Effect Of Low-dose Gamma Irradiation Research Articles

The use of the aquatic plant Elodea canadensis to assess the effects of low-dose gamma irradiation

Responses of cytogenetic and growth endpoints of the aquatic plant Elodea canadensis were studied using the plants collected from non-contaminated control areas of the Yenisei River and exposed to external γ-radiation for 11–13 days in the laboratory. Elodea canadensis was exposed to 0.5–25 mGy/day γ-radiation dose rates from a 137Cs source. The total number of aberrant cells and total root length were more sensitive elodea endpoints to γ-radiation than total shoot length and mitotic index of elodea. Radiation sensitivity of elodea can be compared with the sensitivity of such a Reference Plant as Wild Grass (1–10 mGy/day) recommended by the ICRP. Thus, the aquatic plant Elodea canadensis can be used as a radiation bioindicator.

The Effect of Low-Dose Gamma Irradiation on the Uptake of Boronophenylalanine to Enhance the Efficacy of Boron Neutron Capture Therapy in an Orthotopic Oral Cancer Model.

The success of boron neutron capture therapy (BNCT) mainly depends on the boron concentration in the tumor and a high tumor/normal tissue (T/N) boron ratio or a high tumor/blood (T/B) boron ratio. Therefore, the effective enhancement of boron ratios is the first priority. Our study investigated whether a low-dose of γ-radiation (LDR) could improve boron ratios and enhance the therapeutic effects of BNCT in an orthotopic human oral squamous cell carcinoma-bearing animal model. SAS/luc cells were used to establish the orthotopic tumor-bearing model. The pharmacokinetics of boronophenylalanine (BPA) administration with 400 mg/kg of body weight both alone and in combination with LDR (0.1 Gy) was evaluated, and BNCT was performed at the Tsing Hua Open-pool Reactor (THOR). The radiation doses were evaluated using a treatment planning system. Moreover, tumor growth and metastasis were monitored via bioluminescence imaging (BLI). The therapeutic effects after BNCT were evaluated using BLI, histopathological findings and the overall survival rate. LDR increased the BPA accumulation in tumors by 52.2%. T/N and T/B ratios were enhanced from 3.77 to 5.31 and from 3.47 to 4.46, respectively. Radiation dose was increased by 44.3%. Notably, tumor recurrence and cervical lymph node metastasis were observed in the BNCT group, which had a survival rate of 50%. Complete responses were found in the combined-treatment group, which had a survival rate of 100%. No toxicity was found according to the histopathological findings. Conclusively, LDR increased BPA accumulation in the tumor and the T/N and T/B ratios, resulting in BNCT efficacy improvement and the overall survival rate extension.

Effect of Low-dose Gamma Irradiation on the Quality of Tilapia Fish Muscle with Storage at 0°C

The effect of gamma irradiation, followed by storage in ice, on Tilapia (Oreochromis sp.) fillets was investigated by monitoring microbiological and chemical changes after low-dose irradiation (1 and 3 kGy). Control and irradiated samples were stored in ice, and were analyzed at 7-day intervals. Bacterial counts showed that the shelf-life of 3 kGy irradiated Tilapia was extended to 70 days, and 1 kGy irradiated Tilapia had a shelf-life of 56 days. By comparison, control samples had a shelf-life of 7 days. Coliform bacteria was eliminated by 1 kGy irradiation, and was not detected again during the study. Peroxide and thiobarbituric acid levels increased up to the 28th day of storage, and then underwent reductions. The percentage of free fatty acid increased with the duration of storage in each treatment. Saturated fatty acids were significantly reduced with 1 kGy irradiation, whereas 3 kGy and control samples didn’t fluctuate. Levels of monounsaturated fatty acids were significantly increased in irradiated Tilapia, whereas control samples showed reductions with storage. Polyunsaturated fatty acids in Tilapia muscle treated with 1 kGy irradiation showed significant increases over time; however, with a 3 kGy irradiation dose, significant reductions were observed with storage. Palmitic acid (C 16:0), linoleic acid (C 18:2), and docosahexaenoic acid (C 22:6) showed significant reductions with storage. The present study indicates that 1 kGy is the safest irradiation dose for the preservation of Tilapia muscle stored in ice.

Effect of functional chitosan coating and gamma irradiation on the shelf-life of chicken meat during refrigerated storage

The present study was conducted to evaluate the combined effect of low-dose gamma irradiation (2.5kGy) and chitosan edible coating (2%) containing grape seed extract (GSE) (0.1%) on the microbial, chemical and sensorial quality of chicken breast meat during 21 days of storage at 4°C. The samples were periodically analyzed for microbiological (aerobic mesophilic and psychrotrophic counts), chemical (TBA, pH, aw) and sensorial (odor, appearance, and overall acceptability) characteristics. Results indicated that irradiation and the active coating had significant (P ≤ 0.05) effects on reduction of bacterial growth with at least a 14-day extension of shelf life. Results represented the protective effect of chitosan coating containing GSE against induced lipid oxidation by irradiation. All chitosan-coated samples showed lower TBA and pH values than other treatments during storage, and no significant (P > 0.05) difference was observed due to irradiation in TBA values. Results also indicated that the application of chitosan coating significantly improved the sensorial quality of the samples, and none of the evaluated sensorial attributes was significantly affected by irradiation. Based on the results obtained in this study, the application of low-dose gamma irradiation and chitosan coating containing GSE was effective in preserving the quality of fresh chicken meats and is recommended in meat products.

Genipin cross-linked antimicrobial nanocomposite films and gamma irradiation to prevent the surface growth of bacteria in fresh meats

Abstract A 125 μg/mL of nisin and 30 mM of disodium ethylenediaminetetraacetate (EDTA) were immobilized on the surface of the nanocrystal (CNC)/chitosan nanocomposite films by using genipin as a cross-linking agent. The effect of low-dose gamma irradiation on the antimicrobial activity of the films was tested in vitro against Escherichia coli and Listeria monocytogenes. The genipin cross-linked films prepared by irradiating at 1.5 kGy demonstrated the highest antimicrobial activity against both the bacteria at the end of 35 days of storage at 37 °C showing an inhibition zone of 27.1 mm for E. coli and 27.7 mm for L. monocytogenes as compared to 23.4 mm and 23.8 mm for the same respective bacteria at day 1. The films restricted the growth of psychrotrophs, mesophiles and Lactobacillus spp. (LAB) in fresh pork loin meats and increased the microbiological shelf-life of meat sample by more than 5 weeks. The films also reduced the count of E. coli and L. monocytogenes in meat samples by 4.4 and 5.7 log CFU/g, respectively, after 35 days of storage. Industrial relevance Foodborne diseases are responsible for 9.4 million illnesses, 55,961 hospitalization and 1,391 deaths each year in the United States. In the context of a constantly growing population and globalization of markets, and the increase of the demand for ready to eat foods without synthetic additives, the development of new technologies to prevent food contamination and to reduce foodborne illnesses is important. The development of antimicrobial packaging containing natural antimicrobials has been proposed as a novel technology to assure food safety. This technology is gaining interest from researchers and industries due to its potential to prevent the surface growth of pathogenic bacteria in meat products. The limit of the use of natural polymers, in order to reduce the packaging wastes, is their high water permeability and low resistance. The use of nanocellulose can permit to reinforce film and can improve their physico-chemical properties. We have developed a novel biopolymeric matrix reinforced with a nanofiber. The nanofiber is non-toxic, natural and obtainable from renewable sources. Chitosan, is also obtained from renewable sources, non-toxic, biodegradable, has biocompatible properties, and found application in several fields including food packaging.

Biosynthesis of artemisinin in gamma-irradiated Artemisia annua plantlet proceeds via a mixed origin of isoprene units

Artemisia annua is a traditional herb that used for antimalarial drug in China. The well-known antimalarial agent, artemisinin, is a sesquiterpene lactone bearing an endoperoxide and theoretically biosynthesized from the terpenoid pathway. The present study, the wild type A. annua shoots were irradiated with gamma ray 650 of cobalt-60, obtaining A. annua TBB strain [1]. The A. annua TBB plantlets were then induced and propagated in Murashige and Skoog medium (MS) supplemented with 3% (w/v) sucrose and 0.8% (w/v) agar, under 16h of photo-period (2000 lux). Plantlets containing high-yield artemisinin were selected from A. annua TBB and used as plant materials for isotopic glucose feeding experiment. Plantlet cultures of irradiated A. annua TBB (10-day old) from MS agar medium were transferred into 250-ml erlenmeyer flasks and grown for 30 days on shelf culture, in distilled water supplemented with 3% (w/v) glucose solution, a mixture of [1 – 13C]glucose (99% 13C enrichment) and unlabeled D-glucose (1:1 ratio). Artemisinin was isolated and their 13C-labeling patterns examined using quantitative NMR spectroscopy. Analysis of the patterns of 13C-enrichment revealed that all the isoprene units in the skeleton of artemisinin were supplied from both the DXP and the MVA pathways.

ROS and ABA signaling are involved in the growth stimulation induced by low-dose gamma irradiation in Arabidopsis seedling.

It has been well established that gamma rays at low doses have stimulatory effects on plant growth and development. However, our knowledge regarding the molecular mechanism underlying the growth stimulation remains limited. In this study, we report the role of reactive oxygen species (ROS) and abscisic acid (ABA) in the growth stimulation using irradiated Arabidopsis seeds. The results indicated that 50 Gy gamma irradiation presented maximal beneficial effects on germination index, root length, and fresh weight. The contents of hydrogen peroxide (H2O2) and activities of antioxidant enzymes under gamma irradiation were markedly higher than those of controls. ROS scavenging significantly suppressed the growth of the irradiated plants. Furthermore, endogenous ABA was induced under low-dose gamma irradiation. The growth stimulation and elevated H2O2 level were affected in the irradiated ABA-deficient mutant aba2-1 compared with the mutant control. Transcriptional expression analysis of selected genes revealed that several genes for ABA biosynthesis were upregulated, and the genes for ABA catabolic pathway and transport were differentially regulated in response to low-dose gamma irradiation. Our results suggest that ROS and ABA signaling play an essential role in the stimulatory effects of low-dose gamma irradiation and that ROS, as secondary molecules, mediate ABA signal transduction under irradiation in response to stress factors during plant growth.

Effect of low-dose gamma radiation and active equilibrium modified atmosphere packaging on shelf life extension of fresh strawberry fruits

Abstract The effect of low-dose gamma irradiation (1 kGy) and active equilibrium modified atmosphere packaging (EMAP1: CO 2 10%: O 2 5%; N 2 85% and EMAP2: CO 2 5%: O 2 10%; N 2 85%) on quality of strawberry fruits stored at 4 °C was investigated. Several quality parameters were monitored during the storage period. Fruit firmness, fungal decay and sensory evaluation were analyzed on days 1, 7, 14 and 21. Strawberries kept in active EMAP1 maintained their texture and appearance better than those packaged under air and EMAP2. Strawberries stored in active EMAP were firmer than those stored in air during the storage time (21 days). The irradiated strawberry samples were not attacked by Botrytis cinerea during 7 days. Irradiation and EMAP1 increased the postharvest life of strawberries to 14 days, without any attack of fungus or any change in their external appearance. Low-dose gamma irradiation in combination with EMAP will enable food processors to deliver larger amounts of high quality strawberry with extended shelf life.

Bony Incorporation of Soft Tissue Anterior Cruciate Ligament Grafts in an Animal Model

Background: The effect of low-dose gamma irradiation on healing of soft tissue allografts remains largely unknown. Hypothesis: The authors hypothesized that soft tissue allograft healing to bone would be delayed compared with that of autograft tissue and that low-dose (1.2 Mrad) gamma irradiation would not affect the healing response of allograft tissue after anterior cruciate ligament (ACL) reconstruction. Study Design: Controlled laboratory study. Methods: Forty-eight New Zealand White rabbits underwent bilateral ACL reconstructions with semitendinosus tendon graft. Sixteen rabbits were reconstructed with autografts and the remainder with allografts. The 32 allograft rabbits each received 1 irradiated allograft (1.2 Mrad), with the contralateral leg receiving a nonirradiated allograft. Animals were euthanized at 2 weeks or 8 weeks postoperatively. Tensile stiffness, maximum load, and displacement at maximum load were measured. Tibial and femoral segments were sectioned perpendicular to the tunnel axis allowing for histologic and histomorphometric analyses at the tendon-bone interface. Results: There were no significant differences between the maximum load or stiffness values among all groups at 8 weeks. At 2 weeks, autograft exhibited significantly (P < .01) lower maximum load than did the nonirradiated grafts. Regarding histology, at both 2- and 8-week time points, autograft tendon displayed more advanced degenerative and remodeling processes in comparison with irradiated allograft and nonirradiated allograft. Discussion: The maximum load and stiffness of a healing tendon allograft in ACL reconstruction appear to be unaltered by low-dose (1.2 Mrad) irradiation. At 8 weeks, there were no biomechanical differences in tendon-bone healing of allografts when compared with autograft controls. Histologic analyses suggested a faster remodeling response in autograft specimens in comparison with allografts at both time points. Clinical Relevance: The findings support the contention that low-dose gamma irradiation is safe for sterilization of ACL soft tissue allografts without compromise of graft properties at early time points.

Effect of gamma irradiation on photoconductivity and photosensitivity of Si1 − x Sn x solid solutions

The results of studies of the structural feature and the effect of low-dose gamma irradiation (up to 105 rad) on the photoconductivity relaxation and the spectral photosensitivity of pSi-nSi1 − xSnx (0 ≤ x ≤ 0.04) structures are described. It is shown that exposure to radiation leads to an increase in the relaxation time constant from 55 to 83 μs and an enhancement in the sensitivity of the structures in the short-wavelength emission spectrum, which is attributed to the radiation-stimulated gettering of crystal lattice defects localized in the near-boundaries regions between Si1 −xSnx subcrystallites and Si1 − xSnx-Sn and Si1 − xSnx-SiO2 phases.

Quality changes of the Mediterranean horse mackerel ( Trachurus mediterraneus) during chilled storage: The effect of low-dose gamma irradiation

Pelagic fishes represent the main Mediterranean fisheries in terms of quantity. However, waste and spoilage of pelagic fish are substantial for a variety of reasons, such as their high perishability and the lack or inadequate supply of ice and freezing facilities. In this work, fresh Mediterranean horse mackerel ( Trachurus mediterraneus) were irradiated at 1 and 2 kGy and stored in ice for 18 days. Quality changes during storage were followed by the determination of microbial counts, trimethylamine (TMA) and volatile basic nitrogen contents. Similarly, lipid composition and sensory analysis were carried out. Irradiation treatment was effective in reducing total bacterial counts throughout storage. Total basic volatile nitrogen content (TVB-N) and TMA levels increased in all lots with storage time, their concentrations being significantly reduced by irradiation, even when the lower level (1 kGy) was used. According to the quality index method, the control lot had a sensory shelf-life of 4 days, whereas those of the irradiated lots were extended by 5 days. Also, low-dose irradiation had no adverse effect on the nutritionally important polyunsaturated fatty acids (PUFA) of Mediterranean horse mackerel. In the same way, thiobarbituric acid-reactive substances values increased with irradiation during the first day, but these values were lower at the end of storage, compared to the control. Results confirm the practical advantages of using γ irradiation as an additional process to chilled storage to enhance the microbiological quality and to extend the shelf-life of small pelagic species.

Repeated 0.5-Gy γ Irradiation Attenuates Experimental Autoimmune Encephalomyelitis with Up-regulation of Regulatory T Cells and Suppression of IL17 Production

We recently reported attenuation of autoimmune disease by low-dose gamma irradiation (repeated doses of 0.5 Gy) in MRL-lpr/ lpr mice. Here we studied the effect of low-dose gamma irradiation on experimental autoimmune encephalomyelitis (EAE), which is a rodent model of multiple sclerosis. SJL/J mice were immunized with myelin basic protein for the induction of EAE and were exposed to 0.5 Gy gamma rays once a week for 4 weeks. Radiation suppressed incidence and disease severity scores and delayed the onset of pathological changes. Pro-inflammatory cytokines (IFN-gamma and IL6), autoantibody and CD8+ cytotoxic T cells are involved in the appearance of EAE. Radiation suppressed the increases in these cytokines and the autoantibody production and blocked the increase in the population of CD8+ cytotoxic T cells. Production of IL17 by Th17 cells and/or gammadelta T cells, which plays a crucial role in EAE, was also significantly suppressed by radiation. Furthermore, a significant increase in regulatory T cells, which are involved in suppression of autoimmune disease, was found in irradiated EAE mice. These data suggest that low-dose gamma irradiation attenuates EAE through suppression of pro-inflammatory cytokines, reduction of cytotoxic T cells and induction of regulatory T cells.

Effects of low-dose gamma irradiation on artemisinin content and amorpha-4,11-diene synthase activity in Artemisia annua L

Purpose: This research work aimed to create in vitro plantlet variants of Artemisia annua through gamma irradiation. The obtained variants were then evaluated for the correlation between their artemisinin content and enzyme activity of amorpha-4,11-diene synthase (ADS), the first enzyme of the artemisinin pathway.Materials and methods: Shoot tips from plantlets of A. annua were exposed to gamma rays at a low-dose range and transferred to hormone-free MS medium for in vitro cultivation. A dose-response curve and the value of 50% of lethal dose (LD50) were then obtained. This LD50 dose of gamma rays was used for treating another batch of shoot tips. The surviving plantlets after four subsequent subcultures were evaluated for their ability to accumulate artemisinin in correlation with the enzyme activity of ADS.Results: The dose-response curve showed that the LD50 value was at 8 Gray (Gy). The surviving irradiated plantlets from this dose treatment had artemisinin content ranging from 0.03–0.70% (w/w) of dry weight, comparing with only 0.18% present in the original non-irradiated samples. Their correlation coefficient between the ADS activity and the artemisinin content appeared to be R2 = 0.090 for all the 18 samples tested, although, selectively, more than half of these (11 samples) showed their R2 value of as high as 0.851.Conclusions: There was no correlation between the artemisinin content and ADS activity found in the whole population, but the correlation was observed in the main subpopulation of the irradiated A. annua plantlets.

The effects of low-dose gamma irradiation and storage time on carotenoids, antioxidant activity, and phenolics in the potato cultivar atlantic

Potatoes are stored to ensure a continuous supply; however, losses due to shrinkage and sprouting can be large. It is believed that low-dose ionizing irradiation will become more prominent for sprout inhibition due to the increasingly higher operating costs of low-temperature storage and the possible phase-out of chemical sprout inhibitors. The effects of storage and gamma irradiation on carotenoid content, antioxidant activity (AOA), and phenolic content were analyzed for the potato cultivar Atlantic. Tubers were subjected to 0, 75, and 200 Gy gamma irradiation doses, stored at 20 C, and analyzed after 0, 10, 20, 75, and 110 days in storage. Total carotenoid content determined via spectrophotometry decreased, while lutein content increased with storage. AOA appeared to first decrease and then increase, possibly due to dehydration, concentration, and/or induced stress. Phenolic content increased more with storage than with gamma irradiation. However, levels of some phenolic compounds, such as quercetin dehydrate, decreased with storage. Irradiation dose exerted a limited influence on AOA and phenolic and carotenoid contents. Interaction between storage time and irradiation dose was significant for AOA and phenolic content, but not for carotenoid content. Overall, storage exerted a much greater influence on carotenoid content, AOA, and phenolic content than did low-dose gamma irradiation.

Effects of low-dose gamma-irradiation on production of shikonin derivatives in callus cultures of Lithospermum erythrorhizon S.

The yield increase of secondary metabolite production was examined in plant cell cultures with the use of relatively low to high doses gamma irradiation. Suspension culture of Lithospermum erythrorhizon cells was irradiated to 2, 16, and 32 Gy. The gamma irradiation significantly stimulated the shikonin biosynthesis of the cells and increased the total shikonin yields (intracellular+extracellular shikonin yields) by 400% at 16 Gy and by only 240% and 180% at 2 and 32 Gy, respectively. One of the key enzymes for the shikonin biosynthesis of cells, p-hydroxylbenzoic acid (PHB) geranyltransferase, was found to be stimulated by the gamma-radiation treatments. The activity of PHB geranyltransferase was increased at 2 and 16 Gy with a negligible change at 32 Gy. In contrast, the activity of PHB glucosyltransferase was slightly changed at all doses of gamma radiation compared with the control cells. Therefore, the increase in PHB geranyltransferase activity leads to the accumulation of secondary metabolites such as a shikonin, which may contribute to plant defense against the stresses induced by gamma irradiation.

Comparative study of the effect of low-dose gamma irradiation on phase transitions in single crystals of triglycine sulfate and its deuterated analog

The effect of low γ-radiation doses (< 0.5 MR) on the specific heat Cp of crystals of triglycine sulfate and its deuterated analog was studied using precision vacuum adiabatic calorimetry in the temperature range 80–350 K. Appreciable changes in the behavior of Cp of nominally pure and γ-irradiated crystals were detected near the phase transition temperature (Tc), which decreased as the dose was lowered.

Investigation of the low-dose γ-irradiation effect on the spontaneous and high-dose radiation-induced level of cytogenetic damage in mouse bone marrow cells in vivo

The effect of low-dose gamma-irradiation (0.1 or 0.2 Gy with a dose rate of 0.125 Gy/min) of mice on the spontaneous and high-dose radiation-induced level of cytogenetic damage during ageing of animals was studied using the micronucleus test. It was shown that a single low dose of gamma-radiation induces a cytogenetic adaptive response in mouse bone marrow cells, which persists for up to 12 months after irradiation; the ability of inducing the adaptive response does not depend on the age of animals at the moment of adapting irradiation; single low-dose γ-irradiation decreases the cytogenetic damage to a level below the spontaneous rate at the end of the lifetime (20 months) of animals. The mechanisms underlying adaptive response not only protect from cytogenetic damage induced by high-dose irradiation but also may play a role during spontaneous mutagenesis.

The effect of low-dose gamma irradiation and temperature on the microbiological and chemical changes during ripening of Cheddar cheese

The effect of 4 kGy ionisation irradiation, combined with ripening temperatures at 8°C and 16°C on the ripening of Cheddar cheese was investigated. Changes in cheeses were monitored by sensory, microbiological, and chemical analyses. Sensorically, no cheese was preferred above the other. At 16°C ripening, irradiation affected the bacterial groups, but not the psychrotrophs. The free fatty acid content of the cheeses was not affected by irradiation, but higher thiobarbituric acid-values were observed after ripening at 16°C, as well as higher water-soluble nitrogen/total nitrogen. Differences in proteolysis products were detected by urea-page and RP-HPLC.

Effect of Low-Dose Gamma Irradiation on Staphylococcus aureus and Product Packaging in Ready-to-Eat Ham and Cheese Sandwiches

Staphylococcus aureus is a common pathogen that causes foodborne illness. Traditional methods for controlling S. aureus do not address postprocess contamination. Low-dose gamma irradiation is effective in reducing pathogens in a variety of foods and may be effective in reducing S. aureus in ready-to-eat foods. The effects of gamma irradiation on product packaging should also be considered. The objective of this study was to determine the effects of gamma irradiation on product packaging and on S. aureus in ready-to-eat ham and cheese sandwiches. The effects of refrigerated storage on irradiated and nonirradiated sandwiches were also investigated. Ham and cheese sandwiches were inoculated with 106 or 107 CFU of S. aureus per g, frozen, irradiated, and analyzed by a standard plate count method. D10-values, the amount of irradiation needed to elicit a 1-log10 reduction of bacteria, were calculated. In addition, irradiated sandwiches were analyzed after 1, 13, 27, and 39 days of storage at 4°C. The integrity of postirradiated packaging material was analyzed using Fourier transform infrared (FTIR) spectroscopy. Two experiments yielded D10-values of 0.62 and 0.63. During refrigerated storage, sandwiches irradiated with 5.9 kGy showed no S. aureus growth at any time; sandwiches irradiated with 3.85 kGy showed a 6.18-log reduction in S. aureus after 13 days; and nonirradiated sandwiches showed a 0.53-log increase in S. aureus after 39 days. FTIR spectroscopy showed that the label side and the bulge side were composed of polyethylene terephthalate and nylon 6, respectively. No significant change in the packaging due to irradiation was detected. In this study, low-dose gamma irradiation was shown to be an effective method for reducing S. aureus in ready-to-eat ham and cheese sandwiches and proved to be more efficacious than refrigeration alone. Additionally, package integrity was not adversely affected by gamma irradiation.

Characteristic features of induced mutagenesis in hybrid dysgenesis systems of Drosophila melanogaster

The mutagenic effect of low-dose gamma-irradiation was studied in Drosophila melanogaster systems of hybrid dysgenesis by estimating polytene chromosome rearrangements, recombination frequency, and viability at the embryonic and postembryonic developmental stages. A dose of gamma-irradiation which had no effect detectable by routine line crossing proved to significantly reduce the number of recombinants in the H-E and P-M systems and mortality at postembryonic stages. However, this combined effect was obtained if irradiation followed transposition, i.e., it depended on the application sequence of the mutagenic factors. The reverse order of the mutagenic treatment led to summation of the effects: as compared to either control, the frequencies of the dominant allele mutations as well as the larval and pupal mortality in F2 increased significantly (at the level of 99.9%). This allowed us to estimate the contribution of extremely low-dose gamma-irradiation into the mutagenic effect, which was impossible under routine conditions.