Preservation of the knee joint in limb salvage of osteosarcoma in the proximal tibia. A case report.

A 12-year-old boy with osteosarcoma in the proximal tibia underwent a successful limb-saving operation with preservation of the epiphyseal and articular cartilage of the proximal tibia as a result of his remarkable response to chemotherapy. There was no evidence of tumour invasion to the adjacent physis, as demonstrated by image findings. The bone defect was reconstructed using autoclaved autogeneous bone with a vascularized fibula. The patient exhibits excellent function of the affected limb, and the knee joint remains disease-free 55 months postoperatively.

Alterations of expression and distribution of the Ca(2+)-storing proteins in endo/sarcoplasmic reticulum during differentiation of rat cardiomyocytes.

Calsequestrin (CS) is a Ca(2+)-storing protein present in the sarcoplasmic reticulum (SR) of muscle cells. Calreticulin (CR) is a functional homologue of CS in the endoplasmic reticulum (ER) of non-muscle cells. During skeletal muscle differentiation, the major Ca(2+)-storing protein switches from CR to CS. To study the regulation of CS and CR expression in cardiomyocytes and the morphological maturation of Ca(2+)-storing sites in the SR, we examined rat hearts at various developmental stages and cultured adult cardiomyocytes by Western blotting and immunocytochemical analyses. CR was expressed in 14-day-old fetal rat cardiomyocytes, but disappeared gradually by 1 week after birth. CR reappeared in dedifferentiated adult cardiomyocytes in long-term culture. On Western blots, the concentration of CS in the heart did not change during development. Immunostaining for CS in fetal or neonatal rat cardiomyocytes revealed as scattered dots. CS-positive structures increased with development, and the regular striated distribution of CS at Z lines was completed around 3 weeks after birth. These results indicated that (1) CR expression is downregulated during cardiac differentiation and upregulated during dedifferentiation, and (2) maturation of SR involves the organization of CS-positive structure after birth.