Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0851184 (thinning)
 11,252 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We examined trends in sea ice cover between 1979 and 2002 in four months (March, June, September, and November) for four large (approximately 100,000 km2) and 12 small (approximately 10,000 km2) regions of the western Arctic in habitats used by bowhead whales (Balaena mysticetus). Variation in open water with year was significant in all months except March, but interactions between region and year were not. Open water increased in both large and small regions, but trends were weak with least-squares regression accounting for < or =34% of the total variation. In large regions, positive trends in open water were strongest in September. Linear fits were poor, however, even in the East Siberian, Chukchi, and Beaufort seas, where basin-scale analyses have emphasized dramatic sea ice loss. Small regions also showed weak positive trends in open water and strong interannual variability. Open water increased consistently in five small regions where bowhead whales have been observed feeding or where oceanographic models predict prey entrainment, including: (1) June, along the northern Chukotka coast, near Wrangel Island, and along the Beaufort slope; (2) September, near Wrangel Island, the Barrow Arc, and the Chukchi Borderland; and (3) November, along the Barrow Arc. Conversely, there was very little consistent change in sea ice cover in four small regions considered winter refugia for bowhead whales in the northern Bering Sea, nor in two small regions that include the primary springtime migration corridor in the Chukchi Sea. The effects of sea ice cover on bowhead whale prey availability are unknown but can be modeled via production and advection pathways. Our conceptual model suggests that reductions in sea ice cover will increase prey availability along both pathways for this population. This analysis elucidates the variability inherent in the western Arctic marine ecosystem at scales relevant to bowhead whales and contrasts basin-scale depictions of extreme sea ice retreats, thinning, and wind-driven movements.
 ...
PMID:Trends in sea ice cover within habitats used by bowhead whales in the western Arctic. 1682 93

We report the cyclic voltammetry, chronoamperometry, and scanning electrochemical microscopy of ferrocene dissolved in deep eutectic solvents (DES), consisting of choline chloride (ChCl) and either trifluoroacetamide (TFA) or malonic acid as the hydrogen-bond donor. Despite the use of ultramicroelectrodes, which were required due to the modest conductivities of the DES employed, linear diffusion behavior was observed in cyclic voltammetric experiments. The high viscosity of 1:2 ChCl/TFA relative to non-aqueous electrochemical solvents leads to a low diffusion coefficient, 2.7 x 10(-8) cm2 s(-1) for ferrocene in this medium. Because of the difficulties in achieving steady-state conditions, SECM approach curves were tip velocity dependent. Under certain conditions, SECM approach curves to an insulating substrate displayed a positive-feedback response. Satisfactory simulation of this unexpected behavior was obtained by including convection terms into the mass transport equations typically used for SECM theory. The observance of positive-feedback behavior at an insulating substrate can be described in terms of a dimensionless parameter, the Peclet number, which is the ratio of the convective and diffusive timescales. Fitting insulator approach curves of ferrocene in 1:2 ChCl/TFA shows an apparent increase in the diffusion coefficient with increasing tip velocity, which can be explained by DES behaving as a shear thinning non-Newtonian fluid.
 ...
PMID:Electrochemistry in deep eutectic solvents. 1797 21

Red blood cells (RBCs) generally deform to adopt a parachute-like, torpedo-like, or other configuration to align and flow through a capillary that is narrower than their major axis. As described herein, even in a narrow tube (25 microm) with diameter much larger than that of a capillary, flowing RBCs at 1 mm/s align axially and deform to a paraboloid shape in a viscous Newtonian fluid (505 kDa dextran medium) with viscosity of 23.4-57.1 mPa.s. A high-speed digital camera image showed that the silhouette of the tip of RBCs fits a parabola, unlike the shape of RBCs in capillaries, because of the longer distance of the RBC-free layer between the tube wall and the RBC surface ( approximately 8.8 microm). However, when RBCs are suspended in a "non-Newtonian" viscous fluid (liposome-40 kDa dextran medium) with a shear-thinning profile, they migrate toward the tube wall to avoid the axial lining, as "near-wall-excess," which is usually observed for platelets. This migration results from the presence of flocculated liposomes at the tube center. In contrast, such near-wall excess was not observed when RBCs were suspended in a nearly Newtonian liposome-albumin medium. Such unusual flow patterns of RBCs would be explainable by the principle; a larger particle tends to flow near the centerline, and a small one tends to go to the wall to flow with least resistance. However, we visualized for the first time the complete axial aligning and near-wall excess of RBCs in the noncapillary size tube in some extreme conditions.
 ...
PMID:Peculiar flow patterns of RBCs suspended in viscous fluids and perfused through a narrow tube (25 microm). 1950 57

Cell aggregates are a tool for in vitro studies of morphogenesis, cancer invasion, and tissue engineering. They respond to mechanical forces as a complex rather than simple liquid. To change an aggregate's shape, cells have to overcome energy barriers. If cell shape fluctuations are active enough, the aggregate spontaneously relaxes stresses ("fluctuation-induced flow"). If not, changing the aggregate's shape requires a sufficiently large applied stress ("stress-induced flow"). To capture this distinction, we develop a mechanical model of aggregates based on their cellular structure. At stress lower than a characteristic stress tau*, the aggregate as a whole flows with an apparent viscosity eta*, and at higher stress it is a shear-thinning fluid. An increasing cell-cell tension results in a higher eta* (and thus a slower stress relaxation time t(c)). Our constitutive equation fits experiments of aggregate shape relaxation after compression or decompression in which irreversibility can be measured; we find t(c) of the order of 5 h for F9 cell lines. Predictions also match numerical simulations of cell geometry and fluctuations. We discuss the deviations from liquid behavior, the possible overestimation of surface tension in parallel-plate compression measurements, and the role of measurement duration.
 ...
PMID:The role of fluctuations and stress on the effective viscosity of cell aggregates. 1980 70

Sample thinning for TEM observation introduces large changes with respect to the initial strain state of the bulk sample and particularly relaxation via the free surfaces which leads to HOLZ lines splitting in the CBED pattern. This phenomenon has been simulated owing to extensive calculations either in the kinematical or the dynamical framework of electron diffraction mainly using displacement fields resulting from finite element modelling of the sample relaxation. HOLZ line splitting is well reproduced and numerical fits can be used to compare experimental and calculated curves. This paper proposes new analytical solutions for the kinematical equation of electron diffraction. Simple mathematical functions are used to approximate the deformation profiles. We showed that, under certain conditions, the rocking curve profile can be analytically calculated, thus providing some clue to separate different contributions to the rocking curves against deformation profile. These simplified analytical expressions are used to extract the maximum amplitude displacement within the sample with about 10% accuracy. This accuracy can even be improved to 1% with a short adjustment routine. The influence of the shape of the displacement profile on the rocking curves is demonstrated.
 ...
PMID:HOLZ lines splitting on SiGe/Si relaxed samples: analytical solutions for the kinematical equation. 2009 47

Implantable devices in direct contact with flowing blood are associated with the risk of thromboembolic events. This study addresses the need to improve our understanding of the thrombosis mechanism and to identify areas on artificial surfaces susceptible to thrombus deposition. Thrombus deposits on artificial blood step transitions are quantified experimentally and compared with shear stress and shear rate distributions using computational fluid dynamics (CFD) models. Larger steps, and negative (expanding) steps result in larger thrombus deposits. Fitting CFD results to experimental deposit locations reveals a specific shear stress threshold of 0.41 Pa or a shear rate threshold of 54 s(-1) using a shear thinning blood viscosity model. Thrombosis will occur below this threshold, which is specific to solvent-polished polycarbonate surfaces under in vitro coagulation conditions with activated clotting time levels of 200-220 s. The experimental and computational models are valuable tools for thrombosis prediction and assessment that may be used before proceeding to clinical trials and to better understand existing clinical problems with thrombosis.
 ...
PMID:In vitro and computational thrombosis on artificial surfaces with shear stress. 2096

Many RNAs, proteins, and organelles are present in such low numbers per cell that random segregation of individual copies causes large "partitioning errors" at cell division. Even symmetrically dividing cells can then by chance produce daughters with very different composition. The size of the errors depends on the segregation mechanism: Control systems can reduce low-abundance errors, but the segregation process can also be subject to upstream sources of randomness or spatial heterogeneities that create large errors despite high abundances. Here we mathematically demonstrate how partitioning errors arise for different types of segregation mechanisms and how errors can be greatly increased by upstream heterogeneity but remarkably hard to avoid through controlled partitioning. We also show that seemingly straightforward experiments cannot be straightforwardly interpreted because very different mechanisms produce identical fits and present an approach to deal with this problem by adding binomial counting noise and testing for convexity or concavity in the partitioning error as a function of the binomial thinning parameter. The results lay a conceptual groundwork for more effective studies of heterogeneity among growing and dividing cells, whether in microbes or in differentiating tissues.
 ...
PMID:Random partitioning of molecules at cell division. 2187 52

The conformation and eventual morphology of silk fibroin (SF) chains are crucial for the mechanical properties of SF materials, and are strongly related to the solvation step as a key stage in their processing conditions. In this work, a novel SF/AmimCl (1-allyl-3-methylimidazolium chloride) solution with unique properties is reported and compared with conventional regenerated SF aqueous solutions, based on an investigation of its rheological properties. The steady shearing behavior suggested that AmimCl is a good solvent for SF molecules, and shear thinning of semidiluted SF/AmimCl solution at high shear rates showed behavior similar to that in native spinning, which is due to the rearrangement and orientation of SF molecular chains. Fitting of experimental dynamic viscoelastic data to the Rouse model provided an effective method to estimate the molecular weight of SF. We believe that this work not only provides a better understanding of the relationship between properties of silk protein and aggregation states of their molecular chains, but also provides tools to fabricate high-performance SF-based materials.
 ...
PMID:Investigation of rheological properties and conformation of silk fibroin in the solution of AmimCl. 2245 62

Epiboly is the first coordinated cell movement in most vertebrates and marks the onset of gastrulation. During zebrafish epiboly, enveloping layer (EVL) and deep cells spread over the vegetal yolk mass with a concomitant thinning of the deep cell layer. A prevailing model suggests that deep cell radial intercalations directed towards the EVL would drive deep cell epiboly. To test this model, we have globally recorded 3D cell trajectories for zebrafish blastomeres between sphere and 50% epiboly stages, and developed an image analysis framework to determine intercalation events, intercalation directionality, and migration speed for cells at specific positions within the embryo. This framework uses Voronoi diagrams to compute cell-to-cell contact areas, defines a feature-based spatio-temporal model for intercalation events and fits an anatomical coordinate system to the recorded datasets. We further investigate whether epiboly defects in MZspg mutant embryos devoid of Pou5f1/Oct4 may be caused by changes in intercalation behavior. In wild-type and mutant embryos, intercalations orthogonal to the EVL occur with no directional bias towards or away from the EVL, suggesting that there are no directional cues that would direct intercalations towards the EVL. Further, we find that intercalation direction is independent of the previous intercalation history of individual deep cells, arguing against cues that would program specific intrinsic directed migration behaviors. Our data support a dynamic model in which deep cells during epiboly migrate into space opening between the EVL and the yolk syncytial layer. Genetic programs determining cell motility may control deep cell dynamic behavior and epiboly progress.
...
PMID:Non-directional radial intercalation dominates deep cell behavior during zebrafish epiboly. 2395 11

Over the last two decades, MRI has emerged as an important clinical tool to assist in the diagnosis and management of rheumatic disease. In rheumatoid arthritis (RA), MRI has improved our understanding of the pathological basis of disease and has provided new information about imaging features that reflect joint inflammation and damage. Using MRI, we can now directly observe inflammation involving the synovial membrane and tenosynovium, plus joint damage including bone erosion and cartilage thinning. Inflammation of bone beneath the joint (osteitis) appears as bone oedema which is a feature unique to MRI and yields important diagnostic and prognostic information in patients with inflammatory arthritis. With the introduction of biologics to rheumatology clinical practice, sensitive tools are required to monitor disease activity and progression, so that the disease suppressing effect of these new agents can be measured. MRI fits the bill for this role as it can inform the clinician about the development of bone erosions well before plain radiography, and its ability to reveal cartilage damage is emerging. The use of MRI as a marker of outcome in clinical trials is being paralleled by its increasing role in the clinic. Both extremity and high field MRI have clinical applications in RA and need to be considered along with other advanced imaging techniques as useful tools to add to the clinician's armamentarium. This review will summarise recent advances in this field and will apply current knowledge to specific clinical scenarios relevant to modern rheumatology practice.
...
PMID:MRI in rheumatoid arthritis: a useful tool for the clinician? 2467 86


<< Previous 1 2 3 Next >>