A simple 1H (12C/13C) filtered experiment to quantify and trace isotope enrichment in complex environmental and biological samples.

Nuclear magnetic resonance (NMR) based 13C tracing has broad applications across medical and environmental research. As many biological and environmental samples are heterogeneous, they experience considerable spectral overlap and relatively low signal. Here a 1D 1H-12C/13C is introduced that uses "in-phase/opposite-phase" encoding to simultaneously detect and discriminate both protons attached to 12C and 13C at full 1H sensitivity in every scan. Unlike traditional approaches that focus on the 12C/13C satellite ratios in a 1H spectrum, this approach creates separate sub-spectra for the 12C and 13C bound protons. These spectra can be used for both quantitative and qualitative analysis of complex samples with significant spectral overlap. Due to the presence of the 13C dipole, faster relaxation of the 1H-13C pairs results in slight underestimation compared to the 1H-12C pairs. However, this is easily compensated for, by collecting an additional reference spectrum, from which the absolute percentage of 13C can be calculated by difference. When combined with the result, 12C and 13C percent enrichment in both 1H-12C and 1H-13C fractions are obtained. As the approach uses isotope filtered 1H NMR for detection, it retains nearly the same sensitivity as a standard 1H spectrum. Here, a proof-of-concept is performed using simple mixtures of 12C and 13C glucose, followed by suspended algal cells with varying 12C /13C ratios representing a complex mixture. The results consistently return 12C/13C ratios that deviate less than 1 % on average from the expected. Finally, the sequence was used to monitor and quantify 13C% enrichment in Daphnia magna neonates which were fed a 13C diet over 1 week. The approach helped reveal how the organisms utilized the 12C lipids they are born with vs. the 13C lipids they assimilate from their diet during growth. Given the experiments simplicity, versatility, and sensitivity, we anticipate it should find broad application in a wide range of tracer studies, such as fluxomics, with applications spanning various disciplines.

Low-field, not low quality: 1D simplification, selective detection, and heteronuclear 2D experiments for improving low-field NMR spectroscopy of environmental and biological samples.

Understanding environmental change is challenging and requires molecular-level tools to explain the physicochemical phenomena behind complex processes. Nuclear magnetic resonance (NMR) spectroscopy is a key tool that provides information on both molecular structures and interactions but is underutilized in environmental research because standard "high-field" NMR is financially and physically inaccessible for many and can be overwhelming to those outside of disciplines that routinely use NMR. "Low-field" NMR is an accessible alternative but has reduced sensitivity and increased spectral overlap, which is especially problematic for natural, heterogeneous samples. Therefore, the goal of this study is to investigate and apply innovative experiments that could minimize these challenges and improve low-field NMR analysis of environmental and biological samples. Spectral simplification (JRES, PSYCHE, singlet-only, multiple quantum filters), selective detection (GEMSTONE, DREAMTIME), and heteronuclear (reverse and CH3/CH2/CH-only HSQCs) NMR experiments are tested on samples of increasing complexity (amino acids, spruce resin, and intact water fleas) at-high field (500 MHz) and at low-field (80 MHz). A novel experiment called Doubly Selective HSQC is also introduced, wherein 1H signals are selectively detected based on the 1H and 13C chemical shifts of 1H-13C J-coupled pairs. The most promising approaches identified are the selective techniques (namely for monitoring), and the reverse and CH3-only HSQCs. Findings ultimately demonstrate that low-field NMR holds great potential for biological and environmental research. The multitude of NMR experiments available makes NMR tailorable to nearly any research need, and low-field NMR is therefore anticipated to become a valuable and widely used analytical tool moving forward.

Development of Low-Magnetic Susceptibility Microcoils via 5-Axis Machining for Analysis of Biological and Environmental Samples.

In environmental research, it is critical to understand how toxins impact invertebrate eggs and egg banks, which, due to their tiny size, are very challenging to study by conventional nuclear magnetic resonance (NMR) spectroscopy. Microcoil technology has been extensively utilized to enhance the mass-sensitivity of NMR. In a previous study, 5-axis computer numerical control (CNC) micromilling (shown to be a viable alternative to traditional microcoil production methods) was used to create a prototype copper slotted-tube resonator (STR). Despite the excellent limit of detection (LOD) of the resonator, the quality of the line shape was very poor due to the magnetic susceptibility of the copper resonator itself. This is best solved using magnetic susceptibility-matched materials. In this study, approaches are investigated that improve the susceptibility while retaining the versatility of coil milling. One method involves machining STRs from various copper/aluminum alloys, while the other involves machining ones from an aluminum 2011 alloy and electroplating them with copper. In all cases, combining copper and aluminum to produce resonators resulted in improved line shape and SNR compared to pure copper resonators due to their reduced magnetic susceptibility. However, the copper-plated aluminum resonators showed optimal performance from the devices tested. The enhanced LOD of these STRs allowed for the first 1H-13C heteronuclear multiple quantum coherence (HMQC) of a single intact 13C-labeled Daphnia magna egg (∼4 µg total biomass). This is a key step toward future screening programs that aim to elucidate the toxic processes in aquatic eggs.

Exploring the Potential of Broadband Complementary Metal Oxide Semiconductor Micro-Coil Nuclear Magnetic Resonance for Environmental Research.

With sensitivity being the Achilles' heel of nuclear magnetic resonance (NMR), the superior mass sensitivity offered by micro-coils can be an excellent choice for tiny, mass limited samples such as eggs and small organisms. Recently, complementary metal oxide semiconductor (CMOS)-based micro-coil transceivers have been reported and demonstrate excellent mass sensitivity. However, the ability of broadband CMOS micro-coils to study heteronuclei has yet to be investigated, and here their potential is explored within the lens of environmental research. Eleven nuclei including 7Li, 19F, 31P and, 205Tl were studied and detection limits in the low to mid picomole range were found for an extended experiment. Further, two environmentally relevant samples (a sprouting broccoli seed and a D. magna egg) were successfully studied using the CMOS micro-coil system. 13C NMR was used to help resolve broad signals in the 1H spectrum of the 13C enriched broccoli seed, and steady state free precession was used to improve the signal-to-noise ratio by a factor of six. 19F NMR was used to track fluorinated contaminants in a single D. magna egg, showing potential for studying egg-pollutant interactions. Overall, CMOS micro-coil NMR demonstrates significant promise in environmental research, especially when the future potential to scale to multiple coil arrays (greatly improving throughput) is considered.

Exploring Proton-Only NMR Experiments and Filters for Daphnia In Vivo: Potential and Limitations.

Environmental metabolomics provides insight into how anthropogenic activities have an impact on the health of an organism at the molecular level. Within this field, in vivo NMR stands out as a powerful tool for monitoring real-time changes in an organism's metabolome. Typically, these studies use 2D 13C-1H experiments on 13C-enriched organisms. Daphnia are the most studied species, given their widespread use in toxicity testing. However, with COVID-19 and other geopolitical factors, the cost of isotope enrichment increased ~6-7 fold over the last two years, making 13C-enriched cultures difficult to maintain. Thus, it is essential to revisit proton-only in vivo NMR and ask, "Can any metabolic information be obtained from Daphnia using proton-only experiments?". Two samples are considered here: living and whole reswollen organisms. A range of filters are tested, including relaxation, lipid suppression, multiple-quantum, J-coupling suppression, 2D 1H-1H experiments, selective experiments, and those exploiting intermolecular single-quantum coherence. While most filters improve the ex vivo spectra, only the most complex filters succeed in vivo. If non-enriched organisms must be used, then, DREAMTIME is recommended for targeted monitoring, while IP-iSQC was the only experiment that allowed non-targeted metabolite identification in vivo. This paper is critically important as it documents not just the experiments that succeed in vivo but also those that fail and demonstrates first-hand the difficulties associated with proton-only in vivo NMR.

Endoscopic Ultrasound for Diagnosis and Management of Pediatric Gastrointestinal Stromal Tumor.

Gastrointestinal (GI) stromal tumors arise from the interstitial cells of Cajal and are rare in the pediatric population. The most common clinical manifestation is anemia secondary to GI bleeding. Endoscopy is commonly used for diagnostic and therapeutic interventions of an obstructing mass or gastrointestinal bleed, while experience with endoscopic ultrasound (EUS) and EUS fine needle aspiration (EUS-FNA) for pediatric patients with suspected gastric tumors is limited. We report 2 cases, a 14-year-old male and an 11-year-old female, who presented with symptomatic anemia. Both patients were diagnosed with GI stromal tumors of the stomach using EUS and EUS-FNA. This report shows that EUS and EUS-FNA are safe and effective diagnostic tools for pediatric patients.

Detection of graft fibrosis by vibration-controlled transient elastography in pediatric liver transplant recipients.

Pediatric liver transplant recipients are at risk of developing graft fibrosis which can affect patient survival. VCTE is a non-invasive tool that measures LSM and has been shown to correlate with hepatic fibrosis. The aim of this study was to therefore evaluate the ability of LSM to predict fibrosis in pediatric liver transplant recipients with different graft types. We performed a cross-sectional study evaluating LSM of 28 pediatric liver transplant recipients who underwent a total of 20 liver biopsies within 1 month of LSM. LSM was compared to liver histology as well as graft type: WL or PL. The median LSM of all post-transplant patients was 5.6 kPa (range = 2.7-18.3). There was a statistically significant correlation between LSM and METAVIR fibrosis score (P = .001) and LAF score (P < .001). There was no difference in LSM between graft type (P = .088). The AUROC curve for LSM predicting any significant fibrosis (F ≥ 2) was 0.863. A cutoff value of 7.25 had a sensitivity of 71%, specificity of 100%, NPV of 87%, and PPV of 100% for significant fibrosis. LSM by VCTE is feasible in pediatric liver transplant recipients regardless of graft type. We found a significant correlation between LSM and hepatic fibrosis and established a cutoff value that may help determine which patients warrant further evaluation for graft fibrosis.

Liver Stiffness Measurement by Vibration Controlled Transient Elastography Does Not Correlate to Hepatic Iron Overload in Children With Sickle Cell Disease.

BACKGROUND: Children with sickle cell disease (SCD) are at risk of liver injury because of sickle cell hepatopathy and iron overload from chronic transfusions (CT). The authors examine the association between iron overload and liver stiffness measurement (LSM) by vibration controlled transient elastography (VCTE), which has been shown to correlate with fibrosis. METHODS: Patients 21 years of age and less with SCD had VCTE performed; those who received CT underwent magnetic resonance imaging T2* for iron quantification. RESULTS: The authors enrolled 42 patients, 17 (40%) of whom received CT. There was no difference in LSM between patients who underwent CT (5.5±1.5 kPa) and those who did not (5.2±2.3 kPa) (P=0.923). There was no correlation between iron quantification and LSM (r=-0.077, P=0.769). However, children 12 years of age and older had abnormal LSM when compared with a reference range (P=0.013). CONCLUSION: VCTE is a noninvasive technology that is feasible in children with SCD. LSM values were elevated in older children but did not correlate with iron overload, suggesting that fibrosis may not be affected by iron overload alone. Though additional data are needed, LSM may be a useful test for the progression of liver disease in SCD regardless of iron burden.

Use of Lumen-apposing Metal Stents for Endoscopic Drainage of Intra-abdominal Fluid Collections in Pediatric Patients.

INTRODUCTION: Intraabdominal fluid collections that previously required surgical intervention can now be drained with less invasive techniques. The use of lumen-apposing metal stents (LAMS) to treat pancreatic pseudocysts and perirectal abscesses has been shown to be a safe and effective technique in adults. We aim to evaluate the indications, outcomes, and complications of the use of LAMS in pediatric patients at our institution. METHODS: A retrospective chart review was performed to study patients up to 18 years of age at the Children's Hospital at Montefiore who underwent drainage of intraabdominal fluid collections with the use of LAMS. The main outcome measures were technical and clinical success and associated adverse events with LAMS placement. RESULTS: Seven patients (2 girls) ranging from 9 to 18 years were identified. Four patients had perirectal abscess postperforated appendicitis and 3 patients had pancreatic pseudocysts. All of the patients had complete resolution of the collections, with no recurrence, and our technical and clinical success rate was 100%. Only 1 patient had mild bleeding after placement that spontaneously resolved. DISCUSSION: Our study demonstrates the efficacy and safety of the use of LAMS for the drainage of intraabdominal fluid collections in pediatric patients, although the number of patients included is limited.

Estimating the global burden of endemic canine rabies.

BACKGROUND: Rabies is a notoriously underreported and neglected disease of low-income countries. This study aims to estimate the public health and economic burden of rabies circulating in domestic dog populations, globally and on a country-by-country basis, allowing an objective assessment of how much this preventable disease costs endemic countries. METHODOLOGY/PRINCIPAL FINDINGS: We established relationships between rabies mortality and rabies prevention and control measures, which we incorporated into a model framework. We used data derived from extensive literature searches and questionnaires on disease incidence, control interventions and preventative measures within this framework to estimate the disease burden. The burden of rabies impacts on public health sector budgets, local communities and livestock economies, with the highest risk of rabies in the poorest regions of the world. This study estimates that globally canine rabies causes approximately 59,000 (95% Confidence Intervals: 25-159,000) human deaths, over 3.7 million (95% CIs: 1.6-10.4 million) disability-adjusted life years (DALYs) and 8.6 billion USD (95% CIs: 2.9-21.5 billion) economic losses annually. The largest component of the economic burden is due to premature death (55%), followed by direct costs of post-exposure prophylaxis (PEP, 20%) and lost income whilst seeking PEP (15.5%), with only limited costs to the veterinary sector due to dog vaccination (1.5%), and additional costs to communities from livestock losses (6%). CONCLUSIONS/SIGNIFICANCE: This study demonstrates that investment in dog vaccination, the single most effective way of reducing the disease burden, has been inadequate and that the availability and affordability of PEP needs improving. Collaborative investments by medical and veterinary sectors could dramatically reduce the current large, and unnecessary, burden of rabies on affected communities. Improved surveillance is needed to reduce uncertainty in burden estimates and to monitor the impacts of control efforts.

Truncated outlier filtering.

The statistical analysis of data can be heavily influenced by measurements of extreme value. If such measurements are contained in the remote tail ends of the true population distribution from which they are drawn, they are referred to as outliers. Neglecting to filter outliers from a sample can distort statistical computations and result in faulty conclusions. Conventional techniques identify measurements, whose distances from the mean exceed a selected multiple of the sample standard deviation, as outliers. Such approaches, however, can fail to classify measurements with large normalized distances as outliers. The truncated outlier filtering method first replaces the minimum and maximum of the population before computing the exclusion criterion. This mitigates the influence of abnormally large (or small) measurements on the normalized distance and hence yields a more compact criterion for outlier determination. Moreover, the method generalizes to two or more dimensions. Simulated one-dimensional and multidimensional data are analyzed. A discussion of the results is also presented.

The global availability of rabies immune globulin and rabies vaccine in clinics providing direct care to travelers.

BACKGROUND: Rabies, which is globally endemic, poses a risk to international travelers. To improve recommendations for travelers, we assessed the global availability of rabies vaccine (RV) and rabies immune globulin (RIG). METHODS: We conducted a 20-question online survey, in English, Spanish, and French, distributed via e-mail to travel medicine providers and other clinicians worldwide from February 1 to March 30, 2011. Results were compiled according to the region. RESULTS: Among total respondents, only 190 indicated that they provided traveler postexposure care. Most responses came from North America (38%), Western Europe (19%), Australia and South and West Pacific Islands (11%), East and Southeast Asia (8%), and Southern Africa (6%). Approximately one third of 187 respondents stated that patients presented with wounds from an animal exposure that were seldom or never adequately cleansed. RIG was often or always accessible for 100% (n = 5) of respondents in the Middle East and North Africa; 94% (n = 17) in Australia and South and West Pacific Islands; 20% (n = 1) in Tropical South America; and 56% (n = 5) in Eastern Europe and Northern Asia. Ninety-one percent (n = 158) of all respondents reported that RV was often or always accessible. For all regions, 35% (n = 58) and 26% (n = 43) of respondents felt that the cost was too high for RIG and RV, respectively. CONCLUSION: The availability of RV and RIG varied by geographic region. All travelers should be informed that RIG and RV might not be readily available at their destination and that travel health and medical evacuation insurance should be considered prior to departure. Travelers should be educated to avoid animal exposures; to clean all animal bites, licks, and scratches thoroughly with soap and water; and to seek medical care immediately, even if overseas.

Hydrophobicity of methylated DNA as a possible mechanism for gene silencing.

AFM images show that chromatin reconstituted on methylated DNA (meDNA) is compacted when imaged under water. Chromatin reconstituted on unmethylated DNA is less compacted and less sensitive to hydration. These differences must reflect changes in the physical properties of DNA on methylation, but prior studies have not revealed large differences between methylated and unmethylated DNA. Quasi-elastic light scattering studies of solutions of methylated and unmethylated DNA support this view. In contrast, AFM images of molecules at a water/solid interface yield a persistence length that nearly doubles (to 92.5 ± 4 nm) when 9% of the total DNA is methylated. This increase in persistence length is accompanied by a decrease in contour length, suggesting that a significant fraction of the meDNA changes into the stiffer A form as the more hydrophobic meDNA is dehydrated at the interface. This suggests a simple mechanism for gene silencing as the stiffer meDNA is more difficult to remove from nucleosomes.

Interface micromotion of uncemented femoral components from postmortem retrieved total hip replacements.

Axial torsional loads representative of gait and stair climbing conditions were applied to transverse sections of 8 uncemented postmortem retrievals and a high-resolution imaging system with digital image correlation was used to measure local micromotion along the bone-implant interface. For 7 components that were radiographically stable, there was limited micromotion for gait loading (1.42 ± 1.33 µm) that increased significantly (P = .0032) for stair climb loading (7.32 ± 9.96 µm). A radiographically loose component had motions on the order of 2.3 mm with gait loading. There was a strong inverse relationship between the amount of bone-implant contact (contact fraction) (P = .001) and micromotion. The uncemented components had greater contact fraction (41.8% ± 14.4% vs 11.5% ± 10.2%, P = .0033) and less median micromotion (0.81 ± 0.79 µm vs 28.8 ± 51.1 µm) compared to a previously reported study of cemented retrievals.

Renewed global partnerships and redesigned roadmaps for rabies prevention and control.

Canine rabies, responsible for most human rabies deaths, is a serious global public health concern. This zoonosis is entirely preventable, but by focusing solely upon rabies prevention in humans, this "incurable wound" persists at high costs. Although preventing human deaths through canine rabies elimination is feasible, dog rabies control is often neglected, because dogs are not considered typical economic commodities by the animal health sector. Here, we demonstrate that the responsibility of managing rabies falls upon multiple sectors, that a truly integrated approach is the key to rabies elimination, and that considerable progress has been made to this effect. Achievements include the construction of global rabies networks and organizational partnerships; development of road maps, operational toolkits, and a blueprint for rabies prevention and control; and opportunities for scaling up and replication of successful programs. Progress must continue towards overcoming the remaining challenges preventing the ultimate goal of rabies elimination.