Eosinophils Recruited during Pulmonary Vaccination Regulate Mucosal Antibody Production.

Eosinophils have been previously shown to be able to regulate early humoral responses during systemic vaccination. Here we investigated the role of eosinophils during pulmonary vaccination, comparing vaccine-induced responses in eosinophil-deficient (ΔdblGATA) and wild-type mice using a Th2 adjuvant. We observed that eosinophils were needed to induce a complete vaccine response, thereby eliciting specific antibody-secreting plasma cells in the regional lymph nodes and antibody secretion in the BAL at the early stage of the immune response. Reintroduction of eosinophils in the lungs of ΔdblGATA mice during the priming stage enhanced both specific IgM and IgG plasma cells but not specific IgA plasma cells. Upon vaccination, eosinophils migrated to the lungs and secreted cytokines involved in B-cell activation, which might promote antibody production. Importantly, however, the absence of eosinophils did not impair late immune responses in a prime/boost protocol because, in that setup, we uncovered a compensating mechanism involving a Th17 pathway. In conclusion, our data demonstrate for the first time a new role for eosinophils during lung mucosal vaccination, whereby they accelerate early immune responses (IgM and IgG) while regulating IgA production at the late stages.

Assessing Nephrology Fellows' Skills in Communicating About Kidney Replacement Therapy and Kidney Biopsy: A Multicenter Clinical Simulation Study on Breaking Bad News.

RATIONALE & OBJECTIVE: Interpersonal communication skills and professionalism competencies are difficult to assess among nephrology trainees. We developed a formative "Breaking Bad News" simulation and implemented a study in which nephrology fellows were assessed with regard to their skills in providing counseling to simulated patients confronting the need for kidney replacement therapy (KRT) or kidney biopsy. STUDY DESIGN: Observational study of communication competency in the setting of preparing for KRT for kidney failure, for KRT for acute kidney injury (AKI), or for kidney biopsy. SETTING & PARTICIPANTS: 58 first- and second-year nephrology fellows assessed during 71 clinical evaluation sessions at 8 training programs who participated in an objective structured clinical examination of simulated patients in 2017 and 2018. PREDICTORS: Fellowship training year and clinical scenario. OUTCOME: Primary outcome was the composite score for the "overall rating" item on the Essential Elements of Communication-Global Rating Scale 2005 (EEC-GRS), as assessed by simulated patients. Secondary outcomes were the score for EEC-GRS "overall rating" item for each scenario, score < 3 for any EEC-GRS item, Mini-Clinical Examination Exercise (Mini-CEX) score < 3 on at least 1 item (as assessed by faculty), and faculty and fellow satisfaction with simulation exercise (via a survey they completed). ANALYTICAL APPROACH: Nonparametric tests of hypothesis comparing performance by fellowship year (primary goal) and scenario. RESULTS: Composite scores for EEC-GRS overall rating item were not significantly different between fellowship years (P = 0.2). Only 4 of 71 fellow evaluations had an unsatisfactory score for the EEC-GRS overall rating item on any scenario. On Mini-CEX, 17% scored < 3 on at least 1 item in the kidney failure scenario; 37% and 53% scored < 3 on at least 1 item in the AKI and kidney biopsy scenarios, respectively. In the survey, 96% of fellows and 100% of faculty reported the learning objectives were met and rated the experience good or better in 3 survey rating questions. LIMITATIONS: Relatively brief time for interactions; limited familiarity with and training of simulated patients in use of EEC-GRS. CONCLUSIONS: The fellows scored highly on the EEC-GRS regardless of their training year, suggesting interpersonal communication competency is achieved early in training. The fellows did better with the kidney failure scenario than with the AKI and kidney biopsy scenarios. Structured simulated clinical examinations may be useful to inform curricular choices and may be a valuable assessment tool for communication and professionalism.

Sharing innovations to enhance renal fellow education in dialysis.

Dialysis care is an integral part of the practice of nephrology. Despite this, education of fellows in providing dialysis often remains rudimentary, relying on a combination of didactics and learning through experience. This runs the risk of training nephrologists who can provide dialysis care without truly being experts on the subject. In this article, a collection of novel or innovative teaching methods is presented that are meant to provide training programs with additional tools with which to improve the training of their fellows in dialysis.

Implementation of nephrology subspecialty curricular milestones.

Beginning in the 2014-2015 training year, the US Accreditation Council for Graduate Medical Education (ACGME) required that nephrology Clinical Competency Committees assess fellows' progress toward 23 subcompetency "context nonspecific" internal medicine subspecialty milestones. Fellows' advancement toward the "ready for unsupervised practice" target milestone now is tracked in each of the 6 competencies: Patient Care, Medical Knowledge, Professionalism, Interpersonal Communication Skills, Practice-Based Learning and Improvement, and Systems-Based Practice. Nephrology program directors and subspecialty societies must define nephrology-specific "curricular milestones," mapped to the nonspecific ACGME milestones. Although the ACGME goal is to produce data that can discriminate between successful and underperforming training programs, the approach is at risk to produce biased, inaccurate, and unhelpful information. We map the ACGME internal medicine subspecialty milestones to our previously published nephrology-specific milestone schema and describe entrustable professional activities and other objective assessment tools that inform milestone decisions. Mapping our schema onto the ACGME subspecialty milestone reporting form allows comparison with the ACGME subspecialty milestones and the curricular milestones developed by the American Society of Nephrology Program Directors. Clinical Competency Committees may easily adapt and directly translate milestone decisions reached using our schema onto the ACGME internal medicine subspecialty competency milestone-reporting format.

Assessing achievement in nephrology training: using clinic chart audits to quantitatively screen competency.

BACKGROUND: Entrustable professional activities (EPAs) are complex tasks representing vital physician functions in multiple competencies, used to demonstrate trainee development along milestones. Managing a nephrology outpatient clinic has been proposed as an EPA for nephrology fellowship training. STUDY DESIGN: Retrospective cohort study of nephrology fellow outpatient clinic performance using a previously validated chart audit tool. SETTING & PARTICIPANTS: Outpatient encounter chart audits for training years 2008-2009 through 2012-2013, corresponding to participation in the Nephrology In-Training Examination (ITE). A median of 7 auditors (attending nephrologists) audited a mean of 1,686±408 (SD) charts per year. 18 fellows were audited; 12, in both of their training years. PREDICTORS: Proportion of chart audit and quality indicator deficiencies. OUTCOMES: Longitudinal deficiency and ITE performance. MEASUREMENTS & RESULTS: Among fellows audited in both their training years, chart audit deficiencies were fewer in the second versus the first year (5.4%±2.0% vs 17.3%±7.0%; P<0.001) and declined between the first and second halves of the first year (22.2%±6.4% vs 12.3%±9.5%; P=0.002). Most deficiencies were omission errors, regardless of training year. Quality indicator deficiencies for hypertension and chronic kidney disease-associated anemia recognition and management were fewer during the second year (P<0.001). Yearly audit deficiencies ≥5% were associated with an ITE score less than the 25th percentile for second-year fellows (P=0.03), with no significant association for first-year fellows. Auditor-reported deficiencies declined between the first and second halves of the year (17.0% vs 11.1%; P<0.001), with a stable positive/neutral comment rate (17.3% vs 17.8%; P=0.6), suggesting that the decline was not due to auditor fatigue. LIMITATIONS: Retrospective design and small trainee numbers. CONCLUSIONS: Managing a nephrology outpatient clinic is an EPA. The chart audit tool was used to assess longitudinal fellow performance in managing a nephrology outpatient clinic. Failure to progress may be quantitatively identified and remediated. The tool identifies deficiencies in all 6 competencies, not just medical knowledge, the primary focus of the ITE and the nephrology subspecialty board examination.

Expanding the role of objectively structured clinical examinations in nephrology training.

Objectively structured clinical examinations (OSCEs) are widely used in medical education, but we know of none described that are specifically for nephrology fellowship training. OSCEs use simulation to educate and evaluate. We describe a technically simple, multidisciplinary, low-cost OSCE developed by our program that contains both examination and training features and focuses on management and clinical knowledge of rare hemodialysis emergencies. The emergencies tested are venous air embolism, blood leak, dialysis membrane reaction, and hemolysis. Fifteen fellows have participated in the OSCE as examinees and/or preceptors since June 2010. All have passed the exercise. Thirteen responded to an anonymous survey in July 2013 that inquired about their confidence in managing each of the 4 tested emergencies pre- and post-OSCE. Fellows were significantly more confident in their ability to respond to the emergencies after the OSCE. Those who subsequently saw such an emergency reported that the OSCE experience was somewhat or very helpful in managing the event. The OSCE tested and trained fellows in the recognition and management of rare hemodialysis emergencies. OSCEs and simulation generally deserve greater use in nephrology subspecialty training; however, collaboration between training programs would be necessary to validate such exercises.

Genomic, transcriptomic, and metabolomic profiles of hiPSC-derived dopamine neurons from clinically discordant brothers with identical PRKN deletions.

We previously reported on two brothers who carry identical compound heterozygous PRKN mutations yet present with significantly different Parkinson's Disease (PD) clinical phenotypes. Juvenile cases demonstrate that PD is not necessarily an aging-associated disease. Indeed, evidence for a developmental component to PD pathogenesis is accumulating. Thus, we hypothesized that the presence of additional genetic modifiers, including genetic loci relevant to mesencephalic dopamine neuron development, could potentially contribute to the different clinical manifestations of the two brothers. We differentiated human-induced pluripotent stem cells (hiPSCs) derived from the two brothers into mesencephalic neural precursor cells and early postmitotic dopaminergic neurons and performed wholeexome sequencing and transcriptomic and metabolomic analyses. No significant differences in the expression of canonical dopamine neuron differentiation markers were observed. Yet our transcriptomic analysis revealed a significant downregulation of the expression of three neurodevelopmentally relevant cell adhesion molecules, CNTN6, CNTN4 and CHL1, in the cultures of the more severely affected brother. In addition, several HLA genes, known to play a role in neurodevelopment, were differentially regulated. The expression of EN2, a transcription factor crucial for mesencephalic dopamine neuron development, was also differentially regulated. We further identified differences in cellular processes relevant to dopamine metabolism. Lastly, wholeexome sequencing, transcriptomics and metabolomics data all revealed differences in glutathione (GSH) homeostasis, the dysregulation of which has been previously associated with PD. In summary, we identified genetic differences which could potentially, at least partially, contribute to the discordant clinical PD presentation of the two brothers.

Latent alterations in swimming behavior by developmental methylmercury exposure are modulated by the homolog of tyrosine hydroxylase in Caenorhabditis elegans.

Methylmercury (MeHg) is a persistent environmental neurotoxicant that may cause adverse neurodevelopmental effects. Previous studies showed that developmental MeHg exposure caused damage to brain functions that were unmasked after a silent period of years or decades. However, the underlying mechanisms of the latent neurotoxicity associated with MeHg exposure from earlier developmental stages have yet to be fully understood. Herein, we established a Caenorhabditis elegans (C. elegans) model of developmental MeHg latent toxicity. Synchronized L1 stage worms were exposed to MeHg (0, 0.05, 0.5 and 5 µM) for 48 h. Swimming moving speeds at adulthood were analyzed in worms exposed to MeHg exposure at early larvae stages. Worms developmentally exposed to MeHg had a significant decline in swimming moving speed on day 10 adult stage, but not on day 1 or 5 adult stage, even though the mercury level in the worms exposed to 0.05 or 0.5 µM MeHg were below the quantification limit on day 10 adult. Day 10 adult worms treated with MeHg showed a significant decrease in bending angle and bending frequency during swimming. Furthermore, their reduced moving speeds tended to increase during the 300-s swimming experiment. Dopamine signaling is known to be involved in the regulation of worms' moving speed. Accordingly, the moving speed of worms with cat-2 (mammalian tyrosine hydroxylase homolog) mutation or dat-1 deletion were assayed on day 10 adult. The cat-2 mutant worms did not show a decline in moving speeds, body bends or bending angles during swimming on day 10 adult stage. Analyses of moving speeds of worms with dat-1 deletion showed that the moving speeds were further reduced after MeHg exposure. However, the effects of MeHg and dat-1 deletion were not synergistic, as the interaction between these parameters did not attain statistical significance. Altogether, our results suggest that developmental MeHg exposure reduced moving speed, and this latent toxicity was less pronounced in the context of deficient production of dopamine synthesis. Tyrosine hydroxylase plays an important role in regulating dopamine-mediated modulation of neurobehavioral functions. These findings uncovered a pivotal role of dopamine and its metabolism in the latent neurotoxic effects of MeHg.

Chronic exposure to methylmercury disrupts ghrelin actions in C57BL/6J mice.

Methylmercury (MeHg) is a neurotoxic pollutant widely present in the environment. Initial symptoms of MeHg may include loss of body weight. However, the mechanisms by which MeHg induces body weight changes have yet to be fully elucidated. Body weight is regulated by multiple mechanisms. Whereas multiple peripheral peptides lead to food intake cessation, ghrelin is the only recognized peripheral hormone that stimulates food intake. It exerts its action on Neuropeptide Y/Agouti-related peptide neurons in the hypothalamus. To test if MeHg affects ghrelin signaling C57BL/6J mice (males and females) were exposed to 5 ppm MeHg via drinking water during a month. On days 15 and 30 of MeHg exposure ghrelin was administered intraperitoneally and changes in body weight and food intake were recorded. In addition, changes in ghrelin-induced signaling pathways in hypothalamus were also analyzed. Here, we show that in males, MeHg enhanced ghrelin-induced body weight gain by activating the AMP-activated Kinase (AMPK)/Uncoupled protein 2 (UCP2) signaling pathway. In contrast, in females, MeHg inhibited ghrelin-induced mTOR signaling activation and decreased Npy mRNA expression, thus mitigating the ghrelin-induced weight gain. Combined, our novel results demonstrate, for the first time, that MeHg disrupts the physiological functions of ghrelin differently in males and females.

The peritoneal dialysis orders objective structured clinical examination (OSCE): A formative assessment for nephrology fellows.

BACKGROUND: Peritoneal dialysis (PD) management is a fundamental nephrology skill, especially with the recent emphasis on home dialysis. We report a prospective multicentre cohort study of a formative objective structured clinical examination (OSCE) assessing competence in managing PD-associated bacterial peritonitis, using the unified model of construct validity. METHODS: The OSCE was developed by the principal investigators and reviewed by two subject matter experts. The test committee (eight nephrologists and one PD nurse) assessed test item difficulty/relevance and determined passing score. There were 22 test items (7 evidence-based/standard-of-care questions). Passing score was 16/22 (73%). No item had median relevance less than 'important', and all were easy to medium difficulty. Content validity index was 0.91. Preliminary validation (16 board-certified volunteers): mean score was 19 ± 2, with 94% (15/16) passing. Kappa = 0.85 [95% confidence interval (CI) 0.77-0.94]. Cronbach's α = 0.70. RESULTS: Eighty-seven fellows (16 programmes) were tested; 67% passed. Fellows scored significantly less than validators: 17 ± 3 versus 19 ± 2, p < 0.001 [95% CI 1.2-3.6]. Eighty-six per cent of evidence-based/standard-of-care questions were answered correctly by validators versus 54% by fellows; p < 0.001. Ninety-three per cent of fellows recognized that sufficient criteria were present to diagnose peritonitis, but only 17% correctly indicated all three. Seventy-seven per cent recognized peritonitis-associated ultrafiltration failure, but only 17% prescribed 21 days of antibiotic treatment for gram-negative peritonitis. Eighty-five per cent of fellows surveyed agreed/strongly agreed that the OSCE was useful in self-assessing proficiency. Second-year in-training examination and OSCE scores were positively correlated (Pearson's r = 0.57, p < 0.00). CONCLUSIONS: The OSCE may be used to formatively assess fellow proficiency in managing PD-associated peritonitis.

Single cell RNA sequencing detects persistent cell type- and methylmercury exposure paradigm-specific effects in a human cortical neurodevelopmental model.

The developing human brain is uniquely vulnerable to methylmercury (MeHg) resulting in lasting effects especially in developing cortical structures. Here we assess by single-cell RNA sequencing (scRNAseq) persistent effects of developmental MeHg exposure in a differentiating cortical human-induced pluripotent stem cell (hiPSC) model which we exposed to in vivo relevant and non-cytotoxic MeHg (0.1 and 1.0 µM) concentrations. The cultures were exposed continuously for 6 days either once only during days 4-10, a stage representative of neural epithelial- and radial glia cells, or twice on days 4-10 and days 14-20, a somewhat later stage which includes intermediate precursors and early postmitotic neurons. After the completion of MeHg exposure the cultures were differentiated further until day 38 and then assessed for persistent MeHg-induced effects by scRNAseq. We report subtle, but significant changes in the population size of different cortical cell types/stages and cell cycle. We also observe MeHg-dependent differential gene expression and altered biological processes as determined by Gene Ontology analysis. Our data demonstrate that MeHg results in changes in gene expression in human developing cortical neurons that manifest well after cessation of exposure and that these changes are cell type-, developmental stage-, and exposure paradigm-specific.

Chronic exposure to methylmercury enhances the anorexigenic effects of leptin in C57BL/6J male mice.

Several studies have demonstrated that heavy metals disrupt energy homeostasis. Leptin inhibits food intake and decreases body weight through activation of its receptor in the hypothalamus. The impact of heavy metals on leptin signaling in the hypothalamus is unclear. Here, we show that the environmental pollutant, methylmercury (MeHg), favors an anorexigenic profile in wild-type males. C57BL/6J mice were exposed to MeHg via drinking water (5 ppm) up to 30 days. Our data shows that MeHg exposure was associated with changes in leptin induced activation of Janus kinase 2 (JAK2)/signal transducer and activator of transcription 3 (STAT3) signaling pathway in the hypothalamus. In males, the activation of JAK2/STAT3 signaling pathway was sustained by an increase in SOCS3 protein levels. In females, MeHg-activated STAT3 was inhibited by a concomitant increase in PTP1B. Taken together, our data suggest that MeHg enhanced leptin effects in males, favoring an anorexigenic profile in males, which notably, have been shown to be more sensitive to the neurological effects of this organometal than females. A better understanding of MeHg-induced molecular mechanism alterations in the hypothalamus advances the understanding of its neurotoxicity and provides molecular sites for novel therapies.

Environmentally relevant developmental methylmercury exposures alter neuronal differentiation in a human-induced pluripotent stem cell model.

Developmental methylmercury (MeHg) exposure selectively targets the cerebral and cerebellar cortices, as seen by disruption of cytoarchitecture and glutamatergic (GLUergic) neuron hypoplasia. To begin to understand the mechanisms of this loss of GLUergic neurons, we aimed to develop a model of developmental MeHg neurotoxicity in human-induced pluripotent stem cells differentiating into cortical GLUergic neurons. Three dosing paradigms at 0.1 µM and 1.0 µM MeHg, which span different stages of neurodevelopment and reflect toxicologically relevant accumulation levels seen in human studies and mammalian models, were established. With these exposure paradigms, no changes were seen in commonly studied endpoints of MeHg toxicity, including viability, proliferation, and glutathione levels. However, MeHg exposure induced changes in mitochondrial respiration and glycolysis and in markers of neuronal differentiation. Our novel data suggests that GLUergic neuron hypoplasia seen with MeHg toxicity may be due to the partial inhibition of neuronal differentiation, given the increased expression of the early dorsal forebrain marker FOXG1 and corresponding decrease in expression on neuronal markers MAP2 and DCX and the deep layer cortical neuronal marker TBR1. Future studies should examine the persistent and latent functional effects of this MeHg-induced disruption of neuronal differentiation as well as transcriptomic and metabolomic alterations that may mediate MeHg toxicity.

Rodent hair is a Poor biomarker for internal manganese exposure.

Hair is used as a biomarker of manganese (Mn) exposure, yet there is limited evidence to support its utility to quantify internal vs external Mn exposure. C57BL/6 J mice and Sprague-Dawley rats were exposed in two blocks of 3 subcutaneous injections every 3 days starting on day 0 or 20. The control group received two blocks of saline (vehicle); Treatment A received the first block as Mn (50 mg/kg MnCl2 tetrahydrate), with the second block as either methylmercury (MeHg at 2.6 or 1.3 mg/kg) for mice or vehicle for rats; and Treatment B received Mn for both blocks. Hair was collected on days 0 and 60 from all treatment groups and Mn quantified by inductively coupled plasma-mass spectrometry (ICP-MS) and total Hg by Direct Mercury Analyzer (DMA). No correlation between internal Mn dose and hair Mn was observed, whereas hair Hg was significantly elevated in MeHg exposed vs non-exposed mice. Whole body Mn content at day 60 was quantified postmortem by neutron activation analysis, which detected significantly elevated Mn for Treatment B in mice and rats. Overall, we find no evidence to support the use of hair as a valid biomarker for internal exposure to Mn at a neurotoxic level.

The Acute Dialysis Orders Objective Structured Clinical Examination (OSCE): Fellow Performance on a Formative Assessment of Acute Kidney Replacement Therapy Competence.

BACKGROUND AND OBJECTIVES: Acute kidney replacement therapy (KRT) prescription is a critical nephrology skill. We administered a formative objective structured clinical examination (OSCE) to nephrology fellows to assess acute KRT medical knowledge, patient care, and systems-based practice competencies. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS: Prospective cohort study of an educational test using the unified model of construct validity. We tested 117 fellows: 25 (four programs) in 2016 and 92 (15 programs) in 2017; 51 first-year and 66 second-year fellows. Using institutional protocols and order sets, fellows wrote orders and answered open-ended questions on a three-scenario OSCE, previously validated by board-certified, practicing clinical nephrologists. Outcomes were overall and scenario pass percentage and score; percent correctly answering predetermined, evidence-based questions; second-year score correlation with in-training examination score; and satisfaction survey. RESULTS: A total of 76% passed scenario 1 (acute continuous RRT): 92% prescribed a ≥20 ml/kg per hour effluent dose; 63% estimated clearance as effluent volume. Forty-two percent passed scenario 2 (maintenance dialysis initiation); 75% correctly prescribed 3-4 mEq/L K+ dialysate and 12% identified the two absolute, urgent indications for maintenance dialysis initiation (uremic encephalopathy and pericarditis). Six percent passed scenario 3 (acute life-threatening hyperkalemia); 20% checked for rebound hyperkalemia with two separate blood draws. Eighty-three percent correctly withheld intravenous sodium bicarbonate for acute hyperkalemia in a nonacidotic, volume-overloaded patient on maintenance dialysis, and 32% passed overall. Second-year versus first-year fellow overall score was 44.4±4 versus 42.7±5 (one-tailed P=0.02), with 39% versus 24% passing (P=0.08). Second-year in-training examination and OSCE scores were not significantly correlated (r=0.15; P=0.26). Seventy-seven percent of fellows agreed the OSCE was useful in assessing "proficiency in ordering" acute KRT. Limitations include lack of a validated criterion test, and unfamiliarity with open-ended question format. CONCLUSIONS: The OSCE can provide quantitative data for formative Accreditation Council for Graduate Medical Education competency assessments and identify opportunities for dialysis curriculum development. PODCAST: This article contains a podcast at https://www.asn-online.org/media/podcast/CJASN/2019_08_08_CJASNPodcast_19_09_.mp3.

Human-induced pluripotent stems cells as a model to dissect the selective neurotoxicity of methylmercury.

Methylmercury (MeHg) is a potent neurotoxicant affecting both the developing and mature central nervous system (CNS) with apparent indiscriminate disruption of multiple homeostatic pathways. However, genetic and environmental modifiers contribute significant variability to neurotoxicity associated with human exposures. MeHg displays developmental stage and neural lineage selective neurotoxicity. To identify mechanistic-based neuroprotective strategies to mitigate human MeHg exposure risk, it will be critical to improve our understanding of the basis of MeHg neurotoxicity and of this selective neurotoxicity. Here, we propose that human-based pluripotent stem cell cellular approaches may enable mechanistic insight into genetic pathways that modify sensitivity of specific neural lineages to MeHg-induced neurotoxicity. Such studies are crucial for the development of novel disease modifying strategies impinging on MeHg exposure vulnerability.

Drosophotoxicology: Elucidating Kinetic and Dynamic Pathways of Methylmercury Toxicity in a Drosophila Model.

The risks of methylmercury (MeHg) toxicity are greatest during early life where it has long been appreciated that the developing nervous system is an especially sensitive target. Yet, understanding the discrete mechanisms of MeHg toxicity have been obscured by the wide variation in the nature and severity of developmental outcomes that are typically seen across individuals in MeHg exposed populations. Some insight has come from studies aimed at identifying a role for genetic background as a modifier of MeHg toxicity, which have predominantly focused on factors influencing MeHg toxicokinetics, notably, polymorphisms in genes related to glutathione (GSH) metabolism. For example, variants in genes encoding the catalytic and modifier subunits of glutamyl-cysteine ligase (GCLc and GCLm), the rate limiting enzyme for GSH synthesis, have been reported to associate with Hg body burden (Hg levels in blood or hair) in humans. However, GSH can facilitate both toxicokinetics and toxicodynamics of MeHg by forming MeHg-GSH conjugates, which are readily transported and excreted, and by acting indirectly as an anti-oxidant. In this study, we refine a model to distinguish kinetic and dynamic traits of MeHg toxicity using a paradigm of Drosophotoxicolgy. First, we identify that the pupal stage is selectively sensitive to MeHg toxicity. Using a protocol of larval feeding, measurements of Hg body burden, and assays of development to adulthood (pupal eclosion), we identify strain-dependent variation in MeHg elimination as a potential kinetic determinant of differential tolerance to MeHg. We also find that global upregulation of GSH levels, with GCLc trans-gene expression, can induce MeHg tolerance and reduce Hg body burden. However, we demonstrate that MeHg tolerance can also be achieved independently of reducing Hg body burden, in both wild-derived strains and with targeted expression of GCLc in developing neuronal and muscle tissue, pointing to a robust toxicodynamic mechanism. Our findings have important implications for understanding variation in MeHg toxic potential on an individual basis and for informing the process of relating a measurement of Hg body burden to the potential for adverse developmental outcome.

Survey of non-tunneled temporary hemodialysis catheter clinical practice and training.

BACKGROUND: Nephrologists are placing fewer non-tunneled temporary hemodialysis catheters. Requiring competence for nephrology fellow graduation is controversial. METHODS: Anonymous, online survey of all graduates from a single, military nephrology training program (n = 81; 1985-2017) and all US Nephrology program directors (n = 150). RESULTS: Graduate response and completion rates were 59% and 100%, respectively; 93% agreed they had been adequately trained; 58% (26/45) place non-tunneled temporary hemodialysis catheters, independent of academic practice or time in practice, but 12/26 did ⩽5/year and 23/26 referred some or all. The most common reason for continuing non-tunneled temporary hemodialysis catheter placement was that it is an essential emergency procedure (92%). The single most significant barrier was time to do the procedure (49%). Program director response and completion rates were 50% and 79%, respectively. The single most important barrier to fellow competence was busyness of the service (36%), followed by disinterest (21%); 55% believed that non-tunneled temporary hemodialysis catheter insertion competence should be required, with 81% indicating it was an essential emergency procedure. The majority of graduates and program directors agreed that simulation training was valuable; 76% of programs employ simulation. Graduates who had simulation training and program directors with ⩽20 years of practice were significantly more likely to agree that simulation training was necessary. CONCLUSION: Of the graduate respondents from a single training program, 58% continue to place non-tunneled temporary hemodialysis catheters; 55% of program directors believe non-tunneled temporary hemodialysis catheter procedural competence should be required. Graduates who had non-tunneled temporary hemodialysis catheter simulation training and younger program directors consider simulation training necessary. These findings should be considered in the discussion of non-tunneled temporary hemodialysis catheter curriculum requirements.

Methylmercury exposure causes a persistent inhibition of myogenin expression and C2C12 myoblast differentiation.

Methylmercury (MeHg) is a ubiquitous environmental toxicant, best known for its selective targeting of the developing nervous system. MeHg exposure has been shown to cause motor deficits such as impaired gait and coordination, muscle weakness, and muscle atrophy, which have been associated with disruption of motor neurons. However, recent studies have suggested that muscle may also be a target of MeHg toxicity, both in the context of developmental myogenic events and of low-level chronic exposures affecting muscle wasting in aging. We therefore investigated the effects of MeHg on myotube formation, using the C2C12 mouse myoblast model. We found that MeHg inhibits both differentiation and fusion, in a concentration-dependent manner. Furthermore, MeHg specifically and persistently inhibits myogenin (MyoG), a transcription factor involved in myocyte differentiation, within the first six hours of exposure. MeHg-induced reduction in MyoG expression is contemporaneous with a reduction of a number of factors involved in mitochondrial biogenesis and mtDNA transcription and translation, which may implicate a role for mitochondria in mediating MeHg-induced change in the differentiation program. Unexpectedly, inhibition of myoblast differentiation with MeHg parallels inhibition of Notch receptor signaling. Our research establishes muscle cell differentiation as a target for MeHg toxicity, which may contribute to the underlying etiology of motor deficits with MeHg toxicity.