Effects Of Low-dose X-irradiation Research Articles

Effect of low dose X-irradiation on osteoblastic UMR-106 cells in the osteogenesis microenvironment

Objective To observe the effect of low dose X-irradiation on the proliferation,osteogenic differentiation and mineralization of osteoblastic UMR-106 cells in the osteogenesis microenvironment.Methods After exposure,cell proliferation,osteogenic differentiation and calcium deposition were evaluated by cell counting kit-8 (CCK-8) assay,alkaline phosphatase (ALP) viability,Alizarin Red S staining,respectively.The mRNA and protein levels of Runt-related transcription factor 2 (Runx2) and Osteocalcin (OC) were detected.Results The relative proliferation rate of the cells exposed to 1.0 Gy was significantly lower than that of control (P ＜ 0.05).The ALP activity of 0.1 Gy group [(5.88 ± 0.14) nmol p-Nitrophenyl Phosphate (pNPP)/μg protein] was significantly increased than that of control group [(4.75 ± 0.05) nmol pNPP/μg protein,P ＜ 0.05].The optical density (OD) value of calcium deposition of 0.1 Gy group (6.57 ± 0.20) was significantly increased than that of control group (5.39 ± 0.28) (P ＜0.05).In osteogenesis microenvironment groups,the Runx2 mRNA expression of 0.1 Gy group (5.51 ± 1.52) was significantly increased than that of 0 Gy group (2.43 ± 0.3) (P ＜ 0.05),the OC mRNA expression of 0.1 Gy group (2.92 ± 1.34) was significantly increased than that of 0 Gy group (1.03 ± 0.41) (P ＜ 0.05).In osteogenesis microenvironment groups,the Runx2 protein expression of 0.1 Gy group (0.84 ± 0.03) was significantly increased than that of 0 Gy group (0.44 ± 0.02,P ＜ 0.05),the OC protein expression of 0.1 Gy group (427.7 ± 64.2) ng/L was significantly increased than that of 0 Gy group(278.9 ±53.7) ng/L (P＜0.05).Conclusion The osteogenesis microenvironment plays a present role of low dose X-irradiation promoting osteogenic differentiation and mineralization on osteoblastic cells. Key words: The microenvironment; Low dose X-irradiation; Runt-related transcription factor 2 ; Osteocalcin

Increased susceptibility to delayed genetic effects of low dose X-irradiation in DNA repair deficient cells

Purpose: To examine whether the levels of micronuclei induction, as a marker for genomic instability in the progeny of X-irradiated cells, correlates with DNA repair function.Materials and methods: Two repair deficient cell lines (X-ray repair cross-complementing 1 [XRCC1] deficient cell line [EM9] and X-ray repair cross complementing 5 [XRCC5; Ku80] deficient X-ray sensitive Chinese hamster ovary [CHO] cell line [xrs5]) were used in addition to wild-type CHO cells. These cells were irradiated with low doses of X-rays (up to 1 Gy). Seven days after irradiation, micronuclei formed in binucleated cells were counted. To assess the contribution of the bystander effect micronuclei induction was measured in progeny of non-irradiated cells co-cultured with cells that had been irradiated with 1Gy.Results: The delayed induction of micronuclei in 1 Gy-irradiated cells was observed in normal CHO and EM9 but not in xrs5. In the clone analysis, progenies of xrs5 under bystander conditions showed significantly higher levels of micronuclei, while CHO and EM9 did not.Conclusion: Genomic instability induced by X-irradiation is associated with DSB (double-strand break) repair, even at low doses. It is also suggested that bystander signals, which lead to genomic instability, may be enhanced when DSB repair is compromised.

Effects of low dose X-irradiation on intra-uterine death in mice subjected to exposure when young or at foetal stage.

Tests were carried out with the view of establishing the effect of X-ray doses of 4 and 8 rad on intrauterine death rate in mouse. Young suckling females whose oocytes are known for their somatic sensitivity as well as two week old foetuses in the oocytes of which DNA synthesis takes place were irradiated. The females subjected to irradiation originated either from an inbred strain or they were hybrids. When mating for analysis the males were taken from the inbred or an unrelated strain. No significant differences as regards intra-uterine death rate were established between single irradiated and non-irradiated series, although the controls in two out of three experiments on the whole showed the lowest values. However, the tests have plainly shown that there exists a considerable variation in the frequency of early and late intra-uterine deaths in different types of matings and the important role males can play as regards the rate of implants.

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.

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 effects of low-dose X-irradiation on the oxidative burst in stimulated macrophages

Purpose : Local irradiation with a dose of around 0.5 Gy is an effective treatment of acute necrotizing inflammations. The hypothesis that low doses of X-rays modulate the oxidative burst in activated macrophages, which plays a major role in the acute inflammatory process, was tested. Materials and methods : Murine RAW 264.7 macrophages were stimulated with LPS/ γIFN, PMA or zymosan and oxidative burst was measured using either DCFH-DA or by reduction of cytochrome-C. Radiation doses of 0.3-10 Gy were given shortly before or after stimulation. Results : Low X-ray doses of <1 Gy significantly reduced the oxidative burst in activated macrophages, whereas higher doses had little effect on oxidative burst. Conclusions : The modulation of oxidative burst by low radiation doses may contribute to the therapeutic effectiveness of low-dose radiotherapy of acute necrotizing inflammations.

Anti-inflammatory effect of low-dose X-irradiation and the involvement of a TGF-β 1 -induced down-regulation of leukocyte/endothelial cell adhesion

Purpose : Low-dose radiotherapy (LD-RT) is known to exert an anti-inflammatory effect, but the underlying radiobiological and immunological mechanisms remain elusive. In recent studies, we observed a reduced adhesion of peripheral blood mononuclear cells (PBMC) to endothelial cells (EC) after LD-RT (0.3-0.7 Gy). This shows that this treatment affects the initial steps of the inflammatory response. To explore the role of inflammatory mediators in this process, we investigated the expression of Transforming growth factor β 1 (TGF- β 1) and Interleukin 6 (IL-6) after LD-RT. Materials and Methods : EC were grown to subconfluence and irradiated with single-dose LD-RT. Twenty-hours after irradiation, EC were treated with IL-1 β for 4 h and then incubated with peripheral blood mononuclear cells (PBMC). Adherent PBMC were counted when using light microscopy. Expression of the cytokines TGF- β 1 and IL-6 was measured by ELISA, and mRNA levels were analysed by the RNAse-protection assay (RPA). Surface expression of E-selectin was quantified by flow cytometry. Results : A relative minimum of adhesion was observed after LD-RT between 0.3 and 0.7 Gy. This was paralleled by an expression maximum of TGF- β 1 and IL-6, as shown by protein and mRNA levels, respectively. Neutralization of TGF- β 1 by monoclonal antibodies, but not of IL-6, increased PBMC adhesion to EC nearly to control levels. In addition, fluorescence activated cell sorter (FACS) analysis of irradiated EC demonstrated a down-regulation of E-selectin in the same dose range. Conclusion : Low-dose X-irradiation between 0.3 and 0.7 Gy induced a relative maximum of TGF- β 1 production by stimulated EC. This results in a down-regulation of leukocyte/PBMC adhesion and may contribute to the anti-inflammatory effect of LD-RT.

Effects of low-dose X-irradiation on the development of the mouse cerebellar cortex.

We labeled proliferating cells of the cerebellum of 6-day-old mice with 5-bromo-2'-deoxyuridine (BrdU) followed by a single exposure to 0.5, 1 or 2 Gy of X-rays. We then studied the effects of low-dose irradiation on the migration and survival of granule neurons in the mouse cerebellum. The animals were killed at 4 days, or at 2, 4 or 6 weeks after irradiation. Brains were fixed and BrdU-labeled cells in the cerebella were immunohistochemically analyzed. BrdU was predominantly distributed in the superficial layer of the external granular layer soon after injection. Four days after irradiation with 0.5 or 1 Gy, labeled cells were mainly seen in the inner granular layer, which was also the case in non-irradiated mice. However, following 2 Gy irradiation BrdU was found not only in the inner granular layer, but also in the Purkinje cell layer. This distribution was also seen at 2 and 4-6 weeks after irradiation. In animals irradiated with 1 Gy 4-6 weeks after irradiation, the proportion of labeled cells present in the inner granular layer decreased, while labeled cells in the Purkinje cell layer increased. On the other hand, 0.5 Gy irradiation did not change the distribution of labeled cells, except that the proportion of labeled cells in the inner granular layer decreased at 2 weeks after irradiation. The number of labeled cells in the cerebellar cortex per unit area decreased with time and dose. These results suggest that 2 Gy irradiation induces a migratory delay, abnormal distribution, and cell death of the granule neurons of the mouse cerebellum.

Stimulatory effect of low dose X-irradiation on the expression of the human T lymphocyte CD2 surface antigen.

We investigated the early effects of low doses of ionizing radiation on the CD2 gene expression in normal human T lymphocytes in order to clarify if low-dose ionizing radiation has an enhancing and/or stimulatory effect on the immune response. The results indicate that even low doses of X-irradiation strongly enhance the appearance of CD2 antigen, both in PHA-stimulated and in resting T lymphocytes as demonstrated by a rosette assay or by immunofluorescence. Moreover, an accumulation of CD2 mRNA is observed in X-irradiated cells compared with non-irradiated, a fact that is attributed mainly to transcriptional activation of the CD2 gene and not to stabilization of preformed mRNA.

Effects of low-dose X-irradiation on mouse-brain aggregation cultures.

Biochemical and morphological differentiation in reaggregating mouse-brain cell cultures after low-dose radiation (0.5 Gy) in vitro was studied. Cells were irradiated on culture day 2, corresponding to embryonic day 15-16, and different glial and neuronal markers were followed through development to postnatal day 40. The shape and size of irradiated aggregates were more irregular and smaller compared with controls. Total amounts of DNA and protein were significantly lower in irradiated aggregates than in controls between days 8 and 20. After 30 days in culture activities of the glial markers glutamine synthetase (GS) and 2',3'-cyclic nucleotide 3'-phosphodiesterase (CNP) were lower in X-irradiated aggregates than in controls. However, after 40 days the CNP activity in irradiated aggregates increased to levels above those of the controls. Irradiated and control aggregates did not differ significantly in neuronal marker enzyme activities, i.e. choline acetyltransferase (ChAT), acetylcholine esterase (AChE) and glutamic acid decarboxylase (GAD) measured on a per mg protein basis. On days 20 and 30 the amount of nerve growth factor (NGF) was two-fold higher in irradiated aggregates compared with non-irradiated ones, suggesting that, after irradiation, surviving cells in culture were induced to produce more NGF. After 40 days the amount of NGF in irradiated aggregates had decreased to the level found in the control aggregates.

The effect of low-dose X-irradiation on numerical and structural chromosome anomaly induction in mouse immature oocytes

The ability of low doses of X-rays to induce numerical and structural chromosome anomalies in immature oocytes was examined in two experiments. In the first, 10–11-day-old females were given 0.1 or 0.2 Gy of X-rays and sampled at intervals up to 32 weeks later. In the second, 4–5-week-old females were given 0.1 Gy of X-rays and sampled up to 36 weeks post-irradiation. Chromosome anomalies were assessed in metaphase II oocytes. In the first experiment, there was evidence of dose-related increase in both hyperhaploidy ( n + 1) and structural chromosome anomalies. In the second experiment, only the frequency of structural chromosome anomalies was found to increase consistently after irradiation. There was no indication that radiotion-induced depletion of the oocyte population was associated with an early onset of the maternal age effect on nondisjunction.

Effects of Sublethal Irradiation on Changes in Crypts of the Mouse Colon During Treatment With 1,2-Dimethylhydrazine&lt;xref ref-type="fn" rid="fn2"&gt;2&lt;/xref&gt;&lt;xref ref-type="fn" rid="fn3"&gt;3&lt;/xref&gt;

The effects of low-dose X-irradiation on the progression of early neoplastic changes induced in the colon by 1,2-dimethylhydrazine (DMH) were assessed. Outbred female Swiss-Webster mice were treated with DMH only, DMH-irradiation, irradiation only, or 0.001 M EDTA. Animals were pulsed with [3H]thymidine for 1 hour, and the distal colon was radioautographed. The number of labeled cells per crypt in animals tested with DMH-irradiation was greater (P less than 0.01) than the number in "DMH-only" animals, but a corresponding increase in the length of the crypts did not occur. After 16 weeks of treatment, the percentage of animals with focal atypia was similar in the DMH-irradiation group (87%), and the DMH-only group (100%), but there were more focal atypias per animal in the DMH-only group. After 20 weeks, 14% of the DMH-irradiation group had visible tumors compared to 63% of the DMH-only group. The results suggest that DMH increased the number of cells at risk for irradiation; thus the surge in proliferation subsequent to cell depletion was amplified. However, the development of precancerous lesions was not promoted.

Effects of low-dose X-irradiation in utero on the development of pyramidal cells of tne cerebral cortex in mice. (The 2nd report)

Effects of low-dose X-irradiation in utero on the development of pyramidal cells of tne cerebral cortex in mice. (The 2nd report)

Effects of low-dose X-irradiation in utero on the development of pyramidal cells of the cerebral cortex in mice

Effects of low-dose X-irradiation in utero on the development of pyramidal cells of the cerebral cortex in mice

Effects of low-dose X-irradiation and age of females on intra-uterine death in mice

Pilot-tests were carried out on the effect of low X-ray doses (0, 2, 4, 8, 12, 16 and 32 rad) and age of females on intra-uterine death. The tests included the effects of various ages of females at exposure, of fractionated irradiation and pre-partal exposure. Females and males were taken from our inbred CBA strain. Virgin females, as well as females that had produced some litters, were used. From the results it is obvious that the age of the females at the time of mating had a considerable effect on the death rate (varying from about 8% in young females to 25–30% in old ones). The low-dose X-ray exposure does not seem to have had any detectable influence on the rate of intra-uterine death.

Effects of low-dose X-irradiation and age of females on intra-uterine death in mice

Pilot-tests were carried out on the effect of low X-ray doses (0, 2, 4, 8, 12, 16 and 32 rad) and age of females on intra-uterine death. The tests included the effects of various ages of females at exposure, of fractionated irradiation and pre-partal exposure. Females and males were taken from our inbred CBA strain. Virgin females, as well as females that had produced some litters, were used. From the results it is obvious that the age of the females at the time of mating had a considerable effect on the death rate (varying from about 8% in young females to 25–30% in old ones). The low-dose X-ray exposure does not seem to have had any detectable influence on the rate of intra-uterine death.

Effects of low-dose x-irradiation and age of females on intra-uterine death in mice

Pilot-tests were carried out on the effect of low X-ray doses (0, 2, 4, 8, 12, 16 and 32 rad) and age of females on intra-uterine death. The tests included the effects of various ages of females at exposure, of fractionated irradiation and pre-partal exposure. Females and males were taken from our inbred CBA strain. Virgin females, as well as females that had produced some litters, were used. From the results it is obvious that the age of the females at the time of mating had a considerable effect on the death rate (varying from about 8% in young females to 25–30% in old ones). The low-dose X-ray exposure does not seem to have had any detectable influence on the rate of intra-uterine death.

Effects of low-dose x-irradiation on chromosomal non-disjunction in aged mice.

THE factors responsible for the increasing incidence of offspring with Down's syndrome in older women are a continuing subject of debate. The demonstration of a greater frequency of aneuploid embryos in old mice1,2 may open the way for further experimental studies of the causes of some types of chromosomally abnormal conceptuses.

Stimulation of Growth in Ocimum Kilimandscharicum by Low-Dose X-Irradiation

The effect of low-dose X-irradiation (125-2500 R) of O. kilimandscharicum seeds on germination, growth, and development was studied. Exposure to 1500 and 2500 R brought about marked stimulation in growth and flowering. The increase in foliar growth has resulted in a higher net yield of essential oil and camphor.

Effects of Low-Dose X-Irradiation on Early Mouse Embryos

Effects of Low-Dose X-Irradiation on Early Mouse Embryos