Biomedical subjects

J T Lau

Publications and source records attributed to J T Lau.

At least 55 records · Page 3Linked to original sources

PubMed1996

Risk of further ulcer complications after an episode of peptic ulcer bleeding.

To identify the risk factors for developing recurrent ulcer complications after recovery from an episode of peptic ulcer bleeding 611 patients admitted with peptic ulcer bleeding were studied. Some 557 (91 per cent) were discharged without operation. A total of 22 patients were lost to follow-up and five were excluded as maintenance H2 blockers were required. Of the remaining 530 patients at risk, 169 (32 per cent) developed another complication (166 bleeding, three perforations) over a median follow-up period of 36 months. Patients with duodenal ulcers at the time of bleeding, previous history of peptic ulcer, previous bleeding, history of dyspepsia longer than 3 months, and a short interval between previous ulcer complications and the index bleed were more likely to develop further complications. Sex, age, smoking, coexisting illness, non-steroidal anti-inflammatory drugs intake and time taken to achieve ulcer healing had no predictive value.

Adolescent↗

PubMed1996

Differentiation -dependent expression of human beta-galactoside alpha 2,6-sialyltransferase mRNA in colon carcinoma CaCo-2 cells.

We have previously documented a dramatic elevation in the activity of alpha 2,6-sialytransferase towards Gal beta 1,4GlcNAc (EC 2.4.99.1) (alpha 2,6ST) in CaCo-2 cells maintained in culture for several days after confluence to elicit a high degree of enterocytic differentiation phenotype. Northern analysis performed with a probe complementary to a region of human alpha 2,6ST mRNA common to all known transcripts demonstrated that the expression of alpha 2,6ST mRNA in CaCo-2 cells increased with the degree with the degree of differentiation. When probes complementary to 5'-untranslated exons (Y + Z or X) previously identified in transcripts isolated from human placenta and from several human lymphoblastoid cell lines were used, no hybridization signal with mRNA of CaCo-2 cells was found, as reported for the mRNA of hepatoma cell line HepG2 (Wang XC, Vertino A, Eddy RL, Byers MG, Jani-Sait SN, Shows TB, Lau JTY (1993) J Biol Chem 268: 4355-61). These results support the notion that the major alpha 2,6ST transcript of CaCo-2 cells was the hepatoma isoform or a new one, so far unreported. Consistent with the differentiation-dependent increase in alpha 2,6ST-mRNA expression, an elevation of the reactivity with Sambucus nigra agglutinin of differentiated CaCo-2 cell-surface was observed, indicating an enhanced alpha 2,6-sialylation of membrane glycoconjugates.

Base Sequence↗

PubMed1996

Transcription of the beta-galactoside alpha 2,6-sialyltransferase gene in B lymphocytes is directed by a separate and distinct promoter.

A single human gene, SIAT1, encodes the beta-galactoside alpha 2,6-sialyltransferase from which multiple mRNA isoforms are generated. In rat, expression of the hepatic mRNA isoform (Form 1) has been defined with respect to the transcriptional initiation site and promoter region. We show here that a similar hepatic SIAT1 mRNA isoform exists in human. Another human mRNA isoform, a mature B-cell-specific mRNA isoform (Form 2), was previously reported. Here, we used 5'-RACE and S1 nuclease protection analysis to define the 5'-untranslated region of Form 2 human SIAT1 mRNA. We demonstrate conclusively that Form 2 mRNA is initiated from a point completely distinct from that of Form 1 mRNA. A number of cis-acting regulatory elements residing immediately 5'of the Form 2 initiation site includes AP-1, AP-2, NF-kappa B, NF-IL6, C/EBP, and CREB. A TATAA box is also present 29 bp 5' of the transcriptional initiation site. CAT reporter gene expression from serially-truncated segments of the 5'-flanking region of the Form 2 initiation site indicates that the segment between -784 and +125 was sufficient to promote high level CAT expression in Louckes, a mature B-cell line. The 5'-flanking region to the human Form 1 initiation site is competent in expression of CAT upon transfection of the fusion construct into HepG2, a human hepatoma cell line. Cellular specificity of expression is apparently retained. Louckes cells expressed CAT efficiently from Form 2 promoter but only marginally from the Form 1 promoter. In contrast, CAT expression from Form 1 promoter is more efficient than from the Form 2 promoter in HepG2 cells.

Animals↗

PubMed1996

Weight-for-age and weight-for-height references for Hong Kong children from birth to 18 years.

OBJECTIVE: Childhood obesity is an emerging problem in Asia. Sequential monitoring of the growth of an individual can detect a change in body fatness, provided there are ethnically appropriate growth references. METHODOLOGY: A territory wide cross-sectional growth survey of Hong Kong on 24709 individuals from the age of newborn to 18 years was performed in 1993. Weight-for-age and weight-for-height percentile charts were prepared separately for boys and girls. RESULTS: There was an average increase of 8.5 kg and 5.1 kg in the 18 year old boys and girls, respectively, compared to those surveyed 30 years ago. The percentile curves between 6 and 18 years were similar to those of Singapore. Weight-for-height percentile curves were close to those of America in the prepubertal years. CONCLUSIONS: These Hong Kong growth standards for weight-for-age and weight-for-height are important tools for the assessment of nutritional status of an individual and for monitoring changes in nutritional status of the population.

Adolescent↗

PubMed1996

Secular trend in the sexual maturation of southern Chinese boys.

A random sample of 3872 southern Chinese boys ranging from 7 to 21 years of age were selected from primary and secondary schools in Hong Kong for the assessment of sexual maturation. The median ages of onset of puberty and pubic hair development were 11.4 and 12.7 years, respectively. The advancement of sexual maturation coincides with the secular increase in height and weight for Chinese children in Hong Kong.

Adolescent↗

PubMed1996

The relationship between upper gastrointestinal hemorrhage and drug use: a case control study.

The relationship between upper gastrointestinal hemorrhage and drug use was studied in 251 Chinese patients (179 men, 72 women) admitted to the Prince of Wales Hospital, Hong Kong, and control subjects matched for age and sex. There was a highly significant difference between the cases and control subjects in the use of NSAIDs (odds ratio 14.0, p < 0.00001), ulcer healing drugs (odds ratio 12.5, p < 0.00001), and Chinese proprietary medicines (odds ratio 16.0, p < 0.00001). There was also a significant difference in the use of analgesics (odds ratio 14.0, p = 0.001), paracetamol (odds ratio 2.5, p = 0.01), antacids (odds ratio 2.7, p < 0.001) and unknown drugs (odds ratio 4.7, p < 0.001). Cases also differed from control subjects regarding the use of tobacco (odds ratio 2.3, p < 0.001) and alcohol (odds ratio 1.7, p = 0.02), and the presence of peptic ulcer symptoms (odds ratio 29.8, p < 0.00001). Significantly more control subjects than cases were receiving aspirin, cardiovascular drugs, bronchodilators, oral hypoglycemic drugs/lipid-lowering drugs, and anticonvulsants/hypnotics, due to the inevitable differences in disease pattern between the 2 groups. NSAID use was a major factor associated with upper gastrointestinal hemorrhage from primarily peptic ulcers. Differences in the use of other drugs may reflect variations in disease patterns between cases and controls, the common practice of self-medication in Hong Kong, and the concomitant use of NSAIDs and ulcer healing drugs/antacids.

Adolescent↗

PubMed1996

Relationship between myopia and optical components--a study among Chinese Hong Kong student population.

PURPOSE: To establish the prevalence and severity of myopia among the Chinese Hong Kong students and to study the relationship between myopia and optical components. METHODS: One thousand and seventy-five freshmen of the 1993-1994 academic year in the Chinese University of Hong Kong underwent the eye examination including evaluation of refractive error, keratometry, and A-scan ultrasonic biometry. The data were analyzed with the SPSS/PC+4.01 statistical package. RESULTS: The prevalence of myopia was 91.7% with the mean refraction being -4.00 +/- 2.64D in this young adult population. The statistical analyses demonstrated a significant correlation between refractive value and axial length of the globe (r = -0.78), vitreous length (r = -0.76), anterior chamber depth (r = -0.33), lens thickness (r = 0.13) and corneal curvature (r = 0.19). CONCLUSION: The refractive status is mainly dependent on the axial length. In general, the higher the myopia was, the longer the eyeball, the deeper the anterior chamber, the steeper the cornea, and the thinner the lens would be.

Adolescent↗

PubMed1995

Human colon cancer cell lines permanently expressing alpha 2,6-sialylated sugar chains by transfection with rat beta-galactoside alpha 2,6 sialyltransferase cDNA.

A role of alpha 2,6-linked sialic acid in the development of an invasive phenotype in colon cancer has been suggested by several observations but never conclusively demonstrated. An experimental model to clarify this tissue was established by the creation and characterization of a bank of cell lines that differ mainly, if not exclusively, in the degree of alpha 2,6-sialylation. Human colon cancer cell lines SW48 and SW948, normally unable to elaborate the alpha 2,6-sialyl linkage, were transfected with the beta-galactoside alpha 2,6-sialyltransferase (alpha 2,6ST) cDNA driven by the cytomegaloviral promoter and screened for cell surface alpha 2,6-sialylated sugar chains using fluorescein isothiocyanate-conjugated Sambucus nigra agglutinin (SNA-FITC). A panel of SNA-FITC-positive clones was established that expresses alpha 2,6ST activity of varying degrees. Only the SNA-FITC-positive recombinants express the 1.2 Kb mRNA predicted to be generated from the transfected sequence. No 4.3-4.7 Kb transcripts that are indicative of transcription from the native alpha 2,6ST gene were detected.

Animals↗

PubMed1995

The effect of percutaneous oestrogen replacement therapy on Lp(a) and other lipoproteins.

OBJECTIVES: To determine the effect of percutaneous oestrogen replacement therapy on lipoprotein (a) and other plasma lipoproteins. METHODS: Open longitudinal prospective study conducted at the hormone replacement clinic of the Prince of Wales Hospital, New Territories, Hong Kong. Thirty women who had undergone a total abdominal hysterectomy and bilateral salpingo-oophorectomy for benign gynaecological conditions were treated with 1.5 mg of percutaneous 17 beta-oestradiol gel applied daily for a period of 12 consecutive months. Measurements of plasma lipoproteins were made before the commencement of treatment and repeated at 6- and 12-month intervals. RESULTS: There was a significant reduction in the concentrations of Lp(a) during the first 6 months of treatment, with median values falling from 7.87 mg dL-1 to 6.16 mg dL-1 (P = 0.004, 0-6 months). During the second 6 months, the median concentration increased to 9.38 mg dL-1, (P = 0.072, 6-12 months), which did not significantly differ from the baseline level (P = 0.545, 0-12 months). Significant reductions in the concentrations of apoprotein A-I (apo A-I), apoprotein B (apo B), high density lipoprotein cholesterol (HDL-C), and HDL3-C were also present after 6 months (P = 0.043, 0.049, 0.028, 0.013, respectively), but there were no differences between the baseline values of these lipoproteins and those at the completion of the study (P = 0.948, 0.244, 0.839, 0.117 respectively). Drug compliance was maintained throughout the study, with similar mean oestradiol concentrations at 6 and 12 months. CONCLUSIONS: The percutaneous administration of 17 beta-oestradiol has variable short term effects on plasma lipoproteins which are not maintained over a longer duration of treatment. By avoiding the 'first pass' effect on the liver, this method of delivery does not appear to produce the sustained changes in lipoproteins seen with oral treatment.

Administration, Cutaneous↗

PubMed1995

Three genes that encode human beta-galactoside alpha 2,3-sialyltransferases. Structural analysis and chromosomal mapping studies.

The synthesis of alpha 2,3-linked sialic acid to Gal(beta 1,3)GalNAc is mediated by at least three beta-galactoside alpha 2,3-sialyltransferases (EC 2.4.99.4, SiaT-4) that are encoded by three distinct genes. In contrast, only a single gene encodes the beta-galactoside alpha 2,6-sialyltransferase (EC 2.4.99.1, SiaT-1). This report assesses the relationship and nature of the SiaT-4 genes. Analysis of human-mouse somatic cell hybrids demonstrates that the sialyltransferase genes are dispersed in the human genome. The gene for SiaT-4 resides in chromosome 8, that for SiaT-4b resides in p21-p34 of chromosome 1 and that for SiaT-4c in q23.3-qter of chromosome 11. The gene symbols for these genes have been designated SIAT4A, SIAT4B and SIAT4C, respectively. To assess the structural organization of one of the SiaT-4 genes, a human SiaT-4a cDNA from submaxillary glands was isolated and characterized. Rapid amplification of cDNA 5' ends (5'-RACE) analysis indicates an unusually long 1 kb 5'-untranslated leader. The catalytic domain of the cloned sequence was expressed in transfected cells and was shown to be competent in mediating the specific synthesis of sialic acid alpha 2,3 to Gal(beta 1,3)GalNAc-R. Genomic sequences for SiaT-4a were also isolated and examined. The data demonstrate that coding information for SiaT-4a protein is dispersed into seven discrete exon segments in a manner reminiscent of the SiaT-1 gene. Furthermore, as in the SiaT-1 gene, intervening sequences interrupt both sialylmotif domains, regions that are conserved among all known sialyltransferases.

Amino Acid Sequence↗

PubMed1995

Carriage of Haemophilus influenzae and Streptococcus pneumoniae in healthy Chinese and Vietnamese children in Hong Kong.

Nasopharyngeal carriage of Haemophilus influenzae and Streptococcus pneumoniae was studied in 621 healthy Chinese children and 300 healthy Vietnamese children aged from 2 months to 5 years in Hong Kong. The carriage rate of H. influenzae type b in Vietnamese children was 1.3% (CI 0.04-2.63); it was zero in Chinese. The carriage rate of non-typable H. influenzae was 5.8% (CI 1.4-7.6%) in Chinese and 65.4% (CI 58.9-69.8%) in Vietnamese. The carriage rates of S. pneumoniae were 10.8% (CI 8.3-13.2%) and 55.7% (CI 50.1-61.3%) in Chinese and Vietnamese children, respectively. Univariate and multivariate logistic regression analyses were performed to search for factors associated with differences in carriage rates of both H. influenzae and S. pneumoniae between Chinese and Vetnamese children. Although older age, smaller living area and parental smoking were associated with higher carriage rates, these could not explain the remarkably low carriage rates of both bacteria in Chinese children.

Adolescent↗

PubMed1995

The risk of aspiration in Dettol poisoning: a retrospective cohort study.

1. To determine if the risk of aspiration is increased in 'Dettol' (4.8% chloroxylenol, pine oil and isopropyl alcohol) poisoning and the factors that may be responsible, a study was made of 89 patients and 89 matched control subjects with other forms of poisoning admitted to the Prince of Wales Hospital, Hong Kong. 2. Aspiration was more common in patients with Dettol poisoning (8% vs 3%, P = 0.16). There were more control subjects with drowsiness at presentation (54% vs 24%, P < 0.0001), but the use of gastric lavage (88% vs 64%, P < 0.001) and the occurrence of vomiting (62% vs 17%, P < 0.0001) were more common in patients with Dettol poisoning. 3. Our findings suggest that Dettol poisoning may be associated with an increased risk of aspiration. This increase in risk may be related to the use of gastric lavage and the common occurrence of vomiting in patients with Dettol poisoning.

Adolescent↗

PubMed1994

Developmental regulation of beta-galactoside alpha 2,6-sialyltransferase in small intestine epithelium.

A striking biochemical alteration to the epithelium of the small intestine upon weaning is the loss of microvillar sialic acids. Antibody and cDNA probes to the beta-galactoside alpha 2,6-sialyltransferase (SiaT-1, EC 2.4.99.1) were used to characterize the expression of this sialyltransferase in the small intestine of suckling rats. SiaT-1 mRNA and protein in the intestinal epithelium are rapidly lost upon weaning, in agreement with the loss of mucosal sialic acids and general sialyltransferase activity. Developmental repression of SiaT-1 is manifested in a proximal to distal gradient; SiaT-1 mRNA and protein are lost first from the duodenum and persist the longest in the ileum. We have previously documented that SiaT-1 gene expression can be transcriptionally initiated from a number of distinct tissue-specific promoter regions. Here, by criteria of mRNA mobility on agarose gels, primer extension analysis, and differential Northern hybridization, we show that the promoter previously considered to be liver-specific is operative in SiaT-1 expression in the small intestine of suckling animals. Comparison of this SiaT-1 promoter region with promoter regions of other genes exhibiting dual intestine-hepatic tissue specificity revealed a number of striking sequence similarities. Regulatory implications and consequences of small intestinal SiaT-1 expression in suckling but not in weaned animals are discussed.

Animals↗

PubMed1994

A prospective randomized trial comparing R1 subtotal gastrectomy with R3 total gastrectomy for antral cancer.

OBJECTIVE: The authors determined if more radical surgery with extended lymphadenectomy improves the results of gastrectomy in patients with adenocarcinoma of the gastric antrum. SUMMARY BACKGROUND DATA: The overall survival in patients with gastric cancer is disappointing. Improved survival has been reported by Japanese authors. Whether this is because of a higher number of early gastric cancers in the Japanese series, different biologic behavior in Asians, or the adoption of radical surgery with lymphadenectomy remains unclear. METHODS: R1 subtotal gastrectomy with omentectomy and R3 total gastrectomy (omentectomy, splenectomy, distal pancreatectomy, lymphatic clearance of the celiac axis, and skeletonization of vessels in the porta hepatis) were evaluated in a prospective, randomized comparison. RESULTS: Fifty-five patients were randomized--25 to the R1 group and 30 to the R3 group. The two groups were comparable for age, sex, tumor size, TNM stage, and length of follow-up. The R3 group had a longer operating time (140 vs. 260 min; p < 0.05), a greater transfusion requirement (0 vs. 2 units, p < 0.05) and a longer hospital stay (8 vs. 16 days; p < 0.05) (medians; Mann-Whitney U test). The only postoperative death was in the R3 group and was caused by intra-abdominal sepsis. Fourteen patients in the R3 group developed left subphrenic abscesses. There were no major complications in the R1 group. Overall survival was significantly better in the R1 group (median survival estimated by Kaplan-Meier method, 1511 vs. 922 days, p < 0.05, log-rank test). CONCLUSIONS: R3 total gastrectomy can be performed with a low mortality, but it has a high morbidity because of intra-abdominal sepsis. The data do not support the routine use of R3 total gastrectomy for treatment of patients with antral cancer.

Adenocarcinoma↗

PubMed1994

The respiratory depressant effect of morphine. A comparative study in three ethnic groups.

The respiratory response to carbon dioxide was measured in 130 ASA 1 adult male patients from three ethnic groups, European, Nepalese, and Chinese, both before and after premedication with intramuscular morphine sulphate (200 micrograms.kg-1 body weight). Satisfactory results were obtained from 125 patients. Overall, there was no ethnic difference in the effect of morphine on the respiratory response to carbon dioxide, but initially the Chinese group appeared to be more sensitive in their response to carbon dioxide than the Europeans and Nepalese. However, there was a significant correlation between respiratory response to carbon dioxide and pulse rate and on restricting analysis to those patients with a pulse rate equal to or less than 72 beat.min-1, the ethnic difference in carbon dioxide response disappeared. It was concluded that there were no ethnic differences in the respiratory response to carbon dioxide before or after morphine in male Europeans, Nepalese and Chinese but that the respiratory response to carbon dioxide may be influenced by long term physical training.

Adolescent↗

PubMed1993

Chromosome mapping and organization of the human beta-galactoside alpha 2,6-sialyltransferase gene. Differential and cell-type specific usage of upstream exon sequences in B-lymphoblastoid cells.

The human beta-galactoside alpha 2,6-sialyltransferase (EC 2.4.99.1) (SiaT-1) gene is localized to human chromosome 3 (q21-q28) by Southern analysis of somatic cell hybrids and by in situ hybridization of metaphase chromosomes. Comparative analysis between the human and the previously reported rat SiaT-1 genomic sequences demonstrates precise conservation of the intron/exon boundaries throughout the coding domains. Furthermore, there is extensive inter-species sequence similarity in some of the exons that contain information only for the 5'-leader regions. Human genomic sequences were also analyzed to reconcile reported differences in the 5'-untranslated region in SiaT-1 mRNAs. In cultured cell lines of the B-lineage, Reh, Nalm-6, Jok-1, Ball-1, Daudi, and Louckes, the study demonstrates that three upstream exons, Exons(Y+Z) and Exon(X), are mutually exclusively utilized, resulting in at least two distinct populations of SiaT-1 mRNA being synthesized. None of these exons is present in the SiaT-1 mRNA isotype expressed in HepG2 human hepatoma cells. In all B-lymphoblastoid cell lines examined, the basal level SiaT-1 mRNA is maintained by the expression of an isotype containing the Exons(Y+Z) sequence. The slightly smaller SiaT-1 mRNA, which contains the Exon(X) sequence but not Exons(Y+Z) sequence, is synthesized at a high level and found only in Jok-1, Daudi, and Louckes, the cell lines with mature B-cell phenotype. The study also provides further evidence that induced SiaT-1 expression accompanies the appearance of CDw75, a putatively sialylated cell surface epitope and a marker of human mature B-lymphocytes. The SiaT-1 induction is the result of the appearance of a novel form of SiaT-1 mRNA isotype.

Animals↗

PubMed1993

Thyrotropin regulation of sialic acid expression in rat thyroid cells.

The present study, utilizing the hormone-responsive rat thyroid cell line FRTL-5, presents evidence establishing the regulatory role of thyrotropin in modulating mRNA for beta-galactoside alpha 2,6-sialytransferase, the enzyme responsible for the expression of alpha 2,6-linked sialic acid. Both the cell surface membrane and the thyroglobulin secreted by cells grown in the presence of this hormone exhibit a marked decrease in the level of alpha 2,6-bound sialic acid with little or no change in the number of alpha 2,3-sialic acid residues. An additional, and unexpected, sequel is the finding of a coordinated decrease in all of the core monosaccharide constituents of the secreted thyroglobulin. Both of the above phenomenological changes appear to be at some variance with previously described systems wherein thyrotropin was deemed to increase glycosylation. It is anticipated that further resolution of this apparent difference may provide a clearer definition for the role of the carbohydrate moiety in affecting the biological function of thyroglobulin.

Animals↗

PubMed1993

The Shatin community mental health survey in Hong Kong. II. Major findings.

A large-scale community survey in Shatin, Hong Kong, is presented with a modified two-phase design using flagged and nonflagged subsamples. A modified Self-Reporting Questionnaire and the Diagnostic Interview Schedule (version III) were used as the screening and diagnostic instruments, respectively. Lifetime rates for 19 Diagnostic Interview Schedule/DSM-III diagnoses are presented. The most common diagnoses in Shatin were tobacco dependence, generalized anxiety disorder, alcohol abuse and/or dependence, all phobias, and dysthymic disorder. The male-predominant disorders were tobacco dependence, alcohol abuse/dependence, pathological gambling, and antisocial personality. The female-predominant disorders were generalized anxiety disorder, all phobias, dysthymic disorder, major depressive disorder, obsessive-compulsive disorder, and bereavement.

Adolescent↗