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.     

The radioenhancement of two human head and neck squamous cell carcinomas by 2'-2' difluorodeoxycytidine (gemcitabine; dFdC) is mediated by an increase in radiation-induced residual chromosome aberrations but not residual DNA DSBs

PURPOSE: The present study aimed at investigating if 2'-2' difluorodeoxycytidine (dFdC) radioenhancement was mediated by an effect on induction and/or repair of radiation-induced DNA DSBs and chromosome aberrations in cells with different intrinsic radiosensitivity. METHODS: Confluent human head and neck squamous cell carcinoma cell lines designated SCC61 and SQD9 were treated with 5 microM dFdC for 3 or 24 h prior to irradiation. DNA DSBs induction and repair were analyzed by PFGE. Radiation-induced chromosome aberrations were examined with a FISH technique. RESULTS: In both cell lines, dFdC did not modify radiation-induced DNA DSBs in a dose range between 0 and 40 Gy. After a single dose of 40 Gy, dFdC affected neither the kinetic of repair nor the residual amount of DNA DSBs up to 4 h after irradiation. Whereas dFdC did not increase the induction of chromosome aberrations, after a single dose of 5 Gy, the percentage of aberrant cells and the number of aberrations per aberrant cells were significantly higher in combination with dFdC. CONCLUSION: Our data suggest that under experimental conditions yielding substantial radioenhancement, dFdC decreases the repair of genomic lesions inducing secondary chromosome breaks but has no effect on DNA DSBs repair as measured by PFGE.     

Comparative kinetics of the early repair of intestines and lung in mice after fast neutron and gamma-ray irradiation

Early repair (Elkind) after d(50) + Be neutron and gamma irradiation is assessed by determining the additional dose Dr necessary to reach a given biological effect when a single fraction Ds is split into 2 equal fractions 2Di separated by a time interval "i". LD50 at 180 days after thoracic irradiation is used as an evaluation of late pulmonary tolerance; LD50 at 5 days after abdominal irradiation is used as an evaluation of early intestinal tolerance. Dr is reduced but still important after neutron irradiation as compared to gamma irradiation. For LD50/180, after fast neutron irradiation Dr reaches 66, 90, 64, 162, 195, 150 cGy for "i" = 1, 2, 3, 5, 4, 12, and 24 hours respectively; after gamma irradiation, Field and Hornsey reported Dr = 390, 530, and 376 cGy for "i" = 2, 6, and 24 hours respectively; after neutron irradiation, they reported Dr = 190 cGy for "i" = 24 hours. For LD50/5, after fast neutron irradiation, Dr = 14, 45, 43, and 133 cGy for "i" = 1,5, 3,5, 5,5 and 24 hours respectively. Early repair is faster after gamma irradiation: Dr reaches a maximum for "i" = 3-4 hours. For neutrons, Dr reaches its maximum at 24 hours for both criteria.     

Vascular response to fractionated irradiation in the rat lung.

The effects of fractionated hemithorax irradiation on normal lung tissue were examined by measuring changes in the vascular permeability surface area product (PS) and relative lung blood flow in Sprague-Dawley rats. The rats received five daily fractions per week of either 3.0 or 4.0 Gy for 4 weeks to the left lung. Between 3 and 5 weeks after the start of irradiation, the average PS was approximately 50% above normal for the group of rats that received 3.0 Gy/day and 200-300% above normal in the group of rats that received 4.0 Gy/day. Treatment with cyproheptadine, indomethacin, or theophylline had no effect, but treatment with dexamethasone significantly reduced PS to near normal levels. Left-to-right blood flow ratios in the group of rats that received 3.0 Gy/day decreased to 66% of normal levels by 4 weeks. In the group of rats that received 4.0 Gy/day, blood flow decreased to 46% of normal levels by 4 weeks. Treatment with dexamethasone maintained normal blood flow until the drug dose was reduced. These results agree with earlier studies using single-dose irradiation and indicate that the methods used to measure PS and blood flow are sensitive at low doses.     

Dose-response curves for late functional changes in the normal rat brain after single carbon-on doses evaluated by magnetic resonance imaging: influence of follow-up time and calculation of relative biological effectiveness

This study investigated late effects in the brain after irradiation with carbon ions using a rat model. Thirty-six animals were irradiated stereotactically at the right frontal lobe using an extended Bragg peak with maximum doses between 15.2 and 29.2 Gy. Dose-response curves for late changes in the normal brain were measured using T1- and T2-weighted magnetic resonance imaging (MRI). Tolerance doses were calculated at several effect probability levels and times after irradiation. The MRI changes were progressive in time up to 17 months and remained stationary after that time. At 20 months the tolerance doses at the 50% effect probability level were 20.3 +/- 2.0 Gy and 22.6 +/- 2.0 Gy for changes in T1- and T2-weighted MRI, respectively. The relative biological effectiveness (RBE) was calculated on the basis of a previous animal study with photons. Using tolerance doses at the 50% effect probability level, RBE values of 1.95 +/- 0.20 and 1.88 +/- 0.18 were obtained for T1- and T2-weighted MRI. A comparison with data in the literature for the spinal cord yielded good agreement, indicating that the RBE values for single-dose irradiations of the brain and the spinal cord are the same within the experimental uncertainty.     

Radiobiological aspects of intraoperative radiotherapy (IORT) with isotropic low-energy X rays for early-stage breast cancer

The purpose of this study was to model the distribution of biological effect around a miniature isotropic X-ray source incorporating spherical applicators for single-dose or hypo-fractionated partial-breast intraoperative radiotherapy. A modification of the linear-quadratic formalism was used to calculate the relative biological effectiveness (RBE) of 50 kV X rays as a function of dose and irradiation time for late-reacting normal tissue and tumor cells. The response was modeled as a function of distance in the tissue based on the distribution of equivalent dose and published dose-response data for pneumonitis and subcutaneous fibrosis after single-dose conventional irradiation. Furthermore, the spatial distribution of tumor cell inactivation was assessed. The RBE for late reactions approached unity at the applicator surface but increased as the absorbed dose decreased with increasing distance from the applicator surface. The ED50 for pneumonitis was estimated to be reached at a depth of 6-11 mm in the tissue and that for subcutaneous fibrosis at 3-6 mm, depending on the applicator diameter and whether the effect of recovery was included. Thus lung tissue would be spared because of the thickness of the thorax wall. The RBE for tumor cells was higher than for late-reacting tissue. The applicator diameter is an important parameter in determining the range of tumor cell control in the irradiated tumor bed.     

Intestinal tolerance in mice after low dose rate 60CO irradiation. Implications for radiotherapy]

Influence of absorbed dose rate has been studied in BALB/c mice for early intestinal tolerance. After selective abdominal irradiation, LD50 at 5.5 days increases from 12.36 to 20.22 and 21.79 Gy when dose rate decreases from 0.61 to 0.054 and 0.026 Gy/mn. LD50 at 6.5 days increases from 12.05 to 19.22 and 21.58 Gy respectively. The LD50 ratios are then 1.6 and 1.8 for both endpoints. After total body irradiation. LD50 at 5.5 days increases from 9.92 to 15.20and 16.83 Gy when dose rate decreases from 0.56 to 0.049 and 0.024 Gy/mn. The corresponding LD50 ratios, i.e. 1.5 and 1.7, are then similar to the former ones. Increase of LD50 when decreasing dose rate is in agreement with that expected taking into account only repair of sublethal lesions, for the generally accepted cellular models.     

MDR1 gene transfer using a lentiviral SIN vector confers radioprotection to human CD34+ hematopoietic progenitor cells

Tumor radiotherapy with large-field irradiation results in an increase in apoptosis of the radiosensitive hematopoietic stem cells (CD34(+)). The aim of this study was to demonstrate the radioprotective potential of MDR1 overexpression in human CD34(+) cells using a lentiviral self-inactivating vector. Transduced human undifferentiated CD34(+) cells were irradiated with 0-8 Gy and held in liquid culture under myeloid-specific maturation conditions. After 12 days, MDR1 expression was determined by the rhodamine efflux assay. The proportion of MDR1-positive cells in cells from four human donors increased with increasing radiation dose (up to a 14-fold increase at 8 Gy). Determination of expression of myeloid-specific surface marker proteins revealed that myeloid differentiation was not affected by transduction and MDR1 overexpression. Irradiation after myeloid differentiation also led to an increase of MDR1-positive cells with escalating radiation doses (e.g. 12.5-16% from 0-8 Gy). Most importantly, fractionated irradiation (3 x 2 Gy; 24-h intervals) of MDR1-transduced CD34(+) cells resulted in an increase in MDR1-positive cells (e.g. 3-8% from 0-3 x 2 Gy). Our results clearly support a radioprotective effect of lentiviral MDR1 overexpression in human CD34(+) cells. Thus enhancing repopulation by surviving stem cells may increase the radiation tolerance of the hematopoietic system, which will contribute to widening the therapeutic index in radiotherapy.     

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.     

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).     

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)     

Radioprotective effect of polyethylene glycol

Polyethylene glycol of molecular weight 400 (PEG-400) had a radioprotective effect of about 20% against lethality when given ip 20 min prior to single or fractionated X-ray doses to the head and neck. Dose modification factors (DMF) based on LD50/15 values ranged from 1.14 to 1.24. A similar DMF of 1.12 based on LD50/30 values was obtained using single doses of whole-body X irradiation. Mice given head and neck irradiation had significantly reduced rectal temperatures (31.3 +/- 3.0 degrees C) 9 days post irradiation compared with unirradiated controls (35.4 +/- 0.6 degrees C). No such reduction was observed when PEG-400 was given with radiation (36.3 +/- 0.9 degrees C). PEG-400 also lessened, but not significantly, the frequency of shivering in irradiated animals. Histopathologic examination of the oral structures demonstrated only marginal protection by PEG-400. Estimation of the alpha/beta ratio from LD50 data on head and neck-irradiated mice yielded values of 4.4 +/- 1.9 (95% confidence limits) Gy without PEG-400 and 7.9 +/- 1.4 Gy with PEG-400. Since it is a non-thiol radioprotector, PEG-400 may be more useful when combined with more conventional thiol-containing radioprotectors.     

Medical-prophylactic properties of the low-molecular-weight chitosan at environmental radiation injury

The possibility of the successful modification of radiation injury by chitosan with low molecular weight (10 kDa) has been established under experimental conditions. The survival of mice increased up to 72.7 and 44.7% respectively at intravenous and intramuscular injection 30 min before gamma-irradiation with a dose 8 Gy (LD97). In guinea pigs the effect was 50-52.6% at intravenous and 40% at intramuscular administration 1-3 h after irradiation with a dose 5 Gy (LD90). Radioprotective efficiency of 10 kDa chitosan is close to that of high-molecular-weight (65-70 kDa) preceding (medicine RS-10 and RS-11).     

Bone marrow toxicity of total-body irradiation combined with radiosensitizers

The effect of the addition of radiosensitizers to low-dose total-body irradiation was studied. SR2508 (1 g/kg) or misonidazole (0.35 g/kg) was given 30 min prior to single-dose total-body irradiation, delivered at 0.1 Gy/min. Six dogs received either SR2508 or misonidazole and 2 Gy irradiation, and 14 dogs served as controls, receiving no drug and either 2 or 3 Gy of total-body irradiation. All dogs had a decline in their white blood cell and platelet counts and were supported with prophylactic antibiotics and platelet transfusions. High plasma levels of both radiosensitizers were achieved. The degree of cytopenia with 2 Gy total-body irradiation when combined with either radiosensitizer was not significantly greater than that seen with 2 Gy alone, and the neutropenia was significantly less than that seen with 3 Gy alone. The only observed toxicity of the drugs was vomiting, which started shortly after the infusion of SR2508 and before the radiation treatment. A single high-dose infusion of a radiosensitizer combined with total-body irradiation appears to cause a mild increase in bone marrow toxicity but is otherwise well tolerated.     

Determination of parameters of the survival curve of the stem cells of the intestinal crypts by LD50 and the regenerated crypt count. Determination of the RBE of p(65) + Be neutrons

The early effects of an irradiation on the intestinal epithelium have been evaluated, at the tissular level, by LD50 after single and multifraction irradiation, and, at the cellular level, by numeration of the regenerated intestinal crypts (Withers technique) after a single fraction irradiation. From the set of informations provided by both criteria, one derived the values of the parameters defining the survival curve of the intestinal clonogenic crypt cells after irradiation by gamma-rays (two component model): D0 = 1.5 Gy, 1D0 = 4.5 Gy, nD0 = 2.25 Gy and n = 20. In other respects, the p(65) + Be neutrons RBE (ref. 60-Cobalt) after a single fraction irradiation is equal to 1.75 +/- 0.2 and 1.64 +/- 0.25 for the LD50 at the 5th day and for the regeneration of 50 crypts after 3.5 days respectively.     

Genotoxicity of pemetrexed in human peripheral blood lymphocytes

Pemetrexed (PMX) is an antineoplastic antifolate used in the treatment of non-small cell lung cancer, mesothelioma and several types of neoplasms. Its toxicity in tumor cells has been linked with the potent inhibition of thymidylate synthase, dihydrofolate reductase and glycinamide ribonucleotide formyl transferase, and subsequent depletion of both purine and pyrimidine nucleotides. However, cytogenetic toxicity of PMX in non-diseased cells has not been adequately studied; despite the increasing data on the DNA-damaging potential of antineoplastic agents on normal cells. In the present study, the genotoxic potential of PMX was evaluated in peripheral blood lymphocytes obtained from healthy human subjects using chromosome aberration (CA), sister chromatid exchange (SCE) and micronucleus (MN) assays as the cytogenetic damage markers. Human peripheral blood lymphocytes were exposed to four different concentrations (25, 50, 75 and 100 μg/mL) of PMX for 24- and 48-h treatment periods. PMX significantly increased the formation of CA in 24-h treatment, but not in 48-h treatment. PMX did not increase the mean SCE frequency in 24- and 48-h treatment periods; however, there was a striking increase (although not statistically significant, p > 0.05) in the number of SCEs at 25 μg/mL (24- and 48-h treatment) and 50 μg/mL (24-h treatment) due to an increase of SCE at the single-cell level. Interestingly, PMX did not induce MN formation in either 24- or 48-h treatment periods. PMX strongly decreased the mitotic index (MI), proliferation index (PI) and nuclear division index (NDI) in 24- and 48-h treatment periods. Our results suggest that PMX has a potent cytotoxic effect against human peripheral blood lymphocytes at concentrations which are reached in vivo in the blood plasma.     

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.     

Radioprotective activity and toxicity of copolymer 2-methyl-5-vinyl pyridine with 2-methyl-5-vinylpyridinium-n-oxide

In experiments in mice, hamsters and dogs therapeutic radioprotective efficiency and toxicity of new water-soluble copolymer were studied. It was found that at intramuscular injection of the copolymer to dogs in a dose of 5 mg/kg 24 h after irradiation with a dose of 3.30 Gy (LD85/45) it showed pronounced therapeutic effect (68.1%). In mice and hamsters, the effect was less pronounced: 42-21% after irradiation with a dose of 8.0 Gy. The copolymer is low toxic substance and according to the State standards of Russian Federation belongs to the fourth class (harmless).     

Measurement of the anticancer agent gemcitabine and its deaminated metabolite at low concentrations in human plasma by liquid chromatography-mass spectrometry

A liquid chromatography/mass spectrometry (LC-MS) method has been developed and validated for the determination of the anticancer agent gemcitabine (dFdC) and its metabolite 2',2'-difluoro-2'-deoxyuridine (dFdU) in human plasma. An Oasis((R)) HLB solid phase extraction cartridge was used for plasma sample preparation. Separation of the analytes was achieved with a YMC ODS-AQ (5 microm, 120A, [Formula: see text] mm) column. The initial composition of the mobile phase was 2% methanol/98% 5mM ammonium acetate at pH 6.8 (v/v), and the flow rate was 0.2 ml/min. An isocratic gradient was used for 3min, followed by a linear gradient over 4 min to 30% methanol/70% 5mM ammonium acetate at pH 6.8. The gradient returned to the initial conditions over 2 min and remained there for 6 min. The retention times of dFdC, dFdU, and the internal standard 5'-deoxy-5-fluorouridine (5'-DFUR) were 11.46, 12.63, and 13.58 min. The mass spectrometer was operated under negative electrospray ionization conditions. Single-ion-monitoring (SIM) mode was used for analyte quantitation at m/z 262 for [dFdC-H](-), m/z 263 for [dFdU-H](-), and m/z 245 for [5'-DFUR-H](-). The average recoveries for dFdC, dFdU, and 5'-DFUR were 88.4, 84.6, and 99.3%, respectively. The linear calibration ranges were 5-1000 ng/ml for dFdC, and 5-5000 ng/ml for dFdU. The intra- and inter-assay precisions (%CV) were 相似文献   

Increasing the radioprotective therapeutic efficacy of typhoid vaccine using sexta-anatoxin in combination with the antimetabolite methotrexate]

A typhoid vaccine with sexta-anatoxin delivered to mice 4.5-5 h after gamma-irradiation has a pronounced therapeutic effect: survival rate is 42% with radiation dose of 8.2 Gy (LD85/30) and 19% with radiation dose of 8.7 Gy (LD95/30). The vaccine of 2.5 and 5 mg/kg combined with methotrexate has a more pronounced therapeutic effect increasing the survival rate up to 65% (LD85/30) and up to 35-40% (LD95/30).