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H C Slavkin

Publications and source records attributed to H C Slavkin.

At least 181 records · Page 10Linked to original sources
PubMed1987

Immunochemical and biochemical studies of human enamel proteins during neonatal development.

The present communication provides descriptions of the developmental, biochemical, and immunological properties of the human enamel extracellular matrix proteins. We report the isolation and partial characterization of the major human enamel proteins, the production of polyclonal antibodies directed against the human enamelins, and a comparison between the immunogenicity of enamelins and amelogenins from human and mouse enamel extracellular matrices. Our results indicate that although enamelins and amelogenins share some epitopes, each one of these proteins appears to invoke a different degree of immunogenicity.

Amelogenin↗
PubMed1987

Immunochemical homology between elasmobranch scale and tooth extracellular matrix proteins in Cephaloscyllium ventriosum.

Studies were designed to test the hypothesis that homologous proteins are expressed in elasmobranch scale, tooth enameloid, and mammalian enamel. Using indirect immunohistochemistry and high-resolution two-dimensional gel electrophoresis with immunoblotting, mouse enamel proteins were compared with placoid scale and enameloid proteins from the swell shark, Cephaloscyllium ventriosum. Swiss Webster mouse molar teeth show a characteristic enamel protein pattern consisting of two anionic enamel proteins of 72 kDa (pI 5.8) and 46 kDa (pI 5.5) and several more basic and lower-molecular-weight enamel polypeptides. Both anionic and basic classes of enamel proteins cross-reacted with either antiamelogenin or antienamelin antibodies. Placoid scale and tooth enameloid contained two anionic proteins identified as 58 kDa (pI 5.7) and 46 kDa (pI 5.5), which cross-reacted with either antimouse amelogenin or antihuman enamelin IgG antibodies. A minor antigenically related protein of 43 kDa (pI 6.2) was detected. Immunochemical staining showed localization within placoid scale, swell shark inner enamel epithelia, enameloid, and mouse inner enamel epithelia and enamel. We interpret these results to suggest that both placoid scale and enameloid proteins share epitopes and that these epitopes are also shared with mammalian enamel proteins. Based on molecular weights, isoelectric pH values, and amino acid compositions, placoid scale and enameloid ECM proteins do not contain amelogenin proteins. We suggest that enamelinlike proteins are highly conserved during vertebrate evolution and that these relatively anionic macromolecules may serve a primary function in the initiation of calcium hydroxyapatite formation during enameloid biomineralization.

Animals↗
PubMed1987

Ultrastructural analysis of enamel formation during in vitro development using chemically-defined medium.

To test the hypothesis that enamel biomineralization is regulated by sequential expression of an intrinsic genetic program, we designed experiments to determine if a serumless, chemically-defined medium is permissive for position-dependent ameloblast differentiation and subsequent enamel tissue-specific biomineralization in vitro. In the absence of serum or other exogenous growth factors, Swiss Webster strain mouse embryonic (15- and 16-days gestation) mandibular first molar tooth organs (cap stage) developed within 21 days in vitro into well-defined molar tooth organs expressing dentine and enamel biomineralization. Analysis of data obtained from von Kossa histochemistry for calcium salt formation, as well as ultrastructural information obtained from x-ray microanalysis, electron diffraction, transmission electron microscopy and scanning electron microscopy documented tissue-specific patterns of calcium hydroxyapatite formation in the absence of serum within organotypic cultures in vitro. An as yet unknown intrinsic genetic program regulates enamel formation in vitro.

Animals↗
PubMed1986

Comparison of tryptophan-labeled constituents of developing rodent molar enamel matrix, non-enamel occlusal cusp, Hertwig's epithelial root sheath, and presumptive root furcation regions: light microscopic autoradiography.

During the process of organogenesis involving the developing rodent molar and incisor tooth organs, novel gene products termed enamel proteins are expressed by ectodermally-derived enamel organ epithelia at precise times and positions within the course of morphogenesis. The present studies were designed to identify the relative distribution of tryptophan-labeled, non-collagenous, epithelial-derived proteins associated with rat maxillary first molar crown (M') and initial root formation. Our experimental strategy was to utilize semi-quantitative autoradiography methods to compare and contrast the distribution of silver grains resulting from tryptophan incorporation into developing postnatal pups associated with enamel matrix, non-enamel occlusal cusp, Hertwig's Epithelial Root Sheath (HERS), and presumptive root furcation regions of M'. Five-day-old Wistar rats were injected with 14C-labeled tryptophan. Four animals were sacrificed at 15 minutes and then at 1, 2, 4, and 24 hour intervals following the administration of this essential aromatic amino acid. Following fixation and subsequent processing for autoradiography, semiquantitative analyses were performed of the silver grain distribution localized within selected regions of the developing M' tooth organs. All enamel organ epithelia were found to incorporate tryptophan and silver grains were identified (above background) in the extracellular matrices (ECM) of the enamel matrix, non-enamel occlusal cusp adjacent to the inner enamel epithelia, and the ECM (2-4, micron) adjacent to presumptive root furcation and HERS regions. Tryptophan incorporation was not significant in the odontoblasts or dentine ECM of the crown or forming presumptive root regions. These results support the hypothesis that inner enamel epithelia associated with rat molar crown formation, as well as HERS, synthesize tryptophan-labeled, non-collagenous, ECM molecules. We speculate that HERS participates in root development by possibly producing non-collagenous proteins for intermediate cementum formation.

Amelogenesis↗
PubMed1985

Production and characterization of antibodies against murine dentine phosphoprotein.

Experiments were designed to produce and characterize a polyclonal antibody directed against mouse dentine phosphoprotein, the major non-collagenous protein of the dentine extracellular matrix. Dental extracellular matrix proteins from 2-day-postnatal Swiss-Webster-mouse tooth organs were extracted with 0.5 M-acetic acid, followed by 4 M-guanidinium chloride/0.5 M-EDTA. Mouse dentine phosphoprotein yields were further increased by precipitation with 1 M-CaCl2. Final purification was achieved by excising and eluting dentine phosphoprotein polypeptide bands from preparative sodium dodecyl sulphate/urea/polyacrylamide gels. Mouse dentine phosphoprotein is a single component of approx. 72 kDa and has a characteristic amino acid composition of 33% aspartic acid and 55% serine/phosphoserine. A polyclonal antibody was raised in rabbits against purified mouse dentine phosphoprotein and was shown to be monospecific by enzyme-linked immunoabsorbent, dot-immunobinding and 'Western transfer' assays. This antibody was used to detect the expression and localization of dentine phosphoprotein in 1-day-postnatal mouse tooth organs. This antigen was localized intracellularly within the monolayer of odontoblasts, which line the perimeter of the dental papilla mesenchyme, and within the odontoblastic cell processes, which traverse the predentine matrix. Newly forming mineralized dentine matrix was also cross-reactive with the dentine phosphoprotein specific antibody. The non-mineralized predentine matrix did not contain any detectable cross-reactive antigens.

Amino Acids↗
PubMed1985

DNA sequence for cloned cDNA for murine amelogenin reveal the amino acid sequence for enamel-specific protein.

Enamel is the unique and highly mineralized extracellular matrix that covers vertebrate teeth. Amelogenin proteins represent the predominate subfamily of gene products found in developing mammalian enamel, and are implicated in the regulation of the formation of the largest hydroxyapatite crystals in the vertebrate body. Previous attempts to isolate, purify and characterize amelogenins extracted from developing matrix have proven difficult. We now have determined the DNA sequence for a cDNA for the 26-kDa class of murine amelogenin and deduced its corresponding amino acid sequence. The murine amino acid sequence is homologous to bovine or porcine amelogenins extracted from developing enamel matrices. However, an additional 10-residues were found at the carboxy terminus of the murine amelogenin. This is the most complete sequence database for amelogenin peptides and the only DNA sequence for enamel specific genes.

Amelogenin↗
PubMed1985

Enamel protein biosynthesis and secretion in mouse incisor secretory ameloblasts as revealed by high-resolution immunocytochemistry.

Mouse secretory ameloblasts express a number of enamel proteins, which have been divided into amelogenin and enamelin subfamilies. We have used polyclonal antibodies to murine amelogenins to reveal enamel proteins in mouse ameloblasts using the protein A-gold immunocytochemical technique. Specific immunolabeling was detected over the extracellular enamel matrix and over the rough endoplasmic reticulum, the saccules of the Golgi apparatus, and the secretory granules of the ameloblasts. In addition, some lysosome-like granules were also labeled. Only background labeling was obtained over mitochondria, nuclei, cytosol, adjacent odontoblasts, and dentin. Quantitation of the intensity of labeling showed the presence of an increasing gradient along the secretory pathway, which may correspond to the concentration or the maturation of these proteins as they are processed by the cell. These findings indicate that the ameloblast displays an intracellular distribution of its secretory products similar to that of other merocrine secreting cells. The presence of enamel proteins in lysosomes suggests that crinophagy and/or resorption occurs in these cells.

Ameloblasts↗
PubMed1985

Regional specification of cell-specific gene expression during craniofacial development.

The core problem in craniofacial development is regional specification of cell-specific gene expression. Regional specification is also referred to as pattern formation or spatial organization. During early embryogenesis, regional specification is possibly operant following blastula, and is apparent during gastrulation and thereafter during embryonic and fetal stages of development. Current interdisciplinary approaches toward understanding embryonic development incorporate a number of scientific approaches including those of recombinant DNA technology. Three major advances have significantly enhanced the utility of so-called "genetic engineering," including the discovery of restriction nuclease enzymes that cleave DNA sequences at specific sites; the discovery of DNA ligase enzymes that facilitate ligation and annealing of DNA sequences to one another, so as to facilitate the joining of foreign DNA sequences with host DNA; and the discovery of effective techniques for the introduction of foreign DNA sequences into previously refractory organisms. The present discussion analyzes the problem of regional specification of ameloblast-specific gene expression as a paradigm for utilizing recombinant DNA technology in studies of normal and abnormal craniofacial development.

Animals↗
PubMed1985

Quantitative localization of polystyrene microspheres following microinjection in the avian metencephalic neural crest pathway.

Polystyrene microspheres were microinjected into crest populations at two preotic sites in Hamburger-Hamilton stage 10 and 11 chick embryos to investigate factors modulating cephalic neural crest fate. Analyses of microsphere localization and comparisons with cephalic crest fate maps indicated the following: microspheres injected at stage 10 localized with derivatives reflecting the fate of the crest population at the injection site; microspheres injected at stage 11 exhibited minimal displacement; and localization in ectoderm was similar in embryos injected at either stage. These results suggest that microinjected microspheres can be used to investigate normal and abnormal craniofacial morphogenesis.

Animals↗
PubMed1984

Differentiation of cultured palatal shelves from alligator, chick, and mouse embryos.

Palatal shelves from embryonic alligators, chicks, and mice were explanted at various stages of development and organ cultured in either chemically defined, serumless media or the same media supplemented with 10% fetal calf serum. Shelves from each vertebrate were either cultured singly or in contact, and heterologous combinations of palatal shelves from different animals were made: chick/mouse, chick/alligator, and mouse/alligator. Epithelial differentiation (particularly that of the medial shelf edge) was assayed by vital staining, histology, and scanning electron microscopy. In vitro medial edge epithelial differentiation, and consequently the mechanisms of palatal closure, were identical to those normally seen in vivo for each species, i.e., cobble-stoned migrating epithelia in the alligator, cell death and fusion in the mouse, and keratinisation and cleft palate in the chick. Differentiation was optimal in the chemically defined, serumless media and was independent of shelf contact in all three species. No heterologous combinations of palatal shelves closed with each other: Evidently, the modes of palatal closure in mice and alligators are sufficiently different to prevent them forming a chimeric palate, whilst neither is capable of inducing closure in a cocultured chick palatal shelf. These unified defined culture conditions make possible a large number of epithelial-mesenchymal recombination studies as well as specific inhibitor, teratogenic, and hormonal investigations.

Alligators and Crocodiles↗
PubMed1984

Concepts of epithelial-mesenchymal interactions during development: tooth and lung organogenesis.

One of the major problems in developmental biology concerns how differential gene activity is regionally controlled. One approach to this problem is the use of mesenchyme specification of epithelial-specific gene expression, such as, during tooth morphogenesis or lung morphogenesis. In the example of tooth morphogenesis, dental papilla ectomesenchyme induces de novo gene expression as assayed by detection of amelogenin transcripts, or immunodetection of amelogenin polypeptides within ameloblast cells. This process does not require serum supplementation or exogenous factors during epithelial-mesenchymal interactions in vitro. In contrast, lung morphogenesis requires hormones to mediate mesenchyme-derived influences upon type II epithelial cell differentiation and the production of pulmonary surfactant (eg, neutral and phospholipids, surfactant proteins). Glucocorticoids are required to stimulate the release of fetal pneumonocyte factor (FPF) from fibroblasts which, in turn, enhance the production of pulmonary surfactant. Thyroxin appears to regulate the relative responsiveness of progenitor type II cells to steroid-stimulated release of FPF. This review will highlight key concepts associated with these developing organ systems and emphasize the problem of regional controls which regulate epithelial cell-specific gene activity.

Ameloblasts↗