Possible examples of chemical hormesis in a previously published study

Low Doses of Tetracycline Trigger the E. coli Growth: A Case of Hormetic Response

Hormesis is a biphasic dose-response relationship, occurring when low concentrations of toxic agents elicit apparent improvements. In this work, the ability of sub-inhibitory concentrations of Tetracycline to induce hormetic response in a model organism was investigated. To this aim a reference strain of Escherichia coli, MG1655, was exposed to six decreasing doses of Tetracycline (between 0.12 and 0.00375 μg/ml), much lower than the Minimal Inhibitory Concentration (4 μg/ml). An hormetic increase was observed at the intermediate concentrations (0.015-0.03 μg/ml) of the tested range. The Colony Forming Unit number, indeed, rose up to 141% and 121% as compared to the control. At the highest (0.12 μg/ml) and lowest (0.00375 μg/ml) concentrations a slight decrease in CFU number was found. Results demonstrated that, in Escherichia coli, low concentrations of Tetracycline bias the bacterial numerical increase through a hormetic response; the dose-response curve describing this numerical increase is an U-inverted curve. Furthermore, these data confirm that hormesis is common to many - if not all - living systems, including bacteria; they underline the relevance of a deepened knowledge of both the effects and the possible consequences of exposure to low doses of contaminants.

Effect of sublethal concentrations of chlorpyrifos on three successive generations of Daphnia carinata

Effects of sublethal concentrations of chlorpyrifos (ranging from 0.005 (0.01 LC(50)) to 0.500 microg/L (1 LC(50))) on population characteristics of individual cultures of Daphnia carinata were investigated over 21 days with subsequent testing of the two next generations. The endpoints for the first and second generations observed were survival, fecundity, time to first brood, and number of offspring per female. The results were incorporated into the computation of the intrinsic rate of natural increase for daphnids in each of the treatments. Exposure to chlorpyrifos affected survival and fecundity of animals in the first generation. In the second generation, the most affected endpoint was time to the first brood with an indication of hormesis. The LC(50) tests were then conducted using animals of the third generation from each of the exposures in individual tests. Despite the absence of a negative effect of chlorpyrifos in the second generation, results of testing the third generation showed constant significant decline in LC(50) from control daphnids through to 0.1 LC(50) preexposed daphnids (0.1 LC(50), 0.05 microg/L, being the highest concentration in which animals survived exposure to the toxicant in the second generation).

Applying weight gain in Pomacea lineata (Spix 1824) (Mollusca: Prosobranchia) as a measure of herbicide toxicity

Pomacea lineata, an extremely ubiquitous snail and pest to rice farmers throughout Asia, holds promise as a valuable resource for monitoring water quality in northeast Brazil. In this paper, we present data demonstrating the rate of weight gain in P. lineata neonates as a consistent measure of the stress imposed by sublethal concentrations of the herbicides Paraquat and Round-up. Our secondary agenda is to demonstrate the feasibility of incorporating bioassay into the standard municipal and state procedure of monitoring water quality. Growth data to assess chronic toxicity were generated in experiments of four and four, eight, twelve and sixteen days for Paraquat and Round-up, respectively. We estimated a 96 h no observed effect concentration (NOEC) and lowest observed effect concentration (LOEC) for Paraquat of 0.12 and 0.25 mg/L. The 96 h Round-up data yielded NOEC and LOEC values, respectively, of 0.25 and 0.5 mg/L. All concentrations of Round-up tested for the 192 h exposure yielded significantly lower growth than the control. Consequently, no NOEC could be derived. The LOEC was < 0.12 mg/L. Furthermore, there was no mortality during the test. At the lowest concentrations of Paraquat tested (0.005 mg/L) there was a significant increase in growth compared with the controls, suggesting a hormetic effect.

Fluorescence analysis of aldolase dissociation from the N-terminal of the cytoplasmic domain of band 3 induced by lanthanide

The cytoplasmic domain of band 3 (CDB3) offers binding sites for several glycolytic enzymes and regulates the glycolysis of erythrocyte. The interaction between recombinant (His)(6)-tagged CDB3 and aldolase, one of the key enzymes that participated in erythrocyte glycolysis, was investigated in the presence of lanthanide. The results indicate that trace lanthanide blocks the inhibition of CDB3-(His)(6) to aldolase and leads to enhancement of aldolase activity. In agreement with activity studies, fluorescence spectra reveal that 4 microM lanthanum ions induce the complete dissociation of aldolase from the N-terminal of CDB3-(His)(6). Interestingly, the synchronous scanning fluorescence spectra of proteins in the presence of various concentrations of lanthanum ions suggest that the conformational change of CDB3-(His)(6) is significantly attributed to the alteration of tryptophan cluster microenvironment, while the aldolase conformation change is mainly derived from tyrosine microenvironment changes. Based on the observation that lanthanide ions induce the dissociation of aldolase from CDB3-(His)(6), it is suggested that the existence of trace lanthanide may affect the glycolysis of erythrocyte.

Hormesis responses of free and immobilized light-emitting bacteria

The stimulatory effect of sublethal or low concentrations of toxic chemicals on organismal metabolism, referred to as hormesis, has been found to be common in the widely used Vibrio fischeri luminescence bioassay. In addition to the "normal" type alpha, we have demonstrated type beta and, possibly, type gamma, dose-response curves in free and immobilized V. fischeri bioassays developed. Understanding and utilizing data from hormesis responses are necessary in determining the toxicity of chemicals, singly or in complex mixtures, to natural biota without imposing excessive penalties to dischargers. At the same time, care must be taken not to relax environmental standards. This can only arise by fully investigating and understanding the role of hormesis in toxicity data used for risk assessment.

Homeopathy

Especially in the United States, homeopathy has not become integrated into mainstream medical practice; this is partly because of the historical paucity of quality published research studies or quality educational programs. More recently, there have been better-designed studies in reputable journals, although historically most studies have been inconclusive or of poor methodology. The confusion around homeopathy in the United States exists for several reasons: 1. One of the main reasons for the relative disinterest or opposition to homeopathy is that even well-designed clinical studies on homeopathy leave the reader without any protocol-driven tools to take into daily practice. Individualization of treatment, or, as it is called today, differential therapeutics, is the main requirement of successful homeopathic prescribing. Only well-trained homeopathic practitioners are able to carry out such a task. In many articles that reported positive outcomes for homeopathy, numerous homeopathic remedies had been prescribed for the same diagnostic category. Critics suggest that the pooling of data from trials using different therapeutic agents to assess the overall success of homeopathic prescribing is incorrect. Research protocols that employ combination remedies, in which a medication contains several homeopathic remedies, fall into the same category. 2. Many of the positive and negative studies published are flawed with numerous methodologic problems. One of the most common problems is a lack of objective validated outcome measures. Another common problem is a small sample size. In most positive and negative meta-analyses published to date, research data are pulled together artificially based on either a diagnostic category or a particular remedy. Frequently the concentration of the remedy used and the conditions to which it has been applied are different. Ernst and Pittler published a letter with a critique of the methodology used in one of the meta-analyses of clinical trials of homeopathy. Most importantly, professional homeopaths and conventional scientists criticize the choice of remedy or the condition to which it was applied or both. The design and follow-up in migraine studies has been criticized extensively by one of the world's leading homeopaths, Vithoulkas (personal communication, 1997). Most of the Arnica studies have been designed with either an inappropriate dosing regimen or an inappropriately chosen procedure. In most positive studies on homeopathy, the outcome measures were subjective and poorly quantifiable. 3. Few well-designed studies have been reproduced by independent research teams. This situation exists for two major reasons: lack of sufficient funding and lack of a sufficient number of well-trained homeopaths qualified and interested to participate in research. 4. More rigorous educational programs on homeopathy for professionals need to be encouraged. Most of the existing programs are designed for consumers; academic continuing medical education-quality courses are needed. Meanwhile, while the debate around homeopathy still continues in conventional medical circles, the general public has been using the services of homeopathic practitioners and homeopathic remedies increasingly. In many countries, homeopathy and other complementary modalities have been integrated successfully into a larger armamentarium for the modern physician. According to a study published in 1995 in the Journal of the American Board of Family Practice, 69% of family practice physicians expressed interest in learning more about homeopathy. Increasing public and professional interest calls for attempts to study homeopathy in a more systematic way and to provide quality academic overview for medical practitioners. The growing number of complementary and alternative medicine centers affiliated with major teaching hospitals should provide a solid interface between evidence-based biologic medicine and many emerging complementary and alternative medicine modalities, including homeopathy.

Environmental law applications of hormesis concepts: risk assessment and cost-benefit implications

This article focuses on legal structures that influence the degree to which hormesis can be incorporated into environmental law and policy. Three statutes-the Occupational Safety and Health Act, the Food Quality Protection Act, and the Clean Air Act-are used to illustrate the varied ways in which Congress, agencies and the courts have approached risk assessment and cost-benefit analyses that are relevant to the hormesis issue. This discussion features several examples of regulations and judicial decisions that have begun to recognize hormetic effects. The article concludes that hormesis concepts could be incorporated effectively into present risk assessment and cost-benefit mechanisms. In the context of agency action, an express policy decision might be made to broaden the typical scope of risk assessment and cost-benefit processes by including hormetic effects. In the judicial context, recognition of hormesis may occur where relevant statutory language is read to contemplate that an agency will consider both the beneficial and the detrimental effects of a particular substance in formulating regulations; in this circumstance, a reviewing court could reverse an agency decision that focuses solely on detrimental effects and ignores hormetic effects. Based on these evolving trends, the time may be ripe to seek further incorporation of hormesis concepts into environmental law and policy decisions.

A protein disulfide-thiol interchange protein with NADH: protein disulfide reductase (NADH oxidase) activity as a molecular target for low levels of exposure to organic solvents in plant growth

A number of solvents including ethyl, amyl, butyl, octyl and benzyl alcohols, ethylene glycol, ethyl acetate, acetone, diethyl ether, propylene oxide, rho-dioxane, benzene, xylene, chloroform and carbon tetrachloride stimulate the growth of plants or plant parts at low concentrations and inhibit at high concentrations. These same solvents, at low dilutions, stimulate the activity of a growth-related protein disulfide-thiol interchange protein (TIP) with NADH: protein disulfide reductase (NADH oxidase) (NOX) activity with plasma membrane vesicles isolated from elongating regions cut from dark grown seedlings of soybeans. Based on these and other findings, we suggest the TIP/NOX protein to be the molecular target of the biological effects of low levels of exposure (hormesis) involved in the stimulation of plant growth.

Radiation hormesis - fact or fiction?

Deriving from the Greek verbhormein, which means to stimulate and excite, hormesis literally refers to any kind of stimulation and excitation. As a medical and geomedical term (though of unsettled status) it has a more restricted meaning however, indicating merely the putative or real stimulatory and beneficial effects observed when a biological system is exposed to a low dose of an agent known to be toxic or hazardous at a significantly larger dose. Depending on the type of stimulatory agent, one can speak of chemical or physical hormesis, radiation hormesis being a member of the latter group. The present paper reviews and evaluates the history and origins of the concept of radiation hormesis and its present status - fact or fiction. It is concluded that despite the numerous, sometimes undeniably strong, individual pieces of evidence that have been presented in favour of this phenomenon, the bulk of the evidence is so far not strong enough to establish it as a scientifically proven fact. It is also evident that, instead of speaking of radiation hormesis as an entity, one should pay attention separately to the effects of alpha, beta and gamma radiation, the deleterious and possible beneficial hormetic effects being different in each case.