Use of the isolated perfused kidney model to assess the acute pharmacologic effects of cyclosporine and its vehicle, cremophor EL

"Nephrotoxicity" secondary to cyclosporine and its clinically used vehicle, Cremophor EL, was examined in the isolated perfused rat kidney model. This model allows the serial determination of renal hemodynamic and tubular functional studies over a 3-hr duration using a normothermic, low hematocrit (13-15%) perfusion system. Initial studies indicated that the addition of small quantities of Cremophor EL resulted in marked renal vasoconstriction with decreased renal blood flow and deterioration in renal tubular function. These effects were highly significant and were of the same magnitude whether or not cyclosporine was present in the system. Cyclosporine was therefore examined after being dissolved in another vehicle, methanol. A 10% (v/v) amount of plasma was necessary in the perfusate to prevent significant adsorption of cyclosporine to the perfusion apparatus. Cyclosporine at concentrations below 100 ng/ml resulted in minor changes in renal hemodynamics. Beginning at 100 ng/ml glomerular filtration rate dropped significantly and renal vascular resistance increased three-fold. Fractional excretion of sodium significantly increased and the urine:plasma inulin ratio significantly decreased. We conclude that the clinically used drug vehicle, Cremophor EL, has significantly adverse effects on renal hemodynamics and tubular function. In addition, CsA causes similar renal toxicity in a dose-dependent fashion. Simultaneous administration of these two nephrotoxic agents could contribute to the high incidence of acute renal failure seen after transplantation. These observations suggest that an alternate vehicle with less renal toxicity might significantly decrease the incidence of this clinical problem.     

The introduction of new vaccines into developing countries. IV: Global Access Strategies

This paper offers a framework for managing a comprehensive Global Access Strategy for new vaccines in developing countries. It is aimed at strengthening the ability of public-sector entities to reach their goals. The Bill and Melinda Gates Foundation and The Rockefeller Foundation have been leaders in stimulating the creation of new organizations - public/private product development partnerships (PDPs) - that seek to accelerate vaccine development and distribution to meet the health needs of the world's poor. Case studies of two of these PDPs - the Salmonella Anti-pneumococcal Vaccine Program and the Pediatric Dengue Vaccine Initiative - examine development of such strategies. Relying on the application of innovation theory, the strategy leads to the identification of six Components of Innovation which cover all aspects of the vaccine innovation process. Appropriately modified, the proposed framework can be applied to the development and introduction of other products in developing countries including drugs, and nutritional and agricultural products.     

Respiratory motor function in individuals with centronuclear myopathies

Introduction: Individuals with X‐linked myotubular myopathy (XLMTM) and other centronuclear myopathies (CNMs) frequently have profound respiratory insufficiency that requires support early in life. Still, few quantitative data exist to characterize respiratory motor function in CNM. Methods: We evaluated the reliance upon mechanical ventilation (MV), ventilatory kinematics, unassisted tidal volumes, and maximal respiratory pressures in 14 individuals with CNMs, including 10 boys with XLMTM. Results: Thirteen participants required full‐time, invasive MV. Maximal inspiratory pressures were higher in subjects who breathed unsupported at least 1 hour/day as compared with 24‐hour MV users [33.7 (11.9–42.3) vs. 8.4 (6.0–10.9) cm H₂O, P < 0.05]. Years of MV dependence correlated significantly with MEP (r = ?0.715, P < 0.01). Conclusions: Respiratory function in CNMs may be related to deconditioning from prolonged MV and/or differences in residual respiratory muscle strength. Results from this study may assist in evaluating severe respiratory insufficiency in neuromuscular clinical care and research. Muscle Nerve 53: 214–221, 2016     

Interventional nephrology: from episodic to coordinated vascular access care

In recent years, nephrologists have taken the initiative of performing vascular access-related procedures themselves. Because of their unique clinical perspective on dialysis access and better understanding of the intricacies of renal replacement therapy, nephrologists are ideally suited for this activity. This approach has minimized delays, decreased hospitalizations and decreased the use of temporary catheters, thereby improving medical care, decreasing costs and increasing patient convenience. Vascular access interventions commonly employed by nephrologists include vascular access education, vascular mapping, percutaneous balloon angioplasty, thrombectomy, intravascular coil and stent insertion and tunneled hemodialysis catheter-related procedures. While the performance of these procedures by nephrologists offers many advantages, appropriate training to develop the necessary procedural skills is critical. Recent data have emphasized that a nephrologist can be successfully trained to become a competent interventionalist. In addition to documenting excellent outcome data, multiple reports have demonstrated the safety and success of an interventional nephrology approach. The last decade has been a period of significant advances in this new field. This has been driven in part by the formation of the American Society of Diagnostic and Interventional Nephrology (ASDIN), whose mission includes training, quality assurance and certification. Recently, the ASDIN has published guidelines for training in nephrology-related procedures and has begun certifying physicians in specific procedures related to chronic kidney disease. It is anticipated that this will promote the skillful performance of these procedures by nephrologists and lead to substantial improvements in the care of renal patients. Challenges for the future include awareness of this subspecialty and development of training programs at academic centers on a larger scale.     

Vascular mapping techniques: advantages and disadvantages

At present, an arteriovenous fistula is the best available access when compared with an arteriovenous graft or a tunneled hemodialysis catheter. Preoperative vascular mapping has been shown to result in an increased placement of arteriovenous fistulae. In general, 3 modalities (physical examination, ultrasound examination and angiographic evaluation) are available for vascular evaluation. Both arterial as well as venous examination can be conducted using physical examination. However, this technique is known to miss veins, especially in the obese, and result in exclusion of patients who do not show adequate veins on clinical inspection, but who have suitable veins (proven by the other modalities) for AVF construction. Ultrasound examination of the vessels is an objective assessment. It provides an excellent evaluation of both arteries and veins for creation of an arteriovenous fistula. The technique is limited by its inability to directly visualize the central veins. Although imaging of the veins by the administration of radiocontrast dye optimally visualizes peripheral as well as central veins, it exposes the patient to the risk of radiocontrast-induced nephropathy. This article presents advantages and disadvantages of the 3 mapping techniques and proposes a strategy to conduct vascular mapping in patients with chronic kidney disease.     

Hemoglobin Variability in Nondialysis Chronic Kidney Disease: Examining the Association with Mortality

Background and objectives: Anemia and hemoglobin (Hb) variability are associated with mortality in hemodialysis patients who are on erythropoiesis-stimulating agents (ESA). Our aim was to describe the degree of Hb variability present in nondialysis patients with chronic kidney disease (CKD), including those who were not receiving ESA, and to investigate the association between Hb variability and mortality.Design, setting, participants, & measurements: Hb variability was determined using 6 mo of “baseline” data between January 1, 2003, and October 31, 2005. A variety of definitions for Hb variability were examined to ensure consistency and robustness.Results: A total of 6165 patients from 22 centers in seven countries were followed for a mean of 34.0 ± 15.8 mo; 49% were prescribed an ESA. There was increased Hb variability with ESA use; the residual SD of Hb was 4.9 ± 4.4 g/L in patients who were not receiving an ESA, compared with 6.8 ± 4.8 g/L. Hb variability was associated with a small but significantly increased risk for death per g/L residual SD, irrespective of ESA use. Multivariate linear regression model explained only 11% of the total variance of Hb variability.Conclusions: Hb variability is increased in patients who have CKD and are receiving ESA and is associated with an increased risk for death (even in those who are not receiving ESAs). This analysis cannot determine whether Hb variability causally affects mortality. Thus, the concept of targeting Hb variability with specific agents needs to be examined within the context of factors that affect both Hb variability and mortality.Substantial numbers of epidemiologic studies have described the association of anemia with worse outcomes in all populations, including chronic kidney disease (CKD) populations. More recently, the identified phenomenon of hemoglobin (Hb) variability (the oscillations or fluctuations of an individual dialysis patient''s Hb over time) (1–5) has also been associated with adverse outcomes and has received increasing attention as a therapeutic target (4,6–9). It remains unclear what the best method is to define or measure Hb variability and whether its association with adverse outcomes is simply an epiphenomenon or a causal relationship. Furthermore, CKD studies to date have been primarily restricted almost exclusively to hemodialysis patients who were receiving erythropoiesis-stimulating agents (ESA) (1–8)Debate exists on which factors may influence the severity and frequency of Hb variability. Identification of these factors is necessary if manipulation of Hb variability in experimental or clinical settings is a goal (3,4,8,10,11,12). There are some data to suggest that physician prescribing patterns of ESA and the type of ESA affect variability; however, because both may be confounded by other factors, the specific contribution of these and other factors to Hb variability remains uncertain (3,4,10,11,12).The goal of this analysis was to assess the presence of anemia and Hb variability within a culturally diverse, nondialysis CKD population that included patients who were not receiving ESA therapy. We assessed the association of Hb variability with mortality and explored factors that are associated with Hb variability.     

A high-resolution association mapping panel for the dissection of complex traits in mice

Systems genetics relies on common genetic variants to elucidate biologic networks contributing to complex disease-related phenotypes. Mice are ideal model organisms for such approaches, but linkage analysis has been only modestly successful due to low mapping resolution. Association analysis in mice has the potential of much better resolution, but it is confounded by population structure and inadequate power to map traits that explain less than 10% of the variance, typical of mouse quantitative trait loci (QTL). We report a novel strategy for association mapping that combines classic inbred strains for mapping resolution and recombinant inbred strains for mapping power. Using a mixed model algorithm to correct for population structure, we validate the approach by mapping over 2500 cis-expression QTL with a resolution an order of magnitude narrower than traditional QTL analysis. We also report the fine mapping of metabolic traits such as plasma lipids. This resource, termed the Hybrid Mouse Diversity Panel, makes possible the integration of multiple data sets and should prove useful for systems-based approaches to complex traits and studies of gene-by-environment interactions.Human complex trait genetics has been revolutionized by the ability to carry out association studies on a genome-wide basis. Such genome-wide association studies (GWAS) have now been applied to numerous complex traits and have resulted in the identification of hundreds of novel genes for traits, such as diabetes, cancer, and various inflammatory diseases (Altshuler et al. 2008; Manolio 2009). This success can be attributed to many factors, including technological developments in acquiring high-throughput genotype data (Matsuzaki et al. 2004; Gunderson et al. 2005), development of catalogs of common human variation, such as the HapMap (The International HapMap Consortium 2005), and development of analytic methodologies for association studies (de Bakker et al. 2005). These have allowed the human genetics community to leverage the increased power and resolution of association studies compared to linkage analyses. Despite these successes, the fraction of the genetic component that is explained by the associated genes in GWA studies has been relatively modest for most traits (Hardy and Singleton 2009). For example, traits such as type 2 diabetes and lipoprotein levels have relatively high heritability, in the range of 50%, and yet the genes discovered by GWAS for these traits explain in aggregate less than 10% of the phenotypic variance. This can likely be attributed to several factors; in particular, the effects of a single common variant on a disease trait tend to be very weak and GWA studies have low power to detect rare variation involved in disease (Cohen et al. 2004; Frikke-Schmidt et al. 2004).Mouse models have been used effectively for the identification of genes contributing to simple Mendelian traits, but unfortunately there have been few successes for genes contributing to complex, multigenic traits. Traditional genetic analysis in mice involves crossing different inbred strains and mapping the traits of interest using linkage analysis. An important problem has been the lack of resolution in identifying the causal gene(s) from the results of a linkage study. Fine mapping in such cases generally requires the construction of congenic strains, in which the region of interest from one strain is transferred onto the background of the second strain by a series of crosses. But this frequently proves difficult because the alleles contributing to complex traits generally exhibit subtle effects that approach the levels of noise (Flint and Mott 2008), and several closely linked genes may influence the trait at a given locus.Encouraged by the success of human association studies, several groups have proposed mouse genome-wide association studies. These initial pioneering studies demonstrated the potential of mouse genome-wide association studies with their early successes, but they have also raised some important challenges including complex population stratification among the mouse strains and concerns about the lack of power to detect loci with modest effects (Pletcher et al. 2004; de Bakker et al. 2005; Payseur and Place 2007). In fact, these two issues are intimately related. Population structure inflates the association statistics, both creating spurious associations, as well as artificially increasing the apparent strength of true association signals. The initial mouse genome-wide association studies reported a tremendous number of genome-wide significant signals, some of which overlapped with known loci. This, combined with the knowledge that mouse strains have high heritability for traits, suggested that mouse association studies had sufficient statistical power. However, these initial studies did not adequately correct for population structure, which when taken into account, eliminates the vast majority of predicted associations (Kang et al. 2008). Thus, the inability to correct for population structure in the initial studies led them to severely overestimate their statistical power.We have explored a wide range of possible designs for mouse association studies using simulations that can accurately measure statistical power after correction for population structure. We assembled a combined set of inbred strains, which we term the “Hybrid Mouse Diversity Panel” (HMDP) that includes 100 commercially available inbred strains consisting of 29 classic inbred (CI) strains and three sets of recombinant inbred (RI) strains. Here, we report that the HMDP has sufficient power to map traits that contribute to 10% of the overall variance. Importantly, the resolution of the panel is an order of magnitude better than linkage analysis. Practical advantages of the HMDP include the elimination of costly genotyping, as these strains have now been genotyped at over 135,000 SNPs (http://mouse.cs.ucla.edu/mouseHapMap/), and the availability of the strains from The Jackson Laboratory. In addition, each strain is renewable and, therefore, diverse molecular and phenotypic data can be collected ad infinitum. Thus, this panel should be useful for the analysis of gene-by-environment interactions where multiple individuals of the same genotype need to be studied. Moreover, the fact that the data involving clinical, expression, proteomic, and metabolic traits are cumulative makes this resource ideal for systems biology.     

Development and evaluation of the advanced trauma operative management course

BACKGROUND: The Advanced Trauma Operative Management (ATOM) course was developed as a model for teaching operative trauma techniques to surgical residents, fellows, and attending surgeons as the number of these cases decreases. METHODS: The ATOM course consists of lectures and a porcine operative experience. Comprehensive evaluation of ATOM was designed to assess participant learning in the cognitive, affective, and psychomotor domains. Data on the first 50 participants were prospectively collected and analyzed. RESULTS: Participants included 20 expert traumatologists, 9 general surgeons, 9 trauma fellows, 8 general surgery fifth-year residents, and 4 general surgery fourth-year residents. All groups showed improvement in knowledge, with results in the expert and fellow groups reaching statistical significance. Self-efficacy (self-confidence) also improved, with all groups reaching statistical significance. CONCLUSION: This course creates life-like situations in a standardized fashion that, along with didactic instruction, improves knowledge and operative confidence for practicing surgeons and surgeons-in-training.     

A randomized controlled trial of oral versus intravenous iron in chronic kidney disease

BACKGROUND: It is unknown whether intravenous iron or oral iron repletion alone can correct anemia associated with chronic kidney disease (CKD). We conducted a randomized multicenter controlled trial in adult anemic, iron-deficient non-dialysis CKD (ND-CKD) patients (>or=stage 3) not receiving erythropoiesis-stimulating agents (ESAs). METHODS: The participants were randomized to receive either a sodium ferric gluconate complex (intravenous iron) 250 mg i.v. weekly x 4 or ferrous sulfate (oral iron) 325 mg t.i.d. x 42 days. Hemoglobin (Hgb), ferritin and transferrin saturation (TSAT) were measured serially, and the Kidney Disease Quality of Life (KDQoL) questionnaire was administered on days 1 and 43. The primary outcome variable was change from baseline (CFB) to endpoint in Hgb values. RESULTS: Seventy-five patients were analyzed (intravenous iron n = 36, oral iron n = 39). CFB in Hgb was similar in the two groups (intravenous iron 0.4 g/dl vs. oral iron 0.2 g/dl, p = n.s.). However, the increase in Hgb was only significant with intravenous iron (p < 0.01). In comparison to oral iron, intravenous iron achieved greater improvements in ferritin (232.0 +/- 160.8 vs. 55.9 +/- 236.2 ng/ml, p < 0.001) and TSAT (8.3 +/- 7.5 vs. 2.9 +/- 8.8%, p = 0.007). Intravenous iron caused greater improvements in KDQoL scores than oral iron (p < 0.05). The most common side effect reported with intravenous iron was hypotension, while constipation was more common with oral iron. CONCLUSIONS: Oral and intravenous iron similarly increase Hgb in anemic iron-depleted ND-CKD patients not receiving ESAs. Although in comparison to oral iron, intravenous iron may result in a more rapid repletion of iron stores and greater improvement in quality of life, it exposes the patients to a greater risk of adverse effects and increases inconvenience and cost.