Proliferation-promoting intercellular hormones

our studies of proliferation-promoting factors from injured animal tissue cells have been carried out with tissue cultures as a means of assaying the products obtained [Sperti, Loofbourow & Lane, 1937; Loofbourow, Cueto & Lane, 1939].In the case of similar proliferation-promoting factors from injured yeast cells, the assays on yeast have afforded much more accurate quantitative data [Loofbourow, Dwyer & Morgan, 1938].Since it is desirable to obtain a comparable degree of accuracy in the assay of animal-cell products in order to answer various questions regarding the physiological production and chemical nature of the factors, we endeavoured to see if the animal-cell products could be assayed on yeast.The yeast assay technique having proved to be practicable, we wish to present here the results of quantitative studies by this method of the products from injured animal tissue cells.The name "intercellular hormones" [Loofbourow & Morgan, 1938] has been suggested for factors controlling cellular metabolism which are released by cells and act from cell to cell through the intermediary of the intercellular fluids.Thus the respiratory, glycolytic and proliferation-controlling factors investigated in our laboratories, as well as Toro's [1937, etc.] corhormone, Wildiers' [1901] bios, Williams' [1933, etc.] pantothenic acid, Bonner's [1937, etc.] traumatin, the auxins and many other such substances are probably all "intercellular hormones" in this sense.The particular proliferation-promoting intercellular hormone discussed in what follows appears to be produced especially by injured cells, and is thus a "wound hormone" in the sense used by Wiesner [1892], Haberlandt [1921], Reiche [1924] and others for growth factors obtained from injured plant tissues.For this reason, we have at times called it an "intercellular wound hormone", but it should be pointed out that the same proliferationpromoting factor appears to occur in the intercellular fluids from uninjured cells, only to a less extent, and the relation to injury is therefore evidently a quantitative rather than a qualitative one. ExPERIMENTALAs a means of injuring the tissue cells, lethal ultraviolet from a 500 w.Burdick quartz mercury arc, operated at 65 v. across the arc, was used in all of the following experiments.The irradiation distance was unifbrmly 25 cm.