Biomedical subjects

S K Wong

Publications and source records attributed to S K Wong.

At least 19 recordsLinked to original sources

PubMed2007

Trans-cutaneous electrogastrographic study of gastric myoelectric activity in transposed intrathoracic stomach after esophagectomy.

We examined the feasibility of trans-cutaneous electrogastrography (EGG) in recording myoelectric activity of the transposed thoracic stomach after esophagectomy. Nineteen patients who had Ivor-Lewis esophagectomy were studied. The EGG signal was recorded using cutaneous electrodes placed over the lower sternum. Eleven patients who underwent total gastrectomy served as controls. Normal rhythm pattern (2.4-3.6 cpm > or = 70%) and power ratio (PR > or = 2) was observed in five and 12 patients, respectively, after esophagectomy. The observation of normal gastric rhythm was more frequent in the postprandial period in the esophagectomy group (median 42.6%vs. 7.4%, P = 0.01), and the PR was significantly higher (median 2.27 vs. 1.38, P = 0.013) than the gastrectomy group. Feeding further increased the prevalence of normal gastric slow wave in the esophagectomy group (median 14.8% to 42.6%, P = 0.002) and improved the stability of dominant frequency (median 78% to 67%, P = 0.015). We conclude that gastric myoelectric activities of thoracic transposed stomach can be detected from cutaneous sternal electrodes. This represented a preservation of gastric motility even when the stomach is pulled up to the thorax as a substitute for the esophagus.

Case-Control Studies↗

PubMed2006

A case of cystic schwannoma of the lesser sac.

INTRODUCTION: Benign cystic schwannoma of the lesser sac is an extremely rare condition and only 3 reports were found in our review of the English literature. CLINICAL PICTURE: We describe a 58-year-old man with a large (5.2 x 6.7 x 7.6 cm) epigastric mass with solid and cystic components detected on sonography and computed tomography. Close association with the pancreas, stomach and liver led to a mistaken diagnosis of pancreatic cystadenoma/cystadenocarcinoma. TREATMENT AND OUTCOME: The mass was surgically resected and our patient has been well since. CONCLUSION: This case draws the reader's attention to a rare condition that may mimic other sinister lesions, and highlights the pitfalls of diagnosis. Depending on the size and extent of the lesion, imaging may assist in characterisation of a schwannoma of the lesser sac. Surgical resection would still be the end point of management, especially when mass effect causes debilitating symptoms. Surgery is usually associated with good outcome, and tumour recurrence is unusual, provided adequate margins are resected.

Abdominal Neoplasms↗

PubMed2003

Toxoplasma gondii, Neospora caninum, Sarcocystis neurona, and Sarcocystis canis-like infections in marine mammals.

Toxoplasma gondii, Neospora caninum, Sarcocystis neurona, and S. canis are related protozoans that can cause mortality in many species of domestic and wild animals. Recently, T. gondii and S. neurona were recognized to cause encephalitis in marine mammals. As yet, there is no report of natural exposure of N. caninum in marine mammals. In the present study, antibodies to T. gondii and N. caninum were assayed in sera of several species of marine mammals. For T. gondii, sera were diluted 1:25, 1:50, and 1:500 and assayed in the T. gondii modified agglutination test (MAT). Antibodies (MAT > or =1:25) to T. gondii were found in 89 of 115 (77%) dead, and 18 of 30 (60%) apparently healthy sea otters (Enhydra lutris), 51 of 311 (16%) Pacific harbor seals (Phoca vitulina), 19 of 45 (42%) sea lions (Eumetopias jubatus) [corrected] 5 of 32 (16%) ringed seals (Phoca hispida), 4 of 8 (50%) bearded seals (Erignathus barbatus), 1 of 9 (11.1%) spotted seals (Phoca largha), 138 of 141 (98%) Atlantic bottlenose dolphins (Tursiops truncatus), and 3 of 53 (6%) walruses (Odobenus rosmarus). For N. caninum, sera were diluted 1:40, 1:80, 1:160, and 1:320 and examined with the Neospora agglutination test (NAT) using mouse-derived tachyzoites. NAT antibodies were found in 3 of 53 (6%) walruses, 28 of 145 (19%) sea otters, 11 of 311 (3.5%) harbor seals, 1 of 27 (3.7%) sea lions, 4 of 32 (12.5%) ringed seals, 1 of 8 (12.5%) bearded seals, and 43 of 47 (91%) bottlenose dolphins. To our knowledge, this is the first report of N. caninum antibodies in any marine mammal, and the first report of T. gondii antibodies in walruses and in ringed, bearded, spotted, and ribbon seals. Current information on T. gondii-like and Sarcocystis-like infections in marine mammals is reviewed. New cases of clinical S. canis and T. gondii infections are also reported in sea lions, and T. gondii infection in an Antillean manatee (Trichechus manatus manatus).

Agglutination Tests↗

PubMed2003

Large-aspect-ratio limit of neoclassical transport theory.

This paper presents a comprehensive description of neoclassical transport theory in the banana regime for large-aspect-ratio flux surfaces of arbitrary shapes. The method of matched-asymptotic expansions is used to obtain analytical solutions for plasma distribution functions and to compute transport coefficients. The method provides justification for retaining only the part of the Fokker-Planck operator that involves the second derivative with respect to the cosine of the pitch angle for the trapped and barely circulating particles. It leads to a simple equation for the freely circulating particles with boundary conditions that embody a discontinuity separating particles moving in opposite directions. Corrections to the transport coefficients are obtained by generalizing an existing boundary layer analysis. The system of moment and field equations is consistently taken in the cylinder limit, which facilitates the discussion of the treatment of dynamical constraints. It is shown that the nonlocal nature of Ohm's law in neoclassical theory renders the mathematical problem of plasma transport with changing flux surfaces nonstandard.

Journal Article↗

PubMed2002

Helical CT imaging of clinically suspected appendicitis: correlation of CT and histological findings.

PURPOSE: The diagnosis of appendicitis is traditionally made on the basis of clinical findings supported by laboratory results. The aim of our study was to determine the accuracy and feasibility of using a relatively new technique of computed tomography (CT) using only colonic contrast medium. MATERIALS AND METHODS: A total of 50 patients clinically diagnosed as having appendicitis were prospectively examined before surgery with thin-collimation helical CT from the L3 level to the acetabular roof with only rectally administered colon contrast medium. The hard copy CT images were reviewed jointly by two radiologists and a consensus was reached for each patient. The results were then compared with the surgical and histological findings at appendicectomy. RESULTS: There were 35 true-positives, one false-positive, 12 true-negatives and two false-negatives for CT. This yielded an accuracy of 94%, sensitivity of 95%, specificity of 92%, positive predictive value of 97% and negative predictive value of 86%. The appendix was identified in 45 patients (90%) and obscured by an inflammatory mass in the remaining five. An alternative diagnosis was found in 10 of 12 normal CT examinations (83%). CONCLUSION: Helical CT with rectal contrast medium is a quick, well tolerated and accurate test to diagnose appendicitis. It can offer alternative, possibly non-surgical diagnosis in patients who would otherwise have undergone laparotomy.

Administration, Rectal↗

PubMed2002

Emergency laparoscopic surgery--the Changi General Hospital experience.

INTRODUCTION: This paper analyses the emergency laparoscopic procedures undertaken by our unit over a 1-year period in an effort to evaluate the diagnostic-therapeutic use of laparoscopy in an emergency situation. MATERIALS AND METHODS: This is a retrospective study that analysed 137 emergency laparoscopic procedures that were performed for patients who presented with acute abdominal pain over a 1-year period from 31 December 1999 to 31 December 2000. RESULTS: A definitive diagnosis was made in 91.2% (125). Of the 78 cases that required surgical intervention, 71.8% (56) were performed laparoscopically. The conversion rate (to open surgery) was 16.8% (23) and the morbidity rate was 8% (11); with no mortalities. CONCLUSION: We conclude that laparoscopic surgery is effective and safe in the non-elective setting and it offers a high potential for diagnosis and therapy in selected patients in whom the diagnoses are equivocal.

Abdomen, Acute↗

PubMed2001

Herbal medicine.

Explore the source record for details and available documents.

Attitude of Health Personnel↗

PubMed2001

Neoclassical radial electric field and transport with finite orbits.

Neoclassical transport in a toroidal plasma with finite ion orbits is studied, including for the first time the self-consistent radial electric field. Using a low-noise deltaf particle simulation, we demonstrate that a deep electric-field well develops in a region with a steep density gradient, because of the self-collision-driven ion flux. We find that the electric field agrees with the standard neoclassical expression, when the toroidal rotation is zero, even for a steep density gradient. Ion thermal transport is modified by the electric-field well in a way which is consistent with the orbit squeezing effect, but smoothed by the finite orbits.

Journal Article↗

PubMed2001

Modified lattice Boltzmann method for compressible fluid simulations.

A modified lattice Boltzmann algorithm is shown to have much better stability to growing temperature perturbations, when compared with the standard lattice Boltzmann algorithm. The damping rates of long-wavelength waves, which determine stability, are derived using a collisional equilibrium distribution function which has the property that the Euler equations are obtained exactly in the limit of zero time step. Using this equilibrium distribution function, we show that our algorithm has inherent positive hyperviscosity and hyperdiffusivity, for very small values of viscosity and thermal diffusivity, which are lacking in the standard algorithm. Short-wavelength modes are shown to be stable for temperatures greater than a lower limit. Results from a computer code are used to compare these algorithms, and to confirm the damping rate predictions made analytically. Finite amplitude sound waves in the simulated fluid steepen, as expected from gas dynamic theory.

Journal Article↗

PubMed2001

Early clinical outcomes after subfascial endoscopic perforator surgery (SEPS) and saphenous vein surgery in chronic venous insufficiency.

BACKGROUND: Subfascial endoscopic perforator surgery (SEPS) has recently become popular as a minimally invasive way to treat chronic venous insufficiency (CVI) of the lower extremities. We report the early clinical outcomes of SEPS and saphenous vein surgery in a prospective series of Chinese patients who presented with severe CVI. METHODS: All patients referred to our hospital for the management of severe CVI (class IV disease or above) after January 1998 underwent SEPS using an ultrasonic scalpel in conjunction with saphenous vein surgery. All patients were followed up prospectively to assess ulcer healing, ulcer recurrence, and symptoms after SEPS. Clinical outcome was evaluated by the scoring system suggested by the Consensus Committee of the American Venous Forum on Chronic Venous Disease. RESULTS: Over a 24-month period, we performed 36 SEPS on 31 patients. Nineteen lower extremities (53%) had active or healing ulcers. Sapheno-femoral ligation was also performed in 33 limbs (92%). Four limbs (11%) developed superficial wound infection, and two (6%) had saphenous nerve dysesthesia. The mean clinical score and disability score decreased from 8.42 to 3.42 and 1.45 to 0.31 respectively, after a median follow-up of 14 months (range, 6-22) (p < 0.005). Eleven ulcers (58%) healed within 6 weeks after surgery. At 1-year follow-up, ulcer recurrence was found in two legs (11%). CONCLUSION: SEPS is safe and feasible. Early clinical results have shown a promising outcome in patients with severe chronic venous insufficiency.

Adult↗

PubMed2001

Pelvic wall involvement denotes a poor prognosis in T4 rectal cancer.

PURPOSE: An aggressive surgical approach with en bloc resection of involved structures is often possible with anterior rectal cancers that invade adjacent visceral organs, but is rarely possible in tumors that invade the pelvic wall. However, most staging systems include both situations in the same group of T4 rectal cancers. We performed a retrospective study of patients with stage T4 rectal cancer undergoing surgery to assess the influence of different organ involvement on resectability and survival. METHODS: A retrospective review was conducted of 84 patients with T4 rectal cancer treated at the University of Minnesota and affiliated hospitals over a ten-year period. Forty-seven patients (56 percent) were staged for local invasion on the basis of final pathology, 19 (23 percent) on the basis of operative findings, and 18 (21 percent) on the basis of ultrasound images. Patients were divided into two groups, those with or without pelvic wall involvement. Resectability, local control, and overall survival were compared between groups. Survival curves were estimated by the Kaplan-Meier method and compared by log-rank test. Multivariate analysis was performed with Cox proportional and logistic regression. RESULTS: Thirty-one patients (37 percent) had involvement of the pelvic wall, whereas 53 patients (63 percent) had visceral involvement only. All 29 patients with distant metastasis died of their disease. Forty-seven of the 55 patients without distant metastasis underwent tumor resection. Age and pelvic wall involvement were the only two factors independently associated with the probability of resection in logistic regression analysis (P = 0.0067 and P = 0.037, respectively). The only factor that affected median survival in patients without distant metastasis was tumor resection (49.1 months for resection vs. 6.1 months for no resection, P = 0.017). Patients with visceral involvement had a longer median survival (49.2 months) than those with pelvic wall involvement (13.2 months), but the difference did not reach statistical significance (P = 0.058). CONCLUSION: Rectal cancers with pelvic and visceral involvement have different rates of resectability and median survival. These differences should be reflected in the TNM classification system.

Adult↗

PubMed2001

Laparoscopic total colectomy for acute colitis: a case-control study.

INTRODUCTION: There are no previous comparative studies of total abdominal colectomy by laparoscopic methods in ulcerative colitis and Crohn's disease patients requiring urgent colectomy. This study aimed to determine the safety and efficacy of laparoscopic colectomy in these patients compared with those undergoing conventional urgent colectomy. METHODS: Patients undergoing laparoscopic total colectomy for acute colitis were identified in a prospective registry. All patients underwent a total colectomy with creation of an end ileostomy and buried mucous fistula. No patient had fulminant disease (tachycardia, fever, marked leukocytosis, peritonitis), but all were failing to respond to medical treatment. Patients undergoing conventional total colectomy were matched for age, gender, body mass index, diagnosis, disease severity, and operative period. Median values (range) are listed. RESULTS: From 1997 to 1999, there were 19 laparoscopic and 29 matched conventional patients. There were no inadvertent colotomies or conversions in the laparoscopic group. Although there was no difference in operative blood loss in the laparoscopic group (100 (range, 50-700) ml) when compared with the conventional group (150 (range, 50-500) ml), the operative times were significantly longer in the laparoscopic group (210 (range, 150-270) vs. 120 (range, 60-180) minutes, P < 0.001). Bowel function returned more quickly in the laparoscopic group (1 (range, 1-3) vs. 2 (range, 1-4) days; P = 0.003) and the length of stay was shorter (4 (range, 3-13) vs. 6 (range, 4-24) days; P = 0.04). Complications occurred in three (16 percent) laparoscopic patients (2 wound infection and 1 ileus) and in seven (24 percent) conventional patients (3 wound infection, 3 deep venous thrombosis, 1 upper gastrointestinal bleed). CONCLUSIONS: Laparoscopic total colectomy is feasible and safe in patients with acute nonfulminant colitis and may lead to a faster recovery than conventional resection.

Acute Disease↗

PubMed2001

Subfascial endoscopic perforator vein surgery (SEPS) using the ultrasonic scalpel.

Subfascial endoscopic perforator vein surgery (SEPS) was recently introduced as a minimally invasive method to ligate incompetent perforating veins in patients with severe chronic venous insufficiency of the lower extremities. Herein we describe a technique in which we used a 5-mm ultrasonic scalpel for the transection of perforating veins in 16 SEPS performed in 14 patients. The use of the ultrasonic scalpel allowed for the precise coagulation and transection of the perforator vein with hemostasis, while avoiding the use of metal clips. Our initial results showed that the technique was feasible with minimal morbidity. We recommend the use of the ultrasonic scalpel as an alternative tool to transect perforating veins in SEPS.

Adult↗

PubMed2001

Substrate recognition by ADAR1 and ADAR2.

RNA editing catalyzed by ADAR1 and ADAR2 involves the site-specific conversion of adenosine to inosine within imperfectly duplexed RNA. ADAR1- and ADAR2-mediated editing occurs within transcripts of glutamate receptors (GluR) in the brain and in hepatitis delta virus (HDV) RNA in the liver. Although the Q/R site within the GluR-B premessage is edited more efficiently by ADAR2 than it is by ADAR1, the converse is true for the +60 site within this same transcript. ADAR1 and ADAR2 are homologs having two common functional regions, an N-terminal double-stranded RNA-binding domain and a C-terminal deaminase domain. It is neither understood why only certain adenosines within a substrate molecule serve as targets for ADARs, nor is it known which domain of an ADAR confers its specificity for particular editing sites. To assess the importance of several aspects of RNA sequence and structure on editing, we evaluated 20 different mutated substrates, derived from four editing sites, for their ability to be edited by either ADAR1 or ADAR2. We found that when these derivatives contained an A:C mismatch at the editing site, editing by both ADARs was enhanced compared to when A:A or A:G mismatches or A:U base pairs occurred at the same site. Hence substrate recognition and/or catalysis by ADARs could involve the base that opposes the edited adenosine. In addition, by using protein chimeras in which the deaminase domains were exchanged between ADAR1 and ADAR2, we found that this domain played a dominant role in defining the substrate specificity of the resulting enzyme.

Adenosine Deaminase↗

PubMed2001

Dysfunction of oesophageal motility in Helicobacter pylori-infected patients with reflux oesophagitis.

BACKGROUND: Helicobacter pylori infection has been suggested to be protective against gastro-oesophageal reflux disease. However, a significant proportion of patients with gastro-oesophageal reflux disease are infected by H. pylori. AIM: To study oesophageal motor function in H. pylori-infected patients with reflux oesophagitis. METHODS: Patients with erosive reflux oesophagitis were recruited prospectively for stationary oesophageal manometry and 24-h ambulatory oesophageal pH monitoring. H. pylori status was determined by biopsy urease test. Non-reflux volunteers were recruited as controls. RESULTS: Seventy-four patients with erosive oesophagitis (34 H. pylori-positive, 40 H. pylori-negative) and 48 non-reflux patient controls (22 H. pylori-positive, 26 H. pylori-negative) were recruited. There was no difference in severity of oesophagitis (median grade, 1; P=0.53) or oesophageal acid exposure (total percentage time oesophageal pH < 4, 7.6% vs. 6.8%; P=0.57) between H. pylori-positive and H. pylori-negative groups. Compared to H. pylori-negative patients, H. pylori-positive patients had significantly lower basal lower oesophageal sphincter pressure (12.2 mmHg vs. 15.3 mmHg; P=0.03) and amplitude of distal peristalsis (56.9 mmHg vs. 68.4 mmHg; P=0.03). Ineffective oesophageal motility (14% vs. 7%; P=0.02) and failed oesophageal peristalsis were also significantly more prevalent in H. pylori-positive patients. CONCLUSIONS: Among patients with a similar degree of reflux oesophagitis, H. pylori-infected patients have more severe oesophageal dysmotility and lower oesophageal sphincter dysfunction. Oesophageal motor dysfunction probably plays a dominant role in the development of gastro-oesophageal reflux disease in patients with H. pylori infection.

Adult↗

PubMed2001

Effectiveness of a multimedia programme and therapist-instructed training for children with autism.

The present study aimed to evaluate the effectiveness of an interactive multimedia training programme and a conventional therapist-instructed training in improving the learning behaviours of children with autism. A multiple-subject, single case-study time-series research design was adopted in the study. Six children with autism, aged 2 years 4 months to 2 years 10 months, were recruited by convenience sampling. They attended a 12-session training programme on basic concepts (e.g. colours, shapes) that was presented as an interactive multimedia training programme and also as a conventional, therapist-led training programme. The attending behaviours and appropriate responses of the subjects were videotaped for further analysis. Participants who attended the conventional therapist-instructed training programme generally showed improvement in attending behaviours and response rates; participants attending the multimedia programme also showed improvement in their attending behaviours and response rates. The results support the hypothesis that both training programmes are effective in improving the attending behaviours and appropriate responses of children with autism. The authors suggest that, because children with autism respond differently to different training approaches, customized training programmes should be considered for individual children. The implications of the methodology and the potential impact of the present study on the training of children with autism are discussed.

Autistic Disorder↗

PubMed2001

Hepatitis delta virus minimal substrates competent for editing by ADAR1 and ADAR2.

A host-mediated RNA-editing event allows hepatitis delta virus (HDV) to express two essential proteins, the small delta antigen (HDAg-S) and the large delta antigen (HDAg-L), from a single open reading frame. One or several members of the ADAR (adenosine deaminases that act on RNA) family are thought to convert the adenosine to an inosine (I) within the HDAg-S amber codon in antigenomic RNA. As a consequence of replication, the UIG codon is converted to a UGG (tryptophan [W]) codon in the resulting HDAg-L message. Here, we used a novel reporter system to monitor the editing of the HDV amber/W site in the absence of replication. In cultured cells, we observed that both human ADAR1 (hADAR1) and hADAR2 were capable of editing the amber/W site with comparable efficiencies. We also defined the minimal HDV substrate required for hADAR1- and hADAR2-mediated editing. Only 24 nucleotides from the amber/W site were sufficient to enable efficient editing by hADAR1. Hence, the HDV amber/W site represents the smallest ADAR substrate yet identified. In contrast, the minimal substrate competent for hADAR2-mediated editing contained 66 nucleotides.

Adenosine Deaminase↗

PubMed2001

Substrate sequence selection by retroviral integrase.

Integration of retrovirus DNA is a specific process catalyzed by the integrase protein acting to join the viral substrate DNA (att) sequences of about 10 bases at the ends of the long terminal repeat (LTR) to various sites in the host target cell DNA. Although the interaction is sequence specific, the att sequences of different retroviruses are largely unrelated to one another and usually differ between the two ends of the viral DNA. To define substrate sequence specificity, we designed an "in vitro evolution" scheme to select an optimal substrate sequence by competitive integration in vitro from a large pool of partially randomized substrates. Integrated substrates are enriched by PCR amplification and then regenerated and subjected to subsequent cycles of selection and enrichment. Using this approach, we obtained the optimal substrate sequence of 5'-ACGACAACA-3' for avian sarcoma-leukosis virus (ASLV) and 5'-AACA(A/C)AGCA-3' for human immunodeficiency virus type 1, which differed from those found at both ends of the viral DNA. Clonal analysis of the integration products showed that ASLV integrase can use a wide variety of substrate sequences in vitro, although the consensus sequence was identical to the selected sequence. By a competition assay, the selected nucleotide at position 4 improved the in vitro integration efficiency over that of the wild-type sequence. Viral mutants bearing the optimal sequence replicated at wild-type levels, with the exception of some mutations disrupting the U5 RNA secondary structure important for reverse transcription, which were significantly impaired. Thus, maximizing the efficiency of integration may not be of major importance for efficient retrovirus replication.

Alpharetrovirus↗