One touch is all it takes: the supramolecular interaction between ubiquitin and lanthanide complexes revisited by paramagnetic NMR and molecular dynamics.

The supramolecular interaction between lanthanide complexes and proteins is at the heart of numerous chemical and biological studies. Some of these complexes have demonstrated remarkable interaction properties with proteins or peptides in solution and in the crystalline state. Here we have used the paramagnetism of lanthanide ions to characterize the affinity of two lanthanide complexes for ubiquitin. As the interaction process is dynamic, the acquired NMR data only reflect the time average of the different steps. We have used molecular dynamics (MD) simulations to get a deeper insight into the detailed interaction scenario at the microsecond scale. This NMR/MD approach enabled us to establish that the tris-dipicolinate complex interacts specifically with arginines and lysines, while the crystallophore explores the protein surface through weak interactions with carboxylates. These observations shed new light on the dynamic interaction properties of these complexes, which will ultimately enable us to propose a crystallization mechanism.

Examining chronic kidney disease screening frequency among diabetics: a POMDP approach.

Forty percent of diabetics will develop chronic kidney disease (CKD) in their lifetimes. However, as many as 50% of these CKD cases may go undiagnosed. We developed screening recommendations stratified by age and previous test history for individuals with diagnosed diabetes and unknown proteinuria status by race and gender groups. To do this, we used a Partially Observed Markov Decision Process (POMDP) to identify whether a patient should be screened at every three-month interval from ages 30-85. Model inputs were drawn from nationally-representative datasets, the medical literature, and a microsimulation that integrates this information into group-specific disease progression rates. We implement the POMDP solution policy in the microsimulation to understand how this policy may impact health outcomes and generate an easily-implementable, non-belief-based approximate policy for easier clinical interpretability. We found that the status quo policy, which is to screen annually for all ages and races, is suboptimal for maximizing expected discounted future net monetary benefits (NMB). The POMDP policy suggests more frequent screening after age 40 in all race and gender groups, with screenings 2-4 times a year for ages 61-70. Black individuals are recommended for screening more frequently than their White counterparts. This policy would increase NMB from the status quo policy between $1,000 to  $8,000 per diabetic patient at a willingness-to-pay of $150,000 per quality-adjusted life year (QALY).

Genome-wide association study in the Taiwan Biobank identifies four novel genes for human height: NABP2, RASA2, RNF41 and SLC39A5.

Numerous genome-wide association studies (GWASs) have been conducted for the identification of genetic variants involved with human height. The vast majority of these studies, however, have been conducted in populations of European ancestry. Here, we report the first GWAS of adult height in the Taiwan Biobank using a discovery sample of 14 571 individuals and an independent replication sample of 20 506 individuals. From our analysis, we generalize to the Taiwanese population genome-wide significant associations with height and 18 previously identified genes in European and non-Taiwanese East Asian populations. We also identify and replicate, at the genome-wide significance level, associated variants for height in four novel genes at two loci that have not previously been reported: RASA2 on chromosome 3 and NABP2, RNF41 and SLC39A5 at 12q13.3 on chromosome 12. RASA2 and RNF41 are strong candidates for having a role in height with copy number and loss of function variants in RASA2 previously found to be associated with short stature disorders, and decreased expression of the RNF41 gene resulting in insulin resistance in skeletal muscle. The results from our analysis of the Taiwan Biobank underscore the potential for the identification of novel genetic discoveries in underrepresented worldwide populations, even for traits, such as height, that have been extensively investigated in large-scale studies of European ancestry populations.

Assessment of cellular responses in three-dimensional cell cultures through chemical exchange saturation transfer and 1 H MRS.

The article from this special issue was previously published in NMR In Biomedicine , Volume 35, Issue 9, 2022. For completeness we are including the title page of the article below. The full text of the article can be read in Issue 35:9 on Wiley Online Library: https://doi.org/10.1002/nbm.4757.

Patient Frailty and Functional Use of Hemodialysis Vascular Access: A Retrospective Study of the US Renal Data System.

RATIONALE & OBJECTIVE: Despite the high prevalence of frailty among dialysis patients, it is unknown whether frailty is associated with dialysis vascular access failure. This study examined the association between frailty and functional use of vascular access. STUDY DESIGN: Retrospective observational study. SETTING & PARTICIPANTS: Patients who initiated hemodialysis through a tunneled catheter in the US Renal Data System database from 2012 through 2017 and underwent subsequent creation of an arteriovenous fistula or graft. PREDICTORS: The "claims-based frailty indicator" (CFI) was calculated using a validated claims-based disability status model anchored to a well-described frailty phenotype. OUTCOMES: Time to functional use for fistulas and grafts defined as the time from initiation of hemodialysis to treatments using the index vascular access with 2 needles. ANALYTICAL APPROACH: Fine and Gray competing risk models separately examining fistula and graft outcomes. Patient survival was modeled for the entire cohort using Cox proportional hazards regression. RESULTS: A total of 41,471 patients met inclusion criteria, including 33,212 who underwent fistula creation and 8,259 who underwent graft placement. Higher CFI quartiles were associated with a greater rate of mortality. Patients in the highest CFI quartile had more than 2 times the rate of mortality compared with patients in the lowest CFI quartile (hazard ratio [HR], 2.49 [95% CI, 2.41-2.58]). In multivariable analyses, the highest CFI quartile was significantly associated with longer time to functional use of fistulas (HR, 0.65 [95% CI, 0.62-0.69]) and grafts (HR, 0.88 [95% CI, 0.79-0.98]). LIMITATIONS: Generalizability may be limited by the requirement of 12 months of Medicare claims availability before initiation of dialysis. There were no data on patient anatomic characteristics or surgeon characteristics and limited patient-specific sociodemographic data. CONCLUSIONS: Higher degrees of frailty are associated with longer times to vascular access functional use. Frailty may be useful for informing clinical decision-making regarding choice of vascular access.

Assessment of cellular responses in three-dimensional cell cultures through chemical exchange saturation transfer and 1 H MRS.

Metabolic responses to physiological changes have been detected using chemical exchange saturation transfer (CEST) imaging in clinical settings. Similarly to other MRI techniques, the CEST technique was based originally on phantoms from buffer solutions and was then further developed through animal experiments. However, CEST imaging can capture certain dynamics of metabolism that solution phantoms cannot model. Cell culture phantoms can fill the gap between buffer phantoms and animal models. In this study, we used 1 H NMR and CEST in a B0 field of 9.4 T to investigate HEK293T cells from two-dimensional (2D) cultures, three-dimensional (3D) cultures, and 3D cultures seeded with cell spheroids. Two CEST dips were observed: the magnitude of the amine dip at 2.8 ppm increased during the incubation period, whereas the hydroxyl dip at 1.2 ppm remained approximately the same or modestly increased. We also observed a CEST dip at 2.8 ppm from the 2D culture responding dramatically to doxorubicin treatment. By cross-validating with pH values and the concentrations of amine and hydroxyl protons extracted through 1 H NMR, we observed that they did not correspond to an increase in the amine pool. We believe that the denaturation or degradation of proteins from the fetal bovine serum increased the size of the amine pool. Although 3D culture conditions can be further improved, our study suggests that 3D cultures have the potential to bridge studies of solution phantoms and those on animals.

De Novo Peptide and Protein Design Using Generative Adversarial Networks: An Update.

Nowadays, machine learning and deep learning approaches are widely utilized for generative chemistry and computer-aided drug design and discovery such as de novo peptide and protein design, where target-specific peptide-based/protein-based therapeutics have been suggested to cause fewer adverse effects than the traditional small-molecule drugs. In light of current advancements in deep learning techniques, generative adversarial network (GAN) algorithms are being leveraged to a wide variety of applications in the process of generative chemistry and computer-aided drug design and discovery. In this review, we focus on the up-to-date developments for de novo peptide and protein design research using GAN algorithms in the interdisciplinary fields of generative chemistry, machine learning, deep learning, and computer-aided drug design and discovery. First, we present various studies that investigate GAN algorithms to fulfill the task of de novo peptide and protein design in the drug development pipeline. In addition, we summarize the drawbacks with respect to the previous studies in de novo peptide and protein design using GAN algorithms. Finally, we depict a discussion of open challenges and emerging problems for future research.

Association Between Preoperative Hemodialysis Timing and Postoperative Mortality in Patients With End-stage Kidney Disease.

Importance: For patients with end-stage kidney disease treated with hemodialysis, the optimal timing of hemodialysis prior to elective surgical procedures is unknown. Objective: To assess whether a longer interval between hemodialysis and subsequent surgery is associated with higher postoperative mortality in patients with end-stage kidney disease treated with hemodialysis. Design, Setting, and Participants: Retrospective cohort study of 1 147 846 procedures among 346 828 Medicare beneficiaries with end-stage kidney disease treated with hemodialysis who underwent surgical procedures between January 1, 2011, and September 30, 2018. Follow-up ended on December 31, 2018. Exposures: One-, two-, or three-day intervals between the most recent hemodialysis treatment and the surgical procedure. Hemodialysis on the day of the surgical procedure vs no hemodialysis on the day of the surgical procedure. Main Outcomes and Measures: The primary outcome was 90-day postoperative mortality. The relationship between the dialysis-to-procedure interval and the primary outcome was modeled using a Cox proportional hazards model. Results: Of the 1 147 846 surgical procedures among 346 828 patients (median age, 65 years [IQR, 56-73 years]; 495 126 procedures [43.1%] in female patients), 750 163 (65.4%) were performed when the last hemodialysis session occurred 1 day prior to surgery, 285 939 (24.9%) when the last hemodialysis session occurred 2 days prior to surgery, and 111 744 (9.7%) when the last hemodialysis session occurred 3 days prior to surgery. Hemodialysis was also performed on the day of surgery for 193 277 procedures (16.8%). Ninety-day postoperative mortality occurred after 34 944 procedures (3.0%). Longer intervals between the last hemodialysis session and surgery were significantly associated with higher risk of 90-day mortality in a dose-dependent manner (2 days vs 1 day: absolute risk, 4.7% vs 4.2%, absolute risk difference, 0.6% [95% CI, 0.4% to 0.8%], adjusted hazard ratio [HR], 1.14 [95% CI, 1.10 to 1.18]; 3 days vs 1 day: absolute risk, 5.2% vs 4.2%, absolute risk difference, 1.0% [95% CI, 0.8% to 1.2%], adjusted HR, 1.25 [95% CI, 1.19 to 1.31]; and 3 days vs 2 days: absolute risk, 5.2% vs 4.7%, absolute risk difference, 0.4% [95% CI, 0.2% to 0.6%], adjusted HR, 1.09 [95% CI, 1.04 to 1.13]). Undergoing hemodialysis on the same day as surgery was associated with a significantly lower hazard of mortality vs no same-day hemodialysis (absolute risk, 4.0% for same-day hemodialysis vs 4.5% for no same-day hemodialysis; absolute risk difference, -0.5% [95% CI, -0.7% to -0.3%]; adjusted HR, 0.88 [95% CI, 0.84-0.91]). In the analyses that evaluated the interaction between the hemodialysis-to-procedure interval and same-day hemodialysis, undergoing hemodialysis on the day of the procedure significantly attenuated the risk associated with a longer hemodialysis-to-procedure interval (P<.001 for interaction). Conclusions and Relevance: Among Medicare beneficiaries with end-stage kidney disease, longer intervals between hemodialysis and surgery were significantly associated with higher risk of postoperative mortality, mainly among those who did not receive hemodialysis on the day of surgery. However, the magnitude of the absolute risk differences was small, and the findings are susceptible to residual confounding.

New Class of Radially Adjustable Stentrievers for Acute Ischemic Stroke: Primary Results of the Multicenter TIGER Trial.

[Figure: see text].

Chemical exchange rotation transfer imaging of phosphocreatine in muscle.

In chemical exchange saturation transfer (CEST) imaging, the signal at 2.6 ppm from the water resonance in muscle has been assigned to phosphocreatine (PCr). However, this signal has limited specificity for PCr since the signal is also sensitive to exchange with protein and macromolecular protons when using some conventional quantification methods, and will vary with changes in the water longitudinal relaxation rate. Correcting for these effects while maintaining reasonable acquisition times is challenging. As an alternative approach to overcome these problems, here we evaluate chemical exchange rotation transfer (CERT) imaging of PCr in muscle at 9.4 T. Specifically, the CERT metric, AREXdouble,cpw at 2.6 ppm, was measured in solutions containing the main muscle metabolites, in tissue homogenates with controlled PCr content, and in vivo in rat leg muscles. PCr dominates CERT metrics around 2.6 ppm (although with nontrivial confounding baseline contributions), indicating that CERT is well-suited to PCr specific imaging, and has the added benefit of requiring a relatively small number of acquisitions.

Challenging Assumptions of Outcomes and Costs Comparing Peritoneal and Hemodialysis.

OBJECTIVES: Policy makers have suggested increasing peritoneal dialysis (PD) would improve end-stage kidney disease (ESKD) outcomes and reduce Medicare spending compared with hemodialysis (HD). We compared mortality, hospitalizations, and Medicare spending between PD and HD among uninsured adults with incident ESKD. METHODS: Using an instrumental variable design, we exploited a natural experiment encouraging PD among the uninsured. Uninsured patients usually receive Medicare at dialysis month 4. For those initiating PD, Medicare covers the first 3 dialysis months, including predialysis services in the calendar month when dialysis started. Starting dialysis later in a calendar month increases predialysis coverage that is essential for PD catheter placements. The policy encourages PD incrementally when ESKD develops later in the month. Dialysis start day appears to be unrelated to patient characteristics and effectively "randomizes patients" to dialysis modality, mitigating selection bias. RESULTS: Starting dialysis later in the month was associated with an increased PD uptake: every week later in the month was associated with an absolute increase of 0.8% (95% confidence interval [CI] 0.6%-0.9%) at dialysis day 1 and 0.5% (95% CI 0.3%-0.7%) at dialysis month 12. We observed no significant absolute difference between PD and HD for 12-month mortality (-0.9%, 95% CI -3.3% to 0.8%), hospitalizations during months 7 to 12 (-0.05, 95% CI -0.20 to 0.07), and Medicare spending during months 7 to 12 (-$702, 95% CI -$4004 to $2909). CONCLUSIONS: In an instrumental variable analysis, PD did not result in improved outcomes or lower costs than HD.

Deep Learning with Neuroimaging and Genomics in Alzheimer's Disease.

A growing body of evidence currently proposes that deep learning approaches can serve as an essential cornerstone for the diagnosis and prediction of Alzheimer's disease (AD). In light of the latest advancements in neuroimaging and genomics, numerous deep learning models are being exploited to distinguish AD from normal controls and/or to distinguish AD from mild cognitive impairment in recent research studies. In this review, we focus on the latest developments for AD prediction using deep learning techniques in cooperation with the principles of neuroimaging and genomics. First, we narrate various investigations that make use of deep learning algorithms to establish AD prediction using genomics or neuroimaging data. Particularly, we delineate relevant integrative neuroimaging genomics investigations that leverage deep learning methods to forecast AD on the basis of incorporating both neuroimaging and genomics data. Moreover, we outline the limitations as regards to the recent AD investigations of deep learning with neuroimaging and genomics. Finally, we depict a discussion of challenges and directions for future research. The main novelty of this work is that we summarize the major points of these investigations and scrutinize the similarities and differences among these investigations.

Sympathetic Denervation Alters the Inflammatory Response of Resident Muscularis Macrophages upon Surgical Trauma and Ameliorates Postoperative Ileus in Mice.

Interactions between the peripheral nervous system and resident macrophages (MMs) modulate intestinal homeostatic functions. Activation of ß2-adrenergic receptors on MMs has been shown to reduce bacterial challenges. These MMs are also crucial for the development of bowel inflammation in postoperative ileus (POI), an iatrogenic, noninfectious inflammation-based motility disorder. However, the role of the sympathetic nervous system (SNS) in the immune modulation of these MMs during POI or other noninfectious diseases is largely unknown. By employing 6-OHDA-induced denervation, we investigated the changes in the muscularis externa by RNA-seq, quantitative PCR, and flow cytometry. Further, we performed transcriptional phenotyping of sorted CX3CR1+ MMs and ex vivo LPS/M-CSF stimulation on these MMs. By combining denervation with a mouse POI model, we explored distinct changes on CX3CR1+ MMs as well as in the muscularis externa and their functional outcome during POI. Our results identify SNS as an important mediator in noninfectious postoperative inflammation. Upon denervation, MMs anti-inflammatory genes were reduced, and the muscularis externa profile is shaped toward a proinflammatory status. Further, denervation reduced MMs anti-inflammatory genes also in the early phase of POI. Finally, reduced leukocyte infiltration into the muscularis led to a quicker recovery of bowel motility in the late phase of POI.

A deep adversarial variational autoencoder model for dimensionality reduction in single-cell RNA sequencing analysis.

BACKGROUND: Single-cell RNA sequencing (scRNA-seq) is an emerging technology that can assess the function of an individual cell and cell-to-cell variability at the single cell level in an unbiased manner. Dimensionality reduction is an essential first step in downstream analysis of the scRNA-seq data. However, the scRNA-seq data are challenging for traditional methods due to their high dimensional measurements as well as an abundance of dropout events (that is, zero expression measurements). RESULTS: To overcome these difficulties, we propose DR-A (Dimensionality Reduction with Adversarial variational autoencoder), a data-driven approach to fulfill the task of dimensionality reduction. DR-A leverages a novel adversarial variational autoencoder-based framework, a variant of generative adversarial networks. DR-A is well-suited for unsupervised learning tasks for the scRNA-seq data, where labels for cell types are costly and often impossible to acquire. Compared with existing methods, DR-A is able to provide a more accurate low dimensional representation of the scRNA-seq data. We illustrate this by utilizing DR-A for clustering of scRNA-seq data. CONCLUSIONS: Our results indicate that DR-A significantly enhances clustering performance over state-of-the-art methods.

Pivotal Trial of the Neuroform Atlas Stent for Treatment of Anterior Circulation Aneurysms: One-Year Outcomes.

BACKGROUND AND PURPOSE: Stent-assisted coil embolization using the new generation Neuroform Atlas Stent System has shown promising safety and efficacy. The primary study results of the anterior circulation aneurysm cohort of the treatment of wide-neck, saccular, intracranial, aneurysms with the Neuroform Atlas Stent System (ATLAS trial [Safety and Effectiveness of the Treatment of Wide Neck, Saccular Intracranial Aneurysms With the Neuroform Atlas Stent System]) are presented. METHODS: ATLAS IDE trial (Investigational Device Exemption) is a prospective, multicenter, single-arm, open-label study of wide-neck (neck ≥4 mm or dome-to-neck ratio <2) intracranial aneurysms in the anterior circulation treated with the Neuroform Atlas Stent and approved coils. The primary efficacy end point was complete aneurysm occlusion (Raymond-Roy class 1) on 12-month angiography, in the absence of retreatment or parent artery stenosis (>50%) at the target location. The primary safety end point was any major stroke or ipsilateral stroke or neurological death within 12 months. Adjudication of the primary end points was performed by an independent Imaging Core Laboratory and the Clinical Events Committee. RESULTS: A total of 182 patients with wide-neck anterior circulation aneurysms at 25 US centers were enrolled. The mean age was 60.3±11.4 years, 73.1% (133/182) women, and 80.8% (147/182) white. Mean aneurysm size was 6.1±2.2 mm, mean neck width was 4.1±1.2 mm, and mean dome-to-neck ratio was 1.2±0.3. The most frequent aneurysm locations were the anterior communicating artery (64/182, 35.2%), internal carotid artery ophthalmic artery segment (29/182, 15.9%), and middle cerebral artery bifurcation (27/182, 14.8%). Stents were placed in the anticipated anatomic location in all patients. The study met both primary safety and efficacy end points. The composite primary efficacy end point of complete aneurysm occlusion (Raymond-Roy 1) without parent artery stenosis or aneurysm retreatment was achieved in 84.7% (95% CI, 78.6%-90.9%) of patients. Overall, 4.4% (8/182, 95% CI, 1.9%-8.5%) of patients experienced a primary safety end point of major ipsilateral stroke or neurological death. CONCLUSIONS: In the ATLAS IDE anterior circulation aneurysm cohort premarket approval study, the Neuroform Atlas stent with adjunctive coiling met the primary end points and demonstrated high rates of long-term complete aneurysm occlusion at 12 months, with 100% technical success and <5% morbidity. Registration: URL: https://www.clinicaltrials.gov. Unique identifier: NCT02340585.

Hospitalizations among adults with chronic kidney disease in the United States: A cohort study.

BACKGROUND: Adults with chronic kidney disease (CKD) are hospitalized more frequently than those without CKD, but the magnitude of this excess morbidity and the factors associated with hospitalizations are not well known. METHODS AND FINDINGS: Data from 3,939 participants enrolled in the Chronic Renal Insufficiency Cohort (CRIC) Study between 2003 and 2008 at 7 clinical centers in the United States were used to estimate primary causes of hospitalizations, hospitalization rates, and baseline participant factors associated with all-cause, cardiovascular, and non-cardiovascular hospitalizations during a median follow up of 9.6 years. Multivariable-adjusted Poisson regression was used to identify factors associated with hospitalization rates, including demographics, blood pressure, estimated glomerular filtration rate (eGFR), and proteinuria. Hospitalization rates in CRIC were compared with rates in the Nationwide Inpatient Sample (NIS) from 2012. Of the 3,939 CRIC participants, 45.1% were female, and 41.9% identified as non-Hispanic black, with a mean age of 57.7 years, and the mean eGFR is 44.9 ml/min/1.73m2. CRIC participants had an unadjusted overall hospitalization rate of 35.0 per 100 person-years (PY) [95% CI: 34.3 to 35.6] and 11.1 per 100 PY [95% CI: 10.8 to 11.5] for cardiovascular-related causes. All-cause, non-cardiovascular, and cardiovascular hospitalizations were associated with older age (≥65 versus 45 to 64 years), more proteinuria (≥150 to <500 versus <150 mg/g), higher systolic blood pressure (≥140 versus 120 to <130 mmHg), diabetes (versus no diabetes), and lower eGFR (<60 versus ≥60 ml/min/1.73m2). Non-Hispanic black (versus non-Hispanic white) race/ethnicity was associated with higher risk for cardiovascular hospitalization [rate ratio (RR) 1.25, 95% CI: 1.16 to 1.35, p-value < 0.001], while risk among females was lower [RR 0.89, 95% CI: 0.83 to 0.96, p-value = 0.002]. Rates of cardiovascular hospitalizations were higher among those with ≥500 mg/g of proteinuria irrespective of eGFR. The most common causes of hospitalization were related to cardiovascular (31.8%), genitourinary (8.7%), digestive (8.3%), endocrine, nutritional or metabolic (8.3%), and respiratory (6.7%) causes. Hospitalization rates were higher in CRIC than the NIS, except for non-cardiovascular hospitalizations among individuals aged >65 years. Limitations of the study include possible misclassification by diagnostic codes, residual confounding, and potential bias from healthy volunteer effect due to its observational nature. CONCLUSIONS: In this study, we observed that adults with CKD had a higher hospitalization rate than the general population that is hospitalized, and even moderate reductions in kidney function were associated with elevated rates of hospitalization. Causes of hospitalization were predominantly related to cardiovascular disease, but other causes contributed, particularly, genitourinary, digestive, and endocrine, nutritional, and metabolic illnesses. High levels of proteinuria were observed to have the largest association with hospitalizations across a wide range of kidney function levels.

Relayed nuclear Overhauser enhancement sensitivity to membrane Cho phospholipids.

PURPOSE: Phospholipids are key constituents of cell membranes and serve vital functions in the regulation of cellular processes; thus, a method for in vivo detection and characterization could be valuable for detecting changes in cell membranes that are consequences of either normal or pathological processes. Here, we describe a new method to map the distribution of partially restricted phospholipids in tissues. METHODS: The phospholipids were measured by signal changes caused by relayed nuclear Overhauser enhancement-mediated CEST between the phospholipid Cho headgroup methyl protons and water at around -1.6 ppm from the water resonance. The biophysical basis of this effect was examined by controlled manipulation of head group, chain length, temperature, degree of saturation, and presence of cholesterol. Additional experiments were performed on animal tumor models to evaluate potential applications of this novel signal while correcting for confounding contributions. RESULTS: Negative relayed nuclear Overhauser dips in Z-spectra were measured from reconstituted Cho phospholipids with cholesterol but not for other Cho-containing metabolites or proteins. Significant contrast was found between tumor and contralateral normal tissue signals in animals when comparing both the measured saturation transfer signal and a more specific imaging metric. CONCLUSION: We demonstrated specific relayed nuclear Overhauser effects in partially restricted phospholipid phantoms and similar effects in solid brain tumors after correcting for confounding signal contributions, suggesting possible translational applications of this novel molecular imaging method, which we name restricted phospholipid transfer.

Role of the cholesterol hydroxyl group in the chemical exchange saturation transfer signal at -1.6 ppm.

Chemical exchange saturation transfer (CEST) can provide metabolite-weighted images in the clinical setting; therefore, understanding the origin of each CEST signal is essential to revealing the changes in diseases at the molecular level, which would provide further insight for diagnoses and treatments. The CEST signal at -1.6 ppm is attributed to the choline methyl group of phosphatidylcholines. The methyl groups have no exchangeable protons, so the corresponding CEST signals must result from the relayed nuclear Overhauser effect (rNOE); however, the detailed mechanism remains unclear. Cholesterol is a major component of biological membranes, and its content is closely related to the dynamics and phases of these lipids. However, cholesterol has a hydroxyl group, which could participate in proton exchange to complete the rNOE process. In this study, we used liposomes containing cholesterol and its analogs (5α-cholestane and progesterone), which presumably have similar capabilities of influencing lipid bilayers, and found that the steroid hydroxyl group is the key to inducing the rNOE at -1.6 ppm. Our results suggest that the origin of the rNOE at -1.6 ppm likely requires an intermolecular NOE between the proton of the choline methyl group and that of the cholesterol hydroxyl group, and a chemical exchange between the cholesterol hydroxyl group and bulk water. However, the phenomenon in which the rNOE at -1.6 ppm appears when the cholesterol concentration is high seems to contradict the in vivo results, suggesting a more complicated mechanism associated with the rNOE at -1.6 ppm in biological membranes.

Early Delays in Insurance Coverage and Long-term Use of Home-based Peritoneal Dialysis.

BACKGROUND: Uninsured patients with end-stage renal disease face barriers to peritoneal dialysis (PD), a type of home dialysis that is associated with improved quality of life and reduced Medicare costs. Although uninsured patients using PD at dialysis start receive retroactive Medicare coverage for required predialysis services, coverage only applies for the calendar month of dialysis start. Thus, initiating dialysis later in the month yields longer retroactive coverage. OBJECTIVES: To examine whether differences in retroactive Medicare were associated with decreased long-term PD use. RESEARCH DESIGN: We exploited the dialysis start date using a regression discontinuity design on a national cohort from the US Renal Data System. SUBJECTS: 36,256 uninsured adults starting dialysis between January 1, 2006 and December 31, 2014. MEASURES: PD use at dialysis days 1, 90, 180, and 360. RESULTS: Starting dialysis on the first versus last day of the calendar month was associated with an absolute decrease in PD use of 2.7% [95% confidence interval (CI), 1.5%-3.9%], or a relative decrease of 20% (95% CI, 12%-27%) at dialysis day 360. The absolute decrease was 5.5% (95% CI, 3.5%-7.2%) after Medicare established provider incentives for PD in 2011 and 7.2% (95% CI, 2.5%-11.9%) after Medicaid expansion in 2014. Patients were unlikely to switch from hemodialysis to PD after the first month of dialysis (probability of 6.9% in month 1, 1.5% in month 2, and 0.9% in month 4). CONCLUSIONS: Extending retroactive coverage for preparatory dialysis services could increase PD use and reduce overall Medicare spending in the uninsured.

Conflicts of interest in dialysis: A barrier to policy reforms.

Conflicts of interest involving physicians are commonplace in the US, occurring across many different specialties and subspecialties in a variety of clinical settings. In nephrology, two important scenarios in which conflicts of interest arise are dialysis facility joint venture (JV) arrangements and financial participation in End-stage Kidney Disease Seamless Care Organizations (ESCOs). Whether conflicts of interest occurring in either of these settings influence decision-making or patient care outcomes is not known due to a lack of transparent, publicly available information, and opportunities to conduct independent study. We discuss possible benefits and risks of nephrologist's financial participation in JVs and ESCOs and possible mechanisms for disclosure and reporting of such arrangements as well as risk mitigation.