Correlated observations and analysis of maturation-ameloblast morphology and enamel mineralization

A combined HCl-collagenase digestion technique and scanning electron microscopy were used to isolate the enamel organ and to confirm the presence of maturation ameloblasts of both ruffle-ended (RA) and smooth-ended (SA) types on maturing enamel in kitten permanent tooth germs. EDTA perfusion of animals fixed with aldehyde produced two or three belt-like shallow grooves (from 30 to 100 micron wide) running horizontally through the maturing enamel surface, coinciding closely with the SA distribution pattern. In animals that had been perfusion-fixed with unbuffered osmium tetroxide containing 2.5% potassium pyroantimonate, SEM-EDX analysis detected K in a superficial enamel layer overlaid by the SA layer. Potassium concentration decreased gradually toward the deeper layers. Very little K penetrated the enamel under the RA layer. Energy-dispersive x-ray analysis of Ca and P concentrations in the enamel revealed an even distribution of these elements throughout the superficial layer of maturing enamel. These results suggest that the SA layer forms an access route for K and EDTA and that, in spite of the obvious morphological and functional differences between RA and SA, the maturing enamel surfaces overlaid by these two cell types show similar degrees of mineralization.

The relationship between the keratocyst antigen (KCA) and keratin

The relationship of the keratocyst antigen (KCA), the soluble component present in most keratocyst fluids, and keratin, was studied with immunofluorescence microscopy comparing their distribution in developing mouse embryonic teeth and in human ameloblastomas. In these tissues both molecules showed a strong codistribution in epithelial cells. In the embryonic teeth both molecules were present in the stratum intermedium cells between the stellate reticulum cells and ameloblasts, but the secretory ends of the ameloblasts showed fluorescent staining only for keratin. The relationship was further investigated by comparing the physicochemical characteristics of KCA and keratin. Results on immunoblotting and two-dimensional gel electrophoresis showed that KCA existed in keratocyst fluid as a 60-68,000 dalton polypeptide with an isoelectric point of pI 6.8. Immunoblotting analysis of various isolated keratins revealed a typical polypeptide pattern of each keratin when anti-KCA antiserum was used for staining. These findings suggest that KCA and keratin are related molecules and that KCA may be a soluble component of keratin.

Effects of different extraction media on the electrophoretic pattern of proteins from partly mineralized bovine enamel

Five different extraction solutions were used to isolate matrix proteins from immature bovine enamel, to evaluate the effect of this procedure on the pattern obtained after electrophoresis. By sodium dodecyl sulfate-polyacrylamide gel electrophoresis, the dominating protein fraction in the ethylenediaminetetraacetic acid extract had a molecular weight of 67,000 daltons. The acetic acid and phosphate buffer extracts contained mostly low molecular weight proteins. Isoelectric focusing showed that most of the enamel proteins had isoelectric points below pH 7.0.

Immunohistochemical studies with a monoclonal antibody on the distribution of phosphophoryn in predentin and dentin

A monoclonal antibody was raised against phosphophoryn, a unique noncollagenous phosphoprotein in dentin. Mouse myeloma NS-I cells were fused with spleen cells obtained from BALB/c mice immunized with phosphophoryn from fetal calf tooth germs. Mice inoculated with the hybridoma produced ascites fluid containing the antibody and this reacted only with a band of phosphophoryn transblotted from polyacrylamide gel. Immunohistochemical studies with the antibody showed that phosphophoryn was present in odontoblasts, odontoblastic processes and dentin, but not in the matrix of predentin, and that the phosphophoryn content of the dentin layer was high at and around the predentin-dentin junction and gradually decreased toward the enamel layer. The area corresponding to mantle dentin was not stained with the antibody.

Localization of calcium in differentiating odontoblasts and ameloblasts before and during early dentinogenesis and amelogenesis in hamster tooth germs

Potassium pyroantimonate-osmium tetroxide cytochemistry has been used to study the distribution of ionic calcium in hamster tooth germs during cell differentiation and during early dentinogenesis and amelogenesis. Before the onset of mineralization, pyroantimonate (PA) reaction product was found in the nucleus of differentiating preameloblasts and preodontoblasts. In the predentin, it was preferentially located along striated collagen fibrils, lying perpendicular to the basal lamina. At the onset of mineralization, a pronounced increase of PA reaction product was evident in the predentin and on the plasma membrane and in mitochondria of both preodontoblasts and preameloblasts opposite the mineralizing mantle dentin. During early enamel mineralization, PA reaction product was present in the "growing" crystal ends, while in the secretory ameloblasts, most of the PA reaction product was localized on the cytoplasmic side of the apical plasma membranes and in mitochondria. When Tomes' processes developed, PA reaction product, both cytoplasmic and membrane bound, was low or absent deep in the processes, but gradually increased toward the apical terminal web. A corresponding gradient of PA reaction product was observed on the opposing enamel crystallites. From this study we conclude that both preodontoblasts and preameloblasts seem to be involved in calcium acquisition necessary for the early stages of mantle dentin mineralization. Tomes' processes seem to regulate the entry of calcium into the enamel mineralization front.

Ampicillin concentrations in human serum, gingiva, mandibular bone, dental follicle, and dental pulp following a single oral dose of talampicillin

Eighty-one patients who underwent the extraction of impacted mandibular third molars in the nonfasting state were given a single oral dose of talampicillin (500 mg) preoperatively. Specimens of venous blood (n = 132), gingiva (n = 70), mandibular bone (n = 78), dental follicle (n = 63), and dental pulp (n = 59) were obtained during the operation and assayed for ampicillin content. The mean peak concentrations in serum (9.64 micrograms/ml), gingiva (4.72 micrograms/mg), mandibular bone (1.77 micrograms/ml), dental follicle (3.46 micrograms/ml), and dental pulp (5.53 micrograms/mg) all occurred at approximately 150 minutes after administration of talampicillin. The ratios of the corresponding serum concentration to the peak concentrations in the various oral tissues when both were plotted as drug concentration curves were: gingiva, 0.50; mandibular bone, 0.16; dental follicle, 0.34; and dental pulp, 0.52. Talampicillin was absorbed well by the intestine, and sufficient concentrations of the resulting metabolite, ampicillin, were found in oral tissues.

Ultrastructural distribution of acidic glycosaminoglycans associated with matrix vesicle-mediated calcification in mouse progenitor predentine

The ultrastructural localization of acidic glycosaminoglycans, presumed to be proteoglycans, was examined during initial matrix vesicle-mediated calcification in dentine, by using ruthenium red (RR) staining, high iron diamine thiocarbohydrazide silver proteinate (HID-TCH-SP) staining, and an enzymatic digestion method. Progenitor predentine 2-10 micron width of developing mouse molar tooth germs was used throughout the present study. The outer surface membrane of the intact matrix vesicles had a strong affinity for RR. The RR positive materials appeared beaded and extended perpendicularly from the vesicle membrane. They tended to disappear with the disruption of the vesicular membrane, which resulted from overextension due to needle-like, crystal-like structures. The HID-TCH-SP stain deposits, approximately 10 nm in diameter, were densely distributed around the intact matrix vesicles, though few were found inside them. Some matrix vesicles that were presumably disrupted, however, contained smaller stain deposits. On the outer surface membrane of the disrupted vesicles, HID-TCH-SP stain deposits were fewer in number. The results obtained from enzymatic degradation studies showed that the anionic materials on the outer surface membrane of the matrix vesicles were represented by chondroitin-4-sulfate and/or chondroitin-6-sulfate. We suggest that chondroitin sulfates attached to the outer leaflet of the vesicular membrane play an important role during the incipient stage of the matrix vesicle-mediated calcification process.

Effects of maternal caffeine intake on the growth of rat tooth germs in protein-energy malnourished neonates

Fourteen rat dams with 8 pups each were fed either a 6, 12 or 20 per cent protein diet upon birth. Another group of 12 dams with the same number of pups was pair-fed either a 6, 12 or 20 per cent protein diet supplemented with caffeine (2 mg/100 g body weight). At day 15, randomly-selected pups were injected with [14C]-proline to determine collagen synthesis of the incisor and molar tooth germs. Another group of pups was used to determine calcium content of these tooth germs. Body weight, incisor weight and total calcium contents of tooth germs of pups from dams fed with 6 per cent protein diet were greater in the caffeine-supplemented group, whereas in the 20 per cent protein diet with caffeine group, these parameters were lower. The molar weights of the 12 per cent protein diet with caffeine animals were greater than the 12 per cent group without caffeine. The total hydroxyproline content of the incisor tooth germs from animals in the 12 per cent protein diet with caffeine was greater than is the non-caffeine group. However, total hydroxyproline of the molar tooth germs in the 20 per cent protein groups with caffeine was less than in the non-caffeine group. The rate of collagen synthesis of the incisor and molar tooth germs showed no difference in the presence or absence of caffeine in the 6, 12 and 20 per cent protein groups. Incisor and molar tooth germs are thus affected differently by the interaction of protein and caffeine, possibly due to differences in the pattern of tooth development.

An investigation of S-100 protein in embryonic dental papillae of rats

We attempted to identify S-100 protein, a marker of neural crest tissue, within cells of the developing dental papillae of 18-day rat fetuses by means of the immunoperoxidase technique. Although there is experimental evidence that dental papillae are derived from neural crest, no marker protein was identified in this study.

Glycosaminoglycans in embryonic mouse tooth germs. A histochemical analysis

Glycosaminoglycans (GAG) were localized in embryonic mouse molars by Alcian-blue staining in a critical-electrolyte-concentration (CEC) method (Scott and Dorling, 1965). Sulfated GAG were distinguished from hyaluronate (HA) by combining the binding specificity of Alcian blue and substrate specificity of GAG-lytic enzymes. The stratum reticulum was found to contain a small amount of HA, but no chondroitin sulfate (CS). The amount of HA decreased gradually during odontogenesis. No GAG were detected in the outer and inner dental epithelia. The basement membrane and the predentine were intensely stained, and shown to be rich in HA and CS. The preodontoblastic layer contained small amounts of HA and CS. These decreased progressively during odontogenesis. No GAG was found at the odontoblastic layer. The lower dental papilla contained a constant amount of HA (the major component) and CS.

Glycosaminoglycans in embryonic mouse teeth and the dissociated dental constituents

The nature, amounts and distribution of glycosaminoglycans (GAG) before and during odontoblast terminal differentiation were studied. GAG have been isolated from intact mouse tooth germs and from dissociated dental epithelia and dental papillae after labeling with [3H]glucosamine or 35SO2-(4) asd precursor. The kinds and relative amounts of 3H-labeled GAG were analyzed by chromatography on a DEAE-cellulose column and cellulose thin-layer sheets. The amounts of individual GAG relative to total GAG were determined from the elution profiles, whereas their nature was identified by the selective removal of chromatographic peaks after enzymatic or chemical degradation. We found hyaluronate and probably a minute quantity of heparan sulfate in the dental epithelium, while hyaluronate, heparan sulfate, and chondroitin sulfate were the main types of GAG in the dental papilla. The chondroitin sulfate recovered was further fractionated by cellulose thin-layer chromatography into two isomers, namely chondroitin-2-sulfate (the major component) and chondroitin-6-sulfate. Changes in the elution profile from DEAE-cellulose chromatography of tooth GAG extracted from different developmental stages suggest that modifications of GAG occur during odontogenesis. Alcian blue staining localized large amounts of hyaluronate and sulfated GAG along the epithelio-mesenchymal junction. Tissue specificity and changing patterns of GAG were demonstrated during odontogenesis.

Acid-soluble bovine fetal enamelins

High molecular weight enamelin proteins were recovered from conventional acetic acid extracts of fetal bovine enamel and were analyzed by gel filtration and ion-exchange chromatography. This procedure is simple and straightforward, and recovers approximately half of the total tissue enamelin content.

Calmodulin-like activity in a mineralising tissue: the rat molar tooth germ

Calmodulin, a calcium binding protein, has been implicated in the regulation of many calcium-dependent biological processes. Since calcium has an important role in hard tissue genesis, both at intra- and extracellular levels, we anticipate that calcium binding proteins may modulate this process. The present study investigated a mineralising tissue, the rat molar tooth germ, to determine the presence of calmodulin-like activity. A heat-treated cell-free extract of tooth germs provided enhancement of Ca2+-dependent Mg2+-ATPase and 3':5'-nucleotide phosphodiesterase activity. No enhancement occurred in the absence of calcium or in the presence of trifluoperazine. SDS-polyacrylamide gel electrophoresis of this extract revealed a protein band of approximately 18,000 mol. wt. These findings indicate the presence of calmodulin-like activity in rat molar tooth germs and support the proposal that calcium and calcium binding proteins, in particular calmodulin, have a major regulatory role in the biology of mineralising tissues.

Proteolytic enzyme in porcine immature enamel

A proteolytic enzyme cleaving the main component of enamel proteins obtained from immature enamel has been purified from a soluble extract of porcine immature enamel. It is optimally active around pH 6 against enamel protein. It is completely inhibited by phenylmethylsulfonyl fluoride and diisopropyl phosphofluoridate, and partially by benzamidine. EDTA does not affect its activity. The enzyme seems to sever initially its activity. The enzyme seems to sever initially enamel protein into two segments, one containing lysine, arginine and tyrosine and the other being free from these amino acids.

Mobility of concanavalin A receptors and distribution of cytoplasmic actin in odontogenic epithelial and mesenchymal cells

The distribution of concanavalin A (Con A) surface receptors and cytoplasmic actin in the same cell was studied in monolayer cultures of 2 odontogenic epithelial cells of different developmental age and in ecto-mesenchymal cells derived from the same tooth germ. Con A receptors were demonstrated by fluorescein-isothiocyanate-labelled Con A (FITC-Con A) and cytoplasmic actin by a specific anti-actin autoantibody (AAA) traced with a rhodamine-labelled goat anti-human globulin (R-AHG). All 3 cell types, incubated with FITC-Con A at 37 degrees C for increasing time periods, showed progressive changes in staining patterns from clusters, caps to perinuclear globules. Capping was seen in the majority of immature epithelial cells at 120–180 min, in cells of more mature epithelium at 180–240 min and in ecto-mesenchymal cells at 240–360 min. Binding of FITC-Con A to cell surfaces resulted in sequential changes in AAA staining from filamentous to an aggregated or diffuse pattern, co-capping of aggregated or diffusely stained areas with those capped by FITC-Con A, presence of aggregated or diffusely stained areas in sites similar to the perinuclear globules stained by FITC-Con A, to final re-emergence of filamentous staining. Prior treatment of cells with cytochalasin B or colchicine promoted capping in epithelial but not in ecto-mesenchymal cells while presence of either drug throughout the staining procedure inhibited capping. The results show that Con A receptors are more mobile in epithelial compared to ecto-mesenchymal cells and in immature epithelial cells compared to their more mature counterparts, and that binding and mobility of Con A receptors on the cell surface is associated with redistribution of cytoplasmic actin. The cytochalasin B and colchicine experiments suggest that both microfilaments and microtubules may have synergistic roles in the opposing functions of receptor anchorage and mobility, and that the relative receptor immobility of ectomesenchymal compared to epithelial cells may be attributed to firmer receptor anchorage to the cytoskeleton.

Ultrastructural and cytochemical studies on the matrix vesicle calcification in the teeth of the killifish, Oryzias latipes

Tooth germs of killifish were examined by both ultrastructural and cytochemical methods. The ultrastructure of the dentin in the early calcification stage of its development resembled that of mammals. Numerous extracellular membrane-bounded vesicles, matrix vesicles, were seen in the predentinal space, especially abundantly in the basal portion of the tooth germ. They were more numerous and more uniform in appearance than in any other higher vertebrates. Where calcification was going to start, slightly identifiable needles of apatite crystals were found in the vesicular structures. Crystals increase in number filling up the vesicles and then ther surroundings, finally to form many calcified spherules. Where calcification was more extensive, the matrix vesicles were no longer visible having been buried calcified among spherules. Contrary, to popular belief, there was no relationship seen between collagen fibrils and the initial deposits of minerals, that is, collagen fibrils did not seem to work as the initial site of calcification. Instead, matrix vesicles and plasma membranes of odontoblasts likely were involved in calcification as they both showed alkaline phosphatase activity. The ultrastructural and cytochemical findings from this study thus indicated that calcification of the killifish tooth germs was initiated not in the enamel, but in their dentin by the matrix vesicles which were liberated into the dentin matrix from odontoblasts mainly by way of fragmentation of cell processes.

Study on the biosynthesis of bovine enamel protein in vitro

Biosynthesis of enamel protein was investigated by incubating bovine tooth germs with 3H-proline containing medium. The radioactivity was incorporated into two protein fractions: one had a molecular weight of about 25,000, being secreted from the ameloblast to the enamel matrix, another having a higher molecular weight was supposed to be a cell associated protein.

The early mineralization of enamel. Fine structural observations on the cellular localization of calcium with the potassium pyroantimonate technique

The potassium pyronatimonate technique was used to study the cellular distribution of calcium during the early mineralization of enamel in rat molar tooth germs at the electron microscope level. Differing patterns of calcium distribution were observed in the ameloblast seemingly associated with the appearance of Tomes' process. In the early secretory ameloblast calcium pyroantimonate deposits were observed within the Golgi apparatus, within coated vesicles, within mitochondria and associated with the inner aspect of the cell membrane. However, with the development of Tomes' process the ameloblast no longer demonstrated these discrete deposits of calcium pyroantimonate. Instead they showed a diffuse cytoplasmic staining pattern with no preference for any particular organelle.

The effects of ascorbic acid deficiency on collagen synthesis by mouse molar tooth germs in organ culture

Second molar tooth germs from 2-day-old Swiss-Webster mice, grown in organ culture for 7 days in ascorbic-acid-deficient medium, synthesized about 65% as much protein (measured by incorporation of [14C]proline during a 24-h pulse) as did ascorbic-acid-supplemented controls. The newly synthesized proteins from ascorbic-acid-deficient cultures contained only about 7% of the hydroxyproline content of the controls. Collagenase digestion of the newly synthesized proteins showed that collagen comprised the same fraction of the total protein synthesized under both culture conditions. This result indicates that the ascorbate-deficient cultures made significant quantities of underhydroxylated collagen. Partial characterization of the collagen alpha chains on carboxymethyl cellulose columns showed an alpha1/alpha2 ratio of about 5, suggesting that at least two different species of collagen were synthesized. The alpha1/alpha2 ratio of the chains recovered from the ascorbate-deficient cultures was also about 5 but the chains were slightly underhydroxylated and the total amount of these chains which could be identified accounted for only a small fraction of the total collagen which was synthesized. A large fraction of the synthesized collagenous protein was found in the culture medium, mostly in the form of lower molecular weight peptides. It is concluded that most of the collagen which is synthesized by ascorbate-deficient tooth-bud cultures is not utilized by the component tissues, but is probably degraded and released into the medium.