EFFECT OF EXCESS DIETARY GLUCOSE ON GROWTH AND IMMUNE-RESPONSE OF MANDUCA-SEXTA

The injection of bacteria into the haemocoel of M. sexta larvae is followed by a rapid drop in haemolymph glucose levels. The fall in glucose levels appears to be primarily due to a temporary cessation of feeding by larvae rather than an alteration in metabolism. In an attempt to compromise the activity of the glucose-lectin, scolexin (earlier termed M13), the haemolymph glucose levels were increased by culture on a diet containing an excess of either glucose or the glucose-containing disaccharide, sucrose. Although an increase in glucose in the diet did not appear to influence survival of the fifth-instar larvae, without or following injection, their development was slowed. Further, either excess sucrose or glucose diets but not the excess fructose diet led to the synthesis of a larger, modified form of scolexin. The possible nature of the alteration in scolexin, as well as its possible effect on the activity of this protein are discussed.