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V Everts

Publications and source records attributed to V Everts.

101 records · Page 6Linked to original sources
PubMed1977

Fine structure of an end organ in the periodontal ligament of the mouse incisor.

Nerve endings were observed between collagen fiber bundles in the alveolar compartment of the periodontal ligament. In close relation to these endings, cells were observed with a rounded cell body from which cytoplasmic extensions protruded, each forming part of a sheath around the terminal region of a small nerve fiber. The nuclei of these cells occupied an eccentric position in the cytoplasm and were characterized by a typical kidney shape. In the cell's center a prominent Golgi complex was present. In the peripheral cytoplasm ladder-like structures with a periodicity of 160 nm were occasionally observed. The cell bodies were surrounded by a basal lamina, while the cytoplasmic extensions investing the nerve endings were surrounded by an envelope consisting of alternating electron dense and electron translucent layers containing material that stained with PAS and Alcian Blue. Where these envelopes bordered on the connective tissue, areas of filamentous material with a periodicity of 100-150 nm were occasionally found. The end organs may be considered to form part of a receptor system.

Animals↗
PubMed1977

The site of remodeling of collagen in the periodontal ligament of the mouse incisor.

In an attempt to localize the site of remodelling of collagen in the periodontal ligament of the continuously erupting mouse incisor a radioautographic and stereologic investigation was undertaken. Grain distributions in radioautographs for light microscopy were studied at various time intervals after administration of [3H]-proline. The distribution of rough endoplasmic reticulum cisternae in fibroblasts and the incidence of collagen phagocytosis across the ligament were studied by means of stereologic methods at the electron microscopic level. No significant differences were found in half lives of [3H]-labelled substances among the various regions across the ligament. Rough endoplasmic reticulum cisternae within fibroblasts were distributed more or less uniformly throughout the entire width of the ligament. Analysis of the distribution of collagen phagocytosis, however, revealed that in the midregion of the ligament the amount of phagocytosed collagen was approximately four times as high as in the area adjacent to the tooth and about nine times as high as in the alveolar compartment. It is concluded that synthesis and turnover of total protein occurs throughout the periodontal ligament but that remodelling of collagen predominantly takes place in an intermediate area of the ligament.

Animals↗
PubMed1977

The epithelium in healing experimental standard lesions in the gastric mucosa of the rat. A light microscopical and scanning electron microscopical study.

In a series of experiments in rats, the movement of the advancing sheet of epithelial cells streaming from a border region into the woind bed of standardized defects in the glandular mucosa of the stomach was studied using the light microscope and the scanning electron microscope (SEM). A very high synthetic activity of mucus in gastric lining cells of the border region (with a typical shift in its reaction product towards a more acidly reacting product showing metachromasia with toluidine blue) was observed histochemically, together with a loss of characteristic features of glandular cells in the border region with an increase in mitotic activity. The SEM images enabled a detailed analysis of the advancing epithelial front in its relation to the border regions. Considerable local differences were noted in the moving pattern of the migrating epithelium, possibly in relation with the nature of the base on which it has to move. The lesion of 3 mm diameter appeared to close usually after 10 days; in some instances, however, small epithelial defects were later found which could easily be traced with the SEM.

Animals↗
PubMed1975

Frequency of occurrence and position of cilia in fibroblasts of the periodontal ligament of the mouse incisor.

Solitary cilia occur in motile as well as in non-motile fibroblasts of the peridontal ligament. The cells which moved with the erupting incisor are bipolar and oriented with their long axes parallel to the tooth surface. In cross section these cells have a flattened appearance. Cilia are localized in close vicinity to the nuclear area and show a definite orientation with respect to the transverse cell axis. The frequency of occurrence of this organelle was estimated from the percentage of diplosomes containing a basal body. Analysis of the composition of the paired structures indicated that at least 70 per cent of the fibroblasts are ciliated. The frequency of cilia in motile fibroblasts does not differ from that in non-motile cells suggesting that the presence of this organelle is not directly associated with cell locomotion.

Animals↗
PubMedDate not supplied

Perichondrium-wrapped collagenous matrices to induce chondroneogenesis: an in vitro study.

OBJECTIVE: To develop a model for cartilage regeneration in vitro, to be used for cartilage reconstruction in vivo. METHODS: Collagenous matrices were wrapped in a perichondrium layer. The matrices served as carriers to allow migration of cells from the perichondrium into the matrix. Culture conditions stimulated cell growth and proliferation. RESULTS: After 4 weeks of culturing, microscopic examination showed an increase of cell layers around the matrices but also of cells migrated into porous matrices. Immunohistochemical staining of these cultured cells expressed type II collagen intracellularly. CONCLUSIONS: This model seems appropriate to culture mucoperichondrial explants in combination with collagenous matrices. Cells migrate into the pores of the matrix, survive, and synthesize matrix components. Actual formation of cartilage has not been shown to occur. Adding growth factors to this model may influence induction of this activity.

Animals↗
PubMedDate not supplied

Inhibition of contact sensitizer-induced migration of human Langerhans cells by matrix metalloproteinase inhibitors.

Emigration of Langerhans cells (LC) from the epidermis upon exposure to contact sensitizers is regarded as an essential event in the development of contact sensitization. Since migration of several types of cells depends on the activity of matrix metalloproteinases (MMPs), in the present study we tested whether MMP inhibitors (BB94, BB2116 and CT1166) can prevent the emigration of LC in cultured skin explants, which were exposed to a contact sensitizer (NiSO4). Epicutaneous application of NiSO4 significantly reduced the number of LC within the epidermis and the remaining LC were localized along the epidermal-dermal junction indicating the emigration of LC. In the presence of each of the MMP inhibitors tested, NiSO4-induced migration of LC was strongly decreased. Since after the epicutaneous application of contact sensitizer, its presentation by skin LC is essential for the development of contact sensitization instead of the development of antigen-specific tolerance, our results suggest that the use of MMP inhibitors may be beneficial for the prevention of contact sensitization of the host.

Amides↗
PubMedDate not supplied

Electron microscopic study of the localization of ferric iron in chorionic epithelium of the sheep placenta.

The ferrocyanide method has been used to study, at the ultrastructural level, the maternal-fetal iron transfer in the chorionic epithelium of the haemophagous regions of the sheep placenta during the third trimester of gestation (at the 126th and the 145th day of gestation). No significant differences could be found in the distribution pattern of the ferrocyanide precipitate product with the chorionic epithelium in both stages of gestation. The presence of ferrocyanide reaction product in lysosomal structures, involved in the breakdown of maternal erythrocytes ingested by chorionic epithelial cells, confirmed that trivalent iron is liberated from digested haemoglobin. Ferric iron was also detected in the epithelial cytoplasmic matrix especially in the vicinity of erythrolysosomal structures, between the lateral surfaces of neighbouring epithelial cells, along the complex of interdigitating folds and the basal plasma membrane. Only on one occasion was the presence of ferric iron observed in the basal lamina, between the junctions of the endothelial cells and in their cytoplasmic matrix. The results of the present study indicate that after the ferric iron is liberated from maternal haemoglobin its ionic state, subcellular distribution and, probably, its route of transport seem to be similar to that in the guinea-pig placenta which is characterized by the uptake of iron from maternal transferrin.

Animals↗
PubMedDate not supplied

Host-derived proteinases and degradation of dentine collagen in situ.

Dentine root caries is a process of demineralization and degradation of the organic matrix by proteinases. In this in situ study, the presence and activity of the matrix metalloproteinases 1, 2 and 9 (MMP-1, MMP-2, MMP-9) in saliva and in completely demineralized dentine specimens were investigated. Furthermore, the activity of cathepsin B was determined in saliva. A correlation between these enzymes and the level of degraded collagen was investigated. Demineralized dentine specimens were mounted in the partial prosthesis of 17 volunteers. Saliva samples were taken at 0, 2 and 4 weeks. After 4 weeks, the enzymes were extracted from the dentine specimens and the collagen loss was assessed. The collagen loss varied between 0 and 40.3%. Zymography of the saliva and the dentine extract samples showed that (pro-)MMP-2 and (pro-)MMP-9 were present. The levels of active MMPs were assessed, using fluorogenic MMP-specific substrates. All but 3 of the 51 saliva samples showed MMP-1 activity ranging from 1.5 to 101.1 relative fluorescence units (RFU)/s. Forty-eight saliva samples showed gelatinolytic MMP-2/MMP-9 activity (1.7-141.1 RFU/s). MMP-1 activity was shown in all dentine extracts varying between 3.5 and 295.0 RFU/s. From the dentine extracts, 15 showed MMP-2/MMP-9 activity (0.2-13.7 RFU/s). The MMP activity from both saliva and dentine extracts did not correlate with the collagen loss. The activity of salivary cathepsin B varied from 4.8 to 42.2 arbitrary units/min. A positive correlation was found between salivary MMP activity and cathepsin B activity. This study revealed that gelatinolytic enzyme activity was present both in saliva and dentine collagen. No correlation could be observed, however, between the level of enzyme activity and the collagen loss of the dentine specimens.

Aged↗
PubMedDate not supplied

Use of frozen biologic material for combined light and electron microscopy.

A simple and rapid method that enables the use of unfixed frozen material for light and electron microscopic purposes is described. At the light microscopic (LM) level, unfixed cryostat sections were used for enzyme histochemistry. When electron microscopic (EM) inspection was needed, tissue blocks, which were stored at -80 degrees C, were fixed at 4 degrees C and prepared for EM according to standard procedures. Ultrastructural analysis of this material demonstrated that most morphologic aspects of normal (human pancreas and rat liver) and pathologic (human pancreatic adenocarcinoma and rat colon carcinoma metastases in liver) tissue were rather well retained. Cryostat sectioning at -25 degrees C did not appear to have damaging effects on the morphology. The method was applied to correlate enzyme histochemical (LM) data with ultrastructural (EM) aspects of mineralization of stroma in explants of human pancreatic adenocarcinoma grown in nude mice and of nonparenchymal cells around metastases of colon carcinoma in rat liver.

Adenocarcinoma↗