OBJECTIVES: Although ionizing radiation is recognized as being harmful to humans, debate continues regarding the effects of low doses of ionizing radiation. Some studies have reported that low doses of ionizing radiation have a bio-positive effect, namely hormesis, and many researchers have attempted to find concrete and scientific evidence to prove this. To determine whether the discrepancy in effects of low doses of ionizing radiation arises from genetic differences, a study with a multicellular organism system such as fruit flies is needed. METHODS: After irradiation at a low-dose rate of gamma radiation with chronic (0.2 Gy) and acute (0.2, 0.75 and 4 Gy), the pupa rate, eclosion rate and life span were examined with various wild type strains of Drosophila melanogaster such as W1118, Oregon-R, and Canton-S. RESULTS: The life span of Oregon-R exposed to both acute and chronic, low-dose radiation (0.2 Gy) was increased. Although there was some difference in the longevity between the acute and chronic radiation rate, no other differences were found. In Canton-S, only acute dose (0.75 Gy) increased the life span, but it did not in W1118. CONCLUSIONS: Although there were some differences between wild type fruit fly strains in longevity, the low doses of ionizing radiation extended the life span of D. melanogaster. Further studies need to be carried out to explain the difference according to dose and dose rate of radiation in the tested strains.
Diptera ; Drosophila ; Drosophila melanogaster ; Fruit ; Gamma Rays ; Hormesis ; Humans ; Longevity ; Pupa ; Radiation, Ionizing

Hormesis is the generally-favorable biological responses to low exposures to toxins and other stressors. Radiation hormesis is the theory that ionizing radiation is benign at low levels of exposure, and that doses at the level of natural background radiation can be beneficial. The purpose of this study is to reveal the hormetic effect of low-dose radiation of ionizing radiation on the ovarian follicles of 4-week old female mice. Mice were grouped into control group, 2 cGy irradiated group, 2 cGy and 2 Gy irradiated group (2 cGY pre-exposure group), and 2 Gy irradited group. Mice were sacrificed by cervical dislocation 24 hours after irradiation, removed ovaries, fixed in neutral formaldehyde solution for 24 hours, embedded with paraffin, stained with hematoxylin and eosin and TUNEL immunohistochemically, and observed light microscopically the atretic follicles and normal follicles in various follicular developmental stages. In this experiment, the ratrio of atretic follicles to entire follicles in an ovary increased significantly in 2 Gyirradiated group compared with 2 cGY pre-exposure group, and the ratio of normal follicles to the entire follicles in an ovary in all the developmental stages were increased significantly in the 2 cGY pre-exposure group compared with 2 Gy-irradiated group. These results mean that low-dose radiation pre-exposure can induce the hormetic effect in the developing ovarian follicle.
Animals ; Background Radiation ; Dislocations ; Eosine Yellowish-(YS) ; Female ; Follicular Atresia ; Formaldehyde ; Hematoxylin ; Hormesis ; Humans ; In Situ Nick-End Labeling ; Mice ; Ovarian Follicle* ; Ovary ; Paraffin ; Radiation, Ionizing ; Rats*

Mitochondrial function is crucial for the maintenance of cellular homeostasis under physiological and stress conditions. Thus, chronic exposure to environmental chemicals that affect mitochondrial function can have harmful effects on humans. We argue that the concept of hormesis should be revisited to explain the non-linear responses to mitochondrial toxins at a low-dose range and develop practical methods to protect humans from the negative effects of mitochondrial toxins. Of the most concern to humans are lipophilic chemical mixtures and heavy metals, owing to their physical properties. Even though these chemicals tend to demonstrate no safe level in humans, a non-linear dose-response has been also observed. Stress response activation, i.e., hormesis, can explain this non-linearity. Recently, hormesis has reemerged as a unifying concept because diverse stressors can induce similar stress responses. Besides potentially harmful environmental chemicals, healthy lifestyle interventions such as exercise, calorie restriction (especially glucose), cognitive stimulation, and phytochemical intake also activate stress responses. This conceptual link can lead to the development of practical methods that counterbalance the harm of mitochondrial toxins. Unlike chemical hormesis with its safety issues, the activation of stress responses via lifestyle modification can be safely used to combat the negative effects of mitochondrial toxins.
Dementia ; Diabetes Mellitus, Type 2 ; Environmental Exposure ; Environmental Pollutants ; Homeostasis ; Hormesis ; Humans ; Life Style ; Metals, Heavy ; Mitochondria ; Nonlinear Dynamics ; Organic Chemicals