Potassium-dependent sodium-calcium exchange through the eye of the fly.

In this review, we describe the characterization of a Drosophila sodium/calcium-potassium exchanger, Nckx30C. Sodium/calcium (-potassium) exchangers (NCX and NCKX) are required for the rapid removal of calcium in excitable cells. The deduced protein topology for NCKX30C is similar to that of mammalian NCKX, with 5 hydrophobic domains in the amino terminus separated from 6 at the carboxy-terminal end by a large intracellular loop. NCKX30C functions as a potassium-dependent sodium-calcium exchanger and is expressed in adult neurons and during ventral nerve cord development in the embryo. Nckx30C is expressed in a dorsal/ventral pattern in the eye-antennal disc, suggesting that large fluxes of calcium may be occurring during imaginal disc development in the larvae. NCKX30C may play a critical role in modulating calcium during development as well as in the removal of calcium and maintenance of calcium homeostasis in adults.

Valved central venous catheter connected to subcutaneous port: A multicenter phase IV study based on a cohort of 50 oncology patients.

PURPOSE: Since technical aspects and clinical features of central venous valved catheters are far from being completely understood, a multinational group of investigators has decided to assess a new distally-valved catheter connected to a port, in the clinical setting of oncology patients undergoing chemotherapy, in an attempt to verify its safety and viability, while also investigating its practical features. METHODS: Our project was structured as a phase IV multicenter study. Hospitalized adults (ages 18-80 years) who had solid tumors and were candidate for intravenous chemotherapy met the criteria to enter the study. One single type of port was used (made of titanium, plastic and silicone) connected to a silicone, distally valved catheter (as manufactured by B. Braun Aesculap). A case report form was provided for each treated case; all relevant data regarding implantation and follow-up were entered into the form, mailed to a coordinating center (G. Chevillon, B. Braun Medical, France) and stored in a software database for statistical analysis. RESULTS: 50 patients (from 6 participating centers) were included in this study. No major complications occurred at insertion. The most frequent clinical problem during follow-up was inability to draw blood samples (9% during the first chemotherapy cycle; 8% after the second cycle); blood obtained from the device was defined 'unsuitable for hematology test' in 9% of the cases at first chemotherapy cycle and in 23% of the cases after the second cycle. No catheter obstruction occurred. CONCLUSION: The distally valved catheter port tested in this study was reliable, safe and practical for long-term treatment of an oncology patients' population undergoing chemotherapy. As most other reports and clinical trials dealing with other types of distally valved catheters pointed out, inability to draw viable blood samples (so called withdrawal occlusion) is a major concern in their clinical use. Mechanisms underlying this technical problem are still unclear.

Expression of rhodopsin and arrestin during the light-dark cycle in Drosophila.

PURPOSE: To determine the protein and transcript levels for rhodopsin (Rh1), arrestin 1 (Arr1), and arrestin 2 (Arr2) over a 12 h light/12 h dark cycle in the retina of the fruit fly, Drosophila melanogaster. This information is important for understanding the process of photoreceptor membrane turnover. METHODS: Drosophila were entrained for several generations to a daily 12 h light/12 h dark cycle. They were sacrificed at 4 h intervals, beginning at the time of onset of the light phase. Proteins were resolved by polyacrylamide gel electrophoresis (PAGE) and subjected to immunoblot analysis using antibodies directed to rhodopsin, NinaA, Arr1, and Arr2. Northern blots were incubated with riboprobes corresponding to the rhodopsin gene (ninaE), arrestin1 (arr1), and arrestin2 (arr2). RESULTS: In entrained Drosophila, protein and mRNA levels for rhodopsin, arrestin1, and arrestin2 were constant during a 12 h light/12 h dark cycle. CONCLUSIONS: These results indicate that rhodopsin and arrestin protein synthesis in Drosophila photoreceptors do not fluctuate on a daily cycle. These findings are similar to those obtained in Xenopus laevis, but in contrast to a variety of other vertebrate and invertebrate species.

Cloning and characterization of a potassium-dependent sodium/calcium exchanger in Drosophila.

Sodium/calcium(-potassium) exchangers (NCX and NCKX) are critical for the rapid extrusion of calcium, which follows the stimulation of a variety of excitable cells. To further understand the mechanisms of calcium regulation in signaling, we have cloned a Drosophila sodium/calcium-potassium exchanger, Nckx30C. The overall deduced protein topology for NCKX30C is similar to that of mammalian NCKX, having five membrane-spanning domains in the NH(2) terminus separated from six at the COOH-terminal end by a large intracellular loop. We show that NCKX30C functions as a potassium-dependent sodium/calcium exchanger, and is not only expressed in adult neurons as was expected, but is also expressed during ventral nerve cord development in the embryo and in larval imaginal discs. Nckx30C is expressed in a dorsal-ventral pattern in the eye-antennal disc in a pattern that is similar to, but broader than that of wingless, suggesting that large fluxes of calcium may be occurring during imaginal disc development. Nckx30C may not only function in the removal of calcium and maintenance of calcium homeostasis during signaling in the adult, but may also play a critical role in signaling during development.