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It is generally acknowledged that the popular cyan and yellow fluorescent proteins carried by genetically encoded reporters suffer from strong pH sensitivities close to the physiological pH range. We studied the consequences of these pH responses on the intracellular signals of model Förster resonant energy transfer (FRET) tandems and FRET-based reporters of cAMP-dependent protein kinase activity (AKAR) expressed in the cytosol of living BHK cells, while changing the intracellular pH by means of the nigericin ionophore. Although the simultaneous pH sensitivities of the donor and the acceptor may mask each other in some cases, the magnitude of the perturbations can be very significant, as compared to the functional response of the AKAR biosensor. Replacing the CFP donor by the spectrally identical, but pH-insensitive Aquamarine variant (pK1/2 = 3.3) drastically modifies the biosensor pH response and gives access to the acid transition of the yellow acceptor. We developed a simple model of pH-dependent FRET and used it to describe the expected pH-induced changes in fluorescence lifetime and ratiometric signals. This model qualitatively accounts for most of the observations, but reveals a complex behavior of the cytosolic AKAR biosensor at acid pHs, associated to additional FRET contributions. This study underlines the major and complex impact of pH changes on the signal of FRET reporters in the living cell. [ABSTRACT FROM AUTHOR]

This paper presents the design of a novel antenna duplexer based on a mixed ladder lattice topology using advanced Solidly Mounted Resonator–Bulk Acoustic Wave (SMR–BAW) and Integrated Passive Device (IPD) technologies. The duplexer is designed for application on W-CDMA handsets (Tx: 1920–1980 MHz, Rx: 2110–2170 MHz). The design methodology and implementation issues are discussed. A combined electromagnetic acoustic analysis results in a maximum insertion loss of 1.75 and 2.3 dB for Tx and Rx paths. The Tx–Rx isolation is better than 47/57 dB. The assembly of both Rx and Tx filters on the IPD will be discussed, as well as the simulated and measurement results. [ABSTRACT FROM AUTHOR]

Signaling cascades involving cyclic nucleotides play key roles in signal transduction in virtually all cell types. Elucidation of the spatiotemporal regulation of cyclic nucleotide signaling requires methods for tracking the dynamics of cyclic nucleotides and the activities of their regulators and effectors in the native biological context. Here we review a series of genetically encoded FRET-based probes for real-time monitoring of cyclic nucleotide signaling with a particular focus on their implementation in neurons. Current data indicate that neurons have a very active metabolism in cyclic nucleotide signaling, which is tightly regulated through a variety of homeostatic regulations. [ABSTRACT FROM AUTHOR]

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Childhood absence epilepsy is an idiopathic, generalized, nonconvulsive epilepsy with a multifactorial genetic etiology. The KCNK9 gene coding for the TASK3 ( Twik-like acid- sensitive K +) channel is present on chromosome 8 at position 8q24, a locus that has shown positive linkage to the human absence epilepsy phenotype. Sequencing of the KCNK9 gene in the genetic absence epilepsy rats from Strasbourg (GAERS), a well established genetic model of this disease, reveals an additional alanine residue in a polyalanine tract within the C-terminal intracellular domain. This additional alanine is absent in the inbred nonepileptic control (NEC) strain, Wistar, and Wistar albino Glaxo strain bred in Rijswijk, another inbred rat model of absence epilepsy. Expression of the mutant channel in CHO cells produces a K+ current that is blocked by acidic pH and millimolar concentrations of barium or ruthenium red and is not different from the wild-type channel. In brain slices, thalamic neurons display a prominent pH-sensitive tonic K+ current, but no difference was observed between GAERS and NEC or Wistar rats. Ruthenium red had no effect in cortical, reticular thalamic, or sensory thalamic neurons in either GAERS or NEC, indicating that the TASK3 homodimer is not present in these structures. Twik-like acid-sensitive K+ (TASK3) channels, therefore, are probably associated with TASK1 to form ruthenium red-insensitive heterodimers in these neurons. Finally, no difference was found between GAERS and NEC rats in the modulation of the leak K+ current following activation of muscarinic receptors. These studies describe the first mutation found in a genetic model of absence epilepsy. Although our experiments showed no difference in the leak K+ current between GAERS and NEC rats, further work is needed to ascertain whether this mutation contributes to the generation of absence seizures, possibly by mechanisms related to the expansion of the polyalanine run. [ABSTRACT FROM AUTHOR]

Reports on the results of the use of the cAMP-indicator dye FICRhR to investigate the effect of several neuromodulators (octopamine, dopamine, acetylcholine, serotonin and proctolin) on cAMP distribution in indentified neurons of the lobster stomatogastric ganglion (STG). The production of a unique pattern of cAMP transients among the different neurons of the STG; Possible explanation of the production of long-range effects by transient localized inputs.

Copyright of Bulletin of Volcanology is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)