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Biomedical subjects

W F Chan

Publications and source records attributed to W F Chan.

At least 19 recordsLinked to original sources
PubMed2005

Resection of phaeochromocytoma extending into the right atrium in a patient with multiple endocrine neoplasia type 2A.

We report the first case of successful surgical resection of a malignant phaeochromocytoma with tumour extension into vena cava and right atrium in a patient with multiple endocrine neoplasia type 2A. A 21-year-old woman with genetic confirmation of multiple endocrine neoplasia type 2A syndrome was diagnosed with a very rare case of malignant phaeochromocytoma with tumour thrombus extension into vena cava and right atrium causing Budd-Chiari syndrome. It posed a challenge to the surgeons with regard to complete tumour resection and vascular control. Reviewing the limited literature, surgical resection by means of cardiopulmonary bypass with hypothermic circulatory arrest has been reported with success in phaeochromocytoma with advance vascular involvement. Adopting this approach, adrenalectomy with complete thrombus excision by inferior vena cava exploration and right atriotomy were performed successfully by a multidisciplinary team.

Adrenal Gland Neoplasms↗
PubMed2004

Multiple endocrine neoplasia type 2B in a Chinese patient.

Multiple endocrine neoplasia type 2B syndrome is rarely reported in Chinese patients. A 25-year-old Chinese male presented with full-blown clinical features of this syndrome, including bilateral phaeochromocytomas, medullary thyroid carcinoma, and characteristic phenotypic features. One-stage surgical treatment was performed and subsequent genetic analysis confirmed a point mutation at codon 918 in exon 16 of the RET proto-oncogene. The mutation was arising de novo as there was no corresponding mutation found in both his parents or younger sister. Data published to date suggest there is no difference in the genetic and pathophysiologic basis, nor clinical characteristics of multiple endocrine neoplasia type 2B in Chinese patients. As the disease can be lethal, early diagnosis by prompt recognition of the characteristic phenotypic features followed by surgical treatment should improve the outcome. Family screening is essential to identify at-risk family members for prophylactic treatment.

Adrenalectomy↗
PubMed2003

Minimally invasive endoscopic-assisted parathyroidectomy for primary hyperparathyroidism.

BACKGROUND: Minimally invasive surgery for primary hyperparathyroidism (pHPT) depends on both an accurate preoperative localization and the availability of intraoperative parathyroid hormone monitoring. METHODS: Patients with sporadic pHPT and one unequivocally enlarged parathyroid gland on preoperative imaging underwent endoscopic-assisted parathyroidectomy. Intraoperative rapid parathyroid hormone (quick PTH) monitoring was performed, and surgical success was confirmed when there was a >50% decrease in quick PTH level 10 min after excision as compared with the baseline level at induction. The surgical outcome and the use of preoperative localization, together with the role played by quick PTH assay in enhancing the operative success, were evaluated. RESULTS: From 1999 to 2002, 66 of 107 patients (62%) were selected for this approach. The accuracy of 99mTc-Sestamibi scintigraphy and ultrasonography was 97% and 70%, respectively. Conversion was required in four cases due to technical problems, and four additional patients failed to show a significant decline in quick PTH levels postexcision. Two patients underwent cervical exploration without the finding of any additional pathology, and another two patients had a delayed drop in quick PTH that was confirmed 30 min postexcision. All patients had a solitary adenoma and were cured of hypercalcemia during a median follow-up of 9 months. CONCLUSIONS: Minimally invasive endoscopic-assisted parathyroidectomy can be performed expeditiously in a select group of patients based on 99mTc-Sestamibi scintigraphy. The use of quick PTH assay can ensure surgical success, but careful interpretation of the results is mandatory.

Adenoma↗
PubMed2003

Duplex ultrasonography after total hip or knee arthroplasty.

We prospectively studied all patients admitted for total hip (THR) or knee (TKR) arthroplasty from July 2000 to February 2001. No pharmacological anticoagulation was given. All patients received a standardized postoperative rehabilitation regimen. Forty-six patients with known risk factors for deep vein thrombosis (DVT) were excluded. Eighty patients were studied (22 THR, 58 TKR; 55 women, 25 men). Mean age was 68 (30-90) years. Duplex ultrasonography on both lower limbs was performed on days 5-7 postoperatively. Location and extent of any thrombus were documented. In patients with distal DVT, a follow-up scan was done on days 10-14. If proximal propagation was observed, patients received full anticoagulation. If no propagation was detected, the distal thrombus was considered stable and clinical observation was continued. In the THR group, 1/22 and in the TKR group 9/58 were found to have distal DVT. All were asymptomatic. On follow-up scanning, none showed proximal propagation. All patients were followed up for at least 18 months, and none showed postthrombotic symptoms. Isolated distal DVT in "low-risk" Chinese patients after THR or TKR is not uncommon. Clinically they are usually "silent." If routine perioperative pharmacologic antithrombotic prophylaxis is not practiced, monitoring with duplex ultrasonography may need to be considered.

Adult↗
PubMed2003

Deep venous thrombosis after total hip or knee arthroplasty in a "low-risk" Chinese population.

Scarcely any information has been published on deep vein thrombosis (DVT) in Chinese patients after total hip arthroplasty (THA) or total knee arthroplasty (TKA). However, generally, no prophylaxis is given to patients who do not have conventional high-risk factors because they are believed to be at "low risk." We performed a prospective study on 80 such "low risk" patients undergoing THA or TKA (58 TKA and 22 THA) without prophylaxis and performed duplex ultrasonography on both lower limbs 6 to 8 days after surgery. A total of 22 patients (27.5%) showed ultrasonographic evidence of DVT. Eighteen (31%) TKAs and 4 (18.1%) THAs were complicated by DVT. Three patients showed bilateral involvement, all of whom underwent TKA. Two patients had symptomatic pulmonary embolism. The sensitivity and positive predictive value of the clinical examination was 27.2% and 31.6%, respectively. This study showed that patients who are labeled "low risk" for DVT actually had a significant risk and suggests that the current practice of providing prophylaxis to only patients deemed at "high risk" should be revised.

Adult↗
PubMed2000

Defatting of skin flaps using arthroscopic instruments--an effective alternative.

Defatting is often required when skin flaps are transferred to the hand. We present three patients with skin flaps which were defatted using an arthroscopic shaver and a standard suction device. There were no complications and all three patients were satisfied with their outcomes. This method provided an effective treatment for our patients and did not require the purchase of specialised equipment.

Adipose Tissue↗
PubMed1999

Isolation of Deinococcus species from commercial oyster extract.

Deinococci with radiation resistance greater than that of Deinococcus radiophilus (ATCC 27603) were isolated from three commercial oyster extracts stored at 4, 20, and 30 degreesC. During storage the number of other bacteria declined and deinococci became the predominant group in the microflora, particularly at 20 degreesC, although at 30 degreesC the number of deinococci as well rapidly declined. The results suggest that the natural habitat of deinococci is an aerobic environment containing a slightly elevated saline content, soluble protein, and low sugar levels.

Animals↗
PubMed1999

From open to laparoscopic adrenalectomy: a review of 16-year experience.

OBJECTIVE: To review the experience with adrenal surgery which was associated with significant morbidity and notable mortality in the past, although laparoscopic approach is beginning to be accepted as the procedure of choice. METHODS: The indications and results of adrenalectomy in 104 patients (36 men, 68 women) over the past 16 years were reviewed. Any potential improvement of surgical results over time was analyzed. RESULTS: Ninety-three patients (89%) had functional problems while malignancy was present in 11 patients (11%). Anterior approach was employed in 27 patients, posterior in 56, lateral in 10, and laparoscopic in 11. One patient required conversion from laparoscopic to anterior approach. No operative mortality was seen, but the morbidity occurred in 16.7%. Complication rate decreased significantly in this study period (1981-1990 versus 1991-1996, 22% versus 5%; P = 0.02). Laparoscopic adrenalectomy was successfully performed for 59% of the patients requiring adrenalectomy recently, compared to 68% of posterior adrenalectomy in the past. CONCLUSIONS: Adrenal surgery is a safe procedure, associated with acceptable morbidity, which has decreased over time. Laparoscopic adrenalectomy is becoming the preferred approach for the majority of patients requiring adrenalectomy.

Adolescent↗
PubMed1998

Clock-face drawing, reading and setting tests in the screening of dementia in Chinese elderly adults.

Comprehensive neuropsychological batteries focus on the subtle cognitive deficits in dementia, but a brief screening instrument is also of immense practical value. As the clock-drawing test encompasses a number of cognitive domains frequently disturbed by the dementing process, it is considered to be a suitable screening instrument for the disorder. We documented the usefulness of a new scoring method of the clock-drawing test for screening of dementia in the elderly Chinese in Hong Kong. Fifty-three demented individuals and 53 healthy elderly controls were assessed. At a cutoff score of 3/4, the sensitivity and specificity of the clock-drawing test in screening of dementia was 83% and 79%. With a composite test of clock reading and clock setting, the positive predictive value of the clock face test was 98%. This new scoring method of clock-drawing proved to be a valid measure for screening of dementia. It is applicable in non-English speaking populations and should be a useful adjunct for quick screening assessment of dementia.

Aged↗
PubMed1997

Screening for dementia: a preliminary study on the validity of the Chinese version of the Blessed-Roth Dementia Scale.

Blessed-Roth Dementia Scale has been one of the most widely used rating scales in dementia. Previous studies indicated that this behavioral assessment scale is a useful tool for differentiating elderly subjects with no or minimal intellectual decline from those with cognitive deterioration. In the present study, the authors examined the validity of the Chinese version of the Blessed-Roth Dementia Scale (CDS) in Hong Kong. A total of 106 Chinese subjects were recruited from a social center, an old-age home, and psychogeriatric outpatient clinics. At a cutoff score of 3 of 4, the CDS achieved a sensitivity of 90.5% and specificity of 98.1% in differentiating demented from healthy control subjects. In the Chinese population studied, the scale was readily acceptable and considered to be an useful adjunct in screening of dementia.

Aged↗
PubMed1997

Employee stress levels and the intention to participate in a worksite smoking cessation program.

This study examines the nature and extent of the relationship between stress levels and intentions to participate in a worksite smoking cessation program among male current smokers (n = 220) employed in an automobile manufacturing plant. A plantwide survey was conducted which measured job stress, nonjob stress, smoking behavior, and intent to participate. The results of polychotomous logistic regressions suggest that among the current smokers in this plant, job and nonjob stress were positively associated with workers' intentions to participate in a worksite smoking cessation program. Thus, contrary to the popular notion that stress diminishes the motivation to quit, employees under high levels of stress may be most receptive to educational interventions intended to persuade smokers to commit to quitting.

Adult↗
PubMed1997

The modified Fuld Verbal Fluency Test: a validation study in Hong Kong.

Recent studies in the West have found that verbal fluency tests are useful in the detection of dementia. In this study, the Fuld Verbal Fluency Test (FVFT) was modified and tested for its usefulness as a screening instrument for differentiating demented from normal elderly Chinese in Hong Kong. Fifty-three normal and 56 demented subjects were administered the FVFT, the Cantonese version of the Mini-Mental State Examination (CMMSE), and the Chinese version of the Hamilton Depression Rating Scale. In addition to bearing significant correlation with the CMMSE, the verbal fluency scores for all semantic categories (animals, fruits, vegetables) were found to produce significant differentiation between the normal and demented groups. However, test-retest reliability for the individual verbal fluency scores was shown to be unsatisfactory, and a composite measure was recommended for use in future screening on the grounds of its enhanced reliability.

Aged↗
PubMed1994

Trabecular cells express the TGF-beta 2 gene and secrete the cytokine.

We investigated whether trabecular cells contain TGF-beta 2 mRNA and whether they synthesize this cytokine. By using a primer pair for TGF-beta 2 and the highly specific and sensitive techniques of reverse transcriptase-polymerase chain reaction, a single amplified sequence was obtained from cultured trabecular cells and tissue samples of trabecular meshwork, corneal epithelium, iris and ciliary body ex vivo from fresh porcine eyes. Regression analysis with standard DNA size markers indicated that the products were of the anticipated size of 310 base pairs. Southern hybridization further confirmed that all of the products were specific for TGF-beta 2. Enzyme-linked immunosorbent assay (ELISA) with a specific antibody against TGF-beta 2 revealed that this cytokine was secreted by cultured trabecular cells in the conditioned medium. The TGF-beta 2 produced by trabecular cells was in a latent form, and no intrinsically active protein was detected. The results suggest that TGF-beta 2 has an autocrine and/or paracrine action in the trabecular meshwork system, and that trabecular cells could contribute to the presence of TGF-beta 2 in their microenvironment as well as in aqueous humor. It is hypothesized that abnormal changes in the production of TGF-beta s by trabecular cells and/or in the activation of these growth modulators contribute to the excess accumulation of extracellular matrix components in the aqueous outflow system as observed in aging and glaucomatous eyes.

Animals↗
PubMed1994

Aqueous humor in glaucomatous eyes contains an increased level of TGF-beta 2.

By using the highly sensitive and specific technique of enzyme-linked immunosorbent assay, we investigated the presence and amount of transforming growth factor-beta 2 (TGF-beta 2) in samples of aqueous humor obtained from 15 patients who had a clinically established diagnosis of advanced primary open-angle glaucoma (POAG), as well as from ten age-matched normal human subjects undergoing cataract surgery. The total amount of TGF-beta 2 in the samples of normal aqueous humor ranged from 0.41 to 2.24 ng ml-1 (mean +/- S.D.: 1.48 +/- 0.68 ng ml-1) of which 4.88 to 37.05% (11.99 +/- 9.95%) was intrinsically active. Compared with normal subjects, the aqueous humor from POAG patients had a statistically significantly greater amount of total TGF-beta 2 (2.70 +/- 0.76 ng ml-1, P < 0.01), as well as a higher level of intrinsically active TGF-beta 2 (0.45 +/- 0.28 ng ml-1, P < 0.05) which corresponded to 1.09 to 60.84% (18.33 +/- 15.50%) of the total amount. No linear correlation was found between the age of the subjects and the protein concentration of the aqueous humor from either normal or glaucomatous eyes, nor between the age of the patient and the total amount of TGF-beta 2. The negligible amount of TGF-beta 2 present in serum argues against its influx into the aqueous humor after breakdown of the blood-aqueous barrier that is known to occur in glaucomatous eyes; rather, our present findings support the concept of the intraocular derivation of this cytokine.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1991

Interaction of berberine with human platelet alpha 2 adrenoceptors.

Berberine, an alkaloid, has been found to have a myriad of pharmacological effects including hypotensive, antisecretory, sedative, and antimicrobial effects, some of which are similar to those of clonidine, an alpha 2 adrenoceptor partial agonist. The interaction of berberine with human platelet alpha 2 adrenoceptor was investigated in this study. Berberine was found to inhibit competitively the specific binding of [3H]-yohimbine. The displacement curve was parallel to those of clonidine, epinephrine, norepinephrine, with the rank order of potency (IC50) being clonidine (0.4 microM) greater than epinephrine (7.5 microM) greater than norepinephrine (14.5 microM) = berberine (16.6 microM). Increasing concentrations of berberine from 0.1 microM to 10 microM inhibited [3H]-yohimbine binding, shifting the saturation binding curve to the right without decreasing the maximum binding capacity. In platelet cyclic AMP accumulation experiments, berberine at concentrations of 0.1 microM to 0.1 mM inhibited the cAMP accumulation induced by 10 microM prostaglandin E1 in a dose dependent manner, acting as an alpha 2 adrenoceptor agonist. In the presence of L-epinephrine, berberine blocked the inhibitory effect of L-epinephrine behaving as an alpha 2 adrenoceptor antagonist. These properties are similar to those of clonidine on human platelets, suggesting that berberine is a partial agonist of platelet alpha 2 adrenoceptors. These findings may provide potential mechanisms for the hypotensive, antisecretory, and sedative effects of berberine.

Adult↗
PubMed1983

Clinical observation on the uterotonic effect of I-mu Ts'ao (Leonurus artemisia).

Normal fertile women given an oral dose of I-mu Ts'ao decoction (30 g. dry weight equivalent) showed an increase in intra-uterine pressure in 41.3% of 121 cases. The increase ranged from 150% to over 300% of spontaneous activity before dosing. A slightly higher success rate was observed with 2 successive doses or with improved experimental skill in later cases. Ergonovine (0.2 mg i.m.) scored a success rate of 61%. Therefore, I-mu Ts'ao decoction appeared to have a relative potency of 91% compared with ergonovine when the highest success rate (55.5%) of the former is considered. Blank control with water yield a positive response rate of 2.7%. There are no observable side-effects apart from diuresis.

China↗
PubMed1978

Mucinous cystadenoma, serous cystadenoma and benign cystic teratoma of the ovary: clinico-pathologic differences observed in a Malaysian hospital.

A study of 207 benign ovarian tumors seen at the University Hospital, Kuala Lumpur between 1968 and 1975 was made to evaluate the clinical features that might be useful in the preoperative differentiation of mucinous cystadenoma, serous cystadenoma, and cystic teratoma of the ovary. This study indicated that the pertinent information included the mean age of the patient, the marital and menstrual status, and the estimated tumor size. The racial background was an additional factor in serous cystadenoma. Features like parity, the location of the tumor, and ABO blood group pattern were of no value in the preoperative differentiation.

Adult↗