Dr. Harry A. Hogan, an associate professor in the Department of Mechanical Engineering at Texas A&M University, will give a talk on his musculoskeletal research Wednesday (Sept. 23) at 3:30 p.m. in Room 203 of the Zachry Engineering Center on campus.

Dr. Harry A. Hogan

Hogan’s talk, “Musculoskeletal Response to Simulated Microgravity and Exercise in an Adult Rat Animal Model,” is part of the Department of Biomedical Engineering’s seminar series.

Abstract
The adult hindlimb unloaded (HU) rat has gained wide acceptance and usage as a ground-based analog model for studying musculoskeletal effects of microgravity. This model is employed extensively in a wide range of investigations aimed at better understanding of the effects of long-term space flight on the musculoskeletal system. Obvious advantages of the animal model include the ability to tightly control experimental variables, to include destructive tissue assays, and to complete tests in a relatively short period of time, particularly compared to long duration astronaut missions. Current countermeasure strategies employed on the International Space Station (ISS) have not yet proven to be sufficiently effective, so important questions remain. We have conducted a series of studies in recent years using the rat HU model to seek greater insight into the various contributing factors. More specifically, we have used a muscle stimulation protocol that simulates resistive exercise as a countermeasure during HU and quantified the response of both muscle and bone. Primary muscle outcomes include muscle mass and strength.

Bone outcomes have been derived from peripheral Quantitative Computed Tomography (pQCT) scans as well as direct mechanical testing. Several pQCT variables show bone loss and recovery patterns that match analogous astronaut data impressively well. Results also show a dramatic mismatch in the recovery rates of muscle and bone; muscle recovers strength much more rapidly than bone. A series of studies have been conducted varying the details of the muscle stimulation protocol, and the consistent finding has been a very potent anabolic effect on bone but only modest effects on muscle. In order to gain better insight into possible reasons for the responses observed, companion studies were also conducted in which strain gages were implanted on the bone surfaces in order to quantify the strain characteristics experienced by the bone during the exercise protocols. The seminar will also include descriptions of some of the challenges unique to mechanical testing of specimens from the rat. In addition, an overview will be provided on related new projects and future directions.

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