Stretch-activated single K+ channels account for whole-cell currents elicited by swelling

Functionally significant stretch-activated ion channels have been clearly identified in excitable cells. Although single-channel studies suggest their expression in other cell types, their activity in the whole-cell configuration has not been shown. This discrepancy makes their physiological significance doubtful and suggests that their mechanical activation is artifactual. Possible roles for these molecules in nonexcitable cells are acute cell-volume regulation and, in epithelial cells, the complex adjustment of ion fluxes across individual cell membranes when the rate of transepithelial transport changes. We report the results of experiments on isolated epithelial cells expressing in the basolateral membrane stretch-activated K+ channels demonstrable by the cell-attached patch-clamp technique. In these cells, reversible whole-cell currents were elicited by both isosmotic and hyposmotic cell swelling. Cation selectivity and block by inorganic agents were the same for single-channel and whole-cell currents, indicating that the same entity underlies single-channel and whole-cell currents and that the single-channel events are not artifactual. In these cells, when the rate of apical-membrane NaCl entry increases, the cell Na+ content and volume also increase, stimulating the Na+,K+-ATPase at the basolateral membrane, i.e., both Na+ extrusion and K+ uptake increase. We speculate that, under these conditions, the parallel activation of basolateral K+ channels (by the swelling) elevates conductive K+ loss, tending to maintain the cell K+ content constant (“pump-leak parallelism”). This study describes a physiologically relevant stretch-activated channel, at both the single-channel and whole-cell levels, in a nonneural cell type.

Stimulation of mouse mammary tumor virus superantigen expression by an intragenic enhancer.

The mechanisms regulating expression of mouse mammary tumor virus (MMTV)-encoded superantigens from the viral sag gene are largely unknown, due to problems with detection and quantification of these low-abundance proteins. To study the expression and regulation of the MMTV sag gene, we have developed a sensitive and quantitative reporter gene assay based on a recombinant superantigen-human placental alkaline phosphatase fusion protein. High sag-reporter expression in Ba/F3, an early B-lymphoid cell line, depends on enhancers in either of the viral long terminal repeats (LTRs) and is largely independent of promoters in the 5' LTR. The same enhancer region is also required for general expression of MMTV genes from the 5' LTR. The enhancer was mapped to a 548-bp fragment of the MMTV LTR lying within sag and shown to be sufficient to stimulate expression from a heterologous simian virus 40 promoter. No enhancer activity of the MMTV LTR was observed in XC sarcoma cells, which are permissive for MMTV. Our results demonstrate a major role for this enhancer in MMTV gene expression in early B-lymphoid cells.

Simulation of nutrient loss from soils due to rainfall acidity /

Bibliography: p. 43-44.

Plant uptake of cadmium from phosphate fertilizer /

Mode of access: Internet.

Les églises protestantes d'Alsace pendant la révolution (1789-1802) : esquisse historique /

Includes bibliographical references.

Centralgebiet der Schweiz enthalten auf Blatt 13,

I. Emmen- und Schlierengegenden, von F. J. Kaufmann.--II. Systematisches Verzeichniss der Kreide- und Tertiär-Versteinerungen der Umgegend von Thun, von K. Mayer-Eymar.--III. Geologische Beschreibung der Kalk- und Schiefergebirge zwischen dem Reuss- und Kienthal, von C. Moesch.--IV. Das Aarmassiv (mittlerer Theil) von A. Baltzer.

Die fossilen Korallen des Österreichungarischen Miocäns /

"Vorgelegt in der sitzung am 23 märz 1871"

Strassburger zunft- und polizei-verordnungen des 14. und 15. jahrhunderts.

"Vorwort" signed: Rud. Reuss.

Beschreibung merkwürkiger Bücher aus der Universitäts-Bibliothek zu Tübingen vom Jahr 1468-1477, und zweyer hebräischen Fragmente.

Bibliographical footnotes.

Bau- und Kunstdenkmäler Thüringens.

Edited by Paul Lehfeldt.

Der Frühlingszaun : Geschichten und Bilder /

Mode of access: Internet.

La Bible : traduction nouvelle avec introductions et commentaires /

Vol. numbering from spine.

Adolf von Thadden-Trieglaff; ein Lebensbild gezeichnet nach Erinnerungen seiner Kinder und Freunde.

Mode of access: Internet.

La constitution civile du clergé et la crise religieuse en Alsace (1790-1795) d'après des documents en partie inédits ...

At head of title: Rodolphe Reuss.

Ioannis Calvini opera quae supersunt omnia /

In Goddard Library copy v. 1-2, which are bound together and made to appear uniform with this set, are of the separate ed. of the Institutio and have title: Ioannis Calvini Institutio religionis Christianae ... Editio iterata ex operibus Calvini separatim recusa. Brunsvigae : C.A. Schwetschke, 1869 (Brunsvigae : M. Bruhn). Series title, Corpus Reformatorum, wanting. (Cf. OCLC #9335951.)