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PubMed2000

Comparison of three methods of CD34+ cell enumeration in peripheral blood: dual-platform ISHAGE protocol versus single-platform, versus microvolume fluorimetry.

BACKGROUND: Quantitation of peripheral blood (PB) CD34(+) cells is now an established method for timing PBPC harvesting. Recent refinements to the dual-platform ISHAGE gating strategy for CD34(+) cells has seen the introduction of microbeads to enable absolute counting of cells on a single instrument platform. This eliminates the need for total WBCC performed on an automated hematology analyzer and potentially increases the analytical precision of the methodology. At the same time, alternative methods for CD34(+) cell enumeration have started to emerge, notably microvolume fluorimetry, which forms the basis of the fully-automated STELLer CD34 method using the Imagn 2000. METHODS: We performed a three-way evaluation of these methods. Sixty-eight samples of PB from 42 patients undergoing PBPC mobilization were analyzed by all three methods and correlations between all three calculated. The two-platform ISHAGE method was used as the reference method. RESULTS: Precision and linearity of the single-platform and STELLer CD34 assays were excellent. Correlation with the dual-platform reference method was also excellent (single-platform method slope = 1.03, intercept = -0.03 and R(2) = 0.9325, STELLer CD34 assay slope = 0.827, intercept = 4.27, R(2) =0.8215). Bias, determined by Bland-Altman analysis, was 1.16 and -1.62 for single platform and STELLer CD34 assay respectively. CONCLUSION: The three methods of CD34(+) cell enumeration gave equivalent results. The single-platform methodology negated the need for a separate white cell analyzer, while the STELLer CD34 methodology was technically the simplest.

Antigens, CD34↗

PubMed2026

Effects of carbohydrate mouth rinse on psychophysiological responses, kinematic variables and technical actions during small-sided soccer games.

BACKGROUND: This study investigated the effects of carbohydrate mouth rinsing (CHOMR) on various psychophysiological, kinematic, and technical actions during 4-a-side small-sided soccer games (SSGs). METHODS: In a randomized, crossover, double-blind design, 16 young male soccer players (age: 15 ± 1 years; height: 172.6 ± 7.0 cm; body mass: 57.8 ± 7.9 kg) participated in two 4-a-side SSGs separated by one week following either CHOMR or placebo (PLA). During each SSGs, heart rate (HRmean, %HR, and HRmax), rating of perceived exertion (RPE), enjoyment, visual analogue scale (VAS) to perceived mental fatigue, mood states, total distance (TD), high-speed running distance (HSRD), average metabolic power (AMP), high metabolic load distance (HMLD), sprint distance (SD), acceleration (ACC), deceleration (DEC), and technical actions (e.g. passing, tackling, shooting, and interceptions) were assessed. RESULTS: Compared with PLA, CHOMR resulted in significantly higher RPE (p = 0.025, g = 0.86) and significantly lower VAS scores (p = 0.010, g = -0.71). In addition, the CHOMR condition showed significantly higher values for interceptions, successful tackles, unsuccessful tackles, unsuccessful shots, and goals (p < 0.05, g = 0.96-2.02), whereas block values were significantly higher in the PLA condition. There were no statistically significant differences in HRmean, %HR, HRmax, enjoyment, TD, HSRD, AMP, HMLD, SD, ACC, DEC, successful passes, unsuccessful passes, successful shots, or mood states between the conditions (p > 0.05). CONCLUSION: The current study findings suggest that CHOMR may enhance selected technical actions and lower VAS scores during 4-a-side SSGs, although it was also associated with higher RPE and did not alter the kinematic responses. In conclusion, CHOMR was associated with higher RPE, lower mental fatigue, and selective improvements in technical actions, with no significant effects on kinematic variables or HR.

Humans↗

PubMed2003

Significance levels for stability pooling test: a simulation study.

Shelf life of a drug product is defined as the length of time under specific conditions of storage that the product will remain within specifications established to ensure its identity, strength, quality, and purity. The objective of an new drug application (NDA) stability study is to collect and evaluate the evidence in support of the sponsor-proposed shelf life. The proposed shelf life is supported when each batch of the drug products in the study has shelf life no shorter than the proposed shelf life. When the value of the batch mean changes linearly, sometimes batches of the same product may share the same slope or regression line. In practice, batches are pooled to have a common estimate of slope or regression line when there is no significant difference in slope or regression line. Such practice is often applied in pooling across levels of a design factor such as package or strength in a stability study designed with multiple factors. However, falsely pooling different slopes or intercepts may increase false positive rates on the decision of approval for the proposed shelf life. The proposed algorithm used with the simulation technique tries to reduce false pooling rates for testing slope or intercept differences in order to bring down the false positive rates on the decision of approval for the proposed shelf life to the prespecified Type-I error rate of 5 or 10%.

Algorithms↗

PubMed2000

A comparison of some different methods for purifying core temperature data from humans.

Nine healthy females were studied about the time of the spring equinox while living in student accommodations and aware of the passage of solar time. After 7 control days, during which a conventional lifestyle was lived under a 24h "constant routine," the subjects lived 17 x 27h "days" (9h sleep in the dark and 18h wake using domestic lighting, if required). Throughout the experiment, recordings of wrist activity and rectal (core) temperature were taken. The raw temperature data were assessed for phase and amplitude by cosinor analysis and another method, "crossover times," which does not assume that the data set is sinusoidal. Two different purification methods were used in attempts to remove the masking effects of sleep and activity from the core temperature record and so to measure more closely the endogenous component of this rhythm; these two methods were "purification by categories" and "purification by intercepts." The former method assumes that the endogenous component is a sinusoid, and that the masking effects can be estimated by putting activity into a number of bands or categories. The latter method assumes that a temperature that would correspond to complete inactivity can be estimated from measured temperatures by linear regression of these on activity and extrapolation to a temperature at zero activity. Three indices were calculated to assess the extent to which exogenous effects had been removed from the temperature data by these purification methods. These indices were the daily variation of phase about its median value; the ratio of this variation to the daily deviation of phase about midactivity; and the relationship between amplitude and the square of the deviation of phase from midactivity. In all cases, the index would decrease in size as the contribution of the exogenous component to a data set fell. The purification by categories approach was successful in proportion to the number of activity categories that was used, and as few as four categories produced a data set with significantly less masking than raw data. The method purification by intercepts was less successful unless the raw data had been "corrected" to reflect the direct effects of sleep that were independent of activity (a method to achieve this being produced). Use of this purification method with the corrected data then gave results that showed least exogenous influences. Both this method and the purification by categories method with 16 categories of activity gave evidence that the exogenous component no longer made a significant contribution to the purified data set. The results were not significantly influenced by assessing amplitude and phase of the circadian rhythm from crossover times rather than cosinor analysis. The relative merits of the different methods, as well as of other published methods, are compared briefly; it is concluded that several purification methods, of differing degrees of sophistication and ease of application to raw data, are of value in field studies and other circumstances in which constant routines are not possible or are ethically undesirable. It is also concluded that such methods are often somewhat limited insofar as they are based on pragmatic or biological, rather than mathematical, considerations, and so it is desirable to attempt to develop models based equally on mathematics and biology.

Body Temperature↗

PubMed2005

Conduction through the inward rectifier potassium channel, Kir2.1, is increased by negatively charged extracellular residues.

Ion channel conductance can be influenced by electrostatic effects originating from fixed "surface" charges that are remote from the selectivity filter. To explore whether surface charges contribute to the conductance properties of Kir2.1 channels, unitary conductance was measured in cell-attached recordings of Chinese hamster ovary (CHO) cells transfected with Kir2.1 channels over a range of K+ activities (4.6-293.5 mM) using single-channel measurements as well as nonstationary fluctuation analysis for low K+ activities. K+ ion concentrations were shown to equilibrate across the cell membrane in our studies using the voltage-sensitive dye DiBAC4(5). The dependence of gamma on the K+ activity (a(K)) was fit well by a modified Langmuir binding isotherm, with a nonzero intercept as a(K) approaches 0 mM, suggesting electrostatic surface charge effects. Following the addition of 100 mM N-methyl-D-glucamine (NMG+), a nonpermeant, nonblocking cation or following pretreatment with 50 mM trimethyloxonium (TMO), a carboxylic acid esterifying agent, the gamma-a(K) relationship did not show nonzero intercepts, suggesting the presence of surface charges formed by glutamate or aspartate residues. Consistent with surface charges in Kir2.1 channels, the rates of current decay induced by Ba2+ block were slowed with the addition of NMG or TMO. Using a molecular model of Kir2.1 channels, three candidate negatively charged residues were identified near the extracellular mouth of the pore and mutated to cysteine (E125C, D152C, and E153C). E153C channels, but not E125C or D152C channels, showed hyperbolic gamma-a(K) relationships going through the origin. Moreover, the addition of MTSES to restore the negative charges in E53C channels reestablished wild-type conductance properties. Our results demonstrate that E153 contributes to the conductance properties of Kir2.1 channels by acting as a surface charge.

Animals↗

PubMed1975

Actions of external hypertonic urea, ADH, and theophylline on transcellular and extracellular solute permeabilities in frog skin.

Increases in transepithelial solute permeability were elicited in the frog skin with external hypertonic urea, theophylline, and vasopressin (ADH). In external hypertonic urea, which is known to increase the permeability of the extracellular (paracellular) pathway, the unidirectional transepithelial fluxes of Na (passive), K, Cl, and urea increased substantially while preserving a linear relationship to each other. The same linear relationship was also observed for the passive Na and urea fluxes in regular Ringer and under stimulation with ADH or 10 mM theophylline, indicating that their permeation pathway was extracellular. A linear relationship between Cl and urea fluxes could be demonstrated if the skins were separated according to their open circuit potentials; parallel lines were obtained with increasing intercepts on the Cl axis as the open circuit potential decreased. The slopes of the Cl vs. urea lines were not different from that obtained in external hypertonic urea, indicating that this relationship described the extracellular movement of Cl. The intercept on the ordinate was interpreted as the contribution from the transcellular Cl movement. In the presence of 0.5 mM theophylline or 10 mU/ml of ADH, mainly the transcellular movement of Cl increased, whereas 10 mM theophylline caused increases in both transcellular and extracellular Cl fluxes. These and other data were interpreted in terms of a possible intracellular control of the theophylline-induced increase in extracellular fluxes. The changes in passive solute permeability were shown to be independent of active transport. The responses of the active transport system, the transcellular and paracellular pathways to theophylline and ADH could be explained in terms of the different resulting concentrations of cyclic 3'-5'-AMP produced by each of these substances in the tissue.

Animals↗

PubMed2000

Precise U-Pb Zircon Constraints on the Earliest Magmatic History of the Carolina Terrane.

The early magmatic and tectonic history of the Carolina terrane and its possible affinities with other Neoproterozoic circum-Atlantic arc terranes have been poorly understood, in large part because of a lack of reliable geochronological data. Precise U-Pb zircon dates for the Virgilina sequence, the oldest exposed part, constrain the timing of the earliest known stage of magmatism in the terrane and of the Virgilina orogeny. A flow-banded rhyolite sampled from a metavolcanic sequence near Chapel Hill, North Carolina, yielded a U-Pb zircon date of 632.9 +2.6/-1.9 Ma. A granitic unit of the Chapel Hill pluton, which intrudes the metavolcanic sequence, yielded a nearly identical U-Pb zircon date of 633 +2/-1.5 Ma, interpreted as its crystallization age. A felsic gneiss and a dacitic tuff from the Hyco Formation yielded U-Pb zircon dates of 619.9 +4.5/-3 Ma and 615.7 +3.7/-1.9 Ma, respectively. Diorite and granite of the Flat River complex have indistinguishable U-Pb upper-intercept dates of 613.9 +1.6/-1.5 Ma and 613.4 +2.8/-2 Ma. The Osmond biotite-granite gneiss, which intruded the Hyco Formation before the Virgilina orogeny, crystallized at 612.4 +5.2/-1.7 Ma. Granite of the Roxboro pluton, an intrusion that postdated the Virgilina orogeny, yielded a U-Pb upper intercept date of 546.5 +3.0/-2.4 Ma, interpreted as the time of its crystallization. These new dates both provide the first reliable estimates of the age of the Virgilina sequence and document that the earliest known stage of magmatism in the Carolina terrane had begun by 633 +2/-1.5 Ma and continued at least until 612.4 +5.2/-1.7 Ma, an interval of approximately 25 m.yr. Timing of the Virgilina orogeny is bracketed between 612.4 +5.2/-1.7 Ma and 586+/-10 Ma (reported age of the upper Uwharrie Formation). The U-Pb systematics of all units studied in the Virgilina sequence are simple and lack any evidence of an older xenocrystic zircon component, which would indicate the presence of a continental-type basement. This observation, together with the juvenile Nd isotopic character of the Virgilina volcanic arc sequence, suggests that the oldest part of the Carolina terrane was built on oceanic crust away from a continental crustal influence.

Journal Article↗

PubMed1988

A theoretical analysis of the accuracy of single-energy CT bone-mineral measurements.

A relationship has been derived between the in vivo concentration of calcium hydroxyapatite and the in vitro concentration of K2HPO4 solution in a single-energy quantitative computed tomography (QCT) bone-mineral determination. Under certain simplifying assumptions this relationship is linear. The gradient term has been calculated as a function of scanner effective energy using the measured variation of solvent water density with K2HPO4 concentration; it ranges from 1.17 at 60 keV to 1.21 at 80 keV. The intercept term has been calculated as a function of effective energy, patient age and trabecular bone volume (TBV) by modelling the constituents of whole trabecular bone and using published normal composition data. It varies from about 15 to 25 mg cm-3 at an effective energy of 70 keV and within a TBV range of 5 to 20%. This intercept term may be used as an additive correction which improves the accuracy of single-energy QCT results without significant loss of precision. However, the method is limited by the uncertainties of tissue composition in an individual patient.

Bone and Bones↗

PubMed1991

Dose-response characteristics of a ferrous-sulphate-doped gelatin system for determining radiation absorbed dose distributions by magnetic resonance imaging (Fe MRI).

The nuclear magnetic resonance (NMR) longitudinal relaxation rate R1 dose-response characteristics of a ferrous-sulphate-doped chemical dosimeter system (Fe MRI) immobilized in a gelatin matrix were explored. Samples containing various concentrations of the FeSO4 dosimeter were irradiated to absorbed doses of 0-150 Gy. R1 relaxation rates were determined by imaging the samples at a field strength of 1.5T(1H Lamor frequency of 63.8 MHz). The response of the system was found to be approximately linear up to doses of 50 Gy for all FeSO4 concentrations studied (0.1-2.0 mM). Changing concentrations in the range of 0.1-0.5 mM affected both the slope and intercept of the dose-response curve. For concentrations of 0.5-2.0 mM, the slope of the dose-response curves remained constant at approximately 0.0423 s-1 Gy-1 in the dose range of 0-50 Gy. However, the intercept of the curve continued to increase in that region, as expected, because of the additional paramagnetic ions. The reproducibility of the absorbed dose estimates for measurements made over a 22 cm field of view was found to be 5% in the range of 20-50 Gy (an uncertainty of 0.81 Gy on average), decreasing to approximately 10% in the dose range of 5-10 Gy.

Dose-Response Relationship, Radiation↗

PubMed1998

Improving calibration accuracy in gel dosimetry.

A new method of calibrating gel dosimeters (applicable to both Fricke and polyacrylamide gels) is presented which has intrinsically higher accuracy than current methods, and requires less gel. Two test-tubes of gel (inner diameter 2.5 cm, length 20 cm) are irradiated separately with a 10 x 10 cm2 field end-on in a water bath, such that the characteristic depth-dose curve is recorded in the gel. The calibration is then determined by fitting the depth-dose measured in water, against the measured change in relaxivity with depth in the gel. Increased accuracy is achieved in this simple depth-dose geometry by averaging the relaxivity at each depth. A large number of calibration data points, each with relatively high accuracy, are obtained. Calibration data over the full range of dose (1.6-10 Gy) is obtained by irradiating one test-tube to 10 Gy at dose maximum (Dmax), and the other to 4.5 Gy at Dmax. The new calibration method is compared with a 'standard method' where five identical test-tubes of gel were irradiated to different known doses between 2 and 10 Gy. The percentage uncertainties in the slope and intercept of the calibration fit are found to be lower with the new method by a factor of about 4 and 10 respectively, when compared with the standard method and with published values. The gel was found to respond linearly within the error bars up to doses of 7 Gy, with a slope of 0.233 +/- 0.001 s(-1) Gy(-1) and an intercept of 1.106 +/- 0.005 Gy. For higher doses, nonlinear behaviour was observed.

Acrylamides↗

PubMed2026

RR-interval-based atrial fibrillation detection and burden estimation: cross-dataset validation and calibration-aware probability analysis.

Objective.Atrial fibrillation (AF) burden has become an increasingly important endpoint in long-duration rhythm monitoring, but reliable burden estimation requires more than accurate AF detection alone. In particular, when burden is derived by aggregating predicted AF probabilities over time, probability calibration may directly affect burden validity under external dataset shift.Approach.This study developed an interpretable-interval feature model for AF detection and evaluated it using record-wise cross-validation on a development cohort and independent cross-dataset external validation on public Holter electrocardiographic databases. Window-level performance was assessed using the area under the receiver operating characteristic curve (ROC-AUC), area under the precision-recall curve (PR-AUC), Brier score, expected calibration error (ECE), and calibration intercept and calibration slope. Recording-level AF burden was estimated using both probability-based and hard-label aggregation and evaluated using mean absolute error (MAE) and agreement analyses.Main results.The model showed high discrimination in both development and external evaluation, with external ROC-AUC ofand PR-AUC of. However, external calibration deteriorated despite preserved ranking performance, with Brier score of, ECE(15) of, calibration intercept of, and calibration slope of. In the external cohort, probability-based burden estimation preserved strong association with reference burden but showed weaker raw agreement than hard-label aggregation, with MAE ofversus, consistent with systematic probability underprediction. Repeated external recalibration across record-level splits substantially improved probability quality and probability-based burden estimation. Median probability-burden MAE decreased fromwithout recalibration toafter Platt recalibration andafter isotonic recalibration, while median ECE(15) decreased fromtoand, respectively.Significance.These findings indicate that-interval-based AF detection maintained strong ranking performance in the tested external cohort, but probability calibration should be evaluated explicitly when predicted probabilities are aggregated into AF-burden estimates.

Atrial Fibrillation↗

PubMed2002

Comparison of glucose levels in capillary blood samples obtained from a variety of body sites.

The AtLast Blood Glucose System was developed to eliminate painful finger punctures by testing samples from less sensitive body sites. Studies were designed to evaluate subjects under various glycemic states and to compare glucose concentrations in samples obtained from the forearm and palm to those found in the finger. The palm is more similar to the finger in blood flow rates, while the forearm is less perfused. AtLast measurements of forearm samples from subjects at a minimum of 2 h postprandial produced good regression statistics when compared to reference finger results with a correlation coefficient of 0.978. Agreement was quite weakened in subjects undergoing extreme glucose loads, resulting in a slope of 0.85, an intercept of 30.82, and a correlation coefficient of 0.938. Time course data indicate that forearm glucose levels often appear lower than finger concentrations when glucose is rapidly rising and somewhat higher when glucose is quickly falling. On the other hand, glucose levels of palm samples produced a close correlation to finger concentrations under all glycemic states. In participants undergoing rapid glucose change, the linear correlation resulted in a slope of 1.01, an intercept of 2.46, and a high correlation coefficient of 0.983, with steady tracking of palm and finger concentrations throughout the study. The palm of the hand was also identified as a comfortable testing site that equals the forearm in affording painless testing. Glucose monitoring of blood samples from the forearm is suitable when expecting steady state glycemic conditions. At times of rapid glucose change, the palm of the hand offers a painless sampling site that compares well with the finger.

Adolescent↗

PubMed2003

The role of the independent variable to glucose sensor calibration.

In vivo subcutaneous glucose sensor accuracy depends on the calibration method. Sensor accuracy was assessed during standard oral glucose tolerance tests in six non-diabetic subjects each wearing six subcutaneous glucose sensors (Medtronic MiniMed). Paired blood glucose (B(G)) and sensor current readings were used for retrospective sensor calibration using either B(G) or sensor current as the independent variable. Sensor accuracy after calibration was assessed using three criteria: linear regression between B(G) and sensor glucose (S(G)); correlation; and mean absolute difference (MAD), defined as 100 x |B(G) - S(G)|/B(G). Calibration with B(G) as the independent variable resulted in unbiased estimates of regression slope (1.02, not different than 1, p< 0.01) and y-intercept (-1.06 mg/dL, not different than 0, p< 0.01). In contrast, calibration with sensor current as the independent variable resulted in biased estimates of slope (0.76, different than 1, p< 0.01) and y-intercept (31.25 mg/dL, different than 0, p< 0.01). However, with sensor current as the independent variable, the MAD was lower than the corresponding value for calibration with B(G) at the x-axis (15.00 +/- 0.47% vs. 18.35 +/- 0.63%, p< 0.01). The Pearson correlation coefficient between B(G) and S(G) was higher when using sensor current as the independent variable (R = 0.82 vs. R = 0.79 when using glucose on the x-axis). We suggest that despite the fact that calibration with sensor current as the independent variable leads to a bias in the estimate of B(G), it is a more appropriate calibration method when the primary concern is minimization of the MAD between S(G) and B(G).

Biosensing Techniques↗

PubMed1995

Influence of body composition and resting metabolic rate on variation in total energy expenditure: a meta-analysis.

The influence of body composition, resting metabolic rate (RMR), and sex on variation in total energy expenditure (TEE) was examined by using meta-analysis (13 published studies in a total of 162 adults). TEE (10.9 +/- 3.2 MJ/d) was significantly correlated with body mass (BM; weighted mean converted r = 0.68, P < 0.05) and resting metabolic rate (RMR; weighted mean converted r = 0.66, P < 0.05). The correlation coefficients, regression coefficients, and intercepts for the regression between TEE and RMR and between TEE and BM were highly variable between studies. When TEE was adjusted for RMR, there was no significant correlation with body fat, and females had a significantly lower TEE than males by 1.1 MJ/d (P = 0.005). We conclude that 1) the relationships between TEE and RMR and TEE and BM are highly variable between studies with nonzero intercepts, precluding use of the traditionally used ratios of TEE to RMR or TEE to BM for data comparison; 2) after adjustment of TEE for RMR, TEE is not associated with adiposity, and women have a significantly lower TEE than men; and, 3) there are insufficient published data to develop prediction models for TEE in adults.

Adipose Tissue↗

PubMed1996

Utility of creatinine excretion in body-composition studies of healthy men and women older than 60 y.

This study evaluated whether aging alters the usefulness of creatinine excretion as an index of lean body mass (LBM) or muscle mass in healthy men and women. Creatinine excretion was determined while 24 young (15 men and 9 women aged < 32 y) and 38 older (23 men and 15 women aged > 60 y) healthy volunteers stayed at a clinical research center for 3 d. Total LBM was determined by 40K counting in all subjects, and cross-sectional areas of upper arm and thigh muscles were determined in some subjects (10 young, 20 old) by magnetic resonance imaging. The slopes and intercepts of the regression equations relating LBM to average daily creatinine excretion were the same in the younger and older groups, and the precision with which LBM could be determined from creatinine excretion was not diminished by aging. Creatinine excretion was closely correlated with cross-sectional areas of upper arm (r = 0.85) and thigh (r = 0.88) muscles, and the slopes and intercepts of the regression equations were not significantly affected by age. The older group had a mean LBM smaller than that of the younger group, which was accounted for entirely by a smaller muscle mass. Mean resting metabolic rate (RMR), whole-body protein turnover rate, and thigh strength were lower in the older group than in the young group. Adjustment of RMR and protein turnover for creatinine excretion or LBM eliminated the age effects. Strength was lower in the older group even after adjustment for creatinine excretion or LBM. This study indicates that creatinine excretion is useful for evaluating body composition in both young and old subjects.

Adult↗

PubMed1985

Discrepant fibrinogen values during thrombolytic therapy. Comparison of aca and Data-Fi results using immunofixation. Electrophoresis as a reference.

The authors compared aca and Data-Fi fibrinogen values and used a combination of plasma protein electrophoresis and immunofixation with anti-fibrinogen anti-serum to observe changes in fibrinogen from four patients receiving streptokinase (STK) therapy. For three patients, aca and Data-Fi values pre-STK and greater than or equal to 24 hours post-STK correlated well (r = 0.96, slope = 0.92, y-intercept = 2.3; n = 13 pairs); aca and Data-Fi values during STK therapy correlated poorly (r = 0.67, slope = 0.36, y-intercept = 4.1; n = 20 pairs), with aca values up to sixfold higher than Data-Fi. Protein electrophoresis and immunofixation showed loss of the discrete fibrinogen band during STK therapy; instead there was a diffuse electrophoretic zone of anti-fibrinogen reactive material having a slightly different mobility than intact fibrinogen; aca fibrinogen values were inconsistent with fibrinogen band absence. The remaining patient showed no change in the fibrinogen band. Clinically he showed no response to STK therapy. In nonresistant patients, STK results in the degradation of fibrinogen into a mixture of products (FDP), all sharing antigenic determinants with fibrinogen and at least one being still clottable. Our results exemplify loss of intact fibrinogen with persisting anti-fibrinogen reactive FDP during STK therapy. Discrepancies in aca versus Data-Fi results may be due to ways in which FDP interact with different methods--fibrometer versus turbidimetric.

Adult↗

PubMed1988

Discrepant changes in plasminogen by two different assays in patients receiving streptokinase.

The fluorogenic synthetic substrate and radial immunodiffusion assays of plasma plasminogen were compared before and after administration of intravenous streptokinase in differing doses to 57 patients being treated for acute myocardial infarction. There was a moderate correlation (r = 0.73, slope = 0.221, intercept = 1.005, n = 57 pairs) in the two assays of plasma plasminogen before the administration of streptokinase. After streptokinase, however, the correlation of the two assays was poor (r = 0.28, slope = 0.03, y-intercept = 0.003, n = 57 pairs). The decrease in plasma plasminogen by the fluorogenic synthetic substrate assay after streptokinase averaged 95 +/- 5%, with little variation between doses. In contrast, the percentage decrease in plasma plasminogen after streptokinase by the radial immunodiffusion assay averaged only 30 +/- 11%. The percentage change in plasma plasminogen by the two assays is significantly different (P = 0.001). The discrepancy in the percentage change in plasma plasminogen after streptokinase as measured by the fluorogenic synthetic substrate assay and the radial immunodiffusion assay can be explained by a lack of specificity for the antibody to plasminogen in the radial immunodiffusion kit. Antigen-antibody precipitin rings were observed after incubation of antibody with a mixture presumed to contain plasmin, plasmin-alpha 2 antiplasmin complexes, and plasmin-fibrin/fibrinogen degradation products. Based on these data, the fluorogenic synthetic substrate assay for plasma plasminogen is a superior means of following plasminogen depletion in response to thrombolytic therapy after streptokinase treatment for acute myocardial infarction.

Dose-Response Relationship, Drug↗

PubMed2004

The use of a principal axis model to examine individual plant harvest index in four grain legumes.

BACKGROUND AND AIMS: A principal axis model (PAM) has been proposed to enable the selection of crop ideotypes. The PAM enables plant-to-plant variability within crops to be quantified and compared. The aim of this paper is to validate the PAM for four grain legumes. METHODS: Four grain legumes (Cicer arietinum, Lens culinaris, Lupinus angustifolius, Pisum sativum) were used to quantify the influence of plant-to-plant variability on crop yields. To create variability, populations of 10, 100 and 400 plants m(-2) were established 'on-the-square' with sowing depths of 2, 5 and 10 cm. Further, a central plant was treated with nitrogen and the impact of this on its four neighbouring plants was examined. Seeds were sown and plants harvested individually by hand. KEY RESULTS: Mean individual plant seed weight (SWT) and plant weight (PWT) decreased as plant population increased but there was a consistent and strong (R2 > 0.90) linear relationship between SWT and PWT, with a negative SWT-axis intercept in all species. These components form the basis of the principal axis model (PAM). The PAM was used to summarize the performance of individual plants within a crop and quantify the variability caused by N treatment and the lowest and highest yielding individual plants. A negative SWT-axis intercept indicated that a minimum plant weight (MPW) was required for seed production and therefore the relationship between plant harvest index (PHI) and PWT was asymptotic. The heaviest MPW was calculated for plants grown at the lowest plant population and it was species-dependent, being higher in the larger seeded species. CONCLUSIONS: Agronomic or physiological characteristics that lead to variability in PWT within a population will decrease PHI, and crop yield. The PAM may be useful in breeding programmes to identify plant phenotypes that minimize this plant-to-plant variability.

Cicer↗