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Query: UMLS:C0276640 (TEM)
 20,729 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The development of the temporomandibular joint of 400 fetal mice at stages ranging from the 13th to the 20th day after insemination was investigated under the light, scanning (SEM) and transmission electron (TEM) microscopes. The differentiation and development of a cartilaginous tissue were observed at the supero-posterior end of the mandible at the 13 days after insemination. This tissue grew backward, upward and lateralward continuously and maintained a constant articulation with the squamosal part of the temporal bone. Seventeen days after insemination, cell layers in the condylar process and articular disc were arranged regularly. An supero- and inferno-directional cellular differentiation initiated from the subfibrous (SF) layer toward the articular spaces and cartilaginous layer was observed. The perichondrial ossification had taken place with the invasion of capillaries and the differentiation of osteoblasts in the SF layer, and was followed with a hypertrophic degeneration and endochondral ossification in the condylar process. Such a bi-directional growth of collagen and elastic fibers starting from the SF layer was also observed. Observation under SEM and TEM on the autoclaved condylar process revealed a complicated network consisted of main elastic fibers running in the sagittal direction. These fibers as well as the proteoglycan which contributes to the resilient property of the condylar cartilage and the ability to endure tensile or compressive stress from surrounding tissues during the growth and development of the mandibular condyle. The developing cartilaginous tissue was stimulated with the pressure from the masticatory muscles to initiate an active differentiation of the fibrous layer, which was invaded by the blood capillary system closely related with the subsequent endochondral ossification. These results elucidate that the development of the temporomandibular joint has closely kept relations with the functional influences from surrounding tissues, which also play an important role in regulating postnatal growth of the mandible.
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PMID:A serial study on the development of the temporomandibular joint in the fetal mouse--in particular on the fibrous component in the condylar cartilage. 213 77

Because of its general effects on connective tissue metabolism diabetes mellitus is becoming more and more important in the orthopaedic field. For investigation of morphologic changes in the cartilage a model of streptozotocin-induced diabetes was used in 80 rats. Studies were performed by light-, scanning- and transmission-electron microscopy and by biochemical analysis of proteoglycan and collagen metabolism. Three months after onset of diabetes the chondrocytes show increased metabolic activity and at the same time first stage regressive changes. The morphologic changes correlate with a significant decrease of hexosamine content in the cartilage. There is no evidence for any disturbance of collagen metabolism at that time. After seven months the cartilage is widely necrotic, the collagen fibers are swollen and show almost total loss of their microstructure. There is no sign for reparation of the necrotic zones at this time. It is most remarkable that in many specimen crystal deposits are found just below the cartilage surface which from the TEM-findings look very much like calciumpyrophosphate crystals. The morphologic and biochemical results show that in the rat diabetes leads to a special type of cartilage changes with crystallic arthropathy which seems to be a valuable model for the study of metabolic osteoarthrosis.
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PMID:[Morphological and biochemical studies of the cartilage in the diabetic rat--a model for metabolism-induced arthritis]. 371 47

We studied proteoglycan distribution in areas of spontaneously occurring high and low permeability by TEM examination of ruthenium red-stained sections of the aortic arch of normolipemic and hyperlipemic pigs. We noted granules of two sizes: those smaller than 20 nm contained heparan sulphate, and those from 20 to 50 nm in size contained chondroitin or dermatan sulphate. In the aortas of pigs fed a normal diet, there were significantly more granules of both types in low permeability areas than in areas permeable to Evans blue dye. This is consistent with the theory that glycosaminoglycan provides a component for the control of aortic permeability. In the aortas of pigs fed cholesterol, there was an accumulation of lipid-filled monocytes in areas of high permeability and an increase in proteoglycan granule concentration, suggesting an increase in glycosaminoglycan concentration, which may be the precursor to extracellular lipid deposition.
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PMID:Proteoglycan distribution in areas of differing permeability to Evans blue dye in the aortas of young pigs. An ultrastructural study. 618 72

After intraperitoneal implantation into Swiss Silver rabbits, V2 rabbit carcinoma cells invade the mesentery where they form nodules of different size and texture: compact (less than 120 microns in diameter), loose (120-250 microns) and mixed (above 200 microns). Together with tumor development, certain changes take place in the loose connective tissue of the mesentery. Application of TEM, together with use of safranin O, has shown that, in areas free of tumor growth, collagen bundles become thick and heavy and proteoglycan density is increased. Concurrently, the number of fibrocytes, now transformed to fibroblasts, increases. Small, compact nodules are surrounded by a concentrically arranged extracellular matrix. Its overall density is similar to that of nodule-free areas. In the immediate vicinity of large, loose nodules, all constituents of the extracellular matrix disappear. Adjacent connective tissue is partly destroyed but still contains collagen fibers and proteoglycans. These findings suggest the following: The presence of V2 carcinoma cells induces marked alterations in the structured and non-structured components of the extracellular matrix. These changes are, at the same time, progressive and regressive and the occurrence of one or the other depends on local tumor progression. Progressive alterations may result from an increased activity of fibroblasts. Since degradative effects, on the other hand, are only seen in the immediate vicinity of larger tumor aggregates, it is assumed that a minimal number of tumor cells is essential for destruction of extracellular matrix.
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PMID:Morphology of peritumoral proteoglycan alterations in the rabbit mesentery invaded by V2 carcinoma cells. 649 Feb 6

The morphological features of avian epiphyseal cartilage have been investigated by freeze-fracture techniques. Progressive changes occurred in both the cells and the matrix during differentiation. Chondrocytes changed in shape from small flattened cells with few, short cellular processes, to enlarged ovoid cells with numerous long processes often associated with extracellular vesicles. In the matrix these vesicles appeared first in the cellular lacunae, then in the extralacunar matrix, becoming larger and more numerous. Large membrane-associated particles (MAPS) were seen on the p faces of the plasmalemma. These became progressively concentrated on and around the cellular processes, with few large MAPS being seen on the e face. Similar distribution of MAPS was seen in the matrix vesicles. Domains of hydrated proteoglycan aggregates were manifest as regular fracture patterns in the extralacunar matrix of the upper regions of the plate. Collagen fibrils progressively increased in size and state of aggregation, often being associated with matrix vesicles and in the end, with long plate-like mineral crystals. These findings, while in basic agreement with patterns observed with TEM, reveal important new features concerning cellular and matrix structure during cartilage differentiation.
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PMID:A freeze-fracture study of avian epiphyseal cartilage differentiation. 727 Sep 8

The effect of removal of glycosylaminoglycans on the mineralization of sheep periodontal ligament was determined using enzyme digests followed by incubation in solutions supersaturated with respect to hydroxyapatite at pH 7.4. TEM revealed that control periodontal ligament remained unmineralized. However, tissue from which glycosylaminoglycans had been removed contained plate-like crystals arranged parallel to and within the collagen fibrils. Electron probe and electron diffraction studies suggested that the crystals were apatitic with a similar order of crystallinity to dentine, and a Ca:P ratio of 1.61. In addition, the glycosylaminoglycan content of periodontal ligament, cementum and alveolar bone was compared using cellulose acetate electrophoresis. Periodontal ligament contained predominantly dermatan sulfate while cementum and alveolar bone contained mostly chondroitin sulfate. A role for glycosylaminoglycans in maintaining the unmineralized state of the periodontal ligament is suggested. Control of expression of specific proteoglycan species on a spatially restricted basis is presumably central to this role.
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PMID:The effect of glycosylaminoglycans on the mineralization of sheep periodontal ligament in vitro. 755 59

We previously reported that mutation of the transforming growth factor-beta3 (TGF-beta3) gene caused cleft palate in homozygous null (-/-) mice. TGF-beta3 is normally expressed in the medial edge epithelial (MEE) cells of the palatal shelf. In the present study, we investigated the mechanisms by which TGF-beta3 deletions caused cleft palate in 129 x CF-1 mice. For organ culture, palatal shelves were dissected from embryonic day 13.5 (E13.5) mouse embryos. Palatal shelves were placed singly or in pairs on Millipore filters and cultured in DMEM/F12 medium. Shelves were placed in homologous (+/+ vs +/+, -/- vs -/-, +/- vs +/-) or heterologous (+/+ vs -/-, +/- vs -/-, +/+ vs +/-) paired combinations and examined by macroscopy and histology. Pairs of -/- and -/- shelves failed to fuse over 72 hours of culture whereas pairs of +/+ (wild-type) and +/+ or +/- (heterozygote) and +/-, as well as +/+ and -/- shelves, fused within the first 48 hour period. Histological examination of the fused +/+ and +/+ shelves showed complete disappearance of the midline epithelial seam whereas -/- and +/+ shelves still had some seam remnants. In order to investigate the ability of TGF-beta family members to rescue the fusion between -/- and -/- palatal shelves in vitro, either recombinant human (rh) TGF-beta1, porcine (p) TGF-beta2, rh TGF-beta3, rh activin, or p inhibin was added to the medium in different concentrations at specific times and for various periods during the culture. In untreated organ culture -/- palate pairs completely failed to fuse, treatment with TGF-beta3 induced complete palatal fusion, TGF-beta1 or TGF-beta2 near normal fusion, but activin and inhibin had no effect. We investigated ultrastructural features of the surface of the MEE cells using SEM to compare TGF-beta3-null embryos (E 12. 5-E 16.5) with +/+ and +/- embryos in vivo and in vitro. Up to E13.5 and after E15.5, structures resembling short rods were observed in both +/+ and -/- embryos. Just before fusion, at E14.5, a lot of filopodia-like structures appeared on the surface of the MEE cells in +/+ embryos, however, none were observed in -/- embryos, either in vivo or in vitro. With TEM these filopodia are coated with material resembling proteoglycan. Interestingly, addition of TGF-beta3 to the culture medium which caused fusion between the -/- palatal shelves also induced the appearance of these filopodia on their MEE surfaces. TGF-beta1 and TGF-beta2 also induced filopodia on the -/- MEE but to a lesser extent than TGF-beta3 and additionally induced lamellipodia on their cell surfaces. These results suggest that TGF-beta3 may regulate palatal fusion by inducing filopodia on the outer cell membrane of the palatal medial edge epithelia prior to shelf contact. Exogenous recombinant TGF-beta3 can rescue fusion in -/- palatal shelves by inducing such filopodia, illustrating that the effects of TGF-beta3 are transduced by cell surface receptors which raises interesting potential therapeutic strategies to prevent and treat embryonic cleft palate.
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PMID:Pathogenesis of cleft palate in TGF-beta3 knockout mice. 1043 15

Spinal motor neurons possess reticular coats of extracellular matrix proteoglycans on their somata and proximal dendrites. In order to define the anatomical background of the network, spatial relationships of the perineuronal proteoglycans with synaptic boutons and astrocyte processes were analyzed in rat motor neurons by TEM after histochemical detection of the substances with cationic iron colloid, and by SEM after exposure of the cytoarchitecture with NaOH maceration. Narrow intercellular channels filled with proteoglycan were found to extend along the surface of the neurons to form a homogeneous network of a mesh size of about 1 microm. The system of perineuronal channels consisted of two parts: a primary intervaricose net which meandered among synaptic boutons on the surface of the motor neuron, and secondary subvaricose nets which irrigated interfaces between larger boutons and the neuron. No elements in the perineuronal cytoarchitecture coincided with the meshwork of proteoglycan, indicating the involvement of postsynaptic factors in the distribution of the substance. Thin astrocyte processes surrounding the neurons formed a distinct network with heterogeneous meshes corresponding to boutons of various sizes. The perineuronal glial nets extended their surface area in contact with the intervaricose nets of proteoglycan by complex cellular interdigitations. The subvaricose nets of proteoglycan compartmentalized multiple synapses on large boutons, suggesting an involvement in the division of the synapses during development.
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PMID:Three-dimensional microanatomy of perineuronal proteoglycan nets enveloping motor neurons in the rat spinal cord. 1045 28

Tendon is composed of type I collagen fibers, interspersed with proteoglycan matrix and cells. Glycosaminoglycans may play a role in maintaining the structural integrity of tendon, preventing excessive shearing between collagen components. This study tests the hypothesis that tendon extension mechanisms can be altered by modifying the composition of noncollagenous matrix. Tendon explants were treated with phosphate buffered saline (PBS) or PBS + 0.5 U ml(-1) chondroitinase ABC. Structural changes were examined using TEM and biochemical analysis, while strain response was examined using confocal microscopy and gross mechanical characterization. Chondroitinase ABC removed 90% of glycosaminoglycans from the matrix. Results demonstrated significant swelling of fibrils and surrounding matrix when incubated in either solution. In response to applied strain, PBS incubated samples demonstrated significantly less sliding between adjacent fibers than nonincubated, and a 33% reduction in maximum force. By contrast, fascicles incubated in chondroitinase ABC demonstrated a similar strain response to nonincubated. Data indicate that collagen-proteoglycan binding characteristics can be influenced by incubation and this, in turn, can influence the preferred extension mechanisms adopted by fascicles. This highlights the importance of maintaining fascicles within their natural environment to prevent structural or mechanical changes prior to subsequent analysis.
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PMID:The influence of noncollagenous matrix components on the micromechanical environment of tendon fascicles. 1613 17

To develop a single-unit osteochondral tissue with demineralized bone matrix gelatin (BMG), rabbit chondrocytes were cultured on demineralized bone matrix gelatin for 6 weeks. The engineered osteochondral tissue was characterized with histology, immunolocalization, TEM, SEM, biochemical assay, and gene expression analysis. About 1.3mm viable neo-cartilage was produced on demineralized BMG. RT-PCR, immunohistochemistry, TEM, biochemical assay, and histology revealed hyaline-like cartilage with zonal layers, intense type II collagen expression, and abundant proteoglycan content formed upon BMG compared with normal cartilage. But hydroxyproline content and type I collagen gene and protein expressions were significantly lower. We consider engineering cartilage tissue with chondrocytes cultured on allogenic demineralized BMG is a good approach for osteochondral tissue engineering.
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PMID:Demineralized bone matrix gelatin as scaffold for osteochondral tissue engineering. 1634 11


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