Biventricular finite element modeling of the fetal heart in health and during critical aortic stenosis.

Finite Element simulations are a robust way of investigating cardiac biomechanics. To date, it has only been performed with the left ventricle (LV) alone for fetal hearts, even though results are likely different with biventricular (BiV) simulations. In this research, we conduct BiV simulations of the fetal heart based on 4D echocardiography images to show that it can capture the biomechanics of the normal healthy fetal heart, as well as those of fetal aortic stenosis better than the LV alone simulations. We found that performing LV alone simulations resulted in overestimation of LV stresses and pressures, compared to BiV simulations. Interestingly, inserting a compliance between the LV and right ventricle (RV) in the lumped parameter model of the LV only simulation effectively resolved these overestimations, demonstrating that the septum could be considered to play a LV-RV pressure communication role. However, stresses and strains spatial patterns remained altered from BiV simulations after the addition of the compliance. The BiV simulations corroborated previous studies in showing disease effects on the LV, where fetal aortic stenosis (AS) drastically elevated LV pressures and reduced strains and stroke volumes, which were moderated down with the addition of mitral regurgitation (MR). However, BiV simulations enabled an evaluation of the RV as well, where we observed that effects of the AS and MR on pressures and stroke volumes were generally much smaller and less consistent. The BiV simulations also enabled investigations of septal dynamics, which showed a rightward shift with AS, and partial restoration with MR. Interestingly, AS tended to enhance RV stroke volume, but MR moderated that down.

The development of an egg-soaking method for delivering dsRNAs into spider mites.

Recently, the first sprayable RNAi biopesticide, Ledprona, against the Colorado potato beetle, Leptinotarsa decemlineata, has been registered at the United States Environmental Protection Agency. Spider mites (Acari: Tetranychidae), a group of destructive agricultural and horticultural pests, are notorious for rapid development of insecticide/acaricide resistance. The management options, on the other hand, are extremely limited. RNAi-based biopesticides offer a promising control alternative to address this emerging issue. In this study, we i) developed an egg-soaking dsRNA delivery method; ii) evaluated the factors influencing RNAi efficiency, and finally iii) investigated the potential mode of entry of this newly developed egg-soaking RNAi method. In comparison to other dsRNA delivery methods, egg-soaking method was the most efficient, convenient/practical, and cost-effective method for delivering dsRNAs into spider mites. RNAi efficiency of this RNAi method was affected by target genes, dsRNA concentration, developmental stages, and mite species. In general, the hawthorn spider mite, Amphitetranychus viennensis, is more sensitive to RNAi than the two-spotted spider mite, Tetranychus urticae, and both of them have dose-dependent RNAi effect. For different life stages, egg and larvae are the most sensitive life stages to dsRNAs. For different target genes, there is no apparent association between the suppression level and the resultant phenotype. Finally, we demonstrated that this egg-soaking RNAi method acts as both stomach and contact toxicity. Our combined results demonstrate the effectiveness of a topically applied dsRNA delivery method, and the potential of a spray induced gene silencing (SIGS) method as a control alternative for spider mites.

Identification and Functional Characterization of Two Chitin Synthases in the Black Cutworm, Agrotis ipsilon (Hufnagel) (Lepidoptera: Noctuidae).

The black cutworm, Agrotis ipsilon (Hufnagel), a seasonal migrant and a prolific generalist, can feed on nearly all vegetables and grain crops, causing considerable economic impacts on a global scale. Given its cryptic nature, A. ipsilon management has been extremely challenging. Chitin synthase (CHS), a key enzyme involved in chitin biosynthetic pathway and crucially important for the growth and development of insects, is the molecular target of chitin synthesis inhibitors, a group of broad-spectrum insecticides that is compatible with Integrated Pest Management practices. In this study, we investigated the potential of targeting chitin synthases to control A. ipsilon. As a result, two chitin synthases, AiCHS1 and AiCHS2, were identified and cloned from A. ipsilon. The temporal-spatial distribution study showed that AiCHS1 was predominantly expressed at the pupal stage and most abundant among tissues of head capsule and integument, while AiCHS2 was mainly expressed at the sixth instar larval stage and tissues of foregut and midgut. RNAi-based functional study confirmed gene silencing caused significant reduction in the expression levels of the corresponding mRNA, as well as resulted in abnormal pupation and mortality, respectively. Furthermore, under the treatment of lufenuron, a chitin synthesis inhibitor, A. ipsilon responded with an elevated expression in AiCHS1 and AiCHS2, while larvae showed difficulty in shedding old cuticle, and a cumulative mortality of 69.24% at 48 h. In summary, chitin synthases are crucial for chitin biosynthesis in A. ipsilon and can be targeted for the control (e.g., RNAi-based biopesticides) of this devastating insect pest.

Contribution of Ventricular Motion and Sampling Location to Discrepancies in Two-Dimensional Versus Three-Dimensional Fetal Ventricular Strain Measures.

BACKGROUND: Echocardiographic quantification of fetal cardiac strain is important to evaluate function and the need for intervention, with both two-dimensional (2D) and three-dimensional (3D) strain measurements currently feasible. However, discrepancies between 2D and 3D measurements have been reported, the etiologies of which are unclear. This study sought to determine the etiologies of the differences between 2D and 3D strain measurements. METHODS: A validated cardiac motion-tracking algorithm was used on 3D cine ultrasound images acquired in 26 healthy fetuses. Both 2D and 3D myocardial strain quantifications were performed on each image set for controlled comparisons. Finite element modeling of 2 left ventricle (LV) models with minor geometrical differences were performed with various helix angle configurations for validating image processing results. RESULTS: Three-dimensional longitudinal strain (LS) was significantly lower than 2D LS for the LV free wall and septum but not for the right ventricular (RV) free wall, while 3D circumferential strain (CS) was significantly higher than 2D CS for the LV, RV, and septum. The LS discrepancy was due to 2D long-axis imaging not capturing the out-of-plane motions associated with LV twist, while the CS discrepancy was due to the systolic motion of the heart toward the apex that caused out-of-plane motions in 2D short-axis imaging. A timing mismatch between the occurrences of peak longitudinal and circumferential dimensions caused a deviation in zero-strain referencing between 2D and 3D strain measurements, contributing to further discrepancies between the 2. CONCLUSIONS: Mechanisms for discrepancies between 2D and 3D strain measurements in fetal echocardiography were identified, and inaccuracies associated with 2D strains were highlighted. Understanding of this mechanism is useful and important for future standardization of fetal cardiac strain measurements, which we propose to be important in view of large discrepancies in measured values in the literature.

The dependency of fetal left ventricular biomechanics function on myocardium helix angle configuration.

The helix angle configuration of the myocardium is understood to contribute to the heart function, as finite element (FE) modeling of postnatal hearts showed that altered configurations affected cardiac function and biomechanics. However, similar investigations have not been done on the fetal heart. To address this, we performed image-based FE simulations of fetal left ventricles (LV) over a range of helix angle configurations, assuming a linear variation of helix angles from epicardium to endocardium. Results showed that helix angles have substantial influence on peak myofiber stress, cardiac stroke work, myocardial deformational burden, and spatial variability of myocardial strain. A good match between LV myocardial strains from FE simulations to those measured from 4D fetal echo images could only be obtained if the transmural variation of helix angle was generally between 110 and 130°, suggesting that this was the physiological range. Experimentally discovered helix angle configurations from the literature were found to produce high peak myofiber stress, high cardiac stroke work, and a low myocardial deformational burden, but did not coincide with configurations that would optimize these characteristics. This may suggest that the fetal development of myocyte orientations depends concurrently on several factors rather than a single factor. We further found that the shape, rather than the size of the LV, determined the manner at which helix angles influenced these characteristics, as this influence changed significantly when the LV shape was varied, but not when a heart was scaled from fetal to adult size while retaining the same shape. This may suggest that biomechanical optimality would be affected during diseases that altered the geometric shape of the LV.

Biventricular biaxial mechanical testing and constitutive modelling of fetal porcine myocardium passive stiffness.

The evaluation of fetal heart mechanical function is becoming increasingly important for determining the prognosis and making subsequent decisions on the treatment and management of congenital heart diseases. Finite Element (FE) modelling can potentially provide detailed information on fetal hearts, and help perform virtual interventions to assist in predicting outcomes and supporting clinical decisions. Previous FE studies have enabled an improved understanding of healthy and diseased fetal heart biomechanics. However, to date, the mechanical properties of the fetal myocardium have not been well characterized which limits the reliability of such modelling. Here, we characterize the passive mechanical properties of late fetal and neonatal porcine hearts via biaxial mechanical testing as a surrogate for human fetal heart mechanical properties. We used samples from both the right and left ventricles over the late gestational period from 85 days of gestation to birth. Constitutive modelling was subsequently performed with a transversely isotropic Fung-type model and a Humphrey-type model, using fiber orientations identified with histology. We found no significant difference in mechanical stiffness across all age groups and between the right and left ventricular samples. This was likely due to the similarity in LV and RV pressures in the fetal heart, and similar gestational maturity across these late gestational ages. We thus recommend using the constitutive model for the average stress-stress behaviour of the tissues in future modelling work. Furthermore, we characterized the variability of the stiffness to inform such work.

Identification and RNAi-based functional analysis of chitinase family genes in Agrotis ipsilon.

BACKGROUND: Chitin is a major component in the extracellular matrix of insects, and its metabolism largely affects insect development and molting. As essential degradative enzymes, chitinases are encoded by multiple genes that differ in size, expression pattern and function in insects. However, our limited knowledge on the functions of different chitinases in Agrotis ipsilon has prevented our application of new technologies to target these genes as new pest management strategies. RESULTS: We revealed 11 full-length complementary DNA sequences of chitinase genes (AiChts) from A. ipsilon transcriptome. Although the domain architecture of these chitinases varied greatly, they all contained at least one chitinase catalytic domain. Developmental stage- and tissue-dependent expression profiles showed that most AiChts had the highest expression in the pupal stage. Furthermore, AiCht2, AiCht6, AiCht7 and AiCht10 were mainly expressed in the integument, whereas AiCht8 and AiCht-h had the highest expression in the midgut. The RNA interference (RNAi) experiment revealed that knockdown of AiCht10 or the imaginal disc growth factor gene (AiIDGF) induced high larval mortality. Larvae failed to shed the old cuticle during molting after the injection of double-stranded RNA targeting AiCht10 (dsAiCht10), whereas the larval bodies shrunk and blackened after the injection of dsRNA targeting AiIDGF (dsAiIDGF). CONCLUSION: Our results revealed for the first time the important functions of AiCht10 and AiIDGF in A. ipsilon. These genes are essential for larval development, and can potentially serve as new targets for RNAi-based pest management. © 2022 Society of Chemical Industry.

Selection of Reference Genes for RT-qPCR Analysis in the Hawthorn Spider Mite, Amphitetranychus viennensis (Acarina: Tetranychidae), Under Acaricide Treatments.

Hawthorn spider mite, Amphitetranychus viennensis Zacher, one of the most damaging arthropod pests for Rosaceaous fruit trees and ornamentals, has developed resistance to most of the commercially available acaricides. To understand the molecular basis of acaricide resistance, a standardized protocol for real-time quantitative reverse transcription PCR (RT-qPCR) following the MIQE (minimum information for publication of quantitative real time PCR experiments) guidelines is needed. In this study, we screened for the internal references in A. viennensis to study in acaricide resistance. In total, 10 candidate reference genes, including EF1A, 28S rRNA, 18S rRNA, α-tubulin, Actin3, RPS9, GAPDH, V-ATPase B, RPL13, and V-ATPase A, were assessed under the treatments of four commonly used acaricides with distinct mode-of-actions (MOAs). Based on the Insecticide Resistance Action Committee MOA classification, avermectin, bifenazate, spirodiclofen, and fenpropathrin belong to group 6, 20D, 23, and 3A, respectively. The expression profiles of these candidate genes were evaluated using geNorm, Normfinder, BestKeeper, and ∆Ct methods, respectively. Eventually, different sets of reference genes were recommended for each acaricide according to RefFinder, a comprehensive platform integrating all four above-mentioned algorithms. Specifically, the top three recommendations were 1) 28S, V-ATPase A, and Actin 3 for avermectin, 2) GAPDH, RPS9, and 28S for bifenazate, 3) Actin 3, V-ATPase B, and α-tubulin for spirodiclofen, and 4) Actin 3, α-tubulin, and V-ATPase A for fenpropathrin. Although unique sets of genes are proposed for each acaricide, α-tubulin, EF1A, and GAPDH are the most consistently stably expressed reference genes when A. viennensis was challenged chemically. Our findings lay the foundation for the study of acaricide resistance in the phytophagous mites in general, and in the hawthorn spider mite, A. viennensis, in particular.

Real-Time Hierarchical Classification of Time Series Data for Locomotion Mode Detection.

OBJECTIVE: Accurate real-time estimation of motion intent is critical for rendering useful assistance using wearable robotic prosthetic and exoskeleton devices during user-initiated motions. We aim to evaluate hierarchical classification as a strategy for real-time locomotion mode recognition for the control of wearable robotic prostheses and exoskeletons during user-initiated motions. METHODS: We collect motion data from 8 subjects using a set of 7 inertial sensors for 16 lower limb locomotion modes of different specificities. A CNN based hierarchical classifier is trained to classify the modes into a specified label hierarchy. We measure the accuracy, stability, behaviour during mode transitions and suitability for real-time inference of the classifier. RESULTS: The method achieves stable classification of locomotion modes using [Formula: see text] of time history data. It achieves average classification accuracy of 94.34% and an average AU(PRC) of 0.773 - comparable to similar classifiers. The method produces more informative classifications at transitions between modes. Less specific classes are classified earlier than more specific classes in the hierarchy. The inference step of the classifier can be executed in less than 2 ms on embedded hardware, indicating suitability for real-time operation. CONCLUSION: Hierarchical classification can achieve accurate detection of locomotion modes and can break up mode transitions into multiple transitions between modes of different specificity. SIGNIFICANCE: Multi-specific hierarchical classification of locomotion modes could lead to smoother, more fine grained control adaptation of wearable robots during locomotion mode transitions.

Biomechanics of Human Fetal Hearts with Critical Aortic Stenosis.

Critical aortic stenosis (AS) of the fetal heart causes a drastic change in the cardiac biomechanical environment. Consequently, a substantial proportion of such cases will lead to a single-ventricular birth outcome. However, the biomechanics of the disease is not well understood. To address this, we performed Finite Element (FE) modelling of the healthy fetal left ventricle (LV) based on patient-specific 4D ultrasound imaging, and simulated various disease features observed in clinical fetal AS to understand their biomechanical impact. These features included aortic stenosis, mitral regurgitation (MR) and LV hypertrophy, reduced contractility, and increased myocardial stiffness. AS was found to elevate LV pressures and myocardial stresses, and depending on severity, can drastically decrease stroke volume and myocardial strains. These effects are moderated by MR. AS alone did not lead to MR velocities above 3 m/s unless LV hypertrophy was included, suggesting that hypertrophy may be involved in clinical cases with high MR velocities. LV hypertrophy substantially elevated LV pressure, valve flow velocities and stroke volume, while reducing LV contractility resulted in diminished LV pressure, stroke volume and wall strains. Typical extent of hypertrophy during fetal AS in the clinic, however, led to excessive LV pressure and valve velocity in the FE model, suggesting that reduced contractility is typically associated with hypertrophy. Increased LV passive stiffness, which might represent fibroelastosis, was found to have minimal impact on LV pressures, stroke volume, and wall strain. This suggested that fibroelastosis could be a by-product of the disease progression and does not significantly impede cardiac function. Our study demonstrates that FE modelling is a valuable tool for elucidating the biomechanics of congenital heart disease and can calculate parameters which are difficult to measure, such as intraventricular pressure and myocardial stresses.

Insecticidal Activity of 11 Bt toxins and 3 Transgenic Maize Events Expressing Vip3Aa19 to Black Cutworm, Agrotis ipsilon (Hufnagel).

Black cutworm (BCW), Agrotis ipsilon (Hufnagel), is an occasional pest of maize that can cause considerable economic loss and injury to corn seedlings. This research mainly assessed the susceptibility of BCW neonates to 11 Bt toxins (Cry1Ab, Cry1Ac, Cry1Ah, Cry1F, Cry1Ie, Cry1B, Cry2Aa, Vip3_ch1, Vip3_ch4, Vip3Ca2, Vip3Aa19) by exposing neonates to an artificial diet containing Bt toxins and evaluated the efficacy of three transgenic maize events (C008, C009, C010) expressing Vip3Aa19 toxin against BCW. The toxin-diet bioassay data indicated that Vip3Aa19 protein (LC50 = 0.43 µg/g) was the most active against BCW. Chimeric protein Vip3_ch1 (LC50 = 5.53 µg/g), Cry1F (LC50 = 83.62 µg/g) and Cry1Ac (LC50 = 184.77 µg/g) were less toxic. BCW was very tolerant to the other Bt toxins tested, with LC50 values more than 200 µg/g. Greenhouse studies were conducted with artificial infestations at the whorl stage by placing second-instar BCW larvae into whorl leaf and the fourth-instar larvae at the base of maize seedings. These results suggest that these transgenic maize events expressing Vip3Aa19 can provide effective control for BCW.

Up-regulation of ABCB1/P-glycoprotein by escaping promoter hypermethylation indicates poor prognosis in hematologic malignancy patients with and without bone marrow transplantation.

We investigated the correlation between MDR1 promoter methylation status and MDR1 expression in 228 hematologic malignancies patients and 90 healthy controls. High level of MDR1 mRNA correlated to promoter hypomethylation and strongly associated with poor prognosis indicated by 2-year survival rates, poor CR rate (without BMT) and high relapse rate (with BMT). Furthermore, relative luciferase activity of methylated MDR1 at promoter -50 region was significantly higher than that of the unmethylated. In addition, MDR1 in K562 cells elevated significantly after 5-Aza-dC treatment. In summary, MDR1 promoter hypomethylation conferred its up-regulation and indicated poor prognosis in patients with and without BMT.