Fig. 1. Photographs of isolated and perfused tubules taken using an inverted Zeiss
microscope equipped with Nomarski optics. Tubules were identified according to
their position within the nephron. The cellular boundaries in collecting ducts
appear sharper under the light microscope when compared to collecting tubules.
(A) Isolated and perfused ramification of collecting ducts. The pipette
arrangement consists, on the perfusion side (right), of a constricted holding
pipette and a single-barrelled perfusion pipette. On the left, a holding
pipette holds the tubule. Scale bar, 300 µm. (B) Isolated and perfused
collecting duct. Individual cells are clearly recognizable. The apical surface
of the intercalated cells possesses microvilli and bulges slightly into the
lumen of the tubule. Scale bar, 50 µm. (C) Isolated and perfused collecting
tubule. Note the perfusion pipette, which has been advanced into the lumen of
tubule. Scale bar, 50 µm. (D) Cellular impalement of a perfused collecting
tubule. Cells were impaled across the basal cell membrane with glass
microelectrodes. The tip of the microelectrode is below resolution limits.
Scale bar, 10 µm. cp, constriction pipette; el, electrode; hp, holding
pipette; ic, intercalated cell; lu, lumen; pp, perfusion pipette.
