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Sampling Schedule (sampling + schedule)

Distribution by Scientific Domains

Medical Sciences	50%

Selected Abstracts

Soluble urokinase plasminogen activator receptor is a marker of dysmetabolism in HIV-infected patients receiving highly active antiretroviral therapy

JOURNAL OF MEDICAL VIROLOGY, Issue 2 2008
Ove Andersen
Abstract Circulating soluble urokinase plasminogen activator receptor (suPAR) reflects the immune and pro-inflammatory status of the HIV-infected patient. Highly active antiretroviral therapy (HAART) suppresses suPAR. Independent of the immune response to HAART, suPAR remains elevated in some HIV-infected patients, reflecting possibly a low-grade pro-inflammatory state. Low-grade inflammation has been implicated in insulin resistance and other features of dysmetabolism. Accordingly it is hypothesized that circulating suPAR is associated with the metabolic status of HIV-infected patients on HAART. Fasting plasma suPAR was determined in 36 normoglycaemic HIV-infected patients on HAART (n,=,18 lipodystrophic, and n,=,18 non-lipodystrophic) who had estimated insulin sensitivity (Rd) and non-oxidative glucose disposal (NOGM) by euglycaemic hyperinsulinaemic clamps, indirect calorimetry, and glucose tracer infusion. Five patients had circadian suPAR concentrations measured (24 hr, 20 min-intervals). suPAR and non-HDL-cholesterol were higher and Rd, NOGM, and limb fat were lower in lipodystrophic patients than in non-lipodystrophic patients (P,<,0.05). suPAR correlated positively with non-HDL-cholesterol and inversely with Rd, NOGM and limb fat (P,<,0.005, n,=,36). suPAR also correlated positively with leukocyte count and TNF-, (P,<,0.01, n,=,36) but not with IL-6. In multiple regression analyses suPAR was a stronger predictor of dysmetabolism than TNF-, and IL-6. Circadian suPAR did not systematically fluctuate. In conclusion, suPAR may reflect the metabolic status of the HIV-infected patient on HAART, thus linking low-grade inflammation, immune constitution, lipid and glucose metabolism, and fat redistribution. Circadian suPAR concentration appeared stable, suggesting that sampling schedule does not affect measurement. Further studies addressing whether suPAR predicts lipodystrophy and dysmetabolism in HIV-infected patients are warranted. J. Med. Virol. 80:209,216, 2008. © 2007 Wiley-Liss, Inc. [source]

Real-time adaptive sequential design for optimal acquisition of arterial spin labeling MRI data

MAGNETIC RESONANCE IN MEDICINE, Issue 1 2010
Jingyi Xie
Abstract An optimal sampling schedule strategy based on the Fisher information matrix and the D-optimality criterion has previously been proposed as a formal framework for optimizing inversion time scheduling for multi-inversion-time arterial spin labeling experiments. Optimal sampling schedule possesses the primary advantage of improving parameter estimation precision but requires a priori estimation of plausible parameter distributions that may not be available in all situations. An adaptive sequential design approach addresses this issue by incorporating the optimal sampling schedule strategy into an adaptive process that iteratively updates the parameter estimates and adjusts the optimal sampling schedule accordingly as data are acquired. In this study, the adaptive sequential design method was experimentally implemented with a real-time feedback scheme on a clinical MRI scanner and was tested in six normal volunteers. Adapted schedules were found to accommodate the intrinsically prolonged arterial transit times in the occipital lobe of the brain. Simulation of applying the adaptive sequential design approach on subjects with pathologically reduced perfusion was also implemented. Simulation results show that the adaptive sequential design approach is capable of incorporating pathologic parameter information into an optimal arterial spin labeling scheduling design within a clinically useful experimental time. Magn Reson Med, 2010. © 2010 Wiley-Liss, Inc. [source]

Salivary cortisol and psychosocial hazards at work

AMERICAN JOURNAL OF INDUSTRIAL MEDICINE, Issue 3 2009
Giovanni Maina MD
Abstract Background Experimental and clinical evidence suggest that stress can lead to ill-health through the disregulation of the hypothalamic,pituitary,adrenal (HPA) axis. Studies to date have produced equivocal results likely due to different methodologies and failure to account for confounding factors. This investigation aimed to assess the relation between self-reported work-related stressors and salivary cortisol and to clarify the role of the potential confounders. Methods Thirty-six call-handlers completed a self-administered job content questionnaire and collected seven daily salivary samples on two workdays and a weekend. The diurnal salivary cortisol output was expressed as cortisol awakening response (CAR), and cortisol output in the rest of the day. Salivary cortisol data were normalized by means of square root transformation. The generalized estimating equations method was used to assess the relation between job strain and cortisol levels after adjusting for gender, weekdays and adherence to the sampling schedule. Results Job strain significantly influenced the total amount of cortisol response to waking (high strain vs. low strain: 1.1 (0.3,2.0) nmol/L). The cortisol response to waking showed gender-specific differences [women excreting greater cortisol than men: 1.1 (0.3,1.9) nmol/L], and weekday differences [workdays vs. weekend: 1.0 (0.3,1.6) nmol/L]. Non-compliance with the sampling protocol was associated with lower salivary cortisol than in adherent subjects. Conclusions Our results provide further evidence for the HPA axis involvement in the physiological response to work stress. The measure of the CAR showed to be the sensitive index to assess the physiological response to psychosocial factors. Gender, weekday, and protocol compliance were confounding factors. Am. J. Ind. Med. 52:251,260, 2009. © 2008 Wiley-Liss, Inc. [source]

Calculation of Elapsed Decimal Time for Tracing Studies

GROUND WATER, Issue 1 2008
Malcolm S. Field
Calculation of time of travel from tracing studies in hydrologic systems is critical to establishing pollutant arrival times from points of inflow to points outflow, calculating subsurface flow velocities, and determining other important transport parameters such as longitudinal dispersion. In addition, breakthrough curve modeling demands accurate time of travel calculations if model results are to have any realistic meaning. However, accurate time of travel calculations are very difficult for long tracer tests in which sampling schedules are not consistent, or when there are major disruptions such as may occur when adverse weather conditions cause automatic sampling equipment to fail. Long and inconsistent sampling times may be accurately converted to decimal times of travel by converting the conventionally recorded Coordinated Universal Time for sampling date and time event to a baseline time standard. By converting to a baseline time standard, all recorded dates and times are linked to the established baseline standard so that each succeeding sampling date and time are correctly determined relative to the previous sampling date and time and to the injection date and time. [source]