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At least 19 recordsLinked to original sources
PubMed1988

26-[125I]iodoponasterone A is a potent ecdysone and a sensitive radioligand for ecdysone receptors.

The effects of ecdysone, the steroid molting hormone of arthropods, are of considerable interest both to insect physiologists and to those studying steroid-regulated gene expression. Yet progress in understanding ecdysone receptors has been inhibited by the lack of a suitable highly radioactive hormone analog with high affinity for the receptor. Here we report that the synthetic ecdysteroid 26-iodoponasterone A is one of the most active ecdysones known, inducing half-maximal morphological transformation in Drosophila Kc167 cells when present at 0.5 nM. 26-[125I]Iodoponasterone A can be prepared at a specific activity of 2175 Ci/mmol (1 Ci = 37 GBq) by reaction of the precursor 26-mesylinokosterone with carrier-free Na125I. The radiolabeled material binds to Kc167 cell ecdysone receptors specifically and with affinity (Kd ca. 3.8 X 10(-10) M). Thus, 26-[125I]iodoponasterone A appears to be a superior radioligand for ecdysone receptors on grounds both of affinity and of specific activity. Its ready availability should greatly facilitate studies of these receptors.

Animals↗
PubMed1990

Molecular interactions within the ecdysone regulatory hierarchy: DNA binding properties of the Drosophila ecdysone-inducible E74A protein.

The E74 early ecdysone-inducible gene plays a key role in the regulatory hierarchy activated by ecdysone at the onset of Drosophila metamorphosis. We show here that E74A protein binds to three adjacent sites in the middle of the E74 gene. The consensus sequence for E74A protein binding, determined by random-sequence oligonucleotide selection, contains an invariant purine-rich core sequence, C/AGGAA. This sequence is also present in the binding sites of two mammalian proteins that, like E74A, are related to the ets oncoprotein. Antibody staining of larval salivary gland polytene chromosomes revealed that E74A protein binds to both early and late ecdysone-inducible puffs. This study supports Ashburner's proposal that the early puffs encode site-specific DNA binding proteins that directly interact with the early and late ecdysone-inducible puffs.

Animals↗
PubMed1987

Identification of ecdysone 25-O-beta-D-glucopyranoside as a new metabolite of ecdysone in the nematode Parascaris equorum.

A major metabolite of [3H]ecdysone injected into adults of the nematode Parascaris equorum maintained in vitro for 48 h was secreted into the culture medium. The compound could be hydrolysed with a crude hydrolase preparation from Helix pomatia, yielding ecdysone. Sufficient quantity of this material for identification was produced by administration of ecdysone to the parasites. The resulting compound was purified by h.p.l.c. and identified as ecdysone 25-O-beta-D-glucopyranoside by n.m.r. spectroscopy and by fast atom bombardment mass spectrometry of the conjugate and of the sugar released by enzymic hydrolysis. The significance of formation of the glucoside is uncertain.

Animals↗
PubMed1987

The effect of alpha-ecdysone and phenobarbital on the alpha-ecdysone 20-monooxygenase of house fly larva.

The NADPH-dependent cytochrome P-450 20-monooxygenation of alpha-ecdysone is catalyzed both by mitochondria and microsomes isolated from Musca domestica, L. larvae, but about 50% of the activity is associated with mitochondria and 37% with microsomes. The mitochondrial activity is increased by pretreatment with alpha-ecdysone with a concomitant decrease in Km values. This effect is not observed in microsomes. Induction with phenobarbital represses the mitochondrial 20-monooxygenase but does not change the microsomal activity, although a large increase in cytochrome P-450 is observed in the latter fraction. It is concluded that only the mitochondrial 20-monooxygenase appears to be regulated by alpha-ecdysone which suggests that mitochondrial cytochrome P-450 forms are involved in the moulting phenomenon; whereas, microsomal cytochrome P-450 activity may be of a nonspecific nature and not relevant to development.

Animals↗
PubMed1991

Regulation of cytochrome P-450 dependent steroid hydroxylase activity in Manduca sexta: effects of the ecdysone agonist RH 5849 on ecdysone 20-monooxygenase activity.

The non-steroidal ecdysone agonist RH 5849 (1,2-dibenzoyl-1-tert-butylhydrazine) was found to inhibit in a dose-response and apparently competitive fashion the cytochrome P-450 dependent ecdysone 20-monooxygenase activity in the midgut of wandering stage last instar larvae of the tobacco hornworn, Manduca sexta. More effectively on a per molar basis than the naturally occurring molting hormones ecdysone and 20-hydroxyecdysone, RH 5849 was also found to elicit the dramatic 50-fold increase in midgut steroid hydroxylase activity (which normally occurs with the onset of the wandering stage) when injected into competent head or thoracic ligated pre-wandering last instar larvae. These data support and extend the potential usefulness of RH 5849 as a pharmacological probe for further investigating the actions of ecdysteroids and their role(s) in the regulation of ecdysteroid monooxygenases.

Animals↗