Protein Metabolism of Tissue Cells in vitro

Abstract

Summary.1. In a treatment of the problems concerning the growth substances acting upon animal tissue cells in vitro it is pointed out that it is necessary to distinguish between the nature and mode of action of the growth promoting substances, termed embryonin, which are high molecular protein fractions present in an embryo extract, and the accessory growth substances of low‐molecular nature present in a variety of biological systems. Both of these groups were found to be essential to the growth of tissue cells in vitro.2. When studying the properties of the low‐molecular substances several difficulties are encountered which are inherent in the test method available and therefore unavoidable. The meaning of the term “accessory growth substances” for tissue cultures in vitro is discussed.3. The purification of the barley malt extracts previously investigated was carried further with only partial success. The activity of the fractions diminish as the purification proceeds. In some cases completely inactive fractions result, which when mixed regain a considerable activity indicating the presence of at least two groups of accessory growth substances essential to the tissue cells.4. From embryonic extracts it is possible to isolate as a stable dry powder purified preparation which is superior to the best malt extracts in producing normal growth and appearance of the tissue cultures.