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		The connection between face and limb chondrogenesis is important because it may tell us something about anterior/posterior patterning in chick embryos. If the face cells react more like the fore limbs than the hind limbs, we may be able to hypothesize that this difference is due to the fact that the face and the fore limbs are more anterior in the embryo, while the hind limbs are more posterior. Ryan Smith, Gloria DiLullo and Michael Higgins (Bio 306, 1998) performed an experiment which examined the effects of exogenous factors on wing and hind limb chondrogenesis. They tested FGF, calcium (a well known requirement for healthy bones and cartilage), fibronectin, and poly-l-lysine (poly cation that stimulates cell condensation) (Smith et al. 1998). Although Smith WAS able to discern whether or not each of the exogenous factors induced or repressed cartilage nodule formation, he DID NOT get quantifiable results. If craniofacial mesenchyme and limb mesenchyme respond to the factors in a similar ways, it would imply that the same chondrogenesis mechanisms are at work in both regions. For example, if poly-l-lysine induces chondrogenesis in both the limbs and the craniofacial region, whereas RAstimulates face and wing/fore limb chondrogenesis, we can possibly say that they both affect chondrocytes in the same way. Conversely, if RA inhibits hind limb and stimulates face chondrogenesis, then we would propose that different chondrogenic mechanisms are acting. Studying chondrogenesis may lead to further studies which look for the effects of growth factors on chondrogenesis in humans. Specifically, we hope that our research may someday be a stepping stone in the search for possible therapeutic treatments for deficiency or over- production of cartilage.