Franklin Chang

Effects of vertebrate adipokinetic hormones on the rate of in vitro lipid release in insects

1. 1. The adipokinetic effects of l-epinephrine, glucagon, insulin and cyclic 3′,5′-AMP (adenosine 3′,5′-cyclic-monophosphoric acid) on the rates of lipid release from fat body tissue of the monarch butterfly [Danaus plexippus (L.)] and sweetpotato hornworm [Agrius cingulata (Fabricius)] larvae were studied. 2. 2. In vitro time-course profiles of lipid release from 14C-labelled monarch butterfly fat body (incubated over a 2-hr period with each of the above hormones in buffer-saline) reveal appreciable rates of lipid release in the order: triglyceride >diglyceride>free fatty acid>monoglyceride>cholesteryl ester (TGL>DGL>FFA>MGL>CE). 3. 3. When whole hemolymph (inclusive of hemocytes) is used as the incubation medium, the rates are FFA>DGL>MGL>TGL>CE. 4. 4. Short-term 60 min experiments with 14C-labelled sweetpotato hornworm fat body (incubated with each of the above hormones in buffer-saline) exhibits rates of lipid release in the order: TGL>FFA>MGL>DGL>CE. 5. 5. When whole hemolymph is used as the incubation medium, the rates of lipid release are low and in the order: FFA>DGL>MGL>TGL>CE. 6. 6. The results are discussed in the light of available information on the effects of these hormones on other insects and the vertebrates.

The effect of ligation on tanning in the larva of a tachinid parasite, Lespesia archippivora

Abstract When single ligations are made behind the brain of third instar larvae of Lespesia archippivora , subsequent tanning occurs posterior to the ligations. Double-ligated larvae only exhibit tanning posterior to the second ligature (from the anterior end). This suggests that ecdysone may be produced and/or secreted from an area in the abdominal region of the larva. This hypothesis as well as neural inhibition of puparium formation is discussed in the light of the results obtained in this study.

The presence of lipoprotein lipase activity and its relationship to lipid transport in the oleander hawkmoth, Deilephila nerii☆

Abstract 1. 1. Supernatant fractions from fat body and flight muscle homogenates as well as whole hemolymph from adult oleander hawkmoths exhibit lipase activity when isotopically assayed with tripalmitin-(carboxyl-) 14 C as substrate. 2. 2. Preliminary characterization of flight muscle lipase reveals pH and temperature optima of 8.5–8.8 and 32–37°C respectively. 3. 3. Decreased lipase activity is observed when 4 M NaCl is added to the substrate, suggesting similarity with mammalian lipoprotein lipase. 4. 4. The results obtained are discussed in regards to the lipid release patterns found in this insect.