1,721,258 research outputs found
USE OF ENDOGENOUS BIOMARKERS TO ACHIEVE PERSONALISED IMMUNOSUPPRESSION IN TRANSPLANT RECIPIENTS
No full textUSE OF ENDOGENOUS BIOMARKERS TO ACHIEVE PERSONALISED IMMUNOSUPPRESSION IN TRANSPLANT RECIPIENTS
No full text
The MEGX test: A tool for the real-time assessment of hepatic function
No full textThe dynamic liver function test based on the hepatic conversion of lidocaine to monoethylglycinexylidide (MEGX) can complement established static liver function tests if prognostic information is of particular interest. Because of its ease of use and rapid turnaround, the MEGX test has found widespread application for real-time assessment of hepatic function in transplantation, critical care medicine, and various experimental models. Lidocaine is metabolized primarily by the liver cytochrome P450 system through sequential oxidative N-dealkylation, the major initial metabolite in humans being MEGX. Because of the relatively high extraction ratio of lidocaine, this liver function test depends not only on hepatic metabolic capacity but also on hepatic blood flow. For the determination of MEGX in serum, an immunoassay based on the fluorescence polarization immunoassay technique high-performance liquid chromatography and gas liquid chromatography methods have been described. Whereas high-performance liquid chromatography and gas liquid chromatography are specific for MEGX, the fluorescence polarization immunoassay also cross-reacts with 3-OH-MEGX. Although this is not a problem in humans, some species, such as the rat, produce significant amounts of this metabolite. The findings of most studies published so far suggest that the MEGX test is a useful tool that can improve our decision-making process with respect to the selection of transplant candidates. Patients with a MEGX 15- or 30-minute test value g/L have a particularly poor I-year survival rate. Serial monitoring of liver graft recipients early after transplantation with the MEGX test may initially alert the clinician to a major change in liver function; if used with other tests, such as serum hyaluronic acid concentrations, it may become more discriminatory. In critically ill patients, several studies have shown that an initially rapid decrease in MEGX test values is associated with an enhanced risk for the development of multiple organ dysfunction syndrome and a poor outcome. Further, this decrease appears to be associated with an enhanced systemic inflammatory response. The MEGX test has potential for investigating the pathogenesis of multiple organ dysfunction syndrome with regard to early hepatic functional impairment in critically ill patients after polytrauma or sepsis
Two-hour cyclosporine concentration determination: An appropriate tool to monitor neoral therapy?
No full textCyclosporine is a critical dose drug for which individualisation by therapeutic drug monitoring is indisputable. Current evidence suggests that a single concentration (C-2) taken two hours after cyclosporine administration with the microemulsion formulation better predicts exposure and events than the trough concentration (C-0), which is routinely used for adjusting the dosage of this drug. Studies have shown that the greatest calcineurin inhibition and the maximum inhibition of IL-2 production occur in the first 1 to 2 hours after dosing. These findings support the concept that the C-2 level better reflects immunosuppressive efficacy than the trough concentration. Preliminary data from an outcome study in liver transplant recipients have shown that the incidence of biopsy proven moderate to severe acute rejection was significantly lower in patients managed by C-2 monitoring compared with those monitored by C-0. The critical importance of achieving adequate cyclosporine exposure during the first 3 to 5 posttransplant days to prevent acute rejection has been documented in prospective studies with de novo renal and liver transplant recipients. Conversion of maintenance liver and heart transplant patients to C-2 monitoring resulted in an amelioration of renal function. Time-dependent target values have been proposed for liver and renal transplant recipients. These require further prospective validation. For routine monitoring of C-2 levels on-site validated dilution guidelines are necessary for most of the available immunoassays. C-2 monitoring necessitates further organizational requirements which may be judged differently between transplant centers. In particular during the early posttransplant period C-2 monitoring is a promising new option to make immunosuppressive therapy with the microemulsion formulation of cyclosporine safer and more efficient
Total genotyping of thiopurine methyltransferase with the LightCycler (TM): examples for anchor sharing, three colour multiplexing and thermodynamic model based probe design.
No full textGenotyping of eight thiopurine methyltransferase mutations: Three-color multiplexing, "two-color/shared" anchor, and fluorescence-quenching hybridization probe assays based on thermodynamic nearest-neighbor probe design
No full textBackground: The inherited deficiency of thiopurine methyltransferase (TPMT) leads to severe myelosuppression in homozygous patients treated with thiopurine derivatives. One in 300 Caucasians has a homozygous TPMT deficiency with no measurable enzyme activity. To date, eight single-point mutations have been characterized; one group (TPMT 3) accounts for 75% of these. Methods: We used four LightCycler(TM) capillaries to investigate all eight mutations. The three mutations on exon 10 were detected in one capillary with a single "shared" anchor labeled 5' with Cy5.5 and 3' with fluorescein. A wild-type-compatible 3'-fluorescein-labeled probe 5' adjacent to the anchor covered the TPMT 7 mutation, and a 5'-LC-RED640-labeled probe 3' adjacent to the anchor covered the TPMT 3C mutation. For TPMT 4, the forward amplification primer was internally labeled with a fluorescence quencher [6-carboxytetramethylrhodamine (TAMRA), and a 3'-fluorescein-labeled antisense wild-type-compatible probe was placed at the mutation. For TPMT 2 and TPMT 3D, Located on exon 5, a shared anchor approach was chosen. TPMT 3B and TPMT 6 were detected in multiplex technique and TPMT 5 in conventional manner. Anchors and probes were designed using a thermodynamic nearest-neighbor model. Results: All mutations were detected using four capillaries with one amplification protocol in 40 min. The concentrations of the shared anchors had to be decreased to reduce their intrinsic fluorescence resonance energy transfer signals. The quenching approach using TAMRA produced a very reproducible upside-down-shaped melting curve in channel 1 of the LightCycler. Deviations from wild type were easily detected because the smallest melting point shift for any possible mutation under the core of the probes was 1.5 degreesC. Conclusions: This total TPMT genotyping approach shows that it is possible to use double site-labeled anchor oligonucleotides, that channel 1 of the LightCycler can be used as detection channel for mutations using a quenching design, and that the designed probes enable detection of wild types with 100% likelihood. (C) 2000 American Association for Clinical Chemistry
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