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231.
祁连山地区植被特征及其分布规律 总被引:22,自引:0,他引:22
分析和讨论了祁连山地区主要植被类型及其分布特征。祁连山地区随着青藏高原的强烈隆升表现为整体抬升,植被具有明显的生态地理边缘效应特征和高原地带性规律。该区植被虽然受到四周的较大影响,但各类高寒植被占有绝对优势,表现出与青藏高原植被整体明显的相似性和广泛的一致性。另一方面,本区植被也有其特殊性及与高原面存在一些差异。因此,建议把祁连山地区做为青藏高原植被区的次一级独立单元 相似文献
232.
目前,对胚状体发生过程中的生理生化研究表明,这一过程伴随有核酸、蛋白质等大分子物质合成速度的增加及与胚胎发生有关的特异性蛋白的合成;一些同工酶,如过氧化物酶、脂酶、细胞色素氧化酶和谷氨酸脱氢酶 相似文献
233.
Haiman Mu Haiwen Liu Jiayi Zhang Jianhua Huang Chen Zhu Yue Lu Yueping Shi Yi Wang 《Journal of cellular and molecular medicine》2019,23(3):2174-2183
In addition to the known antitumour effects of ursolic acid (UA), increasing evidence indicates that this molecule plays a role in cardiac protection. In this study, the effects of ursolic acid on the heart in mice treated with doxorubicin (DOX) were assessed. The results showed that ursolic acid improved left ventrical fractional shortening (LVFS) and left ventrical ejection fraction (LVEF) of the heart, increased nitrogen oxide (NO) levels, inhibited reactive oxygen species (ROS) production and decreased cardiac apoptosis in mice treated with doxorubicin. Mechanistically, ursolic acid increased AKT and endothelial nitric‐oxide synthase (eNOS) phosphorylation levels, and enhanced eNOS expression, while inhibiting doxorubicin induced eNOS uncoupling through NADPH oxidase 4 (NOX4) down‐regulation. These effects of ursolic acid resulted in heart protection from doxorubicin‐induced injury. Therefore, ursolic acid may be considered a potential therapeutic agent for doxorubicin‐associated cardiac toxicity in clinical practice. 相似文献
234.
Changtian Pan Dandan Yang Xiaolin Zhao Chen Jiao Yanqiu Yan Anthony Tumbeh Lamin‐Samu Qiaomei Wang Xiangyang Xu Zhangjun Fei Gang Lu 《Plant, cell & environment》2019,42(4):1205-1221
High temperature (HT) is becoming an increasingly serious factor in limiting crop production with global climate change. During hot seasons, owing to prevailing HT, cultivated tomatoes are prone to exhibiting stigma exsertion, which hampers pollination and causes fruit set failure. However, the underlying regulatory mechanisms of the HT‐induced stigma exsertion remain largely unknown. Here, we demonstrate that stigma exsertion induced by HT in cultivated tomato is caused by more seriously shortened stamens than pistils, which is different from the stigma exsertion observed in wild tomato species. Under the HT condition, the different responses of pectin, sugar, expansin, and cyclin cause cell wall remodelling and differentially localized cell division and selective cell enlargement, which further determine the lengths of stamens and pistils. In addition, auxin and jasmonate (JA) are implicated in regulating cell division and cell expansion in stamens and pistils, and exogenous JA instead of auxin treatment can effectively rescue tomato stigma exsertion through regulating the JA/COI1 signalling pathway. Our findings provide a better understanding of stigma exsertions under the HT condition in tomato and uncover a new function of JA in improving plant abiotic stress tolerance. 相似文献
235.
【目的】γ-丁基甜菜碱羟化酶是生物体内合成L-肉碱的关键酶。从假单胞菌(Pseudomonas sp.)L-1中克隆γ-丁基甜菜碱羟化酶基因,实现其在大肠杆菌(Escherichia coli)中的高效表达,并对表达产物进行酶学性质分析,为生物转化生产L-肉碱奠定基础。【方法】通过PCR克隆γ-丁基甜菜碱羟化酶基因,并将其开放阅读框(ORF)克隆至融合表达载体pET-15b;表达产物经His.Bind Resin纯化后对BBH进行酶学性质及三维空间结构分析;并以静止细胞进行L-肉碱的转化。【结果】成功地克隆了一个γ-丁基甜菜碱羟化酶基因bbh(GenBank:JQ250036),并实现了其在E.coli中的高效表达。融合蛋白以同源二聚体的形式存在,单个亚基的分子量约46.5 kDa,最适反应温度为30℃,最适反应pH为7.5。该酶在45℃以下稳定。在pH6.0时该酶有最高的pH稳定性。以表达bbh基因的重组大肠杆菌静止细胞转化L-肉碱,L-肉碱产量可达12.7mmol/L。【结论】Pseudomonas sp.L-1γ-丁基甜菜碱羟化酶与现有报道的bbh基因有较大的差异。由该基因表达的γ-丁基甜菜碱羟化酶能有效地转化γ-丁基甜菜碱生成L-肉碱。本研究不仅丰富了γ-丁基甜菜碱羟化酶基因资源,而且为L-肉碱的生物转化提供了一种新的转化方案。 相似文献
236.
Paraoxonase is an HDL-associated enzyme that plays a preventive role against oxidative stress, which is thought to contribute
to cancer development. PON1 activity varies widely among individuals, which is in part related to two common nonsynonymous
polymorphisms in the PON1 gene (Q192R and L55M). The polymorphisms in PON1 have been implicated in cancer risk. However, results
from the studies to date have been conflicting. To clarify the association, a meta-analysis was performed for 7,073 cases
and 9,520 controls from 25 published case–control studies. Odds ratios (ORs) with 95% confidence intervals (CIs) were used
to assess the strength of the association. Significant associations between PON1-L55M but not Q192R polymorphism and total
cancer were observed from all the comparisons. In stratified analyses, PON1-55M allele was a risk factor for breast cancer.
Similarly, increased risk was observed for prostate cancer (OR = 1.18, 95% CI: 1.01–1.36, P
heterogeneity = 0.260) and Caucasian population (OR = 1.18, 95% CI: 1.02–1.38, P
heterogeneity = 0.1) of the LM genotype, compared with the LL genotype. For PON1-Q192R polymorphism, PON1-192R allele was a decreased risk
factor for cancer in the Asian group (RR vs QQ: OR = 0.61, 95% CI: 0.38–0.98, P
heterogeneity = 0.268; QR vs QQ: OR = 0.71, 95% CI: 0.52–0.96, P
heterogeneity = 0.130; RR + QR vs QQ: OR = 0.71, 95% CI: 0.53–0.95, P
heterogeneity = 0.135). Although some modest bias could not be eliminated, this meta-analysis suggests that the PON1-55M allele is a risk factor for the development of cancer, in particular for breast cancer. Future studies with larger sample
sizes are warranted to further evaluate these associations. 相似文献
237.
大比例尺土壤保持服务制图分级方法研究 总被引:2,自引:1,他引:2
科学地编制生态系统服务空间分布图,有助于识别生态系统优先保护热点及空缺,能够为国土安全规划提供基础信息。但由于缺乏统一科学的生态系统服务分级方法,生态系统服务分布图的展示效果和制图效率都受到限制。不恰当的分级制图会误导决策者对生态系统服务空间分布特征的判断,增加生态保护决策的不确定性。以构建生态服务制图分级标准为目标,对我国6个典型县区的土壤保持服务数据展开1:25万比例尺制图分级案例研究。采用分级精度、面积均衡性、极差一致性、空间自相关一致性4个分级质量评价指标评价并比较了目前地图编制中常用的自然断点法、几何间隔法、累积比例法、等差法、分位数法5种分级算法的分级制图效果。结果表明,6个县区有相似的土壤保持服务分布特征:低值区覆盖面积大,高值区覆盖面积小。各县区土壤保持服务制图最优分级方法有差异:延庆区、丰满区最优分级方法为自然断点法;永靖县、天山区、安宁市最优分级方法为累积比例法;富阳区最优分级方法为几何间隔法。各分级方法中,累积比例法在6个县区综合制图效果最优或接近最优,适用性最好,能够较好的刻画各县区的土壤保持服务空间分布特征。本文提出的分级评价方法及其结果,可为生态系统土壤保持服务制图规范化和自动化提供科学依据。 相似文献
238.
239.
Yifeng Miao Yongming Qiu Yuchang Lin Zengli Miao Jing Zhang Xiaojie Lu 《Molecular biology reports》2011,38(5):3235-3242
Pyruvate, an endogenous metabolite of glycolysis, is an anti-toxicity agent. Recent studies have suggested possible roles
for pyruvate in protecting CNS neurons from excitotoxic and metabolic insults. Utilizing cultures derived from embryonic rat
cortex, the studies presented in this paper indicate that an astroglia-mediated mechanism is involved in the neuroprotective
effects of pyruvate against glutamate toxicity. Glutamate-induced toxicity could be reversed by pyruvate in a mixed culture
of cortex cells. Importantly, in pure neuronal cultures from the same tissue, pyruvate failed to protect against glutamate
toxicity. Addition of astroglia to the pure neuronal cultures restores the ability of pyruvate to protect neurons from glutamate-induced
toxicity. Our results further suggest that pyruvate can induce glia to up-regulate the synthesis of glutathione (GSH), an
antioxidant that protects cells from toxins such as free radicals. Taken together, our data suggest that astroglia in mixed
cultures are essential for mediating the effects of pyruvate, revealing a novel mechanism by which pyruvate, an important
intermediate of tricarboxylic acid cycle in the body, may act to protect neurons from damage during insults such as brain
ischemia. 相似文献
240.
Liu T Yu H Zhang C Lu M Piao Y Ohba M Tang M Yuan X Wei S Wang K Ma A Feng X Qin S Mukai C Tsuji A Jin F 《Applied and environmental microbiology》2012,78(13):4752-4754
A novel rutin-α-L-rhamnosidase hydrolyzing α-L-rhamnoside of rutin, naringin, and hesperidin was purified and characterized from Aspergillus niger DLFCC-90, and the gene encoding this enzyme, which is highly homologous to the α-amylase gene, was cloned and expressed in Pichia pastoris GS115. The novel enzyme was classified in glycoside-hydrolase (GH) family 13. 相似文献