Composition and metabolism of the extracellular matrix in the periodontal ligament of impeded and unimpeded rat incisors.

Potential differences were studied in the composition and metabolism of the connective tissue components (collagen, non-collagenous proteins and glycosaminoglycans) of the periodontal ligament (PDL) as a result of alterations in the rate of eruption. The amount of collagen, glycosaminoglycan (GAG) or the water content of the tissue was the same in the unimpeded and impeded situation. The only difference was in the amount of structural non-collagenous proteins: 33 per cent increase in the unimpeded PDL. The rate of turnover of insoluble collagen, structural non-collagenous proteins and the sulphated GAG, studied in vivo by administration of [3H]-proline or [35S]-sulphate, did not differ significantly in both situations: their extremely short half-lives were respectively 9.7, 3.5 and 1.7 days. Increase in the rate of eruption and hence in the remodelling process does not result in alterations in the metabolic activity of the PDL components. Their metabolism is probably already at maximal rate and may permit the more rapid rate of eruption when the opposing force of the antagonists is diminished during the non-occlusional state of the incisors.

Lathyrogens and the role of collagen in the eruption of rat incisors.

Collagen fibres in the periodontal ligament may have two functions: to resist displacing forces and to cause the tooth to erupt. Their function was examined in the continuously-erupting incisor of the rat using various concentrations and types of lathyrogens. Lathyrogens retarded tooth eruption and increased the quantity of salt-soluble collagen in the ligament, indicating inhibition of the maturation of salt-soluble (young) collagen into salt-insoluble (old) collagen, which would lead to reduction in the tensile strength of the fibres and decrease resistance to occlusal forces. The easy extractability of the teeth is explained by the greater susceptibility to lathyrogens of the fibres in the alveolar-related part of the periodontal ligament, compared with those in the other parts.

The concentration, extractability and characterization of collagen in human dental pulp.

Premolar and third molar dental pulps were studied. The amount of collagen in the dried pulps was 25.7 per cent in premolars and 31.9 per cent in third molars. These percentages are much higher than those reported for pulps in other species. Significant differences were further found in the collagen content and cell distribution (DNA) of the coronal, middle and apical parts of the pulp. Collagen content was the lowest in the coronal part, while the cell content was the lowest in the middle part. The extractability of collagen in a neutral salt solution or 0.5 M acetic acid was found to be extremely low (less than 1 per cent). Pretreatment of the pulp with hyaluronidase in order to remove proteoglycans had no effect on the solubility. It is concluded that human pulp collagen is highly cross-linked and cannot be considered as immature. Characterization of collagen was performed by methods in which limited pepsin digestion or CNBr cleavage was used. The digests were analysed by means of quantitative electrophoresis which revealed an amount of 42.6 per cent type III of the total collagen. Because of the large differences between dental pulps from man and experimental animals, extreme caution should be exercised in drawing conclusions from data of other species to explain phenomena observed in human teeth.

Immunofluorescent localization and extractability of fibronectin in human dental pulp.

Fibronectin, visualized in premolar pulps by indirect immunofluorescence, was abundant in the odontoblast layer, around blood vessels and in the core of the pulp. Similarity of alignment of fibronectin with the argyrophilic fibres and von Korff fibres was evident. Fibronectin was extracted from pulps after first removing blood by washing with water, confirmed by eventual negative reaction on alpha 2-macroglobulin. Extraction of fibronectin from this remaining tissue was most effectively achieved by treatment with collagenase or hyaluronidase, though in all cases some fibronectin remained, indicating that fibronectin in pulp is not exclusively associated with collagen and/or proteoglycans. The fibronectin quantified by electro-immunoassay and expressed as percentage of dry weight was 0.030 per cent in the water extract, 0.094 per cent in the collagenase extract and 0.109 per cent in the hyaluronidase extract. Twice as much fibronectin was extracted from the apical pulp as from the coronal and middle parts, in accord with earlier findings of a higher collagen content in the radicular part. It is suggested that with the loss of collagen type III during odontoblast differentiation and its reappearance with advancing vascularization of the dental papilla, the amount of fibronectin is similarly altered.

Simultaneous determination of uronic acids, hexosamines, and galactose of glycosaminoglycans by gas-liquid chromatography.

A quantitative gas-liquid chromatographic method has been developed for the simultaneous determination of the several monosaccharides present in glycosaminoglycans from animal tissues. In order to achieve a high degree of depolymerization of the glycosaminoglycans, it was found necessary to make them more susceptible to methanolysis by re-N-acetylation during the methanolysis procedure. Good resolution of all common monosaccharides, such as pertrimethylsilyl methyl glycosides, was achieved by the use of a capillary column of fused silica with the liquid phase CPtm leads to Sil 5. The method described was tested on glycosaminoglycans isolated from bovine periodontal ligament and the sensitivity (down to 3 micrograms monosaccharide) makes this method useful in the analysis of small amounts of soft connective tissues with low glycosaminoglycan contents.

Evidence of duplication of the human salivary amylase gene.

Isoelectric focusing of human parotid saliva reveals different alpha-amylase patterns reflecting qualitative and quantitative variations. A puzzling pattern, which shows three different amylase gene products, was found in four individuals. Based on this observation a model is presented in which the salivary amylase gene is duplicated. Family studies show that the AMY1*A2 gene forms a haplotype with the normal gene, AMY1*A1, whereas the AMY1*A3 gene still exists in a single form. The absence of homozygote 2-2 in offspring of 1-2 X 1-2 marriages and in population material, and the fact that the variant protein makes up about only 20-30% of the total amylase protein in heterozygotes can be considered as additional evidence supporting the hypothesis. The possibility that cis-acting regulatory variants are involved in the patterns with quantitative variation is discussed.