短暂性脱髓鞘导致长期认知障碍、髓鞘改变和神经网络同步缺陷

在成年大脑中,活动依赖性髓鞘可塑性是正确学习和记忆巩固所必需的。因此,髓鞘的丢失、改变,甚至细微的结构变更都会损害神经网络活动,导致功能障碍。在多发性硬化症中,虽然自发的髓鞘修复过程是可能的,但患者之间存在异质性。髓鞘修复有时会导致功能恢复,这通常在运动水平比在认知水平更明显。在铜宗处理的小鼠模型中,大量脑脱髓鞘随后发生自发且强烈的髓鞘再生。然而,重组髓鞘虽然具有功能,但可能不会表现出与发育髓鞘相同的形态特征,这可能会对神经网络的活动产生影响。基于此,本研究使用铜腙处理的小鼠模型来分析短暂性脱髓鞘对脑结构、功能和认知的长期影响。本研究结果表明,尽管脱鞘事件后存在髓鞘再生,但仍会导致长期认知障碍,例如空间工作记忆、社交记忆、认知灵活性和多动症的缺陷。这些缺陷与内侧前额叶皮质(m PFC)和海马体(HPC)髓鞘含量的减少以及结构髓鞘修饰有关,表明这些结构中的髓鞘再生过程可能不完善。在体电生理记录表明,脱髓鞘事件改变了HPC-mPFC活动的同步性,这对于记忆过程至关重要。总而言之,本研究数据表明,短暂脱髓鞘后的髓鞘修复过程不允许完全恢复皮质结构中的初始髓鞘特性。这些细微的变更改变了神经网络特征并导致小鼠长期认知缺陷。

Salinity effect on the compaction behaviour,matric suction,stiffness and microstructure of a silty soil

To better understand the salinity effect on the compaction behaviour of soil,standard Proctor compaction test was conducted on soil samples with different salinities.Matric suction and small-strain shear modulus,G_(max),were determined and pore size distribution was also investigated on samples statically compacted at different water contents.Results showed that with the decrease of soil salinity from initial value of 2.1‰(g of salt/kg of dry soil)to zero,the maximum dry density increased and the optimum water content decreased,whereas there was no significant change with the increase of soil salinity from 2.1‰ to 6.76‰.Interestingly,it was observed that G_(max) also decreased when the soil salinity decreased from initial value of 2.1‰ to zero and kept almost constant when the soil salinity increased from 2.1‰ to 6.76‰,for dry samples with similar matric suction and also for samples compacted at optimum state and on wet side whose matric suctions were slightly different due to the difference in remoulded water content.Furthermore,the effect of salinity on compaction behaviour and G_(max) decreased for samples compacted from dry side to wet side.The pore size distribution exhibited bi-modal characteristics with two populations of micro-and macro-pores not only for samples compacted on dry side and at optimum state,but also for those compacted on wet side.Further examination showed that the modal size of micro-pores shifted to lower values and that of macro-pores shifted to higher values for saline soil compared to the soil without salt.

Distinct influence of trimethylamine N-oxide and high hydrostatic pressure on community structure and culturable deep-sea bacteria

Trimethylamine N-oxide(TMAO)is one of the most important nutrients for bacteria in the deep-sea environment and is capable of improving pressure tolerance of certain bacterial strains.To assess the impact of TMAO on marine microorganisms,especially those dwelling in the deep-sea environment,we analyzed the bacterial community structure of deep-sea sediments after incubated under different conditions.Enrichments at 50 MPa and 0.1 MPa revealed that TMAO imposed a greater influence on bacterial diversity and community composition at atmospheric pressure condition than that under high hydrostatic pressure(HHP).We found that pressure was the primary factor that determines the bacterial community.Meanwhile,in total,238 bacterial strains were isolated from the enrichments,including 112 strains a ffiliated to 16 genera of 4 phyla from the Yap Trench and 126 strains a ffiliated to 11 genera of 2 phyla from the Mariana Trench.Treatment of HHP reduced both abundance and diversity of isolates,while the presence of TMAO mainly af fected the diversity of isolates obtained.In addition,certain genera were isolated only when TMAO was supplemented.Taken together,we demonstrated that pressure primarily defines the bacterial community and culturable bacterial isolates.Furthermore,we showed for the first time that TMAO had distinct influences on bacterial community depending on the pressure condition.The results enriched the understanding of the significance of TMAO in bacterial adaptation to the deep-sea environment.

Archaeal community structure in sediments from a seamount in the Mariana Volcanic Arc

Seamounts are subsurface mountains in the ocean. Examination of the abundance and distribution of Archaea in seamount ecosystems may provide a better understanding of their ecological functions. Most studies of marine archaeal assemblages in seamount area have focused on hydrothermal vents or ferromanganese crusts. We investigated the archaeal communities from a seamount of the Mariana Volcanic Arc, in the tropical western Pacific Ocean by using high-throughput sequencing. Thaumarchaeota was dominant in the sediments of all sample stations. Community diversity and species richness were greatest at stations near the top of the seamount, and lowest at the deepest station. One sample station on the steep southeast slope that faced the Yap-Mariana trench had a unique composition of Archaea. In summary, depth has an important influence on archaeal community structure, and the geographic properties and sediment characteristics may explain the unique distribution patterns of Archaea in this seamount. This study provides a foundation for future research on Archaea in seamounts.

A person-centered approach to achievement goal orientations in competitive tennis players: Associations with motivation and mental toughness

Background:Research on achievement goal orientations in sport has typically relied on the use of variable-centered approaches that tend to overlook population heterogeneity.In this study,we used a person-centered approach to identify subgroups of competitive tennis players according to unique combinations of achievement goal orientations and tested for subgroup differences in motivation and mental toughness.Methods:A sample of 323 competitive tennis athletes(69.35%male)between 15 and 25 years of age(17.60±2.40 years,mean±SD)completed the 3×2 Achievement Goal Questionnaire for Sport,Sport Motivation Scale Ⅱ,and Mental Toughness Index.Latent profile analysis was used to identify unique combinations of achievement goal orientations.Comparisons between latent subgroups on autonomous motivation,controlled motivation,and mental toughness were performed using analysis of variance.Results:Latent profile analysis supported 3 distinct patterns of achievement goal profiles that were primarily distinguishable based on valence of competence(i.e.,approach vs.avoidance).Analyses of variance indicated that athletes who were classified into subgroups that endorsed approach types of goals(regardless of the types of avoidance goals they endorsed)reported higher levels of autonomous motivation and mental toughness.Conclusion:Results indicated that athletes tend to pursue a number of achievement goals collectively rather than in isolation.Although approach goals are more commonly linked to adaptive psychological functioning and positive outcomes,avoidance goals may also be associated with desirable psychological characteristics if they are pursued in conjunction with approach types of achievement goals.

Observations on a magnetotactic bacteria-grazing ciliate in sediment from the intertidal zone of Huiquan Bay,China

Magnetotactic bacteria(MTB)are a group of prokaryotes having the ability to orient and swim along geomagnetic field lines because they contain intracellular magnetosomes that are synthesized through a biomineralization process.Magnetosomes have recently also been found in unicellular eukaryotes,which are referred to as magnetically responsive protists(MRPs).The magnetosomes have three origins in MRPs.In this study,we characterized a MTB-grazing ciliated MRP that was magnetically collected from intertidal sediment of Huiquan Bay,Qingdao,China.Based on 18S rRNA gene sequence analysis,the ciliated MRP was tentatively identified as Uronemella parafi lificum HQ.Using transmission electron microscopy,we observed that magnetosomes having 2-3 shapes were randomly distributed within this ciliate.Energydispersive X-ray spectroscopy and high-resolution transmission electron microscopy images of the magnetosomes were consistent with them being composed of magnetite.Magnetosomes having the same shape and mineral composition were also detected in MTB that occurred in the same environment as the ciliated MRP.Statistical analysis showed that the size and shape of the magnetosomes in the ciliated MRP were similar to those in MTB.The results suggest that this ciliated MRP can graze,ingest,and digest various types of MTB.It is certainly worth noting that this is the first record of MRPs in Asian aquatic sediment and suggesting they might be widely distributed.These results also support the assertion that MRPs probably contribute to the ecological cycles of iron,and expand possibilities for research into the mechanism of magnetoreception in eukaryotes.

Characterization and diversity of magnetotactic bacteria from sediments of Caroline Seamount in the Western Pacific Ocean

Magnetotactic bacteria(MTB)are a group of microorganisms capable of orientating and swimming along magnetic fields because they contain intracellular biomineralized magnetosomes composed of magnetite(Fe 3 O 4)or/and greigite(Fe_(3)S_(4)).They are ubiquitous in freshwater,brackish,and marine habitats,and are cosmopolitan in distribution.However,knowledge of their occurrence and distribution in seamount ecosystems is limited.We investigated the diversity and distribution of MTB in the Caroline Seamount(CM4).The abundance of living MTB in 12 stations in depth varying from 90 to 1545 m was 1.1×10^(3)-43.7×10^(3) inds./dm 3.Despite diverse shapes of MTB observed,magnetotactic cocci were the dominant morphotype and could be categorized into two types:1)typical cocci that appeared to have peritrichous fl agella;and 2)those characterized by having a drop-shaped form and one bundle of fl agella located at the thin/narrow end of the cell.Transmission electron microscopy(TEM)analysis revealed that the magnetosomes formed by those magnetotactic cocci are magnetite(Fe 3 O 4)with octahedral crystal habit.A total of 41 operational taxonomic units(OTUs)of putative MTB(2702 reads)were acquired from nine stations,based on high-throughput sequencing.Of these,40 OTUs belonged to the Proteobacteria phylum and one belonged to the Nitrospirae phylum.We found apparent connectivity between the MTB populations on the Caroline and Kexue(Science in Chinese)seamounts,although the diversity of MTB on Caroline was much richer than on the Kexue Seamount.Our results imply that the unique topography of seamounts and other as-yet unclear environmental factors could lead to evolution of different fl agella arrangements in magnetotactic cocci,and the occurrence of octahedral magnetite magnetosomes.

Magnetotactic bacteria and magnetoreception

A broad range of organisms have evolved abilities to exploit the Earth’s magnetic field for orientation and navigation-a behavior known as magnetoreception(Nordmann et al.,2017).Magnetotactic bacteria(MTB),diverse microbes with a patchy distribution across the bacterial tree of life,are the best known and most extensively studied magnetosensitive microorganisms.In order to efficiently achieve magnetotactic behavior,MTB biomineralize intracellular chain-arranged magnetic single-domain crystals of magnetite(Fe_(3)O_(4))and/or greigite(Fe_(3)S_(4))called magnetosomes,which are unique prokaryotic organelles that confer a magnetic moment to the cell and act as an internal compass needle(Bazylinski and Frankel,2004).

Distribution and U-Pb Ages of Newly Recognized Regional-Scale Dyke Swarms of the Leo Man Craton

Over 20 sets of dolerite dykes crosscutting Paleoproterozoic basement in West Africa were distinguished via the interpretation of regional and high resolution magnetic airborne data of West African Craton

What is a tree in the Mediterranean Basin hotspot?A critical analysis

Background: Tree species represent 20% of the vascular plant species worldwide and they play a crucial role in the global functioning of the biosphere. The Mediterranean Basin is one of the 36 world biodiversity hotspots, and it is estimated that forests covered 82% of the landscape before the first human impacts, thousands of years ago. However, the spatial distribution of the Mediterranean biodiversity is still imperfectly known, and a focus on tree species constitutes a key issue for understanding forest functioning and develop conservation strategies. Methods: We provide the first comprehensive checklist of all native tree taxa (species and subspecies) present in the Mediterranean-European region (from Portugal to Cyprus). We identified some cases of woody species difficult to categorize as trees that we further called "cryptic trees". We collected the occurrences of tree taxa by"administrative regions", i.e. country or large island, and by biogeographical provinces. We studied the species-area relationship, and evaluated the conservation issues for threatened taxa following IUCN criteria. Results: We identified 245 tree taxa that included 210 species and 35 subspecies, belonging to 33 families and 64 genera. It included 46 endemic tree taxa (30 species and 16 subspecies), mainly distributed within a single biogeographical unit. The countries with the highest tree richness are Greece (146 taxa), Italy (133), Albania (122), Spain (155), Macedonia (116), and Croatia (110). The species-area relationship clearly discriminated the richest central-eastern (Balkans) and northern (Alpine and Cevenno-Pyrenean) biogeographical provinces, against the five western provinces in the Iberian Peninsula. We identified 44 unrecognized "cryptic trees", representing 21% of the total trees. Among the 245 taxa identified, 19 are considered to be threatened (15 CR+EN+VU) or near threatened (4 NT) by IUCN. Conclusions: The Mediterranean-European region includes an unsuspectedly high number of tree taxa, almost 200 tree taxa more than in the central European region. This tree diversity is not distributed evenly and culminates in the central-eastern part of the Mediterranean region, whereas some large Tyrrhenian islands shelter several narrow endemic tree taxa. Few taxa are recognized as threatened in the IUCN Red list, and the vulnerability of these species is probably underestimated.

Chemoselective electrochemical seleno-cyclization of dienes to medium-sized benzo[b]azocines

The preparation of medium-sized benzo[b]azocines has always been challenging because of inherently unfavorable enthalpy and entropy factors.This report presents a novel approach for accessing 8-membered seleno-benzo[b]azocines via electrochemically-driven seleno-cyclization.This method enables room-temperature preparation of various structurally diverse medium-sized seleno-benzo[b]azocines.The facile deselenation of the seleno-cyclization products to generate functionalized dienes is an additional benefit of this indispensable reaction.Mechanistic insights are presented based on radical inhibition experiments and cyclic voltammetry measurements,which elucidate the radical pathway.Finally,density functional theory calculations further rationalize the rate-determining step and the unique chemoselectivity observed in this transformation.

Mitochondria-targeted atovaquone promotes anti-lung cancer immunity by reshaping tumor microenvironment and enhancing energy metabolism of anti-tumor immune cells

Dear Editor,Atovaquone(ATO),a mitochondrial inhibitor,has anti-cancer effects[1].Based on ATO,we developed mitochondria-targeted atovaquone(Mito-ATO)that had even stronger anti-tumor efficacy than ATO[2].We syn-thesized Mito-ATO by attaching the bulky triphenylphos-phonium(TPP)group to ATO via a ten-carbon alkyl chain(Supplementary file of methods;Supplementary Figure S1).

The Adjacency Codes of the First Yellow Graphs

The authors study the binary codes spanned by the adjacency matrices of the strongly regular graphs(SRGs)on at most two hundred vertices whose existence is unknown.The authors show that in length less than one hundred they cannot be cyclic,except for the exceptions of the SRGs of parameters(85,42,20,21)and(96,60,38,36).In particular,the adjacency code of a(85,42,20,21)is the zero-sum code.In the range[100,200]the authors find 29 SRGs that could possibly have a cyclic adjacency code.

Self-Dual Hadamard Bent Sequences

A new notion of bent sequence related to Hadamard matrices was introduced recently,motivated by a security application(Solé,et al.,2021).The authors study the self-dual class in length at most 196.The authors use three competing methods of generation:Exhaustion,Linear Algebra and Gr?bner bases.Regular Hadamard matrices and Bush-type Hadamard matrices provide many examples.The authors conjecture that if v is an even perfect square,a self-dual bent sequence of length v always exists.The authors introduce the strong automorphism group of Hadamard matrices,which acts on their associated self-dual bent sequences.The authors give an efficient algorithm to compute that group.

JUNO sensitivity on proton decay p→νK^(+)searches

The Jiangmen Underground Neutrino Observatory(JUNO)is a large liquid scintillator detector designed to explore many topics in fundamental physics.In this study,the potential of searching for proton decay in the p→νK^(+)mode with JUNO is investigated.The kaon and its decay particles feature a clear three-fold coincidence signature that results in a high efficiency for identification.Moreover,the excellent energy resolution of JUNO permits suppression of the sizable background caused by other delayed signals.Based on these advantages,the detection efficiency for the proton decay via p→νK^(+)is 36.9%±4.9%with a background level of 0.2±0.05(syst)±0.2(stat)events after 10 years of data collection.The estimated sensitivity based on 200 kton-years of exposure is 9.6×1033 years,which is competitive with the current best limits on the proton lifetime in this channel and complements the use of different detection technologies.

Search for the doubly heavy baryon Ξ_(bc)^(+)→ decaying to J/ψΞ_(c)^(+)

A first search for the Ξ_(bc)^(+)J/ψΞ_(c)^(+) decay is performed by the LHCb experiment with a data sample of proton-proton collisions, corresponding to an integrated luminosity of 9 fb−1 recorded at centre-of-mass energies of 7, 8, and 13 TeV. Two peaking structures are seen with a local (global) significance of 4.3(2.8) and 4.1(2.4) standard deviations at masses of 6571 and 6694 MeV/c2, respectively. Upper limits are set on the Ξ+bc baryon production cross-section times the branching fraction relative to that of the B+c→J/ψD+s decay at centre-of-mass energies of 8 and 13 TeV, in the Ξ+bc and in the B+c rapidity and transverse-momentum ranges from 2.0 to 4.5 and 0 to 20GeV/c, respectively. Upper limits are presented as a function of the Ξ+bc mass and lifetime.

Search for the rare decays W^(+)→D_(s)^(+)γ and Z→D^(0)γ at LHCb

A search for the rare decays W^(+)→D_(s)^(+)γ and Z→D0γis performed using proton-proton collision data collected by the LHCb experiment at a centre-of-mass energy of 13TeV,corresponding to an integrated luminosity of 2.0fb−1.No significant signal is observed for either decay mode and upper limits on their branching fractions are set using W^(+)→D_(s)^(+)γ and Z→μ+μ−decays as normalization channels.The upper limits are 6.5×10^(−4) and 2.1×10^(−3) at 95% confidence level for the W^(+)→D_(s)^(+)γ and Z→D^(0)γ decay modes,respectively.This is the first reported search for the Z→D^(0)γ decay,while the upper limit on the W+→D+sγbranching fraction improves upon the previous best limit.

New insights into the cell-and tissue-specificity of glucocorticoid actions

Glucocorticoids(GCs)are endogenous hormones that are crucial for the homeostasis of the organism and adaptation to the external environment.Because of their anti-inflammatory effects,synthetic GCs are also extensively used in clinical practice.However,almost all cells in the body are sensitive to GC regulation.As a result,these mediators have pleiotropic effects,which may be undesirable or detrimental to human health.Here,we summarize the recent findings that contribute to deciphering the molecular mechanisms downstream of glucocorticoid receptor activation.We also discuss the complex role of GCs in infectious diseases such as sepsis and COVID-19,in which the balance between pathogen elimination and protection against excessive inflammation and immunopathology needs to be tightly regulated.An understanding of the cell type-and context-specific actions of GCs from the molecular to the organismal level would help to optimize their therapeutic use.

CD28胞内域对初始T细胞CD28受体与配体结合具有关键调控作用

初始T细胞活化是由T细胞受体(TCR)及共刺激分子与其配体结合引起的,其中CD28共刺激信号在促进初始T细胞的活化过程中起关键作用.本文研究了小鼠CD4^(+)T细胞中CD28与B7配体的结合活性在CD28介导的信号通路激活中的调控机制.结果发现虽然初始CD4^(+)T细胞表面CD28-B7的本底结合力很低,但当同步给予TCR刺激可触发CD28胞内域激酶SRC酪氨酸磷酸化,并由此显著增强CD28-B7的结合力.此外通过CD28胞内域缺失的小鼠模型,进一步验证CD28胞内结构域的存在是TCR刺激信号增强CD28-B7结合力的必要条件.据此,本研究证实CD28胞内域在其配体结合过程中承担了关键性的调控作用,并为TCR和CD28相互作用介导初始T细胞活化提供了新的证据.

Revisiting dynamics and models of microsegregation during polycrystalline solidification of binary alloy

Microsegregation formed during solidification is of great importance to material properties.The conventional Lever rule and Scheil equation are widely used to predict solute segregation.However,these models always fail to predict the exact solute concentration at a high solid fraction because of theoretical assumptions.Here,the dynamics of microsegregation during polycrystalline solidification of refined Al-Cu alloy is studied via two-and three-dimensional quantitative phase-field simulations.Simulations with different grain refinement level,cooling rate,and solid diffusion coefficient demonstrate that solute segregation at the end of solidification(i.e.when the solid fraction is close to unit)is not strongly correlated to the grain morphology and back diffusion.These independences are in accordance with the Scheil equation which only relates to the solid fraction,but the model predicts a much higher liquid concentration than simulations.Accordingly,based on the quantitative phase-field simulations,a new analytical microsegregation model is derived.Unlike the Scheil equation or the Lever rule that respectively overestimates or underestimates the liquid concentration,the present model predicts the liquid concentration in a pretty good agreement with phase-field simulations,particularly at the late solidification stage.