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Final Attempt

We found that as we increased the dosage of lead acetate, the frequency of abnormalities also increased (Graph 2). We also concluded that lead causes morphological and neural defects, including undistinguishable regions in the brain, blood pooling in the tail, upper-back and brain region (Figures 4,5,6,7). This was similar to the neural defects that Anwer discovered, such as hydrocephalus and cranioschisis. We hypothesize that the lead interfered with the signaling pathways of the Pax transcription factors and FGF-8 paracrine factors to cause the neural deformities. FGF-8 is thought to create the brain boundry between the mid- and hind-brain. This barrier allows pressure to build in the brain cavity which is linked to brain development. Since lead is believed to interfere with FGF-8 signaling, it is possible that this barrier does not form properly in lead exposed chicks causing them to have underdeveloped brains. If we were to repeat this experiment we would look into the interactions between the Pax and FGF-8 factors and lead acetate. We would try to enhance transcription of the Pax or FGF-8 to observe if a surplus of the factors could compensate for the effects of lead. Anwer et al. studied how zinc compensated for the damage caused by lead to chick embryos. If we had the opportunity to repeat this experiment we would also want to stain for neural crest cells to see if they had migrated away from the neural tube. We could decipher if the cells were migrating away from the neural tube or if the lead acetate somehow disrupted the migration of the cells to prevent normal neural and brain formation.
The significance of our results is that lead causes blood pooling and underdevelopment in young chick embryos. Various studies of lead exposure on other organisms in the embryonic stage, such as the chicken, have been very helpful in drawing parallels to human lead poisoning. The chicken can be successfully utilized in experiments to determine the level of lead exposure that leads to severe damage and defects. Lead poising affects the entire human body particularly the nervous system, the gastrointestinal tract, and the blood-forming tissues. Children with lead poising often have severe brain damage that leads to blindness, deafness, convulsions, coma, and eventually death (Britannica).

© Cebra-Thomas, 2001

Last Modified: 31 May 2001

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