Search results for "Nitroso"

Synthesis and antimicrobial activity of new 3-(1-R-3(5)-methyl-4-nitroso-1H-5(3)-pyrazolyl)-5-methylisoxazoles.

2000

A number of new 3-(1-R-3(5)-methyl-4-nitroso-1H-5(3)-pyrazolyl)-5-methylisoxazoles 6a-g (7b-f) were synthesized and tested for antibacterial and antifungal activity. Some of these compounds displayed antifungal activity at non-cytotoxic concentrations. Derivative 6c was 9 times more potent in vitro than miconazole and 20 times more selective against C. neoformans. 6c was also 8- and 125-fold more potent than amphotericin B and fluconazole, respectively. None of the compounds was active against bacteria. Preliminary structure-activity relationship (SAR) studies showed that the NO group at position 4 of the pyrazole ring is essential for the activity. Lipophilicity of the pyrazole moiety, N-a…

Synthesis and antimicrobial activity of new 1-R-3-(2-Piridyl)-4-nitroso-5 carboxiethyl-1H-Pyrazoles

SYNTHESIS AND ANTIMICROBIAL ACTIVITY OF NEW 1-R-3-(2-PIRIDYL)- 4-NITROSO- 5-CARBOXIETHYL-1H-PYRAZOLES. Stefania Aielloa , Carmelo Massimo Maidab, Fabio Venturellab, Diego Planetac Marco Giammancod, M.Milicib a Dipartimento di Scienze e Tecnologie Molecolari e Biomolecolari, Università degli Studi di Palermo bDipartimento di Scienze per la Promozione della Salute G. D’ Alessandro, Università degli Studi di Palermo cDipartimento dei Sistemi Agro-Abientali,Università degli Studi di Palermo d Dipartimednto di Studi Giuridici, Economici, Biomedici e Psicosociopedagogici delle Scienze Motorie e Sportive, Università degli Studi di Palermo Corresponding author: Stefania Aiello, Dipartimento di Scie…

Effect of antibodies against cytochrome P-450 on demethylation and denitrosation of N-nitrosodimethylamine and N-nitrosomethylaniline.

1988

Rat liver microsomes which were induced either with ethanol or PB were incubated with NDMA or NMA. Formaldehyde generation and nitrite formation were measured as metabolic parameters for oxidative bioactivation and denitrosation, respectively. The influence of antiserum PB3a1 and PB22 containing antibodies against the corresponding cytochrome P-450 species on both metabolic functions was investigated. The results showed that the influence on formaldehyde production and denitrosation varied independently in that both parameters were either not affected, or influenced in an opposite way, or inhibited to a different degree. Especially remarkable was the 80% inhibition of formaldehyde generatio…

HONO Emissions from Soil Bacteria as a Major Source of Atmospheric Reactive Nitrogen

2013

From Soil to Sky Trace gases emitted either through the activity of microbial communities or from abiotic reactions in the soil influence atmospheric chemistry. In laboratory column experiments using several soil types, Oswald et al. (p. 1233 ) showed that soils from arid regions and farmlands can produce substantial quantities of nitric oxide (NO) and nitrous acid (HONO). Ammonia-oxidizing bacteria are the primary source of HONO at comparable levels to NO, thus serving as an important source of reactive nitrogen to the atmosphere.

Expression of DNA repair proteins hMSH2, hMSH6, hMLH1,O6-methylguanine-DNA methyltransferase and N-methylpurine-DNA glycosylase in melanoma cells wit…

1999

Malignant melanoma is well known for its primary unresponsiveness to chemotherapy. The mechanisms conferring this intrinsic resistance are unclear. In this study, we investigated the role of genes involved in DNA repair in a panel of human melanoma cell variants exhibiting low and high levels of resistance to 4 commonly used drugs in melanoma treatment, i.e., vindesine, etoposide, fotemustine and cisplatin. We show that in melanoma cells exhibiting resistance to cisplatin, etoposide and vindesine, the nuclear content of each of the DNA mismatch repair (MMR) proteins hMLH1, hMSH2 and hMSH6 was reduced by 30–70%. A decreased expression level of up to 80% of mRNAs encoding hMLH1 and hMSH2 was …

Acquired resistance of melanoma cells to the antineoplastic agent fotemustine is caused by reactivation of the DNA repair gene mgmt

2001

Acquired resistance to antineoplastic agents is a frequent obstacle in tumor therapy. Malignant melanoma cells are particularly well known for their unresponsiveness to chemotherapy; only about 30% of tumors exhibit a transient clinical response to treatment. In our study, we investigated the molecular mechanism of acquired resistance of melanoma cells (MeWo) to the chloroethylating drug fotemustine. Determination of O6-methylguanine-DNA methyltransferase (MGMT) activity showed that MeWo cells that acquired resistance to fotemustine upon repeated treatment with the drug display high MGMT activity, whereas the parental cell line had no detectable MGMT. The resistant cell lines exhibit cross-…

DNA repair protein MGMT protects against N-methyl-N-nitrosourea-induced conversion of benign into malignant tumors

2003

Tumor formation is a multi-step process that can be divided into the stages of tumor initiation, promotion and progression. Previously, we showed that overexpression in skin of mice of the DNA repair protein O(6)-methylguanine-DNA methyltransferase (MGMT) protects against N-methyl-N-nitrosourea (MNU)-induced tumor initiation without affecting tumor promotion. This indicated that O(6)-methylguanine, which is specifically repaired by MGMT, is a major tumor-initiating lesion. Here we extended this transgenic approach to the study of tumor progression. Benign papillomas that arose on the skin of CkMGMT transgenic mice upon initiation with 7,12-dimethylbenz[a]anthracene (DMBA) and promotion by 1…

On the Derivatization of Drugs Using 1-Nitroso-2-naphthol, 4-aminoantipyrine and 2,6-Dihaloquinone Chlorimides

1992

Coupling of 1-nitroso-2-naphthol (1N2N), 4-aminoantipyrine (4-AAP), 2,6-dichloroquinone chlorimide (DCQC) and 2,6-dibromoquinone chlorimide (DBQC) with several bioactive substances, including adren...

Preparation and structural studies on diorganotin(IV) complexes of N-nitroso-N-phenylhydroxylaminates

2007

Abstract Diorganotin(IV)-complexes of the N -nitroso- N -phenylhydroxylaminates (hereinafter cupf), Et 2 Sn(cupf) 2 ( 1 ), Bu 2 Sn(cupf) 2 ( 2 ), {[Bu 2 Sn(cupf)] 2 O} 2 ( 3 ), t -Bu 2 Sn(cupf) 2 ( 4 ) and Oc 2 Sn(cupf) 2 ( 5 , 6 ) were prepared and characterised by FT-IR and Mossbauer spectroscopic measurements. The binding modes of the ligand were identified by FT-IR spectroscopy, and it was found that the ligand is coordinated in chelating or bridging mode to the organotin(IV) center. The 119 Sn Mossbauer and FT-IR studies support the formation of trans -O h ( 1 – 6 ) structures. The X-ray diffraction analysis of 4 revealed that the tin centre is in a skew-trapezoidal geometry defined by…

Nuclear Translocation of Mismatch Repair Proteins MSH2 and MSH6 as a Response of Cells to Alkylating Agents

2000

Mammalian mismatch repair has been implicated in mismatch correction, the prevention of mutagenesis and cancer, and the induction of genotoxicity and apoptosis. Here, we show that treatment of cells specifically with agents inducing O(6)-methylguanine in DNA, such as N-methyl-N'-nitro-N-nitrosoguanidine and N-methyl-N-nitrosourea, elevates the level of MSH2 and MSH6 and increases GT mismatch binding activity in the nucleus. This inducible response occurs immediately after alkylation, is long-lasting and dose-dependent, and results from translocation of the preformed MutSalpha complex (composed of MSH2 and MSH6) from the cytoplasm into the nucleus. It is not caused by an increase in MSH2 gen…