Mauricio B. Andujar

Distribution and synthesis of type I and type III collagens in developing mouse molar tooth root

SummaryThe distribution and synthesis of type I and type III collagens in the mouse molar tooth root have been investigated by correlating light and electron immunohistochemical data. Purified rabbit antibodies were raised against mouse type I and type III collagens and indirect immunoperoxidase procedures were used. In these conditions, predentin, pre-bone, and pre-acellular cementum were intensely immunostained for type I collagen. Both optic and ultrastructural data confirmed the presence of type I collagen at the epithelio-mesenchymal junction, but Hertwigs basement membranes remained unlabelled. The odontoblasts including the short polarized ones, osteoblasts, some cells of pulp mesenchyme and the perifollicular cells possessed type I collagen immunoreactivity in the rough endoplasmic reticulum (RER), Golgi complex and the secretory vesicles.Type III collagen immunoreactivity was strong in the perifollicular mesenchyme, light in the pulp mesenchyme and absent from the epithelio-mesenchymal junction, the predentin, pre-bone and pre-acellular cementum. Intracellular immunolabelling was detected at the ultrastructural level in the perifollicular cells by a faint homogeneous peroxidase deposit in the RER cisternae.Finally, these results, compared with previous biochemical and morphological data, represent the first dynamic aspect of collagens distribution and synthesis in the mouse molar root development. In terms of cell differentiation, our data also suggest that type III collagen synthesis does not occur during the odontoblast process of differentiation.

Fibronectin in basement membrane of hertwig's epithelial sheath

SummaryThe distribution of fibronectin throughout the basement membrane of Hertwigs epithelial sheath was studied using specific antibodies with the immunoperoxidase technique in both light and electron microscopy.—Our results demonstrate that, after collagenase digestion in situ, the basement membrane was strongly labelled by antifibronectin antibodies on the lamina lucida, the lamina densa and the lamina (pars) fibroreticularis which contained aperiodic fibrils of 5–10 nm in diameter.

Histopathological and ultrastructural alterations in the aorta in experimental Solanum malacoxylon poisoning

SummaryA histopathological and electron microscopic study of the aortic wall of rabbits intoxicated withSolanum malacoxylon was performed.Histological examination showed local loss of the normal waviness of the elastic fibers and calcium deposits. Electron microscopic study of the corresponding areas showed a modified aspect of the smooth muscle cells with loss of some of their differential characteristics, especially their intracytoplasmic fibrils and densifications. The neighbouring elastic fibers showed an electron-dense peripheral band and sometimes a crystal deposit. X-ray microanalysis revealed the presence of a large amount of calcium in these crystals. Collagen fibers played no apparent role in this calcification.These findings support the idea that a local cellular alteration is necessary prior to elastic calcification. Two hypothetical mechanisms are proposed.

Immunolocalization of cathepsin D in dental tissues

Cathepsin D antigenicity was localized at the light and electron microscopic levels within dental cells, but not in extracellular matrix. Different intracellular sites for cathepsin D were found depending on the cell type: the enzyme was detected in secretory vesicles of the odontoblasts and in the lysosome-like structures of the ameloblasts. Otherwise, these results suggest that the secretory vesicles of the odontoblasts may contain both cathepsin D and type I collagen. These data might implicate cathepsin D in the enamel and the dentin formations.

Myofibroblast-like cells in non-pathological bovine endometrial caruncle

The fine structure of the fibroblastic cells of the normal bovine endometrial caruncle was described. These cells appeared different when compared with the classical fibroblasts encountered throughout the rest of the stromal endometrium. They possess some features similar to those of myofibroblasts reported in various pathological states, to those of epithelioid fibroblasts and to those of cultured fibroblasts. However, they appeared distinct by a few other aspects. We described here the ultrastructure of these particular fibroblastic cells, as they appeared in the caruncle in vivo and under physiological conditions.

Immunoelectron Microscopic Localization of Dentin Gamma-Carboxyglutamic Acid-Containing Proteins in Differentiating Rat Odontoblasts

The intracellular synthesis of the dentin-gamma-carboxyglutamic acid-containing proteins (DGPs) by rat odontoblasts was investigated at the electron microscopic level using a sensitive pre-embedding immunoperoxidase technique. The DGPs were detected in the rough endoplasmic reticulum and secretory vesicles, but not in the Golgi apparatus of the odontoblasts, while dentin matrix is not yet reactive. These results suggest that the DGPs synthesis is independent of mineral deposition.

Influence of fixative on the fine structure of mouse odontoblasts: a study on undemineralized tissue

The present report describes techniques of fixation and embedding suitable for studying the fine structure of odontoblasts without demineralization. The quality of the procedures employed was verified by comparing the ultrastructural preservation of the odontoblasts prepared by simple fixation and by the double-fixation method. Simple fixation by immersion in osmium tetroxide in vacuum preserves the longitudinal arrangement of the rough endoplasmic reticulum and Golgi apparatus, showing various vesicles which often contain filamentous threads of weak electron density aligned in parallel at repeating intervals typical of odontoblastic cells. The results obtained with this method are compared to previous descriptions of the ultrastructure of odontoblasts.