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Biomedical subjects

D H Kang

Publications and source records attributed to D H Kang.

At least 91 records · Page 5Linked to original sources
PubMed1998

Intravascular ultrasound findings in stenting of unprotected left main coronary artery stenosis.

We evaluated the role of intravascular ultrasound (IVUS) in 16 patients with unprotected left main coronary artery (LMCA) stenting compared with 80 patients with other (non-LMCA) native coronary artery stenting and found that (1) additional high-pressure or larger size balloon dilations were more frequently performed in LMCA stenting than in non-LMCA stenting (p <0.05) and (2) after IVUS-guided stent implantation, minimum lumen area was > or = 9 mm2 in 88% of patients who underwent LMCA stenting and in 19% of those who underwent non-LMCA stenting (p <0.001). IVUS guidance may be a more important adjunctive imaging modality in the stenting of unprotected LMCA stenoses than in stenting of non-LMCA stenoses.

Aged↗
PubMed1998

Clinical and echocardiographic outcomes of aortic intramural hemorrhage compared with acute aortic dissection.

Aortic intramural hemorrhage (IMH), which presents clinical manifestations identical to those of acute aortic dissection, is different from aortic dissection in terms of the absence of intimal tear and communication of blood flow between the true and false lumen. This study was conducted for the purpose of diagnosing IMH by transesophageal echocardiography (TEE) prospectively and comparing the clinical and echocardiographic outcome of IMH with aortic dissection. Between August 1991 and November 1996, 27 IMHs and 73 acute aortic dissections were diagnosed using TEE in 202 consecutive patients with suspected aortic dissections. The TEE diagnoses of IMH and aortic dissection were initially compared with computed tomography and magnetic resonance imaging and later confirmed by operative findings (n = 37) or follow-up changes (n = 12). In the 49 patients whose diagnosis was confirmed by operation or follow-up changes, the sensitivity and specificity of TEE for the diagnosis of IMH were 27 of 27 (100%) and 20 of 22 (91%), respectively. There were 11 deaths in 73 patients (15%) from acute aortic dissection and 1 death in 27 patients (4%) from IMH during a follow-up of 1.7+/-1.5 years (p = NS). Stanford classification and types of treatment were not related to death in both groups. Complications developed less often in patients with IMH (3 of 27) than in those with acute aortic dissection (24 of 73), and no death occurred in patients with uncomplicated IMH who were medically treated. A follow-up imaging study of 12 IMH patients showed complete resolution in 8, regression in 3, and progression in 1 patient. TEE is accurate in the diagnosis of IMH and IMH has a lower incidence of complications than aortic dissection because of the absence of intimal tear and communication of blood flow in the false lumen.

Acute Disease↗
PubMed1998

Comparison of outcomes of percutaneous mitral valvuloplasty versus mitral valve replacement after resolution of left atrial appendage thrombi by warfarin therapy.

This study assesses the efficacy of oral anticoagulation in resolving left atrial appendage (LAA) thrombi and evaluates clinical outcomes of percutaneous mitral valvuloplasty after resolution of LAA thrombi compared with mitral valve replacement. Warfarin therapy is successful in resolving LAA thrombi; percutaneous mitral valvuloplasty after resolution of LAA thrombi is an effective alternative to surgical treatment.

Aged↗
PubMed1998

Relationship of social support to stress responses and immune function in healthy and asthmatic adolescents.

Although most clinicians believe that social support has beneficial effects on health, the mechanisms mediating this relationship have not been clearly established. We examined the direct effect of social support on several immune measures and its role in moderating the response to academic exams in healthy and asthmatic adolescents. Three types of students--healthy, mild asthma, and severe asthma--completed social support and stress questionnaires and gave blood samples during the midsemester and final exam periods. Social support and natural killer cell (NK) function showed a significant reduction during exams in both healthy and asthmatic adolescents. Social support, however, did not have a direct effect on immune responses. Nevertheless, high social support appeared to attenuate the magnitude of exam-induced reduction in NK activity, suggesting a role for social support in protecting against immune decrements during times of stress.

Adolescent↗
PubMed1998

Acute effects of recombinant human erythropoietin on plasma levels of proendothelin-1 and endothelin-1 in haemodialysis patients.

BACKGROUND: The pathogenesis of rHuEpo-induced hypertension in haemodialysis (HD) patients still remains uncertain. Endothelin-1 (ET-1) is produced from proendothelin-1 (proET-1) by an endothelin-converting enzyme. Since proET-1 is known to have approximately 1/100 the potency of ET-1 for contracting an isolated blood vessel, the change in the activity of endothelin-converting enzyme (ECE) has been proposed as an important factor in the pathophysiology of various hypertensive diseases. However there is no report on whether a change in the rate of conversion of proET-1 to ET-1 may be involved in the pathogenesis of rHuEpo-induced hypertension. The purpose of this study was to ascertain the potential role of ECE in the development of rHuEpo-induced hypertension. METHODS: The levels of plasma erythropoietin, proET-1, ET-1, and mean arterial blood pressure (MAP) were measured following a single dose of rHuEpo (100 U/kg) in HD patients with 24-h ambulatory blood pressure monitoring. Different routes of administration (19 intravenous group, 10 subcutaneous group) were compared to a placebo-injected control group (10 HD patients). RESULTS: Plasma erythropoietin levels reached maximal value 5 min after i.v. injection of rHuEpo (13.1+/-2.4 vs 2780.9+/-290.1 mU/ml, P<0.01), whereas it was 6 h in the s.c. group (14.7+/-3.8 vs 38.9+/-17.7 mU/ml, P<0.05). A significant increase in MAP was noted 30 min after rHuEpo injection, which lasted for 3 h in the i.v. group. However, no significant changes in MAP were noted in patients given rHuEpo subcutaneously. Both the plasma concentrations of proET-1 and ET-1 started to increase from 10 min after i.v. rHuEpo administration, with the proET-1 reaching a peak level at 30 min (13.5+/-7.4 vs 21.6+/-3.8 pg/ml, P<0.05) and the ET-1 at 1 h (4.2+/-2.6 vs 9.9+/-4.8 pg/ml, P<0.05). In patients with significant interdialysis hypertension following a single i.v. injection of rHuEpo, the molar ratio of ET-1 over proET-1 (ET-1/proET-1) was significantly higher than in patients without hypertension. In addition, the increase in ET-1 levels was significantly greater in patients with interdialysis hypertension, while changes in proET-1 level were similar in both hypertensive and non-hypertensive groups. Changes in interdialysis MAP (delta IDMAP) was significantly correlated with delta ET-1 during the interdialysis period, but not with delta proET-1. CONCLUSION: Differences in ET-1/proET-1 ratio in relation to changes in MAP after a single intravenous administration of rHuEpo suggest a potential role for ECE in the pathogenesis of rHuEpo-induced hypertension.

Adult↗
PubMed1998

Endoscopic treatment in a case with extensive spontaneous intramural dissection of the oesophagus.

Spontaneous intramural dissection of the oesophagus has been recognized as a separate clinical entity between a transmural oesophageal rupture (Boerhaave syndrome) and an oesophageal mucosal tear (Mallory-Weiss syndrome). It is important to differentiate this condition from myocardiac infarction, dissecting aneurysm and other acute surgical conditions. Conservative management is usually thought to be adequate. We report a case of spontaneous intramural oesophageal dissection, in which the symptom of dysphagia did not improve with the conservative management and an endoscopic incision of the septum between true and false lumens using a needle-type diathermy knife was done safely and effectively.

Endoscopy↗
PubMed1997

Cytokine profiles of stimulated blood lymphocytes in asthmatic and healthy adolescents across the school year.

T cell cytokines play an important role in mediating airway inflammation in asthma. The predominance of a Th2 cytokine profile, particularly interleukin (IL)-4 and IL-5, is associated with the pathogenesis and course of asthma. The aim of this study was to test the hypothesis that a stressful life event alters the pattern of cytokine release in asthmatic individuals. Thirteen healthy controls and 21 asthmatic adolescents gave blood samples three times over a semester: midsemester, during the week of final examinations, and 2-3 weeks after examinations. Interferon-gamma (IFN-gamma), IL-2, IL-4, and IL-5 were measured from supernatants of cells stimulated with PHA/PMA for 24 h. Cells from asthmatic subjects released significantly more IL-5 during the examination and postexamination periods, whereas cells from healthy controls released significantly more IL-2 during the midsemester and examination periods, thereby indicating a bias for a Th2-like pattern in asthmatics and a Th1-like pattern in healthy controls. IL-4 and IL-5 production showed a marked decrease during and after examinations in healthy controls, whereas this decline was absent in asthmatics. The ratios of IFN-gamma:IL-4 and IFN-gamma:IL-5 also revealed significant changes in the profile of cytokine release across the semester. These results indicate differential cytokine responses in asthmatics that may become pronounced during periods of cellular activation.

Adolescent↗
PubMed1996

Increased basal tone and hyperresponsiveness to acetylcholine and ergonovine in spasm-related coronary arteries in patients with variant angina.

We compared the basal coronary artery tone and the constrictive responses to acetylcholine (Ach) and ergonovine (Erg) among three groups of patients: 31 patients (group 1) with variant angina in whom spasm was provoked by low doses of acetylcholine (intracoronary 20 micrograms) or ergonovine (intravenous 50 micrograms); 35 patients (group 2) in whom spasm was provoked by higher doses of acetylcholine (intracoronary 100 micrograms) or ergonovine (intravenous cumulative dose of 350 micrograms); and 26 control subjects. Patients with variant angina in whom spasm was provoked by low doses of acetylcholine or ergonovine, had a higher incidence of coexisting angiographic evidence of coronary artery disease, multi-vessel spasm and more frequent episodes of angina. The basal coronary artery tone at the spastic and non-spastic sites of the spasm-related artery was significantly elevated in group 1 compared to group 2 (44 +/- 17 vs. 14 +/- 11% and 26 +/- 14 vs. 16 +/- 10%, respectively, P < 0.05), but not in the non-spasm related artery. The magnitude of vasoconstrictive responses to acetylcholine and ergonovine at the non-spastic sites was also greater in group 1 than in group 2 and the control groups (acetylcholine: 40 +/- 20 vs. 26 +/- 11, 27 +/- 12%; ergonovine: 37 +/- 18 vs. 12 +/- 8, 13 +/- 10%, respectively, P < 0.05). However, the basal coronary artery tone was not elevated at the spastic and non-spastic sites in group 2 compared to that in the control subjects. These findings suggest that the basal coronary artery tone is increased in patients with variant angina, with increased frequency of angina suggestive of higher disease activity at the spastic and non-spastic sites of the spasm-related artery, and this may be related to pathogenesis of coronary artery spasm.

Acetylcholine↗
PubMed1996

Academic examinations significantly impact immune responses, but not lung function, in healthy and well-managed asthmatic adolescents.

The influence of academic examinations on immunity and lung function was investigated in 64 adolescents to determine if stress-related changes would differ between healthy and asthmatic students. Blood samples were collected on three occasions: 1 month prior, during, and 2-3 weeks after exams. Leukocyte subsets were enumerated, and in vitro assays were conducted to assess lymphocyte proliferative and cytolytic responses and neutrophil production of superoxides. Examinations elicited significant changes in several lymphocyte subsets and marked alterations in the three functional measures in all students. However, the magnitude and pattern of change did not differ between healthy and asthmatic students. Similarly, neither mild nor more severe asthmatics showed an exam-related decrement in lung function, as reflected by peak expiratory flow rate. This research validated that examinations are a salient cause of altered immune responses, but indicates that there is not a concomitant aggravation of inflammatory disease in well-managed asthmatics.

Adolescent↗
PubMed1996

Ergonovine echocardiography as a screening test for diagnosis of vasospastic angina before coronary angiography.

OBJECTIVES: In patients with chest pain suggestive of variant angina, we performed this prospective study to test the specificity and diagnostic validity of ergonovine echocardiography (detection of regional wall motion abnormality during bedside ergonovine challenge) as a screening procedure before coronary angiography. BACKGROUND: Spasm provocation test outside the catheterization room has generally not been accepted as a safe diagnostic method. METHODS: Ergonovine echocardiography was performed in 80 consecutive patients with chest pain syndrome after confirmation of negative treadmill or normal stress myocardial perfusion scan results using thallium-201. A bolus of ergonovine maleate was injected at 5-min intervals up to a total cumulative dosage of 0.35 mg with echocardiographic monitoring of left ventricular wall motion. A 12-lead electrocardiogram (ECG) was also recorded every 3 min after each ergonovine injection. Positive test results were development of regional wall motion abnormalities or transient ST segment elevation or depression >0.1 mV in any single lead of the 12-lead ECG. Coronary angiography was undertaken within 2 +/- 4 days (mean +/- SD) after ergonovine echocardiography, and the spasm provocation test with acetylcholine or ergonovine was performed in patients with normal angiographic findings or lumen diameter narrowing <70%. RESULTS: On the basis of angiographic criteria, 56 patients had coronary vasospasm; this finding was later ruled out in 19 patients with near-normal angiographic results by a negative response on the spasm provocation test. In the remaining five patients, coronary spasm provocation was not performed because they revealed a high degree of fixed stenosis (lumen diameter narrowing 97 +/- 4%). Ergonovine echocardiography could diagnose coronary vasospasm before angiography, with a sensitivity of 91% (51 of 56 patients, 95% confidence interval [CI] 84% TO 98%) and specificity of 88% (21 of 24 patients, 95% CI 75% to 100%). Of 53 patients showing regional wall motion abnormalities during ergonovine echocardiography, characteristic ST segment elevation in the simultaneously recorded ECG was observed in only 20 (38%). There were no complications, including myocardial infarction or fatal arrhythmia, during the test. CONCLUSIONS: Ergonovine echocardiography before coronary angiography is safe and can be used as a reliable diagnostic screening test for coronary vasospasm in patients with negative treadmill or normal stress myocardial perfusion scan results. These findings suggest that invasive coronary angiography can be avoided in selected patients for the diagnosis of vasospastic angina.

Adult↗
PubMed1996

Increased basal tone and hyperresponsiveness to acetylcholine and ergonovine in spasm related coronary arteries in patients with variant angina--basal coronary artery tone in patients with variant angina.

In patients with variant angina, previous data have been inconclusive as to whether basal coronary artery tone is elevated at the spastic and non-spastic sites. Thus, the purpose of this study was to assess the basal coronary artery tone and the responsiveness to acetylcholine (Ach) and ergonovine (Erg) in patients with variant angina. We compared the basal coronary artery tone and the constrictive responses to Ach and Erg between 31 patients (Group 1) with variant angina in whom spasm was provoked by the low doses of Ach (intracoronary 20 micrograms) or Erg(intravenous 50 micrograms) and 35 patients (Group 2) provoked by higher doses of Ach (intracoronary 100 micrograms) or Erg (intravenous cumulative dose of 350 micrograms), and 26 control subjects. Patients with variant angina in whom spasm was provoked by low doses of Ach or Erg, had a higher incidence of mixed disease, multi-vessel spasm and higher disease activity. The basal coronary artery tone at the spastic and nonspastic sites of spasm related artery was significantly more elevated in Group 1 than that in Group 2 (44 +/- 17 vs 14 +/- 11% and 26 +/- 14 vs 16 +/- 10% respectively, P < 0.05), but not in the nonspasm related artery, The magnitudes of vasoconstrictive responses to Ach and Erg at the nonspastic sites were also greater in Group 1 than those in Group 2 and the control groups (Ach; 40 +/- 20 vs 26 +/- 11, 27 +/- 12%: Erg; 37 +/- 18 vs 12 +/- 8, 13 +/- 10% respectively, P < 0.05). However, the basal coronary artery tone was not elevated at the spastic and nonspastic sites in Group 2 compared to the in control subjects. These findings suggest that the basal coronary artery tone is increased in patients with variant angina with higher disease activity at the spastic sites and nonspastic sites of the spasm-related artery, and this may be related to the occurrence of coronary artery spasm.

Acetylcholine↗
PubMed1995

Interindividual differences in the concentration of 1-hydroxypyrene-glucuronide in urine and polycyclic aromatic hydrocarbon-DNA adducts in peripheral white blood cells after charbroiled beef consumption.

Biological markers of internal dose and macromolecular dose from PAHs provide a potential means of assessing environmental exposure to PAHs through inhalation, ingestion and percutaneous absorption. In this study we examined the time course and interindividual variation of 1-hydroxypyrene-glucuronide (1-OHP-gluc) excretion in urine and PAH-DNA adduct formation in peripheral white blood cells (WBCs) after charbroiled (CB) beef consumption. As a marker of internal dose, 1-OHP-gluc was measured in human urine using immunoaffinity chromatography and synchronous fluorescence spectroscopy. PAH-DNA adducts were measured in WBCs by enzyme-linked immunosorbent assay (ELISA) in order to assess macromolecular dose. Ten healthy non-smoking males consumed identical amounts of CB beef on five consecutive days. Multiple blood and urine samples were collected before, during, and after the feeding period. The morning after the first day of CB beef consumption, individual urinary concentrations of 1-OHP-gluc increased 10- to 80-fold (range: 2.0-16.6 pmol/ml urine) above pre-feed baseline concentrations (0.23 +/- 0.11 pmol/ml) in the 10 subjects. 1-OHP-gluc concentration decreased to near baseline levels by 24-72 h after CB beef consumption ended. In contrast, PAH-DNA adducts in WBCs increased markedly in only four of 10 subjects during or after CB beef consumption. Significant interindividual variation was observed for both urinary 1-OHP-gluc concentration (P < 0.001 by Kruskal-Wallis) and PAH-DNA adduct levels (P < 0.005) during the feeding period. The mean urinary 1-OHP-gluc concentration for each subject during and immediately after (days 2-8) the feeding period was significantly correlated with their mean PAH-DNA adduct level in WBCs during the same time period (Spearman r = 0.79, P < 0.01). Evidence of segregation of the subjects into separate response groups based on level of urinary 1-OHP-gluc was observed, suggesting that discrete determinants may regulate the absorption, metabolism and/or excretion of ingested pyrene.

Adult↗
PubMed1994

The effect of psychological stress on neutrophil superoxide release.

Stress has long been suggested to exacerbate symptom expression in people with chronic inflammatory disorders. The release of oxidative metabolites from activated PMN plays a significant role in the pathophysiology of inflammation. Thus, we examined the effects of psychological stress on release of superoxide anions from PMN of rats with or without an inflammation induced by injection of shellfish glycogen (SFG). Psychological stress was found to significantly increase PMN superoxide release in both healthy and SFG-injected animals. Total amounts of superoxide release were similar between the two groups, suggesting that PMN from animals with a mild inflammatory condition were not more susceptible to the effects of stress than PMN from healthy animals. However, this study should be repeated using an animal model of chronic inflammation, such as airway hyperactivity or rheumatoid arthritis.

Analysis of Variance↗
PubMed1994

Fatty acids directly increase the activity of Ca(2+)-activated K+ channels in rabbit coronary smooth muscle cells.

The large conductance Ca2+ activated K+ channel (BK channel) has been considered to play an important role in the excitability and contractility of vascular smooth muscle cells. Activation of the BK channel causes the hyperpolarization and relaxation of vascular smooth muscle cells. It has been reported that fatty acids can affect the BK channel activity and its concentration is increased significantly during myocardial ischemia. These reports suggest that fatty acids may contribute to the ischemic coronary vasodilation by increasing the BK channel activity. However, the underlying mechanism of fatty acid-induced activation of the BK channel is still uncertain. In the present study, we measured the effect of fatty acids on the BK channel activity in rabbit coronary smooth muscle cells by using patch clamp method and also examined its underlying mechanism. Arachidonic acid (AA) dissolved in DMSO activated the BK channel in a dose-dependent manner (from 0.5 to 10 microM), and DMSO (0.1%) alone had no effect on the activity of the BK channel. Arachidonic acid activated BK channels in both cell-attached and inside-out patches, but the onset and recovery of this effect were slower in the cell-attached patch configuration. The BK channel activity was also increased by other fatty acids, including myristic acid, linoleic acid, palmitoleic acid and palmitic acid. Long chain fatty acids were more effective than short chain fatty acids (myristic acid), and there was no statistical difference between the effect of saturated (palmitic acid) and unsaturated fatty acids (palmitoleic acid) on the BK channel activity. The concentration of Ca2+ and Mg2+ in the bathing solution had no appreciable effects on the AA-induced increase of BK channel activity. From the above results, it may be concluded that fatty acids directly increase the BK channel activity and may contribute to the ischemic coronary vasodilatation in rabbit coronary smooth muscle cells.

Animals↗