Glycosaminoglycans and semisynthetic sulfated polysaccharides: an overview of their potential application in treatment of patients with urolithiasis.
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Animals↗
Biomedical subjects
W C de Bruijn
Publications and source records attributed to W C de Bruijn.
New developments and applications in quantitative electron spectroscopic imaging of iron in human liver biopsies.
Reliable iron concentration data can be obtained by quantitative analyses of image sequences, acquired by electron spectroscopic imaging. A number of requirements are formulated for the successful application of this recently developed in situ quantitative type of analysis. A demonstration of the procedures is given. By application of the technique it is established that there are no significant differences in the average iron loading of structures analysed in liver parenchymal cells of a patient with an iron storage disease, before and after phlebotomy. This supports the hypothesis that the process of iron unloading is an organelle specific process. Measurement of the binary morphology, represented by the area and contour ratio of the iron containing objects revealed no information about differences between the objects. This finding contradicts the visual suggestion that ferritin clusters are more irregularly shaped than the other iron objects. Also, no differences could be found in this sense between the situations before and after phlebotomy. With respect to the density appearance, objects that have an inhomogeneous iron loading averagely contain more iron. This observation does correspond well with the visual impression of the increasingly irregular appearance of more well-loaded structures.
Biopsy↗
Does urinary oxalate interfere with the inhibitory role of glycosaminoglycans and semisynthetic sulfated polysaccharides in calcium oxalate crystallization?
OBJECTIVES: Previously it was shown that the polysaccharide G872 in vitro strongly inhibits calcium oxalate monohydrate crystallization processes. However, when rats on a stone-inducing diet of ethylene glycol plus vitamin D3 are given this polysaccharide, no changes in the urine capacity for crystallization inhibition were found. We investigated here how the inhibitory action of polysaccharides changes under high oxalate conditions, as they exist in the stone inducing diet. METHODS: Calcium oxalate monohydrate (COM) crystals were incubated in a series of 0.05 M PBS buffers containing polysaccharides with increasing oxalate concentrations (0-0.4 mmol/l). The coated crystals were collected, washed and resuspended in an artificial urine. We then measured the zeta potential of the crystals, using a Coulter DELSA 440, and the initial rates for crystal growth and agglomeration, using the Coulter Multisizer II. RESULTS: Addition of oxalate to the medium shifts the negative zeta potential distribution of COM crystals coated by polysaccharides in positive direction. Particle size analysis demonstrated that the initial rates of COM crystal growth and agglomeration responding to oxalate concentration changes (0.1-->0.4 mmol/l) in the presence of G872 (0.2 mg/l) are approximately 2.5 times faster than that in the absence of G872. CONCLUSIONS: Oxalate interferes with the binding of polysaccharides to crystals. This can be envisioned to occur through changes in the crystal surface properties or by induction of functional and secondary structural changes of urinary macromolecular inhibitors such as GAGs, resulting in a decrease of their inhibitory activity against COM crystallization. Thus, in urine, a high oxalate may increase the rate of crystallization both by increasing the supersaturation and by decreasing the inhibitory potential of the urine.
Calcium Oxalate↗
Ultrastructural osteopontin localization in papillary stones induced in rats.
OBJECTIVES: To detect in situ the precise osteopontin (OPN) localization in papillary stones. METHODS: Immunocytochemical labelling procedures are applied to detect OPN localizations in crystalline material of renal papillary stones. The tissue-processing procedure for electron microscopy, which includes OsO4 postfixation, preserves both immunocytochemical OPN reactivity and cellular membrane contrast up to the ultrathin section. Reflection-contrast light microscopical images are correlated with high resolution transmission-electron microscopical observations from consecutive ultrathin epon sections. RESULTS: Preserved crystalline material in interstitial and peripheral papillary stones is recognized as calcium oxalate monohydrate. After section incubation with markers conjugated to an antibody against OPN (alpha OPN) the crystals are converted into ghosts. In the ghosts, alpha OPN markers are present around microcrystals. The size of these microcrystals ranges from several nanometers to micrometers. It is observed (due to the OsO4-preserved membranes) that interstitial cells are separated from the stone surfaces by unidentified extracellular material, also present in the center as a stone matrix. CONCLUSION: The microcrystal-growth inhibitor OPN is detected in situ in interstitial stones induced in the rat's papilla and at the surface of the papilla.
Animals↗
Zeta potential measurement and particle size analysis for a better understanding of urinary inhibitors of calcium oxalate crystallization.
To better understand urinary inhibitors of calcium oxalate crystallization, both zeta potential measurement and particle size analysis were chosen to illustrate: (1) the potential therapeutic efficacy of G872, a semi-synthetic sulfated polysaccharide, in stone prevention; and (2) the relative contribution of various urinary fractions ¿e.g., ultrafiltered urine (UFU), Tamm-Horsfall protein (THP), urinary polyanions precipitated with cetylpyridinium chloride (CPC), urinary macromolecular substances with different concentration ratios (UMS10,50,90 and UMS'10,50,90) and THP-free urine (THPFU)¿ to total urinary inhibitory activity. The results showed: (1) addition of G872 significantly enhances urinary inhibitory activity and negative zeta potential values; (2) re-addition of the CPC to UFU completely restores urinary inhibitory activity; and (3) artificial urines prepared by mixing UMS'10,50,90 from THPFU with UFU differed in inhibitory activity from that prepared by mixing UMS10,50,90 from a pooled normal urine with UFU. Based on these experimental results, the following speculations can be made: (1) normal human urines are considered to be a protective colloidal system; (2) urinary inhibitory activity originates mainly from CPC and/or UMS; (3) normal THP is a protective material to maintain urinary inhibitory activity; and (4) mutual interaction between urinary inhibitors may change the total urinary inhibitory activity.
Calcium Oxalate↗
Lectin-cytochemistry of experimental rat nephrolithiasis.
Lectin reactivity in epithelial apical cell coats of normal rat kidneys was compared to that from animals subjected to crystal inducing diets (CID). The aim was to see whether the absence of lectin reactivity in cell coats is related to intratubular calcium oxalate crystal retention. In normal rat kidneys, after a pre-embedding procedure, it was observed that at the ultrastructural level, reactivity was present but that the lectin specificity for the various parts of the nephron might have to be reconsidered. There was heterogeneity between the epithelial cells with respect to the presence of coat material in the tubular cell apices. Tubular epithelial cell apices from CID rats showed no obvious changes in lectin reactivity pattern. Lectin reactivity was present at the periphery of intratubular crystals but undetectable at true crystal attachment sites or reduced at cell apices in the vicinity of recently attached crystals or agglomerates. After a post-embedding reaction procedure, wheat-germ agglutinin (WGA)-lectin reactivity confirmed the presence of coat material in the cleft between cell apex and retained crystal at crystal-attachment sites. The WGA/Au-10 nm reaction products were also seen inside epithelial cells. WGA/Au-10 nm reaction products mark a crystal matrix component inside intratubular and retained crystals. A similar matrix was also marked by an alpha-osteopontin (alpha OPN/Au-10 nm) reaction product.
Animals↗
Pathological and immunocytochemical changes in chronic calcium oxalate nephrolithiasis in the rat.
In the present study, we exposed rats to a crystal-inducing diet (CID) consisting of vitamin D3 and 0.5% ethylene glycol (EG), and we investigated histologically the kidney damage induced by the deposition of calcium oxalate (CaOx) crystals. After 28 days, 50% of the animals had renal CaOx crystals, of which 60% also had small papillary stones. Most crystals were present in the cortex. The occurrence of these crystals coincided with morphological and cytochemical changes: glomerular damage, tubular dilatation and necrosis, and an enlargement of the interstitium. The number of epithelial and interstitial cells positive for the proliferating cell nuclear antigen (PCNA) was increased. Tamm-Horsfall protein (THP) was not only demonstrable in the thick ascending limb of the loop of Henle (TAL), but also frequently in glomeruli, in the proximal tubular epithelium, and in the papilla. In the lumen of the tubular system, it was associated with urinary casts. Reflection contrast microscopy (RCM) showed that the crystals were coated with a thin layer of THP. In spite of the high urinary oxalate concentrations, the above described cellular changes were not observed in CID-fed rats without renal crystals. We conclude, therefore, that in the kidney, the retained CaOx crystals rather than the urinary oxalate ions are responsible for the observed morphological and immunocytochemical changes.
Animals↗
Experimental nephrolithiasis in rats: the effect of ethylene glycol and vitamin D3 on the induction of renal calcium oxalate crystals.
Using ethylene glycol (EG) and vitamin D3 as crystal-inducing diet (CID) in rats, we investigated the effect of the dosage of EG on the generation of chronic calcium oxalate (CaOx) nephrolithiasis. We collected weekly 24 hour urines and measured herein the amount of oxalate, calcium, glycosaminoglycans (GAG's), creatinine, protein, alkaline phosphatase (AP), gamma-glutamyl transpeptidase (gamma-GT), and N-acetyl-beta-glucosaminidase (NAG). The potential of these urines to inhibit crystal growth and agglomeration was also evaluated. After four weeks, the kidneys were screened by histology and radiography for the presence of CaOx crystals and the amount of kidney-associated oxalate was biochemically measured. Using 0.5 vol.% EG, only a part of the rats showed CaOx deposition in the renal cortex and/or medulla, without obvious differences between Wistar and Sprague-Dawley (SD) rats. If a dietary EG concentration of 0.75, 1.0, or 1.5 vol.% was used, the amount of kidney-associated oxalate was proportionally higher and CaOx crystal formation was consistently found in all rats. Most crystals were encountered in the cortex, whereas in the medulla and the papillary region, crystals were only occasionally detected. From these data, we conclude that in the chronic rat model, based on EG and vitamin D3, a consistent deposition of CaOx crystals is obtained using a EG concentration of at least 0.75%.
Animals↗
Biocompatibility study of as-polymerized poly(L-lactide) in rats using a cage implant system.
To evaluate the biocompatibility of in vitro predegraded as polymerized poly(L-lactide) (PLLA), a cage implant system was used to investigate white cell and enzyme concentrations with time. The use of a cage permits in a serial fashion a quantitative and qualitative measurement of exudate components formed around an implant. Subcutaneously in rats, caped cages manufactured from stainless-steel mesh were implanted with in vitro predegraded, as-polymerized PLLA, as-polymerized PLLA cylinders, and empty cages serving as controls. In vitro predegradation was used to simulate the degradation products of long-term in vitro degradation. Predegraded PLLA particles were obtained by in vitro hydrolysis at elevated temperatures. The first 7 days of implantation were characterized by an acute inflammatory reaction; the exudate extracted from the cages showed predominantly neutrophils for all types of implants. After day 7, there was a more chronic inflammatory reaction with predominantly macrophages and lymphocytes. There were no significant differences in the total leukocyte concentration or macrophage concentration for any of the cages in the period from 10-21 days. Extracellular enzyme activity also did not show any significant differences among the three types of cages. A possible explanation for the absence of any significant differences could be that the in vitro predegraded particles were sieved before implantation, thus eliminating all small particles (< 70 microns) that are probably mandatory to provoke an increased cellular reaction.
Animals↗
Late degradation tissue response to poly(L-lactide) bone plates and screws.
Patients with fractures of the zygomatic bone were treated with high molecular weight poly(L-lactic) acid (PLLA) bone plates and screws. Three years after implantation four patients returned to our department with a swelling at the site of implantation. At the recall of the remaining patients we found an identical type of swelling after the same implantation period. To investigate the nature of the tissue reaction, eight patients were reoperated for the removal of the swelling. The implantation period of the PLLA material varied from 3.3 to 5.7 years. Microscopic evaluation and molecular weight measurements were performed. The excised material showed remnants of degraded PLLA material surrounded by a dense fibrous capsule. Ultrastructural investigation showed crystal-like PLLA material internalized by various cells. The results of this investigation suggest that the PLLA material slowly degrades into particles with a high crystallinity. The intra- and extracellular degradation rate of these particles is very low. After 5.7 years of implantation, these particles were still not fully resorbed.
Acid Phosphatase↗
In vivo degradation and biocompatibility study of in vitro pre-degraded as-polymerized polyactide particles.
The degradation of high molecular weight as-polymerized poly(L-lactide) (PLLA) is very slow; it takes more than 5.6 yr for total resorption. Moreover, the degradation products of as-polymerized PLLA bone plates, consisting of numerous stable particles of high crystallinity, are related with a subcutaneous swelling in patients 3 yr postoperatively. In order to avoid these complications, polymers were developed that are anticipated to have comparable mechanical properties but a higher degradation rate and do not degrade into highly stable particles that can induce a subcutaneous swelling. On chemical grounds it can be expected that copolymerization of PLLA with 4% D-lactide (PLA96) or by modifying PLLA through cross-linking (CL-PLLA) will lead to less stable particles and a higher degradation rate. To evaluate the long-term suitability of these as-polymerized polymers, the biocompatibility of the degradation products should be studied. Considering the very slow degradation rate of as-polymerized PLLA, in vitro pre-degradation at elevated temperatures was used to shorten the in vivo follow-up periods. In this study, the biocompatibility and degradation of as-polymerized PLLA, PLA96 and CL-PLLA were investigated by implanting pre-degraded particulate materials subcutaneously in rats. Animals were killed after a postoperative period varying from 3 to 80 wk. Light and electron microscopical analysis and quantitative measurements were performed. The histological response of all three pre-degraded materials showed a good similarity with in vivo implanted material. Pre-degraded PLLA induced a mild foreign body reaction and showed a slow degradation rate.(ABSTRACT TRUNCATED AT 250 WORDS)
Animals↗
Association of calcium oxalate monohydrate crystals with MDCK cells.
Many factors are presently known which determine the risk of calcium oxalate (CaOx) stone formation in the kidney, although the early events in the pathogenesis of this disease are still to be elucidated. One of these early events is the interaction of intraluminal crystals with the epithelial cells lining the renal tubules. In this study we determined the interaction of approximately 2 microns calcium oxalate monohydrate (COM) crystal with monolayers of Madin-Darby canine kidney (MDCK) cells grown on porous supports in a two-compartment culture system. Crystal-cell interaction studies were performed after the monolayers reached their highest level of gamma-glutamyltranspeptidase (gamma GT) enzyme activity, a marker for brush border development. Technical aspects were evaluated, such as the size and morphology of the crystals and the influence of incubation time, temperature and pH on crystal-cell interaction. Kinetic data demonstrated that an equilibrium between free and associated particles was reached within 30 minutes. Crystal-cell interaction was often associated with cell damage. However, evidence is provided that in an environment that was saturated with calcium oxalate, MDCK cells in an environment that was a certain amount of COM crystals without sustaining measurable injury. After initial attachment to the cell surface, crystals were taken up and subsequently eliminated again from the monolayers. The model system described in this paper provides a tool for detailed studies of processes that are involved in renal cellular handling of luminal COM crystals.
Analysis of Variance↗
The difference in liver pathology between sporadic and familial forms of porphyria cutanea tarda: the role of iron.
Porphyria cutanea tarda is a disorder of porphyrin metabolism, of which familial and sporadic forms have been described. Factors such as iron seem necessary for porphyria cutanea tarda to become clinically manifest. To study the relationship between iron and uroporphyrins in hepatocytes of patients with porphyria cutanea tarda, a morphological and morphometrical study was performed in 13 liver biopsies of patients with porphyria cutanea tarda (eight with sporadic porphyria cutanea tarda and five with familial porphyria cutanea tarda). In addition, possible differences in clinical and biochemical features and in histopathological findings between patients with sporadic porphyria cutanea tarda and familial porphyria cutanea tarda were investigated. Familial porphyria cutanea tarda patients presented at a younger age than sporadic porphyria cutanea tarda patients (42.4 +/- 5.3 vs. 57.3 +/- 8.6 years). Biochemical features were not different between sporadic porphyria cutanea tarda and familial porphyria cutanea tarda patients. Uroporphyrin crystals and a variable degree of liver siderosis were detected in the biopsies of all 13 patients. Uroporphyrin crystals were often found close to ferritin-like iron deposits. The morphometrical analysis showed that an increased mean area fraction of ferritin iron was associated with an increased mean area fraction of uroporphyrin crystals in hepatocytes of sporadic porphyria cutanea tarda and familial porphyria cutanea tarda patients. Moreover, the amount of uroporphyrin crystals was significantly higher in livers of familial porphyria cutanea tarda than sporadic porphyria cutanea tarda patients. These findings are consistent with the hypothesis that uroporphyria is precipitated by an iron-dependent process.(ABSTRACT TRUNCATED AT 250 WORDS)
Adult↗
Etiology of calcium oxalate nephrolithiasis in rats. I. Can this be a model for human stone formation?
Crystal retention is studied in a rat-model system as a possible mechanism for the etiology of human nephrolithiasis. A crystal-inducing diet (CID) of ethylene glycol plus NH4Cl in their drinking-water is offered to healthy rats to generate intratubular crystals. Subsequently, the fate of retained crystals is investigated by allowing the rats a tissue recovery/crystalluria phase for three, five and ten days, respectively, on normal drinking water. The process of exotubulosis is observed in cortex and medulla of aldehyde-fixed kidneys after three days recovery. After five days, crystals are predominantly seen there in the interstitium. After ten days, cortex and medulla are virtually free of crystals. However, in the papillary regions after five and ten days recovery, three types of calcium oxalate monohydrate (COM) crystals are present: (1) free in the calycine space, (2) sub-epithelially located surrounded by interstitial cells within, and (3) covered by macrophage-like cells, outside the original papillary surface. After a CID plus three days recovery, a further thirty-seven days extra oxalate challenge with solely 0.3 vol% ethylene glycol induced intratubular and interstitial oxalate crystals. In the papillary region, large sub-epithelial crystals are seen. However, no crystals are seen in kidneys from rats given solely (0.5 or 0.8 vol.%) ethylene glycol for thirty days. An oxalate re-challenge retards crystal removal.
Ammonium Chloride↗
Etiology of calcium oxalate nephrolithiasis in rats. II. The role of the papilla in stone formation.
In kidneys of healthy rats submitted to a crystal-inducing diet (CID) with ethylene glycol (EG) and NH4Cl, the fate of retained crystals in the papillar region is studied during a recovery period of one, five or ten days, as model system for human nephrolithiasis. Scanning electron microscopy (SEM) shows, at papillary tips bulging into the calycine space, crystal masses covered either by the epithelium or a thin fibrous veil, or by unidentified mobile cuboidal cells. After CID plus one or five days recovery, small sub-epithelial swellings are seen of large sub-epithelial crystals at or around the papillary tip. After CID plus ten days, massive sub-surface crystal-containing micrometer-sized stones are seen in which the presence of calcium is confirmed by X-ray microanalysis. The papillary tip of rats after a re-challenge with an oxalate load from 0.1 vol% EG for twelve or forty-two days shows minor lesions. But a re-challenge with 0.3 vol% EG for thirty-seven days induces large sub-epithelial papillary millimeter-sized stones. The Von Kossa section staining converts the crystals into a black precipitate, but large peri-tubular or peri-vascular calcium deposits are absent. A new hypothesis about the etiology of an inductive calcium oxalate monohydrate nephrolithiasis is formulated which differs from the one proposed by Randall based on his deductive human kidney studies.
Ammonium Chloride↗
Immunohistochemical light and electron microscopy of basal laminar deposit.
The formation of basal laminar deposit (BLD) is one of the histopathologic changes in the aging human macula. BLD is assumed to be an early stage of age-related macular degeneration. The location of BLD, between the RPE plasma membrane and its basement membrane and in the outer collagenous zone of Bruch's membrane, and its ultrastructure suggest that it is composed of excessive amounts of basement membrane material. The main components of basement membranes are type IV collagen, heparan sulfate proteoglycans (HSPG) and laminin. Labeled antibodies against these components can therefore be used for the identification and localization of basement membrane material by means of immunohistochemical techniques. In this study the presence of type IV collagen, laminin and HSPG was determined in aged human maculae by immunohistochemistry and immunoelectron microscopy. Tests for the presence of type VI collagen and fibronectin were also performed. We obtained 76 eyes from 68 human subjects at autopsy or after surgical enucleation for anteriorly located choroidal melanomas. The finely granular component of BLD stained positive with antibodies against type IV collagen, HSPG and laminin, but the long-spacing collagen component of BLD did not. Neither component of BLD was stained with antibodies against type VI collagen or fibronectin. We conclude that BLD consists partly of excess basement membrane material.
Adult↗
Glycosaminoglycans and other sulphated polysaccharides in calculogenesis of urinary stones.
Naturally occurring glycosaminoglycans (GAGs) and other, semisynthetic, sulphated polysaccharides are thought to play an important role in urolithiasis. Processes involved in urinary stone formation are crystallization and crystal retention. Oxalate transport and renal tubular cell injury are determining factors in these processes. In this article experimental results concerning the possible mechanisms of action of GAGs and other sulphated polysaccharides are reviewed. GAGs are inhibitors of crystal growth and agglomeration and possibly also of nucleation. They can prevent crystal adherence, correct an abnormal oxalate flux and prevent renal tubular cell damage.
Animals↗
Increased prevalence of disciform macular degeneration after cataract extraction with implantation of an intraocular lens.
After cataract extraction with implantation of an intraocular lens the increased transmission of ultraviolet and blue light may accelerate the development of age-related macular degeneration by producing free radicals in the retina. The maculae of 82 randomly selected postmortem human pseudophakic eyes and 16 fellow phakic eyes were examined by light microscopy. The presence of a basal laminar deposit, hard and soft drusen, thickening and calcification of Bruch's membrane, geographic atrophy, subretinal neovascularisation, and disciform scars was assessed in a standardised way. An age-matched series of 126 postmortem phakic eyes was used as control group. There was no difference between the two groups, except for a higher prevalence of hard drusen (exact trend test, p = 0.038) and disciform scars for the pseudophakic eyes (Fisher's exact test, p = 0.007). There was no significant correlation between either age-related changes in the macula or disciform degeneration and the length of time between cataract surgery and death. No significant difference was found between pseudophakic eyes with or without ultraviolet filter. These findings do not confirm that disciform scar formation is caused by an increase in ultraviolet or blue light.
Age Distribution↗