Electrokinetic shape changes of cochlear outer hair cells

Rapid mechanical changes have been associated with electrical activity in a variety of non-muscle excitable cells. Recently, mechanical changes have been reported in cochlear hair cells. Here we describe electrically evoked mechanical changes in isolated cochlear outer hair cells (OHCs) with characteristics which suggest that direct electrokinetic phenomena are implicated in the response. OHCs make up one of two mechanosensitive hair cell populations in the mammalian cochlea; their role may be to modulate the micromechanical properties of the hearing organ through mechanical feedback mechanisms. In the experiments described here, we applied sinusoidally modulated electrical potentials across isolated OHCs; this produced oscillatory elongation and shortening of the cells and oscillatory displacements of intracellular organelles. The movements were a function of the direction and strength of the electrical field, were inversely related to the ionic concentration of the medium, and occurred in the presence of metabolic uncouplers. The cylindrical shape of the OHCs and the presence of a system of membranes within the cytoplasm--laminated cisternae--may provide the anatomical substrate for electrokinetic phenomena such as electro-osmosis.     

Effect of body weight on free fatty acid release by adipose tissuein vitro

Zusammenfassung Die Absonderung freier Fettsäuren aus dem Fettgewebe wurde bei verschieden alten Ratten (1. Gruppe unter 100 g, 2. Gruppe 180–300 g und 3. Gruppe 380–500 g)in vitro ermittelt. Für das Fettgewebe der Nebenhoden ergab sich in der 1. Gruppe die stärkste Absonderung freier Fettsäuren und deren wirksamste Förderung durch Epinephrin. Hingegen war der Gehalt an 3-Glyceriden in der 1. Gruppe am niedrigsten, in der 3. Gruppe am höchsten.

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Supported in part by grant G-13084 from the National Science Foundation.     

In vitro release of free fatty acids by adipose tissue in young and old nephrotic rats

Zusammenfassung Bei nephrotischen Ratten verschiedenen Alters wurdein vitro die Abgabe freier Fettsäuren aus dem Fettgewebe untersucht. Bei jungen Tieren war letztere am grössten, der Fettgehalt des Gewebes am niedrigsten. Diese Resultate stimmen mit an normalen Tieren gewonnenen überein und stützen die Ansicht, dass die nephrotische Lipämie nicht durch Mobilisation des Depotfettes entsteht.

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Supported in part by grant G-13084 from the National Science Foundation.     

Pixel switching of epitaxial Pd/YHx/CaF2 switchable mirrors

Exposure of rare-earth films to hydrogen can induce a metal-insulator transition, accompanied by pronounced optical changes. This 'switchable mirror' effect has received considerable attention from theoretical, experimental and technological points of view. Most systems use polycrystalline films, but the synthesis of yttrium-based epitaxial switchable mirrors has also been reported. The latter form an extended self-organized ridge network during initial hydrogen loading, which results in the creation of micrometre-sized triangular domains. Here we observe homogeneous and essentially independent optical switching of individual domains in epitaxial switchable mirrors during hydrogen absorption. The optical switching is accompanied by topographical changes as the domains sequentially expand and contract; the ridges block lateral hydrogen diffusion and serve as a microscopic lubricant for the domain oscillations. We observe the correlated changes in topology and optical properties using in situ atomic force and optical microscopy. Single-domain phase switching is not observed in polycrystalline films, which are optically homogeneous. The ability to generate a tunable, dense pattern of switchable pixels is of technological relevance for solid-state displays based on switchable mirrors.