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Biomedical subjects

C M Wong

Publications and source records attributed to C M Wong.

At least 91 records · Page 5Linked to original sources
PubMed1994

Cloning and sequencing show that 4-hydroxybenzoate hydroxylase (PobA) is required for uptake of 4-hydroxybenzoate in Rhizobium leguminosarum.

Mutants of Rhizobium leguminosarum bv. viciae MNF300 and R. leguminosarum bv. trifolii WU95 unable to accumulate 4-hydroxybenzoate lack 4-hydroxybenzoate hydroxylase. The capacity of these mutants to take up and grow on 4-hydroxybenzoate was restored by a 2.0 kb EcoRI-PstI DNA fragment. This contained only one ORF which had over 60% DNA sequence similarity with the structural gene for 4-hydroxybenzoate hydroxylase (pobA) from Pseudomonas spp. and Acinetobacter. Reported effects of metabolic inhibitors and substrate analogues on the apparent uptake of 4-hydroxybenzoate have now been shown to be due to their direct effect on 4-hydroxybenzoate hydroxylase. We propose that uptake of 4-hydroxybenzoate is via a metabolic 'drag' mechanism dependent on the activity of the pobA gene product.

4-Hydroxybenzoate-3-Monooxygenase↗
PubMed1994

Bronchial responsiveness in children exposed to atmospheric pollution in Hong Kong.

Bronchial responsiveness was studied by histamine challenge in 423 school children with mean (SEM) age of 10.85 (0.05) years living in two districts of Hong Kong with contrasting levels of air pollution. Differences between districts of residence were observed, with a higher prevalence of bronchial hyperreactivity (BHR) in children living in the more polluted district (chi 2 = 7.74, df = 3, p = 0.052). Bronchial hyperreactivity was defined as a 20 percent or greater drop in FEV1. The district effect remained after exclusion of children with a history of wheeze and those diagnosed asthmatic for prevalence of BHR (chi 2 = 8.93, df = 3, p = 0.030) and for degree of bronchial reactivity (BR) after adjustment for other socioeconomic factors and smoking in the home (z = 1.97, p = 0.049). Bronchial reactivity was defined as the percentage drop in FEV1 per cumulative histamine dose from postsaline to end dose. The results demonstrate that studies on bronchial responsiveness can be used to assess the effects of air quality on the respiratory health of children and will be employed to measure the impact of new air quality control measures in Hong Kong.

Air Pollution↗
PubMed1994

Surgical treatment of aortic coarctation in infants younger than three months: 1985 to 1990. Success of extended end-to-end arch aortoplasty.

There remains controversy regarding the appropriate surgical treatment of coarctation of the aorta in infants. In 1985 we introduced the extended end-to-end repair into our practice and now wish to present a review of our recent experience. One hundred fifty-one infants younger than 3 months of age underwent repair of coarctation between 1985 and 1990. In 25% and 33% of the patients, there was hypoplasia of the isthmus and of the transverse arch, respectively. Surgical procedures were as follows: subclavian flap angioplasty in 15 patients, resection with a traditional end-to-end anastomosis in 43, and resection with an extended end-to-end anastomosis into the arch in 77. In 30 patients, the extension was proximal to the origin of the left carotid artery (radically extended end-to-end anastomosis). Other procedures were used in 16 patients. Mortality (13 early and 12 late deaths) was related on multivariate analysis to the presence of an associated major heart defect, preoperative resuscitation, and direct postoperative gradient over the arch. This immediate postoperative gradient was significantly lower after both extended and radically extended end-to-end anastomosis if there was a hypoplastic isthmus, and after radically extended end-to-end anastomosis if the transverse arch was hypoplastic. Actuarial freedom from recoarctation at 4 years was 57% (confidence limits 28% to 78%) after subclavian flap angioplasty, 77% (confidence limits 60% to 87%) after end-to-end anastomosis, 83% (confidence limits 66% to 92%) after extended end-to-end anastomosis and 96% (confidence limits 77% to 100%) after radically extended end-to-end anastomosis. We conclude that the extended end-to-end anastomosis and radical end-to-end anastomosis appear to offer the best prognosis for all infants with coarctation. The technique can be applied successfully to almost all types of arch anomalies.

Age Factors↗
PubMed1993

Two years experience with the Palmaz-Schatz coronary stent in a heterogeneous patient population.

Between January 1991 and December 1992, 136 Palmaz-Schatz coronary stents were implanted in 113 native coronary arteries in 106 patients. Forty-seven patients presented with stable angina, 50 with unstable angina, 7 with congestive cardiac failure and unstable angina and 2 were asymptomatic. Stenting was carried out in 15 patients for restenosis after coronary angioplasty (PTCA), 32 for significant dissection during PTCA (with 19 acute and 13 threatened closure), 10 for suboptimal PTCA results and 56 for de novo lesions, 52 (92.9%) of which were either ACC/AHA type B or C. Successful delivery was achieved in 97.2% (103/106) of patients or 97.3% (110/113) of vessels. Percent diameter stenosis was reduced from 78 +/- 13% to 4 +/- 11%. There were two subacute stent thromboses (1.9%), resulting in Q-Wave myocardial infarction. Three deaths (2.9%) occurred, all from the group with congestive cardiac failure and unstable angina. Major bleeding/vascular complications occurred in 4 patients (3.9%). All patients were followed up for a mean of 18 months (6 months to 30 months). Eighty-five patients were asymptomatic. Three patients were angina-free but continued to have, albeit improved, congestive cardiac failure. Ten patients had recurrence of angina, all within 6 months of the stenting procedure. Four were treated medically and 4 had PTCA of whom one eventually had coronary bypass surgery. Two patients had new lesions, successfully treated by PTCA or stenting. In conclusion, a high rate of successful delivery of the Palmaz-Schatz coronary stent can be achieved in a wide spectrum of patients with few complications which are mostly related to anticoagulation. It offers very effective bailout for acute closure during PTCA. Despite the presence of unfavorable pre-procedure patient and lesion characteristics, the acute and long term clinical results are encouraging.

Adult↗
PubMed1992

Prenatal exposure to alcohol enhances thymocyte mitogenic responses postnatally.

Previous studies have shown altered cell-mediated immune responses in animals prenatally exposed to ethanol. The present study was designed to determine the ontogeny of proliferative responses of thymocytes postnatally following prenatal exposure to ethanol. Thymocytes obtained from 44-day old Sprague-Dawley male rats exposed to 5% (w/v) ethanol during the last two weeks of gestation had a significantly greater response to mitogenic stimulation by concanavalin A (Con A, 5.0 micrograms/ml) than controls. A similar trend was observed in rats at postnatal days 30 and 72, but not at day 16. Con A-conditioned thymoblasts from day-44 fetal alcohol-exposed animals were less responsive to further activation by a crude Con A supernatant than controls, but this response normalized by day 72. These findings reveal that the effects of ethanol exposure in utero in male rats include alterations in the development of thymoproliferative responses to mitogen which persist through the peripubertal period and normalize in part by young adulthood.

Animals↗
PubMed1991

Studies on the respiratory health of primary school children in urban communities of Hong Kong.

The first stage of a 2-year survey of respiratory morbidity in primary school children was conducted in two districts of Hong Kong in April/May 1989. One group (2009) of children was from Kwai Tsing District, which had high levels of exhaust emission from factories. The other group (1837) was from Southern District where atmospheric pollution was considered to be relatively low. After adjustment for gender, age, socioeconomic factors, child smoking and exposure to parental smoking, the prevalence ratios of sore throat, evening cough, cough for more than 3 months, morning phlegm and wheezing were found to be significantly higher in Kwai Tsing. The difference between the districts is likely to be related to the environmental air quality. The study, which is continuing, will provide the basis for an evaluation of the impact of new low sulphur fuel regulations introduced in July 1990.

Acute Disease↗
PubMed1991

Changes with age in the proliferative response of splenic T cells from rats exposed to ethanol in utero.

The fetal alcohol syndrome is associated with altered immunity. Several laboratories have confirmed that rodents exposed to ethanol in utero demonstrate both diminished proliferative responses of T cells to mitogens and diminished proliferative responses of T-blast cells to human recombinant interleukin 2 (rIL2). We examined the developmental time course of these altered immune responses by testing the immune function of in utero ethanol-exposed rats at various ages. We found that while diminished splenic T cell proliferative responses could not be detected at 2 weeks, they were present at 6 weeks after birth and suppression was maximal at 6 weeks and 3 months. Thereafter, at 5 and 7 months, the altered immune responses gradually declined and normalized at 8 months of age. Thus, both altered T cell mitogenesis and the blunted IL2-induced proliferative response of T-blast cells could serve as biomarkers of fetal exposure to ethanol.

Age Factors↗
PubMed1991

[Pelvic lipomatosis associated with cystitis glandularis--case report].

Pelvic lipomatosis is a rare benign disease of unknown etiology characterized by the proliferation of infiltrating fatty tissue within the deep bony pelvis. These fatty tissue may enclose the pelvic and retroperitoneal organs and various degrees of luminal compression and obstruction may happen. There is no typical presenting symptoms of pelvic lipomatosis. The major diagnostic methods are radiological examinations. CT scan is the definitive test to confirm the diagnosis. Open biopsy may be necessary when the diagnosis is inconclusive. Various treatment modalities have been tried, but only the diet therapy and complete ablation of fatty tissue ever reported to be successful. Cystitis glandularis, a rare proliferative inflammatory disease of the bladder, is reported to occur concurrently with pelvic lipomatosis in a patient. Herein we report a similar case. A middle-aged male patient was admitted with the chief complaint of painless gross hematuria for two weeks. After admission a series of radiological examinations and endoscopic bladder biopsy were performed. He was proved to be a rare case of pelvic lipomatosis associated with cystitis glandularis.

Adult↗
PubMed1990

Cochlear implant in Hong Kong Cantonese.

Cochlear implant surgery was performed in four Cantonese-speaking postlingually deaf Chinese adults, using the House/3M single channel device. This article outlines the methodology, including preoperative assessment and postoperative rehabilitation; and explains the necessary modifications in speech and audiologic work-up in Cantonese-speaking patients. Salient features of Cantonese phonetics, especially its tonal characteristics, are described. The findings of the study are presented. The results of the cochlear implant would suggest a performance superior to that of the hearing aid. Furthermore, the cochlear implant is able to detect tonal cues. This quality of the cochlear implant may prove to be a valuable asset to a tonal language-speaking cochlear implantee.

Adult↗
PubMed1988

Interaction of estrogen-nitrosourea conjugates with the estrogen receptor in rat uterus.

Several estrogen-nitrosourea conjugates have been synthesized with the aim of producing more selective cytotoxic agents. The conjugates were shown to compete with estradiol for binding to cytosolic estrogen receptor in rat uterus; the relative binding affinities for N-(2-chloroethyl)-N'-(3,17 beta-dihydroxyestra-1,3,5(10)-trien-17 alpha-yl)methyl-N-nitrosourea (17 alpha-CNU), N-(2-chloroethyl)-N'-(3-hydroxyestra-1,3,5(10)-trien-17 beta-yl)-N-nitrosourea (17 beta-CNU), and N-(2-chloroethyl)-N'-2,3-di(p-hydroxyphenyl)-pentanyl-N-nitrosoure a (HEX-CNU) were 2, 0.4, and 0.2, respectively, using a binding affinity of 100 for estradiol. In the ligand exchange assay, cytosolic receptors preloaded with 17 alpha-CNU and HEX-CNU were found to lose some of their estradiol (E2) binding sites, suggesting that binding to estrogen receptor (ER) may be irreversible. An increase of nuclear accumulation of ER was observed in the presence of 17 alpha-CNU and HEX-CNU. In the rat system, even at a 10,000-fold excess, these two agents failed to show any antagonism of the uterotrophic effect of E2 in vivo. The low binding affinity and instability of these conjugates may account for their lack of antiestrogen activity. On the other hand, 17 alpha-CNU at 100 or 1000 micrograms/day and HEX-CNU at 1000 micrograms/day demonstrated significant uterotrophic activity. This study did not resolve whether the stimulation of uterine growth was due to the parent estrogen-nitrosourea conjugate or to decomposition and/or metabolic products.

Animals↗
PubMed1987

Byssinosis and other respiratory problems in the cotton industry of Hong Kong.

Between February 1982 and October 1984, a total of 2,317 workers from all levels of cotton processing--carding, blowing, spinning and weaving--were studied in a citywide cross-sectional survey. The workers were administered the British MRC Questionnaire in local dialect and their pre- and postshift lung functions were assessed by portable spirometers. The prevalence of byssinosis for the whole industry was 2.3%, being much greater in the more dusty processes (blowing and carding, 5.6%; weaving 1.6%). Even more important was the prevalence of chronic obstructive airways disease (COAD) (13.8%) and a combination of nonspecific respiratory symptoms (10.0%), characterized by chest tightness and dyspnea, but not related to any specific day of the week such as those seen in typical byssinosis. The importance of these two large groups of respiratory problems in relation to byssinosis and the pathogenesis of respiratory diseases in people exposed to cotton dust is discussed.

Adult↗
PubMed1987

Redox reactions occurring during secondary ion mass spectrometry of some heteroanthracycline antitumor antibiotic precursors.

Positive and negative secondary ion mass spectra of the title compounds were produced by bombardment of solid deposits by 13 and 23 KeV cesium ions, respectively, and analyzed with a time-of-flight mass spectrometer. In addition to familiar protonation and alkali (mainly sodium) ion addition processes observed in the positive ion spectra and proton abstractions in the negative ion spectra (which enable determination of molecular weight) there is evidence from both spectral modes for oxidation-reduction processes in which species such as [M - H]+, [M - H + Na]+. and [M + 1]- are formed. It is argued that these may be formed rapidly from pre-associated molecules during bombardment/ionization rather than as a result of radiation damage. Sodium ion addition is apparently facilitated by the presence of electron pair donor groups, especially if chelation is possible.

Antibiotics, Antineoplastic↗
PubMed1987

Peptides with antilipolytic and lipogenic activities from seeds of the bitter gourd Momordica charantia (family Cucurbitaceae).

Decorticated Momordica charantia seeds were extracted with acidic ethanol. The pH of the extract was adjusted to 8 and the resulting precipitate was chromatographed on CM Sepharose CL-6B and then desalted on Sephadex G-10. A number of factors which exhibited antilipolytic and lipogenic activities in rat adipocytes were isolated. Two of the factors were demonstrated to be peptides with similar amino acid compositions and a molecular weight of approximately 8000. However the peptides greatly differed in their chromatographic behavior on CM-Sepharose CL-6B and in their mobilities in agarose and polyacrylamide gel electrophoresis.

Abortifacient Agents, Nonsteroidal↗
PubMed1987

Smoking, passive smoking and histological types in lung cancer in Hong Kong Chinese women.

In a case control study in Hong Kong, 445 cases of Chinese female lung cancer patients all confirmed pathologically were compared with 445 Chinese female healthy neighbourhood controls matched for age. The predominant histological type was adenocarcinoma (47.2%). The relative risk (RR) in ever-smokers was 3.81 (P less than 0.001, 95% CI = 2.86, 5.08). The RRs were statistically significantly raised for all major cell types with significant trends between RR and amount of tobacco smoked daily. Among never smoking women, RR for passive smoking due to a smoking husband was 1.65 (P less than 0.01, 95% CI = 1.16, 2.35) with a significant trend between RR and amount smoked daily by the husband. When broken down by cell types, the numbers were substantial only for adenocarcinoma (RR = 2.12, P less than 0.01, 95% CI = 1.32, 3.39) with a significant trend between RR and amount smoked daily by the husband. The results suggest that passive smoking is a risk factor for lung cancer, particularly adenocarcinoma in Hong Kong Chinese women who never smoked.

Adenocarcinoma↗
PubMed1987

Acid-ethanol extractable compounds from fruits and seeds of the bitter gourd Momordica charantia: effects on lipid metabolism in isolated rat adipocytes.

Fruits and seeds of the bitter gourd Momordica charantia (Family Cucurbitaceae) were extracted with acidic ethanol. The extract was adjusted to pH 3 and proteins and peptides were precipitated by addition of a copious volume of acetone. The precipitate was dissolved, dialyzed and lyophilized. The resulting material, designated "p-fraction" was tested for antilipolytic and lipogenic activities. Seed "p-fraction" was further chromatographed on fetuin agarose to yield an unadsorbed fraction (F) which could be fractionated by gel filtration on Sephadex G-10 to give an unretarded fraction (F1) and a retarded fraction (F2). Fruit "p-fraction" exhibited antilipolytic activity in hamster adipocytes and stimulated 3H-glucose incorporation into lipids. F1, a saponin containing fraction, inhibited both lipolysis and 3H-glucose incorporation into lipids. F2 enhanced 3H-glucose incorporation into lipid. The results are indicative of the presence of compounds with insulinomimetic activities in M. charantia fruits and seeds.

Animals↗