Evaluation of the mutagenic effects of SV40 in mouse, hamster, and mouse-human hybrid cells

We have examined the ability of SV40 to induce changes in drug or temperature resistance in mouse, hamster, and mouse-human hybrid cells. SV40 induced a substantial increase of cells resistant to 5-bromodeoxyuridine + trifluorothymidine in Balb/c 3T3 cells and induced an increase of hybrid cells resistant to 6-thioguanine. SV40 was found to be nonmutagenic or weakly mutagenic in other test systems. The 3T3 cells were T-antigen positive, exhibited a marked reduction in TK activity, were heterogeneous for [ 3 H]BrdU incorporation by autoradiography, and exhibited instability of the drug-resistance phenotype, suggesting that SV40 may be inducing resistance by an epigenetic process. SV40-induced 6-thioguanine resistance in the hybrids appears to occur predominantly by chromosome loss.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/45539/1/11188_2005_Article_BF01233058.pd

Necrotroph Attacks on Plants: Wanton Destruction or Covert Extortion?

Necrotrophic pathogens cause major pre- and post-harvest diseases in numerous agronomic and horticultural crops inflicting significant economic losses. In contrast to biotrophs, obligate plant parasites that infect and feed on living cells, necrotrophs promote the destruction of host cells to feed on their contents. This difference underpins the divergent pathogenesis strategies and plant immune responses to biotrophic and necrotrophic infections. This chapter focuses on Arabidopsis immunity to necrotrophic pathogens. The strategies of infection, virulence and suppression of host defenses recruited by necrotrophs and the variation in host resistance mechanisms are highlighted. The multiplicity of intraspecific virulence factors and species diversity in necrotrophic organisms corresponds to variations in host resistance strategies. Resistance to host-specific necrotophs is monogenic whereas defense against broad host necrotrophs is complex, requiring the involvement of many genes and pathways for full resistance. Mechanisms and components of immunity such as the role of plant hormones, secondary metabolites, and pathogenesis proteins are presented. We will discuss the current state of knowledge of Arabidopsis immune responses to necrotrophic pathogens, the interactions of these responses with other defense pathways, and contemplate on the directions of future research