Biomedical subjects

W Cheng

Publications and source records attributed to W Cheng.

At least 37 records · Page 2Linked to original sources

PubMed2000

Apoptosis in murine duodenum during embryonic development.

Duodenum is thought to go through a solid-core stage followed by recanalization during its development. This study investigates the role of apoptosis in normal duodenal development, especially during widening of the lumen, and hence, the possible role of apoptosis in duodenal atresia (DA). Twenty-four time-mated Sprague-Dawley rats were killed from day 13 to day 20 of gestation. Duodenums of 3 fetuses were chosen randomly from each rat and processed. Apoptosis was determined by the terminal deoxytransferase-mediated biotin dUTP nick-end labeling (TUNEL) technique (ApopTag). Apoptosis count and cross-sectional areas were measured with an image analyzer (MetaMorph). The number of apoptotic cells per unit area duodenum peaked on day 15 for the mucosal/submucosal layer and on day 14 for the muscular/mesenchymal layer. The maximal number of apoptotic cells per cross-section of duodenum was between 7 and 8. The cross-sectional areas of the duodenal wall and lumen increased exponentially between day 17 and day 19 while duodenal-wall thickness remained relatively constant throughout duodenal development. The localization, timing, and intensity of apoptosis do not suggest that apoptosis is responsible for the widening of the duodenal lumen; enlargement of the lumen is related to the increase in duodenal circumference. Apoptosis thus may not be involved in the pathogenesis of DA.

Animals↗

PubMed2000

Regression of hypertrophy after Carpentier-Edwards pericardial aortic valve replacement.

BACKGROUND: The purpose of this study was to determine whether significant regression of left ventricular hypertrophy is seen after implantation of small sizes (19 to 23 mm) of the Carpentier-Edwards (CE) pericardial valve, a stented pericardial valve. METHODS: Echocardiograms and electrocardiograms (ECGs) were performed at least 1 year after surgery (mean 18 months) in patients with 19-, 21-, and 23-mm CE pericardial aortic valves and compared with preoperative echocardiograms and ECGs. RESULTS: A total of 41 patients, mean age 79 +/- 9 years (range 46 to 93 years), were studied, including 7 19-mm, 22 21-mm, and 12 23-mm patients. The mean postoperative gradient was 22 +/- 7 mm Hg for 19-mm valves, 18 +/- 5 mm Hg for 21-mm valves, and 16 +/- 4 mm Hg for 23-mm valves. The postoperative valve areas were 1.1 +/- 0.3 cm2 for the 19-mm, 1.3 +/- 0.3 cm2 for the 21-mm, and 1.5 +/- 0.4 cm2 for the 23-mm valves. Left ventricular end diastolic diameter, end systolic diameter, septal thickness, and posterior wall thickness all decreased significantly (p <0.05) postoperatively. The proportion of patients with significant left ventricular hypertrophy on ECG decreased from 63% to 47% (p = 0.001). Left ventricular mass decreased significantly by echocardiography from 265 g preoperatively to 208 g postoperatively (p = 0.004). Left ventricular mass decreased for each valve size, and the greatest absolute reduction in mass occurred in the 19-mm valve recipients. CONCLUSIONS: Implantation of the 19-, 21-, and 23-mm CE pericardial valves results in significant reductions in left ventricular mass. These findings suggest that stented pericardial valves can be used in the small aortic root without the need for aortic root enlargement procedures.

Aged↗

PubMed2000

Single strand conformation polymorphism analysis of K-ras gene mutations by capillary electrophoresis with laser-induced fluorescence (LIF) detector.

Mutations of K-ras gene play an important role in neoplastic progression. The capillary electrophoresis-single strand conformation polymorphism (CE-SSCP) technique is available for the detection of gene mutations. Using an automated capillary electrophoresis with short-chain linear polyacrylamide, after denaturation of PCR products, injections were performed at reverse polarity of 5 kV for 15 s and the separations were carried out under a constant voltage of 8 kV. Of 16 specimens of lung cancer tissue, two specimens were found to have abnormal peaks in the electrophoretogram. CE-SSCP is rapid, automated, and has high performance.

Electrophoresis, Capillary↗

PubMed2000

Gastric electrical activity normalises in the first decade of life.

AIM: Electrogastrography (EGG) is emerging as a non-invasive modality for clinical investigation, especially in children. Yet the results of EGG are influenced by many factors, including age. The objective of this study was to establish the relationship between EGG parameters and age. METHODS: Fasting surface EGG (Digitrapper, Synectics) was recorded on 24 healthy boys. The data were analyzed using ANOVA, taking p < 0.05 as being statistically significant. RESULTS: The age of the boys studied ranged from 1.0 to 11 years (mean = 6.0 years). The percentage of bradygastria was high, accounting for 34% of the recording. Normal rhythm increased (p = 0.013) and the bradygastria decreased with age (p = 0.026). The dominant frequency instability coefficient also decreased to a certain extent with age (p = 0.065). CONCLUSION: Compared to the adult population, bradygastria is common in children. The EGG progressively approaches adult pattern as the enteric development matures in the first decade of life. This justifies the conservative approach in managing conditions like gastro-oesophageal reflux in young children.

Age Factors↗

PubMed2000

Esophageal atresia and tracheal stenosis: use of three-dimensional CT and virtual bronchoscopy in neonates, infants, and children.

OBJECTIVE: The objective of this study was to evaluate the use of three-dimensional CT and virtual bronchoscopy in the treatment of neonates, infants, and children with esophageal atresia and tracheal stenosis. CONCLUSION: Long-gap (n = 1) and short-gap (n = 5) esophageal atresia, long-segment stenosis (n = 2), patent poststenting trachea (n = 1), normal trachea without fistula (n = 1), and tracheal bronchus (n = 1) were studied. Fistulas between the lower esophagus and carina were noted in all six cases of esophageal atresia. All CT findings correlated with operative or bronchoscopy findings. Sensitivity and specificity were 100%. Three-dimensional CT and virtual bronchoscopy are accurate and useful techniques in the preoperative assessment of esophageal atresia and tracheal stenosis in neonates, infants, and children.

Bronchoscopy↗

PubMed1999

Discountinuous lung sounds and hysteresis in control and Tween 20-rinsed excised rat lungs.

In the past, the relationship between pulmonary hysteresis and a model of the recruitment-derecruitment of lung units has been explored (Cheng, W., DeLong, D.S., Franz, G.N., Petsonk, E.L., Frazer, D.G., 1995, Resp. Physiol. 102, 205-215). The recruitment process is characterized by a sequence of events which represents discrete configurational changes in lung structure. It is assumed that energy released during the opening of lung units is associated with the formation of discontinuous lung sounds. The goal of this study was to record tracheal sounds for lungs inflated from different end-expiratory pressures and to relate the sound power to the normalized hysteresis of individual pressure-volume (PL-VL) loops. PL-VL curves and lung sounds were recorded for control lungs and lungs rinsed with Tween 20 in order to estimate the role of alveolar surfactant on the recruitment-derecruitment process. Results indicate that there may be two populations of lung units, one which is altered by Tween 20 and another which is not. The population not affected by Tween 20 appears to be responsible for producing discrete lung sounds and may represent the opening of larger conducting airways. The second population, possibly within the respiratory zone, is affected by alterations in surface tension and contributes to pulmonary hysteresis, but, apparently, does not contribute significantly to lung sound power measured at the trachea.

Animals↗

PubMed1999

A null mutation in murine CD36 reveals an important role in fatty acid and lipoprotein metabolism.

A null mutation in the scavenger receptor gene CD36 was created in mice by targeted homologous recombination. These mice produced no detectable CD36 protein, were viable, and bred normally. A significant decrease in binding and uptake of oxidized low density lipoprotein was observed in peritoneal macrophages of null mice as compared with those from control mice. CD36 null animals had a significant increase in fasting levels of cholesterol, nonesterified free fatty acids, and triacylglycerol. The increase in cholesterol was mainly within the high density lipoprotein fraction, while the increase in triacylglycerol was within the very low density lipoprotein fraction. Null animals had lower fasting serum glucose levels when compared with wild type controls. Uptake of 3H-labeled oleate was significantly reduced in adipocytes from null mice. However, the decrease was limited to the low ratios of fatty acid:bovine serum albumin, suggesting that CD36 was necessary for the high affinity component of the uptake process. The data provide evidence for a functional role for CD36 in lipoprotein/fatty acid metabolism that was previously underappreciated.

Adipocytes↗

PubMed1999

High affinity binding of fluorescein isothiocyanate to eosinophils detected by laser scanning cytometry: a potential source of error in analysis of blood samples utilizing fluorescein-conjugated reagents in flow cytometry.

BACKGROUND: In samples of peripheral blood cells processed using the commercial kits for detection of apoptosis based on DNA strand break labeling, a subpopulation of cells characterized by high green fluorescence, similar in intensity to that of apoptotic cells but more uniform, was consistently observed by flow cytometry. The labeled cells had no other features of apoptosis. The labeling was observed regardless of the fixative used and was evident in control samples lacking terminal deoxynucleotidyltransferase. Common to all the kits that generated this labeling pattern was the presence of fluorescein (f) conjugated reagents, f-dUTP, f-avidin, or f-antibody. METHODS: Laser scanning cytometry was used to identify the labeled cells and study the mechanism of labeling. Because it was suspected that the traces of unconjugated f-isothiocyanate (FITC) that may contaminate the reagents were responsible for the labeling, FITC binding affinity to white blood cells was studied. Gel electrophoresis was used to detect the presence of unconjugated FITC in the reagents. RESULTS: After staining with Giemsa, the strongly fluorescent objects were identified as eosinophils with normal morphology and no evidence of apoptosis. The fluorescence was localized exclusively within the cytoplasmic granules. Labeling of eosinophils was observed at 2 nM concentration of FITC, which was over three orders of magnitude lower than that needed to label neutrophils, monocytes, or lymphocytes. Gel electrophoresis of the f-conjugated reagents revealed only minor contamination with FITC. CONCLUSIONS: (1) Trace amounts of unconjugated FITC contaminating the reagents are adequate to strongly label eosinophils thereby introducing experimental bias in analysis of apoptosis and in other studies on blood cells utilizing f-labeled antibodies, e.g., in detecting cytokines. (2) FITC at concentration 2-500 nM can be used as a marker of eosinophiles; (3) Because of high affinity to FITC, eosinophiles (or the protein from these cells) may serve as a means of removing traces of unconjugated FITC from the reagents during their manufacture or prior to use.

Apoptosis↗

PubMed1999

Vibrational Spectra of Tetrahedral Fullerenes.

From the topological structures of the following classes of tetrahedral fullerenes-(1) Cn(h, h; -i, i), Cn(h, 0; -i, 2i), Cn(2h + i, -h + i; i, i), Cn(h - i, h + 2i; -i, 2i), and Cn(h, i; 0, i) for Td symmetry; (2) Cn(h, k; k, h), Cn(h, k; -h - k, k), and Cn(h, k; -h, h + k) for Th symmetry; (3) Cn(h, k; i, j) for T symmetry-we have obtained theoretically the formulas for the numbers of their IR and Raman active modes for all of the tetrahedral fullerenes through the decomposition of their nuclear motions into irreducible representations by means of group theory. Copyright 1999 Academic Press.

Journal Article↗

PubMed1999

Abnormal enteric nerve morphology in atretic esophagus of fetal rats with adriamycin-induced esophageal atresia.

Gastroesophageal reflux is common in children after successful repair of esophageal atresia (EA), and may be related to a congenital neuronal abnormality of the esophagus. This study employed a fetal rat model of adriamycin-induced EA to investigate whether the innervation of the esophagus is abnormal in EA. The fetal rats were divided into four groups: (1) normal controls; (2) a saline-injected controls; (3) adriamycin administered but without the development of EA; and (4) adriamycin-induced EA. The distal esophageal segments were immunostained with a general neural marker, protein gene product 9.5 (PGP). Immunoreactivity per cross-sectional area (/xsa) was measured with an image analyzer. The extent of the esophageal circumference encircled by PGP-stained nerve tissue was assessed. While there was no significant difference in PGP immunoreactivity/xsa between the groups, the near-complete ring of nerve tissue along the plane of the myenteric plexus was replaced by clusters of nerve tissue in the atretic group (normal vs EA, P = 0. 001, Mann-Whitney U test). The abnormal distribution of nerve tissue in the atretic esophagus may be contributing factor in the esophageal dysmotility seen in EA.

Abnormalities, Drug-Induced↗

PubMed1999

Surgical intervention in necrotizing enterocolitis in neonates with symptomatic congenital heart disease.

The commonly accepted indication for surgical intervention in necrotizing enterocolitis (NEC) is perforation of the bowel. In this study, the indication and role of surgery was assessed in neonates born with symptomatic congenital heart disease (CHD). Records of neonates admitted to a single institution in Hong Kong between January 1981 and December 1997 with symptomatic CHD who subsequently developed NEC were reviewed. The patients were categorized into cyanotic and acyanotic groups. Of 850 neonates with CHD admitted during the period, 30 developed NEC (3.5%); 17 had cyanotic and 13 had acyanotic heart disease. The average Apgar scores at 1 and 5 min were 7.5 and 8.6, respectively. The mean gestational age was 37.7 weeks and the mean birth weight was 2.5 kg. The mean age at which NEC developed was 16 days. The overall mortality in the proven cases of NEC was 57%. After excluding the suspected NEC cases (stage I), it was found that surgery in the proven NEC cases without perforation, i.e., stages II and IIIA, resulted in higher survival than in those managed medically (75% vs 44%). The cyanotic patients had higher mortality than the acyanotic group (71% vs 39%). Neonates with CHD who develop NEC belong to a unique group of mature babies with reasonable birth weights and Apgar scores, unlike the common NEC patient population. The mortality of these patients is extremely high, and a modified management approach is required. Surgical intervention may be indicated at a much earlier stage of proven NEC before gut perforation occurs.

Enterocolitis, Necrotizing↗

PubMed1999

CT appearance of midgut volvulus with malrotation in a young infant.

Computed tomography (CT) appearances of small bowel malrotation and midgut volvulus (MGV) have rarely been described in paediatric patients. We present spiral CT images of a surgically proven case in a young infant. The literature on imaging techniques to diagnose these conditions is reviewed. Radiation doses of upper gastrointestinal series (UGI) and spiral CT are estimated and compared.

Humans↗

PubMed1999

Electrogastrographic changes in children who undergo day-surgery anesthesia.

BACKGROUND/PURPOSE: Postoperative nausea and vomiting is common after general anesthesia. The timing of resuming oral input is arbitrary. This study aims to estimate the duration of emetic effects of general anesthesia after day surgery in children with electrogastrography (EGG). METHODS: Children between the age of 3 and 12 years undergoing elective nonabdominal surgery were recruited. The standard anesthesia protocol of thiopentone (5 mg/kg), O2 (30%), N2O (70%), and isoflurane (1.5%) was adopted. Caudal block was applied to the patients. A laryngeal mask was used. A mobile electrogastrogram (EGG) machine (Synectic; International Medtronic Synectics, Stockholm, Sweden) was attached to the epigastrium of the patient at least 1 hour before the operation and the recording continued through the operation and for a further 2 hours after the operation. The first half hour of preoperative recording was taken as normal control period. The results were analyzed using paired t test. RESULTS: Twenty patients who underwent circumcision under general anesthesia were studied. The mean age was 6.6 years. The mean anesthetic duration was 33.2 min. The tachygastria component (associated with nausea and vomiting) became prominent immediately after induction and returned to normal 1 half hour after cessation of general anesthesia. The dominant frequency instability coefficient of EGG (DFIC) and the dominant power instability coefficient (DPIC) peaked during the first half hour period postoperatively and returned to baseline 1 hour postoperatively (DPIC, P>.05). Bradygastria became prominent during the periods 1 half-hour before and 1 half-hour after the general anesthesia and returned to baseline 1 hour postoperatively (P<.05). CONCLUSIONS: Significant EGG changes occur during day-surgery general anesthesia for children undergoing nonabdominal surgery. These changes return to baseline 1 hour after reversal of anesthesia. It is probably safe to restart feeding 1 hour later after day-surgery general anesthesia without causing nausea and vomiting.

Ambulatory Surgical Procedures↗

PubMed1999

Foreign-body ingestion in children: experience with 1,265 cases.

BACKGROUND/PURPOSE: This study aims to elucidate the clinical presentation, the effectiveness of investigations, and treatment of foreign body ingestion in children and to formulate an algorithm of management. METHODS: The records of children admitted to a single institution who had a history of foreign body ingestion over 33 years were reviewed. Symptoms, radiological findings, and endoscopic findings were assessed. RESULTS: Foreign bodies were detected in 552 (43%) of the 1,265 children admitted. The age of the children ranged from 6 months to 16 years (mean, 5.2 years). The preschool toddlers (mean age, 3.8 years) were most prone to ingest inanimate objects. The most common objects were coins (49%) and nonmetallic sharp objects (NMSO; 31%). Although x-rays could detect all the metallic objects and 86% of glass objects, the sensitivity of fish bone detection is only 26%. Absence of symptoms was common (50% in metallic group and 29% in NMSO group). Forty-one percent of coins and 95% of NMSO were lodged at sites suitable for removal by direct laryngoscopy alone with success rates of 86% and 77%, respectively. There were 3 disease-related complications and 1 mortality. Two of these children were mentally retarded and presented late. CONCLUSIONS: Efforts for prevention of ingestion of inanimate foreign body should focus on the preschool toddler group. Particular attention should be paid to mentally retarded children with vague gastrointestinal symptoms. Absence of symptoms does not preclude presence of foreign body in children. Children with history of NMSO ingestion should undergo direct laryngoscopy despite negative radiological finding, both as a screening procedure or treatment.

Child↗

PubMed1999

Residual bladder dysfunction 2 to 10 years after acute transverse myelitis.

OBJECTIVE: Acute transverse myelitis (ATM) is a relatively rare condition in children. The recovery rate is reported to be generally complete. In the current study, the long-term urological outcome of children with ATM was assessed. METHODOLOGY: The medical records of children with ATM admitted to Queen Mary Hospital, Hong Kong, over the last 15 years, were reviewed. RESULTS: The median age of the five children with ATM at the time of onset was 6 years (range = 2-12 years). The median length of follow up was 5 years (2-10 years). Four children recovered completely from paraparesis; two had no urinary symptoms with normal micturition. However, video-urodynamic studies 3 years after the acute onset revealed that four out of the five children, including one without any urinary symptom, suffered from residual bladder dysfunction - two from contractile neurogenic bladder and two from intermediate type of neurogenic bladder. CONCLUSION: Residual bladder dysfunction is common in children suffering from ATM despite improvement of paraparesis and apparent lack of urological symptoms. Long-term follow up of urological function in these patients is recommended.

Acute Disease↗

PubMed1999

Selenium-dependent cellular glutathione peroxidase protects mice against a pro-oxidant-induced oxidation of NADPH, NADH, lipids, and protein.

Since our prior work indicated that Se-dependent cellular glutathione peroxidase (GPX1) was necessary for protection against paraquat lethality, the present studies were to elucidate the biochemical mechanisms related to that protection. Four groups of mice [Se-deficient or -adequate GPX1 knockout and wild-type (WT)] were injected (i.p.) with 50 mg paraquat/kg body weight and tissues were collected 0, 0.5, 1, 2, 3, or 4 h after the injection. Whereas the ratios of NADPH/NADP and NADH/NAD in lung were reduced by 50-70% only 0.5 h after the injection in all groups, these two ratios in liver of the Se-adequate WT were significantly higher than those of the three GPX1 knockout or deficient groups 2-4 h after the injection. The paraquat-induced pulmonary lipid peroxidation and hepatic protein oxidation, measured as F(2)-isoprostanes and carbonyl contents, respectively, peaked at 1 h in these three groups. No such oxidative events were shown in any tissue of the Se-adequate WT throughout the time course. Whereas the F(2)-isoprostane formation was accelerated by both GPX1 knockout and Se deficiency in liver, it was not significantly elevated by the paraquat treatment in brain of any group. The paraquat injection also resulted in temporal changes in lung GPX activity and GPX1 protein in the Se-adequate WT, and significant reductions in lung total SOD activity in the GPX1 knockout or deficient groups. In conclusion, GPX1 plays a critical role in maintaining the redox status of mice under acute oxidative stress, and protects against paraquat-induced oxidative destruction of lipids and protein in vivo. These protections of GPX1 seem to be inducible and coordinated with those of other antioxidant enzymes.

Animals↗

PubMed1999

Characterization of a soluble ternary complex formed between human interferon-beta-1a and its receptor chains.

The extracellular portions of the chains that comprise the human type I interferon receptor, IFNAR1 and IFNAR2, have been expressed and purified as recombinant soluble His-tagged proteins, and their interactions with each other and with human interferon-beta-1a (IFN-beta-1a) were studied by gel filtration and by cross-linking. By gel filtration, no stable binary complexes between IFN-beta-1a and IFNAR1, or between IFNAR1 and IFNAR2 were detected. However, a stable binary complex formed between IFN-beta-1a and IFNAR2. Analysis of binary complex formation using various molar excesses of IFN-beta-1a and IFNAR2 indicated that the complex had a 1:1 stoichiometry, and reducing SDS-PAGE of the binary complex treated with the cross-linking reagent dissucinimidyl glutarate (DSG) indicated that the major cross-linked species had an apparent Mr consistent with the sum of its two individual components. Gel filtration of a mixture of IFNAR1 and the IFN-beta-1a/IFNAR2 complex indicated that the three proteins formed a stable ternary complex. Analysis of ternary complex formation using various molar excesses of IFNAR1 and the IFN-beta-1a/IFNAR2 complex indicated that the ternary complex had a 1:1:1 stoichiometry, and reducing SDS-PAGE of the ternary complex treated with DSG indicated that the major cross-linked species had an apparent Mr consistent with the sum of its three individual components. We conclude that the ternary complex forms by the sequential association of IFN-beta-1a with IFNAR2, followed by the association of IFNAR1 with the preformed binary complex. The ability to produce the IFN-beta-1a/IFNAR2 and IFN-beta-1a/IFNAR1/IFNAR2 complexes make them attractive candidates for X-ray crystallography studies aimed at determining the molecular interactions between IFN-beta-1a and its receptor.

Chromatography, Gel↗

PubMed1999

Two antiatherogenic effects of progesterone on human macrophages; inhibition of cholesteryl ester synthesis and block of its enhancement by glucocorticoids.

The effects of progesterone and estradiol on cholesteryl ester (CE) formation by monocyte-derived human macrophages were examined. Formation was assessed from incorporation of 14C-cholesterol during a 20-h incubation with hormone and from that of 3H-oleate (3 h) after hormone removal. Progesterone inhibited cholesterol into CE and decreased CE cellular levels. Inhibition: 1) was reversed by progesterone removal; 2) was independent of the progesterone receptor (not blocked by the receptor antagonist RU40555); and 3) exhibited specific structural requirements; 11alpha-OH-progesterone was inhibitory, whereas its stereoisomer 11beta-OH-progesterone was not. In contrast to progesterone, estradiol was ineffective. We had reported that dexamethasone enhanced CE accumulation by human macrophages (1). In this study, we describe similar effects of the endogenous steroid, cortisol, and of the most widely prescribed glucocorticoid, prednisolone. Both steroids increased CE formation from two folds, in the presence of cholesterol-liposomes, to five folds, in the presence of modified low-density lipoprotein. Progesterone (0.1-1 micromol/L), added during glucocorticoid treatment, blocked this increase. The progesterone block: 1) was duplicated by the steroid receptor inhibitor RU40555; 2) was not reversed by hormone removal; and 3) reflected inhibition of glucocorticoid-induced increases in messenger RNA for acyl-CoA-cholesterol:acyl transferase. Thus, progesterone exerted two effects on macrophages: it acutely inhibited CE formation, and it prevented glucocorticoid-induced increases in acyl-CoA-cholesterol-acyl transferase gene expression and CE synthesis.

Arteriosclerosis↗