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Biomedical subjects

C C Leung

Publications and source records attributed to C C Leung.

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

Characteristics of workers attending the pneumoconiosis clinic for silicosis assessment in Hong Kong: retrospective study.

OBJECTIVE: To describe and analyse the baseline characteristics of workers attending the pneumoconiosis clinic for assessment of silicosis. DESIGN: Retrospective cross-sectional study. SETTING: Outpatient clinic. PATIENTS: One thousand and fifty-six patients with silica dust exposure attending the pneumoconiosis clinic for compensation assessment. MAIN OUTCOME MEASURES: Baseline demographic characteristics, lung function parameters, and radiographic findings. RESULTS: Six hundred and forty-eight patients were diagnosed with silicosis, of which 10 were female. Excluding the data on female patients, the mean duration of dust exposure was 24.2 years. The majority of patients were involved in caisson work and stone splitting. Most newly diagnosed patients had simple silicosis. Less than a quarter (24.8%) had progressive massive fibrosis. Lung function parameters at diagnosis were within the normal range. Pulmonary tuberculosis remained an important co-existing disease. CONCLUSION: The major cause of silicosis in Hong Kong is chronic silica dust exposure in the construction industry. Simple silicosis predominated at diagnosis, with normal lung function parameters seen in the majority of patients.

Adult↗
PubMed2000

Antituberculosis drug-related liver dysfunction in chronic hepatitis B infection.

Liver toxicity is a common side effect of antituberculosis (anti-TB) drugs. We studied the differences in liver dysfunction observed during anti-TB treatment between hepatitis B virus carriers (HBV) and noncarriers. Three hundred twenty-four patients on anti-TB drugs were recruited and followed up for 1 year. Forty-three patients with HBV and 276 non-HBV patients were included for analysis. Liver function tests and viral markers were monitored monthly. Liver biopsy was requested whenever the alanine transaminase (ALT) was persistently abnormal. Eighty-six HBV carriers who were not given anti-TB drugs were chosen as a second control and evaluated prospectively. The incidence of liver dysfunction was significantly higher in HBV carriers given anti-TB drugs (34.9%) when compared to noncarriers (9.4%, P <.001) and with HBV carriers not given anti-TB drugs (8.1%, P <.001). For patients given anti-TB drugs, HBV carriers who developed liver dysfunction were younger (P =.011) and had more severe liver injury compared with noncarriers (P =.008). By multiple logistic regression analysis, age (P =.002) and hepatitis B infection (P <.001) were the only 2 significant risk factors for hepatotoxicity related to anti-TB therapy.

Adult↗
PubMed2000

Lung cancer mortality among a cohort of men in a silicotic register.

To examine any association between silicosis and lung cancer, the clinic records of a cohort of 1502 silicotic workers diagnosed after 1981 were reviewed. All of the essential data, including occupational exposure, smoking habits, radiographic extent of silicosis, and vital status of each subject, were noted. The standardized mortality ratio for various causes of death was calculated. Thirty-three patients died from lung cancer, giving a standardized mortality ratio of 1.94 (95% confidence interval, 1.35 to 2.70). However, smoking accounted for most of the excess of lung cancer deaths among the silicotic workers in the cohort, and no consistent relationship between lung cancer mortality risk and either duration of exposure to silica dust or severity of silicosis was observed. There is no conclusive evidence in our data to support the hypothesis that lung cancer may be associated with silicosis.

Adult↗
PubMed2000

Effect of pre-incision skin infiltration on post-hysterectomy pain--a double-blind randomized controlled trial.

In this double-blind placebo-controlled randomized trial, we compared the analgesic effect of preoperative 0.25% bupivacaine (n = 21) skin infiltration with normal saline (n = 19) in patients undergoing abdominal hysterectomy through a lower midline incision. All patients received postoperative patient-controlled analgesia with morphine and were followed for 72 hours. The main outcome measures were morphine consumption and pain score at rest, and the contribution of different components of pain was also assessed prospectively. No statistically significant differences were found. All except one patient (n = 39) could distinguish the different characteristics of somatic and visceral pain. Visceral pain predominated in the first 48 hours. We concluded that local anaesthetic infiltration is not effective in reducing pain after abdominal hysterectomy. Effective postoperative analgesia should aim to eliminate the visceral pain component.

Analgesia, Patient-Controlled↗
PubMed2000

Outcomes of patients with multidrug-resistant pulmonary tuberculosis treated with ofloxacin/levofloxacin-containing regimens.

OBJECTIVE: To analyze outcomes of patients with multidrug-resistant tuberculosis (MDR-TB) treated with ofloxacin/levofloxacin-containing regimens. MATERIALS AND METHODS: From February 1990 through June 1997, 63 MDR-TB patients (with bacillary resistance to at least isoniazid and rifampin in vitro) were analyzed retrospectively. Twenty-two patients (34.9%) had had no previous antituberculosis chemotherapy. Each patient received either ofloxacin (53) or levofloxacin (10) even though 13 patients had bacilli resistant to ofloxacin in vitro. The other accompanying drugs mainly included aminoglycosides, cycloserine, ethionamide/prothionamide, and pyrazinamide. Sputum smear and culture examinations for acid-fast bacilli (AFB) were performed monthly for the initial 6 months and then at 2- to 3-month intervals until the end of treatment. Comparison was made between clinical successes and failures using univariate and multiple logistic regression analyses for the following variables: age, sex, presence of cavitation, extent of disease, sputum smear positivity, in vitro resistance to ofloxacin, in vitro resistance to streptomycin and/or ethambutol, treatment adherence, and the number of drugs per regimen. RESULTS: Fifty-one patients (81.0%) were cured, nine patients (14.3%) failed, and three patients (4.7%) died. For the entire group, the mean duration of treatment was 14.0 months, and the mean number of drugs was 4.7. Mean durations of chemotherapy in successful and failed patients were 14.5 and 14.2 months, respectively. Mean time for sputum smear and culture conversions were 1.7 and 2.1 months, respectively. Only cavitation, resistance to ofloxacin, and poor adherence were found to be variables independently associated with adverse outcomes (p < 0.05; odds ratios = 15.9, 13.5, 12.8, respectively). Negative sputum cultures after 2 and 3 months of therapy were 100% predictive of cure. Positive sputum cultures after 2 and 3 months were 52.3% and 84.6% predictive of failure, respectively. One patient (2.1%) relapsed after apparent cure. Twenty-five patients experienced adverse drug reactions, but only 12 of them needed drug modifications. CONCLUSION: Most MDR-TB patients can be treated effectively with ofloxacin/levofloxacin-containing regimens. Presence of cavitation, resistance to ofloxacin in vitro, and poor adherence to therapy portend treatment failure. Monitoring monthly sputum culture for AFB in the initial months of chemotherapy helps predict clinical outcomes.

Adult↗
PubMed2000

An unusual case of double tuberculous broncho-oesophageal fistulas in an adult.

Broncho-oesophageal fistula associated with tuberculosis is rarely reported in the literature and has not been reported in Hong Kong. We describe a 30-year-old Chinese human immunodeficiency virus (HIV)-negative man with double tuberculous broncho-oesophageal fistulas proven by histology. Constitutional symptoms of active tuberculosis were absent and chest radiograph did not show an obvious lung lesion. Our case shows that broncho-oesophageal fistula can be the sole manifestation of active tuberculosis and that the diagnosis should be suspected in patients who are seen with chronic respiratory symptoms in areas where the prevalence of tuberculosis is high.

Adult↗
PubMed1998

Rifapentine and isoniazid in the continuation phase of treating pulmonary tuberculosis. Initial report.

A randomized comparison has been made of three times weekly rifampin plus isoniazid (HR3) with rifapentine plus isoniazid given once weekly (HRp1) or on 2 of 3 wk (HRp1.2/3) in the continuation phase of 6-mo regimens (each starting with an initial 2 mo of 4-drug therapy) for the treatment of pulmonary tuberculosis in 672 Chinese patients in Hong Kong. Because of poor bioavailability of the rifapentine used (produced in China), its dose size was increased from 600 mg initially to about 750 mg in the last third of patients to obtain serum concentrations similar to those with rifapentine of Western origin; all doses were given after a meal promoting absorption. After initial exclusions, an intent to treat analysis, done on the remaining 592 patients, showed 45 adverse treatment events in 7 of 190 HR3 patients, in 17 of 199 HRp1 patients, and in 21 of 203 HRp1.2/3 patients; of these, 42 were bacteriological or radiographic relapses after the end of treatment (HR3 versus HRp1, p = 0.04; HR3 versus HRp1.2/3, p = 0.01). Patients with organisms initially sensitive or resistant to isoniazid or streptomycin had similar relapse rates. The high relapse rate in the HRp1 regimen suggests that the rifapentine dose should be increased. Similarity of relapse rates, 8.9% and 10.4%, after the HRp1 and HRp1.2/3 regimens, respectively, indicates that irregularity in taking rifapentine/isoniazid could be tolerated. The few adverse side effects in the continuation phase in the rifapentine regimens were less frequent than in the HR3 regimen.

Adolescent↗
PubMed1995

Activation of NADPH-oxidase and its associated whole-cell H+ current in human neutrophils by recombinant human tumor necrosis factor alpha and formyl-methionyl-leucyl-phenylalanine.

Proton accumulation and efflux associated specifically with NADPH oxidation in neutrophils remains to be elucidated. Using confocal fluorescence and patch-clamp recordings from single human neutrophils, in the presence of protein kinase C inhibitors, we studied the transient cytosolic acidification and whole-cell H+ current induced by N-formyl-methionyl-leucyl-phenylalanine (fMLP) and recombinant human tumor necrosis factor alpha (rhTNF alpha). Intracellular pH changes were monitored utilizing the ratiometric imaging of the dual emission fluoroprobe, carboxyseminaphthorhodafluor-1, AM acetate. Bath application of 1000 units/ml rhTNF alpha or 0.1 microM fMLP changed the fluorescence of fluoroprobe-loaded cells, indicating generation of cytosolic H+ ions. In the absence of Ca2+ in the pipette solution, exposure of cells to rhTNF alpha or fMLP for 10 s activated voltage-dependent H+ currents. From tail current analysis, the threshold voltage for H+ current activation was approximately -50 mV. These fMLP- or rhTNF alpha-activated voltage-dependent H+ currents were augmented further in the presence of 0.1 mM of NADPH in the pipette solution, and they were inhibited by bath application of 50 microM of apocynin, an NADPH oxidase inhibitor. These results indicate that rhTNF alpha- or fMLP-induced NADPH oxidase in human neutrophils gives rise to the activation of voltage-dependent H+ currents.

Amino Acid Sequence↗
PubMed1995

TNF-alpha induces tyrosine phosphorylation of mitogen-activated protein kinase in adherent human neutrophils.

Recombinant human TNF-alpha induces increased tyrosine phosphorylation of several proteins in human neutrophils (PMN) adhered to serum-coated plastic. When PMN are kept in suspension, TNF does not induce significant tyrosine phosphorylation. In adherent PMN, a 42-kDa protein (p42) displayed the most striking increase in tyrosine phosphorylation after TNF stimulation. Cell lysates of TNF-stimulated PMN were separated by two-dimensional gel electrophoresis and were immunoblotted with either anti-phosphotyrosine (alpha-PY) mAb or anti-mitogen-activated protein kinase (alpha-MAPK) mAb. Both Abs detected p42, and the spots were superimposable. Cell lysates were immunoprecipitated with agarose-conjugated alpha-PY mAb, electrophoresed, and then immunoblotted with alpha-MAPK Ab; alternatively, cell lysates were immunoprecipitated with agarose-conjugated alpha-MAPK Ab, electrophoresed, and then immunoblotted with alpha-PY mAb. In both cases, p42 was detected. These results demonstrate that p42 is a member of the MAPK family. TNF induces a time-and dose-dependent increase in tyrosine phosphorylation of p42 and MAPK activity. The degree of p42 tyrosine phosphorylation parallels the level of MAPK activity. MAPK activity was determined by measuring 32P phosphorylation of a synthetic peptide containing the recognition site on myelin basic protein for MAPK. PMN pretreatment with genistein, a tyrosine kinase inhibitor, inhibited the TNF-induced increase in tyrosine phosphorylation and MAPK activity. These results indicate that TNF signaling involves activation of MAPK.

Amino Acid Sequence↗
PubMed1992

Immunocytochemical localization of cyclooxygenase in the rat lens.

The localization of rat lens fatty acid cyclooxygenase (prostaglandin synthase) was studied using indirect immunofluorescent and indirect streptavidin-biotin immunoperoxidase staining techniques. Both methods employed monoclonal and polyclonal antibodies directed against fatty acid cyclooxygenase, the key enzyme in the conversion of arachidonic acid to prostaglandins. The immunocytochemical studies demonstrate that (1) fatty acid cyclooxygenase is present in the rat lens epithelial cell layer; (2) the enzyme appears predominantly in the cytoplasm; (3) there is an apparent higher concentration of the enzyme in the region designated as germinative and transitional zones, and meridional rows; and (4) the enzyme appears to be absent in the lens capsule and in the nucleus of the lens. The presence of the cyclooxygenase enzyme in the lens epithelium, especially the relative intense staining in the epithelial mitogenic region, suggests that oxygenation of polyunsaturated fatty acids by the fatty acid cyclooxygenase may have an important role in cellular differentiation.

Animals↗
PubMed1991

Localization of interleukin-1 beta in human periodontal tissue.

Interleukin-1 beta (IL-1 beta) is the predominant form of IL-1 produced by macrophages. IL-1 beta possesses numerous and diverse biological activities. Several of these activities, including fibroblast proliferation, potentiation of the immune response, and stimulation of bone resorption may be of relevance to the pathogenesis of periodontal disease. This study was designed to examine the presence of IL-1 beta in human periodontal tissue. An antiserum directed against the N-terminal segment (117-131) of human IL-1 beta was used to detect IL-1 beta using immunofluorescent staining techniques. IL-1 beta positive staining cells were observed in both normal and diseased tissue and were limited to the lamina propria. Brightly staining cells were increased by almost 3-fold in periodontally diseased tissue when compared to normal tissue. Low intensity staining cells were equally distributed in the normal and diseased specimens. We propose that IL-1 beta and IL-1 beta produced by cells in periodontal tissues may be related to the pathological processes associated with periodontal disease.

Adult↗
PubMed1990

Autologous immune complex glomerulonephritis induces abnormal embryonic development.

Young female random-bred Wistar rats were immunized with homologous renal brush border membranes. The immunized animals exhibited all the clinical and immunopathological characteristics of chronic autologous immune complex glomerulonephritis (Heymann nephritis) closely resembling the idiopathic membranous glomerulonephritis in humans. The animals were subsequently mated. Congenital malformations and fetal growth retardation were observed in the offspring of the nephritic mothers; high incidence of embryonic/fetal resorptions was also observed. The types of anomalies were microphthalmia, cataractic lens, abnormal retina, micrognathia, cleft palate, lordosis, fetal edema, variable hemorrhage, omphalocele, syndactaly and cryptochidism. The most frequently observed anomaly was associated with the eye. Immunofluorescent studies indicated that no rat IgG was detected in the extraembryonic membranes, embryo or fetuses. Rat complement C3 was also absent around the conceptuses. The pathophysiologic mechanism leading to such deleterious embryonic/fetal effect is not clear.

Animals↗
PubMed1990

Sleep apnoea syndrome--a study of 5 cases.

Sleep apnoea syndrome (SAS) is common in the West but its prevalence is uncertain in Southeast Asia. Five Chinese patients seen in a Sleep Assessment Unit in Hong Kong are presented to illustrate the spectrum of clinical features and treatment methods involved in obstructive and central sleep apnoea. The first patient is a 45-year old woman with severe obstructive SAS and cardiopulmonary complications who improved significantly after tracheostomy. The second patient is a 43-year old man who improved with weight reduction and protriptyline. The third is a 42-year old man whose SAS did not improve with uvulopalatopharyngoplasty but with continuous positive airway pressure (CPAP). The fourth is a 12-year old girl with obstructive SAS who improved significantly after tonsillectomy. The last patient is a 52-year old man with central SAS who improved with CPAP.

Child↗
PubMed1989

Teratogenic antibodies are directed against a coated-pit glycoprotein.

It has been well established that heterologous antibodies against certain tissue components may cause congenital abnormalities when injected into pregnant rats during the critical period of organogenesis. A glycoprotein antigen (gp340) of rat renal proximal tubules was isolated (C.C.K. Leung: (J. Exp. Med., 156:372-384, 1982); antibodies against gp340 were teratogenic. Indirect colloidal gold immunocytochemical method was utilized to study the ultrastructural localization of gp340. For comparative studies, both preembedding and postembedding immunostaining procedures were used. The results indicate that gp340 is a resident of coated pits and possibly also of coated vesicles of the rat renal proximal tubules and visceral yolk-sac (VYS) endodermal cells. It appears that gp340 may also be associated with the microvilli and some as-yet-unidentified cytoplasmic structures of the same tissues. However, gp340 is absent on the epithelium of the small intestine. It is hypothesized that the teratogenic antibodies may interact with gp340 on the coated pits and interfere with receptor-mediated endocytosis, causing yolk-sac placenta dysfunction which in turn causes abnormal embryonic development.

Animals↗
PubMed1989

Anti-kidney antibody teratogenesis: evidence for a direct action on the rat conceptus by a mechanism involving the yolk sac.

IgG from anti-rat kidney antiserum (anti-K) was added to 48-h cultures of 9.5-day whole rat conceptuses. At concentrations of 25 micrograms/ml and above, dysmorphogenesis of embryos (optic vesicle defects) was observed. Significant embryonic growth retardation was apparent at 75 micrograms/ml and above. Other abnormalities (neural tube defects, deficits in axial rotation, reduced somite numbers) were seen at 100 and 150 micrograms/ml. In separate experiments, anti-K inhibited pinocytosis of 125I-polyvinylpyrrolidone by isolated yolk sacs. All of these effects of anti-K are similar to those produced by anti-visceral yolk sac antiserum suggesting a similar mechanism of teratogenic action, namely interference with yolk-sac-mediated embryotrophic nutrition.

Abnormalities, Multiple↗
PubMed1988

Intact teratogenic immunoglobulins may reach the rat embryo.

It is known that heterologous antiserum against rat kidney homogenate may induce congenital malformations when injected into pregnant rats during the period of organogenesis. Teratogenic rabbit antibodies against a purified rat renal tubular glycoprotein were isolated, labelled with 125I and injected into pregnant rats on the 10th day of gestation. Extracts of visceral yolk-sacs (VYS) and embryos were obtained 16 h later and chromatographed separately on a Sephacryl S-300 gel filtration column. The resultant chromatograms showed several radioactive peaks, one of which coincided with the eluate of intact rabbit immunoglobulins G (IgG). We interpret the result as an indication that some undigested intact teratogenic IgG were present in VYS and the embryo.

Animals↗
PubMed1988

Teratogenic antibody internalization by rat visceral yolk-sac endoderm in vitro: an ultrastructural colloidal gold tracer study.

Previous work from our laboratory has demonstrated that specific rabbit immunoglobulins G (IgG) against a glycoprotein antigen of rat kidney proximal tubule or a cross-reacting visceral yolk-sac endodermal cell antigen will induce abnormal embryonic development when they are injected into pregnant rats during the period of organogenesis. It has been proposed that these antibodies may induce embryopathy by interfering with functions of the visceral yolk-sac placenta, an important organ providing nutrients to the embryo at this stage of development. In order to gain some insight into the underlying pathogenic mechanism(s) in which specific teratogenic IgG may interfere with visceral yolk-sac functions, we examined the uptake of these teratogenic IgG by the visceral yolk-sac endodermal cells at the electron microscopic level. The results demonstrated that teratogenic rabbit IgG specifically localized on the fuzzy coat of the external apical cell membrane of the visceral yolk-sac endoderm at the intermicrovillous region. Within 5 min, the IgG were rapidly internalized via coated pits and micropinocytic vesicles. Within 30 min, an increasing proportion of gold particles appeared within uncoated vesicles or vacuoles of various sizes; most of the gold particles were in close proximity to the inner membranous lining of the vesicles. Similar findings were observed after 1- or 2-hr incubation. After 24- to 48-hr culture, however, the gold particles appeared to have dissociated from the inner surface of the vesicle membrane.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗