Effect of ultraviolet light, methyl methanesulfonate and ionizing radiation on the genotoxic response and apoptosis of mouse fibroblasts lacking c-Fos, p53 or both

Mutagenesis ◽  
2001 ◽  
Vol 16 (3) ◽  
pp. 233-241 ◽  
Author(s):  
D. Lackinger
Keyword(s):  
Ionizing Radiation ◽  
Ultraviolet Light ◽  
Methyl Methanesulfonate ◽  
Mouse Fibroblasts

PURE AND MOSAIC CLONES — A REFLECTION OF DIFFERENCES IN MECHANISMS OF MUTAGENESIS BY DIFFERENT AGENTS IN SACCHAROMYCES CEREVISIAE

1981 ◽  
Vol 23 (1) ◽  
pp. 73-79 ◽  
Author(s):  
A. Nasim ◽  
M. A. Hannan ◽  
Earle R. Nestmann
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Ultraviolet Light ◽  
Nitrous Acid ◽  
Repair Process ◽  
Dna Lesions ◽  
Ethyl Methanesulfonate ◽  
Methyl Methanesulfonate ◽  
Mechanisms Of Mutagenesis ◽  
G1 Cells

The induction of pure and mosaic clones has been studied in haploid G1 cells of Saccharomyces cerevisiae. Following treatments with ultraviolet light, methyl methanesulfonate, ethyl methanesulfonate, nitrous acid, and N-methyl-N′-nitro-N-nitrosoguanidine, the relative proportions of pure mutant clones varied from 25 to 100% at comparable survival levels. Ultraviolet light and methyl methanesulfonate produced mainly pure mutant clones, whereas ethyl methanesulfonate and nitrous acid produced mainly mosaics at 59 to 100% survival levels. The ratio of pure to mosaic clones induced by nitrosoguanidine fell between these two classes. These results are consistent with a classification of mutagens on the basis of repair and replication-dependent mechanisms of mutagenesis in other organisms. Agents having actions similar to ultraviolet light may produce mainly pure clones through a pre-replicative process involving an error-prone DNA repair process. Others may produce mainly mosaic mutants due to the different nature of DNA lesions which may require a replication-dependent process for fixation of mutations. Preliminary data from combined treatments of mutagens belonging to two different classes (i.e. ultraviolet light and nitrous acid) suggest the possibility of an interaction between these agents, resulting in a higher proportion of pure clones, possibly due to an inducible process. Studies of induced frequencies of pure and mosaic clones may be useful in the characterization of mutagens with functional differences.

Degradation of Polymers

1962 ◽  
Vol 35 (5) ◽  
pp. 1157-1221 ◽  
Author(s):  
Leo A. Wall ◽  
Joseph H. Flynn
Keyword(s):  
Ionizing Radiation ◽  
Thermal Degradation ◽  
Natural Rubber ◽  
Ultraviolet Light ◽  
Recent Literature ◽  
Chain Scission ◽  
Experimental Results ◽  
Gel Formation ◽  
Vinyl Polymers ◽  
Kinetic Mechanisms

Abstract Recent literature pertaining to both the theoretical aspects and experimental results of the degradation of polymers by heat and radiation is reviewed and critically evaluated. Theories of random and chain thermal degradation of vinyl polymers and co-polymers are reviewed. The degradation of polymethacrylates, polyacrylates, poly-α-methylstyrene, polyolefins, polystyrene, other vinyl polymers, cellulose, polyesters, polyamides, dienes, natural rubber, and copolymers are discussed in the light of these theories. The thermodynamics and energetics of the degradation of these polymers is also reviewed. Chain scission, crosslinking, and gel formation and the kinetic mechanisms of these processes which take place during degradation of polymers by ionizing radiation and ultraviolet light are included. Degradative, rather than synthetic, effects are emphasized in the discussion.

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