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Studies on oxidation-reduction. X. Reduction potentials in cell-suspensions
0 Studies on oxidation-reduction. X. Reduction potentials in cell-suspensions, By R. K. CANNAN, BARNETT COHEN and MANSFIELD CLARK. Supplement no. 55 to the Public Health Reports of the United States Public Health Service. From the Hygienic Laboratory , Washington 1926 , USA
paper with its mass of experimental evidence may be considered as very valuable. Chemical cytologists will in the future have no excuse for using paraphenylenediamine and benzidine tests with their innumerable variants, except in conditions which are very accurately understood. ,~'OSEPHNEEDHAM, DOROTHYNEEDHAM(Cambridge).
This is the first paper of the series t o embark definitely on the
experimental solution of biological problems, though in one at least of the
previous ones there were accounts of experiments with plant juices and
bacteria. Most of the work was carried out on suspensions of bacteria and
yeast cells, and with the aid of unattackable electrodes immersed in the
culture. A practically continuous record of potential could thus be got, as
would hardly have been the case if the experiments had been confined to
the observation of indicator colour-changes.
The change of potential with time in suspensions of cells is discussed
and many experiments are described. The effect of adding TI1UNBERG'S
"metabolites" is investigated and also that of adding glutathione.
Interesting curves obtained with rapidly growing bacterial cultures are also given
and the significance of the time: potential relation is appraised. One of the
principal conclusions of the whole paper is that aerated cell suspensions
have an oxidation-reduction potential within the indophenol zone. Again~
"Deprived of free access of oxygen, the cell-suspension develops a
progressively more negative potential. I t traverses in order the zones characteristic
of the reversible indicators. If one of these indicators is present, the
potentials pass smoothly into the equilibrium potentials of the dye system, the
dye is progressively reduced, an and the potentials then pass smoothly out of the
zone characteristic of the indicator and take up their normal course.
Successive small doses of oxidant produce temporary checks or reversals upon
the course of potential-change followed by a very decided recovery of the
negative drift. The suspension therefore acts as if there were present very
small quantities of active poising material fed from a large reserve which
is slowly but decidedly mobilised".
In the aerobic cell, there is probably some kind of balance between
its reducing tendencies and the entering oxygen, leading to a "more or less
permanent stabilization of its oxidation-reduction chemistry".
The authors consider that the data they have accumulated and the
further advance of other workers along the same lines will in all likelihood
reconcile the views of WIELAND and WARBURG on biological oxidations.
They believe that the discrepancies arise from the fact that the prevalent
use of methylene blue illuminates only a small part of the whole field of
potential actually capable of being occupied by living processes. The entire
memoir is a most important contribution to our knowledge of intracellular