Individual Calibration Curves Research Articles

Quantitative spatial distribution of sirolimus and polymers in drug‐eluting stents using confocal Raman microscopy

Raman spectroscopy was used to differentiate each component found in the CYPHER Sirolimus-eluting Coronary Stent. The unique spectral features identified for each component were then used to develop three separate calibration curves to describe the solid phase distribution found on drug-polymer coated stents. The calibration curves were obtained by analyzing confocal Raman spectral depth profiles from a set of 16 unique formulations of drug-polymer coatings sprayed onto stents and planar substrates. The sirolimus model was linear from 0 to 100 wt % of drug. The individual polymer calibration curves for poly(ethylene-co-vinyl acetate) [PEVA] and poly(n-butyl methacrylate) [PBMA] were also linear from 0 to 100 wt %. The calibration curves were tested on three independent drug-polymer coated stents. The sirolimus calibration predicted the drug content within 1 wt % of the laboratory assay value. The polymer calibrations predicted the content within 7 wt % of the formulation solution content. Attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectra from five formulations confirmed a linear response to changes in sirolimus and polymer content.

Nano-HPLC-inductively coupled plasma mass spectrometry for arsenic speciation

A nano-high performance liquid chromatography-inductively coupled plasma mass spectrometry (nano-HPLC-ICPMS) method is developed, using a demountable direct injection high efficiency nebulizer (d-DIHEN), to reduce sample and mobile phase consumption, minimize organic waste generation, decrease analysis time, and enhance separation efficiency. A HPLC column (50 mm × 0.3 mm id), packed with 3.5 μm C18 material, is explored for chromatographic separation of five arsenic species naturally present in the environment or introduced as a pollutant: sodium (meta)arsenite [As(III)], arsenic acid [As(V)], dimethylarsenic acid (DMA), disodium methylarsenate (MA), and p-arsanilic acid (p-ASA). A fast chromatographic separation of five arsenic species is achieved in less than 12 min at a solution flow rate of 0.9 μL min−1 using a 50 nL sample injection. The HPLC-ICPMS interface provides well defined flow injection profiles at various concentrations, giving a correlation coefficient of 0.999 for each individual arsenic species calibration curve. Precision values for peak height and area of five arsenic species range from 0.5 to 6.5% RSD and absolute detection limits are within 0.4 to 5.4 pg arsenic, which are comparable to previously reported data at higher solution uptake rates (20 μL min−1 to 1 mL min−1) and larger sample injection volumes (20–100 μL).

Monitoring lipase-catalyzed methanolysis of sunflower oil by reversed-phase high-performance liquid chromatography: Elucidation of the mechanisms of lipases

Reversed-phase high-performance liquid chromatography (RP-HPLC) with UV detection at 210 nm was used to monitor the formation of the major compounds during the lipase-catalyzed transesterification reaction of sunflower oil with methanol. Individual triacylglycerols, diacylglycerols, monoacylglycerols as well as fatty acids and their corresponding methyl esters were separated using acetonitrile/acetone as a mobile phase and a combined linear gradient-isocratic-step gradient-isocratic elution procedure. Another relatively short method consisting of a linear gradient elution followed by an isocratic elution gave similar results, yet with lower resolution. HPLC/mass spectrometry with an ion trap analyzer and atmospheric pressure chemical ionization source was used for the identification of the individual compounds. Individual calibration curves obtained with UV detection at 210 nm were found to be of use for quantitative analyses of double-bond containing methyl esters and acylglycerols. The use of the RP-HPLC methods in the elucidation of the mechanisms of three immobilized lipases, namely Lipozyme TL IM, Lipozyme RM IM and Novozym 435, in biodiesel production was described.

Intra-laboratory Comet Assay Sample Scoring Exercise for Determination of Formamidopyrimidine DNA Glycosylase Sites in Human Mononuclear Blood Cell DNA

Oxidative DNA damage detected by the comet assay as formamidopyrimidine DNA glycosylase (FPG) senstitive sites, almost as a rule is reported as comet assay score rather than numerical sites in the genome, probably because the latter requires X-ray calibration. We compared the ability of five experienced and five inexperienced comet assay investigators to detect a dose-response relationship in irradiated A549 lung epithelial cell culture samples (0, 10 Gy and three samples of 5 Gy), based on an arbitrary five class scoring system. The samples were scored on three different occasions, thus allowing determination of the variation in sample scoring. All investigators qualitatively distinguished between samples in a dose-dependent manner, albeit with large variation in the slope and intercept of dose-response curves. There was a tendency that investigators with experience in scoring A549 cells had more consistent results than experienced investigators who had only scored lymphocytes or inexperienced investigators. The inexperienced investigators improved their scoring ability during the three sessions. Subsequently we showed that the variation in baseline level of FPG modifications in mononuclear blood cells of five healthy humans was lower when investigators used their individual X-ray calibration curve as compared to a common calibration curve. In conclusion, this study showed that comet assay investigators score differently when using a five class scoring system, which indicates that more consistent estimations of FPG sites in the genome are obtained by use of investigators' individual X-ray calibrations.

Cardiovascular Surgery Without Cardiopulmonary Bypass in Patients with Heparin-Induced Thrombocytopenia Type II Using Anticoagulation with Recombinant Hirudin

Cardiovascular Surgery Without Cardiopulmonary Bypass in Patients with Heparin-Induced Thrombocytopenia Type II Using Anticoagulation with Recombinant Hirudin

The assessment of 24-hour energy expenditure in elderly women by minute-by-minute heart rate monitoring.

To test the suitability of minute-by-minute heart rate (HR) monitoring for estimating 24-hour total energy expenditure (TEE) in elderly women, 13 volunteers, mean (SD) age 73 +/- 3 years, participated in this study. Energy expenditure during five standardized activities, ranging from sitting quietly to walking at 3 km/h, was measured by indirect calorimetry (ventilated hood) simultaneously with HR. From these data, individual calibration curves were obtained by linear regression. The mean correlation coefficient was 0.89 +/- 0.10 (range 0.69-0.99). A group calibration curve was also calculated (r = 0.93, p < 0.02), based on the mean values of energy expenditure during standardized activities and simultaneous HR of the 13 subjects. For 3 days, minute-by-minute HR was registered continuously. The mean 24-hour HR over these days was 75.7 +/- 8.5 beats/min. In addition, activity questionnaires were used to calculate energy expenditure from time/motion data, using individual measured energy expenditure values. TEE calculated from HR using individual calibration curves (8.8 +/- 3.5 MJ/day) was only moderately correlated (r = 0.60, p < 0.001) with TEE calculated from the activity questionnaire (8.6 +/- 0.9 MJ/day). Calculated TEE using the group calibration curve was 8.1 +/- 5.2 MJ/day, which was not significantly correlated with TEE calculated from the activity questionnaire or with TEE using individual calibration curves. The mean values of TEE calculated from the three methods were not statistically significantly different. However, individual values differed markedly sometimes. Individual physical activity levels (TEE/resting metabolic rate), calculated from 24-hour HR monitoring, were unreliably high in some subjects. Minute-by-minute HR monitoring did not appear to be a valid method for predicting TEE for individuals or small groups.

The ductus arteriosus, pre- and post-ductal oxygen saturation measurements in fetal lambs

In the fetus, the arterial oxygen saturation (Sao 2) in the ascending aorta is higher than in the descending aorta. We questioned whether this difference over the ductus arteriosus (ΔSao 2) would change during hypoxaemia. Therefore, six chronically instrumented fetal lambs (119–126 days of gestation) were studied, by changing the inspired oxygen (FIo 2) via a tracheal tube to the ewe. The Sao 2 was measured intermittently every 15 min with blood samples obtained from the ascending and descending aorta, and continuously with 2 pulse oximeters at both sides of the ductus arteriosus. ΔSao 2 was at a level of 3.4–5.3% and had a tendency to decrease at preductal Sao 2 levels of 10–20% and at pH levels below 7.25. The precision of the pulse oximeters, expressed as standard deviation of the differences between sample Sao 2 and pulse oximeter SaO 2, was around 5.0% for the individual calibration curves. This precision was not enough to show details of the course of ΔSaO 2 between the blood samples. Our results show that there is no change in ΔSao 2 across the ductus arteriosus.

A critical evaluation of heart rate monitoring to assess energy expenditure in individuals

The prediction of energy expenditure (EE) from minute-by-minute heart rate (HR) recording was evaluated in 40 female workers, with emphasis on the inter- and intraindividual variation of this method. The results show that the relationship between EE and HR varied greatly between and within subjects. The inter- and intraindividual CVs were 14-18% and 11-20%, respectively. The poor limits of agreement in EE (mean difference +/- 2 SD) between group and individual calibration curves indicate that estimated EE from group curves is inferior to estimated EE from individual curves. Therefore, it is concluded that to have the best estimates of individual EE, only individual calibration curves should be used. At different occasions these curves should be generated again. Because the limits of agreement in EE between individual curves based on 18 and 9 different activities were wide (-2399 to 1817 kJ/16 h), it is preferable to have a wide range of different activities in the individual calibration procedure.

Determination of Steryl Glycosides in Concentrated Phospholipids by HPLC with an Evaporative Light Scattering Detector

A method was developed for determining of steryl glycosides (SG) in commercially available concentrated phospholipids. ASG (acylated SG) and NASG (non-acylated SG) were separated by TLC and determined by HPLC equipped with an evaporative light scattering detector (ELSD). Two separation modes [gel permeation (GP) and reversed phase (RP)] were examined in this study. A good linear correlation was obtained between the logarithm of concentration and peak intensity in ELSD. Individual calibration curves were essential for the determining of NAGS and ASG due to the dependency of ELSD on molecular weight. To simplify the method, ASG was determined following hydrolysis with 0.25 N KOH in methanol. Data for steryl and acyl group in ASG were obtained from acetylated ASG using the RP mode for separation. The limit of detection was 0.05 % for commercial concentrated phospholipids.

Development of the Abbott MatrixTMAero Assay for the Measurement of Specific Ige

An enzyme immunoassay has been developed for the quantitation of specific immunoglobulin E (IgE) in human serum to a panel of allergens. The assay system, called the Abbott MATRIX Aero, includes an instrument, reagents and test cell disposables. Each test cell contains fourteen airborne allergens individually localized on a nitrocellulose solid phase. Individual calibration curves for each allergen are established by the manufacturer and included in barcode form with each test kit. Stable factory calibration eliminates the need to establish a calibration curve with each assay run. The instrument automatically incubates, washes, and reads the test cell and prints each result, which ensures assay reproducibility and provides ease-of-use. Analysis of test results shows good agreement with another in vitro assay for specific IgE. The Abbott MATRIX Aero is a sensitive, reproducible and easy-to-use system for the measurement of specific IgE to a panel of fourteen allergens simultaneously using a single, small volume of serum.

The use of heart rate monitoring in the estimation of energy expenditure: a validation study using indirect whole-body calorimetry

1. A modified heart rate (HR) method for predicting total energy expenditure (TEE) was cross-validated against whole-body calorimetry (CAL). Minute-by-minute HR was converted to energy expenditure (EE) using individual calibration curves when HR exceeded a pre-determined 'FLEX' value designed to discriminate periods of activity. ('FLEX' HR was defined as the mean of the highest HR during rest and the lowest HR during the lightest imposed exercise.) Sedentary EE (below FLEX) was calculated as the mean EE during lying down, sitting and standing at rest. Sleeping EE was calculated as basal metabolic rate (BMR) predicted from standard equations. 2. Calibration curves of oxygen consumption v. HR for different postures at rest and during exercise were obtained for twenty healthy subjects (eleven male, nine female); mean r 0.941 (SD 0.04). The mean FLEX HR for men and women were 86 (SD 10) and 96 (SD 6) beats/min respectively. 3. Simultaneous measurements of HR and EE were made during 21 h continuous CAL, which included 4 x 30 min imposed exercise (cycling, rowing, stepping, jogging). HR exceeded FLEX for a mean of 98 (SD 41) min. Mean TEE by CAL (TEE.CAL) was 8063 (SD 1445) kJ. 4. The HR method yielded a mean non-significant underestimate in TEE (TEE.HR) of 1.2 (SD 6.2)% (range -11.4 to +10.6%). Regression of TEE.HR (Y) v. TEE.CAL (X) yielded Y = 0.868 X + 927 kJ, r 0.943, SE of the estimate 458 kJ, n 20. 5. The satisfactory predictive power and low cost of the method makes it suitable for many field and epidemiological applications.

A DirectJ-RCurve Analysis of Fracture Toughness Tests

AbstractA method is proposed to evaluate fracture toughness in a J-R curve format directly from load displacement records without the need for automatic crack length measurement devices. This method uses the calibration curve in which the flow properties of a material for a stationary crack provide the relationships between load, displacement, and crack length. Crack growth is then evaluated by comparing load and displacement pairs for the growing crack case with this stationary crack curve. This is similar to the approach in which a common “key curve” was used to determine crack length; however, in this case, individual calibration curves are developed for each specimen. The calibration curve is described by separate elastic and plastic components of displacement. The relationship between load and elastic displacement is described by a compliance function and between load and plastic displacement by a power term with constant coefficient and exponent. Three methods are suggested for evaluating the power term exponent and coefficient. The first assumes that the exponent coming from a fit of the true-stress true-strain tensile test results can be used, the second determines all information directly from the test record, and a third does the same but uses a plastic zone adjustment.The method is applied to a set of results from an A508 steel in which the J-R curve had previously been determined using the elastic compliance method of crack length measurement. These tests were conducted on compact specimens with a range of sizes varying by a factor of 20 (10T to 1/2T). The method is also applied to a 4340 steel and stainless steel weld metal. The results show that second approach works best. Although further evaluation of the method is needed, it showed promise as a replacement for automatic crack length measurement techniques in the evaluation of J-R curves.

Determination of molecular weights of coal derived liquids by gel permeation chromatography—high-performance liquid chromatography

A rapid gel permeation chromatographic—high-performance liquid chromatographic procedure for the determination of qualitative and quantitative molecular weight data of coal derived liquids (CDLs) is described. The method analyses class fractions from a CDL and individual calibration curves for each class are derived using standards with similar structures, polarity and functionalities to those present in the particular fraction. The combination of appropriate class calibration data points allowed the derivation of calibration curves for the more complex materials such as the total CDL. This approach minimizes elution behavioural effects peculiar to particular compound classes e.g., H-bonding complexation of phenols, as they are included in the class calibration curve. A comparison of the number average molecular weights determined by this method with those by vapor pressure osmometry gave excellent agreement.

Plasma prednisolone concentrations: Comparison of radioimmunoassay and competitive protein binding assay

A comparison was made between plasma concentrations of prednisolone measured by both competitive protein binding radioassay (CPB) and radioimmunoassay (RIA) and, with each assay, using a calibration curve generated from individual subject data and from pooling the individual calibration curve data. The plasma samples were obtained from six normal adult male volunteers who were pretreated with dexamethasone to suppress endogenous hydrocortisone and who then ingested 10 mg of prednisolone. Both the standard curve data and the plasma concentrations were evaluated statistically. It was shown that the CPB method has considerably greater precision than the RIA method and could be employed in bioavailability and pharmacokinetic studies of both prednisolone and prednisone. It was also shown that corticosteroid binding globulin cross-reacts considerably less with the major metabolite of prednisolone, 20β-dihydroprednisolone, than the particular antiserum used in the RIA.

Ultrasound assessment of residual urine in children.

Ultrasound has been used to assess residual urine in children and found to have considerable advantages over other methods. Using a B-mode scan in the sagittal plane the presence or absence of residual urine can be confidently determined. Quantitative measurements of volume are subject to considerable error but semi-quantitative information in individual cases can be obtained by comparison of records made at subsequent examinations. More accurate quantitative values might be achieved by constructing an individual calibration curve. The advantages of ultrasound for assessing residual urine are that it is simple, quick, harmless and non-invasive. Because of these features the examination can be readily repeated, is suitable for out-patient use and is acceptable to children.

Effect of a sudden change in sodium concentration on repetitively evoked action potentials of single nodes of Ranvier.

1. The experiments were done on motor nerve fibres of the frog,Rana esculenta, with the double air gap method. 2. Single superfused nodes of Ranvier were repetitively stimulated (80 impulses/sec) and either the amplitude (VS) or the maximum rate of rise (\(\dot V_A \)) was recorded during a sudden change in Na concentration from 57 to 228 mM and back. 3. The change ofVS or\(\dot V_A \) was translated into the time course of [Na] o at the membrane by means of individual calibration curves that were determined after equilibrating the preparations in 57, 90, 142, and 228 mM Na. 4. In the majority of the experiments the time course of [Na] o was approximately exponential with a time constant of 30–50 msec. A simultaneous small change of [TEA] o did not significantly influence the Na exchange. 5. The small increase of spike duration on changing from Na-poor to Na-rich solution lagged behind the development ofVS. 6. It is concluded that the speed of Na exchange is determined by diffusion through an unstirred layer of 15–30 μm covering the nodal membrane.

Calibration of turbo-tachometric flowmeters

1. The proposed form of the calibration relationship is confirmed satisfactorily by experiments with flowmeters of two different constructions. 2. The existence of a self-simulating region with respect to π2 in the receivers types R-I and R-II opens up possibilities for making turbo-tachometric flowmeters insensitive in the range of measured flows to variations of viscosity and, hence, to the temperature of the liquid. 3. The compiling of general or individual calibration curves for existing types of turbo-tachometric flowmeters will provide the possibility of introducing corrections to the instrument readings taking into consideration the viscosity and density of liquids. 4. Further extended research is necessary in order to standardize the receiving converters for turbo-tachometric flowmeters.