• The Korean Journal of Zoology
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• v.32 no.1
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• pp.55-73
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• 1989

The effect of tryptophan or serotonin on the early stage of chick brain development has been morphologically investigated using an electron microscope. The electron micrographs of neural plate cells of 1-day chick embryo treated with tryptophan or serotonin showed irregularity, evagination and disruption of nuclear membrane and nuclear chromatin condenstation, nucleolar margination and segregation. Hypertrophy of stalks, vesicles and vaculoes were seen and dilated and disrupted rough endoplasmic reticulum and underdeveloped neurotubules were also observed. In mesenchyme cells of tryptophan or serotonin administered 18 hr embryo, irregular nuclear membrane, swollen mitochondria, dilated rough endoplasmic reticulum and very large yolk granules were observed. Furthermore, DNA, RNA and protein contents of the embryos treated with typtophan or serotonin were considerably lower than those of control group. The amount of tubulin of the experimental groups was also greatly lower than that of control, suggesting that the impairment of microtubule formation occurred. Tryptophan or serotonin administration might depress the biosynthesis, of nucleic acid and protein including some enzymes tested. It seems that the serotonin formed from exogeneous tryptophan might inhibit the degradation of yolk granule by feedback regulation mechanism so as to impair microtububle and microvilli formation followed by a malformation of chick embryos.

• Parasites, Hosts and Diseases
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• v.25 no.2
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• pp.99-109
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• 1987

The present study was carried out to examine the effect of a calcinogen, aflatoxin B1 on the ultrastructural changes of ciliary epithelial cells in mice infected with Clonerchis sinensis. A total of 93 male albino mice(BALB/c strain) was divided into 3 groups; group I, treated with 1.0 ppm aflatoxin Bl for 12 weeks; group II, given 50 C. sinensis n;etacercariae, and group III, given 50 metacercariae and treated with 1.0 ppm aflatoxin Bl for 12 weeks. Three mice served for untreated-uninfected controls. From 4 weeks after the treatsment and/or in(ection, three mice from each group were sacrificed at 4 week intervals up to the 40th week, and their hepatobiliary tissues were prepared for transmission electron microscopy. The most prominent ultrastructural changes in group I were remarkable enlargement of nuclear size, separation of nucleolus, dispersed chromatin granules in nuclei and increased dense granules along the inner membrane of nuclei. In the cytoplasm there was slight proliferation of mitochondria and endoplasmic reticulum (ER) at earlier stage. At the 12th week separation of fibrillar and granular components of the nucleolus was a characteristic finding. As the time elapsed, epithelial cells showed fiattened-cuboidal form and a tendency of atrophy. Most of the nuclei were elongated and polygonal in shape. In group II the appearance of elaborate interwoven folds of lateral cytoplasm forming a labyrinth of interconnected intercellular space and variety in nuclear shape were the prominent fadings at earlier stage. The cytoplasm showed slight proliferation and dilatation of mitochondria and ER, and a small number of mucin droplets. In the basement membrane scanty fibrous cells were seen. With time, variety in nuclear shape, marked proliferation and dilatation of rough ER and some collagen fibrils were demonstrated. Other features of intracellular organelles and mucin droplets persisted. In group III cuboidal epithelial cells showed their remarkably enlarged and irregular nuclei, increased chromatin granules in the nuclei, separated nucleoli, proliferated and dilated rough ER. With time, sequestered mitochondria showed blob-like evaginations which lacked cristae and dense matrix, and were limited by a single membrane. Since the 20th week, microvilli were relatively scanty and poorly developed. Organelles and inclusions in the cytoplasm of metaplastic cells were poor. Nuclei were variable in shape. The nlost prominent changes at later stage were separation of nuclei from the cytoplasm, and appearance of numerous and irregularly angled electron dense granules in the nuclei.

• Journal of Periodontal and Implant Science
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• v.29 no.1
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• pp.51-63
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• 1999

Exposure of the root surface due to gingival recession after periodontal surgery, elicit pain response when exposed to mechanical, heat, chemical or osmotic irritation. Especially patients treated with periodontal surgery, show high frequency. There have been reports that the 1 out of 7 patients complains of dentinal hypersensitivity. There have been many studies on the clinical effects of various materials on the treatment of dentinal hypersensitivity. The purposes of this study were to evaluate the effect of sodium chloride and potassium oxalate and to observe the relationship between the dentinal hypersensitivity and surface characteristics such as dentinal tubule size and number. This study included 20 teeth which were scheduled for extraction and had no pulpal disease. These teeth were divided into Root planing group, EDTA group, NaCl group and Oxalate group. Dentinal hypersensitivity is measured by tactile, pressured air and cold water using NRS (Numerical Rating Scales). Teeth were extracted under local anesthesia and each specimen was sectioned to a size about 3 X 5 mm and was examined under the scanning electron microscope (X2,000) The results were as follows, 1. The EDTA group exhibited significantly increased dentinal hypersensitivity comparing with the other groups. 2. The NaCl and Oxalate groups showed significantly reduced dentinal hypersensitivity comparing with the EDTA group. 3. As a method for dentinal hypersensitivity measurement, it was presumed thet tactile sensitivity test was not sensitive method but air blast test and cold water test were adequate method. 4. In a SEM study, the root planing group exhibited amorphous smear layer and showed no dentinal tubule orifice, but the EDTA group showed the large number of dentinal tubules. On the other hand, the NaCl and Oxalate groups did not show exposed dentinal tubules. The NaCl group showed more rough root surface than the EDTA group, and the Oxalate group showed many participates to be presumed as calcium oxalate particle. As the results from this study, root planing couldn't expose the dentinal tubule and NaCl and potassium oxalate occluded exposed dentinal tubule effectively. Dentinal hypersensitivity has close relationship with the exposure of dentinal tubules, especially with it's size and number.

• The Journal of Korean Academy of Prosthodontics
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• v.44 no.6
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• pp.740-750
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• 2006

Statement of problems. In an attempt to reduce screw loosening, dry lubricant coatings such as pure gold or tefron have been applied to the abutment screw. However, under repeated tightening and loosening procedures, low wear resistance and adhesion strength of coating material produced free particles on the surface of abutment screw and increased frictional resistance resulting in screw tightening problems. Purpose. The aim of this study was to compare friction coefficient, adhesion strength, vickers hardness and evaluate coating surface of titanium alloy specimens coated with TiN(titanium nitride), ZrN(zirconium nitride) and WC(tungsten carbide). Material and method. Titanium alloy(Ti-6Al-4V) discs of 12mm in diameter and 1mm in thickness divided into 4 groups. TiN, ZrN and WC was coated for the specimens of 3 groups respectively, and those of 1 group were not coated. Each group was made up of 4 specimens. In this study, sputtering method was used among the PVD(Physical Vapor Deposition) techniques available for TiN, ZrN and WC coatings. Friction coefficient, adhesion strength, vickers hardness and coating surface of 4 groups were measured. Results. 1. For all three coating conditions, friction coefficient was significantly decreased. Especially, ZrN coated surface showed the lowest value. $TiN(0.39{\pm}0.02)$, $ZrN(0.24{\pm}0.01)$, $WC(0.31{\pm}0.03)$. 2. TiN coating showed the highest adhesion strength, however ZrN coating had the lowest value. $TiN(25.3N{\pm}1.6)$, $ZrN(14.8N{\pm}0.6)$, $ WC(18.4N{\pm}0.7)$. 3. Vickers hardness of all three coatings was remarkably increased as compared with that of none coated specimen. TiN coating had the highest Vickers hardness, however WC coating showed the lowest value. $TiN(1865.2{\pm}33.8)$, $ZrN(1814.4{\pm}18.6)$, $WC(1008.5{\pm}35.9)$. 4. The ZrN or WC coated specimen showed a homogeneous and smooth surface, however the rough surface with defects was observed for TiN coating. Conclusions. When TiN, ZrN and WC coating applied to the abutment screw, frictional resistance would be reduced, as a result, the greater preload and prevention of the screw loosening could be expected.

• Korean Journal of Veterinary Research
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• v.38 no.3
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• pp.441-449
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• 1998

This study was carried out to investigate the fine structural changes of rat hepatocytes by repeated treatment of cyclosporin A that has been widely used for immunosuppressive drug in organ transplantation. Sprague-Dawley rats were kept in experimental circumstances for 2 weeks and 50mg/kg B.W of cyclosporin A was injected once a day subcutaneously for 7 days and sacrificed at 1 hour, 1 day, 3 days, 7 days, 14 days, 28 days after the last injection. Fine structural changes were observed by transmission electron microscope (JEM 1200EX II) and the results obtained were as follows. 1. Accumulation of lipid droplets in hepatocytes was prominently increased in 1 hour and 1 day lapse groups, and this finding was slightly reduced in 3 days lapse group and remarkably reduced from 7 days lapse group enough to be recovered completely in 14 days lapse group. 2. Dilatation of rough endoplasmic reticule cisternae, detachment of membrane bound ribosomes, proliferation of smooth endoplasmic reticula were observed in 1 hour and 1 day lapse groups, and these findings were mild in 3 days lapse group and abruptly reduced from 7 days lapse group enough to be recovered completely in 28 days lapse group. 3. Small myelin figures were observed in 3 days lapse group after CsA-treatment. 4. Swelling of mitochondria and destruction of their cristae were observed in 1 hour and 1 day lapse groups, and these findings were recovered from 3 days lapse group. 5. Dilatation of bile canaliculi and remarkable loss of microvilli in the pericanalicular wall were observed in 1 hour lapse group and the most severe change was shown in 1 day lapse group and lasted to 3 days lapse group, and these findings were reduced gradually from 7 days lapse group enough to recovered completely in 28 days lapse group.

• Journal of Science and Technology Studies
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• v.10 no.1
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• pp.73-106
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• 2010

Internet users want to use IP sharing routers for reducing their cost and managing their terminals easy. Network service providers(NSPs) forced their subscribers pay extra charges to use extra terminal like IP router, since 1998 in Korea. The NSPs asserted that IP sharing routers would harm their networks or would impose extra load on their networks, but they were unable to prove their assertion. Users and manufacturing companies insisted on the legitimacy of IP routers, because the IP router is a kind of terminal for end-users, and as such, the right of selection of an IP router belongs to the user. The interest in and beliefs of the relevant social groups about IP router will be deduced through their interpretation. It draws the technological frame of two social groups, NSPs and IP router-manufacturing companies. The rough struggle between two social groups come from their frames. The article shows how society constructs a particular information technology.

• Applied Microscopy
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• v.27 no.2
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• pp.197-215
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• 1997

A morphologic study on the effect of butylated hydroxytoluene (BHT) on experimental hepatocarcinogenesis induced by 3'-methyl-4-dimethyl aminoazobenzene (3'-MeDAB) was investigated. A total of 110 Sprague-Dowley male rats weighting about 200 g each were used for the experiment, and divided into 4 groups; the 3'-MeDAB, BHT, 3'-MeDAB/BHT treated group, and the control group. Four to eight rats of each group were sacrified on the 4th, 8th, 14th and 16th experimental weeks, with continuous pelletized feeding containing 0.09% 3'-MeDAB and 0.5% BHT. The liver was examined by transmission and scanning electron microscopy. The results were as follows; Electron microscopically, the fine structure of the hepatocytes remained consistently abnormal up to 16 weeks after the 3'-MeDAB treatment. There was no significant difference in the groups observed earlier than in the ones observed later. Many subcellular changes were observed : nuclear change, decreased glycogen, mitochondrial abnormalities, disaggregated rough endoplasmic reticulum, marked proliferation of smooth endoplasmic reticulum, dilatation and distortion of bile canaliculi, increased lysosomes, apoptotic bodies, migration of bile ductule cell. In the BHT treated group, the ultrastructural changes of hepatocytes were not significant, except for the lipid droplets and proliferated smooth endoplasmic reticulum among hepatocytes depending on the experimental duration. The various subcellular changes of 3'-MeDAB/BHT treated groups were simillar to those of the 3'-MeDAB treated group, but the degree of changes in the 3'-MeDAB/ BHT treated group decreased compared with those of the 3'-MeDAB treated group. These results suggest that dietary butylated hydroxytoluene has a protective/inhibitory effect on the hepatocarcinogenesis induced by 3'-methyl-4-dimethyl -aminoazobenzene.

• Applied Microscopy
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• v.33 no.2
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• pp.155-168
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• 2003

The purpose of this study was to evaluate the effect the radiation-resistance of chitosan on the mice. A healthy male ICR mice were used for experiment. The SOD and MDA activity was measured from the liver of mice at 48 and 72 hours after the irradiation. The ultrastructural changes of the liver by irradiation was observed at 24, 48 and 72 hours after irradiation. The experimental groups were divided into three groups. Group 1 was the control group which was not treated with chitosanoligosaccharide before or after iradiation. Group 2 was the prefeeding group which chitosanoligosaccharide solution was supplied by feeding ad libitum for 30 days before irradiation. Group 3 was the postfeeding group which chitosanoligosaccharide solution was supplied by feeding after irradiation. In all groups 10 mice were used. The results were as follow: The SOD and MDA activity of the prefeeding group was decreased significantly (P<0.01). Control group - The nuclei were condensed. The mitochondria and rough endoplasmic reticulum (rER) were extended and the ribosome was dropped from the rER. Prefeeding group - The nuclei were rounded. The mitochondria was elongated. And the rER attached ribosomes. Postfeeding group - The nuclei were slightly condensed. The mitochondria and the rER were extended and the ribosome was dropped from the rER. It was concluded that the chitosanoligosaccharide was effective in the radiation-protection. So, chitosan would have the potential as the radiation-protection materials.

• Journal of KIISE:Software and Applications
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• v.33 no.8
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• pp.730-740
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• 2006

In recent years, bullied students and rogue groups in teenagers make many serious social problems. In this paper we propose a novel approach that more objectively analyzes peer relationships among students. As the data for objective analysis, we use communication history records that are collected from various communication tools such as telephones, e-mails, and messengers. We use the simple intuition that communication history records implicitly contain peer relationship information. And, we adopt data mining techniques for the more systematic analysis. The proposed peer relationship analysis consists of the following steps. First, we formally define the notion of degree of familiarity between friends, and present mathematical equations that compute the degree based on communication history records. In the proposed method, we use the intuition that the degree of familiarity from student x to student y becomes higher as x makes the more communications with y. Second, by using the degree of familiarity between students, we find out the students who are potentially bullied. This procedure is based on the assumption that a bullied student may have a very small number of history records from other students to him. Third, we adopt the clustering technique, one of the most representative data mining techniques, to find out meaningful student groups by using the degree of familiarity. To use the clustering technique, we formally define the notion of similarity between friends based on the degree of familiarity, and perform clustering using the notion. Last, to show the practicality of the proposed method, we have implemented the method and interpreted the meaning of the experimental results. Overall, we believe that our research result provides an effective framework that analyzes peer relationships more objectively and more systematically.

• Restorative Dentistry and Endodontics
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• v.23 no.1
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• pp.183-196
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• 1998

The purpose of this study was to determine the effect of bleaching technique on the shear bond strength of esthetic restorative materials to bovine enamel. The bleaching agent was used 35% $H_2O_2$(Hi-Lite, Shofu, U.S.A.). Experimental groups were divided into two divisions as group A and B. Experimental A groups for the effect of number of bleaching were as follows ; Group Al : no bleaching Group A2 : bleaching 1 time ( for 5 minutes ) Group A3 : bleaching 3 times ( each for 5 minutes ) Group A4 : bleaching 6 times ( each for 5 minutes ) Group A5 : bleaching 9 times ( each for 5 minutes ) Experimental B groups for the effect of storage period in artificial saliva were as follows ; Group B1 : not stored in artificial saliva after bleaching Group B2 : stored in artificial saliva for 1 day after bleaching Group B3 : stored in artificial saliva for 1 week after bleaching Group B4 : stored in artificial saliva for 2 weeks after bleaching Group B5 : stored in artificial saliva for 4 weeks after bleaching Composite resin and glass ionomer cement were bonded to all specimens, and the shear bond strength between enamel and r~storative material were measured in Instron Universal Testing Machine(Instron, 4467, U.S.A,), Additionally, the bleached enamel specimens were examed after etching with 37.4% $H_3PO_4$ for 1 min under SEM(S-2300, Hitachi Co., Japan) to observe the effect of bleaching procedure on enamel surface morphology. The result were as follows ; 1. In SEM findings, bleached bovine enamel was found to be superficially rough. 2. In bleached bovine enamel, the effect of acid etching was reduced with the increase of number of bleaching. 3. The mean shear bond strength of composite resin and glass ionomer cement to bleached enamel surface tended to be lower than those to non-bleached enamel surface. 4. With the increase of number of bleaching, the shear bond strength of composite resin and glass ionomer cement to bleached enamel were progressively decreased. 5. Increasing the, storage period in artificial saliva after bleaching, the shear bond strength of composite resin and glass ionomer cement to bleached enamel were progressively increased. 6. The mean shear bond strength of glass ionomer cement to bleached bovine enamel tended to be clearly lower than that of composite resin.