Sequential observation of morphogenesis of cutaneous nerve fibers in fetal rat skin: an immunohistochemical and electron microscopic study.

Skin of DA/Slc rat fetuses removed on the fetal days 11 to 20 and on delivery day (21 days post-fertilization) was used. In the immunohistochemistry, the anti-neurofilament 69 kDa (NF68)-positive fibers appeared in the subepidermal dermis on the fetal day 12. The subepidermal and intraepidermal NF68-positive fibers reached to a maximum number on the fetal day 14. They disappeared completely on the fetal day 16. After the fetal day 19, a small number of the subepidermal and intraepidermal NF68-positive fibers were seen again. As for anti-nerve growth factor (NGF), intermediate cells, spinous cells and granular cells of the epidermis showed strongly positive stain. In the electron microscopy, there were bundles of immature axons which were packed by abundant microtubules and neurofilaments during the entire fetal period. On the fetal days 16 and 17, a considerable number of axons showed severe degenerative changes. From these findings, the subepidermal and intraepidermal nerve fibers in the fetal rat skin increased temporarily to a maximum number, and soon after they disappeared completely, followed by another period of re-appearance until delivery day. Such a dynamic change of the number of the cutaneous nerve fibers was not synchronous with expression of NGF of the epidermal cells.

Two arthroderma benhamiae isolates showing mitochondrial DNA type of Trichophyton verrucosum.

Two Trichophyton mentagrophytes isolates from skin lesions on a girl and her rabbit, which were identified as Arthroderma benhamiae by mating tests, were studied by mtDNA (mitochondrial DNA) analysis and sequencing of ITS (internal transcribed spacer) regions of nuclear ribosomal RNA genes. The mtDNA-RFLP (restriction fragment length polymorphism) patterns showed the two isolates to be T. verrucosum rather than A. benhamiae. The ITS sequence showed the isolates to be closer to A. benhamiae Americano-European race than to T. verrucosum and closer to T. verrucosum than to their mating partner A. benhamiae African race. These results suggest that there are three genetic types of A. benhamiae - an Americano-European type, an African type and a T. verrucosum type - and that T. verrucosum is an anamorph of A. benhamiae.