Journal articles on the topic 'Plasma volume measurement technique'
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Rehm, Markus, Mathias Haller, Victoria Orth, Uwe Kreimeier, Mathias Jacob, Holger Dressel, Sabine Mayer, Heinz Brechtelsbauer, and Udilo Finsterer. "Changes in Blood Volume and Hematocrit during Acute Preoperative Volume Loading with 5% Albumin or 6% Hetastarch Solutions in Patients before Radical Hysterectomy." Anesthesiology 95, no. 4 (October 1, 2001): 849–56. http://dx.doi.org/10.1097/00000542-200110000-00011.
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Background The impact of acute preoperative volume loading with colloids on blood volume has not been investigated sufficiently. Methods Before surgery, in 20 patients undergoing major gynecologic procedures, volume loading was performed during anesthesia by infusing approximately 20 ml/kg of colloid at a rate of 90 ml/min (group I: 5% albumin solution; group II: 6% hetastarch solution; n = 10 each). Plasma volume (indocyanine green dilution technique), erythrocyte volume (labeling erythrocytes with fluorescein), hematocrit, total protein, and hetastarch plasma concentrations (group II) were measured before and 30 min after the end of infusion. Results More than 1,350 ml of colloid (approximately 50% of the baseline plasma volume) were infused within 15 min. Thirty minutes after the infusion had been completed, blood volume was only 524 +/- 328 ml (group I) and 603 +/- 314 ml (group II) higher than before volume loading. The large vessel hematocrit (measured by centrifugation) dropped more than the whole body hematocrit, which was derived from double-label measurements of blood volume. Conclusions The double-label measurements of blood volume performed showed that 30 min after the infusion of approximately 20 ml/kg of 5% albumin or 6% hetastarch solution (within 15 min), only mean 38 +/- 21% and 43 +/- 26%, respectively, of the volume applied remained in the intravascular space. Different, i.e., earlier or later, measuring points, different infusion volumes, infusion rates, plasma substitutes, or possibly different tracers for plasma volume measurement might lead to different results concerning the kinetics of fluid or colloid extravasation.
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Hinghofer-Szalkay, H. "Volume and density changes of biological fluids with temperature." Journal of Applied Physiology 59, no. 6 (December 1, 1985): 1686–89. http://dx.doi.org/10.1152/jappl.1985.59.6.1686.
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High-precision (10(-5) g/ml) mass density measurements on human blood, plasma, plasma ultrafiltrate (using PM-10 membranes), and erythrocyte concentrate samples were performed with the mechanical oscillator technique. Measurement temperatures varied between 4 and 48 degrees C and were accurate to +/- 1 X 10(-2) K. The coefficient of thermal expansion (beta), defined as relative volume change with temperature, was calculated. It was shown that beta increases with temperature in these fluid samples over the entire temperature range investigated; the magnitude of this increase declines with increasing temperature; beta increases with density at temperatures below 40 degrees C but is independent of density above 40 degrees C; and the beta of the intracellular fluid has about twice the value of the beta for extracellular fluid at low (4–10 degrees C) temperatures but is equal for both fluids at greater than or equal to 40 degrees C. The mechanical oscillator technique provides data with an accuracy sufficient to perform precise (10(-5) K) calculations of beta of small volumes of biological fluids.
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Kelly, Kevin Lawrence, Alex R. Carlson, Bradley B. Cierzan, Jennifer Isautier, Wayne L. Miller, and Bruce D. Johnson. "3092 Measuring Fluid Compartments Before and After Rapid Saline Infusion." Journal of Clinical and Translational Science 3, s1 (March 2019): 48–49. http://dx.doi.org/10.1017/cts.2019.115.
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OBJECTIVES/SPECIFIC AIMS: To evaluate the ability of various techniques to track changes in body fluid volumes before and after a rapid infusion of saline. METHODS/STUDY POPULATION: Eight healthy participants (5M; 3F) completed baseline measurements of 1) total body water using ethanol dilution and bioelectrical impedance analysis (BIA) and 2) blood volume, plasma volume and red blood cell (RBC) volume using carbon monoxide rebreathe technique and I-131 albumin dilution. Subsequently, 30mL saline/kg body weight was administered intravenously over 20 minutes after which BIA and ethanol dilution were repeated. RESULTS/ANTICIPATED RESULTS: On average, 2.29±0.35 L saline was infused with an average increase in net fluid input-output (I/O) of 1.56±0.29 L. BIA underestimated measured I/O by −3.4±7.9%, while ethanol dilution did not demonstrate a measurable change in total body water. Carbon monoxide rebreathe differed from I-131 albumin dilution measurements of blood, plasma and RBC volumes by +0.6±2.8%, −5.4±3.6%, and +11.0±4.7%, respectively. DISCUSSION/SIGNIFICANCE OF IMPACT: BIA is capable of tracking modest changes in total body water. Carbon monoxide rebreathe appears to be a viable alternative for the I-131 albumin dilution technique to determine blood volume. Together, these two techniques may be useful in monitoring fluid status in patients with impaired fluid regulation.
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Jacob, Matthias, Peter Conzen, Udilo Finsterer, Alexander Krafft, Bernhard F. Becker, and Markus Rehm. "Technical and physiological background of plasma volume measurement with indocyanine green: a clarification of misunderstandings." Journal of Applied Physiology 102, no. 3 (March 2007): 1235–42. http://dx.doi.org/10.1152/japplphysiol.00740.2006.
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The indocyanine green (ICG) dilution technique (DT) is frequently used for plasma volume (PV) measurement. However, because of inadequate knowledge about the properties of this dye, lack of accuracy has been attributed to the method. The aim of this report is to provide physiological background information about the ICG-DT to avoid some profound misunderstandings. When performing tracer dilution, one has to consider the tracer's distribution space before interpreting the result. For ICG, the distribution space is the total PV, i.e., circulating + noncirculating PV, fixed within the endothelial glycocalyx. The distribution space of red blood cells and large molecules, in contrast, is only the circulating part of PV. Therefore, it is erroneous to compare directly PV derived from different tracer dilution methods. The transcapillary escape rate of ICG should not relevantly influence measured PV if the method is performed properly, i.e., if a short time window of measurement is subjected to monoexponential extrapolation. A major problem of PV measurement in general is that the target itself is very inconstant. Thus, checking for constancy of ICG-DT with two consecutive measurements is unreliable. Nevertheless, the ICG-DT is a useful tool for determining PV, provided it is well understood by the investigator to enable correct interpretation of the results.
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Burczynski, F. J., K. L. Pushka, D. S. Sitar, and C. V. Greenway. "Hepatic plasma flow: accuracy of estimation from bolus injections of indocyanine green." American Journal of Physiology-Heart and Circulatory Physiology 252, no. 5 (May 1, 1987): H953—H962. http://dx.doi.org/10.1152/ajpheart.1987.252.5.h953.
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Experiments were performed to determine the validity of the indocyanine green (ICG) clearance technique, with and without allowances for incomplete hepatic extraction, as an estimate of hepatic plasma flow. This technique was compared with that of directly measured hepatic blood flow using a hepatic venous long-circuit preparation in the anesthetized cat. This preparation allowed direct measurement and alteration of hepatic blood flow and collection of arterial, portal, and hepatic venous blood samples without depletion of the animal's blood volume. Measurements of ICG by spectrophotometry and high-pressure liquid chromatography (HPLC) were equally accurate, but the HPLC was 100 times more sensitive and allowed smaller sample volumes. It was determined that systemic clearance of ICG after a bolus dose (1.3 mumol/kg) was much smaller than hepatic blood flow. Allowance must be made for the incomplete extraction. When the clearance was multiplied by extraction, mean estimated hepatic plasma flow exceeded the measured flow values by 20-30%, and this difference was attributed to temporary extrahepatic distribution. In all experiments estimated hepatic plasma flows were highly variable, and reasons for this are discussed. In hepatectomized cats ICG was found to be distributed into extrahepatic tissues.
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Zohoori, F. Vida, Anne Maguire, E. Angeles Martinez-Mier, Marília Afonso Rabelo Buzalaf, Roy Sanderson, and George J. Eckert. "A Comparison of Simple Analytical Methods for Determination of Fluoride in Microlitre-Volume Plasma Samples." Caries Research 53, no. 3 (October 8, 2018): 275–83. http://dx.doi.org/10.1159/000492339.
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The aim was to compare potential methods for fluoride analysis in microlitre-volume plasma samples containing nano-gram amounts of fluoride. Methods: A group of 4 laboratories analysed a set of standardised biological samples as well as plasma to determine fluoride concentration using 3 methods. In Phase-1, fluoride analysis was carried out using the established hexamethyldisiloxane (HMDS)-diffusion method (1 mL-aliquot/analysis) to obtain preliminary measurement of agreement between the laboratories. In Phase-2, the laboratories analysed the same samples using a micro-diffusion method and known-addition technique with 200 µL-aliquot/analysis. Coefficients of Variation (CVs) and intra-class correlation coefficients (ICCs) were estimated using analysis of variance to evaluate the amount of variation within- and between-laboratories. Based on the results of the Phase-2 analysis, 20 human plasma samples were analysed and compared using the HMDS-diffusion method and known-addition technique in Phase-3. Results: Comparison of Phase-1 results showed no statistically significant difference among the laboratories for the overall data set. The mean between- and within-laboratory CVs and ICCs were < 0.13 and ≥0.99, respectively, indicating very low variability and excellent reliability. In Phase-2, the overall results for between-laboratory variability showed a poor CV (1.16) and ICC (0.44) for the micro-diffusion method, whereas with the known-addition technique the corresponding values were 0.49 and 0.83. Phase-3 results showed no statistically significant difference in fluoride concentrations of the plasma samples measured with HMDS-diffusion method and known- addition technique, with a mean (SE) difference of 0.002 (0.003) µg/mL. In conclusion, the known-addition technique could be a suitable alternative for the measurement of fluoride in plasma with microlitre-volume samples.
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Biswas, MA Karim, MA Shayed, RD Hund, and Ch Cherif. "Surface modification of Twaron aramid fiber by the atmospheric air plasma technique." Textile Research Journal 83, no. 4 (November 9, 2012): 406–17. http://dx.doi.org/10.1177/0040517512464291.
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Twaron aramid fibers (AFs) were modified by atmospheric air dielectric barrier discharge plasma with various parameters. The wettability of plasma-treated AF was observed by means of contact angle and surface free energy measurement. Surface roughness was investigated with the help of scanning electron microscopy. Energy-dispersive X-ray analysis was used to measure the chemical composition of AF in volume with one micrometer dimension. The tensile test of AF roving was carried out to determine the effect of plasma surface treatments on the mechanical properties of the fibers. A pull-out force test was carried out to observe the adhesion effect with matrix material. Lower contact angles, increase of oxygen concentration at the fiber surface, surface roughness and increase of pull-out force with the rubber matrix were observed after the air plasma treatment.
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Molitoris, Bruce A., Anthony G. George, Patrick T. Murray, Daniel Meier, Erinn S. Reilly, Erin Barreto, Ruben M. Sandoval, Dana V. Rizk, Andrew D. Shaw, and W. Frank Peacock. "A Novel Fluorescent Clinical Method to Rapidly Quantify Plasma Volume." Cardiorenal Medicine 9, no. 3 (2019): 168–79. http://dx.doi.org/10.1159/000496480.
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Objectives: To determine the performance of a rapid fluorescent indicator technique for measuring plasma volume (PV). Methods: This was an open-label, observational evaluation of a two-component intravenous visible fluorescent dye technique to rapidly measure PV in 16 healthy subjects and 16 subjects with chronic kidney disease (8 stage 3 and 8 stage 4 CKD), at 2 clinical research sites. The method consisted of a single intravenous injection of 12 mg of a large 150-kDa carboxy-methyl dextran conjugated to a fluorescent rhodamine-derived dye as the PV marker (PVM), and 35 mg of a small 5-kDa carboxy-methyl dextran conjugated to fluorescein, the renal clearance marker. Dye concentrations were quantified 15 min after the injections for initial PV measurements using the indicator-dilution principle. Additional samples were taken over 8 h to evaluate the stability of the PVM as a determinant of PV. Blood volumes (BV) were calculated based on PV and the subject’s hematocrit. Pharmacokinetic parameters were calculated from the plasma concentration data taken over several days using noncompartmental methods (Phoenix WinNonlin®). Linear correlation and Bland-Altman plots were used to compare visible fluorescent injectate-measured PV compared to Nadler’s formula for estimating PV. Finally, 8 healthy subjects received 350 mL infusion of a 5% albumin solution in normal saline over 30 min and a repeat PV determination was then carried out. Results: PV and BV varied according to weight and body surface area, with PV ranging from 2,115 to 6,234 mL and 28.6 to 41.9 mL/kg when weight adjusted. Both parameters were stable for > 6 h with repeated plasma measurements of the PVM. There was no difference between healthy subjects and CKD subjects. Overall, there was general agreement with Nadler’s estimation formula for the mean PV in subjects. A 24-h repeat dose measurement in 8 healthy subjects showed PV variability of 98 ± 121 mL (mean = 3.8%). Additionally, following an intravenous bolus of 350 mL of a 5% albumin solution in normal saline in 8 healthy subjects, the mean (SD) measured increase in PV was 356 (±50.0) mL post-infusion. There were no serious adverse events reported during the study. Conclusions: This minimally invasive fluorescent dye approach safely allowed for rapid, accurate, and reproducible determination of PV, BV, and dynamic monitoring of changes following fluid administration.
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Gillen, C. M., A. Takamata, G. W. Mack, and E. R. Nadel. "Measurement of plasma volume in rats with use of fluorescent-labeled albumin molecules." Journal of Applied Physiology 76, no. 1 (January 1, 1994): 485–89. http://dx.doi.org/10.1152/jappl.1994.76.1.485.
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We describe a method for measuring plasma volume (PV) in small animals that allows small sample sizes but does not require the use of radioisotopes and thus is a convenient approach for making repeated measurements. Texas Red covalently bound to albumin (TR-A) was used in a typical indicator-dilution technique to measure PV. The relative fluorescent intensity of TR-A is linear to its concentration (up to 0.15 mg/ml) at an excitation lambda of 590 nm and an emission lambda of 610 nm. Catheters were inserted through the right jugular vein of anesthetized rats and threaded into the vena cava. A 0.5-ml control blood sample was taken, a measured quantity of TR-A was injected, and the catheter was flushed with saline. A 0.5-ml postinjection sample was taken 5 min after TR-A injection. PV was calculated by comparing the difference between the relative fluorescent intensity of control and postinjection plasma samples to a standard. The PV of 22 rats [362 +/- 14 (SE) g] was 14.1 +/- 0.4 ml (39.6 +/- 0.9 ml/kg body wt) measured by the TR-A method and 12.8 +/- 0.4 ml (35.9 +/- 1.0 ml/kg body wt) measured by a standard radioiodinated albumin method. There was a strong correlation between PV measured by both methods in the same rat (r = 0.90, P < 0.01). Infusion experiments indicated that the TR-A method can detect acute changes in PV, and repeated measurements of PV made on a chronically instrumented rat demonstrated that the method can reliably measure PV on consecutive days.
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Kasireddy, Nithya, Jeremy C. Orie, and Damir Khismatullin. "Resonant Acoustic Tweezing Spectroscopy for Small-Volume Noncontact Assessment of Blood Coagulation." Blood 132, Supplement 1 (November 29, 2018): 3785. http://dx.doi.org/10.1182/blood-2018-99-117902.
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Abstract Introduction: Measurement and interpretation of mechanical properties of whole blood and blood plasma are important diagnosis and treatment monitoring of various conditions like coagulopathy, hemophilia, sickle cell disease and many cardiovascular disorders. Many of the current techniques like thromboelastography, micro-viscometry or microfluidic devices used for this purpose require a large sample volume and/or may be prone to measurement errors due to sample contact with device walls. To address these issues, we developed a single-drop non-contact method for blood rheological analysis, referred to as "acoustic tweezing rheometry". With sample volume as small as 4 μL, our innovative technology has been successfully applied for assessment of whole blood and blood plasma coagulation. Here, we present the extension of this technology to resonant spectroscopic measurement of blood viscoelasticity. Materials and Methods: The schematic of the acoustic tweezing device is shown in (Figure 1A). The standing acoustic wave field between the transducer and reflector generates the acoustic radiation force on the biological sample that traps it in a host fluid (e.g., air). Sample tweezing (force-induced deformation and translational motion of the trapped sample) is achieved by amplitude modulation of the acoustic tweezing signal at high frequency and then decrease the frequency continuously until the lower limit for sample trapping is reached. During this frequency sweep, shape changes of the sample were recorded (Figure 1B) by a photodetector and a high-speed camera (Figure 1A). The amplitude-frequency response of the sample was obtained from raw data analysis, with the amplitude being the maximum deflection of the sample height from its equilibrium value. Dynamic (shear) viscosity and elasticity of the sample were assessed from the quality factor of the amplitude-frequency response (Figure 1C) and the resonance frequency, respectively. Results and Discussion: The quality factor analysis predicted that the dynamic viscosity of commercial normal control blood plasma was 1.5 mPa·s at room temperature, which agreed with previous large-sample-volume measurements. Once re-calcified, the resonance frequency of blood plasma and thus its shear elasticity increased due to clot formation until reaching a plateau in 5 min (Figure 1D). Using this graphical output (referred to as "tweezograph"), the following coagulation parameters can be extracted: clot initiation time, clotting rate, clotting time, and maximum clot elasticity. Conclusions: Resonant acoustic tweezing spectroscopy can accurately measure dynamic viscosity and elasticity of whole blood and blood plasma with a small drop of the sample and without artefacts or measurement errors due to sample contact with device walls. This technique can be applied for rapid assessment of whole blood and blood plasma coagulation. Acknowledgments: This study has been supported by U.S. National Science Foundation grant 1438537, American Heart Association Grant-in-Aid 13GRNT17200013, and Tulane University intramural grants. The acoustic tweezing technology is protected by pending patents PCT/US14/55559 and PCT/US2018/014879. Disclosures Khismatullin: Levisonics Inc: Equity Ownership, Membership on an entity's Board of Directors or advisory committees, Patents & Royalties.
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J Hay, Halcro, and Donald B Cheek. "Proton Induced X-ray Emission for Measurement of Bromine in Micro Quantities of Human Blood Plasma." Australian Journal of Physics 40, no. 2 (1987): 207. http://dx.doi.org/10.1071/ph870207.
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Studies have been made with proton induced X-ray emission to measure bromine in human blood plasma, and thereby estimate the extracellular fluid volume which is a determinant of biological importance. With careful attention to sample preparation, the method is precise. Since only very small amounts (less than O� 1 ml) of material are needed, the technique is applicable to the newborn and to small mammals.
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Heltne, J. K., M. Farstad, T. Lund, M. E. Koller, K. Matre, S. E. Rynning, and P. Husby. "Determination of plasma volume in anaesthetized piglets using the carbon monoxide (CO) method." Laboratory Animals 36, no. 3 (July 1, 2002): 344–50. http://dx.doi.org/10.1258/002367702320162333.
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Based on measurements of the circulating red blood cell volume (VRBC) in seven anaesthetized piglets using carbon monoxide (CO) as a label, plasma volume (PV) was calculated for each animal. The increase in carboxyhaemoglobin (COHb) concentration following administration of a known amount of CO into a closed circuit re-breathing system was determined by diode-array spectrophotometry. Simultaneously measured haematocrit (HCT) and haemoglobin (Hb) values were used for PV calculation. The PV values were compared with simultaneously measured PVs determined using the Evans blue technique. Mean values (SD) for PV were 1708.6 (287.3)ml and 1738.7 (412.4)ml with the CO method and the Evans blue technique, respectively. Comparison of PVs determined with the two techniques demonstrated good correlation ( r = 0.995). The mean difference between PV measurements was -29.9 ml and the limits of agreement (mean difference ±2SD) were -289.1 ml and 229.3 ml. In conclusion, the CO method can be applied easily under general anaesthesia and controlled ventilation with a simple administration system. The agreement between the compared methods was satisfactory. Plasma volume determined with the CO method is safe, accurate and has no signs of major side effects.
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Rizk, Dana V., Daniel Meier, Ruben M. Sandoval, Teresa Chacana, Erinn S. Reilly, Jesse C. Seegmiller, Emmanuel DeNoia, James S. Strickland, Joseph Muldoon, and Bruce A. Molitoris. "A Novel Method for Rapid Bedside Measurement of GFR." Journal of the American Society of Nephrology 29, no. 6 (May 10, 2018): 1609–13. http://dx.doi.org/10.1681/asn.2018020160.
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Background Direct quantitative measurement of GFR (mGFR) remains a specialized task primarily performed in research settings. Multiple formulas for estimating GFR have been developed that use the readily available endogenous biomarkers creatinine and/or cystatin C. However, eGFR formulas have limitations, and an accurate mGFR is necessary in some clinical situations and for certain patient populations. We conducted a prospective, open-label study to evaluate a novel rapid technique for determining plasma volume and mGFR.Methods We developed a new exogenous biomarker, visible fluorescent injectate (VFI), consisting of a large 150-kD rhodamine derivative and small 5-kD fluorescein carboxymethylated dextrans. After a single intravenous injection of VFI, plasma volume and mGFR can be determined on the basis of the plasma pharmacokinetics of the rhodamine derivative and fluorescein carboxymethylated dextrans, respectively. In this study involving 32 adults with normal kidney function (n=16), CKD stage 3 (n=8), or CKD stage 4 (n=8), we compared VFI-based mGFR values with values obtained by measuring iohexol plasma disappearance. VFI-based mGFR required three 0.5-ml blood draws over 3 hours; iohexol-based mGFR required five samples taken over 6 hours. Eight healthy participants received repeat VFI injections at 24 hours.Results VFI-based mGFR values showed close linear correlation with the iohexol-based mGFR values in all participants. Injections were well tolerated, including when given on consecutive days. No serious adverse events were reported. VFI-based mGFR was highly reproducible.Conclusions The VFI-based approach allows for the rapid determination of mGFR at the bedside while maintaining patient safety and measurement accuracy and reproducibility.
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Ikezawa, Satoshi, Muneaki Wakamatsu, Joanna Pawłat, and Toshitsugu Ueda. "Control of a Micro-Droplet for Laser-Induced Breakdown Spectroscopy Solution Measurement." Solid State Phenomena 147-149 (January 2009): 639–44. http://dx.doi.org/10.4028/www.scientific.net/ssp.147-149.639.
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In this paper, laser-induced breakdown spectroscopy (LIBS) using micro-droplet NaCl solution and set-up for control of micro-droplets are described. Micro-droplets controlling technique is important for solution quantitative analysis. In this study, micro-droplet ejection system for sampling is designed and presented. This micro-droplet ejection system enable a constant volume of the sample liquid to be obtained and it takes advantage of the liquid physical state; the density of the solution can be controlled accurately. The method presented here generates small droplets (diameter 30 μm) by confining the entire volume of the sample material in the laser beam spot area (minimum beam spot diameter: 53.2 μm) and separating it from its surroundings. Using this liquid micronizing method, improved sensitivities are obtained. The Advantage of LIBS is a useful method for determining the elemental composition of various materials regardless of their physical state (solid, liquid, or gas) and without any preprocessing; it is a type of atomic emission spectroscopy (AES). Despite the advantage of qualitative analysis, quantitative analysis is difficult because of sample and plasma fluctuations. Generating constant volume of micro-size sample and proper sample control technique contribute to LIBS quantitative analysis.
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Ceriotti, F., P. A. Bonini, M. Murone, L. Barenghi, M. Luzzana, A. Mosca, M. Ripamonti, and L. Rossi-Bernardi. "Measurement of lipase activity by a differential pH technique." Clinical Chemistry 31, no. 2 (February 1, 1985): 257–60. http://dx.doi.org/10.1093/clinchem/31.2.257.
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Abstract This is a new electrochemical method for determination of lipase activity in biological fluids, including serum, plasma, and duodenal juice. Advantages of turbidimetric methods--short reaction time, and small sample and reagent volumes--are combined with those of titrimetric methods: measurement of absolute activity (i.e., no standardization required), saturated substrate conditions, and direct measurement of reaction products. The proposed method is easy, inexpensive, and takes only 3 min. Precision is good: CV = 3.74% within day and 7.3% between days at the clinical-decision concentration, CV = 1.86% within day and 4.65% between days for above-normal lipase activities. The standard curve is linear up to 4500 U/L. Results (y) correlate well with those by turbidimetry (x): y = 0.9287x - 65.3 (r = 0.9719). Reference values are between 0 and 130 U/L.
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Sambataro, M., K. Thomaseth, G. Pacini, C. Robaudo, A. Carraro, M. Bruseghin, E. Brocco, et al. "Plasma clearance rate of 51Cr-EDTA provides a precise and convenient technique for measurement of glomerular filtration rate in diabetic humans." Journal of the American Society of Nephrology 7, no. 1 (January 1996): 118–27. http://dx.doi.org/10.1681/asn.v71118.
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It has not yet been fully clarified whether the plasma or renal clearance approach is the most reliable to investigate GFR in humans. The study presented here aimed to compare plasma decay with renal clearance of 51Cr-EDTA in 27 diabetic patients with patterns of renal function broadly dispersed in a wide range of values. Moreover, the comparison was also performed with renal clearance of nonlabeled iothalamate in a subgroup of 17 patients. A biexponential function was found to fulfill statistical and heuristic criteria for the modeling analysis of plasma 51Cr-EDTA decay with 19 samples after bolus intravenous 51Cr-EDTA injection. Individual GFR values from 51Cr-EDTA plasma clearance highly correlated with those from renal clearance (r2 = 0.977, P < 0.0001), but resulted on average about 2.5 mL.min-1.1.73 m-2 higher (66.8 +/- 6.5 mL.min-1.1.73 m-2 (mean +/- SE) versus 64.3 +/- 6.4, P < 0.02). This difference remained relatively constant from patients with normal renal function to those with impaired renal function, suggesting that the plasma clearance is slightly less accurate than renal clearance approach because of a constant extrarenal clearance rate. In the subgroup studied, a similar difference was found between GFR values from 51Cr-EDTA plasma clearance (84.7 +/- 7.3) and renal clearance of iothalamate (82.8 +/- 7.3), although not statistically significant (P = 0.4). Individual GFR values well correlated (r2 = 0.913, P < 0.0001). The precision and reproducibility of the experimental approaches were assessed by comparing three coefficients of variation: (1) CVb of the bolus injection, because of measurement errors; (2) CVc of the continuous infusion, which additionally includes errors of urine volume measurement and physiological variability in the same day; and (3) CVr of repeated measurements by using bolus injection, which also accounts for physiological variability in different days. CVc of iothalamate and 51Cr-EDTA infusions were 7.5 +/- 1.9% and 7.4 +/- 1.2% respectively. CVb and CVr of bolus injection of 51Cr-EDTA were 2.6 +/- 0.3% and 3.5 +/- 0.8% respectively. CVb and CVr of bolus injection of 51Cr-EDTA, but not CVc of iothalamate and 51Cr-EDTA infusions were twofold to tenfold lower than the percent yearly change reported in IDDM and NIDDM patients. More particularly, CVr was significantly less than CVc. In order to make the test less cumbersome, a reduced sampling schedule with seven samples was designed and validated. GFR measured with seven samples was 66.1 +/- 6.4 (P = 0.1 when compared with the full 19-sample schedule) with a CVb of 3.5 +/- 0.5%. This seven-sample protocol was not different from that obtained with the previously described simplified method of Brøchner-Mortensen (63.9 +/- 6.8, P = 0.16), yet yielding a statistically more accurate estimate (coefficient of variation for Brøchner-Mortensen method = 12.1 +/- 2.9, P = 0.004). Moreover, only bolus injection, along with modeling analysis of plasma clearance rate, allows the accurate measurement of the extracellular fluid volume, an important parameter in diabetic patients. It was concluded that the reduced seven-plasma sample protocol is able to detect as small as 4 to 5% changes per year in a single patient. Moreover, it provides precise and accurate estimate of GFR in diabetic patients with hyperfiltration, who are postulated to be at higher risk to develop renal damage.
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Atherton, N. D. "HPLC measurement of phenylalanine by direct injection of plasma onto an internal-surface reversed-phase silica support." Clinical Chemistry 35, no. 6 (June 1, 1989): 975–78. http://dx.doi.org/10.1093/clinchem/35.6.975.
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Abstract Direct-injection analysis for phenylalanine in plasma by isocratic "high-performance" liquid chromatography (HPLC) is described. For chromatographic separation I use an internal-surface reversed-phase silica support. The method involves ultraviolet detection, requires as little as 10 microL of plasma (routinely 20 microL), and supplies results in less than 7.5 min from injection. The intra-batch coefficient of variation for phenylalanine in human plasma samples (197-1104 mumol/L) ranged between 3.0% and 6.0% and the range of linearity was 10-1250 mumol/L for a 20-microL sample injection loop. The upper limit can readily be extended by using a smaller volume loop. Phenylalanine results from direct plasma injection (y) correlated well with those of a protein precipitation/HPLC technique (x): y = 0.931x + 46.4 (r = 0.951, n = 41, range 78-1344 mumol/L).
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Margarson, Michael P., and Neil C. Soni. "Plasma volume measurement in septic patients using an albumin dilution technique: comparison with the standard radio-labelled albumin method." Intensive Care Medicine 31, no. 2 (November 4, 2004): 289–95. http://dx.doi.org/10.1007/s00134-004-2481-4.
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Crawford, Matthew L., Bradley B. Collier, Meghan N. Bradley, Patricia L. Holland, Christopher M. Shuford, and Russell P. Grant. "Empiricism in Microsampling: Utilizing a Novel Lateral Flow Device and Intrinsic Normalization to Provide Accurate and Precise Clinical Analysis from a Finger Stick." Clinical Chemistry 66, no. 6 (May 13, 2020): 821–31. http://dx.doi.org/10.1093/clinchem/hvaa082.
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Abstract Background Phlebotomy plays a key role in clinical laboratory medicine but poses certain challenges for the patient and the laboratory. Dried blood spots simplify collection and stabilize specimens effectively, but clinical reference intervals are based primarily on serum or plasma. We evaluated use of dried separated blood plasma specimens to simplify plasma sample collection via finger stick; however, this sampling technique posed substantial analytical challenges. We discuss herein our efforts to overcome these challenges and provide accurate and precise clinical measurements. Methods Microsamples of whole blood were collected via finger stick using a collection device employing laminar-flow separation of cellular blood and plasma fractions with subsequent desiccation. Samples were analyzed on modern autoanalyzers with FDA-approved reagent and calibration systems, as well as commercially available reagents with laboratory-developed assay parameters. Measured analyte concentrations from extracted dried plasma samples were normalized to a coextracted endogenous analyte, chloride. Results Chloride normalization reduced variability incurred through extraction and undefined plasma volume. Excellent correlation of normalized measurements from dried finger-stick samples (whole blood and plasma) versus matched venous samples facilitated developing mathematical transformations to provide concordance between specimen types. Independent end-to-end performance verification yielded mean biases <3% for the 5 analytes evaluated relative to venous drawn samples analyzed on FDA-approved measurement systems. Conclusion Challenges inherent with this microsampling technique and alternate sample matrix were obviated through capabilities of modern autoanalyzers and implementation of chloride normalization. These results demonstrate that self-collected microsamples from a finger stick can give results concordant with those of venous samples.
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Gonçalves, Rilvani C., Carlos Alberto Buschpigell, and Antonio Augusto Lopes. "Circulating blood volumes in pulmonary hypertension associated with erythrocytosis – the effects of therapeutic hemodilution." Cardiology in the Young 13, no. 6 (December 2003): 544–50. http://dx.doi.org/10.1017/s1047951103001148.
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In the Eisenmenger syndrome, indirect estimation of blood volumes may provide quite inaccurate information when seeking to define therapeutic strategies. With this in mind, we analyzed directly the red cell mass, plasma volume, and total blood volume in patients with pulmonary hypertension associated with congenital cardiac defects and erythrocytosis, comparing the results with the respective estimated volumes, and examining the changes induced by therapeutic hemodilution.Thus, we studied 17 patients with the Eisenmenger syndrome, aged from 15 to 53 years, in the basal condition, studying 12 of them both before and after hemodilution. We also investigated five individuals with minimal cardiac lesions, aged from 14 to 42 years, as controls. Red cell mass and plasma volumes were measured using [51 chromium]-sodium chromate and [131iodine]-albumin respectively. Hemodilution was planned so as to exchange 10% of the total blood volume, using 40,000 molecular weight dextran simultaneously to replace the removed volume. The mean values of the red cell mass, plasma volume and total blood volume as assessed by radionuclide techniques were 32%, 31% and 32% higher than the respective volumes as estimated using empirical mathematical formulas (p < 0.002). The measured total blood volume was also 19% higher in the patients compared with controls. Following a period of 5 days after hemodilution, we noted a 13% reduction in red cell mass (p = 0.046), and 10% reduction in total blood volume (p = 0.02), albeit with no changes in the plasma volume.We conclude that direct measurement of blood volumes is useful for proper management of these patients, and provides results that are considerably different from those obtained by empirical estimations.
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Baldassarre, Damiano, Mauro Amato, Carlo Palombo, Carmela Morizzo, Linda Pustina, and Cesare R. Sirtori. "Time course of forearm arterial compliance changes during reactive hyperemia." American Journal of Physiology-Heart and Circulatory Physiology 281, no. 3 (September 1, 2001): H1093—H1103. http://dx.doi.org/10.1152/ajpheart.2001.281.3.h1093.
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Ultrasonic studies have shown that arterial compliance increases after prolonged ischemia. The objective of the present study was to develop an alternative plethysmographic method to investigate compliance, exploring validity and clinical applicability. Forearm pulse volume (FPV) and blood pressure (BP) were used to establish the FPV-BP relationship. Forearm arterial compliance (FAC) was measured, and the area under the FAC-BP curve (FACAUC) was determined. The time course curve of compliance changes during reactive hyperemia was obtained by continuous measurements of FACAUCfor 20 s before and for 300 s after arterial occlusion. This technique allows us to effectively assess compliance changes during reactive hyperemia. Furthermore, the selected measurement protocol indicated the necessity for continuous measurements to detect “true” maximal FACAUCchanges. On multivariate analysis, preischemic FACAUCwas mainly affected by sex, peak FACAUCwas affected by sex and systolic BP, percent changes were affected by plasma high-density and low-density lipoprotein cholesterol, peak time was affected by age and body mass index, and descent time was affected by plasma triglyceride levels. The proposed technique is highly sensitive and well comparable with the generally accepted echotracking system. It may thus be considered as an alternative tool to detect and monitor compliance changes induced by arterial occlusion.
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Pavlin, D. J., R. Haschke, M. L. Nessly, and F. W. Cheney. "Endogenous plasma proteins in edematous lungs and alveolar fluid in rabbits." Journal of Applied Physiology 59, no. 6 (December 1, 1985): 1971–77. http://dx.doi.org/10.1152/jappl.1985.59.6.1971.
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In this study, we compared two methods of differentiating hydrostatic and permeability types of pulmonary edema. The first method entailed measurement of protein concentrations directly in samples of alveolar fluid (AF); the second method was an indirect technique in which protein concentration in extravascular extracellular water (EVECW) was calculated on the basis of separate measurements of the quantity of protein in the lung and the volume of EVECW. The concentration of albumin (Alb) and gamma-G-globulin was measured in EVECW and alveolar fluid in excised edematous rabbit lungs. Edema was caused by elevation of left ventricular end-diastolic pressure to 25 Torr (hydrostatic edema, HE) or by intravenous oleic acid, 0.09 ml/kg (permeability edema, PE). The volume of distribution of Na+ was utilized as a measure of EVECW in the lung. Protein concentration in EVECW and AF relative to plasma (EV/PL and AF/PL, respectively) was compared in the two types of edema. The EV/PL was 0.61 +/- 0.12 (SD) for Alb in He compared with 1.18 +/- 0.47 in PE (P less than 0.02). The AF/PL was 0.54 +/- 0.12 and 1.25 +/- 0.33 in HE and PE, respectively (P less than 0.001). There was good correlation between EV/PL and AF/PL for Alb (r = 0.74, P less than 0.001) but not for gamma-G-globulin. Thus EV/PL for Alb, AF/PL for Alb, and gamma-G-globulin all differentiated hydrostatic from permeability edema.
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Cousins, C., N. D. Jonker, L. M. Banks, S. Mohammadtaghi, M. J. Myers, and A. M. Peters. "Non-Invasive Measurement of Microvascular Permeability to a Small Solute in Man: Validation of the Technique." Clinical Science 89, no. 2 (August 1, 1995): 191–200. http://dx.doi.org/10.1042/cs0890191.
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1. The purpose of the study was to evaluate a non-invasive technique for measurement of microvascular permeability to a small hydrophilic solute. 2. The technique measures the clearance of 99mTc-labelled diethylenetriaminepenta-acetic acid (99mTc-DTPA) from plasma into interstitial fluid in a limb after intravenous injection and uses a scintillation probe and a technique of graphical analysis called the Patlak plot, the uptake constant of which reflects 99mTc-DTPA transfer from plasma to interstitial fluid. Using deconvolution analysis, the retention function in the limb of intravenous 99mTc-DTPA was also measured. 3. The clearance values given by these two analytical techniques were compared with clearance from the same vascular bed after bolus femoral intra-arterial injection of 99mTc-DTPA. 4. Sixteen patients undergoing routine diagnostic arteriography were studied: six received sequential femoral intra-arterial injections of 99mTc-labelled human serum albumin (HSA) and 99mTc-DTPA, two received sequential intra-arterial and intravenous injections of 99mTc-HSA and eight received sequential intra-arterial and intravenous injections of 99mTc-DTPA. Tissue uptake and clearance were recorded from the limb with a scintillation probe and plasma clearance by arterial blood sampling. Tracer recirculation was addressed using a second scintillation probe over the contralateral limb. 5. After intra-arterial injection, 99mTc-HSA clearance was monoexponential, reflecting intravascular transit, and was completed by 2–5 min in seven subjects and in about 10 min in one. The corresponding 99mTc-DTPA clearance curves in the six subjects who also received intra-arterial DTPA were biexponential, analysis of which yielded a 99mTc-DTPA extraction fraction of about 0.6. By comparison with 99mTc-HSA clearance, the first exponential clearly corresponded to intravascular transit of unextracted 99mTc-DTPA. 6. In the eight patients given sequential intra-arterial and intravenous injections of 99mTc-DTPA, the second exponential recorded after intra-arterial injection, representing 99mTc-DTPA clearance from the interstitial fluid, agreed well with (a) the Patlak uptake constant recorded over the limb after intravenous injection, representing clearance from plasma into the interstitial fluid and (b) the retention function of 99mTc-DTPA in a limb calculated by deconvolution analysis. The mean clearance following intraarterial injection (expressed in relation to extracellular fluid volume) was 9.6 (SD 2.4) ml min−1 100 ml−1, while the corresponding mean clearance after intravenous injection was 8.8 (2.1) ml min−1 100 ml−1 calculated by Patlak analysis and 10.5 (2.7) ml min−1 100 ml−1 by deconvolution analysis. 7. We conclude that, under the conditions of measurement, 99mTc-DTPA is about 60% extracted into the interstitial fluid in a single pass through an extremity and that clearance into the extravascular space can be measured with reasonable accuracy after intravenous injection.
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Klassen, D. K., M. R. Weir, and E. U. Buddemeyer. "Simultaneous measurements of glomerular filtration rate by two radioisotopic methods in patients without renal impairment." Journal of the American Society of Nephrology 3, no. 1 (July 1992): 108–12. http://dx.doi.org/10.1681/asn.v31108.
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Isotopic clearance techniques have been widely used to measure GFR but may give variable results depending on the level of renal function and the technique used. GFR, measured by the technique of plasma disappearance of 99mTc-labeled diethylenetriaminopentacetic acid ([99mTc]DTPA) was compared with simultaneously obtained urinary clearance of [99mTc]DTPA. GFR was also measured by concurrent 24-h clearance of creatinine. Forty-six measurements of GFR were obtained in 12 patients who had no evidence of renal disease. Plasma disappearance was measured from three timed plasma samples collected 60 to 180 min after the bolus injection of 200 microCi of [99mTc]DTPA and was calculated as the product of the volume of distribution (milliliters) at time zero and the clearance rate (per minute) as determined by the regression of the monoexponential plot. Urinary clearance was measured as the average of 3 1-h urinary clearances collected after a water diuresis was established. GFR measured by plasma disappearance was significantly greater (P less than 0.001) than GFR measured simultaneously by urinary clearance. There was a linear correlation between GFR measured by urinary clearance and that measured by plasma clearance (r = 0.994). Plasma clearance exceeded urinary clearance by a constant factor of 1.3 over the range studied (urinary clearance range, 49 to 94 mL/min/1.73 m2). It was concluded that at relatively a normal GFR, the plasma clearance of [99mTc]DTPA consistently overestimates the urinary clearance of [99mTc]DTPA.
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Beckett, W. S., N. B. Vroman, D. Nigro, S. Thompson-Gorman, J. E. Wilkerson, and S. M. Fortney. "Effect of prolonged bed rest on lung volume in normal individuals." Journal of Applied Physiology 61, no. 3 (September 1, 1986): 919–25. http://dx.doi.org/10.1152/jappl.1986.61.3.919.
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Pulmonary function was assessed in supine subjects before, during, and after three separate bed-rest studies of 11 and 12 days duration. Forced vital capacity (FVC) increased during bed rest in each subject. Total lung capacity (TLC) was measured by helium dilution in one bed-rest study and increased in each subject, while residual volume and functional residual capacity of the respiratory system did not change. No change in FVC was found in an ambulatory control group using identical measurement techniques. Maintaining base-line plasma volume during one bed rest by the use of exogenous estrogen did not prevent an increase in FVC, and decreasing plasma volume with diuretics in ambulatory subjects to the same degree as seen in the bed rests did not cause an increase in FVC. We conclude that prolonged bed rest results in a small significant increase in TLC and that this change is not dependent on alterations in plasma volume.
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Ball, M. J., I. K. Robertson, and M. Woods. "Reflotron Cholesterol Measurement in General Practice: Accuracy and Detection of Errors." Annals of Clinical Biochemistry: International Journal of Laboratory Medicine 31, no. 6 (November 1994): 556–60. http://dx.doi.org/10.1177/000456329403100605.
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Comparison of cholesterol determinations by nurses using a Reflotron analyser in a general practice setting showed a good correlation with plasma cholesterol determinations by wet chemistry in a clinical biochemistry laboratory. A limited number of comparisons did, however, give a much lower result on the Reflotron. In an experimental situation, small sample volumes (which could result from poor technique) were shown to produce falsely low readings. A simple method which may immediately detect falsely low Reflotron readings is discussed.
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Fraser, W. D., B. H. Durham, J. L. Berry, and E. B. Mawer. "Measurement of Plasma 1,25 Dihydroxyvitamin D Using a Novel Immunoextraction Technique and Immunoassay with Iodine Labelled Vitamin D Tracer." Annals of Clinical Biochemistry: International Journal of Laboratory Medicine 34, no. 6 (November 1997): 632–37. http://dx.doi.org/10.1177/000456329703400606.
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We evaluated a novel assay for the measurement of 1,25 dihydroxyvitamin D (1,25 (OH)2D). Immunoextraction of 1,25 (OH)2D is performed using a mini column containing a solid-phase monoclonal antibody followed by radioimmunoassay (RIA) using an 125I-labelled 1,25 (OH)2D derivative tracer and Sac-cell separation. The mean recovery of 1,25(OH)2D3 was 101%, linearity was excellent, inter- and intra-assay coefficients of variation were 9, 8 and 13% and 11, 10 and 14% at low, medium and high concentrations of 1,25(OH)2D3, respectively. The cross-reactivity of vitamin D metabolites was <0·0015% for 25-hydroxyvitamin D3, 24, 25 dihydroxyvitamin D3 and dihydrotachysterol and 0·54% for lα calcidol. 1,25 dihydroxyvitamin D2 cross-reactivity was 79%. The detection limit of the assay was 5pmol/L. Comparison with a commercial radio receptor assay (RRA) and an in-house RIA gave regression equations of y = 0·94x+11·8 ( r = 0·98) and y = 0·91x-1·7 ( r = 0.95), respectively, with no major discrepancies between the methods in all patient groups studied. Plasma concentrations of 1,25 (OH)2D obtained with the assay were as follows: normal, unsupplemented subjects: mean 88, range 48–155 pmol/L, n = 68, patients with chronic renal failure: mean 11, range 3–36 pmol/L, n = 27, primary hyperparathyroidism: mean 198, range 130–299 pmol/L, n = 23, Paget's disease: mean 92, range 42–149 pmol/L, n = 24, osteomalacia: mean 43, range 27–61 pmol/L, n = 9. A minimum sample volume of 300 μL is required, the hands-on time is significantly less than other commercial assays and the measuring procedure is gamma counting rather than scintillation counting. The assay offers several advantages over previous methods and should allow more laboratories to offer measurement of 1,25 (OH)2D as part of their repertoire.
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Hinghofer-Szalkay, H. "Method of high-precision microsample blood and plasma mass densitometry." Journal of Applied Physiology 60, no. 3 (March 1, 1986): 1082–88. http://dx.doi.org/10.1152/jappl.1986.60.3.1082.
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The reliability of the mechanical oscillator technique (MOT) for blood and plasma mass density measurements on small samples is quantified in this paper. Sources of measurement errors that can reduce both the accuracy and precision of density determinations include storage of plasma samples, inhomogeneity of blood samples, and density reading before adequate temperature equilibration. Measurements on fractions from identical samples and repeated samplings from test subjects under steady-state conditions revealed a 10(-2) g/l reproducibility of density readings. The mean plasma density (PD) readings did not change significantly after up to 1-wk storage at +4 degrees C or up to 2 mo storage at -20 degrees C. The variability of the PD findings increased with storage time and were generally higher with storage at -20 degrees C, compared with +4 degrees C. Densitometers of different sizes were used to evaluate rheological influences on blood density (BD) readings. Linear correlations between PD and plasma protein concentration, between BD and blood hemoglobin concentration, and between erythrocyte density and mean corpuscular hemoglobin concentration were significant (P less than 0.001). Rapid density measurements with up to 10(-2) g/l reliability on small (less than 0.1 ml) volumes of biological fluids and continuous blood densitometry can be performed with use of the MOT.
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Chen, Zhensheng, Ian J. Griffin, Yana L. Kriseman, Lily K. Liang, and Steven A. Abrams. "Inductively Coupled Plasma Mass Spectrometric Analysis of Calcium Isotopes in Human Serum: A Low-Sample-Volume Acid-Equilibration Method." Clinical Chemistry 49, no. 12 (December 1, 2003): 2050–55. http://dx.doi.org/10.1373/clinchem.2003.025692.
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Abstract Background: Analytical methods for measuring the calcium isotope distribution in enriched human serum samples that use low blood volumes, simple preparation methods, and rapid analysis are important in clinical studies of calcium kinetics. Previously, sample preparation by oxalate precipitation typically required 500 μL of serum. This method was time-consuming, and the blood volume required was limiting in circumstances when only a small amount of serum could be obtained. Methods: Serum was collected from humans who were administered 42Ca, and 20 μL of serum was mixed with 2 mL of 0.22–0.67 mol/L HNO3 at room temperature for between 1 min and 16 h. The 42Ca/43Ca ratio in the supernatant was measured by a magnetic sector inductively coupled plasma mass spectrometer (ICP-MS). Calcium isotope ratios from these equilibration solutions were compared with data from oxalate-precipitated serum samples to determine the optimum equilibrium time and the effect of acid concentration on equilibrium. Results: Various amounts of aggregated particles developed in different acid-serum mixtures. These affected the time required for isotope equilibration in the mixture. The shortest equilibrium time needed for the calcium isotopes varied from 1 to 6 h for samples acidified with 0.22–0.45 mol/L HNO3. Data obtained from these solutions were consistent with data from oxalate-precipitated calcium. The precision of 42Ca/43Ca ratio measurements was better than 0.5%. Conclusions: We have developed a simple, rapid sample preparation technique for ICP-MS analysis in which 20 μL of serum can be used for accurate measurement of the calcium isotope distribution in a sample with good precision and a rapid analysis time.
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Logan, Jean, Joanna S. Fowler, Nora D. Volkow, Gene-Jack Wang, Yu-Shin Ding, and David L. Alexoff. "Distribution Volume Ratios without Blood Sampling from Graphical Analysis of PET Data." Journal of Cerebral Blood Flow & Metabolism 16, no. 5 (September 1996): 834–40. http://dx.doi.org/10.1097/00004647-199609000-00008.
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The distribution volume ratio (DVR), which is a linear function of receptor availability, is widely used as a model parameter in imaging studies. The DVR corresponds to the ratio of the DV of a receptor-containing region to a nonreceptor region and generally requires the measurement of an arterial input function. Here we propose a graphical method for determining the DVR that does not require blood sampling. This method uses data from a nonreceptor region with an average tissue-to-plasma efflux constant k2 to approximate the plasma integral. Data from positron emission tomography studies with [15C]raclopride (n = 20) and [11C] d-threo-methylphenidate ([11C]dMP) (n = 8) in which plasma data were taken and used to compare results from two graphical methods, one that uses plasma data and one that does not. k2 was 0.163 and 0.051 min−1 for [11C]raclopride and [11C]dMP, respectively. Results from both methods were very similar, and the average percentage difference between the methods was −0.11% for [11C]raclopride and 0.46% for [11C]dMP for DVR of basal ganglia (BG) to cerebellum (CB). Good agreement between the two methods was also achieved for DVR images created by both methods. This technique provides an alternative method of analysis not requiring blood sampling that gives equivalent results for the two ligands studied. It requires initial studies with blood sampling to determine the average kinetic constant and to test applicability. In some cases, it may be possible to neglect the b̅2 term if the BG/CB ratio becomes reasonably constant for a sufficiently long period of time over the course of the experiment.
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Fouda, Genevieve G., Rose F. G. Leke, Carole Long, Pierre Druilhe, Ainong Zhou, Diane Wallace Taylor, and Armead H. Johnson. "Multiplex Assay for Simultaneous Measurement of Antibodies to Multiple Plasmodium falciparum Antigens." Clinical and Vaccine Immunology 13, no. 12 (October 11, 2006): 1307–13. http://dx.doi.org/10.1128/cvi.00183-06.
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ABSTRACTAntibodies toPlasmodium falciparumare classically measured using the enzyme-linked immunosorbent assay (ELISA). Although highly sensitive, this technique is labor-intensive when large numbers of samples must be screened against multiple antigens. The suspension array technology (SAT) might be an alterative to ELISA, as it allows measurement of antibodies against multiple antigens simultaneously with a small volume of sample. This study sought to adapt the new SAT multiplex system for measuring antibodies against nine malarial vaccine candidate antigens, including recombinant proteins from two variants of merozoite surface protein 1, two variants of apical merozoite antigen 1, erythrocyte binding antigen 175, merozoite surface protein 3, and peptides from the circumsporozoite protein, ring erythrocyte surface antigen, and liver-stage antigen 1. Various concentrations of the antigens were coupled to microspheres with different spectral addresses, and plasma samples from Cameroonian adults were screened by SAT in mono- and multiplex formats and by ELISA. Optimal amounts of protein required to perform the SAT assay were 10- to 100-fold less than that needed for ELISA. Excellent agreement was found between the single and multiplex formats (R≥ 0.96), even when two variants of the same antigen were used. The multiplex assay was rapid, reproducible, required less than 1 μl of plasma, and had a good correlation with ELISA. Thus, SAT provides an important new tool for studying the immune response to malaria rapidly and efficiently in large populations, even when the amount of plasma available is limited, e.g., in studies of neonates or finger-prick blood.
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Gore, Christopher J., Will G. Hopkins, and Caroline M. Burge. "Errors of measurement for blood volume parameters: a meta-analysis." Journal of Applied Physiology 99, no. 5 (November 2005): 1745–58. http://dx.doi.org/10.1152/japplphysiol.00505.2005.
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The volume of red blood cells (VRBC) is used routinely in the diagnostic workup of polycythemia, in assessing the efficacy of erythropoietin administration, and to study factors affecting oxygen transport. However, errors of various methods of measurement of VRBCand related parameters are not well characterized. We meta-analyzed 346 estimates of error of measurement of VRBCfor techniques based on Evans blue (VRBC,Evans),51chromium-labeled red blood cells (VRBC,51Cr), and carbon monoxide (CO) rebreathing (VRBC,CO), as well as hemoglobin mass with the carbon-monoxide method (MHb,CO), in athletes and active and inactive subjects undergoing various experimental and control treatments lasting minutes to months. Subject characteristics and experimental treatments had little effect on error of measurement, but measures with the smallest error showed some increase in error with increasing time between trials. Adjusted to 1 day between trials and expressed as coefficients of variation, mean errors for MHb,CO(2.2%; 90% confidence interval 1.4–3.5%) and VRBC,51Cr(2.8%; 2.4–3.2%) were much less than those for VRBC,Evans(6.7%; 4.9–9.4%) and VRBC,CO(6.7%; 3.4–14%). Most of the error of VRBC,Evanswas due to error in measurement of volume of plasma via Evans blue dye (6.0%; 4.5–7.8%), which is the basis of VRBC,Evans. Most of the error in VRBC,COwas due to estimates from laboratories with a relatively large error in MHb,CO, the basis of VRBC,CO. VRBC,51Crand MHb,COare the best measures for research on blood-related changes in oxygen transport. With care, VRBC,Evansis suitable for clinical applications of blood-volume measurement.
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Johansen, Lars Bo, Regitze Videbæk, Mette Hammerum, and Peter Norsk. "Underestimation of plasma volume changes in humans by hematocrit/hemoglobin method." American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 274, no. 1 (January 1, 1998): R126—R130. http://dx.doi.org/10.1152/ajpregu.1998.274.1.r126.
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During water immersion in humans, the use of changes in hematocrit (Hct) and hemoglobin concentration (Hb) underestimates the relative changes in plasma volume (PV) as measured directly with Evans blue (EB). It is not known whether the same is the case during posture changes. Therefore, changes in PV were determined with an EB dilution technique in 10 males before, during, and after an acute posture change from seated to 6° head-down tilt (HDT). The EB method was improved to take into account changes in transcapillary escape rate of albumin-bound EB. Furthermore, blood was sampled from a central venous catheter. Hct and Hb were simultaneously measured. During HDT, PV determined with EB increased by 9.3 ± 2.0% but increased only 4.5 ± 0.9% when calculated with the Hct/Hb method ( P < 0.05 vs. EB measurements). Thus use of the Hct/Hb method in humans leads to underestimation of the change in PV by as much as 50% during an acute change in posture. Therefore, a direct tracer-dilution method must be used for accurate estimations of changes in PV during changes in posture or other antiorthostatic maneuvers.
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Kasperczuk, A., T. Pisarczyk, T. Chodukowski, Z. Kalinowska, W. Stepniewski, K. Jach, R. Swierczynski, et al. "Efficiency of ablative plasma energy transfer into a massive aluminum target using different atomic number ablators." Laser and Particle Beams 33, no. 3 (April 30, 2015): 379–86. http://dx.doi.org/10.1017/s0263034615000452.
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AbstractThis paper aims at investigation of efficiency of an ablative plasma energy transfer into a massive aluminum target using different atomic number ablators. For this reason, several target materials representing a wide range of atomic numbers (Z = 3.5–73) were used. The experiment was carried out at the iodine Prague Asterix Laser System. The laser provided a 250 ps pulse with energy of 130 J at the third harmonic frequency (λ3 = 0.438 μm). To study the plasma stream configurations a four-frame X-ray pinhole camera was used. The electron temperature of the plasma in the near-surface target region was measured by means of an X-ray spectroscopy. The efficiency of the plasma energy transport to the target was determined via the crater volume measurement using the crater replica technique. The experimental results were compared with two-dimensional numerical simulations where the plasma dynamics was based on the one-fluid, two temperature model, including radiation transport in diffusive approximation and ionization kinetics. It was shown that the plasma expansion geometry plays an important role in the ablative plasma energy transfer into the target.
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De Campeneere, S., L. O. Fiems, J. M. Vanacker, B. G. Cottyn, and Ch V. Boucqué. "In vivo estimation of body composition in Belgian Blue double-muscled bulls from urea space and fasted live weight." Proceedings of the British Society of Animal Science 1999 (1999): 50. http://dx.doi.org/10.1017/s1752756200002052.
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Urea is non-toxic, not foreign to the body and it shows an even and rapid distribution throughout the total body water without any physiological effect or toxic manifestation. For these reasons and for its easy and accurate measurement, urea is an ideal tracer to estimate body composition in vivo. Total body water volume (urea space) can be estimated by dividing the total amount of urea infused by the increase in plasma urea concentration between prior to infusion and 12, 18 or 24 min after mean infusion time (Preston and Kock, 1973). In this experiment the urea infusion technique was evaluated to estimate body composition of Belgian Blue double-muscled bulls.
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Phippard, A. F., M. G. Garner, J. F. Thompson, J. M. Maclean, P. J. Fletcher, J. S. Horvath, G. G. Duggin, and D. J. Tiller. "Nonocclusive chronic vascular catheterization of conscious unrestrained baboons." Journal of Applied Physiology 61, no. 5 (November 1, 1986): 1955–58. http://dx.doi.org/10.1152/jappl.1986.61.5.1955.
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A surgical technique is described for chronic arterial and venous catheterization of unrestrained adult baboons. Vascular access was achieved through a small (5 cm) abdominal incision and an extraperitoneal approach to the iliac vessels, which minimizes postoperative morbidity, discomfort, and restriction of movement. The method permits secure but nonocclusive catheterization, confirmed by angiography. Catheters were removed without further surgery, leaving the baboons intact for reuse. Catheters placed in the distal common or proximal external iliac vessels were all patent when removed at 46–61 days. The results demonstrate arterial pressure, pulse rates, drug administration, blood sampling, and plasma volume measurement as examples of the technique's application in conscious unrestrained baboons.
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Chinard, F. P. "Quantitative assessment of epithelial lining fluid in the lung." American Journal of Physiology-Lung Cellular and Molecular Physiology 263, no. 6 (December 1, 1992): L617—L618. http://dx.doi.org/10.1152/ajplung.1992.263.6.l617.
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Current techniques for the measurement lung epithelial fluid (ELF) volume depend on the dilution by a known volume of wash fluid (bronchoalveolar lavage) of a resident solute, such as urea, in the ELF or of a foreign solute introduced at known concentration in the lavage fluid. Knowledge of the ELF volume allows calculation of solute ELF concentrations. Urea concentration in ELF is assumed to be the same as in plasma. Although epithelial permeability to urea is low, entry of urea from tissues to lavage fluid occurs during the procedure and may lead to erroneous estimates of ELF volume as may loss of foreign solutes. Ideally, the extent of urea entry or of foreign solute loss should be estimated in each lavage. Other cautions are 1) equal osmolality of wash fluid and plasma, 2) minimizing residence time of wash fluid, 3) minimizing wash fluid-to-ELF volume ratio, and 4) adequate analytic procedures.
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Agnew, R. E., W. J. McCaughey, J. D. McEvoy, D. C. Patterson, M. G. Porter, R. W. J. Steen, and T Yan. "In vivo estimation of body composition of lactating dairy cattle from urea space measurements." Proceedings of the British Society of Animal Science 2001 (2001): 206. http://dx.doi.org/10.1017/s1752756200005883.
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San Pietro and Rittenberg (1953) reported that urea appeared to meet all the requirements of a satisfactory tracer. Urea is non toxic, not foreign to the body and it shows an even and rapid distribution throughout the total body water without any physiological effect. For these reasons in addition to its easy and accurate measurement, urea is an ideal candidate tracer to estimate empty body water in vivo. Total body water volume (urea space) can be estimated by dividing the total amount of urea infused by the increase in plasma urea concentration from prior to infusion until 12 or 30 minutes after mean infusion time. Kock and Preston (1973) reported significant relationships between urea space measurements and percentage of empty body fat and water in cattle. However, Andrew et al. (1995) using 21 Holstein cows showed that prediction of empty body water using the urea space technique only explained 31 % of the variation. The objective of this experiment was to use the urea dilution technique to estimate the body composition of lactating dairy cows and produce relationships between urea space and body fat and protein content.
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Rivers, Richard J., Judy B. Beckman, and Mary D. S. Frame. "Technique for Using Video Microscopy and Indicator Dilution for Repeated Measurements of Cardiac Output in Small Animals." Anesthesiology 94, no. 3 (March 1, 2001): 489–95. http://dx.doi.org/10.1097/00000542-200103000-00021.
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Background The authors developed an indicator dilution technique for small animals to repeatedly determine cardiac output and blood volume without cardiac instrumentation or blood sampling. Methods Observations were made in the hamster (N = 32, 70 mg/kg pentobarbital) cremaster using in vivo fluorescence videomicroscopy. Fluorescein isothiocyanate-conjugated bovine serum albumin (10 mg/ml) was injected as a bolus dose (right jugular) while video recording the light intensity in a 20-microm arteriole (intensified charge-coupled device [CCD] camera at fixed gain). The intensity signal was analyzed over time (background subtracted) and calibrated to the dye concentration. The ex vivo calibration was performed using a constant optical path length (20 microm) and a range of dye and hematocrit concentrations. In vivo tube hematocrit was determined using standard methods with fluorescently labeled erythrocytes. Thus, quenching of the fluorescence signal by hemoglobin was corrected for the calibration, and the plasma space in the arteriole was determined. The steady state dye concentration measured by the light intensity at 2 min was not different from the dye concentration found by direct spectrophotometric analysis of the plasma. Results Cardiac index was calculated as milliliters of blood per minute per kilogram body weight. The calculated cardiac index was 359 +/- 18 ml.min(-1).kg(-1), which is not different from the reported values for hamsters. Cardiac output was increased twofold when enough intravenous nitroprusside or nitroglycerine was injected to decrease mean arterial pressure from 90 to 70 mmHg. Cardiac output was elevated during dobutamine infusion (16 microg.kg(-1).min(-1)) and decreased during esmolol infusion (50, 75.kg(-1).min(-1)). Blood volume determined from the steady state dye concentrations was 6.2 +/- 0.5 ml/100 g body weight, within the normal range for hamsters. Conclusions Fluorescent dye dilution and video microscopy can be used to repeatedly determine cardiac output or blood volume in small animals.
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Klaesner, Joseph W., N. Adrienne Pou, Richard E. Parker, Charlene Finney, and Robert J. Roselli. "Optical measurement of isolated canine lung filtration coefficients at normal hematocrits." Journal of Applied Physiology 83, no. 6 (December 1, 1997): 1976–85. http://dx.doi.org/10.1152/jappl.1997.83.6.1976.
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Klaesner, Joseph W., N. Adrienne Pou, Richard E. Parker, Charlene Finney, and Robert J. Roselli. Optical measurement of isolated canine lung filtration coefficients at normal hematocrits. J. Appl. Physiol. 83(6): 1976–1985, 1997.—In this study, lung filtration coefficient ( K fc) values were measured in eight isolated canine lung preparations at normal hematocrit values using three methods: gravimetric, blood-corrected gravimetric, and optical. The lungs were kept in zone 3 conditions and subjected to an average venous pressure increase of 10.24 ± 0.27 (SE) cmH2O. The resulting K fc(ml ⋅ min−1 ⋅ cmH2O−1 ⋅ 100 g dry lung wt−1) measured with the gravimetric technique was 0.420 ± 0.017, which was statistically different from the K fc measured by the blood-corrected gravimetric method (0.273 ± 0.018) or the product of the reflection coefficient (ςf) and K fc measured optically (0.272 ± 0.018). The optical method involved the use of a Cellco filter cartridge to separate red blood cells from plasma, which allowed measurement of the concentration of the tracer in plasma at normal hematocrits (34 ± 1.5). The permeability-surface area product was measured using radioactive multiple indicator-dilution methods before, during, and after venous pressure elevations. Results showed that the surface area of the lung did not change significantly during the measurement of K fc. These studies suggest that ςf K fccan be measured optically at normal hematocrits, that this measurement is not influenced by blood volume changes that occur during the measurement, and that the optical ςf K fcagrees with the K fc obtained via the blood-corrected gravimetric method.
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Elia, M., and L. C. Ward. "New techniques in nutritional assessment: Body composition methods." Proceedings of the Nutrition Society 58, no. 1 (February 1999): 33–38. http://dx.doi.org/10.1079/pns19990005.
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New techniques in air-displacement plethysmography seem to have overcome many of the previous problems of poor reproducibility and validity. These have made body-density measurements available to a larger range of individuals, including children, elderly and sick patients who often have difficulties in being submerged underwater in hydrodensitometry systems. The BOD POD air-displacement system (BOD POD body composition system; Life Measurement Instruments, Concord, CA, USA) is more precise than hydrodensitometry, is simple and rapid to operate (approximately 1 min measurements) and the results agree closely with those of hydrodensitometry (e.g. ± 3.4 % for estimation of body fat). Body line scanners employing the principles of three-dimensional photography are potentially able to measure the surface area and volume of the body and its segments even more rapidly (approximately 10s), but the validity of the measurements needs to be established. Advances in i.r. spectroscopy and mathematical modelling for calculating the area under the curve have improved precision for measuring enrichment of 2H2O in studies of water dilution (CV 0.1–0.9 % within the range of 400–1000 μl/1) in saliva, plasma and urine. The technique is rapid and compares closely with mass spectrometry (bias 1 (SD 2) %). Advances in bedside bioelectrical-impedance techniques are making possible potential measurements of skinfold thicknesses and limb muscle mass electronically. Preliminary results suggest that the electronic method is more reproducible (intra- and inter-individual reproducibility for measuring skinfold thicknesses) and associated with less bias (+ 12 %), than anthropometry (+40%). In addition to these selected examples, the ‘mobility’ or transfer of reference methods between centres has made the distinction between reference and bedside or field techniques less distinct than in the past.
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Luzin, Vladimir, Jiří Matějíček, and Thomas Gnäupel-Herold. "Through-Thickness Residual Stress Measurement by Neutron Diffraction in Cu+W Plasma Spray Coatings." Materials Science Forum 652 (May 2010): 50–56. http://dx.doi.org/10.4028/www.scientific.net/msf.652.50.
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A range of different spraying techniques can be used to coat the surfaces of engineering components. These techniques are based on different principles and can involve high temperature (plasma spray), high kinetic energy (cold spray) or both (HVOF spray – High-Velocity Oxi-Fuel). Resultant residual stress in such coatings, being a characteristic of the spraying process, can reveal details of the stress formation mechanism. When its dependence on the physical parameters and conditions of the spraying process is established, this knowledge can be used for the prediction and control of stress that occurs in applications. Neutron diffraction is a suitable method for obtaining stress distribution in such coatings. Residual stresses in two-phase Cu+W coatings made by water stabilized plasma spraying were studied. Two-phase coatings develop both significant microstress (inter-phase stress) and the stress dependence on phase content of the coating constituents. Through-thickness residual stress profiles have been measured by neutron diffraction with spatial resolution of 0.5 mm for a series of Cu+W coatings with varying volume fractions. Measurements were made in both phases in order to separate micro- and macro-stresses. Comprehensive sample characterization, measurements of the residual stresses, mechanical and thermal properties of the composite coatings enabled quantitative modeling and interpretation of the experimental data.
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Mallik, B., K. Sikdar, and D. Roy. "Synthesis and Characterization of Aluminium Base in situ Metal Matrix Composites by Spark Plasma Sintering." Journal of Materials Science Research 7, no. 1 (December 29, 2017): 14. http://dx.doi.org/10.5539/jmsr.v7n1p14.
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Fe-aluminide and alumina reinforced in-situ aluminium based metal matrix composite was prepared by spark plasma sintering (SPS) of aluminium and nanosized Fe2O3 powder mixture. In-situ reinforcements were formed during SPS by exothermal reaction between aluminium and nano-size Fe2O3 particle. The thermal characteristics of the in-situ reaction were studied by differential scanning calorimetry (DSC). Field Emission Scanning Electron Microscopy (FESEM) along with the Energy Dispersive Spectroscopy (EDS) and X-ray diffraction (XRD) techniques were used to study the microstructural architecture of the composites as a function of SPS temperature and the volume fraction of reinforcement. Microhardness measurement of the composite shows significant increase in hardness with increase in SPS temperature and volume fraction of secondary phase.
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Jones, Charlotte, Gareth J. Dunseath, Jessica Lemon, and Stephen D. Luzio. "Microsampling Collection Methods for Measurement of C-peptide in Whole Blood." Journal of Diabetes Science and Technology 12, no. 5 (March 9, 2018): 1024–28. http://dx.doi.org/10.1177/1932296818763464.
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Background: Microsampling techniques are alternative methods to venous sampling for obtaining blood for measurement of circulating biomarkers, offering the convenience of reduced sample volume and elimination of the need for phlebotomists. Dried blood spot (DBS) microsampling methods have been used for many years while more recently a volumetric absorptive microsampling device (VAMS™) has been introduced. In diabetes mellitus, circulating C-peptide is commonly used as an indicator of endogenous insulin secretion and clinical measurement can aid in diagnosis as well as informing on therapy. This pilot study investigated the effectiveness of microsampling collection of capillary blood for measurement of C-peptide. Methods: Capillary blood was collected into capillary tubes and centrifuged for plasma samples. Simultaneous samples were also collected using both microsampling methods (DBS and VAMS). Blood from both microsamplers was extracted prior to assaying for C-peptide alongside the corresponding plasma samples, using specific immunoassays and results obtained from microsampling compared to the reference plasma concentrations. Stability was determined by collecting duplicate DBS and VAMS and assaying both in a single assay after storing one at −20°C immediately and one at room temperature for 48 hours post-collection. Results: Good agreement was observed between C-peptide concentrations in plasma and equivalent DBS and VAMS samples ( R2 = .929 and .9231, DBS and VAMS, respectively), with mean differences of 75.7 and 8.4 pmol/L observed for DBS and VAMS. Small decreases in C-peptide of 11.6% and 0.1% were observed after 48 hours storage for DBS and VAMS, respectively. Conclusions: C-peptide collected using DBS and VAMS showed good agreement with reference plasma concentrations, suggesting both would be an effective microsampling method for collection and measurement of C-peptide.
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Morla, Luciana, Oliver Shore, I. Jeanette Lynch, Matthew E. Merritt, and Charles S. Wingo. "A noninvasive method to study the evolution of extracellular fluid volume in mice using time-domain nuclear magnetic resonance." American Journal of Physiology-Renal Physiology 319, no. 1 (July 1, 2020): F115—F124. http://dx.doi.org/10.1152/ajprenal.00377.2019.
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Maintaining water homeostasis is fundamental for cellular function. Many diseases and drugs affect water balance and plasma osmolality. Water homeostasis studies in small animals require the use of invasive or terminal methods that make intracellular fluid volume and extracellular fluid volume (ECF) monitoring over time stressful and time consuming. We examined the feasibility of monitoring mouse ECF by a noninvasive method using time-domain nuclear magnetic resonance (TD-NMR). This technique allows differentiation of protons in a liquid environment (free fluid) from protons in soft tissues containing a majority of either small molecules (lean) or large molecules (fat). Moreover, this apparatus enables rapid, noninvasive, and repeated measurements on the same animal. We assessed the feasibility of coupling TD-NMR analysis to a longitudinal metabolic cage study by monitoring mice daily. We determined the effect of 24-h water deprivation on mouse body parameters and detected a sequential and overlapping decrease in free fluid and lean mass during water deprivation. Finally, we studied the effect of mineralocorticoids that are known to induce a transient increase in ECF but for which no direct measurements have been performed in mice. We showed, for the first time, that mineralocorticoids induced a transient ~15% increase in free fluid in conscious mice. TD-NMR is, therefore, the first method to allow direct measurement of discrete changes in ECF in conscious small animals. This method allows analysis of kinetic changes to stimuli before investigating with terminal methods and will allow further understanding of fluid disorders.
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Johansen, L. B., N. Foldager, C. Stadeager, M. S. Kristensen, P. Bie, J. Warberg, M. Kamegai, and P. Norsk. "Plasma volume, fluid shifts, and renal responses in humans during 12 h of head-out water immersion." Journal of Applied Physiology 73, no. 2 (August 1, 1992): 539–44. http://dx.doi.org/10.1152/jappl.1992.73.2.539.
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Changes in plasma volume (PV) throughout 12 h of thermoneutral (34.5 degrees C) water immersion (WI) were evaluated in eight subjects by an improved Evans blue (EB) technique and by measurements of hematocrit (Hct), hemoglobin (Hb), and plasma protein concentrations (Pprot). Appropriate time control studies (n = 6) showed no measurable change in PV. At 30 min of immersion, EB measurements demonstrated an increase in PV of 16 +/- 2% (457 +/- 70 ml). Calculations, however, based on concomitant changes in Hct, Hb, and Pprot showed an increase in PV of only 6.9 +/- 0.9 to 10.0 +/- 0.8% at 30 min of WI. PV values based on EB measurements subsequently declined throughout WI to (but not below) the preimmersion level. Concomitantly, changes in PV calculated from Pprot values remained increased, whereas estimations of changes in PV based on Hct and Hb values returned to prestudy levels after 4 h of immersion. It is concluded that PV initially increases by 16 +/- 2% during WI and does not decline below preimmersion and control levels during 12 h of immersion despite a loss of 0.9 +/- 0.2 liter of body fluid. Furthermore, changes in Hct, Hb, and Pprot do not provide accurate measures of the changes in PV during WI in humans.
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Barbee, R. W., B. D. Perry, R. N. Re, and J. P. Murgo. "Microsphere and dilution techniques for the determination of blood flows and volumes in conscious mice." American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 263, no. 3 (September 1, 1992): R728—R733. http://dx.doi.org/10.1152/ajpregu.1992.263.3.r728.
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Although the mouse is the most commonly used transgenic species, little is known regarding cardiovascular and fluid homeostasis in this animal. Therefore, the reference microsphere and dilution techniques were adapted for the measurement of cardiac output (CO), regional blood flows, and intravascular fluid volumes in the conscious mouse. Previously acclimatized C3H mice were studied 4-5 h after surgery and recovery from anesthesia. Approximately 40,000 85Sr-labeled microspheres were injected into the left ventricle while a reference sample was withdrawn at one of two rates from the femoral artery. 51Cr and 125I were used for the determination of blood volume (BV), plasma volume (PV), and Fcells ratio (whole body hematocrit/large vessel hematocrit). CO and BV in the conscious mouse were 16 +/- 1.4 ml/min and 2.3 +/- 0.1 ml, respectively. Anesthesia lowered heart rate, blood pressure, PV, and altered the distribution of CO. Two successive injections of 15,000-20,000 microspheres were tolerated in the mouse without an increase in total peripheral resistance. The results indicate that the microsphere and indicator dilution techniques can be applied to study cardiovascular and fluid homeostasis in the mouse.
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Hutschala, Doris, Keso Skhirtladze, Andreas Zuckermann, Wilfried Wisser, Peter Jaksch, Bernhard Xaver Mayer-Helm, Heinz Burgmann, Ernst Wolner, Markus Müller, and Edda M. Tschernko. "In Vivo Measurement of Levofloxacin Penetration into Lung Tissue after Cardiac Surgery." Antimicrobial Agents and Chemotherapy 49, no. 12 (December 2005): 5107–11. http://dx.doi.org/10.1128/aac.49.12.5107-5111.2005.
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ABSTRACT Nosocomial pneumonia is a severe complication after cardiac surgery (CS). Levofloxacin, a fluoroquinolone, qualifies for the therapy of postoperative pneumonia. However, penetration properties of levofloxacin into the lung tissue could be substantially affected by CS: atelectasis, low cardiac output after CS, high volume loads, and inflammatory capillary leak potentially influence drug distribution. The aim of our study was to gain information on interstitial antibiotic concentrations in lung tissue in patients undergoing coronary artery bypass grafting with cardiopulmonary bypass. Therefore, six patients undergoing elective CS participated in this prospective study. A dose of 500 mg of levofloxacin was administered intravenously in addition to standard antibiotic prophylaxis immediately after the end of surgery. Time versus concentration profiles of levofloxacin in the interstitial lung tissue and plasma were determined. A microdialysis technique was used for lung interstitial concentration measurements. The microdialysis procedure was well tolerated in all patients and no adverse events were observed. The median area under the concentration curve (AUC) of levofloxacin in interstitial lung fluid was 18.6 μg · h/ml (range, 10.1 to 33.6). The median AUC for tissue (AUCtissue) of unbound levofloxacin/AUCtotal in plasma was 0.6 (range, 0.4 to 0.9). The median unbound AUCtissue/MIC was 2.4 (range, 1.3 to 4.2) for Pseudomonas aeruginosa. Our study demonstrated the feasibility and safety of microdialysis in human lung tissue in vivo after CS. The unbound AUC/MIC ratio revealed that levofloxacin used in the described manner was borderline sufficient for the treatment of nosocomial pneumonia caused by Klebsiella pneumoniae and insufficient for the treatment of pneumonia caused by Pseudomonas aeruginosa, because the breakpoint of 30 to 40 for AUC/MIC could not be reached by the conventionally used dosage schema in our post-CS setting. Penetration was lower than in previous reports.
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Jobin, J., and J. P. Bonjour. "Measurement of glomerular filtration rate in conscious unrestrained rats with inulin infused by implanted osmotic pumps." American Journal of Physiology-Renal Physiology 248, no. 5 (May 1, 1985): F734—F738. http://dx.doi.org/10.1152/ajprenal.1985.248.5.f734.
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A method is described for determining glomerular filtration rate (GFR) in conscious unrestrained rats without extracellular volume expansion. The glomerular marker used was 14C-labeled inulin infused in the minimal fluid volume of 1 microliter/h by intraperitoneally implanted osmotic minipumps. The workability, reproducibility, and precision of the technique was evaluated in sham-operated (sham) and uninephrectomized (UNI-NX) rats for 6 days. In six sham-operated rats the clearance of [14C]-inulin calculated from the plasma value obtained in a blood sample taken at 10 A.M. before food consumption was (means +/- SE): day 1 after pump implantation: 1.38 +/- 0.05; day 2: 1.27 +/- 0.05; day 3: 1.46 +/- 0.16; day 4: 1.45 +/- 0.15; day 5: 1.33 +/- 0.08; day 6: 1.38 +/- 0.11 ml/min. In six UNI-NX rats the corresponding values were: day 1: 0.88 +/- 0.04; day 2: 0.79 +/- 0.05; day 3: 0.91 +/- 0.03; day 4: 0.91 +/- 0.03; day 5: 0.83 +/- 0.06; day 6: 0.87 +/- 0.05 ml/min. When determined on day 2, 3, or 6 at 6 P.M., i.e., at the end of the food consumption period, [14C]inulin clearance was increased in all animals compared with the value determined at 10 A.M. in the fasted state. The use of implanted osmotic minipumps for delivering a glomerular marker such as [14C]inulin allows the determination of GFR in conscious unrestrained rats with normal fluid balance conditions. This method appears to be particularly appropriate for studying the influence of the intake and composition of food on GFR in physiological conditions.
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Katz, H., P. Butler, M. Homan, A. Zerman, A. Caumo, C. Cobelli, and R. Rizza. "Hepatic and extrahepatic insulin action in humans: measurement in the absence of non-steady-state error." American Journal of Physiology-Endocrinology and Metabolism 264, no. 4 (April 1, 1993): E561—E566. http://dx.doi.org/10.1152/ajpendo.1993.264.4.e561.
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The isotope dilution technique has been extensively used to assess insulin action in humans. To determine if nonsteady state (NSS) has led to erroneous estimates of hepatic and extrahepatic insulin sensitivity, we measured glucose turnover in healthy subjects during infusion of insulin at rates of 0.25, 0.6, and 2.0 mU.kg-1.min-1. Turnover was calculated using Steele's traditional NSS equations [fixed-effective volume (pV) method] as well as with methods [radioactive infused glucose (hot-GINF) or variable pV] designed to minimize NSS error. In contrast to the fixed-pV method, both the hot-GINF and variable-pV methods indicated that several hours were required for suppression of hepatic glucose release at all insulin concentrations and that small increases in plasma insulin (approximately 100 pmol/l) had comparable effects on glucose disappearance and hepatic glucose release. Nevertheless, despite these differences, when turnover during the final hour of the insulin infusions was plotted vs. the prevailing insulin concentration, all three methods yielded similar insulin dose-response curves for suppression of hepatic glucose release. Thus despite previous errors in measurement of glucose turnover, the widely accepted belief that the human liver is exquisitely sensitive to small changes in insulin is correct.