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8 recordsLinked to original sources
PubMed1979

Immunofluorescent evidence for the similarity of amelogenins in calf, mouse and pig teeth.

Antiserum was prepared to fetal bovine enamel matrix and was used to localize the amelogenins in developing bovine molars by immunofluorescent microscopy. Amelogenins could be identified to preameloblasts, secretory ameloblasts, stratum intermedium cells, and the newly deposited enamel matrix. Mature enamel matrix did not fluoresce except in a thin line along the DEJ and adjacent to the ameloblasts. Immature enamel matrix of murine and porcine teeth fluoresced when treated with antiserum to bovine enamel matrix. No other portions of tooth buds or other tissues reacted with the specific antiserum.

Animals↗
PubMed1979

The amelogenin problem: a comparison of purified enamel matrix proteins.

Using a combination of gel filtration and DEAE-cellulose chromatography, together with small-scale preparative polyacrylamide gel electrophoresis, we isolated five proteins (amelogenins) from demineralized bovine fetal dental enamel matrix. These purified proteins were characterized by amino acid analysis and gel electrophoresis. Comparisons of these data with those of other workers suggest that, although there are similarities in the published data between components of comparable electrophoretic mobility, there are gross differences in the reported amino acid compositions. It is suggested that these differences are due not to separative problems arising from reversible aggregations, but to inadequate comparisons of the electrophoretic and amino acid analytical data.

Amelogenesis↗
PubMed1979

A simple procedure for the isolation of a major amelogenin polypeptide component.

A simple, reproducible gel-filtration procedure for the isolation of one of the major 'J-Group' polypeptides of the bovine foetal dental-enamel matrix is described. The purified polypeptide was characterized by amino acid analysis, electrophoresis, cleavage with CNBr and N-terminal analyses. The isolated component is shown to be closely similar to an amelogenin component described by other workers.

Amino Acids↗
PubMed2016

Ultrastructure of early amelogenesis in wild-type, Amelx-/-, and Enam-/- mice: enamel ribbon initiation on dentin mineral and ribbon orientation by ameloblasts.

INTRODUCTION: Dental enamel is comprised of highly organized, oriented apatite crystals, but how they form is unclear. METHODS: We used focused ion beam (FIB) scanning electron microscopy (SEM) to investigate early enamel formation in 7-week-old incisors from wild-type, Amelx-/-, and Enam-/- C56BL/6 mice. FIB surface imaging scans thicker samples so that the thin enamel ribbons do not pass as readily out of the plane of section, and generates serial images by a mill and view approach for computerized tomography. RESULTS: We demonstrate that wild-type enamel ribbons initiate on dentin mineral on the sides and tips of mineralized collagen fibers, and extend in clusters from dentin to the ameloblast membrane. The clustering suggested that groups of enamel ribbons were initiated and then extended by finger-like membrane processes as they retracted back into the ameloblast distal membrane. These findings support the conclusions that no organic nucleator is necessary for enamel ribbon initiation (although no ribbons form in the Enam-/- mice), and that enamel ribbons elongate along the ameloblast membrane and orient in the direction of its retrograde movement. Tomographic reconstruction videos revealed a complex of ameloblast membrane processes and invaginations associated with intercellular junctions proximal to the mineralization front and also highlighted interproximal extracellular enamel matrix accumulations proximal to the interrod growth sites, which we propose are important for expanding the interrod matrix and extending interrod enamel ribbons. Amelx-/- mice produce oriented enamel ribbons, but the ribbons fuse into fan-like structures. The matrix does not expand sufficiently to support formation of the Tomes process or establish rod and interrod organization. CONCLUSION: Amelogenin does not directly nucleate, shape, or orient enamel ribbons, but separates and supports the enamel ribbons, and expands the enamel matrix to accommodate continued ribbon elongation, retrograde ameloblast movement, and rod/interrod organization.

Ameloblast↗
PubMed1979

Enamel protein chemistry--past, present and future.

Past progress in the chemistry of enamel proteins is reviewed and the current state of knowledge assessed. The matrix of young enamel is a complex system in which some 20 distinct components with molecular weights in the region of 3,000 to 16,000 are in dynamic equilibrium with much larger aggregates. During maturation, most of these components are selectively lost, more or less completely, from the enamel. 'Amelogenin' components rich in proline and histidine are removed first and 'tuft protein', characterized by high serine and glycine, is often partially retained in mature enamel. Some components have been isolated in a state approaching purity and a measure of agreement has been reached between laboratories concerning their characteristics. Partial amino acid sequences are known for two components, which contain phosphoserine. Though the mechanisms of mineralization and protein removal are not known, various possibilities are discussed. The essential unsolved problem is the nature of the overall protein system.

Amelogenesis↗
PubMed1979

Enamel matrix: structural proteins.

Cell-free, fetal bovine enamel tissue was examined intact by high resolution. 13C Fourier transform, nuclear magnetic resonance spectroscopy. Two types of protein chains were observed under these conditions, one exhibiting rapid mobility and accounting for approximately two-thirds of the enamel matrix, while the other exhibited restricted or anisotropic segmental motion and accounted for the remaining third of the matrix. Sequential extraction of this fetal enamel under non-degradative conditions with dissociative solvents yielded two biochemically distinct populations of matrix protein. As expected, the bulk of the matrix consisted of proline-rich amelogenins, although the SDS-gel electrophoresis molecular weights for these proteins were somewhat higher than those reported using other extraction methods. Approximately fifteen percent of the total matrix consisted of much higher molecular weight phosphoproteins (46,000-72,000 daltons) whose amino acid composition closely resembled that reported for mature enamel protein. These high molecular weight proteins were tightly bound to the fetal enamel apatite crystallites.

Animals↗
PubMed1979

Matrix and mineral changes in developing enamel.

An investigation of the changes taking place in the enamel and the enamel organ during enamel development has been carried out by analyzing small samples of tissue dissected from developing incisors of rat and bovine incisors. Observations showed that the synthesis of the enamel matrix and its subsequent loss were associated chiefly with a change in the major matrix components. This consisted of a selective loss of amelogenin components prior to secondary mineralization. Before this loss, some increase in the proportion of smaller molecular weight components suggested the possibility of limited breakdown. Even at the earliest stages examined, significant concentration of mineral ions was present. This increased steeply after most of the organic matrix had been removed. The Ca/P ratio of this mineral was constant throughout development. The concentration of minor inorganic ions (F, Mg and CO3) decreased as the tissue developed and a tendency was observed for certain ions (F, 32PO4) to penetrate and concentrate in the enamel, apparently as a consequence of the lost matrix being replaced by water, just prior to the steep increase in mineral content of the tissue.

Amelogenesis↗