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971.
Audun Stien Rolf A. Ims Steve D. Albon Eva Fuglei R. Justin Irvine Erik Ropstad Odd Halvorsen Rolf Langvatn Leif Egil Loe Vebj?rn Veiberg Nigel G. Yoccoz 《Biology letters》2012,8(6):1002-1005
Assessing the role of weather in the dynamics of wildlife populations is a pressing task in the face of rapid environmental change. Rodents and ruminants are abundant herbivore species in most Arctic ecosystems, many of which are experiencing particularly rapid climate change. Their different life-history characteristics, with the exception of their trophic position, suggest that they should show different responses to environmental variation. Here we show that the only mammalian herbivores on the Arctic islands of Svalbard, reindeer (Rangifer tarandus) and sibling voles (Microtus levis), exhibit strong synchrony in population parameters. This synchrony is due to rain-on-snow events that cause ground ice and demonstrates that climate impacts can be similarly integrated and expressed in species with highly contrasting life histories. The finding suggests that responses of wildlife populations to climate variability and change might be more consistent in Polar regions than elsewhere owing to the strength of the climate impact and the simplicity of the ecosystem. 相似文献
972.
Lars Behrendt Anthony W D Larkum Erik Trampe Anders Norman S?ren J S?rensen Michael Kühl 《The ISME journal》2012,6(6):1222-1237
We assessed the microbial diversity and microenvironmental niche characteristics in the didemnid ascidian Lissoclinum patella using 16S rRNA gene sequencing, microsensor and imaging techniques. L. patella harbors three distinct microbial communities spatially separated by few millimeters of tunic tissue: (i) a biofilm on its upper surface exposed to high irradiance and O2 levels, (ii) a cloacal cavity dominated by the prochlorophyte Prochloron spp. characterized by strong depletion of visible light and a dynamic chemical microenvironment ranging from hyperoxia in light to anoxia in darkness and (iii) a biofilm covering the underside of the animal, where light is depleted of visible wavelengths and enriched in near-infrared radiation (NIR). Variable chlorophyll fluorescence imaging demonstrated photosynthetic activity, and hyperspectral imaging revealed a diversity of photopigments in all microhabitats. Amplicon sequencing revealed the dominance of cyanobacteria in all three layers. Sequences representing the chlorophyll d containing cyanobacterium Acaryochloris marina and anoxygenic phototrophs were abundant on the underside of the ascidian in shallow waters but declined in deeper waters. This depth dependency was supported by a negative correlation between A. marina abundance and collection depth, explained by the increased attenuation of NIR as a function of water depth. The combination of microenvironmental analysis and fine-scale sampling techniques used in this investigation gives valuable first insights into the distribution, abundance and diversity of bacterial communities associated with tropical ascidians. In particular, we show that microenvironments and microbial diversity can vary significantly over scales of a few millimeters in such habitats; which is information easily lost by bulk sampling. 相似文献
973.
974.
Jorde PE 《Molecular ecology resources》2012,12(3):476-480
A general expression for the covariance of allele frequencies among cohorts in age-structured populations is derived. The expression is used to extend the so-called temporal method for estimating effective population size from allele frequency shifts among samples from cohorts born any number of years apart. Computer simulations are used to check on the accuracy and precision of the method, and an application to coastal Atlantic cod is presented. 相似文献
975.
Enteroaggregative Escherichia coli (EAEC) is an important cause of endemic and epidemic diarrheal disease worldwide. Although not classically considered an inflammatory pathogen in the style of Shigella and Salmonella species, clinical data from patients suggests that inflammatory responses may play an important role during EAEC disease. However, the specific role of inflammation during EAEC pathogenesis has not been investigated in detail. To better understand how EAEC may induce inflammation, we have focused our attention on the intimate interactions between EAEC and the host epithelium and the subsequent induction of host cell signaling events leading to innate immune responses. Here, we discuss our recent findings on the signaling pathway by which EAEC promotes transepithelial migration of polymorphonuclear leukocytes (PMNs), the role of aggregative adherence fimbriae in triggering this event and the implementation of human intestinal xenografts in immunodeficient mice for studying EAEC pathogenesis in vivo. Our findings suggest that EAEC shares conserved mechanisms of inducing PMN recruitment with other intestinal pathogens, providing new insight into the potential pathological consequences of EAEC-induced inflammation. 相似文献
976.
Grauer OM Molling JW Bennink E Toonen LW Sutmuller RP Nierkens S Adema GJ 《Journal of immunology (Baltimore, Md. : 1950)》2008,181(10):6720-6729
Local TLR stimulation is an attractive approach to induce antitumor immunity. In this study, we compared various TLR ligands for their ability to affect murine GL261 cells in vitro and to eradicate established intracerebral murine gliomas in vivo. Our data show that GL261 cells express TLR2, TLR3, and TLR4 and respond to the corresponding TLR ligands with increasing MHC class I expression and inducing IL-6 secretion in vitro, while TLR5, TLR7, and TLR9 are essentially absent. Remarkably, CpG-oligonucleotides (CpG-ODN, TLR9) appeared to inhibit GL261 cell proliferation in a cell-type specific, but CpG-motif and TLR9-independent manner. A single intratumoral injection of CpG-ODN most effectively inhibited glioma growth in vivo and cured 80% of glioma-bearing C57BL/6 mice. Intratumoral injection of Pam3Cys-SK4 (TLR1/2) or R848 (TLR7) also produced a significant survival benefit, whereas poly(I:C) (TLR3) or purified LPS (TLR4) stimulation alone was not effective. Additional studies using TLR9(+/+) wild-type and TLR9(-/-) knockout mice revealed that the efficacy of local CpG-ODN treatment in vivo required TLR9 expression on nontumor cells. Additional experiments demonstrated increased frequencies of tumor-infiltrating IFN-gamma producing CD4(+) and CD8(+) effector T cells and a marked increase in the ratio of CD4(+) effector T cells to CD4(+)FoxP3(+) regulatory T cells upon CpG-ODN treatment. Surviving CpG-ODN treated mice were also protected from a subsequent tumor challenge without further addition of CpG-ODN. In summary, this study underlines the potency of local TLR treatment in antiglioma therapy and demonstrates that local CpG-ODN treatment most effectively restores antitumor immunity in a therapeutic murine glioma model. 相似文献
977.
Ayme-Southgate AJ Southgate RJ Philipp RA Sotka EE Kramp C 《Journal of molecular evolution》2008,67(6):653-669
All striated muscles respond to stretch by a delayed increase in tension. This physiological response, known as stretch activation,
is, however, predominantly found in vertebrate cardiac muscle and insect asynchronous flight muscles. Stretch activation relies
on an elastic third filament system composed of giant proteins known as titin in vertebrates or kettin and projectin in insects.
The projectin insect protein functions jointly as a “scaffold and ruler” system during myofibril assembly and as an elastic
protein during stretch activation. An evolutionary analysis of the projectin molecule could potentially provide insight into
how distinct protein regions may have evolved in response to different evolutionary constraints. We mined candidate genes
in representative insect species from Hemiptera to Diptera, from published and novel genome sequence data, and carried out
a detailed molecular and phylogenetic analysis. The general domain organization of projectin is highly conserved, as are the
protein sequences of its two repeated regions—the immunoglobulin type C and fibronectin type III domains. The conservation
in structure and sequence is consistent with the proposed function of projectin as a scaffold and ruler. In contrast, the
amino acid sequences of the elastic PEVK domains are noticeably divergent, although their length and overall unusual amino
acid makeup are conserved. These patterns suggest that the PEVK region working as an unstructured domain can still maintain
its dynamic, and even its three-dimensional, properties, without the need for strict amino acid conservation. Phylogenetic
analysis of the projectin proteins also supports a reclassification of the Hymenoptera in relation to Diptera and Coleoptera.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
978.
Hannon RM Kelly SA Middleton KM Kolb EM Pomp D Garland T 《The Journal of heredity》2008,99(4):349-354
From outbred Hsd:ICR mice, we selectively bred 4 replicate lines for high running (High-Runner [HR] lines) on wheels while maintaining 4 nonselected lines as controls (C lines). An apparent Mendelian recessive, the "mini-muscle" (MM) allele, whose main phenotypic effect is to reduce hindlimb muscle mass by 50%, was discovered in 2 HR lines and 1 C line. This gene of major effect has gone to fixation in one selected line, remains polymorphic in another, and is now undetectable in the one C line. Homozygotes exhibit various pleiotropic effects, including a doubling of mass-specific muscle aerobic capacity, and larger hearts, livers, and spleens. To create a population suitable for mapping the genomic location of the MM allele and to better characterize its pleiotropic effects, we crossed females fixed for the MM allele with male C57BL/6J. F(1) males were then backcrossed to the MM parent females. Backcross (BC) mice (N = 404) were dissected, and a 50:50 ratio of normal to MM phenotype was observed with no overlap in relative muscle mass. In the BC, analysis of covariance revealed that MM individuals ran significantly more on days 5 and 6 of a 6-day exposure to running wheels (as in the routine selective-breeding protocol), were smaller in body mass, and had larger ventricles and spleens. 相似文献
979.
Memory CD8+ T cells protect dendritic cells from CTL killing 总被引:1,自引:0,他引:1
Watchmaker PB Urban JA Berk E Nakamura Y Mailliard RB Watkins SC van Ham SM Kalinski P 《Journal of immunology (Baltimore, Md. : 1950)》2008,180(6):3857-3865
CD8(+) T cells have been shown to be capable of either suppressing or promoting immune responses. To reconcile these contrasting regulatory functions, we compared the ability of human effector and memory CD8(+) T cells to regulate survival and functions of dendritic cells (DC). We report that, in sharp contrast to the effector cells (CTLs) that kill DCs in a granzyme B- and perforin-dependent mechanism, memory CD8(+) T cells enhance the ability of DCs to produce IL-12 and to induce functional Th1 and CTL responses in naive CD4(+) and CD8(+) T cell populations. Moreover, memory CD8(+) T cells that release the DC-activating factor TNF-alpha before the release of cytotoxic granules induce DC expression of an endogenous granzyme B inhibitor PI-9 and protect DCs from CTL killing with similar efficacy as CD4(+) Th cells. The currently identified DC-protective function of memory CD8(+) T cells helps to explain the phenomenon of CD8(+) T cell memory, reduced dependence of recall responses on CD4(+) T cell help, and the importance of delayed administration of booster doses of vaccines for the optimal outcome of immunization. 相似文献
980.
Inducing antitumor T cell immunity: comparative functional analysis of interstitial versus Langerhans dendritic cells in a human cell line model 总被引:1,自引:0,他引:1
Santegoets SJ Bontkes HJ Stam AG Bhoelan F Ruizendaal JJ van den Eertwegh AJ Hooijberg E Scheper RJ de Gruijl TD 《Journal of immunology (Baltimore, Md. : 1950)》2008,180(7):4540-4549
Dendritic cells (DC) are increasingly applied as a cellular adjuvant in immunotherapy of cancer. Two major myeloid DC subsets are recognized: interstitial DC (IDC) that infiltrate connective tissues and Langerhans cells (LC) that line epithelial surfaces. Yet, functional differences between IDC and LC remain to be defined. We recently showed that the CD34(+) acute myeloid leukemia cell line MUTZ-3 supports differentiation of both DC-SIGN(+) IDC and Langerin-positive Birbeck granule-expressing LC. By comparative functional characterization of MUTZ-3 IDC and MUTZ-3 LC, we aimed to elucidate the relative abilities of these two DC subsets to induce a specific T cell response and reveal the more suitable candidate for use as a clinical vehicle of tumor vaccines. Although mature LC and IDC displayed comparable lymph node-homing potential, mature LC showed higher allogeneic T cell stimulatory capacity. Nevertheless, IDC supported the induction of tumor Ag-specific CD8(+) T cells at an overall higher efficiency. This might be related to the observed inability of LC to release T cell stimulatory cytokines such as IL-12p70, IL-23, and IL-15. Although this inability did not result in a detectable deviation in the cytokine expression profile of primed T cells, transduction with IL-12p70 significantly improved priming efficiency of LC, and ensured a functional equivalence with IDC in this regard. In conclusion, except for the inability of LC to release distinct type 1 T cell stimulatory cytokines, in vitro function of LC and IDC suggests comparable abilities of both subsets for the in vivo induction of antitumor T cells. 相似文献