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Biomedical subjects

C Y Yeung

Publications and source records attributed to C Y Yeung.

At least 19 recordsLinked to original sources
PubMed2006

Negative effect of heat sterilization on the free amino acid concentrations in infant formula.

Infant formulas are often heat sterilized in hospitals where water contamination or nosocomial infection is a concern, but there are few studies of the effect of high heat on the nutritional value of infant formula. In particular, the effect of heat sterilization on free amino acid (FAA) concentrations is seldom discussed. In view of the importance of these nutrients for infant growth, we investigated the FAA concentrations of infant formula after heat sterilization. Powdered infant formulas were reconstituted with hot water (80 degrees C) in glass bottles and placed in an autoclave for 5 min at 105 degrees C and 5600 kg/m2 of pressure. Additional samples of formula were prepared by conventional methods to serve as controls. After autoclaving, we measured the FAA concentrations with ion exchange chromatography. The results were compared with those obtained after conventional preparation. We found a 19.5% lower amount of total protein after autoclaving compared with conventional preparation. Concentrations of total FAA were significantly lower after autoclaving (696.5 +/- 101.4 vs 899.4 +/- 152.2 micromol/l, P = 0.01). The concentrations of individual amino acids were also lower in autoclaved infant formulas, with differences ranging from -4.1 to 71.5% (mean 22.6%). Concentrations of certain amino acids were more than 30% lower, such as valine (71.5%), citrulline (61.1%), glutamine (60.6%), ethanolamine (54%), and lysine (39.2%). Both essential and nonessential amino acids were similarly affected by autoclaving, 28.17 and 27.13%, respectively, lower than in controls (P = 0.37). The concentration of ammonia was significantly higher after autoclaving (645.2 +/- 76.2 vs 393.2 +/-140.7 micromol/l, P = 0.0003). However, the urea level was significantly lower after autoclaving than after conventional preparation (1110.8 +/- 162.7 vs 1426.5 +/- 209.5 micromol/l, P = 0.0004). The accumulation of ammonia may reflect degradation of protein and amino acids. Autoclaving clearly results in decreased concentrations of FAA in infant formula. The increased concentration of ammonia after autoclaving is of concern if it leads to deleterious effects.

Amino Acids↗
PubMed2004

Feasibility of implementing a universal neonatal hearing screening programme using distortion product otoacoustic emission detection at a university hospital in Hong Kong.

OBJECTIVE: To assess the feasibility of implementing a universal neonatal hearing screening programme using distortion product otoacoustic emission detection at a major teaching hospital in Hong Kong. DESIGN: Descriptive study and questionnaire. SETTING. Teaching hospital, Hong Kong. METHODS: A total of 1064 infants, together with their mothers, were successfully recruited for the study. The participation rate was 99.3%. A three-stage hearing screening protocol using distortion product otoacoustic emission detection was adopted. Each of the participating infants was screened on three separate occasions (day 1-4, day 5-14, and day 21-30 after birth), irrespective of the test results. A questionnaire was administered to 364 randomly selected mothers to determine whether as consumers of the hearing screening service, mothers would find screening desirable. RESULTS: Results of the screening demonstrated an incidence of permanent bilateral hearing loss (>or=40 dB in the better ear) of 0.28%. The results also showed that 3.5% of the screened infants were referred for subsequent diagnostic audiological assessment, including those suspected with unilateral as well as bilateral hearing loss. Data obtained were comparable to other reported results obtained using multi-stage screening protocols. Taking both the false positive rate and the default rate into consideration, the most appropriate time for screening in this hospital setting appeared to be around day 5 to 14 when infants returned to the hospital's day centre as out-patients for routine medical follow-up. Since this day centre service is not generally provided by all maternity hospitals in Hong Kong, an alternative time for screening would be around day 21 to 30 when infants could return as out-patients solely for the hearing test. The results of the questionnaire suggested that most mothers thought a neonatal hearing screening would be desirable (91.35%). The majority (81.70%) indicated a preference for screening either within a few days of birth at the maternity ward prior to discharge from the hospital, or between 5 and 30 days when returning to the hospital as an out-patient. CONCLUSION: It was concluded that a universal neonatal hearing screening programme could be readily implemented in a maternity hospital setting in Hong Kong.

Clinical Protocols↗
PubMed2001

Monitoring patient satisfaction with university dental services under two fee-paying systems.

AIMS: The aim of this survey was to study patients' satisfaction with the dental service of a university in Hong Kong under a recently introduced item-based fee-paying system and reasons for non-attendance at the clinic; and to compare results of the present survey with that of a similar survey of the same dental service under a time-based fee-paying system in 1996. METHOD: A modified Dental Satisfaction Questionnaire was distributed to a random sample of students (n=194) in their lecture rooms and they were asked to complete the questionnaire on the spot. The same questionnaire was sent to a random sample of staff and their spouses (n=207) by mail. RESULTS: Dental Satisfaction Index (DSI) scores calculated from the returned questionnaires were 66 for students and 70 for staff and their spouses. Compared to the scores in 1996, there was no significant difference for that of the students (DSI=65 in 1996) but there was a significant improvement in that of the staff and their spouses (DSI=66 in 1996). Moreover, in the present survey, "busy/no time" and "no perceived dental problem" were the major reasons for non-attendance, in contrast to "long waiting time for an appointment" in the 1996 survey, were the major reasons for non-attendance. CONCLUSION: The recent attempts by the University Dental Clinic to shorten patient waiting time and the change in fee-paying system might have improved the patients' satisfaction with the service.

Chi-Square Distribution↗
PubMed2001

Cytokine- and endotoxin-enhanced bilirubin cytotoxicity.

AIM: To determine the effects of endotoxin and cytokines on the cytotoxic effects of bilirubin. METHODS: A cell-culture model was developed to simulate the effect of an infection by adding endotoxin from E. coli (LPS) and pro-inflammatory cytokines (TNF-alpha, IL-Ialpha, IL-1beta, and IL-6) to the medium. The cytotoxic effects were measured by a modified MTT method. Four cell lines were tested; they were neuroblastoma, glioblastoma, liver, and endothelial cells. RESULTS: Both endotoxin and pro-inflammatory cytokines were demonstrated to enhance bilirubin cytotoxicity on all the cell lines tested, as illustrated by endothelial cell from umbilical vein. Endotoxin and TNF-alpha also showed an additive effect. TNF-alpha concentrations at much lower than clinical sepsis levels have been shown to produce significant cytotoxic effects. CONCLUSION: We speculate that in the jaundiced neonate, infection may increase the risk of tissue damage or kernicterus.

Bilirubin↗
PubMed2001

Prediction of hyperbilirubinemia in near-term and term infants.

OBJECTIVE: The purpose of this study was to determine whether end-tidal carbon monoxide (CO) corrected for ambient CO (ETCOc), as a single measurement or in combination with serum total bilirubin (STB) measurements, can predict the development of hyperbilirubinemia during the first 7 days of life. METHODS: From nine multinational clinical sites, 1370 neonates completed this cohort study from February 20, 1998 through February 22, 1999. Measurements of both ETCOc and STB were performed at 30+/-6 hours of life; STB also was measured at 96+/-12 hours and subsequently following a flow diagram based on a table of hours of age-specific STB. An infant was defined as hyperbilirubinemic if the hours of age-specific STB was greater than or equal to the 95th percentile as defined by the table at any time during the study. RESULTS: A total of 120 (8.8%) of the enrolled infants became hyperbilirubinemic. Mean STB in breast-fed infants was 8.92+/-4.37 mg/dl at 96 hours versus 7.63+/-3.58 mg/dl in those fed formula only. The mean ETCOc at 30+/-6 hours for the total population was 1.48+/-0.49 ppm, whereas those of nonhyperbilirubinemic and hyperbilirubinemic infants were 1.45+/-0.47 and 1.81+/-0.59 ppm, respectively. Seventy-six percent (92 of 120) of hyperbilirubinemic infants had ETCOc greater than the population mean. An ETCOc greater than the population mean at 30+/-6 hours yielded a 13.0% positive predictive value (PPV) and a 95.8% negative predictive value (NPV) for STB > or =95th percentile. When infants with STB > or =95th percentile at <36 hours of age were excluded, the STB at 30+/-6 hours yielded a 16.7% PPV and a 98.1% NPV for STB >75th percentile. The combination of these two measurements at 30+/-6 hours (either ETCOc more than the population mean or STB >75th percentile) had a 6.4% PPV with a 99.0% NPV. CONCLUSIONS: This prospective cohort study supports previous observations that measuring STB before discharge may provide some assistance in predicting an infant's risk for developing hyperbilirubinemia. The addition of an ETCOc measurement provides insight into the processes that contribute to the condition but does not materially improve the predictive ability of an hours of age-specific STB in this study population. The combination of STB and ETCOc as early as 30+/-6 hours may identify infants with increased bilirubin production (eg, hemolysis) or decreased elimination (conjugation defects) as well as infants who require early follow-up after discharge for jaundice or other clinical problems such as late anemia. Depending on the incidence of hyperbilirubinemia within an institution, the criteria for decision making should vary according to its unique population.

Bilirubin↗
PubMed2001

Capillary electrophoresis for the determination of albumin binding capacity and free bilirubin in jaundiced neonates.

This study develops a capillary electrophoresis/frontal analysis (CE/FA) method to separate free bilirubin from its albumin bound complex, with only small-sized samples. Under our optimized conditions, CE/FA is proven to be a simple and accurate method in assaying the concentration of free bilirubin in the jaundiced serum. Upon saturation of albumin-binding, the amount of bilirubin added to the serum bears a linear relationship with the absorbance at OD44OnM (R = .9987, P < .00001). Application of this method to study jaundiced neonates has yielded precise data on the residual binding capacity, which may be of significant therapeutic implications. The CE/FA method we have developed appears to be promising and applicable for clinical use as it is highly reproducible and it only requires a small sample size for tests. Our method should be an invaluable adjunct to the neonatal management of hyperbilirubinaemia.

Aspirin↗
PubMed2001

Prediction of hyperbilirubinemia in near-term and term infants.

OBJECTIVE: The purpose of this study was to determine whether end-tidal carbon monoxide (CO) corrected for ambient CO (ETCOc), as a single measurement or in combination with serum total bilirubin (STB) measurements, can predict the development of hyperbilirubinemia during the first 7 days of life. METHODS: From 9 multinational clinical sites, 1370 neonates completed this cohort study from February 20, 1998, through February 22, 1999. Measurements of both ETCOc and STB were performed at 30 +/- 6 hours of life; STB also was measured at 96 +/- 12 hours and subsequently following a flow diagram based on a table of hours of age-specific STB. An infant was defined as hyperbilirubinemic if the hours of age-specific STB was greater than or equal to the 95th percentile as defined by the table at any time during the study. RESULTS: A total of 120 (8.8%) of the enrolled infants became hyperbilirubinemic. Mean STB in breastfed infants was 8.92 +/- 4.37 mg/dL at 96 hours versus 7.63 +/- 3.58 mg/dL in those fed formula only. The mean ETCOc at 30 +/- 6 hours for the total population was 1.48 +/- 0.49 ppm, whereas those of nonhyperbilirubinemic and hyperbilirubinemic infants were 1.45 +/- 0.47 ppm and 1.81 +/- 0.59 ppm, respectively. Seventy-six percent (92 of 120) of hyperbilirubinemic infants had ETCOc greater than the population mean. An ETCOc greater than the population mean at 30 +/- 6 hours yielded a 13.0% positive predictive value (PPV) and a 95.8% negative predictive value (NPV) for STB >/=95th percentile. When infants with STB >95th percentile at <36 hours of age were excluded, the STB at 30 +/- 6 hours yielded a 16.7% PPV and a 98.1% NPV for STB >75th percentile. The combination of these 2 measurements at 30 +/- 6 hours (either ETCOc more than the population mean or STB >75th percentile) had a 6.4% PPV with a 99.0% NPV. Conclusions. This prospective cohort study supports previous observations that measuring STB before discharge may provide some assistance in predicting an infant's risk for developing hyperbilirubinemia. The addition of an ETCOc measurement provides insight into the processes that contribute to the condition but does not materially improve the predictive ability of an hours of age-specific STB in this study population. The combination of STB and ETCOc as early as 30 +/- 6 hours may identify infants with increased bilirubin production (eg, hemolysis) or decreased elimination (conjugation defects) as well as infants who require early follow-up after discharge for jaundice or other clinical problems such as late anemia. Depending on the incidence of hyperbilirubinemia within an institution, the criteria for decision making should vary according to its unique population.

Bilirubin↗
PubMed2000

Capillary electrophoresis for determination of free and albumin-bound bilirubin and the investigation of drug interaction with bilirubin-bound albumin.

Capillary electrophoresis (CE) is a promising technique for assessment of free bilirubin and its interaction with albumin, as it requires only a small sample volume and provides a rapid and efficient separation of free bilirubin from its albumin-bound complex in a one-phase system. In order to maintain the equilibrium without dissociation of bilirubin from the albumin/bilirubin complex as in real clinical conditions, the coupling of CE with frontal analysis (FA) was investigated. A very large sample plug was introduced hydrodynamically into the capillary (36 cm length, 50 microm inner diameter) at 15 psi x s to develop the frontal conditions during CE separation. The working conditions for CE/FA separation of bilirubin and albumin were optimized as follows: +20 kV; running buffer, 10 mmol/L phosphate and 1 mmol/L ethylenediaminetetraacetic acid (EDTA), pH 7.4. The working range for bilirubin was found to vary from 5 to 206 micromol/L; precision with relative standard deviation (RSD) <2.0% for n = 3 and detection limit (signal to noise, S/N = 2) was 2 micromol/L. The residual binding capacity of a simulated cord blood serum for bilirubin was 26 mg/100 mL at pH 7.4. Bilirubin was shown to be displaced from albumin when aspirin was added. The free bilirubin concentration was found to increase to clinical significant concentrations from 11.9 to 21.1% when increasing aspirin was added in the range of 5-50 mg/100 mL, respectively. Thus, the investigation of aspirin displacement of bilirubin from albumin is clinically important and the CE/ FA method is a suitable procedure for this purpose.

Bilirubin↗
PubMed2000

Difference in susceptibilities of different cell lines to bilirubin damage.

OBJECTIVE: To investigate if there are differences in susceptibilities to bilirubin toxicity of different cell lines. METHODOLOGY: A modified 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) method was adopted to study the cytotoxic effect of bilirubin on several commercially available cell lines including human glioblastoma (ATCC CRL 1690, T98G), human neuroblastoma (ATCC HTB-10, SK-N-MC), human liver (ATCC CCL 13, Chang Liver, HeLa markers) and a mouse fibroblast (ATCC CCL-1, NCTC Colon 929). RESULTS: Cytotoxicity was observed when certain bilirubin:albumin molar ratios were exceeded in the medium of a cell line in culture. Different cells exhibited different susceptibilities to the cytotoxic effects of bilirubin; neuroblastoma and glioblastoma were most susceptible, fibroblasts were the least vulnerable. CONCLUSIONS: Our findings have confirmed the clinical impression that different cells sustain different degrees of cytotoxicities caused by bilirubin.

Albumins↗
PubMed2000

Surfactant tracheobronchial lavage for the management of a rabbit model of meconium aspiration syndrome.

We evaluated the effect of tracheobronchial lavage with diluted surfactant solution (bovine lipid extract surfactant, bLES) in a rabbit model of meconium aspiration. All animals were anaesthetized, tracheotomized and given 3-4 ml/kg of 25% slurry of human meconium into the endotracheal tube and mechanically ventilated for 1 h. The animals were then randomly assigned to surfactant lavage (n = 12) with 15 ml/kg of diluted surfactant at a concentration of 5.4 mg phospholipid/ml administered in aliquots of 2 ml; or simple endotracheal suction (control n = 12) when the oxygenation index (OI) was >/=15. Changes in the arterial blood gases and the histomorphological and radiological appearances of the lungs were recorded. The OI and arterial/alveolar oxygen tension (a/A PO2) of the surfactant lavage group improved significantly at 5 min post-treatment, and these improvements were observed throughout the ensuing 4 h of ventilation. There was significantly more solid content recovered by surfactant lavage compared with the control group (p = 0.0001). Radiologically, the post-treatment air space opacification scores of the lavage group were significantly lower compared with the control (p = 0.002). The post-treatment radiographs of the lavage-treated rabbits were rated by the radiologist, who was blinded to the treatment groups, as much improved in 5 and improved in 4, whereas the control rabbits were rated as much worse in 3 and worse in 4. Histological examination showed the lungs of the lavaged rabbits had significantly more normal airway (p < 0.0001), more fields showing completely normal airspace (p = 0.0001) and less fields showing severe overdistension with meconium (p = 0.0005). We concluded that lavage with diluted surfactant solution effectively washed out the meconium, improved gases exchanges, and improved the histological and radiological appearances in the rabbit model of MAS.

Animals↗
PubMed2000

Dilatation of the biliary tree in children: sonographic diagnosis and its clinical significance.

We evaluated sonographically 162 children who met the criteria for biliary tract dilatation in the past 18 years. Of these, 131 patients were diagnosed as having anomalous dilatations of the biliary tree (including 112 with choledochal cysts and 19 with biliary duct dilatation and biliary atresia). Biliary tract dilatations in the other 31 patients were due to secondary causes or normal variants. All cases of intrahepatic biliary tree dilatation and those with both intra- and extrabiliary duct dilatations were anomalous. In 117 cases of extrahepatic biliary tract dilatation only, the mean diameter was widest in cases of choledochal cyst (21.4 +/- 12.1 mm, compared with cases of biliary tract dilatation with biliary atresia (10 +/- 2.4 mm), secondary biliary duct dilatation (8.5 +/- 1.5 mm), and normal variants (4.4 +/- 1.2 mm) (P < 0.001). Of the 43 infants with biliary tree dilatation, 24 (56%) had choledochal cysts and 19 (44%) had biliary tract dilatation associated with biliary atresia. Excluding cases associated with biliary atresia, the accuracy of diagnosing choledochal cysts in extrahepatic biliary tract dilatation was 71% and 97% using cutoffs of 7 mm and 10 mm as the minimum diameter, respectively.

Bile Ducts↗
PubMed1999

Gastro-intestinal bleeding caused by leiomyoma of the small intestine in a child with neurofibromatosis.

UNLABELLED: Gastro-intestinal bleeding is an uncommon presentation in children with neurofibromatosis. Gastro-intestinal involvement caused by jejunal leiomyoma has only been described in adults. To the best of our knowledge, this is the first paediatric case of jejunal leiomyoma associated with neurofibromatosis. We present a 10-year-old girl with a 9-month history of anaemia and low gastro-intestinal bleeding. Abdominal sonography and small bowel series showed a submucosal mass in the proximal jejunum. On surgery, a submucosal tumour was excised and histological examination suggested a diagnosis of "smooth muscle tumour of undetermined malignant potential". There were no recurrence of symptoms for 4 years after the operation. CONCLUSION: Jejunal leiomyoma should be considered in a child with neurofibromatosis presenting with gastro-intestinal bleeding.

Child↗
PubMed1999

Additive effect of tumor necrosis factor-alpha and endotoxin on bilirubin cytotoxicity.

Clinical observations suggest that sepsis may enhance the risk of kernicterus. This study investigated the combined effects of bilirubin, endotoxin, and tumor necrosis factor-alpha (TNF-alpha), which simulate sepsis in a jaundiced mouse fibroblast cell line. The horseradish peroxidase oxidation method was applied for bilirubin-albumin titration studies to test the effect of endotoxin and TNF-alpha on bilirubin-albumin binding. A modified 3-(4, 5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide method was used to study cytotoxicity. Bilirubin caused cytotoxicity in a dose-dependent manner in the cultured mouse fibroblasts. Such an effect was significantly amplified by TNF-alpha and endotoxin. TNF-alpha and endotoxin had no effect on the bilirubin-albumin titration curves. Our results have shown that TNF-alpha and endotoxin increase the cytotoxicity of bilirubin. These findings provide supportive evidence that sepsis would increase the risk of tissue damage by bilirubin.

Analysis of Variance↗
PubMed1999

Surfactant lavage for meconium aspiration syndrome: a pilot study.

OBJECTIVE: Meconium aspiration syndrome (MAS) is a major cause of respiratory morbidity and mortality in term infants. We reported our pilot experience on the use of diluted bovine lung surfactant lipid extract solution (Survanta [Ross Laboratories, Ohio, USA]) as a tracheobronchial lavage fluid for the treatment of infants with severe MAS. Our goal was to establish the safety and the effectiveness of this procedure before organizing a randomized controlled trial. METHOD: Six infants with severe MAS necessitating mechanical ventilation with an oxygen index of >/=15 within 6 hours of life recruited consecutively during a 11/2-year period were treated with tracheobronchial lavage with 15 mL/kg of diluted surfactant solution (Survanta) at a phospholipid concentration of 5 mg/mL administered in 2-mL aliquots. The outcome of treatment was assessed by comparison with 6 consecutive historic control infants with equally severe MAS of similar inclusion criteria retrospectively. RESULTS: The mean oxygen index, mean airway pressure, fraction of inspired oxygen, and arterial/alveolar oxygen tension ratio improved significantly within the first 48 hours after treatment in the lavage group. The duration of ventilation (mean +/- SEM, 55.3 +/- 4.6 hours vs 131 +/- 60 hours) and oxygen therapy (mean +/- SEM, 4.1 +/- 0.5 days vs 20.8 +/- 8.2 days) were also significantly reduced in the lavage-treated group compared with the control group. All 6 patients in the lavage group survived without sequelae whereas there were 2 deaths in the control group. The process of administering the surfactant lavage was well tolerated with no air leak complications. CONCLUSIONS: Our experience suggested that surfactant lavage seems to be an effective and safe method for treatment of severe MAS. A multicenter randomized control trial is indicated to further study the efficacy of this treatment.

Animals↗
PubMed1999

Variable levels of mosaicism for trisomy 21 in a non-immune hydropic infant with chylothorax.

We report the first case of mosaic trisomy 21 with non-immune hydrops fetalis and bilateral chylothoraces. Prenatal fetal blood karyotype analysis of 15 fetal cells revealed a 46,XX karyotype. Aggressive prenatal management, including fetal thoracocentesis and pleuro-amniotic shunt, was performed. A clinical phenotype of Down syndrome was apparent after the gross oedema had subsided. Subsequent chromosome study of neonatal blood lymphocytes showed mosaic trisomy 21 with 23 per cent trisomic cells. Review of the initial fetal blood sample identified trisomy in 5 per cent of 134 cells. Follow-up study at five months showed no trisomy 21 in 100 cells. This case illustrates the variable levels of mosaicism manifest in the peripheral blood of an infant with obvious Down syndrome phenotype, and the limitation of cytogenetic analysis of peripheral lymphocytes alone in prenatal and postnatal detection of low levels of mosaicism.

Adult↗