An ultrastructural study of development of the leptomeninx of the rabbit spinal cord.

Development of the rabbit spinal cord leptomeninges was examined in embryos and fetuses aged 12 to 30 d post-conception. In the early stages of development all mesenchymal cells surrounding the neural tube were structurally similar, resembling immature fibroblasts. At 16 d post-conception cells adjacent to the glia limitans showed little structural change, apart from an increase in the amount of rough endoplasmic reticulum, but cells in the presumptive arachnoid became packed with glycogen. By E22 glycogen was present in pial cells but never in the amounts found in the arachnoid. As development proceeded the amount of glycogen in the leptomeninges declined. Pial collagen increased both in amount and in fibre diameter with age.