Biomedical subjects

W de Lange

Publications and source records attributed to W de Lange.

2 recordsLinked to original sources

PubMed1999

Disease-specific ex vivo stimulation of whole blood for cytokine production: applications in the study of tuberculosis.

As a simple method for field studies to assess the cytokine-status of patients with tuberculosis (TB), the use of whole blood instead of isolated cells has advantages, especially since the risk of contamination is minimal. Therefore, cytokine production in whole blood cultures was determined using non-specific and disease-specific stimuli. Heparinized blood from healthy volunteers was either incubated in closed vacutainer tubes or in tissue culture wells after dilution in culture medium. Dose-response and kinetics were investigated for the production of TNFalpha, IL-1beta, IL-1ra, IL-10 and IFNgamma. Patients with TB and healthy individuals were examined for IFN-gamma production in whole blood. In the absence of a stimulus, the production of cytokines is negligible in whole blood cultures. LPS induces the production of TNFalpha, IL-1beta, IL-1ra and IL-10; PHA induces the production of IFNgamma and IL-10. Live BCG induces the production of proinflammatory cytokines, irrespective of tuberculin skin status. In contrast, PPD and MTB-culture filtrate induce production of IFNgamma in skin-test positive and not in skin-test negative healthy subjects. Five out of 13 patients with TB had a low antigen-specific IFNgamma production, suggestive of a minimal or absent specific T-cell response. For most purposes, cultures in closed vacutainer tubes are optimal. If one wishes to focus on T-cell cytokines or if only small volumes of blood are available, dilution of whole blood in culture medium before incubation in tissue culture wells may be preferable.

Blood Cell Count↗

PubMedDate not supplied

Selecting MODFLOW cell sizes for accurate flow fields.

Contaminant transport models often use a velocity field derived from a MODFLOW flow field. Consequently, the accuracy of MODFLOW in representing a ground water flow field determines in part the accuracy of the transport predictions, particularly when advective transport is dominant. We compared MODFLOW ground water flow rates and MODPATH particle traces (advective transport) for a variety of conceptual models and different grid spacings to exact or approximate analytic solutions. All of our numerical experiments concerned flow in a single confined or semiconfined aquifer. While MODFLOW appeared robust in terms of both local and global water balance, we found that ground water flow rates, particle traces, and associated ground water travel times are accurate only when sufficiently small cells are used. For instance, a minimum of four or five cells are required to accurately model total ground water inflow in tributaries or other narrow surface water bodies that end inside the model domain. Also, about 50 cells are needed to represent zones of differing transmissivities or an incorrect flow field and (locally) inaccurate ground water travel times may result. Finally, to adequately represent leakage through aquitards or through the bottom of surface water bodies it was found that the maximum allowable cell dimensions should not exceed a characteristic leakage length lambda, which is defined as the square root of the aquifer transmissivity times the resistance of the aquitard or stream bottom. In some cases a cell size of one-tenth of lambda is necessary to obtain accurate results.

Forecasting↗