Dr. John Davies is a Canadian doctor who's now looking into one of these problems. He leads the University of Toronto's Institute for Biomaterials and Biomedical Engineering, one of the world's top institutes looking into osteoporosis. Osteoporosis is known primarily as a disease that strikes the elderly and especially elderly women. Victims of this disease frequently don't know that they have it until it is too late. Gradually, over time, their bones become increasingly less dense, shrinking in both size and mass until they are so weak that a minor fall can lead to fractures or even broken bones.
Osteoporosis is a gradual thinning of bone tissue that strikes both aging humans and astronauts.
But in spite of the fact that NASA has instituted a comprehensive exercise routine for astronauts both before and during flight, it hasn't completely eradicated bone loss like it has eradicated muscle-loss. You can imagine that if the cells that eat bone eat more bone or that the cells that make bone make less bone the result is the same. A number of control samples will also be kept in Florida and in Canada for later comparison. They will be carried in a special bone substitute his lab invented and which is now produced by Millenium Biologix of Kingston, Ontario. Immediately before the Space Shuttle returns from orbit, astronauts will 'fix' the cultures, killing and permanently freezing the cells.