• KOREAN JOURNAL OF CROP SCIENCE
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• v.2
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• pp.46-49
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• 1964

1. 본 시험에 사용된 선량범위내에서는 기건종자에 의한 Thermal neutron이나 X-ray의 처리가 발아율에 크게 영향을 미치지 못하였는데 Fast neutorn 처리종자의 발아율은 선량의 증가에 따라 거의 직선적 저하를 보였다. 2. 선량의 증가에 따라 기형엽발생율은 증가하였으며 특히 Fast neutron에서는 동일 flux일망정 Thermal neutron 조사구에 비해 발생율은 높다. 3. 저선량에서의 기형엽출현은 유식물기에서만 봇 수 있으며 성장함에 따라 회복한다. 이는 정상세포와 이상세포간의 분열속도의 차에 기인되는 상 싶다. 4. 같은 선량에서는 Fast neutron이 Thermal neutron에 비해 그 영향력이 크다는 것이 확실하며 이는 Energy의 차에서 오는 결과이다. 5. 일반적으로 선량의 증가에 따라 성숙이 연장되는 경향이 있었으며, 반면에 아주 희귀하기는 하나 개화와 성숙이 촉진되는 고체도 발견되었다. 6. 선량의 증가에따라 다소 왜소화되기는 하나 저선량에서는 오히려 유의성은 없으나 초장이 증가하였다. 7. 생육초기와 생육종기에 있어서의 선량에 따르는 초장에 대한 영향은 그 초기에 있어서 더 현저하며 성장함에 따라 회복되는 경향을 보인다. 8. 발아와 생육에 별 지장이 없이 재배할 수 있는 선량범위는 Thermal neutron에서 $1O^13$ N/$cm^2$, Fast neutron에서 5$\times$$1O^12$N/$cm^2$ 이하이면 무난할 것이며, X-ray는 본 시험에 이용한 32 Kr 이상에서도 이용에 지장이 없을 것이다.

• Journal of radiological science and technology
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• v.34 no.4
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• pp.333-339
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• 2011

The purpose of this study is to compare DNA repair characteristics of normal fibroblast cell (MRC-5) and neuroblastoma cell (SK-N-SH) induced by proton beam. Cells were irradiated with 2Gy, 5Gy and 8Gy proton beam. The rate of DNA rejoining was measured by alkaline version of the comet assay. After a repair time, tail moment was measured again. The tail moment of MRC-5 was lower than SK-N-SH. However, after 8Gy of exposure, the tail moment of MRC-5 was measured as 50.320223.17155 which represents dangerous level of DNA damage. The cells were repaired practically within 25 hours after 2 and 5Gy of exposure while they were not fully recovered after 8Gy of exposure. Especially, tail moment of MRC-5 after 25 hours was 18.15364.42849. In the distal declining edge of SOBP, the RBE value is increased by high LET. The RBE differences of SOBP in high-dose were greater than low-dose. After the high-dose exposure, MRC-5 of normal fibroblast cell could lead to lasting DNA damage as shown in this study. In conclusion, we has to pay special attention when the region of the treatment volume is close to sensitive tissues.

• Radiation Oncology Journal
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• v.5 no.1
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• pp.1-11
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• 1987

Total 390 mice were irradiated with $2{\times}3cm$ abdominal field and $200{\times}5/wk$ regimen with orthovoltage x-ray machine. All animals were divided into 2 large groups, damage and recovery, and histopathologic changes were analyzed at various total dose level (1,000 cCy-5,000 cCy) and intervals (1 week-15 weeks). Almost acute changes such as decreased mitotic activity, villi shortening and focal erosion of mucosa recovered within 1-2 weeks in 1,000-3,000 cGy irradiated group but mild changes persisted in 4,000 and 5,000 cCy irradiated groups. Chronic delayed changes such as thickening of vessel wall with focal thrombosis, submucosal fibrosis, mucosal atrophy and chronic ulcer were observed from 2-3 week specimens in 4,000 and 5,000 cGy groups, These late changes recovered slightly, as increasing time intervals after irradiation but mild, persistant changes were observed throught all follow up period. These data suggest hat even 4,000 cCy is not completely safe for possible permanent damage and judicious modificiation of total dose, dose rate, fraction size, and field size should be considered for better results.

• Korean Journal of Environmental Agriculture
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• v.17 no.1
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• pp.76-83
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• 1998

The most remarkable aspect in the hormesis law is that dose of harmful agents can produce effect that are diametrically opposite to the effect found with high doses of the same agent. Minute quantities of a harmful agent bring about very small change in the organism and control mechanisms appear to subjugate normal processes to place the organism in a state of albert and repair. The stimulated organism in more responsive to changes in environmental factors than it did before being alerted. Routine functions, including repair and defense, have priority for available energy and matetial. The alerted organism utilizes nutrients more efficiently, grows faster, shows improved defense, and lives longer. Accelerated germination, sprouting, growth, development, blooming and ripening, and increased crop yield and resistance to disease are found in plants. Another concept supported by the data in that low doses of ionizing radiation provide increased resistance to subsequent high doses of radiation. The hormesis varies with subject plant, variety, state of seed, environmental and cultural conditions, physiologic function measured, dose rate and total exposure. The results of hormesis are less consistently found, probably due to the great number of uncontrolled variables in the experiments. The general dosage for radiation homlesis in about 100 (10 to 1,000) times ambient or 100 (10 to 1,000) times less than a definitely harmful dose, but these must be modified to the occasion. Although little is known about most mechanisms of homzesis reaction, overcompensation of repair mechanism is offered as one mechanism.

• Radiation Oncology Journal
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• v.8 no.2
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• pp.151-154
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• 1990

The acute effects of variable dos rates to total body irradiation (TBI) were investigaed with 600 cGy of single exposure in the mice as a preclinical model. Total 80 mice (ICR) were used. Twenty of which sewed as controls, receiving no irradiation. All irradiated mice showed a universal decline in their weight and white blood cell count. The degree of weight loss and leukopenia were similar at 3 different dos rate but slightly prominent with 15 cGy/minute group. The degree of recovery among the groups showed no dose rate dependence. Our results suggest that TBI with 15 cGy/mimute may be applicable for clinical therapy with careful evaluation of patient's condition.

• Radiation Oncology Journal
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• v.6 no.1
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• pp.1-11
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• 1988

Recovery from potentially lethal damage (PLDR) after irradiation was studied in plateau-phase culture of Vero cells in vitro. Unfed plateau-phase cells were irradiated with dose of 1 to 9Gy using Cs-137 irradiator. Cells then were incubated again and left in situ for 0, 1, 2, 3, 4, 5, 6, and 24 hours and then were trypsinized explanted, and subcultured in fresh RPMI-1640 media containing $0.33\%$ agar. Cell survival was measured by colony forming ability. An adequate number of heavily irradiated Vero cells were added as feeder cells to make the total cell number constant in every culture dish. As the postirradiation in situ incubation time increased, surviving fraction increased by PLDR. The rate of PLDR was so rapid that increased surviving fraction reached saturation level at 2 to 4 hours after in situ incubation. As the radiation dose increased, the rate of PLDR fastened and the magnitude of increased surviving fraction at saturation level by PLOR also increased. In analysis of cell survival curve fitted to the linear-quadratic model, the linear inactivation coefficient $(\alpha)$ decreased largely and reached nearly to zero but the quadratic inactivation coefficient $(\beta)$ increased minimally by increment of postirradiation in situ incubation time. So PLDR mainly affected the damage expressed as $\alpha$, In the multitarget model, significant change was not obtained in $D_0\;but\;in D_q$. Therefore, shoulder region in cell survival curve was mainly affected by PLDR and terminal slope was not influenced at all. And dose-modifying factor by PLDR was relatively higher in shoulder region, that is, in low dose area below 3 Gy.

• Journal of the Korean Society of Radiology
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• v.11 no.4
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• pp.177-181
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• 2017

Dose response curves using absorbed dose to the biological effect are usually available in case of conventional X beam. However, absorbed dose is not consider in treatment planning for carbon beam such as heavy ions. Because the biological effects also depend on other quantities such as the local variation, which is often characterized by the linear energy transfer (LET). So LQ model cannot explain the entire response of fractionated carbon beam irradiation. The variation in LET with penetration depth leads to substantial differences in biological effect of carbon beam. And it is therefore essential in treatment planning to calculate not only the absorbed dose but also the LET to estimate the biological outcome of the radiation of interest. LET variation plays an important role in the fractionated irradiations. It is suggested that consideration of LET is necessary in biophysical model.

• Journal of Radiation Protection and Research
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• v.39 no.3
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• pp.134-141
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• 2014

Along with the wide use of radiotherapy in cancer treatment, there is growing interest in beneficial effect of low-dose irradiation (LDI) in cancer therapy. Therefore, we investigate how LDI affects immune responses in mice model. Total body irradiation (TBI) on C57BL/6 mice was given at low-dose rate of $1mGy{\cdot}min^{-1}$ using $^{137}Cs$ source at three times for consecutive three days. Hematological examination, total cell numbers of spleen, populations and characteristics of splenocytes were determined. Total numbers of RBC or platelet in irradiated mice showed no significant changes. WBC counts were decreased in a dose-dependent manner 2 days after TBI, however, these differences are gradually waned until 28 days. Dose-dependent decrease in the number of splenocytes of TBI mice at day 2 was also improved as time progressed. While the level of Foxp3 mRNA was decreased, the frequency of $CD4^+$ T cells and $CD69^+$ cells in spleen was increased at day 2 and 14. Fractionated low-dose TBI on mice exhibited normal body weight with no distinguishable behavior during whole experimental periods. These results suggest that some parameters of immune system could be altered and evaluated by fractionated low-dose TBI and be used to broaden boundary of low dose radiation research.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.16 no.10
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• pp.2287-2292
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• 2012

In this study, $Co^{60}$ gamma-ray induced loss on Ge-doped single mode (SM) fiber has been measured. Gamma-ray is irradiated for 4 hours at the dose rate of 0.5 kGy/hr, 2 kGy/hr, 8 kGy/hr. Consequently, gamma-ray induced loss based on radiation effects in Ge-doped SM fiber occur significantly. Furthermore, dose rate effect was observed, that dose rate using the same total dose increased higher, then optical fiber loss increased more. Also annealing effect was observed, that the loss after irradiation, increased higher, then the recovery rate of loss was increased. This results are foreseen to be base data in the future radiation-hardened optical fiber study.

• Radiation Oncology Journal
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• v.4 no.2
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• pp.89-97
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• 1986

Using as assay for jejunal crypt stem cell survival, dose-response curves for the reproductive capacity of crypt stem cells of mouse jejunum exposed to multifractionated gamma-ray irradiation (single, 2, 3, 4, 5, 8, 10, 12, and 16 fractions) were analyzed and single-dose survival curve of these cells was constructed. The following conclusion were drawn: 1) Survival curves for higher numbers of dose fractions were displaced to higher dose, and characterized by increasingly shallower slopes. 2) The single-dose survival curve had broad shoulder, Dq=460 cGy, remaining near-exponential over initial dose range 0 to 300 cGy, with initial slope 1Do=474 cGy. 3) At fractionated dose En the range of 180 to 450 cGy, the average recovered dose per fraction interval was approximately $50\%$ of the dose per fraction. 4) The value of $\alpha/\beta$ ratio by using of linear regression analysis for the reciprocal dose plots was 8.3 Gy which lied in the range of 6-14 Gy for early-reacting tissues. 5) The linear-quadratic model for dose-response formula offers valid approximations for at 1 doses to be used in radiotherapy, only two parameters to be determined, and considerable convenience in practical applications.