The immunolocalization of periostin, previously termed osteoblast-specific factor 2, was investigated in developing long bones of 17-day-old fetal mice and of 1-, 2-, 3-and 8-week-old mice at the light and electron microscopic levels. Fetal femurs showed innnunoreactions for periostin in the periosteum, perichondrium, articular surface of the epiphyscal cartilage, joint ligaments, and fascias of surrounding muscles. In particular, intense immunoreactivity for periostin was found in the fibrous layer of the periosteum and perichondrium. At postnatal 1-and 2-weeks, in contrast, the immunoreactivity was restricted to the periosteum and thick fascias of surrounding muscles wl1e11 compared with the fetal bones. lmmunoclectron microscopic observation of the periosteum demonstrated immunoreaction products for periostin at the junction of periosteal fibroblasts and collagen bundles, suggesting its competence in the cell-to-matrix interaction. Mice at 3 and 8 weeks, unlike 2-week-old mice, showed a periostin-innnunoreaction dominantly in the osteoblastic layer but not in the fibroblastic layer of the periosteum. Furthermore, the perichondrium and fascias of surrounding muscles were devoid of innnunoreaction. Thus, periostin was confirmed to be widely distributed in bone and concomitant tissues at the fetal stage. As mice grew, however, its immunoreactivity gradually came to be restricted to the osteoblastic layer of the periosteum. Our findings suggest that periostin acts at the site of the cell-to-matrix interaction in periosteum, fascias, and joint ligament during morphogenesis of these tissues.Periostin, originally reported as osteoblast-specific and a computer analysis of its amino acid sequence factor 2 by Takeshita er al. (23), is a disulfate linked has revealed an assumed complex protein structure 90kDa protein secreted by osteoblasts. This protein with four repeats of a characteristic domain. The has been isolated in previous studies aimed at identiamino acid sequence of periostin has a high homolfying novel genes expressed specifically in the osteoogy with Fasciclin I that is expressed in the central blasts. Mouse periostin consists of 811 amino acids, nervous system of insects, serving in neural cell-tocell contact (1, 24). Therefore, periostin has been re-_ _ _ garded as a member of Fasciclin I family including fifigleig£50302?Sfggfiegflztul?keI);1Si1_tl:i: §ila;]fD(:]i Big-113 (21), Algal-CAM (7), and midline fasciclin ' Y p (6), mimicking a function of Fasciclin I. Unlike Fas-

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Thirty-three cases of acute closed rupture of the Achilles tendon were treated by per-cutaneous repair from 1988 through 1993. Subjects consisted of 20 males and 13 females with a mean age of 40 years. The follow-up period was a mean 38.3 months. The ruptured Achilles tendon occurred as a sports injury in 32 cases, including volleyball 16, badminton 6, running 4 and others 6. Mean operatiye time was 22 minutes. Mean duration of cast immobilization after surgery was 40 days. Full weight-bearing gait was started at a mean of 57.9 days. Regarding postoperative range of motion, the mean angle of dorsiflexion was 14.0 degrees and 51.4 degrees of plantarflexion. Compared with the intact site, both types of flexion decreased but all cases regained normal ADL. Three cases reruptured and 5 cases developed nerve injuries as a postoperative complication. In 66.7% of males, sporting activity returned to the preoperative level, but many females tended to become less active in sports following the injury. We concluded that this method achieved excellent results but attention should be paid for nerve injury and postoperative rehabilitation.