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Use of nonlinear statistical methods and models are ubiquitous in scientific research. However, these methods may not be fully understood, and as demonstrated here, commonly-reported parameter p-values and confidence intervals may be inaccurate. The gentle introduction to nonlinear regression modelling and comprehensive illustrations given here provides applied researchers with the needed overview and tools to appreciate the nuances and breadth of these important methods. Since these methods build upon topics covered in first and second courses in applied statistics and predictive modelling, the target audience includes practitioners and students alike. To guide practitioners, we summarize, illustrate, develop, and extend nonlinear modelling methods, and underscore caveats of Wald statistics using basic illustrations and give key reasons for preferring likelihood methods. Parameter profiling in multiparameter models and exact or near-exact versus approximate likelihood methods are discussed and curvature measures are connected with the failure of the Wald approximations regularly used in statistical software. The discussion in the main paper has been kept at an introductory level and it can be covered on a first reading; additional details given in the Appendices can be worked through upon further study. The associated online Supplementary Information also provides the data and R computer code which can be easily adapted to aid researchers to fit nonlinear models to their data. [ABSTRACT FROM AUTHOR]

Polycyclic aromatic hydrocarbons (PAHs) are naturally occurring or anthropogenic organic chemicals that can activate the aryl hydrocarbon receptor 2 (AhR2) and induce toxicity in fishes. Alkyl PAHs are more abundant than nonalkylated PAHs in certain environmental matrices and there is growing evidence that alkylation can increase potency, dependent on the position of alkylation. However, it is unknown if the effect of alkylation on potency is conserved across species. In addition, relatively little is known regarding the extent of interspecies variation in sensitivity to PAHs and alkyl PAHs. Therefore, objectives of the present study were to characterize potency of benz[a]anthracene (BAA) and three alkylated homologues representing different alkylation positions in nine phylogenetically diverse species of fish using a standardized in vitro AhR2 transactivation assay. BAA and each alkylated homologue activated the AhR2 in a concentration‐dependent manner in each species. Position‐dependent effects on potency were observed in every species, but these effects were not consistent across species. Interspecies variation in sensitivity to AhR2 activation by each PAH was observed and ranged by up to 561‐fold. Alkylation both increased and decreased the range of interspecies variation and sensitivity, but the potency of each alkylated homologue relative to BAA ranged by less than an order of magnitude among species. These results represent an early step toward the consideration of alkylated homologues for more objective ecological risk assessments of PAHs to native fishes. Environ Toxicol Chem 2023;42:1575–1585. © 2023 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC. [ABSTRACT FROM AUTHOR]

Per- and polyfluoroalkyl substances (PFASs) are omnipresent and have been shown to induce a wide range of adverse health effects, including hepatotoxicity, developmental toxicity, and immunotoxicity. The aim of the present work was to assess whether human HepaRG liver cells can be used to obtain insight into differences in hepatotoxic potencies of a series of PFASs. Therefore, the effects of 18 PFASs on cellular triglyceride accumulation (AdipoRed assay) and gene expression (DNA microarray for PFOS and RT-qPCR for all 18 PFASs) were studied in HepaRG cells. BMDExpress analysis of the PFOS microarray data indicated that various cellular processes were affected at the gene expression level. From these data, ten genes were selected to assess the concentration–effect relationship of all 18 PFASs using RT-qPCR analysis. The AdipoRed data and the RT-qPCR data were used for the derivation of in vitro relative potencies using PROAST analysis. In vitro relative potency factors (RPFs) could be obtained for 8 PFASs (including index chemical PFOA) based on the AdipoRed data, whereas for the selected genes, in vitro RPFs could be obtained for 11–18 PFASs (including index chemical PFOA). For the readout OAT5 expression, in vitro RPFs were obtained for all PFASs. In vitro RPFs were found to correlate in general well with each other (Spearman correlation) except for the PPAR target genes ANGPTL4 and PDK4. Comparison of in vitro RPFs with RPFs obtained from in vivo studies in rats indicate that best correlations (Spearman correlation) were obtained for in vitro RPFs based on OAT5 and CXCL10 expression changes and external in vivo RPFs. HFPO-TA was found to be the most potent PFAS tested, being around tenfold more potent than PFOA. Altogether, it may be concluded that the HepaRG model may provide relevant data to provide insight into which PFASs are relevant regarding their hepatotoxic effects and that it can be applied as a screening tool to prioritize other PFASs for further hazard and risk assessment. [ABSTRACT FROM AUTHOR]

Objective: In this study, applicability of an in-vitro ELISA method, which reduces or eliminates the need for animal trials in establishing the efficacy of inactive Newcastle disease vaccines was investigated. Methods: For this purpose, the efficacy of nine (9) inactivated Newcastle disease vaccines and two non-Newcastle related vaccines (negative controls) were evaluated by in-vivo and in-vitro methods. As in-vivo tests, vaccines were applied to the Spesific Pathogen Free (SPF) chicks and antibody response was determined via hemagglutination inhibiton test. As in-vitro, antigen amount in vaccines were calculated with a sandwich ELISA test based on the determination of hemagglutinin and neuraminidase levels developed for inactive Newcastle vaccines. Relative potency values of vaccines were calculated by using the parallel line analysis method with Combistats statistical analysis software program by using optical density results obtained from ELISA test. Results: Hemagglutination inhibition test results were found to be between 23,3 and 26,1; immunization/challenge results ranged between 56 and 136 PD50 and ELISA test results were between 6,02 and 98,23 antigen units. A correlation was found between the ELISA test and in-vivo methods. Sensitivity and specificity were found to be %89, %100 respectively. Conclusion: In our study according to these results, we have demonstrated the ability of ELISA method to give similar results on the same samples, its compatibility with the standard procedure and its applicability under laboratory conditions. [ABSTRACT FROM AUTHOR]

Plant‐based 1,2‐unsaturated Pyrrolizidine Alkaloids (PAs) are responsible for liver genotoxicity/carcinogenicity following metabolic activation, making them a relevant concern for safety assessment. Due to 21st century toxicology approaches, risk of PAs can be better discerned though an understanding of differing toxic potencies, but it is often mixtures of PAs that are found as contaminants in foods, for example, herbal teas and honey, food supplements and herbal medicines. Our study investigated whether genotoxicity potency of PAs dosed individually or in mixtures differed when measured using micronuclei formation in vitro in HepaRG human liver cells, which we and others have shown to be suitable for observing genotoxic potency differences across different PA structural classes. When equipotent concentrations of up to six different PAs representing a wide range of potencies in vitro were tested as mixtures, the observed genotoxic potency aligned favorably with results for single PAs. Similarly, when the BMD confidence intervals of these equipotent mixtures were compared with the confidence intervals of the individual PAs, only minimal variation was observed. These data support a conclusion that for this class of plant impurities, all acting via the same DNA‐reactive mode of action, genotoxic potency can be regarded as additive when assessing the risk of mixtures of PAs. [ABSTRACT FROM AUTHOR]

World Health Organization toxic equivalency factors (WHO-TEFs) are recommended for risk management of brominated dioxins in aquatic environments because limited information is available on their toxicity to fish. To validate this approach, we obtained the relative potencies of polybrominated dibenzo-p-dioxins and polybrominated dibenzofurans and mixed-halogenated furans (PXDF, X = Cl/Br) against 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) based on their toxicity to the early-life stage of Japanese medaka (Oryzias latipes). 2,3,7,8-substituted brominated dibenzofurans caused typical dioxin exposure effects, such as blue-sac disease. The TCDD-relative potency factors (REPs) of test substances were calculated based on the concentrations in water and eggs that caused 20% lethality on day 28 post-fertilization, and were in the order of: 2-chloro-3,7,8-tribromodibenzofuran (REPwater 3.3, REPegg 4.6) > 2,3,7,8-tetrabromodibenzofuran (0.85, 0.92) > 2,3,4,7,8-pentabromodibenzofuran (0.053, 0.55) > 1,2,3,7,8-pentabromodibenzofuran (0.0091, 0.19). The transfer rate from water to eggs was lower for pentabrominated furans than tetrabrominated congeners, and was expected to decrease with the log Kow of the test substance. Although the REPegg value can be used to compare the toxicity potential of brominated dioxins, REPwater may be more suitable for environmental risk assessment because the uptake potential of these compounds from water should be considered. This study is the first to report higher toxicity of a PXDF congener compared with TCDD in vivo, further investigations of the toxicity of mixed-halogenated dioxins and environmental behavior are necessary for environmental risk assessment.

Polycyclic aromatic hydrocarbons (PAHs) are structurally diverse organic chemicals that can have adverse effects on the health of fishes through activation of aryl hydrocarbon receptor 2 (AhR2). They are ubiquitous in the environment, but alkyl PAHs are more abundant in some environmental matrices. However, relatively little is known regarding the effects of alkylation on the toxicity of PAHs to fishes in vivo and how this relates to potency for activation of AhR2 in vitro. Therefore, the objectives of the present study were to determine the toxicity of benz[a]anthracene and three alkylated homologs representing various alkylation positions to early life stages of zebrafish (Danio rerio) and to assess the potency of each for activation of the zebrafish AhR2 in a standardized in vitro AhR transactivation assay. Exposure of embryos to each of the PAHs caused a dose‐dependent increase in mortality and malformations characteristic of AhR2 activation. Each alkyl homolog had in vivo toxicities and in vitro AhR2 activation potencies different from those of the parent PAH in a position‐dependent manner. However, there was no statistically significant linear relationship between responses measured in these assays. The results suggest a need for further investigation into the effect of alkylation on the toxicity of PAHs to fishes and greater consideration of the contribution of alkylated homologs in ecological risk assessments. Environ Toxicol Chem 2022;41:1993–2002. © 2022 SETAC [ABSTRACT FROM AUTHOR]

In Algeria, vaccination against pertussis is carried out using the whole-cell pertussis vaccine combined with the diphtheria and tetanus toxoids (DTwp). The quality control of vaccines locally produced or imported is carried out before the batch release. The aim of our work was to evaluate the potency of pertussis vaccines. In the present study, five consecutive trials of potency were conducted on samples of the same batch of (DTwp) using the mouse protection test (MPT) against experimental infection of Bordetella pertussis strain 18323, based on the Kendrick test. The virulence of B. pertussis strain 18–323 was verified by the mortality of mice, with an average LD50 of 338.92, as well as the dose of the lethal test containing a mean number of LD50 of 324.43. The (MPT) test recorded a relative potency of 8.02 IU/human dose, with 95% CL of (3.56–18.05) IU/human dose. The development of the (MPT) at the laboratory of quality control of vaccines and sera at the Pasteur Institute of Algeria was effective in evaluating the potency of whole-cell pertussis vaccines. Interestingly, our study indicates that this potency is necessary for the vaccine quality assurance. Further validation is needed to strengthen the application and routine use of the test. [ABSTRACT FROM AUTHOR]

Potency assays are essential for the development and quality control of biopharmaceutical drugs, but they are often a time limiting factor due to manual handling steps and consequently low analytical throughput. On the other hand, automation of potency assays can be challenging due to their complexity and the use of biological materials. ELISA (enzyme-linked immunosorbent assay) is widely used for potency determination and is a good candidate for automation as all ELISA types depend on the same basic steps: coating, blocking, sample incubation, detection, and signal measurement. Nevertheless, ELISA for relative potency measurements still require drug-specific development and assay validation thereby complicating automation efforts. To simplify potency testing by ELISA, we first developed a manual protocol generally applicable to different drugs and then adapted this protocol for automated measurements. We identified unexpected critical parameters which had to be adapted to transfer the manual ELISA to an automated liquid handling system and we demonstrated that gravimetric sample dilution is unnecessary with the automated protocol. Both manual and automated protocols were validated and compared using multiple biotherapeutics. The automated protocol showed similar or higher precision and accuracy when compared to the manual method. • Generic ELISA protocol was established for measuring potency of antibody drugs. • The generic ELISA protocol was adapted for manual as well as automated measurements. • Automated protocol allows volumetric pipetting of highly concentrated protein samples. • Observed plate position effects have general implications for potency assay automation. • The manual and the automated protocol were validated for quality control of biopharmaceuticals. [ABSTRACT FROM AUTHOR]

Nowadays, use of botanical compounds as pesticides is becoming increasingly important, because of their acceptable efficiency and relative safety to human and environment. The present study aimed to investigate oral toxicity of different extracts of Achillea millefolium L. and Marrubium vulgare L., against larvae of potato tuber moth and compare their potency with some conventional insecticides. Larvae of potato tuber moth, reared on potato tubers in controlled conditions. Extraction was carried out by maceration method using hexane, ethyl acetate, methanol and water as solvents. Foliage of A. millefolium and M. vulgare collected, well washed with distilled water, air dried in shadow then used for extraction. For bioassays fresh potato leaves dipped in each concentration of extracts for 5 seconds, air dried for 20 minutes. Potato tuber moth larvae transferred on treated leaves. Mortality was recorded after 48 hours. The results revealed that, aqueous and ethyl acetate extracts of A. millefolium showed the most and the least toxicity against 1st larval instar, with LC50 values of 2.96 and 44.03 gr/lrespectively. Methanol extract of A. millefolium and ethyl acetate extracts of M. vulgare were more and less toxic against 2nd larval instar of PTM with LC50 values of 9.03 and 34.79 gr/l, respectively. The toxicity comparison of plants extracts with Fenvalerate, Imidacloprid and Acetamiprid showed that, in all cases the synthetic pesticides were more toxic than plant extracts. Acetamiprid with LC50 values of 0.18 and 0.31 gr/l was more toxic than other pesticides against 1st and 2nd larval instars of PTM, respectively but relative potency of plant extracts was comparable with Fenvalerate.

In order to evaluate the potential of citogate and turnip vegetable oil in increasing the performance of barnyardgrass (Echinochloa crus-galli) control by colthodim and haloxyfop-r-methyl ester herbicides, two greenhouse experiments were carried out in the Research Greenhouse of the Faculty of Agriculture, Birjand, Iran, in 2016; this study was based on a factorial arrangement as a completely randomized design with three replications. Treatments in each experiment included herbicide concentrations at seven levels (0, 6.25, 12.5, 25, 50, 75, and 100% of the recommended dose) and additives were applied at three levels (turnip oil, citogate, and without additives). The application of additives with colthodim herbicide on barnyardgrass (based on the shoot dry weight) led to 4.5% and 5.4% decreases in ED50 in the presence of turnip oil and citogate, respectively. Based on the root dry weight, ED50 was reduced to 22.9% and 21.6% in the presence of turnip oil and citogate, respectively. The results of the use of additives with Haloxyfop-r-methyl ester also showed a similar trend. However, the increase in the efficiency of Haloxyfop-r-methyl ester was higher than that of colthodim herbicide. The Haloxyfop-r-methyl ester ED50 values for the shoot dry weight of barnyardgrass were reduced by 14% and 16.3% in the presence of turnip oil and citogate, respectively. The Haloxyfop-r-methyl ester ED50 values for the root dry weight in the presence of turnip oil and citogate were 10 and 7 times higher than those in the treatments without additives, respectively. According to the results of this study, application of appropriate additives may lead to decrease in the extent of herbicide contamination of soil and water resources.

The logit binomial logistic dose response model is commonly used in applied research to model binary outcomes as a function of the dose or concentration of a substance. This model is easily tailored to assess the relative potency of two substances. Consequently, in instances where two such dose response curves are parallel so one substance can be viewed as a dilution of the other, the degree of that dilution is captured in the relative potency model parameter. It is incumbent that experimental researchers working in fields including biomedicine, environmental science, toxicology and applied sciences choose efficient experimental designs to run their studies to both fit their dose response curves and to garner important information regarding drug or substance potency. This article provides far-reaching practical design strategies for dose response model fitting and estimation of relative potency using key illustrations. These results are subsequently extended here to handle situations where the assessment of parallelism and the proper dose-scale are also of interest. Conclusions and recommended strategies are supported by both theoretical and simulation results. [ABSTRACT FROM AUTHOR]

[Display omitted] • Inhibition zone measurements from smartphone app were comparable values from regular callipers. • Bootstrapping method for measurement uncertainty evaluation was implemented in Python. • Both improvements were successfully applied to three different antibiotic substances. Usually, inhibition zone sizes in agar diffusion microbiological assay of antibiotics are measured using regular callipers. In this study, we proposed the use of a smartphone app for measuring inhibition zone sizes. The smartphone app allows for standardized measurements with a reference scale, which provides measured values comparable to those obtained using regular callipers. The main uncertainty source associated with antibiotic potency is inhibition zone size variability. Here, we suggest using the bootstrapping method, a resampling technique, to estimate measurement uncertainty without complex calculations. This simplifies the process and yields comparable results to the usual measurement uncertainty calculations. Both improvements were successfully applied to determine the potency of gentamicin, linezolid, and cefazolin. The results showed that smartphone-based measurements and the bootstrapping approach are valuable tools in agar diffusion microbiological assays. [ABSTRACT FROM AUTHOR]

In Algeria, vaccination against pertussis is carried out using the whole-cell pertussis vaccine combined with the diphtheria and tetanus toxoids (DTwp). The quality control of vaccines locally produced or imported is carried out before the batch release. The aim of our work was to evaluate the potency of pertussis vaccines. In the present study, five consecutive trials of potency were conducted on samples of the same batch of (DTwp) using the mouse protection test (MPT) against experimental infection of Bordetella pertussis strain 18323, based on the Kendrick test. The virulence of B. pertussis strain 18–323 was verified by the mortality of mice, with an average LD50 of 338.92, as well as the dose of the lethal test containing a mean number of LD50 of 324.43. The (MPT) test recorded a relative potency of 8.02 IU/human dose, with 95% CL of (3.56–18.05) IU/human dose. The development of the (MPT) at the laboratory of quality control of vaccines and sera at the Pasteur Institute of Algeria was effective in evaluating the potency of whole-cell pertussis vaccines. Interestingly, our study indicates that this potency is necessary for the vaccine quality assurance. Further validation is needed to strengthen the application and routine use of the test.

Relative potency is widely used in toxicological and pharmacological studies to characterize potency of chemicals. The relative potency of a test chemical compared to a standard chemical is defined as the ratio of equally effective doses (standard divided by test). This classical concept relies on the assumption that the two chemicals are toxicologically similar—that is, they have parallel dose–response curves on log‐dose scale—and thus have constant relative potency. Nevertheless, investigators are often faced with situations where the similarity assumption is deemed unreasonable, and hence the classical idea of constant relative potency fails to hold; in such cases, simply reporting a single constant value for relative potency can produce misleading conclusions. Relative potency functions, describing relative potency as a function of the mean response (or other quantities), is seen as a useful tool for handling nonconstant relative potency in the absence of similarity. Often, investigators are interested in assessing nonconstant relative potency at a finite set of some specific response levels for various regulatory concerns, rather than the entire relative potency function; this simultaneous assessment gives rise to multiplicity, which calls for efficient statistical inference procedures with multiplicity adjusted methods. In this paper, we discuss the estimation of relative potency at multiple response levels using the relative potency function, under the log‐logistic dose–response model. We further propose and evaluate three approaches to calculating multiplicity‐adjusted confidence limits as statistical inference procedures for assessing nonconstant relative potency. Monte Carlo simulations are conducted to evaluate the characteristics of the simultaneous limits. [ABSTRACT FROM AUTHOR]

Per‐ and polyfluoroalkyl substances (PFAS) often occur together as contamination in exposure media such as drinking water or food. The relative potency factor (RPF) methodology facilitates the risk assessment of mixture exposure. A database of liver endpoints was established for 16 PFAS, using data with the same species (rat), sex (male), and exposure route (oral) and comparable exposure duration (42–90 d). Dose–response analysis was applied to derive the relative potencies of 3 perfluoroalkyl sulfonic acids (perfluorobutane sulfonic acid, perfluorohexane sulfonic acid, perfluorooctane sulfonic acid), 8 perfluoroalkyl carboxylic acids (perfluorobutanoic acid, perfluorohexanoic acid, perfluorononanoic acid, perfluoroundecanoic acid, perfluorododecanoic acid, perfluorotetradecanoic acid, perfluorohexadecanoic acid, perfluorooctadecanoic acid), 2 perfluoroalkyl ether carboxylic acids (tetrafluoro‐2‐[heptafluoropropoxy]propanoic acid, 3H‐perfluoro‐3‐[(3‐methoxy‐propoxy)propanoic acid]), and 2 fluorotelomer alcohols (6:2 FTOH, 8:2 FTOH) compared to perfluorooctanoic acid (PFOA), based on liver effects. In addition, the RPFs of 7 other perfluoroalkyl acids were estimated based on read‐across. This resulted in the relative potencies of 22 PFAS compared to the potency of index compound PFOA. The obtained RPFs can be applied to measured PFAS quantities, resulting in the sum of PFOA equivalents in a mixture. This sum can be compared with an established PFOA concentration limit (e.g., in drinking water or food) or an external health‐based guidance value (e.g., tolerable daily intake, acceptable daily intake, or reference dose) to estimate the risk resulting from direct oral exposure to mixtures. Assessing mixture exposure is particularly relevant for PFAS, with omnipresent exposure in our daily lives. Environ Toxicol Chem 2021;40:859–870. © 2020 SETAC [ABSTRACT FROM AUTHOR]

Use of nonlinear statistical methods and models are ubiquitous in scientific research. However, these methods may not be fully understood, and as demonstrated here, commonly-reported parameter p-values and confidence intervals may be inaccurate. The gentle introduction to nonlinear regression modelling and comprehensive illustrations given here provides applied researchers with the needed overview and tools to appreciate the nuances and breadth of these important methods. Since these methods build upon topics covered in first and second courses in applied statistics and predictive modelling, the target audience includes practitioners and students alike. To guide practitioners, we summarize, illustrate, develop, and extend nonlinear modelling methods, and underscore caveats of Wald statistics using basic illustrations and give key reasons for preferring likelihood methods. Parameter profiling in multiparameter models and exact or near-exact versus approximate likelihood methods are discussed and curvature measures are connected with the failure of the Wald approximations regularly used in statistical software. The discussion in the main paper has been kept at an introductory level and it can be covered on a first reading; additional details given in the Appendices can be worked through upon further study. The associated online Supplementary Information also provides the data and R computer code which can be easily adapted to aid researchers to fit nonlinear models to their data., (© 2024. The Author(s).)

In order to evaluate the potential of citogate and turnip vegetable oil in increasing the performance of barnyardgrass (Echinochloa crus-galli) control by colthodim and haloxyfop-r-methyl ester herbicides, two greenhouse experiments were carried out in the Research Greenhouse of the Faculty of Agriculture, Birjand, Iran, in 2016; this study was based on a factorial arrangement as a completely randomized design with three replications. Treatments in each experiment included herbicide concentrations at seven levels (0, 6.25, 12.5, 25, 50, 75, and 100% of the recommended dose) and additives were applied at three levels (turnip oil, citogate, and without additives). The application of additives with colthodim herbicide on barnyardgrass (based on the shoot dry weight) led to 4.5% and 5.4% decreases in ED50 in the presence of turnip oil and citogate, respectively. Based on the root dry weight, ED50 was reduced to 22.9% and 21.6% in the presence of turnip oil and citogate, respectively. The results of the use of additives with Haloxyfop-r-methyl ester also showed a similar trend. However, the increase in the efficiency of Haloxyfop-r-methyl ester was higher than that of colthodim herbicide. The Haloxyfop-r-methyl ester ED50 values for the shoot dry weight of barnyardgrass were reduced by 14% and 16.3% in the presence of turnip oil and citogate, respectively. The Haloxyfop-r-methyl ester ED50 values for the root dry weight in the presence of turnip oil and citogate were 10 and 7 times higher than those in the treatments without additives, respectively. According to the results of this study, application of appropriate additives may lead to decrease in the extent of herbicide contamination of soil and water resources. [ABSTRACT FROM AUTHOR]

Comparing the harmful health effects related to two different tobacco products by applying common risk assessment methods to each individual compound is problematic. We developed a method that circumvents some of these problems by focusing on the change in cumulative exposure (CCE) of the compounds emitted by the two products considered. The method consists of six steps. The first three steps encompass dose‐response analysis of cancer data, resulting in relative potency factors with confidence intervals. The fourth step evaluates emission data, resulting in confidence intervals for the expected emission of each compound. The fifth step calculates the change in CCE, probabilistically, resulting in an uncertainty range for the CCE. The sixth step estimates the associated health impact by combining the CCE with relevant dose‐response information. As an illustrative case study, we applied the method to eight carcinogens occurring both in the emissions of heated tobacco products (HTPs), a novel class of tobacco products, and tobacco smoke. The CCE was estimated to be 10‐ to 25‐fold lower when using HTPs instead of cigarettes. Such a change indicates a substantially smaller reduction in expected life span, based on available dose‐response information in smokers. However, this is a preliminary conclusion, as only eight carcinogens were considered so far. Furthermore, an unfavorable health impact related to HTPs remains as compared to complete abstinence. Our method results in useful information that may help policy makers in better understanding the potential health impact of new tobacco and related products. A similar approach can be used to compare the carcinogenicity of other mixtures. [ABSTRACT FROM AUTHOR]

Comparing the harmful health effects related to two different tobacco products by applying common risk assessment methods to each individual compound is problematic. We developed a method that circumvents some of these problems by focusing on the change in cumulative exposure (CCE) of the compounds emitted by the two products considered. The method consists of six steps. The first three steps encompass dose-response analysis of cancer data, resulting in relative potency factors with confidence intervals. The fourth step evaluates emission data, resulting in confidence intervals for the expected emission of each compound. The fifth step calculates the change in CCE, probabilistically, resulting in an uncertainty range for the CCE. The sixth step estimates the associated health impact by combining the CCE with relevant dose-response information. As an illustrative case study, we applied the method to eight carcinogens occurring both in the emissions of heated tobacco products (HTPs), a novel class of tobacco products, and tobacco smoke. The CCE was estimated to be 10- to 25-fold lower when using HTPs instead of cigarettes. Such a change indicates a substantially smaller reduction in expected life span, based on available dose-response information in smokers. However, this is a preliminary conclusion, as only eight carcinogens were considered so far. Furthermore, an unfavorable health impact related to HTPs remains as compared to complete abstinence. Our method results in useful information that may help policy makers in better understanding the potential health impact of new tobacco and related products. A similar approach can be used to compare the carcinogenicity of other mixtures. [ABSTRACT FROM AUTHOR]

The World Health Organization (WHO) assesses potential health risks of dioxin-like compounds using Toxic Equivalency Factors (TEFs). This study systematically updated the relative potency (REP) database underlying the 2005 WHO TEFs and applied advanced methods for quantitative integration of study quality and dose-response. Data obtained from fifty-one publications more than doubled the size of the previous REP database (∼1300 datasets). REP quality and relevance for these data was assessed via application of a consensus-based weighting framework. Using Bayesian dose-response modeling, available data were modeled to produce standardized dose/concentration-response Hill curves. Study quality and REP data were synthesized via Bayesian meta-analysis to integrate dose/concentration-response data, author-calculated REPs and benchmark ratios. The output is a prediction of the most likely relationship between each congener and its reference as model-predicted TEF uncertainty distributions, or the 'best estimate TEF' (BE-TEF). The resulting weighted BE-TEFs were similar to the 2005 TEFs, though provide more information to inform selection of TEF values as well as to provide risk assessors and managers with information needed to quantitatively characterize uncertainty around TEF values. Collectively, these efforts produce an updated REP database and an objective, reproducible approach to support development of TEF values based on all available data. • The dioxin-like congener relative potency (REP) database has been updated for the first time since 2004. • Systematic methods documented by an a priori protocol increase transparency and reliability of the database. • The size of the database available to update toxic equivalency factors (TEFs) was increased by over 100%. • Best Estimate TEFs (BE TEFs) were developed via Bayesian dose-response modeling and meta-analysis. • Modeled BE TEFs are within an order of magnitude of WHO 2005 TEF values. [ABSTRACT FROM AUTHOR]

The toxic equivalency factors (TEFs) approach for dioxin-like chemicals (DLCs) is currently based on a qualitative assessment of a heterogeneous data set of relative estimates of potency (REPs) spanning several orders of magnitude with highly variable study quality and relevance. An effort was undertaken to develop a weighting framework to systematically evaluate and quantitatively integrate the quality and relevance for development of more robust TEFs. Six main-study characteristics were identified as most important in characterizing the quality and relevance of an individual REP for human health risk assessment: study type, study model, pharmacokinetics, REP derivation method, REP derivation quality, and endpoint. Subsequently, a computational approach for quantitatively integrating the weighting framework parameters was developed and applied to the REP 2004 database. This was accomplished using a machine learning approach which infers a weighted TEF distribution for each congener. The resulting database, weighted for quality and relevance, provides REP distributions from >600 data sets (including in vivo and in vitro studies, a range of endpoints, etc.). This weighted database provides a flexible platform for systematically and objectively characterizing TEFs for use in risk assessment, as well as providing information to characterize uncertainty and variability. Collectively, this information provides risk managers with information for decision making. • Study quality and relevance underlying REPs are highly variable. • A consensus-based weighting framework was developed. • A machine-learning approach was used to apply the framework to underlying data. • The resulting database provides REP distributions from >600 data sets. • Information can be used by risk managers. [ABSTRACT FROM AUTHOR]

Aim: To investigate the impact of sample replication number (duplicate vs triplicate) on the validation of ELISA methodology. Materials & methods: The methodology was validated with reference sample and test sample as an 11-point triplicate dilution series. The data were reanalyzed post-validation as if conducted as a duplicate dilution series. Results: The triplicate methodology was validated with a precision of 5.3% and mean bias of -1.7%. The duplicate methodology generated a precision of 5.7% and mean bias of -2.2%. Conclusion: Both the triplicate (method capability index = 1.37) and duplicate (method capability index = 1.25) ELISA methodology can support an 80-125% relative potency specification with a 0.004% or 0.018% probability of out-of-specification results, respectively.

The USP<1032> guidelines recommend the screening of bioassay data for outliers prior to performing a relative potency (RP) analysis. The guidelines, however, do not offer advice on the size or type of outlier that should be removed prior to model fitting and calculation of RP. Computer simulation was used to investigate the consequences of ignoring the USP<1032> guidance to remove outliers. For biotherapeutics and vaccines, outliers in potency data may result in the false acceptance/rejection of a bad/good lot of drug product. Biological activity, measured through a potency bioassay, is considered a critical quality attribute in manufacturing. If the concentration‐response potency curve of a test sample is deemed to be similar in shape to that of the reference standard, the curves are said to exhibit constant RP, an essential criterion for the interpretation of a RP. One or more outliers in the concentration‐response data, however, may result in a failure to declare similarity or may yield a biased RP estimate. Concentration‐response curves for test and reference were computer generated with constant RP from four‐parameter logistic curves. Single outlier, multiple outlier, and whole‐curve outlier scenarios were explored for their effects on the similarity testing and on the RP estimation. Though the simulations point to situations for which outlier removal is unnecessary, the results generally support the USP<1032> recommendation and illustrate the impact on the RP calculation when application of outlier removal procedures are discounted. [ABSTRACT FROM AUTHOR]

The post-fusion form of Respiratory Syncytial Virus (RSV) fusion (F) protein has been used recently in clinical trials as a potential vaccine antigen with the objective of eliciting protective immune response against RSV. In this paper, in vitro antigenicity and in vivo immunogenicity of recombinant, soluble F protein of RSV (RSVsF) were evaluated by several assays. In Vitro Relative Potency (IVRP) of RSVsF was measured in a sandwich ELISA using two antibodies, each specific for epitope site A or C. Therefore, IVRP reflected the integrity of the antigen in terms of changes in antibody binding affinity of either or both of these sites. RSVsF samples with a wide range of IVRP values were generated by applying UV irradiation (photo) and high temperature (heat) induced stress for varying lengths of time. These samples were characterized in terms of stress induced modifications in primary and secondary structures as well as aggregation of RSVsF. Immunogenicity, also referred to as In vivo potency, was measured by induction of total F-protein specific IgG and RSV-neutralizing antibodies in mice dosed with these RSVsF samples. Comparison of results between IVRP and these immunogenicity assays revealed that IVRP provided a sensitive read-out of the integrity of epitope sites A and C, and a conservative and reliable evaluation of the potency of RSVsF as a vaccine antigen. This high throughput and fast turn-around assay allowed us to efficiently screen many different RSVsF antigen lots, thereby acting as an effective filter for ensuring high quality antigen that delivered in vivo potency. In vitro and in vivo potencies were further probed at the level of individual epitope sites, A and C. Results of these experiments indicated that site A was relatively resistant to stress induced loss of potency, in vitro or in vivo , compared to site C. [ABSTRACT FROM AUTHOR]

Abstract: In the present study 42 polycyclic aromatic compounds (PACs) were investigated for their estrogenic potential using the VM7Luc4E2 transactivation assay. Relative potencies were determined for mass‐balance analysis. In addition, compounds were tested in combination with the estrogen receptor (ER) antagonist ICI182,780 (ICI) and the aryl hydrocarbon receptor antagonist/CYP1A1 inhibitor α‐naphthoflavone. Luciferase induction and CYP1A1‐dependent ethoxyresorufin‐O‐deethylase (EROD) activity were measured to assess whether the estrogenic activity was elicited by the compound itself and/or by its metabolites. Relative potencies ranged between 10−7 and 10−4. The ability of ICI to decrease luciferase activity stimulated by all compounds indicated that the induction responses were ER‐dependent. The aryl hydrocarbon receptor antagonist/CYP1A1 inhibitor α‐naphthoflavone decreased luciferase induction and EROD activity by several compounds, including the methylated chrysenes, suggesting that metabolites of these chemicals contributed to ER activation. Several PACs, such as acridine and its derivatives, appear to directly activate the ER. Furthermore, extracts of soils from industrial areas were examined using this bioassay, and estrogenic activity was detected in all soil samples. Mass‐balance analysis using a combination of relative potencies and chemical analysis of the samples suggested that polycyclic aromatic hydrocarbons (PAHs) and alkylated PAHs, such as 1‐ and 3‐methylchrysene, are important contributors to the overall estrogenic activity. However, these results revealed that a considerable proportion of the estrogenic activity in the soil remained unexplained, indicating the presence of other significant estrogenic compounds. Environ Toxicol Chem 2018;37:385–397. © 2017 SETAC [ABSTRACT FROM AUTHOR]

ABSTRACT Pollutant loads are a means for assessing regulatory compliance and setting targets to reduce pollution entering receiving waterbodies. However, a pollutant load is often comprised of multiple chemicals, which may exert joint toxicity on biota. When the ultimate goal for assessing pollutant loads is to protect ecosystems from adverse effects of toxicants, then the total pollutant load needs to be calculated based on the principles of mixture toxicology. In this article, an improved method is proposed to convert a pollutant load to a toxicity-based load (toxic load) using a modified toxic equivalency factor (TEF) derivation method. The method uses the relative potencies (RePs) of multiple species to represent the response of the ecological community. The TEF is calculated from a percentile of a cumulative distribution function (CDF) fitted to the RePs. The improvements permit the determination of which percentile of the CDF generates the most environmentally relevant and robust toxic loads. That is, environmental relevance ensures that a reduction in the toxic load is likely to result in a corresponding improvement in ecosystem health and robustness ensures that the calculation of the toxic loads is not biased by the reference chemical used. The improved methodology will therefore ensure that correct management decisions will be made and ultimately, a reduction in the toxic load will lead to a commensurate improvement in water quality. Integr Environ Assess Manag 2017;13:746-753. © 2016 SETAC [ABSTRACT FROM AUTHOR]

Aims To study the expression of cleaved synaptosomal associated protein of 25 kDa (cSNAP-25) in the bladder wall injected with onabotulinumtoxinA (onabotA) or abobotulinumtoxinA (abobotA) and compare the relative potency of these two brands. Methods One injection of 0.5 U of onabotA or abobotA diluted in 2 µl of saline was carried out in the bladder dome of adult female mice, whose bladders were exposed by laparotomy. Three days later bladders were collected, divided in five segments (dome, upper, middle and lower body, and trigone) and each one was sectioned and immunoreacted against cSNAP-25, the end product of botulinum toxin type A (BoNT/A) activity. From each of the five segments one section was taken at random and the number of cSNAP-25 immunoreactive (IR) fibers was determined. Results Each injection resulted in the cleavage of SNAP-25 in all bladder sections, including those of the more distant segment from the injection point. The average number of cSNAP-25 positive fibers was higher in the onabotA, 341 ± 301, than in the abobotA-treated mice, 208 ± 152 ( P = 0.003). The number of cSNAP-25 IR fibers varied three to five-fold between animals of each experimental group. Conclusions These findings confirm that, when injected in the bladder wall, in the same unit amount and same volume, onabotA is 1.6 times more potent to cleave SNAP-25 than abobotA. The conversion ratio suggested by these experiments is 1:1.6 between onabotA and abobotA. Each injection, although preformed in the same way, may induce substantially different amounts of cSNAP-25. Neurourol. Urodynam. 36:86-90, 2017. © 2015 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

Biological assays are essential tools in biomedical and pharmaceutical research. In simplest terms, such an assay is an analytical method used to measure or predict a response in a biological system in the presence of a given stimulus (e.g., drug). The inherent complexity involved in evaluating a biological system requires the use of rigorous and appropriate tools for data analysis. Linear and nonlinear regression models represent critically important statistical analyses used to define the relationships between variables of interest in biological systems. Recent challenges relating to the reproducibility of published data suggest the absence of standardized and routine use of statistics to support experimental results across a wide range of scientific disciplines. The current situation warrants an introductory review of basic regression concepts using current, practical examples, along with references to in-depth resources. The goal is to provide the necessary information to help standardize the analysis of biological assays in academic research and drug discovery and development, elevating their utility and increasing data transparency and reproducibility. © 2023 The Authors. Current Protocols published by Wiley Periodicals LLC., (© 2023 The Authors. Current Protocols published by Wiley Periodicals LLC.)