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41.
Nucleotide sequences of two fragments from the coat-protein cistron of bacteriophage R17 ribonucleic acid 总被引:2,自引:2,他引:0
P. G. N. Jeppesen B. G. Barrell F. Sanger A. R. Coulson 《The Biochemical journal》1972,128(5):993-1006
Bacteriophage R17 RNA was labelled with 32P and was subjected to partial digestion with ribonuclease T1. The products were fractionated by ionophoresis on polyacrylamide gel. Two fragments were purified and their nucleotide sequences determined by methods involving complete and further partial digestion with ribonucleases A and T1. Fragment 20 had a sequence that coded for the amino acids in positions 32–53 of the coat protein of the bacteriophage. Fragment 20X, on further purification in 7m-urea, gave rise to two smaller nucleotides whose sequences coded for the amino acids in positions 56–66 and 67–76 of the coat protein. The sequence of the two fragments was such that they could be written in the form of loops stabilized by base-pairing. 相似文献
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Effect of a nitrogen pulse on ecosystem N processing at different temperatures: A mesocosm experiment with 15NO3− addition 下载免费PDF全文
Saara Olsen Yu Cao María Florencia Gutierrez Sandra Brucet Frank Landkildehus Torben L. Lauridsen Thomas A. Davidson Martin Søndergaard Erik Jeppesen Nils Risgaard‐Petersen 《Freshwater Biology》2017,62(7):1232-1243
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Factors controlling the stable isotope composition and C:N ratio of seston and periphyton in shallow lake mesocosms with contrasting nutrient loadings and temperatures 下载免费PDF全文
Carolina Trochine Marcelo Guerrieri Lone Liboriussen Priscila Willems Torben L. Lauridsen Martin Søndergaard Erik Jeppesen 《Freshwater Biology》2017,62(9):1596-1613
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Size‐based interactions and trophic transfer efficiency are modified by fish predation and cyanobacteria blooms in Lake Mývatn,Iceland 下载免费PDF全文
Zeynep Ersoy Erik Jeppesen Serena Sgarzi Ignasi Arranz Miguel Cañedo‐Argüelles Xavier D. Quintana Frank Landkildehus Torben L. Lauridsen Mireia Bartrons Sandra Brucet 《Freshwater Biology》2017,62(11):1942-1952
47.
Sarian Kosten Gissell Lacerot Erik Jeppesen David da Motta Marques Egbert H. van Nes Nestor Mazzeo Marten Scheffer 《Ecosystems》2009,12(7):1117-1129
A positive feedback between submerged vegetation and water clarity forms the backbone of the alternative state theory in shallow
lakes. The water clearing effect of aquatic vegetation may be caused by different physical, chemical, and biological mechanisms
and has been studied mainly in temperate lakes. Recent work suggests differences in biotic interactions between (sub)tropical
and cooler lakes might result in a less pronounced clearing effect in the (sub)tropics. To assess whether the effect of submerged
vegetation changes with climate, we sampled 83 lakes over a gradient ranging from the tundra to the tropics in South America.
Judged from a comparison of water clarity inside and outside vegetation beds, the vegetation appeared to have a similar positive
effect on the water clarity across all climatic regions studied. However, the local clearing effect of vegetation decreased
steeply with the contribution of humic substances to the underwater light attenuation. Looking at turbidity on a whole-lake
scale, results were more difficult to interpret. Although lakes with abundant vegetation (>30%) were generally clear, sparsely
vegetated lakes differed widely in clarity. Overall, the effect of vegetation on water clarity in our lakes appears to be
smaller than that found in various Northern hemisphere studies. This might be explained by differences in fish communities
and their relation to vegetation. For instance, unlike in Northern hemisphere studies, we find no clear relation between vegetation
coverage and fish abundance or their diet preference. High densities of omnivorous fish and coinciding low grazing pressures
on phytoplankton in the (sub)tropics may, furthermore, weaken the effect of vegetation on water clarity. 相似文献
48.
We have shown that stevioside (SVS) enhances insulin secretion and thus may have a potential role as antihyperglycemic agent in the treatment of type 2 diabetes mellitus. However, whether SVS stimulates basal insulin secretion (BIS) and/or cause desensitization of beta cells like sulphonylureas (SU), e.g. glibenclamide (GB), is not known. To explore and compare the effects of SVS pretreatment with those of GB and glucagon-like peptide-1 (GLP-1), we exposed isolated mouse islets to low or high glucose for 1 h after short-term (2 h) or long-term (24 h) pretreatment with SVS, GB or GLP-1, respectively. BIS at 3.3 or 5.5 mM glucose were not changed after short-term pretreatment with SVS (10(-7) M), while it increased about three folds after pretreatment with GB (10(-7) M). Glucose stimulated insulin secretion (GSIS) (16.7 mM) increased dose-dependently after long-term pretreatment with SVS at concentrations from 10(-7) to 10(-5) M. Pretreatment for 24 h with GB (10(-7) M) increased the subsequent BIS (3.3 mM glucose) (p < 0.001), but decreased GSIS (16.7 mM glucose) (p < 0.001). In contrast SVS (10(-7) M) and GLP-1 (10(-7) M) did not stimulate BIS but both enhanced the subsequent GSIS (16.7 mM glucose) (p < 0.05 and p < 0.05, respectively). While SVS pretreatment increased the intracellular insulin content, GB pretreatment decreased the insulin content. Our study suggests that SVS pretreatment does not cause a stimulation of BIS and does not desensitize beta-cells, i.e. SVS seems to have advantageous characteristics to GB as a potential treatment of type 2 diabetes. 相似文献
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