What dosage of MPTP kills worms within three days? (I read an article and took notes on it, but I forgot to write down the dosage.) Also, how long should worms live if exposed to 1.2mM MPTP?
I would guess the article is Braungart et al, titled “Caenorhabditis elegans MPP+ Model of Parkinson’s Disease for High-Throughput Drug Screenings” - it was the first hit in a Google search, and the second hit was a review by Nikos Kourtis and Nektarios Tavernarakis that cited only the Brangart paper for the use of MPTP in elegans. If your paper wasn’t the Braungart paper, it might be one of the six papers that Google says cites it.
The relevant passage is probably this one:
Up to 340 microM (100 microg/ml) MPP+ no mobility reduction was observed, whereas higher concentrations [590 microM (175 microg/ml) to 840 microM (250 microg/ml)] resulted in an increasing amount of immobile animals (fig. 2). Viability of the animals was not notably affected up to 840 microM, whereas at 1.0 mM MPP+ 50% and at 1.5 mM eventually more than 90% of the animals died. At those higher MPP+ concentrations we also observed a developmental delay after 3 days, since animals treated with 1.0 mM MPP+ or 1.5 mM MPP+ had only reached larval stage 4 (L4) and stage 2–3 (L2–3), respectively. In comparison, untreated animals had already fully developed into egg-laying adults at this time point.
I would, however, keep in mind another passage from the same paper:
since loss of function of the dopaminergic neurons has been shown to cause a rather mild phenotype (30), other, yet unidentified side effects of MPP+ seem to be responsible for the motility defects and the lethality at high MPP+ concentrations.
Although we have not worked with MPTP, MPP+ has a very steep dose response curve. So small experimental parameter changes can change worm sensitivities. Studies by Sawin et al also suggest that all the DA neurons must be absent before a relatively strong behavioral phenotype is observed; we generally do not observe complete DA neuron cell death following exposure, unless the animal is very sick…and many other cells are affected. We have also found that small changes in composition, type of growth media, or strain of bacteria can change the sensitivity of C. elegans to toxins. Even synchronization methods and incubation times can modify the dose response curves.
I would like to thank everyone for answering my questions. Even though the questions probably seemed really simple/(dumb?), your answers really helped and pointed me in the right direction.
Just so you know, I got 3rd Grand in Fair II (basically, I had the 3rd best project among the categories of Medicine and Health, Microbiology, and Biochemistry.) and a special award. Unfortunately, only 1st and 2nd Grand qualify for the International Science Fair, but I will be going to State and will try to achieve the impossible to qualify for International.
I acknowledged you all in my Acknowledgments, but since you can’t see it, I thought I’d let you guys know how much I appreciate your help.