Medulloblastomas and primitive neuroectodermal tumors rarely contain polyomavirus DNA sequences.

To address the hypothesis that medulloblastoma or supratentorial primitive neuroectodermal tumor (sPNET) can arise through infection by polyomaviruses, we examined genomic DNA isolated from 15 primary medulloblastoma and 5 sPNET biopsy specimens and from 2 medulloblastoma cell lines for the presence of DNA sequences from the polyomaviruses simian virus 40 (SV40), JC virus, and BK virus. These polyomaviruses have oncogenic potential in animals, and their DNA sequences have been detected in other surveys of various solid tumors, including childhood brain tumors. The tumor DNA samples were analyzed by Southern blot hybridization of polymerase chain reaction products that employed probes designed to detect specific polyomavirus sequences. Neither JC virus nor BK virus DNA sequences were detected in any of the specimens. None of the primary medulloblastoma or sPNET specimens contained SV40 sequences. However, SV40 DNA coding and noncoding sequences were detected in the D283-Med (medulloblastoma) cell line. Immunocytochemical studies of D283-Med revealed nuclear expression of SV40 large T antigen. In contrast to childhood ependymomas and choroid plexus tumors, medulloblastomas and sPNETs infrequently express evidence of polyomavirus infection.

Epidemiologic analysis of injury in five years of Canadian professional rodeo.

Longitudinal studies of rodeo injuries are rare. We prospectively investigated injuries in professional rodeo in Canada over a 5-year period. Our specific interests included injury incidence density in specific rodeo events, risk factors such as past injury, and the incidence of head injury. Of 323 professional rodeos from 1995 through 1999, 63 rodeos provided a convenience sample. These rodeos were selected because the Canadian Professional Rodeo Sport Medicine Team was in attendance at these events, thus providing both competitor health care and data collection. Four hundred fifty-one injuries were reported during 30,564 competitor-exposures. The greatest injury frequency and injury incidence density were in the rough stock events (bull riding, bareback riding, and saddle bronc). Bull riding accounted for the greatest injury frequency (141) and incidence density (32.2 injuries per 1000 competitor-exposures). Bull riding had a relative injury risk of 1.32 when compared with bareback riding; bareback riding had a relative injury risk of 1.39 when compared with saddle bronc riding. Concussions accounted for 8.6% of all reported injuries. Concussions and other head injuries (65) were second only to knee injuries (76) in frequency of injury to specific body parts. This concussion frequency is higher than has previously been reported.