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Higher-level snake phylogeny inferred from mitochondrial DNA sequences of 12S rRNA and 16S rRNA genes 总被引:3,自引:0,他引:3
Portions of two mitochondrial genes (12S and 16S ribosomal RNA) were
sequenced to determine the phylogenetic relationships among the major
clades of snakes. Thirty-six species, representing nearly all extant
families, were examined and compared with sequences of a tuatara and three
families of lizards. Snakes were found to constitute a monophyletic group
(confidence probability [CP] = 96%), with the scolecophidians (blind
snakes) as the most basal lineages (CP = 99%). This finding supports the
hypothesis that snakes underwent a subterranean period early in their
evolution. Caenophidians (advanced snakes), excluding Acrochordus, were
found to be monophyletic (CP = 99%). Among the caenophidians, viperids were
monophyletic (CP = 98%) and formed the sister group to the elapids plus
colubrids (CP = 94%). Within the viperids, two monophyletic groups were
identified: true vipers (CP = 98%) and pit vipers plus Azemiops (CP = 99%).
The elapids plus Atractaspis formed a monophyletic clade (CP = 99%). Within
the paraphyletic Colubridae, the largely Holarctic Colubrinae was found to
be a monophyletic assemblage (CP = 98%), and the Xenodontinae was found to
be polyphyletic (CP = 91%). Monophyly of the henophidians (primitive
snakes) was neither supported nor rejected because of the weak resolution
of relationships among those taxa, except for the clustering of Calabaria
with a uropeltid, Rhinophis (CP = 94%).
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Molecular dynamics of synthetic leucine-serine ion channels in a phospholipid membrane 总被引:2,自引:0,他引:2 下载免费PDF全文
Molecular dynamics calculations were carried out on models of two synthetic leucine-serine ion channels: a tetrameric bundle with sequence (LSLLLSL)(3)NH(2) and a hexameric bundle with sequence (LSSLLSL)(3)NH(2). Each protein bundle is inserted in a palmitoyloleoylphosphatidylcholine bilayer membrane and solvated by simple point charge water molecules inside the pore and at both mouths. Both systems appear to be stable in the absence of an electric field during the 4 ns of molecular dynamics simulation. The water motion in the narrow pore of the four-helix bundle is highly restricted and may provide suitable conditions for proton transfer via a water wire mechanism. In the wider hexameric pore, the water diffuses much more slowly than in bulk but is still mobile. This, along with the dimensions of the pore, supports the observation that this peptide is selective for monovalent cations. Reasonable agreement of predicted conductances with experimentally determined values lends support to the validity of the simulations. 相似文献
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Purpose and methodsMicrobial tolerance represents a diminished pro-inflammatory response following repeated stimulation by a host of pathogen-associated molecular patterns (PAMPs) of varying origins. Toll-like receptors (TLRs) have been centrally implicated in the development of tolerance. The purpose of this study was to investigate the impact of tolerance in a previously described murine model.C57BL/6 mice were pretreated intraperitoneally with phosphate buffered saline (PBS), heat-killed Klebsiella 2 × 108 CFU (hkKlebsiella), LPS 10 mg/kg (LPS 10), or BLP 10 mg/kg (BLP 10). Following pretreatment, peritonitis was induced 24 h later using 103 intraperitoneal Klebsiella CFU. Peritoneal concentrations of TNF-α, IL-10 and nitric oxide (NO), as well as characteristic cell patterns, were determined. Long-term consequences of microbial tolerance were assessed by measuring survival and weight-loss.ResultsFollowing in vitro stimulation with Klebsiella 105 and 103 CFU, TNF-α and IL-10 secretion were diminished in macrophages harvested from mice pretreated with hkKlebsiella, LPS 10 and BLP 10. Pretreated animals had significantly lower bacterial counts. Conversely, local NO levels were elevated. Survival was not different between the groups.ConclusionPretreatment with TLR ligands induced microbial tolerance, with reduced peritoneal cytokine concentrations and enhanced early bacterial clearance. However, this did not translate into improved survival. 相似文献
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Qadan LR Perez-Stable CM Anderson C D'Ippolito G Herron A Howard GA Roos BA 《Biochemical and biophysical research communications》2001,285(5):1259-1266
Few therapeutic treatment options are available for patients suffering from metastatic androgen-independent prostate cancer. We investigated the ability of the estrogen metabolite 2-methoxyestradiol to inhibit the proliferation of a variety of human prostate cancer cell lines in vitro and to inhibit the growth of androgen-independent prostate cancer in a transgenic mouse model in vivo. Our results showed that 2-methoxyestradiol is a powerful growth inhibitor of LNCaP, DU 145, PC-3, and ALVA-31 prostate cancer cells. Cell flow cytometry of 2-methoxyestradiol-treated DU 145 cells showed a marked accumulation of cells in the G2/M phase of the cell cycle and an increase in the sub-G1 fraction (apoptotic). In addition, staining for annexin V, changes in nuclear morphology, and inhibition of caspase activity support a role for apoptosis. More importantly, we showed that 2-methoxyestradiol inhibits prostate tumor progression in the Ggamma/T-15 transgenic mouse model of androgen-independent prostate cancer without toxic side effects. These results in cell culture and an animal model support investigations into the clinical use of 2-methoxyestradiol in patients with androgen-independent prostate cancer. 相似文献
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采用关联指数(IC)和决定系数(CD)两种方法,度量混合线性模型遗传评估下猪群体间的遗传关联性。结果表明,加拿大安大略省的大约克夏猪、长白猪、杜洛克猪和汉普夏猪4个主要品种群体间具有良好的遗传联系。CD法既组合了数据结构和信息量,又考虑了预测误差方差和遗传变异性,是一个选择判断遗传评估精度的好方法。 相似文献
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BK Clapperton TD Day DKJ Morgan F Huddart N Cox LR Matthews 《New Zealand journal of zoology.》2013,40(2):104-118
Repellents used to reduce by-kill of birds during pest control must not compromise acceptance by target species. Two repellents combined, anthraquinone (AQ; 0.4 g kg?1) and d-pulegone (DP; 1.0) did not reduce the palatability of blue-coloured carrot baits to laboratory rats (Rattus norvegicus); nor did DP (2.0). Green-coloured carrot baits coated with AQ, DP or AQ + DP were taken from bait stations by wild possums (Trichosurus vulpecula) and rats. Toxic (1080) bait coated with AQ (0.4) and peanut oil (0.1) had reduced palatability but was accepted by laboratory rats. However, laboratory rats did not consume enough baits coated with AQ and bacon, peanut butter, cinnamon or DP to be killed. Anthraquinone (0.4 or 0.8) plus cinnamon and DP (0.5) did not affect palatability or lethality to captive ship rats (R. rattus) or possums. Anthraquinone and DP as surface coatings on baits are therefore acceptable to possums and possibly rats, at concentrations that deter some bird species. 相似文献
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A requirement for trypsin-sensitive cell-surface components for cell-cell interactions of embryonic neural retina cells 总被引:2,自引:3,他引:2 下载免费PDF全文
A quantitative assay was used to measure the rate of collection of a population of embryonic neural retina cells to the surface of cell aggregates. The rate of collection of freshly trysinized cells was limited in the initial stages by the rate of replacement of trypsin-sensitive cell- surface components. When cells were preincubated, or "recovered," and then added to cell aggregates, collection occurred at a linear rate and was independent of protein and glycoprotein synthesis. The adhesion of recovered cells was temperature and energy dependent, and was reversibly inhibited by cytochalasin B. Colchicine had little effect on collection of recovered cells. Antiserum directed against recovered cell membranes was shown to bind to recovered cells by indirect immunofluorescence. The antiserum also was shown to inhibit collection of recovered cells to aggregates, suggesting that at least some of the antigens identified might be involved in the adhesion process. The inhibitory effect of the antiserum was dose dependent . Freshly trypsinized cells absorbed neither the immunofluorescence activity nor the adhesion-inhibiting activity. Recovered cells absorbed away both activities. In specificity studies, dorsal neural retina cells adhered to aggregates of ventral optic tectum in preference to aggregates of dorsal optic tectum. The adhesive specificity of the dorsal retina cells was less sensitive to trypsin than the adhesive specificity of ventral retina cells which adhered preferentially to dorsal tectal aggregates only after a period of recovery. 相似文献