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SILVIA HIRSCH 《American anthropologist》2006,108(2):417-418
Landscapes of Devils: Tensions of Place and Memory in the Argentinean Chaco . Gastón R. Gordillo. Durham, NC: Duke University Press, 2005. 304 pp. 相似文献
55.
The purpose of this study was to investigate the association between physical fitness and mild cognitive impairment (MCI) in elderly Koreans. This was a cross-sectional study that involved 134 men and 299 women aged 65 to 88 years. Six senior fitness tests were used as independent variables: 30 s chair stand for lower body strength, arm curl for upper body strength, chair-sit-and-reach for lower body flexibility, back scratch for upper body flexibility, 8-ft up-and-go for agility/dynamic balance, and 2-min walk for aerobic endurance. Global cognitive function was assessed using the Korean version of the Mini-Mental State Examination (MMSE). Potential covariates such as age, education levels, blood lipids, and insulin resistance (IR) markers were also assessed. Compared to individuals without MMSE-based MCI, individuals with MMSE-based MCI had poor physical fitness based on the senior fitness test (SFT). There were significant positive trends observed for education level (p=0.001) and MMSE score (p<0.001) across incremental levels of physical fitness in this study population. Individuals with moderate (OR=0.341, p=0.006) and high (OR=0.271, p=0.007) physical fitness based on a composite score of the SFT measures were less likely to have MMSE-based MCI than individuals with low physical fitness (referent, OR=1). The strength of the association between moderate (OR=0.377, p=0.038) or high (OR=0.282, p=0.050) physical fitness and MMSE-based MCI was somewhat attenuated but remained statistically significant even after adjustment for the measured compounding factors. We found that poor physical fitness was independently associated with MMSE-based MCI in elderly Koreans. 相似文献
56.
Determining the evolutionary potential of a gene 总被引:4,自引:0,他引:4
In addition to information for current functions, the sequence of a gene
includes potential information for the evolution of new functions. The
wild-type ebgA (evolved beta-galactosidase) gene of Escherichia coli
encodes a virtually inactive beta-galactosidase, but that gene has the
potential to evolve sufficient activity to replace the lacZ gene for growth
on the beta-galactoside sugars lactose and lactulose. Experimental
evidence, which has suggested that the evolutionary potential of Ebg enzyme
is limited o two specific amino acid replacements, is limited to examining
the consequences of single base- substitutions. Thirteen
beta-galactosidases homologous with the Ebg beta-galactosidase are widely
dispersed, being found in gram-negative and gram-positive eubacteria and in
a eukaryote. A comparison of Ebg beta-galactosidase with those 13
beta-galactosidases shows that Ebg is part of an ancient clade that
diverged from the paralogous lacZ beta- galactosidase over 2 billion years
ago. Ebg differs from other members of its clade at only 2 of the 15
active-site residues, and the two mutations required for full Ebg
beta-galactosidase activity bring Ebg into conformity with the other
members of its clade. We conclude that either these are the only acceptable
amino acids at those positions, or all of the single-base-substitution
replacements that must arise as intermediates on the way to other
acceptable amino acids are so deleterious that they constitute a deep
selective valley that has not been traversed in over 2 billion years. The
evolutionary potential of Ebg is thus limited to those two replacements.
相似文献
57.
The acidophilic alga Dunaliella acidophila exhibits optimalgrowth at pH 1. We have investigated the regulation of phosphateuptake by this alga using tracer techniques and by performingintracellular phosphate measurements under different growthconditions including phosphate limitation. In batch culturewith 2·2 mol m3 phosphate in the medium the uptakeof phosphate at micromolar phosphate concentrations followeda linear time dependence in the range of minutes and rates werein the range of 1 µmol phosphate mg1 chl h1,only. However, under discontinuous phosphate-limited growthconditions, tracer influx revealed a biphasic pattern at micromolarphosphate concentrations: An initial burst phase resulted ina 104-fold internal phosphate accumulation and levelled offafter about 10 s. A double reciprocal plot of the initial influxrates obtained for phosphate-limited and unlimited algae exhibitedMichaelis-Menten kinetics. Phosphate limitation caused a significantactivation of the maximum velocity of uptake, yielding Vmaxup to 1 mmol mg1 chl h1 as compared to valuesin the order of 50 µmol phosphate mg1 chl h1for the second phase (this magnitude is also representativefor non-limited batch cultures). Concomitantly the Michaelisconstant was altered from 4 mmol m3 to 0·7 mmolm3. The rapid uptake of phosphate was inhibited by arsenateand FCCP and was not stimulated by Na+. The pH dependence oftracer accumulation and measurements of the intracellular phosphatepool under different growth conditions indicate that at lowpH and low external phosphate concentrations the high protongradient present under these conditions is utilized for a H3PO4uptake or a H+/H2PO4 cotransport. However, when the externalphosphate concentration was increased to levels sufficientlyhigh for transport to be driven by the positive membrane potential(10 mol m3 phosphate), the pH dependence of phosphateuptake was more complex, but could be explained by the uptakeof H3PO4 or a H+/H2PO4-cotransport at low pH and a differenttype H2PO4-transport (with unknown type of ion coupling)at high pH-values. It is suggested that this flexible couplingof phosphate transport is of essential importance for the acidresistance of Dunaliella acidophila. Key words: Acid resistance, Dunaliella acidophila, phosphate cotransport, phosphate limitation, plasma membrane, sodium 相似文献
58.
Dafna D Gladman Philip J Mease Ernest HS Choy Christopher T Ritchlin Renee J Perdok Eric H Sasso 《Arthritis research & therapy》2010,12(3):R113
Introduction
To identify independent predictors of radiographic progression in psoriatic arthritis (PsA) for patients treated with adalimumab or placebo in the Adalimumab Effectiveness in PsA Trial (ADEPT). 相似文献59.
Molecular dynamics of synthetic leucine-serine ion channels in a phospholipid membrane 总被引:2,自引:0,他引:2 下载免费PDF全文
Molecular dynamics calculations were carried out on models of two synthetic leucine-serine ion channels: a tetrameric bundle with sequence (LSLLLSL)(3)NH(2) and a hexameric bundle with sequence (LSSLLSL)(3)NH(2). Each protein bundle is inserted in a palmitoyloleoylphosphatidylcholine bilayer membrane and solvated by simple point charge water molecules inside the pore and at both mouths. Both systems appear to be stable in the absence of an electric field during the 4 ns of molecular dynamics simulation. The water motion in the narrow pore of the four-helix bundle is highly restricted and may provide suitable conditions for proton transfer via a water wire mechanism. In the wider hexameric pore, the water diffuses much more slowly than in bulk but is still mobile. This, along with the dimensions of the pore, supports the observation that this peptide is selective for monovalent cations. Reasonable agreement of predicted conductances with experimentally determined values lends support to the validity of the simulations. 相似文献
60.
MARY J. PACKARD LARY K. BURNS KARL F. HIRSCH GARY C. PACKARD 《Zoological Journal of the Linnean Society》1982,75(4):297-316
Female zebra-tailed lizards (Iguanidae: Callisaurus draconoides ) lay roughly ovoid eggs with thin, highly extensible shells. The outer surface of the eggshell is a thin, calcareous crust of calcium carbonate in the calcite morph. Immediately beneath the crystalline matrix is a shell membrane composed of multiple layers of fibres organized into an undulating series of troughs and crests, apparent in both cross-section and surface view. The outer surface of the shell membrane is differentiated into a tightly woven fibrous mat that may serve to anchor the calcareous layer to the membrane. Organization of the eggshell into a series of troughs and crests serves to increase the surface area available for contact with the substrate and, presumably, to increase the capacity of the eggshell to stretch as the egg absorbs water. 相似文献