Search PubMed⌕ Search

Biomedical subjects

E C Carlson

Publications and source records attributed to E C Carlson.

At least 37 records · Page 2Linked to original sources
PubMed1990

SEM and TEM analyses of isolated human retinal microvessel basement membranes in diabetic retinopathy.

Human retinas from persons with diabetic retinopathy and age-matched controls were rendered acellular by sequential detergent treatment. The resulting network of microvascular extracellular matrix (ECM) materials, including basement membranes (BMs), was compared by TEM and, following cryofracture, by SEM. Our study demonstrates that in diabetics, retinal capillary BM complexes are generally thickened and that their ECM subcomponents, including BM leaflets and BM-like pericytic matrix (PCM), are differentially altered. Two diabetic microvessel types were identified. In type A vessels, ECM expansion is manifested by loosely arranged combinations of concentric PCM layers and collagen fibrils with thickened subendothelial (EBM) and pericyte (PBM) BM leaflets. Type B vessels show densely compact central PCM masses and poorly recognizable EBMs and PBMs. In both types, Müller cell BMs (MBMs) are relatively unaffected. High-resolution SEM shows tissue-specific features in normal EBM and MBM surfaces, but disease-related topographic changes are not evident. It is possible that the ECM arrangements identified in our study relate to different microvessel domains and that their specific morphological features may play important roles in the pathogenesis of diabetic retinopathy including capillary closure and neovascularization.

Aged↗
PubMed1990

High resolution SEM analysis of acellular glomerular basement membrane following pepsin digestion: intrinsic fibrillar structures.

Microdissection of acellular rat renal cortex with pepsin was carried out to investigate the morphological substructure of glomerular basement membrane (GBM) by high resolution SEM. Renal cortical blocks (less than 5 mm3) from adult male Sprague Dawley rats were rendered acellular by sequential detergent extraction and digested up to 184 hrs with 5 mg/ml pepsin (185 U/mg) in 0.5 M acetic acid (pH 2) at 10-15 degrees C. Samples were conventionally prepared for SEM, and observed at original magnifications of 500-100,000 diameters. At low magnifications (500-5,000x), acellular GBM surfaces appeared smooth at all digestion times. At higher magnifications (50,000-100,000x), control GBM surfaces were finely granular. Granule diameter ranged from 20-80 nm, with most between 30-40 nm. Pepsin digestion did not affect average granule size. Beginning at 44 hrs of digestion, intrinsic fibrillar structures comprised of linear arrays of 20-40 nm granules were observed on/in GBM surfaces. At later incubation times, this component of GBM became more extensive. At 160 hrs, the fibrillar arrays frequently bifurcated and showed distinctive "forked" termini, some of which comprised two sides of a triangle (120-150 nm on a side). Fork "handles" (310-350 nm in length) radiated from each angle of the triangle. These sometimes terminated in large granules (approximately 100 nm in diameter), two of which appeared to connect fibrillar arrays end-to-end. Together with other arrays, the interconnected triangles appeared to comprise a three-dimensional meshwork extending into the GBM and possibly providing support for, its granular components.

Animals↗
PubMed1989

Human retinal capillary basement membrane leaflets are morphologically distinct: a correlated TEM and SEM analysis.

Because retinal capillaries and their associated basement membranes (BMs) are significantly altered in a number of diseases (most notably diabetic retinopathy), the human retinal microvasculature is of interest to both basic scientists and clinicians. Consequently, numerous TEM studies centered primarily on cellular elements of retinal microvessels have been carried out. Ultrastructural studies emphasizing retinal capillary extracellular matrix (ECM) materials including BMs however, are nearly non-existent. Accordingly, the current correlated TEM/SEM investigation was undertaken. The study shows that retinal capillary walls are comprised of a continuous layer of endothelial cells and a discontinuous layer of intramural pericytes which are in frequent contact. These are underlain and/or surrounded by a retinal capillary BM complex which includes pericytic matrix, fibrillar collagen, and subendothelial, pericytic and Müller cell BM leaflets. Following sequential detergent treatment, all retinal cells are solubilized. Vessel ECM components, however, maintain their in vivo histoarchitectural relationships. Moreover, on the basis of substructure, susceptibility to non-specific proteases and anionic site density, BM leaflets are morphologically distinct. In addition, high-resolution SEM studies show that BM surface characteristics are tissue specific. It is concluded that retinal capillary BM complexes are comprised of structurally unique subcomponents the characteristics of which should be considered in future studies of retinal capillary BM structure, composition and function and particularly in investigations in which retinal capillaries are pathologically altered.

Adult↗
PubMed1989

Ultrastructural analyses of acellular glomerular basement membranes and mesangial matrix in a spontaneously diabetic rhesus monkey.

Renal changes similar to those considered diagnostic for diabetes in humans are infrequently observed in spontaneous noninsulin-dependent (NID) diabetic monkeys. In the current study, renal cortical tissue blocks are rendered acellular to demonstrate glomerular basement membrane (GBM) and mesangial matrix (MM) changes in a naturally occurring NID diabetic rhesus monkey (Macaca mulatta). Transmission electron micrographs of these specimens show axial MM accumulations with numerous striated collagen fibrils that frequently extend onto internal (endothelial) surfaces of peripheral GBM. The outer (epithelial) component, although compact, appears bilaminar due to folded external surfaces not coinciding with similar irregularities on internal surfaces. By scanning electron microscopy, external surfaces of sclerotic GBMs are extensively wrinkled and, following cryofracture, show congestion and expanded MM. A fenestrated meshwork of MM, which appears less dense and compact than epithelial BM, extends from axial regions onto GBM internal surfaces. The true thickness of randomly sampled peripheral GBM thickness (approximately 400 nm) is approximately double that of normal rhesus GBM. Diabetic GBMs exhibit ruthenium red positivity for surface polyanions with linear site densities not significantly different from normal. These observations indicate that sclerotic GBMs in diabetic rhesus monkeys closely resemble those seen in human end-stage diabetic glomerulopathy and suggest that this nonhuman primate may offer an excellent model for studies of chronic diabetic BM disease.

Animals↗
PubMed1989

Alveolar bone of BB/W rats: a morphometric and histochemical study.

The present study reported histochemical changes in alveolar bone glycosaminoglycans (GAG) (using Safranin O) and in interdental bone height in three groups of BB/W rats: diabetic, diabetes prone, and diabetes resistant. Safranin O staining intensity suggested that total GAG levels were highest in diabetic bone (p less than 0.05 compared to diabetes resistant, p less than 0.005 compared to diabetes prone) but not significantly different between diabetes prone and resistant groups. Following chondroitinase AC and ABC digestion, staining reactions suggested that the highest levels of dermatan sulfate were in the diabetes resistant group (p less than 0.001 compared to diabetic, p less than 0.001 compared to diabetes prone) and the highest levels of chondroitin sulfates were in the diabetes prone group (p less than 0.001). Coincidently the mean height of diabetes prone interdental septum was significantly less than that of diabetes resistant or diabetic groups (p less than 0.05). The study suggested that 1) diabetes and "prediabetes" produce significant changes in levels of chondroitin 4, 6, and dermatan sulfates within alveolar bone, 2) in "prediabetic" animals, interdental bone loss occurs prior to the onset of clinical symptoms and in the absence of local irritating factors, the bone height appears to return to normal levels, and 3) there may be a correlation between alveolar bone height and relative levels of dermatan sulfate.

Animals↗
PubMed1989

Intrinsic fibrillar components of human glomerular basement membranes: a TEM analysis following proteolytic dissection.

At the level of ultrastructure, basement membranes (BMs) are usually described as thin layers of extracellular matrix comprised of an interwoven mat of fine 3-4 nm fibrils embedded in a granular matrix. In order to improve the resolution of the fibrillar components, we have carried out TEM studies on human glomerular BMs (GBMs) made acellular by sequential detergent solubilization. Some GBMs were pretreated with pronase, trypsin, or pepsin for 30 min to 72 h prior to preparation for microscopy. Our study shows that irrespective of which enzyme is employed, background granular matrix is first solubilized leaving a three dimensional fibrillar network comprised of 3-8 nm fibrils. Larger 7-8 nm fibrils are concentrated near subepithelial portions of the GBM and are most resistant to proteolysis. Smaller 3-4 nm fibrils are located primarily subjacent to endothelium and mesangial cells and are more protease-sensitive. An unexpected finding in pepsinized samples was a quasi-hexagonal fibrillocrystalline structure associated with mesangial matrix and subendothelial portions of the GBM. These data suggest that intrinsic fibrillar components of human GBMs are heterogeneously distributed throughout the thickness of their laminae densae. We speculate that the network consists of type IV collagen and that the hexagonal crystals may represent type VI or some previously unreported BM collagen type.

Basement Membrane↗
PubMed1989

Nerve suture and grafting.

Nerve anatomy, terminology, and techniques for nerve restoration are reviewed in sufficient detail to allow the reader to quickly update his or her knowledge in this area. Ideas for future directions of study are presented.

Hand↗
PubMed1989

Acute renal failure and fluid retention and kidney damage in copper-deficient rats fed a high-NaCl diet.

The effect of an interaction between Cu status and dietary NaCl level on kidney structure, water balance, and the plasma renin-angiotensin-aldosterone system (RAAS) was examined in 64 male Sprague-Dawley rats (178 gm) fed a copper-supplemented diet (CuS) (10 micrograms Cu per gram) or a copper-deficient diet (CuD) (less than 0.7 micrograms Cu per gram), with (CuSNa, CuDNa) or without 3% NaCl for 42 days. NaCl did not affect growth, fluid retention, or kidney ultrastructure in Cu-supplemented rats. Cu deficiency decreased growth rate and kidney Cu, increased plasma cholesterol concentration, and suppressed plasma RAAS. NaCl increased the magnitude of these changes in Cu-deficient rats. The mortality rate was higher in CuDNa (8/16) than in Cu-deficient (2/16) rats. An acute renal failure syndrome characterized by tissue edema, pleural effusion, and ascites occurred in rats fed CuDNa. Bioelectric impedence analysis indicated that body water content was similar in rats fed CuS, CuSNa, and CuD but was higher in edematous and nonedematous rats fed CuDNa. Transmission electron microscopy indicated that glomeruli from Cu-deficient rats were poorly perfused and often occluded by expanded mesangium and contained numerous lysozome-like bodies. Fusion of podocyte foot processes, derangement of glomerular basement membrane, and hypertrophy and lipid accumulation by glomerular capillary endothelium were present in tissue from rats fed CuDNa. These results indicate that Cu deficiency reduces NaCl tolerance in rats. Ultrastructural changes in kidney tissue and the suppression of RAAS in rats fed CuDNa suggest that the edema and ascites result from acute renal failure and not from increased fluid and electrolyte reabsorption.

Acute Kidney Injury↗
PubMed1989

Fenestrated subendothelial basement membranes in human retinal capillaries.

A correlated TEM and SEM study of human retinal capillaries and their associated basement membranes (BMs) was carried out. Control tissues show that these vessels are comprised of a continuous layer of endothelial cells separated from overlying intramural pericytes by a discontinuous subendothelial BM (EBM) which accommodates endothelial cell-pericyte (periendothelial) junctions. Three types of junctions exist, including: (1) "peg-and-socket" arrangements where cytoplasmic processes of the two cell layers interdigitate; (2) adhering plaques similar to desmosomes; and (3) cell/cell contacts where adjacent cell membranes appear to fuse or remain separated by a approximately 2 nm space. Following detergent solubilization, acellular retinal capillaries maintain their cylindrical histoarchitectures and all BM components are imaged by TEM and SEM. Topographical (SEM) studies of cryofractured samples show EBM surfaces with numerous (approximately 1.5/microns 2) oval fenestrations (100-450 nm diameter) that correlate well with EBM discontinuities occupied by periendothelial junctions in control tissues. It seems possible that these structures may play an important role in diabetic retinal neovascularization where pericytes are known to degenerate selectively. In this condition, preformed EBM deficiencies could facilitate endothelial cell migration and sprout formation, leading ultimately to the sequelae of proliferative diabetic retinopathy.

Basement Membrane↗
PubMed1988

Topographical specificity in isolated retinal capillary basement membranes: a high-resolution scanning electron microscope analysis.

Numerous investigations have demonstrated that basement membranes (BMs) are composed of type IV collagen, laminin, heparan sulfate proteoglycan, nidogen, and possibly fibronectin. The precise proportion and supramolecular organization of these molecules within BMs is unclear, but is believed to be tissue-specific. In an effort to provide morphological evidence for BM specificity, we studied isolated bovine retinal capillary BMs by high-resolution SEM. Cryofractured specimens demonstrated that surfaces of BM leaflets and pericytic matrix (PCM) within the retinal capillary BM complex are composed of 20- to 100-nm granules and beaded fibrils arranged in patterns which are specific for each cell type. Subendothelial BMs and the subjacent PCM are composed of 20- to 30-nm granules loosely arranged and marked by numerous pits, features that are consistent with their TEM morphology and known susceptibility to proteolytic attack. These BMs also frequently exhibit large openings or fenestrations. These compare favorably with their fragmented image by TEM and probably represent BM discontinuities necessary for direct contact of pericytes and endothelial cells. Muller cell BMs are also composed of granules though they are much larger (40-100 nm) and more densely packed then those of subendothelial BMs. Moreover, they frequently contain interstitial collagen fibrils which could account for the tube-like structural rigidity exhibited by acellular retinal vessel BMs in SEM views. Data in the current study provide morphological evidence for direct contact of pericytes and endothelial cells in vivo and support the view that tissue specificity of BMs may be more exquisite than previously believed, extending even to surface topography of BM leaflets within capillary BM complexes.

Animals↗
PubMed1988

Synergism of Candida albicans and delta toxin producing Staphylococcus aureus on mouse mortality and morbidity: protection by indomethacin.

Twelve Staphylococcus aureus strains, six positive and six negative for delta-toxin production, were studied for synergistic effects on mouse mortality and morbidity when combined with Candida albicans and inoculated intraperitoneally (i.p.). S. aureus strains producing delta-toxin were found to exhibit a relatively great synergistic decrease (between near 10(3)-10(5)-fold) in LD50 (dose necessary to kill 50% of exposed animals in five days) when combined with a nonlethal dose of C. albicans and injected i.p. S. aureus strains which did not produce delta showed less of a synergistic effect with C. albicans (10-10(2)-fold drop in LD50). A synergistic effect on mortality could also be produced when animals were dually injected with C. albicans and sterile growth filtrates from the delta-toxin producing strains or the purified delta-toxin. The lethal agent in the culture filtrate was, like delta-toxin, sensitive to lecithin and insensitive to heat. Indomethacin protected animals from the C. albicans-filtrate induced death. Blood measurements made following i.p. injection of delta-toxin and C. albicans revealed chemistry changes indicative of shock, kidney and liver damage; delta-toxin alone caused no significant chemistry changes whereas C. albicans alone caused some blood chemistry changes but liver and kidney damage was not indicated. No synergism on mortality was found between C. albicans and purified alpha-toxin or toxic shock syndrome toxin-1.

Animals↗
PubMed1988

Ultrastructural evidence for morphological specificity in isolated bovine retinal capillary basement membranes.

Because of its relative availability, large size, and presumed similarity to human, the bovine retina has been used by numerous investigators as a source of vessels, cells, and basement membranes (BMs) for biochemical analyses and in vitro studies of cells and extracellular matrix. Careful morphological studies of these vessels and their associated BMs, however, have not been done. Accordingly, we carried out experimental ultrastructural studies in an effort to show their cellular composition, their histoarchitectural relationships within retinal capillary walls, and the disposition and features of their isolated BMs. Our study shows that these vessels are complex, multicomponent structures composed of endothelial cells and intramural pericytes, which frequently communicate via direct cell/cell contacts, and a system of BMs. The latter includes continuous Muller cell BMs, interrupted subendothelial BMs, and pericytic BMs with masses of pericytic matrix (PCM) intervening. Isolated subendothelial BMs are remarkable for fenestrations, selective susceptibility to nonspecific proteases, and high density of ruthenium red (RR)-positive anionic sites. On the contrary, Muller cell BMs are continuous (completely surrounding retinal capillaries), relatively refractory to proteases, and show significantly fewer anionic sites by RR. Acellular capillary BMs frequently show ghost-like "pockets" previously occupied by pericytes. These are surrounded by pericytic BMs and interstitial spaces are "filled-in" by a BM-like material (PCM) which frequently contains striated collagen fibrils and is positionally and morphologically homologous to glomerular mesangial matrix. These data indicate that tissue specificity of BMs may be far more precise than previously thought and that each capillary BM leaflet may possess a peculiar macromolecular architecture commensurate with its specific function.

Animals↗
PubMed1988

Ultrastructural analyses of enzyme-treated microfibrils in rabbit corneal stroma.

Microfibrils have been identified within and between corneal collagen lamellae in a number of vertebrate species in a variety of developmental and pathological conditions, but they are relatively rare in normal adult animals. The present study was undertaken to analyze corneal microfibrils in adult rabbits using enzymatic digestion techniques. Transmission electron microscopy (TEM) showed clusters of 10-15 nm microfibrils arranged in quasi-parallel bundles within or between orthogonally arranged stromal collagen lamellae. When corneas were fixed with tannic acid/glutaraldehyde, the entire stroma showed increased electron density and microfibrillar bundles were heterogeneously stained. Peripheral fibrils were more electron-dense than those located more centrally. Following sequential detergent solubilization of unfixed corneas, all cellular elements were removed and collagen lamellae were distorted. Microfibrillar bundles remained intact, however, and resembled untreated controls. Subsequent treatment with pepsin, trypsin or elastase resulted in swollen corneal tissues in which collagen lamellae were no longer distinguishable but individual collagen fibrils maintained their morphological integrity. In these tissues microfibrillar bundles were rarely identifiable and were reduced to randomly oriented fragments or clusters of filamentous material. Testicular hyaluronidase or chondroitinase ABC did not affect the fibrils. These data indicate that rabbit corneal microfibrils are proteinaceous and that the tannic acid-staining component of the bundles is not glycosaminoglycan. The fibrils are indistinguishable from those identified as oxytalan in cornea and other ocular tissues. Moreover, their sensitivity to elastase and preferential staining with tannic acid/glutaraldehyde strongly suggest they may be related to the elastic system of fibrils.

Animals↗
PubMed1986

SEM studies of acellular glomerular basement membrane in human diabetic glomerulopathy.

Previous transmission electron microscopic studies have demonstrated glomerular basement membrane (GBM) thickening and mesangial matrix (MM) expansion in chronic stages of diabetes. It is difficult, however, to achieve an appreciation of GBM surface features and distribution of MM in planar views. In the current study, autopsy human renal cortical tissue from patients with end-stage diabetic nephropathy were minced and rendered acellular with detergents prior to fixation, cryofracture, and preparation for light microscopic (LM), transmission electron microscopic (TEM), and scanning electron microscopic (SEM) observation in an effort to visualize extracellular materials in three dimensions. Our studies demonstrated that although diabetic glomerular changes vary widely within and between individuals, most showed alterations primarily affecting peripheral (epithelial) GBM (with MM increased but diffusely distributed), or they exhibited similar GBM changes but with variable nodular MM expansion leading ultimately to capillary occlusion. Both types showed peripheral GBM thickening and demonstrated external surface irregularities that by SEM appeared as "cauliflower-like" lobulations. In these glomeruli, GBM lamellation or reduplication was common with internal layers frequently thrown into lumenward projections. Glomeruli with diffusely distributed MM generally showed patent capillary channels with little evidence of occlusion. By TEM, highly compact, epithelial GBMs were clearly distinguishable from the electron-lucent MM. In these preparations the matrix was concentrated in relatively small discrete masses sometimes covered by a finely fibrillar material, which extended intermittently onto lumenal surfaces of epithelial GBMs. In more advanced stages of MM involvement, glomeruli typically exhibited smooth-surfaced nodules that were increased at the expense of capillary surface area. By TEM, MM nodules were comprised of a meshwork of very fine (20-A) fibrils surrounding a variety of detergent-resistant structures including collagenous fibrils and non-collagenous 30-nm circular fibrils with 16-nm subunits. By SEM, GBM and MM nodules were not distinguishable and merged to form substantial barriers to capillary blood flow. In those capillary channels remaining patent, inwardly projecting folds and ridges were common GBM features, and frequently thin fenestrated layers, distinctly separate from epithelial GBMs, formed sieve-like linings for the channels. These three-dimensional observations provide unique views of the processes leading to diabetic glomerular occlusion and suggest a potential for this technique in the study of renal BM disease.

Aged↗
PubMed1986

Ultrastructural analysis of major basement membrane types in rhesus monkey Macaca mulatta acellular renal cortex.

Increasing interest in animal models of human nephropathies have led to a number of renal studies in nonhuman primates. In the current investigation, sequential detergent extraction of cellular elements was carried out on renal cortical tissue blocks from rhesus monkey in an effort to demonstrate clearly the morphological features of major basement membrane (BM) types and their associated extracellular matrix (ECM). LM and TEM views of acellular tissue blocks demonstrate planar arrangements of ECM components, while SEM studies provide striking three-dimensional images of their surface characteristics. All major BM types maintain their in vivo histoarchitectures despite the absence of cells. We propose that the intrinsic structural rigidity of tubular (TBM), Bowman's capsule (BCBM) and peritubular capillary BM (PTCBM) may be related to to their close external association with collagenous fibrils, while glomerular BM (GBM) may be internally supported by a network of mesangial matrix (MM) plates and trabeculae which extend onto internal surfaces of peripheral GBM loops. Thicknesses of rhesus monkey renal BMs show that they are similar to those seen in the laboratory rat and, in general, BCBM greater than TBM greater than GBM greater than PTCBM. We conclude that rhesus monkey renal BMs closely resemble those described by us in the human [J. Ultrastruct. Res. 82: 96-110, 1983] and that this species offers an attractive model for studies of renal diseases of BM origin-notably diabetes mellitus.

Animals↗
PubMed1983

A topographical (SEM) analysis of acellular glomerular mesangial matrix in situ.

Normal kidneys from human and New Zealand white rabbits were made acellular by vascular perfusion with detergents. Cortical regions were dissociated from the central renal mass and further minced to 2 mm3 and fixed for TEM and SEM analyses. In an effort to visualize the internal histoarchitecture of glomerular basement membranes (GBM) and associated mesangial matrix (MM), some of the fixed samples were cryofractured prior to preparation for SEM observations. By this technique, the in situ MM exhibits a lacy network of fenestrated plates (septa) that separate and support peripheral glomerular channels. It seems possible that these structures may be intrinsically rigid and that their shape-preserving properties may be transmitted to the entire GBM. The matrix is not restricted to centrolobular zones, but extends throughout the glomerulus via a loose inner (endothelial-mesangial) layer of GBM. This filamentous layer is similar to MM in texture and surface characteristics and is often thrown into folds or trabeculae. In contrast, the outer (epithelial) surface of GBMs is more compact and smoothly contoured. Our SEM and correlative TEM studies indicate that the inner layer is continuous with MM septa distally and extends proximally to the glomerular vascular pole via arteriolar BMs where it reaches the extraglomerular interstitium. This establishes an extracellular morphological pathway from centrolobular zones to the polar cushion.

Animals↗
PubMed1983

Effect of hypothermic perfusion on corneal endothelial morphology.

The effect of moderate in-vivo hypothermic perfusion on corneal endothelial integrity was studied in the cat. Eleven cats underwent in-vivo anterior chamber perfusion for 30 minutes with either normothermic (23 degrees C) or hypothermic (5 degrees C) perfusate. Corneas were then evaluated clinically (biomicroscopy), functionally (vital staining), and morphologically (scanning electron microscopy) for changes attributable to hypothermic perfusion. All 3 modes of evaluation suggested no difference in corneal endothelial integrity under the 2 experimental perfusion conditions. At the clinical and scanning electron microscope levels hypothermic perfusion does not show any effects on the corneal endothelium. Regional hypothermia is of theoretical and potential utility in procedures involving prolonged intraocular perfusion.

Animals↗