Retrograde amnesia produced by electron beam exposure: causal parameters and duration of memory loss

The production of retrograde amnesia (RA) upon electron beam exposure has been investigated. RA production was evaluated using a single-trial avoidance task across a 10(4) dose range for 10-, 1-, and 0.1-microsecond pulsed exposures. The dose-response curve obtained at each pulse duration showed significant RA production. The most effective dose range was 0.1-10 rad at a dose rate of 10(6) rad/sec. By employing a 10 rad (10(6) rad/sec) pulse, a memory loss of the events occurring in the previous 4 sec was demonstrated. The conclusion was that the RA effect might be due to sensory system activation which provided a novel stimulus that masked previous stimuli.     

Effects of mixed neutron-gamma total-body irradiation on physical activity performance of rhesus monkeys

Behavioral incapacitation for a physical activity task and its relationship to emesis and survival time following exposure to ionizing radiation were evaluated in 39 male rhesus monkeys (Macaca mulatta). Subjects were trained to perform a shock avoidance activity task for 6 hr on a 10-min work/5-min rest schedule in a nonmotorized physical activity wheel. Following stabilization of performance, each subject received a single, pulsed dose of mixed neutron-gamma, whole-body radiation (n/gamma = 3.0) ranging between 1274 and 4862 rad. Performance testing was started 45 sec after exposure. A dose-response function for early transient incapacitation (ETI) during the first 2 hr after irradiation was fitted, and the median effective dose (ED50) was calculated to be 1982 rad. More subjects experienced both incapacitation and emesis in this study than has been reported for other behavioral tasks in similar radiation fields. Analysis done on the relationship of dose to ETI, emesis, and survival time found (a) a significant relationship between the radiation dose and the number and duration of ETIs; (b) no correlation between emesis and dose, survival time, or ETI; (c) no relation between survival time and ETI at any dose; and (d) no significant difference in survival time for dose groups between 1766 +/- 9 (SEM) and 2308 +/- 23 rad.     

Calculation of the dose-rate dependence of the decentric yield after Co gamma-irradiation of human lymphocytes.

The dose relation for dicentrics after in vitro Co gamma-irradiation of human lymphocytes with dose rates of 50 and 1.7 rad/min fit the linear-quadratic function y=alpha D + beta D2. Compared with 50 rad/min, after 1.7 rad/min alpha D was unchanged, whereas beta D2 was decreased by 36 percent. By applying the mean interaction time t approximate to 110 min for primary breaks, determined in an earlier experiment, and Lea's G-function, a theoretical dose relation for 1.7 rad/min can be calculated from the corresponding experimental curve. Thus, from calibration curves with conventional dose rates dose-effect curves for low dose rates can be derived without the need for time-consuming chromosome analyses.     

Life shortening in BALB/c mice following brief, protracted, or fractionated exposures to neutrons

The effects of acute, protracted, or fractionated exposures to fission neutrons on survival times of female BALB/c mice were examined and compared. Mice were given single, brief exposures or exposures given in equal fractions at either 1- or 30-day intervals to doses of 0, 2.5, 5, 10, 20, 50, and 200 rad at the Health Physics Research Reactor (HPRR) or protracted exposures at rates ranging from 0.1 to 10 rad/day using a moderated 252Cf source to doses of 0, 2.5, 5, 10, 20, and 40 rad. The 252Cf source was moderated to have a similar spectron to that of the HPRR facility. After single or fractionated exposures the extent of life shortening increased rapidly over the 0-50 rad range and then began the plateau. No simple model adequately described the dose response over this entire dose range. Over the 0-50 rad dose range for exposures at the HPRR and over the 0-40 rad dose range for protracted exposures the dose response could be adequately described by either a linear model or a square root of the dose regression model except when the dose was fractionated using a 30-day interval. In this instance a linear model provided an adequate fit while a square root of the dose model could be rejected. No increase in effectiveness after fractionation or protraction was observed for neutron-induced life shortening at doses below 50 rad, while at 50 and 200 rad an increase in effectiveness was observed in this and in previous studies. These data were interpreted to suggest that in the dose range below 20-40 rad the dose-effect curve for life shortening may be linear and begins to flatten at higher doses rather than continuously bending at low doses.     

Combined application of misonidazole and piotron pions on mouse embryos

Mouse embryos on day 8 of gestation were irradiated with negative pions (12.5-100 rad) or 200 kV X-rays (12.5-150 rad). Misonidazole (MISO), a hypoxic cell radiosensitizer, was applied 30 min before exposure. On day 13 the fetuses were examined for lethality, growth retardation and malformation. No significant embryolethal effects were observed after irradiation alone in the dose range of 12.5-100 rad (X-rays or pions). However, MISO alone and in combination with radiation led to high rates of lethality. The frequency of growth retardation was significantly increased at 100 rad and in combined treatments at low radiation doses. MISO and irradiation with 50 rad and more induced complex damages consisting of multiple and severe malformations and growth retardation. The relative biological effectiveness (RBE) for teratogenic effects was 1.6. In conclusion, the combined application of MISO and radiation of different LET revealed a strong enhancing action compared to single treatments. The extent of enhancement depends on both radiation quality and dose.     

Toxicity and mutagenicity of low dose rates of ionizing radiation from tritiated water in human lymphoblastoid cells

In order to study the toxic and mutagenic effects of low-dose-rate exposure to ionizing radiation, human lymphoblast cells were grown continuously in tritiated water (3H2O) for up to 8 days. Dose rates ranged from 0.0054 to 0.064 rad/min. Mutation to trifluorothymidine resistance (TK locus) and 6-thioguanine resistance (HGPRT locus) was measured; comparable results were observed at both loci. The mutant fraction as a function of total absorbed dose was independent of dose rate over the range studied. At the lower doses, the dose-response curve was linear, with no indication of a threshold. Overall, it appeared to be slightly biphasic with a diminished slope at higher total doses. These data are discussed in relation to earlier studies utilizing high-dose-rate X-irradiation and incorporated [3H]TdR; 3H2O and [3H]TdR were more mutagenic per rad than X-rays, but 3H2O was less cytotoxic than either X-rays or [3H]TdR.     

Effect of fractionation and rate of radiation dose on human leukemic cells, HL-60

The capacity of HL-60 cells, human acute promyelocytic leukemic cells established in culture, to repair sublethal radiation damage was estimated from the response of the cells to fractionated irradiation or to a single irradiation at different dose rates. The HL-60 cells grown as a suspension culture in RPMI 1640 medium supplemented with 10% calf serum and antibiotics showed a cloning efficiency of about 0.46 in an agar culture bed. After exposure of cells to a single dose of X rays at a dose rate of 78 rad/min, the survival curve was characterized by n = 2.5, Dq = 80 rad, and D0 = 83.2 rad. Split-dose studies demonstrated that the cells were able to repair a substantial portion of sublethal radiation damage in 2 hr. The response of the cells to irradiation at different dose rates decreased with a decrease in the dose rates, which could be attributed to repair of sublethal radiation damage. The radiation response of leukemic cells is only one of the many factors which affect the clinical outcome of total-body irradiation (TBI) followed by bone marrow transplantation. Nevertheless, the possibility that some of the malignant hemopoietic cells, if not all, may possess a substantial capacity to repair sublethal radiation damage should not be underestimated in planning total-body irradiation followed by bone marrow transplantation.     

Cytogenetic effects of fractionated or unfractionated X-ray exposures to mouse spermatogonia

The induction of chromosomal aberrations in mouse spermatogonia was studied, after single (50 and 100 rad) and fractionated doses (50 + 50 rad spaced 24 h apart), a short time after irradiation, by analysis of mitotic stages. From 17 to 21 h after the second fraction of the dose, the recorded frequencies of chromosomal deletions and exchanges were fully additive when compared with single “control” doses. Thus there was no suggestion of any sensitization effect of the first exposure. Possible reasons for this are discussed.     

Influence of X-ray dose fractionation on the frequency of somatic mutations induced in tradescantia stamen hairs

X-rays were used to investigate the influence of dose fractionation on the induction of pink and colorless somatic mutations in stamen hair cells of Tradescantia clone 02. Inflorescences were exposed to a single acute dose of 60 rad, two acute doses of 30 rad, or three acute doses of 20 rad. The dose rate in all cases was 30 rad/min. Intervals between dose fractions were varied from 35 sec to 48 h and the mutation frequency was compared with that resulting after the single dose of 60 rad. The data show a reduction in mutation frequency for fractionation intervals longer than 15 and 6 min for pink and colorless mutations, respectively, but not for shorter intervals.One interpretation of the data predicts that pink mutation frequencies are reduced by 11% for fraction intervals of from 30 min to 6 h, and that colorless mutation frequencies are reduced by 24% for intervals of from 15 min to 6 h. The corresponding sparing effect of dose fractionation is equal to 6 rad for pink mutations and 9 rad at the colorless mutation endpoint. A calculation has been made which indicates that the percentages of the total repairable (presumably two-hit) damage that is repaired during fraction intervals up to 6 h, are 16 and 35% for pink and colorless mutations respectively.     

Chromosome rearrangements from spermatogonial chronic neutron irradiation in mice.

Adult male mice were given a range of neutron doses at 80 +/- 20 mrad/h from a plutonium-beryllium source. Cytogenetic analysis indicated that chronic spermatogonial exposure to a mean total dose of 10, 30, 52, 98 or 150 rad produced translocations, sampled in spermatocytes four months later, amounting to 0.32, 0.99. 1.69, 1.91 and 1.65%, respectively. The dose response for the 0-52 rad range was linear. For higher doses, a better fit to the data was an expression with dose exponent above unity.     

RBE/absorbed dose relationship of d(50)-Be neutrons determine for early intestinal tolerance in mice]

RBE/absorbed dose realtionship of d(50)-Be neutrons (ref.: 60Co) was determined using intestinal tolerance in mice (LD50) after single and fractionated irradiation. RBE is 1.8 for a single fraction (about 1000 rad 60Co dose); it increases when decreasing dose and reaches the plateau value of 2.8 for a 60Co dose of about 200 rad. This RBE value is used for the clinical applications with the cyclotron "Cyclone" at Louvain-la-Neuve.     

Effects of bremsstrahlung and electron radiation on rat motor performance

Relatively high, rapidly delivered doses of ionizing radiation have been reported to produce an immediate decrement in performance (PD) in a number of animal species. This study investigated the effects of bremsstrahlung and electron radiation on the performance of rats unilaterally exposed by a linear accelerator (LINAC facility) at a midline tissue dose rate of 2000 rad/min. Relative radiation effects were determined by establishing median effective doses (ED50) for rats trained on the accelerod, which is a shock-avoidance test of motor performance. The ED50s were based on 10-min postexposure performance. Subjects were also tested at 15, 30, 60, and 120 min and 24 hr after exposure. Fifty-seven trained rats were exposed to bremsstrahlung radiation, and 40 trained rats were exposed to electrons. The ED50 was 8121 rad for the bremsstrahlung field and 6110 rad for the electron field, for a significantly different relative effectiveness of the electron field in producing PD of 1.35. The data imply that different radiation fields are not equally effective in producing PD.     

Dose-rate effects of 8-methoxypsoralen plus 365-NM irradiation on cell killing in Saccharomyces cerevisiae.

Tow types of dose-rate effect that alter the survival response of haploid yeast cells to 8-methoxypsoralen (8-MOP) plus treatment with irradiation at 365 nm were studied. (1) When the concentration of 8-MOP was varied between 9.2 X 10(-5) and 2.3 X 10(-8) M and the dose rate of 365-nm irradiation kept constant, the efficiency of the irradiation for killing increased relatively to that of 8-MOP whe the concentration of 8-MOP decreased. This indicated that there was no strict reciprocity between radiation dose and concentration of drug. (2) When the dose rate of radiation was varied between 0.66 X 10(3) and 108 X 10(3) J m-2 h-1 and the concentration of 8-MOP was kept constant, the survival of wild-type cells increased strikingly at low dose rates of radiation as compared with high dose rates. Cells responded more to changes at low dose rates than to equal changes a high dose rates. The high resistance of wild-type cells to 8-MOP plus radiation delivered at low dose rates absent from rad 1-3 cells defective in excision-repair. This suggests that the dose-rate effect seen in wild-type cells depended at least in part on an active excision-repair function. At low dose rates of radiation, the shoulder of the survival curve for rad1-3 cells, i.e. the ability to accumulate sub-lethal damage, was increased by a factor of about 2 when compared with that seen at a high dose rate. Thus it is likely that at low dose rates a repair function other than excision-resynthesis may operate in rad1-3 cells.     

The rate of progression of radiation-transformed mammary epithelial cells is enhanced after low-dose-rate neutron irradiation

Studies in this laboratory have shown enhancement of the mammary tumorigenic effects of neutron irradiation after low-dose-rate neutron exposures. To investigate possible reasons, a mammary cell system was used which allows quantitation of initiated mammary epithelial cells and examination of the progression of these radiation-altered cells toward the neoplastic phenotype. Female BALB/c mice were irradiated with fission-spectrum neutrons at dose rates of 1 rad/min or 1 rad/day. Twenty-four hours or 16 weeks after irradiation, mammary cells were obtained by enzymatic dissociation. Mammary outgrowths were derived by injection of 10(4) cells into gland-free fat pads of 3-week-old female BALB/c mice. The frequency of ductal dysplasias in outgrowths from cells irradiated at high or low dose rates was similar. Persistence of dysplasias differed markedly. Few of the dysplasias in outgrowths derived from cells irradiated at the high dose rate persisted, while a large fraction of the dysplasias in outgrowths derived from cells irradiated at low dose rate persisted. When cells remained in situ for 16 weeks prior to dissociation a higher frequency of persistent altered cells was also observed in outgrowths derived from cells irradiated at low neutron dose rates. These data suggest that low-dose-rate neutron exposures enhance the probability of progression of carcinogen-altered cells rather than increase the numbers of initiated cells.     

Dose—response relationship for X-ray-induced reciprocal translocations in stem-cell spermatogonia of the rhesus monkey (Macaca mulatta)

The induction of reciprocal translocation in stem-cell spermatogonia of the rhesus monkey (Macaca mulatta) was studied after testicular X-irradiation of mature males (50, 100 and 200 rad) or whole-body irradiation of young males (200 and 300 rad). After the recovery of the germinal epithelium, cytogenetic analysis was carried out on spermatocytes descended from irradiation spermatogonia. Preparations of C-banded diakinesis-metaphase I were screened for translocation configurations. The frequencies of abberations obtained were 0% at 0 rad, 0.36% at 50% rad, 0.86% at 100 rad, 0.99% at 200 rad and 0.68% at 300 rad, suggesting a humped dose—response relationship. There was no evidence for the contribution of a quadratic component to the yield in the lower dose range. A comparison of these results with those obtained for other mammals by a number on investigators shows that the frequencies of translocations in the rhesus monkey are much lower than those published for most other mammalian species.     

Tumor induction in BALB/c female mice after fission neutron or gamma irradiation

This study was designed to examine the dose-response relationships for tumor induction after neutron irradiation in female BALB/c mice, with emphasis on the response in the dose range 0 to 50 rad. Tumors induced after radiation exposure included ovarian tumors, lung adenocarcinomas, and mammary adenocarcinomas. For comparison the dose responses for induction of these tumors after 137Cs gamma irradiation were also examined. As previously described for the female RFM mouse, the data for ovarian tumor induction after neutron and gamma irradiation were consistent with a threshold model. For lung and mammary tumors the dose-response curve after neutron irradiation appeared to "bend over" in the dose range 10 to 20 rad. The factors responsible for this bend-over and their relative contributions to the overall form of the dose-response relationship are not presently known. However, these data strongly indicate that extrapolation from data above 50 rad could result in a significant underestimate of risks. Further, it is clear that current models of neutron carcinogenesis are inadequate, since such a bend-over is not predicted at these low dose levels.     

Effect of dose rate on the induction of experimental lung cancer in hamsters by alpha radiation

The effect of dose rate on the induction of lung cancer in Syrian hamsters by 5.3 MeV alpha particles was examined by varying the number of weekly intratracheal instillations of carrier-free 210Po. By this technique, most of the radiation dose to the lungs was delivered over intervals ranging from 10 to 120 days. Protraction of exposure over 120 days was slightly more carcinogenic at lower total lung doses (24 rad), but slightly less carcinogenic at higher doses (240 rad), than exposure limited to a 10-day interval. No synergism was observed between very low radiation exposures (2.4 rad) and simultaneously administered benzo[a]pyrene. The carcinogenic effect of a single intratracheal instillation of 210Po in isotonic saline was markedly enhanced by subsequent weekly instillations of 0.2 ml of saline alone, emphasizing the importance of noncarcinogenic secondary factors in the expression of radiation-induced lung cancer.     

Occupational Exposure to Hydrazine and Subsequent Risk of Lung Cancer: 50-Year Follow-Up

Purpose

Hydrazine is carcinogenic in animals, but there is inadequate evidence to determine if it is carcinogenic in humans. This study aimed to evaluate the association between hydrazine exposure and the risk of lung cancer.

Methods

The cause specific mortality rates of a cohort of 427 men who were employed at an English factory that produced hydrazine between 1945 and 1971 were compared with national mortality rates.

Results

By the end of December 2012 205 deaths had occurred. For men in the highest exposure category with greater than two years exposure and after more than ten years since first exposure the relative risks compared with national rates were: 0.85 (95% CI: 0.18–2.48) for lung cancer, 0.61 (95% CI: 0.07–2.21) for cancers of the digestive system, and 0.44 (95% CI: 0.05–1.57) for other cancers.

Conclusions

After 50 years of follow up, the results provide no evidence of an increased risk of death from lung cancer or death from any other cause.     

倍频Nd：YAG激光对紫球藻生长与胞外多糖产量的影响

紫球藻经Nd:YAG激光（波长1060nm)照射,以不同时间设置处理剂量,比较紫球藻细胞活力,生长速率,生物量,胞外多糖产量等方面的变化。高剂量处理组（Y-20、Y-30和Y-40）致死率为17-44%,继代培养后生长迅速,K值分别比对照组提高18%、23.4%和15.3%,各处理组培养10天后收获的生物量与对照组无显著差异,但胞外多糖产量均有较大幅度提高,增幅达50-150%。此外,YAG激光照射对藻细胞叶绿素含量也有影响,YAG激光有望成为紫球藻优良藻株选育的较佳诱变剂。     

Haematocytometrical changes in chicken blood to acute 60Co gamma radiation

Newly hatched white leghorn chicks (Gallus domesticus) subjected to single whole body 2.25 Gy (225 rads) gamma radiation exposure at the dose rate of 0.50 Gy/sec (50 rads/sec), were studied for changes in a number of haematological parameters at days 1,3,5,7,14 and 28 post irradiation during development. The sudden decline and gradual recovery in total RBC and WBC counts and the level of Hb and Hct along with MCV, MCH and MCHC values evaluation indicates a high regenerative capability of leghorn chicks.