반려동물과 관련∙종사자에서 분리된 항생제 내성 대장균의 상관성 분석

학위논문 (박사)-- 서울대학교 대학원 수의과대학 수의학과, 2017. 8. 박용호.Livestocks today are not that much more valuable than they were long ago, we treat our companion animals as if they were far more valuable. In addition, we have seen a huge switch in animal medicine, from a focus on livestocks to a focus on companion animals such as horses, dogs and cats. In the Korean companion animal industry, the market size associated with companion animals is rapidly increasing and estimated to be $5.4 billion by 2020. In addition, more and more Korean people have recognized the importance of horse industry according to the increasing trend of horse-riding. However, limited information is available regarding horse-associated antimicrobial resistant (AR) bacteria in Korea. As first study, we evaluated the frequency and characterize the pattern of AR Escherichia coli (E. coli) from healthy horse-associated samples. Thirty of the E. coli isolates (21%) showed antimicrobial resistance to at least one antimicrobial agent, and four of the AR E. coli (13.3%) were defined as multi-drug resistance. Pulsed-field gel electrophoretic analysis showed the cross-transmissions between horses or horses and environments were detected in two facilities. Although cross-transmission of AR E. coli in horses and their environments was generally low, our study suggests a risk of transmission of AR bacteria between horses and humans. Quinolone (Q) and fluoroquinolone (FQ) are broad-spectrum synthetic antimicrobials used to treat bacterial infections in humans and animals. Since they are very potent antimicrobial agents against Gram-negative bacteria including E. coli, these agents have been widely used to treat a range of infections in companion animals. Consequently, (F)Q resistance has markedly increased worldwide, posing a significant threat to the health of animals and humans. In the second study, we investigated the prevalence and the mechanisms of FQ/Q resistance in E. coli isolates from companion animals, owners, and non-owners. A total of 27 nalidixic acid (NA)-resistant isolates were identified. Of these, 10 isolates showed ciprofloxacin (CIP) resistance. Efflux pump activity was detected in 18 isolates (66.7%), but this was not correlated with the increased minimum inhibitory concentration (MIC). Target gene mutations in Q resistance-determining regions (QRDRs) were the main cause of (F)Q resistance in E. coli. The number of point mutations in QRDRs was strongly correlated with increased MIC (R = 0.878 for NA and 0.954 for CIP). Interestingly, (F)Q resistance mechanisms observed in isolates from companion animals were the same as those in humans. Therefore, a prudent use of (F)Q in veterinary medicine is warranted to prevent the dissemination of (F)Q-resistant bacteria from animals to humans. Companion animals such as horses and dogs are considered as one of the reservoirs of AR bacteria that can be cross-transmitted to humans. The inherent risk of any use of antimicrobials to select for AR bacteria poses a relevant risk for public health by spreading of antimicrobial resistance from animals to humans via direct or indirect contacts. However, limited information is available on the possibility of AR bacteria originating from companion animals being transmitted secondarily from owners to non-owners sharing the same space. To address this issue, in the third place, we investigated clonal relatedness among AR E. coli isolated from dog owners and non-owners in the same college classroom or household. Of 31 E. coli, 20 isolates (64.5%) were resistant to at least one antimicrobial, and 16 isolates (51.6%) were determined as multi-drug resistant E. coli. Pulsed-field gel electrophoretic analysis identified three different E. coli clonal sets among isolates, indicating that cross-transmission of AR E. coli can easily occur between owners and non-owners. The findings emphasize a potential risk of spread of AR bacteria originating from companion animals within human communities, once they are transferred to humans. Antimicrobial resistance is an urgent global problem. There are increasing concerns about the emergence of multi-drug resistant bacteria in humans, animals and environments. The antimicrobial resistance is a complex phenomenon driven by many factors such as the interaction of humans, animals and environmental sources for antimicrobial resistance. Our study also showed that they could be not only reservoirs but also transmitters of antimicrobial-resistant bacteria. Therefore, the aims of combating antimicrobial-resistant bacteria and preserving the efficacy of the currently available antimicrobials in human and veterinary medicine as well as in ecological systems should be addressed in an interdisciplinary effort within a One Health approaches. Addressing this urgent threat requires the multifaceted strategies. Elements include strengthened surveillance of antimicrobial usageimproved antimicrobial stewardship in humans and animalsapproaches to incentivize new antimicrobials developmentincreased research on mechanisms of resistancea prudent use of antimicrobials by veterinarians as well as clinicians.Literature Review 1 I. The genus Escherichia coli 2 II. Use of antimicrobials in animals 5 III-1. Mechanisms of antimicrobial resistance in bacteria 9 III-2. Mechanisms of quinolone resistance 12 1. Mutations in DNA gyrase and topoisomerase IV 13 2. The presence of PMQR genes 15 3. Efflux pump activity 16 IV. The emergence of antimicrobial resistance in animals 18 General Introduction 23 Chapter I. Isolation and characterization of antimicrobial-resistant E. coli from national horse racetracks and private horse-riding courses in Korea 27 I. Introduction 28 II. Materials and methods 29 1. Sampling 30 2. Isolation and identification of E. coli 30 3. Antimicrobial resistance profiling of E. coli isolates 31 4. Detection of antimicrobial resistance and integrase genes 32 5. Determination of O and H serotypes 33 6. Molecular fingerprinting 33 III. Results 34 1. E. coli isolation from the horse-associated samples 34 2. Phenotypic characterization of antimicrobial resistance of E. coli isolates 35 3. Detection of the antimicrobial resistance and integrase genes in AR E. coli isolates 35 4. Serotyping of E. coli isolates 36 5. Genotyping of AR E. coli by PFGE 36 IV. Discussion 37 Chapter II. Mechanisms of quinolone resistance in Escherichia coli isolated from companion animals, owners, and non-owners 50 I. Introduction 51 II. Materials and methods 52 1. Sampling 52 2. Isolation of NA-resistant E. coli from swab samples 53 3. Antimicrobial resistance profiling of NA-resistant E. coli isolates 53 4. Determination of minimum inhibitory concentrations (MICs) of NA and CIP 54 5. Detection of PMQR genes and mutations in QRDRs 55 6. Organic solvent tolerance (OST) assay 55 7. Evaluation of the effect of each (F)Q resistance mechanism on MICs of NA and CIP 56 III. Results 56 1. Isolation of NA or CIP resistant E. coli from companion animals and humans 56 2. Susceptibility of NA-resistant E. coli isolates to other antimicrobials 57 3. Determination of MICs 57 4. Analysis of mutations in QRDRs and detection of PMQR genes 58 5. Measurement of efflux pump activity 59 6. Relative contribution of each (F)Q resistance mechanism to increases in MIC 59 IV. Discussion 60 Chapter III. Probable secondary transmission of antimicrobial-resistant Escherichia coli between people living with and without companion animals 70 I. Introduction 71 II. Materials and methods 72 1. Sampling 72 2. E. coli isolation and identification 73 3. Antimicrobial susceptibility test 73 4. Detection of integrase genes in E. coli isolates 74 5. Molecular fingerprinting 74 III. Results 75 1. Isolation of E. coli from swab samples 75 2. Antibiogram of 31 E. coli isolates 75 3. Detection of integrase genes in E. coli isolates 76 4. Genetic relatedness of E. coli isolates from owners and non-owners 76 IV. Discussion 77 References 85 General Conclusion 118 국문초록 120Docto

Anti-proliferative and apoptotic activities of Müllerian inhibiting substance combined with calcitriol in ovarian cancer cell lines

의과대학/박사Purpose This study aimed to investigate whether Müllerian inhibiting substance (MIS) in combination with calcitriol modulates proliferation and apoptosis of human ovarian cancer (OCa) cell lines (SKOV3, OVCAR3, and OVCA433) and identify the signaling pathway by which MIS mediates apoptosis. Materials and Methods OCa cell lines were treated with MIS in the absence or presence of calcitriol. Cell viability and proliferation were evaluated using the Cell Counting Kit-8 assay and apoptosis was evaluated by DNA fragmentation assay. Western blot and enzyme-linked immunosorbent assay were used to determine the signaling pathway. Results The cells showed specific staining for the MIS type II receptor. Treatment of OCa cells with MIS and calcitriol led to dose- and time- dependent inhibition of cell growth and survival. The combination treatment significantly suppressed cell growth, down-regulating the expression of B-cell lymphoma 2 (Bcl-2); and up-regulating the expression of Bcl-2 associated X protein (BAX), caspase-3, and caspase-9 through the extracellular signal-regulated kinase signaling pathway. Conclusion These results, coupled with a much-needed decrease in the toxic side effects of currently employed therapeutic agents, provide a strong rationale for testing the therapeutic potential of MIS, alone or in combination with calcitriol, in the treatment of OCa.ope

A therapeutic experience of diffuse cerebellopontine angle meningioma through combined translabyrinthine, infratemporal fossa, and suboccipital craniotomy approach

Meningioma is a slow growing tumor that mainly originates from the intracranial region, but rarely occurs at extracranial region. Once the extracranial meningioma shows diffuse and extensive involvement along the cranial nerves, surgical extirpation of the tumor becomes extremely difficult, and surgical morbidity often follows. We present a single case of en plaque meningioma extended to temporal area and parapharyngeal space, and reviewed the surgical technique for manipulation of facial nerve and postoperative cranial nerve palsy.ope

Fasting and Postprandial Analysis of Bowel Sounds and Plasma 5-hydroxytryptamine Level

Background/Aims: Auscultation of bowel sounds is a traditional technique for evaluating patients with abdominal symptoms. It is, however, subjective and qualitative method in general. Recently, analysis of bowel sounds becomes possible. We analyzed bowel sounds in healthy volunteers and measured platelet depleted plasma 5-hydroxytryptamine (5-HT) that may be associated with postprandial symptoms in irritable bowel syndrome. Methods: We recorded both fasting and postprandial bowel sounds for 30 minutes in 16 healthy volunteers with a sensitive electronic stethoscope attached to a digital recorder. The files were saved in computer as wav files and analyzed with a specialized program. Blood samples were also taken before and 1 hour after meal for 5-HT analysis. Results: Meal challenge made no statistically significant changes in the 5-HT concentrations and all the sound parameters including sound to sound interval, sounds/minute, average of sound amplitudes, sound length, percentage of bowel sounds representing sound clustering and dominant frequency of sounds. Conclusions:Postprandial changes in bowel sounds and plasma 5-HT were insignificant in healthy Korean volunteers.ope

Is obstructive sleep apnea associated with erythrocytosis? A systematic review and meta-analysis

Objective: The aim of this systematic review and meta-analysis was to investigate the association between obstructive sleep apnea (OSA) and erythrocytosis. Methods: The PubMed, Web of Science, and Cochrane Library databases were searched for articles examining hematocrit values in patients with OSA and control individuals published till September 1, 2021. The pooled standardized mean difference (SMD) with 95% confidence interval (CI) was calculated, and subgroup analyses were performed. Results: Eleven eligible studies with a total of 4608 patients with OSA were included in this meta-analysis. Pooled outcomes revealed that hematocrit values were significantly higher in patients with OSA than in controls (SMD, 0.19; 95% CI, 0.08-0.29; p < .01). When studies were stratified by disease severity, the significant differences in hematocrit values between patients and controls were only observed in the severe OSA group (SMD, 0.34; 95% CI, 0.08-0.59; p < .01), but not in the mild and moderate OSA groups. In subgroup analyses according to sex and publication year, significant differences in hematocrit values between patients and controls remained stable in studies with only female patients (SMD, 0.25; 95% CI, 0.12-0.38; p < .01) and in studies published after 2012 (SMD, 0.17; 95% CI, 0.06-0.28, p < .01). Conclusion: Our meta-analysis revealed that the hematocrit value was significantly increased in patients with OSA, particularly in severe patients, compared with that in controls. However, the elevation was modest, and the hematocrit value is expected to be within the normal range in patients with OSA. These data suggest that OSA leads to slight increases in hematocrit but does not cause clinically significant erythrocytosis.ope

Pyloric Injection of Botulinum Toxin for Treatment of Diabetic Gastroparesis: A Report of Four Cases

Gastroparesis is a disorder of gastric motility that results in delayed gastric emptying. Up to 58% of patients with diabetes mellitus may have diabetic gastroparesis, a syndrome characterized by nausea, vomiting, early satiety, and bloating. The pathophysiology of this disorder is not completely understood, but it is believed to include fundic dysaccommodation, a decrease in gastroduodenal pressure gradient and antral hypomotility. In addition to antral and fundic dysfunction, patients with diabetes may typically have pyloric dysfunction or spasm. Treatment consists of a change in diet to small volume, frequent meals and the use of the prokinetic agents. This case report describes the four patients with severe diabetic gastroparesis whose symptoms persisted despite of dietary changes and the use of prokinetic agents in high doses. All of them were treated with pyloric injection of botulinum toxin and three had significant symptomatic and scintigraphic improvement.ope

Association between Vitamin D Status and Risk of Metabolic Syndrome among Korean Postmenopausal Women

This study aimed to investigate the association between serum levels of 25-hydroxyvitamin D [25(OH)D] and metabolic syndrome along with its associated risk factors in Korean postmenopausal women. This study was performed using data from the KNHANES 2008–2010 study and included 4,364 postmenopausal Korean women. Clinical and other objective characteristics, seasonality, and presence of metabolic syndrome with its five components were evaluated and correlated with the serum levels of 25(OH)D. Although no statistically significant associations were observed between the levels of serum 25(OH)D and the prevalence of metabolic syndrome, the adjusted OR for elevated blood pressure, elevated triglycerides (TGs), and reduced high-density lipoprotein cholesterol (HDL-C) showed tendency to decrease sequentially as tertiles of serum 25(OH)D levels increased (p for trends = 0.066, 0.043, and 0.010, respectively). Women in the highest tertile of serum 25(OH)D showed a significant decrease in the prevalence of elevated blood pressure, elevated TGs, and reduced HDL-C as compared with those in the lowest tertile of serum 25(OH)D (p = 0.020, 0.014, and 0.002, respectively). Based on these results, we consider that adequate serum levels of 25(OH)D in Korean postmenopausal women may not entirely indicate a lower risk of developing metabolic syndrome. However, adequate serum levels of 25(OH)D are significantly associated with a decrease in elevated blood pressure, elevated TGs, and reduced HDL-C levels in postmenopausal women.ope

Usefulness of Urinary Trypsinogen-2 Dipstick Test for Diagnosis of Acute Pancreatitis

Background/Aims: The clinical usefulness of urinary trypsinogen-2 dipstick test is still in controversy. We evaluated the usefulness of urinary trypsinogen-2 dipstick test in patients with acute pancreatitis. Methods: Urinary trypsinogen-2 dipstick test was prospectively performed in 50 patients with acute pancreatitis, 50 patients with non-pancreatic abdominal pain, and 50 healthy controls. Results: On admission, urinary trypsinogen-2 dipstick test was positive in 36 of 50 patients with acute pancreatitis (sensitivity, 72%) and in 4 of 50 patients with non-pancreatic abdominal pain (specificity, 92%). On the other hand, it was all negative in controls. The sensitivity and specificity of serum lipase were 78% and 94%, respectively. At 24 hours after admission, the positive rate of urinary trypsinogen-2 dipstick test rose from 72% to 94% (p＝0.02). The results of urinary trypsinogen-2 dipstick test was positive in 14 of 15 patients with severe pancreatitis and 22 of 35 patients with mild pancreatitis according to the criteria by Atlanta International Symposium, 1992. Conclusions: Urinary trypsinogen-2 dipstick test is comparable to serum lipase in diagnosing acute pancreatitis. Delayed measurement and severe pancreatitis are more likely to yield positive results with urinary trypsinogen-2 dipstick test. Thus, we suggest that the cut-off value of urinary trypsinogen-2 dipstick test should be lowered to increase its sensitivity.ope

Type of Electric Currents Used for Standard Endoscopic Sphincterotomy Does Not Determine the Type of Complications

Background/Aims: The blended current is usually used for endoscopic sphincterotomy (EST) to minimize bleeding. The pure cutting current may induce less edema of the ampulla and therefore result in less injury to the pancreas theoretically. The aim of this study was to evaluate effects of electric currents used on the development of serum pancreatic enzyme evaluation, clinical pancreatitis or bleeding after EST. Methods: One hundred and eighteen consecutive patients who underwent EST with standard papillotome alone for the treatment of choledocholithiasis were reviewed. All EST had been performed by two endoscopists whose experience on EST was similar: one uses "blended current"(BC group, n=74), while the other uses "pure cutting current" (PC group, n=44). Results: Baseline clinical, laboratory, and procedural parameters were similar in both groups. The incidences of hyperamylasemia and hyperlipasemia were similar between two groups. There was no significant difference in the incidence of clinical pancreatitis between two groups (BC 6.8% vs PC 0.0%, p=0.1557). All episodes of pancreatitis were mild. No episodes of significant bleeding occurred after EST. The incidences of sepsis, cholangitis and perforation were also not different between two groups. Conclusions: Development of complications after standard EST such as hyperamylasemia, clinical pancreatitis, and bleeding may not depend on the electric current used.ope

The Effects of the Degree of Text Simplification and Elaboration on Korean High School Students&amp;apos; English Reading Comprehension

외국어 교수·학습에 있어 읽기는 영어로 된 텍스트를 읽고 정보를 얻는 측면 뿐 아니라 읽기를 통해 언어 습득에 필요한 언어 입력을 제공받을 수 있다는 측면에서도 중요하다. 특히 우리나라와 같은 EFL 환경에서는 영어 입력에 노출될 기회가 부족해 읽기를 통해 입력에 노출되는 기회를 증가시키는 것이 더욱 중요하다. 이러한 필요성에 의해 학습자들의 수준에 맞는 이해 가능한 입력을 제공하고 학습자들의 언어능력을 향상시키는데 도움이 되는 읽기 자료 및 읽기 자료 수정 방법에 대한 연구가 필요하다. 본 연구는 읽기 텍스트 수정의 두 가지 방법인 단순화 및 상세화 수준이 읽기 이해에 미치는 영향을 알아보기 위하여 실제적 텍스트, 3단계로 단순화한 텍스트, 3단계로 상세화한 텍스트의 7가지의 텍스트 수정 유형별로 읽기 이해도를 측정하여 분석하였다. 고등학교 2학년 7개 집단을 대상으로 2개의 지문과 10개의 읽기 이해 문항으로 구성된 실제적, 단순화I, 단순화II, 단순화III, 상세화I, 상세화II, 상세화III 텍스트 수정 유형을 읽고, 읽기 이해 문제를 풀도록 하였다. 단순화는 실제적 텍스트의 어려운 어휘를 쉬운 어휘로 바꾸고, 복잡하고 긴 문장구조를 간단하고 짧은 문장으로 수정하여 단순화I에서 단순화III로 갈수록 더 쉽고 간단한 문장이 되도록 수정하였다. 상세화는 어려운 어휘나 복잡한 문장을 삭제하지 않고, 잉여 정보를 추가하여 이해를 돕는 방식으로 이루어졌다. 즉, 어려운 어휘에 대해 동의어나 정의를 제공하거나 예를 들어 설명하고, 바꾸어 말하기 등을 이용하여 문장의 의미를 분명히 하였다. 읽기 이해도 측정을 위한 읽기 이해 문항은 전체적인 이해, 세부적인 이해, 추론적인 이해를 묻는 질문으로 구성되어 텍스트 수정의 유형별로 서로 다른 이해의 과정을 요구하는 읽기 이해에 어떤 영향을 미치는지 살펴보고자 하였다. 연구의 결과로, 첫째, 전체 실험 집단을 대상으로 텍스트 수정 유형별로 읽기 이해도를 비교했을 때, 수정된 텍스트는 실제적 텍스트 보다 높은 점수를 나타냈고, 전반적으로 단순화의 정도가 커질수록 높은 점수를 보였고, 상세화 정도가 커질수록 이해도 점수가 낮아지는 경향을 보였다. 통계적으로 유의미한 차이는 총점의 경우, 단순화II와 단순화III 유형의 텍스트에서 지문2의 점수에 대해서는 단순화III 유형의 텍스트 집단에서 나타났다. 즉, 전체 실험 집단에 대해서 단순화I 정도의 단순화는 점수 향상을 보이는데 부족하고, 단순화II와 단순화III는 점수 향상을 보였으며, 두 유형간의 차이는 없었다. 둘째, 상·하위 수준별 텍스트 수정 유형에 따른 읽기 이해도를 비교했을 때, 텍스트 수정 유형과 상·하위 수준은 상호작용이 없는 것으로 나타났고, 상위 집단의 경우, 텍스트 수정 유형별로 유의미한 읽기 점수의 차이가 나타나지 않았지만 수정된 텍스트가 실제적 텍스트 보다 1.5점 정도 높은 점수를 기록했다. 하위 집단의 경우는 텍스트 수정 유형별로 유의미한 차이를 나타냈다. 유의미한 차이는 단순화III 수정 텍스트와 실제적 텍스트 집단에서 나타났고, 전반적으로 단순화를 많이 적용할수록 높은 이해도를 보였다. 즉, 상위 집단의 경우, 6가지 유형의 텍스트에 비슷한 수준으로 도움을 받았고 하위 집단의 경우, 상세화한 수정 보다 단순화적인 수정의 도움을 더 많이 받은 것으로 나타났다. 셋째, 전체 실험 집단을 대상으로 읽기 이해 측정 영역별 텍스트 수정 수준의 영향을 분석하였다. 전체적인 이해 문항의 경우, 텍스트 수정 유형별로 유의미한 차이를 보이지 않았고, 상세화II, 단순화II, 상세화I, 단순화I, 상세화III, 단순화III, 실제적 텍스트 집단의 순으로 높은 점수를 보였다. 세부적 이해 문항의 경우 전반적으로 단순화 유형의 텍스트가 상세화 유형의 텍스트 보다 높은 점수를 보였고, 단순화III 텍스트 집단의 경우 실제적 텍스트 집단과 유의미한 차이를 보였다. 추론적 이해 문항의 경우, 텍스트 수정 유형 간에 유의미한 차이가 없었고, 상세화III, 단순화III, 상세화II, 단순화II, 단순화I, 상세화I, 실제적 텍스트 집단의 순으로 점수가 높았다. 각 수정 유형의 세 번째 단계의 수정 수준의 텍스트에서 높은 점수를 보였음을 확인할 수 있다. 넷째, 상·하위 수준별 읽기 이해 측정 영역별 텍스트 수정 수준의 영향을 분석하였다. 먼저 전체적 이해 문항에 대해서 상·하위 집단 모두 텍스트 수정 유형별로 유의미한 점수 차이를 보이지 않았고 텍스트 수정 유형과 상·하위 수준 간의 상호작용도 나타나지 않았다. 전체적인 이해를 묻는 문항의 수가 2개로 너무 적기 때문에 텍스트 수정 유형별 특성을 충분히 반영하지 못한 것으로 보인다. 다음으로 세부적인 이해 문항의 경우에도 상·하위 집단 모두 텍스트 수정 유형별로 유의미한 점수 차이를 보이지 않았고 텍스트 수정 유형과 상·하위 수준 간의 상호작용도 나타나지 않았다. 통계적으로 유의미한 결과는 아니지만, 상·하위 집단 모두 단순화III 텍스트가 가장 높은 세부적 이해 문항 점수를 보여주었다. 마지막으로 추론적 이해 문항의 경우, 상위 집단과 하위 집단 모두 텍스트 수정 집단별로 유의한 차이가 없는 것으로 나타났고, 텍스트 수정 유형과 상·하위 수준 간에 상호작용이 없었다. 그러나 추론적인 이해를 요하는 문항을 처리할 때, 상위 학습자는 대체적으로 상세화의 도움을 많이 받고 하위 학습자의 경우는 단순화한 텍스트의 도움을 많이 받는 것으로 나타났다. 결론적으로 본 연구에서는 전반적으로 단순화 방식의 텍스트 수정이 유의한 차이로 학습자들의 이해를 향상시켰다. 특히 하위 수준의 학습자의 경우 단순화를 가장 많이 한 유형의 텍스트에서 가장 많은 도움을 받은 것으로 나타났다. 반면 상위 학습자들의 경우는 6개의 수정된 텍스트 수정 유형에 대해 전반적으로 도움을 받은 것으로 보인다. 단순화하는 방식의 수정이 학습자들이 읽기 이해 전략을 연습하는 기회를 감소시키고, 언어 습득에 나쁜 영향을 미친다는 지적이 많고, 단순화를 대체하는 텍스트 수정 방식으로 어휘와 문법구조에 잉여정보를 주어 명확성을 높이는 상세화가 사용되어야 한다는 주장이 있다. 그러나 본 연구의 결과를 고려할 때, 단순화하는 방식으로 수정된 텍스트도 학습자의 영어 능숙도나 학습 상황에 따라 이해 가능한 입력을 제공하고, 학습자가 진정성 있는 자료를 읽을 수 있도록 돕는 중간과정으로서의 긍정적인 역할을 할 수 있을 것으로 생각된다. 즉, 읽기 교재를 개발하거나 읽기 수업을 설계할 때, 일률적으로 단순화 혹은 상세화하는 방법으로 텍스트를 수정하는 것이 아니라, 다양한 학습자의 수준이나 수업의 목표에 따라 적절한 유형의 입력 자료를 선택할 수 있도록 다양한 방법과 수준으로 텍스트를 수정하여 사용하는 것이 중요하며, 이러한 변인이 학습자의 이해와 언어 습득에 미치는 영향에 대한 연구가 필요하다고 생각된다.;Reading is an important skill in second language teaching and learning not only because second language learners can obtain information by reading materials in English but also because they can receive language input from reading them. Especially reading is important for Korean students living in the EFL (English as a Foreign Language) environment where there are very little opportunity to experience the target language. Therefore it is necessary to explore the appropriate reading materials and reading instruction which can help student have comprehensible input and acquire language. Also, second language learners usually begin to learn to read before exposure to the spoken language. They are assumed not to have a certain amount of linguistic knowledge to process all of the authentic texts written for native speakers of the target language. So when second language learners read an authentic text, which is lexically and syntactically complex or conceptually unfamiliar or dense, it can be too much burden to them. As a result, a lot of second language texts have been modified to make reading material more comprehensible and to help the learners prepare to read authentic texts. Simplification is the most common way to modify authentic texts in commercial second language materials. Texts can be simplified by making sentences shorter and replacing complicated lexis and syntax with simpler ones. Elaboration is another way to modify texts. Authentic texts are elaborated in a way that redundant information is added and thematic relations are expressed more explicitly. Current studies in second language acquisition have tested the relative effects of two different types of text modification on reading comprehension or vocabulary acquisition. However they are only concerned with whether simplification or elaboration is better but not with the effect of different degree of modification. Thus, this study investigates the effects of the degree of text simplification and elaboration on English reading comprehension of Korean high school students by comparing one authentic text, three levels of simplified texts and three levels of elaborated texts. This study investigates whether these seven different degrees of text modification have effect on the learners&amp;apos; reading comprehension. The subject participated in this study consisted of two hundred thirty second year high school students who were divided into seven groups. Each group was divided into two subgroups according to their language proficiency level: the lower level, and the upper level. They were respectively given one of seven texts: an authentic text, a simplified text (Simplification I), a more simplified text (Simplification II), a most simplified text (Simplification III), an elaborated text (Elaboration I), a more elaborated text (Elaboration II), and a most elaborated text. Three item types of reading comprehension questions with the given text were carried out for investigating the effects of the text modification type and reading comprehension test item type: general, specific, and inference test items. The major results of this study are as follows: First, in the whole, the modified text group gained higher scores on reading comprehension and there was a significant difference in comprehension between Simplification II and the authentic text, and between Simplification III and the authentic text. It indicates that simplified text facilitated Korean high school students&amp;apos; reading comprehension, and especially Simplification II and Simplification III versions did. And, there was no interaction effect between the modification type and learner proficiency. Only lower level group of Simplification III showed a significant difference from authentic text group. Second, considering the types of comprehension test item, all six types of text modification improved the students&amp;apos; performance on general and inference comprehension test items, but only Simplification III text significantly improved their performance on specific items. And there was no interaction effect between the modification type and learner proficiency on the types of comprehension test item. In conclusion, the results of this study imply that there are differences in participants&amp;apos; reading comprehension according to the degree of text simplification or elaboration. Generally simplified versions were more successful in promoting comprehension, especially for lower level students. This study suggests that learners need to be exposed to authentic material, but at some points, modified texts should be provided in order to help students to prepare to read authentic reading materials. And in the course of developing reading materials, the appropriate text types including how to modify texts and how much to modify them should be considered according to learners&amp;apos; proficiency level and each learning situation.Ⅰ. 서론 = 1 Ⅱ. 이론적 배경 = 4 A. 제 2언어 습득과 언어 입력 = 4 B. 텍스트 수정 = 6 1. 진정성 있는 자료와 수정된 자료 = 6 2. 텍스트 수정의 유형 = 7 C. 선행연구 = 11 Ⅲ. 연구 방법 = 20 A. 연구 질문 = 20 B. 연구 대상 = 21 C. 실험 자료 = 23 1. 사전 독해 평가지 = 23 2. 실험 독해 평가지 = 23 D. 실험 절차 및 자료 분석 방법 = 36 1. 실험 절차 = 36 2. 자료 분석 방법 = 37 E. 연구의 제한점 = 38 Ⅳ. 연구 결과 및 논의 = 39 A. 텍스트 수정 유형별 읽기 이해도 비교 = 39 B. 상하위 수준별 텍스트 수정 유형별 읽기 이해도 비교 = 43 C. 읽기 이해 측정 영역별 텍스트 수정 유형별 읽기 이해도 비교 = 47 D. 상하위 수준별 읽기 이해 측정 영역별 읽기 이해도 비교 = 50 Ⅴ. 결론 및 제언 = 58 참고문헌 = 61 부록 = 65 ABSTRACT = 10