scholarly journals Dose-Response—A Challenge for Allelopathy?

2005 ◽  
Vol 3 (2) ◽  
pp. nonlin.003.02.0 ◽  
Author(s):  
Regina G. Belz ◽  
Karl Hurle ◽  
Stephen O. Duke
Keyword(s):  
Dose Response ◽  
Basic Principles ◽  
Nonlinear Regression Models ◽  
Research Fields ◽  
Secale Cereale L ◽  
Valid Comparison ◽  
Effective Doses ◽  
Allelopathic Effects ◽  
Allelopathic Interactions ◽  
Dose Responses

The response of an organism to a chemical depends, among other things, on the dose. Nonlinear dose-response relationships occur across a broad range of research fields, and are a well established tool to describe the basic mechanisms of phytotoxicity. The responses of plants to allelochemicals as biosynthesized phytotoxins, relate as well to nonlinearity and, thus, allelopathic effects can be adequately quantified by nonlinear mathematical modeling. The current paper applies the concept of nonlinearity to assorted aspects of allelopathy within several bioassays and reveals their analysis by nonlinear regression models. Procedures for a valid comparison of effective doses between different allelopathic interactions are presented for both, inhibitory and stimulatory effects. The dose-response applications measure and compare the responses produced by pure allelochemicals [scopoletin (7-hydroxy-6-methoxy-2 H-1-benzopyran-2-one); DIBOA (2,4-dihydroxy-2 H-1,4-benzoxaxin-3(4 H)-one); BOA (benzoxazolin-2(3 H)-one); MBOA (6-methoxy-benzoxazolin-2(3 H)-one)], involved in allelopathy of grain crops, to demonstrate how some general principles of dose responses also relate to allelopathy. Hereupon, dose-response applications with living donor plants demonstrate the validity of these principles for density-dependent phytotoxicity of allelochemicals produced and released by living plants ( Avena sativa L., Secale cereale L., Triticum L. spp.), and reveal the use of such experiments for initial considerations about basic principles of allelopathy. Results confirm that nonlinearity applies to allelopathy, and the study of allelopathic effects in dose-response experiments allows for new and challenging insights into allelopathic interactions.

Hormesis is central to toxicology, pharmacology and risk assessment

2010 ◽  
Vol 29 (4) ◽  
pp. 249-261 ◽  
Author(s):  
Edward J Calabrese
Keyword(s):  
Risk Assessment ◽  
Dose Response ◽  
Low Dose ◽  
Assessment Practices ◽  
Biological Organization ◽  
Setting Process ◽  
Toxicological Research ◽  
Multiple Levels ◽  
Dose Responses ◽  
Chemical Class

This paper summarizes numerous conceptual and experimental advances over the past two decades in the study of hormesis. Hormesis is now generally accepted as a real and reproducible biological phenomenon, being highly generalized and independent of biological model, endpoint measured and chemical class/physical stressor. The quantitative features of the hormetic dose response are generally highly consistent, regardless of the model and mechanism, and represent a quantitative index of biological plasticity at multiple levels of biological organization. The hormetic dose-response model has been demonstrated to make far more accurate predictions of responses in low dose zones than either the threshold or linear at low dose models. Numerous therapeutic agents widely used by humans are based on the hormetic dose response and its low dose stimulatory characteristics. It is expected that as low dose responses come to dominate toxicological research that risk assessment practices will incorporate hormetic concepts in the standard setting process.

Differential Response of Arkansas Palmer Amaranth (Amaranthus palmeri) to Glyphosate and Mesotrione

2018 ◽  
Vol 32 (5) ◽  
pp. 579-585 ◽  
Author(s):  
Shilpa Singh ◽  
Nilda Roma-Burgos ◽  
Vijay Singh ◽  
Ed Allan L. Alcober ◽  
Reiofeli Salas-Perez ◽  
...  
Keyword(s):  
Dose Response ◽  
Differential Response ◽  
Palmer Amaranth ◽  
Amaranthus Palmeri ◽  
Susceptible Population ◽  
Tolerance Level ◽  
Crop Fields ◽  
Greenhouse Study ◽  
Effective Doses

AbstractWe conducted a greenhouse study to evaluate the differential response of Palmer amaranth to glyphosate and mesotrione and to quantify the level of tolerance to mesotrione in recalcitrant (difficult-to-control) accessions and their offspring. Seeds were collected from 174 crop fields (corn, cotton, and soybean) across Arkansas between 2008 and 2016. Palmer amaranth seedlings (7 to 10 cm tall) were treated with glyphosate at 840 g ae ha–1or mesotrione at 105 g ha–1. Overall, 47% of the accessions (172) were resistant to glyphosate with 68% survivors. Almost 35% of accessions were highly resistant, with 90% survivors. The majority of survivors from glyphosate application incurred between 31% and 60% injury. Mesotrione killed 66% of the accessions (174); the remaining accessions had survivors with injury ranging from 61% to 90%. Accessions with the least response to mesotrione were selected to determine tolerance level. Dose–response assays were conducted with four recalcitrant populations and their F1progeny. The average effective doses (ED50) for the parent accessions and F1progeny of survivors were 21.5 g ha–1and 27.5 g ha–1, respectively. The recalcitrant parent populations were three- to five-fold more tolerant to mesotrione than the known susceptible population, as were the F1progeny.

scholarly journals Defining Hormesis: Evaluation of a Complex Concentration Response Phenomenon

2010 ◽  
Vol 29 (3) ◽  
pp. 235-246 ◽  
Author(s):  
Eric L. Kendig ◽  
Hoa H. Le ◽  
Scott M. Belcher
Keyword(s):  
Dose Response ◽  
Ad Hoc ◽  
Scientific Evidence ◽  
Biological Molecules ◽  
Response Theory ◽  
Inappropriate Use ◽  
Toxicological Studies ◽  
History Of ◽  
High Doses ◽  
Dose Responses

Hormesis describes dose-response relationships characterized by a reversal of response between low and high doses of chemicals, biological molecules, physical stressors, or other initiators of a response. Acceptance of hormesis as a viable dose-response theory has been limited until recently, in part, because of poor conceptual understanding, ad hoc and inappropriate use, and lack of a defined mechanism. By examining the history of this dose-response theory, it is clear that both pharmacological and toxicological studies provide evidence for hormetic dose responses, but retrospective examination of studies can be problematic at best. Limited scientific evidence and lack of a common lexicon with which to describe these responses have left hormesis open to inappropriate application to unrelated dose-response relationships. Future studies should examine low-dose effects using unbiased, descriptive criteria to further the scientific understanding of this dose response. A clear, concise definition is required to further the limited scientific evidence for hormetic dose responses.

Intrapleural Administration of Fibres Induces Mesothelioma in Rats in the same Relative Order of Hazard as Occurs in Man after Exposure

1992 ◽  
Vol 11 (6) ◽  
pp. 530-534 ◽  
Author(s):  
P. Carthew ◽  
R.J. Hill ◽  
R.E. Edwards ◽  
P.N. Lee
Keyword(s):  
Dose Response ◽  
Relative Sensitivity ◽  
Route Of Administration ◽  
Published Data ◽  
Relative Order ◽  
Response Data ◽  
Effect Level ◽  
Dose Responses ◽  
The Relationship ◽  
Intrapleural Administration

1 The dose—response data for the induction of mesothelioma, in rats, by the intrapleural administration of the fibrous zeolite, erionite, has been compared to the published data for the crocidolite and chrysotile forms of asbestos. Erionite is more than two orders of magnitude more carcinogenic than either of the two forms of asbestos examined. 2 The relative sensitivity of the intrapleural and intraperitoneal routes of injection were also examined. The sensitivity of the intraperitoneal over the intrapleural route of administration was considerably greater for all the forms of asbestos examined but not for erionite. 3 The relationship for different fibres, between the number of fibres required to give animals mesothelioma, at the 50% or 10% observable tumour effect level (OTEL) was examined, and a ranking of relative carcinogenicity was made. 4 This showed that the data derived from the dose responses obtained by the intrapleural administration of fibres to rats ranked the relative carcinogenicity of erionite, crocidolite and chrysotile in accord with the known clinical mesothelioma induction in man after exposure to these fibres. Examination of the carcinogenicity ranking from data derived from intraperitoneal injections of fibres was not in accord with the known clinical mesothelioma induction in man for the various asbestos types examined.

DCMU-Induced Fluorescence Changes and Photodestruction of Pigments Associated with an Inhibition of Photosystem I Cyclic Electron Flow

1984 ◽  
Vol 39 (5) ◽  
pp. 351-353 ◽  
Author(s):  
Stuart M. Ridley ◽  
Peter Horton
Keyword(s):  
Electron Transport ◽  
Photosystem Ii ◽  
Photosystem I ◽  
Dose Response ◽  
Electron Flow ◽  
Cyclic Electron Flow ◽  
Cyclic Flow ◽  
Working Hypothesis ◽  
Dose Responses

Diuron (DCMU) induces the photodestruction of pigments, which is the initial herbicidal symptom. As a working hypothesis, it is proposed that this symptom can only be produced when the herbicide dose is sufficiently high to inhibit not only photosystem II electron transport almost completely, but also inhibit (through over oxidation) the natural cyclic electron flow associated with photosystem I as well. Using freshly prepared chloroplasts, studies of DCMU-induced fluorescence changes, and dose responses for inhibition of electron transport, have been compared with a dose response for the photodestruction of pigments in chloroplasts during 24 h illumination. Photodestruction of pigments coincides with the inhibition of cyclic flow.

Comparisons of thresholds for carcinogenicity on linear and logarithmic dosage scales

2005 ◽  
Vol 24 (6) ◽  
pp. 325-332 ◽  
Author(s):  
William J Waddell
Keyword(s):  
Dose Response ◽  
Mouse Liver ◽  
Goodness Of Fit ◽  
Ethyl Carbamate ◽  
Logarithmic Scale ◽  
Linear Extrapolation ◽  
Human Haemoglobin ◽  
High Background ◽  
Dose Responses ◽  
Comparative Information

Comparisons on a linear and the Rozman logarithmic scale for dosage versus carcinogenicity in rodents are presented for methyl eugenol (ME), nitrosodiethylamine (NDEA), ethyl carbamate (EC) and 2-acetylaminofluorene (AAF). Each of these chemicals has been shown to be carcinogenic in experimental animals and, in addition, humans are regularly exposed to at least three of these compounds (ME, NDEA, EC) in foods. Although the source of adducts from AAF is not known, the aminofluorene (AF) adduct is present in humans. Plotted on the same graphs are either some doses from common foods (ME, NDEA, EC) or adducts (AF) on human haemoglobin, for perspective, with their thresholds for carcinogenesis in animals. Use of a linear scale when comparing doses administered to animals in studies of carcinogenicity with doses of those same chemicals to which humans are exposed does not provide useful, comparative information. On the other hand, the Rozman logarithmic scale for dose allows one to put these relative doses in perspective. It is also evident that forcing a linear extrapolation through the zero, zero origin does not agree with the experimental data. Further analyses for goodness of fit for these dose responses reveal that the dose response for three of these compounds (ME, NDEA, EC) appears to be linear with the logarithm of the dose. However, AAF appears to be linear with the logarithm of the dose for bladder, but not for liver. It is suggested that the high background incidence of tumours in the BALB/c StCrlfC3Hf/Nctr mouse liver may confound the interpretation of dose response from AAF carcinogenesis in mouse liver.

Inhibition of glycolysis potentiates hypoxic vasoconstriction in rat lungs

1983 ◽  
Vol 55 (5) ◽  
pp. 1467-1473 ◽  
Author(s):  
H. S. Stanbrook ◽  
I. F. McMurtry
Keyword(s):  
Dose Response ◽  
Salt Solution ◽  
Lactate Production ◽  
Physiological Salt Solution ◽  
Rat Lungs ◽  
Pressor Responses ◽  
Hypoxic Vasoconstriction ◽  
Inhibition Of Glycolysis ◽  
Lactate And Pyruvate ◽  
Dose Responses

The purpose of this study was to test whether inhibition of glycolysis would potentiate hypoxic vasoconstriction in isolated rat lungs, and, if so, to evaluate whether potentiation was due to decreased aerobic production of the mitochondrial substrate, pyruvate, or to inhibition of anaerobic synthesis of ATP. In blood-perfused lungs, both iodoacetate and 2-deoxyglucose inhibited lactate production and increased pressor responses to ventilation with gases containing from 15 to 3% O2. In lungs perfused with physiological salt solution, both 2-deoxyglucose and glucose-free perfusion inhibited lactate and pyruvate production and potentiated the dose-response curve to hypoxia. Dose responses to angiotensin II and KCl were not increased by glucose-free perfusion. Lungs perfused with glucose-free salt solution containing increased levels of lactate and pyruvate did not show an increased dose response to hypoxia. In contrast, lungs perfused with the inhibitor of citric acid cycle, malonate, in addition to the increased lactate and pyruvate, did show an increased dose response to hypoxia. These results indicate that potentiation of hypoxic vasoconstriction by inhibition of glucose metabolism is due to decreased production of pyruvate, rather than to decreased glycolytic generation of ATP. The potentiation might be directly related to either limitation of mitochondrial oxidative phosphorylation in an oxygen-sensing cell or to a decreased level of some intra- or intercellular modulating peptide, fatty acid, or lipid.

scholarly journals Pharmacogenetic Impact of VKORC1 and CYP2C9 Allelic Variants on Warfarin Dose Requirements in a Hispanic Population Isolate

2009 ◽  
Vol 16 (1) ◽  
pp. 83-90 ◽  
Author(s):  
Lina Palacio ◽  
Diana Falla ◽  
Ignacio Tobon ◽  
Fernando Mejia ◽  
John E. Lewis ◽  
...  
Keyword(s):  
Dose Response ◽  
Linear Regression Analysis ◽  
Interaction Model ◽  
Warfarin Dose ◽  
Inverse Correlation ◽  
International Normalized Ratio ◽  
Multivariate Linear Regression Analysis ◽  
Response Variance ◽  
Standard Values ◽  
Dose Responses

Warfarin is the most prescribed oral anticoagulant worldwide. Because of the complexity of warfarin therapy, we attempted to dissect genetic from bioenvironmental factors influencing warfarin dose responses in individuals of a genetic isolate of Hispanic ancestry. A total of 191 patients with standard values of international normalized ratio were recruited. Three groups with a significantly different warfarin dose response were identified, that is, sensitive (2.28 ± 0.50 mg/d), intermediate (4.2 ± 0.76 mg/d), and resistant (7.40 ± 1.54 mg/d; Tukey test, P < .001). Age had a significant inverse correlation with warfarin dose (P < .001; effective dose diminished 0.56 mg/d/decade). Required doses were higher for individuals with CYP2C9 variants containing the allele *1 compared to those individuals with variants composed of other alleles (P = .006). Similarly, individuals with VKORC1-1639GG and VKORC1-1639GA genotypes also required higher doses compared to the AA genotype (P < .001). Evaluation of potential gene-gene interactions between CYP2C9 and VKORC1 polymorphisms showed significant differences in dosing for CYP2C9 genotypes within the VKORC1-1639G/A subgroup (P = .013). A stepwise multivariate linear regression analysis showed that 38.2% of the warfarin dose response variance was accounted for by a model involving age (20.9%), VKORC1-1639G/A (11.3%), and CYP2C9*1, *2, and *3 variants (7.1%). These results corroborate previous findings on warfarin pharmacogenetics and define a contrastable gene-bioenvironment interaction model suited to be used in Hispanic populations.

scholarly journals Inheritance of Evolved Glyphosate Resistance in a North Carolina Palmer Amaranth (Amaranthus palmeri) Biotype

2012 ◽  
Vol 2012 ◽  
pp. 1-7 ◽  
Author(s):  
Aman Chandi ◽  
Susana R. Milla-Lewis ◽  
Darci Giacomini ◽  
Philip Westra ◽  
Christopher Preston ◽  
...  
Keyword(s):  
North Carolina ◽  
Dose Response ◽  
Genome Analysis ◽  
Copy Number ◽  
Single Gene ◽  
Nuclear Genome ◽  
Glyphosate Resistance ◽  
Palmer Amaranth ◽  
Amaranthus Palmeri ◽  
Dose Responses

Inheritance of glyphosate resistance in a Palmer amaranth biotype from North Carolina was studied. Glyphosate rates for 50% survival of glyphosate-resistant (GR) and glyphosate-susceptible (GS) biotypes were 1288 and 58 g ha−1, respectively. These values for F1 progenies obtained from reciprocal crosses (GR×GSandGS×GRwere 794 and 501 g ha−1, respectively. Dose response of F1 progenies indicated that resistance was not fully dominant over susceptibility. Lack of significant differences between dose responses for reciprocal F1 families suggested that genetic control of glyphosate resistance was governed by nuclear genome. Analysis of F1 backcross (BC1F1) families showed that 10 and 8 BC1F1 families out of 15 fitted monogenic inheritance at 2000 and 3000 g ha−1glyphosate, respectively. These results indicate that inheritance of glyphosate resistance in this biotype is incompletely dominant, nuclear inherited, and might not be consistent with a single gene mechanism of inheritance. Relative 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) copy number varied from 22 to 63 across 10 individuals from resistant biotype. This suggested that variableEPSPScopy number in the parents might be influential in determining if inheritance of glyphosate resistance is monogenic or polygenic in this biotype.

Amylin and insulin in rat soleus muscle: dose responses for cosecreted noncompetitive antagonists

1992 ◽  
Vol 263 (2) ◽  
pp. E274-E281 ◽  
Author(s):  
A. A. Young ◽  
B. Gedulin ◽  
D. Wolfe-Lopez ◽  
H. E. Greene ◽  
T. J. Rink ◽  
...  
Keyword(s):  
Soleus Muscle ◽  
Dose Response ◽  
Muscle Glycogen ◽  
Insulin Action ◽  
Molar Ratio ◽  
Constant Ratio ◽  
Rat Soleus Muscle ◽  
Human Amylin ◽  
Dose Responses ◽  
Bell Shaped Curve

Increasing concentrations of amylin progressively depressed the maximal insulin-stimulated radioglucose incorporation into soleus muscle glycogen, but did not substantively change the EC50 (range 0.78 to 1.52 nM); these findings show noncompetitive, insurmountable antagonism of insulin action by amylin. The results from 36 combinations of different insulin and amylin concentrations were used to construct a response surface that can be used to predict the response for any combination of insulin and amylin concentration. The predicted response to a constant ratio of insulin and amylin concentration is a bell-shaped curve. The experimentally determined response to increasing amounts of an amylin-insulin mixture (molar ratio of 0.14:1, within the range measured for pancreatic secretion and plasma levels) gave a bell-shaped response rather than the sigmoidal response seen with insulin alone. The amylin dose-response relation in the soleus system provides a useful bioassay for amylin agonists. The dose response for highly purified, synthetic human amylin obtained by measuring amylin concentrations by radioimmunoassay in the incubation medium gave an EC50 of 456 pM (+/- 0.18 log units). Human amylin had a potency greater than or equal to that of human insulin in this highly insulin-sensitive preparation.

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