Abstract
Barron et al. 1 have adduced evidence in support of the hypothesis that methylene blue and other dyes stimulate the oxygen consumption of certain cells by promoting the oxidation of carbohydrates or some of their degradation products. They suggest, moreover, that the catalytic process depends upon the reversible reduction and reoxidation of the dyestuff and that this is independent of the function of the respiration enzymes, for when these are poisoned by cyanide and carbon monoxide the addition of methylene blue or other dyes restores respiration to the normal levels.
Recently Reid 2 has shown that leuco-methylene blue is not autoxidizable, as is commonly supposed, but that the process involves a metal catalysis and is sensitive to CO poisoning. Cook, Haldane and Mapson 3 have demonstrated a CO sensitivity of methylene blue stimulated oxidations in B. coli. Likewise, Chang and Gerard 4 have shown that the stimulation of nerve respiration by cresyl blue is depressed by CO. We 5 have previously pointed out that the methylene blue stimulation of respiration in diapause (blocked) grasshopper embryos (Melanoplus differentialis) is sensitive to CO, whereas the normal respiration of such embryos is little if at all affected by this substance. In actively developing embryos the stimulation due to methylene blue as well as a large fraction of the normal respiration is depressed by CO. Our inability to obtain antagonism by methylene blue of cyanide inhibition of respiration except in cases where very low concentrations of cyanide were used and the results obtained by other workers as well as ourselves on the CO sensitivity of methylene blue stimulation strongly suggests that in some living systems methylene blue catalysis of respiration depends upon and functions through the normal respiratory mechanism of the cells.
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