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Small Animal Imaging and Therapy
Published in George C. Kagadis, Nancy L. Ford, Dimitrios N. Karnabatidis, George K. Loudos, Handbook of Small Animal Imaging, 2018
Most of the commercially available pharmaceuticals are small molecules whose mechanism of action is typically based on direct interactions as an agonist or antagonist with the target tissue or cells. When labeled with radioactive metals, paramagnetic moieties, or optical molecules, small pharmaceutical compounds become powerful tools to assess the pathophysiology of the disease process, which allows not only the early detection of pathological processes but also the monitoring of the response to the therapeutic intervention. For example, a glucose analogue radiolabeled with fluorine-18 fluorodeoxyglucose is commonly used to measure tissue glucose consumption associated with enhanced metabolism. This phenomenon has been used in several PET imaging applications in neuroscience (activation of certain brain areas), cardiology (myocardial metabolism), and oncology (detection of primary tumors and metastases) (Rudd et al. 2002; Ogawa et al. 2004; Tawakol et al. 2006; Mullani et al. 2008).
Hazard Characterization and Dose–Response Assessment
Published in Ted W. Simon, Environmental Risk Assessment, 2019
Mechanism of action refers to the specific sequence of events at the molecular, cellular, organ, and organism level leading from the absorption of an effective dose of a chemical to the production of a specific biological response in the target organ.23,24 To understand the mechanism of action underlying a particular adverse outcome, one would need knowledge of the likely causal and temporal relationships between the events at the various levels of biological organization, including those events that lead to an effective dose of the chemical at the site of biological action. To specify a mechanism of action, data are needed regarding: metabolism and distribution of the chemical in the organism affecting the dose delivered to the molecular site of biological action;molecular target(s) or sites of biological action;biochemical pathways affected by interaction of the chemical with the site of biological action;cellular- and organ-level consequences of affecting these biochemical pathways;target organs/tissues in which the molecular sites of action and biochemical effects occur;physiological responses to these biochemical and cellular effects;target organ response to the biochemical, cellular, and physiological effects;the overall effect on the organism;likely causal and temporal relationships between these various steps;dose–response parameters associated with each step. In contrast, mode of action is a more general description of the toxic action of a chemical action.23,25,26 Mode of action refers to the type of response produced in an exposed organism or to only those key events that constitute necessary and critical aspects of the particular biological response. Hence, mode of action is known if the full mechanism is known, but the reverse is not true. The distinctions between mode and mechanism are important for understanding and describing the biological effects of chemicals, including both environmental chemicals and drugs. However, it is important to remain aware that many risk assessors may be less than rigorous in the use of these terms.
Identifying features of apps to support using evidence-based language intervention with children
Published in Assistive Technology, 2020
Turkstra, Norman, Whyte, Dijkers, and Hart (2016) propose a Rehabilitation Treatment Taxonomy (RTT) in order to specify the details of treatment based on the underlying theory rather than surface characteristics. The RTT is specified using three elements of treatment theory: (a) the “targets” which are the aspects of functioning that will change as a result of the treatment; (b) the “ingredients,” which are the specific actions taken by the clinician to effect changes in the target, and (c) “mechanisms of action,” which are the known or hypothesized means by which ingredients exert their effects and transforms therapy into effective change. In this framework, the mechanism of action involves learning and is generally unobservable and must be inferred. Identification of the kind of learning that is taking place will allow the clinician to modify the ingredients if necessary. Turkstra et al. (2016) emphasize that it is important to divide big targets into smaller subskills in order to identify the treatment components and the active ingredients. Identification of the active ingredients that effect change on the target may enable clinicians to think more critically about the effect of the treatment. This may result in improved treatment efficiency.