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Sample records for dose-response efeitos biologicos

  1. Exploring the dose response of radiochromic dosimeters

    NASA Astrophysics Data System (ADS)

    Skyt, P. S.; Wahlstedt, I.; Yates, E. S.; Muren, L. P.; Petersen, J. B. B.; Balling, P.

    2013-06-01

    The aim of this study was to explore the dose response of a newly developed radio-chromic hydrogel dosimeter based on leuco malachite green dye in a gelatine matrix. The original dosimeter composition was first investigated in terms of dose response and dose-rate dependence. In addition, the initiating compounds producing chlorine radicals were substituted with compounds producing fluorine radicals, oxygen-centered radicals, carbon-centered radicals and bromine radicals. Also the surfactant was substituted by other compounds of different molecular size and charge. The original composition gave a dose response of 3.5·10-3 Gy-1cm-1 at 6 Gy/min with a dose rate dependence giving a 27 % increase when decreasing the dose rate to 1 Gy/min. None of the substituted initiating components contributed to an increase in dose response while only one surfactant increased the dose response slightly.

  2. Dose response signal detection under model uncertainty.

    PubMed

    Dette, Holger; Titoff, Stefanie; Volgushev, Stanislav; Bretz, Frank

    2015-12-01

    We investigate likelihood ratio contrast tests for dose response signal detection under model uncertainty, when several competing regression models are available to describe the dose response relationship. The proposed approach uses the complete structure of the regression models, but does not require knowledge of the parameters of the competing models. Standard likelihood ratio test theory is applicable in linear models as well as in nonlinear regression models with identifiable parameters. However, for many commonly used nonlinear dose response models the regression parameters are not identifiable under the null hypothesis of no dose response and standard arguments cannot be used to obtain critical values. We thus derive the asymptotic distribution of likelihood ratio contrast tests in regression models with a lack of identifiability and use this result to simulate the quantiles based on Gaussian processes. The new method is illustrated with a real data example and compared to existing procedures using theoretical investigations as well as simulations.

  3. Dose Response Data for Hormonally Active Chemicals ...

    EPA Pesticide Factsheets

    The shape of the dose response curve in the low dose region has been debated since the late 1940s. The debate originally focused on linear no threshold (LNT) vs threshold responses in the low dose range for cancer and noncancer related effects. For noncancer effects the default assumption is that noncancer effects generally display threshold rather than LNT responses. More recently, claims have arisen that the chemicals, like endocrine disrupters (EDS), which act via high affinity, low capacity nuclear receptors, may display LNT or nonmonotonic low dose responses: responses that could be missed in multigenerational guideline toxicity testing. This presentation will discuss LNT, threshold and nonmonotonic dose response relationships from case studies of chemicals that disrupt reproductive development and function via the ER, AR and AhR pathways and will include in vitro and in vivo multigenerational data. The in vivo studies in this discussion include only robust, well designed, comprehensive studies that administered the chemical via a relevant route(s) of exposure over a broad dose response range, including low dose(s) in the microgram/kg/d range. The chemicals include ethinyl estradiol, estradiol, genistein, bisphenol a, trenbolone, finasteride, flutamide, phthalate esters and 2,3,7,8 TCDD. The objective is to critically evaluate the data from well done studies in this field to address concerns that current multigenerational reproductive test gui

  4. Dose-response-a challenge for allelopathy?

    PubMed

    Belz, Regina G; Hurle, Karl; Duke, Stephen O

    2005-04-01

    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-2H-1-benzopyran-2-one); DIBOA (2,4-dihydroxy-2H-1,4-benzoxaxin-3(4H)-one); BOA (benzoxazolin-2(3H)-one); MBOA (6-methoxy-benzoxazolin-2(3H)-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.

  5. Simplified Warfarin Dose-response Pharmacodynamic Models

    PubMed Central

    Kim, Seongho; Gaweda, Adam E.; Wu, Dongfeng; Li, Lang; Rai, Shesh N.; Brier, Michael E.

    2014-01-01

    Warfarin is a frequently used oral anticoagulant for long-term prevention and treatment of thromboembolic events. Due to its narrow therapeutic range and large inter-individual dose-response variability, it is highly desirable to personalize warfarin dosing. However, the complexity of the conventional kinetic-pharmacodynamic (K-PD) models hampers the development of the personalized dose management. To avert this challenge, we propose simplified PD models for warfarin dose-response relationship, which is motivated by ideas from control theory. The simplified models were further applied to longitudinal data of 37 patients undergoing anticoagulation treatment using the standard two-stage approach and then compared with the conventional K-PD models. Data analysis shows that all models have a similar predictive ability, but the simplified models are most parsimonious. PMID:25750489

  6. Single toxin dose-response models revisited

    PubMed Central

    Glaholt, SP; Kyker-Snowman, E; Shaw, JR; Chen, CY

    2016-01-01

    The goal of this paper is to offer a rigorous analysis of the sigmoid shape single toxin dose-response relationship. The toxin efficacy function is introduced and four special points, including maximum toxin efficacy and inflection points, on the dose-response curve are defined. The special points define three phases of the toxin effect on mortality: (1) toxin concentrations smaller than the first inflection point or (2) larger then the second inflection point imply low mortality rate, and (3) concentrations between the first and the second inflection points imply high mortality rate. Probabilistic interpretation and mathematical analysis for each of four models, Hill, logit, probit, and Weibull is provided. Two general model extensions are introduced: (1) the multi-target hit model that accounts for the existence of several vital receptors affected by the toxin, and (2) model with a nonzero mortality at zero concentration to account for natural mortality. Special attention is given to statistical estimation in the framework of the generalized linear model with the binomial dependent variable as the mortality count in each experiment, contrary to the widespread nonlinear regression treating the mortality rate as continuous variable. The models are illustrated using standard EPA Daphnia acute (48 hours) toxicity tests with mortality as a function of NiCl or CuSO4 toxin. PMID:27847315

  7. The Dose Response Relationship for Radiation Carcinogenesis

    NASA Astrophysics Data System (ADS)

    Hall, Eric

    2008-03-01

    Recent surveys show that the collective population radiation dose from medical procedures in the U.S. has increased by 750% in the past two decades. It would be impossible to imagine the practice of medicine today without diagnostic and therapeutic radiology, but nevertheless the widespread and rapidly increasing use of a modality which is a known human carcinogen is a cause for concern. To assess the magnitude of the problem it is necessary to establish the shape of the dose response relationship for radiation carcinogenesis. Information on radiation carcinogenesis comes from the A-bomb survivors, from occupationally exposed individuals and from radiotherapy patients. The A-bomb survivor data indicates a linear relationship between dose and the risk of solid cancers up to a dose of about 2.5 Sv. The lowest dose at which there is a significant excess cancer risk is debatable, but it would appear to be between 40 and 100 mSv. Data from the occupation exposure of nuclear workers shows an excess cancer risk at an average dose of 19.4 mSv. At the other end of the dose scale, data on second cancers in radiotherapy patients indicates that cancer risk does not continue to rise as a linear function of dose, but tends towards a plateau of 40 to 60 Gy, delivered in a fractionated regime. These data can be used to estimate the impact of diagnostic radiology at the low dose end of the dose response relationship, and the impact of new radiotherapy modalities at the high end of the dose response relationship. In the case of diagnostic radiology about 90% of the collective population dose comes from procedures (principally CT scans) which involve doses at which there is credible evidence of an excess cancer incidence. While the risk to the individual is small and justified in a symptomatic patient, the same is not true of some screening procedures is asymptomatic individuals, and in any case the huge number of procedures must add up to a potential public health problem. In the

  8. Dose-response relationships for carcinogens: a review

    SciTech Connect

    Zeise, L.; Wilson, R.; Crouch, E.A.C.

    1987-08-01

    The authors review the experimental evidence for various shapes of dose-response relationships for carcinogens and summarize those experiments that give the most information on relatively low doses. A brief review of some models is given to illustrate the shapes of dose-response curve expected from them. Their major interest is in the use of dose-response relationships to estimate risks to humans at low doses, and so they pay special attention to experimentally observed and theoretically expected nonlinearities. There are few experimental examples of nonlinear dose-response relations in humans, but this may simply be due to the limitations in the data. The several examples in rodents, even though for high dose data, suggest that nonlinearity is common. In some cases such nonlinearities may be rationalized on the basis of the pharmacokinetics of the test compound or its metabolites.

  9. Dose-response relationships for carcinogens: a review.

    PubMed Central

    Zeise, L; Wilson, R; Crouch, E A

    1987-01-01

    We review the experimental evidence for various shapes of dose-response relationships for carcinogens and summarize those experiments that give the most information on relatively low doses. A brief review of some models is given to illustrate the shapes of dose-response curve expected from them. Our major interest is in the use of dose-response relationships to estimate risks to humans at low doses, and so we pay special attention to experimentally observed and theoretically expected nonlinearities. There are few experimental examples of nonlinear dose-response relations in humans, but this may simply be due to the limitations in the data. The several examples in rodents, even though for high dose data, suggest that nonlinearity is common. In some cases such nonlinearities may be rationalized on the basis of the pharmacokinetics of the test compound or its metabolites. PMID:3311725

  10. Curious cases: Altered dose-response relationships in addiction genetics.

    PubMed

    Uhl, George R; Drgonova, Jana; Hall, F Scott

    2014-03-01

    Dose-response relationships for most addictive substances are "inverted U"-shaped. Addictive substances produce both positive features that include reward, euphoria, anxiolysis, withdrawal-relief, and negative features that include aversion, dysphoria, anxiety and withdrawal symptoms. A simple model differentially associates ascending and descending limbs of dose-response curves with rewarding and aversive influences, respectively. However, Diagnostic and Statistical Manual (DSM) diagnoses of substance dependence fail to incorporate dose-response criteria and don't directly consider balances between euphoric and dysphoric drug effects. Classical genetic studies document substantial heritable influences on DSM substance dependence. Linkage and genome-wide association studies identify modest-sized effects at any locus. Nevertheless, clusters of SNPs within selected genes display 10(-2)>p>10(-8) associations with dependence in many independent samples. For several of these genes, evidence for cis-regulatory, level-of-expression differences supports the validity of mouse models in which levels of expression are also altered. This review documents surprising, recently defined cases in which convergent evidence from humans and mouse models supports central influences of altered dose-response relationships in mediating the impact of relevant genomic variation on addiction phenotypes. For variation at loci for the α5 nicotinic acetylcholine receptor, cadherin 13, receptor type protein tyrosine phosphatase Δ and neuronal cell adhesion molecule genes, changed dose-response relationships conferred by gene knockouts in mice are accompanied by supporting human data. These observations emphasize desirability of carefully elucidating dose-response relationships for both rewarding and aversive features of abused substances wherever possible. They motivate consideration of individual differences in dose-response relationships in addiction nosology and therapeutics.

  11. Dose-Response Calculator for ArcGIS

    USGS Publications Warehouse

    Hanser, Steven E.; Aldridge, Cameron L.; Leu, Matthias; Nielsen, Scott E.

    2011-01-01

    The Dose-Response Calculator for ArcGIS is a tool that extends the Environmental Systems Research Institute (ESRI) ArcGIS 10 Desktop application to aid with the visualization of relationships between two raster GIS datasets. A dose-response curve is a line graph commonly used in medical research to examine the effects of different dosage rates of a drug or chemical (for example, carcinogen) on an outcome of interest (for example, cell mutations) (Russell and others, 1982). Dose-response curves have recently been used in ecological studies to examine the influence of an explanatory dose variable (for example, percentage of habitat cover, distance to disturbance) on a predicted response (for example, survival, probability of occurrence, abundance) (Aldridge and others, 2008). These dose curves have been created by calculating the predicted response value from a statistical model at different levels of the explanatory dose variable while holding values of other explanatory variables constant. Curves (plots) developed using the Dose-Response Calculator overcome the need to hold variables constant by using values extracted from the predicted response surface of a spatially explicit statistical model fit in a GIS, which include the variation of all explanatory variables, to visualize the univariate response to the dose variable. Application of the Dose-Response Calculator can be extended beyond the assessment of statistical model predictions and may be used to visualize the relationship between any two raster GIS datasets (see example in tool instructions). This tool generates tabular data for use in further exploration of dose-response relationships and a graph of the dose-response curve.

  12. Bayesian Isotonic Regression Dose-response (BIRD) Model.

    PubMed

    Li, Wen; Fu, Haoda

    2016-12-21

    Understanding dose-response relationship is a crucial step in drug development. There are a few parametric methods to estimate dose-response curves, such as the Emax model and the logistic model. These parametric models are easy to interpret and, hence, widely used. However, these models often require the inclusion of patients on high-dose levels; otherwise, the model parameters cannot be reliably estimated. To have robust estimation, nonparametric models are used. However, these models are not able to estimate certain important clinical parameters, such as ED50 and Emax. Furthermore, in many therapeutic areas, dose-response curves can be assumed as non-decreasing functions. This creates an additional challenge for nonparametric methods. In this paper, we propose a new Bayesian isotonic regression dose-response model which features advantages from both parametric and nonparametric models. The ED50 and Emax can be derived from this model. Simulations are provided to evaluate the Bayesian isotonic regression dose-response model performance against two parametric models. We apply this model to a data set from a diabetes dose-finding study.

  13. Pseudomonas aeruginosa dose response and bathing water infection.

    PubMed

    Roser, D J; van den Akker, B; Boase, S; Haas, C N; Ashbolt, N J; Rice, S A

    2014-03-01

    Pseudomonas aeruginosa is the opportunistic pathogen mostly implicated in folliculitis and acute otitis externa in pools and hot tubs. Nevertheless, infection risks remain poorly quantified. This paper reviews disease aetiologies and bacterial skin colonization science to advance dose-response theory development. Three model forms are identified for predicting disease likelihood from pathogen density. Two are based on Furumoto & Mickey's exponential 'single-hit' model and predict infection likelihood and severity (lesions/m2), respectively. 'Third-generation', mechanistic, dose-response algorithm development is additionally scoped. The proposed formulation integrates dispersion, epidermal interaction, and follicle invasion. The review also details uncertainties needing consideration which pertain to water quality, outbreaks, exposure time, infection sites, biofilms, cerumen, environmental factors (e.g. skin saturation, hydrodynamics), and whether P. aeruginosa is endogenous or exogenous. The review's findings are used to propose a conceptual infection model and identify research priorities including pool dose-response modelling, epidermis ecology and infection likelihood-based hygiene management.

  14. A Generalized QMRA Beta-Poisson Dose-Response Model.

    PubMed

    Xie, Gang; Roiko, Anne; Stratton, Helen; Lemckert, Charles; Dunn, Peter K; Mengersen, Kerrie

    2016-10-01

    Quantitative microbial risk assessment (QMRA) is widely accepted for characterizing the microbial risks associated with food, water, and wastewater. Single-hit dose-response models are the most commonly used dose-response models in QMRA. Denoting PI(d) as the probability of infection at a given mean dose d, a three-parameter generalized QMRA beta-Poisson dose-response model, PI(d|α,β,r*), is proposed in which the minimum number of organisms required for causing infection, Kmin , is not fixed, but a random variable following a geometric distribution with parameter 0dose-response mechanism. Since a maximum likelihood solution is not easily available, a likelihood-free approximate Bayesian computation (ABC) algorithm is employed for parameter estimation. By fitting the generalized model to four experimental data sets from the literature, this study reveals that the posterior median r* estimates produced fall short of meeting the required condition of r* = 1 for single-hit assumption. However, three out of four data sets fitted by the generalized models could not achieve an improvement in goodness of fit. These combined results imply that, at least in some cases, a single-hit assumption for characterizing the dose-response process may not be appropriate, but that the more complex models may be difficult to support especially if the sample size is small. The three-parameter generalized model provides a possibility to investigate the mechanism of a dose-response process in greater detail than is possible under a single-hit model.

  15. Computer Simulation of Quantal Dose-Response Relationships.

    ERIC Educational Resources Information Center

    McGilliard, Kip L.

    1985-01-01

    Describes a program which simulates animal pharmacology experiments involving "all-or-none" responses. Use of the Applesoft BASIC program in the pharmacology teaching laboratory provides students with a rapid and economical way to gain experience in the design and statistical analysis of quantal dose-response experiments. Information on…

  16. A Framework for "Fit for Purpose" Dose Response Assessment

    EPA Science Inventory

    The NRC report Science and Decisions: Advancing Risk Assessment made several recommendations to improve chemical risk assessment, with a focus on in-depth chronic dose-response assessments conducted by the U.S. Environmental Protection Agency. The recommendations addressed two ...

  17. A Bayesian Semiparametric Model for Radiation Dose-Response Estimation.

    PubMed

    Furukawa, Kyoji; Misumi, Munechika; Cologne, John B; Cullings, Harry M

    2016-06-01

    In evaluating the risk of exposure to health hazards, characterizing the dose-response relationship and estimating acceptable exposure levels are the primary goals. In analyses of health risks associated with exposure to ionizing radiation, while there is a clear agreement that moderate to high radiation doses cause harmful effects in humans, little has been known about the possible biological effects at low doses, for example, below 0.1 Gy, which is the dose range relevant to most radiation exposures of concern today. A conventional approach to radiation dose-response estimation based on simple parametric forms, such as the linear nonthreshold model, can be misleading in evaluating the risk and, in particular, its uncertainty at low doses. As an alternative approach, we consider a Bayesian semiparametric model that has a connected piece-wise-linear dose-response function with prior distributions having an autoregressive structure among the random slope coefficients defined over closely spaced dose categories. With a simulation study and application to analysis of cancer incidence data among Japanese atomic bomb survivors, we show that this approach can produce smooth and flexible dose-response estimation while reasonably handling the risk uncertainty at low doses and elsewhere. With relatively few assumptions and modeling options to be made by the analyst, the method can be particularly useful in assessing risks associated with low-dose radiation exposures.

  18. Radiation Dose-Response Relationships and Risk Assessment

    SciTech Connect

    Strom, Daniel J.

    2005-07-05

    The notion of a dose-response relationship was probably invented shortly after the discovery of poisons, the invention of alcoholic beverages, and the bringing of fire into a confined space in the forgotten depths of ancient prehistory. The amount of poison or medicine ingested can easily be observed to affect the behavior, health, or sickness outcome. Threshold effects, such as death, could be easily understood for intoxicants, medicine, and poisons. As Paracelsus (1493-1541), the 'father' of modern toxicology said, 'It is the dose that makes the poison.' Perhaps less obvious is the fact that implicit in such dose-response relationships is also the notion of dose rate. Usually, the dose is administered fairly acutely, in a single injection, pill, or swallow; a few puffs on a pipe; or a meal of eating or drinking. The same amount of intoxicants, medicine, or poisons administered over a week or month might have little or no observable effect. Thus, before the discovery of ionizing radiation in the late 19th century, toxicology ('the science of poisons') and pharmacology had deeply ingrained notions of dose-response relationships. This chapter demonstrates that the notion of a dose-response relationship for ionizing radiation is hopelessly simplistic from a scientific standpoint. While useful from a policy or regulatory standpoint, dose-response relationships cannot possibly convey enough information to describe the problem from a quantitative view of radiation biology, nor can they address societal values. Three sections of this chapter address the concepts, observations, and theories that contribute to the scientific input to the practice of managing risks from exposure to ionizing radiation. The presentation begins with irradiation regimes, followed by responses to high and low doses of ionizing radiation, and a discussion of how all of this can inform radiation risk management. The knowledge that is really needed for prediction of individual risk is presented

  19. Bayesian multimodel inference for dose-response studies

    USGS Publications Warehouse

    Link, W.A.; Albers, P.H.

    2007-01-01

    Statistical inference in dose?response studies is model-based: The analyst posits a mathematical model of the relation between exposure and response, estimates parameters of the model, and reports conclusions conditional on the model. Such analyses rarely include any accounting for the uncertainties associated with model selection. The Bayesian inferential system provides a convenient framework for model selection and multimodel inference. In this paper we briefly describe the Bayesian paradigm and Bayesian multimodel inference. We then present a family of models for multinomial dose?response data and apply Bayesian multimodel inferential methods to the analysis of data on the reproductive success of American kestrels (Falco sparveriuss) exposed to various sublethal dietary concentrations of methylmercury.

  20. [Dose-response relation: relevance for clinical practice].

    PubMed

    Klinkhardt, U; Harder, S

    1998-12-15

    Dose-finding studies are performed routinely in patients and--if appropriate surrogate models exist--also in healthy volunteers. Such studies aim at establishing the optimal dose range for further clinical studies on the efficacy and the risk-benefit ratio of a new drug. The dose-response relationship of a drug is most often described by a sigmoidal curve. Its parameters include the mean effective dose, the maximal effect and the steepness. Interpretation of such curves should be done in the context of the intended clinical indications of the drug. The risk-benefit ratio of a drug can be assessed by overlapping the dose-response curve of wanted and unwanted clinical effects, again, any overlapping (which can be described e.g. by the therapeutic index) should be seen in the context of the indication and available therapeutic alternatives.

  1. [Dose-response relationship: relevance for medical practice].

    PubMed

    Klinkhardt, U; Harder, S

    2000-05-01

    Dose-finding studies are performed routinely in patients and--if appropriate surrogate models exist--also in healthy volunteers. Such studies aim at establishing the optimal dose range for further clinical studies on the efficacy and the risk-benefit ratio of a new drug. The dose-response relationship of a drug is most often described by a sigmoidal curve. Its parameters include the mean effective dose, the maximal effect and the steepness. Interpretation of such curves should be done in the context of the intended clinical indications of the drug. The risk-benefit ratio of a drug can be assessed by overlapping the dose-response curve of wanted and unwanted clinical effects, again, any overlapping (which can be described e.g. by the therapeutic index) should be seen in the context of the indication and available therapeutic alternatives.

  2. Analytical modelling of regional radiotherapy dose response of lung

    NASA Astrophysics Data System (ADS)

    Lee, Sangkyu; Stroian, Gabriela; Kopek, Neil; AlBahhar, Mahmood; Seuntjens, Jan; El Naqa, Issam

    2012-06-01

    Knowledge of the dose-response of radiation-induced lung disease (RILD) is necessary for optimization of radiotherapy (RT) treatment plans involving thoracic cavity irradiation. This study models the time-dependent relationship between local radiation dose and post-treatment lung tissue damage measured by computed tomography (CT) imaging. Fifty-eight follow-up diagnostic CT scans from 21 non-small-cell lung cancer patients were examined. The extent of RILD was segmented on the follow-up CT images based on the increase of physical density relative to the pre-treatment CT image. The segmented RILD was locally correlated with dose distribution calculated by analytical anisotropic algorithm and the Monte Carlo method to generate the corresponding dose-response curves. The Lyman-Kutcher-Burman (LKB) model was fit to the dose-response curves at six post-RT time periods, and temporal change in the LKB parameters was recorded. In this study, we observed significant correlation between the probability of lung tissue damage and the local dose for 96% of the follow-up studies. Dose-injury correlation at the first three months after RT was significantly different from later follow-up periods in terms of steepness and threshold dose as estimated from the LKB model. Dependence of dose response on superior-inferior tumour position was also observed. The time-dependent analytical modelling of RILD might provide better understanding of the long-term behaviour of the disease and could potentially be applied to improve inverse treatment planning optimization.

  3. Biphasic dose response in low level light therapy - an update.

    PubMed

    Huang, Ying-Ying; Sharma, Sulbha K; Carroll, James; Hamblin, Michael R

    2011-01-01

    Low-level laser (light) therapy (LLLT) has been known since 1967 but still remains controversial due to incomplete understanding of the basic mechanisms and the selection of inappropriate dosimetric parameters that led to negative studies. The biphasic dose-response or Arndt-Schulz curve in LLLT has been shown both in vitro studies and in animal experiments. This review will provide an update to our previous (Huang et al. 2009) coverage of this topic. In vitro mediators of LLLT such as adenosine triphosphate (ATP) and mitochondrial membrane potential show biphasic patterns, while others such as mitochondrial reactive oxygen species show a triphasic dose-response with two distinct peaks. The Janus nature of reactive oxygen species (ROS) that may act as a beneficial signaling molecule at low concentrations and a harmful cytotoxic agent at high concentrations, may partly explain the observed responses in vivo. Transcranial LLLT for traumatic brain injury (TBI) in mice shows a distinct biphasic pattern with peaks in beneficial neurological effects observed when the number of treatments is varied, and when the energy density of an individual treatment is varied. Further understanding of the extent to which biphasic dose responses apply in LLLT will be necessary to optimize clinical treatments.

  4. Biphasic dose response in low level light therapy.

    PubMed

    Huang, Ying-Ying; Chen, Aaron C-H; Carroll, James D; Hamblin, Michael R

    2009-09-01

    The use of low levels of visible or near infrared light for reducing pain, inflammation and edema, promoting healing of wounds, deeper tissues and nerves, and preventing cell death and tissue damage has been known for over forty years since the invention of lasers. Despite many reports of positive findings from experiments conducted in vitro, in animal models and in randomized controlled clinical trials, LLLT remains controversial in mainstream medicine. The biochemical mechanisms underlying the positive effects are incompletely understood, and the complexity of rationally choosing amongst a large number of illumination parameters such as wavelength, fluence, power density, pulse structure and treatment timing has led to the publication of a number of negative studies as well as many positive ones. A biphasic dose response has been frequently observed where low levels of light have a much better effect on stimulating and repairing tissues than higher levels of light. The so-called Arndt-Schulz curve is frequently used to describe this biphasic dose response. This review will cover the molecular and cellular mechanisms in LLLT, and describe some of our recent results in vitro and in vivo that provide scientific explanations for this biphasic dose response.

  5. Biphasic Dose Response in Low Level Light Therapy

    PubMed Central

    Huang, Ying-Ying; Chen, Aaron C.-H.; Carroll, James D.; Hamblin, Michael R.

    2009-01-01

    The use of low levels of visible or near infrared light for reducing pain, inflammation and edema, promoting healing of wounds, deeper tissues and nerves, and preventing cell death and tissue damage has been known for over forty years since the invention of lasers. Despite many reports of positive findings from experiments conducted in vitro, in animal models and in randomized controlled clinical trials, LLLT remains controversial in mainstream medicine. The biochemical mechanisms underlying the positive effects are incompletely understood, and the complexity of rationally choosing amongst a large number of illumination parameters such as wavelength, fluence, power density, pulse structure and treatment timing has led to the publication of a number of negative studies as well as many positive ones. A biphasic dose response has been frequently observed where low levels of light have a much better effect on stimulating and repairing tissues than higher levels of light. The so-called Arndt-Schulz curve is frequently used to describe this biphasic dose response. This review will cover the molecular and cellular mechanisms in LLLT, and describe some of our recent results in vitro and in vivo that provide scientific explanations for this biphasic dose response. PMID:20011653

  6. The Radiation Dose-Response of the Human Spinal Cord

    SciTech Connect

    Schultheiss, Timothy E.

    2008-08-01

    Purpose: To characterize the radiation dose-response of the human spinal cord. Methods and Materials: Because no single institution has sufficient data to establish a dose-response function for the human spinal cord, published reports were combined. Requisite data were dose and fractionation, number of patients at risk, number of myelopathy cases, and survival experience of the population. Eight data points for cervical myelopathy were obtained from five reports. Using maximum likelihood estimation correcting for the survival experience of the population, estimates were obtained for the median tolerance dose, slope parameter, and {alpha}/{beta} ratio in a logistic dose-response function. An adequate fit to thoracic data was not possible. Hyperbaric oxygen treatments involving the cervical cord were also analyzed. Results: The estimate of the median tolerance dose (cervical cord) was 69.4 Gy (95% confidence interval, 66.4-72.6). The {alpha}/{beta} = 0.87 Gy. At 45 Gy, the (extrapolated) probability of myelopathy is 0.03%; and at 50 Gy, 0.2%. The dose for a 5% myelopathy rate is 59.3 Gy. Graphical analysis indicates that the sensitivity of the thoracic cord is less than that of the cervical cord. There appears to be a sensitizing effect from hyperbaric oxygen treatment. Conclusions: The estimate of {alpha}/{beta} is smaller than usually quoted, but values this small were found in some studies. Using {alpha}/{beta} = 0.87 Gy, one would expect a considerable advantage by decreasing the dose/fraction to less than 2 Gy. These results were obtained from only single fractions/day and should not be applied uncritically to hyperfractionation.

  7. Modeling Effective Dosages in Hormetic Dose-Response Studies

    PubMed Central

    Belz, Regina G.; Piepho, Hans-Peter

    2012-01-01

    Background Two hormetic modifications of a monotonically decreasing log-logistic dose-response function are most often used to model stimulatory effects of low dosages of a toxicant in plant biology. As just one of these empirical models is yet properly parameterized to allow inference about quantities of interest, this study contributes the parameterized functions for the second hormetic model and compares the estimates of effective dosages between both models based on 23 hormetic data sets. Based on this, the impact on effective dosage estimations was evaluated, especially in case of a substantially inferior fit by one of the two models. Methodology/Principal Findings The data sets evaluated described the hormetic responses of four different test plant species exposed to 15 different chemical stressors in two different experimental dose-response test designs. Out of the 23 data sets, one could not be described by any of the two models, 14 could be better described by one of the two models, and eight could be equally described by both models. In cases of misspecification by any of the two models, the differences between effective dosages estimates (0–1768%) greatly exceeded the differences observed when both models provided a satisfactory fit (0–26%). This suggests that the conclusions drawn depending on the model used may diverge considerably when using an improper hormetic model especially regarding effective dosages quantifying hormesis. Conclusions/Significance The study showed that hormetic dose responses can take on many shapes and that this diversity can not be captured by a single model without risking considerable misinterpretation. However, the two empirical models considered in this paper together provide a powerful means to model, prove, and now also to quantify a wide range of hormetic responses by reparameterization. Despite this, they should not be applied uncritically, but after statistical and graphical assessment of their adequacy. PMID

  8. Dose response relationship in anti-stress gene regulatory networks.

    PubMed

    Zhang, Qiang; Andersen, Melvin E

    2007-03-02

    To maintain a stable intracellular environment, cells utilize complex and specialized defense systems against a variety of external perturbations, such as electrophilic stress, heat shock, and hypoxia, etc. Irrespective of the type of stress, many adaptive mechanisms contributing to cellular homeostasis appear to operate through gene regulatory networks that are organized into negative feedback loops. In general, the degree of deviation of the controlled variables, such as electrophiles, misfolded proteins, and O2, is first detected by specialized sensor molecules, then the signal is transduced to specific transcription factors. Transcription factors can regulate the expression of a suite of anti-stress genes, many of which encode enzymes functioning to counteract the perturbed variables. The objective of this study was to explore, using control theory and computational approaches, the theoretical basis that underlies the steady-state dose response relationship between cellular stressors and intracellular biochemical species (controlled variables, transcription factors, and gene products) in these gene regulatory networks. Our work indicated that the shape of dose response curves (linear, superlinear, or sublinear) depends on changes in the specific values of local response coefficients (gains) distributed in the feedback loop. Multimerization of anti-stress enzymes and transcription factors into homodimers, homotrimers, or even higher-order multimers, play a significant role in maintaining robust homeostasis. Moreover, our simulation noted that dose response curves for the controlled variables can transition sequentially through four distinct phases as stressor level increases: initial superlinear with lesser control, superlinear more highly controlled, linear uncontrolled, and sublinear catastrophic. Each phase relies on specific gain-changing events that come into play as stressor level increases. The low-dose region is intrinsically nonlinear, and depending on

  9. Dose-response model for teratological experiments involving quantal responses

    SciTech Connect

    Rai, K.; Van Ryzin, J.

    1985-03-01

    This paper introduces a dose-response model for teratological quantal response data where the probability of response for an offspring from a female at a given dose varies with the litter size. The maximum likelihood estimators for the parameters of the model are given as the solution of a nonlinear iterative algorithm. Two methods of low-dose extrapolation are presented, one based on the litter size distribution and the other a conservative method. The resulting procedures are then applied to a teratological data set from the literature.

  10. TESS-based dose-response using pediatric clonidine exposures

    SciTech Connect

    Benson, Blaine E. . E-mail: jebenson@salud.unm.edu; Spyker, Daniel A.; Troutman, William G.; Watson, William A. . E-mail: http://www.aapcc.org/

    2006-06-01

    Objective: The toxic and lethal doses of clonidine in children are unclear. This study was designed to determine whether data from the American Association of Poison Control Centers Toxic Exposure Surveillance System (TESS) could be utilized to determine a dose-response relationship for pediatric clonidine exposure. Methods: 3458 single-substance clonidine exposures in children <6 years of age reported to TESS from January 2000 through December 2003 were examined. Dose ingested, age, and medical outcome were available for 1550 cases. Respiratory arrest cases (n = 8) were classified as the most severe of the medical outcome categories (Arrest, Major, Moderate, Mild, and No effect). Exposures reported as a 'taste or lick' (n = 51) were included as a dose of 1/10 of the dosage form involved. Dose ranged from 0.4 to 1980 (median 13) {mu}g/kg. Weight was imputed based on a quadratic estimate of weight for age. Dose certainty was coded as exact (26% of cases) or not exact (74%). Medical outcome (response) was examined via logistic regression using SAS JMP (release 5.1). Results: The logistic model describing medical outcome (P < 0.0001) included Log dose/kg (P 0.0000) and Certainty (P = 0.045). Conclusion: TESS data can provide the basis for a statistically sound description of dose-response for pediatric clonidine poisoning exposures.

  11. Confidence bounds for nonlinear dose-response relationships.

    PubMed

    Baayen, C; Hougaard, P

    2015-11-30

    An important aim of drug trials is to characterize the dose-response relationship of a new compound. Such a relationship can often be described by a parametric (nonlinear) function that is monotone in dose. If such a model is fitted, it is useful to know the uncertainty of the fitted curve. It is well known that Wald confidence intervals are based on linear approximations and are often unsatisfactory in nonlinear models. Apart from incorrect coverage rates, they can be unreasonable in the sense that the lower confidence limit of the difference to placebo can be negative, even when an overall test shows a significant positive effect. Bootstrap confidence intervals solve many of the problems of the Wald confidence intervals but are computationally intensive and prone to undercoverage for small sample sizes. In this work, we propose a profile likelihood approach to compute confidence intervals for the dose-response curve. These confidence bounds have better coverage than Wald intervals and are more precise and generally faster than bootstrap methods. Moreover, if monotonicity is assumed, the profile likelihood approach takes this automatically into account. The approach is illustrated using a public dataset and simulations based on the Emax and sigmoid Emax models.

  12. Characterization of Statin Dose-response within Electronic Medical Records

    PubMed Central

    Wei, Wei-Qi; Feng, Qiping; Jiang, Lan; Waitara, Magarya S.; Iwuchukwu, Otito F.; Roden, Dan M.; Jiang, Min; Xu, Hua; Krauss, Ronald M.; Rotter, Jerome I.; Nickerson, Deborah A.; Davis, Robert L.; Berg, Richard L.; Peissig, Peggy L.; McCarty, Catherine A.; Wilke, Russell A.; Denny, Joshua C.

    2013-01-01

    Efforts to define the genetic architecture underlying variable statin response have met with limited success possibly because previous studies were limited to effect based on one-single-dose. We leveraged electronic medical records (EMRs) to extract potency (ED50) and efficacy (Emax) of statin dose-response curves and tested them for association with 144 pre-selected variants. Two large biobanks were used to construct dose-response curves for 2,026 (simvastatin) and 2,252 subjects (atorvastatin). Atorvastatin was more efficacious, more potent, and demonstrated less inter-individual variability than simvastatin. A pharmacodynamic variant emerging from randomized trials (PRDM16) was associated with Emax for both. For atorvastatin, Emax was 51.7 mg/dl in homozygous for the minor allele versus 75.0 mg/dl for those homozygous for the major allele. We also identified several loci associated with ED50. The extraction of rigorously defined traits from EMRs for pharmacogenetic studies represents a promising approach to further understand of genetic factors contributing to drug response. PMID:24096969

  13. Maximum likelihood estimation for cytogenetic dose-response curves

    SciTech Connect

    Frome, E.L.; DuFrain, R.J.

    1986-03-01

    In vitro dose-response curves are used to describe the relation between chromosome aberrations and radiation dose for human lymphocytes. The lymphocytes are exposed to low-LET radiation, and the resulting dicentric chromosome aberrations follow the Poisson distribution. The expected yield depends on both the magnitude and the temporal distribution of the dose. A general dose-response model that describes this relation has been presented by Kellerer and Rossi (1972, Current Topics on Radiation Research Quarterly 8, 85-158; 1978, Radiation Research 75, 471-488) using the theory of dual radiation action. Two special cases of practical interest are split-dose and continuous exposure experiments, and the resulting dose-time-response models are intrinsically nonlinear in the parameters. A general-purpose maximum likelihood estimation procedure is described, and estimation for the nonlinear models is illustrated with numerical examples from both experimental designs. Poisson regression analysis is used for estimation, hypothesis testing, and regression diagnostics. Results are discussed in the context of exposure assessment procedures for both acute and chronic human radiation exposure.

  14. PHYSIOLOCIGALLY BASED PHARMACOKINETIC (PBPK) MODELING AND MODE OF ACTION IN DOSE-RESPONSE ASSESSMENT

    EPA Science Inventory

    PHYSIOLOGICALLY BASED PHARMACOKINETIC (PBPK) MODELING AND MODE OF ACTION IN DOSE-RESPONSE ASSESSMENT. Barton HA. Experimental Toxicology Division, National Health and Environmental Effects Laboratory, ORD, U.S. EPA
    Dose-response analysis requires quantitatively linking infor...

  15. Appropriate statistical methods to compare dose responses of methionine sources.

    PubMed

    Kratzer, D D; Littell, R C

    2006-05-01

    Two sources of methionine (Met) activity are frequently used in commercial feed formulation: DL-2-hydroxy-4-(methylthio) butanoic acid (HMTBA), most commonly available as an 88% solution with 12% water; and DL-methionine (DLM, 99% powder). Despite the fact that both compounds have been in commercial use for over 50 yr, controversy and confusion remain with respect to their relative bioefficacy (RBE). This paper presents a review of the use of a nonlinear common plateau asymptotic regression technique (NLCPAR) that has been used to compare the 2 Met sources with particular emphasis on the validity of the basic assumptions of that model. The thesis of this paper is that the controversy is due, at least in part, to the misapplication of this regression technique to estimate the RBE of HMTBA and DLM. The NLCPAR model is a bioassay with the key dependent assumptions that HMTBA is a dilution of DLM, and that each follows dose-response curves of the same form and approach a common plateau. Because both provide Met activity, it may be considered reasonable to accept these assumptions; however, specifically testing them demonstrated that the assumption of a common dose-response is not supported by data. The common plateau assumption was tested with an alternative approach of fitting nonlinear separate plateaus asymptotic regression (NLSPAR) to a set of 13 published broiler studies in which the NLCPAR model had been used to estimate RBE of HMTBA and DLM. The hypothesis of a common plateau was rejected (P < 0.01), meaning that the conclusion that HMTBA had lower bioefficacy than DLM based on the NLCPAR methodology was not valid. An example using published data demonstrated that the NLSPAR model was a significantly better fit than the NLCPAR model, and showed that HMTBA and DLM followed different dose responses. Consequently, there was no single value for RBE for the entire dose range; rather, the RBE of the 2 compounds varied with use level. The evidence presented here

  16. A broadly applicable function for describing luminescence dose response

    SciTech Connect

    Burbidge, C. I.

    2015-07-28

    The basic form of luminescence dose response is investigated, with the aim of developing a single function to account for the appearance of linear, superlinear, sublinear, and supralinear behaviors and variations in saturation signal level and rate. A function is assembled based on the assumption of first order behavior in different major factors contributing to measured luminescence-dosimetric signals. Different versions of the function are developed for standardized and non-dose-normalized responses. Data generated using a two trap two recombination center model and experimental data for natural quartz are analyzed to compare results obtained using different signals, measurement protocols, pretreatment conditions, and radiation qualities. The function well describes a range of dose dependent behavior, including sublinear, superlinear, supralinear, and non-monotonic responses and relative response to α and β radiation, based on change in relative recombination and trapping probability affecting signals sourced from a single electron trap.

  17. Dose-response curve estimation: a semiparametric mixture approach.

    PubMed

    Yuan, Ying; Yin, Guosheng

    2011-12-01

    In the estimation of a dose-response curve, parametric models are straightforward and efficient but subject to model misspecifications; nonparametric methods are robust but less efficient. As a compromise, we propose a semiparametric approach that combines the advantages of parametric and nonparametric curve estimates. In a mixture form, our estimator takes a weighted average of the parametric and nonparametric curve estimates, in which a higher weight is assigned to the estimate with a better model fit. When the parametric model assumption holds, the semiparametric curve estimate converges to the parametric estimate and thus achieves high efficiency; when the parametric model is misspecified, the semiparametric estimate converges to the nonparametric estimate and remains consistent. We also consider an adaptive weighting scheme to allow the weight to vary according to the local fit of the models. We conduct extensive simulation studies to investigate the performance of the proposed methods and illustrate them with two real examples.

  18. Prediction of the mortality dose-response relationship in man

    SciTech Connect

    Morris, M.D.; Jones, T.D.

    1987-01-01

    Based upon an extensive data base including 100 separate animal studies, an estimate of the mortality dose-response relationship due to continuous photon radiation is predicted for 70 kg man. The model used in this prediction exercise includes fixed terms accounting for effects of body weight and dose rate, and random terms accounting for inter- and intra-species variation and experimental error. Point predictions and 95% prediction intervals are given for the LD/sub 05/, LD/sub 10/, LD/sub 25/, LD/sub 50/, LD/sub 75/, LD/sub 90/, and LD/sub 95/, for dose rates ranging from 1 to 50 R/min. 6 refs., 5 tabs.

  19. Bayesian Dose-Response Modeling in Sparse Data

    NASA Astrophysics Data System (ADS)

    Kim, Steven B.

    This book discusses Bayesian dose-response modeling in small samples applied to two different settings. The first setting is early phase clinical trials, and the second setting is toxicology studies in cancer risk assessment. In early phase clinical trials, experimental units are humans who are actual patients. Prior to a clinical trial, opinions from multiple subject area experts are generally more informative than the opinion of a single expert, but we may face a dilemma when they have disagreeing prior opinions. In this regard, we consider compromising the disagreement and compare two different approaches for making a decision. In addition to combining multiple opinions, we also address balancing two levels of ethics in early phase clinical trials. The first level is individual-level ethics which reflects the perspective of trial participants. The second level is population-level ethics which reflects the perspective of future patients. We extensively compare two existing statistical methods which focus on each perspective and propose a new method which balances the two conflicting perspectives. In toxicology studies, experimental units are living animals. Here we focus on a potential non-monotonic dose-response relationship which is known as hormesis. Briefly, hormesis is a phenomenon which can be characterized by a beneficial effect at low doses and a harmful effect at high doses. In cancer risk assessments, the estimation of a parameter, which is known as a benchmark dose, can be highly sensitive to a class of assumptions, monotonicity or hormesis. In this regard, we propose a robust approach which considers both monotonicity and hormesis as a possibility. In addition, We discuss statistical hypothesis testing for hormesis and consider various experimental designs for detecting hormesis based on Bayesian decision theory. Past experiments have not been optimally designed for testing for hormesis, and some Bayesian optimal designs may not be optimal under a

  20. The use of mode of action information in risk assessment: quantitative key events/dose-response framework for modeling the dose-response for key events.

    PubMed

    Simon, Ted W; Simons, S Stoney; Preston, R Julian; Boobis, Alan R; Cohen, Samuel M; Doerrer, Nancy G; Fenner-Crisp, Penelope A; McMullin, Tami S; McQueen, Charlene A; Rowlands, J Craig

    2014-08-01

    The HESI RISK21 project formed the Dose-Response/Mode-of-Action Subteam to develop strategies for using all available data (in vitro, in vivo, and in silico) to advance the next-generation of chemical risk assessments. A goal of the Subteam is to enhance the existing Mode of Action/Human Relevance Framework and Key Events/Dose Response Framework (KEDRF) to make the best use of quantitative dose-response and timing information for Key Events (KEs). The resulting Quantitative Key Events/Dose-Response Framework (Q-KEDRF) provides a structured quantitative approach for systematic examination of the dose-response and timing of KEs resulting from a dose of a bioactive agent that causes a potential adverse outcome. Two concepts are described as aids to increasing the understanding of mode of action-Associative Events and Modulating Factors. These concepts are illustrated in two case studies; 1) cholinesterase inhibition by the pesticide chlorpyrifos, which illustrates the necessity of considering quantitative dose-response information when assessing the effect of a Modulating Factor, that is, enzyme polymorphisms in humans, and 2) estrogen-induced uterotrophic responses in rodents, which demonstrate how quantitative dose-response modeling for KE, the understanding of temporal relationships between KEs and a counterfactual examination of hypothesized KEs can determine whether they are Associative Events or true KEs.

  1. CALUX measurements: statistical inferences for the dose-response curve.

    PubMed

    Elskens, M; Baston, D S; Stumpf, C; Haedrich, J; Keupers, I; Croes, K; Denison, M S; Baeyens, W; Goeyens, L

    2011-09-30

    Chemical Activated LUciferase gene eXpression [CALUX] is a reporter gene mammalian cell bioassay used for detection and semi-quantitative analyses of dioxin-like compounds. CALUX dose-response curves for 2,3,7,8-tetrachlorodibenzo-p-dioxin [TCDD] are typically smooth and sigmoidal when the dose is portrayed on a logarithmic scale. Non-linear regression models are used to calibrate the CALUX response versus TCDD standards and to convert the sample response into Bioanalytical EQuivalents (BEQs). Several complications may arise in terms of statistical inference, specifically and most important is the uncertainty assessment of the predicted BEQ. This paper presents the use of linear calibration functions based on Box-Cox transformations to overcome the issue of uncertainty assessment. Main issues being addressed are (i) confidence and prediction intervals for the CALUX response, (ii) confidence and prediction intervals for the predicted BEQ-value, and (iii) detection/estimation capabilities for the sigmoid and linearized models. Statistical comparisons between different calculation methods involving inverse prediction, effective concentration ratios (ECR(20-50-80)) and slope ratio were achieved with example datasets in order to provide guidance for optimizing BEQ determinations and expand assay performance with the recombinant mouse hepatoma CALUX cell line H1L6.1c3.

  2. A normal tissue dose response model of dynamic repair processes

    NASA Astrophysics Data System (ADS)

    Alber, Markus; Belka, Claus

    2006-01-01

    A model is presented for serial, critical element complication mechanisms for irradiated volumes from length scales of a few millimetres up to the entire organ. The central element of the model is the description of radiation complication as the failure of a dynamic repair process. The nature of the repair process is seen as reestablishing the structural organization of the tissue, rather than mere replenishment of lost cells. The interactions between the cells, such as migration, involved in the repair process are assumed to have finite ranges, which limits the repair capacity and is the defining property of a finite-sized reconstruction unit. Since the details of the repair processes are largely unknown, the development aims to make the most general assumptions about them. The model employs analogies and methods from thermodynamics and statistical physics. An explicit analytical form of the dose response of the reconstruction unit for total, partial and inhomogeneous irradiation is derived. The use of the model is demonstrated with data from animal spinal cord experiments and clinical data about heart, lung and rectum. The three-parameter model lends a new perspective to the equivalent uniform dose formalism and the established serial and parallel complication models. Its implications for dose optimization are discussed.

  3. Emesis in Ferrets Following Exposure to Different Types of Radiation: A Dose-Response Study

    DTIC Science & Technology

    1992-08-01

    SR92-34 Emesis in Ferrets Following Exposure to Different Types of Radiation: N A Dose -Response Study L51 BERNARD M. RABIN, Ph.D., WALTER A. HUNT...fission neutrons (1500-2000 following exposure to different types o" radiation: a dose -response cGy), Young (13) reported that increasing the propor...order to establish the dose -response relationships monkey, but did not produce an increase in the total for emesis following exposure to different types

  4. Photobacterial Response to Cadmium Chloride, Mercuric Chloride, and Selenium Dioxide: Dose-Response and Interaction Studies.

    DTIC Science & Technology

    1980-07-01

    activity) and producing a dose - response curve by adding different concentrations of the second compound. The EC50 values from such paired compounds...fixing the dose of the first metal at its ECIo concentra- tion and varying the concentration of the second to produce a dose - response curve . The EC5 0...concentration of one metal at approximately its EC10 and varying the concentration of the second metal to produce a dose - response curve . The six possible

  5. Dose Response Effects of Hypertonic Saline and Dextran on Cardiovascular Responses in Sheep

    DTIC Science & Technology

    1995-02-01

    137-144, 1995 DOSE RESPONSE EFFECTS OF HYPERTONIC SALINE AND DEXTRAN ON CARDIOVASCULAR RESPONSES AND PLASMA VOLUME EXPANSION IN SHEEP Michael A...addressed the dose - response effects of HS or D-70 solutions or their possible synergistic combinations to evaluate optimal concentrations of the HS and D...205-217, 1989. 13. Halvorsen L, Günther RA, Dubick MA, Holcroft JW: Dose response characteristics of hypertonic saline dextran solution. J Trauma

  6. Shared Dosimetry Error in Epidemiological Dose-Response Analyses

    PubMed Central

    Stram, Daniel O.; Preston, Dale L.; Sokolnikov, Mikhail; Napier, Bruce; Kopecky, Kenneth J.; Boice, John; Beck, Harold; Till, John; Bouville, Andre

    2015-01-01

    Radiation dose reconstruction systems for large-scale epidemiological studies are sophisticated both in providing estimates of dose and in representing dosimetry uncertainty. For example, a computer program was used by the Hanford Thyroid Disease Study to provide 100 realizations of possible dose to study participants. The variation in realizations reflected the range of possible dose for each cohort member consistent with the data on dose determinates in the cohort. Another example is the Mayak Worker Dosimetry System 2013 which estimates both external and internal exposures and provides multiple realizations of "possible" dose history to workers given dose determinants. This paper takes up the problem of dealing with complex dosimetry systems that provide multiple realizations of dose in an epidemiologic analysis. In this paper we derive expected scores and the information matrix for a model used widely in radiation epidemiology, namely the linear excess relative risk (ERR) model that allows for a linear dose response (risk in relation to radiation) and distinguishes between modifiers of background rates and of the excess risk due to exposure. We show that treating the mean dose for each individual (calculated by averaging over the realizations) as if it was true dose (ignoring both shared and unshared dosimetry errors) gives asymptotically unbiased estimates (i.e. the score has expectation zero) and valid tests of the null hypothesis that the ERR slope β is zero. Although the score is unbiased the information matrix (and hence the standard errors of the estimate of β) is biased for β≠0 when ignoring errors in dose estimates, and we show how to adjust the information matrix to remove this bias, using the multiple realizations of dose. The use of these methods in the context of several studies including, the Mayak Worker Cohort, and the U.S. Atomic Veterans Study, is discussed. PMID:25799311

  7. Beetroot juice and exercise: pharmacodynamic and dose-response relationships.

    PubMed

    Wylie, Lee J; Kelly, James; Bailey, Stephen J; Blackwell, Jamie R; Skiba, Philip F; Winyard, Paul G; Jeukendrup, Asker E; Vanhatalo, Anni; Jones, Andrew M

    2013-08-01

    Dietary supplementation with beetroot juice (BR), containing approximately 5-8 mmol inorganic nitrate (NO3(-)), increases plasma nitrite concentration ([NO2(-)]), reduces blood pressure, and may positively influence the physiological responses to exercise. However, the dose-response relationship between the volume of BR ingested and the physiological effects invoked has not been investigated. In a balanced crossover design, 10 healthy men ingested 70, 140, or 280 ml concentrated BR (containing 4.2, 8.4, and 16.8 mmol NO3(-), respectively) or no supplement to establish the effects of BR on resting plasma [NO3(-)] and [NO2(-)] over 24 h. Subsequently, on six separate occasions, 10 subjects completed moderate-intensity and severe-intensity cycle exercise tests, 2.5 h postingestion of 70, 140, and 280 ml BR or NO3(-)-depleted BR as placebo (PL). Following acute BR ingestion, plasma [NO2(-)] increased in a dose-dependent manner, with the peak changes occurring at approximately 2-3 h. Compared with PL, 70 ml BR did not alter the physiological responses to exercise. However, 140 and 280 ml BR reduced the steady-state oxygen (O2) uptake during moderate-intensity exercise by 1.7% (P = 0.06) and 3.0% (P < 0.05), whereas time-to-task failure was extended by 14% and 12% (both P < 0.05), respectively, compared with PL. The results indicate that whereas plasma [NO2(-)] and the O2 cost of moderate-intensity exercise are altered dose dependently with NO3(-)-rich BR, there is no additional improvement in exercise tolerance after ingesting BR containing 16.8 compared with 8.4 mmol NO3(-). These findings have important implications for the use of BR to enhance cardiovascular health and exercise performance in young adults.

  8. Shared dosimetry error in epidemiological dose-response analyses

    DOE PAGES

    Stram, Daniel O.; Preston, Dale L.; Sokolnikov, Mikhail; ...

    2015-03-23

    Radiation dose reconstruction systems for large-scale epidemiological studies are sophisticated both in providing estimates of dose and in representing dosimetry uncertainty. For example, a computer program was used by the Hanford Thyroid Disease Study to provide 100 realizations of possible dose to study participants. The variation in realizations reflected the range of possible dose for each cohort member consistent with the data on dose determinates in the cohort. Another example is the Mayak Worker Dosimetry System 2013 which estimates both external and internal exposures and provides multiple realizations of "possible" dose history to workers given dose determinants. This paper takesmore » up the problem of dealing with complex dosimetry systems that provide multiple realizations of dose in an epidemiologic analysis. In this paper we derive expected scores and the information matrix for a model used widely in radiation epidemiology, namely the linear excess relative risk (ERR) model that allows for a linear dose response (risk in relation to radiation) and distinguishes between modifiers of background rates and of the excess risk due to exposure. We show that treating the mean dose for each individual (calculated by averaging over the realizations) as if it was true dose (ignoring both shared and unshared dosimetry errors) gives asymptotically unbiased estimates (i.e. the score has expectation zero) and valid tests of the null hypothesis that the ERR slope β is zero. Although the score is unbiased the information matrix (and hence the standard errors of the estimate of β) is biased for β≠0 when ignoring errors in dose estimates, and we show how to adjust the information matrix to remove this bias, using the multiple realizations of dose. The use of these methods in the context of several studies including, the Mayak Worker Cohort, and the U.S. Atomic Veterans Study, is discussed.« less

  9. Shared Dosimetry Error in Epidemiological Dose-Response Analyses

    SciTech Connect

    Stram, Daniel O.; Preston, Dale L.; Sokolnikov, Mikhail; Napier, Bruce; Kopecky, Kenneth J.; Boice, John; Beck, Harold; Till, John; Bouville, Andre; Zeeb, Hajo

    2015-03-23

    Radiation dose reconstruction systems for large-scale epidemiological studies are sophisticated both in providing estimates of dose and in representing dosimetry uncertainty. For example, a computer program was used by the Hanford Thyroid Disease Study to provide 100 realizations of possible dose to study participants. The variation in realizations reflected the range of possible dose for each cohort member consistent with the data on dose determinates in the cohort. Another example is the Mayak Worker Dosimetry System 2013 which estimates both external and internal exposures and provides multiple realizations of "possible" dose history to workers given dose determinants. This paper takes up the problem of dealing with complex dosimetry systems that provide multiple realizations of dose in an epidemiologic analysis. In this paper we derive expected scores and the information matrix for a model used widely in radiation epidemiology, namely the linear excess relative risk (ERR) model that allows for a linear dose response (risk in relation to radiation) and distinguishes between modifiers of background rates and of the excess risk due to exposure. We show that treating the mean dose for each individual (calculated by averaging over the realizations) as if it was true dose (ignoring both shared and unshared dosimetry errors) gives asymptotically unbiased estimates (i.e. the score has expectation zero) and valid tests of the null hypothesis that the ERR slope β is zero. Although the score is unbiased the information matrix (and hence the standard errors of the estimate of β) is biased for β≠0 when ignoring errors in dose estimates, and we show how to adjust the information matrix to remove this bias, using the multiple realizations of dose. Use of these methods for several studies, including the Mayak Worker Cohort and the U.S. Atomic Veterans Study, is discussed.

  10. Dose-response relationship between light exposure and cycling performance.

    PubMed

    Knaier, R; Meister, S; Aeschbacher, T; Gemperle, D; Rossmeissl, A; Cajochen, C; Schmidt-Trucksäss, A

    2016-07-01

    Light has a stimulating effect on physical performance if scheduled according to the chronotype, but dose-dependent effects on performance have not yet been examined. Three groups of healthy men (25.1 ± 3.1 years) were exposed to light for different durations in a parallel group design before a 40-min time-trial. In each group, subjects were exposed to either bright light (BL, 4420 lx) or moderate light (ML, 230 lx) in a randomized order in a crossover design. The durations of light exposure were 120 min prior to and during exercise (2HEX; n = 16), 60 min prior to and during exercise (1HEX; n = 10), or only for 60 min prior to exercise (1H; n = 15). Total work performed during the time-trial in kJ in the 2HEX group was significantly higher in the BL setting (527 kJ) than in ML (512 kJ) (P = 0.002), but not in 1HEX (BL: 485 kJ; ML: 498 kJ) or 1H (BL: 519 kJ; ML: 514 kJ) (P = 0.770; P = 0.485). There was a significant (P = 0.006) positive dose-response relationship between the duration of light exposure and the work performed over the three doses of light exposure. A long duration light exposure is an effective tool to increase total work in a medium length time-trial in subjects normalized for their individual chronotype.

  11. Cryptosporidium Infection Risk: Results of New Dose-Response Modeling.

    PubMed

    Messner, Michael J; Berger, Philip

    2016-10-01

    Cryptosporidium human dose-response data from seven species/isolates are used to investigate six models of varying complexity that estimate infection probability as a function of dose. Previous models attempt to explicitly account for virulence differences among C. parvum isolates, using three or six species/isolates. Four (two new) models assume species/isolate differences are insignificant and three of these (all but exponential) allow for variable human susceptibility. These three human-focused models (fractional Poisson, exponential with immunity and beta-Poisson) are relatively simple yet fit the data significantly better than the more complex isolate-focused models. Among these three, the one-parameter fractional Poisson model is the simplest but assumes that all Cryptosporidium oocysts used in the studies were capable of initiating infection. The exponential with immunity model does not require such an assumption and includes the fractional Poisson as a special case. The fractional Poisson model is an upper bound of the exponential with immunity model and applies when all oocysts are capable of initiating infection. The beta Poisson model does not allow an immune human subpopulation; thus infection probability approaches 100% as dose becomes huge. All three of these models predict significantly (>10x) greater risk at the low doses that consumers might receive if exposed through drinking water or other environmental exposure (e.g., 72% vs. 4% infection probability for a one oocyst dose) than previously predicted. This new insight into Cryptosporidium risk suggests additional inactivation and removal via treatment may be needed to meet any specified risk target, such as a suggested 10(-4) annual risk of Cryptosporidium infection.

  12. Shared dosimetry error in epidemiological dose-response analyses

    SciTech Connect

    Stram, Daniel O.; Preston, Dale L.; Sokolnikov, Mikhail; Napier, Bruce; Kopecky, Kenneth J.; Boice, John; Beck, Harold; Till, John; Bouville, Andre; Zeeb, Hajo

    2015-03-23

    Radiation dose reconstruction systems for large-scale epidemiological studies are sophisticated both in providing estimates of dose and in representing dosimetry uncertainty. For example, a computer program was used by the Hanford Thyroid Disease Study to provide 100 realizations of possible dose to study participants. The variation in realizations reflected the range of possible dose for each cohort member consistent with the data on dose determinates in the cohort. Another example is the Mayak Worker Dosimetry System 2013 which estimates both external and internal exposures and provides multiple realizations of "possible" dose history to workers given dose determinants. This paper takes up the problem of dealing with complex dosimetry systems that provide multiple realizations of dose in an epidemiologic analysis. In this paper we derive expected scores and the information matrix for a model used widely in radiation epidemiology, namely the linear excess relative risk (ERR) model that allows for a linear dose response (risk in relation to radiation) and distinguishes between modifiers of background rates and of the excess risk due to exposure. We show that treating the mean dose for each individual (calculated by averaging over the realizations) as if it was true dose (ignoring both shared and unshared dosimetry errors) gives asymptotically unbiased estimates (i.e. the score has expectation zero) and valid tests of the null hypothesis that the ERR slope β is zero. Although the score is unbiased the information matrix (and hence the standard errors of the estimate of β) is biased for β≠0 when ignoring errors in dose estimates, and we show how to adjust the information matrix to remove this bias, using the multiple realizations of dose. The use of these methods in the context of several studies including, the Mayak Worker Cohort, and the U.S. Atomic Veterans Study, is discussed.

  13. Chronic periodontitis and smoking Prevalence and dose-response relationship

    PubMed Central

    Khan, Shahrukh; Khalid, Taimur; Awan, Kamran H.

    2016-01-01

    Objectives: To determine the prevalence and dose-response relationship of chronic periodontitis among smokers in Pakistan. Methods: This is a cross-sectional study among participants seeking dental care in Karachi Medical and Dental College, Karachi, Pakistan. A total of 443 participants with a mean age of 44.3 (±6.5) participated in the study from April 2011 to December 2011. Males comprised 64.7%, and females comprised 35.2%. Participants were interviewed on social demographics and oral habits. Participants with shallow pockets (3.5-5.5 mm) and deep pockets (>5.5 mm) were considered suffering from chronic periodontitis. The characteristics of participants were assessed using frequency distribution for categorical variables and mean (standard deviation) for continuous variables. Results: Among 443 participants, smokers were distributed as 55.1% and non-smokers as 44.9%. Smoking was found to be significantly related to young adults (p<0.007), male gender (p<0.001), and lower education level (p<0.01). Overall prevalence of chronic periodontitis among smokers was estimated at 81.6%. Heavy smoking was found to have significantly high prevalence (p<0.001) and severity (p<0.001) of periodontitis as compared with moderate and light smokers. The multivariate unadjusted model depicted 3.5 times higher risk of chronic periodontitis among smokers (p<0.001). Conclusion: Chronic periodontitis had a high prevalence among smokers. Heavy smoking was found to have a higher risk for having periodontitis. PMID:27464867

  14. Shared dosimetry error in epidemiological dose-response analyses.

    PubMed

    Stram, Daniel O; Preston, Dale L; Sokolnikov, Mikhail; Napier, Bruce; Kopecky, Kenneth J; Boice, John; Beck, Harold; Till, John; Bouville, Andre

    2015-01-01

    Radiation dose reconstruction systems for large-scale epidemiological studies are sophisticated both in providing estimates of dose and in representing dosimetry uncertainty. For example, a computer program was used by the Hanford Thyroid Disease Study to provide 100 realizations of possible dose to study participants. The variation in realizations reflected the range of possible dose for each cohort member consistent with the data on dose determinates in the cohort. Another example is the Mayak Worker Dosimetry System 2013 which estimates both external and internal exposures and provides multiple realizations of "possible" dose history to workers given dose determinants. This paper takes up the problem of dealing with complex dosimetry systems that provide multiple realizations of dose in an epidemiologic analysis. In this paper we derive expected scores and the information matrix for a model used widely in radiation epidemiology, namely the linear excess relative risk (ERR) model that allows for a linear dose response (risk in relation to radiation) and distinguishes between modifiers of background rates and of the excess risk due to exposure. We show that treating the mean dose for each individual (calculated by averaging over the realizations) as if it was true dose (ignoring both shared and unshared dosimetry errors) gives asymptotically unbiased estimates (i.e. the score has expectation zero) and valid tests of the null hypothesis that the ERR slope β is zero. Although the score is unbiased the information matrix (and hence the standard errors of the estimate of β) is biased for β≠0 when ignoring errors in dose estimates, and we show how to adjust the information matrix to remove this bias, using the multiple realizations of dose. The use of these methods in the context of several studies including, the Mayak Worker Cohort, and the U.S. Atomic Veterans Study, is discussed.

  15. Nonmonotonic Dose-Response Curves and Endocrine-Disrupting Chemicals: Fact or Falderal?**

    EPA Science Inventory

    Nonmonotonic Dose-Response Curves and Endocrine-Disrupting Chemicals: Fact or Falderal? The shape of the dose response curve in the low dose region has been debated since the 1940s, originally focusing on linear no threshold (LNT) versus threshold responses for cancer and noncanc...

  16. Continuous Toxicological Dose-Response Relationships Are Pretty Homogeneous (Society for Risk Analysis Annual Meeting)

    EPA Science Inventory

    Dose-response relationships for a wide range of in vivo and in vitro continuous datasets are well-described by a four-parameter exponential or Hill model, based on a recent analysis of multiple historical dose-response datasets, mostly with more than five dose groups (Slob and Se...

  17. Shape and Steepness of Toxicological Dose-Response Relationships of Continuous Endpoints

    EPA Science Inventory

    A re-analysis of a large number of historical dose-response data for continuous endpoints indicates that an exponential or a Hill model with four parameters both adequately describe toxicological dose-responses. The four parameters relate to the background response, the potency o...

  18. ENDOCRINE ACTIVE SUBSTANCES AND DOSE-RESPONSE FOR INDIVIDUALS AND POPULATIONS

    EPA Science Inventory

    Endocrine Active Substances and Dose-Response for Individuals and Populations
    Hugh A. Barton

    Abstract for IUPAC-SCOPE article

    Dose-response characteristics for endocrine disruption have been major focuses in efforts to understand potential impacts on human and ec...

  19. EVALUATING QUANTITATIVE FORMULAS FOR DOSE-RESPONSE ASSESSMENT OF CHEMICAL MIXTURES

    EPA Science Inventory

    Risk assessment formulas are often distinguished from dose-response models by being rough but necessary. The evaluation of these rough formulas is described here, using the example of mixture risk assessment. Two conditions make the dose-response part of mixture risk assessment d...

  20. BY HOW MUCH DO SHAPES OF TOXICOLOGICAL DOSE-RESPONSE RELATIONSHIPS VARY? (SOT)

    EPA Science Inventory

    A re-analysis of a large number of historical dose-response data for continuous endpoints showed that the shapes of the dose-response relationships were surprisingly homogenous. The datasets were selected on the sole criterion that they were expected to provide relatively good in...

  1. Kalman Filter Models for Extrapolations in Dose-Response Experiments and Accelerated Life-Tests.

    DTIC Science & Technology

    1988-09-09

    Kalman-Filter models with Gaussian innovations provide a useful and easy to implement tool for inference from dose - response experiments and...proposed dose - response relationship. This is in contrast to the currently used approaches wherein there is an implicit commitment to the validity of

  2. Non-Linear Dose-Response Relationships in Biology, Toxicology and Medicine

    DTIC Science & Technology

    2007-11-02

    The purpose of the conference was to attract researchers from diverse backgrounds who are working in the common area of non-linear dose - response relationships...This unique interdisciplinary conference represents an important step in furthering the understanding of the occurrence, origin, mechanisms, significance and practical applications of non-linear dose - response relationships.

  3. NEUROTOXIC EFFECTS OF ENVIRONMENTAL AGENTS: DATA GAPS THAT CHALLENGE DOSE-RESPONSE ESTIMATION

    EPA Science Inventory

    Neurotoxic effects of environmental agents: Data gaps that challenge dose-response estimation
    S Gutter*, P Mendola+, SG Selevan**, D Rice** (*UNC Chapel Hill; +US EPA, NHEERL; **US EPA, NCEA)

    Dose-response estimation is a critical feature of risk assessment. It can be...

  4. The analysis of dose-response curve from bioassays with quantal response: Deterministic or statistical approaches?

    PubMed

    Mougabure-Cueto, G; Sfara, V

    2016-04-25

    Dose-response relations can be obtained from systems at any structural level of biological matter, from the molecular to the organismic level. There are two types of approaches for analyzing dose-response curves: a deterministic approach, based on the law of mass action, and a statistical approach, based on the assumed probabilities distribution of phenotypic characters. Models based on the law of mass action have been proposed to analyze dose-response relations across the entire range of biological systems. The purpose of this paper is to discuss the principles that determine the dose-response relations. Dose-response curves of simple systems are the result of chemical interactions between reacting molecules, and therefore are supported by the law of mass action. In consequence, the shape of these curves is perfectly sustained by physicochemical features. However, dose-response curves of bioassays with quantal response are not explained by the simple collision of molecules but by phenotypic variations among individuals and can be interpreted as individual tolerances. The expression of tolerance is the result of many genetic and environmental factors and thus can be considered a random variable. In consequence, the shape of its associated dose-response curve has no physicochemical bearings; instead, they are originated from random biological variations. Due to the randomness of tolerance there is no reason to use deterministic equations for its analysis; on the contrary, statistical models are the appropriate tools for analyzing these dose-response relations.

  5. USE OF MECHANISTIC DATA TO HELP DEFINE DOSE-RESPONSE CURVES

    EPA Science Inventory

    Use of Mechanistic Data to Help Define Dose-Response Curves

    The cancer risk assessment process described by the U.S. EPA necessitates a description of the dose-response curve for tumors in humans at low (environmental) exposures. This description can either be a default l...

  6. Estimation of dose-response models for discrete and continuous data in weed science

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Dose-response analysis is widely used in biological sciences and has application to a variety of risk assessment, bioassay, and calibration problems. In weed science, dose-response methodologies have typically relied on least squares estimation under an assumption of normality. Advances in computati...

  7. Testing the Capacity of the National Biological Dose Response Plan (NBDRP) EX40801

    DTIC Science & Technology

    2009-11-01

    Testing the capacity of the National Biological Dose Response Plan (NBDRP) EX40801 Ruth Wilkins, James McNamee, Hillary...2. REPORT TYPE 3. DATES COVERED 4. TITLE AND SUBTITLE Testing the capacity of the National Biological Dose Response Plan (NBDRP) EX40801 5a...Report July 2009 Page 2 of 11 Testing the capacity of the NBDRP

  8. Statistical strategies for averaging EC50 from multiple dose-response experiments.

    PubMed

    Jiang, Xiaoqi; Kopp-Schneider, Annette

    2015-11-01

    In most dose-response studies, repeated experiments are conducted to determine the EC50 value for a chemical, requiring averaging EC50 estimates from a series of experiments. Two statistical strategies, the mixed-effect modeling and the meta-analysis approach, can be applied to estimate average behavior of EC50 values over all experiments by considering the variabilities within and among experiments. We investigated these two strategies in two common cases of multiple dose-response experiments in (a) complete and explicit dose-response relationships are observed in all experiments and in (b) only in a subset of experiments. In case (a), the meta-analysis strategy is a simple and robust method to average EC50 estimates. In case (b), all experimental data sets can be first screened using the dose-response screening plot, which allows visualization and comparison of multiple dose-response experimental results. As long as more than three experiments provide information about complete dose-response relationships, the experiments that cover incomplete relationships can be excluded from the meta-analysis strategy of averaging EC50 estimates. If there are only two experiments containing complete dose-response information, the mixed-effects model approach is suggested. We subsequently provided a web application for non-statisticians to implement the proposed meta-analysis strategy of averaging EC50 estimates from multiple dose-response experiments.

  9. An automated fitting procedure and software for dose-response curves with multiphasic features

    PubMed Central

    Veroli, Giovanni Y. Di; Fornari, Chiara; Goldlust, Ian; Mills, Graham; Koh, Siang Boon; Bramhall, Jo L; Richards, Frances M.; Jodrell, Duncan I.

    2015-01-01

    In cancer pharmacology (and many other areas), most dose-response curves are satisfactorily described by a classical Hill equation (i.e. 4 parameters logistical). Nevertheless, there are instances where the marked presence of more than one point of inflection, or the presence of combined agonist and antagonist effects, prevents straight-forward modelling of the data via a standard Hill equation. Here we propose a modified model and automated fitting procedure to describe dose-response curves with multiphasic features. The resulting general model enables interpreting each phase of the dose-response as an independent dose-dependent process. We developed an algorithm which automatically generates and ranks dose-response models with varying degrees of multiphasic features. The algorithm was implemented in new freely available Dr Fit software (sourceforge.net/projects/drfit/). We show how our approach is successful in describing dose-response curves with multiphasic features. Additionally, we analysed a large cancer cell viability screen involving 11650 dose-response curves. Based on our algorithm, we found that 28% of cases were better described by a multiphasic model than by the Hill model. We thus provide a robust approach to fit dose-response curves with various degrees of complexity, which, together with the provided software implementation, should enable a wide audience to easily process their own data. PMID:26424192

  10. The Maturing of Hormesis as a Credible Dose-Response Model

    PubMed Central

    Calabrese, Edward J.

    2003-01-01

    Hormesis is a dose-response phenomenon that has received little recognition, credibility and acceptance as evidenced by its absence from major toxicological/risk assessment texts, governmental regulatory dose-response modeling for risk assessment, and non-visibility in major professional toxicological society national meetings. This paper traces the historical evolution of the hormetic dose-response hypothesis, why this model is not only credible but also more common than the widely accepted threshold model in direct comparative evaluation, and how the toxicological community made a critical error in rejecting hormesis, a rejection sustained over 70 years. PMID:19330138

  11. The Use of Mode of Action Information in Risk Assessment: Quantitative Key Events/Dose-Response Framework for Modeling the Dose-Response for Key Events

    EPA Science Inventory

    The HESI RISK21 project formed the Dose-Response/Mode-of-Action Subteam to develop strategies for using all available data (in vitro, in vivo, and in silico) to advance the next-generation of chemical risk assessments. A goal of the Subteam is to enhance the existing Mode of Act...

  12. Cancer Dose-Response Assessment for Polychlorinated Biphenyls (PCBs) and Application to Environmental Mixtures

    EPA Pesticide Factsheets

    This report updates the cancer dose-response assessment for PCBs and shows how information on toxicity, disposition, and environmental processes can be considered together to evaluate health risks from PCB mixtures in the environment.

  13. RASS SOT Webinar - Nonmonotonic Dose Response Curves (NMDRCs) Common after Estrogen or Androgen Signaling Pathway Disruption

    EPA Science Inventory

    The presentation provides the listening and viewing audience with Dr Gray's scientific information on the relevance of nonmonotonic dose response curves to the risk assessment of estrogenic and androgenic chemicals

  14. A strategy to model nonmonotonic dose-response curve and estimate IC50.

    PubMed

    Zhang, Hui; Holden-Wiltse, Jeanne; Wang, Jiong; Liang, Hua

    2013-01-01

    The half-maximal inhibitory concentration IC[Formula: see text] is an important pharmacodynamic index of drug effectiveness. To estimate this value, the dose response relationship needs to be established, which is generally achieved by fitting monotonic sigmoidal models. However, recent studies on Human Immunodeficiency Virus (HIV) mutants developing resistance to antiviral drugs show that the dose response curve may not be monotonic. Traditional models can fail for nonmonotonic data and ignore observations that may be of biologic significance. Therefore, we propose a nonparametric model to describe the dose response relationship and fit the curve using local polynomial regression. The nonparametric approach is shown to be promising especially for estimating the IC[Formula: see text] of some HIV inhibitory drugs, in which there is a dose-dependent stimulation of response for mutant strains. This model strategy may be applicable to general pharmacologic, toxicologic, or other biomedical data that exhibits a nonmonotonic dose response relationship for which traditional parametric models fail.

  15. Dose-response relationships and extrapolation in toxicology - Mechanistic and statistical considerations

    EPA Science Inventory

    Controversy on toxicological dose-response relationships and low-dose extrapolation of respective risks is often the consequence of misleading data presentation, lack of differentiation between types of response variables, and diverging mechanistic interpretation. In this chapter...

  16. A grid algorithm for high throughput fitting of dose-response curve data.

    PubMed

    Wang, Yuhong; Jadhav, Ajit; Southal, Noel; Huang, Ruili; Nguyen, Dac-Trung

    2010-10-21

    We describe a novel algorithm, Grid algorithm, and the corresponding computer program for high throughput fitting of dose-response curves that are described by the four-parameter symmetric logistic dose-response model. The Grid algorithm searches through all points in a grid of four dimensions (parameters) and finds the optimum one that corresponds to the best fit. Using simulated dose-response curves, we examined the Grid program's performance in reproducing the actual values that were used to generate the simulated data and compared it with the DRC package for the language and environment R and the XLfit add-in for Microsoft Excel. The Grid program was robust and consistently recovered the actual values for both complete and partial curves with or without noise. Both DRC and XLfit performed well on data without noise, but they were sensitive to and their performance degraded rapidly with increasing noise. The Grid program is automated and scalable to millions of dose-response curves, and it is able to process 100,000 dose-response curves from high throughput screening experiment per CPU hour. The Grid program has the potential of greatly increasing the productivity of large-scale dose-response data analysis and early drug discovery processes, and it is also applicable to many other curve fitting problems in chemical, biological, and medical sciences.

  17. The Key Events Dose-Response Framework: A Cross-Disciplinary Mode-of-Action Based Approach to Examining Dose-Response and Thresholds

    PubMed Central

    JULIEN, ELIZABETH; BOOBIS, ALAN R.; OLIN, STEPHEN S.

    2009-01-01

    The ILSI Research Foundation convened a cross-disciplinary working group to examine current approaches for assessing dose-response and identifying safe levels of intake or exposure for four categories of bioactive agents—food allergens, nutrients, pathogenic microorganisms, and environmental chemicals. This effort generated a common analytical framework—the Key Events Dose-Response Framework (KEDRF)—for systematically examining key events that occur between the initial dose of a bioactive agent and the effect of concern. Individual key events are considered with regard to factors that influence the dose-response relationship and factors that underlie variability in that relationship. This approach illuminates the connection between the processes occurring at the level of fundamental biology and the outcomes observed at the individual and population levels. Thus, it promotes an evidence-based approach for using mechanistic data to reduce reliance on default assumptions, to quantify variability, and to better characterize biological thresholds. This paper provides an overview of the KEDRF and introduces a series of four companion papers that illustrate initial application of the approach to a range of bioactive agents. PMID:19690994

  18. Parameterizing dose-response models to estimate relative potency functions directly.

    PubMed

    Dinse, Gregg E; Umbach, David M

    2012-10-01

    Many comparative analyses of toxicity assume that the potency of a test chemical relative to a reference chemical is constant, but employing such a restrictive assumption uncritically may generate misleading conclusions. Recent efforts to characterize non-constant relative potency rely on relative potency functions and estimate them secondarily after fitting dose-response models for the test and reference chemicals. We study an alternative approach of specifying a relative potency model a priori and estimating it directly using the dose-response data from both chemicals. We consider a power function in dose as a relative potency model and find that it keeps the two chemicals' dose-response functions within the same family of models for families typically used in toxicology. When differences in the response limits for the test and reference chemicals are attributable to the chemicals themselves, the older two-stage approach is the more convenient. When differences in response limits are attributable to other features of the experimental protocol or when response limits do not differ, the direct approach is straightforward to apply with nonlinear regression methods and simplifies calculation of simultaneous confidence bands. We illustrate the proposed approach using Hill models with dose-response data from U.S. National Toxicology Program bioassays. Though not universally applicable, this method of estimating relative potency functions directly can be profitably applied to a broad family of dose-response models commonly used in toxicology.

  19. Modeling Dose-response at Low Dose: A Systems Biology Approach for Ionization Radiation.

    PubMed

    Zhao, Yuchao; Ricci, Paolo F

    2010-03-18

    For ionization radiation (IR) induced cancer, a linear non-threshold (LNT) model at very low doses is the default used by a number of national and international organizations and in regulatory law. This default denies any positive benefit from any level of exposure. However, experimental observations and theoretical biology have found that both linear and J-shaped IR dose-response curves can exist at those very low doses. We develop low dose J-shaped dose-response, based on systems biology, and thus justify its use regarding exposure to IR. This approach incorporates detailed, molecular and cellular descriptions of biological/toxicological mechanisms to develop a dose-response model through a set of nonlinear, differential equations describing the signaling pathways and biochemical mechanisms of cell cycle checkpoint, apoptosis, and tumor incidence due to IR. This approach yields a J-shaped dose response curve while showing where LNT behaviors are likely to occur. The results confirm the hypothesis of the J-shaped dose response curve: the main reason is that, at low-doses of IR, cells stimulate protective systems through a longer cell arrest time per unit of IR dose. We suggest that the policy implications of this approach are an increasingly correct way to deal with precautionary measures in public health.

  20. [Dose response curve of paclitaxel measured by histoculture drug response assay].

    PubMed

    Yoshimasu, Tatsuya; Oura, Shoji; Hirai, Issei; Kokawa, Yozo; Okamura, Yoshitaka; Furukawa, Tomoko

    2005-04-01

    Dose response curves of paclitaxel were measured by histoculture drug response assay (HDRA) in 11 lung cancer patients. Inhibition rates of paclitaxel at several concentrations were measured and fitted to the sigmoid dose response curve, using non-linear least square analysis, with fitting equation y=A (1-1/(1+exp (b (x-log (ED50)). Parameters A, b, and ED50 were 88.3+/-6.0 (80.0-100.0) %, 9.57+/-4.32 (2.25-15.0), and 26.8+/-8.1 (15.0-41.0) microg/ml, respectively. The parameter b was lower in well-differentiated tumors compared with moderately and poorly-differentiated tumors. Dose response curves of paclitaxel could be measured by HDRA in lung cancer. This method provides us more information for drug sensitivity than the usual HDRA method. This may lead to the improved accuracy of HDRA.

  1. Dose-response curve for anaesthetics based on the Monod-Wyman-Changeux model.

    PubMed

    Iwai, T; Kihara, H; Imaiand, K; Uchida, M

    1996-10-01

    We have analysed the dose-response curve for halothane and isoflurane according to the Monod-Wyman-Changeux (MWC) model. This model describes the nature of the physiological data reported by Wakamori, Ikemoto and Akaike for inhibitory Cl currents induced by GABA or glycine in dissociated rat brain neurones and by Herrington and colleagues for Ca2+ currents in clonal pituitary cells. With some assumptions on the difference in response to anaesthetics between patients, the model is applicable in vivo, and it also describes well the human dose-response curve for isoflurane reported by Mather, Raftery and Prys-Roberts. However, the steeply sigmoidal dose-response curve in humans for halothane presented by deJong and Eger is difficult to understand with the same model, because it gives rise to unrealistic MWC variables.

  2. Adaptive dose finding based on t-statistic for dose-response trials.

    PubMed

    Ivanova, Anastasia; Bolognese, James A; Perevozskaya, Inna

    2008-05-10

    The goals of phase II dose-response studies are to prove that the treatment is effective and to choose the dose for further development. Randomized designs with equal allocation to either a high dose and placebo or to each of several doses and placebo are typically used. However, in trials where response is observed relatively quickly, adaptive designs might offer an advantage over equal allocation. We propose an adaptive design for dose-response trials that concentrates the allocation of subjects in one or more areas of interest, for example, near a minimum clinically important effect level, or near some maximal effect level, and also allows for the possibility to stop the trial early if needed. The proposed adaptive design yields higher power to detect a dose-response relationship, higher power in comparison with placebo, and selects the correct dose more frequently compared with a corresponding randomized design with equal allocation to doses.

  3. An adaptive two-stage dose-response design method for establishing Proof of Concept

    PubMed Central

    Franchetti, Yoko; Anderson, Stewart J.; Sampson, Allan R.

    2013-01-01

    We propose an adaptive two-stage dose-response design where a pre-specified adaptation rule is used to add and/or drop treatment arms between the stages. We extend the multiple comparison procedures-modeling (MCP-Mod) approach into a two-stage design. In each stage, we use the same set of candidate dose-response models and test for a dose-response relationship or proof of concept (PoC) via model-associated statistics. The stage-wise test results are then combined to establish ‘global’ PoC using a conditional error function. Our simulation studies showed good and more robust power in our design method compared to conventional and fixed designs. PMID:23957520

  4. Testing the dose-response specification in epidemiology: public health and policy consequences for lead.

    PubMed

    Rothenberg, Stephen J; Rothenberg, Jesse C

    2005-09-01

    Statistical evaluation of the dose-response function in lead epidemiology is rarely attempted. Economic evaluation of health benefits of lead reduction usually assumes a linear dose-response function, regardless of the outcome measure used. We reanalyzed a previously published study, an international pooled data set combining data from seven prospective lead studies examining contemporaneous blood lead effect on IQ (intelligence quotient) of 7-year-old children (n = 1,333). We constructed alternative linear multiple regression models with linear blood lead terms (linear-linear dose response) and natural-log-transformed blood lead terms (log-linear dose response). We tested the two lead specifications for nonlinearity in the models, compared the two lead specifications for significantly better fit to the data, and examined the effects of possible residual confounding on the functional form of the dose-response relationship. We found that a log-linear lead-IQ relationship was a significantly better fit than was a linear-linear relationship for IQ (p = 0.009), with little evidence of residual confounding of included model variables. We substituted the log-linear lead-IQ effect in a previously published health benefits model and found that the economic savings due to U.S. population lead decrease between 1976 and 1999 (from 17.1 microg/dL to 2.0 microg/dL) was 2.2 times (319 billion dollars) that calculated using a linear-linear dose-response function (149 billion dollars). The Centers for Disease Control and Prevention action limit of 10 microg/dL for children fails to protect against most damage and economic cost attributable to lead exposure.

  5. The Emergence of the Dose-Response Concept in Biology and Medicine.

    PubMed

    Calabrese, Edward J

    2016-12-05

    A historical assessment of the origin of the dose-response in modern toxicology and its integration as a central concept in biology and medicine is presented. This article provides an overview of how the threshold, linear and biphasic (i.e., hormetic) dose-response models emerged in the late 19th and early 20th centuries and competed for acceptance and dominance. Particular attention is directed to the hormetic model for which a general description and evaluation is provided, including its historical basis, and how it was marginalized by the medical and pharmacology communities in the early decades of the 20th century.

  6. Comparison of Risk Predicted by Multiple Norovirus Dose-Response Models and Implications for Quantitative Microbial Risk Assessment.

    PubMed

    Van Abel, Nicole; Schoen, Mary E; Kissel, John C; Meschke, J Scott

    2016-06-10

    The application of quantitative microbial risk assessments (QMRAs) to understand and mitigate risks associated with norovirus is increasingly common as there is a high frequency of outbreaks worldwide. A key component of QMRA is the dose-response analysis, which is the mathematical characterization of the association between dose and outcome. For Norovirus, multiple dose-response models are available that assume either a disaggregated or an aggregated intake dose. This work reviewed the dose-response models currently used in QMRA, and compared predicted risks from waterborne exposures (recreational and drinking) using all available dose-response models. The results found that the majority of published QMRAs of norovirus use the 1 F1 hypergeometric dose-response model with α = 0.04, β = 0.055. This dose-response model predicted relatively high risk estimates compared to other dose-response models for doses in the range of 1-1,000 genomic equivalent copies. The difference in predicted risk among dose-response models was largest for small doses, which has implications for drinking water QMRAs where the concentration of norovirus is low. Based on the review, a set of best practices was proposed to encourage the careful consideration and reporting of important assumptions in the selection and use of dose-response models in QMRA of norovirus. Finally, in the absence of one best norovirus dose-response model, multiple models should be used to provide a range of predicted outcomes for probability of infection.

  7. Dose-Response Issues Concerning the Relations between Regular Physical Activity and Health.

    ERIC Educational Resources Information Center

    Rankinen, Tuomo; Bouchard, Claude

    2002-01-01

    This paper categorizes the many benefits of physical activity, offering information concerning the type of dose necessary to get that benefit. In 2000, Health Canada and the United States Centers for Disease Control and Prevention, along with other agencies, sponsored a symposium to determine whether there was a dose-response relationship between…

  8. Development of a biologically based dose response (BBDR) model for arsenic induced cancer

    EPA Science Inventory

    We are developing a biologically based dose response (BBDR) model for arsenic carcinogenicity in order to reduce uncertainty in estimates of low dose risk by maximizing the use of relevant data on the mode of action. Expert consultation and literature review are being conducted t...

  9. Non-Targeted Effects and the Dose Response for Heavy Ion Tumorigenesis

    NASA Technical Reports Server (NTRS)

    Chappell, Lori J.; Cucinotta, Francis A.

    2010-01-01

    There is no human epidemiology data available to estimate the heavy ion cancer risks experienced by astronauts in space. Studies of tumor induction in mice are a necessary step to estimate risks to astronauts. Previous experimental data can be better utilized to model dose response for heavy ion tumorigenesis and plan future low dose studies.

  10. Empirical Evaluation of Meta-Analytic Approaches for Nutrient and Health Outcome Dose-Response Data

    ERIC Educational Resources Information Center

    Yu, Winifred W.; Schmid, Christopher H.; Lichtenstein, Alice H.; Lau, Joseph; Trikalinos, Thomas A.

    2013-01-01

    The objective of this study is to empirically compare alternative meta-analytic methods for combining dose-response data from epidemiological studies. We identified meta-analyses of epidemiological studies that analyzed the association between a single nutrient and a dichotomous outcome. For each topic, we performed meta-analyses of odds ratios…

  11. Concord grape juice polyphenols and cardiovascular risk factors: dose-response relationships

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Pure fruit juices provide nutritional value with evidence suggesting some of their benefits on biomarkers of cardiovascular disease risk may be derived from their constituent polyphenols, particularly flavonoids. However, few data from clinical trials are available on the dose-response relationship ...

  12. Development of the dose-response relationship for human toxoplasma gondii infection associated with meat consumption

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Toxoplasma gondii is a protozoan parasite that is responsible for approximately 24% of deaths attributed to foodborne pathogens in the United States.A substantial portion of human T. gondii infections may be acquired through the consumption of meats. The dose-response relationship for human exposure...

  13. Adaptive Responses to Prochloraz Exposure That Alter Dose-Response and Time-Course Behaviors

    EPA Science Inventory

    Dose response and time-course (DRTC) are, along with exposure, the major determinants of health risk. Adaptive changes within exposed organisms in response to environmental stress are common, and alter DRTC behaviors to minimize the effects caused by stressors. In this project, ...

  14. DEVELOPMENT AND EVALUATION OF NOVEL DOSE-RESPONSE MODELS FOR USE IN MICROBIAL RISK ASSESSMENT

    EPA Science Inventory

    This document contains a description of dose-response modeling methods designed to provide a robust approach under uncertainty for predicting human population risk from exposure to pathogens in drinking water.

    The purpose of this document is to describe a body of literatu...

  15. Pharmacogenetic Predictors of Methylphenidate Dose-Response in Attention-Deficit/Hyperactivity Disorder

    ERIC Educational Resources Information Center

    Froehlich, Tanya E.; Epstein, Jeffery N.; Nick, Todd G.; Melguizo Castro, Maria S.; Stein, Mark A.; Brinkman, William B.; Graham, Amanda J.; Langberg, Joshua M.; Kahn, Robert S.

    2011-01-01

    Objective: Because of significant individual variability in attention-deficit/hyperactivity disorder (ADHD) medication response, there is increasing interest in identifying genetic predictors of treatment effects. This study examined the role of four catecholamine-related candidate genes in moderating methylphenidate (MPH) dose-response. Method:…

  16. Evaluating quantitative formulas for dose-response assessment of chemical mixtures.

    PubMed

    Hertzberg, Richard C; Teuschler, Linda K

    2002-12-01

    Risk assessment formulas are often distinguished from dose-response models by being rough but necessary. The evaluation of these rough formulas is described here, using the example of mixture risk assessment. Two conditions make the dose-response part of mixture risk assessment difficult, lack of data on mixture dose-response relationships, and the need to address risk from combinations of chemicals because of public demands and statutory requirements. Consequently, the U.S. Environmental Protection Agency has developed methods for carrying out quantitative dose-response assessment for chemical mixtures that require information only on the toxicity of single chemicals and of chemical pair interactions. These formulas are based on plausible ideas and default parameters but minimal supporting data on whole mixtures. Because of this lack of mixture data, the usual evaluation of accuracy (predicted vs. observed) cannot be performed. Two approaches to the evaluation of such formulas are to consider fundamental biological concepts that support the quantitative formulas (e.g., toxicologic similarity) and to determine how well the proposed method performs under simplifying constraints (e.g., as the toxicologic interactions disappear). These ideas are illustrated using dose addition and two weight-of-evidence formulas for incorporating toxicologic interactions.

  17. Estimating the predictive quality of dose-response after model selection.

    PubMed

    Hu, Chuanpu; Dong, Yingwen

    2007-07-20

    Prediction of dose-response is important in dose selection in drug development. As the true dose-response shape is generally unknown, model selection is frequently used, and predictions based on the final selected model. Correctly assessing the quality of the predictions requires accounting for the uncertainties caused by the model selection process, which has been difficult. Recently, a new approach called data perturbation has emerged. It allows important predictive characteristics be computed while taking model selection into consideration. We study, through simulation, the performance of data perturbation in estimating standard error of parameter estimates and prediction errors. Data perturbation was found to give excellent prediction error estimates, although at times large Monte Carlo sizes were needed to obtain good standard error estimates. Overall, it is a useful tool to characterize uncertainties in dose-response predictions, with the potential of allowing more accurate dose selection in drug development. We also look at the influence of model selection on estimation bias. This leads to insights into candidate model choices that enable good dose-response prediction.

  18. EVALUATION OF BIOLOGICALLY BASED DOSE-RESPONSE MODELING FOR DEVELOPMENTAL TOXICITY: A WORKSHOP REPORT

    EPA Science Inventory

    Evaluation of biologically based dose-response modeling for developmental toxicity: a workshop report.

    Lau C, Andersen ME, Crawford-Brown DJ, Kavlock RJ, Kimmel CA, Knudsen TB, Muneoka K, Rogers JM, Setzer RW, Smith G, Tyl R.

    Reproductive Toxicology Division, NHEERL...

  19. A Meta-Analysis To Determine the Dose Response for Strength Development.

    ERIC Educational Resources Information Center

    Rhea, Matthew R.; Alvar, Brent A.; Burkett, Lee N.; Ball, Stephen D.

    2003-01-01

    Examined the quantitative dose-response relationship for strength development by calculating the magnitude of gains elicited by various levels of training intensity, frequency, and volume; thus clarifying the effort to benefit ratio. A meta-analysis of 140 studies with 1,433 effect sizes (ES) was conducted. ES demonstrated different responses…

  20. DOSE -RESPONSE RELATIONSHIP OF CRUDE COBRA VENOM (NAJA JANA) IN THE DOG

    DTIC Science & Technology

    The study was conducted to determine the dose - response effects of crude cobra venom (Naja naja) in the anesthetized dog. It was concluded that the LD50 is about 0.105 mg/kg, and the LD99 is 0.148 mg/kg.

  1. Duration of Exposure and the Dose-Response Model of PTSD

    ERIC Educational Resources Information Center

    Kaysen, Debra; Rosen, Gerald; Bowman, Marilyn; Resick, Patricia A.

    2010-01-01

    A dose-response model underlies posttraumatic stress disorder (PTSD) and posits a relationship between event magnitude and clinical outcome. The present study examines whether one index of event magnitude--duration of exposure--contributes to risk of PTSD among female victims of sexual assault. Findings support a small but significant contribution…

  2. The Dose-Response Relationship of Adolescent Religious Activity and Substance Use: Variation across Demographic Groups

    ERIC Educational Resources Information Center

    Steinman, Kenneth J.; Ferketich, Amy K.; Sahr, Timothy

    2008-01-01

    This article addresses two inconsistent findings in the literature on adolescent religious activity (RA) and substance use: whether a dose-response relationship characterizes the association of these variables, and whether the association varies by grade, gender, ethnicity, family structure, school type, and type of substance. Multinomial logistic…

  3. LARGE SCALE CARCINOGEN DOSE RESPONSE STUDIES WITH JAPANESE MEDAKA (ORYZIAS LATIPES)

    EPA Science Inventory

    To investigate the responses to low carcinogen doses in animal models, large sample sizes are needed and it is an advantage if the model has a low spontaneous tumor rate. Three large scale dose response studies were conducted using Japanese medaka and the carcinogen diethylnitros...

  4. Dose Response Effects of Lisdexamfetamine Dimesylate Treatment in Adults with ADHD: An Exploratory Study

    ERIC Educational Resources Information Center

    Faraone, Stephen V.; Spencer, Thomas J.; Kollins, Scott H.; Glatt, Stephen J.; Goodman, David

    2012-01-01

    Objective: To explore dose-response effects of lisdexamfetamine dimesylate (LDX) treatment for ADHD. Method: This was a 4-week, randomized, double-blinded, placebo-controlled, parallel-group, forced-dose titration study in adult participants, aged 18 to 55 years, meeting "Diagnostic and Statistical Manual of Mental Disorders" (4th ed., text rev.)…

  5. Modeling and regression analysis of semiochemical dose-response curves of insect antennal reception and behavior

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Dose-response curves with semiochemicals are reported in many articles in insect chemical ecology regarding neurophysiology and behavioral bioassays. Most such curves are shown in figures where the x-axis has order of magnitude increases in dosages versus responses on the y-axis represented by point...

  6. Toxicokinetics to identify nonlinearities in dose-response and implications for risk assessment

    EPA Science Inventory

    For presentation at the 45th Annual Symposium of the Society of Toxicology of Canada. The meeting will be held on 4-5 December 2013 at the Ottawa Convention Centre. Toxicokinetics to identify nonlinearities in dose-response and implications for risk assessment. Rory Conolly, Offi...

  7. The effect of measurement error on the dose-response curve

    SciTech Connect

    Yoshimura, I. )

    1990-07-01

    In epidemiological studies for an environmental risk assessment, doses are often observed with errors. However, they have received little attention in data analysis. This paper studies the effect of measurement errors on the observed dose-response curve. Under the assumptions of the monotone likelihood ratio on errors and a monotone increasing dose-response curve, it is verified that the slope of the observed dose-response curve is likely to be gentler than the true one. The observed variance of responses are not so homogeneous as to be expected under models without errors. The estimation of parameters in a hockey-stick type dose-response curve with a threshold is considered on line of the maximum likelihood method for a functional relationship model. Numerical examples adaptable to the data in a 1986 study of the effect of air pollution that was conducted in Japan are also presented. The proposed model is proved to be suitable to the data in the example cited in this paper.

  8. Mode of Action (MOA) and Dose-Response Approaches for Nuclear Receptors

    EPA Science Inventory

    Abstract: The presence of sub-threshold doses for non-cancer and (in appropriate cases) cancer has been the dominant paradigm for the practice of risk assessment, but the application of dose-response modeling approaches that include a threshold have been questioned in a 2009 NRC ...

  9. QUANTITATION OF MOLECULAR ENDPOINTS FOR THE DOSE-RESPONSE COMPONENT OF CANCER RISK ASSESSMENT

    EPA Science Inventory

    Cancer risk assessment involves the steps of hazard identification, dose-response assessment, exposure assessment and risk characterization. The rapid advances in the use of molecular biology approaches has had an impact on all four components, but the greatest overall current...

  10. THYROID INSUFFICIENCY AND GENE EXPRESSION IN DEVELOPING RAT BRAIN: A DOSE RESPONSE STUDY.

    EPA Science Inventory

    Thyroid Insufficiency and Gene Expression in Developing Rat Brain: A Dose Response Study. JE Royland and ME Gilbert, Neurotox. Div., U.S. EPA, RTP, NC, USA. Endocrine disruption is an area of major concern in environmental neurotoxicity. Deficits in thyroid hormone (TH) levels h...

  11. IS THE DOSE-RESPONSE LINEAR OR NONLINEAR FOR GENOTOXIC EFFECTS?

    EPA Science Inventory

    IS THE DOSE-RESPONSE LINEAR OR NONLINEAR FOR GENOTOXIC EFFECTS?
    Preston, RJ. Environmental Carcinogenesis Division, NHEERL, U.S. Environmental Protection Agency, Research Triangle Park, NC 27711

    For considerations of cancer risk assessment from exposure to environmenta...

  12. Dose Response Data for Hormonally Active Chemicals: Estrogens, Antiandrogens and Androgens

    EPA Science Inventory

    The shape of the dose response curve in the low dose region has been debated since the late 1940s. The debate originally focused on linear no threshold (LNT) vs threshold responses in the low dose range for cancer and noncancer related effects. For noncancer effects the defaul...

  13. Curvilinearity in the dose-response curve for cancer in Japanese atomic bomb survivors.

    PubMed Central

    Little, M P; Muirhead, C R

    1997-01-01

    Recently released data on cancer incidence in Japanese atomic bomb survivors are analyzed using a variety of relative risk models that take account of errors in estimates of dose to assess the dose response at low doses. If a relative risk model with a threshold (the dose response is assumed linear above the threshold) is fitted to solid cancer data, a threshold of more than about 0.2 Sv is inconsistent with the data, whereas these data are consistent with there being no threshold. Among solid cancer subtypes there is strong evidence for a possible dose threshold only for nonmelanoma skin cancer. If a relative risk model with a threshold (the dose response is assumed linear above the threshold) is fitted to the leukemia data, a threshold of more than about 0.3 Sv is inconsistent with the data. In contrast to the estimates for the threshold level for solid cancer data, the best estimate for the threshold level in the leukemia data is significantly different from zero even when allowance is made for a possible quadratic term in the dose response, albeit at borderline levels of statistical significance (p = 0.04). There is little evidence for curvature in the leukemia dose response from 0.2 Sv upwards. However, possible underestimation of the errors in the estimates of the dose threshold as a result of confounding and uncertainties not taken into account in the analysis, together with the lack of biological plausibility of a threshold, makes interpretation of this finding questionable. PMID:9467073

  14. Dose-Responsive Gene Expression in Suberoylanilide Hydroxamic Acid (SAHA) Treated Resting CD4+ T Cells

    PubMed Central

    Reardon, Brian; Beliakova-Bethell, Nadejda; Spina, Celsa A.; Singhania, Akul; Margolis, David M.; Richman, Douglas R.; Woelk, Christopher H.

    2015-01-01

    Design Persistent latently infected CD4+ T cells represent a major obstacle to HIV eradication. Histone deacetylase inhibitors (HDACis) are a proposed activation therapy. However, off-target effects on expression in host immune cells are poorly understood. We hypothesized that HDACi-modulated genes would be best identified with dose-response analysis. Methods Resting primary CD4+ T cells were treated with 0.34, 1, 3, or 10 μM of the HDACi, SAHA, for 24 hours and subjected to microarray gene expression analysis. Genes with dose-correlated expression were filtered to identify a subset with consistent up or downregulation at each SAHA dose. Histone modifications were characterized in 6 SAHA dose-responsive genes by chromatin immunoprecipitation (ChIP-RT-qPCR). Results A large number of genes were shown to be up (N=657) or downregulated (N=725) by SAHA in a dose-responsive manner (FDR p-value < 0.05, fold change ≥ |2|). Several genes (CTNNAL1, DPEP2, H1F0, IRGM, PHF15, and SELL) are potential in vivo biomarkers of SAHA activity. SAHA dose-responsive genes included transcription factors, HIV restriction factors, histone methyltransferases, and host proteins that interact with HIV. Pathway analysis suggested net downregulation of T cell activation with increasing SAHA dose. Histone acetylation was not correlated with host gene expression, but plausible alternative mechanisms for SAHA-modulated gene expression were identified. Conclusions Numerous genes in CD4+ T cells are modulated by SAHA in a dose-responsive manner, including genes that may negatively influence HIV activation from latency. Our study suggests that SAHA influences gene expression through a confluence of several mechanisms, including histone modification, and altered expression and activity of transcription factors. PMID:26258524

  15. Effects of chewing gum on stress and health: a replication and investigation of dose-response.

    PubMed

    Smith, Andrew

    2013-04-01

    Research suggests that chewing gum may be associated with reduced stress, depression and a reduced likelihood of having high cholesterol and blood pressure. The present study aimed to replicate these findings and extend them by examining dose-response. A web-based survey was completed by a sample of 388 workers from public sector organisations (68.5% female; mean age: 42 years, range 17-64 years). The results showed that chewing gum was associated in a linear dose-response manner with lower levels of perceived stress (both at work and life in general), anxiety and depression. Occasional gum chewers also reported a reduced risk of high cholesterol and blood pressure. Intervention studies are now required to extend these findings, and the mechanisms underlying the effects reported here need further investigation.

  16. A review of uncertainties in radiotherapy dose reconstruction and their impacts on dose-response relationships.

    PubMed

    Vũ Bezin, Jérémi; Allodji, Rodrigue S; Mège, Jean-Pierre; Beldjoudi, Guillaume; Saunier, Fleur; Chavaudra, Jean; Deutsch, Eric; de Vathaire, Florent; Bernier, Valérie; Carrie, Christian; Lefkopoulos, Dimitri; Diallo, Ibrahima

    2017-03-20

    Proper understanding of the risk of radiation-induced late effects for patients receiving external photon beam radiotherapy requires the determination of reliable dose-response relationships. Although significant efforts have been devoted to improving dose estimates for the study of late effects, the most often questioned explanatory variable is still the dose. In this work, based on a literature review, we provide an in-depth description of the radiotherapy dose reconstruction process for the study of late effects. In particular, we focus on the identification of the main sources of dose uncertainty involved in this process and summarise their impacts on the dose-response relationship for radiotherapy late effects. We provide a number of recommendations for making progress in estimating the uncertainties in current studies of radiotherapy late effects and reducing these uncertainties in future studies.

  17. Mixed-effects Gaussian process functional regression models with application to dose-response curve prediction.

    PubMed

    Shi, J Q; Wang, B; Will, E J; West, R M

    2012-11-20

    We propose a new semiparametric model for functional regression analysis, combining a parametric mixed-effects model with a nonparametric Gaussian process regression model, namely a mixed-effects Gaussian process functional regression model. The parametric component can provide explanatory information between the response and the covariates, whereas the nonparametric component can add nonlinearity. We can model the mean and covariance structures simultaneously, combining the information borrowed from other subjects with the information collected from each individual subject. We apply the model to dose-response curves that describe changes in the responses of subjects for differing levels of the dose of a drug or agent and have a wide application in many areas. We illustrate the method for the management of renal anaemia. An individual dose-response curve is improved when more information is included by this mechanism from the subject/patient over time, enabling a patient-specific treatment regime.

  18. A Theoretical Model for the Hormetic Dose-response Curve for Anticancer Agents.

    PubMed

    Yoshimasu, Tatsuya; Ohashi, Takuya; Oura, Shoji; Kokawa, Yozo; Kawago, Mitsumasa; Hirai, Yoshimitsu; Miyasaka, Miwako; Nishiguchi, Haruka; Kawashima, Sayoko; Yata, Yumi; Honda, Mariko; Fujimoto, Takahiro; Okamura, Yoshitaka

    2015-11-01

    In the present article, we quantitatively evaluated the dose-response relationship of hormetic reactions of anticancer agents in vitro. Serial dilutions of gemcitabine, cisplatin, 5-fluorouracil, vinorelbine, and paclitaxel were administered to the A549 non-small-cell lung cancer cell line. The bi-phasic sigmoidal curve with hormetic and cytotoxic effects is given by the formula y=(a-b/(1+exp(c(*)log(x)-d)))/(1+exp(e(*)log(x)-f)), that was used to perform a non-linear least square regression. The dose-responses of the five anticancer agents were fitted to this equation. Gemcitabine and 5-fluorouracil, which had the lowest ED50 for their hormetic reaction, had the most pronounced promotive effects out of the five anticancer agents tested. The hormetic reaction progressed exponentially with culturing time. Our theoretical model will be useful in predicting how hormetic reactions affect patients with malignant tumors.

  19. Exploring the dose-response relationship between resistance exercise intensity and cognitive function.

    PubMed

    Chang, Yu-Kai; Etnier, Jennifer L

    2009-10-01

    The purpose of this study was to explore the dose-response relationship between resistance exercise intensity and cognitive performance. Sixty-eight participants were randomly assigned into control, 40%, 70%, or 100% of 10-repetition maximal resistance exercise groups. Participants were tested on Day 1 (baseline) and on Day 2 (measures were taken relative to performance of the treatment). Heart rate, ratings of perceived exertion, self-reported arousal, and affect were assessed on both days. Cognitive performance was assessed on Day 1 and before and following treatment on Day 2. Results from regression analyses indicated that there is a significant linear effect of exercise intensity on information processing speed, and a significant quadratic trend for exercise intensity on executive function. Thus, there is a dose-response relationship between the intensity of resistance exercise and cognitive performance such that high-intensity exercise benefits speed of processing, but moderate intensity exercise is most beneficial for executive function.

  20. Nonmonotonic dose response curves (NMDRCs) are common after Estrogen or Androgen signaling pathway disruption. Fact or Falderal?##

    EPA Science Inventory

    Nonmonotonic dose response curves (NMDRCs) are common after Estrogen or Androgen signaling pathway disruption. Fact or Falderal? Leon Earl Gray Jr, USEPA, ORD, NHEERL, TAD, RTB. RTP, NC, USA The shape of the dose response curve in the low dose region has been debated since th...

  1. Systems Cancer Biology and the Controlling Mechanisms for the J-Shaped Cancer Dose Response: Towards Relaxing the LNT Hypothesis.

    PubMed

    Lou, In Chio; Zhao, Yuchao; Wu, Yingjie; Ricci, Paolo F

    2012-01-01

    The hormesis phenomena or J-shaped dose response have been accepted as a common phenomenon regardless of the involved biological model, endpoint measured and chemical class/physical stressor. This paper first introduced a mathematical dose response model based on systems biology approach. It links molecular-level cell cycle checkpoint control information to clonal growth cancer model to predict the possible shapes of the dose response curves of Ionizing Radiation (IR) induced tumor transformation frequency. J-shaped dose response curves have been captured with consideration of cell cycle checkpoint control mechanisms. The simulation results indicate the shape of the dose response curve relates to the behavior of the saddle-node points of the model in the bifurcation diagram. A simplified version of the model in previous work of the authors was used mathematically to analyze behaviors relating to the saddle-node points for the J-shaped dose response curve. It indicates that low-linear energy transfer (LET) is more likely to have a J-shaped dose response curve. This result emphasizes the significance of systems biology approach, which encourages collaboration of multidiscipline of biologists, toxicologists and mathematicians, to illustrate complex cancer-related events, and confirm the biphasic dose-response at low doses.

  2. DOSE-RESPONSE BEHAVIOR OF ANDROGENIC AND ANTIANDROGENIC CHEMICALS: IMPLICATIONS FOR LOW-DOSE EXTRAPOLATION AND CUMULATIVE TOXICITY

    EPA Science Inventory

    DOSE-RESPONSE BEHAVIOR OF ANDROGENIC AND ANTIANDROGENIC CHEMICALS: IMPLICATIONS FOR LOW-DOSE EXTRAPOLATION AND CUMULATIVE TOXICITY. LE Gray Jr, C Wolf, J Furr, M Price, C Lambright, VS Wilson and J Ostby. USEPA, ORD, NHEERL, EB, RTD, RTP, NC, USA.
    Dose-response behavior of a...

  3. TOWARD A BIOLOGICALLY BASED DOSE-RESPONSE MODEL FOR DEVELOPMENTAL TOXICITY OF 5-FLUOROURACIL IN THE RAT: A MATHEMATICAL CONSTRUCT

    EPA Science Inventory

    Biologically based dose-response (BBDR) models comprise one way to incorporate mechanistic information into a dose-response assessment to be used for risk assessments. The chemotherapeutic drug 5-fluorouracil (5-FU) has been used as a prototypic compound for the construction of ...

  4. Diethylene glycol-induced toxicities show marked threshold dose response in rats

    SciTech Connect

    Landry, Greg M.; Dunning, Cody L.; Abreo, Fleurette; Latimer, Brian; Orchard, Elysse; McMartin, Kenneth E.

    2015-02-01

    Diethylene glycol (DEG) exposure poses risks to human health because of widespread industrial use and accidental exposures from contaminated products. To enhance the understanding of the mechanistic role of metabolites in DEG toxicity, this study used a dose response paradigm to determine a rat model that would best mimic DEG exposure in humans. Wistar and Fischer-344 (F-344) rats were treated by oral gavage with 0, 2, 5, or 10 g/kg DEG and blood, kidney and liver tissues were collected at 48 h. Both rat strains treated with 10 g/kg DEG had equivalent degrees of metabolic acidosis, renal toxicity (increased BUN and creatinine and cortical necrosis) and liver toxicity (increased serum enzyme levels, centrilobular necrosis and severe glycogen depletion). There was no liver or kidney toxicity at the lower DEG doses (2 and 5 g/kg) regardless of strain, demonstrating a steep threshold dose response. Kidney diglycolic acid (DGA), the presumed nephrotoxic metabolite of DEG, was markedly elevated in both rat strains administered 10 g/kg DEG, but no DGA was present at 2 or 5 g/kg, asserting its necessary role in DEG-induced toxicity. These results indicate that mechanistically in order to produce toxicity, metabolism to and significant target organ accumulation of DGA are required and that both strains would be useful for DEG risk assessments. - Highlights: • DEG produces a steep threshold dose response for kidney injury in rats. • Wistar and F-344 rats do not differ in response to DEG-induced renal injury. • The dose response for renal injury closely mirrors that for renal DGA accumulation. • Results demonstrate the importance of DGA accumulation in producing kidney injury.

  5. Analysis of Dose Response for Circulatory Disease After Radiotherapy for Benign Disease

    SciTech Connect

    Little, Mark P.; Kleinerman, Ruth A.; Stovall, Marilyn; Smith, Susan A.; Mabuchi, Kiyohiko

    2012-12-01

    Purpose: To assess the shape of the dose-response for various circulatory disease endpoints, and modifiers by age and time since exposure. Methods and Materials: This was an analysis of the US peptic ulcer data testing for heterogeneity of radiogenic risk by circulatory disease endpoint (ischemic heart, cerebrovascular, other circulatory disease). Results: There were significant excess risks for all circulatory disease, with an excess relative risk Gy{sup -1} of 0.082 (95% CI 0.031-0.140), and ischemic heart disease, with an excess relative risk Gy{sup -1} of 0.102 (95% CI 0.039-0.174) (both p = 0.01), and indications of excess risk for stroke. There were no statistically significant (p > 0.2) differences between risks by endpoint, and few indications of curvature in the dose-response. There were significant (p < 0.001) modifications of relative risk by time since exposure, the magnitude of which did not vary between endpoints (p > 0.2). Risk modifications were similar if analysis was restricted to patients receiving radiation, although the relative risks were slightly larger and the risk of stroke failed to be significant. The slopes of the dose-response were generally consistent with those observed in the Japanese atomic bomb survivors and in occupationally and medically exposed groups. Conclusions: There were excess risks for a variety of circulatory diseases in this dataset, with significant modification of risk by time since exposure. The consistency of the dose-response slopes with those observed in radiotherapeutically treated groups at much higher dose, as well as in lower dose-exposed cohorts such as the Japanese atomic bomb survivors and nuclear workers, implies that there may be little sparing effect of fractionation of dose or low-dose-rate exposure.

  6. The effect of anabolic steroids on lean body mass: the dose response curve.

    PubMed

    Forbes, G B

    1985-06-01

    Data from human subjects given various amounts of anabolic steroids show that the resultant increment in lean body mass (LBM) has the features of a typical dose response curve. Low doses produce a very modest effect, while large doses result in a progressive augmentation of the LBM. Endogenous testosterone production during male adolescence is accompanied by a sex differential in LBM that is comparable to the LBM increment generated by exogenous steroids given to adults.

  7. Dose-response trend tests for tumorigenesis, adjusted for body weight.

    PubMed

    Gaylor, D W; Kodell, R L

    1999-06-01

    Several studies have demonstrated a relationship between rodent body weight and tumor incidence for some tissue/organ sites. It is not uncommon for a chemical tested for carcinogenicity to also affect body weight. In such cases, comparisons of tumor incidence may be biased by body-weight differences across dose groups. A simple procedure was investigated for reducing this bias. This procedure divides the animals into a few groups based on body weight. Body weight at 12 months was used, before the appearance of a tumor was likely to affect body weight. Statistics for dose-response trend tests are calculated within body weight strata and pooled to obtain an overall dose-response trend test. This procedure is analogous to that currently used, of stratifying animals, based on their age at the time of removal from a study. Age stratification is used to account for differences in animal age across dose groups, which can affect comparisons of tumor incidence. Several examples were investigated where the high-dose group had reduced body weights and associated reductions in tumor incidence. When the data were analyzed by body-weight strata, some positive dose-response trends for tumor incidence were demonstrated. In one case, the weight-adjusted analysis indicated that a negative dose-response trend in tumor incidence was a real effect, in addition to a body weight reduction. These examples indicate that it is important to consider the effects of body weight changes as low as 10%, and perhaps below, that were caused by chemicals in 2-year bioassays for carcinogenesis. The simple procedure of analyzing tumor incidence within body-weight strata can reduce the bias introduced by weight differences across dose groups.

  8. Optimal experimental designs for dose-response studies with continuous endpoints.

    PubMed

    Holland-Letz, Tim; Kopp-Schneider, Annette

    2015-11-01

    In most areas of clinical and preclinical research, the required sample size determines the costs and effort for any project, and thus, optimizing sample size is of primary importance. An experimental design of dose-response studies is determined by the number and choice of dose levels as well as the allocation of sample size to each level. The experimental design of toxicological studies tends to be motivated by convention. Statistical optimal design theory, however, allows the setting of experimental conditions (dose levels, measurement times, etc.) in a way which minimizes the number of required measurements and subjects to obtain the desired precision of the results. While the general theory is well established, the mathematical complexity of the problem so far prevents widespread use of these techniques in practical studies. The paper explains the concepts of statistical optimal design theory with a minimum of mathematical terminology and uses these concepts to generate concrete usable D-optimal experimental designs for dose-response studies on the basis of three common dose-response functions in toxicology: log-logistic, log-normal and Weibull functions with four parameters each. The resulting designs usually require control plus only three dose levels and are quite intuitively plausible. The optimal designs are compared to traditional designs such as the typical setup of cytotoxicity studies for 96-well plates. As the optimal design depends on prior estimates of the dose-response function parameters, it is shown what loss of efficiency occurs if the parameters for design determination are misspecified, and how Bayes optimal designs can improve the situation.

  9. Bayesian fitting of a logistic dose-response curve with numerically derived priors.

    PubMed

    Huson, L W; Kinnersley, N

    2009-01-01

    In this report we describe the Bayesian analysis of a logistic dose-response curve in a Phase I study, and we present two simple and intuitive numerical approaches to construction of prior probability distributions for the model parameters. We combine these priors with the expert prior opinion and compare the results of the analyses with those obtained from the use of alternative prior formulations.

  10. Guidelines for Use of the Approximate Beta-Poisson Dose-Response Model.

    PubMed

    Xie, Gang; Roiko, Anne; Stratton, Helen; Lemckert, Charles; Dunn, Peter K; Mengersen, Kerrie

    2016-10-05

    For dose-response analysis in quantitative microbial risk assessment (QMRA), the exact beta-Poisson model is a two-parameter mechanistic dose-response model with parameters α>0 and β>0, which involves the Kummer confluent hypergeometric function. Evaluation of a hypergeometric function is a computational challenge. Denoting PI(d) as the probability of infection at a given mean dose d, the widely used dose-response model PI(d)=1-(1+dβ)-α is an approximate formula for the exact beta-Poisson model. Notwithstanding the required conditions α<β and β>1, issues related to the validity and approximation accuracy of this approximate formula have remained largely ignored in practice, partly because these conditions are too general to provide clear guidance. Consequently, this study proposes a probability measure Pr(0 < r < 1 | α̂, β̂) as a validity measure (r is a random variable that follows a gamma distribution; α̂ and β̂ are the maximum likelihood estimates of α and β in the approximate model); and the constraint conditions β̂>(22α̂)0.50 for 0.02<α̂<2 as a rule of thumb to ensure an accurate approximation (e.g., Pr(0 < r < 1 | α̂, β̂) >0.99) . This validity measure and rule of thumb were validated by application to all the completed beta-Poisson models (related to 85 data sets) from the QMRA community portal (QMRA Wiki). The results showed that the higher the probability Pr(0 < r < 1 | α̂, β̂), the better the approximation. The results further showed that, among the total 85 models examined, 68 models were identified as valid approximate model applications, which all had a near perfect match to the corresponding exact beta-Poisson model dose-response curve.

  11. Arsenite Effects on Mitochondrial Bioenergetics in Human and Mouse Primary Hepatocytes Follow a Nonlinear Dose Response

    PubMed Central

    Christudoss, Pamela; Mickey, Kristen; Tessman, Robert; Ni, Hong-min; Swerdlow, Russell

    2017-01-01

    Arsenite is a known carcinogen and its exposure has been implicated in a variety of noncarcinogenic health concerns. Increased oxidative stress is thought to be the primary cause of arsenite toxicity and the toxic effect is thought to be linear with detrimental effects reported at all concentrations of arsenite. But the paradigm of linear dose response in arsenite toxicity is shifting. In the present study we demonstrate that arsenite effects on mitochondrial respiration in primary hepatocytes follow a nonlinear dose response. In vitro exposure of primary hepatocytes to an environmentally relevant, moderate level of arsenite results in increased oxidant production that appears to arise from changes in the expression and activity of respiratory Complex I of the mitochondrial proton circuit. In primary hepatocytes the excess oxidant production appears to elicit adaptive responses that promote resistance to oxidative stress and a propensity to increased proliferation. Taken together, these results suggest a nonlinear dose-response characteristic of arsenite with low-dose arsenite promoting adaptive responses in a process known as mitohormesis, with transient increase in ROS levels acting as transducers of arsenite-induced mitohormesis. PMID:28163822

  12. Adaptive urn designs for estimating several percentiles of a dose--response curve.

    PubMed

    Mugno, Raymond; Zhus, Wei; Rosenberger, William F

    2004-07-15

    Dose--response experiments are crucial in biomedical studies. There are usually multiple objectives in such experiments and among the goals is the estimation of several percentiles on the dose--response curve. Here we present the first non-parametric adaptive design approach to estimate several percentiles simultaneously via generalized Pólya urns. Theoretical properties of these designs are investigated and their performance is gaged by the locally compound optimal designs. As an example, we re-investigated a psychophysical experiment where one of the goals was to estimate the three quartiles. We show that these multiple-objective adaptive designs are more efficient than the original single-objective adaptive design targeting the median only. We also show that urn designs which target the optimal designs are slightly more efficient than those which target the desired percentiles directly. Guidelines are given as to when to use which type of design. Overall we are pleased with the efficiency results and hope compound adaptive designs proposed in this work or their variants may prove to be a viable non-parametric alternative in multiple-objective dose--response studies.

  13. Concord Grape Juice Polyphenols and Cardiovascular Risk Factors: Dose-Response Relationships.

    PubMed

    Blumberg, Jeffrey B; Vita, Joseph A; Chen, C-Y Oliver

    2015-12-02

    Pure fruit juices provide nutritional value with evidence suggesting some of their benefits on biomarkers of cardiovascular disease risk may be derived from their constituent polyphenols, particularly flavonoids. However, few data from clinical trials are available on the dose-response relationship of fruit juice flavonoids to these outcomes. Utilizing the results of clinical trials testing single doses, we have analyzed data from studies of 100% Concord grape juice by placing its flavonoid content in the context of results from randomized clinical trials of other polyphenol-rich foods and beverages describing the same outcomes but covering a broader range of intake. We selected established biomarkers determined by similar methods for measuring flow-mediated vasodilation (FMD), blood pressure, platelet aggregation, and the resistance of low density lipoprotein cholesterol (LDL) to oxidation. Despite differences among the clinical trials in the treatment, subjects, and duration, correlations were observed between the dose and FMD. Inverse dose-response relationships, albeit with lower correlation coefficients, were also noted for the other outcomes. These results suggest a clear relationship between consumption of even modest serving sizes of Concord grape juice, flavonoid intake, and effects on risk factors for cardiovascular disease. This approach to dose-response relationships may prove useful for testing other individual foods and beverages.

  14. Dose-response relationship for light intensity and ocular and electroencephalographic correlates of human alertness

    NASA Technical Reports Server (NTRS)

    Cajochen, C.; Zeitzer, J. M.; Czeisler, C. A.; Dijk, D. J.

    2000-01-01

    Light can elicit both circadian and acute physiological responses in humans. In a dose response protocol men and women were exposed to illuminances ranging from 3 to 9100 lux for 6.5 h during the early biological night after they had been exposed to <3 lux for several hours. Light exerted an acute alerting response as assessed by a reduction in the incidence of slow-eye movements, a reduction of EEG activity in the theta-alpha frequencies (power density in the 5-9 Hz range) as well as a reduction in self-reported sleepiness. This alerting response was positively correlated with the degree of melatonin suppression by light. In accordance with the dose response function for circadian resetting and melatonin suppression, the responses of all three indices of alertness to variations in illuminance were consistent with a logistic dose response curve. Half of the maximum alerting response to bright light of 9100 lux was obtained with room light of approximately 100 lux. This sensitivity to light indicates that variations in illuminance within the range of typical, ambient, room light (90-180 lux) can have a significant impact on subjective alertness and its electrophysiologic concomitants in humans during the early biological night.

  15. Perception and annoyance due to wind turbine noise--a dose-response relationship.

    PubMed

    Pedersen, Eja; Waye, Kerstin Persson

    2004-12-01

    Installed global wind power increased by 26% during 2003, with U.S and Europe accounting for 90% of the cumulative capacity. Little is known about wind turbines' impact on people living in their vicinity. The aims of this study were to evaluate the prevalence of annoyance due to wind turbine noise and to study dose-response relationships. Interrelationships between noise annoyance and sound characteristics, as well as the influence of subjective variables such as attitude and noise sensitivity, were also assessed. A cross-sectional study was performed in Sweden in 2000. Responses were obtained through questionnaires (n = 351; response rate 68.4%), and doses were calculated as A-weighted sound pressure levels for each respondent. A statistically significant dose-response relationship was found, showing higher proportion of people reporting perception and annoyance than expected from the present dose-response relationships for transportation noise. The unexpected high proportion of annoyance could be due to visual interference, influencing noise annoyance, as well as the presence of intrusive sound characteristics. The respondents' attitude to the visual impact of wind turbines on the landscape scenery was found to influence noise annoyance.

  16. Interpreting 'dose-response' curves using homeodynamic data: with an improved explanation for hormesis.

    PubMed

    Stebbing, A R D

    2009-04-15

    A re-interpretation of the 'dose-response' curve is given that accommodates homeostasis. The outcome, or overall effect, of toxicity is the consequence of toxicity that is moderated by homeodynamic responses. Equilibrium is achieved by a balance of opposing forces of toxic inhibition countered by a stimulatory response. A graphical model is given consisting of two linked curves (response vs concentration and effect vs concentration), which provide the basis for a re-interpretation of the 'dose-response' curve. The model indicates that such relationships are non-linear with a threshold, which is due to homeodynamic responses. Subthreshold concentrations in 'dose-response' curves provide the sum of toxic inhibition minus the homeodynamic response; the response itself is unseen in serving its purpose of neutralizing perturbation. This interpretation suggests why the alpha- and beta-curves are non-linear. The beta-curve indicates adaptive overcorrection to toxicity that confers greater resistance to subsequent toxic exposure, with hormesis as an epiphenomenon.

  17. Quality control procedures for dose-response curve generation using nanoliter dispense technologies.

    PubMed

    Quintero, Catherine; Rosenstein, Craig; Hughes, Bethany; Middleton, Richard; Kariv, Ilona

    2007-09-01

    With the advancement of high-throughput biomolecular screening techniques to the lead optimization stage, there is a critical need to quality control (QC) dose-response curves generated by robotic liquid handlers to ensure accurate affinity determinations. One challenge in evaluating the performance of liquid handlers is identifying and validating a robust method for testing dispense volumes across different instruments. Although traditional automated liquid handlers are still considered the standard platform in many laboratories, nanoliter dispensers are becoming more common and pose new challenges for routine quality control procedures. For example, standard gravimetric measurements are unreliable for testing the accuracy of nanoliter liquid dispenses. However, nanoliter dispensing technology allows for the conservation of compound, reduces compound carryover from well to well through discrete dispenses, and eliminates the need for intermediate compound dilution steps to achieve a low final DMSO assay concentration. Moreover, an intermediate dilution step in aqueous solution might result in compound precipitation at high concentrations. This study compared representative automation procedures done on a variety of liquid dispensers, including manual, traditional, and nanodispense volumes. The data confirmed the importance of establishing robust QC procedures for dose-response generation in addition to accuracy and precision determinations for each instrument, and they validated the use of nanoliter pipettors for dose-response testing. The results of this study also support the requirement for thorough mixing during serial compound dilutions prepared for high-throughput lead optimization strategies using traditional liquid handlers.

  18. Dose-response model of Rocky Mountain spotted fever (RMSF) for human.

    PubMed

    Tamrakar, Sushil B; Haas, Charles N

    2011-10-01

    Rickettsia rickettsii is the causative agent of Rocky Mountain spotted fever (RMSF) and is the prototype bacterium in the spotted fever group of rickettsiae, which is found in North, Central, and South America. The bacterium is gram negative and an obligate intracellular pathogen. The disease is transmitted to humans and vertebrate host through tick bites; however, some cases of aerosol transmission also have been reported. The disease can be difficult to diagnose in the early stages, and without prompt and appropriate treatment, it can be fatal. This article develops dose-response models of different routes of exposure for RMSF in primates and humans. The beta-Poisson model provided the best fit to the dose-response data of aerosol-exposed rhesus monkeys, and intradermally inoculated humans (morbidity as end point of response). The average 50% infectious dose among (ID₅₀) exposed human population, N₅₀, is 23 organisms with 95% confidence limits of 1 to 89 organisms. Similarly, ID₁₀ and ID₂₀ are 2.2 and 5.0, respectively. Moreover, the data of aerosol-exposed rhesus monkeys and intradermally inoculated humans could be pooled. This indicates that the dose-response models fitted to different data sets are not significantly different and can be described by the same relationship.

  19. Concord Grape Juice Polyphenols and Cardiovascular Risk Factors: Dose-Response Relationships

    PubMed Central

    Blumberg, Jeffrey B.; Vita, Joseph A.; Chen, C. -Y. Oliver

    2015-01-01

    Pure fruit juices provide nutritional value with evidence suggesting some of their benefits on biomarkers of cardiovascular disease risk may be derived from their constituent polyphenols, particularly flavonoids. However, few data from clinical trials are available on the dose-response relationship of fruit juice flavonoids to these outcomes. Utilizing the results of clinical trials testing single doses, we have analyzed data from studies of 100% Concord grape juice by placing its flavonoid content in the context of results from randomized clinical trials of other polyphenol-rich foods and beverages describing the same outcomes but covering a broader range of intake. We selected established biomarkers determined by similar methods for measuring flow-mediated vasodilation (FMD), blood pressure, platelet aggregation, and the resistance of low density lipoprotein cholesterol (LDL) to oxidation. Despite differences among the clinical trials in the treatment, subjects, and duration, correlations were observed between the dose and FMD. Inverse dose-response relationships, albeit with lower correlation coefficients, were also noted for the other outcomes. These results suggest a clear relationship between consumption of even modest serving sizes of Concord grape juice, flavonoid intake, and effects on risk factors for cardiovascular disease. This approach to dose-response relationships may prove useful for testing other individual foods and beverages. PMID:26633488

  20. Dose-response relationship for light intensity and ocular and electroencephalographic correlates of human alertness.

    PubMed

    Cajochen, C; Zeitzer, J M; Czeisler, C A; Dijk, D J

    2000-10-01

    Light can elicit both circadian and acute physiological responses in humans. In a dose response protocol men and women were exposed to illuminances ranging from 3 to 9100 lux for 6.5 h during the early biological night after they had been exposed to <3 lux for several hours. Light exerted an acute alerting response as assessed by a reduction in the incidence of slow-eye movements, a reduction of EEG activity in the theta-alpha frequencies (power density in the 5-9 Hz range) as well as a reduction in self-reported sleepiness. This alerting response was positively correlated with the degree of melatonin suppression by light. In accordance with the dose response function for circadian resetting and melatonin suppression, the responses of all three indices of alertness to variations in illuminance were consistent with a logistic dose response curve. Half of the maximum alerting response to bright light of 9100 lux was obtained with room light of approximately 100 lux. This sensitivity to light indicates that variations in illuminance within the range of typical, ambient, room light (90-180 lux) can have a significant impact on subjective alertness and its electrophysiologic concomitants in humans during the early biological night.

  1. The Key Events Dose-Response Framework: Its Potential for Application to Foodborne Pathogenic Microorganisms

    PubMed Central

    BUCHANAN, ROBERT L.; HAVELAAR, ARIE H.; SMITH, MARY ALICE; WHITING, RICHARD C.; JULIEN, ELIZABETH

    2009-01-01

    The Key Events Dose-Response Framework (KEDRF) is an analytical approach that facilitates the use of currently available data to gain insight regarding dose-response relationships. The use of the KEDRF also helps identify critical knowledge gaps that once filled, will reduce reliance on assumptions. The present study considers how the KEDRF might be applied to pathogenic microorganisms, using fetal listeriosis resulting from maternal ingestion of food contaminated with L. monocytogenes as an initial example. Major biological events along the pathway between food ingestion and the endpoint of concern are systematically considered with regard to dose (i.e., number of organisms), pathogen factors (e.g., virulence), and protective host mechanisms (e.g., immune response or other homeostatic mechanisms). It is concluded that the KEDRF provides a useful structure for systematically evaluating the complex array of host and pathogen factors that influence the dose-response relationship. In particular, the KEDRF supports efforts to specify and quantify the sources of variability, a prerequisite to strengthening the scientific basis for food safety decision making. PMID:19690997

  2. Biphasic Dose Response in Low Level Light Therapy – An Update

    PubMed Central

    Huang, Ying-Ying; Sharma, Sulbha K; Carroll, James; Hamblin, Michael R

    2011-01-01

    Low-level laser (light) therapy (LLLT) has been known since 1967 but still remains controversial due to incomplete understanding of the basic mechanisms and the selection of inappropriate dosimetric parameters that led to negative studies. The biphasic dose-response or Arndt-Schulz curve in LLLT has been shown both in vitro studies and in animal experiments. This review will provide an update to our previous (Huang et al. 2009) coverage of this topic. In vitro mediators of LLLT such as adenosine triphosphate (ATP) and mitochondrial membrane potential show biphasic patterns, while others such as mitochondrial reactive oxygen species show a triphasic dose-response with two distinct peaks. The Janus nature of reactive oxygen species (ROS) that may act as a beneficial signaling molecule at low concentrations and a harmful cytotoxic agent at high concentrations, may partly explain the observed responses in vivo. Transcranial LLLT for traumatic brain injury (TBI) in mice shows a distinct biphasic pattern with peaks in beneficial neurological effects observed when the number of treatments is varied, and when the energy density of an individual treatment is varied. Further understanding of the extent to which biphasic dose responses apply in LLLT will be necessary to optimize clinical treatments. PMID:22461763

  3. Multiple confidence intervals for selected parameters adjusted for the false coverage rate in monotone dose-response microarray experiments.

    PubMed

    Peng, Jianan; Liu, Wei; Bretz, Frank; Shkedy, Ziv

    2016-12-26

    Benjamini and Yekutieli () introduced the concept of the false coverage-statement rate (FCR) to account for selection when the confidence intervals (CIs) are constructed only for the selected parameters. Dose-response analysis in dose-response microarray experiments is conducted only for genes having monotone dose-response relationship, which is a selection problem. In this paper, we consider multiple CIs for the mean gene expression difference between the highest dose and control in monotone dose-response microarray experiments for selected parameters adjusted for the FCR. A simulation study is conducted to study the performance of the method proposed. The method is applied to a real dose-response microarray experiment with 16, 998 genes for illustration.

  4. Dose response of selected solid state detectors in applied homogeneous transverse and longitudinal magnetic fields

    SciTech Connect

    Reynolds, M.; Fallone, B. G.; Rathee, S.

    2014-09-15

    Purpose: MR-Linac devices under development worldwide will require standard calibration, commissioning, and quality assurance. Solid state radiation detectors are often used for dose profiles and percent depth dose measurements. The dose response of selected solid state detectors is therefore evaluated in varying transverse and longitudinal magnetic fields for this purpose. Methods: The Monte Carlo code PENELOPE was used to model irradiation of a PTW 60003 diamond detector and IBA PFD diode detector in the presence of a magnetic field. The field itself was varied in strength, and oriented both transversely and longitudinally with respect to the incident photon beam. The long axis of the detectors was oriented either parallel or perpendicular to the photon beam. The dose to the active volume of each detector in air was scored, and its ratio to dose with zero magnetic field strength was determined as the “dose response” in magnetic field. Measurements at low fields for both detectors in transverse magnetic fields were taken to evaluate the accuracy of the simulations. Additional simulations were performed in a water phantom to obtain few representative points for beam profile and percent depth dose measurements. Results: Simulations show significant dose response as a function of magnetic field in transverse field geometries. This response can be near 20% at 1.5 T, and it is highly dependent on the detectors’ relative orientation to the magnetic field, the energy of the photon beam, and detector composition. Measurements at low transverse magnetic fields verify the simulations for both detectors in their relative orientations to radiation beam. Longitudinal magnetic fields, in contrast, show little dose response, rising slowly with magnetic field, and reaching 0.5%–1% at 1.5 T regardless of detector orientation. Water tank and in air simulation results were the same within simulation uncertainty where lateral electronic equilibrium is present and expectedly

  5. Effects of glycerol co-solvent on the rate and form of polymer gel dose response

    NASA Astrophysics Data System (ADS)

    Jirasek, A.; Hilts, M.; Berman, A.; McAuley, K. B.

    2009-02-01

    A factor currently limiting the clinical utility of x-ray CT polymer gel dosimetry is the overall low dose sensitivity (and hence low dose resolution) of the system. Hence, active research remains in the investigation of polymer gel formulations with increased CT dose response. An ideal polymer gel dosimeter will exhibit a sensitive CT response which is linear over a suitable dose range, making clinical implementation reasonably straightforward. This study reports on the variations in rate and form of the CT dose response of irradiated polymer gels manufactured with glycerol, which is a co-solvent that permits dissolution of additional bisacrylamide above its water solubility limit (3% by weight). This study focuses on situations where the concentration of bisacrylamide is kept at or below its water solubility limit so that the influence of the co-solvent on the dose response can be explored separately from the effects of increased cross-linker concentration. CT imaging and Raman spectroscopy are used to construct dose-response curves for irradiated gels varying in (i) initial total monomer (%T) and (ii) initial co-solvent concentration. Results indicate that: (i) for a fixed glycerol concentration, gel response increases linearly with %T. Furthermore, the functional form of the dose response remains constant, in agreement with a previous model of polymer formation. (ii) Polymer gels with constant %T and increasing co-solvent concentrations also show enhanced CT response. In addition, the functional form of the response is altered in these gels as co-solvent concentration is increased. Raman data indicate that the fraction of bis-acrylamide incorporated into polymerization, as opposed to cyclization, increases as co-solvent concentration increases. The changes in functional form indicate varying polymer yields (per unit dose), akin to relative fractional monomer/cross-linker (i.e. %C) changes in earlier studies. These results are put into context of the model of

  6. Probabilistic dose-response modeling: case study using dichloromethane PBPK model results.

    PubMed

    Marino, Dale J; Starr, Thomas B

    2007-12-01

    A revised assessment of dichloromethane (DCM) has recently been reported that examines the influence of human genetic polymorphisms on cancer risks using deterministic PBPK and dose-response modeling in the mouse combined with probabilistic PBPK modeling in humans. This assessment utilized Bayesian techniques to optimize kinetic variables in mice and humans with mean values from posterior distributions used in the deterministic modeling in the mouse. To supplement this research, a case study was undertaken to examine the potential impact of probabilistic rather than deterministic PBPK and dose-response modeling in mice on subsequent unit risk factor (URF) determinations. Four separate PBPK cases were examined based on the exposure regimen of the NTP DCM bioassay. These were (a) Same Mouse (single draw of all PBPK inputs for both treatment groups); (b) Correlated BW-Same Inputs (single draw of all PBPK inputs for both treatment groups except for bodyweights (BWs), which were entered as correlated variables); (c) Correlated BW-Different Inputs (separate draws of all PBPK inputs for both treatment groups except that BWs were entered as correlated variables); and (d) Different Mouse (separate draws of all PBPK inputs for both treatment groups). Monte Carlo PBPK inputs reflect posterior distributions from Bayesian calibration in the mouse that had been previously reported. A minimum of 12,500 PBPK iterations were undertaken, in which dose metrics, i.e., mg DCM metabolized by the GST pathway/L tissue/day for lung and liver were determined. For dose-response modeling, these metrics were combined with NTP tumor incidence data that were randomly selected from binomial distributions. Resultant potency factors (0.1/ED(10)) were coupled with probabilistic PBPK modeling in humans that incorporated genetic polymorphisms to derive URFs. Results show that there was relatively little difference, i.e., <10% in central tendency and upper percentile URFs, regardless of the case

  7. Population variability in biological adaptive responses to DNA damage and the shapes of carcinogen dose-response curves

    SciTech Connect

    Conolly, Rory B. . E-mail: Conolly.Rory@epa.gov; Gaylor, David W.; Lutz, Werner K.

    2005-09-01

    Carcinogen dose-response curves for both ionizing radiation and chemicals are typically assumed to be linear at environmentally relevant doses. This assumption is used to ensure protection of the public health in the absence of relevant dose-response data. A theoretical justification for the assumption has been provided by the argument that low dose linearity is expected when an exogenous agent adds to an ongoing endogenous process. Here, we use computational modeling to evaluate (1) how two biological adaptive processes, induction of DNA repair and cell cycle checkpoint control, may affect the shapes of dose-response curves for DNA-damaging carcinogens and (2) how the resulting dose-response behaviors may vary within a population. Each model incorporating an adaptive process was capable of generating not only monotonic dose-responses but also nonmonotonic (J-shaped) and threshold responses. Monte Carlo analysis suggested that all these dose-response behaviors could coexist within a population, as the spectrum of qualitative differences arose from quantitative changes in parameter values. While this analysis is largely theoretical, it suggests that (a) accurate prediction of the qualitative form of the dose-response requires a quantitative understanding of the mechanism (b) significant uncertainty is associated with human health risk prediction in the absence of such quantitative understanding and (c) a stronger experimental and regulatory focus on biological mechanisms and interindividual variability would allow flexibility in regulatory treatment of environmental carcinogens without compromising human health.

  8. Fractional poisson--a simple dose-response model for human norovirus.

    PubMed

    Messner, Michael J; Berger, Philip; Nappier, Sharon P

    2014-10-01

    This study utilizes old and new Norovirus (NoV) human challenge data to model the dose-response relationship for human NoV infection. The combined data set is used to update estimates from a previously published beta-Poisson dose-response model that includes parameters for virus aggregation and for a beta-distribution that describes variable susceptibility among hosts. The quality of the beta-Poisson model is examined and a simpler model is proposed. The new model (fractional Poisson) characterizes hosts as either perfectly susceptible or perfectly immune, requiring a single parameter (the fraction of perfectly susceptible hosts) in place of the two-parameter beta-distribution. A second parameter is included to account for virus aggregation in the same fashion as it is added to the beta-Poisson model. Infection probability is simply the product of the probability of nonzero exposure (at least one virus or aggregate is ingested) and the fraction of susceptible hosts. The model is computationally simple and appears to be well suited to the data from the NoV human challenge studies. The model's deviance is similar to that of the beta-Poisson, but with one parameter, rather than two. As a result, the Akaike information criterion favors the fractional Poisson over the beta-Poisson model. At low, environmentally relevant exposure levels (<100), estimation error is small for the fractional Poisson model; however, caution is advised because no subjects were challenged at such a low dose. New low-dose data would be of great value to further clarify the NoV dose-response relationship and to support improved risk assessment for environmentally relevant exposures.

  9. Dose-response relationship of temozolomide, determined by the Pig-a, comet, and micronucleus assay.

    PubMed

    Guérard, M; Johnson, G; Dertinger, S; Duran-Pacheco, G; Funk, J; Zeller, A

    2017-02-15

    Temozolomide (TMZ), a monofunctional alkylating agent, was selected as a model compound to determine its quantitative genotoxic dose-response relationship in different tissues (blood, liver, and jejunum) and endpoints [Pig-a-, comet-, and micronucleus assay (MNT)] in male rats. TMZ was administered p.o. over 5 consecutive days (day 1-5), followed by a treatment-free period of 50 days (day 6-56) and a final administration prior to necropsy (day 57-59). TMZ showed a dose-dependent increase in DNA damage in all interrogated endpoints. A statistically significant increase in Pig-a mutant phenotypes was observed on day 44 starting at 7.5 mg/kg/day for mutant reticulocytes (for RET(CD59-)) and at 3.75 mg/kg/day for mutant red blood cells (RBC(CD59-)), respectively. In addition, a statistically significant increase in cytogenetic damage, as measured by micronucleated reticulocytes, was observed starting at 3.75 mg/kg/day on day 3 and 1.5 mg/kg/day on day 59. DNA strand breaks, as detected by the comet assay, showed a dose-dependent and statistically significant increase in liver, blood, and jejunum starting at doses of 3.75, 3.75, and 7.5 mg/kg/day, respectively. The dose-response relationships of the Pig-a, MNT, and comet data were analyzed for possible points of departure (PoD) using the benchmark-dose (BMD) software PROAST with different critical effect sizes (CES) (BMD0.1, BMD0.5, BMD1, and BMD1SD). Overall, PoD values show a high concordance between different tissues and endpoints, underlining the suitability of this experimental design to explore quantitative dose-response relationships in a variety of different tissues and endpoints, while minimizing animal use.

  10. Dose-response curve of a microfluidic magnetic bead-based surface coverage sandwich assay.

    PubMed

    Cornaglia, Matteo; Trouillon, Raphaël; Tekin, H Cumhur; Lehnert, Thomas; Gijs, Martin A M

    2015-09-25

    Magnetic micro- and nanoparticles ('magnetic beads') have been used to advantage in many microfluidic devices for sensitive antigen (Ag) detection. Today, assays that use as read-out of the signal the number count of immobilized beads on a surface for quantification of a sample's analyte concentration have been among the most sensitive and have allowed protein detection lower than the fgmL(-1) concentration range. Recently, we have proposed in this category a magnetic bead surface coverage assay (Tekin et al., 2013 [1]), in which 'large' (2.8μm) antibody (Ab)-functionalized magnetic beads captured their Ag from a serum and these Ag-carrying beads were subsequently exposed to a surface pattern of fixed 'small' (1.0μm) Ab-coated magnetic beads. When the system was exposed to a magnetic induction field, the magnet dipole attractive interactions between the two bead types were used as a handle to approach both bead surfaces and assist with Ag-Ab immunocomplex formation, while unspecific binding (in absence of an Ag) of a large bead was reduced by exploiting viscous drag flow. The dose-response curve of this type of assay had two remarkable features: (i) its ability to detect an output signal (i.e. bead number count) for very low Ag concentrations, and (ii) an output signal of the assay that was non-linear with respect to Ag concentration. We explain here the observed dose-response curves and show that the type of interactions and the concept of our assay are in favour of detecting the lowest analyte concentrations (where typically either zero or one Ag is carried per large bead), while higher concentrations are less efficiently detected. We propose a random walk process for the Ag-carrying bead over the magnetic landscape of small beads and this model description explains the enhanced overall capture probability of this assay and its particular non-linear dose response curves.

  11. Changes in the Dose-Response Relationship of One Toxicant Under Simultaneous Exposure to Another Toxicant.

    PubMed

    Katsnelson, B A; Panov, V G; Varaksin, A N; Minigalieva, I A; Privalova, L I; Sutunkova, M P

    2016-01-01

    We considered, in general form for a 2(2) full factorial experiment, linear approximations of the organism's dose-response relationship for some factors operating alone and modification of this relationship by another factor operating in the background. A typological classification of such modifications is suggested. An analysis of the outcomes obtained in a number of subchronic animal experiments on rats in which this response was assessed by changes in a large number of biomedical indices revealed that all theoretically possible variants (types) of the modification under consideration are actually observed depending on a specific index and specific harmful exposure. Statistical significance estimation procedures are formulated for each of them.

  12. Benthic injury dose-response models for polychlorinated biphenyl-contaminated sediment using equilibrium partitioning.

    PubMed

    Finkelstein, Kenneth; Beckvar, Nancy; Dillon, Tom

    2016-10-25

    The study goal was to develop a sediment polychlorinated biphenyl (PCB) dose-response model based on benthic invertebrate effects to PCBs. The authors used an equilibrium partitioning (EqP) approach to generate predicted PCB sediment effect concentrations (largely Aroclor 1254) associated with a gradient of toxic effects in benthic organisms from effects observed in aquatic toxicity studies. The present study differs from all other EqP collective sediment investigations in that the authors examined a common dose-response gradient of effects for PCBs rather than a single, protective value. The authors reviewed the chronic aquatic toxicity literature to identify measured aqueous PCB concentrations and associated benthic invertebrate effects. The authors control-normalized the aquatic toxic effect data and expressed results from various studies as a common metric, percent injury. Then, they calculated organic carbon-normalized sediment PCB concentrations (mg/kg organic carbon) from the aqueous PCB toxicity data set using EqP theory based on the US Environmental Protection Agency's (EPIWEB 4.1) derivation of the water-organic carbon partition coefficient (KOC ). Lastly, the authors constructed a nonlinear dose-response numerical model for these synoptic sediment PCB concentrations and biological effects: Y = 100/1 + 10(([logEC50-logX] × [Hill slope])) (EC50 = median effective concentration). These models were used to generate "look-up" tables reporting percent injury in benthic biota for a range of Aroclor-specific sediment concentrations. For example, the model using the EPIWEB KOC estimate predicts mean benthic injury of 23.3%, 46.0%, 70.6%, 87.1%, and 95% for hypothetical sediment concentrations of 1 mg/kg, 2 mg/kg, 4 mg/kg, 8 mg/kg, and 16 mg/kg dry weight of Aroclor 1254, respectively (at 1% organic carbon). The authors recommend the model presented for screening but suggest, when possible, determining a site-specific KOC that, along

  13. An analysis of the dose-response relationship at voltage-clamped frog neuromuscular junctions.

    PubMed Central

    Dionne, V E; Steinbach, J H; Stevens, C F

    1978-01-01

    1. Frog neuromuscular junctions were viewed with Nomarski optics and voltage clamped. Agonist was applied ionophoretically and agonist concentrations were measured using a micro-electrode sensitive to quaternary amines. 2. The dose-response relationship was studied using the agonists carbamylcholine, suberyldicholine and hydroxyphenyl-propyltrimethylammonium. 3. With all of these agonists, it appeared that the ACh receptor could be active when either one or two agonist binding sites were occupied. The receptor was much more likely to be active when both sites were occupied. Agonist dissociation constants and receptor activation probabilities were estimated by non-linear regression techniques for several possible receptor activation schemes. PMID:309004

  14. Patients who do not respond to the "usual" dose: why Terry fell off the dose-response curve.

    PubMed

    Preskorn, Sheldon H

    2009-11-01

    Clinical trials are aimed at determining what happens in the "usual" patient; however, clinicians are interested in what happens in their patients even if they are not usual. The usual dose-response relationship is determined as part of the drug development process required for approval of a new drug. However, clinicians are likely to encounter patients who "fall off" the usual dose-response curve because they are either sensitive or resistant to the beneficial (efficacy) or adverse effects of a drug. This column is the first in a series that will examine why specific patients fall off the usual dose-response curve and how clinicians can manage such patients when they encounter them. This column discusses what a dose-response curve is, how it is determined, and why it is clinically important.

  15. Dose-response approaches for nuclear receptor-mediated modes of action for liver carcinogenicity: Results of a workshop

    EPA Science Inventory

    A public workshop, organized by a Steering Committee of scientists from government, industry, universities, and research organizations, was held at the National Institute of Environmental Health Sciences (NIEHS) in September, 2010. The workshop explored the dose-response implicat...

  16. Mathematical Modeling of Allelopathy. III. A Model for Curve-Fitting Allelochemical Dose Responses

    PubMed Central

    Liu, De Li; An, Min; Johnson, Ian R.; Lovett, John V.

    2003-01-01

    Bioassay techniques are often used to study the effects of allelochemicals on plant processes, and it is generally observed that the processes are stimulated at low allelochemical concentrations and inhibited as the concentrations increase. A simple empirical model is presented to analyze this type of response. The stimulation-inhibition properties of allelochemical-dose responses can be described by the parameters in the model. The indices, p% reductions, are calculated to assess the allelochemical effects. The model is compared with experimental data for the response of lettuce seedling growth to Centaurepensin, the olfactory response of weevil larvae to α-terpineol, and the responses of annual ryegrass (Lolium multiflorum Lam.), creeping red fescue (Festuca rubra L., cv. Ensylva), Kentucky bluegrass (Poa pratensis L., cv. Kenblue), perennial ryegrass (L. perenne L., cv. Manhattan), and Rebel tall fescue (F. arundinacea Schreb) seedling growth to leachates of Rebel and Kentucky 31 tall fescue. The results show that the model gives a good description to observations and can be used to fit a wide range of dose responses. Assessments of the effects of leachates of Rebel and Kentucky 31 tall fescue clearly differentiate the properties of the allelopathic sources and the relative sensitivities of indicators such as the length of root and leaf. PMID:19330111

  17. A prototype microfluidic platform for miniaturization and automation of serial dilution and dose-response assays.

    PubMed

    Koehler, Jeffrey; Vajjhala, Surekha; Coyne, Courtney; Flynn, Terence; Pezzuto, Marci; Williams, Manda; Levine, Leanna

    2002-11-01

    A novel microfluidic device was designed and developed to miniaturize, multiplex, and automate serial dilution and three-reagent dose-response assays using submicroliter quantities of reagents. This prototype microfluidic device can be used to measure enzyme kinetics and to test a chemical lead's response to a target by fluorescent readout using common plate readers and detection systems. The prototype microfluidic system yielded serial dilution and dose-response assay data comparable to results obtained from manual titrations and reagent additions performed using a microwell plate. Enzyme kinetics were highly reproducible using these devices, although Michaelis-Menten kinetics results differed from those obtained in the microwell plate. In all cases reported here, assays performed on the microfluidic format required lower volumes of reagents compared with the microwell plate. In addition to savings in reagent consumption, the microfluidic devices and bench-top instruments offer additional advantages over conventional solutions, including a small footprint and compatibility with commercially available fluorescence detectors. Future directions for the prototype technology are discussed.

  18. The dose response of normoxic polymer gel dosimeters measured using X-ray CT.

    PubMed

    Hill, B; Venning, A; Baldock, C

    2005-07-01

    X-ray CT was used to determine the dose response of normoxic polymer gel dosimeters. Normoxic polymer gel dosimeters were manufactured and irradiated up to 150 Gy. Up to 50 CT images were acquired on a Toshiba Aquilion Multislice CT scanner using protocols for 80 kV and 135 kV to determine dose response. HU-dose sensitivity, the linear regression of data for the HU versus dose for the linear part of the curve up to 60 Gy was 0.38+/-0.07 HU Gy(-1) for 135 kV and 0.37+/-0.01 HU Gy(-1) for 80 kV. Dose resolution was found to be < 1.3 Gy for an absorbed dose range up to 70 Gy for 135 kV, similar to that measured previously for polyacrylamide gel (PAG). Although the HU-dose sensitivity was lower than that previously measured for PAG gel dosimeters it had a greater range of absorbed dose indicating that normoxic polymer gel dosimeters have potential in CT gel dosimetry.

  19. Dose responsive effects of cisplatin in L02 cells using NMR-based metabolomics.

    PubMed

    Liu, Shu; Wang, Wei; Zhou, Xueyi; Gu, Runhuan; Ding, Zongli

    2014-01-01

    Cisplatin is an effective chemotherapeutic agent for the treatment of various cancers, such as bladder cancer, epithelial ovarian cancer, cervical cancer, and so on. However, cisplatin can cause various side effects. In this study, the dose-responsive effects of cisplatin were investigated in an in vitro model of human liver cells (L02) using NMR-based metabolomics. The inverted U-shaped curve of cell proliferation confirmed the hormetic effects of cisplatin (from 1 nM to 1 mM) in L02 cells. However, the metabolite changes revealed both U-shaped (ethanol, lactate, aspartate, choline, etc.) and inverted U-shaped (glutamate, glutamine, 4-aminobutyrate, myo-inositol, etc.) curves induced by three typical concentrations of cisplatin which covered the inverted U-shaped curve as indicated by the cell proliferation assay. These findings suggested that a macroscopic hormesis phenomenon on the cell proliferation could be reflected by both stimulated and inhibited metabolites and corresponding metabolic pathways to cisplatin treatments. Therefore, a global analysis using metabolomics may give a broader view into the dose-response relationship than using a single endpoint at molecular levels.

  20. Non-parametric estimators of a monotonic dose-response curve and bootstrap confidence intervals.

    PubMed

    Dilleen, Maria; Heimann, Günter; Hirsch, Ian

    2003-03-30

    In this paper we consider study designs which include a placebo and an active control group as well as several dose groups of a new drug. A monotonically increasing dose-response function is assumed, and the objective is to estimate a dose with equivalent response to the active control group, including a confidence interval for this dose. We present different non-parametric methods to estimate the monotonic dose-response curve. These are derived from the isotonic regression estimator, a non-negative least squares estimator, and a bias adjusted non-negative least squares estimator using linear interpolation. The different confidence intervals are based upon an approach described by Korn, and upon two different bootstrap approaches. One of these bootstrap approaches is standard, and the second ensures that resampling is done from empiric distributions which comply with the order restrictions imposed. In our simulations we did not find any differences between the two bootstrap methods, and both clearly outperform Korn's confidence intervals. The non-negative least squares estimator yields biased results for moderate sample sizes. The bias adjustment for this estimator works well, even for small and moderate sample sizes, and surprisingly outperforms the isotonic regression method in certain situations.

  1. Heavy particle irradiation, neurochemistry and behavior: thresholds, dose-response curves and recovery of function

    NASA Technical Reports Server (NTRS)

    Rabin, B. M.; Joseph, J. A.; Shukitt-Hale, B.

    2004-01-01

    Exposure to heavy particles can affect the functioning of the central nervous system (CNS), particularly the dopaminergic system. In turn, the radiation-induced disruption of dopaminergic function affects a variety of behaviors that are dependent upon the integrity of this system, including motor behavior (upper body strength), amphetamine (dopamine)-mediated taste aversion learning, and operant conditioning (fixed-ratio bar pressing). Although the relationships between heavy particle irradiation and the effects of exposure depend, to some extent, upon the specific behavioral or neurochemical endpoint under consideration, a review of the available research leads to the hypothesis that the endpoints mediated by the CNS have certain characteristics in common. These include: (1) a threshold, below which there is no apparent effect; (2) the lack of a dose-response relationship, or an extremely steep dose-response curve, depending on the particular endpoint; and (3) the absence of recovery of function, such that the heavy particle-induced behavioral and neural changes are present when tested up to one year following exposure. The current report reviews the data relevant to the degree to which these characteristics are common to neurochemical and behavioral endpoints that are mediated by the effects of exposure to heavy particles on CNS activity. c2004 COSPAR. Published by Elsevier Ltd. All rights reserved.

  2. High-resolution dose-response screening using droplet-based microfluidics.

    PubMed

    Miller, Oliver J; El Harrak, Abdeslam; Mangeat, Thomas; Baret, Jean-Christophe; Frenz, Lucas; El Debs, Bachir; Mayot, Estelle; Samuels, Michael L; Rooney, Eamonn K; Dieu, Pierre; Galvan, Martin; Link, Darren R; Griffiths, Andrew D

    2012-01-10

    A critical early step in drug discovery is the screening of a chemical library. Typically, promising compounds are identified in a primary screen and then more fully characterized in a dose-response analysis with 7-10 data points per compound. Here, we describe a robust microfluidic approach that increases the number of data points to approximately 10,000 per compound. The system exploits Taylor-Aris dispersion to create concentration gradients, which are then segmented into picoliter microreactors by droplet-based microfluidics. The large number of data points results in IC(50) values that are highly precise (± 2.40% at 95% confidence) and highly reproducible (CV = 2.45%, n = 16). In addition, the high resolution of the data reveals complex dose-response relationships unambiguously. We used this system to screen a chemical library of 704 compounds against protein tyrosine phosphatase 1B, a diabetes, obesity, and cancer target. We identified a number of novel inhibitors, the most potent being sodium cefsulodine, which has an IC(50) of 27 ± 0.83 μM.

  3. Dose-response Relationships between Mouse Allergen Exposure and Asthma Morbidity Among Urban Children and Adolescents

    PubMed Central

    Torjusen, Erika N.; Diette, Gregory B.; Breysse, Patrick N.; Curtin-Brosnan, Jean; Aloe, Charles; Matsui, Elizabeth C.

    2012-01-01

    Home mouse allergen exposure is associated with asthma morbidity, but little is known about the shape of the dose-response relationship or the relevance of location of exposure within the home. Asthma outcome and allergen exposure data were collected every three months for 1 year in 150 urban children with asthma. Participants were stratified by mouse sensitization and relationships between continuous measures of mouse allergen exposure and outcomes of interest were analyzed. Every ten-fold increase in the bed mouse allergen level was associated with an 87% increase in the odds of any asthma-related health care use among mouse sensitized (OR (95% CI): 1.87 (1.21–2.88)), but not non-mouse sensitized participants. Similar relationships were observed for emergency department visit and unscheduled doctor visit among mouse sensitized participants. Kitchen floor and bedroom air mouse allergen concentrations were also associated with greater odds of asthma-related healthcare utilization; however, the magnitude of the association was less than that observed for bed mouse allergen concentrations. In this population of urban children with asthma, there is a linear dose-response relationship between mouse allergen concentrations and asthma morbidity among mouse-sensitized asthmatics. Bed and bedroom air mouse allergen exposure compartments may have a greater impact on asthma morbidity than other compartments. PMID:23067271

  4. Bayesian penalized log-likelihood ratio approach for dose response clinical trial studies.

    PubMed

    Tang, Yuanyuan; Cai, Chunyan; Sun, Liangrui; He, Jianghua

    2017-02-13

    In literature, there are a few unified approaches to test proof of concept and estimate a target dose, including the multiple comparison procedure using modeling approach, and the permutation approach proposed by Klingenberg. We discuss and compare the operating characteristics of these unified approaches and further develop an alternative approach in a Bayesian framework based on the posterior distribution of a penalized log-likelihood ratio test statistic. Our Bayesian approach is much more flexible to handle linear or nonlinear dose-response relationships and is more efficient than the permutation approach. The operating characteristics of our Bayesian approach are comparable to and sometimes better than both approaches in a wide range of dose-response relationships. It yields credible intervals as well as predictive distribution for the response rate at a specific dose level for the target dose estimation. Our Bayesian approach can be easily extended to continuous, categorical, and time-to-event responses. We illustrate the performance of our proposed method with extensive simulations and Phase II clinical trial data examples.

  5. Mathematical Modeling of Allelopathy. III. A Model for Curve-Fitting Allelochemical Dose Responses.

    PubMed

    Liu, De Li; An, Min; Johnson, Ian R; Lovett, John V

    2003-01-01

    Bioassay techniques are often used to study the effects of allelochemicals on plant processes, and it is generally observed that the processes are stimulated at low allelochemical concentrations and inhibited as the concentrations increase. A simple empirical model is presented to analyze this type of response. The stimulation-inhibition properties of allelochemical-dose responses can be described by the parameters in the model. The indices, p% reductions, are calculated to assess the allelochemical effects. The model is compared with experimental data for the response of lettuce seedling growth to Centaurepensin, the olfactory response of weevil larvae to alpha-terpineol, and the responses of annual ryegrass (Lolium multiflorum Lam.), creeping red fescue (Festuca rubra L., cv. Ensylva), Kentucky bluegrass (Poa pratensis L., cv. Kenblue), perennial ryegrass (L. perenne L., cv. Manhattan), and Rebel tall fescue (F. arundinacea Schreb) seedling growth to leachates of Rebel and Kentucky 31 tall fescue. The results show that the model gives a good description to observations and can be used to fit a wide range of dose responses. Assessments of the effects of leachates of Rebel and Kentucky 31 tall fescue clearly differentiate the properties of the allelopathic sources and the relative sensitivities of indicators such as the length of root and leaf.

  6. Hierarchical Bayesian inference for ion channel screening dose-response data

    PubMed Central

    2016-01-01

    Dose-response (or ‘concentration-effect’) relationships commonly occur in biological and pharmacological systems and are well characterised by Hill curves. These curves are described by an equation with two parameters: the inhibitory concentration 50% (IC50); and the Hill coefficient. Typically just the ‘best fit’ parameter values are reported in the literature. Here we introduce a Python-based software tool, PyHillFit, and describe the underlying Bayesian inference methods that it uses, to infer probability distributions for these parameters as well as the level of experimental observation noise. The tool also allows for hierarchical fitting, characterising the effect of inter-experiment variability. We demonstrate the use of the tool on a recently published dataset on multiple ion channel inhibition by multiple drug compounds. We compare the maximum likelihood, Bayesian and hierarchical Bayesian approaches. We then show how uncertainty in dose-response inputs can be characterised and propagated into a cardiac action potential simulation to give a probability distribution on model outputs. PMID:27918599

  7. A Hypothesis Concerning the Biphasic Dose-response of Tumors to Angiostatin and Endostatin.

    PubMed

    Parris, George E

    2015-01-01

    This manuscript proposes a hypothesis to explain the U-shaped dose-response observed for angiostatin and other high-molecular-weight drugs in various anti-cancer bio-assays. The dose-response curves for angiostatin and endostatin (measured as suppression of tumor growth) go through an optimum (i.e., minimum tumor growth) and then becomes less effective at higher doses. The literature suggests that at lower doses the primary action of these high-molecular-weight drugs is to counteract the angiogenic effects of vascular endothelial growth factor (VEGF). To do this, the drugs must pass out of the blood vessel and enter the extra-cellular matrix (ECM) where VEGF induces the growth and fusion of tip cells. Ironically, VEGF actually facilitates access of the drugs to the ECM by making the vascular endothelium leaky. At higher doses, the high-molecular-weight drugs seem to reverse VEGF-induced permeability of the endothelium. Thus, at high dose rates, it is hypothesized that the drugs are not able to enter the ECM and block the angiogenic effects of VEGF there. As a result, high doses of the drugs do not suppress vascularization of the tumor or tumor growth. Moreover, if the permeability of the vessels is suppressed, the VEGF released by the stroma is concentrated in the ECM where it amplifies the angiogenic activity around the tumor.

  8. Intervention Engagement Moderates the Dose-Response Relationships in a Dietary Intervention.

    PubMed

    Lippke, Sonia; Corbet, Jana M; Lange, Daniela; Parschau, Linda; Schwarzer, Ralf

    2016-01-01

    Behavioral interventions could lead to changes in behavior through changes in a mediator. This dose-response relationship might only hold true for those participants who are actively engaged in interventions. This Internet study investigated the role of engagement in a planning intervention to promote fruit and vegetable consumption in addition to testing the intervention effect on planning and behavior. A sample of 701 adults (mean = 38.71 years, 81% women) were randomly assigned either to a planning intervention (experimental group) or to one of 2 control conditions (untreated waiting list control group or placebo active control group). Moderated mediation analyses were carried out. Significant changes over time and time × group effects revealed the effectiveness of the intervention. The effect of the intervention (time 1) on changes in behavior (time 3; 1 month after the personal deadline study participants set for themselves to start implementing their plans) was mediated by changes in planning (time 2; 1 week the personal deadline). Effects of planning on behavior were documented only at a moderate level of intervention engagement. This indicates an inverse U-shaped dose-response effect. Thus, examining participants' intervention engagement allows for a more careful evaluation of why some interventions work and others do not.

  9. Dose-Response Modeling with Summary Data from Developmental Toxicity Studies.

    PubMed

    Fox, John F; Hogan, Karen A; Davis, Allen

    2016-08-27

    Dose-response analysis of binary developmental data (e.g., implant loss, fetal abnormalities) is best done using individual fetus data (identified to litter) or litter-specific statistics such as number of offspring per litter and proportion abnormal. However, such data are not often available to risk assessors. Scientific articles usually present only dose-group summaries for the number or average proportion abnormal and the total number of fetuses. Without litter-specific data, it is not possible to estimate variances correctly (often characterized as a problem of overdispersion, intralitter correlation, or "litter effect"). However, it is possible to use group summary data when the design effect has been estimated for each dose group. Previous studies have demonstrated useful dose-response and trend test analyses based on design effect estimates using litter-specific data from the same study. This simplifies the analysis but does not help when litter-specific data are unavailable. In the present study, we show that summary data on fetal malformations can be adjusted satisfactorily using estimates of the design effect based on historical data. When adjusted data are then analyzed with models designed for binomial responses, the resulting benchmark doses are similar to those obtained from analyzing litter-level data with nested dichotomous models.

  10. Application of the Key Events Dose-response Framework to Folate Metabolism.

    PubMed

    Hu, Jing; Wang, Bing; Sahyoun, Nadine R

    2016-06-10

    Folate is a vitamin that plays a role as a cofactor and coenzyme in many essential reactions. These reactions are interrelated and any change in folate homeostasis could affect other reactions. With food fortified with folic acid, and use of multivitamin, unmetabolized folic acid (UMFA) has been detected in blood circulation, particularly among older adults. This has raised concern about the potential harmful effect of high folic acid intake and UMFA on health conditions such as cognitive dysfunction and cancer. To examine what is known about folate metabolism and the release of circulating UMFA, the Key Events Dose-Response Framework (KEDRF) was used to review each of the major key events, dose-response characteristics and homeostatic mechanisms of folate metabolism. The intestine, liver and kidneys each play essential roles in regulating body folate homeostasis. But the determining event in folate metabolism leading to the release of UMFA in circulation appears to be the saturation of dihydrofolate reductase in the liver. However, at each of the key events in folate metabolism, limited information is available on threshold, homeostatic regulation and intracellular effects of folic acid. More studies are needed to fill in the knowledge gaps for quantitatively characterizing the dose-effect relationship especially in light of the call for extending folate fortification to other foods.

  11. Hierarchical Bayesian inference for ion channel screening dose-response data.

    PubMed

    Johnstone, Ross H; Bardenet, Rémi; Gavaghan, David J; Mirams, Gary R

    2016-01-01

    Dose-response (or 'concentration-effect') relationships commonly occur in biological and pharmacological systems and are well characterised by Hill curves. These curves are described by an equation with two parameters: the inhibitory concentration 50% (IC50); and the Hill coefficient. Typically just the 'best fit' parameter values are reported in the literature. Here we introduce a Python-based software tool, PyHillFit , and describe the underlying Bayesian inference methods that it uses, to infer probability distributions for these parameters as well as the level of experimental observation noise. The tool also allows for hierarchical fitting, characterising the effect of inter-experiment variability. We demonstrate the use of the tool on a recently published dataset on multiple ion channel inhibition by multiple drug compounds. We compare the maximum likelihood, Bayesian and hierarchical Bayesian approaches. We then show how uncertainty in dose-response inputs can be characterised and propagated into a cardiac action potential simulation to give a probability distribution on model outputs.

  12. Hierarchical dose-response modeling for high-throughput toxicity screening of environmental chemicals.

    PubMed

    Wilson, Ander; Reif, David M; Reich, Brian J

    2014-03-01

    High-throughput screening (HTS) of environmental chemicals is used to identify chemicals with high potential for adverse human health and environmental effects from among the thousands of untested chemicals. Predicting physiologically relevant activity with HTS data requires estimating the response of a large number of chemicals across a battery of screening assays based on sparse dose-response data for each chemical-assay combination. Many standard dose-response methods are inadequate because they treat each curve separately and under-perform when there are as few as 6-10 observations per curve. We propose a semiparametric Bayesian model that borrows strength across chemicals and assays. Our method directly parametrizes the efficacy and potency of the chemicals as well as the probability of response. We use the ToxCast data from the U.S. Environmental Protection Agency (EPA) as motivation. We demonstrate that our hierarchical method provides more accurate estimates of the probability of response, efficacy, and potency than separate curve estimation in a simulation study. We use our semiparametric method to compare the efficacy of chemicals in the ToxCast data to well-characterized reference chemicals on estrogen receptor α (ERα) and peroxisome proliferator-activated receptor γ (PPARγ) assays, then estimate the probability that other chemicals are active at lower concentrations than the reference chemicals.

  13. Dose-Response Analysis of RNA-Seq Profiles in Archival ...

    EPA Pesticide Factsheets

    Use of archival resources has been limited to date by inconsistent methods for genomic profiling of degraded RNA from formalin-fixed paraffin-embedded (FFPE) samples. RNA-sequencing offers a promising way to address this problem. Here we evaluated transcriptomic dose responses using RNA-sequencing in paired FFPE and frozen (FROZ) samples from two archival studies in mice, one 20 years old. Experimental treatments included 3 different doses of di(2-ethylhexyl)phthalate or dichloroacetic acid for the recently archived and older studies, respectively. Total RNA was ribo-depleted and sequenced using the Illumina HiSeq platform. In the recently archived study, FFPE samples had 35% lower total counts compared to FROZ samples but high concordance in fold-change values of differentially expressed genes (DEGs) (r2 = 0.99), highly enriched pathways (90% overlap with FROZ), and benchmark dose estimates for preselected target genes (2% difference vs FROZ). In contrast, older FFPE samples had markedly lower total counts (3% of FROZ) and poor concordance in global DEGs and pathways. However, counts from FFPE and FROZ samples still positively correlated (r2 = 0.84 across all transcripts) and showed comparable dose responses for more highly expressed target genes. These findings highlight potential applications and issues in using RNA-sequencing data from FFPE samples. Recently archived FFPE samples were highly similar to FROZ samples in sequencing q

  14. Dose-response effects for disease management programs on hospital utilization in Illinois Medicaid.

    PubMed

    Berg, Gregory D; Donnelly, Shawn; Miller, Mary; Medina, Wendie; Warnick, Kathleen

    2012-12-01

    The objective of this study is to estimate a dose-response impact of disease management contacts on inpatient admissions. Multivariate regression analysis of panel data was used to test the hypothesis that increased disease management contacts lower the odds of an inpatient admission. Subjects were 40,452 members of Illinois' noninstitutionalized Medicaid-only aged, blind, or disabled population diagnosed with asthma, coronary artery disease, chronic obstructive pulmonary disease, diabetes, and/or heart failure. All members are also in the state's Illinois Health Connect program, a medical home strategy in place for most of the 2.4 million Illinois Medicaid beneficiaries. The statistical measure is the odds ratio, which is a measure of association between the monthly inpatient admission indicator and the number of contacts (doses) a member has had for each particular disease management intervention. Statistically significant contacts are between 8 and 12 for heart failure, between 4 and 12 contacts for diabetes, and between 8 and 13 contacts for asthma. Total inpatient savings during the study period is estimated to be $12.4 million. This study shows the dose-response pattern of inpatient utilization improvements through the number of disease management contacts.

  15. Heavy particle irradiation, neurochemistry and behavior: thresholds, dose-response curves and recovery of function

    NASA Astrophysics Data System (ADS)

    Rabin, B. M.; Joseph, J. A.; Shukitt-Hale, B.

    2004-01-01

    Exposure to heavy particles can affect the functioning of the central nervous system (CNS), particularly the dopaminergic system. In turn, the radiation-induced disruption of dopaminergic function affects a variety of behaviors that are dependent upon the integrity of this system, including motor behavior (upper body strength), amphetamine (dopamine)-mediated taste aversion learning, and operant conditioning (fixed-ratio bar pressing). Although the relationships between heavy particle irradiation and the effects of exposure depend, to some extent, upon the specific behavioral or neurochemical endpoint under consideration, a review of the available research leads to the hypothesis that the endpoints mediated by the CNS have certain characteristics in common. These include: (1) a threshold, below which there is no apparent effect; (2) the lack of a dose-response relationship, or an extremely steep dose-response curve, depending on the particular endpoint; and (3) the absence of recovery of function, such that the heavy particle-induced behavioral and neural changes are present when tested up to one year following exposure. The current report reviews the data relevant to the degree to which these characteristics are common to neurochemical and behavioral endpoints that are mediated by the effects of exposure to heavy particles on CNS activity.

  16. Heavy particle irradiation, neurochemistry and behavior: thresholds, dose- response curves and recovery of function

    NASA Astrophysics Data System (ADS)

    Rabin, B.; Joseph, J.; Shukitt-Hale, B.

    Exposure to heavy particles can affect the functioning of the central nervous system (CNS), particularly the dopaminergic system. In turn, the radiation- induced disruption of dopaminergic function disrupts a variety of behaviors that are dependent upon the integrity of the dopaminergic system, including motor behavior (upper body strength), amphetamine (dopamine)-mediated taste aversion learning, spatial learning and memory (Morris water maze), and operant conditioning (fixed-ratio bar pressing). Although the relationships between heavy particle irradiation and the effects of exposure depend, to some extent, upon the specific behavioral or neurochemical endpoint under consideration, a review of the available research leads to the hypothesis that the endpoints mediated by the CNS have certain characteristics in common. These include: (1) a threshold, below which there is no apparent effect; (2) the lack of a dose-response relationship, or an extremely steep dose-response curve, depending on the particular endpoint; and (3) the absence of recovery of function, such that the heavy particle-induced behavioral and neural changes are present when tested up to one year following exposure. The current presentation will review the data relevant to the degree to which these characteristics are in fact common to neurochemical and behavioral endpoints that are mediated by the effects of exposure to heavy particles on CNS activity. Supported by N.A.S.A. Grant NAG9-1190.

  17. Nut intake and stroke risk: A dose-response meta-analysis of prospective cohort studies

    PubMed Central

    Shao, Chuan; Tang, Hui; Zhao, Wei; He, Jianquan

    2016-01-01

    We aim to quantify the effects of nut intake on risk of stroke by a dose-response meta-analysis with a random-effects model. Two databases (PubMed and Emabse) were searched for prospective cohort studies regarding nut intake and stroke risk. Studies were included if they fulfilled the predefined criteria. Eleven articles encompassing fourteen cohort studies were included in final analysis. The pooled relative risk (RR) of stroke for the highest versus (vs.) lowest category of nut intake was 0.88 (95% confidence interval [CI] 0.80-0.97). The power to detect a RR of 0.88 for the highest versus vs. lowest category of nut intake was 86.2%. In multiple subset analyses by gender, location, and stroke subtype, the inverse association was only found in women (RR = 0.84, 95% CI 0.73–0.96) and Asia (RR = 0.79, 95% CI 0.67–0.93). In the dose-response meta-analysis, evidence for a nonlinear association between nut intake and stroke risk was observed and a RR of 0.86 was conferred for 12 g/day. Based on the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) system, the quality of evidence was moderate. In conclusions, finding from current meta-analysis of fourteen cohort studies indicates that nut intake may be related to decreased risk of stroke. PMID:27469072

  18. Heavy particle irradiation, neurochemistry and behavior: thresholds, dose-response curves and recovery of function.

    PubMed

    Rabin, B M; Joseph, J A; Shukitt-Hale, B

    2004-01-01

    Exposure to heavy particles can affect the functioning of the central nervous system (CNS), particularly the dopaminergic system. In turn, the radiation-induced disruption of dopaminergic function affects a variety of behaviors that are dependent upon the integrity of this system, including motor behavior (upper body strength), amphetamine (dopamine)-mediated taste aversion learning, and operant conditioning (fixed-ratio bar pressing). Although the relationships between heavy particle irradiation and the effects of exposure depend, to some extent, upon the specific behavioral or neurochemical endpoint under consideration, a review of the available research leads to the hypothesis that the endpoints mediated by the CNS have certain characteristics in common. These include: (1) a threshold, below which there is no apparent effect; (2) the lack of a dose-response relationship, or an extremely steep dose-response curve, depending on the particular endpoint; and (3) the absence of recovery of function, such that the heavy particle-induced behavioral and neural changes are present when tested up to one year following exposure. The current report reviews the data relevant to the degree to which these characteristics are common to neurochemical and behavioral endpoints that are mediated by the effects of exposure to heavy particles on CNS activity.

  19. Application of the International Life Sciences Institute Key Events Dose-Response Framework to food contaminants.

    PubMed

    Fenner-Crisp, Penelope A

    2012-12-01

    Contaminants are undesirable constituents in food. They may be formed during production of a processed food, present as a component in a source material, deliberately added to substitute for the proper substance, or the consequence of poor food-handling practices. Contaminants may be chemicals or pathogens. Chemicals generally degrade over time and become of less concern as a health threat. Pathogens have the ability to multiply, potentially resulting in an increased threat level. Formal structures have been lacking for systematically generating and evaluating hazard and exposure data for bioactive agents when problem situations arise. We need to know what the potential risk may be to determine whether intervention to reduce or eliminate contact with the contaminant is warranted. We need tools to aid us in assembling and assessing all available relevant information in an expeditious and scientifically sound manner. One such tool is the International Life Sciences Institute (ILSI) Key Events Dose-Response Framework (KEDRF). Developed as an extension of the WHO's International Program on Chemical Safety/ILSI mode of action/human relevance framework, it allows risk assessors to understand not only how a contaminant exerts its toxicity but also the dose response(s) for each key event and the ultimate outcome, including whether a threshold exists. This presentation will illustrate use of the KEDRF with case studies included in its development (chloroform and Listeriaonocytogenes) after its publication in the peer-reviewed scientific literature (chromium VI) and in a work in progress (3-monochloro-1, 2-propanediol).

  20. Does a dose-response relation exist between spinal pain and temporomandibular disorders?

    PubMed Central

    Wiesinger, Birgitta; Malker, Hans; Englund, Erling; Wänman, Anders

    2009-01-01

    Background The aim of this study was to test whether a reciprocal dose-response relation exists between frequency/severity of spinal pain and temporomandibular disorders (TMD). Methods A total of 616 subjects with varying severity of spinal pain or no spinal pain completed a questionnaire focusing on symptoms in the jaw, head and spinal region. A subset of the population (n = 266) were sampled regardless of presence or absence of spinal pain. We used two different designs, one with frequency/severity of spinal pain, and the other, with frequency/severity of TMD symptoms as independent variable. All 616 participants were allocated to four groups, one control group without spinal pain and three spinal pain groups. The subjects in the subset were allocated to one control group without TMD symptoms and three TMD groups. Odds ratios (ORs) were calculated for presence of frequent TMD symptoms in the separate spinal pain groups as well as for frequent spinal pain in the separate TMD groups. Results The analysis showed increasing ORs for TMD with increasing frequency/severity of spinal pain. We also found increasing ORs for spinal pain with increasing frequency/severity of TMD symptoms. Conclusion This study shows a reciprocal dose-response-like relationship between spinal pain and TMD. The results indicate that these two conditions may share common risk factors or that they may influence each other. Studies on the temporal sequence between spinal pain and TMD are warranted. PMID:19254384

  1. Dose-response relationship for rat liver DNA damage caused by 1,2-dimethylhydrazine.

    PubMed

    Kitchin, K T; Brown, J L

    1996-12-02

    An experimental approach was taken to the question of dose-response curves for chemical carcinogenesis, using DNA damage as a biomarker. Female rats were give 13 different doses of 1,2-dimethylhydrazine (from 1.4 to 135,000 micrograms/kg) and the subsequent hepatic DNA damage was determined by the alkaline elution technique. DMH doses below 450 micrograms/kg did not significantly damage DNA; all DMH doses of 1000 micrograms/kg or higher damaged rat hepatic DNA (P < 0.05). In this study the x values (dose) ranged over five orders of magnitude and the y values (DNA damage) ranged 30-fold. Ten different regression models (linear, quadratic, cubic, power, and six nonlinear transition models) were compared in their ability to fit the experimental data. With respect to log transformed dose, the six nonlinear transition equations fit the data considerably better than the four power type of equations. A sigmoid model fit to the log transformed dose of 1,2-dimethylhydrazine had an r2 of 0.9979, a degree of freedom adjusted r2 of 0.9969, a F-statistic of 1,457, and a fit standard error of 0.50. With respect to untransformed dose, only three equations (sigmoid, cascade and gaussian cumulative) could creditably fit the DMH data. The experimental results are interpreted with respect to hormesis, use of log transformed dose, sigmoid dose-response models, thresholds of biological response and cancer risk assessment.

  2. Steepness of the radiation dose-response curve for dose-per-fraction escalation keeping the number of fractions fixed.

    PubMed

    Bentzen, Søren M

    2005-01-01

    Clinically, there is growing interest in strategies for intensifying radiation therapy by escalating the dose per fraction. This paper considers the steepness of the dose-response curve in this case. The steepness of a radiation dose-response curve is most conveniently quantified by the normalized dose-response gradient, gamma. Under the assumption of a linear-quadratic dose-effect model, a simple analytical relationship is derived between the gamma-value for a dose-response curve generated by varying the total dose while keeping the number of fractions constant, i.e. escalating the dose per fraction, and the gamma-value for a dose-response curve generated by varying the total dose while keeping the dose per fraction constant. This formulation is compared with clinical dose-response data from the literature and shown to be in good agreement with the observations. Some implications of this formulation for non-uniform dose distributions delivered using 3D conformal radiotherapy or intensity modulated radiotherapy (IMRT) are briefly discussed.

  3. Dose-response relationships between pollination and fruiting refine pollinator comparisons for cranberry (Vaccinium macrocarpon [Ericaceae]).

    PubMed

    Cane, James H; Schiffhauer, Daniel

    2003-10-01

    Comparisons of pollinator efficacy using pollen received on stigmas can be refined by incorporating experimental dose-response relationships for pollen deposition and fruiting responses. A range of discrete pollen doses applied to cranberry stigmas resulted in decelerating curvilinear responses for fruiting, berry size, and seed set. Minimum thresholds and maximum asymptotes bounded reproductive responses to incremental stigmatic pollen loads. Four bee species were compared for their pollination efficacies on commercial cranberries, using counts of pollen received by stigmas during single bee visits to previously virgin flowers. Differences between these bee species were found to be exaggerated when raw pollen counts were used for comparison because foragers of some species often delivered pollen in excess of that needed to maximize fruit and seed production. Sixfold differences between species in mean pollen deposition translated into 1.5-2-fold differences in predicted cranberry fruit set and size. Implications for pollen tube competition and agricultural production are discussed.

  4. Dose-response characteristics of ketamine effect on locomotion, cognitive function and central neuronal activity.

    PubMed

    Imre, Gabor; Fokkema, Dirk S; Den Boer, Johan A; Ter Horst, Gert J

    2006-04-14

    The present dose-response study sought to determine the effects of subanesthetic dosages (4-16 mg/kg) of ketamine on locomotion, sensorimotor gating (PPI), working memory, as well as c-fos expression in various limbic regions implicated in the pathogenesis of schizophrenia. In addition, we examined whether ketamine-induced locomotion was influenced by the dark/light cycle. We found that ketamine increased locomotor activity in a dose dependent manner, but found no influence of the dark-light cycle. Additionally, ketamine dose-dependently interrupted PPI, resulting in prepulse facilitation at doses of 8 and 12 mg/kg. The dose of 12 mg/kg also induced impairments in working memory assessed by the discrete-trial delayed-alternation task. C-fos expression indicated that the dose-dependent behavioral effects of ketamine might be related to changes in the activity of limbic regions, notably hippocampus and amygdala.

  5. No-threshold dose-response curves for nongenotoxic chemicals: Findings and applications for risk assessment

    SciTech Connect

    Sheehan, Daniel M. . E-mail: dansheeh@swbell.net

    2006-01-15

    We tested the hypothesis that no threshold exists when estradiol acts through the same mechanism as an active endogenous estrogen. A Michaelis-Menten (MM) equation accounting for response saturation, background effects, and endogenous estrogen level fit a turtle sex-reversal data set with no threshold and estimated the endogenous dose. Additionally, 31 diverse literature dose-response data sets were analyzed by adding a term for nonhormonal background; good fits were obtained but endogenous dose estimations were not significant due to low resolving power. No thresholds were observed. Data sets were plotted using a normalized MM equation; all 178 data points were accommodated on a single graph. Response rates from {approx}1% to >95% were well fit. The findings contradict the threshold assumption and low-dose safety. Calculating risk and assuming additivity of effects from multiple chemicals acting through the same mechanism rather than assuming a safe dose for nonthresholded curves is appropriate.

  6. Quantitative aspects of informed consent: considering the dose response curve when estimating quantity of information.

    PubMed

    Lynöe, N; Hoeyer, K

    2005-12-01

    Information is usually supposed to be a prerequisite for people making decisions on whether or not to participate in a clinical trial. Previously conducted studies and research ethics scandals indicate that participants have sometimes lacked important pieces of information. Over the past few decades the quantity of information believed to be adequate has increased significantly, and in some instances a new maxim seems to be in place: the more information, the better the ethics in terms of respecting a participant's autonomy. The authors hypothesise that the dose-response curve from pharmacology or toxicology serves as a model to illustrate that a large amount of written information does not equal optimality. Using the curve as a pedagogical analogy when teaching ethics to students in clinical sciences, and also in engaging in dialogue with research institutions, may promote reflection on how to adjust information in relation to the preferences of individual participants, thereby transgressing the maxim that more information means better ethics.

  7. Mass shootings: a meta-analysis of the dose-response relationship.

    PubMed

    Wilson, Laura C

    2014-12-01

    A meta-analysis was conducted to examine the dose-response theory as it relates to posttraumatic stress symptoms (PTSSs) following mass shootings. It was hypothesized that greater exposure to a mass shooting would be associated with greater PTSSs. Trauma exposure in the current study was broadly defined as the extent to which a person experienced or learned about a mass shooting. The meta-analysis identified 11 qualifying studies that included 13 independent effect sizes from a total of 8,047 participants. The overall weighted mean effect size, based on a random effects model, was r = .19, p < .001, 95% CI [.13, .25]. Maximum likelihood meta-regressions revealed no significant linear effects of participant gender, participant age, or time elapsed since the shooting on the relationship between exposure and PTSSs. Because so few studies satisfied the inclusion criteria, the present study also documents that this area of the literature is underresearched.

  8. Dose-response fallacy in human reproductive studies of toxic exposures

    SciTech Connect

    Selevan, S.G.; Lemasters, G.K.

    1987-05-01

    The manner in which exposure is defined can affect the findings of reproductive studies of toxic exposures. The individual end points potentially examined, such as fetal loss, subfertility, and congenital malformations observed at birth, are on a continuum by severity of effect: The most extreme effect of the three being infertility because no pregnancy is possible, and the least extreme, congenital malformations recognized at birth. End points observed at birth are survivors of a long and complex process. The process yielding one of these adverse end points may result from a number of factors, including level of exposure. For example, a very high exposure could result in early fetal loss, whereas a lower one might result in a congenital malformation observed at birth. If the probability of a less severe end point falls due to increasing probability of more severe end points with increasing exposure, then a nontraditional dose-response relationship may be observed in the study of one type of outcome.

  9. Dose-response fallacy in human reproductive studies of toxic exposures

    SciTech Connect

    Selevan, S.G.; Lemasters, G.K.

    1987-01-01

    The manner in which exposure is defined can affect the findings of reproductive studies of toxic exposures. The individual end points potentially examined, such as fetal loss, subfertility, and congenital malformations observed at birth, are on a continuum by severity of effect: the most extreme effects of the three being infertility because no pregnancy is possible, and the least extreme, congenital malformations recognized at birth. End points observed at birth are survivors of a long and complex process. The process yielding one of these adverse end points may result from a number of factors, including level of exposure could result in early fetal loss, whereas a lower one might result in a congenital malformation observed at birth. If the probability of a less-severe end point falls due to increasing probability of more-severe end points with increasing exposure, then a nontraditional dose-response relationship may be observed in the study of one type of outcome.

  10. SO/sub 2/ dose-response sensitivity classification data for crops and natural vegetation species

    SciTech Connect

    Irving, P.M.; Ballou, S.W.

    1980-09-01

    Over the past several years studies have been made on the interaction of sulfur dioxide (SO/sub 2/) and vegetation by performing field research and by developing analytical procedures for applying field observation data to energy impact assessments. As a result of this work, numerous reports have been prepared on crop-pollutant interactions, such as dose-response data; on the applications of such data to screening approaches for identifying crops at risk; and on models that predict crop yield reductions from point source emissions of SO/sub 2/. Data that were used for these studies, such as the crop-at-risk screening procedure, are presented in this report. Maps are also presented that show the national distribution of SO/sub 2/-sensitive crops and natural vegetation.

  11. Therapeutic efficacy of endostatin exhibits a biphasic dose-response curve.

    PubMed

    Celik, Ilhan; Sürücü, Oguzkan; Dietz, Carsten; Heymach, John V; Force, Jeremy; Höschele, Iris; Becker, Christian M; Folkman, Judah; Kisker, Oliver

    2005-12-01

    We show here that recombinant endostatin protein has a biphasic effect on the inhibition of endothelial cell migration in vitro. In tumor-bearing animals, there is a similar biphasic effect on the inhibition of tumor growth and on circulating endothelial cells after once-daily s.c. injections. This biphasic effect is revealed as a U-shaped curve in which efficacy is optimal between very low and very high doses depending on the tumor type. This result may be applicable to other inhibitors of endothelial growth and to angiogenesis. Furthermore, these results have important implications for clinicians who administer angiogenesis inhibitors for cancer or other angiogenesis-dependent diseases. When these results are taken together with two previous reports of angiogenesis inhibitors with a U-shaped dose-response, they suggest that other regulators of endothelial growth may display a similar pattern.

  12. Clinical application of Chamomilla recutita in phlebitis: dose response curve study.

    PubMed

    Reis, Paula Elaine Diniz Dos; Carvalho, Emilia Campos de; Bueno, Paula Carolina Pires; Bastos, Jairo Kenupp

    2011-01-01

    This experimental and dose-response curve study aimed to carry out the quality control of the Chamomilla recutita sample, as well as to estimate the ideal dose, for anti-inflammatory effect, of the extract of its capitula, in patients with phlebitis due to peripheral intravenous infusion of antineoplastic chemotherapy and to evaluate the toxicity of this extract in human beings. The therapeutic efficacy, concerning the anti-inflammatory potential, of different doses of Chamomilla recutita extract were analyzed and compared in 25 patients. The time of regression of phlebitis was shorter for groups with 2.5% concentration (mean=29.2h, standard deviation = 8.98) and 5% concentration (mean = 38.8h, standard deviation = 17.47). Local toxicity was almost not observed. This research contributes to the innovation of the nursing clinical practice, since it suggests an alternative for the treatment of phlebitis through the clinical use of phytotherapeutic drugs.

  13. Dose Response of MARV/Angola Infection in Cynomolgus Macaques following IM or Aerosol Exposure

    PubMed Central

    Johnston, Sara C.; Lin, Kenny L.; Twenhafel, Nancy A.; Raymond, Jo Lynne W.; Shamblin, Joshua D.; Wollen, Suzanne E.; Wlazlowski, Carly B.; Wilkinson, Eric R.; Botto, Miriam A.; Goff, Arthur J.

    2015-01-01

    Marburg virus infection in humans causes a hemorrhagic disease with a high case fatality rate. Countermeasure development requires the use of well-characterized animal models that mimic human disease. To further characterize the cynomolgus macaque model of MARV/Angola, two independent dose response studies were performed using the intramuscular or aerosol routes of exposure. All animals succumbed at the lowest target dose; therefore, a dose effect could not be determined. For intramuscular-exposed animals, 100 PFU was the first target dose that was not significantly different than higher target doses in terms of time to disposition, clinical pathology, and histopathology. Although a significant difference was not observed between aerosol-exposed animals in the 10 PFU and 100 PFU target dose groups, 100 PFU was determined to be the lowest target dose that could be consistently obtained and accurately titrated in aerosol studies. PMID:26413900

  14. Severity of killer whale behavioral responses to ship noise: a dose-response study.

    PubMed

    Williams, Rob; Erbe, Christine; Ashe, Erin; Beerman, Amber; Smith, Jodi

    2014-02-15

    Critical habitats of at-risk populations of northeast Pacific "resident" killer whales can be heavily trafficked by large ships, with transits occurring on average once every hour in busy shipping lanes. We modeled behavioral responses of killer whales to ship transits during 35 "natural experiments" as a dose-response function of estimated received noise levels in both broadband and audiogram-weighted terms. Interpreting effects is contingent on a subjective and seemingly arbitrary decision about severity threshold indicating a response. Subtle responses were observed around broadband received levels of 130 dB re 1 μPa (rms); more severe responses are hypothesized to occur at received levels beyond 150 dB re 1 μPa, where our study lacked data. Avoidance responses are expected to carry minor energetic costs in terms of increased energy expenditure, but future research must assess the potential for reduced prey acquisition, and potential population consequences, under these noise levels.

  15. Dose-response functions for the soiling of heritage materials due to air pollution exposure.

    PubMed

    Watt, John; Jarrett, David; Hamilton, Ron

    2008-08-01

    A set of materials (Portland limestone, white painted steel, white plastic and polycarbonate filter material) was exposed at locations in London, Athens and Krakow. Regular measurements of reflectance were taken over a period of twelve months. Co-located measurements of PM(10) concentrations were available. Based on these results, the relationship between soiling (measured as loss of reflectance) and ambient PM(10) concentrations was quantified leading to the development of dose-response functions for the soiling of materials. The results for limestone revealed too much scatter for a prediction to be made. Implications for air quality management and for the conservation of cultural heritage buildings are considered, including public acceptability and economic factors.

  16. Dose response of surfactants to attenuate gas embolism related platelet aggregation

    NASA Astrophysics Data System (ADS)

    Eckmann, David M.; Eckmann, Yonaton Y.; Tomczyk, Nancy

    2014-03-01

    Intravascular gas embolism promotes blood clot formation, cellular activation, and adhesion events, particularly with platelets. Populating the interface with surfactants is a chemical-based intervention to reduce injury from gas embolism. We studied platelet activation and platelet aggregation, prominent adverse responses to blood contact with bubbles. We examined dose-response relationships for two chemically distinct surfactants to attenuate the rise in platelet function stimulated by exposure to microbubbles. Significant reduction in platelet aggregation and platelet activation occurred with increasing concentration of the surfactants, indicating presence of a saturable system. A population balance model for platelet aggregation in the presence of embolism bubbles and surfactants was developed. Monte Carlo simulations for platelet aggregation were performed. Results agree qualitatively with experimental findings. Surfactant dose-dependent reductions in platelet activation and aggregation indicate inhibition of the gas/liquid interface's ability to stimulate cellular activation mechanically.

  17. Coffee consumption and risk of colorectal cancer: a dose-response analysis of observational studies.

    PubMed

    Tian, Changwei; Wang, Wenming; Hong, Zhiqiang; Zhang, Xingliang

    2013-06-01

    Coffee consumption has been linked to risk of colorectal cancer theoretically, but the findings were conflicting from observational studies. Results from the recent meta-analysis suggested a moderate favorable effect of coffee consumption on colorectal cancer risk, especially for colon cancer. However, the relationship, if exists, between coffee consumption and colorectal cancer risk is unclear. Thus, the dose-response relationship was assessed by restricted cubic spline model and multivariate random-effect meta-regression. The results suggested that a significant association was found between coffee consumption and decreased risk of colorectal and colon cancer among subjects consuming ≥4 cups of coffee per day. A potential nonlinear relationship should be assessed before assuming a linear relationship.

  18. The effect of site-to-site variability in ultrasensitive dose responses.

    PubMed

    Enciso, German A; Ryerson, Shane

    2017-01-01

    In this paper we study the ultrasensitive behavior of multisite phosphorylation or ligand binding systems, under site-to-site variations in the modification rates. Using computational methods and mathematical analysis, we prove that the Hill coefficient reaches its maximum value when all sites are identical to each other. This is shown for a non-cooperative multisite system with arbitrary activation function as well as for the well known MWC model. We also show that the Hill coefficient of the dose response is locally robust to variations in individual modification rates. The results suggest that maximal ultrasensitivity is reached when sites are similar to each other but not necessarily identical, a conformation found in unstructured modification domains present in many experimental systems.

  19. A latent pharmacokinetic time profile to model dose-response survival data.

    PubMed

    Jacobs, Tom; Straetemans, Roel; Molenberghs, Geert; Adriaan Bouwknecht, J; Bijnens, Luc

    2010-07-01

    The accelerating rotarod test is a preclinical pharmacodynamic test to assess the effect of a treatment on an animal's motor coordination. Two models are proposed to analyze the dose-response time-to-event data that typically result from such experiments: (1) a linear regression model and (2) an E(max) model with latent drug concentration at the site of action. Both cope with the survival character of the data. The latter model allows a direct comparison of compounds, but raises the question of whether the study design would benefit from the inclusion of additional mice for plasma concentration sampling on the one hand or whether additional time-to-event data without plasma concentration sampling should be ascertained from these additional mice on the other hand. A simulation study explores the impact on operational characteristics of this change of study design.

  20. New flux based dose-response relationships for ozone for European forest tree species.

    PubMed

    Büker, P; Feng, Z; Uddling, J; Briolat, A; Alonso, R; Braun, S; Elvira, S; Gerosa, G; Karlsson, P E; Le Thiec, D; Marzuoli, R; Mills, G; Oksanen, E; Wieser, G; Wilkinson, M; Emberson, L D

    2015-11-01

    To derive O3 dose-response relationships (DRR) for five European forest trees species and broadleaf deciduous and needleleaf tree plant functional types (PFTs), phytotoxic O3 doses (PODy) were related to biomass reductions. PODy was calculated using a stomatal flux model with a range of cut-off thresholds (y) indicative of varying detoxification capacities. Linear regression analysis showed that DRR for PFT and individual tree species differed in their robustness. A simplified parameterisation of the flux model was tested and showed that for most non-Mediterranean tree species, this simplified model led to similarly robust DRR as compared to a species- and climate region-specific parameterisation. Experimentally induced soil water stress was not found to substantially reduce PODy, mainly due to the short duration of soil water stress periods. This study validates the stomatal O3 flux concept and represents a step forward in predicting O3 damage to forests in a spatially and temporally varying climate.

  1. Recent odour regulation developments in Flanders: ambient odour quality standards based on dose-response relationships.

    PubMed

    Van Broeck, G; Van Langenhove, H; Nieuwejaers, B

    2001-01-01

    Until now there has been little uniformity in the approach of odour nuisance problems in Flanders. A switch to a standardised and scientifically underpinned approach is essential and is currently in full development. This paper mainly discusses the results of five year research on odour concentration standard developments in Flanders, executed in the period 1996-2000. The research was focused on five pilot sectors: pig farms, slaughterhouses, paint spray installations, sewage treatment plants and textile plants. The general approach of the method to determine the dose-response relation was found to be sufficient. The methodology used is fully described in the paper presented by Van Broeck and Van Langenhove at the CIWEM and IAWO Joint International Conference on Control and Prevention of Odours in the Water Industry in September 1999. For each location (16 locations in total) an unambiguous dose-response relation could be derived (rising nuisance for rising concentrations). In most cases, a "no effect" level could be determined. The background percentage nuisance fluctuated between 0 and 15%. For the sectors of the slaughterhouses, paint spray installations and sewage treatment plants a no effect level was 0.5, 2.0 and 0.5 sniffing units m(-3) as 98th percentile (sniffing units are odour concentrations measured by means of sniffing measurements on the field) was determined. For the sectors of the textile plants and pig farms, no unambiguous no effect level was found. Currently research is undertaken to translate the no effect levels to odour standards. Other initiatives, taken to underpin the Flemish odour regulations, such as the development of an odour source inventory and a complaint handling system, are also briefly discussed.

  2. Dose-response effects of zinc and fluoride on caries lesion remineralization.

    PubMed

    Lippert, F

    2012-01-01

    The present mechanistic in vitro study aimed to investigate dose-response effects of zinc and fluoride on caries lesion remineralization and subsequent protection from demineralization. Artificial caries lesions were created using a methylcellulose acid gel system. Lesions were remineralized for 2 weeks using citrate-containing artificial saliva which was supplemented with zinc (0-153 μmol/l) and fluoride (1.1 or 52.6 μmol/l) in a 7 × 2 factorial design. Lesions were also remineralized in the absence of zinc and citrate, but in the presence of fluoride. After remineralization, all lesions were demineralized for 1 day under identical conditions. Changes in mineral distribution characteristics of caries lesions after remineralization and secondary demineralization were studied using transverse microradiography. At 1.1 μmol/l fluoride, zinc exhibited detrimental effects on remineralization in a dose-response manner and mainly by preventing remineralization near the lesion surface. At 52.6 μmol/l fluoride, zinc retarded remineralization only at the highest concentration tested. Zinc enhanced overall remineralization at 3.8-15.3 μmol/l. At 76.5 and less so at 153 μmol/l, zinc showed extensive remineralization of deeper parts within the lesions at the expense of remineralization near the surface. Citrate did not interfere with remineralization at 1.1 μmol/l fluoride, but enhanced remineralization at 52.6 μmol/l fluoride. Lesions exhibiting preferential remineralization in deeper parts showed higher mineral loss after secondary demineralization, suggesting the formation of more soluble mineral phases during remineralization. In summary, zinc and fluoride showed synergistic effects in enhancing lesion remineralization, however only at elevated fluoride concentrations.

  3. Meta-analysis on occupational exposure to pesticides--neurobehavioral impact and dose-response relationships.

    PubMed

    Meyer-Baron, Monika; Knapp, Guido; Schäper, Michael; van Thriel, Christoph

    2015-01-01

    While the health impact of high exposures to pesticides is acknowledged, the impact of chronic exposures in the absence of acute poisonings is controversial. A systematic analysis of dose-response relationships is still missing. Its absence may provoke alternative explanations for altered performances. Consequently, opportunities for health prevention in the occupational and environmental field may be missed. Objectives were (1) quantification of the neurotoxic impact of pesticides by an analysis of functional alterations in workers measured by neuropsychological performance tests, (2) estimates of dose-response relationships on the basis of exposure duration, and (3) exploration of susceptible subgroups. The meta-analysis employed a random effects model to obtain overall effects for individual performance tests. Twenty-two studies with a total of 1758 exposed and 1260 reference individuals met the inclusion criteria. At least three independent outcomes were available for twenty-six performance variables. Significant performance effects were shown in adults and referred to both cognitive and motor performances. Effect sizes ranging from dRE=-0.14 to dRE=-0.67 showed consistent outcomes for memory and attention. Relationships between effect sizes and exposure duration were indicated for individual performance variables and the total of measured performances. Studies on adolescents had to be analyzed separately due to numerous outliers. The large variation among outcomes hampered the analysis of the susceptibility in this group, while data on female workers was too scant for the analysis. Relationships exist between the impact of pesticides on performances and exposure duration. A change in test paradigms would help to decipher the impact more specifically. The use of biomarkers appropriate for lower exposures would allow a better prevention of neurotoxic effects due to occupational and environmental exposure. Intervention studies in adolescents seem warranted to

  4. Cerebral radioprotection by pentobarbital: Dose-response characteristics and association with GABA agonist activity

    SciTech Connect

    Olson, J.J.; Friedman, R.; Orr, K.; Delaney, T.; Oldfield, E.H. )

    1990-05-01

    Pentobarbital reduces cerebral radiation toxicity; however, the mechanism of this phenomenon remains unknown. As an anesthetic and depressant of cerebral metabolism, pentobarbital induces its effects on the central nervous system by stimulating the binding of gamma-aminobutyric acid (GABA) to its receptor and by inhibiting postsynaptic excitatory amino acid activity. The purpose of this study is to investigate the role of these actions as well as other aspects of the radioprotective activity of pentobarbital. Fischer 344 rats were separated into multiple groups and underwent two dose-response evaluations. In one set of experiments to examine the relationship of radioprotection to pentobarbital dose, a range of pentobarbital doses (0 to 75 mg/kg) were given intraperitoneally prior to a constant-level radiation dose (70 Gy). In a second series of experiments to determine the dose-response relationship of radiation protection to radiation dose, a range of radiation doses (10 to 90 Gy) were given with a single pentobarbital dose. Further groups of animals were used to evaluate the importance of the timing of pentobarbital administration, the function of the (+) and (-) isomers of pentobarbital, and the role of an alternative GABA agonist (diazepam). In addition, the potential protective effects of alternative methods of anesthesia (ketamine) and induction of cerebral hypometabolism (hypothermia) were examined. Enhancement of survival time from acute radiation injury due to high-dose single-fraction whole-brain irradiation was maximal with 60 mg/kg of pentobarbital, and occurred over the range of all doses examined between 30 to 90 Gy. Protection was seen only in animals that received the pentobarbital before irradiation. Administration of other compounds that enhance GABA binding (Saffan and diazepam) also significantly enhanced survival time.

  5. GLP-1-induced alterations in the glucose-stimulated insulin secretory dose-response curve.

    PubMed

    Brandt, A; Katschinski, M; Arnold, R; Polonsky, K S; Göke, B; Byrne, M M

    2001-08-01

    The present study was undertaken to establish in normal volunteers the alterations in beta-cell responsiveness to glucose associated with a constant infusion of glucagon-like peptide-1 (GLP-1) or a pretreatment infusion for 60 min. A high-dose graded glucose infusion protocol was used to explore the dose-response relationship between glucose and insulin secretion. Studies were performed in 10 normal volunteers, and insulin secretion rates (ISR) were calculated by deconvolution of peripheral C-peptide levels by use of a two-compartmental model that utilized mean kinetic parameters. During the saline study, from 5 to 15 mM glucose, the relationship between glucose and ISR was linear. Constant GLP-1 infusion (0.4 pmol x kg(-1) x min(-1)) shifted the dose-response curve to the left, with an increase in the slope of this curve from 5 to 9 mM glucose from 71.0 +/- 12.4 pmol x min(-1) x mM(-1) during the saline study to 241.7 +/- 36.6 pmol x min(-1) x mM(-1) during the constant GLP-1 infusion (P < 0.0001). GLP-1 consistently stimulated a >200% increase in ISR at each 1 mM glucose interval, maintaining plasma glucose at <10 mM (P < 0.0007). Pretreatment with GLP-1 for 60 min resulted in no significant priming of the beta-cell response to glucose (P = 0.2). Insulin clearance rates were similar in all three studies at corresponding insulin levels. These studies demonstrate that physiological levels of GLP-1 stimulate glucose-induced insulin secretion in a linear manner, with a consistent increase in ISR at each 1 mM glucose interval, and that they have no independent effect on insulin clearance and no priming effect on subsequent insulin secretory response to glucose.

  6. Dose-response effects of diphenylhydantoin on pregnant dams and embryo-fetal development in rats.

    PubMed

    Kim, Sung-Hwan; Lee, In-Chul; Baek, Hyung-Seon; Lim, Jeong-Hyeon; Moon, Changjong; Shin, Dong-Ho; Kim, Sung-Ho; Park, Seung-Chun; Kim, Jong-Choon

    2012-10-01

    Despite the widespread use of diphenylhydantoin (DPH), there is a lack of reliable information on the teratogenic effects, correlation with maternal and developmental toxicity, and dose-response relationship of DPH. This study investigated the dose-response effects of DPH on pregnant dams and embryo-fetal development as well as the relationship between maternal and developmental toxicity. DPH was orally administered to pregnant rats from gestational days 6 through 15 at 0, 50, 150, and 300 mg/kg/day. At 300 mg/kg, maternal toxicity including increased clinical signs, suppressed body weight, decreased food intake, and increased weights of adrenal glands, liver, kidneys, and brain were observed in dams. Developmental toxicity, including a decrease in fetal and placental weights, increased incidence of morphological alterations, and a delay in fetal ossification delay also occurred. At 150 mg/kg, maternal toxicity manifested as an increased incidence of clinical signs, reduced body weight gain and food intake, and increased weights of adrenal glands and brain. Only minimal developmental toxicity, including decreased placental weight and an increased incidence of visceral and skeletal variations, was observed. No treatment-related maternal or developmental effects were observed at 50 mg/kg. These results show that DPH is minimally embryotoxic at a minimal maternotoxic dose (150 mg/kg/day) but is embryotoxic and teratogenic at an overt maternotoxic dose (300 mg/kg/day). Under these experimental conditions, the no-observed-adverse-effect level of DPH for pregnant dams and embryo-fetal development is considered to be 50 mg/kg/day. These data indicate that DPH is not a selective developmental toxicant in the rat.

  7. Curve fitting toxicity test data: Which comes first, the dose response or the model?

    SciTech Connect

    Gully, J.; Baird, R.; Bottomley, J.

    1995-12-31

    The probit model frequently does not fit the concentration-response curve of NPDES toxicity test data and non-parametric models must be used instead. The non-parametric models, trimmed Spearman-Karber, IC{sub p}, and linear interpolation, all require a monotonic concentration-response. Any deviation from a monotonic response is smoothed to obtain the desired concentration-response characteristics. Inaccurate point estimates may result from such procedures and can contribute to imprecision in replicate tests. The following study analyzed reference toxicant and effluent data from giant kelp (Macrocystis pyrifera), purple sea urchin (Strongylocentrotus purpuratus), red abalone (Haliotis rufescens), and fathead minnow (Pimephales promelas) bioassays using commercially available curve fitting software. The purpose was to search for alternative parametric models which would reduce the use of non-parametric models for point estimate analysis of toxicity data. Two non-linear models, power and logistic dose-response, were selected as possible alternatives to the probit model based upon their toxicological plausibility and ability to model most data sets examined. Unlike non-parametric procedures, these and all parametric models can be statistically evaluated for fit and significance. The use of the power or logistic dose response models increased the percentage of parametric model fits for each protocol and toxicant combination examined. The precision of the selected non-linear models was also compared with the EPA recommended point estimation models at several effect.levels. In general, precision of the alternative models was equal to or better than the traditional methods. Finally, use of the alternative models usually produced more plausible point estimates in data sets where the effects of smoothing and non-parametric modeling made the point estimate results suspect.

  8. Probiotics reduce symptoms of antibiotic use in a hospital setting: a randomized dose response study.

    PubMed

    Ouwehand, Arthur C; DongLian, Cai; Weijian, Xu; Stewart, Morgan; Ni, Jiayi; Stewart, Tad; Miller, Larry E

    2014-01-16

    Probiotics are known to reduce antibiotic associated diarrhea (AAD) and Clostridium difficile associated diarrhea (CDAD) risk in a strain-specific manner. The aim of this study was to determine the dose-response effect of a four strain probiotic combination (HOWARU(®) Restore) on the incidence of AAD and CDAD and severity of gastrointestinal symptoms in adult in-patients requiring antibiotic therapy. Patients (n=503) were randomized among three study groups: HOWARU(®) Restore probiotic 1.70×10(10) CFU (high-dose, n=168), HOWARU(®) Restore probiotic 4.17×10(9) CFU (low-dose, n=168), or placebo (n=167). Subjects were stratified by gender, age, and duration of antibiotic treatment. Study products were administered daily up to 7 days after the final antibiotic dose. The primary endpoint of the study was the incidence of AAD. Secondary endpoints included incidence of CDAD, diarrhea duration, stools per day, bloody stools, fever, abdominal cramping, and bloating. A significant dose-response effect on AAD was observed with incidences of 12.5, 19.6, and 24.6% with high-dose, low-dose, and placebo, respectively (p=0.02). CDAD was the same in both probiotic groups (1.8%) but different from the placebo group (4.8%; p=0.04). Incidences of fever, abdominal pain, and bloating were lower with increasing probiotic dose. The number of daily liquid stools and average duration of diarrhea decreased with higher probiotic dosage. The tested four strain probiotic combination appears to lower the risk of AAD, CDAD, and gastrointestinal symptoms in a dose-dependent manner in adult in-patients.

  9. Trenbolone acetate/estradiol combinations in feedlot steers: dose-response and implant carrier effects.

    PubMed

    Bartle, S J; Preston, R L; Brown, R E; Grant, R J

    1992-05-01

    Two experiments were conducted at three locations to determine the correct dosage and carrier for trenbolone acetate (TBA) and estradiol (E2) implants in feedlot steers. In the dose-response experiment, 1,296 steers were allotted to six implant treatments (48 pens per location): control, 140 mg of TBA (140/0), 30 mg of E2 (0/30), 20 mg of TBA + 4 mg of E2(20/4), 80 mg of TBA + 16 mg of E2(80/16), and 140 mg of TBA + 28 mg of E2 (140/28). In the carrier experiment, 575 steers were allotted to five implant treatments (25 pens per location): control, 140 mg of TBA + 28 mg of E2 in lactose (140/28-LA), 140 mg of TBA + 28 mg of E2 in cholesterol (140/28-CH), 140 mg of TBA + 20 mg of E2 in LA (140/20-LA), and 200 mg of progesterone + 20 mg of E2 benzoate (SS, reimplanted). In both experiments steers were fed a finishing diet for 140 to 168 d. In the dose-response experiment, response to TBA alone (140/0) did not differ from control (P greater than .2). Estradiol alone (0/30) improved ADG by 7% (P less than .01) and tended to improve feed efficiency over control (3%, P = .17). The highest dosage (140/28) improved ADG by 18% (P less than .001) and feed efficiency by 10% (P less than .001) over control and 10% (P less than .001) and 7% (P less than .01) over E2 alone, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

  10. Dose-response behavior of the bacterium Vibrio fischeri exposed to pharmaceuticals and personal care products.

    PubMed

    Ortiz de García, Sheyla; García-Encina, Pedro A; Irusta-Mata, Rubén

    2016-01-01

    The presence of pharmaceuticals and personal care products (PPCPs) in the environment has become a real and widespread concern in recent years. Therefore, the primary goal of this study was to investigate 20 common and widely used PPCPs to assess their individual and combined effect on an important species in one trophic level, i.e., bacteria. The ecotoxicological effects of PPCPs at two different concentration ranges were determined in the bacterium Vibrio fischeri using Microtox(®) and were statistically analyzed using three models in the GraphPad Prism 6 program for Windows, v.6.03. A four-parameter model best fit the majority of the compounds. The half maximal effective concentration (EC50) of each PPCP was estimated using the best-fitting model and was compared with the results from a recent study. Comparative analysis indicated that most compounds showed the same level of toxicity. Moreover, the stimulatory effects of PPCPs at environmental concentrations (low doses) were assessed. These results indicated that certain compounds have traditional inverted U- or J-shaped dose-response curves, and 55% of them presented a stimulatory effect below the zero effect-concentration point. Effective concentrations of 0 (EC0), 5 (EC5) and 50% (EC50) were calculated for each PPCP as the ecotoxicological points. All compounds that presented narcosis as a mode of toxic action at high doses also exhibited stimulation at low concentrations. The maximum stimulatory effect of a mixture was higher than the highest stimulatory effect of each individually tested compound. Moreover, when the exposure time was increased, the hormetic effect decreased. Hormesis is being increasingly included in dose-response studies because this may have a harmful, beneficial or indifferent effect in an environment. Despite the results obtained in this research, further investigations need to be conducted to elucidate the behavior of PPCPs in aquatic environments.

  11. Dose-Response Modeling for Inhalational Anthrax in Rabbits Following Single or Multiple Exposures.

    PubMed

    Gutting, Bradford W; Rukhin, Andrey; Marchette, David; Mackie, Ryan S; Thran, Brandolyn

    2016-11-01

    There is a need to advance our ability to characterize the risk of inhalational anthrax following a low-dose exposure. The exposure scenario most often considered is a single exposure that occurs during an attack. However, long-term daily low-dose exposures also represent a realistic exposure scenario, such as what may be encountered by people occupying areas for longer periods. Given this, the objective of the current work was to model two rabbit inhalational anthrax dose-response data sets. One data set was from single exposures to aerosolized Bacillus anthracis Ames spores. The second data set exposed rabbits repeatedly to aerosols of B. anthracis Ames spores. For the multiple exposure data the cumulative dose (i.e., the sum of the individual daily doses) was used for the model. Lethality was the response for both. Modeling was performed using Benchmark Dose Software evaluating six models: logprobit, loglogistic, Weibull, exponential, gamma, and dichotomous-Hill. All models produced acceptable fits to either data set. The exponential model was identified as the best fitting model for both data sets. Statistical tests suggested there was no significant difference between the single exposure exponential model results and the multiple exposure exponential model results, which suggests the risk of disease is similar between the two data sets. The dose expected to cause 10% lethality was 15,600 inhaled spores and 18,200 inhaled spores for the single exposure and multiple exposure exponential dose-response model, respectively, and the 95% lower confidence intervals were 9,800 inhaled spores and 9,200 inhaled spores, respectively.

  12. Bayesian dose-response analysis for epidemiological studies with complex uncertainty in dose estimation.

    PubMed

    Kwon, Deukwoo; Hoffman, F Owen; Moroz, Brian E; Simon, Steven L

    2016-02-10

    Most conventional risk analysis methods rely on a single best estimate of exposure per person, which does not allow for adjustment for exposure-related uncertainty. Here, we propose a Bayesian model averaging method to properly quantify the relationship between radiation dose and disease outcomes by accounting for shared and unshared uncertainty in estimated dose. Our Bayesian risk analysis method utilizes multiple realizations of sets (vectors) of doses generated by a two-dimensional Monte Carlo simulation method that properly separates shared and unshared errors in dose estimation. The exposure model used in this work is taken from a study of the risk of thyroid nodules among a cohort of 2376 subjects who were exposed to fallout from nuclear testing in Kazakhstan. We assessed the performance of our method through an extensive series of simulations and comparisons against conventional regression risk analysis methods. When the estimated doses contain relatively small amounts of uncertainty, the Bayesian method using multiple a priori plausible draws of dose vectors gave similar results to the conventional regression-based methods of dose-response analysis. However, when large and complex mixtures of shared and unshared uncertainties are present, the Bayesian method using multiple dose vectors had significantly lower relative bias than conventional regression-based risk analysis methods and better coverage, that is, a markedly increased capability to include the true risk coefficient within the 95% credible interval of the Bayesian-based risk estimate. An evaluation of the dose-response using our method is presented for an epidemiological study of thyroid disease following radiation exposure.

  13. Dose-Response Effects of the Text4baby Mobile Health Program: Randomized Controlled Trial

    PubMed Central

    Nielsen, Peter E; Szekely, Daniel R; Bihm, Jasmine W; Murray, Elizabeth A; Snider, Jeremy; Abroms, Lorien C

    2015-01-01

    Background Mobile health (mHealth) is growing rapidly, but more studies are needed on how to optimize programs, including optimal timing of messaging, dose of exposure, and value of interactive features. This study evaluates final outcomes of text4baby (a text message service for pregnant and postpartum women) from a randomized trial performed in a population of pregnant female soldiers and family members. Objective The study aims were to evaluate (1) treatment effects and (2) dose-response effects of text4baby on behavioral outcomes compared to control (no text4baby) condition. Methods The study was a randomized trial of text4baby at Madigan Army Medical Center. Female military health beneficiaries who met inclusion criteria were eligible for the study. Participants provided consent, completed a baseline questionnaire, and then were randomized to enroll in text4baby or not. They were followed up at 3 time points thereafter through delivery of their baby. Generalized estimating equation models were used to evaluate outcomes. We examined treatment effects and the effects of higher doses of text4baby messages on outcomes. Results We report descriptive statistics including dosage of text messages delivered. The main finding was a significant effect of high exposure to text4baby on self-reported alcohol consumption postpartum (OR 0.212, 95% CI 0.046-0.973, P=.046), as measured by the question “Since you found out about your pregnancy, have you consumed alcoholic beverages?” The text4baby participants also reported lower quantities of alcohol consumed postpartum. Conclusions Studies of text4baby have helped to build the mHealth evidence base. The effects of text4baby offer lessons for future scalable mHealth programs and suggest the need to study dose-response effects of these interventions. PMID:25630361

  14. Hormones and Endocrine-Disrupting Chemicals: Low-Dose Effects and Nonmonotonic Dose Responses

    PubMed Central

    Colborn, Theo; Hayes, Tyrone B.; Heindel, Jerrold J.; Jacobs, David R.; Lee, Duk-Hee; Shioda, Toshi; Soto, Ana M.; vom Saal, Frederick S.; Welshons, Wade V.; Zoeller, R. Thomas

    2012-01-01

    For decades, studies of endocrine-disrupting chemicals (EDCs) have challenged traditional concepts in toxicology, in particular the dogma of “the dose makes the poison,” because EDCs can have effects at low doses that are not predicted by effects at higher doses. Here, we review two major concepts in EDC studies: low dose and nonmonotonicity. Low-dose effects were defined by the National Toxicology Program as those that occur in the range of human exposures or effects observed at doses below those used for traditional toxicological studies. We review the mechanistic data for low-dose effects and use a weight-of-evidence approach to analyze five examples from the EDC literature. Additionally, we explore nonmonotonic dose-response curves, defined as a nonlinear relationship between dose and effect where the slope of the curve changes sign somewhere within the range of doses examined. We provide a detailed discussion of the mechanisms responsible for generating these phenomena, plus hundreds of examples from the cell culture, animal, and epidemiology literature. We illustrate that nonmonotonic responses and low-dose effects are remarkably common in studies of natural hormones and EDCs. Whether low doses of EDCs influence certain human disorders is no longer conjecture, because epidemiological studies show that environmental exposures to EDCs are associated with human diseases and disabilities. We conclude that when nonmonotonic dose-response curves occur, the effects of low doses cannot be predicted by the effects observed at high doses. Thus, fundamental changes in chemical testing and safety determination are needed to protect human health. PMID:22419778

  15. Time and dose-response effects of honokiol on UVB-induced skin cancer development.

    PubMed

    Guillermo, Ruth F; Chilampalli, Chandeshwari; Zhang, Xiaoying; Zeman, David; Fahmy, Hesham; Dwivedi, Chandradhar

    2012-06-01

    Honokiol has shown chemopreventive effects in chemically-induced and UVB-induced skin cancer in mice. In this investigation, we assessed the time-effects of a topical low dose of honokiol (30 μg), and then the effects of different honokiol doses (30, 45, and 60 μg) on a UVB-induced skin cancer model to find an optimal dose and time for desirable chemopreventive effects. UVB radiation (30 mJ/cm(2), 5 days/week for 25 or 27 weeks) was used to induce skin carcinogenesis in SKH-1 mice. For the time-response experiment 30 μg honokiol in acetone was applied topically to the animals before the UVB exposure (30 min, 1 h, and 2 h) and after the UVB exposure (immediately, 30 min, and 1 h). Control groups were treated with acetone. For the dose-response study, animals were treated topically with acetone or honokiol (30, 45, and 60 μg) one hour before the UVB exposure. In the time-response experiment, honokiol inhibited skin tumor multiplicity by 49-58% while reducing tumor volumes by 70-89%. In the dose-response study, honokiol (30, 45, and 60 μg) significantly decreased skin tumor multiplicity by 36-78% in a dose-dependent manner, while tumor area was reduced by 76-94%. Honokiol (60 μg) significantly reduced tumor incidence by 40% as compared to control group. Honokiol applied in very low doses (30 μg) either before or after UVB radiation shows chemopreventive effects. Honokiol (30, 45, and 60 μg) prevents UVB-induced skin cancer in a dose-dependent manner. Honokiol can be an effective chemopreventive agent against skin cancer.

  16. KINETIC SIMULATIONS OF THERMOLUMINESCENCE DOSE RESPONSE: LONG OVERDUE CONFRONTATION WITH THE EFFECTS OF IONISATION DENSITY.

    PubMed

    Horowitz, Y S; Eliyahu, I; Oster, L

    2016-12-01

    The reader will time-travel through almost seven decades of kinetic models and mathematical simulations of thermoluminescence (TL) characteristics based on the band-gap theory of the solid state. From post-World-War II, ideas concerning electron trapping mechanisms to the highly idealised one trap-one recombination (OTOR) model first elaborated in 1956 but still in 'high gear' today. The review caresses but purposely avoids in-depth discussion of the endless stream of papers discussing the intricacies of glow peak shapes arising from first-order, second-order, mixed-order and general-order kinetics predominantly based on non-interacting systems, and then on to the more physically realistic scenarios that have attempted to analyse complex systems involving ever greater numbers of interacting trapping centres, luminescent centres and non-luminescent centres. The review emphasises the difficulty the band-gap models have in the simulation of dose response linear/supralinear behaviour and especially the dependence of the supralinearity on ionisation density. The significance of the non-observation of filling-rate supralinearity in the absorption stage is emphasised since it removes from consideration the possibility of TL supralinearity arising from irradiation stage supralinearity. The importance of the simultaneous action of both localised and delocalised transitions has gradually penetrated the mindset of the community of kinetic researchers, but most simulations have concentrated on the shape of glow peaks and the extraction of the glow peak parameters, E (the thermal activation energy) and s (the attempt-to-escape frequency). The simulation of linear/supralinear dose response and its dependence on ionisation density have been largely avoided until recently due to the fundamental schism between the effects of ionisation density and some basic assumptions of the band-gap model. The review finishes with an in-depth presentation and discussion of the most recent

  17. Olestra dose response on fat-soluble and water-soluble nutrients in humans.

    PubMed

    Schlagheck, T G; Riccardi, K A; Zorich, N L; Torri, S A; Dugan, L D; Peters, J C

    1997-08-01

    Ninety normal healthy adults were given 0, 8, 20 or 32 g/d olestra for 8 wk as part of a diet that provided 1 +/- 0.2 of the recommended dietary allowance (RDA) of vitamins A, D, E and K, folate zinc, calcium and iron. In addition, a 20 microg/d supplement of vitamin D was supplied. The diet provided 15% of energy from protein, 35% from fat and 55% from carbohydrate. The purpose of the study was to determine the dose response of olestra on vitamins D, E and K, carotenoids, vitamin B12, folate and zinc. Circulating concentrations of retinol, carotenoids, tocopherols, 25-hydroxy- and 1,25-dihydroxyvitamin D metabolites, phylloquinone, des-gamma-carboxyprothrombin, prothrombin, folate and hematological parameters were measured biweekly, as were urine concentrations of zinc and gamma-carboxyglutamic acid (Gla). Clinical chemistry, urinalysis and vitamin B12 absorption were measured at wk 0 and 8. Olestra reduced serum concentrations of carotenoids, alpha-tocopherol, 25-hydroxyergocalciferol and phylloquinone in a dose-responsive manner. Olestra did not affect Gla excretion, plasma des-gamma-carboxyprothrombin or prothrombin concentrations, prothrombin time, vitamin B12 absorption, overall vitamin D status or the status of folate or zinc. Laboratory evaluations showed no health-related effects of olestra. Subjects in all groups reported common gastrointestinal symptoms such as loose stools, fecal urgency and flatulence, which were transient and generally mild to moderate in severity. These symptoms did not affect protocol compliance or the ability to measure the potential for olestra to affect nutrient availability.

  18. Application of Dempster-Shafer theory in dose response outcome analysis

    NASA Astrophysics Data System (ADS)

    Chen, Wenzhou; Cui, Yunfeng; He, Yanyan; Yu, Yan; Galvin, James; Hussaini, Yousuff M.; Xiao, Ying

    2012-09-01

    The Quantitative Analysis of Normal Tissue Effects in the Clinic (QUANTEC) reviews summarize the currently available three-dimensional dose/volume/outcome data from multi-institutions and numerous articles to update and refine the normal tissue dose/volume tolerance guidelines. As pointed out in the review, the data have limitations and even some inconsistency. However, with the help of new physical and statistical techniques, the information in the review could be updated so that patient care can be continually improved. The purpose of this work is to demonstrate the application of a mathematical theory, the Dempster-Shafer theory, in dose/volume/outcome data analysis. We applied this theory to the original data obtained from published clinical studies describing dose response for radiation pneumonitis. Belief and plausibility concepts were introduced for dose response evaluation. We were also able to consider the uncertainty and inconsistency of the data from these studies with Yager's combination rule, a special methodology of Dempster-Shafer theory, to fuse the data at several specific doses. The values of belief and plausibility functions were obtained at the corresponding doses. Then we applied the Lyman-Kutcher-Burman (LKB) model to fit these values and a belief-plausibility range was obtained. This range could be considered as a probability range to assist physicians and treatment planners in determining acceptable dose-volume constraints. Finally, the parameters obtained from the LKB model fitting were compared with those in Emami and Burman's papers and those from other frequentist statistics methods. We found that Emami and Burman's parameters are within the belief-plausibility range we calculated by the Dempster-Shafer theory.

  19. The energy dependence of the lateral dose response functions of detectors with various densities in photon-beam dosimetry

    NASA Astrophysics Data System (ADS)

    Khee Looe, Hui; Harder, Dietrich; Poppe, Björn

    2017-02-01

    The lateral dose response function is a general characteristic of the volume effect of a detector used for photon dosimetry in a water phantom. It serves as the convolution kernel transforming the true absorbed dose to water profile, which would be produced within the undisturbed water phantom, into the detector-measured signal profile. The shape of the lateral dose response function characterizes (i) the volume averaging attributable to the detector’s size and (ii) the disturbance of the secondary electron field associated with the deviation of the electron density of the detector material from the surrounding water. In previous work, the characteristic dependence of the shape of the lateral dose response function upon the electron density of the detector material was studied for 6 MV photons by Monte Carlo simulation of a wall-less voxel-sized detector (Looe et al 2015 Phys. Med. Biol. 60 6585-07). This study is here continued for 60Co gamma rays and 15 MV photons in comparison with 6 MV photons. It is found (1) that throughout these photon spectra the shapes of the lateral dose response functions are retaining their characteristic dependence on the detector’s electron density, and (2) that their energy-dependent changes are only moderate. This appears as a practical advantage because the lateral dose response function can then be treated as practically invariant across a clinical photon beam in spite of the known changes of the photon spectrum with increasing distance from the beam axis.

  20. Generation of dose-response relationships to assess the effects of acidity in precipitation on growth and productivity of vegetation

    SciTech Connect

    Evans, L.S.

    1981-01-01

    Experiments were performed with several plant species in natural environments as well in a greenhouse and/or tissue culture facilities to establish dose-response functions of plant responses to simulated acidic rain in order to determine environmental risk assessments to ambient levels of acidic rain. Response functions of foliar injury, biomass of leaves and seed of soybean and pinto beans, root yields of radishes and garden beets, and reproduction of bracken fern are considered. The dose-response function of soybean seed yields with the hydrogen ion concentration of simulated acidic rainfalls was expressed by the equation y = 21.06-1.01 log x where y = seed yield in grams per plant and x = the hydrogen concentration if ..mu..eq l/sup -1/. The correlation coefficient of this relationship was -0.90. A similar dose-response function was generated for percent fertilization of ferns in a forest understory. When percent fertilization is plotted on logarithmic scale with hydrogen ion concentration of the simulated rain solution, the Y intercept is 51.18, slope -0.041 with a correlation coefficient of -0.98. Other dose-response functions were generated that assist in a general knowledge as to which plant species and which physiological processes are most impacted by acidic precipitation. Some responses did not produce convenient dose-response relationships. In such cases the responses may be altered by other environmental factors or there may be no differences among treatment means.

  1. Biological stress response terminology: Integrating the concepts of adaptive response and preconditioning stress within a hormetic dose-response framework.

    PubMed

    Calabrese, Edward J; Bachmann, Kenneth A; Bailer, A John; Bolger, P Michael; Borak, Jonathan; Cai, Lu; Cedergreen, Nina; Cherian, M George; Chiueh, Chuang C; Clarkson, Thomas W; Cook, Ralph R; Diamond, David M; Doolittle, David J; Dorato, Michael A; Duke, Stephen O; Feinendegen, Ludwig; Gardner, Donald E; Hart, Ronald W; Hastings, Kenneth L; Hayes, A Wallace; Hoffmann, George R; Ives, John A; Jaworowski, Zbigniew; Johnson, Thomas E; Jonas, Wayne B; Kaminski, Norbert E; Keller, John G; Klaunig, James E; Knudsen, Thomas B; Kozumbo, Walter J; Lettieri, Teresa; Liu, Shu-Zheng; Maisseu, Andre; Maynard, Kenneth I; Masoro, Edward J; McClellan, Roger O; Mehendale, Harihara M; Mothersill, Carmel; Newlin, David B; Nigg, Herbert N; Oehme, Frederick W; Phalen, Robert F; Philbert, Martin A; Rattan, Suresh I S; Riviere, Jim E; Rodricks, Joseph; Sapolsky, Robert M; Scott, Bobby R; Seymour, Colin; Sinclair, David A; Smith-Sonneborn, Joan; Snow, Elizabeth T; Spear, Linda; Stevenson, Donald E; Thomas, Yolene; Tubiana, Maurice; Williams, Gary M; Mattson, Mark P

    2007-07-01

    Many biological subdisciplines that regularly assess dose-response relationships have identified an evolutionarily conserved process in which a low dose of a stressful stimulus activates an adaptive response that increases the resistance of the cell or organism to a moderate to severe level of stress. Due to a lack of frequent interaction among scientists in these many areas, there has emerged a broad range of terms that describe such dose-response relationships. This situation has become problematic because the different terms describe a family of similar biological responses (e.g., adaptive response, preconditioning, hormesis), adversely affecting interdisciplinary communication, and possibly even obscuring generalizable features and central biological concepts. With support from scientists in a broad range of disciplines, this article offers a set of recommendations we believe can achieve greater conceptual harmony in dose-response terminology, as well as better understanding and communication across the broad spectrum of biological disciplines.

  2. Dose-Response Relation between Work Hours and Cardiovascular Disease Risk: Findings from the Panel Study of Income Dynamics

    PubMed Central

    Conway, Sadie H.; Pompeii, Lisa A.; Roberts, Robert E.; Follis, Jack L.; Gimeno, David

    2015-01-01

    Objectives To examine the presence of a dose-response relationship between work hours and incident cardiovascular disease (CVD) in a representative sample of U.S. workers. Methods Retrospective cohort study of 1,926 individuals from the Panel Study of Income Dynamics (1986–2011) employed for at least 10 years. Restricted cubic spline regression was used to estimate the dose-response relationship of work hours with CVD. Results A dose-response relationship was observed in which an average workweek of 46 hours or more for at least 10 years was associated with increased risk of CVD. Compared to working 45 hours per week, working an additional 10 hours per week or more for at least 10 years increased CVD risk by at least 16%. Conclusions Working more than 45 work hours per week for at least 10 years may be an independent risk factor for CVD. PMID:26949870

  3. Drug development and hormesis: changing conceptual understanding of the dose response creates new challenges and opportunities for more effective drugs.

    PubMed

    Calabrese, Edward J; Staudenmayer, John W; Stanek, Edward J

    2006-01-01

    This review proposes that the emerging acceptance of the hormetic dose-response model in toxicology and pharmacology has the potential to significantly change important aspects of drug development. Two situations where the hormesis concept may affect drug development are considered: one in which low-dose stimulation may represent an adverse/unwanted effect (eg, stimulation of tumor cell proliferation by antitumor drugs), the other in which low-dose stimulation defines the therapeutic zone (ie, a beneficial or intended effect; eg, cognition enhancement in Alzheimer's disease treatment). Examples are used to demonstrate that the hormetic dose-response model has implications for the definition of an ideal candidate for a therapeutic agent, as well as implications for study designs needed to assess the quantitative features of the dose-response relationship.

  4. Coffee and tea consumption and risk of lung cancer: a dose-response analysis of observational studies.

    PubMed

    Wang, Yaopeng; Yu, Xuyi; Wu, Yili; Zhang, Dongfeng

    2012-11-01

    Results from the recent meta-analysis suggested a favorable effect of green tea consumption and risk of lung cancer, while no significant association was found between black tea consumption and risk of lung cancer. Besides, a significantly positive association was found between coffee consumption and risk of lung cancer. However, the relationship of green tea and coffee consumption is unclear. Thus the dose-response relationship was assessed by restricted cubic spline model and multivariate random-effect meta-regression. Results suggested that a linear dose-response relationship exists between coffee consumption and risk of lung cancer, while the dose-response relationship is nonlinear between green tea consumption and risk of lung cancer.

  5. Biological stress response terminology: Integrating the concepts of adaptive response and preconditioning stress within a hormetic dose-response framework

    SciTech Connect

    Calabrese, Edward J. . E-mail: edwardc@schoolph.umass.edu; Bachmann, Kenneth A.; Bailer, A. John; Bolger, P. Michael; Borak, Jonathan; Cai, Lu; Cedergreen, Nina; Cherian, M. George; Chiueh, Chuang C.; Clarkson, Thomas W.; Cook, Ralph R.; Diamond, David M.; Doolittle, David J.; Dorato, Michael A.; Duke, Stephen O.; Feinendegen, Ludwig; Gardner, Donald E.; Hart, Ronald W.; Hastings, Kenneth L.; Hayes, A. Wallace; Hoffmann, George R.; Ives, John A.; Jaworowski, Zbigniew; Johnson, Thomas E.; Jonas, Wayne B.; Kaminski, Norbert E.

    2007-07-01

    Many biological subdisciplines that regularly assess dose-response relationships have identified an evolutionarily conserved process in which a low dose of a stressful stimulus activates an adaptive response that increases the resistance of the cell or organism to a moderate to severe level of stress. Due to a lack of frequent interaction among scientists in these many areas, there has emerged a broad range of terms that describe such dose-response relationships. This situation has become problematic because the different terms describe a family of similar biological responses (e.g., adaptive response, preconditioning, hormesis), adversely affecting interdisciplinary communication, and possibly even obscuring generalizable features and central biological concepts. With support from scientists in a broad range of disciplines, this article offers a set of recommendations we believe can achieve greater conceptual harmony in dose-response terminology, as well as better understanding and communication across the broad spectrum of biological disciplines.

  6. Complex, non-monotonic dose-response curves with multiple maxima: Do we (ever) sample densely enough?

    PubMed Central

    Cvrčková, Fatima; Luštinec, Jiří; Žárský, Viktor

    2015-01-01

    We usually expect the dose-response curves of biological responses to quantifiable stimuli to be simple, either monotonic or exhibiting a single maximum or minimum. Deviations are often viewed as experimental noise. However, detailed measurements in plant primary tissue cultures (stem pith explants of kale and tobacco) exposed to varying doses of sucrose, cytokinins (BA or kinetin) or auxins (IAA or NAA) revealed that growth and several biochemical parameters exhibit multiple reproducible, statistically significant maxima over a wide range of exogenous substance concentrations. This results in complex, non-monotonic dose-response curves, reminiscent of previous reports of analogous observations in both metazoan and plant systems responding to diverse pharmacological treatments. These findings suggest the existence of a hitherto neglected class of biological phenomena resulting in dose-response curves exhibiting periodic patterns of maxima and minima, whose causes remain so far uncharacterized, partly due to insufficient sampling frequency used in many studies. PMID:26336980

  7. Dose-responses from multi-model inference for the non-cancer disease mortality of atomic bomb survivors.

    PubMed

    Schöllnberger, H; Kaiser, J C; Jacob, P; Walsh, L

    2012-05-01

    The non-cancer mortality data for cerebrovascular disease (CVD) and cardiovascular diseases from Report 13 on the atomic bomb survivors published by the Radiation Effects Research Foundation were analysed to investigate the dose-response for the influence of radiation on these detrimental health effects. Various parametric and categorical models (such as linear-no-threshold (LNT) and a number of threshold and step models) were analysed with a statistical selection protocol that rated the model description of the data. Instead of applying the usual approach of identifying one preferred model for each data set, a set of plausible models was applied, and a sub-set of non-nested models was identified that all fitted the data about equally well. Subsequently, this sub-set of non-nested models was used to perform multi-model inference (MMI), an innovative method of mathematically combining different models to allow risk estimates to be based on several plausible dose-response models rather than just relying on a single model of choice. This procedure thereby produces more reliable risk estimates based on a more comprehensive appraisal of model uncertainties. For CVD, MMI yielded a weak dose-response (with a risk estimate of about one-third of the LNT model) below a step at 0.6 Gy and a stronger dose-response at higher doses. The calculated risk estimates are consistent with zero risk below this threshold-dose. For mortalities related to cardiovascular diseases, an LNT-type dose-response was found with risk estimates consistent with zero risk below 2.2 Gy based on 90% confidence intervals. The MMI approach described here resolves a dilemma in practical radiation protection when one is forced to select between models with profoundly different dose-responses for risk estimates.

  8. SU-E-J-51: Dose Response of Common Solid State Detectors in Homogeneous Transverse and Longitudinal Magnetic Fields

    SciTech Connect

    Reynolds, M; Fallone, B; Rathee, S

    2014-06-01

    Purpose: Solid state radiation detectors are often used for dose profiles and percent depth dose measurements. The dose response of selected solid state detectors is evaluated in varying transverse and longitudinal magnetic fields for eventual use in MR-Linac devices. Methods: A PTW 60003 and IBA PFD detector were modeled in the Monte Carlo code PENELOPE, incorporating a magnetic field which was varied in strength and oriented both transversely and longitudinally with respect to the incident photon beam. The detectors' long axis was in turn oriented either parallel or perpendicular to the photon beam. Dose to the active volume of each detector was scored, and its ratio to dose with zero magnetic field strength (dose response) was determined. Accuracy of the simulations was evaluated by measurements using both chambers taken at low field with a small electromagnet. Simulations were also performed in a water phantom to compare to the in air results. Results: Significant dose response was found in transverse field geometries, nearing 20% at 1.5T. The response is highly dependent on relative orientations to the magnetic field and photon beam, and on detector composition. Low field measurements confirm these results. In the presence of longitudinal magnetic fields, the detectors exhibit little dose response, reaching 0.5–1% at 1.5T regardless of detector orientation. Water tank simulations compared well to the in air simulations when not at the beam periphery, where in transverse magnetic fields only, the water tank simulations differed from the in air results. Conclusion: Transverse magnetic fields can cause large deviations in dose response, and are highly position orientation dependent. Comparatively, longitudinal magnetic fields exhibit little to no dose response in each detector as a function of magnetic field strength. Water tank simulations show longitudinal fields are generally easier to work with, but each detector must be evaluated separately.

  9. New data, strategies, and insights for Listeria monocytogenes dose-response models: summary of an interagency workshop, 2011.

    PubMed

    Hoelzer, K; Chen, Y; Dennis, S; Evans, P; Pouillot, R; Silk, B J; Walls, I

    2013-09-01

    Listeria monocytogenes is a leading cause of hospitalization, fetal loss, and death due to foodborne illnesses in the United States. A quantitative assessment of the relative risk of listeriosis associated with the consumption of 23 selected categories of ready-to-eat foods, published by the U.S. Department of Health and Human Services and the U.S. Department of Agriculture in 2003, has been instrumental in identifying the food products and practices that pose the greatest listeriosis risk and has guided the evaluation of potential intervention strategies. Dose-response models, which quantify the relationship between an exposure dose and the probability of adverse health outcomes, were essential components of the risk assessment. However, because of data gaps and limitations in the available data and modeling approaches, considerable uncertainty existed. Since publication of the risk assessment, new data have become available for modeling L. monocytogenes dose-response. At the same time, recent advances in the understanding of L. monocytogenes pathophysiology and strain diversity have warranted a critical reevaluation of the published dose-response models. To discuss strategies for modeling L. monocytogenes dose-response, the Interagency Risk Assessment Consortium (IRAC) and the Joint Institute for Food Safety and Applied Nutrition (JIFSAN) held a scientific workshop in 2011 (details available at http://foodrisk.org/irac/events/). The main findings of the workshop and the most current and relevant data identified during the workshop are summarized and presented in the context of L. monocytogenes dose-response. This article also discusses new insights on dose-response modeling for L. monocytogenes and research opportunities to meet future needs.

  10. Dose response and factors related to interstitial pneumonitis after bone marrow transplant

    SciTech Connect

    Sampath, Sagus; Schultheiss, Timothy E. . E-mail: schultheiss@coh.org; Wong, Jeffrey

    2005-11-01

    Purpose: Total body irradiation (TBI) and chemotherapy are common components of conditioning regimens for bone marrow transplantation. Interstitial pneumonitis (IP) is a known regimen-related complication. Using published data of IP in a multivariate logistic regression, this study sought to identify the parameters in the bone marrow transplantation conditioning regimen that were significantly associated with IP and to establish a radiation dose-response function. Methods and Materials: A retrospective review was conducted of articles that reported IP incidence along with lung dose, fractionation, dose rate, and chemotherapy regimen. In the final analysis, 20 articles (n = 1090 patients), consisting of 26 distinct TBI/chemotherapy regimens, were included in the analysis. Multivariate logistic regression was performed to determine dosimetric and chemotherapeutic factors that influenced the incidence of IP. Results: A logistic model was generated from patients receiving daily fractions of radiation. In this model, lung dose, cyclophosphamide dose, and the addition of busulfan were significantly associated with IP. An incidence of 3%-4% with chemotherapy-only conditioning regimens is estimated from the models. The {alpha}/{beta} value of the linear-quadratic model was estimated to be 2.8 Gy. The dose eliciting a 50% incidence, D {sub 50}, for IP after 120 mg/kg of cyclophosphamide was 8.8 Gy; in the absence of chemotherapy, the estimated D {sub 50} is 10.6 Gy. No dose rate effect was observed. The use of busulfan as a substitute for radiation is equivalent to treating with 14.8 Gy in 4 fractions with 50% transmission blocks shielding the lung. The logistic regression failed to find a model that adequately fit the multiple-fraction-per-day data. Conclusions: Dose responses for both lung radiation dose and cyclophosphamide dose were identified. A conditioning regimen of 12 Gy TBI in 6 daily fractions induces an IP incidence of about 11% in the absence of lung shielding

  11. Linearization of dose-response curve of the radiochromic film dosimetry system

    SciTech Connect

    Devic, Slobodan; Tomic, Nada; Aldelaijan, Saad; DeBlois, Francois; Seuntjens, Jan; Chan, Maria F.; Lewis, Dave

    2012-08-15

    Purpose: Despite numerous advantages of radiochromic film dosimeter (high spatial resolution, near tissue equivalence, low energy dependence) to measure a relative dose distribution with film, one needs to first measure an absolute dose (following previously established reference dosimetry protocol) and then convert measured absolute dose values into relative doses. In this work, we present result of our efforts to obtain a functional form that would linearize the inherently nonlinear dose-response curve of the radiochromic film dosimetry system. Methods: Functional form [{zeta}= (-1){center_dot}netOD{sup (2/3)}/ln(netOD)] was derived from calibration curves of various previously established radiochromic film dosimetry systems. In order to test the invariance of the proposed functional form with respect to the film model used we tested it with three different GAFCHROMIC Trade-Mark-Sign film models (EBT, EBT2, and EBT3) irradiated to various doses and scanned on a same scanner. For one of the film models (EBT2), we tested the invariance of the functional form to the scanner model used by scanning irradiated film pieces with three different flatbed scanner models (Epson V700, 1680, and 10000XL). To test our hypothesis that the proposed functional argument linearizes the response of the radiochromic film dosimetry system, verification tests have been performed in clinical applications: percent depth dose measurements, IMRT quality assurance (QA), and brachytherapy QA. Results: Obtained R{sup 2} values indicate that the choice of the functional form of the new argument appropriately linearizes the dose response of the radiochromic film dosimetry system we used. The linear behavior was insensitive to both film model and flatbed scanner model used. Measured PDD values using the green channel response of the GAFCHROMIC Trade-Mark-Sign EBT3 film model are well within {+-}2% window of the local relative dose value when compared to the tabulated Cobalt-60 data. It was also

  12. Habitual Chocolate Consumption May Increase Body Weight in a Dose-Response Manner

    PubMed Central

    Greenberg, James A.; Buijsse, Brian

    2013-01-01

    Objective Habitual chocolate intake was recently found to be associated with lower body weight in three cross-sectional epidemiological studies. Our objective was to assess whether these cross-sectional results hold up in a more rigorous prospective analysis. Methods We used data from the Atherosclerosis Risk in Communities cohort. Usual dietary intake was assessed by questionnaire at baseline (1987–98), and after six years. Participants reported usual chocolate intake as the frequency of eating a 1-oz (∼28 g) serving. Body weight and height were measured at the two visits. Missing data were replaced by multiple imputation. Linear mixed-effects models were used to evaluate cross-sectional and prospective associations between chocolate intake and adiposity. Results Data were from 15,732 and 12,830 participants at the first and second visit, respectively. More frequent chocolate consumption was associated with a significantly greater prospective weight gain over time, in a dose-response manner. For instance, compared to participants who ate a chocolate serving less often than monthly, those who ate it 1–4 times a month and at least weekly experienced an increase in Body Mass Index (kg/m2) of 0.26 (95% CI 0.08, 0.44) and 0.39 (0.23, 0.55), respectively, during the six-year study period. In cross-sectional analyses the frequency of chocolate consumption was inversely associated with body weight. This inverse association was attenuated after excluding participants with preexisting obesity-related illness. Compared to participants without such illness, those with it had higher BMI and reported less frequent chocolate intake, lower caloric intake, and diets richer in fruits and vegetables. They tended to make these dietary changes after becoming ill. Conclusions Our prospective analysis found that a chocolate habit was associated with long-term weight gain, in a dose-response manner. Our cross-sectional finding that chocolate intake was associated with lower body

  13. Leisure Time Physical Activity and Mortality: A Detailed Pooled Analysis of the Dose-Response Relationship

    PubMed Central

    Arem, Hannah; Moore, Steven C.; Patel, Alpa; Hartge, Patricia; de Gonzalez, Amy Berrington; Visvanathan, Kala; Campbell, Peter T.; Freedman, Michal; Weiderpass, Elisabete; Adami, Hans Olov; Linet, Martha S.; Lee, I-Min; Matthews, Charles E.

    2015-01-01

    Importance The 2008 Physical Activity Guidelines for Americans recommended a minimum of 75 vigorous-intensity or 150 moderate-intensity minutes per week (7.5 metabolic equivalent hours per week (MET h/wk)) of aerobic activity for “substantial” health benefit, and suggested “additional” benefits by doing more than double this amount. However, the upper limit of longevity benefit or possible harm with more physical activity is unclear. Objective To quantify the dose-response association between leisure-time physical activity and mortality, and to define the upper limit of benefit or harm associated with more physical activity. Design We pooled data from six studies in the NCI Cohort Consortium (baseline 1992–2003). We used Cox proportional hazards regression with cohort stratification to generate multivariable-adjusted hazard ratios (HR) and 95% confidence intervals (CI). Median follow-up time was 14.2 years. Setting Population-based prospective cohorts in the U.S. and Europe with self-reported physical activity. Participants 661,137 men and women (116,686 deaths); median age 62 (range 21–98) years. Exposure Leisure-time moderate- to vigorous-intensity physical activity Main Outcome Mortality Results Compared to those reporting no leisure-time physical activity, we observed a 20% lower mortality risk among those performing less than the recommended 7.5 MET h/wk minimum (HR=0.80, 95% CI 0.78–0.82), a 31% lower risk at 1–2 times the recommended minimum (0.69, 0.67–0.70), and a 37% lower risk at 2–3 times the minimum (0.63, 0.62–0.65). An upper threshold for mortality benefit occurred at 3–5 times the physical activity recommendation (0.61, 0.59–0.62), but compared to the recommended minimum, the additional benefit was modest (31% vs. 39%). There was no evidence of harm at 10+ times the recommended minimum (0.68, 0.59–0.78). A similar dose-response was observed for mortality due to cardiovascular disease and to cancer. Conclusions and

  14. Influence of image slice thickness on rectal dose-response relationships following radiotherapy of prostate cancer

    NASA Astrophysics Data System (ADS)

    Olsson, C.; Thor, M.; Liu, M.; Moissenko, V.; Petersen, S. E.; Høyer, M.; Apte, A.; Deasy, J. O.

    2014-07-01

    When pooling retrospective data from different cohorts, slice thicknesses of acquired computed tomography (CT) images used for treatment planning may vary between cohorts. It is, however, not known if varying slice thickness influences derived dose-response relationships. We investigated this for rectal bleeding using dose-volume histograms (DVHs) of the rectum and rectal wall for dose distributions superimposed on images with varying CT slice thicknesses. We used dose and endpoint data from two prostate cancer cohorts treated with three-dimensional conformal radiotherapy to either 74 Gy (N = 159) or 78 Gy (N = 159) at 2 Gy per fraction. The rectum was defined as the whole organ with content, and the morbidity cut-off was Grade ≥2 late rectal bleeding. Rectal walls were defined as 3 mm inner margins added to the rectum. DVHs for simulated slice thicknesses from 3 to 13 mm were compared to DVHs for the originally acquired slice thicknesses at 3 and 5 mm. Volumes, mean, and maximum doses were assessed from the DVHs, and generalized equivalent uniform dose (gEUD) values were calculated. For each organ and each of the simulated slice thicknesses, we performed predictive modeling of late rectal bleeding using the Lyman-Kutcher-Burman (LKB) model. For the most coarse slice thickness, rectal volumes increased (≤18%), whereas maximum and mean doses decreased (≤0.8 and ≤4.2 Gy, respectively). For all a values, the gEUD for the simulated DVHs were ≤1.9 Gy different than the gEUD for the original DVHs. The best-fitting LKB model parameter values with 95% CIs were consistent between all DVHs. In conclusion, we found that the investigated slice thickness variations had minimal impact on rectal dose-response estimations. From the perspective of predictive modeling, our results suggest that variations within 10 mm in slice thickness between cohorts are unlikely to be a limiting factor when pooling multi-institutional rectal dose data that include slice thickness

  15. Nano-silver induces dose-response effects on the nematode Caenorhabditis elegans.

    PubMed

    Ellegaard-Jensen, Lea; Jensen, Keld Alstrup; Johansen, Anders

    2012-06-01

    Toxicity of nano-formulated silver to eukaryotes was assessed by exposing nematodes (Caenorhabditis elegans) to two types of silver nanoparticles (AgNPs): with average primary particle diameters of 1 nm (AgNP1) and 28nm (AgNP28, PVP coated), respectively. Tests were performed with and without presence of Escherichia coli to evaluate how the presence of a food bacterium affects the AgNP toxicity. A pre-exposure experiment was also conducted with nematodes pre-exposed to 0 and 1mgAgNPL(-1), respectively, for 20 h prior to exposure at higher concentrations of AgNP. Both AgNP1 and AgNP28 showed adverse dose-response effects and mortality on C. elegans. LC(50) for AgNP28 was lower than for AgNP1 and, hence, at the present test conditions the PVP-coated AgNP28 was more toxic than AgNP1. Including E. coli in the test medium as a food source increased AgNPs toxicity towards nematodes compared to when bacteria were not present. Pre-exposure to a low-level AgNP1 concentration made the nematodes slightly more sensitive to further exposure at higher concentrations compared to no pre-exposure, indicating that nematodes have no efficient physiological ability to counteract nano-silver toxicity by acclimation. The amount of dissolved Ag(+) was 0.18 to 0.21 mg L(-1) after 20 h at the highest AgNP1 (10 mg L(-1)) and AgNP28 (3 mg L(-1)) doses in the exposure medium, respectively. The upper limit of Ag(+) solubility cannot immediately explain the dose-response-related toxic effects of the AgNP nor the difference between AgNP1 and AgNP28. Higher toxicity of AgNP28 than AgNP1 may be explained by a combination of effects of coating, Ag-solubility and higher uptake rates due to agglomeration into μm-size agglomerates in the exposure medium.

  16. Prenatal intravenous cocaine and the heart rate-orienting response: a dose-response study.

    PubMed

    Foltz, Tara L; Snow, Diane M; Strupp, Barbara J; Booze, Rosemarie M; Mactutus, Charles F

    2004-01-01

    Attentional dysfunction is a persistent behavioral abnormality that is emerging as one of the cardinal features in the investigations of the teratogenic effects of cocaine in humans and rodents. The present study sought to extend this work by using a dose-response design with an alternate strain of rat. Virgin Long-Evans female rats, implanted with an IV access port prior to breeding were administered saline, 0.5, 1.0, or 3.0 mg/kg of cocaine HCl from gestational day (GD) GD8-21 (1x per day-GD8-14, 2x per day-GD15-21). Cocaine had no significant effect on maternal or litter parameters. At 14-15 days of age, 1 male and 1 female from each litter were tested to evaluate the heart rate orienting response (HR-OR). Following 20 min for acclimation, pups were presented an olfactory stimulus for 20s per trial, across four trials, and with an intertrial interval of 2 min. The initial baseline HR was not significantly different across the treatment groups, although cocaine did alter the stability of the QRS complex duration. The magnitude of the HR-OR averaged across trials increased as a linear function of dosage of cocaine. A more complex (quadratic) interaction between cocaine dose and sex of the offspring was also noted. When examined across trials, the controls failed to display any significant within-session variation in the HR-OR; in contrast all of the prenatal cocaine treated groups displayed either sensitization (low and high dose) or habituation of the response (middle dose). Analysis of the peak HR-OR confirmed that the controls were indeed displaying the response on at least one trial of the session, albeit not consistently on any specific trial. The more vigorous HR-OR of the prenatal cocaine groups, relative to vehicle controls, most likely reflects an alteration in development of the neural basis of response; as previously shown, the most vigorous response to the olfactory stimulus is seen early (12 days of age) and progressively decreases across the

  17. Transmission and dose-response experiments for social animals: a reappraisal of the colonization biology of Campylobacter jejuni in chickens.

    PubMed

    Conlan, Andrew J K; Line, John E; Hiett, Kelli; Coward, Chris; Van Diemen, Pauline M; Stevens, Mark P; Jones, Michael A; Gog, Julia R; Maskell, Duncan J

    2011-12-07

    Dose-response experiments characterize the relationship between infectious agents and their hosts. These experiments are routinely used to estimate the minimum effective infectious dose for an infectious agent, which is most commonly characterized by the dose at which 50 per cent of challenged hosts become infected-the ID(50). In turn, the ID(50) is often used to compare between different agents and quantify the effect of treatment regimes. The statistical analysis of dose-response data typically makes the assumption that hosts within a given dose group are independent. For social animals, in particular avian species, hosts are routinely housed together in groups during experimental studies. For experiments with non-infectious agents, this poses no practical or theoretical problems. However, transmission of infectious agents between co-housed animals will modify the observed dose-response relationship with implications for the estimation of the ID(50) and the comparison between different agents and treatments. We derive a simple correction to the likelihood for standard dose-response models that allows us to estimate dose-response and transmission parameters simultaneously. We use this model to show that: transmission between co-housed animals reduces the apparent value of the ID(50) and increases the variability between replicates leading to a distinctive all-or-nothing response; in terms of the total number of animals used, individual housing is always the most efficient experimental design for ascertaining dose-response relationships; estimates of transmission from previously published experimental data for Campylobacter spp. in chickens suggest that considerable transmission occurred, greatly increasing the uncertainty in the estimates of dose-response parameters reported in the literature. Furthermore, we demonstrate that accounting for transmission in the analysis of dose-response data for Campylobacter spp. challenges our current understanding of the

  18. Dose-Response Effect of Sunlight on Vitamin D2 Production in Agaricus bisporus Mushrooms.

    PubMed

    Urbain, Paul; Jakobsen, Jette

    2015-09-23

    The dose response effect of UV-B irradiation from sunlight on vitamin D2 content of sliced Agaricus bisporus (white button mushroom) during the process of sun-drying was investigated.Real-time UV-B and UV-A data were obtained using a high-performance spectroradiometer. During the first hour of sunlight exposure, the vitamin D2 content of the mushrooms increased in a linear manner, with concentrations increasing from 0.1 μg/g up to 3.9 ± 0.8 μg/g dry weight (DW). At the subsequent two measurements one and 3 h later, respectively, a plateau was reached. Two hours of additional exposure triggered a significant decline in vitamin D2 content. After just 15 min of sun exposure and an UV-B dose of 0.13 J/cm(2), the vitamin D2 content increased significantly to 2.2 ± 0.5 μg/g DW (P < 0.0001), which is equivalent to 17.6 μg (704 IU) vitamin D2 per 100 g of fresh mushrooms and comparable to levels found in fatty fish like the Atlantic salmon.

  19. Dose Response in Rodents and Nonhuman Primates After Hydrodynamic Limb Vein Delivery of Naked Plasmid DNA

    PubMed Central

    Hegge, Julia O.; Zhang, Guofeng; Sebestyén, Magdolna G.; Noble, Mark; Griffin, Jacob B.; Pfannes, Loretta V.; Herweijer, Hans; Hagstrom, James E.; Braun, Serge; Huss, Thierry; Wolff, Jon A.

    2011-01-01

    Abstract The efficacy of gene therapy mediated by plasmid DNA (pDNA) depends on the selection of suitable vectors and doses. Using hydrodynamic limb vein (HLV) injection to deliver naked pDNA to skeletal muscles of the limbs, we evaluated key parameters that affect expression in muscle from genes encoded in pDNA. Short-term and long-term promoter comparisons demonstrated that kinetics of expression differed between cytomegalovirus (CMV), muscle creatine kinase, and desmin promoters, but all gave stable expression from 2 to 49 weeks after delivery to mouse muscle. Expression from the CMV promoter was highest. For mice, rats, and rhesus monkeys, the linear range for pDNA dose response could be defined by the mass of pDNA relative to the mass of target muscle. Correlation between pDNA dose and expression was linear between a threshold dose of 75 μg/g and maximal expression at approximately 400 μg/g. One HLV injection into rats of a dose of CMV-LacZ yielding maximal expression resulted in an average transfection of 28% of all hind leg muscle and 40% of the gastrocnemius and soleus. Despite an immune reaction to the reporter gene in monkeys, a single injection transfected an average of 10% of all myofibers in the targeted muscle of the arms and legs and an average of 15% of myofibers in the gastrocnemius and soleus. PMID:21338336

  20. Standard error of inverse prediction for dose-response relationship: approximate and exact statistical inference.

    PubMed

    Demidenko, Eugene; Williams, Benjamin B; Flood, Ann Barry; Swartz, Harold M

    2013-05-30

    This paper develops a new metric, the standard error of inverse prediction (SEIP), for a dose-response relationship (calibration curve) when dose is estimated from response via inverse regression. SEIP can be viewed as a generalization of the coefficient of variation to regression problem when x is predicted using y-value. We employ nonstandard statistical methods to treat the inverse prediction, which has an infinite mean and variance due to the presence of a normally distributed variable in the denominator. We develop confidence intervals and hypothesis testing for SEIP on the basis of the normal approximation and using the exact statistical inference based on the noncentral t-distribution. We derive the power functions for both approaches and test them via statistical simulations. The theoretical SEIP, as the ratio of the regression standard error to the slope, is viewed as reciprocal of the signal-to-noise ratio, a popular measure of signal processing. The SEIP, as a figure of merit for inverse prediction, can be used for comparison of calibration curves with different dependent variables and slopes. We illustrate our theory with electron paramagnetic resonance tooth dosimetry for a rapid estimation of the radiation dose received in the event of nuclear terrorism.

  1. Dose-response modeling in mental health using stein-like estimators with instrumental variables.

    PubMed

    Ginestet, Cedric E; Emsley, Richard; Landau, Sabine

    2017-02-21

    A mental health trial is analyzed using a dose-response model, in which the number of sessions attended by the patients is deemed indicative of the dose of psychotherapeutic treatment. Here, the parameter of interest is the difference in causal treatment effects between the subpopulations that take part in different numbers of therapy sessions. For this data set, interactions between random treatment allocation and prognostic baseline variables provide the requisite instrumental variables. While the corresponding two-stage least squares (TSLS) estimator tends to have smaller bias than the ordinary least squares (OLS) estimator; the TSLS suffers from larger variance. It is therefore appealing to combine the desirable properties of the OLS and TSLS estimators. Such a trade-off is achieved through an affine combination of these two estimators, using mean squared error as a criterion. This produces the semi-parametric Stein-like (SPSL) estimator as introduced by Judge and Mittelhammer (2004). The SPSL estimator is used in conjunction with multiple imputation with chained equations, to provide an estimator that can exploit all available information. Simulated data are also generated to illustrate the superiority of the SPSL estimator over its OLS and TSLS counterparts. A package entitled SteinIV implementing these methods has been made available through the R platform. © 2017 The Authors. Statistics in Medicine Published by John Wiley & Sons Ltd.

  2. Tests of the linear, no-threshold dose-response relationship for high-LET radiation

    SciTech Connect

    Cohen, B.L.

    1987-05-01

    It is pointed out that induction of lung cancer by exposure to Rn daughters, applied at high doses to miners and at low doses to exposures in homes, provides a very stringent and sensitive test of the linear, no-threshold dose-response relationship for high-LET radiation, because this relationship predicts that a substantial fraction of lung cancer among non-smokers is due to average Rn levels. Therefore, it predicts an easily observable elevation of lung cancer rates in areas where Rn levels are many times greater than the average, especially at times before cigarette smoking began to have important effects on lung cancer statistics. While more data are needed (and will be forthcoming), some of the early indications of these studies are reviewed here. Several cases are now known where average Rn levels are very high, and in all of these cases lung cancer rates are well below average. Methods for analyzing these data are discussed, and it is concluded that, based on current evidence, they indicate at least a factor of 4 disagreement with linear, no-threshold predictions.

  3. The risk of chronic myeloid leukemia: can the dose-response curve be U-shaped?

    PubMed

    Radivoyevitch, Tomas; Kozubek, Stanislav; Sachs, Rainer K

    2002-01-01

    Chronic myeloid leukemia (CML) is caused by a BCR-ABL chromosome translocation in a primitive hematopoietic stem cell. The number of hematopoietic stem cells in the body is thus a major factor in CML risk. Evidence suggests that the number of hematopoietic stem cells in the body is only loosely regulated, having a broad "dead-band" of physiologically acceptable values. The existence of a dead-band is important, because it would imply that low levels of hematopoietic stem cell killing can be permanent; i.e., it would imply that low doses of ionizing radiation can cause permanent reductions in the total number of CML target cells and thus permanent reductions in the subsequent risk of spontaneous CML. Such reductions in risk could be substantial if hematopoietic stem cells are also hypersensitive to radiation killing at low dose. Our calculations indicate that, due to dead-band hematopoietic stem cell control, if hematopoietic stem cells are as hypersensitive to killing at low doses as epithelial cells, reductions in the spontaneous CML risk could exceed the low-dose risks of induced CML; i.e., the net lifetime CML risk could have a U-shaped dose-response curve.

  4. [Dose-response curve in the study of the effects of exposure to crystalline silica].

    PubMed

    Di Lorenzo, L; Cassano, F

    2003-01-01

    The cumulative exposure to crystalline silica (SiO2) implies a linear relation between duration of exposure and SiO2 concentration, not always suitable to working situations of the last decades. A more correct definition of dose-response curve has currently to consider also different characteristics of SiO2, specifically: possible short-term increases in environmental SiO2 concentration, different mineralogical and surface properties of natural silica polymorphs, age of SiO2 particles, presence of contaminants on the surface of silica particles or even in the respirable fraction of total dust, respirable dust concentration in which SiO2 is diluted and other conditions, also affecting the host, able to slow alveolar clearance and lengthen permanence time of particles in the lung. Many models of definition of cumulative exposure so conceived have been proposed. However, to define the occupational risk threshold to contract silicosis and other silica-related diseases a number of models of cumulative exposure, i.e. biologically effective dose of SiO2, are likely to be delineated that take into account only factors specifically present in different occupational situations.

  5. The notion of hormesis and the dose-response theory: a unified approach.

    PubMed

    Murado, M A; Vázquez, J A

    2007-02-07

    According to an opinion which is vigorous and insistently defended for approximately one decade, hormesis (the response of a biological entity to an effector, with stimulatory results at low doses and inhibitory results at high doses) radically puts into question the classic theory of dose-response (DR) relationships and demands a profound revision of environmental protection policies. Herein we show that DR theory, with the modifications which we propose, allows the modelling of various kinds of biphasic responses which are phenomenologically similar to hormetic ones and of well-defined origin, as well as responses which have been treated as genuinely hormetic. Our descriptive approach may also represent a useful resource for experimental design, directed towards identifying some of the potentially heterogeneous mechanisms which underlie the hormetic phenomenon. Finally, it also allows to discuss some factors which prevent the use of the notion of hormesis-perhaps useful in a clinical context, under strictly controlled conditions-to make decisions on environmental protection measures.

  6. Dose response effect of Paracoccidioides brasiliensis in an experimental model of arthritis.

    PubMed

    Loth, Eduardo Alexandre; Biazim, Samia Khalil; Dos Santos, José Henrique Fermino Ferreira; Puccia, Rosana; Brancalhão, Rosimeire Costa; Chasco, Lucinéia de Fátima; Gandra, Rinaldo Ferreira; Simão, Rita de Cássia Garcia; de Franco, Marcello Fabiano

    2014-01-01

    Paracoccidioidomycosis (PCM) is caused by the dimorphic fungus Paracoccidioides brasiliensis (Pb) and corresponds to prevalent systemic mycosis in Latin America. The aim of the present work was to evaluate the dose response effect of the fungal yeast phase for the standardization of an experimental model of septic arthritis. The experiments were performed with groups of 14 rats that received doses of 103, 104 or 105 P. brasiliensis (Pb18) cells. The fungi were injected in 50 µL of phosphate-buffered saline (PBS) directly into the knee joints of the animals. The following parameters were analyzed in this work: the formation of swelling in knees infused with yeast cells and the radiological and anatomopathological alterations, besides antibody titer by ELISA. After 15 days of infection, signs of inflammation were evident. At 45 days, some features of damage and necrosis were observed in the articular cartilage. The systemic dissemination of the fungus was observed in 11% of the inoculated animals, and it was concluded that the experimental model is able to mimic articular PCM in humans and that the dose of 105 yeast cells can be used as standard in this model.

  7. Magnetization transfer proportion: a simplified measure of dose response for polymer gel dosimetry

    NASA Astrophysics Data System (ADS)

    Whitney, Heather M.; Gochberg, Daniel F.; Gore, John C.

    2008-12-01

    The response to radiation of polymer gel dosimeters has most often been described by measuring the nuclear magnetic resonance transverse relaxation rate as a function of dose. This approach is highly dependent upon the choice of experimental parameters, such as the echo spacing time for Carr-Purcell-Meiboom-Gill-type pulse sequences, and is difficult to optimize in imaging applications where a range of doses are applied to a single gel, as is typical for practical uses of polymer gel dosimetry. Moreover, errors in computing dose can arise when there are substantial variations in the radiofrequency (B1) field or resonant frequency, as may occur for large samples. Here we consider the advantages of using magnetization transfer imaging as an alternative approach and propose the use of a simplified quantity, the magnetization transfer proportion (MTP), to assess doses. This measure can be estimated through two simple acquisitions and is more robust in the presence of some sources of system imperfections. It also has a dependence upon experimental parameters that is independent of dose, allowing simultaneous optimization at all dose levels. The MTP is shown to be less susceptible to B1 errors than are CPMG measurements of R2. The dose response can be optimized through appropriate choices of the power and offset frequency of the pulses used in magnetization transfer imaging.

  8. Identifying ultrasensitive HGF dose-response functions in a 3D mammalian system for synthetic morphogenesis

    PubMed Central

    Senthivel, Vivek Raj; Sturrock, Marc; Piedrafita, Gabriel; Isalan, Mark

    2016-01-01

    Nonlinear responses to signals are widespread natural phenomena that affect various cellular processes. Nonlinearity can be a desirable characteristic for engineering living organisms because it can lead to more switch-like responses, similar to those underlying the wiring in electronics. Steeper functions are described as ultrasensitive, and can be applied in synthetic biology by using various techniques including receptor decoys, multiple co-operative binding sites, and sequential positive feedbacks. Here, we explore the inherent non-linearity of a biological signaling system to identify functions that can potentially be exploited using cell genome engineering. For this, we performed genome-wide transcription profiling to identify genes with ultrasensitive response functions to Hepatocyte Growth Factor (HGF). We identified 3,527 genes that react to increasing concentrations of HGF, in Madin-Darby canine kidney (MDCK) cells, grown as cysts in 3D collagen cell culture. By fitting a generic Hill function to the dose-responses of these genes we obtained a measure of the ultrasensitivity of HGF-responsive genes, identifying a subset with higher apparent Hill coefficients (e.g. MMP1, TIMP1, SNORD75, SNORD86 and ERRFI1). The regulatory regions of these genes are potential candidates for future engineering of synthetic mammalian gene circuits requiring nonlinear responses to HGF signalling. PMID:27982133

  9. Association between vitamin C intake and lung cancer: a dose-response meta-analysis

    PubMed Central

    Luo, Jie; Shen, Li; Zheng, Di

    2014-01-01

    Epidemiological studies evaluating the association between the intake of vitamin C and lung cancer risk have produced inconsistent results. We conducted a meta-analysis to assess the association between them. Pertinent studies were identified by a search of PubMed, Web of Knowledge and Wan Fang Med Online through December of 2013. Random-effect model was used to combine the data for analysis. Publication bias was estimated using Begg's funnel plot and Egger's regression asymmetry test. Eighteen articles reporting 21 studies involving 8938 lung cancer cases were included in this meta-analysis. Pooled results suggested that highest vitamin C intake level versus lowest level was significantly associated with the risk of lung cancer [summary relative risk (RR) = 0.829, 95%CI = 0.734–0.937, I2 = 57.8%], especially in the United States and in prospective studies. A linear dose-response relationship was found, with the risk of lung cancer decreasing by 7% for every 100 mg/day increase in the intake of vitamin C [summary RR = 0.93, 95%CI = 0.88–0.98]. No publication bias was found. Our analysis suggested that the higher intake of vitamin C might have a protective effect against lung cancer, especially in the United States, although this conclusion needs to be confirmed. PMID:25145261

  10. Aspergillus flavus dose-response curves to selected natural and synthetic antimicrobials.

    PubMed

    López-Malo, Aurelio; Alzamora, Stella M; Palou, Enrique

    2002-03-01

    The effects of selected concentrations of antimicrobials from natural (vanillin, thymol, eugenol, carvacrol or citral) or synthetic (potassium sorbate or sodium benzoate) origin on Aspergillus flavus lag time inoculated in laboratory media formulated at water activity (a(w)) 0.99 and pH 4.5 or 3.5, were evaluated. Time to detect a colony with a diameter > 0.5 mm was determined. Mold response was modeled using the Fermi function. Antimicrobial minimal inhibitory concentration (MIC) was defined as the minimal required inhibiting mold growth for 2 months. Fermi function successfully captured A. flavus dose-response curves to the tested antimicrobials with a highly satisfactory fit. Fermi equation coefficients, Pc and k, were used to compare antimicrobials and assess the effect of pH. Important differences in Pc and k were observed among antimicrobials, being natural antimicrobials less pH dependent than synthetic antimicrobials. A large Pc value represents a small antimicrobial effect on A. flavus lag time; thus, high concentrations are needed to delay growth. A. flavus exhibited higher sensitivity to thymol, eugenol, carvacrol, potassium sorbate (at pH 3.5), and sodium benzoate (at pH 3.5) than to vanillin or citral. MICs varied from 200 ppm of sodium bcnzoate at pH 3.5 to 1800 ppm of citral at both evaluated pHs.

  11. Cardiorespiratory dose-response relationship of isoflurane in Cinereous vulture (Aegypius monachus) during spontaneous ventilation

    PubMed Central

    SEOK, Seong-Hoon; JEONG, Dong-Hyuk; HONG, Il-Hwa; LEE, Hee-Chun; YEON, Seong-Chan

    2016-01-01

    Anesthesia is an inevitably important component of diagnosis and treatments examining the health condition of wild animals. Not only does anesthesia become an essential tool in minimizing stress of the patients and providing an opportunity to deliver accurate and safe procedures, but it also ensures the safety of the medical crew members. This study was conducted to investigate the dose-response cardiorespiratory effects of isoflurane during spontaneous ventilation in ten cinereous vultures. Each bird was administered isoflurane at initial concentration of 1.0, 1.5, 2.0, 2.5 and 3.0 and then an end-tidal isoflurane concentrations (ETiso) of 1.0% for an equilibration period of 15 min in the given order. At the end of the equilibration period, the direct blood pressure (BP), heart rate (HR), respiratory rate (RR) and end tidal CO2 partial pressure (PETCO2) were recorded, and blood gas analysis was performed. Increasing isoflurane concentrations during spontaneous ventilation led to dose-dependent increases in HR and PETCO2, with minimal changes in RR, decreased arterial BP and respiratory acidosis. Overall, isoflurane for anesthesia of spontaneously breathing cinereous vultures is a suitable choice for diagnostic or surgical procedures. PMID:27725351

  12. Dose-response curve slope helps predict therapeutic potency and breadth of HIV broadly neutralizing antibodies.

    PubMed

    Webb, Nicholas E; Montefiori, David C; Lee, Benhur

    2015-09-29

    A new generation of HIV broadly neutralizing antibodies (bnAbs) with remarkable potency, breadth and epitope diversity has rejuvenated interest in immunotherapeutic strategies. Potencies defined by in vitro IC50 and IC80 values (50 and 80% inhibitory concentrations) figure prominently into the selection of clinical candidates; however, much higher therapeutic levels will be required to reduce multiple logs of virus and impede escape. Here we predict bnAb potency at therapeutic levels by analysing dose-response curve slopes, and show that slope is independent of IC50/IC80 and specifically relates to bnAb epitope class. With few exceptions, CD4-binding site and V3-glycan bnAbs exhibit slopes >1, indicative of higher expected therapeutic effectiveness, whereas V2-glycan, gp41 membrane-proximal external region (MPER) and gp120-gp41 bnAbs exhibit less favourable slopes <1. Our results indicate that slope is one major predictor of both potency and breadth for bnAbs at clinically relevant concentrations, and may better coordinate the relationship between bnAb epitope structure and therapeutic expectations.

  13. Melatonin entrains free-running blind people according to a physiological dose-response curve.

    PubMed

    Lewy, Alfred J; Emens, Jonathan S; Lefler, Bryan J; Yuhas, Krista; Jackman, Angela R

    2005-01-01

    The specific circadian role proposed for endogenous melatonin production was based on a study of sighted people who took low pharmacological doses (500 microg) of this chemical signal for the "biological night": the magnitude and direction of the induced phase shifts were dependent on what time of day exogenous melatonin was administered and were described by a phase-response curve that turned out to be the opposite of that for light. We now report that lower (physiological) doses of up to 300 microg can entrain (synchronize) free-running circadian rhythms of 10 totally blind subjects that would otherwise drift later each day. The resulting log-linear dose-response curve in the physiological range adds support for a circadian function of endogenous melatonin in humans. Efficacy of exogenous doses in the physiological range are of clinical significance for totally blind people who will need to take melatonin daily over their entire lifetimes in order to remain entrained to the 24 h day. Left untreated, their free-running endocrine, metabolic, behavioral, and sleep/wake cycles can be almost as burdensome as not having vision.

  14. Dose response of dairy cows to ammonium salts of volatile fatty acids.

    PubMed

    Otterby, D E; Johnson, D G; Towns, R; Cook, R M; Erdman, R A; Van Horn, H H; Rogers, J A; Clark, W A

    1990-08-01

    In previous studies ammonium salts of a mixture of isobutyrate, 2-methylbutyrate, isovalerate, and valerate were fed in a corn silage, corn, corn gluten meal, and urea diet to Holstein cows throughout lactation to define the optimum level of ammonium salts of milk production. The objective of this work was to conduct another dose response study using other forage and protein sources and to determine the effects of decreasing VFA intakes as lactation advanced. The concentrate portion of the diet contained 0, .4, .8, 1.2, or 1.6% ammonium salts of VFA. The forage to concentrate ratio was 50:50, 60:40, and 70:30 for the first, middle, and last third of lactation, respectively. The study was conducted at four university locations using 191 Holstein cows. Feeds used included corn silage, alfalfa silage or hay, corn, soybean meal, minerals, and vitamins. Treatment x location interactions were significant for milk yield during early lactation. During mid- and late lactation, supplemental VFA (.8%) improved milk and protein yield. Milk composition was not greatly affected by feeding VFA. In mid-lactation, cows fed .8% ammonium salts of VFA ate more feed than did controls. Feed efficiencies were similar among groups throughout the experiment. Cows fed VFA tended to gain less BW during lactation than did controls. Health and reproduction were not different among groups.

  15. Parity and Cardiovascular Disease Mortality: a Dose-Response Meta-Analysis of Cohort Studies.

    PubMed

    Lv, Haichen; Wu, Hongyi; Yin, Jiasheng; Qian, Juying; Ge, Junbo

    2015-08-24

    Parity has been shown to inversely associate with cardiovascular disease (CVD) mortality, but the evidence of epidemiological studies is still controversial. Therefore, we quantitatively assessed the relationship between parity and CVD mortality by summarizing the evidence from prospective studies. We searched MEDLINE (PubMed), EMBASE and ISI Web of Science databases for relevant prospective studies of parity and CVD mortality through the end of March 2015. Fixed- or random-effects models were used to estimate summary relative risks (RRs) and 95% confidence intervals (CIs). Heterogeneity among studies was assessed using the I(2) statistics. All statistical tests were two-sided. Ten prospective studies were included with a total of 994,810 participants and 16,601 CVD events. A borderline significant inverse association was observed while comparing parity with nulliparous, with summarized RR = 0.79 (95% CI: 0.60-1.06; I(2) = 90.9%, P < 0.001). In dose-response analysis, we observed a significant nonlinear association between parity number and CVD mortality. The greatest risk reduction appeared when the parity number reached four. The findings of this meta-analysis suggests that ever parity is inversely related to CVD mortality. Furthermore, there is a statistically significant nonlinear inverse association between parity number and CVD mortality.

  16. Dose response of a new phytase on dry matter, calcium, and phosphorus digestibility in weaned piglets.

    PubMed

    Bento, M H L; Pedersen, C; Plumstead, P W; Salmon, L; Nyachoti, C M; Bikker, P

    2012-12-01

    The present study evaluated the dose response of Buttiauxella phytase on apparent total tract digestibility (ATTD) of DM, Ca, and P in weaned pigs at 2 locations. Experimental diets fed to weaned pigs were a positive control (PC), a negative control (NC), and NC supplemented with increasing levels of Buttiauxella phytase. In Trial A, ATTD of P was 57.2% for PC, 32.5% for NC, and 59.4, 62.0, 63.8, 66.0, and 67.3% for 250, 500, 750, 1000, and 2000 phytase units (FTU) added to NC, respectively. In Trial B, ATTD of P was 45.2% for PC, 28.4% for NC, and 58.7, 64.1, 67.9, and 70.9% for 250, 500, 1000, and 2000 FTU added to NC, respectively. In both studies, the reduction in P in the NC diets reduced (P < 0.01) ATTD of P when compared with the PC diets. Phytase supplementation linearly and quadratically increased (P < 0.01) ATTD of P at all inclusion levels to the NC diet. In conclusion, the average digestible P increase from Buttiauxella phytase (vs. the NC diet) was 1.3, 1.5, 1.6, and 1.7 g digestible P/kg feed for 250, 500, 1000, and 2000 FTU/kg, respectively.

  17. Dose-Responsive Gene Expression Changes in Juvenile and Adult Mummichogs (Fundulus heteroclitus) After Arsenic Exposure

    PubMed Central

    Gonzalez, Horacio O.; Hu, Jianjun; Gaworecki, Kristen M.; Roling, Jonathan A.; Baldwin, William S.; Gardea-Torresdey, Jorge L.; Bain, Lisa J.

    2010-01-01

    The present study investigated arsenic's effects on mummichogs (Fundulus heteroclitus), while also examining what role that gender or exposure age might play. Adult male and female mummichogs were exposed to 172ppb, 575ppb, or 1,720ppb arsenic as sodium arsenite for 10 days immediately prior to spawning. No differences were noted in the number or viability of eggs between the groups, but there was a significant increase in deformities in 1,720ppb arsenic exposure group. Total RNA from adult livers or 6-week old juveniles was used to probe custom macroarrays for changes in gene expression. In females, 3% of the genes were commonly differentially expressed in the 172 and 575ppb exposure groups compared to controls. In the males, between 1.1-3% of the differentially expressed genes were in common between the exposure groups. Several genes, including apolipoprotein and serum amyloid precursor were commonly expressed in either a dose-responsive manner or were dose-specific, but consistent across genders. These patterns of regulation were confirmed by QPCR. These findings will provide us with a better understanding of the effects of dose, gender, and exposure age on the response to arsenic. PMID:20451245

  18. Meat, fish, and esophageal cancer risk: a systematic review and dose-response meta-analysis.

    PubMed

    Salehi, Maryam; Moradi-Lakeh, Maziar; Salehi, Mohhamad Hossein; Nojomi, Marziyeh; Kolahdooz, Fariba

    2013-05-01

    Risk factors for esophageal squamous cell carcinoma (ESCC) and esophageal adenocarcinoma (EAC) are well defined, while the role of diet in these conditions remains controversial. To help elucidate the role of particular dietary components, major bibliographic databases were searched for published studies (1990-2011) on associations between esophageal cancer risk (EC) and consumption of various types of meat and fish. Random-effects models and dose-response meta-analyses were used to pool study results. Subgroup analyses were conducted by histological subtype, study design, and nationality. Four cohorts and 31 case-control studies were identified. The overall pooled relative risk (RR) of EC and the confidence intervals (CIs) for the groups with the highest versus the lowest levels of intake were as follows: 0.99 (95% CI: 0.85-1.15) for total meat; 1.40 (95%CI: 1.09-1.81) for red meat; 1.41 (95%CI: 1.13-1.76) for processed meat; 0.87 (95%CI: 0.60-1.24) for poultry; and 0.80 (95%CI: 0.64-1.00) for fish. People with the highest levels of red meat intake had a significantly increased risk of ESCC. Processed meat intake was associated with increased risk of EAC. These results suggest that low levels of red and processed meat consumption and higher levels of fish intake might reduce EC risk.

  19. Results of animal studies suggest a nonlinear dose-response relationship for benzene effects

    SciTech Connect

    Parodi, S.; Taningher, M. ); Lutz, W.K. ); Colacci, A.; Mazzullo, M.; Grilli, S. )

    1989-07-01

    Considering the very large industrial usage of benzene, studies in risk assessment aimed at the evaluation of carcinogenic risk at low levels of exposure are important. Animal data can offer indications about what could happen in humans and provide more diverse information than epidemiological data with respect to dose-response consideration. The authors have considered experiments investigating metabolism, short-term genotoxicity tests, DNA adduct formation, and carcinogenicity long-term tests. According to the different experiments, a saturation of benzene metabolism and benzene effects in terms of genotoxicity seems evident above 30 to 100 ppm. Below 30 to 60 ppm the initiating effect of benzene seems to be linear for a large interval of dosages, at least judging from DNA adduct formation. Potential lack of a promoting effect of benzene (below 10 ppm) could generate a sublinear response at nontoxic levels of exposure. This possibility was suggested by epidemiological data in humans and is not confirmed or excluded by their observations with animals.

  20. A Dose-Response Study of Arsenic Exposure and Markers of Oxidative Damage in Bangladesh

    PubMed Central

    Harper, Kristin N.; Liu, Xinhua; Hall, Megan N.; Ilievski, Vesna; Oka, Julie; Calancie, Larissa; Slavkovich, Vesna; Levy, Diane; Siddique, Abu; Alam, Shafiul; Mey, Jacob L.; van Geen, Alexander; Graziano, Joseph H.; Gamble, Mary V.

    2014-01-01

    Objective To evaluate the dose-response relationship between arsenic exposure and markers of oxidative damage in Bangladeshi adults. Methods We recruited 378 participants drinking from wells assigned to five water arsenic exposure categories; the distribution of subjects was as follows: 1) <10 μg/L (n=76); 2) 10–100 μg/L (n=104); 3) 101–200 μg/L (n=86); 4) 201–300 μg/L (n=67); and 5) > 300 μg/L (n=45). Arsenic concentrations were measured in well water, as well as in urine and blood. Urinary 8-oxo-2’-deoxyguanosine (8-oxo-dG) and plasma protein carbonyls were measured to assess oxidative damage. Results None of our measures of arsenic exposure were significantly associated with protein carbonyl or 8-oxo-dG levels. Conclusions We found no evidence to support a significant relationship between chronic exposure to arsenic-contaminated drinking water and biomarkers of oxidative damage among Bangladeshi adults. PMID:24854259

  1. Western red cedar dust exposure and lung function: a dose-response relationship.

    PubMed

    Noertjojo, H K; Dimich-Ward, H; Peelen, S; Dittrick, M; Kennedy, S M; Chan-Yeung, M

    1996-10-01

    The relationship between levels of cumulative red cedar dust exposure and decline in lung function was explored in an 11-yr follow-up study of 243 sawmill workers who participated in at least two occasions. We also studied 140 office workers in a similar manner as control subjects. Workers with asthma were excluded from the analysis. During the period of the study, 916 personal and 216 area samples of dust were collected from the sawmill. Cumulative wood dust exposure was calculated for each sawmill worker according to the duration and exposure in each job, based on the geometric mean of all dust measurements for that job. Average daily dust exposure was calculated by dividing the total cumulative exposure by the number of days of work. Workers were divided into low-, medium-, and high-exposure groups with mean daily level of exposure of < 0.2, 0.2 to 0.4, and > 0.4 mg/m3, respectively. Sawmill workers had significantly greater declines in FEV1 and FVC compared with office workers adjusted for age, smoking, and initial lung function. A dose-response relationship was observed between the level of exposure and the annual decline in FVC. We conclude that exposure to Western red cedar dust is associated with a greater decline in lung function which may lead to development of chronic airflow limitation.

  2. Estimation and uncertainty analysis of dose response in an inter-laboratory experiment

    NASA Astrophysics Data System (ADS)

    Toman, Blaza; Rösslein, Matthias; Elliott, John T.; Petersen, Elijah J.

    2016-02-01

    An inter-laboratory experiment for the evaluation of toxic effects of NH2-polystyrene nanoparticles on living human cancer cells was performed with five participating laboratories. Previously published results from nanocytoxicity assays are often contradictory, mostly due to challenges related to producing a reliable cytotoxicity assay protocol for use with nanomaterials. Specific challenges include reproducibility preparing nanoparticle dispersions, biological variability from testing living cell lines, and the potential for nano-related interference effects. In this experiment, such challenges were addressed by developing a detailed experimental protocol and using a specially designed 96-well plate layout which incorporated a range of control measurements to assess multiple factors such as nanomaterial interference, pipetting accuracy, cell seeding density, and instrument performance. Detailed data analysis of these control measurements showed that good control of the experiments was attained by all participants in most cases. The main measurement objective of the study was the estimation of a dose response relationship between concentration of the nanoparticles and metabolic activity of the living cells, under several experimental conditions. The dose curve estimation was achieved by imbedding a three parameter logistic curve in a three level Bayesian hierarchical model, accounting for uncertainty due to all known experimental conditions as well as between laboratory variability in a top-down manner. Computation was performed using Markov Chain Monte Carlo methods. The fit of the model was evaluated using Bayesian posterior predictive probabilities and found to be satisfactory.

  3. Linearization of EBT3 film dose response and virtual film dosimetry for SBRT quality assurance

    NASA Astrophysics Data System (ADS)

    Cai, M.; Archibald-Heeren, B.; Wang, Y.; Metcalfe, P.

    2017-01-01

    EBT3 film offers high spatial resolution and low energy dependence, making it a suitable choice for quality assurance where high dose gradients are present, such as the case for SBRT. This work presents a simple method to adjust scanner settings so that dose response becomes linear. This linearity eliminates the need to obtain a calibration curve and associated uncertainties in curve fitting. Relative dosimetry can be performed after dose normalization to a reference point. Linearity is also a more robust condition than calibration curve with respect to scanner warm-up conditions, resulting in reduced uncertainty in dose measurement. An in-house developed program reads the film scan and a 2D dose map then constructs both to virtual films using grayscale values. Film intensity value was normalized to dose at reference point. Relative dosimetry was performed by comparing the two resulting images. Patient specific quality assurance was conducted for two SBRT cases. In both plans more than 95% gamma function points passed the gamma criteria of 2%/3mm.

  4. Comparative haemodynamic dose response effects of propranolol and labetalol in coronary heart disease.

    PubMed Central

    Silke, B; Nelson, G I; Ahuja, R C; Taylor, S H

    1982-01-01

    The immediate haemodynamic dose response effects of beta blockade (propranolol: 2 to 16 mg) were compared with those of combined alpha beta blockade (labetalol: 10 to 80 mg) in a randomised study of 20 patients with stable angina pectoris. After control measurements, the circulatory changes induced by four logarithmically cumulative intravenous boluses of each drug in equivalent beta blocking doses were evaluated at rest, after which comparison of the effects of the maximum cumulative dose of each was undertaken during a four minute period of supine bicycle exercise. Propranolol, at rest, induced significant dose related reductions in heart rate and cardiac output, with reciprocal increases in the systemic vascular resistance and pulmonary artery occluded pressure; systemic arterial pressure was unchanged. Labetalol was followed by significant dose related decreases in systemic blood pressure and vascular resistance associated with a significant increase in cardiac output; heart rate and pulmonary artery occluded pressure were unchanged. The slope of the left ventricular pumping function curve relating output to filling pressure from rest to exercise was significantly depressed by propranolol but unchanged after labetalol. The less deleterious effects on left ventricular haemodynamic performance after alpha beta blockade in contrast to beta blockade alone in ischaemic heart disease may be attributable to the concomitant reduction in left ventricular afterload associated with the alpha blocking activity of labetalol. PMID:7126388

  5. Dual effects of phytoestrogens result in u-shaped dose-response curves.

    PubMed Central

    Almstrup, Kristian; Fernández, Mariana F; Petersen, Jørgen H; Olea, Nicolas; Skakkebaek, Niels E; Leffers, Henrik

    2002-01-01

    Endocrine disruptors can affect the endocrine system without directly interacting with receptors, for example, by interfering with the synthesis or metabolism of steroid hormones. The aromatase that converts testosterone to 17beta-estradiol is a possible target. In this paper we describe an assay that simultaneously detects aromatase inhibition and estrogenicity. The principle is similar to that of other MCF-7 estrogenicity assays, but with a fixed amount of testosterone added. The endogenous aromatase activity in MCF-7 cells converts some of the testosterone to 17beta-estradiol, which is assayed by quantifying differences in the expression level of the estrogen-induced pS2 mRNA. Potential aromatase inhibitors can be identified by a dose-dependent reduction in the pS2 mRNA expression level after exposure to testosterone and the test compound. Using this assay, we have investigated several compounds, including synthetic chemicals and phytoestrogens, for aromatase inhibition. The phytoestrogens, except genistein, were aromatase inhibitors at low concentrations (< 1 micro M) but estrogenic at higher concentrations (greater than or equal to 1 micro M), resulting in U-shaped dose-response curves. None of the tested synthetic chemicals were aromatase inhibitors. The low-dose aromatase inhibition distinguished phytoestrogens from other estrogenic compounds and may partly explain reports about antiestrogenic properties of phytoestrogens. Aromatase inhibition may play an important role in the protective effects of phytoestrogens against breast cancer. PMID:12153753

  6. Quantitative radiation dose-response relationships for normal tissues in man - I. Gustatory tissues response during photon and neutron radiotherapy

    SciTech Connect

    Mossman, K.L.

    1982-08-01

    Quantitative radiation dose-response curves for normal gustatory tissue in man were studied. Taste function, expressed as taste loss, was evaluated in 84 patients who were given either photon or neutron radiotherapy for tumors in the head and neck region. Patients were treated to average tumor doses of 6600 cGy (photon) or 2200 cGy intervals for photon patients and 320-cGy intervals for neutron patients during radiotherapy. The dose-response curves for photons and neutrons were analyzed by fitting a four-parameter logistic equation to the data. Photon and neutron curves differed principally in their relative position along the dose axis. Comparison of the dose-response curves were made by determination of RBE. At 320 cGy, the lowest neutron dose at which taste measurements were made, RBE = 5.7. If this RBE is correct, then the therapeutic gain factor may be equal to or less than 1, indicating no biological advantage in using neutrons over photons for this normal tissue. These studies suggest measurements of taste function and evaluation of dose-response relationships may also be useful in quantitatively evaluating the efficacy of chemical modifiers of radiation response such as hypoxic cell radiosensitizers and radioprotectors.

  7. Nonmonotonic dose response curves (NMDRCs) are common after Estrogen or Androgen signaling pathway disruption. Fact or Falderal? ###SETAC

    EPA Science Inventory

    The shape of the dose response curve in the low dose region has been debated since the late 1940s. The debate originally focused on linear no threshold (LNT) vs threshold responses in the low dose range for cancer and noncancer related effects. Recently, claims have arisen tha...

  8. NONMONOTONIC DOSE RESPONSE CURVES (NMDRCS) ARE COMMON AFTER ESTROGEN OR ANDROGEN SIGNALING PATHWAY DISRUPTION. FACT OR FALDERAL?

    EPA Science Inventory

    ABSTRACT BODY: The shape of the dose response curve in the low dose region has been debated since the 1940s, originally focusing on linear no threshold (LNT) versus threshold responses for cancer and noncancer effects. Recently, it has been claimed that endocrine disrupters (EDCs...

  9. An empirical approach to sufficient similarity in dose-responsiveness: Utilization of statistical distance as a similarity measure.

    EPA Science Inventory

    Using statistical equivalence testing logic and mixed model theory an approach has been developed, that extends the work of Stork et al (JABES,2008), to define sufficient similarity in dose-response for chemical mixtures containing the same chemicals with different ratios ...

  10. Empirical evaluation of sufficient similarity in dose-response for environmental risk assessment of a mixture of 11 pyrethroids.

    EPA Science Inventory

    Chemical mixtures in the environment are often the result of a dynamic process. When dose-response data are available on random samples throughout the process, equivalence testing can be used to determine whether the mixtures are sufficiently similar based on a pre-specified biol...

  11. Household physical activity and cancer risk: a systematic review and dose-response meta-analysis of epidemiological studies.

    PubMed

    Shi, Yun; Li, Tingting; Wang, Ying; Zhou, Lingling; Qin, Qin; Yin, Jieyun; Wei, Sheng; Liu, Li; Nie, Shaofa

    2015-10-07

    Controversial results of the association between household physical activity and cancer risk were reported among previous epidemiological studies. We conducted a meta-analysis to investigate the relationship of household physical activity and cancer risk quantitatively, especially in dose-response manner. PubMed, Embase, Web of science and the Cochrane Library were searched for cohort or case-control studies that examined the association between household physical activity and cancer risks. Random-effect models were conducted to estimate the summary relative risks (RRs), nonlinear or linear dose-response meta-analyses were performed to estimate the trend from the correlated log RR estimates across levels of household physical activity quantitatively. Totally, 30 studies including 41 comparisons met the inclusion criteria. Total cancer risks were reduced 16% among the people with highest household physical activity compared to those with lowest household physical activity (RR = 0.84, 95% CI = 0.76-0.93). The dose-response analyses indicated an inverse linear association between household physical activity and cancer risk. The relative risk was 0.98 (95% CI = 0.97-1.00) for per additional 10 MET-hours/week and it was 0.99 (95% CI = 0.98-0.99) for per 1 hour/week increase. These findings provide quantitative data supporting household physical activity is associated with decreased cancer risk in dose-response effect.

  12. Evaluation of iodide deficiency in the lactating rat and pup using a biologically based dose response (BBDR) Model***

    EPA Science Inventory

    A biologically-based dose response (BBDR) model for the hypothalamic-pituitary thyroid (HPT) axis in the lactating rat and nursing pup was developed to describe the perturbations caused by iodide deficiency on the 1-IPT axis. Model calibrations, carried out by adjusting key model...

  13. Modified Maxium Likelihood Estimation Method for Completely Separated and Quasi-Completely Separated Data for a Dose-Response Model

    DTIC Science & Technology

    2015-08-01

    MODIFIED MAXIMUM LIKELIHOOD ESTIMATION METHOD FOR COMPLETELY SEPARATED AND QUASI-COMPLETELY SEPARATED DATA...Likelihood Estimation Method for Completely Separated and Quasi-Completely Separated Data for a Dose-Response Model 5a. CONTRACT NUMBER 5b. GRANT...quasi-completely separated , the traditional maximum likelihood estimation (MLE) method generates infinite estimates. The bias-reduction (BR) method

  14. EFFECTS OF PRENATAL TESTOSTERONE PROPIONATE ON THE SEXUAL DEVELOPMENT OF MALE AND FEMALE RATS: A DOSE-RESPONSE STUDY

    EPA Science Inventory

    Effects of Prenatal Testosterone Propionate on the Sexual Development of Male and Female Rats: A Dose-Response Study
    Cynthia J. Wolf1,2, Andrew Hotchkiss3, Joseph S. Ostby1, Gerald A. LeBlanc2 and
    L. Earl Gray1,4, Jr.

    ABSTRACT
    Testosterone plays a major role in ...

  15. EFFECTS OF PRENATAL TESTOSTERONE PROPIONATE ON SEXUAL DEVELOPMENT OF MALE AND FEMALE RATS: A DOSE-RESPONSE STUDY

    EPA Science Inventory

    Effects of Prenatal Testosterone Propionate on Sexual Development of Male and Female Rats: A Dose-Response Study
    Cynthia Wolf1,2, Joe Ostby1*, Andrew Hotchkiss3, Gerald LeBlanc2, and L. Earl Gray, Jr.1
    1USEPA, NHEERL, Reproductive Toxicology Division, RTP, NC; 2Dept. of To...

  16. Construction and validation of a dose-response curve using the comet assay to determine human radiosensitivity to ionizing radiation.

    PubMed

    Güerci, A; Zúñiga, L; Marcos, R

    2011-01-01

    Individual radiosensitivity is an individual characteristic associated with an increased reaction to ionizing radiation. The purpose of our work is to establish a dose-response curve useful to classify individuals as radiosensitive or radioresistant. Thus, a dose-response curve was constructed by measuring in vitro responses to increasing doses (0 to 8 Gy) of gamma radiation in the comet assay. The obtained curve fit well with a linear equation in the range of 0 to 8 Gy. The overall dose-response curve was constructed for percent DNA in tail, as a measure of the genetic damage induced by irradiation. To probe the goodness of the constructed curve, a validation study was carried out with whole blood from two donors in a blind study. Results show that, for the two applied doses (2 and 6 Gy), the obtained values fit well inside the interval of confidence of the curve. In conclusion, our results demonstrate the usefulness of the comet assay in determining individual responses to defined doses of gamma radiation. The standard dose-response curve constructed may be used to detect individuals departing from reference values.

  17. Statistical methods for clinical verification of dose response parameters related to esophageal stricture and AVM obliteration from radiotherapy

    NASA Astrophysics Data System (ADS)

    Mavroidis, Panayiotis; Lind, Bengt K.; Theodorou, Kyriaki; Laurell, Göran; Fernberg, Jan-Olof; Lefkopoulos, Dimitrios; Kappas, Constantin; Brahme, Anders

    2004-08-01

    The purpose of this work is to provide some statistical methods for evaluating the predictive strength of radiobiological models and the validity of dose-response parameters for tumour control and normal tissue complications. This is accomplished by associating the expected complication rates, which are calculated using different models, with the clinical follow-up records. These methods are applied to 77 patients who received radiation treatment for head and neck cancer and 85 patients who were treated for arteriovenous malformation (AVM). The three-dimensional dose distribution delivered to esophagus and AVM nidus and the clinical follow-up results were available for each patient. Dose-response parameters derived by a maximum likelihood fitting were used as a reference to evaluate their compatibility with the examined treatment methodologies. The impact of the parameter uncertainties on the dose-response curves is demonstrated. The clinical utilization of the radiobiological parameters is illustrated. The radiobiological models (relative seriality and linear Poisson) and the reference parameters are validated to prove their suitability in reproducing the treatment outcome pattern of the patient material studied (through the probability of finding a worse fit, area under the ROC curve and khgr2 test). The analysis was carried out for the upper 5 cm of the esophagus (proximal esophagus) where all the strictures are formed, and the total volume of AVM. The estimated confidence intervals of the dose-response curves appear to have a significant supporting role on their clinical implementation and use.

  18. Dose-Response Analysis of RNA-Seq Profiles in Archival Formalin-fixed paraffin-embedded (FFPE) Samples

    EPA Science Inventory

    Formalin-fixed paraffin-embedded (FFPE) samples provide a vast untapped resource for chemical safety and translational science. To date, genomic profiling of FFPE samples has been limited by poor RNA quality and inconsistent results with limited utility in dose-response assessmen...

  19. Dose response effect of NutriTek on leukocyte functionality during a dexamethasone challenge in Holstein steer calves.

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The objective of this study was to determine the dose response effects of supplementing NutriTek® on leukocyte functionality and ex vivo cytokine production during a dexamethasone (DEX) challenge. Holstein steers (125.1±8.16kg; N=32) were assigned to treatments including 0, 20, 40, or 60g/head/d of ...

  20. Dose-Response Analysis of RNA-Seq Profiles in Archival Formalin-Fixed Paraffin-Embedded (FFPE) Samples.

    EPA Science Inventory

    Use of archival resources has been limited to date by inconsistent methods for genomic profiling of degraded RNA from formalin-fixed paraffin-embedded (FFPE) samples. RNA-sequencing offers a promising way to address this problem. Here we evaluated transcriptomic dose responses us...

  1. Evaluation of iodide deficiency in the lactating rat and pup using a biologically based dose-response model

    EPA Science Inventory

    A biologically-based dose response (BBDR) model for the hypothalamic-pituitary thyroid (BPT) axis in the lactating rat and nursing pup was developed to describe the perturbations caused by iodide deficiency on the HPT axis. Model calibrations, carried out by adjusting key model p...

  2. RESEARCH TOWARD THE DEVELOPMENT OF A BIOLOGICALLY BASED DOSE RESPONSE ASSESSMENT FOR INORGANIC ARSENIC CARCINOGENICITY: A PROGRESS REPORT

    EPA Science Inventory

    Cancer risk assessments for inorganic arsenic have been based on human epidemiological data, assuming a linear dose-response below the range of observation of tumors. Part of the reason for the continued use of the linear approach in arsenic risk assessments is the lack of an ad...

  3. Acute Effects of Classroom Exercise Breaks on Executive Function and Math Performance: A Dose-Response Study

    ERIC Educational Resources Information Center

    Howie, Erin K.; Schatz, Jeffrey; Pate, Russell R.

    2015-01-01

    Purpose: The purpose of this study was to determine the acute dose-response relationship of classroom exercise breaks with executive function and math performance in 9- to 12-year-old children by comparing 5-min, 10-min, or 20-min classroom exercise breaks to 10 min of sedentary classroom activity. Method: This study used a within-subjects…

  4. Dose response on the 110 °C thermoluminescence peak of un-heated, synthetic Merck quartz

    NASA Astrophysics Data System (ADS)

    Kaya Keleş, Şule; Meriç, Niyazi; Polymeris, George S.

    2016-07-01

    Studies on 110 °C TL peak have been carried out using natural quartz from different origins and synthetic quartz produced by different suppliers. The interest in quartz is due to its usage in dating and retrospective dosimetry as a main material; both synthetic and natural types of quartz yield the 110 °C TL peak in their glow curve. In most studies to understand the physical mechanism behind the TL system, synthetic quartz samples are used and there are many investigations about dose response, in both low and high radiation dose region. In these studies generally synthetic quartz samples produced by Sawyer Research Products are used and the studies showed that both heated and un-heated synthetic quartz samples have intense supra-linear responses. Supra-linearity was enhanced by applying a pre-irradiation while several models have been developed towards an explanation to these supra-linearity effects. In this study commercially available synthetic Merck quartz was used. Different combinations of optical filters were used to obtain dose response curves upto 266 Gy and the effect of pre-dose to these dose response curves was studied. Un-pre-dosed Merck quartz samples dose supra-linearity index is below 1 independently on the optical filters; so Merck quartz showed linear or sub-linear dose response.

  5. X-ray dose response of calcite-A comprehensive analysis for optimal application in TL dosimetry

    NASA Astrophysics Data System (ADS)

    Kalita, J. M.; Wary, G.

    2016-09-01

    The effect of various annealing treatments on dosimetric characteristics of orange calcite (CaCO3) mineral has been studied in detail. Quantitative analysis on the dose response shows that the 573 K annealed sample showed sublinear dose response from 10 mGy to 1 Gy. The fading and reproducibility of this sample are also good enough for dosimetric application. However, a specific annealing treatment after irradiation shows some significant improvements in the dosimetric characteristics of the sample. The 773 K pre-annealed sample, after X-ray irradiation post-annealing at 340 K for 6 min provides linear dose response from 10 mGy to 3.60 Gy, very less fading and good reproducibility. Moreover, this sample after post-annealing at 380 K for 6 min shows linear dose response from 10 mGy to 5.40 Gy when analyzed from the ∼408 K thermoluminescence (TL) glow peak. Analysis of TL glow curves confirmed that the 1.30 eV trap center in calcite crystal is the most effective trapping site for dosimetric application.

  6. Body Mass Index and Risk of Breast Cancer: A Nonlinear Dose-Response Meta-Analysis of Prospective Studies

    PubMed Central

    Xia, Xiaoping; Chen, Wei; Li, Jiaoyuan; Chen, Xueqin; Rui, Rui; Liu, Cheng; Sun, Yu; Liu, Li; Gong, Jing; Yuan, Peng

    2014-01-01

    The role of Body Mass Index (BMI) for Breast Cancer (BC) remains to be great interest for a long time. However, the precise effect of nonlinear dose-response for BMI and BC risk is still unclear. We conducted a dose-response meta-analysis to quantitatively assess the effect of BMI on BC risk. Twelve prospective studies with 4,699 cases identified among 426,199 participants and 25 studies of 22,809 cases identified among 1,155,110 participants in premenopausal and postmenopausal groups, respectively, were included in this meta-analysis. Significant non-linear dose-response (P < 0.001) association was identified between BMI and BC risk in postmenopausal women. Individuals with BMI of 25, 30, and 35 kg/m2 yielded relative risks (RRs) of 1.02 [95% confidence interval (CI): 0.98–1.06], 1.12 (95% CI: 1.01–1.24), and 1.26 (95% CI: 1.07–1.50), respectively, when compared to the mean level of the normal BMI range. However, inverse result though not significant was observed in premenopausal women. In conclusion, the results of this meta-analysis highlighted that obesity contributed to increased BC risk in a nonlinear dose-response manner in postmenopausal women, and it is important to realize that body weight control may be a crucial process to reduce BC susceptibility. PMID:25504309

  7. TOWARDS A BIOLOGICALLY BASED DOSE-RESPONSE MODEL FOR DEVELOPMENTAL TOXICITY OF 5-FLUOROUACIL IN THE RAT: A MATHEMATICAL CONSTRUCT

    EPA Science Inventory

    CREATING A BIOLOGICALLY-BASED DOSE-RESPONSE MODEL FOR DEVELOPMENTAL TOXICITY OF 5-FLUOROURACIL IN THE RAT. R W Setzer1, C Lau2, M L Mole2, M F Copeland2, J M Rogers2 and R J Kavlock2. 1ETD, 2RTD, NHEERL, ORD, US EPA, Research Triangle Park, NC, USA.
    Biologically based dose-...

  8. Dose response of micronuclei induced by combination radiation of α-particles and γ-rays in human lymphoblast cells.

    PubMed

    Ren, Ruiping; He, Mingyuan; Dong, Chen; Xie, Yuexia; Ye, Shuang; Yuan, Dexiao; Shao, Chunlin

    2013-01-01

    Combination radiation is a real situation of both nuclear accident exposure and space radiation environment, but its biological dosimetry is still not established. This study investigated the dose-response of micronuclei (MN) induction in lymphocyte by irradiating HMy2.CIR lymphoblast cells with α-particles, γ-rays, and their combinations. Results showed that the dose-response of MN induced by γ-rays was well-fitted with the linear-quadratic model. But for α-particle irradiation, the MN induction had a biphasic phenomenon containing a low dose hypersensitivity characteristic and its dose response could be well-stimulated with a state vector model where radiation-induced bystander effect (RIBE) was involved. For the combination exposure, the dose response of MN was similar to that of α-irradiation. However, the yield of MN was closely related to the sequence of irradiations. When the cells were irradiated with α-particles at first and then γ-rays, a synergistic effect of MN induction was observed. But when the cells were irradiated with γ-rays followed by α-particles, an antagonistic effect of MN was observed in the low dose range although this combination radiation also yielded a synergistic effect at high doses. When the interval between two irradiations was extended to 4h, a cross-adaptive response against the other irradiation was induced by a low dose of γ-rays but not α-particles.

  9. Nonmonotonic Dose Responses as They Apply to Estrogen, Androgen, and Thyroid Pathways and EPA Testing and Assessment Procedures

    EPA Pesticide Factsheets

    A state of the science document providing a judgment on the degree to which nonmonotonic dose-responses are evidenced in the scientific literature and to evaluate the extent to which they may impact U.S. EPA’s chemical testing and risk assessment.

  10. Dose-response approaches for nuclear receptor-mediated modes of action for liver carcinogenicity: Results of a workshop.

    PubMed

    Andersen, Melvin E; Preston, R Julian; Maier, Andrew; Willis, Alison M; Patterson, Jacqueline

    2014-01-01

    A public workshop, organized by a Steering Committee of scientists from government, industry, universities and research organizations, was held at the National Institute of Environmental Health Sciences (NIEHS) in September, 2010. The workshop explored the dose-response implications of toxicant modes of action (MOA) mediated by nuclear receptors. The dominant paradigm in human health risk assessment has been linear extrapolation without a threshold for cancer, and estimation of sub-threshold doses for non-cancer and (in appropriate cases) cancer endpoints. However, recent publications question the application of dose-response modeling approaches with a threshold. The growing body of molecular toxicology information and computational toxicology tools has allowed for exploration of the presence or absence of sub-threshold doses for a number of receptor-mediated MOAs. The workshop explored the development of dose-response approaches for nuclear receptor-mediated liver cancer, within a MOA Human Relevance Framework (HRF). Case studies addressed activation of the AHR, the CAR and the PPARα. This article describes the workshop process, key issues discussed and conclusions. The value of an interactive workshop approach to apply current MOA/HRF frameworks was demonstrated. The results may help direct research on the MOA and dose-response of receptor-based toxicity, since there are commonalities for many receptors in the basic pathways involved for late steps in the MOA, and similar data gaps in early steps. Three additional papers in this series describe the results and conclusions for each case-study receptor regarding its MOA, relevance of the MOA to humans and the resulting dose-response implications.

  11. Development of Dose-Response Models to Predict the Relationship for Human Toxoplasma gondii Infection Associated with Meat Consumption.

    PubMed

    Guo, Miao; Mishra, Abhinav; Buchanan, Robert L; Dubey, Jitender P; Hill, Dolores E; Gamble, H Ray; Jones, Jeffrey L; Du, Xianzhi; Pradhan, Abani K

    2016-05-01

    Toxoplasma gondii is a protozoan parasite that is responsible for approximately 24% of deaths attributed to foodborne pathogens in the United States. It is thought that a substantial portion of human T. gondii infections is acquired through the consumption of meats. The dose-response relationship for human exposures to T. gondii-infected meat is unknown because no human data are available. The goal of this study was to develop and validate dose-response models based on animal studies, and to compute scaling factors so that animal-derived models can predict T. gondii infection in humans. Relevant studies in literature were collected and appropriate studies were selected based on animal species, stage, genotype of T. gondii, and route of infection. Data were pooled and fitted to four sigmoidal-shaped mathematical models, and model parameters were estimated using maximum likelihood estimation. Data from a mouse study were selected to develop the dose-response relationship. Exponential and beta-Poisson models, which predicted similar responses, were selected as reasonable dose-response models based on their simplicity, biological plausibility, and goodness fit. A confidence interval of the parameter was determined by constructing 10,000 bootstrap samples. Scaling factors were computed by matching the predicted infection cases with the epidemiological data. Mouse-derived models were validated against data for the dose-infection relationship in rats. A human dose-response model was developed as P (d) = 1-exp (-0.0015 × 0.005 × d) or P (d) = 1-(1 + d × 0.003 / 582.414)(-1.479) . Both models predict the human response after consuming T. gondii-infected meats, and provide an enhanced risk characterization in a quantitative microbial risk assessment model for this pathogen.

  12. Non-Targeted Effects and the Dose Response for Heavy Ion Tumorigenesis

    NASA Technical Reports Server (NTRS)

    Chappelli, Lori J.; Cucinotta, Francis A.

    2010-01-01

    BACKGROUND: There is no human epidemiology data available to estimate the heavy ion cancer risks experienced by astronauts in space. Studies of tumor induction in mice are a necessary step to estimate risks to astronauts. Previous experimental data can be better utilized to model dose response for heavy ion tumorigenesis and plan future low dose studies. DOSE RESPONSE MODELS: The Harderian Gland data of Alpen et al.[1-3] was re-analyzed [4] using non-linear least square regression. The data set measured the induction of Harderian gland tumors in mice by high-energy protons, helium, neon, iron, niobium and lanthanum with LET s ranging from 0.4 to 950 keV/micron. We were able to strengthen the individual ion models by combining data for all ions into a model that relates both radiation dose and LET for the ion to tumor prevalence. We compared models based on Targeted Effects (TE) to one motivated by Non-targeted Effects (NTE) that included a bystander term that increased tumor induction at low doses non-linearly. When comparing fitted models to the experimental data, we considered the adjusted R2, the Akaike Information Criteria (AIC), and the Bayesian Information Criteria (BIC) to test for Goodness of fit.In the adjusted R2test, the model with the highest R2values provides a better fit to the available data. In the AIC and BIC tests, the model with the smaller values of the summary value provides the better fit. The non-linear NTE models fit the combined data better than the TE models that are linear at low doses. We evaluated the differences in the relative biological effectiveness (RBE) and found the NTE model provides a higher RBE at low dose compared to the TE model. POWER ANALYSIS: The final NTE model estimates were used to simulate example data to consider the design of new experiments to detect NTE at low dose for validation. Power and sample sizes were calculated for a variety of radiation qualities including some not considered in the Harderian Gland data

  13. Dose-response study of sodium cromoglycate in exercise-induced asthma.

    PubMed Central

    Patel, K R; Berkin, K E; Kerr, J W

    1982-01-01

    Ten patients with exercise-induced asthma participated in a single-blind dose-response study comparing the protective effect of inhaled sodium cromoglycate in increasing concentrations from 2 to 40 mg/ml. Saline was used as a control. Effects were assessed from the mean maximal percentage fall in forced expiratory volume in one second (FEV1) after the patients had run on a treadmill for eight minutes. There was slight bronchodilation evident from the increase in baseline FEV1 after inhalation of sodium cromoglycate, the difference reaching statistical significance with the highest concentration (5.7%, p less than 0.05). After exercise the maximal percentage falls in FEV1 (means and SEM) after saline and after sodium cromoglycate at 2, 10, 20, and 40 mg/ml were 37.3 +/- 4.7, 17.3 +/- 4.1, 10 +/- 3.3, 7.6 +/- 2.4, and 12 +/- 2.9. Sodium cromoglycate inhibited the exercise-induced fall in FEV1 at all the concentrations used in the study (p less than 0.001) and its inhibitory effect increased from 2 to 20 mg/ml. The mean FEV1 returned to baseline values within 15 minutes at higher concentrations of sodium cromoglycate (20 and 40 mg/ml) and a small bronchodilator effect was noted at 30 minutes. The findings suggest that the protective effect of sodium cromoglycate in exercise asthma is dose related. At higher concentration the drug suppresses chemical mediator release from the lung mast cells and may also modify the bronchial reactivity to release mediators. PMID:6818707

  14. Effect of Photon Hormesis on Dose Responses to Alpha Particles in Zebrafish Embryos

    PubMed Central

    Ng, Candy Yuen Ping; Cheng, Shuk Han; Yu, Kwan Ngok

    2017-01-01

    Photon hormesis refers to the phenomenon where the biological effect of ionizing radiation with a high linear energy transfer (LET) value is diminished by photons with a low LET value. The present paper studied the effect of photon hormesis from X-rays on dose responses to alpha particles using embryos of the zebrafish (Danio rerio) as the in vivo vertebrate model. The toxicity of these ionizing radiations in the zebrafish embryos was assessed using the apoptotic counts at 20, 24, or 30 h post fertilization (hpf) revealed through acridine orange (AO) staining. For alpha-particle doses ≥ 4.4 mGy, the additional X-ray dose of 10 mGy significantly reduced the number of apoptotic cells at 24 hpf, which proved the presence of photon hormesis. Smaller alpha-particle doses might not have inflicted sufficient aggregate damages to trigger photon hormesis. The time gap T between the X-ray (10 mGy) and alpha-particle (4.4 mGy) exposures was also studied. Photon hormesis was present when T ≤ 30 min, but was absent when T = 60 min, at which time repair of damage induced by alpha particles would have completed to prevent their interactions with those induced by X-rays. Finally, the drop in the apoptotic counts at 24 hpf due to photon hormesis was explained by bringing the apoptotic events earlier to 20 hpf, which strongly supported the removal of aberrant cells through apoptosis as an underlying mechanism for photon hormesis. PMID:28208665

  15. Dose Response Effects of 810 nm Laser Light on Mouse Primary Cortical Neurons

    PubMed Central

    Sharma, Sulbha K.; Kharkwal, Gitika B.; Sajo, Mari; Huang, Ying-Ying; De Taboada, Luis; McCarthy, Thomas; Hamblin, Michael R.

    2011-01-01

    Background and Objectives In the past four decades numerous studies have reported the efficacy of low level light (laser) therapy (LLLT) as a treatment for diverse diseases and injuries. Recent studies have shown that LLLT can biomodulate processes in the central nervous system and has been extensively studied as a stroke treatment. However there is still a lack of knowledge on the effects of LLLT at the cellular level in neurons. The present study aimed to study the effect of 810 nm laser on several cellular processes in primary cortical neurons cultured from embryonic mouse brains. Study Design/Materials and Methods Neurons were irradiated with fluences of 0.03, 0.3, 3, 10, or 30 J/cm2 of 810-nm laser delivered over varying times at 25 mW/cm2 and intracellular levels of reactive oxygen species (ROS), nitric oxide and calcium were measured using fluorescent probes within 5 minutes of the end of irradiation. The changes in mitochondrial function in response to light were studied in terms of adenosine triphosphate (ATP) and mitochondrial membrane potential (MMP). Results Light induced a significant increase in calcium, ATP and MMP at lower fluences and a decrease at higher fluences. ROS was significantly induced at low fluences, followed by a decrease and a second larger increase at 30 J/cm2. Nitric oxide levels showed a similar pattern of a double peak but values were less significant compared to ROS. Conclusions The results suggest that LLLT at lower fluences is capable of inducing mediators of cell signaling processes which in turn may be responsible for the beneficial stimulatory effects of the low level laser. At higher fluences beneficial mediators are reduced and high levels of Janus-type mediators such as ROS and NO (beneficial at low concentrations and harmful at high concentrations) may be responsible for the damaging effects of high-fluence light and the overall biphasic dose response. PMID:21956634

  16. Qualitative and quantitative approaches in the dose-response assessment of genotoxic carcinogens.

    PubMed

    Fukushima, Shoji; Gi, Min; Kakehashi, Anna; Wanibuchi, Hideki; Matsumoto, Michiharu

    2016-05-01

    Qualitative and quantitative approaches are important issues in field of carcinogenic risk assessment of the genotoxic carcinogens. Herein, we provide quantitative data on low-dose hepatocarcinogenicity studies for three genotoxic hepatocarcinogens: 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx), 2-amino-3-methylimidazo[4,5-f]quinoline (IQ) and N-nitrosodiethylamine (DEN). Hepatocarcinogenicity was examined by quantitative analysis of glutathione S-transferase placental form (GST-P) positive foci, which are the preneoplastic lesions in rat hepatocarcinogenesis and the endpoint carcinogenic marker in the rat liver medium-term carcinogenicity bioassay. We also examined DNA damage and gene mutations which occurred through the initiation stage of carcinogenesis. For the establishment of points of departure (PoD) from which the cancer-related risk can be estimated, we analyzed the above events by quantitative no-observed-effect level and benchmark dose approaches. MeIQx at low doses induced formation of DNA-MeIQx adducts; somewhat higher doses caused elevation of 8-hydroxy-2'-deoxyquanosine levels; at still higher doses gene mutations occurred; and the highest dose induced formation of GST-P positive foci. These data indicate that early genotoxic events in the pathway to carcinogenesis showed the expected trend of lower PoDs for earlier events in the carcinogenic process. Similarly, only the highest dose of IQ caused an increase in the number of GST-P positive foci in the liver, while IQ-DNA adduct formation was observed with low doses. Moreover, treatment with DEN at low doses had no effect on development of GST-P positive foci in the liver. These data on PoDs for the markers contribute to understand whether genotoxic carcinogens have a threshold for their carcinogenicity. The most appropriate approach to use in low dose-response assessment must be approved on the basis of scientific judgment.

  17. Dose-response relationship between sports activity and musculoskeletal pain in adolescents.

    PubMed

    Kamada, Masamitsu; Abe, Takafumi; Kitayuguchi, Jun; Imamura, Fumiaki; Lee, I-Min; Kadowaki, Masaru; Sawada, Susumu S; Miyachi, Motohiko; Matsui, Yuzuru; Uchio, Yuji

    2016-06-01

    Physical activity has multiple health benefits but may also increase the risk of developing musculoskeletal pain (MSP). However, the relationship between physical activity and MSP has not been well characterized. This study examined the dose-response relationship between sports activity and MSP among adolescents. Two school-based serial surveys were conducted 1 year apart in adolescents aged 12 to 18 years in Unnan, Japan. Self-administered questionnaires were completed by 2403 students. Associations between time spent in organized sports activity and MSP were analyzed cross-sectionally (n = 2403) and longitudinally (n = 374, students free of pain and in seventh or 10th grade at baseline) with repeated-measures Poisson regression and restricted cubic splines, with adjustment for potential confounders. The prevalence of overall pain, defined as having pain recently at least several times a week in at least one part of the body, was 27.4%. In the cross-sectional analysis, sports activity was significantly associated with pain prevalence. Each additional 1 h/wk of sports activity was associated with a 3% higher probability of having pain (prevalence ratio = 1.03, 95% confidence interval = 1.02-1.04). Similar trends were found across causes (traumatic and nontraumatic pain) and anatomic locations (upper limbs, lower back, and lower limbs). In longitudinal analysis, the risk ratio for developing pain at 1-year follow-up per 1 h/wk increase in baseline sports activity was 1.03 (95% confidence interval = 1.02-1.05). Spline models indicated a linear association (P < 0.001) but not a nonlinear association (P ≥ 0.45). The more the adolescents played sports, the more likely they were to have and develop pain.

  18. Tea Consumption and Risk of Bladder Cancer: A Dose-Response Meta-Analysis

    PubMed Central

    Weng, Hong; Zeng, Xian-Tao; Li, Sheng; Kwong, Joey S. W.; Liu, Tong-Zu; Wang, Xing-Huan

    2017-01-01

    Background and Objective: Controversial results of the association between tea (black tea, green tea, mate, and oolong tea) consumption and risk of bladder cancer were reported among epidemiological studies. Thus, we performed a meta-analysis of observational studies to investigate the association. Methods: We searched the PubMed and Embase for studies of tea consumption and bladder cancer that were published in any language up to March, 2016. Cohort or case-control studies were included in the meta-analysis. All statistical analyses were performed in Stata 12.0 software. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated to assess the relationship between tea consumption and risk of bladder cancer. Results: Totally, 25 case-control studies (15 643 cases and 30 795 controls) and seven prospective cohort studies (1807 cases and 443 076 participants) were included. The meta-analysis showed that tea consumption was not significantly associated with bladder cancer risk (OR = 0.96, 95% CI 0.86–1.06) (in a comparison of highest vs. lowest category). No non-linearity association was observed between tea consumption and bladder cancer risk (P = 0.51 for non-linearity). Specific analysis for black tea, green tea, and mate yielded similar results. The dose-response analysis showed the summary OR for an increment of 1 cup/day of tea consumption was 1.01 (95% CI 0.97–1.05). Conclusion: Results based on current meta-analysis indicated that no significant association was observed between tea consumption and risk of bladder cancer. PMID:28167914

  19. Ondansetron: A newer aspect of dose response relationship on ileal smooth muscles of rabbit.

    PubMed

    Afzal, Ayesha; Khan, Bushra Tayyaba; Bakhtiar, Salman

    2016-01-01

    There are several life threatening deadly diseases in our world but ‘Cancer’ out powers them all in recent years. Chemotherapy may be used on its own or an adjunct to other forms of therapy. Despite the advancement in cytotoxic drug therapy and supportive treatment almost 70% of patient suffer from chemotherapy induced nausea and vomiting (CINV). Ondansetron, a 5-HT(3) receptor antagonist has now become a gold standard in the treatment of chemotherapy induced nausea and vomiting. The central actions of ondansetron are well established but its peripheral actions are not well recognized. The aim of our study was to explore the peripheral actions of ondansetron. Experiments were performed in five groups (n=6) and ileal smooth muscles activity was recorded on power lab (USA). The effects of increasing concentrations of acetylcholine, serotonin & ondansetron alone was observed in first three groups. In the next two groups effects of acetylcholine and serotonin pretreated with fixed concentration (1ml) of ondansetron (10¯ϖ M)were studied. The maximum response obtained by acetylcholine served as a control for our study. Maximum response with acetylcholine was taken as 100% and with serotonin was 177 percent of control. Cumulative dose response curve with ondansetron was triphasic. At 10¯ψM it was 28.8%, whereas with 10¯ξM the amplitude decreased to 16.87%, it reached to plateau at 10¯ϖ M. Response of acetylcholine & serotonin was decreased to 57% and 78% respectively in the presence of fixed concentration of ondansetron (10¯ϖ M). Ondansetron reduces the acetylcholine and serotonin induced gastrointestinal motility. Our study has indicated that ondansetron apart from having central action also has marked peripheral actions that play an important role in CINV and may act as a partial agonist.

  20. Dose-response relationship of autonomic nervous system responses to individualized training impulse in marathon runners.

    PubMed

    Manzi, Vincenzo; Castagna, Carlo; Padua, Elvira; Lombardo, Mauro; D'Ottavio, Stefano; Massaro, Michele; Volterrani, Maurizio; Iellamo, Ferdinando

    2009-06-01

    In athletes, exercise training induces autonomic nervous system (ANS) adaptations that could be used to monitor training status. However, the relationship between training and ANS in athletes has been investigated without regard for individual training loads. We tested the hypothesis that in long-distance athletes, changes in ANS parameters are dose-response related to individual volume/intensity training load and could predict athletic performance. A spectral analysis of heart rate (HR), systolic arterial pressure variability, and baroreflex sensitivity by the sequences technique was investigated in eight recreational athletes during a 6-mo training period culminating with a marathon. Individualized training load responses were monitored by a modified training impulse (TRIMP(i)) method, which was determined in each athlete using the individual HR and lactate profiling determined during a treadmill test. Monthly TRIMP(i) steadily increased during the training period. All the ANS parameters were significantly and very highly correlated to the dose of exercise with a second-order regression model (r(2) ranged from 0.90 to 0.99; P < 0.001). Variance, high-frequency oscillations of HR variability (HRV), and baroreflex sensitivity resembled a bell-shaped curve with a minimum at the highest TRIMP(i), whereas low-frequency oscillations of HR and systolic arterial pressure variability and the low frequency (LF)-to-high frequency ratio resembled an U-shaped curve with a maximum at the highest TRIMP(i). The LF component of HRV assessed at the last recording session was significantly and inversely correlated to the time needed to complete the nearing marathon. These results suggest that in recreational athletes, ANS adaptations to exercise training are dose related on an individual basis, showing a progressive shift toward a sympathetic predominance, and that LF oscillations in HRV at peak training load could predict athletic achievement in this athlete population.

  1. Prespecified dose-response analysis for A Very Early Rehabilitation Trial (AVERT)

    PubMed Central

    Churilov, Leonid; Ellery, Fiona; Collier, Janice; Chamberlain, Jan; Langhorne, Peter; Lindley, Richard I.; Moodie, Marj; Dewey, Helen; Thrift, Amanda G.; Donnan, Geoff

    2016-01-01

    Objective: Our prespecified dose-response analyses of A Very Early Rehabilitation Trial (AVERT) aim to provide practical guidance for clinicians on the timing, frequency, and amount of mobilization following acute stroke. Methods: Eligible patients were aged ≥18 years, had confirmed first (or recurrent) stroke, and were admitted to a stroke unit within 24 hours of stroke onset. Patients were randomized to receive very early and frequent mobilization, commencing within 24 hours, or usual care. We used regression analyses and Classification and Regression Trees (CART) to investigate the effect of timing and dose of mobilization on efficacy and safety outcomes, irrespective of assigned treatment group. Results: A total of 2,104 patients were enrolled, of whom 2,083 (99.0%) were followed up at 3 months. We found a consistent pattern of improved odds of favorable outcome in efficacy and safety outcomes with increased daily frequency of out-of-bed sessions (odds ratio [OR] 1.13, 95% confidence interval [CI] 1.09 to 1.18, p < 0.001), keeping time to first mobilization and mobilization amount constant. Increased amount (minutes per day) of mobilization reduced the odds of a good outcome (OR 0.94, 95% CI 0.91 to 0.97, p < 0.001). Session frequency was the most important variable in the CART analysis, after prognostic variables age and baseline stroke severity. Conclusion: These data suggest that shorter, more frequent mobilization early after acute stroke is associated with greater odds of favorable outcome at 3 months when controlling for age and stroke severity. Classification of evidence: This study provides Class III evidence that shorter, more frequent early mobilization improves the chance of regaining independence after stroke. PMID:26888985

  2. Dose-response relationships using brain–computer interface technology impact stroke rehabilitation

    PubMed Central

    Young, Brittany M.; Nigogosyan, Zack; Walton, Léo M.; Remsik, Alexander; Song, Jie; Nair, Veena A.; Tyler, Mitchell E.; Edwards, Dorothy F.; Caldera, Kristin; Sattin, Justin A.; Williams, Justin C.; Prabhakaran, Vivek

    2015-01-01

    Brain–computer interfaces (BCIs) are an emerging novel technology for stroke rehabilitation. Little is known about how dose-response relationships for BCI therapies affect brain and behavior changes. We report preliminary results on stroke patients (n = 16, 11 M) with persistent upper extremity motor impairment who received therapy using a BCI system with functional electrical stimulation of the hand and tongue stimulation. We collected MRI scans and behavioral data using the Action Research Arm Test (ARAT), 9-Hole Peg Test (9-HPT), and Stroke Impact Scale (SIS) before, during, and after the therapy period. Using anatomical and functional MRI, we computed Laterality Index (LI) for brain activity in the motor network during impaired hand finger tapping. Changes from baseline LI and behavioral scores were assessed for relationships with dose, intensity, and frequency of BCI therapy. We found that gains in SIS Strength were directly responsive to BCI therapy: therapy dose and intensity correlated positively with increased SIS Strength (p ≤ 0.05), although no direct relationships were identified with ARAT or 9-HPT scores. We found behavioral measures that were not directly sensitive to differences in BCI therapy administration but were associated with concurrent brain changes correlated with BCI therapy administration parameters: therapy dose and intensity showed significant (p ≤ 0.05) or trending (0.05 < p < 0.1) negative correlations with LI changes, while therapy frequency did not affect LI. Reductions in LI were then correlated (p ≤ 0.05) with increased SIS Activities of Daily Living scores and improved 9-HPT performance. Therefore, some behavioral changes may be reflected by brain changes sensitive to differences in BCI therapy administration, while others such as SIS Strength may be directly responsive to BCI therapy administration. Data preliminarily suggest that when using BCI in stroke rehabilitation, therapy frequency may be less important than dose

  3. Therapeutic Time Window and Dose Response of Autologous Bone Marrow Mononuclear Cells for Ischemic Stroke

    PubMed Central

    Yang, Bing; Strong, Roger; Sharma, Sushil; Brenneman, Miranda; Mallikarjunarao, Kasam; Xi, XiaoPei; Grotta, James C.; Aronowski, Jaroslaw; Savitz, Sean I.

    2012-01-01

    Although mononuclear cells (MNCs) from bone marrow are being investigated in phase I clinical trials in stroke patients, dose response, therapeutic time window and biodistribiton have not been well-characterized in animal stroke models. Long Evans rats underwent common carotid artery/middle cerebral artery occlusion (CCA/MCAo) and 24 hrs later were randomized to receive saline IV or a bone marrow aspiration followed by an IV infusion of autologous separated MNCs (1 million, 10 million or 30 million cells/kg). In another experiment, rats underwent CCAo/MCAo and were randomized at 24 hrs, 72 hrs or 7 days after stroke to receive a saline injection or 10 million/kg MNCs. All animals were evaluated on the cylinder and corner tests up to 28 days. MNCs were tracked using Q-dot nanocrystals to monitor biodistribution. Animals treated with MNCs at 10 million and 30 million cells/kg at 24 hrs after stroke had significant reductions in neurological deficits and lesion size compared to saline controls or animals treated with 1 million cells/kg. There was no difference in neurological deficits in the 10 and 30 million cell/kg groups at 28 days. Animals treated with MNCs at 72 hrs but not at 7 days showed a significant reduction in neurological deficits by 28 days. Labeled MNCs were found in the brain, spleen, lung, liver, and kidney at 1 hr and exponentially decreased over the ensuing week. In conclusion, we found a maximum reduction in neurological deficits at 10 and 30 million cells/kg and a therapeutic time window up to 72 hrs after stroke. PMID:21412816

  4. Tea Consumption and Risk of Bladder Cancer: A Dose-Response Meta-Analysis.

    PubMed

    Weng, Hong; Zeng, Xian-Tao; Li, Sheng; Kwong, Joey S W; Liu, Tong-Zu; Wang, Xing-Huan

    2016-01-01

    Background and Objective: Controversial results of the association between tea (black tea, green tea, mate, and oolong tea) consumption and risk of bladder cancer were reported among epidemiological studies. Thus, we performed a meta-analysis of observational studies to investigate the association. Methods: We searched the PubMed and Embase for studies of tea consumption and bladder cancer that were published in any language up to March, 2016. Cohort or case-control studies were included in the meta-analysis. All statistical analyses were performed in Stata 12.0 software. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated to assess the relationship between tea consumption and risk of bladder cancer. Results: Totally, 25 case-control studies (15 643 cases and 30 795 controls) and seven prospective cohort studies (1807 cases and 443 076 participants) were included. The meta-analysis showed that tea consumption was not significantly associated with bladder cancer risk (OR = 0.96, 95% CI 0.86-1.06) (in a comparison of highest vs. lowest category). No non-linearity association was observed between tea consumption and bladder cancer risk (P = 0.51 for non-linearity). Specific analysis for black tea, green tea, and mate yielded similar results. The dose-response analysis showed the summary OR for an increment of 1 cup/day of tea consumption was 1.01 (95% CI 0.97-1.05). Conclusion: Results based on current meta-analysis indicated that no significant association was observed between tea consumption and risk of bladder cancer.

  5. Alcohol consumption and dementia risk: a dose-response meta-analysis of prospective studies.

    PubMed

    Xu, Wei; Wang, Huifu; Wan, Yu; Tan, Chenchen; Li, Jieqiong; Tan, Lan; Yu, Jin-Tai

    2017-01-01

    It is widely believed that light-to-moderate alcohol intake may protect against dementia while excessive drinking may instead increase the risk. Nonetheless, these findings need cautious interpretations due to varying methodologies and lack of standard definition, which hindered our transferring into preventative practice. The objective of this study is to investigate the potential dose-response association between alcohol consumption and risk of dementia. A systematic search was conducted in electronic databases to identify relevant studies. Risk estimates were combined using a random-effect model. Eleven studies with 73,330 participants and 4586 cases for all-cause dementia (ACD), five studies with 52,715 participants and 1267 cases for Alzheimer's dementia (AD) and four studies with 49,535 participants and 542 cases for vascular dementia were included. We observed a nonlinear association between alcohol consumption and ACD risk (p nonlinearity < 0.05). The alcohol dose associated with lower risk of dementia was confined to at most 12.5 g/day, with the risk hitting bottom (RR ≈ 0.9) at roughly 6 g/day. Of note, the ACD risk seemed to be elevated (≈10%) when the dose surpasses certain levels: 23 drinks/week or 38 g/day. For the alcohol type, recommendation for wine is prioritized. The subgroup analysis further indicated that the effect of alcohol may be greater in younger adults (<60 years old) with regard to fighting against dementia. Modest alcohol consumption (≤12.5 g/day) is associated with a reduced risk of dementia with 6 g/day of alcohol conferring a lower risk than other levels while excessive drinking (≥38 g/day) may instead elevate the risk.

  6. Dose-response of EBT3 radiochromic films to proton and carbon ion clinical beams.

    PubMed

    Castriconi, Roberta; Ciocca, Mario; Mirandola, Alfredo; Sini, Carla; Broggi, Sara; Schwarz, Marco; Fracchiolla, Francesco; Martišíková, Mária; Aricò, Giulia; Mettivier, Giovanni; Russo, Paolo

    2017-01-21

    We investigated the dose-response of the external beam therapy 3 (EBT3) films for proton and carbon ion clinical beams, in comparison with conventional radiotherapy beams; we also measured the film response along the energy deposition-curve in water. We performed measurements at three hadrontherapy centres by delivering monoenergetic pencil beams (protons: 63-230 MeV; carbon ions: 115-400 MeV/u), at 0.4-20 Gy dose to water, in the plateau of the depth-dose curve. We also irradiated the films to clinical MV-photon and electron beams. We placed the EBT3 films in water along the whole depth-dose curve for 148.8 MeV protons and 398.9 MeV/u carbon ions, in comparison with measurements provided by a plane-parallel ionization chamber. For protons, the response of EBT3 in the plateau of the depth-dose curve is not different from that of photons, within experimental uncertainties. For carbon ions, we observed an energy dependent under-response of EBT3 film, from 16% to 29% with respect to photon beams. Moreover, we observed an under-response in the Bragg peak region of about 10% for 148.8 MeV protons and of about 42% for 398.9 MeV/u carbon ions. For proton and carbon ion clinical beams, an under-response occurs at the Bragg peak. For carbon ions, we also observed an under-response of the EBT3 in the plateau of the depth-dose curve. This effect is the highest at the lowest initial energy of the clinical beams, a phenomenon related to the corresponding higher LET in the film sensitive layer. This behavior should be properly modeled when using EBT3 films for accurate 3D dosimetry.

  7. Dose-response of EBT3 radiochromic films to proton and carbon ion clinical beams

    NASA Astrophysics Data System (ADS)

    Castriconi, Roberta; Ciocca, Mario; Mirandola, Alfredo; Sini, Carla; Broggi, Sara; Schwarz, Marco; Fracchiolla, Francesco; Martišíková, Mária; Aricò, Giulia; Mettivier, Giovanni; Russo, Paolo

    2017-01-01

    We investigated the dose-response of the external beam therapy 3 (EBT3) films for proton and carbon ion clinical beams, in comparison with conventional radiotherapy beams; we also measured the film response along the energy deposition-curve in water. We performed measurements at three hadrontherapy centres by delivering monoenergetic pencil beams (protons: 63-230 MeV; carbon ions: 115-400 MeV/u), at 0.4-20 Gy dose to water, in the plateau of the depth-dose curve. We also irradiated the films to clinical MV-photon and electron beams. We placed the EBT3 films in water along the whole depth-dose curve for 148.8 MeV protons and 398.9 MeV/u carbon ions, in comparison with measurements provided by a plane-parallel ionization chamber. For protons, the response of EBT3 in the plateau of the depth-dose curve is not different from that of photons, within experimental uncertainties. For carbon ions, we observed an energy dependent under-response of EBT3 film, from 16% to 29% with respect to photon beams. Moreover, we observed an under-response in the Bragg peak region of about 10% for 148.8 MeV protons and of about 42% for 398.9 MeV/u carbon ions. For proton and carbon ion clinical beams, an under-response occurs at the Bragg peak. For carbon ions, we also observed an under-response of the EBT3 in the plateau of the depth-dose curve. This effect is the highest at the lowest initial energy of the clinical beams, a phenomenon related to the corresponding higher LET in the film sensitive layer. This behavior should be properly modeled when using EBT3 films for accurate 3D dosimetry.

  8. Dose-response relationships using brain-computer interface technology impact stroke rehabilitation.

    PubMed

    Young, Brittany M; Nigogosyan, Zack; Walton, Léo M; Remsik, Alexander; Song, Jie; Nair, Veena A; Tyler, Mitchell E; Edwards, Dorothy F; Caldera, Kristin; Sattin, Justin A; Williams, Justin C; Prabhakaran, Vivek

    2015-01-01

    Brain-computer interfaces (BCIs) are an emerging novel technology for stroke rehabilitation. Little is known about how dose-response relationships for BCI therapies affect brain and behavior changes. We report preliminary results on stroke patients (n = 16, 11 M) with persistent upper extremity motor impairment who received therapy using a BCI system with functional electrical stimulation of the hand and tongue stimulation. We collected MRI scans and behavioral data using the Action Research Arm Test (ARAT), 9-Hole Peg Test (9-HPT), and Stroke Impact Scale (SIS) before, during, and after the therapy period. Using anatomical and functional MRI, we computed Laterality Index (LI) for brain activity in the motor network during impaired hand finger tapping. Changes from baseline LI and behavioral scores were assessed for relationships with dose, intensity, and frequency of BCI therapy. We found that gains in SIS Strength were directly responsive to BCI therapy: therapy dose and intensity correlated positively with increased SIS Strength (p ≤ 0.05), although no direct relationships were identified with ARAT or 9-HPT scores. We found behavioral measures that were not directly sensitive to differences in BCI therapy administration but were associated with concurrent brain changes correlated with BCI therapy administration parameters: therapy dose and intensity showed significant (p ≤ 0.05) or trending (0.05 < p < 0.1) negative correlations with LI changes, while therapy frequency did not affect LI. Reductions in LI were then correlated (p ≤ 0.05) with increased SIS Activities of Daily Living scores and improved 9-HPT performance. Therefore, some behavioral changes may be reflected by brain changes sensitive to differences in BCI therapy administration, while others such as SIS Strength may be directly responsive to BCI therapy administration. Data preliminarily suggest that when using BCI in stroke rehabilitation, therapy frequency may be less important than dose and

  9. Energy crop (Sida hermaphrodita) fertilization using digestate under marginal soil conditions: A dose-response experiment

    NASA Astrophysics Data System (ADS)

    Nabel, Moritz; Bueno Piaz Barbosa, Daniela; Horsch, David; Jablonowski, Nicolai David

    2014-05-01

    The global demand for energy security and the mitigation of climate change are the main drivers pushing energy-plant production in Germany. However, the cultivation of these plants can cause land use conflicts since agricultural soil is mostly used for plant production. A sustainable alternative to the conventional cultivation of food-based energy-crops is the cultivation of special adopted energy-plants on marginal lands. To further increase the sustainability of energy-plant cultivation systems the dependency on synthetic fertilizers needs to be reduced via closed nutrient loops. In the presented study the energy-plant Sida hermaphrodita (Malvaceae) will be used to evaluate the potential to grow this high potential energy-crop on a marginal sandy soil in combination with fertilization via digestate from biogas production. With this dose-response experiment we will further identify an optimum dose, which will be compared to equivalent doses of NPK-fertilizer. Further, lethal doses and deficiency doses will be observed. Two weeks old Sida seedlings were transplanted to 1L pots and fertilized with six doses of digestate (equivalent to a field application of 5, 10, 20, 40, 80, 160t/ha) and three equivalent doses of NPK-fertilizer. Control plants were left untreated. Sida plants will grow for 45 days under greenhouse conditions. We hypothesize that the nutrient status of the marginal soil can be increased and maintained by defined digestate applications, compared to control plants suffering of nutrient deficiency due to the low nutrient status in the marginal substrate. The dose of 40t/ha is expected to give a maximum biomass yield without causing toxicity symptoms. Results shall be used as basis for further experiments on the field scale in a field trial that was set up to investigate sustainable production systems for energy crop production under marginal soil conditions.

  10. Lead-induced anemia: Dose-response relationships and evidence for a threshold

    SciTech Connect

    Schwartz, J.; Landrigan, P.J.; Baker, E.L. Jr.; Orenstein, W.A.; von Lindern, I.H. )

    1990-02-01

    We conducted a cross-sectional epidemiologic study to assess the association between blood lead level and hematocrit in 579 one to five year-old children living near a primary lead smelter in 1974. Blood lead levels ranged from 0.53 to 7.91 mumol/L (11 to 164 micrograms/dl). To predict hematocrit as a function of blood lead level and age, we derived non-linear regression models and fit percentile curves. We used logistic regression to predict the probability of hematocrit values less than 35 per cent. We found a strong non-linear, dose-response relationship between blood lead level and hematocrit. This relationship was influenced by age, but (in this age group) not by sex; the effect was strongest in youngest children. In one year-olds, the age group most severely affected, the risk of an hematocrit value below 35 percent was 2 percent above background at blood lead levels between 0.97 and 1.88 mumol/L (20 and 39 micrograms/dl), 18 percent above background at lead levels of 1.93 to 2.85 mumol/L (40 to 59 micrograms/dl), and 40 percent above background at lead levels of 2.9 mumol/L (60 micrograms/dl) and greater; background was defined as a blood lead level below 1.88 mumol/L (20 micrograms/dl). This effect appeared independent of iron deficiency. These findings suggest that blood lead levels close to the currently recommended limit value of 1.21 mumol/L (25 micrograms/dl) are associated with dose-related depression of hematocrit in young children.

  11. Dose-response relationship between sleep duration and human psychomotor vigilance and subjective alertness

    NASA Technical Reports Server (NTRS)

    Jewett, M. E.; Dijk, D. J.; Kronauer, R. E.; Dinges, D. F.

    1999-01-01

    Although it has been well documented that sleep is required for human performance and alertness to recover from low levels after prolonged periods of wakefulness, it remains unclear whether they increase in a linear or asymptotic manner during sleep. It has been postulated that there is a relation between the rate of improvement in neurobehavioral functioning and rate of decline of slow-wave sleep and/or slow-wave activity (SWS/SWA) during sleep, but this has not been verified. Thus, a cross-study comparison was conducted in which dose-response curves (DRCs) were constructed for Stanford Sleepiness Scale (SSS) and Psychomotor Vigilance Task (PVT) tests taken at 1000 hours by subjects who had been allowed to sleep 0 hours, 2 hours, 5 hours or 8 hours the previous night. We found that the DRCs to each PVT metric improved in a saturating exponential manner, with recovery rates that were similar [time constant (T) approximately 2.14 hours] for all the metrics. This recovery rate was slightly faster than, though not statistically significantly different from, the reported rate of SWS/SWA decline (T approximately 2.7 hours). The DRC to the SSS improved much more slowly than psychomotor vigilance, so that it could be fit equally well by a linear function (slope = -0.26) or a saturating exponential function (T = 9.09 hours). We conclude that although SWS/SWA, subjective alertness, and a wide variety of psychomotor vigilance metrics may all change asymptotically during sleep, it remains to be determined whether the underlying physiologic processes governing their expression are different.

  12. Reanalysis of dose-response data from the Iraqi methylmercury poisoning episode

    SciTech Connect

    Crump, K.; Clewell, H.; Gearhart, J.

    1995-08-01

    Applying a hockey stick parametric dose-response model to data on late or retarded development in Iraqi children exposed in utero to methylmercury, with mercury (Hg) exposure characterized by the peak Hg concentration in mothers` hair during pregnancy, Cox et al. calculated the {open_quotes}best statistical estimate{close_quotes} of the threshold for health effects as 10 ppm Hg in hair with a 95% range of uncertainty of between 0 and 13.6 ppm. A new application of the hockey stick model to the Iraqi data shows, however, that the statistical upper limit of the threshold based on the hockey stick model could be as high as 255 ppm. Futhermore, the maximum likelihood estimate of the threshold using a different parametric model is virtually zero. These and other analyses demonstrate that threshold estimates based on parametric models exhibit high statistical variability and model dependency, and are highly sensitive to the precise definition of an abnormal response. Consequently, they are not a reliable basis for setting a reference dose (RfD) for methylmercury. Benchmark analyses and statistical analyses useful for deriving NOAELs are also presented. We believe these latter analyses-particularly the benchmark analyses-generally form a sounder basis for determining RfDs than the type of hockey stick analysis presented by Cox et al. However, the acute nature of the exposures, as well as other limitations in the Iraqi data suggest that other data may be more appropriate for determining acceptable human exposures to methylmercury. 24 refs., 5 figs., 2 tabs.

  13. Laser capture microdissection reveals dose-response of gene expression in situ consequent to asbestos exposure.

    PubMed

    Yin, Qi; Brody, Arnold R; Sullivan, Deborah E

    2007-12-01

    The genes that mediate fibroproliferative lung disease remain to be defined. Prior studies from our laboratory showed by in situ hybridization and immunohistochemistry that the genes coding for tumour necrosis factor alpha, transforming growth factor beta, the platelet-derived growth factor A and B isoforms, and alpha-1 pro-collagen are expressed in fibroproliferative lesions that develop quickly after asbestos inhalation. These five genes, along with matrix metalloproteinase 9, a collagenase found to be increased in several lung diseases, are known to control matrix production and cell proliferation in humans and animals. Here we show by laser capture microdissection that (i) The six genes are expressed at significantly higher levels in the asbestos-exposed mice when comparing the same anatomic regions 'captured' in unexposed mice. (ii) The bronchiolar-alveolar duct (BAD) junctions, where the greatest number of fibres initially deposit, were always significantly higher than the other anatomic regions for each gene. The first alveolar duct bifurcation (ADB) generally was higher than the second ADB, the ADBs were always significantly higher than the airway walls and pleura, and the airway walls and pleura were generally higher than the unexposed tissues. (iii) Animals exposed for 3 days always exhibited significantly higher levels of gene expression at the BAD junctions and ADBs than animals exposed for 2 days. To our knowledge, this is the first demonstration of a dose-response to a toxic particle in situ, and this response appears to be dependent on the number of fibres that deposits at the individual anatomic site.

  14. Recombinant human erythropoietin therapy in critically ill patients: a dose-response study [ISRCTN48523317

    PubMed Central

    Georgopoulos, Dimitris; Matamis, Dimitris; Routsi, Christina; Michalopoulos, Argiris; Maggina, Nina; Dimopoulos, George; Zakynthinos, Epaminondas; Nakos, George; Thomopoulos, George; Mandragos, Kostas; Maniatis, Alice

    2005-01-01

    Introduction The aim of this study was to assess the efficacy of two dosing schedules of recombinant human erythropoietin (rHuEPO) in increasing haematocrit (Hct) and haemoglobin (Hb) and reducing exposure to allogeneic red blood cell (RBC) transfusion in critically ill patients. Method This was a prospective, randomized, multicentre trial. A total of 13 intensive care units participated, and a total of 148 patients who met eligibility criteria were enrolled. Patients were randomly assigned to receive intravenous iron saccharate alone (control group), intravenous iron saccharate and subcutaneous rHuEPO 40,000 units once per week (group A), or intravenous iron saccharate and subcutaneous rHuEPO 40,000 units three times per week (group B). rHuEPO was given for a minimum of 2 weeks or until discharge from the intensive care unit or death. The maximum duration of therapy was 3 weeks. Results The cumulative number of RBC units transfused, the average numbers of RBC units transfused per patient and per transfused patient, the average volume of RBCs transfused per day, and the percentage of transfused patients were significantly higher in the control group than in groups A and B. No significant difference was observed between group A and B. The mean increases in Hct and Hb from baseline to final measurement were significantly greater in group B than in the control group. The mean increase in Hct was significantly greater in group B than in group A. The mean increase in Hct in group A was significantly greater than that in control individuals, whereas the mean increase in Hb did not differ significantly between the control group and group A. Conclusion Administration of rHuEPO to critically ill patients significantly reduced the need for RBC transfusion. The magnitude of the reduction did not differ between the two dosing schedules, although there was a dose response for Hct and Hb to rHuEPO in these patients. PMID:16277712

  15. Dose-response relationship for α-tocopherol prevention of ultraviolet radiation induced cataract in rat.

    PubMed

    Wang, Jing; Löfgren, Stefan; Dong, Xiuqin; Galichanin, Konstantin; Söderberg, Per G

    2011-07-01

    The purpose of this study is to establish the dose response relationship for α-tocopherol protection of ultraviolet radiation (UVR) induced cataract in the rat. Four groups of 20 six-week-old albino Sprague Dawley rats received 5, 25, 50, and 100 IU/day α-tocopherol, whilst another group of 20 rats without any α-tocopherol feeding was the control group. After 4 weeks of feeding, each rat was unilaterally exposed to 8 kJ/m(2) UVR-300 nm for 15 min. At 1 week after exposure, the rats were sacrificed and lens light scattering was measured quantitatively. Lens total reduced (GSH) and oxidized (GSSG) glutathione; glutathione reductase (GR) and peroxidase (GPx) were determined spectrophotometrically. The UVR-exposed lenses in the α-tocopherol fed groups developed superficial cataract, whereas lenses in the control group developed cortical and equatorial opacities. Light scattering in lenses from the α-tocopherol-supplemented rats was lower than in lenses from the control group. The difference of light scattering between the exposed and contralateral non-exposed lens decreased with increasing doses of α-tocopherol to an asymptote level. UVR-exposure caused a significant depletion of lens GSH in rats without or at low α-tocopherol supplementation. The depletion of GSH became less with higher α-tocopherol supplementation. There was no detectable difference in lens GSSG, GR or GPx at any level of α-tocopherol supplementation. Orally administered α-tocopherol dose dependently protects against UVR-induced cataract. The protection is associated with an α-tocopherol dose-dependent GSH depletion secondary to UVR exposure. UVR-induced light scattering only occurs if the GSH depletion exceeds a threshold.

  16. Computational systems biology and dose-response modeling in relation to new directions in toxicity testing.

    PubMed

    Zhang, Qiang; Bhattacharya, Sudin; Andersen, Melvin E; Conolly, Rory B

    2010-02-01

    The new paradigm envisioned for toxicity testing in the 21st century advocates shifting from the current animal-based testing process to a combination of in vitro cell-based studies, high-throughput techniques, and in silico modeling. A strategic component of the vision is the adoption of the systems biology approach to acquire, analyze, and interpret toxicity pathway data. As key toxicity pathways are identified and their wiring details elucidated using traditional and high-throughput techniques, there is a pressing need to understand their qualitative and quantitative behaviors in response to perturbation by both physiological signals and exogenous stressors. The complexity of these molecular networks makes the task of understanding cellular responses merely by human intuition challenging, if not impossible. This process can be aided by mathematical modeling and computer simulation of the networks and their dynamic behaviors. A number of theoretical frameworks were developed in the last century for understanding dynamical systems in science and engineering disciplines. These frameworks, which include metabolic control analysis, biochemical systems theory, nonlinear dynamics, and control theory, can greatly facilitate the process of organizing, analyzing, and understanding toxicity pathways. Such analysis will require a comprehensive examination of the dynamic properties of "network motifs"--the basic building blocks of molecular circuits. Network motifs like feedback and feedforward loops appear repeatedly in various molecular circuits across cell types and enable vital cellular functions like homeostasis, all-or-none response, memory, and biological rhythm. These functional motifs and associated qualitative and quantitative properties are the predominant source of nonlinearities observed in cellular dose response data. Complex response behaviors can arise from toxicity pathways built upon combinations of network motifs. While the field of computational cell

  17. The dose-response curve of the gravitropic reaction: a re-analysis.

    PubMed

    Perbal, Gérald; Jeune, Bernard; Lefranc, Agnès; Carnero-Diaz, Eugénie; Driss-Ecole, Dominique

    2002-03-01

    The dose-response curve of the gravitropic reaction is often used to evaluate the gravisensing of plant organs. It has been proposed (Larsen 1957) that the response (curvature) varies linearly as a function of the logarithm of the dose of gravistimulus. As this model fitted correctly most of the data obtained in the literature, the presentation time (tp, minimal duration of stimulation in the gravitational field to induce a response) or the presentation dose (dp, minimal quantity in g.s of stimulation to induce a response) were estimated by extrapolating down to zero curvature the straight line representing the response as a function of the logarithm of the stimulus. This method was preferred to a direct measurement of dp or tp with minute stimulations, since very slight gravitropic response cannot be distinguished from the background oscillations of the extremity of the organs. In the present review, it is shown that generally the logarithmic model (L) does not fit the experimental data published in the literature as well as the hyperbolic model (H). The H model in its simplest form is related to a response in which a ligand-receptor system is the limiting phase in the cascade of events leading to the response (Weyers et al. 1987). However, it is demonstrated that the differential growth, responsible for the curvature (and the angle of curvature), would vary as a hyperbolic function of the dose of stimulation, even if several steps involving ligand-receptor systems are responsible for the gravitropic curvature. In the H model, there is theoretically no presentation time (or presentation dose) since the curve passes through the origin. The value of the derivative of the H function equals a/b and represents the slope of the cune at the origin. It could be therefore used to estimate gravisensitivity. This provides a measurement of graviresponsiveness for threshold doses of stimulation. These results imply that the presentation time (or presentation dose) derived from

  18. Is There a Dose-Response Relationship for Heart Disease With Low-Dose Radiation Therapy?

    SciTech Connect

    Chung, Eugene; Corbett, James R.; Moran, Jean M.; Griffith, Kent A.; Marsh, Robin B.; Feng, Mary; Jagsi, Reshma; Kessler, Marc L.; Ficaro, Edward C.; Pierce, Lori J.

    2013-03-15

    Purpose: To quantify cardiac radiation therapy (RT) exposure using sensitive measures of cardiac dysfunction; and to correlate dysfunction with heart doses, in the setting of adjuvant RT for left-sided breast cancer. Methods and Materials: On a randomized trial, 32 women with node-positive left-sided breast cancer underwent pre-RT stress single photon emission computed tomography (SPECT-CT) myocardial perfusion scans. Patients received RT to the breast/chest wall and regional lymph nodes to doses of 50 to 52.2 Gy. Repeat SPECT-CT scans were performed 1 year after RT. Perfusion defects (PD), summed stress defects scores (SSS), and ejection fractions (EF) were evaluated. Doses to the heart and coronary arteries were quantified. Results: The mean difference in pre- and post-RT PD was −0.38% ± 3.20% (P=.68), with no clinically significant defects. To assess for subclinical effects, PD were also examined using a 1.5-SD below the normal mean threshold, with a mean difference of 2.53% ± 12.57% (P=.38). The mean differences in SSS and EF before and after RT were 0.78% ± 2.50% (P=.08) and 1.75% ± 7.29% (P=.39), respectively. The average heart Dmean and D95 were 2.82 Gy (range, 1.11-6.06 Gy) and 0.90 Gy (range, 0.13-2.17 Gy), respectively. The average Dmean and D95 to the left anterior descending artery were 7.22 Gy (range, 2.58-18.05 Gy) and 3.22 Gy (range, 1.23-6.86 Gy), respectively. No correlations were found between cardiac doses and changes in PD, SSS, and EF. Conclusions: Using sensitive measures of cardiac function, no clinically significant defects were found after RT, with the average heart Dmean <5 Gy. Although a dose response may exist for measures of cardiac dysfunction at higher doses, no correlation was found in the present study for low doses delivered to cardiac structures and perfusion, SSS, or EF.

  19. Lipid metabolic dose response to dietary alpha-linolenic acid in monk parrot (Myiopsitta monachus).

    PubMed

    Petzinger, Christina; Heatley, J J; Bailey, Christopher A; Bauer, John E

    2014-03-01

    Monk parrots (Myiopsitta monachus) are susceptible to atherosclerosis, a progressive disease characterized by the formation of plaques in the arteries accompanied by underlying chronic inflammation. The family of n-3 fatty acids, especially eicosapentaenoic acid (20:5n-3, EPA) and docosahexaenoic acid (22:6n-3, DHA), have consistently been shown to reduce atherosclerotic risk factors in humans and other mammals. Some avian species have been observed to convert α-linolenic acid (18:3n-3, ALA) to EPA and DHA (Htin et al. in Arch Geflugelk 71:258-266, 2007; Petzinger et al. in J Anim Physiol Anim Nutr, 2013). Therefore, the metabolic effects of including flaxseed oil, as a source of ALA, in the diet at three different levels (low, medium, and high) on the lipid metabolism of Monk parrots was evaluated through measuring plasma total cholesterol (TC), free cholesterol (FC), triacylglycerols (TAG), and phospholipid fatty acids. Feed intake, body weight, and body condition score were also assessed. Thus the dose and possible saturation response of increasing dietary ALA at constant linoleic acid (18:2n-6, LNA) concentration on lipid metabolism in Monk parrots (M. monachus) was evaluated. Calculated esterified cholesterol in addition to plasma TC, FC, and TAG were unaltered by increasing dietary ALA. The high ALA group had elevated levels of plasma phospholipid ALA, EPA, and docosapentaenoic acid (DPAn-3, 22:5n-3). The medium and high ALA groups had suppressed plasma phospholipid 20:2n-6 and adrenic acid (22:4n-6, ADA) compared to the low ALA group. When the present data were combined with data from a previous study (Petzinger et al. in J Anim Physiol Anim Nutr, 2013) a dose response to dietary ALA was observed when LNA was constant. Plasma phospholipid ALA, EPA, DPAn-3, DHA, and total n-3 were positively correlated while 20:2n-6, di-homo-gamma-linoleic acid (20:3n-6Δ7), arachidonic acid (20:4n-6), ADA, and total n-6 were inversely correlated with dietary en% ALA.

  20. Caudate neuronal recording in freely behaving animals following acute and chronic dose response methylphenidate exposure.

    PubMed

    Claussen, Catherine M; Dafny, Nachum

    2015-09-01

    The misuse and abuse of the psychostimulant, methylphenidate (MPD) the drug of choice in the treatment of attention deficit hyperactivity disorder (ADHD) has seen a sharp uprising in recent years among both youth and adults for its cognitive enhancing effects and for recreational purposes. This uprise in illicit use has lead to many questions concerning the long-term consequences of MPD exposure. The objective of this study was to record animal behavior concomitantly with the caudate nucleus (CN) neuronal activity following acute and repetitive (chronic) dose response exposure to methylphenidate (MPD). A saline control and three MPD dose (0.6, 2.5, and 10.0mg/kg) groups were used. Behaviorally, the same MPD dose in some animals following chronic MPD exposure elicited behavioral sensitization and other animals elicited behavioral tolerance. Based on this finding, the CN neuronal population recorded from animals expressing behavioral sensitization was also evaluated separately from CN neurons recorded from animals expressing behavioral tolerance to chronic MPD exposure, respectively. Significant differences in CN neuronal population responses between the behaviorally sensitized and the behaviorally tolerant animals were observed for the 2.5 and 10.0mg/kg MPD exposed groups. For 2.5mg/kg MPD, behaviorally sensitized animals responded by decreasing their firing rates while behaviorally tolerant animals showed mainly an increase in their firing rates. The CN neuronal responses recorded from the behaviorally sensitized animals following 10.0mg/kg MPD responded by increasing their firing rates whereas the CN neuronal recordings from the behaviorally tolerant animals showed that approximately half decreased their firing rates in response to 10.0mg/kg MPD exposure. The comparison of percentage change in neuronal firing rates showed that the behaviorally tolerant animals trended to exhibit increases in their neuronal firing rates at ED1 following initial MPD exposure and

  1. Dose response of commercially available optically stimulated luminescent detector, Al2O3:C for megavoltage photons and electrons.

    PubMed

    Kim, Dong Wook; Chung, Weon Kuu; Shin, Dong Oh; Yoon, Myonggeun; Hwang, Ui-Jung; Rah, Jeong-Eun; Jeong, Hojin; Lee, Sang Yeob; Shin, Dongho; Lee, Se Byeong; Park, Sung Yong

    2012-04-01

    This study examined the dose response of an optically stimulated luminescence dosemeter (OSLD) to megavoltage photon and electron beams. A nanoDot™ dosemeter was used to measure the dose response of the OSLD. Photons of 6-15 MV and electrons of 9-20 MeV were delivered by a Varian 21iX machine (Varian Medical System, Inc. Milpitas, CA, USA). The energy dependency was <1 %. For the 6-MV photons, the dose was linear until 200 cGy. The superficial dose measurements revealed photon irradiation to have an angular dependency. The nanoDot™ dosemeter has potential use as an in vivo dosimetric tool that is independent of the energy, has dose linearity and a rapid response compared with normal in vivo dosimetric tools, such as thermoluminescence detectors. However, the OSLD must be treated very carefully due to the high angular dependency of the photon beam.

  2. A study of the shape of dose-response curves for acute lethality at low response: a megadaphnia study'

    SciTech Connect

    Sebaugh, J.L.; Wilson, J.D.; Tucker, M.W.; Adams, W.J. )

    1991-12-01

    Dose-response curves were developed for the immobilization response in Daphnia magna to four toxicants. The purpose of this work was to study the effect of the form of the model and the number of concentration levels used on the estimates of typical low-dose effective concentrations (1%, 5%, 10%). The generalized four-parameter logistic model was used as the reference. When using 12 concentration levels, one of the logistic family two- or three-parameter models was shown reliably to represent each of these various sets of dose-response data, and to provide adequate estimates of EC01 and EC05, as well as EC10 and EC50. For two of the toxicants, an asymmetric model was required. When reducing the number of concentrations to five, the EC10 and EC50 were well estimated by the probit model, with acceptable results at the EC05 level.

  3. Dose response for TCDD promotion of hepatocarcinogenesis in rats initiated with DEN: histologic, biochemical, and cell proliferation endpoints.

    PubMed Central

    Maronpot, R R; Foley, J F; Takahashi, K; Goldsworthy, T; Clark, G; Tritscher, A; Portier, C; Lucier, G

    1993-01-01

    The present study examines the dose-response relationship for 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) promotion of histologic and biochemical parameters by using a two-stage model for hepatocarcinogenesis in female Sprague-Dawley rats initiated with a single intraperitoneal dose of 175 mg of diethylnitrosamine (DEN)/kg body weight at 70 days of age. Starting 2 weeks after initiation, treatment groups of 8-10 rats were given TCDD by gavage in corn oil once every 2 weeks for 30 weeks. Doses were 3.5, 10.7, 35.7, and 125 ng TCDD/kg body weight/day. A significant body weight reduction was present in the noninitiated group that received 125 ng TCDD. Relative liver weight was statistically increased in initiated rats treated with > or = 10.7 ng TCDD and in noninitiated rats treated with > or = 35.7 ng TCDD. Histopathologic evidence of cytotoxicity was dose-related in all TCDD-treated groups. There was a statistically significant dose response in the bromodeoxyuridine (BrdU) S-phase labeling index (LI) in the DEN-initiated rats (p < 0.01) and a marginally significant trend in the saline-treated rats (p = 0.10), but proliferating cell nuclear antigen S-phase LI and growth fraction within altered hepatic foci showed no increase. Among the DEN-initiated groups there was a significant increase in glutathione S-transferase altered hepatic foci stereological parameters in the 125 ng TCDD group. This study demonstrates that dose-response relationships for TCDD's effects on cell proliferation growth of altered hepatic foci are different from previously reported effects on P450 gene expression, indicating that different biological or biochemical responses may exhibit different dose-response relationships.(ABSTRACT TRUNCATED AT 250 WORDS) Images Figure 1. Figure 1. Figure 1. Figure 1. Figure 1. Figure 2. Figure 3. Figure 4. Figure 5. Figure 6. Figure 7. PMID:8143597

  4. Dose response for TCDD promotion of hepatocarcinogenesis in rats initiated with DEN: histologic, biochemical, and cell proliferation endpoints.

    PubMed

    Maronpot, R R; Foley, J F; Takahashi, K; Goldsworthy, T; Clark, G; Tritscher, A; Portier, C; Lucier, G

    1993-12-01

    The present study examines the dose-response relationship for 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) promotion of histologic and biochemical parameters by using a two-stage model for hepatocarcinogenesis in female Sprague-Dawley rats initiated with a single intraperitoneal dose of 175 mg of diethylnitrosamine (DEN)/kg body weight at 70 days of age. Starting 2 weeks after initiation, treatment groups of 8-10 rats were given TCDD by gavage in corn oil once every 2 weeks for 30 weeks. Doses were 3.5, 10.7, 35.7, and 125 ng TCDD/kg body weight/day. A significant body weight reduction was present in the noninitiated group that received 125 ng TCDD. Relative liver weight was statistically increased in initiated rats treated with > or = 10.7 ng TCDD and in noninitiated rats treated with > or = 35.7 ng TCDD. Histopathologic evidence of cytotoxicity was dose-related in all TCDD-treated groups. There was a statistically significant dose response in the bromodeoxyuridine (BrdU) S-phase labeling index (LI) in the DEN-initiated rats (p < 0.01) and a marginally significant trend in the saline-treated rats (p = 0.10), but proliferating cell nuclear antigen S-phase LI and growth fraction within altered hepatic foci showed no increase. Among the DEN-initiated groups there was a significant increase in glutathione S-transferase altered hepatic foci stereological parameters in the 125 ng TCDD group. This study demonstrates that dose-response relationships for TCDD's effects on cell proliferation growth of altered hepatic foci are different from previously reported effects on P450 gene expression, indicating that different biological or biochemical responses may exhibit different dose-response relationships.(ABSTRACT TRUNCATED AT 250 WORDS)

  5. Dose-response relationship of an environmental mixture of pyrethroids following an acute oral administration in the rat

    EPA Science Inventory

    Dose-response relationship of an environmental mixture of pyrethroids following an acute oral administration in the rat M.F. Hughes1, D.G. Ross1, J.M. Starr1, E.J. Scollon1,2, M.J. Wolansky1,3, K.M. Crofton1, M.J. DeVito1,4 1U.S. EPA, ORD, Research Triangle Park, NC, 2U.S. EPA,...

  6. Dose-response curve and time-course of effect of vecuronium in male and female patients.

    PubMed

    Xue, F S; Liao, X; Liu, J H; Tong, S Y; Zhang, Y M; Zhang, R J; An, G; Luo, L K

    1998-06-01

    To determine the differences between men and women in the dose-response curve and the time-course of effect of vecuronium, we studied 60 adult patients (30 male and 30 female), ASA I, age 18-51 yr, undergoing elective plastic surgery. Anaesthesia was maintained with nitrous oxide 60% in oxygen; thiopentone and incremental doses of fentanyl were given as required. Neuromuscular function was assessed mechanomyographically using the train-of-four (TOF) stimulation at the wrist every 12 s. The percentage depression of T1 was used as the study variable. The dose-response relationship of vecuronium was determined by a cumulative dose-response technique. The dose-response curve in men was shifted in a parallel fashion to the right, indicating a decrease in the sensitivity to vecuronium-induced neuromuscular block, compared with women. The ED50, ED90 and ED95 of vecuronium were 23.9 (4.7), 45.4 (11.2) and 55.7 (14.3) micrograms kg-1 in men and 18.4 (3.7), 33.5 (7.8) and 39.8 (9.6) micrograms kg-1 in women respectively. There were statistically significant differences in these values between the two groups (P < 0.01 in each instance). After a total dose of vecuronium 80 micrograms kg-1, neuromuscular block was significantly longer in women than in men. The duration of peak effect, clinical duration, and the total duration were 18.7 (7.1), 26.6 (8.8) and 50.6 (16.0) min respectively in men and 26.0 (7.2), 37.1 (11.2) and 65.9 (20.7) min in women. They differed significantly between men and women (P < 0.005 in each case).

  7. Filtering, Smoothing, and Extrapolations in Dose-Response Experiments: With Application to Data on Respiratory Tumor in Rats.

    DTIC Science & Technology

    1990-01-01

    A method for inference and extrapolations in certain dose- response. damage-assessments and accelerated life-testing studies as been proposed by...Meinhold and Singpurwalla in 1986. The method is based on a use of the Kalman-filter algorithm and involves the double lognormal as the distributional...assumption. In this paper we discuss issues pertaining to a practical implementation of this methodology . This involves some insights based on a

  8. Dose-response studies on the spermatogonial stem cells of the rhesus monkey (Macaca mulatta) after X irradiation

    SciTech Connect

    van Alphen, M.M.; van de Kant, H.J.; Davids, J.A.; Warmer, C.J.; Bootsma, A.L.; de Rooij, D.G. )

    1989-09-01

    Studies of the dose response of the spermatogonial stem cells in the rhesus monkey were performed at intervals of 130 and 160 days after graded doses of X irradiation. The D0 of the spermatogonial stem cells was established using the total numbers of the type A spermatogonia that were present at 130 and 160 days after irradiation and was found to be 1.07 Gy; the 95% confidence interval was 0.90-1.34 Gy.

  9. Resting heart rate and risk of metabolic syndrome in adults: a dose-response meta-analysis of observational studies.

    PubMed

    Liu, Xuejiao; Luo, Xinping; Liu, Yu; Sun, Xizhuo; Han, Chengyi; Zhang, Lu; Wang, Bingyuan; Ren, Yongcheng; Zhao, Yang; Zhang, Dongdong; Hu, Dongsheng; Zhang, Ming

    2017-03-01

    The magnitude of the risk of metabolic syndrome (MetS) with increased resting heart rate (RHR) has been inconsistently reported in some observational studies, and whether a dose-response relationship exists between RHR and MetS is unclear. We performed a meta-analysis including dose-response analysis to quantitatively evaluate this association in adults. We searched PubMed, Web of Knowledge, China National Knowledge Infrastructure, and WanFang databases for articles published up to April 2, 2016. A random-effects model was used to pool relative risks (RRs) and 95% confidence intervals (CIs); restricted cubic spline function was used to assess the dose-response relationship. Seven prospective cohort studies and 10 cross-sectional studies with a total of 169,786 participants were included. The pooled RR was 2.10 (95% CI 1.80-2.46, I (2) = 79.8%, n = 13) for the highest versus reference RHR category and 1.28 (95% CI 1.23-1.34, I (2) = 87.7%, n = 15) for each 10 beats per minute (bpm) increment in RHR. We found no evidence of a nonlinear dose-response association between RHR and MetS (P nonlinearity = 0.201). The relationship was consistent in most subgroup analyses and robust on sensitivity analysis. No significant publication bias was observed. This meta-analysis suggests that risk of MetS may be increased with elevated RHR.

  10. Light exposure at night, sleep duration, melatonin, and breast cancer: a dose-response analysis of observational studies.

    PubMed

    Yang, Wan-Shui; Deng, Qin; Fan, Wen-Yan; Wang, Wei-Ye; Wang, Xin

    2014-07-01

    Evidence from observational studies on light at night (LAN) exposure, sleep duration, endogenous melatonin levels, and risk for breast cancer in women is conflicting. This led us to conduct a dose-response analysis of published observational data. Pertinent studies were identified by searching Medline, Web of Science, and EMBASE through April 2013. The dose-response relationship between sleep duration, urinary 6-sulphatoxymelatonin levels, and breast cancer was assessed using the restricted cubic spline model and by multivariate random-effects metaregression. A separate meta-analysis was also carried out to calculate the relative risks (RRs) with 95% confidence intervals (CIs) for breast cancer for the comparable categories or highest levels of exposure versus the lowest levels. Twelve case-control and four cohort studies were included in the analysis. High artificial LAN exposure is associated with an increased risk for breast cancer (RR=1.17, 95% CI: 1.11-1.23), but not ambient LAN exposure (RR=0.91, 95% CI: 0.78-1.07). The summary RR for breast cancer is 1.00 (95% CI: 0.995-1.01) for an increment of 1 h of sleep per night. No significant dose-response relationship between sleep duration and breast cancer was found either for the linearity test (Ptrend=0.725) or for the nonlinearity (Ptrend=0.091) test. An increasein of 15 ng/mg creatinine in urinary 6-sulphatoxymelatonin is associated with a 14% reduced risk for breast cancer (RR=0.86, 95% CI: 0.78-0.95), with a linear dose-response trend (Ptrend=0.003). There was no evidence of substantial heterogeneity or publication bias in the analysis. Our study adds to the evidence of LAN breast cancer theory. Further research in this area is warranted.

  11. Application of a key events dose-response analysis to nutrients: a case study with vitamin A (retinol).

    PubMed

    Ross, A Catharine; Russell, Robert M; Miller, Sanford A; Munro, Ian C; Rodricks, Joseph V; Yetley, Elizabeth A; Julien, Elizabeth

    2009-09-01

    The methodology used to establish tolerable upper intake levels (UL) for nutrients borrows heavily from risk assessment methods used by toxicologists. Empirical data are used to identify intake levels associated with adverse effects, and Uncertainty Factors (UF) are applied to establish ULs, which in turn inform public health decisions and standards. Use of UFs reflects lack of knowledge regarding the biological events that underlie response to the intake of a given nutrient, and also regarding the sources of variability in that response. In this paper, the Key Events Dose-Response Framework (KEDRF) is used to systematically consider the major biological steps that lead from the intake of the preformed vitamin A to excess systemic levels, and subsequently to increased risk of adverse effects. Each step is examined with regard to factors that influence whether there is progression toward the adverse effect of concern. The role of homeostatic mechanisms is discussed, along with the types of research needed to improve understanding of dose-response for vitamin A. This initial analysis illustrates the potential of the KEDRF as a useful analytical tool for integrating current knowledge regarding dose-response, generating questions that will focus future research efforts, and clarifying how improved knowledge and data could be used to reduce reliance on UFs.

  12. Diverse dose-response effects of yolk androgens on embryo development and nestling growth in a wild passerine.

    PubMed

    Muriel, Jaime; Pérez-Rodríguez, Lorenzo; Puerta, Marisa; Gil, Diego

    2015-07-01

    Avian egg yolks contain various amounts of maternally derived androgens that can modify offspring phenotype and adjust their development to the post-hatching environment. Seemingly adaptive variation in yolk androgen levels with respect to breeding density conditions or male attractiveness has been found in numerous studies. One important consideration that has been overlooked in previous research is the likely non-linear nature of hormone effects. To examine possible complex dose-response effects of maternal androgens on chick development, we experimentally administered three different androgen doses of the naturally occurring mixture of yolk testosterone and androstenedione to spotless starling eggs (Sturnus unicolor). We found that yolk androgens induce a non-linear dose-response pattern in several traits. Androgens had a stimulatory effect on hatchling body mass and nestling skeletal growth, but maximum values were found at intermediate doses, whereas our highest dose resulted in a decrease. However, the opposite U-shaped effect was found on nestling body mass. We also detected linear negative and positive effects on embryonic development period and nestling gape width, respectively. Our results suggest differential tissue responsiveness to yolk androgens, which may result in compromises in maternal allocation to produce adapted phenotypes. Because of the non-linear dose-response pattern, future investigations should carefully consider a wide range of concentrations, as the balance of costs and benefits may strongly differ depending on concentration.

  13. Spatial Prediction of Coxiella burnetii Outbreak Exposure via Notified Case Counts in a Dose-Response Model.

    PubMed

    Brooke, Russell J; Kretzschmar, Mirjam E E; Hackert, Volker; Hoebe, Christian J P A; Teunis, Peter F M; Waller, Lance A

    2017-01-01

    We develop a novel approach to study an outbreak of Q fever in 2009 in the Netherlands by combining a human dose-response model with geostatistics prediction to relate probability of infection and associated probability of illness to an effective dose of Coxiella burnetii. The spatial distribution of the 220 notified cases in the at-risk population are translated into a smooth spatial field of dose. Based on these symptomatic cases, the dose-response model predicts a median of 611 asymptomatic infections (95% range: 410, 1,084) for the 220 reported symptomatic cases in the at-risk population; 2.78 (95% range: 1.86, 4.93) asymptomatic infections for each reported case. The low attack rates observed during the outbreak range from (Equation is included in full-text article.)to (Equation is included in full-text article.). The estimated peak levels of exposure extend to the north-east from the point source with an increasing proportion of asymptomatic infections further from the source. Our work combines established methodology from model-based geostatistics and dose-response modeling allowing for a novel approach to study outbreaks. Unobserved infections and the spatially varying effective dose can be predicted using the flexible framework without assuming any underlying spatial structure of the outbreak process. Such predictions are important for targeting interventions during an outbreak, estimating future disease burden, and determining acceptable risk levels.

  14. Low blood lead level effects on intelligence: can a dose-response curve be determined from the epidemiological data?

    PubMed

    Banner, W; Kahn, C M

    2014-02-01

    CONTEXT. Recent publications have graphically demonstrated a curvilinear relationship between measures of intelligence and blood lead levels at low concentrations (< 10 mcg/dl). This led to speculation that a greater biologic effect occurs at lower concentrations. Critics of this conclusion hypothesized that this graphical relationship may be a function of the underlying distributions of these variables. OBJECTIVE. To study the impact of the distribution of data on the shape of apparent dose-response curves. METHODS. Random data based on varied distributions were constructed to simulate a previous study using a single, randomly generated covariate income (Inc) to demonstrate the impact of normally versus exponentially distributed data on the shape of the graph of intelligence quotient (IQ) versus blood lead. We also used an existing database of US blood lead levels and constructed a similar model of income and IQ using both assumptions of distribution for the intermediate variable income. RESULTS. When both lead and income are exponentially distributed, the graph of lead and IQ will be a curve. CONCLUSION. The apparent shape of a dose-response relationship from simulated epidemiological data is nonlinear when one variable and a covariate are exponentially distributed. A non-linear biological relationship should not be assumed and in fact may be the least likely explanation. The use of observational epidemiological data to discern a dose-response relationship between two variables may be misleading.

  15. Folate intake, serum folate levels and esophageal cancer risk: an overall and dose-response meta-analysis.

    PubMed

    Zhao, Yan; Guo, Chenyang; Hu, Hongtao; Zheng, Lin; Ma, Junli; Jiang, Li; Zhao, Erjiang; Li, Hailiang

    2017-02-07

    Previously reported findings on the association between folate intake or serum folate levels and esophageal cancer risk have been inconsistent. This study aims to summarize the evidence regarding these relationships using a dose-response meta-analysis approach. We performed electronic searches of the Pubmed, Medline and Cochrane Library electronic databases to identify studies examining the effect of folate on the risk of esophageal cancer. Ultimately, 19 studies were included in the meta-analysis. Summary odds ratios (ORs) were estimated using a random effects model. A linear regression analysis of the natural logarithm of the OR was carried out to assess the possible dose-response relationship between folate intake and esophageal cancer risk. The pooled ORs for esophageal cancer in the highest vs. lowest levels of dietary folate intake and serum folate were 0.63 (95% CI: 0.56-0.71) and 0.71 (95% CI: 0.55-0.92), respectively. The dose-response meta-analysis indicated that a 100 μg/day increment in dietary folate intake reduced the estimate risk of esophageal cancer by 12%. These findings suggest that dietary and serum folate exert a protective effect against esophageal carcinogenesis.

  16. Linear and non-linear dose-response functions reveal a hormetic relationship between stress and learning.

    PubMed

    Zoladz, Phillip R; Diamond, David M

    2008-10-16

    Over a century of behavioral research has shown that stress can enhance or impair learning and memory. In the present review, we have explored the complex effects of stress on cognition and propose that they are characterized by linear and non-linear dose-response functions, which together reveal a hormetic relationship between stress and learning. We suggest that stress initially enhances hippocampal function, resulting from amygdala-induced excitation of hippocampal synaptic plasticity, as well as the excitatory effects of several neuromodulators, including corticosteroids, norepinephrine, corticotropin-releasing hormone, acetylcholine and dopamine. We propose that this rapid activation of the amygdala-hippocampus brain memory system results in a linear dose-response relation between emotional strength and memory formation. More prolonged stress, however, leads to an inhibition of hippocampal function, which can be attributed to compensatory cellular responses that protect hippocampal neurons from excitotoxicity. This inhibition of hippocampal functioning in response to prolonged stress is potentially relevant to the well-described curvilinear dose-response relationship between arousal and memory. Our emphasis on the temporal features of stress-brain interactions addresses how stress can activate, as well as impair, hippocampal functioning to produce a hormetic relationship between stress and learning.

  17. Design and sample size for evaluating combinations of drugs of linear and loglinear dose-response curves.

    PubMed

    Fang, Hong-Bin; Tian, Guo-Liang; Li, Wei; Tan, Ming

    2009-07-01

    The study of drug combinations has become important in drug development due to its potential for efficacy at lower, less toxic doses and the need to move new therapies rapidly into clinical trials. The goal is to identify which combinations are additive, synergistic, or antagonistic. Although there exists statistical framework for finding doses and sample sizes needed to detect departure from additivity, e.g., the power maximized F-test, different classes of drugs of different does-response shapes require different derivation for calculating sample size and finding doses. Motivated by two anticancer combination studies that we are involved with, this article proposes dose-finding and sample size method for detecting departures from additivity of two drugs with linear and log-linear single dose-response curves. The first study involves combination of two drugs, where one single drug dose-response curve is linear and the other is log-linear. The second study involves combinations of drugs whose single drug dose-response curves are linear. The experiment had been planned with the common fixed ratio design before we were consulted, but the resulting data missed the synergistic combinations. However, the experiment based on the proposed design was able to identify the synergistic combinations as anticipated. Thus we shall summarize the analysis of the data collected according to the proposed design and discuss why the commonly used fixed ratio method failed and the implications of the proposed method for other combination studies.

  18. Influence of the Culture Medium in Dose-Response Effect of the Chlorhexidine on Streptococcus mutans Biofilms

    PubMed Central

    de Queiroz, Vanessa Salvadego; Ccahuana-Vásquez, Renzo Alberto; Tedesco, Alcides Fabiano; Lyra, Luzia; Cury, Jaime Aparecido; Schreiber, Angélica Zaninelli

    2016-01-01

    The aim of this study was to evaluate the influence of culture medium on dose-response effect of chlorhexidine (CHX) on Streptococcus mutans UA159 biofilm and validate the use of the cation-adjusted-Müller-Hinton broth (MH) for the evaluation of antibacterial activity. Ultrafiltered Tryptone-Yeast Extract Broth (UTYEB) was compared against MH and MH with blood supplementation (MHS). For each medium, six groups (n = 4) were assessed: two negative control groups (baseline 48 and 120 h) and four experimental groups (0.0001, 0.001, 0.012, and 0.12% CHX). S. mutans biofilm grew on glass slides of each media containing 1% sucrose. After 48 h of growth, biofilms of baseline 48 h were collected and the other groups were treated for 1 min, twice a day, for 3 days, with their respective treatments. The media were changed daily and pH was measured. After 120 h, biofilms were collected and dry weight and viable microorganisms were determined. Results showed CHX dose-response effect being observed in all media for all the variables. However, MH and MHS showed higher sensitivity than UTYEB (p < 0.05). We can conclude that the culture medium does influence dose-response effect of CHX on Streptococcus mutans biofilm and that MH can be used for antibacterial activity. PMID:27293967

  19. Dose-response of x-ray-induced anaphase aberrations in the mitotic root tip chromosomes of allium

    SciTech Connect

    Ma, T.H.; Lee, K.H.; Kong, M.S.

    1995-11-01

    A simplified Allium root mitotic chromosome aberration assay by using only the aberrant anaphases (fragments, laggards and bridges) as the end-points were developed by Rank and Nielsen (1993) for screening water soluble chemicals and complex mixtures. A dose-response curve was established by Meir et al., (1994) using a known clastogen, 4-nitroquinolene-N-oxide between the dose range of 0.1-0.5 ug/ml. In order to further validate this assay for clastogen detection, a series of X-ray dose response experiments was carried out. Allium roots were germinated in tapwater for 48 h and treated with a series of 10, 20, 30, 40, 50, 60 R (80 Kvp, 5 ma, dose rate 60 R/min) dosages. After an 18 hr recovery time, the root tips were hydrolyzed in 45% acetic and 1 N HC1 acid (9:1 ratio) solution under 50{degrees} C for 5 min and stained with aceto-carmine. Each of the data points were derived from scoring 7-10 slides (15-50 anaphases/slide). The corrrelation coefficient, slope and intercept values of the dose-response curve are: 0.954, 0.515 and 1.155 respectively.

  20. Application of a Key Events Dose-Response Analysis to Nutrients: A Case Study with Vitamin A (Retinol)

    PubMed Central

    ROSS, A. CATHARINE; RUSSELL, ROBERT M.; MILLER, SANFORD A.; MUNRO, IAN C.; RODRICKS, JOSEPH V.; YETLEY, ELIZABETH A.; JULIEN, ELIZABETH

    2009-01-01

    The methodology used to establish tolerable upper intake levels (UL) for nutrients borrows heavily from risk assessment methods used by toxicologists. Empirical data are used to identify intake levels associated with adverse effects, and Uncertainty Factors (UF) are applied to establish ULs, which in turn inform public health decisions and standards. Use of UFs reflects lack of knowledge regarding the biological events that underlie response to the intake of a given nutrient, and also regarding the sources of variability in that response. In this paper, the Key Events Dose-Response Framework (KEDRF) is used to systematically consider the major biological steps that lead from the intake of the preformed vitamin A to excess systemic levels, and subsequently to increased risk of adverse effects. Each step is examined with regard to factors that influence whether there is progression toward the adverse effect of concern. The role of homeostatic mechanisms is discussed, along with the types of research needed to improve understanding of dose-response for vitamin A. This initial analysis illustrates the potential of the KEDRF as a useful analytical tool for integrating current knowledge regarding dose-response, generating questions that will focus future research efforts, and clarifying how improved knowledge and data could be used to reduce reliance on UFs. PMID:19690996

  1. In situ protocol for the determination of dose-response effect of low-fluoride dentifrices on enamel remineralization

    PubMed Central

    AFONSO, Rebeca Lima; PESSAN, Juliano Pelim; IGREJA, Bruna Babler; CANTAGALLO, Camila Fernandes; DANELON, Marcelle; DELBEM, Alberto Carlos Botazzo

    2013-01-01

    No in situ protocol has assessed the dose-response effects of fluoride dentifrices involving low-fluoride formulations. Objective To assess the ability of an in situ remineralization model in determining dose-response effects of dentifrices containing low fluoride concentrations ([F]) on bovine enamel. Material and Methods Volunteers wore palatal appliances containing demineralized enamel blocks and brushed their teeth and devices with the dentifrices supplied (double-blind, crossover protocol) separately for 3 and 7 days. Surface hardness (SH), integrated subsurface hardness (ΔKHN) and [F] in enamel were determined. Data were analyzed by ANOVA, Tukey's test and Pearson's correlation (p<0.05). Results Dose-response relationships were verified between [F] in dentifrices and SH, ΔKHN and enamel [F]. Higher correlation coefficients between enamel [F] and SH and ΔKHN were obtained for the 3-day period. Significant differences in SH and ΔKHN were observed among all groups for the 3-day period, but not between 0-275, 275-550, and 550-1,100 µg F/g dentifrices for the 7-day period, nor between 3- and 7-day periods for the 1,100 µg F/g groups. Conclusions Considering that the peak remineralization capacity of the conventional dentifrice (1,100 µg F/g) was achieved in 3 days, this experimental period could be used in future studies assessing new dentifrice formulations, especially at low-fluoride concentrations. PMID:24473718

  2. Dose-response relation between arsenic concentration in well water and mortality from cancers and vascular diseases

    SciTech Connect

    Wu, M.M.; Kuo, T.L.; Hwang, Y.H.; Chen, C.J. )

    1989-12-01

    Age-adjusted mortality rates were analyzed to examine the dose-response relation between ingested arsenic levels and risk of cancers and vascular diseases among residents in the endemic area of blackfoot disease, a unique peripheral vascular disease associated with long-term exposure to high-arsenic artesian well water and confined to the southwestern coast of Taiwan. The arsenic levels in well water determined in 1964-1966 were available in 42 villages of the study area, while mortality and population data during 1973-1986 were obtained from the local household registration offices and Taiwan Provincial Department of Health. Age-adjusted mortality rates from various cancers and vascular diseases by sex were calculated using the 1976 world population as the standard population. A significant dose-response relation was observed between arsenic levels in well water and cancers of the bladder, kidney, skin, and lung in both males and females, and cancers of the prostate and liver in males. However, there was no association for cancers of the nasopharynx, esophagus, stomach, colon, and uterine cervix, and for leukemia. Arsenic levels in well water were also associated with peripheral vascular diseases and cardiovascular diseases in a dose-response pattern, but not with cerebrovascular accidents. The dual effect of arsenic on carcinogenesis and arteriosclerosis and the interrelation between these two pathogenic mechanisms deserve more intensive study.

  3. Influence of the Culture Medium in Dose-Response Effect of the Chlorhexidine on Streptococcus mutans Biofilms.

    PubMed

    de Queiroz, Vanessa Salvadego; Ccahuana-Vásquez, Renzo Alberto; Tedesco, Alcides Fabiano; Lyra, Luzia; Cury, Jaime Aparecido; Schreiber, Angélica Zaninelli

    2016-01-01

    The aim of this study was to evaluate the influence of culture medium on dose-response effect of chlorhexidine (CHX) on Streptococcus mutans UA159 biofilm and validate the use of the cation-adjusted-Müller-Hinton broth (MH) for the evaluation of antibacterial activity. Ultrafiltered Tryptone-Yeast Extract Broth (UTYEB) was compared against MH and MH with blood supplementation (MHS). For each medium, six groups (n = 4) were assessed: two negative control groups (baseline 48 and 120 h) and four experimental groups (0.0001, 0.001, 0.012, and 0.12% CHX). S. mutans biofilm grew on glass slides of each media containing 1% sucrose. After 48 h of growth, biofilms of baseline 48 h were collected and the other groups were treated for 1 min, twice a day, for 3 days, with their respective treatments. The media were changed daily and pH was measured. After 120 h, biofilms were collected and dry weight and viable microorganisms were determined. Results showed CHX dose-response effect being observed in all media for all the variables. However, MH and MHS showed higher sensitivity than UTYEB (p < 0.05). We can conclude that the culture medium does influence dose-response effect of CHX on Streptococcus mutans biofilm and that MH can be used for antibacterial activity.

  4. Different behavioral effect dose-response profiles in mice exposed to two-carbon chlorinated hydrocarbons: influence of structural and physical properties.

    PubMed

    Umezu, Toyoshi; Shibata, Yasuyuki

    2014-09-01

    The present study aimed to clarify whether dose-response profiles of acute behavioral effects of 1,2-dichloroethane (DCE), 1,1,1-trichloroethane (TCE), trichloroethylene (TRIC), and tetrachloroethylene (PERC) differ. A test battery involving 6 behavioral endpoints was applied to evaluate the effects of DCE, TCE, TRIC, and PERC in male ICR strain mice under the same experimental conditions. The behavioral effect dose-response profiles of these compounds differed. Regression analysis was used to evaluate the relationship between the dose-response profiles and structural and physical properties of the compounds. Dose-response profile differences correlated significantly with differences in specific structural and physical properties. These results suggest that differences in specific structural and physical properties of DCE, TCE, TRIC, and PERC are responsible for differences in behavioral effects that lead to a variety of dose-response profiles.

  5. Modeling the dose-response relationship for cytotoxicity of human cells exposed to chemical carcinogens. [N-acetoxy-2-acetylaminofluorene

    SciTech Connect

    Miller, J.H.; Heflich, R.H.

    1980-09-01

    Compounds like N-acetoxy-2-acetylaminofluorene (N-AcO-AAF) result from the in vivo reduction of nitrate derivatives of benzo(..cap alpha..)pyrene. The dose-response relationship for survival of cloning ability in human fibroblasts exposed to N-AcO-AAF is being investigated to obtain a better understanding of the carcinogenic potential of coal-related air pollutants. A model is presented which correlates the survival of normal human fibroblasts after exposure to N-AcO-AAF with the rate of excision of carcinogen residues bound to DNA. The model predicts that the survival of normal cells, S/sub N/, is related to the survival of repair deficient cells, S/sub XPA/, by the equation 1n(S/sub N/) = 1n(S/sub XPA/) (1-f) where f is the fraction of potentially lethal damage repaired in the normal cell at a given dose of carcinogen. The rate of excision of AAF residues from the DNA of confluent human fibroblasts was measured over the same dose range as the survival studies. This information together with the dose-response relationship for survival of normal and repair deficient cells permits a determination of the mean number of adducts required to produce a potentially lethal lesion and the effective time available for repair. The model can be used to predict the mean lifetime of carcinogen residues on the DNA of partially repair deficient cells and the effect of recovery on the survival of normal cells. Extensions of the model to account for shoulders on the dose-response relationship curves are also discussed.

  6. Dose-Response Relationship between Alanine Aminotransferase Levels within the Reference Interval and Metabolic Syndrome in Chinese Adults

    PubMed Central

    Wu, Peipei; Chen, Qicai; Chen, Lili; Zhang, Pengpeng; Xiao, Juan; Chen, Xiaoxiao; Liu, Meng

    2017-01-01

    Purpose Elevation in serum alanine aminotransferase (ALT) levels is a biomarker for metabolic syndrome (MS); however, the relationship has not been fully investigated within the reference interval of ALT levels. Our objective was to explore the relationship between serum ALT levels within the reference interval and MS in Chinese adults. Materials and Methods This cross-sectional study included 16028 adults, who attended routine health check-ups at Shengli Oilfield Central Hospital from January 2006 to March 2012. The reference interval of serum ALT level was defined as less than 40 U/L. Logistic regression models and restricted cubic spline were used to evaluate the association of ALT with MS. Results The prevalence of MS in the total population was 13.7% (6.4% for females and 18.4% for males). Multiple logistic regression showed that ALT levels were positively associated with MS after adjustment for potential confounding factors. The odds ratio of MS in the top quartile was 4.830 [95% confidence interval (CI): 2.980–7.829] in females and 3.168 (95% CI: 2.649–3.790) in males, compared with the ALT levels in the bottom quartile. The restricted cubic spline models revealed a positive non-linear dose-response relationship between ALT levels and the risk of MS in women (p for nonlinearity was 0.0327), but a positive linear dose-response relationship in men (p for nonlinearity was 0.0659). Conclusion Serum ALT levels within the reference interval are positively associated with MS in a dose-response manner. Elevated ALT levels, even within the reference interval, may reflect early dysmetabolic changes. PMID:27873509

  7. Second Solid Cancers After Radiation Therapy: A Systematic Review of the Epidemiologic Studies of the Radiation Dose-Response Relationship

    SciTech Connect

    Berrington de Gonzalez, Amy; Gilbert, Ethel; Curtis, Rochelle; Inskip, Peter; Kleinerman, Ruth; Morton, Lindsay; Rajaraman, Preetha; Little, Mark P.

    2013-06-01

    Rapid innovations in radiation therapy techniques have resulted in an urgent need for risk projection models for second cancer risks from high-dose radiation exposure, because direct observation of the late effects of newer treatments will require patient follow-up for a decade or more. However, the patterns of cancer risk after fractionated high-dose radiation are much less well understood than those after lower-dose exposures (0.1-5 Gy). In particular, there is uncertainty about the shape of the dose-response curve at high doses and about the magnitude of the second cancer risk per unit dose. We reviewed the available evidence from epidemiologic studies of second solid cancers in organs that received high-dose exposure (>5 Gy) from radiation therapy where dose-response curves were estimated from individual organ-specific doses. We included 28 eligible studies with 3434 second cancer patients across 11 second solid cancers. Overall, there was little evidence that the dose-response curve was nonlinear in the direction of a downturn in risk, even at organ doses of ≥60 Gy. Thyroid cancer was the only exception, with evidence of a downturn after 20 Gy. Generally the excess relative risk per Gray, taking account of age and sex, was 5 to 10 times lower than the risk from acute exposures of <2 Gy among the Japanese atomic bomb survivors. However, the magnitude of the reduction in risk varied according to the second cancer. The results of our review provide insights into radiation carcinogenesis from fractionated high-dose exposures and are generally consistent with current theoretical models. The results can be used to refine the development of second solid cancer risk projection models for novel radiation therapy techniques.

  8. Editor's Highlight: Dose-Response Analysis of RNA-Seq Profiles in Archival Formalin-Fixed Paraffin-Embedded Samples.

    PubMed

    Hester, Susan D; Bhat, Virunya; Chorley, Brian N; Carswell, Gleta; Jones, Wendell; Wehmas, Leah C; Wood, Charles E

    2016-12-01

    Use of archival resources has been limited to date by inconsistent methods for genomic profiling of degraded RNA from formalin-fixed paraffin-embedded (FFPE) samples. RNA-sequencing offers a promising way to address this problem. Here, we evaluated transcriptomic dose responses using RNA-sequencing in paired FFPE and frozen (FROZ) samples from 2 archival studies in mice, one <2 years old and the other >20 years old. Experimental treatments included 3 different doses of di(2-ethylhexyl)phthalate or dichloroacetic acid for the recently archived and older studies, respectively. Total RNA was ribo-depleted and sequenced using the Illumina HiSeq platform. In the recently archived study, FFPE samples had 35% lower total counts compared to FROZ samples but high concordance in fold-change values of differentially expressed genes (DEGs) (r(2)  =( )0.99), highly enriched pathways (90% overlap with FROZ), and benchmark dose estimates for preselected target genes (<5% difference vs FROZ). In contrast, older FFPE samples had markedly lower total counts (3% of FROZ) and poor concordance in global DEGs and pathways. However, counts from FFPE and FROZ samples still positively correlated (r(2 ) = 0.84 across all transcripts) and showed comparable dose responses for more highly expressed target genes. These findings highlight potential applications and issues in using RNA-sequencing data from FFPE samples. Recently archived FFPE samples were highly similar to FROZ samples in sequencing quality metrics, DEG profiles, and dose-response parameters, while further methods development is needed for older lower-quality FFPE samples. This work should help advance the use of archival resources in chemical safety and translational science.

  9. Methods for meta-analysis of pharmacodynamic dose-response data with application to multi-arm studies of alogliptin.

    PubMed

    Langford, Oliver; Aronson, Jeffrey K; van Valkenhoef, Gert; Stevens, Richard J

    2016-03-17

    Standard methods for meta-analysis of dose-response data in epidemiology assume a model with a single scalar parameter, such as log-linear relationships between exposure and outcome; such models are implicitly unbounded. In contrast, in pharmacology, multi-parameter models, such as the widely used Emax model, are used to describe relationships that are bounded above and below. We propose methods for estimating the parameters of a dose-response model by meta-analysis of summary data from the results of randomized controlled trials of a drug, in which each trial uses multiple doses of the drug of interest (possibly including dose 0 or placebo). We assume that, for each randomized arm of each trial, the mean and standard error of a continuous response measure and the corresponding allocated dose are available. We consider weighted least squares fitting of the model to the mean and dose pairs from all arms of all studies, and a two-stage procedure in which scalar inverse-variance meta-analysis is performed at each dose, and the dose-response model is fitted to the results by weighted least squares. We then compare these with two further methods inspired by network meta-analysis that fit the model to the contrasts between doses. We illustrate the methods by estimating the parameters of the Emax model to a collection of multi-arm, multiple-dose, randomized controlled trials of alogliptin, a drug for the management of diabetes mellitus, and further examine the properties of the four methods with sensitivity analyses and a simulation study. We find that all four methods produce broadly comparable point estimates for the parameters of most interest, but a single-stage method based on contrasts between doses produces the most appropriate confidence intervals. Although simpler methods may have pragmatic advantages, such as the use of standard software for scalar meta-analysis, more sophisticated methods are nevertheless preferable for their advantages in estimation.

  10. Dose-response curve slope is a missing dimension in the analysis of HIV-1 drug resistance.

    PubMed

    Sampah, Maame Efua S; Shen, Lin; Jilek, Benjamin L; Siliciano, Robert F

    2011-05-03

    HIV-1 drug resistance is a major clinical problem. Resistance is evaluated using in vitro assays measuring the fold change in IC(50) caused by resistance mutations. Antiretroviral drugs are used at concentrations above IC(50), however, and inhibition at clinical concentrations can only be predicted from IC(50) if the shape of the dose-response curve is also known. Curve shape is influenced by cooperative interactions and is described mathematically by the slope parameter or Hill coefficient (m). Implicit in current analysis of resistance is the assumption that mutations shift dose-response curves to the right without affecting the slope. We show here that m is altered by resistance mutations. For reverse transcriptase and fusion inhibitors, single resistance mutations affect both slope and IC(50). For protease inhibitors, single mutations primarily affect slope. For integrase inhibitors, only IC(50) is affected. Thus, there are fundamental pharmacodynamic differences in resistance to different drug classes. Instantaneous inhibitory potential (IIP), the log inhibition of single-round infectivity at clinical concentrations, takes into account both slope and IC(50), and thus provides a direct measure of the reduction in susceptibility produced by mutations and the residual activity of drugs against resistant viruses. The standard measure, fold change in IC(50), does not correlate well with changes in IIP when mutations alter slope. These results challenge a fundamental assumption underlying current analysis of HIV-1 drug resistance and suggest that a more complete understanding of how resistance mutations reduce antiviral activity requires consideration of a previously ignored parameter, the dose-response curve slope.

  11. Time-course, dose-response, and age comparative sensitivity of N-methyl carbamates in rats.

    PubMed

    Moser, Virginia C; McDaniel, Katherine L; Phillips, Pamela M; Lowit, Anna B

    2010-03-01

    N-Methyl carbamate insecticides are reversible inhibitors of central and peripheral acetylcholinesterase (ChE). Despite their widespread use, there are few studies of neurotoxicity in young animals. To study potential age-related differences, we evaluated seven carbamates (carbaryl, carbofuran, formetanate, methiocarb, methomyl, oxamyl, and propoxur) in preweanling (17 days old or postnatal day [PND] 17) male rats. Motor activity was monitored, and ChE inhibition was measured in brain and red blood cells (RBCs) using a radiometric assay that minimized reactivation of ChE. First, we conducted time-course studies in PND17 Long-Evans male rats, using a single oral dose of each carbamate. Almost all carbamates showed maximal ChE inhibition at a 45-min time point; only methomyl showed an earlier peak effect (15 min). At 24 h, most inhibition had recovered. Next, dose-response data were collected for each carbamate, using four doses and control, with motor activity testing beginning 15 min after dosing and tissue collection at 40-45 min. RBC ChE was generally inhibited to a greater degree than brain. Motor activity was not as sensitive a measure for some of the carbamates, with some differences across carbamates in the shapes of the dose-response curves. Additional studies documented age-related differences by comparing ChE inhibition in PND11, PND17, and adult rats following administration of carbaryl or carbofuran. Only the youngest (PND11) rats were more sensitive than adults to carbaryl, but both younger ages showed more effects than adults with carbofuran. Comparisons of the other carbamates to previous studies in adult rats suggest similar age-related sensitivity. Thus, these data show the time-course and dose-response characteristics for each carbamate and document greater sensitivity of the young for carbofuran and carbaryl.

  12. Dose-response impact of various tocotrienols on serum lipid parameters in 5-week-old female chickens.

    PubMed

    Yu, Suzanne G; Thomas, Ann M; Gapor, Abdul; Tan, Barrie; Qureshi, Nilofer; Qureshi, Asaf A

    2006-05-01

    The cholesterol-suppressive action of the tocotrienol-rich-fraction (TRF) of palm oil may be due to the effect of its constituent tocotrienols on beta-hydroxy-beta-methylglutaryl coenzyme A (HMG-CoA) reductase activity. The tocotrienols, modulate HMG-CoA reductase activity via a post-transcriptional mechanism. As a consequence small doses (5-200 ppm) of TRF-supplemented diets fed to experimental animals lower serum cholesterol levels. These findings led us to evaluate the safety and efficacy of large supplements of TRF and its constituents. Diets supplemented with 50, 100, 250, 500, 1000, or 2000 ppm of TRF, alpha-tocopherol, alpha-tocotrienol, gamma-tocotrienol, or 6-tocotrienol were fed to chickens for 4 wk. There were no differences between groups or within groups in weight gain, or in feed consumption at the termination of the feeding period. Supplemental TRF produced a dose-response (50-2000 ppm) lowering of serum total and LDL cholesterol levels of 22% and 52% (P < 0.05), respectively, compared with the control group. alpha-Tocopherol did not affect total or LDL-cholesterol levels. Supplemental alpha-tocotrienol within the 50-500 ppm range produced a dose-response lowering of total (17%) and LDL (33%) cholesterol levels. The more potent gamma and delta isomers yielded dose-response (50-2,000 ppm) reductions of serum total (32%) and LDL (66%) cholesterol levels. HDL cholesterol levels were minimally impacted by the tocotrienols; as a result, the HDL/LDL cholesterol ratios were markedly improved (123-150%) by the supplements. Serum triglyceride levels were significantly lower in sera of pullets receiving the higher supplements. The safe dose of various tocotrienols for human consumption might be 200-1000 mg/d based on this study.

  13. In Situ Dose-Response Relationships for a Mammalian Multiparameter Model for Assessing Petrochemical-Induced Ecotoxicity.

    DTIC Science & Technology

    2007-11-02

    r.z D^cae sf 1. AGENCY USE ONLY Heave blank) 2. REPORT DATE 3. REPORT TYPE AND DATES COVERED Final 01 Apr 95 To 31 Dec 97 4. TITLE AND...SUBTITLE IN SITU DOSE-RESPONSE RELATIONSHIPS FOR A MAMMALIAN MULTIPARAMETER MODEL FOR ASSESSING PETROCHEMICAL-INDUCED ECOTOXICITY > 61102F 5 ...MONITORING AGENCY NAME(S) AND ADDRESS(ES) ! AFOSR/NL 1 110 Duncan Ave Room B115 | Boiling AFB DC 20332- 8050 l Dr Walter Kozumbo 10. SPONSORING

  14. Ecological versus case-control studies for testing a linear-no threshold dose-response relationship.

    PubMed

    Cohen, B L

    1990-09-01

    The two basic problems with ecological studies are (A) individuals studied are not necessarily the individuals who are at risk, and (B) they are very vulnerable to confounding factors. It is shown that where the study is designed to test a linear-no threshold dose-response theory, (A) does not apply. Where the ecological study deals with the average dose and response in a large number of US counties, the available data and computer capability for reducing effects of confounders are so powerful that (B) may be no more important for the ecological than for a case-control study. The migration problem is treated and found to be relatively unimportant.

  15. SU-E-T-466: Implementation of An Extension Module for Dose Response Models in the TOPAS Monte Carlo Toolkit

    SciTech Connect

    Ramos-Mendez, J; Faddegon, B; Perl, J; Schuemann, J; Paganetti, H; Shin, J

    2015-06-15

    Purpose: To develop and verify an extension to TOPAS for calculation of dose response models (TCP/NTCP). TOPAS wraps and extends Geant4. Methods: The TOPAS DICOM interface was extended to include structure contours, for subsequent calculation of DVH’s and TCP/NTCP. The following dose response models were implemented: Lyman-Kutcher-Burman (LKB), critical element (CE), population based critical volume (CV), parallel-serials, a sigmoid-based model of Niemierko for NTCP and TCP, and a Poisson-based model for TCP. For verification, results for the parallel-serial and Poisson models, with 6 MV x-ray dose distributions calculated with TOPAS and Pinnacle v9.2, were compared to data from the benchmark configuration of the AAPM Task Group 166 (TG166). We provide a benchmark configuration suitable for proton therapy along with results for the implementation of the Niemierko, CV and CE models. Results: The maximum difference in DVH calculated with Pinnacle and TOPAS was 2%. Differences between TG166 data and Monte Carlo calculations of up to 4.2%±6.1% were found for the parallel-serial model and up to 1.0%±0.7% for the Poisson model (including the uncertainty due to lack of knowledge of the point spacing in TG166). For CE, CV and Niemierko models, the discrepancies between the Pinnacle and TOPAS results are 74.5%, 34.8% and 52.1% when using 29.7 cGy point spacing, the differences being highly sensitive to dose spacing. On the other hand, with our proposed benchmark configuration, the largest differences were 12.05%±0.38%, 3.74%±1.6%, 1.57%±4.9% and 1.97%±4.6% for the CE, CV, Niemierko and LKB models, respectively. Conclusion: Several dose response models were successfully implemented with the extension module. Reference data was calculated for future benchmarking. Dose response calculated for the different models varied much more widely for the TG166 benchmark than for the proposed benchmark, which had much lower sensitivity to the choice of DVH dose points. This work

  16. Biphasic and triphasic dose responses in zebrafish embryos to low-dose 150 kV X-rays with different levels of hardness

    PubMed Central

    Kong, Eva Yi; Cheng, Shuk Han; Yu, Kwan Ngok

    2016-01-01

    The in vivo low-dose responses of zebrafish (Danio rerio) embryos to 150 kV X-rays with different levels of hardness were examined through the number of apoptotic events revealed at 24 h post fertilization by vital dye acridine orange staining. Our results suggested that a triphasic dose response was likely a common phenomenon in living organisms irradiated by X-rays, which comprised an ultra-low-dose inhibition, low-dose stimulation and high-dose inhibition. Our results also suggested that the hormetic zone (or the stimulation zone) was shifted towards lower doses with application of filters. The non-detection of a triphasic dose response in previous experiments could likely be attributed to the use of hard X-rays, which shifted the hormetic zone into an unmonitored ultra-low-dose region. In such cases where the subhormetic zone was missed, a biphasic dose response would be reported instead. PMID:26951078

  17. Biologically Based Dose-Response Modeling. What is the potential for accurate description of the biological linkages in the applied dose - tissue dose-health effect continuum?

    EPA Science Inventory

    Given knowledge of exposure, the shape of the dose response curve is the key to predicting health risk, which in turn determines allowable levels of exposure and the associated economic costs of compliance.

  18. The Key Events Dose-Response Framework: A cross-Disciplinary Mode-of-Action Based Approach to Examining Does-Response and Thresholds

    EPA Science Inventory

    the ILSI Research Foundation conveded a cross-disciplinary working group to examine current approaches for assessing dose-response and identifying safe levels of intake or exposure for four categoreis of bioactive agents: food allergens, nutrients, pathogenic microorganisms, and ...

  19. Occupational Exposure to Diesel Motor Exhaust and Lung Cancer: A Dose-Response Relationship Hidden by Asbestos Exposure Adjustment? The ICARE Study

    PubMed Central

    Matrat, Mireille; Guida, Florence; Cénée, Sylvie; Févotte, Joelle; Carton, Matthieu; Cyr, Diane; Menvielle, Gwenn; Paget-Bailly, Sophie; Radoï, Loredana; Schmaus, Annie; Bara, Simona; Velten, Michel; Luce, Danièle; Stücker, Isabelle; The Icare Study Group

    2015-01-01

    Background. In a French large population-based case-control study we investigated the dose-response relationship between lung cancer and occupational exposure to diesel motor exhaust (DME), taking into account asbestos exposure. Methods. Exposure to DME was assessed by questionnaire. Asbestos was taken into account through a global indicator of exposure to occupational carcinogens or by a specific JEM. Results. We found a crude dose response relationship with most of the indicators of DME exposure, including with the cumulative exposure index. All results were affected by adjustment for asbestos exposure. The dose response relationships between DME and lung cancer were observed among subjects never exposed to asbestos. Conclusions. Exposure to DME and to asbestos is frequently found among the same subjects, which may explain why dose-response relationships in previous studies that adjusted for asbestos exposure were inconsistent. PMID:26425123

  20. Dose-response relationships for the onset of avoidance of sonar by free-ranging killer whales.

    PubMed

    Miller, Patrick J O; Antunes, Ricardo N; Wensveen, Paul J; Samarra, Filipa I P; Alves, Ana Catarina; Tyack, Peter L; Kvadsheim, Petter H; Kleivane, Lars; Lam, Frans-Peter A; Ainslie, Michael A; Thomas, Len

    2014-02-01

    Eight experimentally controlled exposures to 1-2 kHz or 6-7 kHz sonar signals were conducted with four killer whale groups. The source level and proximity of the source were increased during each exposure in order to reveal response thresholds. Detailed inspection of movements during each exposure session revealed sustained changes in speed and travel direction judged to be avoidance responses during six of eight sessions. Following methods developed for Phase-I clinical trials in human medicine, response thresholds ranging from 94 to 164 dB re 1 μPa received sound pressure level (SPL) were fitted to Bayesian dose-response functions. Thresholds did not consistently differ by sonar frequency or whether a group had previously been exposed, with a mean SPL response threshold of 142 ± 15 dB (mean ± s.d.). High levels of between- and within-individual variability were identified, indicating that thresholds depended upon other undefined contextual variables. The dose-response functions indicate that some killer whales started to avoid sonar at received SPL below thresholds assumed by the U.S. Navy. The predicted extent of habitat over which avoidance reactions occur depends upon whether whales responded to proximity or received SPL of the sonar or both, but was large enough to raise concerns about biological consequences to the whales.

  1. Radiation dose response simulation for biomechanical-based deformable image registration of head and neck cancer treatment

    NASA Astrophysics Data System (ADS)

    Al-Mayah, Adil; Moseley, Joanne; Hunter, Shannon; Brock, Kristy

    2015-11-01

    Biomechanical-based deformable image registration is conducted on the head and neck region. Patient specific 3D finite element models consisting of parotid glands (PG), submandibular glands (SG), tumor, vertebrae (VB), mandible, and external body are used to register pre-treatment MRI to post-treatment MR images to model the dose response using image data of five patients. The images are registered using combinations of vertebrae and mandible alignments, and surface projection of the external body as boundary conditions. In addition, the dose response is simulated by applying a new loading technique in the form of a dose-induced shrinkage using the dose-volume relationship. The dose-induced load is applied as dose-induced shrinkage of the tumor and four salivary glands. The Dice Similarity Coefficient (DSC) is calculated for the four salivary glands, and tumor to calculate the volume overlap of the structures after deformable registration. A substantial improvement in the registration is found by including the dose-induced shrinkage. The greatest registration improvement is found in the four glands where the average DSC increases from 0.53, 0.55, 0.32, and 0.37 to 0.68, 0.68, 0.51, and 0.49 in the left PG, right PG, left SG, and right SG, respectively by using bony alignment of vertebrae and mandible (M), body (B) surface projection and dose (D) (VB+M+B+D).

  2. Augmentation index (AI) in a dose-response relationship with smoking habits in males: The Tanushimaru study.

    PubMed

    Tsuru, Tomoko; Adachi, Hisashi; Enomoto, Mika; Fukami, Ako; Kumagai, Eita; Nakamura, Sachiko; Nohara, Yume; Kono, Shoko; Nakao, Erika; Sakaue, Akiko; Morikawa, Nagisa; Fukumoto, Yoshihiro

    2016-12-01

    We investigated the relationship between augmentation index (AI) and smoking habits in community-dwelling Japanese.This cross-sectional study enrolled 1926 subjects (769 males and 1157 females) aged 40 to 95 years who underwent a health check-up in a Japanese cohort of the Seven Countries Study, in Tanushimaru, a typical farming town in Kyushu Island in 2009. The subjects' medical history, alcohol intake, smoking habit, and current medications for hypertension, dyslipidemia, and diabetes were ascertained by questionnaire. Radial arterial pressure wave analysis was used to obtain AI. We analyzed the data stratified by gender.Age-adjusted means of AI in males showed a clear dose-response relationship in 4 categories of smoking habits (P = 0.010). There was no significant relationship between AI and smoking habits in females (P = 0.127). The significant dose-response relationship (P = 0.036) in males between AI and 4 categories of smoking habits still remained even after adjustment for age, body mass index, systolic blood pressure, estimated glomerular filtration rate, glucose, hypertensive medication, and alcohol intake.The present study demonstrated that AI values were significantly associated with smoking habits in a dose-dependent manner in Japanese males.

  3. Induction of MRSA Biofilm by Low-Dose β-Lactam Antibiotics: Specificity, Prevalence and Dose-Response Effects.

    PubMed

    Ng, Mandy; Epstein, Samuel B; Callahan, Mary T; Piotrowski, Brian O; Simon, Gary L; Roberts, Afsoon D; Keiser, John F; Kaplan, Jeffrey B

    2014-01-01

    Methicillin-resistant Staphylococcus aureus (MRSA) is a leading cause of hospital- and community-associated infections. The formation of adherent clusters of cells known as biofilms is an important virulence factor in MRSA pathogenesis. Previous studies showed that subminimal inhibitory (sub-MIC) concentrations of methicillin induce biofilm formation in the community-associated MRSA strain LAC. In this study we measured the ability sub-MIC concentrations of eight other β-lactam antibiotics and six non-β-lactam antibiotics to induce LAC biofilm. All eight β-lactam antibiotics, but none of the non-β-lactam antibiotics, induced LAC biofilm. The dose-response effects of the eight β-lactam antibiotics on LAC biofilm varied from biphasic and bimodal to near-linear. We also found that sub-MIC methicillin induced biofilm in 33 out of 39 additional MRSA clinical isolates, which also exhibited biphasic, bimodal and linear dose-response curves. The amount of biofilm formation induced by sub-MIC methicillin was inversely proportional to the susceptibility of each strain to methicillin. Our results demonstrate that induction of biofilm by sub-MIC antibiotics is a common phenotype among MRSA clinical strains and is specific for β-lactam antibiotics. These findings may have relevance to the use of β-lactam antibiotics in clinical and agricultural settings.

  4. Association between dietary vitamin C intake and risk of esophageal cancer: A dose-response meta-analysis.

    PubMed

    Bo, Yacong; Lu, Yan; Zhao, Yan; Zhao, Erjiang; Yuan, Ling; Lu, Weiquan; Cui, Lingling; Lu, Quanjun

    2016-04-15

    While several epidemiological studies have investigated the association between vitamin C and risk of esophageal cancer, the results remain inconsistent. In the present study, a meta-analysis was conducted to assess the impact of dietary vitamin C intake on esophageal cancer risk. Online databases were searched up to March 29, 2015, for studies on the association between dietary vitamin C intake and esophageal cancer risk. Pooled risk ratios (RRs) or odds ratios (ORs) and 95% confidence intervals (CIs) were calculated using a random-effects model. Dose-response analyses were performed using the method of restricted cubic splines with four knots at percentiles of 5, 35, 65 and 95% of the distribution. Publication bias was estimated using Egger's tests and funnel plots. In all, 15 articles were included in this meta-analysis, including 20 studies, containing 7063 controls and 3955 cases of esophageal cancer. By comparing the highest vs. the lowest categories of vitamin C intake, we found that vitamin C was inversely associated with the risk of esophageal cancer [overall OR = 0.58, 95% CI = 0.49-0.68, I(2) = 56%]. A linear dose-response relationship was found. With an increase in dietary vitamin C intake of 50 mg/day, the risk of esophageal cancer statistically decreased by 13% (OR = 0.87, 95% CI = 0.80-0.93, p(linearity) = 0.0002). In conclusion, our analysis suggested that the higher intake of dietary vitamin C might have a protective effect against esophageal cancer.

  5. Untargeted Metabolomics Reveals Dose-Response Characteristics for Effect of Rhubarb in a Rat Model of Cholestasis.

    PubMed

    Zhang, Cong-En; Niu, Ming; Li, Rui-Yu; Feng, Wu-Wen; Ma, Xiao; Dong, Qin; Ma, Zhi-Jie; Li, Guang-Quan; Meng, Ya-Kun; Wang, Ya; Yin, Ping; He, Lan-Zhi; Li, Yu-Meng; Tan, Peng; Zhao, Yan-Ling; Wang, Jia-Bo; Dong, Xiao-Ping; Xiao, Xiao-He

    2016-01-01

    Cholestasis is a serious manifestation of liver diseases with limited therapies. Rhubarb, a widely used herbal medicine, has been frequently used at a relatively large dose for treating cholestasis. However, whether large doses are optimal and the therapeutic mechanism remain unclear. To explore these questions, the anti-cholestatic effect of five doses of rhubarb (0.21, 0.66, 2.10, 6.60, and 21.0 g/kg) in an alpha-naphthylisothiocyanate (ANIT)-induced rat model of cholestasis was examined by histopathology and serum biochemistry. A dose-dependent anti-cholestatic effect of rhubarb (0.21-6.6 g/kg) was observed, and an overdose of 21.0 g/kg showed a poor effect. LC-MS-based untargeted metabolomics together with pathway analysis were further applied to characterize the metabolic alterations induced by the different rhubarb doses. Altogether, 13 biomarkers were identified. The dose-response curve based on nine important biomarkers indicated that doses in the 0.42-6.61 g/kg range (EC20-EC80 range, corresponding to 4.00-62.95 g in the clinic) were effective for cholestasis treatment. The pathway analysis showed that bile acid metabolism and excretion, inflammation and amino acid metabolism were altered by rhubarb in a dose-dependent manner and might be involved in the dose-response relationship and therapeutic mechanism of rhubarb for cholestasis treatment.

  6. Is There a Dose-Response Relationship of Cement Volume With Cement Leakage and Pain Relief After Vertebroplasty?

    PubMed

    Fu, Zhiyi; Hu, Xiaopeng; Wu, Yujie; Zhou, Zihui

    2016-01-01

    The aim of this study was to determine if there were dose-response relationships of cement volume with cement leakage and pain relief after percutaneous vertebroplasty (PVP) for osteoporosis vertebral compression fractures (OVCFs). We collected the patient and procedural characteristics on 108 patients with OVCFs in our hospital who received PVP. Univariate and multivariate analyses were performed to explore the relationships between these potential influential variables and cement leakage and pain relief at 1 month postoperatively. Multivariate linear and logistic regression analyses were conducted with the pain score reduction and the bone cement leakage as dependent variables and the potential risk factors as independent variables, respectively. The results showed that the independent risk factors for the pain relief were the cement volume injected and fracture age, and for bone cement leakage were the cement volume injected and low-viscosity cement. In conclusion, the present study indicated that there were positive dose-response correlation relationships of cement volume with the incidence of cement leakage and the degree of pain relief after PVP, respectively. Thus, the cement should be injected into the vertebrae as much as possible during the PVP procedure.

  7. Length of surgery and pressure ulcers risk in cardiovascular surgical patients: a dose-response meta-analysis.

    PubMed

    Chen, Hong-Lin; Shen, Wang-Qin; Liu, Peng; Liu, Kun

    2017-03-02

    The aim of this study was to assess the relationship between length of surgery (LOS) and pressure ulcer (PU) risk in cardiovascular surgery patients. PubMed and Web of Science were systematically searched. We compared LOS difference between PU (+) group and PU (-) group. We also examined the dose-response effect of this relationship. The mean LOS in the PU(+) groups ranged from 252·5 to 335·7 minutes, compared with 233·0 to 298·3 minutes in PU(-) groups. The LOS was higher in PU(+) groups compared with PU(-) groups [weighted mean difference (WMD) = 36·081 minutes; 95% CI: 21·640-50·522 minutes; Z = 4·90, P = 0·000]. The funnel plot showed no publication bias. A significant dose-response association was also found between the LOS and the risk of surgery-related pressure ulcers (SRPU, model χ(2)  = 9·29, P = 0·000). In the linear model, the PU OR was 1·296 (95% CI 1·097-1·531) for a 60-minute increase in the LOS intervals and 13·344 (95% CI 2·521-70·636) for a 600-minute increase. In a spline model, the OR of PU increased almost linearly along with the LOS. Our meta-analysis indicated that LOS was an important risk factor for pressure ulcers in cardiovascular surgical patients.

  8. Changing the Risk Paradigms Can be Good for Our Health: J-Shaped, Linear and Threshold Dose-Response Models.

    PubMed

    Ricci, P F; Straja, S R; Cox, A L

    2012-01-01

    Both the linear (at low doses)-no-threshold (LNT) and the threshold models (S-shapes) dose-response lead to no benefit from low exposure. We propose three new models that allow and include, but do not require - unlike LNT and S-shaped models - this strong assumption. We also provide the means to calculate benefits associated with bi-phasic biological behaviors, when they occur and propose:THREE HORMETIC (PHASIC) MODELS: the J-shaped, inverse J-shaped, the min-max, andMethod for calculating the direct benefits associated with the J and inverse J-shaped models.The J-shaped and min-max models for mutagens and carcinogenic agents include an experimentally justified repair stage for toxic and carcinogenic damage. We link these to stochastic transition models for cancer and show how abrupt transitions in cancer hazard rates, as functions of exposure concentrations and durations, can emerge naturally in large cell populations even when the rates of cell-level events increase smoothly (e.g., proportionally) with concentration. In this very general family of models, J-shaped dose-response curves emerge. These results are universal, i.e., independent of specific biological details represented by the stochastic transition networks. Thus, using them suggests a more complete and realistic way to assess risks at low doses or dose-rates.

  9. Limitations in dose-response and surrogate species methodologies for risk assessment of Cry toxins on arthropod natural enemies.

    PubMed

    Paula, Débora P; Andow, David A; Bellinati, André; Timbó, Renata Velozo; Souza, Lucas M; Pires, Carmen S S; Sujii, Edison R

    2016-04-01

    Dose-response assays and surrogate species are standard methods for risk analysis for environmental chemicals. These assume that individuals within a species have unimodal responses and that a surrogate species can predict responses of other related taxa. We exposed immature individuals of closely related aphidophagous coccinellid predators, Cycloneda sanguinea and Harmonia axyridis, to Cry1Ac and Cry1F toxins through uniform and constant artificial tritrophic exposure through Myzus persicae aphids. Both toxins were detected in coccinellid pupae, with individual and interspecific variation. Uptake was significantly higher in H. axyridis than in C. sanguinea, both in the proportion of individuals and the concentrations per individual. We also observed bimodal uptake of the Cry toxins by H. axyridis, which indicated that some individuals had low bioaccumulation and some had high bioaccumulation. This suggests that standard dose-response assays need to be interpreted with caution and future assays should examine the modality of the responses. In addition, the similarity in the biological effects of the Cry toxins in the two predators was due to different biological exposure mechanisms. The majority of H. axyridis were exposed both internally and in the gut, while C. sanguinea was exposed primarily in the gut. Thus, despite their close phylogenetic relatedness, these species would not be good surrogates for each other and the surrogate species methodology should be tested more rigorously.

  10. The cytokinesis-blocked micronucleus assay: dose-response calibration curve, background frequency in the population and dose estimation.

    PubMed

    Rastkhah, E; Zakeri, F; Ghoranneviss, M; Rajabpour, M R; Farshidpour, M R; Mianji, F; Bayat, M

    2016-03-01

    An in vitro study of the dose responses of human peripheral blood lymphocytes was conducted with the aim of creating calibrated dose-response curves for biodosimetry measuring up to 4 Gy (0.25-4 Gy) of gamma radiation. The cytokinesis-blocked micronucleus (CBMN) assay was employed to obtain the frequencies of micronuclei (MN) per binucleated cell in blood samples from 16 healthy donors (eight males and eight females) in two age ranges of 20-34 and 35-50 years. The data were used to construct the calibration curves for men and women in two age groups, separately. An increase in micronuclei yield with the dose in a linear-quadratic way was observed in all groups. To verify the applicability of the constructed calibration curve, MN yields were measured in peripheral blood lymphocytes of two real overexposed subjects and three irradiated samples with unknown dose, and the results were compared with dose values obtained from measuring dicentric chromosomes. The comparison of the results obtained by the two techniques indicated a good agreement between dose estimates. The average baseline frequency of MN for the 130 healthy non-exposed donors (77 men and 55 women, 20-60 years old divided into four age groups) ranged from 6 to 21 micronuclei per 1000 binucleated cells. Baseline MN frequencies were higher for women and for the older age group. The results presented in this study point out that the CBMN assay is a reliable, easier and valuable alternative method for biological dosimetry.

  11. Deciphering dynamic dose responses of natural promoters and single cis elements upon osmotic and oxidative stress in yeast.

    PubMed

    Dolz-Edo, Laura; Rienzo, Alessandro; Poveda-Huertes, Daniel; Pascual-Ahuir, Amparo; Proft, Markus

    2013-06-01

    Fine-tuned activation of gene expression in response to stress is the result of dynamic interactions of transcription factors with specific promoter binding sites. In the study described here we used a time-resolved luciferase reporter assay in living Saccharomyces cerevisiae yeast cells to gain insights into how osmotic and oxidative stress signals modulate gene expression in a dose-sensitive manner. Specifically, the dose-response behavior of four different natural promoters (GRE2, CTT1, SOD2, and CCP1) reveals differences in their sensitivity and dynamics in response to different salt and oxidative stimuli. Characteristic dose-response profiles were also obtained for artificial promoters driven by only one type of stress-regulated consensus element, such as the cyclic AMP-responsive element, stress response element, or AP-1 site. Oxidative and osmotic stress signals activate these elements separately and with different sensitivities through different signaling molecules. Combination of stress-activated cis elements does not, in general, enhance the absolute expression levels; however, specific combinations can increase the inducibility of the promoter in response to different stress doses. Finally, we show that the stress tolerance of the cell critically modulates the dynamics of its transcriptional response in the case of oxidative stress.

  12. Effect of inorganic salts and glucose additives on dose-response, melting point and mass density of genipin gel dosimeters.

    PubMed

    Al-jarrah, A M; Abdul Rahman, Azhar; Shahrim, Iskandar; Razak, Nik Noor Ashikin Nik Ab; Ababneh, Baker; Tousi, Ehsan Taghizadeh

    2016-01-01

    Genipin gel dosimeters are hydrogels infused with a radiation-sensitive material which yield dosimetric information in three dimensions (3D). The effect of inorganic salts and glucose on the visible absorption dose-response, melting points and mass density of genipin gel dosimeters has been experimentally evaluated using 6-MV LINAC photons. As a result, the addition of glucose with optimum concentration of 10% (w/w) was found to improve the thermal stability of the genipin gel and increase its melting point (Tm) by 6 °C accompanied by a slight decrease of dose-response. Furthermore, glucose helps to adjust the gel mass density to obtain the desired tissue-equivalent properties. A drop of Tm was observed when salts were used as additives. As the salt concentration increased, gel Tm decreased. The mass density and melting point of the genipin gel could be adjusted using different amounts of glucose that improved the genipin gel suitability for 3D dose measurements without introducing additional toxicity to the final gel.

  13. A meta-analysis including dose-response relationship between night shift work and the risk of colorectal cancer.

    PubMed

    Wang, Xiao; Ji, Alin; Zhu, Yi; Liang, Zhen; Wu, Jian; Li, Shiqi; Meng, Shuai; Zheng, Xiangyi; Xie, Liping

    2015-09-22

    A meta-analysis was conducted to quantitatively evaluate the correlation between night shift work and the risk of colorectal cancer. We searched for publications up to March 2015 using PubMed, Web of Science, Cochrane Library, EMBASE and the Chinese National Knowledge Infrastructure databases, and the references of the retrieved articles and relevant reviews were also checked. OR and 95% CI were used to assess the degree of the correlation between night shift work and risk of colorectal cancer via fixed- or random-effect models. A dose-response meta-analysis was performed as well. The pooled OR estimates of the included studies illustrated that night shift work was correlated with an increased risk of colorectal cancer (OR = 1.318, 95% CI 1.121-1.551). No evidence of publication bias was detected. In the dose-response analysis, the rate of colorectal cancer increased by 11% for every 5 years increased in night shift work (OR = 1.11, 95% CI 1.03-1.20). In conclusion, this meta-analysis indicated that night shift work was associated with an increased risk of colorectal cancer. Further researches should be conducted to confirm our findings and clarify the potential biological mechanisms.

  14. Coffee consumption and mortality from all causes, cardiovascular disease, and cancer: a dose-response meta-analysis.

    PubMed

    Crippa, Alessio; Discacciati, Andrea; Larsson, Susanna C; Wolk, Alicja; Orsini, Nicola

    2014-10-15

    Several studies have analyzed the relationship between coffee consumption and mortality, but the shape of the association remains unclear. We conducted a dose-response meta-analysis of prospective studies to examine the dose-response associations between coffee consumption and mortality from all causes, cardiovascular disease (CVD), and all cancers. Pertinent studies, published between 1966 and 2013, were identified by searching PubMed and by reviewing the reference lists of the selected articles. Prospective studies in which investigators reported relative risks of mortality from all causes, CVD, and all cancers for 3 or more categories of coffee consumption were eligible. Results from individual studies were pooled using a random-effects model. Twenty-one prospective studies, with 121,915 deaths and 997,464 participants, met the inclusion criteria. There was strong evidence of nonlinear associations between coffee consumption and mortality for all causes and CVD (P for nonlinearity < 0.001). The largest risk reductions were observed for 4 cups/day for all-cause mortality (16%, 95% confidence interval: 13, 18) and 3 cups/day for CVD mortality (21%, 95% confidence interval: 16, 26). Coffee consumption was not associated with cancer mortality. Findings from this meta-analysis indicate that coffee consumption is inversely associated with all-cause and CVD mortality.

  15. A sex-specific dose-response curve for testosterone: could excessive testosterone limit sexual interaction in women?

    PubMed

    Krapf, Jill M; Simon, James A

    2017-04-01

    Testosterone treatment increases sexual desire and well-being in women with hypoactive sexual desire disorder; however, many studies have shown only modest benefits limited to moderate doses. Unlike men, available data indicate women show a bell-shaped dose-response curve for testosterone, wherein a threshold dosage of testosterone leads to desirable sexual function effects, but exceeding this threshold results in a lack of further positive sexual effects or may have a negative impact. Emotional and physical side-effects of excess testosterone, including aggression and virilization, may counteract the modest benefits on sexual interaction, providing a possible explanation for a threshold dose of testosterone in women. In this commentary, we will review and critically analyze data supporting a curvilinear dose-response relationship between testosterone treatment and sexual activity in women with low libido, and also explore possible explanations for this observed relationship. Understanding optimal dosing of testosterone unique to women may bring us one step closer to overcoming regulatory barriers in treating female sexual dysfunction.

  16. Cancer chemoprevention: Evidence of a nonlinear dose response for the protective effects of resveratrol in humans and mice.

    PubMed

    Cai, Hong; Scott, Edwina; Kholghi, Abeer; Andreadi, Catherine; Rufini, Alessandro; Karmokar, Ankur; Britton, Robert G; Horner-Glister, Emma; Greaves, Peter; Jawad, Dhafer; James, Mark; Howells, Lynne; Ognibene, Ted; Malfatti, Michael; Goldring, Christopher; Kitteringham, Neil; Walsh, Joanne; Viskaduraki, Maria; West, Kevin; Miller, Andrew; Hemingway, David; Steward, William P; Gescher, Andreas J; Brown, Karen

    2015-07-29

    Resveratrol is widely promoted as a potential cancer chemopreventive agent, but a lack of information on the optimal dose prohibits rationally designed trials to assess efficacy. To challenge the assumption that "more is better," we compared the pharmacokinetics and activity of a dietary dose with an intake 200 times higher. The dose-response relationship for concentrations generated and the metabolite profile of [(14)C]-resveratrol in colorectal tissue of cancer patients helped us to define clinically achievable levels. In Apc(Min) mice (a model of colorectal carcinogenesis) that received a high-fat diet, the low resveratrol dose suppressed intestinal adenoma development more potently than did the higher dose. Efficacy correlated with activation of adenosine monophosphate-activated protein kinase (AMPK) and increased expression of the senescence marker p21. Nonlinear dose responses were observed for AMPK and mechanistic target of rapamycin (mTOR) signaling in mouse adenoma cells, culminating in autophagy and senescence. In human colorectal tissues exposed to low dietary concentrations of resveratrol ex vivo, we measured enhanced AMPK phosphorylation and autophagy. The expression of the cytoprotective NAD(P)H dehydrogenase, quinone 1 (NQO1) enzyme was also increased in tissues from cancer patients participating in our [(14)C]-resveratrol trial. These findings warrant a revision of developmental strategies for diet-derived agents designed to achieve cancer chemoprevention.

  17. Indications of a dose-response relationship between cannabis use and age at onset in bipolar disorder.

    PubMed

    Lagerberg, Trine Vik; Kvitland, Levi Røstad; Aminoff, Sofie R; Aas, Monica; Ringen, Petter Andreas; Andreassen, Ole Andreas; Melle, Ingrid

    2014-01-30

    Cannabis use seems to play a causal role in the development of psychotic disorders. Recent evidence suggests that it may also precipitate onset in bipolar disorder. We here investigate if there is a dose-response relationship between cannabis use and age at onset in bipolar disorder, and whether there are interactions between cannabis use and illness characteristics (presenting polarity and presence of psychosis). Consecutively recruited patients with a DSM-IV, SCID verified diagnosis of bipolar I, II or NOS disorder (n=324) participated. Two-way ANCOVAS were used to investigate the effect of levels of cannabis use (<10 times during one month lifetime, >10 times during one month lifetime or a cannabis use disorder) on age at onset, including interaction effects with illness characteristics, while controlling for possible confounders. There was a significant association indicating a dose-response relationship between cannabis use and age at onset, which remained statistically significant after controlling for possible confounders (gender, bipolar subtype, family history of severe mental illness and alcohol or other substance use disorders). There were no interaction effects between cannabis use and presenting polarity or presence of psychosis. Doses of cannabis used may affect the age at onset of bipolar disorder.

  18. Interpretation of the margin of exposure for genotoxic carcinogens - elicitation of expert knowledge about the form of the dose response curve at human relevant exposures.

    PubMed

    Boobis, Alan; Flari, Villie; Gosling, John Paul; Hart, Andy; Craig, Peter; Rushton, Lesley; Idahosa-Taylor, Ehi

    2013-07-01

    The general approach to risk assessment of genotoxic carcinogens has been to advise reduction of exposure to "as low as reasonably achievable/practicable" (ALARA/P). However, whilst this remains the preferred risk management option, it does not provide guidance on the urgency or extent of risk management actions necessary. To address this, the "Margin of Exposure" (MOE) approach has been proposed. The MOE is the ratio between the point of departure for carcinogenesis and estimated human exposure. However, interpretation of the MOE requires implicit or explicit consideration of the shape of the dose-response curve at human relevant exposures. In a structured elicitation exercise, we captured expert opinion on available scientific evidence for low dose-response relationships for genotoxic carcinogens. This allowed assessment of: available evidence for the nature of dose-response relationships at human relevant exposures; the generality of judgments about such dose-response relationships; uncertainties affecting judgments on the nature of such dose-response relationships; and whether this last should differ for different classes of genotoxic carcinogens. Elicitation results reflected the variability in experts' views on the form of the dose-response curve for low dose exposure and major sources of uncertainty affecting the assumption of a linear relationship.

  19. Health effects assessment for environmental perchlorate contamination: the dose response for inhibition of thyroidal radioiodine uptake in humans.

    PubMed Central

    Greer, Monte A; Goodman, Gay; Pleus, Richard C; Greer, Susan E

    2002-01-01

    Application of a sensitive new detection method has revealed widespread perchlorate contamination of groundwater in the southwestern United States, typically at 0.005-0.020 mg/L (5-20 ppb). Perchlorate is a competitive inhibitor of the process by which iodide is actively transported from the bloodstream into the thyroid. This inhibitory action of perchlorate is the basis of its pharmaceutical use (in the treatment of hyperthyroidism) as well as its potential toxicity. To establish the dose response in humans for perchlorate inhibition of thyroidal iodide uptake and any short-term effects on thyroid hormones, we gave perchlorate in drinking water at 0.007, 0.02, 0.1, or 0.5 mg/kg-day to 37 male and female volunteers for 14 days. In 24 subjects we performed 8- and 24-hr measurements of thyroidal (123)I uptake (RAIU) before exposure, on exposure days 2 (E2) and 14 (E14), and 15 days postexposure (P15). In another 13 subjects we omitted both E2 studies and the 8-hr P15 study. We observed a strong correlation between the 8- and 24-hr RAIU over all dose groups and measurement days. We found no difference between E2 and E14 in the inhibition of RAIU produced by a given perchlorate dose. We also found no sex difference. On both E2 and E14, the dose response was a negative linear function of the logarithm of dose. Based on the dose response for inhibition of the 8- and 24-hr RAIU on E14 in all subjects, we derived estimates of the true no-effect level: 5.2 and 6.4 micro g/kg-day, respectively. Given default body weight and exposure assumptions, these doses would be ingested by an adult if the drinking-water supply contained perchlorate at concentrations of approximately 180 and 220 micro g/L (ppb), respectively. On P15, RAIU was not significantly different from baseline. In 24 subjects we measured serum levels of thyroxine (total and free), triiodothyronine, and thyrotropin in blood sampled 16 times throughout the study. Only the 0.5 mg/kg-day dose group showed any effect

  20. Establishing a dose-response relationship between acute resistance-exercise and the immune system: Protocol for a systematic review.

    PubMed

    Szlezak, Adam Michael; Szlezak, Siri Lauluten; Keane, James; Tajouri, Lotti; Minahan, Clare

    2016-12-01

    Exercise immunology research has traditionally focussed on aerobic-exercise, however it has become apparent in more recent years that resistance-exercise can also considerably affect host immunobiology. To date however, no systematic process has been used to establish a dose-response relationship between resistance-exercise and the immune system. The present systematic review was thus conducted to determine the dose-response effects of a bout of resistance-exercise on acute leukocyte counts. In accordance with the PRISMA guidelines, a systematic literature search was conducted in the electronic databases, PubMed, Web of Science, and Google Scholar, over the date range of 1989-2016. Following the PICO elements, eligibility criteria included: i) participants: healthy humans aged 18-40; ii) intervention: a single bout of resistance-exercise; iii) comparator: at least one comparator group; iv) outcome: acute measures of circulating leukocyte counts. Specific exclusion criteria were also applied. Risk of bias and quality of evidence was assessed using the PEDro scale. Due to the individual designs of the admitted studies, a qualitative analysis (systematic narrative synthesis) was employed in the present review. The results of the present review demonstrate that a single bout of resistance-exercise induces an acute monocytosis, neutrophilia, and lymphocytosis. It became apparent that the reviewed literature either does not consistently specify, or does not describe with sufficient detail, the time-course between the onset of exercise and the collection of blood. We recommend that researchers consider addressing this in future studies, and also collect blood measures during exercise to aid with comparison of temporal effects. Regarding the determination of a dose-response relationship, an acute neutrophilia, monocytosis and lymphocytosis appears to occur more rapidly and to a greater magnitude following a single bout of high-dose vs low-dose resistance

  1. Harnessing the theoretical foundations of the exponential and beta-Poisson dose-response models to quantify parameter uncertainty using Markov Chain Monte Carlo.

    PubMed

    Schmidt, Philip J; Pintar, Katarina D M; Fazil, Aamir M; Topp, Edward

    2013-09-01

    Dose-response models are the essential link between exposure assessment and computed risk values in quantitative microbial risk assessment, yet the uncertainty that is inherent to computed risks because the dose-response model parameters are estimated using limited epidemiological data is rarely quantified. Second-order risk characterization approaches incorporating uncertainty in dose-response model parameters can provide more complete information to decisionmakers by separating variability and uncertainty to quantify the uncertainty in computed risks. Therefore, the objective of this work is to develop procedures to sample from posterior distributions describing uncertainty in the parameters of exponential and beta-Poisson dose-response models using Bayes's theorem and Markov Chain Monte Carlo (in OpenBUGS). The theoretical origins of the beta-Poisson dose-response model are used to identify a decomposed version of the model that enables Bayesian analysis without the need to evaluate Kummer confluent hypergeometric functions. Herein, it is also established that the beta distribution in the beta-Poisson dose-response model cannot address variation among individual pathogens, criteria to validate use of the conventional approximation to the beta-Poisson model are proposed, and simple algorithms to evaluate actual beta-Poisson probabilities of infection are investigated. The developed MCMC procedures are applied to analysis of a case study data set, and it is demonstrated that an important region of the posterior distribution of the beta-Poisson dose-response model parameters is attributable to the absence of low-dose data. This region includes beta-Poisson models for which the conventional approximation is especially invalid and in which many beta distributions have an extreme shape with questionable plausibility.

  2. Dose-response of serum 25-hydroxyvitamin D in association with risk of colorectal cancer: A meta-analysis.

    PubMed

    Garland, Cedric F; Gorham, Edward D

    2017-04-01

    Fifteen nested case-control or cohort studies in 14 countries have examined the association between serum 25-hydroxyvitamin D [25(OH)D] and risk of colorectal cancer. A meta-analysis of these studies would provide a useful dose-response gradient curve based on pooling of the results of known studies to date. An up-to-date dose-response curve that combines the findings of these studies has not been reported, to our knowledge. This curve would help in designing interventions for future studies. A new meta-analysis would be more precise than any previous analysis due to its larger sample size. Therefore a search of PubMed and other resources was performed in May 2016 for all cohort or nested case-control observational studies that reported risk of colon or colorectal cancer by quantiles of 25(OH)D. All but two of the 15 studies found a trend toward lower risk of colorectal cancer associated with higher serum 25(OH)D. There was a linear reduction in the odds ratio (OR) with each 10ng/ml-increment in 25(OH)D concentration. The lowest quantile of the serum 25(OH)D concentration was generally<20ng/ml. The downward trend in ORs associated with higher serum 25(OH)D concentrations was statistically significant in 3 studies. The pooled OR from all studies comparing highest with lowest quantile of 25(OH)D was 0.67 (95% confidence interval [CI], 0.59-0.76), meaning there was a 33% lower risk associated with the highest compared with the lowest quantile of serum 25(OH)D. A dose-response analysis revealed that a serum 25(OH)D of 50ng/ml was associated with an OR of 0.4 (95% CI, 0.2-1.0) compared with a concentration of 5ng/ml. The formula for the linear relationship was OR=0.008x. For example, individuals with a 25(OH)D concentration of 50ng/ml had an approximately 60% lower risk of colorectal cancer than those with a concentration of 5ng/ml. Those with a 25(OH)D concentration of 30ng/ml had a 33% lower risk than those with a concentration of 5ng/ml. The inverse association

  3. Effect of intravenous fructose on the P-31 MR spectrum of the liver: dose response in healthy volunteers.

    PubMed

    Terrier, F; Vock, P; Cotting, J; Ladebeck, R; Reichen, J; Hentschel, D

    1989-05-01

    Dynamic phosphorus-31 magnetic resonance (MR) spectroscopy of the liver after intravenous administration of fructose has been suggested as a test of liver function. To establish dose-response curves of the phosphorus metabolites in the normal human liver, each of four healthy volunteers was given two to four different fructose doses on separate days: 62.5, 125, 250, 375, or 500 mg per kilogram of body weight. P-31 MR spectra of the liver were acquired with a 2-T whole-body magnetic, both before and after fructose administration, at 2.5-minute intervals over at least 30 minutes. The fructose load caused a significant, linearly dose-dependent accumulation of phosphomonoesters (r = .72, P less than .01) and a decrease in inorganic phosphate (r = .78, P less than .005) and adenosine triphosphate (r = .73, P less than .01). On the basis of these experiments, dynamic P-31 MR spectroscopy seems promising in the assessment of liver function.

  4. Plasma adrenocorticotropin responses to opioid blockade with naloxone: generating a dose-response curve in a single session.

    PubMed

    Mangold, D; McCaul, M E; Ali, M; Wand, G S

    2000-08-15

    We examined two methods of generating a dose-response curve to the opioid receptor antagonist naloxone. In 15 healthy male subjects (18-25 years) plasma adrenocorticotropin (ACTH) responses to five doses of naloxone studied over 5 separate days were compared to plasma ACTH responses to five incremental doses of naloxone studied within a single session. There was a statistically significant positive correlation in ACTH responses (area under the curve and peak) between dosing methods. Furthermore, the doses of naloxone that produced half-maximal and maximal ACTH response were similar. The comparability of ACTH responses between the two naloxone dosing techniques, combined with the safety and ease associated with the single-session methodology, underscores the usefulness of the single-session technique for future investigations.

  5. Evaluation of the Comet Assay for Assessing the Dose-Response Relationship of DNA Damage Induced by Ionizing Radiation

    PubMed Central

    Wang, Yan; Xu, Chang; Du, Li Qing; Cao, Jia; Liu, Jian Xiang; Su, Xu; Zhao, Hui; Fan, Fei-Yue; Wang, Bing; Katsube, Takanori; Fan, Sai Jun; Liu, Qiang

    2013-01-01

    Dose- and time-response curves were combined to assess the potential of the comet assay in radiation biodosimetry. The neutral comet assay was used to detect DNA double-strand breaks in lymphocytes caused by γ-ray irradiation. A clear dose-response relationship with DNA double-strand breaks using the comet assay was found at different times after irradiation (p < 0.001). A time-response relationship was also found within 72 h after irradiation (p < 0.001). The curves for DNA double-strand breaks and DNA repair in vitro of human lymphocytes presented a nice model, and a smooth, three-dimensional plane model was obtained when the two curves were combined. PMID:24240807

  6. Bioaccumulation of heavy metals by shrimp (Litopenaeus schmitti): A dose-response approach for coastal resources management.

    PubMed

    Nascimento, Juliana Ribeiro; Sabadini-Santos, Elisamara; Carvalho, Cassia; Keunecke, Karina Annes; César, Ricardo; Bidone, Edison D

    2017-01-30

    We reveal a dose-response relationship for bioaccumulation of Zn, Cu and Cr in shrimp Litopenaeus schmitti from Sepetiba Bay, Rio de Janeiro, Brazil. Our model estimates the current risk (AD50 was 70% of the legal limit) and the daily metal uptake rate for each metal. It can also evaluate the relative reliability of predictions for tissue concentrations reaching the legal limits for human consumption (approximately 1year) and predictions related to asymptotic length, arising from (i) direct regression of the metal concentration (MeC) versus total length (TL) and age (duration of exposure), and (ii) correlation of the incorporation rate (IR=MeC/TL) with age. Metal incorporation rates (IR), i.e. a kinetic proxy for absorption during growth up to attainment of asymptotic length, decrease with age, reflecting a slow-down in metal absorption. This pattern mitigates the high initial concentrations observed for juveniles.

  7. Accumulative dose response of CdZnTe detectors to 14.1 MeV neutrons

    NASA Astrophysics Data System (ADS)

    Chen, Xiang; Han, He-tong; Li, Gang; Lu, Yi

    2017-03-01

    The accumulative dose response of CdZnTe (CZT) detectors to 14.1 MeV neutrons is discussed experimentally in this paper. The Cockcroft-Walton Accelerator is used to obtain a steady neutron beam of 14.1 MeV neutrons. A pulsed X-ray source is used to test the response parameters of the neutron-exposed CZT detectors under the pulse mode. The irradiation time (hours) is shorter relative to the time scales (years) where annealing effects occur. Time and linearity response is analyzed to evaluate the maximum dose rate of the CZT detectors and the pulse shape. The result shows that the experimental CZT detectors maintain stable response behaviors, while the maximum dose rate and the total accumulative dose are less than 106 neutrons/(cm2·s) and 1010 neutrons/cm2, respectively.

  8. Stage specificity, dose response, and doubling dose for mouse minisatellite germ-line mutation induced by acute radiation.

    PubMed

    Dubrova, Y E; Plumb, M; Brown, J; Fennelly, J; Bois, P; Goodhead, D; Jeffreys, A J

    1998-05-26

    Germ-line mutation induction at mouse minisatellite loci by acute irradiation with x-rays was studied at premeiotic and postmeiotic stages of spermatogenesis. An elevated paternal mutation rate was found after irradiation of premeiotic spermatogonia and stem cells, whereas the frequency of minisatellite mutation after postmeiotic irradiation of spermatids was similar to that in control litters. In contrast, paternal irradiation did not affect the maternal mutation rate. A linear dose-response curve for paternal mutation induced at premeiotic stages was found, with a doubling dose of 0.33 Gy, a value close to those obtained in mice after acute spermatogonia irradiation using other systems for mutation detection. High frequencies of spontaneous and induced mutations at minisatellite loci allow mutation induction to be evaluated at low doses of exposure in very small population samples, which currently makes minisatellite DNA the most powerful tool for monitoring radiation-induced germ-line mutation.

  9. Mutations induced in Tradescantia by small doses of X-rays and neutrons - Analysis of dose-response curves.

    NASA Technical Reports Server (NTRS)

    Sparrow, A. H.; Underbrink, A. G.; Rossi, H. H.

    1972-01-01

    Dose-response curves for pink somatic mutations in Tradescantia stamen hairs were analyzed after neutron and X-ray irradiation with doses ranging from a fraction of a rad to the region of saturation. The dose-effect relation for neutrons indicates a linear dependence from 0.01 to 8 rads; between 0.25 and 5 rads, a linear dependence is indicated for X-rays also. As a consequence the relative biological effectiveness reaches a constant value (about 50) at low doses. The observations are in good agreement with the predictions of the theory of dual radiation action and support its interpretation of the effects of radiation on higher organisms. The doubling dose of X-rays was found to be nearly 1 rad.

  10. Manganese Exposure and Cognition Across the Lifespan: Contemporary Review and Argument for Biphasic Dose-Response Health Effects.

    PubMed

    Vollet, Kaitlin; Haynes, Erin N; Dietrich, Kim N

    2016-12-01

    Manganese (Mn) is both an essential micronutrient and potential neurotoxicant. This dual role underlies a growing body of literature demonstrating that Mn exhibits a biphasic dose-response relationship with neurocognitive outcomes. We reviewed recent epidemiologic studies from 2007 to 2016 that investigated the relationship between Mn exposure and cognitive outcomes across the lifespan: early life, school-aged children, and adulthood. In total, 27 research articles were included in this review: 12 pediatric and 15 adult studies (10 occupational and five environmental exposures). The majority of these studies provided evidence of the negative effects of Mn exposure on cognition. The pediatric literature provides evidence that both high and low levels of Mn are negatively associated with intellectual development. Future Mn research should include examination of non-linear relationships and multiple neurotoxicants across the lifespan and particularly during critical developmental windows.

  11. A New Drug Combinatory Effect Prediction Algorithm on the Cancer Cell Based on Gene Expression and Dose-Response Curve.

    PubMed

    Goswami, C Pankaj; Cheng, L; Alexander, P S; Singal, A; Li, L

    2015-02-01

    Gene expression data before and after treatment with an individual drug and the IC20 of dose-response data were utilized to predict two drugs' interaction effects on a diffuse large B-cell lymphoma (DLBCL) cancer cell. A novel drug interaction scoring algorithm was developed to account for either synergistic or antagonistic effects between drug combinations. Different core gene selection schemes were investigated, which included the whole gene set, the drug-sensitive gene set, the drug-sensitive minus drug-resistant gene set, and the known drug target gene set. The prediction scores were compared with the observed drug interaction data at 6, 12, and 24 hours with a probability concordance (PC) index. The test result shows the concordance between observed and predicted drug interaction ranking reaches a PC index of 0.605. The scoring reliability and efficiency was further confirmed in five drug interaction studies published in the GEO database.

  12. Phase II dose-response trials: A simulation study to compare analysis method performance under design considerations.

    PubMed

    Rekowski, Jan; Köllmann, Claudia; Bornkamp, Björn; Ickstadt, Katja; Scherag, André

    2017-02-21

    Phase II trials are intended to provide information about the dose-response relationship and to support the choice of doses for a pivotal phase III trial. Recently, new analysis methods have been proposed to address these objectives, and guidance is needed to select the most appropriate analysis method in specific situations. We set up a simulation study to evaluate multiple performance measures of one traditional and three more recent dose-finding approaches under four design options and illustrate the investigated analysis methods with an example from clinical practice. Our results reveal no general recommendation for a particular analysis method across all design options and performance measures. However, we also demonstrate that the new analysis methods are worth the effort compared to the traditional ANOVA-based approach.

  13. Parity and All-cause Mortality in Women and Men: A Dose-Response Meta-Analysis of Cohort Studies.

    PubMed

    Zeng, Yun; Ni, Ze-min; Liu, Shu-yun; Gu, Xue; Huang, Qin; Liu, Jun-an; Wang, Qi

    2016-01-13

    To quantitatively assess the association between parity and all-cause mortality, we conducted a meta-analysis of cohort studies. Relevant reports were identified from PubMed and Embase databases. Cohort studies with relative risks (RRs) and 95% confidence intervals (CIs) of all-cause mortality in three or more categories of parity were eligible. Eighteen articles with 2,813,418 participants were included. Results showed that participants with no live birth had higher risk of all-cause mortality (RR= 1.19, 95% CI = 1.03-1.38; I(2) = 96.7%, P < 0.001) compared with participants with one or more live births. Nonlinear dose-response association was found between parity and all-cause mortality (P for non-linearity < 0.0001). Our findings suggest that moderate-level parity is inversely associated with all-cause mortality.

  14. The dose-response relationship for tumourigenesis by UV radiation in the region 311-312 nm.

    PubMed

    Sterenborg, H J; van Weelden, H; van der Leun, J C

    1988-09-01

    Groups of hairless mice were irradiated daily with Philips TL01 UVB sources. This type of lamp has become available recently and was developed for UVB phototherapy of psoriasis. The TL01 emits radiation in a narrow band around 311-312 nm. Tumours developed on all animals. The dose-response relationship had practically the same shape as that found in a similar experiment with Westinghouse FS40 sunlamps; the tumour induction time appeared to be proportional to the daily dose to a power of -0.58. An additional experiment was performed with a TL01 from which the shorter wavelengths were filtered away. This reduced the carcinogenic effectiveness by a factor of 2.3. The potential of the filtered lamp for phototherapy of psoriasis is discussed.

  15. Implementation of the New Approach for the Dose-Response Functions Development for the Case of Athens and Greece

    NASA Astrophysics Data System (ADS)

    Christodoulakis, J.; Tzanis, C. G.; Varotsos, C. A.; Kouremadas, G.

    2016-08-01

    Dose-response functions (DRFs) are functions used for estimating corrosion and/or soiling levels of materials used in constructions and cultural monuments. In order to achieve this, DRFs lean on ground-based measurements of specific air pollution and climatic parameters like nitrogen oxides, ozone, temperature and others. In DRAGON 3 2015 Symposium we presented a new approach which proposed a technique for using satellite-based data for the necessary parameters instead of ground-based expanding in this way: a) the usage of DRFs in cases/areas where there is no availability of in situ measurements, b) the applicability of satellite-based data. In this work we present mapping results of deterioration levels (corrosion and soiling) for the case of Athens, Greece but also for the whole Greece country.

  16. Radiation alone in the treatment of cancer of the uterine cervix: Analysis of pelvic failure and dose response relationship

    SciTech Connect

    Kim, R.Y.; Trotti, A.; Wu, C.J.; Soong, S.J.; Salter, M.M. )

    1989-11-01

    This retrospective analysis involves 569 patients with invasive cancer of the uterine cervix treated with irradiation alone between 1969 and 1980. Treatment consisted of external and intracavitary irradiation and treatment policy remained consistent throughout the study interval. In early stage disease (FIGO IA, IB, and IIA), pelvic failure was 4.6%, 11.2%, and 8.2%, respectively. In late stage disease (FIGO IIB, III, and IVA), pelvic failure was 30.1%, 52.3%, and 69.2%, respectively. Further analysis revealed that total dose at point A is well correlated with pelvic control. An aggressive treatment is crucial in late stage disease in determining the probability of pelvic tumor control and survival. Methods of dose prescription, dose-response relationships, treatment philosophy and its therapeutic implications are discussed.

  17. Quantitative global sensitivity analysis of a biologically based dose-response pregnancy model for the thyroid endocrine system

    PubMed Central

    Lumen, Annie; McNally, Kevin; George, Nysia; Fisher, Jeffrey W.; Loizou, George D.

    2015-01-01

    A deterministic biologically based dose-response model for the thyroidal system in a near-term pregnant woman and the fetus was recently developed to evaluate quantitatively thyroid hormone perturbations. The current work focuses on conducting a quantitative global sensitivity analysis on this complex model to identify and characterize the sources and contributions of uncertainties in the predicted model output. The workflow and methodologies suitable for computationally expensive models, such as the Morris screening method and Gaussian Emulation processes, were used for the implementation of the global sensitivity analysis. Sensitivity indices, such as main, total and interaction effects, were computed for a screened set of the total thyroidal system descriptive model input parameters. Furthermore, a narrower sub-set of the most influential parameters affecting the model output of maternal thyroid hormone levels were identified in addition to the characterization of their overall and pair-wise parameter interaction quotients. The characteristic trends of influence in model output for each of these individual model input parameters over their plausible ranges were elucidated using Gaussian Emulation processes. Through global sensitivity analysis we have gained a better understanding of the model behavior and performance beyond the domains of observation by the simultaneous variation in model inputs over their range of plausible uncertainties. The sensitivity analysis helped identify parameters that determine the driving mechanisms of the maternal and fetal iodide kinetics, thyroid function and their interactions, and contributed to an improved understanding of the system modeled. We have thus demonstrated the use and application of global sensitivity analysis for a biologically based dose-response model for sensitive life-stages such as pregnancy that provides richer information on the model and the thyroidal system modeled compared to local sensitivity analysis

  18. The influences of nitric oxide, epinephrine, and dopamine on vascular tone: dose-response modeling and simulations

    PubMed Central

    Eugene, Andy R.

    2016-01-01

    Introduction Sodium Nitroprusside has successfully been an excellent choice when considering a decrease in systemic vascular resistance in the critical care setting. However, reflex tachycardia and ventilation-perfusion mismatch are possible side effects of this agent. To maintaining cardiac output, cerebral perfusion pressure, and concurrently drop SVR, low-dose epinephrine or dopamine are viable options. The aim of this paper is to conduct dose-response simulations to identify the equivalent dopamine, epinephrine, and nitroprusside infusion doses to decrease the systemic vascular resistance by 20% and by 40% from baseline resting values. Methods Three studies were identified in the literature with reported epinephrine, dopamine, and sodium nitroprusside infusion doses with corresponding systemic vascular resistance responses. Infusion doses were normalized to mcg/kg/min and SVR values were normalized and scaled to the percent decrease (%SVR) in SVR from baseline resting values. The original published studies were mathematically modeled and the Hill equation parameters used for further dose-response simulations of a virtual population. One-hundred patients were simulated various doses resulting in corresponding %SVR responses for each of the three drugs. Results Equivalent infusion doses achieving in an approximate 20-25% decrease in SVR, from baseline, were identified for epinephrine, dopamine, and sodium nitroprusside. Moreover, equivalent infusion doses were identified for epinephrine and nitroprusside to decrease the SVR by 40% from baseline. Conclusion Even though sodium nitroprusside is traditionally used in decreasing SVR, low doses of dopamine or epinephrine are viable alternatives to patients with contraindications to nitroprusside infusions or who will require prolonged infusions to avoid toxicity. The multiple comparisons procedure-modeling approach is an excellent methodology for dose-finding exercises and has enabled identification of equivalent

  19. Dose-response relationships of three amphotericin B formulations in a non-neutropenic murine model of invasive aspergillosis.

    PubMed

    Mouton, J W; te Dorsthorst, D T A; Meis, J F G M; Verweij, P E

    2009-12-01

    New lipid-associated formulations of amphotericin B (AmB) have been developed in order to reduce toxicity and enhance the efficacy of AmB by allowing administration of higher doses of the drug. We determined the in vivo dose-response relationships of 1 day and 7 day treatment of AmB, Ambisome (AmBi) and Abelcet (ABLC) in a non-neutropenic murine model of invasive aspergillosis by using survival as an endpoint. Female CD-1 mice were infected intravenously 48 h prior to start therapy with Aspergillus fumigatus (1 x 10(7) conidia/mouse). Groups of 10 mice were treated iv for 1 day or 7 days with increasing 2-fold doses of AmB, ABLC and AmBi up to a maximum of 20 mg/kg/day. Mortality was determined twice daily until day 15. Results were analyzed using product-moment survival analysis and by determining the dose response relationships on day 15. Survival at day 15 of mice with 7 day AmBi or ABLC treatment was significantly better than that of controls or AmB. The ED50s of AmBi and ABLC were 0.06 (95% CI: 0.03-0.127) mg/kg and 0.21 (0.06-0.66) mg/kg respectively. In addition, the maximum effect was higher for AmBi than ABLC, 90% survival versus 68%, respectively. Most of the effects of treatment with AmBi were reached after 1 day of treatment, indicating that the first dose given is most important in predicting survival. This study shows that AmBi and ABLC were significantly more efficacious than AmB in a non-neutropenic murine model of invasive aspergillosis, and that the effect observed was primarily dependent on the first dose administered.

  20. Dose-response relation between exposure to two types of hand-arm vibration and sensorineural perception of vibration.

    PubMed Central

    Virokannas, H

    1995-01-01

    OBJECTIVES--31 railway workers and 32 lumberjacks were examined to compare the dose-response relation between the exposure to two types of hand-arm vibration and the sensory disturbances in peripheral nerves as evaluated by the vibration perception thresholds (VPTs). METHODS--Clinical examinations were carried out that included measurements of the VPTs, and electroneuromyography (ENMG), and an inquiry to confirm the use of vibrating tools. Diseases of the central nervous system and neuropathies were checked by inquiry and a clinical examination, diabetes was excluded by a blood sample analysis, and the subjects with carpal tunnel syndrome confirmed with ENMG were excluded from the study. RESULTS--Lifetime use of hand held tamping machines (railway workers) and chain saws (lumberjacks) had a significant correlation with the VPTs at frequencies from 32 to 500 Hz. The increase of the VPTs (250 Hz) in relation to use of vibrating tools was 1.8-fold higher on average in the whole group and 2.3-fold higher in the young (< 45) railway workers who had used hand held tamping machines, than in the corresponding groups of lumberjacks, who had used chain saws, whereas the frequency weighted acceleration of vibration in tamping machines was fourfold. CONCLUSION--There was a significant dose-response relation between the exposure to hand-arm vibration and the VPTs. The VPTs as a function of the frequency weighted acceleration of vibration and the exposure to vibration gave promising results for assessment of the risk of damage to sensory nerves induced by vibration. PMID:7795756

  1. An overall and dose-response meta-analysis of red blood cell distribution width and CVD outcomes

    PubMed Central

    Hou, Haifeng; Sun, Tao; Li, Cheng; Li, Yuanmin; Guo, Zheng; Wang, Wei; Li, Dong

    2017-01-01

    Red blood cell distribution width (RDW) is the coefficient of variation of red blood cell size, considered to be associated with cardiovascular disease (CVD). This study aimed to comprehensively synthesize previous studies on RDW and CVD outcomes through an overall and dose-response meta-analysis. PubMed, Embase and Web of Science were searched systematically for English and Chinese language publications up to November 30, 2015. We extracted data from publications matching our inclusion criteria for calculating pooled hazard ratio (HR), which was used to assess prognostic impact of RDW on CVD. Twenty-seven articles, consisting of 28 studies and 102,689 participants (mean age 63.9 years, 63,703 males/36,846 females, 2,140 gender-unmentioned subjects) were included in the present meta-analysis. The pooled HRs are 1.12 (95% CI = 1.09–1.15) for the association of all-cause mortality (ACM) per 1% increase of RDW, 1.12(95% CI = 1.08–1.17) for major adverse cardiac events (MACEs) per 1% increase of RDW. A dose-response curve relating RDW increase to its effect on CVD outcomes was established (pcurve < 0.001). For every 1-unit increase of RDW, there is an increased risk of occurrence of ACM (pooled HR = 1.03, 95% CI = 1.02–1.04) and MACEs (pooled HR = 1.04, 95% CI = 1.01–1.06). This study indicates RDW may be a prognostic indicator for CVD outcomes. PMID:28233844

  2. Functional MRI determination of a dose-response relationship to lower extremity neuromuscular electrical stimulation in healthy subjects.

    PubMed

    Smith, Gerald V; Alon, Gad; Roys, Steven R; Gullapalli, Rao P

    2003-05-01

    Although empirical evidence supports the use of neuromuscular electrical stimulation (NMES) to treat physical impairments associated with stroke, the mechanisms underlying the efficacy of this modality are poorly understood. Recent studies have employed functional imaging to investigations of brain responses to median nerve stimulation. These studies suggest a dose-response relationship may exist between selected stimulation parameters and hemodynamic responses in sensorimotor regions. However, substantial gaps exist in this literature. The present study was designed to address these deficiencies. Ten healthy subjects participated. In phase one, four stimulus intensity levels were established: (1). sensory threshold [Th], (2). (MM-Th)x0.333+Th [low-intermediate level, LI], (3). (MM-Th)x0.666+Th [high-intermediate level, HI], and (4). maximal motor (MM). In phase two, subjects were scanned using a spiral-echoplanar imaging technique at each stimulus level. Image sets were analyzed to determine hemodynamic responses at the highest Pearson correlation level ( r) ascertained for each of five areas of interest (AOI): (1). primary sensory, (2). primary motor, (3). cingulate gyrus, (4). thalamus, and (5). cerebellum. ANOVA demonstrated significant main effects for BOLD signal amplitude ( p<0.05) changes in all AOI. Similarly, ANOVA showed significant differences in the volume of activation ( p<0.05) with increasing stimulus intensity in four AOI. Secondary analyses of pooled data showed increasing probabilities of activation at higher stimulus intensities within each AOI. Collectively, these data indicate a dose-response relationship exists between lower extremity NMES and brain activation in specific neural regions. The current results, while limited in their generalizability, are foundational for future studies of interventions using NMES.

  3. Association between physical activity and all cancer mortality: Dose-response meta-analysis of cohort studies.

    PubMed

    Li, Yingjun; Gu, Mengjia; Jing, Fangyuan; Cai, Shaofang; Bao, Chengzhen; Wang, Jianbing; Jin, Mingjuan; Chen, Kun

    2016-02-15

    The relationship between physical activity (PA) before cancer diagnosis and all cancer mortality among the general population is not well defined because of inconsistent results from published studies. Thus, the lack of a meta-analysis that addresses that issue prompted the current report. We conducted a literature search of PubMed and Web of Science to identify all relevant epidemiological studies published before February 28, 2015. We performed categorical and dose-response meta-analyses to evaluate and quantify the association between pre-diagnosis PA and all cancer mortality. A total of 32 prospective cohort studies involving 59,362 cancer deaths were included in this meta-analysis. The pooled relative risks (RRs) of all cancer mortality were 0.80 [95% confidence interval (CI) = 0.76-0.85)] for highest versus lowest PA group and 0.85 (95% CI = 0.82-0.88) for PA versus non/occasional PA group. Dose-response analysis showed that the increment in pre-diagnosis PA level was associated with a decreased risk of cancer death continuously. Moreover, an increment of 10 MET-h/week was related to a 7% lower risk for all cancer mortality (RR = 0.93, 95% CI = 0.91-0.95). In conclusion, the present meta-analysis provides evidence of an inverse association between pre-diagnosis PA and all cancer mortality among the general population. High-quality epidemiological studies that employ standardized PA assessments and unified definitions of PA levels should be developed in future.

  4. Predicting the probability of successful efficacy of a dissociated agonist of the glucocorticoid receptor from dose-response analysis.

    PubMed

    Conrado, Daniela J; Krishnaswami, Sriram; Shoji, Satoshi; Kolluri, Sheela; Hey-Hadavi, Judith; McCabe, Dorothy; Rojo, Ricardo; Tammara, Brinda K

    2016-06-01

    PF-04171327 is a dissociated agonist of the glucocorticoid receptor (DAGR) being developed to retain anti-inflammatory efficacy while reducing unwanted effects. Our aim was to conduct a longitudinal dose-response analysis to identify the DAGR doses with efficacy similar to or greater than prednisone 10 mg once daily (QD). The data included were from a Phase 2, randomized, double-blind, parallel-group study in 323 subjects with active rheumatoid arthritis on a background of methotrexate. Subjects received DAGR 1, 5, 10 or 15 mg, prednisone 5 or 10 mg, or placebo QD for 8 weeks. The Disease Activity Score 28-4 calculated using C-Reactive Protein (DAS28-4 CRP) was the efficacy endpoint utilized in this dose-response model. For DAGR, the maximum effect (Emax) on DAS28-4 CRP was estimated to be -1.2 points (95 % CI -1.7, -0.84), and the evaluated dose range provided 31-87 % of the Emax; for prednisone 5 and 10 mg, the estimated effects were -0.27 (95 % CI -0.55, 0.006) and -0.94 point (95 % CI -1.3, -0.59), respectively. Stochastic simulations indicated that the DAGR 1, 5, 10 and 15 mg have probabilities of 0.9, 29, 54 and 62 %, respectively, to achieve efficacy greater than prednisone 10 mg at week 8. DAGR 9 mg estimated probability was 50 % suggesting that DAGR ≥9 mg QD has an effect on DAS28-4 CRP comparable to or greater than prednisone 10 mg QD. This work informs dose selection for late-stage confirmatory trials.

  5. Genotoxicity testing: moving beyond qualitative "screen and bin" approach towards characterization of dose-response and thresholds.

    PubMed

    Pottenger, Lynn H; Gollapudi, B Bhaskar

    2010-01-01

    For more than 40+ years, genotoxicity data have been interpreted in a qualitative, binary mode; a chemical is considered either positive or negative for a response in the test system. Although dose-response information is sometimes used in this decision, it is not routine to obtain the amount of information needed to inform risk assessment, for example to determine no-observed-genotoxic-effect-levels, primarily due to the historical view of genotoxic responses as "linear, no-threshold." Only recently have researchers begun to address this issue through robust experimental designs and application of statistical models. A growing body-of-evidence supports the existence of response thresholds for a number of mutagenic agents, in vitro and in vivo. Clearly, simple observation of a "hockey-stick" dose-response curve is not sufficient to establish a threshold. Collection of robust empirical data must be supported with an analysis of biological plausibility for the observed threshold. In this context, a chemical-specific mode-of-action (MOA) approach, which identifies key events responsible for the observed mutagenic effect, is extremely valuable. Biomarkers of key events, providing qualitative and quantitative information, can be integrated in a weight-of-evidence-based assessment of genotoxicity data from multiple test systems and used to identify data gaps to resolve/reduce uncertainties during the risk assessment process. To this end, specific recommendations on study design and data analysis are proposed. As the Environmental Mutagen Society celebrates its 40th anniversary, the field of genetic toxicology is marking a milestone on the path to a new paradigm, using a MOA, data-driven approach to answer questions about thresholds for genotoxic agents.

  6. An overall and dose-response meta-analysis of red blood cell distribution width and CVD outcomes.

    PubMed

    Hou, Haifeng; Sun, Tao; Li, Cheng; Li, Yuanmin; Guo, Zheng; Wang, Wei; Li, Dong

    2017-02-24

    Red blood cell distribution width (RDW) is the coefficient of variation of red blood cell size, considered to be associated with cardiovascular disease (CVD). This study aimed to comprehensively synthesize previous studies on RDW and CVD outcomes through an overall and dose-response meta-analysis. PubMed, Embase and Web of Science were searched systematically for English and Chinese language publications up to November 30, 2015. We extracted data from publications matching our inclusion criteria for calculating pooled hazard ratio (HR), which was used to assess prognostic impact of RDW on CVD. Twenty-seven articles, consisting of 28 studies and 102,689 participants (mean age 63.9 years, 63,703 males/36,846 females, 2,140 gender-unmentioned subjects) were included in the present meta-analysis. The pooled HRs are 1.12 (95% CI = 1.09-1.15) for the association of all-cause mortality (ACM) per 1% increase of RDW, 1.12(95% CI = 1.08-1.17) for major adverse cardiac events (MACEs) per 1% increase of RDW. A dose-response curve relating RDW increase to its effect on CVD outcomes was established (pcurve < 0.001). For every 1-unit increase of RDW, there is an increased risk of occurrence of ACM (pooled HR = 1.03, 95% CI = 1.02-1.04) and MACEs (pooled HR = 1.04, 95% CI = 1.01-1.06). This study indicates RDW may be a prognostic indicator for CVD outcomes.

  7. Dose--response of initial G2-chromatid breaks induced in normal human fibroblasts by heavy ions

    NASA Technical Reports Server (NTRS)

    Kawata, T.; Durante, M.; Furusawa, Y.; George, K.; Takai, N.; Wu, H.; Cucinotta, F. A.; Dicello, J. F. (Principal Investigator)

    2001-01-01

    PURPOSE: To investigate initial chromatid breaks in prematurely condensed G2 chromosomes following exposure to heavy ions of different LET. MATERIAL AND METHODS: Exponentially growing human fibroblast cells AG1522 were irradiated with gamma-rays, energetic carbon (13 keV/ microm, 80 keV/microm), silicon (55 keV/microm) and iron (140 keV/microm, 185keV/microm, 440keV/microm) ions. Chromosomes were prematurely condensed using calyculin-A. Initial chromatid-type and isochromatid breaks in G2 cells were scored. RESULTS: The dose response curves for total chromatid breaks were linear regardless of radiation type. The relative biological effectiveness (RBE) showed a LET-dependent increase, peaking around 2.7 at 55-80keV/microm and decreasing at higher LET. The dose response curves for isochromatid-type breaks were linear for high-LET radiations, but linear-quadratic for gamma-rays and 13 keV/microm carbon ions. The RBE for the induction of isochromatid breaks obtained from linear components increased rapidly between 13keV/microm (about 7) and 80keV/microm carbon (about 71), and decreased gradually until 440 keV/microm iron ions (about 66). CONCLUSIONS: High-LET radiations are more effective at inducing isochromatid breaks, while low-LET radiations are more effective at inducing chromatid-type breaks. The densely ionizing track structures of heavy ions and the proximity of sister chromatids in G2 cells result in an increase in isochromatid breaks.

  8. Dose-response modeling of occupational exposure to polycyclic aromatic hydrocarbons with biomarkers of exposure and effect.

    PubMed

    Pesch, Beate; Kappler, Martin; Straif, Kurt; Marczynski, Boleslaw; Preuss, Ralf; Rossbach, Bernd; Rihs, Hans-Peter; Weiss, Tobias; Rabstein, Sylvia; Pierl, Christiane; Scherenberg, Michael; Adams, Ansgar; Käfferlein, Heiko Udo; Angerer, Jürgen; Wilhelm, Michael; Seidel, Albrecht; Brüning, Thomas

    2007-09-01

    In regulatory toxicology, the dose-response relationship between occupational exposure and biomarkers is of importance in setting threshold values. We analyzed the relationships between occupational exposure to polycyclic aromatic hydrocarbons (PAH) and various biomarkers of internal exposure and DNA damage with data from 284 highly exposed male workers. Personal exposure to phenanthrene and other PAHs was measured during shift and correlated with the sum of 1-, 2+9-, 3-, and 4-hydroxyphenanthrenes in post-shift urine. PAHs and hydroxyphenanthrenes were associated with DNA damage assessed in WBC as 8-oxo-7,8-dihydro-2'-deoxyguanosine/10(6) dGuo and strand breaks by Comet assay as Olive tail moment. Hydroxyphenanthrenes correlated with phenanthrene (Spearman r(s) = 0.70; P < 0.0001). No correlations could be found between strand breaks and exposure (r(s) = 0.01, P < 0.0001 for PAHs; r(s) = -0.03, P = 0.68 for hydroxyphenanthrenes). Correlations with 8-oxo-7,8-dihydro-2'-deoxyguanosine/10(6) dGuo were weakly negative (r(s) = -0.22, P = 0.004 for PAHs) or flat (r(s) = -0.08, P = 0.31 for hydroxyphenanthrenes). Linear splines were applied to assess the relationships between the log-transformed variables. All regression models were adjusted for smoking and type of industry. For hydroxyphenanthrenes, 51.7% of the variance could be explained by phenanthrene and other predictors. Up to 0.77 microg/m(3) phenanthrene, no association could be found with hydroxyphenanthrenes. Above that point, hydroxyphenanthrenes increased by a factor of 1.47 under a doubling of phenanthrene exposure (slope, 0.56; 95% confidence interval, 0.47-0.64). Hydroxyphenanthrenes may be recommended as biomarker of occupational PAH exposure, whereas biomarkers of DNA damage in blood did not show a dose-response relation to PAH exposure.

  9. Gamma-glutamyltransferase and risk of cardiovascular mortality: A dose-response meta-analysis of prospective cohort studies

    PubMed Central

    Huang, Rongzhong; Li, Xingsheng; Huang, Wenxiang

    2017-01-01

    Background Serum gamma-glutamyltransferase (GGT) elevation likely contributes to cardiovascular (CV) mortality, however it has remained unknown whether a dose-response relationship exists between serum GGT and CV mortality. Methods We searched the PubMed, EMBASE, and Cochrane library databases for prospective cohort studies published up to October 2, 2016. Summary hazard ratios (HRs) with their corresponding 95% confidence intervals (CIs) were calculated using a fixed effects model. Findings Nine prospective studies, including 527,589 participants and more than 7,011 cases, were included in this meta-analysis. For the moderate, high, and highest levels of GGT, the pooled HRs of CV mortality were 1.11 (95% CI = 1.04–1.19), 1.29 (95% CI = 1.21–1.38) and 1.59 (95% CI = 1.47–1.72), respectively (all p < 0.05 as compared to the lowest levels of GGT). Additionally, the HR per incremental increase of GGT by 10 U/L was 1.10 (95% CI = 1.08–1.11). Evidence of a positive relationship with nonlinear trend for GGT elevation with CV mortality in females was found (P = 0.04 for nonlinearity). However, a linear model was better fit to illustrate the GGT-CV mortality among males (P = 0.304 for nonlinearity). Conclusions These findings indicate that serum GGT activity within the reference interval is positively associated with increased risk of CV mortality in a dose-response manner. PMID:28231268

  10. Recognizing the importance of exposure-dose-response dynamics for ecotoxicity assessment: nitrofurazone-induced antioxidase activity and mRNA expression in model protozoan Euplotes vannus.

    PubMed

    Hong, Yazhen; Liu, Shuxing; Lin, Xiaofeng; Li, Jiqiu; Yi, Zhenzhen; Al-Rasheid, Khaled A S

    2015-06-01

    The equivocality of dose-response relationships has, in practice, hampered the application of biomarkers as a means to evaluate environmental risk, yet this important issue has not yet been fully recognized or explored. This paper evaluates the potential of antioxidant enzymes in the ciliated protozoan Euplotes vannus for use as biomarkers. Dose-response dynamics, together with both the enzyme activity and the gene expression of the antioxidant enzymes, superoxide dismutase, and glutathione peroxidase, were investigated when E. vannus were exposed to graded doses of nitrofurazone for several discrete durations. Mathematical models were explored to characterize the dose-response profiles and, specifically, to identify any equivocality in terms of endpoint. Significant differences were found in both enzyme activity and messenger RNA (mRNA) expression in the E. vannus treated with nitrofurazone, and the interactions between exposure dosage and duration were significant. Correlations between enzyme activity, mRNA expression, and nitrofurazone dose varied with exposure duration. Particularly, the dose-responses showed different dynamics depending on either endpoint or exposure duration. Our findings suggest that both the enzyme activity and the gene expression of the tested antioxidant enzymes can be used as biomarkers for ecotoxicological assessment on the premise of ascertaining appropriate dosage scope, exposure duration, endpoint, etc., which can be achieved by using dose-response dynamics.

  11. Characterizing dose-responses of catalase to nitrofurazone exposure in model ciliated protozoan Euplotes vannus for ecotoxicity assessment: enzyme activity and mRNA expression.

    PubMed

    Li, Jiqiu; Zhou, Liang; Lin, Xiaofeng; Yi, Zhenzhen; Al-Rasheid, Khaled A S

    2014-02-01

    In environmental studies, some biological responses, known as biomarkers, have been used as a powerful bioassay tool for more than four decades. Disparity between enzyme activity and mRNA abundance leads to correlation equivocality, which makes the application of biomarkers for environmental risk assessment more complicated. This study investigates this disparity in the case of catalase when used as a biomarker for detecting ecotoxicity induced by antibiotics in aquatic ecosystems. In particular, dose-responses for catalase activity and mRNA expression abundance were investigated in Euplotes vannus which were exposed to graded doses of nitrofurazone for several discrete durations, and dose-response models were developed to characterize the dose-response dynamics. Significant differences were found in both catalase activity and mRNA expression abundance among the E. vannus treated with nitrofurazone. Catalase activity showed a hormetic-like effect in terms of dose-response, characterized by a biphasic relationship which was more clearly evident after a longer exposure period, while mRNA expression abundance increased linearly with the exposure duration. Additionally, the correlation between catalase activity and mRNA expression abundance reversed along with the duration of exposure to nitrofurazone. Taken together, our results demonstrate that catalase mRNA expression offers a more straightforward dose-response model than enzyme activity. Our findings suggest that both catalase enzyme activity and mRNA expression abundance can be used jointly as bioassay tools for detecting ecotoxicity induced by nitrofurazone in aquatic ecosystems.

  12. Kinetic Modeling Reveals the Roles of Reactive Oxygen Species Scavenging and DNA Repair Processes in Shaping the Dose-Response Curve of KBrO₃-Induced DNA Damage.

    PubMed

    Spassova, Maria A; Miller, David J; Nikolov, Alexander S

    2015-01-01

    We have developed a kinetic model to investigate how DNA repair processes and scavengers of reactive oxygen species (ROS) can affect the dose-response shape of prooxidant induced DNA damage. We used as an example chemical KBrO3 which is activated by glutathione and forms reactive intermediates that directly interact with DNA to form 8-hydroxy-2-deoxyguanosine DNA adducts (8-OH-dG). The single strand breaks (SSB) that can result from failed base excision repair of these adducts were considered as an effect downstream from 8-OH-dG. We previously demonstrated that, in the presence of effective base excision repair, 8-OH-dG can exhibit threshold-like dose-response dependence, while the downstream SSB can still exhibit a linear dose-response. Here we demonstrate that this result holds for a variety of conditions, including low levels of GSH, the presence of additional SSB repair mechanisms, or a scavenger. It has been shown that melatonin, a terminal scavenger, inhibits KBrO3-caused oxidative damage. Our modeling revealed that sustained exposure to KBrO3 can lead to fast scavenger exhaustion, in which case the dose-response shapes for both endpoints are not substantially affected. The results are important to consider when forming conclusions on a chemical's toxicity dose dependence based on the dose-response of early genotoxic events.

  13. Implementation of a dose-response curve for γ-radiation in the Portuguese population by use of the chromosomal aberration assay.

    PubMed

    Martins, V; Antunes, A C; Monteiro Gil, O

    2013-01-20

    An in vitro dose-response curve following exposure to γ-radiation was determined at the IST/ITN, by use of the chromosomal aberration assay. This is the first study of this kind carried out among the Portuguese population. Un-irradiated and γ-irradiated peripheral blood lymphocytes from 16 healthy donors were cultured. A total of 22,395 metaphases were analyzed for frequency and distribution of dicentrics and centric rings, as a function of the radiation dose. The dose-response data for dicentrics and dicentrics plus centric rings were fitted by use of a linear-quadratic model: Y(dic)=(0.0011±0.0006)+(0.0105±0.0035)D+(0.0480±0.0019)D(2) and Y(dic+rings)=(0.0011±0.0006)+(0.0095±0.0036)D+(0.0536±0.0020)D(2). Also, calibration curves related to age and gender were determined, but no significant differences were found. Following the establishment of the dose-response curves, a validation experiment was carried out with three individuals. Real and estimated doses, obtained with the dose-response curves, were in agreement. These results give us confidence to apply both dose-response calibration curves in future biological dosimetry requirements.

  14. A U-shaped dose-response relationship between x radiation and sex-linked recessive lethal mutation in male germ cells of Drosophila.

    PubMed

    Koana, Takao; Tsujimura, Hidenobu

    2010-07-01

    We reported previously that low-dose X irradiation of DNA repair-proficient immature sperm of wild-type Drosophila melanogaster at a low dose rate (50 mGy/min) resulted in a mutation frequency that was lower than that in the sham-irradiated group. Therefore, a U-shaped dose-response relationship was suggested. Here we show that the dose-response curve is actually U-shaped by carrying out a large-scale sex-linked recessive lethal assay using Drosophila. No reduction of the mutation frequency was observed in a strain mutant for the nucleotide excision repair gene mei-9a (Drosophila homologue of human XPF). Introduction of a chromosome fragment containing mei-9+ into the mei-9a mutant strain restored the reduction of the mutation frequency in the low-dose-irradiated group. These results showed that DNA repair was responsible for the U-shaped dose-response relationship in Drosophila.

  15. How much is enough? Modulation of dose-response curve for steroid receptor-regulated gene expression by changing concentrations of transcription factor.

    PubMed

    Simons, S Stoney

    2006-01-01

    The position of the dose-response curve for steroid-regulated gene expression determines how much variation in response will accompany the normal physiological changes in circulating steroid. Over the last several years, it has become clear that the concentration of steroid hormone required for half-maximal induction or repression by a given receptor-steroid complex, which is normally called the EC50, is not constant for all responsive genes. Thus, the position of the dose-response curve can change so that a single concentration of steroid produces very different percentages of maximal activity. This, in turn, allows for the differential expression of genes by a common steroid hormone concentration during development, differentiation, and homeostasis. Here we review the variety of factors that influence the EC50 and position of the dose-response curve for steroid hormone receptors, discuss what is known about the mechanisms, and highlight promising areas for future research.

  16. The Hematopoietic Syndrome of the Acute Radiation Syndrome in Rhesus Macaques: A Systematic Review of the Lethal Dose Response Relationship.

    PubMed

    MacVittie, Thomas J; Farese, Ann M; Jackson, William

    2015-11-01

    Well characterized animal models that mimic the human response to potentially lethal doses of radiation are required to assess the efficacy of medical countermeasures under the criteria of the U.S. Food and Drug Administration "animal rule." Development of a model requires the determination of the radiation dose response relationship and time course of mortality and morbidity across the hematopoietic acute radiation syndrome. The nonhuman primate, rhesus macaque, is a relevant animal model that may be used to determine the efficacy of medical countermeasures to mitigate major signs of morbidity and mortality at selected lethal doses of total body irradiation. A systematic review of relevant studies that determined the dose response relationship for the hematopoietic acute radiation syndrome in the rhesus macaque relative to radiation quality, dose rate, and exposure uniformity has never been performed. The selection of data cohorts was made from the following sources: Ovid Medline (1957-present), PubMed (1954-present), AGRICOLA (1976-present), Web of Science (1954-present), and U.S. HHS REPORT (2002 to present). The following terms were used: Rhesus, total body-irradiation, total body x irradiation, TBI, irradiation, gamma radiation, hematopoiesis, LD50/60, Macaca mulatta, whole-body irradiation, nonhuman primate, NHP, monkey, primates, hematopoietic radiation syndrome, mortality, and nuclear radiation. The reference lists of all studies, published and unpublished, were reviewed for additional studies. The total number of hits across all search sites was 3,001. There were a number of referenced, unpublished, non-peer reviewed government reports that were unavailable for review. Fifteen studies, 11 primary (n = 863) and four secondary (n = 153) studies [n = 1,016 total nonhuman primates (NHP), rhesus Macaca mulatta] were evaluated to provide an informative and consistent review. The dose response relationships (DRRs) were determined for uniform or non-uniform total

  17. Dose-Response Modeling of the Visual Pathway Tolerance to Single-Fraction and Hypofractionated Stereotactic Radiosurgery.

    PubMed

    Hiniker, Susan M; Modlin, Leslie A; Choi, Clara Y; Atalar, Banu; Seiger, Kira; Binkley, Michael S; Harris, Jeremy P; Liao, Yaping Joyce; Fischbein, Nancy; Wang, Lei; Ho, Anthony; Lo, Anthony; Chang, Steven D; Harsh, Griffith R; Gibbs, Iris C; Hancock, Steven L; Li, Gordon; Adler, John R; Soltys, Scott G

    2016-04-01

    Patients with tumors adjacent to the optic nerves and chiasm are frequently not candidates for single-fraction stereotactic radiosurgery (SRS) due to concern for radiation-induced optic neuropathy. However, these patients have been successfully treated with hypofractionated SRS over 2-5 days, though dose constraints have not yet been well defined. We reviewed the literature on optic tolerance to radiation and constructed a dose-response model for visual pathway tolerance to SRS delivered in 1-5 fractions. We analyzed optic nerve and chiasm dose-volume histogram (DVH) data from perioptic tumors, defined as those within 3mm of the optic nerves or chiasm, treated with SRS from 2000-2013 at our institution. Tumors with subsequent local progression were excluded from the primary analysis of vision outcome. A total of 262 evaluable cases (26 with malignant and 236 with benign tumors) with visual field and clinical outcomes were analyzed. Median patient follow-up was 37 months (range: 2-142 months). The median number of fractions was 3 (1 fraction n = 47, 2 fraction n = 28, 3 fraction n = 111, 4 fraction n = 10, and 5 fraction n = 66); doses were converted to 3-fraction equivalent doses with the linear quadratic model using α/β = 2Gy prior to modeling. Optic structure dose parameters analyzed included Dmin, Dmedian, Dmean, Dmax, V30Gy, V25Gy, V20Gy, V15Gy, V10Gy, V5Gy, D50%, D10%, D5%, D1%, D1cc, D0.50cc, D0.25cc, D0.20cc, D0.10cc, D0.05cc, D0.03cc. From the plan DVHs, a maximum-likelihood parameter fitting of the probit dose-response model was performed using DVH Evaluator software. The 68% CIs, corresponding to one standard deviation, were calculated using the profile likelihood method. Of the 262 analyzed, 2 (0.8%) patients experienced common terminology criteria for adverse events grade 4 vision loss in one eye, defined as vision of 20/200 or worse in the affected eye. One of these patients had received 2 previous courses of radiotherapy to the optic structures

  18. Radiation dose response estimation with emphasis on low dose range using restricted cubic splines: application to all solid cancer mortality data, 1950-2003, in atomic bomb survivors.

    PubMed

    Nakashima, Eiji

    2015-07-01

    Using the all solid cancer mortality data set of the Life Span Study (LSS) cohort from 1950 to 2003 (LSS Report 14) data among atomic bomb survivors, excess relative risk (ERR) statistical analyses were performed using the second degree polynomial and the threshold and restricted cubic spline (RCS) dose response models. For the RCS models with 3 to 7 knots of equally spaced percentiles with margins in the dose range greater than 50 mGy, the dose response was assumed to be linear at less than 70 to 90 mGy. Due to the skewed dose distribution of atomic bomb survivors, the current knot system for the RCS analysis results in a detailed depiction of the dose response as less than approximately 0.5 Gy. The 6 knot RCS models for the all-solid cancer mortality dose response of the whole dose or less than 2 Gy were selected with the AIC model selection criterion and fit significantly better (p < 0.05) than the linear (L) model. The usual RCS includes the L-global model but not the quadratic (Q) nor linear-quadratic (LQ) global models. The authors extended the RCS to include L or LQ global models by putting L or LQ constraints on the cubic spline in the lower and upper tails, and the best RCS model selected with AIC criterion was the usual RCS with L-constraints in both the lower and upper tails. The selected RCS had a linear dose-response model in the lower dose range (i.e., < 0.2-0.3 Gy) and was compatible with the linear no-threshold (LNT) model in this dose range. The proposed method is also useful in describing the dose response of a specific cancer or non-cancer disease incidence/mortality.

  19. Dose-Response Relationship between Dietary Magnesium Intake and Risk of Type 2 Diabetes Mellitus: A Systematic Review and Meta-Regression Analysis of Prospective Cohort Studies

    PubMed Central

    Fang, Xin; Han, Hedong; Li, Mei; Liang, Chun; Fan, Zhongjie; Aaseth, Jan; He, Jia; Montgomery, Scott; Cao, Yang

    2016-01-01

    The epidemiological evidence for a dose-response relationship between magnesium intake and risk of type 2 diabetes mellitus (T2D) is sparse. The aim of the study was to summarize the evidence for the association of dietary magnesium intake with risk of T2D and evaluate the dose-response relationship. We conducted a systematic review and meta-analysis of prospective cohort studies that reported dietary magnesium intake and risk of incident T2D. We identified relevant studies by searching major scientific literature databases and grey literature resources from their inception to February 2016. We included cohort studies that provided risk ratios, i.e., relative risks (RRs), odds ratios (ORs) or hazard ratios (HRs), for T2D. Linear dose-response relationships were assessed using random-effects meta-regression. Potential nonlinear associations were evaluated using restricted cubic splines. A total of 25 studies met the eligibility criteria. These studies comprised 637,922 individuals including 26,828 with a T2D diagnosis. Compared with the lowest magnesium consumption group in the population, the risk of T2D was reduced by 17% across all the studies; 19% in women and 16% in men. A statistically significant linear dose-response relationship was found between incremental magnesium intake and T2D risk. After adjusting for age and body mass index, the risk of T2D incidence was reduced by 8%–13% for per 100 mg/day increment in dietary magnesium intake. There was no evidence to support a nonlinear dose-response relationship between dietary magnesium intake and T2D risk. The combined data supports a role for magnesium in reducing risk of T2D, with a statistically significant linear dose-response pattern within the reference dose range of dietary intake among Asian and US populations. The evidence from Europe and black people is limited and more prospective studies are needed for the two subgroups. PMID:27869762

  20. Cryptosporidium parvum: determination of ID₅₀ and the dose-response relationship in experimentally challenged dairy calves.

    PubMed

    Zambriski, J A; Nydam, D V; Wilcox, Z J; Bowman, D D; Mohammed, H O; Liotta, J L

    2013-10-18

    The objectives were to determine the median infective dose (ID₅₀) of Cryptosporidium parvum and to describe the dose-response relationship including associated clinical illness in experimentally challenged dairy calves. Within the first 24h of life, 27 test calves were experimentally challenged with C. parvum oocysts and 3 control calves were sham dosed. Test calves received 1 of 8 possible doses (25, 50, 100, 500, 1 × 10(3), 1 × 10(4), 1 × 10(5), and 1 × 10(6) oocysts). All 27 test calves developed diarrhea. Fecal oocyst shedding occurred in 25 (92.6%) test calves and in 0 control calves. The 2 non-shedding test calves both received 25 oocysts. There was an inverse relationship between dose and time to onset of fecal oocyst shedding (P=0.005). There was no relationship found between dose and duration (P=0.2) or cessation (P=0.3) of fecal oocyst shedding. In addition, there was not a significant relationship between log-dose and the log-peak oocysts (P=0.2) or log-total oocysts (P=0.5) counted/g of feces across the dose groups. There was a positive dose-response relationship between log-dose and diarrhea (P=0.01). However, when controlling for other factors, such as onset and cessation of fecal oocyst shedding, dose was not a significant predictor of diarrhea (P=0.5). Onset and cessation of fecal oocyst shedding were found to be the best predictors of diarrhea (P=0.0006 and P=0.04, respectively). The ID₅₀ for fecal oocyst shedding was 5.8 oocysts, for diarrhea was 9.7 oocysts, and for fecal oocyst shedding with diarrhea was 16.6 oocysts. Given that the ID₅₀ of C. parvum is far less than would be excreted into the environment by a naturally infected calf, prevention and control of cryptosporidiosis is a formidable challenge.

  1. Dose-Response and Efficacy of Spinal Manipulation for Care of Chronic Low Back Pain: A Randomized Controlled Trial

    PubMed Central

    Haas, Mitchell; Vavrek, Darcy; Peterson, David; Polissar, Nayak; Neradilek, Moni B.

    2013-01-01

    BACKGROUND CONTEXT There have been no full-scale trials of the optimal number of visits for the care of any condition with spinal manipulation. PURPOSE To identify the dose-response relationship between visits to a chiropractor for spinal manipulation and chronic low back pain (cLBP) outcomes; to determine the efficacy of manipulation by comparison to a light-massage control. STUDY DESIGN/SETTING Practice-based randomized controlled trial. PATIENT SAMPLE Four hundred participants with cLBP. OUTCOME MEASURES The primary cLBP outcomes were the100-point Modified Von Korff pain intensity and functional disability scales evaluated at the 12 and 24-week primary endpoints. Secondary outcomes included days with pain and functional disability, pain unpleasantness, global perceived improvement, medication use, and general health status. METHODS One hundred participants with cLBP were randomized to each of four dose levels of care: 0, 6, 12, or 18 sessions of spinal manipulation from a chiropractor. Participants were treated three times per week for six weeks. At sessions when manipulation was not assigned, they received a focused light massage control. Covariate-adjusted linear dose effects and comparisons to the no-manipulation control group were evaluated at 6, 12, 18, 24, 39, and 52 weeks. RESULTS For the primary outcomes, mean pain and disability improvement in the manipulation groups was 20 points by 12 weeks and sustainable to 52 weeks. Linear dose-response effects were small, reaching about two points per six manipulation sessions at 12 and 52 weeks for both variables (P < .025). At 12 weeks, the greatest differences from the no-manipulation control were found for 12 sessions (8.6 pain and 7.6 disability points, P < .025); at 24 weeks, differences were negligible. At 52 weeks, the greatest group differences were seen for 18 visits (5.9 pain and 8.8 disability points, P < .025). CONCLUSIONS The number of spinal manipulation visits had modest effects on cLBP outcomes

  2. No Dose-Response Effect of Carbohydrate Mouth Rinse Concentration on 5-km Running Performance in Recreational Athletes.

    PubMed

    Clarke, Neil D; Thomas, James R; Kagka, Marion; Ramsbottom, Roger; Delextrat, Anne

    2017-03-01

    Clarke, ND, Thomas, JR, Kagka, M, Ramsbottom, R, and Delextrat, A. No dose-response effect of carbohydrate mouth rinse concentration on 5-km running performance in recreational athletes. J Strength Cond Res 31(3): 715-720, 2017-Oral carbohydrate rinsing has been demonstrated to provide beneficial effects on exercise performance of durations of up to 1 hour, albeit predominately in a laboratory setting. The aim of the present study was to investigate the effects of different concentrations of carbohydrate solution mouth rinse on 5-km running performance. Fifteen healthy men (n = 9; mean ± SD age; 42 ± 10 years; height, 177.6 ± 6.1 cm; body mass, 73.9 ± 8.9 kg) and women (n = 6; mean ± SD age, 43 ± 9 years; height, 166.5 ± 4.1 cm; body mass, 65.7 ± 6.8 kg) performed a 5-km running time trial on a track on 4 separate occasions. Immediately before starting the time trial and then after each 1 km, subjects rinsed 25 ml of 0, 3, 6, or 12% maltodextrin for 10 seconds. Mouth rinsing with 0, 3, 6, or 12% maltodextrin did not have a significant effect on the time to complete the time trial (0%, 26:34 ± 4:07 minutes:seconds; 3%, 27:17 ± 4:33 minutes:seconds; 6%, 27:05 ± 3:52 minutes:seconds; 12%, 26:47 ± 4.31 minutes:seconds; p = 0.071; (Equation is included in full-text article.)= 0.15), heart rate (p = 0.095; (Equation is included in full-text article.)= 0.16), rating of perceived exertion (p = 0.195; (Equation is included in full-text article.)= 0.11), blood glucose (p = 0.920; (Equation is included in full-text article.)= 0.01), and blood lactate concentration (p = 0.831; (Equation is included in full-text article.)= 0.02), with only nonsignificant trivial to small differences between concentrations. Results of this study suggest that carbohydrate mouth rinsing provides no ergogenic advantage over an acaloric placebo (0%) and that there is no dose-response relationship between carbohydrate solution concentration and 5-km track running performance.

  3. The dose response relation for rat spinal cord paralysis analyzed in terms of the effective size of the functional subunit

    NASA Astrophysics Data System (ADS)

    Adamus-Górka, Magdalena; Mavroidis, Panayiotis; Brahme, Anders; Lind, Bengt K.

    2008-11-01

    Radiobiological models for estimating normal tissue complication probability (NTCP) are increasingly used in order to quantify or optimize the clinical outcome of radiation therapy. A good NTCP model should fulfill at least the following two requirements: (a) it should predict the sigmoid shape of the corresponding dose-response curve and (b) it should accurately describe the probability of a specified response for arbitrary non-uniform dose delivery for a given endpoint as accurately as possible, i.e. predict the volume dependence. In recent studies of the volume effect of a rat spinal cord after irradiation with narrow and broad proton beams the authors claim that none of the existing NTCP models is able to describe their results. Published experimental data have been used here to try to quantify the change in the effective dose (D50) causing 50% response for different field sizes. The present study was initiated to describe the induction of white matter necrosis in a rat spinal cord after irradiation with narrow proton beams in terms of the mean dose to the effective volume of the functional subunit (FSU). The physically delivered dose distribution was convolved with a function describing the effective size or, more accurately, the sensitivity distribution of the FSU to obtain the effective mean dose deposited in it. This procedure allows the determination of the mean D50 value of the FSUs of a certain size which is of interest for example if the cell nucleus of the oligodendrocyte is the sensitive target. Using the least-squares method to compare the effective doses for different sizes of the functional subunits with the experimental data the best fit was obtained with a length of about 9 mm. For the non-uniform dose distributions an effective FSU length of 8 mm gave the optimal fit with the probit dose-response model. The method could also be used to interpret the so-called bath and shower experiments where the heterogeneous dose delivery was used in the

  4. Dose-response and time-course of neurobehavioral changes following oral chlorpyrifos in rats of different ages.

    PubMed

    Moser, V C

    2000-01-01

    Young rats have been shown in several laboratories to be more sensitive to the neurotoxic effects of acute exposure to chlorpyrifos. To examine the neurobehavioral effects of chlorpyrifos as a function of age and dose, we conducted dose-response and time-course assessments in rats of three different ages (postnatal day, or PND, 17, 27, and adults). Doses were selected to span the effective dose range in each age group: PND17 - 4, 10, 20 mg/kg; PND27 - 10, 25, 50 mg/kg; adult - 10, 50, 100 mg/kg. Rats were tested at the time of peak effect on the day of dosing, and again at 1 and 3 days, and at 1 and 2 weeks after a single oral dose. There were age- and sex-related differences in the recovery of these behavioral effects; the adult males recovered from the behavioral effects more quickly than the other age groups, and the adult females showed the slowest recovery (up to at least 3 days). Although these doses had been shown previously to produce a similar degree of cholinesterase inhibition, the neurobehavioral alterations fell into the following three patterns of effect as a function of age. (1) Some endpoints (e.g., gait abnormalities, tremor) showed a dose-response curve that was shifted to the right in the older animals. Calculated ED50 values indicated that the PND17 rats were three- to five-fold more sensitive than the adults. (2) Some measures showed less effect in the youngest rats; for example, maximal motor activity decreases were half as great as with adults. (3) A few effects that were typically observed in adults, e.g., salivation, were not seen at all in the PND17 rats. Thus, differential responses on these neurobehavioral endpoints were observed as a function of age. These data suggest that, for some endpoints, young rats are more sensitive to a range of chlorpyrifos doses; however, the magnitude of age-related differences depends on the specific endpoint and time of assessment, as well as age and sex of the test subject.

  5. Phototherapy in Gunn rats. A study to assess the photobiologically most effective radiant energy and dose/response relationships.

    PubMed

    Ballowitz, L; Geutler, G; Krochmann, J; Pannitschka, R; Roemer, G; Roemer, I

    1977-01-01

    In order to get a more realistic spectral efficiency curve and to evaluate dose/response relationships in phototherapy, homozygous weanling Gunn rats -- nondepilated, with fur -- were illuminated under standardized conditions with 8 different fluorescent tubes. Some of the tubes were operated with different electric power. Clear spectal differences in the extent and the rapidity of the bilirubin decay could be ascertained. Furthermore, the sharpness of the bilirubin decrease depended on the baseline concentration. For the calculations the animals were therefore divided into 3 groups with starting levels of larger than or equal to 8 mg%, 6.5--7.9 mg% and less than 6.5 mg%. Correlating the spectral power distribution of the lamps with the bilirubin decomposition found in the experiment, the spectral response function s(lambda)bili, rel was calculated by an integral method. A comparison of our results with data from the literature shows that so far near UV radiation was evaluated too high. A new radiometer for digital measuring the effective irradiance Ebili was developed. On a logarithmic scale a comparatively sharp dose/response relationship could be demonstrated in dependence on the measured effective radiant exposure. Serum bilirubin decrease is directly proportional to log Ebili. A dose of about 2.5 mW - h/cm2 is necessary to achieve a constant serum bilirubin decrease at all. Good results were obtained at doses of about 35 mW - h/cm2 with the most efficient being at 160 mW - h/cm2. Highly effective doses can be applied with different types of lamps. However, there are great differences in the time of illumination required. 24 h are necessary with daylight tubes (Osram L 20 W/19) to apply 20 mW - h/cm2, whereas the same dose is already attained after 4 h with BAM blue tubes (Philips). The accuracy of the radiometer was finally controlled by screening Westinghouse special blue and Osram standard blue tubes with black tapes, so that the effective irradiance (Ebili

  6. Dose-response analysis of heavy metal toxicants in man. Direct in vivo assessment of body burden

    SciTech Connect

    Ellis, K.J.

    1985-06-01

    Differences in uptake, metabolism, and excretion of heavy metals makes selection of a suitable biological media as a monitor of body burden very difficult. Exposure assessments based on body fluid levels can provide, at best, only general population estimates. The most frequently monitored media are blood, urine, nail or hair clippings, sweat, and saliva. Unfortunately each of these tissues can be influenced by recent exposure conditions and are not accurate indices of the total dose or body burden. However, direct in vivo measurements of body burden in humans, have recently been performed. This nuclear technique has focused on the measurements of kidney and liver cadmium (Cd) by neutron activation analysis and bone lead (Pb) determinations using x-ray fluorescence. The dose-response relationship for renal dysfunction based on the direct in vivo body burden for Cd is presented. The most probable Cd value for the kidney associated with renal impairment is approximately 35 mg. Approximately 10% of the subjects with 20 mg Cd in the kidney will have moderately elevated ..beta../sub 2/-microglobulin, an early indicator of potential renal functional changes. 11 refs., 5 figs., 2 tabs.

  7. Home dampness, childhood asthma, hay fever, and airway symptoms in Shanghai, China: associations, dose-response relationships, and lifestyle's influences.

    PubMed

    Hu, Y; Liu, W; Huang, C; Zou, Z J; Zhao, Z H; Shen, L; Sundell, J

    2014-10-01

    Numerous studies of associations between dampness and respiratory diseases have been conducted, but their implications remain inconclusive. In this study of 13,335 parent-reported questionnaires (response rate: 85.3%), we analyzed associations between home dampness and asthma and related symptoms in 4- to 6-year-old children in a cross-sectional study of Shanghai. Indicators of home dampness were strongly and significantly associated with dry cough, wheeze, and rhinitis symptoms. In the current residence, children with visible mold spots (VMS) exposure had 32% higher risk of asthma (adjusted OR, 95% CI: 1.32, 1.07-1.64); damp clothing and/or bedding (frequently) was strongly associated with dry cough (1.78, 1.37-2.30); condensation on windows was strongly associated with hay fever (1.60, 1.27-2.01). In the early-life residence, VMS or damp stains (frequently) were strongly associated with dry cough (2.20, 1.55-3.11) and rhinitis ever (1.57, 1.11-2.21). Associations between dampness and diseases among children with or without family history of atopy were similar. The total number of dampness indicators had strong dose-response relationships with investigated health outcomes. Actions, including opening windows of the child's room at night and cleaning the child's room frequently, could potentially mitigate 25% of home VMS, thereby preventing more than 1.5% of attributable risk of the studied symptoms.

  8. Non-monotonic dose responses in studies of endocrine disrupting chemicals: bisphenol a as a case study.

    PubMed

    Vandenberg, Laura N

    2014-05-01

    Non-monotonic dose response curves (NMDRCs) have been demonstrated for natural hormones and endocrine disrupting chemicals (EDCs) in a variety of biological systems including cultured cells, whole organ cultures, laboratory animals and human populations. The mechanisms responsible for these NMDRCs are well known, typically related to the interactions between the ligand (hormone or EDC) and a hormone receptor. Although there are hundreds of examples of NMDRCs in the EDC literature, there are claims that they are not 'common enough' to influence the use of high-to-low dose extrapolations in risk assessments. Here, we chose bisphenol A (BPA), a well-studied EDC, to assess the frequency of non-monotonic responses. Our results indicate that NMDRCs are common in the BPA literature, occurring in greater than 20% of all experiments and in at least one endpoint in more than 30% of all studies we examined. We also analyzed the types of endpoints that produce NMDRCs in vitro and factors related to study design that influence the ability to detect these kinds of responses. Taken together, these results provide strong evidence for NMDRCs in the EDC literature, specifically for BPA, and question the current risk assessment practice where 'safe' low doses are predicted from high dose exposures.

  9. Dose Response for Chromosome Aberrations in Human Lymphocytes and Fibroblasts after Exposure to Very Low Doses of High LET Radiation

    NASA Technical Reports Server (NTRS)

    Hada, M.; George, Kerry; Cucinotta, Francis A.

    2011-01-01

    The relationship between biological effects and low doses of absorbed radiation is still uncertain, especially for high LET radiation exposure. Estimates of risks from low-dose and low-dose-rates are often extrapolated using data from Japanese atomic bomb survivors with either linear or linear quadratic models of fit. In this study, chromosome aberrations were measured in human peripheral blood lymphocytes and normal skin fibroblasts cells after exposure to very low dose (1-20 cGy) of 170 MeV/u Si-28- ions or 600 MeV/u Fe-56-ions. Chromosomes were analyzed using the whole chromosome fluorescence in situ hybridization (FISH) technique during the first cell division after irradiation, and chromosome aberrations were identified as either simple exchanges (translocations and dicentrics) or complex exchanges (involving greater than 2 breaks in 2 or more chromosomes). The curves for doses above 10 cGy were fitted with linear or linear-quadratic functions. For Si-28- ions no dose response was observed in the 2-10 cGy dose range, suggesting a non-target effect in this range.

  10. Dose-response modelling with two agents: application to the bioassay of oil and shoreline cleaning agents.

    PubMed

    Murado, Miguel A; Vázquez, José A; Rial, Diego; Beiras, Ricardo

    2011-01-30

    Single and joint effects of hydrocarbons and a shoreline cleaning agent (SCA) were studied by measuring the inhibition of the larval growth of sea urchin. Different dosage methods of hydrophobic compounds were compared. The results obtained in the evaluation of CytoSol toxicity revealed that the method of variable dilution of water accommodated fraction (WAF) led to the more conservative toxicological approach. Regarding to Libyan oil, the use of DMSO as carrier allowed us the evaluation of its potential toxicity in comparison with the limitations imposed to the use of WAF method. A reparametrised form of the Weibull equation was slightly modified to be useful for dose-response analysis. This was the basis for modelling single sigmoid responses, which were used to simulate biphasic profiles with addition of effects and to describe both the concentration addition (CA) and independent action (IA) hypotheses. In all cases, its descriptive ability was graphically and statistically satisfactory. The IA model was the best option to explain the combined experimental responses obtained.

  11. U-shaped dose-response curves: implications for risk characterization of essential elements and other chemicals.

    PubMed

    Douron, Michael

    2010-01-01

    The existing risk assessment and management model is a general framework that can incorporate the assessment of numerous types of chemicals, such as essential elements. The general nature of the framework, however, often precludes precise statements of risk and only gives assurances of accuracy by way of a judicious use of conservative assumptions. A mode-of-action framework may provide approaches that are both more precise and accurate, and that may be used for characterizing both risk and benefit of essential elements, but such a framework needs to address the differing severity of adverse effects. Current dose-response data gaps often hinder the evaluation of the risk and benefit of several essential elements; however, new modeling methods, such as categorical regression, need to be further explored. Finally, the essentiality of certain elements provides evidence that two thresholds likely exist in an individual for adverse effect, one at low doses for undernutrition, and another at high doses for toxicity, for the element of concern. This evidence may aid in the estimation of such thresholds in populations.

  12. A Novel Method of Estimating Dose Responses for Polymer Gels Using Texture Analysis of Scanning Electron Microscopy Images

    PubMed Central

    Shih, Cheng-Ting; Hsu, Jui-Ting; Han, Rou-Ping; Hsieh, Bor-Tsung; Chang, Shu-Jun; Wu, Jay

    2013-01-01

    Polymer gels are regarded as a potential dosimeter for independent validation of absorbed doses in clinical radiotherapy. Several imaging modalities have been used to convert radiation-induced polymerization to absorbed doses from a macro-scale viewpoint. This study developed a novel dose conversion mechanism by texture analysis of scanning electron microscopy (SEM) images. The modified N-isopropyl-acrylamide (NIPAM) gels were prepared under normoxic conditions, and were administered radiation doses from 5 to 20 Gy. After freeze drying, the gel samples were sliced for SEM scanning with 50×, 500×, and 3500× magnifications. Four texture indices were calculated based on the gray level co-occurrence matrix (GLCM). The results showed that entropy and homogeneity were more suitable than contrast and energy as dose indices for higher linearity and sensitivity of the dose response curves. After parameter optimization, an R2 value of 0.993 can be achieved for homogeneity using 500× magnified SEM images with 27 pixel offsets and no outlier exclusion. For dose verification, the percentage errors between the prescribed dose and the measured dose for 5, 10, 15, and 20 Gy were −7.60%, 5.80%, 2.53%, and −0.95%, respectively. We conclude that texture analysis can be applied to the SEM images of gel dosimeters to accurately convert micro-scale structural features to absorbed doses. The proposed method may extend the feasibility of applying gel dosimeters in the fields of diagnostic radiology and radiation protection. PMID:23843998

  13. Dose-response curve and optimal dosing regimen of cyclosporin A after traumatic brain injury in rats.

    PubMed

    Sullivan, P G; Rabchevsky, A G; Hicks, R R; Gibson, T R; Fletcher-Turner, A; Scheff, S W

    2000-01-01

    Acute neuropathology following experimental traumatic brain injury results in the rapid necrosis of cortical tissue at the site of injury. This primary injury is exacerbated in the ensuing hours and days via the progression of secondary injury mechanism(s) leading to significant neurological dysfunction. Recent evidence from our laboratory demonstrates that the immunosuppressant cyclosporin A significantly ameliorates cortical damage following traumatic brain injury. The present study extends the previous findings utilizing a unilateral controlled cortical impact model of traumatic brain injury in order to establish a dose-response curve and optimal dosing regimen of cyclosporin A. Following injury to adult rats, cyclosporin A was administrated at various dosages and the therapy was initiated at different times post-injury. In addition to examining the effect of cyclosporin A on the acute disruption of the blood-brain barrier following controlled cortical impact, we also assessed the efficacy of cyclosporin A to reduce tissue damage utilizing the fluid percussion model of traumatic brain injury. The findings demonstrate that the neuroprotection afforded by cyclosporin A is dose-dependent and that a therapeutic window exists up to 24h post-injury. Furthermore, the optimal cyclosporin dosage and regimen markedly reduces disruption of the blood-brain barrier acutely following a cortical contusion injury, and similarly affords significant neuroprotection following fluid percussion injury. These findings clearly suggest that the mechanisms responsible for tissue necrosis following traumatic brain injury are amenable to pharmacological intervention.

  14. Dose response and time course of manganese-enhanced magnetic resonance imaging for visual pathway tracing in vivo

    PubMed Central

    Wang, Wei-ling; Xu, Hui; Li, Ying; Ma, Zhi-zhong; Sun, Xiao-dong; Hu, Yun-tao

    2016-01-01

    Axonal tracing is useful for detecting optic nerve injury and regeneration, but many commonly used methods cannot be used to observe axoplasmic flow and synaptic transmission in vivo. Manganese (Mn2+)-enhanced magnetic resonance imaging (MEMRI) can be used for in vivo longitudinal tracing of the visual pathway. Here, we explored the dose response and time course of an intravitreal injection of MnCl2 for tracing the visual pathway in rabbits in vivo using MEMRI. We found that 2 mM MnCl2 enhanced images of the optic nerve but not the lateral geniculate body or superior colliculus, whereas at all other doses tested (5–40 mM), images of the visual pathway from the retina to the contralateral superior colliculus were significantly enhanced. The images were brightest at 24 hours, and then decreased in brightness until the end of the experiment (7 days). No signal enhancement was observed in the visual cortex at any concentration of MnCl2. These results suggest that MEMRI is a viable method for temporospatial tracing of the visual pathway in vivo. Signal enhancement in MEMRI depends on the dose of MnCl2, and the strongest signals appear 24 hours after intravitreal injection. PMID:27630707

  15. Vigabatrin pediatric dosing information for refractory complex partial seizures: results from a population dose-response analysis.

    PubMed

    Nielsen, Jace C; Tolbert, Dwain; Patel, Mahlaqa; Kowalski, Kenneth G; Wesche, David L

    2014-12-01

    We predicted vigabatrin dosages for adjunctive therapy for pediatric patients with refractory complex partial seizures (rCPS) that would produce efficacy comparable to that observed for approved adult dosages. A dose-response model related seizure-count data to vigabatrin dosage to identify dosages for pediatric rCPS patients. Seizure-count data were obtained from three pediatric and two adult rCPS clinical trials. Dosages were predicted for oral solution and tablet formulations. Predicted oral solution dosages to achieve efficacy comparable to that of a 1 g/day adult dosage were 350 and 450 mg/day for patients with body weight ranges 10-15 and >15-20 kg, respectively. Predicted oral solution dosages for efficacy comparable to a 3 g/day adult dosage were 1,050 and 1,300 mg/day for weight ranges 10-15 and >15-20 kg, respectively. Predicted tablet dosage for efficacy comparable to a 1 g/day adult dosage was 500 mg/day for weight ranges 25-60 kg. Predicted tablet dosage for efficacy comparable to a 3 g/day adult dosage was 2,000 mg for weight ranges 25-60 kg. Vigabatrin dosages were identified for pediatric rCPS patients with body weights ≥10 kg.

  16. Study of the dose response of the system ferrous ammonium sulfate-sucrose-xylenol orange in acid aqueous solution

    NASA Astrophysics Data System (ADS)

    Juarez-Calderon, J. M.; Negron-Mendoza, A.; Ramos-Bernal, S.

    2014-11-01

    An aqueous solution of ammonium ferrous sulfate-sucrose-xylenol orange in sulfuric acid (FSX) is proposed as a dosimetric system for the processes of gamma irradiation in a range between 0.3 and 6 Gy. This system is based on the indirect oxidation of ferrous ion by an organic compound (sucrose) to ferric ion and on the formation of a color complex of Fe3+ in an acidic medium with xylenol orange (a dye). After gamma radiation, an observable change occurs in the color of the system. Irradiation was executed at three different temperatures (13 °C, 22 °C, and 40 °C). A spectrometric readout method at 585 nm was employed to evaluate the system's dose response. In all of the cases analyzed, the responses had a linear behavior, and a slight effect of irradiation temperature was observed. Post-irradiation response was also evaluated and showed the stability of the solutions 24 h after the irradiation. The results obtained suggest that FSX might be used as a dosimeter for low doses of gamma irradiation because it provides a stable signal, good reproducibility, and an accessible technique for analysis.

  17. In vivo dose response and in vitro mechanistic analysis of enhanced immunoglobulin A production by Lactobacillus plantarum AYA

    PubMed Central

    KIKUCHI, Yosuke; YOSHIDA, Hikaru; OGITA, Tasuku; OKITA, Kimiko; FUKUDOME, Shin-ichi; SUZUKI, Takuya; TANABE, Soichi

    2015-01-01

    Secretory immunoglobulin A (IgA) mediates the mucosal immune system, which provides the first line of defense against inhaled and ingested pathogenic bacteria and viruses. Lactobacillus plantarum AYA increases the IgA level of Peyer’s patch (PP) cells, but the recommended amount of consumption and the mechanism of action remains unclear. Better understanding of these is essential to development of L. plantarum AYA for use in functional foods. Therefore, we investigated the dose-response effect (in vivo) and mechanism (in vitro) of IgA enhancement induced by L. plantarum AYA. In the small intestine of the mice fed a diet containing 0.03% or 0.3% of L. plantarum AYA powder for 4 weeks, the IgA levels were significantly increased. Thus, it is suggested that the recommended amount of consumption of L. plantarum AYA is about 0.72 mg per day. In addition, the bacterial cell wall fraction significantly enhanced the IgA production level of murine PP cells in the in vitro assay. The ability of whole cells and the cell wall fraction to enhance IgA levels was significantly inhibited by an anti-Toll-like receptor-2 (TLR-2) antibody, which suggests that the cell wall fraction of L. plantarum AYA increases the IgA level via TLR-2. These findings indicate that L. plantarum AYA is a potential functional food source that maintains mucosal immunity. PMID:26221576

  18. Dose response explorer: an integrated open-source tool for exploring and modelling radiotherapy dose volume outcome relationships

    NASA Astrophysics Data System (ADS)

    El Naqa, I.; Suneja, G.; Lindsay, P. E.; Hope, A. J.; Alaly, J. R.; Vicic, M.; Bradley, J. D.; Apte, A.; Deasy, J. O.

    2006-11-01

    Radiotherapy treatment outcome models are a complicated function of treatment, clinical and biological factors. Our objective is to provide clinicians and scientists with an accurate, flexible and user-friendly software tool to explore radiotherapy outcomes data and build statistical tumour control or normal tissue complications models. The software tool, called the dose response explorer system (DREES), is based on Matlab, and uses a named-field structure array data type. DREES/Matlab in combination with another open-source tool (CERR) provides an environment for analysing treatment outcomes. DREES provides many radiotherapy outcome modelling features, including (1) fitting of analytical normal tissue complication probability (NTCP) and tumour control probability (TCP) models, (2) combined modelling of multiple dose-volume variables (e.g., mean dose, max dose, etc) and clinical factors (age, gender, stage, etc) using multi-term regression modelling, (3) manual or automated selection of logistic or actuarial model variables using bootstrap statistical resampling, (4) estimation of uncertainty in model parameters, (5) performance assessment of univariate and multivariate analyses using Spearman's rank correlation and chi-square statistics, boxplots, nomograms, Kaplan-Meier survival plots, and receiver operating characteristics curves, and (6) graphical capabilities to visualize NTCP or TCP prediction versus selected variable models using various plots. DREES provides clinical researchers with a tool customized for radiotherapy outcome modelling. DREES is freely distributed. We expect to continue developing DREES based on user feedback.

  19. Enhancement of Dose Response and Nuclear Magnetic Resonance Image of PAGAT Polymer Gel Dosimeter by Adding Silver Nanoparticles.

    PubMed

    Sabbaghizadeh, Rahim; Shamsudin, Roslinda; Deyhimihaghighi, Najmeh; Sedghi, Arman

    2017-01-01

    In the present study, the normoxic polyacrylamide gelatin and tetrakis hydroxy methyl phosphoniun chloride (PAGAT) polymer gel dosimeters were synthesized with and without the presence of silver (Ag) nanoparticles. The amount of Ag nanoparticles varied from 1 to 3 ml with concentration 3.14 g/l, thus forming two types of PAGAT polymer gel dosimeters before irradiating them with 6 to 25 Gy produced by 1.25-MeV 60Co gamma rays. In this range, the predominant gamma ray interaction with matter is by Compton scattering effect, as the photoelectric absorption effect diminishes. MRI was employed when evaluating the polymerization of the dosimeters and the gray scale of the MRI film was determined via an optical densitometer. Subsequent analyses of optical densities revealed that the extent of polymerization increased with the increase in the absorbed dose, while the increase of penetration depth within the dosimeters has a reverse effect. Moreover, a significant increase in the optical density-dose response (11.82%) was noted for dosimeters containing 2 ml Ag nanoparticles.

  20. Coffee consumption and risk of endometrial cancer: a dose-response meta-analysis of prospective cohort studies

    PubMed Central

    Zhou, Quan; Luo, Mei-Ling; Li, Hui; Li, Min; Zhou, Jian-Guo

    2015-01-01

    This is a dose-response (DR) meta-analysis to evaluate the association of coffee consumption on endometrial cancer (EC) risk. A total 1,534,039 participants from 13 published articles were added in this meta-analysis. The RR of total coffee consumption and EC were 0.80 (95% CI: 0.74–0.86). A stronger association between coffee intake and EC incidence was found in patients who were never treated with hormones, 0.60 (95% CI: 0.50–0.72), and subjects with a BMI ≥25 kg/m2, 0.57 (95% CI: 0.46–0.71). The overall RRs for caffeinated and decaffeinated coffee were 0.66 (95% CI: 0.52–0.84) and 0.77 (95% CI: 0.63–0.94), respectively. A linear DR relationship was seen in coffee, caffeinated coffee, decaffeinated coffee and caffeine intake. The EC risk decreased by 5% for every 1 cup per day of coffee intake, 7% for every 1 cup per day of caffeinated coffee intake, 4% for every 1 cup per day of decaffeinated intake of coffee, and 4% for every 100 mg of caffeine intake per day. In conclusion, coffee and intake of caffeine might significantly reduce the incidence of EC, and these effects may be modified by BMI and history of hormone therapy. PMID:26302813

  1. A novel method of estimating dose responses for polymer gels using texture analysis of scanning electron microscopy images.

    PubMed

    Shih, Cheng-Ting; Hsu, Jui-Ting; Han, Rou-Ping; Hsieh, Bor-Tsung; Chang, Shu-Jun; Wu, Jay

    2013-01-01

    Polymer gels are regarded as a potential dosimeter for independent validation of absorbed doses in clinical radiotherapy. Several imaging modalities have been used to convert radiation-induced polymerization to absorbed doses from a macro-scale viewpoint. This study developed a novel dose conversion mechanism by texture analysis of scanning electron microscopy (SEM) images. The modified N-isopropyl-acrylamide (NIPAM) gels were prepared under normoxic conditions, and were administered radiation doses from 5 to 20 Gy. After freeze drying, the gel samples were sliced for SEM scanning with 50×, 500×, and 3500× magnifications. Four texture indices were calculated based on the gray level co-occurrence matrix (GLCM). The results showed that entropy and homogeneity were more suitable than contrast and energy as dose indices for higher linearity and sensitivity of the dose response curves. After parameter optimization, an R (2) value of 0.993 can be achieved for homogeneity using 500× magnified SEM images with 27 pixel offsets and no outlier exclusion. For dose verification, the percentage errors between the prescribed dose and the measured dose for 5, 10, 15, and 20 Gy were -7.60%, 5.80%, 2.53%, and -0.95%, respectively. We conclude that texture analysis can be applied to the SEM images of gel dosimeters to accurately convert micro-scale structural features to absorbed doses. The proposed method may extend the feasibility of applying gel dosimeters in the fields of diagnostic radiology and radiation protection.

  2. Non-monotonic dose-response effect of bisphenol A on rare minnow Gobiocypris rarus ovarian development.

    PubMed

    Zhang, Yingying; Tao, Shiyu; Yuan, Cong; Liu, Yan; Wang, Zaizhao

    2016-02-01

    Bisphenol A (BPA) is widely spread in the environment, and can cause various reproductive disrupting effects on different organisms, including fish. Our previous published study showed that BPA has non-monotonic (inverted U-shaped) dose-response effect on rare minnow Gobiocypris rarus ovarian weight at different concentrations. To investigate the potential mechanism, we exposed female rare minnow to 1, 15 and 225 µg L(-1) BPA for 7 days in the present study. The levels of vitellogenin (Vtg), sex hormones, hydrogen peroxide (H2O2), glutathione (GSH) and triglyceride (TG) were measured. RNA-seq of ovary tissues was also performed. Result showed that Vtg, sex hormone and TG levels showed an inverted U-shaped increased response, while H2O2 and GSH levels showed a U-shaped inhibited response. RNA-seq data showed that many genes involved in lipid metabolism, oxidative stress, and proteolysis processes were altered. The change of Vtg, H2O2, GSH and TG levels was possibly related to the altered sex hormone levels. Sex hormone's direct effect, Vtg accumulation, TG accumulation and oxidative stress induced proteolysis may contribute to the change of ovary weight.

  3. Dose-effect and dose-response relationships of blood lead to erythrocytic protoporphyrin in young children

    SciTech Connect

    Hammond, P.B.; Bornschein, R.L.; Succop, P.

    1985-10-01

    Dose-effect and dose-response relationships were analyzed for blood lead concentration (PbB) vs blood protoporphyrin concentration using multiple data points from 165 children, ages 3-36 months. Protoporphyrin concentrations were measured using a front-face flurometer designed to measure zinc protoporphyrin (ZPP) and an extraction method designed to measure total protoporphyrin as the free base (FEP). Estimations were made of the thresholds for PbB effects on FEP and ZPP, as well as the slopes of the PbB-FEP and PbB-ZPP interactions. There was essentially no difference in thresholds estimated using ZPP vs FEP as the effect parameter. There was no apparent effect of age on threshold. However, the slope for PbB vs ZPP was less steep than the slope for PbB vs FEP. Moreover, the average ratio FEP:ZPP was markedly elevated at 3 months (1.84:1) and decreased slowly, attaining unity at 33 months. The possible reasons for this discrepancy are discussed, as well as the implications for interpretation of lead screening program data.

  4. Dose-response curve slope sets class-specific limits on inhibitory potential of anti-HIV drugs.

    PubMed

    Shen, Lin; Peterson, Susan; Sedaghat, Ahmad R; McMahon, Moira A; Callender, Marc; Zhang, Haili; Zhou, Yan; Pitt, Eleanor; Anderson, Karen S; Acosta, Edward P; Siliciano, Robert F

    2008-07-01

    Highly active antiretroviral therapy (HAART) can control HIV-1 replication, but suboptimal treatment allows for the evolution of resistance and rebound viremia. A comparative measure of antiviral activity under clinically relevant conditions would guide drug development and the selection of regimens that maximally suppress replication. Here we show that current measures of antiviral activity, including IC(50) and inhibitory quotient, neglect a key dimension, the dose-response curve slope. Using infectivity assays with wide dynamic range, we show that this slope has noteworthy effects on antiviral activity. Slope values are class specific for antiviral drugs and define intrinsic limitations on antiviral activity for some classes. Nucleoside reverse transcriptase inhibitors and integrase inhibitors have slopes of approximately 1, characteristic of noncooperative reactions, whereas non-nucleoside reverse transcriptase inhibitors, protease inhibitors and fusion inhibitors unexpectedly show slopes >1. Instantaneous inhibitory potential (IIP), the log reduction in single-round infectivity at clinical drug concentrations, is strongly influenced by slope and varies by >8 logs for anti-HIV drugs. IIP provides a more accurate measure of antiviral activity and in general correlates with clinical outcomes. Only agents with slopes >1 achieve high-level inhibition of single-round infectivity, a finding with profound implications for drug and vaccine development.

  5. Non-Monotonic Dose Responses in Studies of Endocrine Disrupting Chemicals: Bisphenol A as a Case Study

    PubMed Central

    Vandenberg, Laura N.

    2014-01-01

    Non-monotonic dose response curves (NMDRCs) have been demonstrated for natural hormones and endocrine disrupting chemicals (EDCs) in a variety of biological systems including cultured cells, whole organ cultures, laboratory animals and human populations. The mechanisms responsible for these NMDRCs are well known, typically related to the interactions between the ligand (hormone or EDC) and a hormone receptor. Although there are hundreds of examples of NMDRCs in the EDC literature, there are claims that they are not ‘common enough’ to influence the use of high-to-low dose extrapolations in risk assessments. Here, we chose bisphenol A (BPA), a well-studied EDC, to assess the frequency of non-monotonic responses. Our results indicate that NMDRCs are common in the BPA literature, occurring in greater than 20% of all experiments and in at least one endpoint in more than 30% of all studies we examined. We also analyzed the types of endpoints that produce NMDRCs in vitro and factors related to study design that influence the ability to detect these kinds of responses. Taken together, these results provide strong evidence for NMDRCs in the EDC literature, specifically for BPA, and question the current risk assessment practice where ‘safe’ low doses are predicted from high dose exposures. PMID:24910584

  6. Advancing Dose-Response Assessment Methods for Environmental Regulatory Impact Analysis: A Bayesian Belief Network Approach Applied to Inorganic Arsenic

    PubMed Central

    Zabinski, Joseph W.; Garcia-Vargas, Gonzalo; Rubio-Andrade, Marisela; Fry, Rebecca C.; Gibson, Jacqueline MacDonald

    2016-01-01

    Dose-response functions used in regulatory risk assessment are based on studies of whole organisms and fail to incorporate genetic and metabolomic data. Bayesian belief networks (BBNs) could provide a powerful framework for incorporating such data, but no prior research has examined this possibility. To address this gap, we develop a BBN-based model predicting birthweight at gestational age from arsenic exposure via drinking water and maternal metabolic indicators using a cohort of 200 pregnant women from an arsenic-endemic region of Mexico. We compare BBN predictions to those of prevailing slope-factor and reference-dose approaches. The BBN outperforms prevailing approaches in balancing false-positive and false-negative rates. Whereas the slope-factor approach had 2% sensitivity and 99% specificity and the reference-dose approach had 100% sensitivity and 0% specificity, the BBN's sensitivity and specificity were 71% and 30%, respectively. BBNs offer a promising opportunity to advance health risk assessment by incorporating modern genetic and metabolomic data. PMID:27747248

  7. Identification of low-dose responsive metabolites in X-irradiated human B lymphoblastoid cells and fibroblasts

    PubMed Central

    Tsuyama, Naohiro; Mizuno, Hajime; Katafuchi, Atsushi; Abe, Yu; Kurosu, Yumiko; Yoshida, Mitsuaki; Kamiya, Kenji; Sakai, Akira

    2015-01-01

    Ionizing radiation (IR) induces cellular stress responses, such as signal transduction, gene expression, protein modification, and metabolite change that affect cellular behavior. We analyzed X-irradiated human Epstein-Barr virus-transformed B lymphoblastoid cells and normal fibroblasts to search for metabolites that would be suitable IR-responsive markers by Liquid Chromotography–Mass spectrometry (LC–MS). Mass spectra, as analyzed with principal component analysis, showed that the proportion of peaks with IR-induced change was relatively small compared with the influence of culture time. Dozens of peaks that had either been upregulated or downregulated by IR were extracted as candidate IR markers. The IR-changed peaks were identified by comparing mock-treated groups to 100 mGy-irradiated groups that had recovered after 10 h, and the results indicated that the metabolites involved in nucleoside synthesis increased and that some acylcarnitine levels decreased in B lymphoblastoids. Some peaks changed by as much as 20 mGy, indicating the presence of an IR-sensitive signal transduction/metabolism control mechanism in these cells. On the other hand, we could not find common IR-changed peaks in fibroblasts of different origin. These data suggest that cell phenotype-specific pathways exist, even in low-dose responses, and could determine cell behavior. PMID:25227127

  8. Red Meat and Processed Meat Consumption and Nasopharyngeal Carcinoma Risk: A Dose-response Meta-analysis of Observational Studies.

    PubMed

    Li, Fuqin; Duan, Fujiao; Zhao, Xia; Song, Chunhua; Cui, Shuli; Dai, Liping

    2016-01-01

    The purpose of this study is to clarify and quantify the potential dose-response association between the intake of total red and total processed meat and risk of nasopharyngeal carcinoma (NPC). Relevant studies were identified by searching PubMed, EMBASE, and Chinese databases (CNKI and Wanfang). The summary relative risk (RR) with 95% confidence interval (95%CI) was calculated. A total of 15 independent studies with 12,735 subjects were identified. Compared with the low-rank intake, the summary RR of NPC was 1.35 (95%CI, 1.21-1.51) for total red meat and 1.46 (95%CI, 1.34-1.64) for total processed meat. For the moderate-rank intake, the summary RR of NPC was 1.54 (95%CI, 1.36-1.79) for total red meat and 1.59 (95%CI, 1.3-1.90) for total processed meat. The summary RR for high-rank intake was 1.71 (95%CI, 1.14-2.55) for total red meat and 2.11 (95%CI, 1.31-3.42) for total processed meat. The combined estimates showed obvious evidence of statistically significant association between total red and total processed meat consumption dose and risk of NPC (Ptrend< 0.01). In conclusion, our data suggest that a high intake of total red or total processed meat is associated with a significantly increased risk of NPC.

  9. Coffee consumption and risk of endometrial cancer: a dose-response meta-analysis of prospective cohort studies.

    PubMed

    Zhou, Quan; Luo, Mei-Ling; Li, Hui; Li, Min; Zhou, Jian-Guo

    2015-08-25

    This is a dose-response (DR) meta-analysis to evaluate the association of coffee consumption on endometrial cancer (EC) risk. A total 1,534,039 participants from 13 published articles were added in this meta-analysis. The RR of total coffee consumption and EC were 0.80 (95% CI: 0.74-0.86). A stronger association between coffee intake and EC incidence was found in patients who were never treated with hormones, 0.60 (95% CI: 0.50-0.72), and subjects with a BMI ≥25 kg/m(2), 0.57 (95% CI: 0.46-0.71). The overall RRs for caffeinated and decaffeinated coffee were 0.66 (95% CI: 0.52-0.84) and 0.77 (95% CI: 0.63-0.94), respectively. A linear DR relationship was seen in coffee, caffeinated coffee, decaffeinated coffee and caffeine intake. The EC risk decreased by 5% for every 1 cup per day of coffee intake, 7% for every 1 cup per day of caffeinated coffee intake, 4% for every 1 cup per day of decaffeinated intake of coffee, and 4% for every 100 mg of caffeine intake per day. In conclusion, coffee and intake of caffeine might significantly reduce the incidence of EC, and these effects may be modified by BMI and history of hormone therapy.

  10. Dose response of benzo(a)pyrene-induced mutagenesis using the BigBlue{reg_sign} transgenic mouse assay

    SciTech Connect

    Kotturi, G.; Holcroft, J.; Boer, J. de

    1997-10-01

    To investigate the dose response of benzo(a)pyrene-induced mutagenesis, groups of five BigBlue{reg_sign} transgenic mice were injected with a single intra-peritoneal dose were injected with corn oil containing benzo(a)pyrene to achieve the following concentrations: 0, 62.5, 125, 250, 500 mg/kg. Tissues were harvested after a 14 day expression time and analysed for mutational events. DNA adducts were measured in the liver of mice that were sacrificed 1 day after injection. The mutant frequency in the mouse liver linearly increased from 5.2 to 53.5 x 10{sup -5} in a dose-specific manner from 0 to 500 mg/kg benzo(a)pyrene. Mutants were sequenced to give an estimate of the number of clonal events as a function of benzo(a) pyrene with a total of 20 exposed animals (4 doses and five animals/dose), we established frequently mutated sites or `mutational hotspots` as well as a full mutational spectrum. Various other factors associated with the BigBlue{reg_sign} assay were analysed such as the effect of plating density on the purity of mutant plaques during the phage purification step.

  11. In vivo dose response and in vitro mechanistic analysis of enhanced immunoglobulin A production by Lactobacillus plantarum AYA.

    PubMed

    Kikuchi, Yosuke; Yoshida, Hikaru; Ogita, Tasuku; Okita, Kimiko; Fukudome, Shin-Ichi; Suzuki, Takuya; Tanabe, Soichi

    2015-01-01

    Secretory immunoglobulin A (IgA) mediates the mucosal immune system, which provides the first line of defense against inhaled and ingested pathogenic bacteria and viruses. Lactobacillus plantarum AYA increases the IgA level of Peyer's patch (PP) cells, but the recommended amount of consumption and the mechanism of action remains unclear. Better understanding of these is essential to development of L. plantarum AYA for use in functional foods. Therefore, we investigated the dose-response effect (in vivo) and mechanism (in vitro) of IgA enhancement induced by L. plantarum AYA. In the small intestine of the mice fed a diet containing 0.03% or 0.3% of L. plantarum AYA powder for 4 weeks, the IgA levels were significantly increased. Thus, it is suggested that the recommended amount of consumption of L. plantarum AYA is about 0.72 mg per day. In addition, the bacterial cell wall fraction significantly enhanced the IgA production level of murine PP cells in the in vitro assay. The ability of whole cells and the cell wall fraction to enhance IgA levels was significantly inhibited by an anti-Toll-like receptor-2 (TLR-2) antibody, which suggests that the cell wall fraction of L. plantarum AYA increases the IgA level via TLR-2. These findings indicate that L. plantarum AYA is a potential functional food source that maintains mucosal immunity.

  12. Enhancement of Dose Response and Nuclear Magnetic Resonance Image of PAGAT Polymer Gel Dosimeter by Adding Silver Nanoparticles

    PubMed Central

    Sabbaghizadeh, Rahim; Shamsudin, Roslinda; Deyhimihaghighi, Najmeh; Sedghi, Arman

    2017-01-01

    In the present study, the normoxic polyacrylamide gelatin and tetrakis hydroxy methyl phosphoniun chloride (PAGAT) polymer gel dosimeters were synthesized with and without the presence of silver (Ag) nanoparticles. The amount of Ag nanoparticles varied from 1 to 3 ml with concentration 3.14 g/l, thus forming two types of PAGAT polymer gel dosimeters before irradiating them with 6 to 25 Gy produced by 1.25-MeV 60Co gamma rays. In this range, the predominant gamma ray interaction with matter is by Compton scattering effect, as the photoelectric absorption effect diminishes. MRI was employed when evaluating the polymerization of the dosimeters and the gray scale of the MRI film was determined via an optical densitometer. Subsequent analyses of optical densities revealed that the extent of polymerization increased with the increase in the absorbed dose, while the increase of penetration depth within the dosimeters has a reverse effect. Moreover, a significant increase in the optical density-dose response (11.82%) was noted for dosimeters containing 2 ml Ag nanoparticles. PMID:28060829

  13. ESTIMATING A DOSE-RESPONSE RELATIONSHIP BETWEEN LENGTH OF STAY AND FUTURE RECIDIVISM IN SERIOUS JUVENILE OFFENDERS.

    PubMed

    Loughran, Thomas A; Mulvey, Edward P; Schubert, Carol A; Fagan, Jeffrey; Piquero, Alex R; Losoya, Sandra H

    2009-01-01

    The effect of sanctions on subsequent criminal activity is of central theoretical importance in criminology. A key question for juvenile justice policy is the degree to which serious juvenile offenders respond to sanctions and/or treatment administered by the juvenile court. The policy question germane to this debate is finding the level of confinement within the juvenile justice system that maximizes the public safety and therapeutic benefits of institutional confinement. Unfortunately, research on this issue has been limited with regard to serious juvenile offenders. We use longitudinal data from a large sample of serious juvenile offenders from two large cities to 1) estimate a causal treatment effect of institutional placement, as opposed to probation, on future rate of rearrest and 2) investigate the existence of a marginal effect (i.e., benefit) for longer length of stay once the institutional placement decision had been made. We accomplish the latter by determining a dose-response relationship between the length of stay and future rates of rearrest and self-reported offending. The results suggest that an overall null effect of placement exists on future rates of rearrest or self-reported offending for serious juvenile offenders. We also find that, for the group placed out of the community, it is apparent that little or no marginal benefit exists for longer lengths of stay. Theoretical, empirical, and policy issues are outlined.

  14. Human muscle protein synthesis is modulated by extracellular, not intramuscular amino acid availability: a dose-response study.

    PubMed

    Bohé, Julien; Low, Aili; Wolfe, Robert R; Rennie, Michael J

    2003-10-01

    To test the hypothesis that muscle protein synthesis (MPS) is regulated by the concentration of extracellular amino acids, we investigated the dose-response relationship between the rate of human MPS and the concentrations of blood and intramuscular amino acids. We increased blood mixed amino acid concentrations by up to 240 % above basal levels by infusion of mixed amino acids (Aminosyn 15, 44-261 mg kg-1 h-1) in 21 healthy subjects, (11 men 10 women, aged 29 +/- 2 years) and measured the rate of incorporation of D5-phenylalanine or D3-leucine into muscle protein and blood and intramuscular amino acid concentrations. The relationship between the fold increase in MPS and blood essential amino acid concentration ([EAA], mM) was hyperbolic and fitted the equation MPS = (2.68 x [EAA])/(1.51 + [EAA]) (P < 0.01). The pattern of stimulation of myofibrillar, sarcoplasmic and mitochondrial protein was similar. There was no clear relationship between the rate of MPS and the concentration of intramuscular EAAs; indeed, when MPS was increasing most rapidly, the concentration of intramuscular EAAs was below basal levels. We conclude that the rates of synthesis of all classes of muscle proteins are acutely regulated by the blood [EAA] over their normal diurnal range, but become saturated at high concentrations. We propose that the stimulation of protein synthesis depends on the sensing of the concentration of extracellular, rather than intramuscular EAAs.

  15. Human Muscle Protein Synthesis is Modulated by Extracellular, Not Intramuscular Amino Acid Availability: A Dose-Response Study

    PubMed Central

    Bohé, Julien; Low, Aili; Wolfe, Robert R; Rennie, Michael J

    2003-01-01

    To test the hypothesis that muscle protein synthesis (MPS) is regulated by the concentration of extracellular amino acids, we investigated the dose-response relationship between the rate of human MPS and the concentrations of blood and intramuscular amino acids. We increased blood mixed amino acid concentrations by up to 240 % above basal levels by infusion of mixed amino acids (Aminosyn 15, 44-261 mg kg−1 h−1) in 21 healthy subjects, (11 men 10 women, aged 29 ± 2 years) and measured the rate of incorporation of D5-phenylalanine or D3-leucine into muscle protein and blood and intramuscular amino acid concentrations. The relationship between the fold increase in MPS and blood essential amino acid concentration ([EAA], mM) was hyperbolic and fitted the equation MPS = (2.68 × [EAA])/(1.51 + [EAA]) (P < 0.01). The pattern of stimulation of myofibrillar, sarcoplasmic and mitochondrial protein was similar. There was no clear relationship between the rate of MPS and the concentration of intramuscular EAAs; indeed, when MPS was increasing most rapidly, the concentration of intramuscular EAAs was below basal levels. We conclude that the rates of synthesis of all classes of muscle proteins are acutely regulated by the blood [EAA] over their normal diurnal range, but become saturated at high concentrations. We propose that the stimulation of protein synthesis depends on the sensing of the concentration of extracellular, rather than intramuscular EAAs. PMID:12909668

  16. Normal Liver Tissue Density Dose Response in Patients Treated With Stereotactic Body Radiation Therapy for Liver Metastases

    SciTech Connect

    Howells, Christopher C.; Stinauer, Michelle A.; Diot, Quentin; Westerly, David C.; Schefter, Tracey E.; Kavanagh, Brian D.; Miften, Moyed

    2012-11-01

    Purpose: To evaluate the temporal dose response of normal liver tissue for patients with liver metastases treated with stereotactic body radiation therapy (SBRT). Methods and Materials: Ninety-nine noncontrast follow-up computed tomography (CT) scans of 34 patients who received SBRT between 2004 and 2011 were retrospectively analyzed at a median of 8 months post-SBRT (range, 0.7-36 months). SBRT-induced normal liver tissue density changes in follow-up CT scans were evaluated at 2, 6, 10, 15, and 27 months. The dose distributions from planning CTs were mapped to follow-up CTs to relate the mean Hounsfield unit change ({Delta}HU) to dose received over the range 0-55 Gy in 3-5 fractions. An absolute density change of 7 HU was considered a significant radiographic change in normal liver tissue. Results: Increasing radiation dose was linearly correlated with lower post-SBRT liver tissue density (slope, -0.65 {Delta}HU/5 Gy). The threshold for significant change (-7 {Delta}HU) was observed in the range of 30-35 Gy. This effect did not vary significantly over the time intervals evaluated. Conclusions: SBRT induces a dose-dependent and relatively time-independent hypodense radiation reaction within normal liver tissue that is characterized by a decrease of >7 HU in liver density for doses >30-35 Gy.

  17. Dose-response effect of a novel functional fibre, PolyGlycopleX(®), PGX(®), on satiety.

    PubMed

    Solah, Vicky A; Brand-Miller, Jennie C; Atkinson, Fiona S; Gahler, Roland J; Kacinik, Veronica; Lyon, Michael R; Wood, Simon

    2014-06-01

    The objective of this research was to determine the dose-response effects of a palatable, viscous and gel forming fibre, PolyGlycopleX(®) (PGX(®)), [(α-D-glucurono-α-manno-β-D-manno-β-D-gluco), (α-Lgulurono-β-D mannurono), (β-D-gluco-β-D-mannan)] on satiety, and to gain insight into the underlying mechanisms that lead to appetite inhibition. Healthy subjects (n = 10), aged between 20.3 and 29.2 years, consumed PGX(®), in granular form at 2.5, 5.0 and 7.5 g, and a 5g inulin control, with a standard breakfast. The PGX(®) doses of 2.5 and 7.5 g mixed with water at the start of breakfast increased satiety (iAUC of 140.0 and 157.7, P = 0.025 and 0.001, respectively) compared to the control. The most effective dose (7.5g) was palatable and corresponded to a 34% increase in fullness, measured using a visual analogue scale and incremental area under the curve, and resulted in a delayed postprandial glycaemic response when compared with the control.

  18. Dose-response study and threshold estimation of griseofulvin-induced aneuploidy during female mouse meiosis I and II.

    PubMed

    Marchetti, F; Mailhes, J B; Bairnsfather, L; Nandy, I; London, S N

    1996-03-01

    The relative sensitivity of the two meiotic divisions of mouse oogenesis to griseofulvin (GF)-induced aneuploidy was investigated. The first meiotic division was studied by administering GF 4 h after human chorionic gonadotrophin (HCG) injection and analyzing metaphase II (MII) oocytes, whereas study of the second meiotic division involved treating the females 10 h after HCG and analyzing one-cell (1-Cl) zygotes. Data from previous studies have shown that these treatment times represented the most sensitive times for aneuploidy induction during meioses I and II. The statistical analyses of the data showed that the dose-response curves for aneuploidy induction did not differ quantitatively or qualitatively between the two meiotic divisions. The percentages of hyperploid MII oocytes and 1-Cl zygotes were significantly higher (P < 0.001) than in the controls for all doses except 125 mg/kg GF. The highest percentages of hyperploid cells were found after administering 1500 mg/kg GF. However, these percentages were not different (P > 0.05) from those observed after 500 or 1000 mg/kg GF, suggesting saturation of the GF aneuploid target(s). These results suggest that the relative sensitivity to GF-induced aneuploidy between the two meiotic divisions of oogenesis are similar. They also suggest the presence of a lower (125 mg/kg) and an upper 500 mg/kg) threshold for GF-induced aneuploidy.

  19. Dose-response studies with nitrosoheptamethyleneimine and its alpha-deuterium-labeled derivative in F344 rats

    SciTech Connect

    Lijinsky, W.; Reuber, M.D.; Davies, T.S.; Riggs, C.W.

    1982-11-01

    A dose-response study of the carcinogenicity of nitrosoheptamethyleneimine (N-HEP) in inbred F344 male and female rats was performed by administration of the nitrosamine at several concentrations in drinking water to groups of 20 rats. The concentrations differed by a factor of nearly 2.5 and ranged from 1.0 to 100 mg/liter. The duration of treatment was 13, 25, 50, or 100 weeks, after which the animals were allowed to die naturally of tumors induced. In most treated groups the incidence of tumors of the upper gastrointestinal tract approached 100%. However, at the higher doses there was an inverse relationship between total dose and survival time of the rats. Matched treatment of groups of rat with N-HEP labeled with deuterium in the alpha positions resulted in longer survival. The slower action of the deuterium-labeled compound, as measured by a lower rate of death from tumors, suggests that cleavage of a carbon-hydrogen bond at an alpha position is a rate-limiting step in carcinogenesis by N-HEP in rats.

  20. On the combination of c- and D-optimal designs: General approaches and applications in dose-response studies.

    PubMed

    Holland-Letz, Tim

    2017-03-01

    Dose-response modeling in areas such as toxicology is often conducted using a parametric approach. While estimation of parameters is usually one of the goals, often the main aim of the study is the estimation of quantities derived from the parameters, such as the ED50 dose. From the view of statistical optimal design theory such an objective corresponds to a c-optimal design criterion. Unfortunately, c-optimal designs often create practical problems, and furthermore commonly do not allow actual estimation of the parameters. It is therefore useful to consider alternative designs which show good c-performance, while still being applicable in practice and allowing reasonably good general parameter estimation. In effect, using optimal design terminology this means that a reasonable performance regarding the D-criterion is expected as well. In this article, we propose several approaches to the task of combining c- and D-efficient designs, such as using mixed information functions or setting minimum requirements regarding either c- or D-efficiency, and show how to algorithmically determine optimal designs in each case. We apply all approaches to a standard situation from toxicology, and obtain a much better balance between c- and D-performance. Next, we investigate how to adapt the designs to different parameter values. Finally, we show that the methodology used here is not just limited to the combination of c- and D-designs, but can also be used to handle more general constraint situations such as limits on the cost of an experiment.

  1. Cytogenetic dose-response in vitro for biological dosimetry after exposure to high doses of gamma-rays.

    PubMed

    Vinnikov, Volodymyr A; Maznyk, Nataliya A

    2013-04-01

    The dose response for dicentrics plus centric rings and total unstable chromosome-type aberrations was studied in the first mitoses of cultured human peripheral blood lymphocytes irradiated in vitro to doses of ∼2, 4, 6, 8, 10, 16 and 20 Gy of acute (60)Со gamma-rays. A dose-dependent increase of aberration yield was accompanied by a tendency to the underdispersion of dicentrics and centric rings among cells distributions compared with Poisson statistics at doses ≥6 Gy. The formal fitting of the data to a linear-quadratic model resulted in an equation with the linear and quadratic coefficients ranged 0.098-0.129×cell(-1)×Gy(-1) and 0.039-0.034×cell(-1)×Gy(-2), respectively, depending on the fitting method. The actual radiation-induced aberration yield was markedly lower than expected from a calibration curve, generated earlier within a lower dose range. Interlaboratory variations in reported dicentric yields induced by medium-to-high radiation doses in vitro are discussed.

  2. Application of extracorporeal shock wave lithotripter (ECSWL) in orthopaedics. II. Dose-response and pressure distribution measurements.

    PubMed

    Park, J B; Park, S H; Weinstein, J N; Loening, S; Oster, D

    1991-01-01

    In order to apply the extracorporeal shock wave lithotripter (ECSWL) technique to the loosening of the bone-cement interface for the extraction of the cement during revision arthroplasty it is essential to know the dose-response characteristics. The present study shows that the number of shocks needed to break the interface between a 2- and 6-mm-thick bovine femoral bone and bone cement is similar to the fatigue behavior of a material, that is, Log(N) = C(kV) + D, where N is the number of shock impulses, kV is the power setting of the lithotripter machine in kilovolts, and C and D are constants. Iso-pressure distribution of the traveling shock wave front through a simulated bone in a Plexiglass tube using Fuji pressure film showed quantitative pressure contours from which one can understand the effective area of shock wave and its distribution. The most effective area of the shock wave was about 1.5 cm in diameter at 23 and 25 kV with pressure at least 7.0 MPa which is more than sufficient to break the bone-cement interface in tension.

  3. Dose-Response Functions for the Olfactory, Nasal Trigeminal, and Ocular Trigeminal Detectability of Airborne Chemicals by Humans.

    PubMed

    Cometto-Muñiz, J Enrique; Abraham, Michael H

    2016-01-01

    We gathered from the literature 47 odor and 37 trigeminal (nasal and ocular) chemesthetic psychometric (i.e., detectability or dose-response) functions from a group of 41 chemicals. Vapors delivered were quantified by analytical methods. All functions were very well fitted by the sigmoid (logistic) equation: y = 1 / (1 + e({-(x-C)/D})), where parameter C quantifies the detection threshold concentration and parameter D the steepness of the function. Odor and chemesthetic functions showed no concentration overlap: olfactory functions grew along the parts per billion (ppb by volume) range or lower, whereas trigeminal functions grew along the part per million (ppm by volume) range. Although, on average, odor detectability rose from chance detection to perfect detection within 2 orders of magnitude in concentration, chemesthetic detectability did it within one. For 16 compounds having at least 1 odor and 1 chemesthetic function, the average gap between the 2 functions was 4.6 orders of magnitude in concentration. A quantitative structure-activity relationship (QSAR) using 5 chemical descriptors that had previously described stand-alone odor and chemesthetic threshold values, also holds promise to describe, and eventually predict, olfactory and chemesthetic detectability functions, albeit functions from additional compounds are needed to strengthen the QSAR.

  4. The influence of TRP53 in the dose response of radiation-induced apoptosis, DNA repair and genomic stability in murine haematopoietic cells

    DOE PAGES

    Lemon, Jennifer A.; Taylor, Kristina; Verdecchia, Kyle; ...

    2014-01-01

    Apoptotic and DNA damage endpoints are frequently used as surrogate markers of cancer risk, and have been well-studied in the Trp53+/- mouse model. We report the effect of differing Trp53 gene status on the dose response of ionizing radiation exposures (0.01-2 Gy), with the unique perspective of determining if effects of gene status remain at extended time points. Here we report no difference in the dose response for radiation-induced DNA double-strand breaks in bone marrow and genomic instability (MN-RET levels) in peripheral blood, between wild-type (Trp53+/+) and heterozygous (Trp53+/-) mice. The dose response for Trp53+/+ mice showed higher initial levelsmore » of radiation-induced lymphocyte apoptosis relative to Trp53+/- between 0 and 1 Gy. Although this trend was observed up to 12 hours post-irradiation, both genotypes ultimately reached the same level of apoptosis at 14 hours, suggesting the importance of late-onset p53-independent apoptotic responses in this mouse model. Expected radiation-induced G1 cell cycle delay was observed in Trp53+/+ but not Trp53+/-. Although p53 has an important role in cancer risk, we have shown its influence on radiation dose response can be temporally variable. This research highlights the importance of caution when using haematopoietic endpoints as surrogates to extrapolate radiation-induced cancer risk estimation.« less

  5. TIME COURSE AND DOSE RESPONSE ASSESSMENT OF CHOLINESTERASE (CHE) INHIBITION IN ADULT RATS TREATED ACUTELY WITH CARBARYL, METHOMYL, METHIOCARB, OXAMYL, OR PROPOXUR.

    EPA Science Inventory

    To compare the toxicity of 5 N-methyl carbamates, the time course and dose response profiles for ChE inhibition were established for each. For the time course comparison, adult male Long Evans rats (n=5 dose group) were dosed orally with either carbaryl (CB; 30 mg/kg in corn oi...

  6. DOSE-RESPONSE FOR UV-INDUCED IMMUNE SUPPRESSION IN PEOPLE OF COLOR: DIFFERENCES BASED ON ERYTHEMAL REACTIVITY RATHER THAN SKIN PIGMENTATION

    EPA Science Inventory

    Ultraviolet radiation (UVR) is known to suppress immune responses in human subjects. The purpose of this study was to develop dose responses across a broad range of skin pigmentation in order to facilitate risk assessment. UVR was administered using FS 20 bulbs. Skin pigmentation...

  7. 2,3,7,8-Tetrachlorodibenzo-P-Dioxin (Tcdd) Dose-Response Studies: Preliminary Literature Search Results and Request for Additional Studies

    EPA Science Inventory

    EPA invited the public to comment on the preliminary list of in vivo mammalian dose-response citations for 2,3,7,8 tetrachlorodibenzo-p-dioxin (TCDD). This list was compiled as a first step in the development of EPA’s response to the National Academy of Sciences comments (NAS, 2...

  8. A dose-response of consuming high fructose corn syrup-sweetened beverages on lipid/lipoprotein risk factors for cardiovascular disease in young adults

    Technology Transfer Automated Retrieval System (TEKTRAN)

    National Health and Nutrition Examination Survey data show increased risk of cardiovascular disease (CVD) mortality with increased intake of added sugar across quintiles. Objective: To determine the dose response effects of consuming beverages sweetened with high fructose corn syrup (HFCS) at zero, ...

  9. The influence of Trp53 in the dose response of radiation-induced apoptosis, DNA repair and genomic stability in murine haematopoietic cells.

    PubMed

    Lemon, Jennifer A; Taylor, Kristina; Verdecchia, Kyle; Phan, Nghi; Boreham, Douglas R

    2014-07-01

    Apoptotic and DNA damage endpoints are frequently used as surrogate markers of cancer risk, and have been well-studied in the Trp53+/- mouse model. We report the effect of differing Trp53 gene status on the dose response of ionizing radiation exposures (0.01-2 Gy), with the unique perspective of determining if effects of gene status remain at extended time points. Here we report no difference in the dose response for radiation-induced DNA double-strand breaks in bone marrow and genomic instability (MN-RET levels) in peripheral blood, between wild-type (Trp53+/+) and heterozygous (Trp53+/-) mice. The dose response for Trp53+/+ mice showed higher initial levels of radiation-induced lymphocyte apoptosis relative to Trp53+/- between 0 and 1 Gy. Although this trend was observed up to 12 hours post-irradiation, both genotypes ultimately reached the same level of apoptosis at 14 hours, suggesting the importance of late-onset p53-independent apoptotic responses in this mouse model. Expected radiation-induced G1 cell cycle delay was observed in Trp53+/+ but not Trp53+/-. Although p53 has an important role in cancer risk, we have shown its influence on radiation dose response can be temporally variable. This research highlights the importance of caution when using haematopoietic endpoints as surrogates to extrapolate radiation-induced cancer risk estimation.

  10. Use of mode of action data to inform a dose-response assessment for bladder cancer following exposure to inorganic arsenic.

    PubMed

    Gentry, P R; Yager, J W; Clewell, R A; Clewell, H J

    2014-10-01

    In the recent National Research Council report on conducting a dose-response assessment for inorganic arsenic, the committee remarked that mode of action data should be used, to the extent possible, to extrapolate below the observed range for epidemiological studies to inform the shape of the dose-response curve. Recent in vitro mode of action studies focused on understanding the development of bladder cancer following exposure to inorganic arsenic provide data to inform the dose-response curve. These in vitro data, combined with results of bladder cancer epidemiology studies, inform the dose-response curve in the low-dose region, and include values for both pharmacokinetic and pharmacodynamic variability. Integration of these data provides evidence of a range of concentrations of arsenic for which no effect on the bladder would be expected. Specifically, integration of these results suggest that arsenic exposures in the range of 7-43 ppb in drinking water are exceedingly unlikely to elicit changes leading to key events in the development of cancer or noncancer effects in bladder tissue. These findings are consistent with the lack of evidence for bladder cancer following chronic ingestion of arsenic water concentrations <100 ppb in epidemiological studies.

  11. Dose response effect of NutriTek on leukocyte functionality and ex vivo cytokine production during a dexamethasone challenge in Holstein steer calves

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The objective of this study was to determine the dose response effects of supplementing NutriTek on leukocyte functionality and ex vivo cytokine production during a dexamethasone (DEX) challenge. Holstein steers (125.1 ± 8.16 kg; N = 32) were assigned to treatments including 0, 20, 40, or 60 g/head/...

  12. NITRO MUSK ADDUCTS OF RAINBOW TROUT HEMOGLOBIN: DOSE-RESPONSE AND TOXICOKINETICS DETERMINATION BY GC-NICI-MS FOR A SENTINEL SPECIES

    EPA Science Inventory

    Rainbow trout and other fish species can serve as 'sentinel' species for the assessment of ecological status and the presence of certain environmental contaminants. As such they act as bioindicators of exposure. Here we present seminal data regarding dose-response and toxicokinet...

  13. DEVELOPING AN EXPOSURE-DOSE-RESPONSE MODEL FOR THE ACUTE NEUROTOXICITY OF ORGANIC SOLVENTS: OVERVIEW AND PROGRESS ON IN VITRO MODELS AND DOSIMETRY.

    EPA Science Inventory

    This article provides an overview of the current status of an exposure-dose-response (EDR) model for the volatile organic compound toluene. This model is being developed as a vehicle for understanding the neurotoxicity of organic solvents and will be used to support risk assessme...

  14. Dose-response and time-course of neurotoxicity and tissue concentrations of carbaryl in Brown Norway rats from preweaning to senescence.

    EPA Science Inventory

    Factors impacting sensitivity to chemicals across life stages include toxicokinetic and toxicodynamic changes. We systematically compared the dose-response (3, 7.5, 15,22.5 mg/kg) and time-course (3 or 15 mg/kg at 30, 60, 120, 240 min) of acute effects of carbaryl (oral gavage) i...

  15. Assessment of microvascular function by study of the dose-response effects of iontophoretically applied drugs (acetylcholine and sodium nitroprusside)--methods and comparison with in vitro studies.

    PubMed

    Henricson, Joakim; Tesselaar, Erik; Persson, Karin; Nilsson, Gert; Sjöberg, Folke

    2007-03-01

    Current knowledge about vascular function stems mainly from pharmacological in vitro studies using mounted vascular strips on a strain gauge. We know of no paper that has systematically examined the possibility of assessing the conventional dose-response effects of iontophoresis and laser Doppler investigation of vasoactive substances and compared those relations to data obtained from strips mounted on a strain gauge. We used the vasoactive substances acetylcholine (endothelium dependent) and sodium nitroprusside (endothelium independent) and an antagonist (atropine) to enable further investigations in the receptor physiology of iontophoresis. Dose-response curves from the iontophoresis experiments showed close similarity to those obtained by vascular strips mounted on a strain gauge. The coefficient of variation (CV) of the dose-response factors found in iontophoresis (both inter and intra experimental variability) was low. The iontophoretic effective dose of 50% (ED50) for acetylcholine and nitroprusside had only CVs of 25% and 26%, respectively, compared with 71% and 77% for the vascular strips. Acetylcholine-induced response was antagonized by iontophoresis of atropine. Contrary to expectations, this antagonism was not competitive. The results show that iontophoresis in combination with laser Doppler technology produces reproducible and reliable dose-response curves that picture the vascular effects of vasoactive drugs.

  16. Dose-response effect of exercise frequency on bone mineral density in post-menopausal, osteopenic women.

    PubMed

    Kemmler, W; von Stengel, S

    2014-06-01

    The purpose of this study was to determine the long-term dose-response relationship of exercise frequency on areal bone mineral density (aBMD) in early post-menopausal women with osteopenia. Based on the 12-year results of the consequently supervised exercise group (EG) of the Erlangen Fitness and Osteoporosis Prevention Study, we retrospectively structured two exercise groups according to the overall exercise frequency. Changes in aBMD at lumbar spine and proximal femur as assessed by dual-energy x-ray absorptiometry technique were compared between a low-frequency exercise group (LEF-EG, n = 16) with 1.5-<2 sessions/week and a high-frequency exercise group (HEF-EG, n = 25) with ≥ 2-3.5 sessions/week. Changes in aBMD at the lumbar spine and proximal femur were significantly more favorable in the HEF-EG compared with the LEF-EG; lumbar spine: (mean value ± standard deviation) 1.1 ± 4.7% vs -4.1 ± 3.0%; P = 0.001, ES: d' = 1.26; total hip: -4.4 ± 3.9% vs -6.7 ± 3.5%, P = 0.045, ES: d' = 0.70). BMD results of the LEF-EG did not significantly differ from the data of the non-training control group (lumbar spine: -4.4 ± 5.2%, total hip: -6.9 ± 5.0%). Although this result might not be generalizable across all exercise types and cohorts, it indicates that to impact bone, an overall exercise frequency of at least 2 sessions/week may be crucial, even if exercise is applied with high intensity/impact.

  17. Dose-response relationships of polycyclic aromatic hydrocarbons exposure and oxidative damage to DNA and lipid in coke oven workers.

    PubMed

    Kuang, Dan; Zhang, Wangzhen; Deng, Qifei; Zhang, Xiao; Huang, Kun; Guan, Lei; Hu, Die; Wu, Tangchun; Guo, Huan

    2013-07-02

    Polycyclic aromatic hydrocarbons (PAHs) are known to induce reactive oxygen species and oxidative stress, but the dose-response relationships between exposure to PAHs and oxidative stress levels have not been established. In this study, we recruited 1333 male coke oven workers, monitored the levels of environmental PAHs, and measured internal PAH exposure biomarkers including 12 urinary PAH metabolites and plasma benzo[a]pyrene-r-7,t-8,t-9,c-10-tetrahydotetrol-albumin (BPDE-Alb) adducts, as well as the two oxidative biomarkers urinary 8-hydroxydeoxyguanosine (8-OHdG) and 8-iso-prostaglandin-F2α (8-iso-PGF2α). We found that the total concentration of urinary PAH metabolites and plasma BPDE-Alb adducts were both significantly associated with increased 8-OHdG and 8-iso-PGF2α in both smokers and nonsmokers (all p < 0.05). This exposure-response effect was also observed for most PAH metabolites (all p(trend) < 0.01), except for 4-hydroxyphenanthrene and 8-OHdG (p(trend) = 0.108). Furthermore, it was shown that only urinary 1-hydroxypyrene has a significant positive association with both 8-OHdG and 8-iso-PGF2α after a Bonferroni correction (p < 0.005). Our results indicated that urinary ΣOH-PAHs and plasma BPDE-Alb adducts can result in significant dose-related increases in oxidative damage to DNA and lipids. Furthermore, when a multianalyte method is unavailable, our findings demonstrate that urinary 1-hydroxypyrene is a useful biomarker for evaluating total PAHs exposure and assessing oxidative damage in coke oven workers.

  18. Prospective Evaluation to Establish a Dose Response for Clinical Oral Mucositis in Patients Undergoing Head-and-Neck Conformal Radiotherapy

    SciTech Connect

    Narayan, Samir Lehmann, Joerg; Coleman, Matthew A.; Vaughan, Andrew; Yang, Claus Chunli; Enepekides, Danny; Farwell, Gregory; Purdy, James A.; Laredo, Grace; Nolan, Kerry A.S.; Pearson, Francesca S.; Vijayakumar, Srinivasan

    2008-11-01

    Purpose: We conducted a clinical study to correlate oral cavity dose with clinical mucositis, perform in vivo dosimetry, and determine the feasibility of obtaining buccal mucosal cell samples in patients undergoing head-and-neck radiation therapy. The main objective is to establish a quantitative dose response for clinical oral mucositis. Methods and Materials: Twelve patients undergoing radiation therapy for head-and-neck cancer were prospectively studied. Four points were chosen in separate quadrants of the oral cavity. Calculated dose distributions were generated by using AcQPlan and Eclipse treatment planning systems. MOSFET dosimeters were used to measure dose at each sampled point. Each patient underwent buccal sampling for future RNA analysis before and after the first radiation treatment at the four selected points. Clinical and functional mucositis were assessed weekly according to National Cancer Institute Common Toxicity Criteria, Version 3. Results: Maximum and average doses for sampled sites ranged from 7.4-62.3 and 3.0-54.3 Gy, respectively. A cumulative point dose of 39.1 Gy resulted in mucositis for 3 weeks or longer. Mild severity (Grade {<=} 1) and short duration ({<=}1 week) of mucositis were found at cumulative point doses less than 32 Gy. Polymerase chain reaction consistently was able to detect basal levels of two known radiation responsive genes. Conclusions: In our sample, cumulative doses to the oral cavity of less than 32 Gy were associated with minimal acute mucositis. A dose greater than 39 Gy was associated with longer duration of mucositis. Our technique for sampling buccal mucosa yielded sufficient cells for RNA analysis using polymerase chain reaction.

  19. Dose-response analysis of testosterone replacement therapy in patients with female to male gender identity disorder.

    PubMed

    Nakamura, Aya; Watanabe, Masami; Sugimoto, Morito; Sako, Tomoko; Mahmood, Sabina; Kaku, Haruki; Nasu, Yasutomo; Ishii, Kazushi; Nagai, Atsushi; Kumon, Hiromi

    2013-01-01

    Gender identity disorder (GID) is a conflict between a person's actual physical gender and the one they identify him or herself with. Testosterone is the key agent in the medical treatment of female to male GID patients. We conducted a dose-response analysis of testosterone replacement therapy (TRT) in 138 patients to determine the onset of the therapeutic effects. The TRT consisted of intramuscular injection of testosterone enanthate and patients were divided into three groups; 250 mg every two weeks, 250 mg every three weeks and 125 mg every two weeks. The onset of deepening of voice, increase in facial hair and cessation of menses was evaluated in each group. At one month after the start of TRT, the onset of these physical changes was more prevalent in the group receiving the higher dose of testosterone, and there were dose-dependent effects observed between the three treatment groups. On the other hand, at six months after the start of TRT, most of the patients had achieved treatment responses and there were no dose-dependent effects with regard to the percentage of patients with therapeutic effects. No significant side effects were observed in any of the treatment groups. We demonstrated that the early onset of the treatment effects of TRT is dose-dependent, but within six months of starting TRT, all three doses were highly effective. Current study provides useful information to determine the initial dose of TRT and to suggest possible changes that should be made in the continuous dosage for long term TRT.

  20. Dose Response of Listeria monocytogenes Invasion, Fetal Morbidity, and Fetal Mortality after Oral Challenge in Pregnant and Nonpregnant Mongolian Gerbils

    PubMed Central

    Roulo, Rebecca M.; Fishburn, Jillian D.; Amosu, Mayowa; Etchison, Ashley R.

    2014-01-01

    Listeria monocytogenes is a food-borne pathogen that can result in adverse pregnancy outcomes, such as stillbirth or premature delivery. The Mongolian gerbil was recently proposed as the most appropriate small-animal model of listeriosis due to its susceptibility to the same invasion pathways as humans. The objectives of this study were to investigate invasion and adverse pregnancy outcomes in gerbils orally exposed to L. monocytogenes, to compare the dose-response data to those of other animal models, and to investigate differences in the responses of pregnant versus nonpregnant gerbils. Gerbils were orally exposed to 0 (control), 103, 105, 107, or 109 CFU L. monocytogenes in whipping cream. L. monocytogenes was recovered in a dose-dependent manner from fecal samples, adult organs, and pregnancy-associated tissues. Dams exposed to 109 CFU had more invaded organs and higher concentrations of L. monocytogenes in almost all organs than nonpregnant animals, though no differences in fecal shedding were seen between the two groups. Adverse pregnancy outcomes occurred only in the dams treated with 109 CFU. A 50% infectivity dose (ID50) of 2.60 × 106 CFU for fetuses was calculated by fitting the data to a logistic model. Our results suggest that the 50% lethal dose (LD50) falls within the range of 5 × 106 to 5 × 108 CFU. This range includes the guinea pig and nonhuman primate LD50s, but the observation that L. monocytogenes-induced stillbirths can be seen in guinea pigs and primates exposed to lower doses than those at which stillbirths were seen in gerbils indicates that gerbils are not more sensitive to L. monocytogenes invasion. PMID:25156729

  1. Evaluation of dose-response curve analysis in delineating shared or different molecular sites of action for osteolathyrogens.

    PubMed

    Dawson, Douglas A; Scott, Brenda D; Ellenberger, M Jason; Pöch, Gerald; Rinaldi, Andrea C

    2004-03-01

    Single-chemical and mixture concentration-response curves generated using a frog embryo model were examined for value in assessing whether chemicals exert toxic effects at the same or at different molecular sites of action. Toxicity tests were conducted on a series of osteolathyrogens, i.e. chemicals that inhibit cross-linking of developing connective tissue fibers. Induction of osteolathyrism, which manifests as lesions in the notochord of exposed tadpoles, has several possible molecular sites of action, including agent-cofactor reactivity during the enzyme-mediated cross-linking process. UV-VIS spectrophotometry of osteolathyrogen-cofactor reactivity (i.e. in vitro analysis) was coupled with the 96-h frog embryo mixture toxicity assay (i.e. in vivo toxicity) to compare molecular sites of action for several osteolathyrogens with the combined osteolathyritic effects of the agents. Single-chemical concentration-response curves were used to calculate theoretical curves for the dose-addition model of combined effect. Slope and EC(50) values for both theoretical and experimental mixture curves were then generated to statistically examine the hypothesis that agents with shared sites of action have dose-response curve (DRC) slopes that are similar when given alone and in combination, and slope and EC(50) values that, when administered together, are consistent with those calculated for dose-addition. For combinations of cofactor-binding agents (semicarbazide, thiosemicarbazide, aminoacetonitrile), slope values were generally similar with additivity quotients near 1.0 (1.0=dose-additive) and combined osteolathyritic effects that were consistent with dose-addition. None of these were true for combinations that included agents that did not show rapid cofactor binding (β-aminopropionitrile, methyleneaminoacetonitrile). The results suggest that DRC analysis could be a useful tool for delineating common or different molecular sites of toxic action and that the approaches used

  2. SnET2 for the treatment of vascular disease: dose/response study in New Zealand white (NZW) rabbits

    NASA Astrophysics Data System (ADS)

    Narciso, Hugh L., Jr.; Anderson, Steven C.; DeHoratius, Sandra L.; Guerrero, Jan; Wang, T.; Spears, J. Richard

    1995-05-01

    Tin ethyl etiopurpurin, SnET2, is presently undergoing clinical trials for the treatment of cutaneous cancers and AIDS related Kaposi's sarcoma. Extensive pre-clinical work has been performed investigating the uptake, localization, and retention of SnET2 in catheter induced atheromatous plaques in New Zealand White (NZW) rabbits and juvenile female swine. The ultimate goal is to employ SnET2 for the prevention of intimal hyperplasia following various forms of angioplasty, thus enabling the prevention of a significant cause of restenosis. To that end, a dose/response study was undertaken to investigate the effect of varying total light dose (200, 100, and 50 J/cm2) and light dose rate (637, 318, 159 mW/cm2) during SnET2-Photodynamic Therapy, SnET2-PDT, of catheter induced plaque in a NZW rabbit iliac artery model. The SnET2 dose was held constant at 1.0 mg/kg b.w. and light was delivered intraluminally via a guidewire compatible light diffusing balloon catheter. The greatest light dose of those tested without inducing thermal damage was found to be 318 mW/cm2 while the total light dose of 50 J/cm2 produced PDT effect which was limited to the neo-intima. A relatively substantial total light dose of 200 J/cm2 was shown to produce a transmural PDT effect. This study demonstrated that the depth of PDT effect can be modulated by varying the total light dose.

  3. Dose-response of 1, 3, and 5 sets of resistance exercise on strength, local muscular endurance, and hypertrophy.

    PubMed

    Radaelli, Regis; Fleck, Steven J; Leite, Thalita; Leite, Richard D; Pinto, Ronei S; Fernandes, Liliam; Simão, Roberto

    2015-05-01

    The study's purpose was to compare the response of performing 1, 3, and 5 sets on measures of performance and muscle hypertrophy. Forty-eight men, with no weight training experience, were randomly assigned to one of the 3 training gro