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PubMedDate not supplied

Clefts in intradermal nevi: an ultrastructural study.

Six intradermal melanocytic nevi, two with and four without intercellular slitlike spaces, were examined by light microscopy and electron microscopy of deparaffinized tissue. The spaces were partially lined by elongated nevus cells and contained a few collagen fibrils. Other features in both groups included an abundance of (1) immature elastic tissue comprised of aggregates of microfibrils lacking an amorphous component and (2) collagen fibrils that were finer than in normal dermis and did not form compact bundles. We propose that these elastic tissue and collagen fiber changes diminish the resistance of the dermis to the mechanical stress of the biopsy procedure and histologic processing, resulting in the formation of artifactual clefts.

Adult↗

PubMedDate not supplied

Elastofibroma: an in vivo model of abnormal neoelastogenesis.

Thirteen cases of elastofibroma have been studied by conventional light and electron microscopy, as well as by histochemistry and immunohistochemistry. By light microscopy elastinophilic material appeared as huge fibers crossing collagen bundles. Immunohistochemistry demonstrated a strong positivity for elastin in numerous and circumscribed areas of the extracellular matrix. By electron microscopy, collagen consisted of 40-50-nm wide fibrils, and elastin was made of large aggregates of moderately electron-dense material surrounding a very thin, apparently normal, elastin core. At high magnification these aggregates consisted of short tubules, often in regular arrays, surrounded by microfibrils and microfilaments. These data, associated with selective digestions on thin sections with elastase, purified collagenase, hyaluronidase, and chondroitinase ABC, revealed that elastic fibers in elastofibroma seem to be made of true elastin surrounded by an enormous amount of hydrophilic material, in which some elastin, chondroitin sulfates, and collagenase type-VII sensitive material are aggregated forming a rather ordered array of short tubules.

Adult↗

PubMedDate not supplied

Fibro-osseous lesion with calcified spherules (cementifying fibromalike lesion) of the tibia.

The histologic and ultrastructural features of a tibial lesion strongly resembling cementifying fibroma of the jaws are described. Histologically the lesion consisted of fibrous tissue containing small calcified spherules. In some areas acellular trabeculae or islets with lobulated margins of a cementlike substance occurred. Spherules and small calcified bodies were composed of apatite crystal depositions along the collagen fibers and were often in close contact with membrane-surrounded cytoplasmic processes resembling matrix vesicles. In fibrous tissue fibroblasts, myofibroblasts, and undifferentiated cells with numerous cytoplasmic processes and intracytoplasmic microfibrils were present. The character of the cellular component of this lesion and the presence of calcified spherules arranged in a manner rarely observed in fibrous dysplasia indicate a histogenic relationship between the two lesions.

Adult↗

PubMed1992

Synthesis of extracellular matrix components by human ciliary muscle cells in culture.

The production and spatial organization of connective tissue components in ciliary muscle cell cultures was studied with immunohistochemical and ultrastructural methods. Antibodies against collagen types IV and VI, fibronectin and laminin were used. Laminin stains as pericellular network surrounding individual muscle cells. Type IV collagen shows positive cytoplasmic staining and only small foci of extracellular immunofluorescence. Staining for type VI collagen and fibronectin is seen near the ends of the bipolar cells, while the lateral sides of the cells remain unstained. Electronmicroscopy shows that cultured ciliary muscle cells are surrounded by an incomplete basal lamina. In addition, bundles of 5-20 nm thick extracellular microfibrils are seen. The bundles are oriented parallel to the axis of the cells and are in close contact with the cell membrane in areas where membrane-bound dense bands are formed. Immunoelectronmicroscopy indicates that the bundles contain fibronectin and type VI collagen fibrils. While the fibronectin fibrils approach the cell membrane directly, type VI collagen fibrils are usually separated from the cell membrane by fine fibrillous material of different nature. Quality and spatial organization of the extracellular material in ciliary muscle cell cultures shows marked similarities with the extracellular matrix of ciliary muscle in situ.

Adolescent↗

PubMed1979

Fibrogenesis and biosynthesis of elastin in cartilage.

This study presents direct evidence that dissociated chondroblasts from rabbit ear cartilage grown in vitro are capable of synthesizing insoluble elastin. Ultrastructural examination indicated that at an early stage of tissue development, elastogenesis is initiated producing a form of primary fibrils which later condense into an electron dense amorphous material which, unlike other elastin-containing tissues, is heavily stained by metal cations and lacks peripheral microfibrils. Native elastic fibrils and the mature elastic fiber bundles are both susceptible to elastase digestion. Transmission electronmicroscopy demonstrated the presence of many intracellular filaments all showing a substructural organization and localized in close proximity to the nucleus. Their possible contractile nature is discussed. Amino acid analysis of cartilage elastin and of the elastin synthesized in vitro revealed a close chemical similarity between the two molecules. Ultrastructural analysis of the in vitro elastin demonstrated a substructural organization quite similar to that of the elastin observed in an in vivo system.

Amino Acids↗

PubMed1981

Elastogenesis and microfibrillar glycoprotein synthesis by bovine ligamentum nuchae cells in culture.

Cell cultures propagated from fetal bovine ligamentum nuchae were found to accumulate an extensive extracellular matrix containing collagen and elastic fibers when maintained for periods up to 8 weeks. The synthesis by these cells of two glycoproteins, designated MFP I and MFP II, which are immunologically related to components of the elastic fiber microfibrils was investigated. MFP II, apparent mol. t. 300,000, was shown to be a non-collagenous glycoprotein whereas MFP I, apparent mol. wt. 150,000, was found to be a novel collagenous glycoprotein containing hydroxyproline and glycosylated hydroxylysine residues but exhibiting properties of distinct from the known collagens. Two glycoproteins having characteristics similar to MFP I and MFP II were also identified in an extract of the cell layer and in a "microfibrillar protein preparation" from intact nuchal ligament.

Animals↗

PubMed1981

Elastin formation in heterotopic transplants of isolated arterial smooth muscle cells.

Smooth muscle cells were isolated from the aorta of 5 day old rats by collagenase digestion and injected intramuscularly into animals of the same strain, where the cells reconstituted an elastic tissue with many similarities to that found in the media of the intact aortic wall. The transplants consisted of partly aligned smooth muscle cells surrounded by an extracellular matrix of microfibrils, elastic fibers, bundles of collagen fibrils, and small granules believed to represent proteoglycans. The production of extracellular matrix was much more efficient than in cultures of arterial smooth muscle cells. This cell transplantation system may be valuable in elucidating the mechanisms of normal growth and development of the arterial wall as well as the pathogenesis of various pathological processes.

Animals↗

PubMed1981

Identification of elastin in developing aortic tissue by immunological methods.

Antibodies raised in rabbits to tropoelastin isolated from lathyritic chick aorta were conjugated with ferritin and used to identify and locate elastin-containing elements in sections of aortic tissue from developing chicks. The ferritin-antibody conjugate was associated with a network of fine filaments with a diameter of 3-5 nm which, in the 8-10 day old chick embryo aorta, was distributed between and around small but recognizable elastic fibers. In older aortic tissue this ferritin-labelled material was seen principally in loose association with the periphery of developing elastic fibers. The microfibrils did not interact with the ferritin-antibody conjugate. Treatment of chicks with beta aminopropionitrile did not interfere with the accumulation of ferritin-labelled filaments on these small elastic fibers, suggesting that the mechanism of addition of new material onto growing fibers may be independent of cross-linking.

Amino Acids↗

PubMed1982

The biosynthesis of glycoproteins by cultured bovine tendon fibroblasts.

Confluent bovine fetal tendon fibroblasts maintained in a chemically defined medium incorporated L-[6-3H]fucose and L-[5-3H]proline in a linear manner into non-diffusible macromolecules for up to 48 hrs. Equilibrium CsCl density gradient centrifugation indicated that [3H]fucose-labelled macromolecules released into the medium were predominantly glycoproteins. The [3H]fucose-labelled glycoproteins in the culture medium were analyzed by sodium dodecyl sulfate/polyacrylamide gel electrophoresis. This technique demonstrated the presence of a number of high mol. wt. fucosylated components, the most notable of which was a glycoprotein of apparent mol. wt. 150,000. Immunological procedures allowed the tentative identification of four glycoproteins including fibronectin which was found in the cell medium and in extracts of the cell layer. Two of the glycoproteins (mol. wts. 150,000 and 270,000) released into the incubation medium were shown to be related to the microfibrillar components of elastic tissue. One or more of the newly synthesized [3H]fucose labelled molecules was shown to be immunologically related to a glycoprotein (mol. wt. 60,000) extracted from bovine Achilles tendon. These studies represent the first demonstration of the synthesis of microfibril-related and tendon glycoprotein-related macromolecules by tendon fibroblasts in culture.

Achilles Tendon↗

PubMed1982

Structure and assembly of the native collagen fibril.

Assembly in vitro of the native collagen fibril is a multistep process involving an initial intermediate of unknown structure, linear growth of thin filaments, lateral growth to form the fibril, and stabilization by covalent crosslinks. A model for the structure of the fibril is proposed consisting of a substructure of five-stranded microfibrils laterally compressed to place molecules in cross section on a near-hexagonal lattice.

Animals↗

PubMed1984

Ultrastructural analysis of the microfibrillar component of mouse and human periodontal oxytalan fibers.

Microfibrillar populations were quantified for mouse and human periodontal ligament oxytalan fibers in cross-section. Ten mouse fibers (Group 1) and ten human fibers (Group 2) were randomly selected from representative levels of the ligament and digitized for the total fiber area (TFA) and the microfibrillar component area (MFA). A third group of specific mouse oxytalan fibers (RER) was also evaluated. Quantified fiber dimensions varied markedly as did the percentage microfibrillar area for each group. Staining revealed morphologically different components within each fiber. Mouse and human microfibrils were composed of varying numbers of microfilaments. Analysis of covariance showed that the structural relationship between MFA and TFA was linear for each of the three groups. Slopes for the Group 1 mouse and human microfibrillar components were the same (p greater than 0.1) but different (p less than 0.05) for the RER group. Intercepts for all three groups were significantly different at the 1% level. The relevance of these species specific findings is discussed.

Actin Cytoskeleton↗

PubMed1993

Elastin and fibrillin mRNA and protein levels in the ontogeny of normal human aorta.

Elastin associated microfibrils (EAMF) are ubiquitous connective tissue structures that are believed to provide tensile strength and flexibility to numerous tissues. In this study the ontogeny of EAMF in normal human aorta was examined using immunohistochemical analysis of fibrillin, an EAMF component, and mRNA levels of fibrillin and elastin. Specimens of infra-renal aorta from ages 11 months to 44 years were obtained following organ procurement. Decreasing amounts, as judged by computer digitized image analysis, of immunoreactive fibrillin when compared to elastin auto-fluorescence were observed in aortic sections with increasing age. Elastase treatment would un-mask the anti-fibrillin reactive epitope reinforcing the suggestion that EAMF act as a "scaffold" for elastin deposition. Northern and dot blot hybridizations demonstrated a decrease in relative fibrillin message levels with increasing age. The abundance of fibrillin in relation to elastin may suggest a role for EAMF independent of their association with elastin.

Actin Cytoskeleton↗

PubMed1998

Temporal expression of elastic fiber components in bladder development.

Fetal and postnatal bovine bladders were examined for expression of elastic fiber components by immunohistochemistry as well as by measurement of steady state mRNA levels. Expression of fibrillin-1, microfibril-associated glycoprotein (MAGP) and elastin during the fetal period were compared with that of postnatal two year old animals (heifers) and adults. Each bladder was separated into two distinct tissue samples: 1) the outer smooth muscle layer (detrusor) and 2) the inner epithelium (urothelium) lined lamina propria (urotherial-lamina propria). Each of these samples was analyzed separately. Distribution of the elastic fiber components, determined by immunohistochemistry with matrix-specific antibodies, was different depending upon the region of the bladder wall examined and its developmental stage. In particular, MAGP and fibrillin-1 were conspicuously present in the urothelium during the later fetal stages. RNA products of elastic fiber genes were detectable both in the detrusor smooth muscle and urothelial-lamina propria fractions. The highest level of expression occurred in the urothelial-lamina propria fraction during the late second-early third trimester. Elastin expression was different from that of MAGP and fibrillin-1. The highest levels of steady-state elastin mRNA occurred at the earliest developmental stages examined and then progressively decreased through term. A high level of elastin expression occurred within the inner or lamina propria layer of the bladder. Since this layer is the functional capacitance layer within the bladder, its flexibility is likely related to the structural integration of elastin and associated microfibrillar components.

Animals↗

PubMed1999

Remodeling of elastic fiber components in scleroderma skin.

The skin of patients with scleroderma is characterized by an excess accumulation of collagen in the extracellular matrix of the fibrotic reticular dermis. Elastic fibers are also disrupted in this disease, however, in contrast to collagen, relatively few studies have provided information concerning the changes that occur to elastic fiber components in scleroderma. In the present study, the extracellular matrix in scleroderma skin was examined with a specific focus on the integrity of elastic fibers. Electron microscopic observations confirmed an excess of 10 nm microfibrils present in small bundles independent of amorphous elastin in the fibrotic reticular dermis. In the same area, a population of stellate-shaped fibroblasts was identified in close association with the dermal elastic fibers. In contrast to the uniform black appearance of the elastic fibers seen in the papillary dermis and in areas of the reticular dermis not infiltrated by these cells, the elastic fibers apposed to the cells were mottled in density and often almost electron-lucent. These observations suggest that the elastic fibers in the reticular dermis were being actively degraded. Results from this study provide evidence for disintegration of elastic fibers in the skin of scleroderma patients and suggest the possibility that degradation products from the elastic matrix in the diseased tissues may act as a feedback signal for increased matrix production.

Elastic Tissue↗

PubMed1992

Effect of dibutyryl cyclic adenosine 3',5'-monophosphate on morphological features and biological markers of human salivary myoepithelial cell line in culture.

We have found the emergence of myoepithelial cells (HSG-AZA1) in neoplastic human salivary intercalated duct cell line HSG in culture after treatment with 5-azacytidine. When HSG-ZAZ1 cells were cultured in the presence of N6,O2-dibutyryl cyclic adenosine 3',5'-monophosphate (dB-cAMP), they formed long cytoplasmic processes which were densely packed with ample microfibrils in addition to microtubule bundles. The expression of neuron-specific enolase, synaptophysin, and catecholamine as well as neurofilaments in the treated HSG-AZA1 cells was found by the immunofluorescence staining technique, immunoblotting, immunoelectron microscopy, or catecholamine fluorescence. Both the anchorage-independent and anchorage-dependent growths of HSG-AZA1 cells were suppressed in the presence of dB-cAMP. After the removal of dB-cAMP from the culture, the treated cells returned rapidly to the phenotype and growth rate of the untreated cells. These findings indicate that reversible differentiation into the neuron-like cells of HSG-AZA1 cells occurs in growth medium containing dB-cAMP.

Analysis of Variance↗

PubMed1998

Spontaneous occurrence of anti-fibrillin-1 autoantibodies in tight-skin mice.

Tight-skin (TSK) mouse represents an experimental for systemic sclerosis, displaying cutaneous hyperplasia, connective tissue alterations in the internal organs and developing autoantibodies against several scleroderma target autoantigens. TSK mouse syndrome is associated with a mutation in fibrillin-1 (Fbn-1), the major component of 10 nm microfibrils. Here, we have investigated whether TSK mouse develops autoimmunity to Fbn-1 similar to scleroderma target autoantigens. Our results show that anti-Fbn-1 IgG autoantibodies are present in high titer in many TSK mice. Specificity of these antibodies was confirmed by competitive inhibition assays and Western blotting analysis using recombinant human Fbn-1 protein. TSK mouse autoantibodies recognize a conserved epitope present in the C region of Fbn-1. These results indicate the presence of Fbn-1 specific T and B cells in TSK mouse repertoire.

Animals↗

PubMed1998

A high resolution ultrastructural comparison of isolated and in situ murine AA amyloid fibrils.

There is an inconsistency between the ultrastructural organization of AA amyloid fibrils that have been isolated, which are composed of a slowly twisting set of two or more protofibrils, and those seen in situ, which are tubular entities with a tight helical substructure. In this study, the ultrastructure of fibrils isolated from experimental murine AA amyloid were observed at high resolution and compared with those seen in situ in the hope of clarifying the reason for this inconsistency. The fibrils in situ were composed of a microfibril-like 8-9 nm wide core covered by a layer of heparan sulfate proteoglycan (HSPG) to which 1 nm wide filaments, immunohistochemically identified as AA protein, were externally associated. Following isolation with the standard distilled water washing procedure, the HSPG layer and AA protein filaments detached from their core and dispersed into the water. The remaining denuded, variously loosened cores lost their typical appearance. In distilled water the detached 1 nm wide AA protein filaments became quite conspicuous and coiled themselves into 3 nm wide tight helices which in turn assembled into the characteristic slowly twisting sets of two parallel protofibrils similar to that previously reported as "isolated amyloid fibrils". The results emphasize that great caution must be taken in extrapolating amyloid fibril structure from isolated preparations to in situ tissue conditions.

Animals↗

PubMed1977

On ultrastructure of the trabeculae in the interlamellar membranes of nacre conchiolin of the Nautilus shell.

The ultrastructure of the interlamellar and intercrystalline membranes of nacre conchiolin of Nautilus has been studied on shadow-cast preparations and on ultrathin sections after various fixation and/or decalcification procedures. After immersion in osmium tetroxyde, glutaraldehyde, EDTA, ascorbic acid and CPC solutions, the nautiloid pattern of conchiolin structure (sturdy trabeculae, elongated fenestration) was observed in all samples. The representative ultrastructure of the sectioned trabeculae was composed of micro-meshworks. Microfibrils were not found. In contrast with the other substance, chromium sulphate produces a shrinkage of the nautiloid pattern into continuous rug-like membranes. In the sections, a distinct condensation of the micro-meshworks occurs at the periphery of both interlamellar and intercrystalline membranes. These observations are discussed namely in relation to the problem of structural identification of the EDTA soluble fraction of the nacre conchiolin.

Animals↗