Cellular telephone use and time trends in brain tumour mortality in Switzerland from 1969 to 2002

A rising concern exists that with the widespread use of mobile communication technologies, the incidence of brain tumours may increase. On the basis of data from the Swiss national mortality registry from 1969 to 2002, annual age-standardized brain tumour mortality rates per 100,000 person-years were calculated using the European standard population. Time trend analyses were performed by the Poisson regression for six different age groups in men and women separately. The study period was divided into two intervals: before and after 1987, when the analogue mobile technology was introduced in Switzerland. Age-standardized brain tumour mortality rates ranged between 3.7 and 6.7 for men and 2.5 and 4.4 for women per 100,000 person-years. For the whole study period, a significant increase in brain tumour mortality was observed for men and women in the older age groups (60-74 and 75+ years) but not in the younger ones in whom mobile phone use was more prevalent. Time trend analyses restricted to data from 1987 onwards revealed relatively stable brain tumour mortality rates in all age groups. For instance, the annual change in brain tumour mortality rate for the 45-59-year age group was -0.3% (95% confidence interval: -1.7; 1.1) for men and -0.4% (95% confidence interval:-2.2; 1.3) for women. We conclude that after the introduction of mobile phone technology in Switzerland, brain tumour mortality rates remained stable in all age groups. Our results suggest that mobile phone use is not a strong risk factor in the short term for mortality from brain tumours. Ecological analyses like this, however, are limited in their ability to reveal potentially small increases in risk for diseases with a long latency period.

Compression Loading Induced Cellular Stress Response of Intervertebral Disc Cells in Organ Culture

Introduction: Mechanical stress is often associated to interverterbal disc (IVD) degeneration and the effect of mechanical loading on IVD has been studied and reviewed.1,2 Previously, expression of heat shock proteins, HSP70 and HSP27 has been found in pathological discs.3 However, there is no direct evidence on whether IVD cells respond to the mechanical loading by expression of HSPs. The objective of this study is to investigate the stress response of IVD cells during compressive loading in an organ culture. Materials and Methods: Fresh adult bovine caudal discs were cultured with compressive loading applied at physiological range. Effect of loading type (static and dynamic) and repeated loading (2 hours per day for 2 days) were studied. Nucleus pulposus (NP) and annulus fibrosus (AF) of the IVD were retrieved at different time points: right after loading and right after resting. Positive control discs were heat shocked (43°C). Cell activity was assessed and expression of stress response genes (HSP70 and HSF1) and matrix remodeling genes (ACAN, COL2, COL1, ADAMTS4, MMP3 and MMP13) were studied. Results: Cell activity was maintained in all groups. Both NP and AF expressed high level of HSP70 in heat shock groups, confirming their expression in response to stress. In NP, expression of HSP70 was up-regulated after static loading and dynamic loading with higher fold change was observed after static loading. During repeated loading, HSP70 appeared to be upregulated right after loading and decreased after resting. Such trend was not observed in AF and HSF1 levels. Expressions of matrix remodeling genes did not change significantly with loading except ADAMTS4 decreased in AF during static loading. Conclusion: This study demonstrated that NP cells upregulate expression of HSP70 in response to loading induced stress without changing cell activity and matrix remodeling significantly. Acknowledgments: This project was funded by AO Spine (AOSPN) (grant number: SRN_2011_14) and a fellowship exchange award by AO Spine Scientific Research Network (SRN).