The late effects of radiation on lifespan,lymphocyte proliferation and p53 haplodeficiency in mice

Purpose:?We investigated the effect of irradiation on the lifespan of eight-week-old mice, the number of lymphocytes in bone marrow and the levels of p53 protein expression in the splenocytes.

Methods and materials:?Eight-week-old mice, wild-type p53 (p53^+/+) and heterozygous p53 (p53^+/?), were irradiated with 3 Gy. The cell numbers and cell cycle phases of bone marrow cells were determined by flow cytometry. The splenocyte proliferation was evaluated by a fluorescent cell viability assay. The p53 expression was evaluated by Western blotting.

Results:?The lifespan of the irradiated mice was shorter than that of the non-irradiated mice. In irradiated 72-week-old p53^+/+ mice and 56-week-old p53^+/? mice, the number of lymphocytes in bone marrow decreased as compared to that in the non-irradiated mice. In 56-week-old p53^+/? mice, the S- and G2/M-phases of lymphocytes in the irradiated mice were increased compared to that in the non-irradiated mice. The splenocyte proliferation in p53^+/+ mice decreased with age, and the proliferation in the irradiated mice was much lower than that in the non-irradiated mice. In 72-week-old p53^+/+ mice after re-irradiation, the p53 protein expression in the splenocytes of the irradiated mice was delayed as compared to those from the non-irradiated mice.

Conclusion:?We suggest that the decrease in the number of lymphocytes in bone marrow and the delayed p53 expression in splenocytes from the irradiated mice are related to the shortened lifespan after irradiation at a young age.     

Luminescence characteristics for identifying irradiated black soybeans

Abstract

Purpose: Considering the commercial use of food irradiation and the prevalence of international trade of irradiated food and agricultural commodities, black soybeans originating from China or Korea were irradiated at 0–5 kGy. Photostimulated luminescence (PSL) and thermoluminescence (TL) were investigated for their ability to identify characteristics that would distinguish irradiated from non-irradiated samples.

Materials and methods: Dried black soybeans [Glycine max (L.) Merr.] were irradiated using a Co-60 gamma irradiator or an electron-beam accelerator and then analysed by PSL and TL.

Results: PSL photon counts were higher in irradiated samples than in non-irradiated ones and increased with applied doses, making it possible to distinguish irradiated from non-irradiated samples. The TL analysis revealed glow curves (TL₁) with low intensity for non-irradiated samples but a higher intensity (~200°C) for irradiated samples, showing increased intensities with radiation dose. The minerals were re-irradiated at 1 kGy and the second TL glow curve (TL₂) was measured. Based on the calculated TL ratios (TL₁/TL₂) and the shape of TL₁ glow curves, the irradiated samples could be distinguished from non-irradiated ones.

Conclusions: PSL and TL are effective screening and reference methods for distinguishing gamma ray or electron beam irradiated black soybeans from non-irradiated black soybeans.     

Enhanced transplantability of a cell line from a murine ovary granulosa cell tumour in syngeneic B6C3F1 mice continuously irradiated with low dose-rate gamma-rays

Purpose:?To understand the mechanisms of life-shortening due to early neoplastic death caused by chronic low dose-rate (LDR; 20 mGy/22 h/day) radiation which accumulates to a high dose (HD; 8 Gy) (LDR/HD) as reported previously.

Materials and methods:?Female B6C3F₁ mice were continuously exposed to LDR/HD gamma-rays under specific-pathogen-free (SPF) conditions for 400 days. OV3121 cells, which were derived from an ovarian granulosa cell tumour that arose in irradiated B6C3F₁ mice, were inoculated into LDR/HD irradiated and age-matched non-irradiated control mice. The transplantability of tumour cells as well as T cell subsets and the proliferative activities of T cells were compared between irradiated and non-irradiated mice.

Results:?We found that tumour formation of subcutaneously inoculated tumour cells occurred earlier in irradiated mice than in non-irradiated mice. Proliferative activity of draining lymph node lymphocytes against transplanted tumour cells as well as allogeneic mixed lymphocyte reactions were significantly reduced in irradiated mice compared to non-irradiated mice.

Conclusions:?These results suggest that decreased tumour-specific immune response due to LDR/HD irradiation may enhance tumorigenesis resulting in life-shortening of mice after chronic LDR/HD irradiation.     

Abscopal effect of radiation therapy: Interplay between radiation dose and p53 status

Abstract

Purpose: This study investigates whether the abscopal effect induced by radiation-therapy (RT) is able to sterilize non-irradiated tumour cells through bystander signals.

Material and methods: Wild-type (wt)-p53 or p53-null HCT116 human colon cancer cells were xenografted into both flanks of athymic female nude mice. When tumours reached a volume of 0.2 cm³, irradiation was performed, under strict dose monitoring, with a dedicated mobile accelerator designed for intra-Operative-RT (IORT). A dose of 10 or 20 Gy (IR groups), delivered by a 10 MeV electron beam, was delivered to a tumour established in one side flank, leaving the other non-irradiated (NIR groups). A subset of mice were sacrificed early on to carry out short-term molecular analyses.

Results: All directly-irradiated tumours, showed a dose-dependent delayed and reduced regrowth, independent of the p53 status. Importantly, a significant effect on tumour-growth inhibition was also demonstrated in NIR wt-p53 tumours in the 20 Gy-irradiation group, with a moderate effect also evident after 10 Gy-irradiation. In contrast, no significant difference was observed in the NIR p53-null tumours, independent of the dose delivered. Molecular analyses indicate that p53-dependent signals might be responsible for the abscopal effect in our model system, via a pro-apoptotic pathway.

Conclusions: We suggest that the interplay between delivered dose and p53 status might help to sterilize out-of-field tumour cells.     

Radiation decreases murine small intestinal HCO3− secretion

Purpose:?While secretagogue-induced diarrhea is rich in chloride (Cl^?) and bicarbonate (HCO₃ ^?) anions, little is known about diarrhea or its anionic composition following irradiation. We performed studies to characterize the differences between cyclic adenosine monophosphate (cAMP)-stimulated anion secretions in irradiated and non-irradiated mice.

Materials and methods:?HCO₃ ^? secretion was examined in basal, cAMP-stimulated, and irradiated jejunal tissues from BALB/c (Bagg albino) mice. The abdomens of the mice were γ-irradiated using a caesium-137 source.

Results:?Ussing-chamber experiments performed in an HCO₃^?-containing, Cl^?-free solution on the bath side showed inhibition of HCO₃^? in irradiated mice. Non-irradiated mice exhibited bumetanide-sensitive and insensitive current, while irradiated mice displayed bumetanide-sensitive current. pH-stat experiments showed inhibition of basal and cAMP-stimulated HCO₃^? secretions in irradiated mice. Immunohistochemistry and Western blot analysis displayed a sodium-bicarbonate cotransporter expression in the villus and not the crypt of non-irradiated mice, while its expression and protein levels decreased in irradiated mice.

Conclusions:?Anion secretions in irradiated mice, being primarily Cl^? and minimally HCO₃^?, differ from that of secretagogue-induced anion secretions. Understanding anion loss will help us correct electrolyte imbalances, while reduced HCO₃^? secretion in the upper-gastrointestinal tract might also have implications for irradiation-induced nausea and vomiting.     

Irradiation of normal mouse tissue increases the invasiveness of mammary cancer cells

Purpose:?Treatment of breast tumours frequently involves irradiating the whole breast to reach malignant microfoci scattered throughout the breast. In this study, we determined whether irradiation of normal tissues could increase the invasiveness of breast cancer cells in a mouse model.

Materials and methods:?Non-irradiated MC7-L1 mouse mammary carcinoma cells were injected subcutaneously in irradiated and non-irradiated thighs of Balb/c mice. The invasion volume, tumour volume, blood vessel permeability and interstitial volumes were monitored by magnetic resonance imaging (MRI). Slices of normal tissue invaded by cancer cells were examined by histology. Activity of matrix metalloproteinase -2 and -9 (MMP -2 and -9) in healthy and irradiated tissues was determined, and the proliferation index of the invading cancer cells was evaluated.

Results:?Three weeks after irradiation, enhancement of MC7-L1 cells invasiveness in irradiated thighs was already detected by MRI. The tumour invasion volume continued to extend 28- to 37-fold compared to the non-irradiated implantation site for the following three weeks, and it was associated with an increase of MMP-2 and -9 activities in healthy tissues. The interstitial volume associated with invading cancer cells was significantly larger in the pre–irradiated sites; while the blood vessels permeability was not altered. Cancer cells invading the healthy tissues were proliferating at a lower rate compared to non-invading cancer cells.

Conclusion:?Implantation of non-irradiated mammary cancer cells in previously irradiated normal tissue enhances the invasive capacity of the mammary cancer cells and is associated with an increased activity of MMP-2 and -9 in the irradiated normal tissue.     

Effects of gamma radiation (γ) on biochemical and antioxidant properties in black gram (Vigna mungo L. Hepper)

Abstract

Purpose: The present study focused on the role of primary metabolites, antioxidant activities in black gram (Vigna mungo L. Hepper) variety Vamban-4 under the impact of gamma irradiation.

Materials and methods: The black gram seeds were irradiated at a different dose of gamma rays viz., 200, 400, 600, 800, 1000 and 1200 Gray (Gy), and analyzed the changes of biochemical and antioxidant contents.

Results: Biochemical contents increased with increasing doses up to 800?Gy and reduced at higher dose viz.,1000 and 1200?Gy of gamma-ray treatment, while malondialdehyde content increased at higher dose 1200?Gy compared to control, this indicates that the formation of more lipid peroxidation at higher radiation level. Gamma irradiation enhanced the activity of antioxidant enzymes such as catalase, peroxidase and superoxide dismutase with increasing doses rather than control plants. These studies depict that the effect of gamma irradiation on seeds increased the free radicals compared to control, which emphasize by the Electron spin resonance spectroscopy (ESR). Gamma irradiated seed samples contain more fractions of protein, lipids, amino acid and polysaccharides compared to control plants observed from the Fourier infrared transform spectroscopy (FTIR).

Conclusion: The present result concludes that cellular metabolites and the antioxidant enzymes increased and these alterations of metabolism due to the effect of gamma rays which induced free radical production in seeds and plants grown under irradiation stress. These results confirm that the exposure of gamma irradiation produced free radicals as well as counteract by antioxidant enzymes and in addition to that accumulation and alteration of primary metabolites.     

Numerical chromosome abnormalities in 8-cell embryos generated from γ-irradiated male mice in the absence and presence of vitamin E

Purpose:?To investigate the effects of γ-rays on male NMRI mice, in the absence or presence of vitamin E, on abnormalities in chromosome number in 8-cell embryos generated after mating with non-irradiated female mice.

Materials and methods:?The 8 – 11 week old male NMRI mice were irradiated whole body with 4 Gy of γ-rays alone or in combination with 200 international units (IU)/kg vitamin E administered 1 h prior to irradiation. After 4 days, they were mated at weekly intervals with superovulated, non-irradiated female mice in successive 6 weekly periods. About 68 h post coitous (p.c.), 8-cell embryos were fixed on slides using standard methods in order to screen for abnormalities in chromosome number.

Results:?In control embryos, 8% of metaphases were aneuploid whereas in embryos generated from irradiated mice, the frequency of aneuploidy increased dramatically at all post irradiation sampling times (p < 0.001). Administration of vitamin E one hour before irradiation, significantly decreased chromosomal aberrations in all 6 groups (p < 0.05).

Conclusion:?Data indicate that γ-irradiation affects spermatogenesis and causes DNA alterations in sperm that may lead to chromosome abnormalities in subsequent embryos. Administration of vitamin E before irradiation effectively reduced the frequency of chromosomal abnormalities. The mechanism(s) by which vitamin E reduces genotoxic effects of radiation could be via radical scavenging or antioxidative effects.     

Involvement of bystander effect in suppression of the cytokine production induced by heavy-ion broad beams

Purpose: Immune cells accumulate in and around cancers and cooperate with each other using specific cytokines to attack the cancer cells. The heavy-ion beams for cancer therapy may stimulate immune cells and affect on the immune system. However, it is still poorly understood how the immune cells are stimulated by ion-beams. Here, we irradiated immune cells using heavy-ion beams and analyzed changes in production of tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) that are important cytokine for the cancer treatment.

Materials and methods: The human THP-1 monocytes were differentiated into macrophages and then irradiated using carbon-ion broad-beams (108 keV μm^?1). To examine the bystander response after heavy-ion irradiation, a very small fraction (approx. 0.45%) of the cell population was irradiated using heavy-ion microbeams. After irradiation, we examined the cytokine productions.

Results: When cells were irradiated with 5 Gy, cytokine levels were reduced after both microbeam irradiation and broad-beam irradiation. TNF-α production of macrophages with the nitric oxide (NO) inhibitor-treatment increased after carbon-ion broad-beam. NO was involved in the radiation-induced suppression of TNF-α production.

Conclusions: The suppression of cytokine production arose after irradiation with heavy-ions, and may also be induced in the surrounding non-irradiated cells via the bystander effect.     

Chronic exposure to gamma irradiation at low-dose rates accelerates blood pressure decline associated with aging in female B6C3F1 mice

Abstract

Purpose: Many studies are focusing on the biological effects of gamma irradiation at low-dose rates. Studies have shown that chronic exposure to gamma irradiation at low-dose rates shortened the lifespan of mice due to neoplasm formation. The aim of this study was to clarify the physiological effects of long-term exposure to gamma irradiation at low-dose rates in mice, measured with noninvasive parameters such as blood pressure.

Materials and methods: Specific-pathogen-free female B6C3F₁ mice were irradiated with gamma rays at a low dose of 20 mGy/day – a dose rate shown to shorten the life span in previous studies. The blood pressure parameters (systolic, diastolic, and mean blood pressure), heart rate, tail blood volume, and blood flow of the mice were measured every 7 weeks. Age-matched, non-irradiated mice were used as controls.

Results and conclusion: The blood pressure levels of the irradiated mice decreased at an earlier age compared to the non-irradiated control mice. The expression levels of the marker genes of aging that are also associated with regulation of blood pressure showed significant differences between non-irradiated and irradiated mice. These results indicated that long-term exposure to gamma irradiation at low-dose rates induce the expression levels of Rap1a and reduces Panx1 and Sirt3, which may have contributed to the accelerated blood pressure decline in female mice.     

Increased 3H-thymidine Incorporation into DNA of Irradiated Slime Mould

Summary

Synchronous cultures of the slime mould Physarum polycephalum were incubated in ³H-thymidine. Some cultures were exposed to 25 kr of x-rays. The specific activity of DNA from irradiated cultures was 40 per cent greater than that from non-irradiated preparations. Feulgen spectrophotometric measurements indicated the same amount of DNA per nucleus in both cases. After exposure of samples to ultra-violet light the proportion of thymine to thymine dimers was the same in irradiated and non-irradiated samples, indicating there had been no large addition of thymine to DNA. Heating and cooling in 1 per cent formaldehyde did not release any pieces of low molecular weight that were separable from DNA on Sephadex columns, a finding that argues against loose association of precursor and DNA. The possibility that specific activity of the precursor pool may be changed by irradiation, or that replacement of damaged sites on DNA may occur, are offered as possible explanations.     

The induction of a radiation-induced bystander effect in fish transcends taxonomic group and trophic level

Abstract

Purpose: To extend the investigations of bystander effect induction in fish of the same species as the irradiated fish, to bystander effect induction between fish species and between trophic levels.

Materials and methods: To investigate interspecies bystander effect induction, zebrafish and medaka were irradiated with a 0.5 Gy X-ray dose and then swum with non-irradiated fish of the same and opposite species. To investigate trophic level bystander effect induction, California blackworms were irradiated with the same X-ray dose and then fed to non-irradiated rainbow trout.

Results: Reductions in clonogenic survival of the HPV-G (non-transformed human keratinocytes, immortalized with the human papilloma virus) reporter cell line, treated with tissue explant media, revealed that zebrafish and medaka induced a pro-apoptotic bystander effect in the other species and that, in trout, the normally anti-apoptotic effect caused by the consumption of non-irradiated blackworms was significantly reduced or lost if the blackworms had been irradiated.

Conclusions: These results are the first to show that a radiation- induced bystander effect can transcend taxonomic group and trophic level in fish. This provides further evidence that bystander signals are widespread and conserved and may be transmitted through an ecosystem, as well as between individuals of the same species.     

Radiation tolerance in the tardigrade Milnesium tardigradum

Purpose: Tardigrades are known to survive high doses of ionizing radiation. However, there have been no reports about radiation effects in tardigrades under culture conditions. In this study, we investigated tolerance of the tardigrade, Milnesium tardigradum, against gamma-rays and heavy ions by determining short-term or long-term survival, and reproductive ability after irradiation.

Materials and methods: Hydrated and anhydrobiotic animals were exposed to gamma-rays (1000 – 7000 Gy) or heavy ions (1000 – 8000 Gy) to evaluate short-term survival at 2, 24 and 48 h post-irradiation. Long-term survival and reproduction were observed up to 31 days after irradiation with gamma-rays (1000 – 4000 Gy).

Results: At 48 h after irradiation, median lethal doses were 5000 Gy (gamma-rays) and 6200 Gy (heavy ions) in hydrated animals, and 4400 Gy (gamma-rays) and 5200 Gy (heavy ions) in anhydrobiotic ones. Gamma-irradiation shortened average life span in a dose-dependent manner both in hydrated and anhydrobiotic groups. No irradiated animals laid eggs with one exception in which a hydrated animal irradiated with 2000 Gy of gamma-rays laid 3 eggs, and those eggs failed to hatch, whereas eggs produced by non-irradiated animals hatched successfully.

Conclusion: M. tardigradum survives high doses of ionizing radiation in both hydrated and anhydrobiotic states, but irradiation with >1000 Gy makes them sterile.     

Possible role of vitamin E,coenzyme Q10 and rutin in protection against cerebral ischemia/reperfusion injury in irradiated rats

Purpose:?To investigate the possible role of vitamin E, coenzyme Q10 and rutin in ameliorating the biochemical changes in brain and serum induced by cerebral ischemia/reperfusion (I/R) in whole body γ-irradiated rats.

Materials and methods:?Cerebral ischemia was induced in male Wistar rats (either irradiated or non-irradiated) followed by reperfusion.

Results:?I/R increased brain content of malondialdehyde (MDA) and depleted its glutathione (GSH) content with a compensatory elevation in cytosolic activities of glutathione peroxidase (GPx) and glutathione reductase (GR) enzymes. It also raised brain cytosolic lactate dehydrogenase (LDH) activity and calcium (Ca²⁺) level. Furthermore, I/R provoked an inflammatory response reflected by an increment in serum levels of the proinflammatory cytokines tumour necrosis factor-α (TNF-α) and interlukin-1β (IL-1β). Moreover, induction of I/R in irradiated rats resulted in a further increase in brain oxidative stress and cytosolic LDH activity, disturbed brain Ca²⁺ homeostasis and exaggerated the inflammatory reaction. During irradiation, administration of each of vitamin E, coenzyme Q10 (CoQ10) and rutin to irradiated rats before induction of I/R, alleviated the brain oxidative stress. Moreover, these antioxidants caused attenuation of the rise of the cytosolic activities of GPx and GR. A lowering effect of the cytosolic LDH activity and Ca²⁺ level were caused by treatment with antioxidants. Each of vitamin E and rutin revealed an anti-inflammatory action of these antioxidants, while CoQ10 had no effect on serum levels of TNF-α and IL-1β.

Conclusion:?These findings indicate that supplementation with either vitamin E, CoQ10 or rutin ameliorated most of the biochemical changes induced by I/R in irradiated rat brain and serum.     

Differential expression of flowering genes in Arabidopsis thaliana under chronic and acute ionizing radiation

Abstract

Purpose: Chronic and acute irradiations have drastic effects on flowering stage that plays an important role in further seed development and can determine seed yield. The expression of the key flowering genes, AP1, CO, GI, FT, FLC, and LFY, sensitive to irradiation repair gene RAD51 and the proliferation gene PCNA2 were studied in the wild-type Arabidopsis thaliana (Columbia ecotype) under chronic and acute irradiations.

Materials and methods: Chronic irradiation was performed using the radioactive isotope ¹³⁷СsCl in two total doses of 3 cGy and 17 cGy, with the dose rate of 10^?7 cGy/s and 6.8 10^?6 cGy/s, respectively. The plants were grown under chronic irradiation during 6 weeks, from seeds till the 6.3 stage of flowering. For acute exposure, the plants were X-ray irradiated one time at the 5.0 development stage (20 days old) by a total dose of 15?Gy with the dose rate of 89 cGy/s.

Results: After chronic irradiation with the 3 cGy dose the irradiated plants demonstrated 8?±?2.8 days earlier flowering than in the control group. However, at the 17 cGy chronic and at the 15?Gy acute doses plants showed 14?±?3.7 and 2?±?1.4 days later flowering, respectively. The 3 cGy chronic exposure significantly increased the expression of the CO gene by a factor of 1.152 (1.087–1.217 95% C.I.) and decreased the expression of the FT gene by a factor of 0.128 (0.021–0.396 95% C.I.). The 17 cGy chronic exposure decreased expression of the AP1 gene by a factor of 0.872 (0.803–0.940 95% C.I.) and the LFY gene by a factor of 0.471 (0.306–0.687 95% C.I.). The 15?Gy acute exposure decreased the expression of the AP1 gene by a factor of 0.104 (0.074–0.144 95% C.I.) and the PCNA2 gene by a factor of 0.346 (0.238–0.488 95% C.I.).

Conclusions: The increased expression of the CO gene and decreased expression of the AP1 and FT genes under the lower dose of chronic exposure were associated with earlier flowering. The acute exposure increased the expression of the PCNA2 gene and decreased the expression of the flowering genes, except AP1. The flowering was delayed under both the higher dose of chronic exposure and under acute exposure, but it was less affected by the latter. Presumably, it was related to the activation of DNA repair under the 3 cGy chronic and 15?Gy acute irradiations.     

Ameliorative effect of black grape juice on systemic alterations and mandibular osteoradionecrosis induced by whole brain irradiation in rats

Purpose: Whole brain irradiation (WBI) causes a variety of secondary side-effects including anorexia and bone necrosis. We evaluated the radiomodifying effect of black grape juice (BGJ) on WBI alterations in rats measuring food and water intake, body weight, hemogram, and morphological and histological mandibular parameters.

Materials and methods: Forty male rats (200–250?g) were exposed to eight sessions of cranial X-ray irradiation. The total dose absorbed was 32?Gy delivered over 2 weeks. Four groups were defined: (i) NG: non-irradiated, glucose and fructose solution-supplemented (GFS); (ii) NJ: non-irradiated, BGJ-supplemented; (iii) RG: irradiated, GFS-supplemented; and (iv) RJ: irradiated, BGJ-supplemented. Rats received daily BGJ or GFS dosing by gavage starting 4 days before, continuing during, and ending 4 days after WBI.

Results: RJ rats ingested more food and water and showed less body weight loss than RG rats during the irradiation period. Forty days after WBI, irradiated animals started losing weight again compared with controls as a consequence of masticatory hypofunction by mandibular osteoradionecrosis (ORN). Osteoclastic activity and inflammation were apparent in RG rat mandibles. BGJ was able to attenuate the severity of ORN as well as to improve white and red blood cell counts.

Conclusions: Fractionated whole brain irradiation induces mandibular changes that interfere with normal feeding. BGJ can be used to mitigate systemic side-effects of brain irradiation and ORN.     

Biological effects of protons targeted to different ranges in Arabidopsis seeds

Purpose: To investigate the biological effects of radiation damage induced at different depths of a plant seed and to investigate the difference in radiation response between dry seeds and water-imbibed seeds to the same type of radiation.

Materials and methods: Arabidopsis seeds of the wild-type Columbia ecotype were used in our experiments. Dry or water-imbibed Arabidopsis seeds were irradiated with 1.1 MeV, 2.6 MeV or 6.5 MeV protons (H⁺). For comparison, 30 keV nitrogen ions (N⁺) were also used to irradiate dry Arabidopsis seeds. The germination and survival rates of the seeds were measured after each irradiation.

Results: After irradiation with 2.6 MeV H⁺ and 6.5 MeV H⁺, the fluence-response curves for germination and survival had distinct shoulders and then survival was reduced rapidly with increasing fluence. 2.6 MeV H⁺ was more effective than 6.5 MeV H⁺ in inhibiting germination and survival and water-imbibed seeds were more sensitive to the 6.5 MeV H⁺ irradiation than dry seeds. For 1.1 MeV H⁺ the germination and survival rates were reduced gradually and an intermediate plateau emerged for germination, which was similar to that observed for survival following 30 keV N⁺ irradiation. One of the key morphologic malformations, the multi-SAM (shoot apical meristem), was observed both for dry and water-imbibed seeds after all proton irradiations and for the dry seeds after 30 keV N⁺ irradiation.

Conclusions: Radiation-induced damage produced at different ranges in Arabidopsis seeds results in different fluence-response curves with water-imbibed seeds being more sensitive to proton irradiation than dry seeds. As well as the shoot apical meristem (SAM) being the primary target for irradiation, there exists a secondary target around the SAM that also contributes to the radiation response.     

Radiation-induced Tissue Breakdown

Summary

1. An attempt was made to determine the source of excess ¹⁴C -labelled glycine and phenylalanine observed in ‘free’ metabolic pools of rats loaded with glycine-2-¹⁴C and phenylalanine-3-¹⁴C before irradiation.

2. Tissues from various organs of irradiated and non-irradiated rats were fractionated into three protein fractions. Glycine, phenylalanine, tyrosine, serine and alanine were isolated from these fractions, and the respective specific activities were determined.

3. Differences in specific activities were : decreased activity in muscle collagen and soluble-protein fractions of thymus and spleen; increased activity in soluble-protein fractions of liver and muscle; and variable changes in the activity of certain amino acids of the soluble-protein fraction of kidney.

4. The significance of these changes is discussed in terms of known biological effects of radiation on cells and cellular metabolism.

5. Muscle collagen seems radio-sensitive and its increased catabolism in irradiated rats could explain much of the excess ¹⁴C-activity in ‘free’ -amino-acid pools.     

IL‐1β, TNFα and IL‐6 induction in the rat brain after partial‐body irradiation: role of vagal afferents

Purpose: To evaluate the central nervous system neuroimmune and inflammatory responses during the prodromal phase of the acute irradiation syndrome in rat brains after partial‐body exposure (head‐protected) and to investigate the potential neural signalling pathways from the irradiated periphery to the non‐irradiated brain.

Material and methods: The study included four groups of rats: one irradiated group and one sham irradiated group, each containing non‐vagotomized and vagotomized rats. In vagotomized rat groups, the subdiaphragmatic vagal section surgery was carried out 45 days before the irradiation exposure. The rats were partial‐body irradiated with the head shielded with ⁶⁰Co γ‐rays to a dose of 15?Gy. They were sacrificed 6?h after the end of exposure. The hypothalamus, hippocampus, thalamus and cortex were then collected, and the concentrations of IL‐1β, TNFα and IL‐6 in each were measured by ELISA assays.

Results: Six hours after irradiation, IL‐1β levels had increased in the hypothalamus, thalamus and hippocampus, and TNFα and IL‐6 levels had increased significantly in the hypothalamus. Vagotomy before irradiation prevented these responses.

Conclusions: It was concluded that the hypothalamus, hippocampus, thalamus and cortex react rapidly to peripheral irradiation by releasing pro‐inflammatory mediators. The results also show that the vagus nerve is one of the major ascending pathways for rapid signalling to the brain with respect to partial body irradiation.     

The influence of irradiation on the potential chondroprotective effect of aqueous extract of propolis in rats

Purpose:?Cartilage degradation usually results as a consequence of inflammatory processes in the joints. To study this phenomenon experimentally, adjuvant-induced arthritis (AIA) was used as a model of chronic inflammation under the influence of irradiation. The potential chondroprotective effect of 13% aqueous extract of propolis (AEP) in arthritic rats was investigated.

Materials and methods:?The influence of whole body irradiation on the arthritic inflammatory response was investigated by subjecting rats to a Gamma source before the induction of arthritis. 13% AEP was injected intraperitoneally in a dose of 5 ml/kg and diclofenac was used as reference non-steroidal anti-inflammatory drug (NSAID) in a dose of 3 mg/kg. The chosen parameters for cartilage integrity were glycosaminoglycan (GAG), hydroxyproline contents in cartilage and cartilage oligomeric matrix protein (COMP) in serum. The serum levels of tumour necrosis factor-alpha (TNF-α), nitric oxide (NO) and the oxidative stress biomarkers such as blood glutathione (GSH) and plasma malondialdehyde (MDA) levels.

Results:?Induction of arthritis led to a reduction in GAG and hydroxyproline content of femoral cartilage and a corresponding rise in COMP in serum. Previous exposure to irradiation resulted in a milder reduction of GAG and hydroxyproline and a lesser rise in COMP. Treatment of arthritic irradiated and non-irradiated rats with 13% AEP markedly prevented the breakdown of cartilage in a much more effective manner than diclofenac. Both AEP and diclofenac were equipotent in reducing the level of TNF-α and were able to normalize NO and the oxidative stress biomarkers in non-irradiated and irradiated arthritic rats.

Conclusion:?The ability of propolis to protect cartilage degradation could therefore prove of value in the treatment of chronic arthritic diseases, offering an advantage over some NSAID, particularly those with a potential detrimental effect on cartilage integrity.