EFFECTS ON GROWTH AND MITOSIS 



769 



EFFECTS ON GROWTH AND MITOSIS 



The often controversial effects of the arsenicals on animal growth have 

 been briefly mentioned, but it is difficult to interpret such results in terms 

 of cellular growth or proliferation since many other factors are involved. 

 There is no doubt that toxic doses of the arsenicals reduce total growth 

 and can depress mitosis in certain tissues. A generalized inhibition of the 

 hematopoietic system can occur, the arsenicals interfering with the forma- 

 tion of erythrocytes and leucocytes, and causing the appearance of ab- 

 normal cells and mitotic disturbances. Depression of thrombocytes and 

 granulocytes may be noted. These effects will be discussed in greater detail 

 in the following section with regard to the treatment of leukemias. We 

 shall therefore restrict our attention for the present to results on isolated 

 cells and tissues. 



Many tissues are susceptible to the antimitotic action of the arsenicals, 

 but some microorganisms, as we have noted, are quite resistant and can 

 grow and divide in fairly high concentrations. Inhibition frequently occurs 

 in the range 0.002-0.01 mM. Development of red algal {Plumaria elegans) 

 sporelings is reduced 75% by 0.0077 mM arsenite (Boney et al., 1959), 

 the growth of cress, onion, and pea seedlings is inhibited by 0.005 mM 

 arsenite (Cobet, 1919), elongation of oat coleoptiles is depressed 55% 

 by 0.01 mM arsenite (Thimann and Bonner, 1949), Cecropia silkworm 

 spermatogenesis is 50% inhibited by 0.002 mM arsenite (Schneiderman 

 et al., 1953), and tissue cultures of chicken fibroblasts are inhibited almost 

 completely by 0.005 mM arsenite (Meier, 1933), of connective tissue 30% 

 by 0.004 mM arsenite (Bucher, 1950), and of rat lymph node 50% by 

 0.0022 mM arsenite (Trowell, 1960). These data will serve to illustrate the 

 potency of arsenite and it is likely that the organic arsenoxides would be 

 even more effective, as has been shown in the recent study of Savchuck 

 et al. (1960) on cultures of various mammalian cells (see accompanying 

 tabulation). Earle's L-929 strain mouse fibroblast is inhibited minimally 

 by 0.000067 mM phenylarsenoxide and completely by 0.00067 mM. No 



