Periodate-labile structures at the normal human cutaneous basement membrane zone.
The distribution of carbohydrates containing 1,2-glycol groups at the basement membrane zones of the dermo-epidermal junction and dermal blood vessels was investigated using the periodic acid-thiosemicarbazide-silver proteinate technique. Controls included pre-incubation with dimedone, dimedone treatment both before and after periodate oxidation, and dimedone treatment followed by thiosemicarbazide and silver proteinate. At the dermo-epidermal junction the anchoring fibrils were stained selectively after both short (45 min) and long (71 h) thiosemicarbazide incubation periods, there being no staining of the lamina densa; however, the lamina densa surrounding blood vessels was labelled. After prolonged treatment with thiosemicarbazide, fibrils were observed traversing the lamina lucida at the dermo-epidermal junction, and collagen fibres were stained faintly. Pre-incubation with dimedone to block aldehyde groups did not affect the staining. However, when periodic acid treatment was omitted, or when sections were incubated with dimedone both before and after periodate oxidation, only melanin granules and the cytoplasm of fibroblasts were stained. Thus, anchoring fibrils are rich in carbohydrates containing 1,2-glycol groups susceptible to periodate oxidation, and correspond to the periodic acid Schiff-positive layer seen at the dermo-epidermal junction. Furthermore, the basement membrane zones of dermal blood vessels and the dermo-epidermal junction differ in their carbohydrate distribution.