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991.
Borrelia burgdorferi outer surface protein C (OspC) binds complement component C4b and confers bloodstream survival 下载免费PDF全文
Jennifer A. Caine Yi‐Pin Lin Julie R. Kessler Hiromi Sato John M. Leong Jenifer Coburn 《Cellular microbiology》2017,19(12)
Borrelia burgdorferi (Bb) is the causative agent of Lyme disease in the United States, a disease that can result in carditis, and chronic and debilitating arthritis and/or neurologic symptoms if left untreated. Bb survives in the midgut of the Ixodes scapularis tick, or within tissues of immunocompetent hosts. In the early stages of infection, the bacteria are present in the bloodstream where they must resist clearance by the innate immune system of the host. We have found a novel role for outer surface protein C (OspC) from B. burgdorferi and B. garinii in interactions with the complement component C4b and bloodstream survival in vivo. Our data show that OspC inhibits the classical and lectin complement pathways and competes with complement protein C2 for C4b binding. Resistance to complement is important for maintenance of the lifecycle of Bb, enabling survival of the pathogen within the host as well as in the midgut of a feeding tick when ospC expression is induced. 相似文献
992.
Thomas Kvalnes Thor Harald Ringsby Henrik Jensen Ingerid Julie Hagen Bernt Rønning Henrik Pärn Håkon Holand Steinar Engen Bernt‐Erik Sæther 《Evolution; international journal of organic evolution》2017,71(8):2062-2079
A general assumption in quantitative genetics is the existence of an intermediate phenotype with higher mean individual fitness in the average environment than more extreme phenotypes. Here, we investigate the evolvability and presence of such a phenotype in wild bird populations from an eleven‐year experiment with four years of artificial selection for long and short tarsus length, a proxy for body size. The experiment resulted in strong selection in the imposed directions. However, artificial selection was counteracted by reduced production of recruits in offspring of artificially selected parents. This resulted in weak natural selection against extreme trait values. Significant responses to artificial selection were observed at both the phenotypic and genetic level, followed by a significant return toward preexperimental means. During artificial selection, the annual observed phenotypic response closely followed the predicted response from quantitative genetic theory ( = 0.96, = 0.56). The rapid return to preexperimental means was induced by three interacting mechanisms: selection for an intermediate phenotype, immigration, and recombination between selected and unselected individuals. The results of this study demonstrates the evolvability of phenotypes and that selection may favor an intermediate phenotype in wild populations. 相似文献
993.
Decoupled leaf and root carbon economics is a key component in the ecological diversity and evolutionary divergence of deciduous and evergreen lineages of genus Rhododendron 下载免费PDF全文
994.
K. Nawrot‐Chorabik 《Plant biosystems》2013,147(2):377-385
Abstract The somaclonal variation analysis was conducted on callus of 57 lines obtained by the method of somatic embryogenesis from six zygotic embryos (with different genotypes) of silver fir (Abies alba Mill.) located in two mountain regions in the south of Poland. The somaclonal variation at the DNA level was estimated using RAPD markers and the data produced were used to estimate the level of similarity using Jaccard’s coefficient. For RAPD analysis, 24 ten‐nucleotide primers from the groups OPA, OPB and OPG were used. Two genotypes deriving from Krynica and My?lenice showed high genetic similarity (Jaccard’s coefficient 0.74 and 0.83), which provides a substantial chance for producing firs with the parental genotype. The remaining four genotypes showed somaclonal variation (average Jaccard’s coefficient approx. 0.5). The significance in variation of the research sites was ascertained by the ANOVA statistical test, which showed the impact of genotype, type of medium and phytohormones included in it on the variation among the fir lines bred in vitro. The somaclonal variation data in silver fir could be useful for its propagation through in vitro culture, and in generating detailed genetic maps of this species. 相似文献
995.
Sung-Min Kim Heejaung Kim Jeong-Seon Lee Kyung Seok Park Gye Sun Jeon Jeeheun Shon Suk-Won Ahn Seung Hyun Kim Kyung Min Lee Jung-Joon Sung Kwang-Woo Lee 《PloS one》2013,8(11)
Background
Patients with ALS may be exposed to variable degrees of chronic intermittent hypoxia. However, all previous experimental studies on the effects of hypoxia in ALS have only used a sustained hypoxia model and it is possible that chronic intermittent hypoxia exerts effects via a different molecular mechanism from that of sustained hypoxia. No study has yet shown that hypoxia (either chronic intermittent or sustained) can affect the loss of motor neurons or cognitive function in an in vivo model of ALS.Objective
To evaluate the effects of chronic intermittent hypoxia on motor and cognitive function in ALS mice.Methods
Sixteen ALS mice and 16 wild-type mice were divided into 2 groups and subjected to either chronic intermittent hypoxia or normoxia for 2 weeks. The effects of chronic intermittent hypoxia on ALS mice were evaluated using the rotarod, Y-maze, and wire-hanging tests. In addition, numbers of motor neurons in the ventral horn of the spinal cord were counted and western blot analyses were performed for markers of oxidative stress and inflammatory pathway activation.Results
Compared to ALS mice kept in normoxic conditions, ALS mice that experienced chronic intermittent hypoxia had poorer motor learning on the rotarod test, poorer spatial memory on the Y-maze test, shorter wire hanging time, and fewer motor neurons in the ventral spinal cord. Compared to ALS-normoxic and wild-type mice, ALS mice that experienced chronic intermittent hypoxia had higher levels of oxidative stress and inflammation.Conclusions
Chronic intermittent hypoxia can aggravate motor neuronal death, neuromuscular weakness, and probably cognitive dysfunction in ALS mice. The generation of oxidative stress with activation of inflammatory pathways may be associated with this mechanism. Our study will provide insight into the association of hypoxia with disease progression, and in turn, the rationale for an early non-invasive ventilation treatment in patients with ALS. 相似文献996.
Taane G. Clark Kim Mallard Francesc Coll Mark Preston Samuel Assefa David Harris Sam Ogwang Francis Mumbowa Bruce Kirenga Denise M. O’Sullivan Alphonse Okwera Kathleen D. Eisenach Moses Joloba Stephen D. Bentley Jerrold J. Ellner Julian Parkhill Edward C. Jones-López Ruth McNerney 《PloS one》2013,8(12)
Background
Understanding the emergence and spread of multidrug-resistant tuberculosis (MDR-TB) is crucial for its control. MDR-TB in previously treated patients is generally attributed to the selection of drug resistant mutants during inadequate therapy rather than transmission of a resistant strain. Traditional genotyping methods are not sufficient to distinguish strains in populations with a high burden of tuberculosis and it has previously been difficult to assess the degree of transmission in these settings. We have used whole genome analysis to investigate M. tuberculosis strains isolated from treatment experienced patients with MDR-TB in Uganda over a period of four years.Methods and Findings
We used high throughput genome sequencing technology to investigate small polymorphisms and large deletions in 51 Mycobacterium tuberculosis samples from 41 treatment-experienced TB patients attending a TB referral and treatment clinic in Kampala. This was a convenience sample representing 69% of MDR-TB cases identified over the four year period. Low polymorphism was observed in longitudinal samples from individual patients (2-15 SNPs). Clusters of samples with less than 50 SNPs variation were examined. Three clusters comprising a total of 8 patients were found with almost identical genetic profiles, including mutations predictive for resistance to rifampicin and isoniazid, suggesting transmission of MDR-TB. Two patients with previous drug susceptible disease were found to have acquired MDR strains, one of which shared its genotype with an isolate from another patient in the cohort.Conclusions
Whole genome sequence analysis identified MDR-TB strains that were shared by more than one patient. The transmission of multidrug-resistant disease in this cohort of retreatment patients emphasises the importance of early detection and need for infection control. Consideration should be given to rapid testing for drug resistance in patients undergoing treatment to monitor the emergence of resistance and permit early intervention to avoid onward transmission. 相似文献997.
The granular layer is the input layer of the cerebellar cortex. It receives information through mossy fibers, which contact local granular layer interneurons (GLIs) and granular layer output neurons (granule cells). GLIs provide one of the first signal processing stages in the cerebellar cortex by exciting or inhibiting granule cells. Despite the importance of this early processing stage for later cerebellar computations, the responses of GLIs and the functional connections of mossy fibers with GLIs in awake animals are poorly understood. Here, we recorded GLIs and mossy fibers in the macaque ventral-paraflocculus (VPFL) during oculomotor tasks, providing the first full inventory of GLI responses in the VPFL of awake primates. We found that while mossy fiber responses are characterized by a linear monotonic relationship between firing rate and eye position, GLIs show complex response profiles characterized by “eye position fields” and single or double directional tunings. For the majority of GLIs, prominent features of their responses can be explained by assuming that a single GLI receives inputs from mossy fibers with similar or opposite directional preferences, and that these mossy fiber inputs influence GLI discharge through net excitatory or inhibitory pathways. Importantly, GLIs receiving mossy fiber inputs through these putative excitatory and inhibitory pathways show different firing properties, suggesting that they indeed correspond to two distinct classes of interneurons. We propose a new interpretation of the information flow through the cerebellar cortex granular layer, in which mossy fiber input patterns drive the responses of GLIs not only through excitatory but also through net inhibitory pathways, and that excited and inhibited GLIs can be identified based on their responses and their intrinsic properties. 相似文献
998.
Jong-Kuen Lee Sae-Ra Park Bong-Kwang Jung Yoon-Kyung Jeon Yeong-Shin Lee Min-Kyoung Kim Yong-Goo Kim Ji-Young Jang Chul-Woo Kim 《PloS one》2013,8(12)
Exosomes are small membrane vesicles released by a variety of cell types. Exosomes contain genetic materials, such as mRNAs and microRNAs (miRNAs), implying that they may play a pivotal role in cell-to-cell communication. Mesenchymal stem cells (MSCs), which potentially differentiate into multiple cell types, can migrate to the tumor sites and have been reported to exert complex effects on tumor progression. To elucidate the role of MSCs within the tumor microenvironment, previous studies have suggested various mechanisms such as immune modulation and secreted factors of MSCs. However, the paracrine effects of MSC-derived exosomes on the tumor microenvironment remain to be explored. The hypothesis of this study was that MSC-derived exosomes might reprogram tumor behavior by transferring their molecular contents. To test this hypothesis, exosomes from MSCs were isolated and characterized. MSC-derived exosomes exhibited different protein and RNA profiles compared with their donor cells and these vesicles could be internalized by breast cancer cells. The results demonstrated that MSC-derived exosomes significantly down-regulated the expression of vascular endothelial growth factor (VEGF) in tumor cells, which lead to inhibition of angiogenesis in vitro and in vivo. Additionally, miR-16, a miRNA known to target VEGF, was enriched in MSC-derived exosomes and it was partially responsible for the anti-angiogenic effect of MSC-derived exosomes. The collective results suggest that MSC-derived exosomes may serve as a significant mediator of cell-to-cell communication within the tumor microenvironment and suppress angiogenesis by transferring anti-angiogenic molecules. 相似文献
999.
Shengjun Wu Zhengyu Jin Jin Moon Kim Qunyi Tong Hanqing Chen 《Carbohydrate polymers》2009,77(4):750-753
pullulan, a water soluble extracellular polysaccharide, was produced by downstream fermentation employing the strain Aureobasidium pullulans. To obtain pure biopolymer from the fermentation broth, it is necessary to harvest cells, heat the broth, remove the melanin pigments co-produced during fermentation, concentration, precipitate and dry. Centrifugation of the fermentation broth at 10,000 rpm for 15 min gave cell pellets that were discarded and a green–black supernatant containing melanin pigment was subjected to the heat treatment at 80 °C for 20 min in order to remove the protein in the fermentation broth. The supernatant was demelanized by oxidation with hydrogen peroxide, concentrated under vacuum, precipitated with ethanol and dried at 60 °C for 30 min. This procedure produced high purity pullulan that was comparable in color and texture to the commercial samples. 相似文献
1000.
A total of 492 cattle sera was screened by IgG-ELISA against Neospora caninum (Nc-1 strain and a Korean isolate, KBA-2) and Toxoplasma gondii. Out of 492, 113 sera (23.0%) reacted positively to either Nc-1 or KBA-2 strains of N. caninum. Among the 113 positive sera, 92 sera (81.4%) reacted with antigens of both strains, but 6 sera (5.3%) with Nc-1 and 15 sera (13.3%) with KBA-2 strain only. And with T. gondii antigen, 6 sera (1.2%) were positive but all reacted with N. caninum antigen also. Western blot revealed typical binding pattern according to ELISA values, such that high OD group reacted specifically to the major surface proteins including 43 kDa protein. Seroprevalence of 23.0% indicates that neosporosis seemed to be one of major causes of abortion in cattle. It is suggested here to establish more epidemiological researches nationwide systematically. 相似文献