304 EARLY DETERMINATION IN DEVELOPMENT 



proteins has seemed important since the early stages of this 

 research (Arosio et ah, 1946). The embryonic differentiation is 

 a cytoplasmic phenomenon and some protein fractions which are 

 anisodiametric to viscosimetric analysis and which show in some 

 instances flow birefringence can be extracted from the cytoplasm 

 (Cigada et al., 1954). These fractions can be purified. Therefore, 

 when animalizing and vegetalizing agents induce then- opposite 

 effects on the development, those proteins which may be extracted 

 in a fibrillar shape from cytoplasm are involved. 



Proteins Are Denatured by Animalizing Agents 



Viscosimetric data of the action of animalizing agents on glob- 

 ular protein solutions (increasing viscosity) and on fibrillar 

 protein solutions ( decreasing viscosity ) suggest protein denatura- 

 tion. This denaturation by breaking some bonds increases the 

 volume of globular particles and induces a reduction in the 

 anisotropy of the fibrillar particles. This phenomenon was ob- 

 served with the electron microscope on actomyosin treated with 

 SCN~ and I~ (Ranzi, 1947). The research carried out with the 

 Signer apparatus of flow birefringence shows that actomyosin and 

 myosin particles decrease in length after treatment with animahz- 

 ing substances (Rocca, unpublished research). 



Also the study of chemically detectable free groups favors the 

 conclusion that there is a denaturation process. It is possible to 

 show a greater amount of OH groups and of phenolic groups in 

 actomyosin treated with animalizing substances (Arosio and 

 Bossi, 1954). The same occurs in denaturation processes induced 

 by urea or heat. 



The ATPase activity of myosin is considerably reduced by the 

 action of animalizing substances. 



The precipitin test was used to study the action of SCN~ and 

 I~ on actomyosin solutions. SCN~ and I~ induce changes in the 

 antigens and the immunological properties of the changed an- 

 tigens are similar in both cases. The changes indicate a denatura- 

 tion process ( Arosio, 1953 ) . 



That a denaturation process is the basis of the action of ani- 

 malizing substances is shown ( as mentioned before ) by the fact 



