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951.
952.
用未标记氧化修饰极低密度脂蛋白(ox-VLDL)、n-VLDL、乙酰LDL竞争125I-ox-VLDL与巨噬细胞的结合。在浓度为200μg蛋白/ml时,分别抑制标记ox-VLDL结合量的70~78%、60~70%和25~35%。用未标记ox-VLDL竟争125I-n-VLDL与巨噬细胞的结合,能抑制77%。结果说明ox-VLDL主要通过n-VLDL受体进入巨噬细胞。以ox-VLDL与ox-LDL进行交叉竞争时,ox-VLDL与ox-LDL自身可抑制标记ox-VLDL或ox-LDL的75~82%,而ox-VLDL或ox-LDL的交叉竞争仅38~40%。表明ox-VLDL与ox-LDL有部分共同的构象与巨噬细胞的脂蛋白受体结合,但ox-VLDL不是经ox-LDL受体被巨噬细胞摄取。 相似文献
953.
954.
超微粒TiO2对U937细胞光杀伤效应及机理研究 总被引:7,自引:0,他引:7
超微粒TiO2经光催化氧化后对U937白血病细胞有明显的杀伤作用,DNA琼脂糖凝胶电泳图证明了光激发TiO2能够损伤细胞内的DNA,从而导致细胞死亡,提出了一种杀伤癌细胞的新思路. 相似文献
955.
Vertical CO2 profiles (between 0.02 and 14.0 m) were studied in forest canopies of Pinus contorta, Populus tremuloides, and in a riparian forest with Acer negundo and Acer grandidentatum during two consecutive growing seasons. Profiles, measured continuously during 1- to 13-day periods in four to five stands differing in overstorey canopy area index (CAI < 4.5; including leaves, branches and stems), were well stratified, with highest [CO2] just above the forest floor. Canopy [CO2] profiles were influenced by stand structure (CAI, presence of understorey vegetation), and were highly dependent on vegetation type (deciduous and evergreen). A doubling of CAI in Acer spp. and P. tremuloides stands did not show an effect on upper canopy [CO2], when turbulent mixing was high. However, increasing understorey biomass in Acer spp. stands had a profound effect on lower canopy [CO2]. In open stands with a vigorous understorey layer, higher soil respiration rates were offset by increased understorey gas exchange, resulting in [CO2] below those of the convective boundary layer (CBL). Midday depletions up to 20 ppmv below CBL values could be frequently observed in deciduous canopies. In evergreen canopies, [CO2] stayed generally above the CBL background values, [CO2] profiles were more uniform, and gradients were smaller than in deciduous stands with similar CAI. Seasonal changes of canopy [CO2] reflected changes in soil respiration rates as well as plant phenology and gas exchange of both dominant tree and understorey vegetation. Seasonal patterns were less pronounced in evergreen than in deciduous forests. 相似文献
956.
Selective suppression of rod signal transmission by cobalt ions was reported in carp retina. Using 10 μnol/L Co2+, rod-driven horizontal cells were hyperpolarized and light responses were completely suppressed in superfused, isolated retina,
while cone-driven horizontal cells were almost unaffected. Similarly, scotopic electroretinographic bwave was suppressed by
10 μnol/L Co2+, while the photopic b-wave remained unaffected. Furthermore, the glutamate-isolated receptor potential (PIII) was not altered
by low Co2+ under dark-adapted conditions. Other divalent ions with high affinity to calcium channels, such as cadmium and manganese
ions, did not show similar suppressive effect on the rod horizontal cells. When rod horizontal cells were hyperpolarized by
10 μnol/L Co2+, the use of 3 mmol/L glutamate caused a significant depolarization of the cells, indicating that Co2+ application did not impair the ability of these cells to respond to glutamate. On the other hand, application of 200 μnol/L
β-hydroxyaspartate, a glutamate transport blocker, mimicked the effect of low Co2+, suggesting a possibility that the low Co2+ effect might be related to a blockade of glutamate uptake by rods.
Project supported by the State Commission of Science and Technology of China, the National Natural Science Foundation of China,
the National Eye Institute, the Human Frontier Science Program. 相似文献
957.
重庆市蔬菜硝酸盐、亚硝酸盐含量及其与环境的关系 总被引:71,自引:0,他引:71
在重庆市的主要蔬菜中,硝酸盐含量依次为根菜类>叶菜类>葱蒜类>瓜类>豆类>茄果类,前3类的硝酸盐含量超标,但各种蔬菜的亚硝酸盐含量一般较低,未超过卫生标准。就同一种蔬菜的不同样品而言,硝酸盐和亚硝酸盐含量的差异很大,说明品种或环境条件可显著影响其含量。重庆市多雾少光,冬春低温,土壤含氮量和钠高子含量较高,有效钾含量较低可能是导致蔬菜大量积累硝酸盐的环境因素。蔬菜不同器官硝酸盐和亚硝酸盐含量各异,根>茎>叶柄>叶片。 相似文献
958.
孤啡肽在大鼠脑内对抗吗啡镇痛 总被引:8,自引:0,他引:8
脑内全新的阿片受体样受体(1994)及其内源性配体孤啡肽(1995)的发现形成了中枢神经系统阿片/抗阿片相互关系的研究领域中一个新的推动力。基于它们与阿片家族的高同源性及在脑内痛觉整合相关区域的丰富表达,本实验观察了OFQ在大鼠脑内对吗啡镇痛作用的影响。结果表明:(1)OFQ可以对抗脑室注射生理盐水引起的镇痛,后者可能是一种由内源性阿片系统介导的应激镇痛。(2)脑室注射OFQ在很大的剂量范围(40 相似文献
959.
孕酮诱发豚鼠精子顶体反应过程中的Ca^2+内流通道 总被引:5,自引:1,他引:4
在体外,孕酮和γ-氨基丁酸可明显地引起豚鼠精子顶体反应,并且两者合并使用,对顶体瓜在的诱发有协同作用,这种反应不依赖于细胞外Cl^-,在含Cl^-培养液中,GABAA受体拮抗剂picrotoxin和bocuculline不抑制孕酮诱发的顶体反应,而抑制GABA诱发的顶体反应。相反在缺Cl^-培养液中,picrotoxin则可明显地抑制孕酮和GABA诱发的顶体反应。孕酮和GABA诱发的顶体反应均可被 相似文献
960.
The effects of some inhibitors on the rates of photosynthesis and respiration by Chlorella 下载免费PDF全文
The effects of several inhibitors on the rates of photosynthesis and of respiration by Chlorella pyrenoidosa have been studied. The inhibitors used in this study include potassium cyanide, hydroxylamine hydrogen chloride, dinitrophenol,and sodium azide. Each inhibitor seems to have its own characteristic action in photosynthesis and in respiration. With the exception of hydroxylamine, all the inhibitors show a stimulation of respiration at low concentrations of the inhibitors. Only dinitrophenol inhibits respiration to a marked extent. Potassium cyanide, hydroxylamine, and dinitrophenol are about equally effective in inhibiting photosynthesis, but sodium azide is nearly ten times as effective. 相似文献