Parkinson's disease(PD) affects roughly ten million people across the globe, yet it is still incurable and not fully comprehensible. Identifying specific causes of the disease can help the database of knowledge being collected to fight the disease by inducing better preventative steps or inspiring discoveries of cures through medication. It is known that heavy metals are a potential factor in causing PD, but the specific heavy metals have not been identified. Since Cadmium is a heavy metal present in the Earth's crust, natural ground/surface water, fertilizers, batteries, food, and in tobacco, it could be a cause of PD over accumulated exposure. To test if Cd can causc PD, Caenorhabditis elegans, or roundworms, were used as a model organism based on their inexpensive maintenance, short life cycles, and reliable model in neurotoxicology. PD is a dopaminergic neuron degeneration disease with symptoms of impaired motor skills, such as characteristic hand tremors. C. elegans have inner labial I (ILT) neurons, also motor neurons, to represent the dopamine neurons in humans.

Since heavy metals are known causes of Parkinson's disease, Cadmium is prevalent in the environment, and C. elegans are reliable model organisms for neurotoxicology, I hypothesized accumulated exposure to Cd should cause impaired mobility and neurodegeneration of the ILT neurons in C. elegans to indicate Cd is a potential cause of Parkinson's disease.

The C. elegans were continuously cultured by making sterile agar plates-by boiling bottles of nematode agar to pour on plates and then incubate with E. coli for food- and taking chunks of agar from 2 week old, healthy cultures onto the new, sterile plates. To test the effect of Cd on the C. elegans IL1 neurons, I first did a mobility study by videoing worms movement in environments with different levels of Cd (OuM, 0.175uM, 0.35LM, and 0.7MM) on days 1, 5, and 10. I used a camera-Imaging Source DMK 23UP1300- mounted on a microscope-AmScope FM690T- and analyzed the videos with Image) to calculate average speeds (mm/sec) and thrashing rates (head movement/sec) to compare across the different levels of exposure. Then, the worms were dyed with Dil dye, a IL1 fluorescent labeler, for 24 hours before being transferred onto 2% agar plates with a nichrome loop to take pictures with the camera under the fluorescent light from the microscope. To measure the neurodegeneration the highest points of intensity on the head of the neuron were compared to analyze and graph.

Adjustments had to be made to bring Cadmium concentrations below high mortality rates for extended exposure with final concentrations being 0.1750M, 0.35uM and 0.70M. The mobility tests revealed there is a shift from the control worms based on Cd exposures. On day 10, the average speed of the control (OuM) group was 0.185 mm/sec which was lower than the highest Cd concentration (0.7uM) at 0.305 mm/sec. The thrashing of the worm- the number of head movements/second-on day 10 for the control was 2.037 bcats/sec while thc 0.7HM exposed worms was 3.672 bcats/scc. The speed and thrashing rates across all worms increased over time as the worms grew bigger and stronger. However, the Cd concentrations differed from the control groups as they aged and adds uncertainty to the data. The mean CTAF of the control group was 4.752 with a 0.906 standard deviation. The CTAF at 0.175uM and 0.35uM Cd concentrations decreased from the control to 3.552 and 3.653 with standard deviations of 1.878 and 3.047 respectively. These variations in the results from the 0.175uM and 0.35uM indicate a source of error. However, the data analysis from the 0.7uM exposed worms had a mean CTAF of 1.874 and lower standard deviation of 0.367. While the 0.175uM and 0.35uM groups have high standard deviations indicating inconclusive data, the low standard deviations in the OuM and 0.7uM data increases confidence of the neurodegeneration present from the Cd exposure. Based on changes in mobility and ILI neuron dye fluorescence of Cadmium exposed C. elegan worms in the control and 0.7MM exposures, there is an indication that exposure to Cadmium affects mobility and causes degeneration of motor neurons. As previously stated, PD is a dopaminergic neural degenerative disease that results in impaired mobility. This initial study indicates that Cd has the potential to cause degeneration of motor neurons such as those dopamine, motor, neurons affected in PD in humans.