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Biomedical subjects

W Cheng

Publications and source records attributed to W Cheng.

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

Radiation-induced progressive decreasing in the expression of reverse transcriptase gene of hEST2 and telomerase activity.

OBJECTIVES: In order to identify the relationship between telomerase and the biological effect of radiation injury, and investigate the role of human telomerase catalytic subunit gene (hEST2) reverse transcriptase(RT) segment in the expression of telomerase activity. METHODS: Tumor HeLa cells, KB cells and A431 cells were employed to measure the change in telomerase activity after 60Co-ray irradiation at RNA level and protein level. Quantitative PCR and Northern blotting were used to determine the expression of hEST2 RT segment that encodes seven motifs of the human telomeres, a PCR-based telomeric repeat amplification protocol (TRAP) was used to assay telomerase activity after exposure to radiation. RESULTS: Both of telomerase activity and the expression hEST2 RT segment were decreased with increasing dosage of radiation. In addition, testing the expression of motifs domain is similar to the measurement of telomerase activity. CONCLUSION: The detection of the hEST2 RT segment by Northern blotting and quantitative PCR are new methods for testing telomerase activity. Furthermore, radiation can cause a dose-dependent decrease in telomerase activity. The effect of radiation on telomerase is one possible reason for the death of cancer cells after irradiation.

Catalytic Domain↗
PubMed2000

Cytotoxic chemotherapy has minimal direct effect on gastric myoelectric activity in children with 5HT(3) antagonist prophylaxis.

BACKGROUND: Cancer patients receiving cytotoxic chemotherapy frequently develop nausea and vomiting. The direct effect of chemotherapy on gastric pacemaker is not clear. The objective of this study was to assess the direct interference of gastric electrical activity by chemotherapeutic agents as a possible cause of vomiting using electrogastrography (EGG). PROCEDURE: Fasting surface EGGs were recorded in 24 children with malignancy and 24 age-matched controls. All oncology patients received the intravenous prophylatic ondansetron. According to the known emetic potential of the medications they received, the children were divided into mild, moderate, and severe groups. The EGG recordings of oncology patients were segmented into prechemotherapy period, chemotherapy period, and emetic period. The EGG data from each period were collected and analyzed (paired t-test and Mann-Whitney U test). RESULTS: There were 24 children (M:F ratio: 14:10), with a mean age of 9.6 years. Eight children vomited during the course of recording (0/3 from the mild group, 2/6 from the moderate group, and 6/15 from the severe group). The average duration of intravenous medication infusion was 7.8 hr (range 2 min to 24 hr). There was no difference between the EGG of normal control and the prechemotherapy EGG of the oncology patients. No difference was detected between the EGG data from the prechemotherapy period and the chemotherapy period. A statistically significant increase in tachygastria was detected in emetic periods (28 episodes, mean duration 5 min; P = 0.01). CONCLUSIONS: Insignificant EGG changes during chemotherapy suggest that chemotherapy has a minimal direct effect on gastric pacemaker. Tachygastria seemed to be a secondary effect of vomiting rather than the cause of it. These preliminary findings suggest that efforts to modify gastric electrical rhythm as a means of management of chemotherapy-induced vomiting may be futile. Further studies to identify factors responsible for vomiting are warranted.

Adolescent↗
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↗
PubMed2000

[Role of P53, nm23 proteins and vascular endothelial growth factor in angiogenesis and metastasis of laryngeal cancer].

OBJECTIVE: To elucidate the role of P53, nm23 proteins and vascular endothelial growth factor (VEGF) on angiogenesis and metastasis of laryngeal cancer. METHODS: Specimens of 42 laryngeal carcinomas were studied by immunohistochemical staining for P53 protein, nm23 protein, VEGF and CD34 antibody. RESULTS: Positive expressions of P53 protein, nm23 protein and VEGF were found in 47.6%, 57.1% and 71.42% of laryngeal cancer specimens respectively. There was a positive relationship between P53 and VEGF expression. The microvessel density (MVD) in P53- or VEGF--positive tumors was significantly higher in patients with cervical lymph node metastases than those without metastases. No correlation was identified between nm23 and VEGF staining. The MVD in nm23-negative and VEGF--positive tumors was significantly high. These phenomena were more easily found in patients with cervical lymph node metastases than in patients without metastases. CONCLUSION: P53 gene play roles in the metastasis of laryngeal cancer through regulating VEGF expression and reacting MVD in tumor; and nm23 gene reacts through approaches other than regulating VEGF expression.

Adult↗
PubMed2000

[Partial laryngectomy plus radiotherapy versus partial laryngectomy alone for laryngeal carcinoma].

OBJECTIVE: To investigate the effect of radiotherapy in the combined treatment of laryngeal cancer with partial laryngectomy. METHODS: One hundred and seventy-one cases of laryngeal cancer were randomly separated into three groups of partial laryngectomy, partial laryngectomy with preoperative radiotherapy (dose 40-50Gy) and partial laryngectomy with postoperative radiotherapy(dose 51-70 Gy). The surgical procedures included cordectomy, vertical partial laryngectomy, horizontal partial laryngectomy and near total laryngectomy. RESULTS: The overall 5-year survival rate was 82% (123/150). The 5-year survival rates for surgery alone group (56 cases), surgery with preoperative radiotherapy group(65 cases) and surgery with postoperative radiotherapy group(50 cases) were 85.7%, 80.7% and 79.5% respectively. There was no significant difference among the groups(chi 2 = 0.703, P = 0.704). Analysis of survival rates revealed a significant difference among the different stages(chi 2 = 12.248, P = 0.007). All 171 cases except 3 that had near total laryngectomy achieved satisfactory phonation. CONCLUSION: Neither preoperative radiotherapy nor postoperative radiotherapy can improve the 5-year survival rate of laryngeal cancer with partial laryngectomy. All patients with partial laryngectomy got satisfactory phonation.

Adolescent↗
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↗