NERVE REGENERATION IN THE COCKROACH, LEUCOPHAEA MADERAE: THE EFFECT OF HUMORAL SUBSTANCES IN VITRO

¹ Metabolism and Radiation Research Laboratory, Entomology Research Division, Agricultural Research Service, United States Department of Agriculture, Fargo, North Dakota 58102

An in vitro system was used to study the effects of diffusible substances from various endocrine tissues on the growth of nerve tissue from regenerating cockroach legs. Incubates prepared from endocrine glands and gland combinations were tested for their effect on regenerative growth from the stump of the fifth mesothoracic nerve of 8-day leg regenerates from late instar nymphs of Leucophaea maderae. Incubates prepared from the prothoracic ganglion produced a stimulatory effect, while the prothoracic gland, allatum-cardiacum complex, and brain showed no effect. When prothoracic gland and prothoracic ganglion incubates were combined, the results were the same as with ganglion incubate alone. When the glands were incubated together and allowed to interact, the nerve growth stimulating effect of the ganglion was reduced by 50%. To explain these findings, it is postulated that a diffusible substance is released by the prothoracic ganglion which stimulates regenerative nerve growth from the leg regenerate. The release of this nerve growth stimulating factor is inhibited by interaction with the prothoracic gland. The possible effect of this interaction on the process of leg regeneration as it occurs in vivo is discussed.