1. Confocal Microscopy Group, Department of Molecular Cell Biology, University of Amsterdam, Pl. Muidergr. 14, 1018 TV, Amsterdam, The Netherlands,
2. Centre for Ultrafast Optical Science, University of Michigan, 2200 Bonisteel, IST Bldg RM 1006, Ann Arbor, MI 48109‐2099, U.S.A.,
3. Meridian Instruments, Inc., 2310 Science Parkway, Okemos, MI 48864, U.S.A.,
4. Department of Anatomy and Cell Biology, University of Michigan, Medical School, Ann Arbor, MI 48109‐0616, U.S.A.