• Title/Summary/Keyword: 평활도

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EFFECT OF VARIOUS MECHANICAL TREATMENTS OF HYDROXYAPATITE-COATED IMPLANT SURFACES (Hydroxyapatite 피막 처리된 임프란트에 대한 여러가지 기계적 표면처리방법이 임프란트 표면조도 및 성상에 미치는 영향)

  • Yang, Kyung-Ran;Jung, Oh-Chul;Lee, Jae-Mok;Suh, Jo-Young
    • Journal of Periodontal and Implant Science
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    • v.24 no.1
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    • pp.131-143
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    • 1994
  • For maintenance of exposed implant in healthy state, it is necessary to treat the surface of implant fixture and provide the surface adjustable to surrounding tissues. Variable techniques have been introduced such as citric acid and air-abrasive system to treat the failed implant. Although when the rough surface of HA coated implant was exposed to oral environment, the surface treatment method with citric acid or air-abrasive system is effective for removal of bacterial endotoxin, it is unsuccessful to prevent plaque deposition due to difficulty in removal of rough surface of HA coated implant. Thus, in this study the method that removes bacterial endotoxin and makes smooch surface without alteration of surface characteristics was studied. HA coated disc manufactured by IMZ Co. Was treated with high speed diamond bur, low speed diamond bur, stone bur, rubber point, jetpolisher. And then its surface state was examined with profilometer and SEM to evaluate the surface smoothness, and its surface component was analyzed with EDX to evaluate wheter the surface characteristics were altered or not. As a result, following results were obtained. When the surface roughness of each implant disc was measured by profilometer, the group I showed a $R_{max}\;2.11{\mu}m$ and the group II, III, IV, V showed a $R_{max2}\;4.17{\mu}m$, $7.28{\mu}m$, $8.61{\mu}m$ and $39.44{\mu}m$ respectively. That is, surface smoothness was highest in the group I and it has been gradually decreased in the group II, III, IV and V. Under the SEM examination, the group I showed relatively smooth surface and the group II showed slightly rougher surface than the group I due to partially remaining HA particles while most HA particle was removed. The group III and IV showed rough topography due to HA particles that was not grinded, and HA coated surface in group V showed very irregular surface with deep groove and prominence. In cross-sectional view, the group I showed uniform surface, and the group III, IV showed rough surface due to remaining HA particles but the thickness of HA coating was remarkably reduced. The group II has similar pattern in group I, and the group V showed about $40{\mu}m$ thickness although it was not constant. By analysis of surface component with EDX, the group II in which the grinding was effective showed a small quantity of calcium and phosphorous and the group III, IV, in which the grinding was incomplete showed calcium and phosphorus peak. In all experimental group, no other than titanium, aluminum, calcium, phosphorus was observed.

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Influence of Ginseng Saponins on the Isolated Aortic Contractile Response of the Spontaneously Hypertensive Rat

  • Lim, Dong-Yoon;Cha, Dong-Seok
    • Journal of Ginseng Research
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    • v.26 no.4
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    • pp.178-186
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    • 2002
  • The present study was attempted to investigate the effects of total ginseng saponin (G75), panaxadiol-type (PDS) and panaxatriol-type saponin (PTS) on contractile responses of vasoconstrictors in aortic smooth muscle stripes of normotensive (NR) and spontaneous hypertensive rats (SHR). Phenylephrine (an adrenergic $\alpha$$\_$1/-receptor agonist) and high potassium (a membrane depolarizing agent) caused greatly contractile responses in both NR and AHR aorta, respectively. Phenylephrine- and high potassium-induced contractile responses were greater in NA than those in SHR aortic smooth muscle stripes. In NR, the contractile responses of high potassium (5.6$\times$10$\^$-2/ M) were not affected in the presence of GTS (300 $\mu$g/ml), PDS (300 $\mu$g/ml), and PTS (300 $\mu$g/ml), respectively whereas phenylephrine (10$\^$-6/ M)-induced contractile responses were markedly inhibited. In SHR, the contractile responses of high potassium (5.6$\times$10$\^$-2/ M) were not affected in the presence of GTS (300 $\mu$g/ml), PDS (300 $\mu$g/ml), and moderate doses of PTS (150-300 $\mu$g/ml), respectively but greatly blocked by high concentration of PTS (600 $\mu$g/ml). Phenylephrine (10$\^$-6/ M)-induced contractile responses were inhibited in a dose dependent fashion (150-600 $\mu$g/ml) by the pretreatment with PTS while not altered in the presence of GTS (300 $\mu$g/ml) and PDS (300 $\mu$g/ml), respectively. Taken together, these experimental results suggest that ginseng saponins cause vascular relaxation through blockade of adrenergic $\alpha$$\_$1/-receptors and some unknown mechanisms, and that there is some difference in sensitivity of vascular smooth muscle between NR and SHR in responses to ginseng saponins. It seems that panaxatriol type of some ginseng saponins has the greatest potency in vascular relaxation.

Drugs Most Frequently Used in OPD of Yeungnam University Hospital: March to August, 1985 (영남대학교 의과대학 부속병원 외래환자에 대한 약물처방 동향의 분석)

  • Lee, Kwang-Youn;Kim, Won-Joon;Kim, Sung-Hoon
    • Journal of Yeungnam Medical Science
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    • v.2 no.1
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    • pp.95-102
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    • 1985
  • This report offers descriptive data about the drugs utilized in out patient department (OPD) of Yeungnam University Hospital (YUH) in the period of march to august in 1985. The data in this report were produced by the computerized totalization of the number of mentions of individual drugs included in the prescriptions. The 100 drug entries that were most frequently recorded are listed in rank order. The listing is arbiturarily restricted to the drugs that were prescribed as single preparations, the drugs of basis of compound preparations and the drugs of adjuvent or corrective of compound preparations that have significant therapeutic effects either by generic names. And in addition, the listing also involves the compound preparations used in relatively large frequency, and the individual components of which have the unique pharmacological actions each other by proprietary names. And all routes of administrations were allowed. The 10 drugs most frequently named are diazepam, aluminum compounds, acetaminophen, isoniazid, metoclopramide, $polaramine^{(R)}$, carboxymethylcystem, ephedrine, codeine and caroverine in order. The 521,855 drug mentions listed as above are described by the chief therapeutic usage that each is intended to apply generally. The drugs which account the largest proportion of total mentions were those acting on the central nervous system (20.57%), including tranquilhzers and sedative hypnotics (11.71%), analgesic antipyretics (5.55%), antidepressants (2.15%) etc. Gastrointestinal drugs and smooth muscle preparations (18.64%) included antacids and anti-ulcer drugs (9.24%), antiemetics (3.57%), spasmolytics (3.14%) and others. Respiratory drugs (16.11%) included expectorants and cough preparations (10.99%) and bronchodilators (5.12%). Chemotherapeutic agents (15.12%) included the antiTbc drugs (7.09%) most frequently, and the penicillins (3.33%) accounted the largest proportion among the antibiotics. Cardiovascular drugs (5.64%) included cardiac drugs and coronary vasodilator (4.12%) and antihypertensives and vasodilators (1.06%). And anti-inflammatory drugs (4.33%), vitamins of single preparations (3.76%), hormones and their antagonists (3.29%), common cold preparations (3.12%), diuretics (2.81%), drugs supporting liver function (2.02%), drugs affecting autonomic nervous system(1.89%) including anti-glaucomas, atropine and cerebral vasodilators, antihistamine drugs (1.02%) and disinfectants (0.74%) were following in order. The data in this report were compared to those reported by H. Koch, et al. in United States (US), 1981 as "Drugs Most Frequently Used in Office Practice:National Ambulatory Medical Case Survey, 1981." Cardiovascular drugs prescribed in YUH were much less in proportion than in US (10.56%), but gastrointestinal drugs accounted the larger proportion than in US (3.72%). Expectorants and cough preparations in YUH also accounted the larger proportion than in US (2.74%). In conclusion, in the period of march to august, 1985, OPD of YUH prescribed the CNS drugs including diazepam most frequently, and gastrointestinal, repiratory and chemotherapeutic drugs in next orders. It is supposed that the eating habits of Koreans and a unique atmospheric condition in Taegu as a basin were some important factors that affected the proportions of drugs acting on gastrointestinal and respiratory tracts.

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Expressions of Matrix Metalloproteinase-9 and Tissue Inhibitor of Metalloproteinase-2 with Changes of Interleukin-6 and Interleukin-18 in Atherosclerotic Lesions of Hypercholesterolemic Rabbits (고콜레스테롤혈증 가토의 죽상경화성 병변에서 Interleukin-6와 Interleukin-18의 변화 및 Matrix Metalloproteinase-9과 Tissue Inhibitor of Metalloproteinase-2의 발현)

  • 권영무;김성숙;장봉현
    • Journal of Chest Surgery
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    • v.35 no.6
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    • pp.407-419
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    • 2002
  • Atherosclerosis is a chronic inflammatory disease of the arterial wall characterized by progressive accumulation of lipids, cells, and extracellular matrix. Matrix metalloproteinases(MMPs) and tissue inhibitor of metalloproteinases(TIMPS) contribute to vascular matrix remodeling in atherosclerosis, and some cytokines may play role in the synthesis or activation of MMPs or TIMPs. Material and Method: We produced experimental atherosclerotic plaques in 9 rabbits by atherogenic hypercholesterol diet for 12 weeks, and 10 other rabbits were used as control group with standard laboratory chow, At that time, 19 rabbits were sacrificed and aorta, coronary arteries and blood specimens were prepared. The expressions of MMP-9, TIMP-2 and interleukin(IL)-18, and the bioactivity of IL-6 were investigated with H&E stain, immunohistochemical stain, immunoblotting(Western blot analysis), and bioassay. Result: Serum cholesterol in the experimental group increased up to 1258$\pm$262 mg/dL(control group: 41$\pm$7 mg/dL). All experimental group showed well-developed atherosclerotic plaques in aorta and coronary artery. The expression of MMP-9 in aorta and coronary artery of the experimental group showed significant increase than that of the control group by immunohistochemistry. Among the experimental group, complicated lesions with intimal rupture or complete luminal occlusion, demonstrated stronger expression of MMP-9. Interestingly, there was no difference in expression of TIMP-2 between the experimental and the control group. These findings were confirmed by Western blot analysis. The bioassay revealed significant up-regulation of serum bioactivity of IL-6 in the experimental group(4819.60$\pm$2021.25 IU/$m\ell$) compared to that of IL-6 in the control group(27.20 $\pm$ 12.19 IU/$m\ell$). IL-18 was expressed in all atherosclerotic plaques, whereas little or no expression was detected in the control group. Conclusion: The increased MMP-9 expression along with the unchanged TIMP-2 expression seem to be contributory factors in extracellular matrix degradation in atherosclerosis. Focal overexpression of MMP-9 may promote plaque destabilization and cause complications of atherosclerotic plaques such as thrombosis with/without acute coronary syndrome. Elevation of IL-6 and IL-18 may be more than just markers of atherosclerosis but actual participants in lesion development. Identification of critical regulatory pathway is important to improve the understanding of the cellular and molecular basis of atherosclerosis and may open the way for novel therapeutic strategies.

Impact of Weather on Prevalence of Febrile Seizures in Children (소아의 열성경련에 날씨가 미치는 영향)

  • Woo, Jung Hee;Oh, Seok Bin;Yim, Chung Hyuk;Byeon, Jung Hye;Eun, Baik-Lin
    • Journal of the Korean Child Neurology Society
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    • v.26 no.4
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    • pp.227-232
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    • 2018
  • Purpose: Febrile seizure (FS) is the most common type of seizure in children between 6 months to 5 years of age. A family history of febrile seizures can increase the risk a child will have a FS. Yet, prevalence of FS regarding external environment has not been clearly proved. This study attempts to determine the association between prevalence of FS and weather. Methods: This study included medical records from the Korea National Health Insurance Review and Assessment Service. Data were collected from 29,240 children, born after 2004, diagnosed with FS who were admitted to one of the hospitals in Seoul, Korea, between January 2009 and December 2013. During the corresponding time period, data from the Korea Meteorological Administration on daily monitoring of four meteorological factors (sea-level pressure, amount of precipitation, humidity and temperature) were collected. The relationships of FS prevalence and each meteorological factor will be designed using Poisson generalized additive model (GAM). Also, the contributory effect of viral infections on FS prevalence and weather will be discussed. Results: The amount of precipitation was divided into two groups for comparison: one with less than 5 mm and the other with equal to or more than 5 mm. As a result of Poisson GAM, higher prevalence of FS showed a correlation with smaller amount of precipitation. Smoothing function was used to classify the relationships between three variables (sea-level pressure, humidity, and temperature) and prevalence of FS. FS prevalence was correlated with lower sea-level pressure and lower humidity. FS prevalence was high in two temperature ranges (-7 to $-1^{\circ}C$ and $18-21^{\circ}C$). Conclusion: Low sea-level pressure, small amount of precipitation, and low relative air humidity may increase FS prevalence risk.

Effects of Corni Fructus on Testosterone-induced Benign Prostatic Hyperplasia in Sprague Dawley Rats (Sprague Dawley 흰쥐에서 테스토스테론에 의하여 유발된 전립선 비대증에 미치는 산수유 추출물의 영향)

  • Kwon, Da He;Hwangbo, Hyun;Choi, Eun Ok;Kim, Min Yeong;Ji, Seon Yeong;Kim, Kyung-Il;Park, No-Jin;Kim, Sung Ok;Hong, Su-Hyun;Park, Cheo;Hwang, Hye-Jin;Jeong, Ji-Suk;Choi, Yung Hyun
    • Journal of Life Science
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    • v.28 no.12
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    • pp.1507-1515
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    • 2018
  • Benign prostatic hyperplasia (BPH) is characterized by prostatic hypertrophy mainly in the elderly. Corni Fructus is reportedly effective in the prevention and treatment of various diseases, but its efficacy on BPH has not been previously studied. In the present study, we investigated whether or not a Corni Fructus water extract (CF) could prevent testosterone-induced prostatic hyperplasia in rats. To induce BPH, castrated rats were subcutaneously injected with testosterone propionate (TP). CF was administered daily by oral gavage, along with the TP injections, and finasteride, a selective inhibitor of $5{\alpha}$-reductase type 2, was used as a positive control. The results show that CF significantly reduces prostate weight and histopathologic changes while also decreasing levels of serum dihydrotestosterone, similar to the finasteride-treated group. CF also suppresses TP-induced $5{\alpha}$-reductase expression and concentration in prostate tissue and serum, respectively. Furthermore, CF markedly inhibited TP-induced expression of the androgen receptor (AR) and the steroid receptor coactivator 1, an AR coactivator, which was associated with a decrease in prostate-specific antigen levels in both serum and prostate tissue. In conclusion, the results of this study indicate that CF weakens BPH status by inactivation of $5{\alpha}$-reductase and AR.

A Comparative Study on the Subjective Sensation and Tactile Preferences for Casual Shirt Fabrics Compared by the Nationality of Female University Students (여대생의 국적에 따른 캐주얼 셔츠 소재의 주관적 감각과 촉감 선호도 비교)

  • Meng, Yu;Choi, Jongmyoung
    • Science of Emotion and Sensibility
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    • v.24 no.1
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    • pp.105-114
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    • 2021
  • This study determines the differences between Korean female university students and their Chinese counterparts residing in Korea by evaluating the subjective sensation and tactile preference in fabrics for casual shirts. Seven types of white causal shirt fabrics were selected as specimens from those available in spring and autumn shirt collection. The fabrics were made from various fibers (cotton 100%, polyester 100%, flax 100%, polyester 80%/cotton 20%, polyester 65%/cotton 35%, polyester 50%/cotton 45%/spandex 5%, and polyester 50%/modal 50%). Forty Korean and Chinese female university students subjectively assessed the subjective sensation of fabrics used for casual shirts. Participants were asked to observe the seven types of fabrics and complete the questionnaire. The subjective sensation to be assessed for white casual shirt fabrics was classified into the following four factors: smoothness, lightness, softness, and stretchiness. Subjective sensation factors showed partially significant differences by nationality. Korean female students evaluated cotton fabric as being light, whereas their Chinese counterparts evaluated the polyester/cotton/spandex blended fabric as light. Korean female students evaluated polyester/modal blended fabric as being stretchable. The tactile preference for fiber composition of the fabrics showed partially significant differences by nationality. Korean female students preferred cotton 80%/polyester 20% blended fabric, polyester 50%/cotton 45%/spandex 5% blended fabric, and flax 100% fabric. The subjective sensation of the fabrics had different effects on preferences by nationality. Smoothness and softness had positive effects on preferences for the fabrics of Korean students. However, smoothness, softness, and stretchiness had positive effects on the preferences of Chinese students. The subjective sensation and tactile preference for casual shirt fabrics showed a difference between Korean female students and their Chinese counterparts. Therefore, when planning casual shirt fabrics for female university students, it is necessary to reflect on these differences in subjective sensation and tactile preference.

Regulatory Mechanism of Vascular Contractility by Extracellular $\textrm{K}^{+}$: Effect on Endothelium-Dependent Relaxation and Vascular Smooth Muscle Contractility (세포 외 $\textrm{K}^{+}$의한 혈관 수축신 조절 기전: 혈관평활근 수축성과 내피세포 의존성 이완에 미치는 영향)

  • 유지영;설근희;서석효;안재호
    • Journal of Chest Surgery
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    • v.37 no.3
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    • pp.210-219
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    • 2004
  • Extracellular $K^{+}$ concentration ([ $K^{+}$]$_{0}$ ) can be increased within several mM by the efflux of intracellular $K^{+}$. To investigate the effect of an increase in [ $K^{+}$]$_{0}$ on vascular contractility, we attempted to examine whether extracellular $K^{+}$ might modulate vascular contractility, endothelium-dependent relaxation (EDR) and intracellular $Ca^2$$^{+}$ concentration ([C $a^2$$^{+}$]$_{i}$ ) in endothelial cells (EC). We observed isometric contractions in rabbit carotid, superior mesenteric, basilar arteries and movse aorta. [C $a^2$$^{+}$]$_{i}$ was recorded by microfluorimeter using Fura-2/AM in EC. No change in contractility was recorded by the increase in [ $K^{+}$]$_{0}$ from 6 to 12 mM in conduit artery such as rabbit carotid artery. whereas resistant vessels, such as basilar and branches of superior mesenteric arteries (SMA), were relaxed by the increase. In basilar artery, the relaxation by the increase in [ $K^{+}$]$_{0}$ to from 1 to 3 mM was bigger than that by the increase from 6 to 12 mM. In contrast, in branches of SMA, the relaxation by the increase in [ $K^{+}$]$_{0}$ to from 6 to 12 mM is bigger than that by the increase from 1 to 3 mM. $Ba^2$$^{+}$ (30 $\mu$M) did not inhibit the relaxation by the increase in [ $K^{+}$]$_{0}$ from 1 to 3 mM but did inhibit the relaxation by the increase from 6 to 12 mM. In the mouse aorta without the endothelium or treated with $N^{G}$_nitro-L-arginine (30 $\mu$M), nitric oxide synthesis blocker, the increase in [ $K^{+}$]$_{0}$ from 6 to 12 mM did not change the magnitude of contraction induced either norepinephrine or prostaglandin $F_2$$_{\alpha}$. The increase in [ $K^{+}$]$_{0}$ up to 12 mM did not induce contraction of mouse aorta but the increase more than 12 mM induced contraction. In the mouse aorta, EDR was completely inhibited on increasing [ $K^{+}$]$_{0}$ from 6 to 12 mM. In cultured mouse aorta EC, [C $a^2$$^{+}$]$_{i}$ , was increased by acetylcholine or ATP application and the increased [C $a^2$$^{+}$]$_{i}$ , was reduced by the increase in [ $K^{+}$]$_{0}$ reversibly and concentration-dependently. In human umbilical vein EC, similar effect of extracellular $K^{+}$ was observed. Ouabain, a N $a^{+}$ - $K^{+}$ pump blocker, and N $i^2$$^{+}$, a N $a^{+}$ - $Ca^2$$^{+}$ exchanger blocker, reversed the inhibitory effect of extracellular $K^{+}$. In resistant arteries, the increase in [ $K^{+}$]$_{0}$ relaxes vascular smooth muscle and the underlying mechanisms differ according to the kinds of the arteries; $Ba^2$$^{+}$-insensitive mechanism in basilar artery and $Ba^2$$^{+}$ -sensitive one in branches of SMA. It also inhibits [C $a^2$$^{+}$]$_{i}$ , increase in EC and thereby EDR. The initial mechanism of the inhibition may be due to the activation of N $a^{+}$ - $K^{+}$pump. activation of N $a^{+}$ - $K^{+}$pump.p.p.p.

The Effect of Dexamethasone on Airway Goblet Cell Hyperplasia and Inflammation in $TiO_2$-Treated Sprague-Dawley Rats ($TiO_2$로 처치된 백서에서 기도내 배상세포 증식과 염증에 대한 Dexamethasone의 효과)

  • Lim, Gune-Il;Kim, Do-Jin;Park, Choon-Sik
    • Tuberculosis and Respiratory Diseases
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    • v.49 no.1
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    • pp.37-48
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    • 2000
  • Backgrounds : The pathophysiology of chronic airflow obstruction, such as bronchial asthma, is characterized by mucus hypersecretion, goblet cell hyperplasia(GCH), smooth muscle hypertrophy, and inflammatory cells infiltration. In fatal asthma patients, one distinct findings is mucus hypersecretion due to GCH. However, the mechanisms of GCH in these hypersecretory diseases remain still unknown. In this study, a rat model was rapidly induced with GCH by instillation of $TiO_2$, intratracheally. We intend to confirm GCH and association of concomitant inflammatory cells infiltration and to observe the effect of potent antiinflammatory agent, that is dexamethasone, on GCH with inflammatory cells. Methods : Twenty-one 8-weeks-old male Sprague-Dawley rats were divided into three groups. Endotoxinfree water was instilled intratracheally in group 1(control) ; $TiO_2$, was instilled in the group 2 ; and dexamethasone was injected intraperitoneally to group 3 before $TiO_2$ instillation. After 120 hours, all rats were sacrificed, and trachea, bronchi, and lungs were resected respectively. These tissues were made as paraffin blocks and stained as PAS for goblet cells and Luna stain for eosinophils. We calculated the ratio of goblet cell to respiratory epithelium and number of infiltrated eosinophils from each tissue. Results : (1) Fraction of goblet cells was significantly increased in group 2 than in group 1 in the trachea and in the main bronchus. (10.19$\pm$11.33% vs 4.09$\pm$8.28%, p<0.01 and 34.09$\pm$23.91% vs 3.61$\pm$4.84%, p<0.01, respectively). (2) Eosinophils were significantly increased in the airway of group 2 than that of group 1. (5.43$\pm$3.84% vs 0.17$\pm$0.47 in trachea and 47.71$\pm$16.91 vs 2.71$\pm$1.96 in main bronchi). (3) There was a positive correlation between goblet cells and eosinophils(r=0.719, p=0.001). (4) There was significant difference in the decrease of goblet cells after dexamethasone injection between group 2 and group 3 (p<0.01). Also, infiltration of eosinophils was suppressed by dexamethasone. Conclusion : We made an animal model of $TiO_2$-induced goblet cell hyperplasia. GCH was observed mainly in the main bronchi with concomitant eosinophilic infiltration. Both goblet cell hyperplasia and eosinophilic infiltration were suppressed by dexamethasone. This animal model may serve as a useful tool in understanding of the mechanism of GCH in chronic airway diseases.

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A Study of Endothelium-dependent Pulmonary Arterial Relaxation and the Role of Nitric oxide on Acute Hypoxic Pulmonary Vasoconstriction in Rats (흰쥐 폐동맥의 내피세포의존성 혈관이완과 급성 저산소성 폐동맥수축에서 산화질소의 역할)

  • In, Kwang-Ho;Lee, Jin-Goo;Cho, Jae-Youn;Shim, Jae-Jung;Kang, Kyung-Ho;Yoo, Se-Hwa
    • Tuberculosis and Respiratory Diseases
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    • v.41 no.3
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    • pp.231-238
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    • 1994
  • Backgroud: Since the demonstration of the fact that vascular relaxation by acetylcholine(Ach) results from the release of relaxing factor from the endothelium, the identity and physiology of this endothelium-derived relaxing factor(EDRF) has been the target for many researches. EDRF has been identified as nitric oxide(NO). With the recent evidences that EDRF is an important mediator of vascular tone, there have been increasing interests in defining the role of the EDRF as a potential mediator of hypoxic pulmonary vasoconstriction. But the role of EDRF in modulating the pulmonary circulation is not compeletely clarified. To investigate the endothelium-dependent pulmonary vasodilation and the role of EDRF during hypoxic pulmonary vasoconstriction, we studied the effects of $N^G$-monomethyl-L-arginine(L-NMMA) and L-arginine on the precontracted pulmonary arterial rings of the rat in normoxia and hypoxia. Mothods: The pulmonary arteries of male Sprague Dawley(300~350g) were dissected free of surrounding tissue, and cut into rings. Rings were mounted over fine rigid wires, in organ chambers filled with 20ml of Krebs solution bubbled with 95 percent oxygen and 5 percent carbon dioxide and maintained at $37^{\circ}C$. Changes in isometric tension were recorded with a force transducer(FT.03 Grass, Quincy, USA) Results: 1) Precontraction of rat pulmonry artery with intact endothelium by phenylephrine(PE, $10^{-6}M$) was relaxed completely by acetylcholine(Ach, $10^{-9}-10^{-5}M$) and sodium nitroprusside(SN, $10^{-9}-10^{-5}M$), but relaxing response by Ach in rat pulmonary artery with denuded endothelium was significantly decreased. 2) L-NMMA($10^{-4}M$) pretreatment inhibited Ach($10^{-9}-10^{-5}M$)-induced relaxation, but L-NMMA ($10^{-4}M$) had no effect on relaxation induced by SN($10^{-9}-10^{-5}M$). 3) Pretreatment of the L-arginine($10^{-4}M$) significantly reversed the inhibition of the Ach ($10^{-9}-10^{-5}M$)-induced relaxation caused by L-NMMA($10^{-4}M$) 4) Pulmonary arterial contraction by PE($10^{-6}M$) was stronger in hypoxia than normoxia but relaxing response by Ach($10^{-9}-10^{-5}M$) was decreased, 5) With pretreatment of L-arginine($10^{-4}M$), pulmonary arterial relaxation by Ach($10^{-9}-10^{-5}M$) in hypoxia was reversed to the level of relaxation in normoxia. Conclusion: It is concluded that rat pulmonary arterial relaxation by Ach is dependent on the intact endothelium and is largely mediated by NO. Acute hypoxic pulmonary vasoconstriction is related to the suppression on NO formation in the vascular endothelium.

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