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Biomedical subjects

H S Chung

Publications and source records attributed to H S Chung.

At least 37 records · Page 2Linked to original sources
PubMed2001

Anesthetic management of a patient with relapsing polychondritis--a case report.

Relapsing polychondritis is a rare multisystem disorder of uncertain etiology. It is characterized by recurrent and progressive destruction of both elastic and hyaline cartilages as well as connective tissue. Respiratory tract involvement is associated with high mortality and morbidity. General anesthesia may be required in these patients for tracheostomy, bronchoscopy, nasal reconstruction, aortic valve replacement, and recent tracheobronchial stenting which they usually sustain. Tracheostomy was once the most likely surgical procedure in relapsing polychondritis. However, this procedure is only effective in patients with upper subglottic involvement. In cases of extensive tracheobronchial involvement, tracheostomy is ineffective because the distant tracheal collapse below the tracheostomy is still unresolved. We would like to report a case of relapsing polychondritis with tracheobronchial involvement, who underwent an emergent tracheostomy. Tracheostomy with continuous positive airway pressure (CPAP) effectively improved her airway collapse. Herein, we also discuss the anesthetic management after review of the current literature.

Anesthesia↗
PubMed2000

A comparative study of betaxolol and dorzolamide effect on ocular circulation in normal-tension glaucoma patients.

OBJECTIVE: To determine whether dosages of a selective beta-blocking agent (betaxolol) and a topical carbonic anhydrase inhibitor (dorzolamide), sufficient to significantly lower intraocular pressure (IOP), have similar or disparate impact on the retinal and retrobulbar circulation. DESIGN: Counterbalanced crossover, with open-label use of medications. PARTICIPANTS: Nine persons with normal-tension glaucoma (NTG). INTERVENTION: After a 3-week drug washout, NTG patients were studied after 1 month of treatment with either dorzolamide or betaxolol, with determinations of IOP and retinal and retrobulbar hemodynamics. MAIN OUTCOME MEASURES: At baseline and after treatment with each drug, retinal arteriovenous passage time was determined by scanning laser ophthalmoscopy after fluorescein dye injection, and flow velocities in the central retinal and ophthalmic arteries were measured with color Doppler ultrasonography imaging. RESULTS: Betaxolol and dorzolamide each lowered IOP significantly, with these changes apparent and maximal after 2 weeks (each P < 0.05). In contrast, dorzolamide (but not betaxolol) accelerated arteriovenous passage of fluorescein dye in the inferior temporal quadrant of the retina (P < 0.05). Neither drug affected arteriovenous passage in the superotemporal retina or any aspect of central retinal or ophthalmic artery flow velocity after either 2 or 4 weeks. CONCLUSIONS: Although both dorzolamide and betaxolol are effective ocular hypotensive agents and their topical instillation leaves retrobulbar hemodynamics unaltered, dorzolamide alone accelerates inferotemporal retinal dye transit.

Adrenergic beta-Antagonists↗
PubMed2000

Characteristics of lung cancer in Korea, 1997.

The high proportion of smokers and the incidence of advanced, unresectable lung cancer in Korea were examined to aid the development of a national anti-smoking program and the early detection of lung cancer. Koreans are a single racial group with a high smoking rate among men and a contrastingly low smoking rate among women. This report documents a retrospective investigation conducted by The Korean Academy of Tuberculosis and Respiratory Disease into the characteristics of all lung cancers diagnosed between 1 January 1997 and 31 December 1997 in Korea. Among the 3794 patients included in this study, 76.8% were smokers and, in particular, 89.8% of the males were smokers. Squamous cell carcinoma was the most frequent type of lung cancer encountered (44.7%), followed by adenocarcinoma (27.9%). The smoking rate in the case of adenocarcinoma was significantly lower than that found in both squamous cell carcinoma and small cell cancer. The most common symptom was a cough. Only 7.2% of patients were asymptomatic. Bronchoscopic biopsy has a primary role in the diagnosis of squamous cell carcinoma and small cell cancer, but percutaneous needle biopsy has a more important role in the case of adenocarcinoma. Two-thirds of the nonsmall cell lung cancer patients were detected in the unresectable advanced stages (IIIB and IV). In contrast to other countries, squamous cell carcinoma is still the most frequent type of lung cancer in Korea. The high proportion of smokers and the incidence of advanced, unresectable lung cancer at diagnosis have urged development of a national anti-smoking program to promote the cessation of smoking and the early detection of lung cancer.

Adult↗
PubMed2000

Effect of mitomycin-C on posterior capsule opacification in rabbit eyes.

PURPOSE: To determine whether mitomycin-C can inhibit posterior capsule opacification (PCO) without causing ocular toxicity. SETTING: Yonsei Institute of Vision Research, Department of Ophthalmology, Yonsei University College of Medicine, Seoul, Korea. METHODS: Mitomycin-C dissolved in sodium hyaluronate (0.2 cc of 0.2 mg/mL) was injected into the empty capsular bag for 3 minutes after endocapsular phacoemulsification in rabbit eyes. Three months after surgery, the obstruction rate of visible light caused by PCO was measured using an optical power meter. RESULTS: The mean obstruction rate of visible light was 81.0% +/- 8.3% (SD) in the control group in which sodium hyaluronate without mitomycin-C was used, 30.5% +/- 10.1% in the group in which mitomycin-C was dissolved in sodium hyaluronate, and 71.9% +/- 6.8% in the group in which mitomycin-C was dissolved in a balanced salt solution. Statistically significant differences were found among all 3 groups. CONCLUSIONS: Our results suggest that the application of mitomycin-C dissolved in sodium hyaluronate effectively reduces PCO in rabbit eyes.

Adjuvants, Immunologic↗
PubMed2000

Regional differences in optic disc and retinal circulation.

PURPOSE: To determine regional differences in the circulation of the optic disc, the peripapillary choroid and the retinal vessels using the techniques of computerized image analysis and fluorescein angiography. METHODS: Ten young normal subjects were studied. Fluorescein angiography was performed with a scanning laser ophthalmoscope. The rate of filling of fluorescein or slope was measured in the four quadrants of the optic disc, the peripapillary choroid and the major retinal arteries and veins. A total of 125 points was measured from each image of the fluorescein angiograms for a total of 20 to 30 images. Retinal vessel width was measured using computerized image analysis. RESULTS: Comparison of the rates of filling of fluorescein or slopes showed significant differences from zero among the four quadrants of the optic disc (p= 0.01 to <0.02), of the peripapillary choroid (p=0.01 to <0.05) and among the major retinal arteries (p=0.01 to <0.02) and retinal veins (p=0.02 to <0.05). No significant differences were noted between the quadrants for retinal arterial width with the retinal veins only showing a significant difference between the inferior nasal and inferior temporal vein (p=0.02 to <0.05). CONCLUSION: Evaluation of the circulation of the optic disc, retina, and peripapillary choroid should take into account regional differences among these structures.

Adult↗
PubMed2000

ATP-induced [Ca(2+)](i) changes and depolarization in GH3 cells.

Extracellular ATP is a neurotransmitter and mediates a variety of responses. In the endocrine system, there are data suggesting a physiological role for ATP in Ca(2+) signalling and hormone secretion. However, the ATP receptor subtype involved has not been clearly elucidated in GH3 cells, a rat anterior pituitary cell line. BzATP- and ATP-induced [Ca(2+)](i) responses had EC(50) values of 18 and 651 microM, respectively. The maximal response to ATP was only 59+/-8% of that for BzATP. The BzATP-induced [Ca(2+)](i) increase was dependent upon the extracellular Ca(2+) concentration. Preincubation with oxidized ATP (oATP) nearly abolished the ATP- and BzATP-induced [Ca(2+)](i) increases. Both BzATP and ATP induced depolarization in GH3 cells, with EC(50) values of 31 microM and 1 mM, respectively. The maximal depolarization to BzATP and ATP were 152+/-21 and 146+/-16% of that elicited by 30 mM KCl. The rank order of agonist potency for [Ca(2+)](i) and depolarization responses was BzATP > > ATP >2-MeSATP and purine derivatives such as ADP, AMP, adenosine were ineffective. Neither UTP nor alpha, beta-methylene ATP showed any effect. In low-divalent conditions BzATP evoked non-desensitizing inward currents, which were reversed at approximately 0 mV. This nonselective cationic conductance was increased by repeated applications of BzATP and the cells became very permeable to NMDG. Longer applications (30 min) of BzATP stimulated ethidium bromide influx in low divalent conditions, suggesting increased permeability to larger molecules. We also identified the existence of P2X(7) mRNA on GH3 cells by using reverse transcriptase (RT)-polymerase chain reaction (PCR). These results suggest that the GH3 cells have an endogenous P2X(7) receptor and purinergic stimulation may play a potential role in neuroendocrine modulation on these cells.

Adenosine Triphosphate↗
PubMed2000

Bronchoscopic assessment of the evolution of endobronchial tuberculosis.

BACKGROUND: We previously classified forms of endobronchial tuberculosis (EBTB) into seven subtypes by bronchoscopic finding: actively caseating, edematous-hyperemic, fibrostenotic, tumorous, granular, ulcerative, and nonspecific bronchitic. STUDY OBJECTIVE: To evaluate the value of this classification in predicting the therapeutic outcome of EBTB. DESIGN: A prospective study with serial bronchoscopy performed from the diagnosis of EBTB to the completion of antituberculosis chemotherapy. PARTICIPANTS: Eighty-one patients with biopsy-proven EBTB. INTERVENTIONS: Fiberoptic bronchoscopy was done every month until there was no subsequent change in the endobronchial lesions, every 3 months thereafter, and at the end of treatment. RESULTS: Twenty-two of the 34 cases of actively caseating EBTB changed into the fibrostenotic type, and the other 12 healed without sequelae. Seven of the 11 cases of edematous-hyperemic EBTB changed into the fibrostenotic type, and the other 4 healed. Nine of the 11 cases of granular EBTB, 6 cases of nonspecific bronchitic EBTB, and 2 cases of ulcerative EBTB resolved completely. However, the other two cases of granular EBTB changed into the fibrostenotic type. Seven cases of fibrostenotic EBTB did not improve despite antituberculosis chemotherapy. These various changes in bronchoscopic findings occurred within 3 months of treatment. In 10 cases of tumorous EBTB, 7 progressed to the fibrostenotic type. In addition, new lesions appeared in two cases, and the size of the initial lesions increased in another two cases, even at 6 months after treatment. CONCLUSIONS: The therapeutic outcome of each subtype of EBTB can be predicted by follow-up bronchoscopy during the initial 3 months of treatment, with the exception of the tumorous type. In tumorous EBTB, close and long-term follow-up is advisable because the evolution of the lesions during treatment is very complicated and bronchial stenosis may develop at a later time.

Adult↗
PubMed2000

Chronic subdural hematoma: evaluation of the clinical significance of postoperative drainage volume.

OBJECT: A wide variation in postoperative drainage volumes is observed during treatment of chronic subdural hematoma (CSDH) with twist-drill or burr-hole craniostomy and closed-system drainage. In this study the authors investigate the causes of the variation, the clinical significance thereof, and its influence on treatment outcome. METHODS: A total of 175 cases were investigated between January 1991 and December 1997. Of these, 145 patients had surgery for CSDH, of whom 30 had bilateral lesions. The cases of CSDH were divided into five subtypes (low-density, isodense, high-density, mixed-density, and layering types) on the basis of the brain computerized tomography (CT) findings. Burr-hole craniostomies with closed-system drainage were performed in all patients and the drainage was maintained for 5 days, during which daily amounts of fluid were measured. The mean drainage volume over 5 days was 320 ml, with the largest volume (413 ml) seen in the low-density type and the smallest (151 ml) in the mixed-density type of CSDH. There were recurrences in six patients (seven instances, 4%). The mixed-density type had the highest recurrence rate (8.6%), whereas there was no recurrence for the low-density type. There were no recurrences in 81 patients in whom the total drainage volumes for 5 days were more than 200 ml, but there were recurrences in six (seven instances) of 94 patients in whom the total drainage volume was less than 200 ml. CONCLUSIONS: The postoperative drainage volumes varied greatly because of differences in the outer membrane permeability of CSDH, and such variation seems to be related to the findings on the CT scans obtained preoperatively. Patients with CSDH in whom there is less postoperative drainage than expected should be carefully observed, with special attention paid to the possibility of recurrence.

Adult↗
PubMed2000

The effective concentration and exposure time of mitomycin-C for the inhibition of lens epithelial cell proliferation in rabbit eyes.

The proliferation of residual lens epithelial cells following cataract surgery is assumed to be a major cause of posterior capsular opacification. To assess the efficacy of mitomycin-C in preventing posterior capsular opacification, we determined the effective concentration and exposure time of mitomycin-C in inhibiting rabbit lens epithelial cell proliferation. The fourth-passaged rabbit lens epithelial cells were maintained for one day and then exposed to mitomycin-C for 1, 2, 3, and 5 minutes, respectively. There were 9 different plating concentrations of mitomycin-C with two-fold serial dilution. The maintenance of the phenotypic properties of lens epithelial cells was confirmed by continuous transcription of lambda-crystalline mRNA determined by reverse transcription-polymerase chain reaction and the polymorphism of the restriction fragment. Cell proliferation was assayed with 3H-thymidine incorporation into DNA. The fourth-passaged cells maintained the expression of lambda-crystalline mRNA, suggesting that they are phenotypically authentic lens epithelial cells. The effective concentrations and exposure time of mitomycin-C were 0.1 mg/ml for 1 minute and 2 minutes, and 0.025 mg/ml for 2 minutes. By these results, we postulated that mitomycin-C at relatively short incubation times could be clinically used for prevention of posterior capsular opacification after cataract surgery.

Animals↗
PubMed2000

Bronchoscopic, radiologic and pulmonary function evaluation of endobronchial tuberculosis.

OBJECTIVE: Endobronchial tuberculosis (EBTB) causes problems in both making a diagnosis and following up the endobronchial lesion, because the lesion is not evident in simple chest radiograph. Frequently, the diagnosis and follow up of EBTB lesion during treatment mainly depend on bronchoscopy. Chest computed tomography (CT) and pulmonary function test (PFT) have also been used in evaluating EBTB and differentiating it from the other diseases. Primary purpose of the present study was to observe the change of EBTB lesion during treatment and determine the optimal time and the indication of follow-up bronchoscopy. We also evaluate the usefulness of chest CT and PFT in EBTB. METHODOLOGY: Eighty-one biopsy-proven EBTB patients were enrolled from 1992 to 1997. Endobronchial tuberculosis was classified into seven subtypes: actively caseating, fibrostenotic, oedematous-hyperaemic, tumorous, ulcerative, granular, and non-specific bronchitic type according to bronchoscopic features by Chung's Classification. The change of bronchoscopic findings during treatment in each subtype of EBTB was evaluated prospectively. Follow-up bronchoscopy was done each month until there was no subsequent change in endobronchiat lesion, and every 3 months thereafter, and at the end of treatment. Chest CT and PFT were performed in 26 and 68 patients respectively, at initial bronchoscopy. RESULTS: Twenty-two of the 34 cases of actively caseating EBTB changed into the fibrostenotic type, and the other 12 healed without sequelae. Seven of the 11 cases of oedematous-hyperaemic EBTB changed into the fibrostenotic type, and the other four healed. Nine of the 11 cases of granular EBTB, six cases of non-specific bronchitic EBTB, and two cases of ulcerative EBTB resolved completely. However, the other two cases of granular EBTB changed into the fibrostenotic type. Seven cases of fibrostenotic EBTB did not improve despite antituberculosis chemotherapy. These various changes in bronchoscopic findings occurred within 3 months of treatment. In 10 cases of tumorous EBTB, seven progressed to the fibrostenotic type. In addition, new lesions appeared in two cases, and the size of the initial lesions increased in another two cases, even at 6 months after treatment. On chest CT findings of 26 EBTB patients, the length of bronchial involvement was measured from 10 to 55 mm. Bronchial stricture was noticed in 25 cases and the range of narrowing was from total occlusion to near normal, and there was wide variation in bronchial stricture even within same subtype of EBTB. The dominant feature of PFT in EBTB at the diagnosis was restrictive pattern. CONCLUSION: The therapeutic outcome of each subtype of EBTB can be predicted by follow-up bronchoscopy during the initial 3 months, with the exception of the tumorous type. In tumorous EBTB, the evolution of the lesions during treatment is very complicated, and bronchial stenosis may develop at a later time. Chest CT was useful in measuring the length of involved bronchus and degree of stricture in EBTB. PFT may be useful in differential diagnosis and follow up of EBTB.

Biopsy↗
PubMed1999

mRNA expression of netrin-1, an axon guidance protein in chick and rat embryos.

The guidance of axons to their targets in developing neurons is believed to be mediated by diffusible chemotropic factors secreted by target cells. In vertebrates, commissural axons pioneer a circumferential pathway to the floor plate at the ventral midline of the embryonic spinal cord. Floor plate cells secrete a diffusible factor called 'netrin', that promotes the outgrowth of axons in the embryonic chick brain. The cloning of cDNAs encoding netrin showed that it is homologous to UNC-6, a laminin-related protein which is required for the circumferential migration of cells and axons in Caenorhabditis elegans. The differential expression of the netrin-1 gene was examined by slot blot analysis in various chick embryonic tissues, especially in the embryonic brain at various developmental stages. The netrin-1 transcript was most strongly expressed in the brain at the early developmental stages of E3 to E7 that corresponds to the time of emergence and full generation of commissural axons in the chick brain. In order to study whether netrin-1 can act as a global cue to guide all circumferentially migrating axons in the CNS, the localization of netrin-1 mRNA expression in the rat embryos was examined by in situ hybridization. Netrin-1 mRNA was detected in the neuroepithelial cells of the ventral midline along the entire rostrocaudal axis of the E18 rat embryo. These results suggest that netrin-1 functions as a global guidance cue for ventrally directed circumferential migrations toward the midline at all axial levels where the floor plate is found.

Animals↗
PubMed1999

Development of dried liposomes containing beta-galactosidase for the digestion of lactose in milk.

The hydrolyzed-lactose milk for lactase-deficient subjects has a sweeter taste than whole milk, and some subjects dislike its taste. In order to cope with this shortcoming, we examined whether beta-galactosidase, which hydrolyzes lactose, added to the whole milk in the form of dried liposomes, would be able to digest lactose in milk following the lysis of liposomes in the presence of bile salts. Dried liposomes containing beta-galactosidase were prepared in the presence of trehalose by the dehydration-rehydration vesicle method to overcome the instability of the conventional liposome suspension. The stability of liposomal membranes was evaluated by measuring the activity of entrapped beta-galactosidase under various storage conditions. By treating liposomes with trehalose, which was found to prevent the fusion of liposomes and the leakage of entrapped drug, the entrapping efficiency increased up to fourfold. Over 95% of dried liposomes which had been stored at 17 degrees C for 60 days were reconstituted to liposomes upon rehydration process. From the stability study, dried liposomes were found to retain 87% of beta-galactosidase activity at 17 degrees C after 60 days and to be more stable than the multilamellar vesicle suspension prepared without trehalose. The lysis study showed that dried liposomes were hardly lyzed in the simulated gastric fluid with pepsin, but lyzed immediately more than 90% in 0.01 M deoxycholic acid. Lactose hydrolysis in the presence of deoxycholic acid after the addition of dried liposome-entrapped beta-galactosidase to whole milk was proportional to the quantity of entrapped beta-galactosidase and the amount of dried liposomes added. These results demonstrate that beta-galactosidase entrapped in liposome is stable and reconstituted mostly upon rehydration, and can digest lactose in milk after the efficient lysis of liposomes in the presence of bile salts. This study implies that beta-galactosidase entrapped in liposome may be applied to whole milk for lactase-deficient subjects.

Animals↗
PubMed1999

Screening and selection of acid and bile resistant bifidobacteria.

Human fecal samples were used as a source of Bifidobacterium strains which are resistant to both acid and bile. The procedure used for screening was as follows: enrichment of Bifidobacterium strains with Bifidobacterium-selective transgalacto-oligosaccharide-propionate (TP) medium followed by acid (pH 2.0) and bile salt stressing (1.5% bile salt (w/v)). Two selected Bifidobacterium strains, designated HJ 30 and SI 31, showed considerably higher rates of survival when incubated in 50 mM phosphate buffer solution adjusted to pH 2.0 or 3.0 or in 50 mM phosphate buffer (pH 7.0) containing 0.5 or 1.0% (w/v) bile salt. HJ 30 and SI 31 were the only strains to have significant growth in Man Rogosa Sharpe (MRS) medium at 0.15% bile salt. All strains tested had similar growth rates in the absence of bile or at an initial pH value of 5.0 or 7.0 as determined by optical density measurements. For SI 31 the number of viable cell counts remained high (6 x 10(7) cfu/ml) for up to 72 h when grown in the skim milk medium, whereas all other strains examined declined to below 10(5) cfu/ml. These results demonstrate that the screening procedures developed in this study are effective for the selection of acid and bile resistant Bifidobacterium strains.

Adult↗