1. Wellcome Trust Centre for Cell-Matrix Research, School of Biological Sciences, University of Manchester, Stopford Building 2.205, Oxford Road, Manchester M13 9PT, U.K.
2. University of New Mexico School of Medicine, Department of Anatomy, Albuquerque, NM 87131, U.S.A.
3. Department of Medical Biophysics, University of Manchester, Stopford Building 2.205, Oxford Road, Manchester M13 9PT, U.K.