channels, regulators of protein synthesis, and interactions of extracellular matrix and membrane proteins with the cytoskeleton.

The total expenditure for the Biomedical Research and Countermeasure (BR&C) program in FY 1999 was about $2.805 million distributed among approximately 18 projects in the NASA Research Announcement (NRA) and National Space Biomedical Research Institute (NSBRI) programs (see Table 4.1). Current funding is distributed as approximately 60 percent for human studies and 40 percent for animal studies. About nine investigations with at least a partial emphasis on muscle physiology are supported by the NRA process ($1.801 million), and there are six main projects in the NSBRI program ($1.087 million).

The human studies focus primarily on countermeasures, including the utility of lower-body negative pressure (LBNP) and resistance exercise. Three human flight protocols funded in FY 1999 involved a pre-post muscle biopsy study, a test of foot function during spaceflight, and an examination of protein turnover during spaceflight.

Investigators in NASA centers, NSBRI, and NRA extramural programs collaborate on exercise testing during bed rest, rodent hindlimb unloading (exercise, pharmacological and hormonal countermeasures), calcium signaling in human skeletal muscle cultures, and gravity effects on sarcolemmal structure and function. Parabolic flights producing brief periods of reduced gravity are used to probe rapid changes in muscle cell membranes.

The First Biennial Space Biomedical Investigators’ Workshop in 1999 demonstrated that excellent mechanistic research is being conducted on skeletal muscle that is in line with the 1998 Strategy report recommendations (NASA and USRA, 1999; NRC, 1998). The presentations included fundamental studies on fiber-type differentiation, multiple signaling pathways, hormonal regulation, and control of fiber-type gene expression. Investigators pursued novel genetic and biochemical strategies for combating muscle atrophy during rodent hindlimb unloading, such as growth hormone (GH)/insulin-like growth factor-I (IGF-I) gene therapy in genetically engineered mice and pharmacologic blockage of the ubiquitin degradation pathway. The inclusion of genetically modified organisms in the muscle research program is consistent with the Strategy report recommendation to exploit these animal models.

The Fundamental Biology Research Program (FBRP) also supports through the NRA process muscle physiology studies that explore fundamental mechanisms. Five of these investigations probe the signaling of muscle atrophy, skeletal muscle artery adaptation, muscle growth and repair, insulin signal