264 research outputs found
Calcium oxalate crystal adherence to hyaluronan-, osteopontin-, and CD44-expressing injured/regenerating tubular epithelial cells in rat kidneys
Retention of crystals in the kidney is an essential early step in renal
stone formation. Studies with renal tubular cells in culture indicate that
hyaluronan (HA) and osteopontin (OPN) and their mutual cell surface
receptor CD44 play an important role in calcium oxalate (CaOx) crystal
binding during wound healing. This concept was investigated in vivo by
treating rats for 1, 4, and 8 d with ethylene glycol (0.5 and 0.75%) in
their drinking water to induce renal tubular cell damage and CaOx
crystalluria. Tubular injury was morphologically scored on periodic
acid-Schiff-stained renal tissue sections and tissue repair assessed by
immunohistochemical staining for proliferating cell nuclear antigen. CaOx
crystals were visualized in periodic acid-Schiff-stained sections by
polarized light microscopy, and renal calcium deposits were quantified
with von Kossa staining. HA was visualized with HA-binding protein and OPN
and CD44 immunohistochemically with specific antibodies and quantified
with an image analyzer system. Already after 1 d of treatment, both
concentrations of ethylene glycol induced hyperoxaluria and CaOx
crystalluria. At this point, there was neither tubular injury nor crystal
retention in the kidney, and expression of HA, OPN, and CD44 was
comparable to untreated controls. After 4 and 8 d of ethylene glycol,
however, intratubular crystals were found adhered to injured/regenerating
(proliferating cell nuclear antigen positive) tubular epithelial cells,
expressing HA, OPN, and CD44 at their luminal membrane. In conclusion, the
expression of HA, OPN, and CD44 by injured/regenerating tubular cells
seems to play a role in retention of crystals in the rat kidney
Security in transnational interoperable PPDR communications: threats and requirements
The relevance of cross border security operations
has been identified as a priority at European level for a long time.
A European network where Public Protection and Disaster Relief
(PPDR) forces share communications processes and a legal
framework would greatly enforce response to disaster recovery
and security against crime. Nevertheless, uncertainty on costs,
timescale and functionalities have slowed down the
interconnection of PPDR networks across countries and limited
the transnational cooperation of their PPDR forces so far. In this
context, the European research project ISITEP is aimed at
developing the legal, operational and technical framework to
achieve a cost effective solution for PPDR interoperability across
European countries. Inter alia, ISITEP project is specifying a
new Inter-System-Interface (ISI) interface for the
interconnection of current TETRA and TETRAPOL networks
that can be deployed over Internet Protocol (IP) connectivity.
This approach turns communications security as a central aspect
to consider when deploying the new IP ISI protocol between
PPDR national networks. Ensuring that threats to the
interconnected communications systems and terminals are
sufficiently and appropriately reduced by technical, procedural
and environmental countermeasures is vital to realise the trusted
and secure communication system needed for the pursued PPDR
transnational cooperation activities. In this context, this paper
describes the framework and methodology defined to carry out
the development of the security requirements and provides a
discussion on the undertaken security risk and vulnerability
analysis.Peer ReviewedPostprint (author's final draft
Increased calcium oxalate monohydrate crystal binding to injured renal tubular epithelial cells in culture
The retention of crystals in the kidney is considered to be a crucial step
in the development of a renal stone. This study demonstrates the
time-dependent alterations in the extent of calcium oxalate (CaOx)
monohydrate (COM) crystal binding to Madin-Darby canine kidney (MDCK)
cells during their growth to confluence and during the healing of wounds
made in confluent monolayers. As determined by radiolabeled COM crystal
binding studies and confirmed by confocal-scanning laser microscopy,
relatively large amounts of crystals (10.4 +/- 0.4 micrograms/cm2) bound
to subconfluent cultures that still exhibited a low transepithelial
electrical resistance (TER < 400 omega.cm2). The development of junctional
integrity, indicated by a high resistance (TER > 1,500 omega.cm2), was
followed by a decrease of the crystal binding capacity to almost
undetectable low levels (0.13 +/- 0.03 microgram/cm2). Epithelial injury
resulted in increased crystal adherence. The highest level of crystal
binding was observed 2 days postinjury when the wounds were already
morphologically closed but TER was still low. Confocal images showed that
during the repair process, crystals selectively adhered to migrating cells
at the wound border and to stacked cells at sites were the wounds were
closed. After the barrier integrity was restored, crystal binding
decreased again to the same low levels as in undamaged controls. These
results indicate that, whereas functional MDCK monolayers are largely
protected against COM crystal adherence, epithelial injury and the
subsequent process of wound healing lead to increased crystal binding
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
Absence of a Transcellular Oxalate Transport Mechanism in LLC-PK1 and MDCK Cells Cultured on Porous Supports
Transepithelial oxalate transport across polarized monolayers of LLC-PK1 cells, grown on collagen-coated microporous membranes in Transwell culture chambers, was studied in double-label experiments using [14C]-oxalate together with [3H]-D-mannitol as an extracellular marker. The [14C]-labeled glucose analog α-methyl-glucoside (α-MG) was used as functional marker for active proximal tubular sugar transport. Cellular uptake of oxalate and α-MG at both the apical and basolateral plasma membrane was determined. When added to the upper compartment, α-MG was actively taken up at the apical membrane, directed through the cells to the basolateral membrane and transported to the lower compartment, indicating functional epithelial sugar transport by LLC-PK1 cells. In LLC-PK1 cells, the uptake of α-MG at the apical membrane was approximately 50 times higher than that at the basolateral membrane. In contrast to this active transport of sugar, LLC-PK1 cells did not demonstrate oxalate uptake either at the apical or basolateral plasma membrane. The apical-to-basolateral (A- \u3e B) flux of oxalate in LLC-PK1 cells was identical to the basolateral-to-apical (B- \u3e A) oxalate flux in these cells. Moreover these flux characteristics were similar to those found for D-mannitol, indicating paracellular movement for both compounds. From these data, it is concluded that, under the experimental conditions used, LLC-PK1 cells do not exhibit a specific transcellular transport system for oxalate
Cell type-specific acquired protection from crystal adherence by renal tubule cells in culture
Cell type-specific acquired protection from crystal adherence by renal tubule cells in culture.BackgroundAdherence of crystals to the surface of renal tubule epithelial cells is considered an important step in the development of nephrolithiasis. Previously, we demonstrated that functional monolayers formed by the renal tubule cell line, Madin-Darby canine kidney (MDCK), acquire protection against the adherence of calcium oxalate monohydrate crystals. We now examined whether this property is cell type specific. The susceptibility of the cells to crystal binding was further studied under different culture conditions.MethodsCell-type specificity and the influence of the growth substrate was tested by comparing calcium oxalate monohydrate crystal binding to LLC-PK1 cells and to two MDCK strains cultured on either permeable or impermeable supports. These cell lines are representative for the renal proximal tubule (LLC-PK1) and distal tubule/collecting duct (MDCK) segments of the nephron, in which crystals are expected to be absent and present, respectively.ResultsWhereas relatively large amounts of crystals adhered to subconfluent MDCK cultures, the level of crystal binding to confluent monolayers was reduced for both MDCK strains. On permeable supports, MDCK cells not only obtained a higher level of morphological differentiation, but also acquired a higher degree of protection than on impermeable surfaces. Crystals avidly adhered to LLC-PK1 cells, irrespective of their developmental stage or growth substrate used.ConclusionsThese results show that the prevention of crystal binding is cell type specific and expressed only by differentiated MDCK cells. The anti-adherence properties acquired by MDCK cells may mirror a specific functional characteristic of its in situ equivalent, the renal distal tubule/collecting ducts
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 polyanionsprecipitated with cetylpyridinium chloride (CPC), urinary macromolecular substances with different concentration ratios (UMSl0,50,90 and UMS\u27l0,50,90) 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\u27 10,50,90 from THPFU with UFU differed in inhibitory activity from that prepared by mixing UMSl0,50,90 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
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