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排序方式: 共有200条查询结果,搜索用时 15 毫秒
1.
Klas Ostwald Masami Hayashi Megumi Nakamura †Seiichi Kawashima 《Journal of neurochemistry》1994,63(3):1069-1076
Abstract: Rabbits were subjected to hypoxia (5% O2 ) for up to 90 min and allowed to recover for a maximum of 4 days. Hippocampus homogenate was assayed for fodrin breakdown product (BDP). After separation into a nuclear and mitochondrial fraction (NMF), a membrane and microsomal fraction (MMF), and a cytosolic fraction (CF), samples were assayed for μ-calpain, m-calpain, and calpastatin immunoreactivity. Calpain and calpastatin immunoreactivity decreased in the NMF and CF but increased in the MMF during hypoxia and short-term recovery. This translocation occurred in parallel with the increase in fodrin BDP. Because the increase in the MMF was not large enough to explain the decrease in the other two fractions, it was assumed that the translocation and activation was accompanied by a reduction in the total amounts of calpains and calpastatin. Glucocorticoid pretreatment (beta-methasone, 0.4 mg × kg−1 × day−1 ) for 7 days produced a decrease in the ratio of activated μ-calpain in all three fractions in nearly all samples before, during, and after hypoxia, compared with untreated animals. Glucocorticoid pretreatment also prevented the increase in fodrin BDP that occurred in untreated animals during hypoxia and short-term recovery, indicating impairment of calpain activation. 相似文献
2.
Klas Arvidsson Jüri Jarvet Peter Allard Anders Ehrenberg 《Journal of biomolecular NMR》1994,4(5):653-672
Summary A peptide consisting of 20 amino acid residues, derived from a C-terminal fragment of neuropeptide Y (NPY) and showing high affinity to NPY receptors, was synthesised. Its sequence is PAADLARYRHYIN-LITRQRY-NH2, and the solution structure was calculated from NMR-derived distance and torsion angle restraints, obtained at 15°C in a solvent mixture of water and 30% (v/v) 1,1,1,3,3,3-hexafluoro-2-propanol, by using DIANA and restrained energy minimisation. The structure was found to consist of a well-defined -helix in the centre, with a few residues at the termini having less well defined conformations. The spinlattice and spin-spin relaxation rates of -carbons have been determined on 13C at natural abundance. From 1D experiments the global rotational correlation time was determined and from 2D experiments the dynamics of each individual residue was obtained. The results demonstrate that the C-H vectors in the -helix essentially follow the global motion. Towards the termini, contributions from local dynamics increase. This tendency is correlated to the increasing uncertainty of the structure towards the peptide ends. An effective molecular volume was calculated from the temperature dependence of the global rotational correlation time. This is well compatible with a monomeric peptide, solvated by water and 1,1,1,3,3,3-hexafluoro-2-propanol. The presence of peptide dimers was ruled out as being inconsistent with the relaxation data.Supplementary material available from the authors: Two data tables and 10 PDB coordinate files of the calculated NMR structures of P7. One data table contains all detected and integrated NOE intensities; the other connects each proton and pseudoatom to an atom number used in the NOE table. The table contents served as input data files for CALIBA.Currently on leave from the Institute of Chemical Physics and Biophysics, Tallinn, Estonia. 相似文献
3.
This study examined nest-site choice in a migratory population of pied flycatchers (Ficedula hypoleuca) and sympatric populations of three resident tit species (Parus major, P. caeruleus and P. palustris) in central Sweden. All four species are secondary-cavity nesters which naturally breed in pre-formed tree cavities but readily use artificial nest boxes. We asked whether flycatchers and tits discriminate between nest boxes that: 1. Are ‘empty’; 2. Contain old nests without ectoparasites (fleas Ceratophyllus sp.); or 3. Contain old nests with ectoparasites. We found that pied flycatchers preferred nest boxes containing old nests, regardless of whether these nests held parasites. In contrast, tits did not discriminate between the three types of boxes. Tits may pay a cost for their lack of choosiness: after the breeding season, tit nests contained more fleas than flycatcher nests. Nevertheless, parasites did not affect the choice of a nest site in any of the species studied. We suggest that the migratory flycatchers are in a hurry to start breeding upon arrival and use the presence of an old nest as a shortcut cue to assess nest-site quality. Also, they may save valuable time by copying the choice of previous breeders. Non-migratory tits may have more time to inspect nest sites, but do not seem to use the same cues in nest-site selection as the pied flycatcher. 相似文献
4.
We have investigated the phylogenetic relationships of monotremes and marsupials using nucleotide sequence data from the
neurotrophins; nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), and neurotrophin-3 (NT-3). The study included
species representing monotremes, Australasian marsupials and placentals, as well as species representing birds, reptiles,
and fish. PCR was used to amplify fragments encoding parts of the neurotrophin genes from echidna, platypus, and eight marsupials
from four different orders. Phylogenetic trees were generated using parsimony analysis, and support for the different tree
structures was evaluated by bootstrapping. The analysis was performed with NGF, BDNF, or NT-3 sequence data used individually
as well as with the three neurotrophins in a combined matrix, thereby simultaneously considering phylogenetic information
from three separate genes. The results showed that the monotreme neurotrophin sequences associate to either therian or bird
neurotrophin sequences and suggests that the monotremes are not necessarily related closer to therians than to birds. Furthermore,
the results confirmed the present classification of four Australasian marsupial orders based on morphological characters,
and suggested a phylogenetic relationship where Dasyuromorphia is related closest to Peramelemorphia followed by Notoryctemorphia
and Diprotodontia. These studies show that sequence data from neurotrophins are well suited for phylogenetic analysis of mammals
and that neurotrophins can resolve basal relationships in the evolutionary tree.
Received: 27 January 1997 / Accepted: 20 March 1997 相似文献
5.
6.
Characterization of QCM sensor surfaces coated with molecularly imprinted nanoparticles 总被引:1,自引:0,他引:1
Reimhult K Yoshimatsu K Risveden K Chen S Ye L Krozer A 《Biosensors & bioelectronics》2008,23(12):1908-1914
Molecularly imprinted polymers (MIPs) are gaining great interest as tailor-made recognition materials for the development of biomimetic sensors. Various approaches have been adopted to interface MIPs with different transducers, including the use of pre-made imprinted particles and the in situ preparation of thin polymer layers directly on transducer surfaces. In this work we functionalized quartz crystal microbalance (QCM) sensor crystals by coating the sensing surfaces with pre-made molecularly imprinted nanoparticles. The nanoparticles were immobilized on the QCM transducers by physical entrapment in a thin poly(ethylene terephthalate) (PET) layer that was spin-coated on the transducer surface. By controlling the deposition conditions, it was possible to gain a high nanoparticle loading in a stable PET layer, allowing the recognition sites in nanoparticles to be easily accessed by the test analytes. In this work, different sensor surfaces were studied by micro-profilometry and atomic force microscopy and the functionality was evaluated using quartz crystal microbalance with dissipation (QCM-D). The molecular recognition capability of the sensors were also confirmed using radioligand binding analysis by testing their response to the presence of the test compounds, (R)- and (S)-propranolol in aqueous buffer. 相似文献
7.
Fuchs Marc Klas Ferdinand E. McFerson James R. Gonsalves Dennis 《Transgenic research》1998,7(6):449-462
Transgenic melon and squash containing the coat protein (CP) gene of the aphid transmissible strain WL of cucumber mosaic cucumovirus (CMV) were grown under field conditions to determine if they would assist the spread of the aphid non-transmissible strain C of CMV, possibly through heterologous encapsidation and recombination. Transgenic melon were susceptible to CMV strain C whereas transgenic squash were resistant although the latter occasionally developed chlorotic blotches on lower leaves. Transgenic squash line ZW-20, one of the parents of commercialized cultivar Freedom II, which expresses the CP genes of the aphid transmissible strains FL of zucchini yellow mosaic (ZYMV) and watermelon mosaic virus 2 (WMV 2) potyviruses was also tested. Line ZW-20 is resistant to ZYMV and WMV 2 but is susceptible to CMV. Field experiments conducted over two consecutive years showed that aphid-vectored spread of CMV strain C did not occur from any of the CMV strain C-challenge inoculated transgenic plants to any of the uninoculated CMV-susceptible non- transgenic plants. Although CMV was detected in 3% (22/764) of the uninoculated plants, several assays including ELISA, RT- PCR-RFLP, identification of CP amino acid at position 168, and aphid transmission tests demonstrated that these CMV isolates were distinct from strain C. Instead, they were non-targeted CMV isolates that came from outside the field plots. This is the first report on field experiments designed to determine the potential of transgenic plants expressing CP genes for triggering changes in virus-vector specificity. Our results indicate that transgenic plants expressing CP genes of aphid transmissible strains of CMV, ZYMV, and WMV 2 are unlikely to mediate the spread of aphid non-transmissible strains of CMV. This finding is of practical relevance because transgenic crops expressing the three CP genes are targeted for commercial release, and because CMV is economically important, has a wide host range, and is widespread worldwide. 相似文献
8.
Klas Gustafsson Gunnar Aronsson Staffan Marklund Anders Wikman Birgitta Floderus 《PloS one》2013,8(11)
Purpose
The aim was to examine the potential influence of social isolation and low societal participation on the future risk of receiving disability pension among individuals in Sweden. A specific aim was to describe differences depending on disability pension diagnoses, and how the results were modified by sex and age.Method
The study comprised representative samples of Swedish women and men, who had been interviewed in any of the annual Swedish Surveys of Living Conditions between 1990 and 2007. Information on disability pension and diagnoses was added from the Swedish Social Insurance Agency’s database (1991-2011). The mean number of years of follow-up for the 53920 women and men was twelve years (SD 5.5), and the study base was restricted to the ages 20 to 64 years of age. The predictors were related to disability pension by Cox’s proportional hazards regression.Results
Social isolation and low societal participation were associated with future disability pension also after control for age, year of interview, socio demographic conditions and self reported longstanding illness. Lone individuals were at increased risk of disability pension, and the effect of living without children was modified by sex and age. An increase in risk was particularly noticeable among younger women who reported that they had sparse contacts with others, and no close friend. Both women and men who reported that they did not participate in political discussions and who could not appeal on a decision by a public authority were also at increased risk. The effects of social isolation were mainly attributed to disability pension with mental diagnoses, and to younger individuals.Conclusions
The study suggests that social isolation and low societal participation are predictors of future disability pension. Social isolation and low societal participation increased particularly the risk of future disability pension in mental diagnoses among younger individuals. 相似文献9.
Szymon ??ski Henrik Lindén Tom Tetzlaff Klas H. Pettersen Gaute T. Einevoll 《PLoS computational biology》2013,9(7)
Despite its century-old use, the interpretation of local field potentials (LFPs), the low-frequency part of electrical signals recorded in the brain, is still debated. In cortex the LFP appears to mainly stem from transmembrane neuronal currents following synaptic input, and obvious questions regarding the ‘locality’ of the LFP are: What is the size of the signal-generating region, i.e., the spatial reach, around a recording contact? How far does the LFP signal extend outside a synaptically activated neuronal population? And how do the answers depend on the temporal frequency of the LFP signal? Experimental inquiries have given conflicting results, and we here pursue a modeling approach based on a well-established biophysical forward-modeling scheme incorporating detailed reconstructed neuronal morphologies in precise calculations of population LFPs including thousands of neurons. The two key factors determining the frequency dependence of LFP are the spatial decay of the single-neuron LFP contribution and the conversion of synaptic input correlations into correlations between single-neuron LFP contributions. Both factors are seen to give low-pass filtering of the LFP signal power. For uncorrelated input only the first factor is relevant, and here a modest reduction (<50%) in the spatial reach is observed for higher frequencies (>100 Hz) compared to the near-DC () value of about . Much larger frequency-dependent effects are seen when populations of pyramidal neurons receive correlated and spatially asymmetric inputs: the low-frequency () LFP power can here be an order of magnitude or more larger than at 60 Hz. Moreover, the low-frequency LFP components have larger spatial reach and extend further outside the active population than high-frequency components. Further, the spatial LFP profiles for such populations typically span the full vertical extent of the dendrites of neurons in the population. Our numerical findings are backed up by an intuitive simplified model for the generation of population LFP. 相似文献
10.