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Biomedical subjects

A Giacomello

Publications and source records attributed to A Giacomello.

At least 55 records · Page 3Linked to original sources
PubMed1983

Adenine-induced hypoxanthine release from IMP-enriched human erythrocytes.

Adenine uptake and hypoxanthine release by IMP-enriched human erythrocytes has been studied. The presence of IMP within the erythrocytes leads to an increase in the rate of adenine incorporation. Adenine is taken up by IMP-enriched erythrocytes as AMP, even when intracellular 5-phosphoribosyl-1-pyrophosphate concentration is undetectable and too low to allow IMP synthesis from hypoxanthine. During adenine uptake and AMP synthesis, hypoxanthine is released by the cells. The possibility that 5-phosphoribosyl-1-pyrophosphate, necessary for AMP synthesis, is formed through the hypoxanthine guanine phosphoribosyltransferase-catalyzed IMP pyrophosphorolysis is considered.

Adenine↗
PubMed1981

Action of D-penicillamine on immunocomplexes containing rheumatoid factor.

The affinity between purified rheumatoid factors (RF) and native or heat aggregated human IgG has been studied in vitro by polarization fluorescence in the presence and in the absence of D-penicillamine. The value of the dissociation constant was the same using native and heat aggregated IgG suggesting that binding to the aggregated protein is not dependent on the exposure of a new determinant lacking in the native molecule. The results obtained in the presence of D-penicillamine suggest that the concentration of the drug necessary to get a pronounced effect on the apparent dissociation constant of the immunocomplex between IgG and RF is not reached in vivo, in clinical situations.

Antigen-Antibody Complex↗
PubMed1981

Human hypoxanthine guanine phosphoribosyltransferase. The role of magnesium ion in a phosphoribosylpyrophosphate-utilizing enzyme.

The role of Mg ions in the hypoxanthine guanine phosphoribosyltransferase-catalyzed reaction have been studied using accurate values of proton and Mg stability constants of phosphoribosylpyrophosphate (P-Rib-PP) determined from pH titration data. The results obtained favor the conclusion that the dimagnesium salt of P-Rib-PP is the true substrate of the enzyme. The other species of P-Rib-PP do not appreciably affect the initial reaction rate. The inhibition of the hypoxanthine guanine phosphoribosyltransferase-catalyzed reaction observed at high MgCl2 concentration can be attributed to a competitive inhibition of Mg2+ with respect to the dimagnesium salt of P-Rib-PP, suggesting that these ionic species bind to the same enzyme form. At a fixed [P-Rib-PPtot], the concentration of its dimagnesium complex is a sigmoidal function of MgCl2 concentration, suggesting that caution must be employed in the interpretation of sigmoidal saturation curves for P-Rib-PP-utilizing enzymes when low and not constant concentrations of the divalent cation are used.

Erythrocytes↗
PubMed1980

An improved viscosimetric assay for vertebrate collagenase activity.

An improved viscosimetric assay for vertebrate collagenase acitivity is described. The assay is carried out at 35 degrees C in the presence of 1 M glucose to prevent fibril formation. The decrease in viscosity is linear with ime and proportional to enzyme concentration.

Animals↗
PubMed1980

Collagenase activity in human synovial fluids from joint diseases of diverse etiology.

The content of collagenase in latent as well as in apparent active form has been determined in synovial fluids from 21 patients with rheumatoid arthritis, 16 with non-rheumatoid inflammatory joint diseases, and 15 with degenerative joint disease. Collagenase activity was measured before and after activation of the latent enzyme by NaSCN treatment. Before activation, collagenase activity was present in the synovial fluids from 1 case of rheumatoid arthritis, 3 cases of degenerative joint disease, and 1 case of Behçet's syndrome. An excess of inhibitor was present in inactive synovial fluids. The incidence of collagenolytic activity markedly increased after treatment with NaSCN. When NaSCN-dependent collagenolytic activity was present, its value was of the same order of magnitude in all patients regardless of disease type. The diagnostic value of the finding of collagenase activity in synovial fluid, and the physiological meaning of the enzyme with reference to joint diseases, are discussed.

Arthritis↗
PubMed1979

Human hypoxanthine-guanine phosphoribosyltransferase. IMP-GMP exchange stoichiometry and steady state kinetics of the reaction.

Steady state kinetics of hypoxanthine guanine phosphoribosyltransferase-catalyzed reactions are studied. The results obtained suggest that IMP, GMP, P-Rib-PP, and pyrophosphate bind to the same enzyme form, while hypoxanthine and guanine bind to a different form. Guanine activates IMP-pyrophosphorolysis. During the reaction guanine and IMP are consumed with formation of GM

Erythrocytes↗
PubMed1979

A spectrophotometric method for the determination of 5-phosphoribosyl-1-pyrophosphate.

A new, sensitive, specific and simple spectrophotometric method for the determination of 5-phosphoribosyl-l-pyrophosphate (PRPP) is presented. PRPP is reacted with excess hypoxanthine in the presence of hypoxanthine-guanine phosphoribosyltransferase. At the end of the reaction, PRPP concentration is measured from the extent of conversion of hypoxanthine to inositate. The concentration of the purine base is determined spectrophotometrically in the presence of xanthine oxidase.

Erythrocytes↗
PubMed1979

Radioisotope X-ray fluorescence technique in the study of joint inflammation.

An X-ray fluorescence technique was employed to study the clearance rate from the knee joint of an intraarticularly injected stable tracer. Clearance curves, determined in two normal volunteers and in three patients with various articular diseases, were found to be of the monoexponential type in agreement with results obtained by authors employing radioactive tracers. Clearance half-time values in basal conditions were higher in the normal knee joint than in the inflamed knee joint. The effect of a corticosteroid suspension injected into the knee joint was also studied. Preliminary results obtained indicate that the X-ray fluorescence technique can be employed, with some advantages compared with the radiotracer technique, for quantitative determination of spontaneous or pharmacologically induced changes in joint inflammation.

Humans↗