城市扩张过程中建设用地景观格局演变特征及其驱动力

剖析城市扩张过程中建设用地景观格局演变特征及其驱动力,不仅有助于城市生态环境问题的解决,而且为城市用地结构优化、城市景观规划等工作提供科学依据。以快速城市化的中型城市—扬州市为例,利用多期(1995、2000、2005、2010年和2015年)Landsat卫星影像、乡镇水平的扬州统计年鉴等数据,运用景观格局分析、增强回归树(Boosted regression trees)等方法,研究建设用地的扩张模式、形态及景观格局,定量探究地理、社会和经济因子对景观格局的影响机制,从而明晰景观格局演变特征及其驱动力。结果表明,1995—2015年,建设用地面积持续增加,填充式(Infilling)、边缘式(Edge-expansion)和跳跃式(Leapfrog)3种扩张模式在各时段均有出现,但其优势度随着城市发展而改变。建设用地的形态在城市扩张的过程中经历着"集聚"和"扩散"的交替变化过程,景观格局则出现了同质化倾向,景观破碎化下降、聚合度增加。地理因子(海拔和到县市中心的距离)对景观格局的综合影响虽然高于社会经济,但它的影响力却随着城市发展呈现出下降趋势,社会经济的作用则逐渐增强。海拔和人口...     

Actomyosin-like ATPase extracted from plain synaptic vesicle fractions

Ca²⁺-sensitive Mg²⁺-dependent ATP phosphohydrolase (EC 3.6.1.3, ATPase) was extracted from the plain synaptic vesicle fractions that were virtually devoid of contamination. The protein pattern of the ATPase preparation on SDS polyacrylamide gel electrophoresis closely resembled that of actomyosin from skeletal muscle. The finding suggests that the main components of the ATPase are actin- and myosin-like proteins of the brain (stenin and neurin). Microsome and synaptosomal plasmalemma fractions were extracted under the same conditions to examine the possibility that the ATPase extracted derived from contaminating particulates. An entirely different ATPase was extracted from microsomes, and no protein from plasma membranes. Although Ca²⁺-sensitive Mg²⁺-dependent ATPase was extracted from coated vesicle fraction, the electrophoretic pattern was dissimilar to that of the ATPase from plain synaptic vesicle fractions. It may be inferred that the whole complex of neurostenin is located in plain synaptic vesicles from the brain.     

Identification of a new small molecule chemotype of Melanin Concentrating Hormone Receptor-1 antagonists using pharmacophore-based virtual screening

MCH receptor is a G protein-coupled receptor with two subtypes R1 and R2. Many studies have demonstrated the role of MCH-R1 in feeding and energy homeostasis. It has been proven that oral administration of small molecule MCH-R1 antagonists significantly reduces food intake and causes a dose-dependent weight loss. In this study, two ligand-based pharmacophores were developed and validated based on recently published MCH-R1 antagonists with diverse structures. Successful pharmacophores had one hydrogen bond acceptor, one positive ionizable, one ring aromatic and two or three hydrophobic groups. These 3D-QSAR models were used for virtual screening of the ZINC chemical database resulting in the identification of nine compounds with more than 50% displacement of radiolabeled MCH at a 20 μM concentration. Moreover, four of these compounds showed antagonistic activities in Aequorin functional assay, including MH-3 which is the first MCH-R1 antagonist based on a diazaspiro[4.5]decane scaffold. The most active compounds were also docked into our previously published MCH-R1 homology model to gain insights into their binding determinants. These compounds could represent a viable starting scaffold for the design of potent MCH-R1 antagonists with improved pharmacokinetic properties as an effective treatment for obesity.     

高速公路生态景观质量评价指标体系和评价方法:以江苏南通为例

公路生态景观建设不仅是公路建设的重要组成部分,也是美丽乡村建设和生态园林城市建设的重要标志,对于实现社会经济的可持续发展具有重要作用.公路生态景观质量的评价指标和方法是衡量公路及其外部环境建设质量的重要依据.本研究以江苏省南通市5条主要干线高速公路G15、G228、G204、S334和S335为例,建立了定量和定性评价指标相结合的公路生态景观质量评价指标体系,包括景观功能、生态效能和安全设计3大类12个评价指标.通过现场调查和计算,建立了12个评价指标的变量矩阵,并进行了主成分(PC)分析.结果表明: 公路绿化景观生态评价综合得分模型为: H=0.694PC1+0.191PC2+0.115PC3, 5条高速公路得分排序结果为: G204>G15>S334>G228>S335.本研究结果将为高速公路生态景观质量评价提供方法和参考.     

CLEC1B Expression and PD-L1 Expression Predict Clinical Outcome in Hepatocellular Carcinoma with Tumor Hemorrhage

Spontaneous tumor hemorrhage (TH) is frequently observed in solid tumors including human hepatocellular carcinoma (HCC). TH implies fast-growing and worse tumor immunological microenvironment; however, the underlying mechanism remains largely unknown. CLEC1B is a signature gene highly associated with tumor progression. PD-L1 expression is a key biomarker predictive of immune checkpoint therapies, which showed astonishing effect on various types of tumor. We assume that, in HCC, TH may closely associate with the expression of these two molecules. In this study, 136 patients with HCC were enrolled. qRT-PCR showed that CLEC1B expression is significantly lower in HCC tumor tissue. Immunohistochemistry of HCC tissue microarrays demonstrated that PD-L1_high and CLEC1B_low expressions were significantly correlated with TH and clinicopathological features indicating worse HCC progression. According to univariate/multivariate analysis, a combination of PD-L1_high and CLEC1B_low expression was an independent prognostic factor indicating the poor outcome. The prognostic value of PD-L1_high and CLEC1B_low was validated by Cox proportional-hazard analyses. Collectively, tumor with TH is closely associated with CLEC1B_low & PD-L1_high expression, which may imply high response of PD-L1/PD-1 immune checkpoint therapies. CLEC1B may be a potential therapeutic target for PD-L1/PD-1 immunotherapy. PD-L1_high and CLEC1B_low can be a valuable prognosis factor implying worse clinical outcomes.     

Long‐term outcomes of forest restoration in an urban park

Creating, restoring, and sustaining forests in urban areas are complicated by habitat fragmentation, invasive species, and degraded soils. Although there is some research on the outcomes of urban reforestation plantings during the first 5 years, there is little research on longer term outcomes. Here, we compare the successional trajectories of restored and unrestored forest sites 20 years after initiating restoration. The sites are located within the Rodman's Neck area of Pelham Bay Park, in the northeast corner of the Bronx in New York City (NYC), U.S.A. Compared with unrestored sites, we saw improvements in species diversity, greater forest structure complexity, and evidence of the regeneration and retention of native tree species in restored sites. In addition, we found differences in restoration outcomes depending on the level of intervention: clearing exotic shrubs and vines and planting native trees and shrubs improved tree diversity and canopy closure to a greater extent than clearing exotics alone, and the mechanical removal of invasive plants after the native plantings further improved some measures of restoration, such as tree species diversity and native tree regeneration. The results of this study suggest that the goal of a sustainable forest ecosystem dominated by native trees and other plant species may not be achievable without continued human intervention on site. In addition, these results indicate that the restoration approach adopted by NYC's reforestation practitioners is moving the site toward a more desirable vegetative community dominated by native species.     

Mitochondrial DNA synthesis in cell cycle mutants of saccharomyces cerevisiae

Mitochondrial DNA replication was examined in mutants for seven different Saccharomyces cerevisiae genes which are essential for nuclear DNA replication. In cdc8 and cdc21, mutants defective in continued replication during the S phase of the cell cycle, mitochondrial DNA replication ceases at the nonpermissive temperature. Replication is temperature sensitive even when these mutants are arrested in the G1 phase of the cell cycle with α factor, a condition where mitochondrial DNA replication continues for the equivalent of several generations at the permissive temperature. Therefore the cessation of replication results from a defect in mitochondrial replication per se, rather than from an indirect consequence of cells being blocked in a phase of the cell cycle where mitochondrial DNA is not normally synthesized. Since the temperature-sensitive mutations are recessive, the products of genes cdc8 and cdc21 must be required for both nuclear and mitochondrial DNA replication. In contrast to cdc8 and cdc21, mitochondrial DNA replication continues for a long time at the nonpermissive temperature in five other cell division cycle mutants in which nuclear DNA synthesis ceases within one cell cycle: cdc4, cdc7, and cdc28, which are defective in the initiation of nuclear DNA synthesis, and cdc14 and cdc23, which are defective in nuclear division. The products of these genes, therefore, are apparently not required for the initiation of mitochondrial DNA replication.     

Structural change of myofibrils during mitosis of newt embryonic myocardial cells in culture

Newt embryonic myocardial cells can undergo mitosis in culture. The successive changes in the striation pattern of sarcomeres of myofibrils during mitosis were studied by polarization microscopy without fixing or killing the cells. Birefringence of well-organized striation patterns, i.e., bright A-bands and dark I-bands, was clearly visible in interphase cells and did not show any detectable changes during incubation for 3 h or more. Electron microscopy showed the presence of well-organized myofibrils with Z-bands in these interphase cells. When myocardial cells entered the mitotic stage, the birefringence of striation pattern of their myofibrils gradually changed with the pattern in small parts of the myofibrils gradually becoming indistinct (called 'indistinct striation' in this paper). These indistinct regions increased in size during the mitotic stage. In addition, in some regions of the indistinct striation, the birefringence of sarcomeres gradually decreased and finally disappeared (called 'disappearance of sarcomeres' in this paper). No myocardial cells underwent mitosis without these disruptive changes of the myofibril striation patterns. In the post-mitotic stage, the well-organized striation of the myofibrils reappeared. Electron microscopy showed disorganized sarcomeres without Z-bands in the regions of indistinct striation, and no well-organized myofibrils in the regions where the sarcomeres had disappeared. Thus the well-organized myofibrils with Z-bands became transiently disorganized at least in some parts, during mitosis. They were then reorganized into daughter myocardial cells.