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排序方式: 共有704条查询结果,搜索用时 140 毫秒
641.
Epidemiology of Helicobacter pylori infection 总被引:5,自引:0,他引:5
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Olof Söder 《Analytical biochemistry》1982,123(2):236-243
A method enabling the direct assay in a cell culture system of material separated by thinlayer chromatography (TLC) without prior elution of active material from the TLC sheet is described. After chromatographic development on a plastic cellulose sheet, small disks were punched out from the sheet and transferred to microwells used for cell culture. Lymphoid cells in culture medium were incubated with the disks and the DNA synthesis was measured by [3H]thymidine incorporation. The reliability of the method was tested with l-alanine and thymidine, which are known to enhance the DNA synthesis of lymphoid cells and to interfere with the uptake of labeled thymidine, respectively. The incorporation of [3H]thymidine was stimulated with disks containing l-alanine and inhibited with disks containing unlabeled thymidine, completely in agreement with the expected results. Elution experiments showed that more than 75% of l-alanine and thymidine on the TLC disks was eluted into the culture medium within 1 h. Elution of material of higher molecular weight was also demonstrated. The method was used for the separation and assay of a thymocyte-specific growth factor isolated from calf thymus and greatly facilitated the detection of the active material after TLC. 相似文献
644.
The effect of UV-B and UV-C radiation on Hibiscus leaves determined by ultraweak luminescence and fluorescence induction 总被引:1,自引:0,他引:1
The effects of UV-C (254 nm) and UV-B (280-320 nm) on chlorophyll fluorescence induction and ultraweak luminescence (UL) in detached leaves of Hibiscus rosa-sinensis L. were investigated. UL from leaves exposed to UV-B and UV-C radiation reached a maximum 72 h after irradiation. In both cases most of the light was of a wavelength over 600 nm. An increase in the percentage of long wavelength light with time was detected. UV radiation increased peroxidase activity, which also reached a maximum 72 h after irradiation. UV-B and UV-C both reduced variable chlorophyll fluorescence. No effect on the amount of chlorophyll or UV screening pigments was observed with the short-term irradiation used in this investigation. 相似文献
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Olof Ryding 《Nordic Journal of Botany》1994,14(2):205-207
A new species from southern and Eastern Ethiopia, Plantago annua is described and illustrated. 相似文献
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Olof Reimer 《Aquatic Ecology》1999,33(2):185-192
The presence of invertebrate predators can induce morphological, physiological, and behavioural changes in sessile marine
prey species. In this study, I investigated whether the risk of predation can alter the reproductive effort in the blue mussel
Mytilus edulis. In the field, I cultured blue mussels in the presence and in the absence of the starfish, Asterias rubens,
using enclosures with two compartments. Two experiments were performed with field periods of 19 and 30 days, respectively.
After the field exposure, the mussels were examined for weight of flesh and gonad tissue. In both experiments, the starfish-exposed
mussels developed a significantly larger gonad to flesh ratio, compared with that of the unexposed control mussels. After
30 days, the exposed mussels had also lost flesh weight significantly, probably due to spawning. These changes suggest that
M. edulis accelerates the gonad development and/or increases its reproductive effort in the presence of predators. Predator-inducible
adjustment of life-history characters should be a beneficial trait for this sessile species, that typically encounters a high
and variable predation pressure.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献