Fig. 5

Mouse 4, Wedging vertebra with a conjoined rib (male mouse, 78 weeks old at the MRI and 80 weeks old at specimen Xray and histology) A-G: Soft X-ray images. A, B: specimen, C: 10 weeks, D: 13 weeks, E: 16 weeks, F: 22 weeks, and G: 27 weeks after birth. Steep sigmoid deformity was observed but did not develop during the observation period. Intervertebral spaces are difficult to see in the X-ray images of the living mouse. H, I: Histology of the wedging vertebra (H × 40, I: joint between vertebra and conjoined rib, × 100). In the adjacent intervertebral space, the NP, AF, and CEP were observed. Conjoined ribs have a large RH and no cortex or GP. A thick fibrous structure occupies the space between the vertebra and the RH. J, K; T1-weighted and T2-weighted MR images. In both images, the abnormal RH is well demarcated. High-intensity cranial and caudal intervertebral disc space is observed on T1WI, and the bright high-intensity area on T2WI consistently indicates the presence of the NP. Histologically, the region between the rib heads and vertebrae is filled with fibrous connective tissue. This region is observed at high intensity in both T1WI and T2WI