UNLABELLED: The development of the thymus of the heterozygous (nu/+) mouse is indistinguishable from that of "normal" mice (Groscurth and Kistler, 1975). However, previous studies have shown that the thymus anlage of the homozygous (nu/nu) mouse differs significantly from that of its nu/+ counterpart. This morphological deviation becomes detectable by light microscopy during the 13th day post conceptionem (p.c.). It was assumed that, at the ultrastructural level, this maldifferentiation could become manifest at an earlier developmental stage. Therefore, the thymus anlage of 12 and 13 day-old nu/nu and ICR embryos was investigated electron microscopically. MATERIALS AND METHODS: The "nude" mice with the genetic background BALB/c were kept under the same conditions as described previously (Groscurth and Kistler, 1975). Mice of the strain ICR were used as controls. Virgin nu/nu females were mated with nu/nu males and the pregnant animals were sacrificed on the 12th of 13th day p. c. The embryos were fixed in 2.5% glutaraldehyde, postfixed in I% OsO4 and embedded in Epon.
UNLABELLED: The development of the thymus of the heterozygous (nu/+) mouse is indistinguishable from that of "normal" mice (Groscurth and Kistler, 1975). However, previous studies have shown that the thymus anlage of the homozygous (nu/nu) mouse differs significantly from that of its nu/+ counterpart. This morphological deviation becomes detectable by light microscopy during the 13th day post conceptionem (p.c.). It was assumed that, at the ultrastructural level, this maldifferentiation could become manifest at an earlier developmental stage. Therefore, the thymus anlage of 12 and 13 day-old nu/nu and ICR embryos was investigated electron microscopically. MATERIALS AND METHODS: The "nude" mice with the genetic background BALB/c were kept under the same conditions as described previously (Groscurth and Kistler, 1975). Mice of the strain ICR were used as controls. Virgin nu/nu females were mated with nu/nu males and the pregnant animals were sacrificed on the 12th of 13th day p. c. The embryos were fixed in 2.5% glutaraldehyde, postfixed in I% OsO4 and embedded in Epon.