摘要:

Basement membranes perform several functions including filtration and elastic support. In the glomerular capillary two regions of extracellular matrix are recognized: the laminae rarae and the lamina densa. Procollagen and noncollagen glycoproteins occupy the laminae rarae and lamina densa. Proteoglycans are present in the laminae rarae. The nature and spatial organization of the macromolecules within the basement membrane determine their filtration and elastic properties. The persistence of the procollagen molecules assures the low order of fibril organization and permits selective filtration, whereas the persistence of the noncollagen extension peptides in the procollagen and the presence of the glycoproteins confers elasticity. The anionic nature of basement membranes is determined primarily by the acidic amino acid content and to much lesser extent by sialic acid and proteoglycans.

ISSN:1420-4096    

DOI:10.1159/000172806

出版商:S. Karger AG    

年代:1981

数据来源: Karger

摘要:

Sub fractions of human glomerular basement membrane isolated by enzymatic procedures were analyzed for their chemical structure and biological activity. Pepsin or collagenase digestion of purified basement membranes released three groups of components: collagenous and noncollagenous fractions and also a mixed material consisting of a proteolysis-resistant association between collagen sequences and heteropolysaccharidic glycopeptides. These different fractions were explored in vitro for their ability to interact with cell membranes. In fact, only fractions containing the heterogenous material agglutinated human transformed or embryonic cells within 2 h. The cell agglutination was specifically inhibited by N-acetylosamines and N-acetylneuraminic acid. An additional incubation of 20 h at 3 7 °C of the agglutinated cells, maintained in a minimal medium devoid of serum, led to a morphological change of the transformed cells due to an increased cell adhesion and cell spreading. These experimental data suggest that the basement membrane possesses active sites -consisting of an association between collagen and structural glycoproteins – which could play a primordial role in cell matrix interactio

ISSN:1420-4096    

DOI:10.1159/000172807

出版商:S. Karger AG    

年代:1981

数据来源: Karger

摘要:

Using the adenylate cyclase assay after Ross we examined hormone sensitivity of isolated glomerular cells. cAMP production was increased 1.3–1.6-fold by stimulation with isoproterenol, 1.5–1.8 times by prostaglandin E1 and 1.4–1.5 times by histamine. The isoproterenol reaction could be completely inhibited by propranolol, the histamine effect was abolished by the H2-blocking agent cimetidine. As control we applied sodium fluoride, which directly activates the catalytic adenylate cyclase unit, increasing the activity 1.8–2.7 times (depending on the method of homogenization). These findings could reflect some physiological or pathophysiological implications, which are discussed in the present

ISSN:1420-4096    

DOI:10.1159/000172808

出版商:S. Karger AG    

年代:1981

数据来源: Karger

摘要:

Immune complex deposition along the glomerular basement membrane (GBM) and in the mesangium in C57BL/6 mice bearing a transplantable syngeneic B16 melanoma is described. By immunofluorescence studies, IgG, IgM and C3 were found deposited along the GBM and the mesangium. Electron microscopy showed electron-dense deposits localized in GBM and mesangial matrix. The intensity of the immune complexes deposited in the glomeruli was correlated with progression of tumor size. In order to study the evolution of deposits, a monitoring protocol was designed. One group consisted of mice bearing B16 melanoma. They showed decreased immune complex deposition after tumor removal. Control mice inoculated with saline did not present immune complex deposition. Sham-operated mice bearing B16 melanoma showed progressive renal deposition of immune complexes. Immune complexes were made up of tumor antigen and antimelanoma antibodies and were partially characterized by elution, immunofluorescence and immuno-diffusion procedures. Antimelanoma antibodies eluted from kidneys of tumor-bearing mice were of IgG class and reacted with a soluble product extracted from B16 melanoma cells.

ISSN:1420-4096    

DOI:10.1159/000172809

出版商:S. Karger AG    

年代:1981

数据来源: Karger

摘要:

Perfusion fixation of the rat kidneys with aldehydes and alcian blue demonstrates within the glomerular mesangium various components displaying anionic binding sites. These are the surface coat of the mesangial cells, numerous mesangial microfibrils (probably glycoproteins), and polygonal particles (presumably proteoglycans). These particles lie close to the mesangial cells and form assemblies of various extension within the mesangial matrix as well. In addition, a discontinuous basement membrane can be recognized which surrounds the mesangial cells. In the hagfish glomeruli (fixed without cationic dye), a prominent layer of microfibrils is interposed between mesangial and endothelial cells. Both these cells show incomplete basement membranes.

ISSN:1420-4096    

DOI:10.1159/000172810

出版商:S. Karger AG    

年代:1981

数据来源: Karger

摘要:

To test the hypothesis that increased nonenzymatic glycosylation contributes to the microangiopathic sequelae of diabetes, we examined the interaction of glucose with basement membranes in vivo and in vitro. The level of nonenzymatic glycosylation, determined by hydroxymethylfurfuraldehyde (HMF) generation, in glomerular basement membrane (GMB) collagen purified from rats with streptozotocin diabetes was significantly greater than that of nondiabetic GMB. Incubation of purified rat GBM and lens capsule basement membrane with [14C]-glucose in vitro resulted in the incorporation of [14C] into acid precipitable radioactivity in a reaction that was dependent on time, temperature, and glucose concentration. Glucose-dependent nonenzymatic glycosylation of GBM in vitro was documented by measurement of HMF generation after incubation with unlabeled glucose. These results provide direct experimental evidence that hyperglycemia, via nonenzymatic glycosylation, modifies the chemistry of proteins specifically involved in diabetic glomerulosclerosis.

ISSN:1420-4096    

DOI:10.1159/000172811

出版商:S. Karger AG    

年代:1981

数据来源: Karger

摘要:

The collagen glucosyltransferase of renal cortex is increased in experimental diabetes and this increase may be partially reversed or prevented by insulin treatment. The absence of any consistent increase in the plasma collagen glucosyltransferase level in diabetes argues against the enzyme’s having a significant role in the pathological thickening of capillary basement membranes. The biological significance of the increased renal glucosyltransferase activity in chemically-induced diabetes must therefore remain in doubt but it is possible that the high glucose concentration in the blood simply stimulates the synthesis of new enzyme protein in the kidne

ISSN:1420-4096    

DOI:10.1159/000172812

出版商:S. Karger AG    

年代:1981

数据来源: Karger

摘要:

Glomerular basement membrane (GBM) were isolated from the kidneys of rats suffering from daunomycin nephrosis or nephrotoxic serum nephritis. The GBM from daunomycin nephrotic rats contained significantly less hydroxyproline, hydroxylysme and glycine than that of control rats. There was an increase in glucosamine content in the membrane. No significant change was found in the neutral sugar content. In nephrotoxic serum nephritis, the relative amounts of hydroxyproline, glycine and half-cystine were decreased, whereas the relative amounts of aspartic acid, alanine, lysine and hydroxylysine were increased. The ratio of hydroxyproline to proline and the ratio of hydroxylysine to lysine were decreased. An increase in sialic acid content and a decrease in fucose and hexosamine content and glucosyl-galactosyl-hydroxylysine content were noted in nephrotoxic nephritic GBM. These chemical structural alterations could account for the functional disorders of diseased GBM.

ISSN:1420-4096    

DOI:10.1159/000172813

出版商:S. Karger AG    

年代:1981

数据来源: Karger

摘要:

Diabetic rats were treated intraperitoneally for 2 weeks with (+)-catechιn in two different dosages or calcium dobesilate and the influence of these substances on protein and basement membrane collagen synthesis was investigated. Both drugs did not alter the diabetic metabolic situation. At the lower dose, (+)-catechin led to a slight decrease and at the higher dose to a small increase of basement membrane collagen synthesis. But compared to untreated controls these differences were statistically not significant. Calcium dobesilate inhibited markedly the raised basement membrane collagen synthesis. However, this effect does not appear to be specific, since the raised general protein synthesis was also reduced. These findings show that the disturbed basement membrane metabolism in diabetes can be influenced without altering the metabolic situation

ISSN:1420-4096    

DOI:10.1159/000172814

出版商:S. Karger AG    

年代:1981

数据来源: Karger

摘要:

In contrast to the fragmentation and loss of spatial arrangement seen in preparations of basement membrane isolated after sonic disruption, the architectural integrity of glomerular basement membrane is preserved with the described technique of osmotic lysis and sequential detergent treatment. The biochemistry of components solubilized without pepsin digestion from GBM prepared with this technique is described.

ISSN:1420-4096    

DOI:10.1159/000172815

出版商:S. Karger AG    

年代:1981

数据来源: Karger