FIGURE 1.

Generation of intracellular H₂O₂ in human articular chondrocytes treated with menadione. Human articular chondrocytes were transduced with a baculovirus that expresses the H₂O₂ redox sensor Orp1-roGFP. The cells were treated with or without 25 μm menadione, and the images were collected and analyzed as detailed in the methods. Images from one representative cell for control and menadione-treated conditions are shown in heat map format. Scale bar, 5 μm. Quantified data from 10 individual cells were taken from three independent donors. The data are presented as means ± S.E. showing the relative mean 405:488 ratio. Asterisks represent significant differences comparing menadione-treated chondrocytes to DMSO control. *, p < 0.05 (t test). DIC, differential interference contrast.