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S Grilli

Publications and source records attributed to S Grilli.

At least 91 records · Page 5Linked to original sources
PubMed1977

An in vitro study on the interaction between dimethylnitrosamine and nucleic acids via a microsomal system.

Radioactive alkylated bases, ribose or phosphate, were never found either in acid and alkaline hydrolysates of polyribonucleotides or in alkaline hydrolysates of DNA after incubation with 14C-dimethylnitrosamine (DMNA) in a microsomal system. Two radioactive compounds, which were co-chromatographed with methylamine and N-methylhydrazine, respectively, on column, paper, and thin-layer, were always detected. They differed from the compound derived from 7-methylguanosine after the alkali-mediated fission of the imidazole ring in its molecule. The in vitro system employed well represents the in vivo situation (7-methylguanine which is liberated from DNA after acid hydrolysis); however, it has given results which do not agree with the generally-accepted mechanism of DMNA alkylation at the N-7 position of guanine.

Animals↗
PubMed1975

Effect of urethan on the synthesis of nucleic acids in thymus, spleen, and bone marrow.

Urethan, in a single dose of 1 mg/g body weight, exerts a strong inhibitory effect on DNA synthesis in lymphoid organs and bone marrow of rat. The inhibition observed in spleen and thymus is longer lasting than that exerted on bone marrow or regenerating liver, demonstrating a marked sensitivity of lymphoid cells to the drug. This effect can explain the rapid reduction of weight and cell number in thymus and spleen under urethan treatment, in absence of any lymphocytolytic action. The different effect of urethan on the different subpopulations of lymphoid cells therefore appears to be due to their kinetics rather than to a specific sensitivity of some of them.

Animals↗
PubMed1975

Non-enzymatic and microsome-dependent binding of poly-cyclic hydrocarbons to DNA and polynucleotides.

The binding of tritium-labeled 7,12-dimethylbenz[a]anthracene (DMBA), benzo[a]pyrene (BP) and 3-methylcholanthrene (MCA) to DNA or polynucleotides in vitro was re-examined both in the presence and in the absence of rat liver or human placental microsomes. A high level of non-enzymatic binding was evident when thymus DNA was used as acceptor. This non-enzymatic binding made it difficult to determine the effect of microsomes, except in the case of BP when induced rat microsomes were used. Better results were obtained using polynucleotides: a definite microsome-dependent binding occurred between all the polynucleotides and all the hydrocarbons tested. No clear evidence of binding catalysed by microsomes from human placenta was found except in polynucleotide-BP interactions: further studies are required to completely evaluate the ability of such nucleic acid-microsomal system for testing in vitro possible oncogenic substances in animals and humans.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1975

The binding of dimethylnitrosamine to nucleic acids catalyzed by liver enzymic fractions.

The in vitro binding of a metabolite of dimethylnitrosamine (DMNA) to calf thymus DNA catalyzed by a microsomal system from rat liver is reported. The amount ob binding is unaffected by using microsomes induced by 3-methylcholanthrene and/or normal or induced pH 5 enzymes. The microsomal system is also effective in catalyzing covalent binding of the nitroso compound with synthetic polyribonucleotides.

Animals↗
PubMed1975

Identification of dimethylnitrosoamine metabolites in vitro.

The incubation of dimethylnitrosoamine (DMNA) in the presence of rat liver microsomes leads to production of formaldehyde, formic acid, methylamine, and N-methylhydrazine. When pH 5-enzymes are added to the medium there is also the formation of N-methylhydroxylamide and N,N-dimethylhydrazine. The last compound is the only metabolite produced, to a lesser extent, by the pH 5-enzymes. Thus, the denitrosated or non-denitrosated metabolites are produced either by an oxidative dealkylation and by a reduction of DMNA, catalysed by microsomal and cellular soluble enzymes.

Animals↗
PubMed1975

Degradation of dimethylnitrosoamine catalysed by physical and chemical agents.

Decomposition of dimethylnitrosoamine (DMNA) by chemical and physical agents was further investigated. Both photoirradiation with sunlight or ultraviolet ray and reductive reactions under acid conditions (likely occurring in the stomach) led to the formation of formaldehyde, formic acid, and N-methydrazine, in addition to denitrosated compounds such as methylamine, dimethylamine, and N-methylhydroxylamine. N-Methylhydrazine was the only compound which was not detected by photoirradiation under neutral conditions. The agreement between physiochemical and metabolic degradation products and the possible biological meaning are discussed together with the problem of environmental contamination by the nitroso compound.

Dimethylnitrosamine↗
PubMedDate not supplied

Dexamethasone modulation of in vitro growth pattern and of lung colonization ability in clones of a metastatic BALB/c mammary carcinoma cell line.

The expression of steroid receptors and the in vitro responsiveness to steroids were used to investigate the cell heterogeneity of a BALB/c mammary carcinoma cell line (TS/A) by means of its high- and low-metastatic clones previously selected in vitro. All the clones studied contained appreciable levels of receptors for oestrogens and for glucocorticoids. The in vitro responses of clones to 17 beta-oestradiol were very poor and comparable; conversely, a heterogeneous pattern of responsiveness to glucocorticoids was observed. In the presence of dexamethasone, the in vitro growth of high-metastatic clones was either unaffected or stimulated and dome formation was significantly increased. Dexamethasone treatment of low-metastatic clones caused inhibition of in vitro proliferation and a morphological shift from a fibroblast-like growth pattern towards the epithelial phenotype. One out of the three low-metastatic clones tested acquired the ability to form domes in the presence of dexamethasone, albeit sporadically. The in vitro treatment with dexamethasone significantly increased the lung colonization ability of the two low-metastatic clones studied, whereas no significant effect was observed with high-metastatic clones. Data presented here suggest that TS/A cell line consists of heterogeneous populations with peculiar proliferative and differentiative responses to glucocorticoids.

Animals↗
PubMedDate not supplied

Effects of the protease inhibitor antipain on cell malignant transformation.

BACKGROUND: Several natural products have been found to exhibit a chemopreventive activity both in in vivo and in vitro experimental systems. Among them, protease inhibitors seem to play a key role in the regulation of growth and phenotypic expression of transformed cells as well as in the regulation of the late events of carcinogenesis. We evaluated the effect of antipain (AP), a natural protease inhibitor, on chemically induced BALB/c 3T3 cell transformation, on invasion and chemotactic motility of transformed cells and on their gelatinase expression. METHODS: BALB/c 3T3 cells were plated and exposed to 2.5 micrograms/ml 3-MCA or 50 micrograms/ml, 1,2-DBE. The effect of a non-cytotoxic dosage of AP (10 microM) was studied by: a) pretreating cells with AP for 48 hours before the carcinogen exposure; b) adding AP simultaneously to the carcinogen treatment; c) chronic addition of AP at each medium change throughout the experimental duration. The effectiveness of the treatment was analysed as the ability to reduce or inhibit the occurrence of transformed foci. Modulation of the invasive phenotype by anti-transforming dosages of AP was evaluated by in vitro Matrigel invasion assay. Gelatin zymography was performed in order to assess AP regulation of proteolytic enzymes, such as metalloproteases, involved in invasion and metastasis. RESULTS: AP treatment can reduce the transformation rate both in 3-MCA- and 1,2-DBE-initiated cells. Its effectiveness depends on the administration schedule, and chronic addition seems to be the most effective treatment. The concentration of AP, which is effective in the antitransformation assay, is not able to significantly affect the migration and invasion of chemically transformed cells or their gelatinase activity. CONCLUSIONS: AP can suppress chemically induced BALB/c 3T3 cell transformation through mechanisms which do not involve modulation of the invasive phenotype.

3T3 Cells↗