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At least 19 recordsLinked to original sources
PubMed1990

Comparison of non-collagenous type IV collagen subunits in human glomerular basement membrane, alveolar basement membrane, and placenta.

This study examines the similarities and differences in the noncollagenous domain (NC1) of type IV collagen from human glomerular basement membrane (hGBM), alveolar basement membrane (hABM), and placenta (hPBM). Following collagenase digestion, NC1 domain was isolated on Bio-Gel A-0.5m or by cation exchange chromatography on S-Sepharose. NC1 from each source was characterized by SDS PAGE, and two dimension NEPHGE/SDS PAGE. Immunoblotting and ELISA inhibition was performed using antibody probes specific for M28 , M28+, M26 and M24 monomer subunits of human NC1. It was observed that all NC1 subunits were present in hGBM and hABM derived material, however M28 and M28+ monomers were absent in hPBM NC1. These findings indicate that while alpha 1(IV) and alpha 2(IV) collagen chains are present in hGBM, hABM and hPBM, alpha 3(IV) and alpha 4(IV) collagen chains are only found in hGBM and hABM but are absent in hPBM. It can now be appreciated that heterogeneity of alpha (IV) chain composition exists in basement membranes from various organs.

Basement Membrane↗
PubMed1989

Biochemistry of basement membranes.

Basement membranes are thin (20 to 300 nm) extracellular matrices with a ubiquitous occurrence in the body. They consist mainly of collagenous and noncollagenous glycoproteins, are formed early during embryonic development, and in mature tissues they compartmentalize various types of cells and tissue structures. The close apposition to cells is the most remarkable feature of basement membranes, which can either surround cells completely (muscle, fat, nerve axons) or separate them from underlying stroma in a polarized fashion (epithelium, endothelium). These cell contacts are mediated by cellular receptors and specific matrix components and have profound effects on polarization, differentiation, and proliferation of cells and on the control of their migratory behavior. In addition, basement membranes represent barriers regulating filtration of macromolecules and penetration by cells. The supramolecular organization of basement membranes is still insufficiently known. In transmission electron microscopy cross-sections show a two-layered morphology that includes an electron dense (lamina densa) and an electron lucent (lamina rara) zone, the latter being closer to the cells. Other specialized basement membranes such as those in renal glomeruli appear more complex and contain two laminae rarae. Here, presumably epithelial and invading endothelial cells each produce their own basement membrane, which then fuse together to form the filtration units of the glomerulus. Further structural and functional study of authentic basement membranes has been limited because these membranes comprise only a small fraction of tissues and most of their components are notoriously insoluble. Rodent tumors that produce large amounts of basement membrane material and the use of recombinant DNA technology in the past decade have paved the way for a more precise biochemical characterization of several basement membrane proteins. These components include collagen type IV, the cell-binding protein laminin, several proteoglycans, and other proteins. In the following pages we will briefly review the biochemical properties of the basement membranes and discuss their possible functions and contributions to supramolecular structures. For more extensive discussions, including certain biologic and pathologic aspects of basement membrane function, we refer the reader to several recent reviews.

Basement Membrane↗
PubMed1975

The relation between connective tissue cells and intercellular substances, including basement membranes.

Basement membranes are distributed widely in the body forming an extracellular matrix for epithelial and endothelial cells. The collagenous and glycoprotein constituents of basement membranes are synthesized by these two cell types. Disturbance of the interactions between basement membranes and their associated epithelial and endothelial cells can lead to the pathological changes seen in diseases involving basement membranes. These changes are illustrated here by reference to glomerulonephritis induced by the deposition of immune complexes in the glomerulus of the kidney, and chronic inflammatory changes occurring in the lung after inhalation of asbestos. In these diseases basement membrane changes can occur in several ways. Hydrolytic enzymes released from inflammatory cells degrade basement membranes while other constituents by epithelial and endothelial cells. Alternatively the physical separation of epithelial and endothelial cells from their basement membrances by space-occupying substances such as immune complexes can interfere with feedback mechanisms leading to synthesis of basement membrane constituents and cell proliferation. Studies of these pathological changes at a cellular level should shed new light on the ways in which cells interact with their pericellular environment.

Asbestos↗
PubMed1987

Interaction of toxic cations with the glomerulus: binding of Ni to purified glomerular basement membrane.

Basement membrane was prepared from the glomeruli of bovine kidneys using either detergent extraction, sonication or trichloroacetic acid (TCA) treatment. An assay was developed to measure the binding of radiolabelled metal salts to particulate suspensions of the membrane. 63Ni bound to the anionic glycosaminoglycan (GAG) sites of the membrane. This binding could be blocked by the cationic dye ruthenium red, and was sensitive to treatment with heparitinase but not to mild collagenase digestion. At pH 7.4 at low ionic strength (5 mM Tris-HCl), a high affinity (Ka = 4.5 X 10(6) M-1) binding site was distinguished. It was insensitive to increasing salt concentration, but was abolished by desulfation of the basement membrane preparation. 54Mn showed a similar binding pattern to Ni, while 65Zn and 109Cd lacked the high affinity site. In all cases the bulk of binding was of lower affinity and was of a non-specific electrostatic nature. Most, but not all, was abolished by salt concentrations comparable to those of the plasma filtrate (140 mM NaCl). These results are discussed in the context of sensitivity of the glomerular charge barrier to toxic divalent ions.

Amino Acids↗
PubMed1990

Molecular architecture of basement membranes.

Basement membranes are specialized extracellular matrices with support, sieving, and cell regulatory functions. The molecular architectures of these matrices are created through specific binding interactions between unique glycoprotein and proteoglycan protomers. Type IV collagen chains, using NH2-terminal, COOH-terminal, and lateral association, form a covalently stabilized polygonal framework. Laminin, a four-armed glycoprotein, self-assembles through terminal-domain interactions to form a second polymer network, Entactin/nidogen, a dumbbell-shaped sulfated glycoprotein, binds laminin near its center and interacts with type IV collagen, bridging the two. A large heparan sulfate proteoglycan, important for charge-dependent molecular sieving, is firmly anchored in the basement membrane and can bind itself through a core-protein interaction to form dimers and oligomers and bind laminin and type IV collagen through its glycosaminoglycan chains. Heterogeneity of structure and function occur in different tissues, in development, and in response to different physiological needs. The molecular architecture of these matrices may be regulated during or after primary assembly through variations in compositions, isoform substitutions, and the modifying influence of exogenous macromolecules such as heparin and heparan sulfate.

Animals↗
PubMed1990

Morphometric analysis of glomerular basement membranes (GBM) in thin basement membrane disease (TBMD).

We measured the thickness of glomerular basement membrane in 46 patients with thin basement membrane disease (TBMD), (age range 15-50 years, almost equal M:F ratio), and compared with that in a control group of 5 patients (age range 5-38 years) with normal glomerular morphology. The measurements of glomerular basement membrane taken from electron micrographs (magnification x 12,500) were analyzed using an interactive image analysis system assembled around an INTEL 10 microcomputer, with a high resolution touch sensitive screen as the interactive peripheral. Calculation was done by printing on an electron micrograph a grating replica (21,600 lines/cm), with the same magnification as the electron micrographs of the glomeruli and calibrating the arithmetic (AM) and harmonic (HM) mean for each case. Comparing the results of TBMD cases (AM 129-202 nm; HM 128-213 nm) with those of the control group consisting of 5 cases of "minimal change nephrotic syndrome" (AM 287-317 nm; HM 300-333 nm) it was found that GBM in TBMD is remarkably thin. The thinning was caused mainly by the decreased width of the lamina densa (TBMD group: 71.4-147.0 nm; HM 72.4-154.4 nm in comparison with the control group: AM 174.4-235.5 nm; HM 184.2-249.6 nm). This finding allows us to differentiate thin basement membrane disease from other glomerulopathies presenting primarily with isolated or recurrent hematuria.

Adolescent↗
PubMed1978

Electron microscopy of nephropathia epidemica. Renal tubular basement membrane.

Tubular basement membranes in kidney biopsies from 18 patients with nephropathia epidemica were studied by electron microscopy. Both in the cortex and in the medulla there was splitting of the basement membrane. Thickened basement membrane around occasional tubules contained membrane vesicles, usually empty but also with a core and a diameter of approximately 180 nm. Membranous convoluted structures and light finely fibrillar areas in the basement membranes were seen. Splitting of the basement membrane was most prominent in the medulla, and the membrane was filled with round to oval particles 55 to 470 nm in diameter. Of the possible mechanisms of damage at the basement membrane level in this disease, the findings suggest liberation of antigen from the tubular cells and reaction of circulating antibodies with the antigen in the basement membrane.

Adolescent↗
PubMed1990

Membranous nephropathy, antitubular basement membrane antibodies and alveolar hemorrhage in a diabetic child.

We describe an 8-year-old boy who was diagnosed as having diabetes mellitus at the age of 3 months. During the follow-up the diabetes was uncontrolled, and he presented nephrotic syndrome with renal function impairment, a renal biopsy showing a membranous nephropathy. Subsequently he had episodes of anemia and dyspnea, due to alveolar hemorrhage, and he also developed Fanconi's syndrome. A later renal biopsy showed membranous glomerulonephritis and interstitial nephritis. The presence of antitubular basement membrane antibodies was noted but antialveolar basement membrane antibodies were not detected. We do not believe that this unusual clinical picture was a coincidence, and we speculate about a possible explanation.

Antibodies↗
PubMed1991

Calcium-dependent binding of basement membrane protein BM-40 (osteonectin, SPARC) to basement membrane collagen type IV.

Basement membrane protein BM-40, prepared from the mouse Engelbreth-Holm-Swarm tumor, was used in native, denatured and proteolytically processed form for binding to various extracellular matrix proteins. BM-40 and its derivatives were also characterized by CD spectroscopy, calcium binding and epitope analysis. Of several basement membrane proteins tested only collagen IV showed a distinct and calcium-dependent binding of BM-40 in an immobilized ligand assay. This interaction was specific as shown by a low activity of other collagen types (I, III, V, VI) in direct binding and competition assays. The binding was reduced or abolished by metal-ion-chelating or chaotropic agents, high salt and reduction of disulfide bonds in BM-40. Fragment studies indicated that domains III (alpha-helix) and/or IV (EF hand) of BM-40 possess the binding site(s) for collagen IV, while the N-terminal domains I and II provide the major antigenic determinants. A major BM-40-binding site on collagen IV was dependent on a triple-helical conformation and could be localized to a pepsin fragment from the central portion of the triple-helical domain, in agreement with electron microscopic visualization of BM-40--collagen-IV complexes.

Amino Acid Sequence↗
PubMed1976

Chemical properties of human glomerular basement membrane in the nephropathy with electron dense deposits inside the basement membrane.

Glomerular basement membranes containing electron dense deposits have been isolated from human kidneys. The presence of electron dense material could not be accounted for by the accumulation of an exogenous substance such as gamma globulin. Chemical analyses of abnormal membranes demonstrated that the electron microscopic findings are the consequence of the accumulation of a basement membrane glycoprotein material slightly different from that normally present.

Adult↗
PubMed1976

Platelet interaction with human umbilical cord vascular basement membrane.

The basement membrane of the human umbilical vein was studied by electron microscopy with respect to its ultrastructure, susceptibility to digestion by collagenase or trypsin, and reactivity with human platelets. Electron microscopic examination of this vessel showed a continuous reticulated basement membrane which morphologically resembled those of mammalian capillaries and rabbit heart valves. The vascular endothelium was removed by freezing and thawing, thus uncovering the underlying connective tissue. The vessels were sliced into rings which were incubated with collagenase or trypsin. The basement lamella appeared to be susceptible to digestion by either enzyme. Platelet interaction with exposed vascular basement mambrane was studied by rotating frozen-thawed everted and noneverted rings in anticoagulated whole human blood. In heparinized or citrated blood, large aggregates of degranulated platelets adhered to collagenous controls; in contrast, the test rings with exposed basement membrane were partially covered with a monolayer of platelets which appeared to retain discoid or spherical shape and granules. In EDTA-anticoagulated blood, the collagen control rings accumulated a platelet monolayer, whereas little or no adhesion occurred on the basement membrane surface. In this system the basement membrane of the human umbilical vein appears to be a poor platelet reactive surface as compared to collagen.

Basement Membrane↗
PubMed1992

Studies of the permeation properties of glomerular basement membrane: cross-linking renders glomerular basement membrane permeable to protein.

Cross-linking glomerular basement membrane (GBM) has been shown to render it more permeable to protein. Isolated pig GBM was cross-linked with dimethylmalonimidate which reacts selectively with lysine epsilon-NH2 groups or with glutaraldehyde, a less selective cross-linking agent. Studies of the ultrafiltration properties of these materials in vitro using cytochrome c, myoglobin, bovine serum albumin and immunoglobulin showed that cross-linking had markedly increased solvent and protein fluxes as compared with native membranes particularly at higher pressures. Filtration studies with serum demonstrated that the cross-linked membranes were more permeable to serum proteins. Thickness measurements under pressure indicated that cross-linked membrane was less compressed than native membrane as pressure was increased. Pore theory did not provide a suitable model for analysis of the results, but analysis of the results using the fibre-matrix hypothesis indicated that cross-linking had the effect of bundling together the fibres (type IV collagen) in the GBM matrix. The effect of cross-linking on filtration could be explained by a combination of contraction of the membrane, fibre bundling and increased rigidity compared with native membrane. Cross-linking of GBM might lead to long-term damage of the glomerular capillary wall in nephritis, so promoting proteinuria.

Animals↗
PubMed1990

Heparan sulfate proteoglycan from human tubular basement membrane. Comparison with this component from the glomerular basement membrane.

Heparan sulfate proteoglycan (HSPG) was extracted from human tubular basement membrane (TBM) with guanidine and purified by ion-exchange chromatography and gel filtration. The glycoconjugate was sensitive to heparitinase and resistant to chondroitinase ABC, had an apparent molecular mass of 200-400 kDa and consisted of 70% protein and 30% glycosaminoglycan. The amino acid composition was characterized by its high content of glycine, proline, alanine and glutamic acid. Hydrolysis with trifluoromethanesulfonic acid yielded core proteins of 160 and 110 kDa. The heparan sulfate (HS) chains obtained after alkaline NaBH4 treatment had a molecular mass of about 18 kDa. Results of heparitinase digestion and HNO2 treatment suggest a clustering of sulfate groups in the distal portion of the HS side chains. These chemical data are comparable to those obtained previously on glomerular basement membrane (GBM) HSPG (Van den Heuvel et al. (1989) Biochem. J. 264, 457-465). Peptide patterns obtained after trypsin, clostripain or V8 protease digestion of TBM and GBM HSPG preparations showed a large similarity. Polyclonal antisera and a panel of monoclonal antibodies raised against both HSPG preparations and directed against the core protein showed complete cross-reactivity in ELISA and on Western blots. They stained all basement membranes in an intense linear fashion in indirect immunofluorescence studies on human kidneys. Based on these biochemical and immunological data we conclude that HSPGs from human GBM and TBM are identical, or at least very closely related, proteins.

Amino Acids↗
PubMed1987

Glycosaminoglycan composition of electric organ basement membranes.

The basement membranes of the innervated surface of the electric organ of Discopyge tschudii present a high concentration of mucopolysaccharides as revealed by intense ruthenium red-positive reaction. Glycosaminoglycans (GAGs) were isolated and characterized from these pure basement membranes by using a combination of agarose gel electrophoresis and enzymatic degradation with specific enzymes. The isolated basement membrane showed a high concentration of GAGs (130 mg/g of dry tissue); of this amount 49% was hyaluronic acid, 24% was chondroitin-6-sulfate, 12% was heparan sulfate, and 14% was dermatan sulfate. Controlled digestion with heparinase and heparitinases I and II was used to study the structural features of the heparan sulfate. Four unsaturated disaccharide units were found in the heparan sulfate: disulfated, N-sulfated, N-acetylated, and N-acetylated O-sulfated disaccharides. The disaccharide units of the cholinergic heparan sulfate present a high amount of disulfated disaccharides and a low amount of N-acetylated O-sulfated disaccharides. The N-sulfated disaccharides, in contrast to the N-acetylated ones, were found through all the structure of the cholinergic heparan sulfate. Finally our work shows for the first time the presence of dermatan sulfate in the basal lamina of the electric organ.

Animals↗
PubMed1976

Isolation and characterization of an epithelial basement membrane glycoprotein from murine kidney and further characterization of an epithelial basement membrane glycoprotein secreted by murine teratocarcinoma cells in vitro.

A glycoprotein component of epithelial basement membranes (EBM) has been isolated from murine kidney homogenates by extraction with 0.05 M phosphate buffer, pH 7.2, precipitation with (NH4)2SO4 and chromatography on controlled pore glass. Antiserum produced against this glycoprotein reacts specifically with the basement membranes of renal glomeruli and tublules. The EBM glycoprotein of renal origin is antigenically identical with a glycoprotein component of epithelial basement membrane secreted by a murine teratocarcinoma grown in vitro, and the amino acid composition of the two EBM glycoproteins is markedly similar. Both glycoproteins were isolated as high molecular weight aggregates. Disaggregation with sodium dodecyl sulfate and 2-mercaptoethanol resulted in release of monomers of 32 000 and 34 000 daltons for kidney EBM glycoprotein and teratocarcinoma EBM glycoprotein, respectively. The difference in molecular weight is apparently due to increased amounts of fucose, mannose, N-acetylglucosamine and sialic acid in the glycoprotein secreted by the teratocarcinoma. In addition, both EBM glycoproteins contain galactose, glucose and N-acetylgalactosamine.

Amino Acids↗
PubMed1975

Basement membranes: structural and biosynthetic considerations.

Basement membranes are extracellular matrices synthesized by a variety of cells including the basal cells of the epidermis; the respiratory, gastrointestinal, and glandular epithelium; the capillary endothelium; the epithelial cells of the glomerulus, the renal tubule, and the lens capsule; and the endothelium of Descemet's membrane. Basement membranes in the mature animal are free of lipids, DNA, and proteoglycans and are composed of dissimilar protein subunits. One of these is a procollagen-like molecule associated with a noncollagenous matrix glycoprotein. The proportion of the latter component varies among basement membranes. These various subunits are stabilized by hydrogen bonds, disulfide bonds, and aldehyde-derived cross-links which are so extensive that they render the basement membranes highly insoluble. Immunochemical studies indicate three distinct antigenic components which correspond to the collagenous moiety, its nonhelical extension, and the matrix glycoprotein. The collagen component of basement membranes, free of the nonhelical extension, is composed of three identical alpha-chains. It is highly rich in hydroxylysine, 3- and 4-hydroxyproline and contains 4 to 8 residues of half-cystine. It contains 38 residues of glucosyl-galactosyl-hydroxylysine per chain and minimal amounts of mannose, glucosamine, and fucose. Newly synthesized basement membrane collagen is secreted in the extracellular space as the precursor molecule "procollagen." This molecule does not undergo conversion to collagen but interacts with the matrix glycoprotein to give rise to the appropriate structure.

Amino Acids↗