Standardization of Assay for Unidentified Growth Factors

Abstract

IN SPITE of the efforts of many workers, our knowledge of the character and function of unidentified chick growth factors in such materials as whey, distillers solubles, fish products and fermentation residues, is still quite limited. Obviously, some handicap common to all investigators has hindered progress. Waibel el al. (1955) referred to “the well-known, but usually unpublished, difficulties in studying unidentified chick growth factors.” Attempts to fractionate unknown growth factors were discontinued in this laboratory in 1953 because the growth response was lost. It is believed that many other researchers have encountered this same problem. This investigation deals with attempts to restore the chick’s ability to respond to such materials and to determine the reason for the loss of this ability. METHODS AND RESULTS Chicks in all trials were reared in electrically heated battery brooders with raised wire floors. All depleted chicks were from New Hampshire hens maintained in cages …