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排序方式: 共有105条查询结果,搜索用时 15 毫秒
71.
AE Clarke S Bernatsky KH Costenbader MB Urowitz DD Gladman PR Fortin M Petri S Manzi DA Isenberg A Rahman D Wallace C Gordon C Peschken MA Dooley EM Ginzler C Aranow SM Edworthy O Nived S Jacobsen G Ruiz-Irastorza E Yelin SG Barr L Criswell G Sturfelt L Dreyer I Blanco L Gottesman CH Feldman R Ramsey-Goldman 《Arthritis research & therapy》2012,14(Z3):A16
72.
Jayne E Rattray Marc Strous Huub JM Op den Camp Stefan Schouten Mike SM Jetten Jaap S Sinninghe Damsté 《Biology direct》2009,4(1):8-16
Background
The fatty acids of anaerobic ammonium oxidizing (anammox) bacteria contain linearly concatenated cyclobutane moieties, so far unique to biology. These moieties are under high ring strain and are synthesised by a presently unknown biosynthetic pathway. 相似文献73.
Susanne M. Krug Salah Amasheh Jan F. Richter Susanne Milatz Dorothee Günzel Julie K. Westphal Otmar Huber J?rg D. Schulzke Michael Fromm 《Molecular biology of the cell》2009,20(16):3713-3724
Tricellulin is a tight junction protein localized in tricellular tight junctions (tTJs), the meeting points of three cells, but also in bicellular tight junctions (bTJs). To investigate its specific barrier functions in bTJs and tTJs, TRIC-a was expressed in low-level tricellulin–expressing cells, and MDCK II, either in all TJs or only in tTJs. When expressed in all TJs, tricellulin increased paracellular electrical resistance and decreased permeability to ions and larger solutes, which are associated with enhanced ultrastructural integrity of bTJs toward enhanced strand linearity. In tTJs in contrast, ultrastructure was unchanged and tricellulin minimized permeability to macromolecules but not to ions. This paradox is explained by properties of the tTJ central tube which is wide enough for passage of macromolecules, but too rare to contribute significantly to ion permeability. In conclusion, at low tricellulin expression the tTJ central tube forms a pathway for macromolecules. At higher expression, tricellulin forms a barrier in tTJs effective only for macromolecules and in bTJs for solutes of all sizes. 相似文献
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Background
Analysis of heart rate variation (HRV) has become a popular noninvasive tool for assessing the activities of the autonomic nervous system (ANS). HRV analysis is based on the concept that fast fluctuations may specifically reflect changes of sympathetic and vagal activity. It shows that the structure generating the signal is not simply linear, but also involves nonlinear contributions. These signals are essentially non-stationary; may contain indicators of current disease, or even warnings about impending diseases. The indicators may be present at all times or may occur at random in the time scale. However, to study and pinpoint abnormalities in voluminous data collected over several hours is strenuous and time consuming. 相似文献77.
J.D. Schulzke A.H. Gitter J. Mankertz U. Seidler M. Saitou M. Fromm 《生物化学与生物物理学报:生物膜》2005,1669(1):34-42
Background and Aims
This study aimed at functional characterization of the tight junction protein occludin using the occludin-deficient mouse model.Methods
Epithelial transport and barrier functions were characterized in Ussing chambers. Impedance analysis revealed the ionic permeability of the epithelium (Re, epithelial resistance). Conductance scanning differentiated transcellular (Gc) and tight junctional conductance (Gtj). The pH-stat technique quantified gastric acid secretion.Results
In occludin+/+ mice, Re was 23±5 Ω cm2 in jejunum, 66±5 Ω cm2 in distal colon and 33±6 Ω cm2 in gastric corpus and was not altered in heterozygotic occludin+/− or homozygotic occludin−/− mice. Additionally, [3H]mannitol fluxes were unaltered. In the control colon, Gc and Gtj were 7.6±1.0 and 0.3±0.1 mS/cm2 and not different in occludin deficiency. Epithelial resistance after mechanical perturbation or EGTA exposition (low calcium switch) was not more affected in occludin−/− mice than in control. Barrier function was measured in the urinary bladder, a tight epithelium, and in the stomach. Control Rt was 5.8±0.8 kΩ cm2 in urinary bladder and 33±6 Ω cm2 in stomach and not altered in occludin−/− mice. In gastric corpus mucosa, the glandular structure exhibited a complete loss of parietal cells and mucus cell hyperplasia, as a result of which acid secretion was virtually abolished in occludin−/− mice.Conclusion
Epithelial barrier characterization in occludin-deficiency points against an essential barrier function of occludin within the tight junction strands or to a substitutional redundancy of single tight junction molecules like occludin. A dramatic change in gastric morphology and secretory function indicates that occludin is involved in gastric epithelial differentiation. 相似文献78.
Schulzke JD Gitter AH Mankertz J Spiegel S Seidler U Amasheh S Saitou M Tsukita S Fromm M 《Biochimica et biophysica acta》2005,1669(1):34-42
BACKGROUND AND AIMS: This study aimed at functional characterization of the tight junction protein occludin using the occludin-deficient mouse model. METHODS: Epithelial transport and barrier functions were characterized in Ussing chambers. Impedance analysis revealed the ionic permeability of the epithelium (Re, epithelial resistance). Conductance scanning differentiated transcellular (Gc) and tight junctional conductance (Gtj). The pH-stat technique quantified gastric acid secretion. RESULTS: In occludin+/+ mice, Re was 23+/-5 Omega cm2 in jejunum, 66+/-5 Omega cm2 in distal colon and 33+/-6 Omega cm2 in gastric corpus and was not altered in heterozygotic occludin+/- or homozygotic occludin-/- mice. Additionally, [3H]mannitol fluxes were unaltered. In the control colon, Gc and Gtj were 7.6+/-1.0 and 0.3+/-0.1 mS/cm2 and not different in occludin deficiency. Epithelial resistance after mechanical perturbation or EGTA exposition (low calcium switch) was not more affected in occludin-/- mice than in control. Barrier function was measured in the urinary bladder, a tight epithelium, and in the stomach. Control Rt was 5.8+/-0.8 kOmega cm2 in urinary bladder and 33+/-6 Omega cm2 in stomach and not altered in occludin-/- mice. In gastric corpus mucosa, the glandular structure exhibited a complete loss of parietal cells and mucus cell hyperplasia, as a result of which acid secretion was virtually abolished in occludin-/- mice. CONCLUSION: Epithelial barrier characterization in occludin-deficiency points against an essential barrier function of occludin within the tight junction strands or to a substitutional redundancy of single tight junction molecules like occludin. A dramatic change in gastric morphology and secretory function indicates that occludin is involved in gastric epithelial differentiation. 相似文献
79.
Evolution of transposable elements: an IS10 insertion increases fitness in Escherichia coli 总被引:3,自引:0,他引:3
Strains of Escherichia coli carrying Tn10, a transposon consisting of two
IS10 insertion sequences flanking a segment encoding for a
tetracycline-resistance determinant, gain a competitive advantage in
chemostat cultures. All Tn10-bearing strains that increase in frequency
during competition have a new IS10 insertion that is found in the same
location in the genome of those strains. We mapped, by a gradient of
transmission, the position of the new IS10 insertion. We examined 11
isolates whose IS10 insertion was deleted by recombinational crossing-
over, and in all cases the competitive fitness of the isolates was
decreased. These results show that the IS10-generated insertion increases
fitness in chemostat cultures. We named the insertion fit::IS10 and suggest
that transposable elements may speed the rate of evolution by promoting
nonhomologous recombination between preexisting variations within a genome
and thereby generating adaptive variation.
相似文献
80.