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PubMed1993

Electron microscopic studies on reticular fibers in the pig sheathed artery and splenic cords.

The reticular fibers of the capillary sheath and splenic cord were studied in the pig spleen by transmission electron microscopy to reveal their components and the presence of sialic acid in the amorphous ground substance. Collagen fibrils, elastic fibers, microfibrils, nerve fibers and smooth muscle cells were observed in the reticular fibers of the splenic cord, while only microfibrils were recognized in the reticular fibers of the capillary sheath. The binding of LFA lectin to the splenic cord was stronger than the capillary sheath. These findings may suggest that the reticular fibers of the splenic cord include numerous functional elements and perform an important role during contraction or dilation of the spleen. On the other hand, it seems to be reasonable to term the capillary sheath as "capillary basement membranous reticular tissue", since the reticular fiber of the capillary sheath resembles the basement membrane of the capillary in its components.

Animals↗
PubMed2006

Association genetics in Pinus taeda L. I. Wood property traits.

Genetic association is a powerful method for dissecting complex adaptive traits due to (i) fine-scale mapping resulting from historical recombination, (ii) wide coverage of phenotypic and genotypic variation within a single experiment, and (iii) the simultaneous discovery of loci and alleles. In this article, genetic association among single nucleotide polymorphisms (58 SNPs) from 20 wood- and drought-related candidate genes and an array of wood property traits with evolutionary and commercial importance, namely, earlywood and latewood specific gravity, percentage of latewood, earlywood microfibril angle, and wood chemistry (lignin and cellulose content), was tested using mixed linear models (MLMs) that account for relatedness among individuals by using a pairwise kinship matrix. Population structure, a common systematic bias in association studies, was assessed using 22 nuclear microsatellites. Different phenotype:genotype associations were found, some of them confirming previous evidence from collocation of QTL and genes in linkage maps (for example, 4cl and percentage of latewood) and two that involve nonsynonymous polymorphisms (cad SNP M28 with earlywood specific gravity and 4cl SNP M7 with percentage of latewood). The strongest genetic association found in this study was between allelic variation in alpha-tubulin, a gene involved in the formation of cortical microtubules, and earlywood microfibril angle. Intragenic LD decays rapidly in conifers; thus SNPs showing genetic association are likely to be located in close proximity to the causative polymorphisms. This first multigene association genetic study in forest trees has shown the feasibility of candidate gene strategies for dissecting complex adaptive traits, provided that genes belonging to key pathways and appropriate statistical tools are used. This approach is of particular utility in species such as conifers, where genomewide strategies are limited by their large genomes.

Chromosome Mapping↗
PubMed1982

Formation of reticular fibers in the developing spleen of the chick embryo.

An electron microscope study was made to elucidate the manner in which reticular fibers form in the developing spleen of the chick embryo. On the 7th day of incubation, the splenic reticulum consisted of dendritic reticular cells without reticular fibers. From the 9th day onward, the intercellular gaps between processes of adjacent reticular cells were expanded, becoming occupied by fine flocculent materials. With the growth of the embryos, these materials were aggregated into felt-like bands, exhibiting the characteristics of mature reticular fibers. In the interstices of the reticulum, there appeared microfibrils of 8-30 nm in diameter. The reticular cells possessed numerous free ribosomes and polysomes, well-developed Golgi apparatuses, dilated rough-surfaced endoplasmic reticula, and many coated vesicles. The coated vesicles contained fine flocculent materials as presumable fiber precursors. The vesicles were enlarged as they approached the cell periphery, where they appeared to discharge their contents by reverse pinocytosis. some vesicles close to the cell membrane contained ruthenium red-positive materials which were considered to be glycosaminoglycan in nature and to compose the matrix of fibers. These materials also seemed to be secreted by reverse pinocytosis, being densely accumulated in the intercellular gaps. The differentiation of fibrous proteins into felt-like reticular fibers or striated microfibrils seems, therefore, to be intimately associated with the amount of glycosaminoglycan.

Animals↗
PubMed1994

Nature of the fine fibrils of the basilar membrane in the cochlea.

Fine fibrils in the basilar membranes of mouse and guinea-pig cochleae were examined by transmission electron microscopy. The fibrils were 10 nm in diameter and ran straight without branching. The fibrils appeared as two parallel lines in longitudinal sections, and round or polygonal in cross-sections, displaying tubular structures with a lumen. They were similar in ultrastructural details to the elastin-associated and elastin-independent microfibrils of Low (1962) in the subcutaneous tissue. It is concluded that the fibrils in the basilar membrane are the microfibrils.

Animals↗
PubMed2002

Collagen fibers, reticular fibers and elastic fibers. A comprehensive understanding from a morphological viewpoint.

Fibrous components of the extracellular matrix are light-microscopically classified into three types of fibers: collagen, reticular and elastic. The present study reviews the ultrastructure of these fibrous components as based on our previous studies by light, electron, and atomic force microscopy. Collagen fibers present a cord- or tape-shape 1-20 microm wide and run a wavy course in tissues. These fibers consist of closely packed thin collagen fibrils (30-100 nm thick in ordinary tissues of mammals), and exhibit splitting and joining in altering the number of the fibrils to form a three-dimensional network as a whole. Individual collagen fibrils (i.e., unit fibrils) in collagen fibers have a characteristic D-banding pattern whose length is ranges from 64 to 67 nm, depending on tissues and organs. During fibrogenesis, collagen fibrils are considered to be produced by fusing short and thin fibrils with tapered ends. Reticular fibers are usually observed as a delicate meshwork of fine fibrils stained black by the silver impregnation method. They usually underlie the epithelium and cover the surface of such cells of muscle cells, adipose cells and Schwann cells. Electronmicroscopically, reticular fibers are observed as individual collagen fibrils or a small bundle of the fibrils, although the diameter of the fibrils is thin (about 30 nm) and uniform. Reticular fibers are continuous with collagen fibers through the exchange of these collagen fibrils. In silver-impregnated specimens, individual fibrils in reticular fibers are densely coated with coarse metal particles, probably due to the high content of glycoproteins around the fibrils. Elastic fibers and laminae are composed of microfibrils and elastin components. Observations of the extracted elastin have revealed that elastin components are comprised of elastin fibrils about 0.1-0.2 microm thick. Elastic fibers and laminae are continuous with networks and/or bundles of microfibrils (or oxytalan fibers), and form an elastic network specific to individual tissues. The fibrous components of the extracellular matrix are thereby morphologically categorized into two systems: the collagen fibrillar system as a supporting framework of tissues and cells, and the microfibrilelastin system for uniformly distributing stress to maintain the resilience adapted to local tissue requirements.

Collagen↗
PubMed1984

Tympanosclerosis of the ear drum in secretory otitis media.

Tympanosclerosis of the ear drum in children with SOM differs from normal ear drums in children with SOM. In tympanosclerosis the numbers of fibroblasts, fibrocytes and macrophages are increased in lamina propria and in the submucosa. The collagen microfibrils and procollagen filaments have increased in numbers with a partly disorganized pattern. Fibrolysis of microfibrils is conspicuous and hyaline degeneration appears in areas. Calcareous deposits are found scattered to a limited extent in lamina propria and in the submucosa. Profound calcification could only be found in children with tympanosclerosis coexisting with chronic perforation of the ear drum.

Adolescent↗
PubMed1993

Ultrastructure of the endolymphatic duct in the rat. Fixation and preservation.

Ten rats were vascular-perfused at subphysiologic as well as physiologic pressures, 80 mmHg and 120 mmHg, respectively, employing a pressure feed-back controlled peristaltic pump and an isotonic perfusate/fixative with colloids (2% Dextran) and a hypertonic perfusate/fixative without colloids, 300 and 530 mOsm, respectively. In both experiments the endolymphatic duct and sac were isolated by microdissection after primary fixation. When comparing micrographs from the two experiments we observed that rats perfused at low pressure in isotonic fixative with colloids added had non-dilated lateral intercellular spaces and a subepithelial ground substance loaded with uniformly arranged microfibrils, not previously discovered. In rats perfused at high pressure in hypertonic fixative with no colloids added, we observed an edematous state in the subepithelial space between the solid bony aqueduct and the endolymphatic duct, with a concomitant derangement of previously well organized microfibrils. Furthermore, the epithelium was quite clearly displaced from the capillaries, the intercellular spaces were widely dilated and the endolymphatic duct was compressed into its lumen. Methods of fixation and current theories of endolymph resorption by the endolymphatic duct are discussed.

Animals↗
PubMedDate not supplied

Ultrastructural histochemistry of infantile digital fibromatosis.

A case of infantile digital fibromatosis was studied by light and electron microscopy histochemistry. Using two different acidic solutions of phosphotungstic acid at varying pHs, the round inclusions characteristic of this tumor were shown to have a high protein content with little or no carbohydrates. The histochemical reactivity of the inclusions was similar to that of the cytoplasmic microfibrils in the tumors cells and consistent with the idea that both the inclusions and the microfibrils represent actin. There is, however, no definite proof that the tumor cells are myofibroblasts. At the present time, this tumor should be viewed as a peculiar expression of deranged assembly or metabolism of filamentous proteins or both.

Actins↗
PubMedDate not supplied

"Aberrant elastic" in elastofibroma: an immunohistochemical and ultrastructural study.

Elastofibroma is a rare lesion characterized by the presence of abundant abnormal elastic fibers with a unique morphology, fibroblastic proliferation, and collagen deposition. Whether the altered morphology of the elastic fibers is a degenerative phenomenon or is due to abnormal elastogenesis is controversial. We studied fetal skin and three cases of elastofibroma by light microscopy and immunohistochemistry using an antibody to lysozyme, and one case of elastofibroma by electron microscopy (EM). Our previous studies have shown that normal elastic fibers in adult skin do not stain for lysozyme whereas abnormal elastic fibers in solar elastosis and pseudoxanthoma elasticum react positively for lysozyme. In the fetal skin and all three cases of elastofibroma the elastic fibers were negative for lysozyme. EM showed the abnormal flowerlike configuration of the elastic fibers, which consisted of a central core of normal or degenerating elastin surrounded by radiating spokes of granular and filamentous material of variable electron densities, suggesting that the structure and organization of the microfibrils is abnormal. The absence of lysozyme in the aberrant elastic did not differentiate whether there was excessive production of fetal or adult elastic. However, the excessive amount of microfibrils seen at the ultrastructural level suggests that there may be excessive fetal elastic production. The elastic fibers were intimately related to the fibroblasts and were often present within their caveolae, suggesting that the abnormal elastic fibers are produced by the fibroblast. Our study suggests that abnormal elastogenesis with subsequent degeneration plays a role in the production of the abnormal elastic fibers in elastofibroma.

Elastic Tissue↗
PubMed1996

Distribution and characterization of proteoglycans associated with exfoliation material.

PURPOSE: To examine the distribution of proteoglycans in the exfoliation materials in order to investigate the nature of the materials. METHODS: The anterior parts of two eyes with exfoliation syndrome were examined by electron microscopy after staining with cupromeronic blue (cmb). Some specimens were treated with enzymes and/or nitrous acid prior to staining. The effects of the enzymes were evaluated statistically by counting the density of the cmb-positive filaments in the exfoliation materials, using a computer. One eye with exfoliation syndrome stained with alcian blue was observed with light microscopy. RESULTS: Exfoliation materials were observed along the epithelial cells of the iris and ciliary body, and in the trabecular meshwork and zonules. In tissue specimens treated with cmb, electron-dense filaments were seen associated with the exfoliation materials. Microfibrils in the trabecular meshwork and iris, and zonular fibrils themselves were free of any filament staining, while the exfoliation materials located closely to the fibrils contained the electron-dense filaments. In the tissue specimens treated with chondroitinase AC, chondroitinase B, chondroitinase ABC or nitrous acid before cmb staining, the amount of the filament associated with exfoliation materials decreased in comparison to the controls. Digestion with keratinase did not demonstrate any significant changes in staining. A combination treatment with chondroitinase ABC and nitrous acid eliminated almost all filaments associated with the exfoliation materials. In the eye stained with alcian blue, the zonules that did not stain for the dye demonstrated an accumulation of exfoliation materials that stained strongly for alcian blue. CONCLUSIONS: Exfoliation materials contain chondroitin sulfate, dermatan sulfate, heparan sulfate proteoglycans. Depositions of proteoglycans on the microfibrils may be closely associated with the formation of exfoliation materials.

Aged↗
PubMed1976

The effects of Z plasty on hypertrophic scars.

Hypertrophic scar tissue has been observed to soften and thin following Z plasty without removal of any of the scar tissue. Histochemical studies of tissue before and after Z plasty showed that abnormally sulfated mucopolysaccharides were replaced by normal acid mucopolysaccahrides within 14 days. Collagen in hypertrophic scar appeared in nodules and fibers perpendicular to the surface of the skin rather than as long straight fibers parallel to the skin surface as normally seen. Elastic fibers were reduced and scar was relatively avascular. Following Z plasty the amount of collagen decreased and fibers were oriented in bundles at right angles to each other, parallel to the surface. When tissue was examined by electron microscopy collagen fibers showed marked variation in diameter. Microfibrils were increased and there were aggregates of fibrils with periodicity of 1500 to 1600 A. Following Z plasty, areas which previously contained only microfibrils now had unit collagen fibers with normal periodicity. Urinary excretions of hydroxyproline and hydroxylysine, amino acids found only in collagen, were increased following Z plasty, coinciding with the softening of the scar. Excretion of the disaccharide, glucosylgalactosylhydroxylysine, predominantly found in skin, increased following Z plasty, while excretion of the monosaccharide, galactosyl-hydroxylysine, predominant in bone collagen, remained constant. Amino acid composition of collagen, remained constant. Amino acid composition of collagen isolated from hypertrophic scars was similar to that present in skin and tendon, and unlike that in cartilage or infant dermis. Hydroxyproline content was slightly decreased and hydroxylysine content slightly increased compared to skin or tendon. Histochemical, ultrastructural and biochemical studies of the same specimens suggested that collagen with disordered fibril formation was present in the hypertrophic scar and was degraded following Z plasty. Changes in the molecule which occurred after synthesis of the protein core might be responsible both for the failure of normal maturation of the scar and for its sensitivity to degradative enzymes following Z plasty.

Adolescent↗
PubMed1986

Differences in the fibril structure of corneal and tendon collagen. An electron microscopy and X-ray diffraction investigation.

A detailed analysis of the D-period and axial electron density distribution of cornea and tendon collagen was carried out by means of X-ray diffraction and electron microscopy. Ultrastructural observations were made on replicas of freeze fractured and deep-etched specimens. Synchrotron radiation was used to obtain high resolution small angle X-ray diffraction patterns. The data provide evidence that D-period and intraperiod distances in cornea are shorter than in tendon collagen fibrils. The observed different banding observed is interpreted on the basis of the different morphological arrangement of the microfibrils in the two tissues: "helicoidal" in cornea and "straight" in tendon microfibrils.

Animals↗
PubMed2002

Spontaneous spinal cerebrospinal fluid leaks and minor skeletal features of Marfan syndrome: a microfibrillopathy.

OBJECT: Spontaneous spinal cerebrospinal fluid (CSF) leaks are increasingly recognized as a cause of postural headaches. The authors examined a group of patients suffering from spontaneous spinal CSF leaks who also had minor skeletal features of Marfan syndrome for abnormalities of fibrillin-containing microfibrils. METHODS: Patients with spontaneous CSF leaks were evaluated for the clinical characteristics of connective tissue disorders. Skin biopsies were obtained in three patients with skeletal manifestations that constitute part of the Marfan syndrome phenotype. Cultured fibroblasts were studied for fibrillin-1 synthesis and incorporation into the extracellular matrix (ECM) by performing quantitative metabolic labeling and immunohistochemical analysis. Among 20 consecutive patients found to have spinal CSF leaks, four (20%) exhibited minor skeletal features of Marfan syndrome, but lacked any ocular or cardiovascular abnormalities. The mean age of these patients (30 years) was lower than that of the 16 patients without skeletal abnormalities (44 years; p = 0.01). Abnormalities in fibrillin-1 metabolism and immunostaining were detected in all three patients with the skeletal abnormalities who underwent examination, but not in a control patient without these skeletal manifestations. CONCLUSIONS: Twenty percent of patients who experience spontaneous spinal CSF leaks have minor skeletal features of Marfan syndrome. The authors demonstrated abnormalities in fibrillin-1 protein deposition in all patients examined, but only one person was found to have a fibrillin-1 abnormality typically found in classic Marfan syndrome. The results indicate that there is a heterogeneous involvement of other components of ECM microfibrils at the basis of this cerebrospinal manifestation. In addition, the authors identified a connective-tissue etiological factor in a group of disorders not previously classified as such.

Adult↗
PubMed2005

Autoantibodies to fibrillin-1 activate normal human fibroblasts in culture through the TGF-beta pathway to recapitulate the "scleroderma phenotype".

Fibroblasts from patients with systemic sclerosis (SSc) are activated producing excessive amounts of extracellular matrix (ECM) components. Recently, we identified a new SSc-specific autoantibody against portions of fibrillin-1, a major component of ECM microfibrils and regulator of TGF-beta1 signaling. To examine a potential pathogenic role of anti-fibrillin-1 autoantibodies, normal human fibroblasts were treated with affinity-purified autoantibodies isolated from SSc sera and then examined for alterations in gene and protein expression levels using microarrays, quantitative RT-PCR, immunoblots, and immunofluorescence. Compared with fibroblasts cultured in normal medium or in medium containing normal human IgG, anti-fibrillin-1 autoantibody-treated normal dermal fibroblasts showed increased expression of COL and several other ECM components characteristically overexpressed in SSc fibroblasts. This was accompanied by phosphorylation and nuclear translocation of Smad3. Neutralization of TGF-beta1 with anti-TGF-beta1 Abs significantly diminished the activation of fibroblasts by anti-fibrillin-1 autoantibodies. These data indicate that anti-fibrillin-1 autoantibodies can induce the activation of normal dermal fibroblasts into a profibrotic phenotype resembling that of SSc by potentially causing the release of sequestered TGF-beta1 from fibrillin-1-containing microfibrils in the ECM.

Active Transport, Cell Nucleus↗
PubMed1990

IgA immunoreactive deposits collocal with fibrillin immunoreactive fibers in dermatitis herpetiformis skin.

The IgA immunoreactive granules or fibrils, characteristically found in dermal papillae of patients with dermatitis herpetiformis, were previously reported to be associated with microfibrillar bundles. Recently, fibrillin, a component of such 8-12 nm microfibrils, was identified. In normal skin, the fibrillin immunoreactive microfibrils are present at the periphery of elastic fibers and are also present without concomitant amorphous elastin in the dermal papillae close to the lamina densa. The localization of the IgA immunoreactive material in the dermal papillae of 17 patients with dermatitis herpetiformis was compared with the distribution of the fibrillin immunoreactive fiber network. Immunofluorescence methods using FITC- and TRITC-labelled antibodies, an avidin-biotin-peroxidase complex technique, and standard elastin staining procedures, were used in several sequential and double staining procedures. In 13 specimens, in which the IgA reactivity was granular, most of the granules were located at the sites of fibrillin-reactive structures. As it could not be excluded that the collocality was coincidental, it could not be ascertained whether the IgA granules were in fact related to the fibrillin immunoreactive fibers in these specimens. However, in 4 specimens with both granular and fibrillar IgA immunoreactive deposits, these were clearly related to and located at the sites of fibrillin-reactive fibrils in the dermal papillae. The results confirm earlier reports of an association of IgA reactive deposits with microfibrillar bundles in dermatitis herpetiformis skin, though the possibility of their binding to other extracellular matrix component(s) has not been ruled out. The findings suggest that fibrillin may be the structural component (or one of them) to which IgA reactive deposits bind in the skin of patients with dermatitis herpetiformis.

Complement C3↗
PubMed1990

Immunohistochemical studies on fibrillin in amyloidosis, lichen ruber planus and porphyria.

The pathogenesis of macular amyloidosis and lichen amyloidosis remains unsolved and the primary amyloid fibril protein(s) has not yet been identified. Ultrastructural association of skin amyloid with elastin associated microfibrils has been noted earlier. The presence of fibrillin in conjunction with such microfibrils was recently demonstrated immunohistochemically. The presence of fibrillin immunoreactivity in the amyloid deposits in skin biopsies from 3 patients with macular amyloidosis and 3 patients with lichen amyloidosis was studied, using monoclonal anti-fibrillin antibodies. For comparison, skin specimens were studied from five patients with lichen ruber planus, four patients with erythropoietic protoporphyria and from a patient with myeloma-associated cutaneous amyloidosis. Renal specimens from two cases of the amyloid A type of renal amyloidosis also were investigated. There was no immunostaining either of the keratin bodies in specimens of lichen ruber planus, the cutaneous PAS-positive vascular deposits in patients with erythropoietic protoporphyria, or the amyloid deposits in specimens of systemic amyloidosis and it was faint or absent in amyloid deposits in the specimens from patients with lichen amyloidosis. In contrast, distinct fibrillin immunoreactivity could be demonstrated in amyloid deposits in specimens from patients with macular amyloidosis. It was sometimes absent in deposits located in the upper part of the papillary dermis, close to the dermal epidermal junction zone, while consistently strong in deposits located lower down in the dermis. The results suggest that fibrillin or part of the fibrillin molecule may be present in some of the amyloid deposits in specimens of macular amyloidosis.

Amyloidosis↗
PubMed1999

Transglutaminase activity in the eye: cross-linking in epithelia and connective tissue structures.

PURPOSE: To assess the distribution of transglutaminase (TGase) activity in ocular tissues and the target structures for cross-linking. METHODS: Cryosections from human and cynomolgus monkey eyes were incubated with the biotinylated amine donor substrate cadaverine (biotC), which was subsequently visualized with streptavidin-peroxidase. Confocal laser scanning was used to colocalize biotC and fibrillin, a major component of elastic microfibrils and the zonular fibers in particular. Cryosections and isolated bovine zonules were treated with purified TGase 2 and biotC. The distribution of different TGases (1, 2, 3, and factor XIII) was confirmed immunohistochemically. RESULTS: Virtually all ocular tissues showed TGase activity with a remarkable preponderance for the ciliary body, zonular fibers, and blood vessel walls. Confocal laser scanning revealed fibrillin-containing microfibrils as a major target for TGase activity, in particular the ciliary zonules. Corneal epithelium and basement membrane showed a TGase cross-linking pattern similar to skin. Treatment of cryosections and isolated bovine zonular fibers with purified TGase 2 led to additional incorporation of biotC into extracellular matrix, particularly zonular fibers. The immunohistochemically predominant TGase 2 was associated with epithelia and particularly with connective tissue fibers. TGase 1 was restricted to the corneal epithelium, whereas factor XIII was found to be associated only with blood vessels. TGase 3 was absent. CONCLUSIONS: TGase 2 appears to be an important cross-linker and thus stabilizer of ocular connective tissue. In particular, the zonular fibers are a major target for TGase 2. This is of relevance in hereditary microfibrillopathies such as Marfan syndrome, which exhibits distinct ocular manifestations such as elongated bulbus, retinal detachment, and subluxation of the lens. Purified or recombinant TGase might be of therapeutic use in the future.

Aged↗
PubMed1975

The ulstratructure of reticulin.

The electron microscopic examination of various organs and tumours of different species proved that the ultrastructural equivalent of reticulin fibres is not a uniform substance. Reticulin fibres are either basement membranes or an amorphous mass which appears as argyrophil fibres under the light microscope. Microfibrils may in some cases produce an argyrophilic reticulum. The claimed identity of reticulin and collagen can partly be explained by the chemical similarity of collagen and basement membranes. It seems possible, moreover, that the amorphous mass and microfibrils, which may be an ultrastructural substrate of reticulin, are composed of a material essentially similar to that of collagen.

Animals↗