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1.
Electron microscope observations on the carbohydrate-rich cell coat present at the surface of cells in the rat 总被引:41,自引:23,他引:18
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Periodic acid-silver methenamine, a fairly specific technique for glycoprotein detection, was used to stain a variety of rat tissues, in the hope of confirming the existence of a carbohydrate-rich "cell coat" at the surface of mammalian cells. It was found that nearly all cells are coated by a thin layer of stained material. Around fibrocytes and migrating blood cells, the layer is uniform and merges with the ground substance. In the nervous system, cells and processes are surrounded with a layer whose density increases in synaptic clefts. Around epithelial cells, the layer outlines apical microvilli, follows lateral interspaces, and extends between cells and basement membrane. The layer is continuous with the middle plate of desmosomes and can be followed within the wide portion of terminal bars. In contrast, staining usually vanishes when two adjacent plasma membranes fuse to form tight junctions. These findings indicate that the stained layer is a "cell coat" located outside the plasma membrane. Since the cell coat is also stained by colloidal thorium, a technique for detection of acidic carbohydrates, this structure presumably contains not only glycoprotein(s) but also acidic residues. The carbohydrates may play a role in holding cells together and in controlling the interactions between cells and environment. 相似文献
2.
《The Journal of cell biology》1978,79(2):314-328
Filtration studies suggest similar size pores in the glomerular filters of mammals and amphibians. However, the glomerular wall in the bullfrog exhibits several structural features not found in mammals. The subendothelial space of the basement membrane is often greatly enlarged and infiltrated by cellular elements. The lamina densa of the basement membrane shows extensive variation in thickness and packing of its filaments. On the other hand, the epithelial slits in the bullfrog are closed by a slit diaphragm which appears similar in size and structure to the slit diaphragm in mammals. Horse spleen ferritin, a protein with a hydrodynamic radius of 61 A, was used as an ultrastructural tracer to determine whether the highly variable structure of the basement membrane renders this layer more permeable than its mammalian counterpart. Within 10 min after intravenous injection, ferritin was found throughout the basement membrane and often in clusters within the subepithelial layer adjacent to the slit diaphragm. Virtually no ferritin was found within the urinary space, podocytes, or cells of the proximal tubule. Ferritin distribution was the same in both superficial glomeruli and more deeply lying glomeruli regardless of the method of fixation. These results indicate that in the bullfrog the slit diaphragm is a principal filtration barrier to ferritin and thus to smaller plasma proteins. 相似文献
3.
An electron microscope study of kidney basement membrane changes in the mouse by lipoteichoic acid from Streptococcus pyogenes 总被引:4,自引:0,他引:4
Mice injected repeatedly, intraperitoneally or intravenously, for approximately 1 month with a total of 1.04 mg lipoteichoic acid from a nephritogenic strain of Streptococcus pyogenes lost weight. Analysis by electron microscopy revealed that they also exhibited extensive kidney changes in basement membrane morphology which resembled, in part, those observed in human poststreptococcal glomerulonephritis. For example, the glomerular basement membrane became electron dense and exhibited at least a twofold increase in width sporadically within the same preparation after exposure to lipoteichoic acid. Also, whereas appreciable loss or reduction in epithelial foot processes as a result of fusion was clearly evident, epithelial slits and slit membranes or diaphragms between normal foot processes were not selectively affected. In addition, another mostly thickened, highly coiled or serpentinelike basement membrane with amorphous nodules appeared in these preparations. This type membrane was not observed surrounding the capillary lumina and was the most pronounced abnormality apparent in almost all preparations from mice exposed to lipoteichoic acid. Likewise, the proximal tubular basement membrane became variable in width and increased in electron density in mice given lipoteichoic acid as compared with controls. In addition, this membrane was often punctuated with various morphological protrusions originating from only its thickened areas and which extended away from, and not into, the capillary space. This change was only associated with the basement membrane of the proximal tubular capillaries. All membrane changes persisted but gradually subsided, with normal kidney membrane morphology reappearing on the 4th day following the last injection of lipoteichoic acid.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
4.
Hurskainen T Moilanen J Sormunen R Franzke CW Soininen R Loeffek S Huilaja L Nuutinen M Bruckner-Tuderman L Autio-Harmainen H Tasanen K 《Cell and tissue research》2012,348(3):579-588
The kidney filtration barrier consists of the capillary endothelium, the glomerular basement membrane and the slit diaphragm localized between foot processes of neighbouring podocytes. We report that collagen XVII, a transmembrane molecule known to be required for epithelial adhesion, is expressed in podocytes of normal human and mouse kidneys and in endothelial cells of the glomerular filtration barrier. Immunoelectron microscopy has revealed that collagen XVII is localized in foot processes of podocytes and in the glomerular basement membrane. Its role in kidney has been analysed in knockout mice, which survive to birth but have high neonatal mortality and skin blistering and structural abnormalities in their glomeruli. Morphometric analysis has shown increases in glomerular volume fraction and surface densities of knockout kidneys, indicating an increased glomerular amount in the cortex. Collagen XVII deficiency causes effacement of podocyte foot processes; however, major slit diaphragm disruptions have not been detected. The glomerular basement membrane is split in areas in which glomerular and endothelial basement membranes meet. Differences in the expression of collagen IV, integrins α3 or β1, laminin α5 and nephrin have not been observed in mutant mice compared with controls. We propose that collagen XVII has a function in the attachment of podocyte foot processes to the glomerular basement membrane. It probably contributes to podocyte maturation and might have a role in glomerular filtration. 相似文献
5.
“Treasure your exceptions”: recent advances in molecular genetics of glomerular disease 总被引:1,自引:0,他引:1
Ciechanowicz A Brodkiewicz A Bińczak-Kuleta A Parczewski M Czekalski S 《Journal of applied genetics》2008,49(1):93-99
The glomerular filtration barrier consists of endothelial cells, the glomerular basement membrane, and podocytes. The membrane is a highly crosslinked macromolecular meshwork composed of specific extracellular matrix proteins. The adjacent foot processes of podocytes are bridged along their basolateral surfaces by a slit diaphragm (a porous filter structure of nephrin molecules). Recent discoveries of mutations in the range of genes encoding proteins involved in the structure or function of the glomerular filtration barrier have provided new insights into mechanisms of glomerular diseases. In this review, we summarize recent progress in the elucidation of the genetic basis of some glomerulopathies in humans. 相似文献
6.
A daily injection protocol with puromycin aminonucleoside (PAN) causes loss of sialic acid from the glomerular filter. These changes have been studied previously by colloidal iron staining, but we have recently shown that phosphotungstic acid (PTA) at low pH allows the demonstration of sialic acid groups in the glomerular basement membrane in ultrathin sections of glycolmethacrylate(GMA)-embedded rat kidney. With this technique the slit diaphragm is seen as a continuation of the luminal cell coat and the method also gives an idea of the sialic acid distribution at the podocyte plasma membrane. The availability of this method made it possible to reevaluate the results obtained earlier in aminonucleoside (PAN) nephrosis indicating a decrease in the sialic acid content of the glomerulus. Although there are changes in the epithelial architecture, the ultrastructural appearances of the basement membrane are only slightly altered in PAN nephrosis. Detachment of epithelial cells was variable in different animals. Seven days after the first injection of PAN, staining with PTA revealed local defects in the lamina rara externa which later became more extensive. In PAN-treated animals the luminal cell coat showed reduced staining and large areas of the plasma membrane were completely devoid of a cell coat. These changes coincided with the onset of heavy proteinuria. The results indicate that both the basement membrane and the epithelial plasma membrane are affected in PAN nephrosis, as revealed by decreased staining for sialic acid-containing molecules in the basement membrane and by changes in the epithelial cell coat. The defects in the cell coat material point to functional alterations at the level of the slit pores and it is suggested that the decrease in sialic acid content of the lamina rara externa may be partly responsible for defects in the size-selective filtration barrier in PAN nephrosis. 相似文献
7.
Podocytes of the renal glomerulus are unique cells with a complex cellular organization consisting of a cell body, major processes and foot processes. Podocyte foot processes form a characteristic interdigitating pattern with foot processes of neighboring podocytes, leaving in between the filtration slits that are bridged by the glomerular slit diaphragm. The highly dynamic foot processes contain an actin-based contractile apparatus comparable to that of smooth muscle cells or pericytes. Mutations affecting several podocyte proteins lead to rearrangement of the actin cytoskeleton, disruption of the filtration barrier and subsequent renal disease. The fact that the dynamic regulation of the podocyte cytoskeleton is vital to kidney function has led to podocytes emerging as an excellent model system for studying actin cytoskeleton dynamics in a physiological context. 相似文献
8.
Florian Tesch Florian Siegerist Eleonora Hay Nadine Artelt Christoph Daniel Kerstin Amann Uwe Zimmermann Panagiotis Kavvadas Olaf Grisk Christos Chadjichristos Karlhans Endlich Christos Chatziantoniou Nicole Endlich 《Journal of cellular and molecular medicine》2021,25(16):7631-7641
Under healthy conditions, foot processes of neighbouring podocytes are interdigitating and connected by an electron-dense slit diaphragm. Besides slit diaphragm proteins, typical adherens junction proteins are also found to be expressed at this cell-cell junction. It is therefore considered as a highly specialized type of adherens junction. During podocyte injury, podocyte foot processes lose their characteristic 3D structure and the filtration slits typical meandering structure gets linearized. It is still under debate how this change of structure leads to the phenomenon of proteinuria. Using super-resolution 3D-structured illumination microscopy, we observed a spatially restricted up-regulation of the tight junction protein claudin-5 (CLDN5) in areas where podocyte processes of patients suffering from minimal change disease (MCD), focal and segmental glomerulosclerosis (FSGS) as well as in murine nephrotoxic serum (NTS) nephritis and uninephrectomy DOCA-salt hypertension models, were locally injured. CLDN5/nephrin ratios in human glomerulopathies and NTS-treated mice were significantly higher compared to controls. In patients, the CLDN5/nephrin ratio is significantly correlated with the filtration slit density as a foot process effacement marker, confirming a direct association of local CLDN5 up-regulation in injured foot processes. Moreover, CLDN5 up-regulation was observed in some areas of high filtration slit density, suggesting that CLND5 up-regulation preceded the changes of foot processes. Therefore, CLDN5 could serve as a biomarker predicting early foot process effacement. 相似文献
9.
A stereological study of the glomerular filter in the rat. Morphometry of the slit diaphragm and basement membrane 总被引:6,自引:0,他引:6
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Kidney from normal male albino rats, of body weight 170-200 g, was fixed by arterial perfusion with buffered tannic acid-glutaraldehyde, and postfixed with osmium tetroxide. Random and isotropic ultrathin sections from 23 different glomeruli from five rats were mounted on slot grids for staining and electron microscopy. Prints of whole glomeruli at a magnification of 3,909 were analyzed by stereological methods. The mean glomerular volume was (8.048 +/- 0.474) X 10(5) mum3 if the glomeruli are treated as spheres. The area of the basement membrane was 0.281 +/- 0.017 mm2 per glomerulus, of which 0.184 +/- 0.011 mm2 represents peripheral basement membrane. The aggregate epithelial slit length per glomerulus was 65.19 +/- 3.84 cm, of which 48.69 +/- 2.87 cm represents epithelial slits abutting on the peripheral basement membrane. Assuming that a slit diaphragm is 390 A wide, and that the pores of the slit diaphragm represent 26% of its area, the mean pore area is 3.96 cm2, of which 2.96 cm2 represents the area of peripheral pores. These findings are discussed in the context of the hydrodynamic theory of glomerular ultrafiltration. We conclude that the porous substructure of the glomerular slit diaphragm is significant in determining the hydraulic conductivity of the glomerulus and hence also solute flux during ultrafiltration. 相似文献
10.
A cell type structurally resembling the podocyte of the renal glomerulus is situated in the gill of the crustacean Panulirus argus. These cells adjoin the medial septum of the gill filament and invariably face the efferent haemolymph channel. The basal cell surface is produced into a series of regular ridges, between which are inserted elongated cell processes, together constituting a palisade that includes narrow slits (250 A or more in width) resembling the filtration pores between the foot process of the glomerular epithelium. In each instance, the slit is traversed by a diaphragm which in the crustacean 'podocyte' is ca. 30 A in width and contiguous with the outer leaflet of the unit membrane limiting the cell. Numerous coated vesicles originate from the cell surface beneath the diaphragms. The possible role of these cells in detoxification by withdrawal of materials from the circulation is discussed. 相似文献
11.
Sawanobori E Terada N Fujii Y Higashida K Nakazawa S Ohno S 《Histology and histopathology》2008,23(3):297-307
Immunoglobulin A (IgA) nephropathy shows great variability regarding the histological features of the lesions of human renal glomeruli. In the present study, the quick-freezing and deep-etching (QF-DE) method was used to analyze the glomerular ultrastructure of biopsied kidney tissues from children with IgA nephropathy. Biopsied renal tissues were routinely prepared for light microscopy, immunofluorescence microscopy, conventional electron microscopy, and replica electron microscopy. The three-dimensional ultrastructure of glomeruli of the kidney was clearly observed by using the QF-DE method. Three layers of glomerular basement membranes, i.e., middle, inner and outer layers, were clearly detected in the replica electron micrographs. The middle layer was 343.0+/-24.2 nm (n=20) in width and formed polygonal meshwork structures. We also observed slit diaphragms, electron-dense mesangial deposits, and increased amounts of mesangial matrix and foot process effacement. Many delicate filaments were found to be distributed from the apical to the bottom portions between neighboring foot processes. The ultrastructural difference between the replica electron micrographs and conventional electron micrographs was found to be especially marked in the appearance of foot processes and connecting filaments between the neighboring foot processes. The examination of extracellular matrix changes, as revealed at high resolution by the QF-DE method, gave us some morphofunctional information relevant to the mechanism of proteinuria with IgA nephropathy. 相似文献
12.
Eichi Yamada 《The Journal of cell biology》1955,1(6):551-566
13.
Characterization of a novel glycoprotein isolated from the basement membrane matrix of the Engelbreth-Holm-Swarm tumor 总被引:1,自引:0,他引:1
L K Robinson V A Murrah M P Moyer D H Rohrbach 《The Journal of biological chemistry》1989,264(9):5141-5147
A previously undescribed protein has been isolated and purified from the extracellular matrix of the Engelbreth-Holm-Swarm (EHS) tumor, a murine tumor that synthesizes an extensive matrix composed of basement membrane molecules. Molecular characterization of the molecule determined that it is a glycoprotein with internal disulfide bonds and an isoelectric point of 6.0. Electrophoretic mobility on sodium dodecyl sulfate-polyacrylamide gel electrophoresis indicated that the glycoprotein migrated as a diffuse band with a molecular weight of approximately 72,000-80,000. The amino acid composition was significantly different from known basement membrane components. Polyclonal antibodies that specifically recognize the glycoprotein localized it to the kidney glomerular basement membrane. These antibodies did not cross-react with either known basement membrane components (laminin, type IV collagen, and heparan sulfate proteoglycan), with 70K "culture shock" protein or with components of normal mouse serum (including mouse transferrin, albumin, or alpha-fetoprotein), when analyzed by "Western" immunoblots. Our data indicate that the glycoprotein is synthesized by the EHS tumor cells and is present at relatively high levels in the EHS tumor matrix. 相似文献
14.
Hindered transport of macromolecules in isolated glomeruli. I. Diffusion across intact and cell-free capillaries. 总被引:1,自引:0,他引:1
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The filtrate formed by renal glomerular capillaries must pass through a layer of endothelial cells, the glomerular basement membrane (GBM), and a layer of epithelial cells, arranged in series. To elucidate the relative resistances of the GBM and cell layers to movement of uncharged macromolecules, we measured the diffusional permeabilities of intact and cell-free capillaries to narrow fractions of Ficoll with Stokes-Einstein radii ranging from 3.0 to 6.2 nm. Glomeruli were isolated from rat kidneys, and diffusion of fluorescein-labeled Ficoll across the walls of single capillary loops was monitored with a confocal microscopy technique. In half of the experiments the glomeruli were treated first to remove the cells, leaving skeletons that retained the general shape of the glomerulus and consisted almost entirely of GBM. The diffusional permeability of cell-free capillaries to Ficoll was approximately 10 to 20 times that of intact capillaries, depending on molecular size. Taking into account the blockage of much of the GBM surface by cells, the contribution of the GBM to the diffusional resistance of the intact barrier was calculated to be 13% to 26% of the total, increasing with molecular size. Thus, the GBM contribution, although smaller than that of the cells, was not negligible. The structure that is most likely to be responsible for the cellular part of the diffusional resistance is the slit diaphragm, which spans the filtration slit between epithelial foot processes. A novel hydrodynamic model was developed to relate the diffusional resistance of the slit diaphragm to its structure, which was idealized as a single layer of cylindrical fibers in a ladder-like arrangement. 相似文献
15.
Alterations in lung basement membrane during fetal growth and type 2 cell development 总被引:3,自引:0,他引:3
We studied basement membrane development in the late fetal and in the neonatal rat lung, from the 18th day of gestation (term = 22 days) through the 8th postnatal day, with particular emphasis on the gas-exchange region of the lung. In the periphery of the lung, as type 2 cells differentiate, the continuous basement membrane develops openings beneath these cells. Basal cytoplasmic foot processes extend through these discontinuities into the underlying interstitium, often approaching interstitial cells closely. These discontinuities and extensive foot processes are associated only with type 2 epithelial cells and not with either differentiated airway cells or with the type 1 alveolar lining cells derived from type 2 cells. The type 2 cell basement membrane discontinuities and penetrating foot processes are maximal in the perinatal period and decrease in the week after birth. The appearance of openings in type 2 cell basement membrane and changes in distribution, linear density, and ruthenium red staining of anionic sites suggest that the epithelial basement membrane undergoes continuous remodeling throughout development, particularly in association with type 2 cell differentiation and growth of lung surface area. Epithelial cell foot processes may interact with underlying interstitial cells and affect the coordination of lung surface growth with the development of its connective tissue framework. 相似文献
16.
Glomerular lysozyme binding in protein-overload proteinuria 总被引:1,自引:0,他引:1
D J Bliss D B Brewer 《Virchows Archiv. B, Cell pathology including molecular pathology》1985,48(4):351-359
Binding of the cationic molecule lysozyme to the glomerular basement membrane and to the glomerular epithelial cell coat was investigated in the glomerulus of normal female Wistar rats and in rats in which heavy proteinuria was induced by the daily administration of 1 g of bovine serum albumin. In normal rats the binding of lysozyme to the anionic groups in the glomerular basement membrane and the cell coat had no effect on the ultrastructure of the glomerular epithelial cell, in particular the foot processes were unchanged. In the proteinuric rats the lysozyme-binding to the glomerular basement membrane and the epithelial cell coat was completely lost in the damaged glomeruli. In the apparently normal glomeruli present in these proteinuric animals binding was similar to that seen in normal rats. These results suggest that in protein-overload proteinuria there is a loss of glomerular anion and hence a reduction in the glomerular charge barrier. This may account, at least in part, for the increased glomerular leak of negatively charged serum albumin in this experimental model of proteinuria. 相似文献
17.
Aunapuu M Roosaar P Järveots T Kurrikoff K Kõks S Vasar E Arend A 《Transgenic research》2008,17(6):1079-1089
Although cholecystokinin is a regulatory peptide with a predominant role in the brain and the gastrointestinal tract, there
is an increasing evidence for its role in the kidney. The aim of this study was to reveal morphological changes in the structure
of kidney of mice with cholecystokinin overexpression by means of light, transmission and scanning electron microscope, and
atomic force microscopy. Using immunohistochemistry the expression of important basement membrane proteins collagen IV, laminin
and fibronectin, as well the distribution of cholecystokinin-8 in the renal structures was evaluated. The altered morphology
of kidneys of mice with cholecystokinin overexpression was seen by all microscopic techniques used. The renal corpuscles were
relatively small with narrow capsular lumen. The basement membranes of renal tubules were thickened and the epithelial cells
were damaged, which was more pronounced for distal tubules. Characteristic feature was the increased number of vesicles seen
throughout the epithelial cells of proximal and especially in distal tubules reflecting to the enhanced cellular degeneration.
The relative expression of laminin but not collagen IV in the glomerular basement membrane was higher than in the tubular
basement membranes. The content of fibronectin, in opposite, was higher in tubular membranes. Cholecystokinin-8 was clearly
expressed in the glomeruli, in Bowman’s capsule, in proximal and distal tubules, and in collecting ducts. Ultrastructural
studies showed irregularly thickened glomerular basement membranes to which elongated cytopodia of differently shaped podocytes
were attached. As foot processes were often fused the number of filtration pores was decreased. In conclusion, cholecystokinin
plays important role in renal structural formation and in functioning as different aspects of urine production in mice with
cholecystokinin overexpression are affected-the uneven glomerular basement membrane thickening, structural changes in podocytes
and in filtration slits affect glomerular filtration, while damaged tubular epithelial cells and changed composition of thickened
tubular basement membranes affect reabsorption. 相似文献
18.
Ultrastructure of the kidney of a South American caecilian,Typhlonectes compressicaudus (Amphibia,Gymnophiona) 总被引:1,自引:0,他引:1
Prof. Dr. Tatsuo Sakai Ralph Billo Rainer Nobiling Karin Gorgas Wilhelm Kriz 《Cell and tissue research》1988,252(3):589-600
The ultrastructure of the renal corpuscle, the neck segment, the proximal tubule and the intermediate segment of the kidney of a South American caecilian, Typhlonectes compressicaudus (Amphibia, Gymnophiona) was examined by means of transmission electron microscopy (TEM), scanning electron microscopy (SEM) and freeze-fracture technique. The glomerular filter apparatus consists of the podocyte epithelium, a distinct basement membrane, a subendothelial space and the capillary endothelium. Emanating from the podocyte cell body, several long primary processes encircle neighboring capillaries. The short slender foot processes originating from the primary processes interdigitate with those from other primary processes, thereby forming the meandering filtration slit. Thick bundles of microfilaments are found in the primary processes, but absent in the foot processes. The basement membrane consists of a lamina rara externa and a rather thin lamina densa (50 nm thickness). The wide subendothelial space contains abundant microfibrils, a few collagen fibrils and many thin processes of mesangial cells. The endothelium is flat and fenestrated (compared to mammals displaying relatively few fenestrations); some of the fenestrations are bridged by a diaphragm. The glomerular mesangium is made up of the mesangial cells and a prominent mesangial matrix containing microfibrils and collagen fibrils. The cells of the neck and intermediate segments display numerous cilia with their microtubules arranged in the typical 9 + 2 pattern. The basal bodies of the cilia are attached to thick filaments with a clear crossbanding pattern of 65 nm periodicity. The proximal tubule is composed of cells typical for this segment (PT cells) and light cells lacking a brush border (bald-headed cells). The PT cells measure 10-25 micron in height and 15-30 micron in width and do not interdigitate at their lateral borders with each other. Their basolateral cell membrane is amplified by many folds projecting into lateral intercellular spaces and into basal recesses. The brush border is scarce and composed of loosely arranged short microvilli. 相似文献
19.
M. Vacatello 《Molecular simulation》2013,39(4-5):245-255
Abstract The molecular arrangements of liquid tridecane near solid surfaces and in narrow slits have been studied by atomistic Monte Carlo computer simulations. A single surface perturbs the liquid over a distance of 1.5 nm, inducing the formation of progressively less dense and ordered layers of thickness 0.4 nm. Chains with atoms in the first layer tend to run parallel to the surface. The tendency to form layer structures is maintained or destroyed in narrow slits, depending on the slit thickness. For instance, it is slighly increased in slits of thickness 1.2 nm, while it is practically destroyed when the slit thickness is reduced to 1.0 nm. When added in small amounts, shorter-chain components are preferentially adsorbed at the solid surface, making the first layer of liquid in contact with these surfaces much less ordered. 相似文献
20.
POROUS SUBSTRUCTURE OF THE GLOMERULAR SLIT DIAPHRAGM IN THE RAT AND MOUSE 总被引:47,自引:12,他引:35
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The highly ordered, isoporous substructure of the glomerular slit diaphragm was revealed in rat and mouse kidneys fixed by perfusion with tannic acid and glutaraldehyde. The slit diaphragm was similar in both animal species and appeared as a continuous junctional band, 300–450 Å wide, consistently present within all slits formed by the epithelial foot processes. The diaphragm exhibited a zipper-like substructure with alternating, periodic cross bridges extending from the podocyte plasma membranes to a central filament which ran parallel to and equidistant from the cell membranes. The dimensions and spacing of the cross bridges defined a uniform population of rectangular pores approximately 40 by 140 Å in cross section and 70 Å in length. The total area of the pores was calculated to be about 2–3% of the total surface area of the glomerular capillaries. Physiological data indicate that the glomerular filter functions as if it were an isoporous membrane which excludes proteins larger than serum albumin. The similarity between the dimensions of the pores in the slit diaphragm and estimates for the size and shape of serum albumin supports the conclusion from tracer experiments that the slit diaphragm may serve as the principal filtration barrier to plasma proteins in the kidney. 相似文献