Exposure of zebrafish embryos to solvents. The statistical issues

Current work Exposure of Zebrafish embryos –Various concentrations (0.002 – 4.0 % v/v) DMSO DMF Zebrafish embryo test –48hr exposure –Observe embryos at 24 & 48 hrs 1-2 hrs 24hrs 48hrs

Current Work II Observe developmental abnormalities –Coagulation –Oedema –Lack of circulation –Reduced/No heart beat Produce dose response curves Determine toxicology statistics –NOECs –LDCs –ECs

Current Work III Gene expression changes –Microarrays Microarray representing ~16,000 Zebrafish genes Dye coupled samples Ratio of CY 5 & CY 3 fluorescence

Statistical Issues II Microarrays –17,000+ pieces of data per array –Eliminate poor spots –Eliminate variation Dye effect, probe length, background, technical –Normalise data –Determine significance of any up or down regulation ANOVER Statistical programs (Genespring, R)

Statistical Issues III Problems –Lack replicates –False positives Use very small p values –Variation within arrays can be greater than variation between arrays Come out with different results every time

Torture the data long enough and they will confess to anything. (David G, Merck Co.)