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61.
Ultrastructure of the sodium pump: Comparison of thin sectioning, negative staining, and freeze-fracture of purified, membrane-bound (Na+, K+)-ATPase
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Purified (Na+, K+)-ATPase was studied by electron microscopy after thin sectioning, negative staining, and freeze-fracturing, particular emphasis being paid to the dimensions and frequencies of substructures in the membranes. Ultrathin sections show exclusively flat or cup-shaped membrane fragments which are triple-layered along much of their length and have diameters of 0.1-0.6 μm. Negative staining revealed a distinct substructure of particles with diameters between 30 and 50 A and with a frequency of 12,500 +/- 2,400 (SD) per μm(2). Comparisons with sizes of the protein components suggest that each surface particle contains as its major component one large catalytic chain with mol wt close to 100,000 and that two surface particles unite to form the unit of (Na+,K+)-ATPase which binds one molecule of ATP or ouabain. The further observations that the surface particles protrude from the membrane surface and are observed on both membrane surfaces in different patterns and degrees of clustering suggest that protein units span the membrane and are capable of lateral mobility. Freeze-fracturing shows intramembranous particles with diameters of 90-110 A and distributed on both concave and convex fracture faces with a frequency of 3,410 +/- 370 per μm(2) and 390 +/- 170 per μm(2), respectively. The larger diameters and three to fourfold smaller frequency of the intramembranous particles as compared to the surface particles seen after negative staining may reflect technical differences between methods, but it is more likely that the intramembranous particle is an oliogomer composed of two or even more of the protein units which form the surface particles. 相似文献
62.
Wanessa LF Tavares Gleidice E Lavalle Mariana S Figueiredo Aline G Souza Angelica C Bertagnolli Fernando AB Viana Paulo RO Paes Rubens A Carneiro Guilherme AO Cavalcanti Marilia M Melo Geovanni D Cassali 《Acta veterinaria Scandinavica》2010,52(1):1-6
Background
Hypertension and proteinuria are medical complications associated with the multisystemic effects of long-term hypercortisolism in dogs with hyperadrenocorticism (HAC).Methods
This study investigated the relationships among adrenocorticotropic hormone (ACTH)-stimulation test results, systemic blood pressure, and microalbuminuria in clinically-healthy dogs (n = 100), in dogs affected with naturally occurring pituitary-dependent (PDH; n = 40), or adrenal-dependent hyperadrenocorticism (ADH; n = 30).Results
Mean systemic blood pressure was similar between clinically healthy dogs and dogs with HAC (p = 0.803). However the incidence of hypertension was highest in dogs with ADH (p = 0.017), followed by dogs with PDH, with the lowest levels in clinically healthy dogs (p = 0.019). Presence of microalbuminuria and albuminuria in clinically healthy dogs and dogs affected with HAC was significantly different (p < 0.001); incidences of albuminuria followed the same pattern of hypertension; highest incidence in dogs with ADH, and lowest level in clinically healthy dogs; but microalbuminuria showed a different pattern: clinically healthy dogs had highest incidences and dogs with ADH had lowest incidence. The presence of albuminuria was not associated with blood pressure values, regardless of whether dogs were clinically healthy or affected with ADH or PDH (p = 0.306).Conclusions
Higher incidence of hypertension and albuminuria, not microalbuminuria was seen in dogs affected with HAC compared to clinically healthy dogs; incidence of hypertension and albuminuria was significantly higher in dogs affected with ADH compared to PDH. However, presence of albuminuria was not correlated with systemic blood pressure. 相似文献63.
Stefan Vordenbäumen Leo AB Joosten Johannes Friemann Matthias Schneider Benedikt Ostendorf 《Arthritis research & therapy》2009,11(6):256-6
Synovial biopsies, gained either by blind needle biopsy or minimally invasive arthroscopy, offer additional information in
certain clinical situations where routine assessment has not permitted a certain diagnosis. In research settings, synovial
histology and modern applications of molecular biology increase our insight into pathogenesis and enable responses to treatment
with new therapeutic agents to be assessed directly at the pathophysiological level. This review focuses on the diagnostic
usefulness of synovial biopsies in the light of actual developments. 相似文献
64.
Alzheimer and prion diseases are neurodegenerative disorders characterised by the abnormal processing of amyloid-β (Aβ) peptide and prion protein (PrPC), respectively. Recent evidence indicates that PrPC may play a critical role in the pathogenesis of Alzheimer disease. PrPC interacts with and inhibits the β-secretase BACE1, the rate-limiting enzyme in the production of Aβ. More recently PrPC was identified as a receptor for Aβ oligomers and the expression of PrPC appears to be controlled by the amyloid intracellular domain (AICD). Here we review these observations and propose a feedback loop in the normal brain where PrPC exerts an inhibitory effect on BACE1 to decrease both Aβ and AICD production. In turn, the AICD upregulates PrPC expression, thus maintaining the inhibitory effect of PrPC on BACE1. In Alzheimer disease, this feedback loop is disrupted, and the increased level of Aβ oligomers bind to PrPC and prevent it from regulating BACE1 activity.Key words: alzheimer disease, amyloid-β, Aβ oligomers, amyloid intracellular domain, BACE1, presenilin, prion protein 相似文献
65.
Background
Cancer treatments are complex and involve different actions, which include many times a surgical procedure. Medical imaging provides important information for surgical planning, and it usually demands a proper segmentation, i.e., the identification of meaningful objects, such as organs and lesions. This study proposes a methodology to segment the liver, its vessels and nodules from computer tomography images for surgical planning. 相似文献66.
Jessica AB van Nies Celina Alves Audrey LS Radix-Bloemen Cécile Gaujoux-Viala Tom WJ Huizinga Johanna MW Hazes Elisabeth Brouwer Bruno Fautrel Annette HM van der Helm-van Mil 《Arthritis research & therapy》2015,17(1)
IntroductionMorning stiffness is assessed daily in the diagnostic process of arthralgia and arthritis, but large-scale studies on the discriminative ability are absent. This study explored the diagnostic value of morning stiffness in 5,202 arthralgia and arthritis patients and the prognostic value in early rheumatoid arthritis (RA).MethodsIn arthralgia patients referred to the Early Arthritis Recognition Clinics (EARC) of Leiden (n = 807) and Groningen (n = 481) or included in the Rotterdam Early Arthritis Cohort (REACH) study (n = 353), the associations (cross-sectional analyses) between morning stiffness and presence of arthritis at physical examination were studied. In early arthritis patients, included in the Leiden Early Arthritis Clinic (EAC) (n = 2,748) and Evaluation et Suivi de POlyarthrites Indifférenciées Récentes (ESPOIR) (n = 813), associations with fulfilling the 2010-RA criteria after one year were assessed. In 2010-RA patients included in the EAC (n = 1,140) and ESPOIR (n = 677), association with the long-term outcomes of disease-modifying antirheumatic drug (DMARD)-free sustained remission and radiological progression were determined. Morning stiffness was defined as a duration ≥60 minutes; sensitivity analyses were performed for other definitions.ResultsIn arthralgia, morning stiffness (≥60 minutes) associated with the presence of arthritis; Leiden EARC odds ratio (OR) 1.49 (95% CI 1.001 to 2.20), Groningen EARC OR 2.21 (1.33 to 3.69) and REACH OR 1.55 (0.97 to 2.47) but the areas under the receiver operating characteristic curve (AUCs) were low (0.52, 0.57, 0.54). In early arthritis, morning stiffness was associated with 2010-RA independent of other predictors (Leiden EAC OR 1.72 (95% CI 1.31 to 2.25, AUC 0.68), ESPOIR OR 1.68 (1.03 to 2.74, AUC 0.64)). Duration of ≥30 minutes provided optimal discrimination for RA in early arthritis. Morning stiffness was not associated with radiological progression or DMARD-free sustained remission.ConclusionsMorning stiffness in arthralgia and early arthritis is associated with arthritis and RA respectively. This supports the incorporation of morning stiffness in the diagnostic process.
Electronic supplementary material
The online version of this article (doi:10.1186/s13075-015-0616-3) contains supplementary material, which is available to authorized users. 相似文献67.
Interaction between RNA polymerase and a ribosomal RNA promoter of E. coli. 总被引:3,自引:2,他引:1
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The interaction between RNA polymerase and the E. coli ribosomal (r) RNA promoter(s) of the rrnE operon has been studied by the filter-binding method. The extent of complex formation between RNA polymerase and rrnE promoter(s) is salt-dependent; ppGpp specifically inhibits interaction of RNA polymerase with the rrnE promoter(s). A tentative model is proposed for the molecular events in the early steps of rRNA initiation: a transition of the primarily formed, labile RNA polymerase-rRNA promoter complex to a more stable form is the determining step. This step is salt-sensitive; ppGpp acts on this "isomerization". 相似文献
68.
69.
Ihab?AB?Awad Christian?A?Rees Tina?Hernandez-Boussard Catherine?A?Ball Gavin?SherlockEmail author 《BMC bioinformatics》2004,5(1):151
Background
Microarray-based comparative genome hybridization experiments generate data that can be mapped onto the genome. These data are interpreted more easily when represented graphically in a genomic context. 相似文献70.