Search PubMed⌕ Search

Biomedical subjects

S Incerpi

Publications and source records attributed to S Incerpi.

At least 37 records · Page 2Linked to original sources
PubMed1986

Insulin effects on human red blood cells.

The effect of insulin on human red blood cells was investigated, both on intact cells and on isolated plasma membranes, testing the responsiveness of membrane-bound enzymes--such as (Na+-K+)-ATPase and 5'-nucleotidase--as well as the ouabain binding and ionic fluxes. It appears that insulin stimulates Na-pumping mechanisms increasing (Na+-K+)-ATPase activity through an enhanced availability of pumping sites, as can be inferred from the increased ouabain binding. The apparent unresponsiveness of fluorescence polarization parameters, following insulin treatment of isolated plasma membranes and intact cells, rules out--at present--an involvement of membrane lipid fluidity in the mechanism of action of insulin on human erythrocytes.

5'-Nucleotidase↗
PubMed1984

Tyrosine aminotransferase activity of frog (Rana esculenta) liver. III. A circannual study.

A circannual study of tyrosine aminotransferase and other metabolic enzymes in frog liver is reported. The subcellular distribution of all enzymatic activities under investigation was also studied. Results show significant oscillations of all enzymatic activities throughout the year; in particular tyrosine aminotransferase has a marked summer maximum. The subcellular distribution of tyrosine aminotransferase shows significant variations: the soluble activity of the enzyme presents a bimodal circannual distribution, which has its counterpart in an increased activity of heavier fractions.

Acid Phosphatase↗
PubMed1983

Glucocorticoid receptor of frog (Rana esculenta) liver.

The presence of a glucocorticoid soluble receptor is demonstrated in frog liver cytosol. The kinetic characterization of frog liver cytosolic receptor for glucocorticoids is reported and its steroid specificity assessed. Results indicate a gross similarity between frog liver and mammalian glucocorticoid receptor, being a major difference the reduced binding capacity.

Animals↗
PubMed1982

Tyrosine aminotransferase activity of frog (Rana esculenta) liver--II. Comparative aspects of intracellular distribution.

1. A subcellular fractionation procedure for frog liver is reported and validated by the distribution pattern of several marker enzymes, also in comparison with rat liver. 2. The subcellular distribution of tyrosine aminotransferase was investigated in frog liver as compared to rat liver: a different distribution of the enzyme was observed, being the activity mostly recovered in mitochondrial and cytosolic compartments. 3. Results indicate that mitochondrial tyrosine aminotransferase of both frog and rat liver is a matrix enzyme, even if differences are observed concerning its release from the organelles upon detergent treatment.

Animals↗
PubMed1982

Tyrosine aminotransferase activity of frog (Rana esculenta) liver.

1. The presence of tyrosine aminotransferase is reported both in particulate and soluble fractions of frog liver. 2. The activity of the soluble enzyme of frog liver was investigated with regard to its dose and time dependence, its substrate specificity and concentration dependence, its thermal sensitivity as well as pH and temperature dependence. 3. It appears that the properties of the soluble tyrosine aminotransferase of frog liver are in close agreement with those reported for the mammalian liver enzyme.

Animals↗
PubMed1981

Insulin binding and internalization in rat hepatocytes during prenatal and postnatal life.

Insulin binding to isolated rat hepatocytes was studied during prenatal and postnatal life. Results show that in hepatocytes isolated from prenatal, postnatal and adult rat there is a constant increase in the number of insulin binding sites per cell, whereas the affinity of plasma membrane receptors for the hormonal ligand remains unaltered from prenatal to adult hepatocytes. Autoradiographic studies indicate a greater internalization of hormone during prenatal life and, taking into account the increase of cell size, suggest an unchanged surface density of receptor sites before and after birth.

Aging↗
PubMed1981

Insulin effect in vitro on human erythrocyte plasma membrane.

The effect of porcine insulin has been tested in vitro on human erythrocyte plasma membrane (Na+-K+) and Mg2+-ATPase activities as well as on membrane fluidity. The results indicate that the hormonal treatment significantly inhibits (Na+-K+)-ATPase activity, and at the same time decreases membrane fluidity.

Adenosine Triphosphatases↗
PubMed1980

Transfer of insulin receptors and of glucose transport-inducing proteins onto phospholipid vesicles.

Insulin receptors and glucose transport-inducing proteins have been extracted from rat liver membranes onto positively charged lipid bilayer vesicles. The extraction was carried out during the incubation of the vesicles with lipid vesicles caused an overall enhancement of specific insulin binding and of glucose transport inducement. The latter has been inferred from the oxidation rate of transported glucose through a spherical bilayer membrane entrapping the oxidizing glucose oxidase. Glucose transport is not enhanced by insulin binding, indicating that the two functions baecome dissociated when the proteins are transferred from the plasma membrane onto the bilayer vesicles.

Animals↗
PubMed1980

Effect of colchicine on rat liver plasma membrane.

Colchicine effect has been tested on rat liver plasma membrane-bound enzymes after in vitro or in vivo treatment. It appears that the in vitro treatment does not affect 5'-nucleotidase, Mg2+-ATPase and (Na+ + K+)-ATPase, whereas adenylate cyclase is sensitive to both in vitro and in vivo treatment, the latter condition being also effective for 5'-nucleotidase.

Adenosine Triphosphatases↗
PubMed1979

[Effect of chlorpropamide and of phenformin on isolated liver plasmatic membranes].

Previous observations from this laboratory suggest that chlorpropamide and phenformin, two hypoglycemic drugs belonging to sulfonylureas and biguanides respectively, act on liver plasma membranes altering the activity of enzymes bound to plasma membrane as (Na+-K+)-ATPase. This enzyme, an integral membrane protein which shows a cooperative behavior, has been used as an allosteric probe able to give information on plasma membrane. Our experiments show that (Na+-K+)-ATPase has a positive cooperative behaviour, as suggested from Hill coefficient n > l. The two hypoglycemic drugs decrease the Hill coefficient; in addition both chlorpropamide and phenformin inhibit (Na+-K+)-dependent but not Mg2+-dependent ATPase activity.

Animals↗