On the formation and its natures of the aperiodic microfibrils closely related to basal lamina of mouse molar tooth germ.

Abstract

The formation of aperiodic microfibrils perpendicular to the basal lamina of a mouse tooth germ and its nature were observed by light and electron microscopy. In addition, some histochemical examination of mucopolysaccharide and enzyme digestion were also carried out using the tooth germ of one-day-old mouse. In the dental bud stage of a 10 to 14-day-old mouse embryo, the basal lamina has been clearly formed, however aperiodic microfibrils and collagen fibers can not be observed. In the 16-day-old mouse embryo, a few formative aperiodic microfibrils were first observed in association with the basal lamina. In the epithelial-mesenchymal junction of the 18-day-old mouse embryo, fine collagenous fibrils appeared in addition to aperiodic microfibrils. A large number of aperiodic microfibrils which seemed to derive from the lamina rara interna were observed in the tooth germ of 20-day-old mouse embryo. Furthermore, in the predentine formative zone of the tooth germ of the one-day-old mouse, aperiodic microfibrils were well-developed, and distributed among the processes of the preameloblast. In the mineralization zone of the dentine matrix the aperiodic microfibrils were still present at the invaginated portion of the preameloblasts, but they had disappeared as a secretion of enamel matrix in the tooth germ of 2-day-old mouse.

The histochemical examination indicated that the aperiodic microfibrils were positive for RR and PAM staining, but they were negative for PAM staining after treatment by hyaluronidase or neu-raminidase. Also, aperiodic microfibrils were resistant to collagenase, pepsin and trypsin after hyaluronidase and/or neuraminidase treatment. These results indicate that the aperiodic microfibrils include hyaluronic acid and sialic acid. From these results, it was indicated that the aperiodic microfibrils were more similar to basal lamina than to collagen fibers.