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1.
Jo Peters 《Mammalian genome》2009,20(9-10):529-531
2.
Maria João Feio Trefor B. Reynoldson Verónica Ferreira Manuel Augusto S. Graça 《Hydrobiologia》2007,579(1):55-68
We sampled macroinvertebrates at 75 locations in the Mondego river catchment, Central Portugal, and developed a predictive
model for water quality assessment of this basin, based on the Reference Condition Approach. Sampling was done from June to
September 2001. Fifty-five sites were identified as “Reference sites” and 20 sites were used as “Test sites” to test the model.
At each site we also measured 40 habitat variables to characterize water physics and chemistry, habitat type, land use, stream
hydrology and geographic location. Macroinvertebrates were generally identified to species or genus level; a total of 207
taxa were found. By Unweighted Pair Group Method with Arithmetic mean (UPGMA) clustering and analysis of species contribution
to similarities percentage (SIMPER), two groups of reference sites were established. Using Discriminant Analysis (stepwise
forward), four variables correctly predicted 78% of the reference sites to the appropriate group: stream order, pool quality,
substrate quality and current velocity. Test sites’ environmental quality was established from their relative distance to
reference sites, in MDS ordination space, using a series of bands (BEAST methodology). The model performed well at upstream
sites, but at downstream sites it was compromised by the lack of reference sites. As with the English RIVPACS predictive model,
the Mondego model should be continually improved with the addition of new reference sites. The adaptation of the Mondego model
methodology to the Water Framework Directive is possible and would consist mainly of the integration of the WFD typology and
increasing the number of ellipses that define quality bands.
Handling editor: K. Martens 相似文献
3.
Three Approaches to the Study of Language and Gender 总被引:1,自引:0,他引:1
Bonnie McElhinny 《American anthropologist》2003,105(4):848-852
Gender across Languages: The Linguistic Representation of Women and Men. Vol. 2. Marlis Hellinger and Hadumod Bußmann eds. Amsterdam: John Benjamins, 2002. 348 pp.
Gender Identity and Discourse Analysis. Lia Litosseliti and Jane Sunderland eds. Amsterdam: John Benjamins, 2002. 335 pp.
Talking Gender and Sexuality. Paul McIlvenny. ed. Amsterdam: John Benjamins, 2002. 327 pp. 相似文献
Gender Identity and Discourse Analysis. Lia Litosseliti and Jane Sunderland eds. Amsterdam: John Benjamins, 2002. 335 pp.
Talking Gender and Sexuality. Paul McIlvenny. ed. Amsterdam: John Benjamins, 2002. 327 pp. 相似文献
4.
An electron histochemical study was undertaken to localize calcium with ammonium oxalate precipitation technique in soleus muscle of rat in normal cases and in myopathy induced experimentally by a prolonged treatment of 2,4-dichlorophenoxyacetate (2,4-D). The calcium content of precipitates was detected by energy-dispersive X-ray microanalysis. In normal cases, the electron dense precipitates containing calcium were mainly found in the vesicles of sarcoplasmic reticulum, whereas in 2,4-D induced myopathy the deposits were shifted near the Z line into the myofibrils. Calcium, because the uptake into sarcoplasmic vesicles was inhibited by 2,4-D, could attach to other binding sites, such as to the troponin-C.A long-lasting binding of calcium might lead to a prolonged activation of the actin-myosin system. 相似文献
5.
Effects on NaeI-DNA recognition of the leucine to lysine substitution that transforms restriction endonuclease NaeI to a topoisomerase: a model for restriction endonuclease evolution. 总被引:1,自引:0,他引:1 下载免费PDF全文
Substituting lysine for leucine at position 43 (L43K) transforms NaeI from restriction endonuclease to topoisomerase and makes NaeI hypersensitive to intercalative anticancer drugs. Here we investigated DNA recognition by Nael-L43K. Using DNA competition and gel retardation assays, NaeI-L43K showed reduced affinity for DNA substrate and the ability to bind both single- and double-stranded DNA with a definite preference for the former. Sedimentation studies showed that under native conditions NaeI-L43K, like NaeI, is a dimer. Introduction of mismatched bases into double-stranded DNA significantly increased that DNA's ability to inhibit NaeI-L43K. Wild-type NaeI showed no detectable binding of either single-stranded DNA or mismatched DNA over the concentration range studied. These results demonstrate that the L43K substitution caused a significant change in recognition specificity by NaeI and imply that NaeI-L43K's topoisomerase activity is related to its ability to bind single-stranded and distorted regions in DNA. A mechanism is proposed for the evolution of the NaeI restriction-modification system from a topoisomerase/ligase by a mutation that abolished religation activity and provided a needed change in DNA recognition. 相似文献
6.
Alcohol dehydrogenase thermostability variants in Drosophila melanogaster: Comparison of activity ratios and enzyme levels 总被引:2,自引:0,他引:2
Representatives of five allozymic classes of Drosophila alcohol dehydrogenase have been compared with respect to their activity levels on two alcohol substrates, quantities of ADH protein, and stability in crude extracts. Within each allozymic class, strains from widely diverse geographic locations differ in their enzyme activity levels but are identical for a measure known as "activity ratio," which is obtained by dividing the average activity reading on isopropanol by that obtained with ethanol. They are also similar in the rate at which ADH activity declines in crude extracts held at 25 degrees C. For several of the fast-resistant and fast-moderate strains, differences in ADH activity are associated with differences in the amount of enzyme present. The catalytic efficiencies of the fast-resistant forms are considerably lower than those of the fast-moderate allozymes. The origin and persistence of the rare but ubiquitous fast-resistant allozyme is discussed. 相似文献
7.
Chromosomal polymorphism regarding number of NOR sites in the cyprinid fish Chondrostoma lusitanicum was examined using C-banding, silver-staining (Ag), and fluorescent staining with chromomycin A3 (CMA3). The analysis of heterochromatic regions allowed a more precise identification of the centromeric regions and the proposal of a revised haploid chromosome formula (7M: 15S: 3A). We describe variability in the number of NOR regions per genome, number of active NOR sites per cell, and relative size of individual NORs. Individuals expressed two or four NOR-bearing chromosomes. Polymorphism was detected in all the populations studied and sex-related differences were not found. The observed chromosomal NOR phenotypes suggest the occurrence of structural rearrangements during the evolutionary process of this diploid leuciscine cyprinid. 相似文献
8.
Switch and Bait: Probing the Discriminative Basis of Odor Identification via Recognition Memory 总被引:7,自引:7,他引:0
When people misidentify everyday odors, as they often do, theirerrors may conceivably lie in faulty perceptions or in faultyaccess to the names. Discussions of the matter usually focuson the latter, as if people had no problems with perceptualaccuracy. (The problem of faulty access may get attention becauseits high subjective impact makes it particularly memorable,when it does occur.) However, studies have demonstrated breakdownsin ability to discriminate quality, from which it follows thatpeople will misidentify items through perceptual confusions.Furthermore, misidentifications often contain considerable informationabout the identities of items, as if people simply did not perceivethe items accurately, but perhaps fuzzily or with some perceptualbias. Recognition memory, with a 2-day interval between inspectionand test, provided a vehicle to address two questions on thistopic: (i) Would people notice that we had switched items andhad presented for recognition items that matched their misidentificationsrather than the original items inspected? (ii) Would peoplenot only fall for the false bait, but actually identify theswitched items correctly, and thereby imply that they were tunedto perceive those odors? People commonly failed to notice theswitches, i.e. took the bait and commonly identified the switcheditems with veridical names. Although subject to further study,the outcome suggests that when people give such names as garlicfor vinegar, orange for lime, soy sauce for molasses and manyothers, the errors often lie largely at a perceptual stage ofprocessing, i.e. at input rather than output. Chem. Senses 21:3544, 1996. 相似文献
9.
Summary Explants of tomato (Lycopersicon esculentum Mill cv. Ailsa Craig) were co-cultivated with Agrobacterium tumefaciens C58C1Rifr::pGSFR1161 in the presence of 20 (M acetosyringone). Transformed root clones were selected on kanamycin medium and the presence of the nptII gene in the plant DNA confirmed by the polymerase chain reaction. Root clones derived from acetosyringone treatment grew more vigorously in the presence of kanamycin and synthesized a greater amount of NPT-II enzyme. The conclusion is that acetosyringone treatment enhances the transformation process, possibly by stimulating multiple insertions of the T-DNA into the host genome.Abbreviations AS
acetosyringone
- CTAB
hexadecyltrimethylammonium bromide
- EDTA
ethylenediaminetetraacetic acid
- ELISA
enzyme-linked immunosorbant assay
- MS
Murashige and Skoog (1962) medium
- PCR
polymerase chain reaction 相似文献
10.
Jo Ann Render 《Development genes and evolution》1983,192(3-4):120-129
Summary The embryo ofSabellaria cementarium (Polychaeta) forms a polar lobe at each of the first two cleavage divisions which becomes absorbed into one of the blastomeres at the end of the division. Lobe removal experiments show that the polar lobe preceding first cleavage is necessary for the development of the apical tuft and the posttrochal region of the trochophore larva. The polar lobe preceding second cleavage is smaller than the first polar lobe and is necessary only for post-trochal region development. In blastomere isolation experiments, isolates containing the C but not the D blastomere form apical tufts. Isolates containing the D but not the C blastomere do not form apical tufts. When the polar lobe preceding second cleavage is removed and the C and D blastomeres are separated and raised in isolation, each can form an apical tuft. When the second cleavage is equalized with sodium dodecyl sulfate (SDS) such that both the C and the D blastomeres receive second polar lobe material, no apical tuft is formed. These results suggest that apical tuft determinants are distributed to both the C and D blastomeres at second cleavage but that the second polar lobe contains an inhibitor for apical tuft formation which is shunted to the D blastomere after the completion of second cleavage. 相似文献