Figure 2.

Substratum concentration regulates transient membrane protrusion in CHO cells. Quantitative analysis was performed to assay transient membrane protrusion in CHO cells. Cells were plated onto intermediate (1), high (2), and very high (3) concentrations of fibronectin for 2–4 h before analysis. (A) Examples of serum-starved cells used in transient membrane protrusion analysis (performed as described in MATERIALS AND METHODS). Images were taken at 15-s intervals for 5 min. Subsequent images were overlaid and pixels undergoing a change in gray level value of 5% or more were scored as positive (white pixels on black background in far right column). This was done for all images in the stack and results were quantified as described in MATERIALS AND METHODS. (B) Summarized results from three experiments using transient membrane protrusion analysis. Gray bars represent data from cells plated in CCMI and white bars represent data from serum-starved cells plated in serum-free media. The transient protrusion index is the average number of pixels per cell undergoing a 5% or more change in gray level value per 15-s interval. Data are the average of three experiments and error bars represent the SD. Transient membrane protrusion is maximal at an intermediate fibronectin concentration and reduced on higher concentrations.