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Results for “Measurement Fidelity”

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PubMed2003

Determination of optimal conditions for analysis of p53 status in leukemic cells using functional analysis of separated alleles in yeast.

Tumor suppressor p53 is transcription factor that participates in control of many cellular functions. Somatic mutations of the p53 gene are frequently detected in human cancers. Several methods can be used for identification of p53 mutations, including FASAY - functional analysis of separated alleles in yeast. FASAY distinguishes yeast colonies expressing functional p53 protein from colonies producing a dysfunctional p53 protein simply on the basis of color. The validity of the method depends on a low background level. There are several sources of background as PCR-induced point mutations, low quality of RNA and alternative splicing of intron 9 affecting the p53 carboxy-terminus. In the present work we show that FASAY can be successfully used for analysis of mRNA isolated from blood samples that were collected and stored for 24 hours at 0 degrees C without undesired increase of background. We also measured fidelity of several commonly used DNA polymerases and determined the most suitable kinds of Pfu DNA polymerases for FASAY. Reaction conditions described in this report allow routine analysis of p53 status in leukemic cells using FASAY.

Alleles↗

PubMed1993

Long-term (3-month) effects of a new beta-blocker (nebivolol) on cardiac performance in dilated cardiomyopathy.

OBJECTIVES: This study examined the long-term (3-month) effects of nebivolol, a new beta-adrenergic blocking agent, on cardiac performance in patients with dilated cardiomyopathy. BACKGROUND: Several beta-blocking drugs have been reported to have a beneficial hemodynamic effect in patients with dilated cardiomyopathy, but few data obtained in a placebo-controlled randomized study have addressed the mechanisms of improvement. METHODS: Twenty-four patients with dilated idiopathic (n = 22) or ischemic (n = 2) cardiomyopathy (ejection fraction 0.15 to 0.40) in stable New York Heart Association functional class II or III were entered into a double-blind randomized trial of nebivolol, a new, potent, selective beta 1-antagonist. Exercise time, invasive hemodynamic data (12- and 24-h monitoring) and variables of left ventricular function were examined at baseline and after 3 months of orally administered nebivolol (1 to 5 mg/day, n = 11) or placebo (n = 13). RESULTS: Heart rate decreased (group mean 85 to 71 beats/min vs. 87 to 87 beats/min with placebo) and stroke volume increased significantly (group mean 43 to 55 ml vs. 42 to 43 ml) with nebivolol; decreases in systemic resistance, systemic arterial pressure, wedge pressure and pulmonary artery pressure were not significantly different from those with placebo. Similar hemodynamic results were obtained in the catheterization laboratory. Analysis of high fidelity measurements of left ventricular pressure showed a decrease in left ventricular end-diastolic pressure in the nebivolol group (group mean 21 to 15 vs. 24 to 20 mm Hg with placebo) but no change in the maximal rate of pressure development or in two variables of left ventricular relaxation (maximal negative rate of change of left ventricular pressure [dP/dtmax] and the time constant tau). Left ventricular mass decreased (p = 0.04). Despite a decrease in heart rate with nebivolol, there was a slight decrease in left ventricular end-diastolic volume (p = NS). End-systolic volume tended to decrease (p = 0.07) despite no reduction in end-systolic stress. The net result was a significant increase in ejection fraction (group mean 0.23 to 0.33 vs. 0.21 to 0.23 with placebo), presumably as a result of an increase in contractile performance. This effect was corroborated by an increase in a relatively load-independent variable of myocardial performance. CONCLUSIONS: Nebivolol improved stroke volume, ejection fraction and left ventricular end-diastolic pressure, not through a measurable reduction in afterload or a lusitropic effect, but by improving systolic contractile performance.

Adrenergic beta-Antagonists↗

PubMed1997

High-speed, random-access fluorescence microscopy: I. High-resolution optical recording with voltage-sensitive dyes and ion indicators.

The design and implementation of a high-speed, random-access, laser-scanning fluorescence microscope configured to record fast physiological signals from small neuronal structures with high spatiotemporal resolution is presented. The laser-scanning capability of this nonimaging microscope is provided by two orthogonal acousto-optic deflectors under computer control. Each scanning point can be randomly accessed and has a positioning time of 3-5 microseconds. Sampling time is also computer-controlled and can be varied to maximize the signal-to-noise ratio. Acquisition rates up to 200k samples/s at 16-bit digitizing resolution are possible. The spatial resolution of this instrument is determined by the minimal spot size at the level of the preparation (i.e., 2-7 microns). Scanning points are selected interactively from a reference image collected with differential interference contrast optics and a video camera. Frame rates up to 5 kHz are easily attainable. Intrinsic variations in laser light intensity and scanning spot brightness are overcome by an on-line signal-processing scheme. Representative records obtained with this instrument by using voltage-sensitive dyes and calcium indicators demonstrate the ability to make fast, high-fidelity measurements of membrane potential and intracellular calcium at high spatial resolution (2 microns) without any temporal averaging.

Animals↗

PubMed1996

Noninvasive doppler echocardiographic evaluation of left ventricular filling pressures in patients with cardiomyopathies: a simultaneous Doppler echocardiographic and cardiac catheterization study.

OBJECTIVES: The purpose of this study was to examine the relation of the mitral flow velocity curves to left ventricular filling pressures in patients with two different types of myocardial problems: hypertrophic cardiomyopathy and severe left ventricular systolic dysfunction. BACKGROUND: Previous studies have suggested that assessment of Doppler-derived mitral flow velocity curves can be used to predict left ventricular filling pressures in specific disease entities. However, it is unclear whether information derived from specific mitral flow velocity curves obtained from one disease entity can be valid in other disease states. METHODS: The study group consisted of 42 patients with left ventricular systolic dysfunction (group A) and 55 patients with hypertrophic cardiomyopathy (group B); both groups underwent simultaneous cardiac catheterization and were studied by Doppler echocardiography. High fidelity measures of left atrial and left ventricular pressures were obtained simultaneously with mitral flow velocity curves. RESULTS: There was a significant relation between the Doppler echocardiographic variables and mean left atrial pressure in group A patients. The left atrial pressure was directly related to the E/A ratio (r = 0.49, p = 0.004) and inversely related to the deceleration time (r = 0.73, p < 0.001). The sensitivity and specificity of the deceleration time, < 180 m/s, which indicated a mean left atrial pressure > or = 20 mm Hg, were both 100%. In group B patients, there was no significant relation between mean left atrial pressure and deceleration time. CONCLUSIONS: Doppler echocardiographic mitral flow velocity curves are useful in predicting and estimating left ventricular filling pressures in patients with left ventricular dysfunction. However, because of the complexity of the multiple interrelated factors that determine diastolic filling of the left ventricle, these flow velocity curves cannot be used in patients with other disease entities, such as hypertrophic cardiomyopathy. Future studies of different disease states are necessary to fully understand the role of Doppler echocardiography in the assessment of diastolic filling.

Adult↗

PubMed1998

Sympathetic blockade blunts hypercapnic pulmonary arterial vasoconstriction in newborn piglets.

OBJECTIVE: Hypercapnia has been implicated in the pathophysiology of pulmonary hypertensive disease in newborns. However, little has been done to determine how its vasoconstrictive actions are mediated. The purpose of this study is to define the role of the sympathetic nervous system in modulating the response of the newborn pulmonary circulation to hypercapnia. Specifically, we studied the effect of sympathetic blockade on mean and pulsatile pulmonary arterial hemodynamics in 48-h-old, intact, open-chest Yorkshire piglets during hypercapnic ventilation. METHODS: All animals were anesthetized and then instrumented for high fidelity measurement of pulmonary artery pressure (PAP), flow (PAF), aortic pressure and radius of the main pulmonary artery (Rmn). Baseline data were acquired in all animals. Control animals (n = 7) were subjected to 30 s intervals of hypercapnia (inspired CO2 fraction (FiCO2) = 0.20). Experimental animals (n = 7) were pre-treated with an intravenous bolus of the adrenergic blocking agent guanethidine (20 mg/kg) before being subjected to the hypercapnic stress. Characteristic impedance (Zo) and input mean impedance (Zm) were determined through application of a Fourier analysis of the PAP and PAF waveforms. The modulus of elasticity (Ey) was calculated from Zo and Rmn. Pulmonary vascular resistance (PVR) was calculated as (PAP - LAP/PAF). RESULTS: Control animals underwent significant increases in PVR (4860 +/- 341 dyne cm s(-5) versus 8090 +/- 387 dyne cm s(-5), P < 0.01) and Zm (7215 +/- 495 dyne cm s(-5) versus 10228 +/- 993 dyne cm s(-5), P < 0.01) when exposed to hypercapnia. Pre-treatment with guanethidine attenuated this response (PVR, 5552 +/- 368 dyne cm s(-5) versus 7105 +/- 611 dyne cm s(-5), P = 0.31 and ZM, 7922 +/- 446 dyne cm s(-5) versus 9745 +/- 600 dyne cm s(-5), P = 0.31). Characteristic impedance, modulus of elasticity and the radius of the main pulmonary artery were unchanged in both groups. CONCLUSIONS: These data indicate that vasoconstriction secondary to hypercapnia in the neonatal pulmonary arterial circulation occurs at the level of the distal arteriolar bed, rather than the more proximal pulmonary arteries. In addition, this response is partially modulated by the sympathetic nervous system and may therefore respond clinically to manipulation of sympathetic input to the pulmonary arterial circulation.

Animals↗

PubMed2000

A checklist for critiquing treatment fidelity studies.

My assignment was to critique and integrate the previous papers. I have organized this paper as follows: (1) a description and rationale for a checklist which can be used in judging the quality of a fidelity measure; (2) a critique of the Schaedle and Epstein paper; (4) a critique of the Lucca paper; and (4) a review of the paper by Bond, Evans, Salyers, Williams, and Kim.

Humans↗

PubMed2004

Deterministic quantum teleportation with atoms.

Teleportation of a quantum state encompasses the complete transfer of information from one particle to another. The complete specification of the quantum state of a system generally requires an infinite amount of information, even for simple two-level systems (qubits). Moreover, the principles of quantum mechanics dictate that any measurement on a system immediately alters its state, while yielding at most one bit of information. The transfer of a state from one system to another (by performing measurements on the first and operations on the second) might therefore appear impossible. However, it has been shown that the entangling properties of quantum mechanics, in combination with classical communication, allow quantum-state teleportation to be performed. Teleportation using pairs of entangled photons has been demonstrated, but such techniques are probabilistic, requiring post-selection of measured photons. Here, we report deterministic quantum-state teleportation between a pair of trapped calcium ions. Following closely the original proposal, we create a highly entangled pair of ions and perform a complete Bell-state measurement involving one ion from this pair and a third source ion. State reconstruction conditioned on this measurement is then performed on the other half of the entangled pair. The measured fidelity is 75%, demonstrating unequivocally the quantum nature of the process.

Journal Article↗

PubMed1991

Exonucleolytic proofreading of leading and lagging strand DNA replication errors.

We have asked whether exonucleolytic proofreading occurs during simian virus 40 origin-dependent, bidirectional DNA replication in extracts of human HeLa cells. In addition, we have compared the fidelity of leading and lagging strand DNA synthesis. In a fidelity assay that scores single-base substitution errors that revert a TGA codon in the lacZ alpha gene in an M13mp vector, providing an excess of a single dNTP substrate over the other three dNTP substrates in a replication reaction generates defined, strand-specific errors. Fidelity measurements with two vectors having the origin of replication on opposite sides of the opal codon demonstrate that error rates for two different A.dCTP and T.dGTP mispairs increase when deoxyguanosine monophosphate is added to replication reaction mixtures or when the concentration of deoxynucleoside triphosphates is increased. The data suggest that exonucleolytic proofreading occurs on both strands during bidirectional replication. Measurements using the two simian virus 40 origin-containing vectors suggest that base substitution error rates are similar for replication of the leading and lagging strands.

Antigens, Polyomavirus Transforming↗

PubMed1995

Replication error rates for G.dGTP, T.dGTP, and A.dGTP mispairs and evidence for differential proofreading by leading and lagging strand DNA replication complexes in human cells.

We have determined the fidelity of DNA replication by human cell extracts in reactions containing excess dGTP. Replication errors were scored using two M13 DNA substrates having the replication origin on opposite sides of the lacZ alpha-complementation gene. The data suggest that the average rates for replication errors resulting from G(template), T.dGTP, and A.dGTP mispairs are 25 x 10(-6), 12 x 10(-6), and 3 x 10(-6), respectively. The data also suggest that error rates for both the (+) and (-) strands differ by less than 2-fold when they are replicated either as the leading or lagging strand. This is in contrast to the 33- and 8-fold differences observed earlier for G.dTTP and C.dTTP mispairs on the (+) strand when replicated by the leading or lagging strand complex (Roberts, J. D., Izuta, S., Thomas, D. C., and Kunkel, T. A. (1994) J. Biol. Chem. 269, 1711-1717). Thus, the relative fidelity of the leading and lagging strand replication proteins varies with the mispair and sequence considered. Misincorporation of dGTP preferentially occurs at template positions where dGTP is the next correct nucleotide to be incorporated. This "next nucleotide" effect is characteristic of reduced exonucleolytic proofreading and suggests that these replication errors are normally proofread efficiently. Fidelity measurements performed in the absence or presence of dGMP, an inhibitor of proofreading exonuclease activity, suggest that the leading strand replication complex proofreads some mispairs more efficiently than does the lagging strand replication complex.

Base Sequence↗

PubMed1985

DNA polymerase alpha and models for proofreading.

Using a modified system to measure fidelity at an amber site in phi X174, we have employed DNA polymerase alpha to test different mechanisms for proofreading. DNA polymerase alpha does not exhibit the characteristics of "kinetic proofreading" seen with procaryotic polymerases. Polymerase alpha shows no evidence for a "next nucleotide" effect, and added deoxynucleoside monophosphates do not alter fidelity. Pyrophosphate, which increases error rates with a procaryotic polymerase, appears to weakly improve polymerase alpha fidelity. DNA polymerase alpha does exhibit a dramatic increase in error rate in the presence of a deoxycytidine thiotriphosphate (dCTP alpha S), but this enhanced mutagenesis also occurs under conditions where kinetic proofreading should be otherwise defeated. This particular effect with dCTP alpha S appears specific for DNA polymerase alpha and is not seen with the other polymerases tested.

Animals↗

PubMed2004

Contextual, optimal, and universal realization of the quantum cloning machine and of the NOT gate.

A simultaneous realization of the universal optimal quantum cloning machine and of the universal-NOT gate by a quantum injected optical parametric amplification, is reported. The two processes, forbidden in their exact form for fundamental quantum limitations, are found universal and optimal, and the measured fidelity F<1 is found close to the limit values evaluated by quantum theory. This work may enlighten the yet little explored interconnections of fundamental axiomatic properties within the deep structure of quantum mechanics.

Journal Article↗

PubMed2006

Calibration of a wide-field frequency-domain fluorescence lifetime microscopy system using light emitting diodes as light sources.

High brightness light emitting diodes are an inexpensive and versatile light source for wide-field frequency-domain fluorescence lifetime imaging microscopy. In this paper a full calibration of an LED based fluorescence lifetime imaging microscopy system is presented for the first time. A radio-frequency generator was used for simultaneous modulation of light emitting diode (LED) intensity and the gain of an intensified charge coupled device (CCD) camera. A homodyne detection scheme was employed to measure the demodulation and phase shift of the emitted fluorescence, from which phase and modulation lifetimes were determined at each image pixel. The system was characterized both in terms of its sensitivity to measure short lifetimes (500 ps to 4 ns), and its capability to distinguish image features with small lifetime differences. Calibration measurements were performed in quenched solutions containing Rhodamine 6G dye and the results compared to several independent measurements performed with other measurement methodologies, including time correlated single photon counting, time gated detection, and acousto optical modulator (AOM) based modulation of excitation sources. Results are presented from measurements and simulations. The effects of limited signal-to-noise ratios, baseline drifts and calibration errors are discussed in detail. The implications of limited modulation bandwidth of high brightness, large area LED devices ( approximately 40 MHz for devices used here) are presented. The results show that phase lifetime measurements are robust down to sub ns levels, whereas modulation lifetimes are prone to errors even at large signal-to-noise ratios. Strategies for optimizing measurement fidelity are discussed. Application of the fluorescence lifetime imaging microscopy system is illustrated with examples from studies of molecular mixing in microfluidic devices and targeted drug delivery research.

Calibration↗

PubMedDate not supplied

Expression profile of ovarian tumors: distinct signature of Sertoli-Leydig cell tumor.

Epithelial ovarian tumors are the most common subtype of ovarian cancer. In this study, we reveal distinct expression signatures of previously uncharacterized ovarian carcinoma subtypes, including endometrioid component of mixed ovarian tumor and Sertoli-Leydig tumor. Both subtypes were compared to the most common and well-characterized ovarian epithelial carcinoma of the serous type. These comparisons were performed by complementaryDNA (cDNA) microarrays allowing high-fidelity measurements of the expression levels of 39,360 human individual cDNA species representing both known and unknown human genes. Functional analysis of differentially expressed genes in Sertoli-Leydig tumor revealed an upregulation in sonic hedgehog pathway, deregulation of several metabolic pathways especially in amino acid metabolism and overexpression of genes associated with protein synthesis, including ribosomal genes.

Female↗

PubMed2006

Dual-probe laser interferometer for structural health monitoring.

In this note we present the development of a dual-probe laser interferometer that uses the filtering properties of a polarized beamsplitter to enable two independent (uncoupled) detection probes. The robustness of this system is demonstrated by making broadband, noncontact, high fidelity measurements of Lamb waves in an aluminum plate.

Journal Article↗

PubMed1983

Pressure-derived indices of left ventricular isovolumic relaxation in patients with hypertrophic cardiomyopathy.

High fidelity measurements of left ventricular pressure were made at increasing pacing rates in 21 patients with hypertrophic cardiomyopathy and a control group of 11 patients investigated for chest pain who proved to have normal hearts. In both groups the fall in pressure during isovolumic relaxation from the point of min dp/dt approximated closely to a monoexponential, and could be described by a time constant and asymptote. The time constant shortened and the asymptote increased as heart rate rose in both groups. The time constant was longer and min dp/dt less in the cardiomyopathy group than controls at all heart rates. In the cardiomyopathy patients min dp/dt, but not the time constant, was related to systolic pressure. During pacing, eight cardiomyopathy patients developed metabolic evidence of myocardial ischaemia, but indices of relaxation did not differ between these eight and the other 13 either at basal heart rate or the highest pacing rate. In 10 cardiomyopathy patients measurements were repeated at comparable pacing rates after propranolol (0.2 mg/kg). Left ventricular end-diastolic pressure and indices of contractility decreased after the drug, but the time constant did not change. Eight patients received verapamil (20 mg) after which there were substantial reductions in systolic pressure and contractility. Min dp/dt decreased in proportion to systolic pressure, but the time constant was unchanged. At the highest pacing rate before drug administration three patients had abnormal lactate extraction which was corrected by either propranolol (one patient) or verapamil (two patients). Despite abolition of metabolic evidence of ischaemia, relaxation did not improve. It is concluded that abnormal isovolumic relaxation is common in patients with hypertrophic cardiomyopathy, but its severity correlates poorly with other features of the disease. Abnormal relaxation is not the result of ischaemia, and pressure derived indices of relaxation do not improve after the administration of propranolol or verapamil.

Adult↗

PubMed1977

Physiologic determinants of left ventricular strength-interval curve of the dog.

Strength-interval curves, relating an index of the contractile vigor of premature beats to their coupling intervals, were elicited in anesthetized, open-chest dogs prepared for atrial or ventricular pacing and the high-fidelity measurement of left ventricular pressure. During inotropic interventions, changes of the curves were evaluated in terms of the parameters (slopes and intercepts) of their straight lines of best fit. These parameters were altered by isoproterenol, propranolol, and heart rate, and were correlated closely with paired values of isovolumic Vmax (of driven beats). The strength-interval curves were reproducible and were not affected by large changes of venous return or arterial blood pressure. These results provide a basis for the use of strength-interval curves for the evaluation of ventricular contractile state, using fluid-filled catheters for the measurement of left ventricular pressure.

Animals↗

PubMed1976

Ventricular pressure-volume curve indices change with end-diastolic pressure.

Many indices have been proposed to describee the diastolic pressure-volume curve mathematically and permit quantification of the elastic properties of the myocardium itself in hopes that changes in the muscle caused by disease would b.e reflected in the diastolic pressure-volume curve. To date, none of the proposed indices has been shown convincingly to discriminate one group of patients from another. While this situation in part arises from the relatively large amount of noise introduced by the technical difficulties of measuring synchronous pressures and volumes during diastole in man, ther is a more fundamental difficulty. In practice, one can measure only a short segment of the entire pressure-volume curve, and the values of all diastolic pressure-volume curve parameters investigated change significantly when one uses different segments of the same pressure-volume curve to compute them. These results were derived from relatively noise-free pressure-volume curves obtained by filling nine excised dog left ventricles at a known rate and monitoring pressure-volume curve used to compute the parameter. Merely increasing measurement fidelity will not resolve this problem, because none of these parameters accurately characterizes the entire diastolic pressure-volume curbe from a segment like that which one can reasonably expect to obtain from humans.

Animals↗

PubMed2003

Ionworks HT: a new high-throughput electrophysiology measurement platform.

To address the throughput restrictions of classical patch clamp electrophysiology, Essen Instruments has developed a plate-based electrophysiology measurement platform. The instrument is an integrated platform that consists of computer-controlled fluid handling, recording electronics, and processing tools capable of voltage clamp whole-cell recordings from thousands of individual cells per day. To establish a recording, the system uses a planar, multiwell substrate (a PatchPlate). The system effectively positions 1 cell into a hole separating 2 fluid compartments in each well of the substrate. Voltage control and current recordings from the cell membrane are made subsequent to gaining access to the cell interior by applying a permeabilizing agent to the intracellular side. Based on the multiwell design of the PatchPlate, voltage clamp recordings of up to 384 individual cells can be made in minutes and are comparable to measurements made using traditional electrophysiology techniques. An integrated pipetting system allows for up to 2 additions of modulation agents. Typical throughput, measurement fidelity, stability, and comparative pharmacology of a recombinant voltage-dependent sodium channel (hNav1.3) and a voltage-gated potassium channel (hKv1.5) exogenously expressed in CHO cells are presented. The IonWorks HT device can be used in biophysical and pharmacological profiling of ion channels in an environment compatible with high-capacity screening.

Animals↗