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Summary Cultured L cells were found previously to have an oscillating membrane potential. Current-voltage (I–V) curves were measured during these oscillations. TwoI–V curves were recorded, one at the maximum and one at the minimum of oscillations. Each curve is nonlinear, and when they are subtracted from one another, the result gives theI–V curve for the K+ current producing oscillations. ThisIK–V curve is zero for -85 to -90mV and saturates for positive and high negative membrane potentials. When the external K+ is increased theI–V curve is shifted and its zero current potential is reduced. The K+ zero current potential follows a Nernst relation when plotted against the external K+ concentration. TheIK–V curves all have a similar shape at different K+ concentrations, showing a saturation on each side of the zero current potential. The results can be explained satisfactorily in term of a carrier model for K+ ions.

Single-channel patch-clamp experiments were performed on MDCK cells in order to characterize the ionic channels participating in regulatory volume decrease (RVD). Subconfluent layers of cultured cells were exposed to a hypotonic medium (150 mOsm), and the membrane currents at the single-channel level were measured in cell-attached experiments. The results indicate that MDCK cells respond to a hypotonic swelling by activating several different ionic conductances. In particular, a potassium and a chloride channel appeared in the recordings more frequently than other channels, and this allowed a more detailed study of their properties in the inside-out configuration of the patch-clamp technique. The potassium channel had a linear I/V curve with a unitary conductance of 24±4 pS in symmetrical K+ concentrations (145 mm). It was highly selective for K+ ions vs. Na- ions: PNa/PK<0.04. The time course of its open probability (P0)showed that the cells responded to the hypotonic shock with a rapid activation of this channel. This state of high activity was maintained during the first minute of hypotonicity. The chloride channel participating in RVD was an outward-rectifying channel: outward slope conductance of 63.3+ 4.7 pS and inward slope conductance of 26.1±4.9 pS. It was permeable to both Cl- and NO3-and its maximal activation after the hypotonic shock was reached after several seconds (between 30 and 100 sec). The activity of this anionic channel did not depend on cytoplasmic calcium concentration. Quinine acted as a rapid blocker of both channels when applied to the cytoplasmic side of the membrane. In both cases, 1 mm quinine reversibly reduced single-channel current amplitudes by 20 to 30%. These results indicate that MDCK cells responded to a hypotonic swelling by an early activation of highly selective potassium conductances and a delayed activation of anionic conductances. These data are in good agreement with the changes of membrane potential measured during RVD.

The article discusses the Québec Breast Cancer Screening Program (PQDCS) and presents advice for clinicians who need to help their patients make informed decisions about participating in the program. Topics include the efficacy of mammograms for early cancer detection, informational materials provided to prospective participants in the PQDCS, and overdiagnosis of breast cancer.

• Metastatic cardiac tamponade was the presenting manifestation of a colonic carcinoma. The patient's condition improved after surgical treatment and shows no sign of recurrence of pericardial effusion after more than eight months of systemic chemotherapy. Metastatic pericardial effusions and their treatment are discussed.(Arch Intern Med 1984;144:622-623)

• Minocycline hydrochloride hepatotoxic effect occurred in one patient. Unlike the usual histologic features of tetracycline-induced hepatic injury, fatty metamorphosis was predominantly macrovesicular. The patient recovered when drug therapy was withdrawn. Close observation of liver function variables is recommended in patients treated with high parenteral doses of minocycline, particularly in cases of pregnancy or renal disease.(Arch Intern Med 1984;144:1491-1492)

Features the needle-punched nonwoven based three-dimensional structures produced without any threads. Description of a textile machine used in manufacturing the structures; Characteristics of the structures; Details of a manufacturing process involved in producing the structures.