Mitigation of whole-body gamma radiation-induced damages by Clerodendron infortunatum in mammalian organisms

Several phytoceuticals and extracts of medicinal plants are reported to mitigate deleterious effects of ionizing radiation. The potential of hydro-alcoholic extract of Clerodendron infortunatum (CIE) for providing protection to mice exposed to gamma radiation was investigated. Oral administration of CIE bestowed a survival advantage to mice exposed to lethal doses of gamma radiation. Radiation-induced depletion of the total blood count and bone marrow cellularity were prevented by treatment with CIE. Damage to the cellular DNA (as was evident from the comet assay and the micronucleus index) was also found to be decreased upon CIE administration. Radiation-induced damages to intestinal crypt cells was also reduced by CIE. Studies on gene expression in intestinal cells revealed that there was a marked increase in the Bax/Bcl-2 ratio in mice exposed to whole-body 4 Gy gamma radiation, and that administration of CIE resulted in significant lowering of this ratio, suggestive of reduction of radiation-induced apoptosis. Also, in the intestinal tissue of irradiated animals, following CIE treatment, levels of expression of the DNA repair gene Atm were found to be elevated, and there was reduction in the expression of the inflammatory Cox-2 gene. Thus, our results suggest a beneficial use of Clerodendron infortunatum for mitigating radiation toxicity.

The in vivo Pig-a gene mutation assay is useful for evaluating the genotoxicity of ionizing radiation in mice

The in vivo Pig-a mutation assay has been adapted for measuring mutation in rats, mice, monkeys, and humans. To date, the assay has been used mainly to assess the mutagenicity of chemicals that are known to be powerful point mutagens. The assay has not been used to measure the biological effects associated with ionizing radiation. In this study, we modified the Pig-a gene mutation assay (Kimoto et al. [2011b]: Mutat Res 723:36-42) and used 3-color staining with fluorescently labeled anti-CD24, anti-TER-119, and anti-CD71 to detect the Pig-a mutant frequencies in total red blood cells (RBCs) and in reticulocytes (RETs) from X-irradiated mice. Single exposures to X-irradiation resulted in dose- and time-dependent increases in Pig-a mutant frequencies, and these subsequently declined over time returning to background frequencies. The same total amount of radiation, delivered either as a single dose or as four repeat doses at weekly intervals, increased Pig-a mutant frequencies to comparable levels, reaching maxima 2-3 weeks after the single dose or 2-3 weeks after the last of the repeat doses. These increased frequencies subsequently returned to background levels. Our results indicated that the 3-color Pig-a assay was useful for evaluating the in vivo genotoxicity of radiation.

[Radiation lesion formation and character of repair processes in the hematopoietic system of primates exposed to continuous and fractionated gamma-irradiation by equally effective doses]

The article is dedicated to comparison of the biological effectiveness of continuous and fractionated gamma-irradiation of rhesus macaques by equally effective doses. These radiation conditions are broadly used in radiobiological experiments. Specifically, they are applied in modeling radiation effects on cosmonauts during extended exploration mission. A model of radiation damage and repair on the cell, tissue and organism levels, i.e., a model of effective residual dose responsible for change in mammals' resistance to irradiation of varying duration was used to calculate equally effective doses in the experiment with primates subject to continuous and fractionated exposure. The authors publish data related to formation of radiation lesion and rate of ensuing hemopoiesis reparation. Two groups of animals were compared in resistance modification followed after testing by acute irradiation. The test was to reproduce a radiation situation for cosmonauts in the event of a cannonade of powerful solar proton events resulting in an effective residual dose of 1 Sv total The experiment evidenced close resemblance of the hemopoietic effects in primates exposed to the compared radiation conditions.

[Induction of micronuclei in peripheral blood and bone marrow reticulocytes of male mice after subchronic exposure to x-rays and bisphenol A]

BACKGROUND

Ionizing radiation and xenoestrogens are widely present in the human environment. Bisphenol A (BPA) is used to manufacture polycarbonate plastics, epoxy and polyester resins. BPA is present in a great variety of products including: baby bottles, compact disks, thermal paper, safety helmets, bullet resistant laminate, plastic windows, car parts, adhesives, protective coatings, powder paints, polycarbonate bottles and containers, the sheathing of electrical and electronic parts, dental fillings. Food and beverage cans are protected from rusting and corrosion by the application of epoxy resins as inner coatings. Human activities involving the use of radiation and radioactive materials in industry, agriculture and research cause radiation exposure in addition to natural exposure coming from cosmic rays and naturally occurring radioactive substances.

OBJECTIVE

The aim of the study was to estimate the effects of bisphenol A, X-rays and combined exposure to X-rays and bisphenol A on the induction of micronuclei in the peripheral blood and in bone marrow reticulocytes of laboratory mice.

MATERIAL AND METHOD

Pzh-Sfis male mice were exposed for 8 weeks. Animals were treated with bisphenol A diluted in drinking water (5 mg/kg bw, 10 mg/kg bw, 20 mg/kg bw), irradiated 0.05 Gy of X-rays or exposed to a combination of both (0.05 Gy + 5 mg/kg bw BPA). The samples of peripheral blood were taken at 1, 4 and 8 week following the start of exposure, whereas the bone marrow after the end of experiment, only. The induction of micronuclei in reticulocytes were evaluated by using fluorescence microscope.

RESULTS

Bisphenol A as well as ionizing radiation stimulated induction of micronuclei in peripheral blood and bone marrow reticulocytes. After the irradiation the level of micronuclei increased, whereas after exposure to BPA decreased related to time expired from beginning of experiment. Combined exposure of ionizing radiation and bisphenol A induced significantly higher frequency of micronuclei compared to the effect produced by BPA alone. The frequency of micronuclei in peripheral blood reticulocytes increased during the experiment. In all groups, the significantly lower induction ofmicronuclei in reticulocytes of bone marrow than of peripheral blood were observed. The levels ofmicronuclei in mice exposed to a combination of X-rays and BPA or to irradiation alone were slightly higher compared to those administered to BPA alone.

CONCLUSIONS

Bisphenol A induced micronuclei in peripheral blood and bone marrow reticulocytes. Subchronic BPA exposure leads to diminished sensitivity of genetic material of reticulocytes on the induction of damage. X-rays is probably the agent which decided about DNA damage following combined exposure.

Biological impact of low dose-rate simulated solar particle event radiation in vivo

C57Bl6-lacZ animals were exposed to a range of low dose-rate simulated solar particle event (sSPE) radiation at the NASA-sponsored Research Laboratory (NSRL) at Brookhaven National Laboratory (BNL). Peripheral blood was harvested from animals from 1 to 12 days after total body irradiation (TBI) to quantify the level of circulating reticulocytes (RET) and micronucleated reticulocytes (MN-RET) as an early indicator of radiation-induced genotoxicity. Bone marrow lymphocytes and hippocampal tissues from each animal were collected at 12 days and up to two months, to evaluate dose-dependent late effects after sSPE exposure. Early hematopoietic changes show that the % RET was reduced up to 3 days in response to radiation exposure but recovered at 12 days postirradiation. The % MN-RET in peripheral blood was temporally regulated and dependant on the total accumulated dose. Total chromosome aberrations in lymphocytes increased linearly with dose within a week after radiation and remained significantly higher than the control values at 4 weeks after exposure. The level of aberrations in the irradiated animals returned to control levels by 8 weeks postirradiation. Measurements of chromosome 2 and 8 specific aberrations indicate that, consistent with conventional giemsa-staining methods, the level of aberrations is also not significantly higher than in control animals at 8 weeks postirradiation. The hippocampus was surveyed for differential transcriptional regulation of genes known to be associated with neurogenesis. Our results showed differential expression of neurotrophin and their associated receptor genes within 1 week after sSPE exposure. Progressive changes in the profile of expressed genes known to be involved in neurogenic signaling pathways were dependent on the sSPE dose. Our results to date suggest that radiation-induced changes in the hematopoietic system, i.e., chromosome aberrations in lymphocytes, are transient and do not persist past 4 weeks after radiation. On the other hand, alteration in the profile of genes known to be involved in neurotrophic functions in the hippocampal tissue appears to persist for up to 8 weeks after radiation exposure. Such temporal changes confirm that, although cytogenetic changes after a single dose of low-dose and low-dose-rate protons appear to be transient, the impact of this exposure is sufficient to lead to persistent dynamic changes in neuronal tissues long after the initial radiation exposure.

Flow cytometric scoring of micronucleated reticulocytes as a possible high-throughput radiation biodosimeter

Micronucleated reticulocyte (MN-RET) scoring by flow cytometry (FCM) has been used in assessment of the clastogenic effects of chemicals. However, its dose-response to acute whole body irradiation (WBI) at moderate dose rates remains to be established. We show that FCM scoring of MN-RET in peripheral blood from male ICR mice exposed to WBI X-ray doses of 0.5-5 Gy at a dose rate of 0.488 Gy/min exhibits a linear dose-response relationship 24, 48, and 72 hr following WBI. Parallel microscopic counting of micronucleated polychromatic erythrocytes (MN-PCE) in bone marrow smears from the same animals showed similar linear dose-response patterns at the same time points. Indeed, MN-RET and MN-PCE were highly correlated at all doses and time points. In view of the speed and accuracy of this method, in addition to the small blood sample size needed for the assay, the flow cytometric protocol for MN-RET scoring may provide a minimally-invasive, high throughput radiation biodosimeter.

Validating high-throughput micronucleus analysis of peripheral reticulocytes for radiation biodosimetry: benchmark against dicentric and CBMN assays in a mouse model

Automation of radiation biodosimetry is one of the top priority tasks considered by the Office of Science and Technology Policy and the Homeland Security Council in preparation for the nation's readiness for a possible radionuclear terrorist attack. The Center for Biophysical Assessment and Risk Management Following Irradiation, a consortium of researchers and institutions centered at the University of Rochester, has been investigating automated scoring of radiation-induced micronucleus formation in reticulocytes for high-throughput radiation biodosimetry. The collaborative project is based on a commercially-available product by Litron Laboratories in Rochester, New York. The study was designed to validate the flow-cytometry based analysis of micronucleated reticulocyte expression for radiation biodosimetry by benchmarking against the standard lymphocyte-based biodosimetry methods in a mouse model. C57B1/6 mice and C3H mice were exposed to Cs total-body radiation from 0-3 Gy. Blood samples were subsequently analyzed for CD71+ micronucleated reticulocyte and reticulocyte frequencies by flow cytometry. Results showed a linear dose-response of MN-RET up to 1 Gy for C57B1/6 and 2 Gy for C3H mice. On the other hand, robust and good dose-response curves were obtained with lymphocyte-based dicentric assay and cytokinesis-block micronucleus assay up to 3 Gy. High-throughput, automated analyses of micronucleated reticulocytes is a sensitive and reproducible method for detecting recent radiation exposure. In mice, the dose range of detection is useful up to 1 Gy (C57Bl/6) and 2 Gy (C3H) but not reliable beyond these dose limits. The utilization of this automated analysis for human radiation biodosimetry is currently under investigation.

[Frequency of micronuclei in reticulocytes of male mice exposed to bisphenol A and to a combination of x-rays and bisphenol A]

The aim of the study was to estimate the effects of bisphenol A and combined exposure to X-rays and bisphenol A on the induction of micronuclei in the blood and bone marrow reticulocytes. Pzh:Sfis male mice were irradiated (0.05 Gy and 0.10 Gy) or/and treated with bisphenol A (5 mg/kg mc, 10 mg/kg mc, 15 mg/kg mc, 20 mg/kg mc, 40 mg/kg mc) or exposed to combination of both (0.05 Gy + 5 mg/kg mc BPA lub 0.10 Gy + 10 mg/kg mc BPA) for 2 weeks. Bisphenol A as well as ionizing radiation alone stimulated induction of micronuclei in peripheral blood and bone marrow reticulocytes. Combined exposure of X-rays and bisphenol A induced higher frequency of micronuclei compared to effect produced by BPA alone. Sometimes, especially after combined exposure to low doses of both agents, observed effects enhanced that obtained following exposure to X-rays alone. Ionising radiation is probably the agent which decided about damage and/or unequal distribution of chromosomes following combined exposure together with bisphenol A, which seems to be weak mutagen.

Gamma-radiation induces micronucleated reticulocytes in 3D bone marrow bioreactors in vitro

Radiation injury to the bone marrow is potentially lethal due to the potent DNA-damaging effects on cells of the hematopoietic system, including bone marrow stem cell, progenitor, and the precursor cell populations. Investigation of radiation genotoxic effects on bone marrow progenitor/precursor cells has been challenged by the lack of optimal in vitro surrogate organ culture systems, and the overall difficulty to sustain lineage-specific proliferation and differentiation of hematopoiesis in vitro. We report the investigation of radiation genotoxic effects in bone marrow cultures of C57Bl/6 mice established in 3D bioreactors, which sustain long-term bone marrow cultures. For these studies, genotoxicity is measured by the induction of micronucleated reticulocytes (MN-RETs). The kinetics and dose-response relationship of MN-RET induction in response to gamma-radiation of bioreactor-maintained bone marrow cultures are presented. Our data showed that 3D long-term bone marrow cultures had sustained erythropoiesis capable of generating reticulocytes up to 8 weeks. The peak time-interval of viable cell output and percentage of reticulocytes increased steadily and reached the initial peak between the 14th and 21st days after inoculations. This was followed by a rebound or staying relatively constant until week 8. The percentage of MN-RET reached the maximum between 24 h and 32 h post 1 Gy gamma-ray. There was a near linear MN-RET induction by gamma-radiation from 0 Gy to 1.0 Gy, followed by an attenuated increase to 1.5-2.0 Gy. The MN-RET response showed a downtrend beyond 2 Gy. Our data suggest that bone marrow culture in the 3D bioreactor may be a useful organ culture system for the investigation of radiation genotoxic effect in vitro.

Lack of DNA polymerase theta (POLQ) radiosensitizes bone marrow stromal cells in vitro and increases reticulocyte micronuclei after total-body irradiation

Abstract Mammalian POLQ (pol theta) is a specialized DNA polymerase with an unknown function in vivo. Roles have been proposed in chromosome stability, as a backup enzyme in DNA base excision repair, and in somatic hypermutation of immunoglobulin genes. The purified enzyme can bypass AP sites and thymine glycol. Mice defective in POLQ are viable and have been reported to have elevated spontaneous and radiation-induced frequencies of micronuclei in circulating red blood cells. To examine the potential roles of POLQ in hematopoiesis and in responses to oxidative stress responses, including ionizing radiation, bone marrow cultures and marrow stromal cell lines were established from Polq(+/+) and Polq(-/-) mice. Aging of bone marrow cultures was not altered, but Polq(-/-) cells were more sensitive to gamma radiation than were Polq(+/+) cells. The D(0) was 1.38 +/- 0.06 Gy for Polq(+/+) cells compared to 1.27 +/- 0.16 and 0.98 +/- 0.10 Gy (P = 0.032) for two Polq(-/-) clones. Polq(-/-) cells were moderately more sensitive to bleomycin than Polq(+/+) cells and were not hypersensitive to paraquat or hydrogen peroxide. ATM kinase activation appeared to be normal in gamma-irradiated Polq(-/-) cells. Inhibition of ATM kinase activity increased the radiosensitivity of Polq(+/+) cells slightly but did not affect Polq(-/-) cells. Polq(-/-) mice had more spontaneous and radiation-induced micronucleated reticulocytes than Polq+/+ and (+/-) mice. The sensitivity of POLQ-defective bone marrow stromal cells to ionizing radiation and bleomycin and the increase in micronuclei in red blood cells support a role for this DNA polymerase in cellular tolerance of DNA damage that can lead to double-strand DNA breaks.

Reticulocyte and micronucleated reticulocyte responses to gamma irradiation: dose-response and time-course profiles measured by flow cytometry

A flow cytometric, anti-CD71-based method was used to measure peripheral blood reticulocyte and micronucleated reticulocyte frequencies in response to (137)Cs total body irradiation (TBI). In three independent experiments, groups of five female C57BL/6N mice were irradiated at graded doses up to 3 Gy, and peripheral blood specimens were collected at 43 h post-irradiation. Whereas the frequency of reticulocytes declined over the range of doses studied, micronucleated reticulocyte incidence was observed to increase in a dose-dependent manner up to 1 Gy. At doses greater than approximately 1 Gy, micronucleated reticulocyte frequencies declined with increasing exposure. These responses were highly reproducible, with significant effects on reticulocyte and micronucleated reticulocyte frequencies observed for the lowest dose studied (0.125 Gy). A time-course experiment was performed to test whether radiation-induced cell cycle delay may explain saturation of the micronucleated reticulocyte endpoint at doses >1 Gy. For this experiment, groups of four female C57BL/6N mice were exposed to 1, 1.5, or 2 Gy TBI, and blood collection occurred at 12h intervals from 43 to 115 h post-exposure. Reduced reticulocyte frequencies were observed for each dose studied, and the recovery of reticulocytes was increasingly delayed with higher radiation doses. Maximal micronucleated reticulocyte frequencies were observed at 43 or 55 h, with progressively lower values at later time points. At no time did micronucleated reticulocyte frequencies induced by 1.5 or 2 Gy significantly exceed that observed for 1 Gy at 43 h. These time-course data suggest that radiation-induced cell cycle delay cannot account for the micronucleated reticulocyte downturn phenomenon observed at doses greater than 1 Gy. An alternate hypothesis is discussed whereby apoptotic elimination of severely damaged bone marrow erythroid precursors plays a dominant role in saturating the radiation-induced micronucleated reticulocyte response observed for C57BL/6N mice.

Effect of gamma-linolenic acid and prostaglandins E1 on gamma-radiation and chemical-induced genetic damage to the bone marrow cells of mice

The effect of gamma-linolenic acid (GLA) and prostaglandin E1 (PGE1) on gamma-radiation, diphenylhydantoin (DPH), benzo(a)pyrene (BP), and 4-alpha-phorbol-induced genetic damage to the bone marrow cells of mice, using the sensitive micronucleus (MN) test was investigated. PGE1 and its precursor GLA prevented gamma-radiation, DPH, BP, and 4-alpha-phorbol-induced genetic damage.

Proton-induced genetic damage in lacZ transgenic mice

The plasmid-based lacZ transgenic mouse model system was used to evaluate the mutagenic and genotoxic potential of 250 MeV/nucleon proton radiation by evaluating the frequency of micronucleated polychromatic reticulocytes in peripheral blood and bone marrow and the mutant frequencies of the lacZ reporter transgene in spleen and brain, respectively. Doses of 0.1-2 Gy produced dose- and time-dependent changes in the frequency of micronucleated polychromatic reticulocytes within 48 h, with peak induction up to sixfold above control levels. The frequency of micronucleated polychromatic reticulocytes returned to control levels within 1 week after exposure. With doses of 4 Gy, the elevation in the frequency of micronucleated polychromatic reticulocytes was delayed up to 1 week after exposure, but complete recovery to control levels was observed at 16 weeks postirradiation. Significant increase in mutant frequencies in brain tissue was observed at 8 week after proton exposure at doses as low of 0.1 Gy. Mutant frequencies in spleen increased up to twofold above spontaneous mutant frequencies at 8 weeks after exposure to 0.5-1 Gy. These effects appeared saturated at doses >1 Gy for both tissues, possibly due to elimination of damaged cells from the tissue systems. These in vivo results highlight the importance of considering tissue specificity, dose and temporal dependence when assessing radiation effects.

Cytotoxic and genotoxic effect of the [166Dy]Dy/166Ho-EDTMP in vivo generator system in mice

Multiple myeloma and other hematological malignancies have been treated by myeloablative radiotherapy/chemotherapy and subsequent stem cell transplantation. [(166)Dy]Dy/(166)Ho-ethylenediaminetetramethylene phosphonate (EDTMP) forms a stable in vivo generator system with selective skeletal uptake in mice; therefore, it could work as a potential and improved agent for marrow ablation. Induced bone marrow cytotoxicity and genotoxicity are determined by the reduction of reticulocytes (RET) and elevation of micronucleated reticulocyte (MN-RET) in peripheral blood and ablation by bone marrow histological studies. The aim of this study was to determine the bone marrow cytotoxic and genotoxic effect of the [(166)Dy]Dy/(166)Ho-EDTMP in vivo generator system in mice and to evaluate by histopathology its myeloablative potential. Enriched (166)Dy(2)O(3) was irradiated and [(166)Dy]DyCl(3) was added to EDTMP in phosphate buffer (pH 8.0) in a molar ratio of 1:1.75. QC was determined by TLC. Dy-EDTMP complex was prepared the same way with nonirradiated dysprosium oxide. A group of BALB/c mice were intraperitoneally injected with the radiopharmaceutical and two groups of control animals were injected with the cold complex and with 0.9% sodium chloride, respectively. A blood sample was taken at the beginning of the experiments and every 48 h for 12 days postinjection. The animals were sacrificed, organs of interest taken out and the radioactivity determined. The femur was used for histological studies. Flow cytometry analysis was used to quantify the frequency of RET and MN-RET in the blood samples. The MCNP4B Monte Carlo computer code was used for dosimetry calculations. Radiochemical purity was 99% and the mean specific activity was 1.3 MBq/mg. The RET and MN-RET frequency were statistically different in the treatment at the end of the 12-day period demonstrating cytotoxicity and genotoxicity induced by the in vivo generator system. The histology studies show that there was complete, or almost complete, acellularity, which means significant suppression of the bone marrow activity. Bone marrow absorbed dose was 18-23 Gy. [(166)Dy]Dy/(166)Ho-EDTMP induces cytotoxicity, genotoxicity and severe myelosuppression in mice. Potentially, it is a good agent for use in humans.

Analysis of micronuclei in the transferrin-receptor positive reticulocytes from peripheral blood of nasopharyngeal cancer patients undergoing radiotherapy by a single-laser flow cytometer

The automated micronucleus test is now accepted as a simple, objective, and accurate method for evaluating potential mutagenic effects caused by physical, chemical or biotic factors. This paper describes a single-laser flow cytometry, based on an immunomagnetic isolation technique in combination with acridine orange staining, to detect frequencies of micronucleated transferrin-receptor positive reticulocytes from human peripheral blood. Using this flow cytometric system, we detected the frequencies of micronucleated transferrin-receptor positive reticulocytes from 10 nasopharyngeal cancer patients undergoing radiotherapy and the baseline of the frequencies of micronucleated transferrin-receptor positive reticulocytes from 7 healthy donors. The results showed that the mean frequency of micronucleated transferrin-receptor positive reticulocytes from healthy donors was 0.236% and that from nasopharyngeal cancer patients before radiotherapy was 0.297%. After radiotherapy it was significantly elevated. When the cumulative dose of radiotherapy was about 20Gy, it reached a maximum of 6.905%, and then, as the cumulative dose of radiotherapy continued to increase to 30Gy, 40Gy and 50Gy, the frequency decreased to 6.258%, 5.119% and 5.007% respectively. Our results indicated that the single-laser flow cytometric system was quick, reasonable and acceptable for detecting the frequency of micronucleated transferrin-receptor positive reticulocytes from human peripheral blood.

Relative biological effectiveness of fission neutrons for induction of micronucleus formation in mouse reticulocytes in vivo

Following whole-body irradiation of ICR mice with various doses of fission neutrons or X-rays, the frequency of micronuclei (MNs) in peripheral blood reticulocytes was measured at 12 h intervals beginning immediately after irradiation and ending at 72 h after irradiation. The resulting time-course curve of MN frequency had a clear peak 36 h after irradiation, irrespective of the type of radiation applied and the dose used. The MN frequency, averaged as the unweighted mean over the experimental time course, showed a linear increase with increasing dose of either fission neutrons or X-rays. The linear response to X-rays supports reported conclusion that induction of MN formation in reticulocytes is a dose-rate independent phenomenon. The relative biological effectiveness (RBE) of fission neutrons to X-rays for MN induction was estimated to be 1.9 +/- 0.3. This value is considerably lower than the RBE value of 4.6 +/- 0.5 reported for the same fission neutrons for induction of lymphocyte apoptosis in the thymus of ICR mice that represents dose-rate independent, one-track event. Based on these results, we propose that MNs increased in reticulocytes after irradiation mostly represent acentric fragments caused by single chromosome breaks, and that some confounding factor is operating in erythroblasts for the formation of aberrations from non-rejoining DNA double-strand breaks more severely after high-LET radiation than after low-LET radiation.

Pilot study for comparison of reticulocyte-micronulei with lymphocyte-micronuclei in human biomonitoring

Biomonitoring tries to determine the consequences for humans of exposures to environmental or pharmaceutical agents. Different end points have been employed to assess the burden of genomic damage. This is the first report comparing a recently introduced new end point, the reticulocyte-micronuclei analyzed by flow cytometry with the widely used lymphocyte-micronucleus assay, applied to two exposure scenarios leading to enhanced genomic damage. Radioiodine therapy was chosen to represent a short time exposure and hemodialysis treatment in end-stage renal failure was chosen to represent a chronic exposure. The results show that iodine radiation induced measurable genomic damage in the lymphocyte-micronucleus assay as well as in the reticulocyte-micronucleus test. Of two groups of patients under hemodialysis treatment, a reduced genomic damage was found with the lymphocyte-micronucleus test, but not with the reticulocyte-micronucleus test in the group undergoing daily hemodialysis, which removes uremic toxins more efficiently as compared to conventional hemodialysis, the treatment applied in the other group. The limited life-span of reticulocytes may make them less suitable for accumulation of chronic low level damage than lymphocytes. In conclusion, the lymphocyte-micronucleus test may be applicable to more exposure situations (including low chronic exposure), but the reticulocyte-micronucleus assay may be easier to perform in a clinical setting. The latter reflects a more rapid reduction of genomic damage after an acute exposure.

Evaluation of DNA damage in a population of bats (Chiroptera) residing in an abandoned monazite mine

Ionising radiation has the ability to induce DNA damage. While the effects of high doses of radiation of short duration have been well documented, the biological effects of long-term exposure to low doses are poorly understood. This study evaluated the clastogenic effects of low dose ionising radiation on a population of bats (Chiroptera) residing in an abandoned monazite mine. Bats were sampled from two chambers in the mine, where external radiation levels measured around 20 microSv/h (low dose) and 100 microSv/h (higher dose), respectively. A control group of bats was sampled from a cave with no detectable radiation above normal background levels. The micronucleus assay was used to evaluate residual radiation damage in binucleated lymphocytes and showed that the micronucleus frequency per 500 binucleated lymphocytes was increased in the lower radiation-exposed group (17.7) and the higher radiation-exposed group (27.1) compared to the control group (5.3). This study also showed that bats exposed to radiation presented with an increased number of micronuclei per one thousand reticulocytes (2.88 and 10.75 in the lower and high radiation-exposed groups respectively) when compared to the control group (1.7). The single-cell gel electrophoresis (comet) assay was used as a means of evaluating clastogenecity of exposure to radiation at the level of individual cells. Bats exposed to radiation demonstrated increased DNA damage as shown by the length of the comet tails and showed an increase in cumulative damage. The results of the micronucleus and the comet assays indicated not only a statistically significant difference between test and control groups (P<0.001), but also a dose-dependent increase in DNA damage (P<0.001). These assays may thus be useful in evaluating the potential clastogenecity of exposure to continuous low doses of ionising radiation.

Effect of 60Co irradiation on characteristics of hemorheology in rabbits

A high-dose (7 Gy) whole-body 60Co irradiation for a short period caused disturbances of hematopoietic function. A decrease in the hematocrit of the circulating blood lasted for about 15 days, thus forming an anemic animal model. We studied the influence of high-dose 60Co irradiation on hemorheologic parameters: percentage of reticulocytes, RBC deformability, sedimentation rate and plasma fibrinogen concentration in the rabbit. It was found that the plasma fibrinogen concentration increased to twice more than control level and that percentage of reticulocytes in circulation disappeared immediately after irradiation. The deformation index of RBCs in shear flow decreased from a value of 58% down to a value of 42% in the first two weeks and gradually returned to control levels about 40 days after 60Co irradiation. Our results showed that a short period of high-dose 60Co irradiation caused severe and relatively long-lasting damage of hematopoietic system in animals' body.

Effect of ubiquinone-10 on the blood system in rats exposed to radiation

The use of synthetic ubiquinone-10 (2 and 10 mg/kg) as a therapeutic food additive normalized the counts of erythrocytes, reticulocytes, and leukocytes and the content of hemoglobin in the blood and inhibited lipid peroxidation in erythrocytes in irradiated rats (3 Gy).

Biologic dosimetry of bone marrow: induction of micronuclei in reticulocytes after exposure to 32P and 90Y

Bone marrow is the dose-limiting organ in targeted radionuclide therapy. Hence, determination of the absorbed dose to bone marrow from incorporated radionuclides is a critical element in treatment planning. This study investigated the potential of the micronucleus assay in peripheral blood reticulocytes (MnRETs) as an in vivo biologic dosimeter for bone marrow.

METHODS

After intravenous administration of 32P-orthophosphate or 90Y-citrate in Swiss Webster mice, DNA damage induced in bone marrow erythroblastoid cells was measured by subsequent scoring of MnRETs in peripheral blood. The response to exponentially decreasing dose rates was calibrated by irradiating animals with external 137Cs-gamma-rays. The gamma-ray dose rate was decreased exponentially, with the dose-rate decrease half-time corresponding to the effective clearance half-time (Te) of the radioactivity from the femoral bone (Te = 64 h for 90Y-citrate and Te = 255 h for 32P-orthophosphate).

RESULTS

The maximum MnRETs frequency occurred on the second and third day after injection of 90Y-citrate and 32P-orthophosphate, respectively. The same pattern was observed for exponentially decreasing dose rates of 137Cs-gamma-rays. For each type of exposure, the maximum MnRETs frequency increased in a dose-dependent manner. Using the calibrated dosimeter, the initial dose rates to the marrow per unit of injected activity were 0.0020 cGy/h/kBq and 0.0026 cGy/h/kBq for 32P-orthophosphate and 90Y-citrate, respectively.

CONCLUSION

Micronuclei in peripheral blood reticulocytes can be used as a noninvasive biologic dosimeter for measuring absorbed dose rate and absorbed dose to bone marrow from incorporated radionuclides.

Impact of p53 status on heavy-ion radiation-induced micronuclei in circulating erythrocytes

Transgenic mice that differed in their p53 genetic status were exposed to an acute dose of highly charged and energetic (HZE) iron particle radiation. Micronuclei (MN) in two distinct populations of circulating peripheral blood erythrocytes, the immature reticulocytes (RETs) and the mature normochromatic erythrocytes (NCEs), were measured using a simple and efficient flow cytometric procedure. Our results show significant elevation in the frequency of micronucleated RETs (%MN-RETs) at 2 and 3 days post-radiation. At 3 days post-irradiation, the magnitude of the radiation-induced MN-RET was 2.3-fold higher in the irradiated p53 wild-type animals compared to the unirradiated controls, 2.5-fold higher in the p53 hemizygotes and 4.3-fold higher in the p53 nullizygotes. The persistence of this radiation-induced elevation of MN-RETs is dependent on the p53 genetic background of the animal. In the p53 wild-type and p53 hemizygotes, %MN-RETs returned to control levels by 9 days post-radiation. However, elevated levels of %MN-RETs in p53 nullizygous mice persisted beyond 56 days post-radiation. We also observed elevated MN-NCEs in the peripheral circulation after radiation, but the changes in radiation-induced levels of MN-NCEs appear dampened compared to those of the MN-RETs for all three strains of animals. These results suggest that the lack of p53 gene function may play a role in the iron particle radiation-induced genomic instability in stem cell populations in the hematopoietic system.

[Radiation induced adaptation in peripheral blood reticulocytes of mice]

An in vivo micronucleus assay in mice reticulocytes of peripheral blood for identifying the possibility of induction of adaptive response to various doses of radiation: 2.5 cGy or 5.0 cGy as adapting and 50 cGy or 100 cGy as challenging doses was performed. The most effective inhibition of frequency appearance of micronucleus in RETs of mice (i.e. adaptive response) takes place et the following experimental conditions: 5.0 cGy as adaptive dose and 50 cGy challenging dose. The interval between them were 4 hours. The maximum inhibition of frequency of micronucleus was et 24 h sampling time after exposure of challenging dose. This reduction was statistically significant (p < 0.05; p < 0.01-chi square test).

[Evaluation of individual radiation resistance of rats based on reactions to non-radiation testing]

Presented are the data on radiation sensitivity of various groups of animals preliminary differentiated by their tolerance of acute hypoxia. The processes of blood forming system impairment and reparation are detailed. As was shown, highly resistant to hypoxia rats are distinguished by the best radiation resistance. Survivability of these rats was significantly higher as compared with other groups of animals. Recovery of blood formation by both the red and white chits following exposure to [symbol: see text] of the mean lethal dose proceeded more rapidly in the radiation resistant rats.

Feeding mice palm carotene prevents DNA damage in bone marrow and reduction of peripheral leukocyte counts, and enhances survival following X-ray irradiation

This study examined the effects of palm carotene feeding on DNA damage of bone marrow, recovery of peripheral leukocyte counts, and the survival of mice that received whole-body X-ray irradiation. The palm carotene was composed of alpha- and beta-carotene in a ratio of 1:3. Mice were fed either a basal diet or a carotene diet (50 mg carotene/100 g diet) for 2 weeks, then irradiated. The carotene diet was prepared by the dietary protocol that markedly enhanced the accumulation of carotene in tissues (J. Nutr. 125, 3081, 1995). DNA damage in bone marrow was evaluated by micronucleus assay using peripheral blood. When mice received X-ray (1.5 Gy), marked DNA damage in bone marrow and reduction of peripheral leukocyte count were observed. These changes were significantly attenuated in mice fed the carotene diet. In addition, X-ray (6.5 Gy)-induced survival of mice fed the carotene diet was higher than those fed the basal diet. In mice fed the carotene diet, alpha- and beta-carotene were detected in bone marrow and liver, and concentration of vitamin A in liver was about four times higher compared with that in mice fed the basal diet. These findings suggest that feeding mice palm carotene prevents radiation-induced damages by way of its antioxidant activity and/or vitamin A activity.

Radioprotection of beta-carotene evaluated on mouse somatic and germ cells

In the present paper, the protective effect of beta-carotene was evaluated after whole body exposure of mice to 2 Gy of X-rays. Splenocytes, reticulocytes, bone marrow cells and spermatids were evaluated for the frequency of micronuclei (MN) induced by X-rays. Mice were treated (gavage) with beta-carotene (10, 25 and 50 mg/kg b.w.) for 5 consecutive days and, 4 h after the last treatment, the animals were irradiated. The results obtained showed different frequencies of X-ray-induced-MN between different cell populations analysed and also different response of these cells to the beta-carotene treatment. The radioprotective effect of beta-carotene was observed in splenocytes, reticulocytes, and spermatids but not in bone marrow cells. No dose-response relationship for beta-carotene was detected. The time of sampling, the sensitivity of the cells as well as the antioxidant activity of beta-carotene are discussed as important factors for the radioprotective action of this provitamin.

The micronucleus assay using peripheral blood reticulocytes from X-ray-exposed mice

A new 'fluorescence' variant of the micronucleus assay using supravital staining of peripheral blood reticulocytes with an acridine orange coated slide was recently developed. In this study the application of this method to detect a mutagenic response to low-dose exposure of X-irradiation is reported. The mice were exposed to a single dose of 2.5, 5, 10, 15, 25, and 50 cGy. The induction of micronuclei in peripheral blood reticulocytes was recorded with sampling times of 0, 24, 48, 72, and 96 h after exposure without killing of mice. Dose-dependent effects were observed at sampling times of 24-72 h reaching maximum levels at 48 h after X-ray exposure. A highly significant (p < 0.01) increase of the micronucleated reticulocytes was found for doses of 10, 15, 25, and 50 cGy. Neither the dose of 2.5 nor 5 cGy induced the significant increase in the incidence of micronucleated reticulocytes compared with the respective control group.

Erythropoietin increases hemoglobin during radiation therapy for cervical cancer

PURPOSE

Anemia during radiation therapy independently predicts poor outcome in patients with cervical cancer. Despite a randomized trial demonstrating red cell transfusions improve local control and survival, many patients are not transfused due to toxicity concerns. This study evaluates the efficacy of recombinant human erythropoietin (r-HuEPO) in reversing anemia in patients undergoing radiation therapy.

METHODS AND MATERIALS

Twenty patients with criteria of anemia (Hgb < 12.5 g/dL) and surgically staged cervical cancer FIGO stages IB (n = 7), IIA (n = 1), IIB (n = 9), and IIIB (n = 3), ranging in ages from 23-75 years (median 43), were included in this Phase I/II study. Fifteen were treated with r-HuEPO (200 U/kg/day) and ferrous sulfate 5-10 days prior to initiation of external beam radiation therapy, continuing until Hgb was < or = 14 g/dL or completion of radiation therapy. Five patients were treated with ferrous sulfate alone. An additional 61 historical controls meeting eligibility criteria were analyzed. All received external beam radiation therapy and two intracavitary cesium applications. Cisplatinum chemotherapy (20 mg/m2/week) was given as a radiosensitizer in 14 r-HuEPO patients, 4 concurrent controls, and 17 historical controls.

RESULTS

A marked reticulocytosis was seen in the r-HuEPO group, but not the study controls. In the r-HuEPO group, the mean +/- SD serum Hgb rose + 30% over the course of radiation therapy from a baseline of 10.3 +/- 1.04 g/dL to 13.2 +/- 1.7 g/dL. Average increase in Hgb was 0.5 g/dL per week. Average Hgb during RT was 13.4 g/dL. In study and historical controls, mean initial Hgb levels were 10.7 +/- 1.04 g/dL and 11.1 +/- 1.3g/dL, respectively, remaining unchanged over the course of radiation therapy. Average Hgb levels during radiation therapy were 11.1 g/dL in study controls and 11.4 g/dL in historical controls, significantly lower than r-HuEPO patients (p = 0.0001). Erythropoietin was well tolerated. There were no significant differences in white blood counts (p = 0.6) or platelet counts (p = 0.4) between r-HuEPO patients and both control groups. No patients had blood pressure changes during r-HuEPO therapy. The only possible side effect was deep venous thrombosis, occurring in two patients who were withdrawn from r-HuEPO therapy. Two additional patients developed deep venous thrombosis 9 and 10 days after radiation therapy and r-HuEPO were completed.

CONCLUSION

Erythropoietin appears to be both safe and effective at raising Hgb levels in anemic cervical cancer patients receiving radiation therapy and chemotherapy.

Radioprotective effect of stobadine in the mouse micronucleus test

Induction of micronuclei was studied 40 h post irradiation in peripheral blood reticulocytes of male mice treated or not with stobadine dipalmitate (70.07 mg/kg body weight) at two time intervals (2 h or 1 h) prior to and immediately after 6.5 Gy 60Co exposure. A significant decrease of micronucleated reticulocytes was observed in the group of mice pretreated 2 h (P < 0.05) or 1 h (P < 0.01) before irradiation. 60Co irradiation followed by treatment with stobadine did not lead to the same protective effect in the micronucleus assay. It is therefore assumed that a radical-scavenging mechanism must be involved in radioprotection by stobadine.

[The information value of clinico-hematologic criteria for the early diagnosis of acute radiation sickness in pig-tailed macaques]

Ten pig-tailed monkeys (Macaca nemestrina) were subjected to 60Co radiation at a dose of 6.0-6.5 Gy and a dose rate of 1.2 Gy/min. Acute radiation sickness has developed in the monkeys causing their death on the 16-20 day. In spite of this, the initial reaction was weakly expressed and according to its manifestation it was impossible to evaluate severity and possible outcome of the lesion. At an early stage of the disease (6-24 hours) insufficient was uranin fluorescence in blood plasma, but more informative were the changes in adhesive properties of leukocytes the dynamics of lymphocytes (lymphopenia), reticulocytes (reticulocytopenia) and shifts in reticulograms (increased per cent of juvenile forms).

Establishment of permanent chimerism in a lactate dehydrogenase-deficient mouse mutant with hemolytic anemia

Pluripotent hemopoietic stem cell function was investigated in the homozygous muscle type lactate dehydrogenase (LDH-A) mutant mouse using bone marrow transplantation experiments. Hemopoietic tissues of LDH-A mutants showed a marked decreased in enzyme activity that was associated with severe hemolytic anemia. This condition proved to be transplantable into wild type mice (+/+) through total body irradiation (TBI) at a lethal dose of 8.0 Gy followed by engraftment of mutant bone marrow cells. Since the mutants are extremely radiosensitive (lethal dose50/30 4.4 Gy vs 7.3 Gy in +/+ mice), 8.0-Gy TBI followed by injection of even high numbers of normal bone marrow cells did not prevent death within 5-6 days. After a nonlethal dose of 4.0 Gy and grafting of normal bone marrow cells, a transient chimerism showing peripheral blood characteristics of the wild type was produced that returned to the mutant condition within 12 weeks. The transfusion of wild type red blood cells prior to and following 8.0-Gy TBI and reconstitution with wild type bone marrow cells prevented the early death of the mutants and permanent chimerism was achieved. The chimeras showed all hematological parameters of wild type mice, and radiosensitivity returned to normal. It is concluded that the mutant pluripotent stem cells are functionally comparable to normal stem cells, emphasizing the significance of this mouse model for studies of stem cell regulation.

[Effect of single 60Co whole-body irradiation on the absolute count and degree-of-maturity distribution of reticulocytes in the rat]

Wistar-rats were exposed to a single 60Co-gamma-total body irradiation with 1.5 Gy, 3.0 Gy and 4.5 Gy. The trend of reticulocyte count and the reticulocyte maturation distribution were measured with an automatic analysis system over a period of 30 days. In all animals the reticulocyte count as well as the maturation distribution showed minima at the second and the twelfth day post irradiation. The duration of the minima were dose dependent. The changes of the reticulocyte count and the maturation distribution are equivalent.

Identification of the proteins in direct contact with duck globin mRNA

Proteins in direct contact with translationally active and repressed duck globin mRNA were determined by irradiating blood or lysates with ultraviolet light. Cross-linked proteins from polyribosomes and free mRNP particles were 14C-labeled by reductive methylation and identified on SDS-polyacrylamide gels upon autoradiography. Results indicate that ten cross-linked proteins are common to both polysomal and free mRNP, however, a 44 kDa protein appears to be specific for repressed mRNP particles. Furthermore, the notable lack of cross-linked proteins in the 20-30 kDa range in free mRNP supports the view that the characteristic low molecular mass 'prosomal' proteins, previously found associated with translationally repressed duck globin free mRNP [(1984) EMBO J. 3, 29-34], do not interact directly with the mRNA molecule.

The sensitivity of an actinic reticuloid cell strain to near-ultraviolet radiation and its modification by trolox-C, a vitamin E analogue

Near-UV radiation (365 nm)-induced lethality, as measured by colony-forming ability, showed an actinic reticuloid cell strain to be sensitive relative to normal human fibroblasts, when irradiated at 25 degrees C. This effect was not seen after far-UV (254 nm) irradiation. Trolox-C, a water-soluble analogue of vitamin E, incorporated in the pre-irradiation growth medium or in the post-irradiation plating medium, protected the actinic reticuloid cells to the extent that they were as resistant as normal cells. Plating medium containing Trolox-C did not provide differential protection against inactivation of the two cell strains by wavelengths in the far-UV region. The protection provided by Trolox-C, an analogue of the natural antioxidant vitamin E, suggests some free radical involvement in the aetiology of the disease.

[Experimental study of the antimutagenic properties of 5-methylresorcinol]

A study was made of the effect of 5-methylresorcinol (5-MR) on mutagenic activity of benzo(a)pyrene (BP) and of the action of gamma-radiation in in-vitro and in-vivo systems. The induction of direct gene mutations in Chinese hamster cells V-79 and micronuclei in mouse bone marrow reticulocytes was efficiently suppressed by 5-MR treatment. The antimutagenic activity of 5-MR can be explained by inhibition of free-radical processes.

[Dynamics of changes in the number and proportion of different forms of rat peripheral blood reticulocytes during the initial days after whole body uniform irradiation by 60Co gamma quanta]

In experiments on mongrel albino male rats a study was made of the dynamics of changes in the number of peripheral blood reticulocytes and their count during the first 24 h after total-body uniform exposure to gamma-quanta (60Co, LD100/11, LD45/30, LD12,5/30 and LD0/30). After 12 and 24 h, the number of reticulocytes was shown to be a function of radiation dose. The degree of the reticulocytopenia and a change in the reticulocytograms permitted to estimate the presence of affection as well as its degree and outcome.

Virulent and nonvirulent forms of Plasmodium yoelii are not restricted to growth within a single erythrocyte type

The present studies were designed to investigate whether the erythrocyte preferences displayed by both virulent and nonvirulent forms of Plasmodium yoelii were fastidious growth requirements of these parasites. When inoculated into mice depleted of reticulocytes by lethal irradiation (900 rad), virulent parasites, which have been reported to grow predominantly in mature erythrocytes, gave rise to high parasitemias which were equivalent to those seen in unirradiated, normal mice. In addition, virulent parasites serially passaged in lethally irradiated mice showed properties of enhanced virulence upon inoculation back into normal mice. When inoculated into lethally irradiated mice, nonvirulent P. yoelii, which were reported to preferentially invade reticulocytes, invaded mature erythrocytes, and the infection progressed at a higher level of parasitemia than in unirradiated, normal mice. The inoculation of virulent parasites into mice made reticulocytemic by pretreatment with phenylhydrazine produced infections marked by the invasion of reticulocytes rather than mature erythrocytes, yet these infections remained lethal for the murine host. When nonvirulent parasites were inoculated into reticulocytemic mice, lethal infections resulted in which the parasites predominantly invaded reticulocytes. These results indicate that both the virulent and nonvirulent forms of P. yoelii possess the ability to invade and proliferate within more than one erythrocyte type and that their apparent erythrocyte preferences are not strict growth requirements.

Daily variation in radiosensitivity of circulating blood cells and bone marrow cellularity of mice

Random bred, nocturnal, male Mus musculus (DUB-ICR), on a 12/12 light/dark cycle with lights on at 6 a.m., were exposed to 100 R or 200 R of X-radiation at either noon or midnight to study diurnal radiosensitivity in circulating blood cells and bone marrow cellularity. Hematocrits, reticulocyte and white blood cell counts, daily white blood cell rhythm, and bone marrow cellularity indicate that these mice are more radiosensitive at night. At low doses it is possible that diurnal rhythms in natural, biological radioprotectors such as corticosterone may have more influence on radiation sensitivity than mitotic activity.

Amount of peripheral reticulocytes as biologic dosimetry of ionizing radiation. Experiments in the rabbit

The amount of reticulocytes in peripheral blood generally reflect the bone-marrow status of erythropoiesis and may therefore be useful in evaluating radiation injury. The blood reticulocytes in rabbits exposed to various doses of ionizing radiation were examined using an apparatus capable of microfluorometric quantification of reticulocytes as well as the conventional technique of reticulocyte count. A dose-dependent decrease of reticulocytes was observed. The possibilities of further improvements of the technique using flow cytometry and its application for screening human population are discussed.

Cyclic erythropoiesis in W/Wv mice following a single small dose of 89Sr

Young adult female W/Wv mice were given 0.5 microCi 89Sr/g intravenously, a dose which produces no anemia and only mild transient thrombocytopenia in normal mice. In the W/Wv animals platelet counts fell from 10(6) to 3 x 10(5)/mm3, and hematocrits from 39% to 25% in two weeks. In the following 2 weeks, platelet counts rose to 7 x 10(5), stabilizing at this level. Average hematocrit values were observed to oscillate from a nadir of 26% to a zenith of 42%, with a periodicity of about 16 days. In a repeat experiment we found the average hematocrit fluctuation from 28 to 40%, amplitude of reticulocyte fluctuation 6 to 31%, periodicity of cycle 16 days. Several animals have been observed through as many as six complete cycles. Further study of cyclical erythropoiesis in the W/Wv mouse following hematopoietic injury produced by 89Sr may shed light on the causes of cyclical hematopoiesis observed occasionally in man and other animals.

[Hematologic toxicity of total body irradiation (author's transl)]

Eleven patients with malignant lymphoma were treated with total body irradiation. This therapy was performed during 3 weeks with a midline dose of 70 to 100 rd. Two patients were treated two times after an internal of 3 months. The authors studied the hematologic side effects of this therapy. The irradiation caused a diminution of leucocytes of 73% of the initial value (range 16,7 to 98,4%), the neutrophilic granulocytes were reduced by 60% (24-95%), the thrombocytes were reduced by 57% (12-73%). The lowest values were seen during the fourth and sixth week of observation or one to three weeks after the end of therapy. In patients with hypoplastic anemia the number of reticulocytes was reduced to zero with a further fall of hematocrit and replacement therapy was necessary. The pool of circulating CFUc was reduced to zero in nine of twelve observations up to six weeks after therapy.

[Ultrastructure of the lymph nodes of dogs under prolonged external gamma irradiation]

The purpose of the present investigation was electron microscopy study of lymph nodes of dogs exposed to chronic gamma-irradiation during 6 years (with a total dose of 125 rad/year). The exposure induced changes in the cell composition of the paracortical regions due to a decrease of the count of small lymphocytes and a predominant increase of young blast cells with an altered ultrastructure. Chronic gamma-irradiation led to an increase of the number of plasma cells and emergence of intermediate cell forms due to "plasmatization" of lymphocytes and reticular cells.