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The osteogenic factor from murine osteosarcoma was soluble in 4M guanidine-HCl. The precipitate that appeared after dialysis of the guanidine solution against deionized water showed a higher osteogenetic activity than did the initial dry powder of tumor tissue. Electron-microscopically, this bone-inducing fraction seems to be homogenous. Neither a fibrous nor collagenous cross-banded structure was observed in the fraction. Since the chemical analysis of the fraction also showed a relatively low content of hydroxyproline, the osteogenic factor is probably not collagen.
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Takaoka et al. (1980) studied this question.
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