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排序方式: 共有75条查询结果,搜索用时 15 毫秒
31.
Austin J Rice Frances JD Alvarez Amy L Davidson Heather W Pinkett 《Channels (Austin, Tex.)》2014,8(4):327-333
In order to shuttle substrates across the lipid bilayer, membrane proteins undergo a series of conformation changes that are influenced by protein structure, ligands, and the lipid environment. To test the effect of lipid on conformation change of the ABC transporter MolBC, EPR studies were conducted in lipids and detergents of variable composition. In both a detergent and lipid environment, MolBC underwent the same general conformation changes as detected by site-directed EPR spectroscopy. However, differences in activity and the details of the EPR analysis indicate conformational rigidity that is dependent on the lipid environment. From these observations, we conclude that native-like lipid mixtures provide the transporter with greater activity and conformational flexibility as well as technical advantages such as reconstitution efficiency and protein stability. 相似文献
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Deficiency of mitogen-activated protein kinase phosphatase-1 results in iNOS-mediated hypotension in response to low-dose endotoxin 总被引:1,自引:0,他引:1
Calvert TJ Chicoine LG Liu Y Nelin LD 《American journal of physiology. Heart and circulatory physiology》2008,294(4):H1621-H1629
Mitogen-activated protein kinase phosphatase-1 (MKP-1) is essential in limiting the proinflammatory response to lipopolysaccharide (LPS). We hypothesized that Mkp-1(-/-) mice would respond to low-dose LPS with a fall in blood pressure due to augmented expression of inducible nitric oxide (NO) synthase (iNOS). To test this hypothesis, Mkp-1(-/-) mice and their wild-type littermates were treated with 10 microg/kg iv LPS, and mean arterial blood pressure (MAP) and exhaled NO production (exNO) were measured. Tissues were harvested for an assessment of iNOS protein levels. Wild-type mice had no change in MAP or exNO during the experimental period, whereas Mkp-1(-/-) mice had a fall (P < 0.005) in MAP [79 +/- 5% of baseline (BL)] and an increase (P < 0.01) in exNO (266 +/- 50% of BL) after 150 min. The tissue levels of iNOS were greater in Mkp-1(-/-) than in wild-type mice. In additional experiments, 60 min after LPS treatment, Mkp-1(-/-) and wild-type mice were given N(omega)-nitro-l-arginine methyl ester (l-NAME) or aminoguanidine, and MAP and exNO were monitored for 90 min. Treatment with l-NAME prevented the LPS-induced increase in exNO and decrease in MAP but resulted in decreased exNO and elevated MAP in wild-type mice. Aminoguanidine prevented the increase in exNO and the fall in MAP caused by LPS in Mkp-1(-/-) mice, without significantly affecting MAP or exNO in wild-type mice. These results demonstrate that a deficiency of MKP-1 results in an exaggerated hypotensive response to LPS mediated by augmented iNOS expression. We speculate that defects in the Mkp-1 gene may increase susceptibility for the development of septic shock. 相似文献
34.
Rick Brouwer Wilma TM Vree Egberts Gerald JD Hengstman Reinout Raijmakers Baziel GM van Engelen Hans Peter Seelig Manfred Renz Rudolf Mierau Ekkehard Genth Ger JM Pruijn Walther J van Venrooij 《Arthritis research & therapy》2001,4(2):1-5
The autoantigenic polymyositis/scleroderma (PM/Scl) complex was recently shown to be the human homologue of the yeast exosome, which is an RNA-processing complex. Our aim was to assess whether, in addition to targeting the known autoantigens PM/Scl-100 and PM/Scl-75, autoantibodies also target recently identified components of the PM/Scl complex. The prevalence of autoantibodies directed to six novel human exosome components (hRrp4p, hRrp40p, hRrp41p, hRrp42p, hRrp46p, hCsl4p) was determined in sera from patients with idiopathic inflammatory myopathy (n = 48), scleroderma (n = 11), or the PM/Scl overlap syndrome (n = 10). The sera were analyzed by enzyme-linked immunosorbent assays and western blotting using the affinity-purified recombinant proteins. Our results show that each human exosome component is recognized by autoantibodies. The hRrp4p and hRrp42p components were most frequently targeted. The presence of autoantibodies directed to the novel components of the human exosome was correlated with the presence of the anti-PM/Scl-100 autoantibody in the sera of patients with idiopathic inflammatory myopathy (IIM), as was previously found for the anti-PM/Scl-75 autoantibody. Other clear associations between autoantibody activities were not found. These results further support the conception that the autoimmune response may initially be directed to PM/Scl-100, whereas intermolecular epitope spreading may have caused the autoantibody response directed to the associated components. 相似文献
35.
Enzyme activity dot blots: a rapid and convenient assay for acetyltransferase or protein kinase activity immobilized on nitrocellulose 总被引:2,自引:0,他引:2
Methods are described for assaying (Tetrahymena) histone acetyltransferase activity and (Drosophila) casein kinase II activity by spotting extracts on nitrocellulose filters. The methods are quantitative over a wide range of enzyme concentrations and are almost as sensitive as liquid assays. Examples are presented for illustrating the use of these methods for enzyme purification, concentration, and desalting, as well as for electrophoretic blotting from agarose gels. A simple method for autoradiographic enhancement of nitrocellulose filters is also described. 相似文献
36.
A characteristic feature of the sperm P1 protamines of eutherian mammals is
the constant presence of six to nine cysteine residues per molecule. During
spermiogenesis these residues become oxidized to form a three-dimensional
network of disulfide bridges between, and within, protamine molecules in
the sperm chromatin. This covalent cross linking strongly stabilizes
eutherian sperm nuclei. In contrast, protamines sequenced from teleost
fish, birds, monotremes, and marsupials all lack cysteine residues and
their sperm nuclei, without the stabilizing cross links, are easily
decondensed in vitro. We have now found that one genus of tiny, shrewlike
dasyurid marsupials, the Planigales, possess P1 protamines containing five
to six cysteine residues. These residues appear to have evolved since the
divergence of Planigales from other members of the family Dasyuridae, such
as the marsupial mouse, Sminthopsis crassicaudata. We believe this
constitutes a case of convergent evolution in a subfamily of dasyurid
marsupials toward the cysteine-rich eutherian form of sperm protamine P1.
相似文献
37.
Louis G Chicoine Jose W Avitia Cody Deen Leif D Nelin Scott Earley Benjimen R Walker 《Journal of applied physiology》2002,93(1):311-318
Chronic hypoxia (CH) increases pulmonary endothelial nitric oxide synthase (eNOS) protein levels in adult rats but decreases eNOS protein levels in neonatal pigs. We hypothesized that this differing response to CH is due to developmental rather than species differences. Adult and neonatal rats were placed in either hypobaric hypoxia or normoxia for 2 wk. At that time, body weight, hematocrit, plasma nitrite/nitrate (NOx(-)), and right ventricular and total ventricular heart weights were measured. Percent pulmonary arterial wall area of 20-50 and 51-100 microm arteries were also determined. Total lung protein extracts were assayed for eNOS levels by using immunoblot analysis. Compared with their respective normoxic controls, both adult and neonatal hypoxic groups demonstrated significantly decreased body weight, elevated hematocrit, and elevated right ventricular-to-total ventricular weight ratios. Both adult and neonatal hypoxic groups also demonstrated significantly larger percent pulmonary arterial wall area compared with their respective normoxic controls. Hypoxic adult pulmonary eNOS protein and plasma NOx(-) were significantly greater than levels found in normoxic adults. In contrast, hypoxic neonatal pulmonary eNOS protein and plasma NOx(-) were significantly less compared with normoxic neonates. We conclude that there is a developmental difference in eNOS expression and nitric oxide production in response to CH. 相似文献
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Macronuclei of Tetrahymena thermophila contain a typical H1 which has been shown to be missing from micronuclei. Instead, micronuclei contain three unique polypeptides, alpha, beta, and gamma, which are associated with linker regions of micronuclear chromatin. In this report polyclonal antibodies raised against macronuclear H1 are shown to react with alpha, beta, and gamma by immunoblotting analyses. This result suggests that these polypeptides share some common structural feature(s). Also consistent with this result is the finding that both macro- and micronuclei in growing and mating cells stain positively with H1 antibodies by in situ indirect immunofluorescence. However, these analyses demonstrate that the level of linker histone is greatly reduced in the micronucleus of starved cells and in young macronuclear anlagen. These results are in agreement with earlier biochemical studies and together provide strong evidence that dramatic changes in linker histone accompany nuclear differentiation (and dedifferentiation) in Tetrahymena. 相似文献