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Biomedical subjects

G Ronca

Publications and source records attributed to G Ronca.

At least 73 records · Page 4Linked to original sources
PubMed1985

Effect of creatine phosphate administration on the rat heart adenylate pool.

Creatine phosphate (CP) has been shown to possess some pharmacological properties. When added to cardioplegic solutions it improves their myocardial protection. Furthermore exogenous creatine phosphate shows an anti-arrhythmic effect in the experimental animal and appears to decrease lactate formation following haemorrhagic shock. These properties have been ascribed to the conservation of the tissue stores of ATP. Recently Down et al. have observed higher rat heart levels of ATP and creatine phosphate after the intravenous administration of creatine phosphate. Since it is difficult to find the conditions for an increase of the adenylate pool, it seems of interest to establish whether the ATP increase is due to a rise of the total adenylate pool or of the energy charge or of both. Similarly the higher creatine phosphate concentration may be ascribed to a variation of the CP/creatine ratio or to an increase in the creatine plus CP pool. In the present paper we report that the administration of creatine phosphate raises both the adenylate pool and the energy charge. An increase of creatine and the creatine phosphate pool was also observed.

Adenine Nucleotides↗
PubMed1985

Studies on the effects of anthracyclines on mitochondrial respiration in vitro.

Aclacinomycin, 4'-epi-doxorubicin and 4'-epi-tetrahydropyranyl-adriamycin, three novel anthraquinone derivatives under investigation for their antitumour activity, showed an inhibitory effect on the in vitro respiration of mitochondria from rat hearts. The inhibition proved to be concentration-dependent in the range 0.05 to 1.40 mM and both the NADH-oxidase and the succinate oxidase systems were affected to different extents. Among the compounds tested, 4'-epi-tetrahydropyranyl-adriamycin appeared to be the least powerful effector, requiring a significantly higher concentration for 50% inhibition of oxidation than doxorubicin and the other analogues examined.

Aclarubicin↗
PubMed1985

Inhibitory effects of several anthracyclines on mitochondrial respiration and coenzyme Q10 protection.

A set of three novel anthracyclines, active as antitumour agents, has been examined for their possible effects on rat heart mitochondrial respiration. The in vitro inhibiting effects of the compounds have been compared with that of the older doxorubicin. Aclacinomycin was generally more inhibitory than doxorubicin, 4'-epi-doxorubicin and 4'-epi-tetrahydropyranyl-adriamycin, with both succinate and NAD+-linked substrates. Attempts to prevent anthracycline from inhibiting the succinate oxidase activity by means of adding exogenous coenzyme Q10 gave encouraging results, the inhibiting effect being in fact reduced.

Aclarubicin↗
PubMed1984

Effect of some smooth muscle relaxant drugs on calcium-related phenomena.

Some smooth muscle relaxant drugs devoid of anticholinergic action have been tested for their interaction with calmodulin, calmodulin-stimulated cyclic nucleotide phosphodiesterase activity, and uterine membrane binding sites for nitrendipine and adenosine. The myolytic activity of octylonium bromide and pinaverium bromide may be due to their interaction with calmodulin-dependent systems. Trimebutine maleate does not bind either to calmodulin or to nitrendipine and adenosine receptors. Tiropramide has no effect on calmodulin-dependent systems and on Ca2+ channels but it shows a competition for the A2-type adenosine receptors.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1984

beta 2-Microglobulin and other low molecular weight proteins in haemodiafiltrates and in haemofiltrates.

Uraemic patients underwent haemodialysis by cuprophan membrane, or haemodiafiltration by polyacrylonitrile membrane, or haemofiltration by acetate cellulose membrane. Plasma samples drawn before and after treatment with the dialyser were gel-filtered on Sephadex G-75. A comparison of the chromatograms showed that the treatment causes a removal of middle molecules, which is more consistent when haemodiafiltration and haemofiltration are used. Protein removal was examined in the fluids from the three dialysers. It was observed that proteins (300 +/- 45 mg and 410 +/- 60 mg respectively) were removed when polyacrylonitrile and acetate cellulose membranes were used, but not in the case of cuprophan membrane. beta 2-Microglobulin was the protein lost in the greatest amount.

Acrylic Resins↗
PubMed1982

Isolation of putative benzodiazepine receptors from rat brain membranes by affinity chromatography.

The benzodiazepine receptor from rat brain was solubilised and purified 5200-fold by affinity chromatography. The affinity column contained an immobilized benzodiazepine (delorazepam) and biospecific elution with 6 mM-chlorazepate was achieved. The purified receptor is apparently homogeneous in SDS-polyacrylamide gel electrophoresis. The native protein had a molecular weight of 240,000, and the subunit one of 60,000. The dissociation constant (KD) is 8 nM for [3H]diazepam. A correlation exists between the value of affinity obtained for benzodiazepine derivatives and their known pharmacological effectiveness.

Animals↗
PubMed1981

Specific adsorbents for affinity chromatography of benzodiazepine binding proteins.

The use of affinity chromatography as means of isolating/purifying proteins which have an affinity for benzodiazepine is described. Three such drugs are employed: chlorazepate, clonazepam and delorazepam. The results presented in this paper indicate that the proposed technique only works for chlorazepate and delorazepam. In fact these benzodiazepine-Sepharose derivatives are able to retain specifically proteins from human serum and rat kidney, lung, skeletal muscle and brain.

Animals↗
PubMed1979

Affinity labeling of histidine and lysine residue in the adenosine deaminase substrate binding site.

1. Adenosine deaminase was inactivated by 9-(4-bromoacetamidobenzyl)-adenine (I) and 9-(2-bromoacetamidobenzyl)adenine (II), two affinity labels. 2. The stoichiometry of the reaction with reagent II is reported: 1 mol reagent is bound per mol inactive enzyme. Amino acid analysis of the 6 N HCl hydrolyzate of the inactive enzyme identified CM-histidine as the main alkylation product. This is the first evidence of the presence of a histidine in the active site region. 3. The alkylation rate and involved amino acid residues were studied for both reagents I and II, at pH 8 and 5.5. The particular reactivity of a lysine near or in the active site is discussed.

Adenine↗
PubMed1977

Blood lymphocytes in chronic lymphocytic leukaemia and Hodgkin's disease: Immunological features and enzymes of nucleoside metabolism.

Purified lymphocytes from venous blood of sixteen healthy adult subjects, eight patients with chronic lymphocytic leukaemia (CLL) and ten with Hodgkin's disease (HD), were examined for adenosine deaminase (ADA), cytidine deaminase (CDA), purine nucleoside phosphorylase (PNPase) and adenosine monophosphate deaminese (AMPA), after thawing and homogenization. The same cells were examined for the capacity to form E rosettes and to respond to phytohaemagglutinin (PHA) stimulation. In CLL a significant reduction (P less than 0-001) of AMPA, PNPase and ADA activities was observed without variation of CDA. In contrast in HD PNPase, AMPA and CDA were increased (P less than 0-01) while ADA was in the normal range. The E-rosette forming cells were significantly reduced in both diseases and the capacity to respond to PHA-stimulation was strongly impaired in CLL. By this experimental approach it seems possible to demonstrate different states of functional activity of the lymphocytic cells in two diseases characterized by reduced T-cell-mediated immunity.

AMP Deaminase↗
PubMed1977

[Biochemical evaluation of damage due to lead: importance and significance of erythrocyte zinc-protoporhyrin IX and urinary amino acid determination].

The early detection of lead intoxitation needs practical, simple, reproducible and diagnostically valid screening test. The determination of ALA-D (delta-amino-levulinic acid-dehydratase) in erythrocytes is one of the most reliable test for the evaluation of the occupational exposure to lead. However this test is difficult to standardize, sensible to lead contamination of laboratory glassware and the activity of enzyme decreases rapidly if stored. The determination of erythrocytes ZPP (zinco-protoporphyrin IX) was proposed as useful, alternative test. The protoporphyrin IX is a metabolic intermediate in heme biosynthesis; in erythrocytes is present as free form and zinc-boundend compound. The ZPP give high values only in lead intoxication and sideropenic anemia. The ALA-D and ZPP in erythrocytes were measured and compared in a group of workers exposed to lead. We have shown a good correlation between these two biochemical parameters. Aminoacid excretion in urine from workers exposed to lead was measured and compared with other biochemical parameters of intoxication. All lead workers examined had excessive urinary CP (coproporphyrin) and ALA (delta-amino-levulinic acid) excretion. An abnormal excretion of glycine was present in eight workers (32%), whereas in other four (15%) the glycinuria was at limit of normal values. An abnormal excretion of lysine was present in six workers (21%). The last data appear very interesting because the action of lead in lysine metabolism was not known.

Aminolevulinic Acid↗