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Biomedical subjects

K L Chua

Publications and source records attributed to K L Chua.

At least 37 records · Page 2Linked to original sources
PubMed1993

Patients with various types of human papillomavirus: covariation and diagnostic relevance of cytological findings in Papanicolaou smears.

Human papillomavirus (HPV) infection in the genital tract is associated with a number of cytological changes which are accepted as standard criteria for a cytological diagnosis. We evaluated the covariation and diagnostic accuracy of these criteria in 210 patients, i.e. 150 cases who were positive for HPV types 6, 11, 16, 18, 31, 33 or 35, and 60 cases who were HPV-negative by simultaneous Southern blot analysis. This was done by re-examining cervical smears obtained at the same time, without knowing the results of the Southern blot analysis, for the presence of koilocytosis, dyskeratosis-parakeratosis, nuclear smudging, hyperchromasia, binucleation, multinucleation, karyorrhexis and macrocytosis. We found that all these cytological changes correlated with the presence of an HPV infection. However, analysis of variance showed that koilocytosis, dyskeratosis-parakeratosis and karyorrhexis were of particular diagnostic value, while the other features provided little or no additional information. By omitting these features and making the diagnosis when two out of three of the key criteria, i.e. koilocytosis, dyskeratosis-parakeratosis and karyorrhexis were present, we diagnosed HPV infection with a specificity of 100% in 36% of the 150 cases, which were positive by Southern blot analysis. The various HPV types produced different morphological patterns which may reflect differences in action on the host cell. In the individual patient, however, such differences in cytology do not provide a sound basis for distinguishing between viral types.

Adult↗
PubMed1993

Prevalence in Sweden of human papillomavirus type 16 infection in CIN II-III cases assessed by a PCR method.

The presence of human papillomavirus (HPV) 16 in cervical intraepithelial neoplasia (CIN)II-III cases was studied by means of a polymerase chain reaction (PCR)-based method applied to paraffin-embedded tissues. Twenty-two of 45 (49%) cases showed a positive signal determined by direct visualization on gel stained with ethidium bromide. Fourteen of these cases were confirmed by dot blot hybridization, which accords with a prevalence of HPV 16 infection in 31% of Stockholm patients with CIN II-III. The latter value is lower than that published elsewhere (Young et al. 1989; Maki et al. 1991; Skydberg et al. 1991).

Base Sequence↗
PubMed1993

RAPD analysis: an efficient method of DNA fingerprinting in fishes.

Random Amplified Polymorphic DNA (RAPD) generated using arbitrary primers of 9, 10, 16 and 20 nucleotide lengths by Polymerase Chain Reaction (PCR) was investigated in 12 species of fishes. We found that the amplification products were best resolved by Urea-SDS-PAGE and detected by silver staining. The amplification products ranged from 25 to 75 depending on the primer and template combination. The random primers generated unique fingerprints for each species of fish in terms of number and position of RAPDs. Our results showed that the fish species can be distinguished from each other by RAPDs. The complexity of the RAPDs in the fingerprints may be manipulated to suit the requirement of the study. The use of RAPD in taxonomy, fishery management and fish culture is discussed.

Animals↗
PubMed1993

Hepatitis B virus infection in patients with systemic lupus erythematosus.

Sera from 76 patients with systemic lupus erythematosus (SLE) were examined for HBsAg, anti-HBsAb and total anti-HBcAB by radioimmunoassay. Fifteen patients (19.7%) had one or more of these serological markers of HBV infection. This is comparable to the sero-prevalence in 100 sex- and age-matched healthy individuals (19%). There was no significant difference in the prevalence of HBV infection in patients who had received immunosuppressants compared with those who had not. Patients who had received transfusion of blood or blood products had a higher prevalence of serological markers but this was not statistically significant.

Adolescent↗
PubMed1993

Glycosylation and high-level secretion of human tumour necrosis factor-beta in recombinant baculovirus-infected insect cells.

Human tumour necrosis factor-beta (TNF-beta) was produced in eukaryotic cells using the insect baculovirus cloning and expression system. A novel insect signal sequence, the honey-bee (Apis mellifera) prepromelittin secretory sequence, was used to aid in the post-translational modifications, glycosylation and secretion of recombinant human TNF-beta. Human TNF-beta cDNA was cloned using the insect baculovirus vector pAcC4s. Expression of the human TNF-beta was regulated by the insect Autographa californica nuclear-polyhedrosis-virus polyhedrin promoter. The 5' end of the TNF-beta cDNA was fused to the honey-bee prepromelittin signal sequence on the baculovirus vector. Insect [Spodoptera frugiperda (Sf9)] cells infected with the recombinant baculovirus secreted high levels of recombinant human TNF-beta into the culture medium. The amount of TNF-beta secreted by the Sf9 cells was estimated to be 28 micrograms of TNF-beta/ml of culture medium at 60-72 h post infection. The secreted human TNF-beta was a 22.5 kDa polypeptide which was glycosylated. Amino acid sequencing of the N-terminus of the recombinant human TNF-beta purified from the infected Sf9-cell culture confirmed that the secreted product was indeed human TNF-beta. This demonstrates that the honey-bee prepromelittin signal sequence was efficiently recognized and accurately cleaved in the Sf9 insect cells. The insect-derived TNF-beta exhibited a high cytotoxic activity similar to that of the native human TNF-beta when assessed by cytotoxic assays using murine L929 cells. Thus the insect baculovirus expression vector can be used for the production of abundant quantities of biologically active, glycosylated human TNF-beta protein.

Amino Acid Sequence↗
PubMed1992

Intramolecular homologous recombination of linearized plasmids in Escherichia coli K12.

The efficacy of linear DNA as a substrate for general homologous recombination was demonstrated using BamHI-linearized pKLC8.5, a plasmid that carries internal direct repeats flanking the unique BamHI site. An analogous plasmid, pKLC2.31, was used in a parallel and comparative study of intramolecular homologous recombination in circular DNA substrates. When the rec+ wild-type strain, AB1157, and its isogenic rec- derivatives were transformed with linear pKLC8.5 DNA, intramolecular homologous recombination was independent of recA, recB, recN, recO and exonuclease III (xth-1) functions. Although the recBCsbcA and recBCsbcBC cells were both very recombination proficient, only linear but not circular DNA was used as substrate for intramolecular homologous recombination in the recBCsbcA cells. In both the recBCsbcA and recBCsbcBC genetic backgrounds, the recombination frequencies for linearized pKLC8.5 DNA were 100%. A notable difference between the two strains was that none of the recBCsbcA transformants obtained with circular pKLC8.5 DNA were Tcs recombinants, whereas 11% of the corresponding recBCsbcBC transformants were Tcs recombinants. The sbcB mutation was responsible for the recombination proficiency of the recBCsbcBC cells. Unlike the case in recBCsbcA cells, intramolecular homologous recombination of linear DNA in the recBCsbcBC cells was dependent on recA and recF as well as recN and recO gene functions, but was independent of recJ and recL gene functions.

DNA, Bacterial↗
PubMed1992

Detection of human papillomavirus (HPV) using dot blot and Southern blot, hybridizing with a mixture of seven probes.

A previously presented method for the detection and typing of human papillomavirus (HPV) DNA has been modified for the simultaneous analysis of HPV types 6, 11, 16, 18, 31, 33 and 35. The method has two steps, where a dot blot test is used to exclude cases that do not hybridize with HPV-DNA. The remaining cases are then analysed by a Southern blot procedure, using a mixture of subgenomic probes for the simple and accurate analysis of HPV types. When the procedure was used for the analysis of clinical samples, patient groups at varying risk were found to differ with regard to the prevalence of HPV infections. Thus, the virus was detected in only 8.8% of otherwise healthy young women - i.e. women without clinical signs of HPV-related disease - as compared to 48% of women who also had cervical intraepithelial neoplasia (CIN). A similarly high prevalence was found in patients in whom CIN persisted (42%) as compared to those in whom the morphological lesion regressed to normal (8%).

Blotting, Southern↗
PubMed1991

Prevalence of antibody to hepatitis C in patients with liver disease.

We studied the seroprevalence of antibody to hepatitis C virus (HCV) in patients with liver disease using the Abbott HCV EIA. Twenty-four patients with acute sporadic nonA nonB hepatitis, 19 patients with chronic hepatitis, 28 patients with cirrhosis and 47 patients with hepatocellular carcinoma (HCC) were assayed. The seroprevalence was 8.3% (2/24) in acute hepatitis; 10.5% (2/19) in chronic hepatitis; 3.6% (1/28) in cirrhosis and 14.9% (7/47) in hepatocellular carcinoma. The seroprevalence rates were lower in all categories of liver disease compared to figures reported in developed countries. Possible reasons included a delayed or missed seroconversion in the acute hepatitis group. Other etiologies like hepatitis B and alcohol may play a more important role in chronic liver disease. On the other hand, the seroprevalence locally may actually be low. Sporadic, non-blood transfusion appears to be a common method of acquiring the infection.

Adult↗
PubMed1989

Quality of the home environment of toddlers: a validation study of the home inventory.

The Home Observation for Measurement of the Environment (HOME) Inventory is introduced in this study to examine the home environments of children (three to four and a half years) in Singapore. The Inventory comprises eight subscales and a total of 54 items with a higher score indicating an environment which provides more possibilities for development and growth. Various statistical tests were carried out to determine the validity of the Inventory for use in the local context. These showed the Inventory to be internally consistent and to possess construct validity in particular the HOME Inventory had been validated in correlation tests with demographic variables such as social class index (F = 8.01, p less than 0.0001), people to room ratio (r = -0.37, p less than 0.0001) and a measure of IQ (r = 0.0003). Norms for local toddlers were also provided. It was concluded that the Inventory would play a useful role in detecting children who are physically and intellectually less advanced due to a poorer home environment. This finding could possibly be used in an intervention programme in ameliorating these conditions.

Child Care↗
PubMed1988

Child-rearing practices of Chinese parents and their relationship to behavioural problems in toddlers.

The aim of this study was to examine the relationship between behavioural deviance and parental involvement in childrearing and disciplinary practices in a sample of 401 toddlers. Mothers of each subject were interviewed to assess for the degree of parental involvement and the disciplinary methods used with the child. A Behavioural Screening Questionnaire (BSQ) was used to assess for behavioural deviance in the toddlers. Results indicated that father involvement in childrearing was significantly lower than mother involvement (p = 0.0001). Although consistent with cultural expectations, both low paternal involvement and punitive types of discipline were significantly related to behavioural deviance.

Child Behavior Disorders↗
PubMed1986

Legionnaires' disease--report of Singapore's first local case.

A previously healthy 27 year-old male plumber presented with six days of fever, nausea, vomiting, malaise and headache. The subsequent development of cough, dyspnoea and pleuritic pain coincided with the simultaneous development of progressive bilateral cavitary pneumonia with pleural effusion. Leucocytosis, thrombocytopenia, hyponatraemia, hypoalbuminaemia, hypophosphataemia and hypoxaemia were the main laboratory abnormalities. Clinical suspicion of Legionnaires' disease was confirmed by the presence of serum antibody to Legionella pneumophila (titre 1:512) by an indirect fluorescent antibody test. Treatment with erythromycin and rifampicin resulted in clinical recovery with minimal residual bilateral pleural effusion six months after presentation. This patient is the first to acquire Legionnaires' disease in Singapore.

Adult↗
PubMed1983

Zollinger-Ellison syndrome--report of four cases and review of literature.

Four patients with Zollinger-Ellison Syndrome (ZES) are presented to highlight the difficulties in the recognition, diagnosis and management of this rare disease. The presentation of ZES is usually indistinguishable from ordinary peptic ulcer disease and in those patients with symptoms not related to peptic ulcer, i.e., diarrhoea, as their main complaint, the diagnosis is often not even considered. A high index of suspicion is required, however, in patients with recurrent ulcers, multiple ulcers and in those with resistant or rapidly relapsing ulcers after conventional therapy. A presumptive diagnosis can be made by the demonstration of grossly elevated fasting serum gastrin levels combined with a secretin stimulation test in doubtful cases. The main problem is the location of the gastrin-secreting tumour which is usually pancreatic but often too small to be detected by currently available techniques. Histamine H2-receptor antagonists in high doses are effective in controlling the gastric acid hypersecretion which is chiefly responsible for the morbidity and mortality in ZES. They provide the treatment of choice in patients where the tumour cannot be located, though every attempt should be made to do this as surgery is the treatment of choice for this invariably malignant tumour. Total gastrectomy is now reserved for those patients in whom medical therapy has failed. The role of chemotherapy in metastatic disease has yet to be established.

Adult↗
PubMed1983

Recent advances in upper gastrointestinal endoscopy.

During the past decade considerable advances have been made in the field of gastrointestinal endoscopy. Newer and narrower-bodied endoscopes are now available for more comprehensive examination of the upper gastrointestinal tract. More lengthy instruments have made feasible the examination of most parts of the small intestine in children. The introduction of multivariate accessory equipment has given operative endoscopy a new burst of life, and the 1980s have seen renewed activity in such therapeutic modalities as endoscopic sphincterotomy and its various recent modifications. Similarly, endoscopic oesophageal sclerotherapy has been gaining momentum since interest was revived in the technique about five years ago. A brief review is made of these recent developments, including the less well-known subject of dye indicators. An attempt is made to assess their relative significance in the light of recent trends.

Adult↗
PubMed1980

Primary hepatocellular carcinoma developing in a female patient on long term oral contraceptives--a case report.

The association between hepatic tumours and oestrogen and progestogen therapy is well established. The risk of developing primary hepatocellular carcinoma (PHC) is small. In Africa and Asia where hepatitis B virus (HBV) infections are common, the development of PHC is also high. The presence of Hepatitis B core antibody indicates previous exposure to HBV and carries a risk of developing PHC by more than 34 times of non-infected normal. A Chinese female 29 years who had been on oral oestrogen and progestogen contraceptives continuously for 8 years developed PHC. She had no known illness due to HBV but was found to have concomitantly positive Hepatitis B core antibody in her sera. The presence of this HB core antibody and the long term consumption of oestrogen/progesterone derivatives may have been responsible for the early presentation of PHC in this patient. It is the first report in this country of PHC developing in a pill consumer since the introduction of oral contraceptives a decade ago In view of the prevalence of Hepatitis B in the region, this case finding warrants further study to determine whether (a) there is a higher frequency in pill consumers (b) an earlier age of presentation of hepatic malignancy. Meanwhile, it may be prudent to recommend alternative methods of birth control in individuals known to have been previously exposed to HBV infection, clinically or otherwise.

Adult↗