ABSTRACT
The genotoxic effects due to in vivo treatment with zinc dithiocarbamates were evaluated in rat and mouse liver. The two pesticides Zineb and Ziram, belonging to this chemical class, induced an increase in single-strand DNA breaks, as measured by the alkaline elution technique. The nuclear enzyme poly(ADP-ribose) polymerase (pADPRP), a chromatin-bound catalytic protein, utilizing NAD+ as a substrate, was tested by a radiometric procedure. A close relationship between the increased extent of DNA damage and the enhanced level of endogenous pADPRP activity was obtained in rat liver, whereas both parameters remained unchanged in mouse liver.
Subject(s)
DNA Damage , DNA Repair , Poly(ADP-ribose) Polymerases/metabolism , Zineb/toxicity , Ziram/toxicity , Animals , Carbamates/toxicity , Dose-Response Relationship, Drug , Enzyme Activation , Liver/enzymology , Male , Mice , Rats , Rats, Wistar , Zinc/toxicityABSTRACT
Single cells from enzymatically dissociated chick embryo tibiae have been cloned and expanded in fresh or conditioned culture media. A cloning efficiency of approximately 13% was obtained using medium conditioned by dedifferentiated chondrocytes. A cloning efficiency of only 1.4% was obtained when conditioned medium from hypertrophic chondrocytes was used, and efficiencies of essentially 0 were found with fresh medium or medium conditioned by J2-3T3 mouse fibroblasts. Cell clones were selected by morphological criteria and clones showing a dedifferentiated phenotype (fibroblast-like) were further characterized. Out of 38 clones analyzed, 17 were able to differentiate to the hypertrophic chondrocyte stage and reconstitute hypertrophic cartilage when placed in the appropriate culture conditions. Cells from these clones expressed the typical markers of chondrocyte differentiation, i.e., type II and type X collagens. Clones not undergoing differentiation continued to express only type I collagen. Hypertrophic chondrocytes from differentiating clones were analyzed at the single cell level by immunofluorescence; all the cells were positive for type X collagen, while approximately 50% of them showed positivity for type II collagen.
