Biomedical subjects

K H Yi

Publications and source records attributed to K H Yi.

7 recordsLinked to original sources

PubMed2000

Cellular electrophysiology of fast pathway ablation of rabbit atrioventricular node.

Discrete radiofrequency lesion at the atrial insertion site of the tendon of Todaro in the perfused rabbit preparation lengthens A-H interval, mimicking fast pathway input ablation. This study attempts to define the cellular electrophysiology of the ablation region prior to and after the elimination of fast AV node conduction. In six superfused rabbit AV node preparations, the cellular electrophysiology around the region of the atrial insertion to the tendon of Todaro was recorded using standard microelectrode technique prior to and after ablation. Before ablation, the action potentials recorded in the area of proposed lesion were exclusively from atrial or AN cells. At postablation, the superior margin of the lesion was populated with atrial or AN cells. AN, N, or NH cells bordered the lower part of the lesion. Electrophysiology of surviving cells at the edges of the lesion showed no significant changes in their Vmax, APD50 or APD90 and MDP from preablation values. Fast AV node pathway input ablation in the rabbit heart can be accomplished with a singular lesion around the atrial insertion site of the tendon of Todaro, involving atrial or AN cells. The results of the studies imply that inputs to the compact node may act as a substrate for successful ablation of AV node reentry tachycardia.

Action Potentials↗

PubMed2000

An international feasibility study of parental decision making in pediatric oncology.

PURPOSE/OBJECTIVES: To describe parental decision making about treatment options for children with cancer and determine the feasibility of a similar but larger international study. DESIGN: Exploratory. SETTINGS: A pediatric catastrophic illness research hospital in the United States and children's hospitals in Australia and Hong Kong. SAMPLE: A convenience sample of 43 parents (5 fathers and 38 mothers ages 23-59 years). METHODS: Six open-ended interview questions posed to parents during private individual interviews. Content analysis techniques were used. MAIN RESEARCH VARIABLES: Parental perceptions of (a) factors considered in the decision-making process, (b) behaviors of healthcare professionals that affected the process, and (c) satisfaction with the process. Feasibility of a larger study was estimated by considering ease of access to parents, number of refusals to participate, understanding of the interview questions, and level of interest at each setting. FINDINGS: Access to parents was possible at all sites. Refusal to participate was reported only at the U.S. site. Certain factors (e.g., getting information from the healthcare team, trusting staff) were important to all parents considering end-of-life decisions. Site-specific factors included considering alternative therapies (at the Australian site) and strengthening faith (at the U.S. site). CONCLUSIONS: A larger international study of parental decision making is feasible. Sufficient similarities in parental decision making exist across these sites to justify future efforts to identify universal decision-making factors that, in conjunction with site-specific differences, could be helpful in developing guidelines for healthcare professionals who assist parents in making treatment-related decisions for a sick child.

Adolescent↗

PubMed1996

LC50 of 2-bromopropane.

LC50 of 2-bromopropane was reexamined by using the OECD guideline in ICR mouse. The mice, 3 males and 3 females, were exposed to 2-bromopropane at five different concentrations for 4 h in inhalation chambers. The exposed animals were observed for 14 days. The animals which had survived and died were counted for the LC50 determination. The LC50 was calculated by using a dose-mortality curve at a 95 percent confidence level. The LC50 was 31,171 ppm, and the lowest lethal concentration (LLC) was lower than 29,528 ppm and the lethal concentration at 100% (LC100) was higher than 32,905 ppm.

Administration, Inhalation↗

PubMed1995

High prevalence and little change in TSH receptor blocking antibody titres with thyroxine and antithyroid drug therapy in patients with non-goitrous autoimmune thyroiditis.

OBJECTIVE: We have reevaluated the prevalence and pathogenetic importance of TSH receptor blocking antibodies (TRBAb) in autoimmune hypothyroidism, and investigated the changes in TRBAb activities during thyroxine and antithyroid drug treatment. DESIGN: Serum TSH binding inhibitor immunoglobulin (TBII) and thyroid stimulation blocking antibody (TSBAb) were measured serially in all patients with non-goitrous autoimmune thyroiditis (AT) and measured monthly during methimazole treatment in 6 patients. PATIENTS: Ninety patients with non-goitrous AT and 95 patients with goitrous AT were entered consecutively into this study. All patients with non-goitrous AT were treated with thyroxine and followed at intervals of 6 months for 2 years initially and then yearly intervals. The duration of follow-up was 1-8 years. Six patients from the TRBAb-positive non-goitrous AT group who were treated with thyroxine were randomly selected and given additional treatments with methimazole (40 mg per day) for 6 months. MEASUREMENTS: Serum TBII was measured by a radioreceptor assay, TSBAb by using FRTL-5 cells, and antithyroid peroxidase and antithyroglobulin antibodies by radioimmunoassay. RESULTS: The prevalences of TBII and TSBAb is non-goitrous AT were 47.8 and 58.9%, respectively, which were significantly higher than those in goitrous AT (6.3% for TBII, 10.5% for TSBAb). All but one patient showed persistent TBII and TSBAb activities during the thyroxine treatment for up to 8 years. A high dose of methimazole (40 mg per day) did not affect the titres of TBII and TSBAb in 5 out of 6 patients with non-goitrous AT tested. However, antithyroid peroxidase and antithyroglobulin antibodies activities were significantly decreased during the methimazole treatment. CONCLUSION: The high prevalence of TSH receptor blocking antibodies (TRBAb) suggests that TRBAb may play a major role in the development of hypothyroidism and thyroid atrophy in the vast majority of patients with non-goitrous autoimmune thyroiditis. Most TRBAb activities are stable for at least 8 years and are now affected by thyroxine and antithyroid drug treatment.

Adult↗

PubMed1995

Effect of growth factors on the expression of proto-oncogenes c-fos and c-myc in FRTL-5 cell line.

This study was performed to prove the hypothesis that oncogene expressions would have the same patterns with those of cellular growth to growth factors in FRTL-5 cells. Ribonucleic acids of FRTL-5 were extracted at 15', 30', 60' and 120' after administration of growth factors to quiescent FRTL-5, and blotted to the nitrocellulose membrane. They were hybridized with radiolabelled c-fos, c-myc and beta-actin probes. Hybridized dot blots were autoradiographed and the amount of radioactivity was measured by densitometry. Densitometric readings were used as the indices of oncogene expressions. Expressions of c-fos and c-myc were more prominent in combined administrations of TSH (10 mU/ml) and IGF-I (100 ng/ml) or IgG of Graves' disease (Graves' IgG; 1 mg/ml) and IGF-I than in combined administration of TSH and Graves' IgG. IgG of primary myxedema suppressed oncogene expressions by TSH or Graves' IgG, but not by IGF-I. From the above results, it was suggested that expressions of c-fos and c-myc to growth factors would have similar patterns with those of cell growth to growth factors in FRTL-5, and the actions of TSH and Graves' IgG would be manifested through same signal transduction system, but IGF-I would be manifested by its own.

Animals↗

PubMed1993

Contraceptive practice before female sterilization.

The reproductive profile and contraceptive practice of 402 women undergoing female sterilization at the Central Women's Hospital are presented. Most (89%) of the interviewees were urban-dwellers and housewives with primary school education. Fifty-two percent were between 30 and 34 years with a mean of 4.2 living children. Sixty-nine percent were past contraceptive users, of them; 29.9% had used more than one method. A considerable gap between knowledge and practice of different methods was found. Education level and employment had a significant effect on contraceptive practice (p < 0.01 and p < 0.5). The majority knew and used combined oral contraceptive pills and injectable progestogens, whereas rhythm, withdrawal and barrier contraception were lesser known methods. Contraceptive use was primarily for child-spacing whereas the main reasons for female sterilization were socioeconomic and achievement of desired family size.

Adult↗

PubMed1992

Evaluation of serum basal thyrotrophin levels and thyrotrophin receptor antibody activities as prognostic markers for discontinuation of antithyroid drug treatment in patients with Graves' disease.

OBJECTIVE: We evaluated whether antithyroid drug treatment could be terminated more appropriately when both the serum basal thyrotrophin (TSH) level and TSH receptor antibody activity have become normal. DESIGN: This was a prospective randomized study of patients with Graves' disease followed for a mean of 28 months after the withdrawal of antithyroid drug treatment. PATIENTS AND INTERVENTIONS: A total of 174 patients with hyperthyroid Graves' disease were entered consecutively into this study, 11 of whom were subsequently excluded. One hundred and sixty-three patients were divided randomly into two groups having different criteria for the discontinuation of the antithyroid drug. Group 1 consisted of 79 patients whose antithyroid drug treatment was discontinued if both their serum TSH level and thyrotrophin binding inhibitor immunoglobulin (TBII) activity normalized. Group 2 consisted of 84 patients who were treated for 24 months irrespective of their serum TSH level and TBII activity. All patients were treated initially with 400 mg/day of propylthiouracil followed by decreasing doses that maintained a euthyroid state. MEASUREMENTS: Serum basal TSH levels and TBII activities were measured using a radioimmunometric assay and a radioreceptor assay, respectively, every 2 months during the antithyroid drug treatment. RESULTS: The remission rate of Group 1 (51.9%) was not significantly different from that (63.1%) of Group 2. The mean duration of treatment in Group 1 was 10.2 +/- 4.5 months (range 5-24, median 10). Median duration of treatment in Group 1 was 14 months shorter than in Group 2. In Group 1, the relapse rate was independent of the duration of the treatment. Further, the mean duration of treatment in the relapsed patients was not significantly different from that for patients who went into remission (9.9 +/- 3.8 vs 10.7 +/- 5.7 months; P greater than 0.1). In Group 2, the relapse rate was dependent on the time when both the serum TSH level and TBII activity were normalized (chi 2 = 27.0, d.f. = 4; P less than 0.001). When both the serum TSH level and TBII activity were normalized, the relapse rate of Group 2 was not significantly different from that of Group I for treatment periods of 6-12 months (25 vs 24.2%, P greater than 0.1), 12-18 months (33.3 vs 40%, P greater than 0.1), and 18-24 months (46.2 vs 50%, P greater than 0.1). However, the relapse rate of Group 2 was significantly lower than that of Group 1 when there was only a 6-month treatment period (5.6 vs 42.9%, P less than 0.05). Of the clinical and laboratory parameters measured, male sex, change of goitre size during treatment, and TSH levels and TBII values at the end of treatment, were of prognostic significance in predicting a relapse. CONCLUSION: The present study suggests that antithyroid drugs treatment can be terminated more appropriately when both the serum TSH level and TBII activity are made normal, thus avoiding prolonged and unnecessary drug treatment.

Adult↗