THE HORMESIS OF THE GREEN MACROALGA ULVA FASCIATA WITH LOW‐DOSE 60COBALT GAMMA RADIATION1

Homogenous germlings of the marine macroalga Ulva fasciata D. (synonym, Ulva lactuca L.) were used to study hormesis effects in macroalgae grown under a low dose of ⁶⁰Co γ‐ray radiation. The results of this study are the first to confirm the effects of macroalgal hormesis. Here it was demonstrated that growth of U. fasciata germlings was promoted substantially under 15 Gy of ⁶⁰Co γ‐ray radiation, with an average increase of algal biomass of 47.43%. The levels of polysaccharides and lipids varied among the tested material and showed no effects from the ⁶⁰Co γ‐ray radiation. However, the amount of protein was higher in the irradiated algae than in the control; the highest protein content of the irradiated algae was 3.958% (dry weight), in contrast to 2.318% in nonirradiated samples. This technique was applied to a field algal mass culture, which decreased the harvest time from 90 to 60 d. The mass culture approach may facilitate the production of macroalgae under unstable weather conditions such as typhoons in the summer or strong waves in the winter. The mass‐cultured macroalgae could be used as a source of bioenergy through the fermentation of algal simple sugars that derived from polysaccharides to produce ethanol.     

Do U.S. county data disprove linear no‐threshold predictions of lung cancer risk for residential radon?‐A preliminary assessment of biological plausibility

Lung‐cancer mortality (LCM) is elevated in underground miners who chronically inhaled the mutagenic, cytotoxic α‐decay products of radon gas. Epidemiologie studies of LCM rates vs. residential‐radon concentration levels are generally considered inconclusive. However, Cohen (Health Physics 68, 157–174, 1995) has hypothesized that data on LCM vs. residential radon concentrations at the U.S. county level are clearly inconsistent with a linear no‐threshold (LN) dose‐response model, and rather are consistent with threshold or hormesis model. Cohen's hypothesis has been criticized as “ecological fallacy,”; particularly because LN (but not threshold or hormesis) models are generally considered biologically plausible for agents like α radiation that damage DNA in linear proportion to dose. To assess the biological plausibility of Cohen's hypothesis, a preliminary study was made of whether a biologically realistic, cytodynamic 2‐stage (CD2) cancer model can provide a good, joint fit to Cohen's set of U.S. county data as well as to underground‐miner data. The CD2 model used adapts a widely applied, mechanistic, 2‐stage stochastic model of carcinogenesis to realistically account for interrelated cell killing and mutation (both assumed to have a LN dose‐response), cell turnover, and incomplete exposure of stem cells. A CD2 fit was obtained to combined summary data on LCM vs. radon‐exposure in white males in 1, 601 U.S. counties (from Cohen) and in white male Colorado Plateau (CP) uranium miners (from the National Research Council's “BEIRIV”; report). The CD2 fit is shown to: (i) be consistent with the combined data; (ii) have parameter values all consistent with biological data; and (iii) predict inverse dose‐rate‐effects data for CP and other radon‐exposed miners, despite the fact that optimization had not involved any of these dose‐rate data. The latter data were not predicted by a simplified CD2 model in which all stem cells were presumed to be exposed. It is concluded that this study provides preliminary evidence that Cohen's hypothesis is biologically plausible.     

数学建模在生物化感及其赫米西斯(Hormesis)现象中的应用

简述了国内外对生物化感数学建模的研究近况,包括通过数学模型描述化感物质的赫米西斯(Hormesis)现象,化感作用在受体植物不同密度条件下的表达,植物残茬中化感物质的分解动态及受体植物的动态响应,环境中化感物质的动态变化规律及在植物-昆虫-天敌系统中的应用等。并对化感数学建模领域的先驱机理模型An-Hormesis模型,An-Liu-Johnson-Lovett模型,和An_Residue模型做了简介。     

Impairing L-Threonine Catabolism Promotes Healthspan through Methylglyoxal-Mediated Proteohormesis

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Theories of biological aging: genes, proteins, and free radicals

Traditional categorization of theories of aging into programmed and stochastic ones is outdated and obsolete. Biological aging is considered to occur mainly during the period of survival beyond the natural or essential lifespan (ELS) in Darwinian terms. Organisms survive to achieve ELS by virtue of genetically determined longevity assuring maintenance and repair systems (MRS). Aging at the molecular level is characterized by the progressive accumulation of molecular damage caused by environmental and metabolically generated free radicals, by spontaneous errors in biochemical reactions, and by nutritional components. Damages in the MRS and other pathways lead to age-related failure of MRS, molecular heterogeneity, cellular dysfunctioning, reduced stress tolerance, diseases and ultimate death. A unified theory of biological aging in terms of failure of homeodynamics comprising of MRS, and involving genes, milieu and chance, is acquiring a definitive shape and wider acceptance. Such a theory also establishes the basis for testing and developing effective means of intervention, prevention and modulation of aging.     

Acetaldehyde utilization in Drosophila: an example of hormesis

For survival measured by longevity, acetaldehyde is beneficial at low and stressful at high concentrations in Drosophila utilizing ethanol as a major resource. This is an example of the increasingly common observation of hormesis which is the stimulatory effect by toxic agents at subinhibitory levels. Organic metabolites such as acetaldehyde and organisms such as Drosophila offer the possibility of model genetical and molecular studies of hormesis. This may assist our understanding of suggestions of enhanced fitness at natural background radiation levels and in habitats simulating these levels.     

Oxidative stress delays development and alters gene expression in the agricultural pest moth,Helicoverpa armigera

Stress is a widespread phenomenon that all organisms must endure. Common in nature is oxidative stress, which can interrupt cell homeostasis to cause cell damage and may be derived from respiration or from environmental exposure through diet. As a result of the routine exposure from respiration, many organisms can mitigate the effects of oxidative stress, but less is known about responses to oxidative stress from other sources. Helicoverpa armigera is a major agricultural pest moth that causes significant damage to crops worldwide. Here, we examined the effects of oxidative stress on H. armigera by chronically exposing individuals to paraquat—a free radical producer—and measuring changes in development (weight, developmental rate, lifespan), and gene expression. We found that oxidative stress strongly affected development in H. armigera, with stressed samples spending more time as caterpillars than control samples (>24 vs. ~15 days, respectively) and therefore living longer overall. We found 1,618 up‐ and 761 down‐regulated genes, respectively, in stressed versus control samples. In the up‐regulated gene set, was an over‐representation of biological processes related to cuticle and chitin development, glycine metabolism, and oxidation–reduction. Oxidative stress clearly impacts physiology and biochemistry in H. armigera and the interesting finding of an extended lifespan in stressed individuals could demonstrate hormesis, the phenomenon whereby toxic compounds can actually be beneficial at low doses. Collectively, our findings provide new insights into physiological and gene expression responses to oxidative stress in invertebrates.