1 Medical Research Council Centre for Regenerative Medicine, University of Edinburgh, 5 Little France Drive, Edinburgh, EH16 4UU, Scotland, UK.
2 Institute of Medical Sciences, University of Aberdeen, Foresterhill, Aberdeen, AB25 2ZD, UK.
3 Department of Forensic Science, College of Criminal Justice, Sam Houston State University, Huntsville, TX, USA.
4 University of Maryland School of Medicine, Baltimore, MD, 21201, USA.
5 University of Bristol, Senate House, Tyndall Avenue, Bristol, BS8 1TH, UK.
6 Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, Glasgow, G61 1QH, UK.
7 Medical Research Council Centre for Regenerative Medicine, University of Edinburgh, 5 Little France Drive, Edinburgh, EH16 4UU, Scotland, UK. davehay@talktalk.net.