排序方式: 共有44条查询结果,搜索用时 15 毫秒
21.
Andrew D Morgan Michael A Brockhurst Laura DC Lopez-Pascua Csaba Pal Angus Buckling 《BMC evolutionary biology》2007,7(1):1
Background
The dynamics of antagonistic host-parasite coevolution are believed to be crucially dependent on the rate of migration between populations. We addressed how the rate of simultaneous migration of host and parasite affected resistance and infectivity evolution of coevolving meta-populations of the bacterium Pseudomonas fluorescens and a viral parasite (bacteriophage). The increase in genetic variation resulting from small amounts of migration is expected to increase rates of adaptation of both host and parasite. However, previous studies suggest phages should benefit more from migration than bacteria; because in the absence of migration, phages are more genetically limited and have a lower evolutionary potential compared to the bacteria. 相似文献22.
Xiaocui Zhu Leah A Santat Mi Sook Chang Jamie Liu Joelle R Zavzavadjian Estelle A Wall Christine Kivork Melvin I Simon Iain DC Fraser 《BMC molecular biology》2007,8(1):98
Background
Effective and stable knockdown of multiple gene targets by RNA interference is often necessary to overcome isoform redundancy, but it remains a technical challenge when working with intractable cell systems. 相似文献23.
Lúcia de Paula Célio L Silva Daniela Carlos Camila Matias-Peres Carlos A Sorgi Edson G Soares Patrícia RM Souza Carlos RZ Bladés Fábio CS Galleti Vânia LD Bonato Eduardo DC Gonçalves Érika VG Silva Lúcia H Faccioli 《Genetic vaccines and therapy》2007,5(1):1-7
The great challenges for researchers working in the field of vaccinology are optimizing DNA vaccines for use in humans or large animals and creating effective single-dose vaccines using appropriated controlled delivery systems. Plasmid DNA encoding the heat-shock protein 65 (hsp65) (DNAhsp65) has been shown to induce protective and therapeutic immune responses in a murine model of tuberculosis (TB). Despite the success of naked DNAhsp65-based vaccine to protect mice against TB, it requires multiple doses of high amounts of DNA for effective immunization. In order to optimize this DNA vaccine and simplify the vaccination schedule, we coencapsulated DNAhsp65 and the adjuvant trehalose dimycolate (TDM) into biodegradable poly (DL-lactide-co-glycolide) (PLGA) microspheres for a single dose administration. Moreover, a single-shot prime-boost vaccine formulation based on a mixture of two different PLGA microspheres, presenting faster and slower release of, respectively, DNAhsp65 and the recombinant hsp65 protein was also developed. These formulations were tested in mice as well as in guinea pigs by comparison with the efficacy and toxicity induced by the naked DNA preparation or BCG. The single-shot prime-boost formulation clearly presented good efficacy and diminished lung pathology in both mice and guinea pigs. 相似文献
24.
25.
26.
Restriction mapping and sequencing have shown that humans have
substantially lower levels of mitochondrial genome diversity (d) than
chimpanzees. In contrast, humans have substantially higher levels of
heterozygosity (H) at protein-coding loci, suggesting a higher level of
diversity in the nuclear genome. To investigate the discrepancy further, we
sequenced a segment of the mitochondrial genome control region (CR) from 49
chimpanzees. The majority of these were from the Pan troglodytes versus
subspecies, which was underrepresented in previous studies. We also
estimated the average heterozygosity at 60 short tandem repeat (STR) loci
in both species. For a total sample of 115 chimpanzees, d = 0.075 +/0
0.037, compared to 0.020 +/- 0.011 for a sample of 1,554 humans. The
heterozygosity of human STR loci is significantly higher than that of
chimpanzees. Thus, the higher level of nuclear genome diversity relative to
mitochondrial genome diversity in humans is not restricted to
protein-coding loci. It seems that humans, not chimpanzees, have an unusual
d/H ratio, since the ratio in chimpanzees is similar to that in other
catarrhines. This discrepancy in the relative levels of nuclear and
mitochondrial genome diversity in the two species cannot be explained by
differences in mutation rate. However, it may result from a combination of
factors such as a difference in the extent of sex ratio disparity, the
greater effect of population subdivision on mitochondrial than on nuclear
genome diversity, a difference in the relative levels of male and female
migration among subpopulations, diversifying selection acting to increase
variation in the nuclear genome, and/or directional selection acting to
reduce variation in the mitochondrial genome.
相似文献
27.
TL Kieft EM Murphy DL Haldeman PS Amy BN Bjornstad EV McDonald DB Ringelberg DC White J Stair RP Griffiths TC Gsell WE Holben DR Boone 《Microbial ecology》1998,36(3):336-348
Abstract Two chronosequences of unsaturated, buried loess sediments, ranging in age from <10,000 years to >1 million years, were investigated to reconstruct patterns of microbial ecological succession that have occurred since sediment burial. The relative importance of microbial transport and survival to succession was inferred from sediment ages, porewater ages, patterns of abundance (measured by direct counts, counts of culturable cells, and total phospholipid fatty acids), activities (measured by radiotracer and enzyme assays), and community composition (measured by phospholipid fatty acid patterns and Biolog substrate usage). Core samples were collected at two sites 40 km apart in the Palouse region of eastern Washington State, near the towns of Washtucna and Winona. The Washtucna site was flooded multiple times during the Pleistocene by glacial outburst floods; the Winona site elevation is above flood stage. Sediments at the Washtucna site were collected from near surface to 14.9 m depth, where the sediment age was approximately 250 ka and the porewater age was 3700 years; sample intervals at the Winona site ranged from near surface to 38 m (sediment age: approximately 1 Ma; porewater age: 1200 years). Microbial abundance and activities declined with depth at both sites; however, even the deepest, oldest sediments showed evidence of viable microorganisms. Same-age sediments had equal quantities of microorganisms, but different community types. Differences in community makeup between the two sites can be attributed to differences in groundwater recharge and paleoflooding. Estimates of the microbial community age can be constrained by porewater and sediment ages. In the shallower sediments (<9 m at Washtucna, <12 m at Winona), the microbial communities are likely similar in age to the groundwater; thus, microbial succession has been influenced by recent transport of microorganisms from the surface. In the deeper sediments, the populations may be considerably older than the porewater ages, since microbial transport is severely restricted in unsaturated sediments. This is particularly true at the Winona site, which was never flooded. 相似文献
28.
Hidenori Takahashi Shigetaka Shimodaira Masahiro Ogasawara Shuichi Ota Masanori Kobayashi Hirofumi Abe Yuji Morita Kazuhiro Nagai Shunichi Tsujitani Masato Okamoto Yukio Suzuki Yoichi Nakanishi Yoshikazu Yonemitsu for the DC Vaccine Study Group at the Japanese Society of Immunotherapy Cell Therapy 《Cancer immunology, immunotherapy : CII》2016,65(9):1099-1111
29.
30.
Ryan G. Drum Christine A. Ribic Katie Koch Eric Lonsdorf Evan Grant Marissa Ahlering Laurel Barnhill Thomas Dailey Socheata Lor Connie Mueller David C. Pavlacky Jr. Catherine Rideout David Sample 《PloS one》2015,10(11)
Grassland bird habitat has declined substantially in the United States. Remaining grasslands are increasingly fragmented, mostly privately owned, and vary greatly in terms of habitat quality and protection status. A coordinated strategic response for grassland bird conservation is difficult, largely due to the scope and complexity of the problem, further compounded by biological, sociological, and economic uncertainties. We describe the results from a collaborative Structured Decision Making (SDM) workshop focused on linking social and economic drivers of landscape change to grassland bird population outcomes. We identified and evaluated alternative strategies for grassland bird conservation using a series of rapid prototype models. We modeled change in grassland and agriculture cover in hypothetical landscapes resulting from different landowner decisions in response to alternative socio-economic conservation policy decisions. Resulting changes in land cover at all three stages of the annual cycle (breeding, wintering, and migration) were used to estimate changes in grassland bird populations. Our results suggest that successful grassland bird conservation may depend upon linkages with ecosystem services on working agricultural lands and grassland-based marketing campaigns to engage the public. With further development, spatial models that link landowner decisions with biological outcomes can be essential tools for making conservation policy decisions. A coordinated non-traditional partnership will likely be necessary to clearly understand and systematically respond to the many conservation challenges facing grassland birds. 相似文献