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Biomedical subjects

C Biondi

Publications and source records attributed to C Biondi.

At least 73 records · Page 4Linked to original sources
PubMed1992

Adenylate cyclase from Hirudo medicinalis segmental ganglia: modulation by physiological and non-physiological agents.

1. In Hirudo medicinalis segmental ganglia GTP is essential for the full expression of the stimulatory action of serotonin on the adenylate cyclase activity. The amine, in turn, increases the overall affinity of the enzymatic system for GTP. 2. GTP gamma S and Gpp(NH)p, non-hydrolysable analogues of GTP, dose-dependently enhance the basal enzyme activity, but impair the stimulatory effect of serotonin. 3. Fluoride ions biphasically modulate the leech adenylate cyclase both in the absence and in the presence of GTP. The ion effect is also influenced by non-physiological guanine nucleotides.

Adenylyl Cyclases↗
PubMed1992

Betamethasone-induced lecithin release in vitro from the fetal membranes.

Lecithin release from fetal membranes and placental tissue was assayed in basal conditions as well as under betamethasone administration. In the absence of the steroid, amnion and chorion released lecithin as a function of incubation time. Both tissues responded to betamethasone by increasing the lecithin release, the amnion exhibited a higher basal level and a greater responsiveness to the hormone than the chorion. Basal lecithin release from placental tissue was unaffected by any steroid concentration.

Amnion↗
PubMed1991

Receptor-mediated supra-additive activation of guinea pig superior cervical ganglion adenylate cyclase: role of Mn2+ ions and calmodulin.

The effects of Mn2+ and calmodulin were studied on the basal and agonist-modulated adenylate cyclase activity of the guinea pig superior cervical ganglion. The divalent cation strongly stimulates the basal and agonist-modulated enzyme in a concentration-dependent manner. Moreover, in the presence of Mn2+ the inhibitory effects of "high" GTP concentrations and of D-Ala2-Met-enkephalinamide on adenylate cyclase are eliminated, while the stimulation exerted by prostaglandin E2 and the supra-additive activation of the enzyme by the combination of the two drugs are unaffected. In EGTA-washed, calmodulin-depleted membrane preparations, Mn2+ still activates the cyclase but the enkephalin inhibition and the superactivation of the enzyme induced by the combination of opiate and prostaglandin are lost, both in the absence and in the presence of the cation. Reconstituting the depleted membranes with exogenous Ca2+/calmodulin fully restored the enzyme responsivity to the combination and, partially, to the enkephalin. The findings suggest the existence in the guinea pig superior cervical ganglion of both the calmodulin-sensitive and differently regulated calmodulin-insensitive adenylate cyclase.

ADP-Ribosylation Factors↗
PubMed1990

RMI 12330A, an inhibitor of adenylate cyclase and cyclic AMP-phosphodiesterase activities in the segmental ganglia of the leech Hirudo medicinalis.

The effect of RMI 12330A, an inhibitor of basal as well as serotonin-stimulated adenylate cyclase in the segmental ganglia of the leech Hirudo medicinalis, has been tested on cyclic AMP-phosphodiesterase activity in the same tissue. The drug dose-dependently inhibits high and low affinity enzyme, an effect first evident at an RMI 12330A concentration of 0.5 mM. For both enzyme activities the drug reduces Vmax without substantially influencing Km values. Both basal and serotonin-stimulated adenylate cyclase as well as cyclic AMP-phosphodiesterase activities are inhibited by RMI 12330A in a non-competitive manner.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1990

Supra-additive activation of guinea-pig superior cervical ganglion adenylate cyclase by PGE2 and D-Ala2-Met-enkephalinamide: role of GTP.

The effects of guanine nucleotides were tested on basal and agonist-modulated adenylate cyclase in guinea-pig superior cervical ganglion crude membrane preparations. GTP gamma S and Gpp(NH)p dose-dependently stimulate, while GDP beta S inhibits, both the basal and the prostaglandin E2-stimulated enzyme activity. Low GTP doses, up to 10(-5) M, stimulate, while higher doses inhibit, the ganglionic adenylate cyclase. The GTP-induced diphasic pattern is maintained also in the presence of prostaglandin E2, D-Ala2-Met-enkephalinamide, or a combination of the two drugs. However, the opioid inhibits the enzyme activity, but only at high GTP doses, while the prostaglandin stimulates the enzyme at all GTP concentrations. The effect is potentiated by a combination of prostaglandin and enkephalin. The enhancing effect of the prostaglandin and of the combination with enkephalin is maximally expressed at high, almost physiological, GTP doses.

Adenylyl Cyclases↗
PubMed1989

Supra-additive stimulation of adenylate cyclase activity by prostaglandin E2 and D-Ala2-met-enkephalinamide in the guinea-pig superior cervical ganglion: role of Mg2+ions.

Agonists modulation of Mg2(+)-dependent adenylate cyclase activity has been studied in guinea-pig superior cervical ganglion crude membrane preparations. In the absence of receptors ligands, Mg2+ stimulates the enzyme in a concentration-dependent manner. The dose-activation curve shows heterogeneity and two components with "higher" and "lower" apparent affinity states, are extrapolated. In the presence of D-Ala2-met-enkephalinamide only one component is present and the apparent affinity of the ganglionic adenylate cyclase system for the divalent cation as well as Vmax are inhibited. On the contrary, prostaglandin E2 increases affinity and Vmax values of the lower and, to a lesser extent, of the higher Km component. When the two drugs are tested in combination, not only the inhibitory effect of the opiate is overcome, but a large increase of the apparent affinities and Vmax values for both components is obtained, suggesting the involvement of the Mg2(+)-regulated subunits of the adenylate cyclase system in the supra-additive stimulation mechanism of the enzyme.

Adenylyl Cyclases↗
PubMed1989

Adenylate cyclase and cyclic AMP-phosphodiesterase activities of fetal membranes: effect of insulin.

Basal activity and response to insulin of adenylate cyclase and cyclic AMP-phosphodiesterase were measured in the fetal membranes before and after labor. Basal activity of adenylate cyclase showed only slight variations after delivery when compared to that observed before labor. Enzyme activity was significantly although weakly decreased by insulin both in the amnion and in chorion before labor, while after delivery a weaker non-significant inhibition was observed. Basal activity of cyclic AMP-phosphodiesterase was lower after delivery with respect to that observed before labor. Insulin inhibited enzyme activity in all conditions. Cyclic AMP levels in intact tissue were not substantially modified by insulin.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1988

Interactions between prostaglandin E2 and D-ala2-met-enkephalinamide on adenylate cyclase activity in the guinea-pig superior cervical ganglion.

Crude membrane fractions, obtained from superior cervical ganglia of normal and sympathectomized guinea-pigs, have been used to investigate the role of prostaglandin E2 and D-ala2-met-enkephalinamide in the modulation of ganglionic adenylate cyclase as well as their functional interrelationship. In ganglia from normal animals the enzyme activity was stimulated and inhibited, respectively, by the prostaglandin (10(-4)M) and by the opiate pentapeptide (10(-4)M), while little or no effects were observed in denervated preparations. When the two substances were tested in combination, a supra-additive stimulation of adenylate cyclase activity was obtained both in normal and denervated ganglia. In the latter preparation the opiate increased prostaglandin E2 specific binding, suggesting that the mechanism of supra-additivity could involve interactions at receptors level. Furthermore, the supra-additive stimulation of adenylate cyclase activity by the combination of the two drugs was obtained in a narrow range of concentrations since at low prostaglandin E2 doses (10(-7)-10(-6)M) or at very high doses of the opiate (10(-3)M), only the inhibitory effect of D-ala2-met-enkephalinamide was evidenced.

Adenylyl Cyclases↗
PubMed1986

Opiates modulation of cAMP levels and PGE2 binding in mammalian sympathetic ganglia.

The effects of opiates on cyclic adenosine monophosphate (cAMP) levels have been studied in sympathetic ganglia of guinea-pig, rat and rabbit. D-[Ala2]-Met-enkephalinamide inhibits cAMP synthesis in guinea pig and rat but not in rabbit ganglia, while morphine is always ineffective. In the presence of the enkephalin plus prostaglandin E2 (PGE2) a synergistic increase of the nucleotide levels is observed in guinea pig. This effect is not induced by morphine plus PGE2 and is not shared by rat and rabbit. In guinea pig alpha-endorphin inhibits both basal and PGE2-stimulated cAMP synthesis. In the same preparation the enkephalin increases [3H]PGE2 binding. In guinea pig ganglia a cooperative effect of the enkephalin and PGE2 on the cAMP system is suggested.

Adenylyl Cyclases↗
PubMed1986

Some properties of adenosine 3',5'-cyclic monophosphate phosphodiesterase in the superior cervical ganglion of the guinea pig.

Adenosine 3',5'-cyclic monophosphate (cAMP) phosphodiesterase activity in crude guinea-pig superior cervical ganglion homogenates was assayed under a variety of experimental conditions. Two forms of cAMP phosphodiesterase were found, one with high and the other with low affinity for the substrate. The Km values were about 1 and 110 microM respectively. Imidazole slightly but constantly stimulated the former enzyme form over a wide range of concentrations and 1-methyl-3-isobutylxanthine was a weak competitive inhibitor with a Ki value of 90 microM. Low affinity cAMP phosphodiesterase activity was increased by calmodulin and Ca2+. This stimulation was not observed in the presence of trifluoperazine, a specific inhibitor of calmodulin. On the other hand, neither [D-Ala2]met-enkephalinamide nor prostaglandin E2, alone or in combination, influenced high affinity cAMP phosphodiesterase.

1-Methyl-3-isobutylxanthine↗
PubMed1985

"In vitro" effect of progesterone on alpha-L-fucosidase activity of human endometrium.

Alpha-L-fucosidase activity was found to be increased in organ cultured normal endometrium and in endometrial adenocarcinoma compared with non cultured tissue. The enzyme activity was lowered with addition of progesterone to the medium. Non cultured adenocarcinoma showed a higher activity compared with non cultured normal endometrium.

Adenocarcinoma↗