High-Fidelity RNA Copying via 2',3'-Cyclic Phosphate Ligation

Templated ligation offers an efficient approach to replicate long strands in an RNA world. The 2',3'-cyclic phosphate (>P) is a prebiotically available activation that also forms during RNA hydrolysis. Using gel electrophoresis and high-performance liquid chromatography, we found that the templated ligation of RNA with >P proceeds in simple low-salt aqueous solutions with 1 mM MgCl2 under alkaline pH ranging from 9 to 11 and temperatures from -20 to 25 °C. No additional catalysts were required. In contrast to previous reports, we found an increase in the number of canonical linkages to 50%. The reaction proceeds in a sequence-specific manner, with an experimentally determined ligation fidelity of 82% at the 3' end and 91% at the 5' end of the ligation site. With splinted oligomers, five ligations created a 96-mer strand, demonstrating a pathway for the ribozyme assembly. Due to the low salt requirements, the ligation conditions will be compatible with strand separation. Templated ligation mediated by 2',3'-cyclic phosphate in alkaline conditions therefore offers a performant replication and elongation reaction for RNA on early Earth.

Heat flows enrich prebiotic building blocks and enhance their reactivity

The emergence of biopolymer building blocks is a crucial step during the origins of life1-6. However, all known formation pathways rely on rare pure feedstocks and demand successive purification and mixing steps to suppress unwanted side reactions and enable high product yields. Here we show that heat flows through thin, crack-like geo-compartments could have provided a widely available yet selective mechanism that separates more than 50 prebiotically relevant building blocks from complex mixtures of amino acids, nucleobases, nucleotides, polyphosphates and 2-aminoazoles. Using measured thermophoretic properties7,8, we numerically model and experimentally prove the advantageous effect of geological networks of interconnected cracks9,10 that purify the previously mixed compounds, boosting their concentration ratios by up to three orders of magnitude. The importance for prebiotic chemistry is shown by the dimerization of glycine11,12, in which the selective purification of trimetaphosphate (TMP)13,14 increased reaction yields by five orders of magnitude. The observed effect is robust under various crack sizes, pH values, solvents and temperatures. Our results demonstrate how geologically driven non-equilibria could have explored highly parallelized reaction conditions to foster prebiotic chemistry.

Achievement of Target Gain Larger than Unity in an Inertial Fusion Experiment

On December 5, 2022, an indirect drive fusion implosion on the National Ignition Facility (NIF) achieved a target gain G_{target} of 1.5. This is the first laboratory demonstration of exceeding "scientific breakeven" (or G_{target}>1) where 2.05 MJ of 351 nm laser light produced 3.1 MJ of total fusion yield, a result which significantly exceeds the Lawson criterion for fusion ignition as reported in a previous NIF implosion [H. Abu-Shawareb et al. (Indirect Drive ICF Collaboration), Phys. Rev. Lett. 129, 075001 (2022)PRLTAO0031-900710.1103/PhysRevLett.129.075001]. This achievement is the culmination of more than five decades of research and gives proof that laboratory fusion, based on fundamental physics principles, is possible. This Letter reports on the target, laser, design, and experimental advancements that led to this result.

Replication elongates short DNA, reduces sequence bias and develops trimer structure

The origin of molecular evolution required the replication of short oligonucleotides to form longer polymers. Prebiotically plausible oligonucleotide pools tend to contain more of some nucleobases than others. It has been unclear whether this initial bias persists and how it affects replication. To investigate this, we examined the evolution of 12-mer biased short DNA pools using an enzymatic model system. This allowed us to study the long timescales involved in evolution, since it is not yet possible with currently investigated prebiotic replication chemistries. Our analysis using next-generation sequencing from different time points revealed that the initial nucleotide bias of the pool disappeared in the elongated pool after isothermal replication. In contrast, the nucleotide composition at each position in the elongated sequences remained biased and varied with both position and initial bias. Furthermore, we observed the emergence of highly periodic dimer and trimer motifs in the rapidly elongated sequences. This shift in nucleotide composition and the emergence of structure through templated replication could help explain how biased prebiotic pools could undergo molecular evolution and lead to complex functional nucleic acids.

White and green rust chimneys accumulate RNA in a ferruginous chemical garden

Mechanisms of nucleic acid accumulation were likely critical to life's emergence in the ferruginous oceans of the early Earth. How exactly prebiotic geological settings accumulated nucleic acids from dilute aqueous solutions, is poorly understood. As a possible solution to this concentration problem, we simulated the conditions of prebiotic low-temperature alkaline hydrothermal vents in co-precipitation experiments to investigate the potential of ferruginous chemical gardens to accumulate nucleic acids via sorption. The injection of an alkaline solution into an artificial ferruginous solution under anoxic conditions (O2  < 0.01% of present atmospheric levels) and at ambient temperatures, caused the precipitation of amakinite ("white rust"), which quickly converted to chloride-containing fougerite ("green rust"). RNA was only extractable from the ferruginous solution in the presence of a phosphate buffer, suggesting RNA in solution was bound to Fe2+ ions. During chimney formation, this iron-bound RNA rapidly accumulated in the white and green rust chimney structure from the surrounding ferruginous solution at the fastest rates in the initial white rust phase and correspondingly slower rates in the following green rust phase. This represents a new mechanism for nucleic acid accumulation in the ferruginous oceans of the early Earth, in addition to wet-dry cycles and may have helped to concentrate RNA in a dilute prebiotic ocean.

Sequence self-selection by cyclic phase separation

The emergence of functional oligonucleotides on early Earth required a molecular selection mechanism to screen for specific sequences with prebiotic functions. Cyclic processes such as daily temperature oscillations were ubiquitous in this environment and could trigger oligonucleotide phase separation. Here, we propose sequence selection based on phase separation cycles realized through sedimentation in a system subjected to the feeding of oligonucleotides. Using theory and experiments with DNA, we show sequence-specific enrichment in the sedimented dense phase, in particular of short 22-mer DNA sequences. The underlying mechanism selects for complementarity, as it enriches sequences that tightly interact in the dense phase through base-pairing. Our mechanism also enables initially weakly biased pools to enhance their sequence bias or to replace the previously most abundant sequences as the cycles progress. Our findings provide an example of a selection mechanism that may have eased screening for auto-catalytic self-replicating oligonucleotides.

Alkaline vents recreated in two dimensions to study pH gradients, precipitation morphology, and molecule accumulation

Alkaline vents (AVs) are hypothesized to have been a setting for the emergence of life, by creating strong gradients across inorganic membranes within chimney structures. In the past, three-dimensional chimney structures were formed under laboratory conditions; however, no in situ visualization or testing of the gradients was possible. We develop a quasi-two-dimensional microfluidic model of AVs that allows spatiotemporal visualization of mineral precipitation in low-volume experiments. Upon injection of an alkaline fluid into an acidic, iron-rich solution, we observe a diverse set of precipitation morphologies, mainly controlled by flow rate and ion concentration. Using microscope imaging and pH-dependent dyes, we show that finger-like precipitates can facilitate formation and maintenance of microscale pH gradients and accumulation of dispersed particles in confined geometries. Our findings establish a model to investigate the potential of gradients across a semipermeable boundary for early compartmentalization, accumulation, and chemical reactions at the origins of life.

Thermophoresis beyond Local Thermodynamic Equilibrium

We measure the thermophoresis of polysterene beads over a wide range of temperature gradients and find a pronounced nonlinear phoretic characteristic. The transition to the nonlinear behavior is marked by a drastic slowing down of thermophoretic motion and is characterized by a Péclet number of order unity as corroborated for different particle sizes and salt concentrations. The data follow a single master curve covering the entire nonlinear regime for all system parameters upon proper rescaling of the temperature gradients with the Péclet number. For low thermal gradients, the thermal drift velocity follows a theoretical linear model relying on the local-equilibrium assumption, while linear theoretical approaches based on hydrodynamic stresses, ignoring fluctuations, predict significantly slower thermophoretic motion for steeper thermal gradients. Our findings suggest that thermophoresis is fluctuation dominated for small gradients and crosses over to a drift-dominated regime for larger Péclet numbers in striking contrast to electrophoresis.

Thermophoretic motion of a charged single colloidal particle

We calculate the thermophoretic drift of a charged single colloidal particle with hydrodynamically slipping surface immersed in an electrolyte solution in response to a small temperature gradient. Here we rely on a linearized hydrodynamic approach for the fluid flow and the motion of the electrolyte ions while keeping the full nonlinearity of the Poisson-Boltzmann equation of the unperturbed system to account for possible large surface charging. The partial differential equations are transformed into a coupled set of ordinary differential equations in linear response. Numerical solutions are elaborated for parameter regimes of small and large Debye shielding and different hydrodynamic boundary conditions encoded in a varying slip length. Our results are in good agreement with predictions from recent theoretical work and successfully describe experimental observations on thermophoresis of DNA. We also compare our numerical results with experimental data on polystyrene beads.

Ribozyme-mediated RNA synthesis and replication in a model Hadean microenvironment

Enzyme-catalyzed replication of nucleic acid sequences is a prerequisite for the survival and evolution of biological entities. Before the advent of protein synthesis, genetic information was most likely stored in and replicated by RNA. However, experimental systems for sustained RNA-dependent RNA-replication are difficult to realise, in part due to the high thermodynamic stability of duplex products and the low chemical stability of catalytic RNAs. Using a derivative of a group I intron as a model for an RNA replicase, we show that heated air-water interfaces that are exposed to a plausible CO₂-rich atmosphere enable sense and antisense RNA replication as well as template-dependent synthesis and catalysis of a functional ribozyme in a one-pot reaction. Both reactions are driven by autonomous oscillations in salt concentrations and pH, resulting from precipitation of acidified dew droplets, which transiently destabilise RNA duplexes. Our results suggest that an abundant Hadean microenvironment may have promoted both replication and synthesis of functional RNAs.

Sequence dependent UV damage of complete pools of oligonucleotides

Understanding the sequence-dependent DNA damage formation requires probing a complete pool of sequences over a wide dose range of the damage-causing exposure. We used high throughput sequencing to simultaneously obtain the dose dependence and quantum yields for oligonucleotide damages for all possible 4096 DNA sequences with hexamer length. We exposed the DNA to ultraviolet radiation at 266 nm and doses of up to 500 absorbed photons per base. At the dimer level, our results confirm existing literature values of photodamage, whereas we now quantified the susceptibility of sequence motifs to UV irradiation up to previously inaccessible polymer lengths. This revealed the protective effect of the sequence context in preventing the formation of UV-lesions. For example, the rate to form dipyrimidine lesions is strongly reduced by nearby guanine bases. Our results provide a complete picture of the sensitivity of oligonucleotides to UV irradiation and allow us to predict their abundance in high-UV environments.

A heated rock crack captures and polymerizes primordial DNA and RNA

Life is based on informational polymers such as DNA or RNA. For their polymerization, high concentrations of complex monomer building blocks are required. Therefore, the dilution by diffusion poses a major problem before early life could establish a non-equilibrium of compartmentalization. Here, we explored a natural non-equilibrium habitat to polymerize RNA and DNA. A heat flux across thin rock cracks is shown to accumulate and maintain nucleotides. This boosts the polymerization to RNA and DNA inside the crack. Moreover, the polymers remain localized, aiding both the creation of longer polymers and fostering downstream evolutionary steps. In a closed system, we found single nucleotides concentrate 10⁴-fold at the bottom of the crack compared to the top after 24 hours. We detected enhanced polymerization for 2 different activation chemistries: aminoimidazole-activated DNA nucleotides and 2',3'-cyclic RNA nucleotides. The copolymerization of 2',3'-cGMP and 2',3'-cCMP in the thermal pore showed an increased heterogeneity in sequence composition compared to isothermal drying. Finite element models unravelled the combined polymerization and accumulation kinetics and indicated that the escape of the nucleotides from such a crack is negligible over a time span of years. The thermal non-equilibrium habitat establishes a cell-like compartment that actively accumulates nucleotides for polymerization and traps the resulting oligomers. We argue that the setting creates a pre-cellular non-equilibrium steady state for the first steps of molecular evolution.

Prebiotic Foam Environments to Oligomerize and Accumulate RNA

When water interacts with porous rocks, its wetting and surface tension properties create air bubbles in large number. To probe their relevance as a setting for the emergence of life, we microfluidically created foams that were stabilized with lipids. A persistent non-equilibrium setting was provided by a thermal gradient. The foam's large surface area triggers capillary flows and wet-dry reactions that accumulate, aggregate and oligomerize RNA, offering a compelling habitat for RNA-based early life as it offers both wet and dry conditions in direct neighborhood. Lipids were screened to stabilize the foams. The prebiotically more probable myristic acid stabilized foams over many hours. The capillary flow created by the evaporation at the water-air interface provided an attractive force for molecule localization and selection for molecule size. For example, self-binding oligonucleotide sequences accumulated and formed micrometer-sized aggregates which were shuttled between gas bubbles. The wet-dry cycles at the foam bubble interfaces triggered a non-enzymatic RNA oligomerization from 2',3'-cyclic CMP and GMP which despite the small dry reaction volume was superior to the corresponding dry reaction. The found characteristics make heated foams an interesting, localized setting for early molecular evolution.

Regulating DNA-Hybridization Using a Chemically Fueled Reaction Cycle

Molecular machines, such as ATPases or motor proteins, couple the catalysis of a chemical reaction, most commonly hydrolysis of nucleotide triphosphates, to their conformational change. In essence, they continuously convert a chemical fuel to drive their motion. An outstanding goal of nanotechnology remains to synthesize a nanomachine with similar functions, precision, and speed. The field of DNA nanotechnology has given rise to the engineering precision required for such a device. Simultaneously, the field of systems chemistry developed fast chemical reaction cycles that convert fuel to change the function of molecules. In this work, we thus combined a chemical reaction cycle with the precision of DNA nanotechnology to yield kinetic control over the conformational state of a DNA hairpin. Future work on such systems will result in out-of-equilibrium DNA nanodevices with precise functions.

CT-determined tricuspid annular dilatation is associated with persistence of tricuspid regurgitation after transcatheter aortic valve replacement

Introduction

Moderate or severe tricuspid regurgitation (TR) can be observed in 11% to 27% of patients with severe aortic stenosis (AS) undergoing transcatheter aortic valve replacement (TAVR). Even though in most patients an improvement of TR can be achieved after TAVR, the persistence of severe or massive TR after the procedure is associated with increased all-cause mortality.

Purpose

The aim of this study was to investigate if tricuspid annular dilatation (TAD) measured in pre-procedural CT among TAVR patients who had at least moderate TR at baseline could serve as a predictor for the persistence of TR. Moreover, the predictive value of TR persistence on the composite of 2-year mortality or tricuspid valve intervention was analysed.

Methods

We examined 151 patients with severe AS and at least moderate concomitant TR at baseline, who were treated with TAVR from April 2013 to December 2019. TR persistence was defined as the same or a higher grade of TR in the follow-up echocardiography at least 30 days after the procedure compared to preprocedural TR grade. To identify patients with TAD, the maximum septolateral diameter of the tricuspid annulus was measured in pre-procedural cardiac computed tomography images and normalized to the body surface area.

Results

The median value of 25.5 mm/m2 was determined as cut-off value for TAD. Out of 151 patients with moderate or more TR before TAVR, 75 patients (49.7%) were above the threshold of 25.5 mm/m2. Improvement of TR after TAVR of at least one grade was significantly more frequent in patients without TAD than with TAD (59% vs. 32%, corresponding odds ratio for persistence of TR: 3.06, 95% confidence interval: 1.50–6.35, p=0.001) (Figure 1A). Multivariable logistic regression analysis with adjustment for baseline TR severity confirmed that the predictive value of TAD for TR persistence after TAVR was irrespective of baseline TR (adjusted odds ratio: 2.79, 95% confidence interval: 1.42–5.59, p=0.003). Tricuspid valve intervention was conducted in 11 patients with TAD after TAVR (14.6%) and in no patients without TAD. Accordingly, at 2-years, tricuspid valve intervention-free survival was lowest among patients with TAD and persistent TR (Figure 1B).

Conclusion

Our analysis demonstrates for the first time that in patients undergoing TAVR for severe AS and at least moderate concomitant TR, CT-derived TAD is associated with persistence of TR after the procedure. Furthermore, TR persistence is associated with an adverse outcome.

Funding Acknowledgement

Type of funding sources: None.

Three-year outcomes following transcatheter tricuspid valve edge-to-edge repair

Background

Tricuspid regurgitation (TR) has long been neglected due to limited therapeutic options. Within the past five years, transcatheter tricuspid valve edge-to-edge repair (T-TEER) has become a valuable tool in the treatment of TR besides diuretic medical therapy and valve surgery. Owing its novelty, data on long-term survival after T-TEER for relevant TR are sparse. Beyond that, there is uncertainty on the impact of TR reduction on outcomes after successful T-TEER.

Purpose

This study sought to investigate long-term survival outcome after T-TEER for relevant symptomatic TR. We evaluated the impact of TR reduction on outcome in patients with successful T-TEER.

Methods

Consecutive patients who underwent successful isolated T-TEER for relevant TR from 2016 until 2022 at a high-volume university center were included in the study. Procedural success was defined as at least one degree TR reduction. Long-term survival endpoint was three-year all-cause mortality. Survival follow-up was completed via phone calls with the patients themselves, the next of kin, local practitioners and using the German national population registry. Post-procedural TR was assessed by interventionalist and echocardiographer at the end of the T-TEER procedure.

Results

A total of 244 patients who underwent successful T-TEER in the study period were included in the present analysis (mean age 77.7±8.7 years; 50.8% female). Patients were highly symptomatic as represented by New York Heart Association functional class ≥ III in 95.9% of cases. TR was 4+ in 128 patients (52.2%), 3+ in 106 patients (43.4%) and 2+ in 10 patients (6.1%). The etiology of TR was predominately functional (88.5%), while 5.4% presented with degenerative TR and 6.1% with TR of mixed etiology. Median time to last contact or death was 365 days (interquartile range 166–809 days). Three-year follow-up was available in 98% of eligible patients. T-TEER was performed using a mean number of 2.0±0.6 devices (Mitra-/TriClip 53%; PASCAL 47%). Post-procedural TR was 1+ in 126 patients (51.6%), 2+ in 101 patients (41.4%) and 3+ in 17 patients (7.0%). Survival rates at one, two and three years were 76%, 68% and 56%. Among patients with procedural success (at least 1° TR reduction), a higher degree in post-procedural TR was associated with a trend towards reduced postinterventional survival (Figure 1). The absolute degree of TR reduction did not impact survival rates in patients with procedural success (Figure 2).

Conclusion

T-TEER effectively reduces TR severity and shows high rates of procedural success. While the extent of TR reduction did not yield prognostic value in terms of long-term survival, the degree of post-procedural TR showed a trend regarding survival outcome. These results indicate that procedural techniques and strategies should be refined to achieve TR1+ at the end of the procedure.

Funding Acknowledgement

Type of funding sources: None.

Right ventricular reverse remodeling after mitral valve transcatheter edge-to-edge repair

Background

Right ventricular dysfunction (RVD) is an important predictor for outcome in patients undergoing transcatheter mitral or tricuspid valve edge-to-edge repair (M/T-TEER). Due to the unique anatomy and contraction pattern of the RV, three-dimensional echocardiography (3DE) has emerged as a valuable tool in the assessment of RV function. While 3DE data showed RV reverse remodeling (RVRR) following T-TEER, respective data are absent in the setting of M-TEER.

Purpose

We sought to assess RVRR after M-TEER using 3DE comparing baseline and follow-up RV measurements.

Methods

Patients undergoing M-TEER treatment for relevant MR between August 2016 and February 2021 with eligible transthoracic 3DE of the RV at baseline and follow-up were included in the study. 3DE comprised RV end-diastolic and end-systolic volumes (RVEDV3D, RVESV3D), total RV stroke volume (RVSV3D) and RV ejection fraction (RVEF3D). Further, RV length (RVL3D) as well as RV basal (RVbase3D) and mid-ventricular diameters (RVmid3D) were derived from 3DE. RVRR was assessed as change in the respective 3DE parameters of RV dimensions between baseline and follow-up.

Results

A total of 66 patients (45.5% female; age 78.5±8.2 years; EuroScore II 4.6±3.6%) were included in the study. From baseline to latest available follow-up (median interval 364 days, interquartile range 180–728 days), a significant reduction of RVEDV3D and RVESV3D was observed (RVEDV3D 140.2±50.2 ml to 128.1±46.1 ml, p&lt;0.01 and RVESV3D 93.1±37.8ml to 87.1±34.7ml, p=0.04). The decrease in 3D-derived linear RV dimensions primarily occurred in the septolateral direction, while RV length did not change significantly. The observed RVRR was associated with significant reduction of TR severity. Of note, patients with RVRR showed also left ventricular reverse remodeling (LVRR).

Conclusion

M-TEER is an effective treatment option for patients with MR which leads to LVRR and RVRR.

Funding Acknowledgement

Type of funding sources: None.

Propofol versus midazolam sedation in patients with cardiogenic shock – an observational propensity-matched study

Introduction

Benzodiazepines are recommended as first line sedative agent in ventilated cardiogenic shock patients, although data regarding the optimal sedation strategy are sparse. On our cardiac ICU, midazolam was used as first line sedation until 2016, whereas soybean oil formulated propofol was used preferentially since 2017.

Purpose

The aim of this study was to investigate the hemodynamic effects of propofol versus midazolam sedation in our cardiogenic shock registry.

Methods

Mechanically ventilated patients suffering from cardiogenic shock were retrospectively enrolled from a cardiogenic shock registry. 174 patients treated predominantly with propofol were matched by propensity-score to 174 patients treated predominantly with midazolam.

Results

Catecholamine doses were similar on admission but significantly lower in the propofol group on days 1–4 of ICU stay (Figure 1). Mortality rate was 38% in the propofol and 52% in the midazolam group after 30 days (p=0.002, Figure 2). Rate of ≥BARC3 bleeding was significantly lower in the propofol group compared to the midazolam group (p=0.008). Age, gender, first lactate measured on ICU, first GFR measured on ICU, cardiac arrest, coaxial left ventricular assist device and sedation with midazolam were significantly associated with ICU mortality.

Conclusion

In this observational cohort study, sedation with propofol in comparison to midazolam was linked to a reduced dose of catecholamines, decreased mortality and bleeding rates for patients with cardiogenic shock. Based on this study and in contrast to current recommendations, propofol should be given consideration for sedation in cardiogenic shock patients.

Funding Acknowledgement

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Deutsche Forschungsgemeinschaft

Characteristics and outcomes of normal-flow low-gradient aortic stenosis patients compared to high-gradient aortic stenosis patients undergoing TAVI

Background

Guidelines recommend aortic valve replacement for aortic stenosis (AS) depending on mean pressure gradients (dPmean) and flow status. It is indicated when dPmean is ≥40 mmHg (high-gradient, HG) or when patients have low-flow low-gradient AS. Normal-flow (stroke volume index, SVi &gt;35 ml/m2) low-gradient (dPmean &lt;40 mmHg) (NFLG) AS is subject of scientific debate and severe AS is considered unlikely in current European guidelines.

Purpose

We hypothesized that NFLG patients are heterogenous, containing a subgroup similar to HG patients in terms of characteristics and outcomes. The purpose of this study was to identify and assess this subgroup by dividing NFLG patients by dPmean.

Methods

All patients undergoing transcatheter aortic valve implantation (TAVI) at our centre between 2013 and 2019 were analysed and categorised into groups according to dPmean, left-ventricular ejection fraction, and SVi. Among 2,326 patients analysed, 386 patients fulfilled criteria for NFLG AS (dPmean &lt;40 mmHg, LV-EF ≥50%, SVi &gt;35 ml/m2). They were further subdivided into two groups according to the median dPmean and were compared to 956 HG AS patients (dPmean ≥40 mmHg). Groups were compared for baseline characteristics, mortality, and outcomes according to Valve Academic Research Consortium (VARC) 3 definitions.

Results

Median dPmean was 33 mmHg in NFLG patients. Accordingly, they were split into two groups, with 204 patients above (higher gradient NFLG) and 182 patients below (lower gradient NFLG) this value. Characteristics of lower gradient NFLG patients differed from HG patients in many aspects while they were similar between higher gradient NFLG and HG patients. This was underscored by higher Society of Thoracic Surgeons (STS) scores in lower gradient NFLG compared to the other two groups (Table).

Procedural and short-term clinical complications were similar between groups. The VARC-3 composite endpoint of technical failure occurred in 42 HG (4.4%), 12 higher gradient NFLG (5.9%), and 5 lower gradient NFLG patients (2.7%, p=0.32). The rates of the VARC-3 composite endpoint of device failure at 30 days were 108 patients (11.3%), 21 patients (10.3%), and 17 patients (9.3%), respectively (p=0.71). At follow-up, symptoms of patients from all three groups improved equally by at least one New York Heart Association class (p=0.47). Hazard ratio (HR) for 3-year mortality for all NFLG patients vs. HG patients was 1.4 [95% confidence interval, CI, 1.1–1.8]. Estimated 3-year all-cause mortality was significantly higher in lower gradient NFLG compared to HG patients, whereas mortality rate of higher gradient NFLG was similar to HG (Figure).

Conclusions

The data show that a large subgroup of NFLG patients has characteristics similar to those of HG patients, with similar clinical and procedural outcomes and comparable mortality rates. If severe AS was identified as the main clinical problem in this subgroup, aortic valve replacement can be justified.

Funding Acknowledgement

Type of funding sources: None.

Lawson Criterion for Ignition Exceeded in an Inertial Fusion Experiment

For more than half a century, researchers around the world have been engaged in attempts to achieve fusion ignition as a proof of principle of various fusion concepts. Following the Lawson criterion, an ignited plasma is one where the fusion heating power is high enough to overcome all the physical processes that cool the fusion plasma, creating a positive thermodynamic feedback loop with rapidly increasing temperature. In inertially confined fusion, ignition is a state where the fusion plasma can begin "burn propagation" into surrounding cold fuel, enabling the possibility of high energy gain. While "scientific breakeven" (i.e., unity target gain) has not yet been achieved (here target gain is 0.72, 1.37 MJ of fusion for 1.92 MJ of laser energy), this Letter reports the first controlled fusion experiment, using laser indirect drive, on the National Ignition Facility to produce capsule gain (here 5.8) and reach ignition by nine different formulations of the Lawson criterion.

Cortisol awakening response in the airborne rescue service

BACKGROUND

Work-related stress may lead to mental and physical illnesses. Emergency physicians may be particularly vulnerable to developing such diseases due to their extreme emotional working environment.

AIMS

The purpose of the study was to analyse the hormonal stress burden of emergency physicians in the airborne rescue service to create an empirical basis for developing appropriate measures against chronic stress in the rescue service.

METHODS

Three salivary cortisol samples were collected after awakening in 15 min intervals-each on a flight rescue day, a clinic day and a free day-to calculate the extent of the hormonal stress load of the emergency physicians. A nested linear mixed-model analysis was used in 40 cases to investigate hormonal stress. Furthermore, professional years and gender were included in the calculations.

RESULTS

The mixed model showed neither a main effect for measurement time nor for day but a significant interaction effect (P = 0.002). The cortisol level rises strongly on the flight rescue and the clinic day, while on the free day it shows a moderate increase. Professional years and gender also proved to be statistically significant for the cortisol level of emergency physicians (P < 0.001).

CONCLUSIONS

The results show a significantly higher cortisol increase on working days compared with a free day, which indicates a stronger stress burden on working days of emergency physicians in the airborne rescue service. Future studies should examine the stress level of emergency physicians in more detail to prove whether the working conditions of emergency physicians need to be modified.

Assessing Adverse Health Effects of Long-Term Exposure to Low Levels of Ambient Air Pollution: Implementation of Causal Inference Methods

This report provides a final summary of the principal findings and key conclusions of a study supported by an HEI grant aimed at "Assessing Adverse Health Effects of Long-Term Exposure to Low Levels of Ambient Air Pollution." It is the second and final report on this topic. The study was designed to advance four critical areas of inquiry and methods development. First, it focused on predicting short- and long-term exposures to ambient fine particulate matter (PM2.5), nitrogen dioxide (NO2), and ozone (O3) at high spatial resolution (1 km × 1 km) for the continental United States over the period 2000-2016 and linking these predictions to health data. Second, it developed new causal inference methods for estimating exposure-response (ER) curves (ERCs) and adjusting for measured confounders. Third, it applied these methods to claims data from Medicare and Medicaid beneficiaries to estimate health effects associated with short- and long-term exposure to low levels of ambient air pollution. Finally, it developed pipelines for reproducible research, including approaches for data sharing, record linkage, and statistical software. Our HEI-funded work has supported an extensive portfolio of analyses and the development of statistical methods that can be used to robustly understand the health effects of short- and long-term exposure to low levels of ambient air pollution. Our Phase 1 report (Dominici et al. 2019) provided a high-level overview of our statistical methods, data analysis, and key findings, grouped into the following five areas: (1) exposure prediction, (2) epidemiological studies of ambient exposures to air pollution at low levels, (3) sensitivity analysis, (4) methodological contributions in causal inference, and (5) an open access research data platform. The current, final report includes a comprehensive overview of the entire research project.

Considering our (1) massive study population, (2) numerous sensitivity analyses, and (3) transparent assessment of covariate balance indicating the quality of causal inference for simulating randomized experiments, we conclude that conditionally on the required assumptions for causal inference, our results collectively indicate that long-term PM2.5 exposure is likely to be causally related to mortality. This conclusion assumes that the causal inference assumptions hold and, more specifically, that we accounted adequately for confounding bias. We explored various modeling approaches, conducted extensive sensitivity analyses, and found that our results were robust across approaches and models. This work relied on publicly available data, and we have provided code that allows for reproducibility of our analyses.

Our work provides comprehensive evidence of associations between exposures to PM2.5, NO2, and O3 and various health outcomes. In the current report, we report more specific results on the causal link between long-term exposure to PM2.5 and mortality, even at PM2.5 levels below or equal to 12 μg/m3, and mortality among Medicare beneficiaries (ages 65 and older). This work relies on newly developed causal inference methods for continuous exposure.

For the period 2000-2016, we found that all statistical approaches led to consistent results: a 10-μg/m3 decrease in PM2.5 led to a statistically significant decrease in mortality rate ranging between 6% and 7% (= 1 - 1/hazard ratio [HR]) (HR estimates 1.06 [95% CI, 1.05 to 1.08] to 1.08 [95% CI, 1.07 to 1.09]). The estimated HRs were larger when studying the cohort of Medicare beneficiaries that were always exposed to PM2.5 levels lower than 12 μg/m3 (1.23 [95% CI, 1.18 to 1.28] to 1.37 [95% CI, 1.34 to 1.40]).

Comparing the results from multiple and single pollutant models, we found that adjusting for the other two pollutants slightly attenuated the causal effects of PM2.5 and slightly elevated the causal effects of NO2 exposure on all-cause mortality. The results for O3 remained almost unchanged.

We found evidence of a harmful causal relationship between mortality and long-term PM2.5 exposures adjusted for NO2 and O3 across the range of annual averages between 2.77 and 17.16 μg/m3 (included >98% of observations) in the entire cohort of Medicare beneficiaries across the continental United States from 2000 to 2016. Our results are consistent with recent epidemiological studies reporting a strong association between long-term exposure to PM2.5 and adverse health outcomes at low exposure levels. Importantly, the curve was almost linear at exposure levels lower than the current national standards, indicating aggravated harmful effects at exposure levels even below these standards.

There is, in general, a harmful causal impact of long-term NO2 exposures to mortality adjusted for PM2.5 and O3 across the range of annual averages between 3.4 and 80 ppb (included >98% of observations). Yet within low levels (annual mean ≤53 ppb) below the current national standards, the causal impacts of NO2 exposures on all-cause mortality are nonlinear with statistical uncertainty.

The ERCs of long-term O3 exposures on all-cause mortality adjusted for PM2.5 and NO2 are almost flat below 45 ppb, which shows no statistically significant effect. Yet we observed an increased hazard when the O3 exposures were higher than 45 ppb, and the HR was approximately 1.10 when comparing Medicare beneficiaries with annual mean O3 exposures of 50 ppb versus those with 30 ppb.

institutions, including those that support the Health Effects Institute; therefore, it may not reflect the views or policies of these parties, and no endorsement by them should be inferred.

A list of abbreviations and other terms appears at the end of this volume.

Non-equilibrium conditions inside rock pores drive fission, maintenance and selection of coacervate protocells

Key requirements for the first cells on Earth include the ability to compartmentalize and evolve. Compartmentalization spatially localizes biomolecules from a dilute pool and an evolving cell, which, as it grows and divides, permits mixing and propagation of information to daughter cells. Complex coacervate microdroplets are excellent candidates as primordial cells with the ability to partition and concentrate molecules into their core and support primitive and complex biochemical reactions. However, the evolution of coacervate protocells by fusion, growth and fission has not yet been demonstrated. In this work, a primordial environment initiated the evolution of coacervate-based protocells. Gas bubbles inside heated rock pores perturb the coacervate protocell distribution and drive the growth, fusion, division and selection of coacervate microdroplets. Our findings provide a compelling scenario for the evolution of membrane-free coacervate microdroplets on the early Earth, induced by common gas bubbles within heated rock pores.

Acid-Catalyzed RNA-Oligomerization from 3',5'-cGMP

The assembly of ancient informational polymers from nucleotide precursors is the central challenge of life's origin on our planet. Among the possible solutions, dry polymerization of 3’,5’‐cyclic guanosine monophosphate (3’,5’‐cGMP) has been proposed as a candidate to create oligonucleotides of 15–20 units in length. However, the reported sensitivity of the reaction to the presence of cations raised questions of whether this chemistry could be relevant in a geological context. The experiments in this study show that the presence of cations is not restrictive as long as the reaction is conducted in an acidic environment, in contrast to previous reports that suggested optimal conditions at pH 9.

TAVR in patients with low-flow low-gradient aortic stenosis – outcome data after three years from one large centre

Background

The outcome of patients with low-flow low-gradient (LFLG) aortic stenosis after transcatheter aortic valve replacement (TAVR) is not well evaluated. Long-term clinical success is thought to be less pronounced in LFLG patients compared to patients with high gradient (HG) aortic stenosis.

Purpose

The purpose of this study was to characterise different LFLG groups and determine their outcome after TAVR. We hypothesised that there would be relevant differences in baseline characteristics and patient survival after TAVR.

Methods

All patients undergoing TAVR for severe aortic stenosis at our centre between 2013 and 2019 were included in the study. Patients have been split into groups according preinterventional echocardiography data according to mean pressure gradient (dPmean), ejection fraction (EF), and stroke volume index (SVi). Patients with a dPmean &lt;40 mmHg and SVi ≤35 ml/m2 were subdivided into classical low-flow low-gradient (cLFLG, EF &lt;50%) and paradoxical low-flow (pLFLG, EF ≥50%). Patients with previous aortic valve replacement or severe aortic regurgitation were excluded from the analysis.

Results

1,772 patients were analysed (mean follow-up 2.2 years, median age 81.7 [77.5–85.7] years) and split into groups: HG, 953 patients (54.3%), cLFLG, 446 patients (25.2%), and pLFLG 373 patients (21.1%). Baseline characteristics showed significant differences (p&lt;0.01), among others, in sex (male sex, HG 46.1% vs. cLFLG 69.5% vs. pLFLG 44.5%), rate of atrial fibrillation (HG 20.3% vs. cLFLG 36.3% vs. pLFLG 41.6%), coronary artery disease (HG 56.2% vs. cLFLG 73.5% vs. pLFLG 63.4%), and grade 3 or 4 mitral regurgitation (HG 2.2% vs. cLFLG 5.5% vs. pLFLG 6.8%). Accordingly, Society of Thoracic Surgeons (STS) Scores differed significantly: HG, 3.0 [2.0–5.0], cLFLG, 5.0 [3.0–7.3] pLFLG, 3.9 [2.2–6.0] (p&lt;0.01).

Rates of periprocedural complications including death, device failure, pericardial effusion, stroke or myocardial infarction were comparable between groups. Mortality rate (figure 1) was highest for cLFLG patients (43.4% [95% confidence interval, 37.3–48.6%]) compared to HG (25.1% [21.6–28.5%]) or pLFLG (32.9% [26.9–38.4%]), Log-rank test, &lt;0.001. Corresponding hazard ratios were 2.1 [1.7–2.6] (p&lt;0.001) for cLFLG and 1.5 [1.2–2.0] (p&lt;0.001) for pLFLG. Similar results were obtained when adjusting to STS score (figure 2).

Conclusion

In this all-comer analysis, almost half of the patients belong toLFLG groups with considerable differences in patient characteristics. While equally safe during the procedure, patients with LFLG aortic stenosis show increased 3-year mortality rates compared to patients with HG aortic stenosis. Further studies evaluating this are needed.

Funding Acknowledgement

Type of funding sources: None. Figure 1. 3-year mortalityFigure 2. STS score-adjusted mortality

Impact of the cardio-hepatic syndrome on outcomes after transcatheter mitral valve edge-to-edge repair

Background

The prognostic value of impaired liver function in the presence of moderate-to-severe and severe mitral regurgitation (MR), also called cardio-hepatic syndrome (CHS), for outcomes in patients undergoing transcatheter edge-to-edge repair (TEER) has not been studied yet.

Purpose

In this work, we aimed at identifying the prognostic impact of the CHS on two-year all-cause mortality in patients undergoing TEER compared to established risk factors. Furthermore, we evaluated the change in hepatic function after TEER.

Methods

Hepatic function was assessed by laboratory parameters of liver function (bilirubin, gamma glutamyl transferase [GGT], alkaline phosphatase [AP], aspartate and alanine aminotransferase [AST and ALT]). We defined CHS as elevation of at least two out of three laboratory parameters of hepatic cholestasis (bilirubin, GGT, AP). The impact of CHS on two-year mortality was evaluated using a proportional hazards Cox model. The change in hepatic function after TEER was evaluated by repeat laboratory testing at follow-up.

Results

We included 1083 patients who underwent TEER for highly symptomatic primary or secondary MR at four high volume academic European centers between 2008 and 2019. In 66.4% of patients, we observed elevated levels of either bilirubin, GGT or AP. CHS was present in 23% of patients and showed strong association with a reduced two-year survival (52.9% vs. 87.0% in patients without CHS, p&lt;0.01). In a multivariate Cox regression model, CHS was identified as a strong and independent predictor of increased two-year mortality (hazard ratio 1.49, p=0.03). In patients with successful MR reduction ≤2+ (90.7% of patients), parameters of hepatic function significantly improved from baseline to follow-up (−0.2 mg/dl for bilirubin; −21 U/l for GGT, respectively, p&lt;0.01), while they did not in case of residual postprocedural MR &gt;2+.

Conclusions

CHS can be observed in up to 25% of patients undergoing TEER and is associated with impaired two-year survival rates. Successful TEER is associated with decreased levels of hepatic enzymes at follow-up evaluation.

Funding Acknowledgement

Type of funding sources: None. Cardio-hepatic syndrome TEER

Asymmetric leaflet tethering is associated with worse outcomes after edge-to-edge mitral valve repair for secondary mitral regurgitation

Background

The impact of mitral valve (MV) tethering patterns on outcomes of patients undergoing transcatheter edge-to-edge mitral valve repair (TEER) for severe secondary mitral regurgitation (SMR) is unknown.

Purpose

The purpose of this study was to evaluate the impact of asymmetric postero-anterior and medio-lateral MV leaflet tethering on procedural and survival outcomes after TEER for SMR.

Methods

Symmetry of postero-anterior leaflet tethering was defined as the ratio of the posterior to anterior MV leaflet angle (PLA/ALA) in the central MV segment 2. The ratio of the tenting area between MV segments 3 and 1 (S3/S1 ratio) was defined as medio-lateral tethering symmetry. We used receiver operating characteristics and a proportional Cox model to identify cut-off values of asymmetric postero-anterior and medio-lateral tethering for prediction of two-year survival after TEER.

Results

178 patients receiving TEER for SMR were included. Asymmetric postero-anterior tethering was observed in 67 patients (37.6%, PLA/ALA ratio cut-off &gt;1.54). Medio-lateral tethering was asymmetric in 49 patients (27.5%, S3/S1 ratio cut-off &gt;1.49). MR was reduced to MR ≤2+ in 91.6% of patients, while postprocedural MR remained higher in the presence of asymmetric postero-anterior tethering (p=0.01). After adjustment for potential clinical and echocardiographic confounders, multivariable Cox regression analysis confirmed asymmetric postero-anterior tethering (HR=2.77, CI=1.43–5.38, p&lt;0.01) and asymmetric medio-lateral tethering (HR=2.90, CI=1.54–5.45, p&lt;0.01) as independent predictors for two-year survival.

Conclusions

Asymmetric postero-anterior and medio-lateral MV leaflet tethering patterns independently increase two-year all-cause mortality in patients undergoing TEER for SMR. Detailed echocardiographic patient selection might improve outcomes after TEER.

Funding Acknowledgement

Type of funding sources: None. Postero-anterior tetheringMedio-lateral tethering

Prevention of pacemaker lead induced tricuspid regurgitAtion by transesophageal eCho guidEd implantation (PLACE Pilot)

Background

Lead-induced tricuspid regurgitation (TR) is a frequent complication after pacemaker- and ICD-implantation that is associated with increased mortality and hospitalizations.

Purpose

The aim of this pilot study was to investigate if lead implantation guided by transesophageal echocardiography (TEE) is feasible and might be able to reduce lead-associated TR.

Methods

21 patients with indication for new pacemaker/ICD including a trans-tricuspid lead implantation and TR &lt; grade 2+ were prospectively enrolled and underwent TEE-guided lead implantation in addition to fluoroscopy. Leads were placed according to a dedicated echo protocol with focus on a transgastric en face view of the tricuspid valve targeting a lead position in a tricuspid valve commissure (preferentially postero-septal) and an apical ventricular lead position. (Figure 1) Transthoracic echocardiography (TTE) was performed before implantation and at discharge. 121 consecutive patients with standard lead implantation guided by fluoroscopy only served as a historical control group. TR was assessed by an experienced cardiologist and graded according to current guidelines.

Results

Key baseline characteristics of overall 124 patients with a mean age of 74 years didn't differ between groups. Of note, there was no significant difference regarding device type and baseline TR.

TEE-guided lead implantation was possible in all 21 patients in the TEE-group in deep conscious sedation without occurrence of serious adverse events. Lead placement in a commissure, mostly postero-septal, was possible in 95.2% of patients without worsening of TR (20/21 pts). Based on TEE-guidance, lead position or length was altered in 52.4% of patients (11/21 pts, 6 pts with lead repositioning, 5 pts with modification of lead length).

Compared to baseline, the 21 patients in the TEE-group did not show worsening of TR at discharge. In contrast, TR worsening by one grade occurred in 13.6% of patients (14/103 pts) with new onset of TR ≥2+ in 6.8% of patients (07/103 pts) in the control group (p=0.001).

At discharge, lead position was evaluated using 2D and 3D TTE in a subset of patients. In all examined patients (14/14 pts) lead position was unchanged compared to intraprocedural position and stable during inspiration vs. expiration as well as in upright vs. horizontal position.

Conclusion

TEE-guidance during PM/ICD-implantation was safe and feasible and resulted in steps to optimize lead position in a relevant number of patients. At discharge lead position remained stable and TEE-guided lead implantation was associated with less worsening of TR than standard lead implantation guided by fluoroscopy.

Funding Acknowledgement

Type of funding sources: None. TEE view with targeted lead position

Three-dimensional echocardiography in transcatheter edge-to-edge tricuspid valve repair

Background

Transcatheter tricuspid valve repair (TTVR) is a new treatment option for severe tricuspid regurgitation (TR). First reports have reported conflicting results on development of right ventricular (RV) function after TTVR and questioned the role of conventional echocardiographic parameters to predict outcome.

Purpose

The aim of this study was to evaluate 3D echocardiography for the comprehensive assessment of RV function and its prognostic value for TTVR-treated patients.

Methods

We included patients undergoing TTVR from February 2017 to July 2019 who had preprocedural 3D assessment of RV volumes and ejection fraction. At follow-up (FU), 3D echo was performed to evaluate right ventricular reverse remodeling. All-cause mortality was assessed as clinical endpoint.

Results

75 patients treated with TTVR for isolated, severe TR had 3D echo assessment. TTVR reduced TR from grade ≥3+ to ≤2+ in 83.1% of patients at discharge. 3D-RV end-diastolic volume (−46.3 ml, p&lt;0.001), end-systolic volume (−22.0 ml, p=0.027) and 3D-RV ejection fraction (−4.7%, p&lt;0.001) decreased at short-term FU at 1-month and remained stable at 6-month FU. An impaired preprocedural 3D-RVEF &lt;44% conferred higher mortality risk (Figure), and was an independent predictor for 1-year mortality (hazard ratio 5.32, p=0.033) in multivariable analysis. Tricuspid annular systolic excursion (TAPSE) and RV fractional area change were not predictive for this endpoint. Importantly, the observed decrease of 3D-RVEF function after TTVR was not associated with outcome (p=0.22 for decrease of 3D-RVEF vs. no decrease of 3D-RVEF in Kaplan-Meier analysis). Instead, left ventricular stroke volume index increased by 9.2% from 26.0 to 28.4 ml/m2 (p&lt;0.01)

Conclusion

TTVR leads to right ventricular reverse remodeling and decrease of RV systolic function after TTVR. Impaired preprocedural RV systolic function is associated with worse clinical outcome. In contrast, the observed decrease of RV systolic function after TTVR was not associated with outcome.

Funding Acknowledgement

Type of funding sources: Public hospital(s). Main funding source(s): Klinikum der Universtität München Figure 1

Quantification of physical activity with activity tracking after transfemoral aortic valve replacement (TAVR)

Background and hypothesis

TAVR is a well-established, safe and effective therapy for severe symptomatic aortic stenosis (AS), but improvement of physical activity after TAVR is difficult to assess objectively. The aim of this study was to quantify improvement of physical activity with Activity Tracking after TAVR with special focus on the different low-gradient subtypes of AS.

Methods

All patients who underwent TAVR for severe AS in our center between 01/2019 and 12/2019 were screened. Participants received an Activity Tracker for 7 days at two times: after hospital discharge following TAVR procedure and 6 months thereafter. The difference of mean daily steps was defined as study endpoint.

Results

The analysis is based on 230 patients. The median age was 79.7 years with 53.7% male participants. The median aortic valve area (AVA) was 0.75 cm2 and median mean pressure gradient was 38.7 mmHg (Table 1). The median amount of daily steps was 4409 [IQR 2581–7487] steps/day after hospital discharge and 5326 [IQR 3045–8668] steps/day 6 months thereafter. On a patient base, median difference of steps per day was Δ 529 [IQR −702–2152]). Whenever possible, patients were categorized into different subgroups of AS. Patients with high-gradient (HG) AS showed significant improvement in difference of daily steps at 6 months-FUP (Δ 951 [IQR −378–2.323], p&lt;0.001), as well as patients with paradox low-flow-low-gradient (LFLG) AS (Δ 1392 [IQR −609–4444], p=0.02). Patients with classical LFLG AS also showed an improvement of daily steps at 6-months-FUP but without statistical significance (Δ 192 [IQR −687–770], p=0.79). Patients with a normal-flow-low-gradient (NFLG) AS have no significant difference in daily steps after 6-months and show a tendency of decline in daily steps at 6-months-FUP (Δ −300 [IQR −1334–1406], p=0.67) (Figure 1).

Conclusions

This is the first study of this sample size to evaluate physical activity after TAVR with an objective and reproducible method. Overall, physical activity improved significantly 6 months after TAVR and daily steps per day increased in all subtypes of AS besides NFLG AS, where a tendency of decline in daily steps without statistical significance was shown. However the increase in daily steps did not reach statistical significance in classical LFLG AS patients.

Funding Acknowledgement

Type of funding sources: None. Table 1Figure 1

A new model for silicification of cyanobacteria in Proterozoic tidal flats

Microbial fossils preserved by early diagenetic chert provide a window into the Proterozoic biosphere, but seawater chemistry, microbial processes, and the interactions between microbes and the environment that contributed to this preservation are not well constrained. Here, we use fossilization experiments to explore the processes that preserve marine cyanobacterial biofilms by the precipitation of amorphous silica in a seawater medium that is analogous to Proterozoic seawater. These experiments demonstrate that the exceptional silicification of benthic marine cyanobacteria analogous to the oldest diagnostic cyanobacterial fossils requires interactions among extracellular polymeric substances (EPS), photosynthetically induced pH changes, magnesium cations (Mg²⁺ ), and >70 ppm silica.

Heat flows in rock cracks naturally optimize salt compositions for ribozymes

Catalytic nucleic acids, such as ribozymes, are central to a variety of origin-of-life scenarios. Typically, they require elevated magnesium concentrations for folding and activity, but their function can be inhibited by high concentrations of monovalent salts. Here we show that geologically plausible high-sodium, low-magnesium solutions derived from leaching basalt (rock and remelted glass) inhibit ribozyme catalysis, but that this activity can be rescued by selective magnesium up-concentration by heat flow across rock fissures. In contrast to up-concentration by dehydration or freezing, this system is so far from equilibrium that it can actively alter the Mg:Na salt ratio to an extent that enables key ribozyme activities, such as self-replication and RNA extension, in otherwise challenging solution conditions. The principle demonstrated here is applicable to a broad range of salt concentrations and compositions, and, as such, highly relevant to various origin-of-life scenarios.

Kinetic Microscale Thermophoresis for Simultaneous Measurement of Binding Affinity and Kinetics

Microscale thermophoresis (MST) is a versatile technique to measure binding affinities of binder-ligand systems, based on the directional movement of molecules in a temperature gradient. We extended MST to measure binding kinetics as well as binding affinity in a single experiment by increasing the thermal dissipation of the sample. The kinetic relaxation fingerprints were derived from the fluorescence changes during thermodynamic re-equilibration of the sample after local heating. Using this method, we measured DNA hybridization on-rates and off-rates in the range 10⁴ -10⁶  m^-1  s^-1 and 10^-4 -10^-1  s^-1 , respectively. We observed the expected exponential dependence of the DNA hybridization off-rates on salt concentration, strand length and inverse temperature. The measured on-rates showed a linear dependence on salt concentration and weak dependence on strand length and temperature. For biomolecular interactions with large enthalpic contributions, the kinetic MST technique offers a robust, cost-effective and immobilization-free determination of kinetic rates and binding affinity simultaneously, even in crowded solutions.

tRNA sequences can assemble into a replicator

Can replication and translation emerge in a single mechanism via self-assembly? The key molecule, transfer RNA (tRNA), is one of the most ancient molecules and contains the genetic code. Our experiments show how a pool of oligonucleotides, adapted with minor mutations from tRNA, spontaneously formed molecular assemblies and replicated information autonomously using only reversible hybridization under thermal oscillations. The pool of cross-complementary hairpins self-selected by agglomeration and sedimentation. The metastable DNA hairpins bound to a template and then interconnected by hybridization. Thermal oscillations separated replicates from their templates and drove an exponential, cross-catalytic replication. The molecular assembly could encode and replicate binary sequences with a replication fidelity corresponding to 85-90 % per nucleotide. The replication by a self-assembly of tRNA-like sequences suggests that early forms of tRNA could have been involved in molecular replication. This would link the evolution of translation to a mechanism of molecular replication.

Role of soluble guanylyl cyclase in renal afferent and efferent arterioles

Renal arteriolar tone depends considerably on the dilatory action of nitric oxide (NO) via activation of soluble guanylyl cyclase (sGC) and cGMP action. NO deficiency and hypoxia/reoxygenation are important pathophysiological factors in the development of acute kidney injury. It was hypothesized that the NO-sGC-cGMP system functions differently in renal afferent arterioles (AA) compared with efferent arterioles (EA) and that the sGC activator cinaciguat differentially dilates these arterioles. Experiments were performed in isolated, perfused mouse glomerular arterioles. Hypoxia (0.1% oxygen) was achieved by using a hypoxia chamber. Phosphodiesterase 5 (PDE5) and sGC subunits were considerably expressed on the mRNA level in AA. PDE5 inhibition with sildenafil, which blocks cGMP degradation, diminished the responses to ANG II bolus application in AA, but not significantly in EA. Vasodilation induced by sildenafil in ANG II-preconstricted vessels was stronger in EA than AA. Cinaciguat, an NO- and heme-independent sGC activator, dilated EA more strongly than AA after N^G-nitro-l-arginine methyl ester (l-NAME; NO synthase inhibitor) treatment and preconstriction with ANG II. Cinaciguat-induced dilatation of l-NAME-pretreated and ANG II-preconstricted arterioles was similar to controls without l-NAME treatment. Cinaciguat also induced dilatation in iodinated contrast medium treated AA. Furthermore, it dilated EA, but not AA, after hypoxia/reoxygenation. The results reveal an important role of the NO-sGC-cGMP system for renal dilatation and that EA have a more potent sGC activated dilatory system. Furthermore, AA seem to be more sensitive to hypoxia/reoxygenation than EA under these experimental conditions.

Air pollution and COVID-19 mortality in the United States: Strengths and limitations of an ecological regression analysis

Assessing whether long-term exposure to air pollution increases the severity of COVID-19 health outcomes, including death, is an important public health objective. Limitations in COVID-19 data availability and quality remain obstacles to conducting conclusive studies on this topic. At present, publicly available COVID-19 outcome data for representative populations are available only as area-level counts. Therefore, studies of long-term exposure to air pollution and COVID-19 outcomes using these data must use an ecological regression analysis, which precludes controlling for individual-level COVID-19 risk factors. We describe these challenges in the context of one of the first preliminary investigations of this question in the United States, where we found that higher historical PM_2.5 exposures are positively associated with higher county-level COVID-19 mortality rates after accounting for many area-level confounders. Motivated by this study, we lay the groundwork for future research on this important topic, describe the challenges, and outline promising directions and opportunities.

Air pollution and COVID-19 mortality in the United States: Strengths and limitations of an ecological regression analysis

Assessing whether long-term exposure to air pollution increases the severity of COVID-19 health outcomes, including death, is an important public health objective. Limitations in COVID-19 data availability and quality remain obstacles to conducting conclusive studies on this topic. At present, publicly available COVID-19 outcome data for representative populations are available only as area-level counts. Therefore, studies of long-term exposure to air pollution and COVID-19 outcomes using these data must use an ecological regression analysis, which precludes controlling for individual-level COVID-19 risk factors. We describe these challenges in the context of one of the first preliminary investigations of this question in the United States, where we found that higher historical PM_2.5 exposures are positively associated with higher county-level COVID-19 mortality rates after accounting for many area-level confounders. Motivated by this study, we lay the groundwork for future research on this important topic, describe the challenges, and outline promising directions and opportunities.

Air pollution and COVID-19 mortality in the United States: Strengths and limitations of an ecological regression analysis

Assessing whether long-term exposure to air pollution increases the severity of COVID-19 health outcomes, including death, is an important public health objective. Limitations in COVID-19 data availability and quality remain obstacles to conducting conclusive studies on this topic. At present, publicly available COVID-19 outcome data for representative populations are available only as area-level counts. Therefore, studies of long-term exposure to air pollution and COVID-19 outcomes using these data must use an ecological regression analysis, which precludes controlling for individual-level COVID-19 risk factors. We describe these challenges in the context of one of the first preliminary investigations of this question in the United States, where we found that higher historical PM_2.5 exposures are positively associated with higher county-level COVID-19 mortality rates after accounting for many area-level confounders. Motivated by this study, we lay the groundwork for future research on this important topic, describe the challenges, and outline promising directions and opportunities.

Air pollution and COVID-19 mortality in the United States: Strengths and limitations of an ecological regression analysis

Assessing whether long-term exposure to air pollution increases the severity of COVID-19 health outcomes, including death, is an important public health objective. Limitations in COVID-19 data availability and quality remain obstacles to conducting conclusive studies on this topic. At present, publicly available COVID-19 outcome data for representative populations are available only as area-level counts. Therefore, studies of long-term exposure to air pollution and COVID-19 outcomes using these data must use an ecological regression analysis, which precludes controlling for individual-level COVID-19 risk factors. We describe these challenges in the context of one of the first preliminary investigations of this question in the United States, where we found that higher historical PM2.5 exposures are positively associated with higher county-level COVID-19 mortality rates after accounting for many area-level confounders. Motivated by this study, we lay the groundwork for future research on this important topic, describe the challenges, and outline promising directions and opportunities.

Incremental prognostic value of tricuspid annular dilatation over the STS score

Background

Transcatheter aortic valve replacement (TAVR) is the treatment of choice in most patients with severe aortic stenosis. The Society of Thoracic Surgeons (STS) score is a well established risk score to estimate morbidity, mortality and procedural risk of patients undergoing TAVR. However, tricuspid annular Dilatation (TAD), which is an increasingly recognized pathology associated with increased mortality, is not implemented in the STS Score.

Purpose

The purpose of this analysis was to investigate the incremental prognoctic value of TAD over the STS score.

Methods

Maximal septo-lateral diameter of the tricuspid annulus was measured in 923 patients on 3-dimensional MDCT datasets. A cut-off of 23 mm/m2 body-surface area was revealed by receiver-operating curve statistics and used to define TAD. Incremental prognostic Information was tested with c-index statistics and continuous net reclassification improvement (NRI). Patients were followed for 2 years and all-cause mortality was defined as study endpoint.

Results

Of 923 patients included in this analyis, TAD was found in 370 patients (40%). Patients with TAD had a significantly higher mortality (hazard ratio 2.18 with 95% CI 1.71 and 2.78, p&lt;0.001). The mean STS score in the investigated patient cohort was 5.6±5.0. TAD provided incremental prognostic Information over the STS score when assessed with c-index statistics (rise from 0.63 to 0.66, p&lt;0.01) or continuous NRI (0.209 with 95% CI 0.127 and 0.292, p&lt;0.001). Estimated survival rates at 2 years were 88.2% (95% CI 84.5 and 92.1) in patients with a low STS score (&lt;4) and no TAD and 57.5% (95% CI 51.1 and 64.7) in patients with a high STS score (&gt;4) and TAD. Estimated survival rates in patients with a low STS score and TAD and patients with a high STS score and no TAD were similiar (75.8% with 95% CI 68.9 and 83.5 and 74.8% with 95% CI 69.2 and 80.7, respectively). Kaplan-Meier curves are shown in Figure 1.

Conclusion

TAD is a common entity in patients undergoing TAVR for severe aortic stenosis. It is associated with significantly higher mortality and provides incremental prognostic Information over the STS score.

Funding Acknowledgement

Type of funding source: None

Thermal Habitat for RNA Amplification and Accumulation

The RNA world scenario posits replication by RNA polymerases. On early Earth, a geophysical setting is required to separate hybridized strands after their replication and to localize them against diffusion. We present a pointed heat source that drives exponential, RNA-catalyzed amplification of short RNA with high efficiency in a confined chamber. While shorter strands were periodically melted by laminar convection, the temperature gradient caused aggregated polymerase molecules to accumulate, protecting them from degradation in hot regions of the chamber. These findings demonstrate a size-selective pathway for autonomous RNA-based replication in natural nonequilibrium conditions.

Evaluating the impact of long-term exposure to fine particulate matter on mortality among the elderly

Many studies link long-term fine particle (PM2.5) exposure to mortality, even at levels below current U.S. air quality standards (12 micrograms per cubic meter). These findings have been disputed with claims that the use of traditional statistical approaches does not guarantee causality. Leveraging 16 years of data-68.5 million Medicare enrollees-we provide strong evidence of the causal link between long-term PM2.5 exposure and mortality under a set of causal inference assumptions. Using five distinct approaches, we found that a decrease in PM2.5 (by 10 micrograms per cubic meter) leads to a statistically significant 6 to 7% decrease in mortality risk. Based on these models, lowering the air quality standard to 10 micrograms per cubic meter would save 143,257 lives (95% confidence interval, 115,581 to 170,645) in one decade. Our study provides the most comprehensive evidence to date of the link between long-term PM2.5 exposure and mortality, even at levels below current standards.

Assessing Adverse Health Effects of Long-Term Exposure to Low Levels of Ambient Air Pollution: Phase 1

INTRODUCTION

This report provides a summary of major findings and key conclusions supported by a Health Effects Institute grant aimed at "Assessing Adverse Health Effects of Long-Term Exposure to Low Levels of Ambient Pollution." Our study was designed to advance four critical areas of inquiry and methods development.

METHODS

First, our work focused on predicting short- and long-term exposures to ambient PM2.5 mass (particulate matter ≤ 2.5μm in aerodynamic diameter) and ozone (O3) at high spatial resolution (1 km × 1 km) for the continental United States during the period 2000-2012 and linking these predictions to health data. Second, we developed new causal inference methods for exposure-response (ER) that account for exposure error and adjust for measured confounders. We applied these methods to data from the New England region. Third, we applied standard regression methods using Medicare claims data to estimate health effects that are associated with short- and long-term exposure to low levels of ambient air pollution. We conducted sensitivity analyses to assess potential confounding bias due to lack of extensive information on behavioral risk factors in the Medicare population using the Medicare Current Beneficiary Survey (MCBS) (nationally representative sample of approximately 15,000 Medicare enrollees per year), which includes abundant data on individual-level risk factors including smoking. Finally, we have begun developing tools for reproducible research - including approaches for data sharing, record linkage, and statistical software.

RESULTS

Our HEI-funded work has supported an extensive portfolio of analysis and the development of statistical methods that can be used to robustly understand the health effects of long- and short-term exposure to low levels of ambient air pollution. This report provides a high-level overview of statistical methods, data analysis, and key findings, as grouped into the following four areas: (1) Exposure assessment and data access; (2) Epidemiological studies of ambient exposures to air pollution at low levels; (3) Methodological contributions in causal inference; and (4) Open science research data platform.

CONCLUSION

Our body of work, advanced by HEI, lends extensive evidence that short- and long-term exposure to PM2.5 and O3 is harmful to human health, increasing the risks of hospitalization and death, even at levels that are well below the National Ambient Air Quality Standards (NAAQS).

P5567Clinical characteristics, diagnosis and risk stratification of pulmonary hypertension in severe tricuspid regurgitation and implications for transcatheter tricuspid valve repair

Objective

To assess the role of pulmonary hypertension (PHT) in severe tricuspid regurgitation (TR) and its implications for transcatheter tricuspid valve repair (TTVR).

Background

PHT patients are often excluded from surgical TR therapies. TTVR with the MitraClipTM technique is a novel treatment option for these patients.

Methods

A total of 164 patients at high surgical risk (median age 78 years) and TR underwent TTVR at two centers. Seventy patients were grouped as iPHT+, defined as invasive systolic pulmonary artery pressure (PAPs) >50 mmHg. Patients were similarly stratified according to echocardiographic PAPs (ePHT). The occurrence of the combined clinical endpoint (death, heart failure hospitalization, reintervention) was investigated.

Results

iPHT+ patients were at higher pre-operative risk (p<0.01), had more severe symptoms (p=0.01), higher NT-pro-BNP levels (p<0.01) and more impaired biventricular function (left: p=0.03; right: p=0.02).

Procedural TTVR success was achieved in 86 vs. 82% in iPHT+ and iPHT- patients respectively (p=0.52). Tricuspid valve effective regurgitant orifice area (EROA) was reduced from 0.49 cm2 to 0.20 cm2 (p<0.01) similarly in both groups.

While iPHT+ conveyed risk (HR 1.7 (95% CI 1.1–2.8), p=0.03) for the occurrence of the clinical endpoint, ePHT+ paradoxically conveyed protection (HR 0.61 (95% CI 0.36–0.98), p=0.04). This discrepancy was explained by the highest event rates in patients with iPHT+/ePHT- (n=28). Conversely, iPHT+/ePHT+ patients had comparable outcomes to iPHT- patients.

Conclusions

PHT in TR is associated with worse clinical status and advanced HF, but not procedural failure. Symptomatic benefit can be achieved irrespective of PHT status by TTVR. Although echocardiographic PHT diagnosis is unreliable, the combination of echocardiographic and invasive assessment may identify ideal candidates for TTVR among PHT patients.