• 제목/요약/키워드: Passive Administration

검색결과 234건 처리시간 0.027초

제품 시장 경쟁 및 기업의 사회적 책임 활동 (Product Market Competition and Corporate Social Responsibility Activities)

  • 류혜영;채수준
    • 산경연구논집
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    • 제10권11호
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    • pp.49-56
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    • 2019
  • Purpose: Corporate social responsibility is a self-regulating business model that helps a firm be socially accountable to the public. By practicing corporate social responsibility, firms can be conscious of the kind of impact they are having on all aspects of society, including economic, social, and environmental. Corporate social responsibility activities are not directly linked to increasing corporate performance and corporate value, but rather involve spending expenses. Based on these facts, this study verifies whether the effects of corporate social responsibility activities differ depending on the firm's situation. Research design, data and methodology: This study analyzed the effect of market competition on corporate social responsibility activities using logistic regression analysis on listed companies in the KOSPI and KOSDAQ for fiscal years 2014 through 2016. In this study, market competition was measured using the Herfindahl-Herschman Index(HHI). Higher HHI value can be interpreted as a lower degree of market competition. We also measured corporate social responsibility activities using the KEJI Index published by the Korea Economic Justice Institute (KEJI). If a firm-year is included in the top 200 companies of the KEJI Index, it is classified as a good corporate social responsibility activity firm. Results: We find that companies in less competitive market were not included in the KEJI Index. This result indicates that firms in the market with lower market competition perform less corporate social responsibility activities that incur costs. An additional analysis showed that there was a significant negative relationship between the market competition and the corporate social responsibility activity scores published by the KEJI Index. These result adds robustness to the result of the hypothesis that firms that have a monopolistic place in the market practice passive corporate social responsibility activities. Conclusions: The results show that managers of a firm in the lower market competition have a lower incentive to use limited resources for projects that are not directly related to revenue. The results of this study imply that corporate social responsibility activities vary according to the position of the business. Therefore, this study suggests that market investors should consider the degree of competition in the market when they evaluate corporate social responsibility activities.

체위변화가 두부 및 하지의 분시혈류량에 미치는 영향 (Changes of Minute Blood Flow in the Large Vessels during Orthostasis and Antiorthostasis, before and after Atropine Administration)

  • 박원균;채의업
    • The Korean Journal of Physiology
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    • 제19권2호
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    • pp.139-153
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    • 1985
  • 기립 및 도립의 체위면화가 두부 및 하지의 혈액순환계에 미치는 영향을 관찰하고, atropine의 정주에 의한 부교감신경의 차단이 체위변화에 대한 심맥관계의 내성을 증가시키는 지를 보기위하여 개를 경사대에 수평위로 고정하여 수동적으로 기립 및 도립위로 체위를 변화시키고, 각 체위에서 10분간 유지시켜 경동맥, 외경정맥, 고동맥 및 고정맥의 분시 혈류량, 분시 심박수 및 분시 호흡수, 그리고 혈액의 pH, $PCO_2$, $PO_2$ 및 Hct를 측정하였다. 다시 수평위에서 atropine 0.5mg을 1회 정주한 후 위의 실험과정을 반복하여 시행하고 atropine투여전과 비교 관찰하였던 바 다음과 같은 결과를 얻었다. 기립시 두부 및 하지 동정맥혈의 분시 혈류량은 감소하였고, 특히 두부로 가는 혈류량의 감소가 더 컸으나, atropine의 투여는 경동맥의 분시 혈류량의 감소를 억제하였다. 도립시 두부 및 하지의 분시 혈류량은 유의한 변화를 보이지 않았고, 개체에 따라 변화양상도 다르게 나타났다. atropine의 투여는 투여전에 비하여 유의한 차이를 보이지 않았다. 분시 심박수는 기립 및 도립시 모두 증가하였다. atropine의 투여는 수평위에서 분시 심박수는 투여전 보다 증가하나, 체위변화에 의한 분시 심박수의 증가를 경감시켰다. 분시 호흡수는 개체에 따라 변화양상에 차이가 있으나, 대체로 기립시는 감소하고 도립시는 증가하였다. atropine의 투여는 기립 및 도립시 다 같이 분시 호흡수의 변화를 억제하였다. 혈액소견은 기립시 정맥철의 pH 및 $PO_2$는 감소하였고, $PCO_2$는 증가하나 동맥혈의 $PCO_2$는 감소하였다. 도립시 동정맥혈의 소견은 수평위에 비해 별 변화가 없었으며 , atropine의 투여후도 기립 및 도립시 모두에서 투여전에 비하러 유의한 변하는 없었다. Hct는 기립 및 도립시 증가하였으며 atropine투여에 의한 변화는 관찰할 수 없었다. 이상에서와 같이 atropine의 투여는 기립시 두부로 가는 혈류량을 증가시키며, 기립 및 도립시 발생할 수 있는 분시 심박수의 과도한 증가를 억제함으로서 체위변화에 대한 심맥관계의 내성을 증가시키는데 어느정도 효과가 있다고 하겠다.

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A comparison study of the effects of loratadine-pharmacopuncture and loratadine-oral administration based on traditional Korean medicine theory on anaphylactic reaction in mice

  • Kim, Hyun-Min;Kim, Hyun-Min;Lee, Min-Jung;Cho, Min-Gi;Kang, Deok;Kim, Yu-Kyung;Kim, Changmin;Kang, Do-Hyun;Jeong, Si-Hwa;Ahn, Ik-Gyun;Hwang, Jun-Hyeok;Kim, Jae-Hyun;Lee, Hyun-Jin;Jang, Jun-Yeong;Park, Ho-Jung;Kang, Sin woo;Youm, Jieun;Baek, Seung-won;Kim, Eu Jin;Shin, Moon-Kou;Park, Chan;Son, Chang-Bin;Yim, Tae-Bin;Lim, Jung Hyun;Hong, Sung-eun;Choi, Jun-Hyuk;Kim, Jun-Dong;Yoon, Dong-ju;Lee, Dong-Min;Yu, Soo-Min;Hong, Ye-Im;Lee, Yeong-Seok;Koo, Bon-Cheol;Park, Hyoung-Jun;Uem, Chae-Yoon;Kim, Min-Jeong;Oh, Jayoung;Park, NamGyeong;Kim, Eun-Jong;Cho, Whi-Sung;Lee, Ho-Sung;Kim, Tae-oh;Yoon, Cheol;Kwon, Sung-Keun;Jeong, Dong-Hyeon;Lee, Changwon;Yu, Sang-Yeol;Shon, Chae-won;Jeon, Gyu-Ri;Hong, Yang-Seok;Moon, Phil-Dong
    • 셀메드
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    • 제8권1호
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    • pp.5.1-5.4
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    • 2018
  • Pharmacopuncture, or herbal acupuncture, is a new form of therapy derived from combinations of two traditional therapeutic methods, herbal medicine and acupuncture therapy. To compare the efficacy between loratadine-pharmacopuncture (LP) and loratadine-oral administration (LO), the effect of loratadine was investigated in murine models. Anti-anaphylactic effects of loratadine treatments were investigated in compound 48/80-induced systemic anaphylactic reaction and passive cutaneous anaphylaxis (PCA). LP treatment significantly inhibited the compound 48/80-induced systemic anaphylactic reaction and PCA. The effect between LP and LO were on a similar level. These results indicate that LP can be used as an alternative method for LO in case of emergency.

고지방 식이로 유도된 실험동물의 당뇨성 인지기능 장애에 대한 고사리 아세트산에틸 분획물의 개선효과 (Ethyl acetate fraction from Pteridium aquilinum ameliorates cognitive impairment in high-fat diet-induced diabetic mice)

  • 권봉석;궈텐쟈오;박선경;김종민;강진용;박상현;강정은;이창준;이욱;허호진
    • 한국식품과학회지
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    • 제49권6호
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    • pp.649-658
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    • 2017
  • 본 연구는 고지방 식이를 통해 유도되는 혈당 상승과 이로 인한 인지기능 장애에 대한 고사리(Pteridium aquilinum) 아세트산에틸 분획물(EFPA)의 개선 효과를 확인하기 위해서 수행되었다. 고지방 식이를 섭취시킨 실험동물에 고사리 아세트산에틸 분획물을 식이를 하였을 때, 공복혈당을 낮추었고 인슐린 저항성을 확인하기 위한 내당능 시험에서 개선효과를 나타내었다. 또한 실험동물의 혈액을 이용한 혈청분석 결과 혈청 내 총 콜레스테롤(TCHO)과 저밀도지단백질 콜레스테롤(LDLC)과 같은 지방질 대사 수준이 유의적으로 개선되었다. 실험동물을 이용한 행동학적 시험(Y-maze, passive avoidance, Morris water maze tests)을 통해 인지기능 개선효과를 확인해본 결과, 공간인지 능력, 단기 학습 능력, 장기 기억 능력이 고지방 식이군(HFD)에 비해 유의적으로 개선되었다. 또한 동물 행동 실험 후 적출된 뇌 조직에서 산화방지 효소인 초과산화물제거효소(SOD)의 함량과 지방질과산화 정도(MDA level)를 측정해본 결과 고사리 아세트산에틸 분획물이 조직에서의 산화방지 능력을 증가시켜 주는 것을 확인 할 수 있었다. 그리고 인지능력에 영향을 주는 아세틸콜린(ACh)과 아세틸콜린 가수분해효소(AChE)에 미치는 영향을 확인해 본 결과, 아세틸콜린 가수분해효소의 활성이 억제되었고 그 결과 아세틸콜린의 함량이 증가하였다. 고지방 식이로 유도되는 혈당 상승 및 인지기능 장애의 개선에 도움이 되는 고사리 아세트산에틸 분획물의 주요 생리활성 물질이 무엇인지 확인하기 위하여 QTRAP LC-MS/MS를 시행한 결과, 주요 물질은 kaempferol-3-O-glucoside로 동정되었고 이 이외에 caffeolyshikimic acid, quercetin-3-O-glucoside, kaempferol-3-O-rutinoside 등이 확인 되었다. 이러한 연구결과를 고려할 때, 캠페롤(kaempferol) 등과 같은 플라보노이드류와 폴리페놀 화합물을 함유한 고사리 아세트산에틸 분획물(EFPA)은 고지방 식이로 인한 혈당 상승과 이로 인한 인지기능 장애의 개선에 도움을 줄 수 있는 건강 기능성 식품 소재로 이용될 수 있을 것으로 판단된다.

스트렙토조토신으로 유도된 당뇨 마우스에서 Monascus purpureus을 이용한 발효 쑥의 기억력 개선 효과 (Memory improvement effect of Artemisia argyi H. fermented with Monascus purpureus on streptozotocin-induced diabetic mice)

  • 이창준;이두상;강진용;김종민;박선경;강정은;권봉석;박상현;박수빈;하기정;허호진
    • 한국식품과학회지
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    • 제49권5호
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    • pp.550-558
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    • 2017
  • 본 연구는 쑥 추출물(AA)과 홍국균(Monascus purpureus)으로 발효된 쑥(AAFM)을 이용하여 STZ로 인한 당뇨성 인지장애 개선효과를 확인하고자 수행되었다. C57BL/6L 마우스에 streptozotocin(STZ)을 복강 주사하여 당뇨를 유발시킨 후 4개의 군으로 분리하였고, 6주간 24시간 간격으로 AA 10 mg/kg BW와 AAFM 10 mg/kg BW을 경구투여 하였다. 7일 간격으로 혈당을 측정하였으며, 혈당 측정 결과 AA와 AAFM을 섭취한 군에서 STZ군 대비 유의적인 혈당감소를 나타내었다. Passive avoidance, Morris water maze 및 Y-maze test를 통해 STZ로 유도한 당뇨 동물모델에서 기억력 장애를 확인하였으며, 발효 쑥(AAFM)군에서 학습에 의한 기억력과 운동능력이 더 회복된 것을 확인하였다. 혈청분석 결과 STZ군에서는 GOT, GPT, BUN와 혈중 지질 함량이 높게 나타난 반면 발효 쑥(AAFM)군에서는 GOT, GPT 및 BUN이 STZ그룹에 비해 유의적으로 감소하였으며, HTR이 높게 나타났고 TG와 LDLC가 낮게 나타나 혈중 지질 성분이 개선됨을 확인할 수 있었다. 마우스 뇌 조직에서 발효 쑥(AAFM)은 아세틸콜린에스터레이스 활성을 저해시키고 아세틸콜린 함량을 증가시킴으로써 STZ로 인한 당뇨병에서의 신경전달시스템을 개선효과를 나타내었다. 발효 쑥(AAFM)의 경우, 마우스의 뇌 조직에서 SOD 함량을 증가시키고, 뇌와 간에서의 MDA 함량을 감소 시킴으로써 STZ와 같은 산화적 스트레스 인자에 대한 산화방지 효과를 나타내었다. 이러한 결과들을 종합해볼 때, 홍국균을 활용한 발효 쑥(AAFM)은 STZ로 유도된 당뇨 모델에서 당뇨성 인지장애에 대한 기억력 개선효과를 나타내었다. 특히, 쑥 추출물(AA)보다 마우스의 운동능력을 개선시켰으며, 혈중 지질 개선효과를 나타냈다. 더불어 산화방지 효과를 나타내 고혈당으로 발생될 수 있는 산화적 스트레스로부터 뇌 조직 등을 보호할 수 있음을 확인하였다. 결국 고혈당으로 인한 인지장애의 예방과 치료에도 효과를 나타낼 것으로 사료되어 고부가가치 식품으로 활용될 수 있는 산업적 가능성이 있다고 판단된다.

조미료가 창자 운동과 흡수기능에 미치는 영향 -소장의 피동적 흡수에 대한 고추의 영향- (The Effect of Seasoning on the Intestinal Absorption -Absorption by Passive Transport and the Effect of Red Pepper-)

  • 신동훈;김중수;고재평;안승운
    • The Korean Journal of Physiology
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    • 제7권1호
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    • pp.23-31
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    • 1973
  • Numerous factors concern with the absorption of substances through the membrane of the gastrointestinal tract. To simplify the experimental condition, present work has been restricted to observe the disappearance rate of substance from the intestinal loop which was made in the jejunum, 70 cm apart from the pylorus of the adult rabbit. The purpose of the study is to clarify the absorption of urea through the jejunal wall is solely attributable to the concentration difference between the luminal fluid and plasma, and to observe the effect of adding red pepper upon the rate of absorption. The rabbits were anesthetized with nembutal, 35mg/kg I.V. Jejunal loop was made by ligating at 2 spots, 70 cm and 80cm apart from the pylorus. After rinsing with normal saline solution through the polyethylene tubing inserted from the end of the loop, 8 ml of test solution was placed through the same tubing. The test solution contained 200 mg% of urea and 150mg% of polyethylene glycol(M.W. 4,000) in normal saline solution. Right after placing the test solution the first specimen was taken through the tubing, and successive samplings were performed at 5, 10, 20, and 30 minutes. Logarithm of the difference of urea concentration between the luminal fluid and plasma was plotted against time elapsed after the onset of the experiment. If straight line is revealed, it would verify the nature of transport mechanism as diffusion, obeying the Fick's principle. The concentration of polyethylene glycol (PEG) was also measured in order to examine the change in the volume. PEG was used as the marker substance because it is not absorbable in the intestinal tract. Consequently the concentration of PEG relates inversely to the volume of the loop. Instantaneous concentration of urea in the loop times the volume will give the amount of urea remaining in the luminal fluid. The change in the amount of any substance is directly relate to the volume of the compartment and differs from the change in the concentration which is independent of the volume. After completion of the experiment without red pepper, it was added in the test solution and was centrifuged after thorough mixing. Supernatant of the mixture was placed in the loop and similar sampling were performed with the same time intervals that of previous run in order to observe the effects of the red pepper on the passive transport of the water soluble small substance, urea. The results obtained were as follows: 1. Logarithm of the concentration difference of urea between the luminal fluid and plasma was diminished exponentially as time elapsed. The decay constant in the experiment without red pepper was 0.0563/min. By adding red pepper in the test solution as much as the concentration rose to 4,000 mg% and 8,000 mg%, the decay constants were lowered to 0.0493/min and to 0.0506/min, respectively. The time interval by which the concentration difference dropped to one half of the initial value was prolonged. Without red pepper the half concentration time was 13.30 minutes, and by adding extract of red pepper, 15.31 minutes and 15.71 minutes were revealed. 2. The profile of the diminishing rate of tile amount of urea was quite different from that of the concentration because of the change in the volume of the loop during the observed period. 3. By adding the extract of red pepper, it slowed down the rate of absorption of urea in the intestinal loop, suggesting an increase in the diffusional barrier. 4. Larger dosage of red pepper brought an increase in the secretion of intestinal fluid with concomitant expansion of the luminal volume, and the retardation of the absorption of urea was noticed. This effect was largely dependent on the sensitivity of the individual animal to the red pepper, extract. The amount of urea remained after 10 minutes interval was 55.5% of the initial amount in the experiment without red pepper. On the other hand it was not consistent after administration of red pepper, showing 50.6% and 66.5% of the initial figures by adding 400 mg and 800 mg of red pepper in the test solution, respectively. It was postulated that symptom of diarrhea often encountered by taking a hot (red pepper) food might be attributable to the increase of secretion and the retardation of absorption in the intestinal tract.

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대중문화 흐름 속의 청소년문화 (Youth Culture in the Stream of Popular Culture)

  • 김천영
    • 문화기술의 융합
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    • 제4권3호
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    • pp.105-111
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    • 2018
  • 본 연구는 관계적 접근으로 대중문화흐름 속의 청소년문화를 탐구하고자 한다. 이를 위하여 대중문화의 흐름속에서 청소년문화의 관계를 파악하였다. 이를 통하여 청소년문화의 의미와 실천과제가 확인되었는데, 그것의 주요내용은 청소년문화가 가능성을 갖는 문화적 의미를 갖는다는 사실이다. 수동적인 문화나 수신자 문화, 소비자의 문화가 아니라 능동적인 문화와 발신자의 문화, 생산자의 문화적 성격을 갖는 문화라는 점이다. 아울러 대중문화의 흐름 속에서 새로운 가능성을 갖는 문화로서의 청소년문화의 실천과제는 인식적 실천과제와 제도적 실천과제 속에서 접근되어야 함이 발견되었다. 청소년문화의 인식적 실천의 중요성은 대중문화의 접근시각의 중요성으로 드러난다. 청소년문화가 배제적 관점 속에서 접근되는 것은 닫힌 청소년문화의 한계성을 가져오는 반면, 수렴적 관점 속에서 접근될 수 있어야 열린 청소년문화의 가능성이 수반될 수 있다. 따라서 청소년문화의 열린 가능성은 열린 관점에 의한 열린 문화의 개념 속에서 새로운 가능성을 가질 것이다. 그것은 작은 협의의 문화개념이 아닌 큰 광의의 문화개념 속에서 열려진다.

Spinosin, a C-Glucosylflavone, from Zizyphus jujuba var. spinosa Ameliorates Aβ1-42 Oligomer-Induced Memory Impairment in Mice

  • Ko, Sang Yoon;Lee, Hyung Eun;Park, Se Jin;Jeon, Se Jin;Kim, Boseong;Gao, Qingtao;Jang, Dae Sik;Ryu, Jong Hoon
    • Biomolecules & Therapeutics
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    • 제23권2호
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    • pp.156-164
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    • 2015
  • Alzheimer's disease (AD) is a neurodegenerative disorder associated with progressive memory loss and neuronal cell death. Although numerous previous studies have been focused on disease progression or reverse pathological symptoms, therapeutic strategies for AD are limited. Alternatively, the identification of traditional herbal medicines or their active compounds has received much attention. The aims of the present study were to characterize the ameliorating effects of spinosin, a C-glucosylflavone isolated from Zizyphus jujuba var. spinosa, on memory impairment or the pathological changes induced through amyloid-${\beta}_{1-42}$ oligomer ($A{\beta}O$) in mice. Memory impairment was induced by intracerebroventricular injection of $A{\beta}O$ ($50{\mu}M$) and spinosin (5, 10, and 20 mg/kg) was administered for 7 days. In the behavioral tasks, the subchronic administration of spinosin (20 mg/kg, p.o.) significantly ameliorated $A{\beta}O$-induced cognitive impairment in the passive avoidance task or the Y-maze task. To identify the effects of spinosin on the pathological changes induced through $A{\beta}O$, immunohistochemistry and Western blot analyses were performed. Spinosin treatment also reduced the number of activated microglia and astrocytes observed after $A{\beta}O$ injection. In addition, spinosin rescued the $A{\beta}O$-induced decrease in choline acetyltransferase expression levels. These results suggest that spinosin ameliorated memory impairment induced through $A{\beta}O$, and these effects were regulated, in part, through neuroprotective activity via the anti-inflammatory effects of spinosin. Therefore, spinosin might be a useful agent against the amyloid ${\beta}$ protein-induced cognitive dysfunction observed in AD patients.

Inhibitory effects of Cortex Mori on Compound 48/80-induced Anaphylactic Shock and Cutaneous Reaction

  • Jun, Byoung-Deuk;Chai, Ok-Hee;Park, Myoung-Hee-;Lee, Hern-Ku-;Lee, Moo-Sam-
    • 한국응용약물학회:학술대회논문집
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    • 한국응용약물학회 1994년도 춘계학술대회 and 제3회 신약개발 연구발표회
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    • pp.243-243
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    • 1994
  • Although active systemic anaphylaxis and passive cutaneous anaphylaxis have been empolyed to study anaphylactic hypersensitivity, it is difficult and time-consuming to induce these reactions in experimental animals. In recent, Jun et al have found a simple method to induced anaphylactic hypersensitivity such as anaphylactic shock(AS) and cutaneous reaction(CR) using compound48/80. Cortex mori (Morus alba L.), the root bark of mulberry tree has been used as an antiphlogistic, diuretic, and expectorant in herbal medicine. The purpose of this study was to determine whether the methanol extract of Cortex mori could inhibit the compound 48/80-induced AS and CR. To induce AS, various doses of compound 48/80 (5, 7.5, 10, 15$\mu\textrm{g}$/gm B.W.) were injected intraperitoneally (i.p.) into ICR mice. The animals were pretreated by three injection(i.p.) of Cortex mori before compound 48/80 administration. Peripheral blood was collected from the right ventricle to estimate the level of serum histamine at 15 minutes after the injctin(i.p.) of various concentration of compound48/80. Mortility rate, mean death time and mesenteric mast cell degranulation rate were evaluated over a 72 hour period. To estimate the effect of Cortex mori on compound 48/80-induced cutaneous reaction, various doses of compound 48/80 with or without Cortex mori were injected intradermally(i.d.) into the shaved flank of Sprague-Dawley rats, and the blue cutaneous patchs induced by Evans'blue injection at the compound 48/80 alone and Cortex mori plus compound 48/80 injection sites were observed. As a Parameter of these reactions, the levels of histamine in the supernatant, calcium uptake and intracellular CAMP of RPMC were measured. supernatant, 1)compound 48/80-induced mortility rate, mean death time, mesenteric mast cell degranulation rate, and serum histamine level in ICR mice were significantly inhibited by pretreatment of Cortex mori, 2) cutaneous reaction inducd by compound48/80 was well developed in Sprague-Dawley rat, but Cortex mori inhibited the compound 48/80-induced blue patch formation remarkably, 3) the compound 48/80-induced degranulation, histamine release and calcium uptake of RPMC pretreated with Cortex mori were significantly inhibited, compared to those of control without Cortex mori pretreatment, and 4)the level of cAMP of RPMC was reduced bythe increased concentration of compound 48/80, pretreatment of Cortex mori not only inhibited the compound 48/80-induced reduction of CAMP but also significantly increased the level of cAMP naturally, from the above results, it is suggested that Cortex mori has an some substances with an ability to inhibits the compound 48/80-induced AS,CR, and mast cell activation.

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Preparation of Alzheimers Animal Model and Brain Dysfunction Induced by Continuous $\beta$-Amyloid Protein Infusion

  • Akio Itoh;Kiyofumi Yamada;Kim, Hyoung-Chun;Toshitaka Nabeshima
    • Toxicological Research
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    • 제17권
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    • pp.47-57
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    • 2001
  • Alzheimer's disease (AD) is the most common cause of dementia in the elderly, and its pathology is characterized by the presence of numerous numbers of senile plaques and neurofibrillary tangles. Several genetic and transgenic studies have indicated that excess amount of $\beta$-amyloid protein (A$\beta$) is produced by mutations of $\beta$TEX>$\beta$-amyloid precursor protein and causes learning impairment. Moreover, $A\beta$ has a toxic effect on cultured nerve cells. To prepare AD model animals, we have examined continuous (2 weeks) infusion of $A\beta$ into the cerebral ventricle of rats. Continuous infusion of $A\beta$ induces learning impairment in water maze and passive avoidance tasks, and decreases choline acetyltransferase activity in the frontal cortex and hippocampus. Immunohistochemical analysis revealed diffuse depositions of $A\beta$ in the cerebral cortex and hippocampus around the ventricle. Furthermore, the nicotine-evoked release of acetylcholine and dopamine in the frontal cortex/hippocampus and striatum, respectively, is decreased in the $A\beta$-infused group. Perfusion of nicotine (50 $\mu\textrm{M}$) reduced the amplitude of electrically evoked population spikes in the CA1 pyramidal cells of the control group, but not in those of the $A\beta$-infused group, suggesting the impairment of nicotinic signaling in the $A\beta$-infused group. In fact, Kd, but not Bmax, values for [$^3H$] cytisine binding in the hippocampus significantly increased in the $A\beta$-infused rats. suggesting the decrease in affinity of nicotinic acetylcholine receptors. Long-term potentiation (LTP) induced by tetanic stimulations in CA1 pyramidal cells, which is thought to be an essential mechanism underlying learning and memory, was readily observed in the control group, whereas it was impaired in the $A\beta$-infused group. Taken together, these results suggest that $A\beta$ infusion impairs the signal transduction mechanisms via nicotinic acetylcholine receptors. This dysfunction may be responsible, at least in part, for the impairment of LTP induction and may lead to learning and memory impairment. We also found the reduction of glutathione- and Mn-superoxide dismutase-like immunoreactivity in the brains of $A\beta$-infused rats. Administration of antioxidants or nootropics alleviated learning and memory impairment induced by $A\beta$ infusion. We believe that investigation of currently available transgenic and non-transgenic animal models for AD will help to clarify the pathogenic mechanisms and allow assessment of new therapeutic strategies.

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