Comparative study of chromosome aberration formation in lymphocytes culture under pulsed and continuous neutron irradiation

Frequencies of chromosome aberration induced by prolong (continuous) neutron radiation (dose-rate 0.17 Gy/min) and pulsed neutron radiation with ultra-high dose-rate (1-4) x 10(5) Gy/s have been studied in human blood lymphocytes at G0-stage. It was demonstrated that cytogenetic efficiency of pulsed neutrons (after the substraction of approximately 50% gamma-component from the total dose) was 2 times higher than that of continuous neutron radiation.     

Metallothionein induction as a potent means of radiation protection in mice

A striking resistance to lethal damage from a single dose of 6-8 Gy of X rays has been found in mice which had received various pretreatments to induce metallothionein (MT) synthesis in the liver prior to irradiation. Mice were injected with manganese (10 mg Mn/kg) or cadmium (3 mg Cd/kg) salt subcutaneously, or a patch of dorsal skin (2 X 2 cm2) was excised 1 or 2 days prior to irradiation. The increased tolerance of these mice to radiation was established by a marked decrease of mortality rate, an increase of mean survival time, a reduction of weight loss, and a smaller decrease in the number of leukocytes as compared with the control group. The LD50/30 for control mice was 6.3 Gy, while the corresponding values for the groups pretreated with Mn, Cd, and skin excision were 7.5, 7.7, and 7.9 Gy, respectively. The normal level of MT in mouse liver was approximately 25 micrograms/g tissue. This level increased 2.5- to 3-fold 24 h after 6.3 Gy irradiation. The MT levels of mice pretreated with Cd, Mn, and skin excision were increased 8-, 5-, and 7-fold, respectively, prior to irradiation as compared with the preirradiation control. These results indicate that the induction of MT in mouse liver is a significant factor in the mechanism of protection against radiation.     

Trehalose dimycolate enhances survival of fission neutron-irradiated mice and Klebsiella pneumoniae-challenged irradiated mice

The survival of B6D2F1 female mice exposed to lethal doses of fission neutron radiation is increased when trehalose dimycolate (TDM) preparations are given either 1 h after exposure or 1 day before exposure to radiation. TDM in an emulsion of squalene, Tween 80, and saline was the most effective formulation for increasing the 30-day survival of mice when given 1 day before (90%) or 1 h after (88%) exposure to radiation. An aqueous suspension of a synthetic analog of TDM was less effective at increasing 30-day survival (60%) when given 1 day prior to radiation exposure and not effective when given 1 h after radiation. Mice receiving a sublethal dose (3.5 Gy) of fission neutron radiation and either the TDM emulsion or synthetic TDM 1 h after irradiation were substantially more resistant to challenge with 10, 100, 1000, or 5000 times the LD50/30 dose of Klebsiella pneumoniae than untreated mice.     

Using MT(-/-) mice to study metallothionein and oxidative stress

Mice with null mutations for metallothionein genes MT-1 and MT-2 were used to study the role that metallothionein plays in protecting cellular targets in vivo from oxidative stress. Wild-type (MT(+/+)) and MT-null (MT(-/-)) mice were treated with either saline or zinc and exposed to two types of oxidative stress: gamma-irradiation or 2-nitropropane. There was no alteration in the antioxidant defense system (superoxide dismutase, catalase, or glutathione peroxidase and glutathione levels) to compensate for the lack of the metallothionein in the MT(-/-) mice. The amount of oxidative damage to liver DNA, lipids, and proteins were similar for the MT(-/-) and MT(+/+) mice even though the levels of metallothionein in the livers of the saline- or zinc-pretreated MT(+/+) mice were 5- to 100-fold greater than found in the MT(-/-) mice. To determine if metallothionein can protect mice from the lethal effects of ionizing radiation, the mean survivals of MT(-/-) and MT(+/+) mice exposed to whole body gamma-irradiation were measured and found to be similar. However, the mean survival increased significantly after zinc pretreatment for both the MT(-/-) and MT(+/+) mice. These results demonstrate that tissue levels of metallothionein do not protect mice in vivo against oxidative stress.     

Dynamics of changes in the ultrastructure of the rat cerebral cortex in the early period of acute radiation sickness caused by neutron irradiation

A 24-hour electron microscopic examination of neuronal and capillary ultrastructure in sensorimotor complex was performed after whole-body neutron irradiation of mature rats in the dose of 10 Gy. The results suggest that postradiation neuronal changes, observed for 6 hours after irradiation, are mainly caused by direct effect of ionizing radiation. At later terms this process is influenced by blood capillary lesions. The effect of neutron irradiation at the ultrastructural level is similar to that of rarely ionizing radiation.     

Action of mixed gamma-neutron radiation with various dose rates on the number of cells in thymus and chromosomes of mice bone marrow and human lymphocytes

The irradiation with mixed gamma-neutron radiation was carried out at the pulse nuclear reactor on fast neutrons BARS-6 in a regimen of one pulse (100 micros) and in a regimen of continuous irradiation during 60 minutes. Was shown, that the irradiation of mice with pulse radiation was 1.3-1.8 times more effective in the induction of the chromosome aberrations in bone marrow cells in comparison with the continuous regimen of irradiation. At the same time, other biological tests (yield of chromosome aberrations in human lymphocytes, decreasing the number of cells in thymus) demonstrated that pulsed and continuous regimens have almost equal biological effectiveness.     

Effects of split fast neutron doses on the liver cells of albino Swiss mice

The effect of neutron doses from a D-T compact neutron generator on the liver cells of adult male and female albino Swiss mice was investigated. Fast neutrons (14.5 MeV) were delivered to the whole body in a single dose or in two, four, six or eight equal doses separated by 3-day intervals. The lowest dose, 100 rem, was given for an exposure time of 6 hours and was then steadily raised to 912 rem for an exposure time of 48 hours. During exposure the neutron flux was controlled by the activation foil technique. Animals were killed for testing after each irradiation. Histological examination of the hepatocytes in the light microscope showed marked degenerative changes only after the longer irradiation periods (24, 36 and 48 h). Electron microscopy showed cytological (cytoplasmic and nuclear) changes in the hepatocytes after only 12 hours' irradiation. Densitometric scans of electron micrographs of control and 12 h-irradiated livers indicated that the control hepatocyte interphase nucleus contains approximately 72% heterochromatin, while the irradiated nucleus contains only 64% heterochromatin.     

增强UV-B辐射和He-Ne激光对小麦原生质体微管骨架的影响

以小麦叶片原生质体为材料,采用间接免疫荧光定位法标记其微管系统,并利用激光共聚焦扫描显微系统进行观察。研究了低剂量He-Ne激光(5mW.mm-2)、增强UV-B辐射(10.08kJ.m-2.d-1)及二者的复合处理对小麦幼苗叶肉细胞中微管骨架的影响。结果表明,增强UV-B辐射后,小麦叶片细胞中微管骨架发生解聚,呈短棒状或点状分布,微管束弥散且荧光强度减弱;而增强UV-B辐射后再施以He-Ne激光处理,小麦叶肉细胞微管骨架有部分断裂,但较单独UV-B处理组的损伤程度轻,说明低剂量的He-Ne激光可以部分修复增强UV-B辐射对微管骨架的损伤,且对微管的聚合有促进作用。     

Changes in the antigenic properties of proteins of laboratory mice during oxidative stress

Changes in the level of oxidative damage to proteins in CD1 outbred mice γ irradiated with a dose of 3 Gy have been studied. The changes were estimated from the amount of carbonyl groups (CG) in the proteins. It was found that two hours after exposure to γ radiation, the amount of CG in the cytoplasmic and nuclear fractions of the liver, heart, brain, and spleen sharply increased. Two months after irradiation, the level of CG in the cytoplasmic and nuclear subcellular fractions of the liver and brain decreased to the level of CG in the control animals, which were not exposed to radiation. In the subcellular fractions of the heart and spleen, the increase in the degree of damage was more significant and a high level of damage was observed even two months after irradiation. An enhancement of the antigenic properties of proteins from the liver, heart, and spleen in the postirradiation period was found. Spleen proteins were most immunogenic. A comparison of the antigenic properties of proteins isolated from the tissues 60 days after irradiation revealed a correlation between the level of oxidative damage and the immunogenicity of the total protein fraction.     

Radioprotective properties of ATP and modification of acid phosphatase response after a lethal dose of whole body p(66MeV)/Be neutron radiation to BALB/c mice.

The intraperitoneal administration of exogenous ATP prior to a lethal dose (7 Gy) of whole body neutron irradiation increased the radioresistance of BALB/c mice. This radiation used the beam from a neutron therapy facility produced by the reaction p(66 MeV)/Be. Survival of the mice, determined 7 days post-irradiation as the endpoint, was increased from 26% to 86% by the action of the exogenous ATP. Furthermore, the response of acid phosphatase activity as an indicator of the acute radiation effects showed a marked augmentation in both tissues studied, testes and small intestine. The activity of the enzyme after neutron irradiation with prior administration of ATP showed smaller increases when compared with the increases observed after neutron irradiation alone. This implies that exogenous ATP reduces the effect of the lytic enzyme and, hence, damage. Finally, changes were observed in the activity of acid phosphatase in the testes and intestine with different concentrations of exogenous ATP. In both tissues there was a monotonic decrease in the activity of the enzyme with increase of the concentration of exogenous ATP administrated before radiation. These results reflect the protective ability of exogenous ATP as an adaptive defence mechanism to reduce radiation damage in normal tissues after a lethal dose of neutron radiation.     

Suppressive effects of continuous low-dose-rate γ irradiation on diabetic nephropathy in type II diabetes mellitus model mice

It has been proposed that the development of diabetic nephropathy is caused in large part by oxidative stress. We previously showed that continuous exposure of mice to low-dose-rate γ radiation enhances antioxidant activity. Here, we studied the ameliorative effect of continuous whole-body irradiation with low-dose-rate γ rays on diabetic nephropathy. Ten-week-old female db/db mice, an experimental model for type II diabetes, were irradiated with low-dose-rate γ rays from 10?weeks of age throughout their lives. Nephropathy was studied by histological observation and biochemical analysis of serum and urine. Antioxidant activities in kidneys were determined biochemically. Continuous low-dose-rate γ radiation significantly increases life span in db/db mice. Three of 24 irradiated mice were free of glucosuria after 80?weeks of irradiation. Histological studies of kidney suggest that low-dose irradiation increases the number of normal capillaries in glomeruli. Antioxidant activities of superoxide dismutase, catalase and glutathione are significantly increased in kidneys of irradiated db/db mice. Continuous low-dose-rate γ irradiation ameliorates diabetic nephropathy and increases life span in db/db mice through the activation of renal antioxidants. These findings have noteworthy implications for radiation risk estimation of non-cancer diseases as well as for the clinical application of low-dose-rate γ radiation for diabetes treatment.     

Efficacy of radiation countermeasures depends on radiation quality

The detonation of a nuclear weapon or a nuclear accident represent possible events with significant exposure to mixed neutron/γ-radiation fields. Although radiation countermeasures generally have been studied in subjects exposed to pure photons (γ or X rays), the mechanisms of injury of these low linear energy transfer (LET) radiations are different from those of high-LET radiation such as neutrons, and these differences may affect countermeasure efficacy. We compared 30-day survival in mice after varying doses of pure γ and mixed neutron/γ (mixed field) radiation (MF, Dn/Dt = 0.65), and also examined peripheral blood cells, bone marrow cell reconstitution, and cytokine expression. Mixed-field-irradiated mice displayed prolonged defects in T-cell populations compared to mice irradiated with pure γ photons. In mouse survival assays, the growth factor granulocyte colony-stimulating factor (G-CSF) was effective as a (post-irradiation) mitigator against both γ-photons and mixed-field radiation, while the thrombopoietin (TPO) mimetic ALXN4100TPO was effective only against γ irradiation. The results indicate that radiation countermeasures should be tested against radiation qualities appropriate for specific scenarios before inclusion in response plans.     

Reduction of copper and metallothionein in toxic milk mice by tetrathiomolybdate, but not deferiprone.

Copper is both essential for life and toxic. Aberrant regulation of copper at the level of intracellular transport has been associated with inherited diseases, including Wilson's disease (WND) in humans. WND results in accumulation of copper and the copper and zinc-binding protein metallothionein (MT) in liver and other tissues, liver degeneration, and neurological dysfunction. The toxic milk (TX) mutation in mice results in a phenotype that mimics human WND, and TX has been proposed to be a model of the disease. We characterized TX mice as a model of altered metal ion and MT levels during development, and after treatment with the metal ion chelators tetrathiomolybdate (TTM) and deferiprone (L1). We report that hepatic, renal and brain copper and MT are elevated in TX mice at 3 and 12 months of age. Zinc was significantly higher in TX mouse liver, but not brain and kidney, at both time points. Nodules appeared spontaneously in TX mouse livers at 8-12 months that maintained high copper levels, but with more normal morphology and decreased MT levels. Treatment of TX mice with TTM significantly reduced elevated hepatic copper and MT. Transient increases in blood and kidney copper accompanied TTM treatment and indicated that renal excretion was a significant route of removal. Treatment with L1, on the other hand, had no effect on liver or kidney copper and MT, but resulted in increased brain copper and MT levels. These data indicate that TTM, but not L1, may be useful in treating diseases of copper overload including WND.     

Effects of dexamethasone on late radiation injury following partial-body and local organ exposures.

Dexamethasone was evaluated as a treatment for radiation-induced lung, kidney, liver, and spinal cord injuries in rats. One experimental group was partial-body-irradiated (22.5 Gy) with the head, femur, and exteriorized intestine shielded to prevent acute mortality. Other animals received local irradiation to the kidney (20 Gy), liver (25 Gy), or a 1-cm segment of cervical spinal cord (18 to 40 Gy). Following irradiation half of the animals in each radiation group were given drinking water containing 188 micrograms/liter of dexamethasone. Tests were done to assess kidney function (hematocrit, plasma urea nitrogen, ethylenediaminetetraacetic acid clearance), liver function (rose bengal clearance, plasma glutamic oxaloacetic acid transaminase), or spinal cord injury (paralysis). The effectiveness of dexamethasone in preventing radiation injury was tissue specific. Dexamethasone eliminated lethal pleural fluid accumulation after partial-body irradiation and delayed development of kidney dysfunction after local kidney irradiation. As a result, dexamethasone increased the median survival time from 63 to 150 days after partial-body irradiation and from 126 to 175 days after local kidney irradiation. After whole-liver irradiation, development of hepatic functional injury was retarded by dexamethasone treatment but without significantly changing survival time. Dexamethasone had no effect on spinal cord tolerance but significantly shortened the latent period between radiation and paralysis.     

Effect of stress,adrenalectomy and changes in glutathione metabolism on rat kidney metallothionein content: comparison with liver metallothionein

Eighteen hours of immobilization stress, accompanied by food and water deprivation, increased liver metallothionein (MT) but decreased kidney MT levels. Food and water deprivation alone had a significant effect only on liver MT levels. In contrast, stress and food and water deprivation increased both liver and kidney lipid peroxidation levels, indicating that the relationship between MT and lipid peroxidation levels (an index of free radical production) is unclear. Adrenalectomy increased both liver and kidney MT levels in basal conditions, whereas the administration of corticosterone in the drinking water completely reversed the effect of adrenalectomy, indicating an inhibitory role of glucocorticoids on MT regulation in both tissues. Changes in glutathione (GSH) metabolism produced significant effects on kidney MT levels. Thus, the administration of buthionine sulfoximine, an inhibitor of GSH synthesis, decreased kidney GSH and increased kidney MT content, suggesting that increased cysteine pools because of decreased GSH synthesis might increase kidney MT levels through an undetermined mechanism as it appears to be the case in the liver. However, attempts to increase kidney MT levels by the administration of cysteine or GSH were unsuccesful, in contrast to what is known for the liver. The present results suggest that there are similarities but also substantial differences between liver and kidney MT regulation in these experimental conditions.     

Early cell repair of the lung and the intestine in mice, after irradiation by fast neutrons and gamma rays

Lung tolerance is assessed from LD50 at 180 days after thoracic irradiation, in mice, with d(50) + Be neutrons and 60Co gamma rays. Early intestinal tolerance is assessed from LD50 at 7 days after abdominal irradiation. Additional dose (Dr) to reach LD50 when a single dose Ds is split into 2 equal fractions Di separated by different time intervals "i", is determined (Dr = 2Di - Ds), Dr is larger after gamma than after neutron irradiation, for lung and intestine. After thoracic irradiation with gamma rays, Dr reaches 3.36, 4.38, 5.12 and 5.37 Gy for "i" = 2, 6, 12 and 24 hours respectively; after neutron irradiation, Dr reaches 0.66, 0.9, 1.29, 1.95 and 1.50 Gy for "i" = 1, 2, 4, 12 and 24 hours. Dr is smaller for intestine; after abdominal irradiation with gamma rays, it reaches 1.99, 2.59, 2.74, 3.11, 3.34, 4.44 and 4.56 Gy for "i" = 1, 2, 3.5, 8, 12, 18 and 24 hours; after neutron irradiation, it reaches 0.13, 0.45, 0.42 and 1.33 Gy for "i" = 1.5, 3.5, 5.5 and 24 hours. After gamma irradiation, early repair is complete after 3.5 hours for intestine and needs 12 hours for lung.     

A Comparative Study of the Bactericidal Activity and Daily Disinfection Housekeeping Surfaces by a New Portable Pulsed UV Radiation Device

Daily cleaning and disinfecting of non-critical surfaces in the patient-care areas are known to reduce the occurrence of health care-associated infections. However, the conventional means for decontamination of housekeeping surfaces of sites of frequent hand contact such as manual disinfection using ethanol wipes are laborious and time-consuming in daily practice. This study evaluated a newly developed portable pulsed ultraviolet (UV) radiation device for its bactericidal activity in comparison with continuous UV-C, and investigated its effect on the labor burden when implemented in a hospital ward. Pseudomonas aeruginosa, Multidrug-resistant P. aeruginosa, Escherichia coli, Acinetobacter baumannii, Amikacin and Ciprofloxacin-resistant A. baumannii, Staphylococcus aureus, Methicillin-resistant S. aureus and Bacillus cereus were irradiated with pulsed UV or continuous UV-C. Pulsed UV and continuous UV-C required 5 and 30 s of irradiation, respectively, to attain bactericidal activity with more than 2Log growth inhibition of all the species. The use of pulsed UV in daily disinfection of housekeeping surfaces reduced the working hours by half in comparison to manual disinfection using ethanol wipes. The new portable pulsed UV radiation device was proven to have a bactericidal activity against critical nosocomial bacteria, including antimicrobial-resistant bacteria after short irradiation, and was thus found to be practical as a method for disinfecting housekeeping surfaces and decreasing the labor burden.     

Revisiting emergency anti-apoptotic cytokinotherapy: erythropoietin synergizes with stem cell factor, FLT-3 ligand, trombopoietin and interleukin-3 to rescue lethally-irradiated mice

We have re-evaluated the benefit of using erythropoietin (Epo) as a pleiotropic cytokine to counteract hematological and extra-hematological toxicity following lethal irradiation. B6D2F1 mice were exposed to a dose of 9 Gy gamma radiation resulting in 90% mortality at 30 days, and then injected with stem cell factor, FLT-3 ligand, thrombopoietin and interleukin-3 [i.e. SFT3] at two and 24 hours with or without Epo (1,000 IU/kg) at 2 hours and day 8. As controls, two groups of irradiated mice were given only Epo or Phosphate-buffered saline. Epo synergized with SFT3 to rescue lethally-irradiated mice from radiation-induced death (survival: 60%, 95% and 5% respectively for SFT3, SFT3+Epo and controls at 30 days, p<0.05), whereas Epo alone exhibited no protective effect. Hematopoietic parameters did not differ significantly between SFT3 and SFT3+Epo groups during the animal death period. Some beneficial effects on gastro-intestinal toxicity were noticed following administration of Epo, although lung, liver and kidney were not protected. Further studies are necessary to understand fully the mechanisms involved in these effects of Epo in order to optimize treatment with cytokines following high-dose irradiation.