Juvenile hormone radioimmunoassays— Theory and practice

Purification and characterization of a mandibular organ protein from the American lobster, Homarus americanus: a putative farnesoic acid O-methyltransferase

Methyl farnesoate (MF) appears to have important roles in the development, morphogenesis, and reproduction of crustaceans. To better understand the regulation of MF synthesis, we studied farnesoic acid O-methyltransferase (FAOMeT, the final enzyme in the MF biosynthetic pathway) in the American lobster (Homarus americanus). FAOMeT purified from mandibular organ (MO) homogenates had a MW of approximately 38,000. The sequences of trypsin fragments of purified FAOMeT were used to design PCR primers to amplify a cDNA fragment, which was used to isolate a full-length cDNA containing a single open reading frame (ORF) of 828 bp encoding a protein of 276 amino acids. The deduced amino acid sequence of this putative FAOMeT protein contained two copies of a conserved approximately 135 amino acid domain we term the CF (CPAMD8/FAOMeT) domain; single copies of this domain also occur in the human CPAMD8 protein (a member of the alpha-2 macroglobulin family) and an uncharacterized Drosophila protein. The recombinant protein had no FAOMeT activity. However, its addition to MO homogenates from eyestalk ablated (ESA) lobsters increased enzyme activity by up to 75%, suggesting that FAOMeT may require an additional factor or modification (e.g., phosphorylation) for its activation. The mRNA for the putative FAOMeT was primarily found in the proximal region of the MO, the predominant site of MF synthesis. FAOMeT transcripts were found in muscle tissue from ESA animals, but not in green gland, hepatopancreas, or in muscle tissue from intact animals. FAOMeT mRNA was also detected in embryos and larval stages. This is the first comprehensive report of this protein in the lobster, and is an important step in elucidating the functions of MF in these animals.

Time-course haemolymph juvenile hormone titres in solitarious and gregarious adults of Schistocerca gregaria, and their relation to pheromone emission, CA volumetric changes and oocyte growth

The haemolymph JH III titres in solitarious and gregarious adult desert locusts, Schistocerca gregaria, were examined in relation to corpus allatum (CA) volumes, aggregation-maturation pheromone production in males and oocyte growth in females. The JH titres of gregarious females were generally higher than those of solitarious females at all ages studied. The titre patterns, however, were similar: relatively high on day 10, dropping to low levels between days 20 and 25, before rising again by day 25. In the solitarious males, the JH titre was very low on day 10 after fledging, but increased gradually and reached a maximal amount on day 30. The JH titre in gregarious males was low on day 10, elevated on day 15 coinciding with the start of the production of the pheromone, and dropped to a relatively low level on day 20 around the time of maximal pheromone production, then rising again by day 25. These results suggest that biosynthesis of the pheromone is associated with a high JH titre peak in the haemolymph. Although a clear relationship was found during the first gonadotropic cycle between JH titres, on one hand, and CA volume and oocyte growth, on the other, in both phases, no such correlation could be discerned in the second cycle.

Development changes in juvenile hormone and juvenile hormone acid titers in the hemolymph and in-vitro juvenile hormone synthesis by corpora allata of the silkworm, Bombyx mori

A simple method was developed to quantify hemolymph juvenile hormone (JH) and JH acid in hemolymph extracts from Bombyx mori with an established radioimmunoassay (RIA) for JH I. When various organic solvent extracts of hemolymph were assayed by RIA, levels of non-specific binding of the labeled ligand in the assay were determined to be greater than 50% of the maximum amount of the label bound by the antiserum. When hemolymph was diluted with methanol:water:8.4N ammonium hydroxide (10:9:1) and extracted with isooctane, non-specific binding was only 50% higher than control levels obtained with the assay buffer alone. The organic phase contained only JH and aqueous phase, JH acid. Consequently, this extraction method was used to prepare samples for RIA and enabled the separate measurement of JH and JH acid in hemolymph. With this method, changes in the hemolymph titers of JH and JH acid were determined from the third instar through early pupal stage of Bombyx mori. Changes in the in vitro secretory activity of corpora allata and brain-corpora cardiaca-corpora allata complexes from fifth instar larvae were also determined by using JH I RIA of the incubation medium.

Effects of larval tapeworm (Taenia taeniaeformis) infection on reproductive functions in male and female host rats

This report examined the effects of larval tapeworm infection on the reproductive functions in both male and female host rats. Female rats were matched by age, then randomly assigned to control and treatment groups (infected with larval tapeworms). Estrous cycles were determined by vaginal smear with 95% of the control group exhibiting 4-day normal cyclicity and only 55% of the treated group exhibiting normal cycles. Female fertility was then evaluated for the normally cycling rats based on the percentage of successful matings on the evening of proestrus, number of implantation sites on Day 8 of pregnancy, and number of pups born at term. The normally cycling rats exhibited 96% successful mating, 12.95 +/- 1.80 implantation sites, and 11.20 +/- 1.80 pups born. Five months after larval tapeworm infection, the fertility parameters were decreased to 79%, 9.10 +/- 1.20, and 7.50 +/- 1.50, respectively. The control females were then used in a study of male fertility after larval tapeworm infection employing the same parameters used to test female fertility. At the onset of the study, control groups exhibited 95% successful mating, 12.50 +/- 1.50 implantation sites, and 11.60 +/- 1.60 pups born at full term. After the 5-month infection period, the parameters were substantially reduced to 29%, 6.20 +/- 0.80 implantation sites, and 5.10 +/- 0.80 pups, respectively. Average testosterone concentrations in serum and testis from control male rats were 8.80 +/- 0.95 ng/ml and 3.88 +/- 0.25 ng/mg protein, respectively. After the 5-month infection period, these levels were reduced to 2.47 +/- 0.31 ng/ml and 1.28 +/- 0.12 ng/mg protein, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

The intrinsic synthesis of juvenile hormone-III diol by locust corpora allata in vitro

Juvenile hormone (JH)-III 10-11-diol is intrinsically synthesized and released from the corpora allata (CA) of adult locust females in vitro, together with JH-III. JH-III synthesis is preferentially stimulated and diol production only slightly enhanced, by cerebral locust allatotropin. The identification of JH-III diol is based on: similar ratio of incorporation of 14C/3H from radiolabelled [2-14C]acetate and [methyl-3H]methionine, to that of JH-III; similar chromatographic properties to those of synthetic diol on an RP-18 column eluted with acetonitrile, and similar chromatographic properties of acetylated derivatives; mass spectrometric analysis of derivatives and fragmentation products. Exogenous radiolabelled JH-III is not degraded during incubation with locust CA in vitro, corroborating the endogenous production of JH-III diol. Allatal diol formation may be an additional mechanism for the control of JH-III levels in locusts, preceding release into the hemolymph.

A Drosophila melanogaster mutant resistant to a chemical analog of juvenile hormone

Methoprene, a chemical analog of juvenile hormone, is toxic when applied to late third-instar larvae of Drosophila melanogaster. Using an ethyl methane sulfonate mutagenesis screen, we have selected two noncomplementing mutants, one of which is nearly 100 times more resistant than wild-type to either methoprene or juvenile hormone III topically applied or incorporated into the diet. The mutation, named methoprene-tolerant (Met), also confers resistance to methoprene-induced pseudotumor formation in larvae as well as to juvenile hormone III- or methoprene-induced vitellogenic oocyte development in adult females. Met adults show little or no cross-resistance to four other insecticides. The mutation was mapped by recombination to a location 35.4 on the X-chromosome and uncovered by chromosomes deficient for the region 10C2-10D4. Complementation was observed between Met and a lethal allele of the RNA polymerase II locus, which is also found in this region. Since the Met mutation also confers resistance to methoprene-induced abnormalities in adult cuticle formation, the autonomy of Met expression could be evaluated in flies mosiac for this mutation. Autonomous expression of Met was found both in abdominal cuticle as well as in external male genitalia. The characteristics of Met are consistent with those expected of a mutant having altered juvenile hormone reception in target tissue.