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81.
Prions are the infectious agents responsible for prion diseases, which appear to be composed exclusively by the misfolded prion protein (PrP(Sc)). Disease is transmitted by the autocatalytic propagation of PrP(Sc) misfolding at the expense of the normal prion protein. The biggest challenge of the prion hypothesis has been to explain the molecular mechanism by which prions can exist as different strains, producing diseases with distinguishable characteristics. Here, we show that PrP(Sc) generated in vitro by protein misfolding cyclic amplification from five different mouse prion strains maintains the strain-specific properties. Inoculation of wild-type mice with in vitro-generated PrP(Sc) caused a disease with indistinguishable incubation times as well as neuropathological and biochemical characteristics as the parental strains. Biochemical features were also maintained upon replication of four human prion strains. These results provide additional support for the prion hypothesis and indicate that strain characteristics can be faithfully propagated in the absence of living cells, suggesting that strain variation is dependent on PrP(Sc) properties. 相似文献
82.
83.
The construction of a new phagemid vector for display of peptides on the pVIII major coat protein of filamentous bacteriophage
is described, in which expression of pVIII-peptide fusions was placed under the control of the arabinose-inducible PBAD promoter. The new phagemid showed excellent capacity for the regulation of peptide expression, as judged by enzyme-linked
immunosorbent assay (ELISA) and electron microscopy of immunogold-labeled FLAG peptides displayed on phages. Regulation of
the density of peptide fusions displayed on phages may offer advantages in the search for new peptide ligands due to the possibility
of regulating the stringency of binding, reducing selection based on avidity effects during biopanning. Furthermore, the peptide
expression in the absence of inducer was effectively shut off, minimizing growth bias of individual clones. A 9-mer phage
display library prepared using the constructed phagemid was generated by insertion of randomly synthesized oligonucleotides
close to the N-terminal of the pVIII protein. The library comprised a total of 9.4 × 109 unique transformants, and was confirmed to show high diversity. The functional utility of the library was confirmed by the
successful affinity selection of peptides binding to matrix metalloproteinase-9 (MMP-9). The majority of selected peptides
shared the consensus motif R(D/N)XXG(M/L)(V/I)XQ, not previously selected during biopanning against MMP-9. 相似文献
84.
Mariëtte van Amstel Claar de Brauw Peter Driessen Pieter Glasbergen 《Biodiversity and Conservation》2007,16(14):4109-4129
This paper seeks to understand why multinationals prefer to launch a label specific to their own product and examines how
reliable these product-specific eco-labels are. A new methodology is applied to assess the extent to which eco-labels live
up to claims about their contribution to conservation and the sustainable use of agricultural biodiversity. Product-specific
eco-labels are considered as industry self-regulation and all three regulatory stages are studied: the planning, implementation
and outcome stage. There are major differences between the product specific eco-labels in the degree in which agrobiodiversity
management is part of the normative labeling schemes. Although there are some problems of reliability, such as transparency
in the implementation stage and the monitoring in the outcome stage, the degree of reliability of product-specific labels
is comparable with eco-labels of international labeling families. The conclusion is that only one of the product-specific
eco-labels examined here is reliable when examined in the light of all three stages. The main reason why multinationals establish
a product-specific eco-label instead of adopting one from an existing labeling family is that they want to profile themselves
as distinct from other companies. The unique character of a product-specific label creates a market opportunity for them. 相似文献
85.
86.
Genetic variations and phylogeography of the swallowtail butterfly Papilio machaon on the Japanese Islands
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Misa Miyakawa Mari Hosoi Ai Kawakita Sayoko Ito‐Harashima Takashi Yagi Michihiro Ishihara 《Entomological Science》2018,21(3):248-259
The swallowtail butterfly Papilio machaon Linnaeus, 1758 is widely distributed in the Holarctic region, including all of the main islands of Japan, as well as Sakhalin, and on other smaller islands south to Yakushima Island. The Japanese population is situated at the margin of the Eurasian distribution range of this species. It is morphologically different from other populations and has been classified as the subspecies hippocrates C. & R. Felder, 1864. The population of the Japanese Islands is considered to be genetically distinct from the continental populations in relation to the geographical history of the Japanese Islands. Therefore, we examined a part of the ND5 gene sequence of the mitochondrial DNA for P. machaon individuals of various localities in Japan and some nearby countries, and found 68 haplotypes in 400 individuals from the Japanese Islands and Sakhalin. A DNA polymorphism analysis revealed that the genetic structure of the Hokkaido population was significantly different from that of the southern populations on the main Japanese islands. These results imply that P. machaon expanded its range from the Amur region of Russia southward through Sakhalin to the Japanese Islands, and that the Tsugaru Strait between Hokkaido and Honshu may have subsequently limited their gene flow as a geographical barrier. 相似文献
87.
Mari Kawaji Shingo Kaneko Ryunosuke Tateno Yuji Isagi Tsuyoshi Yoneda 《Conservation Genetics》2009,10(4):1049-1051
Quercus miyagii is an endemic tree species in the Ryukyu Islands, Japan. We isolated and characterized 15 microsatellite loci in this species.
The number of alleles ranged from 2 to 16 and expected heterozygosities from 0.07 to 0.92. This set of markers is potentially
useful to investigate the genetic structure, gene flow, and the biogeographic history of Q. miyagii in the Ryukyu Islands, Japan. 相似文献
88.
Terrestrial carbon balance in a drier world: the effects of water availability in southwestern North America 总被引:1,自引:0,他引:1
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Joel A. Biederman Russell L. Scott Michael L. Goulden Rodrigo Vargas Marcy E. Litvak Thomas E. Kolb Enrico A. Yepez Walter C. Oechel Peter D. Blanken Tom W. Bell Jaime Garatuza‐Payan Gregory E. Maurer Sabina Dore Sean P. Burns 《Global Change Biology》2016,22(5):1867-1879
Global modeling efforts indicate semiarid regions dominate the increasing trend and interannual variation of net CO2 exchange with the atmosphere, mainly driven by water availability. Many semiarid regions are expected to undergo climatic drying, but the impacts on net CO2 exchange are poorly understood due to limited semiarid flux observations. Here we evaluated 121 site‐years of annual eddy covariance measurements of net and gross CO2 exchange (photosynthesis and respiration), precipitation, and evapotranspiration (ET) in 21 semiarid North American ecosystems with an observed range of 100 – 1000 mm in annual precipitation and records of 4–9 years each. In addition to evaluating spatial relationships among CO2 and water fluxes across sites, we separately quantified site‐level temporal relationships, representing sensitivity to interannual variation. Across the climatic and ecological gradient, photosynthesis showed a saturating spatial relationship to precipitation, whereas the photosynthesis–ET relationship was linear, suggesting ET was a better proxy for water available to drive CO2 exchanges after hydrologic losses. Both photosynthesis and respiration showed similar site‐level sensitivity to interannual changes in ET among the 21 ecosystems. Furthermore, these temporal relationships were not different from the spatial relationships of long‐term mean CO2 exchanges with climatic ET. Consequently, a hypothetical 100‐mm change in ET, whether short term or long term, was predicted to alter net ecosystem production (NEP) by 64 gCm?2 yr?1. Most of the unexplained NEP variability was related to persistent, site‐specific function, suggesting prioritization of research on slow‐changing controls. Common temporal and spatial sensitivity to water availability increases our confidence that site‐level responses to interannual weather can be extrapolated for prediction of CO2 exchanges over decadal and longer timescales relevant to societal response to climate change. 相似文献
89.
90.
Induction of Bcl-xL Expression by Human T-Cell Leukemia Virus Type 1 Tax through NF-κB in Apoptosis-Resistant T-Cell Transfectants with Tax
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Tomonori Tsukahara Mari Kannagi Takashi Ohashi Hirotomo Kato Masaaki Arai Gabriel Nunez Youichi Iwanaga Naoki Yamamoto Kiyoshi Ohtani Masataka Nakamura Masahiro Fujii 《Journal of virology》1999,73(10):7981-7987
Human T-cell leukemia virus type 1 (HTLV-1) Tax is thought to play a pivotal role in immortalization of T cells. We have recently shown that the expression of Tax protected the mouse T-cell line CTLL-2 against apoptosis induced by interleukin-2 (IL-2) deprivation and converted its growth from being IL-2 dependent to being IL-2 independent. In this study, we demonstrate that constitutive expression of bcl-xl but not bcl-2, bcl-xs, bak, bad, or bax was associated with apoptosis resistance after IL-2 deprivation in CTLL-2 cells that expressed Tax. Transient-transfection assays showed that bcl-x promoter was transactivated by wild-type Tax. Similar effects were observed in mutant Tax retaining transactivating ability through NF-kappaB. Deletion or substitution of a putative NF-kappaB binding site identified in the bcl-x promoter significantly decreased Tax-induced transactivation. This NF-kappaB-like element was able to form a complex with NF-kappaB family proteins in vitro. Furthermore, Tax-induced transactivation of the bcl-x promoter was also diminished by the mutant IkappaBalpha, which specifically inhibits NF-kappaB activity. Our findings suggest that constitutive expression of Bcl-x(L) induced by Tax through the NF-kappaB pathway contributes to the inhibition of apoptosis in CTLL-2 cells after IL-2 deprivation. 相似文献