Diffusive and convective transfer of cytokine-inducing bacterial products across hemodialysis membranes

Diffusive and convective transfer of cytokine-inducing bacterial products across hemodialysis membranes. The widespread use of bicarbonate dialysate, and high-flux and high-efficiency dialyzers have raised concerns regarding the transmembrane passage of bacterial products from the dialysate into the blood compartment. To study the mechanisms as well as magnitude of the transmembrane transfer of bacterial products from the dialysate, we developed a computerized in vitro dialysis model which provides continuous pressure recording from the arterial, venous, dialysate inflow and outflow ports. By virtue of a computer controlled on-line infusion pump, this model permits control of ultrafiltration/backfiltration. Heparinized (10 U/ml) whole blood (150 ml) was circulated through the blood compartment for 120 minutes at 100ml/min. Bicarbonate dialysate contaminated with Pseudomonas maltophilia filtrate was circulated through the dialysate compartment at 100ml/min. A two-point pressure of +10mm of Hg (ultrafiltration) was maintained for the first 60 minutes and -10mm of Hg (backfiltration) for the next 60 minutes. Whole blood samples (10 ml) were drawn from the blood at 0, 60 and 120 minutes. Peripheral blood mononuclear cells (PBMC) harvested from these samples were incubated for 24 hours in tissue culture medium. In addition, 0.5ml samples of dialysate were collected at 0, 60 and 120 minutes and incubated with PBMC from the same donor for 24 hours. After 24 hour incubation, total cell-associated IL-1Ra and IL-1β were measured by specific radioimmunoassay. Paired experiments were performed with eight high-flux synthetic membranes (polyamide) and eight low-flux cellulose membranes (hemophan). Cytokine production is expressed as pg/2.5 million PBMC. During the mandatory ultrafiltration phase of the experiment (first hour), the production of IL-1Ra by PBMC from the blood compartment rose from 515 ± 118 to 785 ± 209 with polyamide membranes, and from 1175 ± 365 to 3865 ± 1847 with hemophan membranes, suggesting diffusive transport of bacterial products across the membrane. In contrast, at the end of the backfiltration phase (second hour), there was no further rise in the production of IL-1Ra by PBMC from the blood compartment (702 ± 123 with polyamide, and 2284 ± 886 with hemophan). The production of IL-1Ra by PBMC harvested from the blood compartment of polyamide membranes at 0, 60 and 120 minutes was lower than that with hemophan membranes (P = 0.01). In contrast to IL-1Ra, the production of IL-1β by PBMC harvested from the blood compartment with both membranes was uniformly low. The results of this study demonstrate the diffusive transfer of bacterial products across dialysis membranes. Therefore, any condition that increases diffusive transport such as dialyzers with large surface areas and high blood and dialysate flow rates could potentially increase the reverse transfer of bacterial products from the dialysate. This risk is not greater for synthetic high-flux membranes such as polyamide. Further, IL-1β is a less sensitive indicator than IL-1Ra of the transmembrane passage of cytokine-inducing substances from the dialysate to blood compartment

Time--Distance Helioseismology Data Analysis Pipeline for Helioseismic and Magnetic Imager onboard Solar Dynamics Observatory (SDO/HMI) and Its Initial Results

The Helioseismic and Magnetic Imager onboard the Solar Dynamics Observatory (SDO/HMI) provides continuous full-disk observations of solar oscillations. We develop a data-analysis pipeline based on the time-distance helioseismology method to measure acoustic travel times using HMI Doppler-shift observations, and infer solar interior properties by inverting these measurements. The pipeline is used for routine production of near-real-time full-disk maps of subsurface wave-speed perturbations and horizontal flow velocities for depths ranging from 0 to 20 Mm, every eight hours. In addition, Carrington synoptic maps for the subsurface properties are made from these full-disk maps. The pipeline can also be used for selected target areas and time periods. We explain details of the pipeline organization and procedures, including processing of the HMI Doppler observations, measurements of the travel times, inversions, and constructions of the full-disk and synoptic maps. Some initial results from the pipeline, including full-disk flow maps, sunspot subsurface flow fields, and the interior rotation and meridional flow speeds, are presented.Comment: Accepted by Solar Physics topical issue 'Solar Dynamics Observatory

Comparison of large-scale flows on the Sun measured by time-distance helioseismology and local correlation tracking technique

We present a direct comparison between two different techniques time-distance helioseismology and a local correlation tracking method for measuring mass flows in the solar photosphere and in a near-surface layer: We applied both methods to the same dataset (MDI high-cadence Dopplergrams covering almost the entire Carrington rotation 1974) and compared the results. We found that after necessary corrections, the vector flow fields obtained by these techniques are very similar. The median difference between directions of corresponding vectors is 24 degrees, and the correlation coefficients of the results for mean zonal and meridional flows are 0.98 and 0.88 respectively. The largest discrepancies are found in areas of small velocities where the inaccuracies of the computed vectors play a significant role. The good agreement of these two methods increases confidence in the reliability of large-scale synoptic maps obtained by them.Comment: 14 pages, 6 figures, just before acceptance in Solar Physic

Coronal Magnetic Field Evolution from 1996 to 2012: Continuous Non-potential Simulations

Coupled flux transport and magneto-frictional simulations are extended to simulate the continuous magnetic-field evolution in the global solar corona for over 15 years, from the start of Solar Cycle 23 in 1996. By simplifying the dynamics, our model follows the build-up and transport of electric currents and free magnetic energy in the corona, offering an insight into the magnetic structure and topology that extrapolation-based models cannot. To enable these extended simulations, we have implemented a more efficient numerical grid, and have carefully calibrated the surface flux-transport model to reproduce the observed large-scale photospheric radial magnetic field, using emerging active regions determined from observed line-of-sight magnetograms. This calibration is described in some detail. In agreement with previous authors, we find that the standard flux-transport model is insufficient to simultaneously reproduce the observed polar fields and butterfly diagram during Cycle 23, and that additional effects must be added. For the best-fit model, we use automated techniques to detect the latitude–time profile of flux ropes and their ejections over the full solar cycle. Overall, flux ropes are more prevalent outside of active latitudes but those at active latitudes are more frequently ejected. Future possibilities for space-weather prediction with this approach are briefly assessed

Glucocorticoids Decrease Hippocampal and Prefrontal Activation during Declarative Memory Retrieval in Young Men

Glucocorticoids (GCs, cortisol in human) are associated with impairments in declarative memory retrieval. Brain regions hypothesized to mediate these effects are the hippocampus and prefrontal cortex (PFC). Our aim was to use fMRI in localizing the effects of GCs during declarative memory retrieval. Therefore, we tested memory retrieval in 21 young healthy males in a randomized placebo-controlled crossover design. Participants encoded word lists containing neutral and emotional words 1 h prior to ingestion of 20 mg hydrocortisone. Memory retrieval was tested using an old/new recognition paradigm in a rapid event-related design. It was found that hydrocortisone decreased brain activity in both the hippocampus and PFC during successful retrieval of neutral words. These observations are consistent with previous animal and human studies suggesting that glucocorticoids modulate both hippocampal and prefrontal brain regions that are crucially involved in memory processing