Modifications by BCG of the mortality of the irradiated mouse]

Freeze-dried Bacillus Calmette Guerin (B.C.G.) of Institut Pasteur was given by intravenous route to mice at 1,2 and 4 mg/kg before and after gamma irradiation of animals by 1 000 rad. B.C.G. 1 mg/kg injected the day or the day after irradiation has a protective effect (mortality reduced from 77% for controls to 58% and 50% for treated mice). B.C.G. given before irradiation in single or double doses increased mortality.     

Studies on the radiosensitivity of the function of the Golgi complex.

The uptake of 3H-glucosamine into primary human-embryo fibroblasts and into the Golgi-rich fraction isolated from liver of mice labelled in vivo was studied, after various doses of X-radiation, by autoradiography and biochemical methods. A dose of 90 rad resulted in an increased precursor uptake in interphase cells at 24 hours and in mitotic cells at 48 hours after irradiation; 226 rad had virtually no effect on the grain counts of interphase cells, but reduced the labelling of mitotic forms. The characteristic intracellular localization of the grains were not influenced by these doses. Although no immediate radiation-induced reaction could be observed in liver cells either, significant stimulation of the 3H-glucosamine incorporation was measured in isolated Golgi-rich fractions 24 hours after whole-body irradiation with 90, 450, or 905 rad. This phenomenon is discussed as a part of the somatic regeneration of membrane structures.     

Strain differences in the response of mouse testicular stem cells to fractionated radiation

The survival of spermatogonial stem cells in CBA and C3H mice after single and split-dose (24-hr interval) irradiation with fission neutrons and gamma rays was compared. The first doses of the fractionated regimes were either 150 rad (neutrons) or 600 rad (gamma). For both strains the neutron survival curves were exponential. The D0 value of stem cells in CBA decreased from 83 to 25 rad upon fractionation; that of C3H stem cells decreased only from 54 to 36 rad. The survival curves for gamma irradiation, which all showed shoulders, indicated that C3H stem cells had larger repair capacities than CBA stem cells. However, the most striking difference between the two strains in response to gamma radiation was in the slopes of the second-dose curves. Whereas C3H stem cells showed a small increase of the D0 upon fractionation (from 196 to 218 rad), CBA stem cells showed a marked decrease (from 243 to 148 rad). The decreases in D0 upon fractionation, observed in both strains with neutron irradiation and also with gamma irradiation in CBA, are most likely the result of recruitment or progression of radioresistant survivors to a more sensitive state of proliferation or cell cycle phase. It may be that the surviving stem cells in C3H mice are recruited less rapidly and synchronously into active cycle than in CBA mice. Thus, it appears that the strain differences may be quantitative, rather than qualitative.     

Cytogenetic effects of protracted gamma exposures from conception of male mice

In order to gain an overall picture of the genetic effects of an increased level of background radiation it is necessary to study the results of protracted exposures to embryonic and immature germ-cell stages as well as to stages found in the mature organism. For this purpose, litters produced by female mice, kept in a 10 or 20 rad/day ⁶⁰Co-γ-irradiation field, were kept in the same fields from conception until about 60 days later, having absorbed doses of 526 and 1078 rad respectively. Tests on exposed female offspring showed them to be sterile. 8 weeks after removal from the gamma field, mean testis masses of males in the 20 rad/day series were only half normal but those receiving 10 rad/day were little affected. Frequencies of translocations in spermatocytes at diakinesis/metaphase I were only slightly increased in the exposed series, differences not being significant. Estimated rates of translocation induction were around 5 × 10^?6 per rad, about one-third of those found after protracted γ-irradiation of stem-cell spermatogonia in the adult. Embryonic lethality in progeny of other similarly irradiated males (absorbed doses of 560 and 1040 rad), mated 2 months after removal from the radiation fields, was also increased slightly, but not significantly. Results are compared with others on the induction of chromosome aberrations and gene mutations, mainly by acute irradiation, in prenatal and neonatal male mice. It is concluded that early male germ-cell stages generally show a reduced genetic radiosensitivity after both acute and chronic exposures.     

Activation of mouse lymphocytes inhibits induction of rapid cell death by x-irradiation

A distinctive property of the resting lymphocyte is its ability to die rapidly in interphase after x-irradiation. Suspensions of thymocytes and peripheral lymphocytes from BALB/c mice were irradiated with doses ranging from 10 to 10,000 rad (0.1 to 100 Grays), and their viability was measured by eosin dye exclusion at intervals through 3 days of culture. After an initial latent period of a few hours, viability declined exponentially in a dose-dependent fashion. Doses as low as 20 rad caused some lymphocytes to die rapidly. After 1000 rad, 90% of the cells became nonviable in 15 to 20 hr and 99% in 25 to 35 hr. Peripheral lymphocytes showed a somewhat earlier loss of viability than did thymocytes, and were killed especially rapidly by 10,000 rad. Enriched T cells and B cells were killed by irradiation at equal rates, and medullary thymocytes were killed at the same rate as the whole thymocyte population. In contrast with resting cells, T and B lymphocytes activated by mitogens were not subject to such rapid induction of cell death. Irradiation with 1000 rad reduced the viability of activated cells by only 50% at a time when less than 1% of nonstimulated lymphocytes remained alive. Similarly, cloned lines of antigen-specific helper and cytotoxic T cells showed only a delayed and slow loss of viability after receiving 1000 rad. The state of activation can therefore be a significant determinant of the immunologic consequences of irradiation.     

Effects of gamma irradiation on histomorphology of some endocrine glands of the rain quail, Coturnix coromandelica (Gmelin)

Effects of single, whole-body 60Co-gamma irradiation in different doses (250 rad to 15 k rad) on histology of thyroid, adrenal and pancreatic islets of the rain quail were studied. A low dose of 250 rad failed to evoke any change in histology of the glands studied. Doses of 500 rad and 1 k rad resulted in hypoactivity of thyroid but could not affect adrenal and pancreatic islets. Exposure to 1.5 k rad and higher doses caused hyperplasia and hypertrophy of thyroid and hypertrophy of adrenal gland. Thyroid was injured by heavy irradiation. Doses up to 3 k rad did not bring about any change in islet cells, however, higher doses resulted in degenerative changes in islet cells. alpha-islets were affected by 7 and 15 k rad but necrotic changes in beta-islets were observed only after exposure to 15 k rad. The results indicate that thyroid is the most sensitive and pancreatic islet, highly resistant to gamma radiation.     

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.     

DNA damage-inducible and RAD52-independent repair of DNA double-strand breaks in Saccharomyces cerevisiae

Chromosomal repair was studied in stationary-phase Saccharomyces cerevisiae, including rad52/rad52 mutant strains deficient in repairing double-strand breaks (DSBs) by homologous recombination. Mutant strains suffered more chromosomal fragmentation than RAD52/RAD52 strains after treatments with cobalt-60 gamma irradiation or radiomimetic bleomycin, except after high bleomycin doses when chromosomes from rad52/rad52 strains contained fewer DSBs than chromosomes from RAD52/RAD52 strains. DNAs from both genotypes exhibited quick rejoining following gamma irradiation and sedimentation in isokinetic alkaline sucrose gradients, but only chromosomes from RAD52/RAD52 strains exhibited slower rejoining (10 min to 4 hr in growth medium). Chromosomal DSBs introduced by gamma irradiation and bleomycin were analyzed after pulsed-field gel electrophoresis. After equitoxic damage by both DNA-damaging agents, chromosomes in rad52/rad52 cells were reconstructed under nongrowth conditions [liquid holding (LH)]. Up to 100% of DSBs were eliminated and survival increased in RAD52/RAD52 and rad52/rad52 strains. After low doses, chromosomes were sometimes degraded and reconstructed during LH. Chromosomal reconstruction in rad52/rad52 strains was dose dependent after gamma irradiation, but greater after high, rather than low, bleomycin doses with or without LH. These results suggest that a threshold of DSBs is the requisite signal for DNA-damage-inducible repair, and that nonhomologous end-joining repair or another repair function is a dominant mechanism in S. cerevisiae when homologous recombination is impaired.     

Fluorescence study of thymus lymphocytes of X-irradiated mice and their progeny.

The mechanisms of changes in the ultra-violet fluorescence (U.V.F.) intensity of mouse thymus lymphocytes 24 hours and 30 days after whole-body X-irradiation have been studied. The thymus lymphocytes of the first generation offspring (F1) from X-irradiated males and unirradiated females were also investigated. At 24 hours after irradiation the U.V.F. intensity decreased for small doses (50 and 65 rad) and increased for doses of more than 100 rad. The changes in U.V.F. intensity were related to a size-independent mechanism. It was found that the U.V.F. increase for doses of 100-700 rad was not connected with the appearance of non-viable (eosin test) cells. The changes in U.V.F. intensity and cellular composition of the thymus were the same 30 days after irradiation and for F1 mice. The increase in U.V.F. intensity was about 14% and did not depend on dose between 50 and 500 rad. About one-half of this increase was connected with an increase in the proportion of medium and large lymphocytes in the thymus. The rest of the effect was related to a size-independent mechanism.     

Induction of lethal mutations in female mice by 9 generations of gamma-irradiation during foetal development.

Female CBA mice were chronically gamma-irradiated in utero during either of two periods, the 10th to 14th days or the 14th to 18th days of gestation. The doses administered were 34 rad/generation in the earlier group and 160 rad/generation in the latter with dose rates of 0.3 rad/h and 1.7 rad/h, respectively. The doses were given through 9 generations. The effect of the irradiation was expressed as an increased frequency in the rate of recessive lethal equivalents by just above 4%. This corresponds to a mutation rate of 1.5 X 10(-4) mutation/rad/genome in the animals irradiated during the 10th to 14th gestational days and 0.3 X 10(-4) mutation/rad/genome in the 14th to 18th day group. As in earlier investigations, neither dominant mutations nor dominance effects of induced recessive lethal equivalents were found.     

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.     

Quantitative analysis of radiation-induced changes in sperm morphology

When developing spermatogenic cells are exposed to radiation, chemical carcinogens or mutagens, the transformation in the morphology of the mature sperm can be used to determine the severity of the exposure. In this study five groups of mice with three mice per group received testicular doses of X irradiation at dosage levels ranging from 0 rad to 120 rad. A random sample of 100 mature sperm per mouse was analyzed five weeks later for the quantitative morphologic transformation as a function of dosage level. The cells were stained with gallocyanin chrome alum (GCA) so that only the DNA in the sperm head was visible. The ACUity quantitative microscopy system at Lawrence Livermore National Laboratory was used to scan the sperm at a sampling density of 16 points per linear micrometer and with 256 brightness levels per point. The contour of each cell was extracted using conventional thresholding techniques on the high-contrast images. For each contour a variety of shape features was then computed to characterize the morphology of that cell. Using the control group and the distribution of their shape features to establish the variability of a normal sperm population, the 95% limits on normal morphology were established. Using only four shape features, a doubling dose of approximately 39 rad was determined. That is, at 39 rad exposure the percentage of abnormal cells was twice that occurring in the control population. This compared to a doubling dose of approximately 70 rad obtained from a concurrent visual procedure.     

Quantitative changes in the arterial blood gases of mice following localized irradiation of the lungs

The arterial pH and partial pressures of oxygen (PaO2) and carbon dioxide (PaCO2) were evaluated in LAF 1 mice 15 and 38 weeks after localized irradiation of the animals' thoraxes. Graded radiation doses of 900 to 1200 rad were administered. These doses resulted in 0 to 100% lethality by 26 weeks (180 days) after irradiation. At 15 weeks after treatment mice receiving radiation doses which would subsequently result in lethality (by 180 days) exhibited significant reductions in their PaO2 and elevations in their PaCO2 values, respectively. However, there was no clear dose-response relationship between blood gas values and radiation dose, which may reflect the animals' ability to compensate for their poor blood gas exchange by an increased breathing frequency. At 38 weeks after irradiation the blood gas values were abnormal in mice from groups which had normal blood gas values at Week 15 (and no fatalities by Week 26) but in which animal deaths had occurred between Weeks 26 and 38. These data therefore indicated (i) that abnormal blood gas values occurred in the mice prior to fatalities resulting from the acute radiation pneumonitis syndrome and (ii) that mice surviving the initial radiation pneumonitis phase could still succumb to progressive pulmonary toxicity which was reflected by the increasing levels of animal lethality and altered blood gas tensions at the later times.     

The mutagenic effect of repeated small radiation doses to mouse spermatogonia: III. Does repeated irradiation reduce translocation yield from a large radiation dose?

Previous results had suggested that daily repeated doses of 10 rad X- or γ-rays to mouse spermatogonia decreased their sensitivity to translocation yield. This was tested by comparing the effects of a dose of 300 rad γ-rays given before, 24 h after, or 8 days after, 30 daily doses of 10 rad γ-rays to male mice. The yield of translocations per cell from those receiving the 300 rad dose 24 h after the repeated ones (7.3%) was significantly lower than that from the other two regimes (9.4 and 9.7% respectively). This was consistent with the explanation that the repeated irradiation had temporarily increased the resistance of the spermatogonial cell population to translocation yield. However, there must remain some doubt about this interpretation since the absolute values of translocations found were too high, and the yield from those which had received the 300-rad dose 24 h after the repeated ones was not significantly below the sum of those from a single dose and from repeated doses given separately.     

Dose-response curves for radiation-induced gene mutations in mouse oocytes and their interpretation

Previous work, in which female mice had been given fractionated doses of 20 X 10 rad X-rays, had confirmed and extended Russell's observations that the dose-response relationship for specific-locus mutations in mature-mouse oocytes is curved at low doses. The present work was intended to study the relationship at relatively high doses. Adult female mice were given doses of 200, 400 or 600 rad x-rays at 52 or 72 rad/min, and mated immediately. Offspring conceived in the first 7 days (i.e. using oocytes which were mature at time of treatment) were scored for specific-locus mutations. The data indicate that the departure from linearity of the dose-response curve is marginally significant at the 5% level. A quadratic dose-response curve (y = c + aD + bD2) and a square-law relationship (y = c + bD2) both give a good fit to the data. Both curves fit data of other authors obtained at low doses or dose-rates. These results could be interpreted either in terms of dose-dependent repair phenomena, or by considering specific-locus mutations as two-track events. In view of knowledge of other phenomena concerning mutation and cell killing in mouse oocytes, such as the variation in sensitivity of different cell stages, the interpretation in terms of repair phenomena is preferred.     

Radiation-resistance of the local tumor rejection response

Summary The effect of single -dose local treatment with 400 to 1600 rad of gamma irradiation on the growth of syngeneic mammary carcinoma (MC) and fibrosarcoma (FS) subcutaneous (SC) implants was investigated in female C3H/He hosts. The mice were prepared so as to present the tumor implant in various stages of growth at the time of irradiation and with the implantation site at various stages of development of the local immune rejection response. With the doses of radiation used, the growth of the tumors was, under all experimental conditions, reduced by irradiation, and the incidences of complete rejection were increased. On the basis of these observations, and supported by histological examinations, it appears that therapeutic doses of small field irradiation are unlikely to compromise a local tumor rejection response.     

Different radiosensitivities of mast-cell precursors in the bone marrow and skin of mice

Although tissue mast cells are derived from the bone marrow, some descendants of bone marrow-derived precursors retain the ability to proliferate and differentiate into mast cells even after localization in the skin. The purpose of the present study was to determine the D0 values for mast-cell precursors in the bone marrow and those localized in the skin. Bone marrow cells were removed from (WB X C57BL/6)F1-+/+ mice after various doses of irradiation and injected into the skin of the congenic W/Wv mice which were genetically without mast cells. Radiosensitivity of mast-cell precursors in the bone marrow was evaluated by determining the proportion of the injection sites at which mast cells did not appear. For the assay of the radiosensitivity of mast-cell precursors localized in the skin, pieces of skin were removed from beige C57BL/6 (bgJ/bgJ. Chediak-Higashi syndrome) mice after various doses of irradiation and grafted onto the back of the normal C57BL/6 mice. Radiosensitivity of mast-cell precursors in the skin was evaluated by determining the decrease of beige-type mast cells which possessed giant granules. Mast-cell precursors in the bone marrow were much more radiosensitive than those localized in the skin. D0 value was about 100 rad for the former and about 800 rad for the latter.     

Skin response to X-irradiation in the guinea-pig.

Skin reaction to X-irradiation has been studied in the albino guinea-pig; early response in limited-field irradiations of the flank is comparable to that commonly seen in rodents, swine and man, and is dose-dependent with a dynamic range from mild erythema to moist desquamation. The peak early skin reaction is seen between 14 and 21 days after irradiation, and declines before 30 days except at the highest doses used. Fractionation of the X-ray dose at 24 hours results in a 'sparing' of about 340 rad. Permanent partial epilation is detectable at doses in excess of 1400 rad, and complete epilation at 1 year occurs in 50 per cent of irradiated fields at 1740 rad. Twenty-four hour two-dose fractionation results in a 'sparing' of about 500 rad for epilation. Palpable dermal 'fibrosis' is detectable at 3 months after irradiation in fields given more than 2070 rad, and at 1 year after irradiation in fields given more than 1800 rad; 50 per cent of fields showed palpable 'fibrosis' at 1 year at 1930 rad. Unlike domestic swine and man, skin fields in the guinea-pig showed no dimensional contraction after X-ray doses which produced gross early skin damage.     

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.     

电子束辐照对嗜虫书虱存活与繁殖力的影响

采用电子加速器产生电子束辐照处理嗜虫书虱Liposcelis entomophila(Enderlein),分别以0、50、100、200、300、400、500、1000Gy的剂量处理成虫和若虫,观察受辐照后的存活情况和成虫的繁殖情况;以0、25、50、100、200、300、400、500Gy的剂量辐照卵,观察受辐照后卵的孵化情况。结果表明:经50Gy及以上剂量辐照后嗜虫书虱的卵不能孵化,也不能存活;在300Gy及其以上剂量经过不到8周的时间后成虫和若虫都不能存活,且在300、400、500、1000Gy的剂量范围内,嗜虫书虱成虫和若虫受辐照后的剂量越大,存活率降低幅度越大。嗜虫书虱各虫态对电子束辐照的敏感性由高至低依次为卵、若虫、成虫;经300Gy辐照后的成虫和若虫分别在8周和6周内完全死亡,300Gy的剂量可作为电子束有效防治嗜虫书虱的参考剂量。所有50Gy以上剂量下都可明显降低此种害虫的繁殖力,300Gy以上剂量的处理可导致试虫零产卵。