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Biomedical subjects

V Everts

Publications and source records attributed to V Everts.

At least 91 records · Page 5Linked to original sources
PubMed1987

The role of microtubules in the phagocytosis of collagen by fibroblasts.

The effects of the anti-microtubular agents, colchicine and vinblastine, on the phagocytosis of collagen by fibroblasts were assessed quantitatively in cultured mouse bone explants. It was found that in the absence of the microtubular system the volume density of lysosomal vacuoles containing cross-banded collagen fibrils in periosteal cells did not differ from that seen in controls. In contrast, cytochalasin B which interferes with the microfilament system prevented the accumulation of collagen-containing vacuoles in the cytoplasm. The data indicate that the phagocytosis of collagen fibrils by fibroblasts does not depend on the integrity of the microtubular apparatus, but seems to require an intact microfilament system.

Animals↗
PubMed1986

Resorption of the mouse incisor after the application of cold to the periodontal attachment apparatus.

In order to study in detail the processes leading to the resorption and ankylosis of teeth after trauma, the effects of cold application on the periodontal tissues were studied in the mouse. Liquid nitrogen was applied locally to the outer surface of the lower jaw which resulted in a freezing of the incisor and its surrounding tissues. The healing processes in the damaged periodontal ligament and the accompanying phenomena of ankylosis and dental root resorption were investigated histologically at both the light and electron microscopic levels. As a result of cold application, the cells in the periodontal ligament were killed. After a few days, the ligament started to be repopulated with cells like fibroblasts and macrophages. From 3 days on, mineral crystallites were deposited along the cementum covering the lingual, mesial, and lateral surfaces of the incisor, finally resulting in a 4-6 micron thick layer. During the period of 7-12 days following cold application, this layer of mineralized material started to be phagocytosed and degraded, presumably by mononuclear cells. Finally, extensive root resorption and some ankylosis between the tooth and the alveolar bone were observed. In the resorbed areas, cells were seen which could not be distinguished from osteoclasts. In some instances, their ruffled border was in close apposition with each of the three mineralized tissues--dentin, cementum, and alveolar bone. It is hypothesized that the deposition and subsequent phagocytosis of mineralized material along the root surface may be an important factor in the initiation of dental root resorption.

Animals↗
PubMed1986

Influence of oral 15(R)-15-methyl prostaglandin E2 on human gastric mucosa. A light microscopic, cell kinetic, and ultrastructural study.

Histomorphometric, electron microscopic, and cell kinetic studies of gastric mucosa were performed in 12 healthy men treated with 100 micrograms of 15(R)-15-methyl prostaglandin E2 (PGE2) orally q.i.d. for 2 mo followed by 2 mo of placebo. Results were compared with 13 control subjects receiving placebo for 4 mo. After PGE2 administration, total antral mucosal thickness and antral and corpus foveolar thicknesses increased 36%, 44%, and 51%, respectively, over baseline values. The total number and height of the foveolar cells also increased. These morphologic changes reversed completely within 2 mo of stopping PGE2 therapy. After PGE2 administration, no evidence of mucosal inflammation or atypia was observed, nor was there any evidence of ultrastructural changes in the overall appearance of the parietal and gastrin cells. The increased thickness of the gastric mucosa could not be explained by alteration of the proliferative activity, as the labeling index and localization of the proliferative compartment remained unchanged after PGE2 therapy. Presumably PGE2 retards senescence and exfoliation of epithelial cells, which explains the foveolar expansion in the presence of unaltered proliferation.

Adolescent↗
PubMed1986

Experimental gingivitis in relation to susceptibility to periodontal disease. II. Phase-contrast microbiological features and some host-response observations.

In the present investigation, a number of histological and immunohistochemical characteristics of periodontal tissues as well as the phase-contrast microscopy of dental plaque were studied after experimentally-induced gingival inflammation in relation to susceptibility to periodontal disease. The study included a younger (mean age 34.1 years) and an older age group (mean age 48 years) with a reduced but healthy periodontium. Both age groups had the same amount of loss of attachment which may suggest that they had different degrees of susceptibility to periodontal disease. At the start of the experiment, each patient was instructed to abstain from oral hygiene in one quadrant of the mouth for a period of 18 days. At the end of the 18-day period, supra-gingival plaque and gingival tissue samples were taken. As determined by phase-contrast microscopy, the plaque samples of both age groups contained relatively high proportions of spirochetes. This may indicate that the patients are at risk for recurrence of periodontal breakdown. The general histopathologic picture of the gingival tissue samples of both age groups was similar to the so-called 'early lesion'. However, IgA-producing plasma cells were found in most tissue samples of both age groups. The first part of this study showed that the younger, in comparison to the older, patients developed inflammation in terms of bleeding on probing more rapidly. These clinical results cannot be explained by the host-parasite parameters investigated in the present study.

Adult↗
PubMed1985

Effects of 1-hydroxyethylidene-1, 1-bisphosphonate (HEBP) on the formation of dentin and the periodontal attachment apparatus in the mouse.

The effects of the bisphosphonate HEBP on dentin formation and the structural relationship between the dentin and the developing periodontal attachment apparatus have been studied in the continuously growing mouse incisor. It was observed that HEBP (in doses greater than or equal to 8 mg P/kg b.w/day) not only inhibited the deposition of mineral crystallites in newly formed dentin matrix, but also entirely prevented the formation of a layer of acellular root cementum. It was further noticed that the drug interfered with the deposition of 3H-serine-containing substances at the predentin-dentin border. This was not always accompanied by an inhibition of dentin mineralization, thereby suggesting that 3H-serine-containing proteins (presumably phosphoproteins) do not play a critical role in the deposition of mineral layers onto previously formed ones. The absence of a cementum layer did not prevent the developing periodontal ligament from establishing matrix-to-matrix connections with the root-analogue dentin. Collagen fibrils of the ligament intermingled with those of the mantle dentin, which in contrast to teeth not exposed to the drug were clearly visible and not masked by electron-dense matrix components. Finally, it was found that the drug had distinct effects on the formation of root-analogue and crown-analogue dentin. Whereas during the course of the experiment the odontoblasts along the crown-analogue aspect of the tooth continued to produce circumpulpal dentin matrix, those along the root-analogue aspect of the tooth did so only when the mantle dentin layer had been mineralized prior to HEBP administration. This phenomenon is interpreted as being indicative of fundamental differences between the formation of crown and root dentin.

Animals↗
PubMed1985

Phagocytosis of bone collagen by osteoclasts in two cases of pycnodysostosis.

Electron microscopic examination of bone biopsies obtained from two patients suffering from pycnodysostosis revealed that osteoclasts contained (sometimes large) cytoplasmic vacuoles filled with bone collagen fibrils. These vacuoles stained positive for acid phosphatase activity, thereby suggesting that bone matrix had been phagocytosed and subsequently exposed to hydrolytic enzymes of the lysosomal apparatus. Collagen-containing vacuoles were not observed in osteoclasts of individuals not suffering from this disease.

Adult↗
PubMed1985

The digestion of phagocytosed collagen is inhibited by the proteinase inhibitors leupeptin and E-64.

Using morphometric methods the effects of the thiol-proteinase inhibitors leupeptin and E-64 on the digestion of intracytoplasmic collagen fibrils were studied in cultured mouse bone explants. Both drugs caused a dose-dependent increase of lysosomal structures containing cross-banded collagen fibrils (CCV) in periosteal fibroblasts. After an incubation period of 48 hours, leupeptin (in a concentration of 65 microM) caused a thirty-fold increase in the volume fraction of CCV. This effect proved to be reversible following upon the withdrawal of the drug. Since the leupeptin-related accumulation of intracellular collagen fibrils was not significantly inhibited by alpha, alpha dipyridyl (a drug that interferes with collagen fibril formation), it is thought unlikely that the fibrils represented newly synthesized collagen. This view is further substantiated by data obtained from explants incubated in the presence of the phagocytosis-inhibiting agent cytochalasin B. This compound completely inhibited the leupeptin-related accumulation of CCV. The data strongly suggest that collagen fibrils found in cytoplasmic vacuoles of periosteal fibroblasts represent collagen taken up by phagocytosis, the integrity of cytoplasmic actin filament systems is a prerequisite for phagocytosis of collagen to occur, and thiol-proteinases, such as cathepsin B, L, and/or N, play an essential role in the digestion of internalized collagen.

2,2'-Dipyridyl↗
PubMed1979

Resorption of connective tissue in the gingiva of the mouse incisor.

During eruption of the mouse incisor part of the periodontal ligament moves along with the tooth in occlusal direction and is degraded in the gingiva, just apically of the junctional epithelium. When studied with the electron microscope some connective tissue cells (fibroblasts) showed disorganization of both nucleus and cytoplasm. In other cells vacuoles were observed containing partly degraded cellular constituents. Sometimes within these vacuoles electron dense material with the appearance of clumped chromatin was observed. On the basis of this observation it is concluded that heterophagocytosis contributes to the process of fibroblast breakdown. The ultrastructure of these heterophagic cells resembled that of fibroblasts. Collagenous fibrils were observed within cytoplasmic vacuoles of fibroblasts indicating that collagen is phagocytosed and probably digested in the lysosomal apparatus. Part of the intercellular space was filled with a homogeneous material of moderate electron density, intermingled with some collagenous fibrils. Within some cells of the junctional epithelium partly degraded material was observed which may indicate that the epithelium contributes to the removal of residual products of connective tissue degradation.

Animals↗
PubMed1979

Unipolarity of fibroblasts in rodent periodontal ligament.

In order to investigate whether fibroblasts in rodent periodontal ligament have a structural polarity, the position of the Golgi apparatus or the centriolar region in the cells was studied using light and electron microscopy. It appeared that, in the periodontal ligament of continuously erupting mouse and rat incisors, centrioles in fibroblasts on the tooth side of the ligament are preferably located in the anterior (occlusally directed) part of the cytoplasm. Polarity of fibroblasts in a single direction was less pronounced or absent on the bone side of the tissue. In the mouse, fibroblasts in the connective tissue adjacent to the incisor also contained an extensive system of cytoplasmic microtubules, whereas in the fibroblasts on the bone side of the ligament microtubules were less frequent. Unipolarity of fibroblasts was also observed in the periodontal ligament of the rat maxillary first molar, which is characterized by a limited eruption. Here, the Golgi region was usually situated in that pole of the cells that was directed towards the alveolar wall and the occlusal plane. It is suggested that structural polarity of fibroblasts in the periodontal ligament of rodent teeth is associated with orientation of functional activities of the cells, such as unidirectional movement or unidirectional deposition or phagocytosis of collagen.

Animals↗
PubMed1978

The site of collagen resorption in the periodontal ligament of the rodent molar.

In an attempt to determine the pattern of collagen phagocytosis by fibroblasts in the periodontal ligament, a stereologic investigation of the mesial root of the maxillary first molar of the rat was undertaken. The distribution of fibroblasts containing intracellular collagen fibrils was studied at the electron microscope level in the periodontal ligament along resorbing and non-resorbing surfaces of the alveolar wall. It appeared that fibroblasts with collagen-containing vacuoles were more or less randomly distributed across the width of the periodontal ligament. No major differences were observed among the alveolar, cemental and intermediate zones of the ligament. However, local variations in the occurrence of cells containing intracellular collagen fibrils may occur. A relatively high concentration of ingested collagen fibrils was seen in fibroblasts located in the direct vicinity of osteoclasts, but not in the vicinity of osteoblasts. These observations suggest that remodelling of collagen is evenly distributed throughout the ligament, but may be influenced by local circumstances, such as the occurrence of bone resorption.

Animals↗
PubMed1978

Identity of a population of progenitor cells in gingival connective tissue of the mouse incisor.

In the gingiva of the mouse incisor, connective tissue cells were observed which were undergoing mitosis and contained collagen fibrils enclosed in vacuoles in their cytoplasm. The presence of intracellular collagen was noted in the majority of the dividing cells. On the basis of this observation it is suggested that renewal of the fibroblast population in the gingiva occurs preferentially by division of differentiated fibroblasts rather than by division of cells with a lower degree of differentiation.

Animals↗