Functional morphology of the caudal skeleton in teleostean fishes

The basic function of the caudal skeleton in teleostean fishes is to support the caudal fin, but its parts contribute to this function in somewhat different ways. The main axis for this support is the upturned terminal end of the vertebral column, which ends at the base of the uppermost principal rays. The uroneural struts just ahead of this axis provide support for it. The parts of the caudal skeleton behind and below this upturned axis, the hypurals and parhypural, not only support the caudal rays but also provide a means for differential movements between the upper and lower parts of the fin base. This basic caudal skeleton varies with the position of the fish in the sequence of teleosten evolution, the way in which the fish uses its caudal fin, and to some extent with the shape of the fin.     

7,9-Diaryl-1,6,8-trioxaspiro[4.5]dec-3-en-2-ones: Readily accessible and highly potent anticancer compounds

7,9-Diaryl-1,6,8-trioxaspiro[4.5]dec-3-en-2-ones are a recently described group of spirocyclic butenolides that can be generated rapidly and as a single diastereomer through a cascade process between γ-hydroxybutenolides and aromatic aldehydes. The following outlines our findings that these spirocycles are potently cytotoxic and have a dramatic structure–function profile that provides excellent insight into the structural features required for this potency.     

Distinct functions of maternal and somatic Pat1 protein paralogs

We previously identified Xenopus Pat1a (P100) as a member of the maternal CPEB RNP complex, whose components resemble those of P-(rocessing) bodies, and which is implicated in translational control in Xenopus oocytes. Database searches have identified Pat1a proteins in other vertebrates, as well as paralogous Pat1b proteins. Here we characterize Pat1 proteins, which have no readily discernable sequence features, in Xenopus oocytes, eggs, and early embryos and in human tissue culture cells. xPat1a and 1b have essentially mutually exclusive expression patterns in oogenesis and embryogenesis. xPat1a is degraded during meiotic maturation, via PEST-like regions, while xPat1b mRNA is translationally activated at GVBD by cytoplasmic polyadenylation. Pat1 proteins bind RNA in vitro, via a central domain, with a preference for G-rich sequences, including the NRAS 5′ UTR G-quadruplex-forming sequence. When tethered to reporter mRNA, both Pat proteins repress translation in oocytes. Indeed, both epitope-tagged proteins interact with the same components of the CPEB RNP complex, including CPEB, Xp54, eIF4E1b, Rap55B, and ePAB. However, examining endogenous protein interactions, we find that in oocytes only xPat1a is a bona fide component of the CPEB RNP, and that xPat1b resides in a separate large complex. In tissue culture cells, hPat1b localizes to P-bodies, while mPat1a-GFP is either found weakly in P-bodies or disperses P-bodies in a dominant-negative fashion. Altogether we conclude that Pat1a and Pat1b proteins have distinct functions, mediated in separate complexes. Pat1a is a translational repressor in oocytes in a CPEB-containing complex, and Pat1b is a component of P-bodies in somatic cells.     

Differentiation of subspecies and sexes of Beringian Dunlins using morphometric measures

Five subspecies of Dunlins (Calidris alpina) that breed in Beringia are potentially sympatric during the non‐breeding season. Studying their ecology during this period requires techniques to distinguish individuals by subspecies. Our objectives were to determine (1) if five morphometric measures (body mass, culmen, head, tarsus, and wing chord) differed between sexes and among subspecies (C. a. actites, arcticola, kistchinski, pacifica, and sakhalina), and (2) if these differences were sufficient to allow for correct classification of individuals using equations derived from discriminant function analyses. We conducted analyses using morphometric data from 10 Dunlin populations breeding in northern Russia and Alaska, USA. Univariate tests revealed significant differences between sexes in most morphometric traits of all subspecies, and discriminant function equations predicted the sex of individuals with an accuracy of 83–100% for each subspecies. We provide equations to determine sex and subspecies of individuals in mixed subspecies groups, including the (1) Western Alaska group of arcticola and pacifica (known to stage together in western Alaska) and (2) East Asia group of arcticola, actites, kistchinski, and sakhalina (known to winter together in East Asia). Equations that predict the sex of individuals in mixed groups had classification accuracies between 75% and 87%, yielding reliable classification equations. We also provide equations that predict the subspecies of individuals with an accuracy of 22–96% for different mixed subspecies groups. When the sex of individuals can be predetermined, the accuracy of these equations is increased substantially. Investigators are cautioned to consider limitations due to age and feather wear when using these equations during the non‐breeding season. These equations will allow determination of sexual and subspecies segregation in non‐breeding areas, allowing implementation of taxonomic‐specific conservation actions.     

Using species traits to assess human impacts on near shore benthic ecosystems in the Canadian Arctic

Human activities have the potential to alter the diversity and composition of biological communities in natural environments, which can cause changes in ecosystem functioning. This has led to the development of environmental assessment techniques that take into account species identity, as species can contribute differently to various ecosystem processes. Biological Traits Analysis (BTA) is used to compare the abundances of specific biological traits in samples to produce information about how ecosystem functioning may change across a specific terrestrial or aquatic system. In the present study, BTA was used to assess the influence of municipal wastewater effluent on benthic marine communities in near shore soft sediments in four locations across the Canadian Arctic Territory of Nunavut, Canada. Shifts in trait composition were assessed relative to indicators of sediment enrichment (sediment chlorophyll, organic content, degree of anoxia), and natural variation in habitat characteristics (water depth, porosity, average grain size) at a site receiving wastewater and a reference site in each sampling location. The results indicated a mild enrichment effect of wastewater, as evidenced by changes in trait composition at three of the four sites that received wastewater inputs. However, the amount of variance in trait composition explained by metrics of wastewater enrichment in these locations were generally equal to or lower than the amount of variance explained by sediment characteristics related to natural processes. These results provide greater insight into the underlying causes and consequences of human activities than more traditional methods for environmental impact assessment, and can be directly applied in a management context.     

Structural determinants of multimerization and dissociation in 2-Cys peroxiredoxin chaperone function

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间充质干细胞在2019新型冠状病毒肺炎(COVID-19)中的治疗潜能、临床研究与应用前景*

当前因SARS-CoV-2感染而引起的2019新型冠状病毒肺炎(COVID-19)肆虐全球,严重危害人类健康。SARS-CoV-2感染性强,危重症患者死亡率高,尽管各种各样的治疗正在进行临床试验,但目前尚无有效的治疗方法。间充质干细胞(mesenchymal stem cell,MSC)在临床前试验中对多种疾病有良好的治疗效果,因而受到了广泛地关注。MSC可能利用分化潜能诱导分化成功能性肺样细胞、免疫调节与免疫细胞互作、抑制炎症来降低促炎细胞因子分泌、迁移和归巢靶向损伤肺部、抗病毒作用来减少肺上皮细胞中的病毒复制、产生细胞外囊泡来修复受损的组织,进而使COVID-19患者肺功能逐渐恢复正常,缓解并达到治疗COVID-19的目的。综合讨论了COVID-19的基本特征和当前主要治疗手段,同时总结了MSC在COVID-19中的临床研究和当前面临的挑战,探讨了MSC治疗COVID-19的应用前景,为MSC在COVID-19中的治疗提供了理论基础和现实依据。