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991.
A B Jones J J Acton A D Adams W Yuen E A Nichols C D Schwartz L S Wicker J D Hermes 《Bioorganic & medicinal chemistry letters》1999,9(14):2115-2118
Tetrapeptide derived major histocompatability (MHC) II ligands have been developed that contain no unadulterated peptide bonds. These are the 'least peptidic' ligands for any MHC protein yet reported. 相似文献
992.
993.
James Gelsleichter John A. Musick Stephanie Nichols 《Environmental Biology of Fishes》1999,54(2):205-217
Diet and feeding habits of the smooth dogfish, Mustelus canis, Atlantic sharpnose, Rhizoprionodon terraenovae, dusky, Carcharhinus obscurus, and the sand tiger, Carcharias taurus sharks, were investigated through analysis of stomach contents. Diet in M. canis was relatively homogeneous and was dominated by crustaceans, consisting mostly of rock crabs, Cancer irroratus. Diet in R. terraenovae was more heterogeneous and consisted largely of crustaceans and teleosts, in similar levels of prey importance. Use of cumulative prey curves as a measure of precision indicated that data were insufficient to fully describe the diets of C. obscurus and C. taurus. Nonetheless, these data suggested that both species are generalized feeders and consume a variety of teleost and elasmobranch prey. Further studies are necessary to fully characterize diet in these two species. 相似文献
994.
The naturally occurring mutants of DDB are impaired in stimulating nuclear import of the p125 subunit and E2F1-activated transcription.
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995.
Comparisons of species composition among isolated ecological communities of different size have often provided evidence that the species in communities with lower species richness form nested subsets of the species in larger communities. In the vast majority of studies, the question of nested subsets has been addressed using information on presence‐absence, where a “0” is interpreted as the absence of a given species from a given location. Most of the methodological discussion in earlier studies investigating nestedness concerns the approach to generation of model‐based matrices corresponding to the null hypothesis of a nonnested pattern. However, it is most likely that in many situations investigators cannot detect all the species present in the location sampled. The possibility that zeros in incidence matrices reflect nondetection rather than absence of species has not been considered in studies addressing nested subsets, even though the position of zeros in these matrices forms the basis of earlier inference methods. These sampling artifacts are likely to lead to erroneous conclusions about both variation over space in species richness, and the degree of similarity of the various locations. Here we propose an approach to investigation of nestedness, based on statistical inference methods explicitly incorporating species detection probability, that take into account the probabilistic nature of the sampling process. We use presence‐absence data collected under Pollock's robust capture‐recapture design, and resort to an estimator of species richness originally developed for closed populations to assess the proportion of species shared by different locations. We develop testable predictions corresponding to the null hypothesis of a nonnested pattern, and an alternative hypothesis of perfect nestedness. We also present an index for assessing the degree of nestedness of a system of ecological communities. We illustrate our approach using avian data from the North American Breeding Bird Survey collected in Florida Keys. 相似文献
996.
Jean Ann Nichols 《International Review of Hydrobiology》1977,62(2):235-244
Birge-Ekman box cores were used to sample the benthic invertebrate fauna near the Woods Hole, Massachusetts sewage outfall and a nearby control area. Community structure in terms of numbers and taxa fluctuated seasonally at both control site and at the outfall. The outfall fauna was dominated by small nematode worms, and the year-round maintenance of a nematode-dominated community may be a mechanism for utilization of the unpredictable, unnatural, excess organic material available around the outfall. Based on the small size of the invertebrates at the outfall compared to the other areas, it is suggested that the relationship between macrofaunal abundance and average individual size in an assemblage is a measurement of community structure which can be useful in assessing environmental disturbance. 相似文献
997.
Isolation and Characterisation of a Δ5-fatty Acid Elongase from the Marine Microalga Pavlova salina 总被引:1,自引:0,他引:1
Robert SS Petrie JR Zhou XR Mansour MP Blackburn SI Green AG Singh SP Nichols PD 《Marine biotechnology (New York, N.Y.)》2009,11(3):410-418
The marine microalga Pavlova salina (Haptophyta, Pavlovophyceae) produces lipids containing approximately 50% n-3 long-chain polyunsaturated fatty acids including
eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). A full-length cDNA sequence, designated PsElo5, was isolated from
P. salina. Sequence alignment showed that the gene was homologous to corresponding ELO-type elongases from other microalgae. Heterologous
expression of PsElo5 in yeast and in higher plants confirmed that it encodes a specific Δ5-elongase activity as predicted
and, furthermore, within the n-3 pathway, the elongation activity was confined exclusively to EPA. 相似文献
998.
Coassembly of flotillins induces formation of membrane microdomains, membrane curvature, and vesicle budding 总被引:4,自引:0,他引:4
Frick M Bright NA Riento K Bray A Merrified C Nichols BJ 《Current biology : CB》2007,17(13):1151-1156
Endocytosis has a crucial role in many cellular processes. The best-characterized mechanism for endocytosis involves clathrin-coated pits [1], but evidence has accumulated for additional endocytic pathways in mammalian cells [2]. One such pathway involves caveolae, plasma-membrane invaginations defined by caveolin proteins. Plasma-membrane microdomains referred to as lipid rafts have also been associated with clathrin-independent endocytosis by biochemical and pharmacological criteria [3]. The mechanisms, however, of nonclathrin, noncaveolin endocytosis are not clear [4, 5]. Here we show that coassembly of two similar membrane proteins, flotillin1 and flotillin2 [6-8], is sufficient to generate de novo membrane microdomains with some of the predicted properties of lipid rafts [9]. These microdomains are distinct from caveolin1-positive caveolae, are dynamic, and bud into the cell. Coassembly of flotillin1 and flotillin2 into microdomains induces membrane curvature, the formation of plasma-membrane invaginations morphologically similar to caveolae, and the accumulation of intracellular vesicles. We propose that flotillin proteins are defining structural components of the machinery that mediates a clathrin-independent endocytic pathway. Key attributes of this machinery are the dependence on coassembly of both flotillins and the inference that flotillin microdomains can exist in either flat or invaginated states. 相似文献
999.
Gasper BJ McCreight JC Banschbach K Bustion A Davis C Divecha R Donoho M Elmore AG Garrison CM Glenn S Goeman DC Haby M Hooks T Korman AM Kowal J Kuschke S Mellencamp JE Meyer M Myers AN Nichols MF Pfeifer A Porucznik A Qu X Ramos-Miller M Reed RR Sagintayev A Singel JM Smith A Valle ME Venderley A Weber CA Zaffino AJ Csonka LN Gardner SM 《DNA and cell biology》2012,31(6):956-967
In Enterobacteriaceae, the ProP protein, which takes up proline and glycine betaine, is subject to a post-translational control mechanism that increases its activity at high osmolarity. In order to investigate the osmoregulatory mechanism of the Salmonella enterica ProP, we devised a positive selection for mutations that conferred increased activity on this protein at low osmolarity. The selection involved the isolation of mutations in a proline auxotroph that resulted in increased accumulation of proline via the ProP system in the presence of glycine betaine, which is a competitive inhibitor of proline uptake by this permease. This selection was performed by first-year undergraduates in two semesters of a research-based laboratory course. The students generated sixteen mutations resulting in six different single amino acids substitutions. They determined the effects of the mutations on the growth rates of the cells in media of high and low osmolarity in the presence of low concentrations of proline or glycine betaine. Furthermore, they identified the mutations by DNA sequencing and displayed the mutated amino acids on a putative three-dimensional structure of the protein. This analysis suggested that all six amino acid substitutions are residues in trans-membrane helices that have been proposed to contribute to the formation of the transport pore, and, thus, may affect the substrate binding site of the protein. 相似文献
1000.
Thomas P. Monath Richard Nichols Lynda Tussey Kelly Scappaticci Thaddeus G. Pullano Mary D. Whiteman Nikos Vasilakis Shannan L. Rossi Rafael Kroon Campos Sasha R. Azar Heidi M. Spratt Brent L. Seaton W. Tad Archambault Yanina V. Costecalde Evan H. Moore Roger J. Hawks Joan Fusco 《PLoS pathogens》2022,18(6)
Nipah virus (NiV) disease is a bat-borne zoonosis responsible for outbreaks with high lethality and is a priority for vaccine development. With funding from the Coalition of Epidemic Preparedness Innovations (CEPI), we are developing a chimeric vaccine (PHV02) composed of recombinant vesicular stomatitis virus (VSV) expressing the envelope glycoproteins of both Ebola virus (EBOV) and NiV. The EBOV glycoprotein (GP) mediates fusion and viral entry and the NiV attachment glycoprotein (G) is a ligand for cell receptors, and stimulates neutralizing antibody, the putative mediator of protection against NiV. PHV02 is identical in construction to the registered Ebola vaccine (Ervebo) with the addition of the NiV G gene. NiV ephrin B2 and B3 receptors are expressed on neural cells and the wild-type NiV is neurotropic and causes encephalitis in affected patients. It was therefore important to assess whether the NiV G alters tropism of the rVSV vector and serves as a virulence factor. PHV02 was fully attenuated in adult hamsters inoculated by the intramuscular (IM) route, whereas parental wild-type VSV was 100% lethal. Two rodent models (mice, hamsters) were infected by the intracerebral (IC) route with graded doses of PHV02. Comparator active controls in various experiments included rVSV-EBOV (representative of Ebola vaccine) and yellow fever (YF) 17DD commercial vaccine. These studies showed PHV02 to be more neurovirulent than both rVSV-EBOV and YF 17DD in infant animals. PHV02 was lethal for adult hamsters inoculated IC but not for adult mice. In contrast YF 17DD retained virulence for adult mice inoculated IC but was not virulent for adult hamsters. Because of the inconsistency of neurovirulence patterns in the rodent models, a monkey neurovirulence test (MNVT) was performed, using YF 17DD as the active comparator because it has a well-established profile of quantifiable microscopic changes in brain centers and a known reporting rate of neurotropic adverse events in humans. In the MNVT PHV02 was significantly less neurovirulent than the YF 17DD vaccine reference control, indicating that the vaccine will have an acceptable safety profile for humans. The findings are important because they illustrate the complexities of phenotypic assessment of novel viral vectors with tissue tropisms determined by transgenic proteins, and because it is unprecedented to use a heterologous comparator virus (YF vaccine) in a regulatory-enabling study. This approach may have value in future studies of other novel viral vectors. 相似文献