1. Cell Biology Section, National Institute of Dental and Craniofacial Research, Bethesda, Maryland
2. NASA/NIH Center for Three Dimensional Tissue Culture, National Institute of Child Health and Human Development, Bethesda, Maryland
3. George Washington University Medical Center, Washington, DC
4. Laboratory of Cellular and Molecular Biophysics, National Institute of Child Health and Human Development, Bethesda, Maryland, USA