基于近邻成分分析算法的原发性肝癌精确放疗后HBV再激活分类预测

原发性肝癌(PLC)患者在精确放疗后乙型肝炎病毒(HBV)再激活是一种常见并发症,及时的预测防护能降低发病率、死亡率。研究表明:多余的特征变量会影响HBV再激活的预测精度。通过提出基于近邻成分分析(NCA)的特征选择方法找出HBV再激活的危险因素及特征组合。之后分别建立经Bayes优化前后的支持向量机模型(SVM)对这些关键特征子集及初始特征集进行分类预测。实验结果表:明HBV DNA水平、KPS评分、分割方式、外放边界、V25、肿瘤分期TNM、ChildPugh等都是影响HBV再激活的危险因素。其中经NCA特征选择之后发现的V25是在乙型肝炎病毒再激活研究中首次提出的危险因素。10折交叉验证下特征组合HBV DNA水平、外放边界、V25的预测精度高达86.11%。支持向量机分类器可以很好的应用于乙型肝炎病毒再激活的研究,特征选择后的关键特征组合具有更优越的分类性能。     

孕期个性化营养干预对妊娠期糖尿病孕妇糖脂水平及妊娠结局的影响

目的:探讨孕期个性化营养干预对妊娠期糖尿病孕妇糖脂水平及妊娠结局的影响。方法:选择2016年8月-2017年10月期间于我院产检的妊娠期糖尿病孕妇160例,以随机数字表法分为研究组(n=80)和对照组(n=80)。对照组给予常规营养干预,研究组则予以孕期个性化营养干预。比较两组干预前后空腹血糖、餐后2h血糖、总胆固醇(TC)、三酰甘油(TG)、高密低脂蛋白胆固醇(HDL-C)、低密度脂蛋白胆固醇(LDL-C)水平,观察孕妇及新生儿并发症发生情况。结果:干预后两组孕妇空腹血糖、餐后2 h血糖显著降低,且研究组低于对照组(P0.05)。干预后对照组孕妇TC、TG、LDL-C较干预前显著升高(P0.05),HDL-C差异无统计学意义(P0.05),研究组血脂水平与干预前比较差异无统计学意义(P0.05),与对照组比较,研究组孕妇TC、TG、LDL-C水平更低(P0.05)。研究组妊娠期高血压、胎膜早破发生率均明显低于对照组(P0.05),两组感染、产后出血发生率比较无统计学差异(P0.05)。与对照组比较,研究组新生儿窘迫、巨大儿、新生儿低血糖、早产儿的发生率降低(P0.05)。结论:孕期个性化营养干预可有效改善妊娠期糖尿病孕妇的糖脂水平,且能够有效降低并发症发生率,从而改善妊娠结局。     

Floral antagonists counteract pollinator‐mediated selection on attractiveness traits in the hummingbird‐pollinated Collaea cipoensis (Fabaceae)

Pollinator‐mediated selection toward larger and abundant flowers is common in naturally pollen‐limited populations. However, floral antagonists may counteract this effect, maintaining smaller‐ and few‐flowered individuals within populations. We quantified pollinator and antagonist visit rates and determined a multiplicative female fitness component from attacked and non‐attacked flowers of the Brazilian hummingbird‐pollinated shrub Collaea cipoensis to determine the selective effects of pollinators and floral antagonists on flower size and number. We predicted that floral antagonists reduce the female fitness component and thus exert negative selective pressures on flower size and number, counteracting the positive effects of pollinators. Pollinators, mainly hummingbirds, comprised 4% of total floral visitation, whereas antagonist ants and bees accounted for 90% of visitation. Nectar‐robbers involved about 99% of floral antagonist visit rates, whereas florivores comprised the remaining 1%. Larger and abundant flowers increased both pollinator and antagonist visit rates and the female fitness component significantly decreased in flowers attacked by nectar‐robbers and florivores in comparison to non‐attacked flowers. We detected that pollinators favored larger‐ and many‐flowered individuals, whereas floral antagonists exerted negative selection on flower size and number. This study confirms that floral antagonists reduce female plant fitness and this pattern directly exerts negative selective pressures on flower size and number, counteracting pollinator‐mediated selection on floral attractiveness traits.     

Green‐wave surfing increases fat gain in a migratory ungulate

Each spring, migratory herbivores around the world track or ‘surf’ green waves of newly emergent vegetation to distant summer or wet‐season ranges. This foraging tactic may help explain the great abundance of migratory herbivores on many seasonal landscapes. However, the underlying fitness benefits of this life‐history strategy remain poorly understood. A fundamental prediction of the green‐wave hypothesis is that migratory herbivores obtain fitness benefits from surfing waves of newly emergent vegetation more closely than their resident counterparts. Here we evaluate whether this behavior increases body‐fat levels – a critically important correlate of reproduction and survival for most ungulates – in elk Cervus elaphus of the Greater Yellowstone Ecosystem. Using satellite imagery and GPS tracking data, we found evidence that migrants (n = 23) indeed surfed the green wave, occupying sites 12.7 days closer to peak green‐up than residents (n = 16). Importantly, individual variation in surfing may help account for up to 6 kg of variation in autumn body‐fat levels. Our findings point to a pathway for anthropogenic changes to the green wave (e.g. climate change) or migrants’ ability to surf it (e.g. development) to impact migratory populations. To explore this possibility, we evaluated potential population‐level consequences of constrained surfing with a heuristic model. If green‐wave surfing deteriorates by 5–15 days from observed, our model predicts up to a 20% decrease in pregnancy rates, a 2.5% decrease in population growth, and a 30% decrease in abundance over 50 years. By linking green‐wave surfing to fitness and illustrating potential effects on population growth, our study provides new insights into the evolution of migratory behavior and the prospects for the persistence of migratory ungulate populations in a changing world.     

Who's In and Who's Out—Compositional Control of Biomolecular Condensates

Biomolecular condensates are two- and three-dimensional compartments in eukaryotic cells that concentrate specific collections of molecules without an encapsulating membrane. Many condensates behave as dynamic liquids and appear to form through liquid–liquid phase separation driven by weak, multivalent interactions between macromolecules. In this review, we discuss current models and data regarding the control of condensate composition, and we describe our current understanding of the composition of representative condensates including PML nuclear bodies, P-bodies, stress granules, the nucleolus, and two-dimensional membrane localized LAT and nephrin clusters. Specific interactions, such as interactions between modular binding domains, weaker interactions between intrinsically disorder regions and nucleic acid base pairing, and nonspecific interactions, such as electrostatic interactions and hydrophobic interactions, influence condensate composition. Understanding how specific condensate composition is determined is essential to understanding condensates as biochemical entities and ultimately discerning their cellular and organismic functions.     

FLCRM: Functional linear cox regression model

Summary

We consider a functional linear Cox regression model for characterizing the association between time‐to‐event data and a set of functional and scalar predictors. The functional linear Cox regression model incorporates a functional principal component analysis for modeling the functional predictors and a high‐dimensional Cox regression model to characterize the joint effects of both functional and scalar predictors on the time‐to‐event data. We develop an algorithm to calculate the maximum approximate partial likelihood estimates of unknown finite and infinite dimensional parameters. We also systematically investigate the rate of convergence of the maximum approximate partial likelihood estimates and a score test statistic for testing the nullity of the slope function associated with the functional predictors. We demonstrate our estimation and testing procedures by using simulations and the analysis of the Alzheimer's Disease Neuroimaging Initiative (ADNI) data. Our real data analyses show that high‐dimensional hippocampus surface data may be an important marker for predicting time to conversion to Alzheimer's disease. Data used in the preparation of this article were obtained from the ADNI database ( adni.loni.usc.edu ).     

Life History theory hypotheses on child growth: Potential implications for short and long‐term child growth,development and health

Life history theory integrates ecological, physiological, and molecular layers within an evolutionary framework to understand organisms’ strategies to optimize survival and reproduction. Two life history hypotheses and their implications for child growth, development, and health (illustrated in the South African context) are reviewed here. One hypothesis suggests that there is an energy trade‐off between linear growth and brain growth. Undernutrition in infancy and childhood may trigger adaptive physiological mechanisms prioritizing the brain at the expense of body growth. Another hypothesis is that the period from conception to infancy is a critical window of developmental plasticity of linear growth, the duration of which may vary between and within populations. The transition from infancy to childhood may mark the end of a critical window of opportunity for improving child growth. Both hypotheses emphasize the developmental plasticity of linear growth and the potential determinants of growth variability (including the role of parent–offspring conflict in maternal resources allocation). Implications of these hypotheses in populations with high burdens of undernutrition and infections are discussed. In South Africa, HIV/AIDS during pregnancy (associated with adverse birth outcomes, short duration of breastfeeding, and social consequences) may lead to a shortened window of developmental plasticity of growth. Furthermore, undernutrition and infectious diseases in children living in South Africa, a country undergoing a rapid nutrition transition, may have adverse consequences on individuals’ cognitive abilities and risks of cardio‐metabolic diseases. Studies are needed to identify physiological mechanisms underlying energy allocation between biological functions and their potential impacts on health.     

Roles of bacteria in the bark beetle holobiont – how do they shape this forest pest?

Bark beetles are well‐known forest pests, some species inducing massive attacks on trees, resulting in the devastation of entire woodlands. Bark beetles are associated with microorganisms, forming an entity known as ‘holobiont’. Beetles and fungi are the best‐studied members of this multipartite symbiosis. However, recent studies have shown that bacteria may play important roles in the bark beetle holobiont, such as providing certain nutrients, promoting the growth of beneficial fungi, detoxifying the environment by lowering the levels of phenolic compounds synthesised by the host tree or by inhibiting the growth of antagonistic fungi whereas some bacterial symbionts have the potential to kill beetles under certain conditions. Therefore, bacteria probably greatly affect the life cycle of bark beetles; hence, more research is needed to clarify the extent to which a bacterial associate is implicated in a bacterial bark beetle symbiosis and how much it determines host's performance. This review summarises all of the known activities of bacteria present in the bark beetle holobiont, indicates some important gaps in the knowledge of this symbiosis and provides some guidance for overcoming the difficulties in investigating this relationship in future studies.