Figure 7.

Ca²⁺-dependent shortening of contractile structures in an A7r5 cell grown for 3 days on a cross-linked (PAH/PAA)₄PAH-coated coverslips. Cells were treated with (A) DMSO carrier alone (control) and (B) DMSO containing A23187 (at a final concentration of 20 μM in the culture media) for 5 min. The cells were fixed and stained with a mouse anti-α-actinin monoclonal primary antibody and an Alexa Fluor 568 goat antimouse IgM secondary antibody. Shortening of the stress fiber-like structures was assessed by measuring the distances between α-actinin foci. Insets show enlarged examples of positions assigned to the α-actinin foci in control (A, inset) and A23187-treated (B, inset) cells. (C) The histogram shows the mean ± SEM distances between α-actinin foci in the cells shown in (A) A and (B) B (n = 50 measurements per cell). The difference in visibility of the nucleus is due to the more flattened nature of the contractile cell and slightly different planes of focus for the images. Scale bars represent 20 μm in images A and B and 1 μm in the insets.