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Biomedical subjects

W K Ho

Publications and source records attributed to W K Ho.

At least 19 recordsLinked to original sources
PubMed2006

Cross-cultural adaptation and validation of the Chinese Voice Handicap Index-10.

OBJECTIVES/HYPOTHESIS: Recent developments in voice assessment propose the use of quality of life measurements. The Voice Handicap Index (VHI) is one of the most psychometrically robust and well-studied instruments among the various instruments for measuring quality of life. Two versions of VHI (VHI-30 and VHI-10) have been shown to be valid instruments for distinguishing dysphonic from nondysphonic individuals and also for documenting treatment effect for dysphonic patients. The VHI has been used worldwide; however, the psychometric properties of the Chinese version of VHI remains untested. This study aimed to investigate such properties of the Chinese VHI-30 and VHI-10 in the Hong Kong Chinese population. STUDY DESIGN: Psychometric analysis of the Chinese VHI-30 and VHI-10 in dysphonic patients and control subjects. METHODS: The original VHI-30 was translated into Chinese and was completed by 131 dysphonic patients and 54 nondysphonic individuals. The dysphonic patients also self-rated their dysphonic severity. RESULTS: Results showed high test-retest reliability and high item-total correlation for both Chinese VHI-30 and VHI-10. Both Chinese versions could be used to distinguish different dysphonic groups and between dysphonic and nondysphonic groups. Significant correlation was found between the VHI scores and the patients' self-rated dysphonic severity. CONCLUSION: The present study supported the original three-factorial structures of the VHI-30 and the use of the VHI for the Chinese population. It is shown that the Chinese VHI-10 is a strong representation of VHI-30 and is recommended for use in clinics because of its validity and ease of use by patients.

Adolescent↗
PubMed2005

Ethnic variation in sinonasal anatomy on CT-scanning.

Computed tomography (CT) scanning of the paranasal sinuses provides valuable information in assessing extent of disease and fine detailed anatomy prior to endoscopic sinus surgery. Awareness of the different anatomic variants of the bony sinonasal anatomy will help the rhinologic surgeon's orientation during the procedure. We conducted a study to look at the incidence of the anatomic variation within the lateral wall of the nose and sinuses and to determine if there is any ethnic difference in these variants between a cohort of 100 Caucasian patients undergoing endoscopic sinus surgery in London and 100 Chinese patients treated in Hong Kong. We compared the two groups with chi-square test and the significant areas are those with p value of less than 0.05. The results show a higher incidence of pneumatisation of the middle turbinate (concha bullosa) and paradoxical bending of the middle turbinate in the Caucasian population. The infraorbital and suprabullar cell development was greater in the Caucasian population though the incidence of sphenoethmoidal cells was much greater in the Chinese population. When asymmetry of the anterior ethmoidal roof was considered, the left was consistently the highest in both groups, though there was no difference in the depth of the cribiform niche between right and left or between Caucasian and Chinese. The incidence of bent uncinate process and of complete absence of a sinus was higher in the Chinese population. There was no difference in the presence of pneumatisation of the agger nasi, of the uncinate process, or of the anterior clinoid process. There was no difference in the presence of septation adjoining the carotid in the lateral wall of sphenoid or in the exposure of the optic nerve within sphenoid or posterior ethmoid sinuses. Although there is no evidence that variants of the sinonasal anatomy seen on CT Scan have a causative effect in the disease process; a knowledge of their presence is paramount in minimising the potential for surgical complications.

Adolescent↗
PubMed2004

Quantitative analysis of plasma cell-free Epstein-Barr virus DNA in nasopharyngeal carcinoma after salvage nasopharyngectomy: a prospective study.

BACKGROUND: The quantity of circulating cell-free Epstein-Barr virus (EBV) DNA in patients with nasopharyngeal carcinoma (NPC) managed by radiotherapy has prognostic relevance. We measured the copy number of EBV DNA in patients with early recurrent NPC before and after salvage nasopharyngectomy. METHODS: Nasopharyngectomy with the maxillary swing approach was performed for 28 patients. Serum blood samples were taken prospectively before nasopharyngectomy and on postoperative day 7. Plasma cell-free EBV DNA copies were measured with a real-time quantitative polymerase chain reaction for the BamHI-W fragment of the EBV genome. RESULTS: Cell-free EBV DNA was detected in 17 patients before nasopharyngectomy. Surgical resection reduced the copy number of EBV DNA significantly (p = .016). Negative surgical margins achieved during nasopharyngectomy is associated with a zero EBV DNA copy postoperatively (p = .022). CONCLUSION: Cell-free EBV DNA was detected in 61% of patients with recurrent NPC, and its quantity postoperatively reflects whether the salvage nasopharyngectomy has achieved a negative surgical margin.

Adult↗
PubMed2004

Pharyngeal entry through the vallecula.

The authors describe a technique of entry into the vallecula with the guide of a small Deaver retractor inserted transorally, beyond the tongue base, into the vallecula. The tip of the Deaver directs the surgeon to the pharyngotomy site and allows pharyngeal entry and access without damaging structures in the region. This technique is particularly useful in total laryngectomy with or without pharyngectomy and is applicable whenever entry to the pharynx through the vallecula is indicated.

Humans↗
PubMed2004

Severe immune haemolysis after standard doses of Penicillin.

Summary Penicillin causes immune haemolytic anaemia by the 'drug-adsorption' mechanism and typically occurs after prolonged exposure to large doses of the drug. Withdrawal of the drug is associated with improved red cell survival and gradual cessation of haemolysis. Although this complication is uncommon, it can be potentially serious. An unusual case is described herein. The patient was exposed to a short course (9 days) of standard dose penicillin but suffered acute severe haemolysis about 1 week after cessation of therapy. A high titre anti-penicillin antibody (1 : 512) not cross-reacting with cephalosporins, was demonstrated. The delay in the development of immune haemolysis vis-à-vis penicillin therapy may be due to the patient being immunologically naive to the drug. Penicillin may persist for weeks in circulation, coating red cells and providing continued antigenic stimulation for the development of anti-penicillin antibody.

Aged↗
PubMed2004

Schwannoma of the larynx-an uncommon cause of vocal cord immobility.

We present a rare case of schwannoma of the larynx in a 26-year-old Chinese patient. The tumour was excised using a lateral thyrotomy approach, with satisfactory restoration of laryngeal function. The presentation, management, and outcome of treatment for this type of tumour are discussed.

Adult↗
PubMed2003

Fibrous dysplasia masquerading as extramedullary relapse after bone marrow transplantation for chronic myeloid leukemia.

A 19-year old girl suffered from relapse of chronic myeloid leukemia (CML) after bone marrow transplantation. The disease was controlled by interferon and imatinib mesylate, but was complicated by autoimmune hyperthyroidism. She presented with unilateral proptosis with no extraocular muscle or visual defect at 26 months follow-up. Systemic investigations showed no recurrence of leukemia or thyrotoxicosis. Magnetic resonance imaging revealed an extensive retro-orbital base of skull lesion. A trans-oral biopsy showed fibrous dysplasia and continuous observation was advised. The unusual sequence of events and the differential diagnoses for unilateral proptosis in post bone marrow transplantation (BMT) cases are discussed.

Adult↗
PubMed2002

Clinicopathologic significance of bcl-2 expression in the surgical treatment of oral tongue carcinoma.

AIM: There is still controversy on the incidence of positive expression of bcl-2 and its prognostic significance for oral tongue carcinoma patients who are treated by surgery. The present study aims at resolving the controversy on the clinicopathologic significance of bcl-2 in a well selected group of patients who satisfy the recruitment criteria: (1) oral tongue carcinoma, (2) squamous cell carcinoma, (3) primary surgical treatment. METHOD: Bcl-2 expression was studied by immunohistochemistry on glossectomy specimens of 73 patients. The expression of bcl-2 was correlated with clinicopathologic data. RESULTS: Of the 73 tumours, 11% had positive expression of bcl-2. Bcl-2 expression was not significantly correlated with tumour grade, stage, nodal metastasis and survival. CONCLUSION: Bcl-2 expression played a minor role in oral tongue carcinoma. It had no significant correlation with tumour grade, stage and nodal metastasis. It also had no prognostic value on survival for patients who were treated by primary surgery.

Adolescent↗
PubMed2002

Analysis of Clonality in Kimura's Disease.

Kimura's disease is a chronic inflammatory disorder of unknown etiology. A 62-year-old man presented with asymptomatic cervical lymphadenopathy associated with eosinophilia and increased serum immunoglobulin E. Excision biopsy showed Kimura's disease. Three years later another groin lymph node appeared and showed similar pathologic features. Polymerase chain reaction for Ig heavy chain and T-cell receptor (TCR) genes on DNA extracted from the cervical lymph node showed smear patterns. However, polymerase chain reaction for TCRdelta gene showed a clonal rearrangement. Sequencing showed a complete VDJ rearrangement (Vdelta1-N-Ddelta2-N-Jdelta), confirming the presence of a clonal T cell population. The same clonal TCRdelta rearrangement was amplified by polymerase chain reaction from the groin lymph node biopsied 3 years later. These results showed that the primary and recurrent lesions were biologically related. Furthermore, the presence of identical T cell clones in different sites and at different times suggested that a clonal T cell population might have contributed to the pathogenesis in this case of Kimura's disease.

Angiolymphoid Hyperplasia with Eosinophilia↗
PubMed2002

Microvascular free tissue reconstruction following extirpation of head and neck tumour: experience towards an optimal outcome.

Familiarity with four types of free tissues transfers allows appropriate reconstruction of most defects in the head and neck region functionally and aesthetically. These include jejunal graft, radial forearm, rectus abdominus myocutaneous and fibula osteocutaneous flaps. Free colonic and gastric patches were used occasionally. We report our experience of 215 free tissue transfers for reconstruction of defects in the head and neck region after tumour extirpation. The overall success rate was 94 per cent. The commonest cause of failure was related to arterial inflow (70 per cent). Three patients died in hospital, but their mortality was not related to the tissue transfers. Complications due to free tissue transfer at both the donor and recipient sites were few and manageable. The co-operation between the two surgical teams, together with the timely application of suitable salvage procedures, contribute to an optimal outcome.

Adolescent↗
PubMed2001

The predictive value of the 1997 American Joint Committee on Cancer stage classification in determining failure patterns in nasopharyngeal carcinoma.

BACKGROUND: A retrospective analysis of treatment outcomes in patients with nasopharyngeal carcinoma (NPC) was performed in which the newly revised 1997 American Joint Committee on Cancer (AJCC) stage classification was applied and compared with the 1988 AJCC and Ho stage classifications, with emphasis on the predictive value of different staging systems in determining failure patterns in NPC. METHODS: Three hundred and twenty-four patients with newly diagnosed NPC treated between September 1989 and August 1991 and originally staged according to Ho stage classification were re-staged according to the 1988 and 1997 AJCC stage classifications. In addition to stage grouping, patients were also classified into the following prognostic categories to study the failure patterns: early disease group (T1-2N0-1), advanced local disease group (T3-4N0-1), advanced nodal disease group (T1-2N2-3), and advanced locoregional disease group (T3-4N2-3). The overall survival (OAS), relapse-free survival (RFS), local relapse-free survival, nodal relapse-free survival, and distant metastases-free survival were compared among different stage groups and prognostic categories in the three staging systems. RESULTS: In the new AJCC system, the percentages of patients with Stage I, II, III, and IV disease were 15.1%, 31.5%, 28.1%, and 25.3%, respectively, whereas most patients were classified as having Stage IV disease (65.7%) in the old AJCC system and Stage II or III disease (74.1%) in the Ho system. The 5 year OAS rates in the 1997 AJCC Stage I, II, III, and IV disease were 97.7%, 78.7%, 79.5%, and 61.4%, respectively. The corresponding 5 year RFS rates were 95.7%, 64.7%, 54.5%, and 41.1%. Using the 1997 AJCC system to define the four prognostic categories, the early disease group had the lowest incidence of relapse (27.6%) and death (18.4%), whereas the advanced locoregional disease group had the highest incidence of relapse (61.4%) and death (43.2%). Both the advanced local disease group and the advanced nodal disease group had similar rates of relapse (46.7% vs. 47.2%), but local relapse was the major cause of failure in the former group (61.8%), whereas distant metastases was the major cause in the latter group (44%). CONCLUSIONS: Using the 1997 AJCC staging system, the authors observed a better distribution of patient numbers as well as segregation of survival curves among different stage groups. Moreover, prognostic categories with distinct prognosis and failure patterns were definable by the new system, which has important implications in selecting appropriate patient treatment strategies.

Adult↗
PubMed2001

Ca2+-dependent membrane currents in vascular smooth muscle cells of the rabbit.

The membrane potential in vascular smooth muscle cells contributes to the regulation of cytosolic [Ca2+], which in turn regulates membrane potential by means of Ca2+i-dependent ionic currents. We investigated the characteristics of Ca2+i-dependent currents in rabbit coronary and pulmonary arterial smooth muscle cells. Ca2+i-dependent currents were recorded using the whole-cell patch-clamp technique while cytosolic [Ca2+] was increased by caffeine. The reversal potentials of caffeine-induced currents were between -80 and -10 mV under normal ionic conditions, whereas they were about 0 mV when K+-free NaCl solutions were used both in pipette and bath. The total substitution of extracellular Na+ with membrane-impermeable cation N-Methyl-D-glucamine did not affect caffeine-induced currents, implying no significant contribution of Na+ as a permeant ion to the currents. The substitution of extracellular NaCl with sucrose reduced outward component of the currents and shifted the reversal potentials according to the change in Cl- equilibrium potential. Upon application of the niflumic acid under K+-free conditions, most of the current induced by caffeine was inhibited. Taken together, the results of the present study indicate that K+ and Cl- currents are major components of Ca2+i-dependent currents in vascular smooth muscles isolated from coronary and pulmonary arteries of the rabbit, and the relative contribution of each type of current to total currents are not different between the two arteries.

Animals↗
PubMed2001

High-performance liquid chromatographic method for simultaneous determination of hawthorn active components in rat plasma.

A simple HPLC method with photodiode-array (PDA) ultraviolet detection was developed for the simultaneous determination of four active polyphenol components of hawthorn (Crataegus), chlorogenic acid, epicatechin, hyperoside and isoquercitrin, in rat plasma. Following extraction from the plasma samples with ethyl acetate-methanol (2:1, v/v), these four compounds were successfully separated using a C18 column with a gradient elution of 5 and 25% acetonitrile in 25 mM phosphate buffer (pH 2.4). The flow-rate was set at 1 ml/min and the eluent was detected at 325 nm for chlorogenic acid, 278 nm for epicatechin, and 360 nm for both hyperoside and isoquercitrin. Narignin (0.82 microg) was used as the internal standard and was detected at 278 nm. The method is linear over the studied range of 0.16-40, 0.63-160, 0.13-32 and 0.13-30 microg/ml for chlorogenic acid, epicatechin, hyperoside and isoquercitrin, respectively. The correlation coefficient for each analyte was greater than 0.995. The intra-day and inter-day precision of the analysis was better than 4 and 7%, respectively. The extraction recoveries at low to high concentration were greater than 85% for both epicatechin and chlorogenic acid, and greater than 94% for both hyperoside and isoquercitrin. The detection limits were 0.04, 0.20, 0.03 and 0.03 microg/ml for chlorogenic acid, epicatechin, hyperoside and isoquercitrin. The developed method was used to analyze the plasma concentrations of the four analytes after the intravenous administration of hawthorn polyphenol extract to rats.

Animals↗
PubMed2001

Inhibition of acetylcholine-activated K(+) current by chelerythrine and bisindolylmaleimide I in atrial myocytes from mice.

The effects of the protein kinase C inhibitors chelerythrine and bisindolylmaleimide I on acetylcholine-activated K+ currents (I(KACh)) were examined in atrial myocytes of mice, using the patch clamp technique. Chelerythrine and bisindolylmaleimide I inhibited I(KACh) in a reversible and dose-dependent manner. Half-maximal effective concentrations were 0.49+/-0.01 microM for chelerythrine and 98.69+/-12.68 nM for bisindolylmaleimide I. However, I(KACh) was not affected either by calphostin C, which is also known as a protein kinase C inhibitor, or by a protein kinase C activator, phorbol 12,13-dibutyrate. When K(ACh) channels were activated directly by adding 1 mM GTPgammaS to the bath solution in inside-out patches, chelerythrine (10 microM) decreased the open probability from 0.043+/-0.01 to 0.014+/-0.007 (n=5), but bisindolylmaleimide I did not affect the channel activity. From these results, it is concluded that both chelerythrine and bisindolylmaleimide I inhibit K(ACh) channels independently of protein kinase C inhibition, but the level of inhibition is different.

Acetylcholine↗
PubMed2001

Modulation of ATP-sensitive potassium channels by cGMP-dependent protein kinase in rabbit ventricular myocytes.

This investigation used a patch clamp technique to test the hypothesis that protein kinase G (PKG) contributes to the phosphorylation and activation of ATP-sensitive K(+) (K(ATP)) channels in rabbit ventricular myocytes. Nitric oxide donors and PKG activators facilitated pinacidil-induced K(ATP) channel activities in a concentration-dependent manner, and a selective PKG inhibitor abrogated these effects. In contrast, neither a selective protein kinase A (PKA) activator nor inhibitor had any effect on K(ATP) channels at concentrations up to 100 and 10 microm, respectively. Exogenous PKG, in the presence of both cGMP and ATP, increased channel activity, while the catalytic subunit of PKA had no effect. PKG activity was prevented by heat inactivation, replacing ATP with adenosine 5'-O-(thiotriphosphate) (a nonhydrolyzable analog of ATP), removing Mg(2+) from the internal solution, applying a PKG inhibitor, or by adding exogenous protein phosphatase 2A. The effects of cGMP analogs and PKG were observed under conditions in which PKA was repressed by a selective PKA inhibitor. The results suggest that K(ATP) channels are regulated by a PKG-signaling pathway that acts via PKG-dependent phosphorylation. This mechanism may, at least in part, contribute to a signaling pathway that induces ischemic preconditioning in rabbit ventricular myocytes.

Adenosine Triphosphate↗