We have fabricated a voltage sensor in the form of a conically shaped nanopore in a polyethylene terephthalate (PET) foil. The pore is produced by irradiation of the foil with a single heavy ion and subsequent etching in alkaline solution. The resulting pore functions as a voltage gate and rectifies ion current due to changes of its diameter in an electrical field. Ion currents through the pore show voltage-dependent fluctuations, whose kinetics are similar as in voltage-gated biological ion channels and pores.

In sensory neurons, Ca(2+) entry is crucial for both activation and subsequent attenuation of signaling. Influx of Ca(2+) is counterbalanced by Ca(2+) extrusion, and Na(+)/Ca(2+) exchange is the primary mode for rapid Ca(2+) removal during and after sensory stimulation. However, the consequences on sensory signaling resulting from mutations in Na(+)/Ca(2+) exchangers have not been described. Here, we report that mutations in the Drosophila Na(+)/Ca(2+) exchanger calx have a profound effect on activity-dependent survival of photoreceptor cells. Loss of CalX activity resulted in a transient response to light, a dramatic decrease in signal amplification, and unusually rapid adaptation. Conversely, overexpression of CalX had reciprocal effects and greatly suppressed the retinal degeneration caused by constitutive activity of the TRP channel. These results illustrate the critical role of Ca(2+) for proper signaling and provide genetic evidence that Ca(2+) overload is responsible for a form of retinal degeneration resulting from defects in the TRP channel.

Background —Loss of cardiomyocytes by apoptosis is proposed to cause heart failure. Reactive oxygen species induce apoptosis in many types of cells including cardiomyocytes. Because insulin has been reported to have protective effects, we examined whether insulin prevents cardiomyocytes from oxidative stress–induced apoptotic death. Methods and Results —Cultured cardiomyocytes of neonatal rats were stimulated by hydrogen peroxide (H 2 O 2 ). Apoptosis was evaluated by means of the TUNEL method and DNA laddering. Incubation with 100 μmol/L H 2 O 2 for 24 hours increased the number of TUNEL-positive cardiac myocytes (control, ≈4% versus H 2 O 2 , ≈23%). Pretreatment with 10 − 6 mol/L insulin significantly decreased the number of H 2 O 2 -induced TUNEL-positive cardiac myocytes (≈12%) and DNA fragmentation induced by H 2 O 2 . Pretreatment with a specific phosphatidylinositol 3 kinase (PI3K) inhibitor, wortmannin, and overexpression of dominant negative mutant of PI3K abolished the cytoprotective effect of insulin. Insulin strongly activated both PI3K and the putative downstream effector Akt . Moreover, a proapoptotic protein, Bad , was significantly phosphorylated and inactivated by insulin through PI3K. Conclusions —These results suggest that insulin protects cardiomyocytes from oxidative stress–induced apoptosis through the PI3K pathway.

Background-Although anthracyclines, such as daunomycin (DM) and adriamycin, are potent chemotherapeutic agents, they have serious adverse effects, including cardiac toxicity. In the present study, we investigated the molecular mechanisms of DM-induced cardiomyocyte impairment. Methods and Results-When cultured cardiac myocytes of neonatal rats were exposed to 1 mol/L DM for 24 hours, many cells became positive for TUNEL staining, with morphological changes characteristic of apoptosis. Fragmentation of DNA into oligonucleosome-size fragments was recognized by agarose gel electrophoresis in DM-treated myocytes. DM activated 3 members of the mitogen-activated protein kinase (MAPK) family dose-dependently, such as extracellular signal-regulated protein kinases (ERKs), c-Jun NH 2 -terminal kinases, and p38 MAPK in cardiac myocytes. Oxyradical scavengers or Ca 2ϩ chelators inhibited DM-induced activation of ERKs and p38 MAPK. DM-induced activation of ERKs was also inhibited by overexpression of dominant negative mutants of Ras (D.N.Ras), and the p38 MAPK activation was attenuated by D.N.Rho. The number of DM-induced apoptotic cells was markedly increased when the ERK signaling pathway was selectively blocked by a specific MAPK/ERK kinase inhibitor, PD98059, whereas pretreatment with a specific inhibitor of p38 MAPK, SB203580, significantly reduced the amount of apoptosis. Conclusions-These results suggest that DM activates MAPKs through reactive oxygen species and Ca 2ϩ and that the MAPK family plays important roles in DM-induced apoptosis in cardiac myocytes. ERKs protect cardiomyocytes from apoptosis, whereas p38 MAPK is involved in the induction of cardiomyocyte apoptosis. (Circulation. 1999;100:2100-2107.)

No abstract