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S Gemma

Publications and source records attributed to S Gemma.

18 recordsLinked to original sources
PubMed2005

Interleukin-1 gene polymorphisms and gastric cancer risk in a high-risk Italian population.

OBJECTIVES: Host genetic factors, including the IL1 gene cluster, play a key role in determining the long-term outcome of Helicobacter pylori infection. The aim of the study was to investigate the relationship between selected IL1 loci polymorphisms and gastric cancer risk in an Italian population. METHODS: In a case-control study we compared the IL1B-31 and IL1B+3954 biallelic and IL1RN pentaallelic variable number of tandem repeats (VNTR) polymorphisms in 185 gastric cancer patients and 546 controls randomly sampled from the general population of an area at high gastric cancer risk (Tuscany, Central Italy). RESULTS: Genotype frequencies of the IL1B-31 T/C, IL1B+3954 C/T, and IL1RN polymorphisms among our population controls were in Hardy-Weinberg equilibrium. In multivariate analyses, no increase in gastric cancer risk was observed for the IL1B-31*C- and IL1B+3954*T- carriers; a significant 50% increase emerged for IL1RN*2 allele carriers (OR = 1.49; 95% CI: 1.01-2.21). Analyses based on combined genotypes showed also that the association with IL1RN*2 allele was limited to two-variant allele carriers who were also homozygous for the IL1B-31*T allele (OR = 2.23; 95% CI: 1.18-4.23) with a statistically significant interaction between these two genotypes (p= 0.043). Haplotype analysis showed an increased risk for the haplotype IL1RN*2/IL1B-31*T. CONCLUSIONS: Our results suggest that host genetic factors (such as the IL1RN and the IL1B-31 polymorphisms) interact in the complex process of gastric carcinogenesis in this high-risk Italian population. Overall, this effect appears more modest than previously reported in other populations, supporting the hypothesis that other still-to-be-defined factors are important in gastric carcinogenesis. These findings might be due to a haplotype effect.

Case-Control Studies↗
PubMed2000

Comparative characterization of CHCl(3) metabolism and toxicokinetics in rodent strains differently susceptible to chloroform-induced carcinogenicity.

A comparative kinetic study in B6C3F1 mice, Osborne-Mendel (OM) and Sprague-Dawley (SD) rats has been undertaken with the major aim to determine the extent of covalent binding of chloroform reactive metabolites produced in vivo through oxidative and/or reductive metabolism in the target organs of chloroform carcinogenicity. Some additional kinetic observations of chloroform biotransformation were also collected comparatively. Expiration of [14C]-CO(2) showed that chloroform metabolism went to saturation in all tested rodent strains. In the B6C3F1 mouse maximal rates of approximately 135 µmol [14C]-CO(2)/kg b.w./h were reached at a dose of approximately 150 mg/kg, while in the two rat strains saturation occurred at a dose of approximately 60 mg/kg, with a maximal rate of approximately 40 µmol [14C]-CO(2)/kg b.w./h. At doses of 150-180 mg/kg b.w., limited differences were found in the distribution and elimination of [14C]-chloroform in the liver and kidney. Species differences have been found in the kinetics of alkali-extractable radioactivity in the blood. The levels of adducts of electrophilic intermediates with the polar heads (PH) of phospholipids (PL) showed a limited variability accross the rodents tested and did not correlate with the species and organ susceptibility to chloroform carcinogenicity. The levels of adducts of radical intermediates with the fatty acyl chains (FC) of PL were much lower than the PH adducts in all the samples analyzed; at the carcinogenicity bioassay doses, statistically significant levels of hepatic FC adducts were present only in the B6C3F1 mouse, where chloroform is hepatocarcinogenic. The observations in the rat kidney were suggestive of the formation of electrophilic reactive metabolites, presumably different from phosgene and associated with an initial chloroform reduction.

Journal Article↗
PubMed1999

Pyrroloquinoxaline derivatives as high-affinity and selective 5-HT(3) receptor agonists: synthesis, further structure-activity relationships, and biological studies.

The synthesis, pharmacological evaluation, and structure-activity relationships (SARs) of a series of novel pyrroloquinoxalines and heteroaromatic-related derivatives are described. The new pyrroloquinoxaline-related ligands were tested in rat cortex, a tissue expressing high density of 5-HT(3) receptors, and on NG108-15 cells and exhibited IC(50) values in the low nanomolar or subnanomolar range, as measured by the inhibition of [(3)H]zacopride binding. The SAR studies detailed herein delineated a number of structural features required for improving affinity. Some of the ligands were employed as "molecular yardsticks" to probe the spatial dimensions of the lipophilic pockets L1, L2, and L3 in the 5-HT(3) receptor cleft, while the 7-OH pyrroloquinoxaline analogue was designed to investigate hydrogen bonding with a putative receptor site H1 possibly interacting with the serotonin hydroxy group. The most active pyrroloquinoxaline derivatives showed subnanomolar affinity for the 5-HT(3) receptor. In functional studies ([(14)C]guanidinium accumulation test in NG108-15 hybrid cells, in vitro) most of the tested compounds showed clear-cut 5-HT(3) agonist properties, while some others were found to be partial agonists. Several heteroaromatic systems, bearing N-substituted piperazine moieties, have been explored with respect to 5-HT(3) affinity, and novel structural leads for the development of potent and selective central 5-HT(3) receptor agonists have been identified. Preliminary pharmacokinetic studies indicate that these compounds easily cross the blood-brain barrier (BBB) after systemic administration with a brain/plasma ratio between 2 and 20, unless they bear a highly hydrophilic group on the piperazine ring. None of the tested compounds showed in vivo anxiolytic-like activity, but potential analgesic-like properties have been possibly disclosed for this new class of 5-HT(3) receptor agonists.

Animals↗
PubMed1999

Identification of the cytochrome P450 isoenzymes involved in the metabolism of diazinon in the rat liver.

The metabolism of diazinon, an organo-phosphorothionate pesticide, to diazoxon and pyrimidinol has been studied in incubations with hepatic microsomes from control Sprague-Dawley (SD) rats or SD rats treated with different P450-specific inducers (phenobarbital, dexamethasone, beta-napthoflavone, and pyrazole). Results obtained indicate an involvement of CYP2C11, CYP3A2, and CYP2B1/2, whereas CYP2E1 and CYP1A1 do not contribute to the pesticide oxidative metabolism. Indeed, diazinon was metabolized by microsomes from control rats; among the inducers, phenobarbital and dexamethasone only increased the production of either metabolites, although to different extents. The production of the two metabolites is self-limiting, due to P450 inactivation; therefore, the inhibition of CYP-specific monooxygenase activities after diazinon preincubation has been used to selectively identify the competent CYPs in diazinon metabolism. Results indicate that, after diazinon preincubation, CYP3A2-catalyzed reactions (2beta- and 6beta-testosterone hydroxylation) are very efficiently inhibited; CYP2C11- and CYP2B1/2-catalyzed reactions (2alpha- and 16beta-testosterone hydroxylation, respectively) are weakly inhibited, while CYP2E1-, CYP2A1/2-, and CYP1A1/2-related activities were unaffected. Results obtained by using chemical inhibitors or antibodies selectively active against specific CYPs provide a direct evidence for the involvement of CYP2C11, CYP3A2, and CYP2B1/2, indicating that each of them contributed about 40-50% of the diazinon metabolism, in hepatic microsomes from untreated, phenobarbital-, and dexamethasone-treated rats, respectively. The higher diazoxon/pyrimidinol ratio observed after phenobarbital-treatment together with the significantly more effective inhibition toward diazoxon production exerted by metyrapone in microsomes from phenobarbital-treated rats supports the conclusion that CYP2B1/2 catalyze preferentially the production of diazoxon.

Animals↗
PubMed1999

Time dependence of chloroform-induced metabolic alterations in the liver and kidney of B6C3F1 mice.

The time course of some biochemical changes in the liver and in the kidney was studied in B6C3F1 male mice dosed with a single i.p. injection of 150 mg/kg body weight (b.w.) CHCl(3). Hepatic and renal microsomal cytochrome P450 (P450) content and some related monooxygenase activities, CHCl(3) oxidative and reductive metabolism, cytosolic reduced glutathione (GSH) content and serum markers of nephrotoxicity were measured. In the liver no biochemical changes were produced up to a week after chloroform treatment. On the contrary, the drug-metabolizing enzyme system in the kidney was dramatically and rapidly inactivated by chloroform treatment. Maximum loss of GSH (50%), P450 (80%) and of different enzymatic activities, including CHCl(3) bioactivation, occurred during the first 5 h. These biochemical alterations are early effects, not secondary to morphological tissue changes. Kidney parameters, altered by chloroform treatment, returned to control values at different times: renal function markers became normal in 48 h; GSH levels were recovered at 96 h and the drug-metabolizing enzyme activities at longer times. The present results clearly show that repeated daily doses of chloroform, as those used in carcinogenicity tests, find renal tubular cells not at their physiological status, due to the changes produced by the first chloroform dose. Therefore the similarity in P450-dependent chloroform metabolism shown in vitro by hepatic and renal microsomes from untreated B6C3F1 male mice or in vivo in animals treated once, is lost during repeated treatments. These features should be considered in understanding the different susceptibility of the liver and the kidney to chloroform-induced tumours.

Aniline Hydroxylase↗
PubMed1996

The role of different cytochrome P450 isoforms in in vitro chloroform metabolism.

The two CHCl3 activation pathways have been studied in incubations at different oxygenation conditions with hepatic microsomes from control Sprague Dawley (SD) rats or SD rats treated with different cytochrome P450 inducers (acetone, phenobarbital, pyrazole, dexamethasone, and beta-naphthoflavone). The present results provide direct evidence that CHCl3 concentration is critical in determining the role of different cytochrome P450 isoforms (CYP) and the related effects of metabolic inducers. At 0.1 mM CHCl3 concentration, the only major contribution to its oxidative biotransformation in liver microsomes from untreated rats was due to CYP2E1, as shown by metabolic inhibition due to 4-methylpyrazole or by anti-CYP2E1 antibodies. Moreover, animal treatments with acetone and pyrazole increased the production of adducts of phosgene to microsomal phospholipid by about 10-15 times. At 5 mM chloroform, in control rat liver microsomes, CYP2B1/2 was the major participant responsible for chloroform activation, while CYP2E1 and CYP2C11 were also significantly involved. Consistently, at this chloroform concentration, the effect of phenobarbital (CYP2B1/2 inducer) was maximal, producing very high levels of adducts. The reductive pathway was expressed at 5 mM CHCl3 only and was not significantly increased by any of the inducers used. Moreover, it was not inhibited by metyrapone and 4-methylpyrazole or by anti CYP2C11 antibodies. Therefore, it may be concluded that, in the range of chloroform concentrations tested, those CYPs involved in CHCl3 oxidative bioactivation do not participate in CHCl3 reduction. Chloroform oxidative metabolism in PB-microsomes could achieve very high absolute rates, much higher than those in C-microsomes; in contrast, the metabolic rates in AC- and PYR-microsomes remained within the activity levels observable in C-microsomes at high chloroform concentration. Therefore, it can be argued that the CYP2B1/2-mediated induction of CHCl3 activation is the basis for the effect of PB in potentiating chloroform hepatotoxicity. Moreover, processes other than CYP2E1-mediated metabolic induction may be more relevant in the ketones potentiation of chloroform-induced acute toxicity.

Acetone↗
PubMed1996

In vivo CHCl3 bioactivation, toxicokinetics, toxicity, and induced compensatory cell proliferation in B6C3F1 male mice.

Chloroform carcinogenicity has often been associated with acute tissue damage and consequent compensatory cell proliferation. However, available data do not fully support this hypothesis, and other biological factors may play a role in the tumor induction by chloroform. The purpose of this study was to characterize the in vivo CHCl3 metabolism and the time course of toxic effects and of cell proliferation in the liver and kidney of B6C3F1 male mice dosed i.p. or by gavage with 150 mg CHCl3/kg body wt. Microsomal phospholipid adducts attributed to (14)CHCl3 metabolism by both oxidative and reductive pathways were detected in both liver and kidney. The levels and composition of the adducts were similar in the liver and kidney of treated animals. In the liver, although no necrosis was histologically detectable, a transient cell proliferation was found starting at 24 and peaking at 48 hr post-treatment. Kidney toxicity was evident by biochemical and cytochemical methods at 5 hr after dosing and progressed to severe necrosis at 48 and 96 hr. An intense kidney cell regeneration began 48 hr after CHCl3 treatment, became maximal at 96 hr, and was sustained for at least the following 3 days. These observations raise questions about the purely epigenetic action of chloroform in tumor induction since bioassays have found tumors in liver but not kidneys of CHCl3-treated B6C3F1 mice.

Animals↗
PubMed1994

The contribution of electrophilic and radicalic intermediates to phospholipid adducts formed by halomethanes in vivo.

The different production of phosgene and free-radicals from CHCl3 and CCl4 was determined in vitro and in vivo, by measuring the regioselective binding to the two intermediates to phospholipid (PL) molecules. Results clearly indicated that this assay can be successfully used to selectively detect electrophilic and radicalic metabolites produced in vivo and selectively quantitate their adducts. The in vivo biotransformation of CCl4, similarly to the in vitro situation, resulted in the formation of radicals only, the contribution of phosgene to the structural damage of PL being negligible. These findings allowed us to rule out the hypothesis of substantial formation of radicalic intermediates from CHCl3 in phenobarbital (PB)-pretreated Sprague-Dawley (SD) rats, derived from in vitro data. While the role of reduced glutathione (GSH) in preventing COCl2-derived damages seems to be less important in vivo than in vitro, it is not possible to rule out the action of radical scavenging systems in decreasing the level of adducts with fatty acyl chains (FC) of PL measured in vivo.

Animals↗
PubMed1994

Effect of ethanol on CHCl3 metabolism in hepatic microsomes from Osborne-Mendel rats.

The treatment of Osborne-Mendel rats with ethanol in drinking water for 2 weeks resulted in a 3-fold increase of hepatic microsomal hydroxylation of both p-nitrophenol and aniline, two substrates considered highly selective for P4502E1. No other forms of P450 seemed to be affected. These results, confirmed by the immunoblot analysis of microsomal protein, showed an induction of P4502E1. The levels of total covalent binding to microsomal phospholipid due to 14CHCl3 reactive intermediates in ethanol-pretreated microsomes were identical to those measured in microsomes from untreated rats at any pO2. The distribution of radioactivity obtained after transmethylation of the adducts of 14CHCl3 intermediates with microsomal phospholipids (PL) indicated that binding to fatty acyl chains (due to .CHCl2 radicals) increased with decreasing pO2. On the contrary, the binding to polar heads due to phosgene decreased. The ethanol treatment did not affect binding to either PL moieties. These results indicated that, in our experimental conditions, the in vitro production of both oxidative and reductive intermediates of CHCl3 in the liver of Osborne-Mendel rats were not influenced by ethanol consumption.

Animals↗
PubMed1994

In vivo production of different chloroform metabolites: effect of phenobarbital and buthionine sulfoximine pretreatment.

The regioselective attack on microsomal phospholipid (PL) polar heads (PH) and fatty acyl chains (FC) demonstrated in vitro has been exploited for the selective quantitation in vivo of the biochemical damages produced by the oxidation and reduction products of CHCl3 metabolism. Five hours after CHCl3 injection (60 mg/kg body weight, ip) to control Sprague-Dawley rats, most of the label covalently bound in the liver was associated to PH, indicating a predominant production of COCl2. The levels of radioactivity bound to both PL moieties increased proportionally when 180 mg/kg body weight 14CHCl3 was administered. Buthionine sulfoximine (BSO) pretreatment resulted in a further increase of binding either to PH or FC. The pretreatment of rats with phenobarbital (PB) reduced the PH/FC binding ratio to 3.4, still indicating the predominance of the oxidative metabolism, but giving some indication of the simultaneous presence of CHCl3 reduction. When reduced glutathione (GSH) was depleted by BSO in PB-induced animals prior to 14CHCl3 administration, only the level of radioactivity associated with oxidative intermediates was increased six times. The present results confirmed that GSH is able to exert an efficient protection mainly toward 14CHCl3 oxidation intermediates. Furthermore, they indicate that in the liver of the Sprague-Dawley rat the major pathway of CHCl3 biotransformation is its oxidation and that pretreatment of rats with a GSH-depleting agent (such as BSO) is more relevant than PB induction in enhancing the biochemical damages produced by CHCl3.

Animals↗
PubMed1992

Bioactivation of chloroform in hepatic microsomes from rodent strains susceptible or resistant to CHCl3 carcinogenicity.

The dependence of adduct formation on oxygen concentration and glutathione (GSH) presence was used to characterize the bioactivation of chloroform in hepatic microsomes of Sprague-Dawley and Osborne-Mendel rats and B6C3F1 and C57Bl/6J mice. Both oxidative and reductive pathways were present in all the animals tested. Oxidative activation, very sensitive to oxygen withdrawal, was the major pathway responsible for the covalent binding to microsomal proteins and lipids at 0.1 mM CHCl3. The relative contribution of either pathway to the covalent binding to microsomal lipids at 5 mM CHCl3 was dependent on the oxygen concentration. At 1% pO2, i.e., in the range of the hepatic physiological oxygenation level, B6C3F1 mouse hepatic microsomes showed an oxidative activation distinctly higher than that of hepatic microsomes of other rodents; on the other hand, reductive activation was present only in B6C3F1 mouse and Osborne-Mendel rat liver microsomes. The reductive intermediates were the only contributors to the covalent binding of CHCl3 equivalents to lipids in the presence of GSH; indeed the reactive intermediates produced by the oxidative pathway were fully scavenged by this compound. These results are discussed with respect to the species specificity of CHCl3 hepatocarcinogenesis.

Animals↗
PubMed1989

Functional assessment of high level ice-dancing.

In these studies the anthropometric characteristics and some functional characteristics of ice-dancers are analysed. It has been shown that the maximum oxygen uptake is similar to that of classical ballet dancers. Tests effected on the ice revealed a high production of lactate, the involvement of the anaerobic metabolism, and high heart rates. It is concluded that the high production of lactate during the free dance on ice is due to the isometric muscular contraction, necessary to maintain certain positions.

Adolescent↗
PubMed1986

[Acute effects of diltiazem in pulmonary hypertension secondary to chronic obstructive bronchitis].

The effect of acute i.v. administration of diltiazem on pulmonary haemodynamics was compared to that produced by oxygen in 10 hypoxemic patients with chronic obstructive lung disease and pulmonary hypertension (PAPm greater than 20 mmHg), without left ventricular dysfunction. Determinations were carried out at baseline, during 100% oxygen inhalation, at least 20 minutes after oxygen withdrawal and 15 minutes after i.v. diltiazem loading dose of 0.25 mg/kg followed by the infusion of 1 mcg/kg/min. Oxygen inhalation produced no significant modifications of haemodynamic variables, whilst a significant (p less than 0.05) decrease of PAPm, pulmonary arteriolar resistance (PAR) and peripheral resistance (TPR) was observed after diltiazem administration (respectively 14%, 23% and 11.6%). Heart rate, cardiac index and blood pressure did not change significantly even with diltiazem. These results could support the inclusion of diltiazem in the therapeutic regimen of pulmonary hypertension due to chronic obstructive lung disease, but further investigations are needed to clarify the predictive value of its acute administration in assessing long term efficacy.

Bronchitis↗