Search PubMed⌕ Search

Biomedical subjects

K Y Chan

Publications and source records attributed to K Y Chan.

At least 55 records · Page 3Linked to original sources
PubMed2000

Posterior fossa subdural hematoma due to ruptured arteriovenous malformation. Case report.

Patients with cerebellar arteriovenous malformations (AVM) commonly present to the neurosurgical department after having suffered hemorrhages. The subarachnoid space is the usual location for these often repeating episodes of bleedings. In addition, these patients can present with parenchymal hemorrhage. Acute subdural hematoma caused by a ruptured cerebellar AVM is a rare entity and is not generally recognized. The authors present a case of acute posterior fossa subdural hematoma resulting from a ruptured cerebellar AVM.

Aneurysm, Ruptured↗
PubMed2000

Mutational analysis of BRCA1 and BRCA2 genes in Chinese ovarian cancer identifies 6 novel germline mutations.

Germline mutations in the BRCA1 and BRCA2 genes predispose women to breast and ovarian cancer. An incidence of 5% and 3.3% respectively has been reported of BRCA1 and BRCA2 mutations in women with ovarian cancer unselected for family history. The contribution of BRCA1 and BRCA2 mutations to ovarian cancer in Chinese women is unknown. A total of 60 samples of ovarian cancer diagnosed in Chinese unselected for age or family history were analyzed for BRCA mutations using the protein truncation test. The entire coding exon of BRCA1 of 53 cases and that of exon 11 of BRCA2 of 43 cases were successfully screened. Six germline (11.3%) mutations (633C>T, 1080delT, 1129delA, 2371-2372delTG, 3976-3979delGTGA, and IVS 22+7 A>G) were detected in BRCA1. One germline mutation (3337C>T) (2.1%) was detected in BRCA2. None of these seven cases were associated with strong family history of breast and/or ovarian cancer. Five out of our six BRCA1 mutations and the one BRCA2 mutation identified are novel. Our 11.3% incidence of BRCA1 mutations in ovarian cancer found amongst Chinese with insignificant family history is apparently higher than that previously reported in other populations. It suggests that BRCA1 mutation may play a significant role in the development of sporadic ovarian cancer in Chinese women.

Adult↗
PubMed2000

Recurrent and novel mutations of GCDH gene in Chinese glutaric acidemia type I families.

Glutaric acidemia type I is caused by mutations of the glutaryl-CoA dehydrogenase (GCDH) gene resulting in loss of GCDH enzyme activity. Patients present with progressive dystonia and lesions in basal ganglia. Dietary treatment, when instituted from the early neonatal period, markedly reduces dystonia and morbidity. Early diagnosis and prenatal diagnosis will be facilitated by knowledge of locally prevalent GCDH mutations. Several common GCDH mutations have been found in different ethnic groups. GCDH mutations were studied in 5 Chinese glutaric acidemia type I families. We detected two novel recurrent mutations (A219T and IVS10-2A>C) which were found in two unrelated families. An asymptomatic carrier of IVS10-2A>C was also found on screening of 120 individuals. Other mutations were identified, including two other novel (R386G & IVS3+1G>A) and two known mutations (G178R & R355H). Fibroblasts from patients carrying the novel mutations were confirmed to be deficient for GCDH activity. This is the first report of GCDH mutations describing recurrent mutations in Chinese patients. The carrier rate of IVS10-2A>C may be particularly high in Chinese.

Alternative Splicing↗
PubMed2000

Quantification of bacterial adhesion forces using atomic force microscopy (AFM).

This study demonstrated that atomic force microscopy (AFM) can be used to obtain high-resolution topographical images of bacteria, and to quantify the tip-cell interaction force and the surface elasticity. Results show that the adhesion force between the Si3N4 tip and the bacteria surface was in the range from -3.9 to -4.3 nN. On the other hand, the adhesion forces at the periphery of the cell-substratum contact surface ranged from -5.1 to -5.9 nN and those at the cell-cell interface ranged from -6.5 to -6.8 nN. The two latter forces were considerably greater than the former one, most likely due to the accumulation of extracellular polymer substance (EPS). Results also show that the elasticity varied on the cell surface.

Aluminum Silicates↗
PubMed2000

Heart rate variability of children with mitral valve prolapse.

Studies have indicated that adult patients with mitral valve prolapse (MVP) may have autonomic dysfunction. The purpose of this study was to evaluate heart rate variability (HRV) in children with MVP. Sixty-seven children with MVP (ages 6 to 18 years; 30 boys and 37 girls) were consecutively studied and subdivided into those with or without symptoms. Thirty-seven normal age-matched children (17 boys and 20 girls) were studied as controls. The patients were further divided into 4 age subgroups. HRV was measured using a 24-hour Holter electrocardiogram (ECG) system (Laser SXP Holter Analysis System, Marquette Electronics, Milwaukee, WI). The ECGs were analyzed in both time domain and frequency domain (spectral analysis). Symptomatic and asymptomatic children with MVP were combined for analysis because they were not significantly different in terms of their HRV. All time-domain indices, with the exception of SDANN (SD of the mean of RR intervals in all 5-minute segments of the 24-hour ECG), were significantly lower in children with MVP than in controls. Children with MVP showed significantly lower spectral power of the high frequency (HF) and low frequency (LF) components when compared with controls. The ratio of LF to HF (LF/HF) was significantly higher in children with MVP. Similar differences were observed in the 4 age subgroups. Sex differences in HRV were observed when girls had lower HRV compared with boys. Lower time-domain and frequency-domain indices of HRV in children with MVP are suggestive of decreased parasympathetic activity and a shift in sympathovagal balance. Various factors including differences in heart rate may contribute to sex differences in HRV.

Adolescent↗
PubMed2000

Concomitant radiotherapy and chemotherapy for early-stage nasopharyngeal carcinoma.

PURPOSE: Early-stage nasopharyngeal carcinoma (NPC) continues to carry a failure rate of 15% to 30% when treated with radiotherapy alone; the benefit of concomitant radiotherapy and chemotherapy (CCRT) in early-stage NPC is unclear. The purpose of this report is to describe our efforts to improve treatment outcome in early-stage NPC after CCRT. PATIENTS AND METHODS: Of 189 newly diagnosed NPC patients without evidence of distant metastases who were treated in our institution between 1990 and 1997, 44 presented with early-stage (stage I and II) disease according to the American Joint Committee on Cancer (AJCC) 1997 NPC staging system. Twelve of these patients were treated with radiotherapy alone and 32 with CCRT. Each patient's head and neck area was evaluated by magnetic resonance imaging or computed tomography. Radiotherapy was administered at 2 Gy per fraction per day, Monday through Friday, for 35 fractions for a total dose of 70 Gy. Chemotherapy consisting of cis-diamine-dichloroplatinum and fluorouracil was delivered simultaneously with radiotherapy in weeks 1 and 6 and sequentially for two monthly cycles after radiotherapy. RESULTS: Patients who were treated with radiotherapy alone primarily had stage I disease, whereas none of those who were treated with CCRT had stage I disease (11 of 12 patients v none of 32 patients; P =.001). The locoregional control rate at 3 years for the radiotherapy group was 91.7% (median follow-up period, 34 months) and was 100% for the CCRT group (median follow-up period, 44 months) (P =.10). The 3-year disease-free survival rate in the radiotherapy group was 91.7% and was 96.9% in the CCRT group (P =.66). CONCLUSION: Our results reveal excellent prognosis of AJCC 1997 stage II NPC treated with CCRT. Stage II patients with a greater tumor burden treated with CCRT showed an equal disease-free survival, compared with stage I patients treated with radiotherapy alone. A prospective randomized trial is underway to confirm the role of CCRT in stage II NPC.

Adult↗
PubMed2000

Safety and effectiveness of percutaneous fluoroscopic gastrostomy in cancer patients.

PURPOSE: To evaluate the safety and effectiveness of percutaneous fluoroscopic gastrostomy (PFG) in cancer patients. METHODS: We retrospectively analyzed the success rate, complication rate, and patient outcomes of PFG performed during a 15-month period in our hospital. The Cope type 10-French and 12-French self-retaining catheters were used for gastrostomy. RESULTS: Of the 113 PFG procedures requested during the study period, 112 (99.1%) were performed successfully; one procedure was cancelled because the nasogastric tube could not be passed through the obstructed esophagus. Thirty-day follow-ups were obtained for 92.0% of the procedures. Of the patients with at least 30 days of follow-up, eight (7.8%) died, but only two deaths (1.9%) were procedure-related. Major complications, including peritonitis and severe wound infection, occurred after eight procedures (7.8%). Minor complications, including superficial wound infection, tube fracture, leakage, severe pain, mild hemorrhage, and tube migration, occurred after 23 procedures (22.3%). The severity of pneumoperitoneum was significantly associated with the frequency of complications (p < 0.05). After placement of the gastrostomy, 68% of the patients maintained or increased their initial body weight; 28% lost 10% or less of their body weight; and 4% lost more than 10% of their body weight. CONCLUSIONS: PFG appears to be effective and relatively safe for long-term nutritional support in cancer patients.

Adult↗
PubMed2000

Interferon treatment for multiple sclerosis patients in Hong Kong.

We report on nine patients with multiple sclerosis who had received interferon beta-1a treatment for 6 months or more. Seven patients were Chinese and two were Caucasian. Seven patients had the relapsing-remitting type of multiple sclerosis, one had the primary-progressive type, and one had the progressive-relapsing type. Among the six compliant patients with the relapsing-remitting type of disease, four had less frequent relapses after treatment. This study could not show whether or not the use of interferon beta-1a was beneficial to non-compliant patients, or patients with other types of multiple sclerosis.

Adolescent↗
PubMed1999

Survival of a 30-week baby with congenital myotonic dystrophy initially ventilated for 55 days.

In previous reports, duration of initial ventilation exceeding 1 month almost always predicts non-survival of babies with congenital myotonic dystrophy. However, a baby with this condition survived beyond infancy after 55 days' ventilation. We describe this case in detail, explain why the baby survived and highlight the importance of individualized assessment, in addition to applying general prognostic terms described in the literature.

Bronchopulmonary Dysplasia↗
PubMed1998

Prognostic features and treatment outcome in locoregionally advanced nasopharyngeal carcinoma following concurrent chemotherapy and radiotherapy.

PURPOSE: Concurrent chemotherapy and radiotherapy (CCRT) are effective in treatment of locoregionally advanced nasopharyngeal carcinoma (NPC). However, the prognostic factors after CCRT have not been evaluated. We therefore attempt to evaluate factors that influence treatment outcomes following CCRT. METHODS AND MATERIALS: Seventy-four (5 in stage III and 69 in stage IV) patients with locoregionally advanced NPC were treated with CCRT. Radiotherapy was delivered either at 2 Gray (Gy) per fraction per day up to 70 Gy or 1.2 Gy, 2 fractions per day, up to 74.4 Gy. Concurrent chemotherapy consisted of cisplatin and 5-fluorouracil. Cox proportional-hazards model was used to analyze the prognostic factors which included age, gender, pathologic type, T, N, lactate dehydrogenase (LDH), and infiltration of the clivus. RESULTS: The primary tumor control rate at 3 years was 96.7% (95% confidence interval [CI]: 92.5-100), distant metastasis-free survival 81.1% (95% CI: 70.6-91.6), disease-free survival 77.0% (95% CI: 65.3-88.7), and overall survival 79.8% (95% CI: 69.2-90.4) with a median follow-up interval of 29 months (range 15-74 months). Cox proportional-hazards model revealed that infiltration of the clivus and serum level of LDH before treatment were the most two important factors that predict distant metastases. Infiltration of the clivus and the serum LDH level greater than 410 U/L were strongly associated with distant metastasis-free survival (p = 0.0004 and p = 0.0002, respectively). When these two risk factors were considered together, no distant metastasis was observed in 40 patients with both intact clivus and LDH < or = 410 U/L. On the contrary, 13 of the remaining 34 patients with at least one risk factor developed distant metastasis (p = 0.0001). CONCLUSION: Our study demonstrates that CCRT can improve the primary tumor control of 96.7% and disease-free survival of 77.0% at 3-year follow-up. Distant metastasis, however, is the major cause of failure. Infiltration of the clivus by the tumor and LDH greater than 410 U/L are the two independent and useful prognostic factors in patients with locoregionally advanced NPC who were treated with CCRT. Good- and poor-risk patients can be distinguished by virtue of their having both conditions.

Adult↗
PubMed1998

Diagnostic thoracic-computed tomography in radiotherapy for loco-regional recurrent breast carcinoma.

PURPOSE: This study was initiated to evaluate whether pretreatment diagnostic thoracic CT scan was useful for patients with loco-regional recurrent breast carcinoma, and to assess its impact on the design of radiotherapeutic treatment. METHODS AND MATERIALS: Between March 1991 and January 1997, 44 patients underwent thoracic CT examination with contrast material before the consideration of radiotherapy for their isolated loco-regional recurrent breast carcinoma. The CT radiographs were prospectively reviewed for additional findings clinically undetected by prior physical examination and plain-chest radiograph. The changes made in treatment design and dosage of radiation as a result of CT findings were recorded for analysis. The correlation between prognostic indicators and the CT findings was also studied. RESULTS: Twenty-two of 44 (50%) patients were found to have additional abnormalities detected only after thoracic CT examinations were performed. The strategy of radiation therapy was altered in 17 of 22 (77%) patients as a result. Patients with shorter disease-free interval (p = 0.08) and multiple sites of recurrence (p = 0.05) tended to have greater numbers of findings on CT scan previously unsuspected. Thus, CT scan is a valuable guide to treating loco-regional recurrent disease. CONCLUSION: Pretreatment diagnostic thoracic CT scan offers essential information that can alter treatment planning and thus optimize treatment strategy for a large proportion of patients with clinically isolated loco-regional recurrent breast carcinoma. In this population of patients we recommend that thoracic CT examination be considered before the initiation of radiation therapy.

Breast Neoplasms↗
PubMed1998

Value of abdominal sonography in the assessment of children with abdominal pain.

PURPOSE: We retrospectively evaluated the usefulness of sonography in the diagnostic assessment of children with abdominal pain. METHODS: From July 1988 to October 1996, 676 children who had abdominal pain and were referred for sonography underwent abdominal and pelvic sonographic examination. Of these, 644 children had recurrent abdominal pain (RAP) and 32 children had acute or subacute abdominal pain (ASAP). The mean ages and relative risks of underlying abnormalities were calculated for children with RAP and ASAP. RESULTS: Abdominal abnormalities were sonographically detected in 10 children with RAP (2%), a significantly lower incidence than in children with ASAP (56%, p < 0.0001), with a relative risk of 0.028 (95% CI, 0.014-0.055). In the RAP group, an underlying abnormality was more likely (p < 0.001) to be sonographically detected in children who had atypical clinical features (5 of 46%; 11%) than in those with typical clinical features (5 of 598; 1%), with a relative risk of 12.94 (95% CI, 3.90-43.30). Children with RAP were found to have hydronephrosis (3), urinary cystitis (2), duplex kidney (1), hypoplastic low-lying kidney (1), choledochal cyst (1), ovarian teratoma (1), and gross gaseous distention with fecal masses (1). Children with ASAP had urinary cystitis (4), intussusception (2), appendicitis (2), appendiceal abscess (1), perforated gut with ascites (1), gut duplication (1), thickened gut wall with fluid from severe gastroenteritis (1), gross gaseous distention with fecal masses (1), hepatosplenomegaly (1), cholecystitis (1), gross hydronephrosis (1), Wilms' tumor (1), and abdominal neuroblastoma (1). CONCLUSIONS: Abdominal sonography is useful in children with ASAP. Although an underlying abnormality was rarely found in children with RAP, children who have RAP with atypical clinical features should have sonographic screening. If no abnormalities are found, the normal sonograms may be reassuring to parents.

Abdomen, Acute↗
PubMed1998

Reversible dementia due to dural arteriovenous fistula: a simple surgical option.

Dural AVMs can produce a wide variety of symptoms related to raised intracranial pressure, venous congestion, and cerebral ischaemia. We present a unique case of reversible dementia, due to venous hypertension. The cerebral ischaemia was caused by extensive bilateral arteriovenous malformations of the external carotid system, which drained into the superior sagittal and transverse sinuses and resulted in venous hypertension. Although partial occlusion by endovascular embolization and ligation procedures had some effect, only 'scalping and silastic implantation' gave satisfactory amelioration of symptoms.

Aged↗
PubMed1998

New method to measure the retention of viscoelastic agents on a rabbit corneal endothelial cell line after irrigation and aspiration.

PURPOSE: To quantify the surface retention of several ophthalmic viscoelastic agents following irrigation and aspiration (I/A) using a new in vitro method. SETTING: Alcon Laboratories, Inc., Fort Worth, Texas, USA. METHODS: A rabbit corneal endothelial cell line was cultured to confluency in 24-well plates, and the cells were labeled quantitatively with internalized neutral red dye. Five ophthalmic viscoelastic agents were applied to cover the monolayer of cells: sodium hyaluronate (Healon, Provisc, and Amvisc Plus), Formulation A (a dispersive, nonproteinaceous, synthetic polymer), and sodium chondroitin sulfate, sodium hyaluronate (Viscoat). Irrigation and aspiration (with fluid turbulence similar to that encountered in phacoemulsification surgery) were performed on each well for 3 minutes, using 120 mL of balanced salt solution with bicarbonate. dextrose, and glutathione (BSS Plus). The cells were treated with an acidified ethanol solution to extract the dye from the cells left without a viscoelastic cover. The extracted dye was measured by spectrophotometry and compared with the total dye recovered from control cells. RESULTS: The retention value, which represented the percentage of cells with viscoelastic retained on the surface, was calculated as follows: Healon, 7; Provisc, 16; Amvisc Plus, 17; Formulation A, 55; Viscoat, 90. On a nonadsorptive, non-cell surface, the retention values of the five viscoelastics were significantly less than those on cells. CONCLUSION: The results of this experimental model suggest that cohesive viscoelastics are readily removed from the cells, while dispersive viscoelastics are highly retained. In addition, mutual surface interaction (electrical charge and other properties) plays a significant role in determining the retention of viscoelastics on the corneal endothelial cell surface following I/A.

Animals↗
PubMed1998

In vitro adherence of Pseudomonas aeruginosa to four intraocular lenses.

PURPOSE: To compare the relative degrees of adherence of a clinical strain of Pseudomonas aeruginosa to the optic material of four intraocular lenses (IOLs). SETTING: Center for Applied and Environmental Microbiology, Georgia State University, Atlanta, Georgia, USA. METHODS: Intraocular lens optics made of poly(methyl methacrylate) (PMMA), AcrySof-acrylic, and silicone were included in this study. The IOLs were incubated in a minimal medium with cells of P. aeruginosa for 2 hours and 18 hours. Cells in the 2 hour experiment were prelabeled with 3H-leucine; those in the 18 hour experiments were postlabeled. After rinsing the IOLs to remove loosely adherent cells, we determined the number of cells adhered to coded lenses from calibration curves of disintegrations per minute versus cells per square millimeter. Additional lenses were incubated with P. aeruginosa and examined with scanning electron microscopy. RESULTS: The adherence of P. aeruginosa in order of increasing magnitude was AcrySof-acrylic < PMMA < silicone 1 < silicone 2. The differences between all groups were statistically significant. The scanning electron microscopy observations were in general agreement with the radiolabel studies. CONCLUSIONS: The AcrySof-acrylic IOL was less susceptible to primary adherence and 18 hour biofilm formation by P. aeruginosa than the PMMA and silicone IOLs, indicating that this material reduced pseudomonad adherence and the risk of endophthalmitis following cataract surgery.

Acrylates↗
PubMed1998

Quantitative method to determine the cohesion of viscoelastic agents by dynamic aspiration.

PURPOSE: To quantitatively determine the cohesion of ophthalmic viscoelastic agents using an in vitro method based on dynamic aspiration kinetics. SETTING: Alcon Laboratories, Inc., Fort Worth, Texas, USA. METHOD: Five viscoelastic agents were tested: Healon GV (sodium hyaluronate 1.4%); Provisc (sodium hyaluronate 1.0%); Healon (sodium hyaluronate 1.0%); Amvisc Plus (sodium hyaluronate 1.6%); Viscoat (sodium hyaluronate 3.0%-chondroitin sulfate 4.0%). Samples were placed into a tared polypropylene container using a positive displacement pipette. Calibrated vacuum was applied for 2 seconds to a polypropylene tip (inner diameter 0.5 mm) lowered into the viscoelastic sample. The quantity of viscoelastic agent remaining in the container after aspiration was determined gravimetrically. The procedure was repeated at various vacuum levels between 100 and 700 mm Hg. The percentage of viscoelastic agent aspirated was plotted against vacuum pressure. The slopes of these curves indicate the relative cohesion of the viscoelastic sample. RESULTS: The cohesion-dispersion indices (percentage viscoelastic agent aspirated/100 mm Hg) were Healon GV (72.3) > Provisc (46.0) > Healon (31.2) = Amvisc Plus (21.4) > Viscoat (3.4). CONCLUSION: The method provided a quantitative basis for the clinical classification of viscoelastic materials as cohesive or dispersive. The aspiration kinetics profile (curve shape), maximum rate of removal, and vacuum levels at which the bolus removal of the viscoelastic agent started (break point) were useful in characterizing the viscoelastic agents. Because the results agree with the clinical impression of cohesion/dispersion, this method may be used to predict the surgical performance of viscoelastic agents.

Adhesiveness↗