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Biomedical subjects

S Gaetani

Publications and source records attributed to S Gaetani.

At least 37 records · Page 2Linked to original sources
PubMed1989

Expression of liver-specific genes coding for plasma proteins in protein deficiency.

Protein deficiency leads to a decreased concentration of plasma proteins, although it is not clear whether this response is caused by alterations in gene transcription or in post-transcriptional events. The aim of this study was to investigate the expression of some liver-specific genes coding for plasma proteins in rats kept on a protein-free diet for 30 days. Cloned cDNA probes for the albumin, transthyretin, retinol-binding protein and prothrombin genes were used in Northern hybridizations to total liver RNA to compare their transcript levels in protein-deficient and control animals. Liver polysomes were also isolated and fractionated from the two groups of animals to examine the possible effects of protein deficiency on translation of the mRNAs. The results indicate that the albumin and transthyretin mRNAs are present in lower amounts in protein deficiency. The distribution profile along sucrose gradients shows that all mRNAs are undergoing translation, but in protein-deficient animals a small but consistent fraction of each mRNA is also present in the non-polysomal, low molecular weight fractions.

Actins↗
PubMed1987

Concentration of NADH-cytochrome b5 reductase in erythrocytes of normal and methemoglobinemic individuals measured with a quantitative radioimmunoblotting assay.

The activity of NADH-cytochrome b5 reductase (NADH-methemoglobin reductase) is generally reduced in red cells of patients with recessive hereditary methemoglobinemia. To determine whether this lower activity is due to reduced concentration of an enzyme with normal catalytic properties or to reduced activity of an enzyme present at normal concentration, we measured erythrocyte reductase concentrations with a quantitative radioimmunoblotting method, using affinity-purified polyclonal antibodies against rat liver microsomal reductase as probe. In five patients with the "mild" form of recessive hereditary methemoglobinemia, in which the activity of erythrocyte reductase was 4-13% of controls, concentrations of the enzyme, measured as antigen, were also reduced to 7-20% of the control values. The concentration of membrane-bound reductase antigen, measured in the ghost fraction, was similarly reduced. Thus, in these patients, the reductase deficit is caused mainly by a reduction in NADH-cytochrome b5 reductase concentration, although altered catalytic properties of the enzyme may also contribute to the reduced enzyme activity.

Animals↗
PubMed1983

Effect of factors of favism on the protein and lipid components of rat erythrocyte membrane.

Erythrocytes prepared from riboflavin- and tocopherol-deficient (RT-) and from control rats were used to investigate the mechanism of oxidative hemolysis by the factors of favism. RT- erythrocytes have a defense system against the oxidative stress which is blocked either where regeneration of GSH occurs or the scavenging of the radicals from the membrane is prevented. The oxidative factors used were isouramil, divicine and diamide. When RT- erythrocytes were treated with isouramil, GSH decreased to undetectable levels and was not regenerated. Complete hemolysis occurred, but no oxidation of SH groups of membrane proteins or formation of spectrin polymers was detected. A similar effect was observed with diamide. However, SH groups of membrane proteins were completely oxidized and spectrin polymers were formed. Extensive lipid peroxidation was also detected together with a 30% fall in the arachidonic acid level. Control erythrocytes treated with either isouramil or diamide were not hemolyzed. When treated with isouramil, after a fall in the first few minutes, the GSH level was completely regenerated after 20 min. Incubation with diamide caused extensive oxidation of SH groups of membrane proteins and formation of spectrin polymers. No lipid peroxidation was detected after treatment with isouramil, but the same decrease of arachidonic acid occurred as in RT- erythrocytes. These results support the hypothesis that oxidative hemolysis by the factors of favism is caused by uncontrolled peroxidation of membrane lipids.

Animals↗
PubMed1983

In vitro synthesis and post-translational insertion into microsomes of the integral membrane protein, NADH-cytochrome b5 oxidoreductase.

RNA extracted from a free polysome fraction from rat liver was used to direct translation in nuclease-treated rabbit reticulocyte lysates, and the [35S]methionine-labelled, in vitro-synthesized, cytochrome b5 reductase was isolated with specific antibodies. Analysis by SDS-polyacrylamide gel electrophoresis, non-equilibrium pH gradient electrophoresis and one-dimensional peptide mapping failed to reveal any difference between the in vitro-synthesized reductase and the enzyme endogenous to rat liver microsomes. To study the integration of the in vitro-synthesized reductase into membranes, carboxypeptidase Y was used as a proteolytic probe. The reductase endogenous to rat liver microsomes was resistant to attack by carboxypeptidase Y, but was degraded to a smaller form when the microsomes were solubilized by detergent. Likewise, the enzyme synthesized in vitro was attacked by carboxypeptidase Y, but became largely resistant after post-translational incubation with dog pancreatic microsomes, indicating that an integration into membranes similar to the physiological one had occurred. It is concluded that cytochrome b5 reductase is probably not synthesized as a precursor and inserts post-translationally into the membrane. The results are discussed in relation to the particular subcellular distribution of the reductase and to the possible topology in the lipid bilayer of its C-terminal non-polar membrane-binding segment.

Animals↗
PubMed1981

Effect of divicine and isouramil on red cell metabolism in normal and G6PD-deficient (Mediterranean variant) subjects. Possible role in the genesis of favism.

Fava beans contain high amounts (up to 6.7 g/100 g dry weight) vicine and convicine. Their active aglycones divicine and isouramil have equivalent metabolic effects. They rapidly oxidize GSH to GSSG in normal and G6PD-deficient red cells. No regeneration of GSH occurs in deficient cells. The stoichiometry of the divicine oxidation of GSH is 1:1. Ascorbic acid is quickly oxidized by isouramil in both normal and deficient cells but regenerates only in normal cells. Isouramil oxidizes NADH at a much lesser extent than NADPH. Glycolysis is activated at the glyceraldehyde 3-phosphate dehydrogenase step. Divicine strongly stimulates hexone monophosphate shunt only in normal red cells. Divicine alone or associated with ascorbic acid has almost no effect in deficient red cells. Malonyl dialdehyde production is slight and virtually the same in normal and deficient cells treated with 5 mM isouramil. Large polypeptide aggregates are formed after 12 and 24 hours incubation with 1 mM divicine in deficient cells only. Divicine (0.25 mM) markedly decreases the filterability of deficient cells. The results are consistent with a causal role of divicine/isouramil in the genesis of the hemolytic crisis occurring in G6PD-deficient subjects after fava bean ingestion.

Ascorbic Acid↗
PubMed1975

Effects of litter size on protein, choline acetyltransferase (cat), and dopamine-beta-hydroxylase (DBH) of a mouse sympathetic ganglion.

Litters of 5, 10 and 17 pups were formed at birth. At 7, 14, 21, 28 and 60 days after birth mice were weighed and the cervical superior ganglia were examined for total protein and for CAT and DBH activities. At each age, the parameters examined were fitted into regression lines on the reciprocal of the litter size (L.S.R.); a highly positive correlation was found at each age between body weight and L.S.R., with maximum differences at weaning (day 21) followed by partial recovery after ad libitum feeding until day 60. A positive correlation was also found for total ganglion protein at days 21 and 28, with recovery practically completed at day 60. For CAT activity a positive correlation with L.S.R. appeared at day 14, with increasing coefficient and significance in later periods, until day 60. The temporal pattern of DBH activity for the 5-pup litter showed a peak at day 21, followed by a 35% decrease at day 28, with a steady level until day 60. A similar trend was observed for the 10- and 17-pup litters, but the peak occurred at day 28. Significant differences were found as early as day 7 between the 5- and the 17-pup litters, the maximum differences in the 3 experimental conditions being found at weaning, with a high and significant correlation coefficient, which persisted at day 60. Thus, the biochemical development and maturation of both presynaptic cholinergic nerve terminals and postsynaptic adrenergic neurones was evidently affected by the itter size during the suckling period, with persistent effects.

Acetyltransferases↗