• Title/Summary/Keyword: Buffer Level

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A Review of the Influence of Sulfate and Sulfide on the Deep Geological Disposal of High-level Radioactive Waste (고준위방사성폐기물 심층처분에 미치는 황산염과 황화물의 영향에 대한 고찰)

  • Jin-Seok Kim;Seung Yeop Lee;Sang-Ho Lee;Jang-Soon Kwon
    • Economic and Environmental Geology
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    • v.56 no.4
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    • pp.421-433
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    • 2023
  • The final disposal of spent nuclear fuel(SNF) from nuclear power plants takes place in a deep geological repository. The metal canister encasing the SNF is made of cast iron and copper, and is engineered to effectively isolate radioactive isotopes for a long period of time. The SNF is further shielded by a multi-barrier disposal system comprising both engineering and natural barriers. The deep disposal environment gradually changes to an anaerobic reducing environment. In this environment, sulfide is one of the most probable substances to induce corrosion of copper canister. Stress-corrosion cracking(SCC) triggered by sulfide can carry substantial implications for the integrity of the copper canister, potentially posing a significant threat to the long-term safety of the deep disposal repository. Sulfate can exist in various forms within the deep disposal environment or be introduced from the geosphere. Sulfate has the potential to be transformed into sulfide by sulfate-reducing bacteria(SRB), and this converted sulfide can contribute to the corrosion of the copper canister. Bentonite, which is considered as a potential material for buffering and backfilling, contains oxidized sulfate minerals such as gypsum(CaSO4). If there is sufficient space for microorganisms to thrive in the deep disposal environment and if electron donors such as organic carbon are adequately supplied, sulfate can be converted to sulfide through microbial activity. However, the majority of the sulfides generated in the deep disposal system or introduced from the geosphere will be intercepted by the buffer, with only a small amount reaching the metal canister. Pyrite, one of the potential sulfide minerals present in the deep disposal environment, can generate sulfates during the dissolution process, thereby contributing to the corrosion of the copper canister. However, the quantity of oxidation byproducts from pyrite is anticipated to be minimal due to its extremely low solubility. Moreover, the migration of these oxidized byproducts to the metal canister will be restricted by the low hydraulic conductivity of saturated bentonite. We have comprehensively analyzed and summarized key research cases related to the presence of sulfates, reduction processes, and the formation and behavior characteristics of sulfides and pyrite in the deep disposal environment. Our objective was to gain an understanding of the impact of sulfates and sulfides on the long-term safety of high-level radioactive waste disposal repository.

Feasibility Assessment on the Application of X-ray Computed Tomography on the Characterization of Bentonite under Hydration (벤토나이트 수화반응 특성화를 위한 X선 단층촬영 기술 적용성 평가)

  • Melvin B., Diaz;Gyung Won, Lee;Seohyeon, Yun;Kwang Yeom, Kim;Chang-soo, Lee;Minseop, Kim;Jin-Seop, Kim
    • Tunnel and Underground Space
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    • v.32 no.6
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    • pp.491-501
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    • 2022
  • Bentonite has been proposed as a buffer and backfill material for high-level radioactive waste repository. Under such repository environment conditions, bentonite is subjected to combined thermal, hydrological, mechanical, and chemical processes. This study evaluates the feasibility of applying X-ray CT technology on the characterization of bentonite under hydration conditions using a newly developed testing cell. The cylindrical cell is made of platic material, with a removable cap to place the sample, enabling to apply vertical pressure on the sample and to measure swelling pressure. The hydration test was carried out with a sample made of Gyeonju bentonite, with a dry density of 1.4 g/cm3, and a water content of 20%. The sample had a diameter of 27.5 mm and a height of 34 mm. During the test, water was injected at a constant pressure of 0.207 MPa, and lasted for 7 days. After one day of hydration, bentonite swelled and filled out the space inside the cell. Moreover, CT histograms showed how the hydration process induced an initial increase and later progressive decrease on the density of the sample. Detailed profiles of the mean CT value, CT standard deviation, and CT gradient provided more details on the hydration process of the sample and showed how the bottom and top regions exhibited a decrease on density while the middle region showed an increase, especially during the first two days of hydration. Later, the differences in CT values with respect to the initial state decreased, and were small at the end of testing. The formation and later reduction of cracks was also characterized through CT scanning.

Studies on the Development of Food Resources from Waste Seeds -II. Chemical Composition of Apple Seed- (폐기종실(廢棄種實)의 식량자원화(食糧資源化)에 관(關)하여 -제(第) 2 보(報) : 사과씨의 화학적(化學的) 조성(組成)-)

  • Yoon, Hyung-Sik;Choi, Cheong;Oh, Man-Jin
    • Korean Journal of Food Science and Technology
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    • v.15 no.2
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    • pp.128-132
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    • 1983
  • The apple seed contained 25.96% of crude fat and 37.62% of crude protein. The lipid fractions obtained by cilicic column chromatography were mainly composed of about 93.52% neutral lipid, whereas compound lipid was only 6.48% level. Among the neutral lipid separated by thin layer chromatography, triglyceride was 92.17%, sterol ester, sterol, diglyceride and free fatty acid were 3.53, 2.25, 1.44 and 0.56, respectively. The predominent fatty acids of total and neutral lipids were linoleic acid (59.79-69.37%) and oleic acid (20.04-29.82%), but those of glycolipid and phojspholipid were linoleic acid (29.20-36.04%). The major fatty acids of triglyceride separated from neutral lipid were oleic acid (44.31%), linoleic acid (36.66%) and palmitic acid (12.48%). The salt soluble protein of apple seed was highly dispersible in 0.02M sodium phosphate buffer containing about 1.0M $MgSO_4$, and the extractability of seed protein was 37%, Glutamic acid was the major amino acid in salt soluble protein, followed by arginine and aspartic acid. The eletrophoretic analysis showed three bands in apple seed protein, and the collection rate of the main protein fraction purified by Sephadex G-100 and G-200 was 76.6%. Glutamic acid, aspartic acid and arginine were the major amino acids of the main apple seed protein. The molecular weight for the main protein of the apple seed was estimated to be 45,000.

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Environmental Equity Analysis of the Accessibility of Urban Neighborhood Parks in Daegu City (대구시 도시근린공원의 접근성에 따른 환경적 형평성 분석)

  • Seo, Hyun-Jin;Jun, Byong-Woon
    • Journal of the Korean Association of Geographic Information Studies
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    • v.14 no.4
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    • pp.221-237
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    • 2011
  • This study aims to investigate the environmental equity of the accessibility to urban neighborhood parks in the city of Daegu. The spatial distribution of urban neighborhood parks was explored by spatial statistics and the spatial accessibility to them was then evaluated by both minimum distance and coverage approaches. Descriptive and inferential statistics such as proximity ratio, Mann Whitney U test, and logistic regression were used for comparing the socioeconomic characteristics over different accessibilities to the neighborhood parks and then testing the distributional inequity hypothesis. The results from the minimum distance method indicated that Dalseo-gu had the best accessibility to the neighborhood parks while Dong-gu had the worst accessibility. It was apparent with the coverage method that Dalseo-gu had the best accessibility whereas Dong-gu and Nam-gu had the worst accessibility to the neighborhood parks at 500m and 1,000m buffer distances. There existed the spatial pattern of environmental inequity in old towns with respect to population density and the percentage of people under the age of 18. The spatial pattern of environmental inequity in new towns was explored on the basis of the percentage of people over the age of 65, the percentage of people below the poverty level, and the percentage of free of charge rental housing. These results were closely related to the development process of urban parks in Daegu stimulated by the quantitative urban park policy, urban development process, and residential location pattern such as permanent rental housing and free of charge rental housing. This study further extends the existing research topics of environmental justice related to the distributional inequity of environmental disamenities and hazards by focusing on environmental amenities such as urban neighborhood parks. The results from this study can be used in making the decisions for urban park management and setting up urban park policy with considering the social geography of Daegu.

Glass Dissolution Rates From MCC-1 and Flow-Through Tests

  • Jeong, Seung-Young
    • Proceedings of the Korean Radioactive Waste Society Conference
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    • 2004.06a
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    • pp.257-258
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    • 2004
  • The dose from radionuclides released from high-level radioactive waste (HLW) glasses as they corrode must be taken into account when assessing the performance of a disposal system. In the performance assessment (PA) calculations conducted for the proposed Yucca Mountain, Nevada, disposal system, the release of radionuclides is conservatively assumed to occur at the same rate the glass matrix dissolves. A simple model was developed to calculate the glass dissolution rate of HLW glasses in these PA calculations [1]. For the PA calculations that were conducted for Site Recommendation, it was necessary to identify ranges of parameter values that bounded the dissolution rates of the wide range of HLW glass compositions that will be disposed. The values and ranges of the model parameters for the pH and temperature dependencies were extracted from the results of SPFT, static leach tests, and Soxhlet tests available in the literature. Static leach tests were conducted with a range of glass compositions to measure values for the glass composition parameter. The glass dissolution rate depends on temperature, pH, and the compositions of the glass and solution, The dissolution rate is calculated using Eq. 1: $rate{\;}={\;}k_{o}10^{(ph){\eta})}{\cdot}e^{(-Ea/RT)}{\cdot}(1-Q/K){\;}+{\;}k_{long}$ where $k_{0},\;{\eta}$ and Eaare the parameters for glass composition, pH, $\eta$ and temperature dependence, respectively, and R is the gas constant. The term (1-Q/K) is the affinity term, where Q is the ion activity product of the solution and K is the pseudo-equilibrium constant for the glass. Values of the parameters $k_{0},\;{\eta}\;and\;E_{a}$ are the parameters for glass composition, pH, and temperature dependence, respectively, and R is the gas constant. The term (1-Q/C) is the affinity term, where Q is the ion activity product of the solution and K is the pseudo-equilibrium constant for the glass. Values of the parameters $k_0$, and Ea are determined under test conditions where the value of Q is maintained near zero, so that the value of the affinity term remains near 1. The dissolution rate under conditions in which the value of the affinity term is near 1 is referred to as the forward rate. This is the highest dissolution rate that can occur at a particular pH and temperature. The value of the parameter K is determined from experiments in which the value of the ion activity product approaches the value of K. This results in a decrease in the value of the affinity term and the dissolution rate. The highly dilute solutions required to measure the forward rate and extract values for $k_0$, $\eta$, and Ea can be maintained by conducting dynamic tests in which the test solution is removed from the reaction cell and replaced with fresh solution. In the single-pass flow-through (PFT) test method, this is done by continuously pumping the test solution through the reaction cell. Alternatively, static tests can be conducted with sufficient solution volume that the solution concentrations of dissolved glass components do not increase significantly during the test. Both the SPFT and static tests can ve conducted for a wide range of pH values and temperatures. Both static and SPFt tests have short-comings. the SPFT test requires analysis of several solutions (typically 6-10) at each of several flow rates to determine the glass dissolution rate at each pH and temperature. As will be shown, the rate measured in an SPFt test depends on the solution flow rate. The solutions in static tests will eventually become concentrated enough to affect the dissolution rate. In both the SPFt and static test methods. a compromise is required between the need to minimize the effects of dissolved components on the dissolution rate and the need to attain solution concentrations that are high enough to analyze. In the paper, we compare the results of static leach tests and SPFT tests conducted with simple 5-component glass to confirm the equivalence of SPFT tests and static tests conducted with pH buffer solutions. Tests were conducted over the range pH values that are most relevant for waste glass disssolution in a disposal system. The glass and temperature used in the tests were selected to allow direct comparison with SPFT tests conducted previously. The ability to measure parameter values with more than one test method and an understanding of how the rate measured in each test is affected by various test parameters provides added confidence to the measured values. The dissolution rate of a simple 5-component glass was measured at pH values of 6.2, 8.3, and 9.6 and $70^{\circ}C$ using static tests and single-pass flow-through (SPFT) tests. Similar rates were measured with the two methods. However, the measured rates are about 10X higher than the rates measured previously for a glass having the same composition using an SPFT test method. Differences are attributed to effects of the solution flow rate on the glass dissolution reate and how the specific surface area of crushed glass is estimated. This comparison indicates the need to standardize the SPFT test procedure.

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Effect of L-ascorbic acid on the degradation of aflatoxin $B_1$ (아스콜빈산에 의한 Aflatoxin $B_1$의 파괴에 관한 연구)

  • Park, Kun-Young;Kweon, Mee-Hyang
    • Journal of the Korean Society of Food Science and Nutrition
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    • v.16 no.1
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    • pp.1-9
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    • 1987
  • Large amount of aflatoxin $B_1(AFB_1)$ is disappeared in the presence of L-ascorbic acid(AA) in buffer solution at pH values from 1 to 7 during 5 days of Incubation at $37^{\circ}C$. $AFB_1$ was quite stable at pH's between 5 and 7 when AA was absent(control), however, $50{\sim}60%$ of APB, was degraded in its presence after 5 days. The rate of disappearance of $AFB_1$ increased with a decreasing of pH in the presence of AA, even though $AFB_1$ in the control degraded increasingly with the decrease in $pH(pH{\leq}4)$. The level of $AFB_1$, decreased as the reaction temperature increased when $AFB_1$ reacted with AA. The aflatoxin could not be detected at all after 3 days when the reaction occurred at $60^{\circ}C$, while the aflatoxin was stable at $5^{\circ}C$ thoughout the reaction period. $90{\sim}96%$ of $AFB_1$ was found to be degraded in a far when $AFB_1$ reacted with AA plus different concentrations of $CuSO_4{\cdot}5H_{2}O$, showing remarkably faster rate than the control; however, different concentrations of L-cysteine instead of $CuSO_4\;5H_{2}O$ protected the degradation of aflatoxin and no $AFB_1$ was degraded for a day and resulted in less $AFB_1$ disappeared than the control. The degradation of $AFB_1$ was dependent on AA concentration and the rate of disappearance as the concentration of AA decrease, but $AFB_1$ concentration did not influence the rate. The product formed when $AFB_1$ reacted with AA was identified to $AFB_{2a}$ by using HPLC chromatographic examinations, and by UV spectrum of $AFB_1$ reacted with AA. The disappearance of $AFB_1$ was correlated well in the appearance of $AFB_2a$. From the results, the degradation of $AFB_1$ in the presence of AA is probably due to one or more of the oxidative products of AA which was produced during the AA oxidation.

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Studies on the Development of Food Resources from Waste Seeds -I. Chemical Composition of Grape Seed- (폐엽종실(廢棄種實)의 식량자원화(貪糧資源化)에 관(關)하여 -제(第) 1 보(報) : 포도씨의 화학적(化學的) 조성(組成)-)

  • Yoon, Hyung-Sik;Kwon, Joong-Ho;Hwang, Joo-Ho;Choi, Jae-Chun;Shin, Dae-Hyn
    • Korean Journal of Food Science and Technology
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    • v.14 no.3
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    • pp.250-256
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    • 1982
  • A series of studies were conducted to find out the possibility of utilizing grape seed as resources of food fats and proteins, and the results of the studies are as follows: The grape seed contained 25.1%, of crude fat and 12.0% of crude protein. The lipid, fractions obtained by silicic acid column chromatography were mainly composed of about 95.5% neutral lipid, whereas compound lipid was only 4.5% level. Among the neutral lipid by thin layer chromatography, triglyceride was 91.89%, sterol ester, sterol, diglyceride and free fatty acid were 3.24%, 2.87%, 1.20% and 0.80%, respectively The predominant fatty acids of total and neutral lipids were linoleic acid $(69.72{\sim}71.72%)$ and oleic acid $18.09{\sim}19.46%)$, but those of glycolipid and phospolipid were linoleic acid $(31.49{\sim}38.18%)$, oleic acid $(20.20{\sim}35.27%)$ and palmitic acid $(26.80{\sim}39.98%)$. The major fatty acids of triglyceride separated from neutral lipid were oleic acid (43.08%), linoleic acid (38.42%) and palmitic acid (11.60%). The salt soluble protein of grape seed was highly dispersible in 0.02M sodium phosphate buffer containing about 1.0M $MgSO_4$, and the extractability of seed protein was 31%. Glutamic acid was the major amino acid in salt soluble protein, followed by arginine and aspartic acid. The electrophoretic analysis showed 3 bands in grape seed protein, and the collection rate of the main protein fraction purified by Sephadex G-100 and G-200 was 82%. Glutamic acid, aspartic acid and arginine were the major amino acids of the main grape seed protein. The molecular weight for the main protein of the grape seed was estimated to be 81,000.

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Effect of Dietary Vitamin E on the Microsomal Mixed Function Oxidase System of Liver and Lung in Streptozotocin-induced Diabetic Rats (식이 Vitamin E가 Streptozotocin 유발 당뇨쥐의 간 및 폐조직에서의 Microsomal Mixed Function Oxidase System에 미치는 영향)

  • 박영란;이순재;임영숙;주길재
    • Journal of the Korean Society of Food Science and Nutrition
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    • v.25 no.6
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    • pp.969-975
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    • 1996
  • The purpose of this study was to investigate the effect of dietary vitamin E on microsomal mixed function oxidase system of liver and lung in streptozotocin(STZ) induced diabetic rats. Sprague-Dawley male rats weighing 140 $\pm$ 10mg were randomly assigned to one control and three STZ-diabetic groups. Diabetic groups were divided into DM-0E(vitamin E free diet), DM-40E(40mg vitamin E kg/diet) and DM-400E(400mg vitamin E kg/diet) according to the level of vitamin E supplementation. Diabetes was experimentally induced by intravenous administration of 55mg/kg b.w of STZ in citrate buffer(pH 4.3) after 4 week feeding of three experimental diets. Animals were sacrificed at the 6th day of diabetic state. The contents of cytochrome P$_{450}$ in DM-0E, DM-40E and DM-400E groups of liver were increased by 162%, 150% and 56%, respectively, compared with that of control. Also the contents of cytochrome P$_{450}$ in lung were similar to liver. The activities of cytochrome bs in DM-0E and DM-40E groups of the liver were increased by 70% and 53%, respectively, compared with that of control, but not in DM-400E group. The activities of bs in DM-0E, DM-40E and DM-400E groups of lung were signficantly increased. Activity of cytochrome P$_{450}$ reductase in DM-0E, DM-40E of liver and lung were higher than that of control group, but the activity of DM-400E group was not different from that of control. The lipid peroxide values of DM-0E, DM-40E and DM-400E groups were 143%, 95% and 31% higher than those of control. It was concluded that dietary vitamin E had protective effects on lipid peroxidation accompanied with increased mixed function of oxidase activity in diabetic rats.

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Alveolar bone turnover during experimental tooth movement in Streptozotocin-induced diabetic rat (스트렙토조토신 유발 당뇨병 백서에서 실험적 치아이동중의 치조골 교체)

  • Lee, Ki-Soo;Lee, Taek-Woo;Kim, Sung-Jin
    • The korean journal of orthodontics
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    • v.31 no.3 s.86
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    • pp.357-367
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    • 2001
  • The purpose of this study was to investigate the alveolar bone turnover in diabetic rat, and to compare the alveolar bone turnover during tooth movement in diabetes with that in normal control Eighty Male Sprague-Dawley strain rats(8th week) were divided into normal control(N), normal-tooth movement (N-tm), diabetes(D), and diabetes-tooth movement(D-tm) groups. Eighteen days before the start of the experiment, diabetes was induced with a single injection of streptozotocin 50 mg/kg of body weight in citrate buffer as vehicle via the tail vein. Maxillary first molars of rats were moved mesially by 40 grams of the closed coil spring. Experimental animals were sacrificed after 1d, 3d, 7d, and 14d experimental period, and the alveolar bone around the maxillary first molars were assayed biochemically for acid phsophatase(ACP) and tartrate-resistant acid phosphatase (TRAP) as bone resorption markers, and alkaline phosphatase(ALP) and osteocalcin(OC) as bone formation markers. TRAP and OC concentration in serum and alveolar bone of D group were lower than those in N group, and especially OC concentration decreased mote following diabetes prolonged, which showed the decreased skeletal and alveolar bone resorption and formation potential in diabetic rats. In N-tm group compared with N group, alveolar bone ACP and TRAP concentrations were highest at 1d and 3d(p<0.01), decreased after then, and showed lowest at 14d, and alveolar bone OC concentration was higher at 3d, 7d, and 14d(p<0.001) and showed a tendency of peak level at 7d. which showed the peak of concentration of bone resorption markets at 1d-3d and those of bone formation markers at 7d. In D-tm group compared with N group, alveolar bone ACP and TRAP concentrations were higher at 3d, 7d and 14d(p<0.001), and tended to reach peak value at 7d and persisted through 14d, and alveolar bone ALP and OC concentration increased but not different from that of N group. The amount of tooth movement in D group were greater than that of N group at all experimental period. Those results were suggested that during diabetes, the alveolar and skeletal bone undergo low bone turnover and the mote amount of tooth movement, hut because the peak time of alveolar bone resorption activity was delayed and sustained in longer period of tooth movement and alveolar bone formation activity is lower than that of normal tooth movement, the periodontal space is supposed to be larger doting tooth movement.

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Effects of YK-209 Mulberry Leaves on Disaccharidase Activites of Small Intestine and Blood Glucose-Lowering in Streptozotocin-Induced Diabetic Rats (YK-209뽕잎이 Streptozotocin 유발 당뇨쥐 소장의 이당류분해 효소 활성과 혈당강하에 미치는 영향)

  • 유수경;김미지;김진원;이순재
    • Journal of the Korean Society of Food Science and Nutrition
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    • v.31 no.6
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    • pp.1071-1077
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    • 2002
  • The purpose of this study was investigated the effects of YK-209 mulberry leaves on disaccharidase activites of small intestine and blood glucose-lowering in diabetic rats induced with streptozotocin (STZ). Male Sprague-Dawley rats weighing 100$\pm$10 g were randomly assigned to one normal and four STZ-induced diabetic groups; YK-209 0% mulberry leaves diet (DM group),0.1% YK-209 mulberry loaves diet (DM-0.1Y group),0.2% YK-209mulberry leaves diet (DM -0.2Y group), and 0.4% YK-209 mulberry leaves diet (DM -0.4Y group). Diabetes was induced by intravenous injection of 55 mg/kg body weight of STZ in sodium citrate buffer (pH 4.3) via tail vein after 3 weeks feeding of experimental diets. Rats were sacrificed at the 9th day of diabetic states. The functional ingredients in the mulberry leaves, the 1-deoxynojirimycin (DNJ) contents of YK-209 mulberry leaves was higher than those of the Cheongil mulberry leaves. ${\gamma}$ -Aminobutyric acid (GABA) and rutin contents of YK-209 mulberry leaves were 1.3 and 1.4 times higher than those of the Cheongil mulberry leaves, respectively, and vitamin C contents of YK-209 mulberry leaves were also higher than those of the Cheongil mulberry leaves. Intestine index was increased in all diabetic groups, compared with normal group but not significantly different among all diadetic groups. Level of blood glucose was decreased in diadetic rats by supplementation YK-209 mulberry leaves. The disaccharidase activities in proximal part of intestine such as maltase, sucrase, and lactase in YK-209 mulberry leaves supplementation groups were significantly lower than those of DM group, In conclusion, this research indicated that the functional ingredients of YK 209 mulberry leaves were higher than those of the Cheongil leaveses, and YK-209 mulberry leaves has the hypoglycemic effect in STZ-induced diabetic rats.