PubMed · 5247927
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J J Bembenek. 1968. Enamel.. https://pubmed.ncbi.nlm.nih.gov/5247927/
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Amelogenesis in the cat has been suggested to closely resemble enamel formation in human teeth. In order to further characterize the sequence of events leading to enamel formation in the cat, the expression and distribution of enamel proteins throughout amelogenesis were examined by postembedding immunocytochemistry using an antibody to mouse amelogenins and the high resolution protein A-gold technique. Enamel proteins were first immunodetected in ameloblasts and in the extracellular matrix during the presecretory stage. Secretory stage ameloblasts showed the most intense cellular reactivity. In these cells, protein synthetic organelles, secretory granules, and large lysosome-like structures were all intensely labeled. Extracellularly, numerous gold particles were observed over enamel and over patches of material found at the baso-lateral surfaces of these ameloblasts. During the early maturation stage, the protein synthetic organelles and secretory granules of ameloblasts still showed some immunoreactivity, although the most conspicuous labeling at this later stage was found over enamel and over material present among the extensive apical membrane infoldings of ruffle-ended ameloblasts. Qualitative analysis of lysosome-like elements in ameloblasts suggested that their frequency and immunoreactivity in the maturation stage were relatively lower than in the secretory stage, where some groups of cells often showed numerous large labeled structures. The enamel matrix was intensely labeled at all stages; however, cervical-occlusal and surface-depth gradients were readily apparent by conventional staining and by quantitative analysis of immunolabeling in the late secretory and early maturation stages. These data suggest that the cellular and extracellular distribution of enamel proteins in the cat is generally similar to that reported in other species, although some particularities were observed, perhaps reflecting variation in the timing of developmental parameters.
The present studies were undertaken to investigate the presence of common epitopes of mammalian amelogenins at the C-terminus and the possible functional importance of the conserved C-terminal domain in enamel mineralization during mammalian amelogenesis. Enamel proteins, including the intact amelogenins and their degraded polypeptides, were isolated from the secretory enamel of pig, cow, rat, and rabbit incisors. Rabbit and rat antipeptide sera, as well as rat anti-25 kD and 20 kD pig amelogenin sera, were used to identify the amelogenins among the isolated matrix proteins of each of the animal species. The antipeptide sera were developed previously (Aoba et al. [19]) using as immunogens the two synthetic peptides, C13 and C25, which correspond to the last 12 (plus Cys for KLH-conjugation) and 25 amino acid residues of pig intact amelogenin, respectively. Reactivity of the enamel proteins with each antiserum was examined by Western blot analysis. The results of immunoblotting showed that a few enamel matrix proteins in each of the mammalian species were recognized by the anti-C13 serum, specifically, pig amelogenin at 25 kD (and trace components at 27, 22, and 18 kD), cow amelogenin at 28 kD (trace components at 26, 22, 19, and 14 kD), rat amelogenins at 28 and 26 kD (and a trace component at 20 kD), and rabbit amelogenins at 24 and 21 kD (and a trace at 13 kD). The anti-C25 serum reacted additionally with pig amelogenin at 23 kD, cow amelogenin at 27 kD (a major matrix constituent), and rabbit protein at 19 kD.(ABSTRACT TRUNCATED AT 250 WORDS)
The solubility of enamel mineral (a carbonated apatite) formed at various stages of porcine amelogenesis was investigated at controlled partial pressures of CO2. Enamel samples were obtained from the outer (young) secretory, inner (old) secretory, early (soft) and late (hard) mature enamel of the permanent dentition of slaughtered piglets. The dissected enamel was pulverized and subjected to a plasma ashing at low temperature to remove organic matter. The composition (Ca, total P, HPO4, and CO3) of the enamel mineral was determined chemically. The enamel mineral contained significant amounts of carbonate and acid phosphate; the model adopted for its stoichiometry was [Ca]5-x [HPO4]v[CO3]w[PO4]3-x[OH]1-x. Each enamel sample was equilibrated in dilute phosphoric acid solutions (0.01-1.2 mM) under Pco2 = 1.86 and 1.75%. Equilibration of the enamel samples usually took 20-25 days; the solution composition (pH, concentrations of Ca, P, Mg, Na, and K, and activity of Ca2+) was determined periodically. The composition of the solution at equilibrium showed that (1) the outer (younger) secretory mineral was the most soluble and the solubility of enamel mineral decreased with advancing developmental stages; (2) the mean activity product in the saturated solutions for the outer secretory enamel was the same as that calculated on the basis of the reported composition of the enamel fluid; and (3) the solubility data obtained with most of the enamel samples were consistent with a model in which the equilibration includes two processes: dissolution of the original enamel mineral and precipitation of a new carbonatoapatite. Analyses of the equilibrated samples, particularly the mature enamel, by electron microscopy, supported the precipitation of carbonatoapatite.(ABSTRACT TRUNCATED AT 250 WORDS)