Serum lipoproteins and albumin in the lecithin: Cholesterol acyltransferase reaction

The unique features of pig ovarian follicular fluids, i.e., presence of high density lipoprotein (HDL) only and lecithin: cholesterol acyltransferase (EC 2.3.1.43; LCAT) activity, provides a good model to study the effect of serum lipoproteins and serum albumin on the LCAT reaction. $\text{In}\text{vitro}$ cholesterol esterification is enhanced when very low density lipoprotein (VLDL) and low density lipoprotein (LDL) fractions are added, but is inhibited when one or the other of these lipoproteins is absent. High concentrations of HDL₂ result in decreased activation which can be compensated for by the addition of the VLDL-LDL mixture. These findings suggest that the rate of cholesterol esterification in ovarian follicular fluid may be enhanced by providing the exogenous VLDL and LDL as the recipients of HDL-cholesteryl ester. The inhibition of LCAT activity caused by free fatty acid and lysophosphatidylcholine can be partially reversed by the addition of serum albumin, suggesting that serum albumin may regulate the LCAT reaction.     

基于土地利用及植被覆盖变化的黄河源区生境质量时空变化特征

位于青藏高原腹地的黄河源地区生态环境脆弱,面临生物多样性锐减、生态系统退化等问题,黄河源区生态系统保护及其高质量发展已成为国家的重点战略之一。土地利用与植被覆盖是影响生境质量的重要因素,定量化土地利用方式、强度及格局和植被覆盖格局对生态质量影响的研究越来越受到关注,但其对黄河源区生态质量的耦合效应尚不明确。基于2000年和2015年黄河源区土地利用类型及生长季归一化植被指数（NDVI）,采用InVEST模型探究了不同时期黄河源区生境质量时空变化,并采用地理加权回归（GWR）模型揭示了生境质量对土地利用和植被覆盖变化的空间响应特征。结果表明,2000年与2015年土地利用类型变化主要为未利用土地向草地的转移。植被覆盖变化方面,源区生长季NDVI整体上升。从生境质量的空间分布来看,黄河源区生境质量总体呈现南高北低的空间格局,高值分布在南部及中部地区,低值分布在北部布青山、东北部高海拔区及黄河乡的黄河沿岸。相较于2000年,2015年黄河源区生境质量平均提高11.47%。草地面积和NDVI与生境质量均呈显著正相关关系,其中NDVI是提高黄河源区生境质量的重要驱动因子。研究结果突出了NDVI对提高黄河源区生境质量的主导作用,可为未来源区生态保护提供借鉴。     

Intravital lipid droplet labeling and imaging reveals the phenotypes and functions of individual macrophages in vivo

Macrophages play pivotal roles in the maintenance of tissue homeostasis. However, the reactivation of macrophages toward proinflammatory states correlates with a plethora of inflammatory diseases, including atherosclerosis, obesity, neurodegeneration, and bone marrow (BM) failure syndromes. The lack of methods to reveal macrophage phenotype and function in vivo impedes the translational research of these diseases. Here, we found that proinflammatory macrophages accumulate intracellular lipid droplets (LDs) relative to resting or noninflammatory macrophages both in vitro and in vivo, indicating that LD accumulation serves as a structural biomarker for macrophage phenotyping. To realize the staining and imaging of macrophage LDs in vivo, we developed a fluorescent fatty acid analog-loaded poly(lactic-co-glycolic acid) nanoparticle to label macrophages in mice with high efficiency and specificity. Using these novel nanoparticles, we achieved in situ functional identification of single macrophages in BM, liver, lung, and adipose tissues under conditions of acute or chronic inflammation. Moreover, with this intravital imaging platform, we further realized in vivo phenotyping of individual macrophages in the calvarial BM of mice under systemic inflammation. In conclusion, we established an efficient in vivo LD labeling and imaging system for single macrophage phenotyping, which will aid in the development of diagnostics and therapeutic monitoring. Moreover, this method also provides new avenues for the study of lipid trafficking and dynamics in vivo.Supplementary key words: macrophage, inflammation, lipid droplet, nanoparticle delivery, in vivo imaging, fatty acid analog, bone marrow, systemic inflammation, lipid trafficking, biomarker

Macrophages, a type of immune cells, almost reside in all tissues of body, from the skin to the bone marrow (BM) (1). Macrophages have remarkable plasticity, and they can be activated into specific subtypes by modifying their physiology and functions in response to local environmental cues. Activated macrophages are commonly divided into proinflammatory killing subtype and anti-inflammatory repairing subtype. Proinflammatory macrophages responding to bacteria, IFN-γ, and lipopolysaccharide (LPS) are involved in host defense and inflammation, whereas anti-inflammatory macrophages responding to interleukin-4 (IL-4), IL-10, and IL-13 play a pivotal role in tissue homeostasis and remodeling (2). Increasing evidence indicates that the reactivation of macrophages toward proinflammatory states under diverse kinds of stress is correlated with a plethora of inflammatory diseases, such as atherosclerosis, diabetes, obesity, rheumatoid arthritis, neurodegeneration, and BM failure syndromes (3, 4). Thus, characterization of macrophage activation status and the underlying molecular mechanism in situ will help elucidate their functions in these diseases; however, in vivo analysis of the macrophage activation status in their native multicellular microenvironment is challenging.Although lipid droplets (LDs) have been initially described as intracellular fat storage organelles in adipocytes, increasing studies indicate that myeloid cells also form LDs under inflammation and stress (5, 6). Macrophages, as the effector cells of innate immunity, are found to form LDs to support their host defense when exposed to pathogens, such as parasites, bacteria, and viruses (7, 8, 9, 10, 11). However, abnormal LD accumulation in tissue-resident macrophages correlates with the pathogenesis of various inflammatory diseases. For instance, foam cells in atherosclerotic lesions can maintain the local inflammatory response by secreting proinflammatory cytokines (12, 13, 14). Moreover, LD-accumulating microglia contribute to neurodegeneration by producing high levels of reactive oxygen species (ROS) and secreting proinflammatory cytokines (15). These findings indicate that LD accumulation might be a hallmark of macrophages with proinflammatory functions.In this study, based on the typical activation of in vitro BM-derived macrophages, we find that proinflammatory M_{(LPS + IFN-γ)} macrophages are characterized by LD accumulation, whereas resting macrophages and anti-inflammatory M_(IL-4) and M_(IL-10) macrophages do not contain any LDs. These features also hold for Matrigel plug-recruited macrophages and tissue-resident macrophages in mice. These findings demonstrate that LD accumulation could serve as a morphological index to distinguish proinflammatory macrophages from others.It is feasible to distinguish LD-containing cells using imaging techniques, which has translational potential for identification of proinflammatory macrophages in vivo. However, current techniques for LD visualization are traditional in vitro staining method, and in vivo staining and imaging of LD in individual macrophages remains a challenge. Through nanocarrier screening, we selected the poly(lactic-co-glycolic acid) (PLGA) nanoparticles (NPs) as nanocarrier to deliver the lipophilic carbocyanine dye (DiI_C18(5) solid (1,1''-dioctadecyl-3,3,3'',3''-tetramethylindodicarbocyanine, 4-chlorobenzenesulfonate salt) [DiD]) and lipid staining dye (C1-BODIPY 500/510-C12) into macrophages. Using these dual fluorescence-labeled PLGA NPs, we achieved in situ and in vivo functional identification of single macrophages in various tissues under systemic or local inflammatory stress. Collectively, this study establishes an efficient in vivo labeling and imaging system of intracellular LDs for phenotyping the activation status and functions of individual macrophages in their dynamic niche, which is pivotal for disease diagnosis and preclinical research.     

天山林区六种灌木生物量的建模及其器官分配的适应性

灌木全株生物量估算模型的构建仍存在一定困难,对灌木生物量在器官分配上所体现的适应性研究也不够充分。以天山林区6种常见灌木为研究对象,在天山的东段、中段、西段林区分别设置样地进行群落调查,由此以全株收获法取得6种常见灌木若干标准株的全株、根、枝、叶及各径级根的生物量,将D~2H(地径平方与高度的乘积)与V(冠幅面积与高度的乘积)分别选为估测模型的自变量,通过回归分析法建立了各种灌木全株生物量的最优估算模型,然后比较了此6种灌木全株生物量在营养器官上分配差异以及根系生物量在径级上的分配差异。结果表明:(1)天山林区6种常见灌木中,小檗(Berberis heteropoda Schrenk)、忍冬(Lonicera hispida Pall.ex Roem.et Schuet.)、栒子(Cotoneaster melanocarpus Lodd.)的全株生物量约为8.48—9.01 kg,蔷薇(Rosa spinosissima L.)、绣线菊(Spiraea hypericifolia L.)、方枝柏(Juniperus pseudosabina Fisch.et Mey.)的全株生物量约为2.71—3.20 kg;(2)蔷薇、绣线菊、栒子的全株生物量最优估测模型是以V为自变量的函数,小檗、忍冬、方枝柏的全株生物量最优估测模型是以D~2H为自变量的函数,各模型R~2值均在0.850以上,且在P0.05水平上达到显著,模型模拟结果达到了较高的准确度;(3)6种灌木全株生物量在根、枝上的分配比重差异不显著,仅在叶上的分配比重有差异(P0.05);根系生物量在径级上的分配均呈现随根系径级下降而减少的规律,6种灌木在径级大于2 mm根上的分配比重存在差异(P0.05,径级大于20 mm根为P0.01水平);(4)6种灌木全株生物量在营养器官上的分配差异以及根系生物量在径级上的分配差异均体现了各物种对其生境选择的适应策略。     

RUS家族对植物生长发育的调控作用

叶绿体基因组编码许多参与光合作用和其他代谢过程的关键蛋白质,在叶绿体中合成的代谢物对于植物正常的生长发育至关重要。根对紫外线-B辐射敏感[Root-UVB (ultraviolet radiation B)-sensitive, RUS]蛋白属于叶绿体蛋白,由高度保守的DUF647结构域组成,在参与植物形态发生、物质运输和能量代谢等多种生命活动的调控中发挥作用。本文就近年来关于RUS家族在植物的胚胎发育、光形态建成、维生素B6稳态、生长素转运和花药发育等生长发育过程中的相关研究进行回顾和总结,为深入研究其在植物生长发育中的分子调控机制提供了参考。     

α-酮戊二酸依赖型双加氧酶催化特性及反应耦联辅因子对其催化羟基化反应的影响

【目的】以重组大肠杆菌表达的枯草芽孢杆菌(Bacillus subtilis)L-异亮氨酸双加氧酶(L-isoleucine dioxygenase,IDO)为研究对象,考察其催化L-异亮氨酸(L-Ile)羟基化反应的影响因素,构建IDO催化合成羟基氨基酸的反应体系。【方法】通过Ni-NTA亲和层析法从重组大肠杆菌(Escherichia coli)BL21/p ET28a-ido中纯化获得重组IDO,以L-Ile为底物,考察重组IDO催化羟基化反应的影响因素,并进一步针对耦联反应优化α-酮戊二酸(α-KG)在重组IDO酶促转化体系中的添加浓度。【结果】基于重组IDO催化L-Ile羟基化的活性测定,计算该酶Km为0.247 mmol/L,kcat为1.260 s-1,kcat/Km为5.101 L/(mmol·s),与其他同源酶动力学参数比较分析表明,重组IDO的底物亲和性及催化效率较高。重组IDO催化反应的最适温度为20°C、最适p H为7.0;在35°C以下较为稳定;反应体系中Fe2+最适浓度为1 mmol/L。重组IDO可催化不同L-氨基酸反应,对L-异亮氨酸、L-正亮氨酸、L-甲硫氨酸的活性较高。通过优化α-KG浓度,反应体系中添加30 mmol/Lα-KG时,可将底物浓度提高至70 mmol/L,产物4-羟基异亮氨酸(4-HIL)的摩尔产率达66.20%,表明α-KG作为反应耦联辅因子,其浓度对重组IDO催化L-Ile羟基化具有显著影响。【结论】重组IDO的底物亲和性、催化效率、最适催化条件、稳定性等基本性质有利于催化L-Ile羟基化反应。在其催化反应体系中,α-KG作为反应耦联辅因子,对酶促转化效果影响显著。研究结果为4-HIL及其他羟基氨基酸的酶促转化提供了研究基础。