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Biomedical subjects

C H Chan

Publications and source records attributed to C H Chan.

At least 91 records · Page 5Linked to original sources
PubMed1995

Scrub typhus pneumonitis with delayed resolution.

A 35-year-old lady was admitted to hospital with fever and dry cough. Chest radiograph showed bilateral basal infiltrate. Her Weil-Felix test was strongly positive (OX-K > 1:160) and her fever came down with intravenous tetracycline. There was no improvement in the lung shadow and spirometry showed a severe restrictive defect. Open lung biopsy confirmed the diagnosis of interstitial pneumonitis. CT of thorax 6 months after presentation showed partial resolution of the interstitial shadow.

Adult↗
PubMed1994

The spectrum of chronic lymphoproliferative disorders in Chinese people. An analysis of 64 cases.

BACKGROUND: Chronic lymphoproliferative disorders are considered rare in Oriental patients and are thought to constitute only 2% of all leukemias in these patients, compared to 20-30% in Western patients. We conducted a retrospective analysis of Chinese patients with chronic lymphoproliferative disorders to define the frequency and spectrum of these disorders. METHODS: A consecutive series of Chinese patients with leukemia and lymphoproliferative disorders seen at two regional hospitals in Hong Kong were analyzed retrospectively. The diagnosis of chronic lymphoproliferative disorders was based on morphologic and immunologic criteria proposed by the French-American-British Cooperative Study Group. RESULTS: Sixty-four Chinese patients with chronic lymphoproliferative disorders were identified, and these patients constituted 19% of a total of 342 cases of leukemia diagnosed in 3 years. Chronic lymphocytic leukemia was the most common form, occurring at a frequency of 12.5% of all leukemias. The clinicopathologic features of these patients were similar to those of Western patients, except that Chinese patients tended to present with more advanced (Rai's Stages III and IV; Binet's Stage C) and bulky (splenomegaly > 9 cm) disease, and expressed lambda light chain about six times more frequently. Other chronic lymphoproliferative disorders identified in this study included prolymphocytic leukemia, mantle zone lymphoma, hairy cell leukemia, splenic lymphoma with villous lymphocytes, large granular lymphocyte leukemia, and Sezary syndrome. The authors did not identify any case of human T-cell lymphotropic virus-I-related lymphoproliferative disorders within the study period. CONCLUSION: In addition to providing the frequencies of various chronic lymphoproliferative disorders in southern Chinese people, this study also showed that these disorders no longer should be considered rare in this population. Inherent biologic differences between lymphoproliferative disorders in Chinese and Western patients also may exist.

Adult↗
PubMed1994

Procoagulant activity of PPD-stimulated human lymphocytes after cryopreservation.

OBJECTIVE: Human mononuclear cells from a previously sensitized donor generate procoagulant activity (PCA) following stimulation with purified protein derivative (PPD). Lymphocytes of tuberculous pleural effusions are also highly responsive to PPD stimulation. We examined the influence of cryopreservation on lymphocytes following stimulation with PPD. DESIGN: Peripheral blood lymphocytes of 5 healthy PPD skin test positive subjects were incubated with either PPD, thromboplastin, or concanavalin A (Con A) at concentrations of 0, 1, and 10 micrograms/ml. PCA was determined by measuring the recalcification time. Tests were repeated following cryopreservation for 4 weeks. RESULTS: Incubation of fresh lymphocytes led to a dose dependent shortening of recalcification time: PPD (0-1-10 micrograms/ml: 100-84-65%), thromboplastin (0-1-10 micrograms/ml: 100-85-62%), and Con A (0-1-10 micrograms/ml: 100-85-42%). These results were highly reproducible when tests were repeated 6 weeks later. Cryopreservation did not significantly affect the expression of PCA following incubation with PPD and with thromboplastin. In contrast, cryopreservation significantly diminished the degree of Con A generated PCA. CONCLUSION: Cryopreservation and storage of human lymphocytes is possible without alteration of PCA expression following their incubation with PPD or thromboplastin.

Blood Coagulation Factors↗
PubMed1994

Endobronchial tuberculosis: diagnostic features and therapeutic outcome.

BACKGROUND: Endobronchial tuberculosis (EBTB) is not seen often in the adult population. In most cases it is associated with pulmonary tuberculosis. During its course significant tracheobronchial stenosis may develop. In this study we report our experience with patients with EBTB. METHODS: The records of 38 patients in whom EBTB had been proved by fibre optic bronchoscopy, microbiology and histology studies were evaluated. RESULTS: Symptoms were non-specific and represented mainly the co-existing pulmonary tuberculosis. Signs characteristic of airway obstruction were rare (localized wheezing in 6%). Indications for bronchoscopy were radiographic features (87%), microscopy smear negatives (8%), wheezing (3%), and blood stained sputum (3%). The lesions were more likely to be seen in the main and upper bronchi. In 5% of patients the lower trachea was involved. Most lesions looked inflamed (51%), followed by caseous (19%), granulomatous (17%), ulcerative (12%), and fibrotic appearance (1%). The degree of stenosis was nil (22%), minor (45%), significant (13%), subtotal (13%), or total (7%). The patients were treated with a combination of antituberculosis drugs. Four patients underwent surgical procedures. Dilatation techniques were used in two patients for a right and left main bronchus stenosis respectively, with significant improvement in one. Dilatation in combination with laser therapy of a right intermediate bronchus stenosis did not result in re-expansion of the dependent part of the lung due to pleural adhesions. Left pneumonectomy was performed in one patient for destroyed lung. Twenty-two patients agreed to follow up bronchoscopy. The macroscopic appearance of the mucosa had improved in most cases but the degree of stenoses was unchanged in a considerable proportion (58%). Bronchial stenosis in one patient subsided during therapy but developed again at a later stage. CONCLUSIONS: Patients with pulmonary tuberculosis and radiographic evidence of volume loss are recommended to undergo bronchoscopy to rule out EBTB. Specific symptoms for EBTB are rare. Biopsy of inflamed areas of bronchial mucosa seems to be indicated. Despite adequate antituberculosis therapy tracheobronchial stenosis may develop. Long term follow up including bronchoscopy seems therefore advocated. Dilatational intervention may be indicated in selected cases.

Adolescent↗
PubMed1994

Increase of both circulating Th1 and Th2 T lymphocyte subsets in IgA nephropathy.

IgA nephropathy (IgAN), characterized by glomerular deposition of IgA and frequently elevated plasma IgA levels, has increased T helper cell activity. In vitro measurement of cytokines in supernatant of cultured peripheral lymphocytes revealed conflicting findings. We examined the profile of cytokine mRNA expressed in purified CD4+ cells in patients with IgAN in order to study their pattern of Th1 (releases IL-2 and interferon-gamma (IFN-gamma)) and Th2 (releases IL-4 and IL-5) T cell response. We assessed the circulating CD4+ T cells in patients and normal controls by the expression of messenger RNA (mRNA) for IL-2, IL-4, IL-5 and IFN-gamma. The cytokine mRNAs were analysed with reverse transcription-polymerase chain reaction and were measured semiquantitatively by using a housekeeping gene, beta-actin. Compared with the control subjects, CD4+ T lymphocytes from patients with IgAN expressed a higher level of IL-2 mRNA (P = 0.007), IFN-gamma mRNA (P = 0.04), IL-4 mRNA (P = 0.048), and IL-5 mRNA (P = 0.016). Within these patients with IgAN, a good correlation was demonstrated between the gene expression of cytokines in Th1 or Th2 cells. The IL-2 mRNA levels in Th1 cells from these patients with IgAN also correlated significantly with the IL-4 or IL-5 mRNA levels in their Th2 cells. Our study revealed IgAN is associated with activation in circulating lymphocytes of the IL-2, IFN-gamma, IL-4 and IL-5 gene cluster, a pattern compatible with activation of both the Th1- and Th2-like T lymphocyte population. The increased transcription of these cytokines genes may be contributory to the immunopathologic findings in IgAN.

Base Sequence↗
PubMed1994

Circulating leukocyte-endothelial adhesion molecules in IgA nephropathy.

There is accumulating evidence that leukocyte-endothelial adhesion molecules are important in inflammatory injury in being involved in the primary step of entrapment and migration of leukocytes to the site of inflammation. We have used an antigen capture ELISA to measure the levels of circulating intercellular adhesion molecule-1 (cVCAM-1), vascular cell adhesion molecule-1 (cVCAM-1) and E selectin (cE selectin) in the peripheral blood of 33 patients with IgA nephropathy (IgAN) during clinical quiescence and 24 healthy controls. The serum levels of cICAM-1 and E selectin in IgA-nephritic patients were not different from that of healthy controls but the cVCAM-1 level was significantly elevated in IgAN despite a lack of clinical activity (p = 0.008). The differential rise of circulating leukocyte-endothelial adhesion molecules in IgAN probably reflects the origins and nature of these molecules as well as the specific immunological profile of IgAN. There was no correlation between the levels of these three circulating adhesion molecules. When the patients with IgA nephropathy were stratified according to the severity of their glomerular and interstitial lesions, there was an apparent increase in cE selectin and cVCAM-1 associated with increased histopathologic grading. The changes in endothelial adhesion molecules during clinical exacerbation were studied in 10 patients. Coinciding with synpharyngitic macrohematuria, there was a significant rise of cVCAM-1 and cE selectin (p = 0.046 and p = 0.016, respectively) but no similar rise was observed in cICAM-1.(ABSTRACT TRUNCATED AT 250 WORDS)

Cell Adhesion↗
PubMed1994

The prevalence of hypercalcaemia in pulmonary and miliary tuberculosis--a longitudinal study.

We studied the prevalence of hypercalcaemia in 34 Chinese patients with pulmonary (n = 32) or miliary (n = 2) tuberculosis. None of these subjects were given vitamin D or calcium supplements. Plasma calcium levels were measured at presentation and at 1- to 2-monthly intervals after treatment. During the 6-month study period, two patients (6%) developed hypercalcaemia (plasma calcium greater than 2.51 mmol/l), as compared to figures of 16% to 28% in the United States and India. By correcting the plasma calcium to a normal albumin, five (15%) of our patients were hypercalcaemic, as compared to a figure of 48% in Greece. Apart from variations in methodology, discrepancies in the reported prevalence of hypercalcaemia in tuberculosis may be due to differences in sun exposure, and vitamin D and calcium intake.

Adolescent↗
PubMed1994

[Roentgen findings in bronchial tuberculosis].

To determine the value of chest roentgenographic findings in the diagnosis and therapy of endobronchial tuberculosis we analysed roentgenograms of 41 patients with endoscopically confirmed tuberculous involvement of the intrathoracic airways. 40 patients had infiltrates typical for pulmonary tuberculosis predominantly in the upper lobes. Signs of diminished air entry in form of collapse or consolidations were found in 52%. 10 patients had cavities and two had a destroyed lung. In only one patient the chest roentgenogram was completely normal demonstrating a case of isolated endobronchial tuberculosis. During antituberculosis drug therapy radiological signs improved in 38 of 41 patients, but in more than half of the cases stenoses persisted as verified by bronchoscopy. We conclude that endobronchial tuberculosis is usually accompanied by lung parenchyma involvement and that roentgenological findings are characterised by signs of pulmonary tuberculosis in most cases. A normal chest roentgenogram does not exclude endobronchial tuberculosis. Despite roentgenographic improvement during therapy tracheobronchial stenoses may persist. These findings justify to perform early fibreoptic bronchoscopy. Sputum conversion during the clinical course may indicate the most appropriate time for this examination.

Adolescent↗
PubMed1994

Abnormal calcium and vitamin D metabolism in tuberculosis.

A variety of abnormalities in calcium and vitamin D metabolism have been reported in patients with active tuberculosis (TB), including hypercalcaemia, hypercalciuria and increased sensitivity to vitamin D. In this article, the frequency and nature of these abnormalities and the importance of extrarenal 1,25(OH)2D production are discussed.

Calcium↗
PubMed1994

Severe hypercalcaemia associated with miliary tuberculosis.

Hypercalcaemia is uncommon among patients with pulmonary tuberculosis in Hong Kong, possibly because of the low dietary calcium intake in this population. We report here a case of severe hypercalcaemia in a patient with miliary tuberculosis and impaired renal function. We suggest that tuberculosis should be excluded in any febrile patient with hypercalcaemia, particularly in countries where it is still a common condition and an important cause of hypercalcaemia.

Adult↗
PubMed1994

Evaluation of three culture media and their combinations for the isolation of Mycobacterium tuberculosis from pleural aspirates of patients with tuberculous pleurisy.

The abilities of three culture systems to detect Mycobacterium tuberculosis from 480 pleural aspirate specimens in 347 patients were compared. The systems were the Bactec 12B radiometric detection system (Bactec 12B), the Middlebrook 7H9 broth (7H9), and two solid media including one pyruvate enriched Lowenstein-Jensen slope (LJP) and one non-selective Middlebrook 7H11 agar slope (7H11). In the 116 specimens obtained from 85 patients of confirmed pleural tuberculosis for the isolation of Mycobacterium tuberculosis, the diagnostic yields were 33 (39%) cases from Bactec 12B, 24 (28%) cases from 7H9 and 21 (25%) cases from LJP/7H11, with median detection times of 18, 47.5 and 44 days respectively. Thirteen isolates were recovered by the Bactec 12B only, 9 by the 7H9 broth only, and 2 by the LJP/7H11 agar only. The use of a combination of the three culture systems substantially increased the diagnostic yield to 47% over the individual systems. These results show that a significantly greater and faster diagnostic yield can be obtained by including Bactec 12B in pleural aspirate cultures for the recovery of Mycobacterium tuberculosis.

Biopsy, Needle↗
PubMed1994

A study of calcium and vitamin D metabolism in Chinese patients with pulmonary tuberculosis.

Hypercalcaemia can occur in patients with tuberculosis. To further characterize the calcium and vitamin D metabolism in this disorder, serum calcium, 25(OH)D, 1,25(OH)2D and parathyroid hormone and the interrelationships between serum calcium, 25(OH)D and 1,25(OH)2D were compared in 24 untreated Chinese patients with culture-positive pulmonary tuberculosis and 24 age and sex-matched controls in Hong Kong. Albumin adjusted serum calcium was significantly higher in patients (2.33 +/- 0.07 compared with 2.20 +/- 0.09 mmol l-1, P < 0.001), despite a lower calcium intake (426 +/- 208 compared with 564 +/- 335 mg day-1). No significant group difference was found in serum 25(OH)D or 1,25(OH)2D concentrations. There was a positive correlation between serum 25(OH)D and 1,25(OH)2D concentrations in the patient group (r = 0.50, P < 0.02), but a negative one in the control group (r = -0.48, P < 0.05). Serum parathyroid hormone was significantly lower in patients (20.9 +/- 8.5 compared with 38.2 +/- 14.5 pmol l-1, P < 0.001). In the patient group, no correlation between the radiographic extent of disease and serum calcium or 1,25(OH)2D concentrations was seen. Our findings confirmed that serum calcium is raised in tuberculosis but the effect may be reduced by a low calcium intake and a low parathyroid hormone level. Although the calcium and vitamin D metabolism appeared to be altered in tuberculosis, no direct relationship between serum calcium and 1,25(OH)2D, was found.

Adult↗
PubMed1993

Studies on quinazolines. 5. 2,3-dihydroimidazo[1,2-c]quinazoline derivatives: a novel class of potent and selective alpha 1-adrenoceptor antagonists and antihypertensive agents.

A series of 2-[(substituted phenylpiperazin-1-yl)methyl]- and 2-[(substituted phenylpiperidin-1-yl)methyl]-2,3-dihydroimidazo[1,2- c]quinazolin-5(6H)-ones or -5(6H)-thiones, and 3-[(substituted phenylpiperazin-1-yl)methyl]-2,3-dihydroimidazo[1,2-c]quinaz oline derivatives were synthesized, as conformationally restricted analogues of SGB-1534 and ketanserin, for evaluation as alpha-antagonists and antihypertensive agents. Most compounds containing a (substituted phenylipiperazinyl)methyl side chain displayed high binding affinity for alpha 1-adrenoceptor with no significant activity at alpha 2-sites. Compounds having a (substituted phenylpiperazinyl)methyl at the 3-position of 2,3-dihydroimidazo[1,2-c]quinazolin-5(6H)-one ring system had a better activity than those with the same substituent at the 2-position. Structure-activity relationships for alpha 1-adrenoceptor affinity are presented and indicate that compounds with substitution at the ortho position on the benzene ring of the phenylpiperazine side chain moiety are more potent than those without substitution and/or substitutions at the 3- and 4-positions. Computer-assisted superimposition of SGB-1534 and 20b showed little structural correspondence between the quinazolinone and 2,3-dihydroimidazo[1,2-c]quinazoline nucleus, and specific interactions of these molecular fragments with the receptor protein appear unlikely. Antihypertensive activity was evaluated via intravenous administration of each compound to spontaneously hypertensive rats, and compounds (16a, 16b, 20b, and 28b) illustrated similar efficacy to SGB-1534 when assessed after 6 h. The pA2 value for 16a against phenylephedrine in rat aorta was much higher than that of prazosin. On the basis of alpha 1-adrenoceptor affinity/selectivity in vitro and duration of antihypertensive action in vivo, compounds 20b and 28b warrant further evaluation.

Adrenergic alpha-Antagonists↗
PubMed1993

Adrenocortical function and involvement in high risk cases of pulmonary tuberculosis.

SETTING: A regional hospital in Hong Kong. OBJECTIVE: To evaluate adrenocortical function in older patients admitted to hospital with active pulmonary tuberculosis (TB) and to determine whether adrenal insufficiency contributes to mortality in this high risk group. DESIGN: Adrenocortical function was assessed in 39 consecutive patients aged over 50 admitted to hospital with active pulmonary TB. Short Synacthen stimulation tests were performed before treatment and repeated at 2 months. In patients who died during treatment, a post-mortem examination was performed. Particular attention was paid to TB involvement of the adrenal glands. RESULTS: None of the patients had a subnormal basal cortisol concentration before treatment. 7 (18%) had raised basal cortisol concentrations and 16 (41%) had suboptimal cortisol responses to Synacthen stimulation. 14 patients (36%) died during treatment. The basal cortisol concentrations were significantly higher in the non-survivors compared to the survivors (743.7 +/- 288.5 vs 460.5 +/- 123.2 nmol/L, P < 0.0001). Autopsies were performed in 9 patients who died during treatment. Tuberculous involvement of the adrenal glands was found in only 1 patient who had a high basal cortisol concentration. After 2 months of treatment, all patients had normal cortisol concentrations and only 4 had borderline suboptimal Synacthen responses. The basal cortisol concentrations were significantly higher at presentation compared to those at 2 months after treatment (570.4 +/- 243.8 vs 386.3 +/- 108.3 nmol/L, P = 0.0014). CONCLUSION: Adrenal insufficiency is uncommon in patients with pulmonary TB. Suboptimal cortisol responses to Synacthen usually reflect a hyperstimulated basal state secondary to stress. Treatment with anti-TB drugs causes reduction in basal cortisol with associated improvement in the Synacthen response.

Adrenal Cortex↗
PubMed1993

Enzyme immunoassay based survey of precipitation and surface water for the presence of atrazine, metolachlor and 2,4-D.

The suitability of enzyme immunoassay (EIA) as a method of analysis for 2,4-D, atrazine and metolachlor contamination in water samples was determined by comparing EIA results to gas chromatography (GC) results. The comparison of EIA and GC results yielded a correlation coefficient of 0.92, 0.98 and 0.92 for 2,4-D, atrazine and metolachlor, respectively. EIA was used to monitor seasonal trends in the concentrations of 2,4-D, atrazine and metolachlor in surface water and precipitation throughout the province of Ontario, Canada. 2,4-D was detected in excess of 4 micrograms/L in urban creeks during the period of application. Concentrations of 43 and 9 micrograms/L of atrazine and metolachlor, respectively, were detected during the field application period in surface water samples from the Kintore Creek watershed. The levels of 2,4-D, atrazine and metolachlor detected exceeded the Canadian Water Quality Guidelines for the protection of fresh water aquatic life. Concentrations as high as 445 and 322 ng/L of atrazine and metolachlor, respectively, were detected in precipitation samples collected from 17 locations in Ontario during the herbicide application period. The EIA was shown to be qualitatively and quantitatively comparable to GC analysis.

2,4-Dichlorophenoxyacetic Acid↗
PubMed1993

Orbital volume measurement in the management of pure blowout fractures of the orbital floor.

With the recent advent of accurate orbital volume assessment by computed tomography, a retrospective analysis was made of 31 patients with 'pure' blowout fracture of the orbital floor, managed either surgically or conservatively, to determine whether orbital volume measurement could provide an additional parameter of use in the management of such fractures. There was a significant difference in orbital volume discrepancy between patients managed surgically or conservatively suggesting that this investigation may be of use in decision making on surgical intervention in patients with orbital blowout fractures.

Anthropometry↗
PubMed1993

Effect of preservative on the efficacy of terbutaline nebuliser solution in atopic asthma.

The efficacy of bronchodilator nebuliser solutions may be influenced by the presence of preservatives. In a double blind, randomised, crossover study the effect of preservatives in determining the airway responses to 5 mg of terbutaline was studied in a group of 21 atopic asthmatic patients. The presence of preservatives affected neither the bronchodilator action of terbutaline nor its protection against bronchoconstriction induced by histamine.

Administration, Inhalation↗