576 5. QUINONES 



above this it is a tanning or fixative action. Fragmentation is initiated in 

 the posterior region and then spreads over the organism. The quinones fall 

 in the following order of decreasing potency: naphthazarin; 1,4-naphtho- 

 quinone; methylnaphthazarin; p-benzoquinone; toliiquinone; 1,2-naphtho- 

 quinone; 2,6-dimethoxy-p-benzoquinone; xyloquinone; 5-methoxytoluqm- 

 none; isonaphthazarin; and lawsone. p-Benzoquinone at 0.2 mM kills in 

 around 75 min but disintegration begins in 10 min (Hoffmann-Ostenhof 

 et al., 1948). Schreier (1949) investigated these effects quantitatively and 

 showed them to depend on the quinone concentration and the type of qui- 

 none used, so that no general pattern of disintegration can be outlined. 

 However, at the lowest concentrations fragmentation is seen to begin at 

 the head end, while at concentrations of 1-3 mM the primary disintegra- 

 tion is at the tail end, higher concentrations fixing the entire animal in a 

 fragmented condition. p-Benzoquinone at 0.03 mM does not alter motility 

 but slowly induces anterior fragmentation which progresses posteriorly; 

 at 0.09 mM there is some abnormal twisting; as the concentration is raised 

 the movements become more abnormal and exaggerated. Numerous curves 

 for (a) time for beginning of head disintegration, (b) time for beginning 

 of tail disintegration, and (c) time for death were plotted relative to the 

 concentration on log-log graphs, linear relationships generally being ob- 

 served (Fig. 5-10). The author assumed that the rate of the toxic action 

 is given by an equation of the type 



dL/dt = W 



where L is the degree of particular toxic effect measured, C is the quinone 

 concentration, and k and n are constants, the latter being determined from 

 the slope of the log- log plots, since 



logt = log (L/k) — 71 log C 



Although this type of approach is valuable in quantitativel}^ characterizing 

 potencies and kinetics, the interpretations given for n in terms of adsorption 

 and other processes cannot be accepted. The values of n differ for head and 

 tail disintegration, but this can be interpreted in various ways, e. g., dif- 

 ferent rates of penetration, different degrees of metabolic activity, different 

 mechanisms by which the quinones exert their action in the two regions, 

 and different degrees of operation of the factors determining cohesion. 

 The effects of quinones on the respiration and glycolysis of Schistosoma 

 mansoni have been discussed (page 487) (Bueding et al., 1947; Bueding and 

 Peters, 1951). Glucose utilization and lactate formation are inhibited more 

 potently than is respiration, and it was felt that glycolytic processes are 

 necessary for the survival of the organism; it was also suggested that cer- 

 tain quinones might be of vahie therapeutically if they were not too ex- 



