• BMB Reports
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• 제48권1호
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• pp.13-18
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• 2015

Alzheimer's disease severely compromises cognitive function. One of the mechanisms to explain the pathology of Alzheimer's disease has been the hypotheses of amyloid-pore/channel formation by complex $A{\beta}$-aggregates. Clinical studies suggested the moderate alcohol consumption can reduces probability developing neurodegenerative pathologies. A recent report explored the ability of ethanol to disrupt the generation of complex $A{\beta}$ in vitro and reduce the toxicity in two cell lines. Molecular dynamics simulations were applied to understand how ethanol blocks the aggregation of amyloid. On the other hand, the in silico modeling showed ethanol effect over the dynamics assembling for complex $A{\beta}$-aggregates mediated by break the hydrosaline bridges between Asp 23 and Lys 28, was are key element for amyloid dimerization. The amyloid pore/ channel hypothesis has been explored only in neuronal models, however recently experiments suggested the frog oocytes such an excellent model to explore the mechanism of the amyloid pore/channel hypothesis. So, the used of frog oocytes to explored the mechanism of amyloid aggregates is new, mainly for amyloid/pore hypothesis. Therefore, this experimental model is a powerful tool to explore the mechanism implicates in the Alzheimer's disease pathology and also suggests a model to prevent the Alzheimer's disease pathology.

• 한국환경과학회지
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• 제20권10호
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• pp.1221-1232
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• 2011

We investigated the toxic effects of difenoconazole on the development in the African clawed frog, Xenopus laevis. To test the toxic effects, frog embryo teratogenesis assays using Xenopus were performed. Embryos were exposed to various concentrations of difenoconazole (0-30 ${\mu}M$). $LC_{100}$ for difenoconazole was 30 ${\mu}M$, and the $LC_{50}$ determined by probit analysis was 27.19 ${\mu}M$. Exposure to difenoconazole concentrations ${\geq}$5 ${\mu}M$ resulted in 10 different types of severe external malformation. Histological examinations revealed dysplasia of the eye, heart, liver, somatic muscle, and swelling of the pronephric ducts. The tissue-specific toxic effects were investigated with an animal cap assay. Blood cells were normally induced at a high frequency by mSCF and activin A. However, the induction of blood cells was strongly inhibited by the addition of difenoconazole. Electron micrographs of tested embryos showed the degeneration of somatic muscle and the shrinkage of microvilli on pronephric duct. The gene expression of cultivated animal cap explants was investigated by reverse transcriptase-polymerase chain reaction (RT-PCR). It revealed that the expression of the blood-specific marker(${\beta}$-globin II) and muscle-specific marker (XMA) were more strongly inhibited than the neural-specific marker(XEn2) by the addition of difenoconazole.

• 한국환경과학회지
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• 제19권8호
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• pp.1001-1012
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• 2010

We investigated the toxic effects of tebuconazole on development in the African clawed frog, Xenopus laevis. To test the toxic effects, frog embryo teratogenesis assays using Xenopus were performed. Embryos were exposed to various concentrations of tebuconazole($0-100\;{\mu}M$). $LC_{100}$ for tebuconazole was $100\;{\mu}M$, and the $LC_{50}$ determined by probit analysis was $82.35\;{\mu}M$. The exposure to tebuconazole concentrations ${\geq}40\;{\mu}M$ resulted in 11 different types of severe external malformations including gut dysplasia. Histological examinations revealed various dysplasia in the eye, heart, liver, intestine, somatic muscle, and in the pronephric ducts. The tissue-specific toxic effects were investigated with an animal cap assay. Blood cells are generally induced at a high frequency by the combination of mSCF and activin A, however, the induction of blood cells was strongly inhibited by the addition of tebuconazole. Electron micrographs of tested embryos showed many of multivesicular bodies and dysplasia of photo-receptive cell, however, the somatic muscle degeneration was not severe. The gene expression of cultivated animal cap explants was investigated by reverse transcriptase-polymerase chain reaction and revealed that expression of the blood-specific marker, $\beta$ globin II and muscle-specific marker, muscle actin were more strongly inhibited than the neural-specific marker, XEn2.

• 대한약리학회지
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• 제27권2호
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• pp.99-108
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• 1991

Racemic ketamine을 사용하여 개구리의 좌골신경 및 toe muscle에 대한 작용을 관찰하였다. 실험방법으로는 214 mM sucrose을 사용하여 서로 다른 두 종류의 투여 방법으로 세포막의 활동 전압에 대한 영향을 electric recording으로 관찰하였다. 즉, intracellular 투여는 single sucrose gap technique으로, extracellar 투여는 double sucrose gap technique을 사용하였으며 그 실험 결과는 아래와 같았다. 1. Racemic ketamine은 개구리의 좌골신경 및 toe muscle의 활동전압을 intracellular 및 extracellular 투여시 모두 의의 있게 억제하였다. 2. 개구의 toe muscle에서 $K^+$-수축을 억제하였다. 3. naloxone은 ketamine의 억제작용을 완전히 차단하지는 못하였다.

• 한국환경생태학회지
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• 제18권3호
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• pp.340-345
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• 2004

본 연구에서는 FETAX의 방법에 따라 PCB(Aroclor)가 산개구리의 배아발생에 미치는 효과를 조사하였다. 배아의 치사율과 기형률은 probit 분석법으로 조사하였다. PCB에 의한 LC$_{50}$은 1.48ppb을 나타냈고 EC$_{50}$은 0.25ppb를 나타냈으며 TI는 5.7을 나타내어 PCB는 높은 치사율을 나타내는 최기형성 물질로 판단된다. 기형양상은 수포형성 기형이 0.1ppb에서 62.0%, 꼬리기형이 1ppb에서 32.0%, profund형의 기형이 5ppb에서 68.0%를 나타냈다. PCB는 비교적 낮은 농도인 1.0ppb에서 머리에서 꼬리까지의 성장을 저해하는 결과를 나타내어 이러한 배아의 성장억제에 의 한 평가는 환경오염물질의 독성을 평가하는 데 민감한 지표로 사용되어질 수 있을 것으로 생각된다. 결론적으로 이러한 결과는 PCB가 산개구리 배아발생과정에 높은 독성을 지닌 것을 나타낸다.

• Journal of Ecology and Environment
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• 제30권1호
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• pp.57-62
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• 2007

To obtain demographic information on threatened gold-spotted pond frog (Rana chosenica Okada, 1931) populations, we determined the ages of 45 male and 13 female frogs (20 males and 9 females from Cheongwon and 25 males and 4 females from Tae-an) and compared the age structures and growth patterns of the two populations in 2006. The snout-vent length (SVL) and body weight of female frogs were greater than those of male frogs in both populations. Male frogs' ages ranged 2 to 7 years old and females' ages ranged 3 to 6 years old. In both populations, 4 years old male frogs were the most abundant age-sex class. The age structures of the two populations were significantly different and the growth coefficients of male frogs from the Cheongwon population were greater than those from the Tae-an population. The mean age of males from the Tae-an population was higher than that from the Cheongwon population. However, the SVL and body weights of male frogs were not different between two populations and there was no difference between the two populations in the mean male SVL at any age. The results could increase our understanding of the life-history of this threatened frog and may be useful in conservation planning.

• Ecology and Resilient Infrastructure
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• 제4권4호
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• pp.200-206
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• 2017

도시화로 인한 서식지의 훼손과 단편화는 전세계적으로 양서류에게 큰 위협이 되고 있다. 본 연구에서는 도시화가 청개구리의 분포와 수도에 미치는 영향을 파악하고자, 인천와 그 주변에 위치한 18개 논에서 청음으로 청개구리의 수도를 측정하고 서식지 환경과 토지 이용을 조사하였다. 인천과 주변 논에서 청개구리의 수도는 0 - 17마리 / 서식지 또는 0 - 41마리 / ha이었다. 청개구리의 수도는 서식지와 도로와의 거리가 멀어짐에 따라서 서식지의 둘레길이 면적이 켜질수록 증가하였다. 일반적인 예측과는 달리 청개구리의 밀도는 서식지의 크기와 음의 상관을, 주변의 토지이용 강도와는 양의 상관관계를 보였다. 따라서 도시화에 의하여 서식지 면적이 감소하고 주변이 개발됨에 따라서 청개구리리가 좁은 서식지로 집중화될 수 있다고 생각된다.

• 한국통신학회논문지
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• 제19권8호
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• pp.1595-1611
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• 1994

본 논문에서는 전자파의 전파현상의 불연속모델로서 시간영역 유한 차분법의 수치적 성질이 연구된다. 시간 공간의 차원에서 막스웰 방정식을 개구리뜀 근사식으로 나타내므로 수치적인 특성과 의존 영역의 항으로 전자파의 전파현상을 모사한다. 시간영역 유한차분법의 수치적모사과정이 기하학적으로 설명된다. 개구리뜀 근사법의 채용으로 인한 수치적인 분산현상이 예시된다. 개구리뜀 근사법을 기초로 한 시간영역 유한차분법은 원래 계산 결과만을 산출하는 모델이 아니고 묘사적인 모델이므로 전자파 전파현상에 대한 몰리적인 현상을 묘사할 뿐만 아니라 이러한 묘사직언 결과로부터 푸리에 변환을 통하여 주파수 영역에서의 결과를 추출할 수 잇는 매우 유연한 수치해석 방법이다. 그래서 본 수치해석 방법을 이용하여 WR-28과 WR-90 도파관의 E-평면 휠터와 인턱티브 아이리스의 특성성분적 결과를 포함시킨다.

• The Korean Journal of Physiology
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• 제16권2호
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• pp.119-128
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• 1982

The frog truncus arterious were studied with conventional glass microelectrode technique in order to elucidate the underlying mechanism of spontaneous pacemaker activity. The analyses were focussed on the ionic nature of pacemaker current by changing the concentrations of extracellular $K^+$ and, $Na^+$, or by using blockers of K- and Ca-current and chronotropic transmitters. 1) The action potential of the spontaneously active truncus arteriosus has some characteristic feature of maximal distolic potential ranged from -65 to -75 mV, resting potential from -45 to -50 mV and overshoot voltage about +30 mV, respectively. Duration of the action potential taken from rapid upstroke to maximal diastolic potential was about 600 msec. Usual discharge rate was $25{\sim}30/min$ at room temperature $(18{\sim}20^{\circ}C)$. 2) The sensitivity of the resting membrane potential to change extracellular potassium concentrations $(0{\sim}12\;mM)$ was relatively low. Transient hyperpolarization was appeared in the 12 mM K Ringer after 10 min exposure to 0 mM K and it could be related to Na-pump reactivation by high potassium. 3) Reduction of extracellular sodium concetrations diminished the amplitude and frequency of the action potential. In Ringer solution containing 30% Na (substituted by equimolar Tris), spontaneous activity stopped but reappeared as very slow and small action potential. There was no spotaneous activity in zero Na Ringer solution. 4) Caesium(10 mM), K-current blocker decreased the frequency of the action potential and also pacemaker depolarization. Manganese (2 mM) known to be Ca-current antagonist, blocked spontaneous activity completely. 5) Adrenaline and acetylcholine had no chronotropic effect. But adrenaline increased the duration of plateau phase and the magnitude of the action potential in the follower cell. It is concluded that K-, Na-and Ca-current components are involved in the genesis of spontaneous activity of the frog truncus arteriosus like cardiac pacemaker tissues. But the insensitivity of truncus arteriosus to adrenaline and acetylcholine indicates that there are some different control mechanisms of spontaneous rhythm in two tissues.

• The Korean Journal of Physiology
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• 제13권1_2호
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• pp.13-22
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• 1979

Studies have been conducted using isolated surviving skin of Rana temporalia in an attempt to evaluate the effect of N-ethylmaleimide (NEM) on the epithelial $Na^+$ transport. Active transport of $Na^+$ across the skin was estimated by measuring short circuit current (SCC). NEM administered to the outside surface of the skin in concentration of $0.5{\times}10^{-4}-2.5{\times}10^{-4}M$ induced $20{\sim}40%$ increase during the first 30 mintues, followed by a gradual reduction in SCC. With NEM above $4{\times}10^{-4}M$, SCC was inhibited from the beginning. Qualitatively similar results were obtained when NEM was added to the inside bathing medium. However, the concentration of NEM for a similar effect was much higher with the drug in the inside bathing medium than in the outside bathing medium. The oxygen consumption of the skin was inhibited by NEM of above $10^{-4}M$, the effect being of approximately the same magnitude as that on SCC. The activity of $Na^+-K^+$ ATPase of the skin was not inhibited by NEM below $10^{-3}M$, but it was dramatically reduced with $1.2{\times}M$ NEM. The effects of NEM $(10^{-4}M)$ on the SCC and oxygen consumption could be eliminated by adding cysteine $(10^{-4}-10^{-3}M)$ in the medium, indicating that the SH group is involved in the action of NEM in the frog skin. On the basis of these results, the mode of action of NEM on the $Na^+$ transport across the frog skin was discussed.