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C W Lam

Publications and source records attributed to C W Lam.

At least 37 records · Page 2Linked to original sources
PubMed2001

Possible case of Pitt-Hopkins syndrome in sibs.

In this article, we describe two sibs, a brother and sister, with severe mental retardation and multiple congenital anomalies including "coarse" facial features, short stature, seizures, hypertrichosis, short great toes, and overbreathing. Comparison of these patients with previous reports suggests that they could represent the first familial cases of the Pitt-Hopkins syndrome. The recurrence in sibs within the same family supports autosomal recessive inheritance for the condition. Variable expression of the respiratory symptoms, which has not been reported earlier, is underlined.

Abnormalities, Multiple↗
PubMed2001

Atypical presentation of dopa-responsive dystonia: generalized hypotonia and proximal weakness.

Dopa-responsive dystonia (DRD) is an autosomal dominant disorder typically presenting as dystonia with diurnal variability. Described is an 8-year-old boy who had had waddling gait, generalized hypotonia, and proximal weakness since early childhood. He responded well to low-dose L-dopa. He had a point mutation of the GTP cyclohydrolase I gene. The patient's father and sister had the same mutation but did not have proximal weakness. GTP cyclohydrolase I deficiency can present with hypotonia and weakness.

Carbidopa↗
PubMed2001

Mutation of proline 409 to arginine in the meander region of cytochrome p450c17 causes severe 17 alpha-hydroxylase deficiency.

We elucidated the molecular basis of 17 alpha-hydroxylase deficiency in a Chinese patient with male pseudohermaphroditism. The patient is a compound heterozygote, carrying two different mutant alleles in the CYP17 gene. The first mutation, g.6333--6341delGACTCTTTCA, located in exon 8, was reported in a Thai patient living in a rural village in Thailand. We suggest that g.6333--6341delGACTCTTTCA may be a prevalent mutation causing P450c17 deficiency in Southeast Asia. The second mutation is a missense mutation, g.5582C>G, located in exon 7, changing the codon 409 from CCG to CGG, and changing the coded amino acid from proline to arginine, i.e., P409R. This proline residue is conserved in P450c17 of other species and other human P450 proteins. Site-directed mutagenesis, in vitro expression, and functional analysis of the P409R mutant in COS-1 cells show that it has a complete lack of 17 alpha-hydroxylase activity. The proline residue probably causes a turn in the meander region of P450c17, and we hypothesize, by comparison to homologous proteins, that the change in the protein conformation may abolish heme incorporation or may prevent P450c17 from interacting with electron donors.

Adolescent↗
PubMed2001

A comparison of cytokine responses in respiratory syncytial virus and influenza A infections in infants.

UNLABELLED: Respiratory syncytial virus (RSV) infection is a major cause of bronchiolitis in infants while influenza A infection usually manifests as upper respiratory tract infection. We hypothesised that the immunological responses of infants to RSV infection and influenza A infection are different. This prospective study was undertaken to compare the cytokine responses during RSV and influenza A infection. Sera and nasopharyngeal aspirates (NPA) were collected from infants with a coryzal illness with or without wheeze who were admitted to the paediatric wards during 1998. Cytokines, adhesion molecules, RANTES, IgE and eosinophil cationic protein (ECP) were measured by enzyme linked immunosorbent assay or fluorescence enzyme immunoassay. The diagnosis of RSV and influenza infections was based on direct immunofluorescence and viral culture. Of the 39 infants studied, RSV infection was confirmed in 11 patients and Influenza A in 10 patients. All RSV patients and one influenza A patient had wheeze during the infection. The serum concentrations of interleukin (IL)-4 and IL-5, regulated upon activation normal T cell expressed and secreted (RANTES) and soluble intercellular adhesion molecule 1 (sICAM-1) in infants with RSV infection were significantly higher than those with influenza A infection (all P < 0.02). The concentration of tumour necrosis factor-alpha (TNF-alpha) in NPA was significantly lower in infants with RSV infection (P < 0.01). CONCLUSION: A predominant T helper cell type 2 cytokine and related immunological response was observed in infants with respiratory syncytial virus infection whereas a predominant pro-inflammatory cytokine response was observed in infants with influenza A infection. This may explain the different clinical manifestations of the two viral infections in infants.

Cell Adhesion Molecules↗
PubMed2001

A polymorphism in the coding region of interleukin-13 gene is associated with atopy but not asthma in Chinese children.

BACKGROUND: Interleukin (IL)-13 is an important cytokine secreted from type 2 helper T lymphocytes. It is essential for modulating IgE synthesis by human B cells. Previous studies showed that polymorphisms in the IL-13 gene were associated with serum total IgE or allergic asthma. The relationship of this marker with sensitization to individual aeroallergens has not been evaluated. OBJECTIVE: We tested whether a polymorphism in the coding region of the IL-13 gene is associated with asthma and atopy in asthmatic children in Hong Kong. METHODS: We used restriction fragment length polymorphism to detect R130Q genotype in Chinese children with asthma and control subjects. Serum total IgE was measured by microparticle immunoassay and specific IgE to common aeroallergens was measured using fluorescent enzyme immunoassay. Pulmonary function studies were performed using spirometry. RESULTS: One hundred and fifty-seven patients and 54 control children were recruited. Their mean serum total IgE concentrations were 994 kIU/L and 473 kIU/L, respectively (P < 0.0001). Atopy as defined by > or = 1 positive RAST was found in 141 patients and 32 control children. The GlnGln form of the R130Q polymorphism in the IL-13 gene was associated with serum total IgE (P = 0.005) as well as specific IgE to Der p 1 (P = 0.021), mixed cockroaches (P = 0.03) and dog (P = 0.003) but not with physician-diagnosed asthma (P = 0.621). In addition, the R130Q polymorphism did not correlate with subjective or objective indicators of asthma severity in our patients. CONCLUSION: Our results suggest that the R130Q polymorphism of the IL-13 gene is associated with elevated serum total and allergen-specific IgE but not asthma in Chinese children.

Adolescent↗
PubMed2001

Proinflammatory cytokines (IL-17, IL-6, IL-18 and IL-12) and Th cytokines (IFN-gamma, IL-4, IL-10 and IL-13) in patients with allergic asthma.

Allergen-reactive T helper type-2 (Th2) cells and proinflammatory cytokines have been suggested to play an important role in the induction and maintenance of the inflammatory cascade in allergic asthma. We compared the plasma concentrations of novel proinflammatory cytokines IL-17 and IL-18, other proinflammatory cytokines IL-6 and IL-12, Th2 cytokines IL-10 and IL-13, and intracellular interferon-gamma (IFN-gamma) and IL-4 in Th cells of 41 allergic asthmatics and 30 sex- and age-matched health control subjects. Plasma cytokines were measured by enzyme-linked immunosorbent assay. Intracellular cytokines were quantified by flow cytometry. Plasma IL-18, IL-12, IL-10, IL-13 concentrations were significantly higher in allergic asthmatic patients than normal control subjects (IL-18: median 228.35 versus 138.72 pg/ml, P < 0.001; IL-12: 0.00 versus 0.00 pg/ml, P = 0.001; IL-10: 2.51 versus 0.05 pg/ml, P < 0.034; IL-13: 119.38 versus 17.89 pg/ml, P < 0.001). Allergic asthmatic patients showed higher plasma IL-17 and IL-6 concentrations than normal controls (22.40 versus 11.86 pg/ml and 3.42 versus 0.61 pg/ml, respectively), although the differences were not statistically significant (P = 0.077 and 0.053, respectively). The percentage of IFN-gamma-producing Th cells was significantly higher in normal control subjects than asthmatic patients (23.46 versus 5.72%, P < 0.001) but the percentage of IL-4 producing Th cells did not differ (0.72 versus 0.79%, P > 0.05). Consequently, the Th1/Th2 cell ratio was significantly higher in normal subjects than asthmatic patients (29.6 versus 8.38%, P < 0.001). We propose that allergic asthma is characterized by an elevation of both proinflammatory and Th2 cytokines. The significantly lower ratio of Th1/Th2 cells confirms a predominance of Th2 cells response in allergic asthma.

Adult↗
PubMed2001

Changes of leptin and metabolic hormones in preterm infants: a longitudinal study in early postnatal life.

OBJECTIVES: Very little is known concerning the physiological role of leptin and growth in the early postnatal period and the association of leptin with other metabolic hormones in preterm infants. This study aims to investigate these relationships, and to explore the longitudinal and dynamic profile of leptin and metabolic hormones including insulin, ACTH, cortisol and FT4 in this category of patient. We also postulate that a rapid increase in body weight and body mass index in the first few weeks of life may be associated with a corresponding increase in serum leptin if the 'adipoinsular axis' is active at this stage. DESIGN: A longitudinal study in a cohort of preterm infants < 34 weeks gestation for the first five weeks of postnatal life. PATIENTS AND METHODS: Sixty-one preterm newborns < 34 weeks gestation were prospectively enrolled. Blood samples were collected in the morning when the newborns were 24 h of age (day 1), and on days 5, 14 and 35 of life. Serum leptin, insulin, cortisol, FT4, glucose and plasma ACTH concentrations were analysed using standard biochemical methods. Spearman's correlation coefficient was used to assess the inter-relationship of different metabolic hormones on the first day of life, and the relationship between metabolic hormones on day 1 and anthropometric or clinical parameters. The mixed-effects models were further used for analysing the multiple longitudinal measurements, and also for comparing the hormone concentrations between day 1 (baseline) and their corresponding levels on days 5, 14 and 35. RESULTS: Serum leptin on day 1 (baseline) was significantly associated with serum insulin (r = 0.30, P < 0.05) and insulin:glucose ratio (r = 0.29, P < 0.05) in infants < 34 weeks gestation. Female preterm infants had significantly higher serum leptin (P < 0.05) and insulin (P < 0.05) levels than male infants. In addition, the duration between the last dose of antenatal dexamethasone and delivery significantly influenced the serum concentrations of leptin (r = - 0.27, P < 0.05), cortisol (r = 0.52, P < 0.001), plasma ACTH (r = 0.28, P < 0.05) and insulin:glucose ratio (r = - 0.27, P < 0.05) on the first day of life. Despite significant increase in body weight (P < 0.00001) and body mass index (P < 0.00001) by day 35 when compared to birth weight, no corresponding significant changes were observed for serum leptin, insulin and FT4. However, there was an increasing though statistically nonsignificant trend in serum leptin after day 14 of life. CONCLUSION: This study characterized the longitudinal profile of leptin and metabolic hormones in preterm infants < 34 weeks gestation in the first 5 weeks of life. Serum leptin was significantly associated with serum insulin and insulin:glucose ratio supporting the hypothesis that an 'adipoinsular axis' exists and is likely to be functional before 34 weeks of gestation. Although a significant increase in body weight was demonstrated by day 35, no significant corresponding changes occurred with regard to serum leptin. We postulate that the limited quantity of adipose tissue at this stage of development might have contributed to this observation. Moreover, our results also showed that the duration between the last dose of antenatal corticosteroid and delivery could influence the postnatal concentrations of adipoinsular and pituitary-adrenal hormones. Thus, it is possible that antenatal dexamethasone might affect fetal growth and development via these neuroendocrine pathways in early intrauterine life.

Adrenocorticotropic Hormone↗
PubMed2001

De novo mutation in the mitochondrial tRNALeu(UUR) gene (A3243G) with rapid segregation resulting in MELAS in the offspring.

A 14-year-old Chinese boy with a normal perinatal and early developmental history presented at 5 years of age with migraine, intractable epilepsy, ataxia, supraventricular tachycardia, paralytic ileus and progressive mental deterioration. Computerized tomography revealed multiple cerebral infarcts in the parieto-occipital region without basal ganglial calcification. Magnetic resonance imaging showed increased signal intensity in T2 weighted images in the same regions. A cerebral digital subtraction angiogram was normal. Venous lactate, pyruvate, lactate to pyruvate ratio and cerebrospinal fluid lactate were elevated. Muscle biopsy did not reveal any ragged red fibres; dinucleotide-tetrazolium reductase activity was normal. Mitochondrial DNA analysis detected an adenine to guanine mutation at nucleotide position 3243 of tRNALeu(UUR). All four tissues analysed demonstrated heteroplasmy: leucocyte 56%, hair follicle 70%; buccal cell 64%; muscle 54%. The mother and brother of the proband, both asymptomatic, were also found to have a heteroplasmic A3243G mutation in the leucocytes, hair follicle and buccal cells. Other members of the maternal lineage, including the maternal grandmother, did not have the mutation. This report describes a patient with mitochondrial encephalopathy, lactic acidosis, stroke-like episodes, who presented with multisystem involvement. The absence of ragged red fibres in muscle biopsy did not preclude the diagnosis. Mutational analysis of mitochondrial DNA conveniently confirmed the diagnosis of the disorder. A de novo mutation is demonstrated in this family.

Adolescent↗
PubMed2001

Normal pulse oximeter reading in a cyanotic infant.

A newborn infant who presented with central cyanosis was found to have hereditary methaemoglobinaemia. The pulse oximeter readings and physical findings were incompatible. Clinical assessment remains an important part in the management of such cases.

Cyanosis↗
PubMed2001

Deceptive hyperbilirubinaemia in a newborn with familial lipoprotein lipase deficiency.

A rare case of familial lipoprotein lipase (LPL) deficiency in a Chinese newborn who presented with severe hyperbilirubinaemia is described. The falsely high serum bilirubin concentration was subsequently found to be a laboratory analytical error caused by interference of optical measurement of the lipaemic serum. Hypertriglyceridaemia and chylomicronaemia could be safely and effectively controlled by a fat-restricted diet using either modified elementary milk formula fortified with protein, calories and minerals, or the commercially available special milk formula such as Monogen or Portagen. DNA sequence analysis of the patient showed a Leu252Arg mutation in exon 6 of both alleles of the LPL gene. Although the parents were unrelated, both were heterozygous carriers of the same genetic defect. Codon 252 in exon 6 appears to be a common and critical site of mutation in the LPL gene of Chinese, but this important association has not been recognized previously.

Antigens, Differentiation↗
PubMed2001

In vitro studies of aquaporins 1 and 3 expression in cultured human proximal tubular cells: upregulation by transferrin but not albumin.

Dysregulated renal water handling is a cardinal feature of nephrotic syndrome that has been shown in animal models of experimental nephrosis to mediate renal aquaporin (AQP) expression. However, data on the effect of proteinuria on the proximal tubule, which is heavily vested with AQP1 and therefore may participate in water homeostasis, are limited. To investigate this, we exposed primary human proximal tubular epithelial cells (PTECs) to two key proteinuric components shown to perturb tubule function: human serum albumin and transferrin. Using reverse-transcriptase polymerase chain reaction and immunocytochemical techniques, PTECs in the quiescent state were found to express AQP3 in addition to AQP1 gene and protein, which was also validated in a human proximal tubule cell line, HK-2. Immunohistochemical staining localized AQP1 synthesis to the apical and basolateral membranes and AQP3 synthesis to the basolateral membrane of proximal tubule epithelium. Transferrin in doses reaching nephrotic range upregulated PTEC transcription and translation of both AQP1 and AQP3 in a time- and dose-dependent manner. After 24 hours of stimulation, transferrin led to a 2.4- and 2.2-fold increase in AQP1 and APQ3 messenger RNA expression, whereas protein synthesis surged by 40.7% +/- 2.48% and 24.2% +/- 0.9% compared with control, respectively. These effects were not observed with albumin challenge and were not caused by osmolality fluctuation with transferrin treatment. In summary, our novel finding of AQP3 in PTECs indicates a role for AQP3 in proximal tubule water reabsorption. The pathophysiological significance of heightened AQP1 and AQP3 expression in PTECs on protein challenge as occurs in the nephrotic state requires further investigation.

Albumins↗
PubMed2001

Novel mutation in the GRHPR gene in a Chinese patient with primary hyperoxaluria type 2 requiring renal transplantation from a living related donor.

We identified a patient with primary hyperoxaluria type 2 (PH2) showing recurrent stone formation, nephrocalcinosis, end-stage renal failure, and rapid oxalate deposition after renal transplantation from a living related donor. Urinary organic acid analysis performed after renal transplantation confirmed the diagnosis of PH2. We analyzed the glyoxylate reductase/hydroxypyruvate reductase (GRHPR) gene of the patient. DNA sequencing of all nine exons and exon-intron boundaries showed a novel homozygous mutation deleting the last two nucleotides of exon 8, ie, 862delTG. This deletion results in a frameshift and introduction of a premature stop codon at codon 310, ie, Ala310Stop. One of the patient's sisters is heterozygous for this mutation, and the other sister, who is the donor, does not have this mutation. The rapid deposition of oxalate in the transplanted kidney indicates that the kidney is not a major site of oxalate production. The more favorable long-term prognosis of PH2 needs to be reevaluated now that the molecular basis of PH2 has been established. DNA-based diagnosis will facilitate carrier detection, prenatal diagnosis, genetic counseling, and selection of living related donors.

Adolescent↗
PubMed2001

Liver iron estimation in beta-thalassaemia: comparison of MRI biochemical assay and histological grading.

AIMS: The aims of the study were to compare the efficacy of magnetic resonance imaging (MRI), biochemical assay and histological grading in estimating liver iron content, and to evaluate the value of liver to muscle signal intensity ratio (L/M ratio) on spin-echo T1-weighted images in this role. MATERIALS AND METHODS: Thirty-nine homozygous beta-thalassaemics had their L/M ratio measured on MRI, followed by ultrasound-guided liver biopsies with histological grading of iron storage and biochemical quantification of liver iron concentration (LIC-b) using atomic absorption spectrophotometry. RESULTS: A significant difference in L/M ratios between the four grades of iron storage on histology was observed (P < 0.001). The coefficient of correlation was -0.67 between L/M ratio and LIC-b ranging from 2 to 21.6 mg/g dry weight. Specific values of L/M ratio reliably reflected liver iron content at clinically important levels. A L/M ratio of < 0.6 has 86% sensitivity and 100% specificity in the prediction of grade 3 or 4 iron storage histologically and 81% sensitivity and 81% specificity in predicting LIC-b > 15 mg/g. A L/M ratio of > 0.8 predicts a histological iron storage grading of 0 or 1 with a 100% sensitivity and 74% specificity. CONCLUSION: L/M ratio on MRI is of value as a non-invasive alternative to repeated liver biopsies for estimating liver iron content at clinically important thresholds.

Adolescent↗