• 환경생물
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• 제20권4호
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• pp.277-286
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• 2002

An increase in the overall biological effect under the combined action of ionizing radiation with another inactivating agent can be explained in two ways. One is the supposition that synergism may attribute to a reduced cellular capacity of damn-ge repair after the combined action. The other is the hypothesis that synergism may be related to an additional lethal or potentially lethal damage that arises from the interaction of sublesions induced by both agents. These sublesions ave considered to be in-effective when each agent is applied separately. Based on this hypothesis, a simple mathematical model was established. The model can predict the greatest value of the synergistic effect, and the dependence of synergy on the intensity of agents applied, as well. This paper deals with the model validation and the peculiarity of simultaneous action of various factors with radiation on biological systems such as bacteriophage, bacterial spores, yeast and mammalian cells. The common rules of the synergism aye as follows. (1) For any constant rate of exposure, the synergy can be observed only within a certain temperature range. The temperature range which synergistically increases the effects of radiation is shifted to the lower temperature fer thermosensitive objects. Inside this range, there is a specific temperature that maximizes the synergistic effect. (2) A decrease in the exposure rate results in a decrease of this specific temperature to achieve the greatest synergy and vice versa. For a constant temperature at which the irradiation occurs, synergy can be observed within a certain dose rate range. Inside this range an optimal intensity of the physical agent may be indicated, which maximizes the synergy. As the exposure temperature reduces, the optimal intensity decreases and vice versa. (3) The recovery rate after combined action is decelerated due to an increased number of irreversible damages. The probability of recovery is independent of the exposure temperature for yeast cells irradiated with ionizing or UV radiation. Chemical inhibitors of cell recovery act through the formation of irreversible damage but not via damaging the recovery process itself.

• Preventive Nutrition and Food Science
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• 제6권4호
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• pp.211-215
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• 2001

The packaging effect on physicochemical changes in irradiated sausage stored at -2$0^{\circ}C$ was studied. Emulsion-type cooked pork sausage was made with (156 ppm) or without NaNO$_2$ (0 ppm), and packaged in three different conditions such as aerobic, vacuum and $CO_2$ (100%). The samples irradiated at 0, 5 and 10 kGy absorbed dose, and the total number of microorganisms, lipid oxidation, color and texture were analyzed during frozen storage at-2$0^{\circ}C$. Irradiation of the sausage at 10 kGy completely controlled microbial growth during storage. An NaNO$_2$ addition to the sausage significantly reduced lipid oxidation, and the TBARS value of the sausage with aerobic packaging was higher than that with the vacuum and $CO_2$ packaging. The NaNO$_2$ addition increased Hunter color a-value dramatically, but no packaging effect was found (p > 0.05). Irradiation influenced shear values resulting in lower shear values in 10 kGy-irradiated sausages with aerobic packaging, and $CO_2$ packaged sausage showed comparatively lower shear value than other packaging methods. From the results, vacuum or $CO_2$ (100%) packaging were better than aerobic packaging for frozen stored pork sausage, especially far microbial quality and lipid oxidation.

• 화훼연구
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• 제19권2호
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• pp.119-125
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• 2011

창포는 한국에 자생하는 수생식물로 약용뿐만 아니라 phytoremediation과 수질정화 식물로도 알려져 있다. 본 연구에서는 창포의 기내 식물체에 다양한 선량(20-500 Gy)의 감마선을 조사하여, 방사선의 효과 및 감수성을 확인하기 위해 2달후 생존율, 신초형성율 및 생장율을 측정하였다. 생존율과 신초형성율은 감마선 선량이 증가할수록 현저하게 감소하였다. 기내에서 저선량을 조사한 식물체의 생장율은 대조구에 비해 오히려 증가하였으나, 250 Gy 이상에서는 생장이 멈추거나 유의하게 감소하였으며, 반치사선량($LD_{50}$)은 240 Gy로 다른 식물종의 $LD_{50}$보다 훨씬 높은 선량이었다. 창포에서 저선량을 조사하였을 때 생장율이 증가하는 방사선호메시스(radiation hormesis) 효과를 확인하였다.

• 한국방사선학회논문지
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• 제13권5호
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• pp.811-817
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• 2019

암 환자의 방사선 치료는 환자의 생존 수명을 연장하기 위해 사용한다. 그러나 방사선 조사 후 피폭으로 인해 정상적인 조직 재생은 치명적인 장해를 수반한다. 방사선 치료 후 발생 할 수 있는 장해는 골세포와 골대사 메커니즘에 결정적인 방사선 장해를 수반하여 방사성골괴사가 발생된다. 따라서 방사성골괴사를 극복하기 위해 방사선 장해의 극복을 위한 조직재생의 연구가 필수적으로 대두된다. 이번 연구에서는 골재생의 대표적인 사이토카인 단백질인 BMP-2가 방사성조사 쥐 두개골 모델에서 골재생의 효과가 있는지 또한 몇 주부터 골재생 효과가 많이 발생되는지를 검증하고자 하였다. 결론적으로 방사선이 조사된 쥐의 두개골 결손모델에서는 8주가 지나야 BMP-2의 효과가 더욱더 효과적으로 발생하는 결과를 얻을 수 있었다. 만일 BMP-2 가 처리된 지지체를 방사선골괴사 치료제로 사용한다면 단시간에 골 재생 효과를 기대하는 것보다는 8주 이상의 시간이 경과 후 골재생 효과를 기대해야 할 것으로 사료된다.

• Nuclear Engineering and Technology
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• 제53권12호
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• pp.4106-4113
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• 2021

Rare earth doped barium tellurite glasses were synthesised and explored for their radiation shielding applications. All the samples showed good thermal stability with values varying between 101 ℃ and 135 ℃ based on dopants. Structural properties showed the dominance of matrix elements compared to rare earth dopants in forming the bridging and non-bridging atoms in the network. Bandgap values varied between 3.30 and 4.05 eV which was found to be monotonic with respective rare earth dopants indicating their modification effect in the network. Various radiation shielding parameters like linear attenuation coefficient, mean free path and half value layer were calculated and each showed the effect of doping. For all samples, LAC values decreased with increase in energy and is attributed to photoelectric mechanism. Thulium doped glasses showed the highest value of 1.18 cm^-1 at 0.245 MeV for 2 mol.% doping, which decreased in the order of erbium, holmium and the base barium tellurite glass, while half value layer and mean free paths showed an opposite trend with least value for 2 mol.% thulium indicating that thulium doped samples are better attenuators compared to undoped and other rare earth doped samples. Studies indicate an increased level of thulium doping in barium tellurite glasses can lead to efficient shielding materials for high energy radiation.

• 한국의학물리학회지:의학물리
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• 제32권4호
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• pp.165-171
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• 2021

Purpose: This study aimed to evaluate the effect of collimator width on effective atomic number (EAN), relative electron density (RED), and stopping power ratio (SPR) measured by dual-layer dual-energy computed tomography (DL-DECT). Methods: CIRS electron density calibration phantoms with two different arrangements of material plugs were scanned by DL-DECT with two different collimator widths. The first phantom included two dense bone plugs, while the second excluded dense bone plugs. The collimator widths selected were 64 mm×0.625 mm for wider collimators and 16 mm×0.625 mm for narrow collimators. The scanning parameters were 120 kVp, 0.33 second gantry rotation, 3 mm slice thickness, B reconstruction filter, and spectral level 4. An image analysis portal system provided by a computed tomography (CT) manufacturer was used to derive the EAN and RED of the phantoms from the combination of low energy and high energy CT images. The EAN and RED were compared between the images scanned using the two different collimation widths. Results: The CT images with the wider collimation width generated more severe artifacts, particularly with high-density material (i.e., dense bone). RED and EAN for tissues (excluding lung and bones) with the wider collimation width showed significant relative differences compared to the theoretical value (4.5% for RED and 20.6% for EAN), while those with the narrow collimation width were closer to the theoretical value of each material (2.2% for EAN and 2.3% for RED). Scanning with narrow collimation width increased the accuracy of SPR estimation even with high-density bone plugs in the phantom. Conclusions: The effect of CT collimation width on EAN, RED, and SPR measured by DL-DECT was evaluated. In order to improve the accuracy of the measured EAN, RED, and SPR by DL-DECT, CT scanning should be performed using narrow collimation widths.

• Archives of Plastic Surgery
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• 제38권6호
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• pp.803-807
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• 2011

Purpose: The safety of radiation therapy after breast reconstruction using transverse rectus abdominis myocutaneous (TRAM) flap is still being debated, and few studies exist on the outcome of irradiation after immediate TRAM breast reconstruction. Some authors presented satisfactory outcomes after adjuvant radiation therapy on reconstructed breast with pedicled TRAM flap, while others reported significant post radiation changes of the flap. Effect of radiation therapy on TRAM flap was evaluated to see whether adjuvant radiation therapy was tolerable. Methods: 1000 immediate TRAM breast reconstruction was done by a single surgeon from July, 2001 to December, 2009. Among them 105 patients required adjuvant radiation therapy because of advanced disease or locoregional recurrence. Fat necrosis, radiation fibrosis, mastectomy skin flap necrosis, need for secondary touch up procedures, patient satisfaction were evaluated. Results: The incidence of fat necrosis was 10.5% and significant radiation fibrosis occurred in only one patient. Delayed wound problem did not occur during or after irradiation. Secondary touch-up procedures were performed in 12.3%, the most common being fat graft (8.6%). Average patient satisfaction score was 8.62/10, which was not significantly different from the authors' previous report involving all the TRAM patients (8.50). Conclusion: Radiation therapy did not increase the complication rate significantly. Aesthetic result was affected but was tolerated in most cases. The fear of adjuvant radiation is not a negative factor in selecting immediate breast reconstruction with TRAM flap.

• Asian Pacific Journal of Cancer Prevention
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• 제15권6호
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• pp.2405-2425
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• 2014

Radiation exposure leads to several pathophysiological conditions, including oxidative damage, inflammation and fibrosis, thereby affecting the survival of organisms. This review explores the radiation countermeasure properties of fourteen (14) plant extracts or plant-derived compounds against these cellular manifestations. It was aimed at evaluating the possible role of plants or its constituents in radiation countermeasure strategy. All the 14 plant extracts or compounds derived from it and considered in this review have shown some radioprotection in different in vivo, ex-vivo and or in vitro models of radiological injury. However, few have demonstrated advantages over the others. C. majus possessing antioxidant, anti-inflammatory and immunomodulatory effects appears to be promising in radioprotection. Its crude extracts as well as various alkaloids and flavonoids derived from it, have shown to enhance survival rate in irradiated mice. Similarly, curcumin with its antioxidant and the ability to ameliorate late effect of radiation exposure, combined with improvement in survival in experimental animal following irradiation, makes it another probable candidate against radiological injury. Furthermore, the extracts of P. hexandrum and P. kurroa in combine treatment regime, M. piperita, E. officinalis, A. sinensis, nutmeg, genistein and ginsan warrants further studies on their radioprotective potentials. However, one that has received a lot of attention is the dietary flaxseed. The scavenging ability against radiation-induced free radicals, prevention of radiation-induced lipid peroxidation, reduction in radiation cachexia, level of inflammatory cytokines and fibrosis, are some of the remarkable characteristics of flaxseed in animal models of radiation injury. While countering the harmful effects of radiation exposure, it has shown its ability to enhance survival rate in experimental animals. Further, flaxseed has been tested and found to be equally effective when administered before or after irradiation, and against low doses (${\leq}5Gy$) to the whole body or high doses (12-13.5 Gy) to the whole thorax. This is particularly relevant since apart from the possibility of using it in pre-conditioning regime in radiotherapy, it could also be used during nuclear plant leakage/accidents and radiological terrorism, which are not pre-determined scenarios. However, considering the infancy of the field of plant-based radioprotectors, all the above-mentioned plant extracts/plant-derived compounds deserves further stringent study in different models of radiation injury.

• 한국식품저장유통학회:학술대회논문집
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• 한국식품저장유통학회 2003년도 제23차 추계총회 및 국제학술심포지움
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• pp.152-152
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• 2003

As utilization of radiation in medicine, industry and biochemical research increases, the protection against radiation damage has become an important issue. Natural products such as herbal medicines are beginning to receive attention as modifiers on the radiation response. In the present study, the protective effect of a herb, Menthae Herba, against radiation-induced DNA damage was evaluated using alkaline single-cell gel electrophoresis (SCGE; comet assay) in the mouse peripheral blood Iymphocytes and the micronucleus formation test in the Chinese hamster ovary (CHO) cells. The tail moment, which was a marker of DNA damage in the SCGE, and the frequency of micronuclei was decreased in groups treated with Mentae Herba extract before exposure to 200 cGy of gamma-ray. We also confirmed its activities to scavenge DPPH and hydroxyl radicals. These experiments demonstrated that Menthae Herba was effective at reducing the radiation-induced damage of DNA and scavenging free radicals. It is plausible that scavenging of free radicals by Menthae Herba may have played an important role in providing the protection against the radiation-induced damage to the DNA. These results indicated that Menthae Herba might be a useful radioprotector and that radical scavenging appears to be one of the mechanisms of radiation protection.

• 방사선산업학회지
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• 제4권1호
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• pp.73-77
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• 2010

In recent day, there is much interest in the biocidal activity of silver since silver is known to be safe and effective as disinifectant and biocidal material against coliforms and viruses. In this study, hydrogels containing silver acetate as antibacterial agent have been prepared using gamma rays irradiation. The hydrogels are composed of poly(vinyl pyrrolidone) (PVP), poly(ethylene glycol) (PEG), carrageenan and silver acetate. The concentration of solution was 9 wt%. The ratio of PVP : PEG : carrageenan was 6 : 1 : 2. The concentration of the silver acetate were 0, 0.01, 0.03, 0.05 and 0.07% and Gamma irradiation dose was 25 kGy. The Gamma irradiation dose in hydrogels with 0.01% silver acetate were 20 kGy, 35 kGy, 50 kGy, 65 kGy, and 80 kGy. The results showed that 0.01% silver acetate concentration of hydrogels by 25 kGy irradiation dose showed the highest antibacterial activity against E. coli and Staphylococcus aureus. Moreover, antibacterial activity of various Gamma irradiation dose in hydrogels treated 0.01% silver acetate showed highest 35 kGy irradiation dose against Staphylococcus aureus.