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Biomedical subjects

M Heritier

Publications and source records attributed to M Heritier.

At least 19 recordsLinked to original sources
PubMed1987

Cellular behaviour in epithelial root sheath following vinblastine administration in mouse.

After injection of vinblastine sulfate (VLB) cells of the epithelial root sheath (ERS) showed accumulation of phagosomes lysosomes and, in particular, of exocytosis vesicles facing the basal lamina. An unusual frequency of cell contacts was also noted between pulp mesenchyme and ERS. In the periradicular zone the cells showed accentuated signs of a squamous-like evolution. In addition, numerous mitotic figures were seen arrested at prometaphase all along the tissue: the mitotic arrest index was higher at the tip of the sheath and decreased more coronally. These findings strongly suggest that ERS participates actively to the formation of the basal lamina. They show that heterogenous cell relations frequently occur during root morphogenesis; however they put into question the role of ERS in cementogenesis. The existence of a high mitotic potential in ERS can explain its consistent morphology and might reflect a process of differential mitotic sequences involved in odontoblast differentiation.

Animals↗
PubMed1983

Ultrastructural study of new connective tissue attachment following phosphoric acid application on human root dentin.

THE PRESENT STUDY was undertaken to verify whether acid conditioning of the root surface can promote new connective tissue attachment in man. A flap was raised over two maxillary central incisors, with 6-mm pockets, which had to be extracted in a 72-year-old woman. Following root planning, a rectangular area was delineated by a groove on the buccal surface of the teeth. Inside these limits, cementum was removed and the denuded dentin was etched with a 50% gelified phosphoric acid solution (pH, 1.3) for 1 minute and the flap was repositioned. Forty-two days later, the experimental teeth were extracted, and undecalcified specimens were prepared routinely for transmission electron microscopy. Results showed that new connective tissue attachment had occurred between healing connective tissues and acid-treated dentin surface, with functionally oriented Sharpey's fibers. The mechanism of new connective tissue attachment could be observed as a typical cementum crystallites deposition on a denuded dentin matrix coupled with an active collagen fibrils synthesis. This process resulted in the incorporation of fibers into the new superficial layer of cementoïd tissue.

Aged↗
PubMed1982

Experimental induction of cementogenesis on the enamel of transplanted mouse tooth germs.

First and second maxillary molar tooth germs with their surrounding bone were removed from 9-day-old mice, freed of the reduced enamel epithelium, re-inserted crown downwards in their bony crypts and then transplanted in the subcutaneous tissue of hosts of the same age and litter. Grafts were removed 14 days later and prepared for light and electron microscopy. In the areas where the reduced enamel epithelium was missing, a layer of cementum-like tissue was present on the enamel surface, always associated with cells showing the typical features of cementoblasts. A thin electron-lucent layer of fine fibrillar material separated the enamel surface from the new hard tissue which was composed of densely-packed collagen mixed with a ground substance. Where the cementum-like tissue was thick, cells were trapped in a collagenous matrix. The cementogenesis on enamel was strictly dependent on the absence of the reduced enamel epithelium. Thus, when exposed to follicular tissue, the surface of immature enamel appears to exert an influence on follicular cells and stimulate cementogenesis. This hypothesis could explain the presence of overgrowths of cementum in the cervical region of tooth crowns where the reduced enamel epithelium may be particularly vulnerable.

Animals↗
PubMed1982

[Scanning and transmission electron microscopy study of the effects of a citric acid solution on the human root dentine].

After removal of the cementum layer, the buccal surface of human roots was been treated in vitro for 60, 120 and 180 seconds with a gel solution of 50% citric acid (pH 2.1). These surfaces were prepared for observation in the scanning electron microscope (SEM) and ultra-thin sections of the treated areas were studied in the transmission electron microscope (TEM). The SEM results showed that application of an acid solution revealed fibrous like structures on the dentinal surface after 60 and 180 seconds of treatment. A correlation between the results obtained in SEM and TEM is not always evident. The ultra-thin sections showed, in the superficial dentine, three distinct zones at the three time intervals chosen: from outside to inside, a very thin crust, a demineralized zone with collagen fibres and a deep dentine zone could be observed. After 120 seconds, the collagenous matrix seemed to be totally freed from the inorganic part.

Adult↗
PubMed1981

[Microscopy and electron microscopy of the Hertwig sheath in the mouse].

The structure and ultrastructure of Hertwig's sheath have been studied in the mice on molar tooth germs collected on day 16. On a morphological basis, two parts, a diaphragm portion and a sheath part could be described. The diaphragm portion consisted of two layers, one internal and one external with in between occasionally cells disposed in quincunx. Mitotic activity was noted in the external layer. This fact raised the possibility of the existence of a cellular flow from this layer towards the internal counterpulpal layer. The permanent existence of the sheath during root elaboration could thus be explained. In the internal layer structural modifications and cell axis variations seemed to be related to the odontoblast differentiation. In the "sheath" part electron microscopy revealed the existence of a fine layer of unmineralized collagen fibrils which remained under the internal epithelial layer. The observations related to the structure of the periradicular sheath cells questioned the hypothesis whether these cells assume secretory potentials.

Animals↗