Lethal and teratogenic effects in two successive generations of the HLG mouse strain after radiation exposure of zygotes -- association with genomic instability?

We analysed the transmission of lethal and teratogenic events to the subsequent generation in HLG/Zte mice after exposure of the zygote stage to 1 Gy X-rays. As observed in previous studies, our results on teratogenic events occurring in the same generation, which was exposed during the zygote stage, reveal a significantly higher risk for the induction of gastroschisis. Interesting new insights came from the study of lethal and teratogenic effects in the generation obtained after mating female mice, which were exposed during their zygote stage, to unexposed males. An approximately 2-fold higher level of damage was manifest in this generation compared with controls, expressed mainly as a significant increase of prenatal mortality (P<0.01). Although there was an increase in the number of malformed fetuses on day 19 of gestation (6.5% cases of gastroschisis compared to 3.5% in the controls), the frequency of gastroschisis in the exposed group was just not statistically significant (P>0.05). These results are in line with the hypothesis that genomic instability is involved in the damage seen after radiation exposure of the zygote stage of HLG mice.     

Lethal and teratogenic effects of long-term low-intensity radio frequency radiation at 428 MHz on developing chick embryo

Exposure of developing chick embryos to 428 MHz radio frequency (RF) radiation at a power density of 5.5 mW/cm2 for more than 20 days resulted in embryolethal and/or teratogenic effects and delayed hatching. These adverse biological effects were not due to any thermal effect of the RF radiation. We have demonstrated teratogenicity in the chick embryo as a result of protracted low-dose RF irradiation.     

Induction of cytogenetic effects in human fibroblast cultures after exposure to formaldehyde or X-rays

Cytogenetic changes induced by formaldehyde (FA) in exponentially growing human fibroblasts were compared with those produced by X-rays. Chromosome aberrations of different types were detected. Exposure to 2 mM FA for 15 min resulted, quantitatively and qualitatively, in effects comparable to those produced by an X-ray dose of 100 rad. X-Rays at higher exposures produced types of chromosome aberrations that differed from those induced by higher exposures to FA.     

Induction of cytogenetic effects in human fibroblast cultures after exposure to formaldehyde or X-rays

Cytogenetic changes induced by formaldehyde (FA) in exponentially growing human fibroblasts were compared with those produced by X-rays. Chromosome aberrations of different types were detected. Exposure to 2 mM FA for 15 min resulted, quantitatively and qualitatively, in effects comparable to those produced by an X-ray dose of 100 rad. X-Rays at higher exposures produced types of chromosome aberrations that differed from those induced by higher exposures to FA.     

Lethal exposure times and preconditioning to upper temperature limits of some temperate North Atlantic red algae

Using the red algaPolyneura hilliae as an example, the minimum time taken for lethal temperature exposure, with no regeneration capacity left, was 2 weeks. Employing this exposure time, the upper temperature limits of the following 13 red algal species belonging to four biogeographical distribution groups were determined:Callophyllis lacinita, Polyneura hilliae, Hypoglossum hypoglossoides, Halurus equisetifolius, Lomentaria articulata, Cryptopleura ramosa, Calliblepharis ciliata (warm-temperate Mediterranean-Atlantic group);Callithamnion tetragonum, Lomentaria orcadensis (amphiatlantic-temperate group);Grinnellia americana, Lomentaria baileyana, Agardhiella subulata (northeast American tropical-temperate group),Solieria tenera (amphiatlantic tropical-temperature group). Pre-incubation temperatures of 10 and 20°C for one month (or 15 and 25°C for the two last-mentioned distribution groups) did not measurably affect the critical survival temperature.     

Radiation-induced signaling results in mitochondrial impairment in mouse heart at 4 weeks after exposure to X-rays

BACKROUND: Radiation therapy treatment of breast cancer, Hodgkin's disease or childhood cancers expose the heart to high local radiation doses, causing an increased risk of cardiovascular disease in the survivors decades after the treatment. The mechanisms that underlie the radiation damage remain poorly understood so far. Previous data show that impairment of mitochondrial oxidative metabolism is directly linked to the development of cardiovascular disease. METHODOLOGY/PRINCIPAL FINDINGS: In this study, the radiation-induced in vivo effects on cardiac mitochondrial proteome and function were investigated. C57BL/6N mice were exposed to local irradiation of the heart with doses of 0.2 Gy or 2 Gy (X-ray, 200 kV) at the age of eight weeks, the control mice were sham-irradiated. After four weeks the cardiac mitochondria were isolated and tested for proteomic and functional alterations. Two complementary proteomics approaches using both peptide and protein quantification strategies showed radiation-induced deregulation of 25 proteins in total. Three main biological categories were affected: the oxidative phophorylation, the pyruvate metabolism, and the cytoskeletal structure. The mitochondria exposed to high-dose irradiation showed functional impairment reflected as partial deactivation of Complex I (32%) and Complex III (11%), decreased succinate-driven respiratory capacity (13%), increased level of reactive oxygen species and enhanced oxidation of mitochondrial proteins. The changes in the pyruvate metabolism and structural proteins were seen with both low and high radiation doses. CONCLUSION/SIGNIFICANCE: This is the first study showing the biological alterations in the murine heart mitochondria several weeks after the exposure to low- and high-dose of ionizing radiation. Our results show that doses, equivalent to a single dose in radiotherapy, cause long-lasting changes in mitochondrial oxidative metabolism and mitochondria-associated cytoskeleton. This prompts us to propose that these first pathological changes lead to an increased risk of cardiovascular disease after radiation exposure.     

Radiation-induced malformations after exposure of murine germ cells in various stages of spermatogenesis

We studied radiation effects in day 19 fetuses of the mouse strain 'Heiligenberger' after exposure (2.8 Gy, 137 Cs gamma rays, dose rate 0.28 Gy/h) of their fathers. We observed an increased lethality (exclusively due to preimplantation death and early resorptions) after exposure of all stages of spermatogenesis with the exception of early spermatogonia. In addition, there was a significant increase in the frequency of malformed fetuses (gastroschises only); this increase was observed primarily after exposure of the meiotic stages.     

Lethal effects of fluorodeoxyuridine on cultured mammalian cells at various stages of the cell cycle

The lethal damage induced by the exposure of synchronized Chinese hamster cells to various concentrations of 5-fluoro-2′deoxyuridine (FUdR) was not selectively restricted to cells exposed during the period of DNA synthesis S. The colony survival fraction observed after treatment for one hour with 5 × 10^?5 M FUdR was very low (0.0001–0.0003) whether the drug was administered during early G₁, late G₁, early S or in middle S. The survival of cells treated with the same concentration of FUdR during mitosis, however, was significantly higher (0.62) showing that mitotic cells were less sensitive to FUdR. Administration of 10^?7M thymidine or “conditioned” medium for one hour reversed the lethal effect of FUdR or improved the survival, depending on the time after removal of the FUdR at which these substances were given.     

Rates of forward and reverse mutation inDrosophila after exposure to mustard gas and X-rays

After treatment with mustard gas, reversions of the mutantforked ³ⁿ were observed with a frequency of 1 in 7,500. In the absence of indications for either suppressors or chromosome-rearrangements, these data provide evidence that a chemical mutagen can produce back mutations inDrosophila. Half the number of reversions was characterized by mosaic manifestation. This shows that delayed appearance after chemical treatment also holds for true gene mutations. One partial reversion to nearly normal type was not due to back mutation, but to a rearrangement, presumably involving a duplication of theforked containing region.The study on reversion off ³ⁿ was combined with tests for recessive visibles at 15 selected loci of the X-chromosome. Mutations at theruby locus were most frequently induced by mustard gas (1 in 1,700). About one quarter of the forward mutations were fractionals. After exposure to 5,000 r X-irradiation both reversions off ³ⁿ and forward mutations at the loci under study were observed with frequencies comparable to those induced by mustard gas. Thus, no indication for mutagenspecific differences in mutational response have been obtained. After treatment with mustard gas a higher ratio of visibles to lethals was observed than after exposure to X-irradiation. It is pointed out that comparisons of the mutagenic effect of a chemical mutagen with that of X-radiation, even if restricted to visible mutations, inevitably involve an underestimate for the chemical, due to delayed effects of the latter.The experiments were carried out mainly at the Department of Genetics, State University of Utrecht (Director: Prof. Dr.C. L. Rümke). A. J. M. van Hedel, G. J. O. Jansen, V. Labordus andS. C. M. Schouten collaborated on parts of this project.     

Population structure and reproductive status of two Banksia shrubs at various times after fire

Populations of the obligate-seeder, Banksia ericifolia, were even-aged. Seedling recruitment occurred only after fire. Mean genet size (height + canopy diameter; H+D) increased progressively with elapsed time since fire in stands last burnt 2–23 years before 1981. Populations of a co-occurring resprouter, B. oblongifolia, were mixed-aged. Genet size varied significantly between stands, but this variation was not explained by regressions of H+D on years since fire. In addition B. oblongifolia seedlings were recruited both after fire and in patches of heath unburnt for 16 years.Most flower and seed production in B. oblongifolia occurred in the stands last burnt less than 10 years previously. More than 30% of genets had not produced cones since the last fire, irrespective of how many years had elapsed. In contrast, few B. ericifolia genets had produced cones five years after fire, but by 16 years after fire nearly 100% had. Overall, about 51% of B. ericifolia inflorescences and about 28% of B. oblongifolia inflorescences set seed. The number of seeds in seed-bearing cones was not significantly different between species.Resprouting B. oblongifolia genets began flowering sooner after fire, but B. ericifolia subsequently overtook them in accumulating a bank of serotinous seeds. In the stand unburnt for 23 years the largest B. ericifolia genets had more than twice as many cones as the largest co-occurring B. oblongifolia. However, when accumulated cone production was compared for genets of equal H+D over all stands, there was no difference between species.We thank the New South Wales National Parks & Wildlife Service for permission to do this work in Ku-ring-gai Chase National Park. We are grateful to Don Adamson, Lynn Day, David Haig and James Sim for constructive comments on earlier drafts.     

Capacitation status of hamster spermatozoa in the oviduct at various times after mating

Female hamsters were mated shortly after the onset of oestrus or immediately after ovulation. At various times after mating, spermatozoa were flushed from the isthmus of the oviduct using a modified Tyrode's medium supplemented with 20% hamster serum. Cumulus oophorus-free eggs were introduced into the suspensions of isthmic spermatozoa. Some eggs were removed every 30 min and examined for evidence of fertilization. For females mated shortly after the onset of oestrus, spermatozoa recovered from the oviducts 8 h after mating (about 1.5 h after ovulation) could penetrate eggs within 30 min and were considered fully capacitated. When spermatozoa were recovered at earlier times (1, 2, 4 and 6 h after mating) they required additional time (2, 1.5, 1 and 1 h respectively) in vitro before penetrating eggs. Therefore, when mating occurs shortly after the onset of oestrus, spermatozoa in the oviduct do not appear to become fully capacitated until about the time of ovulation. For females mated immediately after ovulation, spermatozoa recovered from the oviducts at 4 h after mating could penetrate eggs within 30 min. Spermatozoa recovered at 1 and 3 h after mating required 2 and 1 h respectively in vitro before penetrating eggs. These results suggest that sperm capacitation proceeds at a faster rate when mating occurs after ovulation.     

Oocyte recovery and fertilization rates in women at various times after the administration of hCG

Volunteer women requesting laparoscopic sterilization were subjected to a fixed schedule of ovulation induction and oocyte recovery. Follicle aspiration was carried out in four groups: those to whom hCG was not administered and 12, 24 or 36 h respectively after the administration of hCG. For each group oocytes were cultured in vitro for 42 h, 30 h, 18 h and 6 h respectively, before insemination with donor spermatozoa. Oocyte recovery rates improved with longer hCG-to-recovery intervals (36% with no hCG to 81% 36 h after hCG). Although there was a slight reduction in fertilization rates when oocytes were not exposed to hCG in the follicle, normal cleavage was noted in more than 50% of oocytes in all four groups. It therefore appears that the final maturation stages of the human oocyte are not dependent on the midcycle gonadotrophin surge, provided the oocyte is matured in vitro before insemination. However, it was also evident that the fertilization rates were reduced when oocytes were removed from less mature follicles, as reflected by high androstenedione/oestradiol ratios.     

Murine spermatogonial regeneration after exposure to either X-rays or 15 MeV neutrons*

Summary The long-term regeneration of the semeniferous epithelium after irradiation with 15 MeV neutrons was studied in the mouse on a comparative basis; 150 kV X-rays were used as reference-radiation. The mice received total-body exposures at matched doses. The spermatogonial Regeneration Index (RI) was scored from stained paraffin-sections of testes which were obtained after periodic sacrifice. A biphasic pattern of regeneration was recorded. Dose-independent and dose-dependent effects have been indicated. The radiobiological implications are discussed on a cellular basis.     

Changes in the cytoarchitectonics of the rat thymus at different times after body exposure to dimethyl sulfate]

Change in cytoarchitectonics of the organ at different terms after the action of dimethylsulfate (DMS) vapour on the organism was studied by a morphometrical method in histological preparations of the thymus of albino Wistar rats. The thymus was found to intimately react to DMS. On the 1st day after treatment the lymphocytopoietic function was suppressed, the process of destruction of cells in the organs was intensified, the amount of macrophages and plasma cells was increased. Two weeks after cessation of the treatment the organs became activated: intensified cell proliferation and less disintegration of lymphocytes were noted. However no complete reestablishment of the cell ratio took place even 3 months after cessation of the treatment.