• Journal of Preventive Medicine and Public Health
• /
• v.37 no.2
• /
• pp.157-165
• /
• 2004

Objectives : This study aimed to investigate the toxic effects of chromium (VI) on the placental function and reproduction in rats. For the study, the placental prolactin-growth hormone (PRL-GH) gene expression, placental trophoblast cell differentiation and reproductive data were analyzed. Methods : The pregnancies of F344 Fisher rats were checked by the presence of a copulatory plug or sperm in the vaginal smear, which was defined as day 0 of the pregnancy. Pregnant rats were divided into the three groups. The control group was given tap water (chromium level < 0.001 ppm) and the remaining groups were given 250 or 750 ppm of chromium (VI) [as potassium dichromate], from day 7 to 19 of the pregnancy. Rats were sacrificed at days 11 and 20 of pregnancy. The mRNA levels of PRL-GH and Pit-1a and b isotype genes were analyzed by Northern blot hybridization and reverse transcription-polymerase chain reaction (RT-PCR). The hormonal concentration was analyzed by radioimmunoassay, and the differentiation of placental trophoblast cells were observed by histochemical studies. Reproductive data, such as placental and fetal weights, pregnancy period, and litter size, were surveyed at day 20 of pregnancy and after birth. A statistical analysis was carried out using the SAS program (version 8.1). Results : The mRNA levels of the prolactin-growth hormone (PRL-GH) family of genes were dose dependently reduced by chromium exposure. The mRNA levels of Pit-1a and b isotype genes that induce the expression of the PRL-GH family of genes were also reduced by chromium exposure. The PRL-GH hormonal concentration in the rat placenta, fetus and maternal blood were decreased by chromium exposure. In the middle stage of pregnancy (day 11), a high dose of chromium suppressed the differentiation of spongiotrophoblast cells that secret the PRLGH hormones. In the last stage of pregnancy (day 20), a high dose of chromium induced apoptosis of placental cells. Reproductive data, such as placental and fetal weights, litter size, were reduced, but the pregnancy period was extended in the group exposed to chromium compared with the controls. Conclusion : Chromium (VI) disrupts the ordered functions of the placenta, which leads to reproductive disorders in rats.

• Journal of the Korean Geographical Society
• /
• v.29 no.1
• /
• pp.46-64
• /
• 1994

Among every civilized people salt has been recognized as an essential foodstuff to the human society without which even man's survivor is unthinkable. The cultural-anthropological meaning of salt is estimated highly as well, and in geographical perspective salt itself symbolize regional interrelationship. Playing a decisive role in freeing innermost settlement from isolation, salt aiso made a contribution to expanding human habitats. This study tries to reconstruct historica geography of 18th and 19th century surrounding traditional salt-roasting (chayeom). The Joolpo Inlet area which is located on the mid-western coast in Honem Region is selected for study area. Established on the basis of optimum physical geographical conditions such as topography, climate and vegetation, salt-making of Joolpo Inlet area was run dynamically with the sudden turn of events in the 18-19th century which was chacterized as an age of transition from medieval society to modern one. In this paper the writer attempts to clarify mainly following three points: physical conditions and socio-economic background leading to the initiation and later development of roasting of salt in Joolpo Bay; distribution of saltworks; methods of saltmaking. Main points drawn from these analyses can be summarized as follows: of iron pan and cow-drawn tools rendered labour-saving and output growth. 1, Saltworks of Joolpo Inlet area in the 18-19th century were distributed evenly over Kobu, Puan, Mujang and Heungduck counties among which Kobu's was located in Puanmyon - a sort of exclave. All saltworks belonging to above four counties were clasified as most lucrative ones in Honam Region on government archives. In particular, Gumdang saltwork which belongs to Mujang county is noteworthy in that it was first introduced by one Paekje priest in 6th century and therefore it provides a clue to examine the history of salt-roasting of Joolpo Inlet area. In light of the fact that temple or monastery economy, regardless of East and West, has been closely connected with traditional industry, the case of Gumdang is not unusual. 2. The process of saltmaking follows this order: harrowing of salt field exposed to solar heat; construction of saltern mound with saline earth; acquiring of brine by leaching saline earth; roasting of salt. Salterns (saltworks) are consisted with various salt making facilities such as roasting shed, saltern mound, salt field, salt well) salt pit or brine pit) and seawater reservoir. Among them roasting shed which is constructed chiefly with hundreds of pieces of pine tree as a frame and with straw as roof and wall is customarily considered as an unit of saltwork. And inside it is saltpan made of two kinds of materials, that is iron pan or plaster pan. The area attached to one unit of roasting shed is approximately 1 ha, and that of saltern mound is a tenth of it.

• Journal of the korean academy of Pediatric Dentistry
• /
• v.31 no.3
• /
• pp.421-430
• /
• 2004

The purpose of this study was to measure and compare the amount of unreacted TEGDMA from pit and fissure sealants cured with three different light sources; conventional halogen light curing unit, plasma arc light curing unit and argon laser. The specimens were eluted in distilled water for different time intervals. The time-related release of TEGDMA were analyzed by reverse-phase high performance liquid chromatography(HPLC). The result of present study can be summarized as follows: 1. The time-related release of TEGDMA decreased with increasing curing time in conventional halogen light, however, that not statistically significant difference(p>0.05). 2. The elution from the specimens cured for 6 and 9 seconds with plasma arc light was similar results corresponding with the time-related TEGBMA release, and was significantly lower than that cured for 3 seconds(p<0.05). 3. The elution of TEGDMA from the specimens cured with argon laser was significantly higher than that cured with halogen and plasma arc light(p<0.05). 4. The elution of TEGDMA from under recommended time of three different light sources were showed to be no statistically significant difference(p>0.05). 5. In time-related release of TEGDMA from recommended time of each light sources, the results correspond to 40 seconds of halogen light and 6 seconds of plasma arc light were similar(p>0.05). 6. The elution of TEGDMA, from over recommended time of three different light sources were showed to be no statistically significant difference(p>0.05). In this study, I suggest that curing time of plasma arc light is 6 and/or 9 seconds in the field of clinical pediatric dentistry claiming its effectiveness in optimal polymerization and reduced chair time.

• Journal of Dental Rehabilitation and Applied Science
• /
• v.26 no.2
• /
• pp.179-195
• /
• 2010

In the internal connection system, the loading transfer mechanism within the inner surface of the implant and also the stress distribution occuring to the mandible can be changed according to the abutment form. Therefore it is thought to be imperative to study the difference of the stress distribution occuring at the mandible according to the abutment form. The purpose of this study was to assess the loading distributing characteristics of three different abutments for GS II$^{(R)}$ implant fixture(Osstem, Korea) under vertical and inclined loading using finite element analysis. Three finite element models were designed according to three abutments; 2-piece Transfer$^{TM}$ abutment made of pure titanium(GST), 2-piece GoldCast$^{TM}$ abutment made of gold alloy(GSG), 3-piece Convertible$^{TM}$ abutment with external connection(GSC). This study simulated loads of 100N in a vertical direction on the central pit(load 1), on the buccal cusp tip(load 2) and $30^{\circ}$ inward inclined direction on the central pit(load 3), and on the buccal cusp tip(load 4). The following results were obtained. 1. Without regard to the loading condition, greater stress was concentrated at the cortical bone contacting the upper part of the implant fixture and lower stress was taken at the cancellous bone. 2. When off-axis loading was applied, high stress concentration observed in cervical area. 3. GSG showed even stress distribution in crown, abutment and fixture. GST showed high stress concentration in fixture and abutment screw. GSC showed high stress concentration in fixture and abutment. 4. Maximum von Mises stress in the surrounding bone had no difference among three abutment type. In GS II$^{(R)}$ conical implant system, different stress distribution pattern was showed according to the abutment type and the stress-induced pattern at the supporting bone according to the abutment type had no difference among them.

• Korean Journal of Heritage: History & Science
• /
• v.49 no.2
• /
• pp.142-157
• /
• 2016

In 2008, the oldest wooden tablets, in the Baekje area, were uncovered from the Bogam-ri site in Naju. This paper defines wooden tablets to as objects with inking inscriptions. Of 65 wooden tablets contained in the excavation report of this site, this paper examines the meanings of 13 tablets with inscriptions written in ink by comparing them with other tablets found in the Baekje area. All tablets were unearthed from Pit Feature No. 1, a large-scale feature, at this site. Vertical stratigraphy of the feature is divided into 43 layers; but it seems that it does not reflect the chronological order, since unearthed artefacts, including wooden tablets, pottery, and roof tiles, turned out to be produced at the same age. Wooden tablets were not found in other features, and intentionally buried in this feature. Typological characteristics of wooden tablets indicate that the pit was the secondary refuse place. The inscription of the wooden tablets labeled 'gyeongonyeon(庚午年)' and the radiocarbon dates of them indicate that these tablets were created in the early 7th century AD, centered in 610 AD. On the basis of contents and typological characteristics, these are classified into six documents, six tags, and one tablet for other purpose. Total 89 pieces of wooden tablets have been unearthed in the Baekje area. Except tablets found in Naju and Geumsan, all have been collected in palaces, royal gardens, and temples inside and outside of the Sabi Capital. The significant wooden tablets of Baekje, which can be compared with tablets from Bogam-ri, were unearthed at from the Gwanbuk-ri site, the Gungnamji site, and the Ssangbuk-ri 280-5 site. Comparative studies on wooden tablets have revealed that the place name during the Wungjin Commandery Period, the status marking method standardized in the order of place name, official rank and person's name, the fact that Baekje operated the system of prefecture(郡), and Bogam-ri was one of the places where prefecture was established, and the evidence of family register system. Wooden tablets at Bogam-ri record the documented date (610 AD), the documented place (Duhilseong where the prefecture established), and the writers (advisors and staffs of the prefecture). The recorded contents of them are invaluable data showing the local administrative system of Baekje, such as the status marking method, the means of description, the family-register system, and the land surveying system.

• The Journal of Korean Academy of Prosthodontics
• /
• v.37 no.2
• /
• pp.242-255
• /
• 1999

The purpose of this study was to estimate the morphology and the size of permanent mandibular molar in Korean Adult. The 100 dental college students with a normal dentition and without any dental prosthesis and severe caries were selected for this study The subjects were taken impression to make study model. On the study model, the 5 dentists measured those sizes and estimated morphological structures with a calipers, a Boley gauge and a protractor. The results were as follows; 1. The clinical crown height, width, thickness and the other anatomical structures had symmetrical relationship between the left and right mandibular molar. 2. In the clinical crown height aspect, the buccal crown heights always were higher than the lingual crown height. The heights of the each surface, the buccal or lingual surface, were gradually decreased from the 1st molar to the 2nd molar and the difference on the buccal surface was higher than that on the lingual surface. 3. In the clinical crown width aspect, the mesiodistal measurement of the mandibular 1st molar was higher than that of the mandibular 2st molar. 4. In the clinical crown thickness aspect, the mesial buccolingual measurement was highest on the mandibular 1st molar and the distal buccolingual distance was lowest on the mandibular 2nd molar. This distal thickness of the mandibular molar always was higher than that of the mesial half. 5. The well-developed mesiobuccal groove of the 1st molar was observed more often than that of the 2nd molar. The buccal pit was also observed more frequently at the 1st molar, but the frequency(35%) was not high. 6. The occlusal type according to the number of cusp was almost 5-cusp(98%) in the 1st molar and was also 5-cusp(63%) in the 2nd molar. The frequency of the 6th cusp was 31% in the 1st molar and was 22% in the 2nd molar. The frequency of the 7th cusp was below 2of in the both teeth. 7. In the buccolingual intercuspal distance aspect of the mesial and distal half, the intercuspal distance of distal half was higher than that of the mesial half on the 1st and 2nd molar, but the difference on the 1st molar was higher than that on the 2nd molar. 8. The difference between the widths of the buccal and lingual half was 1.5mm in the 1st molar and 0.8mm in the 2nd molar. Therefore the lingual convergency of the occlusal surface was more higher in the 1st molar. 9. On the mandibular 1st and 2nd molar, the distobuccal external angle was more acute than the mesiobuccal external angle. But the mesiobuccal internal angle was more acute than the distobuccal internal angle. 10. When the mandibular molar was a 5-cusp type, the development of the distal cusp on the 1st molar was better than that on the 2nd molar. The difference between the cusps was around 0.4mm.

• The Journal of the Korea Contents Association
• /
• v.10 no.7
• /
• pp.285-296
• /
• 2010

This study was implemented among 100 students of C College of Public Health who have healthy permanent dentition in order to measure the morphology and sizes of clinical crowns of permanent maxillary molars. The following are conclusions of this study. 1. The cusp height, crown width, crown thickness of clinical crowns appeared to be bilaterally symmetrical. 2. The strong development of the buccal groove showed to be superior in the right first molar. The appearance rate of the buccal pit was high in the right first molar also. 3. The type 4th cusp appeared as 100% in the left and right first molars, and 78%, 75% in the left and right second molars respectively. 4. The distal lingual cusp(DLC) size were bilaterally symmetrical in the type 4th cusp. 5. As for the distance between two cusp tips, it was large between mesial cusp tips in all of the first and second molars at both sides. 6. Development of the Carabelli's cusp was high in both the left and right first molars. 7. The appearance rate of the oblique ridge was 87.0% in the right first molar, 73.0% in the right second molar, 88.0% in the left first molar, and 73.0% in the left second molar. This is considered to be caused by people who have mild dental crown caries in their first molars. 8. The appearance rate of the mesial marginal ridge tubercle(DMRT) was high in both of the left and right first molars. That of the distal tubercle was 16.0% in the right first molar, 26.0% in the right second molar, 14.0% in the left first molar, and 21% in the left second molar.

• The korean journal of orthodontics
• /
• v.43 no.6
• /
• pp.294-301
• /
• 2013

Objective: To determine the interleukin (IL)-6 levels in gingival crevicular fluid (GCF) of patients with severe root resorption after orthodontic treatment and investigate the effects of different static compressive forces (CFs) on IL-6 production by human periodontal ligament (hPDL) cells and the influence of IL-6 on osteoclastic activation from human osteoclastic precursor (hOCP) cells in vitro. Methods: IL-6 levels in GCF samples collected from 20 patients (15 and 5 subjects without and with radiographic evidence of severe root resorption, respectively) who had undergone orthodontic treatment were measured by ELISA. The levels of IL-6 mRNA in hPDL cells and IL-6 protein in conditioned medium after the application of different uniform CFs (0, 1.0, 2.0, or 4.0 $g/cm^2$ for up to 72 h) were measured by real-time PCR and ELISA, respectively. Finally, the influence of IL-6 on mature osteoclasts was investigated by using hOCP cells on dentin slices in a pit-formation assay. Results: Clinically, the IL-6 levels were significantly higher in the resorption group than in the control group. In vitro, IL-6 mRNA expression significantly increased with increasing CF. IL-6 protein secretion also increased in a time- and magnitude-dependent manner. Resorbed areas on dentin slices were significantly greater in the recombinant human IL-6-treated group and group cultured in hPDL cell-conditioned medium with CF application (4.0 $g/cm^2$) than in the group cultured in hPDL cell-conditioned medium without CF application. Conclusions: IL-6 may play an important role in inducing or facilitating orthodontically induced inflammatory root resorption.

• Korean Journal of Agricultural Science
• /
• v.43 no.5
• /
• pp.777-787
• /
• 2016

In the present study, we aimed to investigate the effect of dietary supplementation of palm kernel meal (PKM), as a fermentable carbohydrate source, on the growth performance, meat quality, concentration of odorous compound, and changes in bacterial community in swine manure. Swine (average initial body weight of $51.36{\pm}1.02kg$) were fed diet which included three levels of PKM (0, 2 and 4%), and their manure samples were collected from the slurry pit. Growth performance and meat quality were not affected by PKM treatments (p > 0.05). Levels of phenols and indoles were decreased in the 2 and 4% PKM treatments compared to 0% PKM (control; p < 0.05). Especially, compared to the control, the 2% PKM group showed decreased levels of phenols by 35% and indoles by 34%. Among the dominant bacterial genera, the main change in relative abundance occurred in those belonging to the Firmicutes phylum in PKM treatments. Terrisporobacter and Clostridium were decreased in the PKM groups compared to the control. However, the relative abundance of Intestinibacter, AM406061_g, Coprococcus_g2, Phascolarcotobacterium, EF401875_g, Lactobacillus, and Streptococcus were increased in the PKM group compared to control. Taken together, administration of PKM had a beneficial effect on reducing production of odorous compounds in swine manure, possibly by modulating the communities of predominantly carbohydrate-utilizing bacteria in the large intestine of swine.

• Journal of the Korean Society of School Health
• /
• v.17 no.2
• /
• pp.11-22
• /
• 2004

Purpose: The aim of this study was to evaluate the effects of oral health care programs in 3 school-based oral health care center among primary schoolchildren. Methods: School-based oral health care programs included fluoride mouth rinsing, pit and fissure sealing for permanent premolars and molars, fluoride gel application and chewing of xylitol candy. All of the programs were carried out by one dental hygienist among 'D' primary schoolchildren in Daegu city under the supervision of a dentist. Baseline dental examinations were completed and preventive care was implemented for 544 children during one year. All of the children visited a school-based oral health care center every three months for a regular check-up. The final oral examination was conducted from March 15 to April 1, 2004. The data analysis data was made on the basis of SAS 8.01. Mean differences between 2003 and 2004 data were compared by paired t-test. Corresponding p-values were considered significant at values less than 0.05. Results: The DMF rate and DFT index were reduced to 8.0% and 8.4% during one year respectively, but there were no statistically significant differences. The DMF rate was significantly reduced (16.3%) after a one year program of school-based oral health care practice. The DMFT(Decay Missing Filling Tooth) index was also reduced compared to 2003 throughout the entire grade. Conclusion: School-based oral health care programs can reduce the prevalence of dental caries prevalence among schoolchildren during one year. This program also improved the oral health capacity of schoolchildren. It is recommend that the school-based oral health care program should be extended to every primary school in Korea.