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Biomedical subjects

G Scutari

Publications and source records attributed to G Scutari.

54 records · Page 3Linked to original sources
PubMed1984

Pantethine and pantothenate effect on the CoA content of rat liver.

The role of pantethine as a precursor of CoA in rat liver has been examined. It has been demonstrated that pantethine induces a significant increase in the total CoA content both in perfused liver and in liver homogenate, while it fails to affect the mitochondrial CoA content when added to isolated mitochondria. Pantethine is more efficient than pantothenate in inducing the synthesis of CoA in rat liver, even in the presence of added cysteine. The possible metabolic implications are discussed.

Animals↗
PubMed1983

A simplified and computerizable regulatory enzyme model.

The concept of enzymes as simple biological catalysts has become too limiting and the kinetic behaviour has evidenced that the interaction of an enzyme with its substrate is more complex and can be influenced by various regulatory effectors. The resulting activity should be exactly what is required for the control of the overall flux through the metabolic pathway. A simplified enzyme model which can explain the sigmoidicity and the heterotropic effect involves the introduction of a limited number of kinetic parameters to obtain the best fit from v and s experimental values. This results in a more useful way to evaluate the possible regulatory effects of various substances such as metabolites, hormones and drugs.

Computers↗
PubMed1983

Kinetic alterations of the divalent cation-dependent ATPase activities of human erythrocyte membranes induced by blocking the membrane amino groups.

Treatment of erythrocyte membrane fragments with the amino group reagent sodium trinitrobenzenesulphonate (TNBS) leads to significant alteration of the kinetic properties of the membrane-bound (Ca2+ + Mg2+) and Mg2+-dependent ATPases, which appear to increase their affinity towards divalent cations and to decrease their maximal rates. Although it has not been possible to ascertain whether the amino groups involved in the TNBS effect belong to the membrane phospholipids or to the ATPase proteins, it appears that such groups play an essential role in the hydrolytic activity of the divalent cation-dependent ATPases, either by affecting the enzymes' microenvironment or by being directly involved in the enzymes'catalytic mechanism.

Adenosine Triphosphatases↗
PubMed1983

A new procedure for calculating the kinetic parameters of enzyme reactions.

The possibilities of computer and some mathematical and statistical considerations may renew the interest and reevaluate the advantages of the double reciprocal plot proposed by Lineweaver and Burk. From the experimental values of substrate concentration and reaction velocity, the best-fitting line can be statistically obtained using nonparametric criteria. Computer programs in FORTRAN and BASIC permit easy and elegant resolutions.

Enzymes↗
PubMed1982

Sensitivity to radiations of Mg2+ and (Ca2+ + Mg2+) ATPase activities associated with erythrocyte membrane fragments.

Treatment of disrupted erythrocyte membranes with ionizing radiation induces a partial oxidation of -SH groups (as expected from reported data) and a loss of membrane phospholipids as confirmed by the decrease of membrane amino groups. The resulting disturbance of the membrane assembly strongly affects the membrane bound divalent cation-dependent ATPase activities, possibly by causing the formation of a dead-end enzyme complex unable to complete the ATP splitting cycle.

Adenosine Triphosphatases↗
PubMed1980

Comparative extraction of erythrocyte EDTA-membrane proteins by some ionic and non-ionic detergents.

In order to examine whether it would be possible to obtain, by a simple extraction procedure from EDTA-erythrocyte-membranes, a partially purified preparation of the "band 3 zone" proteins, we have tested four solubilizing agents of common use. Detergents, both ionic (DOC and SDS) and non ionic (Tween 80 and Triton X-100), were not able, in our experimental conditions, to completely solubilize erythrocyte fragmented membranes which had previously been washed in EDTA-buffers. However, they were able to solubilize some of the membrane proteins, which could then be separated by SDS-PGE. The PGE densitometric profiles reported in this communication indicate that the protein mixture extracted by the ionic detergents DOC and SDS qualitatively reflects the protein composition of the membranes. Among the non ionic detergents, on the other hand, Triton X-100 appeared to be able to extract mainly one band (most probably the band 3 zone), while Tween 80 did not apparently extract any of the membrane proteins. Detergent concentrations, medium composition and experimental procedures are described in detail.

Adenosine Triphosphatases↗
PubMed1980

Divalent cation dependent ATPase activities of red blood cell membranes: influence of the oxidation of membrane thiol groups close to each other.

An Mg2+-dependent low ATPase activity can be detected in erythrocyte "white membranes," in addition to that of the well known (Ca2+ + Mg2+)-ATPase. The thiol oxidizing agent diamide affects both activities. The oxidation of neighboring thiols seems to leave the mechanism of the (Ca2+ + Mg2+)-ATPase amplification system evoked by Ca2+ largely unaffected. The perturbation caused by diamide in the membranes seems to affect primarily a step of the ATP hydrolysis mechanism that is common to both ATPase activities. The effectiveness of diamide seems to be the same when either Ca2+ and Mg2+, or Mg2+ alone are present during the reagent action. Reduction of disulfide bonds by DTE after diamide treatment restores the (Ca2+ + Mg2+)-ATPase activity but is unable to take the Mg2+-ATPase activity back to the original level. The hypothesis is discussed that the redox state of one (or more than one) couple of --SH close to each other and possibly connected to the active site, may be an important factor in optimizing the efficiency of Ca action on the (Ca2+ + Mg2+)-ATPase.

Ca(2+) Mg(2+)-ATPase↗
PubMed1979

Diamide inhibited (Ca++ + Mg++) and (Mg++) dependent ATPase in erythrocyte membranes: activity at different temperatures.

After inhibition of the monovalent cation dependent ATPase, a (Ca++ + Mg++) and a (Mg++) dependent ATPase activity can be detected. The inhibition due to diamide on the (Mg++) ATPase, assayed in the 12.5 degrees C - 30 degrees C temperature range, is almost complete. On the contrary the diamide induced inhibition of (Ca++ + Mg++) ATPase, in the same temperature range, is not complete and the residual activity increases with temperature. The reported data indicate that the ATPase activity induced by calcium is much less diamide-sensitive and -SH-dependent than that elicited by Mg++ alone.

Adenosine Triphosphatases↗
PubMed1979

Diamide effect on the ouabain-insensitive APTase activity of red cell membrane.

Membranes from human erythrocytes exhibit a marked decrease of the ouabain-insensitive ATPase activity and of the total membrane thiol content after treatment with diazenedicarboxylic acid bis(N,N-dimethylamide) (diamide). These effects increase with diamide concentrations up to 2-2.5 mM and are persistent after removal of the reagent. Treatment with 2,3-dihydroxy-1,4-dithiolbutane (dithioerythritol or DTE) reduced glutathione or 2-mercaptoethanol partially but significantly restores at about the same extent the ouabain-insensitive ATPase activity. These results indicate that the perturbation of the ATPase microenvironment caused by membrane thiol oxidation is at good extent responsible for alterations of the divalent cation-dependent ATPase activity.

Adenosine Triphosphatases↗
PubMed1978

Diamide effect on the hypertonic calcium uptake by rat red blood cells.

Red blood cells of rat exhibit an enhanced hypertonic calcium uptake after incubation with diazenedicarboxylic acids bis (N,N-dimethylamide) (diamide). Over the ranges reported in this paper the amount of membrane alteration is strongly and linearly dependent on the diamide concentration and on the osmolarity of the incubation medium. Treatment with 2,3-dihydroxy-1,4-dithiolbutane (dithioerythritol or DTE), after diamide removal, restores red blood cells calcium intake to values similar to those of the control. The results indicate that the sinergic action of diamide and hypertonicity can oxidize some thiol groups essential for the cation barrier maintenance.

Animals↗
PubMed1977

Carnitine effect on heart steatosis induced in rats by rapeseed oil.

Myocardial triglyceride levels in rats fed a high erucic acid rapeseed oil diet for three days were five times higher than in controls. The incorporation of erucic acid and, to a lower extent, some unsaturated fatty acids was increased, as well as total cholesterol content, compared to controls. The presence of 5% carnitine in the diet partially prevented these effects. It is assumed that carnitine may be a rate limiting factor in the myocardial catabolism of unsaturated fatty acids and particularly erucic acid, when these substance are ingested in supraoptimal amount.

Animals↗
PubMedDate not supplied

Effects of halothane, enflurane and isoflurane on some energy-converting functions of isolated rat liver mitochondria.

Enflurane and isoflurane appeared equally effective in decreasing the efficiency of oxidative phosphorylation in isolated mitochondria, while halothane was twice as effective as these two anesthetics. On the other hand enflurane and isoflurane exhibited different dose-response relationships when the uptake of calcium was measured (with a calcium-selective electrode) or the transmembrane electrical potential was monitored (with tetraphenylphosphonium-selective electrode) during ATP synthesis or calcium uptake in anesthetic treated mitochondria. The results indicate that the effects of isoflurane and enflurane on the mitochondrial energy converting processes are qualitatively, but not quantitatively, analogous to those previously described for halothane. Moreover the damaging action of isoflurane gradually increases as the anesthetic concentration increases, while that of enflurane suddenly increases above a threshold concentration. It appears that the effects of halothane, enflurane and isoflurane on isolated mitochondria involve both the ATP synthetase and the inner membrane permeability barrier, although the membrane-anesthetic interactions responsible for such effects are probably different for each anesthetic.

Animals↗