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51.
Tapia RA Alegria L Pessoa CD Salas C Cortés MJ Valderrama JA Sarciron ME Pautet F Walchshofer N Fillion H 《Bioorganic & medicinal chemistry》2003,11(10):2175-2182
The synthesis of tetracyclic quinones 10a,b, 14a,b, 19a,b and 20a,b is described. The preparations involve regioselective Diels-Alder reactions via trapping the thiazole o-quinodimethane 9 with several benzofuranquinones and benzothiophenequinones. The structure of the regioisomers was assigned through 2D NMR 1H-13C HMBC experiments performed on 10a and 14a. Compounds 10a,b, 14a as well as phenol 1 and the starting quinones 2, 5, 7 and 15 are evaluated against Leishmania sp., Toxoplasma gondii and THP-1 cells. Almost all the tested compounds exhibit significant antiprotozoal activities with lower cytotoxicities than the reference compounds. Among them, quinones 2 and 14a possess the best activities towards L. donovani and T. gondii with the lowest toxicities. 相似文献
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SHIGERU A. AE 《Systematic Entomology》1979,4(1):1-16
Abstract. Adults of different species of the genus Papilio can easily be mated by hand-pairing. The data on egg hatchability, adult formation and F1 fertility in these interspecific hybrids show notable variations according to the crosses. Using these data, values of a differentiation index for each cross were calculated. These estimates of genetic distance were then used to study the phylo-genetic relationships of the species involved. The data are consistent with the existence of the following groups, each consisting of closely related species: the black Papilio supergroup, the Papilio memnon group, the P.demoleus group, the P.xuthus group, the P.machaon group, the P.bianor group, the P.glaucus group and the P.troilus group. The phylogenetic relationships revealed by these data generally coincide with the relationships established by classical taxonomy. In cases where there are differences of opinion among taxonomists, the writer's data usually support one or other of them. 相似文献
54.
A H Alegria 《Biochimica et biophysica acta》1967,149(2):317-324
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56.
Rogers AR; Fraley AE; Bamshad MJ; Watkins WS; Jorde LB 《Molecular biology and evolution》1996,13(7):895-902
Mismatch distributions are histograms showing the pattern of nucleotide (or
restriction) site differences between pairs of individuals in a sample.
They can be used to test hypotheses about the history of population size
and subdivision (if selective neutrality is assumed) or about selection (if
a constant population size is assumed). Previous work has assumed that
mutations never strike the same site twice, an assumption that is called
the model of infinite sites. Fortunately, the results are surprisingly
robust even when this assumption is violated. We show here that (1)
confidence regions inferred using the infinite- sites model differ little
from those inferred using a model of finite sites with uniform
site-specific mutation rates, and (2) even when site- specific mutation
rates follow a gamma distribution, confidence regions are little changed
until the gamma shape parameter falls well below its plausible range, to
roughly 0.01. In addition, we evaluate and reject the proposition that
mismatch waves are produced by pooling data from several subdivisions of a
structured population.
相似文献
57.
Cultures of Achlya sp., Phytophthora cinnamomi, Saprolegnia diclina, S. ferax, and S. parasitica, treated with 6-carboxyfluorescein diacetate solution, accumulate 6-carboxyfluorescein in a reticulate system of fine tubules. The network shows longitudinal polarity within the hyphae, tubules being finest toward the hyphal tips. In more mature subapical regions the network is connected with large vacuoles that also accumulate 6-carboxyfluorescein. A morphologically similar system has also been identified in freeze-substituted hyphae of S. ferax. The network is considered to be vacuolar, but differs from the tubular vacuole system of true fungi in that tubules are less motile, more frequently branched, and do not alternate with clusters of spherical vacuoles. The appearance of the network resembles patterns of calcium-sensitive dye staining and it is suggested that the vacuolar reticulum in the tip region of oomycete hyphae may act as a Ca2+ sink. The tubular reticulum in oomycetes is very fragile and can be shown with 6-carboxyfluorescein in only those hyphal tips with a motility and organelle distribution characteristic of growing hyphae with normal morphology. Diverse abnormal hyphae show a range of other fluorochrome localizations. These include large irregular compartments filled with fluorochrome, and fluorescent cytoplasm with organelles and vacuoles standing out in negative contrast. These localizations in abnormal hyphae are correlated with other structural changes indicative of damage. Special care is required in experiments with oomycetes to avoid such artefacts of localization. Copyright 1997 Academic Press. Copyright 1997 Academic Press 相似文献
58.
A reassessment of decreased amino acid accumulation by ehrlich ascites tumor cells in the presence of metabolic inhibitors 总被引:2,自引:0,他引:2 下载免费PDF全文
This study was undertaken to examine the mechanism by which metabolic inhibition reduces amino acid active transport in ehrlich ascites tumor cells. At 37 degrees C the metabolic inhibitor combination 0.1 mM 2,4-dinitrophenol (DNP) + 10 mM 2- deoxy-D-glucose (DOG) reduced the cell ATP concentration to 0.10- 0.15 mM in less than 5 min. This inhibition was associated with a 20.6 percent +/- 6.4 percent (SD) decrease in the initial influx of α-aminoisobutyric acid (AIB), and a two- to fourfold increase in the unidirectional efflux. These effects could be dissociated from changes in cell Na(+) or K(+) concentrations. Cells incubated to the steady state in 1.0-1.5 mM AIB showed an increased steady-state flux in the presence of DNP + DOG. Steady- state fluxes were consistent with trans-inhibition of AIB influx and trans-stimulation of efflux in control cells, but trans- stimulation of both fluxes in inhibited cells. In spite of the reduction of the cell ATP concentration to less than 0.15 mM and greatly reduced transmembrane concentration gradients of Na(+) and K(+), cells incubated to the steady state in the presence of the inhibitors still established an AIB distribution ration 13.8 +/- 2.6. The results are interpreted to indicate that a component of the reduction of AIB transport produced by metabolic inhibition is attributable to other actions in addition to the reduction of cation concentration gradients. Reduction of cell ATP alone is not responsible for the effects of metabolic inhibition, and both the transmembrane voltage and direct coupling to substrate oxidation via plasma-membrane-bound enzymes must be considered as possible energy sources for amino acid active transport. 相似文献
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60.
Sharla Alegria 《Ethnic and racial studies》2013,36(2):241-260
Overtly racist statements are socially and politically unacceptable in the USA. Yet black people in the USA continue to experience discrimination and prejudice at both the individual and institutional levels. This paper examines white people's talk about race in focus groups from the North Carolina Traffic Violation Study. The participants discussed race obliquely, by talking about hypothetical behaviour related to crime and police profiling while largely avoiding direct mention of race. At the same time focus group members voice different expectations for white people and black people. By differentiating between behaviours expected from individuals perceived to belong to different racial groups, they reproduced racial difference. Focus group members legitimized racial profiling and did so using language that was largely ‘colour-blind’ and socially acceptable by attributing the disproportionately high rate of stops for black drivers to ostensibly non-racial factors. The groups used mostly colour-blind language, but the result was racializing discourse. 相似文献