Figure 2.
Changes in proportions of dIgA-HRP containing vacuoles, tubules, and cup-shaped vesicles in polarized, filter-grown cells on transfer to 37°C. Polarized, filter-grown cells were loaded with dIgA-HRP at 20°C and then transferred to 37°C for 0, 15, and 30 min. With time at 37°C the proportion of vacuoles decreases, the proportion of tubules increases and then decreases, and the proportion of cup-shaped vesicles increases. The increase in cup-shaped vesicles is twice as rapid in the second 15-min interval. The data were obtained by estimating the surface area of all dIgA-HRP–containing elements within equivalent areas of cytoplasm in cells incubated for the 0–30-min time intervals and then assigning them to four groups; elements of less than 60-nm- diam, vesicles of 100-nm-diam (i.e., cup-shaped vesicles), tubules of 100-nm-diam, and elements of 0.1–0.3-μm-diam (vacuoles). Elements of less than 60 nm in diameter comprised 74% of the total DAB-positive structures.