title: Direct visualization of epithelial morphology in the living amphibian urinary bladder.
abstract: Differential interference-contrast microscopy has been applied to the study of amphibian urinary bladders, in vitro. It is demonstrated that well-resolved images can be obtained with little loss of tissue viability. Direct observations have been made on the structure of microvilli, the distribution of mitochondria in the mitochondria-rich cells, and the patency of lateral intercellular spaces. It is noted that the effective viscosity of cytoplasm is very high--that it is apparently a gel in which there is no Brownian movement of organelles. The frequency, shape, and pattern of distribution of granular and mitochondria-rich cells is determined for the commonly studied varieties of Bufo marinus. Bladders from Colombian toads contain more and larger mitochondria-rich cells than do those of the Dominican variety. There is no specific arrangement of cell-cell contacts to suggest a structural basis for cooperativeness of action. Finally, a longitudinal study of osmotically-induced changes in the structure of the "tight" or "limiting" junctions establishes the validity of previous findings by electron microscopy.
mesh_terms: D000818:Animals; D002024:Bufo marinus; D003593:Cytoplasm / Q000502:physiology; D004848:Epithelium / Q000648:ultrastructure*; D007365:Intercellular Junctions / Q000648:ultrastructure; D008857:Microscopy, Interference; D008871:Microvilli / Q000648:ultrastructure; D008928:Mitochondria / Q000648:ultrastructure; D001743:Urinary Bladder / Q000648:ultrastructure*; D014783:Viscosity