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P Cremonesi

Publications and source records attributed to P Cremonesi.

At least 19 recordsLinked to original sources
PubMed1991

Absorption of iron from iron succinyl-protein complexes by mouse small intestine.

The absorption of iron from iron succinyl-protein complexes was investigated in mice. 59Fe-labelled succinyl-casein and -albumin complexes, [59Fe]ferritin and 59FeSO4, at doses of 20 or 200 micrograms of iron, were administered orally to normal mice or mice with absorption enhanced by chronic hypoxia. 59Fe from iron succinyl-protein was well absorbed in normal mice (greater than 10% of dose) and showed enhanced absorption in hypoxic mice (greater than 40% of dose). Intestinal uptake was predominantly by the duodenum for all compounds studied. In-vivo absorption of 59Fe from an iron succinyl-protein complex was studied using tied-off segments of mouse duodenum, jejunum or ileum of normal or hypoxic mice. Incubation for up to 15 min in duodenum or 60 min in ileum showed very little absorption of 59Fe. No enhancement of absorption was seen in hypoxic mice. It was concluded that absorption of the intact iron succinyl-protein complex cannot explain absorption seen after oral dosing.

Animals↗
PubMed1990

Binding of benzo[a]pyrene to DNA by cytochrome P-450 catalyzed one-electron oxidation in rat liver microsomes and nuclei.

To investigate whether cytochrome P-450 catalyzes the covalent binding of substrates to DNA by one-electron oxidation, the ability of both uninduced and 3-methylcholanthrene (MC) induced rat liver microsomes and nuclei to catalyze covalent binding of benzo[a]pyrene (BP) to DNA and formation of the labile adduct 7-(benzo[a]pyren-6-yl)guanine (BP-N7Gua) was investigated. This adduct arises from the reaction of the BP radical cation at C-6 with the nucleophilic N-7 of the guanine moiety. In the various systems studied, 1-9 times more BP-N7Gua adduct was isolated than the total amount of stable BP adducts in the DNA. The specific cytochrome P-450 inhibitor 2-[(4,6-dichloro-o-biphenyl)oxy]ethylamine hydrobromide (DPEA) reduced or eliminated BP metabolism, binding of BP to DNA, and formation of BP-N7Gua by cytochrome P-450 in both microsomes and nuclei. The effects of the antioxidants cysteine, glutathione, and p-methoxythiophenol were also investigated. Although cysteine had no effect on the microsome-catalyzed processes, glutathione and p-methoxythiophenol inhibited BP metabolism, binding of BP to DNA, and formation of BP-N7Gua by cytochrome P-450 in both microsomes and nuclei. The decreased levels of binding of BP to DNA in the presence of glutathione or p-methoxythiophenol are matched by decreased amounts of BP-N7Gua adduct and of stable BP-DNA adducts detected by the 32P-postlabeling technique. This study represents the first demonstration of cytochrome P-450 mediating covalent binding of substrates to DNA via one-electron oxidation and suggests that this enzyme can catalyze peroxidase-type electron-transfer reactions.

Animals↗
PubMed1989

Tumor-initiating activity in mouse skin and carcinogenicity in rat mammary gland of dibenzo[a]pyrenes: the very potent environmental carcinogen dibenzo[a, l]pyrene.

Comparative studies of tumor-initiating activity in mouse skin and carcinogenicity in rat mammary gland were conducted with several dibenzo[a]-pyrenes (DBPs). SENCAR mice were initiated with DB[a, e]P, DB[a, h]P, DB[a, i]P, DB[a, l]P and anthanthrene, and promoted with tetradecanoyl-phorbol acetate. The same compounds were tested by intramammillary injection in female Sprague-Dawley rats. Anthanthrene was inactive in both mouse skin and rat mammary gland. DB[a, e]P was a very weak tumor-initiator in mouse skin and was inactive in rat mammary gland. DB[a, h]P induced twice as many papillomas in mouse skin as DB[a, i]P, although both compounds exhibited similar tumor latencies and percentages of tumor-bearing mice. These two compounds induced similar numbers of mammary tumors, but treatment of the rats with DB[a, i]P resulted in a significantly larger number of adenocarcinomas. DB[a, l]P was toxic to both the mice and rats. Treatment of mouse skin with this compound led to an erythema, which delayed the beginning of promotion until the 3rd week after initiation. Despite this delay, papillomas began appearing 5 weeks after initiation with DB[a, l]P and the number of tumors increased rapidly. The compound was so toxic in the rats that half of the animals died in the first 9 weeks and the remaining animals were sacrificed after 15 weeks. Nonetheless, DB[a, l]P was the strongest carcinogen tested, inducing seven tumors per rat within 10 weeks. These results demonstrate that DB[a, l]P, which is present in tobacco smoke, is an extremely potent carcinogenic aromatic hydrocarbon. Furthermore, some of these compounds can serve as useful models for elucidating their mechanisms of activation.

Adenocarcinoma↗
PubMed1988

Radical cations as precursors in the metabolic formation of quinones from benzo[a]pyrene and 6-fluorobenzo[a]pyrene. Fluoro substitution as a probe for one-electron oxidation in aromatic substrates.

Three classes of products are formed when benzo[a]pyrene (BP) is metabolized by cytochrome P-450: dihydrodiols, phenols and the quinones, BP 1,6-, 3,6- and 6,12-dione. These products have been thought to arise from attack of a catalytically-activated electrophilic oxygen atom. In this paper we report chemical and biochemical experiments which demonstrate that BP quinones arise from an initial one-electron oxidation of BP to form its radical cation. BP, 6-fluorobenzo[a]pyrene (6-FBP), 6-chlorobenzo[a]pyrene (6-ClBP), and 6-bromobenzo[a]pyrene (6-BrBP) were metabolized by uninduced and 3-methylcholanthrene-induced rat liver microsomes in the presence of NADPH or cumene hydroperoxide (CHP) as cofactor. BP and 6-FBP produced similar metabolic profiles with induced microsomes in the presence of NADPH or 2 mM CHP. With NADPH both compounds produced dihydrodiols, phenols and quinones, whereas with CHP, they yielded only quinones. Metabolism of BP and 6-FBP was also similar with uninduced microsomes and 2 mM CHP, yielding the same BP quinones. With uninduced microsomes in the presence of NADPH, BP produced all three classes of metabolites, whereas 6-FBP afforded only quinones. At a low concentration of CHP (0.10 mM), BP was metabolized to phenols and quinones, whereas 6-FBP gave only quinones. 6-ClBP and 6-BrBP were poor substrates, forming metabolites only with induced microsomes and NADPH. One-electron oxidation of BP by Mn(OAc)3 occurred exclusively at C-6 with predominant formation of 6-acetoxyBP and small amounts of BP quinones. In the one-electron oxidation of 6-FBP by Mn(OAc)3, the major products obtained were 6-acetoxyBP, a mixture of 1,6- and 3,6-diacetoxyBP, and BP quinones. Reaction of BP and 6-FBP radical cation perchlorates with water produced the same BP quinones. Conversely, electrophilic substitution of 6-FBP with bromine or deuterium ion afforded C-1 and/or C-3 derivatives with retention of the fluoro substituent at C-6. These results indicate that metabolic formation of BP quinones from BP and 6-FBP can only derive from their intermediate radical cation.

Animals↗
PubMed1988

Tumorigenicity of 6-halogenated derivatives of benzo[a]pyrene in mouse skin and rat mammary gland.

Studies of the tumorigenicity of 6-halogenated derivatives of benzo[a]pyrene (BP) can provide evidence about the role of the 6 position in the carcinogenic activation of BP. Female Swiss and A-strain mice were treated on the skin with BP, 6-fluorobenzo[a]pyrene (6-FBP), 6-chlorobenzo[a]pyrene (6-C1BP), 6-bromobenzo[a]pyrene (6-BrBP) and 6-iodobenzo[a]pyrene (6-IBP) by repeated application, and in some cases by initiation-promotion. While BP was more potent than 6-FBP, only these two compounds exhibits tumor-initiating and carcinogenic activity in mouse skin. Female Sprague-Dawley rats were treated with BP, 6-FBP, 6-ClBP, and 6-BrBP by intramammillary injection. BP and 6-FBP induced high levels of mammary epithelial tumors and fibrosarcomas. 6-ClBP elicited only a high percentage of fibrosarcomas, whereas 6-BrBP induced a few adenocarcinomas. These results indicate that chloro or bromo substitution at C-6 in BP reduces or eliminates carcinogenic activity. Conversely, 6-FBP, from which the fluoro substituent has been chemically and metabolically removed by one-electron oxidation, displays a moderate carcinogenic activity which is consistent with activation by either one-electron oxidation or monooxygenation.

Animals↗
PubMed1988

Tumor-initiating activity in mouse skin and carcinogenicity in rat mammary gland of fluorinated derivatives of benzo[a]pyrene and 3-methylcholanthrene.

Comparative studies of tumor-initiating activity in mouse skin and carcinogenicity in rat mammary gland were conducted with benzo[a]pyrene (BP) and 3-methylcholanthrene (MC) derivatives. SENCAR mice were initiated with BP, 6-fluorobenzo[a]pyrene (6-FBP), 6-methylBP, 7-FBP, 8-FBP, 9-FBP, 10-FBP, or 10-azaBP and promoted with tetradecanoyl phorbol acetate. The same compounds plus BP 7,8-dihydrodiol were tested by intramammillary injection in female Sprague-Dawley rats. Tumor-initiating activity in mice and/or carcinogenicity in rats were observed for BP, 6-methylBP, 6-, 7-, 8-, and 10-FBP, whereas 9-FBP was inactive in both experiments and 10-azaBP was only marginally active in the mammary gland. BP 7,8-dihydrodiol was carcinogenic in rat mammary gland, although it was less potent than BP. MC, 8-FMC, 10-FMC, and 3-methylcholanthrylene were also tested in Sprague-Dawley rats by intramammillary injection. All compounds were carcinogenic, with MC displaying the most potent activity. The less potent carcinogenic activity of BP 7,8-dihydrodiol in the mammary gland, compared with BP, and the moderate-to-weak tumor-initiating and/or carcinogenic activity of 7-, 8-, and 10-FBP suggest that the bay-region diol-epoxide pathway does not play a significant role in the activation of BP in these two target tissues. Similarly, the carcinogenic activity of 8-FMC and 10-FMC, in which the bay-region diol-epoxide pathway is blocked, suggests that this mechanism of activation is not important in the carcinogenicity of MC in rat mammary gland.

Animals↗
PubMed1988

Comparative absorption kinetics of imidazole and salicylic acid in volunteers after administration of ITF 182 tablets and suppositories.

Comparative absorption kinetics in volunteers of a new antiinflammatory drug (Selezen), in the form of 750 mg tablets and suppositories, were studied. The two components of the drug, imidazole and salicylic acid were found in plasma. Pharmacokinetic parameters were calculated according to a first order absorption. Salicylic acid showed a maximum concentration 59.2 +/- 5 min and 75.4 +/- 7.6 min after the administration of the tablet and suppository respectively; and imidazole after 86.3 +/- 10.8 min and 75.2 +/- 5.4 min, respectively.

Adult↗
PubMed1987

Structure and properties of enzyme graft copolymers: effects of using dissolved agarose on horseradish peroxidase immobilization.

The immobilization of horseradish peroxidase (HRP) onto dissolved agarose by a photochemically initiated graft copolymerization reaction, carried out at room temperature, was studied. Enzyme immobilization parameters such as the catalyst (FeCl3) and the enzyme concentration were considered. Using hexhydro-1,3,5-triacryloyl-s-triazine (HTsT) as vinyl monomer, the agarose/HTsT ratio was the main reaction parameter controlling the copolymer characteristics. By increasing the polymer content of the sample better stability properties were obtained. For the samples with agarose/HTsT ratios of 20/40 and 40/20 (S 20-40, S 40-20) the residual activities after 240 min at 60 degrees C were respectively 47 and 18%. The residual activity in continuous working was 33% for S 40-20 (after 20 h) and 64% for S 20-40 (after 70 h). For both the synthesized copolymers no limitation to substrate diffusion was found but the flexibility of immobilized enzyme decreased with the increase of polymer content as indicated by the Km values that were 0.90 X 10(-4) mol/liter for the sample S 40-20, and 1.50 X 10(-4) mol/liter for the sample S 20-40. Other enzymes (glucose oxidase, alpha-chymotrypsin, and lipoxidase), besides HRP, were immobilized with good yields, showing the wide applicability of the proposed methodology for the preparation of a solid biocatalyst which can be conveniently stored in water suspension or as lyophilized material.

Chymotrypsin↗
PubMed1985

Drug modulation of superoxide anion production from human neutrophils.

The effects of drugs on the production of superoxide anion from neutrophils stimulated by N-formylmethionyl-leucyl-phenylalanine (FMLP) were examined. Drugs acting on specific receptors, such as beta-adrenergic agonists (e.g. fenoterol, salbutamol) inhibited FMLP-evoked superoxide in a dose-dependent fashion. The order of activity: isoprenaline greater than fenoterol greater than salbutamol is the same as that found by assaying their effects on lysosomal enzyme release. Superoxide production from human neutrophils can also be affected in different manners, such as by a scavenging mechanism. A new non-steroidal anti-inflammatory drug, imidazole 2-hydroxybenzoate, by forming complexes with copper, displayed a significant superoxide dismutase activity which would contribute to explain its anti-inflammatory effect in vivo.

Adrenergic beta-Agonists↗
PubMed1979

Immobilized hydroxysteroid dehydrogenases for the transformation of steroids in water--organic solvent systems.

The hydroxysteroid dehydrogenases: beta-HSDH, 20 beta-HSDH, and 3 alpha-HSDH, were immobilized on CNBr-activated Sepharose. The effect of various immobilization conditions on the activity recovery and stability were examined. The presence of cofactor during the immobilization reaction increased the activity recovery (40--60% of the total) and also led to materials highly stable in the presence of organic solvents. For example, beta-HSDH maintained 60% of its original activity two months after continuous use in the water--ethyl-acetate system. Kinetic experiments showed that the increase of the apparent Km values is poor and demonstrated that the organic solvent behaves as a weak inhibitor (ki greater than 0.2M) for the substrate. The immobilized enzymes lyophilized in the presence of sucrose had full activity restored even after several months storage at room temperature. Immobilized hydroxysteroid dehydrogenases were shown to be suitable for preparative transformation of steroids in water--organic solvent systems.

Cortisone↗
PubMed1979

Patterns of transport and binding of sex steroids.

The seminal plasma-sex steroid binding kinetic was evaluated by measuring the amount of labeled hormone extractable after 5 sec to 100 min of incubation. For testosterone in normal subjects, a peak of binding was reached after 30 sec of incubation. In subjects with severe oligoasthenospermia the kinetic pattern for testosterone was different but similar to the binding kinetic between seminal plasma of normal men and estradiol. The phenomena did not occur with frozen plasma samples.

Estradiol↗
PubMed1975

Enzymatic preparation of 20 beta-hydroxysteroids in a two-phase system.

The behavior of 20 beta-hydroxysteroid dehydrogenase in a two-phase system consisting of an emulsion of water with an immiscible organic solvent was investigated. The effect of several organic solvents on the stability, activity, and kinetic profile of the enzyme was considered. The most suitable system for carrying out the enzymatic reaction proved to be water-butyl acetate. The production of high quantitied of 20 beta-hydroxysteroids in 100% yield using catalytic amount of cofactor was achieved by coupling the 20 beta-hydroxysteroid dehydrogenase-and the alcohol dehydrogenase-catalyzed reactions.

20-Hydroxysteroid Dehydrogenases↗
PubMedDate not supplied

Fluorescence line narrowing spectrometric analysis of benzo[a]pyrene-DNA adducts formed by one-electron oxidation.

Fluorescence line narrowing (FLN) was demonstrated for five benzo[a]pyrene (BP)-nucleoside adducts synthesized by one-electron oxidation of BP in the presence of guanosine, deoxyguanosine, and deoxyadenosine. The standard FLN spectra were used to prove that a major depurination adduct from the binding of BP to DNA in rat liver nuclei is 7-(benzo[a]pyren-6-yl)guanine (N7Gua). The structural characterization was performed with only 20 pg of the adduct. Metabolic activation of BP by one-electron oxidation in the horseradish peroxidase catalyzed reaction of BP with DNA (in vitro) was also investigated. The major adduct identified was 8-(benzo[a]pyren-6-yl)guanine (C8Gua).

Animals↗
PubMedDate not supplied

Metabolism and mutagenicity of dibenzo[a,e]pyrene and the very potent environmental carcinogen dibenzo[a,l]pyrene.

Dibenzo[a,l]pyrene (DB[a,l]P) is one of the most potent carcinogens ever tested in mouse skin and rat mammary gland. DB[a,l]P is present in cigarette smoke and, presumably, in other environmental pollutants. Metabolism and mutagenicity studies of this compound compared to the weak carcinogen dibenzo[a,e]pyrene (DB[a,e]P) can provide preliminary evidence on its mechanism of carcinogenesis. The mutagenicity of DB[a,l]P, DB[a,e]P, and benzo[a]pyrene (BP) was compared in the Ames assay with Aroclor-induced rat liver S-9. BP was the strongest mutagen. In strain TA100, DB[a,l]P and DB[a,e]P were marginally mutagenic. In strain TA98 both compounds were mutagenic, and DB[a,l]P induced more than twice as many revertants as DB[a,e]P. The mutagenicity of DB[a,l]P does not correlate with its carcinogenicity, since DB[a,l]P is a much stronger carcinogen, but a much weaker mutagen, than BP. The NADPH-supported metabolism of DB[a,e]P and DB[a,l]P was conducted with uninduced and 3-methylcholanthrene-induced rat liver microsomes. Metabolites were analyzed by reverse-phase HPLC and identified by NMR, UV, and mass spectrometry. Uninduced microsomes produced only traces of metabolites with either compound. The major metabolites of DB[a,l]P with induced microsomes were DB[a,l]P 8,9-dihydrodiol, DB[a,l]P 11,12-dihydrodiol, 7-hydroxyDB[a,l]P, and a DB[a,l]P dione. The metabolites of DB[a,e]P with induced microsomes were DB[a,e]P 3,4-dihydrodiol, 3-hydroxyDB[a,e]P, 7-hydroxyDB[a,e]P, and 9-hydroxyDB[a,e]P. Some of these metabolites are very useful in assessing possible pathways of activation in the initiation of cancer.

Animals↗