The supplementary motor area contributes to the timing of the anticipatory postural adjustment during step initiation in participants with and without Parkinson's disease.

The supplementary motor area (SMA) is thought to contribute to the generation of anticipatory postural adjustments (APAs, which act to stabilize supporting body segments prior to movement), but its precise role remains unclear. In addition, participants with Parkinson's disease (PD) exhibit impaired function of the SMA as well as decreased amplitudes and altered timing of the APA during step initiation, but the contribution of the SMA to these impairments also remains unclear. To determine how the SMA contributes to generating the APA and to the impaired APAs of participants with PD, we examined the voluntary steps of eight participants with PD and eight participants without PD, before and after disrupting the SMA and dorsolateral premotor cortex (dlPMC), in separate sessions, with 1-Hz repetitive transcranial magnetic stimulation (rTMS). Both groups exhibited decreased durations of their APAs after rTMS over the SMA but not over the dlPMC. Peak amplitudes of the APAs were unaffected by rTMS to either site. The symptom severity of the participants with PD positively correlated with the extent that rTMS over the SMA affected the durations of their APAs. The results suggest that the SMA contributes to the timing of the APA and that participants with PD exhibit impaired timing of their APAs, in part, due to progressive dysfunction of circuits associated with the SMA.

Overexpression of glia maturation factor in C6 cells promotes differentiation and activates superoxide dismutase.

In order to evaluate the intracellular function of glia maturation factor (GMF), we overexpressed GMF in C6 rat glioma cells using two methods: stable transfection using the pcDNA3 plasmid, and transient transfection using replication-defective human adenovirus. With both methods, C6 cells transfected with GMF and overexpressing the protein exhibit a lower saturation density in culture compared to non-transfected or vector alone controls. Transfected cells also exhibit morphological differentiation as shown by the outgrowth of cell processes. When inoculated into nude mice, transfected cells are less tumorigenic than controls, and express the mature astrocytic marker glial fibrillary acidic protein. In tissue culture, transfected cells show a 3.5-fold increase in CuZn-dependent superoxide dismutase (CuZnSOD) activity. Western blot analysis reveals a 3.5-fold increase in CuZnSOD protein, suggesting an induction of the enzyme. In view of recent findings that reactive oxygen species (ROS) and the antioxidant enzymes are intricately involved in key physiologic processes such as proliferation, differentiation and apoptosis, the study raises the possibility that CuZnSOD may be a mediator of GMF function.