DOUBLE-BLIND TEST OF MAGNETIC-FIELD EFFECTS ON NEURITE OUTGROWTH

Previous work reported that nerve growth factor-stimulated neurite out growth in PC-12 cells could be altered by exposure to parallel alterna ting current (AC) and direct current (DC) magnetic fields under a vari ety of exposure conditions, producing results that are consistent with the predictions of the ion parametric resonance (IPR) model. The cred ibility of these results, considered extraordinary by some scientists, could be strengthened if the cell response were found to persist unde r alternate assay conditions. We replaced part of our standard assay p rocedure with a double blind procedure. This new procedure obscured 1) whether a particular set of dishes of cells was exposed or not. and 2 ) which individual dish was in which exposure sq stem. The goal was to determine whether the previously observed responses of PC-12 cells to magnetic fields would be sufficiently robust to decode the imposed bl inding, thereby removing any question of experimenter bias in reported results. We placed three coded dishes of cells in each of two otherwi se identical exposure systems, one not energized and one energized to produce exposure conditions predicted to maximally suppress neurite ou tgrowth (B-dc of 36.6 mu T, parallel 45 Hz AC of 23.8 mu T rms). Each of the six dishes were recoded before assay to further obscure the exp osure identity of any individual dish. The combined results of four di stinct runs of these double blind experiments unequivocally demonstrat ed that 1) there was a clear, distinctive, repeatable consistency with the actual energization of the exposure systems and location of each dish, and with the predictions of the IPR model; 2) only the explicitl y stated experimental variables influenced the experiment, and 3) the reported response of the cells was very improbably due to chance(P =.0 00024). (C) 1998 Wiley-Liss, Inc.