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Biomedical subjects

T F Fok

Publications and source records attributed to T F Fok.

At least 109 records · Page 6Linked to original sources
PubMed2001

Oxygen consumption and resting energy expenditure during phototherapy in full term and preterm newborn infants.

OBJECTIVES: To determine the effect of phototherapy on the oxygen consumption and resting energy expenditure of term and preterm newborn infants. METHODS: A total of 202 infants (gestation 30-42 weeks; body weight 1270-4100 g) requiring phototherapy for the treatment of neonatal hyperbilirubinaemia were enrolled in a randomised crossover study. In random sequence, the oxygen consumption and resting energy expenditure were measured twice in each infant by indirect calorimetry, once at the end of six hours of continuous phototherapy and once after a control period of at least six hours without phototherapy. Anterior abdominal wall temperature was servocontrolled at 36.5 degrees C throughout the study. RESULTS: At the end of six hours of continuous phototherapy, oxygen consumption (mean (SD): 6.21 (1.35) v 6.26 (1.51) ml/kg, p = 0.555) and resting energy expenditure (178.11 (37.62) v 180.37 (43.14) kJ/kg/24 h, p = 0.382) did not differ significantly from those measured after the control period. There were also no significant differences in heart rate, respiratory rate, or rectal temperature. Subgroup analysis of those of gestation < 37 weeks or < 34 weeks also showed no effect of phototherapy on either oxygen consumption or resting energy expenditure. CONCLUSION: Phototherapy has no effect on the metabolic rate of thermally stable term or preterm infants.

Basal Metabolism↗
PubMed2001

Asthma, atopy and tuberculin responses in Chinese schoolchildren in Hong Kong.

BACKGROUND: The prevalence rates of asthma and other atopic disorders have increased steadily in many developed countries over the past few decades. Recent epidemiological and animal studies have suggested that BCG vaccination might be beneficial in reducing the subsequent development of atopy. This study investigates the relationship between asthma, allergic symptoms, atopy, and tuberculin response in Chinese schoolchildren who received BCG vaccination at birth. METHODS: A total of 3110 schoolchildren aged 10 years were recruited for the Hong Kong arm of the phase II International Study of Asthma and Allergies in Childhood. Of the 2599 children born in Hong Kong and vaccinated with BCG after birth, 2201 had tuberculin testing performed at a mean (SD) age of 8.4 (1.4) years. A random subsample of 980 children was also recruited for skin prick testing. RESULTS: The prevalence rates of asthma ever, wheeze ever, current wheeze, current rhinoconjunctivitis, and current flexural eczema were not significantly different between tuberculin positive and negative subjects. The mean (SE) tuberculin response was 3.4 (0.2) mm in atopic subjects and 3.3 (0.2) mm in non-atopic subjects (difference not significant). Logistic regression analyses did not reveal any significant relationship between asthma ever, current wheeze, atopy, and positive tuberculin responses. CONCLUSIONS: This study did not find any relationship between asthma, allergic symptoms, atopy, and positive tuberculin reactivity in Chinese schoolchildren vaccinated with BCG at birth.

Asthma↗
PubMed2001

Obstructive sleep apnoea in children with adenotonsillar hypertrophy: prospective study.

OBJECTIVE: To determine clinical and baseline polysomnographic data on obstructive sleep apnoea secondary to adenotonsillar hypertrophy in Hong Kong Chinese children. DESIGN: Prospective study. SETTING: University teaching hospital, Hong Kong. PARTICIPANTS: Fifty children (35 boys and 15 girls) suspected to have obstructive sleep apnoea were recruited between January 1999 and December 1999. MAIN OUTCOME MEASURES: Symptoms questionnaire, electrocardiogram, chest radiograph, and full-night polysomnography. RESULTS: All patients had symptoms suggestive of obstructive sleep apnoea. None were found to have clinical evidence of cor pulmonale. Forty-five (90%) of 50 children had obstructive sleep apnoea with a respiratory disturbance index of greater than five. Central and mixed apnoeas were rare. Tonsil size did not correlate with the severity of obstructive sleep apnoea. CONCLUSION: Symptoms and signs suggestive of obstructive sleep apnoea can lead to a high detection rate and confirmation of obstructive sleep apnoea by polysomnography.

Adenoids↗
PubMed2000

Recurrent and novel mutations of GCDH gene in Chinese glutaric acidemia type I families.

Glutaric acidemia type I is caused by mutations of the glutaryl-CoA dehydrogenase (GCDH) gene resulting in loss of GCDH enzyme activity. Patients present with progressive dystonia and lesions in basal ganglia. Dietary treatment, when instituted from the early neonatal period, markedly reduces dystonia and morbidity. Early diagnosis and prenatal diagnosis will be facilitated by knowledge of locally prevalent GCDH mutations. Several common GCDH mutations have been found in different ethnic groups. GCDH mutations were studied in 5 Chinese glutaric acidemia type I families. We detected two novel recurrent mutations (A219T and IVS10-2A>C) which were found in two unrelated families. An asymptomatic carrier of IVS10-2A>C was also found on screening of 120 individuals. Other mutations were identified, including two other novel (R386G & IVS3+1G>A) and two known mutations (G178R & R355H). Fibroblasts from patients carrying the novel mutations were confirmed to be deficient for GCDH activity. This is the first report of GCDH mutations describing recurrent mutations in Chinese patients. The carrier rate of IVS10-2A>C may be particularly high in Chinese.

Alternative Splicing↗
PubMed2000

Expression of interleukin (IL) 1 type I and type II receptors in megakaryocytic cells and enhancing effects of IL-1beta on megakaryocytopoiesis and NF-E2 expression.

Megakaryocytopoiesis is regulated by thrombopoietin (TPO) and cytokines such as interleukin 3 (IL-3), IL-6 and IL-11. This study investigated the in vitro effects of IL-1beta on megakaryocytopoiesis and the expression of IL-1 type I and type II receptors (IL-1 RI and RII) on mega-karyocytic cell lines and primary cells. Our results demonstrated that IL-1beta alone or in combination with TPO induced megakaryocyte colony forming units (CFU-MK) from murine and human haematopoietic cells. Using reverse-transcription polymerase chain reaction (RT-PCR) and Southern hybridization techniques, the mRNA of IL-1beta, IL-1 RI, IL-1 RII and the transcription factor NF-E2 were detected in CD61+ CD41+ cells cultured from cord blood and four megakaryocytic cell lines, Meg-01, DAMI, CHRF-288-11 and M-07e. The expression of IL-1 RI and RII proteins was confirmed by flow cytometry and immunofluorescence staining. In Meg-01 cells, the expression of NF-E2 was increased at both mRNA and protein levels after treatment with IL-1beta for 4 h. This study demonstrated for the first time the presence of IL-1 receptors on megakaryocytic cells and the induction of NF-E2 by IL-1beta. The mitogenic effect of IL-1beta on this lineage could be mediated through IL-1 receptors and the activation of NF-E2.

Analysis of Variance↗
PubMed2000

Central nervous system candidiasis in preterm infants: limited value of biochemical markers for diagnosis.

Two rare cases of isolated central nervous system (CNS) candidiasis in preterm infants have been diagnosed in a tertiary neonatal centre over the past 6 years. Despite the life-threatening nature of the disease, biochemical infection markers were not useful for the early identification of localized fungal infection. Because the infection was likely to have been blood borne, we postulated that the initial fungal load was probably low and that the organisms were rapidly eliminated from the circulation after a few had been deposited in the CNS. Hence, the absence of fungaemia or systemic involvement precluded the activation of cytokines and cellular markers. Clinicians should be aware of the limitation of biochemical infection markers so that diagnosis and treatment of fungal infection will not be delayed.

Biomarkers↗
PubMed2000

Cerebral blood flow during vasovagal syncope induced by active standing or head up tilt.

BACKGROUND: Vasovagal syncope is usually associated with a sudden drop of blood pressure and/or heart rate. However, occasionally the symptoms of syncope induced by orthostatic stress testing are not associated with obvious haemodynamic changes. The mechanisms of syncope in these patients are not clear. AIM: To evaluate changes in cerebral blood flow velocities during orthostatic stress testing in children and adolescents with vasovagal syncope. METHODS: Electrocardiogram, instantaneous arterial blood pressure, and right middle cerebral artery blood flow velocity were recorded at rest, during active standing, and 80 degrees head up tilt. 32 children and adolescents aged between 7 and 18 years with a history of repeated vasovagal syncope and 23 healthy control subjects were studied. RESULTS: Presyncope occurred in 10 patients during standing, and 13 patients during head up tilt. None of the controls had symptoms during the test. The transcranial Doppler study showed that the symptoms were associated with significant decreases of diastolic cerebral blood flow velocity and an increase of pulsatility. There was no significant change of the systolic cerebral blood flow velocity. The changes of cerebral blood flow velocities occurred in all episodes of presyncope, including those not associated with severe drop of blood pressure or heart rate. CONCLUSIONS: Diastolic cerebral blood flow velocity decreased significantly during episodes of presyncope induced by orthostatic stress. Impairment of autoregulation of cerebral blood flow might play an important role in the pathophysiology of syncope.

Adolescent↗
PubMed2000

Mercury intoxication presenting with tics.

A 5 year old Chinese boy presented with recurrent oral ulceration followed by motor and vocal tics. The Chinese herbal spray he used for his mouth ulcers was found to have a high mercury content. His blood mercury concentration was raised. Isolated tics as the sole presentation of mercury intoxication has not previously been reported.

Child, Preschool↗
PubMed2000

Leptin and metabolic hormones in infants of diabetic mothers.

AIMS: To investigate the effect of maternal diabetes on leptin in term newborns and to determine whether leptin correlates with insulin and its associated biochemical parameters in support of the hypothesis that a functional "adipoinsular axis" might exist at this stage of development. METHODS: A total of 116 term newborns were prospectively enrolled and categorised into three groups: 44 were infants of non-diabetic mothers (control group C); 41 were infants born to mothers with gestational diabetes on dietary treatment (group D); and 31 were infants born to mothers with gestational or pregestational diabetes on insulin treatment (group I). RESULTS: No significant difference in serum leptin was observed between the three groups; the results of the study population were therefore pooled and analysed. Serum leptin correlated significantly with serum insulin, insulin:glucose ratio, birth weight, body length, body mass index, placenta weight, and maternal HbA(1c). Female infants had significantly higher serum leptin than male infants. All parameters except placenta weight and body length remained significantly associated with serum leptin when multivariate stepwise regression analysis was applied. Subgroup analysis revealed a significant correlation between serum leptin and cortisol in group D. CONCLUSIONS: There was no significant difference in serum leptin between infants born to diabetic and non-diabetic mothers, though infants born to mothers requiring insulin treatment had the highest median serum leptin concentrations. The significant association between serum leptin and insulin or insulin:glucose ratio supports the hypothesis that a functional adipoinsular axis might exist in term newborns. Furthermore, the significant correlation between maternal HbA(1c) and circulating leptin of the studied infants suggests that the clinical control of maternal diabetes could affect the regulation of serum leptin in these infants.

Blood Glucose↗
PubMed2000

Leptin and metabolic hormones in preterm newborns.

AIM: To investigate the inter-relation between leptin and other metabolic hormones in preterm and term infants and to explore whether a functional "adipoinsular axis" might exist in preterm newborns. METHODS: A total of 140 preterm and term newborns were prospectively recruited and categorised according to gestation length. Blood samples were taken at 24 hours (day 1), and on day 4-5 of life. RESULTS: Serum leptin, cortisol, free thyroxine, and plasma ACTH on day 1 were significantly higher in term than in preterm infants. The relation between serum leptin and gestation followed a non-linear pattern; the slope of the curve began to increase steeply between 33 and 35 weeks gestation. Serum leptin on day 1 was significantly associated with serum insulin, insulin:glucose ratio, and plasma ACTH in infants less than 34 weeks gestation; serum leptin on day 1 and day 4-5 were significantly correlated with insulin:glucose ratio in infants 34 or more weeks gestation. Significant changes in the pattern of metabolic hormones were observed in the first week of life. Serum insulin and plasma glucose were significantly increased between day 1 and day 4-5; serum leptin was significantly decreased. CONCLUSIONS: The circulating leptin concentration increases markedly after 34 weeks gestation and bears a close temporal relation with the exponential accumulation of body fat mass during that period. The inter-relation between serum leptin and insulin or insulin:glucose ratio before and after 34 weeks gestation indicates that the "adipoinsular axis" is likely to be functional in early (<34 weeks gestation) intrauterine life. The rapid decline in the circulating concentrations of leptin after birth may be of physiological advantage to preterm and term newborns by limiting their body energy expenditure and conserving nutritional reverses for subsequent growth and development.

Adrenocorticotropic Hormone↗
PubMed1999

Ex vivo expansion of enriched CD34+ cells from neonatal blood in the presence of thrombopoietin, a comparison with cord blood and bone marrow.

Neonatal blood (NB) contains substantial numbers of stem and progenitor cells which decline rapidly after birth. Using a combination of cord blood (CB) and NB, we performed a successful, sibling transplant for a thalassaemia patient, leading to the proposal that NB could be used as an adjunct to CB for transplantation. This study was aimed at addressing the feasibility of expanding NB and thus minimizing the volume needed from a NB collection. In the presence of early acting cytokines interleukin-1beta (IL-1beta), IL-3, IL-6, stem cell factor (SCF), flt-3 ligand with and without thrombopoietin (Tpo), we compared the expansion capacity of CD34+ enriched cells from CB, NB and bone marrow (BM). Flow cytometry and colony-forming unit (CFU) analyses show that Tpo significantly increased the expansion of CD34+ cells from CB and NB to early and committed progenitors. No significant difference was observed between the expansion of CB and NB at 7, 14 or 21 days of culture in terms of CFU, CD34+ and CD61+ cell subsets. The expansion capacity of BM was significantly lower than that of NB or CB, possibly related to the low proportion of CD34+ CD38- cells observed at day 0. There was a relatively rapid expansion of NB which was evident at day 7 whilst the expansion of CB and BM remained low, suggesting a speedy maturation process in the postnatal infant. The expanded cells, being heterogeneous in their morphology and cell surface marker expression, were mostly of the myeloid lineage (CD45+, CD33+ and HLA-DR+). Our results showed that the expansion capacity of NB is comparable to that of CB and if transplanted, the expanded products of NB might contribute to the engraftment kinetics of the neutrophil and megakaryocyte lineage.

Antigens, CD34↗
PubMed1999

Human neonatal blood: stem cell content, kinetics of CD34+ cell decline and ex vivo expansion capacity.

Haemopoietic stem cells are present in fetal blood but their levels decline rapidly in the peripheral circulation of the infant after birth. We previously reported a case of stem cell transplant in a beta-thalassaemia boy using a combination of the cord blood (CB) and neonatal blood (NB) of his sister. This transplant resulted in a successful engraftment. To investigate the possibility of using NB to supplement CB for related transplants, we further characterized stem and progenitor cells and lymphocyte subsets in 20 NB samples, comparing the findings with those in 20 CB samples. Our data showed that NB contained substantial levels of CD34+ cells, CD34+CD38- cells, colony-forming units-granulocyte macrophage (CFU-GM), colony forming units-erythroid (CFU-E), burst forming units-erythroid (BFU-E) and long-term culture initiating cells (LTCIC). NB was similar to CB in the levels of T lymphocytes, but the amounts of B lymphocytes and natural killer cells were higher in CB (P = 0.033, P= 0.001, respectively). The kinetics of CD34+ cells in NB was investigated in serial blood samples obtained from 10 full-term infants at 2, 4, 6, 8, 24 and 48h after birth. CD34+ cells decreased rapidly after birth, declining to only 30% of the 2h level at 48h (P<0012). The rate of decline was greatest in the first 4 h of life. NB from four infants was expanded by culturing the blood samples in the presence of thrombopoietin (Tpo), interleukin 1beta (IL1beta), IL-3, IL-6, flt-3 ligand and stem cell factor (SCF) for 7 d. This resulted in the increase of CD34+ cells, CFU-GM and CFU-MK by 271+/-179, 556+/-385 and 113+/-75 fold respectively. Three of the five samples expanded for 7 d contained LTCIC. These findings suggest that NB might be a supplementary or alternative source of stem cells to CB for transplant. The ethics and practicality of this approach deserve further exploration.

Antigens, CD34↗
PubMed1999

Early onset of hypernatraemic dehydration and fever in exclusively breast-fed infants.

Five cases of moderately severe hypernatraemic dehydration were identified within a 5-month period between two regional hospitals in Hong Kong. Unlike previous reported cases, these exclusively breast-fed infants presented with the unusual triad of fever, absence of overt signs of dehydration and within the first week of life. Three of the cases also had high serum bilirubin concentrations at presentation. The fever subsided quickly and the serum bilirubin concentration fell rapidly within a few hours of rehydration. All infants made an uneventful recovery without permanent neurological sequelae. Fever, presumably secondary to dehydration, is an useful early warning sign. These cases emphasize the importance of early and regular measurement of bodyweight in exclusively breast-fed infants so that prompt identification of affected cases may prevent potentially detrimental complications.

Age of Onset↗
PubMed1999

Estimation of pulmonary deposition of aerosol using gamma scintigraphy.

Following delivery of technetium 99m-labeled aerosols through a ventilator circuit, the amount of radioactivity in the lungs of 58 ventilated rabbits was estimated first by gamma scintigraphy via gamma camera and later by direct counting of the excised lungs (n = 116 specimens) with a gamma counter. The in situ radioactivity measured via scintigraphy was closely correlated with the gamma counter ex vivo tissue counts of the radioactivity (R2 = 0.997, P < 0.001). Overall, gamma scintigraphy gave slightly lower values of activity than the tissue counts from the gamma counter, but the limits of agreement between the two measurements were narrow enough for us to consider that the tissue and scintigraphy methods were in agreement. We conclude that gamma scintigraphy provides a convenient and noninvasive means for the accurate estimation of aerosol deposition in the lungs of small animals and possibly in small infants.

Aerosols↗