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.     

Effect of Pseudomonas contamination or antibiotic decontamination of the GI tract on acute radiation lethality after neutron or gamma irradiation

The influence of antibiotic decontamination of Pseudomonas contamination of the GI tract prior to whole-body neutron or gamma irradiation was studied. It was observed that for fission neutron doses greater than 5.5 Gy, cyclotron-produced neutron doses greater than 6.7 Gy, and 137Cs gamma-ray doses greater than 14.4 Gy, the median survival time of untreated rats was relatively constant at 4.2 to 4.5 days, indicating death was due to intestinal injury. Within the dose range of 3.5 to 5.5 Gy of fission neutrons, 4.9 to 6.7 Gy of cyclotron-produced neutrons, and 9.6 to 14.4 Gy of gamma rays, median survival time of these animals was inversely related to dose and varied from 12 to 4.6 days. This change in survival time with dose reflects a transition in the mechanisms of acute radiation death from pure hematopoietic, to a combination of intestinal and hematopoietic, to pure intestinal death. Decontamination of the GI tract with antibiotics prior to irradiation increased median survival time 1 to 5 days in this transitional dose range. Contamination of the intestinal flora with Pseudomonas aeruginosa prior to irradiation reduced median survival time 1 to 5 days in the same radiation dose range. Pseudomonas-contaminated animals irradiated within this transitional dose range had maximum concentrations of total bacteria and Pseudomonas in their livers at the time of death. However, liver bacteria concentration was usually higher in gamma-irradiated animals, due to a smaller contribution of hematopoietic injury in neutron-irradiated animals. The effects of both decontamination of the GI tract and Pseudomonas contamination of the GI tract were negligible in the range of doses in which median survival time was dose independent, i.e., in the pure "intestinal death" dose range. Finally, despite the marked changes in survival time produced by decontamination or Pseudomonas contamination in the "transitional dose range," these treatments had little effect on ultimate survival after irradiation as measured by the LD50/5 day and the LD50/30 day end points. The implications of these results with respect to treatment of acute radiation injury after whole-body irradiation are discussed.     

Effects of gamma-irradiation on survival, growth and productivity of broiler chicken

In experiments with broiler chicken the influence of gamma-irradiation (137Cs) to survive and productivity of meat poultry was studied. LD50/30 increased from 10.0 to 18.7 Gy with increasing of the age of the irradiated chicken from 3 to 40 days and reduced from 18.3 to 11.9 Gy with increasing of a dose rate from 1.0 to 40.0 Gy/h. As a rule, death of chicken was observed between 4th and 15th days after the exposure; the most early dates of poultry death were found at irradiation dose rate of 40.0 Gy/h. The exposure to doses of 8-20 Gy resulted in stunted growth; in comparison with control group the mass reduced by 22-32 g per each 1 Gy, lowering of meat productivity by 36%.     

Radiation-induced rectal complications are not influenced by age: a dose fractionation study in the rat

Radiation-induced complications of the rectum are an important dose-limiting factor in radiotherapy of pelvic malignancies. In general, animal studies demonstrated no differences in acute and late normal tissue toxicity with age, but little is known about rectal complications in relation to age. For this purpose, an extensive histological and dose fractionation study was carried out on the rectum of young (12 weeks) and older (77-80 weeks) rats. In this paper, the results of dose fractionation are presented in relation to age at the time of irradiation. Young and older animals were irradiated with single and fractionated doses. After irradiation, rectal complications could lead to occlusion and stenosis, eventually resulting in the clinical symptoms of a megacolon and a possible fistula. For each dose group, cumulative survival rates were obtained with Kaplan-Meier analysis, from which dose-effect curves and the associated LD(50) values for a megacolon/fistula were calculated. The majority of responders died between 8 and 24 weeks after irradiation, irrespective of age. For both age groups, only the fractionation data showed a reduction in the mean latency with increasing dose. In the older age group, 39% of the responders developed a fistula compared to 26% for the younger animals. The LD(50) values increased from around 30 Gy after single doses to nearly 65 Gy after 10 fractions. The increases in LD(50) values with the number of fractions were independent of the age of the rats. For each of the dose fractionation schedules, log-rank testing indicated no significant differences in cumulative survival rates between younger and older animals (P > 0.10). The high alpha/beta ratios obtained for both the young and older animals strongly suggested that the late rectal complications were a consequence of early epithelial injury. Associated histological findings indicated that blood vessel damage, which was already evident at a high incidence at 4 weeks after irradiation, could also play a significant role in the occurrence of consequential late injuries. In conclusion, data obtained for the latent period of rectal occlusion, for the dose-effect curves, for the log-rank testing of cumulative survival rates, and for the alpha/beta ratios strongly support the hypothesis that the incidence of radiation-induced rectal complications is independent of age. Late rectal complications could be a consequence of radiation-induced acute injury.     

The radioprotective effect of extracts of Archangelica officinalis Hoffm. and Ledum palustre L. on mice

A single injection of Archangelica officinalis Hoffm. and Ledum palustre L. extracts to mice 5-15 min before irradiation with a median lethal dose increased their survival rate. The most favourable effect was produced by a combination of the two preparations: by day 30 100% of animals survived after a dose of 6 Gy (LD50/30); 70% survived after a dose of 7.5 Gy (LD90/30), and 25% after a dose of 8 Gy (LD100/12). DMF for the extract mixture was 1.48.     

16,16-Dimethyl prostaglandin E2 increases survival in mice following irradiation

16,16-Dimethyl prostaglandin E2 (DiPGE2), a stable analog of PGE2, increases the LD50/30 survival in CD2F1 male mice when given prior to ionizing radiation. Subcutaneous administration of 40 micrograms of DiPGE2 30 min prior to 60Co gamma irradiation extends the LD50/30 from 9.39 Gy in the control animals to 16.14 Gy in DiPGE2 treated, with a dose reduction factor of 1.72 [95% confidence limits: 1.62, 1.82]. The degree of protection is dependent on both the time of administration and the dose of the prostaglandin. Ten micrograms administered 5 min prior to receiving a lethal dose of 10 Gy provides 90% survival but only 10% survival if administered 30 min prior to irradiation. Experiments to determine the in vivo concentration of DiPGE2 in organs postinjection show increased levels over time, but these are not correlated with protection. At 30 min after injection, as much as 80% of the DiPGE2 present in the spleen and plasma is unmetabolized. These results suggest that the protection results from the physiologic action of DiPGE2 rather than direct in vivo detoxification of radicals.     

The gastrointestinal syndrome and mucosal clonogenic cells: relationships between target cell sensitivities, LD50 and cell survival, and their modification by antibiotics

The sensitivity of the target cells responsible for the gastrointestinal syndrome in mice was deduced from the steepness of the dose-survival curve for mice assessed on Day 7 after irradiation. The D0 value was 1.25 +/- 0.22 Gy, virtually identical to the value of 1.23 +/- 0.08 measured for microcolony-forming cells (clonogens) over about the same range of dose in concurrent experiments. The survival of clonogens was similar when assayed in mice surviving to Days 3, 4, or 5, but clonogenic sensitivity was lower when assessed on Day 7. This was shown at one dose to be due largely to a selection of mice with high colony counts with only a small contribution from crypt budding. The LD50 for mice corresponded to a surviving fraction of crypts of about 0.35. An injection of 5 mg streptomycin sulphate ip daily for 5 days after irradiation increased the latent period by about 1 day, increased the LD50 by about 1.4 Gy, but did not significantly change the survival of clonogens. These studies are the first to test and satisfy the interpretation of a dose-response curve for animal survival in terms of "target cell" survival, where measurements of both are made over a similar range of dose in concurrent experiments.     

Effect of gemcitabine on the tolerance of the lung to single-dose irradiation in C3H mice.

In an early phase II trial combining gemcitabine (dFdC) and radiotherapy for lung carcinomas, severe pulmonary toxicity was observed. In this framework, the objective of this study was to investigate the effect of dFdC on the tolerance of the lungs of C3H mice to single-dose irradiation. The thoraxes of C3H mice were irradiated with a graded single dose of 8 MV photons; dFdC (150 mg/kg) or saline (control animals) was administered i.p. 3 or 48 h prior to irradiation. Lung tolerance was assessed by the LD50 at 7-180 days after irradiation. For irradiation alone, the LD50 reached 14.45 Gy (95% CI 13.33-15.66 Gy). With a 3-h interval between administration of dFdC and irradiation, the LD50 reached 13.29 (95% CI 12.26-14.44 Gy); the corresponding value with a 48-h interval reached 13.01 Gy (95% CI 11.92-14.20 Gy). Our data also suggested a possible effect of dFdC on radiation-induced esophageal toxicity. dFdC has a minimal effect on lung tolerance after single-dose irradiation. However, a proper phase I-II trial should be designed before any routine use of combined dFdC and radiotherapy in the thoracic region.     

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)     

Cyclic nucleotides and lipids in the realization of the radioprotective effect of ceruloplasmin

Ceruloplasmin administered 60 min before irradiation diminished cAMP and cGMP levels, which were increased by irradiation at LD50 and LD100, and normalized cAMP/cGMP ratio in the rat liver during the first 24 h following irradiation with a dose of 6.24 Gy. The content of phospholipids increased and that of cholesterol decreased under the effect of ceruloplasmin leading to normalization of the molar cholesterol/phospholipid ratio in the rat liver on the 7th day of radiation sickness (LD50, 6.24 Gy).     

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.     

The effect of total body gamma-irradiation on mortality, egg production and egg weight of Japanese quails

Male and female Japanese quail 21 weeks old, that were given total body doses of 60Co gamma-rays ranging from 0 to 30 Gy, showed a peak in mortality at 6-8 days post-irradiation. The LD 50/30 was 22.5 Gy, and the LD 90/30 was 26.7 Gy. No differences were evident in mortality between males and females. The reduction in egg production by 30 days post-irradiation was related linearly to the dose, for doses above 6 Gy. The reduction in egg weight (30 days post-irradiation laying period) was also related linearly to the dose.     

Radiation protection of murine intestine by WR-2721, 16,16-dimethyl prostaglandin E2, and the combination of both agents

The survival of murine intestinal clonogenic cells (ICC) and the survival of mice after whole-body exposure to 137Cs irradiation were used to measure radiation protection by ethiophos (WR-2721), 16,16-dimethyl prostaglandin E2, and the combination of the two. Doses from 2 to 12.5 mg/mouse of WR-2721 increased cell survival linearly from 3.2 +/- 0.3 in controls given 15.0 Gy to 93.1 +/- 5.2 per jejunal circumference. In contrast, 16,16-dm PGE2 increased ICC survival at 15.0 Gy rapidly from 1 to 10 micrograms/mouse, followed by a plateau up to 100 micrograms/mouse. Animal survival at 6 days (LD50/6) increased from 16.3 +/- 0.4 Gy (95% confidence limits) in controls to 20.3 +/- 0.6 Gy in the PG-treated animals. WR-2721 increased the LD50/6 to 26.1 +/- 1.4 Gy. The dose modification factors were 1.25 and 1.60, respectively. The combination of agents increased ICC survival above that seen with each agent alone up to 8 mg WR-2721, above which no additional protection was seen. Animals given 10 micrograms PG plus 10 mg WR-2721 survived longer than with either agent given alone. The LD50/6 was 36.3 +/- 1.8 Gy for a dose modification factor (DMF) of 2.23. In addition, the slope of the probit curve was reduced from those of each agent alone. PG-induced changes in villus epithelial cell morphology and survival may account, in part, for these observations. The results suggest that either the mechanisms for these two types of radiation protectors are different or they act on separate subcellular targets which are critical to survival from radiation injury.     

Estimation of the influence of physical and biological factors on the development of the hematopoietic type of radiation sickness in dogs and two types of monkeys

In this investigation, the analysis of radiobiological experiments on 532 dogs and two types of monkeys (101 animals), irradiated totally in the 1.0 to 6.0 Gy dose range at different irradiation facilities, has been carried out. LD50 values at X-ray and gamma-neutron exposure were close to each other (2.35 and 2.83 Gy, respectively) while at gamma-radiation exposure LD(50/45) increased to 3.09 Gy. Comparison of LD(50/45) values for different kinds of animals allowed us to draw a conclusion of approximately equal radiosensitivities of dogs and Macaca fascicularis monkeys (LD(50/30-45) - 3.09 Gy and 3.17 Gy, respectively); Macaca rhesus monkeys revealed higher radioresistance (LD(50/30-45) - 5.03Gy). Analysis of the influence of several biological factors has not displayed any significant differences in the values of LD(50/45) and average lifespan of male and female dogs. Higher radiosensitivity of dogs with body weight less than 12 kg and lower radiosensitivity of dogs in summer time compared to other seasons have been shown. Dogs at the age of 2 to 3 years appeared to be more radioresistant than animals of the other age.     

Radioprotection by mangiferin in DBAxC57BL mice: a preliminary study

The radioprotective effects of various concentrations (0, 0.25, 0.5, 1, 2, 5, 10, 17.5, 25, 50, 75 and 100 mg/kg b.wt.) of mangiferin (MGN) was studied in the DBAxC57BL mice whole body exposed to 10 Gy of gamma-irradiation. Treatment of mice with different doses of MGN, one hour before irradiation reduced the symptoms of radiation sickness and delayed the onset of mortality when compared with the non-drug treated irradiated controls. The radioprotective action of MGN increased in a dose dependent manner up to 2mg/kg and declined thereafter. The highest radioprotective effect was observed at 2mg/kg MGN, where greatest number of animals survived against the radiation-induced mortality. The administration of 0.5, 1, 2, 5, 10 and 17.5 mg/kg MGN reduced the radiation-induced gastrointestinal death as evident by a greater number of survivors up to 10 days in this group when compared with the DDW + 10 Gy irradiation group. A similar effect of MGN was observed for the radiation-induced bone marrow deaths also. Our study demonstrates that mangiferin, a gluosylxanthone, present in the Mangifera indica protected mice against the radiation-induced sickness and mortality and the optimum protective dose of 2mg/kg was 1/200 of LD50 dose (400 mg/kg) of MGN. The administration of 400 mg/kg MGN induced 50% mortality, therefore LD50 of the drug was considered to be 400 mg/kg.     

Gamma-radiation-induced follicular degeneration in the prepubertal mouse ovary

Prepubertal mice were whole-body irradiated with a mean lethal dose (LD50) of gamma-radiation using a 60Co source with a total dose of 7.2 Gy and a dose rate of 12.0 cGy/min. At day 0 before the irradiation and at day 1, 2, and 3 after the irradiation, the ovaries were collected and the morphological changes were assessed. The ratios (%) of atretic or polymorphonuclear leukocytes (neutrophil)-infiltrated follicles in the largest cross sections were calculated. In the early atretic follicle of the control mouse ovary, both apoptotic and mitotic cells were observed and occasionally neutrophils were infiltrated into the follicle cavity. However, in the atretic follicles 2 days post-irradiation, numerous cell fragments, apoptotic cells and bodies, and especially, a number of neutrophils were observed. In the non-irradiated control, the ratios of atretic follicles were 58.0+/-8.6 and 27.3+/-11.2 (mean+/-S.E.M.) in antral and preantral follicles, respectively. The ratios of the number of antral and preantral follicles with one or more neutrophils to the total number of atretic follicles were 29.3+/-12.0. At 2 days post-irradiation, the ratios of atretic follicles were increased to 94.0+/-3.4 and 86.9+/-7.6 in antral and preantral follicles, respectively. The ratios of neutrophil-containing follicles among the atretic one were increased to 65.9+/-11.5 and 57.8+/-15.4 at 2 and 3 days after the irradiation, respectively. Taken together, the present results show that gamma-radiation induces apoptotic and inflammatory degeneration of mouse ovarian follicles. Besides, neutrophils may be involved in the acute atretic degeneration in gamma-irradiated mouse ovarian follicles.     

The evaluation of the radioprotective effect of Triphala (an ayurvedic rejuvenating drug) in the mice exposed to γ-radiation

The effect of 0, 5, 6.25, 10, 12.5, 20, 25, 40, 50 and 80 mg/kg b. wt. of aqueous extract of triphala (an Ayurvedic herbal medicine) administrered intraperitoneally was studied on the radiation-induced mortality in mice exposed to 10 Gy of gamma-radiation. Treatment of mice with different doses of triphala consecutively for five days before irradiation delayed the onset of mortality and reduced the symptoms of radiation sickness when compared with the non-drug treated irradiated controls. The highest protection against GI (gastrointestinal) death was observed for 12.5 mg/kg triphala, where a highest number of survivors were reported up to 10 days post-irradiation. While 10 mg/kg triphala i.p. provided the best protection as evidenced by the highest number of survivors after 30 days post-irradiation in this group when compared with the other doses of triphala. Toxicity study showed that triphala was non-toxic up to a dose of 240 mg/kg, where no drug-induced mortality was observed. The LD50 dose i.p. of triphala was found to be 280 mg/kg b. wt. Our study demonstrates the ability of triphala as a good radioprotective agent and the optimum protective dose of triphala was 1/28 of its LD50 dose.     

Radiomodifying properties of the synthetic analog of prostaglandin F2 alpha-estrofan

Estrofan (0.1 to 5 mg/kg) administered to rats and mice 5 min prior to gamma irradiation with doses of 8.5 to 9.5 Gy (LD90/30) increases the survival rate up to 30-40 per cent. The drug is ineffective when administered 30 and 60 min before irradiation.     

The radiation modifying properties of carnosine

The influence of carnosine (beta-alanyl-l-histidine) on the survival rate of albino mice subjected to whole-body X-irradiation has been investigated. Carnosine (50-200 mg/kg/day) administered per os during a period of 20 days before irradiation (5.0 Gy) increased the survival rate by 45-65%, whereas the administration of carnosine within 30 days after irradiation (5.5 Gy) produced an insignificant protective effect and caused inhibition of the postirradiation histamine accumulation in the spleen.     

Characteristics of the effect of irradiation at different dose rates on survival, death kinetics and response of critical systems of the C57Bl/6 mice]

A comparison was made of the biological effect on mice of irradiation at different dose rates (70, 5.5 and 1.5 cGy/min) with equally effective, with respect to lethality, doses, or with physically equal doses within the range from 1/4 of LD50/30 to LD99-95/30. Equally effective, with respect to lethality, doses caused similar changes in the intestinal epithelium and in the haemopoietic system. The death rate kinetics was identical with doses of LD80-95/30 within the dose-rate range under study. The equally effective doses caused injuries, different in degrees, to critical systems, including CFUs.