals.

12-Hydroxy-5,8,10,14-eicosatetraenoic Acid↗
PubMedDate not supplied

NMR method for superoxide dismutase assay in brain and liver homogenates.

A method for copper- and manganese-containing superoxide dismutase (Cu- and MnSOD) assay in tissue homogenates such as liver and brain, based on the measurement of the longitudinal nuclear relaxation time (T1) of F-, has been developed as a preliminary approach to in vivo measurement of these enzymes. The relaxation rate of F-, which increases linearly with the SOD concentration, also depends on the oxidation state of the metal ion present in the active site of the enzyme. The relaxivity values of the oxidized, reduced and turnovering CuSOD were found to be 9.6 x 10(6), much less than 1 x 10(2) and 5.2 x 10(6) M-1 s-1, respectively, while for MnSOD the corresponding values were 2.9 x 10(6), 4.2 x 10(6) and 3.6 x 10(6) M-1 s-1, respectively. These high relaxivity values allow the detection of SODs in brain and liver homogenates where, under aerobic conditions, these enzymes appear in the steady-state. The contribution of the two types of SOD to the F- relaxation rate in the homogenates was measured by addition of either diethyldithiocarbamate or cyanide, both of which selectively inhibit the CuSOD. The comparison between NMR and activity data confirmed the possibility of carrying out accurate and precise measurements of SODs in homogenates by NMR.

Animals↗
PubMedDate not supplied

Characterization of thin layers of glucose oxidase.

Glucose Oxidase (GOD) has been covalently bound to functionalized glass cover slips. The surface density of immobilized GOD molecules was measured by a method based on the amperometric determination of Flavin Adenine Dinucleotide (FAD). Atomic Force Microscopy (AFM) images, obtained in aqueous solution for the covalently bound enzyme, show a monomolecular layer of the enzyme on a functionalized glass surface. The catalytic constants were measured for the immobilized GOD and compared with those of the free enzyme.

Glass↗