Juvenile hormone synthesis by ring glands of the blowfly Lucilia cuprina

The major radiolabelled product released from ring gland and brain-ring gland complexes of third instar larval and pre-pupal stages of the sheep blowfly Lucilia cuprina upon incubation with L-[methyl-³H]methionine corresponded to one diastereomer of juvenile hormone III bisepoxide (JHB₃). Endocrine glands incubated with the juvenile hormone precursor 2E,6E-farnesoic acid released increased quantities of JHB₃, together with significant amounts of juvenile hormone III but not the isomeric methyl 2E-6,7-epoxyfarnesoate. Synthesis of JHB₃ was developmentally and neurally regulated. Ring glands and brain-ring gland complexes from third instar larvae released more JHB₃ than comparable preparations from pre-pupae, while isolated corpus allatum segments of the gland were more active than intact brain-gland complexes. These results reinforce the emerging status of JHB₃ as the characteristic juvenile hormone of dipteran insects. Arch. Insect Biochem. Physiol. 34:239–253, 1997. © 1997 Wiley-Liss, Inc.     

Ecdysteroid synthesis by the ring gland of Drosophila melanogaster during late-larval,prepupal and pupal development

Radioimmunoassay has been used to determine the characteristics of ecdysteroid synthesis by ring glands and brain-ring gland preparations from late 3rd-instar larvae of Drosophila melanogaster cultured in vitro. The rate of synthesis and secretion is linear for at least 4 hr in culture. Using a 4-hr culture period, variation in the rate of ecdysteroid synthesis by brain-ring gland preparations during larval, prepupal and pupal development has been examined. The rate of synthesis and secretion is highest in late 3rd-instar larvae and decreases after puparium formation. During pupal development, at a time when the endogenous ecdysteroid titre is again increasing, the rate of ecdysteroid synthesis by brain-ring gland preparations remains low and is only 10% of that prior to puparium formation. It is, therefore, likely that the ring gland is not a major source of ecdysteroids during this period.     

Regulation of Juvenile Hormone synthesis in the blowfly Lucilla cuprina

Abstract. Juvenile Hormone III bisepoxide synthesis by ring gland complexes from third-instar larvae of the blowfly Lucilia cuprina Weidemann (Diptera, Calliphoridae) was measured using a radiochemical assay in vitro. Hormone synthesis is regulated by three distinct mechanisms during development of the final larval instar up to the time of pupariation. The first type of regulation is detected as a rapid decline in hormone release coinciding with the final phase of commitment to pupariation. The second is a neurally mediated inhibition by the brain that acts at all stages of development in third-instar larvae. A protease-sensitive factor from brains of third-instar larvae causes dose-dependent reversible inhibition of Juvenile Hormone III bisepoxide synthesis. The third regulatory signal is a neural inhibition, observed in brain-ring gland complexes of prepupal stages. The first two levels of regulation appear to act early in the synthetic pathway for Juvenile Hormone (JH), whereas the third acts on the final steps of bisepoxide synthesis.     

Development of an in vitro assay for prothoracicotropic hormone of the gypsy moth,Lymantria dispar (L.) following studies on identification,titers and synthesis of ecdysteroids in last-instar females

Summary Hemolymph ecdysteroid titers and in vitro prothoracic gland ecdysteroid synthesis have been examined in last-instar larval (5th instar) females of Lymantria dispar. Ecdysteroids were quantified by radioimmunoassay and characterized by co-elution with known standards of ecdysteroids on reverse-phase high-performance liquid chromatography. Analysis of hemolymph yielded ecdysone and 20-OH-ecdysone in ratios of 1:1 (day 6, shortly after attainment of maximum weight) and 1:28 (day 10, molting peak). Analysis of in vitro culture media from glands challenged with extracts of brains or retrocerebral complexes, or left unchallenged, revealed only immunoreactive material co-eluting with a known standard of ecdysone. Time-course studies of in vitro prothoracic gland ecdysone secretion demonstrated a major peak on day 10, 1–2 days prior to pupal ecdysis, and a small elevation on days 5–6. On days 5 and 6, 2.29±0.41 and 2.65±0.72 ng ecdysone per gland, respectively, were secreted in 6-h cultures. On day 10, 25.69±4.36 ng was secreted in 6-h culture. The ability of prothoracic glands of various ages to respond to brain extracts containing prothoracicotropic hormone activity was tested by determining an activation ratio for each day of the instar. The activation ratio was determined over a 90-min period by dividing the amount of ecdysone secreted by one member of a pair of prothoracic glands in the presence of brain extract by that of its contralateral control gland in Grace's medium. Prior to the addition of brain extract, the activity of the glands was allowed to subside to basal level for 180 min in Grace's medium. The activition ratio was highest on days 3–7 and fell throughout the remainder of the instar as the inherent ability of the prothoracic gland to maintain high levels of ecdysteroid synthesis in vitro in the absence of prothoracicotropic hormone increased. A two-phase in vitro assay for prothoracicotropic hormone was established using activition ratios. This assay showed saturable doseresponse kinetics for prothoracic gland ecdysone secretion and specificity to extracts prepared from brain or retrocerebral complexes. A comparable assay for prothoracicotropic hormone purification, based on net synthesis and requiring half the number of prothoracic glands was also established.Abbreviations A _r activation ratio - HPLC high performance liquid chromatography - HPSEC high performance size-exclusion chromatography - PG prothoracic gland - PTTH prothoracicotropic hormone - RIA radioimmunoassay     

Juvenile hormone stimulation of ornithine decarboxylase activity during vitellogenesis in Drosophila melanogaster

Summary The activity of ornithine decarboxylase (ODC), the rate-limiting enzyme in polyamine biosynthesis, becomes elevated in intact female Drosophila melanogaster shortly after adult eclosion. This activity reaches a peak at 24 h following eclosion, and then drops to lower levels by 48 h. This pattern is not observed in males, consistent with the hypothesis that polyamine synthesis is involved in ovarian maturation in Drosophila. Abdomens isolated within 2 h of adult eclosion do not display elevated ODC activity or ovarian maturation. However, a 250-ng dose of the juvenile hormone analog methoprene (ZR-515) applied in acetone to these abdomens, recovers ovarian maturation and causes a 5–10 fold increase in enzyme activity over controls treated with acetone alone. The same dose of the inactive precursor methyl farnesoate caused no such increase, whereas a 500-ng dose of the newly discovered natural Drosophila JHB₃ stimulated a four-fold response. The response to methoprene was dose-dependent, showing stimulatory activity at a dose as low as 10 ng. This stimulation by JHA is rapid, occurring between 1 and 3 h following hormone treatment, reminiscent of JH induction of fat body vitellogenin synthesis in Drosophila. Elevated ODC activity appeared to be localized in the adult fat body. During embryogenesis, ODC activity remained undetectable until just prior to hatching, when a large increase was detected. We postulate that JH may, either directly or indirectly, regulate polyamine biosynthesis in vivo, and that this synthesis may be required for the production of macromolecules during Drosophila vitellogenesis or embryogenesis.Abbreviations JH juvenile hormone - JHA juvenile hormone analog - ODC ornithine decarboxylase - SAMDC S-adenosyl-methionine decarboxylase - JHB ₃ juvenile hormone III bisepoxide     

Methyl palmitate: a novel product of the Medfly (Ceratitis capitata) corpus allatum

The corpus allatum (CA) of adult female Ceratitis capitata produces methyl palmitate (MP) in vitro, in addition to JHB₃ and JH III. Biosynthesized MP migrates on TLC and co-elutes from RP-18 HPLC with synthetic MP. Its identity is verified herein by GCMS. MP production is up-regulated twofold by mevastatin, an inhibitor of mevalonic acid-dependent isoprene biosynthesis. Fosmidomycin, an inhibitor of mevalonic acid-independent isoprene synthesis in graminaceous plants, up-regulates MP synthesis by about fourfold. However, it does not depress JHB₃ biosynthesis concurrently. This suggests that the initial enzyme(s) in the conversion of 1-deoxy-xylulose 5-phosphate to isoprene is presumably present in C. capitata, but is inhibited by fosmidomycin, and this inhibition diverts precursors to MP synthesis. Phytol, an acyclic diterpene, might be suppressing isoprene biosynthesis by CA, thereby resulting in a fourfold increase in the MP biosynthesis. Linolenic acid is an end-product and its presence in incubation media up-regulates MP biosynthesis by twofold, presumably due to the feedback diversion to biosynthesis of C_16:0 and its methyl ester. Biosynthesis of MP is markedly depressed after mating, while otherwise maintained at significantly higher levels in virgin females. MP biosynthesis is significantly reduced in virgin females by direct axonal control but is less consistent after mating.     

Ring gland and prothoracic gland sensitivity to interspecific prothoracicotropic hormone extracts

Summary Using the techniques of intraspecific in vitro activation of prothoracic glands and ring glands by serial dilutions of prothoracicotropic hormone (PTTH) extracts from pupalManduca sexta (Lepidoptera) and larvalSarcophaga bullata (Diptera), a dose-response of activation was observed for both species. In both species maximum activation was at 0.5 brain equivalents while the number of brain equivalents necessary for half maximal stimulation (ED₅₀) was 0.20 forManduca and 0.15 forSarcophaga. When prothoracic glands or ring glands were challenged with interspecific PTTH extracts from a stage different from that of the gland donor, no dose-response of gland activation was observed. However, whenM. sexta larval prothoracic glands were challenged byS. bullata larval PTTH extract, activation was observed. The dose-response profile fell midway between the dose-response curves obtained for the intraspecific assays. Thus, PTTH extract from one insect has the ability to activate the prothoracic glands of an insect representing another order.     

On the control of ecdysone biosynthesis by the central nervous system of blowfly larvae

Ecdysone was found to be the major secreted steroid of ring glands dissected from blowfly larvae and incubated in vitro. Other secretory products such as 3-dehydroecdysone and 20-deoxy-makisterone A could not be detected when the glands were labelled with tritiated cholesterol. Ecdysone synthesis and secretion were found to be tightly coupled. The highest rate of secretion was observed a few hours before pupariation. In vitro, the rate of ecdysone secretion by ring glands was affected significantly by coincubation with the central nervous system (CNS). Modulating effects from the CNS to the gland were mediated both by culture medium and by nerve connections. Distinct parts of the CNS revealed multiple and partially opposite effects on ecdysone secretion, suggesting a more complex control than had been anticipated. Multiple neural control systems appear to be involved. Moreover, the observed effects changed with development during the second half of the third instar, reflecting a significant plasticity of neural control. © 1993 Wiley-Liss, Inc.     

The role of the Y-organ and cephalic gland in ecdysteroid production and the control of molting in the crayfish,Orconectes limosus

Summary The production of ecdysteroids (monitored by RIA) by Y-organs and cephalic glands in vitro was measured and hemolymph ecdysteroid levels were determined in the crayfish,Orconectes limosus, both after eyestalk ablation and as a function of time during natural premolt. Y-organ synthesis of ecdysteroid increased in parallel with a rise in hemolymph ecdysteroid concentrations under both conditions, peaking in substage D₂ of premolt. Y-organ ecdysteroid output after eyestalk ablation was 3–4 times higher. Thus, removal of the inhibiting system of the eyestalk effectively removes not only the principal control but also any modulation of ecdysteroid secretion by the Y-organs. Ecdysteroid levels remained low in Y-organ-ectomized crayfish, although premolt was initiated in some animals. The cephalic gland does not appear to contribute to the regulation of molting inOrconectes limosus. The Y-organs, on the other hand, are a principal source of ecdysteroids which regulate the major synthetic activities of premolt.     

An ultrastructural and developmental analysis of the corpus allatum of juvenile hormone deficient mutants ofDrosophila melanogaster

Summary The ultrastructure of the corpus allatum of theapterous mutantsap ⁴ andap ^56f ofDrosophila melanogaster during larval-pupal-adult metamorphosis and adult life was correlated with the gland's ability to synthesize juvenile hormone in vitro. During the early wandering period of the third instar of both mutants, a high concentration of smooth endoplasmic reticulum, mitochondria and mitochondrion-scalariform junction complexes are typical features of an active corpus allatum cell. Juvenile hormone biosynthesis by the glands is high at that time and, in fact, only slightly lower than that of wild type glands. In contrast to the wild type gland, the cells of the pupal and pharate adult corpus allatum of both mutants contains highly electron dense mitochondria with tubular cristae but no whorls of smooth endoplasmic reticulum nor glycogen clusters. The frequency and size of the lipid droplets, putatives depots of the juvenile hormone precursors, in cells of theap ^56f gland is a function of the insect's age, but both are lower than in wild type gland cells. Juvenile hormone biosynthesis by both mutant glands remains at the basal level when compared to increased synthesis by the wild type gland. The frequency and density of lipid droplets in cells of theap ⁴ corpus allatum are much lower than in theap ^56f glands. During adult life, the ultrastructural profile of theap ^56f corpus allatum is similar to that of the wild type gland although the in vitro production of juvenile hormone by the former is much lower than that of the wild type gland. The ultrastructural features of the adult corpus allatum ofap ⁴ homozygotes reveal precocious degeneration and support the view that this non-vitellogenic mutant is a juvenile hormone deficient mutation.     

Ecdysterone induced protein synthesis in salivary glands and in fat body of Drosophila melanogaster larvae

Salivary glands of 3rd instar larvae of Drosophila melanogaster were labeled with ³H-leucine in the presence and absence of ecdysterone. Twentysix ecdysterone inducible proteins were detected. Their induction was correlated with puff stage. Synthesis of fifteen proteins commenced during early puff stage (PS2); synthesis of seven others at late puff stages (PS8–10). Synthesis of four proteins was induced between puff stage 3/4 and 7/8. Thus, the hormonal induction of protein synthesis generally reflected the appearance of early and of late puffs as described by Ashburner (1972). Eleven ecdysterone inducible proteins were detected in larval fat body in vitro. Comparison of the fat body to the salivary gland proteins revealed that one of the ecdysterone induced fat body proteins was identical in molecular weight and charge to one of the proteins induced by ecdysterone in salivary glands.     

Regulation of Heliothis virescens prothoracic glands by Cardiochiles nigriceps polydnavirus

Heliothis virescens (F.) Larvae parasitized by the endophagous braconid Cardiochiles nigriceps Viereck fail to attain the pupal stage. This developmental alteration is caused by both an inactivation of prothoracic glands of last-instar larvae and an altered ecdysone metabolism. Decrease in ecdysteroidogenesis in vitro was already evident in glands explanted from larvae that have attained the early cell formation stage (day 4 of fifth instar), 6 h after parasitoid oviposition. Ecdysteroidogenesis nearly ceased by 24 h after parasitoid oviposition. The degree of this biosynthetic depression increased as the time between parasitization and gland dissection increased. A time-course study allowed us to determine if both the degree of phosphorylation of regulatory target proteins, the rate of general protein synthesis and ecdysteroidogenesis decreased in concert over time. The results provide further evidence in support of the hypothesis that these cellular activities in prothoracic gland cells are functionally correlated in steroidogenic responses. Treatment with calyx fluid and venom of C. nigriceps duplicates the parasitism-induced inactivation of host prothoracic glands. A 6-h conditioning in vitro of pupally committed host prothoracic glands with these parasitoid female reproductive secretions resulted in a significant depression of their ecdysteroid production. However, glands lost their sensitivity to calyx fluid and venom treatment when explanted from hosts that had already attained the cell formation stage. This was further supported by the fact that nearly all the host larvae parasitized on day 4 of fifth instar (cell formation stage) pupated, while parasitization on day 3 resulted in only 11% pupation. The coupled trioxsalen/UV irradiation treatment of C. nigriceps calyx fluid and venom eliminated their negative effect on biosynthetic activity in vitro by host prothoracic glands. This result indirectly demonstrates that C. nigriceps polydnavirus is the major regulating factor involved in the host prothoracic gland inactivation. Arch. Insect Biochem. Physiol. 38:1–10, 1998. © 1998 Wiley-Liss, Inc.     

The in vitro synthesis and secretion of alpha-ecdysone by the ring glands of the fly, Sarcophaga bullata.

The in vitro secretory product of larval Sarcophage bullata ring glands has been identified as 2beta, 3beta, 14alpha, 22R, 25-pentahydroxy-5beta-cholest-7-en-6-one (alpha-ecdysone). Mid to late 3rd instar larval ecdysones were isolated and identified as 2beta, 3beta, 14alpha, 20R, 22R, 25-hexahydroxy-5beta-cholest-7-en-6-one (beta-ecdysone) and alpha-ecdysone at a ratio of 27:1. The low level of alpha-ecdysone in vivo, relative to its exclusive in vitro synthesis and secretion by the ring glands, is a function of the very active C20 hydroxylation mechanism in tissues peripheral to the ring gland. The role of alpha-ecdysone as a prohormone in dipteran metamorphosis is discussed.     

The ecdysoneless (ecd1ts) mutation disrupts ecdysteroid synthesis autonomously in the ring gland of Drosophila melanogaster

Ring glands dissected from homozygous l(3)ecd1ts wandering larvae and upshifted in vitro to the restrictive temperature, 29 degrees C, synthesize abnormally low quantities of ecdysteroid. Nevertheless, ecd1 ring glands retain the ability to respond at 29 degrees C to an extract prepared from wild-type larval neural tissues that presumably contain prothoracicotropic hormone (PTTH), although both basal and stimulated levels of synthesis are lower than those in wild-type ring glands. Extracts prepared from ecd1 neural tissue exhibit an unusually high level of PTTH activity. Mutant ring glands downshifted in vitro to the permissive temperature after removal from larvae maintained at 29 degrees C regain the ability to produce normal basal and stimulated ecdysteroid levels. Collectively, these experiments demonstrate that the ecd1 mutation disrupts the physiology of the ring gland at 29 degrees C autonomously and may also interfere with PTTH release.     

Cellular differences in ring glands of flesh fly pupae as a consequence of diapause programming

The ultrastructure of the ring gland (corpus cardiacum (CC), prothoracic gland (PG) and corpus allatum (CA)) was examined in diapausing and nondiapausing flesh fly pupae. The diapause developmental state, which is environmentally regulated and coordinated by the brain-ring gland complex, is associated with differences in the ultrastructure of PG and CA cells but not in the CC. During diapause the PG and CA cells have extensive arrays of rough endoplasmic reticulum and spherical mitochondria. The PG cells also contain lipid droplets surrounded by an electron dense amorphous coat not seen in PG cells from nondiapausing pupae. In nondiapausing pupae, the PG and CA cells contain large amounts of ribosomes throughout the cytoplasm but very little rough endoplasmic reticulum and elongated mitochondria. The fact that ring glands from diapausing pupae readily incorporate (35)S-methioninc indicates that the gland is actively synthesizing proteins, thus the contrasts in ring gland ultrastructure are not due to cellular quiescence during diapause but reflect fundamental cellular and physiological differences between the diapause and nondiapause developmental program.     

Ultrastructure of corpora allata of known activity during the vitellogenic cycle in the cockroach Diploptera punctata

Summary Ultrastructure was correlated with rates of juvenile hormone synthesis in corpora allata from females of the viviparous cockroach Diploptera punctata at seven daily intervals during the first vitellogenic cycle. Synthetic activity of the glands was determined by in vitro radiochemical assay before the glands were fixed for electron microscopic analysis. The cycle in rates of juvenile hormone synthesis progressed from about 20 pmol h^-1 per gland pair (oocytes 0.60 mm long) to a maximum mean rate of 140 pmol h^-1 per pair (oocytes 1.40–1.47 mm long) and declined to about 20 pmol h^-1 per pair at ovulation (oocytes about 1.65 mm long). Conspicuous ultrastructural changes occurred with changing synthetic rates. In glands with increasing rates of synthesis, mitochondria showed less electron-dense matrix, greater diameter and more irregular shape. Smooth endoplasmic reticulum changed from easily seen to obscure tubules, networks, and vesicles. Rough endoplasmic reticulum appeared in longer, more curved segments. Newly formed autophagic vacuoles appeared in all glands of highest activity rates. In glands with decreasing rates of synthesis, the mitochondrial matrix became denser, width smaller, and shapes less irregular. Smooth endoplasmic reticulum again appeared tubular and distinct. Golgi complexes were more conspicuous. Rough endoplasmic reticulum in whorls and large numbers of autophagic vacuoles continued to be present.This work was supported by USPH Grant AI 15230. We thank Kuen-Kuen Chan for skillful and thoughtful technical assistance     

Metamorphosis of the corpus allatum and degeneration of the prothoracic glands during the larval-pupal-adult transformation of Drosophila melanogaster: a cytophysiological analysis of the ring gland

The degeneration of the prothoracic glands of Drosophila melanogaster during pupal-adult metamorphosis was analyzed by light microscopy, scanning, and transmission electron microscopy. The ultrastructural observations were correlated with the ability of the ring gland to synthesize ecdysteroids in vitro. The ring gland is prominent during larval life and is identifiable until just before adult eclosion but undergoes dramatic changes in location, shape, size, ultrastructure, and function during pupal-adult development. Prothoracic gland degeneration is characterized by: a gradual decrease in its ability to synthesize ecdysteroids; a decreasing quantity of smooth endoplasmic reticulum (SER) and mitochondria; the absence of intercellular channels; cytoplasmic fragmentation; and the separation of the prothoracic gland from the corpus allatum and corpus cardiacum. An ultrastructural analysis of the corpus allatum during larval-pupal-adult metamorphosis and adult life was also correlated with function, i.e., juvenile hormone biosynthesis, using a radiochemical assay of ring glands and adult corpora allata in vitro. A relatively high concentration of SER, mitochondria, and mitochondrion-scalariform junction complexes are typical features of an active corpus allatum cell. The migration of the corpus allatum from the ring gland to its position as a separate gland in the adult fly was studied in detail. The capacity of the corpus allatum to synthesize juvenile hormone is at its peak in the ring gland of the early wandering third instar larva, whereas the corpus allatum of 2-day-old female adults displayed the greatest synthetic activity during adult life. The physiological significance of the alterations in gland activity is discussed.     

Modulation of nucleotide binding to the catalytic sites of thermophilic F1-ATPase by the ε subunit: Implication for the role of the ε subunit in ATP synthesis

Effect of ε subunit on the nucleotide binding to the catalytic sites of F₁-ATPase from the thermophilic Bacillus PS3 (TF₁) has been tested by using α₃β₃γ and α₃β₃γε complexes of TF₁ containing βTyr341 to Trp substitution. The nucleotide binding was assessed with fluorescence quenching of the introduced Trp. The presence of the ε subunit weakened ADP binding to each catalytic site, especially to the highest affinity site. This effect was also observed when GDP or IDP was used. The ratio of the affinity of the lowest to the highest nucleotide binding sites had changed two orders of magnitude by the ε subunit. The differences may relate to the energy required for the binding change in the ATP synthesis reaction and contribute to the efficient ATP synthesis.     

Biosynthetic pathways of the sex pheromone components and substrate selectivity of the oxidation enzymes working in pheromone glands of the fall webworm, Hyphantria cunea

The fall webworm, Hyphantria cunea Drury (Lepidoptera: Arctiidae), is a harmful polyphagous defoliator. Female moths produce the following four pheromone components in a ratio of about 5:4:10:2; (9Z,12Z)-9,12-octadecadienal (I), (9Z,12Z,15Z)-9,12,15-octadecatrienal (II), cis-9,10-epoxy-(3Z,6Z)-3,6-henicosadiene (III), and cis-9,10-epoxy-(3Z,6Z)-1,3,6-henicosatriene (IV). Although ¹³C-labeled linolenic acid was not converted into trienal II at the pheromone glands of H. cunea females, GC-MS analysis of an extract of the pheromone gland treated topically with ¹³C-labeled linolenyl alcohol showed the aldehyde incorporating the isotope. Other C₁₈ and C₁₉ fatty alcohols were also oxidized to the corresponding aldehydes in the pheromone gland, indicating a biosynthetic pathway of IIvia linolenyl alcohol and low substrate selectivity of the alcohol oxidase in the pheromone gland. On the other hand, epoxydiene III was expected to be produced by specific 9,10-epoxidation of the corresponding C₂₁ trienyl hydrocarbon, which might be biosynthesized from dietary linolenic acid in oenocytes and transported to the pheromone gland. The final biosynthetic step in the pheromone gland was confirmed by an experiment using deuterated C₂₁ triene, which was synthesized by the chain elongation of linolenic acid and LiAlD₄ reduction as key reactions. When the labeled triene was administered to the female by topical application at the pheromone gland or injection into the abdomen, deuterated III was detected in a pheromone extract by GC-MS analysis. Furthermore, the substrate selectivity of epoxidase and selective incorporation by the pheromone glands were examined by treatments with mixtures of the deuterated precursor and other hydrocarbons such as C₁₉-C₂₃ trienyl, C₂₁ dienyl, and C₂₁ monoenyl hydrocarbons. The 9,10-epoxy derivative of each alkene was produced, while the epoxidation of the C₂₁ monoene was poorer than those of the trienes and diene. The low selectivity indicated that the species-specific pheromone of the H. cunea female was mainly due to the critical formation of the precursor of each component.     

Neural factors that stimulate ecdysteroid synthesis by the larval ring gland ofDrosophila melanogaster

Summary The larval ring gland ofDrosophila melanogaster is the source of ecdysteroids responsible for larval-larval and larval-pupal molting. An extract prepared from theDrosophila larval central nervous system, that presumably contains prothoracicotropic hormone, elicits a significant and dose-dependent in vitro increase in ecdysteroid synthesis by ring glands from wandering third instar larvae. The synthesis of all three ecdysteroids previously identified as ring gland products is elevated by more than two-fold in the presence of neural extract. The maximum response occurs within 30 min and can be sustained for at least two hours after a 30 min exposure to neural extract. No non-neural tissue extracts evoke a response and most of the prothoracicotropic activity originates in the ventral ganglion. However, while extract prepared from larval brains elicits only a slight increase in ecdysteroid synthesis, it enhances the activity of a submaximal dose of ventral ganglion extract. This suggests that two or more neural factors, at least one from the brain lobes and another from the ventral ganglion, interact to stimulate ecdysteroid synthesis by the larval ring gland.Abbreviations CNS central nervous system - HPLC high performance liquid chromatography - PTTH prothoracicotropic hormone - RIA radioimmunoassay