Benzamide, an inhibitor of (ADP-ribose) transferase, augmented chondrocytic differentiation of chick limb bud mesenchymal cells in micromass cultures; the incorporation of 35SO42− into the trichloroacetic-acid-insoluble constituents of cell masses as well as the formation of cartilage nodules (Nishio, Nakanishi, Doull & Uyeki, 1983) occurred about 24h earlier than in untreated cultures and continued to be enhanced in benzamide-treated cultures of stage 23- to 24-chick limb bud cells. Benzamide also significantly increased cell proliferation. However, benzamide did not affect DNA and RNA syntheses except for one period: 24 to 30 h after the start of culture, RNA synthesis was stimulated. From 48h of culture, (ADP-ribose) transferase activity decreased daily in untreated cultures, whereas benzamide treatment diminished (ADP-ribose) transferase activity 24 h earlier. On the other hand, intracellular NAD levels increased daily in untreated cultures, and benzamide significantly increased the NAD levels above untreated cultures. ATP levels did not differ significantly during the culture period, and benzamide did not affect ATP levels.

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