Radiation tolerance in the tardigrade Milnesium tardigradum

Purpose: Tardigrades are known to survive high doses of ionizing radiation. However, there have been no reports about radiation effects in tardigrades under culture conditions. In this study, we investigated tolerance of the tardigrade, Milnesium tardigradum, against gamma-rays and heavy ions by determining short-term or long-term survival, and reproductive ability after irradiation.

Materials and methods: Hydrated and anhydrobiotic animals were exposed to gamma-rays (1000 – 7000 Gy) or heavy ions (1000 – 8000 Gy) to evaluate short-term survival at 2, 24 and 48 h post-irradiation. Long-term survival and reproduction were observed up to 31 days after irradiation with gamma-rays (1000 – 4000 Gy).

Results: At 48 h after irradiation, median lethal doses were 5000 Gy (gamma-rays) and 6200 Gy (heavy ions) in hydrated animals, and 4400 Gy (gamma-rays) and 5200 Gy (heavy ions) in anhydrobiotic ones. Gamma-irradiation shortened average life span in a dose-dependent manner both in hydrated and anhydrobiotic groups. No irradiated animals laid eggs with one exception in which a hydrated animal irradiated with 2000 Gy of gamma-rays laid 3 eggs, and those eggs failed to hatch, whereas eggs produced by non-irradiated animals hatched successfully.

Conclusion: M. tardigradum survives high doses of ionizing radiation in both hydrated and anhydrobiotic states, but irradiation with >1000 Gy makes them sterile.     

Nitrogen-treatment Effects on Rearrangement-induction Patterns in Drosophila Melanogaster

Summary

Recovered rates of Y-chromosome-autosomal translocations (Y-A) induced in spermatids of pupae of Drosophila melanogaster, as well as the chromosomes 2–3 translocations (2–3), were higher in crosses to females having an attached X.Y-chromosome than to regular females. This suggests that numerous position-effect sterility mutations were induced in the Y-chromosome as well as in the autosomes.

Nitrogen treatment after irradiation of 800 r did not increase the frequencies of translocations recovered.

Prolonged nitrogen pre-treatment apparently retarded development so that irradiation involved an earlier and more sensitive stage of spermiogenesis than without pre-treatment. The increase of the 2–3, was higher than that of the Y-A translocations, indicating a lower stage-sensitivity of the latter.

When two irradiations were given 14 hours apart in air, breaks induced in the first irradiation rejoined prior to the second. Prolonged nitrogen treatment after the first irradiation caused a delay in rejoining of most breaks involved in 2–3 translocations, while rejoining of those involved in Y-A translocations was not delayed to a large extent.

The sensitivity differences in recovery of Y-A and 2–3 translocations are perhaps a reflection of different rejoining characteristics of heterochromatic and euchromatic breaks.

The change in the frequency of X-chromosome recessive lethals over the 14 hours separating the two irradiations applied to the spermatids is much larger than that of breaks involved in translocations. This indicates that at least some recessive lethals are caused by intra-genic mutations as opposed to inter-genic breaks.     

The Effect of Triethylene-melamine on the Fertility of Female Mice

Summary

TEM reduces the fertility of female mice, but the effect is much less marked than when males are treated. Embryonic deaths are induced during the ten days following treatment, the highest incidence occurring within the first three days. Thereafter fertility is approximately normal until the twenty-ninth day, when almost complete sterility occurs.

All available evidence indicates that the observed effects are, at least in part, genetical in nature, the embryonic deaths being due to the occurrence of dominant lethals, and the sterility after the fourth week being the result of destruction of the early oocytes.

The ovulation rate in females treated with TEM is significantly higher than the control level during the first ten days after injection.

A comparison is made between the change in fertility following treatment with TEM and that following irradiation.     

Sensitivity of Artemia Eggs to γ-irradiation

Summary

The present experiments pertain to the relationship between radical amount measured by E.S.R. and biological damage of dried Artemia eggs irradiated with γ-rays.

(1) The amount of free radicals increased with the increase of the dose of irradiation; however, the relation was not linear. At the same time, the hatchability rate of the eggs decreased with the exposure dose, producing a sigmoid curve.

(2) The amount of free radicals produced by irradiation in the intact eggs was similar to that in the denuded eggs.

(3) The radical decay was very rapid, immediately after irradiation, then retarded. However, hatchability decreased continuously with time after irradiation.

(4) The hatchability and radical-decay rate of the irradiated eggs stored at 25°c decreased much more rapidly than those at dry-ice temperature.

From these results, it is concluded that decay of free radicals does not imply recover from radiation damage but continues to the point of fixation of the damage.     

Radiation tolerance in the tardigrade Milnesium tardigradum

PURPOSE: Tardigrades are known to survive high doses of ionizing radiation. However, there have been no reports about radiation effects in tardigrades under culture conditions. In this study, we investigated tolerance of the tardigrade, Milnesium tardigradum, against gamma-rays and heavy ions by determining short-term or long-term survival, and reproductive ability after irradiation. MATERIALS AND METHODS: Hydrated and anhydrobiotic animals were exposed to gamma-rays (1000 - 7000 Gy) or heavy ions (1000 - 8000 Gy) to evaluate short-term survival at 2, 24 and 48 h post-irradiation. Long-term survival and reproduction were observed up to 31 days after irradiation with gamma-rays (1000 - 4000 Gy). RESULTS: At 48 h after irradiation, median lethal doses were 5000 Gy (gamma-rays) and 6200 Gy (heavy ions) in hydrated animals, and 4400 Gy (gamma-rays) and 5200 Gy (heavy ions) in anhydrobiotic ones. Gamma-irradiation shortened average life span in a dose-dependent manner both in hydrated and anhydrobiotic groups. No irradiated animals laid eggs with one exception in which a hydrated animal irradiated with 2000 Gy of gamma-rays laid 3 eggs, and those eggs failed to hatch, whereas eggs produced by non-irradiated animals hatched successfully. CONCLUSION: M. tardigradum survives high doses of ionizing radiation in both hydrated and anhydrobiotic states, but irradiation with >1000 Gy makes them sterile.     

Chemical Steps Involved in the Production of Mutations and Chromosome Aberrations by X-irradiation in Drosophila

Summary

Post-treatment with hydrocyanic acid results in a significant increase of the mutation frequency in spermatids, if x-radiation is delivered at a high dose-rate, but not after irradiation at a low dose-rate. A greater overall genetic effect of intensity per se has not been observed.

Following radiation at both low and high intensities, post-treatment with cyanide increases the frequency of translocations in spermatids. Consequently, it has been inferred that cyanide causes a prolonged opening of chromosome breaks in spermatids and thus favours the formation of translocations.

Both this finding and the fact that cyanide post-treatment also raises the mutation rate in a ring-shaped chromosome suggest that the increase in lethal frequency due to post-treatment refers not only to position-effect lethals but also to gene mutations and possibly small deletions.

Data relating differential sensitivity in successive broods to oxygen tension are presented. Post-treatment with cyanide is equally effective in raising the mutation rate if high-intensity radiation is given in pure N₂, as in O₂.

It is assumed that cyanide inhibits a mechanism responsible for repair of the initial radiation damage. Recovery from changes leading to lethal gene mutations then seems a metabolic process, possibly connected with respiratory energy. Injury to this repair system is independent of oxygen tension, and the reparable fraction of the initial damage after radiation in N₂ is equal to that after radiation in O₂.     

The Utilization of Acetate in Rat Liver after Whole-body Roentgen Irradiation

Summary

The acetylation of sulphanilamide and the synthesis of fatty acids from 2-¹⁴C-acetate in rat liver after 450 r whole-body roentgen irradiation was studied.

A depression in the liver's acetylating capacity and fatty acid synthesis was found the third day after irradiation.

Cysteamine given before irradiation had no protective effect, but depressed itself the acetylation of sulphanilamide.

The iodine number of the fatty acids decreased after irradiation and returned to normal on the seventh day after irradiation.     

The Influence of Hypothermia Involving Minimal Hypoxia on the Radiosensitivity of Leucocytes in the Rat

Summary

Rats were irradiated with 357 rads of gamma-rays, some at normal body-temperatures and some at body-temperatures of less than 5°c. The method of induction of hypothermia was designed to produce minimal anoxia. White-cell counts were performed up to seventeen days after irradiation. Depression of the lymphocyte count was seen in all animals irradiated, recovery being nearly complete at the end of the study. The depression observed was similar in the cooled and uncooled groups, apart from the values obtained two days after irradiation. It is concluded that hypothermic radioprotection of the lymphopoietic tissues is dependent on anoxia.     

Analysis of immune cell populations and cytokine profiles in murine splenocytes exposed to whole-body low-dose irradiation

Purpose: In contrast to high-dose therapeutic irradiation, definitive research detailing the physiological effects of low-dose irradiation is limited. Notably, the immunological response elicited after low-dose irradiation remains controversial.

Materials and methods: Female C57BL/6 mice were whole- body-irradiated with a single or three daily fractions up to a total dose of 0.1, 1, or 10 cGy. Blood and spleen were harvested 2, 7 and 14 days after irradiation.

Results: The splenic CD4⁺ T cell subpopulations were temporarily increased at 2 days after single or fractionated irradiation, whereas the percentage of dendritic cells (DC) and macrophages was decreased. Whereas CD8⁺ T cell populations were decreased in single-dose irradiated mice at day 7, early and sustained reduction of CD8⁺ T cell numbers was observed in fractionated- dose-irradiated mice from day 2 until day 14. In addition, single-dose irradiation resulted in a Th1 cytokine expression profile, whereas fractionated-dose irradiation drove a Th2 shift. Additionally, increased expression of immune-related factors was observed at early time-points with single-dose irradiation, in contrast to the dose-independent induction following fractionated-dose irradiation.

Conclusions: Our results demonstrate that low-dose irradiation modulates the immune response in mice, where the sensitivity and kinetics of the induced response vary according to the dosing method.     

Acute transient radiation hepatitis following whole abdominal irradiation

Sporadic cases or radiation hepatitis have been reported following doses above 3500 rad delivered in 3-4 weeks to the liver. The authors report their experience of radiation hepatitis in two out of 117 consecutive lymphoma cases treated with total abdominal irradiation. These two patients developed clinically overt manifestations which lasted for a short period of time and fully recovered. The dose delivered to the whole liver was 3000 rad in six weeks, but in one an additional 1000 rad in five fractions were delivered to the left lobe in an attempt to boost the dose to the central axis lymphatic system up to 4000 rad. The low incidence of radiation hepatitis and its reversible course, when 3000 rad in six weeks are delivered to the whole liver, is emphasised.     

Evaluation of Radio-protective Efficacy of Cysteamine (with Rat-liver-cell Glycogen as Reference System)

Summary

A technique for localization of glycogen in the hepatic-cell cytoplasm of rats was utilized for determination of the radio-protective efficacy of cysteamine with 15 mg dose per animal.

Radiation-induced glycogenesis was at its maximum peak 24 hours after irradiation with 300 r, 500 r and 800 r.

After irradiation with 500 r, protective efficacy was maximal at 4 days and 13 days after irradiation. After 300 r and 800 r, efficacy was maximal at 4 days and 3 days after irradiation, respectively.     

Anti-bacterial Action of Irradiated Glucose

Summary

It is shown that γ-irradiated glucose has a strong, anti-bacterial action on Pseudomonas sp. 128. Irradiation of the water solution of glucose is more effective than irradiation of modifications of crystalline glucose.

Part of the anti-bacterial effect remains after storage of the irradiated solution for six days at 20°c. After treatment with irradiated glucose the surviving bacteria are found to be more resistant to a repeated treatment. The bactericidal action of irradiated glucose increases with decreasing ph of the test solution, and was abolished by added catalase. The possible nature of the anti-bacterial factor(s) in irradiated glucose is discussed.     

The Survival of Germ Cells after Irradiation of the Neonatal Male Rat

Seventy male rats aged four to eight days were exposed to 0–430 r x-irradiation. Counts were made at 12, 24 and 72 hours after irradiation of normal and degenerating germ cells at different developmental stages and of ‘supporting’ cells.

The decrease in the number of gonocytes which normally occurs with advancing age was partially inhibited by irradiation. The number of gonocytes undergoing lysis increased after treatment.

No reduction in the number of type-A spermatogonia was detected until 72 hours after irradiation. In contrast, intermediate-type and type-B spermatogonia, as well as primary spermatocytes, became markedly depleted at 72 hours.

The numbers of normal ‘supporting’ cells decreased sharply after irradiation. Cells undergoing degeneration were consistently more numerous in irradiated than in control animals.

While the radio-sensitivity of intermediate-type and type-B spermatogonia is of the same order in neonatal and adult rats, type-A spermatogonia are slightly more radio-sensitive in the adult.

Irradiation of the testis of the neonatal rat appears to cause inhibition of mitosis as well as cell-death.     

Survival of HeLa Cells Cultured in Vitro and Exposed to Protracted Gamma-irradiation

Summary

Experiments are described in which S₃ HeLa cells were exposed to gamma-radiation at dose-rates of 9·5 and 19 rad/hour (chronic irradiation). The cell-survival, in terms of reproductive integrity, was compared with the same cell-line irradiated at 44·9 rad/min (acute irradiation). It was found that while a ‘type C’ multi-hit curve was necessary to describe the survival of cells irradiated at 44·9 rad/min, a simple exponential function of dose was sufficient to describe the survival at 9·5 and 19 rad/min. The data were compared with the results of Berry and Cohen (1962).     

Radiosensitivity of Oogonia and Oocytes in the Foetal Rat

Pregnant rats were exposed to doses of 25 to 2 × 100 r of x-rays at varying times between the 13th and the 20th days after insemination. Female offspring were killed at 25 days post partum, and the number of oocytes was estimated from serial sections of the ovaries.

The population of oocytes in the irradiated ovaries was found to depend both on the dose of x-rays administered and on foetal age at the time of exposure.

The period of maximum radiosensitivity, which occurred on the 15th day of gestation, was found to coincide with a high rate of mitotic division of oogonia.     

Effects of 60Co Irradiation on Virulent Toxoplasma Gondii and Its Use in Experimental Immunization

Summary

The effects of ⁶⁰Co irradiation on the virulence and immunogenicity of the RH strain of Toxoplasma gondii was studied by infecting batches of mice with graded inocula of tachyzoites that had been exposed to radiation doses ranging from 0 to 20 000 rad. While doses of 15 000 and 20 000 rads appeared to be effective, and 10 000 rad nearly effective in annulling the virulence, irradiation at 5000 rad was only partially effective in rendering the organisms avirulent and could achieve only a prolongation of survival time of the inoculated mice. The survivors of higher irradiation inocula showed no evidence of the development of the parasite in them, but could resist a limited virulent challenge. The use of a booster inoculation improved both the quality and the duration of protective effect.     

Radiotherapy results in brain metastases (118 cases)]

Results of palliative radiation therapy in cerebral metastases of various primary tumors are reported. The radiation therapy consisted in a large-volume irradiation which encompassed the whole cerebrum, using single dose of 200 rd (calculated for the center of the skull) five times a week, amounting to a total dose of 4000 rd, sometimes up to 5000 rd. In some cases, a saturating irradiation of a small volume reached 5000 or 6000 rd. A significant improvement in symptomatics was obtained in about 70% of the patients. The average time of survival after accomplishment of the radiation therapy amounted to six months. Own results and the summarized results of the other authors justify the irradiation of cerebral metastases as a rewarding palliative indication.     

Elucidation of molecular expression associated with abnormal development and sterility caused by electron beam irradiation in Spodoptera litura (F.) (Lepidoptera: Noctuidae)

Abstract

Purpose: The objective of the present study was to elucidate the mode of indirect action of electron beam irradiation at the molecular level against a quarantine pest, Spodoptera litura (F.).

Material and methods: Electron beam irradiation (50–200?Gy) was applied to S. litura eggs, larvae, pupae, and adults, after which the feeding area, body weight, deformity of pupae and adults, ovarian development, expression levels of vitellogenin (Vg) and vitellogenin receptor (VgR) genes, and protein levels were analyzed.

Results: The amount of feeding by S. litura larvae and the synthesis level of 70?kDa storage protein significantly decreased as the electron beam dose increased. When larvae were treated with the electron beam, morphological deformities appeared in the pupae, and abnormal wing disc (AWD) expression significantly decreased. Ovarian development was completely inhibited in emerged adults that had undergone 200?Gy electron beam irradiation as pupae. Quantitative real-time PCR (qRT-PCR) assays showed significant downregulation of the Vg and VgR genes due to electron beam irradiation; whereas the synthesis level of Vg protein (190?kDa) did not decrease with time in eggs unlike in non-irradiated (control) S. litura eggs, exhibiting irradiation induced impairment of Vg functioning.

Conclusions: These findings of radiation-induced abnormal development and sterility in S. litura together with the correlated changes at the molecular level may facilitate the development of a phytosanitary strategy against this quarantine pest using electron beam irradiation.     

The Clinical and Pathological Response of Goats to Whole-body Irradiation by Gamma-rays and Fission Neutrons

Summary

Fifty adult male British Saanen goats in equal numbers were given acute whole-body irradiation with either fission neutrons or gamma-rays of 2·5 mev mean energy. The LD 50/30 was about 505 rad for neutrons and 395 r for gamma-rays, giving an RBE of 0·8.

Higher doses resulted in a fatal ‘gastro-intestinal’ syndrome characterized by severe to absolute anorexia, fluid intake greatly reduced to absent, progressive haemoconcentration from 48 hours and diarrhoea from 4 days after exposure. At post-mortem there were mucus casts within the lumen of the small intestine. Deaths in the third and fourth weeks were commonly the result of widespread haemorrhage with severe thrombocytopenia following bone-marrow damage. Severe anaemia was seen only once and that in a survivor. Although few deaths could be confidently attributed to infection and blood-cultures were sterile, bacterial aggregates were nearly always found in the tissues, most commonly in the intestines, liver and lungs, and fever occurred invariably in the few days before death.

Blood urea, proteins, glucose, chloride and electrolyte measurements showed no radiation-induced changes.

No deaths were seen after 30 days in a one-year follow-up. Platelet recovery when it began was usually rapid. The most reliable prognostic sign was a progressive rise in platelet count. Blood lymphocytes began to increase in number at the end of the first week, even in animals which were going to die, but recovery was so slow that even after one year, values were only about half the pre-irradiation mean.

The response to the two kinds of radiation was qualitatively very similar. However, epilation was common after neutrons and rare after gamma-radiation, and in survivors platelet recovery was distinctly faster after neutron-than after gamma-radiation.     

Whole-brain irradiation increases NREM sleep and hypothalamic expression of IL-1β in rats

Abstract

Purpose: Although it has mainly been described qualitatively, whole brain irradiation induces somnolence in patients with malignant diseases. Therefore, we used a rat model to quantify the effects of irradiation of healthy brain tissue on both sleep-wake patterns and the expression of the pro-inflammatory cytokine interleukin-1β (IL-1β), which is known to induce sleep.

Materials and methods: Different groups were examined at three time points after irradiation (1 day, 30 days and 60 days). Polysomnographic recordings were performed on each rat before and after total cranial irradiation (12 Gy). IL-1β protein levels in several brain regions were assessed by enzyme-linked immunosorbent assays, and site-specific immunoreactivity was observed by immunofluorescence.

Results: We found that both non-rapid eye movement sleep and IL-1β protein expression in the hypothalamus increased 30 days after irradiation.

Conclusions: Whole brain irradiation increases sleep in our rat model, and this finding is similar to qualitative reports from patients. Because IL-1β has been proposed as a sleep-promoting molecule, we propose that the polysomnographic results may be attributable, at least in part, to the delayed overexpression of IL-1β in the hypothalamus.