2. Participants with a clinically significant or unstable medical or surgical condition that, in the opinion of the investigator, might preclude safe completion of the study or might affect the results of the study. These include conditions causing significant central nervous system (CNS) or autonomic dysfunction, including congestive heart failure, recent (<6 months) myocardial infarct, cardiopulmonary disease, severe, uncontrolled hypertension, thrombocytopenia (<50 x 10(9)/L), severe anemia (<8g/dl), immunocompromised state, liver or kidney disease (creatinine >2.3mg/dl), uncontrolled diabetes mellitus (HbA1c >10g%), alcoholism, amyloidosis, uncontrolled hypothyroidism, sympathectomy, unstable peripheral neuropathies, concurrent infections, orthopedic problems that compromise mobility and activity of daily living, cerebrovascular accidents, neurotoxin or neuroactive drug exposure, parkinsonism due to drugs (including neuroleptics, alpha-methyldopa, reserpine, metoclopramide).