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PubMed1995

The comet moment as a measure of DNA damage in the comet assay.

The development of rapid assays of radiation-induced DNA damage requires the definition of reliable parameters for the evaluation of dose-response relationships to compare with cellular endpoints. We have used the single-cell gel electrophoresis (SCGE) or 'comet' assay to measure DNA damage in individual cells after irradiation. Both the alkaline and neutral protocols were used. In both cases, DNA was stained with ethidium bromide and viewed using a fluorescence microscope at 516-560 nm. Images of comets were stored as 512 x 512 pixel images using OPTIMAS, an image analysis software package. Using this software we tested various parameters for measuring DNA damage. We have developed a method of analysis that rigorously conforms to the mathematical definition of the moment of inertia of a plane figure. This parameter does not require the identification of separate head and tail regions, but rather calculates a moment of the whole comet image. We have termed this parameter 'comet moment'. This method is simple to calculate and can be performed using most image analysis software packages that support macro facilities. In experiments on CHO-K1 cells, tail length was found to increase linearly with dose, but plateaued at higher doses. Comet moment also increased linearly with dose, but over a larger dose range than tail length and had no tendency to plateau.

Animals↗
PubMed1998

Improved risk stratification in unstable angina: identification of patients at low risk for in-hospital cardiac events by admission echocardiography.

BACKGROUND: Current protocols for risk stratification of patients with acute chest pain syndromes rely on clinical parameters and are oriented toward identification of patients at high risk for adverse cardiac events; however, this paradigm for risk stratification does not adequately address the observation that adverse cardiac events are relatively uncommon in this population. In an era of cost containment, consideration also should be given to identification of patients at low risk for adverse cardiac events, who may be safely discharged without expensive inpatient hospitalization. HYPOTHESIS: The purpose of this study was to develop echocardiographic predictors that identify unstable angina patients at low risk for adverse cardiac events and that discriminate between low- and high-risk patients. METHODS: The predictive accuracy of retrospectively determined echocardiographic predictors were compared in a population-based sample of 66 consecutive unstable angina patients undergoing echocardiography within 24 h of admission. RESULTS: Echocardiographic predictors of adverse events included wall motion score index > or = 0.2, ejection fraction < or = 40%, and mitral regurgitation severity > 2. One or more echocardiographic predictors of adverse events were present in 32 patients (48%). A composite echocardiographic predictor of adverse events was specific, had a high positive predictive value for the identification of high-risk patients, and discriminated between unstable angina patients at high and low risk for adverse cardiac events. CONCLUSION: Echocardiographic predictors of adverse events are specific and discriminate between unstable angina patients at high and low risk for adverse cardiac events.

Acute Disease↗
PubMed1995

Influence of flow pattern on the parameter estimates of a simple breathing mechanics model.

The first-order model of breathing mechanics is widely used in clinical practice to assess the viscoelastic properties of the respiratory system. Although simple, this model takes the predominant features of the pressure-flow relationship into account but gives highly systematic residuals between measured and model-predicted variables. To achieve a better fit of the entire data set, an approach hypothesizing deterministic time-variations of model parameters, summarized by information-weighted histograms was recently proposed by Bates and Lauzon. The present study uses flow and pressure data measured in intensive care patients to evaluate the real potential of this approach in clinical practice. Information-weighted histograms of the model parameters, estimated by an on-line identification algorithm, were first constructed by taking into account the parameter percentage standard deviations. Then, the influence of the respiratory flow pattern on the calculated histograms was evaluated by the Kolmogorov-Smirnov statistical test. The results show that the method gives good reproducibility under stable experimental conditions. In addition, for a given airflow waveform, an increase in respiratory frequency shifts the histograms representing time-varying viscous properties strongly versus lower values, whereas it shifts the histograms representing time-varying elastic properties slightly versus higher values. On the other hand, the same histograms were highly dependent on the airflow waveform, especially for the viscous properties. Even in a limited experimental work, in all the conditions considered, the method provides results which agree well with the physiological knowledge of nonlinear and multicompartment behavior of respiratory mechanics.

Algorithms↗
PubMed1995

Simple hyperaemia test as a screening method in the postoperative surveillance of infrainguinal in situ vein bypasses.

OBJECTIVES: To develop a simple protocol for ultrasound Duplex surveillance of infrainguinal vein bypasses. DESIGN: The value of three Doppler waveform parameters, obtained from a single point of the bypass, for identification of stenoses was studied in 91 in situ vein bypasses. Midgraft peak systolic velocity (PSV), pulsatility index (PI) and ratio of hyperaemic and resting time-average mean velocities (TAMV), (TAMV ratio = TAMVhyperaemia/TAMVrest) were correlated with the presence and severity of stenoses as assessed by conventional Duplex scanning and ankle-brachial index (ABI) measurements. The optimal value of the waveform parameters for discrimination between bypasses with and without evidence of stenoses was determined by receiver operating characteristics (ROC) analysis. MAIN RESULTS: Complete Duplex scanning of the entire graft revealed an increase in the peak systolic velocity by a factor 2.5 indicative of significant stenoses in 24 (26%) patients. A PSV below 55 cm/s was a poor indicator of stenoses (sensitivity 46%, specificity 76%) and PI < or = 3.8 only allowed suboptimal discrimination between normal and stenotic bypasses (sensitivity 63%, specificity 75%). The hyperaemic response assessed by TAMV ratio proved the best parameter for identification of graft stenoses. A TAMV ratio of 2.0 or less correctly identified 21 of the 24 lesions (sensitivity 88%, specificity 75%) and none of the three bypasses with evidence of stenoses and TAMV ratios exceeding 2.0 failed during follow-up. CONCLUSIONS: Single point waveform analysis of vein bypass velocity profile at rest and during reactive hyperaemia is a simple screening method providing diagnostic and prognostic information which may be of value in the postoperative surveillance of infrainguinal vein bypasses.

Aged↗
PubMed2005

Magnetic resonance stress tagging in ischemic heart disease.

High-dose dobutamine magnetic resonance stress testing has been shown to be superior to dobutamine stress echocardiography for diagnosis of coronary artery disease (CAD). We determined the feasibility of quantitative myocardial tagging during low- and high-dose dobutamine stress and tested the ability of global systolic and diastolic quantitative parameters to identify patients with significant CAD. Twenty-five patients suspected of having significant CAD were examined with a standard high-dose dobutamine/atropine stress magnetic resonance protocol (1.5-T scanner, Philips). All patients underwent invasive coronary angiography as the standard of reference for the presence (n = 13) or absence (n = 12) of significant CAD. During low-dose dobutamine stress, systolic (circumferential shortening, systolic rotation, and systolic rotation velocity) and diastolic (velocity of circumferential lengthening and diastolic rotation velocity) parameters changed significantly in patients without CAD (all P < 0.05 vs. rest) but not in patients with CAD. Identification of patients without and with CAD during low-dose stress was possible using the diastolic parameter of "time to peak untwist." At high-dose stress, none of the global systolic or diastolic parameters showed the potential to identify the presence of significant CAD. With myocardial tagging, a quantitative analysis of systolic and diastolic function was feasible during low- and high-dose dobutamine stress. In our study, the diastolic parameter of time to peak untwist as assessed during low-dose dobutamine stress was the most promising global parameter for identification of patients with significant CAD. Thus quantitative myocardial tagging may become a tool that reduces the need for high-dose dobutamine stress.

Adrenergic beta-Agonists↗
PubMed2003

Genetics in renal cell carcinoma.

PURPOSE OF REVIEW: The combination of several recent molecular technologies, including comparative genomic hybridization, fluorescence in-situ hybridization and complementary DNA and tissue microarrays, has advanced our understanding of renal cancer. However, a great deal of information regarding the genetics of renal neoplasms has also emerged from the extensive cytogenetic investigations in the past decade. RECENT FINDINGS: The correlation between cytogenetic or molecular genetic abnormalities and histomorphology is most consistent in clear cell and papillary types of renal cell carcinoma. However, gene expression profile studies have brought new insights into the classification of renal tumors, and may provide new markers that identify patients with a poor prognosis as well as identifying potential therapeutic targets. SUMMARY: The integration of expression profile data and clinical parameters could serve to enhance the diagnosis and prognosis of renal cell carcinoma. The identification and evaluation of new molecular parameters will be necessities in cancer research and cancer treatment.

Carcinoma, Renal Cell↗
PubMed1988

Identification of andrologic patient groups by cluster analysis.

To test the validity of the current andrologic classification system, we performed cluster analysis in 317 andrologic patients involuntarily barren for more than 1 year. For cluster analysis, the spermatologic parameters sperm density, motility, and morphologic features were used since only these parameters contributed significantly to group identification, as revealed by stepwise discriminant function analysis. The optimal number clusters determined by calculation of the variance criterion was five. The resulting five groups partly correspond to the prevailing descriptive classification system as far as the extreme groups of "high-grade oligoteratoasthenozoospermia" and "polyzoospermia" are concerned. Surprisingly, cluster analysis distinguished between two groups of normozoospermia that differed in their mean sperm density. Cluster analysis may prove to become a powerful tool for andrologic classification.

Humans↗
PubMed1992

The cardiorespiratory control hypothesis for sudden infant death syndrome.

One or more abnormalities in cardiorespiratory control is the most compelling explanation for SIDS. Elucidation of the interrelationships between arousal responsiveness and gasping may be crucial to a better understanding of SIDS pathophysiology. The complex interactions need to be examined between arousal, autoresuscitation, and the other components of cardiorespiratory control. Prospective identification trials will be difficult since no cardiorespiratory control parameter yet identified has sufficient sensitivity and specificity, and trials assessing multiple parameters will be costly and cumbersome. Furthermore, prospective identification will be worthwhile only if an effective intervention has been established. To the extent that SIDS deaths still occur during documented monitoring, detailed analyses of the recorded cardiorespiratory events should finally provide us with objective data as to the terminal pathophysiologic events in SIDS victims and their relationship to aberrant cardiorespiratory control.

Arousal↗
PubMed1998

Optimization of capillary chromatography ion trap-mass spectrometry for identification of gel-separated proteins.

The current paradigm for protein identification using mass spectrometric derived peptide-mass and fragment-ion data employs computer algorithms which match uninterpreted or partially interpreted fragment-ion data to sequence databases, both protein and translated nucleotide sequence databases. Nucleotide sequence databases continue to grow at a rapid rate for some species, providing an unsurpassed resource for protein identification in those species. Ion-trap mass spectrometers with their ability to rapidly generate fragment-ion spectra in a data-dependent manner with high sensitivity and accuracy has led to their increased use for protein identification. We have investigated various parameters on a commercial ion trap-mass spectrometer to enhance our ability to identify peptides separated by capillary reversed phase-high performance liquid chromatography (RP-HPLC) coupled on-line to the mass spectrometer. By systematically evaluating the standard parameters (ion injection time and number of microscans) together with selection of multiple ions from the full mass range, improved tandem mass spectrometry (MS/MS) spectra were generated, facilitating identification of proteins at a low pmol level. Application of this technology to the identification of a standard protein and an unknown from an affinity-enriched mixture are shown.

Amino Acid Sequence↗
PubMed2003

Identification of organic matter from peat, leonardite and lignite fertilisers using humification parameters and electrofocusing.

The organic matter extracted from peats (P), leonardites (Le) and lignites (Li) was characterised by humification parameters and electrofocusing (EF). The degree of humification and the humification index might be used to distinguish P from Le and Li, but not Le from Li because they showed overlapped values, while the humification rate could be used only for the identification of Le and EF profiles of P, Le and Li fertilisers revealed different band patterns: P samples did not show bands in the region with isoelectric point, pI > 4.4; Le samples showed very intense bands in the region with pI > 4.4; Li samples showed a very different band pattern with poorly resolved bands in the region with pI > 3.8. P, Le and Li samples can be distinguished by combining humification parameters and EF.

Fertilizers↗
PubMed1997

SISO nonlinear system identification using a fuzzy-neural hybrid system.

This paper describes a fuzzy-neural hybrid system for the identification of nonlinear dynamic systems with unknown parameters. The proposed model takes the form of a context-sensitive module in which a fuzzy system is used as a function module and a multilayer neural network is used as a context module. Fuzzy-neural hybrid systems with a decomposed structure reduce complexity and thus accelerate the learning process. Also, the parameters of a fuzzy system have clear physical meanings, which makes it possible to incorporate a priori knowledge into the selection of initial parameter values and constraints among parameter values. Since hybrid systems correspond to networks, it is feasible to construct fast, parallel devices to implement these models for practical applications. The gradient descent method for the adjustment of parameters in hybrid systems is discussed. Simulations demonstrate that the hybrid identification models suggested here for SISO dynamic systems are quite effective.

Fuzzy Logic↗
PubMed2000

Optical non-invasive technique for vessel imaging: I. Experimental results.

This paper investigates some prerequisites for vessel imaging based on diffuse reflectance measurements in order to develop an optical non-invasive method for the imaging and monitoring of vessels. The method utilizes near-infrared (NIR) radiation (890 nm) from a light emitting diode. The light is guided into the tissue via an optical fibre (diameter 1.0 mm). The backscattered light is collected by an optical fibre of the same type and detected by an optical power meter. The fibres are moved over the skin in two directions with the aid of two motors operated by a microcomputer. Spatially resolved reflectance at the skin surface could be presented as a vessel-map in a colour-coded form on a computer screen. Experimental results indicate that the vessel imaging facility depends upon source-detector separation, relative position and vessel depth, and does not depend essentially on the radiant power from the light source. It is shown that, by a proper choice of probe parameters, one can improve the vessel identification ability. After vessel imaging the technique can potentially be used to monitor several physiological parameters on a selected vascular bed or to distinguish between injured and healthy tissue by monitoring local blood flow, oxygen saturation and the recirculation, pre- and post-operatively.

Arteries↗
PubMed1998

Value of myocardial hypoxia markers (creatine kinase and its MB-fraction, troponin-T, QT-intervals) and serum creatinine for the retrospective diagnosis of perinatal asphyxia.

Neonatal asphyxia is a major topic of neonatal research. However, no clear-cut physiologic parameters exist which enable an early identification of neonatal infants who are either at risk to develop brain damage or posthypoxic heart failure. Parameters indicating dysfunction of the heart and kidneys as creatinine and creatinine kinase have been evaluated. In our study, 47 asphyxiated infants (umbilical artery pH < 7.18 and either a 1-min Apgar score < 4 or a 5-min Apgar score < 7) were compared to 27 nonasphyxiated controls regarding significant differences in creatinine, creatinine kinase, its MB fraction, and a newly introduced myocardial hypoxia indicator -- troponin T -- to establish the value of these parameters in the retrospective diagnosis of asphyxia. Further we evaluated two subsets of these 47 asphyxiated infants with either subsequent signs of encephalopathy (seizures) or heart failure. Creatinine, creatinine kinase and troponin T were significantly elevated in asphyxiated infants compared with controls; no differences were found in creatinine kinase and its MB fraction. In asphyxiated infants with heart failure, troponin T was significantly higher than in the other asphyxiated infants. However, none of the parameters studied was significantly different in patients with brain damage compared with asphyxiated infants without neurological sequelae. Troponin T has a high positive predictive value in the postnatal diagnosis of asphyxia. The diagnostic power of troponin T equals that of creatinine. However, troponin T is more sensitive in the identification of infants with asphyxia and cardiocirculatory failure than creatinine. Creatinine kinase and its MB fraction have no diagnostic value.

Asphyxia↗
PubMed1998

Analysis of endogenous process behavior in activated sludge.

In this article, an autonomous four-compartment model that describes the endogenous respiration in an aerobic biodegradation process is proposed and analyzed theoretically. First, the multi-time scale of the system's behavior, to be taken into account in subsequent analyses, is emphasized. Then, an identifiability and observability study, given measurements of MLVSS (mixed liquor volatile suspended solids) and respiration rate, is performed for use under practical circumstances, such as in state and parameter estimation. It appears that the process is observable, but not fully identifiable. Hence, for the identification of some of the model parameters, additional measurements or experiments, also indicated here, have to be performed. Furthermore, it is shown that, under quasi-steady state conditions which, in general, appear shortly after initialization of an endogenous respiration experiment, the model can be reduced significantly. Finally, results of parameter estimation from available data are presented and discussed.

Aerobiosis↗
PubMed2005

Detection of hearing loss using 2f2-f1 and 2f1-f2 distortion-product otoacoustic emissions.

Although many distortion-product otoacoustic emissions (DPOAEs) may be measured in the ear canal in response to 2 pure tone stimuli, the majority of clinical studies have focused exclusively on the DPOAE at the frequency 2f1-f2. This study investigated another DPOAE, 2f2-f1, in an attempt to determine the following: (a) the optimal stimulus parameters for its clinical measurement and (b) its utility in differentiating between normal-hearing and hearing-impaired ears at low-to-mid frequencies (<or=2,000 Hz) when measured either alone or in conjunction with the 2f1-f2 DPOAE. Two experiments were conducted. In Experiment 1, the effects of primary level, level separation, and frequency separation (f2/f1) on 2f2-f1 DPOAE level were evaluated in normal-hearing ears for low-to-mid f2 frequencies (700-2,000 Hz). Moderately high-level primaries (60-70 dB SPL) presented at equal levels or with f2 slightly higher than f1 produced the highest 2f2-f1 DPOAE levels. When the f2/f1 ratio that produced the highest 2f2-f1 DPOAE levels was examined across participants, the mean optimal f2/f1 ratio across f2 frequencies and primary level separations was 1.08. In Experiment 2, the accuracy with which DPOAE level or signal-to-noise ratio identified hearing status at the f2 frequency as normal or impaired was evaluated using clinical decision analysis. The 2f2-f1 and 2f1-f2 DPOAEs were measured from both normal-hearing and hearing-impaired ears using 2 sets of stimulus parameters: (a) the traditional parameters for measuring the 2f1-f2 DPOAE (f2/f1 = 1.22; L1, L2 = 65, 55 dB SPL) and (b) the new parameters that were deemed optimal for the 2f2-f1 DPOAE in Experiment 1 (f2/f1 = 1.073, L1 and L2 = 65 dB SPL). Identification of hearing status using 2f2-f1 DPOAE level and signal-to-noise ratio was more accurate when the new stimulus parameters were used compared with the results achieved when the 2f2-f1 DPOAE was recorded using the traditional parameters. However, identification of hearing status was less accurate for the 2f2-f1 DPOAE measured using the new parameters than for the 2f1-f2 DPOAE measured using the traditional parameters. No statistically significant improvements in test performance were achieved when the information from the 2 DPOAEs was combined, either by summing the DPOAE levels or by using logistic regression analysis.

Adolescent↗
PubMed2001

Mycobacterium tuberculosis mycothione reductase: pH dependence of the kinetic parameters and kinetic isotope effects.

The recent identification of the enzyme in Mycobacterium tuberculosis that catalyzes the NADPH-dependent reduction of the unique low molecular weight disulfide mycothione, mycothione reductase, has led us to examine the mechanism of catalysis in greater detail. The pH dependence of the kinetic parameters V and V/K for NADPH, NADH, and an active analogue of mycothione disulfide, des-myo-inositol mycothione disulfide, has been determined. An analysis of the pH profiles has allowed the tentative assignment of catalytically significant residues crucial to the mechanism of disulfide reduction, namely, the His444-Glu449 ion pair and Cys39. Solvent kinetic isotope effects were observed on V and V/K(DIMSSM), yielding values of 1.7 +/- 0.2 and 1.4 +/- 0.2, respectively, but not on V/K(NADPH). Proton inventory studies (V versus mole fraction of D(2)O) were linear, indicative of a single proton transfer in a solvent isotopically sensitive step. Steady-state primary deuterium kinetic isotope effects on V have been determined using NADPH and NADH, yielding values of 1.27 +/- 0.03 and 1.66 +/- 0.14, respectively. The pre-steady-state primary deuterium kinetic isotope effect on enzyme reduction has values of 1.82 +/- 0.04 and 1.59 +/- 0.06 for NADPH and NADH, respectively. The steady-state primary deuterium kinetic isotope effect using NADH coincide with that obtained under single turnover conditions, suggesting the complete expression of the intrinsic primary kinetic isotope effect. Rapid reaction studies on the reductive half-reaction using NADPH and NADH yielded maximal rates of 129 +/- 2 and 20 +/- 1 s(-1), respectively, while similar studies of the oxidation of the two-electron reduced enzyme by mycothiol disulfide yielded a maximum rate of 190 +/- 10 s(-1). These data suggest a unique flavoprotein disulfide mechanism in which the rate of the oxidative half-reaction is slightly faster than the rate of the reductive half-reaction.

Deuterium↗