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Figure 1. Schematic diagram, immunolight micrographs, and quantitative scoring of synovitis in the synovitis-induced and non-induced TMJs. (a) Schematic diagram of the sagittal section of the central portion of the rat TMJ. The joint compartment is divided into upper and lower compartments (UC, LC) by the articular disc (Disc), and the synovial membrane lines parts of these compartments. The boxes indicate the areas described in the RESULTS section of this paper. (b-e) Light micrographs of serial 10-µm-thick sagittal sections of the posterior portion that faces the upper joint compartment of the synovitis-induced (b,c) and non-induced (d,e) rat TMJs, which were immunostained with either the anti-nitrotyrosine (NT) (b,d) or anti-iNOS (c,e) antibody. (b,d) Nitrotyrosine immunoreactivity is expressed at a higher level in the grade 2 (G2; synovial lining is 
7 layers thick) synovitis of the synovitis-induced TMJ (synov-TMJ) (b) than in the grade 0 (G0; synovial lining is 1–3 layers thick) synovitis of the non-forced TMJ (non-TMJ) (d). F: synovial fold. (c,e) Increased iNOS immunoreactivity is seen in the G2 synovitis of the synovitis-induced TMJ (c), as compared with the grade 0 synovitis of the non-induced TMJ (e). Hematoxylin staining. Original magnification: x400 (b-e). Bar = 25 µm (b-e). (f) Scoring the thickness of the synovial cell layers of the synovitis-induced and non-induced rat TMJs. The thickness of the synovial cell layer (synovitis) is graded as follows: grade 0, 1–3 layers; grade 2, 4–6 layers; grade 2, 7 layers. The numbers of joints that were graded are indicated. LC: lower joint compartment. UC: upper joint compartment.
