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Biomedical subjects

F Chan

Publications and source records attributed to F Chan.

At least 19 recordsLinked to original sources
PubMed2002

Magnetic resonance imaging in the diagnosis and follow up of Takayasu's arteritis in children.

BACKGROUND: Takayasu's arteritis (TA) has a mortality rate of up to 40% in children. Because the clinical presentation of TA is often non-specific, accurate and prompt diagnosis depends on a high degree of awareness and appropriate laboratory and imaging studies. OBJECTIVE: To examine the use of advanced magnetic resonance imaging (MRI) in evaluating, gauging activity, and following the complications of TA. METHODS AND RESULTS: T1 weighted, T2 weighted, contrast enhanced MR images, and MR angiograms of the chest and abdomen were obtained in three children (age range 11-14 years). The MRI studies confirmed the diagnosis of active TA and were repeated to evaluate response to treatment. Two patients showed complete resolution of lesions found on MRI at six and 12 months' follow up, while the third patient showed no significant improvement. CONCLUSION: MRI can be used to help establish the initial diagnosis of TA in children, and it can also be used to monitor disease activity and to guide treatment.

Adolescent↗
PubMed2001

Geometry of chemically modified silica.

The effect of alkyl chain length on adsorbent pore volume and void volume of HPLC columns is described. The results provide evidence that alkyl chains attached on silica surface are densely packed. A correlation of a decrease of pore volume with an increase of the alkyl modifier chain length was found. Effective molecular volume of bonded chains was found to be similar to the molecular volume of corresponding liquid alkanes. An absence of noticeable penetration of acetonitrile, methanol, or tetrahydrofuran molecules between bonded chains at any water-organic eluent composition was found.

Adsorption↗
PubMed2001

Interpretation of the excess adsorption isotherms of organic eluent components on the surface of reversed-phase adsorbents. Effect on the analyte retention.

The excess adsorption isotherms of acetonitrile, methanol and tetrahydrofuran from water on reversed-phase packings were studied, using 10 different columns packed with C1-C6, C8, C10, C12, and C18 monomeric phases, bonded on the same type of silica. The interpretation of isotherms on the basis of the theory of excess adsorption shows significant accumulation of the organic eluent component on the adsorbent surface on the top of "collapsed" bonded layer. The accumulated amount was shown to be practically independent of the length of alkyl chains bonded to the silica surface. A model that describes analyte retention on a reversed-phase column from a binary mobile phase is developed. The retention mechanism involves a combination of analyte distribution between the eluent and organic adsorbed layer, followed by analyte adsorption on the surface of the bonded phase. A general retention equation for the model is derived and methods for independent measurements of the involved parameters are suggested. The theory was tested by direct measurement of analyte retention from the eluents of varied composition and comparison of the values obtained with those theoretically calculated values. Experimental and theoretically calculated values are in good agreement.

Acetonitriles↗
PubMed2001

Primary peritoneal mesodermal adenosarcoma: report of a case and review of the literature.

BACKGROUND: Mesodermal (müllerian) adenosarcoma arising from the peritoneum is rare and is thought to arise from pluripotent mesothelial and mesenchymal cells of the pelvic cavity or from endometriotic deposits. CASE: A case of primary peritoneal mesodermal adenosarcoma arising from the omentum is described. A 50-year-old woman presented with sudden abdominal distension. Initial laparotomy revealed a 13-kg mass arising from the omentum, which was determined from frozen and paraffin sections to be serous cystadenofibroma. The tumor recurred within 10 months and weighed 18 kg at a second laparotomy. Histopathology and review of the original tumor established the correct diagnosis of mesodermal adenosarcoma. The patient died from disseminated disease 6 months later. CONCLUSION: Adenosarcomas are difficult to differentiate from adenofibromas or endometriosis histologically because of the presence of large areas of low cellularity and infrequent mitotic figures. In such cases, stromal nuclear atypia and periglandular stromal cuffing are features that are diagnostic of adenosarcoma.

Adenosarcoma↗
PubMed2001

Anesthetic management of renal cell carcinoma with inferior vena caval extension.

We present a case of a patient with renal cell carcinoma extending into the inferior vena cava. Preoperative diagnosis was facilitated by transthoracic and transesophageal echocardiography (TEE), and inferior venacavography. Intraoperatively, monitoring with continuous TEE was used. Preparation was made for cardiopulmonary bypass but surgery was successfully completed using extracorporeal venous shunting. We discuss the important aspects of preoperative diagnosis and the intraoperative anesthetic management of this case.

Anesthesia↗
PubMed2001

Coincidence detection FDG PET in the management of oncological patients: attenuation correction versus non-attenuation correction.

The aim of this study was to determine if attenuation correction (AC) in a dual-head, coincidence, positron emission tomography imaging system (Co-PET) improved image quality, lesion detection, patient staging and management of various malignant neoplasms, compared to non-attenuation corrected (NAC) images. Thirty patients with known or suspected malignant neoplasms underwent fluorodeoxyglucose (FDG) Co-PET, which was correlated with histopathology, computed tomography (CT) and other conventional imaging modalities and clinical follow-up. The number and location of FDG avid lesions detected on the AC images and NAC Co-PET images were blindly assessed by two independent observers. Semi-quantitative grading of image clarity and lesion-to-background quality was performed. This revealed markedly improved image clarity and lesion-to-background quality in the AC versus NAC Co-PET images. AC Co-PET was statistically superior to NAC Co-PET in relation to lesion detection (P<0.01) and tumour staging (P<0.01). NAC Co-PET demonstrated 51 of the 65 lesions (78%) detected by AC Co-PET. AC Co-PET altered tumour staging in five additional patients (16%) compared to NAC Co-PET. Management was altered in two of these five patients.

Adult↗
PubMed2000

Substituted benzamide inhibitors of human rhinovirus 3C protease: structure-based design, synthesis, and biological evaluation.

A series of nonpeptide benzamide-containing inhibitors of human rhinovirus (HRV) 3C protease was identified using structure-based design. The design, synthesis, and biological evaluation of these inhibitors are reported. A Michael acceptor was combined with a benzamide core mimicking the P1 recognition element of the natural 3CP substrate. alpha,beta-Unsaturated cinnamate esters irreversibly inhibited the 3CP and displayed antiviral activity (EC(50) 0.60 microM, HRV-16 infected H1-HeLa cells). On the basis of cocrystal structure information, a library of substituted benzamide derivatives was prepared using parallel synthesis on solid support. A 1.9 A cocrystal structure of a benzamide inhibitor in complex with the 3CP revealed a binding mode similar to that initially modeled wherein covalent attachment of the nucleophilic cysteine residue is observed. Unsaturated ketones displayed potent reversible inhibition but were inactive in the cellular antiviral assay and were found to react with nucleophilic thiols such as DTT.

3C Viral Proteases↗
PubMed2000

Current epidemiology of human plague in Madagascar.

From 1996 to 1998, 5,965 patients with suspected plague were identified in 38 districts of Madagascar (40% of the total population are exposed). Using standard bacteriology, 917 of them were confirmed or presumptive (C + P) cases. However, more than 2,000 plague cases could be estimated using F1 antigen assay. Two out of the 711 Yersinia pestis isolates tested were resistant to chloramphenicol and to ampicillin (both isolates found in the harbour of Mahajanga). Urban plague (Mahajanga harbour and Antananarivo city) accounted for 37.4% of the C + P cases. Bubonic plague represented 97.2% of the cases, and the lethality rate was still high (20%). In comparing the exposed population, plague was more prevalent in males (M:F sex ratio 1.3:1) and patients under 20 years (2.7% babies under two years). Buboes were mainly localised in the inguinal/femoral regions (55.8%). The epidemiological risk factors are discussed.

Adolescent↗
PubMed2000

Performance of the ImmunoCard STAT! E. coli O157:H7 test for detection of Escherichia coli O157:H7 in stools.

ImmunoCard STAT! E. coli O157:H7 (Meridian Diagnostics, Inc., Cincinnati, Ohio) is a novel rapid (10-min) test for the presence of Escherichia coli O157:H7 in stools. The test may be performed either directly on stool specimens or on an overnight broth culture of stool. In a multicenter prospective study, 14 of 14 specimens positive by culture for E. coli O157:H7 were positive by the ImmunoCard STAT! O157:H7 test, and there were no false positives from 263 culture-negative specimens. In a retrospective study, the test was positive in 339 (81%) of 417 stored culture-positive specimens and the specificity was 95% (98 of 103 specimens). No false positives were associated with alternate stool pathogens. The ImmunoCard STAT! O157:H7 test has high sensitivity and specificity.

Enzyme-Linked Immunosorbent Assay↗
PubMed1999

Risk factors for resistance to "first-line" antimicrobials among urinary tract isolates of Escherichia coli in children.

BACKGROUND: There are increasing concerns regarding antimicrobial resistance in Canada. Data are limited on the prevalence, patterns of resistance and risk factors associated with resistant organisms, including coliforms, in children. This study was done to address these issues as they relate to urinary tract isolates of Escherichia coli in a tertiary care pediatric centre in Ottawa. METHODS: A surveillance study was conducted from December 1992 to December 1994. Susceptibility testing of urinary tract isolates of E. coli was performed using a panel of antimicrobial agents. A case-control study was also conducted for subjects with isolates resistant to trimethoprim-sulfamethoxazole (T-S), this drug being used a representative "first-line" agent. RESULTS: A total of 1636 consecutive isolates were obtained from 967 subjects. Of the 1636 isolates, 736 (45.0%) were resistant to ampicillin, 514 (31.4%) were resistant to T-S, 363 (22.2%) were resistant to both ampicillin and T-S, and 27 (1.7%) were resistant to both ampicillin and gentamicin. In the case-control study 274 children with isolates resistant to T-S were matched with 274 children who had T-S-sensitive isolates obtained during the study period or the preceding or subsequent 6 months. Multivariate analyses indicated that subjects who had received antimicrobials for more than 4 weeks in the previous 6 months were about 23 times more likely to have isolates resistant to T-S than were subjects without this risk factor (odds ratio [OR] 23.4, 95% confidence interval [CI] 12.0-47.6). Children with genitourinary tract abnormalities were 2.4 times more likely to have resistant isolates than those without such abnormalities (95% CI 1.2-4.5). Compared with children who had no hospital admissions in the previous year, those with 1 admission in that period were more likely to have resistant isolates (OR 2.3, 95% CI 1.4-7.5), as were those with 2 or more admissions in that period (OR 3.2, 95% CI 1.1-4.8). Compared with children aged 2-6 years, children under 2 years of age were less likely to have resistant isolates (OR 0.3, 95% CI 0.2-0.8). INTERPRETATION: Selective antimicrobial pressure and multiple admissions to hospital were among the risk factors associated with antimicrobial resistance. The finding of a low but definite level of resistance to both ampicillin and gentamicin is important for the selection of empiric therapy for sepsis in neonates. The role of inexpensive first-line agents in the outpatient treatment and prevention of urinary tract infections requires re-examination, particularly in children who have recently received antimicrobial therapy.

Anti-Bacterial Agents↗
PubMed1999

Idiopathic dilated cardiomyopathy presenting in pregnancy.

PURPOSE: To describe the clinical course and management of a patient who presented with idiopathic dilated cardiomyopathy in early pregnancy. CLINICAL FEATURES: A 27 yr old, previously well, Chinese primigravida presented at 18 wk gestation with a history of irregular heart beat and decreased exercise tolerance. Echocardiography showed moderate left ventricular dysfunction with left ventricular ejection fraction of 35-40%. Idiopathic dilated cardiomyopathy was diagnosed. She declined termination of pregnancy and was managed medically with furosemide, digoxin and potassium supplements. Low molecular weight heparin was prescribed. Emergency Cesarean delivery was performed at 31 wk gestation because of deteriorating liver function and a non-reassuring fetal heart rate pattern. General anesthesia was given because of relative urgency, the patient's wish, and concerns about potential risk of spinal hematoma. Invasive monitoring with pulmonary and radial artery catheters was used and low dose inotropic support was given. Postoperatively, she was managed in the intensive care and coronary care units where she was treated with dobutamine, furosemide, digoxin, potassium, captopril, losartin and warfarin. Her postoperative course was complicated by a severe embolic stroke five weeks after delivery and she died five months later. CONCLUSION: Idiopathic dilated cardiomyopathy may rarely present in pregnancy. A multidisciplinary approach and close peripartum monitoring are important in management and termination of pregnancy should be considered. Thromboembolic complications are a major risk.

Adult↗
PubMed1999

Patency and limb salvage for polytetrafluoroethylene bypasses with vein interposition cuffs.

Polytetrafluoroethelene (PTFE) is often utilized in patients with limb-threatening ischemia requiring infrainguinal revascularization in the absence of autologous saphenous vein. To increase long-term patency of PTFE grafts, vein interposition cuffs have been recommended as adjunctive procedures. The purpose of this study was to assess the efficacy of vein interposition cuffs on the long-term patency and limb salvage of patients requiring prosthetic bypass grafts for limb-threatening ischemia. Prosthetic bypass grafts with vein interposition cuffs (PTFE/VC) were performed on 56 limbs in 55 patients (32 men, 23 women; mean age of 67 years) from October 1993 to January 1998. Grafts were prospectively evaluated every 3 months for the first 12 months and biannually thereafter with duplex ultrasonography. PTFE/VC and PTFE bypasses at the popliteal level appear to have comparable patencies. However, PTFE/VC appear to offer an improved patency and limb salvage for infrapopliteal bypasses in patients with critical limb ischemia. When infrapopliteal revascularization is required in the absence of autologous saphenous vein, we recommend the use of PTFE with vein interposition cuffs.

Aged↗
PubMed1999

Advances in imaging techniques for the diagnosis of focal hepatic lesions.

In the past few years, tremendous advances have been made in the fields of ultrasound, computed tomography, magnetic resonance imaging and contrast agent development. The purpose of this article is to highlight the important developments in imaging techniques that can be used for detection and characterization of focal hepatic lesions.

Aged↗
PubMed1999

New approaches to the investigation of focal hepatic lesions.

In the past few years, tremendous advances have been made in the fields of magnetic resonance imaging, computed tomography and ultrasonography. These include the development of novel contrast agents and new approaches to image acquisition and processing. This review provides an overview of the state-of-the-art of imaging investigation of focal hepatic lesions and highlights some of the most exciting emerging technologies.

Diagnosis, Differential↗
PubMed1999

Gastrostomy tubes in patients with recurrent gynaecological cancer and intestinal obstruction.

OBJECTIVE: Women with recurrent gynaecological cancers who are not suitable for exenterative surgery commonly present with gastrointestinal dysfunction. This paper is a retrospective review of the use of gastrostomy tubes in such women. METHODS: We performed a chart review of women with recurrent gynaecological cancer who had a gastrostomy tube placed between January 1991 and April 1998. RESULTS: Thirty-nine women (mean age 53.2 years, range 17-82) had a gastrostomy tube placed. Twenty-eight (72%) had ovarian cancer, eight (21%) had cervical cancer, two had endometrial cancer and one had vaginal cancer. In 14 women a gastrostomy tube was placed as the sole procedure for palliation (11 elective, 3 emergency). In the remaining 25 women, who underwent major surgery, a gastrostomy tube was placed in anticipation of, or in the presence of, significant intestinal distension and expected prolonged post-operative ileus. Eleven women (28%) died without leaving hospital after their operation (median 11 days, range 2-36). All but one of the 28 women who left hospital had satisfactory oral intake. Twenty-one women (54%) died with the gastrostomy tube in place (median 28 days, range 2-157) and 18 (46%) had the gastrostomy tube removed (median 14.5 days, range 9-180), 13 of whom (33%) have since died (median 167 days, range 77 days-7 years). Five women (13%) are alive (median 2.2 years, range 10 months-4.5 years). There were no problems which required the gastrostomy tube to be removed. CONCLUSION: Gastrostomy tubes have an important role in the treatment of women with recurrent gynaecological cancer, allowing gastric drainage and decompression without the disadvantages of nasogastric tubes.

Acute Disease↗
PubMed1999

Argument for the surgical staging of apparent early endometrial cancer.

Cancer of the uterine corpus, commonly referred to as cancer of the endometrium or cancer of the uterus, continues to be the most common pelvic genital malignancy affecting western women (1). In 1998 in the United States 36,100 women were diagnosed with this cancer, and there were 6,300 deaths from this condition in that year. Of concern is that despite a relatively stable incidence over the last decade, the annual number of deaths since 1987 from endometrial cancer has more than doubled (2). Many controversies exist in the management of apparent early endometrial cancer. These include: 1. The role of surgical staging which includes pelvic lymphadenectomy. 2. The role of the subspecialist gynaecological oncologist in primary surgical treatment. 3. Indications for vaginal and external beam radiotherapy. 4. Who is at risk for recurrence? 5. The role of laparoscopic approach to the management of this disease. Despite their importance, these and other issues have not been appropriately addressed by prospective randomized studies. Treatment strategies and algorithms have thus been based upon a combination of clinicopathological studies and uncontrolled reviews. The views expressed in this clinical opinion are those of the Sydney Gynaecologic Oncology Group and reflect our philosophy on the current management of this tumour, supported by recent and appropriate peer reviewed scientific literature.

Brachytherapy↗
PubMed1998

Epidemiology of methicillin-resistant Staphylococcus aureus in three Canadian tertiary-care centers.

OBJECTIVE: To describe the epidemiology and spread of methicillin-resistant Staphylococcus aureus (MRSA) in three tertiary-care centers in Ottawa, Ontario, Canada, where MRSA is encountered infrequently. DESIGN: Retrospective review over a 6-year period, from January 1, 1990, through December 31, 1995. SETTING: Three tertiary-care teaching hospitals in Ottawa. PARTICIPANTS: Patients and healthcare workers (HCWs) with MRSA isolated from any body site. METHODS: Patients and HCWs were identified retrospectively through hospital microbiology and infection control records. Patient charts were reviewed for clinical and epidemiological data, including age, gender, previous hospital admissions (where noted), and current and recent antibiotic use. MRSA isolates that were available were typed using pulsed-field gel electrophoresis (PFGE). Methicillin resistance was confirmed by standard methods and by polymerase chain reaction using mecA-specific primers. RESULTS: MRSA was identified in 53 patients and 2 HCWs. Three patients were excluded from further analysis because medical records were incomplete. Epidemiological data were collected on the remaining 52 individuals. Thirty-nine isolates from 31 patients and 2 HCWs were available for PFGE typing. Five epidemiologically linked nosocomial clusters involving 10 patients and 2 HCWs were identified and were confirmed by PFGE. MRSA isolates from a sixth cluster were not available for PFGE. In each cluster, nosocomial spread was minimized by standard infection control practices, including strict isolation of patients and screening of contacts. There was no evidence of secondary spread of MRSA involving the remaining 36 patients. Recent antibiotic use, surgery, admission to an intensive-care unit, and previous hospitalization were common among patients. There was no evidence of spread of MRSA among the three hospitals, and no endemic strains were apparent in any of these centers. CONCLUSIONS: MRSA remains an infrequent isolate in our centers, with no apparent interhospital spread. In institutions with little or no endemic MRSA, rigorous application of standard infection control practices is effective in limiting nosocomial transmission of this organism.

Hospitals, Teaching↗