Role of tumor necrosis factor-alpha in zebrafish retinal neurogenesis and myelination

AIM： To investigate the role of tumor necrosis factoralpha （TNF-α） in zebrafish retinal development and myelination. METHODS： Morpholino oligonucleotides （MO）, which are complementary to the translation start site of the wild-type embryonic zebrafish TNF-α mRNA sequence, were synthesized and injected into one to four-cell embryos. The translation blocking specificity was verified by Western blotting using an anti-TNF-α antibody, whole-mount in sltuhybridization using a hepatocytespecific mRNA probe ceruloplasmin （cp）, and coinjection of TNF-α MO and TNF-α mRNA. An atonel homolog 7 （atoh7） mRNA probe was used to detect neurogenesis onset. The retinal neurodifferentiation was analyzed by immunohistochemistry using antibodies Zn12, Zprl, and Zpr3 to label ganglion cells, cones, and rods, respectively. Myelin basic protein （mbp）was used as a marker to track and observe the myelination using whole-mount in situ hybridization. RESULTS： Targeted knockdown of TNF-α resulted in specific suppression of TNF-α expression and a severely underdeveloped liver. The co-injection of TNF-α MO and mRNA rescued the liver development. Retinal neurogenesis in TNF-cc morphants was initiated on time. The retina was fully laminated, while ganglion cells, cones, and rods were well differentiated at 72 hours post-fertilization （hpf）. mbp was expressed in Schwann cells in the lateral line nerves and cranial nerves from 3 days post -fertilization （dpf） as well as in oligodendrocytes linearly along the hindbrain bundles and the spinal cord from 4 dpf, which closely resembled its endogenous profile. CONCLUSION： TNF-α is not an essential regulator for retinal neurogenesis and optic myelination.

Influence of helium on the evolution of irradiation-induced defects in tungsten:An object kinetic Monte Carlo simulation

Understanding the evolution of irradiation-induced defects is of critical importance for the performance estimation of nuclear materials under irradiation.Hereby,we systematically investigate the influence of He on the evolution of Frenkel pairs and collision cascades in tungsten(W)via using the object kinetic Monte Carlo(OKMC)method.Our findings suggest that the presence of He has significant effect on the evolution of irradiation-induced defects.On the one hand,the presence of He can facilitate the recombination of vacancies and self-interstitial atoms(SIAs)in W.This can be attributed to the formation of immobile He-SIA complexes,which increases the annihilation probability of vacancies and SIAs.On the other hand,due to the high stability and low mobility of He-vacancy complexes,the growth of large vacancy clusters in W is kinetically suppressed by He addition.Specially,in comparison with the injection of collision cascades and He in sequential way at 1223 K,the average sizes of surviving vacancy clusters in W via simultaneous way are smaller,which is in good agreement with previous experimental observations.These results advocate that the impurity with low concentration has significant effect on the evolution of irradiation-induced defects in materials,and contributes to our understanding of W performance under irradiation.

Effect of titanium dioxide nanoparticles on zebrafish embryos and developing retina

AIM: To investigate the impact of titanium dioxide nanoparticles(Ti O2NPs) on embryonic development and retinal neurogenesis.METHODS: The agglomeration and sedimentation of Ti O2 NPs solutions at different dilutions were observed,and the ultraviolet-visible spectra of their supernatants were measured. Zebrafish embryos were experimentally exposed to Ti O2 NPs until 72 h postfertilization(hpf). The retinal neurogenesis and distribution of the microglia were analyzed by immunohistochemistry and whole mount in situ hybridization.RESULTS: The 1 mg/L was determined to be an appropriate exposure dose. Embryos exposed to Ti O2 NPs had a normal phenotype. The neurogenesis was initiated on time, and ganglion cells, cones and rods were well differentiated at 72 hpf. The expression of fms m RNA and the 4C4 antibody, which were specific to microglia in the central nervous system(CNS), closely resembled their endogenous profile.CONCLUSION: These data demonstrate that short-term exposure to Ti O2 NPs at a low dose does not lead to delayed embryonic development or retinal neurotoxicity.

Correlation between photoreceptor injury-regeneration and behavior in a zebrafish model

Direct exposure to intensive visible light can lead to solar retinopathy, including macular injury. The signs and symptoms include central scotoma, metamorphopsia, and decreased vision. However, there have been few studies examining retinal injury due to intensive light stimulation at the cellular level. Neural network arrangements and gene expression patterns in zebrafish photoreceptors are similar to those observed in humans, and photoreceptor injury in zebrafish can induce stem cell-based cellular regeneration. Therefore, the zebrafish retina is considered a useful model for studying photoreceptor injury in humans. In the current study, the central retinal photoreceptors of zebrafish were selectively ablated by stimulation with high-intensity light. Retinal injury, cell proliferation and regeneration of cones and rods were assessed at 1, 3 and 7 days post lesion with immunohistochemistry and in situ hybridization. Additionally, a light/dark box test was used to assess zebrafish behavior. The results revealed that photoreceptors were regenerated by 7 days after the light-induced injury. However, the regenerated cells showed a disrupted arrangement at the lesion site. During the injury-regeneration process, the zebrafish exhibited reduced locomotor capacity, weakened phototaxis and increased movement angular velocity. These behaviors matched the morphological changes of retinal injury and regeneration in a number of ways. This study demonstrates that the zebrafish retina has a robust capacity for regeneration. Visual impairment and stress responses following high-intensity light stimulation appear to contribute to the alteration of behaviors.

Layer-dependent and light-tunable surface potential of two-dimensional indium selenide(InSe)flakes

As a fundamental surface property of two-dimensional(2 D)materials,surface potential is critical for their emerging electronic applications and essential for van der Waals heterostructure engineering.Here,we report the surface potential of few-layer InSe.The effect of layer count,light intensity and different deposited substrates is considered.Few-layer InSe flakes were exfoliated from bulk InSe crystals on Si/SiO_(2)with 300-nm-thick thermal oxide and Si/SiO_(2)with 300-nm-thick thermal oxide and prefabricated micro-wells with 3μm in diameter.The samples were measured by Kelvin probe force microscopy and tuned by an integrated 405-nm(3.06 eV)laser.Based on the work function of SiO_(2)(5.00 eV),the work functions of supported and suspended InSe are determined.These results show that the work function of InSe decreases with the increase in the layer count of both supported InSe and suspended InSe.Besides,by introducing a tunable laser light,the influence of light intensity on surface potential of supported InSe was studied.The surface potential(SP)and surface potential shift between light and dark states(ASP=SP_(lignt)-SP_(dark))of supported InSe were measured and determined.These results present that the surface potential of supported InSe decreases with the increase in the light intensity and also decreases with the increase in the layer count.This is evident that light excites electrons,resulting in decreased surface potential,and the amount of electrons excited is correlated with light intensity.Meanwhile,⊿SP between light and dark states decreases with the increase in the layer count,which suggests that the influence of light illumination decreases with the increase in the layer count of few-layer InSe flakes.

Role of hydrogen in stability and mobility of vacancy clusters in tungsten

We investigated the influence of hydrogen(H)on the stability and mobility of small vacancy clusters in tungsten(W)using the first-principles calculations.It is found that the presence of H not only increases the binding energy of small vacancy clusters but also changes their most favorable configurations,owing to the strong attractive interaction between H and vacancies in W.Specifically,the binding energy of di-vacancy changes from negative to positive when the H atoms are introduced.These results suggest that the H addition can significantly promote the stability of small vacancy clusters in W.More importantly,although the migration energy barriers of H-vacancy(H-V)complexes are slightly higher than that of pure vacancy clusters,the activation energy required for complexes migration is always lower than that for dissociation.Therefore,contrary to the conventional view,the collaborative motion of H and small vacancy clusters is possible,because of the low migration energy barriers.Based on the energetic results obtained by first-principles calculations,the mean lifetime and mean diffusion distance of small H-V complexes at different temperatures are examined by the object kinetic Monte Carlo simulations.The small H-V complexes are found to be stable and mobile at moderate temperature,and thus may affect the co-evolution of H and vacancies.These results shed light on the important role of H on the vacancy behaviors and provide a good reference for understanding the defects evolution in W.

Temperature-dependent synergistic evolution mechanism of rhenium and irradiation defects in tungsten-rhenium alloys

We have systemically investigated the synergistic evolution of rhenium(Re)and irradiation defects in tungsten(W)-Re alloys under different temperatures and irradiation doses using object Kinetic Monte Carlo method.Our results revealed the underlying mechanism for the transition of Re effect on W from beneficial to harmful during the Re-defects evolution with the increase of irradiation dose,in which tem-perature always plays a critical role.On the one hand,Re will significantly promote the defect annihila-tion at low irradiation doses and high temperatures,thereby effectively reducing their sizes and number densities.This is due to the formation of stable Re-SIAs complexes that can be eliminated by the mobile vacancy-type defects,whereas the transition of the migration pattern of SIAs only plays a weak role in the defect recombination in W-Re system.On the other hand,with the increase of irradiation dose,Re will aggregate to form Re-rich clusters or even precipitates.Interestingly,the formation mechanism of Re-rich clusters is also dependent on temperature.At low temperatures,the interstitial-mediated mech-anism plays a crucial role in the Re-rich cluster formation,while at high temperatures,both SIA-type and vacancy-type defects will act as the transport carriers of Re to promote their clustering.Accordingly,the critical conditions for the transition of Re from beneficial to harmful and the formation of Re-rich clusters at different tem peratures and irradiation doses are given with the help of the phase diagram.Our work presents the temperature dependence of the synergy of Re and irradiation defects in W-Re in fusion-relevant environment,which provides a good reference for the development of radiation-resistant materials and the prediction of W performance in fusion reactors.

Recent progress on the smart membranes based on two-dimensional materials

Inspired by the biosystems,the artificial smart membrane to control the mass transport and molecular conversion has attracted increasing attention in the fields of membrane separation,desalination,nanofiltration,healthcare and environmental remediation.However,the trade-off limitations in polymeric membranes greatly hinder the development of smart membranes with high permeability and manipulability.Recently,inspired by the unique physical/chemical properties of two-dimensional(2 D)materials,2 D materials-based smart membranes(2 DSMs)with the ability of intelligent regulation under different stimuli are highly suitable for membrane applications.According to the desired properties,the 2 DSMs with abundant functional groups can be designed through chemical modification to change the original properties and obtain tunable interlayer spacings under different external conditions.In this review,we summarize the recent progress on artificial smart membranes based on 2 D materials.The design concept and fabrication strategy of 2 DSMs are first introduced.Following that,the developed 2 DSMs are introduced and classified by the type of responsive stimuli,including p H,magnetic field,electric field,light and temperature.Then,the 2 DSMs exhibiting unique performances as membrane separation,pressure sensors,blue energy harvesting,photoelectrochemical sensors and biomimetic devices are presented.Finally,the perspectives and challenges in the developments of 2 DSMs are discussed.

Anisotropic interaction between self-interstitial atoms and 1/2<111> dislocation loops in tungsten

We investigate the interaction between <111> self-interstitial atoms(SIAs) and 1/2<111> self-interstitial dislocation loops in tungsten(W) via atomistic simulations. We explore the variation of the anisotropic distribution of binding energies with the shapes and sizes of the 1/2[111] loop and the nonequivalent configurations of <111> SIAs. For an arbitrarily shaped loop, SIA can be more easily trapped in the concave region of the loop than the convex region, which forms a loop whose curvature is closer to that of a circular loop. The direction of SIAs can largely affect the interaction behaviors with the loop. The capture distance of an SIA by the edge of a circular-shaped 1/2[111] loop is clearly elongated along the direction of the SIA;however, it weakly depends on the size of the loop. Then, we analyze the slanted ring-like capture volume of <111> SIAs formed by the circular loop based on their generated anisotropic stress fields. Furthermore, the binding energies obtained from the elastic theory and atomistic simulations are compared. The results provide a reasonable interpretation of the growth mechanism of the loop and the anisotropic interaction that induces irregular-shaped capture volume, affording an insight into the numerical and Object Kinetic Monte Carlo simulations to evaluate the long-term and large-scale microstructural evolution and mechanical properties of W.