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A M Fallon

Publications and source records attributed to A M Fallon.

81 records · Page 5Linked to original sources
PubMed1977

Cyclic nucleotide phosphodiesterases in the cricket, Acheta domesticus.

Exceptionally high levels of guanosine 3'-5'-cyclic monophosphate (cyclic GMP) in the accessory reproductive gland of the male house cricket, Acheta domesticus, led to an investigation of cyclic nucleotide phosphodiesterase (EC 3.1.4.--) as a possible regulatory enzyme. Cricket cyclic nucleotide phosphodiesterase activity with cyclic GMP or cyclic AMP as substrate had a pH optimum around 9.0, required Mg2+ or Mn2+ for maximal activity, and was inhibited by EDTA and methylxanthines. Cyclic GMP phosphodiesterase occurred mainly in the soluble fraction of homogenates of accessory glands or whole crickets, but cyclic AMP phosphodiesterase in the accessory gland was primarily particulate. Kinetic analysis indicated three forms of cyclic GMP phosphodiesterase, with Km values at 2.9 muM, 71 muM and 1.5 mM. Chromatography of whole cricket or accessory gland extracts on DEAE cellulose gave an initial peak having comparable activity with either cyclic GMP or cyclic AMP, and a second peak specific for cyclic AMP. There were no appreciable changes in the specific activity or kinetic properties of accessory gland cyclic GMP phosphodiesterase during a developmental period over which cyclic GMP levels rise more than 500-fold. Thus, the accumulation of cyclic GMP in the accessory gland is probably not associated with concomitant developmental modulation of phosphodiesterase activity.

Cations, Divalent↗
PubMed1976

Hormonal release of programmed behavior in silk moths: probable mediation by cyclic AMP.

The eclosion hormone triggers a stereotyped preprogrammed pattern of behavior in silk moths. The effects of the hormone were duplicated by the injection of dibutyryl adenosine 3', 5'-monophosphate, adenosine 3', 5'-monophosphate (cyclic AMP), or guanosine 3', 5'-monophosphate (cyclic GMP) into theophylline-treated pharate moths. Treatment with theophylline reduced the latency of the response to a low dose of hormone, presumably by blocking phosphodiesterase. Endogenous levels of cyclic AMP, but not cyclic GMP, increased significantly in the central nervous system within 10 minutes after hormone injection. We conclude that an early step leading to the release of the eclosion motor program is an increase in cyclic AMP in target neurons of the central nervous system.

Animals↗
PubMed1975

Cyclic guanosine 3'-5'-monphosphate. High levels in the male accessory gland of Acheta domesticus and related crickets.

Guanosine 3',5'-monophosphate (cyclic GMP) was found in the accessory gland of reproductively mature male house crickets (Acheta domesticus (L.)) up to the exceptionally high level of 500 pmol/mg protein (10(-4) mol/kg wet weight). The identity of cricket cyclic GMP was confirmed by enzymatic and spectral analysis. A survey of 10 closely related species of Orthoptera indicated that high levels of cyclic GMP in the accessory gland occur in the subfamily Gryllinae, to which A. domesticus belongs. In these crickets, cyclic GMP in the accessory gland increases together with protein content during two weeks after the final molt. Levels are not augmented by dissection, and are independent of the presence of sperm in the seminal vesicles and of the production of spermatophores by the gland. The function of cyclic GMP in the accessory gland is not yet understood.

Animals↗
PubMedDate not supplied

Increased ribonucleotide reductase activity in hydroxyurea-resistant mosquito cells.

Hydroxyurea-resistant Aedes albopictus mosquito cells were selected by incremental exposure of unmutagenized cells to hydroxyurea concentrations ranging from 0.1 to 8 mM. Clonal populations that had become 40-fold more resistant to hydroxyurea than wild-type cells varied in morphology, and their growth rate decreased to a;45 h doubling time, relative to an 18 h doubling time in unselected cells. At this level of resistance, the cells remained diploid, with a modal chromosome number of 6. When labelled with (35)S[methionine/cysteine], clone HU1062, which grew in the presence of 8 mM hydroxyurea, overproduced a labeled protein with the approximate size of the 45,000 dalton M2 subunit of ribonucleotide reductase. Consistent with this observation, ribonucleotide reductase activity in HU-1062 cells was approximately 10-fold higher than in wild-type control cells. This is the first example of an hydroxyurea-resistant insect cell line. [Originally published in Volume 34, Archives of Insect Biochemistry and Physiology, 34:31-41 (1997).]

Aedes↗
PubMedDate not supplied

Primary structure of the ribosomal DNA intergenic spacer from the mosquito, Aedes albopictus.

We have determined the primary structure of a 4.7-kb portion of the ribosomal DNA intergenic spacer from cultured cells of the mosquito, Aedes albopictus. Immediately upstream from the 18S rRNA gene was a 753-bp sequence containing two regions similar to known RNA polymerase I promoters, each preceded by potential transcription termination signals. Upstream from this putative promoter region was a 3.15-kb tandem array of 17 direct repeats with a consensus sequence length of 201 bp. The 201-bp repeats contained imperfect antisense duplications of 11-bp core domain regions in the putative RNA polymerase I promoters, and sequences of possible significance in recombination. Farthest upstream of the 18S rRNA gene was an 803-bp region containing two copies each of 34-, 48-, and 64-bp elements separated by apparently unique sequence. This first detailed structural analysis of a ribosomal DNA intergenic spacer from a member of the lower Diptera has revealed features similar to those described for the higher Diptera as well as conserved motifs presumably critical to rRNA transcription.

Aedes↗