Effect of Sulphydryl Compounds and dl-Alanine on Rate of Development of Eggs of Physa and Lymnaea.

Hammett 1 , 2 , 3 has recently proposed that the sulphydryl (-SH) group is “an essential stimulus to cell proliferation.” He developed the idea from experiments in which an increased growth-rate by means of accelerated cell-division occurred in Zea mays root tips and in Paramecium as a result of treatment with sulphydryl compounds. In later work, Hammett and Reimann 4 , 5 found similar compounds stimulating cell proliferation in the wounds of rats and man.

By making gross length experiments, mitotic counts and cell measurements, Hammett found that treated Zea root tips grew more rapidly than those of control plants and that this was the result of more rapid cell division rather than an increment in cell size. In Paramecium he also reported a markedly increased division rate in the treated organisms. His controls were grown in culture solutions prepared with equivalent concentrations of some related substance lacking the -SH group. For instance, his experiments on thio-glycollic acid (with some exceptions) were controlled with glycollic acid, and those with cysteine were controlled with alanine. In this way he sought to demonstrate the specificity of -SH as the stimulating factor. His results were very consistent and in every case where the reduced -SH grouping was present in a certain optimum range of concentration he found marked acceleration of division. Thio-glycollic acid, Na-dithio-diglycollate, cysteine, glutathione and cystin (to a slight extent) were reported as effective compounds in stimulating cell division. On the basis of these experiments Hammett stated the hypothesis that the -SH group is universally a “cell division hormone.” 1