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 28,634 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Structural changes in the lens and vitreous body exposed to short-pulse Nd:YAG Q-switching laser were under study. The laser was focussed in the lens nucleus or vitreous center plane. A pulse energy was 7.1-9.3 mJ, with a total of 75-100 pulses. Cataract development was induced via the formation of cavities with the guidance spot focal plane localized in the lens nucleus plane. When the focus was in the vitreous body and the laser operated in a similar energy mode, great numbers of small cavities rapidly formed, this evidencing a shock wave propagation. Specific and structural conformational changes in the lens and vitreous protein molecules were detected by nitrate quenching of the triptophane amino acid residue fluorescence. Laser exposure was found to reduce triptophanile availability for nitrates, this evidencing protein complexes aggregation (collapse); besides, laser exposure essentially increased the amino acid residue quenching constants, which fact pointed to a decreased density of the vitreous collagen and lens crystalline negative charges (increased hydratation). These findings permit a conclusion that the shifts connected with injury to the vitreous body, with macular edema, or with detachment of the retina after exposure to Nd:YAG laser may be due to collapse of the vitreous gel liquified components.
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PMID:[Photo damage to the eye in exposure to the radiation from a Nd:YAG Q-switching laser: the physicochemical structural changes to the crystalline lens and the vitreous body]. 237 33

Cupromeronic Blue was used to stain selectively the proteoglycans in rat tail tendons under 'critical electrolyte' conditions. Earlier electron microscopical observations indicated that at least one type of proteoglycan filament is associated with tendon collagen fibrils at the positive staining band 'd'. To ensure that this was not an artefact caused by specimen preparation or the subsequent positive staining of the collagen fibrils, we have analysed low angle meridional diffraction patterns from stained but not dehydrated, embedded or counterstained tissues. Axial electron density profiles of Cupromeronic Blue-stained compared with unstained rat tail tendons revealed the axial locations and relative amounts of dye in both mature and young wet specimens. In mature tendons, the difference electron density profile contained a broad peak centred near residue 180 along the 234-residue D-period. This corresponds to the electron-optical staining band 'd'. In young tendons a similar distribution of stain was observed although in this case there was evidence of a doublet of peaks, one centred near residue 182 (band 'd') and the other near residue 165 (midway between bands d and e1). The wet proteoglycan--Cupromeronic Blue complexes distribute over about 30 nm along the collagen fibril axis. Comparison with the images of filaments seen in the electron microscope suggests that the dye complexes collapse significantly on dehydration and embedding.
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PMID:An X-ray diffraction analysis of rat tail tendons treated with Cupromeronic Blue. 241 14

Blisters have previously been observed in keratinocyte cultures depleted of vitamin A, and in cultures of keratinocytes from patients with epidermolysis bullosa. We have found that blistering may occur in keratinocyte cultures from normal human epidermis, grown under standard conditions, and our aim was to further characterize the mechanism of blister formation. Keratinocytes were seeded at 10(5) cells per 35 mm collagen-coated dish with a 3T3 feeder layer. Blisters were macroscopic, fluid-filled structures which formed irrespective of donor site, or donor age, and were noted on various alternative substrates (collagen, 3T3 + plastic, plastic alone). Blistering commenced around day 12, prior to confluency, and new blisters were formed for up to 5 weeks post-plating. Maximal numbers (up to 70 per dish) were present around days 12 to 20. Cleavage occurred at the cell/collagen interface to form a blister roof composed of 6 to 9 cell layers. The lowest layer appeared metabolically active, but, in contrast to peri-blister regions, lacked hemidesmosomes. The central 2 to 3 layers contained membrane-coating granules and keratohyalin granules while the superficial strata resembled rudimentary corneocytes. Cultures supplemented with 10(-5) M vitamin A formed no blisters, which correlated with suppressed differentiation. Ouabain (10(-7) M) caused blister collapse and a reversible inhibition of new blister formation. We conclude that blisters are a consistent finding in keratinocyte cultures grown under standard conditions. Their formation may be associated with active transport and triggered during differentiation. Further examination of this phenomenon might shed light on whether differentiation itself has an influence on keratinocyte attachment to substrate.
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PMID:Blistering in keratinocyte cultures: a regular phenomenon associated with differentiation. 242 May 91

Expression of intermediate filament (IF) isotypes was studied in six human and two murine melanoma cell lines. With one exception, these lines expressed IFs only of the vimentin type; neurofilament peptides, desmin and GFAP were not detected. However, the M5 human melanoma line also expressed extensive cytokeratin tonofilament arrays, as visualized by immunofluorescence with a panel of eleven monoclonal antibodies and hetero-antisera to cytokeratins; only the keratin 19-specific antibody BA16 did not react. By 2 D gel electrophoresis, five major keratin peptides were detected (keratins 7, 8, 13, 17 and 18), and an additional 57 kD peptide was detected on immunoblots with several antikeratin antibodies. Also observed in M5 cells was focal collapse of tonofilament arrays in mitotic cells. All the melanoma lines tested were positive for S100; M5 and two other cell lines were also positive for the 220-240 kD neuroectoderm-associated cell-surface differentiation antigen defined by monoclonal antibody UJ 127:11. In all the melanoma cell lines, secretion of extracellular matrix proteins (fibronectin, laminin and collagen type IV) was sparse or absent, and all were negative for the epithelial cell markers HMG-1 and HMG-2. Co-expression of keratin and vimentin by a melanoma cell line is discussed in the light of recent controversy concerning expression of cytokeratins by other neoplasms of putative neuroectodermal origins.
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PMID:Phenotypic analysis of cultured melanoma cells. Expression of cytokeratin-type intermediate filaments by the M5 human melanoma cell line. 242 48

After 15 days of mesializing or distalizing orthodontic treatment, 10 permanent premolars of young patients were extracted with the interdental gingiva. The connective tissues of the compressed or stretched interdental papillae were compared to that of untreated samples by light and transmission electron microscope. Large collagen fibres bundles represented by fibrils with a banding pattern of 64 nm and a mean diameter of 75 nm were observed in compressed interdental gingiva. Several elastic fibres with a mean diameter of 950 nm were also present. In some central areas of compressed gingiva collagen fibrils longitudinally split into widely spaced microfibrils were often observed in proximity to the elastic fibres. In stretched and untreated interdental papillae the collagen fibrils presented a mean diameter of 66 nm and 57 nm respectively. In both groups, few elastic fibres ranging in diameter 600 nm were seen. The increased size of the gingival collagen fibrils undergoing pressure and tension is indicative of remodelling of the fibrous collagen system. The fair increase in number and size of elastic fibres in compressed gingiva suggests that the elastic fibre system takes over the place whenever a collapse of the collagenous framework occurs.
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PMID:Ultrastructural changes of collagen and elastin in human gingiva during orthodontic tooth movement. 262 Jan 39

We attempted to ascertain the mechanism of portal hypertension and ascites complicating acute hepatitis in 66 patients who underwent transvenous liver biopsy and measurement of hepatic venous pressure gradient. Increase in hepatic venous pressure gradient was related to the severity of acute hepatitis, as indicated by the significant correlation between the values for hepatic venous pressure gradient and serum bilirubin, serum albumin or coagulation factor V, and by its higher value in patients with, than in patients without, encephalopathy. Hepatic venous pressure gradient was higher in patients with, than in patients without, ascites (12.5 +/- 3.4 vs. 8.4 +/- 3.6 mmHg, respectively; p less than 0.001). No ascites was clinically detectable in the patients in whom hepatic venous pressure gradient was below 6 mmHg. We tested the hypothesis that sinusoidal collapse due to liver cell dropout was a major factor in portal hypertension. Semiautomatic determination of the fractional area of sinusoidal collapse on chromotrope-stained sections and automatic measurement of Sirius red-stained collagen fiber density were performed. Hepatic venous pressure gradient significantly correlated with fractional sinusoidal collapse area (r = 0.61, p less than 0.001) and with Sirius red-stained collagen fiber density (r = 0.43, p less than 0.01). We conclude that portal hypertension in the course of acute hepatitis is related to the severity of liver damage and is a major factor in the development of ascites. Portal hypertension is mainly determined by intrahepatic vascular space being reduced by the collapse of sinusoids.
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PMID:Portal hypertension and ascites in acute hepatitis: clinical, hemodynamic and histological correlations. 277 10

This study describes the alterations induced by Interleukin-1 alpha and -beta (IL-1 alpha and IL-1 beta) on fibroblast-synthesized extracellular matrix. Fibroblasts were grown between pieces of dentin or in collagen-coated Terasaki wells for 3 or 6-9 weeks to create 3-dimensional cell-containing matrices constituted primarily of proteoglycans and collagens, respectively. Following incubation with IL-1 alpha or IL-1 beta (10(-9) M) at 37 degrees C for 24 or 72 hr, samples were prepared for light and electron microscopy. Both IL-1 alpha and IL-1 beta induced collapse of the extracellular matrix by 72 hr, as manifested by a decrease of the cross-sectional area and an increased density of the matrices. Three-week matrices were reduced 26% and 45% by using IL-1 alpha and IL-1 beta, respectively. Comparable values obtained by using 6-week matrices were 14% and 30%. Cells within the matrix, normally stellate in shape with numerous extended processes, attained a more rounded or spindle shape with few and reduced processes and showed apparent alterations at cell matrix attachment sites and rearrangement of the cytoskeleton. Elongated cells at the top of the matrix appeared more compressed. The alterations were more pronounced in cultures incubated with IL-beta than with IL-1 alpha. Immunocytochemistry of extracellular matrix components revealed a decrease in staining intensity of chondroitin and dermatan sulfate in the 3-week matrix following IL-1 beta incubation. There was also a decrease in collagen type 1 staining of 9-week matrices treated with IL-1 alpha or IL-1 beta. These studies show that IL-1 has an effect on fibroblast-synthesized extracellular matrix and indicate that the effects of IL-1 alpha and IL-1 beta may differ. The resulting collapse of the matrix appears at least in part to be due to changes in proteoglycans and collagens.
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PMID:Effects of interleukin-1 on fibroblast extracellular matrix, using a 3-dimensional culture system. 278 80

Titanium dioxide (TiO2) dust has generally been regarded as a "nuisance dust" in experimental animals and men. In this experiment, 16 dogs were exposed intratracheally to TiO2 dust for 9-15 months. The scanning electron microscopy with energy dispersive analysis of X-ray (SEM-EDAX), performed to identify the elemental composition of dust particles used in the study and in the focal lesions of the lungs, showed that dust particles were nearly pure titanium. Dust in the lung deposited mainly in the respiratory bronchioles and adjacent alveoli, with many alveoli filled by compacted dust particles. The pulmonary responses consisted of slight alveolitis, centrilobular emphysema, focal collapse of alveoli, and fibroblast hyperplasia with a few collagen fibres surrounding some of the TiO2-dust foci. Electron microscopically, many alveolar macrophages with intact nuclei contained a great amount of dust particles in their lysosomes, and in the dust foci, most of type I pneumocytes disappeared and type I pneumocytes showed hyperplasia. The alveolar subepithelial basement membrane were markedly thickened and bundles of collagen fibres were formed in the interstice. These findings suggest that TiO2 dust is one of the sorts which probably induce mild lung fibrosis in case a large amount is deposited in the lung tissue.
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PMID:[Pathogenic effects of titanium dioxide dust on the lung of dogs--a histopathological and ultrastructural study]. 279 52

The orientation of collagen fibres in bovine secondary osteons has been investigated in the scanning electron microscope (SEM) by removal independently of firstly the mineral component and secondly the collagen fibres. Demineralization of polished transverse sections reveals a lamellar structure for the collagen component but the precise orientation of the collagen in each ring is not unequivocably determined. However, by using a collagenase solution to etch away the collagen component of a polished surface, holes are produced in the mineral revealing the former position of the fibres. The greater rigidity of the mineral component ensures that the structure does not collapse and produce artifacts. A specimen cut so that transverse and longitudinal sections are simultaneously observed allows the relationship between the structural features on each surface to be revealed. Analysis of such micrographs indicates a model for the collagen component of osteons in which the lamellar structure contains fibres with orientations alternately parallel to and circumferential to the long axis of the osteon. Tilting the samples to look directly down the holes shows that the fibres are not precisely longitudinal and circumferential but are tilted from these ideals by a variable angle (typically 20 degrees) the precise angle probably being an important factor related to the in vivo mechanical property requirements.
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PMID:Collagen fibre orientation in bovine secondary osteons by collagenase etching. 282 98

The collagen structure of the canine anterior cruciate ligament (ACL) and patellar tendon (PT) was examined by using light and scanning electron microscopy. The collagen waviness known as a crimping was found to occur in ACL and PT fascicles. This waviness, seen at the periphery of fascicles, is very smooth, and its amplitude seems to decrease from the periphery toward the fascicular center. It appears as a periodic collapse of the fascicle in two dimensions. Two models of the architectural patterns of the ACL and PT wavy fascicles are presented. The constituent collagen fibrils are either parallel or twisted relative to the fascicle axis, giving rise to planar and helical wave patterns, respectively. There is a distinct difference between the ACL and PT collagen structure. The helical wave pattern occurs in both PT and ACL while the planar waveform is found only in the centrally located ACL fascicles. In addition, there is less variability in fascicular size and density over the PT cross-section than in ACL.
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PMID:Microscopical investigation of canine anterior cruciate ligament and patellar tendon: collagen fascicle morphology and architecture. 291 23


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