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An oxidation increases an oxidation state, recording loss from the formal Electron assignment. For $\mathrm{Zn}\to {\mathrm{Zn}}^{2+}+2e^{-}$, the increase is $0\to +2$. Oxidation need not involve oxygen.^[ref]

In the electrochemistry examples here, oxidation is loss of Electrons by a chemical species; it occurs at the anode. That electrode definition holds in both a galvanic cell and an electrolytic cell; it does not fix terminal polarity. The oxidized chemical species serves as the reducing agent in the coupled redox.

A salt bridge is an ionic connection between electrolyte compartments that limits bulk mixing while permitting electric charge transport. Its mobile ions compensate changes caused by the electrode half-reactions, keeping the bulk chemical solutions approximately electrically neutral during sustained electric current. It does not conduct Electrons like the external wire, and its ions need not be consumed at either electrode. The ionic return path and compensating ion flows are explained in Purdue University, Electrochemical Reactions: salt bridge and charge balance.

In a discharging Daniell cell, anions moving toward the anode compartment and cations moving toward the cathode compartment both contribute to the internal conventional current from anode toward cathode. This charge-balance role is compatible with a negative anode: terminal signs do not imply that the whole anode chemical solution is negatively charged. The simple compensating-inventory example in Daniell cell does not fix all individual ion fluxes; diffusion and the cell's other mobile ions can contribute. A real bridge also introduces electrical resistance and may introduce a junction electric potential difference, so its presence does not guarantee an exact thermodynamic cell reading. See IUPAC Gold Book: salt bridge and liquid-junction potential.

A Western blot detects selected proteins after their separation and transfer to a membrane, using antibodies. In the yeast cross-species complementation experiment, detection helps distinguish failed protein production from failure of an expressed protein to restore growth.

The useful idea is to preserve where proteins migrated in gel electrophoresis, then ask which positions retain an antibody. Western blot separation, Western blot transfer and Western blot antibody detection answer different questions. A band is evidence of retained label at a position; Western blot band interpretation requires Western blot controls before assigning identity or comparing abundance.