PubMed Health⌕ Search

Biomedical subjects

Y L Chan

Publications and source records attributed to Y L Chan.

At least 19 recordsLinked to original sources

The p53 knowledgebase: an integrated information resource for p53 research.

The p53 tumor suppressor protein plays a central role in maintaining genomic integrity by occupying a nodal point in the DNA damage control pathway. Here it integrates a wide variety of signals, responding in one of several ways, that is, cell cycle arrest, senescence or programmed cell death (apoptosis). Mutations in the tumor suppressor gene tp53, which affects the key transcriptional regulatory processes in cell growth and death, occur frequently in cancer and helps explain why p53 has been called the guardian of the genome. There is a vast body of published knowledge on all aspects of p53's role in cancer. To facilitate research, it would be helpful if this information could be collected, curated and updated in a format that is easily accessible to the user community. To this end, we initiated the p53 knowledgebase project (http://p53.bii.a-star.edu.sg). The p53 knowledgebase is a user-friendly web portal incorporating visualization and analysis tools that integrates information from the published literature with other manually curated information to facilitate knowledge discovery. This includes curated information on sequence, structural, mutation, polymorphisms, protein-protein interactions, transcription factors, transcriptional targets, antibodies and post-translational modifications that involve p53. The goal is to collect and maintain all relevant data on p53 and present it in an easily accessible format that will be useful to researchers in the field.

Genes, p53↗

Mesenteric fat thickness as an independent determinant of fatty liver.

OBJECTIVE: Mesenteric fat is drained by the portal circulation and has been suggested to be a key component in obesity-related health risk, notably the metabolic syndrome. There are increasing epidemiological and experimental data showing that fatty liver is another component of this multifaceted syndrome. Given their intimate anatomical and physiological relationships, we hypothesized that mesenteric fat thickness may be independently associated with the risk of fatty liver. To test this hypothesis, we examined the predictive role of various fat deposits including mesenteric fat thickness, and various metabolic variables on the risk of fatty liver. SUBJECTS AND METHODS: A total of 291 Chinese subjects (134 men and 157 women with a mean BMI of 23.7 kg/m2, range: 16.5-33.4 kg/m2) underwent ultrasound examination for measurement of mesenteric, subcutaneous and preperitoneal fat thickness, and for diagnosis of fatty liver. Body mass index, waist circumference, and waist-hip ratio were recorded. Blood pressure was measured. Fasting plasma glucose, insulin resistance, high-density lipoprotein cholesterol (HDL-C), triglycerides, low-density lipoprotein cholesterol (LDL-C), liver enzymes were determined by common methods. RESULTS: The subjects with fatty liver had greater abdominal fat thickness and higher anthropometric indexes than those without fatty liver. The subjects with fatty liver also showed higher blood pressure, worse lipid and glycaemic profile compared with those without fatty liver. Using multiple logistic regression analysis, mesenteric fat thickness was a risk factor of fatty liver, independent of body mass index, age, sex, insulin resistance, fasting plasma glucose, lipid and blood pressure. The odds ratio was 1.5 (95% confidence interval: 1.27-1.77) for every 1 mm increase in the mesenteric fat thickness. Measurement of preperitoneal and subcutaneous fat deposits did not show significant associations with fatty liver. CONCLUSION: Mesenteric fat thickness measured on ultrasound is an independent determinant of fatty liver.

Abdominal Fat↗

Transvenous embolisation of a carotid-trigeminal cavernous fistula.

A carotid cavernous fistula is an abnormal communication between the internal carotid artery and the cavernous sinus. Rarely, this communication is associated with a persistent primitive trigeminal artery, with or without a trigeminal artery aneurysm. We report a case of spontaneous carotid-trigeminal cavernous fistula in which the persistent trigeminal artery was shown only on vertebral artery injection. The absence of an associated trigeminal artery aneurysm allowed a transvenous approach for endovascular treatment with coils and complete obliteration of the cavernous fistula.

Carotid-Cavernous Sinus Fistula↗

Dynamic susceptibility contrast-enhanced perfusion MR imaging in late radiation-induced injury of the brain.

The objective of the study was to evaluate radiation-induced cerebral injury on dynamic susceptibility contrast-enhanced (DSCE) perfusion MR imaging and study its relationship with morphological severity and disease progression. Thirty-one patients with known radiation injury to the temporal lobes where studied. Gradient and spin-echo T2-weighted, gadolinium-enhanced T1-weighted and DSCE perfusion MR imaging were obtained in the coronal plane through the anterior temporal lobe. Regions of interest where selected in the anterior temporal lobes and the superior frontal lobe as control for analysis of perfusion parameters. The mean transit time (MTT) was prolonged in both the High Dose Zone (HDZ) receiving from two-thirds to the total dose of 66-71.2 Gy, and the Intermediary Dose Zone (IDZ) receiving up to 87% of the total dose. The HDZ but not the IDZ showed a low relative cerebral blood volume (rCBV) and relative cerebral blood flow index (rCBFi). The rCBV and rCBFi were significantly lower in both HDZ and LBZ in temporal lobes with severe lesions compared to the temporal lobes with mild lesions but there was no significant difference in bolus transit parameters. The rCBV and rCBFi were significantly lower in both HDZ and IDZ of the swollen temporal lobes compared to those without swelling. It was concluded that DSCE perfusion MR imaging demonstrated a derangement in perfusion in radiation-induced cerebral injury in rCBV, rCBFi and MTT, which were related to the severity of the radiation-induced injury and the dose of irradiation delivered.

Adult↗

Therapeutic relationships: from psychiatric hospital to community.

The objective of this study was to determine the cost and effectiveness of a transitional discharge model (TDM) of care with clients who have a chronic mental illness. The model was tested in a randomized clinical trial using a cluster design. This model consisted of: (1) Peer support for 1 year and (2) Ongoing support from hospital staff until a therapeutic relationship was established with the community care provider. Participants (n = 390) were interviewed at discharge, 1 month post-discharge, 6 months post-discharge and 1 year post-discharge. Data collected included demographics, quality of life, health care utilization, levels of functioning and the degree of intervention received. The intervention group post-discharge costs and quality of life were not significantly improved compared with the control group. Although not predicted a priori, intervention subjects were discharged an average of 116 days earlier per person. Based on the hospital per diem rate this would be equivalent to 12M dollars CDN hospital costs. Both under-implementation among implementation wards and contamination in control wards were found. This study demonstrates some of the multiple challenges in health system research.

Adolescent↗

The preferred magnetic resonance imaging planes in quantifying visceral adipose tissue and evaluating cardiovascular risk.

BACKGROUND: Magnetic Resonance Imaging (MRI) is a well-accepted non-invasive method in the quantification of visceral adipose tissue. However, a standard method of measurement has not yet been universally agreed. OBJECTIVES: The objectives of the present study were 2-fold, firstly, to identify the imaging plane in the Chinese population which gives the best correlation with total visceral adipose tissue volume and cardiovascular risk factors; and secondly to compare the correlations between single-slice and multiple-slice approach with cardiovascular risk factors. METHODS: Thirty-seven Chinese subjects with no known medical history underwent MRI examination for quantifying total visceral adipose tissue volume. The visceral adipose tissue area at five axial imaging levels within abdomen and pelvis were determined. All subjects had blood pressure measured and fasting blood taken for analysis of cardiovascular risk factors. Framingham risk score for each subject was calculated. RESULTS: The imaging plane at the level of 'lower costal margin' (LCM) in both men and women had the highest correlation with total visceral adipose tissue volume (r = 0.97 and 0.99 respectively). The visceral adipose tissue area at specific imaging levels showed higher correlations with various cardiovascular risk factors and Framingham risk score than total visceral adipose tissue volume. The visceral adipose tissue area at 'umbilicus' (UMB) level in men (r = 0.88) and LCM level in women (r = 0.70) showed the best correlation with Framingham risk score. CONCLUSIONS: The imaging plane at the level of LCM is preferred for reflecting total visceral adipose tissue volume in Chinese subjects. For investigating the association of cardiovascular risk with visceral adipose tissue in MRI-obesity research, the single-slice approach is superior to the multiple-slice approach, with the level of UMB in men and LCM in women as the preferred imaging planes.

Abdomen↗

Cervical meningocele with tethered cervical cord in a Chinese infant.

Cervical meningocele and myelomeningocele are rare spinal dysraphic lesions. Unlike lumbosacral dysraphic lesions, there is often no neurological deficit in infants with cervical lesions, thus the subtle features of cervical cord tethering may be overlooked on imaging. We report a case of cervical meningocele in an 8-month-old girl. The tethering band, confirmed intra-operatively, was not evident on imaging. Untethering of the cord was performed together with resection of the sac and repair of the dura. Tethered cord should be suspected in the presence of cervical meningocele and intact neurology. It should be carefully looked for using high-resolution magnetic resonance imaging or computed tomography. Treatment aims to prevent future neurological deterioration, and should include careful intradural exploration with untethering of the cord.

Cervical Vertebrae↗

Temozolomide in the treatment of recurrent malignant glioma in Chinese patients.

OBJECTIVE: To determine the anti-tumour efficacy and safety profile of temozolomide in local Chinese patients with recurrent malignant glioma. DESIGN. Open-label trial. SETTING: University teaching hospital, Hong Kong. PATIENTS: Twenty-two patients had been enrolled in the study since 2001. Patients had to show unequivocal evidence of tumour recurrence or progression on gadolinium-enhanced magnetic resonance imaging after failing conventional radiotherapy and surgery for initial disease. Histology reviewed by a neuropathologist was required to show anaplastic glioma (anaplastic astrocytoma, anaplastic oligodendroglioma, or mixed anaplastic oligoastrocytoma) or glioblastoma multiforme. INTERVENTIONS: Patients were treated with temozolomide (200 mg/m(2) per day for the first 5 days of a 28-day cycle for four cycles) and monitored clinically every month and radiologically (gadolinium magnetic resonance imaging) at 6 months. MAIN OUTCOME MEASURES: Six-month progression-free survival and objective response rate. RESULTS: Twenty-two patients with recurrent malignant glioma were recruited between January 2001 and July 2004. Progression-free survival at 6 months was 54.5%. The mean progression-free survival for all patients was 7.2 months. The objective response rate, determined by gadolinium magnetic resonance imaging, was 9% for patients demonstrating a complete or partial response and a further 45% for patients demonstrating stable disease. Temozolomide was well tolerated orally with minimal adverse events. CONCLUSION. Preliminary results showed that temozolomide had an acceptable safety profile and anti-tumour activity in recurrent malignant glioma in local Chinese population. The results were comparable with those of western studies.

Adolescent↗

Association of carotid intima-media thickness with mesenteric, preperitoneal and subcutaneous fat thickness.

Carotid intima-media thickness (IMT) is an established surrogate marker for atherosclerosis. We have previously reported that abdominal fat, notably mesenteric fat, was a major explanatory variable for multiple cardiovascular risk factors. Given the intimate relationships between visceral fat, cardiovascular risk factors and atherosclerosis, we hypothesize that there are independent relationships between mesenteric fat and carotid IMT. Two hundred and eighty-two Chinese subjects (M: 129, F: 153; mean body mass index (BMI): 23.8 kg/m(2); age range: 20-68 years) were recruited. Maximum carotid IMT as well as maximum mesenteric, preperitoneal and subcutaneous fat thickness were measured by carotid and abdominal ultrasound examinations, respectively. Obesity index and conventional cardiovascular risk factors were assessed by physical examination and blood taking. On univariate analysis, mesenteric but not preperitoneal fat thickness was the major correlate with carotid IMT in both men and women. There was also a weak correlation between carotid IMT and subcutaneous fat thickness in women. On multivariate analysis, mesenteric fat thickness was an independent determinant of carotid IMT after adjustment for subcutaneous and preperitoneal fat thickness, age, gender, blood pressure, insulin resistance, lipid and glycaemic parameters. The association of mesenteric fat thickness with carotid IMT appeared stronger in women than in men, which however was not confirmed on multivariate analysis. In conclusion, mesenteric fat thickness measured on ultrasound showed significant association with carotid IMT, lending further support to the linking role of portal adipose tissue in obesity-related atherosclerosis. Effect of gender on the relationships of mesenteric fat with atherosclerosis risk require further elucidation. Measurement of mesenteric fat thickness may be a useful indicator of regional fat distribution in the assessment of cardiovascular risks.

Adipose Tissue↗

Multiple acute cerebral infarcts on diffusion-weighted imaging and risk of recurrent stroke.

Multiple acute cerebral infarcts (MACIs) detected by diffusion-weighted imaging (DWI) may indicate an unstable source of thromboembolism. The authors studied 119 consecutive acute ischemic stroke patients within 24 hours of onset with DWI. MACIs were present in 20 patients (16.8%). During the follow-up period, there were 15 recurrent strokes, 3 acute coronary syndromes, and 5 deaths. MACI was the only significant independent predictor for vascular events and death (odd ratio [OR]] = 4.34; p = 0.001) and stroke recurrence (OR = 5.93; p = 0.001).

Acute Disease↗

Low literacy Chinese patients: how are they affected and how do they cope with health matters? A qualitative study.

BACKGROUND: Low literacy is common in Hong Kong and China, especially among the females and the elderly. These are often the patients with the greatest health care needs. However little is known about how low literacy affects the ability of patients to obtain adequate medical care and comply with the recommendations of health professionals. METHODS: Qualitative study of subjects' opinions using semi-structured group and individual interviews. Thirty-six participants took part in 6 group and 9 individual interviews. RESULTS: Participants' opinions towards low literacy were explored in the interviews. They expressed diverse views on how they perceived low literacy. Some thought they were handicapped by it but others felt it was not a problem. Age, gender, chronic illnesses and their attitudes towards self were found to be major factors affecting their perception. Despite their low literacy, some had their specific ways to overcome the difficulties, for example, drawing symbols to help with the timing of taking the medications. Most of them felt better explanation by the health care workers was most important. CONCLUSIONS: It is highly relevant for health care workers to be aware of the low literacy status of their patients and to explain information so that patients understand it.

Adaptation, Psychological↗

Comparison of breath-hold 2D phase-contrast with non breath-hold cine phase-contrast MRA in the assessment of azygos venous blood flow in portal hypertension.

Azygos venous blood flow as an index of blood flow through the gastroesophageal collaterals and varices is of value in the prediction of gastrointestinal bleeding. Measurement of azygos venous blood flow has been achieved by non breath-hold (NBH) cine phase-contrast magnetic resonance imaging. The objective of this study was to compare the faster breath-hold (BH) phase-contrast technique with the standard (NBH) cine phase-contrast technique in the measurement of azygos blood flow. Thirty-two cirrhotic patients with esophageal varices were examined by magnetic resonance imaging using a BH technique and a NBH cine phase-contrast technique to measure the flow velocity, flow volume and calibre of the azygos vein at the mid-right atrial level. The flow values were obtained on the velocity image of the phase-contrast study. Values obtained from the two methods were evaluated statistically for the strength and significance of correlation by the Pearson test. Measurement by the BH method performed at full-inspiration as well as end-expiration was also obtained in 15 healthy volunteers. The breath-hold phase-contrast method has significant but weak correlation with non BH cine phase-contrast method in the measurement of azygos venous blood flow volume (r = 0.55, p < 0.01) and flow velocity (r = 0.43, p = 0.01). However, the calibre of the azygos vein gave a strong correlation in these two methods (0.82). In the subgroup of patients whose azygos blood flow velocity was greater than 7.4 cm/s, the correlation of azygos blood flow volume is strong (r = 0.80, p < 0.01). The azygos vein calibre remains highly correlated between the BH and NBH method, in both high flow velocity (r = 0.73) and low flow velocity (r = 0.83) groups. Breath-hold sequence leads to higher values for flow velocity and flow volume in the cirrhotic patients and also the control group. In patients with portal hypertension, BH 2D phase-contrast (PC) magnetic resonance angiography (MRA) could give a comparable estimation of the calibre of the azygos vein as the NBH 2D cine PC MRA but not for azygos flow volume. In patients with high azygos flow velocity, the strong correlation in flow volume between the BH and NBH method suggests that the BH method may be a time-saving alternative to the NBH method.

Azygos Vein↗

Spinal shock in spontaneous cervical spinal epidural haematoma.

A young man presented with quadriparesis and spinal shock because of a spontaneous cervical spinal epidural haematoma was reported. Immediate MRI diagnosis followed by emergency decompression with six hours of presentation resulted in complete recovery.

Adult↗

Asymptomatic microbleeds as a risk factor for aspirin-associated intracerebral hemorrhages.

The authors measured the presence and extent of asymptomatic microbleeds on gradient-recalled-echo MRI in 21 aspirin users who developed intracerebral hemorrhage and 21 aspirin users without history of intracerebral hemorrhage. Microbleeds were more frequent (19 vs 7, p < 0.001) and more extensive (mean number of microbleeds 13.3 vs 0.4, p < 0.001) in the intracerebral hemorrhage group than in the control group. Asymptomatic microbleeds may be a risk factor for aspirin-associated intracerebral hemorrhage.

Aged↗

Sonographic measurement of mesenteric fat thickness is a good correlate with cardiovascular risk factors: comparison with subcutaneous and preperitoneal fat thickness, magnetic resonance imaging and anthropometric indexes.

OBJECTIVE: Visceral fat, notably mesenteric fat, which is drained by the portal circulation, plays a critical role in the pathogenesis of metabolic syndrome through increased production of free fatty acids, cytokines and vasoactive peptides. We hypothesize that mesenteric fat thickness as measured by ultrasound scan could explain most of the obesity-related health risk. We explored the relationships between cardiovascular risk factors and abdominal fat as determined by sonographic measurements of thickness of mesenteric, preperitoneal and subcutaneous fat deposits, total abdominal and visceral fat measurement by magnetic resonance imaging (MRI) and anthropometric indexes. DESIGN: A cross-sectional study. SUBJECTS: Subjects included 18 healthy men and 19 women (age: 27-61 y, BMI: 19-33.4 kg/m(2)). MEASUREMENTS: The maximum thickness of mesenteric, preperitoneal and subcutaneous fat was measured by abdominal ultrasound examination. MRI examinations of whole abdomen and pelvis were performed and the amount of total abdominal and visceral fat was quantified. The body mass index, waist circumference and waist-hip ratio were recorded. Cardiovascular risk factors were assessed by physical examination and blood taking. RESULTS: Men had more adverse cardiovascular risk profile, higher visceral fat volume and thicker mesenteric fat deposits than women. Among all the investigated obesity indexes, the mesenteric fat thickness showed the highest correlations with total cholesterol, LDL-C, triglycerides, fasting plasma glucose, HbA(1c) and systolic blood pressure in men, and with triglycerides and HbA(1c) in women. On stepwise multiple regression analysis with different obesity indexes as independent variables, 30-65% of the variances of triglycerides, total cholesterol, LDL-C and HbA(1c) in men, and triglycerides in women were explained by the mesenteric fat thickness. CONCLUSION: Compared with sonographic measurement of subcutaneous and preperitoneal fat thickness, MRI measurement of total abdominal and visceral fat and anthropometric indexes, sonographic measurement of mesenteric fat thickness showed better associations with some of the cardiovascular risk factors. It may potentially be a useful tool to evaluate regional distribution of obesity in the assessment of cardiovascular risk.

Adipose Tissue↗

A transitional course from high school to medical school in a new medical curriculum in Asia: how do the students see it?

The objective of this study was to examine the students' views on a transitional course for Asian freshers in a revised medical curriculum. Data were collected through the year-end questionnaire distributed to all first-year students over three academic years from 1997 to 2000. The students considered the transitional course had encouraged them to become more active and self-directed although there were different views about its overall effectiveness. Students appeared uncertain as to the depth in which they were expected to master the subjects, thus leading them to call for more clearly stated learning objectives to help relieve the anxiety they had towards the examinations. Lectures and self-assessment exercises were seen to be providing the general guides for that.

Asia↗

Progress of memory function after radiation therapy in patients with nasopharyngeal carcinoma.

The authors evaluated the late neurocognitive profile and progress of memory functions in 60 patients with primary nasopharyngeal carcinoma who had been treated with radiation therapy for more than 2 years. Forty had imaging evidence of temporal lobe injury (TLI-positive), and 20 did not (TLI-negative). The patients and 19 healthy control subjects, matched with the patients for age and educational level, underwent extensive memory assessments. Seventeen patients (10 TLI-positive, 7 TLI-negative) were reassessed after an average of 28 months for progress of memory functions. The patient groups performed significantly worse on most memory tests compared with the normal subjects. Patients with memory complaints had lower scores for verbal memory than those without such complaints. The TLI-positive and TLI-negative groups did not differ significantly from each other in cognitive performance. At follow-up, visual memory performance had deteriorated, while verbal memory remained more stable.

Adult↗

Paraffinoma in anterior abdominal wall mimicking liposarcoma.

Paraffinoma of breast is a recognized complication of paraffin injection for breast augmentation. Liquid paraffin can extend along fascial planes to involve adjacent tissues. A rare case of paraffinoma in anterior abdominal wall, which was misdiagnosed as a soft tissue liposarcoma before surgical excision, is reported. It was heterogeneous with marked posterior acoustic shadowing and small peripheral cysts on ultrasound. On MRI, it had ill-defined margins and was heterogeneous in signal intensity. Small round components which were hypointense on all sequences were demonstrated. There is significant overlapping of imaging features between paraffinoma and soft tissue liposarcoma. Histological differentiation from well-differentiated liposarcoma may also be difficult. A detailed clinical history of previous paraffin injection for breast augmentation is very important for correct interpretation of imaging and histopathological findings.

Abdominal Wall↗