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Biomedical subjects

M Maresca

Publications and source records attributed to M Maresca.

66 records · Page 4Linked to original sources
PubMedDate not supplied

Protein composition in resting and activated platelets of type I diabetic patients.

Protein composition of platelets of eleven type I diabetic patients and thirteen control subjects were analyzed by SDS polyacrylamide gel electrophoresis. Bands have been scanned and quantified. No significant difference was shown between controls and patients in any of the bands identified in electrophoretic patterns of whole platelet, membrane fraction, resting, activated and aggregated cytoskeleton. Data suggest that alterations observed in platelet function of diabetic patients cannot be connected to the changes in protein composition.

Blood Platelets↗
PubMedDate not supplied

Clinical aspects of visceral pain.

Pain producing stimuli in viscera are different from the stimuli which induce somatic pain. Two main clinical aspects of visceral pain are observed: true visceral pain and referred pain. The distinction among visceral pain, referred pain and somatic pain may be difficult in the so-called "intricate conditions". Furthermore, mnemonic traces may play an important role in determining clinical aspects of visceral pain.

Humans↗
PubMedDate not supplied

Glucose transport across plasma membrane in human platelets.

Studies have been carried out in the presence of 2-deoxyglucose, by utilizing a technique of platelet rapid filtration. Kinetic data suggest that glucose uptake across plasma membrane is the rate limiting step in its utilization. 2-deoxyglucose is transported by facilitated diffusion. L-glucose is transferred at only 1/1200 of the rate of glucose. Transport system shows high affinity for substrate. Transport is inhibited by cytochalasin B, phloretin and N-ethylmaleimide. Cytochalasin E does not affect 2-deoxyglucose uptake. Diamide can have activating or inhibitory effect. t-Butyl hydroperoxide is always activating. Insulin has no effect on rate transport. D-glucose, 3-O-methylglucose, non radioactive 2-deoxyglucose and D-mannose are strong competitors, whereas D-galactose and D-fructose compete weakly with 2-deoxyglucose transport.

Biological Transport↗
PubMedDate not supplied

The measurement of pain threshold in man by means of electrical stimuli. A critical appraisal.

The problem of pain threshold measurement in man is critically considered. The advantages of electrical stimuli in determining the cutaneous pain threshold are discussed. The conducting properties of the skin to electric current are carefully examined: in fact, such properties must be taken into account when electrical stimuli are applied to the skin. A series of investigations on pain threshold measurement by means of electrical stimuli are reported. The different sensations induced by stimulating the skin with different kinds of electrodes and different types of stimuli were analysed: trains of 5 square waves of 0.5-2 msec at the frequency of 250 Hz, applied to the skin by means of unpolarizable electrodes, were selected as the best suited stimuli for practical application. This kind of stimulation was applied in physiological and clinical investigations. The measurement of pain threshold by electrical stimuli was especially useful for the clinical examination and for the study of pathogenetic mechanisms of painful diseases.

Electric Conductivity↗
PubMedDate not supplied

Glucose and fructose utilization in human platelets. Effects of diamide.

In this study we have reported that platelets metabolize fructose more slowly than glucose and probably by a different mechanism. While formed lactate is correlated with glucose utilized, in the presence of fructose an overproduction of lactate was demonstrated. The different behaviour of glucose and fructose was also shown by utilizing diamide at various concentrations. Low diamide concentrations increase glucose consumption, whereas higher concentrations inhibit. Fructose is gradually inhibited by increasing oxidant quantities. Data obtained suggests that diamide interferes with the transport process across platelet membrane. It is likely that glucose and fructose do not share the same transport mechanism. On the other hand only high diamide concentrations inhibit sugar metabolism by acting on the glycolytic flux at the level of some key enzymes.

Azo Compounds↗
PubMedDate not supplied

The effect of diamide and glutathione on the uptake of glucose by human erythrocytes.

Diamide, directly added to human erythrocytes, inhibits glucose utilisation. The trend of this process is in good correlation with the intracellular concentration of GSH. Since diamide does not affect the glycolytic and hexose monophosphate-shunt-pathway enzymes, it is likely that the effect of diamide involves the sugar transport across erythrocyte membrane. Kinetic studies carried out on ghosts have shown that diamide decreases Vmax without affecting Km. GSH on the contrary stimulates glucose transport by increasing Vmax. The significance of GSH in the process of transport of sugar is discussed.

Azo Compounds↗
PubMedDate not supplied

Studies on the interaction of fructose 1,6-P2 aldolase with methylglyoxal.

Reaction of rabbit muscle fructose 1,6-P2 aldolase with methylglyoxal results in a biphasic loss of activity. The kinetics of the initial rapid phase are first order with respect to the inhibitor. Dihydroxyacetone phosphate and fructose 1,6 bisphosphate afford complete protection whereas inorganic phosphate provides only a partial protection against inactivation. The treatment with methylglyoxal modifies the aldolase ability to bind D-Ga3P and DHAP. Loss of activity correlates with the modification of 1.7 arginine residues but data suggest that probably one of these arginine residues is essential. A likely role of this residue could be its interaction with the C1 negatively charged phosphate binding site of the enzyme.

Aldehydes↗
PubMedDate not supplied

Cytoskeleton protein composition upon platelet stimulation with thrombin in essential thrombocythemia.

BACKGROUND: Structural and functional platelet alterations are present in essential thrombocythemia (E.T.). Platelet aggregation patterns are highly variable; moreover, structural, biochemical and metabolic platelet defects have also been shown. In this study, data on function and structure of platelets from a group of patients affected with E.T. are reported. Since cytoskeleton proteins are involved in activation and aggregation mechanisms, we investigated the cytoskeleton protein composition of resting, activated and aggregated platelets using electrophoretic analysis. PATIENTS AND METHODS: Studies were performed on 13 patients affected with E.T. On the basis of their functional behavior in response to thrombin, patients were divided into two groups: T1 (5 patients) and T2 (8 patients). A group of 11 healthy subjects was examined as control. Washed platelets were stimulated with 0.05 or 0.25 U/mL thrombin in the presence or the absence of EGTA in order to obtain activated or aggregated platelets. Triton-insoluble residues of activated and aggregated platelets were electrophoresed on 4.5-15% linear gradient SDS polyacrylamide gel, visualized by Coomassie blue stain and scanned with a densitometer. RESULTS: On the basis of the response to thrombin, group T1 was composed of subjects showing completely normal functional behaviour, while group T2 included patients who were more active than controls in response to low thrombin concentrations. By comparing the densitometric data of the two groups of patients it is possible to show that cytoskeleton structures in the T2 group have a significantly higher protein content than normals and than group T1. Platelet treatment with high thrombin concentrations cancels every difference between the two groups of patients with the exceptions of a 33-Kd protein and actin, which remain higher in group T2. CONCLUSION: Abnormal platelet function and quantitative cytoskeleton protein content can be correlated in patients affected with E.T. In the platelets of those patients who display higher responsiveness to thrombin, either altered calcium homeostasis or changes in membrane viscosity leading to altered thrombin receptor expression, or both these events, could be present.

Adult↗