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S Ronca-Testoni

Publications and source records attributed to S Ronca-Testoni.

At least 55 records · Page 3Linked 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↗
PubMed1984

Some properties of a purinergic receptor solubilized from human uterus membranes.

A purinergic receptor was identified in human myometrium membranes using 5'-N-[3H]ethylcarboxamide-adenosine [( 3H] NECA) as radioligand. Scatchard analysis of the binding data gave a Kd of 123 nM with 2.3 pmol ligand bound/mg protein. Displacement studies indicated that the binding site had the characteristics of the A2 adenosine receptors and some of those of the P2 purinoceptors since it was inhibited by two slowly degradable ATP derivatives with IC50 values comparable to that of NECA. The receptor was solubilized with sodium cholate and its binding properties were the same as those of the membrane-bound form. No -SH group appeared to be essential for the binding activity. By density gradient centrifugation the purinergic receptor-detergent complex was estimated to have an apparent molecular mass of 95 kDa.

Adenosine↗
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

Benzodiazepine binding sites in human myometrium.

We report that membrane preparations of human myometrium possess binding sites for [3H] RO 5-4864, a specific ligand for the peripheral type of benzodiazepine receptors. Scatchard analysis shows a high-affinity binding site (Kd = 3.1 +/- 1.1 nM) and a class of low-affinity binding sites (Kd greater than 30nM) with positive cooperativity. Displacement and tryptic digestion experiments indicate that both these benzodiazepine binding sites are specific and proteic in nature. So benzodiazepines might exert their relaxant activity on uterine muscle directly at peripheral level through specific binding sites.

Adult↗
PubMed1983

Direct spectrophotometric assay for angiotensin-converting enzyme in serum.

The appropriate conditions for determining angiotensin-converting enzyme in human serum with use of 2-furanacryloyl-L-phenylalanylglycylglycine as substrate are described. The method, a modification of that reported by Holmquist et al. (Anal. Biochem. 95:540-548, 1979) for purified rabbit lung enzyme, is based on the blue shift of the absorption spectrum that occurs upon hydrolysis of the substrate into furanacryloyl-L-phenylalanine and glycylglycine. The Km value for the substrate is 0.31 mmol/L. Some kinetic properties determined by this method are similar to those previously reported for the purified serum enzyme. Results by the present assay and Cushman's modified method correlate closely (r = 0.995). The normal reference interval for 42 adult donors was 43-137 U/L (mean 90 U/L, SD 23 U/L). The within-run and between-run CVs ranged from 3.0 to 4.1%. Its rapidity, simplicity, sensitivity, and precision make the proposed method very suitable for routine work, clinical investigation, and kinetic and structural studies of the serum enzyme.

Clinical Enzyme Tests↗
PubMed1983

Hydrolysis of cyclomethasone by the human lung.

The hydrolysis rate of 9-chloro-11 beta, 17a-dihydroxy-16 beta-methyl-21-(1'4'N-acetyltransaminomethyl- cyclohexancarbonyloxy) pregna-1,4-diene-3,20-dione (cyclomethasone) and of beclomethasone 17,21-dipropionate was studied on human lung slices. Cyclomethasone is hydrolysed more slowly than beclomethasone 17,21-dipropionate. This difference may be ascribed to a different affinity and/or activity of the tissue esterases towards the two substrates or to a different transport rate in the sites of the esterase activity. Since the steroid moiety is the same for both molecules studied it appears that the hydrolysis and/or the transport rate of the esterified steroids depends on the chemical properties of the substituent at C-21.

Beclomethasone↗
PubMed1978

[Behavior of some enzymes of nucleoside catabolism in circulating lymphocytes during paraproteinemia].

The circulating lymphocytes of 16 normal subjects and of 18 patients with paraproteinemia have been characterized by measuring the levels of ADA, AMPA, PNPase, CDA. The results obtained reveal a highly significant increase in PNPase of subjects affected by paraproteinemia as compared to that of normal subjects (p less than 0.005). The fact that the increased enzymatic levels are found mainly in patients not affected by Bence-Jones proteinuria seems to indicate that the evolution of the paraproteinemia disease is in some way related to the intralymphocyte levels of PNPase.

AMP Deaminase↗
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↗
PubMed1975

Digestion of insulin derivatives with subtilisin: a kinetic study.

Native, denatured, performic acid-oxidized or S-sulfo insulin and S-sulfo or performic acid-oxidized A- and B-chains were digested with subtilisin type Carsberg. The proteolysis was followed by measuring the uptake of alkali through autotitration. The kinetic study shows the existence of 2 first-order reaction classes which differ markedly in rate constant. The number of bonds split with fast and with slow reactions has been calculated. Only one of a total of 12 cleavable bonds in native insulin is opened by fast reaction. In the denatured protein the number of bonds split by the fast reaction increases to 4 and in the oxidized and S-sulfo protein 3 bonds are cleaved, while the slow cleavable bonds number 2 and 7, respectively, The kinetic study of the proteolysis of S-sulfo A-chain and of oxidized or S-sulfo B-chain shows that two bonds are split in A-chain with the fast and slow reactions, while in B-chain only one of the six cleavable bonds is susceptible to fast attack.

Hydrogen Bonding↗