Figure 1.

HA significantly decreases clonal colony size by H₁R activation. Crystal violet-stained clones were used to measure colony area and the number of cells. (A-D) Representative composite pictures of colonies with the indicated treatment. The insets show a magnification of the center of each colony. Note that cell size seems uniform, but in 100 μM HA + chlorpheniramine (Chlorph.) the cells are more separated from each other. Scale bar = 250 μm for the low magnification and 100 μm for the insets. (E) Areas (mm²) quantified from crystal violet-stained clones. HA reduces the colony’s area in a significant manner with respect to control cultures; this effect was prevented by the H₁R antagonist chlorpheniramine (Chlorph.), but not by cimetidine (Cimet.). **P <0.01 and ***P <0.001 versus Control; ^aP <0.01 versus 100 μM HA. (F) Cell counting from the stained clones, showing a non-significant decrease in the total number of cells after HA treatment and a significant increase with HA + Chlorph. *P <0.05 versus Control; ***P <0.001 versus Control; ^bP <0.001 versus clorpherinamine-HA. Results are the mean ± SEM from three independent experiments made in duplicate. HA, histamine; H₁R, histamine receptor type 1; SEM, standard error of the mean.