An ENU-Induced Mutation of Nrg1 Causes Dilated Pupils and a Reduction in Muscarinic Receptors in the Sphincter Pupillae

BACKGROUND: N-ethyl-N-nitrosourea (ENU)-induced mutagenesis is a powerful tool for the study of gene function and the generation of human disease models. A large number of mouse mutants obtained by ENU-induced mutagenesis with a variety of phenotypes have been recovered. However, after genetic confirmation testing, only approximately 50% of the abnormal phenotypes were found to be heritable. METHODOLOGY/PRINCIPAL FINDINGS: A mouse mutant, Dp1, with a dilated pupil phenotype was induced with an N-ethyl-N-nitrosourea (ENU) mutagenesis strategy. Sequence analysis for Nrg1 reveals a G>A base substitution that flanks exon E59, encoding for an EGFβ domain, in the 5' splice donor site. The mutation affects but does not abolish the splicing of EGFβ-type Nrg1 mRNA in Dp1 mice and produces several different transcripts by activating other, cryptic splice sites. These types of protein isoforms are expected, and the result shows that, in the mutant, the effect is a decrease in but not an elimination of the high affinity EGFβ-type Nrg1 isoforms. This is partially compensated for by an increase in expression of the low affinity alpha forms or inactive proteins, suggesting that the mutation results in a hypomorphic allele. Interestingly, genetic model testing shows that Dp1 is a mutation that results in a dilated pupil phenotype that is inherited with very low penetrance when heterozygous and with complete penetrance when homozygous. Pharmacological and immunohistochemical tests show a reduction of muscarinic (M) receptors in the sphincter pupillae of Dp1 mice, which is a major cause of dilated pupils. CONCLUSIONS/SIGNIFICANCE: This study is the first report of an Nrg1 mutation being associated with a dilated pupil phenotype and the reduction of M receptors. This report may help in establishing more mutant mouse lines and models of human genetic disease and can be applied to other organisms. Dp1 mice are a valuable resource for the further clarification of Nrg1 biological function

Omecamtiv mecarbil in chronic heart failure with reduced ejection fraction, GALACTIC‐HF: baseline characteristics and comparison with contemporary clinical trials

Aims: The safety and efficacy of the novel selective cardiac myosin activator, omecamtiv mecarbil, in patients with heart failure with reduced ejection fraction (HFrEF) is tested in the Global Approach to Lowering Adverse Cardiac outcomes Through Improving Contractility in Heart Failure (GALACTIC‐HF) trial. Here we describe the baseline characteristics of participants in GALACTIC‐HF and how these compare with other contemporary trials. Methods and Results: Adults with established HFrEF, New York Heart Association functional class (NYHA) ≥ II, EF ≤35%, elevated natriuretic peptides and either current hospitalization for HF or history of hospitalization/ emergency department visit for HF within a year were randomized to either placebo or omecamtiv mecarbil (pharmacokinetic‐guided dosing: 25, 37.5 or 50 mg bid). 8256 patients [male (79%), non‐white (22%), mean age 65 years] were enrolled with a mean EF 27%, ischemic etiology in 54%, NYHA II 53% and III/IV 47%, and median NT‐proBNP 1971 pg/mL. HF therapies at baseline were among the most effectively employed in contemporary HF trials. GALACTIC‐HF randomized patients representative of recent HF registries and trials with substantial numbers of patients also having characteristics understudied in previous trials including more from North America (n = 1386), enrolled as inpatients (n = 2084), systolic blood pressure < 100 mmHg (n = 1127), estimated glomerular filtration rate < 30 mL/min/1.73 m2 (n = 528), and treated with sacubitril‐valsartan at baseline (n = 1594). Conclusions: GALACTIC‐HF enrolled a well‐treated, high‐risk population from both inpatient and outpatient settings, which will provide a definitive evaluation of the efficacy and safety of this novel therapy, as well as informing its potential future implementation

Stress in triple-row riveted lap joints under the influence of specific factors

Effects of fastener clearance fit, friction coefficient, and corrosion pillowing on the stress state in triple-row riveted lap joints were studied numerically using three-dimensional finite element methods. The material elastoplastic constitutive relationship and geometric nonlinear properties, as well as nonlinear contact boundary conditions, were included in the numerical simulations. The numerical modeling was validated using experimental measurements of the rivet driven-head deformation and in situ strains. The lap joints were loaded in tension after riveting. Three different clearance fits, three different friction coefficients, and four corrosion-pillowing conditions were analyzed. The stress variations along prescribed paths and full-field contours of the maximum principal stress on joint faying surfaces during the tensile loading stage were investigated. Insightful results of the stress state in riveted lap joints were obtained, which could effectively explain the phenomena observed from joint fatigue tests. The phenomena include 1) the potential major factor to cause the joint fatigue-life scatter, 2) crack-nucleation site location in the top rivet-hole vicinity on the outer-sheet faying surface for the noncorroded joints, and 3) the occurrence of the multiplesite damages in aged and corroded lap joints.Peer reviewed: YesNRC publication: Ye

Studies of residual stress in single-row countersunk riveted lap joints

Variations of stress and strain, from the riveting process through the tensile loading stage in lap joints with a single countersunk rivet, were studied experimentally and numerically. In situ microstrain gauges were used to measure the strain variations during the entire loading sequence. Three-dimensional finite element (FE) models were generated to simulate the experimental setup. The material elastoplastic constitutive relationship and geometric nonlinear properties, as well as nonlinear contact boundary conditions, were included in the numerical simulations. The numerical modeling techniques were validated using the experimental data. The residual minimum principal stress resulting from the riveting process and the maximum principal stress when the joints were in tension, determined from the FE analyses, are presented. The stress variations along a prescribed path are also presented. The aim of the research is to develop an accurate three-dimensional numerical technique to study the residual stress and strain as well as the stress and strain variations that occur during the entire loading history.Peer reviewed: YesNRC publication: Ye

Residual stress/strain in three-row countersunk riveted lap joints

The stress/strain variations from the riveting process to the tensile loading stage in lap joints with tliree-row countersunk rivets were studied experimentally and numerically. Three different forces were used in the riveting process. After releasing the rivet squeeze forces, the lap joints were then loaded in tension. Three-dimensional finite element models were developed to simulate the experimental setup. The material elasto-plastic constitutive relationship and geometric non-linear properties, as well as, nonlinear contact boundary conditions were included in the numerical simulations. The numerical modeling techniques were validated using experimental data. The effect of the residual stress on the stress variations, along a prescribed path during the tensile loading stage, is discussed. Full-field contours of the residual minimum principal stress induced by the riveting process, and the maximum principal stress during the tensile loading stage are also analyzed. The aim of this research is to develop an accurate three-dimensional numerical technique to study the complex stress and strain distributions induced by the entire loading sequence, and to use this information to more accurately predict the fatigue life of fuselage lap joints.Peer reviewed: YesNRC publication: Ye

Study of the residual strain in lap joints

Both experiments and finite element analysis were carried out to study the residual strain (stress) in the riveted lap joint for a better understanding of the fatigue life of fuselage lap joints. A force-controlled riveting process was used to apply a constant load ramp to install the rivets. Strain variations on the joint surface were measured using microstrain gauges during the riveting process. Because neutrons are known to penetrate through many centimeters of aluminum alloys, neutron diffraction was used to provide a nondestructive technique to determine strains at certain depths in the joint. Parallel to the experimental testing, a two-dimensional axisymmetric finite element model was developed to simulate the riveting process. Both material and geometric nonlinearities, as well as nonlinear contact boundary conditions, were used in this numerical model. Comparisons between the numerical simulations and experimental results focused on the rivet driven head deformations and strain variations, and the results showed that the current two-dimensional axisymmetric finite element model using the proper boundary conditions can reliably be used to determine the residual strains (stresses) present in joints that were induced during the riveting process.Peer reviewed: YesNRC publication: Ye

Effects of fastener clearance fit and friction coefficient on the stress condition in triple-row riveted lap joints

Effects of fastener clearance fit, friction coefficient, and corrosion pillowing on the stress state in triple-row riveted lap joints were studied numerically using three-dimensional finite element methods. The material elastoplastic constitutive relationship and geometric nonlinear properties, as well as nonlinear contact boundary conditions, were included in the numerical simulations. The numerical modeling was validated using experimental measurements of the rivet driven head deformation and in-situ strains. The lap joints were loaded in tension after riveting. Three different clearance fits, three different friction coefficients, and four corrosion pillowing conditions were analyzed. The stress variation along prescribed paths during the tensile loading stage is discussed for each of these conditions. Full-field contours of the friction and maximum principal stresses during the tensile loading stage were investigated. Numerical results showed that a small increase in the clearance fit considerably increased the joint stress magnitude. The clearance fit magnitude also affected the maximum stress location in the vicinity at the top fastener hole. A large friction coefficient increased the contact and friction stresses in the hole vicinity. These results could explain the scatter degree of the fatigue data and could be used to improve the manufacture quality for high fatigue-rated riveted lap joints. Serious corrosion pillowing significantly increased the stress magnitude at both the middle and top hole regions, and led to the co-existence of the two highly-stressed areas in the outer sheet, which greatly decreased the integrity of the aged riveted lap joint due to the occurrence of the multiple-sited damages during cyclic loading.Peer reviewed: YesNRC publication: Ye

Numerical modeling of a single aluminum sheet containing an interference fit fastener

This paper presents the results of an investigation into the three-dimensional stress field around an interference fit fastener hole. Understanding the stress variations in the vicinity of the hole during the entire loading sequence from the fastener set-up process to the tensile-loading stage is extremely useful for the design and builing of a high-fatigue performance joint. Two specimens were tested, each specimen consisted of a single aluminum sheet and an interference fit fastener. A photoelastic coating was bonded to the outer surface (fastener head side) on one specimen and the inner surface (nut side) of the other. An interference fit fastener was installed in a single sheet and then photoelastic analysis was used to measure the strains under different tensile loads. Four different three-dimensional finite element (FE) models of the sheet and fastener/nut structure with and without a coating were generated. A numerical technique is proposed to analyze the fastener-clamping torque, which was employed in the contact numerical simulations. Multiple-load steps in the FE models were used to simulate the entire joining and then tensile-loading stages. A good correlation was achieved between the experimental results and the finite element predictions for the maximum shear strain. The full-field contours of the maximum principal stress under different clamping values and tensile loads were also studied.Cet article pr\ue9sente les r\ue9sultats d'une recherche sur les champs de tension tridimensionnels autour d'un trou d'assemblage \ue0 ajustement serr\ue9. Il serait extr\ueamement utile pour la conception et la construction d'assemblages tr\ue8s r\ue9sistants \ue0 la fatigue, de comprendre les variations de tension dans le voisinage du trou, pendant toute la s\ue9quence de charge, depuis le processus d'ajustement du joint jusqu'au stade de la mise en charge par la traction. Nous avons exp\ue9riment\ue9 sur deux sp\ue9cimens form\ue9s d'une seule feuille d'aluminium et d'un assemblage \ue0 ajustement serr\ue9. Nous avons li\ue9 un enduit photo\ue9lastique \ue0 la surface externe (du c\uf4t\ue9 de la t\ueate de la fixation) d'un sp\ue9cimen et, de l'autre, \ue0 la surface interne (du c\uf4t\ue9 de l'\ue9crou de serrage). Un assemblage \ue0 ajustement serr\ue9 a \ue9t\ue9 install\ue9 sur une seule feuille et nous avons utilis\ue9 l'analyse photo\ue9lastique pour mesurer la tension r\ue9sultant de diff\ue9rents efforts de traction. Nous avons produit quatre mod\ue8les tridimensionnels par \ue9l\ue9ments finis de la structure form\ue9e par la feuille et la fixation et l'\ue9crou, avec ou sans enduit. Une technique de calcul num\ue9rique a \ue9t\ue9 propos\ue9e pour analyser le couple de serrage et elle a \ue9t\ue9 exploit\ue9e lors des simulations num\ue9riques. Nous avons simul\ue9, par des \ue9tapes multiples de transmission d'effort, tous les stades de l'assemblage, \ue0 la mise en traction. Pour le cisaillement maximal, nous avons trouv\ue9 une bonne corr\ue9lation entre les r\ue9sultats exp\ue9rimentaux et les pr\ue9dictions des mod\ue8les \ue0 \ue9l\ue9ments finis. Nous avons \ue9galement \ue9tudi\ue9 les contours en champ complet de la tension principale maximale pour diff\ue9rentes valeurs de serrage et d'efforts en traction.NRC publication: Ye

MicrobiomeGWAS: A Tool for Identifying Host Genetic Variants Associated with Microbiome Composition

The microbiome is the collection of all microbial genes and can be investigated by sequencing highly variable regions of 16S ribosomal RNA (rRNA) genes. Evidence suggests that environmental factors and host genetics may interact to impact human microbiome composition. Identifying host genetic variants associated with human microbiome composition not only provides clues for characterizing microbiome variation but also helps to elucidate biological mechanisms of genetic associations, prioritize genetic variants, and improve genetic risk prediction. Since a microbiota functions as a community, it is best characterized by β diversity; that is, a pairwise distance matrix. We develop a statistical framework and a computationally efficient software package, microbiomeGWAS, for identifying host genetic variants associated with microbiome β diversity with or without interacting with an environmental factor. We show that the score statistics have positive skewness and kurtosis due to the dependent nature of the pairwise data, which makes p-value approximations based on asymptotic distributions unacceptably liberal. By correcting for skewness and kurtosis, we develop accurate p-value approximations, whose accuracy was verified by extensive simulations. We exemplify our methods by analyzing a set of 147 genotyped subjects with 16S rRNA microbiome profiles from non-malignant lung tissues. Correcting for skewness and kurtosis eliminated the dramatic deviation in the quantile–quantile plots. We provided preliminary evidence that six established lung cancer risk SNPs were collectively associated with microbiome composition for both unweighted (p = 0.0032) and weighted (p = 0.011) UniFrac distance matrices. In summary, our methods will facilitate analyzing large-scale genome-wide association studies of the human microbiome