Biomedical subjects

N Forest

Publications and source records attributed to N Forest.

At least 55 records · Page 3Linked to original sources

PubMed1993

In vitro differentiation and mineralization of cartilaginous nodules from enzymatically released rat nasal cartilage cells.

Nasal cartilage cells from 21-day-old rat fetuses were cultured at high density in the presence of ascorbic acid and beta-glycerophosphate over a 12-day period. Immediately after plating, the cells exhibited a fibroblastic morphology, lost their chondrocyte phenotype and expressed type I collagen. On day 3, clusters of enlarged polygonal cells were found. These cell clusters synthetized type II collagen and formed an alcian-blue-positive matrix. The following days, a progressive increase in the number of cells positive for type II collagen was noted and, on day 8, typical cartilaginous nodules were formed. These nodules increased in size and number, spreading outward, laying down a dense matrix which mineralized. Light and electron microscopy observations of cross-sections of nodules confirmed the cartilaginous nature of this tissue formed in vitro with typical chondrocytes embedded in a hyaline matrix. Furthermore, at the electron microscopic level, matrix vesicles were seen in extracellular matrix associated with the initiation of mineralization. Typical rod-like crystals were present in the intercellular spaces along the collagen fibers. These results indicated that in a specific environment, dedifferentiated chondrocytes were able to redifferentiate and to form nodular structures with morphological ultrastructure of calcified cartilage observed in vivo.

Alcian Blue↗

PubMed1993

[Value of the characterization of cytokeratins in the oropharyngeal epithelium].

Cytokeratins are cytoskeletal components and constitute the intermediate filaments of epithelial cells. They are twenty in number and their distribution characterizes a very specific profile in each kind of epithelium. The authors characterized the cytokeratin repartition of the normal oropharyngeal epithelia in order to study their alterations in pathologic tissues, especially in neoplastic and dysplastic epithelia. The normal oropharyngeal epithelium shows cytokeratin pattern of non keratinized stratified epithelia. Three mucosa samples were studied from inflammatory, dysplastic and neoplastic epithelia. According to the alterations of cytokeratin repartition in the two last samples, cytokeratin pattern analysis could allow a characterization or the differentiation stage of neoplastic tissues before the expression of morphogenic criteria.

Antibodies, Monoclonal↗

PubMed1993

Abnormal incisor-tooth differentiation in transgenic mice expressing the muscle-specific desmin gene.

Immunocytochemistry and electron microscopic observations on the incisor-tooth organ of transgenic mice expressing the muscle-specific desmin gene under the direction of the vimentin promoter, reveal that the expression of the hybrid transgene occurs both in mesenchymal cells and differentiating odontoblasts. The muscle-specific desmin, as estimated by fluorescence intensity, is more expressed in immature mesenchymal cells than in postmitotic differentiated odontoblasts. The expression of the transgene generates alteration of the odontoblast-intermediate filament network and interferes with the secretory activity of both odontoblasts and ameloblasts. Our results are consistent with the hypothesis that odontoblasts have inductive properties on the differentiation of ameloblasts and that intermediate filaments among other factors play the role of cell and tissue organizer.

Animals↗

PubMed1993

[Cell culture model and concept of bone surface].

Cellular differentiation areas leading to bone nodular formation from rat bone calvaria cells were studied under optic and electronic transmission microscope. 3H-thymidine labeling, BrdU proliferating cells and alkaline phosphatase cytoenzymatic reaction allowed us to dynamically describe the development of a cellular group called "Active Osteogenic Unit" (AOU) responsible for bone nodule formation. This AOU was formed by synchronized, localized and increased cell surface proliferation allowing a three dimensional cellular organization leading to an underneath osteoblastic cell proliferation. The osteocyte embedding process observed secondly are in relation with the cell heterogeneity forming the AOU. AOU's final cell activity might be a triggering factor in bone remodeling.

Alkaline Phosphatase↗

PubMed1992

Localization of malachite green positive lipids in the matrix of bone nodule formed in vitro.

An electron histochemical study was carried out on bone nodules formed in vitro in collagenase-released calvarial cells in order to visualize the lipid components of the extracellular matrix (EM). The malachite green aldehyde fixative technique, which allows both preservation and staining of some phospholipids of the extracellular matrix, was used. Controls were performed on sections demineralized, and then submitted to lipid extraction with a chloroformmethanol mixture (2/1 v/v) and to glycosaminoglycans digestion with 0.5% bovine testicular hyaluronidase to verify specificity for lipid staining. This allowed us to visualize the lipids (1) in the osteoid as granules associated to ribbon-like structures connected to the collagen fibers, (2) as electrondense deposits seen as dots on the outer surface membrane of the matrix vesicles, and (3) in the mineralized matrix as roundish patches formed of needle-shaped materials and at the mineralization front as individual ones. This study demonstrated that at the EM level, the lipids are present in the osteoid at locations very similar to what have been observed for the glycosaminoglycans, and in the mineralized matrix as components of the crystal ghosts.

Animals↗

PubMed1992

Expression of collagen, osteocalcin, and bone alkaline phosphatase in a mineralizing rat osteoblastic cell culture.

Rat calvaria bone cells isolated by collagenase digestion form a bone-like matrix which mineralizes in vitro in the presence of beta-glycerophosphate, in less than 2 weeks. The purpose of this work was to investigate, in this mineralizing rat osteoblastic cell culture, the synthesis of collagen, osteocalcin, and bone alkaline phosphatase (ALP). The results obtained indicate (1) After 15 days in culture, the extracellular-matrix contains collagen type I, V, and to some extent type III. Metabolic labeling at day 14, during the phase of nodules mineralization as well as new nodules formation, shows that collagen types I and type V are synthesized; (2) During the phase of cell growth, no osteocalcin could be detected in the medium, however, at the point of nodule formation, the osteocalcin level reached values of 3.55 +/- 1.39 ng/ml, followed by a 30-fold increase after nodules became mineralized. At day 14, after metabolic labeling, de novo synthesized osteocalcin was chromatographed on an immunoadsorbing column. With urea-SDS PAGE the apparent molecular weight was determined to be 9,000 daltons. (3) Specific activity of ALP was found to be 10 nmol/min/mg of proteins at cell confluence. At day 15, when nodules are mineralized, this activity was increased by 40-fold. The Michaelis constant was 1.58 10(-3) M/L. ALP was inhibited by L-homoarginine and levamisole but not by L-phenylalanine. ALP was shown to be heat sensitive at 56 degrees C with two slopes of inhibition.(ABSTRACT TRUNCATED AT 250 WORDS)

Alkaline Phosphatase↗

PubMed1992

Mineralization and bone formation on microcarrier beads with isolated rat calvaria cell population.

Using enzymatically isolated rat bone cells in the presence of cytodex microcarrier beads, osteoblastic cell differentiation and bone nodule formation were studied at the optical and electron microscopic level. Cytochemical method showed an intense alkaline phosphatase activity mainly around the microcarriers where the cells have formed multilayers on day 4 of cultures. On day 7 of experiment cultures, Von Kossa method stained positively only the cytodex microcarriers. During the following days, bone nodule formation was closely associated with cytodex microcarriers. In contrast, in control cultures with negatively charged glass beads, cells failed to pile up around the glass beads, and bone nodule formation occurred randomly in the culture dishes with 24 hour delay. Light microscopy observations of experiment cultures revealed the formation of nodular structures, with active osteoblastic cells forming a mineralized matrix in which osteocytes were present. Transmission electron microscopy revealed first, a mineralization process of the surface of the cytodex microcarriers which appeared like a granular electron-dense, collagen-free layer followed by the deposit of a collagenous matrix. These results indicated that cytodex microcarriers provided an excellent matrix for bone cell differentiation and mineralization.

Animals↗

PubMed1992

Surface-reactive biomaterials in osteoblast cultures: an ultrastructural study.

The tissue/biomaterial interface reactions of three biomaterials selected as candidates for hard tissue replacement were studied at the electron microscopical level after incubation with enzymatically isolated rat bone cells. An electron-dense layer was routinely observed between hydroxyapatite, coral, cytodex polymer and the neighbouring cells. This layer was visible before bone formation occurred, and was collagen free. The ultrastructural features revealed a needle-shaped filamentous layer continuous with coral material, whereas hydroxyapatite or cytodex/tissue interface was granular in appearance. These different structures may indicate reactive surfaces, depending on the composition of the substrate.

Animals↗

PubMed1992

Changes in cytokeratin expression during the development of the human oral mucosa.

The changes in cytokeratin expression by the developing oral mucosa of 10 to 23-week-old human fetuses were studied by indirect immunofluorescence using a panel of 15 monoclonal antibodies. The lining and masticatory mucosae were incompletely differentiated in 10-wk fetuses, since they expressed identical patterns of cytokeratins (CK 4, 5, 8, 13, 18, 19 and probably CK 14, 16, 17) very similar to that of adult alveolar mucosa. The main difference was the presence of cytokeratins 8, 18 and 19 in embryonic tissues. Cytokeratins 1, 2, 10 and 11 began to appear in gingival and hard palate epithelium from wk 11, predicting the differentiation of the masticatory mucosa by wk 16. The patterns of cytokeratin expression in the 23-wk fetus in the lining and masticatory mucosae appear to be different. In lining mucosa, the only difference from the 10th wk is a decrease in cytokeratins 8, 18 and 19, whereas the pattern of cytokeratin expression in masticatory mucosa (CK 1, 2, 4, 5, 8, 10, 11, 13, 18, 19 and probably CK 14, 16 and 17) is now very near that of adult gingiva. This pattern appears, as in the adult, to be similar to that of the epidermis in the same period.

Antibodies, Monoclonal↗

PubMed1992

A switch in cytokeratin expression and intermediate filament organization associated with epithelial stratification.

Low density gingival epithelial cells were cultured on the side of glass slides facing rat's tail collagen lattices. Under these conditions and in the presence of physiological level of calcium, colony formation was enhanced and stratification was slowed down. The strong attachment of the cells to glass slides permitted immunocytochemical examination of cytokeratin (CK) expression and their organization within individual cells during the different stages of epithelial maturation. The present results showed that during the stage of cell migration and colony formation, the cells express the same set of cytokeratins (basal cell marker 14, simple epithelial markers 8, 18 and 19, and marker of hyperproliferation 16) which forms a well-defined network of organized filaments. At the stratification stage, the filament network became dense by the additional expression of the markers of differentiation in non-keratinized stratified epithelia (CK 4 and 13). These appeared once individual cells started to overlap the basal cells, a period during which the cell-temporarily changed morphology. Whilst the suprabasal cells exhibited dense filament network labelled for CK 4 and 13, the density of labelled filaments for CK 14, 8 and 18 was much lower, indicating that these cells contained newly-formed filaments lacking the basal and simple epithelial keratins. The simple epithelial cytokeratins became weakly labelled in older cultures. The uncoupling of paired expression of cytokeratins 4 and 13 was observed in non-colony forming aged cells. This provides an example of altered program of cytokeratin expression during epithelial maturation.

Adult↗

PubMed1992

[Cytokeratins, markers of epithelial cell differentiation: expression in normal epithelia].

Intermediate filaments, the most stable of cytoskeleton components, are extremely diverse and usually correlate with the histological subtype since in nearly all cell types a single type of intermediate filament (IF) is found. The cytokeratins, which are specific of epithelia, are the largest and most diverse class of intermediate filaments. Twenty different cytokeratin polypeptides have been identified in humans and separated on the basis of isoelectrical pH and apparent molecular weight using two-dimensional electrophoresis. These data have been used to establish a cytokeratin catalogue which currently serves as a reference [43, 48]. The number of cytokeratin polypeptides expressed ranges from 2 to 5 for each epithelial cell and from 2 to 10 for each epithelium and even of each cell layer within a given epithelium. A broad spectrum of anticytokeratin antibodies with subgroup or single polypeptide specificity is currently available. The distribution of cytokeratins in normal epithelia is reviewed herein and commercially available anti-cytokeratin antibodies are listed.

Antibodies, Monoclonal↗

PubMed1992

[Expression of cytokeratins during embryogenesis and in pathologic epithelia].

Epithelial cell intermediate filaments, or cytokeratins, are excellent markers for cell differentiation. During embryogenesis, cytokeratins specific of a stage of differentiation step always become detectable before corresponding morphologic changes: for instance, cytokeratins 5 and 14 are found around the eight week, shortly before stratification of the epithelium occurs, and cytokeratins 1 and 10 are produced before morphologic evidence of keratinization becomes detectable. Among potential diagnostic applications, analysis of cytokeratin patterns of epidermal cells desquamated in the amniotic fluid may provide earlier and less invasive diagnosis than fetoscopic biopsies. Similarly, a review of cytokeratins expressed in a variety of epithelial diseases (involving the epidermis, digestive tract, respiratory tract, urogenital tract, or breast) demonstrated persistence of the original tissue pattern in some instances (this was the case for the majority of simple epithelia) but not in others (complex epithelia). This suggests that cytokeratins may prove valuable as markers for specific tumor stages or types and may provide earlier information than morphologic studies.

Breast Neoplasms↗

PubMed1991

Cytokeratin patterns of human oral mucosae in histiotypic culture.

In a three-dimensional culture model, oral epithelial differentiation was investigated ultrastructurally and biochemically for cytokeratin expression. Epithelia from the hard palate, gingiva and alveolar mucosa grown on freely floating collagen lattices populated with fibroblasts from homotypic origins, and fed with medium containing 10% delipidized fetal calf serum for 21 days before analysis, stratified and differentiated to basal cuboidal cells, polyhydral spinous cells and elongated superficial cells. The epithelium of palatal origin had non-nucleated superficial cells resembling orthokeratinized cells. The upper spinous cells had keratohyalin-like granules. The corresponding cells of gingival and alveolar mucosal origins retained their nuclei and had smaller numbers of keratohyalin-like granules. Basal cell keratins (CK 5 and 14) and those of hyperproliferation (CK 6 and 16) were consistently found in all epithelia. Furthermore, simple epithelial keratins (CK 18 and 19) were variably expressed by cells from different oral origins. In epithelial cells from the alveolar mucosa, CK 13 and 19 formed major bands, which correlates with their expression in vivo. In contrast, these polypeptides were either absent or formed minor bands in extracts of gingival and hard palatal cells. Although in small quantities, keratins of terminal differentiation (CK 1, 2, 10 and 11) were detected in gels prepared from palatal epithelia. This expression correlates with the higher morphological differentiation of these cells in this model. The model is of interest for studies of epithelial differentiation, as the differentiation markers of keratinized epithelia (CK 1 and 10) were expressed by cells from palatal origin, and those of non-keratinized epithelia (CK 4, 13 and 19) were prominent in cells from alveolar mucosal origin.

Adult↗

PubMed1991

Cytokeratin profiles in oral epithelial: a review and a new classification.

This article proposes a classification of oral epithelial and summarizes recent literature of cytokeratin expression in the oral cavity. The oral epithelial are subdivided into two major groups: superficial and deep epithelia. Epithelial lining the oral cavity, i.e., superficial, are essentially stratified squamous epithelia, with the exception of taste buds. The epithelium covering the dorsal tongue is a combination of keratinized and non-keratinized epithelia. Deep epithelia are of two kinds, odontogenic and glandular epithelia. This study provides a classification of the cytokeratins expressed in the oral cavity in healthy and pathological situations based on published data and our own studies. The profiles of these polypeptides in different oral epithelia should provide information that may be used in various disciplines of oral medicine.

Classification↗

PubMed1991

Characterization of cytokeratin patterns in the developing human tongue.

The characterization of cytokeratin (CK) in adult oral mucosa and developing teeth have been well documented in human. Cytokeratin distribution in developing oral mucosa has not yet been described. The aim of this study was to identify the expression of CK in human fetal tongue (week 10 to week 23) and to correlate the results with morphological maturation. Simple epithelial CK are expressed in all cell layers during the early stages, essentially in peridermal cells. From the 14th week, CK 18 is present only in the taste buds, making this polypeptide a reliable marker for this sensory organ. CK 4 and 13 are expressed from the 10th to the 23rd week by both ventral and dorsal lingual epithelia. Terminal differentiation keratins (CK 1, 2 and 10-11) can only be detected immunohistochemically at the 14th week in some cells on the external surface of some papillae. The number of these papillae and positive cells increase at the 19th and 23rd weeks. The terminal differentiation markers are expressed several weeks earlier than the formation of a well-distinguished keratinized layer.

Cell Differentiation↗

PubMed1991

How osteoblasts become osteocytes: a decreasing matrix forming process.

Osteocyte matrix inclusion process was studied in an in vitro woven bone nodule formation model where a large number of osteocytes at different degrees of maturation were examined. This work focused on early stages of osteocyte inclusion. This matrix inclusion occurred without a matrix synthesis inversion by the future osteocyte and with maintenance of close cell contacts with the replacing cell. A passive matrix embedding process related to a decreased activity of the osteoblast-osteocyte cell is proposed as a comprehensive pathway from osteoblast to osteocyte. The formation of the osteocyte is therefore presented as a very coordinated space and time related cell-cell interaction between cells of the three cell pools of the bone.

Animals↗

PubMed1990

Cytokeratin expression in human tongue epithelium.

The epithelium of the human tongue shows diverse morphological variations from one site to another and even within the epithelium of the same papilla. This complexity has led to confusion regarding tongue epithelium as being orthokeratinized, parakeratinized, or nonkeratinized. Cytokeratins have been shown to characterize different epithelia. The present paper describes cytokeratin expression by adult tongue epithelia and relates their distribution to morphology. Six healthy human tongue specimens were obtained after plastic surgery and cytokeratin expression was investigated immunohistochemically, using a panel of 15 antibodies for cytoskeletal proteins, and biochemically using two-dimensional gel electrophoresis. The results showed that the ventral and lateral surfaces of the tongue are related to the nonkeratinizing stratified squamous epithelia, esophageal type, whereas the dorsal surface showed mixed expression of cytokeratins. In the tip of filiform and on the surface of fungiform papillae, cytokeratins of terminal differentiation are expressed as skin type; and in the rest of the papillae as well as in interpapillary areas, the epithelium expresses esophageal type cytokeratins. Certain simple epithelial cytokeratins were found in taste buds. Cytokeratin 19 was also detected in the basal cell layer of all esophageal type epithelia in the tongue. The present results provide basis for studies on the biological events in epithelial differentiation during development and in pathology.

Cytoskeletal Proteins↗

PubMed1990

In vitro bone formation on coral granules.

We investigated the ability of fetal rat bone cells isolated after collagenase digestion to differentiate in vitro and to produce a mineralized matrix on coral granules. Scanning electron microscopy examination of the surface of the seeded coral granules revealed that cells attached, spread, and proliferated on the material surface. Bone nodule formation was studied in this in vitro system by direct examination under an inverted phase contrast microscope. The initial event observed was the appearance of cells with phosphatase alkaline activity arranged in several layers and forming a three-dimensional organization around the coral particles. By Day 7, nodule formation began and a refringent material appeared and extended to the background cells during the following days. By Day 15, some coral granules were embedded in a mineralized matrix. Histologic results demonstrated the formation of a mineralized tissue with the appearance of woven bone.

Animals↗