4 resultados para HYDROGEN LINES
em BORIS: Bern Open Repository and Information System - Berna - Suiça
Resumo:
Supernova remnants are among the most spectacular examples of astrophysical pistons in our cosmic neighborhood. The gas expelled by the supernova explosion is launched with velocities ~1000 kilometers per second into the ambient, tenuous interstellar medium, producing shocks that excite hydrogen lines. We have used an optical integral-field spectrograph to obtain high-resolution spatial-spectral maps that allow us to study in detail the shocks in the northwestern rim of supernova 1006. The two-component Hα line is detected at 133 sky locations. Variations in the broad line widths and the broad-to-narrow line intensity ratios across tens of atomic mean free paths suggest the presence of suprathermal protons, the potential seed particles for generating high-energy cosmic rays.
Resumo:
NHA2 is a sodium/hydrogen exchanger with unknown physiological function. Here we show that NHA2 is present in rodent and human β-cells, as well as β-cell lines. In vivo, two different strains of NHA2-deficient mice displayed a pathological glucose tolerance with impaired insulin secretion but normal peripheral insulin sensitivity. In vitro, islets of NHA2-deficient and heterozygous mice, NHA2-depleted Min6 cells, or islets treated with an NHA2 inhibitor exhibited reduced sulfonylurea- and secretagogue-induced insulin secretion. The secretory deficit could be rescued by overexpression of a wild-type, but not a functionally dead, NHA2 transporter. NHA2 deficiency did not affect insulin synthesis or maturation and had no impact on basal or glucose-induced intracellular Ca(2+) homeostasis in islets. Subcellular fractionation and imaging studies demonstrated that NHA2 resides in transferrin-positive endosomes and synaptic-like microvesicles but not in insulin-containing large dense core vesicles in β-cells. Loss of NHA2 inhibited clathrin-dependent, but not clathrin-independent, endocytosis in Min6 and primary β-cells, suggesting defective endo-exocytosis coupling as the underlying mechanism for the secretory deficit. Collectively, our in vitro and in vivo studies reveal the sodium/proton exchanger NHA2 as a critical player for insulin secretion in the β-cell. In addition, our study sheds light on the biological function of a member of this recently cloned family of transporters.
Resumo:
Cation/proton exchange has been recognized for decades in mammalian mitochondria, but the exchanger proteins have eluded identification. In this study, a cDNA from a human brain library, previously designated NHA2 in the genome, was cloned and characterized. The NHA2 transcript bears more similarity to prokaryotic than known eukaryotic sodium/proton exchangers, but it was found to be expressed in multiple mammalian organs and cultured cells. A mAb to NHA2 was generated and found to label an approximately 55-kD native protein in multiple tissues and cell lines. The specificity of this antibody was confirmed by demonstrating the loss of the native NHA2 band on immunoblots when cultured cells were treated with NHA2-specific small interfering RNA. Although NHA2 protein was detected in multiple organs, within each, its expression was restricted to specific cell types. In the kidney, co-localization with calbindin 28k and reverse transcription-PCR of microdissected tubules revealed that NHA2 is limited to the distal convoluted tubule. In cell lines, native NHA2 was localized both to the plasma membrane and to the intracellular compartment; immunogold electron microscopy of rat distal convoluted tubule demonstrated NHA2 predominantly but not exclusively on the inner mitochondrial membrane. Furthermore, co-sedimentation of NHA2 antigen and mitochondrial membranes was observed with differential centrifugation, and two mitochondrial markers co-localized with NHA2 in cultured cells. Regarding function, human NHA2 reversed the sodium/hydrogen exchanger-null phenotype when expressed in sodium/hydrogen exchanger-deficient yeast and restored the ability to defend high salinity in the presence of acidic extracellular pH. In summary, NHA2 is a ubiquitous mammalian sodium proton/exchanger that is restricted to the distal convoluted tubule in the kidney.
Resumo:
Reduced glutathione (GSH) protects cells against injury by oxidative stress and maintains a range of vital functions. In vitro cell cultures have been used as experimental models to study the role of GSH in chemical toxicity in mammals; however, this approach has been rarely used with fish cells to date. The present study aimed to evaluate sensitivity and specificity of three fluorescent dyes for measuring pro-oxidant-induced changes of GSH contents in fish cell lines: monochlorobimane (mBCl), 5-chloromethylfluorescein diacetate (CMFDA) and 7-amino-4-chloromethylcoumarin (CMAC-blue). Two cell lines were studied, the EPC line established from a skin tumour of carp Cyprinus carpio, and BF-2 cells established from fins of bluegill sunfish Lepomis macrochirus. The cells were exposed for 6 and 24 h to low cytotoxic concentrations of pro-oxidants including hydrogen peroxide, paraquat (PQ), copper and the GSH synthesis inhibitor, L-buthionine-SR-sulfoximine (BSO). The results indicate moderate differences in the GSH response between EPC and BF-2 cells, but distinct differences in the magnitude of the GSH response for the four pro-oxidants. Further, the choice of GSH dye can critically affect the results, with CMFDA appearing to be less specific for GSH than mBCl and CMAC-blue.