Expression of Veratrum alkaloid teratogenicity in the mouse.

Jervine, a steroidal alkaloid found as a minor constituent in the teratogenic range plant Veratrum californicum, has produced similar terata in sheep, rabbit, hamster, and chick, although the sensitivity to the alkaloid varies in the different species. Sprague Dawley rats and Swiss Webster mice are relatively insensitive. The aim of this study was to determine the teratogenic potential of jervine in three strains of mice and to ascertain if the response is strain dependent. One strain, Swiss N:GP(S), was retested since a Swiss Webster strain had been found previously to be jervine-resistant. In addition, we tested C57BL/6J and A/J, which are known to differ in their response to the teratogenic action of steroids and vitamin A. Mice were treated by gavage with single doses of jervine (70, 150, or 300 mg/kg body weight) on either day 8, 9, or 10 of gestation. Jervine was teratogenic to C57BL/6J and A/J mice but not to N:GP(S). The induced terata included cleft lip with or without cleft palate, isolated cleft palate, mandibular micrognathia or agnathia, and limb malformations. Fetal teratogenicity and maternal and fetal toxicity were highly correlated. The prevalence of each defect and fetal death was a function of strain, dose, and time of treatment. Maternal death was higher in C57BL/6J than in A/J mice. Although some of the terata were similar, the response pattern between strains was different from corticosteroids and vitamin A for both sensitive period and the strain dose response. An effect on differentiation of chondrocyte precursors may account for many of the defects, but an earlier lethal effect on differentiation of neural crest cells or precordal mesenchyme may also occur.

Genetic variation in spontaneous and diphenylhydantoin-induced craniofacial malformations in mice.

The mouse strain CL/Fr has been produced by selection for high frequency of cleft lip. It is also sensitive to induction of cleft palate by glucocorticoids, as are its A strain relatives. "Star" strain is free of spontaneous clefts, and is resistant to glucocorticoid teratogenic effects. CL/Fr is also sensitive to toxic effects (80% death at 25 mg/kg) of diphenylhydantoin (DPH), whereas Star is not. Reciprocal crosses between CL/Fr and Star parents were followed for three generations of back-crossing to CL/Fr, with treatment by chronic subcutaneous (SC) DPH injection (20 mg/kg daily from day 0 of pregnancy). Two patterns of response were observed for facial clefts. Primary palate clefts (CL, CLP, lip scars) were not affected by DPH treatment, and showed regression on % CL/Fr genome suggestive of a two- or three-locus recessive effect with the sensitive alleles from CL/Fr. Secondary palate clefts and open eyelids, considered as a group as relatively late developmental defects, showed a pattern suggestive of a dominant gene which increases risk of malformation in DPH-treated embryos, expressed in the crosses, but not in the absence of treatment or in the presence of the full "Star" genome.

Blebs and hematomas in the lips of CL/Fr and A/J mice.

Newborn-CL/Fr mice have +/- 20% frequency of cleft lip with or without cleft palate (CLP) depending on environment. However, examination of early fetal development from days 12 to 15 disclosed an increased number of hematomas or fluid-filled blebs in the regions of maxillary process fusion. The earliest stages do not appear to involve the blood supply directly but separate the epithelium from underlying mesenchyme by clear blebs. Similar defects were found in untreated A/J mice. These findings suggest that osmotic and hemodynamic abnormalities may be part of the mechanism of cleft lip formation in these related strains and that these defects may result from a biochemical defect of the connective tissue matrix in regions of process fusion.

Corneal keratinization in the oel/ + mouse.

Several human diseases are accompanied by keratinization of the ocular surface and loss of corneal transparency. We describe a mouse strain in which 2/3 of the viable offspring manifest a corneal disease characterized initially by poor wetting followed by keratinization of the ocular surface, and progressive loss of corneal transparency. The corneal epithelium becomes vacuolated and the basement membrane thickened. Ulceration and perforation were seen in some cases. Standard bacterial cultures yielded no culpable pathogens. Blood antiviral titers and cultures of orbital and ocular tissues for herpes virus were negative. Double masked treatment trials with topical gentamicin, and topical and parenteral vitamin A had no significant effect on the course of the disease. The mouse strain exhibits corneal keratinization unresponsive to vitamin A therapy, and may serve as an excellent model of certain serious human ocular surface diseases.