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91.
Lara D. LaDage Timothy C. Roth II Vladimir V. Pravosudov 《Proceedings. Biological sciences / The Royal Society》2011,278(1702):138-143
It has been hypothesized that individuals who have higher demands for spatially based behaviours should show increases in hippocampal attributes. Some avian species have been shown to use a spatially based representation of their environment during migration. Further, differences in hippocampal attributes have been shown between migratory and non-migratory subspecies as well as between individuals with and without migratory experience (juveniles versus adults). We tested whether migratory behaviour might also be associated with increased hippocampal neurogenesis, and whether potential differences track previously reported differences in hippocampal attributes between a migratory (Zonotrichia leucophrys gambelii) and non-migratory subspecies (Z. l. nuttalli) of white-crowned sparrows. We found that non-migratory adults had relatively fewer numbers of immature hippocampal neurons than adult migratory birds, while adult non-migrants had a lower density of new hippocampal neurons than adult and juvenile migratory birds and juvenile non-migratory birds. Our results suggest that neurogenesis decreases with age, as juveniles, regardless of migratory status, exhibit similar and higher levels of neurogenesis than non-migratory adults. However, our results also suggest that adult migrants may either seasonally increase or maintain neurogenesis levels comparable to those found in juveniles. Our results thus suggest that migratory behaviour in adults is associated with maintained or increased neurogenesis and the differential production of new neurons may be the mechanism underpinning changes in the hippocampal architecture between adult migratory and non-migratory birds. 相似文献
92.
Species‐specific climate responses within ecological communities may disrupt the synchrony of co‐evolved mutualisms that are based on the shared timing of seasonal events, such as seed dispersal by ants (myrmecochory). The spring phenology of plants and ants coincides with marked changes in temperature, light and moisture. We investigate how these environmental drivers influence both seed release by early and late spring woodland herb species, and initiation of spring foraging by seed‐dispersing ants. We pair experimental herbaceous transplants with artificial ant bait stations across north‐ and south‐facing slopes at two contrasting geographic locations. This use of space enables robust identification of plant fruiting and ant foraging cues, and the use of transplants permits us to assess plasticity in plant phenology. We find that warming temperatures act as the primary phenological cue for plant fruiting and ant foraging. Moreover, the plasticity in plant response across locations, despite transplants being from the same source, suggests a high degree of portability in the seed‐dispersing mutualism. However, we also find evidence for potential climate‐driven facilitative failure that may lead to phenological asynchrony. Specifically, at the location where the early flowering species (Hepatica nobilis) is decreasing in abundance and distribution, we find far fewer seed‐dispersing ants foraging during its fruit set than during that of the later flowering Hexastylis arifolia. Notably, the key seed disperser, Aphaenogaster rudis, fails to emerge during early fruit set at this location. At the second location, A. picea forages equally during early and late seed release. These results indicate that climate‐driven changes might shift species‐specific interactions in a plant–ant mutualism resulting in winners and losers within the myrmecochorous plant guild. 相似文献
93.
Evolutionary morphologists and physiologists have long recognized the phylogenetic significance of the ectothermic sauropsids. Sauropids have been classically considered to bridge between early tetrapods, ectotherms, and the evolution of endotherms. This transition has been associated with many modifications in cardiovascular form and function, which have changed dramatically during the course of vertebrate evolution. Most cardiovascular studies have focused upon adults, leaving the development of this critical system largely unexplored. In this essay, we attempt a synthesis of sauropsid cardiovascular development based on the limited literature and indicate fertile regions for future studies. Early morphological cardiovascular development, i.e., the basic formation of the tube heart and the major pulmonary and systemic vessels, is similar across tetrapods. Subsequent cardiac chamber development, however, varies considerably between developing chelonians, squamates, crocodilians, and birds, reflected in the diversity of adult ventricular structure across these taxa. The details of how these differences in morphology develop, including the molecular regulation of cardiac and vascular growth and differentiation, are still poorly understood. In terms of the functional maturation of the cardiovascular system, reflected in physiological mechanisms for regulating heart rate and cardiac output, recent work has illustrated that changes during ontogeny in parameters such as heart rate and arterial blood pressure are somewhat species‐dependent. However, there are commonalities, such as a β‐adrenergic receptor tone on the embryonic heart appearing prior to 60% of development. Differential gross morphological responses to environmental stressors (oxygen, hydration, temperature) have been investigated interspecifically, revealing that cardiac development is relatively plastic, especially, with respect to change in heart growth. Collectively, the data assembled here reflects the current limited morphological and physiological understanding of cardiovascular development in sauropsids and identifies key areas for future studies of this diverse vertebrate lineage. J. Morphol., 2009. © 2009 Wiley‐Liss, Inc. 相似文献
94.
Sugar FJ Jenney FE Poole FL Brereton PS Izumi M Shah C Adams MW 《Journal of structural and functional genomics》2005,6(2-3):149-158
As the natural extension of the genomic sequencing projects, the goal of the various world-wide Structural Genomics projects
is development of techniques for high throughput (HTP) cloning, protein overexpression, purification and structural determination,
with the ultimate goal of determining all possible protein structures. Rapid (small-scale) screening of potential expression
clones under different growth conditions is presumed to be possible and a viable way to increase throughput of protein expression.
In order to test the utility of screening for soluble, heterologous protein expression, we have compared the production of
recombinant proteins on a small scale (1 ml cultures in 96-well plates) in Escherichia coli under two growth conditions [a rich medium and a defined (minimal) medium] using an enzyme-linked immunosorbent assay (ELISA)
against the affinity tag, with the amount of recombinant protein produced during the large-scale (500 ml) growth of E. coli. The large-scale expression products were examined after a single step affinity purification by visualization on SDS-PAGE
gels. Of the open reading frames that were successfully expressed on the 1 ml scale as judged by immunodetection, 80% of them
successfully scaled-up to 500 ml in a rich medium and 81% of them scaled-up in a defined medium. This is significantly higher
than would be expected by a randomly selected expression condition and validates the use of small-scale expression as a screening
tool for more efficient protein production. 相似文献
95.
Oliveira R Christov C Guillamo JS de Boüard S Palfi S Venance L Tardy M Peschanski M 《BMC cell biology》2005,6(1):7
Background
Gliomas are "intraparenchymally metastatic" tumors, invading the brain in a non-destructive way that suggests cooperation between glioma cells and their environment. Recent studies using an engineered rodent C6 tumor cell line have pointed to mechanisms of invasion that involved gap junctional communication (GJC), with connexin 43 as a substrate. We explored whether this concept may have clinical relevance by analyzing the participation of GJC in human glioblastoma invasion. 相似文献96.
Timothy C. Roth II Niels C. Rattenborg Vladimir V. Pravosudov 《Philosophical transactions of the Royal Society of London. Series B, Biological sciences》2010,365(1542):945-959
All animals in which sleep has been studied express signs of sleep-like behaviour, suggesting that sleep must have some fundamental functions that are sustained by natural selection. Those functions, however, are still not clear. Here, we examine the ecological relevance of sleep from the perspective of behavioural trade-offs that might affect fitness. Specifically, we highlight the advantage of using food-caching animals as a system in which a conflict might occur between engaging in sleep for memory/learning and hypothermia/torpor to conserve energy. We briefly review the evidence for the importance of sleep for memory, the importance of memory for food-caching animals and the conflicts that might occur between sleep and energy conservation in these animals. We suggest that the food-caching paradigm represents a naturalistic and experimentally practical system that provides the opportunity for a new direction in sleep research that will expand our understanding of sleep, especially within the context of ecological and evolutionary processes. 相似文献
97.
Vitaly V. Vostrikov Anna E. Daily Denise V. Greathouse Roger E. Koeppe II 《The Journal of biological chemistry》2010,285(41):31723-31730
The membrane-spanning segments of integral membrane proteins often are flanked by aromatic or charged amino acid residues, which may “anchor” the transmembrane orientation. Single spanning transmembrane peptides such as those of the WALP family, acetyl-GWW(LA)nLWWA-amide, furthermore adopt a moderate average tilt within lipid bilayer membranes. To understand the anchor residue dependence of the tilt, we introduce Leu-Ala “spacers” between paired anchors and in some cases replace the outer tryptophans. The resulting peptides, acetyl-GX2ALW(LA)6LWLAX22A-amide, have Trp, Lys, Arg, or Gly in the two X positions. The apparent average orientations of the core helical sequences were determined in oriented phosphatidylcholine bilayer membranes of varying thickness using solid-state 2H NMR spectroscopy. When X is Lys, Arg, or Gly, the direction of the tilt is essentially constant in different lipids and presumably is dictated by the tryptophans (Trp5 and Trp19) that flank the inner helical core. The Leu-Ala spacers are no longer helical. The magnitude of the apparent helix tilt furthermore scales nicely with the bilayer thickness except when X is Trp. When X is Trp, the direction of tilt is less well defined in each phosphatidylcholine bilayer and varies up to 70° among 1,2-dioleoyl-sn-glycero-3-phosphocholine, 1,2-dimyristoyl-sn-glycero-3-phosphocholine, and 1,2-dilauroyl-sn-glycero-3-phosphocholine bilayer membranes. Indeed, the X = Trp case parallels earlier observations in which WALP family peptides having multiple Trp anchors show little dependence of the apparent tilt magnitude on bilayer thickness. The results shed new light on the interactions of arginine, lysine, tryptophan, and even glycine at lipid bilayer membrane interfaces. 相似文献
98.
The RpoS-Mediated Regulation of Isocitrate Dehydrogenase Gene Expression in Escherichia coli 总被引:2,自引:0,他引:2
The Escherichia coli NADP+-dependent isocitrate dehydrogenase (IDH; EC 1.1.1.42), encoded by an icd gene, is a tricarboxylic acid (TCA) cycle enzyme responsible for the oxidative decarboxylation of isocitrate to α-ketoglutarate.
In order to examine how the icd gene expression is regulated, an icd-lacZ reporter fusion was constructed. While the icd gene was induced in exponential growth phase, it was repressed in stationary growth phase. Genetic inactivation of an rpoS gene, whose product is an alternative sigma factor, induced the icd gene expression approximately 4.8 times more in the stationary phase and the IDH enzyme activity in the rpoS mutant was 3.2 times higher than that in the wild type, indicating that the RpoS factor acts as a negative regulator of the
icd gene expression in the stationary phase. 相似文献
99.
Immune system components differ in their functions and costs, and immune defense profiles are likely to vary among species with differing ecologies. We compared adaptive immune defenses in two closely related species that have contrasting inflammatory immune responses, the widespread and abundant house sparrow (Passer domesticus) and the less abundant tree sparrow (Passer montanus). We found that the house sparrow, which we have previously shown mounts weaker inflammatory responses, exhibits stronger adaptive immune defenses, including antibody responses, natural antibody titers, and specific T-cell memory, than the tree sparrow. Conversely, tree sparrows, which mount strong inflammatory responses, also mount stronger nonspecific inflammatory T-cell responses but weaker specific adaptive responses. Prevalence of avian malaria parasite infections, which are controlled by adaptive immune defenses, was higher in the geographically restricted tree sparrow than in the ubiquitous house sparrow. Together these data describe distinct immune defense profiles between two closely related species that differ greatly in numbers and distributions. We suggest that these immunological differences could affect fitness in ways that contribute to the contrasting abundances of the two species in North American and Western Europe. 相似文献
100.
A cold inducible multidomain cystatin from winter wheat inhibits growth of the snow mold fungus, Microdochium nivale 总被引:2,自引:0,他引:2
A novel cold-induced cystatin cDNA clone (TaMDC1) was isolated from cold acclimated winter wheat crown tissue by using a macroarray-based differential screening method. The deduced amino acid sequence consisted of a putative N-terminal secretory signal peptide of 37 amino acids and a mature protein (mTaMDC1) with a molecular mass of 23 kDa. The mTaMDC1 had a highly conserved N-terminal cystatin domain and a long C-terminal extension containing a second region, which exhibited partial similarity to the cystatin domain. The recombinant mTaMDC1 was purified from Escherichia coli and its cysteine proteinase inhibitory activity against papain was analyzed. The calculated Ki value of 5.8×10−7 M is comparable to those reported for other phytocystatins. Northern and western blot analyses showed elevated expression of TaMDC1 mRNA and protein during cold acclimation of wheat. In addition to cold, accumulation of the TaMDC1 message was induced by other abiotic stresses including drought, salt and ABA treatment. Investigation of in vitro antifungal activity of mTaMDC1 showed strong inhibition on the mycelium growth of the snow mold fungus Microdochium nivale. Hyphae growth was totally inhibited in the presence of 50 μg/ml mTaMDC1 and morphological changes such as swelling, fragmentation and sporulation of the fungus were observed. The mechanisms of the in vitro antifungal effects and the possible involvement of TaMDC1 in cold induced snow mold resistance of winter wheat are discussed. 相似文献