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Biomedical subjects

H K Yap

Publications and source records attributed to H K Yap.

At least 55 records · Page 3Linked to original sources
PubMed1994

The diagnosis of tuberculous meningitis using the polymerase chain reaction.

AIM: DNA amplification by the polymerase chain reaction (PCR) was evaluated as a means for rapid diagnosis of tuberculous meningitis (TBM). METHODS: A 240 bp region (nts 460-700) from the MPB 64 protein coding gene specific for Mycobacterium tuberculosis (TB) was selected for amplification. Nineteen clinical samples were studied. Six were obtained from patients with TBM diagnosed by culture (4/6) or by response to therapy (2/6). The remaining 13 samples were obtained from patients with febrile seizu es (8/13), aseptic meningitis (3/13) and septic meningitis (2/13), and these served as negative controls. RESULTS: We detected TB DNA in all the 6 CSF specimens obtained from patients with TBM. PCR alone was sufficient to detect TB DNA in 5 of these 6 samples. However, one sample was positive only when PCR was followed by oligonucleotide hybridisation. In the 2 patients whose CSF were obtained only after commencement of TB therapy, TB cultures were negative but positive on PCR nd oligoprobe labelling. The diagnosis of TBM was confirmed based on their remarkable response to therapy. Twelve of the thirteen negative controls were TB DNA negative. There was one false positive sample, which was thought to be due to TB DNA contamination. CONCLUSION: Taken together, our results indicate that DNA amplification using PCR, followed by oligonucleotide hybridisation offers a rapid (5 working days) means of diagnosis of TBM, provided care is taken to ensure that cross contamination of DNA samples is avoided.

DNA Primers↗
PubMed1993

Modulation of MHC expression on human endothelial cells by sera from patients with systemic lupus erythematosus.

Major histocompatibility complex (MHC) antigen expression on cells is a prerequisite for immune interaction with activated T-cells. This study examined the ability of sera from patients with systemic lupus erythematosus (SLE) to modulate MHC expression on vascular endothelial cells. SLE sera were able to selectively upregulate MHC class I antigen expression on cultured human umbilical venous endothelial (HUVE) cells, without concomitant induction of MHC class II antigen. The stimulation index (SI) for MHC class I expression produced by SLE sera (1.21 +/- 0.23) was significantly higher than those for normal controls (1.01 +/- 0.10) (P < 0.0001) and non-SLE patients (1.12 +/- 0.14) (P < 0.05). Additionally, active SLE patients had higher mean SI than inactive patients (P < 0.001). Preincubation of SLE sera with Protein A-Sepharose beads conjugated with antibodies against tumor necrosis factor-alpha and interferon-alpha was able to significantly reduce their ability to upregulate class I MHC expression by HUVE cells, indicating that these cytokines were responsible for the modulatory effect. This could be an important mechanism for the immune-mediated vascular injury seen in SLE.

Adolescent↗
PubMed1992

T cell immunodeficiency in dyskeratosis congenita.

Dyskeratosis congenita has been found to be associated with abnormal immune function. In this study we report a patient with this association. He developed Pneumocystis carinii interstitial pneumonia, and impaired cell mediated immunity was confirmed by the presence of depressed lymphoproliferative responses to in vitro stimulation with mitogen. Enumeration of T cell subsets showed a severely depressed CD4:CD8 ratio (0.38), which is the likely cause for impaired cell mediated immunity. The T cell activation pathway appeared intact, as his T lymphocytes were able to express activation markers (CD25 and HLA-DR) after mitogen stimulation.

Adolescent↗
PubMed1991

Cell-mediated immunity in patients on hemodialysis: relationship with hepatitis B carrier status.

We compared cell-mediated immune responses in two groups of patients on hemodialysis. One group of patients were chronic carriers of hepatitis B virus (HBV), and the patients of the other group were HBV antigen negative. Our results show that despite the presence of normal numbers of T cells and an increased CD4/CD8 ratio in both groups of patients compared to healthy controls (p less than 0.0001), only the group of patients who were chronic HBV carriers showed depressed lymphoproliferative responses to phytohemagglutinin (p less than 0.001) and concanavalin A (p less than 0.0001). In contrast, a control group of healthy adult HBV carriers showed normal T cell subsets and lymphoproliferative responses to mitogens, indicating that HBV infection per se did not result in depressed lymphoproliferative responses. These results further substantiate the notion that depressed cell-mediated immunity in chronic renal failure is an important factor in predisposing patients to HBV infection with subsequent development of the chronic carrier state.

Adult↗
PubMed1991

Munchausen syndrome by proxy.

Munchausen syndrome by proxy is the falsification of symptoms by parents which results in their children having unnecessary and sometimes harmful hospital procedures. We describe a case of Munchausen syndrome by proxy in a 15 month-old toddler. The diagnosis, management and outcome of this syndrome is also discussed.

Child Abuse↗
PubMed1991

Comparison of progression of renal failure in children with hypoplastic-dysplastic kidneys and chronic glomerulonephritis.

A comparative study was made on two groups of children comprising 20 patients with renal hypoplasia/dysplasia in one group and 12 patients with chronic glomerulonephritis (GN) in the other, presenting with chronic renal failure (CRF) in the Department of Paediatrics, Singapore General Hospital and National University Hospital between 1975 and 1989. The age of onset of CRF, the progression of renal failure and the presence of various clinical complications were analysed and compared. The mean age of onset of CRF was earlier in patients with renal hypoplasia/dysplasia (p less than 0.001) but the progression of renal failure in these patients were slower (p less than 0.005). Hypertension occurred more frequently in the chronic GN group (p less than 0.001) while urinary tract infection (UTI) occurred more frequently in the renal hypoplasia/dysplasia group (p less than 0.004). With the early onset of renal failure and slow deterioration of renal function in patients with renal hypoplasia/dysplasia, the provision of good conservative treatment for renal failure is most important in the management of these patients. In the chronic GN patients however, with the rapidity of deterioration of renal function, early preparation for replacement therapy becomes more imminent. However, renal replacement therapy in end-stage renal failure (ESRF) is costly and not readily available, it is more prudent to delay the onset of ESRF by providing effective conservative treatment of renal failure which includes the early recognition and treatment of hypertension in chronic GN and UTI in renal hypoplasia/dysplasia.

Age Factors↗
PubMed1991

Urine microalbumin/creatinine ratios in Singapore children.

The random urine albumin:creatinine (Ua:Uc) ratio was measured in 139 healthy children from newborn to age 4 years using the immunonephelometric method. This was shown to vary with age, the mean for neonates being 5.24mg/mmol (2SD range: 0.54-14.95mg/mmol) decreasing to 1.34mg/mmol (2SD range: 0.55-3.29mg/mmol) for the 2-4 years age range. The values for newborn to 6 months was significantly higher than the older age group (p less than 0.000001). 14 children with structural renal disease were then studied to determine the value of the random Ua:Uc ratio in detecting glomerular injury. This was found to be abnormal in children with glomerular filtration rate (GFR) less than 80ml/min/1.73m2 as well as in some children with complex bilateral renal structural abnormalities. Further longitudinal studies are required to determine the usefulness of this ratio in predicting progressive glomerular injury in this group of patients.

Albuminuria↗
PubMed1991

Paediatric renal transplantation--current perspectives.

Chronic dialysis is a viable modality for treatment of end-stage renal disease in children, however, its limitation include negative effects on growth, progressive bone disease, and a poorer quality of life. Renal transplantation, on the other hand, allows the child a virtually normal life-style, with good prospects for employment and family life as an adult. Both patient and graft survival are significantly improved in children transplanted in centres with full paediatric facilities where special problems in young children are better addressed, such as that of fluid balance during the perioperative period, the age-related heightened immune responsiveness, and the different pharmacokinetic and pharmacodynamic handling of the various immunosuppressive agents in the child. Moreover, consideration of the problems of growth and developmental is crucial for maximal psychosocial rehabilitation of the paediatric transplant recipient.

Kidney Transplantation↗
PubMed1990

Sonographic screening for renal tract anomalies associated with congenital heart disease.

The incidence of structural renal tract abnormalities in 109 children with documented congenital heart disease (CHD) was studied using real-time sonography. In these children, 11.9% had associated urologic anomalies, which included hydronephrosis, duplication, ectopia, agenesis, and dysplasia of kidneys. Children with associated extracardiac anomalies had a significantly higher incidence of renal tract anomalies (39.1%) compared to those with isolated CHD (4.7%). Therefore, sonographic screening of the renal tract should be performed routinely in patients with CHD, especially in those with multiple congenital defects.

Abnormalities, Multiple↗
PubMed1990

Acute glomerulonephritis--changing patterns in Singapore children.

This study compared the pattern of acute glomerulonephritis (AGN), a disease known to be influenced by socioeconomic and environmental factors, in children 12 years and under, for the years 1971 and 1985. All children admitted to the four major paediatric departments with haematuria and at least two of the following (oedema, hypertension or oliguria) had an initial diagnosis of AGN. A sample population from one unit from 1980 to 1984 showed that over 70% of these children had evidence of a post-streptococcal aetiology. In 1971, 411 children were admitted with AGN, as compared with only 58 in 1985. The age-sex-race standardized rates for 1971 and 1985 were 0.632 and 0.023/1,000 children 12 years and under, respectively (P less than 0.001). The mean age of presentation was lower in 1971. Over this period, Singapore saw a threefold rise in the gross national product, accompanied by rapid urbanization. On analysis of the housing pattern, only 31% of the children lived in high-rise apartments in 1971, in contrast with 86% in 1985 (P less than 0.001). The majority of non-apartment dwellers had homes in rural districts. From an epidemiological perspective, factors which could have led to the highly significant decline in prevalence of AGN in Singapore children included improvement in the socioeconomic status and health care system, and urbanization of the country.

Acute Disease↗
PubMed1990

Anti-vascular endothelial cell antibodies in severe preeclampsia.

There is mounting evidence to suggest that vascular endothelial cell injury plays an important role in the pathogenesis of preeclampsia. In this study an enzyme-linked immunoassay was used to demonstrate increased binding of immunoglobulins G and M to human umbilical vein endothelial cells by sera from women with severe preeclampsia as compared with normal pregnant control women. Fifty percent of women with preeclampsia versus 15.4% of control women had either immunoglobulin G or immunoglobulin M binding. In addition, immunofluorescent staining of normal renal cortical tissue with preeclamptic sera showed increased binding of immunoglobulin G to arterioles in patients with anti-vascular endothelial cell antibodies. These antibodies were not directed at HLA antigens and did not cross react with platelets. Interferon-gamma stimulation did not increase immunoglobulin binding. Antibodies to antigens expressed on vascular endothelial cells may be important in mediating the endothelial damage seen in preeclampsia.

Antibodies↗
PubMed1990

The red cell charge in steroid--responsive nephrotic syndrome.

It has been suggested that the negative charge on the surface of red blood cells (RBC) may reflect the charge on the glomerular capillaries. Measurements were made of RBC charge in patients with steroid-responsive nephrotic syndrome (SRNS) based on the binding of a cationic dye, alcian blue. There was no difference found between patients in relapse and in normal controls. We conclude that RBC charge measurements are not a reliable indicator of the glomerular charge barrier and a more specific method is required.

Adult↗
PubMed1990

Rhabdomyolysis-induced acute renal failure in a child: a case report.

Rhabdomyolysis-induced acute renal failure is rare in a child. In this paper, we describe a young girl with this condition who unfortunately succumbed to adult respiratory distress syndrome. Renal biopsy confirmed the presence of tubular myoglobin casts and acute tubular necrosis but no cause for the rhabdomyolysis could be documented.

Acute Kidney Injury↗
PubMed1990

A child with Henoch-Schonlein nephritis and selective proteinuria--case report.

In this paper, we describe a child with Henoch-Schonlein nephritis presenting with nephrotic syndrome and selective proteinuria. Renal biopsy showed ISKDC Class IIIA nephritis. He responded to steroid treatment and is currently well. The significance of renal involvement in Henoch-Schonlein Purpura is discussed.

Child↗