Biomedical subjects

K Y Ng

Publications and source records attributed to K Y Ng.

At least 19 recordsLinked to original sources

PubMed2006

Prevalence and correlates of depression in Chinese elderly patients with pneumoconiosis.

Recent literature suggests that patients with pneumoconiosis may be at higher risk of developing psychiatric problems, particularly depressive illness. There are no published data on depressive disorders in elderly patients with pneumoconiosis. The aim of this study was to evaluate the prevalence and correlates of depressive disorders in a community sample of elderly Chinese patients with pneumoconiosis in Hong Kong. Two hundred and one patients with pneumoconiosis were randomly selected from the case register of the Pneumoconiosis Compensation Fund Board of Hong Kong. A psychiatrist conducted a structured clinical interview to diagnose depressive disorders according to the Diagnostic Statistical Manual for Mental Disorders, Version IV criteria. Nineteen (9.5%) patients had depressive illness. Univariate logistic regression revealed that the number of comorbid conditions, and the scores on the Lubben Social Network Scale (LSNS) and Instrumental Activities of Daily Living (IADL) were significant predictors of depressive disorders. Multivariate logistic regression analysis found that IADL and LSNS scores were the only independent predictors of depressive disorders. In conclusion, depressive disorders were common and associated with poorer functional ability and social support in patients with pneumoconiosis.

Aged↗

PubMed2004

Is direct large loop electric excision for the transformation zone reasonable in the investigation of high-grade squamous intraepithelial lesions in cervical smears?

PURPOSE OF INVESTIGATION: To evaluate women with cytological high-grade squamous intraepithelial lesions (HGSIL) who received standard colposcopic evaluation and direct diagnostic large loop electric excision for the transformation zone (LLETZ) to determine the feasibility of using LLETZ alone (ie, skipping the colposcopic examination). METHODS: From May 1999 to May 2001, 70 women, with the mean age of 49.58 years (range, 20-82 years) and with cervical HGSIL categorized by the Bethesda system were all evaluated by colposcopic evaluation and LLETZ. Cases with a satisfactory colposcopy examination were classified as group A and those with an unsatisfactory colposcopy examination were classified as group B. "Over-treatment" was determined if the women did not need further LLETZ for evaluation or management. "Under-treatment" was determined if treatment might be potentially inadequate or invasive cancer could be ruled out during a satisfactory colposcopic evaluation. RESULTS: Group A consisted of ten women who were evaluated satisfactorily by colposcopy and group B consisted of 30 women who were not evaluated satisfactorily by colposcopy. Overall 8.6% of the patients (6/70) were considered "over-treated". The rate of over-treatment was 10.0% (4/40) in group A compared with 6.7% (2/30) in group B. In contrast, overall 10% of the patients (7/70) were considered "under-treated". The rate of under-treatment was 10% (1/40) in group A compared with 10% (3/30), in group B. The positive predictive values of group A and B were 90.6% and 88.0%, respectively. The negative predictive values were 33.2% and 40%, respectively. CONCLUSION: Direct diagnostic and therapeutic LLETZ for the management of cervical HGSIL may be a better alternative to colposcopy. This method of treatment avoids the possibility of under-treatment and is associated with an acceptable over-treatment rate, especially for postmenopausal women with cytological HGSIL. LLETZ has a good diagnostic accuracy with minimal morbidity and, most importantly, may help reduce patient anxicty, although further studies are needed to directly examine this effect.

Adult↗

PubMed2002

The epidemiology and treatment of anogenital warts in Singapore: a retrospective evaluation.

INTRODUCTION: A retrospective study in the referral centre for sexually transmitted infections (STIs) in Singapore to describe the epidemiology and treatment outcome of patients with anogenital warts. SUBJECTS AND METHODS: We reviewed the case records of 301 patients with anogenital warts who were seen over a 1-year period (1999). We also attempted to interview every patient by telephone to find out if they had any clinical recurrences for which treatment was sought elsewhere. RESULTS: There were 255 males and 46 females with a mean age of 34 years. Two hundred and nineteen (72.8%) presented with symptoms lasting 12 weeks or less. In males, warts occurred most frequently in the preputial cavity (52.5%) and on the penile shaft (40.8%). In females, they occurred most frequently on the external genitalia (91.3%). Two hundred and thirty-five males were treated with cryotherapy and 69% (95% CI, 62.6% to 74.8%) achieved clinical resolution after a mean of 6 treatment cycles. Seven males were treated with podophyllin 0.25% in ethanol and 71% (95% CI, 29.0% to 96.3%) were clinically cured after a mean of 4 treatment cycles. Thirty-nine females were treated with cryotherapy and 67% (95% CI, 49.8% to 80.9%) achieved clinical cure after a mean of 4 treatment cycles. Of the 290 patients treated at the centre, 212 (73%; 95% CI, 67.3% to 77.8%) patients (184 males, 28 females) achieved clinical cure after a mean of 7 weeks (range, 1 to 34 weeks); 90% (95% CI, 86.0% to 93.2%) of them by 15 weeks. Seven-two patients defaulted follow-up and 6 responded partially to treatment. Of the 212 patients who achieved clinical cure, 195 were interviewed by telephone, on an average, 17.7 months after clinical resolution. Thirty-seven (19%; 95% CI, 13.7% to 25.2%), all males, relapsed clinically after a mean of 100 days (range, 5 to 329 days); 90% (95% CI, 84.6% to 93.6%) relapsed by 228 days. CONCLUSIONS: Podophyllin 0.25% in ethanol was the most cost-effective treatment for males. One in 5 patients had a recurrence of their warts and most had their recurrence within 8 months of initial resolution.

Adolescent↗

PubMed2001

Overcoming MDR by ultrasound-induced hyperthermia and P-glycoprotein modulation.

We assessed the effects of combining ultrasound-induced hyperthermia (USHT) with the P-glycoprotein modulator PSC 833 on cellular retention and cytotoxicity of rhodamine 123 (R123) and doxorubicin in the parent and multidrug resistance (MDR) variants of two human cancer lines. USHT significantly increased cellular uptake of R123 and doxorubicin. Without PSC 833, release of R123 and doxorubicin from both USHT-treated and untreated cells was rapid. As expected, PSC 833 (0.5 microM) only slowed their release into the MDR lines. Interestingly, despite the differences in their starting amounts, PSC 833 was effective in prolonging R123 and doxorubicin release from both USHT-treated and untreated MDR cells. PSC 833 did not augment the cytotoxicity of doxorubicin in parent lines but did cause a significant increase in cytotoxicity of doxorubicin in the MDR lines. However, the combined effect of USHT and PSC 833 on cytotoxicity of doxorubicin far exceeded that produced by USHT or PSC 833 alone.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMed2001

LDL induced association of anionic liposomes with cells and delivery of contents as shown by the increase in potency of liposome dependent drugs.

PURPOSE: To establish whether anionic liposomes interact with the low-density lipoprotein (LDL) receptor, to determine the role of lipoproteins in this interaction, and whether the association causes functional delivery of encapsulated drugs. METHODS: The cell lines used were CV1-P and CHO wild type, both of which express the LDL receptor, and CHOldlA7, which lacks the LDL receptor. Cellular association of encapsulated methotrexate and fluorescein, labeled phosphatidylethanolamine in the lipid bilayer, was measured. Potency of three liposome dependent drugs (N-phosphonacetyl-L-aspartic acid, fluoroorotic acid, and methotrexate-gamma-aspartate) was also measured by growth inhibition. RESULTS: Association of liposomes containing at least 75 mol egg phosphatidylglycerol (ePG)/100 mol phospholipid with cells grown in defined medium supplemented with 1.0 mg/ml LDL was up to 30-fold higher with CV1-P or CHO wild type cells than with CHOldlA7, and 5-fold higher than association in defined medium lacking LDL. The addition of LDL did not yield any elevation of cellular association of distearoylphosphatidylglycerol liposomes. Increased association was paralleled by a corresponding increase in potency of all three liposome dependent drugs tested. CONCLUSIONS: ePG liposomes interact with the LDL receptor in an LDL-dependent fashion, and the interaction results in the delivery of contents to cells.

Animals↗

PubMed2001

Ultrasound-Induced hyperthermia increases cellular uptake and cytotoxicity of P-glycoprotein substrates in multi-drug resistant cells.

PURPOSE: Localized hyperthermia has been shown previously to augment the cytotoxicity of some lipophilic anticancer drugs. Because many of the substrates for the multi-drug resistance (MDR) transporter P-glycoprotein (P-gp) are lipophilic in nature, studies were conducted to test the hypothesis that hyperthermia induced by ultrasound could also increase cellular uptake and cytotoxicity of P-gp substrates by P-gp-expressing cells. METHODS: To test this hypothesis, we studied the effects of hyperthermia and ultrasound on cellular accumulation of putative P-gp substrates, rhodamine 123 (R123) and doxorubicin (DOX), and cytotoxicity of DOX in the parent and MDR variants of two human cancer cell lines. RESULTS: Treatment of cells with hyperthermia or ultrasound (20 min at 41 degrees C) both caused a significant increase over controls (no ultrasound treatment) in R123 and DOX accumulation in the parent and MDR lines of MV522 and KB cells. Ultrasound also substantially increased the antiproliferative effects of DOX in both the parent and MDR variants of MV522 and KB cell lines when compared with controls. Our results also indicated that ultrasound exerted a much greater effect on cellular accumulation of R123 and DOX and cytotoxicity enhancement of DOX in the MDR variants than putative P-gp antagonist such as verapamil. CONCLUSION: The present results point to the potential use of ultrasound-induced hyperthermia as a much safer alternative to P-gp antagonist for reversal of MDR.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMed2001

Justice at the millennium: a meta-analytic review of 25 years of organizational justice research.

The field of organizational justice continues to be marked by several important research questions, including the size of relationships among justice dimensions, the relative importance of different justice criteria, and the unique effects of justice dimensions on key outcomes. To address such questions, the authors conducted a meta-analytic review of 183 justice studies. The results suggest that although different justice dimensions are moderately to highly related, they contribute incremental variance explained in fairness perceptions. The results also illustrate the overall and unique relationships among distributive, procedural, interpersonal, and informational justice and several organizational outcomes (e.g., job satisfaction, organizational commitment, evaluation of authority, organizational citizenship behavior, withdrawal, performance). These findings are reviewed in terms of their implications for future research on organizational justice.

Decision Making↗

PubMed2001

Extended lamivudine treatment in patients with chronic hepatitis B enhances hepatitis B e antigen seroconversion rates: results after 3 years of therapy.

A study in Chinese patients with chronic hepatitis B showed that treatment with lamivudine for 1 year significantly improves liver histology and enhances hepatitis B e antigen (HBeAg) seroconversion compared with placebo. Fifty-eight patients from this 1-year study have received long-term treatment with lamivudine 100 mg; the outcome of 3 years of lamivudine is reported here. Before treatment, all patients had detectable HBeAg. HBeAg seroconversion (HBeAg-negative, anti-HBe-positive), hepatitis B virus (HBV)-DNA suppression, alanine transaminase (ALT) normalization, emergence of YMDD variant HBV, liver histology, and long-term safety were assessed. After 3 years of continuous treatment with lamivudine 100 mg daily, 40% (23 of 58) of patients achieved HBeAg seroconversion. In patients with baseline serum ALT >2 x upper limit of normal (ULN), the rate of HBeAg seroconversion was 65% (17 of 26). Median serum HBV-DNA concentrations were below the level of detection, and median ALT concentrations were within the normal range throughout 3 years of treatment. YMDD variant HBV emerged in 33 of 58 (57%) patients during the 3 years, of whom 9 (27%) achieved HBeAg seroconversion (6 after emergence of YMDD variant HBV). ALT levels and histologic scores after emergence of YMDD variant HBV did not show major deterioration. Lamivudine was well tolerated during 3 years of therapy. In conclusion, these data in Chinese patients with chronic hepatitis B show enhanced seroconversion rates with extended lamivudine treatment. Up to two thirds of patients with moderately elevated pretreatment ALT achieved HBeAg seroconversion after 3 years of therapy.

Adolescent↗

PubMed2000

Carrier-mediated uptake of rhodamine 123: implications on its use for MDR research.

We have examined the effects of verapamil and PSC 833 on cellular uptake and release of rhodamine 123 (R123) in two human cancer cell lines. Both verapamil and PSC 833 were able to increase R123 accumulation in the multidrug resistant (MDR) MV522/Q6 and KB-8-5 lines in the release study. However, the effects of these drugs on R123 accumulation during accumulation study were quite different. Incubation with PSC 833 increased R123 accumulation in both MDR lines. By contrast, incubation with verapamil only increased R123 accumulation in the KB-8-5 line. The failure of verapamil to increase R123 accumulation in the MV522/Q6 cells can be attributed to the presence of a carrier system in the parent MV522 cells that recognizes both R123 and verapamil, but not PSC 833, as substrates. These results imply that performing R123 accumulation study without first ascertaining possible role of a carrier system for cellular uptake of R123 and putative P-gp modulators might inadvertently lead one to draw improper conclusions on P-gp activity.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMed2000

Production of hydrogen sulfide from tetrathionate by the iron-oxidizing bacterium Thiobacillus ferrooxidans NASF-1.

When incubated under anaerobic conditions, five strains of Thiobacillus ferrooxidans tested produced hydrogen sulfide (H2S) from elemental sulfur at pH 1.5. However, among the strains, T. ferrooxidans NASF-1 and AP19-3 were able to use both elemental sulfur and tetrathionate as electron acceptors for H2S production at pH 1.5. The mechanism of H2S production from tetrathionate was studied with intact cells of strain NASF-1. Strain NASF-1 was unable to use dithionate, trithionate, or pentathionate as an electron acceptor. After 12 h of incubation under anaerobic conditions at 30 degrees C, 1.3 micromol of tetrathionate in the reaction mixture was decomposed, and 0.78 micromol of H2S and 0.6 micromol of trithionate were produced. Thiosulfate and sulfite were not detected in the reaction mixture. From these results, we propose that H2S is produced at pH 1.5 from tetrathionate by T. ferrooxidans NASF-1, via the following two-step reaction, in which AH2 represents an unknown electron donor in NASF-1 cells. Namely, tetrathionate is decomposed by tetrathionate-decomposing enzyme to give trithionate and elemental sulfur (S4O6(2-)-->S3O6(2-) + S(o), Eq. 1), and the elemental sulfur thus produced is reduced by sulfur reductase using electrons from AH2 to give H2S (S(o) + AH2-->H2S + A, Eq. 2). The optimum pH and temperature for H2S production from tetrathionate under argon gas were 1.5 and 30 degrees C, respectively. Under argon gas, the H2S production from tetrathionate stopped after 1 d of incubation, producing a total of 2.5 micromol of H2S/5 mg protein. In contrast, under H2 conditions, H2S production continued for 6 d, producing a total of 10.0 micromol of H2S/5 mg protein. These results suggest that electrons from H2 were used to reduce elemental sulfur produced as an intermediate to give H2S. Potassium cyanide at 0.5 mM slightly inhibited H2S production from tetrathionate, but increased that from elemental sulfur 3-fold. 2,4-Dinitrophenol at 0.05 mM, carbonylcyanide-m-chlorophenyl- hydrazone at 0.01 mM, mercury chloride at 0.05 mM, and sodium selenate at 1.0 mM almost completely inhibited H2S production from tetrathionate, but not from elemental sulfur.

Journal Article↗

PubMed2000

Purification and some properties of sulfur reductase from the iron-oxidizing bacterium Thiobacillus ferrooxidans NASF-1.

Thiobacillus ferrooxidans strain NASF-1 grown aerobically in an Fe2+ (3%)-medium produces hydrogen sulfide (H2S) from elemental sulfur under anaerobic conditions with argon gas at pH 7.5. Sulfur reductase, which catalyzes the reduction of elemental sulfur (S0) with NAD(P)H as an electron donor to produce hydrogen sulfide (H2S) under anaerobic conditions, was purified 69-fold after 35-65% ammonium sulfate precipitation and Q-Sepharose FF, Phenyl-Toyopearl 650 ML, and Blue Sepharose FF column chromatography, with a specific activity of 57.6 U (mg protein)(-1). The purified enzyme was quite labile under aerobic conditions, but comparatively stable in the presence of sodium hydrosulfite and under anaerobic conditions, especially under hydrogen gas conditions. The purified enzyme showed both sulfur reductase and hydrogenase activities. Both activities had an optimum pH of 9.0. Sulfur reductase has an apparent molecular weight of 120,000 Da, and is composed of three different subunits (M(r) 54,000 Da (alpha), 36,000 Da (beta), and 35,000 Da (gamma)), as estimated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. This is the first report on the purification of sulfur reductase from a mesophilic and obligate chemolithotrophic iron-oxidizing bacterium.

Journal Article↗

PubMed2000

Effects of extended lamivudine therapy in Asian patients with chronic hepatitis B. Asia Hepatitis Lamivudine Study Group.

BACKGROUND & AIMS: One-year lamivudine therapy significantly suppressed hepatitis B virus (HBV) replication, improved hepatic necroinflammatory activity, and prevented progression of fibrosis. However, the effects of prolonged therapy are unknown. METHODS: A total of 334 Asian patients with chronic hepatitis B from a previously reported 1-year study were randomized to receive either lamivudine (100 or 25 mg) or placebo for another year. The effects of treatment on serum HBV-DNA suppression, alanine transaminase (ALT) normalization, and hepatitis B e antigen (HBeAg) seroconversion were measured. The presence of YMDD variant HBV and its effect were also determined. RESULTS: A significantly greater proportion of patients achieved sustained HBV-DNA suppression and ALT normalization with 100 mg lamivudine daily for 2 years compared with lamivudine for 1 year followed by placebo for the second year (P<0.001). Daily lamivudine therapy for 2 years was safe and resulted in incremental HBeAg seroconversion from 17% at week 52 to 27% at week 104. HBeAg seroconversion during continued lamivudine therapy increased linearly with increasing pretherapy ALT levels (P< 0.001). Despite the emergence of YMDD mutant in 38% of the patients, they continued to clear serum HBeAg and maintain lower median serum HBV-DNA and ALT levels than baseline values. In contrast, ALT levels increased 8-12 weeks after switching from lamivudine to placebo, but returned to normal once lamivudine treatment was resumed. CONCLUSIONS: Treatment with lamivudine for 2 years is both well tolerated and efficacious in patients with chronic hepatitis B.

Adult↗

PubMed2000

Post partum splenic artery aneurysm rupture.

Ruptured splenic artery aneurysm during pregnancy is a rare event with high maternal and fetal mortality rate. A case of ruptured splenic artery aneurysm in the post partum period is presented. The literature is reviewed on pathophysiology, clinical presentation and management of this rare and potentially fatal entity.

Adult↗

PubMed2000

Primary leiomyoma of the liver.

This case report describes a primary hepatic leiomyoma presenting as a mass lesion detected on ultrasonography of the abdomen in an asymptomatic hepatitis B carrier on routine surveillance. Primary leiomyomata of the liver are rare occurrences, with only 9 cases reported in the literature. The presenting features of primary hepatic leiomyomata and diagnostic approach towards such lesions are discussed. The significance of such tumours in the immunocompromised is also mentioned.

Carrier State↗

PubMed1999

Effects of overlapping parametric resonances on the particle diffusion process.

The evolution of the beam distribution in a double-rf system with a phase modulation on either the primary or secondary rf cavity was measured. We find that the particle diffusion process obeys the Einstein relation if the phase space becomes globally chaotic. When dominant parametric resonances still exist in the phase space, particles stream along the separatrices of the dominant resonance, and the beam width exhibits characteristic oscillatory structure. The particle-tracking simulations for the double-rf system are employed to reveal the essential diffusion mechanism. Coherent octupolar motion has been observed in the bunch beam excitation. The evolution of the longitudinal phase space in the octupole mode is displayed.

Journal Article↗

PubMed1999

Active transport of fentanyl by the blood-brain barrier.

Previous studies have shown that uptake of the lipophilic opioid, fentanyl, by pulmonary endothelial cells occurs by both passive diffusion and carrier-mediated processes. To evaluate if the latter mechanism also exists in brain endothelium, transport of [3H]fentanyl was examined in primary cultured bovine brain microvessel endothelial cell (BBMEC) monolayers. Uptake of fentanyl appears to occur via a carrier-mediated process as uptake of [3H]fentanyl by BBMECs was significantly inhibited in a dose-dependent manner by unlabeled fentanyl. Fentanyl uptake was also significantly inhibited by either 4 degrees C or sodium azide/2-deoxyglucose, suggesting that carrier-mediated uptake of fentanyl was an active process. Fentanyl was also tested to determine whether it might be a substrate of the endogenous blood-brain barrier efflux transport system, P-glycoprotein (P-gp). Release of [3H]fentanyl or rhodamine 123, a known substrate of P-gp, previously loaded in the BBMECs was studied in the presence or absence of either fentanyl or verapamil, a known competitive inhibitor of P-gp. Both fentanyl (10 microM) and verapamil (100 microM) decreased release of rhodamine 123 from BBMECs, indicating that fentanyl is a substrate of P-gp in the BBMECs. This was further supported by the observation that uptake of [3H]fentanyl was significantly increased in Mg2+-free medium, a condition known to reduce P-gp activity. However, release of [3H]fentanyl was significantly increased when incubated with either unlabeled fentanyl or verapamil. These results suggest that the active P-gp-mediated extrusion of fentanyl in these cells is overshadowed by an active inward transport process, mediated by an as yet unidentified transporter. In addition, verapamil was shown to be a substrate of both P-gp and the fentanyl uptake transporter.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMed1999

Ectopic pregnancy: uncommon presentations and difficulty in diagnosis.

Diagnosis of ectopic pregnancy prior to rupture is an arduous task even with the availability of many new investigative methods and imaging modalities. Above all, a high index of suspicion is necessary when dealing with women who present in early pregnancy with abdominal pain and vaginal bleeding. With the increased use of ovulation induction agents, the probability of heterotropic pregnancy should be kept in mind. The use of transvaginal ultrasonography (TVS) will help in earlier diagnosis because of its advantages over transabdominal ultrasonography (TAS).

Adult↗

PubMed1998

A one-year trial of lamivudine for chronic hepatitis B. Asia Hepatitis Lamivudine Study Group.

BACKGROUND AND METHODS: In preliminary trials, lamivudine, an oral nucleoside analogue, has shown promise for the treatment of chronic hepatitis B. We conducted a one-year, double-blind trial of lamivudine in 358 Chinese patients with chronic hepatitis B. The patients were randomly assigned to receive 25 mg of lamivudine (142 patients), 100 mg of lamivudine (143), or placebo (73) orally once daily. The patients underwent liver biopsies before entering the study and after completing the assigned treatment regimen. The primary end point was a reduction of at least two points in the Knodell necroinflammatory score. RESULTS: Hepatic necroinflammatory activity improved by two points or more in 56 percent of the patients receiving 100 mg of lamivudine, 49 percent of those receiving 25 mg of lamivudine, and 25 percent of those receiving placebo (P<0.001 and P=0.001, respectively, for the comparisons of lamivudine treatment with placebo). Necroinflammatory activity worsened in 7 percent of the patients receiving 100 mg of lamivudine, 8 percent of those receiving 25 mg, and 26 percent of those receiving placebo. The 100-mg dose of lamivudine was associated with a reduced progression of fibrosis (P=0.01 for the comparison with placebo) and with the highest rate of hepatitis B e antigen (HBeAg) seroconversion (loss of HBeAg, development of antibody to HBeAg, and undetectable HBV DNA) (16 percent), the greatest suppression of HBV DNA (98 percent reduction at week 52 as compared with the base-line value), and the highest rate of sustained normalization of alanine aminotransferase levels (72 percent). Ninety-six percent of the patients completed the study. The incidence of adverse events was similar in all groups, and there were few serious events. CONCLUSIONS: In a one-year study, lamivudine was associated with substantial histologic improvement in many patients with chronic hepatitis B. A daily dose of 100 mg was more effective than a daily dose of 25 mg.

Adolescent↗