The capacity to measure loads was also added to these new devices, but interaction with NASA personnel indicates that further refinements are required to produce accurate load estimates.The ISS provides an excellent research platform for studies that are relevant to missions outside low Earth orbit because the microgravity environment on the ISS presents a greater challenge to the musculoskeletal system than does a partial-gravity environment.At present, several key issues raised in the 1998 NRC report have not been addressed.For instance, the report recommended that genetically altered mice be used in flight experiments to investigate the molecular mechanisms of bone loss, yet these experiments have not been completed.In this model, traction applied to the tail of rodents elevates the lower extremities and eliminates generation of ground reaction forces.In Vitro Studies Bone cell culture experiments have been performed on space shuttle missions, Interpretation of these experiments is a challenge, because cells in culture behave much differently than cells embedded in bone.This task can be daunting because organisms must live for a sufficient time outside the effects of Earth’s gravity, in a state of free-fall.
To fully understand this influence of gravity, living systems must be studied by essentially eliminating the gravity variable.
Effects of Spaceflight Environment on the Structure and Function of Bone Bone loss during spaceflight appears to be due primarily to increased resorption in load-bearing regions of the skeleton.
There is also some evidence of a decrease in bone formation.
To meet its objectives, the AHB Panel focused on the following topics: (1) what is known about the risk and deleterious effects of spaceflight (and ground-based analogs) on the structure and function of the musculoskeletal (bone and muscle), sensory-motor, cardiovascular, pulmonary, endocrine, and immune systems, as well as how animals develop in the absence of gravity; (2) the effectiveness of the countermeasures currently used to maintain organ system homeostasis in the face of microgravity; (3) the knowledge gaps in understanding of the above topics that need to be addressed; (4) the research platforms needed to undertake new research initiatives in the next decade; (5) the overarching issues that have to be addressed in fostering cutting-edge, integrative research in humans and animals, and spanning multiple physiological systems, to generate future countermeasure strategies; and (6) the specific high-priority research initiatives that are needed to sharpen and advance the science knowledge necessary for progress in the next decade.
(It is important to note that certain topics that have a major impact across multiple physiological systems, such as nutrition, are in most cases not covered in this chapter, but rather in Chapter 7, which focuses on crosscutting issues.) Finally, in examining programmatic activities relevant to this chapter, and as discussed in the committee’s interim report to NASA, the AHB Panel was deeply concerned that NASA had severely reduced research initiatives in the life and physical sciences in the latter half of the past decade.