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PubMed2006

The Toronto Risk Score for adverse events following cardiac surgery.

OBJECTIVE: To develop and validate an objective and reliable measure of acuity that will identify high-risk patients and predict length of stay following all cardiac surgery procedures. METHODS: Logistical regression analysis of 12,683 patients undergoing cardiac surgery between 1996 and 2000 was used to identify the independent predictors of postoperative adverse events (AEs, defined as death, myocardial infarction, low cardiac output syndrome, postoperative renal failure, stroke or deep sternal wound infection). The rounded ORs for each of the 18 predictors of AEs were summed to calculate the Toronto Risk Score (TRS) for each patient. Weighted linear regression was used to determine the relationship between TRS and length of stay in the 4378 patients who underwent cardiac surgery between 2001 and 2002. RESULTS: TRS was significantly associated with cardiovascular intensive care unit length of stay (R2=0.85, slope=0.42, intercept=0.4; P<0.001). For each unit increase in TRS, cardiovascular intensive care unit length of stay increased by 0.4+/-0.05 days. TRS was also significantly associated with total postoperative length of stay (R2=0.88, slope=0.71, intercept=4.9; P<0.001). TRS captured a significant increase in acuity from 1996 and 2000 (5.12+/-3.5) to 2001 and 2002 (5.54+/-3.5; P<0.001). Despite increased acuity, AEs were reduced in 2001 and 2002 (8.1%) compared with 1996 to 2000 (9.8%; P=0.012). CONCLUSIONS: The TRS is a valid measure of acuity that can identify patients who are at high risk of experiencing an AE and having prolonged length of stay after any cardiac surgery procedure, capture changes in acuity over time and allow for continuous quality performance evaluation.

Aged↗
PubMed1997

Corneal thickness measurements with the Orbscan Topography System and ultrasonic pachymetry.

PURPOSE: To compare corneal thickness measurements obtained with a new instrument, the Orbscan Topography System, with those obtained with the DGH ultrasonic pachymeter and to assess the agreement and repeatability of the two devices. SETTING: LSU Eye Center, New Orleans, Louisiana, USA. METHODS: Measurement agreement was assessed in 51 eyes of 26 normal volunteers using both Orbscan and ultrasonic pachymetry. Repeatability for the instruments was measured in 10 eyes of 5 additional volunteers. Corneal thicknesses were compared using the analysis of variance (ANOVA). The relationship between the devices was assessed by analysis of regression (ANOR). RESULTS: In the measurement agreement experiment, the mean corneal thickness was 571.3 microm +/- 6.21 SEM with the Orbscan system and 543.3 +/- 7.49 microm with ultrasonic pachymetry; these values were significantly different (F test, ANOVA, P = .0048). In the repeatability experiment, the mean thickness was 561.1 +/- 8.42 microm with the Orbscan system and 537.4 +/- 5.84 microm with ultrasound pachymetry; these values were also significantly different (F test, ANOVA, P = .0003). Analysis of regression showed a significant linear regression between the values obtained with the devices (P = .0001, F test, ANOR). CONCLUSIONS: In both studies, the Orbscan system obtained statistically significantly different and higher values for corneal thickness. Regression analysis suggests that over the range of values in this study, the two devices differ by a constant amount (intercept and slope). The nonzero intercept of this regression shows that the values from the devices differ and cannot be directly substituted for each other. We therefore conclude that in this study, Orbscan system measurements of corneal thickness were 23 to 28 microm greater than ultrasonic pachymeter measurements. Linear regression equations may be developed for the results of measurements from the two devices and used as a precise transformation factor for the values obtained with the two devices.

Adult↗
PubMed2003

Nitric oxide inhibition of free radical-mediated lipid peroxidation in photodynamically treated membranes and cells.

Of the numerous biological activities attributed to nitric oxide ((*)NO), relatively little is known about its ability to intercept lipid-derived free radicals and thus protect cells against the damaging effects of lipid peroxidation, particularly in photodynamic settings. To address this, we asked how the (*)NO donor spermine-NONOate (SPER/NO) would affect porphyrin (PpIX)-photosensitized, iron/ascorbate-amplified chain peroxidation in cholesterol (Ch)/phospholipid (0.8:1.0, mol/mol) liposomes. Several Ch oxidation products (ChOX) were monitored by high performance chromatographic techniques. When added immediately before irradiation, SPER/NO (0.4 mM) had no effect on accumulation of 5alpha-hydroperoxide, a primary singlet oxygen-derived ChOX, but strongly suppressed the secondary species arising from postphotooxidation chain reactions, including 7alpha/7beta-hydroperoxides, 7alpha/7beta-hydroxides, and 5,6-epoxides. Metabolism of exogenous 5-aminolevulinate to PpIX in COH-BR1 tumor cells sensitized them to ChOX photogeneration and necrotic photokilling. When present during irradiation, active (but not decomposed) SPER/NO strongly inhibited both effects. These findings support the hypothesis that suitably presented NO, by intercepting lipid-derived radicals, can antagonize the antitumor effects of photodynamic therapy and other oxidative therapies.

Cell Line, Tumor↗
PubMed1999

Morphometric and biochemical characteristics of short-term effects of ethanol on rat cardiac muscle.

Alcoholism is a very important cause of congestive cardiomyopathy in man. The aim of this study was to examine a short-term effect of ethanol in rat cardiac muscle, using histologic, morphometric and biochemical methods. Experiments were carried out in Wistar male albino rats, divided into two groups: the control group consisting of eight animals receiving tap water, and the experimental group comprising eight animals received ethyl alcohol for ten days, in a single daily dose of 3 g ethanol/kg body weight, per os, using esophageal intubation. The mean volume weighted nuclear volume of cardiac myocytes was estimated by point sampled intercept method, by objective x 100. The mean cubed nuclear intercept length was multiplied by pi and divided by 3. For biochemical analysis, a 10% water tissue homogenate from the left ventricle was made. In the experimental group, the mean volume-weighted nuclear volume (15.08 +/- 5.20 microm3) was significantly lower than in the control group (51.32 +/- 7.83 microm3) (p < 0.001). The treatment of experimental animals with ethanol caused significant increase of aldolase (p < 0.0001) and aspartate transaminase (p < 0.05) activity in the rat cardiac tissue; at the same time, the enzyme activity of creatine phosphokinase, alanine transaminase and alkaline phosphatase were not changed in the experimental group compared to the control values. The amount of the glucose in the cardiac muscle was greater in the experimental group compared to the control animals. Our results suggest that there is depression of cardiomyocyte nuclei in experimental animals treated with ethanol. Alcohol intake results in the loss of Krebs cycle enzymes and as a consequence there is greater utilization of fatty acids for energy production.

Alcoholism↗
PubMed2003

Inhibition of rat testis microsomal 3beta-hydroxysteroid dehydrogenase activity by tributyltin.

In this study, we have examined the effects of a range of organotin compounds (mono-, di-, tributyltin, mono-, di-, trioctyltin) on the activities of rat testis microsomal 3beta-hydroxysteroid dehydrogenase (3beta-HSD), 17-hydroxylase (17-OHase) and 17beta-hydroxysteroid dehydrogenase (17beta-HSD). 17-OHase activity was inhibited by more than 50% compared with the control rate by 59 microM tributyltin (TBT) but other organotin compounds showed no inhibition. 17beta-HSD activity was unaffected by all organotins tested. 3beta-HSD was inhibited by monooctyltin (81 microM) and by TBT at all concentrations tested in a dose-dependent manner, with almost complete loss of activity at TBT concentrations of 12 microM. The mechanism of inhibition of 3beta-HSD was investigated in kinetic analysis with 0-12 microM TBT. Three rat testis microsomal preparations were incubated with dehydroepiandrosterone as the steroid substrate ranging from 1 to 10,000 nM. Tributyltin was primarily a competitive inhibitor of 3beta-HSD activity, causing an increase in the value of the K(m(app)). However, the mechanism was not entirely competitive as while there was an increase in K(m(app)), a decrease in the V(max(app)) was also observed with increasing concentrations of TBT. Slope and intercept replots demonstrated that the K(i)((app)) from slope replots was around 2.7 microM whereas the K(i)((app)) value from intercept replots was around 30 microM. When compared with the K(m(app)) for 3beta-HSD of around 0.42 microM, TBT could be an effective inhibitor of this enzyme.

17-Hydroxysteroid Dehydrogenases↗
PubMed1988

Development of a solid phase RIA for human plasma somatostatin.

Somatostatin is widely distributed in tissues of biological fluids. In the present study we tested the validity of a new radioimmunoassay by a solid phase immunoextraction. Sensitivity was 1.8 pg/mL and the within-assay precision with two different pools of human plasma was 12.2% (CV) at a concentration of 19.2 +/- 2.34 pg/mL (mean +/- SD) and 11.9% at 8.53 +/- 1.02 pg/mL. The between assay precision was 14.2% (CV) at a concentration of 11.8 +/- 1.68 pg/mL. The accuracy was good as tested by the dilution test (slope: 0.956, Y-intercept 3.07 pg/mL, r = 0.997) and the recovery test (slope: 1.008, Y-intercept 2.22 pg/mL, r = 0.999). The method resulted in good correlation with a current extraction method (no. 65, y = 1.45 + 0.975 x, r = 0.862, P less than 0.001). Basal value of somatostatin in the plasma of 32 normal subjects was 11.5 +/- 5.80 pg/mL (mean +/- SD).

Humans↗
PubMed2001

Mean frequency and signal amplitude of the surface EMG of the quadriceps muscles increase with increasing torque--a study using the continuous wavelet transform.

The continuous wavelet transform (CWT), a time-frequency method, was used when calculating mean frequency of the power spectrum (MNF) and signal amplitude (RMS) of the surface EMG to investigate their relationships to force during a gradually increasing knee extension (ramp). Based upon the CWT, MNF was redefined to include time dependence on the EMG signal frequency contents, the short-time MNF (STMNF). Surface EMG was recorded from vastus lateralis, rectus femoris and vastus medialis in 21 clinically healthy subjects during a brief, gradually increasing contraction up to 100% of a maximum voluntary contraction (MVC), with a duration of approximately 10 s. The relationships between the EMG variables and force using linear regression were determined for each subject. For vastus lateralis, we also investigated if certain aspects of the muscle morphology (i.e., proportions and areas of different fibre types) influenced the EMG-force relationship. For the majority of subjects (17-18 out of 21 subjects) there were significant positive correlations between STMNF and force in the three muscles. No sex differences were found in intercepts or regression coefficients of STMNF. The muscle morphology had a significant influence on the STMNF-force intercept and the regression coefficient. Positive and highly significant linear correlations between RMS and force were found for all subjects and all three muscles.In conclusion, time frequency methods can be applied when investigating EMG during brief contractions associated with non-stationarity. In a great majority of the subjects, and in the three muscles, significant linear force dependencies were found for STMNF. Thus, when evaluating muscle fatigue, e.g., in ergonomic situations, it is important to consider the force level as one factor that can influence the results. Morphological variables (fibre proportions and fibre areas) influenced the STMNF-force relationship in vastus lateralis.

Adult↗
PubMed2002

Time-frequency and principal-component methods for the analysis of EMGs recorded during a mildly fatiguing exercise on a cycle ergometer.

Electromyographic signals contain the information on muscle activity and have to be frequently averaged, compared, classified or details need to be extracted. A time-frequency analysis, based on wavelets, was previously presented. The analysis transformed an EMG signal into an EMG-intensity-pattern showing the intensities at any point in time for the frequencies filtered out by the wavelets. The purpose of the present study was:to define and apply a new EMG-pattern-space for the analysis of EMG-intensity-patterns; and to determine the variation of EMG-intensity-patterns while getting mildly fatigued by cycling on a cycle-ergometer. The coordinates spanning the pattern space were principal components of the measured EMG-intensity-patterns. A point in pattern-space thus represented an EMG-intensity-pattern. Fatigue resulted in points moving along a line in pattern space. The line was characterized by an intercept at time 0 and a slope. Thus mild fatigue caused a shift from an initial intensity-pattern representing the intercept to a final intensity-pattern adding gradually larger amounts of the pattern representing the slope. The intensity-pattern of the slope revealed the physiologically important individual strategies for coping with mild fatigue. Changes were observed at different times and at different frequencies during the cycling movement.

Adult↗
PubMed2001

Zinc sulphate-induced anosmia decreases the nerve fibre density in the anterior cerebral artery of the rat.

Detailed quantitative studies have demonstrated a topographical heterogeneity of nerve fibre densities in the cerebral arteries at the base of the brain as well as local changes in ageing and Alzheimer's patients. In this study, we test the hypothesis that local patterns of innervation are influenced by changes in flow fluctuations. This was investigated by inducing chronic anosmia and monitoring the nerve fibre density in the basal cerebral arteries in the adult rat. The olfactory epithelium was examined after staining with hematoxylin and eosin and showed a marked reduction of thickness in the anosmic group compared to the control group. The olfactory bulb was histochemically stained for succinate dehydrogenase (SDH) activity and showed a reduced staining in the anosmic group compared to the controls. Whole mount preparations of the basal cerebral arteries were immunostained for the general neural marker protein gene product (PGP) 9.5. The nerve fibre densities of the vessel walls were quantified by image analysis and expressed as area percentage and intercept density. This analysis showed a significant reduction in area percentage for the first part of the anterior cerebral artery, as well as for the second part of the anterior cerebral artery, and a significant reduction in intercept density for the second part of the anterior cerebral artery in the anosmic group. We conclude that peripherally induced anosmia decreases nerve fibre density in the anterior cerebral artery that may be due to a decreased metabolic activity in the rhinencephalon and, as a consequence, a reduction of flow fluctuations in the blood vessels supplying this area occurs.

Animals↗
PubMed2003

Comparison of a liquid chromatographic method with ultraviolet and ion-trap tandem mass spectrometric detection for the simultaneous determination of sulfadiazine and trimethoprim in plasma from dogs.

A method for the simultaneous determination of sulfadiazine and trimethoprim in plasma from Beagle dogs was developed and validated. Samples were deproteinized with acetonitrile and extracted with ethyl acetate. Sulfachloropyridazine and ormethoprim were used as internal standards for the sulfadiazine and trimethoprim analysis, respectively. The chromatography was carried out both on an LC-UV (liquid chromatography-ultraviolet detection) and ion-trap LC-MS(n) (liquid chromatography-mass spectrometric detection) instrument, operating in the positive APCI mode (atmospheric pressure chemical ionization). The purpose of this work was to compare the quantification results of both methods. Both the LC-UV and LC-MS-MS methods were validated for their linearity, accuracy, precision, limit of detection and limit of quantification, according to the requirements defined by the European Community. Calibration curves using plasma fortified between 0.1 and 1 microg/ml of sulfadiazine, 0.1 and 2 microg/ml of trimethoprim, 1 and 20 microg/ml of sulfadiazine showed a good linear correlation (r> or =0.9990, goodness-of-fit< or =8.4%). The results for the accuracy and precision at 1 microg/ml of sulfadiazine and trimethoprim and at 20 microg/ml of sulfadiazine fell within the ranges specified. The limits of quantification of both methods were 0.1 microg/ml. The limits of detection were 0.019 microg/ml of sulfadiazine and 0.024 microg/ml of trimethoprim for the LC-UV method, and 0.020 microg/ml of sulfadiazine and 0.062 microg/ml of trimethoprim for the LC-MS-MS method. The methods have been successfully applied in a pharmacokinetic study to determine the drug concentrations in plasma samples from dogs. A good correlation between the results of both methods was observed (R=0.9724, slope=1.0239, intercept=-0.2080 microg/ml for sulfadiazine and R=0.9357, slope=1.0433, intercept=0.0325 microg/ml for trimethoprim). The precision of both methods was also tested on the results of the same samples using an F-test (alpha=0.05), indicating that both methods did not differ in precision.

Animals↗
PubMed1995

Evaluation of technical factors affecting the quantification of trabecular bone structure using magnetic resonance imaging.

High resolution magnetic resonance (MR) techniques combined with standard techniques of stereology and texture analysis have been used to quantify trabecular structure. Using dried excised specimens from the tibia (n = 10) and radius (n = 2) we evaluate the impact of using volumetric gradient-echo (GE) and spin-echo (SE) MR imaging sequences, the relative importance of echo time in gradient-echo MR imaging, and the impact of different threshold values to segment the bone and bone marrow on the estimation of trabecular bone structure. We also investigate the inter-relationships between the different structural parameters derived from MR images. Images were obtained using fast gradient-echo and spin-echo imaging sequences, with TE values ranging from 7 to 17 ms using 4.7 and 1.5 Tesla imaging systems. In-plane image resolution ranged from 128 to 156 microns, and slice thickness ranged from 128 to 1000 microns. We derived stereological measures such as the mean intercept length, trabecular width, fractional area of trabecular bone, trabecular number, and trabecular spacing, the fractal dimension as a texture-related parameter and the Euler number as a measure of connectivity from these images. We found that the mean intercept length as a function of angle traced an ellipse with the orientation of the principal axis of the ellipse, a measure of trabecular orientation, identical when measured from the spin-echo or gradient-echo MR images. Absolute measures such as the fractional area, trabecular width, trabecular number, and fractal dimension as measured from gradient echo images were 28%, 30%, 1.3%, and 0.6% greater, respectively, than those calculated from spin-echo images, while the trabecular spacing was 14% less when calculated from gradient-echo images compared to spin-echo images. The structural parameters also depended on the echo time used to obtain the MR image. The choice of the threshold used to segment the high resolution images also affected the estimated structural parameters significantly. Our results indicate that MR may be used to visualize and quantify trabecular bone architecture; however, the different technical factors that could affect the appearance of MR images must be understood and considered in the data analysis and interpretation.

Absorptiometry, Photon↗
PubMed1999

Calibration of trabecular bone structure measurements of in vivo three-dimensional peripheral quantitative computed tomography with 28-microm-resolution microcomputed tomography.

It has recently been shown that high-resolution computed tomography and magnetic resonance imaging have the potential to assess information about the microarchitecture of bone in a noninvasive way. However, due to the limited spatial resolution of the in vivo measurements, the individual trabeculae are not depicted with their true thickness. Nevertheless, the spacing of the structural elements allows the assessment of trabecular number. In a previous publication, the ridge number density (RND) was introduced as a measure for this structural index. It can be extracted from high-resolution three-dimensional (3D) images of patients and shows a reproducibility of 1.6%. In this work the Ridge extraction procedure is compared to and calibrated with microcomputed tomography (microCT) measurements. Three-dimensional measurements of 15 bone biopsies are made with a 28-microm-resolution microCT scanner as well as with a 165-microm-resolution peripheral quantitative computed tomography (pQCT) scanner. For the latter, the same settings are used as for patient examinations. The 15 pairs of measurements are analyzed and the resulting structural indices are compared. The results show that structural indices such as trabecular number, mean thickness, and mean separation can be determined from the 3D pQCT data with an r2 of between 0.81 and 0.96 if the microCT data are taken as the gold standard. The calibration equation found for the bone volume fraction has an intercept of 0.04 and a slope of 0.86 (r2 = 0.98), and trabecular number as the main additional structural index shows a nonsignificant intercept and a calibration slope of 0.91 with the microCT. The calibration procedure can be used directly for patient examinations. Applied to time-series measurements it may be of value for monitoring and quantifying microarchitectural changes due to therapy or aging.

Adult↗
PubMed1999

Constitutive relationships of fabric, density, and elastic properties in cancellous bone architecture.

The hypothesis that trabecular morphology can predict the elastic properties of cancellous bone has only partly been verified and no predictive analytical model is currently available. Such models are becoming increasingly relevant as the resolution levels of three-dimensional scanning techniques approach the size of trabeculae. This study took advantage of micro-finite-element methods and tested the aforementioned hypothesis in normal cancellous bone material collected at six anatomical locations from 56 individuals. Numerical analysis was based on high-resolution three-dimensional computer reconstructions of cancellous bone specimens from which the complete elastic characteristics and trabecular morphology, represented by three different fabric measures (the mean intercept length and two volume-based ones), were calculated. Each fabric measure was analyzed individually using the tensorial relationships derived by Cowin (Mech Mater 4:137-147; 1985). Models for both stiffness and compliance entries were developed. The models based on stiffness entries could explain 93.4%-95.6% of the variance, whereas those based on compliance entries could explain 89.2%-89.4%. When using the former model, the MIL (mean intercept length measure) performed slightly better than the two volume-based measures, VO (volume orientation) and SVD (star volume distribution), with 23% less remaining variance. The high correlations found strongly support the hypothesis and increase the hope that, on the basis of information on trabecular morphology, it will be possible to obtain considerably better estimates of bone quality in vivo compared with the rough two-dimensional density measurements used today.

Adolescent↗
PubMed2006

DSM-IV alcohol dependence: a categorical or dimensional phenotype?

BACKGROUND: Etiologic research on complex disorders including alcohol dependence requires informative phenotypes. Information is lost when categorical variables represent inherently dimensional conditions. We investigated the validity of DSM-IV alcohol dependence as a dimensional phenotype by examining evidence for linearity and thresholds in associations with validating variables. METHOD: Current drinkers in the National Longitudinal Alcohol Epidemiologic Survey (NLAES) (n=18352) and National Epidemiologic Survey of Alcohol and Related Conditions (NESARC) (n=20836) were analyzed. Validating variables included family alcoholism, early-onset drinking, and alcohol treatment. Logistic or Poisson regression modeled the relationships between the validating variables and dependence in categorical, dimensional or hybrid forms, with severity defined as number of current DSM-IV alcohol-dependence criteria. Wald tests assessed differences between models. RESULTS: No evidence was found for boundaries between categories. Instead, the association of alcohol dependence with the validating variables generally increased in linear fashion as the number of alcohol-dependence criteria increased. For NLAES models of family alcoholism, early-onset drinking and treatment, the lines had zero intercepts, with slopes of 0.18, 0.27, 0.70, respectively. For NESARC models of family history and early-onset drinking, the zero intercept lines had slopes of 0.20, 0.33, and 0.77, respectively. Wald tests indicated that models representing alcohol dependence as a dimensional linear predictor best described the association between dependence criteria and the validating variables. CONCLUSIONS: The sample sizes allowed strong tests. Diagnoses are necessary for clinical decision-making, but a dimensional alcohol-dependence indicator should provide more information for research purposes.

Adult↗
PubMedDate not supplied

Visual cortex neurons in monkey and cat: effect of contrast on the spatial and temporal phase transfer functions.

The responses of simple cells (recorded from within the striate visual cortex) were measured as a function of the contrast and the frequency of sine-wave grating patterns in order to explore the effect of contrast on the spatial and temporal phase transfer functions and on the spatiotemporal receptive field. In general, as the contrast increased, the phase of the response advanced by approximately 45 ms (approximately one-quarter of a cycle for frequencies near 5 Hz), although the exact value varied from cell to cell. The dynamics of this phase-advance were similar to the dynamics of the amplitude: the amplitude and the phase increased in an accelerating fashion at lower contrasts and then saturated at higher contrasts. Further, the gain for both the amplitude and the phase appeared to be governed by the magnitude of the contrast rather than the magnitude of the response. For the spatial phase transfer function, variations in contrast had little or no systematic effect; all of the phase responses clustered around a single straight line, with a common slope and intercept. This implies that the phase-advance was not due to a change in the spatial properties of the neuron; it also implies that the phase-advance was not systematically related to the magnitude of the response amplitude. On the other hand, for the temporal phase transfer function, the phase responses fell on five straight lines, related to the five steps in contrast. As the contrast increased, the phase responses advanced such that both the slope and the intercept were affected. This implies that the phase-advance was a result of contrast-induced changes in both the response latency and the shape/symmetry of the temporal receptive field.

Animals↗
PubMed1998

Cognitive and motor slowing in Alzheimer's disease and geriatric depression.

While response slowing on psychological tasks is a symptom of both depression and Alzheimer's disease (AD), the underlying mechanisms may be quite different: a slowing of cognitive processing in AD and a motor retardation in depression. This hypothesis was tested by examining the rate at which participants performed a simple cognitive operation: subvocal pronunciation. Participants were shown words of between one and three syllables and were asked to decide whether each word ended in a particular sound. This task required participants to transform the written word into its phonological representation, an operation thought to involve subvocal pronunciation. Decision time rose linearly with the number of syllables in all three subject groups. The linear function of the AD patients had a significantly greater slope, indicating a slower rate of subvocal pronunciation, whereas the slope was the same for the normal old and depressed. Both the depressed and AD patients had a higher intercept than the normal old, suggesting a sensorimotor slowing. After treatment, the intercept of the linear function for depressed patients fell, but there was no change in the slope. Thus, this study suggests that AD produces a slowing in both cognitive and motor processes, whereas depression results solely in a motor retardation.

Aged↗
PubMed2001

Complexes between monoclonal antibodies and receptor fragments with a common cold virus: determination of stoichiometry by capillary electrophoresis.

Complex formation between monoclonal antibodies or soluble receptor fragments and a human rhinovirus is quantified by relating the concentration of the antibody or receptor under equilibrium conditions to the initial concentration of the virus. Within a given concentration range of the reactants, the shape of the resulting curve depends only on the value of the dissociation constant of the particular system studied. Using antibodies and receptor fragments, cases for high, low, and intermediate affinity were investigated. For high-affinity systems, the curve approximates a decaying straight line and the binding stoichiometry can be accurately determined from the intercept with the x-axis. For the case of intermediate affinity, the curve can be linearized at low virus concentrations with the receptors present in large excess. Extrapolation of this line allows derivation of the binding stoichiometry from the intercept with the x-axis, although with less accuracy. For intermediate affinities, an estimate of the dissociation constant can be obtained from fitting the curve to the data points measured. Finally, in the case of low affinity none of the binding parameters can be quantified, although a rough estimate of the lower limit of the dissociation constant is possible. The method was applied for two different monoclonal antibodies, a Fab fragment and a receptor fragment, binding to human rhinovirus serotype 2. Thirty copies of the monoclonal antibody 8F5 were found to bind to the virion, which is in agreement with data from electron cryomicroscopy. The complex between monovalent human very-low-density lipoprotein receptor encompassing repeats 2 and 3 and human rhinovirus serotype 2 showed 60 receptor molecules bound per virion.

Antibodies, Monoclonal↗
PubMed2003

Rare-earth glass reference materials for near-infrared spectrometry: correcting and exploiting temperature dependencies.

Quantitative descriptions of the location of seven near-infrared absorption bands as functions of temperature 5-50 degrees C are presented here for three recently introduced wavelength/wavenumber Standard Reference Materials (SRMs): SRM 2035, SRM 2065, and SRM 2036. For all bands in all three SRMs, locations are well described as linear models parametrized with the location at 0 degrees C (intercept) and the rate of location change per degrees C (slope). Since these materials were produced from compositionally similar melts, the slopes for each band are identical within measurement imprecision in all three SRMs; only minor differences are observed in the intercepts. Because the direction of change in location differs among the bands, it is possible to use the measured band locations to reliably estimate sample temperature. Two approaches to estimating temperature are evaluated: slope and measurement uncertainty-weighted means. While both methods work well with measurements made under well-characterized and stable environmental conditions, the more complex uncertainty-weighted analysis becomes relatively more predictive as the total measurement uncertainties increase.

Journal Article↗