Recovery of structure and function following transection of the primary olfactory nerves in pigeons

Preliminary experimentation on ring doves to ascertain whether they might regulate any aspects of their reproductive behavior in terms of olfactory cues was vitiated by the discovery that their sectioned olfactory nerves had apparently regenerated. Concurrent work on frogs has shown that the olfactory receptors degenerate after axotomy and are replaced by new ones. This phenomenon was studied in pigeons. All transected nerves were found to be healed. Electrical recording from the regenerated nerves revealed apparently normal receptor function and, indirectly, autonomic reflex responsiveness. Previously untrained pigeons learned an olfactory discrimination after reconstitution of the peripheral olfactory system using a conditioned suppression procedure. The olfactory nerves of trained pigeons were sectioned and the behavioral response recovered within 16-82 days. The gross sizes of primary olfactory nerves and olfactory bulbs were frequently much less than those of controls, but on the ultrastructural level there was no recognizable morphological deficiency in the receptor cellular organelles or terminal synaptic contacts in bulbar glomeruli. Recent results by other workers indicate that pigeons utilize olfactory cues in homing performance.

Rapid Decline of Olfactory and Gustatory Receptor Sensitivities of Wild Catfish (Ictaluridae) after Capture

In several species of catfish (Ictaluridae), comparably high sensitivities of olfactory and gustatory receptors to α-amino acids as a class were confirmed. An important determinant of the frequency of successful electrical recording preparations was found to be the duration of fish captivity. The functional deterioration of olfactory and gustatory receptors may be a stress reaction caused by capture and confinement of the wild fish.

The effect of two soluble thalidomide derivatives on lymphocyte stimulation

The soluble thalidomide derivatives, 1-(morpholinomethyl)-4-phthalimido-piperidindione-2,6 (CG603) and its isomer 1-(morpholinomethyl)-3-phthalimido-piperidindione-2,6 (CG601) have been found to inhibit the production of transformed cells in 90-hr mixed lymphocyte cultures from two unrelated human donors. In 72-hr phytohaemagglutinin cultures however, the incorporation of thymidine into the acid insoluble fraction was not inhibited by the same concentration of drugs. Since the initial event in the mixed lymphocyte reaction is considered to be immunological whereas the response to phytohaemagglutinin is not, one possible explanation is that the compounds act by blocking a step in the lymphocyte stimulation pathway between the reception of the antigen, and the site where the phytohaemagglutinin bypass is effective.

Odor discrimination in pigeons

An operant procedure was employed to investigate odor discrimination in the pigeon. Amyl acetate concentrations of 6-percent saturation in air, and lower, when paired with electric shock markedly reduced key-pecking during the odor stimulus period. Sectioning the olfactory nerves eliminated this selective suppression behavior. After the operation, the suppression was again conditioned when the concentration of amyl acetate was increased to 15-percent saturation in air. This is theoretically possible through mediation by the trigeminal system.