关键词： Hibernation   Ventricular fibrillation   Conduction anisotropy   Optical mapping   Hypothermia  

摘要： BACKGROUND Robust cell-to-cell coupling is critically important in the safety of cardiac conduction and protection against ventricular fibrillation (VF). Hibernating mammals have evolved naturally protective mechanisms against VF induced by hypothermia and reperfusion injury. OBJECTIVE We hypothesized that this protection strategy involves a dynamic maintenance of conduction and repolarization patterns through the improvement of gap junction functions. METHODS We optically mapped the hearts of summer-active (SA) and winter-hibernating (WH) ground squirrels Spermophilus undulatus from Siberia and nonhibernating rabbits during different temperatures (+3 degrees C to +37 degrees C). RESULTS Midhypothermia (+17 degrees C) resulted in nonuniform conduction slowing, increased dispersion of repolarization, shortened wavelength, and consequently enhanced VF induction in SA ground squirrels and rabbits. In contrast, wavelength was increased during hypothermia in WH hearts in which OF was not inducible at any temperature. In SA and rabbit hearts, but not in WH, conduction anisotropy was significantly increased by pacing acceleration, thus promoting VF induction during hypothermia. WH hearts maintained the same rate-independent anisotropic propagation pattern even at 3 degrees C. connexin 43 (Cx43) had more homogenous transmural distribution in WH ventricles as compared to SA. Moreover, Cx43 and N-cadherins (N-cad) densities as well as the percentage of their colocalization were significantly higher in WH compared to SA epicardium. CONCLUSION Rate-independent conduction anisotropy ratio, low dispersion of repolarization, and long wavelength-these are the main electrophysiological mechanisms of antiarrhythmic protection in hibernating mammalian species during hypothermia. This strategy includes the improved gap junction function, which is due to overexpression and enhanced colocalization of Cx43 and N-cad.

关键词： cathodoluminescence   dual-phase heterostructures   field emission   II-VI semiconductors   zinc sulfide  

摘要： We report the growth mechanism, cathodoluminescence and field emission of dual phase ZnS tetrapod tree-like heterostructures. This novel heterostructures consist of two phases: zinc blende for the trunk and hexagonal wurtzite for the branch. Direct evidence is presented for the polarity induced growth of tetrapod ZnS trees through high-resolution electron microscopy study, demonstrating that Zn-terminated ZnS (111)/(0001) polar surface is chemically active and S-terminated ((1) over bar(1) over bar(1) over bar)/(000 (1) over bar) polar surface is inert in the growth of tetrapod ZnS trees. Two strong UV emissions centered at 3.68 and 3.83 eV have been observed at room temperature, which are attributed to the bandgap emissions from the zinc blende trunk and hexagonal wurtzite branch, indicating that such structures can be used as unique electromechanical and optoelectronic components in potential light sources, laser and light emitting display devices. In addition, the low turn-on field (2.66 V mu m(-1)), high field-enhancement factor (over 2600), large current density (over 30 mAcm(-2) at a macroscopic field of 4.33 V mu m(-1)) and small fluctuation (similar to 1%) further indicate the availability of ZnS tetrapod tree-like heterostructures for field emission panel display. This excellent field-emission property is attributed to the specific crystallographic feature with high crystallinity and cone-shape patterned branch with nanometer-sized tips. Such a structure may optimize the FE properties and make a promising field emitter.

关键词： 动物园   事业   实践活动   解放思想  

摘要： 根据石园党字[2008]10号文《关于围绕“三年大变样”开展“双创双树”主题实践活动的实施意见》，结合我园边建设，边开放的实际，紧紧围绕突出创新，突出实践，突出标准，突出解决实际问题这“四突出”，认真组织动员，学习传达，力求以解放思想的新境界开创动物园事业发展的新局面。

关键词： ecosystems   natural selection   Nucifraga columbiana   Pinus albicaulis   Pinus flexilis   plant density   plant recruitment   seed dispersal   seed predation   Tamiasciurus  

摘要： Strongly interacting species often have pronounced direct and indirect effects on other species. Here we focus of the effects of pine squirrels (Tamiasciurus spp.), which are a dominant pre-dispersal seed predator of many conifers including limber pines (Pinus flexilis) and whitebark pines (P. albicaulis). Pine squirrels depress seed abundance by harvesting most limber and whitebark pine cones on their territories. Pine squirrels further reduce seed availability for Clark's Nutcrackers (Nucifraga columbiana), the primary seed disperser of these pines, because selection exerted by pine squirrels has reduced the number of seeds per cone and causes seeds to be less accessible. We predicted that, if fewer seeds were available for dispersal by nutcrackers, pine recruitment should be suppressed in areas with pine squirrels. In support of this prediction, stand densities were about two times greater in areas where pine squirrels are absent than in areas where they are present. Alternative explanations that we considered do not account for these differences;however, precipitation may limit stand densities in the absence of seed limitation by pine squirrels. In sum, pine squirrels apparently depress limber and whitebark pine stand densities, with the potential for ecosystem impacts because these pines are foundation species within Western subalpine ecosystems.

关键词： murid rodents   forest   derived savanna   diversity   distribution   deforestation  

摘要： Southward encroachment of the derived savanna zone with its attendant denudation of the rainforest in Nigeria adversely affects the diversity and distribution of mammals, particularly murid rodents. This study was carried out to establish the identities of murid rodent populations and to compare their diversity between forest and derived savanna sites within south western Nigeria. Identification of captured specimens was carried out by multivariate statistics of body and skull measurements, and also by analysis of certain discrete characters. Six species were identified: Praomys tullbergi, Hylomyscus stella, Mastomys natalensis, Arvicanthis rufinus, Lemniscomys striatus and Lophuromys sikapusi. Forest sites possessed a higher Shannon's diversity index (1.685) than the derived savanna sites (0.978), containing a higher number of taxa and larger abundance of murid rodents. This underscores the negative impact that encroachment of the derived savanna has upon diversity of animals in areas that were once forest.

关键词： Pectinidae   systematics   molecular phylogeny   16S rRNA   12S rRNA   Histone H3   scallops  

摘要： Evolutionary relationships of the Pectinidae were examined using two mitochondrial genes (12S rRNA, 16S rRNA) and one nuclear gene (Histone H3) for 46 species. Outgroup taxa from Propeamussidae, Spondylidae and Limidae were also sequenced to examine the impact of outgroup choice on pectinid topologies. Our phylogenetic analyses resolved the Pectinidae as monophyletic, but many of the subfamilies and tribes within the family do not form monophyletic clades. The paraphyletic Aequipectinini group is the most basal member of the Pectinidae, with the Chlamydinae and Palliolinae representing the most recently derived pectinid groups. These results are in contrast with the current morphological hypothesis of Pectinidae evolution, which suggests the Chlamydinae and Pallioline are basal groups within the Pectinidae. Ingroup topology was found to be sensitive to outgroup choice and increasing taxon sampling within the Pectinidae resulted in more robust phylogenies. (C) 2008 Elsevier Inc. All rights reserved.

关键词： mercury   tree swallows   metals   elements   oxidative stress  

摘要： Elevated mercury concentrations in water were reported in the prairie wetlands at Lostwood National Wildlife Refuge, ND. In order to determine whether wildlife associated with these wetlands was exposed to and then accumulated higher mercury concentrations than wildlife living near more permanent wetlands (e.g. lakes), tree swallow (Tachycineta bicolor) eggs and nestlings were collected from nests near seasonal wetlands, semi-permanent wetlands, and lakes. Mercury concentrations in eggs collected near seasonal wetlands were higher than those collected near semi-permanent wetlands or lakes. In contrast, mercury concentrations in nestling livers did not differ among wetland types. Mercury and other element concentrations in tree swallow eggs and nestlings collected from all wetlands were low. As suspected from these low concentrations, mercury concentrations in sample eggs were not a significant factor explaining the hatching success of the remaining eggs in each clutch. Published by Elsevier Ltd.

关键词： extinction risk   latent risk   mammals  

摘要： Phylogenies describe the origins and history of species. However, they can also help to predict species' fates and so can be useful tools for managing the future of biodiversity. This article starts by sketching how phylogenetic, geographic, and trait information can be combined to elucidate present mammalian diversity patterns and how they arose. Recent diversification rates and standing diversity show different geographic patterns, indicating that cradles of diversity have moved over time. Patterns in extinction risk reflect both biological differences among mammalian lineages and differences in threat intensity among regions. Phylogenetic comparative analyses indicate that for small-bodied mammals, extinction risk is governed mostly by where the species live and the intensity of the threats, whereas for large-bodied mammals, ecological differences also play an important role. This modeling approach identifies species whose intrinsic biology renders them particularly vulnerable to increased human pressure. We outline how the approach might be extended to consider future trends in anthropogenic drivers, to identify likely future battlegrounds of mammalian conservation, and the likely casualties. This framework could help to highlight consequences of choosing among different future climatic and socioeconomic scenarios. We end by discussing priority-setting, showing how alternative currencies for diversity can suggest very different priorities. We argue that aiming to maximize long-term evolutionary responses is inappropriate, that conservation planning needs to consider costs as well as benefits, and that proactive conservation of largely intact systems should be part of a balanced strategy.

关键词： Ediacaran biota   Chengjiang faunas   Phylogeny of deuterostomes   phylum vetulicolia   origin of vertebrates  

摘要： Excluding the sponges the Kingdom Animalia is usually divided into three subkingdoms: Diploblasta, Protostomia and Deuterostomia. The Cambrian Explosion consists of three major episodes, two of which were in the early Early Cambrian (one represented by the small skeletal fossils "SSFs" at the base of the Cambrian and the other represented by the succeeding Chengjiang faunas "CFs"), and the other episode as their prelude took place in the "Eocambrian" (i.e. the latest Precambrian), represented by the Ediacaran faunas. This unique Big Bang of life has been recognized as giving birth to the entire morphological Tree Of Animals (or metazoans), in short the TOA. Its "seed" in the deep Precambrian, represented by some sort of protist from which the complete TOA must have grown, remains unknown paleontologically. However, the fossil evidence suggests that the three major episodes of the Cambrian Explosion are responsible for the earliest radiations of the three subkingdoms. of animals respectively. While the observed Ediacaran fauna might constitute only a small part of the whole Ediacaran biota, our evidence supports that it was dominated by diploblasts (the "trunk" of the TOA) with only a few possible stem-group triploblasts. The Early Cambrian in turn in two phases explosively yielded almost all the major triploblastic crown-branches (Bilateria: the huge "crown" of the TOA), which include the other two subkingdoms: first the extremely diverse protostomes in the Meishucunian Age and then followed by a nearly entire lineage of early deuterostomes from the Chengjiang, including even its most derived member - the earliest true vertebrates. Among the four most significant milestones of morphological origins and radiations in animal history, the first one (i.e. appearance of metazoans) took place in the Ediacaran Period or earlier times, and the other three can be seen in the windows available from the Chengjiang and the Meishucunian fossil assemblages. The newly discovered e

关键词： seed dispersal and predation   fragmentation   regeneration   exclosure experiments   Madagascar  

摘要： The objective of this study was to examine how the processes of seed dispersal and seed predation were altered in forest fragments of the dry forest of Madagascar, where the usual seed dispersers and vertebrate seed predators were absent, using a lemur-dispersed tree species (Strychnos madagascariensis;Loganiaceae) as an example. We then assessed how the changes in vertebrate community composition alter the regeneration pattern and establishment of this tree species and thus, ultimately, the species composition of the forest fragments. By using size-selective exclosures, data from forest fragments were compared with results from continuous forest where vertebrate dispersers and predators were abundant. Visits to the exclosures by mammalian seed predators were monitored with hair traps. In the continuous forest up to 100% of the seeds were removed within the 7 days of the experiments. A substantial proportion of them was lost to seed predation by native rodents. In contrast, practically no predation took place in the forest fragments and almost all seeds removed were dispersed into the safety of ant nests by Aphaenogaster swammerdami, which improves chances of seedling establishment. In congruence with these findings, the abundance of S. madagascariensis in the forest fragments exceeded that of the continuous forest. Thus, the lack of vertebrate seed dispersers in these forest fragments did not lead to a decline in regeneration of this animal-dispersed tree species as would have been expected, but rather was counterbalanced by the concomitant demise of vertebrate seed predators and an increased activity of ants taking over the role of seed dispersers, and possibly even out-doing the original candidates. This study provides an example of a native vertebrate-dispersed species apparently profiting from fragmentation due to flexible animal-plant interactions in different facets, possibly resulting in an impoverished tree species community.