共查询到20条相似文献，搜索用时 15 毫秒
1.
Perceptual deficits and the activity of the color-opponent and broad-band pathways at isoluminance 总被引：2，自引：0，他引：2
N K Logothetis P H Schiller E R Charles A C Hurlbert 《Science (New York, N.Y.)》1990,247(4939):214-217
The deficits in texture, motion, and depth perception incurred in monkeys at isoluminance were compared with the responses of neurons of the color-opponent and broad-band systems in the lateral geniculate nucleus. Texture perception, assumed to be carried by the color-opponent system, and motion and depth perception, ascribed to the broad-band pathway, were all found to be compromised but not abolished at isoluminance. Correspondingly, both the color-opponent and the broad-band systems were affected at isoluminance, but the activity of the neurons in neither system was abolished. These results suggest that impairment of visual capacities at isoluminance cannot be uniquely attributed to either of these systems and that isoluminant stimuli are inappropriate for the psychophysical isolation of these pathways. 相似文献
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UV-B（280nm～320nm）、UV-A（320nm～390nm）和蓝光（390nm-500nm）经不同光受体和信号传递途径控制植物发育的各个方面。已知的蓝光／UV-A受体有隐花色素CRY1和CRY2，向光性受体有趋光素。氧化还原过程在隐花色素和趋光素信号转导过程中起重要作用。专一的UV-B光受体尚未被鉴定出，存在许多可能的UV-B信号传递途径．拟南芥查尔酮合成酶（CHS）的紫外光和蓝光转录调控成为研究热点。光受体突变体实验表明存在不同的UV-A／蓝光和UV-B光感知系统调控CHS的表达。拟南芥细胞悬浮培养物实验表明UV-B和CRY1信号传递途径在动力学上和药理学上不同。影响诱导CHS转录的启动子元件和转录因子现已被鉴定出。UV-B、隐花色素和光敏色素信号传递途径之间的相互作用调控CHS表达。UV-B途径与UV-A／蓝光途径的协同相互作用使CHS最大量表达。另外，专一的光敏色素经不同的增强和相巨作用正调控CRY1途径，负调控UV-B途径。 相似文献
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Zhuo Y Zhou TG Rao HY Wang JJ Meng M Chen M Zhou C Chen L 《Science (New York, N.Y.)》2003,299(5605):417-420
Objects displaced intermittently across the visual field will nonetheless give an illusion of continuous motion [called apparent motion (AM)] under many common conditions. It is believed that form perception is of minor importance in determining AM, and that AM is mediated by motion-sensitive areas in the "where" pathway of the cortex. However, form and motion typically interact in specific ways when natural objects move through the environment. We used functional magnetic resonance imaging to measure cortical activation to long-range AM, compared to short-range AM and flicker, while we varied stability of structural differences between forms. Long-range AM activated the anterior-temporal lobe in the visual ventral pathway, and the response varied according to the form stability. The results suggest that long-range AM is associated with neural systems for form perception. 相似文献
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Nagata T Koyanagi M Tsukamoto H Saeki S Isono K Shichida Y Tokunaga F Kinoshita M Arikawa K Terakita A 《Science (New York, N.Y.)》2012,335(6067):469-471
The principal eyes of jumping spiders have a unique retina with four tiered photoreceptor layers, on each of which light of different wavelengths is focused by a lens with appreciable chromatic aberration. We found that all photoreceptors in both the deepest and second-deepest layers contain a green-sensitive visual pigment, although green light is only focused on the deepest layer. This mismatch indicates that the second-deepest layer always receives defocused images, which contain depth information of the scene in optical theory. Behavioral experiments revealed that depth perception in the spider was affected by the wavelength of the illuminating light, which affects the amount of defocus in the images resulting from chromatic aberration. Therefore, we propose a depth perception mechanism based on how much the retinal image is defocused. 相似文献
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Much is known about the pathways from photoreceptors to higher visual areas in the brain. However, how we become aware of what we see or of having seen at all is a problem that has eluded neuroscience. Recordings from macaque V1 during deactivation of MT+/V5 and psychophysical studies of perceptual integration suggest that feedback from secondary visual areas to V1 is necessary for visual awareness. We used transcranial magnetic stimulation to probe the timing and function of feedback from human area MT+/V5 to V1 and found its action to be early and critical for awareness of visual motion. 相似文献
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植物低温信号的感知、转导与转录调控 总被引：2，自引：0，他引：2
低温是植物生长的主要环境胁迫因子之一。植物对低温的应激是一个复杂的过程,包括低温信号的感知、信号转导和转录调控等阶段。低温可以通过质膜流动性的改变被质膜感知,也可以通过质膜上的钙离子通透性通道、组氨酸激酶、受体激酶和磷酸酯酶感知。低温信号转导包括钙信号途径和其他信号途径,其中钙信号途径是低温应答过程中重要的信号途径。在此途径中,因低温增加的胞质钙离子能被CDPK、磷酸酶和MAPK识别并传导;其他信号途径主要与ABA有关。低温信号最终将启动CBF和非CBF介导的转录调控,提高植物的低温抗性。 相似文献
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Each ommatidium in the compound eye of the Drosophila mutant sevenless lacks photoreceptor number seven (R7) from the normal ommatidial complement of eight photoreceptors. A comparison of mutant and normal development reveals that this deficit is caused by the cell-specific transformation of the cell normally fated to produce R7 into a lens-secreting accessory cell, a cone cell. 相似文献
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MAPK级联信号途径在植物病原真菌的生长、发育、繁殖及致病性等方面起着重要作用。根据已公布的5个水稻纹枯病菌(Rhizoctonia solani)全基因组数据利用生物信息学方法对该病原菌的MAPK(mitogenactivated protein kinase)级联信号途径基因进行了鉴定,并预测水稻纹枯病菌MAPK级联途径图。蛋白结构域和motif分析结果表明,水稻纹枯病菌的MAPK信号途径基因均含有丝氨酸/苏氨酸蛋白激酶结构域,并且基因序列具有较高保守性。多重序列比对结果表明,水稻纹枯病菌基因组中存在11个MAPKKK基因,分属于Ste11、Bck1和Ssk2类;10个MAPKK基因,分别为Ste7、Pbs2及Mkk1类;12个MAPK基因,被分类为Kss1/Fus3、Hog1、Slt2和Ime2。在5个水稻纹枯病菌基因组中,水稻纹枯病菌(taxid:456999)和AG-3 Rhs 1 AP(taxid:1086054)基因组中存在Kss1/Fus3-MAPK、Hog1-MAPK、Slt2-MAPK和Ime2-MAPK信号通路,AG-1 IB(taxid:1108050)基因组中存在Kss1/Fus3-MAPK、Hog1-MAPK和Slt2-MAPK通路,AG-8 WAC10335(taxid:1287689)基因组中仅存在Hog1-MAPK通路,而AG-1 IA(taxid:983506)基因组中只有2个MAPKKK基因未找到完整的信号通路。依据上述研究结果预测了水稻纹枯病菌的Kss1/Fus3、Hog1、Slt2和Ime2级联途径模型,此结果为深入研究水稻纹枯病菌的MAPK家族功能奠定了重要的理论基础。 相似文献
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Light synchronizes mammalian circadian rhythms with environmental time by modulating retinal input to the circadian pacemaker-the suprachiasmatic nucleus (SCN) of the hypothalamus. Such photic entrainment requires neither rods nor cones, the only known retinal photoreceptors. Here, we show that retinal ganglion cells innervating the SCN are intrinsically photosensitive. Unlike other ganglion cells, they depolarized in response to light even when all synaptic input from rods and cones was blocked. The sensitivity, spectral tuning, and slow kinetics of this light response matched those of the photic entrainment mechanism, suggesting that these ganglion cells may be the primary photoreceptors for this system. 相似文献
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通过对四川省5个县蜂农的问卷调查,基于社会认知模型(MPPACC)分析框架,采用有序Probit模型,分析了蜂农对天气变化的感知度及其影响因素。结果显示,蜂农对于天气变化的敏感性感知、严重性感知较强,适应功效感知、自我效能感知较弱,感知到的适应成本较高;蜂农对免费天气变化信息的获取、获取渠道的多少、与其他蜂农交流的频率以及养蜂人数等均会影响蜂农对天气变化的感知,其中,免费天气信息的获取对蜂农敏感性感知、适应性功效感知、自我效能感知以及适应成本感知影响最为显著。最后,从拓宽蜂农获取天气信息的渠道、鼓励其加入农民合作组织以及增强蜂农之间的交流等方面,提出了提高蜂农对天气变化感知能力、增强应对天气变化能力的相关建议。 相似文献
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桑黄花型萎缩病是桑树重大病害之一,会对桑树产生多方面的影响。转录组可检测物种的整体转录活动,为此研究黄花型萎缩病桑树湖桑32叶片转录组的变化,并分析其中的关键UniGenes与代谢途径。结果获得8 265个具有差异表达的UniGenes,其中4 445个表达上调,3 820个表达下调。差异表达基因的GO功能显著性富集获得18 734个具有显著差异的对应关系,其中富集50条UniGenes以上的GO分类涉及了12个亚类。两样品的代谢通路富集分析显示,UniGenes参与的6大类41个亚类代谢通路中8个途径差异显著。与植物抗性基因数据库PRGDB比对,发现37类89个R基因表达模式发生了变化。这为进一步对该病原菌的致病机理研究提供了基础。 相似文献
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基于高空间分辨率卫星影像的新疆阿拉尔市棉花与枣树分类 总被引：1，自引：0，他引：1
【目的】 枣树和棉花是新疆地区的两大优势作物。利用高空间分辨率遥感影像对作物进行识别,更加快速、准确地获取枣树和棉花的种植面积及其分布区域,以利于相关部门政策的制定及农作物的精确管理。【方法】 本文以新疆阿拉尔市主要农作物为研究对象,运用基于像素与面向对象的遥感影像分类方法,通过比较光谱角制图（SAM）、支持向量机（SVM）、CART决策树（DTs）、随机森林（RF）这4种机器学习算法在高空间分辨率卫星影像分类中的作物识别精度,探究影像获取时期（2016-05-10、2016-09-07、2016-10-08）及面向对象的信息提取技术对作物分类精度的影响。【结果】 5月份影像（即棉花覆膜期影像）作物分类精度最高,10月份影像次之,9月份影像最差;与基于像素的作物分类方法相比,面向对象的作物分类方法可以使各时期的作物分类总体精度得到一定提高（除SAM之外）,各时期分类精度分别提高了4.83%、7.77%、7.22%,最高分类精度分别为93.52%（2016-05-10）、85.36%（2016-09-07）、88.88%（2016-10-08）,均实现了较好的作物分类效果。【结论】 5月份（棉花覆膜期）影像对棉花和枣树分类效果最好,该时期的棉花被地膜覆盖,且枣树表现出明显的植被光谱特性,两种作物生长早期呈现出差异化的光谱特征,因此棉花和枣树的遥感识别应在作物生长早期进行;面向对象的分类方法可以综合运用光谱、纹理及空间信息,特别是纹理信息的加入,可以取得比基于像素方法更高的分类精度,且提供一种高效提取田块边界的手段,对当地农田信息化管理具有重要应用价值。在棉花和枣树识别过程中,纹理特征的重要性高于光谱和空间特征,红光和绿光波段在所有波段中对棉花和枣树的识别贡献最大。 相似文献
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TRAIL与5-FU联合诱导白血病细胞凋亡的分子机理研究 总被引：1，自引：1，他引：0
用凋亡诱导配体（TRAIL）及5-氟尿嘧啶（5-FU）联合刺激Jurkat细胞36h,以诱导细胞凋亡;用流式细胞术和MTS比色法检测细胞存活率,计算细胞凋亡率;用免疫印迹（western b-lotting）检测p53的表达和胱天肽酶-3、胱天肽酶-8的变化。结果表明：5-FU能有效增加TRAIL诱导的Jurkat细胞凋亡,并伴随p53表达增加及胱天肽酶-3和胱天肽酶-8的活性增加,提示TRAIL和5-FU联合诱导的T淋巴白血病细胞凋亡的分子机制与p53及胱天肽酶-3、胱天肽酶-8有关,为TRAIL和5-FU联合用于治疗白血病提供理论依据。 相似文献
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Fernald RD 《Science (New York, N.Y.)》2006,313(5795):1914-1918
Light has been exploited for information by organisms through the evolution of photoreceptors and, ultimately, eyes in animals. Only a handful of eye types exist because the physics of light constrains photodetection. In the past few years, genetic tools have revealed several parallel pathways through which light guides behavior and have provided insights into the convergent evolution of eyes. The gene encoding opsin (the primary phototransduction protein) and some developmental genes had very early origins and were recruited repeatedly during eye evolution. Eye lens proteins arose separately and make up a diverse group, many of which were co-opted from other functions. A major challenge now is understanding how newly discovered pathways for processing light evolved and how they collaborate with eyes to harvest information from light. 相似文献
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Meléndez A Tallóczy Z Seaman M Eskelinen EL Hall DH Levine B 《Science (New York, N.Y.)》2003,301(5638):1387-1391
Both dauer formation (a stage of developmental arrest) and adult life-span in Caenorhabditis elegans are negatively regulated by insulin-like signaling, but little is known about cellular pathways that mediate these processes. Autophagy, through the sequestration and delivery of cargo to the lysosomes, is the major route for degrading long-lived proteins and cytoplasmic organelles in eukaryotic cells. Using nematodes with a loss-of-function mutation in the insulin-like signaling pathway, we show that bec-1, the C. elegans ortholog of the yeast and mammalian autophagy gene APG6/VPS30/beclin1, is essential for normal dauer morphogenesis and life-span extension. Dauer formation is associated with increased autophagy and also requires C. elegans orthologs of the yeast autophagy genes APG1, APG7, APG8, and AUT10. Thus, autophagy is a cellular pathway essential for dauer development and life-span extension in C. elegans. 相似文献
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【目的】通过对意大利蜜蜂（Apis mellifera ligustica,简称意蜂）工蜂中肠响应东方蜜蜂微孢子虫（Nosema ceranae）胁迫的差异表达基因（differentially expressed gene,DEG）及免疫通路进行深入细致的分析,揭示宿主的细胞和体液免疫应答,为关键免疫应答基因的筛选及功能研究打下基础。【方法】基于前期获得的正常及东方蜜蜂微孢子虫胁迫的意蜂7日龄和10日龄工蜂中肠（Am7CK、Am7T、Am10CK、Am10T）转录组数据,按照FDR≤1,P≤0.05和|log2 fold change|≥1的标准筛选出各组的DEG,利用相关生物信息学软件对DEG进行Pearson相关性分析、Venn分析、GO分类和KEGG代谢通路富集分析,进而对免疫通路富集基因进行统计和分析,利用实时荧光定量PCR（real-time quantitative PCR,RT-qPCR）验证转录组数据的可靠性。【结果】 差异分析结果显示,Am7CK vs Am7T比较组包含472个上调基因和385个下调基因;Am10CK vs Am10T比较组包含611个上调基因和360个下调基因。Venn分析结果显示,两个比较组特有的DEG分别为739和853个,共有的DEG为118个。GO分类结果显示,Am7CK vs Am7T比较组中上调和下调基因分别涉及23和29个功能条目,其中富集上调基因数最多的前5位分别为结合、催化活性、代谢进程、细胞进程和单组织进程;富集下调基因数最多的前5位分别为代谢进程、单组织进程、催化活性、细胞进程和结合。Am10CK vs Am10T比较组中上调和下调基因分别涉及36和26个功能条目,其中富集上调基因数最多的前5位分别为单组织进程、结合、细胞进程、催化活性和代谢活性;富集下调基因数最多的前5位分别为结合、细胞进程、催化活性、代谢进程和单组织进程。KEGG代谢通路富集分析结果显示,Am7CK vs Am7T比较组中上调和下调基因分别富集在38和33条代谢通路,富集上调基因数最多的前5条分别为胆汁分泌、内质网蛋白加工、泛素介导的蛋白水解、PI3K-Akt信号通路和神经营养因子信号通路;富集下调基因数最多的前5条分别为胞质DNA传感通路、嘌呤代谢、嘧啶代谢、RNA聚合酶和核糖体;涉及泛素介导的蛋白水解等3条细胞免疫通路,以及PI3K-Akt信号通路等7条体液免疫通路。Am10CK vs Am10T比较组中上调和下调基因分别富集在54和43条代谢通路,富集上调基因数最多的前5条分别为Hippo信号通路、药物代谢-细胞色素P450、P450对外源物质的代谢、泛素介导的蛋白水解和鞘脂类代谢;富集下调基因数最多的前5条分别为mRNA监测、鞘脂类信号通路、果糖和甘露糖代谢、半乳糖代谢和鞘脂类代谢;涉及泛素介导的蛋白水解等7条细胞免疫通路,以及NF-κB信号通路等2条体液免疫通路。RT-qPCR验证结果显示6个随机挑选的DEG的表达量变化趋势与测序结果一致,证实了本研究中测序数据的可靠性。进一步分析发现意蜂7日龄和10日龄工蜂中肠的NF-κB信号通路均被东方蜜蜂微孢子虫激活,随即启动了3种抗菌肽apidaecin、defensin-1和hymenoptaecin的合成,体现了它们在宿主抵御东方蜜蜂微孢子虫入侵中的重要性。【结论】在转录组水平解析了意蜂工蜂中肠对东方蜜蜂微孢子虫的免疫应答,揭示宿主在胁迫前期同时作出细胞和体液免疫应答,前者可能在抵御病原入侵方面发挥主要作用;宿主的细胞免疫在胁迫后期持续增强,但体液免疫较大程度地减弱;泛素介导的蛋白水解通路及富集DEG,NF-κB信号通路及富集DEG,以及抗菌肽编码基因apidaecin、defensin-1和hymenoptaecin可能在意蜂工蜂对东方蜜蜂微孢子虫的免疫应答中起到关键作用。 相似文献
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The relation between terminal mitosis and the events that determine the developmental fate of embryonic precursor cells is not well understood. This relation has now been investigated with [3H]thymidine autoradiography to determine the time of cell birth and with a culture system that allows the testing of the developmental potential of cells isolated from the chick embryo retina. Contrary to the situation in vivo, where neuronal differentiation always precedes photoreceptor differentiation, photoreceptor differentiation occurs prematurely and precedes neuronal differentiation when precursor cells are isolated from the retina at early embryonic stages. Thus, cells born by embryonic day 5 (ED-5) give rise predominantly to photoreceptors when isolated for culture on ED-6 but develop mainly as neurons when isolated on ED-8. This suggests that retinal precursor cells retain after terminal mitosis the capacity to develop either as neurons or as photoreceptors. Moreover, photoreceptor differentiation appears to represent a constitutive or "default" pathway that precursor cells follow in the absence of neuron-inducing signals. 相似文献