Photographs (15–20) were taken at 2500× of transverse ultrathin sections of tibial nerve 5 mm from the sciatic notch. The g ratio was calculated for each myelinated fiber (axon diameter see more divided by diameter of the axon and myelin sheath). Statistical difference was measured using Mann Whitney U test. A montage of ultrathin sections (×1000) was made and the number of myelinated fibers counted. For unmyelinated fibers,

30%–40% of each nerve was photographed (×5000). The ratio myelinated:unmyelinated fibers was measured and the total for each nerve/root was multiplied by total myelin fiber count, as described elsewhere (Coggeshall et al., 1997). For counts of Schwann cells and macrophages, ultrathin sections were mounted on film, nuclei counted in every third field and multiplied by 3 to generate totals. Statistical difference was measured using Mann Whitney

U test. Macrophage migration was assessed using 6.5 mm Transwells with 5 μm pores (Corning Costar; see Supplemental Information). Data are presented as arithmetic mean ± standard error of the mean (SEM) unless otherwise stated. Statistical significance was estimated by Student’s t test, two-way ANOVA, or Mann-Whitney U-test. This work was funded by Wellcome Trust Program and project grants to K.R.J. and R. Mirsky and an MRC project grant to K.R.J. and R. Mirsky. The research leading to these results has received funding BMS-777607 cell line from the European Community’s Seventh Framework Program (FP7/2007-2013) under grant agreement No. HEALTH-F2-2008-201535. P.J.A.-F. and B.J. were funded by PhD studentships from the MRC and Wellcome Trust, respectively. A.W. is supported by a Ramon y Cajal fellowship from the Spanish Ministry of Science and a PFIS grant (PS09/00094)

from the Instituto Carlos III. The London Research Institute (A. Behrens) is funded by Cancer Research UK. G.R is supported by BBSRC grants (S20299, B/D009537/1) and Wellcome Trust grant (WT088646MA). We thank P.N. Anderson for help with in vivo injections of c-Jun old virus, D.B. Parkinson for animal husbandry, M. Tillo for pilot experiments and providing mRNA samples, B. Kalmer for help with motoneuron backfilling, K. Malgapo for carrying out axonal degeneration experiments, and G. Menendez and G. Schiavo for materials and help with the microfluidic chambers. We thank M.L. Feltri and L. Wrabetz for the gift of P0-CRE mice. “
“The recent discovery of a new class of retinal photoreceptors, melanopsin-expressing intrinsically photosensitive retinal ganglion cells (ipRGCs), revived interest in the role played by light in regulation of certain animal behaviors.