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Biomedical subjects

S K Cheong

Publications and source records attributed to S K Cheong.

At least 19 recordsLinked to original sources
PubMed1995

Enzyme activity of glucose-6-phosphate dehydrogenase-deficient Malaysian neonates during the first 10 days of life.

OBJECTIVE: The objective of this study was to determine the degree of severity of enzyme deficiency in glucose-6-phosphate dehydrogenase (G6PD)-deficient Malaysian neonates as part of an effort to identify risk factors associated with severe hyperbilirubinaemia in G6PD-deficient infants. METHODOLOGY: During this study, enzyme activity was measured in 53/59 (89.8%) hospital-diagnosed G6PD-deficient neonates (34 Malays, 12 Chinese, and seven other ethnic groups) born consecutively in the Kuala Lumpur Maternity Hospital. All neonates, except one, were males. RESULTS: The mean level of enzyme activity of the 52 males G6PD-deficient neonates (0.47 iu/g Hb, 95% confidence intervals: 0.37, 0.57) was less than 10% of that of normal Malaysian male neonates. The enzyme activity of the only female G6PD-deficient infant, at 1.11 iu/g Hb, was 12.5% of the mean G6PD enzyme activity of normal females. CONCLUSION: Our results showed that G6PD deficiency in Malaysian neonates predominantly affects males and is usually severe.

Analysis of Variance↗
PubMed1995

Infectiousness of HBsAg carriers in Malaysia.

HBV-DNA were analysed in 330 HBsAg-positive carriers in Malaysia by dot-blot hybridization and polymerase chain reaction. Seventy-three (22.12%) were positive for the virus. Of these, 65 (89%) were males and 8 (11%) were females. Statistically, there was no significant difference (P = 0.13). No significant decline in HBV-DNA with age in the Malay and Chinese males was observed (P = 0.2). Prevalence of HBV-DNA was higher in the Chinese carriers than in the Malay carriers for most age groups in both sexes. Sixty-one HBV-DNA-positive carriers were also positive for HBeAg. However, three individuals were positive only for anti-HBe, one was positive for both HBeAg and anti-HBe, and eight were negative for both HBeAg and anti-HBe. Fifty-seven were positive for HBeAg but negative for HBV-DNA. No relation was observed between raised alanine aminotransaminase and aspartate aminotransaminase levels and the presence of HBV-DNA (P = 0.4).

Adolescent↗
PubMed1994

Glucose-6-phosphate dehydrogenase enzyme activity of normal term Malaysian neonates of different ethnic origins.

The cord blood glucose-6-phosphate dehydrogenase (G6PD) enzyme activity of 262 normal term Malaysian neonates (92 Malays, 96 Chinese and 74 Indians) was quantitatively determined by the World Health Organisation method. Analysis of variance for the levels of G6PD enzyme activity by ethnic origin and sex showed that there was a significant difference between mean levels of enzyme activity in the three ethnic groups (P = 0.03) but no difference between the sexes (P = 0.36). Multiple range analysis showed that Malays had significantly higher mean levels of G6PD enzyme activity than those of Chinese (P = 0.01). There was no significant difference between the mean levels of G6PD enzyme activity of Chinese and Indians (P = 0.52), nor was there any difference between those of Malays and Indians (P = 0.08). The difference in levels of G6PD enzyme activity among the different ethnic groups could be due to the existence of different G6PD variants.

Analysis of Variance↗
PubMed1994

Pregnancy in a patient receiving busulphan for chronic myeloid leukaemia.

A 33-year-old Malay lady with chronic myeloid leukaemia (CML) became amenorrhoeic during therapy with busulphan. Pregnancy was diagnosed via a urine pregnancy test and an ultrasound confirmed a viable foetus at 16 weeks. The busulphan was stopped. Her pregnancy was unremarkable and continued till term. She delivered a healthy child.

Adult↗
PubMed1993

Evaluating in-house anti-serum against B cells with flow cytometry.

The applications of antibodies, be it monoclonal or polyclonal, in the diagnostic and research fields are well established. The disadvantage is the high cost of commercially available antibodies. In a diagnostic establishment like ours which also functions as a training ground for laboratory related personnel, it is beneficial to be able to produce in-house reagents. Therefore, we have undertaken this project to produce a rabbit polyclonal antibody against B lymphocytes. We found that the rabbit was a good choice because the titre of antibody produced was high and positive reactions were still detected at a dilution of 1:38400. The antibody showed significant positive reaction only with the lymphocyte subpopulation. A positive reaction was observed between the immunized rabbit serum and B lymphocytes but not T lymphocytes. This shows that the antibody was B lymphocyte specific. There was a positive correlation between the percentage of B lymphocytes labelled using the commercial anti-CD19 monoclonal antibody and the in-house polyclonal antibody (n = 13, r = 0.7, p = 0.02). However, the percentage of cells labelled by the in-house polyclonal anti-B was lower than that by the commercial monoclonal anti-CD19. The fluorescence intensity of the polyclonal antibody was lower than that of the monoclonal. In general, the performance of the in-house polyclonal antibody can be considered as satisfactory. The rabbit serum was stored at -20 degrees C and no significant loss of activity was detected for over a period of 19 months.

B-Lymphocytes↗
PubMed1993

The distribution of immunoregulatory cells in the peripheral blood of normal Malaysian adults.

The distribution of immunoregulatory cells in the peripheral blood of an individual has now been established as an important tool in helping the management of several diseases. It is necessary to set the normal ranges of these cells for the laboratory. We have undertaken in this study to establish the reference ranges for normal Malaysian adults. We found that the mean percentages of T cells, B cells, T Helper cells (CD4), T suppressor cells (CD8), NK cells and the ratio of CD4/CD8 were 70.91%, 11.38%, 38.15%, 37.76%, 17.45%, and 1.00 respectively. There was no significant difference between the sexes. In certain parameters, there was significant differences between Malay, Chinese and Indians. The Chinese and Indians were significantly different in the distribution of B cells and in the CD4/CD8 ratio. In the case of CD4 and NK cells, the Indians were different from the other two groups.

Adult↗
PubMed1992

Immunostaining of formalin-fixed, paraffin-embedded tissues for malignant lymphomas.

With the advent of new monoclonal antibodies that are applicable to formalin-fixed, paraffin embedded sections, immunophenotyping is becoming increasingly important in the diagnosis and classification of lymphomas. However, multiple factors such as fixation, trypsinization and even type of antibodies used have certain effects on the final outcome of the staining procedure. In this paper we report our experience and the problems encountered in our laboratory when we first tried to establish a workable immunostaining protocol for formalin-fixed, paraffin embedded tissue sections using the immunoalkaline phosphatase technique.

Alkaline Phosphatase↗
PubMed1992

In-house microcomputer software package for management of histopathology reports.

A system for computerising histopathology records developed in-house using dBASE IV on IBM-compatible microcomputers in a local area network is described. The software package uses a horizontal main menu bar with associated pull-down submenus as interface between the machine and the user. It is very easy to use. The package provides options for selecting databases by years, entering/editing records, browsing data, making multi-characteristics searches/retrievals, printing data, and maintaining databases that includes backing-up and repairing corrupted databases.

Database Management Systems↗
PubMed1992

All trans-retinoic acid in the treatment of promyelocytic leukaemia--a case report.

A six year old Chinese boy with relapsed Acute Promyelocytic Leukaemia (APML) failed to respond to reinduction with Daunorubicin and Cytarabine infusion. He was successfully treated with all trans-Retinoic Acid (45 mg/m2/day) orally. After four weeks of treatment, he was in complete remission. The side effects of all trans-Retinoic Acid were negligible.

Child↗
PubMed1992

Abnormalities of chromosome 11Q in three cases of acute myeloid leukemia.

The haematological findings and case history of 3 patients with the association of acute myeloid leukemia and translocation involving the long arm of chromosome no. 11 are presented. The recipient chromosome for the translocated material from chromosome 11 differs in all the three cases being namely chromosomes 1, 10 and 17.

Child, Preschool↗
PubMed1991

Single incubation double esterase cytochemical reaction using a single coupling reagent.

Most methods used in double esterase cytochemistry for the diagnosis and classification of acute myeloid leukaemias require double incubation and staining, using separate coupling reagents. We evaluated a method by Swirsky on our normal and abnormal blood and bone marrow smears where only a single incubation and the use of a single coupling reagent is required. Its short incubation period and its strong positive reaction for butyrate esterase in demonstrating cells of monocytic lineage gives it an advantage over the conventional double incubation technique.

Esterases↗
PubMed1991

A freeze-dried method for preparation of G6PD reagent tubes.

Mixed reagents for the Glucose-6-phosphate dehydrogenase (G6PD) deficiency fluorescent screening test were freeze-dried in plastic tubes. The reagents were then reconstituted with distilled water and the test was performed in the usual way. Initial testing with the freeze-dried mixed reagents gave consistent positive reaction to 12 normal blood samples and negative reaction to 9 G6PD deficient blood samples. This will enable a laboratory with freeze-drying facilities to prepare reagent tubes in bulk. As these tubes can be kept at 4 degrees C and do not require to be stored at -20 degrees C, a major laboratory can prepare these tubes and supply small laboratories for screening purposes.

Fluorescence↗
PubMed1991

An in-house assay for serum deoxythymidine kinase.

An in-house method which utilizes 14C-thymidine as a substrate was used to assay deoxythymidine kinase in serum. The method is sensitive enough to detect normal levels of serum deoxythymidine kinase and the assay procedure also enables rapid handling of multiple samples. With a total reaction volume of 60 ul, the enzyme reaction was found to be linear with concentrations for up to 650 U/L of TK activity. On studying serum deoxythymidine kinase (s-TK) activity with incubation time, there was a proportional increase in activity with the length of incubation time. "Within-batch" precision showed a coefficient of variation (CV) of 4.7% for serum with extremely high s-TK levels and a CV of 8.8% for serum with normal s-TK levels. S-TK showed a CV of less than 16.0% in its activity when stored at -8 degrees C and at -20 degrees C. The normal reference range obtained for s-TK activity was 8.6 +/- 7.5 U/L.

Acute Disease↗
PubMed1991

Immunophenotyping of peroxidase-negative acute leukaemias using immunoalkaline phosphatase (APAAP) method.

Immunophenotyping of acute leukaemias has become an important diagnostic tool in haematology laboratories as it is now well recognised that the presence of certain surface markers has prognostic significance. In 1988, we experimented with the alkaline phosphatase anti-alkaline phosphatase (APAAP) method for immunophenotyping of leukaemic cells in our laboratory. 48 cases of peroxidase-negative acute leukaemias were studied. Our study showed that 2 peroxidase-negative cases carried myeloid surface markers, 44% were negative for the markers studied and 5% were unclassified due to technical problems. We concluded that the APAAP method is a useful technique for demonstrating cell markers in leukaemic cells as the reaction is reddish and usually intense. We failed to demonstrate surface markers in 44% of the cases probably because of the choice of a limited panel of monoclonal antibodies.

Adolescent↗