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991.
992.
Segregation distortion genes are widespread in plants and animals and function by their effect on competition among gametes
for preferential fertilization. In this study, we evaluated the segregation distortion of molecular markers in multiple reciprocal
backcross populations derived from unique cytogenetic stocks involving the durum cultivar Langdon (LDN) and wild emmer accessions
that allowed us to study the effects of chromosome 5B in isolation. No segregation distortion of female gametes was observed,
but three populations developed to analyze segregation of male gametes had genomic regions containing markers with skewed
segregation ratios. One region of distortion was due to preferential transmission of LDN alleles over wild emmer alleles through
male gametes. Another region required the presence of LDN 5B chromosomes in the female for preferential fertilization by male
gametes harboring LDN alleles indicating that the corresponding genes in the female gametes can govern genes affecting segregation
distortion of male gametes. A third region of distortion was the result of preferential transmission of wild emmer alleles
over LDN alleles through male gametes. These results indicate the existence of different distorter/meiotic drive elements
among different genotypes and show that distortion factors along wheat chromosome 5B differ in chromosomal location as well
as underlying mechanisms. 相似文献
993.
Western scrub-jays (Aphelocoma californica) hide food and rely on spatial memory to recover their caches at a later date. They also rely on observational spatial memory
to steal caches made by other individuals. Successful pilfering may require an understanding of allocentric space because
the observer will often be in a different position from the demonstrator when the caching event occurs. We compared cache
recovery accuracy of pairs of observers that watched a demonstrator cache food. The pattern of recovery searches showed that
observers were more accurate when they had observed the caching event from the same viewing direction as the demonstrator
than when they had watched from the opposite direction. Search accuracy was not affected by whether or not the tray-specific
local cues provided left–right landmark information (i.e. heterogeneous vs. homogeneous local cues), or whether or not the
caching tray location was rotated. Taken together, these results suggest that observers have excellent spatial memory and
that they have little difficulty with mental rotation. 相似文献
994.
Homology modeling and examination of the effect of the D92E mutation on the H5N1 nonstructural protein NS1 effector domain 总被引:1,自引:0,他引:1
Virulent H5N1 strains of influenza virus often harbor a D92E point mutation in the nonstructural protein NS1. This crucial
mutation has been correlated with increased virulence and/or cytokine resistance, but the structural implications of such
a change are still unclear. Furthermore, NS1 protein could also be a potential target for the development of novel antiviral
agents against H5N1 strains. Therefore, a reasonable 3D model of H5N1 NS1 is important for the understanding of the molecular
basis of increased virulence and the design of novel antiviral agents. Based on the crystal structure of a non-H5N1 NS1 protein,
a model of H5N1 NS1 was developed by homology modeling, molecular mechanics and molecular dynamics simulations. It was found
that the D92E mutation could result in weakened interactions of the carboxylate side chain with other phosphorylated residues,
thereby activating phosphorylation of NS1.
Figure Superposition of snapshots picked from the two molecular dynamic (MD) trajectories: a H5N1 NS1 homology model and b non-H5N1 NS1 crystal structure after 0 (green ribbon), 5 (blue ribbon) and 10 ns (pink ribbon) MD simulation 相似文献
995.
Martin Sander Tatiana Coelho Balbão Michael John Polito Erli Schneider Costa Ana Paula Bertoldi Carneiro 《Polar Biology》2007,30(5):659-661
We examined the breeding populations of chinstrap penguins (Pygoscelis antarctica) on Chabrier Rock and Shag Island within Admiralty Bay, King George Island, South Shetland Islands, Antarctica from 2002
to 2004. When comparing our results to historic data from 1979, we found an overall decline of 57% in the last 25 years, mirroring
the population trend of this species in other regions of the Antarctic Peninsula. Our results are discussed in relation to
factors hypothesized to be driving the declines found at other sites, as well as the importance of consistent annual censuses
to accurately determine population trends. 相似文献
996.
997.
Leonel da Silveira Lobo Sternberg Su Yean Teh Sharon M. L. Ewe Fernando Miralles-Wilhelm Donald L. DeAngelis 《Ecosystems》2007,10(4):648-660
A
bstract
The boundaries between mangroves and freshwater hammocks in coastal ecotones of South Florida are sharp. Further, previous
studies indicate that there is a discontinuity in plant predawn water potentials, with woody plants either showing predawn
water potentials reflecting exposure to saline water or exposure to freshwater. This abrupt concurrent change in community
type and plant water status suggests that there might be feedback dynamics between vegetation and salinity. A model examining
the salinity of the aerated zone of soil overlying a saline body of water, known as the vadose layer, as a function of precipitation,
evaporation and plant water uptake is presented here. The model predicts that mixtures of saline and freshwater vegetative
species represent unstable states. Depending on the initial vegetation composition, subsequent vegetative change will lead
either to patches of mangrove coverage having a high salinity vadose zone or to freshwater hammock coverage having a low salinity
vadose zone. Complete or nearly complete coverage by either freshwater or saltwater vegetation represents two stable steady-state
points. This model can explain many of the previous observations of vegetation patterns in coastal South Florida as well as
observations on the dynamics of vegetation shifts caused by sea level rise and climate change. 相似文献
998.
The conversion of and toxic effects exerted by several mono- and dihalogenated C1 and C2 compounds on cultures of Xanthobacter autotrophicus GJ10 growing on 1,2-dichloroethane were investigated. Bromochloromethane, dibromomethane and 1-bromo-2-chloroethane were
utilized by strain GJ10 in batch culture as a cosubstrate and sole carbon source. The rate of degradation of dihalomethanes
by whole cells was lower than that of 1,2-dichloroethane, but a significant increase of the rate of dihalomethane biodegradation
was observed when methanol or ethanol were added as a cosubstrate. Products of the degradation of several tested compounds
by haloalkane dehalogenase were analyzed and a new metabolic pathway based on hydrolytic conversion to formaldehyde was proposed
for the dihalomethanes. Strain GJ10 growing on 1,2-dichloroethane converted 2-fluoroethanol and 1-chloro-2-fluoroethane to
2-fluoroacetate, which was tolerated up to a concentration of 2.5 mM. On the basis of the results from batch cultures an inert
(dichloromethane), a growth-supporting (dibromomethane) and a toxic (1,2-dibromoethane) compound were selected for testing
their effects on a continuous culture of strain GJ10 growing on 1,2-dichloroethane. The compounds were added as pulses to
a steady-state chemostat and the response of the culture was followed. The effects varied from a temporary decrease in cell
density for dibromomethane to severe toxicity and culture washout with 1,2-dibromoethane. Our results extend the spectrum
of halogenated C1 and C2 compounds that are known to be degraded by strain GJ10 and provide information on toxic effects and
transformation of compounds not serving as a carbon source for this bacterium. 相似文献
999.
1000.
Marcelo De Franco Patrícia dos Santos Carneiro Luciana Carla Peters Francisca Vorraro Andrea Borrego Orlando Garcia Ribeiro Nancy Starobinas Wafa Koury Cabrera Olga Martinez Ibañez 《Mammalian genome》2007,18(4):263-269
Lines of mice were obtained by selective breeding for maximum (AIRmax) or minimum (AIRmin) acute inflammation. They present
distinct neutrophil influx and show frequency disequilibrium of the solute carrier family 11a member 1
(Slc11a1) alleles. This gene is involved in ion transport at the endosomes within macrophages and neutrophils, interfering in their
activation. Homozygous AIRmax and AIRmin sublines for the Slc11a1 gene were produced to examine the interaction of this gene with the acute inflammatory loci. The present work investigated
wound-healing traits in AIRmax and AIRmin mice, in F1 and F2 intercrosses, and in Slc11a1 sublines. Two-millimeter ear punches were made in the mice and hole closure was measured during 40 days. AIRmax mice demonstrated
significant tissue repair while AIRmin mice did not. Significant differences between the responses of male and female mice
were also observed. Wound-healing traits demonstrated a correlation with neutrophil influx in F2 populations. AIRmax
SS
showed higher ear-wound closure than AIRmax
RR
mice, suggesting that the Slc11a1
S allele favored ear tissue repair. QTL analysis has detected two inflammatory loci modulating ear wound healing on chromosomes
1 and 14. These results suggest the involvement of the acute inflammation modifier QTL in the wound-healing phenotype. 相似文献