Incorporation of cysteine into the cerebral neurosecretory system of adult desert locusts

Abstract

Liquid scintillation counting techniques were used as a means of measuring the incorporation of 35S-cysteine into the neurosecretory system of adult female Schistocerca gregaria in different physiological conditions. The methods described were unable to measure uptake of 35S label into the cerebral neurosecretory cells but were successful in measuring incorporation rates into the storage lobes of the corpora cardiaca. The corpora cardiaca become labeled soon after injection of the 35S-cysteine, and the initial amount of label is proportional to the amount of neurosecretion within the gland. Loss of label from the hemolymph occurs very rapidly, and the 35S=cysteine concentrations become limiting for incorporation within the cerebral neurosecretory cells within the first hours of the experiment. Label within the corpora cardiaca increases instead of following the decreasing hemolymph label. The rate and time of increase of label within the corpora cardiaca therefore indicates the influx of newly labeled neurosecretion and enables comparisons to be made of neurosecretory turn-over in different females. Ten-day-old females synthesize and release neurosecretory material at a rapid rate. Immature females also synthesize and release material rapidly although at a lower rate than maturing females. Mature females have much less active neurosecretory systems than either maturing or immature females. The results from this liquid scintillation method of measuring radioactive labeling of neurosecretory systems support and amplify the results gained from autoradiographic techniques.