Cockroach Fat Body Research Articles

Effects of some vertebrate hormones on lipid mobilization in the insect fat body

Several vertebrate adipokinetic hormones were studied for their effects on the release of lipids from the insect fat body, using short term in vitro procedures. ACTH was found to be without effect. Insulin inhibited the release of diglycerides and free fatty acids from the pupal fat body of H. cecropia, an effect analogous to that which it exerts on vertebrate adipose tissue. Growth hormone, gonadotropin (HCG), and thyroxine exerted a stimulatory effect on the release of diglycerides and free fatty acids; that is, they had adipokinetic effects. Epinephrine greatly stimulated the release of free fatty acids from the fat body of four species of cockroaches. In the case of fat body from pupal or adult H. cecropia, epinephrine also stimulated the rate of free fatty acid release, but had a dual effect in that it inhibited the release of diglycerides. Preliminary evidence suggests that increased lipolysis in the cockroach fat body in the presence of epinephrine may be mediated by cyclic 3′,5′-AMP.

Microsomal metabolism of parathion

Studies of the microsomal activation of 35S-labeled parathion showed that a 35S-metabolite was bound onto microsomes probably as the result of desulfuration in the activation reaction. Further work indicated that rabbit liver microsomes also degraded parathion by splitting at the aryl phosphate bond. Both activation and degradation by microsomes required NADPH 2 and O 2, and were inhibited by SKF 525-A and insecticide synergists. The system was specific to parathion and did not degrade paraoxon. The degradation was also demonstrated with microsomes from rat liver and cockroach fat body and a model system (EDTA, Fe 2+, and ascorbate).

Differences in Composition of the Fat Body of Normal and Aposymbiotic Cockroaches (Periplaneta Americana)

Water, free fat, and glycogen were measured in the fat bodies of normal and aposymbiotic nymphs and adults of Periplaneta Americana (L.). No significant differences were found in water content, the averages ranging from 37.1% to 39.0%. Free fat averaged 30.1% and 25.7% of dry weight in normal nymphs and adults; in aposymbiotic insects the corresponding values were 19.9% and 12.9%. Glycogen made up 35.4% and 31.3% of dry weight in normal nymphs and adults, respectively, as compared with 60.2% and 17.3%, respectively, in aposymbiotic nymphs and adults.

GLYCOGEN SYNTHESIS IN THE INSECT FAT BODY.

A tissue extract prepared from the fat body of the american cockroach (Periplaneta americana L.) has been shown to contain UDPG-pyrophosphorylase (EC 2.7.7.9) and UDPG-glycogen transglucosylase (EC 2.4.i.ii) activity. The latter enzyme is not stimulated by Glc-6-P. Addition of Glci-P to the system results in a substantial enhancement of [14C]glucose incorporation from UDPG. The present evidence suggests that Glc-i-P is a true activator of UDPG-glycogen transglucosylase of the cockroach fat body.

Glycogen synthesis in the insect fat body

A tissue extract prepared from the fat body of the american cockroach (Periplaneta americana L.) has been shown to contain UDPG-pyrophosphorylase (EC 2.7.7.9) and UDPG-glycogen transglucosylase (EC 2.4.i.ii) activity. The latter enzyme is not stimulated by Glc-6-P. Addition of Glci-P to the system results in a substantial enhancement of [14C]glucose incorporation from UDPG. The present evidence suggests that Glc-i-P is a true activator of UDPG-glycogen transglucosylase of the cockroach fat body.

Synthesis of Ascorbic Acid by the Normal Fat-Body of the Cockroach, Leucophaea maderae (F.), and by its Symbionts

Filosa1, Cordero2 and Rousell3 found that homogenates of the normal fat-body of the American cockroach, Periplaneta americana, can synthesize ascorbic acid with D-mannose as the substrate. Similar results were obtained by Lisa4 with the fat body of the normal cockroach, Leucophaea maderae. Since the fat-body of these insects contains intra-cellular symbionts, it was suspected that the synthesis of this vitamin may be due to the presence of these micro-organisms. Hence, the present experiments were performed with the aposymbiotic fat-body and the symbionts of Leucophaea maderae to determine whether or not this is the case.

Properties of transaminases and glutamic dehydrogenase in the cockroach periplaneta americana

1. 1. Glutamate-aspartate transaminase was purified from homogenates of cockroaches and of pig heart. 2. 2. The properties of the transaminasses were compared with regard to substrate affinity, pH, equilibrium constant and temperature. 3. 3. It was found that borate had a profound effect on the equilibrium constant which was a function of pH. An explanatioin is proposed in terms of a complex-formation between borate and the cis-diol structure of oxaloacetate at alkaline pH. 4. 4. The transamination of alanine and certain other amino acids with α-ketoglutarate was studied chromatographically. 5. 5. Glutamic dehydrogenase activities from the fat body of cockroaches and beef liver were compared; a difference in the substrate affinity and equilibrium constant was noted. 6. 6. The relationship between the properties of the trasaminases and glutamic dehydrogenase are discussed with regard to the high free amino acid content of the cockroach hemolymph.

Biology and Dehydrogenase Activities of the Fat Body of Late Instar American Cockroaches (Periplaneta Americana)

Spectrophotometric assay of reduced phosphopyridine nucleotides, made at several intervals between sucessive molts, showed that peak activities of malic dehydrogenase and 6-phosphogluconate dehydrogenase in the fat body occurred 4 to 8 days after molting. The maxima were 4 to 10 times the minima, indicating the advantage of using insects of known age when comparing populations. In males the durations of the last two instars were 18 and 26 days, respectively; females molted 1 to 3 days earlier. The differences between sexes and instars were highly significant.