Biomedical subjects
Publications and source records attributed to B Gralak.
We consider a dielectric photonic crystal made of cylindrical holes in a high index matrix. We show that a given finite size photonic crystal can mimic a homogeneous material whose permittivity and permeability are negative. We pay attention to the limitation of the homogeneous medium model and the vital role of the truncation of the crystal.
OBJECTIVE: The aim of this study was to investigate the effect of time on pharmacokinetic (PK) parameters of mycophenolic acid (MPA) in the early post-transplant period in kidney recipients. MPA is the active metabolite of mycophenolate mofetil (MMF), which was introduced into clinical practice ten years ago. METHOD: Mycophenolate mofetil was co-administered with cyclosporin (CsA) in a subgroup of 23 patients and with tacrolimus (Tac) in a subgroup of 10 patients. MPA plasma concentration profiles were measured by a validated high performance liquid chromatography method 1 week, 2 and 3 months after transplantation. RESULTS: Despite a comparable MMF dose, a large inter-patient variability in both MPA area under the curve (AUC) from 0 to 12 h (range 10.03-135.4 microg h/mL) and in predose concentrations (0.31-6.09 microg/mL) was observed. Patients with AUC > 35 microg h/mL showed better (P < 0.1) renal function than patients with AUC < 20 microg h/mL (mean creatinine concentration 1.48 +/- 0.12 vs. 3.35 +/- 0.4 mg/dL respectively). The total MPA trough and AUC did not correlate with biochemical parameters: leucocyte cell count and haematocrit. A higher trough level of the metabolite MPA glucuronide (MPAG) in the 1 week after transplantation was found when compared with the 3-month level (mean 150.1 +/- 146.7; range 17.1 to 560 vs. 75.8 +/- 40.0; range 27.3 to 174.2 microg/mL). The concentration of MPA, and MPA AUC values were significantly lower in patients receiving MMF and CsA than those receiving MMF and Tac during all three periods studied (P < 0.02). The influence of C(0) and MPA AUC values on the risk of graft rejection was investigated using receiver operating characteristic (ROC) curve analysis. The area under the ROC curve for AUC was 0.847, whereas that of C(0) was 0.632. CONCLUSIONS: The MPA AUC(0-12h) appeared to be the more effective PK parameter for predicting acute rejection. We recommend that routine MPA and MPAG therapeutic drug level monitoring should be an important part of MMF therapy.
A comprehensive male linkage map was generated by adding 359 new, informative microsatellites to the International Equine Gene Map half-sibling reference families and by combining genotype data from three independent mapping resources: a full sibling family created at the Animal Health Trust in Newmarket, United Kingdom, eight half-sibling families from Sweden and two half-sibling families from the University of California, Davis. Because the combined data were derived primarily from half-sibling families, only autosomal markers were analyzed. The map was constructed from a total of 766 markers distributed on the 31 equine chromosomes. It has a higher marker density than that of previously reported maps, with 626 markers linearly ordered and 140 other markers assigned to a chromosomal region. Fifty-nine markers (7%) failed to meet the criteria for statistical evidence of linkage and remain unassigned. The map spans 3,740 cM with an average distance of 6.3 cM between markers. Fifty-five percent of the intervals are < or = 5 cM and only 3% > or = 20 cM. The present map demonstrates the cohesiveness of the different data sets and provides a single resource for genome scan analyses and integration with the radiation hybrid map.
A low-density, male-based linkage map was constructed as one of the objectives of the International Equine Gene Mapping Workshop. Here we report the second generation map based on testing 503 half-sibling offspring from 13 sire families for 344 informative markers using the CRIMAP program. The multipoint linkage analysis localized 310 markers (90%) with 257 markers being linearly ordered. The map included 34 linkage groups representing all 31 autosomes and spanning 2262 cM with an average interval between loci of 10.1 cM. This map is a milestone in that it is the first map with linkage groups assigned to each of the 31 automosomes and a single linkage group to all but three chromosomes.
We describe methods of investigating the behavior of photonic crystals. Our approach establishes a link between the dispersion relation of the Bloch modes for an infinite crystal (which describes the intrinsic properties of the photonic crystal in the absence of an incident field) and the diffraction problem of a grating (finite photonic crystal) illuminated by an incident field. We point out the relationship between the translation operator of the first problem and the transfer matrix of the second. The eigenvalues of the transfer matrix contain information about the dispersion relation. This approach enables us to answer questions such as When does ultrarefraction occur? Can the photonic crystal simulate a homogeneous and isotropic material with low effective index? This approach also enables us to determine suitable parameters to obtain ultrarefractive or negative refraction properties and to design optical devices such as highly dispersive microprisms and ultrarefractive microlenses. Rigorous computations add a quantitative aspect and demonstrate the relevance of our approach.
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Often the clinical researcher is confronted with the question of how accurate a particular laboratory test is to identify disease. To confirm the ability of pharmacokinetic (PK) parameters to discriminate between patients with or without acute rejection after kidney transplantation, an analysis of receiver operating characteristic (ROC) curves was performed in 51 adult patients, among whom nearly 50% experienced biopsy-proven acute rejection episodes during the first 90 days posttransplant. All patients received cyclosporine or tacrolimus, prednisone, and mycophenolate mofetil (MMF). The following PK variables were determined for mycophenolic acid, an active metabolite of MMF: predose (C(0)), maximum concentration (C(max)), and area under the concentration-time curve (AUC(0-12h)). ROC plots of sensitivity versus 1-specificity were generated to determine whether a particular PK parameter could discriminate renal transplant recipients with an acute rejection from those who experienced no rejection. Area under the ROC curves and the 95% confidence interval limits were calculated using the method of Hanley and McNeil. The C(0) and C(max) were less predictive values for acute rejection than AUC(0-12h). The AUC parameter appeared the most effective to discriminate an acute rejection episode during MMF therapy. This study indicated the utility of ROC curve analysis to select PK parameters to predict acute rejection episodes.