PhD, University of Wisconsin, Madison, WI, 1972
Postdoctoral, National Institutes of Health
Understanding vibration injury of neural and vascular tissues from hand-held powered tools and the effects of actual and simulated spaceflight unloading on neuromuscular structure and function
Vibration from powered tools can cause debilitating neurodegeneration and vascular dysfunction in the human hand. We have developed a rat-tail vibration model for studying the injury process. The tail contains nerves, arteries, bones, tendons and muscles similar to those in the human hand. Shockwave vibration from impact tools, like the illustrated riveting hammer, produce the most rapid and severe damage. We are examining the damaging effects of vibration energy in the Hz and kHz frequency ranges. Vibration destroys peripheral nerve fibers and leads to loss of normal sensations. Arteries exhibit disruption of vascular smooth muscle cells, endothelial cells and, very likely, the vessel innervation, accounting for the hypercontraction vasospastic-response to cold. In addition to understanding the mechanisms of injury, the protective effects of antivibration glove materials are being evaluated for worker safety.
For many years, we studied the cellular basis for skeletal muscle weakness, fatigue, dyscoordination, and delayed-onset soreness experienced by humans returning from spaceflight to Earth. The experimental models included both rats and humans. Adult rats were flown NASA Space Shuttle missions and Russian Cosmos biosatellite flights. Humans were orbited in the Space Shuttle and for many months on the International Space Station. Antigravity muscles were biopsied before and after flight, demonstrating that exercise was not effective in preventing atrophy, and muscle fibers were susceptible to tearing injury upon return to gravity loading on Earth. Ground-based models were also studied, including hindlimb suspension unloading of rats and for humans, one leg unloading with crutches and chronic bedrest without loading. Prevention of muscle deterioration during prolonged unloading will require countermeasures that deal with the multifactorial nature of the problem.
Currently, we have developed a mouse pediatric model of limb deformities, such as club foot, for elucidating the mechanisms of defect formation, rehabilitation and prevention. These findings are expected to translate to rehabilitating children with musculoskeletal defects.