Charles W. Woods

Larval testes of the tobacco budworm: a new source of insect ecdysteroids.

Testes of last-instar larvae of the tobacco budworm release five times more ecdysteroid into incubation medium (judged by radioimmunoassay) in 2.5 hours than is found in testis homogenates. Incubation of testicular components indicates that the testis sheath may be the site of ecdysteroid synthesis. Fractionation of hemalymph, testis homogenate, and incubation medium by high-performance liquid chromatography produces a distinct ecdysteroid pattern in each case. Thus, released testis ecdysteroids are probably converted to other forms for use, sequestration, or general circulation. Their functions are unknown.

Hormonal regulation of ovarian ecdysteroid production in the autogenous mosquito, Aedes atropalpus

The effects of juvenile hormone (JH) and egg development neurosecretory hormone (EDNH) on ovarian ecdysteroid production during vitellogenesis in the autogenous mosquito, Aedes atropalpus, were investigated using in vitro techniques coupled with radioimmunoassay (RIA) and high-pressure liquid chromatography (HPLC). Normal females were characterized by quantitative, qualitative, and temporal patterns of in vitro ovarian ecdysteroid production. Females decapitated at emergence showed little ovarian ecdysteroid production and did not undergo vitellogenesis. A 500-ng dose of JH-I applied topically to decapitated females restored normal patterns of ecdysteroid production. In both normal and experimental females, ecdysone constituted the major portion of the ecdysteroids secreted by the ovaries in vitro. However, significant amounts of other RIA-active materials were detected, one of which was probably 20-OH-ecdysone. Fat body incubations indicated that these tissues produce little RIA-active material during the peak of vitellogenesis. During that period, the ovaries were the major source of ecdysteroid. Various doses of JH-I, applied to abdomens isolated at emergence, enhanced ovarian responsiveness to subsequent applications of head extracts containing EDNH both in vivo and in vitro. A 500-ng dose of JH-I, applied topically to blood-fed, decapitated Aedes aegypti, stimulated a significant increase in in vitro ovarian ecdysteroid production. Similarities between these data and those demonstrating prothoracicotropic effects of JH in the Lepidoptera are discussed.

Haemolymph ecdysteroid titers of diapause- and nondiapause-bound fifth instars and pupae of the European corn borer, Ostrinia nubilalis (Hübner)☆

Abstract 1. 1. Haemolymph ecdysteroid titers of nondiapause-bound European corn borers (LD 16: 8, 30°C) were low at the beginning of the fifth (last) instar, increased gradually between days 2 and 4 and peaked sharply (4400 pg/μl) just before pharate pupal formation. 2. 2. Time of day influenced prepupal ecdysteroid titers in that levels rose sharply between 14:00 and 24:00 hr AZT (arbitrary Zeitgeber time) in nondiapause-bound animals. 3. 3. Haemolymph ecdysteroid titers decreased in pharate and new pupae, peaked in 2-day pupae (26,000 pg/μl) just before pharate adult formation and then fell more gradually in 3–5-day pupae. 4. 4. In diapause-bound and diapausing 5th instars haemolymph ecdysteroid titers were relatively low, 11–25 pg/μl 5. 5. HPLC followed by RIA of 5th stage larval and pupal haemolymph revealed the presence of a polar peak, 2 small peaks following the polar peak, material that comigrated with 20-hydroxyecdysone and ecdysone, and in 2- and 3-day pupae, material that comigrated with 26-hydroxyecdysone. 6. 6. Before formation of the pharate pupa and pharate adult, ecdysone levels were relatively low as compared to 20-hydroxyecdysone levels.

Ecdysteroid synthesis by testes of 5th instars and pupae of the European corn borer, Ostrinia nubilalis (Hubner)

Summary Testes from young fifth instar Ostrinia nubilalis produced very small amounts of ecdysteroids while those from larvae that had purged their gut produced considerably more immunodetectable ecdysteroid in vitro. Larval testes that had fused produced 2.2 times more ecdysteroid than those that remained separate. It was the sheath of the testes rather than the contents that was physiologically active. Synthesis was questionable in testes from day-1 pupae and was not observed in testes from pharate pupae, from day-2 pupae or from pharate adults. Thus, synthesis only occurred at specific times in the life cycle. Ecdysteroid profiles for testes from wandering larvae whose testes had fused showed a net increase in all normally observed ecdysteroids, with the greatest increase being in 20-hydroxyecdysone. For testes from day-1 pupae, the nature of the ecdysteroid profile changed after 24 h of incubation, with some ecdysteroids showing increases and other decreases. There appear to be considerable difference...

Makisterone A: its distribution and physiological role as the molting hormone of true bugs

Makisterone A, a 28-carbon (C-24 alkyl) hexahydroxy steroid, has been identified by mass spectrometry as the major ecdysteroid in last-stage larvae of the large milkweed bug,Oncopeltus fasciatus, a phytophagous hemipteran. Similarly, it is a major molting hormone in 2 phytophagous and 1 predacious species of Hemiptera belonging to the group, Pentatomomorpha. It is not, however, a major ecdysteroid in another group of Hemiptera, the Cimicomorpha, where 1 predacious and 2 hematophagous species contain ecdysone and 20-hydroxyecdysone as their major molting hormones.

Larval moulting hormone of trichophoran Hemiptera-Heteroptera: Makisterone A, not 20-hydroxyecdysone

Abstract The haemolymph ecdysteroids were examined in fifth-stage larvae of Nezara viridula, Podisus maculiventris and Dysdercus cingulatus (Hemiptera-Heteroptera) using high-pressure liquid chromatography to separate the ecdysteroids and a radioimmunoassay to detect the fractionated ecdysteroids. The length of the fifth stage ranged from 5 to 8 days, and a peak in ecdysteroid titre (1700–2650 ng/ml) occurred 2–3 days prior to ecdysis to the adult. An ecdysteroid matching the retention time of makisterone A (24-methyl-20-hydroxyecdysone) was clearly present in haemolymph taken at the time of peak titre in all 3 of these true bugs, whereas little, if any, ecdysone or 20-hydroxyecdysone was detected. These data, along with previously reported data for the milkweed bug Oncopeltus fasciatus, are persuasive evidence that makisterone A is the larval moulting hormone of a group of closely related Heteroptera called the Trichophora (Lygaeoida, Pentatomoidea, Pyrrhocoroidea and Coreoidea).

Ecdysteroid fluctuations in adult Drosophila melanogaster caused by elimination of pupal reserves and synthesis by early vitellogenic ovarian follicles

Abstract Radioimmunoassay (RIA) of whole body extracts of Drosophila melanogaster males and females demonstrates that at eclosion all individuals contain high levels of ecdysteroid. Highly polar ecdysteroids (presumably metabolites) in the meconium represent approximately half of the total ecdysteroid RIA-activity present at this time and are subsequently eliminated. Ecdysteroids remaining after the elimination of the meconium are also highly polar as shown by reverse-phase high pressure liquid chromatography (RP-HPLC). The amount of ecdysteroid RIA-activity found in whole body extracts declines in both sexes until 18 h post-eclosion when levels begin to increase in the female and drop to undetectable levels in the male. In the female the ovaries are the major source of ecdysteroid. The increase in whole body ecdysteroid in the female coincides with the initiation of ovarian ecdysteroid production and accumulation. Topical application of methoprene, a juvenile hormone (JH) analog, stimulates ovarian ecdysteroid synthesis in apterous-ts 78j (ap ts 78j ) , a temperature-sensitive juvenile hormone-deficient mutant, corroborating previous results suggesting a role of juvenile hormone in ovarian ecdysteroid production. Stage 8–9 follicles, whose development is juvenile hormone dependent, are shown to be the most active in ecdysteroid production. The regulatory potential of these stages is discussed.

Haemolymph ecdysteroid titre in larvae of the cabbage looper Trichoplusia ni, and its modification by juvenile hormone

Abstract The ecdysteroid and juvenile hormone titre of 4th and 5th-instar larvae of Trichoplusia ni was determined by radioimmunoassay and the black mutant bioassay. Application of 50 nmol juvenile hormone II accelerated by several hours the delayed peak of ecdysteroids occurring in neck-ligated larvae. Inject of 20 nmol of 20-hydroxyecdysone initially accelerated prepupal development and later blocked the process. Application of 100 nmol O-ethyl-S-phenol-phosphoroamidothiolate (EPPAT) to post-wandering larvae inhibited the juvenile hormone esterase activity occurring at the time of normal juvenile hormone decline, and indirectly maintained an elevated ecdysteroid titre at the time when the controls moulted. Most of these EPPAT-treated prepupae were delayed in normal prepupal development and/or failed to normally ecdyse. Thus, the interaction of juvenile hormone, its esterase and ecdysteroids is an important aspect of prepupal development in T. ni.

Relationship between the corpus cardiacum-allatum complex and ovaries with the haemolymph ecdysteroid profile in the housefly, Musca domestica☆

Abstract Haemolymph from female houseflies at 4, 48 and 96 h after emergence contained approximately equivalent amounts of 20-hydroxyecdysone that varied from 2.9 to 4.1 pg/μl. Polar ecdysteroids decreased with the insect age from 12.9 pg/μl at 4 h to 5.1 pg/μl at 96 h. At 48 h the haemolymph contained ecdysone and 20,26-dihydroxyecdysone in addition to 20-hydroxyecdysone and the polar materials. When ovaries were culture in vitro , the culture medium contained ecdysone as the major ecdysteroid (70%) with lesser concentrations of 26-hydroxyecdysone, 20-hydroxyecdysone, and 20,26-dihydroxyecdysone. Haemolymph from ovariectomized flies contained 20-hydroxyecdysone, some polar materials, and very little ecdysone. Thus, it appears that the ovaries are the source of ecdysone. Since all samples contained 20-hydroxyecdysone, its source is not known. Removal of the corpus allatum-cardiacum complex decreased the amounts of all ecdysteroids in the haemolymph sample. Ecdysone and 20-hydroxyecdysone were both present in amounts of 1 pg/μl and 20,26-dihydroxyecdysone was barely detectable.

Ecdysteroid conjugates in pupal and pharate adult haemolymph of the European corn borer, Ostrinia nubilalis (Hubner)

Abstract Hydrolysis of a polar ecdysteroid HPLC fraction by treatment with glucuronidase revealed the presence of at least six ecdysteroid conjugates in haemolymph from pupal and pharate adult European corn borers. Conjugates of ecdysone, an ecdysteroid more polar than ecdysone, 26-hydroxyecdysone, 20-hydroxyecdysone and two ecdysteroids more polar than 20-hydroxyecdysone were detected. Titres of conjugates were maximal on day 2, 3 or 4 post-pupation and fell to lower levels on day 5. This pattern is similar to that for the corresponding free haemolymph ecdysteroids.