Among the first 8 patients enrolled in the study, we have observed unexpected and statistically significant changes in the unified PD rating scale part III (UPDRS part III) clinical evaluations for motor function in half of the patients tested. This test, however, is viewed as subjective. To more objectively and analytically score motor functions, biomechanical assessments of the subject's mobility, postural balance, upper extremity motor control and resting state tremor will be performed on the remaining eight PD patients receiving Leukine or placebo. These assessments will occur at baseline, between 7 and 8 weeks of drug treatment, and at 4-5 weeks after cessation of drug treatment. Motor function tests are designed to provide an objective, computer generated score as measured by patient performance on each test. To investigate a possible mechanism for changes in motor function observed within two weeks of therapy, testing for plasma/serum neurotransmitters will be performed to include glutamate, glutamine, serotonin, acetylcholine, gamma-aminobutyric acid (GABA), norepinephrine and epinephrine. These measures will be performed on the last cohort of PD patients of the study before initiation of treatment, 8 weeks after treatment is initiated and at 4 weeks after cessation of drug treatment. The tests will be evaluated by enzyme-linked immunosorbent assay (ELISA) or by ultra-performance liquid chromatography (UPLC). A decision on which assay will be done for which neurotransmitter will be based on sensitivity and standard curve measures. Relationships between neurotransmitter levels and motor function will be determined. These tests are in addition to current ongoing and approved laboratory tests. Eligibility requirements are unchanged from those currently imposed. Measures of motor function and serum/plasma neurotransmitter concentrations will also be completed 4-5 weeks after cessation of treatment. The notion of exploring neurotransmitters in this study is based on role in motor function that include fatigue, bowel, sexual dysfunction and mood changes that are also observed in PD as well as that GM-CSF has been shown to affect neurotransmitter levels (96). This range of listed neurotransmitters was not investigated in the first part of this study and will require limited additional blood and assay resources for the last part of the investigation.