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Results for “Microfibrils”

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At least 289 records · Page 16Linked to original sources
PubMed1991

Rotary shadowing of elastic system microfibrils in the ocular zonule, vitreous, and ligamentum nuchae.

Rotary shadowing of zonular fibrils in human and bovine eyes revealed a "string of beads" configuration with multiple interconnecting filaments, identical to that recently reported in fibrils of unknown type within the vitreous. These 29 nm beaded fibrils were the only macrostructures present in zonular samples, showing ultrastructural features correlating with both the macro and microperiodicity of zonular fibrils in tissues. Interbead periodicity varied from 30-57 nm and interbead filaments appeared capable of stretching even further, possibly explaining the inherent elasticity of zonular fibrils. The junctions between outer filaments and beads were fibrillin-positive. Similar beaded fibrils were found in the human and bovine anterior vitreous along with type II and IX collagen fibrils, proteoglycan filaments and other unidentified fibrils. After collagenase and elastase digestion, bovine ligamentum nuchae showed type VI collagen fibrils and clumps of beaded fibrils like those in zonule and vitreous. This distribution indicates that the beaded fibril is the microfibril which constitutes the basic unit of the elastic system.

Animals↗
PubMed1980

Isolation of elastic tissue microfibrils derived from cultured cells of calf ligamentum nuchae.

Cells cultured from calf ligamentum nuchae produce extracellular microfibrils identical to those of intact elastic tissue as determined by ultrastructural appearance, degradative enzyme susceptibilities and amino acid composition. A method to isolate large amounts of the microfibrillar component using fluorescein mercuric acetate is described. The cultures do not appear to synthesize the amorphous component, elastin, in that radioactive desmosine and isodesmosine were not detected after incubating cultures with labeled lysine nor was elastin seen ultrastructurally.

Amino Acids↗
PubMed1992

Calvasculin, an encoded protein from mRNA termed pEL-98, 18A2, 42A, or p9Ka, is secreted by smooth muscle cells in culture and exhibits Ca(2+)-dependent binding to 36-kDa microfibril-associated glycoprotein.

Calvasculin, an EF-hand protein with a molecular mass of 11 kDa on sodium dodecyl sulfate-polyacrylamide gel electrophoresis, is present abundantly in bovine aorta (Watanabe, Y., Kobayashi, R., Ishikawa, T., and Hidaka, H. (1992) Arch. Biochem. Biophys. 292, 563-569). This protein is synthesized constitutively by bovine aortic smooth muscle (BASM) cells and rat embryo fibroblast 3Y1 cells in culture. We discovered that calvasculin was secreted by BASM cells and 3Y1 cells. Immunofluorescence staining of BASM cells showed a granular distribution for calvasculin that was typical of a secreted protein. This protein bound with an extracellular matrix protein, 36-kDa microfibril-associated glycoprotein (36-kDa MAP), in a Ca(2+)-dependent manner in vitro. A stoichiometry analysis showed that the 36-kDa MAP bound 2.2 calvasculin eq/mol of protein. Solid-phase binding assays indicated a preferential affinity of native calvasculin for 36-kDa MAP among the extracellular matrices in a Ca(2+)-dependent manner. These results suggest that calvasculin, intracellular Ca(2+)-binding protein, is released to the extracellular space and binds with 36-kDa MAP.

Animals↗
PubMed2006

[The analysis of wood microfibril angle by near infrared spectroscopy and X-ray diffractometry].

In the present paper, near infrared (NIR) spectroscopy and X-ray diffractometry were used to rapidly predict the microfibril angle (MFA). MFA is one of the most important factors affecting wood properties. Wood resource utilization and tree improvement programs require cost-effective methods for the rapid analysis of thousands of samples. In the experiment, the average MFA of each sample were rapidly measured by X-ray scanning diffractometry. Then, the PLS model was built between NIR data and MFA by the X-ray measured. As a result, a very strong linear relationship has been found between NIR spectra fitted and X-ray measured, and the coefficients (r2) of calibration and prediction models were 0.867 and 0.816 respectively.

English Abstract↗
PubMed1991

Purification and partial characterization of fibrillin, a cysteine-rich structural component of connective tissue microfibrils.

Fibrillin, a connective tissue macromolecule (Mr = 350,000) which is normally insoluble in its tissue form, has been purified from the medium of human skin fibroblast and ligament cells in culture. Analysis of the amino acid composition indicates that fibrillin contains approximately 14% cysteine, of which one-third appears to be in the free reactive sulfhydryl form. Electron microscopic images of fibrillin reveal an extended, flexible molecule approximately 148 nm long and 2.2 nm wide. These length measurements are consistent with shape calculations based upon velocity sedimentation data. It is likely that the material we have purified from cell culture medium represents monomeric fibrillin consisting of a single polypeptide chain. Additional ultrastructural immunohistochemical data presented here suggest a model for the parallel, head-to-tail alignment of fibrillin molecules in microfibrils.

Amino Acids↗
PubMed1990

Features of the aperiodic microfibrils associated with mouse dental basement membrane demonstrated by ultrastructural histochemistry.

Histochemical features of aperiodic microfibrils (AMF) in mouse tooth germs were examined at the electron microscopic level. Intact and EDTA-isolated materials obtained from one day old first molars were used for ruthenium red (RR) staining, ferritin permeability, periodic acid-silver methenamine (PAM) impregnation, fibronectin localisation, negative staining on cryo-sections and tannic acid fixation. Electron microscopy and negative staining demonstrated that AMF traverse the basal lamina and penetrate below the inner enamel epithelium. In addition to RR staining, PAM impregnation and tannic acid fixation showed deposition on the AMF which was associated with basal laminae. RR staining and tannic acid fixation also indicated the presence of glycoprotein-rich materials in the lamina lucida. The AMF were derived from the lamina lucida which was closely associated with tannic acid-positive granular materials. The precipitation of silver particles by PAM impregnation was seen on banded collagen fibrils, basal lamina and AMF, but the staining features of AMF differed distinctly from those of collagen fibrils. The distribution of ferritin particles revealed that the basal lamina covering EDTA-isolated papilla tissue is a continuous structure. Immuno-reactions for fibronectin were detected on the basal lamina and AMF. Our results suggest that AMF are derived from the glycoprotein-rich lamina lucida and that their histochemical characteristics resemble those of basal lamina.

Animals↗
PubMed1989

Connective tissue microfibrils. Isolation and characterization of three large pepsin-resistant domains of fibrillin.

Human amnion was solubilized using pepsin and the digest supernatant screened for fragments of fibrillin with a previously characterized monoclonal antibody (Sakai, L. Y., Keene, D. R., and Engvall, E. (1986) J. Cell Biol. 103, 2499-2509). One fragment (PF1), with an apparent molecular weight of 94,000, was isolated and characterized. Two other fragments, PF2 and PF3, were isolated and shown to be fragments of fibrillin by preparing a monospecific antisera to PF2 and a monoclonal antibody to PF3. Immunoelectron microscopy and immunoblotting showed that both antibodies were specific for fibrillin. Electron microscope pictures of rotary-shadowed PF1 and PF2 showed them to be short rod-shaped molecules while PF3 has a crab-like appearance and seems to be an aggregate of several fibrillin chain fragments. Amino-terminal amino acid sequencing of PF1 and PF2 gave single unique sequences. Each of the three antibodies used was specific for one fragment and peptide mapping of PF1 and PF2 showed that there was no significant amino acid sequence overlap. Aggregates of PF3 are described which provided insight into the assembly and macromolecular structure of fibrillin in microfibrils.

Actin Cytoskeleton↗
PubMed1988

Cyclosporin-associated microfibrils in cardiac transplant patients.

Endomyocardial biopsies from 21 cyclosporin-treated cardiac transplant patients were studied at the ultrastructural level. Eight patients exhibited focal interstitial accumulation of filaments, which most commonly measured 8-10 nm in diameter (range 7-16 nm). The filaments were straight, hollow, and nonbranching. Filament accumulation was observed as early as 4 days posttransplant. No filament accumulation was observed in 17 donor endomyocardial biopsies obtained at the time of transplantation. The ultrastructure of the filaments was similar to that of amyloid fibrils. Stains for amyloid at the light microscopic level were uniformly negative, however. Until the exact nature of the filaments is determined, we propose that they be referred to as cyclosporin associated microfibrils.

Actin Cytoskeleton↗
PubMed1994

Microfibril-associated glycoprotein binds to the carboxyl-terminal domain of tropoelastin and is a substrate for transglutaminase.

Microfibril-associated glycoprotein (MAGP) is an integral component of microfibrillar structures that play a critical role in the organization of elastic fibers in the extracellular matrix. To study possible molecular interactions between MAGP and other elastic fiber components, we have generated native MAGP using a baculovirus expression system and tested its ability to associate with tropoelastin and fibrillin. MAGP produced by SF9 cells underwent processing similar to the mammalian protein, including correct cleavage of the signal peptide and sulfation of tyrosine residues. When tested in solid-phase binding assays, native MAGP specifically bound to tropoelastin but not fibrillin-1. Binding to tropoelastin was divalent cation-independent and was completely blocked by reduction and alkylation of either protein. Antibody inhibition studies indicated that the carboxyl terminus of tropoelastin mediated its interaction with MAGP. In addition to binding to elastin, MAGP was also a substrate for transglutaminase, which might explain its propensity to form high molecular weight aggregates that cannot be dissociated with reduction or denaturation. Together, the results of this study provide new insights into the functional relationship between microfibrillar proteins and have important implications for understanding elastic fiber assembly.

Amino Acid Sequence↗
PubMed1993

Defective adhesion of blood platelets to vascular microfibrils in the Bernard-Soulier syndrome.

Bernard-Soulier syndrome (BSS) platelets, which lack the membrane glycoprotein complex Ib-IX, do not adhere to subendothelium. The adhesion of platelets from two patients with BSS to subendothelial microfibrils (MFs) and type I collagen was compared in an in vitro assay adapted to patients with low platelet count. With both patients, platelet adhesion to MFs was strongly defective, whereas the adhesion to collagen was normal. The involvement of GPIb in the MFs-induced platelet adhesion was confirmed by the inhibitory effect of a MoAb (AN51) to the von Willebrand (vWF) factor binding domain of GPIb. The adhesion of platelets to MFs thus requires GPIb-IX and an axis MFs-vWF-GPIb-IX seems therefore to be prevalent in the reactivity of platelets with subendothelium.

Actin Cytoskeleton↗