Wild-type C57BL/6J mice were obtained from Jackson Laboratory. Bid-deficient mice backcrossed on to a C57BL/6J background for at least 8 generations have been previously described [30] . Two-day-old mice were inoculated either perorally or intracranially with purified virus diluted in PBS. PO inoculations were delivered in a volume of 50 ml by passage of a polyethylene catheter 0.61 mm in diameter (BD) through the esophagus and into the stomach [90] . The inoculum contained 0.3% (vol/vol) green food coloring to allow the accuracy of delivery to be judged. IC inoculations were delivered to the left cerebral hemisphere in a volume of 5 ml using a Hamilton syringe and a 30-gauge needle (BD Biosciences) [91] . For analysis of viral virulence, mice were monitored for weight loss and symptoms of disease for 21 days. For survival experiments, mice were euthanized when found to be moribund (defined by rapid or shallow breathing, lethargy, or paralysis). For determination of viral titer and immunohistochemical staining, mice were euthanized at various intervals following inoculation and organs were resected. For analysis of virus growth, organs were collected into 1 ml of PBS and homogenized by freezing, thawing, and sonication. Viral titers in organ homogenates were determined by plaque assay using L929 cells [89] . For immunohistochemical staining, organs were fixed overnight in 10% formalin, followed by incubation in 70% ethanol. Fixed organs were embedded in paraffin, and 5-mm histological sections were prepared. Consecutive sections were stained with H&E for evaluation of histopathologic changes or processed for immunohistochemical detection of reovirus antigens or activated caspase-3 [11] . Animal husbandry and experimental procedures were performed in accordance with Public Health Service policy and the recommendations of the Association for Assessment and Accreditation of Laboratory Animal Care and approved by the Vanderbilt University School of Medicine Institutional Animal Care and Use Committee.  Effects of Pulsed Electromagnetic Fields on Human Osteoblastlike Cells (MG-63): A Pilot Study BACKGROUND: Although pulsed electromagnetic fields (PEMFs) are used to treat delayed unions and nonunions, their mechanisms of action are not completely clear. However, PEMFs are known to affect the expression of certain genes. QUESTIONS/PURPOSES: We asked (1) whether PEMFs affect gene expression in human osteoblastlike cells (MG63) in vitro, and (2) whether and to what extent stimulation by PEMFs induce cell proliferation and differentiation in MG-63 cultures. METHODS: We cultured two groups of MG63 cells. One group was treated with PEMFs for 18 hours whereas the second was maintained in the same culture condition without PEMFs (control). Gene expression was evaluated throughout cDNA microarray analysis containing 19,000 genes spanning a substantial fraction of the human genome. RESULTS: PEMFs induced the upregulation of important genes related to bone formation (HOXA10, AKT1), genes at the transductional level (CALM1, P2RX7), genes for cytoskeletal components (FN1, VCL), and collagenous (COL1A2) and noncollagenous (SPARC) matrix components. However, PEMF induced downregulation of genes related to the degradation of extracellular matrix (MMP-11, DUSP4). CONCLUSIONS AND CLINICAL RELEVANCE: PEMFs appear to induce cell proliferation and differentiation. Furthermore, PEMFs promote extracellular matrix production and mineralization while decreasing matrix degradation and absorption. Our data suggest specific mechanisms of the observed clinical effect of PEMFs, and thus specific approaches for use in regenerative medicine. PEMFs have been used for many years [44] . They reportedly are effective for treating nonunions [1, 7, 10] , delayed unions [1, 42, 44] , osteotomies [32] , avascular necrosis of the femoral head [5, 34] , bone grafts [11] , and spinal fusion [36] . Although the therapeutic properties of PEMFs are well known, the sequence of events by which electromagnetic stimulation can bring about its desirable effects on bone healing is not completely understood. PEMFs modify some important physiologic parameters of cells, such as proliferation, transduction, transcription, synthesis, and secretion of growth factors [24] . PEMFs induce cell proliferation in mitogen-stimulated lymphocytes [10] and improve IL-2 receptor expression and IL-2 use in lymphocytes from aged donors, which are characterized by defective production and use of this growth factor [10] . PEMF exposure induces cell proliferation in human osteoblasts and chondrocytes cultured in vitro [18, 20, 38, 44, 45] . PEMFs determine signal transduction by means of intracellular release of Ca 2+ leading to an increase in cytosolic Ca 2+ and an increase in activated cytoskeletal calmodulin [9] . PEMFs induce a dose-dependent increase in bone [2] and cartilage differentiation [2] [3] [4] 33] , and upregulation of mRNA expression of extracellular matrix molecules, proteoglycan, and Type II collagen [3] . The acceleration of chondrogenic differentiation is associated with increased expression of TGF-b1 mRNA and protein [4] , suggesting the stimulation of TGF-b1 may be a mechanism through which PEMFs affect complex tissue behavior such as cell differentiation and through which the effects of PEMFs may be amplified [4] . PEMFs also are postulated to act at a membrane level influencing signal transduction of several hormones or growth factors such as parathyroid hormone, IGF 2, and adenosine A2a, producing the amplification of their transmembrane receptors [1, 19, 21, 23, 31, 46] . Studies of single genes using RT-PCR suggest activation of osteocalcin, osteopontin, and TGF-b transcription during osteogenesis [22] and inhibition of cyclooxygenase 2 in synovial fibroblasts stimulated with TNFa or lipopolysaccharide [21] . A wide analysis of gene expression in cells exposed to PEMFs has not been performed: most studies focus on a few aspects of cell activities or they have been performed using different types of signals in different experimental conditions.