The carcinogenicity of N-nitroso-N-methylurea (NMU) and N-nitroso-N-ethylurea (NEU) has been determined in adult male Syrian golden hamsters following a single i.p. injection or two-thirds of the acute 50% lethal dose, or 30 and 60 mg/kg, respectively. The principal site of action of these agents was the forestomach, squamous cell papillomas of this organ developing in 53 and 61% of the animals...

O6-Benzylguanine (BG) inactivates O6-alkylguanine-DNA alkyltransferase (AGT), resulting in an increase in the sensitivity of cells to the toxic effects of O6-alkylating agents. BG significantly enhances the cytotoxicity and decreases the mutagenicity of nitrogen mustards [i.e., phosphoramide mustard (PM), melphalan, and chlorambucil], a group of alkylating agents not known to produce O6-adducts...

O6-benzylguanine (BG) is a potent, specific inactivator of the DNA repair protein O6-alkylguanine-DNA alkyltransferase (AGT), which enhances sensitivity to nitrosoureas in cells and tumor-bearing animals. BG is presently undergoing clinical trials for development as an agent to enhance the therapeutic index of alkylating agent chemotherapy. It has been reported that a polymorphism exists in the...

transcription start site and silencing of the heterochromatinization of the MGMT (MGMT) CpG island is associated with O6-methylguanine DNA methyltransferase Methylation of discrete regions of the

The role of DNA alkylation at the O6 position of guanine in the induction of gene mutations in vivo was studied in the hprt gene of rat T-lymphocytes from spleen exposed in vivo to the monofunctional ethylating agents ethylmethanesulfonate (EMS) and N-ethyl-N-nitrosourea (ENU), or the hydroxyethylating agent N-(2-hydroxyethyl)-N-nitrosourea (HOENU). All chemicals showed an exposure-dependent in...

O6-Methylguanine in DNA is repaired by the action of a protein termed O6-alkylguanine-DNA alkyltransferase (AT) which transfers the methyl group to a cysteine residue in its own sequence. Since the cysteine which is methylated is not regenerated rapidly, if at all, the capacity for repair of O6-methylguanine is limited by the number of molecules of the AT available within the cell. The level an...

The influence of thermal and thermobaric (TBT) effects on the structure, microstructure, dielectric properties ceramics based solid solutions La1.8Ca0.2Ni0.8M0.2O4+δ (M = Co, Cu) composition was studied. TBT treatment samples leads to a change in grain morphology an increase constant compared its value only after heat treatment. anisotropy coordination (La,Ca)O9 (Ni,M)O6 polyhedra contributed i...