XENO-INDUCTIONS 



441 



speed centrifugation, and have compared the effects of successive precipitates and evapo- 

 rated supernatants. The former are strictly deutogenic, while the latter still show a mixed 

 inductive action. In discussing the various results concerning this problem, the authors 

 admit that only the protein moiety is responsible, and that the difference between the 

 two factors only concerns the degree of stability. The deutogenic effect would be caused 

 by a protein in an unstable state, the acrogenic effect, by the same molecules in a stable 

 state. Physical or chemical differentiation between the samples has been searched for by 

 the most sensitive procedures, flow birefringence, electrophoresis and chromatography, 

 but so far in vain. 



Fig. 91. Inductive effect of a subfraction of pentose nucleoprotein from guinea pig kidney 

 on the isolated ectoderm, somites, notochord, ear vesicle, mesenchyme and melanophores. 



From Yamada, 1958b. 



That the active protein is bound with RNA cannot be extended to another 

 potent indtictor obtainable from the same animal, namely from its bone marrow. 

 Indeed, this potent mesoderm inducer discovered by Toivonen has been sub- 

 mitted to a close examination by Yamada (1958b). It is, as stated, typically noto- 

 genic, the spinal chord being yet mostly absent. Streptomycine treatment per- 

 mitted the separation of the RNP fraction and a non-precipitable proteic fraction. 

 The former was nearly inactive, while the latter preserved the characteristic 

 original effect. It is interesting to quote again that warming the sample from 

 25 to 150 sec. progressively yielded typical notogenesis (with spinal chord), then 

 deutogenesis, and finally acrogenesis^ 



Thus, from these vahxable investigations, it appears that the stibstance 

 responsible for the xeno-induction exerted by organs of guinea pig might well be a 

 protein btit, in the c-.ce of liver (and probably also of kidney, see supra) it is 

 extractable as a ribonr.cleoprotein, while in the case of bone marrow, it is obtained 

 as an apparently free protein. 



' After a closer stvidy c! this heat treatment, Yamada (1959) reasserts his preference for 

 the existence of one inducing factor, but transformable by adequate means (sec p. 434). 



I.ileralure p. 483 



