Lynn M. Riddiford

Comparative metabolism of the cecropia juvenile hormone

Abstract The in vivo and in vitro metabolism of 3 H-Cecropia C18-juvenile hormone (JH) was studied in representative species of eight orders of insects. In all orders the major metabolites were found to be the JH-acid, the JH acid-diol, and conjugated polar metabolites thought to be glucosides or glucuronides. The JH-diol was also present in both Tenebrio and Saturniid pupae. In vitro studies revealed two additional metabolites produced by tissue homogenates in the presence of NADPH. On the basis of chromatographic evidence these are tentatively identified as the JH-tetrol metabolite in Cecropia, Thermobia , and Drosophila , and the JH-bisepoxide in Drosophila .

Hormonal control of cuticle coloration in the tobacco hornworm, Manduca sexta: Basis of an ultrasensitive bioassay for juvenile hormone

Juvenile hormone inhibits cuticular melanization in tobacco hornworm larvae. This action of juvenile hormone was used as the basis of a new bioassay which is sensitive to less than 0·01 ng (3 × 10−14 moles) of topically applied hormone and requires only 2 days.

Trans-2-Hexenal: Mating Stimulant for Polyphemus Moths

The volatile compound from oak leaves which stimulates the female polyphemus moth to release her sex pheromone has been isolated and identified as trans-2-hexenal. Although leaves of other food plants contain trans-2-hexenal, they also release masking odors which block the activity of the hexenal.

Effects of juvenile hormone on the programming of postembryonic development in eggs of the silkworm,Hyalophora cecropia

Summary Juvenile hormone applied to eggs ofHyalophora cecropia has delayed effects on postembryonic development. Early application, i.e., during the formation of the embryo, produces abnormalities in larval development. Late application, i.e., during the period when the larva differentiates within the egg, has latent effects that first appear at metamorphosis. Apparently, the exposure of the egg to juvenile hormone interferes with the sequential “programming” of postembryonic development.

Juvenile hormone: Its assay and effects on pupae of Manduca sexta

Abstract Non-diapausing pupae of Manduca sexta were used to develop a bioassay for juvenile hormone (JH). The period of maximal sensitivity to Cecropia C17-JH injected in olive oil was found to be 24 to 30 hr after pupal ecdysis at the time of the beginning of epidermal retraction. The dose-response curves for C16-, C17-, and C18-JH at 29±1 hr after pupal ecdysis were determined and those for the latter two compounds were found to be similar and to be linear between 10 −2 and 10 μg/g body weight. C16-JH was 300 times less active than C17- and C18-JH in this bioassay. The effectiveness of 0·5 μg/g C18-JH at 29±1 hr was determined by the carrier media in which it was injected. The highest scores were obtained when the carrier was light mineral oil or loive oil whereas the lowest scores were obtained using 10% BSA or Tween 80. These scores are consistent with the kinetics of equilibration of the injected JH with the haemolymph. Thus, the injected hormone is more effective when it slowly leaks into the blood, presumably because it is metabolized much more slowly.

Volatile Principle from Oak Leaves: Role in Sex Life of the Polyphemus Moth

An emanation from oak leaves is necessary for the mating of polyphemus moths under laboratory conditions. This requirement can be satisfied by placing the moths in the presence of oak leaves or aqueous or alcoholic extracts prepared from oak leaves. The active principle is a vola- tile, heat-stable, polar material which has been partially purified. The oak emanation acts on the female and not on the male, and the sensory receptors are located on the female antennae. The reception of the oak emanation is prerequisite for the females release of her sex pheromone, which in turn, is necessary for the sexual activation of the male.

Antennal proteins of Saturniid moths-their possible rôle in olfaction.

Reception of female sex pheromone is reversibly blocked by exposing male silkmoths (Antheraea pernyi) to formaldehyde vapours or by bathing their antennae in saline solution. Electrophoretograms of proteins eluted from the male antennae show two major bands. One of these may correspond to the ‘receptor protein’ for the female sex pheromone. An analogous component is present in electrophoretograms of the proteins eluted from the male antennae of two other species, Antheraea polyphemus and Hyalophora cecropia.

Morphological effects of juvenile hormone mimics on embryonic development in the bug,Pyrrhocoris apterus

SummaryEmbryos ofPyrrhocoris apterus exposed to juvenile hormone mimics (JH) were examined throughout development to determine the progressive effects of treatment. Prior to blastokinesis whole experimental embryos did not differ morphologically from control embryos fixed at the same stage. Treated embryos failed to complete blastokinesis due to abnormal breakage of the extra-embryonic membranes.In the embryo-larva transition, JH exposure interfered with dorsal closure, with the consolidation of the nerve cord, and with the extension of appendages. Yet pigmentation and muscle differentiation occurred.These effects were interpreted and discussed with reference to the role of juvenile hormone in post-embryonic development.

Antibiotics in the Laboratory-Rearing of Cecropia Silkworms

A mixture of aureomycin and kanamycin prevents a fatal intestinal infection that usually occurs in all cecropia silkworms reared in the laboratory. Thus, for the first time, laboratory experimentation with these larvae and with those of other wild silkworms is practical.