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Biomedical subjects

P M Chapman

Publications and source records attributed to P M Chapman.

12 recordsLinked to original sources
PubMed2002

Defining hormesis: comments on Calabrese and Baldwin (2002).

The definition of hormesis should not include non-scientific judgments as to beneficial or harmful effects. Evaluating the significance of hormesis is a separate issue that ultimately requires risk:risk comparisons, particularly since the evolutionary basis for hormesis appears to be Lamarkian rather than Darwinian. It is arguable whether 'hormesis' is the correct umbrella term for all low-dose exposure responses, in particular those at higher organization levels than single species, or whether it includes arousal responses.

Adaptation, Physiological↗
PubMed2001

The implications of hormesis to ecotoxicology and ecological risk assessment.

Changes required for the explicit recognition of hormesis are outlined for both ecotoxicology and ecological risk assessment (ERA). A major research need is the extension of hormesis beyond chemical stressors to abiotic (e.g., habitat) and biotic stressors (e.g., species introductions, organism interactions). An overreaching research need is to determine for all stressors with model organisms, populations, and communities whether hormesis has positive, neutral, or adverse effects. The latter are the least likely; however, neutral effects cannot be ruled out. Based on our present state of knowledge, hormesis is likely to have more of an impact on ecotoxicology than on ERA. In the case of the latter, it is most likely to make a difference only in a detailed-level ecological risk assessment (DLERA), the most complex form of ERA. Further, for hormesis to be accepted fully into ecotoxicology or ERA will require a paradigm shift. Three ongoing paradigm shifts to which hormesis could be linked are: recognition of the low utility of no-observed-effects concentrations (NOECs); recognition of the need for special treatment of essential element dose concentration responses, which are similar to hormesis; and the replacement of environmental toxicology with ecological toxicology (ecotoxicology).

Adaptation, Physiological↗
PubMed2001

An efficient method for modelling soft tissue in virtual environment training systems.

Modelling soft tissues in virtual environment training systems is frequently required. The provision of both visually compelling and physically accurate models presents a number of problems for the developer. The Finite element technique presented in this paper, modal analysis, can be programmed to allow the user to easily trade-off accuracy of simulation for execution speed. It has been successfully used to produce simulations of the lateral meniscus on low powered portable computer systems.

Arthroscopy↗
PubMed2001

Assessing sediment contamination in estuaries.

Historic and ongoing sediment contamination adversely affects estuaries, among the most productive marine ecosystems in the world. However, all estuaries are not the same, and estuarine sediments cannot be treated as either fresh or marine sediments or properly assessed without understanding both seasonal and spatial estuarine variability and processes, which are reviewed. Estuaries are physicochemically unique, primarily because of their variable salinity but also because of their strong gradients in other parameters, such as temperature, pH, dissolved oxygen, redox potential, and amount and composition of particles. Salinity (overlying and interstitial) varies spatially (laterally, vertically) and temporally and is the controlling factor for partitioning of contaminants between sediments and overlying or interstitial water. Salinity also controls the distribution and types of estuarine biota. Benthic infauna are affected by interstitial salinities that can be very different than overlying salinities, resulting in large-scale seasonal species shifts in salt wedge estuaries. There are fewer estuarine species than fresh or marine species (the paradox of brackish water). Chemical, toxicological, and community-level assessment techniques for estuarine sediment are reviewed and assessed, including chemistry (grain size effects, background enrichment, bioavailability, sediment quality values, interstitial water chemistry), biological surveys, and whole sediment toxicity testing (single-species tests, potential confounding factors, community level tests, laboratory-to-field comparisons). Based on this review, there is a clear need to tailor such assessment techniques specifically for estuarine environments. For instance, bioavailability models including equilibrium partitioning may have little applicability to estuarine sediments, appropriate reference comparisons are difficult in biological surveys, and there are too few full-gradient estuarine sediment toxicity tests available. Specific recommendations are made to address these and other issues.

Animals↗