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.

SourceResearch connectionFrom yearThrough year

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

At least 739 records · Page 41Linked to original sources

PubMed1984

[Odontogenesis in the human fetus: an echographic study].

During real-time ultrasound observation of swallowing movements in the human fetus, changes in the echostructure of the jaws were detected. Dense linear echoes (2-6 mm) arose symmetrically in the superior and inferior jaws from the median to the distal level with increasing gestational age. Their localisation and onset suggested they might represent tooth germs. The comparison between radiography after birth and pre- and postnatal echography confirmed that these particular echoes were indeed calcified tooth germs. The implications of this observation will be discussed in terms of fetal growth maturation and gestational age.

Deglutition↗

PubMed2003

Laminin alpha2 is essential for odontoblast differentiation regulating dentin sialoprotein expression.

Laminin alpha2 is subunit of laminin-2 (alpha2beta1gamma1), which is a major component of the muscle basement membrane. Although the laminin alpha2 chain is expressed in the early stage of dental mesenchyme development and localized in the tooth germ basement membrane, its expression pattern in the late stage of tooth germ development and molecular roles are not clearly understood. We analyzed the role of laminin alpha2 in tooth development by using targeted mice with a disrupted lama2 gene. Laminin alpha2 is expressed in dental mesenchymal cells, especially in odontoblasts and during the maturation stage of ameloblasts, but not in the pre-secretory or secretory stages of ameloblasts. Lama2 mutant mice have thin dentin and a widely opened dentinal tube, as compared with wild-type and heterozygote mice, which is similar to the phenotype of dentinogenesis imperfecta. During dentin formation, the expression of dentin sialoprotein, a marker of odontoblast differentiation, was found to be decreased in odontoblasts from mutant mice. Furthermore, in primary cultures of dental mesenchymal cells, dentin matrix protein, and dentin sialophosphoprotein, mRNA expression was increased in laminin-2 coated dishes but not in those coated with other matrices, fibronectin, or type I collagen. Our results suggest that laminin alpha2 is essential for odontoblast differentiation and regulates the expression of dentin matrix proteins.

Animals↗

PubMed1983

Evidence from thiol histochemistry for homology between the Tabby-crinkled syndrome in mice and human ectodermal dysplasia.

Mutant mice carrying the sex-linked gene Tabby (Ta), and others carrying crinkled (cr), an autosomal mimic of Ta, were studied histochemically with respect to the sulfhydryl: disulfide ratios in their skin and hair and the SH levels in their tooth germs. As compared to normal controls, the mutant animals demonstrated significantly elevated SH:S-S ratios (skin and hair) and SH levels (tooth germs) in the ectodermal components of these tissues. This finding corresponds with previously reported biochemical data on a form of human ectodermal dysplasia (ED), and therefore supports the hypothesis that these mutations in mice may be homologous to the genes for human ED.

Animals↗

PubMed1992

Sequential induction of syndecan, tenascin and cell proliferation associated with mesenchymal cell condensation during early tooth development.

The cell surface proteoglycan, syndecan, and the extracellular matrix glycoprotein, tenascin, are expressed in the mesenchyme during early development of many organs. We have studied the expression patterns of syndecan and tenascin during initiation of tooth development and in association with mesenchymal cell condensation and compared these with cell proliferation. Syndecan, tenascin and bromodeoxyuridine (BrdU) incorporation were localized by triple-labelling immunohistochemistry in serial sections of molar tooth germs of mouse embryos. Prior to formation of the epithelial tooth bud, syndecan accumulated in the mesenchymal cells which underlie the presumptive dental epithelium, but tenascin was not detected at this stage. Tenascin appeared during initiation of the epithelial down-growth at the lingual aspect of the tooth germ. During subsequent formation of the epithelial bud, at the late bud stage, syndecan and tenascin became exactly colocalized in the condensed mesenchyme which was clearly demarcated from other jaw mesenchyme. The expression of syndecan and tenascin was accompanied by rapid cell proliferation as indicated by marked BrdU incorporation. When development advanced to the cap stage, syndecan staining intensity in the dental papilla mesenchyme increased further whereas tenascin became reduced. In conclusion, the results demonstrate that the expression patterns of syndecan and tenascin overlap transiently during the period of mesenchymal cell condensation and that this is accompanied by cell proliferation. Syndecan and tenascin may play a role in growth control and in compartmentalization of the dental mesenchymal cells in the condensate.

Animals↗

PubMed1986

Dental papilla cells in culture. Comparison of morphology, growth and collagen synthesis with two other dental-related embryonic mesenchymal cell populations.

The dental papilla is a mesenchymal cell condensation which plays an important regulatory role during tooth development. Dental papilla mesenchymes were enzymatically separated from the dental epithelia from tooth germs of 17-day-old mouse embryos and disaggregated for monolayer culture. These cells were compared with gingival mesenchyme overlying the same tooth germs and with undifferentiated jaw mesenchyme from mandibles of 11-day-old embryos. The dental papilla cells were large and flat with numerous cell processes, whereas the gingival cells resembled typical spindle-shaped fibroblasts and grew to a higher cell density. Although the two mesenchymes differ in their collagen contents in vivo, no differences were detected either in the amount or type of collagen synthesized in vitro. Type I and III collagens were found in the culture media and type V collagen in the cell layer of both cell populations. The mandibular mesenchymal cells of the younger embryos resembled the dental papilla cells in morphology and growth rate. This may reflect retention of undifferentiated embryonic characteristics in the dental papilla. The successful culture of dental papilla cells now enables subsequent studies on the cellular properties related to the unique morphogenetic capabilities of these cells.

Animals↗

PubMed1980

[Conservative surgical treatment for keratocysts of basal cell naevomatosis. Some results (author's transl)].

Excision of keratocysts of basal cell nevomatosis using the principle of conservative surgical treatment of maxillary cysts is usually followed by good secondary bone reconstruction without recurrence. Certain precautions are however necessary, the most important being the resection of the parts of the gums adherent to the cyst wall (where perhaps the cyst developed and where recurrences are most likely to occur). Any tooth germ which may be attached to the cyst must also be removed. Postoperative follow-up must include supervision of the bone reconstruction and tooth germ which have not yet developed (even in the absence of an image of a cyst) until the end of adolescence. In adult age, however, there is very little risk of new keratocysts cysts developing.

Adolescent↗

PubMed1982

Localization of tritiated 1,25-dihydroxy vitamin D3 in fetal rat mandible, kidney, and intestine.

In the fetal rat the specific uptake of this hormone appears in the kidney and in the mandible-tooth germ, but not by the intestine. Furthermore, uptake by the two former tissues was greatly influenced by gestational age. Localization in the mandible and tooth germ increased from approximately 50 DPM/mg wet weight of tissue on day seventeen of gestation to over 300 DPM/mg wet weight on the nineteenth day. A similar, but not as dramatic, increase occurred in the kidney. Thus, these data demonstrate: (1) the development of the specific uptake of 1,25-dihydroxy vitamin D3 in the kidney and bone with gestational age, and (2) the absence of specific receptive sites in the fetal intestine.

Animals↗

PubMed1995

Identification of regulatory elements necessary for the expression of the COL1A1 promoter in murine odontoblasts.

Recent studies have indicated that odontoblasts and osteoblasts have unique regulatory mechanisms that control COL1A1 gene expression. We are currently examining the regulation of COL1A1 gene expression in odontoblasts and have produced transgenic mice containing various collagen promoter constructs fused to the indicator gene, chloramphenicol acetyl transferase (CAT). Mandibular first molars were removed from jaws of transgenic mice. Some teeth were assayed for CAT activity (CAT diffusion assays), others were fixed and prepared for immunohistochemistry (CAT antibodies). Our results indicate the CAT activity was present in tooth germs containing promoter constructs longer than 1.719 kb. Immunoreactivity to CAT was confined to the odontoblast cell layer. No CAT activity was present in tooth germs containing a 1.670 kb construct. These data suggest that there are important regulatory elements located between -1.719 kb and -1.670 kb on the collagen promoter in odontoblasts. Examination of sequences in this region of the promoter demonstrates consensus with those known to be involved with binding of translation products of homeobox genes.

Animals↗

PubMed2003

Normal and abnormal dental development.

Teeth are vertebrate organs that arise from complex and progressive interactions between an ectoderm, the oral epithelium and an underlying mesenchyme. During their early development, tooth germs exhibit many morphological and molecular similarities with other developing epithelial appendages, such as hair follicles, mammary and salivary glands, lungs, kidneys, etc. The developing mouse tooth germ, which is an experimentally accessible model for organogenesis, provides a powerful tool for elucidating the molecular mechanisms that control the development of these organs. Dentition patterning also provides a unique model for understanding how different shapes of teeth arise in different regions of the jaws. We review here the main signalling networks mediating the epithelial-mesenchymal interactions involved in tooth morphogenesis and patterning.

Animals↗

PubMed1997

Lectin binding patterns of odontogenic epithelium in the rat during various phases of molar tooth development.

Light and electron microscopic investigations of lectin binding patterns in rat tooth germs were undertaken in order to elucidate glycoconjugate localization in cells of the reduced enamel epithelia and their derivatives. It was found that Ulex europaeus agglutinin (UEA-1), peanut agglutinin (PNA), soybean agglutinin (SBA), and wheat germ agglutinin (WGA) exhibited variable reactivity patterns with different epithelia. UEA-1 was reactive with cells of the stratum intermedium and stellate reticulum in the tooth germ but unreactive with ameloblasts, outer enamel epithelial cells, and junctional epithelium at later stages. Reaction patterns of PNA in these cells differed from those of UEA-1. Results indicated that inner and outer cells of the reduced enamel epithelium are heterogeneous with regard to lectin binding patterns.

Ameloblasts↗

PubMed2002

The lateral enamel lamina--component of tooth primordia in selected mammalian species.

The lateral enamel lamina (LEL) is a part of the enamel organ, which is probably not involved in tooth formation. It represents, besides the "stalk" of the tooth primordium, a second interconnection between enamel organ and oral epithelium or vestibular lamina. We detected the LEL in the sheep (Ovis aries), the dolphin (Stenella attenuata), and the vole (Microtus agrestis) by light microscopy and computer-aided three-dimensional reconstruction. The LEL could be found in cap to bell stage tooth primordia, most clearly in slowly developing tooth germs. LEL-like structures have been furthermore described or depicted in tooth germs of the mouse, the elk (Alces alces), the dugong (Dugong dugong), the elephant (Loxodonta africana), and the human. Probably it is a part of all mammalian tooth primordia that undergoes regression during morphogenesis of the enamel organ. As a reducing structure, it should be considered in studies of tooth development.

Animals↗

PubMed1983

Carbonate incorporation and carbonic anhydrase activity in developing hamster molars in vitro.

Hamster molar tooth germs were tested in vitro for their capacity to incorporate 45Ca, 32PO4 and H14CO3 into their mineral. Concomitantly, the activities of alkaline phosphatase and carbonic anhydrase were measured in the cultured tooth germs. Incorporation of calcium and phosphate into the dental mineral increased with time in culture (0-10 days), whereas carbonate incorporation decreased slightly. Alkaline phosphatase and carbonic anhydrase increased with time. These results suggest that carbonic anhydrase is probably not involved in carbonate deposition, but in carbonate depletion of the dental mineral, carbonate being probably replaced by phosphate.

Alkaline Phosphatase↗

PubMed2005

LEF1 is a critical epithelial survival factor during tooth morphogenesis.

LEF1 is a cell-type-specific transcription factor and mediates Wnt signaling pathway by association with its co-activator beta-catenin. Wnt signaling is known to be critical for the specification of cranial neural crest (CNC) cells and may regulate the fate diversity of the CNC during craniofacial morphogenesis. Loss of Lef1 results in arrested tooth development at the late bud stage and LEF1 is required for a relay of a Wnt signaling to a cascade of FGF signaling activities to mediate the epithelial-mesenchymal interaction during tooth morphogenesis. It remains unclear, however, what is the cellular mechanism of LEF1 signaling in regulating tooth morphogenesis. To test the hypothesis that LEF1 signaling regulates the fate of the dental epithelial and the CNC-derived mesenchymal cells during tooth morphogenesis, we investigated and compared the cellular migration, proliferation, and apoptotic activity within the tooth germ between the wild-type and Lef1 null mutant mice. Using the Wnt1-Cre/R26R transgenic system for indelibly marking the progenies of CNC cells, we show that there is no CNC migration defect in the Lef1 null mutant mice, indicating that the arrest in tooth development is not the result of shortage of the CNC contribution into the first branchial arch in the Lef1 mutant. Furthermore, there is no alteration in cell proliferation or condensation of the CNC-derived dental mesenchyme in the Lef1 null mutant, suggesting that LEF1 may not affect the cell cycle progression of the multipotential CNC cells during tooth morphogenesis. Importantly, apoptotic activity is significantly increased within the dental epithelium in the Lef1 null mutant mice. As the result of this increased cell death, the bud stage tooth germ fails to advance to the cap stage in the absence of Lef1. Inhibition of apoptotic activity by FGF4 rescues the tooth development in the Lef1 null mutant. Our studies suggest that LEF1 is a critical survival factor for the dental epithelial cells during tooth morphogenesis.

Animals↗

PubMed2001

The distribution pattern of the hyaluronan receptor CD44 during human tooth development.

The aim was to investigate the expression pattern of the major cell-surface hyaluronan receptor CD44, as there are no existing data on its presence or absence in human dental structures at different developmental stages. Immunohistochemical localization of CD44 was studied using a monoclonal antibody, H3, that specifically recognizes an epitope in the common backbone of all CD44 isoforms. The dental lamina displayed a strong CD44 signal; the external enamel epithelium was negative. In the coronal region of the tooth germ the presecretory ameloblasts showed an intense reaction whereas the less differentiated inner enamel epithelial cells showed no signal at the cervical loop where they meet the external enamel epithelium. In the stellate reticulum a moderate reaction was detected. The secretory ameloblasts and the stratum intermedium showed a strong cell-surface CD44 signal. A strong signal was also observed on the odontoblasts and their processes. In the pulp, close to the odontoblastic layer, weak labelling was seen in the walls of capillary vessels. The distribution of CD44 in the human tooth germ corresponds to that of hyaluronan in most locations, suggesting that during tooth development this transmembrane protein plays an important part in hyaluronan-mediated events.

Age Factors↗

PubMed1999

Expression of E-cadherin and alpha-catenin in epithelial odontogenic tumors: an immunohistochemical study.

To clarify the possible role of cell adhesion in epithelial odontogenic tumors, expression of E-cadherin and alpha-catenin was examined by an immunohistochemical method. These molecules showed pericellular distribution in epithelial cells of the tooth germ and its derived tumors. In ameloblastomas, E-cadherin and alpha-catenin were expressed strongly in central polyhedral cells and slightly in peripheral columnar cells. These features resembled those of epithelial components in the tooth germ tissues, retaining cytodifferentiation of odontogenic epithelium. Expression of the molecules in the variants of ameloblastomas showed loss in the keratinizing areas and reduction in the granular cell clusters, suggesting terminal differentiation of the tumor cells. Calcifying epithelial odontogenic tumors and a clear cell odontogenic tumor preserved E-cadherin and alpha-catenin expression without a specific feature for histogenesis or cytodifferentiation. One case of two malignant ameloblastomas showed prominent reduction in expression of E-cadherin and alpha-catenin.

Ameloblastoma↗

PubMed2005

Hyper-expression of osteocalcin mRNA in odontoblasts of Hyp mice.

The Hyp mouse is a murine homologue of human X-linked hypophosphatemia that displays hypo-mineralization in bone and dentin. In this study, we tested the hypothesis that the defect in Hyp mice leads to alterations in the expression of dentin matrix proteins that may be associated with the hypo-mineralization changes in the tissues. Quantitative RT-PCR analyses showed that expression of the osteocalcin gene in Hyp mice tooth germ samples was significantly higher than in wild-type mice, whereas the gene expressions of osteonectin, osteopontin, dentin matrix protein 1, and type I collagen in both types of mice were similar. Further, cultured Hyp mice tooth germ samples exhibited a higher expression of the osteocalcin gene than did those from wild-type mice, which was in accord with the results of our in vivo analysis. These findings suggest that osteocalcin mRNA is highly expressed in Hyp mice odontoblasts and may be associated with dentin hypo-mineralization.

Animals↗

PubMed2001

The spatial and temporal expression of calretinin in developing rat molars (Rattus norvegicus).

Calretinin is a 29-kDa calcium-binding protein abundantly expressed in central and peripheral neural tissues. The aim here was to determine its expression during various stages of odontogenesis. Five categories of embryonic (E) and postnatal (P) rats at various ages (E17, E18, E20, P0, and P7), both male and female, were used to represent the various stages of molar tooth development. The heads of the experimental animals were harvested at the appropriate time and each was cut mid-sagittally and coronally to locate the tooth germs. Selected sections were stained immunohistochemically with polyclonal rabbit anticalretinin at a concentration of 1:25 after microwave irradiation. The results showed that calretinin is distributed widely in epithelium-derived tissues during odontogenesis in rat molar tooth germs. It was expressed focally in the dental lamina, outer enamel epithelium, stellate reticulum and stratum intermedium at different stages. In contrast, it was expressed diffusely and intensely in the inner enamel epithelium and presecretory ameloblasts, although it was discontinuous over the cusp tips. In the secretory ameloblasts, the staining was less intense, being restricted to the cytoplasm, including Tomes' processes. This distribution suggests that calretinin may play a part in enamel formation.

Age Factors↗

PubMed2004

[Expression of matrixmetalloproteinase-8 on the bell-stage in human and rat tooth development].

OBJECTIVE: To study the expression of MMP-8 in human and rat tooth development. METHODS: Immunohistochemistry was used to detect the localization of MMP-8 protein while in situ hybridization was used to examine the expression of MMP-8 mRNA. RESULTS: The expression of MMP-8 protein was localized in odontoblast and dentin matrix at the later bell stage in human tooth germ. The dentin was denser close to the pulp cavity. The expression of MMP-8 mRNA was found in very few polarized odontoblast at the early bell stage and all polarized odontoblast at the later bell stage in rat tooth germ. CONCLUSION: The results suggested that MMP-8 involved in dentin matrix rebuilding in the process of dentin formation in human and rat dental development.

Animals↗