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Biomedical subjects

C M Chan

Publications and source records attributed to C M Chan.

At least 19 recordsLinked to original sources
PubMed2006

Influence of an anti-diabetic foot ulcer formula and its component herbs on tissue and systemic glucose homeostasis.

Complications of diabetes impose major public health burdens worldwide. The positive effect of a Radix Astragali-based herbal preparation on healing diabetic foot ulcers in patients has been reported. Formula 1 is also referred as the 'Herbal drink to strengthen muscle and control swelling'. This formula contains six Chinese medical herbs, including Radix Astragali, Radix Rehmanniae, Rhizoma Smilacis Chinensis, Rhizoma Atractylodis Macrocephalae, Radix Polygoni Multiflori Preparata, and Radix Stephania Tetrandrae. Three of these herbs (Radix Astragali, Radix Rehmanniae, Rhizoma Atractylodis Macrocephalae) are commonly used in different anti-diabetic formulae of Chinese medicine. The objective of the current study is to use an interdisciplinary approach to test the hypothesis that Formula 1 and its components influence tissue and systemic glucose homeostasis. In vitro and in vivo models have been established including: (1) glucose absorption into intestinal brush border membrane vesicles (BBMV); (2) gluconeogenesis by H4IIE hepatoma cells; (3) glucose uptake by 3T3-L1 adipocytes and Hs68 skin fibroblasts; (4) normalization of glycaemic control in a diabetic rat model. The results of in vitro studies indicated that all herbal extracts can modify cellular glucose homeostasis. Since Formula 1 and Rhizoma Smilacis Chinensis extracts demonstrated potent effects on modifying glucose homeostasis in multiple tissues in vitro, they were further studied for their anti-diabetic activities in vivo using a streptozotocin (STZ)-induced diabetic rat model. The results showed that Formula 1 and Rhizoma Smilacis Chinensis extracts did not significantly improve oral glucose tolerance or basal glycaemia in diabetic rats. In conclusion, the anti-diabetic foot ulcer Formula 1 contains ingredients active in modifying tissue glucose homeostasis in vitro but these biological activities could not be associated with improved glycaemic control of diabetes in vivo.

3T3 Cells↗
PubMed2006

A treatable case of dementia--intracranial dural arteriovenous fistula.

Dementia is a common medical problem that affects elderly patients. We report on a 77-year-old man with an intracranial dural arteriovenous fistula who presented with dementia that was initially thought to be irreversible and degenerative. Subsequent neuroendovascular intervention resulted in significant functional and cognitive improvement.

Aged↗
PubMed2005

Randomized clinical trial comparing blue dye with combined dye and isotope for sentinel lymph node biopsy in breast cancer.

BACKGROUND: Use of blue dye alone as a marker for sentinel lymph node (SLN) biopsy is effective, but combining it with isotope marking can improve the success rate. Use of the isotope adds extra cost and there are potential radiation hazards. The two techniques were compared in a randomized trial. METHODS: Women with early breast cancer (less than 3 cm) and no palpable axillary nodes were recruited. Women older than 70 years with multicentric cancers or previous surgery to the breast or axilla were excluded. Patients were randomized to either blue dye alone or combined mapping for SLN biopsy. All women had a level I and II axillary dissection after the SLN biopsy. RESULTS: A total of 123 patients were recruited, of whom five were excluded from analysis. Blue dye alone was used in 57 women and 61 had combined mapping. Baseline demographic data were similar in the two cohorts. The success rate of SLN biopsy was higher with combined mapping than with blue dye alone (100 versus 86 per cent; P = 0.002). The accuracy and false-negative rate were similar (accuracy 100 per cent for combined mapping versus 98 per cent for blue dye; false-negative rate 0 versus 5 per cent). CONCLUSION: Combined mapping was superior to blue dye alone in identification of the SLN, but accuracy and false-negative rates were similar.

Breast Neoplasms↗
PubMed2005

Hyperlipidaemia in chronic kidney disease.

Cardiovascular disease is a major cause of mortality and morbidity in patients with chronic kidney disease (CKD). The prevalence of hyperlipidaemia or dyslipidaemias is much higher compared to the general population. Total or low-density lipoprotein (LDL) cholesterol is highest in patients with chronic renal impairment. The majority of patients with CKD do not develop renal failure; indeed, most of them die of cardiovascular causes before the development of renal failure. The K/DOQI (Kidney Disease Outcomes Quality Initiative) guidelines on dyslipidaemias in CKD suggest that all patients should therefore be evaluated for dyslipidaemias. They should have a complete fasting lipid profile with total, LDL and high-density lipoprotein cholesterol, and triglycerides measured to identify those at risk and those who require treatment. Generally, the treatment approach parallels that suggested by the National Cholesterol Education Program Adult Treatment Panel III guidelines, in which the main focus of treatment is the level of LDL cholesterol. Patients with CKD should be considered a "very high risk" category and aggressive therapeutic intervention initiated to reduce the risk of cardiovascular events.

Cholesterol, LDL↗
PubMed2005

ATRA therapy restores normal renal function and renal reserve and prevents renal failure.

This article presents clinical data which suggest that the current dosage of losartan 50 to 100 mg/day may not be the optimum in many cases, especially if used as monotherapy in the treatment of proteinuria and we may have to increase to 200 mg/day. However, about 30% of patients cannot take angiotensin-converting enzyme inhibitor (ACEI) because of the side effect of cough. To potentiate the anti-proteinuric effect of losartan, especially for patients who do not adhere to a low salt diet, a 12.5-mg dose of hydro-chlorothiazide may further decrease proteinuria. The main message of this article is that we would have to, in many instances, increase the dose of losartan to a minimum of 100 mg/day or 100 mg twice a day for some patients for optimal therapy. The second message is to monitor the creatinine clearance test (CCT) and to start therapy when CCT is reduced and not wait for serum creatinine to rise to abnormal levels (renal impairment) before starting therapy. The first group involves half a dozen patients with hypertension but no proteinuria. Therapy with losartan is shown to improve the renal function. This data suggest that losartan, apart from its use in reduction of proteinuria, can be used in patients with mild renal impairment without proteinuria to reverse the mild renal impairment and preserve renal function. The second group deals with 3 patients with low creatinine clearance. After a followup period of an average of 3 years, they all developed renal impairment. In another 6 patients, the data suggest that we should perhaps treat patients with low CCT as soon as possible and with dose ranging from 100 to 200 mg/day if necessary, to derive maximum beneficial effect. The third group highlights 5 patients with high CCT due to glomerular hyperfiltration. With time, the high CCT decreases and renal impairment sets in. The data suggest that patients with high CCT should be treated early to prevent renal impairment. The fourth group illustrates 6 patients where their proteinuria was markedly reduced with the increase of losartan from 100 mg/day to 200 mg/day, suggesting that losartan 200 mg/day is probably the optimum dose. In conclusion, apart from its traditional usage in reduction of proteinuria to retard progression to renal failure, the data suggest that losartan is also indicated in patients with renal impairment in the absence of proteinuria; patients with low CCT, patients with high CCT and patients who do not respond to a dosage of 100 mg/day should have the dosage increased to 100 mg twice daily to increase efficacy of losartan. It is hoped that with these new and earlier indications as well as increased dosage of losartan starting with 100 mg, whenever possible, and increasing to 200 mg/day, if there is no response, we can prevent more patients from developing renal failure. Based on these observations, further randomised controlled trials should be designed to address these issues.

Adult↗
PubMed2001

Endovascular treatment of radiation-induced petrous internal carotid artery aneurysm presenting with acute haemorrhage. A report of two cases.

Haemorrhage from rupture of petrous ICA aneurysm can be life threatening and emergency treatment is required. We report 2 cases of radiation-induced petrous internal carotid artery (ICA) aneurysm presenting with acute haemorrhage (epistaxis and otorrhagia) after radiotherapy (RT) for nasopharyngeal carcinoma (NPC). Both patients had a history of RT treatment for NPC. The first patient, a 54-year-old man, presented with sudden severe epistaxis and haemorrhagic shock. The second patient, a 35-year-old man, presented with episodes of severe otorrhagia. The first patient was immediately resuscitated. Obliteration of the aneurysm was performed by endovascular occlusion of the ICA with Guglielmi detachable coils and fibered platinum coils. For the second patient, the aneurysm was treated by deploying a self-expandable stent across the aneurysm neck. In an emergency situation, ruptured petrous ICA aneurysm can be treated with endovascular occlusion of the ICA with microcoils if there is a good collateral blood flow. Alternatively, the aneurysm can be treated by deployment of a stent, which can induce stasis and eventual thrombosis of the aneurysm.

Acute Disease↗
PubMed2001

Acute hemorrhage in late radiation necrosis of the temporal lobe: report of five cases and review of the literature.

Hemorrhage in late cerebral radiation necrosis is a rare complication after radiotherapy for intracranial and extracranial neoplasms. We report 5 cases of acute hemorrhage in late radiation necrosis of the temporal lobe following radiation therapy for nasopharyngeal carcinoma. In a review of the literature, the authors identified a total of 27 such cases. The interval period between the onset of hemorrhage and cranial irradiation is long (mean = 7.8 years). The most prominent histological feature was the proliferation of large, dilated and thin-walled new blood vessels in a background of gliosis and fibrinoid necrosis of vessels. Rupture of these thin-walled new blood vessels is the proposed mechanism of hemorrhage in this condition.

Adult↗
PubMed2001

Diagnostic accuracy of vacuum-assisted biopsy device for image-detected breast lesions.

BACKGROUND: Non-palpable breast lesions present diagnostic difficulties. Ultrasound-guided fine-needle aspiration cytology (FNAC) is a common method used to obtain a diagnosis, but FNAC is frequently inconclusive or insufficiently accurate. Recently a vacuum-assisted biopsy device (Mammotome, Ethicon, Endo-surgery, USA) has been introduced. The diagnostic accuracy of this biopsy device was assessed for lesions that were visible on ultrasound. METHODS: Fifty ultrasound-guided mammotome biopsies were performed. All were small breast lesions primarily detected by ultrasound. All received FNAC as initial assessment. Mammotome biopsy was performed whenever the breast lesion was considered indeterminate or if it was considered benign and there were associated risk factors such as a family history of breast cancer. RESULTS: Of 50 mammotome biopsies 45 had benign histology. Three of 45 lesions were excised at the patients' request and were confirmed to be benign. The remaining 42 patients received an ultrasound follow up at 6 months. The lesion size remained static in 39 patients. In three patients the lesion size increased and they were excised and histology was benign. For the four malignancies diagnosed with mammotome biopsy, three patients received definitive treatment and one patient defaulted. There was one failed mammotome biopsy in the present series. CONCLUSIONS: Mammotome biopsy is an acceptable diagnostic method for small breast lesions seen on ultrasound. It reduces the need for open biopsy without compromising diagnostic accuracy.

Adult↗
PubMed2001

Traumatic intracranial aneurysm in infancy.

An anterior cerebral artery traumatic aneurysm in a 15-month-old infant is described. The diagnosis was confirmed by computed tomographic angiography. The patient recovered fully after successful clipping of the aneurysm. As the signs of traumatic intracranial aneurysm may be subtle especially in young children, a high degree of suspicion is essential in patients presenting with delayed neurological deterioration after head trauma.

Accidental Falls↗
PubMed2001

Characterization of AFMP1: a novel target for serodiagnosis of aspergillosis.

We cloned the AFMP1 gene, which encodes the first antigenic cell wall galactomannoprotein in Aspergillus fumigatus. AFMP1 codes for a protein, Afmp1p, of 284 amino acid residues, with a few sequence features that are present in Mp1p, the antigenic cell wall mannoprotein in Penicillium marneffei that we described previously, as well as several other cell wall proteins of Saccharomyces cerevisiae and Candida albicans. It contains a serine- and threonine-rich region for O glycosylation, a signal peptide, and a putative glycosylphosphatidyl inositol attachment signal sequence. Specific anti-Afmp1p antibody was generated with recombinant Afmp1p protein purified from Escherichia coli to allow further characterization of Afmp1p. Afmp1p has a high affinity for Galanthus nivalis agglutinin, a characteristic indicative of a mannoprotein. Furthermore, it was recognized by a rat monoclonal antibody against the galactofuran side chain of galactomannan, indicating that it is a galactomannoprotein. Ultrastructural analysis by immunogold staining indicated that Afmp1p is present in the cell walls of the hyphae and conidia of A. fumigatus. Finally, it was observed that patients with aspergilloma and invasive aspergillosis due to A. fumigatus develop a specific antibody response against Afmp1p. This suggested that the recombinant protein and its antibody may be useful for serodiagnosis in patients with aspergilloma or invasive aspergillosis, and the protein may represent a good cell surface target for host humoral immunity.

Amino Acid Sequence↗
PubMed2001

Vascular patterns in pterygium and conjunctival autografting: a pilot study using indocyanine green anterior segment angiography.

AIMS: To characterise the vasculature of pterygium using indocyanine green (ICG) anterior segment angiography and to demonstrate the pattern of revascularisation following conjunctival autografting. METHODS: ICG anterior segment angiography was performed on nine patients with pterygium. Angiography was repeated at 1-2 weeks and 2 months following conjunctival autografting in these patients. RESULTS: Angiography showed a single feeder vessel originating from the anterior conjunctival circulation in six cases (66.7%). This vessel branched to form the radial vessels of the pterygium. Following conjunctival autografting, reperfusion of the vessels in the conjunctival autograft was demonstrable as early as 1 week postoperatively from the episcleral bed. At 2 months postoperatively, the graft appeared well perfused with mild leakage demonstrable at the edges of the graft. CONCLUSIONS: A single feeder vessel from the anterior conjunctival circulation branches to form the radial vessels in pterygium. Reperfusion of conjunctival autografts occurs as early as 1 week postoperatively from the episcleral bed.

Anterior Eye Segment↗
PubMed2000

BCAR1/p130Cas expression in untreated and acquired tamoxifen-resistant human breast carcinomas.

High BCAR1/p130Cas expression in primary breast tumour cytosol predicts a poor chance of response recurrent disease to tamoxifen treatment in patients with oestrogen receptor (ER)-positive breast carcinomas. In this study, we assessed whether BCAR1/p130Cas expression is altered during acquisition of anti-oestrogen resistance. BCAR1/p130Cas protein was quantitatively measured by chemiluminescent Western blot analysis in the cytosol of 34 predominantly ER(+) carcinomas that initially responded to primary tamoxifen treatment and subsequently progressed (n = 22 ) or developed during adjuvant tamoxifen treatment (n = 12) and compared to 54 untreated ER(+) human breast carcinomas. We did not detect significant differences in the level of BCAR1/p130Cas protein in untreated and acquired tamoxifen-resistant carcinomas. Our results indicate that in tumour progression towards tamoxifen resistance, increase of BCAR1/p130Cas may be only one of the molecular mechanisms. Thus, high BCAR1/p130Cas protein levels appear to be a hallmark for intrinsic resistance to tamoxifen in breast carcinomas.

Adult↗
PubMed2000

Brain abscess formation in radiation necrosis of the temporal lobe following radiation therapy for nasopharyngeal carcinoma.

BACKGROUND: Radiation necrosis is a known complication following radiation therapy for extracranial as well as intracranial tumours. However, brain abscess formation in radiation necrosis has not been reported in the literature. We report the clinical data of 6 patients suffering from this condition. METHOD: Twenty-eight patients with radiation necrosis of the temporal lobe following radiotherapy for nasopharyngeal carcinoma were treated surgically at the Department of Neurosurgery, Queen Elizabeth Hospital, Hong Kong between January 1992 and July 1999. Of these, 6 cases were complicated by brain abscess formation. The clinical data of these 6 patients are retrospectively reviewed. FINDINGS: The patients were 5 males and 1 female, ranging in age from 41 to 67 years. Three patients had previous treatment with steroids for the symptomatic radiation necrosis. A history of nasal infection or otitis media was recognised in all 6 patients. All patients were treated surgically by temporal lobectomy and excision of the necrotic tissue together with the abscess cavity. Intra-operatively, a bony defect was observed between the middle cranial fossa and the sphenoid sinus in 3 patients and the bony defect was repaired with a temporalis muscle flap. The species of organisms could only be identified in 3 patients. In 3 patients, the pus smear was positive but the culture was negative. Subsequently, 4 patients recovered and 2 patients died. INTERPRETATION: Cerebral radiation necrosis is a predisposing cause of brain abscess formation. Surgical excision is recommended as the treatment of choice in this group of patients.

Adult↗
PubMed2000

Application of a luminescence-based pH optrode to monitoring of fermentation by Klebsiella pneumoniae.

The application of an optical sensor based on immobilization of the ruthenium complex [Ru(bpy)2(dhphen)]2+ (bpy = 2,2'-bipyridine, dhphen = 4,7-dihydroxy-1,10-phenanthroline) in Nafion to pH monitoring of fermentation by Klebsiella pneumoniae is described. Interference from the culture medium can be eliminated by addition of a black microporous filter membrane (pore size: 0.45 microm) on top of the sensing film. The response of this pH optrode was found to show good correlation with the conventional pH electrode.

Fermentation↗
PubMed2000

Induction of proliferation and apoptotic cell death via P2Y and P2X receptors, respectively, in rat glomerular mesangial cells.

BACKGROUND: Cell surface receptors for adenosine 5'-triphosphate (ATP; P2 receptors) have been subdivided into two families: ligand-gated ion channels (P2X1-7) and G-protein-coupled (P2Y1-8) receptors. We investigated the potential role of P2 receptors on rat glomerular mesangial cells. METHODS: To investigate cell proliferation, DNA synthesis was assayed by measuring [3H]thymidine incorporation into DNA. For detecting apoptosis, morphological features, DNA fragmentation, and exposure of phosphatidylserine on the outside surface of the cell membrane were investigated. Expression of mRNA and distribution of receptors were detected by reverse transcription-polymerase chain reaction and immunohistochemistry, respectively. RESULTS: ATP triggered a dose-dependent increase in DNA synthesis. This response was also induced by uridine triphosphate (UTP), an agonist equipotent with ATP at P2Y2 and P2Y4 receptors; both P2Y2 and P2Y4 mRNA are expressed in glomerular mesangial cells and isolated glomeruli. In contrast, the P2X7 receptor agonist 2'-83'-O-(4-benzoyl benzoyl) ATP (BzATP) caused a decrease in cell number. BzATP produced DNA cleavage and exposure of phosphatidylserine on the outside of the cell membrane. P2X7 receptors were distributed heterogeneously in unstimulated cells. The expression of P2X7 mRNA was maintained at a low level, but was induced by tumor necrosis factor-alpha. CONCLUSIONS: Stimulation of glomerular mesangial cells via P2Y2 and/or P2Y4 and via P2X7 receptors can induce proliferation and apoptotic cell death, respectively. The balance between proliferation and apoptosis will depend on the relative stimulation and expression of these P2 receptor subtypes, and could play an important role in normal and abnormal glomerular function.

Adenosine Triphosphate↗
PubMed2000

Experience of neoadjuvant chemotherapy for breast cancer at a public hospital: retrospective study.

OBJECTIVE: To review local experience of neoadjuvant chemotherapy in breast cancer. DESIGN: Retrospective study. SETTING: Public hospital, Hong Kong. PATIENTS: Seventeen patients who presented from August 1988 through April 1997 with locally advanced breast cancer, which was treated with neoadjuvant chemotherapy. RESULTS: The clinical response rate was 71% and two of the 12 patients who responded to chemotherapy achieved complete remission. Three patients had their tumours downstaged sufficiently to allow them to undergo breast conservation surgery after neoadjuvant chemotherapy. None of these three patients has so far had a local recurrence of disease. CONCLUSION: Neoadjuvant chemotherapy can achieve a high objective response rate in patients with locally advanced breast cancer and thus enables breast conservation surgery to be performed on patients who are initially not suitable for this procedure.

Adult↗