Effects of gamma radiation on different developmental stages of the oriental tobacco budworm,Helicoverpa assulta (Lepidoptera: Noctuidae)

Ionizing radiation is increasingly used as an alternative to post‐harvest crop fumigation by methyl bromide. We studied the effects of gamma irradiation on Helicoverpa assulta (Lepidoptera: Noctuidae) at different stages of development to determine the minimal dose for the prevention of normal emergence of adults. We selected five doses of gamma rays (100, 200, 300, 400 and 500 Gy) based on preliminary experiments and irradiated eggs, larvae, pupae and adults. A dose of 100 Gy to eggs allowed 21.83% of larvae to pupate, but these all died during the pupal stage. A dose of 100 Gy to last‐instar larvae caused larval or pupal death, or the emergence of abnormal adults; no normal adults developed. Irradiation of pupae with doses of 300 Gy and above resulted either in their death or emergence of abnormal adults; however, after 100 or 200 Gy, normal adults emerged and F₁ eggs were produced, but no eggs hatched. Following irradiation of adults, eggs were produced at all doses, although the numbers were significantly decreased compared to untreated controls (P < 0.05; 69.45–125.50 vs. 475.05 eggs per female); however, none of the eggs hatched. As prevention of normal emergence is a key outcome for measuring the effectiveness of radiation, then the 100 Gy dose was effective for irradiation of eggs and larvae, and 300 Gy for pupae.     

Effects of gamma-irradiation on the infectivity and chromosome aberration of Clonorchis sinensis

Effects of gamma irradiation on the worm survival and chromosomal aberration of Clonorchis sinensis were studied. The metacercariae irradiated with various amounts of gamma radiation (ranging from 5 Gy to 50 Gy) were fed to rats, and the effects were compared with those of non-irradiated controls. Recovery rates of adult worms in irradiated groups were reduced gradually as increasing of the irradiation doses. No worm was recovered from rats which were fed with 50 Gy irradiated metacercariae. The chromosome number was 2n = 56 in all worms from all experimental groups. However, the groups irradiated with 20 Gy, 25 Gy or 30 Gy showed variations in the chromosome number, depending on different cells in the same individual. Radiation doses used in this study did not appear to induce chromosome aberrations, however, irradiation with 30 Gy showed slightly reduced chromosome size.     

Effect of gamma-irradiation on some biological activities of the larval stage of the khapra beetle, Trogoderma granarium Everts (Col., Dermestidae)

Abstract: The present study was carried out on the larval stage of the khapra beetle, Trogoderma granarium Everts to determine some biological effects of gamma irradiation at levels between 20 to 100 Gy on various aspects of larval behaviour such as number of moults, developmental time, larval growth, starvation and mortality, pupal promptness in addition to larval density. Larval mortality of 92.5% was obtained by treating with 80 Gy and no larva lived after an exposure of 100 Gy or more. With increasing doses from 40 Gy or more, half of the male and female larvae had six moults as compared with three to five moults in the control. The larval duration increased gradually and reached 40.2 days for male larvae and 44.2 days for female ones at a dose of 80 Gy as compared to 25.2 and 28.3 days, respectively, for the control. Larvae irradiated with 60 and 80 Gy did not feed as much as those irradiated at 20 and 40 Gy or the control group. A negative correlation was observed between increasing dosage levels and reduction in the fresh body weight of larvae. The highest larval starvation of 79.8% occurred at 80 Gy and the least (23.8%) at 20 Gy. Pupal promptness seems to be lower at the higher radiation doses. With 40, 60 and 80 Gy, approximately 69.5, 19.6 and 7.5%, respectively, of the larvae succeeded in pupation compared with 94.6% in the control. High doses of radiation seem to enhance the production of males. An increase of larval density enhances the effects of radiation doses to retard the developmental time, to increase larval and pupal mortality and to reduce adult eclosion.     

The effects of gamma irradiation on the survival and development of Clonorchis sinensis metacercariae

The effects of gamma irradiation on the survival and development of C. sinensis metacercariae were studied to evaluate the feasibility of irradiation as a control measure for clonorchiasis. Pseudorasbora parva were collected at an endemic river of clonorchiasis and were used for irradiation of the fluke in three schemes. The first (Scheme 1) was irradiation of the isolated metacercariae from the fish followed by infection to experimental rats. The second (Scheme 2) was irradiation of the fish, and then the metacercariae were isolated and infected to rats. The third (Scheme 3) was irradiation on the rat livers after infection with normal metacercariae. Irradiation doses varied from 5 to 100 Gy for Schemes 1 and 2, and 10 to 25 Gy for Scheme 3. The rats were sacrificed 2 to 6 weeks after infection. In Scheme 1, the metacercariae irradiated at 50 Gy failed to survive in the rats after 2 or 6 weeks. However, 1 to 44% of the metacercariae irradiated at 5-30 Gy survived. The estimated LD50 of Scheme 1 was 16.5 Gy. The flukes irradiated in Scheme 2 survived better than those in Scheme 1. The average worm recovery rate in 50 Gy was 28%(7-39% individually). Increasing the dose up to 100 Gy brought a remarkably low survival rate of an average 1%(0-3% individually). The LD50 of Scheme 2 was 47.5 Gy. Worm recovery rates in the 10 Gy group of Scheme 3 were 21-39%, and those in the 25 Gy group were 2% and 34%. Although the metacercariae were irradiated, all of the recovered worms were morphologically normal.(ABSTRACT TRUNCATED AT 250 WORDS)     

Gamma irradiation as a quarantine treatment for apples infested by codling moth (Lep., Tortricidae)

Abstract: Effects of gamma radiation on the fifth instar codling moth, Cydia pomonella (L.), larvae were examined. Mature larvae were exposed to a series of gamma radiation doses ranging from 50 to 250 Gy and survival to pupae and adults was examined. The results showed that pupation and adult emergence decreased with increasing radiation dose. The results also showed that diapausing larvae were more sensitive to irradiation treatment than non-diapausing larvae, and females were more sensitive than males. A dose of 150 Gy reduced adult emergence to less than 2% in non-diapausing larvae, while a dose of 200 Gy completely prevented it. Furthermore, none of the emerging moths exposed to a dose of 150 Gy were females; at 100 Gy dose, the percentage of females was less than 14%. Irradiating larvae in apple fruit in a small-scale laboratory experiment produced similar results. Tests in which >100 000 larvae (in the fifth instar) were irradiated in an artificial rearing medium with a dose of 200 Gy resulted in no adult emergence. Similar results were also obtained when >32 000 larvae in the same stage were exposed in apple fruit to the same dose. The results indicate that the use of ionizing radiation as a quarantine treatment for codling moth infested fruits is feasible and requires a relatively low dose.     

Enhanced body radioresistance resulting from the transfusion of autologous blood irradiated with low doses of ionizing radiation]

Preliminary administration of autogenic blood irradiated in vitro with ionizing radiation in small doses of 0.05, 0.3 or 0.5 Gy resulted in a pronounced increase in the radioresistance of mice [correction of rats] subsequently irradiated in a dose of 9 Gy. The optimum was autotransfusion of blood irradiated in a dose of 0.3 Gy a day or 10 days prior to the total irradiation which increased the survival rate of experimental animals to 80% while, in control groups, the survival rate was only 10%.     

Developmental inhibition of Drosophila suzukii by ionizing radiation

Spotted wing drosophila (SWD) has emerged as a major invasive insect pest of small berry fruits in the Americas and Europe since the late 2000s. Thus, phytosanitary treatment of commodities for export is imperative to prevent the movement of viable SWD to newer areas. In the present study, all developmental stages of SWD were irradiated with different doses of gamma and electron beam radiation to assess developmental inhibition to identify potential quarantine doses of the radiations. Ionizing radiation induced developmental inhibition of all stages of SWD. The effective doses for 99% inhibition (ED₉₉) of hatching, pupariation, and adult emergence from irradiated eggs for gamma radiation were 882, 395 and 39 Gy, respectively, compared with 2849, 687, and 41 Gy, respectively, for electron beam radiation. The ED₉₉ for inhibition of pupariation and adult emergence in irradiated larvae were 703 and 47 Gy, respectively, for gamma radiation, and 619 and 33 Gy, respectively, for electron beam radiation. Pupal irradiation did not completely inhibit adult emergence, even at 300 Gy. However, irradiation with ≥100 Gy of puparia induced adult sterility, with no egg production at all. The ED₉₉ for inhibition of F₁ egg hatchability from adults irradiated with gamma radiation and electron beam radiation was estimated to be 424 and 125 Gy, respectively. The results of the present study suggest that gamma radiation and electron beam radiation are alternatives for phytosanitary treatment. Irradiation with 100 Gy could be suggested as a potential dose for egg, larval, and pupal quarantine treatment of SWD.     

Late ROS accumulation and radiosensitivity in SOD1-overexpressing human glioma cells

This study investigates the hypothesis that CuZn superoxide dismutase (SOD1) overexpression confers radioresistance to human glioma cells by regulating the late accumulation of reactive oxygen species (ROS) and the G(2)/M-checkpoint pathway. U118-9 human glioma cells (wild type, neo vector control, and stably overexpressing SOD1) were irradiated (0-10 Gy) and assayed for cell survival, cellular ROS levels, cell-cycle-phase distributions, and cyclin B1 expression. SOD1-overexpressing cells were radioresistant compared to wild-type (wt) and neo vector control (neo) cells. Irradiated wt and neo cells showed a significant increase (approximately twofold) in DHE fluorescence beginning at 2 days postirradiation, which remained elevated at 8 days postirradiation. Interestingly, the late accumulation of ROS was suppressed in irradiated SOD1-overexpressing cells. The increase in ROS levels was followed by a decrease in cell growth and viability and an increase in the percentage of cells with sub-G(1) DNA content. SOD1 overexpression enhanced radiation-induced G(2) accumulation within 24 h postirradiation, which was accompanied by a decrease in cyclin B1 mRNA and protein levels. These results support the hypothesis that long after radiation exposure a "metabolic redox response" regulates radiosensitivity of human glioma cells.     

Radiation biology and inherited sterility of light brown apple moth (Lepidoptera: Tortricidae): developing a sterile insect release program

The radiation biology of two geographically isolated populations of the light brown apple moth [Epiphyas postvittana (Walker)] was studied in Australia and New Zealand as an initiation of a SIT/F1 sterility program. Pharate and < or = 2 d pre-emergence pupae were exposed to increasing radiation doses up to a maximum dose of 300 Gy. Fertility and other life history parameters were measured in emerging adults (parental) and their progeny (F1-F3 adults). Parental fecundity was significantly affected by increasing irradiation dose in pharate pupae only. For both populations, parental egg fertility declined with increasing radiation. This was most pronounced for the irradiated parental females whose fertility declined at a higher rate than of irradiated males. At 250 Gy, females < or = 2 d preemergence pupae produced few larvae and no adults at F1. No larvae hatched from 250 Gy-irradiated female pharate pupae. At 300 Gy, males still had residual fertility of 2-5.5%, with pharate pupae being the more radio-sensitive. Radiation-induced deleterious inherited effects in offspring from irradiated males were expressed as increased developmental time in F1 larvae, a reduction in percent F1 female survival, decreased adult emergence and increased cumulative mortality over subsequent generations. Males irradiated at > or = 150 Gy produced few but highly sterile offspring at F1 and mortality was > 99% by F2 egg.     

Evaluation of delayed apoptotic response in lethally irradiated human melanoma cell lines

To assess the lethal doses of gamma radiation and corresponding apoptotic response in new established human melanoma cell lines we exposed exponentially growing cultures to 8-100 Gy gamma radiation. The apoptosis and cell survival were determined by trypan blue exclusion, terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) reaction, agarose gel electrophoresis, colony forming assay, and long-term survival assay. The maximal DNA fragmentation 3 days after irradiation was observed in cultures irradiated with 20 Gy (36.9% TUNEL positive cells). The cultures irradiated with 50 and 100 Gy contained 18.7% and 16.4% TUNEL positive cells, respectively. Cultures exposed to 8 and 20 Gy gamma radiation recovered by week 3-4. Lethally irradiated (50 and 100 Gy) cultures which contained less apoptotic cells by day 3 died by week 5. A detectable increase in melanoma cell pigmentation after irradiation was also observed. The survival of human melanoma cell cultures after exposure to gamma radiation does not correlate with the level of apoptotic cells by day 3. At high radiation doses (> 50 Gy) when the radiation induced cell pigmentation is not inhibited the processes of apoptotic DNA fragmentation might be preferentially inactivated.     

Two types of X-ray-induced radioresistance in mice: Presence of 4 dose ranges with distinct biological effects

Preirradiation with 0.05 Gy of X rays 2 months before a second exposure to a mid-lethal dose significantly enhanced the survival rate in both female and male ICR strain mice. The radioresistance was observed between 2–2.5 months after exposure to 0.05 Gy. It did not appear within 1.5 months, and disappeared after 3 months. This radioresistance was induced only by whole-body preirradiation (not by partial irradiation of the head or the trunk). On the other hand, preirradiation with 0.30 Gy as well as 0.50 Gy resulted in radioresistance 2 weeks later, but not 2 months later. The radioresistance was induced by whole-body preirradiation or partial preirradiation of the trunk. No radioresistance was evident after exposure of intermediate preirradiation doses of 0.15 and 0.20 Gy administered before 2 months and 2–5 weeks, respectively. The present and previous results show that the biological effects of ionizing radiation may be distinguished with the following four radiation dose ranges; (1) below 0.025 Gy: no radioresistance after 2 months; (2) 0.05–0.10 Gy: significant radioresistance after 2–2.5 months; (3) 0.20 Gy: no radioresistance after 2–5 weeks; and (4) 0.30–0.50 Gy or more: significant radioresistance after 2 weeks. These results conflict with previous findings of the biological effects of ionizing radiation in which the radiation hazard increases in relation to increasing accumulated doses. Some stimulation, in addition to adaptation, by low dose irradiation may have occurred.     

Effect of radiation dose on the recovery of aerobic and anaerobic bacteria from mice

The presence of aerobic and anaerobic bacteria in the blood, spleen, and liver was investigated in mice that were exposed to 7, 8, 9, or 10 Gy 60Co radiation. Microorganisms were detected more often in animals exposed to higher doses of radiation. The number of mice that were culture positive and the number of isolates in one site increased with increasing dose. Bacteria were recovered in mice killed at various times after radiation, in 3 of 100 mice exposed to 7 Gy, in 13 of 100 irradiated with 8 Gy, in 23 of 90 exposed to 9 Gy, and in 34 of 87 irradiated with 10 Gy. The predominant organisms recovered were Escherichia coli, anaerobic Gram-positive cocci, Proteus mirabilis, Staphylococcus aureus, and Bacteroides spp. Escherichia coli and anaerobes were more often isolated in animals exposed to 10 Gy, while S. aureus was more often recovered in those irradiated with 9 Gy. These data demonstrate a relationship between the dose of radiation and the rate of infection due to enteric aerobic and anaerobic bacteria.     

Identification of a 24 kDa excretory secretory protein in Anisakis simplex

A gene coding for a 24 kDa protein (22 U homologous; As22U) was isolated from the Anisakis simplex third-stage larvae cDNA library during expressed sequence tag analysis. As22U was 636 bp long, and was found to code for 212 amino acid residues with a calculated mass of 23.5 kDa and a PI of 9.06. The As22U deduced amino acid sequence harbored a signal peptide region and 16 highly conserved cysteine residues, and it was identified in both the total extracts and excretory secretory (ES) protein of A. simplex. Its molecular weight was measured at 24 kDa via western blot analysis. The expression levels of thymic stromal lymphopoietin, IL-25, and CXCL1 (Gro-α) genes were increased at 6h after recombinant As22U treatment in mouse intestinal epithelial cells. Additionally, thymus and activation-regulated chemokine gene levels were increased at 14 h after treatment. Although we do not currently have sufficient evidence to determine whether As22U plays a role as an allergen, this remains possible. Further in vivo studies may provide some insight as to the allergenic properties of As22U.     

Radiation effects on expression of FC-receptor of alveolar macrophages of rat and their specific phagocytosis

BCG-activated alveolar macrophages (AM) of Wistar rats were irradiated with different doses of gamma-ray in vitro. The effects of radiation on the expression of their Fc-receptor and specific phagocytic activity were observed. AM, after irradiation with doses of 0, 100, 300 and 500 Gy, showed decreasing phagocytic activity to chicken red blood cells (CRBC) opsonized with anti-CRBC antibody with no change in phagocytic indices. The expression of Fc-receptor of AM was, however, increased.     

Oesophagostomum columbianum: gamma-irradiated third-stage larvae for immunization in lambs

40-kR gamma-irradiated third-stage larvae of Oesophagostomum columbianum were used for the immunization of Kashmir Merino lambs. Male lambs (aged from 8 to 12 weeks) were immunized in two separate experiments by two doses of irradiated larvae, given 21 days apart, and subsequently challenged with normal larvae. Judging by the establishment of worms resulting from the challenge infections in the immunized and control groups of lambs in the two experiments, a high degree of immunity was shown to develop in young lambs vaccinated with 500, followed 21 days later with 2000, 40-kR irradiated larvae. Lambs from the immunized groups showed more nodules in the intestine, a high percentage of which were positive for histotrophic stages of O. columbianum, than did controls. The importance of this finding in relation to the possible use of a vaccine for the immuno-prophylaxis of oesophagostomiasis in sheep and other animals is discussed.     

Evidence for Involvement of Cytosolic Thioredoxin Peroxidase in the Excessive Resistance of Sf9 Lepidopteran Insect Cells against Radiation-Induced Apoptosis

Lepidopteran insect cells display 50–100 times higher radioresistance compared to human cells, and reportedly have more efficient antioxidant system that can significantly reduce radiation-induced oxidative stress and cell death. However, the antioxidant mechanisms that contribute substantially to this excessive resistance still need to be understood thoroughly. In this study, we investigated the role of thioredoxin peroxidase (TPx) in high-dose γ-radiation response of Sf9 cell line derived from Spodoptera frugiperda, the Fall armyworm. We identified a TPx orthologue (Sf-TPx) in Spodoptera system, with primarily cytosolic localization. Gamma-irradiation at 500 Gy dose significantly up-regulated Sf-TPx, while higher doses (1000 Gy–2000 Gy) had no such effect. G2/M checkpoint induced following 500 Gy was associated with transition of Sf-TPx decamer into enzymatically active dimer. Same effect was observed during G2/M block induced by 5 nM okadaic acid or 10 µM CDK1 (cycline dependent kinase-1) inhibitor roscovitine, thus indicating that radiation-induced Sf-TPx activity is mediated by CDKs. Accumulation of TPx dimer form during G2/M checkpoint might favour higher peroxidase activity facilitating efficient survival at this dose. Confirming this, higher lethal doses (1000 Gy–2000 Gy) caused significantly less accumulation of dimer form and induced dose-dependent apoptosis. A ∼50% knock-down of Sf-TPx by siRNA caused remarkable increase in radiation-induced ROS as well as caspase-3 dependent radiation-induced apoptosis, clearly implying TPx role in the radioresistance of Sf9 cells. Quite importantly, our study demonstrates for the first time that thioredoxin peroxidase contributes significantly in the radioresistance of Lepidopteran Sf9 insect cells, especially in their exemplary resistance against radiation-induced apoptosis. This is an important insight into the antioxidant mechanisms existing in this highly stress-resistant model cell system.     

The cytogenetic effects of low doses of accelerated charged particles in human blood lymphocytes in vitro

The aim of the investigation was the study of cytogenetic effects in human blood lymphocytes of low doses of ionizing radiation in vitro. The analysis of unstable chromosome aberrations in human lymphocytes after irradiation by the accelerated ions 12C with the energy 500 MeV/nucleon and LET 10.7 keV/microm was carried out. Blood samples were irradiated on Nuclotron of the High Energy Laboratory of the Joint Institute for Nuclear Research. The doses of irradiation were in the range from 0.05 up to 1.0 Gy. Was shown that the frequency of unstable chromosome aberrations depends from the dose of ionizing radiation and can be described by linear function. At the doses 0.25-0.50 Gy the dose-independent curve was obtained for dicentrics and centric rings. The frequencies of dicentrics and centric rings as markers of the radiation action were slightly different for different donors that could be explained by different radiosensitivity. Using the calibration curve obtained earlier for gamma-rays coefficients of relative biological efficiency of accelerated 12C with the energy 500 MeV/nucleon were defined: they varied from 1.0 at the doses (0.5-1.0 Gy) up to 3.2 at the lower doses (0.05-0.25 Gy).     

Rearing of the fruit fly parasitoid Diachasmimorpha longicaudata (Hymenoptera: Braconidae) on X-ray irradiated larvae of Ceratitis capitata (Diptera: Tephritidae)

We evaluated the effects of X-ray irradiation on larvae of Ceratitis capitata (Wiedemann) (Diptera: Tephritidae), with the aim of finding a treatment that prevented adult fly emergence, yet did not adversely affect larval quality as rearing hosts for the parasitoid Diachasmimorpha longicaudata (Ashmead) (Hymenoptera: Ichneumonidae). Two experiments were carried out. In the first experiment, small numbers of larvae were held in Petri dishes with and without small amounts of rearing media and then irradiated with doses of X-rays ranging from 0 to 8333.6 R (equivalent to 80 Gy). In the second experiment, higher numbers of larvae were held in a manner resembling mass-rearing conditions, and were then irradiated with X-rays ranging from 0 to 10,417 R (equivalent to 100 Gy). In both experiments, the only factor that significantly affected fly emergence was irradiation of larvae. Fly emergence decreased markedly as the irradiation dose increased, and complete suppression of fly emergence was achieved at 6250.2 R (equivalent to 60 Gy) when larvae were irradiated in small batches with or without rearing media. Irradiation also affected the fertility of those flies that did emerge following treatment. In the second experiment, we found the parasitoids reared from irradiated larvae produced a higher parasitism rate and a higher number of female offspring than did parasitoids reared from control (non-irradiated) larvae. Mean fecundity of F1 parasitoids reared from irradiated larvae were affected positively by irradiation only at the 8333.6 R (80 Gy) dose. Our results show that X-ray irradiation can be used to inhibit fruit fly adult emergence and that irradiated larvae are at least as good a rearing substrate as non-irradiated larvae. Future studies should focus on the adjustment of our findings to a mass-rearing scale.     

Combined haploinsufficiency and genetic control of the G2/M checkpoint in irradiated cells

When cells are exposed to a dose of radiation large enough to cause chromosome aberrations, they become arrested at the G(2)/M checkpoint, facilitating DNA repair. Defects in checkpoint control genes can impart radiosensitivity. Arrest kinetics were monitored in mouse embryo fibroblasts at doses ranging from 10 mGy to 5.0 Gy of γ radiation over a time course of 0 to 12 h. We observe no significant checkpoint engagement at doses below 100 mGy. The checkpoint is only fully activated at doses where most of the cells are either bound for mitotic catastrophe or are reproductively dead. Atm null cells with ablated checkpoint function exhibited no robust arrest. Surprisingly, haploinsufficiency for ATM alone or in combination with other radioresistance genes did not alter checkpoint activation. We have shown previously that haploinsufficiency for several radioresistance genes imparts intermediate phenotypes for several end points including apoptosis, transformation and survival. These findings suggest that checkpoint control does not contribute toward these intermediate phenotypes and that different biological processes can be activated at high doses compared to low doses.     

Increased SOD activities and decreased lipid peroxide levels induced by low dose X irradiation in rat organs

After a single exposure to doses ranging from 0.05 to 0.50 Gy, the SOD activities in immune organs of the irradiated rats, at 4 h after whole-body X irradiation, showed significant increases by 50 to 90% (hereinafter p less than 0.05) in comparison with the control groups. The dose in the brain and liver showed tendencies to increase by 30 to 50% for doses ranging from 0.50 to 2.50 Gy. The levels of TBARS (lipid peroxides) in immune organs decreased significantly by 20 to 50% in contrast with the control groups for doses ranging from 0.10 to 1.00 Gy. Decreases by 20 to 30% were observed in brains and livers for doses near 0.50 Gy. When the dose was 0.25 Gy, the SOD activities in the spleen showed a persistent radiation-induced increase for at least 12 weeks, livers for 8 weeks, brains and thymuses for 4 weeks, and bone marrows for about 1 week. The TBARS levels in the brain and thymus showed persistent decreases due to irradiation for at least 12 weeks, and those in bone marrows for 8 h.