wild type cd1 embryos were harvested , staged and stained by wholemount in situ hybridization using established methods , . measurement of palates before dissection and after staining confirmed that no significant shrinkage occurred ( data not shown ) . palatal explants were cultured ( 37c , 5% co2 ) using the trowell technique   in dmem ( sigma ) , 20 u / ml pen - strep ( gibcobrl ) , 10% fbs ( gibcobrl ) , 50 mm transferrin ( sigma ) and 150 g / ml ascorbic acid ( sigma ) . for cutting and inhibitor experiments , serum - free advanced d - mem / f12 ( gibcobrl ) supplemented as above , was used . su5402 ( calbiochem ) was diluted in medium from 10 mm in dmso stock ; cyclopamine ( sigma ) from 20 mg / ml - ethanol stock . explants placed in a minimum volume of pbs in wells cut into 1% agarose were digitally imaged under a stereo dissecting microscope and measurements made using the ruler in imagej ( from the nih imagej website ) calibrated with a micrometer slide . dimensions of fixed material were within 8% of those of fresh , unfixed material ( data not shown ) . simulations of reaction - diffusion patterning were performed using the javascript in ref   with the parameters du=0.03 , d u=0.02 , a u=0.1 , b u=0.06 , c u=0 , fmax=0.2 , dv= 0.06 , d v=0.5 , a v=0.1 , b v=+0 , c v=0.2 , gmax=0.5 . wild type cd1 embryos were harvested , staged and stained by wholemount in situ hybridization using established methods , . measurement of palates before dissection and after staining confirmed that no significant shrinkage occurred ( data not shown ) . palatal explants were cultured ( 37c , 5% co2 ) using the trowell technique   in dmem ( sigma ) , 20 u / ml pen - strep ( gibcobrl ) , 10% fbs ( gibcobrl ) , 50 mm transferrin ( sigma ) and 150 g / ml ascorbic acid ( sigma ) . for cutting and inhibitor experiments , serum - free advanced d - mem / f12 ( gibcobrl ) supplemented as above , su5402 ( calbiochem ) was diluted in medium from 10 mm in dmso stock ; cyclopamine ( sigma ) from 20 mg / ml - ethanol stock . explants placed in a minimum volume of pbs in wells cut into 1% agarose were digitally imaged under a stereo dissecting microscope and measurements made using the ruler in imagej ( from the nih imagej website ) calibrated with a micrometer slide . dimensions of fixed material were within 8% of those of fresh , unfixed material ( data not shown ) . simulations of reaction - diffusion patterning were performed using the javascript in ref   with the parameters du=0.03 , d u=0.02 , a u=0.1 , b u=0.06 , c u=0 , fmax=0.2 , dv= 0.06 , d v=0.5 , a v=0.1 , b v=+0 , c v=0.2 , gmax=0.5 .