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Allometry of Metal Bioaccumulation and Toxicity
Published in Michael C. Newman, Alan W. McIntosh, Metal Ecotoxicology, 2020
Michael C. Newman, Mary Gay Heagler
Allometry is the study of size and its consequences.28 Characters examined are most often morphological,28-32 physiological,28,33,34 or biochemical.35-38 Huxley39 is largely credited for firmly establishing the use of power equations to describe these relationships. Indeed, Huxley’s Law of Simple Allometry is a central paradigm of allometry. By 1987, more than 750 published allometric power relationships had been described.40 Despite their clearly empirical nature, an enormous literature has been generated in an attempt to identify the “basic factor”29 underlying allometric relationships. Numerous hypotheses now exist, but the underpinnings for this law remain ambiguous. For example, Rubner’s Law (metabolic rate is linked to size-dependent change in surface:volume ratio through its influence on heat loss in warm-blooded animals) failed to explain scaling of metabolism because protozoans and cold-blooded metazoans also conform to this relationship. A more recent example involves explanations derived from dimensional analysis41 which are actively being debated at this time.42
Pharmacokinetics
Published in Samuel C. Morris, Cancer Risk Assessment, 2020
Allometry describes the disporportionate relationship of the size or function of isolated features in animals with body size or mass (Lindstedt, 1987). Although all mammals share much in common in bodily structure and function, larger animals are not proportionally scaled to smaller animals. In larger animals, for example, the skeleton comprises a greater proportion of the total mass than in small animals while smaller animals have a higher metabolism rate per unit mass. This relationship is generally described as a power function: Y=aMb
Climate Change Impacts and Mitigation Through Sustainable Agroforestry Practices
Published in Rohini Prasad, Manoj Kumar Jhariya, Arnab Banerjee, Advances in Sustainable Development and Management of Environmental and Natural Resources, 2021
Soumya Kumar Sahoo, Biswajit Lenka, Abhishek Raj, Manoj Kumar Jhariya
Allometry is the investigation of how the characteristics of a living organism alter with size. Allometric relationships are occasionally eluded as empirical models based on observation rather than theory. While empirical models are useful for summing up past data and for interpolation, they commonly contain no information beyond the original data (Thornley and Johnson, 1990). Commercial forestry widely uses allometric relationships such as yield tables describing, for instance, the relationship between tree volume, height, and diameter in relation to predetermined tree density (Burkhart and Tomé, 2002). Data may be used to formulate regression models for further interpretations.
Allometric Scaling Hip Joint Moments Optimally Reduces Anthropometric Differences in Males and Females
Published in Sports Biomechanics, 2023
Bret Freemyer, Samantha Andrews, Christopher Stickley
Ratio scaling of kinetics can be described as acceptable, yet imperfect for partialing out the anthropometric differences of kinetic data. Wannop et al. described several sources of concern when ratio scaling, including an inability to remove all anthropometric variability from the outcome measures, non-linearity between kinetics and anthropometrics, and risk of excessive scaling (Wannop et al., 2012). Because there is no true linear relationship between kinetics and anthropometrics, linear analyses and assumptions will lead to imperfect scaling. The issue of non-linearity of data should be apparent when one considers that not all tall people have similar BM, despite a general trend. Traditional parametric tests using ratio scaled data make the assumption that these data are linearly related and therefore have an additive constant that can be thought of as error across an outcome measure (Vanderburgh, 1998). Additionally, the excessive scaling of data becomes apparent when significant positive correlations between anthropometrics and raw kinetics reverse to negative correlations when kinetics are ratio scaled (Stickley et al., 2018). If all the anthropometric variability in an outcome measure is removed, then researchers can be more confident that differences found across groups are due to the primary factor studied and not related to size differences. A proposed third solution to address these outlined issues of raw or ratio scaled data is to utilise allometric scaling of biomechanics kinetics.
A new approach method for characterizing inter-species toxicodynamic variability
Published in Journal of Toxicology and Environmental Health, Part A, 2021
Sarah D. Burnett, Moumita Karmakar, William J. Murphy, Weihsueh A. Chiu, Ivan Rusyn
These results also have important implications as to the contribution of toxicokinetics and toxicodynamics to inter-species differences. Allometric scaling based upon body weight and caloric demand is a common method for extrapolation of (external) dose equivalencies between species in vivo (Price, Keenan, and Swartout 2008; Schneider, Oltmanns, and Hassauer 2004). Moreover, it is known that many physiological parameters that impact toxicokinetics, such as cardiac output and minute-volume, scale allometrically by ¾ power of body weight, and would be equivalent to interspecies scaling on the basis of internal dose (e.g., serum concentrations). However, there has been some uncertainty as to the extent to which the observed allometric relationships for dose equivalence across species are solely due to toxicokinetics (U.S. U.S. EPA 2011). Because only weak evidence for allometric scaling by body weight or lifespan for toxicodynamic variability was found, our data support the notion that toxicokinetics is the primary driver for overall in vivo allometric scaling. However, also important is our finding of chemical-specific variability in the scaling relationship for toxicodynamics, suggesting that the overall allometric power, combining toxicokinetics and toxicodynamics, may be chemical-specific.
Physiologically-based pharmacokinetic modeling of benzo(a)pyrene and the metabolite in humans of different ages
Published in International Journal of Environmental Health Research, 2021
Linjing Deng, Hui Liu, Qihong Deng
Several studies have attempted to describe chemical toxic kinetics in humans through various approaches. Renwick developed a safety factor of 10 to allow for interindividual differences, and the safety factor value was subdivided into two separate factors to describe toxicokinetic and toxicodynamic differences (Renwick 1993). Simple allometric approaches using a function related to body weight, height, or age were used to predict children dose scaled from adult dose. Simple compartment toxicokinetic models were used by Verner et al. to assess POP levels in blood from birth to 45 months of age (Verner et al. 2013). Those approaches were obviously simple and convenient to qualitatively account for toxicokinetic differences between children and adults. However, as more information becomes available on the rapid changes in rates of organ maturation, body composition, blood flow, and ontogeny of chemical elimination and transport mechanisms occurring in life stage, it is feasible to allow estimation of chemical levels in target tissues or organs (Deng et al. 2019).