Charge immobilization of skeletal muscle Na+ channels: role of residues in the inactivation linker.

We investigated structural determinants of fast inactivation and deactivation in sodium channels by comparing ionic flux and charge movement in skeletal muscle channels, using mutations of DIII-DIV linker charges. Charge altering and substituting mutations at K-1317, K-1318 depolarized the g(V) curve but hyperpolarized the h(infinity) curve. Charge reversal and substitution at this locus reduced the apparent voltage sensitivity of open- and closed-state fast inactivation.

Methods for studying voltage-gated sodium channels in heterologous expression systems.

The discovery that oocytes of the frog Xenopus laevis can be induced to express working membrane ion channels by introducing channel mRNA into their cytoplasm (heterologous expression) has greatly impacted the field of ion channel physiology. With the addition of site-directed mutagenesis techniques, the functional consequences of virtually any mutation can now be specifically and easily assessed. Here, we describe an effective procedure for investigating cardiac sodium channel gating (hNaV1.

Temperature-sensitive defects in paramyotonia congenita mutants R1448C and T1313M.

The biophysical origins of paramyotonia congenita and its exacerbation in cold temperatures were examined. Human skeletal muscle voltage-gated sodium channels were expressed in Xenopus oocytes and macroscopic currents were recorded from cell-attached patches. Wild-type (hNaV1.

Cellular localization of calcium, heavy metals, and metallothionein in lobster (Homarus americanus) hepatopancreas.

This investigation combines confocal microscopy with the cation-specific fluorescent dyes Fluo-3 and BTC-5N to localize calcium and heavy metals along the length of intact lobster (Homarus americanus) hepatopancreatic tubules and isolated cells. A metallothionein-specific antibody, developed in mollusks with cross-reactivity in crustaceans, showed the tissue-specific occurrence of this metal-binding protein in several organ systems in lobster and in single cell types isolated from lobster hepatopancreas. Individual lobster hepatopancreatic epithelial cell types were separated into pure single cell type suspensions for confocal and antibody experiments.

Taxonomic identification of microorganisms by capture and intrinsic fluorescence detection.

Quick and accurate detection of microbial contamination is accomplished by a unique combination of leading edge technologies described in this and the accompanying article. Microbe capture chips, used with a prototype fluorescence detector, are capable of statistically sampling the environment for pathogens (including spores), identifying the specific pathogens/exotoxins, and determining cell viability where appropriate.