Hormesis concept

Despite these impediments to the acceptance of hormesis (even in the presence of compelling data), there are activities that suggest that the hormesis concept could be embraced by society. The widely accepted and well-established observation that ingestion of a daily glass or two of red wine reduces the risk of cardiovascular disease may have preconditioned society to consider the hormetic hypothesis for pollutants and radiation. In addition, the recognition that anticancer agents can both stimulate and inhibit tumor growth via an hormetic dose response may enhance the clinical interest in this concept. 

Despite the strong identification of this concept with Schulz, numerous independent researchers such as Jensen commonly observed this dose-response relationship, often without any apparent knowledge that this biphasic dose-response was actually part of a controversial dose response concept of Schulz. Other investigators created a journal called Cell Stimulation based upon the Arndt-Schulz Law/hormesis concept. However, after what appeared to be a very successful initial six years, the publication was ceased in 1930 for reasons that are unclear. 

Despite its experimental failings, medical opposition, linkage to homeopathy, difficulty to prove, and lack of understanding, scientists continued to publish a flow of papers throughout the decades of the twentieth century that were consistent with the hormesis hypothesis. During this first half of the twentieth century the hormesis concept became embodied in the terms Arndt-Schulz Law or Hueppe s Rule. However, in 1943 Chester Southam and John Ehrlich, apparently... 

These observations should not have lead to a refutation of the Arndt-Schulz Law but to a more refined understanding of its temporal features along with its implications for the quantitative features of the dose response. Yet instead of offering such a biological-based refinement that could account for the low dose stimulatory response, leaders in the field rejected the Arndt-Schulz Law and the hormesis concept and the fields of pharmacology, toxicology, and radiation health followed their lead. 

What is the medical practice of homeopathy How does it address the issue of dose response Why would Hugo Schulz, the developer of the hormesis concept, have thought that he had discovered the underlying principal of homeopathy Critically assess whether there is any scientific relationship between the concept of hormesis and homeopathy. 

Hoffman, G., Stempsev, W., 2008. The hormesis concept and risk assessment are these unique ethical and policy considerations Hum. Exp. Toxicol. 27 (8), 613-620. 

Finally, the concept of hormesis (Section 4.12), threshold of toxicological concern (Section 4.13), and probabilistic methods for effect assessment (Section 4.14) will be briefly addressed. 

Hormesis is the term used for the phenomenon of stimulatory effects at low-level exposure, and inhibition at high-level exposure. The term derives from the Greek word Hormo which means excite or set in motion, and which is also the root of the word hormone. The concept of hormesis dates back to the 1920s. A substance showing hormesis has the opposite effect in small doses compared to effects at large doses. The definition of hormesis does not imply that low-dose effects are necessarily beneficial, only that they are opposite to high-dose effects. 

Hormesis the concept that at low doses of a toxicant there may be positive, beneficial effects, whereas at higher doses there will be toxic effects. 

Dichotomous responses. Some endpoints (e.g., behavioral parameters) can lead to nonmonotonous concentration-response curves, which are more difficult to model than the monotonous concentration-response curves that are observed, for example, in survival studies. Also in case of hormesis, nonmonotonous concentration-response curves are found. Nonmonotonous curves pose inherent problems for the application of both mixture toxicity concepts (Backhaus et al. 2004 Belz et al. 2008). 

Thus, it would appear that low dose irradiation is fully capable of inducing adaptive responses so that the overall response is below that when the adaptive response was not induced. Advocates of hormesis suggest that we may be ignoring the benefits of radiation hormesis (the low level that produces adaptation necessary to combat higher levels of radiation) if we set our allowable radiation limits too high. The next study addresses this concept. 

One of the most intensively studied areas of hormesis research is the effects of exposure to low-level ionizing radiation (LLIR). The concept that LLIR can... 

THE CONCEPT OF HORMESIS IS STRENGTHENED BY ITS OCCURRENCE IN NONTOXICOLOGICAL FIELDS... 

TABLE 2 How quantitative risk assessment could be made responsive to the concept of hormesis [adapted from Sielken Stevenson (61)]... 

Elected administrations, whose EPA accepts the concept of hormesis as central to hazard/risk assessment, will be strongly attacked. This recently happened to John Graham in his senate confirmation hearings when he suggested that dioxin may exhibit such characteristics. 

The legal implications emerging from the concept of hormesis remain to be more fully explored. However, the concept of hormesis has begun to be addressed by legal scholars (74). Of particular interest has been an exploration of the potential means to incorporate the concept of pollutant-induced beneficial effects in the risk assessment and cost-benefit process. Within this general framework, the District Court forced the EPA to recognize the beneficial effects of ozone pollution on the risk of UV-induced skin cancer in its overall assessment of the health effects of ozone (75, 76). 

Calabrese EJ, Baldwin LA. 1998. Can the concept of hormesis be generalized to carcinogenesis Reg. Toxicol. Pharmacol. 28 230-41... 

The data supporting the hormetic dose-response therefore not only far exceeds normal proof of concept criteria but have been employed in the development of drugs for numerous human conditions, thereby satisfying a stronger proof of application requirements. In head-to-head direct comparisons the hormesis model far outcompeted the threshold and linear at low dose models (Calabrese and Baldwin 2001, 2003c Calabrese et al. 2006). In fact, while the threshold model was shown to poorly predict below threshold responses the linear at low-dose models, the LNT models cannot be practically validated in either moderate or large-scale studies. 

Adaptive Response, Preconditioning and Autoprotection How These Concepts Relate to Hormesis 95... 

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