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At least 325 records · Page 18Linked to original sources
PubMed1998

A fluorescence spectroscopic study on the binding of mRNA 5'-cap-analogs to human translation initiation factor eIF4E: a critical evaluation of the sources of error.

Equilibrium constants for the association of human protein translation initiation factor eIF4E with two mRNA 5'-cap analogs, namely 7-methylguanosine 5'-triphosphate and P1-(7-methylguanosine-5') P3-(guanosine-5') triphosphate, and with guanosine 5'-monophosphate have been redetermined by the fluorescence quenching method taking the inner filter effect of the cap-analog into account. It has been shown that neglecting the latter correction may lead to either underestimation or overestimation of the association constant obtained by applying the Eadie-Hofstee plot: the reasonably firm binding of 7-methylated cap-analogs becomes underestimated, while the weak binding of non-methylated nucleotides becomes overestimated.

Binding Sites↗
PubMed2000

Sources of error when tracking irrigation fluids during hysteroscopic procedures.

STUDY OBJECTIVE: To evaluate the ability of circulating nurses to estimate input and outgo of irrigating fluids used during hysteroscopic procedures in a hospital operating room. DESIGN: Simulation of intraoperative measurements (Canadian Task Force classification II-1). SETTING: Operating room. Intervention. Circulating nurses estimated fluid volumes under circumstances simulating actual conditions of hysteroscopic ablative or resection procedures. MEASUREMENTS AND MAIN RESULTS: Three-liter glycine irrigation bags were overfilled by an average of 2.8% (62-125 ml). Estimates of fluid remaining in partially emptied bags were in error by an average ranging from 4% to 50%/bag (largest error 10-55%, 157-401 ml). Estimates of fluid in kick buckets were in error by an average of 10% to 39% (largest error 22-66%, 232-903 ml). Visual estimates of fluid on the operating room floor were in error by an average of 56% to 67% (largest error 65-81%, 182-840 ml). Estimates of fluid in suction canisters were consistent among nurses. The accuracy of measurements for partially filled suction canisters primarily depended on the accuracy of canister calibration. Volume contained in cascaded suction canisters from an actual surgical procedure was grossly different from rated capacity. CONCLUSION: Accurate tracking of irrigation fluid during hysteroscopic procedures is difficult. Even with a mechanical measuring system, fluid lost on the floor can introduce sizable errors. Estimation errors can easily and quickly accumulate to clinically significant volumes. Use of an automated mechanical fluid-tracking system with devices to capture fluid lost from the surgical field is recommended.

Body Fluids↗
PubMed1998

Sources of error in intra-arterial pressure measurements across a stenosis.

OBJECTIVE: To investigate potential errors associated with different techniques of intra-arterial pressure measurement at angiography. MATERIALS AND METHODS: An experimental model of an arterial stenosis was developed. Experiments were performed to assess the relevance of catheter position, catheter direction and catheter type on the recorded intraluminal pressure. Transstenotic pressure gradients were recorded with and without angiographic catheters crossing the stenosis. RESULTS: At physiological flow rates angiographic catheter type does not influence the recorded pressure. At high flow rates through tight stenoses there is a significant catheter-related difference in recorded pressure adjacent to a stenosis. Downstream pressures may be altered by up to 85 mmHg when standard angiographic catheters are placed across a stenosis. CONCLUSION: The different techniques employed to measure pressure differences across a model stenosis may introduce significant errors up to 85 mmHg. Care must be taken when pressure measurements alone are used to interpret the clinical significance of a stenosis. In low flow conditions there may not be a detectable pressure gradient across a 95% stenosis.

Angiography↗
PubMed1999

Chromosomal aneuploidy in leukemic blast crisis: a potential source of error in interpretation of bone marrow engraftment analysis by VNTR amplification.

BACKGROUND: Polymerase chain reaction (PCR) amplification of polymorphic microsatellite or minisatellite DNA markers has proven to be a fast, sensitive, and specific technique in post-transplantation monitoring of bone marrow engraftment, as well as early detection of residual disease and relapse. Deletion or amplification of chromosomal segments carrying marker loci, as can occur in leukemia and other hematologic malignancies, may result in loss or increased dosage of marker alleles. Examination of these marker alleles by PCR therefore may give aberrant results, which might lead to misinterpretation of bone marrow transplantation (BMT) engraftment studies. METHODS AND RESULTS: We report a case of chronic myelogenous leukemia treated by BMT. PCR amplification of the minisatellite at the apoB locus on chromosome 2 was used to monitor the donor bone marrow engraftment. The patient experienced relapse in blast crisis with a near-haploid karyotype with loss of recipient-specific apoB allele causing an aberrant PCR result for bone marrow engraftment that mimicked full donor engraftment. CONCLUSIONS: Loss or gain of polymorphic DNA markers because of chromosomal losses or gains in some hematologic malignancies may affect the interpretation of bone marrow engraftment studies by PCR. When choosing polymorphic markers for such studies, it is important to avoid those that will be affected by expected chromosomal alteration, if possible. In addition, any abberant post-transplantation typing should prompt further investigation to rule out the possibility of chromosomal aberration. Review of all pertinent laboratory studies is important to avoid misinterpretation of results from a single test for engraftment analysis.

Adult↗
PubMed1999

Restriction fragment analysis as a source of error in detection of heteroplasmic mtDNA mutations.

The transition from A to G at nt 5656 (5656A-->G) in mitochondrial DNA has been suggested to be a pathogenic mutation and, furthermore, a heteroplasmic one. We found that the mutation was present in 14 out of 83 healthy controls from northern Finland and that 5656A-->G was exclusively associated with mtDNA haplogroup U. Interestingly, 5656A-->G appeared to be heteroplasmic in NheI digestion of PCR fragments that were amplified by using a mismatched oligonucleotide primer creating a digestion site in the presence of the mutant variant. However, we did not detect the wild type genome in clones from such a sample and subsequent experiments revealed that the apparent heteroplasmy was due to inhibition of NheI by NaCl. Our results suggest that 5656A-->G is a polymorphism and it may be highly characteristic for Finns. Furthermore, new heteroplasmic mutations identified by restriction fragment analysis should be adequately controlled for any false positive results that may be due to incomplete digestion.

DNA↗
PubMed2001

Locating, characterizing and minimizing sources of error for a paper case-based structured oral examination in a multi-campus clerkship.

OBJECTIVE: To determine consistency of assessment in a new paper case-based structured oral examination in a multi-community pediatrics clerkship, and to identify correctable problems in the administration of examination and assessment process. METHOD: Nine paper case-based oral examinations were audio-taped. From audio-tapes five community coordinators scored examiner behaviors and graded student performance. Correlations among examiner behaviors scores were examined. Graphs identified grading patterns of evaluators. The effect of exam-giving on evaluators was assessed by t-test. Reliability of grades was calculated and the effect of reducing assessment problems was modeled. RESULTS: Exam-givers differed most in their "teaching-guiding" behavior, and this negatively correlated with student grades. Exam reliability was lowered mainly by evaluator differences in leniency and grading pattern; less important was absence of standardization in cases. CONCLUSIONS: While grade reliability was low in early use of the paper case-based oral examination, modeling of plausible effects of training and monitoring for greater uniformity in administration of the examination and assigning scores suggests that more adequate reliabilities can be attained.

Clinical Clerkship↗
PubMed2000

Polymorphisms in the CAG repeat--a source of error in Huntington disease DNA testing.

Five of 400 patients (1.3%), referred for Huntington disease DNA testing, demonstrated a single allele on CAG alone, but two alleles when the CAG + CCG repeats were measured. The PCR assay failed to detect one allele in the CAG alone assay because of single-base silent polymorphisms in the penultimate or the last CAG repeat. The region around and within the CAG repeat sequence in the Huntington disease gene is a hot-spot for DNA polymorphisms, which can occur in up to 1% of subjects tested for Huntington disease. These polymorphisms may interfere with amplification by PCR, and so have the potential to produce a diagnostic error.

Adult↗