Ca2؉ and cAMP are important second messengers that regulate multiple cellular processes. Although previous studies have suggested direct interactions between Ca 2؉ and cAMP signaling pathways, the underlying mechanisms remain unresolved. In particular, direct evidence for Ca 2؉ -regulated cAMP production in living cells is incomplete. Genetically encoded fluorescence resonance energy transfer-based biosensors have made possible real-time imaging of spatial and temporal gradients of intracellular cAMP concentration in single living cells. Here, we used confocal microscopy, fluorescence resonance energy transfer, and insulin-secreting MIN6 cells expressing Epac1-camps, a biosynthetic unimolecular cAMP indicator, to better understand the role of intracellular Ca 2؉ in cAMP production. We report that depolarization with high external K ؉ , tolbutamide, or glucose caused a rapid increase in cAMP that was dependent on extracellular Ca 2؉ and inhibited by nitrendipine, a Ca 2؉ channel blocker, or 2,5-dideoxyadenosine, a P-site antagonist of transmembrane adenylate cyclases. Stimulation of MIN6 cells with glucose in the presence of tetraethylammonium chloride generated concomitant Ca 2؉ and cAMP oscillations that were abolished in the absence of extracellular Ca 2؉ and blocked by 2,5-dideoxyadenosine or 3-isobutyl-1-methylxanthine, an inhibitor of phosphodiesterase. Simultaneous measurements of Ca 2؉ and cAMP concentrations with Fura-2 and Epac1-camps, respectively, revealed a close temporal and causal interrelationship between the increases in cytoplasmic Ca 2؉ and cAMP levels following membrane depolarization. These findings indicate highly coordinated interplay between Ca 2؉ and cAMP signaling in electrically excitable endocrine cells and suggest that Ca 2؉ -dependent cAMP oscillations are derived from an increase in adenylate cyclase activity and periodic activation and inactivation of cAMP-hydrolyzing phosphodiesterase.

Both cervical laminectomy and laminoplasty are safe and effective for the treatment of cervical myelopathy or radiculopathy. Cervical laminoplasty results in a shorter hospital stay and greater functional improvement at 4 months follow-up.

ObjectiveRecent reports indicate that first cases of genuine artemisinin resistance have already emerged along the Thai-Cambodian border. The main objective of this trial was to track the potential emergence of artemisinin resistance in Bangladesh, which in terms of drug resistance forms a gateway to the Indian subcontinent.MethodsWe conducted an open-label, randomized, controlled 42-day clinical trial in Southeastern Bangladesh to investigate the potential spread of clinical artemisinin resistance from Southeast Asia. A total of 126 uncomplicated falciparum malaria patients were randomized to one of 3 treatment arms (artesunate monotherapy with 2 or 4 mg/kg/day once daily or quinine plus doxycycline TID for 7 days). Only cases fulfilling a stringent set of criteria were considered as being artemisinin-resistant.FindingsThe 28-day and 42-day cure rates in the artesunate monotherapy (2 and 4 mg/kg) and quinine/doxycyline arms were 97.8% (95% confidence interval, CI: 87.8–99.8%), 100% (95% CI: 91.1–100%), and 100% (95% CI: 83.4–100%), respectively. One case of re-infection was seen in the artesunate high dose arm, and a single case of recrudescence was observed in the low dose group on day 26. No differences in median parasite and fever clearance times were found between the 2 artesunate arms (29.8 h and 17.9 h vs. 29.5 h and 19.1 h). Not a single case fulfilled our criteria of artemisinin resistance. Parasite clearance times were considerably shorter and ex vivo results indicate significantly higher susceptibility (50% inhibitory concentration for dihydroartemisinin was 1.10 nM; 95% CI: 0.95–1.28 nM) to artemisinins as compared to SE-Asia.ConclusionThere is currently no indication that artemisinin resistance has reached Bangladesh. However, the fact that resistance has recently been reported from nearby Myanmar indicates an urgent need for close monitoring of artemisinin resistance in the region.Trial RegistrationClinicalTrials.gov NCT00639873.

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