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Articles 1 - 30 of 32
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Will Radiation-Induced Bystander Effects Or Adaptive Responses Impact On The Shape Of The Dose Response Relationships At Low Doses Of Ionizing Radiation?, William F Morgan
Will Radiation-Induced Bystander Effects Or Adaptive Responses Impact On The Shape Of The Dose Response Relationships At Low Doses Of Ionizing Radiation?, William F Morgan
Dose-Response: An International Journal
Radiation induced bystander effects and adaptive responses are two phenomena that modulate cellular responses to low doses of ionizing radiation. Bystander effects generally exaggerate the effects of low doses of radiation by eliciting detrimental effects in nonirradiated cells, thus making the target for radiation effects greater than the volume irradiated. Adaptive responses on the other hand indicate that low doses of radiation can reduce damage induced by a second challenging dose. The potential impact of these two low dose effects on the shape of the dose response relationship will be discussed.
Adaptive And Bystander Responses In Human And Rodent Cell Cultures Exposed To Low Level Ionizing Radiation: The Impact Of Linear Energy Transfer, Sonia M De Toledo, Edouard I Azzam
Adaptive And Bystander Responses In Human And Rodent Cell Cultures Exposed To Low Level Ionizing Radiation: The Impact Of Linear Energy Transfer, Sonia M De Toledo, Edouard I Azzam
Dose-Response: An International Journal
To understand the potential impact on risk from exposure to low-level ionizing radiation, we have investigated the modulation of gene expression, induction of DNA damage and of neoplastic transformation in human or rodent cells derived from cultures exposed in vitro to low dose γ-rays (a low linear energy transfer radiation) or very low fluences of α-particles (a high linear energy transfer radiation). Pre-exposure of cells to a low γ-ray dose protected cells from the DNA damaging and killing effects induced by a subsequent acute challenge exposure to γ-rays. Furthermore, a low dose chronic exposure to γ-rays decreased the frequency of …
Development Of An In Vivo Assay For Detection Of Nontargeted Radiation Effects, Colin Seymour, Carmel Mothersill
Development Of An In Vivo Assay For Detection Of Nontargeted Radiation Effects, Colin Seymour, Carmel Mothersill
Dose-Response: An International Journal
An adaptive response may be defined as the effect of a small priming dose of radiation modifying the anticipated cellular response of the same tissues so as to alter the predicted response to a larger dose of radiation. We and others have demonstrated that at low radiation doses (less than 0.5 Gy) the lethal and mutational effect of the radiation is mainly, possibly entirely, due to the non-targeted effects. This is the dose range for priming doses in adaptive response protocols. In an associated presentation from our group, we demonstrate that the adaptive response may be explicable as a non …
Radiation-Induced Bystander And Adaptive Responses In Cell And Tissue Models, Kevin M Prise, Melvyn Folkard, Barry D Michael
Radiation-Induced Bystander And Adaptive Responses In Cell And Tissue Models, Kevin M Prise, Melvyn Folkard, Barry D Michael
Dose-Response: An International Journal
The use of microbeam approaches has been a major advance in probing the relevance of bystander and adaptive responses in cell and tissue models. Our own studies at the Gray Cancer Institute have used both a charged particle microbeam, producing protons and helium ions and a soft X-ray microprobe, delivering focused carbon-K, aluminium-K and titanium-K soft X-rays. Using these techniques we have been able to build up a comprehensive picture of the underlying differences between bystander responses and direct effects in cell and tissue-like models. What is now clear is that bystander dose-response relationships, the underlying mechanisms of action and …
Radiation-Induced Bystander Effects: Evidence For An Adaptive Response To Low Dose Exposures?, Carmel Mothersill, Colin Seymour
Radiation-Induced Bystander Effects: Evidence For An Adaptive Response To Low Dose Exposures?, Carmel Mothersill, Colin Seymour
Dose-Response: An International Journal
This paper reviews our current knowledge of the mechanisms underlying the induction of bystander effects by low dose, low-LET ionizing radiation and discusses how they may be related to observed adaptive responses or other protective effects of low dose exposures. Bystander effects appear to be the result of a generalized stress response in tissues or cells. The signals may be produced by all exposed cells, but the response appears to require a quorum in order to be expressed. The major response involving low LET radiation exposure discussed in the existing literature is a death response. This has many characteristics of …
In Vivo Mutagenic Effect Of Very Low Dose Radiation, Pamela J Sykes, Tanya K Day, Sarah J Swinburne, Joanne M Lane, Alexander A Morley, Anthony M Hooker, Madhava Bhat
In Vivo Mutagenic Effect Of Very Low Dose Radiation, Pamela J Sykes, Tanya K Day, Sarah J Swinburne, Joanne M Lane, Alexander A Morley, Anthony M Hooker, Madhava Bhat
Dose-Response: An International Journal
Almost all of our knowledge about the mutational effect of radiation has come from high dose studies which are generally not relevant to public exposure. The pKZ1 mouse recombination mutagenesis assay enables study of the mutational effect of very low doses of low LET radiation (μGy to cGy range) in a whole animal model. The mutational endpoint studied is chromosomal inversion which is a common mutation in cancer. We have observed 1) a non-linear dose response of induced inversions in pKZ1 mice exposed to a wide dose range of low LET radiation, 2) the ability of low priming doses to …
Suppression Of Neoplastic Transformation In Vitro By Low Doses Of Low Let Radiation, J. Leslie Redpath
Suppression Of Neoplastic Transformation In Vitro By Low Doses Of Low Let Radiation, J. Leslie Redpath
Dose-Response: An International Journal
A major concern of exposure to low doses of radiation is the risk of cancer induction. Epidemiologic data are rarely powerful enough to accurately discriminate this risk at doses <10 cGy. In order to gain insight into events at these low doses, laboratory-based studies of relevant endpoints are required. One such endpoint is radiation-induced neoplastic transformation in vitro. Such studies can provide quantitative dose-response data, as well as insights into underlying cellular and molecular mechanisms. Data are presented that indicate that low doses of low LET radiation can suppress neoplastic transformation in vitro to levels below that seen spontaneously. Mechanisms involved include both the death of a subpopulation of cells prone to spontaneous neoplastic transformation and the induction of DNA repair. The relative contributions of these mechanisms is dose-dependent. The relevance of these observations to radiation risk estimation is discussed.
Enhancement Of Bio-Protective Functions By Low Dose/Doserate Radiation, Kazuo Sakai, Takaharu Nomura, Yasihiro Ina
Enhancement Of Bio-Protective Functions By Low Dose/Doserate Radiation, Kazuo Sakai, Takaharu Nomura, Yasihiro Ina
Dose-Response: An International Journal
Effects of low-dose-rate gamma-irradiation on the process of tumorigenesis were investigated in mice treated with a carcinogenic agent or irradiated with high dose X-rays at a high dose rate. A prolonged gamma irradiation at approximately 1 mGy/hr suppressed the appearance of skin tumors induced by methylcholanthrene and delayed the appearance of radiation-induced thymic lymphomas in C57BL/6 mice. We also investigated the effects of low-dose-rate irradiation on disease model mice. In Type II diabetic C57BL/KsJdb/ db (db) mice, the urine glucose level was improved in some of the mice irradiated at 0.70 mGy/hr, but not in non-irradiated control mice. In MRL-lpr/lpr …
The Adaptive Response And Protection Against Heritable Mutations And Fetal Malformation, Dr Boreham, J-A Dolling, C Somers, J Quinn, Rej Mitchel
The Adaptive Response And Protection Against Heritable Mutations And Fetal Malformation, Dr Boreham, J-A Dolling, C Somers, J Quinn, Rej Mitchel
Dose-Response: An International Journal
There are a number of studies that show radiation can cause heritable mutations in the offspring of irradiated organisms. These “germ-line mutations” have been shown to occur in unique sequences of DNA called “minisatellite loci”. The high frequencies of spontaneous and induced mutations at minisatellite loci allow mutation induction to be measured at low doses of exposure in a small population, making minisatellite mutation a powerful tool to investigate radiation-induced heritable mutations. However, the biological significance of these mutations is uncertain, and their relationship to health risk or population fitness is unknown. We have adopted this mutation assay to study …
Dose-Response, Vol 4, No 3, Cover
Dose-Response, Vol 4, No 3, Cover
Dose-Response: An International Journal
No abstract provided.
Radiation, Ecology And The Invalid Lnt Model: The Evolutionary Imperative, Peter A Parson
Radiation, Ecology And The Invalid Lnt Model: The Evolutionary Imperative, Peter A Parson
Dose-Response: An International Journal
Metabolic and energetic efficiency, and hence fitness of organisms to survive, should be maximal in their habitats. This tenet of evolutionary biology invalidates the linear-nothreshold (LNT) model for the risk consequences of environmental agents. Hormesis in response to selection for maximum metabolic and energetic efficiency, or minimum metabolic imbalance, to adapt to a stressed world dominated by oxidative stress should therefore be universal. Radiation hormetic zones extending substantially beyond common background levels, can be explained by metabolic interactions among multiple abiotic stresses. Demographic and experimental data are mainly in accord with this expectation. Therefore, non-linearity becomes the primary model for …
Stress Response Mechanisms: From Single Cells To Multinational Organizations, Richard J Pech
Stress Response Mechanisms: From Single Cells To Multinational Organizations, Richard J Pech
Dose-Response: An International Journal
Can a literal comparison be made between biological phenomena in organisms and phenomena in human organizations? The evidence provided by simplified but useful examples appears to suggest that a phenomenon simulating hormesis can and does occur in organizational contexts. Similarities between stress response behaviors of organisms and stress response behaviors in organizations are discussed. Cellular stress response mechanisms stimulate and repair, as well as defend the organism against further attacks. Organizational hormesis describes actions that stimulate the organization by increasing its focus and protecting it against future attacks. The common aim for the organism as well as the organization is …
Dose-Response, Vol 4, No 3, Table Of Contents
Dose-Response, Vol 4, No 3, Table Of Contents
Dose-Response: An International Journal
No abstract provided.
Modeling The Effect Of Density-Dependent Chemical Interference Upon Seed Germination, Aki Sinkkonen
Modeling The Effect Of Density-Dependent Chemical Interference Upon Seed Germination, Aki Sinkkonen
Dose-Response: An International Journal
A mathematical model is presented to estimate the effects of phytochemicals on seed germination. According to the model, phytochemicals tend to prevent germination at low seed densities. The model predicts that at high seed densities they may increase the probability of seed germination and the number of germinating seeds. Hence, the effects are reminiscent of the density-dependent effects of allelochemicals on plant growth, but the involved variables are germination probability and seedling number. The results imply that it should be possible to bypass inhibitory effects of allelopathy in certain agricultural practices and to increase the efficiency of nature conservation in …
Radiation Hormesis: The Good, The Bad, And The Ugly, Td Luckey
Radiation Hormesis: The Good, The Bad, And The Ugly, Td Luckey
Dose-Response: An International Journal
Three aspects of hormesis with low doses of ionizing radiation are presented: the good, the bad, and the ugly. The good is acceptance by France, Japan, and China of the thousands of studies showing stimulation and/or benefit, with no harm, from low dose irradiation. This includes thousands of people who live in good health with high background radiation. The bad is the nonacceptance of radiation hormesis by the U. S. and most other governments; their linear no threshold (LNT) concept promulgates fear of all radiation and produces laws which have no basis in mammalian physiology. The LNT concept leads to …
Cardiovascular Disease Could Be Contained Based On Currently Available Data!, Okom Nkili Fc Ofodile
Cardiovascular Disease Could Be Contained Based On Currently Available Data!, Okom Nkili Fc Ofodile
Dose-Response: An International Journal
Largely due to better control of infectious diseases and significant advances in biomedical research, life expectancy worldwide has increased dramatically in the last three decades. However, as the average age of the population has risen, the incidence of chronic age-related diseases such as arthritis, Alzheimer’s, Parkinson’s, cardiovascular disease, cancer, osteoporosis, benign prostatic hyperplasia, and late-onset diabetes have increased and have become serious public health problem, as well. The etiology of these disorders is still incompletely understood, therefore, neither preventive strategies nor long-term effective treatment modalities are available for these disorders. In keeping with the aforementioned, the ultimate goal in cardiovascular …
Dose-Response, Vol 4, No 2, Cover
Dose-Response, Vol 4, No 2, Cover
Dose-Response: An International Journal
No abstract provided.
The Pkz1 Recombination Mutation Assay: A Sensitive Assay For Low Dose Studies, Pj Sykes, Aa Morley, Am Hooker
The Pkz1 Recombination Mutation Assay: A Sensitive Assay For Low Dose Studies, Pj Sykes, Aa Morley, Am Hooker
Dose-Response: An International Journal
The majority of mutation studies are performed at high doses of DNA damaging agents due to the insensitivity of most mutation assays. Extrapolation using a linear nothreshold (LNT) dose response model is then used to estimate the extent of possible DNA damage at lower doses. There is increasing evidence to suggest that the LNT model may not be correct at low doses of at least some DNA damaging agents. The pKZ1 in vivo and in vitro recombination assays have proven to be very sensitive for detection of changes in chromosomal inversion in lymphoid tissue in response to low doses of …
Low Doses Of Radiation Are Protective In Vitro And In Vivo: Evolutionary Origins, Rej Mitchel
Low Doses Of Radiation Are Protective In Vitro And In Vivo: Evolutionary Origins, Rej Mitchel
Dose-Response: An International Journal
Research reports using cells from bacteria, yeast, alga, nematodes, fish, plants, insects, amphibians, birds and mammals, including wild deer, rodents or humans show non-linear radio-adaptive processes in response to low doses of low LET radiation. Low doses increased cellular DNA double-strand break repair capacity, reduced the risk of cell death, reduced radiation or chemically-induced chromosomal aberrations and mutations, and reduced spontaneous or radiation-induced malignant transformation in vitro. In animals, a single low, whole body dose of low LET radiation, increased cancer latency and restored a portion of the life that would have been lost due to either spontaneous or radiationinduced …
Dose-Response, Vol 4, No 2, Table Of Contents
Dose-Response, Vol 4, No 2, Table Of Contents
Dose-Response: An International Journal
No abstract provided.
The Unexpected Anabolic Phenotype And Extended Longevity Of Skin Fibroblasts After Chronic Glucocorticoid Excess, Harris Pratsinis, Stylianos Tsagarakis, Irene Zervolea, Dimitri Stathakos, Nikos Thalassinos, Dimitris Kletsas
The Unexpected Anabolic Phenotype And Extended Longevity Of Skin Fibroblasts After Chronic Glucocorticoid Excess, Harris Pratsinis, Stylianos Tsagarakis, Irene Zervolea, Dimitri Stathakos, Nikos Thalassinos, Dimitris Kletsas
Dose-Response: An International Journal
Intense stress can challenge tissue homeostasis and accelerate the ageing process. However, several lines of evidence indicate that repeated mild stresses can have beneficial and even life-prolonging effects. Hypersecretion of glucocorticoids (GC) represents the major hormonal response to stress. Besides its life-sustaining role, GC excess, usually due to several side-effects that promote a “catabolic” phenotype, can be detrimental for several tissues. Cushing’s syndrome patients are characterized by chronic endogenous GC excess and consequently at the time of diagnosis they have an atrophic elderly-like skin. Interestingly, when Cushing’s syndrome fibroblasts were removed from the high-GC milieu in vivo and cultured in …
Detecting Causal Nonlinear Exposure-Response Relations In Epidemiological Data, Louis Anthony Cox Jr
Detecting Causal Nonlinear Exposure-Response Relations In Epidemiological Data, Louis Anthony Cox Jr
Dose-Response: An International Journal
The possibility of hormesis in individual dose-response relations undermines traditional epidemiological criteria and tests for causal relations between exposure and response variables. Non-monotonic exposure-response relations in a large population may lack aggregate consistency, strength, biological gradient, and other hallmarks of traditional causal relations. For example, a u-shaped or n-shaped curve may exhibit zero correlation between dose and response. Thus, possible hormesis requires new ways to detect potentially causal exposure-response relations. This paper introduces information-theoretic criteria for identifying potential causality in epidemiological data that may contain nonmonotonic or threshold dose-response nonlinearities. Roughly, exposure variable X is a potential cause of response …
The Hormetic Effects Of Hypergravity On Longevity And Aging, Nadège Minois
The Hormetic Effects Of Hypergravity On Longevity And Aging, Nadège Minois
Dose-Response: An International Journal
This paper reviews the literature on the effects of hypergravity (HG, gravity levels higher than 1g, the terrestrial gravity) on longevity and aging. The different studies showed that life-long exposures to high gravity levels decreased longevity and accelerated the agerelated decline observed on some physiological and behavioral variables. In contrast, chronic exposure to HG increased resistance to heat in young and middle-aged Drosophila melanogaster. A short exposure to HG at the beginning of adult life increased male longevity and delayed behavioral aging in D. melanogaster. All these results show that HG acts as a hormetic factor. Long exposures to HG …
Dose-Response Relationships In Human Experimental Exposure To Solvents, Ivo Iavicoli, Giovanni Carelli, Alessandro Marinaccio
Dose-Response Relationships In Human Experimental Exposure To Solvents, Ivo Iavicoli, Giovanni Carelli, Alessandro Marinaccio
Dose-Response: An International Journal
Previous studies carried out in the field of experimental toxicology have shown evidence of biphasic dose-response relationships for different experimental models, endpoints and chemicals tested. As these studies excluded humans as the experimental model, we have examined the literature of the last three decades in order to verify data concerning human experimental exposure with the aim of highlighting possible biphasic dose-response relationships. The substances used for experimental exposures included hydrocarbons, esters, alcohols, ketones, ethers, glycoethers, halogenated hydrocarbons, and carbon sulphide; the absorption route was inhalation. We did not detect any biphasic dose-response relationship and, in the studies reviewed, our examination …
Radon Treatment Controversy, Zygmunt Zdrojewicz, Jadwiga (Jodi) Strzelczyk
Radon Treatment Controversy, Zygmunt Zdrojewicz, Jadwiga (Jodi) Strzelczyk
Dose-Response: An International Journal
In spite of long traditions, treatments utilizing radon-rich air or water have not been unequivocally embraced by modern medicine. The objective of this work is to examine factors that contribute to this continuing controversy. While the exact mechanism of radon’s effect on human body is not completely understood, recent advances in radiobiology offer new insights into biochemical processes occurring at low-level exposures to ionizing radiation. Medical evidence and patients’ testimonials regarding effectiveness of radon spa treatments of various ailments, most notably rheumatoid arthritis are accumulating worldwide. They challenge the premise of the Linear-No-Threshold (LNT) theory that the dose-effect response is …
Factors That Determine The Non-Linear Amygdala Influence On Hippocampus-Dependent Memory, Irit Akirav, Gal Richter-Levin
Factors That Determine The Non-Linear Amygdala Influence On Hippocampus-Dependent Memory, Irit Akirav, Gal Richter-Levin
Dose-Response: An International Journal
Stressful experiences are known to either improve or impair hippocampal-dependent memory tasks and synaptic plasticity. These positive and negative effects of stress on the hippocampus have been largely documented, however little is known about the mechanism involved in the twofold influence of stress on hippocampal functioning and about what factors define an enhancing or inhibitory outcome. We have recently demonstrated that activation of the basolateral amygdala can produce a biphasic effect, enhancement or inhibition, of hippocampal synaptic plasticity, depending on the timing of activation (priming or spaced activation). A key question is under which conditions do the effects of amygdala …
Concentration Dependent Actions Of Glucocorticoids On Neuronal Viability And Survival, István M Ábrahám, Peter Meerlo, Paul Gm Luiten
Concentration Dependent Actions Of Glucocorticoids On Neuronal Viability And Survival, István M Ábrahám, Peter Meerlo, Paul Gm Luiten
Dose-Response: An International Journal
A growing body of evidence based on experimental data demonstrates that glucocorticoids (GCs) can play a potent role in the survival and death of neurons. However, these observations reflect paradoxical features of GCs, since these adrenal stress hormones are heavily involved in both neurodegenerative and neuroprotective processes. The actual level of GCs appears to have an essential impact in this bimodal action. In the present short review we aim to show the importance of concentration dependent action of GCs on neuronal cell viability and cell survival in the brain. Additionally, we will summarize the possible GC-induced cellular mechanisms at different …
Introduction, David M Diamond
Introduction, David M Diamond
Dose-Response: An International Journal
No abstract provided.
Dose-Response, Vol 4, No 1, Table Of Contents
Dose-Response, Vol 4, No 1, Table Of Contents
Dose-Response: An International Journal
No abstract provided.