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991.
Beatrice L. Harrison Day Madeline R. Carins-Murphy Timothy J. Brodribb 《Plant, cell & environment》2022,45(1):69-79
Reproductive success largely defines the fitness of plant species. Understanding how heat and drought affect plant reproduction is thus key to predicting future plant fitness under rising global temperatures. Recent work suggests reproductive tissues are highly vulnerable to water stress in perennial plants where reproductive sacrifice could preserve plant survival. However, most crop species are annuals where such a strategy would theoretically reduce fitness. We examined the reproductive strategy of tomato (Solanum lycopersicum var. Rheinlands Ruhm) to determine whether water supply to fruits is prioritized above vegetative tissues during drought. Using optical methods, we mapped xylem cavitation and tissue shrinkage in vegetative and reproductive organs during dehydration to determine the priority of water flow under acute water stress. Stems and peduncles of tomato showed significantly greater xylem cavitation resistance than leaves. This maintenance of intact water supply enabled tomato fruit to continue to expand during acute water stress, utilizing xylem water made available by tissue collapse and early cavitation of leaves. Here, tomato plants prioritize water supply to reproductive tissues, maintaining fruit development under drought conditions. These results emphasize the critical role of water transport in shaping life history and suggest a broad relevance of hydraulic prioritization in plant ecology. 相似文献
992.
Shaik Nayab Rasool Shaik Shabeena Culala Rajasekharaudayar Kesavulu Singarapu Babu Asanapuram Mohan Babu Vemula Venkatramu 《Luminescence》2022,37(5):784-790
Novel erbium(III) ion-doped borate-based glasses (Er3+:BCNF) by conventional melt-quenching technique were designed and synthesized. The glasses were characterized for their structural, vibrational and spectroscopic properties. The nephelauxetic ratio, bonding parameters, and Judd–Ofelt (JO) intensity parameters (Ωλ λ = 2, 4 and 6) were determined by using absorption spectrum of 1 mol% Er2O3 doped glass. These JO parameters were utilized to derive radiative properties for various excited states of erbium(III) ions. Emission cross-section for 4I13/2 → 4I15/2 transition of erbium(III) ions was computed through McCumber theory. The decay curves for (2H11/2, 4S3/2) and 4I13/2 levels were recorded and analysed. All the results of Er3+:BCNF glasses revealed that the studied glasses are efficient and thermally stable and could be suitable for display devices, optical amplification and green laser applications. 相似文献
993.
994.
近场光学显微镜结合量子点标记人胃腺癌SGC-7901细胞靶点的观察 总被引:3,自引:0,他引:3
扫描近场光学显微镜突破衍射极限,具有纳米量级的空间分辨率,量子点(QD s)标记有荧光强度高且抗光漂白能力强等优点。结合上述两种技术,对人胃腺癌SGC-7901细胞膜表面特异性结合的叶酸受体(FR)进行成像探测,获得了叶酸受体在SGC-7901细胞膜表面上的分布,以及细胞内化外源性叶酸过程中叶酸受体在细胞膜表面的分布变化,成像的光学分辨率达到120 nm。实验结果表明:特异性结合的叶酸受体在SGC-7901细胞膜表面的分布,绝大部分是以聚集体的形式存在。随着SGC-7901细胞内化叶酸量的增加,叶酸受体在细胞膜表面的分布密度逐渐降低,并在经过120 m in左右趋于稳定。上述方法和手段为实现单细胞水平上靶点分布和变化的长期监测,肿瘤细胞内化受体的机制研究提供了新的技术途径。 相似文献
995.
近场光学显微镜具有nm量级的空间分辨率,量子点(quantum dots,QDs)荧光探针具有激发谱宽、发射谱线窄、荧光强度高、抗光漂白和稳定性高等优点,两者结合用于生物大分子的成像探测和识别具有广泛的应用前景。用近场光学显微镜对链霉亲和素偶联的QDs进行近场荧光激发,并对其荧光发射特性和光稳定性进行研究,结果表明:近场光学显微镜nm量级的空间分辨率,可以同时观察到了QDs的单体、二聚体和三聚体;QDs的荧光发射强度高,近场荧光像对比度好,单量子点的荧光半高宽达到25nm;对一定入射波长的单色激发光,QDs的近场荧光强度随着激发功率密度的增加线性增加,并很快趋于稳定。与传统的荧光染料如异硫氰酸荧光素相比,QDs的稳定性非常好,在激发功率密度为300W/cm2的近场辐射下,量子点的荧光强度超过6h基本保持不变,其抗光漂白能力远远高于普通荧光染料。 相似文献
996.
检测食源性致病菌的生物传感器 总被引:2,自引:0,他引:2
大肠埃希氏菌、李斯特氏菌和鼠伤寒沙门氏菌等几种食源性致病菌不仅威胁到人们的 生命安全,还会造成巨大的社会经济损失.生物传感器是将生物识别元件和信号转换元件紧 密结合,从而检测目标化合物的分析装置.生物传感器在致病菌检测方面具有分析速度快、 灵敏度高、专一性强等特点;可分为光学式、电化学式、压电式生物传感器等;在检测食源 性致病菌方面生物传感器表现出能够满足实际应用的发展潜力,但是生物传感器目前仍面临 并需要解决一些问题,这也是生物传感器从实验室到市场如此缓慢的原因.最后提出了实际 检测应用中对生物传感器的要求. 相似文献
997.
Bradbury MS Panagiotakos G Chan BK Tomishima M Zanzonico P Vider J Ponomarev V Studer L Tabar V 《Journal of neurochemistry》2007,102(6):2029-2039
Pre-clinical efforts of grafting human embryonic stem cell (hESC)-derived neural precursors have been hampered by problems ranging from graft rejection to overgrowth and tumor formation. The ability to detect such potential complications sensitively and reliably in clinically relevant contexts will rest upon the implementation of suitable non-invasive imaging technologies for continuously probing graft survival, proliferation, and migration. Neural precursors were transduced ex vivo using a lentiviral-mediated gene delivery system expressing firefly D-luciferase, under the control of a cytomegalovirus promoter. Transduced cells revealed no loss of cellular morphology, proliferative capacity, or neural phenotype in vitro. As a novel approach to monitoring the fate of human grafts within the living brain, we adapted optical bioluminescence imaging to assess long-term graft viability in immunodeficient mouse models transplanted with genetically engineered human neural precursor cells. We additionally applied this technology to immunocompetent models for detecting and characterizing the time course of graft rejection. Using this strategy, we define statistically relevant imaging criteria that can predict graft rejection or overgrowth. In conclusion, our data suggest that optical bioluminescence imaging can serve as an essential tool for the development of hESC-based grafting strategies in the CNS. 相似文献
998.
Coordinated variation has been reported for leaf structure, composition and function, across and within species, and theoretically
should occur across populations of a species that span an extensive environmental range. We focused on Hawaiian keystone tree
species Metrosideros polymorpha, specifically, 13-year old trees grown (2–4 m tall) in a common garden (approximately 1 ha field with 2–3 m between trees)
from seeds collected from 14 populations along an altitude–soil age gradient. We determined the genetic component of relationships
among specific leaf area (SLA), the concentrations of nitrogen (N) and pigments (chlorophylls, carotenoids, and anthocyanins),
and photosynthetic light-use efficiency. These traits showed strong ecotypic variation; SLA declined 35% with increasing source
elevation, and area-based concentrations of N, Chl a + b and Car increased by 50, 109 and 96%, respectively. Concentrations expressed on a mass basis were not well related to source
elevation. Pigment ratios expressed covariation that suggested an increased capacity for light harvesting at higher source
elevation; Chl/N and Car/Chl increased with source elevation, whereas Chl a/b declined; Chl a/b was higher for populations on younger soil, suggesting optimization for low N supply. Parallel trends were found for the
photosynthetic reactions; light-saturated quantum yield of photosystem II (Φ
PSII) and electron transport rate (ETR) increased with source elevation. Correlations of the concentrations of photosynthetic
pigments, pigment ratios, and photosynthetic function across the ecotypes indicated a stoichiometric coordination of the components
of the light-harvesting antennae and reaction centers. The constellation of coordinated morphological, biochemical and physiological
properties was expressed in the leaf reflectance and transmittance properties in the visible and near-infrared wavelength
region (400–950 nm), providing an integrated metric of leaf status among and between plant phenotypes. 相似文献
999.
本研究利用光学相干层析术OCT对泼尼松龙诱导的斑马鱼骨质疏松模型进行活体成像,并结合电镜能谱技术定量分析斑马鱼模型骨质的钙磷元素含量及分布情况,共同探讨OCT方法在基于斑马鱼模型开展的骨质疏松研究中的使用价值。选取40条3月龄野生型斑马鱼暴露于50μmol/L泼尼松龙溶液和含0. 5%DMSO的溶液中(对照组),28. 5℃下培养,分别于第5、10、20天取出浸药组和对照组进行OCT活体成像,比较两者光散射特征。在每个时间点的成像之后,将浸药组的5条斑马鱼处死,然后取颅骨进行元素含量电镜扫描能谱分析。本研究利用50μmol/L泼尼松龙溶液培养斑马鱼至第20天,成功构建了斑马鱼骨质疏松模型。与对照组相比,模型组活体OCT成像显示骨组织光散射减弱,光子量明显减少,呈不均匀分布。能谱元素检查结果说明颅骨内所含钙、磷比例明显下降,证实骨质疏松发生,骨量减少。OCT成像方法在对斑马鱼骨质疏松模型进行活体、实时、无创等研究方面具有重要价值,本试验也为骨质疏松疾病的研究和药物筛选等方面提供了新的有效的方法。 相似文献
1000.
Steoporosis is a skeletal disorder that compromises bone resistance and its diagnosis is usually performed using dual energy X‐ray absorptiometry. Thus, the search for efficient diagnostic methods that do not involve the emission of ionizing radiation is necessary. This study proposed to use the Optical Coherence Tomography (OCT) to evaluate osteoporosis in alveolar bone. Osteoporosis lesions is simulated in vitro in porcine bones, and imaging is performed by OCT and micro‐computed tomography (micro‐CT). A developed algorithm is proposed to calculate the optical attenuation coefficient ( μ t), mean optical attenuation coefficient (), integrated reflectivity (ΔR) and bone density ( BD). The , ΔR and BD parameters shows a good correlation to micro‐CT parameters (bone volume/tissue volume and total porosity). The μ t and methods are negatively impacted by non‐uniform intensities distribution in osteoporosis images. In conclusion, BD and ΔR analysis demonstrates to be potential techniques for diagnosis and monitoring of osteoporosis using OCT. 相似文献