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At least 649 records · Page 36Linked to original sources
PubMed1985

Differentiation of extracellular matrix in the cellular cartilage ("Zellknorpel") of the mouse pinna.

Differentiation of cellular cartilage was studied in the mouse pinna with particular reference to matrix material. Fixation of glycosaminoglycans was performed by the use of acridine orange and elastin was identified by staining thin sections with tannic acid and uranyl acetate. Condensation of mesenchymal cells ("prechondroblasts") initiates the formation of a blastema of cartilaginous tissue at postnatal day 4. The synthesis of acidic glycosaminoglycans begins at postnatal day 8 when prechondroblasts transform to chondroblasts. Glycosaminoglycans can be detected within secretory vesicles of chondroblasts at postnatal day 8, in the extracellular space at postnatal day 13. Delicate collagen fibrils and elastic fiber microfibrils are seen between prechondroblasts and chondroblasts. Deposition of elastin begins at postnatal day 11. A network of elastic fibers and lamellae is formed, which replaces both collagen fibrils and elastic fiber microfibrils. In the interstice of mature cellular cartilage only elastin and proteoglycans are present (postnatal day 21). These findings indicate that cellular cartilage represents an independent kind of supporting tissue, which may serve as a progenitor of hyaline or elastic cartilage ("transitional cellular cartilage") but does not differentiate from hyalin cartilage.

Animals↗
PubMed1978

Histochemical demonstration of disulfide-groups in the lamina propria of human seminiferous tubules.

The distribution of disulfide-groups was investigated in the tunica propria of human seminifersou tubules by means of a thiosulfation/Alcian Blue + 0.8 Mol MgCl2-staining reaction. Controls had shown the absence of significant amounts of sulfhydryl- or sulfate-groups in the lamina propria, which groups would also be demonstrated by the method employed. The lamina propria of human seminiferous tubules is rich in disulfide groups. The staining reaction decreases in the region of the tubulus rectus, is only faint in the connective tissue which underlies the epithelium of the rete testis, and is absent in the lamina propria of efferent ducts. It is suggested that microfibrils and type IV collagen (both rich in cystine) are the materials responsible for the histochemical reaction described. The occurrence of multiple layers of basal lamina material (type IV collagen) and bundles of microfibrils is shown in comparative electron microscopic studies.

Disulfides↗
PubMed1976

In vitro elastic fiber formation by aggregated arotic cells of newborn rabbits.

Cells isolated enzymatically from the aortas of newborn rabbits were aggregated and grown in organ culture. Bundles of microfibrils, some of them with an amouphous core (elastin), were evident in 3-day-old aggregates. Furthermore, droplets of elastin surrounded by darker dots and short filaments, corresponding to the elastic units were observed. In 6-day-old aggregates the number of elastic fibers composed of bundles of microfibrils with deposited elastin increased. Elastic elements which probably resulted from a coalescence of elastic units were also present. These two ways of elastic fiber formation in aggregates are compared with those described in papers on aortic development.

Animals↗
PubMed1976

Cell wall formation in zoospores of Allomyces arbuscula. II. Development of surface structure of encysted haploid zoospores, rhizoids, and hyphae.

Development of haploid meiospores of Allomyces arbuscula into germling cells with rhizoids and hyphae was followed during incubation in complete growth medium. The surface structure of encysted meiospores, rhizoids and hyphae before and after extraction of amorphous materials with ethanolic KOH was studied by means of carbon-platinum replicas. After 2--3 min incubation in complete medium 10% of the meiospores were surrounded by a cell wall containing microfibrils embedded in a matrix. Structure of cell walls of encysted meiospores, rhizoids, and hyphae differ from one another by the location of amorphous materials and by the arrangement of chitin microfibrils.

Cell Wall↗
PubMed1988

Distribution and organization of the elastic system fibres in healthy human gingiva. Ultrastructural and immunohistochemical study.

The ultrastructural distribution and organization of the elastic system fibres, i.e. oxytalan, elaunin and elastic fibres, were studied by transmission electron microscopy and by an immunohistochemical method for the detection of elastin in healthy human gingiva. The morphological distribution of these fibres was characterized by the presence of oxytalan, elaunin and elastic fibres, respectively, in the upper, medium, and deep layers of gingival connective tissue. Anti-elastin antibody reacted with microfibrils and amorphous material of the elastic system fibres throughout the gingival connective tissue. These findings were interpreted as indicating that the microfibrils were associated with small amounts of elastin at their surface.

Adult↗
PubMed1980

Influence of beta-alanine on ultrastructure, tanning, and melanization of Drosophila melanogaster cuticles.

In Drosophila melanogaster, the chitinous microfibrils arising from the tips of the epidermal villi in adult cuticles remain irregular and loose in the mutant ebony (which fails in cuticular incorporation of beta-alanine) but closely knit and regular in normal flies. Addition of beta-alanine to cuticles from which nonchitinous materials have been removed with alkali converts the loose arrangement of the microfibrils to a compact and sharply delineated arrangement. beta-alanine also accelerates tyrosinase-catalyzed oxidation of N-acetyldopamine by reacting with the oxidized product of the reaction to produce an orange-red complex. Similarly, beta-alanine accelerates oxidation of N-acetyldopamine when these two substances are added to fluids from the hemocoel, to lead to tanning instead of normal blackening. These findings may help explain why beta-alanine induces tanning while inhibiting melanization in insects.

Alanine↗
PubMed1983

Fine-structural evidence for vascular injury in patients with interstitial cystitis.

Bladder vessel walls of 20 patients with interstitial cystitis were studied by the electron microscope. 14 (70%) had severe endothelial injury. 10 (50%) showed injured smooth muscle cells. Odd basement membrane proliferations and disruptions were seen. Clusters of microfibrils about 10 nm in diameter and numerous partially membrane-bound vesicles of 100-600 nm with granular or tiny vesicular content ("granulovesicular bodies") were also seen. Intercellular junctions of endothelial cells were open and there was emigration of polymorphonuclear leucocytes and platelets. The findings show pronounced vascular injury to have taken place, with neoformation of elastic tissue. It is suggested that the injury is immunologically mediated and that particularly those clusters of connective tissue microfibrils not yet covered by an amorphous elastin component may be involved in the pathogenesis of this disease.

Biopsy↗
PubMed1985

Trichuris muris: structure and formation of the egg polar plugs.

The structure and development of the polar plugs of Trichuris muris eggs were observed by light and electron microscopy. Initial stages in plug formation commenced in the spermatheca of the adult female where two polar papillae became delimited from the remainder of the oocyte cytoplasm. These papillae exhibited a discrete PAS positive reaction and were regarded as prospective plug regions from which cytoplasmic granules were absent. Glycogen rosettes, initially concentrated in these prospective areas, were later transformed into an irregular fine network of chitin-protein microfibrils. This arrangement of microfibrils was in contrast to that of the surrounding collar region which displayed a distinct lamellate organization. The fully developed polar plug was of lower electron density than the shell. Each plug was covered externally by the vitelline layer and lined internally by the lipid layer of the eggshell.

Animals↗
PubMed1995

Composition of plant cell walls.

The present study reviews the most recent research published (starting approximately in the 1980s) on the composition of plant cell walls, with a description of the polysaccharides contained in the microfibrillar and amorphous phases: cellulose, hemicellulose and pectic substances, as well as the other components: lignin, proteins and enzymes. Cellulose is a linear homopolymer made up of microfibrils that form a para-crystalline structure stabilised by hydrogen bridges. The hemicelluloses constitute an important group of polysaccharides, which are inter-linked and also linked to microfibrils of cellulose and/or pectins, the most important being: xylans, arabinoxylans, mannans, galactomannans, glucomannans, arabinogalactan II, beta-1,3-glucan and beta-1,3-beta-1,4-glucans. The pectic substances are a complex mixture of colloidal polysaccharides that can be extracted from the cell wall with water or chelating agents, the most significant being: rhamnogalacturonan I, rhamnogalacturonan II, arabinan, galactan, arabinogalactan I and D-galacturonan.

Carbohydrate Conformation↗
PubMed1975

Characterization of developing antler cartilage matrix, II, An ultrastructural study.

Cartilage from the main beams and tines of deer antler was examined with the electron microscope. The material studied included prechondroblastic, chondroblastic and chondrocytic matrices. Exdysial microfibrils (5-10 nm in diameter) were observed in the matrix of the prechondroblastic zone. These microfibrils and associated amorphous material were continuous with electron-dense material that probably represented extracellular units of collagen polymers. Matrix (proteoglycan) granules were first observed in the chondroblastic zone. They stained positively with colloidal iron and therefore probably represented proteinpolysaccharides. The matrix granules of the chondroxytic (unmineralized and mineralized) zone were twice the diameter of those in the chondroblastic zone. Matrix vesicles were present in all three stages of development. They were in contact with cellular extensions and also arose directly from cell membranes in the immature zones. As in somatic mineralizing cartilage, these vesicles served as the foci for early mineralization. The initial mineralization process was associated with the membrane of the vesicles.

Animals↗
PubMed1978

Elastic fibers in the tunica propria of the seminiferous tubules. Light and electron microscopic investigations.

Histological examination of numerous biopsies from mature testes, repeatedly showed irregularities of the elastin staining in the tunica propria of the seminiferous tubules. Even when abundant elastic fibers were visible by light microscopy, no elastic fibers were demonstrable in the electron microscope in ultrathin sections of testicular tubules embedded in Epon and contrasted with phosphotungstic acid (PTA). In 43 biopsies from 22 men aged 17-39 years (19 investigations of sterility and three patients with hypogonadotropic hypogonadism) we therefore checked for the occurrence of elastic fibers in the wall of the seminiferous tubules. Matrix loci of elastic fibers could indeed by demonstrated by electron microscopy using PTA and potassium permanganate (KMnO4), but only after embedding in araldite. Under these conditions, light and electron microscopic findings agreed with each other. The appearances of moderate and severe testicular tubular atrophy differed slightly from one another with regard to the amount of elastin. In the "Sertoli cells only syndrome", elastic fibers were demonstrable only outside the hyalinized inner layer. In the Klinefelter syndrome, only "uncertain" elastin loci were present, but greatly increased microfibrils were to be seen using the electron microscope. No elastic elements and only very sparse microfibrils were present in the tunica propria of the tubules of young men with hypogonadotropic hypogonadism.

Adolescent↗
PubMed1988

Immunohistochemical studies on the tissue localization of collagen types I, III, IV, V and VI in schwannomas. Correlation with ultrastructural features of the extracellular matrix.

The distinctive tissue localization of collagen types in typical schwannomas with Antoni type A and B areas was demonstrated immunohistochemically using affinity-purified antibodies against types I, III, IV, V and VI collagen and comparative ultrastructural studies were made on the extracellular matrix components. Antoni type A tissue, which was composed of tightly packed spindle cells with long cytoplasmic processes surrounded by a continuous basement membrane and a few fibrillar components of the extracellular matrix, was almost exclusively immunoreactive for type IV collagen, presumably representing the basement membrane. Verocay bodies, which are organoid structures of Antoni type A tissue, had a variety of more abundant extracellular fibrous components, such as banded collagen fibrils, fibrous long-spacing fibrils and microfibrils. These were positive for type I and III, as well as type IV collagen. In Antoni type B areas, where two types to tumor cells designated Schwann cell-like and fibroblast-like were scattered in large amounts of amorphous extracellular matrix containing microfibrils and thick banded collagen fibrils, type VI collagen as well as types I, III and IV collagen were consistently detected. Type V collagen was localized in dense fibrous tissue areas and around blood vessels. These findings indicate that the differently organized cellular patterns of schwannomas, identified as Antoni types A and B, are characterized not only by the ultrastructural features of the extracellular matrix, but also by the distinctive collagen types produced by neoplastic Schwann cells.

Adult↗
PubMed1997

Hyaluronan and chondroitin sulfate proteoglycans are colocalized to the ciliary zonule of the rat eye: a histochemical and immunocytochemical study.

In previous studies, chondroitin sulfate proteoglycans have been localized to the periphery of the zonular fibers and the individual zonular fibrils (or microfibrils) after Cuprolinic blue staining in conjunction with chondroitinase digestions and immunogold labelling with 2-B-6 antibody. In the present study, we wished to determine if these proteoglycans are linked to hyaluronan to form a large multimolecular aggregate. To accomplish this, we localized the hyaluronan using a biotinylated hyaluronan-binding protein fragment of chondroitin sulfate proteoglycan, containing also the link protein, purified from bovine nasal cartilage. The results showed that the ciliary zonule of the rat eye was reactive with the biotinylated hyaluronan-binding probe as demonstrated by streptavidin-peroxidase-diaminobenzidine staining and streptavidin-gold labelling. Hyaluronan-gold labelling showed that the gold particles were mostly localized on the periphery of the zonular fibers, which was similar to the localization pattern of the zonule associated-proteoglycans. This hyaluronan-binding probe also strongly labelled the sites of zonule insertion over the basement membrane of the inner ciliary epithelium at the pars plana and the lens capsule at the equatorial region, which suggests its probable role in the attachment of ciliary zonule to the basement membranes. To demonstrate whether these two molecules are linked to one another, ultrastructural colocalization of both hyaluronan and chondroitin sulfate proteoglycans was performed on the same sections by double-gold labelling, and combined Cuprolinic blue staining and hyaluronan-gold labelling. Gold particles of 15 and 10 nm in sizes labelling both hyaluronan and chondroitin 4-sulfate, were colocalized to the surface of the zonular fibers. The combined Cuprolinic blue staining and hyaluronan-gold labelling showed that the gold particles were localized towards the ends of the Cuprolinic blue-stained rodlets, which strongly suggests that these chondroitin sulfate proteoglycans are linked to the hyaluronan chain to form a large aggregate surrounding the periphery of the zonular fibers. These ciliary zonule-associated proteoglycan-hyaluronan aggregates may play a role in organizing the individual zonular fibrils (microfibrils) into bundles of zonular fibers.

Animals↗
PubMed2002

Micromechanics of plant tissues beyond the linear-elastic range.

We investigated the relation between cell wall structure and the resulting mechanical characteristics of different plant tissues. Special attention was paid to the mechanical behaviour beyond the linear-elastic range, the underlying micromechanical processes and the fracture characteristics. The previously proposed model of reorientation and slippage of the cellulose microfibrils in the cell wall [H.-CH. Spatz et al. (1999) J Exp Biol 202:3269-3272) was supported and is here refined, using measurements of the changes in microfibrillar angle during straining. Our model explains the widespread phenomenon of stress-strain curves with two linear portions of different slope and sheds light on the micromechanical processes involved in viscoelasticity and plastic yield. We also analysed the velocity dependence of viscoelasticity under the perspective of the Kelvin model, resolving the measured viscoelasticity into functions of a velocity-dependent and a velocity-independent friction. The influence of lignin on the above-mentioned mechanical properties was examined by chemical lignin extraction from tissues of Aristolochia macrophylla Lam. and by the use of transgenic plants of Arabidopsis thaliana (L.) Heynh. with reduced lignin content. Additionally, the influence of extraction of hemicelluloses on the mechanical properties was investigated as well as a cell wall mutant of Arabidopsis with an altered configuration of the cellulose microfibrils.

Arabidopsis↗
PubMed2004

Biophysical consequences of remodeling the neutral side chains of rhamnogalacturonan I in tubers of transgenic potatoes.

Two lines of transgenic potato (Solanum tuberosum L.) plants modified in their cell wall structure were characterized and compared to wild type with regard to biomechanical properties in order to assign functional roles to the particular cell wall polysaccharides that were targeted by the genetic changes. The targeted polymer was rhamnogalacturonan I (RG-I), a complex pectic polysaccharide comprised of mainly neutral oligosaccharide side chains attached to a backbone of alternating rhamnosyl and galacturonosyl units. Tuber rhamnogalacturonan I molecules from the two transformed lines are reduced in linear galactans and branched arabinans, respectively. The transformed tuber tissues were found to be more brittle when subjected to uniaxial compression and the side-chain truncation was found to be correlated with the physical properties of the tissue. Interpretation of the force-deflection curves was aided by a mathematical model that describes the contribution of the cellulose microfibrils, and the results lead to the proposition that the pectic matrix plays a role in transmitting stresses to the load-bearing cellulose microfibrils and that even small changes to the rheological properties of the matrix have consequences for the biophysical properties of the wall.

Kinetics↗
PubMed1998

The cyclic reorientation of cortical microtubules in epidermal cells of azuki bean epicotyls: the role of actin filaments in the progression of the cycle.

The orientation of microtubules (MTs) was examined in epidermal cells of azuki bean (Vigna angular is Ohwi et Ohashi) epicotyls. The orientation of MTs adjacent to the outer tangential wall of the cells, which has a crossed polylamellate structure with lamellae of longitudinal cellulose microfibrils alternating with lamellae of transverse cellulose microfibrils, differed from one cell to another. Treatment with an auxin-free solution caused the accumulation of cells with longitudinal MTs and subsequent treatment with a solution that contained auxin resulted in the accumulation of cells with transverse MTs, showing that sequential treatments with auxin-free and auxin-containing solutions can synchronize the reorientation of MTs. The MTs, once reoriented from longitudinal to transverse, returned to longitudinal and then back to transverse once again, the duration of the cycle being about 6h. Gibberellic acid, known to increase the percentage of cells with transverse MTs, promoted reorientation of MTs from longitudinal to transverse and inhibited that from transverse to longitudinal. Cytochalasin D, an agent that disrupts actin filaments, speeded up the reorientation from transverse to longitudinal and slowed down that from longitudinal to transverse. It caused an increase in the percentage of cells with MTs in mixed orientation, and the percentage of such cells was highest when the percentage of cells with longitudinal MTs was decreasing and that of cells with transverse MTs was increasing.

Actin Cytoskeleton↗
PubMed2000

Micromechanics and anatomical changes during early ontogeny of two lianescent Aristolochia species.

The mechanical properties of young stems of Aristolochia macrophylla Lam. and Aristolochia brasiliensis Mart. et Zucc. were studied during elongation growth and primary differentiation. Data for the modulus of elasticity, for the viscoelastic behaviour caused by longitudinal tension and for the shear modulus resulting from torsion around a longitudinal axis were related to the underlying structural changes by quantitative analysis of stem anatomy, tissue distribution, ultrastructure, and cell wall biochemistry. The orientation of cellulose microfibrils was determined by light microscopy and small-angle X-ray diffraction, and the lignin content was determined by thioglycolic acid derivatization and spectroscopic quantification. It was demonstrated that the increase in stability during early development is due to the complementary effects of increase in cell wall material, lignification, and cellulose microfibril alignment. A detailed micromechanical model, considering internal prestresses, is proposed to explain the characteristic biphasic stress-strain behaviour as well as the strain-hardening observed.

Biomechanical Phenomena↗
PubMed2003

Disruption of cellulose synthesis by isoxaben causes tip swelling and disorganizes cortical microtubules in elongating conifer pollen tubes.

In elongating pollen tubes of the conifer Picea abies (Norway spruce), microtubules form a radial array beneath the plasma membrane only at the elongating tip and an array parallel with elongation throughout the tube. Tips specifically swell following microtubule disruption. Here we test whether these radial microtubules coordinate cell wall deposition and maintain tip integrity as tubes elongate. Control pollen tubes contain cellulose throughout the walls, including the tip. Pollen tubes grown in the presence of isoxaben, which disrupts cellulose synthesis, are significantly shorter with a decrease in cellulose throughout the walls. Isoxaben also significantly increases the frequency of tip swelling, with no effect on tube width outside of the swollen tip. The decrease in cellulose is more pronounced in pollen tubes with swollen tips. The effects of isoxaben are reversible. Following isoxaben treatment, the radial array of microtubules persists beneath the plasma membrane of nonswollen tips, while this array is specifically disrupted in swollen tips. Microtubules instead form a random network throughout the tip. Growth in these pollen tubes is turgor driven, but the morphological changes due to isoxaben are not just the result of weakened cell walls since pollen tubes grown in hypoosmotic media are not significantly shorter but do have swollen tips and tubes are wider along their entire length. We conclude that the radial microtubules in the tip do maintain tip integrity and that the specific inhibition of cellulose microfibril deposition leads to the disorganization of these microtubules. This supports the emerging model that there is bidirectional communication across the plasma membrane between cortical microtubules and cellulose microfibrils.

Benzamides↗