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C H Chan

Publications and source records attributed to C H Chan.

At least 55 records · Page 3Linked to original sources
PubMed1999

Fast skeletal muscle-specific expression of a zebrafish myosin light chain 2 gene and characterization of its promoter by direct injection into skeletal muscle.

A zebrafish myosin light chain 2 cDNA clone was isolated and characterized. Sequence analysis of the clone revealed a high homology with the mammalian and avian genes encoding the fast skeletal muscle isoform, MLC2f. In situ hybridization and Northern blot hybridization analyses indicated that the zebrafish MLC2f mRNA is expressed exclusively in the fast skeletal muscle. Ontogenetically, the MLC2f mRNA appears around 16 hours postfertilization (hpf) in the first few well-formed anterior somites. At later stages, the MLC2f mRNA can also be detected in fin buds, eye muscles, and jaw muscles. To develop a useful model system for analyzing muscle gene regulation, the promoter of the zebrafish MLC2f gene was isolated and linked to the chloramphenicol acetyltransferase (CAT) reporter gene. The MLC2f/CAT chimeric constructs were analyzed by direct injection into the zebrafish skeletal muscle, and significant CAT activity was observed; in contrast, little or no CAT activity was generated from a similarly injected prolactin gene promoter/CAT gene construct. Within the 1 kb of the MLC2f promoter region, several MEF2-binding sites and E-boxes were identified, suggesting that MLC2f can be regulated by muscle transcription factors MEF2 and myogenic bHLH proteins. A 5' deletion analysis indicated that the proximal 79 nucleotides from the transcription start site, which contains a single MEF2-binding site, is sufficient to drive a high level of CAT activity in injected muscle. Internal deletion of the MEF2 element in the -79-bp construct caused an 80% decrease in CAT activity, whereas internal deletion of the same MEF2 element in a -1044-bp construct had no effect on induced CAT activity. These observations suggest that an MEF2 element is important to activate the MLC2f gene in muscle cells, and the effect of loss of the proximal MEF2 element can be compensated for by the presence of the upstream MEF2 elements. This study also demonstrated that direct injection of DNA into skeletal muscle is a valid and valuable approach to analyze muscle gene promoters in the zebrafish.

Amino Acid Sequence↗
PubMed1998

Internalization of the lymphocytic surface protein CD22 is controlled by a novel membrane proximal cytoplasmic motif.

CD22 is a key receptor on B-lymphocytes that modulates signaling during antigenic stimulation. We have defined a novel cytoplasmic motif in human CD22 that controls its unusually rapid turnover at the plasma membrane. Chimeric and mutated CD22alpha cDNA vectors were constructed and stably transfected in CD22-negative Jurkat T-lymphocytic cells. Two assays were employed to measure CD22alpha internalization: first, cytoplasmic uptake of radioiodinated anti-CD22 monoclonal antibody; and second, lethal targeting of a toxin, saporin, into cells via CD22 using bispecific F(ab')2 ([anti-CD22 x anti-saporin]) antibody. Results showed that CD22alpha lacking a cytoplasmic tail was not internalized and that replacement of the cytoplasmic tail of CD19 with that of CD22alpha resulted in a chimeric molecule that behaved like CD22alpha and internalized rapidly. Step-wise deletion of the cytoplasmic tail of CD22alpha located the internalization motif to a polar region of 11 residues (QRRWKRTQSQQ) proximal to the plasma membrane, a part of the molecule predicted to form a coil or turn structure. Interestingly, additional CD22 mutants showed that the two glutamine residues sandwiching the serine are critical to internalization but that the serine itself is not.

Antigens, CD↗
PubMed1998

Genetic heterogeneity of adrenocorticotropin (ACTH) resistance syndromes: identification of a novel mutation of the ACTH receptor gene in hereditary glucocorticoid deficiency.

Hereditary primary adrenal insufficiency syndromes due to ACTH resistance include hereditary glucocorticoid deficiency (HGD) and Allgrove's syndrome (AS). Patients with both conditions present in childhood with failure to thrive, weakness, and fatigue or adrenal crisis; patients with AS in addition have alacrima and achalasia (triple A syndrome). We studied four kindreds with HGD and four kindreds with AS for abnormalities of the ACTH receptor (ACTHR) gene. The ACTHR coding sequence in all AS kindreds and two HGD kindreds was normal. Analysis of the ACTHR gene of the proband in one of the HGD kindreds showed him to be homozygous for the previously described G221T transition causing a Ser74Ile substitution of the protein, which has been shown to inactivate the ACTHR in signal transduction. The proband in another HGD kindred was found to be a compound heterozygote with the G221T transition in one allele and a novel C818A transition in the other allele of ACTHR. The C818A transition caused the substitution of the highly conserved Pro273 by His in the receptor protein. In vitro expression of the mutated ACTHR in mouse melanoma M3 cells showed that at a medium ACTH concentration of 3 nM, cells transfected with the wild-type ACTHR produced twofold and threefold, respectively, of the amount of intracellular cAMP when compared to cells transfected with the ACTHR carrying the Pro273His and the Ser74Ile mutation, respectively, confirming that HGD in this kindred is caused by loss-of-function mutations of the ACTHR. These results showed that the genetic cause of the ACTH-resistant syndromes is heterogeneous.

Adrenal Insufficiency↗
PubMed1998

Successful treatment of disseminated coccidioidomycosis with amphotericin B lipid complex.

Coccidioidomycosis is endemic in regions of the Americas, but this infection may be encountered in travellers who return from an endemic region. A case is reported of a disseminated infection in a Hong Kong Chinese man, who was successfully treated with amphotericin B lipid complex (ABLC) after intolerance and toxicity precluded the use of other antifungal agents. Lipid-based formulations of amphotericin B merit further evaluation in the treatment of coccidioidomycosis and other systemic mycoses.

Adult↗
PubMed1998

Vein graft surveillance with scanhead tracking duplex ultrasound imaging: a preliminary report.

A severe arterial occlusion in the leg usually is bypassed by implanting a saphenous vein harvested from the limb. Once implanted, the vein functions well but over time may develop stenoses that may lead to occlusion. In order to detect and correct the stenoses that may lead to graft failure, frequent surveillance of the vein graft is required. A new ultrasound imaging method was developed to display the panoramic view of the vein graft in combination with its blood flow velocity waveform for surveillance. The panoramic view is the projection (ray-casting) image of multiple B-mode images with sequential longitudinal view of the vein graft. The velocity waveform also is recorded along the vessel with pulsed Doppler ultrasound. The acquired images and waveforms from the ultrasound scanner are registered individually in three-dimensional space with an electromagnet-based position and orientation sensor located on the scanhead. A prominent point on the scar from the surgery is used as the fiducial mark for spatial registration, so that the same lesion in the vein graft can be tracked automatically at each visit for retrospective study.

Arterial Occlusive Diseases↗
PubMed1998

Compartmentalization of pro-inflammatory cytokines in tuberculous pleurisy.

Increased levels of interleukin-6 (IL-6) and IL-8 are found in various immunologically mediated inflammatory disorders. Concentrations of IL-6, IL-8 and the soluble form of the IL-6 receptor (sIL-6R) were determined in serum and effusion fluid of 25 patients with tuberculous pleurisy utilizing enzyme linked immunosorbent assays (EIA). Serum IL-6 levels were only slightly increased in patients with tuberculous pleurisy in comparison to controls (11.1 +/- 2.1 vs 7.3 +/- 1.0 pg ml-1). IL-8 could not be detected in the serum of tuberculosis patients, but it was detected in the serum of healthy controls (8.0 +/- 1.5 pg ml-1). In comparison to serum, IL-6 and IL-8 were found in high concentrations in pleural effusions (IL-6: 932 +/- 70 vs 11.1 +/- 2.1 pg ml-1, P < 0.0001; IL-8: 450 +/- 85 vs 0 +/- 0 pg ml-1). In contrast, sIL-6R concentrations were much higher in serum compared to pleural effusion levels [30,477 +/- 1905 vs 9881 +/- 1177 pg ml-1, P < 0.0001 (mean +/- SEM)]. The authors conclude that elevated levels of IL-6 and IL-8 in pleural effusions are compartmentalized at the site of active disease. The low levels of sIL-6R in the presence of high levels of IL-6 in pleural effusions, and the high levels of sIL-6R in the presence of low levels of IL-6 in serum suggest that the expression or shedding of sIL-6R may be downregulated in the presence of excessive amounts of IL-6.

Adult↗
PubMed1998

Characteristics and outcome of delirium in psychiatric inpatients.

Delirium, a transient organic psychiatric syndrome, is a common psychiatric diagnosis. It is associated with increased rates of morbidity and mortality in medical-surgical inpatients. There have been few reports describing the risk factors and prevalence of delirium among psychiatric inpatients. The purpose of the present study was to investigate the rate of delirium, the reasons for admission, the clinical features, the etiologies and the mortality during a 2 year follow-up in psychiatric inpatients admitted to a general hospital during a 3 year period. The results show that the rate of incidence of delirium in psychiatric and geriatric (age > or = 65 years) inpatients was 1.4 and 9.6% respectively. The most common cause of delirium was adverse effects of medication. The inpatient mortality (5.9%) was lower compared with reported mortality rates in medical-surgical inpatients. However, there was a high mortality rate during the 2 year follow-up period (39.4%), especially in older patients. The high mortality during follow-up stressed the importance of after-discharge care in these patients.

Adult↗
PubMed1998

Proinflammatory cytokine levels in patients with lung cancer and carcinomatous pleurisy.

Increased levels of interleukin-6 (IL-6) and interleukin-8 (IL-8) have been reported in various diseases, including lung cancer. The role of the soluble form of the IL-6 receptor (sIL-6R) remains to be explored. We therefore measured IL-6, IL-8 and sIL-6R in effusion fluid and blood serum of 10 lung cancer patients with carcinomatous pleurisy (5 men, 5 women, age 64.3 +/- 4.4 years) by enzyme-linked immunosorbent assays. Serum levels of healthy individuals served as control. Concentrations of sIL-6R were much higher in serum compared to pleural effusion fluids of tumor patients (25,698 +/- 1,993 vs. 9,438 +/- 1,407 pg/ml: p < 0.0001). In contrast, IL-6 and IL-8 were found at high concentrations in carcinomatous pleural effusions in comparison to serum (IL-6: 964 +/- 176 vs. 10.2 +/- 1.3 pg/ml, p < 0.0001; IL-8: 319 +/- 85 vs. 9.6 +/- 9.6 pg/ml, p < 0.0001). The serum concentrations of IL-6 were not significantly increased in lung cancer patients (10.2 +/- 1.3 pg/ml) in comparison to controls (7.3 +/- 1.0 pg/ml). IL-8 was detected in the serum of only 1 patient and in low levels in the serum of controls (8.0 +/- 1.5 pg/ml; all values are mean +/- SEM). We conclude from this study that decreased levels of sIL-6R, but increased levels of IL-6 and IL-8, are found in pleural effusion fluid of patients with lung cancer and carcinomatous pleurisy. The low sIL-6R levels in the presence of high IL-6 levels in pleural effusions and the high sIL-6R levels in the presence of low IL-6 levels in serum may suggest a downregulation of sIL-6R expression of sIL-6R shedding in the presence of excessive amounts of IL-6.

Aged↗
PubMed1997

Cervical necrotising fasciitis--a rare complication of periodontal disease.

Necrotising fasciitis is a potentially fatal soft tissue infection that rarely occurs in the head and neck region. A case is reported of necrotising fasciitis arising from a periodontal abscess. The historical aspects of this infection are sketched through antiquity and its current management summarised. Prompt diagnosis and surgical debridement are the main stay of treatment. Burge and Watson suggested that success depended on 'be bloody, bold and resolute'.

Adult↗
PubMed1997

Nonnasal lymphoma expressing the natural killer cell marker CD56: a clinicopathologic study of 49 cases of an uncommon aggressive neoplasm.

Expression of the natural killer (NK) cell antigen CD56 is uncommon among lymphomas, and those that do are almost exclusively of non-B-cell lineage and show a predilection for the nasal and nasopharyngeal region. This study analyzes 49 cases of nonnasal CD56+ lymphomas, the largest series to date, to characterize the clinicopathologic spectrum of these rare neoplasms. All patients were Chinese. Four categories could be delineated. (1) Nasal-type NK/T cell lymphoma (n = 34) patients were adults 21 to 76 years of age (median, 50 years), including 25 men and 9 women. They presented with extranodal disease, usually in multiple sites. The commonest sites of involvement were skin, upper aerodigestive tract, testis, soft tissue, gastrointestinal tract, and spleen. Only 7 cases (21%) apparently had stage I disease. The neoplastic cells were often pleomorphic, with irregular nuclei and granular chromatin, and angiocentric growth was common. The characteristic immunophenotype was CD2+ CD3/Leu4- CD3epsilon+ CD56+, and 32 cases (94%) harbored Epstein-Barr virus (EBV). Follow-up information was available in 29 cases: 24 died at a median of 3.5 months; 3 were alive with relapse at 5 months to 2.5 years; and 2 were alive and well at 3 and 5 years, respectively. (2) Aggressive NK cell leukemia/lymphoma (n = 5) patients presented with hepatomegaly and blood/marrow involvement, sometimes accompanied by splenomegaly or lymphadenopathy. The neoplastic cells often had round nuclei and azurophilic granules in the pale cytoplasm. All cases exhibited an immunophenotype of CD2+ CD3/Leu4- CD56+ CD16- CD57- and all were EBV+. All of these patients died within 6 weeks. (3) In blastoid NK cell lymphoma (n = 2), the lymphoma cells resembled those of lymphoblastic or myeloid leukemia. One case studied for CD2 was negative and both cases were EBV-. One patient was alive with disease at 10 months and one was a recent case. (4) Other specific lymphoma types with CD56 expression (n = 8) included one case each of hepatosplenic gammadelta T-cell lymphoma and S100 protein+ T-cell lymphoproliferative disease and two cases each of T-chronic lymphocytic/prolymphocytic leukemia, lymphoblastic lymphoma, and true histiocytic lymphoma. All of these cases were EBV-. Six patients died at a median of 6.5 months. Nonnasal CD56+ lymphomas are heterogeneous, but all pursue a highly aggressive clinical course. The nasal-type NK/T-cell lymphoma and aggressive NK cell leukemia/lymphoma show distinctive clinicopathologic features and a very strong association with EBV. Blastoid NK cell lymphoma appears to be a different entity and shows no association with EBV.

Adolescent↗
PubMed1997

Improved treatment outcome in adult acute lymphoblastic leukemia using the intensive German protocol, a preliminary report.

Thirty-nine consecutive patients with acute lymphoblastic leukemia were treated with an intensive chemotherapy protocol. There were 23 males and 16 females with a median age of 37 years (range: 15-65). Eighteen patients had common ALL, seven had pre-B ALL, three early-precursor B ALL, seven T-ALL and four had aberrant expression of myeloid antigens (c-ALL in three and pre-B ALL in one). The median initial leukocyte count was 11.8 x 10(9)/l (range: 0.65-295). Cytogenetic result of the marrow was available in 16 of 39 patients (41 per cent) and showed Philadelphia positivity in six, a normal result in six and one each of t(4,11), t(1,19), hyperdiploidy and del 12p. Hepatosplenomegaly was present in about 20 per cent of the patients. L-Asparaginase-related hepatic toxicity was the commonest toxicity (48.7 per cent) during phase I of induction. Prolonged pancytopenia and hypoplastic death were common during phase II. With the use of growth factors during the neutropenic period of phase II induction, the rate of hypoplastic death was reduced from 40 per cent to 3 per cent. Common causes of treatment failure included early hypoplastic death (27.8 per cent) and leukemia relapses (50 per cent) while primary refractory leukemia, hepatic failure and perforated peptic ulcer contributed to 11.1, 5.5 and 5.5 per cent of the other deaths. A high complete remission (CR) rate (87.4 per cent) was achieved after phase I induction. The median event-free survival (EFS) was 8 months and the 3-year event-free survival was 43 per cent. This result compared favourably to the other regimens previously employed in our institution. In conclusion, satisfactory survival can be achieved with this intensive regimen. Good supportive care was however, essential to minimize toxicities.

Adolescent↗
PubMed1997

Procoagulant activity of purified protein derivative-stimulated pleural effusion mononuclear cells in tuberculous pleurisy.

Mononuclear cells (MNC) generate cell-bound procoagulant activity (PCA) which shortens recalcification time after incubation with an antigen to which the donor has been sensitized. PCA has been demonstrated in various lung diseases, including exudative pleural effusions. To determine the value of measuring cell-bound PCA in the diagnosis of tuberculous pleural effusions we examined pleural effusion MNC of patients with tuberculosis (n = 19), congestive heart failure (n = 7), and carcinoma (n = 7). MNC were isolated, incubated in 0 or 10 micrograms/ml purified protein derivative (PPD) for 15 min and for 20 h, and recalcification time determined. Incubation with thromboplastin was used as control. The recalcification times in serum incubated for 15 min varied within a wide range, the mean values were longest for tuberculous effusion MNC, incubation for 20 h increased variation. Incubation of cells for 15 min with thromboplastin led to a decrease of mean recalcification time in tuberculous (p < 0.001) and heart failure (p < 0.05), and with no significance in carcinomatous effusions. Incubation with PPD led to decrease of recalcification time which was not significant. Comparisons of the mean relative recalcification times after PPD incubation showed that tuberculosis differed from lung cancer (p < 0.001), lung cancer from heart failure (p < 0.05), but not heart failure from tuberculosis. We conclude from our study that pleural effusion MNC express spontaneous PCA in vitro which is strongest in carcinomatous pleural effusions. Incubation of MNC with thromboplastin and less discernable with PPD leads to an increase in PCA which is more pronounced in tuberculous pleural effusions. However, due to substantial intersubject variability and overlap between the study groups, this test does not allow reliable differentiation of tuberculous from other MNC rich pleural effusions.

Blood Coagulation↗
PubMed1997

Hospitalized patients with community-acquired pneumonia in Hong Kong: a randomized study comparing imipenem/cilastatin and ceftazidime.

The aetiology and outcome of hospitalized patients with moderate to severe community-acquired pneumonia (CAP) were evaluated in 60 adult patients (38 male 22 female, mean age 68.4 years). They were randomized for treatment with either ceftazidime or imipenem/cilastatin intravenously for 7 days. Bacteriological diagnoses were made in 25 cases (41.6%): Streptococcus pneumoniae (5), Haemophilus influenzae (5), Pseudomonas spp. in particular Pseudomonas aeruginosa (8), Staphylococcus aureus (4), Chlamydia spp. (2), Mycobacterium tuberculosis (2) and Moraxella catarrhalis (3); mixed organisms were found in 4 patients. Forty-two patients (70%) responded satisfactorily to the regimens with improvement in sputum purulence cough and dyspnoea scores; there was no difference in response between the two groups. Sixteen patients (26.6%) underwent bronchoscopy on day 4 because of inadequate response to the antibiotics regimens, and 9 of them (15%) required a modification of the initial treatment with addition of erythromycin in 5 patients vancomycin in 1 cloxacillin in 1 and antituberculous drugs in 2. Three out of the 60 patients (5%) died of pulmonary sepsis: the aetiological agents were M. tuberculosis in one, Pseudomonas spp./methicillin-resistant S. aureus in another, but were not identified in the third. We conclude that treatment with either ceftazidime or imipenem/cilastatin was efficacious for moderate to severe CAP in Hong Kong.

Adult↗
PubMed1997

Impact of immigration on tuberculosis infection among Canadian-born schoolchildren and young adults in Montreal.

We conducted a cross-sectional tuberculin survey among non-BCG-vaccinated Canadian-born schoolchildren in grades 6 and 10, health professional students, and young adult workers, to estimate the association of tuberculin reactions with indices of contact with tuberculosis. Participants underwent simultaneous tuberculin testing with PPD-T (standard) and PPD-B (from M. intracellulare). Exposure was estimated from questionnaire responses, group, aggregate census, and tuberculosis incidence data. Of 3,710 participants, 88 (2.4%) had positive tuberculin reactions, i.e., of 10+ mm. Positive tuberculin reactions were rarely associated with larger reactions to PPD-B, but were associated with older age (adjusted odds ratio for each 5 years: 1.5 [95% confidence interval, 1.3, 1.8]), household contact (4.2 [1.4, 12.7]), and population group (health professional versus all others: 0.6 [0.3, 1.0]). Estimated annual risk of infection declined by 3% per year. Tuberculin reactions were not associated with any indices of contact in school, work or neighborhood settings with foreign-born from tuberculosis endemic areas, nor with tuberculosis in Canadian-born. There was no evidence of transmission of tuberculosis from affected high risk sub-groups in Montreal to the general population working or attending school.

Adolescent↗
PubMed1997

Cytokine gene expression profile of circulating CD4+ T cells in active pulmonary tuberculosis.

T lymphocytes, particularly CD4+ cells, are thought to play an important role in the immune defense against Mycobacterium tuberculosis through the release of their wide array of cytokines. In vitro studies suggest that Mycobacterium-specific T-cell clones are of the TH1 subtype. Using the technique of reverse transcription-polymerase chain reaction, we have investigated the capacity for cytokine gene expression profile in ex vivo circulating CD4+ T cells from 20 patients with active pulmonary tuberculosis compared with that of 30 normal healthy tuberculin-positive volunteers. Venous blood samples were collected from the former prior to the initiation of chemotherapy. A significant increase in interleukin (IL-2) expression (p < 0.001) and a significant decrease in IL-5 expression (p < 0.0001) were observed in patients with tuberculosis but no differences were seen in the expression of IL-4 and interferon gamma between the two study groups. Our data support a TH1-like immune response in active tuberculosis.

Adolescent↗