Rapid diffusion-state switching underlies stable cytoplasmic gradients in the Caenorhabditis elegans zygote.

Protein concentration gradients organize cells and tissues and commonly form through diffusion away from a local source of protein. Interestingly, during the asymmetric division of the Caenorhabditis elegans zygote, the RNA-binding proteins MEX-5 and PIE-1 form opposing concentration gradients in the absence of a local source. In this study, we use near-total internal reflection fluorescence (TIRF) imaging and single-particle tracking to characterize the reaction/diffusion dynamics that maintain the MEX-5 and PIE-1 gradients. Our findings suggest that both proteins interconvert between fast-diffusing and slow-diffusing states on timescales that are much shorter (seconds) than the timescale of gradient formation (minutes). The kinetics of diffusion-state switching are strongly polarized along the anterior/posterior (A/P) axis by the PAR polarity system such that fast-diffusing MEX-5 and PIE-1 particles are approximately symmetrically distributed, whereas slow-diffusing particles are highly enriched in the anterior and posterior cytoplasm, respectively. Using mathematical modeling, we show that local differences in the kinetics of diffusion-state switching can rapidly generate stable concentration gradients over a broad range of spatial and temporal scales.

Thiol-suppressed I2-etching of AuNRs: acetylcholinesterase-mediated colorimetric detection of organophosphorus pesticides.

For the first time it is demonstrated that sulfhydryl compounds can suppress longitudinal etching of gold nanorods via consuming oxidizers, which provides a new signaling mechanism for colorimetric sensing. As a proof of concept, a colorimetric assay is developed for detecting organophosphorus pesticides, which are most widely used in modern agriculture to improve food production but with high toxicity to animals and the ecological environment. Triazophos was selected as a model organophosphorus pesticide. In the absence of triazophos, the active acetylcholinesterase can catalyze the conversion of acetylthiocholine iodide to thiocholine whose thiol group can suppress the I2-induced etching of gold nanorods. When triazophos is present, the activity of AchE is inhibited, and I2-induced etching of gold nanorods results in triazophos concentration-dependent color change from brown to blue, pink, and red. The aspect ratio of gold nanorods reduced with gradually blue-shifted longitudinal absorption. There was a linear detection range from 0 to 117 nM (R2 = 0.9908), the detection limit was 4.69 nM, and a good application potential was demonstrated by the assay of real water samples. This method will not only contribute to public monitoring of organophosphorus pesticides but also has verified a new signaling mechanism which will open up a new path to develop colorimetric detection methods. It has been first found that sulfhydryl compounds can suppress longitudinal etching of gold nanorods (AuNRs) via consuming oxidizers, which provides a new signaling mechanism for colorimetric sensing. As a proof of concept, a colorimetric assay is developed for sensitively detecting organophosphorus pesticides (OPs). It will not only contribute to public monitoring of OPs but also has verified a new signaling mechanism which will open up a new path to develop multicolor colorimetric methods.

Colorimetric aminotriazole assay based on catalase deactivation-dependent longitudinal etching of gold nanorods.

A colorimetric and visual assay is described for the herbicide aminotriazole (ATZ). It is based on the etching of gold nanorods (AuNRs) by iodine which is formed on oxidation of iodide via H2O2. Longitudinal etching of the AuNRs occurs quickly and is accompanied by a color change from dark blue to red. In the absence of ATZ and the presence of active catalase (CAT), H2O2 is quickly decomposed into water, and the AuNRs will not be etched. In the presence of ATZ, CAT is partially deactivated, and this affects the amount of available H2O2 and, consequently, of the iodine. Hence, the color is significantly changed. The color changes can be easily detected with bare eyes. The assay has a linear response in the 5 to 70 µM concentration range, with a detection limit of 1.3 µM and high selectivity for ATZ. It was applied to the determination of ATZ in water and food samples. Graphical abstract A multicolor colorimetric method is developed for aminotriazole (ATZ) detection based on catalase (CAT) deactivation-dependent longitudinal etching of gold nanorods (AuNRs). The color signals can be visually identified. Good detection performances and capability for evaluating ATZ level in water and food samples is demonstrated.

Initial deployment of the cardiogenic gene regulatory network in the basal chordate, Ciona intestinalis.

The complex, partially redundant gene regulatory architecture underlying vertebrate heart formation has been difficult to characterize. Here, we dissect the primary cardiac gene regulatory network in the invertebrate chordate, Ciona intestinalis. The Ciona heart progenitor lineage is first specified by Fibroblast Growth Factor/Map Kinase (FGF/MapK) activation of the transcription factor Ets1/2 (Ets). Through microarray analysis of sorted heart progenitor cells, we identified the complete set of primary genes upregulated by FGF/Ets shortly after heart progenitor emergence. Combinatorial sequence analysis of these co-regulated genes generated a hypothetical regulatory code consisting of Ets binding sites associated with a specific co-motif, ATTA. Through extensive reporter analysis, we confirmed the functional importance of the ATTA co-motif in primary heart progenitor gene regulation. We then used the Ets/ATTA combination motif to successfully predict a number of additional heart progenitor gene regulatory elements, including an intronic element driving expression of the core conserved cardiac transcription factor, GATAa. This work significantly advances our understanding of the Ciona heart gene network. Furthermore, this work has begun to elucidate the precise regulatory architecture underlying the conserved, primary role of FGF/Ets in chordate heart lineage specification.

Efficacy and safety of endovenous microwave ablation versus laser ablation for great saphenous vein varicosis: study protocol for a multicentre, randomised controlled non-inferiority trial.

INTRODUCTION: Endovenous microwave ablation (EMA) is a relatively novel thermal ablation treatment for great saphenous vein (GSV) varicosis, and its efficacy and safety are rarely reported. This study aims to explore whether EMA can be comparable to endovenous laser ablation (EVLA), which is a widely used thermal ablation treatment in clinical practice. METHODS AND ANALYSIS: This is a multicentre, randomised controlled non-inferiority trial to compare the efficacy and safety of EMA and EVLA in patients with GSV varicosis. We will recruit 180 patients in 6 centres and randomly assign them into treatment group (EMA group) and control group (EVLA group) in a 1:1 ratio. The patients will return to the hospitals at 7 days, 3 months, 6 months and 12 months, and will be called at 1 month after the treatment for follow-up visits. The primary outcome is the occlusion rate of GSV immediately, at 6 months, and at 12 months after the treatment. The secondary outcomes are Venous Clinical Severity Score (VCSS), Aberdeen Varicose Vein Questionnaire (AVVQ) Score, operation time and instrument performance evaluation. ETHICS AND DISSEMINATION: This protocol has been approved by the Clinical Trial Ethics Committee of Beijing Hospital (2020BJYYEC-126-02), Peking Union Medical College Hospital (KS2020393), Beijing Tsinghua Changgung Hospital (No.20279-2-02), Beijing Luhe Hospital.Capital Medical University (2020-LHYW-030-01), the First Hospital of Hebei Medical University (No.2020249), and the First Affiliated Hospital of Xi'an Jiaotong University (XJTU1AF2021LSY-12). The trial results will be published in peer-reviewed journals. TRIAL REGISTRATION NUMBER: NCT04726124.

Study on the mechanism of thrombus ablation in vitro by burst-mode femtosecond laser.

The burst-mode femtosecond laser has the potential to be a novel thrombus removal technique. This paper proposed to investigate the mechanism of thrombus ablation in vitro by burst-mode femtosecond laser. A simulation model of the interaction between femtosecond laser and thrombus was established. An in vitro thrombus model was prepared. Combined with the high-speed galvanometer and femtosecond laser, the ablation experiments in vitro were performed. The experimental results showed that the ablative threshold was 0.27 times and the efficiency was about 1.4 times of burst-mode femtosecond laser as those of traditional mode femtosecond laser. These phenomena were related to the residual temperature and free electrons on the thrombus surface, which confirmed the simulating results and had relationship with incubation effects. The high ablative efficiency and safety of burst-mode femtosecond laser for thrombus ablation were verified, which may help to achieve the femtosecond pulse output through flexible fiber easily and stably. The burst-mode femtosecond laser represents an important technological advancement of the method in terms of endovascular treatment with femtosecond laser.

Filament-guided filament assembly provides structural memory of filament alignment during cytokinesis.

During cytokinesis, animal cells rapidly remodel the equatorial cortex to build an aligned array of actin filaments called the contractile ring. Local reorientation of filaments by active equatorial compression is thought to underlie the emergence of filament alignment during ring assembly. Here, combining single molecule analysis and modeling in one-cell C. elegans embryos, we show that filaments turnover is far too fast for reorientation of individual filaments by equatorial compression to explain the observed alignment, even if favorably oriented filaments are selectively stabilized. By tracking single formin/CYK-1::GFP particles to monitor local filament assembly, we identify a mechanism that we call filament-guided filament assembly (FGFA), in which existing filaments serve as templates to orient the growth of new filaments. FGFA sharply increases the effective lifetime of filament orientation, providing structural memory that allows cells to build highly aligned filament arrays in response to equatorial compression, despite rapid turnover of individual filaments.

Degradation of gas-phase o-xylene via combined non-thermal plasma and Fe doped LaMnO3 catalysts: Byproduct control.

A series of Fe doped LaMnO3 catalysts were prepared to control the production of byproducts such as O3, N2O, and CO, during the degradation of volatile organic compounds with a non-thermal plasma. Eliminating these potentially toxic byproducts will make non-thermal plasma technologies applicable for a wider range of commercial applications. The modified LaMnO3 catalysts are combined in NTP-catalysis reactor with optimal configuration. Experimental results show that doping Fe on LaMnO3 catalysts can not only enhance the oxidation of o-xylene, but also lower the emission levels of byproducts. LaMn0.9Fe0.1O3 catalyst shows the best catalytic activity among the formulations tested herein. In addition to the strong mineralization of 88.1 %, the catalyst has the highest performance for o-xylene conversion (91.3 %), O3 inhibition efficiency (84.9 %), and N2O inhibition efficiency (61.2 %) due to the strong concentration of active oxygen species on the surface of the catalyst. Moreover, the high reducibility of Fe3+ demonstrated with H2-TPR (hydrogen temperature-programed reduction) further enhances the removal of O3 by oxygen species exchange between Mn3+/Mn4+ and Fe2+/Fe3+.

Expression of EGFR variant vIII promotes both radiation resistance and hypoxia tolerance.

BACKGROUND AND PURPOSE: EGFRvIII has been described to function as an oncoprotein with constitutive activation promoting neoplastic transformation and tumorigenicity. The present study was undertaken to test whether EGFRvIII also contributes to hypoxia tolerance. MATERIAL AND METHODS: The human glioma cell line U373 was genetically modified to stably express EGFRvIII. Western blotting and immunohistochemistry verified the expression of EGFRvIII. Tumour xenografts were produced by injecting U373 control and EGFRvIII positive cells subcutaneously into the lateral flank of recipient mice. Colony formation assays were performed after ionizing radiation at 4Gy and after exposure to anoxia for 1-4 days. RESULTS: EGFRvIII accelerated tumour growth leading to a 3.5-fold increase in tumour size compared to control tumours at 40 days after cell injection. EGFRvIII promoted clonogenic survival by almost 2-fold and 4-fold after 4Gy and 4 days of anoxia, respectively. EGFRvIII was also associated with a substantially bigger colony size after anoxic treatment. CONCLUSIONS: EGFRvIII expression stimulates the growth of tumour xenografts and strongly promotes survival after irradiation and under hypoxic stress.

Dynamic Opposition of Clustered Proteins Stabilizes Cortical Polarity in the C. elegans Zygote.

Dynamic maintenance of cell polarity is essential for development and physiology. Here we combine experiments and modeling to elucidate mechanisms that maintain cortical polarity in the C. elegans zygote. We show that polarity is dynamically stabilized by two coupled cross-inhibitory feedback loops: one involves the oligomeric scaffold PAR-3 and the kinase PAR-1, and the other involves CDC-42 and its putative GAP CHIN-1. PAR-3 and CDC-42 are both required locally to recruit PAR-6/PKC-3, which inhibits PAR-1 (shown previously) and inhibits local growth/accumulation of CHIN-1 clusters. Conversely, PAR-1 inhibits local accumulation of PAR-3 oligomers, while CHIN-1 inhibits CDC-42 (shown previously), such that either PAR-1 or CHIN-1 can prevent recruitment of PAR-6/PKC-3, but loss of both causes complete loss of polarity. Ultrasensitive dependence of CHIN-1 cluster growth on PAR-6/PKC-3 endows this core circuit with bistable dynamics, while transport of CHIN-1 clusters by cortical flow can stabilize the AP boundary against diffusive spread of PAR-6/PKC-3.

Binding of cetuximab to the EGFRvIII deletion mutant and its biological consequences in malignant glioma cells.

BACKGROUND AND PURPOSE: Despite the clinical use of cetuximab, a chimeric antibody against EGFR, little is known regarding its interaction with EGFRvIII, a frequently expressed deletion mutant of EGFR. Therefore, we investigated the interaction and the functional consequences of cetuximab treatment on glioma cells stably expressing EGFRvIII. MATERIALS AND METHODS: The human glioma cell line U373 genetically modified to express EGFRvIII was used to measure the binding of cetuximab and its internalization using flow cytometry and confocal microscopy. Proliferation and cell survival were analyzed by cell growth and clonogenic survival assays. RESULTS: Cetuximab is able to bind to EGFRvIII and causes an internalization of the receptor and decreases its expression levels. Furthermore, in contrast to EGF, cetuximab was able to activate EGFRvIII which was evidenced by multiple phosphorylation sites and its downstream signaling targets. Despite this activation, the growth rate and the radiosensitivity of the EGFRvIII-expressing glioma cells were not modulated. CONCLUSIONS: Cetuximab binds to EGFRvIII and leads to the initial activation, internalization and subsequent downregulation of EGFRvIII, but it does not seem to modulate the proliferation or radiosensitivity of EGFRvIII-expressing glioma cells. Thus, approaches to treat EGFRvIII-expressing glioma cells should be evaluated more carefully.

The deletion mutant EGFRvIII significantly contributes to stress resistance typical for the tumour microenvironment.

BACKGROUND AND PURPOSE: The epidermal growth factor receptor (EGFR) is overexpressed or mutated in many tumour types. The truncated, constitutively active EGFRvIII variant has not been detected in normal tissues but is found in many malignancies. In the current study, we have investigated the hypothesis that EGFRvIII contributes to a growth and survival advantage under tumour microenvironment-related stress conditions. MATERIALS AND METHODS: U373MG doxycycline-regulated isogenic cells expressing EGFRwt or EGFRvIII were created and validated using Western blot, FACS and qRT-PCR. In vitro proliferation was evaluated with standard growth assays. Cell survival was assayed using clonogenic survival. Animal experiments were performed using NMRI-nu-xenografted mice. RESULTS: Inducible isogenic cell lines were created and showed high induction of EGFRwt and EGFRvIII upon doxycycline addition. Overexpression of EGFRvIII but not of EGFRwt in this model resulted in a growth and survival advantage upon different tumour microenvironment-related stress conditions in vitro. Induction of EGFRvIII increased tumour growth in vivo, which was reversible upon loss of expression. CONCLUSIONS: Under conditions where nutrients are limited and stress is apparent, as in the tumour microenvironment, expression of EGFRvIII leads to a growth and survival advantage. These data indicate a potential selection of EGFRvIII-expressing tumour cells under such stress conditions.