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Biomedical subjects

R Weill

Publications and source records attributed to R Weill.

At least 37 records · Page 2Linked to original sources
PubMed1985

Collagenase in mineralized tissues of human teeth.

A collagenase cleaving native type I [14C]collagen but inactive against the synthetic substrate Pz-Pro-Leu-Gly-Pro-D-Arg was extracted from mineralized human dental tissue. The enzyme specifically degrades native collagen into characteristic products (3/4) and (1/4). Its apparent molecular mass of 68 kDa is relatively high in comparison with collagenases from other oral tissues. The enzyme is a metalloproteinase inhibited by low concentrations of the chelating agents EDTA, 1, 10-phenanthroline, alpha alpha'-dipyridyl, and not affected by diisopropylfluorophosphate, soybean trypsin inhibitor, and p-chloromercuribenzoate. It is stable to lyophilization and can be stored at-20 degrees C for at least 6 months.

2,2'-Dipyridyl↗
PubMed1984

Treatment of dental decay by CO2 laser beam: preliminary results.

Results obtained from two clinical cases, representative of 1,140 human teeth treated by CO2 laser beam during 3 years, announce a new conception of treatment of dental caries. The beam (P = 4 - 5 W, energy density of 9 to 25 kw/cm2) causes a dentin healing which becomes sterile, chemically and physically more resistant than pathological dentin. In addition, this exposure leads to an activation of the dentinogenesis supported by X-ray, confirming histo-pathological results obtained from experiments performed on animals.

Adolescent↗
PubMed1984

[Intramandibular segment of Meckel's cartilage in the rabbit embryo. Its cytological expression and osteogenetic fate].

Meckel's cartilage undergoes typical endochondral ossification within a model of the mandible, the ossification of which is then intramembranous. The concurrent development of two different osteogenetic processes in the 28 day-old rabbit embryo results in the formation of a single bony framework. These observations are based upon the assumption that Meckel's cartilage is not merely a supportive, primitive shaft without a definite ontogenetic future role, but rather an active participant in mandibular osteogenesis.

Animals↗
PubMed1983

[Immunologic distribution of collagens during the embryogenesis of the secondary palate in the Fauve de Bourgogne rabbit].

The distribution of collagens during development of the palate in the Rabbit embryo is studied using the technique of indirect immunofluorescence. During the phase prior to epithelial contact, only types II and III are found in the mesenchyme. Type I, which is abundant on the free surface of apical epithelial cells, becomes even denser at the time when the palatine projections unite. Type IV fluorescence clearly outlines the basement membrane. When epithelial development regresses, fluorescence in type I and IV decreases in a way such that, in the areas where mesenchymal coalescence is apparent, no immunofluorescent labeling is observed.

Animals↗
PubMed1983

Criteria for distinction of different epithelial phenotypes covering murine palatal shelves at the stage of fusion.

Of the major three positional regions associated with secondary palate morphogenesis, the medial edge epithelium facilitates palate fusion during mouse embryogenesis. The epithelial phenotype appears to be acquired vis-a-vis reciprocal and interdependent epithelial-mesenchymal interactions. The objective of the present study is to describe the histological features of the oral, nasal, and medial edge epithelia as well as adjacent ectomesenchyme in vivo and in vitro, during the 14th day of gestation and through 16 hr incubation. Swiss strain mouse embryos were used to investigate epithelial differentiation in vivo as well as in vitro. Histologic criteria used to distinguish different epithelial phenotypes included: (i) orientation of the nucleus, (ii) staining properties of the nuclei, (iii) pattern of intercellular spaces, and (iv) cell degeneration. These criteria were also effective in identifying different populations of ectomesenchymal cells adjacent to the oral, nasal, and medial edge palatal epithelia.

Animals↗
PubMed1982

[Tooth' non collagenous protein degradation by Streptococcus mutans (author's transl)].

Enzymatic degradation of non collagenic proteins of the organic matrix of bovine teeth by cariogenic Streptococcus mutans has been studied. The activity on glycoaminoglycans of a constitutive bacterial exoenzyme depends on pH. The speed of degradation of each proteic fraction varies depending on the presence of the substrate during the growing phase of the Bacteria.

Animals↗
PubMed1980

[Degradation of collagen by the cariogenic bacteria, Streptococcus mutans].

The behaviour of cariogenic Bacteria (Streptococcus mutans) is studied with regard to collagen, which represents 90% of the dentine organic matrix. Collagenase activity of cariogenic Bacteria is measured with radioactive precursors and gel electrophoresis and compared to reference bacterial collagenase (Clostridium histolyticum). Labelled collagen substrate has been prepared with two different methods: extraction by 0,5 M acetic acid from young Rat skin, previously labelled with L-proline 14C, or reduction by Na B3H4. Both collagen sutstrates have been incubated for 2 h in Terleckyj medium in which the Streptococcus mutans have been inoculated. The experiments show a proteolytic activity of Streptococcus Mutans on the collagen substrate.

Animals↗
PubMed1979

[Effect of concanavalin A on the palatine ridges in vitro].

Concanavalin A acts in three ways on palatal shelves cultivated in vitro: 1. it has a mitogen effect, particularly on the medio palatal epithelium; 2. this produces thickening of this epithelium; 3. a delayed fusion or no fusion of the palatal shelves. The renewed mitogen activity and loss of adhesion properties seem to be linked.

Animals↗
PubMed1979

Ultrastructural study of the protein-polysaccharides distribution in enamel from rat incisors.

The distribution pattern of the protein-polysaccharides in the rat incisor enamel was similar whether stained for glycoproteins (phosphotungstic acid) or for proteoglycans (alcian blue, bismith nitrate). Except for the holes at the dentino-enamel junction, where these components seem to exist as amorphous gel, protein-polysaccharides are closely associated to the proteinic fibrous matrix in rods and interrods structures as in prism sheaths where they are particularly abundant.

Animals↗
PubMed1979

[Late development of human dental enamel].

Planes of longitudinal fractures of human dental enamel observed in scanning electron microscopy showed morphological variations related to age. This late maturation was observed along the enamel sheaths which disappeared in the subsurface and decreased in the rest of the structure. The destructions produced by demineralizing substances (phosphoric acid, citric acid, EDTA) were always more severe in enamel of older teeth when compared to younger samples. A pretreatment of the fragments with a urea solution increased the acid effects only in young enamel. It is suggested that the late maturation of enamel consists in a reduction of matrix components.

Acid Etching, Dental↗
PubMed1979

[Autoradiographic study of the activity of odontoblasts and secretory ameloblasts in the rat incisor: changes induced by vinblastine].

An autoradiographic study conducted on the rat incisor showed the presence 4 hours after (3H) proline injection, of 25-30% of the grains on the secreting cells and 70 to 75% on the extracellular matrics. The simultaneous injection of vinblastine sulphate reversed these percentages to 75-80% on the cellular level and 25-25% on the matrics. The vinblastine therefore inhibited the secretory processes of these cell types. On the other hand, due to the alkaloid, the number of grains present increased over the ameloblasts and principally over the intercellular spaces. The effects of these secretion and permeability variations suggested that a flow of precursor rich material reached the epithelial layer whatever the state of ameloblast activity.

Ameloblasts↗
PubMed1979

Comparative investigations on fluorosed enamel.

Structural observations upon fluorosed enamel were made on human teeth extracted from Nabeul (Tunisia). Longitudinal sections of enamel were made and microradiographed. Topographical observatoons in the S.E.M. showed alterations of the pattern of mineralization. Fissures and clefts filled with plaque material were observed to reach to the surface of the teeth. They penetrated into enamel along the prisms. Acid etching of the surface by 30% H3PO4 revealed enlarged acid-resistant sheaths while the core of the prisms was irregularly etched. Inner portions of the enamel were observed on fractured fragments. The structure was not significantly perturbated except for areas of porosity. After demineralization of the sections by 10% EDTA at pH 7 and critical point drying, the organic matrix was observed in the S.E.M. : It appeared as a fibrous network. Compared with sound teeth the matrix was dense and irregular. Histochemical stainings showed the presence of organic material. Alcian blue and PAS positive contents were very low except near the enamel-dentine junction. Preliminary observations were made using SMI Cameca ion microanalyser and histochemical studies on undecalcified sections were made in order to compare the observations made with light microscopy with S.E.M. findings.

Acids↗
PubMed1978

[Passage of labelled elements between two palatal shelves in vitro].

3H Fucose of 14C Galactosamine have been incorporated in vitro into a palatal shelf. This shelf has been associated with the homologous non-labeled palatal shelf on a normal medium. The mesenchyme of the explants which were incubated with the isotope is densely labeled. In the epithelium the cells are scarcely labeled. The isotope is dense in enlarged intercellular spaces. On the free surface, the tracer is located in front of those intercellular spaces and does not form a continuous coat. When the shelves have fused, the isotope migrates through the intercellular spaces of the non-labeled epithelium into the mesenchyme.

Animals↗
PubMed1978

[Glycoproteins and proteoglycans in the predentin and dentin matrix in the rat: an ultrastructural study].

The ultrastructural distribution of the protein-polysaccharides was studied in the predentinal and dentinal matrices of the rat. Used for the indentification of the glycoproteins, the chromic-phosphotungstic acid mixture (Rambourt, 1967) weakly contrasted the predentine, underlined the mineralization front and impregnated the dentinal matrix. Alcian blue (Goldberg et al., 1977) as well as bismuth nitrate (Serafini-Fracassini and Smith, 1966), cationic stains for the proteoglycans, produced a strong contrast in the predentine, whereas in the dentine, which appeared clear, only 100 to 150 A granules associated with the periodic collagen striations were stained. This inverse variation between non collagenous proteoglycans and glycoproteins is discussed in relation to the mineralization process.

Animals↗