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排序方式: 共有112条查询结果,搜索用时 15 毫秒
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Bryophytes and heavy metals: a literature review 总被引:14,自引:0,他引:14
GERMUND TYLER 《Botanical journal of the Linnean Society. Linnean Society of London》1990,104(1-3):231-253
The literature on heavy metals in bryophytes is reviewed, including mechanisms of metal uptake, retention, toxicity and tolerance. Interspecies differences in particular are discussed, including the development of extreme tolerance encountered in certain taxa. The use of bryophytes in monitoring heavy metal deposition is considered and comparisons are made with direct deposition measurements. 相似文献
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Radial estimates and the test for sphericity 总被引:1,自引:0,他引:1
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Plasminogen activator and collagenase production by cultured capillary endothelial cells 总被引:33,自引:17,他引:16
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Cultured bovine capillary endothelial (BCE) cells produce low levels of collagenolytic activity and significant amounts of the serine protease plasminogen activator (PA). When grown in the presence of nanomolar quantities of the tumor promoter 12-O-tetradecanoyl phorbol-13-acetate (TPA), BCE cells produced 5-15 times more collagenolytic activity and 2-10 times more PA than untreated cells. The enhanced production of these enzymes was dependent on the dose of TPA used, with maximal response at 10(-7) to 10(-8) M. Phorbol didecanoate (PDD), an analog of TPA which is an active tumor promoter, also increased protease production. 4-O-methyl-TPA and 4α-PDD, two analogs of TPA which are inactive as tumor promoters, had no effect on protease production. Increased PA and collagenase activities were detected within 7.5 and 19 h, respectively, after the addition of TPA. The TPA-stimulated BCE cells synthesized a urokinase-type PA and a typical vertebrate collagenase. BCE cells were compared with bovine aortic endothelial (BAE) cells and bovine embryonic skin (BES) fibroblasts with respect to their production of protease in response to TPA. Under normal growth conditions, low levels of collagenolyic activity were detected in the culture fluids from BCE, BAE, and BES cells. BCE cells produced 5-13 times the basal levels of collagenolytic activity in response to TPA, whereas BAE cells and BES fibroblasts showed a minimal response to TPA. Both BCE and BAE cells exhibited relatively high basal levels of PA, the production of which was stimulated approximately threefold by the addition of TPA. The observation that BCE cells and not BAE cells produced high levels of both PA and collagenase activities in response to TPA demonstrates a significant difference between these two types of endothelial cells and suggests that the enhanced detectable activities are a property unique to bovine capillary and microvessel and endothelial cells. 相似文献
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TYLER S. KUHN KERI A. MCFARLANE PAMELA GROVES ARNE Ø. MOOERS BETH SHAPIRO 《Molecular ecology》2010,19(7):1312-1323
The long‐term persistence of forest‐dwelling caribou (Rangifer tarandus caribou) will probably be determined by management and conservation decisions. Understanding the evolutionary relationships between modern caribou herds, and how these relationships have changed through time will provide key information for the design of appropriate management strategies. To explore these relationships, we amplified microsatellite and mitochondrial markers from modern caribou from across the Southern Yukon, Canada, as well as mitochondrial DNA from Holocene specimens recovered from alpine ice patches in the same region. Our analyses identify a genetically distinct group of caribou composed of herds from the Southern Lakes region that may warrant special management consideration. We also identify a partial genetic replacement event occurring 1000 years before present, coincident with the deposition of the White River tephra and the Medieval Warm Period. These results suggest that, in the face of increasing anthropogenic pressures and climate variability, maintaining the ability of caribou herds to expand in numbers and range may be more important than protecting the survival of any individual, isolated sedentary forest‐dwelling herd. 相似文献
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W. TYLER McCRANEY GREG GOLDSMITH DAVID K. JACOBS ANDREW P. KINZIGER 《Molecular ecology》2010,19(16):3315-3327
Habitat fragmentation and its genetic consequences are a critically important issue in evaluating the evolutionary penalties of human habitat modification. Here, we examine the genetic structure and diversity in naturally subdivided and artificially fragmented populations of the endangered tidewater goby (Eucyclogobius newberryi), a small fish restricted to discrete coastal lagoons and estuaries in California, USA. We use five naturally fragmented coastal populations from a 300‐ km spatial scale as a standard to assess migration and drift relative to eight artificially fragmented bay populations from a 30‐ km spatial scale. Using nine microsatellite loci in 621 individuals, and a 522‐base fragment of mitochondrial DNA control region from 103 individuals, we found striking differences in the relative influences of migration and drift on genetic variation at these two scales. Overall, the artificially fragmented populations exhibited a consistent pattern of higher genetic differentiation and significantly lower genetic diversity relative to the naturally fragmented populations. Thus, even in a species characterized by habitat isolation and subdivision, further artificial fragmentation appears to result in substantial population genetic consequences and may not be sustainable. 相似文献
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TYLER ET 《California medicine》1954,80(1):13-15
The one feature that characterizes all shock, regardless of its cause, is a reduction in the effective circulating blood volume. The reduced blood volume leads to decreased venous return, decreased cardiac output, vasoconstriction, tachycardia, hypotension, tissue anoxia and death if the sequence of events is uninterrupted. Immediate therapy must be directed at restoration of the blood volume, preferably with whole blood. Infection must be controlled by use of antibiotics intramuscularly and intravenously. If shock persists, aqueous adrenal extract should be administered in large quantities. As a last resort, a vasopressor should be tried. 相似文献