Radiation chemistry of overirradiated aqueous solutions of hydrogen cyanide and ammonium cyanide

Summary The radiolysis of aqueous solutions (O₂-free) of HCN and NH₄CN was examined at very large doses of⁶⁰Co gamma radiation (up to 230 Mrad). In this dose range the cyanide initially present (0.12 M) is decomposed and only its radiolytic products participate in the radiation-induced chemical process. It has been found that the weight of the dry residue containing the mixture of nonvolatile radiolytic products increases as doses increase up to 40 Mrad (up to about 4 g/l), but with further dose increases remains practically unchanged (NH₄CN) or decreases slightly (HCN). Carboxylic and amino acids are present in overirradiated samples. At increasing doses their concentrations decrease, with the exception of oxalic and malonic acids, which are continually produced and accumulate. This is also the case with the abundant NH₃ and CO₂, as well as with several other products that were generated at lower radiation-chemical yields. The molecular weights of the radiolytic products are up to 20,000 daltons throughout the dose range studied. Their amounts gradually change with increasing doses above 30 Mrad: The compounds with M_w between 2,000 and 6,000 daltons become more abundant, while the amounts of polymers with M_w between 6,000 and 20,000 decrease. The relevance of these findings for studies of chemical evolution is considered.     

Physiological and molecular studies on the effect of gamma radiation in fenugreek (Trigonella foenum-graecum L.) plants

This experiment assessed the biochemical changes in fenugreek plants exposed to gamma radiation. Two pot experiments were carried out during two growing seasons of 2015 and 2016. Seeds were subjected to five doses of gamma irradiation (25, 50, 100, 200 and 400?Gy) and were immediately planted into soil pots in a greenhouse. The experimental analysis was performed in M₁ and M₂ generations. Significant differences between irradiated and control plants were detected for most studied characters in M₁ and M₂ generations. It was demonstrated that low doses of gamma irradiation led to gradually increases in growth, yield characters, leaf soluble protein concomitantly with increases in the contents of phenolic and flavonoids compounds particularly at 100?Gy. These changes were accompanied by a substantial increase in ascorbic acid, α-tocopherol and retinol contents. Proline content was increased under all doses of gamma rays in M₁ generation and the highest amount of proline was obtained at 200?Gy with visible decrease in M₂ generation under the same dose. Meanwhile, the highest dose of gamma radiation (400?Gy) decreased all the studied parameters in both mutagenic generations as compared with control plants. In addition, gamma irradiation doses induced changes in DNA profile on using five primers and caused the appearance and disappearance of DNA polymorphic bands with variation in their intensity. These findings confirm the effectiveness of relatively low doses of gamma rays on improving the physiological and biochemical criteria of fenugreek plants.     

Effect of Temperature of Liquid Nitrogen on Radiation Resistance of Spores of Clostridium botulinum

An apparatus consisting of a Dewar flask and a relay system controlling the flow of liquid nitrogen permitted the irradiation of samples in tin cans or Pyrex tubes at temperatures ranging from 0 ± 1.5 C to -194 ± 2 C. An inoculated pack comprising 320 cans of ground beef containing 5 × 10⁴ spores of Clostridium botulinum 33A per can (10 cans per radiation dose) was irradiated with Co⁶⁰ at 0 and -196 C. Incubation was carried out at 30 C for 6 months. Approximately 0.9 Mrad more radiation was required to inactivate the spores at -196 C than at 0 C. Cans irradiated at -196 C showed partial spoilage at 3.6 Mrad and no spoilage at 3.9 Mrad; the corresponding spoilage-no spoilage doses at 0 C were 2.7 and 3.0, respectively. The majority of positive cans swelled in 2 to 14 days; occasional swelling occurred as late as 20 days. At progressively higher doses, swelling was delayed proportionally to the radiation dose received. The remaining nonswollen cans had no toxin after 6 months of storage, although occasional cans contained very low numbers of viable spores comprising on the average 0.1% of the original spore inoculum. The D₁₀ values in phosphate buffer were 0.290 Mrad for 0 C and 0.396 Mrad for -196 C; in ground beef, the corresponding D₁₀ values were 0.463 Mrad and 0.680 Mrad, respectively. These D₁₀ values indicate that the lethal effect of γ rays decreased at -196 C as compared with 0 C by 13.5% in phosphate buffer, and by 47% in ground beef.     

Caffeine induces a second wave of apoptosis after low dose-rate gamma radiation of HL-60 cells

Most cell lines that lack functional p53 protein are arrested in the G₂ phase of the cell cycle due to DNA damage. It was previously found that the human promyelocyte leukemia cells HL-60 (TP53 negative) that had been exposed to ionizing radiation at doses up to 10 Gy were arrested in the G₂ phase for a period of 24 h. The radioresistance of HL-60 cells that were exposed to low dose-rate gamma irradiation of 3.9 mGy/min, which resulted in a pronounced accumulation of the cells in the G₂ phase during the exposure period, increased compared with the radioresistance of cells that were exposed to a high dose-rate gamma irradiation of 0.6 Gy/min. The D₀ value (i.e. the radiation dose leading to 37% cell survival) for low dose-rate radiation was 3.7 Gy and for high dose-rate radiation 2.2 Gy. In this study, prevention of G₂ phase arrest by caffeine (2 mM) and irradiation of cells with low dose-rate irradiation in all phases of the cell cycle proved to cause radiosensitization (D₀=2.2 Gy). The irradiation in the presence of caffeine resulted in a second wave of apoptosis on days 5–7post-irradiation. Caffeine-induced apoptosis occurring later than day 7 post-irradiation is postulated to be a result of unscheduled DNA replication and cell cycle progress.     

Role of gamma irradiation in regulation of NO3 level in rocket (Eruca vesicaria subsp. sativa) plants

The changes in the growth indices and certain metabolic activities in response to different doses of γ-irradiation (0, 20, 50, 100, and 200 Gy) were studied, using rocket seedlings. The total yield, seed mass, and essential oil content increased significantly by 20 Gy dose of γ-irradiation as compared with the control samples. In addition, total sugars, total free amino acids, total soluble phenols, kinetin, GA₃, nitrate reductase activity, and total protein increased significantly at 20 Gy dose. Meanwhile, NO₃ content decreased significantly at 20 Gy dose. The nitrogen and potassium content increased at the same dose of gamma rays of 20 Gy. While the phosphorus content showed no significant effect at all the γ-irradiation doses used. The results obtained in this work revealed that the most effective dose was 20 Gy of gamma rays. It was suggested that pretreatment of rocket seeds before planting with 20 Gy dose of γ-irradiation, may oppose the harsh effect of NO₃ accumulation and increased the quality and quantity of rocket yield. Published in Russian in Fiziologiya Rastenii, 2006, Vol. 53, No. 2, pp. 215–219. The text was submitted by the author in English.     

Radiosensitivity and Biological Effects of Gamma and X-Rays on Germination and Seedling Vigour of Three Coffea arabica Varieties

Effects of gamma and X-ray treatments were studied on three varieties of Coffea arabica (Kent, Mundo Novo and Geisha) to determine their radiosensitivity and relative biological effects. The coffee varieties seeds were subjected to 0, 50, 100, 150, 200 and 400 Gy of gamma and X-rays from Cobalt 60 (⁶⁰Co) source irradiation. The irradiated seeds were pre-germinated in Petri dishes placed in a germination chamber, whilst some were sown in the greenhouse for germination studies. Data were collected on germination date and rate, root and hypocotyl length to determine the relative biological effectiveness of treatments and the optimum dose. The results showed varieties responding differently to the irradiations and doses. There was a decrease in germination with increasing doses of the irradiation. The X-ray-treated seeds had less germination percentage and seedling vigour measured at 28 days after treatment compared to the gamma-irradiated seeds. The irradiation effects on germination suggest that lower doses of X-rays give the same Relative Biological Effects as higher gamma doses for both growth chamber and greenhouse germination for Geisha at LD₅₀, where the effects were similar for the two irradiations. Whereas 50–100 Gy stimulated germination and seedling vigour, 150 Gy adversely affected germination and no germination occurred at 200–400 Gy. The study concluded that all the coffee varieties evaluated are sensitive to gamma and X-ray irradiation in terms of germination, seedling vigour and biological effects with an optimum dose of 50–100 Gy. Therefore, both gamma and X-rays could be utilized in a future mutational breeding programme for coffee seedlings.

     

Effect of ionizing radiation of the antigenic composition of typhoid bacteria

Changes in the antigenic composition of typhoid bacteria occurring during the exposure of microbial suspension to different doses of gamma irradiation [Co60] ranging between 0.5 and 3.0 Mrad were studied. Immunoelectrophoresis in agar was used to determine the antigenic composition of different samples of irradiated bacteria. The antigenic composition of bacteria irradiated with doses up to 2.5 Mrad was found to be similar to that of non-irradiated bacteria. Antigens demonstrated by means of Vi, H and O ontisera are preserved in these bacteria. However, all irradiated bacteria in general slightly differ from non-irradiated bacteria; this is manifest in a different configuration and position of the precipitation lines in the cathodic part of the immunophoreograms. The content of the component migrating rapidly towards the cathode, evidently the O antigen in the R form, in the irradiated bacteria increases with the dose of radiation. No new serologically active substances, non-existent in non-irradiated bacteria, were found to appear in the process of irradiation.     

Effects of gamma radiation on different developmental stages of the oriental tobacco budworm,Helicoverpa assulta (Lepidoptera: Noctuidae)

Ionizing radiation is increasingly used as an alternative to post‐harvest crop fumigation by methyl bromide. We studied the effects of gamma irradiation on Helicoverpa assulta (Lepidoptera: Noctuidae) at different stages of development to determine the minimal dose for the prevention of normal emergence of adults. We selected five doses of gamma rays (100, 200, 300, 400 and 500 Gy) based on preliminary experiments and irradiated eggs, larvae, pupae and adults. A dose of 100 Gy to eggs allowed 21.83% of larvae to pupate, but these all died during the pupal stage. A dose of 100 Gy to last‐instar larvae caused larval or pupal death, or the emergence of abnormal adults; no normal adults developed. Irradiation of pupae with doses of 300 Gy and above resulted either in their death or emergence of abnormal adults; however, after 100 or 200 Gy, normal adults emerged and F₁ eggs were produced, but no eggs hatched. Following irradiation of adults, eggs were produced at all doses, although the numbers were significantly decreased compared to untreated controls (P < 0.05; 69.45–125.50 vs. 475.05 eggs per female); however, none of the eggs hatched. As prevention of normal emergence is a key outcome for measuring the effectiveness of radiation, then the 100 Gy dose was effective for irradiation of eggs and larvae, and 300 Gy for pupae.     

Change in Microflora of Sewage Sludge by Gamma-ray Irradiation

Total bacteria of activated dewatered sludge cake of Takasaki city which amounted to 2 × 10⁹ per gram diminished rapidly with the radiation dose, but slowly after 0.5 Mrad, and 10³ per gram survived even after 10 Mrad irradiation. However, coliforms which amounted to 8 × 10⁷ per gram were inactivated below 0.5 Mrad irradiation. The predominant bacteria in non-irradiated sludge were Pseudomonas cepacia and it mainly survived up to 2 Mrad, but Bacillus were predominant at 0.5 to 0.7 Mrad irradiation. The main residual flora from 2 to 5 Mrad was composed of Pseudomonas soranacearum, P. cepacia and P. delafieldii, and the main residual flora in more than 5 Mrad irradiated sludge was P. flava . These typical strains of Pseudomonas in phosphate buffer were radiation sensitive, and their D₁₀ values were from 0.005 to 0.021 Mrad under aerobic irradiation conditions.     

The response of denitrifiers in a sandy loam soil affected by a long-term fertilization to organic carbon and nitrate

The response of denitrifiers to carbon in the form of glucose (Glc-C) and nitrate (NO ₃ ⁻ -N) amendments was studied in four differently fertilized plots of sandy-loam soil. Two basically different characteristics of denitrification activity were determined: (1) potential denitrification measured as nitrous oxide production during 1-d incubation in the presence of acetylene, and (2) denitrifying enzyme activity determined in soil slurries as a N₂O production in the presence of acetylene and chloramphenicol during 1 h of incubation. Potential denitrification was strongly influenced by both Glc-C and NO ₃ ⁻ -N amendments in their various combinations, but was also affected by the fertilization practice. The response of denitrifiers to Glc-C and NO ₃ ⁻ -N was generally lower in unfertilized and surprisingly also in highly fertilized soils than in organically and moderately fertilized soils. Denitrifying enzyme activity was stimulated by the fertilization and was, in contrast to potential denitrification, the highest in highly fertilized soil. The results indicate that although active denitrifiers were present in a highly fertilized soil, their ability to develop under optimal conditions was decreased (being similar to that of denitrifiers in unfertilized soil). This suggests long-term changes in soil microbial community in a highly fertilized soil, presumably connected to changes in soil chemistry caused by fertilization.     

Ultrastructural aspects of pollen tube growth inhibition after gamma irradiation in Lycopersicum peruvianum

Summary Gamma ray treatments at various doses were applied to flowers after cross-compatible pollinations (S₁S₄ × S₁₂S₁₃) and self-incompatible pollinations (S₁S₄ × S₁S₄). After 200 kR treatment (highest dose) a high percentage of pollen became non-viable, and tube growth of all the germinated pollen was inhibited at the first third, or just before half the length of the style. Observations on the ultrastructural aspects revealed that the pollen tubes were destroyed by a precise degradation process which led to the disappearance of the inner wall, lysis of the tube, accumulation of several bipartite particles and alteration of endoplasmic reticulum into a whorl of concentric circles. These results indicated that the high dose of gamma rays probably interferes with protein synthesis. The ultrastructural aspects of compatible pollen tubes after gamma irradiation were similar to those of self-incompatible tubes and therefore it is suggested that cessation of protein synthesis might also be a result of incompatibility.Electron microscopy observations after treatment with 200 kR gamma rays on flowers after self-incompatible pollination (S₁S₄ × S₁S₄) showed that gamma irradiation affects the self-incompatibility reaction; but the results obtained so far are difficult to explain.     

Changes in Histamine Content in Fish Products for Animal Feeds and in Aqueous Solution by Gamma-Irradiation

The irradiation effects on histamine in fish meals and fish solubles for animal feeds and in aqueous solution were investigated. The amount of histamine in fish meal (0.4mg/100g) was not changed by up to 5.0 Mrad (50kGy), while the histamine content in fish soluble (45.7 mg/100 g) decreased ca. 16% at 5.0 Mrad. There occurred no accumulation of histamine by irradiation or during storage.

The G values of histamine formation from histidine solution and histamine decomposition by irradiation in deoxygenated neutral solutions were 0.077 and 1.90, respectively. Oxygen inhibited the formation of histamine from histidine but it had little effect on histamine decomposition. Nitrous oxide accelerated the decomposition of histamine and inhibited the accumulation of histamine in histidine solution by irradiation. These results show that there is no problem of histamine accumulation in feedstuffs caused by irradiation since the decomposition of histamine is preferred to its formation.     

Sterilization and protection of protein in combinations of Camellia sinensis green tea extract and gamma irradiation

Sterilization of milk protein without heating is of great interest. Gamma irradiation is a very powerful method to decontaminated casein. Gamma-irradiation of proteins in aqueous media at doses higher than 5kGy is known to induce their aggregation (without oxygen) or degradation (in presence of oxygen). Camellia sinensis green tea extract addition before irradiation of caseins cow milk proteins was examined. It was found that the presence of C. sinensis green tea extract during irradiation in the presence of oxygen conditions prevented the protein aggregation even at doses higher than 10kGy, probably by scavenging oxygen radicals produced by irradiation. The protective role of C. sinensis green tea extract allowing the gamma-irradiation treatment of caseins cow milk proteins in solution, was asserted by sodium dodecyl-sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) and by high performance liquid chromatography inverse phase (RP-HPLC). The total viable microorganisms content evaluated by Plate Count Agar (PCA) incubation for 12h at 37°C, showed that caseins protein preparations gamma-irradiated remained sterile at a dose 2kGy in absence of C. sinensis green tea extract and at a dose lower than 2kGy in the presence of C. sinensis green tea extract.     

The investigation of the combined effects of gamma irradiation and environmental manipulation on mortality and sterility of Rhyzopertha dominica (Fabricius) (Coleoptera: Bostrichidae)

With respect to the limitations use of methyl bromide and phosphine, employing ionizing radiation to control stored product pests has attracted great attention. The aim of this study is the investigation of the combined effects of gamma irradiation as viable alternatives to synthetic insecticides and environmental management on mortality and sterility of Rhyzopertha dominica (Fabricius) in a wheat cultivar (Gascogen). The effect of doses range from 30 to 2000?Gy gamma irradiation in combination with manipulation of temperature (15, 21, 27 and 32?°C) and relative humidity (20%, 50%, 65% and 85%) on 5–10?days old adults of R. dominica in Gascogen cultivar of wheat were explored. The experiments were repeated three times and conducted in The Nuclear Agriculture Research School in Karaj and laboratory of shahid steki silo in shahre-kord. Probit analysis revealed that both temperature and relative humidity had combined effects when used with gamma irradiation. The lowest doses of gamma ray required to kill 25% (14.2?Gy) and 50% (610.8?Gy) of the population (LD₂₅ and LD₅₀) were recorded at 21?°C and 85% relative humidity respectively. The low dose for 99% mortality (LD₉₉; 2386.7?Gy) was recorded for beetles maintained at 21?°C and 50% relative humidity. The effect of temperature (15, 21, 27 and 32?°C) on sterility caused by gamma irradiation was also investigated. The results showed that the F₁ generation emerged only when the beetles were treated with doses of 0–100?Gy at 32?°C and 0–70?Gy at 27?°C. These results indicate that temperature and relative humidity play an important role in the susceptibility of the lesser grain beetle to gamma irradiation. The results suggest that controlling the efficiency of gamma radiation through environmental control allows the use of low doses of gamma radiation that have a less harmful effect on human health, non-target organisms and seed agronomic features.     

Gamma radiation effects on growth and yield attributes of <Emphasis Type="Italic">Psoralea corylifolia</Emphasis> L. with reference to enhanced production of psoralen

The present work describes radiation-induced effects on vegetative, reproductive traits and psoralen content in Psoralea corylifolia L. The effects of gamma radiation on Psoralea seeds were investigated by exposing seeds with doses of 2.5, 5, 10, 15 and 20 kGy at dose rate of 1.65 kGyh⁻¹ and studying the plant growth at three developmental stages: preflowering, flowering and post flowering (seed to seed) after irradiation. Irradiation with lower doses of gamma rays significantly improved vegetative traits while higher doses proved depressing for same parameters. Similar trend was followed in reproductive traits. Psoralen, showed highest concentration in seeds (7.56%) at 20 kGy and lowest in control roots (0.23%). Increment in psoralen was striking for higher gamma doses applied. These long-term changes in plant development may be attributed to alteration in plant genome induced by irradiation. The results show in depth development stimulation and enhancement of secondary metabolite in Psoralea corylifolia L. following low and high dose treatment respectively depicting the potential of gamma rays in plant biotechnology and metabolomics.     

Effect of post-irradiation ageing on onion seeds

Seeds of onion (Allium cepa) cv. Ailsa Craig were exposed to various doses of gamma radiation (0, 10, 20, 40, 80 and 100 krad) and subjected to accelerated ageing (RH 100%, 42°C) for 12 h. Radiation doses significantly affected the percentage of normal seedlings, abnormality types (%) and seedling growth. Seed viability, conductivities of seed leachates, final germination (%), germination speed and time to reach 50% germination (T ₅₀) were not affected by the seed irradiation. Accelerated ageing after irradiation had significant influence on seed viability, conductivities of seed leachates, final germination (%) and percentage of normal seedlings. Germination speed, T ₅₀ and seedling growth were not affected by the accelerated ageing. However, all the parameters studied were significantly influenced by the interaction of radiation doses and accelerated ageing. Accelerated ageing generally enhanced the damaging effects of irradiation on seeds. Therefore, it was concluded that onion seeds should not be exposed to adverse environmental conditions after irradiation.     

Use of gamma-irradiation of soil for analyzing the state of microbial coeneses]

Increasing doses of gamma-irradiation eliminate some physiological and ecologo-trophical groups from microbial cenoses in soil. Soil fungi are least resistant to the action of gamma-irradiation (do not grow on agarized soil (AS) at a dose of 0.5 Mrad). Actinomycetes are more resistant (do not grow on AS at a dose of 0.75 Mrad). Bacteria are most resistant to irradiation. Asporogenous bacteria do not grow on agarized soil at a dose of 1.25 Mrad. Sporogenous bacteria survive at higher doses (1.75 Mrad). The method of gamma-irradiation permits to accomplish differential analysis of ecological groups of soil microflora and experimental synthesis of microbial associations. The effect of gamma-irradiation on soil enzymes is weak compared with autoclaving. gamma-Irradiated soils may serve as a substrate for model experiments during analysis of microbial associations.     

Physiological effects of glycinebetaine on gamma-irradiated stressed fenugreek plants

Irradiation stress adversely affects plant growth and development. The radio protective activity by glycinebetaine in plants has not been reported, and its mechanism has not been known. Gamma rays at doses 0.0, 25, 50, 100, and 150 Gray (Gy) when applied pre-sowingly to dry seeds of fenugreek from a cobalt source (⁶⁰Co) with strength of 500 Ci and the dose rate of 0.54 Gy/min significantly reduced chlorophyll content, total protein, photosynthetic efficiency (¹⁴CO₂-fixation), total dry weight, the accumulation of reducing, non-reducing and total soluble sugars in comparison with un-irradiated control. It also significantly repressed the activities of hydrolytic enzymes (α-amylase and invertase), the carboxylating enzyme (ribulose-1,5-bisphosphate-carboxylase/oxygenase) in the developed fenugreek plants. Soaking irradiated seeds with glycinebetaine (50 mM) for 24 h partially alleviated the depression effects of irradiation in these parameters. γ-irradiation treatment increased significantly H₂O₂ content. Presoaking irradiated seeds with GB decreased significantly the H₂O₂ level. The magnitude of the reversal decreased with increasing the irradiation dose. γ-irradiation induced a significant decrease in the level of nucleic acids (DNA and RNA) accompanied by a corresponding induction of hydrolytic activities of DNase and RNase in the developed plants in comparison with un-irradiated control. Those changes were more significant at higher γ-ray doses. Post-treatment of irradiated seeds with GB partially alleviated the adverse effects of radiation. It significantly increased nucleic acid levels and repressed the activities of DNase and RNase. The protective role played by glycinebetaine was more significant at lower γ-ray doses. Pretreatment of seeds with GB may play an effective role in the radio-repair mechanism.     

Inmobilization-remineralization of NO3-N and total N balance during the decomposition of glucose,sucrose and cellulose in soil incubated at different moisture regimes

A laboratory incubation experiment was conducted to study the effect of organic amendment and moisture regimes on the immobilization-remineralization of NO₃-N and total N balance in soil fertilized with KNO₃. Immobilization of NO₃-N was very rapid in soil amended with glucose and sucrose followed by a remineralization of organic N and accumulation of mineral N. Cellulose caused a slow but continued immobilization and did not show net accumulation of mineral N during 8 weeks of incubation. At the end of incubation, a significant increase in total N and organic N content of the soil was observed which is perhaps attributable to the activity of free living N₂ fixers. Although N losses seemed to have occurred at 100% WHC through denitrification in soil amended with glucose and sucrose, main cause of NO₃ elimination was microbial immobilization.     

Effect of gamma irradiation on immobilized trypsin

The effect of ionizing radiation of 0.05-10 Mrad on trypsin immobilized on dialdehyde cellulose was being studied. After irradiation the activity of native trypsin decreases by 25%, as compared with the initial, while the activity of immobilized trypsin remains constant. Before immobilization cellulose undergoes special pretreatment that leads to a decrease in the initial contamination. Some samples of modified cellulose were contaminated by staphylococcus culture (200,000 microbes per 0.2 g) and then exposed to irradiation of 0.05-0.4 Mrad. A distinct correlation between the irradiation dose (0.05-0.4 Mrad) and contamination of the object was registered.