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Cortical lawns prepared from sea urchin eggs have offered a robust in vitro system for study of regulated exocytosis and membrane fusion events since their introduction by Vacquier almost 40 years ago (Vacquier in Dev Biol 43:62-74, 1975). Lawns have been imaged by phase contrast, darkfield, differential interference contrast, and electron microscopy. Quantification of exocytosis kinetics has been achieved primarily by light scattering assays. We present simple differential interference contrast image analysis procedures for quantifying the kinetics and extent of exocytosis in cortical lawns using an open vessel that allows rapid solvent equilibration and modification. These preparations maintain the architecture of the original cortices, allow for cytological and immunocytochemical analyses, and permit quantification of variation within and between lawns. When combined, these methods can shed light on factors controlling the rate of secretion in a spatially relevant cellular context. We additionally provide a subroutine for IGOR Pro® that converts raw data from line scans of cortical lawns into kinetic profiles of exocytosis. Rapid image acquisition reveals spatial variations in time of initiation of individual granule fusion events with the plasma membrane not previously reported.

To explore an intrinsic bladder defense mechanism we examined interaction between Escherichia coli and bacterial size particles (polystyrene latex balls) and the vesical luminal surface by scanning and transmission electron microscopy. The bacteria and the latex spheres were held in folds of the cellular luminal surface. Voiding (bladder contraction) resulted in the entrapment of a large number of bacteria and particles by these microplicae, with their apparent engulfment in vesicles below the cell surface. Some urine was probably contained in the folds and vesicles, thus reducing the volume of residual urine in the bladder. Since leukocytes were rarely seen in the model studied they presumably do not play an immediate role against acute infection in the normal bladder. These observations indicate that fixation of bacteria to the mucosa is 1 step in the mechanism whereby the normally functioning bladder resists infection.

Infants with posterior urethral valves may seem to have diverse and unrelated symptoms when, in fact, the clinical findings are all related to the primary effect of the valves during various stages of early growth. In some, prenatal urinary obstruction leads to such severe oligohydramnios that the fetus is stillborn. Others, somewhat less affected, are born alive but have severe respiratory distress from hypoplastic (stiff) lungs and die of respiratory problems. Still others can be associated with massive ascites and urinomas, and be stillborn or die soon after birth. In less severe cases the neonates may have unexplained respiratory distress with pneumomediastinum or pneumothorax as the only indication of obstructive urologic disease with deficient urinary output. Urinomas or ascites may later develop beyond the neonatal period as the post-natal obstructive effects of the valves accumulate and the urinary system ruptures and decompresses itself. Finally when the urinary system does not decompress itself, the back pressure can lead to rapid and progressive renal damage until the kidneys can no longer concentrate urine and lose water. The infant becomes dry, acidotic and paradoxically at this stage, puts out large quantities of dilute urine. Physicians caring for infants should be highly suspicious of posterior urethral valves in any male infant with unexplained respiratory distress or metabolic derangements, abdominal distension or flank masses.

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