The effect of beta‐aminoproprionitrile on the periodontal ligament: I. Ultrastructure of fibroblasts and matrix

Administration of Beta‐aminoproprionitrile (B‐APN) to young mice produced a characteristic lesion, the lathyritic body, in the middle region of the PDL. Within these lesions the fibroblasts aggregated to form cell clusters of 10 to 20 cells. The aggregated fibroblasts bordered cell‐free regions of collagenous matrix. Individual fibroblasts maintained cytoplasmic polarity and provided a good model for studying collagen secretion from immobilized fibroblasts. Collagenous matrix appeared to be resorbed in the immediate vicinity of the clustered fibroblasts. ³H‐proline radioautography indicated that labelled collagenous matrix was preferentially lost from the middle region of the PDL of both control and experimental mice. However, the decrease in collagen in the middle region was accentuated by B‐APN treatment and the aggregation of fibroblasts in that zone.