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Biomedical subjects

A Joffre

Publications and source records attributed to A Joffre.

16 recordsLinked to original sources
PubMed1992

Immunohistochemical localization of nerve growth factor (NGF) and NGF receptor (NGF-R) in the developing first molar tooth of the rat.

Nerve growth factor (NGF) is a well established target-derived trophic factor supporting sympathetic and sensory innervation in the peripheral tissues as well as cholinergic innervation in the brain. Despite its name, NGF may have broader biological functions early in development in a wide range of non-neuronal differentiating cells. The many effects of NGF are directly dependent on initial binding of NGF to specific plasma membrane receptors on target cells. Here we use immunohistochemical methods to show that NGF and its receptor (NGF-R) are localized in a variety of embryonic epithelial and mesenchymal cells in the rat developing molar tooth. Dental cells known to play important roles in morphogenesis and inductive tissue interactions show NGF-like reactivity. Thus, labelling is seen in epithelial preameloblasts and mesenchymal odontoblasts. We also show a transient expression of NGF-R in restricted parts of the dental epithelium (inner dental epithelium) and dental mesenchyme differentiating cells (post-mitotic, polarizing odontoblasts). The expression patterns of NGF are different to those of NGF-R during embryogenesis and this is illustrated in detail in the developing tooth. The histochemical findings reported here support the notion that NGF may have multiple roles during morphogenetic and cytodifferentiation events in the tooth.

Animals↗
PubMed1992

Odontoblast response under carious lesions.

The local regulation of odontoblast response to caries is viewed through initiation and elaboration of sclerotic as well as reparative dentin. Dentin tissue represents a multiple source of potent environment factors when teeth are affected by the demineralization phases of carious process. Some of them have already been identified in sound tissue (matrix glycoproteins, proteoglycans, growth factors, Bone Morphogenetic Protein) and may act on the cell through membrane receptors. Thus, the amplification in collagen synthesis and alkaline phosphatase activity previously observed during sclerotic dentin deposition can be related to the interaction between matrix signals and cell receptors such as the 165 kDa protein shown only by odontoblasts under the affected zone. Similarly, under established lesions generating cell death, the specific matrix made of odontoblasts debris and damage tissues, probably rich in active molecules, may trigger pulp cells to elaborate a cartilage-like layer (identified by type II and XI collagen) followed by odontoblast-like cells to give rise to abnormal tubular dentin. Here, odontoblast response is identical to bone-cells response to injury. What remains to be elucidated concern: The nature of signals found in carious dentin (matrix components, growth factors, bacterial products). The nature and regulation of expression of cell membrane receptors during tooth repair. How the odontoblast produces specific responses to each of these signaling molecules will be the focus of important new investigations.

Cell Differentiation↗
PubMed1991

Morphological and immunocytochemical characterization of cultured rat incisor cervical epithelial cells.

Epithelial cells from the cervical loop of the rat incisor were isolated by co-culture of apical explants with growth-arrested 3T3 fibroblasts. The epithelial phenotype of the expanding outgrowths was confirmed 10 days after the seeding of the explants by phase-contrast microscopy and immunocytochemical identification of cytokeratins. After 3 weeks in culture, the epithelial cells covered the entire surface of the coverslips and were then passaged. Subcultures gave rise to a confluent sheet within 10-12 days. Light and electron microscopy showed that confluent cervical epithelial cells generally reconstituted a bi-layered structure similar to Hertwig's epithelial sheath. Epithelial cells from the rat palate, cultured and subcultured according to the same procedure, organized themselves in 5-6 cell layers, the upper cells having generally a squamous morphology. Synthesis of extracellular matrix molecules by rat incisor cervical epithelial cells was studied with specific antibodies. These cells failed to produce type I collagen, but synthesized all the major basement membrane components (type IV collagen, laminin, heparan sulphate proteoglycan and fibronectin). These observations suggest that the culture conditions allowed the reconstitution of a typical Hertwig's epithelial sheath by rat incisor cervical epithelial cells.

Animals↗
PubMed1991

Immunoblotting and cytochemical characterization of human enamel proteins.

Mature enamel proteins (tuft proteins) and fetal enamel proteins were extracted by an homogenizing buffer method, subjected to SDS-PAGE and immunoblotted with a polyclonal antibody raised against the mature enamel proteins. Both fetal and tuft proteins were recognized by this immunoblotting. With the same antibody, immunolocalization of the developing enamel proteins was done on semi-thin-sections of human fetal tissue at the secretory stage, using an immunoperoxidase technique. Specific labelling of the enamel protein matrix was observed. It is concluded that a polyclonal antibody against mature enamel proteins (anti-tuft) can recognize the developing protein matrix at the secretory stage. This suggests that a common antigenic determinant is maintained throughout the course of amelogenesis in human enamel.

Adult↗
PubMed1990

In vitro mineralization of a three-dimensional collagen matrix by human dental pulp cells in the presence of chondroitin sulphate.

These matrices were used as cell culture substrates to investigate the influence of extracellular molecules on mineralization. Pulp cells seeded in type I collagen or type I collagen-chondroitin-4-sulphate sponges were able to grow and were morphologically similar to cells responsible for reparative dentine formation in vivo. In sponges consisting of collagen only, the cells elaborated an abundant new matrix which became organized with time and consisted of collagen fibres surrounded by fibrillar material, but no mineralization was observed. In collagen-chondroitin sulphate sponges, cells deposited less and poorly organized matrix; in these, calcification occurred, increasing with time, and at the ultrastructural level, small needle-like crystals containing calcium and phosphorus were scattered throughout the sponge fibres. These observations suggest that chondroitin sulphate might influence in vitro calcification induced by pulp cells.

Cells, Cultured↗
PubMed1990

Cytokeratins as molecular markers in the evaluation of the precise differentiation stage of human gingival epithelium reconstituted in vitro.

Cytokeratins are considered to be molecular markers for different types of epithelial differentiation. They were used to investigate the precise differentiation stage of gingival epithelium, reconstituted in vitro, following two different culture procedures. Human trypsin-dissociated gingival keratinocytes were seeded either on a feeder layer of irradiated mouse 3T3 fibroblasts or on a connective tissue equivalent (lattice) made up of human fibroblasts in a collagen gel. The cytokeratins were extracted and analysed by two-dimensional gel electrophoresis. Although both methods showed on histological sections that cultured gingival keratinocytes formed a multilayered non-keratinizing epithelium, the cytokeratins patterns showed great differences. The gingival epithelium-like structure reconstituted on 3T3 feeder layer expressed some cytokeratins characteristic of the in situ gingival epithelium (K 5, 6, 14, 16, 17) and some which do not exist in the normal tissue (K 8, 18, 19, traces of K 13 and K 15) and are specific for embryonic, simple and tumour epithelia. However, the gingival epithelium reconstituted on connective tissue equivalent expressed all the cytokeratins present in the normal tissue (K 5, 6, 14, 16, 17), except those specific for terminal differentiation (K 1, 2, and 10/11). These findings suggest that the culture of gingival keratinocytes on connective tissue equivalents allows them to reproduce physiological stages of differentiation.

Biomarkers↗
PubMed1989

[Use of human epithelial cultures in mucogingival surgery].

A clinical technique utilizing autologous cultured epithelial cells in vestibule deepening operations is described. Epithelial cells from oral mucosa were grown in tissue culture on a feeder layer, released from their flasks and placed with the basal side up on the recipient beds. The cultured cells induced rapid healing of the wound, which was free of pain and contractions. The greatest advantage of this technique is that there is no size limitation on wounds that can be covered by cultured epithelial cells.

Adolescent↗
PubMed1988

Localization of 28 kDa calbindin in human odontoblasts.

The presence of 28 kDa calbindin in human odontoblasts was studied by use of specific antibodies raised against chick duodenal 28 kDa calbindin, in immunofluorescence, immuno-peroxidase, and electron-microscopic labelling experiments. The calbindin-like protein was detected mainly in the cytoplasm of odontoblast cell bodies, in their processes and occasionally in their nuclei. Correspondingly, at the ultrastructural level, immunoreactive material was associated with the cytosol, microfilaments and cilia. These findings suggest that human odontoblasts express a 28 kDa vitamin D-dependent calcium-binding protein, unlike those of rats and mice in which ameloblasts are the only cells immunoreactive for the protein.

Animals↗
PubMed1988

Localization and synthesis of type III collagen and fibronectin in human reparative dentine. Immunoperoxidase and immunogold staining.

The injury of dental pulp tissue, following caries, is accompanied by the deposit of a typical hard scar tissue known as reparative dentine which should be regarded as the mineralization of a new organic matrix. Highly purified antibodies were used in combination with immunoperoxidase or immunogold technique at the ultrastructural level to reveal the distribution and synthesis of types I and III collagen and fibronectin elaborated by typical matrix-forming cells in the new tissue. Specific immunoperoxidase labelling, on demineralized teeth, clearly demonstrated that type I collagen represents the main type of collagen (88%). It is associated with bundles of fine striated fibrils of type III collagen and in close vicinity with fibronectin and constituted, at least, the new organic matrix of reparative dentine. Immunogold staining gave precise localization mainly over Golgi apparatus for the 3 components, thus suggesting that the cells concerned should not be considered as new odontoblasts but rather as pulpal cells in the process of differentiation participating in the formation of new dentine. Moreover, these events are very similar to those observed during wound healing in other tissues.

Collagen↗
PubMed1988

Trichomonas tenax: ultrastructure of giant forms.

Trichomonas tenax is a parasitic flagellate of the human mouth. The morphology and the ultrastructure of the protozoan are identical to those of other trichomonads. Giant forms suddenly appeared in a strain maintained in culture for two years. The structure and the ultrastructure of these abnormal forms were studied at the light and electron microscope level. Several nuclei, groups of flagella, undulating membranes and Golgi complexes were observed. The significance of these forms is still unknown.

Animals↗
PubMed1986

Type-I collagen production by human odontoblast-like cells in explants cultured on cyanoacrylate films. Electron-immunolocalization of fibronectin at cell/film interface.

Odontoblast-like cells derived from human tooth pulps were maintained in explant culture and grown either on glass coverslips only (used as control) or on glass coverslips coated with cyanoacrylate films. Ultrastructural and cyto-morphometric evidence showed that cells exposed to cyanoacrylate, in contrast to controls, display a significant decrease of rough endoplasmic reticulum and mitochondria. In addition, immunofluorescent staining and radioimmunoassays for type-I collagen suggested disturbances in production for the exposed cells. The use of anti-fibronectin antibodies with electron-microscopic immunoperoxidase-labelling demonstrated that the adherence of cells to cyanoacrylate can involve both adhesion plaques and fibronectin. These results therefore suggest that there were no apparent differences in the adhesion interaction of cells between glass and cyanoacrylate substrates.

Cell Adhesion↗
PubMed1979

Fine structural observations of calcium storage in human dental pulp cells in primary culture.

Primary culture of explants of human dental pulp tissue allows the study of the cytophysiology and differentiation of the cultured cells over a two-week period. The distribution of calcium was found in two different experimental conditions : with and without a calcium loading, by mean of a lead technique checked by microprobe analysis. The existence of two cell populations was revealed. Intra-mitochondrial ring-like granules characterize type 1 cells when overloaded, while a strong calcium storage is detected in the rough endoplasmic reticulum, Golgi apparatus and mitochondrial (without any inner organization of the deposits) of the type 2 cells. Our results also show the presence of calcium on gap-junctions (revealed) by lanthanum method), and on the extracellular matrix (collagen fibres and complex carbohydrates). The ability of some mitochondria to store calcium (ring-like granules) suggests that the type 1 cells are fully differentiated in odontoblast-like cells and perhaps engaged in mineralization processes. The calcium binding sites, localized on the extracellular matrix may therefore be considered as the earliest foci of calcification.

Calcium↗
PubMedDate not supplied

[Histological aspects of tooth bleaching technics].

The chemical principles of tooth bleaching are detailed in order to analyze scanning microscopy data obtained following internal and external bleaching tooth bleaching appears harmless to the enamel structure providing no etching is applied prior to bleaching. Previous enamel undermining appears to increase the porosity along preexisting cracks. Internal bleaching gives way to enamel and dentinal demineralization, which is of particular importance at the dento enamel junction. The biological effects of bleaching on dental hard tissues must be viewed in light of the clinical indications for these procedures.

Adult↗