Evaluation of an automated real-time transcription-mediated amplification (TMA) assay for detection and quantification of cytomegalovirus DNA in different clinical specimens.

BACKGROUND: Reliable and fast detection and quantification of human cytomegalovirus (CMV) DNA in various diagnostic specimens is essential for care of immunocompromised or congenitally infected individuals. OBJECTIVES: To evaluate the analytical and clinical performance of the Panther Aptima® CMV (Hologic) quantitative real-time transcription mediated amplification (TMA) assay. STUDY DESIGN: Performance of the TMA assay run on the Hologic Panther Fusion was analysed for 32 proficiency testing samples and 21 quantitative reproducibility panel samples; additionally, we compared results of TMA assay and routine quantitative real-time PCR assays ("PCR-A"= Biomérieux CMV R-gene® or "PCR-B"= Laboratory-developed CMV-PCR) in 518 diagnostic specimens (254 plasma, 120 EDTA whole blood, 43 urine, 45 amniotic fluid and 56 breast milk) at two university hospital laboratories. RESULTS: All proficiency panel samples were correctly identified and quantified by the TMA assay; replicate testing of the reproducibility panel samples showed good reproducibility within and between the two laboratories. Sensitivity in plasma and WB was higher for the TMA assay detecting low-level CMV-DNAemia in samples tested negative by routine PCR. Quantitative CMV-DNAemia values correlated well between TMA and real-time PCR. Similarly, urine, AF and BM specimens showed a high rate of concordant results (91%, 98% and 98%, respectively) among TMA and PCR with good correlation of quantitative values. CONCLUSION: The performance of the Aptima® CMV TMA assay for viral blood load testing compared well to established real-time PCRs. In addition, it can be useful for diagnostics in urine, amniotic fluid and breast milk specimens.

Halogen- and hydrogen-bonded self-assembled fibrillar networks of substituted 1,3:2,4-dibenzylidene-D-sorbitols (DBS).

Substituting the sole primary hydroxyl group of the low molecular weight organogelator (LMOG), 1,3:2,4-dibenzylidene-D-sorbitol (DBS), with a halogen atom (Cl, Br, or I; i.e., 6-Cl-DBS, 6-Br-DBS, or 6-I-DBS) drastically alters the supramolecular self-assembled fibrillar network (SAFiN) that forms when the molecules aggregate. The SAFiN varies depending on the solvent properties, impacting the role of non-covalent hydrogen- and halogen-bonding interactions along and between fibers. The halogenated DBS derivatives have more coherent crystalline fibers than DBS, with larger length-to-width aspect ratios. High-resolution synchrotron powder X-ray diffraction of each wet-state gel in toluene and DFT optimization obtained complete structures for the three halogenated DBS derivatives in their SAFiNs. The presence of a halogen atom reduces the reliance on hydrogen bonding by enabling new halogen bonding interactions that impact the self-assembly behavior, especially in solvents of higher polarity. For 6-I-DBS and 6-Br-DBS, the primary forces driving molecular self-assembly are C-H⋯π and intermolecular halogen-to-halogen interactions, and there is one unique molecule in each unit cell. However, the Cl atoms of 6-Cl-DBS are not close, and its SAFiN structures rely more on hydrogen bonding. As a result, the enhanced hydrogen bonding, electronic differences among the halogens, and spatial factors allow its unit cell to include two independent molecules of 6-Cl-DBS.

Consolidation and Forced Elasticity in Double-Network Hydrogels.

This paper discusses two observations that are unique with respect to the mechanics of double network (DN) hydrogels, forced elasticity driven by water diffusion and consolidation, which are analogous to the so-called Gough-Joule effects in rubbers. A series of DN hydrogels were synthesized from 2-acrylamido-2-methylpropane sulfuric acid (AMPS), 3-sulfopropyl acrylate potassium salt (SAPS) and acrylamide (AAm). Drying of AMPS/AAm DN hydrogels was monitored by extending the gel specimens to different stretch ratios and holding them until all the water evaporated. At high extension ratios, the gels underwent plastic deformation. Water diffusion measurements performed on AMPS/AAm DN hydrogels that were dried at different stretch ratios indicated that the diffusion mechanism deviated from Fickian behavior at extension ratios greater than two. Study of the mechanical behavior of AMPS/AAm and SAPS/AAm DN hydrogels during tensile and confined compression tests showed that despite their large water content, DN hydrogels can retain water during large-strain tensile or compression deformations.

Fabrication of Tough Double-Network Hydrogels from Highly Cross-Linked Brittle Neutral Networks Using Alkaline Hydrolysis.

This paper describes a simple method to synthesize tough hydrogels from a highly cross-linked neutral network. It was found that applying alkaline hydrolysis to a highly cross-linked hydrogel synthesized from acrylamide (AAm) can increase its swelling ratio dramatically. Double-network (DN) hydrogels synthesized from polymerization of loosely cross-linked AAm networks inside a highly cross-linked AAm gel were not tough. However, repeating the same recipes with a second polymerization step to synthesize a DN hydrogel from a hydrolyzed highly cross-linked AAm gel resulted in tough hydrogels. Those gels exhibited finite tensile behavior similar to that of conventional DN hydrogels. Moreover, craze-like patterns were observed during tensile loading of a DN hydrogel synthesized from a hydrolyzed highly cross-linked first network and a loosely cross-linked second network. The patterns remained in the gel even after strain hardening at high stretch ratios. The craze-like pattern formation was suppressed by increasing the concentration of cross-linking monomer in the second polymerization step. Crack propagation in DN hydrogels synthesized using hydrolysis was also studied by applying a tensile load on notched specimens.

Relative free-energy calculations for scaffold hopping-type transformations with an automated RE-EDS sampling procedure.

The calculation of relative free-energy differences between different compounds plays an important role in drug design to identify potent binders for a given protein target. Most rigorous methods based on molecular dynamics simulations estimate the free-energy difference between pairs of ligands. Thus, the comparison of multiple ligands requires the construction of a "state graph", in which the compounds are connected by alchemical transformations. The computational cost can be optimized by reducing the state graph to a minimal set of transformations. However, this may require individual adaptation of the sampling strategy if a transformation process does not converge in a given simulation time. In contrast, path-free methods like replica-exchange enveloping distribution sampling (RE-EDS) allow the sampling of multiple states within a single simulation without the pre-definition of alchemical transition paths. To optimize sampling and convergence, a set of RE-EDS parameters needs to be estimated in a pre-processing step. Here, we present an automated procedure for this step that determines all required parameters, improving the robustness and ease of use of the methodology. To illustrate the performance, the relative binding free energies are calculated for a series of checkpoint kinase 1 inhibitors containing challenging transformations in ring size, opening/closing, and extension, which reflect changes observed in scaffold hopping. The simulation of such transformations with RE-EDS can be conducted with conventional force fields and, in particular, without soft bond-stretching terms.

Post-operative hearing among patients with labyrinthine fistula as a complication of cholesteatoma using "under water technique".

INTRODUCTION: During surgery in patients with labyrinthine fistula the mandatory complete removal of the cholesteatoma while preserving inner ear and vestibular function is a challenge. Options so far have been either the complete removal of the cholesteatoma or leaving the matrix on the fistula. We evaluated an alternative "under water" surgical technique for complete cholesteatoma resection, in terms of preservation of postoperative inner ear and vestibular function. METHODS: From 2013 to 2019, 20 patients with labyrinthine fistula due to cholesteatoma were operated. We used the canal wall down approach and removal of matrix on the fistula was done as the last step during surgery using the "under water technique". The pre and postoperative hearing tests and the vestibular function were retrospectively examined. RESULTS: There was no significant difference between pre and post-operative bone conduction thresholds; 20% experienced an improvement of more than 10 dB, with none experiencing a postoperative worsening of sensorineural hearing loss. Among seven patients who presented with vertigo, two had transient vertigo postoperatively but eventually recovered. CONCLUSION: Our data show that the "under water technique" for cholesteatoma removal at the labyrinthine fistula is a viable option in the preservation of inner ear function and facilitating complete cholesteatoma removal.

N-Glycosylation Enhances Conformational Flexibility of Protein Disulfide Isomerase Revealed by Microsecond Molecular Dynamics and Markov State Modeling.

Secreted proteins of eukaryotes are decorated with branched carbohydrate oligomers called glycans. This fact is only starting to be considered for in silico investigations of protein dynamics. Using all-atom molecular dynamics (MD) simulations and Markov state modeling (MSM), we unveil the influence of glycans on the conformational flexibility of the multidomain protein disulfide isomerase (PDI), which is a ubiquitous chaperone in the endoplasmic reticulum (ER). Yeast PDI (yPDI) from Saccharomyces cerevisiae is glycosylated at asparagine side chains and the knowledge of its five modified sites enables a realistic computational modeling. We compare simulations of glycosylated and unglycosylated yPDI and find that the presence of glycan-glycan and glycan-protein interactions influences the flexibility of PDI in different ways. For example, glycosylation reduces interdomain interactions, shifting the conformational ensemble toward more open, extended structures. In addition, we compare our results on yPDI with structural information of homologous proteins such as human PDI (hPDI), which is natively unglycosylated. Interestingly, hPDI lacks a surface recess that is present in yPDI. We find that glycosylation of yPDI facilitates its catalytic site to reach close to this surface recess. Hence, this might point to a possible functional relevance of glycosylation in yeast to act on substrates, while glycosylation seems redundant for the human homologous protein. We conclude that glycosylation is fundamental for protein dynamics, making it a necessity for a truthful representation of the flexibility and function in in silico studies of glycoproteins.

Glycan-protein interactions determine kinetics of N-glycan remodeling.

A hallmark of N-linked glycosylation in the secretory compartments of eukaryotic cells is the sequential remodeling of an initially uniform oligosaccharide to a site-specific, heterogeneous ensemble of glycostructures on mature proteins. To understand site-specific processing, we used protein disulfide isomerase (PDI), a model protein with five glycosylation sites, for molecular dynamics (MD) simulations and compared the result to a biochemical in vitro analysis with four different glycan processing enzymes. As predicted by an analysis of the accessibility of the N-glycans for their processing enzymes derived from the MD simulations, N-glycans at different glycosylation sites showed different kinetic properties for the processing enzymes. In addition, altering the tertiary structure of the glycoprotein PDI affected its N-glycan remodeling in a site-specific way. We propose that the observed differential N-glycan reactivities depend on the surrounding protein tertiary structure and lead to different glycan structures in the same protein through kinetically controlled processing pathways.

[Development of the publication activity at the German university hospitals for Otorhinolaryngology, Head and Neck Surgery during the SARS-CoV-2-pandemic in 2020]. / Entwicklung der Publikationsleistung der Universitätskliniken für Hals-Nasen-Ohrenheilkunde, Kopf- und Hals-Chirurgie während der SARS-CoV-2-Pandemie im Jahr 2020 in Deutschland.

INTRODUCTION: The SARS-CoV-2 pandemic has led to profound limitations in patient care and student teaching at the University Hospitals of Otorhinolaryngology (ORL). In contrast, the impact on research has been variable. To classify the pandemic-related effect on research, the development of the number of scientific publications of the German ORL university hospitals before and during the pandemic was analyzed. MATERIAL AND METHODS: The publication performance between 2015 and 2020 of the 39 current chairmen was surveyed using a literature search (Pubmed). All entries relating to the chairmen of the university hospital as first, last or co-author were included. The absolute and relative development of each author's publication performance was determined and evaluated using nonparametric statistical methods. RESULTS: A total of 2420 publications could be documented. From 2015 to 2019, an average of 368 publications were published per year. In 2020, this number increased by 57.9 % to 581 publications. While the number of monthly publications remained constant between 2015 and 2019, a significant increase was seen from May 2020 up to a maximum of 74 publications in September 2020. In 2020, 34 articles (5.9 %) had a thematic relation to the SARS-CoV-2 pandemic, with 7 of these papers (20.6 %) resulting from cross-site publications. CONCLUSION: In 2020, the number of scientific publications was raised to more than 1.5 times the usual annual publications. This increase was clearly related in time to the reduction of elective patient care during the SARS-CoV-2 pandemic starting in mid-March 2020. Probably, free time capacities enabled this increased publication output. Our results confirm the great scientific potential of the ORL university hospitals, which has been successfully implemented despite the pandemic.

Volume-scaled common nearest neighbor clustering algorithm with free-energy hierarchy.

The combination of Markov state modeling (MSM) and molecular dynamics (MD) simulations has been shown in recent years to be a valuable approach to unravel the slow processes of molecular systems with increasing complexity. While the algorithms for intermediate steps in the MSM workflow such as featurization and dimensionality reduction have been specifically adapted to MD datasets, conventional clustering methods are generally applied to the discretization step. This work adds to recent efforts to develop specialized density-based clustering algorithms for the Boltzmann-weighted data from MD simulations. We introduce the volume-scaled common nearest neighbor (vs-CNN) clustering that is an adapted version of the common nearest neighbor (CNN) algorithm. A major advantage of the proposed algorithm is that the introduced density-based criterion directly links to a free-energy notion via Boltzmann inversion. Such a free-energy perspective allows a straightforward hierarchical scheme to identify conformational clusters at different levels of a generally rugged free-energy landscape of complex molecular systems.

Differential effects of abaloparatide and teriparatide on hip cortical volumetric BMD by DXA-based 3D modeling.

In postmenopausal osteoporotic women in ACTIVE, abaloparatide reduced fracture risk and increased areal bone mineral density (BMD) more than teriparatide at the hip and wrist. DXA-based 3D modeling showed significantly greater increases in hip cortical volumetric BMD with abaloparatide versus teriparatide. This may explain differences reported in aBMD by DXA. INTRODUCTION: In ACTIVE, abaloparatide (ABL) increased bone mineral density (BMD) shown by dual-energy X-ray absorptiometry (DXA) while reducing fracture incidence in postmenopausal osteoporotic women. Changes in DXA BMD with ABL, 80 µg, were significantly greater than with open-label teriparatide (TPTD), 20 µg, at cortical sites including total hip, femoral neck, and 1/3 distal radius. The purpose of this study was to better understand the relative effects of ABL and TPTD on cortical and cancellous compartments in the proximal femur. METHODS: Hip DXA images from a subset of randomly selected patients in the ACTIVE trial (n = 250/arm) were retrospectively analyzed using three-dimensional modeling methods (3D-SHAPER software) to evaluate changes from baseline at months 6 and 18. RESULTS: Similar significant increases in trabecular volumetric BMD (vBMD, + 9%) and cortical thickness (+ 1.5%) were observed with ABL and TPTD by 3D-DXA at 18 months. In contrast, only ABL significantly increased cortical vBMD versus baseline (+ 1.3%), and changes in both cortical vBMD and cortical surface BMD were significantly greater with ABL versus TPTD. In the TPTD group, changes in cortical vBMD were inversely correlated with changes in serum CTX (carboxy-terminal telopeptide of type I collagen) and PINP (procollagen type I N-terminal propeptide), suggesting that higher bone turnover may have attenuated cortical gains. CONCLUSION: These results suggest previously reported differences in areal BMD increases between ABL and TPTD may be due to differential effects on cortical vBMD. Further studies are warranted to investigate how these differences affect therapeutic impact on hip strength in postmenopausal women with osteoporosis.

Brittle-to-Ductile Transition of Sulfonated Polystyrene Ionomers.

This study examines the brittle-to-ductile transition of sulfonated polystyrene ionomers (SPS) with different counterions. The polystyrene precursor was unentangled and had two ionic groups per chain on average. Thus, its terminal relaxation time was comparable to the lifetime of the associating ionic groups. Three types of ionomer samples were used to tune the association lifetime: (1) fully neutralized SPS with different alkali-metal counterions, (2) fully neutralized SPS with mixed sodium and cesium counterions, and (3) partially neutralized SPS with sodium or cesium counterions. For all three systems, the brittle-to-ductile transition could be represented by a diagram of two Weissenberg numbers, Wi and WiR, defined with respect to the terminal and Rouse relaxation times, respectively. A flowable region existed at sufficiently low Wi, independent of WiR. At higher Wi, a brittle-to-ductile transition of the ionomer melt occurred above a critical value of WiR. To achieve ductility during the application of rapid elongational flow, the Rouse-type motions should be sufficiently slow relative to the rate of ion-dissociation, so that the strain-induced breakup of the ionic cross-links would not cause very strong chain retraction that may further lead to the macroscopic fracture.

Audiological benefit and subjective satisfaction with the ADHEAR hearing system in children with unilateral conductive hearing loss.

OBJECTIVE: The ADHEAR system (MED-EL, Innsbruck, Austria) is a new adhesive bone conduction hearing aid. This study evaluates the audiological benefit and subjective satisfaction as well as the manageability in everyday life in children with unilateral conductive hearing loss. METHODS: Ten children with unilateral hearing loss of different origin were included in the study. The audiological assessment included sound field audiometry and speech intelligibility in quiet and in noise, which was tested unaided and after 4 weeks of wearing the hearing system. Subjective benefit and satisfaction with the system was assessed using the SSQ for parents. With a second system-specific questionnaire, suitability for everyday use and quality of life were queried. RESULTS: With ADHEAR, speech perception in quiet improved by 44%. The word recognition score in noise improved from 11.7% in the unaided situation to 46.7% with the ADHEAR system. The SSQ for parents demonstrates a subjective benefit and satisfaction with the system. CONCLUSION: ADHEAR is an effective treatment option for children with unilateral conductive hearing loss. Especially children who are not eligible for semi-implantable hearing systems or do not accept hearing devices on a softband can benefit from this device.

Connecting dynamic reweighting Algorithms: Derivation of the dynamic reweighting family tree.

Thermally driven processes of molecular systems include transitions of energy barriers on the microsecond timescales and higher. Sufficient sampling of such processes with molecular dynamics simulations is challenging and often requires accelerating slow transitions using external biasing potentials. Different dynamic reweighting algorithms have been proposed in the past few years to recover the unbiased kinetics from biased systems. However, it remains an open question if and how these dynamic reweighting approaches are connected. In this work, we establish the link between the two main reweighting types, i.e., path-based and energy-based reweighting. We derive a path-based correction factor for the energy-based dynamic histogram analysis method, thus connecting the previously separate reweighting types. We show that the correction factor can be used to combine the advantages of path-based and energy-based reweighting algorithms: it is integrator independent, more robust, and at the same time able to reweight time-dependent biases. We can furthermore demonstrate the relationship between two independently derived path-based reweighting algorithms. Our theoretical findings are verified on a one-dimensional four-well system. By connecting different dynamic reweighting algorithms, this work helps to clarify the strengths and limitations of the different methods and enables a more robust usage of the combined types.

Evaluation of stallion sperm motility with ImageJ using a cell phone camera and a light microscope / [Avaliação da motilidade espermática de garanhões com ImageJ usando-se câmera de celular e microscópio óptico]

This study aimed to determine the accuracy of assessing stallion sperm motility using a light microscope, a cell phone camera, and a free computer-assisted semen analysis (FCASA) package for ImageJ. The total motility of frozen (n=22) and cooled (n=48) equine semen was determined by FCASA and compared to the results of subjective visual analysis (SVA) by two technicians. Frozen samples were also evaluated by a commercial computer-assisted semen analysis (CCASA) system. The Friedman test revealed no significant differences (P>0.05) between cooled samples analyzed by FCASA (38.0) and SVA (technician 1, 40.0; technician 2, 40.0), nor between frozen samples analyzed by FCASA (23.36 ± 15.9), SVA (25.5 ± 18.8 and 25.8 ± 18.5), and CCASA (25.2 ± 18.3). However, mean FCASA results were underestimated by 7.2% compared with CCASA. The correlation between FCASA and CCASA was significant and strong (P<0.0001, r=0.95). Chi-squared tests indicated that FCASA provided similar results (P=0.14) to the reference method (CCASA), but SVA had lower accuracy (P=0.04). ImageJ analysis of cell phone videos captured under a light microscope can be used for estimation of stallion sperm motility with comparable accuracy to commercial systems.(AU)

O objetivo deste estudo foi testar as configurações necessárias para avaliar a motilidade espermática total de garanhões, mediante o uso de ImageJ, microscópio óptico e câmera de celular. Os valores de motilidade total das amostras de sêmen equino congeladas (22) e refrigeradas (48) foram comparados por análise visual (SVA) e pelo plugin do ImageJ (CASAF). Amostras congeladas também foram comparadas por um CASA comercial (CCASA). O teste de Friedman não resultou em diferença estatística (P>0,05) entre as 48 amostras analisadas com CASAF (38,0) e SVA de dois avaliadores (40,0 e 40,0). A comparação das 22 amostras congeladas entre CASAF (23,36±15,9), SVA (25,5±18,8 e 25,8±18,5) e CCASA (25,2±18,3) também não resultou em diferença estatística, sendo que a média dos resultados obtidos com CASAF subestimou a obtida com o CCASA em 7,2%. A correlação entre CASAF e CCASA foi significativamente elevada (r=0,95, P<0,0001). O teste de qui-quadrado resultou em proporção de acertos semelhantes entre o CASAF e o CCASA (P=0,14), enquanto SVA resultou em proporção diferente (P=0,04), indicando menor acurácia. O uso de microscópio óptico e câmera de celular foi útil para obter vídeos de sêmen de garanhões a serem analisados com ImageJ, proporcionando resultados de motilidade total equiparáveis a sistemas comerciais.(AU)

Characterizing patients initiating abaloparatide, teriparatide, or denosumab in a real-world setting: a US linked claims and EMR database analysis.

We characterized patients initiating abaloparatide (ABL), teriparatide (TPTD), or denosumab (DMAB) in a real-world clinical setting from a large medical and pharmacy claims database. Differences were noted in sex, age, pathologic fractures, comorbidity index, and prior bisphosphonate use for patients initiating ABL and TPTD compared with those receiving DMAB. INTRODUCTION: To characterize patients initiating abaloparatide (ABL), teriparatide (TPTD), or denosumab (DMAB) treatment in a real-world clinical setting. METHODS: Patients aged ≥ 18 years initiating ABL, TPTD, or DMAB between May 1, 2017, and September 24, 2018 (without receiving the same drug in the previous 12 months), were identified using the OM1 Data Cloud, which contains medical and pharmacy claims from approximately 200 million US patients. The index date was the date of initial prescription or dispensing for ABL, TPTD, or DMAB during the study period. RESULTS: During the study period, 2666 patients initiated ABL, 9210 TPTD, and 116,718 DMAB. Mean age (standard deviation) was 69.2 (10.6) years for the ABL cohort, 68.6 (11.3) for TPTD, and 72.1 (10.2) for DMAB (P < 0.001; ABL vs DMAB). Proportionally more patients initiating ABL were female (95.2% ABL, 86.9% TPTD, and 91.3% DMAB, P < 0.001 ABL vs TPTD or DMAB). Nearly twice as many patients initiating ABL (19.1%) and TPTD (18.8%) had a previous pathologic/fragility fracture vs DMAB (9.6%; P < 0.001 ABL vs DMAB). Fewer patients initiating ABL (36.3%) or TPTD (39.7%) had Charlson comorbidity index of ≥ 2 vs DMAB (48.4%; P < 0.001 ABL vs DMAB). Before initiating ABL, TPTD, or DMAB, 44.3%, 33.8%, and 33.9% of patients had prior osteoporosis treatment, respectively. Bisphosphonate use was more common before initiating ABL (19.2%) or TPTD (19.6%), than before initiating DMAB (16.6%; P < 0.001 ABL vs DMAB). CONCLUSIONS: Patients initiating ABL and TPTD differed in sex, age, pathologic fractures, comorbidity index, and prior bisphosphonate use compared with those initiating DMAB.

Old carbon reservoirs were not important in the deglacial methane budget.

Permafrost and methane hydrates are large, climate-sensitive old carbon reservoirs that have the potential to emit large quantities of methane, a potent greenhouse gas, as the Earth continues to warm. We present ice core isotopic measurements of methane (Δ14C, δ13C, and δD) from the last deglaciation, which is a partial analog for modern warming. Our results show that methane emissions from old carbon reservoirs in response to deglacial warming were small (<19 teragrams of methane per year, 95% confidence interval) and argue against similar methane emissions in response to future warming. Our results also indicate that methane emissions from biomass burning in the pre-Industrial Holocene were 22 to 56 teragrams of methane per year (95% confidence interval), which is comparable to today.

Preindustrial 14CH4 indicates greater anthropogenic fossil CH4 emissions.

Atmospheric methane (CH4) is a potent greenhouse gas, and its mole fraction has more than doubled since the preindustrial era1. Fossil fuel extraction and use are among the largest anthropogenic sources of CH4 emissions, but the precise magnitude of these contributions is a subject of debate2,3. Carbon-14 in CH4 (14CH4) can be used to distinguish between fossil (14C-free) CH4 emissions and contemporaneous biogenic sources; however, poorly constrained direct 14CH4 emissions from nuclear reactors have complicated this approach since the middle of the 20th century4,5. Moreover, the partitioning of total fossil CH4 emissions (presently 172 to 195 teragrams CH4 per year)2,3 between anthropogenic and natural geological sources (such as seeps and mud volcanoes) is under debate; emission inventories suggest that the latter account for about 40 to 60 teragrams CH4 per year6,7. Geological emissions were less than 15.4 teragrams CH4 per year at the end of the Pleistocene, about 11,600 years ago8, but that period is an imperfect analogue for present-day emissions owing to the large terrestrial ice sheet cover, lower sea level and extensive permafrost. Here we use preindustrial-era ice core 14CH4 measurements to show that natural geological CH4 emissions to the atmosphere were about 1.6 teragrams CH4 per year, with a maximum of 5.4 teragrams CH4 per year (95 per cent confidence limit)-an order of magnitude lower than the currently used estimates. This result indicates that anthropogenic fossil CH4 emissions are underestimated by about 38 to 58 teragrams CH4 per year, or about 25 to 40 per cent of recent estimates. Our record highlights the human impact on the atmosphere and climate, provides a firm target for inventories of the global CH4 budget, and will help to inform strategies for targeted emission reductions9,10.