Effects of radiation on host-tumor interactions using the multicellular tumor spheroid model

Summary Use of the multicellular tumor spheroid as a tumor model allows separate host or tumor treatment with ionizing radiation and examination of the effects on host-tumor immune interactions. Spheroids of EMT6/Ro, a BALB/c mammary tumor were implanted into the peritoneal cavity of syngeneic immunized mice, recovered, and dissociated into single cells. Cytolytic activity of mature spheroid associated cells and peritoneal cells was resistant to radiation doses as high as 1000 rads when irradiated directly prior to assay. Mice irradiated (200, 400, 700 rads) 24 h prior to spheroid injection had an increased number of tumor cells and decreased number of tumor infiltrating and peritoneal host cells upon spheroid recovery. This was paralleled by an increased colony forming efficiency per spheroid. Cytolytic activity of the spheroid associated cells against radiolabeled EMT6 cells was in many cases decreased with radiation although lysis was the same on a per cell basis. Cytolytic activity by peritoneal cells from these mice increased with dose as measured on a per cell basis. This activity from irradiated animals was carried out by a Thyl⁺ cell.     

The RBE for skin tumors and hair follicle damage in the rat following irradiation with alpha particles and electrons

Rat skin was irradiated with cyclotron-accelerated alpha particles with doses ranging from 210 rads to 6850 rads and monoenergetic electrons with doses ranging from 810 rads to 12,300 rads. The beams were modified so that the depth-dose curves were approximately identical with penetrations of about 1.0 mm. Tumors were counted every 4 weeks for 80 weeks, and at death or sacrifice the hair follicle damage was assessed by using "whole mounts" of separated epithelium. The RBE values determined from a comparison of the dose response curves were: acute skin injury, RBE = 3.0+/-1.0; hair follicle survival, RBE = 2.1 +/- 0.7; hair follicle damage, RBE = 2.6 = 0.4; tumor induction, RBE = 2.9+/- 0.5. Within the experimental error, these values were independent of the dose. For both types of radiation, the tumor incidence increased approximately as the square of time and at low doses approximately as the 4th power of dose. The histological characteristics of the tumors and the correlation between the incidence of tumors and damaged hair follicles were independent of the type of radiation. The results were consistent with the hypothesis that structural damage to the hair follicles is a factor in the tumor induction process.     

The effect of delay on flap survival in an irradiated field

Chronic radiation skin injury without ulceration was induced in rats by administering either 3000 or 5000 rads in staged doses. Either 4 or 8 months later, McFarlane et al. dorsal flaps were elevated, with half being delayed and half non-delayed. Measurements showed that flap survival in irradiated skin was significantly increased by delay [approximately two of four experimental groups (4 months, 5000 rads; and 8 months, 3000 rads)]; flap survival was increased with borderline significance in a third experimental group (8 months, 5000 rads). These data indicate that flap survival can be increased by delay in an irradiated field. The presence of the vascular delay phenomenon suggests that microvascular occlusion alone cannot account for radiation-induced complications in skin.     

Regeneration of CFUs in the marrow of mice exposed to 300 rads after having recovered from 950 rads.

Exposure to 950 rads 60Co radiation has been reported to cause long-lasting damage to the hematopoietic stroma (HS), although the size of the CFUs population recovers to pre-irradiation levels. In these studies HS damage was detected only after subcutaneously implanting the femurs of the irradiated mice into syngeneic hosts. To exclude the possibility that what was considered to be HS damage was merely caused by artifacts due to the process of implantation in a new host, we compared the rate of regeneration of CFUs in mice which had recovered from 950 rads prior to receiving 300 rads 60Co radiation (950 + 300 rads group) with that of mice which received only 300 rads (0 + 300 rads group). The CFUs population in the 950 + 300 rads group grew exponentially for 2 weeks at a rate which did not differ significantly from that of CFUs in the 0 + 300 rads group. However, the rate of CFUs growth reached a plateau before full recovery was achieved in contrast to that in the 0 + 300 rads mice. We therefore conclude that the incomplete regeneration of CFUs in the marrows of 950 + 300 rads mice was most likely caused by X-irradiation-induced damage to the HS rather than damage to the inherent repopulating potential of the CFUs per se.     

Effects of gamma irradiation on the development of Trypanosoma rangeli in the vector Rhodnius prolixus

Studies on the effects of gamma radiation on the infectivity of Trypanosoma rangeli (strain H14) for the vector Rhodnius prolixus revealed that (i) the LD(50) (lethal dose for 50% of bugs) for uninfected insects was 4147 rads; (ii) irradiated insects with a dose of 1200 rads subsequently infected with the flagellates exhibited a mortality of 45%, while uninfected irradiated insects showed a mortality of 5%, and infected nonirradiated insects exhibited 10% mortality; (iii) flagellates were present in the hemolymph of irradiated insects 7 days postinfection (p.i.), while in nonirradiated insects the parasites appeared in the hemocoel 18 days p.i.; (iv) T. rangeli infection decreased the number of hemocytes significantly and induced the formation of nodules in the hemolymph of both irradiated and nonirradiated insects; and (v) gamma irradiation affected the ultrastructural organization of the epithelial cells of the small intestine, principally the perimicrovillar membranes and microvilli. In this paper, we discuss the significance of the intestinal microenvironment of R. prolixus with regard to its interaction with T. rangeli.     

REGENERATION OF CFUs IN THE MARROW OF MICE EXPOSED TO 300 RADS AFTER HAVING RECOVERED FROM 950 RADS

Exposure to 950 rads ⁶⁰Co radiation has been reported to cause long-lasting damage to the hematopoietic stroma (HS), although the size of the CFUs population recovers to pre-irradiation levels. In these studies HS damage was detected only after subcutaneously implanting the femurs of the irradiated mice into syngeneic hosts. To exclude the possibility that what was considered to be HS damage was merely caused by artifacts due to the process of implantation in a new host, we compared the rate of regeneration of CFUs in mice which had recovered from 950 rads prior to receiving 300 rads ⁶⁰Co radiation (950 + 300 rads group) with that of mice which received only 300 rads (0 + 300 rads group). The CFUs population in the 950 + 300 rads group grew exponentially for 2 weeks at a rate which did not differ significantly from that of CFUs in the 0 + 300 rads group. However, the rate of CFUs growth reached a plateau before full recovery was achieved in contrast to that in the 0 + 300 rads mice. We therefore conclude that the incomplete regeneration of CFUs in the marrows of 950 + 300 rads mice was most likely caused by X-irradiation-induced damage to the HS rather than damage to the inherent repopulating potential of the CFUs per se.     

Effect of neutron and gamma radiation on physical endurance of rats in the swimming test

Three groups of adult male Wistar rats were exposed to neutrons (a single dose of 2 Gy) and gamma radiation (a continuous dose of 6 Gy delivered within 10.5 days) and a combination of both types of radiation. The physical fitness of irradiated and control rats was measured using a forced swimming test in the course and after the termination of the irradiation. A marked decrease in the physical fitness of all irradiated animals was followed by its normalization 3 weeks after irradiation.     

The effects of ultraviolet-B radiation and intraspecific competition on growth, pollination success, and lifetime female fitness in Phacelia campanularia and P. purshii (Hydrophyllaceae)

While a considerable amount of attention has been devoted to the effects that increased ultraviolet-B (UV-B) radiation has on vegetative plant growth and physiological function, the impact that UV-B may have on plant fitness has been the focus of fewer studies, with attention given primarily to a few crop species. Further, the possible interactions between UV-B and additional potential stresses found in natural environments have rarely been studied experimentally. Because the reported effects of increased UV-B on plant growth and fitness have been highly variable, studies that focus on factors that may lead to these differences in results are important for the formulation of accurate predictions about future plant success under varying UV-B levels. We examined the effects of UV-B dose and intraspecific competition on growth, phenology, pollen production, pollination success, fruit and seed production, and offspring quality in two species of Phacelia. Increased UV-B was neutral or beneficial for all traits, while competition was neutral or detrimental. There were no significant interactions between UV-B and competition in the parental generation. Phacelia campanularia offspring were unaffected by parental competition, but derived indirect beneficial effects on germination, growth, and fitness traits from parental enhanced UV-B.     

Attractiveness and competitiveness of irradiated light brown apple moths

The sterile insect technique (SIT) potentially provides a socially acceptable approach for insect eradication of new pest incursions. The light brown apple moth, Epiphyas postvittana (Walker) (Lepidoptera: Tortricidae), was discovered in Berkeley (CA, USA) in 2006, leading to an incursion response that included this technology. In this study, we assessed factors affecting mating success from a bisex release of irradiated moths: effects of radiation dose on male multiple mating, male flight competition, female sex pheromone titre and attractiveness of irradiated females to males, and identification of successful mating in vineyards of either irradiated or wild males (identified by isotope analysis of spermatophores from sentinel females). There was a significant negative relationship between male radiation dose and mating frequency. In head‐to‐head flights of irradiated males against non‐irradiated males to a pheromone lure in a wind tunnel, irradiated males reached the lure first only 31% of the time. With increasing radiation dose, the production of the major sex pheromone component in females, (E)‐11‐tetradecenyl acetate, dropped, from 0.7 ± 0.1 ng per female in non‐irradiated females to 0.2 ± 0.07 ng per female when irradiated at 300 Gy. Male catch was reduced to 11% of control females in traps containing females irradiated at 300 Gy. Isotope analysis of spermatophores found in the bursa copulatrix of females indicated that mating success of irradiated males inside the live (entry‐only) traps containing virgin females was lower (13.1 ± 3.3%) than suggested by male catch (21.2 ± 3.8%) in pheromone traps, the current standard for assessing field competitiveness. Impacts of irradiation on male and female moth fitness should be taken into account to improve estimates of irradiated to wild male E. postvittana overflooding ratios needed for population suppression.     

Konformationsänderungen vor und nach DNA-synthese verstärken zellgenetisch letale strahlenschäden

Chinese hamster ovary fibroblasts were synchronized by mitotic selection and showed cytogenetic lethally acting radiation damages, which depended on age at irradiation time. The development of cell cultures was followed by counting of the killed cells in the 3rd daughter generation of the irradiated ones and by evaluation of the colony size spectra 73.5 h after innoculation. At a dose of 300 rads two narrow but high peaks of radiation sensitivity were induced, which appeared at the beginning and at the end of the S-phase of the cell cycle and therefore are reduced to conformation changes of the DNA. Consequently the DNA-super-structures linking pieces of the nucleoprotein-fibre during fastening to, and detaching from, the nuclear membrane are assumed to be the loci of the increased radiation sensitivity.     

Patterns of Microsatellite Variability in the Drosophila Melanogaster Complex

Forty-seven microsatellite loci were amplified in Drosophila melanogaster, Drosophila simulans, Drosophila mauritiana and Drosophila sechellia. The two cosmopolitan species D. melanogaster and D. simulans were found to be the most variable ones, followed by D. mauritiana and D. sechellia. A model based clustering algorithm was applied to the population samples of D. melanogaster, D. simulans and D. sechellia. No evidence for population substructure was detected within species--most likely due to insufficient power. A Markov chain Monte Carlo method developed for demographic inference based on microsatellites provided unambiguous evidence for population contraction in D. melanogaster, D. simulans and D. sechellia, despite that the D. melanogaster and D. simulans population samples were of non-African origin and represented recently expanded populations.     

Effect of ionizing radiation on DNA synthesis in ataxia telangiectasia cells.

The effect of ionizing radiation on DNA synthesis in control and ataxia telangiectasia (AT) lymphoblastoid cell lines was determined. A dose dependent decrease in DNA synthesis was observed in control cells, and the rate and extent of thi decrease in synthesis increased with time after irradiation. No decrease in DNA synthesis was obtained in AT cells, immediately following irradiation, at doses up to 400 rads. At longer times postirradiation, inhibition of synthesis increased but the extent of inhibition was less in AT cell than controls at all doses used. An immediate depression of DNA synthesis was evident in control cells after a radiation dose of 200 rads reaching a maximum at 90 min postirradiation. Little or no decrease in DNA synthesis was evident in AT cells up to 60 min after the same radiation dose, but a decrease occurred between 60 and 90 min after irradiation. The rate of recovery of DNA synthesis to normal levels was more rapid in AT cells than in controls.     

Multiple fluoroscopy of the chest: carcinogenicity for the female breast and implications for breast cancer screening programs.

The risk of radiation carcinogenesis has been established for breast tissue from experience with total body irradiation and multiple fluoroscopy of the chest with the patient prone. The doubling dose has been estimated to lie between 20 and 50 rads. Before undertaking radiologic screening programs for breast cancer, therefore, it is necessary to determine whether exposures below this range are safe. Of 792 women who had had tuberculosis and were followed for a minimum of 20 years, 451 had had multiple fluoroscopy while supine; 341 had not had fluoroscopy. The first group received a total radiation dose to the breast averaging 17 rads (141.5 fluoroscopies); the incidence of breast cancer in this group was not increased. Had fluoroscopy been performed with the patient prone the total radiation dose would have averaged 308 rads. The difference is thought to explain the increased incidence of breast cancer attributable to fluoroscopy given with the patient prone. Mid-breast exposure with mammography or xeroradiography varies between 3 and 6 rads. Repetitive screening would, therefore, appear safe provided total exposure did not exceed 20 rads. With this restriction there would appear to be no reason to curtail screening of women for breast cancer.     

An introgression approach to mapping differences in mating success and sperm competitive ability in Drosophila simulans and D. sechellia

The progeny of Drosophila females doubly-mated to males from the same and a closely related species are mostly sired by conspecific males. We examined the genetic basis for conspecific mating preference and sperm precedence by using 186 Drosophila lines in which random chromosomal fragments of D. sechellia were introgressed into D. simulans. Sperm competition was measured for each of these lines by crossing ebony D. simulans female with ebony D. simulans males followed by wild-type males from the introgressed lines. Variation in sperm competition (proportion of progeny sired by the second male), mating discrimination (proportion of introgressed males that failed to remate), and male fecundity (proportion of progeny sired by introgressed males) were scored. The introgressed lines exhibited highly significant heterogeneity in the three phenotypes scored, motivating an analysis to locate quantitative trait loci (QTLs) responsible for the differences. Applying composite interval mapping, we found eight QTLs that explain a significant level of variation among introgressed lines in the phenotypes scored. Cytological position overlapped among some QTLs suggesting possible pleiotropic effects. Analysis of the joint effects of simulans/sechellia genetic composition at different QTLs and markers suggests that complex interactions among alleles are partially responsible for interspecific differences in sexual traits.     

Ecological and Genetic Interactions in Drosophila–parasitoids Communities: A Case Study with D. Melanogaster, D. Simulans and their Common Leptopilina Parasitoids in Southe-astern France

Drosophila species are attacked by a number of parasitoid wasps, which constitute an important factor of population regulation. Since Drosophila melanogaster and Drosophila simulans share common parasitoid species, their ecology and evolution can hardly be understood without considering parasitoids. After a short review of data available on Drosophila-parasitoid interactions involving D. melanogaster and D. simulans as hosts, we report field and laboratory experiments investigating the ecological role of Leptopilina parasitoids in Drosophila communities of southern France. Seasonal survey of species abundance shows that strong interspecific interactions occur at both tropic levels. D. simulans progressively replaces D. melanogaster in southern areas suggesting competitive displacement. Parasitoids are responsible for very high Drosophila mortality (up to 90% in some fruits). Field data emphasize the importance of selective pressure that parasitoids exert on Drosophila communities. The two Leptopilina parasites (L. heterotoma and L boulardi) have different local abundances, which vary in time, and they also compete for hosts. We show that parasitoids can mediate the coexistence of D. melanogaster and D. simulans in the laboratory, and thus may contribute to their puzzling coexistence in the field. Conversely, hosts exert selective pressures on parasitoids, and development on either D. melanogaster or D. simulans strongly affects fitness of adult wasps in a temperature-dependent fashion. Local variation in host species abundance and diversity could thus account for the genetic differentiation we observed in one parasitoid species. Despite laboratory studies cannot fully explain complex field situations, it is clear that the ecology and evolution of Drosophila populations and communities, especially D. melanogaster and D. simulans, are strongly constrained by parasitoids, which should receive more attention.     

OBSERVATIONS ON THE MICROFLORA OF MINCED CHICKEN MEAT IRRADIATED WITH 4 MeV CATHODE RAYS

SUMMARY: Experiments are described in which minced chicken meat, packed anaerobically, was irradiated at room temperature and in the frozen state with a wide range of doses of 4 MeV cathode rays. Sterility was achieved in 14 out of 15 samples which had received 2 × 10⁶ rads or more. Doses of 0·5 and 1·0 × 10⁶ rads allowed survival of a few bacteria/g, usually spore formers. Bacterial counts indicated an approximately logarithmic decrease in numbers at lower doses, while freezing reduced the bactericidal effect.
The storage life at 5° was prolonged only slightly by doses of 5 × 10⁴ and 10 × 10⁴ rads, and highly variable results were obtained with 17·5 × 10⁴ rads. A dose of 25 × 10⁴ rads, however, increased the storage life very considerably. The types of bacteria present initially, and after irradiation with low doses and storage at 5°, were studied. After storage for 12 days or more various types of nonsporing Gram-positive rods were predominant in almost all samples, both control and irradiated. Streptococci were also important where irradiation with 17·5 × 10⁴ and 25 × 10⁴ rads was followed by long storage.     

THE INACTIVATION OF BACILLUS SUBTILIS SPORES IN PENICILLIN BY GAMMA RADIATION

SUMMARY: Sodium benzylpenicillin, contaminated with Bacillus subtilis spores by freeze-drying a suspension of spores in an aqueous penicillin solution ( c . 50% w/v), was exposed to gamma radiation and a 70-tube dilution method was used to determine the surviving spores after various doses. The correlation coefficient between log₁₀ percentage survival and dose was −0.9523. The regression of the former on the latter was calculated and the decimal reduction dose found to be 20.2 × 10⁴ rads. The regression and the decimal reduction dose were similar to those obtained when suspensions of spores in distilled water were irradiated.     

The growth and development of Schistosoma mansoni in mice exposed to sublethal doses of radiation

The maturation of Schistosoma mansoni was studied in mice exposed to various sublethal doses of radiation. Although the treatment of mice with 500 rads of radiation prior to infection did not alter parasite maturation, doses in excess of 500 rads led to a reduction in worm burden. This could not be attributed to a delay in the arrival of parasites in the hepatic portal system. Worms developing in mice treated with 800 rads commenced egg-laying about 1 wk later than worms in intact mice, and the rate of egg deposition appeared to be lower in irradiated hosts. The data demonstrate that exposure of C57BL/6 mice to doses of radiation in excess of 500 rads impairs their ability to carry infections of S. mansoni. The findings do not support the hypothesis that primary worm burdens in the mouse are controlled by a host immune response.     

The population genetics of the origin and divergence of the Drosophila simulans complex species

The origins and divergence of Drosophila simulans and close relatives D. mauritiana and D. sechellia were examined using the patterns of DNA sequence variation found within and between species at 14 different genes. D. sechellia consistently revealed low levels of polymorphism, and genes from D. sechellia have accumulated mutations at a rate that is approximately 50% higher than the same genes from D. simulans. At synonymous sites, D. sechellia has experienced a significant excess of unpreferred codon substitutions. Together these observations suggest that D. sechellia has had a reduced effective population size for some time, and that it is accumulating slightly deleterious mutations as a result. D. simulans and D. mauritiana are both highly polymorphic and the two species share many polymorphisms, probably since the time of common ancestry. A simple isolation speciation model, with zero gene flow following incipient species separation, was fitted to both the simulans/mauritiana divergence and the simulans/sechellia divergence. In both cases the model fit the data quite well, and the analyses revealed little evidence of gene flow between the species. The exception is one gene copy at one locus in D. sechellia, which closely resembled other D. simulans sequences. The overall picture is of two allopatric speciation events that occurred quite near one another in time.