It is well documented that injury to bone marrow is followed by an osteogenic phase that precedes the complete tissue regeneration. We have recently shown that postablation healing of bone marrow in rat tibiae is associated with a systemic increase in osteogenesis. It was hypothesized that a growth factor(s) with an effect on osteogenic cells is produced in the healing limb, is transferred to the blood circulation, and enhances osteogenesis systemically. To test growth factor production, healing bone marrow-conditioned medium was prepared with tissue separated from rat tibias during the osteogenic phase and assayed for enhancement of mitogenic activity in culture of osteogenic rat osteosarcoma cells (ROS 17/2). Partial purification of healing bone marrow-conditioned medium-derived growth factor(s) consisted of gel filtration on Sephadex G-25, boiling, chromatography on heparin-Sepharose, and gel filtration on Sephadex G-75. Mitogenic activity eluted in the void volume of the Sephadex G-25 column (mol wt greater than 5,000). Potent activity resolved from heparin-Sepharose with PBS, and on filtration by Sephadex G-75 this activity recovered in 3 peaks with mol wt estimates of 35,000, 19,000, and less than 10,000. The partially purified factor also showed considerable stimulatory effect on DNA synthesis in osteoblastic fetal rat calvarial cells and on in vitro elongation of fetal long bone; it had only a small effect on nonosteoblastic ROS and fetal rat calvarial cells. These data indicate that healing bone marrow produces growth factor activity with a preferential effect on osteogenic cells. It is suggested that local growth factors have a role as mediators in the sequence of events whereby bone marrow expresses its osteogenic potential. During postablation healing of bone marrow these factors may also function as systemic promoters to osteogenic cells.
המאמר הנוכחי מניח כי רוב ההגדרות של המושג תעשייה בעלת "טכנולוגיה גבוהה" מבוססות על מאפיין מגדיר אחד בלבד. אנו טוענים כי הגדרה נאותה חייבת להתבסס על תפיסה רב-ממדית של מושג הטכנולוגיה, ומציגים גישה מתודולוגית לסיווג ענפי תעשייה "לטיפוסים טכנולוגיים" על סמך ההיבטים השונים של הטכנולוגיה שהם מייצגים. בהסתמך על מתודולוגיה זו, אנו מגישים בדיקה אמפירית מבוסס על ענפי-משנה של התעשייה הישראלית (ברמת שלוש ספרות בסווג האחיד של ענפי התעשייה). השימוש בניתוח אשכולות ובניתוח שונות מאפשר לנו להראות כי לפרופילים הטכנולוגיים שהוגדרו יש מאפיינים תעשייתיים, משותפים.
In this case the permanent successor was so radiographically indistinct due to the inflammatory process that this three-year-old Arab boy might have been classified as having congenital absence of the mandibular left first premolar, if the mass had not been sent for histological section. The clinical implications are identical.
