Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Tooth Germ”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 199 records · Page 11Linked to original sources
PubMed1975

Calcium-stimulated adenosine triphosphatase in the microsomal fraction of tooth germ from porcine fetus.

The characterization and localization of a Ca(2+)-ATPase (ATP phosphohydrolase, EC 3.6.1.3) in the tooth germ of the porcine fetus are reported. This enzyme, a microsome fraction, is preferentially activated by Ca(2+). In the presence of 0.5 mM ATP, maximal enzyme activity is obtained at 0.5--1.0 mM CaCl2. The maximal rate of ATP hydrolysis is approx. 20 mumol per h per mg of protein as the enzyme preparation is used here. At optimal Ca(2+) concentration, the Mg(2+) has an inhibitory effect. The enzyme does not require Na+ or/and K+ for activation by Ca(2+). Other nucleotide triphosphates may serve as the substrate, but V for ATP is the highest. The Km for ATP is 8.85 - 10(-5) M. The optimal pH for Ca(2+) activation of the enzyme lies around 9.2. Well known inhibitors of (Na+ + K+)-ATPase, mitochondria ATPase and Ca(2+)-ATPase in the erthrocyte do not inhibit the enzyme. In the subcellular order the enzyme may be assumed to be localized in the smooth endoplasmic reticulum fraction containing cell and Golgi body membrane fragments and in the tissue order in the enamel organ containing an ameloblast layer, stratum intermedium and stellate reticulum.

Adenosine Triphosphatases↗
PubMed1997

Light and electron microscopical immunohistochemical localization of large proteoglycans in human tooth germs at the bell stage.

The immunohistochemical localization of large hyaluronate-binding proteoglycans has been studied in human tooth germs at the bell stage using a monoclonal antibody, 5D5, which is derived from bovine sclera and specifically recognizes the core protein of large proteoglycans, such as versican, neurocan and brevican, but not that of aggrecan. In the early bell stage before predentine secretion, when the enamel organs consisted of the inner and outer enamel epithelia, stratum intermedium and stellate reticulum, the enamel organs were not stained by 5D5, but the dental papillae and follicles stained strongly. Concomitant with the secretion of predentine, dentine and subsequent enamel matrix, strong 5D5 immunostaining distributed over the entire cell surfaces of secretory ameloblasts was observed. The forming enamel matrix showed strong staining. While most of the inner and outer enamel epithelia and stratum intermedium lacked staining, the cervical loop region and stellate reticulum showed weak staining. Although the forming dentine and odontoblasts appeared to lack 5D5 affinity, the predentine, dental papilla and dental follicle demonstrated moderate to strong reactivity. At the ultrastructural level, specific immunoreaction by immunogold particle deposition was clearly detected over the basal lamina of presecretory ameloblasts, secretion granules of secretory ameloblasts and the forming enamel matrix. These results indicate that a marked increase in the large proteoglycan associated with secretory ameloblasts may correlate with cell differentiation and enamel matrix biosynthesis.

Humans↗
PubMed1985

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.

Ameloblasts↗
PubMed1987

Guanine salvage by organ cultures of mouse tooth germs.

The effect of mycophenolic acid (MPA) which inhibits the biosynthesis of guanosine monophosphate (GMP) in organ cultures of mouse tooth germs can be partially counteracted by adding guanine to the MPA cultures. This may be due to salvaging guanine by the enzyme hypoxanthine guanine phosphoribosyl transferase (HGPRT), or to competition for a common membrane carrier involved in mediated transport of both guanine and hypoxanthine in normal biosynthesis and also of MPA. Experiments were carried out to compare the effect of either hypoxanthine or guanine on the MPA-caused inhibition. While addition of guanine to the MPA cultures (MPAG) supports growth equal to controls and development of dental-enamel junction (DEJ) to a level intermediate between control and MPA the addition of hypoxanthine (MPAHX) supports growth and DEJ development not better than MPA. This indicates that guanine is salvaged by HGPRT to GMP while hypoxanthine, salvaged to inosinic acid (inosinic monophosphate, IMP) is ineffective because the MPA inhibition is on the pathway from IMP to GMP.

Animals↗
PubMed1985

Immunolocalization of gamma-carboxyglutamic acid-containing proteins in developing molar tooth germs of the rat.

The localization of dentin gamma-carboxyglutamic acid containing proteins (DGP's) was examined in rat molar tooth germs at various stages of development by immunostaining with the peroxidase-antiperoxidase method. Odontoblasts and their processes stained positive, whereas all other cells were negative. No staining was found in predentin. Dentin stained only after a mild demineralization. The results support the concept that DGP's are deposited by odontoblasts directly into the mineralizing dentin.

1-Carboxyglutamic Acid↗
PubMed1992

Changes of cytochemical properties in the Golgi apparatus during in vivo differentiation of the ameloblast in developing rat molar tooth germs.

The cytochemical changes of the Golgi stacks occurring concomitantly with cell differentiation were examined in ameloblasts of developing rat molar tooth germs using osmium impregnation and cytochemistry with nicotinamide adenine dinucleotide phosphatase (NADPase), thiamine pyrophosphatase (TPPase), and acid phosphatase (Acpase). NADPase, TPPase, and Acpase activities were already present in the Golgi stacks of the inner enamel epithelial cells, the undifferentiated form of the ameloblast: NADPase activity existed in the medial Golgi cisternae, TPPase activity in the trans Golgi cisternae, and Acpase activity in almost all cisternae and strongly in the trans-most cisterna of the Golgi stack. At this stage, however, osmium deposits after impregnation were not observed in the cisterna of Golgi stacks but were present in some small vesicles. These vesicles were located throughout the cytoplasm. Osmiophilic cisternae in the Golgi stacks were apparent for the first time at the stage when the Golgi apparatus developed and migrated to the region distal to the nucleus with the progression of cell differentiation. These findings indicate that the cis subcompartment of the Golgi apparatus was incomplete in the inner enamel epithelial cells with regard to appearance of its cytochemical property, as compared with the medial and trans subcompartments. It is suggested that the cis compartment of the Golgi stack may be completed only in the last stage of the compartmentalized Golgi organization during differentiation of the ameloblast.

Acid Phosphatase↗
PubMed1994

Immunohistochemistry of the intercellular matrix components and the epithelio-mesenchymal junction of the human tooth germ.

The immunohistochemical localization of heparan sulphate, collagen type I, III and IV, laminin, tenascin, plasma- and cellular fibronectin was studied in tooth germs from human fetuses. The lamina basalis ameloblastica or membrana preformativa, which separates the pre-ameloblasts from the pre-dentin and dentin, contained heparan sulphate, collagen type IV, laminin and fibronectin. Enamel reacted with antifibronectin, but the reaction varied depending on the type of fibronectin and the source of antibody. In early pre-dentin, collagen type I, laminin, tenascin and fibronectin were present. In late pre-dentin and dentin collagen type I was found in intertubular dentin and in the zone between enamel and dentin. The close relationship between collagen type I in dentin and fibronectin in immature enamel is interesting, as it may contribute to the stabilization of the amelodentinal interface. In dental pulp, collagen type IV and laminin were found in the endothelial basement membranes. Collagen type I and III, tenascin and fibronectin were localized to the mesenchymal intercellular matrix. The results of this study have supported the assumption that the lamina basalis ameloblastica is a basement membrane, and have lead to the suggestion that ameloblasts are producers of fibronectin or a fibronectin-like substance.

Ameloblasts↗
PubMed1993

Changes of lectin staining pattern of the Golgi stack during differentiation of the ameloblast in developing rat molar tooth germs.

Changes of lectin staining patterns in the Golgi stack during cell differentiation were examined in the ameloblasts of developing rat molar tooth germs, using HRP-labeled lectins: Canavalia ensiformis (Con A), Griffonia simplicifolia I (GS-I), Glycine max (SBA), Ulex europeus I (UEA-I), Triticum vulgaris (WGA), and Arachis hypogaea (PNA). The Golgi stacks of the inner enamel epithelial cells and the presecretory ameloblasts were stained with the lectins, although the staining strength and pattern varied among the stacks with each lectin. In some cases, the reaction products for the lectins were observed in most or all saccules of the Golgi stack. In the secretory ameloblasts, however, discrete staining patterns of the Golgi stack were found for each lectin. The reaction products deposited in definite saccules of the Golgi stack of the secretory ameloblast, especially for UEA-I and PNA which stained only the trans Golgi saccules of the stack. The reaction-positive saccules distributed more extensively in the Golgi stack of the inner enamel epithelial cell and the presecretory ameloblast than in the secretory ameloblast. These findings suggest that the Golgi stack is not fully compartmentalized in the inner enamel epithelial cell and the presecretory ameloblast. It is proposed that, in the differentiating ameloblast, various glycosyltransferases may coexist in most saccules of the Golgi stack.

Ameloblasts↗
PubMed1991

Electron probe X-ray microanalysis of calcium and phosphorus distribution in developing hamster tooth germs in vitro and in vivo.

The aim of the present study was to investigate the spatial distribution of Ca and P in dentin and enamel of developing first (M1) and second (M2) maxillary hamster molars (age: 3-5 days) in comparison with cultured molars. For culturing the germs were dissected from 3-day-old hamsters and incubated for 1 and 2 days, respectively, in a modified BGJb medium. Electron probe X-ray measurements were carried out on 3 regions extending in a vertical axis from cusp tip over cusp middle to cusp base next to the cervical loop region. Neither the in vivo nor the in vitro group was statistically different in the Ca and P concentration in the regions of dentin. In both groups the measurements in enamel showed a gradient with an increase in Ca and P from enamel surface towards dentin-enamel junction and a gradient with an increase from cusp base towards cusp tip. Direct comparison of the in vivo group with the in vitro group did not demonstrate a statistical difference between the mineral content of the 4-day-old germs and the 1-day culture germs, respectively the 5-day-old germs and the 2-day culture germs. The results indicate a high correspondence between the mineralization process of in vitro and in vivo tooth germ development.

Aging↗
PubMed1988

Budding of small vesicles from the rough-surfaced endoplasmic reticulum in secretory ameloblasts of rat molar tooth germs.

The budding of small vesicles from the rough-surfaced endoplasmic reticulum (rER) was examined in the secretory ameloblast of rat molar tooth germs by ordinary fixation or prolonged osmium fixation. The budding of small vesicles from the rER was observed not only at the special region (transitional region) of the rER system, which abutted on the cis-face of the Golgi apparatus, but also at other regions of the rER in the secretory ameloblast. Small vesicles (presumed to be transitional vesicles) were adjacent to the rER, which also showed budding of vesicles. After prolonged osmium treatment, osmium deposits appeared in small vesicles, as well as in the cisternae of the cis saccule of the Golgi apparatus. Small vesicles containing osmium deposits were located at various regions of the cell, including the cis-face of the Golgi apparatus. These findings indicate that the budding of small vesicles from the rER is not restricted to the transitional region of the rER system of the secretory ameloblast, but is found at various regions of the cell. This indicates that newly synthesized proteins may be transferred from the rER cisternae to the transitional vesicles not only in the transitional region of the rER system adjacent to the Golgi apparatus, but also in other regions of the secretory ameloblast.

Ameloblasts↗
PubMed2000

[The role of matrix vesicles during development of the mineralizing tissues of tooth germ and craniofacial bone].

OBJECTIVE: To evaluate the role of matrix vesicles (MVs) during the development of mineralizing tissues. METHODS: The ultrastructure of MVs of tooth germ, calvarial bone and mandibular bone were observed by transmission electron microscopy in fetal Wistar rat. RESULTS: (1) The MVs were formed by osteoblast of the secret type, dentinoblast and process; (2) There was a mature process of the MVs in the extracellular matrix. The appearance of the hydroxyapatite (HAP) was a major mature feature; (3) HAP formed initially in the MVs entered into collage matrix and eventually mineralized; (4) The shifting sign of HAP from MVs to the surface of collage fibril was observed. CONCLUSIONS: The MVs played an important role in the biomineralization, but the special arrange pattern of mature collage fiber provided a suitable environment and a model to the growth of HAP for further mineralization.

Animals↗
PubMed1985

Short-term effects of fluoride on biosynthesis of enamel-matrix proteins and dentine collagens and on mineralization during hamster tooth-germ development in organ culture.

The effect of various concentrations of fluoride (F-) on cell proliferation, matrix formation and mineralization was examined in hamster molar tooth germs in premineralizing and mineralizing stages. The exposure lasted 16 h (mineralizing stages) and 24 h (premineralizing stages) and the F- levels ranged from 2.63 microM to 2.63 mM; [3H]-thymidine, [3H]-proline, 45Ca and 32PO4 were used as markers for cell proliferation, matrix formation and mineralization, respectively. The proline-labelled amelogenins were isolated by sequential extraction with water and formic acid and their nature examined by SDS-urea-polyacrylamide electrophoresis. Digestion by collagenase was used to assess the amount of proline incorporated into collagens. F- in concentrations up to 1.31 mM inhibited neither biosynthesis of DNA and amelogenins, nor synthesis of collagens and their hydroxylation. Amelogenins extracted from F- induced, non-mineralizing enamel matrix had the same electrophoretic mobility and the same degree of phosphorylation as amelogenins from normal, mineralizing enamel. However, F- increased the uptake of 45Ca and TCA-soluble 32P dose-dependently, starting with 52 microM. Thus, interference with secretion of enamel matrix by F- takes place at much lower concentrations than required to inhibit biosynthesis of enamel matrix.

Animals↗
PubMed1981

[In vitro dentinogenesis of mice fetuses tooth germs in the presence of fluoride. Morphological nad historical observations].

Observations show that fluoride alters dentinogenesis in vitro. Morphological and cellular alterations are greater when the tooth germs are young and/or when the time of incubation is longer and the dose of fluoride higher. In the predentine, the stainability of proteoglycans is partially reduced. The persistence of alcianophilic zones far from the site of secretion indicates some delay of the process of matricial maturation.

Animals↗
PubMed1998

Amelogenin protein in tooth germs of the snake Elaphe quadrivirgata, immunohistochemistry, cloning and cDNA sequence.

In the snake, Elaphe quadrivirgata, the occurrence of amelogenin was immunohistochemically demonstrated in the enamel of developing tooth germs. Teeth of the snake are covered with a thin true enamel layer about 1-2 microns in thickness. Light and electron microscopic immunohistochemistry indicated an intense amelogenin immunoreactivity occurring in the enamel layer during the secretory stage of tooth development. Cloning and cDNA sequence of snake amelogenin was performed by RT-PCR. The amino acid sequence of the snake amelogenin cDNA--in its portion corresponding to the area from exon 5 to exon 7 of human X189 amelogenin gene--showed 45% homology with humans. Regions of both the N-terminus and C-terminus were well conserved. Furthermore, the positions of prolin in the amino acid alignment of the snake amelogenin corresponded well with those of human amelogenin. It is suggested that prolin is an essential constituent of amelogenin and therefore its positions in the molecule have been conserved after the evolutionary divergence of reptiles and mammals. This study using reptiles is the first detection of specific amelogenin immunoreactivity by high resolutional immunoelectron microscopy and the first cloning of amelogenin cDNA in a non-mammalian animal.

Amelogenin↗
PubMedDate not supplied

Development of tooth germ heterotopically grafted within the ear skin. An histological study in the rat.

The main goal of this study was the analysis of the developmental potentiality of tooth germ from late bell stage on, after its heterotopic placement within the skin. Teeth germs of newborn rats were grafted within a skin pouch of the ear of adult rats. Seven to fourteen days after grafting, dental germs developed normal dental structures in which ameloblasts and odontoblasts were well differentiated. Twenty to forty-one days after graft, the inflammatory host reaction destroyed the dental developed tissues by cell infiltration. The dentin of the grafts was of osteoid characteristics, and its size increased depending on grafting time until the complete substitution of all dental tissues. This atypical dentin showed several degrees of polymerisation from collagen fibres smooth dentin devoid near the graft a to fibres rich dentin far from the dental germ. Present results suggest that this type of dental graft could be a valuable model to study the self-development of dental tissues and the reactive mechanisms taking place after dental injuries.

Animals↗