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Biomedical subjects

G Tolone

Publications and source records attributed to G Tolone.

At least 19 recordsLinked to original sources
PubMed1986

Effects of urea phosphate, ammonium ions and pH on Ureaplasma ATP synthesis.

The effects of various reaction conditions and the influence of urea and its hydrolysis products on Ureaplasma ATP synthesis were assayed using of a pH stat system which avoids the unfavourable changes of the external pH. The results proved that ATP synthesis required the presence of an optimal phosphate concentration and was dependent on the urea content of the reaction mixture. The data suggest that urea is the energetic source for ureaplasma growth and ammonium ions and pH could interfere in an additive way with the production of energy, only when the starting pH of the medium is kept in a slightly basic range.

Adenosine Triphosphate↗
PubMed1984

Influence of urease present in non viable organisms on the decline phase of Ureaplasma growth.

Broth cultures infected with ureaplasmas for 48 hrs were unable to support further growth of reinoculated ureaplasmas even when reconstituted with fresh ureaplasma medium. The apparent toxicity of spent cultures was ascribed to the presence of non viable ureaplasmas still containing a fully active urease since all the procedures adopted to abolish or reduce the urease activity restored the ability of these spent cultures to support ureaplasma growth. However, if the cause of the steep decline phase of ureaplasma cells could be reasonably ascribed to the enzymatic activity of urease present in the dead cells, the reasons for the poor field and the low titers achieved by the organisms during the logarithmic phase of growth remain an enigma.

Ammonium Chloride↗
PubMed1982

Adenosine triphosphatase activity of Ureaplasma urealyticum.

Adenosine triphosphatase activity of U. urealyticum is an integral membrane-bound protein which cannot be detached from the membrane by mild treatment with EDTA in low-ionic strength media nor by ionic detergents which rapidly inactivated the enzyme. The enzyme was Mg++ dependent; Mn++ and Co++ could replace Mg++ to some extent. A slight stimulatory effect was also exerted by sodium and lithium. The enzyme showed a nucleotide triphosphatase activity, but ADP was hydrolyzed at close to 40% the rate of ATP and other nucleotide monophosphatase were hydrolyzed at a very slow rate. Oubain and oligomycin did not inhibit the adenosine triphosphatase activity, whereas DCCD, NBD-Cl and several sulfhydryl-blocking reagents strongly reduced its activity. The enzyme could not be stimulated by trypsin pretreatment. It seems that the complex enzyme is tightly linked to the lipid bilayer of the membrane and differs in many aspects from the F0-F1 (Mg++, Ca++)-ATPase of bacteria.

4-Nitrophenylphosphatase↗
PubMed1980

Adenosine 5'-triphosphate synthesis induced by urea hydrolysis in Ureaplasma urealyticum.

Although considerable attention has been devoted to the urea-hydrolyzing activity of Ureaplasma urealyticum, there is as yet no firmly established function for this enzyme. Present results support the idea that its activity generates a chemical gradient across the membrane which drives adenosine 5'-triphosphate synthesis through a chemiosmotic type of mechanism.

Adenosine Triphosphate↗
PubMed1980

Calcium binding to mastocyte plasma membrane.

Rat mastocyte plasma membrane possess two major classes of calcium binding sites which have widely different affinity. At pH 7.5 the low affinity sites can bind about 88 nmol of Ca2+ per milligram of membrane protein and are half-saturated at 125 micro M Ca2+, whereas the high-affinity sites bind about 12 nmol of Ca2+ per milligram of membrane protein and are half-saturated at 5.5 micro M Ca2+. Membrane phospholipids and neuraminic acid residues account for approximately 87% of calcium binding.

Animals↗
PubMed1979

Hydrocortisone increases the responsiveness of mast cells to beta-adrenergic agonists by an action distal to the beta-adrenoreceptors.

Hydrocortisone in pharmacologically attainable concentrations potentiates beta-adrenergic-stimulated cyclic AMP accumulation in rat peritoneal mast cells. Direct binding studies using 3H-dihydroalprenolol indicated no significant changes in the number of beta-adrenoreceptors or in the kinetics of the interaction of the radio-ligand with receptors after treatment of mast cells with the corticosteroid. Competition binding studies with epinephrine revealed no hydrocortisone-induced change in Kd values for this agonist. It is concluded that hydrocortisone-induced stimulation of cyclic AMP synthesis results from an effect that occurs beyond the interaction of the beta-adrenergic agonist with its receptor.

Adrenergic beta-Agonists↗
PubMed1978

Biosynthesis and release of prostaglandins by mast cells.

Rat mast cells, isolated from peritoneal fluids, were found to release substantial amounts of immunoreactive E-type prostaglandin when stimulated in vitro by foetal calf serum or incubated in the presence of arachidonic acid. Extracellular accumulation of iPGE reflected synthesis, rather than release of preformed material, since it was abolished by indomethacin, a potent and relatively specific inhibitor of prostaglandin synthetase. Hydrocortisone and Compound 48/80, in such experimental conditions, did not affect PGE release.

Animals↗
PubMed1978

Influence of hydrocortisone on the modulation of the inflammatory response.

In vitro hydrocortisone, in pharmacologically attainable concentrations, binds nonspecifically to rat peritoneal mast cells and amplifies the stimulating effects of PGE1 on membrane-bound adenylate cyclase. As a consequence, the intracellular concentration of cyclic AMP in the target cells increases and histamine release is markedly reduced. Deoxycorticosterone, at the same concentrations, has no effect. These findings may in part explain the mechanism of action of anti-inflammatory steroids, possibly related to the modulating effects of E-type prostaglandins.

Animals↗
PubMed1976

Alternative complement pathway: activity levels in allogeneic pregnancy.

Classical and alternative complement pathway activities have been evaluated in sera of women in progressive stages of gestation and in pregnant mice belonging to outbred or inbred matings, as compared to suitable controls. While classical C pathway was found to be unmodified, the alternative one attained in pregnancy significantly higher activity levels. Results are discussed in the light of mother-conceptus relationships.

Animals↗