Effects of Brain and Corpus Cardiacum Extracts on Hæmolymph Trehalose of the Cockroach, Periplaneta americana

Abstract

THE first report relating hormonal factors in insects to the regulation of a particular haemolymph sugar was that of Steele1. He demonstrated that saline extracts of the corpus cardiacum of the cockroach Periplaneta americana (L.) cause about a 100 per cent increase in haemolymph trehalose within 1 h after injection and the effect persists for several hours. The level of reducing sugar (glucose?) was generally lowered in these animals. Later, Steele reported that the extract accelerated the release of inorganic phosphate and that as haemolymph trehalose was elevated fat-body glycogen declined2. Nerve cord glycogen also declined, but gut and muscle glycogen were unaffected. The interpretation is that the hormone appears to increase the activity of phosphorylase and produces a glycogenolic effect. More recently Bowers and Friedman3 reported finding that in the South American cockroach, Blaberus discoidalis (Serville), administration of aqueous extracts of the corpus cardiacum significantly elevate both trehalose and glucose in the haemolymph. They also found a decrease in fat-body glycogen 5 h after injection and extracts of the corpus allatum were also tested and found to be without effect. They note also that animals with heads tied off respond to the active extract, indicating that the effect is not mediated through other cephalic glandular material.