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Biomedical subjects

Y M Chung

Publications and source records attributed to Y M Chung.

At least 19 recordsLinked to original sources
PubMed2003

Applications of the pulsatile flow versatile ECLS: in vivo studies.

INTRODUCTION: T-PLS (Twin-Pulse Life Support) is the first commercial pulsatile ECLS (Extra Corporeal Life Support) device (1). The dual sac structure of T-PLS can effectively reduce high membrane oxygenator inlet pressure and hemolysis. To verify both the use of T-PLS for ECLS and the advantages of T-PLS, we tested various models. METHOD AND RESULTS: In the partial CPB (cardio pulmonary bypass) model (swine), T-PLS (N = 6), and Biopump (N = 2), a single pulsatile pump (N = 2), were compared. In the case of single pulsatile flow, during pump systole, pressure increased to 700 - 800 mmHg at the inlet port of the membrane oxygenator. fHb, a hemolysis measurement value, was about 80 mg/dL at 3 hours. On the contrary, because of T-PLS's dual sac system, the pressure of T-PLS had a maximum value of about 250 mmHg and fHb was similar to that of the commercial centrifugal pumps. In the total CPB model (bovine, N = 6), the heart was stopped via cardioplegia (Kcl). T-PLS flow was maintained at 3.0-4.5 L/min. T-PLS functioned like a natural heart, having a pulse pressure of 26-43 mmHg and a pulse rate of 40-60 bpm (beats per minute). In the emergency case model (canine, N = 6), T-PLS was started 10 minutes after cardiac arrest from electronic shock. In spite of cardiac arrest for a period of 40 minutes, the heart was recovered after defibrillation. In the ARDS (Acute Respiratory Distress Syndrome) model (canine, N = 6), minimal ventilator parameters were set: tidal volume 130 ml, respiration rate = bpm, FiO2 = 10%. Three hours after starting T-PLS, PO2 of the carotid artery blood (after 2 hours: 195 +/- 89.4; after 3 hours: 258 +/- 99.3 mmHg) was above half the value of the femoral artery but was within normal range. CONCLUSION: It is suggested that a portable pulsatile ECLS like T-PLS may be used as a CPB device and as an alternative CPR (cardiopulmonary resuscitation) device in the case of cardiac arrest. Due to the pulsatile flow, oxygenated blood is delivered to the patient without overloading the ARDS patients heart.

Animals↗
PubMed2001

Activity coefficients of the peptide and the electrolyte in ternary systems water+glycylglycine+NaCl, +NaBr, +KCl and +KBr at 298.2 K.

The activity coefficients of glycylglycine in four aqueous electrolyte solutions (+NaCl, +NaBr, +KCl and +KBr) were obtained at 298.2 K. The mean ionic activity coefficient of the electrolyte in aqueous solutions containing the peptide was determined from measurements of the potential differences of a cation and an anion ion-selective-electrode, each vs. a double junction reference electrode. The results show that the nature of the anion has a major effect on the activity coefficients of glycylglycine. Comparison of activity coefficient data for glycylglycine with literature data for glycine, both in aqueous NaCl solutions, indicates that the effect of the electrolyte is larger for the peptide than for the amino acid. For the peptide, in all cases, the effect of the electrolyte is more important at low molalities of the electrolyte. The Wilson equation was used to correlate the activity coefficient data obtained. The correlation results were satisfactory for the region of concentrated electrolyte.

Algorithms↗
PubMed2001

Hepatitis C virus core protein potentiates TNF-alpha-induced NF-kappaB activation through TRAF2-IKKbeta-dependent pathway.

Previous work has implicated that the core protein of hepatitis C virus (HCV) may play a modulatory effect on NF-kappaB activation induced by TNF-alpha. However, it is unclear how HCV core protein modulates TNF-alpha-induced NK-kappaB activation. Here we show that overexpression of HCV core protein potentiates NF-kappaB activation induced by TNF-alpha. Expression of dominant negative form of TRAF2 inhibits the synergistic effects of HCV core protein on NF-kappaB activation, suggesting that HCV core protein potentiates NF-kappaB activation through TRAF2. Moreover, we demonstrate that HCV core protein potentiates TRAF2-mediated NF-kappaB activation via IKKbeta. In addition, HCV core protein associates with TNF-R1-TRADD-TRAF2 signaling complex, resulting in synergistically activation of NF-kappaB induced by TNF-alpha. Thus, these observations indicate that HCV core protein may play an important role in the regulation of the cellular inflammatory and immune responses through NF-kappaB.

Antigens, CD↗
PubMed2001

Caspase-cleaved TRAF1 negatively regulates the antiapoptotic signals of TRAF2 during TNF-induced cell death.

Tumor necrosis factor (TNF) signaling leads to pleiotropic responses in a wide range of cell types, in part by activating antiapoptotic and proapoptotic pathways. Previous studies have suggested that TNF receptor-associated factor (TRAF) 2 can mediate crucial antiapoptotic signals during TNF stimulation. However, it is unclear how the antiapoptotic signals via TRAF2 in TNF-R1 signaling is regulated. Here we show that TRAF1 is cleaved by caspase-8 into two fragments during apoptosis induced by TNF. Overexpression of the C-terminal cleavage product, TRAF1-c, increased TNF-induced cell death of hybridoma T cells. Importantly, we demonstrate that the cleavage product of TRAF1 coimmunoprecipitates with TRAF2 that is released from the TNF-R1 complex in response to prolonged TNF treatment. These results indicate that caspase-dependent cleavage of TRAF1 generates TRAF1-c fragments that are able to bind TRAF2, and then sequester TRAF2 from the TNF-R1 complex, rendering cells, at least in part, sensitive to TNF.

Animals↗
PubMed2000

Establishment and characterization of 5-fluorouracil-resistant gastric cancer cells.

Two 5-fluorouracil (5-FU)-resistant cell lines from a Korean gastric cancer cell line were established by incubation of the cells with increasing concentration of 5-FU, and the resultant cell lines showed an over 800-fold increased resistance to 5-FU. To identify the mechanism of 5-FU resistance, the expressions of genes involved in 5-FU metabolism were examined by reverse transcriptase-polymerase chain reaction (RT-PCR). Expressions of orotate phosphoribosyltransferase (OPRT), thymidine phosphorylase (TP), and uridine phosphorylase (UP) were significantly downregulated in these cell lines, resulting in low incorporation of 5-FU into nucleic acids. In contrast, an increased expression of thymidine kinase (TK) was observed in 5-FU-resistant cells. These results strongly indicate that blocking of 5-FU incorporation into nucleic acids and TK overexpression may play a major role in 5-FU resistance in these cells. Interestingly, these cell lines showed cross-resistance to paclitaxel, cisplatin, and doxorubicin, suggesting that other factors such as HSP27 and Mn-SOD could be also involved in the mechanism of multidrug resistance in these cell lines.

Antimetabolites, Antineoplastic↗
PubMed2000

Ophthalmic findings in patients with acquired immunodeficiency syndrome.

Ocular manifestations have been reported in up to 60% of individuals infected with human immunodeficiency virus (HIV) in the United States, and it is becoming increasing apparent that these ocular manifestations almost invariably reflect extent of progression of the disease. The prevalence of ocular abnormalities among acquired immunodeficiency syndrome (AIDS) patients in Taiwan has not been reported. In the present study, we examined and followed up the ophthalmic conditions of a total of 274 HIV-infected patients during the period from March 1993 to May 1999. The results show that cotton-wool spots was the most common ocular finding in this series of patients with AIDS, occurring in 22 (32.8%) of 67 AIDS patients. Cytomegalovirus (CMV) retinitis was the most commonly seen opportunistic ocular infection, occurring in 14 (20.8%) of 67 AIDS patients. These findings suggest that AIDS patients should be closely followed for signs of opportunistic ocular disease which may initially be asymptomatic. Close co-operation between the ophthalmologist and the internist is essential to ensure timely therapeutic intervention, which can decrease the risk of further complications including visual impairment and blindness.

Acquired Immunodeficiency Syndrome↗
PubMed2000

Diffuse toxoplasmic retinochoroiditis as the initial manifestation of acquired immunodeficiency syndrome.

Toxoplasmic retinochoroiditis is an important opportunistic retinal infection in human immunodeficiency virus (HIV)-infected patients. It may present as diffuse necrotizing retinochoroiditis instead of a focal lesion and may be the initial manifestation of HIV infection. A 50-year-old heterosexual man presented with blurred vision in his left eye of 3 months' duration. Fundus examination revealed diffuse necrotizing retinochoroiditis, mainly at the posterior pole, with marked vitritis in the left eye. Serologic studies and aqueous fluid antibody titers indicated recent toxoplasmic infection. Positive enzyme immunoassays (EIA) and Western blot tests proved HIV infection. The retinochoroiditis and vitritis improved after an antitoxoplasmic regimen with trimethoprim-sulfamethoxazole (TMP-SMX). Nonetheless, toxoplasmic encephalitis developed 6 months after the onset of ocular toxoplasmosis and responded well to TMP-SMX. This is the first case of toxoplasmic retinochoroiditis as the initial manifestation of AIDS reported in Taiwan. We suggest that Toxoplasma infection should be included in the differential diagnosis of diffuse necrotizing retinochoroiditis and vitritis. We also recommend that adults with newly diagnosed ocular toxoplasmosis be screened for HIV infection.

AIDS-Related Opportunistic Infections↗
PubMed2000

Antisense of human peroxiredoxin II enhances radiation-induced cell death.

Human peroxiredoxin II (Prx II) has been known to function as an antioxidant enzyme in cells. Using head-and-neck cancer cell lines, we investigated whether Prx II expression is related to the resistance of cells to radiation therapy in vivo and in vitro, and whether a Prx II antisense serves as a radiosensitizer. Increased expression of Prx II was observed in tissues isolated from the patients who did not respond to radiation therapy, whereas Prx II expression was weak in tissues from the patients with regressed tumors. Enhanced expression of Prx II in UMSCC-11A (11A) cells was also observed after treatment with gamma radiation. This increased expression conferred radiation resistance to cancer cells because overexpression of Prx II protected 11A cells from radiation-induced cell death, suggesting that blocking Prx II expression could enhance radiation sensitivity. Treatment of 11A cells with a Prx II antisense decreased induction of Prx II, enhancing the radiation sensitivity. From these results, we suggest that stress-induced overexpression of Prx II increases radiation resistance via protection of cancer cells from radiation-induced oxidative cytolysis and that a Prx II antisense can be used as a radiosensitizer.

Antioxidants↗
PubMed1999

Progression of cytomegalovirus retinitis in acquired immunodeficiency syndrome: a case report.

We report an AIDS patient with cytomegalovirus (CMV) retinitis that developed from an early minor lesion and progressed to extended involvement of the retina and severe deterioration of vision due to poor compliance with ganciclovir treatment. A 33-year-old man was known to have acquired immunodeficiency syndrome (AIDS) for eight months. The patient had no complaint of visual symptoms. A routine eye examination revealed his visual acuity to be 6/6 in both eyes. The dilated eye fundus examination using indirect ophthalmoscopy disclosed a localized white yellowish granular lesion in the peripheral retina of the right eye and a completely normal left eye. CMV retinitis with initial manifestation in the right eye was diagnosed. Due to incomplete treatment with ganciclovir, the retinal lesion rapidly enlarged and extended to the posterior pole, with eventual destruction of the nerve fiber layer and optic disc. The visual acuity of right eye dropped from 6/6 to 1/60 within six months. This case report indicates the importance of early, dilated eye fundus examination and recognition of early CMV retinitis in order to salvage visual function in AIDS patients. Completion of the anti-CMV treatment course in halting the progression of CMV retinitis is also emphasized.

AIDS-Related Opportunistic Infections↗
PubMed1998

Endogenous Candida endophthalmitis after induced abortion.

PURPOSE: To report two young healthy women who developed endogenous Candida endophthalmitis after undergoing surgically induced abortion. METHOD: Case reports. RESULTS: In two eyes of two patients, a diagnosis of Candida endophthalmitis was established by typical fundus appearance, positive vaginal culture, and, in one case, positive vitreous culture. After vitrectomy and intravitreal amphotericin B injection, one eye of one patient had a best-corrected visual acuity of 20/200, whereas one eye of one patient, who had systemic corticosteroid treatment before the correct diagnosis, developed recurrent retinal detachment and a best-corrected visual acuity of counting fingers. CONCLUSIONS: Induced abortion may cause endogenous Candida endophthalmitis in young healthy pregnant women. Systemic corticosteroid treatment may increase the risk of endophthalmitis.

Abortion, Induced↗
PubMed1998

Choroidal involvement in Wegener's granulomatosis: a case report.

Wegener's granulomatosis is a necrotizing, granulomatous vasculitis. It usually causes sinusitis, pneumonitis and glomerulonephritis. The common ocular manifestations include conjunctivitis, scleritis, peripheral keratitis and orbital inflammation. We report the case of a 50-year-old woman with Wegener's granulomatosis and very severe ocular complications who underwent bilateral enucleation. The pathologic findings of the eyeballs revealed granulomatous necrotizing scleritis, perivasculitis and granulomatous choroiditis. The last, as far as we know, has not yet been reported.

Choroiditis↗
PubMed1997

Effects of antiglaucoma drugs and corticosteroids on the cellular glucose uptake in cultured porcine corneal endothelial cells.

In this study, various commercially used antiglaucoma drugs and corticosteroids were investigated in their effects on porcine corneal endothelial cells especially in cellular glucose uptake. Cellular glucose uptake directly affects the pumping efficiency in corneal endothelial cells. Following the cells' treatment with various antiglaucoma eyedrops for 100 min, the 3H-2-deoxyglucose uptake in cultured porcine corneal endothelial cells was affected by betaxolol from 3.1% (1.6 mM), 181% (0.16 mM) to 158% (0.016 mM), by timolol from 93% (0.79 mM), 227% (0.079 mM) to 151% (0.0079 mM), by carteolol from 141% (3.4 mM), 180% (0.34 mM) to 97% (0.034 mM), by levobunolol from 80% (1.5 mM), 98% (0.15 mM) to 90% (0.015 mM), by dipivefrin from 116% (0.2 mM), 176% (0.02 mM) to 108% (0.002 mM) and by pilocarpine from 115% (9.6 mM), 210% (0.96 mM) to 210% (0.096 mM) when the cells were compared with a control medium. In the presence of various corticosteroids, the glucose uptake in corneal endothelial cells was affected by fluorometholone from 160% (0.26 mM), 139% (0.026 mM) to 107% (0.0026 mM), by dexamethasone from 85% (0.25 mM), 117% (0.025 mM) to 109% (0.0025 mM) and by betamethasone from 95% (0.25 mM), 96% (0.025 mM) to 99% (0.0025 mM). These results show that the commercial eyedrops of antiglaucoma drugs and corticosteroids will not decrease the cellular glucose uptake in cultured porcine corneal endothelial cells except when incubated with high concentrations of betaxolol, levobunolol and dexamethasone.

Adrenal Cortex Hormones↗
PubMed1996

Transfusion-acquired AIDS in Taiwan.

Human immunodeficiency virus type 1 (HIV-1) can be transmitted through blood transfusion. The first transfusion-acquired immunodeficiency syndrome (AIDS) patient in Taiwan was a 46-year-old woman who received two units of whole blood during a hysterectomy at a provincial hospital in 1985. In 1991, she experienced a herpes zoster infection. In March 1993, she had extensive herpetic gingivostomatitis and another herpes zoster attack, and was treated at the same hospital. Two months later, she had oral candidiasis and was treated at a medical center. She was not tested for HIV-1 infection until she developed Pneumocystis carinii pneumonia in June 1993. In February 1994, and developed cytomegalovirus retinitis and died 6 months later. Donor blood given to the patients during the hysterectomy was HIV-1 positive. The donor's HIV infection was discovered in 1991 and he died of AIDS in 1993. As blood centers in Taiwan did not start screening for HIV-1 until January 1988, it is urgently recommended that any individual who received a blood transfusion between 1984 and 1987 in Taiwan and who currently experiences repeated episodes of opportunistic infections have an HIV-1 blood test. The receipt of a blood transfusion between 1984 and 1987 should be listed by the Department of Health as an indication for HIV-1 screening.

Acquired Immunodeficiency Syndrome↗
PubMed1996

Effects of dopamine antagonists and agonist on cultured human Tenon's fibroblast cells.

It was found that long-term therapy with topical antiglaucoma drugs may increase the number of fibroblasts and inflammatory cells in the conjunctiva and Tenon's capsule then decrease the success of glaucoma filtering surgery. Since some dopamine antagonists and agonists are reported to have ocular hypotensive effects, they could potentially be used as clinical antiglaucoma agents in future. In this study, several dopamine antagonists and agonists were evaluated in their effects on the fibroblast proliferation of ocular tissues with cultured human ocular Tenon's fibroblast cells. It was found that dopamine antagonists inhibited [3H]-thymidine uptake to 10.8%, 14.4%, 42.2% and 72.4% of control in domperidone, 28.6%, 67.7%, 96.9% and 99.2% in haloperidol, 9.8%, 18.9%, 103.5% and 104.6% in moperone and 9.8%, 24.7%, 70.8% and 96.9% in loxapine respectively, while the 0.5% concentration of drugs were dissolved in dimethyl sulfoxide (DMSO) followed by dilution in culture medium to final concentrations ranging from 0.05%, 0.005%, 0.0005% to 0.00005%. In the case of dopamine agonist, bromocriptine, the proliferation of cultured human Tenon's fibroblast cells was also inhibited for 25.1% of the control at 0.05% concentration and 92.3% of the control at 0.00005% concentration. These results indicate that these dopamine drugs have a potential long-term application in the treatment of glaucoma without having the stimulating effect on the proliferation of human Tenon's fibroblast cells.

Cells, Cultured↗
PubMed1995

Scleritis in IgA nephropathy: a case report.

Scleritis may occur as an isolated phenomenon or as a manifestation of a variety of rheumatic diseases, infections and metabolic disorders. However, it is not well-known as occurring in IgA nephropathy. A 46-year-old Chinese female who presented with scleritis and was also diagnosed to have IgA nephropathy is reported. The clinical course and pathological findings of both eyes and kidneys are presented.

Female↗