| Budget Amount *help |
¥1,700,000 (Direct Cost: ¥1,700,000)
Fiscal Year 1986: ¥800,000 (Direct Cost: ¥800,000)
Fiscal Year 1985: ¥900,000 (Direct Cost: ¥900,000)
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| Research Abstract |
Morphogenesis of mouse and chick limbs was studied by electron microscopic morphometry and light microscopic immunohistochemistry. The cell process meshwork (CPM) and subepidermal extracellular space (SEECS) in mesenchyme in mouse forelimb buds and in chick leg buds were examined. When the apical ectodermal ridge (AER) was distinct in mice, the SEECS was wide and the CPM was sparse beneath the AER as compared with those beneath the non-ridge epidermis. These findings suggest that the differences of the SEECS width and CPM density are closely associated with the AER development. Examination of fibronectin and laminin revealed that these extracelluar matrices were present along the basal lamina of the limb epidermis. In chick limbs, accumulation of fibronectin was detected beneath the AER, whereas no such accumulation was observed in mouse limbs. Distribution of laminin was not different between the AER area and non-ridge areas. These extracelluar matrices seem not to be related directly
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with the AER function. A slight increase in distribution of fibronectin was observed in the early phase of mesenchymal condensation. However, this may be due to tenascin contaminating fibronectin, and needs reexamination. Abnormal limb morphogenesis was studied after treatment of mouse dams at day 10.5 of gestation (vaginal plug=day 0) with 5-fluorouracil (5-FU), vitamin A (VA), and methoxyacetic acid (MAA), or after direct administration of 5-FU into extraembryonic celom of 3-day chick embryos. 5-FU induced preaxial polydactyly in mouse hind legs and chick legs. Measurements of width of the AER on chick leg buds treated with 5-FU showed an increase of 30% at the peak of the AER development. VA induced limb reduction deformities in mice, and MAA induced various types of malformations including brachydactyly, ectrodactyly, syndactyly, and rarely polydactyly. Distribution of fibronectin and laminin examined during the abnormal morphogenesis induced with these agents showed no specific abnormalities related to the teratogenesis. Less
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