Selective ion permeability and the origin of bioelectric potentials (Ostwald, Bernstein)

Bose (1902) described the electric change in a stimulated nerve as a negative variation, as a current of action running from the more excited to the less excited region, or as a cuproid change.¹ He read the galvanometer deflection as a sign of molecular upset, and its slow return as molecular recovery.¹ In his 1907 book, Bose reports that Biedermann found direct excitation by rapidly alternating shocks to give a negative variation, usually preceded by a positive swing.⁵ Because the current of rest is ingoing, Bose took a negative variation to mean an outgoing current.⁵ Bose tied the electrical change to molecular disturbance and recovery.

Loeb (1906) reports that Ostwald pointed out that semipermeable membranes might be permeable to only one class of ions. Ostwald thought this could explain the currents of muscle and nerve and also the effects of electric fishes.² Loeb says Bernstein and Brünings adopted the view.² Bernstein argued that the current of action required a specific permeability of the membranes for cations.³ Loeb added his own reasoning. Potential differences in tissue could hardly arise except by separating anions from cations.⁴ Ions diffuse at different rates, and protoplasm may be permeable differently to oppositely charged ions. For Loeb this made it easy to see why so many life phenomena carry electrical changes.⁴

Osterhout (1922) worked with the alga Griffithsia. He noted that killing the cell destroys its semipermeable membranes, and the pigment then diffuses out.⁷ He listed several such surfaces: the plasma membrane, the plastid surfaces, the vacuolar surface and the nuclear surface. He expected them to differ somewhat in permeability.⁷ On what the plasma membrane is made of, he cited differing views. Czapek suggested soaps, while Nathanson regarded it as a mosaic of lipoid and non-lipoid particles.⁶ Osterhout observed that a mosaic would admit substances only if each element ran unbroken from the outer surface to the vacuole.⁶

Child (1924) places these proposals in the wider spread of physical chemistry into physiology. He says knowledge of electrolytic dissociation, colloids and semipermeable membranes was applied to excitation and transmission by Bernstein, Nernst, Loeb, Lapicque, Boruttau and many others.⁸ Matsuno and colleagues (2018) study a different problem, ATP production in alkaliphilic Bacillus. Their results indicate that efficient ATP production is attributable to a high membrane potential creating an attractive force for H+ at the outer surface.⁹ They also state that the bulk-base chemiosmotic theory cannot account for ATP production in these bacteria.⁹