The effects of XXXX on cartilage differentiation in micromass cultures of @entity1573 facial primordia and the relationship to a specific @entity154 .

@entity154 @entity4878 @entity71078 @entity1573 @entity1968 @entity554
@entity4878 produce @entity154 in @entity1573 embryos. Outgrowth of the frontonasal mass with accompanying cartilage differentiation and pattern formation is inhibited. In contrast, the development of the mandibular primordia that give rise to the lower beak proceeds normally. To investigate whether the upper beak defect is based on the inhibition of cartilage differentiation specifically in the frontonasal mass, the effects of @entity4878 on chondrogenesis in micromass (high density) cultures of cells from facial primordia have been studied. When either 10(-6) M @entity1968 or 10(-8) M (E)-4-[2-(5,6,7,8-tetrahydro-5,5,8,8-tetramethyl-2-napthalenyl-1- propenyl]benzoic acid ( @entity71078 ; a stable @entity554 ) is added to the culture medium, cartilage differentiation is inhibited. Both frontonasal mass and mandible cultures are equally affected. The concentration of @entity71078 found in both facial primordia in vivo, after a treatment that produces the defect, is also about 10(-8) M. This rules out preferential accumulation of the @entity554 by the frontonasal mass as an explanation for the defect. In fact, the concentration of @entity554 found in vivo, should, from the culture studies, be sufficient to markedly inhibit chondrogenesis in both the frontonasal mass and mandibles. The effects of exposure to @entity4878 in the intact face appear to be different to those in culture. Furthermore, when cells from @entity554 -treated facial primordia are cultured in micromass, the extent and pattern of chondrogenesis in frontonasal mass cultures is identical to that of cells from untreated primordia. Cartilage differentiation in mandible cultures is slightly affected. These findings suggest that @entity4878 do not produce the specific @entity154 by directly interfering with cartilage differentiation.
