• The Journal of Korean Academy of Prosthodontics
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• v.47 no.1
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• pp.21-28
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• 2009

Purpose: The purpose of this study was to compare the wear characteristics of human enamel opposing 2 heat-pressed ceramics (e.max Press and Empress Esthetic), conventional feldspathic porcelain (Ceramco 3) and type III gold alloy. Material and methods: Intact cusps of extracted premolars were used for enamel specimens. Five disk samples were made for each of two heat-pressed ceramics groups, conventional feldspathic porcelain group and type III gold alloy group. Wear tests were conducted in distilled water using a pin-on-disk tribometer. The amount of enamel wear was determined by weighing the enamel specimens before and after wear tests, and the weight was converted to volumes by average density. The wear tracks were analyzed by scanning electron microscopy and surface profilometer to elucidate the wear characteristics. Results: 1. Ceramco 3 led to the greatest amount of enamel wear followed by Empress Esthetic, e.max Press and type III gold alloy. However, there was no significant difference between Ceramco 3 and Empress Esthetic (P>.05), and there were also no significant differences among Empress Esthetic, e.max Press and type III gold alloy (P>.05). 2. The average surface roughness of e.max Press after wear test was smallest followed by Empress Esthetic and Ceramco 3, but there was no significant difference between Empress Esthetic and Ceramco 3 (P>.05). 3. There were no significant differences among the depth of wear tracks of all the groups (P>.05). The group that showed the largest width of wear track was Ceramco 3 followed by Empress Esthetic, e.max Press and type III gold alloy. However, there was no significant difference between e.max Press and Empress Esthetic (P>.05), and there was also no significant difference between Empress Esthetic and Ceramco 3 (P>.05). Conclusion: Within the limits of this study, heat-pressed ceramics were not more abrasive than conventional feldspathic porcelain.

• The Journal of Korean Academy of Prosthodontics
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• v.58 no.1
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• pp.14-22
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• 2020

Purpose: The aim of this study is to evaluate the effectiveness of MnO₂-diatom microbubbler (DM) on the surface of prosthetic materials as a mouthwash by comparing the biofilm removal effect with those previously used as a mouthwash in dental clinic. Materials and methods: DM was fabricated by doping manganese dioxide nanosheets to the diatom cylinder surface. Scanning electron microscopy (SEM) was used to observe the morphology of DM and to analyze the composition of doped MnO₂. Stereomicroscope was used to observe the reaction of DM in 3% hydrogen peroxide. Non-precious metal alloys, zirconia and resin specimens were prepared to evaluate the effect of biofilm removal on the surface of prosthetic materials. And then Streptococcus mutans and Porphyromonas gingivalis biofilms were formed on the specimens. When 3% hydrogen peroxide solution and DM were treated on the biofilms, the decontamination effect was compared with chlorhexidine gluconate and 3% hydrogen peroxide solution by crystal violet staining. Results: Manganese dioxide was found on the surface of the diatom cylinder, and it was found to produce bubble of oxygen gas when added to 3% hydrogen peroxide. For all materials used in the experiments, biofilms of the DM-treated groups got effectively removed compared to the groups used with chlorhexidine gluconate or 3% hydrogen peroxide alone. Conclusion: MnO₂-diatom microbubbler can remove bacterial membranes on the surface of prosthetic materials more effectively than conventional mouthwashes.

• Korean Journal of Poultry Science
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• v.35 no.1
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• pp.85-99
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• 2008

Avian reovirus (ARV) is a causative agent of viral arthritis/tenosynovitis, and malabsorption syndrome in broiler. The characteristics of malabsorption syndrome caused by ARV are diarrhea, poor feed conversion and stunting. Therefore, ARV infection has been recognized as one of the most important disease in the poultry industry because of economical losses. However, few study of ARV infection in broiler industry has been conducted in Korea. To evaluate the presence of ARV infection in broiler farms, epidemiological survey such as serological test and virus isolation has been conducted. For the serological survey using ELISA method, we selected five broiler farms which were located at different area and had a history of growth retardation, lameness, diarrhea and poor feathering. From these farms serum samples were collected at 1 day, 14 days and market age. All these farms had no history of vaccination against ARV. In addition to serological survey, we tried to isolate ARV from birds of designated farms at market age and collected feces and tissue samples such as cecal tonsil, intestine and liver. We were identified ARV by RT-PCR and transmissible electron microscopy. The samples were inoculated into 9-day-old embryonated eggs via the chorioallantoic membrane to observe the pock formation. For the pathogenicity test of ARV isolates, we inoculated with the isolates to the right footpad of 3-week-old SPF chicks and observed clinical signs and pathological changes for 14 days after challenge. Most broilers sampled for serological survey have maternal antibodies which were widely distributed at 1 day and decreased by 14 days. However, at the market age several broiler farms showed fairly high antibody titer against ARV. This increase of antibody titer at market age means the possible infection of ARV during the grow-out period. Among total 15 samples for the isolation of ARV. 2 samples were positive by RT-PCR and finally identified as a ARV. We inoculated these isolates in the SPF birds and observed that the antibody titer was increased from 7 days after challenge. However, we did not find any clinical signs both control and challenge groups. Based on the above results, it is clear that the ARV infection has been circulated in the broiler industry and caused significant economic losses. Further study is needed to evaluate the virulence of the isolates in the digestive system of broiler and the molecular characteristics of isolates.

• Journal of Yeungnam Medical Science
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• v.10 no.2
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• pp.313-337
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• 1993

The aim of this study was to clarify the role of Kupffer cells in the mechanism of endotoxin-induced liver injury. The study on fine structure of Kupffer cells was performed after the injection of endotoxin. The endotoxin(Escherichia coli lipopolysaccharide 026 : B6. 1.5mg/100 g of body weight) was intraperitoneally injected in Sprague-Dewley rats. Animals were sacrificed at 1/4, 1/2, 1, 2, 4, 8, 16, 24, 72 and 120 hours after the injection of endotoxin. Livers were extirpated and processed to be examined by light and electron microscopy. The results obtained were summerized as follows: Early changes observed in liver after endotoxin injection included the increased number and hypertrophy of Kupffer cells, infiltration of neutrophils and presence of fibrin thrombi within the sinusoids. The continuous increase of the Kupffer cells in number with hypertrophy, congestion and infiltration of inflammatory cells within the sinusoids were observed. Hepatocytes showed fatty change and occasional necrosis. At 72 hours the congestion decreased. At 120 hours the number of Kupffer cells was increased, but the morphology of Kupffer cells became similar to that of the control group. The numbers and sizes of primary and secondary lysosomes and amount of euchromatin of Kupffer cells increased. Swellings and increase in number of mitochondria, Golgi complex, smooth endoplasmic reticulum, rough endoplasmic reticulum were evident. Microthrombi were present within the sinusoids. The swelling of rough endoplasmic reticulum and mitochondria, decrease of glycogen particles, fatty change, hypoxic vacuoles, pyknotic nuclei and occasional necrosis were observed in hepatocytes. At 72 hours the number of secondary lysosomes in Kupffer cells decreased. At 120 hours the morphology of Kupffer cells became similar to that of the control group. According to these results, it was postulated that the endotoxin was initially taken up by pinocytosis into Kupffer cells and degraded in secondary lysosomes of activated Kupffer cells. Kupffer cells may play an important role in the defense mechanism of liver during endotoxemia. The dysfunction of Kupffer cells and ischemia by sinusoidal microthrombi may cause liver injury.

• Economic and Environmental Geology
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• v.34 no.1
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• pp.13-23
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• 2001

Bentonite layers are intercalated within the basal conglomerates in the Tertiary sedimentary basins of Kampo, Janggi and Pohang, southeastern Korea. Eighteen samples of the bentonites went through X-ray diffraction, scanning electron microscopy, heavy mineral analyses, chemical analyses and oxygen, hydrogen stable isotope analyses to define the mineralogical characters of the bentonites. Heavy minerals such as zircons, apatites, amphiboles and biotites separated from bentonites show clean and euhedral surfaces, which are the characteristic features of volcanic origin. But biotites from the Chunbook Conglomerate are found as altered and heavily broken flakes which implies longer transportation of these bentonites. $TiO_{2}/Al_{2}O_{3} ratios of <2 $\mu$m particle fractions (the Chunbook Conglomerate 0.031; Janggi 0.029; Kampo 0.025) suggest that those are originated from volcanic tuffs. That is, the higher the value is, the more mafic in chemical compositions of the original tuffs. Authigenic montmorillonite and zeolite minerals were observed by SEM, which indicates diagenesis origin of bentonites. But the samples from the Chunbook Conglomerate showed only chaotically packed clay flakes in the matrix of sands or conglomerates, which implies detrital influence, not authigenic origin. The structural formulae of montmorillonite from these basins reflects their environment of formation. Fe (Ⅵ) can show the redox condition of its past environment and much lower $Fe^{2+}(Ⅵ)/Fe^{3+}(Ⅵ)$ ratios in montmorillonite of the Chunbook Conglomerate imply the greater oxidizing influence. Calculated burial depths from oxygen stable isotope data of the samples from the Chunbook Conglomerate generally fall to the range of 929~963 m whereas the real burial depth of this area is only 530~580 m. This could be explained as the bentonites of the Chunbook conglomerate had not been formed in situ. Discriminant analyses with the data from chemical analyses and structural formulae of montmorillonites show that bentonites from three different basins could definitely be distinguished with each other. This result arises from the different chemical compositions of original volcanic ashes and the difference of sedimentary environments.

• Horticultural Science & Technology
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• v.32 no.4
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• pp.448-453
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• 2014

Influences of shading and irrigation in summer hot pepper cultivation on the plant growth and mesophyll tissue were investigated. Hot pepper plants were exposed to three shade levels (0, $30{\pm}5$ and $80{\pm}5%$) and irrigated or non-irrigated in greenhouse condition. Plant height and leaf area were highest in 30% shading and stem diameter and fresh and dry weights were highest in no shading. Plant growth was better in rain shelters with irrigation than in those without irrigation. The numbers of hot pepper fruits in the beginning of harvest were 49 in rain shelters without irrigation and shading, 22 in those with irrigation and without shading, 5 in those without irrigation with 30% shading, and 1 in those with irrigation and 30% shading. However, 80% shading showed lowest flower number and flower abscission, resulting in no fruit set, regardless of irritation. This is because carbohydrate translocation from leaves to reproductive organs may be not enough for developing fruits due to the lack of sunlight. The yield of hot pepper tended to be higher in rain shelter with irrigation than in those without irrigation. In optical microscopy observation, the thickness and development of mesophyll tissues decreased as increasing the degree of shading but no effect of irrigation on mesophyll tissues was observed. When stomata were observed with scanning electron microscope (SEM), the shape of stomata was normal but tissues surrounding stomata were slightly wrinkled in plants grown under 30% shading. The large number of abnormal stomata and wrinkled leaves was observed among plants grown in rain shelters with 80% shading. In plants grown in rain shelters without irrigation, tissues surrounding stomata were wrinkled and 10-20% decrease in the number of stomata was observed. Therefore, in hot pepper cultivation in summer with high temperature, shading was not effective for fruit yield and mesophyll tissue development; if shading is unavoidable, high degree of shading is not advisable. Further studies are needed for appropriate cultivar selection and environment-control techniques in hot pepper cultivation in summer with high temperature.

• Applied Chemistry for Engineering
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• v.30 no.6
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• pp.749-756
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• 2019

Na-X and Na-A zeolites that give high adsorption capacity for heavy metals in an aqueous system were synthesized from the coal fly ash obtained from a thermoelectric power plant using a fusion method. The characteristics and Cu(II) adsorption capacity of the synthetic zeolites were also compared to those of using a commercial zeolite. For the selection of optimum conditions of zeolite synthesis, the effects of major parameters in the fusion method such as a dosage ratio of NaOH, aging time, hydrothermal reaction time, and also the dosage ratio of NaAlO₂ (Na-A) on the characteristics and Cu(II) adsorption capacity of the synthetic zeolites were studied. For the analysis of characteristics of the synthetic zeolites, X-ray diffraction (XRD), cation exchange capacity (CEC), Brunaue-Emmett-Teller (BET) and scanning electron microscopy (SEM) were used. The optimum conditions for the synthesis of zeolites with a high adsorption capacity for cationic heavy metals including Cu(II) were the aging time of 6 h, hydrothermal reaction time of 6 h and NaOH and NaAlO₂ dosage ratio of 1.5 and 0.5 (Na-A), respectively. According to the Langmuir isotherm test, maximum Cu(II) adsorption capacities of the synthetic and commercial Na-X and Na-A zeolites were found to be 90.1, 105.26, 102.05, and 109.89 mg/g, respectively. This indicates that the adsorption capacity of synthetic zeolites was comparable to commercial ones. The results of this study also suggest that the coal fly ash can be potentially used as a raw material for the zeolite synthesis.

• Journal of Chest Surgery
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• v.34 no.9
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• pp.653-661
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• 2001

Background: Retrograde cerebral perfusion(RCP) is one of the methods used for brain protection during aortic arch surgery. The author previously published the data, however, for the safety of it, there still remains many controversies. The author performed RCP and checked various parameters to clarify the possibility of early detection of cerebral injury. Material and Method: The author used pigs(Landrace species) weighing 25 to 30kg and performed RCP for 120 minutes. After weaning of cardiopulmonary bypass, we observed pigs for another 120 minutes. Rectal temperature, jugular venous oxygen saturation, central venous pressure were continuously monitored, and the hemodynamic values, histological changes, and serum levels of neuron-specific enolose(NSE) and S100$\beta$ protein were checked. Central venous pressure during RCP was maintained in the range of 20 to 25 mmHg. Result: Flow rates(ml/min) during RCP were 224.3$\pm$87.5(20min), 227.1$\pm$111.0(40min), 221.4$\pm$119.5(60min), 230.0$\pm$136.5(80min), 234.3$\pm$146.1(100min), and 184.3$\pm$50.5(120min). Serum levels of NSE did not increase after retrograde cerebral perfusion. Serum levels of S100$\beta$ protein(ng/ml) were 0.12$\pm$0.07(induction of anesthesia), 0.12$\pm$0.07(soon after CPB), 0.19$\pm$0.12(20min after CPB), 0.25$\pm$0.06(RCP 20min), 0.29$\pm$0.08(RCP 40min), 0.41$\pm$0.05(60min), 0.49$\pm$0.03(RCP 80min), 0.51$\pm$0.10(RCP 100min), 0.46$\pm$0.11(RCP 120min), 0.52$\pm$0.15(CPBoff 60min), 0.62$\pm$0.15(60min after rewarming), 0.76$\pm$0.17(CPBoff 30min), 0.81$\pm$0.20(CPBoff 60min), 0.84$\pm$0.23(CPBoff 90min) and 0.94$\pm$0.33(CPBoff 120min). The levels of S100$\beta$ after RCP were significantly higher than thosebefore RCP(p<0.05). The author could observe the mitochondrial swellings using transmission electron microscopy in neocortex, basal ganglia and hippocampus(CA1 region). Conclusion: The author observed the increase of serum S100$\beta$ after 120 minutes of RCP. The correlation between its level and brain injury is still unclear. The results should be reevaluated with longterm survival model also considering the confounding factors like cardiopulmonary bypass.

• Journal of Chest Surgery
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• v.33 no.6
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• pp.445-468
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• 2000

Background: Retrograde cerebral perfusion(RCP) is currently used for brain protection during aorta surgery, however, for the safety of it, various data published so far are insufficient. We performed RCP using pig and investiaged various parameters of cerebral metabolism and brain injury after RCP under deep hypothermia. Material and Method: We used two experimental groups: in group I(7 pigs, 20 kg), we performed RCP for 120 minutes and in group II (5 pigs, 20 kg), we did it for 90 minutes. Nasopharyngeal temperature, jugular venous oxygen saturation, electroencephalogram were continuously monitored, and we checked the parameters of cerebral metabolism, histological changes and serum levels of neuron-specific enolose(NSE) and lactic dehydrogenase(LDH). Central venous pressure during RCP was mainained in the range of 25 to 30 mmHg. Result: Perfusion flow rates(ml/min) during RCP were 130$\pm$57.7(30 minutes), 108.6$\pm$55.2(60 minutes), 107.1$\pm$58.8(90 minutes), 98.6$\pm$58.7(120 minutes) in group I and 72$\pm$11.0(30 minutes), 72$\pm$11.0(60 minutes), 74$\pm$11.4(90 minutes) in group II. The ratios of drain flow to perfusion flow were 0.18(30 minutes), 0.19(60 minutes), 0.17(90 minutes), 0.16(120 minutes) in group I and 0.21, 0.20, 0.17 in group II. Oxygen consumptions(ml/min) during RCP were 1.80$\pm$1.37(30 minutes), 1.72$\pm$1.23(60 minutes), 1.38$\pm$0.82(90 minutes), 1.18$\pm$0.67(120 minutes) in group I and 1.56$\pm$0.28(30 minutes), 1.25$\pm$0.28(60 minutes), 1.13$\pm$0.26(90 minutes). We could observe an decreasing tendency of oxygen consumption after 90 minutes of RCP in group I. Cerebrovascular resistance(dynes.sec.cm-5) during RCP in group I incrased from 71370.9$\pm$369145.5 to 83920.9$\pm$49949.0 after the time frame of 90 minutes(p<0.05). Lactate(mg/min) appeared after 30 minutes of RCP and the levels were 0.15$\pm$0.07(30 minutes), 0.18$\pm$0.10(60 minutes), 0.19$\pm$0.19(90 minutes), 0.18$\pm$0.10(120 minutes) in group I and 0.13$\pm$0.09(30 minutes), 0.19$\pm$0.03(60 minutes), 0.29$\pm$0.11(90 minutes) in group II. Glucose utilization, exudation of carbon dioxide, differences of cerebral tissue acidosis between perfusion blood and drain blood were maintained constantly during RCP. Oxygen saturation levels(%) in drain blood during RCP were 22.9$\pm$4.4(30 minutes), 19.2$\pm$4.5(60 minutes), 17.7$\pm$2.8(90 minutes), 14.9$\pm$2.8(120 minutes) in group I and 21.3$\pm$8.6(30 minutes), 20.8$\pm$17.6(60 minutes), 21.1$\pm$12.1(90 minutes) in group II. There were no significant changes in cerebral metabolic parameters between two groups. Differences in serum levels of NSE and LDH between perfusion blood and drain blood during RCP showed no statistical significance. Serum levels of NSE and LDH after resuming of cardipulmonary bypass decreased to the level before RCP. Brain water contents were 0.73$\pm$0.03 in group I and 0.69$\pm$0.06 in group II and were higher than those of the controls(p<0.05). The light microscopic findings of cerebral neocortex, basal ganglia, hippocampus(CA1 region) and cerebellum showed no evidence of cerebral injury in two groups and there were no different electron microscopy in both groups(neocortex, basal ganglia and hippocampus), but they were thought to be reversible findings. Conclusion: Although we did not proceed this study after survival of pigs, we could perform the RCP successfully for 120 minutes with minimal cerebral metabolism and no evidence of irreversible brain damage. The results of NSE and LDH during and after RCP should be reevaluated with survival data.

• Journal of Chest Surgery
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• v.35 no.5
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• pp.343-349
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• 2002

background: In an attempt to investigate the role of oxidants in the activation of phospholipase $A_2$(PLA$_2$) and endogenous oxidative stress in the lung. acute inflammatory lung injury was induced by the instillation of hydrogen peroxide into the trachea of Sprague-Dawley rats. Material and Method: To prove the hypothesis thats released oxidants from neutrophils activate the PLA$_2$ retrogradely, activities of PLA$_2$ and lysoplatelet activating factor acetyltransferase(lysoPAF AT) were assayed i hours after instillation of hydrogen peroxide. In addition, to confirm the impairing effects of the activation of PLA$_2$ associated with endogenous oxidative stress, lung weight/body weight ratio(L$\times$10$^{-3}$ B), protein contents(mg/two lungs) in bronchoalveolar lavage(BAL) were measured. As neutrophilic respiratory burst has been known to play a pivotal role in the genesis of endogenous oxidative stress associated with acute inflammatory lung injury, BAL neutrophils counts and level of lung myelperoxidase(MPO) were measured after hydorgen peroxide insult. Morphological and histochemical studies were also performed to identify the effect of the endogenous oxidative stress. Result: Five hours after hydrogen peroxide instillation, lungs showed marked infiltration of neutrophils and increased weight. Protein contents in BAL increased significantly compared to those of normal rats. PLA$_2$ activity was enhanced in the hydrogen peroxide instilled group. Interestingly, the accelerated production of platelet activating factor(PAF) was confirmed by the increased activity of lysoPAF AT in the $H_2O$$_2$ employed lung. Morphologically, light microscopic findings of lungs after instillation of hydrogen peroxide showed atelectasis and infiltration of inflammatory cells, which was thought to be caused by lipid mediators produced by PLA$_2$ activation. In cerium chloride cytochemical electron microscopy, dense deposits of cerrous perhydroxide were identified. In contrast, no deposit of cerrous perhydroxide was found in the normal lung.