Studies on the Effects of the Removal of the Frontal Ganglion in Locusta Migratoria L

Abstract

1. Studies were made on the third, fourth-, and fifth-instar nymphs of Locusta migratoria L. from which the frontal ganglion had been removed, on controloperated animals, and on starved animals. 2. The effects of this operation on protein metabolism were observed by study of: electrophoresis of haemolymph proteins, chromatography of haemolymph amino acids, production of protease in the midgut, and the incorporation of 14C-glycine into protein by the body cells. 3. The total protein concentration in the haemolymph of operated locusts did not increase with time as did that of the controls, in which the increase was almost entirely due to changes in the second of the three bands which normally separate out. 4. The concentration of the free amino acids in the haemolymph fell to about 70% of that found in the operated controls. In operated locusts the proportions of the amino acids relative to one another changed. 5. The incorporation of 14C-glycine into protein was slower and the equilibrium concentration less in operated as compared with control-operated animals. The time taken to reach equilibrium was the same in both cases. 6. In both operated and control-operated animals the protease activity of the midgut wall was very low; no difference could be detected between them. The protease activity of the mid-gut contents expressed per mid-gut was lower in operated than in control-operated animals. The protease activity expressed per mg. was found to be the same in operated, control-operated and starved animals. 7. The hypothesis that the effects of the removal of the frontal ganglion were mediated through changes in the secretion of hormones from the corpus cardiacum was tested by giving daily injections of freshly prepared corpus cardiacum extract to locusts from which the frontal ganglion had been removed, and observing the growth in weight of these animals. A permanent increase in weight amounting to 100% of their initial weight was found. Animals injected with distilled water showed a temporary increase amounting to 30% of their initial weight. Uninjected animals maintained approximately constant weight.