4,159 research outputs found
Artifact Rejection Methodology Enables Continuous, Noninvasive Measurement of Gastric Myoelectric Activity in Ambulatory Subjects.
The increasing prevalence of functional and motility gastrointestinal (GI) disorders is at odds with bottlenecks in their diagnosis, treatment, and follow-up. Lack of noninvasive approaches means that only specialized centers can perform objective assessment procedures. Abnormal GI muscular activity, which is coordinated by electrical slow-waves, may play a key role in symptoms. As such, the electrogastrogram (EGG), a noninvasive means to continuously monitor gastric electrical activity, can be used to inform diagnoses over broader populations. However, it is seldom used due to technical issues: inconsistent results from single-channel measurements and signal artifacts that make interpretation difficult and limit prolonged monitoring. Here, we overcome these limitations with a wearable multi-channel system and artifact removal signal processing methods. Our approach yields an increase of 0.56 in the mean correlation coefficient between EGG and the clinical "gold standard", gastric manometry, across 11 subjects (pâ<â0.001). We also demonstrate this system's usage for ambulatory monitoring, which reveals myoelectric dynamics in response to meals akin to gastric emptying patterns and circadian-related oscillations. Our approach is noninvasive, easy to administer, and has promise to widen the scope of populations with GI disorders for which clinicians can screen patients, diagnose disorders, and refine treatments objectively
Tumor necrosis factor alpha and interleukin 1 stimulate the human immunodeficiency virus enhancer by activation of the nuclear factor kappa B.
Continuous, Semi-discrete, and Fully Discretized Navier-Stokes Equations
The Navier--Stokes equations are commonly used to model and to simulate flow
phenomena. We introduce the basic equations and discuss the standard methods
for the spatial and temporal discretization. We analyse the semi-discrete
equations -- a semi-explicit nonlinear DAE -- in terms of the strangeness index
and quantify the numerical difficulties in the fully discrete schemes, that are
induced by the strangeness of the system. By analyzing the Kronecker index of
the difference-algebraic equations, that represent commonly and successfully
used time stepping schemes for the Navier--Stokes equations, we show that those
time-integration schemes factually remove the strangeness. The theoretical
considerations are backed and illustrated by numerical examples.Comment: 28 pages, 2 figure, code available under DOI: 10.5281/zenodo.998909,
https://doi.org/10.5281/zenodo.99890
CâC chemokineâinduced eosinophil chemotaxis during allergic airway inflammation
The production of eosinophilâspecific chemotactic factors during allergic airway responses may be a pivotal event resulting in eosinophil accumulation, activation, and airway damage. Recent studies have identified specific chemokines that may play crucial roles in recruitment of eosinophils to the site of allergic reactions. In this study we have utilized an established model of schistosome egg antigen (SEA)âmediated allergic responses to examine the role of specific CâC chemokines [macrophage inflammatory proteinâ1α (MIPâ1α), RANTES, and monocyte chemoattractant proteinâ1 (MCPâ1)] in eosinophil recruitment. We have previously identified a role for MIPâ1α in eosinophil accumulation in the lung and airway during allergic airway inflammation. We extend those studies using in vitro eosinophil chemotaxis to establish that both MIPâ1α and RANTES are potent eosinophil chemotactic factors in lungs during allergic airway responses. Morphometric analysis demonstrated a peribronchial accumulation of eosinophils within the lungs beginning at 8 h, peaking at 24 h, and plateauing at 48â96 h after allergen (SEA) challenge. Utilizing wholeâlung homogenates from allergenâchallenged mice, in vitro eosinophil chemotactic assays demonstrated significant increases in eosinophil chemotactic activity with 8âh lung homogenates and peak activity with samples from 24âh lung homogenates. These data correlated with the morphometric analysis of peribronchial eosinophil accumulation in situ. When lung homogenates from allergenâchallenged mice were preincubated in vitro with antibodies specific for MIPâ1α, RANTES, or MCPâ1, a significant reduction in eosinophil chemotaxis was observed with only MIPâ1α and RANTES neutralization. Altogether, these studies indicate that RANTES and MIPâ1α are major eosinophil chemotactic factors produced during allergic airway responses. J. Leukoc. Biol. 60:573â578; 1996.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/141543/1/jlb0573.pd
Folding of VemP into translation-arresting secondary structure is driven by the ribosome exit tunnel
The ribosome is a fundamental biomolecular complex that synthesizes proteins in cells. Nascent proteins emerge from the ribosome through a tunnel, where they may interact with the tunnel walls or small molecules such as antibiotics. These interactions can cause translational arrest with notable physiological consequences. Here, we studied the arrest caused by the regulatory peptide VemP, which is known to form alpha-helices inside the ribosome tunnel near the peptidyl transferase center under specific conditions. We used all-atom molecular dynamics simulations of the entire ribosome and circular dichroism spectroscopy to study the driving forces of helix formation and how VemP causes the translational arrest. To that aim, we compared VemP dynamics in the ribosome tunnel with its dynamics in solution. We show that the VemP peptide has a low helical propensity in water and that the propensity is higher in mixtures of water and trifluorethanol. We propose that helix formation within the ribosome is driven by the interactions of VemP with the tunnel and that a part of VemP acts as an anchor. This anchor might slow down VemP progression through the tunnel enabling alpha-helix formation, which causes the elongation arrest
Magellanic Cloud Periphery Carbon Stars IV: The SMC
The kinematics of 150 carbon stars observed at moderate dispersion on the
periphery of the Small Magellanic Cloud are compared with the motions of
neutral hydrogen and early type stars in the Inter-Cloud region. The
distribution of radial velocities implies a configuration of these stars as a
sheet inclined at 73+/-4 degrees to the plane of the sky. The near side, to the
South, is dominated by a stellar component; to the North, the far side contains
fewer carbon stars, and is dominated by the neutral gas. The upper velocity
envelope of the stars is closely the same as that of the gas. This
configuration is shown to be consistent with the known extension of the SMC
along the line of sight, and is attributed to a tidally induced disruption of
the SMC that originated in a close encounter with the LMC some 0.3 to 0.4 Gyr
ago. The dearth of gas on the near side of the sheet is attributed to ablation
processes akin to those inferred by Weiner & Williams (1996) to collisional
excitation of the leading edges of Magellanic Stream clouds. Comparison with
pre LMC/SMC encounter kinematic data of Hardy, Suntzeff, & Azzopardi (1989) of
carbon stars, with data of stars formed after the encounter, of Maurice et al.
(1989), and Mathewson et al. (a986, 1988) leaves little doubt that forces other
than gravity play a role in the dynamics of the H I.Comment: 30 pages; 7 figures, latex compiled, 1 table; to appear in AJ (June
2000
Artificial anterior chamber for the growing of membranes on lens implants
Intraocular lens implants made of glass and plastic were placed into the lumen of short pieces of clear plastic tubing. These were incompletely closed at both ends with nylon sutures, filled with Healon, and used experimentally as artificial anterior chambers for implantation into the peritoneal space of mice. After 7 days macrophages had been attracted into the chambers, become sessile on the implants, and formed a continuous membrane on their surface. The concept of artificial anterior chambers in experimental and future clinical applications is discussed.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/47387/1/417_2005_Article_BF02133805.pd
Mononuclear Cell Adherence Induces Neutrophil Chemotactic Factor/Interleukinâ8 Gene Expression
The accumulation of polymorphonuclear cells (PMN) in tissue is an essential element of the inflammatory response that is important in host defense. Adherence to endothelium constitutes the first step in PMN migration from the vascular compartment to the interstitium. We demonstrate that human peripheral blood mononuclear cells (PBMC) adherent to plastic can result in expression of interleukinâ8 (ILâ8), a potent PMN chemoattractant and activating cytokine. Northern blot analyses showed PBMC adherent to plastic expressed ILâ8 steadyâstate mRNA levels by 30 min, peaked at 8 h, and then decreased over the next 16 h. In contrast, nonadherent PBMC (cultured in teflon chambers) expressed less than 25% of the maximal ILâ8 steadyâstate mRNA levels as compared with adherent PBMC. Adherent PBMCâassociated ILâ8 determined by immunohistochemistry, supernatant chemotactic bioactivity, and extracellular antigenic ILâ8 paralleled ILâ8 mRNA expression. Antigenic and bioactive ILâ8 were significantly apparent by 4â8 h, respectively, and increased significantly to maximal levels by 24 h. Furthermore, adherent PBMC ILâ8 gene expression was suppressed by either concomitant treatment with actinomycinâD or cycloheximide, yet specific neutralizing antibodies directed against either ILâ1ÎČ or tumor necrosis factor (TNF)âα failed to alter adherenceâinduced steadyâstate ILâ8 mRNA levels. These data support the hypothesis that PBMC adherence is an important signal for the production of ILâ8, and may be essential to the development of the inflammatory response through the elicrtation of PMN.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/141636/1/jlb0287.pd
A Simplified Approach for Estimating Soil Carbon and Nitrogen Stocks in Semi-Arid Complex Terrain
We investigated soil carbon (C) and nitrogen (N) distribution and developed a model, using readily available geospatial data, to predict that distribution across a mountainous, semi-arid, watershed in southwestern Idaho (USA). Soil core samples were collected and analyzed from 133 locations at 6 depths (n=798), revealing that aspect dramatically influences the distribution of C and N, with north-facing slopes exhibiting up to 5 times more C and N than adjacent southfacing aspects. These differences are superimposed upon an elevation (precipitation) gradient, with soil C and N contents increasing by nearly a factor of 10 from the bottom (1100 m elevation) to the top (1900 m elevation) of the watershed. Among the variables evaluated, vegetation cover, as represented by a Normalized Difference Vegetation Index (NDVI), is the strongest, positively correlated, predictor of C; potential insolation (incoming solar radiation) is a strong, negatively correlated, secondary predictor. Approximately 62% (as R2) of the variance in the C data is explained using NDVI and potential insolation, compared with an R2 of 0.54 for a model using NDVI alone. Soil N is similarly correlated to NDVI and insolation. We hypothesize that the correlations between soil C and N and slope, aspect and elevation reflect, in part, the inhibiting influence of insolation on semi-arid ecosystem productivity via water limitation. Based on these identified relationships, two modeling techniques (multiple linear regression and cokriging) were applied to predict the spatial distribution of soil C and N across the watershed. Both methods produce similar distributions, successfully capturing observed trends with aspect and elevation. This easily applied approach may be applicable to other semi-arid systems at larger scales
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