The laminae rarae of the glomerular basement membrane. Their manifestation depends on the histochemical and histological techniques.
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Animals↗
Biomedical subjects
E Reale
Publications and source records attributed to E Reale.
Flagellar cells and ciliary cells in the renal tubule of elasmobranchs.
Flagella or cilia are present on most epithelial cells in the renal tubule of elasmobranch fishes (little skate, spiny dogfish, smooth dogfish, Atlantic sharpnose, scalloped hammerhead, cow-nosed ray). Flagellar cells, those with numerous flagella ordered in one, two, or more rows on the luminal surface, are shown here for the first time in a vertebrate. The flagellar cells are intercalated among other epithelial cells, each bearing a single cilium, from Bowman's capsule to the third subdivision of the intermediate segment of the nephron. The flagella form undulated ribbons up to 55 microns long. In every ribbon the axis of the central pair of microtubules in the axoneme is oriented parallel to the long axis of the flagellar row. This suggests a beat perpendicular to these two axes. The arrangement of the flagella in ribbons most likely promotes movement of glomerular filtrate down the renal tubule. Cells bearing numerous cilia occur in the large collecting ducts of spiny dogfish but without apparent preferential orientation of the cilia.
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Granulated peripolar epithelial cells in the renal corpuscle of marine elasmobranch fish.
Granulated epithelial cells at the vascular pole of the renal corpuscle, peripolar cells, have been found in the kidneys of five species of elasmobranchs, the little skate (Raja erinacea), the smooth dogfish shark (Mustelus canis), the Atlantic sharpnose shark (Rhizoprionodon terraenovae), the scalloped hammerhead shark (Sphyrna lewini), and the cow-nosed ray (Rhinoptera bonasus). In a sixth elasmobranch, the spiny dogfish shark (Squalus acanthias), the peripolar cells could not be identified among numerous other granulated epithelial cells. The peripolar cells are located at the transition between the parietal epithelium of Bowman's capsule and the visceral epithelium (podocytes) of the glomerulus, thus forming a cuff-like arrangement surrounding the hilar vessels of the renal corpuscle. These cells may have granules and/or vacuoles. Electron microscopy shows that the granules are membrane-bounded, and contain either a homogeneous material or a paracrystalline structure with a repeating period of about 18 nm. The vacuoles are electron lucent or may contain remnants of a granule. These epithelial cells lie close to the granulated cells of the glomerular afferent arteriole. They correspond to the granular peripolar cells of the mammalian, avian and amphibian kidney. The present study is the first reported occurrence of peripolar cells in a marine organism or in either bony or cartilagenous fish.
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Localization of cholesterol in the colonic epithelium of the guinea pig: regional differences and functional implications.
It is generally accepted that variations in membrane cholesterol content affect the fluidity of the bilayer, thus altering its permeability. In the biological membranes, in physiological conditions, a high cholesterol content rigidifies the bilayer decreasing its permeability, a lower cholesterol content induces the opposite effect by increasing the permeability. Since differences in the epithelial permeability for short chain fatty acids have previously been demonstrated in the proximal and distal colon of the guinea pig, these two regions were investigated to establish whether differences in membrane cholesterol content of the absorbing cells can be demonstrated. Freeze-fracture replicas of filipin-treated colonic tissue were used. The results show that in the proximal colon the density of filipin cholesterol complexes located on the luminal plasma membrane of the columnar absorbing cells was significantly higher (about twice) than in the distal colon. Therefore the lower amount of cholesterol present in the membrane of the absorbing cells in the distal colon indicates a greater fluidity of the membranes of the epithelial cells in this region. Such fluidity could be correlated to the higher absorption rates of shortchain fatty acids characteristic of this region.
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Ultrastructural changes of the basilar artery following experimental subarachnoid haemorrhage. A morphological study on the pathogenesis of delayed cerebral vasospasm.
Recent experimental studies have shown, that the endothelium of cerebral vessels undergoes significant changes after subarachnoid haemorrhage which may lead to biochemical changes at the endothelial surface with disturbance of the delicate homeostasis of vasodilating and vasoconstricting mechanisms which are thought to be responsible for preservation of the tones of the cerebral vasculature. Ultrastructural studies incorporating different forms of microscopic observations of the endothelium after SAH representing a prerequisite for further investigations on the pathogenesis of cerebral vasospasm are scarce. The experimental study was performed in order to investigate and define more precisely the pathomorphological changes at the endothelial surface of the basilar artery of dogs after experimental SAH. Two separate injections of autologous blood into the cisterna magna within 72 hours resulted in extensive angiographic narrowing of the diameter of the basilar artery of all animals. Histological studies of the basilar artery including light microscopic, transmission electron microscopic, scanning electron microscopic and freeze cracking microscopic examinations demonstrated severe pathomorphological changes at the endothelial surface. These consisted mainly of infolding and corrugation of the endothelium, disorientation and desquamation of endothelial cells as well as of vacuolation and ingrowth of fibrous tissue between the endothelial and muscular layer. No pathomorphological changes could be observed in the muscular layer. As the described post-haemorrhagic ultrastructural changes of the endothelium cerebral vessels in spasm are likely to represent the morphological basis of the delayed form of cerebral vasospasm future research on its pathogenesis should primarily focus on the structural and biochemical taking place at the endothelial surface of the cerebral vasculature after SAH.
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Retinal wound healing after surgical contusion injury.
The lesion was caused by a compression injury to the retina with a vitrectomy instrument in a rhesus monkey; the lesion was examined by electron microscopy 8 years later. The inner surface of the choroid was lined by a layer of cells with the characteristics of fibroblasts. The choriocapillaris was missing. Bruch's membrane was extremely thickened and showed numerous changes. In the center of the scar, the retinal pigment epithelium was discontinuous. The neuroretinal portion of the scar was composed of distorted and dislocated nerve cells, nerve fibers, and glial elements that were probably Müller cells. Towards the vitreous cavity, the surface of the scar contained numerous microvillous processes. A band of zonulae adherentes resembling the outer limiting membrane was seen immediately adjacent to the surface. No inner limiting membrane was seen in the entire scar area.
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Alignment of cholesterol in the membrane bilayer.
Freeze-fracture replicas of filipin-treated samples of guinea pig colon mucosa reveal areas in the membrane of the goblet cell granules labeled by filipin-cholesterol complexes (FCC) intermingled with regions patterned by "lines." The FCC and "lines" are arranged in an approximately rhombic pattern. Other membranes of the same cell or of other cells display either FCC only, aligned and occasionally ordered in "rhombs," "lines" only, with a similar pattern, or randomly distributed FCC. Optical diffraction was used to analyze and compare replicas of membranes with ordered FCC and "lines", as well as randomly distributed FCC. The results demonstrate that all these structures are reciprocally related through a common distribution pattern in the membrane. This observation supports the assumption that cholesterol has a preferential ordered distribution within the membrane bilayer.
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Transport of SCFA across the large intestinal epithelium of guinea pig.
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Animals↗
The fine structure of the laminae rarae of the glomerular basement membrane in the rat.
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Animals↗
Osmium impregnation and micromanipulation. Their association in studies using secondary or backscattered electrons.
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Vasopressin-induced intramembrane particle aggregates. A dose-response relationship in the isolated cortical collecting duct of the rabbit kidney.
The water permeability of collecting ducts is greatly increased by the antidiuretic hormone, vasopressin (VP). Freeze-fracture studies were carried out to test if this permeability increase is associated with the appearance of intramembrane particle (IMP) aggregates and whether increased doses of VP lead to an increase in the number and size of particle aggregates in the luminal membrane of principal cells in the isolated cortical collecting duct. Unstimulated cells expressed 17 +/- 6.5 particle aggregates per 100 microns 2. Stimulation with VP at concentrations of 20 or 200 microU/ml increased the number of particle aggregates significantly to 129 +/- 15.8 and 324 +/- 45.8, respectively. The size of the particle aggregates increased from 0.0012 microns 2 under control conditions to 0.025 microns 2 at 20 microU/ml VP and to 0.063 microns 2 at 200 microU/ml VP. In addition, the total area occupied by the IMP increased from 0.02 microns 2/100 microns 2 (controls) to 3.17% and 20.38% (after 20 and 200 microU ADH/ml, respectively). Particle aggregates were also observed in the luminal plasma membrane of isolated collecting ducts fixed immediately after dissection, resembling the in vivo status. These results demonstrate that a dose-dependent relationship exists between the concentration of the applied VP and the number of particle aggregates, as well as the size of the aggregates. Cytoplasmic tubular vesicles in fusion with the apical membrane were observed.
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The elasmobranch renal corpuscle: fine structure of Bowman's capsule and the glomerular capillary wall.
The fine structure of the renal corpuscle of the marine elasmobranch fish, the little skate (Raja erinacea), and two species of dogfish sharks, the spiny dogfish (Squalus acanthias) and the smooth dogfish (Mustelus canis), was studied by light microscopy and by transmission (thin sections, freeze-fracture replicas) and scanning electron microscopy. Bowman's capsule was lined by ciliated cells, similar to those of the first part of the tubule, at the urinary pole and squamous cells in the zone between urinary and vascular poles. At the vascular pole the visceral epithelial cells had some closely apposed cuboidal cell bodies with a few processes inserted along the basement membrane, but foot processes were absent. These cuboidal cells were continuous with podocytes, which had primary, secondary and tertiary processes from which the pedicels arose. An inconsistently present slit membrane bridged the pedicels at varying distance from the urinary space. Small maculae and large fasciae occludentes joined the podocytes and/or their processes among which gap junctions were observed. In the skate kidney, the podocyte plasma membrane facing the basement membrane contained orthogonal arrays of particles. The epithelial basement membrane of the glomeruli in all elasmobranchs was consistently thick. The mesangial cells were numerous and partially enveloped in a basement membrane; their long processes almost completely circumscribed the capillary walls. The mesangial matrix was abundant and consisted of loosely arranged collagen fibrils, microfibrils and occasional anchoring fibrils. The endothelial cells had irregularly distributed fenestrations of various sizes and lay on their discontinuous basement membrane which was separate from that under the epithelial cells. The filtration apparatus resembles that of immature mammals and lower vertebrates.
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The elasmobranch kidney. III. Fine structure of the peritubular sheath.
In the kidney of two elasmobranch fish, the little skate (Raja erinacea) and the spiny dogfish (Squalus acanthias), each tubular bundle is wrapped by a continuous sheath of extremely flattened cells which are ordered in several closely superimposed layers. Thin sections and freeze-fracture replicas demonstrate that extensive tight junctions exist between the cells of this peritubular sheath. The sheath cells lie on a discontinuous basement membrane which suggests that they do not belong to the connective tissue. Conceivably, each peritubular sheath segregates the milieu inside the sheath (surrounding the bundle of 5 tubules and capillaries which form the countercurrent system) from the milieu outside the sheath (connective tissue matrix in which the bundles are embedded).
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Histochemical demonstration of hyaluronic acid molecules by alcian blue.
Specimens of vitreous humour (monkey eye), Wharton jelly (human umbilical cord) and commercial hyaluronates were immersed in buffered fixative solutions containing either aldehydes and Alcian Blue, or aldehydes and Alcian Blue with MgCl2 as electrolyte. Two MgCl2 concentrations were used, 0.025 M and 0.3 M. Immersion in both solutions induced formation of precipitates which were postfixed in OsO4, dehydrated and embedded for thin section electron microscopy. The use of the same fixative solution produced morphologically comparable precipitates from all three materials. The precipitates, especially after fixation in the presence of electrolyte, were composed of linear, unbranched filaments, frequently aggregated into bundles. The filaments were considered to be molecules of hyaluronic acid.
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In-vitro culture of human chondrocytes from adult subjects.
An agarose gel matrix was utilized to grow chondrocytes from human donors of various ages in cell culture. The chondrocytes produced the pericellular matrix characteristic for such cells and synthesized collagen type II as well as glyco-saminoglycans. The latter exhibit the typical distribution pattern of the respective articular cartilage matrix. The electron-microscopic appearance of the cultured chondrocytes closely resembles that of chondrocytes in sections of the original cartilage.
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Age-dependent glomerulosclerosis and proteinuria occurring in rats of the Milan normotensive strain and not in rats of the Milan hypertensive strain.
The development of an age-dependent glomerulosclerosis and proteinuria was investigated in two strains of rats in a model of moderate hypertension comparing rats of the Milan Hypertensive Strain (MHS) with rats of the Milan Normotensive Strain (MNS). Serum creatinine, urinary protein excretion, renal morphology (light- and electronmicroscopy) and morphometry of the media thickness of the intrarenal arteries and of the thickness of the glomerular basement membrane were studied in 2- to 16-month-old MHS and MNS rats. Serum creatinine did not differ between MNS and MHS rats in any age group. MNS rats developed a significant proteinuria which coincided with a glomerulosclerosis in about 22% of the glomeruli at 13 to 16 months. In contrast, urinary protein excretion in MHS rats remained stable during the entire observation period; glomerulosclerosis occurred only in 3% of the glomeruli at 13 to 16 months. As a consequence of hypertension media thickness of intrarenal arteries of MHS rats significantly exceeded that of MNS rats, in the interlobular arteries already at 2 months and in the arcuate arteries at 13 to 16 months. In contrast, thickness of the glomerular basement membrane of MHS rats never exceeded that of MNS rats. From these data we conclude, that glomeruli of MHS rats may be protected against the development of an age-dependent glomerulosclerosis and proteinuria. Further support for this conclusion may also be derived from recent experiments showing that the tubuloglomerular feedback sensitivity is significantly higher in MHS than in MNS rats (41).
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The elasmobranch kidney. II. Sequence and structure of the nephrons.
The nephron and collecting ducts of the little skate (Raja erinacea) and spiny dogfish shark (Squalus acanthias) have been investigated by light microscopy of semi-thin sections. Parts of the tubules (collecting ducts and distal segments) were identified after tubular injections with Microfil or carbon. The bundle zone was studied in serial sections. In the sinus zone transitions between the different segments were recorded. Thus, a complete reconstruction of the nephron, its subdivision into segments, and their localization in the kidney was accomplished. The nephron makes 4 loops. Beginning at Bowman's capsule, which sits between the bundle zone and sinus zone, the first loop is in the bundle zone. The nephron then extends into the sinus zone and turns back forming the second loop. This is followed by a third loop in the bundle zone which descends again into the sinus zone to form the last loop. The tail of the last loop (distal tubule) goes into the bundle zone and joins the collecting ducts. These collecting ducts are in the subcapsular connective tissue and progressively fuse to form a collecting tube. In the skate this tube traverses the thickness of the kidney between adjacent renal lobes to exit on the ventral kidney surface. In the shark, the large collecting ducts run on the surface of each lobe toward the medial margin of the kidney. Loops one and three and the early distal segment--all belonging to the same nephron--and a network of anastomosing capillaries form a bundle enclosed by a sheath of overlapping squamous cells termed "peritubular sheath." This anatomical unit forms the renal countercurrent system of the marine elasmobranch. The tubular bundle has a straight portion in which the nephron segments are arranged in a highly parallel fashion. The remainder of the bundle and of the encasing peritubular sheath are convoluted. The sequence of the tubule morphology beginning at Bowman's capsule is: neck segment (early and late), proximal tubule (four portions), intermediate (six portions), distal tubule (early and late), collecting duct (early and late).
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Cationic dyes reveal proteoglycans on the surface of epithelial and endothelial kidney cells.
The glomerular epithelial cells of the rat kidney fixed by vascular perfusion with an aldehyde solution containing either safranine O or alcian blue (and 0.3 M MgCl2) display filaments which are located close to the outer surface of the plasma membrane. These filaments are similar to those revealed by the same methods in the laminae rarae of the glomerular basement membrane. Alcian blue (and MgCl2) further demonstrates the presence of anionic sites inside the endothelial cell pores of the glomerular and peritubular capillaries, on the luminal surface of endothelial cells of large renal vessels and along the basolateral surface of the epithelial cells of the Bowman capsule and of the proximal convoluted tubule.
Alcian Blue↗