Modulation of K(v)7 potassium channels by a novel opener pyrazolo[1,5-a]pyrimidin-7(4H)-one compound QO-58.

BACKGROUND AND PURPOSE: Modulation of K(v)7/M channel function represents a relatively new strategy to treat neuronal excitability disorders such as epilepsy and neuropathic pain. We designed and synthesized a novel series of pyrazolo[1,5-a] pyrimidin-7(4H)-one compounds, which activate K(v)7 channels. Here, we characterized the effects of the lead compound, QO-58, on K(v)7 channels and investigated its mechanism of action. EXPERIMENTAL APPROACH: A perforated whole-cell patch technique was used to record K(v)7 currents expressed in mammalian cell lines and M-type currents from rat dorsal root ganglion neurons. The effects of QO-58 in a rat model of neuropathic pain, chronic constriction injury (CCI) of the sciatic nerve, were also examined. KEY RESULTS: QO-58 increased the current amplitudes, shifted the voltage-dependent activation curve in a more negative direction and slowed the deactivation of K(v)7.2/K(v)7.3 currents. QO-58 activated K(v)7.1, K(v)7.2, K(v)7.4 and K(v)7.3/K(v)7.5 channels with a more selective effect on K(v)7.2 and K(v)7.4, but little effect on K(v)7.3. The mechanism of QO-58's activation of K(v)7 channels was clearly distinct from that used by retigabine. A chain of amino acids, Val(224)Val(225)Tyr(226), in K(v)7.2 was important for QO-58 activation of this channel. QO-58 enhanced native neuronal M currents, resulting in depression of evoked action potentials. QO-58 also elevated the pain threshold of neuropathic pain in the sciatic nerve CCI model. CONCLUSIONS AND IMPLICATIONS: The results indicate that QO-58 is a potent modulator of K(v)7 channels with a mechanism of action different from those of known K(v)7 openers. Hence, QO-58 shows potential as a treatment for diseases associated with neuronal hyperexcitability.

Characteristics and molecular basis of celecoxib modulation on K(v)7 potassium channels.

BACKGROUND AND PURPOSE: Celecoxib is a selective cyclooxygenase-2 (COX-2) inhibitor used for the treatment of pain and inflammation. Emerging and accumulating evidence suggests that celecoxib can affect cellular targets other than COX, such as ion channels. In this study, we characterized the effects of celecoxib on K(v)7 K(+) channels and compared its effects with the well-established K(v)7 channel opener retigabine. EXPERIMENTAL APPROACH: A perforated whole-cell patch technique was used to record K(v)7currents expressed in HEK 293 cells and M-type currents from rat superior cervical ganglion neurons. KEY RESULTS: Celecoxib enhanced K(v)7.2-7.4, K(v)7.2/7.3 and K(v)7.3/7.5 currents but inhibited K(v)7.1 and K(v)7.1/KCNE1 currents and these effects were concentration dependent. The IC(50) value for inhibition of K(v)7.1 channels was approximately 4 µM and the EC(50) values for activation of K(v)7.2-7.4, K(v)7.2/K(v)7.3 and K(v)7.3/K(v)7.5 channels were approximately 2-5 µM. The effects of celecoxib were manifested by increasing current amplitudes, shifting the voltage-dependent activation curve in a more negative direction and slowing the deactivation of K(v)7 currents. 2,5-Dimethyl-celecoxib, a celecoxib analogue devoid of COX inhibition activity, has similar but greater effects on K(v)7currents. K(v)7.2(A235T) and K(v) 7.2(W236L) mutant channels, which have greatly attenuated responses to retigabine, showed a reversed response to celecoxib, from activation to inhibition. CONCLUSIONS AND IMPLICATIONS: These results suggest that K(v)7 channels are targets of celecoxib action and provide new mechanistic evidence for understanding the effects of celecoxib. They also provide a new approach to developing K(v)7 modulators and for studying the structure-function relationship of K(v)7 channels.

Agrobacterium tumefaciens-mediated transformation of rice with the spider insecticidal gene conferring resistance to leaffolder and striped stem borer.

Immature embryos of rice varieties "Xiushuill" and "Chunjiang 11" precultured for 4d were infected and transformed by Agrobacterium tumefaciens strain EHA101/pExT7 (containing the spider insecticidal gene). The resistant calli were transferred onto the differentiation medium and plants were regenerated. The transformation frequency reached 56% approximately 72% measured as numbers of Geneticin (G418)-resistant calli produced and 36% approximately 60% measured as numbers of transgenic plants regenerated, respectively. PCR and Southern blot analysis of transgenic plants confirmed that the T-DNA had been integrated into the rice genome. Insect bioassays using T1 transgenic plants indicated that the mortality of the leaffolder (Cnaphalocrasis medinalis) after 7d of leaf feeding reached 38% approximately 61% and the corrected mortality of the striped stem borer (Chilo suppressalis) after 7d of leaf feeding reached 16% approximately 75%. The insect bioassay results demonstrated that the transgenic plants expressing the spider insecticidal protein conferred enhanced resistance to these pests.

Transgenic peanut plants obtained by particle bombardment via somatic embryogenesis regeneration system.

After pre-culture and treatment of osmosis, cotyledons of immature peanut (Arachis hypogaea L.) zygotic embryos were transformed via particle bombardment with a plasmid containing a chimeric hph gene conferring resistance to hygromycin and a chimeric intron-gus gene. Selection for hygromycin resistant calluses and somatic embryos was initiated at 10th d post-bombardment on medium containing 10-25 mg/L hygromycin. Under continuous selection, hygromycin resistant plantlets were regenerated from somatic embryos and were recovered from nearly 1.6% of the bombarded cotyledons. The presence and integration of foreign DNA in regenerated hygromycin resistant plants was confirmed by PCR (polymerase chain reaction) for the intron-gus gene and by Southern hybridization of the hph gene. GUS enzyme activity was detected in leaflets from transgenic plants but not from control, non-transformed plants. The production of transgenic plants are mainly based on a newly improved somatic embryogenesis regeneration system developed by us.

Ultraviolet-initiated reactions of H(2) with germanosilicate fibers and H(2) concentration dependence of the Bragg wavelength of a fiber grating.

We present a model with which to calculate the index increase induced in standard single-mode fiber by hydrogen loading. Also, we propose that the dominant products of reaction in UV-written hydrogenated standard communication fibers are GeE? and Si-OH. Based on the above models, we calculate the Bragg wavelength shifts that are due to hydrogen diffusion out of the fiber gratings. The relative effective index change that is due to hydrogen dissolved in fiber can be as much as 6 x 10(-4) if standard telecom fiber is hydrogen loaded with a concentration of ~1.44 mol.%. Theoretical results agree with experimental results.

Intensity-noise suppression by ytterbium codoping in heavily erbium-doped fiber lasers with partly clustered erbium ions.

The effect of ytterbium codoping in heavily erbium-doped fibers with partly clustered erbium ions on the intensity noise stemming from both pump-rate and cavity-loss fluctuations is theoretically investigated with a modified ion-cluster model. Numerical results indicate that low-frequency (below 1 MHz) noise can be greatly suppressed by ytterbium codoping.

Effects of ion clusters on the performance of a heavily doped erbium-doped fiber laser.

A cluster model is proposed for study of the effects of the number of ions per cluster on the performance of a heavily erbium-doped fiber laser. The results indicate that both the threshold pump power and the unstable-operation region of the fiber laser increase with increasing numbers of ions per cluster.

Radiofrequency ablation of ventricular myocardium using active fixation and passive contact catheter delivery systems.

This study examined the qualitative and quantitative effects of radiofrequency energy using active fixation and passive contact catheter delivery systems on normal bovine atrium and ventricle and diseased human ventricle in vitro. Two active fixation (custom screw-in or suction electrode) catheters and two passive contact (custom ring or standard electrode) catheters were used with a 500 kHz radiofrequency current generator. Linear regression analysis between lesion dimensions and power output showed excellent correlation coefficients for all catheter delivery systems except the suction catheter. Lesion sizes also increased with duration of radiofrequency energy delivery at low power using the USCI quadripolar catheter. Lesion size in diseased human ventricle was considerably smaller than in the normal ventricle. Comparison of induced lesion dimensions using pulsed and continuous delivery modes showed only minor differences. Tissue impedance was relatively constant during energy delivery. Arcing was associated with a sudden increase in voltage and impedance and a sudden decline in current. This was most frequently observed at high power and with the suction electrode catheter. The use of high (50 W) power output and prolonged application (up to 180 seconds) in atrium and ventricle did not induce perforation. We conclude that a variety of catheter delivery systems can be used for effective radiofrequency energy delivery and ablation in atrial and ventricular myocardium in the pulsed or continuous mode. Impedance changes during radiofrequency ablation cannot be used to guide the extent of ablation but do detect arcing during the procedure.

Long term survival of radiotherapy for esophageal cancer: analysis of 1136 patients surviving for more than 5 years.

One thousand one hundred and thirty-six patients surviving for more than five years after radiotherapy were studied. The important prognostic factors are: lesion less than 5 cm in length, lesion located in the upper-third segment and lesion that is radiosensitive. The radiation dose given to long term survivors varies greatly, i.e., 2700 to 9300 rad. Yet, for the sensitive type of lesion, doses lower than 5000 rad could also effect a cure. The delivery of an optimum dose determined by serial examinations during radiotherapy could improve the result of treatment. For local recurrent lesions, the value of a second course of radiation is extremely limited and surgery is the only means to offer a cure. For metastasis in the lymph nodes, radiation offers some hope of cure, although the long term outcome may not be satisfactory. For second primary cancer of the esophagus, aggressive radiation still gives encouraging results.