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At least 19 recordsLinked to original sources
PubMed1977

Patterns of protein synthesis in imaginal discs of Drosophila melanogaster.

Patterns of polypeptide synthesis in wing, leg and eye-antenna imaginal discs and in whole larvae of wild-type and and mutant Drosophila melanogaster have been examined using two-dimensional polyacrylamide gel electrophoresis and autoradiography. After 2 hr of labeling with 35S during the third larval instar, the synthesis of more than 318 polypeptides has been detected in imaginal discs. Of these, 268 are present in similar amounts in all three disc types. The remaining polypeptides detected in the three imaginal disc types fall into two categories: those unique to a particular disc type, and those specific for a particular pair of disc types. These results are discussed in relation to the spectrum of gene expression in imaginal discs.

Animals↗
PubMed1979

Specific binding of 20-hydroxyecdysone to nuclei of imaginal discs of Drosophila melanogaster.

Specific binding of the insect steroid hormone 20-hydroxyecdysone to imaginal discs of Drosophila melanogaster has been investigated. Evidence is presented showing that most of the specific binding is located in the nuclear fraction at the time changes in gene function are observed. Nuclear binding is high affinity, analog specific, apparently saturable, and unaffected by inhibitors of RNA and protein synthesis. The association kinetics of nuclear binding are very similar to those of specific binding in whole cells. Specific binding to whole discs and to disc nuclei is temperature-dependent, but equal levels of nuclear binding are achieved after 1 h at 25 degrees C and 8 h at 0-4 degrees C. There is little or no lag in the nuclear location of specific binding at either temperature. The biochemical properties of the specific nuclear binding are consistent with the involvement of these sites in the hormone detection and response system mediating imaginal disc morphogenesis.

Amanitins↗
PubMed1976

Pyridine nucleotide metabolism in imaginal discs of Drosophila melanogaster.

The pyridine nucleotide metabolism of imaginal discs of Drosophila melanogaster has been studied in vitro by incubating discs with labeled nicotinic acid in the presence and absence of ecdysterone. The major labeled compounds found within the discs are NAD, NADP, and nicotinic acid. There is preferential uptake of nicotinamide over nicotinic acid, although the Priess-Handler pathway is used exclusively. The presence of ecdysterone produces a small increase in the NADP/NAD ratio, and an increase in NAD synthesis, probably to compensate for increased NAD turnover.

Animals↗
PubMed1978

Ecdysteroid receptors in imaginal discs of Drosophila melanogaster.

[3H]Ponasterone A (PNA) of high specific activity has been used to identify and begin characterization of ecdysteroid (formerly called ecdysone) receptors in cytoplasmic and nuclear fractions of imaginal discs of Drosophila melanogaster. The equilibrium Kd of the observed macromolecular binding, 3--4 X 10(-9) M PNA, is in good agreement with the minimal concentration required for induction of complete morphogenesis in vitro, 4.2 X 10(-9) M PNA. Binding is analog specific and has kinetics consistent with a role in hormone response. On gentle homogenization, less than 5% of the binding capacity of the cell is released as soluble receptor; the other 95% remains with the nuclear fraction. This nuclear fraction specifically binds [3H]PNA in vitro. Greater than 95% of nuclear PNA receptors are released by extraction with 0.3 M KCl. The binding properties of the nuclear receptors are indistinguishable from those of the cytosol fraction or of the whole cell.

Animals↗
PubMed1977

Active ion transport and beta-acdysone induced differentiation of Drosophila melanogaster imaginal discs cultured in vitro.

The theory that beta-ecdysone initiates developmental changes during insect metamorphosis by causing an increase in intranuclear levels of potassium, together with a concomitant decrease in sodium levels, has been investigated by two methods. First, imaginal discs from late third instar larvae have been cultured with 0-2 microng/ml of beta-ecdysone together with inhibitors of active ion transport. Non-specific inhibitors, which may have general effects on sulphydryl groups, such as iodoacetic acid, N-ethylmaleimide ethacrinic acid and furosemide, inhibit both eversion and differentiation at concentrations of from 10(-3) M to 2 X 10(-3) M. Ouabain, the only specific inhibitor of the active transport of Na+ and K+ across membranes, had no effect on development even at a concentration of 10(-2) M. Second, a medium containing raised levels of K+, and reduced concentrations of Na+, neither initiated disc development in the absence of beta-ecdysone, nor stimulated development induced by suboptimal levels (0-02 microng/ml) of beta-ecdysone, either in the presence or absence of ouabain. These results suggest that beta-ecdysone induced morphogenesis is not dependent upon Na+ and K+ concentrations, or on the activity of an ouabain-sensitive ion pump.

Animals↗
PubMed1975

The influence of hemolymph-binding protein on juvenile hormone stability and distribution in Manduca sexta fat body and imaginal discs in vitro.

The wing discs and fat body of Manduca sexta larvae contain enzymes (i.e. carboxylesterase and epoxide hydratase) that can convert the C18 juvenile hormone (JH) to the acid, diol and acid diol. No evidence of oxidative degradation was noted. In vitro studies suggest that JH can be compartmentalized within the cells of the fat body where it is less accessible to degradative mechanisms. Experiments utilizing a hemolymph-binding protein fraction (BPF) in vitro with fat body and imaginal discs indicate that the BPF retards the uptake of JH by tissues and its subsequent degradation by tissue enzymes. BPF also appears to protect JH from degradation by enzymes released into the medium. By these mechanisms the insect can maintain elevated JH titers for relatively long periods. Binding protein may also keep JH in solution in the hemolymph allowing its rapid distribution throughout the insect. The data suggest that the binding protein plays a key role in maintaining juvenile hormone titers.

Adipose Tissue↗
PubMed1977

The eversion and differentiation of Drosophila melanogaster leg and wing imaginal discs cultured in vitro with an optimal concentration of beta-ecdysone.

The stages of the eversion and differentiation of prothoracic leg and wing discs of Drosophila melanogaster, in Shields and Sang's medium 3, are described. The range of specific imaginal structures produced, including patterns of sensilla trichodea and sensilla campaniformia, are noted, and the relationship of these structures to those differentiated in situ is discussed.

Animals↗