Characterization of vitellogenin in the red imported fire ant, Solenopsis invicta (Hymenoptera: Apocrita: Formicidae).

Vitellin (VN) and vitellogenin (VG) profiles were analyzed in monogyne and polygyne colonies of the red imported fire ant, Solenopsis invicta. Non-denaturing and SDS-polyacrylamide gel electrophoresis (PAGE) analyses indicated that the native VN was likely 350 kDa and comprised of two subunits in the molecular size range of 170-185 kDa. SDS-PAGE of hemolymph showed that the relative mobilities and subunit patterns of VG and VN were similar. VG was present in the hemolymph of reproductive queens; alate, virgin queens; and workers, but not in males. Anti-VN, prepared from polygyne egg homogenates, reacted with egg homogenates and with hemolymph VG from reproductive, monogyne and polygyne queens and alate, virgin polygyne queens. Analysis of circulating VG and ovarian development in alate, virgin queens showed that low levels of VG appeared by five days following adult eclosion, but egg development was not observed until seven weeks. VG was evident in newly inseminated queens, and increased steadily for the first three weeks following dealation. VG levels declined slightly near eclosion of the first workers (= nanitics) and dropped sharply after nanitic emergence at five weeks following dealation. Oocyte maturation peaked at days 15-25 following dealation, but otherwise remained low but steady. These studies provide the basis for future investigations into endocrine regulations of vitellogenesis in S. invicta queens.

Physiological effectors of hyperglycemic neurohormone biosynthesis in an insect.

Biosynthesis of hypertrehalosemic hormone (HTH) by isolated corpora cardiaca (CC) from Blaberus discoidalis cockroaches was measured for the 3-week period following adult ecdysis using an in vitro bioassay based on the incorporation of [3H]tryptophan. Synthetic rates for both males and females were highest following the molt and declined with age. Rates of HTH secretion and levels of stored HTH followed a similar pattern. We found no neural or endocrine brain effects or photophase influence on HTH synthesis. Synthesis was unaffected by treatment with 20-hydroxyecdysone or the juvenile hormone analog methoprene. In starved insects, HTH synthesis doubled and secretion increased 66% relative to fed controls.

Free amino acids in the hemolymph of the cockroach, Blaberus discoidalis.

The concentrations of free amino acids in the hemolymph of adult males of the cockroach Blaberus discoidalis were determined by automated amino acid analysis. Eighteen of the twenty standard amino acids as well as two nonstandard amino acids (hydroxyproline and ornithine) were found. Aspartic acid and cysteine were not present. Proline levels were up to 100-fold higher than those of any other amino acid. Total amino acid concentration was comparable to those reported for most other cockroaches. The reported amino acid profile formed the basis for an organ culture medium which sustained metabolic viability of isolated B. discoidalis neuroendocrine glands and brain-gland complexes for at least 24 hr.

In vitro bioassay for hypertrehalosemic hormone-dependent trehalose biosynthesis by fat body from adult Blaberus discoidalis cockroaches.

An in vitro bioassay suitable for routine use to investigate hypertrehalosemic hormone (HTH)-dependent trehalose biosynthesis was developed for the cockroach fat body. Blaberus discoidalis fat bodies were isolated and divided so that eight matched pieces from a single tissue could be compared for multiple control and experimental treatments. Optimum incubation conditions and the properties of HTH-dependent trehalose synthesis were determined. Dose-response studies determined an EC50 of 0.044 nM. HTH for male fat body and 0.16 nM HTH for female tissue. HTH increased trehalose production by male fat body 3-fold compared to only a 67% maximum increase by the female tissue, and only the male tissue was used in subsequent studies. Fat body required only 5-min exposure to HTH for maximum trehalose production for 1 h. Trehalose synthesis was inhibited by > or = 15 mM trehalose in the incubation medium. The fat body showed a developmental increase in trehalose synthesis in vitro that was reflected by hemolymph trehalose in vivo. Basal and HTH-related trehalose synthesis were low between days 0 and 10, increased 3-fold by day 20, and were high thereafter. These studies have established baseline data for future investigations to identify the signal transduction mechanisms involved in HTH regulation of fat body metabolism.

Neuroendocrine and juvenile hormone effects on fat body protein synthesis during the reproductive cycle in female Blaberus discoidalis cockroaches.

Ovarian protein content and fat body protein synthesis were measured during the first gonotrophic cycle in virgin female Blaberus discoidalis cockroaches. Protein synthesis was measured for in vitro fat bodies from animals treated with combinations of a juvenile hormone analog (JHA = methoprene) and corpora cardiaca (CC) extracts. Ovarian protein content began to increase on Day 5 of adult life and reached its maximum at Days 20-22. Synthesis of proteins secreted by the in vitro fat body increased by 12-fold between emergence and its maximum on Day 18, then declined to nearly its original level by Day 33. Synthesis of nonsecreted, fat body proteins increased by 4-fold between emergence and a maximum on Day 21, then declined. CC extracts and JHA were administered to decapitated females to determine their regulative effects on fat body protein synthesis. The synthesis by the fat body of nonsecreted proteins was increased by both JHA and CC extracts. In contrast, synthesis of secreted proteins increased only in the presence of JHA. CC extracts, alone, had no effects on the synthesis of secreted proteins, but administration of CC extracts in combination with JHA increased the synthesis of the secreted proteins by 55% above that observed with JHA alone. SDS-PAGE of proteins secreted into the medium by the in vitro fat body demonstrated that JHA stimulated the synthesis of specific polypeptides, whereas CC extracts did not affect the synthesis of specific-secreted polypeptides. These results suggest that JH regulates specific protein synthesis by the fat body of B. discoidalis; neurohormones elevate the general capacity of the fat body for protein synthesis and amplify the specific effects of JH.