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Biomedical subjects

W Cheng

Publications and source records attributed to W Cheng.

At least 19 recordsLinked to original sources
PubMed2005

The spectrum of vibration modes in soft opals.

Numerous vibrational modes of spherical submicrometer particles in fabricated soft opals are experimentally detected by Brillouin light scattering and theoretically identified by their spherical harmonics by means of single-phonon scattering-cross-section calculations. The particle size polydispersity is reflected in the line shape of the low-frequency modes, whereas lattice vibrations are probably responsible for the observed overdamped transverse mode.

Journal Article↗
PubMed2005

Reaching the nonlinear regime of Raman amplification of ultrashort laser pulses.

The intensity of a subpicosecond laser pulse was amplified by a factor of up to 1000 using the Raman backscatter interaction in a 2 mm long gas jet plasma. The process of Raman amplification reached the nonlinear regime, with the intensity of the amplified pulse exceeding that of the pump pulse by more than an order of magnitude. Features unique to the nonlinear regime such as gain saturation, bandwidth broadening, and pulse shortening were observed. Simulation and theory are in qualitative agreement with the measurements.

Journal Article↗
PubMed2004

Esophageal atresia and achalasialike esophageal dysmotility.

A 14-year-old boy presented with regurgitation, malnutrition, and chronic lung insufficiency with a history of successful repair of esophageal atresia and tracheoesophageal fistula in the newborn period. Barium swallow and manometry results showed achalasia. Hellar operation with antireflux procedure resulted in complete symptomatic relief. Histology and immunohistochemistry including PGP9.5, MAP5, cKit, and nNOS of myotomy specimen showed intact innervation. Although esophageal dysmotility after esophageal atresia repair usually is caused by gastroesophageal reflux and incoordination of peristalsis, the possibility of achalasia should also be considered, because a casual relationship between esophageal atresia and achalasia may exist.

Adolescent↗
PubMed2002

Anomalies associated with oesophageal atresia in Asians and Europeans.

Oesophageal atresia (OA) is often associated with anomalies of other systems. The genetic contribution to the formation of the VACTERL association is not clear. The objective of this study was to evaluate the incidence of associated anomalies in two different racial populations. The associated anomalies in neonates with OA managed in an Asian and a European paediatric surgical centre from 1982 to 1998 were reviewed. Non-Asian and non-European patients were excluded from the respective centres. The incidence of anomalies was compared using Fisher's exact test, taking #E5/E5# below 0.05 as statistically significant. Forty-eight consecutive Asian (25 boys and 23 girls) and 34 consecutive European patients (20 boys and 14 girls) were included in the analysis. The percentage of patients with at least one associated anomaly was 50% and 74% in the Asian and European populations, respectively, which was significantly different (#E5/E5#=0. 04). There was no statistically significant difference in the incidence of associated cardiovascular (29% vs 39%), anorectal (11% vs 18%), and musculoskeletal (16% vs 22%) anomalies, duodenal atresia (4% vs 3%), or Down's syndrome (3% vs 6%) between the two populations. However, the European patients had a significantly higher incidence of urogenital (UG) anomalies (26% vs 4%, #E5/E5#=0.006), the most common being agenesis (n=4) and dysplasia (n=3) of one or both kidneys. Hereditary factors may influence the incidence of associated anomalies in children with OA, particularly of the UG system. However, environmental factors cannot be excluded.

Abnormalities, Multiple↗
PubMed2001

E. coli Rep oligomers are required to initiate DNA unwinding in vitro.

E. coli Rep protein is a 3' to 5' SF1 superfamily DNA helicase which is monomeric in the absence of DNA, but can dimerize upon binding either single-stranded or duplex DNA. A variety of biochemical studies have led to proposals that Rep dimerization is important for its helicase activity; however, recent structural studies of Bacillus stearothermophilus PcrA have led to suggestions that SF1 helicases, such as E. coli Rep and E. coli UvrD, function as monomeric helicases. We have examined the question of whether Rep oligomerization is important for its DNA helicase activity using pre-steady state stopped-flow and chemical quenched-flow kinetic studies of Rep-catalyzed DNA unwinding. The results from four independent experiments demonstrate that Rep oligomerization is required for initiation of DNA helicase activity in vitro. No DNA unwinding is observed when only a Rep monomer is bound to the DNA substrate, even when fluorescent DNA substrates are used that can detect partial unwinding of the first few base-pairs at the ss-ds-DNA junction. In fact, under these conditions, ATP hydrolysis causes dissociation of the Rep monomer from the DNA, rather than DNA unwinding. These studies demonstrate that wild-type Rep monomers are unable to initiate DNA unwinding in vitro, and that oligomerization is required.

Adenosine Triphosphate↗
PubMed2001

Effects of intrinsic and extrinsic factors on the haemocyte profile of the prawn, Macrobrachium rosenbergii.

The giant freshwater prawn Macrobrachium rosenbergii was investigated for its total haemocyte count (THC) based on season, sex, size and feeding rate. The THC, when the prawns were subjected to injections of foreign materials was also investigated. The prawns displayed the highest and lowest THC in autumn and winter respectively, with no significant difference between male and female, or among animals with a body weight range of 7-115 g. The prawns displayed the lowest THC at D3 stage, and the highest in C stage. The prawns displayed the lowest THC when they were fed at 0.1% feeding rate among feeding rates of 0.1%, 0.5%, 1.0% and 1.5% body weight x day(-1). Prawns injected with carbon powder and Enterococcus showed increased THC during the first 6 h. Prawns injected with saline and carbon powder had the lowest THC after 30 h, and recovered to the normal value after 54 h. Prawns injected with Enterococcus showed the lowest THC after 42 h, and showed delayed recovery.

Animal Feed↗
PubMed2001

Solid-cystic papillary tumor of the pancreas in children.

Solid-cystic papillary tumor (SCPT) of the pancreas is a rare neoplasm in children. The current study attempted to estimate the incidence and possible pathological origin of the tumor. Clinicopathologic features of the children under the age of 16 years with pancreatic tumors managed in a single institution between January 1993 and November 1999 were reviewed. Representative blocks of SCPT specimens were immunostained for neuron-specific enolase (NSE) chromogrannin, synaptophysin, insulin, glucagon, somatostatin, and gastrin. There were three SCPTs, two pancreatic endocrine tumors, and one acinar cell carcinoma during the study period. The estimated yearly incidence in the referral area of 2 million population is about 0.01 pediatric SCPT per year per 100,000 population. The children underwent surgical removal of the tumors. Postoperatively, they were followed up for 6 months to 4 years and were well. Immunostaining for NSE, chromogranin, synaptophysin, insulin, somatostatin, and gastrin was negative in all cases. SCPT may thus be the most common pancreatic tumor in the Asian pediatric population. The pathological origin of the tumor remains unclear and requires further investigations.

Adolescent↗
PubMed2001

H-type tracheo-oesophageal fistula: appearance on three-dimensional computed tomography and virtual bronchoscopy.

H-type tracheo-oesophageal fistula (TOF) is a rare type of fistula without oesophageal atresia. The symptoms are usually present at birth, but the diagnosis is often delayed. Traditionally, contrast oesophagography and/or fiberoptic bronchoscopy are used to confirm the diagnosis. We describe the imaging features of a case of H-type TOF seen on three-dimensional computed tomography and virtual bronchoscopy and the usefulness of these techniques in pre-operative evaluation.

Bronchoscopy↗
PubMed2001

Hirschsprung's disease: a more generalised neuropathy?

BACKGROUND/PURPOSE: Aberrant neural crest migration is implicated in the pathogenesis of hindgut aganglionosis in Hirschsprung's disease (HSCR). Neural crest progenitors also give rise to a variety of cell types outside the gut, including nerves of the inner ear and peripheral nervous system. This study aims to determine whether such nerves are also affected in HSCR. METHODS: Pure tone audiometry and oto-acoustic emission tests were performed on 53 patients with Hirschsprung's disease and 28 age-matched controls. Forty-two children with Hirschsprung's disease and 30 age-matched controls also underwent neurologic evaluation, including quantitative peripheral tests of sensory function. RESULTS: Moderate to severe sensorineural hearing loss (1 profound [Waardenburg syndrome] and 3 high frequency) was detected in 4 children (8%) from the Hirschsprung's group. Abnormal (absent or reduced) oto-acoustic emission was detected in 77 of 102 ears (41 of 51 patients) in the HSCR group and 8 out of 48 ears (6 of 24 children) in the control group (75% v 17%; P<.0001). Two HSCR children had marked abnormalities on tests of peripheral nerve function. Significantly higher thresholds for vibration sensation were detected in HSCR versus controls (P<.05). CONCLUSION: Hirschsprung's disease may have a more generalised neuropathy than just that involving the affected bowel.

Adolescent↗
PubMed2001

Ultrasound assessment of scald scars in Asian children receiving pressure garment therapy.

BACKGROUND/PURPOSE: Scar formation after scald injury in children is managed commonly by application of pressure garment. The duration of the treatment depends on clinical assessment. The objective of the study was to evaluate the efficacy of the pressure garment therapy and to correlate the clinical assessment scar thickness with ultrasound measurement. METHODS: Prospective study of children with hypertrophic scars receiving pressure garment therapy was carried out between 1993 and 1998. The scars were mapped with paper cutting. Representative scar sites were scored clinically according to Vancouver General Hospital Burn Assessment Scale (pigmentation, vascularity, pliability, height, pain, itchiness). Blind to the clinical results, 2 radiologists measured the scar thickness of the same sites with ultrasonography (5 to 10 MHz transducer, General Electric LOGIQ 500). The correlation between the clinical scores and ultrasound measurement of scar thickness were analysed using analysis of variance (ANOVA). RESULTS: The median age of 58 children with scald injury (M:F = 36:22) was 2.8 years (0.5 to 15.8 years). The mean percentage of scald was 8.8% (24% had scald area >10%). In addition, there were 5 children with burn from naked flame and 9 children with keloid secondary to surgical incisions. With pressure garment therapy, the scar thickness reached a plateau 1 (1/2) years after the injury and began to decline gradually thereafter. The clinical estimation of scar thickness correlated well with the ultrasound measurement (ANOVA, P =.003, Adjusted R square = 0.99). The accuracy rate of clinical thickness estimation was 67%. Overestimation and underestimation accounted for 15% and 18%, respectively. There also was good correlation between total clinical score and the ultrasound measurement (ANOVA, P <.001). CONCLUSIONS: In children with scald injury, the pressure garment needs to be continued for a minimum of 1 year. Ultrasound measurement correlates well with overall score of the Vancouver General Hospital Burn Assessment Scale but not individual components of the scoring system except wound height.

Adolescent↗
PubMed2001

Enteric nervous system, interstitial cells of cajal, and smooth muscle vacuolization in segmental dilatation of jejunum.

BACKGROUND/PURPOSE: The etiology of congenital segmental dilatation (CSD) of bowel remains elusive. Intestitial cell of Cajal plays a role in the pace making of the intestine. Its abnormality has been documented in a variety of conditions of abnormal intestinal motility. The current study attempts to evaluate the roles of intestitial cells of Cajal, enteric nervous system, and smooth muscle in segmental dilatation of small bowel. METHODS: Resected specimen from a neonate with segmental dilatation of jejunum was stained with H&E, Alcian blue, Periodic Acid-Schiff (PAS), and immunostained with S100, Ret, MAP5, and c-kit antibodies using the standard immunohistochemical process. RESULTS: The immunostaining of S100, Ret, MAP5 and c-kit of CSD specimen were positive. Localized vacuolization was, however, detected in the circular smooth muscle of the jejunum. The Alcian blue and PAS staining of the vacuolization were negative. CONCLUSIONS: CSD shows no abnormality in the enteric nervous system and pace makers. Localized vacuolization suggests myopathy to be a contributing factor to the disease. J Pediatr Surg 36:930-935.

Dilatation, Pathologic↗
PubMed2001

Glycine preserves function and decreases necrosis in skeletal muscle undergoing ischemia and reperfusion injury.

BACKGROUND: Glycine (GLY) is a neutral amino acid that has been shown to be cytoprotective in the kidneys of dogs and rabbits undergoing ischemia-reperfusion injury. To investigate whether GLY exhibits a protective effect on skeletal muscle subjected to ischemia and reperfusion injury, we used a well-described gracilis muscle model in canines. METHODS: Twelve adult mongrel dogs were subjected to 6 hours of ischemia in 1 randomly selected side. The dogs were randomized into 2 groups: group 1 (6 animals) underwent 15 minutes of perfusion with 2.2% GLY, and group 2 (6 animals) underwent 15 minutes of perfusion with normal saline solution (NS) only. Both groups had normothermic reperfusion for 1 hour along with the corresponding perfusate. Muscle biopsy specimens were taken, frozen in liquid nitrogen, and stored at -70 degrees C. Muscle injury was evaluated at 48 hours by measuring weight gain (edema), maximal contractile force, and percent of muscle necrosis. Adenosine triphosphate (ATP) and phosphocreatine (Pcr) (an energy store for ATP synthesis) levels were determined by using high performance liquid chromatography. RESULTS: In group 1, the average weight gain was 57% +/- 11.27% while in group 2 it was 100% +/- 12.48%. Maximal muscle contractile force was 712.5 +/- 68 g for group 1 and 511 +/- 27.91 g for group 2. The amount of muscle necrosis was 30 +/- 3.7% in group 1, as opposed to 63 +/- 10% in group 2. The ATP content was 0.07 +/- 0.03 nmol/mg wet tissue weight (post-ischemia with NS) and 0.21 +/- 0.08 nmol/mg wet tissue weight (post-ischemia with GLY). Pcr content was 0.19 +/- 0.04 mmol/mg wet tissue weight (post-ischemia with NS) and 0.27 +/- 0.04 micromol/mg wet tissue (post-ischemia and infused with GLY) (P <.05). CONCLUSIONS: These data show that GLY preserves muscle function, decreases edema and the amount of muscle necrosis and preserves energy stores in this canine model. Because GLY can be safely given systemically in human beings in higher concentrations than that given in our model, as it is given in parenteral nutrition, its mechanism of action should be further investigated for its potential use in the clinical setting of ischemia and reperfusion injury.

Adenosine Triphosphate↗
PubMed2001

Radial artery harvesting for coronary bypass operations: neurologic complications and their potential mechanisms.

OBJECTIVES: We sought to determine the incidence of self-reported neurologic hand complications after radial artery harvest for coronary artery bypass grafting. METHODS: Between February 20, 1996, and December 31, 1999, 615 patients underwent coronary bypass operations with radial arteries. A scripted telephone interview was performed, collecting data on perceived thumb weakness and sensation abnormalities in the distribution of the radial nerve in 560 patients. The average time to follow-up interview was 14.5 +/- 9 months. RESULTS: Neurologic complications were reported in 30.1%, decreased thumb strength in 5.5%, and any sensation abnormality in 18.1% of patients. There was a high rate of symptom improvement over an average of 8.7 +/- 7.5 months, such that only 12.1% of patients reported symptoms without any improvement. Associations between thumb weakness and sensory abnormalities imply median nerve damage in some patients. There were statistically significant associations between neurologic complications and diabetes, peripheral vascular disease, elevated creatinine levels, smoking, and number and site of radial artery harvest. CONCLUSIONS: The overall rate of self-reported neurologic complications after radial artery harvest was higher than previously reported. These symptoms may be attributable to radial and median nerve injury caused by trauma and devascularization. These data have important implications not only in attempting to improve harvesting techniques but also in guiding informed consent before coronary artery bypass grafting.

Aged↗
PubMed2001

Twenty-year comparison of tissue and mechanical valve replacement.

OBJECTIVE: We sought to compare outcomes with tissue and St Jude Medical mechanical valves over a 20-year period. METHODS: Valve-related events and overall survival were analyzed in 2533 patients 18 years of age or older undergoing initial aortic, mitral, or combined aortic and mitral (double) valve replacement with a tissue valve (Hancock, Carpentier-Edwards porcine, or Carpentier-Edwards pericardial) or a St Jude Medical mechanical valve. Total follow-up was 13,390 patient-years. There were 666 St Jude Medical aortic valve replacements, 723 tissue aortic valve replacements, 513 St Jude Medical mitral valve replacements, 402 tissue mitral valve replacements, 161 St Jude Medical double valve replacements, and 68 tissue double valve replacements. The mean age was 68 +/- 13.3 years (St Jude Medical valve, 64.5 +/- 12.9; tissue valve, 72.0 +/- 12.6). RESULTS: There were no overall differences in survival between tissue and mechanical valves. Multivariable analysis indicated that the type of valve did not affect survival. Analysis by age less than 65 years or 65 years or older and presence or absence of coronary disease revealed similar long-term survival in all subgroups. The risk of hemorrhage was lower in patients receiving tissue aortic valve replacements but was not significantly different in patients receiving mitral valve or double valve replacements. Thromboembolism rates were similar for tissue and mechanical valve recipients. However, reoperation rates were significantly higher in patients receiving both aortic and mitral tissue valves. The reoperation hazard increased progressively with time both in patients receiving aortic and in those receiving mitral tissue valves. Overall valve complications were initially higher with mechanical aortic valves but not with mechanical mitral valves. However, valve complication rates later crossed over, with higher rates in tissue valve recipients after 7 years in patients undergoing mitral valve replacement and 10 years in those undergoing aortic valve replacement. CONCLUSIONS: Tissue and mechanical valve recipients have similar survival over 20 years of follow-up. The primary tradeoff is an increased risk of hemorrhage in patients receiving mechanical aortic valve replacements and an increased risk of late reoperation in all patients receiving tissue valve replacements. The risk of tissue valve reoperation increases progressively with time.

Adult↗
PubMed2001

A multi-resolution wireless force sensing system based upon a passive SAW device.

Referring to the technology of SAW wireless identification systems, a multi-resolution wireless force sensing system, including a passive time-delay SAW device and a specific interrogation unit, is introduced in this paper. Using an IDT, which connects with an antenna, as the force sensing element is a design to transduce the electromagnetic wave into surface acoustic wave and vice versa. Several reflectors are designed to get multi-resolution. Sample/hold devices are used instead of high-speed A/D converter to construct a low-cost interrogation system. Properties of the sensing system are theoretically predicted and experimentally verified.

Journal Article↗
PubMed2001

[An experimental study of effects of injection of pingyangmycin on activities of enzyme of endothelial cells].

OBJECTIVE: The objective of this study is to investigate the mechanism of acute trauma of endothelium after injection of Pingyangmycin. METHODS: A total of 42 adult Wistar rats were divided randomly into experimental groups (24), positive control groups (12) and normal control group (6), and the rats in the experimental or the positive control groups were injected with Pingyangmycin or sodium morrhuate into the mesenteric veins respectively, and then the enzyme activity of hepatic endothelial cells and hepatocytes was examined histochemically 0.5, 1, 2, 4, 8 and 24 hours after injection. RESULTS: After injection, the activity of 5'-nucleinase(5'-N) in hepatic endothelial cells and that of lactic dehydrogenase (LDH) and succinodehydrogenase (SDH) in hepatocytes decreased gradually, but that injected Pingyangmycin was less than that injected sodium morrhuate. CONCLUSION: The trauma caused by Pingyangmycin is less than that caused by sodium morrhuate, but the reaction of trauma caused by both is nonspecific.

5'-Nucleotidase↗
PubMed2001

[Treatment of lumbar intervertebral disk prolapse by estradural injection of mailuoning and its influence on dynorphin A in cerebrospinal fluid].

OBJECTIVE: To explore the modulating effects of extradural injection of Mailuoning on analgesic function. METHODS: Twenty patients of lumbar intervertebral disk prolapse were treated by extradural injection of Mailuoning, the spontaneous release of dynorphin A (Dyn-A) in cerebrospinal fluid (CSF) before and after treatment were measured and compared with that of the 20 cases in the control group to determine the therapeutic effect of Mailuoning. RESULTS: After treatment, the concentration of Dyn-A in CSF in the treated group increased remarkably, but displayed no significant difference to normal healthy group (P > 0.05), while that in the control group there was significant difference between them (P < 0.01). CONCLUSION: Mailuoning has the modulatory effect on analgesia function and lumbar intervertral disk prolapse was treated by means of its Dyn-A elevating action.

Adult↗