The ecological drivers and consequences of wildlife trade

Wildlife trade is a key driver of extinction risk, affecting at least 24% of terrestrial vertebrates. The persistent removal of species can have profound impacts on species extinction risk and selection within populations. We draw together the first review of characteristics known to drive species use – identifying species with larger body sizes, greater abundance, increased rarity or certain morphological traits valued by consumers as being particularly prevalent in trade. We then review the ecological implications of this trade-driven selection, revealing direct effects of trade on natural selection and populations for traded species, which includes selection against desirable traits. Additionally, there exists a positive feedback loop between rarity and trade and depleted populations tend to have easy human access points, which can result in species being harvested to extinction and has the potential to alter source–sink dynamics. Wider cascading ecosystem repercussions from trade-induced declines include altered seed dispersal networks, trophic cascades, long-term compositional changes in plant communities, altered forest carbon stocks, and the introduction of harmful invasive species. Because it occurs across multiple scales with diverse drivers, wildlife trade requires multi-faceted conservation actions to maintain biodiversity and ecological function, including regulatory and enforcement approaches, bottom-up and community-based interventions, captive breeding or wildlife farming, and conservation translocations and trophic rewilding. We highlight three emergent research themes at the intersection of trade and community ecology: (1) functional impacts of trade; (2) altered provisioning of ecosystem services; and (3) prevalence of trade-dispersed diseases. Outside of the primary objective that exploitation is sustainable for traded species, we must urgently incorporate consideration of the broader consequences for other species and ecosystem processes when quantifying sustainability.     

Site-specific mutations in the N-terminal region of human C5a that affect interactions of C5a with the neutrophil C5a receptor.

C5a is an inflammatory mediator that evokes a variety of immune effector functions including chemotaxis, cell activation, spasmogenesis, and immune modulation. It is well established that the effector site in C5a is located in the C-terminal region, although other regions in C5a also contribute to receptor interaction. We have examined the N-terminal region (NTR) of human C5a by replacing selected residues in the NTR with glycine via site-directed mutagenesis. Mutants of rC5a were expressed as fusion proteins, and rC5a was isolated after factor Xa cleavage. The potency of the mutants was evaluated by measuring both neutrophil chemotaxis and degranulation (beta-glucuronidase release). Mutants that contained the single residue substitutions Ile-6-->Gly or Tyr-13-->Gly were reduced in potency to 4-30% compared with wild-type rC5a. Other single-site glycine substitutions at positions Leu-2, Ala-10, Lys-4, Lys-5, Glu-7, Glu-8, and Lys-14 showed little effect on C5a potency. The double mutant, Ile-6-->Gly/Tyr-13-->Gly, was reduced in potency to < 0.2%, which correlated with a correspondingly low binding affinity for neutrophil C5a receptors. Circular dichroism studies revealed a 40% reduction in alpha-helical content for the double mutant, suggesting that the NTR contributes stabilizing interactions that maintain local secondary or tertiary structure of C5a important for receptor interaction. We conclude that the N-terminal region in C5a is involved in receptor binding either through direct interaction with the receptor or by stabilizing a binding site elsewhere in the intact C5a molecule.     

微生物发酵法生产S-腺苷甲硫氨酸的研究进展

S-腺苷甲硫氨酸(S-adenosyl-l-methionine, SAM)广泛存在于生物体内,主要参与生物体内的转甲基过程、转硫过程及转氨丙基过程,具有重要的生理功能,其生产备受重视。目前SAM生产的研究主要集中于微生物发酵法,该方法与化学合成法和酶催化法相比,成本较低且更容易实现工业化生产。随着需求量的迅速增加,通过菌种改良提高SAM产量备受关注。当前SAM生产菌种改良的主要策略包括常规育种和代谢工程。本文综述了提高微生物生产SAM能力的近期研究进展并探讨了SAM生产中的瓶颈问题及解决方法,以期为进一步提高SAM产量提供思路。     

Relationship between mild iodine deficiency in pregnant women and thyroid function: A meta-analysis

BackgroundPregnant women are among the key groups in iodine nutrition evaluation. The purpose of the present study was to summarize the evidence supporting the relationship between mild iodine deficiency (UIC: 100–150 μg/L) in pregnant women and levels of thyroid function tests.MethodsThis review follows the guidelines for systematic reviews (PRISMA 2020). Three electronic databases (PubMed, Medline, and Embase) were searched for relevant publications in English on the association between mild iodine deficiency in pregnant women and thyroid function. Articles published in Chinese were searched in China’s electronic databases (CNKI, WanFang, CBM, and WeiPu). Pooled effects were presented as standardized mean differences (SMDs) and odds ratios (ORs) with 95% confidence intervals (CIs) using fixed or random effect models, respectively. This meta-analysis was registered at www.crd.york.ac.uk/prospero as CRD42019128120.ResultsWe summarized the results from 7 articles with 8261 participants. The overall pooled results showed that the levels of FT₃, FT4, and abnormal TgAb (the antibody levels exceeded the upper limit of the reference range) were significantly increased in pregnant women with mild iodine deficiency compared to pregnant women with adequate iodine status (FT₃: SMD=0.854, 95% CI: 0.188, 1.520; FT₄: SMD=0.550, 95% CI: 0.050, 1.051; TgAb: OR=1.292, 95% CI: 1.095; 1.524). Subgroup analysis was carried out on the sample size, ethnicity, country, and gestation of FT₃, FT_4, and TSH, but no plausible factor was found. Egger’s tests indicated no publication bias.The increase in FT₃ and FT_4, as well as TgAb levels, in pregnant women is associated with mild iodine deficiency.ConclusionMild iodine deficiency is associated with an increase in FT_3,FT₄ and TgAb levels in pregnant women. Mild iodine deficiency may increase the risk of thyroid dysfunction in pregnant women.     

Addressing high excitation conditions in time-resolved X-ray diffraction experiments and issues of biological relevance

One of the most important fundamental questions connecting chemistry to biology is how chemistry scales in complexity up to biological systems where there are innumerable possible pathways and competing processes. With the development of ultrabright electron and x-ray sources, it has been possible to literally light up atomic motions to directly observe the reduction in dimensionality in the barrier crossing region to a few key reaction modes. How do these chemical processes further couple to the surrounding protein or macromolecular assembly to drive biological functions? Optical methods to trigger photoactive biological processes are needed to probe this issue on the relevant timescales. However, the excitation conditions have been in the highly nonlinear regime, which questions the biological relevance of the observed structural dynamics.     

A mechanistic spatio-temporal modeling of COVID-19 data

Understanding the evolution of an epidemic is essential to implement timely and efficient preventive measures. The availability of epidemiological data at a fine spatio-temporal scale is both novel and highly useful in this regard. Indeed, having geocoded data at the case level opens the door to analyze the spread of the disease on an individual basis, allowing the detection of specific outbreaks or, in general, of some interactions between cases that are not observable if aggregated data are used. Point processes are the natural tool to perform such analyses. We analyze a spatio-temporal point pattern of Coronavirus disease 2019 (COVID-19) cases detected in Valencia (Spain) during the first 11 months (February 2020 to January 2021) of the pandemic. In particular, we propose a mechanistic spatio-temporal model for the first-order intensity function of the point process. This model includes separate estimates of the overall temporal and spatial intensities of the model and a spatio-temporal interaction term. For the latter, while similar studies have considered different forms of this term solely based on the physical distances between the events, we have also incorporated mobility data to better capture the characteristics of human populations. The results suggest that there has only been a mild level of spatio-temporal interaction between cases in the study area, which to a large extent corresponds to people living in the same residential location. Extending our proposed model to larger areas could help us gain knowledge on the propagation of COVID-19 across cities with high mobility levels.     

Some new results on Cox–Czanner divergence and their applications in survival studies

In the present communication, we propose a quantile-based measure for the divergence between two survival functions. This can also be used in a dynamic way where the divergence between survival functions varies with time. Several new properties of the proposed measure are investigated with suitable examples. The behavior of the measure for various reliability models is also investigated. A real data analysis is employed to compare the relative efficacy of two treatment groups using the proposed divergence measure.     

定量分析调控人类免疫缺陷病毒潜伏与激活的动力学机制

目的 治疗艾滋病最大的障碍在于无法根除人类免疫缺陷病毒（HIV）潜伏于人体细胞所形成的病毒存储库。构建描述病毒存储库建立分子机制的动力学模型需考虑生物体内的噪声环境和多重影响因素,本文通过一种全新的动力学结构分解方法将随机微分方程的确定性部分与随机性噪声分开,从而在仅需分析常微分方程不动点的情况下即可判断不同药物靶点的作用效果。方法 使用连续的随机微分方程构建了HIV转录过程的动力学模型,简化了描述系统所需方程的维度,增大了模型的可探索空间,在此基础上,通过计算得到的势能函数和概率分布函数直观表示病毒潜伏与激活的不同表达状态以及它们之间的关系。结果 定量分析了不同动力学参数对系统稳态和势函数的影响程度,分别得到了系统处于双稳态和单稳态时的参数范围,并将不同因素对动力系统分岔的影响程度与生物学实验结果对比,验证了本工作的理论基础。结论 本文突破了以往离散、随机的方法,可以通过常微分方程定量分析HIV转录调控的动力学机制,有利于推广到处理高维情况,进一步研究艾滋病在生物体内的发生发展,从而指导设计实验寻找临床上的治疗方案。     

生长抑素在糖尿病大鼠胰腺外分泌功能降低中的作用

本实验观察到,用链佐霉素造成大鼠糖尿病模型,其胰腺组织中生长抑素含量明显升高。大鼠皮下注射生长抑素(100μg·kg~(-1)·d~(-1))5d,其胰腺组织中淀粉酶的含量明显降低。体外胰腺灌流也表明,生长抑素能抑制CCK—8刺激引起的胰腺淀粉酶释放。以上结果提示,糖尿病时胰腺组织中生长抑素含量的增加可能在胰腺外分泌功能降低中有一定的作用。