Figure 1.

Measurement frames for Safranin O staining of the knee joint cartilage. After elimination of green tones and transformation of all red tones into grey tones, the staining intensity (a measure of the proteoglycan content) was determined in the following layers: S, superficial layer; M, middle layer; D, deep layer; and C, calcified cartilage.

Roth et al. Arthritis Research & Therapy 2005 7:R677-R686   doi:10.1186/ar1725
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