Glomerular filtration of proteins: Clearance of anionic, neutral, and cationic horseradish peroxidase in the rat

Glomerular filtration of proteins: Clearance of anionic, neutral, and cationic horseradish peroxidase in the rat. Glomerular permeability to horseradish peroxidase, a protein slightly smaller than rat albumin but similar in shape, was studied in Wistar-Furth rats by using a purified neutral isozyme (HRP; molecular radius, ae=29.8 Å) as well as an anionic succinyl-derivative (sHRP ae=31.8 Å) and a cationized enzyme (cHRP, ae=30 Å). The clearance rate of the proteins was determined over a 20-min period using the amounts of enzyme actually filtered (i.e., protein in the urine and protein reabsorbed by tubules). Fractional clearance of cationic HRP (0.338 ± 0.019) exceeded that of neutral HRP (0.061 ± 0.005) by a factor of 5.5 and that of anionic HRP (0.007 ± 0.000) by a factor of 48. Tubular reabsorption was less than 10% of the filtered load. The experimental results indicate marked charge dependency of the filtration of proteins across the glomerulus. Fractional clearances for these proteins are significantly lower than those reported in the literature for dextrans of similar molecular radii. Other molecular properties such as shape and deformability may explain these differences.Filtration glomérulaire des protéines: Clearance de la peroxydase de raifort anionique, neutre ou cationique chez le rat. La perméabilité glomérulaire à la peroxydase de raifort, une protéine un peu plus petite que l'albumine de rat mais semblable par sa forme, a été étudiée chez des rats Wistar-Furth au moyen d'un isoenzyme neutre purifié (HRP; rayon moléculaire, ae = 29,8 Å), d'un dérivé succinylé anionique (sHRP, ae = 31,8 Å) et d'un enzyme cationique (cHRP, ae = 30 Å). La clearance des protéines a été déterminée sur une période de 20min en utilisant les quantités de protéines réellement filtrées (c'est-à-dire les protéines de l'urine et les protéines réabsorbées par les tubes). La clearance fractionnelle de HRP cationique (0,338 ± 0,019) est supérieure à celle de HRP neutre (0,061 ± 0,059 d'un facteur 5,5 et à celle de HRP anionique (0,007 ± 0,000) d'un facteur 48. La réabsorption tubulaire est inférieure à 10% de la charge filtrée. Les résultats expérimentaux indiquent que la filtration glomérulaire des protéines dépend de façon importante de leur charge. Les clearances fractionnelles de ces protéines sont significativement inférieures à celles rapportées dans la littérature pour les dextrans de mêmes rayons moléculaires. D'autres propriétés des molécules, telles que leur forme et leur déformabilité, peuvent expliquer ces différences

Influence of antigen distribution on the mediation of immunological glomerular injury

Influence of antigen distribution on the mediation of immunological glomerular injury. To determine if the site of immune reaction could influence the mediation and morphological expression of glomerular injury in experimental anti-glomerular basement membrane (anti-GBM) nephritis and membranous nephropathy, we studied the events that followed the in situ reaction of rat antibody with antigen planted in either the GBM (especially the lamina rara interna) or in the subepithelial space (SE). Non-nephritogenic amounts of noncomplement-fixing sheep anti-GBM or anti-tubular brushborder antibody were injected into separate groups of rats to plant sheep IgG in the GBM and SE, respectively. Kidneys containing sheep IgG were then transplanted into naive recipients that were passively immunized with rat anti-sheep IgG. There was marked proteinuria after 2 days (antigen in GBM: 226 ± 50.7; antigen in SE: 69 ± 50.7 mg/24 hr) that was abrogated by prior depletion of complement in both groups (antigen in GBM: 10.2 ± 1.7; antigen in SE: 14.3 ± 8.7 mg/24 hr). When antigen was planted in SE, inflammatory-cell depletion with either anti-neutrophil (PMN) serum or lethal irradiation had no effect on proteinuria. In contrast, anti-PMN abolished proteinuria (12.0 ± 5.6 mg/24 hr) and irradiation reduced it by 60% when antigen was in GBM. Glomeruli of kidneys with antigen in GBM were significantly larger and more hypercellular than those with antigen in SE after transplantation into immunized recipients. Endothelial cell injury and adherence of inflammatory cells to denuded GBM were prominent in the former (antigen in GBM), while glomeruli with antigen in SE showed only subepithelial deposits, adjacent slit-diaphragm displacement, and epithelial cell foot-process effacement. Thus, the reaction of antigen and antibody in glomeruli produced complement-mediated injury which was cell-independent when complex formation occurred on the outer aspect of the GBM but was cell-dependent when the same reagents reacted more proximally to the circulation. We therefore conclude that antigen distribution can critically influence the mediation and morphologic expression of immune glomerular injury and may, in part, account for variations in the clinical and histological manifestations of antibody-induced glomerular disease in humans.Influence de la distribution antigénique sur la médiation des lésions glomérulaires immunologiques. Afin de déterminer si le site de la réaction immune pourrait influencer la médiation et l'expression morphologique des lésions glomérulaires lors d'une néphrite expérimentale anti-membrane basale glomérulaire (anti-GBM) et d'une néphropathie extra-membraneuse, nous avons étudié les événements qui suivaient la réaction in situ d'anticorps de rat avec un antigène fixé soit dans la GBM (surtout dans la lamina rara interna), soit dans l'espace sous-épithélial (SE). Des quantités non nephritogènes d'anticorps anti-GBM, ou anti-bordure en brosse tubulaire de mouton ne fixant pas le complément ont été injectées à différents groupes de rats pour fixer de l'IgG de mouton dans la GBM et le SE, respectivement. Les reins contenant l'IgG de mouton étaient alors transplantés à des receveurs vierges passivement immunisés avec de l'IgG de rat antimouton. Il existait une protéinurie marquée après deux jours (antigène dans la GBM: 226 ± 50,7; antigène dans SE: 69 ± 50,7 mg/24 hrs) qui à été abrogé par une déplétion du complement dans les deux groupes (antigène dans la GBM: 10,2 ± 1,7; antigène dans SE: 14,3 ± 8,7 mg/24 hr). Lorsque l'antigène était fixé dans SE, une déplétion en cellules inflammatoires par du sérum anti-neutrophile (PMN) ou une irradiation léthale n'avaient pas d'effet sur la protéinurie. A l'opposé, anti-PMN supprimait la protéinurie (12,0 ± 5,6 mg/24 hr) et l'irradiation la réduisait de 60% lorsque l'antigène était dans la GBM. Les glomérules de reins ayant l'antigène dans la GBM étaient significativement plus gros et plus hyper-cellulaires que ceux ayant l'antigène dans SE après transplantation chez des receveurs immunisés. Les lésions cellulaires endothéliales et l'adhérence des cellules inflammatoires à des GBM nues étaient prédominantes chez les premiers (antigène dans la GBM) alors que les glomérules ayant l'antigène dans SE présentaient uniquement des dépôts sous-épithéliaux, un déplacement du slit-diaphragme adjacent et un effacement des pédicelles des cellules épithéliales. Ainsi, la réaction d'un antigène et d'un anticorps dans des glomérules a produit des lésions à médiation complémentaire indépentantes des cellules lorsque la formation de complexes survenait dans la partie extérieure de la GBM, mais dépendantes des cellules lorsque les mêmes réactifs interagissaient de façon plus proximale dans la circulation. Nous concluons donc que la distribution antigénique peut influencer de manière critique la médiation et l'expression morphologique des lésions glomérulaires immunes et qu'elle peut, en partie, rendre compte de variations dans les manifestations cliniques et histologiques de glomérulopathies à médiation par anticorps chez l'homme

Design of MARQUIS2: study protocol for a mentored implementation study of an evidence-based toolkit to improve patient safety through medication reconciliation.

BackgroundThe first Multi-center Medication Reconciliation Quality Improvement Study (MARQUIS1) demonstrated that implementation of a medication reconciliation best practices toolkit decreased total unintentional medication discrepancies in five hospitals. We sought to implement the MARQUIS toolkit in more diverse hospitals, incorporating lessons learned from MARQUIS1.MethodsMARQUIS2 is a pragmatic, mentored implementation QI study which collected clinical and implementation outcomes. Sites implemented a revised toolkit, which included interventions from these domains: 1) best possible medication history (BPMH)-taking; 2) discharge medication reconciliation and patient/caregiver counseling; 3) identifying and defining clinician roles and responsibilities; 4) risk stratification; 5) health information technology improvements; 6) improved access to medication sources; 7) identification and correction of real-time discrepancies; and, 8) stakeholder engagement. Eight hospitalists mentored the sites via one site visit and monthly phone calls over the 18-month intervention period. Each site's local QI team assessed opportunities to improve, implemented at least one of the 17 toolkit components, and accessed a variety of resources (e.g. implementation manual, webinars, and workshops). Outcomes to be assessed will include unintentional medication discrepancies per patient.DiscussionA mentored multi-center medication reconciliation QI initiative using a best practices toolkit was successfully implemented across 18 medical centers. The 18 participating sites varied in size, teaching status, location, and electronic health record (EHR) platform. We introduce barriers to implementation and lessons learned from MARQUIS1, such as the importance of utilizing dedicated, trained medication history takers, simple EHR solutions, clarifying roles and responsibilities, and the input of patients and families when improving medication reconciliation

Deposition of the membrane attack complex in healthy and diseased human kidneys

The membrane attack complex-also known as C5b-9-is the end-product of the classical, lectin, and alternative complement pathways. It is thought to play an important role in the pathogenesis of various kidney diseases by causing cellular injury and tissue inflammation, resulting in sclerosis and fibrosis. These deleterious effects are, consequently, targeted in the development of novel therapies that inhibit the formation of C5b-9, such as eculizumab. To clarify how C5b-9 contributes to kidney disease and to predict which patients benefit from such therapy, knowledge on deposition of C5b-9 in the kidney is essential. Because immunohistochemical staining of C5b-9 has not been routinely conducted and never been compared across studies, we provide a review of studies on deposition of C5b-9 in healthy and diseased human kidneys. We describe techniques to stain deposits and compare the occurrence of deposits in healthy kidneys and in a wide spectrum of kidney diseases, including hypertensive nephropathy, diabetic nephropathy, membranous nephropathy, IgA nephropathy, lupus nephritis, C3 glomerulopathy, and thrombotic microangiopathies such as the atypical hemolytic uremic syndrome, vasculitis, interstitial nephritis, acute tubular necrosis, kidney tumors, and rejection of kidney transplants. We summarize how these deposits are related with other histological lesions and clinical characteristics. We evaluate the prognostic relevance of these deposits in the light of possible treatment with complement inhibitors.Nephrolog