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M G Garrino

Publications and source records attributed to M G Garrino.

14 recordsLinked to original sources
PubMed1997

Particle counting assay for anti-toxoplasma IgG antibodies. Comparison with four automated commercial enzyme-linked immunoassays.

An assay for anti-toxoplasma IgG antibodies based on agglutination of latex particles was set up and compared with commercial immunoassays. The reaction was measured by instrumental counting of particles remaining unagglutinated. The running time was 45 min. This test (PaC) was compared using 243 serum samples with four automated commercial immunoassays: the Enzymum test Toxo IgG (ES300, Boehringer), the Vidas Toxo IgG (Biomérieux), the IMX Toxo IgG (Abbott), the Magia Toxoplasma gondii IgG (Merck). The mean values (+/- SD) obtained by IMX (25 IU +/- 68) and ES300 (45 IU +/- 142) were significantly lower than the values obtained by Vidas (73 IU +/- 237, p < 10(-4) and p = 0.006, respectively), by Magia (80 IU +/- 300, p < 10(-4) and p = 0.0005) and by PaC (70 IU +/- 260, p < 10(-4) and p = 0.0126). The correlations between PaC and Toxo IgG Boehringer, Biomérieux, Abbott, Merck were r = 0.97, r = 0.98, r = 0.94, r = 0.98, respectively. The correlation coefficients between the enzyme-immunoassays ranged from 0.96 to 0.99. All positive samples by PaC were found to be positive by enzyme-immunoassays except for eight sera which were doubtful positives by the Enzymum test ToxoIgG from Boehringer. No negative sample by PaC was found positive by any of the enzyme-immunoassays. In PaC, when two latex preparations coated with different antigen were compared, the correlation was rather weak (r = 0.93) suggesting that the selection of the antigen can be critical. In conclusion, the four automated commercial immunoassays now available gave similar results. However, the discrepancies observed in this study underlined the importance of clinical and biological follow-up of the patients and the necessity to confirm the result. The introduction of a new technique such as PaC, which is now available for a large variety of assays in Clinical Chemistry and Microbiology, is justified by its intrinsic advantage of homogeneity. Therefore, automation is easy as well as the control of possible interference.

Animals↗
PubMed1997

[Manifestations, diagnosis and treatment of non-tuberculous mycobacterial infections in non-immunodepressed patients].

Non-tuberculous mycobacteria (NTM) can be the etiologic agents of chronic pulmonary disease, lymphadenitis, skin and soft-tissue infection and disseminated disease in non-immunocompromised patients. The recognition of disease needs repeated isolation of the NTM from bronchopulmonary secretions or from tissue biopsies, and its identification by specific laboratory methods. A wide spectrum of clinical presentations and severity of disease can be found, from spontaneous healing to progressive and destructive lung disease, and death, according to predisposing conditions and mycobacterial species. The choice of surgical and drug treatment will depend on identification of specific pathogen and clinical evaluation.

Antitubercular Agents↗
PubMed1992

Ionic, electrical, and secretory effects of inhibitors of arachidonic acid metabolism in mouse pancreatic beta-cells.

Mouse islets were used to study the effects of inhibitors of cyclooxygenase and lipoxygenase pathways on insulin release, ionic fluxes, and beta-cell membrane potential. The cyclooxygenase inhibitors, Na-salicylate and Na-acetylsalicylate, potentiated glucose-induced insulin release, despite a decrease in Ca influx evidenced by inhibition of the Ca-dependent electrical activity in beta-cells and 45Ca efflux from islets perifused with a medium containing Ca. This paradox can probably be explained by a mobilization of intracellular Ca (acceleration of 45Ca efflux in the absence of Ca) with subsequent activation of K+ channels (acceleration of 86Rb efflux) and repolarization of the membrane. These effects of salicylate could not be ascribed to a change in intracellular pH because they were not mimicked by 2-Cl-benzoate, which has a similar pK as salicylate but increased insulin release by stimulating Ca influx in beta-cells. Among the other cyclooxygenase inhibitors tested, indomethacin caused a slight potentiation of insulin release accompanied by marginal increases in 45Ca efflux and electrical activity, whereas flurbiprofen and ibuprofen were ineffective. Among the lipoxygenase inhibitors, compound BW 755c reversibly decreased glucose-induced insulin release by inhibiting Ca influx in beta-cells, but nordihydroguaiaretic acid had no effect. Inhibitors of arachidonic acid metabolism have effects on ionic fluxes and beta-cell membrane potential, which may explain some of the changes in insulin release they produce.

4,5-Dihydro-1-(3-(trifluoromethyl)phenyl)-1H-pyraz↗
PubMed1990

B cell adrenoceptors and sulphonylurea-induced insulin release in mouse islets.

Interactions of tolbutamide and glibenclamide with B cell adrenoceptors have been reported. This study evaluated the possible role of such interactions in the stimulation of insulin release. Mouse islets were incubated in the presence of 10 mmol/l glucose alone or with tolbutamide (10 mumol/l) or glibenclamide (0.02 mumol/l). At 0.01-10 mumol/l, blockers of alpha 2-adrenoceptors (yohimbine, idazoxan) or alpha 1-adrenoceptors (prazosin) had practically no effect on glucose-induced insulin release and did not affect its potentiation by sulphonylureas, except for a slight increase by 10 mumol/l prazosin and idazoxan. Nonspecific alpha-blockers (phentolamine, dihydroergotamine) increased control release at 10 mumol/l, but only the latter amplified the response to tolbutamide. Blockers of beta-adrenoceptors were tested at 0.1-100 mumol/l: propranolol (beta 1, beta 2), metoprolol (beta 1) and compound ICI 118-551 (beta 2). They increased glucose-induced insulin release at 100 mumol/l but variably altered the effect of sulphonylureas. Blockers of adrenoceptors have, thus, no effect on insulin release in vitro at therapeutic concentrations. At high concentrations, they non-specifically affect the action of sulphonylureas. We conclude that an interaction with B cell adrenoceptors is not involved in the insulinotropic action of sulphonylureas.

Adrenergic alpha-Antagonists↗
PubMed1989

Effects of putative activators of K+ channels in mouse pancreatic beta-cells.

1 The vasodilator and antihypertensive properties of pinacidil, cromakalim (BRL 34915), nicorandil and minoxidil sulphate may be due, at least in part, to their ability to open K+ channels in vascular smooth muscles. In this study, mouse pancreatic islets were used to determine whether these drugs affect insulin release by acting on K+ channels of beta-cells. Their effects were compared to those of diazoxide. 2 Diazoxide caused a dose-dependent inhibition of insulin release by islets incubated with 15 mM glucose (93% at 100 microM). Pinacidil inhibited release by 36 and 72% at 100 and 500 microM, respectively. Cromakalim and nicorandil were less effective (35 and 25% inhibition at 500 microM). Minoxidil sulphate increased insulin release at 500 microM. 3 In the presence of 7 mM glucose and in the absence of Ca2+ (to avoid activation of Ca2+-dependent K+ channels), 86Rb efflux from islet cells was increased by 100-500 microM pinacidil and 500 microM nicorandil, which were, however, less potent than diazoxide. Cromakalim was ineffective, whereas 500 microM minoxidil sulphate decreased the efflux rate. In the absence of glucose and presence of Ca2+, 500 microM cromakalim and minoxidil sulphate inhibited 86Rb efflux. 4 Like diazoxide, pinacidil (500 microM) abolished glucose-induced electrical activity in beta-cells and hyperpolarized the membrane. 5 ATP-sensitive K+ currents were studied in single beta-cells by the whole cell patch-clamp technique. Pinacidil increased the current less than did diazoxide. In contrast, cromakalim and minoxidil sulphate decreased K+-currents whilst nicorandil was without effect. 6. It is concluded that pinacidil, like diazoxide, inhibits insulin release from beta l-cells by opening ATP-sensitive K+ channels, whereas the smaller inhibitory effects of cromakalim and nicorandil may involve actions other than on K+ channels in these cells. Minoxidil sulphate potentiates glucose-induced insulin release, probably by inhibiting ATP-sensitive K+ channels. However, all these effects of the vasodilators are only seen at high concentrations and are thus unlikely to occur in vivo.

Adenosine Triphosphate↗
PubMed1988

Highly potent and stereoselective effects of the benzoic acid derivative AZ-DF 265 on pancreatic beta-cells.

1. Mouse islets were used to define the characteristics and study the mechanisms of the stimulation of insulin release by compound AZ-DF 265, 4-[[N-(alpha-phenyl-2-piperidino-benzyl) carbamoyl]methyl] benzoic acid, a substituted benzoic acid with an asymmetric carbon atom. 2. At a non-stimulatory concentration of glucose (3 mM), (-)-AZ-DF 265 reversibly inhibited 86Rb efflux from islet cells, depolarized the beta-cell membrane, induced electrical activity, stimulated 45Ca efflux, and triggered insulin release. Maximum inhibition of 86Rb efflux occurred at 0.03 microM (-)-AZ-DF 265, whereas the threshold concentration for stimulation of release was 0.1 microM. Omission of extracellular Ca2+ abolished all effects of the drug but the inhibition of 86Rb efflux. 3. At a stimulatory concentration of glucose (10 mM), (-)-AZ-DF 265 reversibly increased 86Rb efflux, potentiated electrical activity, augmented 45Ca efflux, and increased insulin release. Maximum stimulation of 86Rb efflux and insulin release was obtained with 0.03 microM (-)-AZ-DF 265. Omission of extracellular Ca2+ abolished all effects of the drug. 4. The potency of (-)-AZ-DF 265 was similar to that of glibenclamide, whereas the (+)-enantiomer was about 10 times less potent on 86Rb efflux and insulin release. 5. It is concluded that, like sulphonylureas, compound AZ-DF 265 decreases K+ permeability of the beta-cell membrane and thereby causes depolarization. This activates voltage-dependent Ca channels, permits Ca2+ influx and eventually stimulates insulin release. Its stereoselectivity may help to elucidate the mechanisms of K channel blockade and, hence, lead to the design of more potent and specific insulinotropic drugs.

Animals↗
PubMed1987

Stimulation of insulin release by benzoic acid derivatives related to the non-sulphonylurea moiety of glibenclamide: structural requirements and cellular mechanisms.

A decrease in membrane permeability to K+ is the first critical event occurring in pancreatic B-cells upon stimulation by hypoglycemic sulphonylureas. Compound HB 699 (4-[2-(5-chloro-2-methoxybenzamido)ethyl]benzoic acid), the non-sulphonylurea moiety of glibenclamide stimulates B-cells by the same mechanisms as glibenclamide itself. Selected derivatives of HB 699 were used to test, with isolated mouse islets, whether this property is due to the benzoic acid end of the molecule (not present in glibenclamide) or to another active site (also present in glimenclamide). Of the two halves of HB 699, p-ethylbenzoic acid, but not 5-Cl-2-methoxybenzamide, was weakly effective. Replacement of the carboxyl group of HB 699 by various non-acidic groups decreased but did not abolish the ionic and secretory effects on B-cells. Modifications of the other end of the molecule altered the efficacy in both directions. Removal of the substituents on the benzamide ring decreased the efficacy, whereas replacement of the 5-Cl-2-methoxybenzyl group by a 1,1-diphenylethyl group or a 9-fluorenylmethyl group led to substantially more active compounds. Their cellular mode of action was however not modified. It is concluded that compound HB 699 contains two active sites, both of which can trigger insulin release by decreasing K+ permeability of the B-cell membrane. K channels appear to possess, not a sulphonylurea receptor, but a target site for various chemical groups. The chemical environment of the latter may also determine their efficacy by modulating their access to the channel.

Animals↗
PubMed1987

Inosine partially mimics the effects of glucose on ionic fluxes, electrical activity, and insulin release in mouse pancreatic B-cells.

The purine ribonucleoside inosine is known to be metabolized in islet cells (its ribose moiety feeds into the pentose-phosphate cycle) and stimulate insulin release, but the mechanisms of this stimulation have not been established. These were investigated with mouse islets. In the absence of glucose, 5 mM inosine decreased 86Rb+ efflux from islet cells, depolarized the B-cell membrane, induced electrical activity (slow waves of membrane potential with bursts of spikes on the plateau), accelerated 45Ca2+ efflux and stimulated insulin release with the same efficiency as 10 mM glucose. Raising the concentration of inosine to 20 mM only had a slight further effect and, in particular, failed to cause persistent depolarization of the B-cell membrane. The electrical activity triggered by inosine was blocked by cobalt, and the stimulation of 45Ca2+ efflux and insulin release was abolished in a Ca2+-free medium. The effects of 10 mM glucose on electrical activity, 45Ca2+ efflux and insulin release were augmented by as little as 0.5 mM inosine. All effects of inosine were abolished by an inhibitor of nucleoside transport (nitrobenzylthioguanosine) and markedly impaired by inhibitors of nucleoside phosphorylase (formycin B) or of glycolysis (iodoacetate). In conclusion, inosine metabolism in B-cells induces insulin release by triggering the same sequence of events as glucose metabolism: a decrease of K+ permeability of the B-cell membrane, leading to depolarization and activation of voltage-dependent Ca channels.

Animals↗
PubMed1987

Adamantane derivatives: a new class of insulin secretagogues.

Adamantane derivatives were found to increase insulin release in vitro. Mouse islets were used to study the mechanisms and molecular requirements of that hitherto unrecognised property. At a non-stimulatory concentration of glucose (3 mM), 1-adamantanamine (1 mM) reversibly inhibited 86Rb efflux from islet cells, depolarized the beta-cell membrane, induced electrical activity, stimulated 45Ca uptake and efflux, and triggered insulin release. Omission of extracellular Ca2+ abolished the secretory response but only partially inhibited the acceleration of 45Ca efflux. At a stimulatory concentration of glucose (10 mM), 1-adamantanamine reversibly increased 86Rb efflux, potentiated electrical activity (lengthening of the slow waves with spikes), augmented 45Ca uptake and efflux, and increased insulin release. The effects of adamantanamine were dose-dependent, with a threshold concentration of 10 microM for stimulation release. 2-Adamantanamine was as potent as 1-adamantanamine. In contrast, substitution of the amino group by a carboxyl group (1-adamantanecarboxylic acid) decreased the effectiveness by about 65%, and substitution by a hydroxyl group (1-adamantanol) suppressed it. It is concluded that adamantane derivatives bearing an amino group decrease K+ permeability of the beta-cell membrane and thereby cause depolarization. This activates voltage-dependent Ca channels, permits Ca2+ influx and eventually stimulates insulin release. They may also mobilize cellular Ca2+, but this effect is not sufficient to cause release.

Adamantane↗
PubMed1986

The non-sulfonylurea moiety of gliquidone mimics the effects of the parent molecule on pancreatic B-cells.

Compound UL-DF 9 corresponds to the non-sulfonylurea moiety of gliquidone, a hypoglycaemic sulfonylurea of the second generation. Its effects on the B-cell function were studied in vitro with mouse islets. In the presence of a non-stimulatory concentration of glucose (3 mM), UL-DF 9 decreased 86Rb+ efflux and accelerated 45Ca2+ efflux from islet cells, depolarized the B-cell membrane and induced an electrical activity similar to that triggered by stimulatory concentrations of glucose, and increased insulin release. The changes in 45Ca2+ efflux and insulin release, but not the inhibition of 86Rb+ efflux, were abolished in the absence of Ca2+. In the presence of 10 mM glucose, UL-DF 9 increased 86Rb+ and 45Ca2+ efflux from the islets, augmented the electrical activity in B-cells, and potentiated insulin release. These changes were suppressed by omission of extracellular Ca2+. Qualitatively similar effects were produced by lower concentrations of gliquidone itself. The data suggest that UL-DF 9 and gliquidone decrease the K+ permeability of the B-cell membrane, thereby causing a depolarization which leads to activation of voltage-dependent Ca channels and Ca2+ influx, and thus eventually increase insulin release. Hypoglycaemic sulfonylureas of the second generation therefore seem to contain a second chemical group that interacts with K channels of B-cells as does the sulfonylurea group itself.

Animals↗
PubMed1985

Nutrient insulin secretagogues decrease 45Ca2+ efflux from islet cells by a mechanism other than the inhibition of the Na+-Ca2+ countertransport.

The mechanism whereby nutrient insulin secretagogues decrease 45Ca2+ efflux from islet cells is controversial. It was studied with mouse islets perifused with Ca2+-free solutions. In the presence of Na+, glucose and ketoisocaproate inhibited 45Ca2+ efflux by about 50%. Substitution of choline+ salts for Na+ salts decreased the efflux rate by 45%, but did not prevent glucose from decreasing it further. Ketoisocaproate also inhibited 45Ca2+ efflux, but less markedly than in an Na+ medium. Omission of Na+ decreased the efflux rate even when it was already lowered by glucose or ketoisocaproate. It is thus clear that nutrient insulin secretagogues decrease 45Ca2+ efflux from islet cells by a mechanism other than the inhibition of the Na+-Ca2+ countertransport, possibly by increasing sequestration of the ion in cellular organelles.

Animals↗
PubMed1985

Mechanism of the stimulation of insulin release in vitro by HB 699, a benzoic acid derivative similar to the non-sulphonylurea moiety of glibenclamide.

HB 699 is a benzoic acid derivative similar to the non-sulphonylurea moiety of glibenclamide. The mechanisms whereby it affects B-cell function have been studied in vitro with mouse islets. In the presence of 3 mmol/l glucose, HB 699 decreased 86Rb+ efflux and accelerated 45Ca2+ efflux from islet cells, depolarized the B-cell membrane and induced an electrical activity similar to that triggered by stimulatory concentrations of glucose, and increased insulin release. The changes in 45Ca2+ efflux and insulin release, but not the inhibition of 86Rb+ efflux, were abolished in the absence of Ca2+. In the presence of 10 mmol/l glucose, HB 699 increased 86Rb+ and 45Ca2+ efflux from the islets, caused a persistent depolarization of the B-cell membrane with continuous electrical activity and markedly potentiated insulin release. All these changes were suppressed by omission of extracellular Ca2+. In the presence of 15 mmol/l glucose, diazoxide increased 86Rb+ efflux, hyperpolarized the B-cell membrane, suppressed electrical activity and inhibited insulin release. HB 699 reversed these effects of diazoxide. It is suggested that HB 699 decreases K+ permeability of the B-cell membrane, thereby causing a depolarization which leads to activation of voltage-dependent Ca channels and Ca2+ influx, and eventually increases insulin release. A sulphonylurea group is thus not a prerequisite to trigger the sequence of events that is also thought to underlie the releasing effects of tolbutamide and glibenclamide.

Animals↗