The Effect of γ-Radiation and Desiccation on the Viability of the Soil Bacteria Isolated from the Alienated Zone around the Chernobyl Nuclear Power Plant

Methylobacterium extorquens, M. mesophilicum, and Bacillus subtilis strains were found to be resistant to -radiation, irrespective of whether they were isolated from the alienated zone around the Chernobyl Nuclear Power Plant or outside this zone. The LD₉₀ of Methylobacterium and B. subtilis strains with respect to -radiation was 2.0–3.4 and 3.7–4.4 kGy, respectively, whereas their LD_99.99 values were 4.5–6.9 and more than 10 kGy, respectively. The high threshold levels of -radiation for Methylobacterium and B. subtilis imply the efficient functioning of DNA repair systems in these bacteria. Unlike Bacillus polymyxa cells, the cells of M. extorquens, M. mesophilicum, and B. subtilis were also resistant to desiccation. Pseudomonas sp., Nocardiasp., and nocardioform actinomycetes were sensitive to both -radiation and desiccation. Similar results were obtained when the bacteria studied were exposed to hydrogen peroxide and ultraviolet radiation. The results obtained indicate that the bacteria that are resistant to -radiation are also resistant to desiccation, UV radiation, and hydrogen peroxide. The possibility of using common laboratory tests (such as the determination of bacterial resistance to UV light and desiccation) for the evaluation of bacterial resistance to -radiation is discussed.     

Malic enzyme activity and related Biochemical aspects during ripening of γ-irradiated mango fruit

The increase in malic enzyme (l-malate: NADP⁺ oxidoreductase (oxalacetate-decarboxylating) EC 1.1.1.40) activity, usually observed during the r     

^60Co-γ辐照油茶种子对其幼苗生长的影响

本试验探讨3个油茶品种（‘岑软2号’、‘岑软3号’、‘岑软11号’）种子经不同剂量（1000、2000、3000rad）^60Co-γ辐照后,测量其一年半生幼苗的苗高及地径生长情况。结果表明：1000rad辐射剂量对‘岑软3号’的苗高生长起促进作用;1000rad和2000rad辐射剂量对‘岑软2号’的地径生长有促进作用,1000、3000rad辐射剂量对‘岑软11号’的地径生长起抑制作用。     

4-(4-Hydroxy-3-methoxyphenyl)-2-butanone modulates redox signal in gamma-irradiation-induced nephrotoxicity in rats

Cellular exposure to ionising radiation leads to oxidative stress events, which refer to elevated intracellular levels of reactive oxygen species (ROS). The elevated levels of ROS significantly contributed to γ-radiation (IR) induced cytotoxicity. In an attempt to minimise these cytotoxic effects, antioxidant compounds have been identified to counteract radiation- associated toxicities. We mainly aimed to study the protective effect of 4-(4-hydroxy-3-methoxyphenyl)-2-butanone (HMB) on IR-induced nephrotoxicity, whereas it was previously shown to have anti-inflammatory effects in different inflammation models. Animals were treated orally with HMB (25?mg/kg b.wt daily) then performed by whole-body gamma-irradiation of animals with 6?Gy; a single dose applied on the 15th day and animals were sacrificed at the end of the 23rd day. It was found that IR exposure significantly induced renal oxidative injury that accompanied by inflammatory disturbance. Also, NADPH oxidase and iNOS gene expressions were significantly up-regulated, while the mitochondrial enzymes (complex I &; II) were significantly down-regulated in IR exposed animals. Additionally, Western immunoblotting analysis of signalling growth factor protein; p38 MAPK was significantly overexpressed. Interestingly, HMB treatment showed statistically significant amelioration in parameters with an improved histological structure upon the IR-induced nephrotoxicity. It can be concluded that modulation of NADPH-oxidase, iNOS and mitochondrial enzymes by HMB might be responsible for the amendment of the antioxidant status and impairment of p38 MAPK signal, thus attenuate the nephrotoxicity induced post IR exposure.     

Ferulic acid (FA) abrogates γ-radiation induced oxidative stress and DNA damage by up-regulating nuclear translocation of Nrf2 and activation of NHEJ pathway

The present study was aimed to evaluate the radioprotective effect of ferulic acid (FA), a naturally occurring plant flavonoid in terms of DNA damage and damage related alterations of repair pathways by gamma radiation. FA was administered at a dose of 50?mg/kg body weight for five consecutive days prior to exposing the swiss albino mice to a single dose of 10?Gy gamma radiation. Ionising radiation induces oxidative damage manifested by decreased expression of Cu, Zn-SOD (SOD stands for super oxide dismutase), Mn-SOD and catalase. Gamma radiation promulgated reactive oxygen species (ROS) mediated DNA damage and modified repair pathways. ROS enhanced nuclear translocation of p53, activated ATM (ataxia telangiectasia-mutated protein), increased expression of GADD45a (growth arrest and DNA-damage-inducible protein) gene and inactivated Non homologous end joining (NHEJ) repair pathway. The comet formation in irradiated mice peripheral blood mononuclear cells (PBMC) reiterated the DNA damage in IR exposed groups. FA pretreatment significantly prevented the comet formation and regulated the nuclear translocation of p53, inhibited ATM activation and expression of GADD45a gene. FA promoted the nuclear translocation of nuclear factor (erythroid-derived 2)-like 2 (Nrf2) and activated NHEJ repair pathway to overcome ROS mediated oxidative stress and DNA damage. Therefore, the current study stated that FA can challenge the oxidative stress by (i) inducing nuclear translocation of Nrf2, (ii) scavenging ROS, and (iii) activating NHEJ DNA repair process.     

Coupling of histone mRNA levels to radioresistant DNA synthesis in ataxia-telangiectasia cells

Cloned genomic DNA for human histone H1, H3 and H4 genes has been used to determine the effects of -radiation on histone mRNA levels and synthesis in ataxia-telangiectasia cells. Synthesis of histone mRNA was determined in cells synchronized with aphidicolin. Effects of irradiation on DNA synthesis and passage through S phase were also monitored. Irradiation was found to slow the passage of control cells through the cell cycle but had no effect on progression of ataxia-telangiectasia cells. H1 and core histone mRNA synthesis was inhibited by radiation in two control cell lines after release from aphidicolin block. No inhibition was observed in one ataxia-telangiectasia cell line and a small degree of inhibition in a second. An increased level of mRNA was observed in both irradiated control and ataxia-telangiectasia cells at 5–7 h post-irradiation compared to unirradiated cells. Similar results were obtained in log phase cells. These results demonstrate that histone mRNA synthesis is radioresistant in ataxia-telangiectasia cells and is coupled to radioresistant DNA synthesis in these cells.     

Development of an inexpensive, low attenuation styrofoam primate chair for use in a PET scanner

Pharmacokinetic modelling of radiotracers for positron emission tomography (PET) imaging of neuroreceptors can be performed with time-activity data for brain and blood. We aimed to develop an alternative to withdrawal of arterial blood samples for acquisition of a blood curve. A supportive primate chair was constructed out of styrofoam and fixed to the head portion of the bed of a PET scanner. A lightly anaesthetised rhesus monkey was positioned in the chair in a sitting position and injected with the radiotracer. The styrofoam chair provided sufficient support for the monkey. The presence of the chair in the PET scanner caused negligible attenuation of radiation, allowing simultaneous acquisition of dynamic data from the subject's brain and heart. We conclude that a styrofoam primate chair is an ideal tool to measure blood and brain data from a rhesus monkey with PET. Invasiveness to the animal is reduced, as well as experimenter time.     

α-, β-, and γ-Tubulin Polymerization in Response to DNA Damage

Microtubules provide structural support for a cell and play key roles in cell motility, mitosis, and meiosis. They are also the targets of several anticancer agents, indicating their importance in maintaining cell viability. We have investigated the possibility that alterations in microtubule structure and tubulin polymerization may be part of the cellular response to DNA damage. In this report, we find that γ-radiation stimulates the production and polymerization of α-, β-, and γ- tubulin in hematopoeitic cell lines (Ramos, DP16), leading to visible changes in microtubule structures. We have found that this microtubule reorganization can be prevented by caffeine, a drug that concomitantly inhibits DNA damage-induced cell cycle arrest and apoptosis. Our results support the idea that microtubule polymerization is an important facet of the mammalian response to DNA damage.     

Effect of γ-radiation on the ratio of [18F]2-fluoro-2-deoxy-D-glucose to glucose utilization in human glioblastoma cellsin vitro

The glucose consumption in tumoursin vivo as reflected by uptake of [¹⁸F]2-fluoro-2-deoxy-D-glucose (¹⁸FDG) using positron emission tomography (PET) is currently under investigation as a measure of tumour response to radiotherapy. The calculation of cerebral metabolic rate of glucose from¹⁸FDG-PET data requires a proportionality factor referred to as the lumped constant. In the presentin vitro study, the utilizations of¹⁸FDG and glucose have been measured in a human glioblastoma cell line (86HG-39) as a function of γ-radiation dose with various post-irradiation times and of different fractionation modes. The ratio of utilization of¹⁸FDG to that of glucose (R_F/G), assumed to correspond to the lumped constant, was observed to increase 12 and 24 h after single fraction γ-exposure by factors ranging from 1.2 to 1.5 compared with the non-irradiated controls. It decreased after multiple fraction γ-exposure (4 × 2 Gy) by a factor of 0.7 compared with the single fraction schedule (1 × 8 Gy). The results suggest that the affinities of glucose transporters or hexokiriase enzyme or both for¹⁸FDG and glucose could be influenced by γ-irradiation in this tumour cell linein vitro. Apparent changes of the glucose consumption determined with PET in human tumours following radiotherapy may, therefore, not be solely due to changes in cellular metabolism or cell number but may also be due to changes in R _F/G .