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PubMed2000

A critical review of the structural mechanics of wool and hair fibres.

The potential of genetic engineering gives current importance to the need to clarify the relations between structure, properties and performance of wool. There are at present three different models to explain the tensile stress-strain properties of alpha-keratin fibres: a development by Wortmann and Zahn (W/Z) of Feughelman's series-zone model based on the structure of intermediate filaments and a gel-->sol matrix; a new model by Feughelman (F94) based on a matrix of protein globules surrounded by water; and Chapman's model based on the composite mechanics of microfibrils, characterised by critical and equilibrium stresses for the alpha<-->beta transition, in an elastomeric matrix. This paper examines the arguments related to these theories, with additional attention to the Chapman/Hearle (C/H) treatment. The main area of uncertainty, on which more information is much needed, concerns the chemical and physical structure and properties of the matrix, which is composed of keratin-associated proteins. The conclusion is that the C/H model, which is based on reasonable values of input parameters and gives good agreement with a wide range of experimental results, is most likely to be valid, though it needs some additional refinement and incorporation in a total model, which includes larger-scale structural features.

Animals↗
PubMed2001

Spider silk fibre extrusion: combined wide- and small-angle X-ray microdiffraction experiments.

The major and minor ampullate silks from live Nephila senegalensis (Tetragnathidae) and the major ampullate silk from Euprostenops spp. (Pisauridae) spiders were investigated in situ by X-ray diffraction during forced silking. Wide- (WAXS) and small-angle (SAXS) scattering patterns were obtained at the same time. WAXS data show that the thread at the exit of the spigots already contains beta-sheet poly(alanine) crystallites. SAXS data suggest the presence of microfibrils with an axial repeating period of approximately 8 nm for both Nephila and Euprostenops. Minor ampullate (MI) Nephila silk, however, does not show this axial repeat which is probably due to a higher amount of crystal forming poly(alanine). A microfibrillar morphology, connected by a network of random polymer chains, can explain the presence of highly oriented crystallites, an oriented halo and a diffuse background in the WAXS patterns. At high reeling speeds, bound water is co-extruded with the fibre. It can be squeezed out of the fibre by friction at a needle. Under natural conditions it is the spider's tarsal claws which might serve to squeeze out the water to improve the mechanical properties of the thread during dragline production.

Animals↗
PubMed2002

A molecular description of the gelation mechanism of curdlan.

The gelation of aqueous suspensions of the polysaccharide curdlan has been studied by dynamic rheological measurements, differential scanning calorimetry, and low-resolution time-domain 1H-NMR. Gel formation from several samples, each originating from a curdlan fraction of differing molecular weight, has been observed in order to further clarify the nature of observed phenomena by monitoring their dependence on degree of polymerisation. The results from the complementary techniques described here, in addition to those in existing literature, both for curdlan and for other ss-(1,3) glucans, have been used to build up a consistent framework for the interpretation of results. Broadly, this involves the plasticisation and dissolution of dried material on heating, the time-dependent annealing of native (as biosynthesised) structures, and the trapping of imperfectly formed pseudo-equilibrium states on re-cooling, in concert with the creation of microfibrils and network formation.

Calorimetry, Differential Scanning↗
PubMed1992

Susceptibilities of bacterial cellulose containing N-acetylglucosamine residues for cellulolytic and chitinolytic enzymes.

Detailed characterization of enzyme susceptibility of bacterial cellulose containing N-acetylglucosamine (GlcNAc) residues (N-AcGBC) which possess high susceptibility for cellulase and lysozyme and slight susceptibility for chitinase was studied. Turbidimetric lysozyme assay of N-AcGBC showed that (i) the susceptibilities of various N-AcGBCs for lysozyme were proportional to GlcNAc content, and (ii) N-AcGBC homogenates were divided into two groups based on the rate of turbidity reduction (not dependent on GlcNAc content). High reactivity of N-AcGBC for lysozyme would arise from fine microfibrils characteristic of bacterial cellulose (BC) and random distribution of GlcNAc residues in N-AcGBC because water soluble oligomers of N-AcGBC produced by lysozymic hydrolysis did not inhibit lysozyme activity; however, the random distribution of GlcNAc seemed to result in the slight susceptibility of N-AcGBC for chitinase. The rate of cellulolytic turbidity reduction of N-AcGBC was slower than that of BC, which arose from the inhibition for binding of cellulase by GlcNAc residues.

Acetobacter↗
PubMed2001

Comparison of five procedures for the purification of insoluble elastin.

Elastin is an insoluble, highly cross-linked protein, providing elasticity to organs like lung. aorta, and ligaments. Despite its remarkable mechanical properties. elastin has found little use as a biomaterial. Purification of intact elastin from elastic fibres presents a major challenge, among others for the intimate interwoveness of elastin and microfibrils. Insoluble elastin preparations tend to calcify, which may be due to calcium-binding microfibrillar (e.g. fibrillin). In this study, elastin was purified from horse ligamentum nuchae using five different procedures. One procedure is based on treatment with 0.1 M NaOH, another on autoclaving and treatment with cyanogen bromide. Three other procedures are based on combinations of extraction steps and enzyme digestions. Purity of preparations was assessed by sodium dodecyl sulphate polyacrylamide gel electrophoresis, amino acid analysis, bright field immunofluorescence and transmission electron microscopy. The procedure involving extractions/enzymes combined with an early application of 2-mercaptoethanol and cyanogen bromide gives a highly pure elastin preparation. Electron microscopic analysis showed that this preparation is devoid of microfibrillar components. This procedure is therefore the method of choice for preparation of insoluble elastin as a biomaterial for tissue engineering.

Acetone↗
PubMed1999

Characterization of mutated protein encoded by partially duplicated fibrillin-1 gene in tight skin (TSK) mice.

Fibrillin-1 (Fbn-1) is a ubiquitous protein present in the extracellular matrix of various organs and it is a major component of microfibrils embedded in the core of elastic fibers. In humans, mutations or deletions of the Fbn-1 gene are associated with several genetic diseases. In addition, several microsatellite alleles near Fbn-1 gene were found associated with diffuse scleroderma. In TSK/+ mice, which develop a scleroderma-like syndrome, the Fbn-1 gene exhibits an inframe duplication of exons 17-40. In this study, we report that the synthesis and secretion of wild-type Fbn-1 in TSK/+ is higher than that of the mutated Fbn-1 protein excluding the possibility that TSK genetic defect is due to a loss of the wild allele. We also demonstrate for the first time that TGF-beta, which plays a crucial role in skin fibrosis, binds to both wild-type and mutated Fbn-1. The amount of bound TGF-beta was higher in mutated than wild-type Fbn-1 and appears related to the number of TGF-beta binding motifs.

Animals↗
PubMed1987

Pseudoexfoliative fibrillopathy in the conjunctiva. A relation to elastic fibers and elastosis.

Pseudoexfoliative (PSX) material in the conjunctiva was found to have a close association with elements of the elastic system in 13 eyes of patients with PSX disease studied ultrastructurally. Pseudoexfoliation aggregates were rare within vascular walls but frequent in proximity to the plasmalemma of stromal fibroblasts. No amyloid was found. A striking feature was the association of PSX fibers with the elastosis seen in many of the specimens. Typical PSX fibers were present in clumps of oxytalan and around small elastic fibers. In five cases with more advanced elastosis, the aggregates of PSX fibers were larger and their usual loose fibrogranular matrix was extensively replaced by a dense elastotic one. Morphology of PSX here varied from typical to thicker, fragmented, and sometimes nondiagnostic fibers. This intermingling of PSX and elastotic materials suggested that PSX fibrillopathy is itself a type of elastosis, possibly resulting from abnormal aggregation of components related to elastic microfibrils.

Actin Cytoskeleton↗
PubMed2001

Expression and cellular localization of fibrillin-1 in normal and pathological human liver.

BACKGROUND: The expression and the distribution of fibrillin-1 and elastin were studied in normal and pathological human liver samples. METHODS: As controls, histologically normal/subnormal liver samples (n = 24) were used. Pathological samples corresponded to seven cirrhosis and eight hepatocellular carcinomas (HCC) developed on cirrhotic (four) or noncirrhotic (four) liver. RESULTS: In normal liver, fibrillin-1 and elastin co-localized in vessel walls and portal tract connective tissue. Fibrillin-1 alone was detected along sinusoids and in portal spaces at the interface with the limiting hepatocytic plates and close to the basement membrane of bile ducts. By transmission electron microscopy, typical bundles of microfibrils were detected both in Disse space and in portal zones. Cirrhotic nodules were usually rich in fibrillin-1 along sinusoids; fibrillin-1 and elastin were co-localized in fibrotic septa surrounding nodules. In HCC, fibrillin-1 was present between tumoral hepatocytes; stromal reaction around the tumors contained both fibrillin-1 and elastin. CONCLUSIONS: Fibrillin-1 was associated with elastin in portal mesenchyme and vessel walls of normal liver, in fibrotic septa around cirrhotic nodules and stromal reaction around HCC, but was expressed alone in the perisinusoidal space. The functional roles for fibrillin-1 in non-elastic tissues, such as the liver, remain to be elucidated.

Adult↗
PubMed1983

Distribution of CL glycoprotein in tissues: an immunohistochemical study.

CL glycoprotein is a collagen-like glycoprotein which we have recently isolated from rapidly growing fetal bovine, elastin-rich tissues. This protein has a molecular weight of approximately 140,000 daltons, contains hydroxyproline and hydroxylysine and is digested by highly purified collagenase to yield three large polypeptides. A specific antibody has been developed against this protein and has been used for immunofluorescence microscopy to study the distribution of CL glycoprotein in a range of tissues. It has been shown that the antibody localized in the intercellular matrix of nuchal ligament and aorta, of the non-elastic Achilles tendon and in complex tissues such as kidney, lung, skin and spleen. The antibody also localized to the surface of aortic smooth muscle cells-presumably to the basement membrane, but did not bind to other basement membranes, including the vascular subendothelial basement membrane. The pattern of distribution was similar in adult bovine tissues. As this antibody showed no avidity for elastic tissue elements, it is most unlikely that CL glycoprotein is a constituent of elastin-associated microfibrils. When the pattern of the CL glycoprotein distribution within the tissues was studied, it was found that, apart from its concentration around vascular smooth muscle cells, CL glycoprotein exhibited considerable overlap in distribution with the interstitial collagens. On the basis of these observations and having regard to its biochemical characteristics, it is proposed that CL glycoprotein has a structural role inter-linking interstitial components to one another and to vascular smooth muscle cells.

Animals↗
PubMedDate not supplied

Congo red effect on cyst viability and cell wall structure of encysting. Entamoeba invadens.

BACKGROUND: The cell wall of Entamoeba invadens cysts is composed of chitin microfibrils as the main structural component. It has been demonstrated in yeast that the chitin cell wall assembly is altered by dyes such as Congo red (CR) and Calcofluor. METHODS: The purpose of this work was to study the cell wall assembly under the effect of CR dye on encysting E. invadens by means of light and electron microscopy, after the amebas were subjected to the effect of 100-2,000 micrograms CR/mL. Experiments were performed either in BI-S-33 or in mLG media. RESULTS: Trophozoite growth was not inhibited by 100-1,000 micrograms/mL CR after 8 days of incubation in BI-S-33 medium. However, low levels of growth were observed with 2,000 micrograms/mL of dye. No significant differences in morphologically viable (hyaline) cyst production occurred after 24-48 h, when 100 micrograms CR/mL was used, while the highest concentration of CR (2,000 micrograms/mL) resulted in a significant decrease of hyaline cyst yield; dead cysts prevailed in cultures, particularly at 72 h of CR treatment. Differentiation of amebas incubated in the presence of 500-2,000 micrograms/mL CR produced abnormal chitin deposits, rendering irregularly thick or double cell walls, as shown by transmission and scanning electron microscopy. Cyst cultures obtained under 100 micrograms/mL CR produced as many trophozoites as did the control when they were incubated in BI-S-33, but only low numbers of trophozoites were found in culture cysts obtained under higher CR doses. CONCLUSION: Our results suggest that CR affects E. invadens encystment, alters the cell wall formation, and also affects the cyst viability.

Animals↗
PubMed1980

Elastic tissue changes in skin following PUVA therapy.

Treatment of psoriasis with psoralens and high-intensity long-wave ultraviolet light (PUVA) produces changes in the ultrastructure of elastic tissue in skin. Early alterations consist of a loss of elastin followed by a breakdown of the microfibrils and subsequent fragmentation of the elastic fiber. Tissue examined 15 months after treatment was stopped still showed marked ultrastructural changes in the elastic fibers.

Elastic Tissue↗
PubMed1985

Myofibroblasts in a collagen nevus detected by electron microscopy.

A solitary collagenous connective tissue nevus on the foot of a 1-year-old infant was studied under electron microscopy. The collagen appeared normal in size, appearance, and orientation, although variable in fiber diameter. Relatively little elastic tissue was seen. The presence of myofibroblasts was notable. These large branching specialized fibroblasts were laden with highly aligned 6-8 nm microfibrils, presumably actin.

Collagen↗
PubMed1994

Pachydermoperiostosis: analysis of the connective tissue abnormality in one family.

BACKGROUND: Pachydermoperiostosis (PDP) is a rare hereditary disease characterized by hyperostosis, clubbing of fingers, coarse skin, and abnormalities in other organs, such as the gastrointestinal tract. Previous studies have disclosed several abnormalities in the connective tissue in these patients. OBJECTIVE: The purpose of the study was to investigate connective tissue abnormalities in one family with PDP. METHODS: Clinical features were evaluated; x-ray, immunohistochemical, and electronmicroscopic studies were performed; and markers of collagen metabolism and lysosomal enzymes were determined. RESULTS: Immunohistochemical and ultrastructural studies revealed accumulation of tenascin, glycosaminoglycans, and fibrillar material in apparently disorganized microfibrils of elastic fibers. Osteocalcin levels in the serum were increased, but synthesis and degradation markers of collagen in the serum were not altered. No evidence of a lysosomal enzyme deficiency was found. CONCLUSION: Acidic mucopolysaccharides and some fibrillar material accumulate in the dermis of patients with PDP. Increased levels of osteocalcin in serum indicate higher osteoblastic activity. Markers of synthesis and degradation of collagen were not altered.

Acid Phosphatase↗
PubMed1994

The fibrillary glomerulopathies.

Fibrillary glomerulopathy is a category of glomerular disease that is defined by the ultrastructural feature of organized deposits of extracellular, nonbranching, microfibrils. The best-known disease in this category is amyloidosis, but cryoglobulinemia, light chain deposition disease, systemic lupus erythematosus, immunotactoid glomerulopathy, and diabetic fibrillosis may have similar ultrastructural findings and comprise the differential diagnosis of the fibrillary glomerulopathies. Because they have disease-specific therapeutic and prognostic implications, differentiating among these entities is important for nephrologists and nephropathologists. To aid the physician, we will review the fibrillary glomerulopathies using an algorithm based on morphology, clinical features, and serologic assessment. We believe this approach will prove to be practical and useful to the practicing nephrologist.

Actin Cytoskeleton↗
PubMed1998

Fibrillary glomerulonephritis in siblings.

Fibrillary/immunotactoid glomerulopathy is characterized by organized glomerular deposition of extracellular, nonbranching, immunoglobulin-derived microfibrils, which is not associated with systemic diseases such as amyloidosis, cryoglobulinemia, or monoclonal gammopathy. This is an uncommon condition with an obscure etiology and accounts for approximately 1% of primary glomerular diseases in white populations. We report the first case of familial fibrillary/immunotactoid glomerulopathy affecting a brother and a sister in a Chinese family. Both patients presented with heavy proteinuria, which improved transiently on treatment with prednisolone and cyclophosphamide. Human lymphocyte antigen typing for the siblings showed no haplotype association. Despite the generally poor renal prognosis reported in the literature, with 50% of patients reaching end-stage renal failure within 2 to 4 years, both patients had relative preservation of renal function (creatinine clearance from 79 to 76 mL/min/1.73 m2 after 2 years in one patient and from 111 to 99 mL/min/1.73 m2 after 3 years in the other). Our observations show that fibrillary/immunotactoid glomerulopathy can present as a familial condition. Compared with sporadic cases, patients with familial fibrillary/immunotactoid glomerulopathy may have a more favorable renal prognosis.

Actin Cytoskeleton↗
PubMed1998

Fibrillary glomerulonephritis and Charcot-Marie-Tooth disease.

We report the case of a young white man with Charcot-Marie-Tooth disease type 1 that began at 4 years. At 15 years, he developed proteinuria, arterial hypertension, and renal insufficiency. Renal biopsy specimens studied by electron microscopy showed deposition of nonamyloidotic microfibrils. This is the first report of fibrillary glomerulopathy associated with this neurological disorder.

Actin Cytoskeleton↗
PubMed1979

Electron microscopic cytochemistry of polysaccharides in bacteria Xanthomonas fuscans, the cause of the bean fuscous blight.

High resolution cytochemical staining of polysaccharides in the cells of the bean fuscous blight bacteria Xanthomonas fuscans (Burkholder) Bur. revealed extensive deposits of a periodic acid-oxidizable compound in the cytoplasm, which accumulated at the onset of polysaccharide excretion and occupied a substantial part of the cell volume. In the course of subsequent culture growth the intracellular polysaccharides gradually disappeared and polysaccharide microfibrils were visualized in the medium. Our observations indicate that the exuded phytopathogenic polysaccharides may be synthetized in the cytoplasm of the bacteria.

Cytoplasm↗
PubMed1990

Alkaline phosphatase-positive and negative bone tumors. Ultrastructural and immunohistochemical studies of fibroblast-like tumor cells.

Bone tumors, which consist largely of fibroblast-like cells, were categorized into ALPase-positive (3 ossifying fibromas and 2 fibroblastic osteosarcomas) and negative (4 non-ossifying fibromas and 5 MFHs) groups. They were investigated as to their ultrastructure and immunophenotype using antibodies of fibroblast markers (collagen I, III, aminopeptidase M, dipeptidylpeptidase IV and factor XIIIa), classical macrophage markers (AACT and AAT) and vimentin. In the case of the ALPase-positive group, fibroblast-like cells showed short, branching rough endoplasmic reticulum with bundles of microfibrils in their cytoplasms. They were often intermingled with osteoblastic cells particularly in proximity to osteoid tissue. Furthermore, these cells expressed fibroblast markers of collagen I, aminopeptidase M, dipeptidylpeptidase IV and factor XIIIa. Fibroblast-like cells of the ALPase-negative group more or less revealed phagosomes in addition to fibroblastic features admixed with histiocyte-like cells. They expressed classical macrophage markers, but rarely fibroblast markers. The above findings indicated that derivation from different precursor cells should be proposed between the two groups and that the tumors in the ALPase-positive group might be intimately related to a certain population of the bone marrow stromal cells.

Alkaline Phosphatase↗