EFFECTS ON INVERTEBRATES 575 



delaying action on murine trypanosomiasis. It has recently been found 

 that 4,7-phenanthroline-5,6-quinone is effective in human amebiasis (Car- 



ter, 1961). Clearing of the infection for 2 months was seen in 71 of 76 

 patients given 50 mg 3 times a day for 5 days, and no toxic reactions were 

 noted. 



EFFECTS ON INVERTEBRATES 



Various echinoderms, worms, molluscs, and arthropods when exposed to 

 3-6 mM p-benzohydroquinone exhibit an initial period of excitement or 

 augmented activity and excitability,* but this is eventually followed by 

 paralysis (Danilewsky, 1895). Muscle contracture may occur terminally. 

 Coelenterates are apparently more resistant and succumb to concentrations 

 around 10 times higher than for other invertebrates; this may be partly 

 related to the ability of coelenterates to isolate themselves from their en- 

 vironment. Most of the subsequent work has been on worms. Labes (1930) 

 used leech muscle to further his analysis of the site of action of p-henzo- 

 hydroquinone, and found that oxygen and elevated pH favor activity, so 

 that it was concluded that the quinone is the active form. Concentrations 

 near 0.3 mM under optimal conditions first stimulate the muscle strongly 

 but this soon passes into paralysis. Bergstermann (1944) confirmed these 

 observations and noted that muscle contracture occurs. Both Labes and 

 Bergstermann believed that p-benzoquinone attacks enzymes or coenzymes 

 of the respiratory chain, possibly through their SH groups, but no evidence 

 for this was presented. 



Planaria frequently respond to noxious influences by a histolytic frag- 

 mentation and this occurs upon exposure of the worms to lower concen- 

 trations of quinones. Von Bertalanffy et al. (1946) plotted the disintegration 

 times against the concentration of various quinones and found that a break 

 occurs in the curves near 1 mM; below this concentration for j^-benzo- 

 quinone and 1,4-naphthoquinone the action is primarily histolytic and 



* Among other things, Danilewsky worked with ''abgeschnittene Fuhler von Octopus,''^ 

 and one statement not only illustrates the initial eflfect of p-benzohydroquinone but 

 well expresses the hazards encountered by invertebrate pharmacologists, " Ein Fuhler 

 begann an der Wand des Gefdsses aus dem Wasser herauszukriechen; mit einiger Miihe 

 schob ich denselben zuruck ins Wasser, er kroch aber wieder hinauf, und dies tciederhoUe 

 sich einige Male.'' 



