scholarly journals Various optimality criteria for the prediction of individual response curves

2019 ◽  
Vol 146 ◽  
pp. 36-41 ◽  
Author(s):  
Maryna Prus
Keyword(s):  
Optimality Criteria ◽  
Individual Response ◽  
Response Curves

An Improved Definition of Synergistic and Antagonistic Effects

Weed Science ◽  
1975 ◽  
Vol 23 (1) ◽  
pp. 4-6 ◽  
Author(s):  
F. H. A. Rummens
Keyword(s):  
Response Function ◽  
Growth Regulators ◽  
Individual Response ◽  
Response Curves ◽  
Linear Region ◽  
Antagonistic Effects ◽  
Definition Of ◽  
The Individual

Presently accepted methods for calculating the expected response for combinations of agents such as herbicides or other growth regulators from the responses of individual agents can lead to unacceptable results. This may be true even if responses within the linear region of the individual response curves are used in such calculations. A solution to this problem is to assign parameters to response curves of individual agents and to define the expected response function for combinations of agents by the weighted algebraic means of these parameters.

The Effects of Diallate and Its Isomers on the Growth of Wild Oats

Weed Science ◽  
1975 ◽  
Vol 23 (1) ◽  
pp. 11-14 ◽  
Author(s):  
F. H. A. Rummens ◽  
D. C. M. Rummens-Ditters ◽  
A. E. Smith
Keyword(s):  
Antagonistic Effect ◽  
Avena Fatua ◽  
Individual Response ◽  
Wild Oat ◽  
Response Curves ◽  
Response Data ◽  
Wild Oats ◽  
A New Technique ◽  
The Individual ◽  
Best Parameters

The growth of germinating wild oat seedlings (Avena fatuaL.) in soil treated with a range of concentrations of the individual isomers of diallate [S-(2,3-dichloroallyl)diisopropylthiocarbamate] and mixtures thereof has been studied. on the basis of diallate concentration required to reduce height by 50%, thecisisomer is less effective than thetransisomer by about 65%. A mixture of 42%transand 58%cisdiallate is shown to exhibit an antagonistic effect of about 95%. Thetransisomer is more effective than the 42/58 mixture by a factor of 2.6. It is shown that height vs concentration response curves can be represented by y = A {(x/C)B+ 1}-1, where y = height and x = concentration. A computer program has been developed to find the best parameters A, B, and C from any set of individual response data. A new technique for calculating synergism or antagonism has been employed in the part dealing with mixtures of diallate.

Analysis of linear and mildly nonlinear relationships using pooled subject data

1988 ◽  
Vol 64 (2) ◽  
pp. 854-859 ◽  
Author(s):  
C. S. Poon
Keyword(s):  
Tidal Volume ◽  
Measurement Errors ◽  
Individual Response ◽  
Response Curves ◽  
Simple Method ◽  
Response Data ◽  
State Dependent ◽  
Co2 Output ◽  
Volume Relationship ◽  
The Individual

The detection of mild nonlinearities and/or state-dependent variability in otherwise linear physiological relationships is generally difficult in the presence of significant measurement errors. Conventional approaches using pooled subject data to increase the degree of freedom for statistical inference are enervated by the resultant introduction of intersubject variability. This paper proposes a new, simple method of pooling multiple subject data for linearity analysis. With the use of a special standardization procedure for the individual response curves, this method allows sensitive detection of occult nonlinearities as well as any state-dependent variability in the underlying relationship. Application of this analytic approach to reported hypercapnic exercise-response data in eight healthy subjects showed that 1) the hypercapnic ventilation-CO2 output relationship is nonlinear with a downward concavity; and 2) the ventilation-tidal volume relationship, which is linear at low tidal volume values, is similar in hypercapnic exercise as in resting hypercapnia or eucapnic exercise.

Effects of acute nicotine on brain function in healthy smokers and non-smokers:estimation of inter-individual response heterogeneity

2009 ◽  
Vol 42 (05) ◽  
Author(s):  
U Ettinger ◽  
SCR Williams ◽  
D Patel ◽  
TM Michel ◽  
A Nwaigwe ◽  
...  
Keyword(s):  
Brain Function ◽  
Individual Response

Fibrin-specificity of a Plasminogen Activator Affects the Efficiency of Fibrinolysis and Responsiveness to Ultrasound: Comparison of Nine Plasminogen Activators In Vitro

1999 ◽  
Vol 81 (04) ◽  
pp. 605-612 ◽  
Author(s):  
Dmitry V. Sakharov ◽  
Marrie Barrett-Bergshoeff ◽  
Rob T. Hekkenberg ◽  
Dingeman C. Rijken
Keyword(s):  
Thrombolytic Therapy ◽  
Plasminogen Activator ◽  
Tissue Type ◽  
Bolus Administration ◽  
High Frequency Ultrasound ◽  
Single Chain ◽  
Response Curves ◽  
Maximal Speed ◽  
Frequency Ultrasound

SummaryIn a number of cases, thrombolytic therapy fails to re-open occluded blood vessels, possibly due to the occurrence of thrombi resistant to lysis. We investigated in vitro how the lysis of hardly lysable model thrombi depends on the choice of the plasminogen activator (PA) and is accelerated by ultrasonic irradiation. Lysis of compacted crosslinked human plasma clots was measured after addition of nine different PAs to the surrounding plasma and the effect of 3 MHz ultrasound on the speed of lysis was assessed.Fibrin-specific PAs showed bell-shaped dose-response curves of varying width and height. PAs with improved fibrin-specificity (staphylokinase, the TNK variant of tissue-type PA [tPA], and the PA from the saliva of the Desmodus rotundus bat) induced rapid lysis in concentration ranges (80-, 260-, and 3,500-fold ranges, respectively) much wider than that for tPA (a 35-fold range). However, in terms of speed of lysis, these three PAs exceeded tPA only slightly. Reteplase and single-chain urokinase were comparable to tPA, whereas two-chain urokinase, anistreplase, and streptokinase were inferior to tPA. In the case of fibrin-specific PAs, ultrasonic treatment accelerated lysis about 1.5-fold. For streptokinase no acceleration was observed. The effect of ultrasound correlated with the presence of plasminogen in the outer plasma, suggesting that it was mediated by facilitating the transport of plasminogen to the surface of the clot.In conclusion, PAs with improved fibrin-specificity induce rapid lysis of plasminogen-poor compacted plasma clots in much wider concentration ranges than tPA. This offers a possibility of using single-or double-bolus administration regimens for such PAs. However, it is not likely that administration of these PAs will directly cause a dramatic increase in the rate of re-opening of the occluded arteries since they are only moderately superior to tPA in terms of maximal speed of lysis. Application of high-frequency ultrasound as an adjunct to thrombolytic therapy may increase the treatment efficiency, particularly in conjunction with fibrin-specific PAs.

Dose-response Curves in the Fibrin Plate Assay Fibrinolytic Activity of Proteases

1974 ◽  
Vol 32 (02/03) ◽  
pp. 356-365 ◽  
Author(s):  
F Haverkate ◽  
D. W Traas
Keyword(s):  
Dose Response ◽  
Fibrinolytic Activity ◽  
Enzyme Concentration ◽  
Response Curves ◽  
Agar Gel ◽  
Porcine Tissue ◽  
Plate Assay ◽  
Fibrin Plate ◽  
Different Types ◽  
Dose Response Curves

SummaryIn the fibrin plate assay different types of relationships between the dose of applied proteolytic enzyme and the response have been previously reported. This study was undertaken to determine whether a generally valid relationship might exist.Trypsin, chymotrypsin, papain, the plasminogen activator urokinase and all of the microbial proteases investigated, including brinase gave a linear relationship between the logarithm of the enzyme concentration and the diameter of the circular lysed zone. A similar linearity of dose-response curves has frequently been found by investigators who used enzyme plate assays with substrates different from fibrin incorporated in an agar gel. Consequently, it seems that this linearity of dose-response curves is generally valid for the fibrin plate assay as well as for other enzyme plate bioassays.Both human plasmin and porcine tissue activator of plasminogen showed deviations from linearity of semi-logarithmic dose-response curves in the fibrin plate assay.

Factor VII Clotting Assay: Influence of Different Thromboplastins and Factor VII-Deficient Plasmas

1991 ◽  
Vol 65 (02) ◽  
pp. 160-164 ◽  
Author(s):  
Marina Poggio ◽  
Armando Tripodi ◽  
Guglielmo Mariani ◽  
Pier Mannuccio Mannucci ◽  
Keyword(s):  
Heart Disease ◽  
Ischemic Heart Disease ◽  
Dose Response ◽  
Response Curve ◽  
Ischemic Heart ◽  
Factor Vii ◽  
Response Curves ◽  
Assay Sensitivity ◽  
Clinical Laboratories ◽  
Coagulant Activity

SummaryBeing a putative predictor of ischemic heart disease, the measurement of factor VII (FVTI) coagulant activity will be presumably requested to clinical laboratories with increasing frequency. To assess the influence on FVII assays of different thromboplastins and FVII-deficient plasmas we compared performances of all possible combinations of 5 thromboplastins and 6 deficient plasmas. The reproducibility of the clotting times of the dose-response curves for human and rabbit thromboplastins were acceptable (CV lower than 7%), whereas bovine thromboplastin had a higher CV. Reproducibility was very similar for all deficient plasmas when they were used in combination with a given thromboplastin. Responsiveness of the dose-response curve did not depend on the deficient plasma but rather on the thromboplastin: one rabbit thromboplastin was the least responsive, the bovine thromboplastin the most responsive, the human and the remaining two rabbit thromboplastins had intermediate responsiveness. Assay sensitivity to cold-activated FVII varied according to the thromboplastin: the bovine thromboplastin was the most sensitive, the human thromboplastin the least sensitive, of the three rabbit thromboplastins two were relatively sensitive, one was almost insensitive. In conclusion, our results indicate that thromboplastin rather than deficient plasma is the crucial factor in the standardization of FVII assay.

Evaluation of the Fibrin Plate Method for Estimating Plasminogen Activators

1972 ◽  
Vol 28 (01) ◽  
pp. 075-088 ◽  
Author(s):  
N. A Marsh ◽  
C. L Arocha-Pinango
Keyword(s):  
Tranexamic Acid ◽  
Plasminogen Activators ◽  
Heated Plate ◽  
Plasminogen Activation ◽  
Response Curves ◽  
Plate Method ◽  
Single Plate ◽  
Effect Of Additives ◽  
Threefold Increase ◽  
Fibrin Plate

SummaryA study was carried out in order to evaluate the Astrup and Mullertz fibrin plate method for estimating plasminogen activators.Choice of a suitable fibrinogen substrate was found to be the most important factor in setting up a workable assay. Many preparations contained a large proportion of non-clottable protein and plates made from these fibrinogens were usually unreliable. In addition, plasminogen content varied appreciably between preparations so that sensitivity of the method required careful calibration with each new batch of fibrinogen.The effect of additives in the fibrin plate was considered and it was found that calcium chloride alone was sufficient to ensure a stabilised plate which could be stored at 4° C for some time. The addition of tranexamic acid (AMCHA) was found to be a slightly more convenient way of estimating direct proteolytic activity, compared with the traditional heated plate. However neither method distinguished completely between proteolysis and plasminogen activation.In order to improve the precision of the method, the use of an analysis of variance technique has been studied. This technique provides information on the dose-response curves of test and unknown substances, and in addition produces an approximately threefold increase in precision over single plate tests.

In Vitro Clot Lysis as a Potential Indicator of Thrombus Resistance to Fibrinolysis – Study in Healthy Subjects and Correlation with Blood Fibrinolytic Parameters

1997 ◽  
Vol 77 (04) ◽  
pp. 725-729 ◽  
Author(s):  
Mario Colucci ◽  
Silvia Scopece ◽  
Antonio V Gelato ◽  
Donato Dimonte ◽  
Nicola Semeraro
Keyword(s):  
Plasminogen Activator ◽  
Clot Lysis ◽  
Individual Response ◽  
Plasminogen Activator Inhibitor 1 ◽  
Autologous Plasma ◽  
Wide Range ◽  
Blood Clots ◽  
Physiological Variations ◽  
Pai 1

SummaryUsing an in vitro model of clot lysis, the individual response to a pharmacological concentration of recombinant tissue plasminogen activator (rt-PA) and the influence on this response of the physiological variations of blood parameters known to interfere with the fibrinolytic/thrombolytic process were investigated in 103 healthy donors. 125I-fibrin labelled blood clots were submersed in autologous plasma, supplemented with 500 ng/ml of rt-PA or solvent, and the degree of lysis was determined after 3 h of incubation at 37° C. Baseline plasma levels of t-PA, plasminogen activator inhibitor 1 (PAI-1), plasminogen, α2-anti-plasmin, fibrinogen, lipoprotein (a), thrombomodulin and von Willebrand factor as well as platelet and leukocyte count and clot retraction were also determined in each donor. rt-PA-induced clot lysis varied over a wide range (28-75%) and was significantly related to endogenous t-PA, PAI-1, plasminogen (p <0.001) and age (p <0.01). Multivariate analysis indicated that both PAI-1 antigen and plasminogen independently predicted low response to rt-PA. Surprisingly, however, not only PAI-1 but also plasminogen was negatively correlated with rt-PA-ginduced clot lysis. The observation that neutralization of PAI-1 by specific antibodies, both in plasma and within the clot, did not potentiate clot lysis indicates that the inhibitor, including the platelet-derived form, is insufficient to attenuate the thrombolytic activity of a pharmacological concentration of rt-PA and that its elevation, similarly to the elevation of plasminogen, is not the cause of clot resistance but rather a coincident finding. It is concluded that the in vitro response of blood clots to rt-PA is poorly influenced by the physiological variations of the examined parameters and that factors other than those evaluated in this study interfere with clot dissolution by rt-PA. In vitro clot lysis test might help to identify patients who may be resistant to thrombolytic therapy.

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