Sub-second periodicity in a fast radio burst.

Fast radio bursts (FRBs) are millisecond-duration flashes of radio waves that are visible at distances of billions of light years1. The nature of their progenitors and their emission mechanism remain open astrophysical questions2. Here we report the detection of the multicomponent FRB 20191221A and the identification of a periodic separation of 216.8(1) ms between its components, with a significance of 6.5σ. The long (roughly 3 s) duration and nine or more components forming the pulse profile make this source an outlier in the FRB population. Such short periodicity provides strong evidence for a neutron-star origin of the event. Moreover, our detection favours emission arising from the neutron-star magnetosphere3,4, as opposed to emission regions located further away from the star, as predicted by some models5.

The Exon Junction Complex: A Multitasking Guardian of the Transcriptome.

In a recent issue of Molecular Cell, Boehm et al. (2018), Blazquez et al. (2018), and Gonatopoulos-Pournatzis et al. (2018) uncover novel mechanisms by which the cell regulates splicing of cryptic splice sites and microexons.

Dysregulation of the chromatin environment leads to differential alternative splicing as a mechanism of disease in a human model of autism spectrum disorder.

Autism spectrum disorder (ASD) affects 1 in 44 children. Chromatin regulatory proteins are overrepresented among genes that contain high risk variants in ASD. Disruption of the chromatin environment leads to widespread dysregulation of gene expression, which is traditionally thought of as a mechanism of disease pathogenesis associated with ASD. Alternatively, alterations in chromatin dynamics could also lead to dysregulation of alternative splicing, which is understudied as a mechanism of ASD pathogenesis. The anticonvulsant valproic acid (VPA) is a well-known environmental risk factor for ASD that acts as a class I histone deacetylase inhibitor. However, the precise molecular mechanisms underlying defects in human neuronal development associated with exposure to VPA are understudied. To dissect how VPA exposure and subsequent chromatin hyperacetylation influence molecular signatures involved in ASD pathogenesis, we conducted RNA sequencing (RNA-seq) in human cortical neurons that were treated with VPA. We observed that differentially expressed genes (DEGs) were enriched for mRNA splicing, mRNA processing, histone modification and metabolism related gene sets. Furthermore, we observed widespread increases in the number and the type of alternative splicing events. Analysis of differential transcript usage (DTU) showed that exposure to VPA induces extensive alterations in transcript isoform usage across neurodevelopmentally important genes. Finally, we find that DEGs and genes that display DTU overlap with known ASD-risk genes. Altogether, these findings suggest that, in addition to differential gene expression, changes in alternative splicing correlated with alterations in the chromatin environment could act as an additional mechanism of disease in ASD.

A Phase I Trial of a Methionine Restricted Diet with Concurrent Radiation Therapy.

Methionine is an essential amino acid critical for cell growth and survival. Preclinical evidence suggests a methionine restricted diet (MRD) sensitizes cancer to radiation therapy (RT), without significant adverse effects. However, this has never been evaluated in humans. The purpose of this pilot study was to evaluate the safety and feasibility of concurrent MRD with standard-of-care definitive RT in adults with any non-skin cancer malignancy. The MRD extended from 2 wk before RT initiation, through 2 wk beyond RT completion. The primary endpoint of safety was assessed as rate of grade 3 or higher acute and late toxicities. Feasibility was assessed with quantitative plasma amino acid panel every 2 wk during the MRD (target plasma methionine 13 µM). Nine patients were accrued over a two-year period, with five able to complete the treatment course. The trial was closed due to slow accrual and subjects' difficulty maintaining the diet. No grade 3 or higher adverse events were observed. Subjects' average methionine level was 18.8 µM during treatment, with average nadir 16.8 µM. These findings suggest the safety of concurrent MRD with RT, with toxicities comparable to those expected with RT alone. However, the diet was challenging, and unacceptable to most patients.

Mutations in domain IV of elongation factor EF-G confer -1 frameshifting.

A recent crystal structure of a ribosome complex undergoing partial translocation in the absence of elongation factor EF-G showed disruption of codon-anticodon pairing and slippage of the reading frame by -1, directly implicating EF-G in preservation of the translational reading frame. Among mutations identified in a random screen for dominant-lethal mutations of EF-G were a cluster of six that map to the tip of domain IV, which has been shown to contact the codon-anticodon duplex in trapped translocation intermediates. In vitro synthesis of a full-length protein using these mutant EF-Gs revealed dramatically increased -1 frameshifting, providing new evidence for a role for domain IV of EF-G in maintaining the reading frame. These mutations also caused decreased rates of mRNA translocation and rotational movement of the head and body domains of the 30S ribosomal subunit during translocation. Our results are in general agreement with recent findings from Rodnina and coworkers based on in vitro translation of an oligopeptide using EF-Gs containing mutations at two positions in domain IV, who found an inverse correlation between the degree of frameshifting and rates of translocation. Four of our six mutations are substitutions at positions that interact with the translocating tRNA, in each case contacting the RNA backbone of the anticodon loop. We suggest that EF-G helps to preserve the translational reading frame by preventing uncoupled movement of the tRNA through these contacts; a further possibility is that these interactions may stabilize a conformation of the anticodon that favors base-pairing with its codon.

Analysis of Survival Benefits of Living Versus Deceased Donor Liver Transplant in High Model for End-Stage Liver Disease and Hepatorenal Syndrome.

BACKGROUND AND AIMS: Previous recommendations suggested living donor liver transplantation (LDLT) should not be considered for patients with Model for End-Stage Liver Disease (MELD) > 25 and hepatorenal syndrome (HRS). APPROACH AND RESULTS: Patients who were listed with MELD > 25 from 2008 to 2017 were analyzed with intention-to-treat (ITT) basis retrospectively. Patients who had a potential live donor were analyzed as ITT-LDLT, whereas those who had none belonged to ITT-deceased donor liver transplantation (DDLT) group. ITT-overall survival (OS) was analyzed from the time of listing. Three hundred twenty-five patients were listed (ITT-LDLT n = 212, ITT-DDLT n = 113). The risk of delist/death was lower in the ITT-LDLT group (43.4% vs. 19.8%, P < 0.001), whereas the transplant rate was higher in the ITT-LDLT group (78.3% vs. 52.2%, P < 0.001). The 5-year ITT-OS was superior in the ITT-LDLT group (72.6% vs. 49.5%, P < 0.001) for patients with MELD > 25 and patients with both MELD > 25 and HRS (56% vs. 33.8%, P < 0.001). Waitlist mortality was the highest early after listing, and the distinct alteration of slope at survival curve showed that the benefits of ITT-LDLT occurred within the first month after listing. Perioperative outcomes and 5-year patient survival were comparable for patients with MELD > 25 (88% vs. 85.4%, P = 0.279) and patients with both MELD > 25 and HRS (77% vs. 76.4%, P = 0.701) after LDLT and DDLT, respectively. The LDLT group has a higher rate of renal recovery by 1 month (77.4% vs. 59.1%, P = 0.003) and 3 months (86.1% vs, 74.5%, P = 0.029), whereas the long-term estimated glomerular filtration rate (eGFR) was similar between the 2 groups. ITT-LDLT reduced the hazard of mortality (hazard ratio = 0.387-0.552) across all MELD strata. CONCLUSIONS: The ITT-LDLT reduced waitlist mortality and allowed an earlier access to transplant. LDLT in patients with high MELD/HRS was feasible, and they had similar perioperative outcomes and better renal recovery, whereas the long-term survival and eGFR were comparable with DDLT. LDLT should be considered for patients with high MELD/HRS, and the application of LDLT should not be restricted with a MELD cutoff.

Evidence of Two-Source King Plot Nonlinearity in Spectroscopic Search for New Boson.

Optical precision spectroscopy of isotope shifts can be used to test for new forces beyond the standard model, and to determine basic properties of atomic nuclei. We measure isotope shifts on the highly forbidden ^{2}S_{1/2}→^{2}F_{7/2} octupole transition of trapped ^{168,170,172,174,176}Yb ions. When combined with previous measurements in Yb^{+} and very recent measurements in Yb, the data reveal a King plot nonlinearity of up to 240σ. The trends exhibited by experimental data are explained by nuclear density functional theory calculations with the Fayans functional. We also find, with 4.3σ confidence, that there is a second distinct source of nonlinearity, and discuss its possible origin.

Evidence for Nonlinear Isotope Shift in Yb

We measure isotope shifts for five Yb^{+} isotopes with zero nuclear spin on two narrow optical quadrupole transitions ^{2}S_{1/2}→^{2}D_{3/2}, ^{2}S_{1/2}→^{2}D_{5/2} with an accuracy of ∼300 Hz. The corresponding King plot shows a 3×10^{-7} deviation from linearity at the 3σ uncertainty level. Such a nonlinearity can indicate physics beyond the Standard Model (SM) in the form of a new bosonic force carrier, or arise from higher-order nuclear effects within the SM. We identify the quadratic field shift as a possible nuclear contributor to the nonlinearity at the observed scale, and show how the nonlinearity pattern can be used in future, more accurate measurements to separate a new-boson signal from nuclear effects.

Current Role of the CardioMEMS Device for Management of Patients with Heart Failure.

PURPOSE OF REVIEW: Heart failure (HF) remains a significant burden to our healthcare system and a leading cause of hospitalizations. Current reactive strategies to treat and manage HF have failed to reduce hospitalizations and improve survival. The CardioMEMS device has recently been demonstrated to improve quality of life in HF and reduce HF-related hospitalizations. Current HF management strategies are reviewed with a particular emphasis on the current role of the CardioMEMS device. RECENT FINDINGS: The CHAMPION trial is the only randomized trial looking at the CardioMEMS device. Patients managed with targeted pulmonary artery pressures resulted in 28% reduction in the primary end-point of HF-related hospitalization at 6 months (HR 0.72, 95% CI 0.60-0.85, p = 0.0002) and 37% reduction during the entire follow-up period, which averaged 15 months (HR 0.63, 95% CI 0.52-0.77, p < 0.0001). The prospective open-label post-approval study recently presented a 58% reduction in HF hospitalizations per patient year (HR 0.42, 95% CI 0.38-0.47, p < 0.0001). Management of HF using the CardioMEMS device has been shown to reduce HF hospitalizations and improve quality of life regardless of ejection fraction. Patients best suited for this device are those with recurrent congestive symptoms despite optimal medical therapy.

Cosmic Bell Test Using Random Measurement Settings from High-Redshift Quasars.

In this Letter, we present a cosmic Bell experiment with polarization-entangled photons, in which measurement settings were determined based on real-time measurements of the wavelength of photons from high-redshift quasars, whose light was emitted billions of years ago; the experiment simultaneously ensures locality. Assuming fair sampling for all detected photons and that the wavelength of the quasar photons had not been selectively altered or previewed between emission and detection, we observe statistically significant violation of Bell's inequality by 9.3 standard deviations, corresponding to an estimated p value of ≲7.4×10^{-21}. This experiment pushes back to at least ∼7.8 Gyr ago the most recent time by which any local-realist influences could have exploited the "freedom-of-choice" loophole to engineer the observed Bell violation, excluding any such mechanism from 96% of the space-time volume of the past light cone of our experiment, extending from the big bang to today.

Cosmic Bell Test: Measurement Settings from Milky Way Stars.

Bell's theorem states that some predictions of quantum mechanics cannot be reproduced by a local-realist theory. That conflict is expressed by Bell's inequality, which is usually derived under the assumption that there are no statistical correlations between the choices of measurement settings and anything else that can causally affect the measurement outcomes. In previous experiments, this "freedom of choice" was addressed by ensuring that selection of measurement settings via conventional "quantum random number generators" was spacelike separated from the entangled particle creation. This, however, left open the possibility that an unknown cause affected both the setting choices and measurement outcomes as recently as mere microseconds before each experimental trial. Here we report on a new experimental test of Bell's inequality that, for the first time, uses distant astronomical sources as "cosmic setting generators." In our tests with polarization-entangled photons, measurement settings were chosen using real-time observations of Milky Way stars while simultaneously ensuring locality. Assuming fair sampling for all detected photons, and that each stellar photon's color was set at emission, we observe statistically significant ≳7.31σ and ≳11.93σ violations of Bell's inequality with estimated p values of ≲1.8×10^{-13} and ≲4.0×10^{-33}, respectively, thereby pushing back by ∼600 years the most recent time by which any local-realist influences could have engineered the observed Bell violation.

High resolution structure and double electron-electron resonance of the zebrafish voltage-dependent anion channel 2 reveal an oligomeric population.

In recent years, there has been a vast increase in structural and functional understanding of VDAC1, but VDAC2 and -3 have been understudied despite having many unique phenotypes. One reason for the paucity of structural and biochemical characterization of the VDAC2 and -3 isoforms stems from the inability of obtaining purified, functional protein. Here we demonstrate the expression, isolation, and basic characterization of zebrafish VDAC2 (zfVDAC2). Further, we resolved the structure of zfVDAC2 at 2.8 Šresolution, revealing a crystallographic dimer. The dimer orientation was confirmed in solution by double electron-electron resonance spectroscopy and by cross-linking experiments disclosing a dimer population of ∼20% in lauryldimethine amine oxide detergent micelles, whereas in lipidic bicelles a higher population of dimeric and higher order oligomers species were observed. The present study allows for a more accurate structural comparison between VDAC2 and its better-studied counterpart VDAC1.

Multimerization of glycosylphosphatidylinositol-anchored high density lipoprotein-binding protein 1 (GPIHBP1) and familial chylomicronemia from a serine-to-cysteine substitution in GPIHBP1 Ly6 domain.

GPIHBP1, a glycosylphosphatidylinositol-anchored glycoprotein of microvascular endothelial cells, binds lipoprotein lipase (LPL) within the interstitial spaces and transports it across endothelial cells to the capillary lumen. The ability of GPIHBP1 to bind LPL depends on the Ly6 domain, a three-fingered structure containing 10 cysteines and a conserved pattern of disulfide bond formation. Here, we report a patient with severe hypertriglyceridemia who was homozygous for a GPIHBP1 point mutation that converted a serine in the GPIHBP1 Ly6 domain (Ser-107) to a cysteine. Two hypertriglyceridemic siblings were homozygous for the same mutation. All three homozygotes had very low levels of LPL in the preheparin plasma. We suspected that the extra cysteine in GPIHBP1-S107C might prevent the trafficking of the protein to the cell surface, but this was not the case. However, nearly all of the GPIHBP1-S107C on the cell surface was in the form of disulfide-linked dimers and multimers, whereas wild-type GPIHBP1 was predominantly monomeric. An insect cell GPIHBP1 expression system confirmed the propensity of GPIHBP1-S107C to form disulfide-linked dimers and to form multimers. Functional studies showed that only GPIHBP1 monomers bind LPL. In keeping with that finding, there was no binding of LPL to GPIHBP1-S107C in either cell-based or cell-free binding assays. We conclude that an extra cysteine in the GPIHBP1 Ly6 motif results in multimerization of GPIHBP1, defective LPL binding, and severe hypertriglyceridemia.

A new monoclonal antibody, 4-1a, that binds to the amino terminus of human lipoprotein lipase.

Lipoprotein lipase (LPL) has been highly conserved through vertebrate evolution, making it challenging to generate useful antibodies. Some polyclonal antibodies against LPL have turned out to be nonspecific, and the available monoclonal antibodies (Mabs) against LPL, all of which bind to LPL's carboxyl terminus, have drawbacks for some purposes. We report a new LPL-specific monoclonal antibody, Mab 4-1a, which binds to the amino terminus of LPL (residues 5-25). Mab 4-1a binds human and bovine LPL avidly; it does not inhibit LPL catalytic activity nor does it interfere with the binding of LPL to heparin. Mab 4-1a does not bind to human hepatic lipase. Mab 4-1a binds to GPIHBP1-bound LPL and does not interfere with the ability of the LPL-GPIHBP1 complex to bind triglyceride-rich lipoproteins. Mab 4-1a will be a useful reagent for both biochemists and clinical laboratories.

Equivalent binding of wild-type lipoprotein lipase (LPL) and S447X-LPL to GPIHBP1, the endothelial cell LPL transporter.

The S447X polymorphism in lipoprotein lipase (LPL), which shortens LPL by two amino acids, is associated with low plasma triglyceride levels and reduced risk for coronary heart disease. S447X carriers have higher LPL levels in the pre- and post-heparin plasma, raising the possibility that the S447X polymorphism leads to higher LPL levels within capillaries. One potential explanation for increased amounts of LPL in capillaries would be more avid binding of S447X-LPL to GPIHBP1 (the protein that binds LPL dimers and shuttles them to the capillary lumen). This explanation seems plausible because sequences within the carboxyl terminus of LPL are known to mediate LPL binding to GPIHBP1. To assess the impact of the S447X polymorphism on LPL binding to GPIHBP1, we compared the ability of internally tagged versions of wild-type LPL (WT-LPL) and S447X-LPL to bind to GPIHBP1 in both cell-based and cell-free binding assays. In the cell-based assay, we compared the binding of WT-LPL and S447X-LPL to GPIHBP1 on the surface of cultured cells. This assay revealed no differences in the binding of WT-LPL and S447X-LPL to GPIHBP1. In the cell-free assay, we compared the binding of internally tagged WT-LPL and S447X-LPL to soluble GPIHBP1 immobilized on agarose beads. Again, no differences in the binding of WT-LPL and S447X-LPL to GPIHBP1 were observed. We conclude that increased binding of S447X-LPL to GPIHBP1 is unlikely to be the explanation for more efficient lipolysis and lower plasma triglyceride levels in S447X carriers.

Noninvasive assessments of liver fibrosis with transient elastography and Hui index predict survival in patients with chronic hepatitis B.

BACKGROUND AND AIMS: The prognostic role of noninvasive assessments of liver fibrosis has been evolving. Our aim was to investigate the prognostic value of liver stiffness measurement (LSM) with transient elastography and serum-based Hui index to predict hepatic events and deaths in chronic hepatitis B (CHB) patients. METHODS: The main prospective cohort included 1555 consecutive CHB patients referred for transient elastography examination; a subgroup of 980 patients underwent follow-up assessments at least 3 years later formed the serial cohort. Cox proportional hazard model was performed to determine the relationship of LSM, Hui index and other clinical variables with hepatic events and deaths. RESULTS: During a mean follow-up of 69 ± 9 months, 119 patients (7.6%) developed hepatic events or deaths. Hepatic event-free survival was significantly decreased with increasing stages of LSM and Hui index. The 5-year cumulative probability of hepatic event-free survival of patients of Stage 1-7 of LSM were 99.3%, 98.8%, 95.7%, 90.9%, 89.6%, 74.6%, and 50.0%, respectively; that of Stage 1 to 3 of Hui index were 98.2%, 93.1%, and 77.5%, respectively. Independent predictors of hepatic event-free survival were age, baseline LSM, and follow-up Hui index. Serum ALT and body mass index affected the accuracy of prediction by LSM. Patients remained early stages of LSM or Hui index at follow-up visit had better survival compared to those remained at late stages. CONCLUSION: Baseline and change in noninvasive parameters of liver fibrosis, LSM and Hui index, are accurate to predict hepatic event-free survival in CHB patients.

Effects of Nanowire Length and Surface Roughness on the Electrochemical Sensor Properties of Nafion-Free, Vertically Aligned Pt Nanowire Array Electrodes.

In this paper, vertically aligned Pt nanowire arrays (PtNWA) with different lengths and surface roughnesses were fabricated and their electrochemical performance toward hydrogen peroxide (H2O2) detection was studied. The nanowire arrays were synthesized by electroplating Pt in nanopores of anodic aluminum oxide (AAO) template. Different parameters, such as current density and deposition time, were precisely controlled to synthesize nanowires with different surface roughnesses and various lengths from 3 µm to 12 µm. The PtNWA electrodes showed better performance than the conventional electrodes modified by Pt nanowires randomly dispersed on the electrode surface. The results indicate that both the length and surface roughness can affect the sensing performance of vertically aligned Pt nanowire array electrodes. Generally, longer nanowires with rougher surfaces showed better electrochemical sensing performance. The 12 µm rough surface PtNWA presented the largest sensitivity (654 µA·mM⁻¹·cm⁻²) among all the nanowires studied, and showed a limit of detection of 2.4 µM. The 12 µm rough surface PtNWA electrode also showed good anti-interference property from chemicals that are typically present in the biological samples such as ascorbic, uric acid, citric acid, and glucose. The sensing performance in real samples (river water) was tested and good recovery was observed. These Nafion-free, vertically aligned Pt nanowires with surface roughness control show great promise as versatile electrochemical sensors and biosensors.

Liver stiffness-based optimization of hepatocellular carcinoma risk score in patients with chronic hepatitis B.

BACKGROUND & AIMS: CU-HCC score is accurate to predict hepatocellular carcinoma (HCC) in chronic hepatitis B (CHB) patients. However, diagnosis of cirrhosis may be incorrect based on ultrasonography, leading to some errors in HCC prediction. This study aimed to evaluate the accuracy of LSM-HCC score, refined from CU-HCC score with liver stiffness measurement (LSM) using transient elastography to predict HCC. METHODS: A prospective cohort study of 1555 consecutive CHB patients referred for transient elastography examination; 1035 and 520 patients randomly assigned to training and validation cohorts, respectively. Clinical cirrhosis of CU-HCC score was substituted by LSM and analyzed with multivariable Cox regression analysis with other parameters. RESULTS: During a mean follow-up of 69 months, 38 patients (3.7%) in the training cohort and 17 patients (3.4%) in the validation cohort developed HCC. A new LSM-HCC score composed of LSM, age, serum albumin and hepatitis B virus (HBV) DNA levels were derived, which ranges from 0 to 30. Areas under receiver operating characteristic curves of LSM-HCC score were higher than those of CU-HCC score (0.83-0.89 vs. 0.75-0.81). By applying the cutoff value of 11, the score excluded future HCC with high negative predictive value (99.4%-100%) at 5 years. CONCLUSIONS: LSM-HCC score constructed from LSM, age, serum albumin and HBV DNA level is accurate to predict HCC in CHB patients.

Use of intravascular ultrasound in inferior STEMI due to Type A aortic dissection.

A 57-year-old woman with good past health was admitted to the accident and emergency department at an outside hospital for sudden onset chest pain. Electrocardiogram revealed ST-segment elevation at inferior leads.

Cardiac power output ratio: Novel survival predictor after percutaneous ventricular assist device in cardiogenic shock.

AIMS: Currently, there is limited data on prognostic indicators after insertion of percutaneous ventricular assist device (PVAD) in the treatment of cardiogenic shock (CS). This study evaluated the prognostic role of cardiac power output (CPO) ratio, defined as CPO at 24 h divided by early CPO (30 min to 2 h), in CS patients after PVAD. METHODS AND RESULTS: Consecutive CS patients from the QEH-PVAD Registry were followed up for survival at 90 days after PVAD. Among 121 consecutive patients, 98 underwent right heart catheterization after PVAD, with CPO ratio available in 68 patients. The CPO ratio and 24-h CPO, but not the early CPO post PVAD, were significantly associated with 90-day survival, with corresponding area under curve in ROC analysis of 0.816, 0.740, and 0.469, respectively. In multivariate analysis, only the CPO ratio and lactate level at 24 h remained as independent survival predictors. The CPO ratio was not associated with age, sex, and body size. Patients with lower CPO ratio had significantly lower coronary perfusion pressure, worse right heart indices, and higher pulmonary vascular resistance. A lower CPO ratio was also significantly associated with mechanical ventilation and higher creatine kinase levels in myocardial infarction patients. CONCLUSION: In post-PVAD patients, the CPO ratio outperformed the absolute CPO values and other haemodynamic metrics in predicting survival at 90 days. Such a proportional change of CPO over time, likely reflecting native heart function recovery, may help to guide management of CS patients post-PVAD.