排序方式: 共有47条查询结果,搜索用时 15 毫秒
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记述了南海北部近海水螅虫总纲4新种和2新纪录,即自育水母纲的顶胃穴水母岛Sminthea apicigastrica Xu,Huang et Du,sp.nov.,水螅水母纲的距拟双手水母Codonorchis calcariformis Xu,Huang et Guo,sp.nov.,南海多管水母Aequorea nanhainensis Xu,Huang et Du,sp.nov.,四手多管水母Aequorea tetranema Xu,Huang et Du,sp.nov.,深水拟单手水母Paragotoea bathybia Kramp,1942和母螅镰螅水母Zanclea medusopolypata Boero,Bouillon et Gravili,2000.并讨论了新种与近缘种的区别,模式标本保存在中国水产科学研究院南海水产研究所. 相似文献
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Summers K McKeon S Sellars J Keusenkothen M Morris J Gloeckner D Pressley C Price B Snow H 《Biological reviews of the Cambridge Philosophical Society》2003,78(4):639-675
Parasitic exploitation occurs within and between a wide variety of taxa in a plethora of diverse contexts. Theoretical and empirical analyses indicate that parasitic exploitation can generate substantial genetic and phenotypic polymorphism within species. Under some circumstances, parasitic exploitation may also be an important factor causing reproductive isolation and promoting speciation. Here we review research relevant to the relationship between parasitic exploitation, within species-polymorphism, and speciation in some of the major arenas in which such exploitation has been studied. This includes research on the vertebrate major histocompatibility loci, plant-pathogen interactions, the evolution of sexual reproduction, intragenomic conflict, sexual conflict, kin mimicry and social parasitism, tropical forest diversity and the evolution of language. We conclude by discussing some of the issues raised by comparing the effect of parasitic exploitation on polymorphism and speciation in different contexts. 相似文献
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Kevin Sea Se Hui Sohn Armando Durazo Yuewei Sheng Bryan F. Shaw Xiaohang Cao Alexander B. Taylor Lisa J. Whitson Stephen P. Holloway P. John Hart Diane E. Cabelli Edith Butler Gralla Joan Selverstone Valentine 《The Journal of biological chemistry》2015,290(4):2405-2418
The functional and structural significance of the intrasubunit disulfide bond in copper-zinc superoxide dismutase (SOD1) was studied by characterizing mutant forms of human SOD1 (hSOD) and yeast SOD1 lacking the disulfide bond. We determined x-ray crystal structures of metal-bound and metal-deficient hC57S SOD1. C57S hSOD1 isolated from yeast contained four zinc ions per protein dimer and was structurally very similar to wild type. The addition of copper to this four-zinc protein gave properly reconstituted 2Cu,2Zn C57S hSOD, and its spectroscopic properties indicated that the coordination geometry of the copper was remarkably similar to that of holo wild type hSOD1. In contrast, the addition of copper and zinc ions to apo C57S human SOD1 failed to give proper reconstitution. Using pulse radiolysis, we determined SOD activities of yeast and human SOD1s lacking disulfide bonds and found that they were enzymatically active at ∼10% of the wild type rate. These results are contrary to earlier reports that the intrasubunit disulfide bonds in SOD1 are essential for SOD activity. Kinetic studies revealed further that the yeast mutant SOD1 had less ionic attraction for superoxide, possibly explaining the lower rates. Saccharomyces cerevisiae cells lacking the sod1 gene do not grow aerobically in the absence of lysine, but expression of C57S SOD1 increased growth to 30–50% of the growth of cells expressing wild type SOD1, supporting that C57S SOD1 retained a significant amount of activity. 相似文献
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Jonathan B. Strauss Michael C. Kirk Sea S. Chen Anand P. Shah Benjamin T. Gielda James C. Chu Julius V. Turian Adam Dickler 《Physica medica : PM : an international journal devoted to the applications of physics to medicine and biology : official journal of the Italian Association of Biomedical Physics (AIFB)》2009,25(4):212-215
Patients with breast cancer are often treated with radiation to the breast (or chest wall) and draining regional lymph nodes. This is typically performed with a three-field technique in which an anterior supraclavicular field is matched to opposed tangent fields. A single isocenter technique is not always possible. Several techniques have been described to create a perfect match using a conventional simulator. We describe and test a simple, fast and accurate technique to estimate the couch and collimator angles required for a perfect geometric match using 3-D treatment planning software. This method requires no mathematical formulae and is verifiable relative to patient anatomy.An external skin contour is created on the axial slice at the match line and displayed with a 3-D representation. Using a beam's eye view (BEV) of a tangent field, small couch and collimator rotation adjustments are made sequentially until the contour edges are superimposed. The virtual external contour technique was easy to use, gave verification of the match in the BEV and yielded estimates of couch and collimator rotations very close to those calculated using published formulae. 相似文献
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Pyrene is a spatially sensitive probe that displays an ensemble of monomeric fluorescence emission peaks (375-405 nm) and an additional band (called excimer) at ~460 nm when two fluorophores are spatially proximal. We examined if there is a correlation between distance between two pyrenes on an α-helical structure and excimer/monomer (e/m) ratio. Using structure-guided design, pyrene maleimide was attached to pairs of Cys residues separated by ~5 ? increments on helix 2 of the N-terminal domain of apolipoprotein E3 (apoE3). Fluorescence spectral analysis revealed an intense excimer band when the probes were ~5 ? from each other with an e/m ratio of ~3.0, which decreased to ~1.0 at 20 ?. An inverse correlation between e/m ratio and the distance between pyrenes was observed, with the probe and helix flexibility also contributing to the extent of excimer formation. We verified this approach by estimating the distance between T57C and C112 (located on helices 2 and 3, respectively) to be 5.2 ? (4.9 ? from NMR and 5.7 ? from the X-ray structure). Excimer formation was also noted to a significant extent with probes located in the linker segment, suggesting spatial proximity (10-15 ?) to corresponding sites on neighboring molecules in the tetrameric configuration of apoE. We infer that oligomerization via the C-terminal domain juxtaposes the linker segments from neighboring apoE molecules. This study offers new insights into the conformation of tetrameric apoE and presents the use of pyrene as a powerful probe for studying protein spatial organization. 相似文献
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Interspecific hybrids provide insights into fundamental genetic principles, and may prove useful for biotechnological applications and as tools for the conservation of endangered species. In the present study, interspecies hybrids were generated between the Korean ring-necked pheasant (Phasianus colchicus) and the White Leghorn chicken (Gallus gallus domesticus). We determined whether these hybrids were good recipients for the production of germline chimeric birds. PCR-based species-specific amplification and karyotype analyses showed that the hybrids inherited genetic material from both parents. Evaluation of biological function indicated that the growth rates of hybrids during the exponential phase (body weight/week) were similar to those of the pheasant but not the chicken, and that the incubation period for hatching was significantly different from that of both parents. Primordial germ cells (PGCs) of hybrids reacted with a pheasant PGC-specific antibody and circulated normally in blood vessels. The peak time of hybrid PGC migration was equivalent to that of the pheasant. In late embryonic stages, germ cells were detected by the QCR1 antibody on 15 d male gonads and were normally localized in the seminiferous cords. We examined the migration ability and developmental localization of exogenous PGCs transferred into the blood vessels of 63 h hybrid embryos. Donor-derived PGCs reacted with a donor-specific antibody were detected on 7 d gonads and the seminiferous tubules of hatchlings. Therefore, germ cell transfer into developing embryos of an interspecies hybrid can be efficiently used for the conservation of threatened animals and endangered species, and many biotechnological applications. 相似文献
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Sea H. Kim Shweta Kothari Arti B. Patel John K. Bielicki Vasanthy Narayanaswami 《Biochemical and biophysical research communications》2014
Apolipoprotein E3 (apoE3) is an anti-atherogenic apolipoprotein with the ability to exist in lipid-free and lipoprotein-associated states. During atherosclerosis, its function in promoting cholesterol efflux from macrophages via the ATP-binding cassette transporter A1 (ABCA1) takes a prominent role, leading to generation of nascent high density lipoprotein (nHDL) particles. The objective of this study is to understand the conformation adopted by apoE3 in macrophage-generated nHDL using a fluorescence spectroscopic approach involving pyrene. Pyrene-labeled recombinant human apoE3 displayed a robust ability to stimulate ABCA1-mediated cholesterol efflux from cholesterol-loaded J774 macrophages (which do not express apoE), comparable to that elicited by unlabeled apoE3. The nHDL recovered from the conditioned medium revealed the presence of apoE3 by immunoblot analysis. A heterogeneous population of nHDL bearing exogenously added apoE3 was generated with particle size varying from ∼12 to ∼19 nm in diameter, corresponding to molecular mass of ∼450 to ∼700 kDa. The lipid: apoE3 ratio varied from ∼60:1 to 10:1. A significant extent of pyrene excimer emission was noted in nHDL, indicative of spatial proximity between Cys112 on neighboring apoE3 molecules similar to that noted in reconstituted HDL. Cross-linking analysis using Cys-specific cross-linkers revealed the predominant presence of dimers. Taken together the data indicate a double belt arrangement of apoE molecules on nHDL. A similar organization of the C-terminal tail of apoE on nHDL was noted when pyrene-apoEA277C(201–299) was used as the cholesterol acceptor. These studies open up the possibility of using exogenously labeled apoE3 to generate nHDL for structural and conformational analysis. 相似文献