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At least 1,243 records · Page 69Linked to original sources
PubMed1996

Pharmacokinetics of propofol after a single dose in children aged 1-3 years with minor burns. Comparison of three data analysis approaches.

BACKGROUND: No complete pharmacokinetic profile of propofol is yet available in children younger than 3 yr, whereas clinical studies have demonstrated that both induction and maintenance doses of propofol are increased with respect to body weight in this age group compared to older children and adults. This study was therefore undertaken to determine the pharmacokinetics of propofol after administration of a single dose in aged children 1-3 yr requiring anesthesia for dressing change. METHODS: This study was performed in 12 children admitted to the burn unit and in whom burn surface area was less than or equal to 12% of total body surface area. Exclusion criteria were: unstable hemodynamic condition, inappropriate fluid loading, associated pulmonary injury, or burn injury older than 2 days. Propofol (4 mg.kg(-1))plus fentanyl (2.5 microg.kg(-1)) was administered while the children were bathed and the burn area cleaned during which the children breathed spontaneously a mixture of oxygen and nitrous oxide (50:50). Venous blood samples of 300 microl were obtained at 5, 15, 30, 60, 90, and 120 min, and 3, 4, 8, and 12 thereafter injection; an earlier sample was obtained from 8 of 12 children. The blood concentration curves obtained for individual children were analyzed by three different methods: noncompartmental analysis, mixed effects population model, and standard two-stage analysis. RESULTS: Using noncompartmental analysis, total clearance of propofol (+/-SD) was 0.053+/-0.013l.kg(-1).min(-1), volume of distribution at steady state9.5 +/- 3.7l.kg(-1),and residence time 188 +/- 85 min. Propofol pharmacokinetics were best described by a weight-proportional three-compartmental model in both population and two-stage analysis. Estimated and derived pharmacokinetic parameters were similar using these two pharmacokinetic approaches. Results of population versus two-stage analysis are as follow: systemic clearance 0.049 versus 0.048 l.kg(-).min(-1), volume of central compartment 1.03 versus 0.95 l.kg(-1), volume of steady state 8.09 versus 8.17 l.kg(-1). CONCLUSIONS: The volume of the central compartment and the systemic clearance were both greater than all values reported in older children and adults. This is consistent with the increased propofol requirements for both induction and maintenance of anesthesia in children 1-3 yr. (Key words: Anesthesia: pediatric. Pharmacokinetics: propofol.)

Age Factors↗
PubMed2006

Modeling longitudinal performances on the United States Medical Licensing Examination and the impact of sociodemographic covariates: an application of survival data analysis.

BACKGROUND: This study models time to passing United States Medical Licensing Examination (USMLE) for the computer-based testing (CBT) start-up cohort using the Cox Proportional Hazards Model. METHOD: The number of days it took to pass Step 3 was treated as the dependent variable in the model. Covariates were: (1) gender; (2) native language (English or other); (3) medical school location (United States or other); and (4) citizenship (United States or other). RESULTS: Examinees were .59 times as likely to pass USMLE if they were trained abroad. Additionally, examinees who reported having English as their primary language and U.S. citizenship were more likely to ultimately pass USMLE. Finally, though gender was also associated with passing USMLE, its practical significance was very small. CONCLUSION: Cox regression provides a useful tool for modeling performances in a continuous delivery model. Findings suggest that passing the USMLE sequence tends to be associated with native English-speaking USMGs who also hold U.S. citizenship.

Female↗
PubMed1996

Fluorodopa positron emission tomography with an inhibitor of catechol-O-methyltransferase: effect of the plasma 3-O-methyldopa fraction on data analysis.

Flurodopa (FDOPA) is an analogue of L-di-hydroxyphenylalanine (L-dopa) used to assess the nigrostriatal dopamine system in vivo with positron emission tomography (PET). However, FDOPA/PET quantitation is complicated by the presence of the 3-O-methyl-FDOPA (3OMFD) fraction in brain and plasma. Pretreatment with entacapone (OR-611), a peripheral catechol O-methyl-transferase (COMT) inhibitor, greatly reduces the plasma 3OMFD fraction and provides an ideal situation to evaluate the contribution of the plasma 3OMFD fraction in several kinetic models of FDOPA uptake. We performed FDOPA/PET with and without the OR-611 preadministration in six Parkinson's disease (PD) patients. We measured the time-course of the plasma FDOPA and 3OMFD fractions using high-pressure liquid chromatography (HPLC). We calculated striato-occipital ratios (SOR), and estimated the striatal FDOPA uptake rate constant graphically using the plasma FDOPA and occipital tissue time activity curves (KiFD and KiOCC, respectively). We also estimated striatal dopa decarboxylase (DDC) activity (k3D) using a model incorporating independent measurements of 3OMFD transport kinetic rate constants. With the preadministration of OR-611, the pharmacological efficiency in plasma was prolonged significantly (21.1-37.7%; p < 0.01). We also observed significant mean elevations in SOR and KiOCC by 21.8 and 53.5%, respectively (p < 0.05). KiFD and k3D did not show significant change. We conclude that OR-611 prolongs the circulation time of FDOPA in the plasma but does not alter rate constants for striatal FDOPA uptake or decarboxylation.

Adult↗
PubMed2001

Modeling of nonlinear Lévy processes by data analysis.

The paper presents a method to analyze time series of nonlinear Lévy processes. The Lévy stability index as well as the nonlinear deterministic and stochastic parts of the dynamics together with their uncertainties can be calculated numerically. As last step of the analysis the membership of the investigated system to the regarded class of dynamical systems is validated. For demonstration the algorithm is applied to artificially created time series with different Lévy indices.

Journal Article↗
PubMed1992

Crystallization and preliminary data analysis of Flock House virus.

Flock House virus, purified from infected cultured Drosophila cells, crystallizes into three different forms under identical growth conditions. Two crystal forms grow in the trigonal space group R3, both with equivalent cell constants a = 323.6 A, alpha = 61.7 degrees. The difference between the two trigonal crystal forms is 1.1 degrees in the orientation of the virus particle as determined from the rotation function. Early crystal setups grew in one form, while recent crystals grew in the other form. The third space group, which accounts for 5% of the observed crystals and grows with both trigonal forms, is orthorhombic I222 with cell parameters a = 416.7, b = 332.1, c = 351.2 A. The trigonal crystal forms contain one virion per unit cell and the orthorhombic form contains two particles per cell. All three crystal forms diffract X-rays to 2.8 A resolution.

Animals↗
PubMed2001

Low-resolution data analysis for low-density lipoprotein particle.

The knowledge of the molecular structure of LDL, a large lipoprotein complex, is of great interest for medical investigations. Currently available LDL crystals do not diffract to high resolution and do not allow the application of standard crystallographic techniques. Additional difficulties arise because of a very dense crystal packing and the presence of several components with quite different mean densities. Several ab initio phasing methods previously reported by the authors have been successfully applied to find a crystallographic image of LDL at a resolution of 27 A. The most promising results have been obtained using direct phasing with a connectivity analysis of the electron-density maps. The current image makes it possible to discern a single particle covered by a layer of relatively high density that is asymmetrically distributed on the particle surface. It shows a partition of high and low densities inside the particle and, in particular, strips of varying density in the lipid core.

Crystallography, X-Ray↗
PubMed2002

The use of construct variation and diffraction data analysis in the crystallization of the TRAF domain of human tumor necrosis factor receptor associated factor 6.

Obtaining soluble proteins and diffraction-quality crystals often represents the bottleneck in macromolecular crystallography. Here, it is shown that construct variation can be an efficient strategy in expressing soluble proteins from bacteria and that clues from poor crystals may be used to improve crystal packing and to optimize crystal quality.

Binding Sites↗
PubMed2001

Structural properties of Y1-xYbxNi2B2C synthesized at high pressure: EXAFS data analysis.

Local structure of Y(1-x)Yb(x)Ni2B2C series synthesized at high pressure 8 GPa has been studied using EXAFS. Measurements were performed at the Ni K-edge in temperature range 5-300 K. The results show that the Debye-Waller factor for Ni-Ni bond in the parent YNi2B2C compound is characterized by the Einstein temperature O(E) = 350 K, while a minimum value O(E) = 300 K is reached for the compound with = 0.025, which has the highest critical temperature T(c) = 12.5K of the superconductive transition. This correlates with the further suppressing of superconductivity and with the appearance of the local magnetic moments in the investigated Y(1-x)Yb(x)Ni2B2C series for x > or = 0.05 compounds. Observed changes in the local electronic and the local crystal structure of this system as a function of Yb concentration and of temperature were explained in the frame of the band filling effect.

Journal Article↗