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Biomedical subjects

M Camici

Publications and source records attributed to M Camici.

At least 19 recordsLinked to original sources
PubMed1992

Purine nucleoside phosphorylase from bovine lens: purification and properties.

Purine nucleoside phosphorylase (purine nucleoside: orthophosphate ribosyltransferase, EC 2.4.2.1) was purified 38,750-fold to apparent electrophoretic homogeneity from bovine ocular lens. The enzyme appears to be a homotrimer with a molecular weight of 97,000, and displays non-linear kinetics with concave downward curvature in double-reciprocal plots with orthophosphate as variable substrate. The analysis of the kinetic parameters of bovine lens purine nucleoside phosphorylase, determined both for the phosphorolytic activity on nucleosides and for ribosylating activity on purine bases, indicates the occurrence of a rapid equilibrium random Bi-Bi mechanism with formation of abortive complexes. The effect of pH on the enzyme activity and on the sensitivity of the enzyme to photoinactivation, as well as the effect of thiol reagents on the enzyme activity and stability, strongly suggest the involvement of histidine and cysteine residues in the active site. From the measurements of the kinetic parameters at different temperatures, heats of formation of the enzyme-substrate complex for guanosine, guanine, orthophosphate and ribose 1-phosphate were determined. Activation energies of 15,250 and 14,650 cal/mol were obtained for phosphorolysis and synthesis of guanosine, respectively.

Animals↗
PubMed1992

Deoxyribose 5-phosphate aldolase of Bacillus cereus: purification and properties.

Deoxyribose 5-phosphate aldolase was purified 41 times from Bacillus cereus induced by growth on deoxyribonucleosides. The purification procedure includes ammonium sulphate fractionation, gel filtration on Sephadex G-100, ion-exchange chromatography on DEAE-Sephacel and preparative electrophoresis on 10% polyacrylamide gel. The enzyme is stable above pH 6.5, but is rapidly inactivated by sulfhydryl reagents. Being insensitive to EDTA, it may be considered as a Class I aldolase. Among a number of compounds tested (including some carboxylic acids, free and phosphorylated pentoses, nucleotides and nucleosides), none has been found to affect the enzyme activity. The enzyme appears to be dimeric, with a subunit Mr of 23,600. A Km of 4.4 x 10(-4) M was calculated for dRib 5-P.

Aldehyde-Lyases↗
PubMed1992

Purine salvage as a metabolite and energy saving mechanism in the ocular lens.

The ocular lens is an organ which depends mainly on anaerobic processes to obtain the metabolic energy required for the maintenance of its physiological functions. In these circumstances, the purine salvage pathway enzymes, by using preformed purine rings, and allowing the utilization of the activated ribose moiety of nucleosides, might be of relevance as an energy saving device. In this paper we show that the calf lens possesses many enzymes of the purine salvage pathway, with a particularly high specific activity of purine nucleoside phosphorylase (EC 2.4.2.1), and that the isolated lens epithelium can actively convert adenine and adenosine into adenine nucleotides. In addition, as in bacteria and red blood cells, inosine and adenosine in the lens, acting as ribose donors, exert a profound effect on the process of adenine conversion into ATP.

Adenine↗
PubMed1992

[Ticlopidine and platelet function].

In macular degeneration disease of the eye, we have studied the behaviour of vitro thrombocyte aggregation/deaggregation and ex vivo plasma beta-thromboglobulin level (Born aggregometer, RIA kit) during administration of an antiaggregant platelet drug (ticlopidine). We have observed the presence of a prothrombotic state that improves after 15 days of administration of drug. In fact platelet aggregation and beta-thromboglobulin level significantly decrease while thrombocyte deaggregation significantly increase. The correlations between deaggregation, aggregation and beta-thromboglobulin level suggest that the antiaggregant action of the ticlopidine is linked to the inhibition of platelet release reaction.

Adult↗
PubMed1992

[Lipid behavior during hemodialysis using heparin and prostacyclin].

Ten patients have been studied for lipidic behaviour during hemodialysis using as anticoagulant heparin and prostacyclin. Hearing has been administered at infusion rate of 2000 U/h and prostacyclin in 5 ng/kg/min. Lipidic behaviour (before and after hemodialysis) has been studied for apolipoproteins A and B, total serum cholesterol and serum triglycerides, HDL-cholesterol, lipoprotein. Total serum cholesterol/HDL-cholesterol, apolipoproteins A/apolipoproteins B, apolipoproteins A/HDL-cholesterol ratios have been also studied. Our findings show that heparin produces acute changes in lipidic behaviour after hemodialysis and suggest that administrations may contribute to lipidic derangement of uremic dialytic patient while heparin free dialysis (prostacyclin infusion) doesn't show lipidic derangement after dialytic treatment. Prostacyclin infusion suggests that may be a useful anticoagulant and therapeutic drug especially in uremic dialytic subject with high atherosclerosis involvement, dyslipidemia and arterial hypertension.

Adult↗
PubMed1991

Nucleoside phosphotransferase activity of human colon carcinoma cytosolic 5'-nucleotidase.

A cytosolic 5'-nucleotidase, acting preferentially on IMP and GMP, has been isolated from human colon carcinoma extracts. This enzyme activity catalyzes also the transfer of the phosphate group of 5'-nucleoside monophosphates (mainly, 5'-IMP, 5'-GMP, and their deoxycounterparts) to nucleosides (preferentially inosine and deoxyinosine, but also nucleoside analogs, such as 8-azaguanosine and 2',3'-dideoxyinosine). It has been proposed that the enzyme mechanism involves the formation of a phosphorylated enzyme as an intermediate which can transfer the phosphate group either to water or to the nucleoside. The enzyme is activated by some effectors, such as ATP and 2,3-diphosphoglycerate. Results indicate that the effect of these activators is mainly to favor the transfer of the phosphate of the phosphorylated intermediate to the nucleoside (i.e., the nucleoside phosphotransferase activity). This finding is in accordance with previous suggestions that cytosolic 5'-nucleotidase cannot be considered a pure catabolic enzyme.

2,3-Diphosphoglycerate↗
PubMed1991

[Heparin anticoagulant activity: new knowledge and future prospects].

The present knowledge about the heparin molecular structure has been reported by current scientific literature and especially the relationship between structure and function. From the pharmacological point of view the authors suggest future lines of research in this field. The role of endothelial and the mechanisms of heparin removal from the circulation (saturation and desaturation) are analyzed. From the anticoagulation point of view the authors after the analysis of the anti-thrombin III and anti-factor Xa activity, evaluate the heparin biological action on the platelets, complement, white blood cells. They also evaluate the questions collected to heparin use in non classical clinical situations, alternative routes of administration and new therapeutic and anticoagulant procedure; the association of prostacyclin together with heparin.

Animals↗
PubMed1991

[Risk of disseminated intravascular coagulation in patients undergoing echo-guided transperineal prostatic needle biopsy with transrectal probe].

Disseminated intravascular coagulation (DIC) is a severe life-threatening acute bleeding disorder. Traumatized tissues, tumors, necrotic tissues, or bacterial endotoxines release similar material in the blood to the tissutal factors activating the coagulation cascade. This preliminary study was aimed at verifying the risk of DIC in patients undergoing US-guided transperineal prostatic biopsy with Chiba and Tru-Cut needles. To evaluate the activation degree of coagulation factors in the circulation, the authors measured the concentrations of urinary fibrin degradation products in 10 patients undergoing US-guided transperineal prostatic biopsy, both before and after biopsy, every second hour, for 24 hours. Every tube of urine sample contained soya bean trypsin inhibitor and bovine thrombin to prevent any further fibrin degradation during incubation period for the possible presence of blood in urine samples. The results showed that 7/10 patients had marked increase in urinary fibrin degradation product levels (up to 800 micrograms%), with a 3-phase trend: early peak after 2-6 hours, middle peak after 6-14 hours, and late peak after 18-24 hours, which proved the activation of the coagulation cascade.

Aged↗
PubMed1990

Bovine lens aldose reductase: tight binding of the pyridine coenzyme.

Analysis by HPLC of the protein-free supernatant obtained after denaturation of aldose reductase shows that the native form of the enzyme (ARb) contains a tightly bound NADP+, which is absent in the oxidatively modified form (ARa). The absorption, fluorescence, and circular dichroism spectra of ARb and ARa are consistent with the presence of the cofactor only in the native form of aldose reductase. On the other hand, the modified enzyme, in appropriate thiol reducing conditions, can tightly bind NADP+. This indicates a potential reversibility of the modification of aldose reductase, at least in terms of retention of the cofactor.

Aldehyde Reductase↗
PubMed1990

Purine salvage enzyme activities in normal and neoplastic human tissues.

The enzymatic pattern of five enzymes involved in the purine salvage pathway, namely purine nucleoside phosphorylase (EC 2.4.2.1), adenosine deaminase (EC 3.5.4.4), 5'-nucleotidase (EC 3.1.3.5), alkaline phosphatase (EC 3.1.3.1), and hypoxanthine-guanine phosphoribosyltransferase (EC 2.4.2.8) has been evaluated both in human intestinal and breast carcinomas and compared to that of normal tissues. A higher level of hypoxanthine-guanine phosphoribosyltransferase was associated with tumor tissues. This metabolic alteration should lead to an elevated synthesis of nucleotides in cancer cells, might confer selective growth advantages to neoplastic tissues, and account, at least in part, for the difficulties encountered in the chemotherapy of human tumors, by using compounds affecting only the purine de novo biosynthesis.

5'-Nucleotidase↗
PubMed1990

[Cardiac effects of prostacyclin infusion].

The purpose of this investigation is the evaluation of cardiac effects of short-term prostacyclin intravenous infusion. Prostaglandin I2 has been administered at rate of 5 ng/kg/min. Systolic blood pressure (mmHg) remains unchanged, heart rate (beats/min) significantly increases (p less than 0.01). Diastolic blood pressure (mmHg) significantly decreases (p less than 0.01) during the first hour: this decrease is not significant during the second and third hour. The QTc shortens during the first and third hour and returns to normal values during 60-90 minutes of infusion. This preliminary study suggests that cardiac effects of prostacyclin infusion are indirect.

Adult↗
PubMed1989

Change in stereospecificity of bovine lens aldose reductase modified by oxidative stress.

Bovine lens aldose reductase (alditol:NADP+ oxidoreductase, EC 1.1.1.21) undergoes an oxidative modification, greatly stimulated by high ionic strength, upon incubation in the presence of oxygen radical generating systems (Del Corso, A., Camici, M., and Mura, U. (1987) Biochem. Biophys. Res. Commun. 148, 369-375). The enzyme modification is accompanied by a change in stereospecificity toward the two enantiomers of glyceraldehyde. In particular, the Km for L-glyceraldehyde of the native form increased over 150 times after the enzyme modification, with a decrease in the catalytic efficiency of over 200 times. By contrast, for the D-enantiomer the Km increased only 7 times with respect to the native form, with a concomitant decrease in the catalytic efficiency of only approximately 3 times. This dramatic change in stereospecificity may account for the reported apparent cooperative behavior exhibited also by highly purified electrophoretically homogeneous preparations of aldose reductase.

Aldehyde Reductase↗
PubMed1989

Lens aldo-keto reductase of Camelus dromedarius: purification and properties.

Aldo-keto reductase has been purified 13,000-fold from the lens of the camel (Camelus dromedarius) to a specific activity of 85 U/mg protein. The enzyme is a monomeric protein, exhibiting a Mr = 40,000 upon polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulphate. Camel lens aldo-keto reductase shows a broad substrate specificity, which is strictly dependent on NADPH, and is insensitive to inhibition by Sorbinil and valproate. Aldoses with a carbon chain with more than four residues, as well as glucuronate, are not reduced by the enzyme. On the basis of substrate specificity and sensitivity to inhibition, camel lens aldo-keto reductase appears to be distinct from the so far described aldose, aldehyde and carbonyl reductases.

Alcohol Oxidoreductases↗
PubMed1989

Bovine lens aldose reductase: identification of two enzyme forms.

Two structurally different forms of bovine lens aldose reductase have been identified. Freshly prepared lens extracts contain an unactivated "b form" (ARb) which is sensitive to inhibition by Sorbinil. Upon incubation of the extracts with oxygen radical generating systems, ARb is converted to a more active "a form" (ARa), which is not inhibited by Sorbinil. ARa and ARb were purified to electrophoretic homogeneity.

Aldehyde Reductase↗
PubMed1989

8-azaguanosine-5'-monophosphate synthesis via nucleoside kinase in cultured Chinese hamster lung fibroblasts.

Cultured chinese hamster lung fibroblasts, and a variant clone selected for resistance to 8-azaguanine, that lacks hypoxanthine-guanine phosphoribosyl transferase (EC 2.4.2.8), have been tested for the ability to convert 8-azaguanine into 8-azaguanosine-5'-monophosphate via purine nucleoside phosphorylase and nucleoside kinase. Purine nucleoside phosphorylase of both cell types is able to synthesize 8-azaguanosine from 8-azaguanine with the same efficiency. Wild type cells possess a nucleoside kinase activity acting on 8-azaguanosine, but this activity is considerably lower in the cells displaying resistance to the base analog. Our lines of evidence demonstrate that purine nucleoside phosphorylase and nucleoside kinase constitute a possible way of synthesis of the cytotoxic mononucleotide of 8-azaguanine, and, in fact, cells selected for resistance to the base analog show an impairement in the nucleoside kinase activity.

Animals↗
PubMed1989

NADPH-dependent reduction of glyceraldehyde: a unusually high activity in the lens of the camel (Camelus dromedarius).

The enzymes of the polyol pathway, namely aldose reductase and sorbitol dehydrogenase, were measured in camel lens extracts. A NADPH-dependent glyceraldehyde and erythrose reductase activity 25 times higher than that of calf lens was observed in camel lens. A preliminary comparison between this enzyme activity present in the camel and aldose reductase of calf lens is reported.

Aldehyde Reductase↗