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PubMed1983

Ultrastructure of Reichert's membrane, a multilayered basement membrane in the parietal wall of the rat yolk sac.

The ultrastructure of Reichert's membrane, a thick basement membrane in the parietal wall of the yolk sac, has been examined in 13-14-d pregnant rats. This membrane is composed of more or less distinct parallel layers, each one of which resembles a common basement membrane. After routine fixation in glutaraldehyde followed by osmium tetroxide, the layers appear to be mainly composed of 3-8-nm thick cords arranged in a three-dimensional network. Loosely scattered among the cords are unbranched, straight tubular structures with a diameter of 7-10 nm, which mainly run parallel to the surface and to one another; they are referred to as basotubules. Permanganate fixation emphasizes the presence of a thick feltwork of irregular material around basotubules. Finally, minute dot-like structures measuring 3.5 nm and referred to as double pegs are present within the meshes of the cord network. Reichert's membranes have been treated for 2-48 h at 25 degrees C with plasmin, a proteolytic enzyme known to rapidly digest laminin and fibronectin. After a 2-h treatment, most of the substance of the cords is digested away leaving a three-dimensional network of 1.5-2.0-nm thick filaments. The interpretation is that the cords are formed of a plasmin-resistant core filament and a plasmin-extractable sheath. When plasmin treatment is prolonged for 15 h or longer, the filaments are dissociated and disappear, while basotubules are maintained. Plasmin digestion also reveals that basotubules are composed of two parts: a ribbon-like helical wrapping and tubule proper. Further changes in the tubule under plasmin influence are interpreted as a dissociation into pentagonal units suggestive of the presence of the amyloid P component. After 48 h of plasmin treatment, basotubules are further disaggregated and dispersed, leaving only linearly arranged double pegs. Reichert's membranes with or without a 2-hr plasmin treatment have been immunostained by exposure to antibodies against either laminin or type IV collagen with the help of peroxidase markers. The results indicate that the sheath of the cords contains laminin antigenicity, while the core filament contains type IV collagen antigenicity. It is proposed that Reichert's membrane consists mainly of a three-dimensional network of cords composed of a type IV collagen filament enclosed within a laminin-containing sheath. Also present are basotubules--which may contain the amyloid P component--and double pegs whose nature is unknown.

Animals↗
PubMedDate not supplied

The macula densa tubular basement membrane: a unique plaque of basement membrane specialization.

The inner (luminal) surface of the macula densa (MD) basement membrane (BM) was exposed by solubilization of the overlying epithelium permitting examination of its structural features by scanning electron microscopy (SEM). Nineteen macula densa BM were identified in five autopsy kidneys and seven renal biopsies by this SEM technique. The MD BM consists of an oval plaque of specialized BM, restricted to the glomerular hilum and arteriolar aspect of the thick ascending limb of Henle. It contains haphazardly oriented shallow tunnels, slender pleats, and bridges of BM which do not resemble any other nephron BM examined by this technique. The MD BM, critically located between MD and lacis cells appears to firmly anchor the MD to the juxtaglomerular apparatus and may amplify the extent of interaction between lacis cell processes or lacis cell interstitial space and MD cell processes.

Basement Membrane↗
PubMed1986

Macromolecular organization of basement membranes. Characterization and comparison of glomerular basement membrane and lens capsule components by immunochemical and lectin affinity procedures.

The macromolecular components of bovine glomerular basement membrane (GBM) and lens capsules (anterior and posterior) solubilized by sequential extractions with denaturing agents were quantitated and characterized by polyacrylamide gel electrophoresis, CL-6B filtration, and DEAE-cellulose chromatography with the help of immunochemical techniques. Laminin, entactin, fibronectin, and heparan sulfate proteoglycan were primarily recovered (over 80%) from both basement membranes in a guanidine HCl extract which contained only a limited amount of the total protein (10-14%); most of the remainder of these noncollagenous components could be solubilized by the guanidine in the presence of reducing agent. Although a portion of the Type IV collagen could be obtained by these treatments, effective extraction of this protein depended on exposure to sodium dodecyl sulfate under reducing conditions. Immunoblot analysis revealed a remarkably similar pattern for GBM and lens capsule Type IV collagens with prominent bands of Mr = 390,000, 210,000, and 190,000 being evident. Fibronectin was present in much greater amounts in GBM than lens capsule while the reverse was true for entactin. In both GBM and lens capsules, the entactin (Mr = 150,000) exceeded laminin; the latter protein on immunoblotting was found to contain primarily the alpha-subunit (Mr = 200,000). The size of the heparan sulfate proteoglycan from anterior (Mr = 400,000) and posterior lens capsule (Mr greater than 500,000) was substantially larger than that from GBM (Mr = 200,000). During DEAE-cellulose chromatography under nonreducing conditions in a denaturing solvent, a portion of the Type IV collagen coeluted with the proteoglycan from these membranes. Considerable Bandeiraea simplicifolia I binding activity (alpha-D-galactose specific) was observed in GBM and lens capsule extracts and column fractions which could not be accounted for by laminin alone. Several components which reacted with this lectin were seen on transblots and among these Type IV collagen was identified. In contrast to the basement membranes from bovine tissues, the constituents from human GBM did not react with the B. simplicifolia I lectin.

Animals↗
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↗
PubMed1986

Age-related thickening of retinal capillary basement membranes.

Capillary basement membrane thickness is known to increase in a variety of tissues during aging and as a consequence of certain systemic disease states. In order to determine whether capillary basement membrane thickness increases during senescence in the outer plexiform (OPL) and ganglion cell (GCL) layers of the retina, eyes of pigmented ACI rats aged 4, 11, 17, and 32 mo were examined. Basement membrane thickness in the OPL and GCL were determined at each of these ages using computer-assisted ultrastructural morphometry. Capillary basement membranes in both the OPL and GCL showed a linear increase in thickness over the 4 to 32 mo age span. The increase in thickness averaged 54% for the OPL and 65% for the GCL over this age range. At all ages examined, the GCL basement membranes were 80 to 90% thicker than those in the OPL. Age-related changes in the substructure of the capillary basement membranes differed between the OPL and GCL. It is possible that the observed age-related changes in retinal capillary basement membranes may play a role in the development of senile retinopathies.

Aging↗
PubMed1998

A role for dystroglycan in basement membrane assembly.

Basement membranes are composed of ordered arrays of characteristic extracellular matrix proteins, but little is known about the assembly of these structures in vivo. We have investigated the function of dystroglycan, a cell-surface laminin receptor expressed by cells contacting basement membranes in developing and adult tissues. We find that dystroglycan is required for the formation of a basement membrane in embryoid bodies. Our results further indicate that dystroglycanlaminin interactions are prerequisite for the deposition of other basement membrane proteins. Dystroglycan may exert its influence on basement membrane assembly by binding soluble laminin and organizing it on the cell surface. These data establish a role for dystroglycan in the assembly of basement membranes and suggest fundamental mechanisms underlying this process.

Animals↗
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↗
PubMed1986

Macrophages express a plasma membrane receptor for basement membrane laminin.

Laminin, a noncollagenous extracellular matrix glycoprotein, can serve as an attachment factor for epithelial and endothelial cells to basement membrane collagen. The authors have observed that inflammatory macrophages have the capacity to bind exogenous laminin in a time-, temperature- and dose-dependent manner. The laminin binds to these cells via a specific plasma membrane receptor which is detectable on several macrophage subpopulations as well as isolated macrophage membranes. The isolated receptor is a trypsin-sensitive protein with an apparent molecular weight of 70,000 which binds laminin with relatively high affinity, Kd approximately equal to 4 X 10(-9) M. The inflammatory macrophages attach preferentially to a substrate of laminin compared to Type I or Type IV collagen. Thus, the authors postulate that during tissue inflammation macrophages utilize the laminin receptor to bind to vascular basement membranes.

Animals↗
PubMed1987

Degradation of glomerular basement membrane in diabetes. I. Susceptibility of diabetic and nondiabetic basement membrane to proteolytic degradation of isolated glomeruli.

Degradation of glomerular basement membrane in diabetic and nondiabetic rats was measured by incubating isolated basement membrane with a homogenate of glomeruli obtained from metabolically healthy rats. When diabetic basement membrane was used, there was a marked decrease in the amount of collagen-typical (hydroxyproline, hydroxylysine, glycine) and noncollagen-typical amino acids (proline, lysine, leucine) released in the supernatant of the incubation assay. A negative correlation was found between the amount of collagen-typical amino acids released by diabetic basement membrane and the duration of diabetes. The results indicate that the collagenous and noncollagenous peptides of diabetic basement membrane are less susceptible to proteolytic degradation than those of nondiabetic controls. This may be due to increased nonenzymatic glycosylation of diabetic basement membrane.

Amino Acids↗
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↗
PubMed1980

Reduced susceptibility of nonenzymatically glucosylated glomerular basement membrane to proteases: is thickening of diabetic glomerular basement membranes due to reduced proteolytic degradation?

Glomerular basement membrane (GBM) preparations were enzymatically glucosylated and applied to proteolytic degradation by several enzymes. The split products were then characterized and quantitatively estimated by high pressure liquid chromatography. For this purpose, GBMs were isolated by a sieving and sonication method, incubated with glucose and digested with the proteases trypsin, chymotrypsin, papain, pepsin and a lysosomal preparation. Comparison of the concentrations of split products obtained by proteolytic degradation of normal and nonenzymatically glucosylated membranes showed a remarkable reduced susceptibility of the nonenzymatically glucosylated membranes, possibly due to steric hindrance or altered electrical charge of the glucosylated membrane proteins. This could be interpreted as an additional factor for accumulation of basement membrane material in the diabetic state, that not only increased basement membrane synthesis may occur but also reduced catabolism could possibly contribute to the diabetic changes.

Animals↗
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↗
PubMed1988

A heparin-binding angiogenic protein--basic fibroblast growth factor--is stored within basement membrane.

The basement membranes of bovine cornea are found to contain an angiogenic endothelial cell mitogen, basic fibroblast growth factor (FGF), as determined by heparin-affinity chromatography, immunoblotting, immunofluorescence, and stimulation of capillary endothelial cell proliferation. The growth factor appears to be bound to heparan sulfate and is released from the cornea by treatment with heparin, a hexasaccharide heparin fragment, heparan sulfate, or heparanase, but not by chondroitin sulfate or chondroitinase. These findings indicate that basement membranes of the cornea may serve as physiologic storage depots for an angiogenic molecule. Abnormal release of this growth factor could be responsible for corneal neovascularization in a variety of ocular diseases. Physiologic and pathologic neovascularization in other tissues may also be initiated by release of stored angiogenic factors from the basement membrane. The sequestration of angiogenic endothelial mitogens in the basement membrane may be a general mechanism for regulating their accessibility to vascular endothelium.

Angiogenesis Inducing Agents↗
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↗
PubMed1980

Biological thixotropy of glomerular basement membrane and the implications of thixotropic in explaining basement membrane permeability.

Glomerular basement membranes (GBMs) are considered to exhibit the characteristics of biological thixotropic systems, and because of this GBM permeability is determined by intravascular pressure. The significance of pressure as the major determinant of GBM permeability is discussed. Factors leading to GBM permeability to albumin following interruption of renal blood flow are examined, and a possible explanation for the phenomenon is proposed.

Animals↗
PubMed1999

Renal basement membrane components.

Renal basement membrane components. Basement membranes are specialized extracellular matrices found throughout the body. They surround all epithelia, endothelia, peripheral nerves, muscle cells, and fat cells. They play particularly important roles in the kidney, as demonstrated by the fact that defects in renal basement membranes are associated with kidney malfunction. The major components of all basement membranes are laminin, collagen IV, entactin/nidogen, and sulfated proteoglycans. Each of these describes a family of related proteins that assemble with each other in the extracellular space to form the basement membrane. Over the last few years, new basement membrane components that are expressed in the kidney have been discovered. Here, the major components and their localization in mature and developing renal basement membranes are described. In addition, the phenotypes of basement membrane component gene mutations, both naturally occurring and experimental, are discussed, as is the aberrant deposition of basement membrane proteins in the extracellular matrix in several renal diseases.

Animals↗
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↗