Microscopic investigation of structure and function in living epithelial tissues.

In this paper we shall illustrate the utility of direct microscopic methods for studying living epithelia. Beginning with an exposition on the available strategies for visualization of unstained biological materials, the rationale that leads to the choice of differential interference-contrast optics for examination of epithelia is illustrated. Findings from toad urinary bladder, Necturus gallbladder, and rabbit cortical collecting tubule are reviewed. Emphasis on renal structures is provided with a report on work in progress on proximal tubule volume regulation and on structural examination of the isolated perfused macula densa. Conclusions are drawn with respect to the advantages and shortcomings of discussed optical methods and with respect to the choice of model epithelia.