SummaryWe examined structure and expression of the p53 and Rb genes in a C3HOS transplantable mouse model of osteosarcoma. The results were compared to analogous studies conducted with five human osteosarcoma cell lines. The p53 gene was found rearranged in the mouse tumour. The rearrangement mapped to the first intron region of the p53 gene and as a result, no p53 expression could be detected in C3HOS tumours. Using p53 genomic probes, we have detected the same rearrangement in the original radiation-induced tumour and the various clones that were isolated from it. Deletion and rearrangement of the p53 gene were also found in three out of five of the human osteosarcoma cell lines . No p53 expression could be detected in these three cell lines. In the affected human osteosarcoma cell lines, the rearrangement involved the first intron region. In addition, the mouse tumour was analysed for structural and expression changes in the Rb and the c-myc genes. Normal expression of both genes were detected in the murine tumour. Only one (Saos-2) human osteosarcoma cell line exhibited gross structural alteration in the retinoblastoma gene. The results suggest that the inactivation of p53 may be an important step in the development of osteosarcomas, and that a rearrangement affecting the first intron is common in osteosarcomas.
It is felt that stress fractures are caused by excessive, repetitive muscle forces acting across the affected bone. These fractures should be suspected in participants of athletic endeavors who present with a history of persistent, focal, activity-related pain regardless of their stage of physical conditioning. Associated physical findings are localized tenderness and swelling without evidence of a generalized systemic response. Bone scans and serial roentgenograms including specialized views may be required for documentation. Limitation of the athletic activity is the hallmark of the treatment program.
playing surfaces approximately six years ago brought with it a controversy regarding the effects of these ersatz turfs on player injury rates. Following an initial manufacturer's claim alleging injury reduction on its artificial turf as compared with grassy these synthetic playing surfaces have been either maligned or r staunchly supported by coaches, players and fans. Astro Turf, Tartan Turf, Poly Turf and natural grass football fields were studied to determine the effects of these surfaces on ( 1 ) player speed, (2) impact energy absorption, and (3) shoe traction. We believe this to be the first comparative study to evaluate these parameters on a variety of playing surfaces. MATERIAL AND METHODSAstro Turf&dquo;' (Monsanto) is a synthetic turf made of 1/2 inch nylon ribbon pile of 500 denier (blade thickness) on a polyester nylon mat which is double bonded to a 5/s inch closed cell nitrile rubber and polyvinyl-chlo-ride pad on an asphalt base (Figure 1). Tartan Turf&dquo;' (3M Company) is fabricated of 1/2 inch cut nylon pile of 40-60 denier on a knitted polyester backing which is double bonded to an open cell 5/s inch polyurethane pad over an asphalt base. Poly Turf&dquo;) (U.S. Bilt-Rite) is a }í6 inch polypropylene pile of 450 denier fibers matted on a polypropylene mat and single bonded to 1/2 inch closed cell nitrile rubber and polyvinylchloride pad over an asphalt base. The grass tested was a recently mowed, one year old sodded high-school football field. Timed sprintsSix randomly selected college football players were timed in a series of 40 yd straight line and slalom dashes on grass and Astro Turf. The slalom course had pylons placed at 10, 15, 25 and 30 yd positions. Each player ran each dash 3 times on both grass and Astro Turf and average times were determined (Fig. 2). On Astro Turf an average decrease of .206 seconds per player was noted on the straight sprint and a decrease of .241 seconds per man was recorded on the slalom course as compared with grass. The slower players, who were also the heavier ones, gained the greatest proportion of speed on the synthetic surfaces. Energy absorptionSince football is a collision sport, both between players as well as between combat-From the
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