Fig. 6

Chondrifying cartilage canals. Cyan: Two-photon-excited fluorescence (TPEF), Glowing red: Second harmonic generation (SHG). a The cartilage canal is chondrifying from its distal terminus. The chondrifying segment consists of degenerated blood vessels, debris and chondrocyte-like cells. More proximally, the canal has capillaries filled with blood cells giving intense TPEF. The SHG signal of the adjacent cartilage matrix is stronger around the segment contianing capillaries. b Higher magnification of the transition between the two segments of the canal. c A different chondrifying canal. The chondrifying segment (asterisk) is partly converted to cartilage and is several millimeters in length. Foci with intense SHG signal are located adjacent to the entire canal, but their number decreases more distally. d Higher magnification of the transition to the segment containing capillaries (only TPEF shown). Occasional chondrocyte-like cells are observed in this segment of the canal (arrow head). 25×–focusing objective was used to produce all images. The bars equal 250 μm in a and c and 50 μm in b and d