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Biomedical subjects

A Fazi

Publications and source records attributed to A Fazi.

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

Isoenzymes of phosphoglucomutase from human red blood cells: isolation and kinetic properties.

A procedure has been developed for the purification of phosphoglucomutase from human red cell (phenotype PGM1 a1 or a3) lysates. It yields homogeneous isoenzyme preparations of the products ("primary" and "secondary") of the two PGM1 and PGM2 loci with distinctive pI (from 6.07 to 5.29). There are substantial differences between PGM1 and PGM2 isoenzymes, having single polypeptide chains of 58,500 and 69,000 Mr respectively and showing different thermostability. The kinetic properties of all the isoenzymes for the phosphoglucomutase reaction are essentially the same (apart from the specific activity of 1089-1263 units/mg for PGM1 forms vs 37-42 units/mg for PGM2 forms), but there are striking differences in substrate specificity. In fact the products of PGM1 locus are "true" phosphoglucomutases, being specific to mutate glucose monophosphates, whereas the PGM2 forms also display phosphoribomutase and glucose 1,6-bisphosphate synthetic activities. Some kinetic properties of these "side activities" are also reported.

Chromatography, DEAE-Cellulose↗
PubMed1988

Decrease in frequency of anginal episodes by control of thrombin generation with low-dose heparin: a controlled cross-over randomized study.

Increased thrombin generation is frequently associated with an increase in anginal activity. A cross-over, single-blind, completely randomized study was planned in order to evaluate whether the control of thrombin generation affected the increase in anginal activity. After discharge from the hospital, 24 patients (18 men and 6 women, aged 40 to 69 years) suffering from spontaneous angina were followed up to 12 months and were alternatively treated during two consecutive 6-month periods with calcium heparin, 12,500 IU by the subcutaneous route, or with placebo by the intramuscular route, in addition to the usual antianginal medications. Thrombin generation and clinical activity of angina were assessed every 15 days by measuring fibrinopeptide A (FPA) plasma levels and by grading in three classes (symptomless, mildly symptomatic, and severely symptomatic) the anginal activity on the basis of the number and the time concentration of the ischemic attacks and ECG changes. Low-dose heparin treatment significantly reduced both the FPA plasma level (from 4.1 +/- 3.7 to 2.3 +/- 1.8 ng/ml, p less than 0.001) and the clinical activity of angina. During heparin treatment, the frequency of the observations in the severely and mildly symptomatic classes decreased, respectively, by 53% and by 30%, whereas that in the symptomless class increased by 23% (p less than 0.001) in comparison with the period on placebo. Present results indicate that the control of thrombin generation obtained by low-dose heparin treatment favorably affects the degree of anginal activity in patients with spontaneous angina.

Aged↗
PubMed1988

Simultaneous preparation from human placenta of several enzymes of glucose metabolism.

A procedure for the simultaneous purification to homogeneity of hexokinase, phosphoglucomutase 1 and 2, aldolase, phosphoglucose isomerase and glucose-6-phosphate dehydrogenase from human origin has been developed. Human placenta homogenate was first chromatographed on DE-52 column which retains hexokinase and glucose-6-phosphate dehydrogenase while the other enzymes are recovered in the unabsorbed protein fraction. The other steps in the purification involve Matrex gel and specific affinity chromatography for the DE-52 retained enzymes and phosphocellulose and Matrex gel chromatography for the other enzymes. All the enzymes mentioned were obtained in one week, with recoveries from 14 percent for glucose-6-phosphate dehydrogenase to 75 percent for hexokinase. Thus, the procedures utilized seem to be useful in obtaining large amounts of enzymes in a a homogeneous form from an easily available human tissue.

Chromatography, Affinity↗
PubMed1987

Association between time of increased fibrinopeptide A levels in plasma and episodes of spontaneous angina: a controlled prospective study.

Thirty-seven patients affected by spontaneous angina and 15 comparable control subjects were enrolled in a 12-month prospective study to evaluate the relationship between blood clotting activation (assessed by fibrinopeptide A [FPA] plasma concentration) and the occurrence of myocardial ischemic attacks. FPA measurements and clinical examinations in patients were performed every 2 weeks. In control subjects blood sampling was performed every 4 weeks. Data from 28 patients who completed the study and from the 15 control subjects were analyzed. The clinical activity of angina was divided into three classes (asymptomatic, mildly symptomatic, and severely symptomatic) on the basis of the number and time-concentration of the ischemic attacks and ECG changes during the 15 days preceding each clinical examination. In all but one patient, a cyclic pattern of activity of coronary artery disease was observed. During follow-up studies, 624 FPA measurements were performed in patients and 173 in control subjects. Mean values were 4.68 +/- 4.53 and 1.32 +/- 0.60 ng/ml, respectively (p less than 0.001). FPA levels differed markedly in relation to the activity of angina. A relationship between FPA levels and activity of disease (r = 0.54, p less than 0.01) was found in time course. Bolus heparin administration (100 IU/kg) during the active phase of angina sharply but incompletely lowered FPA plasma levels, indicating thrombin formation both intravascularly and extravascularly. Present results indicate that a marked blood clotting activation occurs simultaneously with the outbursts of clinical activity of spontaneous angina.

Adult↗
PubMed1987

Twenty-four-hour heart rate behavior in patients with impaired left ventricular function due to coronary heart disease.

We performed a 24-hour Holter monitoring study on 45 patients affected by coronary artery disease (CAD) with different degrees of left ventricular impairment, and on 15 controls, in order to observe heart rate (HR) changes. According to the ejection fraction (EF) determined by cardiac angiography, CAD patients were divided into 3 groups of 15 each: the first with EF greater than 0.5; the second with EF between 0.35 and 0.5 and the third with EF less than 0.35. Spontaneous HR variation during 24 h did not differ among controls and CAD patients with normal EF values. On the contrary, with the reduction of ventricular function, CAD patients showed increasingly higher values of HR only during the night. Patients with markedly reduced EF values showed higher values of HR than controls even during some hours of the day. During the night EF and HR showed a good linear correlation with the highest r value at 5 a.m. (r = 0.7, p less than 0.001). Present data show that a reduction in left ventricular performance results in an altered 24-hour HR pattern with a reduced HR slowing at night proportional to the extent of left ventricular dysfunction.

Adult↗
PubMed1986

Impaired cardiac PGI2 and PGE2 biosynthesis in patients with angina pectoris.

Thirty-four patients with unstable angina and 14 patients with stable effort angina were investigated for cardiac prostacyclin and prostaglandin E2 (PGE2) biosynthesis, under resting conditions and after cold pressor testing. Twenty-seven patients undergoing cardiac catheterization and coronary angiography for congenital or acquired heart diseases other than coronary artery disease were studied as a control group. Prostacyclin (as 6-keto-PGF1 alpha) and PGE2 were measured by specific radioimmunoassay of blood from the coronary sinus and aorta. During resting conditions no significant differences in plasma 6-keto-PGF1 alpha and PGE2 concentrations were found between coronary sinus and aortic blood, and no transcardiac gradient existed either in control subjects or in patients with stable and unstable angina, respectively. In control subjects cold pressor testing induced a significant increase in 6-keto-PGF1 alpha and PGE2 levels in blood from the different sampling sites, and a significant transcardiac gradient occurred (+11.2 +/- 6.4 pg/ml for 6-keto-PGF1 alpha and +5.1 +/- 3.4 pg/ml for PGE2). However, in angina patients no significant increase in 6-keto-PGF1 alpha and PGE2 plasma levels was found and no transcardiac gradient was formed after cold pressor testing. These results indicate impaired cardiac prostacyclin and PGE2 biosynthesis both in patients with stable and unstable effort angina.

6-Ketoprostaglandin F1 alpha↗
PubMed1986

Relationships between the age-dependent decay of glucose-1,6-bisphosphate synthesis, phosphoribomutase and phosphoglucomutase in human red cells.

In human red blood cells phosphoglucomutase exists in multiple molecular forms with different isoelectric points determined by two distinct loci called PGM1 and PGM2. With regard to the phosphoglucomutase PGM1 and PGM2 isoenzymes, the latter appear to be more important in erythrocyte metabolism owing to their ability to mutate ribose monophosphates and synthetize glucose-1,6-bisphosphate. In this paper we show that, beside undergoing age-related postranslational modifications, both phosphoglucomutase PGM1 and PGM2 forms decrease their activities as the mean cell age increases. Under the experimental conditions used to separate erythrocytes by age the comparison of the younger erythrocytes with the older shows that total phosphoglucomutase, phosphoribomutase and glucose-1,6-bisphosphate synthetic activities decay by 55%, 26% and 28%, respectively. We consider that these results substantiate the multifunctionality of PGM2 isoenzymes. Furthermore we discuss the role of these forms in the age-related decay of erythrocyte metabolism.

Aging↗
PubMed1985

Regulatory properties of human erythrocyte hexokinase during cell ageing.

Human red blood cell hexokinase exists in multiple molecular forms with different isoelectric points but similar kinetic and regulatory properties. All three major isoenzymes (HK Ia, Ib, and Ic) are inhibited competitively with respect to Mg.ATP by glucose 6-phosphate (Ki = 15 microM), glucose 1,6-diphosphate (Ki - 22 microM), 2,3-diphosphoglycerate (Ki = 4 mM), ATP (Ki = 1.5 mM), and reduced glutathione (Ki = 3 mM). All these compounds are present in the human erythrocyte at concentrations able to modify the hexokinase reaction velocity. However, the oxygenation state of hemoglobin significantly modifies their free concentrations and the formation of the Mg complexes. The calculated rate of glucose phosphorylation, in the presence of the mentioned compounds, is practically identical to the measured rate of glucose utilization by intact erythrocytes (1.43 +/- 0.15 mumol h-1 ml red blood cells-1). Hexokinase in young red blood cells is fivefold higher when compared with the old ones, but the concentration of many inhibitors of the enzyme is also cell age-dependent. Glucose 6-phosphate, glucose 1,6-diphosphate, 2,3-diphosphoglycerate, ATP, and Mg all decay during cell ageing but at different rates. The free concentrations and the hemoglobin and Mg complexes of both ATP and 2,3-diphosphoglycerate with hemoglobin in the oxy and deoxy forms have been calculated. This information was utilized in the calculation of glucose phosphorylation rate during cell ageing. The results obtained agree with the measured glycolytic rates and suggest that the decay of hexokinase during cell ageing could play a critical role in the process of cell senescence and destruction.

Adenosine Triphosphate↗
PubMed1985

Glucose-1,6-P2 synthesis, phosphoglucomutase and phosphoribomutase correlate with glucose-1,6-P2 concentration in mammals red blood cells.

Glucose 1,6-biphosphate (G1,6P2) was measured in human, pig, cow, rabbit, rat and sheep red blood cells. Mean values are variable among the species and range from 33 to 122 nmol/ml RBC for pig and rabbit erythrocytes, respectively. The activities of G1,6P2 synthase, phosphoglucomutase (PGM) and phosphoribomutase (PRM) have also been assayed in red cell haemolysates of the same species. The correlations between the biphosphate content and the occurrence of the three enzymatic activities have been studied in order to gain an insight into the regulation of the G1,6P2 turnover in mammalian erythrocytes.

Animals↗
PubMed1985

Glucose 1,6-bisphosphate decline in human erythrocytes: possible involvement of phosphoglucomutase PGM2 isoenzymes.

Human erythrocytes incubated with various sugars lower their glucose 1,6-bisphosphate (Glc-1,6-P2) content, as do haemolysates containing exogenous Glc-1,6-P2 incubated with sugar monophosphates (sugar-P). Experiments performed with isolated erythrocyte phosphoglucomutase (PGM) isoenzymes indicate that only definite isoenzymatic forms, namely PGM2, are able to consume Glc-1,6-P2 during the mutation of sugar-P other than glucose-P. In this process a phosphate group is released from Glc-1,6-P2 and can be partially recovered in the biphosphate of the mutated sugar-P. The relevance of this mechanism of Glc-1,6-P2 degradation is discussed in regard to the physiological turnover of the biphosphate.

Adenine Nucleotides↗
PubMed1984

Relationship between the rate of erythrocyte hexose monophosphate pathway and the glucose 6-phosphate concentration.

Erythrocytes of individuals with increased (+ 50%) or reduced (-35%) hexokinase activity contain respectively 70 and 17 nmole/ml RBC of glucose-6-phosphate (normal concentration 30 +/- 5nmole/ml RBC) and show comparable rates of the HMP (60 +/- 5nmole/hr/ml RBC). Similarly, in RBC of different ages, obtained by density gradient ultracentrifugation, the glucose-6-phosphate concentration range from 57 (young cells) to 18 (old cells) nmole/ml RBC but the rate at which glucose is utilized in the HMP is unchanged. These data exclude a regulatory role of glucose 6-phosphate in the HMP even if its concentration is under that required for maximal G6PD activity.

Chromosomes, Human, 6-12 and X↗
PubMed1984

[Glucose 1,6-diphosphate in the erythrocytes of various species of mammal].

Red blood cells from human, pig, cow, rabbit, rat and sheep were investigated for the occurrence of phosphoglucomutase multiple forms, G1,6P2 level, PGM, PRM and G1,6P2 synthetic activities. In all cases a species specific pattern of PGM isoenzymes was detected by starch gel electrophoresis. G1,6P2 mean values range from 33 to 122 nmol/ml RBC for pig and rabbit erythrocytes, respectively. The study of the correlation between the biphosphate content and the occurrence of the three measured enzymatic activities indicates a possible role of PRM activity (property of PGM2 isoenzymes) in the erythrocytic G1,6P2 catabolism.

Animals↗
PubMed1984

[Determination of the energy load of erythrocytes in long-distance and medium-distance runners].

In this study erythrocytes drawn from well-trained athletes (middle- and long-distance runners) and from sedentary subjects have been compared for their adenine nucleotide contents. ADP and AMP appeared to be significantly (p less than 0,001) increased only in red cells from athletes in the rest state. After athletes' race this difference with control subjects become insignificant. Nevertheless, the observed ADP and AMP modifications are not great enough to influence the energy charge (CE) of the compared erythrocytes.

Adenine Nucleotides↗
PubMed1984

Acetaldehyde influences glucose 1,6-bisphosphate level of human erythrocytes in vitro and in vivo.

In intact erythrocytes from normal adults, acetaldehyde, besides inducing metabolite modifications otherwise observed, markedly decreases the glucose 1,6-bisphosphate (G1,6P2) level. Pyruvate rapidly reverses the acetaldehyde effects. Also in vivo, the acetaldehyde that occurs in the blood stream after heavy alcohol intake produces a significant decrease of the erythrocyte G1,6P2 concentration. These changes support the role of 1,3-bisphosphoglycerate as the first substrate in the G1,6P2 synthesis. The significance of the glucose bisphosphate as glycolytic modulator is also discussed.

Acetaldehyde↗
PubMed1983

Vanadate affects glucose metabolism of human erythrocytes.

Vanadate causes a rapid breakdown of 2,3-bisphosphoglycerate in intact erythrocytes. This metabolite is nearly stoichiometrically transformed into pyruvate, which changes the cell redox state and enhances the glycolytic flux. The results show that the vanadate effect on 2,3-bisphosphoglycerate, also evident in hemolysates, is attributable to the stimulation of a phosphatase activity of the phosphoglycerate mutase. In agreement with others (J. Carreras, F. Climent, R. Bartrons, and G. Pons (1982) Biochim. Biophys. Acta 705, 238-242), vanadate is thought to destabilize the phosphoryl form of this enzyme which shows competitive inhibition between the ion and 2,3-bisphosphoglycerate in the mutase reaction. A competitive inhibition between vanadate and glucose 1,6-bisphosphate is also found for phosphoglucomutase, without evidence for phosphatase activity toward the bisphosphate cofactor.

2,3-Diphosphoglycerate↗
PubMed1981

Glucose utilization in human erythrocytes during physical exercise.

Red blood cells obtained from well-trained athletes consumed glucose at a higher rate than those from sedentary subjects when incubated in vitro in a glucose containing medium at 37 degrees C. Similar results were obtained when fructose was substituted for glucose, but not when galactose was the monosaccharide. The utilization of glucose by erythrocytes can occur both via the Embden-Meyerhof and Pentose phosphate pathways (PPP). In the present experiments, there were no differences in the activities of select enzymes in these pathways or in metabolic intermediates of the erythrocytes. An exception was an elevated 2,3-diphosphoglycerate (2,3DPG) in the erythrocytes of the athletes. Additional experiments are needed to identify changes in the red blood cells of the athletes which produce the increased consumption of glucose.

Adolescent↗