Effects Of X-irradiation Research Articles

Regional differences in vulnerability of the cerebellar foliations of rats exposed to neonatal X-irradiation

The purpose of the present study was to elucidate regional differences in the vulnerability of cerebellar foliations of rats exposed to X-irradiation. Effects of X-irradiation on foliations were examined with respect to histological changes in Purkinje cells and Bergmann glial fibers by calbindin-D28k (CB) and glial fibrillary acidic protein (GFAP) immunohistochemistry, respectively. Wistar rats were exposed to X-irradiation (1.5 Gy) on postnatal day (PND) 1. At 3 weeks of age, the cerebellum was examined. The cerebella of rats exposed to X-irradiation showed smaller and abnormal foliations compared with controls. Fewer cerebellar foliations due to fusion with neighboring folia were observed in folia I–III and VIa–VII. Moreover, the extent of such abnormalities was more severe in the latter folia. CB-immunoreactive (IR) Purkinje cells exhibited thin, short, disoriented dendrites that had invaded the granular layer or white matter. On the other hand, GFAP-IR Bergmann glial fibers had not extended their processes into the molecular layer perpendicular to the pial surface, and they appeared thin and disoriented. Accordingly, the above cerebellar abnormalities were more severe in folia I–III, VIa–VII and X than in other regions. In contrast to the histological alterations in these folia, there were no apparent qualitative differences in folia IV–V between X-irradiated and controls. These findings indicate regional difference in the vulnerability of cerebellar folia to X-irradiation. Such differences might be attributed to the cerebellar neurogenetic gradient.

Differential effects of x-irradiation on immature and mature hippocampal neurons in vitro

X-irradiation to neuronal progenitor cells causes brain dysfunctions, such as a mental retardation, in adulthood. However, little has been known about the degree of radiosensitivity of neurons in the developmental stages at which they are most vulnerable. In this study we compared the effect of irradiation on mature neurons with that on immature neurons. Primary dissociated neuronal cultures were prepared from fetal rat hippocampi of embryonic day 18. X-irradiations were performed on the cultured cells at 7 or 21 days in vitro (DIV), and the cells were fixed at 12 or 24 h after irradiation. Then the cells were stained with 4′,6-diamidino-2-phenylindole (DAPI) or terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL). The apoptotic changes were measured quantitatively by nuclear pyknosis and DNA fragmentation—both characteristic morphological changes of apoptosis. Light microscopy with differential interference contrast showed that 30 Gy of irradiation increased cellular shrinkage in 7-DIV neurons but not in 21-DIV neurons. Quantitative analysis using DAPI imaging showed that 30 Gy of irradiation significantly enhanced pyknotic changes in 7-DIV neurons after 24 h. In contrast, this irradiation did not enhance any pyknotic changes in 21-DIV neurons after 24 h. Further TUNEL staining also showed that the irradiation did not enhance any DNA fragmentation in nuclei of 21-DIV neurons after 24 h. Hence, we showed that the radiosensitivity of 21-DIV postmitotic neurons was significantly lower than that of 7-DIV neurons, indicating that the susceptibility of such neurons depends on their developmental stage.

Suppressive effect of low-dose X-irradiation on type I diabetes non-obese diabetic (NOD) mice

We examined the effect of X-irradiation (0, 0.25, 0.5 or 1.0 Gy) on the onset of the type I diabetes (insulin dependent diabetes mellitus) in non-obese diabetic (NOD) mice. NOD mice are characterised by a progressive loss of insulin-producing β-cells in the pancreas by autoimmune mechanisms. The destruction of β-cells is known to be due to apoptosis induced by oxidative stress caused by ROS. In non-irradiated NOD mice, an elevation of the urine glucose level was first detected at 15 weeks of age. When the mice were irradiated with 0.5 Gy of X-rays (300 kVp) at 12 weeks of age, the onset of disease delayed to the 22nd week. When irradiated at 13th or 14th week, the suppression was much less effective. One week after the 0.5 Gy irradiation, an increase in the specific activity of superoxide dismutase (SOD) in pancreas was observed. The level was twice as much as that in the non-irradiated control mice. In the dose range we examined 0.5 Gy gave the most effective suppression of the diabetes. The same dose was also most effective in increasing the SOD level. Furthermore, detection of apoptotic cells by TUNEL method revealed far fewer incidences of apoptosis in pancreas of the irradiated mice than in non-irradiated NOD mice. The results suggest that the low dose irradiation delayed the onset of type I diabetes in NOD mice by suppressing apoptotic cell death in pancreas, probably through enhancing antioxidant defence mechanisms.

Early and Late Effects of X-Irradiation on Submandibular Gland: A Morphological Study in Mice

Radiotherapy for head and neck cancers causes permanent salivary gland dysfunction and xerostomia. The aim of this study was to determine changes in mice submandibular glands after X-irradiation. The submandibular glands of male C57BL/6 mice were locally X-irradiated in the head and neck region with a single dose of 7.5 or 15 Gy and analyzed morphologically and morphometrically at 1, 3, 6, 10, 40, and 90 days after irradiation. Two phases of gland reaction to irradiation have been noted. The first, early phase is observed up to 10 days after irradiation. The second, late phase was observed 90 days after irradiation. Also, a dose-related effect was noticed. The most prominent morphological changes were pyknotic nuclei, vacuolization of acinar cells and lysis of acini and granular convoluted tubules. Changes were detected at 3 and 6 days after irradiation followed by tissue regeneration. Ninety days after irradiation, prominent pathological changes (vacuolization and pyknotic nuclei of acinar cells, lysis of acini and granular convoluted tubules and edema) were detected, but the most remarkable change was disseminated mononuclear infiltration. Also, a statistically significant reduction in number of acinar cells was detected in both irradiated glands. Occurrence of disseminated mononuclear infiltration in gland during late post-irradiation phase makes the mouse model potentially better than the rat model for investigation of irradiation-induced salivary gland damage.

The effect of cervical X-irradiation on activity index of thyrocytes and plasma TSH: A pre-clinical model for radiation-induced thyroid damage

Because radiotherapy in the head and neck region is necessary in the treatment of childhood cancer, possibilities to prevent damage to the thyroid gland must be explored. We developed a model in which radiation-induced effects can be investigated in a way that these effects can be quantified, using thyroid dysmorphology and plasma TSH. Thirty-five Wistar rats, 5 weeks old, were X-irradiated on the cervical region, with a single dose varying from 0 to 20 Gy. After 6 weeks, TSH, T4 and T3 were determined, and thyroid glands were processed for histological examination by two independent pathologists. A histological classification scale was developed, using follicular size, colloid density and cell height of thyrocytes to measure hyperplasia and hypertrophy. By the sum of these scores, a cell-activity index was calculated, which was related to plasma TSH concentration. Numbers of PAS-positive droplets and epithelial desquamation were also counted. Inter-observer reliability was assessed. Good to very good reliability was found for scores of follicular size, colloid density and cell height. Significant increase of cell-activity index was found after 10, 15 and 20 Gy. The plasma TSH concentration was positively correlated to the cell-activity index, increasing with radiation-doses up to 15 Gy. The number of desquamated cells was significantly increased after radiation doses >10 Gy, with moderate reliability. In conclusion, this model using cell-activity index of thyrocytes together with plasma thyrotropin concentrations and desquamation of cells can be used for interpretation and future (pre-clinical) studies of prevention of radiation-induced thyroid damage.

Therapeutic effect of gene-therapy in combination with local X-irradiation in a mouse malignant melanoma model

Plasmid containing mIL-18 and B7.1 genes downstream of Egr-1 promoter was constructed and used in gene-radiotherapy on malignant melanoma in C57BL/6J mice implanted with B16 cells followed by exploration of the immunologic mechanism of the therapeutic effect. The treatment with plasmid pEgr-IL-18-B7.1 plus local X-irradiation showed more effective suppression of tumor growth than the treatment with radiation alone, pEgr-IL-18-B7.1 alone, or single gene pEgr-IL-18 (or pEgr-B7.1) combined with local X-irradiation. Anticancer immunity was found to be significantly upregulated in tumor-bearing mice treated with pEgr-IL-18-B7.1 plus local X-irradiation. IL-18 showed no direct killing effect on malignant melanoma cells in vitro, and the mechanism of the combined therapy with pEgr-IL-18-B7.1 and local X-irradiation was apparently related with the stimulation of host anticancer immunity by increased secretion of IL-18 and upregulated immunogenicity of the tumor cells by increased expression of B7.1 on their surface in addition to the direct effect of local X-irradiation on the tumor cells.

Prenatal Low-dose X-irradiation Affects Connexins 43 and 26 in Developing Mouse Neocortex

To investigate the effects of low-dose X-irradiation on the expression of connexins (Cxs) in developing cerebral cortex, C57/BL6 pregnant mice were exposed to whole body irradiation of 0.1 Gy and 0.5 Gy, on embryonic day 14.5. Fetal telencephalons, at 1, 3, 12 and 24 hr after exposure, were studied immunohistochemically using anti-Cx43 and Cx26 antibodies, followed by quantitative image analyses. Cx43 expression was significantly reduced in all zones of developing cerebral cortex until 12 hr after exposure, and tended to recover to control level after 24 hr. Cx26 expression was also suppressed in the ventricular zone and cortical plate after irradiation, although it recovered much earlier. Our observations indicate that the expression of Cxs is affected by ionizing radiation during cortical histogenesis.

Intestinal Tumorigenesis in Min Mice is Enhanced by X-irradiation in an Age-dependent Manner

We examined the effect of X-irradiation on intestinal tumorigenesis in Min (multiple intestinal neoplasia) mice. Single whole-body irradiation was given to mice of various ages from newborn to young adults. On the C57BL/6J (B6) background, X-irradiation increased tumor multiplicity of the small intestine exposed at ages from 2-3 days to 24-25 days, with a peak of 2.7-fold increase at 10-12 days of age; exposure at later ages resulted in only a slight increase. X-irradiation also increased colonic tumors; however, the susceptible age period appeared earlier than that of the small intestine; the peak value of 4.6-fold increase was observed in the exposure at around 2-3 days of age. Irradiation at 24 days or later ages showed almost no effect on the colonic tumor induction. On the (B6 x MSM)F1 background, X-irradiation resulted in 2.7-fold increase in the small intestinal tumors, but no increase in the colonic tumors, and besides, the age dependency observed in the small intestinal tumors was much attenuated. Collectively, we conclude that tumorigenic efficacy of X-irradiation in Min mice was determined by the combination of the target organ, the age at exposure, and the genetic background.

Cross-life stage and cross-generational effects of ? irradiations at the egg stage on Drosophila melanogaster life histories

The long-term effects of X-irradiation with 0.25, 0.5, 0.75 and 1 Gy of 1 h eggs on the fitness-related life history traits in adult Drosophila melanogaster fruit flies and their offspring were investigated. Following irradiation with 0.25, 0.5 and 0.75 Gy, both F0 and F1 flies have decreased adult body weight and increased locomotor (photo- and geotactic) activity, whereas metabolic rate measured as the rate of CO2 production was unchanged or even increased, and female fecundity was slightly reduced compared to appropriate controls. In some cases, irradiation resulted in hormetic effects increased resistance to both starvation and heat shock stresses as well as life extension. An explanation of the beneficial long lasting effects induced by early irradiation is offered, which suggests that these effects are due to cross-life stage and cross-generational adaptive phenotypic plasticity.

Proteolytic cleavage of von Willebrand factor by ADAMTS‐13 prevents uninvited clumping of blood platelets

Proteolytic cleavage of von Willebrand factor by ADAMTS‐13 prevents uninvited clumping of blood platelets

Study of the combined effect of X-irradiation and epigallocatechin-gallate (a tea component) on the growth inhibition and induction of apoptosis in human cancer cell lines

Over the past 15 years, some potential anticarcinogenic and anti-inflammatory effects of antioxidants have been defined. Antioxidants are known to act as powerful free-radical scavengers. Free radicals are able to induce DNA strand breaks and oxidative modifications of DNA bases and are not only produced naturally in the cell following a stress or respiration but also following ionizing radiation. The present study was undertaken in order to explore whether some antioxidants naturally present in the food or in the beverages could enhance apoptosis in cancerous cells submitted to X-irradiation. Epigallocatechin gallate (EGCG), a potent antioxidant present in tea was tested on three human cancerous cell lines: HeLa (derived from cervix carcinoma), K-562 (derived from chronic myelogenous leukaemia) and IM-9 (derived from multiple myeloma). The parameters investigated were cell proliferation, morphological changes, cell cycle effects and apoptosis. When given alone, irradiation induced a decrease of cell proliferation and an increase of apoptosis as well as the appearance of polyploid cells in the three cell lines. All these effects were dose-dependent. Taking into account the various parameters, IM-9 cells appeared as the most radiation sensitive and HeLa cells as the least radiation sensitive, while K-562 cells exhibited an intermediary radiation sensitivity. EGCG had no effect on cell proliferation, while it induced a dose-dependent increase of apoptosis in the three cell lines. IM-9 cells were again most sensitive to this effect, while HeLa and K-562 cells were slightly less sensitive. A combined treatment by X-irradiation and EGCG resulted in a significant enhancement of apoptosis correlated with a decrease of proliferation in IM-9 and K-562 cells and at a lesser extent, in HeLa cells, compared to treatments by either EGCG or ionising radiation alone. In conclusion, these preliminary results show that depending on the concentration and on the cell line, EGCG could act as a radiation enhancer on cancerous cell lines.

Effects of X-Ray Irradiation and Barium Deficiency on Grain Boundary States in BaTiO3:Ta Ceramics

The effects of x-irradiation and Ba deficiency in BaTiO3:Ta ceramics were investigated in conjunction with the mechanism of an abrupt increase in electrical resistivity at the Curie temperature Tc, which was called the mode-I positive temperature coefficient of resistivity (PTCR). X-irradiation decreases the resistivity and the potential barrier height at grain boundaries in the rhombohedral and cubic specimens, but increases the ESR intensity of a singlet signal at g=2.005. On the other hand, introducing Ba deficiency increases the room-temperature resistivity ρRT and the magnitude of resistivity jump ρmode-I at Tc, but both ρRT and ρmode-I become to decrease when Ba deficiency exceeds 0.03 at%. In highly Ba-deficient specimens, the singlet ESR signal also decreases with increasing Ba deficiency. For explaining the irradiation effects, we proposed two models. One is the hole-recombination model, in which trapped-electrons at VBa-associated acceptor levels recombine with the holes created by irradiation. The other is the electron-detrapping model for the electrons trapped by acceptor levels. The explanation of the effects of x-irradiation and Ba deficiency was attempted by assuming VBa-associated centers (VBa, VBa–VO, VBa–F and VBa–F+). We conclude that predominant acceptor states at grain boundaries are VBa–VO-type defects. It is considered that the mode-I PTCR originats from critical changes in the density of states (DOS) of VBa–VO and the Fermi energy at tetragonal-to-cubic transition. This type of trap activation may lead to the formation of VBa–F+ and VBa–F from VBa–VO.

Marked increase in the rate of ocular lens regeneration in the newt, Cynops pyrrhogaster, following partial body exposure to low dose X-rays.

In recent years, concern over the stimulating effects of low-dose X-rays has been growing. Therefore, the effects of low-dose X-irradiation on lens regeneration in the newt were examined. Newts were subjected to sham or whole-body X-ray exposure at a dose of 0.2 Gy or 0.4 Gy, delivered at a rate of 0.43 Gy min(-1). The eyeballs were fixed in formalin solution, embedded in paraffin and assessed histologically. On day 14 after lens removal, unexposed animals showed the formation of a hollow epithelial vesicle of depigmented cells continuous with the laminae of the iris corresponding to the expected regeneration stage (Reyer's regeneration stage II). In contrast, lenses from newts exposed to a 0.2 Gy dose of X-rays showed some formation of the primary lens fibre nucleus corresponding to the fibre differentiation stage (Reyer's regeneration stage III-early). Thus, low-dose X-irradiation induced regeneration compared with the unexposed groups. An acceleration from Reyer's stage II to III-early was also found on day 14 following irradiation of only the upper belly, including the spleen. The effects of low-dose X-irradiation on lens regeneration may be mediated by changes in immune activity.

The Effect of X-irradiation on the Developing Incisor Tooth of the Rat

The Effect of X-irradiation on the Developing Incisor Tooth of the Rat

Effect of X-irradiation at larval stage on adult lifespan in Drosophila melanogaster.

The effects of X-ray irradiation at larval stage with doses of 1.2, 2.1, 4.2, 7.5 and 17.1 Gy on adult longevity and fecundity in Drosophila melanogaster fruit flies were studied. A significant negative trend with increasing dose of irradiation was detected for the median lifespan in both sexes. In all experimental groups, both male and female mortality rates in irradiated flies were above control levels approximately for one month after emergence, and below control levels at older ages. The irradiation with 1.2 and 2.1 Gy resulted in 11.5% and 12.7% increase of male maximum lifespan, respectively. Irradiated females had in most cases a lower fecundity than control females. In all studied age groups, the decrease of fecundity was dose-related, and the negative effect of irradiation on fecundity was no longer observed in flies older than two weeks of age. Mean fecundity for the 4-25-day period of the irradiated females was shortened and dose-related [one-way ANOVA: F(5,414) = 10.56, P < 0.001], but significant differences from control were observed only for flies irradiated with doses of 4.2, 7.5 and 17.1 Gy. Mean fecundity for females irradiated with doses of 1.2 and 2.1 Gy did not differ from that of control females.

Enhancement of effects of irradiation by gemcitabine in a glioblastoma cell line and cell line spheroids.

To determine the cytotoxicity of, and radioenhancement by, gemcitabine on a glioma cell line grown as a monolayer and as spheroid cultures. We used a human glioma cell line, Gli-6, which originated from a biopsy specimen of a patient with a glioblastoma multiforme. Spheroids of Gli-6 were prepared by seeding a single cell suspension on agarose-coated Petri dishes. Clonogenic and growth delay assays were used to determine radio-chemosensitivity of monolayer cultures. The growth delay assay was used to determine that of Gli-6 spheroid cultures. Spheroid cultures were found to be more resistant to irradiation with/or without gemcitabine than monolayer cultures. Whereas gemcitabine significantly enhances the radiation effect of exponentially growing Gli-6 monolayer cultures at minimal cytotoxic concentrations (10 nM, 24 h), no enhancement was seen in confluent monolayer cultures and in large spheroids at the same concentration. In small spheroids no enhancement was observed at a low-dose gemcitabine (10 nM for 24 h), but an enhancement was observed at higher concentrations (100 nM for 24 h). Gemcitabine can lead to enhancement of the effects of X-irradiation in both monolayer as spheroid glioblastoma cultures. The lack of enhancement in confluent monolayer cultures supports the view that cell cycle distribution of cells is important in radiosensitisation by gemcitabine

77 disc Enhancement of effects of X-irradiation by gemcitabine in a glioblastoma cell line and cell line spheroids

77 disc Enhancement of effects of X-irradiation by gemcitabine in a glioblastoma cell line and cell line spheroids

Parental exposure to low-dose X-rays in Drosophila melanogaster induces early emergence in offspring, which can be modulated by transplantation of polar cytoplasm

In recent years there has been growing concern over the biological effects of low-dose X-rays, but few studies have addressed this issue. Our laboratory had observed flies ( Drosophila melanogaster) irradiated with low-dose X-rays tend to emerge earlier than normal flies. This observation led us to quantitatively examine the effects of low-dose X-irradiation on development in the fly. Following exposure of prepupal (day 5) flies to 0.5 Gy X-rays, the time to emergence was slightly shorter than in the sham controls. This tendency was increased when the X-ray exposure came during the pupal stage (day 7). In these flies, the time to eclosion decreased significantly, by an average of 30 h sooner than sham controls. A further experiment examined whether such radiation effects could be observed in the unexposed F1 generation of exposed individuals. Greater radiation effects on early F1 emergence were seen when the time between exposure and mating was 3 days, indicating an effect on early spermatid development. Early F1 emergence was also observed after exposure of female flies to X-rays during late previtellogeny. Furthermore, rapid emergence could be induced in the F1 embryos of unexposed parents by transferring the polar cytoplasm (precursor cells of the germ cell line) from F1 embryos of exposed flies. These results show that radiation-induced effects can be transmitted to the next generation through the germ cell line.

Effect of X-Irradiation on Growth and the Expression of Parathyroid Hormone-Related Peptide and Indian Hedgehog in the Tibial Growth Plate of the Rat

Aim: To study the effect of irradiation on the longitudinal growth and the expression of parathyroid hormone-related peptide (PTHrP) and Indian hedgehog (IHh) in tibial growth plates of rats. Methods: At 3 weeks of age, 30 male rats received a single fraction of irradiation (8 Gy) to their right hind limb, and small groups of animals were sacrificed 1, 2, 3, 5, 7, 10, 15, and 26 weeks after irradiation. Weight and length of both irradiated and nonirradiated tibiae were measured, and sections of the tibiae were stained with HE. PTHrP and IHh were visualized using immunohistochemical techniques. Results: Radiation resulted in persistent growth delay of the irradiated tibiae, with a difference in length of more than 10% between the irradiated and the nonirradiated tibiae 15 weeks or more after irradiation. The growth plate architecture was disturbed, and the expression of both PTHrP and IHh was decreased in the irradiated tibiae. Conclusion: As PTHrP and IHh are key regulators of both the pace and the synchronization of the differentiation of growth plate chondrocytes, the reduced expression of PTHrP and IHh may contribute to the changes found after irradiation.

Effects of X-irradiation in early ontogenesis on the longevity and amount of the S1 nuclease-sensitive DNA sites in adult Drosophila melanogaster.

The long-term consequences of the X-irradiation of Drosophila melanogaster fruit fly one-hour eggs with doses of 0.25, 0.50, 0.75, 1, 2 and 4 Gy were investigated. Longevity hormesis was observed in males exposed to 0.5 Gy and 0.75 Gy, but no longevity increase was observed in females. The electrophoretic analysis has shown that the amount of the DNA segments resulting from cleavage in S1 nuclease-sensitive sites (<3 kb) reached 39.2% of the total DNA from control males. DNA from the irradiated males had a smaller amount of such fragments (10-30% in different experimental groups). These findings indicate that the longevity hormesis may be associated with irradiation-induced long-term structural and/or functional DNA modifications.