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Biomedical subjects

Y Ahn

Publications and source records attributed to Y Ahn.

At least 19 recordsLinked to original sources
PubMed2005

Geographical difference in the prevalence of isolated systolic hypertension in middle-aged men and women in Korea: the Korean Health and Genome Study.

To compare geographical difference in the prevalence of isolated systolic hypertension (ISH) in between urban (Ansan) and rural (Ansung) Korean adults aged 40-69 years, 4351 men and 4604 women enrolled in the Korean Health and Genome Study were analysed. Information was collected regarding gender, alcohol intake, smoking status, household income, occupation, and years of education by trained interviewers. Eligible subjects included untreated hypertensive and normotensive subjects. ISH was defined as a systolic blood pressure (SBP) > or = 140 mmHg and diastolic BP <90 mmHg. The overall age-adjusted prevalence of ISH was 4.1%. The prevalence of ISH in Ansung (5.7%) was higher than in Ansan (2.5%, P < 0.05). Also it increased with increments of age, from 1.0 to 12.8% in Ansung (P < 0.05) and from 0.3 to 13.0% in Ansan (P < 0.05). In those with body mass index (BMI) > or = 30.0 kg/m2 in Ansung, the prevalence of ISH in women was twice as much as in men. The prevalence of ISH in obese men and women with a waist-hip ratio > or =1.0 and > or = 0.85, respectively, was more than that of nonobese men and women in both areas. In Korea, because of industrialization, the age distribution was skewed and the Korean population in rural areas is more aged. ISH will become a truly major health problem in rural area, because ISH is related to age, BMI and waist-hip ratio. Therefore, the Korean government will be required to institute different policies in the hypertension management to target populations in rural and urban areas.

Female↗
PubMed2004

Factors predicting excellent outcome of percutaneous cervical discectomy: analysis of 111 consecutive cases.

Percutaneous cervical discectomy (PCD) has been developed as an effective treatment option for soft cervical disc herniation. However, no prognostic study of this procedure has yet been made. The purpose of this study was to evaluate the surgical outcome of PCD and to determine the factors predicting excellent outcome. A retrospective review was performed of 111 consecutive patients who underwent PCD with a mean follow-up period of 49.4 months (range, 29-64 months). Under local anesthesia, a percutaneous anterior approach was followed by discectomy with microforceps and endoscopic Ho:YAG laser. The surgical outcomes of the 111 patients based on the Macnab criteria were excellent in 52 patients (46.9%), good in 37 (33.3%), fair in 9 (8.1%), and poor in 13 (11.7%), thereby indicating a symptomatic improvement in 88.3% of the patients. In this study, the two major factors predicting an excellent long-term outcome were the symptom of radiating arm pain (P = 0.02) and the location of lateral disc herniation (P < 0.02). Proper patient selection remains critical for the success of this minimally invasive procedure.

Adult↗
PubMed2004

Pacemaker syndrome.

Explore the source record for details and available documents.

Arrhythmias, Cardiac↗
PubMed2003

Hydrolysis and acidogenesis of particulate organic material in mesophilic and thermophilic anaerobic digestion.

The purpose of this study was to evaluate the effect of pH and inorganic nutrient supplementations for anaerobic hydrolysis and acidogenesis of particulate organic materials at both mesophilic (35 degrees C) and thermophilic (55 degrees C) temperatures. Hydrolysis and acidogenesis of a synthetic sludge was observed in batch operation for the evaluation of the pH effect. pH was uncontrolled in one reactor and controlled at 4.5, 5.5, and 6.5 in the other three reactors at both temperatures. The greatest degree of hydrolysis and acidogenesis occurred when the pH was controlled at 6.5. The pH of the uncontrolled reactor dropped to 3.4 at both temperatures severely retarding hydrolysis and acidogenesis. Concentrations of acetic and n-butyric acids predominated with lower concentrations of propionic acid at both temperatures in all reactors. Lactic acid was produced as the earliest intermediate but as the reaction proceeded, short chain VFAs were produced as final end products with a decrease in lactic acid. The higher the pH, the earlier this trend was observed. For the controlled reactors at pH 6.5, the soluble COD production and the VSS reduction peaked in 4 days at 55 degrees C whereas it took about 11 days at 35 degrees C to obtain the same result. During the linear SCOD production period at a pH of 6.5 the hydrolysis rate of the thermophilic reactor was greater than that for mesophilic. Thermophilic conditions appeared to be more sensitive to pH than mesophilic ones for both hydrolysis and acidogenesis. Additional experiments were conducted to establish the effect of inorganic nutrient (Ca, Fe, Co, and Ni) supplementation on hydrolysis and acidogenesis at both temperatures. It has, prior to this, been assumed that only methanogenesis benefited from trace metal supplementation. However, the results demonstrated the importance of inorganic nutrient supplementation to optimize hydrolysis and acidogenesis at both temperatures.

Bacteria, Anaerobic↗
PubMed2002

Physicochemical characterization of UASB sludge with different size distributions.

Upflow anaerobic sludge blanket (UASB) sludges developed in UASB system are used to treat various wastewaters. Methanogenic microbial consortia in UASB sludges convert organic compounds to methane under anaerobic conditions. Sludge granules are developed by self-granulation of microorganisms and dynamic balance between granule growth and decay results in coexistence of UASB sludges with different sizes in the reactor. In this study, UASB sludges taken from a laboratory-scale UASB reactor were classified into 4 groups based on their diameters and their physicochemical characteristics were investigated. Each group was analyzed for settling ability, specific methanogenic activity (SMA), and elemental content. Settling ability was proportional to diameter of UASB sludges, suggesting effective detainment of larger granular sludges in the reactor. When acetate o r glucose was used as a substrate, a ll groups showed a relatively slight difference in SMA. However SMA with a volatile fatty acid mixture showed a significant increase with sludge diameter, suggesting better establishment of syntrophic relationship in larger granular sludges. Larger granular sludges showed a higher value of SMA upon environmental changes(ie., pH, temperature, or toxicant concentration). Comparative analysis of elemental contents showed that content (dry weight %) of most tested elements (Fe, Ca, P, Zn, Ni, and Mn) decreased with sludge diameter, suggesting that the elements could be important for initial granulation. Taken together, this study verified experimentally that physicochemical properties of UASB sludges are related to UASB sludge size distributions. Overall results of physicochemical characterization supports that larger granular sludges are better applicable to UASB systems.

Bacteria, Anaerobic↗
PubMed2002

The role of pH in mesophilic anaerobic sludge solubilization.

The effect of pH on anaerobic solubilization of synthetic sludge (dog food) and domestic primary sludge was investigated and compared. Anaerobic solubilization was carried out in Continuously Stirred Anaerobic Reactors at mesophilic temperature (35 degrees C) and pH was fixed at 6.5 (pH-controlled). The aim of pH control in the reactors consisting of synthetic and primary sludge, was the evaluation of retardation in hydrolysis/acidogenesis at low pH values. Since synthetic and primary sludge have different biodegradation characteristics, the results were compared. In both sludges, acetic acid was the main Volatile Fatty Acids (VFAs) produced. Volatile Suspended Solid (VSS) reduction was found as 67% in about 20 days in the anaerobic digestion of synthetic sludge. whereas for the same interval VSS reduction could only be achieved by 32% in primary sludge at 35 degrees C in the pH-controlled reactors. When both types of sludges were used as substrates, the reactors removed VSS with a corresponding production of VFAs and Soluble Chemical Oxygen Demand (SCOD). However, in the pH-controlled reactors production of VFAs and SCOD was ceased after 5 days in primary sludge whereas VFAs and SCOD production continued after 5 days in synthetic sludge which indicated that hydrolysis and fermentation in the anaerobic solubilization reactors were not complete and continued longer. On the other hand, in the pH-controlled reactor of primary sludge, methanogenic phase could operate after 5 days of operation as hydrolysis/acidogenesis stopped.

Bacteria, Anaerobic↗
PubMed2001

Total synthesis of (+/-)-martinellic acid.

A 14-step synthesis of martinellic acid (1) that proceeds in 3% overall yield has been completed using the reaction of aniline 11 with Meldrum's acid-activated vinylcyclopropane 4 to give vinyl pyrrolidinone 12, condensation of aldehyde 13 with N-benzylglycine to form an azomethine ylide that cyclizes to give 14, selective reduction of 14 to amino alcohol 16 with LiBH(4) and MeOH, and guanidine formation by reaction of a cyanamide with 3-methyl-2-buten-1-amine in hexafluoro-2-propanol at 120 degrees C as key steps. [structure: see text]

Bignoniaceae↗
PubMed2001

Studies toward gymnodimine: development of a single-pot Hua reaction for the synthesis of highly hindered cyclic imines.

[structure: see text]. In studies directed toward gymnodimine and related marine toxins, a single-pot variation of the Hua cyclic imine synthesis has been developed. The reaction involves generation of N-trimethylsilyl lactams in situ followed by alkyllithium addition leading directly to cyclic imines. Importantly, this reaction proceeds efficiently with highly hindered alpha,alpha-dialkyl lactams, provided 1,2-dimethoxyethane (DME) is used as solvent, leading to stable cyclic imines. Overall, this transformation allows a one-pot coupling of an alkyliodide and a lactam to give a cyclic imine.

Animals↗
PubMed2001

Prevalence, awareness, treatment, control and risk factors of hypertension in Korea: the Ansan study.

OBJECTIVES: To determine prevalence, awareness, treatment, and control of hypertension, and its risk factors in an urban Korean population. DESIGN AND SETTING: A cross-sectional survey in Ansan-city, Korea. SUBJECTS AND METHODS: Population-based samples of people aged 18-92 years in Ansan-city, Korea, were selected, yielding 2278 men and 1948 women, and their blood pressures were measured using a highly standardized protocol. Hypertension was defined as a systolic BP > or = 140 mmHg or diastolic BP > or = 90 mmHg or reported treatment with antihypertensive medications, and subclassified according to 1999 WHO-ISH guidelines. Isolated systolic hypertension (ISH) defined as a systolic BP > or = 140 mmHg and diastolic BP < 90 mmHg was also examined. Data were stratified by age and sex. RESULTS: The overall prevalence of hypertension in this study was 33.7%. Among these, 64.9% had Grade 1 hypertension, 22.5% Grade 2, and 12.5% Grade 3. Age-specific prevalence of hypertension increased progressively with age, from 14.19% in 18 to 24 year-olds to 71.39% in those 75 years or older. Hypertension prevalence was significantly higher in men (41.5%) than in women (24.5%) (P < 0.001). Isolated systolic hypertension had significantly lower prevalence (4.33%) within the population, although in the elderly aged 55 years or more it rose by 11.13%. Overall, 24.6% of hypertensive individuals were aware that they had high blood pressure, as much as 78.6% were being treated with antihypertensive medications, and 24.3% were under control. Hypertension awareness as well as treatment and control rates varied by sex, with women higher in all three rates. Multivariate analysis revealed that age, body mass index and abdomen circumference were significantly associated with prevalence of hypertension both in men and women. CONCLUSIONS: Hypertension is highly prevalent in Korea. Despite the high rate of treatment, the rates of awareness and control are relatively low, suggesting the nationwide demand for preventing and controlling high blood pressure in Korea in order to avert an epidemic of cardiovascular disease.

Adult↗
PubMed2001

Interim assessment of a community intervention to improve breast and cervical cancer screening among Korean American women.

Breast and cervical cancer screening practices are suboptimal among Korean American women. A community intervention program was launched in 1996 to improve breast and cervical cancer screening among Korean American women in Alameda County, California. After 18 months, interim program assessment revealed that mammograms improved, but Pap smears, breast self-examinations, and clinical breast examinations did not change significantly. However, results were similar for the control county probably because the program was not implemented fully. Several strategies for improving program implementation are discussed including recommendations for researchers planning community intervention projects.

Adult↗
PubMed2000

Identification of transacting factors responsible for the tissue-specific expression of human glucose transporter type 2 isoform gene. Cooperative role of hepatocyte nuclear factors 1alpha and 3beta.

We investigated transacting factors binding to the cis-element important in tissue-specific expression of the human glucose transporter type 2 isoform (GLUT2) gene. By transient transfection assay, we determined that the 227-base pair fragment upstream of the ATG start site contained promoter activity and that the region from +87 to +132 (site C) was responsible for tissue-specific expression. DNase I footprinting and electrophoretic mobility shift assay indicated that site C contained one binding site for hepatocyte nuclear factor 1 (HNF1) and two binding sites for HNF3. The mutations at positions +101 and +103, which are considered to be critical in binding HNF1 and HNF3, resulted in a 53% decrease in promoter activity, whereas the mutation of the proximal HNF3 binding site (+115 and +117) reduced promoter activity by 28%. The mutations of these four sites resulted in marked decrease (70%) in promoter activity as well as diminished bindings of HNF1 and HNF3. A to G mutation, which causes conversion of the HNF1 and HNF3 binding sequence to the NF-Y binding site, resulted in a 22% decrease in promoter activity. We identified that both HNF1 and HNF3 function as transcriptional activators in GLUT2 gene expression. Coexpression of the pGL+74 (+74 to +301) construct with the HNF1alpha and HNF3beta expression vectors in NIH 3T3 cells showed the synergistic effect on GLUT2 promoter activity compared with the expression of HNF1alpha, HNF3beta, or a combination of HNF1beta and HNF3beta. These data suggest that HNF1alpha and HNF3beta may be the most important players in the tissue-specific expression of the human GLUT2 gene.

Base Sequence↗
PubMed2000

Clinical feature and outcome of pediatric cerebrovascular disease: a neurosurgical series.

To investigate the clinical features and surgical outcome of pediatric cerebrovascular disease (CVD), we retrospectively reviewed 280 children (up to 15 years of age) who underwent neurosurgical procedures for CVD between 1979 and 1998. Open surgery (n=448), endovascular procedures (n=22), and stereotactic radiosurgery (n=14) were the main neurosurgical procedures adopted. Clinical features and surgical outcomes were described according to the etiology of the CVD and the number of years of management. The mean duration of follow-up was 34 months. The mean age was 7.1 years, and the male-to-female ratio was 1.2:1. The most frequent CVD was moyamoya disease (62%). The surgical mortality related to CVD was 0.7%. Eighty-seven percent had Karnofsky Performance Scale scores of more than 70. We demonstrate increasing detection rates and improving outcomes in recent years. The clinical course in this study shows that recovery from CVD in children is good after neurosurgical procedures.

Adolescent↗
PubMed2000

The influence of gastrectomy on the change of bone metabolism and bone density.

OBJECTIVES: Abnormalities of bone metabolism could be followed in gastrectomized patients as a late complication. Nowadays, many biochemical and radiologic measurements are applied to detect these abnormalities. The aim of our study is to determine the valuable parameter as an appropriate screening test during long-term follow-up periods and define the usefulness of new biochemical markers for bone metabolism by comparing with traditional markers. METHODS: Fifteen patients who had undergone partial gastrectomy were chosen randomly and fifteen healthy controls were compared. Then, several biochemical and radiologic tests were measured. We excluded subjects who proved to have other causes of bone metabolism abnormalities. Ten patients and 10 controls were finally selected. RESULTS: Comparing the data with those of a corresponding control group, the lumbar bone density measured by quantitative computed tomography (QCT) was statistically significantly lower in the patient group (p < 0.01). The urinary deoxypyridinoline, a biochemical marker for bone resorption, was statistically higher in the patient group (p < 0.025). Osteocalcin, Procollagen I C-terminal peptide (PICP) and Type I collagen C-terminal telopeptide (ICTP) were slightly but not significantly higher in the patient group. The serum parathyroid hormone (PTH) and 25-hydroxy vitamin D levels were similar in both groups. CONCLUSION: We could suggest that urinary deoxypyridinoline and QCT are appropriate parameters as screening tests for the detection of bone metabolism abnormalities in gastrectomized patients during long-term follow-up. Urinary deoxypyridinoline may be a simple and rapid test which could replace cumbersome 24-hour urinary hydroxyproline.

Absorptiometry, Photon↗
PubMed1999

Selection of Drosophila genes encoding secreted and membrane proteins.

With the use of a yeast-based signal sequence trap (YSST) method, we screened a Drosophila cDNA library to isolate genes encoding secreted and membrane proteins. Of the 136 unique cDNA clones sequenced, 11 clones (8.1%) are identical to previously known Drosophila genes, 18 clones (13.2%) are homologous to other genes identified in various organisms, and 91 clones (66.9%) are novel. Most of these genes are secreted or membrane proteins, or appear to contain putative signal sequences at their amino termini. This indicates that YSST is an effective tool for the isolation and analysis of Drosophila genes that play roles in intercellular communication.

Animals↗
PubMed1999

Analyses of polycyclic aromatic hydrocarbon-degrading bacteria isolated from contaminated soils.

Polycyclic aromatic hydrocarbon (PAH)-degrading bacteria isolated from PAH-contaminated soils were analyzed genotypically and phenotypically for their capacity for metabolism of naphthalene and other PAH substrates. The methods used for the analyses were DNA hybridization using NAH7-derived gene probes, PAH spray plate assays, 14C-PAH mineralization assays, and dioxygenase activity assays. The results of the analyses showed a dominant number of PAH-degrading bacteria with a NAH7-like genotype. The results support the continued use of the nahA probe for contaminated soils to monitor the genetic potential of indigenous microorganisms to degrade PAHs. However, the finding of non-nahA-hybridizing PAH-degrading bacteria show the limitation of NAH7-derived gene probes. Fifteen percent (13/89) of PAH-degrading bacteria isolated were not detected with the nahA gene probe. Four isolates (designated A5PH1, A8AN3, B1PH2, and B10AN1) did not hybridize with any of the NAH7-derived gene probes (nahA, nahG, nahH, and nahR) used in this study. Considering the numerous unculturable microorganisms in nature and their potential genotypes, NAH7-derived gene probes may underestimate the microbial potential to catabolize PAHs. This necessitates development of new gene probes for enumeration and isolation of PAH-degrading bacteria to better understand the in situ microbial potential to degrade PAHs.

Bacteria↗