ABSTRACT
Syndactyly is a common congenital hand anomaly that may occur after exposure to teratogens. We have developed an in vitro model of syndactyly to investigate the molecular mechanisms underlying this malformation of digit development. Retinoic acid, which regulates pattern formation in vertebrate limb development and is associated with teratogenic malformations, was used in the development of this syndactyly model system. Pregnant Swiss-Webster mice were given retinoic acid by oral gavage on days 10 and 11 of embryonic development (E10 and E11, respectively). The mice were sacrificed on gestational days 13 and 17 (E13, E17) and immediately postnatally (PN). The fetuses were removed and the forelimbs dissected under the operating microscope. The E13 limbs were cultured for 4 days (E13+4) in an organ culture system using a serumless, chemically defined medium. The E17, PN, and E13+4 forelimbs were critically examined for malformations of digit separation and digit development. Retinoic acid-induced fetal mouse forelimb syndactyly was observed in all the groups; 81 percent of E17 limbs, 75 percent of PN limbs, and 77 percent of E13+4 limbs had syndactyly. The morphology of the digital malformations was similar in the E17, PN, and E13+4 limbs. This in vitro model permits further studies to characterize the molecular changes that occur during the development of a congenital hand anomaly.
Subject(s)
Disease Models, Animal , Syndactyly/embryology , Animals , Female , Forelimb/embryology , Mice , Organ Culture Techniques , Pregnancy , Teratogens , TretinoinABSTRACT
Planned exposures of rodents to diesel exhaust required development of an exhaust generation and delivery system flexible enough to accommodate varied experimental designs. The features of the exposure system built to meet these needs are summarized. Essential aspects including both the exhaust dilution and delivery system and the computer monitoring and control functions are described. During the first 29 weeks of a study with target particle concentrations of 350, 3500, and 7000 micrograms/m3, the achieved values were 310, 3360, and 6830 micrograms/m3 with coefficients of variation of 23, 10, and 9%, respectively. The system has now operated reliably for more than 24 months.
