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

Collagen shields have been studied in the enhancement of the initial healing of epithelial defects, as an adjunct in the treatment of dry eye, and as a reservoir and delivery system for topical ocular medications. The authors used collagen shields to collect information on the numbers and types of free cells populating the normal and postoperative ocular surface. In addition, correlative microscopic techniques were used to study details of the mechanisms responsible for the dissolution of the shields when applied to the human eye. Collagen shields were applied as a bandage lens on the eyes of patients who underwent extracapsular cataract extraction (n = 10) or penetrating keratoplasty (n = 10) and on normal volunteers (n = 10). The shields were collected at the 1-day postoperative examination and fixed in aldehyde mixtures. Specimens then were processed for correlative light (LM), transmission (TEM), and scanning (SEM) microscopy. Cell accumulation was shown by SEM on both anterior and posterior shield surfaces. Cell adherence occurred primarily on the posterior shield periphery for approximately 2 mm, with the central zone relatively clean. Both LM and TEM evaluation revealed cell counts ranging from 0.066 cells/10(4) microns2 (standard deviation, +/- 0.256) in healthy eyes compared with shields placed on postoperative eyes (194.25 +/- 7.32 cells/10(4) microns2). Various correlative microscopy techniques revealed that most cells were polymorphonuclear leukocytes with a low number of other hematogenous (lymphocytes and monocytes) and exfoliated epithelial cells.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Collagen shields as a vehicle for collecting and studying migratory cells on human corneas. 174 Mar 59

Adhesion durability between dentin pretreated with 10-3 and 4-META/MMA-TBB resin was studied. Reduction of etching periods with 10-3 was not so effective as expected. The weakening of bond strength during immersion in water at 37 degrees C to the dentin pretreated for 1 sec occurred faster than those for either 5 sec or 10 sec. The strength decreased from 12 MPa at 1 day to 9 MPa at 3 months, 3 MPa at 6 months and finally 2 MPa at 1 year in the case of 1 sec pretreated dentin. On the other hand, the strength became half after the storage in water for 1 year in the cases of 5 and 10 sec pretreated dentins. Combination of 10-3 pretreatment and subsequent glutaraldehyde treatment could stabilize the decrease but not completely. SEM and TEM examinations suggested that dentinal collagen exposed by the etching but not entangled and impregnated by poly (4-META-co-MMA) easily deteriorated by water during the longer immersion. Collagen modified with 10-3 and then with glutaraldehyde was also changed by the longer immersion.
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PMID:[Durability of bonding between 4-META/MMA-TBB resin to dentin pretreated with 10-3. The effect of 10-3 pretreating period and subsequent glutaraldehyde treatment]. 213 46

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

Elevations in the lateral and dorsal neck region are known to be highly correlated with chromosomal aberrations in human fetuses. However, the morphology of the elevations is poorly described. Only in the case of Turner's syndrome has lymphatic vessel formation been shown to be deficient leading to swellings in the nuchal area. In Down's syndrome, non-echogenic nuchal oedemata can be visualized in ultrasound scan between the 10th and 15th week of gestation. In the present study, alterations in the extracellular matrix (ECM) of the skin in trisomy 21 fetuses were found to be the morphological basis of the nuchal oedema. The distribution of collagen type VI differs from that in normal fetuses, both in nuchal and leg skin. Collagen VI forms a denser mesh in trisomy 21 than in normal fetal skin, hyaluronan (HA) being the main glycosaminoglycan (GAG) component as judged from the appearance of the TEM precipitate after fixation in the presence of tannic acid. Nuchal oedema in Down's syndrome is therefore found to be an interstitial oedema. The interstitial fluid is bound to HA, leading to a swelling of the fetal dermis. No cysts or dilated vessels were found in the oedematous tissue. The presence of a high amount of HA during development can influence the behaviour of migrating cell populations, which might have a bearing on the pathogenesis of Down's syndrome.
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PMID:Alterations of the fetal extracellular matrix in the nuchal oedema of Down's syndrome. 783 86

A comparative polarized light (PLM), scanning (SEM), and transmission (TEM) electron microscopy study was carried out on cross- and longitudinal sections of human lamellar bone in the tibiae of four male subjects aged 9, 23, 45, and 70 years. SEM analysis was also performed on rectangular-prismatic samples in order to observe each lamella sectioned both transversely and longitudinally. The results obtained do not confirm the model hitherto suggested to explain the lamellar appearance of bone. In particular, the classic description by Gebhardt (still accepted by the majority of bone researchers), which suggests that collagen fibers alternate between longitudinal and transversal in successive lamellae, or that they have spiral paths of different pitches, appears to be no longer acceptable in the light of our findings. In fact, SEM and TEM observations here reported agree in demonstrating that lamellar bone is made up of alternating collagen-rich (dense lamellae) and collagen-poor (loose lamellae) layers, all having an interwoven arrangement of fibers. No interlamellar cementing substance was observed between the lamellae, and collagen bundles form a continuum throughout lamellar bone. Preliminary measurements of lamellar thickness indicate that dense lamellae are significantly (P < 0.001) thinner than loose lamellae. Compared with the classic model of Gebhardt, the dense lamellae correspond to the transverse lamellae and are birifringent under PLM, whereas the loose lamellae correspond to the longitudinal lamellae and are extinguished. Collagen-fiber organization in dense and loose lamellae is discussed in terms of bone biomechanics and osteogenesis.
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PMID:A new theory of bone lamellation. 827 80

The purpose of this study is to evaluate the biocompatibility of zirconium compared with titanium by the in vitro study using human osteosarcoma cell line (HOS). Various characteristics of the HOS cells cultured on zirconium (99.9%) and titanium (99.9%) discs were investigated. On the colony formation of the HOS cells, there were no differences between the zirconium and titanium in colony size and number. Good proliferation of the HOS cells was observed on the zirconium as well as on the titanium. Morphological observation of the HOS cells by SEM revealed that the cells on the zirconium as well as on the titanium were flat and polygonal in shape with radial pseudopods. Collagen fibers and calcified substances were observed in the matrix of the HOS cells by TEM on the zirconium as well as on the titanium. The calcium of the HOS cell layer was stained well by Dahl's method. Analysis of the HOS cell layer by the Fourier transform infrared spectroscopy indicated that the HOS cells formed the same matrices including the apatite on the zirconium as on the titanium. Measurements of the zirconium and titanium elution into the human saliva indicated that the elution of zirconium was less than that of titanium. These results suggest that zirconium possesses as excellent biocompatibility as titanium.
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PMID:[In vitro study on biocompatibility of zirconium and titanium]. 848 10

Corneas of tadpole, mouse, rat, guinea pig, rabbit, cat, cattle, and human were examined by TEM and SEM in a comparative study. The differences between species were noted mainly by using TEM. Bowman's layer showed a tendency to be well developed in higher mammals. Tadpoles lack a Bowman's layer, lower mammals have a thin Bowman's layer, and higher mammals have a thick Bowman's layer. The boundary between the substantia propria and Descemet's membrane was distinct in higher mammals. On the other hand, there are no differences in thickness of the collagen fibrils that constitute Bowman's layer and those of the substantia propria. NaOH digestion was utilized for SEM preparation. SEM imaging revealed a textured appearance of the epithelial side of Bowman's layer. In Descemet's membrane, fibrous long spacing (FLS) fiber-like structures, which are arranged in parallel to the endothelium, were observed by both TEM and SEM. To our knowledge, this is the first report of SEM observations of FLS fiber-like structures on the endothelial surface of Descemet's membrane. SEM at a plane normal to the plane of the cornea showed that Descemet's membrane has a piled laminar structure. Descemet's membrane is closely associated with the collagen layer of the substantia propria. Collagen fibrils invading from the substantia propria into Descemet's membrane were observed with both TEM and SEM.
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PMID:Comparative observations on corneas, with special reference to Bowman's layer and Descemet's membrane in mammals and amphibians. 1238 95

The ciliary zonules of the eye are composed of fibrillar and non-fibrillar components. Fibrils provide tensile strength and elasticity, whereas non-fibrillar components serve as a coating surrounding the fibrils. This coating behaves as a barrier to macromolecules. The present light and transmission electron microscopic (LM and TEM) study identified collagen IV as a novel component of this coating. Collagen IV was demonstrated by pre-embedding and postembedding immunohistochemical (IHC) techniques using monoclonal and polyclonal antibodies. The specificity of the polyclonal anticollagen IV antibody was verified by ELISA.
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PMID:Presence of collagen IV in the ciliary zonules of the human eye: an immunohistochemical study by LM and TEM. 1515 Feb 87

Collagen II is the majority of extracellular matrix components in articular cartilage, which with the major functions of preventing expansion of the tissue and distributing the load of body weight. To obtain man-made ECM, the reconstitution of collagen could be conducted in the presence of negatively charged polysaccharide, such as alginate. Alginate is an anionic polysaccharide capable of eversible gelated in calcium ion solution to prepare different shapes of biomaterials. Its well-known biocompatibility makes it an ideal material in biomedical applications. Thus, the aim of this study was to evaluate the effects of alginate on the fibrillogenesis of type II collagen. The preliminary results revealed that inclusion of alginate into soluble type II collagen solution could inhibit the development of turbidity of collagen solution, and the apparent rate constants in lag and growth phases decreased during collagen formation period, both rate constants decreased to about one-third of the original constants, respectively. From TEM observations, the collagen fibrils were significantly thicker in 0.05% and 0.1% alginate as compared with pure collagen solution. Furthermore, the D-periods of collagen fibers kept unchanged significantly under all reconstituted conditions, which meant the packing of collagen monomer was probably not affected by adding these amounts of alginate.
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PMID:Influence of alginate on type II collagen fibrillogenesis. 1592 68

Endothelialization of biomaterials is a promising way to prevent intimal hyperplasia of small-diameter vascular grafts. The aim of this study was to design a nanofiber mesh (NFM) that facilitates viability, attachment and phenotypic maintenance of human coronary artery endothelial cells (HCAECs). Collagen-coated poly(L-lactic acid)-co-poly(epsilon-caprolactone) P(LLA-CL 70:30) NFM with a porosity of 64-67% and a fiber diameter of 470+/-130 nm was fabricated using electrospinning followed by plasma treatment and collagen coating. The structure of the NFM was observed by SEM and TEM, and mechanical property was studied by tensile test. The presence of collagen on the P(LLA-CL) NFM surface was verified by X-ray photoelectron spectroscopy (XPS) and quantified by colorimetric method. Spatial distribution of the collagen in the NFM was visualized by labelling with fluorescent probe. The collagen-coated P(LLA-CL) NFM enhanced the spreading, viability and attachment of HCAECs, and moreover, preserve HCAEC's phenotype. The P(LLA-CL) NFM is a potential material for tissue engineered vascular graft.
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PMID:Fabrication of collagen-coated biodegradable polymer nanofiber mesh and its potential for endothelial cells growth. 1600 Feb 19


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