scholarly journals Segregation of Ferritin in Glomerular Protein Absorption Droplets

1960 ◽  
Vol 7 (2) ◽  
pp. 297-304 ◽  
Author(s):  
Marilyn G. Farquhar ◽  
George E. Palade
Keyword(s):  
Basement Membrane ◽  
General Circulation ◽  
Time Points ◽  
Dense Bodies ◽  
Partial Digestion ◽  
Cytoplasmic Vesicles ◽  
Pinocytotic Vesicles ◽  
Epithelial Cell Surface ◽  
Visceral Epithelium ◽  
Glomerular Capillaries

Ferritin was used as a tracer to study the mechanism by which proteins are segregated into droplets by the visceral epithelium of glomerular capillaries. In glomeruli from both normal and aminonucleoside-nephrotic rats ferritin molecules introduced into the general circulation penetrated the endothelial openings and were seen at various levels in the basement membrane. Striking differences between nephrotic and controls were seen only in the amount of ferritin incorporated into the epithelium. In normal animals, a few ferritin molecules were seen in small invaginations of the cell membrane limiting the foot processes, within minute vesicles in the epithelium, or within occasional large vacuoles and dense bodies. In nephrotics, epithelial pinocytosis was marked, and numerous ferritin molecules were seen within membrane invaginations and in small cytoplasmic vesicles at all time points. After longer intervals, the concentration of ferritin increased in vacuoles and particularly within the dense bodies or within structures with a morphology intermediate between that of vacuoles and dense bodies. In nephrotic animals cleft-like cavities or sinuses were frequently encountered along the epithelial cell surface facing the urinary spaces. Some of these sinuses contained material resembling that filling the dense bodies except that it appeared less compact. The findings suggest that ferritin molecules—and presumably other proteins which penetrate the basement membrane—are picked up by the epithelium in pinocytotic vesicles and transported via the small vesicles to larger vacuoles which are subsequently transformed into dense bodies by progressive condensation. The content of the dense bodies may then undergo partial digestion and be extruded into the urinary spaces where it disperses. The activity of the glomerular epithelium in the incorporation and segregation of protein is similar in normal and nephrotic animals, except that the rate is considerably higher in nephrosis where the permeability of the glomerular basement membrane is greatly increased.

scholarly journals GLOMERULAR PERMEABILITY

1961 ◽  
Vol 114 (5) ◽  
pp. 699-716 ◽  
Author(s):  
Marilyn G. Farquhar ◽  
George E. Palade
Keyword(s):  
Nephrotic Syndrome ◽  
Basement Membrane ◽  
Kidney Tissue ◽  
Normal Animal ◽  
High Concentration ◽  
Glomerular Permeability ◽  
Cytoplasmic Matrix ◽  
Filtration Barrier ◽  
Dense Bodies ◽  
Cytoplasmic Vesicles

Ferritin was used as a tracer to investigate glomerular permeability in the nephrotic rat. The results were compared with those previously obtained in normal animals. A nephrotic syndrome was induced by 9 daily injections of the aminonucleoside of puromycin. Ferritin was administered intravenously on the 10th day, and kidney tissue was fixed at intervals of 5 minutes to 44 hours after injection of the tracer and examined by electron microscopy. The observations confirmed that at this stage of the experimental nephrotic syndrome the changes affect predominantly the visceral epithelium (loss of foot processes, reduction and modification of urinary slits, and intracellular accumulation of vacuoles and protein absorption droplets). Less extensive changes were found in other layers (reduction of endothelial fenestrae, an increase in the population of "deep" cells, and a thinning and "loosening" of the basement membrane.) At short intervals (5 to 15 minutes) after ferritin administration, the tracer was found at high concentration in the lumen and endothelial fenestrae, and at decreasing concentrations embedded throughout the basement membrane and incorporated into the epithelium (within cytoplasmic vesicles and within invaginations of the plasmalemma facing the basement membrane). After longer intervals (1 to 3 hours) the distribution of the tracer within the capillary wall was similar except that its concentration in the epithelium was higher, and, in addition to plasma membrane invaginations and small vesicles, ferritin also marked larger vacuoles, dense bodies, and intermediate forms. Large accumulations of tracer typically occurred in the spongy areas of the basement membrane, especially in the axial regions. Ferritin also appeared in the endothelium within membrane-limited vacuoles and dense bodies, particularly in the deep cells. After 6 to 44 hours the tracer still occurred in the lumen and throughout the basement membrane. The ferritin deposits in the spongy areas as well as the ferritin-containing vacuoles of the deep endothelium were larger and more numerous. In the epithelium ferritin was found not only within various membrane-limited bodies, but also "free" within the cytoplasmic matrix. These observations indicate that in the nephrotic glomerulus, as in the normal, the basement membrane functions as the main filtration barrier; however, in nephrosis, the basement membrane is defective and allows leakage of increased quantitites of ferritin and presumably plasma proteins. The basement membrane defect appears to be fine and widespread, occurring at or near the molecular level of organization of the filter. The accumulation of unfiltered ferritin in axial regions together with the demonstration of its subsequent phagocytosis by the "deep" endothelial cells suggest that the latter may function in the removal of filtration residues. Finally, the findings indicate that in the nephrotic, as in the normal animal, the epithelium acts as a monitor that recovers, at least in part, the protein which leaks through the filter, and that in nephrosis, the recovering activities of the epithelium are greatly enhanced because of the increased permeability of the basement membrane.

scholarly journals A Simple Method of Staining the Basement Membrane of Glomerular Capillaries

1949 ◽  
Vol s3-90 (12) ◽  
pp. 427-429
Author(s):  
J. E. LINDER
Keyword(s):  
Basement Membrane ◽  
Mercuric Chloride ◽  
Simple Method ◽  
Glomerular Capillaries

A method of staining the basement membrane of glomerular capillaries is described for tissue fixed in formol mercuric chloride. Ten per cent. formol saline proved to be an unsatisfactory fixative.

Temporary effects of circulating Amadori products on glomerular filtration properties in the normal mouse

2001 ◽  
Vol 280 (1) ◽  
pp. F103-F111 ◽  
Author(s):  
I. Londoño ◽  
M. Bendayan
Keyword(s):  
Diabetic Nephropathy ◽  
Basement Membrane ◽  
Glomerular Filtration ◽  
Glomerular Basement Membrane ◽  
Normal Mouse ◽  
Early Diabetes ◽  
Amadori Products ◽  
Time Points ◽  
Glycated Proteins ◽  
Filtration Properties

Previous studies have established a preferential glomerular filtration of glycated BSA (gBSA), as well as a facilitated filtration of BSA in the presence of gBSA. We intend to determine whether these modifications are permanent or transitory. gBSA was intravenously injected into anesthetized normal mice and maintained in circulation for 30 min, 1, 2, 24, and 48 h. Five minutes before death, FITC-BSA was injected. On immunocytochemical evaluations, increased glomerular filtration of FITC-BSA was found at all circulating time points. Changes at 24 and 48 h were less pronounced. Glomerular basement membrane (GBM)-to-lumen gBSA labeling ratios were similar at all time points suggesting no accumulation of gBSA in the GBM. Seventy percent of the gBSA was cleared from the circulation and the GBM after 24 h, and 95% after 48 h. This was confirmed in experiments with radiolabeled tracers. These results suggest that the alteration in GBM permeability to BSA in the normal mouse are due to the presence of gBSA and are gradually overcome along with its clearance from circulation. In early diabetes, increasing concentrations of circulating glycated proteins could be responsible for changes in glomerular permselectivity and probably for the alteration in glomerular filtration properties leading to diabetic nephropathy.

scholarly journals ELECTRON MICROSCOPY OF THE AVIAN RENAL GLOMERULUS

1957 ◽  
Vol 3 (2) ◽  
pp. 183-192 ◽  
Author(s):  
R. K. F. Pak Poy ◽  
J. S. Robertson
Keyword(s):  
Electron Microscopy ◽  
Basement Membrane ◽  
Thin Sheet ◽  
Cell Mass ◽  
Central Cell ◽  
Dense Layer ◽  
Central Mass ◽  
Capillary Basement Membrane ◽  
Glomerular Capillary ◽  
Glomerular Capillaries

Electron microscopy of sections of chicken glomeruli shows them to possess a large central cell mass, occupying the hilum and the centre of the glomerulus, and continuous with the adventitia of the afferent and efferent arterioles. The glomerular capillaries form a much simpler system than in mammals and are spread over the surface of the central cell mass. Between the capillaries the mass is limited externally by the major component of the glomerular capillary basement membrane, which continues over the surface of the mass from one capillary to the next. Projections of the central cell mass characteristically form the support for glomerular capillaries, and smaller knobs of the central mass may project actually into the lumen of the capillaries, but always carry a layer of endothelial cytoplasm before them. They are never in direct contact with blood. The basement membrane of the glomerular capillary loop has a central dense layer and two lateral less dense layers as in mammals. The central dense layer is continuous with similar appearing dense material in the intercellular spaces of the adventitiae of the arterioles, and also with that of the central cell mass. The two less dense layers can also be traced into direct continuity with the less dense regions of this intercellular substance. The endothelial cytoplasm is spread as a thin sheet over the inner surface of the capillary basement membrane, and shows scattered "pores" resembling those described in mammals. Epithelial cells with interlacing pedicels are at least as prominent as those in mammals. Bowman's capsular membrane also possesses three layers similar to but less wide than those of the capillary basement membrane, and all three layers can be traced into continuity with the dark and light regions of the intercellular material of the adventitial cells of the arterioles, and beyond them with that of the central cell mass. At the hilum Bowman's capsular membrane also fuses with the capillary basement membrane.

scholarly journals THE DISTRIBUTION WITHIN THE BRAIN OF FERRITIN INJECTED INTO CEREBROSPINAL FLUID COMPARTMENTS

1965 ◽  
Vol 26 (1) ◽  
pp. 99-123 ◽  
Author(s):  
Milton W. Brightman
Keyword(s):  
Intraventricular Injection ◽  
Multivesicular Bodies ◽  
Intercellular Substance ◽  
Dense Bodies ◽  
Basal Plasma ◽  
Pinocytotic Vesicles ◽  
Additional Protein ◽  
Random Dispersion ◽  
Fluid Compartments ◽  
The Brain

From 10 minutes to 3½ hours after the intraventricular injection into rats of 15 to 100 mg of ferritin, an appreciable fraction of the protein, visualized electron microscopically, traverses the ependymal epithelium by diffusing along the dense intercellular substance of the luminal open junction and thence, by circumventing discrete intercellular fusions which partition rather than seal the interspace. These partitions shunt additional protein into the cell, where ferritin is transported within pinocytotic vesicles to the lateral and basal plasma-lemma and, presumably, back into the interspace again. The basal interspace is irregularly distended by pools of moderately dense "filler" within which ferritin accumulates. The larger fraction of protein enters the ependyma by pinocytosis and is eventually segregated within membrane-enclosed organelles such as vacuoles, multivesicular bodies, and dense bodies, where the molecules may assume a crystalline packing. As a result of the accumulation of ferritin within these inclusions and within filler substance, only a small amount of protein remains to enter the underlying parenchyma. Presentation of ferritin to prefixed cells leads to a random dispersion of free cytoplasmic ferritin. This artifactual distribution in both prefixed and postfixed cells is concurrent with disruption of cell membranes.

scholarly journals FUNCTIONAL EVIDENCE FOR THE EXISTENCE OF A THIRD CELL TYPE IN THE RENAL GLOMERULUS

1962 ◽  
Vol 13 (1) ◽  
pp. 55-87 ◽  
Author(s):  
Marilyn G. Farquhar ◽  
George E. Palade
Keyword(s):  
Basement Membrane ◽  
Kidney Tissue ◽  
Capillary Wall ◽  
Renal Glomerulus ◽  
Sequence Of Events ◽  
Cytoplasmic Bodies ◽  
Cytoplasmic Vesicles ◽  
Spinous Processes ◽  
Luminal Side ◽  
Peripheral Areas

Two types of cells can be recognized on the luminal side of the glomerular basement membrane: the superficial endothelial cells which directly line the lumen and are comparable to endothelia lining the capillaries of other tissues, and the deep cells, ordinarily not in contact with the lumen, which are distinguished by their long cytoplasmic arms extending for some distance in several directions along the capillary wall, numerous spinous processes, and occasional intraluminal pseudopodia. Experiments carried out with electron-opaque tracers indicated that a functional distinction, based on extent of phagocytosis, can be made between the superficial and deep cells, thus supporting the existence of a distinctive "third" cell (in addition to endothelium and epithelium) in the renal glomerulus. Ferritin, colloidal gold, or thorotrast was administered intravenously to normal and, in the case of ferritin, to nephrotic rats. Kidney tissue was fixed at selected intervals from 1 hour to 10 days after the injection and studied by electron microscopy. Within 1 to 4 hours after tracer administration, the particles which did not traverse the glomerular capillary wall gradually accumulated in the less compact, inner strata of the basement membrane and the large spongy areas of axial regions. After 1 day the concentration of circulating tracer declined and the peripheral areas of the capillaries became relatively free of particles while large accumulations developed in the axial regions. During this period increasing quantities of ferritin were taken up by the deep cells and were found within large and small sized invaginations of their cell membrane or concentrated within cytoplasmic vesicles, vacuoles, multivesicular and dense bodies. At the same time the deep cells showed increased numbers of intraluminal pseudopodia. Within 2 to 4 days the deposits in the spongy areas were cleared and concomitantly increased quantities of tracer appeared in the deep cells within dense cytoplasmic bodies, some of which were more compact than before. When ferritin was given to nephrotic animals the sequence of events was generally the same except that the ferritin deposits at any given period were more massive, their incorporation into the deep cells occurred primarily by means of large pockets 1 to 2 µ in diameter and their clearance from the spongy areas was slower. In normal as well as in nephrotic animals, the phagocytic activity of the superficial endothelium was negligible when compared to that of the deep cells.

The ultrastructure of the saccus vasculosus of teleost fishes III supporting tissue, innervation, vascularization

1971 ◽  
Vol 19 (4) ◽  
pp. 327 ◽  
Author(s):  
WJR Lanzing ◽  
Lennep EW van
Keyword(s):  
Supporting Cell ◽  
Distal Region ◽  
Secretory Product ◽  
Nerve Fibres ◽  
Supporting Cells ◽  
Saccus Vasculosus ◽  
The Past ◽  
Cytoplasmic Vesicles ◽  
Pinocytotic Vesicles ◽  
Coronet Cell

The ultrastructure of the supporting cells, the nerve fibres, and the blood vessels of the saccus vasculosus was investigated. Apart from the apical protuberance, the coronet cells are usually enveloped by thin sheets of supporting-cell cytoplasm. Although pinocytotic vesicles were not evident, the distal region of the supporting cells often contains cytoplasmic vesicles. The possibility of transfer of fluid by these cells is discussed. The network of nerve fibres contains both vesiculated and non-vesiculated nerve endings. Some of these endings lie adjacent to coronet cells and, occasionally, to supporting cells. In considering the function of the coronet cell undue emphasis was probably placed in the past on the possible possession of an axon and, also, on the vicarious presence of a secretory product in the lumen of the saccus vasculosus. It is suggested that the coronet cell could function as a chemoreceptor monitoring the composition of the cerebrospinal fluid.

MO070NEW ASPECTS OF THE PATHOMORPHOLOGIC SEQUENCE OF NEPHRON LOSS IN DIABETIC NEPHROPATHY

2021 ◽  
Vol 36 (Supplement_1) ◽  
Author(s):  
Hermann Gröne ◽  
Wilhelm Kriz ◽  
Jana Loewen ◽  
Elisabeth Groene
Keyword(s):  
Diabetic Nephropathy ◽  
Basement Membrane ◽  
Mesangial Cells ◽  
Capillary Endothelium ◽  
Tubular Damage ◽  
Mesangial Matrix ◽  
Nephron Loss ◽  
Bowman's Capsule ◽  
Glomerular Damage ◽  
Glomerular Capillaries

Abstract Background and Aims Diabetic nephropathy (DN) is the leading cause of end-stage-renal disease in western countries. Despite of innumerable studies undertaken to elucidate the pathogenesis of DN the underlying morphologic alterations have been insufficiently analyzed. Method Re-evaluation of more than 800 biopsies was done showing several unknown features. Results: 1. Matrix accumulation in the mesangium: Thickening of the glomerular basement membrane (GBM) and expansion of the mesangial matrix are hallmarks of DN, generally considered to emerge from different sites of overproduction: GBM components from podocytes and mesangial matrix from mesangial cells. We show, that the accumulation of matrix in the mesangium emerges from an overproduction of GBM material by podocytes and endothelial cells and an impaired degradation by mesangial cells. The progressing deposition of worn-out GBM material into the mesangium accounts for the advancement from diffuse mesangial sclerosis (DMS) to nodular sclerosis (NS) and to the herniation of the tuft through the glomerular vascular pole to the outside; the latter is associated with the outgrowth of glomerular capillaries into the peri-glomerular space leading to the destruction of the juxtaglomerular apparatus. 2.The role of podocytes Podocytes have frequently been accused to play a central role in DN. This is correct, but in another way than generally assumed. Damage to podocytes cannot be seen in DMS. The albuminuria regularly seen during this stage derives, as previously suggested by others, from an increased leakiness of the glomerular capillary endothelium based on a deranged glycocalyx. Podocyte detachments start at the transition from DMS to NS, based on the loss of cross talk signals with the capillary endothelium: the increasing deposition of matrix leads to the collapse of many capillaries. These podocytes contribute little to the further progression of the damage: they are lost into primary urine or they undergo cell lysis.In addition to their role in increased matrix production, podocytes take an active role in the formation of tuft adhesions to Bowman’s capsule (BC), starting the progression to NS. Expansion of the matrix within the mesangium has led to expansion of the tuft (frequently associated with nodules) towards Bowman’s capsule (BC) or towards the urinary orifice. Podocytes on the surface of these expansions are in their majority structurally intact, exhibiting an intact pattern of foot processes. These podocytes come into contact with parietal epithelial cells and initiate DN-specific tuft adhesions to BC allowing the proliferation of glomerular capillaries into BC. There they deliver an exudate into BC that spreads around the entire circumference of the glomerulus presenting as giant insudative spaces. Moreover, this process encroaches via the glomerulo-tubular junction onto the tubule constituting the major pathway of glomerular damage extending to the tubulointerstitium. 3. Tubulointerstitial fibrosisIt is current opinion that the tubulointerstitial fibrosis may start from tubular damage resulting in an own, glomerular-independent pathway to nephron loss. However, there is scant evidence for such a mechanism. Studying 162 glomerulo-tubular transitions, we did not see a tubular epithelial or interstitial damage in those biopsies without any evidence of a glomerulo-tubular damage transfer. The only exception consists of the well-known prominent thickening of the tubular basement membrane, which may result in functional loss but does not lead to structural epithelial damage. Conclusion We consistently found that tubulo-interstitial damage develops after encroachment of the glomerular damage onto the tubule, leading first to a gradual degeneration of tubules which subsequently initiate the process of interstitial fibrosis.

Pathomorphological Sequence of Nephron Loss in Diabetic Nephropathy

2021 ◽  
Author(s):  
Jana Löwen ◽  
Elisabeth Gröne ◽  
Marie-Luise Groß-Weißmann ◽  
Felix Bestvater ◽  
Hermann-Josef Gröne ◽  
...  
Keyword(s):  
Diabetic Nephropathy ◽  
Basement Membrane ◽  
Interstitial Fibrosis ◽  
Glomerular Sclerosis ◽  
Structural Aberrations ◽  
Vascular Proliferation ◽  
Advanced Stages ◽  
Nephron Loss ◽  
Bowman's Capsule ◽  
Glomerular Capillaries

Abstract Following our reports on mesangial sclerosis and vascular proliferation in diabetic nephropathy (DN)(25,34) we now describe the advanced stages of DN terminating in glomerular obsolescence and tubulo-interstitial fibrosis based on a total of 918 biopsies. The structural aberrations emerge from two defects: First, an increased synthesis of glomerular basement membrane (GBM) components by podocytes and endothelial cells leading to an accumulation of GBM material in the mesangium. Second, a defect of glomerular vessels consisting of an increased leakiness and an increased propensity to proliferate. Both defects may lead to glomerular degeneration. The progressing compaction of the accumulated worn-out GBM-material together with the retraction of podocytes out of the tuft and the collapse and hyalinosis of capillaries results in a shrunken tuft that fuses with Bowman's capsule to glomerular sclerosis. The most frequent pathway to glomerular decay starts with local tuft expansions that result in contacts of structurally healthy podocytes to the parietal epithelium initiating the formation of tuft adhesions, which include the penetration of glomerular capillaries into BC. Exudation of plasma from such capillaries into the space between the parietal epithelium and its basement membrane causes the formation of insudative fluid accumulations within BC spreading around the glomerular circumference and, via the glomerulo-tubular junction, onto the tubule. Degeneration of the corresponding tubule develops secondarily to the glomerular damage, either due to cessation of filtration in cases of global sclerosis or due to encroachment of the insudative spaces. The degenerating tubules induce the proliferation of myo-fibroblasts resulting in interstitial fibrosis.

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