PubMed Health⌕ Search

Biomedical subjects

M B Andujar

Publications and source records attributed to M B Andujar.

12 recordsLinked to original sources
PubMed1992

Cell migration influences collagen gel contraction.

Collagen gel contraction is a striking feature where the presence of serum factors seems to be critical. However, the mechanism by which these factors control the contraction process is poorly understood. Therefore, the purpose of these studies was to examine by dynamic and morphological approaches, the influence of serum factors on fibroblast-mediated collagen gel contraction. Cellular behavior was assessed in terms of cell migration which was related to the effectiveness of the contraction process. Media containing serum, fibronectin-depleted serum, and a synthetic culture medium were employed to modulate cellular organization in the three-dimensional gel. The data suggested that the gel contraction process is controlled by cell-matrix and cell-cell interactions. The absence of plasma fibronectin in culture medium allowed faster cell adhesion and spreading on collagen fibrils, but did not influence the contraction rate. Serum factors, other than fibronectin, led to a less extensive gel contraction due to the impairment of cell migration. Therefore, cell migration seems to be an important factor by which the effectiveness of gel contraction is controlled.

Cell Adhesion↗
PubMed1991

Differential expression of type I and type III collagen genes during tooth development.

Collagen gene expression during mouse molar tooth development was studied by quantitative in situ hybridization techniques. Different expression patterns of type I and type III collagen mRNAs were observed in the various mesenchymal tissues that constitute the tooth germ. High concentration for pro-alpha 1(I) and pro-alpha 2(I) collagen mRNAs were found within the osteoblasts. We found that the cellular content of type I collagen mRNAs in the odontoblasts varies throughout the tooth formation: whereas mRNA concentration for pro-alpha 1(I) collagen decreases and that of pro-alpha 2(I) increases, during postnatal development. Moreover, different amounts of pro-alpha 1(I) and pro-alpha 2(I) collagen mRNAs were observed in crown and root odontoblasts, respectively. Type III collagen mRNAs were detected in most of the mesenchymal cells, codistributed with type I collagen mRNAs, except in odontoblasts and osteoblasts. Finally, this study reports differential accumulation of collagen mRNAs during mouse tooth development and points out that type I collagen gene expression is regulated by distinct mechanisms during odontoblast differentiation process. These results support the independent expression of the collagen genes under developmental tissue-specific control.

Animals↗
PubMed1990

Collagen gene expression and tooth development. An overview.

The regulation aspects of type I and type III collagen gene expression are examined and the relationships with tooth morphogenesis and differentiation are discussed. Type I and III collagens constitute the major molecular proteins of the dental tissues. In addition the collagen gene expression in the mesenchyme derived odontoblasts represents an important step in the cytodifferentiation at the mesenchymal level. Furthermore, odontoblasts seem to synthesize only type I and type I trimer collagens, but not type III collagen. Therefore, the aim of this overview is to describe the molecular mechanisms that control the expression of specific collagen genes during the process of odontoblast differentiation. The available data support the main transcriptional control and argue for the existence of an independent and developmental regulation during collagen gene expression in odontoblast cells.

Animals↗
PubMed1989

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.

1-Carboxyglutamic Acid↗
PubMed1989

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.

Animals↗
PubMed1988

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

The 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 Hertwig's 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.

Animals↗
PubMed1985

Early mouse molar root development: cellular changes and distribution of fibronectin, laminin and type-IV collagen.

We analysed epithelial-mesenchymal interactions that occur during the early stages of the formation of mouse molar roots using light and electron microscopy. Morphological changes observed in the cells of Hertwig's epithelial sheath, the pulp and the follicular mesenchyme are described. The Hertwig's epithelial cells lose their cuboidal form and become flattened, apparently intermixing with the cells of the follicular mesenchyme. At the light- and electron-microscope levels, immunoperoxidase techniques were used to localize fibronectin, laminin and type-IV collagen. These appear to be closely associated with cell differentiation and matrix deposition in developing tooth roots. In addition, at the ultrastructural level, intracellular immunoreactivity was detected. The rough endoplasmic reticulum and nuclear envelope of some cells of the periodontal ligament facing the acellular cementum exhibited specific reactivity with laminin and type-IV collagen. Moreover, these periodontal ligament cells express keratin, but not vimentin, filaments. Our results demonstrate that Hertwig's epithelial cells maintain their capacity to synthesize laminin and type-IV collagen, as well as to express keratin filaments, despite basement membrane fragmentation and the disorganization of Hertwig's epithelial sheath. Thus, some Hertwig's epithelial cells remain in the periodontal ligament intermixed with follicular mesenchyme cells.

Animals↗
PubMed1985

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.

Animals↗
PubMed1984

Fibronectin in basement membrane of Hertwig's epithelial sheath. Light and electron immunohistochemical localization.

The distribution of fibronectin throughout the basement membrane of Hertwig's 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.

Animals↗
PubMed1983

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.

Animals↗