Biomedical subjects

C W Chan

Publications and source records attributed to C W Chan.

At least 19 recordsLinked to original sources

PubMed1995

Functional reconstitution of ion channels from Paramecium cortex into artificial liposomes.

Toward isolating channel proteins from Paramecium, we have explored the possibility of functionally reconstituting ion channels in an artificial system. Proteins from Paramecium cortex reconstituted with soybean azolectin retained several channels whose activities were readily registered under patch clamp. The most commonly encountered activities were three: (i) a 71-pS cation channel that opens at all voltages unless di- or trivalent cations were added to close them, (ii) a 40 pS monovalent cation channel, and (iii) a large-conductance channel that prefers anions and exhibits many subconductance states. These channels survived mild detergent treatments without observable functional alterations. The possible origin of these channels from internal membranes, the possible role of 71-pS channel in internal Ca2+ release, and the prospects of their purification are discussed.

Animals↗

PubMed1995

A simple and efficient treatment for fingertip injuries.

We have developed a simple, cheap and efficient method of management of fingertip injuries using an occlusive dressing--the fingertip cap (Hyphecan). The results of 156 fingertip injuries treated with this method demonstrate recovery to a near normal fingertip.

Adolescent↗

PubMed1992

Extent of nasopharyngeal carcinoma involvement inside the nasopharynx. Lack of prognostic value on local control.

A study on the use of fiberscopic examination and multiple biopsy specimens taken from the nasopharynx in the assessment of the extent of nasopharyngeal carcinoma (NPC) involvement inside the nasopharynx found that the involvement often was more extensive than the detected with conventional methods. In the current study, 247 patients with NPC were studied with the use of fiberscopic examination, and multiple biopsy specimens were taken from the superior wall, posterior wall, and lateral wall of the nasopharynx on both sides. It was confirmed that the tumor often involved the nasopharynx extensively. Also, the extent of primary tumor involvement inside the nasopharynx was correlated with the American Joint Committee (AJC) T stage and the degree of paranasopharyngeal extension of the tumor (P = 0.0100 and 0.0009, respectively), as well as with the size of the largest node and the lowest neck level involved by the node in the ipsilateral neck (P = 0.0005 and 0.005, respectively). However, the extent of primary tumor involvement inside the nasopharynx, expressed as either the number of the six standard sites or the number of the AJC subsites that were involved, had no predictive value on the control of the primary tumor (P = 0.3773 and 0.7794, respectively) at a median follow-up time of 27 months. Except when salvage brachytherapy is contemplated for persistent or recurrent NPC, the extent of primary tumor involvement inside the nasopharynx should not be routinely studied.

Actuarial Analysis↗

PubMed1992

Radiation therapy for nasopharyngeal carcinoma: histologic appearances and patterns of tumor regression.

Nasopharyngeal carcinoma is a common malignancy in Hong Kong and is treated by external radiotherapy. After 6.5 weeks of radiotherapy, the nasopharynx of 100 patients was examined and biopsy specimens were taken. All patients had repeated examination and biopsies done every 2 weeks until exophytic tumor was not seen and biopsy samples were negative on more than one examination of the nasopharynx. The interval between the cessation of therapy and biopsy ranged from 1 day to 11 weeks. Twenty-three patients had atypical findings and five of these had residual tumor requiring gold grain implantation brachytherapy. We identified a number of distinct pathologic changes in the post-biopsy material. Most of these changes disappeared 8 weeks after the cessation of therapy, but the presence of residual tumor after this time was an indication for subsequent therapy. If the date of the first biopsy was delayed until 6 weeks after the completion of radiotherapy, the percentage of atypical biopsies containing residual tumor rose from 21% to 55%. The posttreatment biopsy should be performed twice, as four patients had negative biopsy findings due to sampling error.

Adolescent↗

PubMed1992

Thermoregulation and fever in normal persons and in those with spinal cord injuries.

Thermoregulation and fever are primarily mediated through the hypothalamus and its effector mechanisms. In persons with complete spinal cord injuries above T-6, thermoregulation is substantially impaired because of the interruption of neuronal pathways to and from the hypothalamus. These same pathways are important in the production of fever in response to infections, and injury to these pathways in patients with high-level spinal cord injuries should diminish their ability to mount a febrile response. In clinical practice, however, measurements of body temperature are used to make decisions in patients with spinal cord injuries in a manner similar to that in patients without spinal cord injuries. In this article, we review the literature on thermoregulation and fever in normal persons and in those with complete spinal cord injuries and propose possible mechanisms for fever in persons with high-level spinal cord injuries.

Body Temperature↗

PubMed1992

Nasopharyngeal carcinoma in situ in nasopharyngeal carcinoma.

AIMS: To assess the presence of carcinoma in situ (CIS) in patients with nasopharyngeal carcinoma (NPC) and to see if the number of biopsy sites facilitates detection of CIS. METHODS: Formalin fixed, paraffin wax embedded biopsy specimens (n = 285) from 187 patients with NPC in 1987 were studied for the presence of CIS as well as for the histological assessment of the subtype of CIS. RESULTS: Fifteen (8.0%) patients had CIS, representing 8.3% of all new patients with NPC and 11.6% of patients with persistent disease or relapse. CIS was undifferentiated or poorly differentiated, no cases of well differentiated squamous cell CIS were identified. There was no significant difference in the incidence of CIS when multiple endoscopic biopsy specimens were taken rather than single forceps biopsy specimens. CONCLUSIONS: CIS can only be identified in a few patients with NPC largely because of late presentation with advanced disease at the time of diagnosis and the focal nature of the dysplastic process. The presence of dysplasia in relapses of NPC suggests that these tumours may be second growths rather than regrowths of a primary tumour.

Carcinoma in Situ↗

PubMed1992

Epstein-Barr virus DNA in nasopharyngeal carcinomas from Chinese patients in Hong Kong.

AIMS: To investigate the presence of Epstein-Barr virus (EBV) in cases of nasopharyngeal carcinoma (NPC) in Chinese patients living in Hong Kong. METHODS: Nasopharyngeal biopsy specimens, formalin fixed and paraffin wax embedded, from 24 patients, eight with undifferentiated nasopharyngeal carcinoma, eight with well differentiated squamous carcinoma, and eight showing normal tissue histology, were analysed for the presence of Epstein-Barr virus (EBV) DNA by slot-blot hybridisation on extracted unamplified DNA, and also after amplification of EBV specific sequences by the polymerase chain reaction (PCR). RESULTS: DNA slot-blot analysis showed viral DNA in all the undifferentiated, five of the well differentiated tumours, and none of the normal biopsy specimens. PCR studies confirmed positivity in the eight undifferentiated tumours, but six of the well differentiated tumours and three of the normal biopsy specimens showed viral DNA by this method, illustrating its greater sensitivity. CONCLUSIONS: EBV genome is present in appreciable copy number in most cases of well differentiated NPC in Chinese patients in Hong Kong.

Base Sequence↗

PubMed1992

Effect of feeding palmitic, oleic, and linoleic acids to Japanese quail hens (Coturnix coturnix japonica). 2. Maternal diets and stage of incubation on the lipid metabolism of quail embryos.

An experiment was conducted to evaluate the effects of diets containing 3% of either palmitic acid (Diet PA), oleic acid (Diet OA), or linoleic acid (Diet LA) and three stages of development (Days 11, 13, and 15 of incubation) on 1) weights of yolk plus yolk sac membrane (TY), yolk sac membrane (YSM), yolk, liver, and extrahepatic tissue (ET); and 2) the fatty acid composition of phospholipid, triglyceride, and cholesterol ester fractions of YSM and ET of quail embryos. Embryos from birds fed Diet LA had the highest (P less than .05) weights of TY and yolk followed by those from birds fed Diet OA and Diet PA. The weight of ET was highest (P less than .05) in embryos from birds fed Diet PA followed by those from birds fed Diet LA and Diet OA. The weights of YSM and liver were not affected by the maternal diet (P greater than .05). The weight of TY decreased whereas the weights of liver and ET increased as incubation progressed (P less than .05). The weight of YSM was maximum at Day 13 of incubation. In the phospholipid, triglyceride, and cholesterol ester fractions of both YSM and ET of embryos, the fatty acid present at the highest level, except palmitic acid, was the one added to the maternal diet. In phospholipids of both YSM and ET the oleic acid content decreased and linoleic acid increased as incubation progressed. In triglycerides and cholesterol esters of both YSM and ET, the levels of palmitic acid increased, but oleic and linoleic acids decreased, with advancing embryonic development. The results of the present study indicate that embryos from birds fed Diet PA mobilize more yolk material and produce heavier ET than embryos from birds fed Diet OA and Diet LA. The fatty acid profiles of phospholipid, triglyceride, and cholesterol esters of embryonic tissues are consistently influenced by dietary fatty acid and the stage of development.

Animals↗

PubMed1991

Visual disability and major causes of blindness in NSW: a study of people aged 50 and over attending the Royal Blind Society 1984 to 1989.

Visual disability in individuals aged 50 years and over seeking services of the Royal Blind Society in the years 1984 to 1989, was studied with respect to changes in frequency of major causes together with age and sex of those affected. The results mirror statistics in the UK. Age-related macular degeneration (AMD) accounts for an increasing proportion of visual disability (34% in 1984 to 43% in 1989). Of particular interest was the frequency of disability attributed to cataract. While decreasing (24% in 1984 to 19% in 1989), cataract still represents a significant cause of potentially treatable disability. The authors conclude that there is a changing prevalence of visual disability caused mainly by an increase in AMD and a subgroup of patients attending for services who appear to have a potentially remediable disability. These conclusions affirm the need for close liaison between ophthalmological practitioners and agencies for the blind.

Aged↗

PubMed1991

Quantitative analysis of the accuracy of linear array transrectal ultrasound in measurement of the prostate.

In 61 prostate autopsy specimens, linear array transrectal ultrasound and electronic vernier calipers were used to measure 3 maximal diameters along the longitudinal, anterior-posterior and transverse axes. The results were comparable. We assessed the reliability of empirical formulae, derived from various combinations of these 3 diameters, for the prediction of prostatic volume and weight. Formulae using all 3 diameters were accurate. The combination of longitudinal and anterior-posterior diameters, which was used clinically for prostate measurement, was less accurate.

Anthropometry↗

PubMed1991

Effect of feeding palmitic, oleic, and linoleic acids to Japanese quail hens (Coturnix coturnix japonica). 1. Reproductive performance and tissue fatty acids.

A study was conducted to evaluate the effects of diets containing 3% of either palmitic acid (Diet PA), oleic acid (Diet OA), or linoleic acid (Diet LA) on reproductive performance, fatty acid composition of egg yolk, plasma, and liver, and total plasma phosphorus of Japanese quail. Each diet was fed to 20 individually caged hens from 5 wk of age. A 24-wk production period started at 8 wk of age. Fertile eggs for incubation were obtained by placing at random a male in the cage with the female for 15 to 20 min twice per week. The males were kept in separate individual cages and fed a turkey grower diet throughout. Feed consumption, egg production, egg output, and the number of chicks per hen were higher (P less than .05) in birds fed Diet PA than in those fed Diet OA or Diet LA. Hatchability was not different (P greater than .05) between Diet PA and Diet OA, but they were higher (P less than .05) than that of Diet LA. Quail weight at hatch from birds fed Diet LA was heavier (P less than .05) than those from Diet OA, but not different (P greater than .05) from those fed Diet PA. Total plasma phosphorus concentration was higher (P less than .05) in birds fed Diet PA than in those fed Diet LA. High levels of oleic and linoleic acids were found in egg yolk, plasma, and liver lipids from birds fed Diet OA and Diet LA, respectively. Feeding Diet PA resulted in elevated levels of palmitoleic acid in all three tissues. The highest overall reproductive performance on Diet PA suggests that palmitic acid has some physiological role in reproduction. The sustained near-maximal levels of egg production and fertility achieved in this trial indicate the superiority of the mating procedure, which would also permit testing the response of male and female birds while minimizing injuries incurred by the females.

Animal Feed↗

PubMed1990

Dissecting aneurysm of coronary artery presenting as cardiac tamponade.

Primary dissecting aneurysm of the coronary arteries usually presents as sudden death or complications of myocardial infarction. The most common site of the dissection has been the anterior descending branch of the left coronary artery. A Chinese woman with primary dissecting aneurysm of the right coronary artery presenting as cardiac tamponade is reported. This is the first case of ruptured coronary aneurysm reported in the Chinese and the only case presenting as cardiac tamponade since 1931.

Aortic Dissection↗

PubMed1990

Nasopharyngeal carcinoma. Pattern of tumor regression after radiotherapy.

The primary tumor regression pattern of 50 patients with nasopharyngeal carcinoma was reported. The tumor regression was monitored either by indirect nasopharyngeal mirror examination and biopsy or fiberoptic endoscope and biopsy. Fiberoptic endoscope and biopsy was found to be more accurate in noting residual tumor. It is recommended that booster radiation dose to the residual primary tumors be withheld unless positive biopsy samples persist at 10 or more weeks after radiotherapy.

Biopsy↗

PubMed1990

Age-related glomerular sclerosis: baseline values in Hong Kong.

A study was undertaken to estimate the incidence of glomerular sclerosis in the normal population in Hong Kong. The percentage glomerular sclerosis in 100 cadavers without clinical evidence of kidney disease or hypertension was determined by histologic examination of the kidneys. The mean percentage values in the normal population at all age groups were calculated based on this sample. The subcapsular cortical area generally had a higher proportion of sclerotic glomeruli than the deeper cortex. Statistical analysis showed that 95% of the normal population up to 40 years of age would be expected to have less than 6% sclerotic glomeruli. After the age of 55, the upper limit containing 95% of the normal population would exceed 10% sclerosis. A broad scatter of observed percentage glomerular sclerosis was present in the elderly after the age of 70 years. The data obtained provide the baseline values of glomerular scarring that would allow age-related involutional changes to be distinguished from those due to disease.

Adolescent↗

PubMed1990

The influence of supplemental corn oil and free fatty acids on the reproductive performance of Japanese quail (Coturnix coturnix japonica).

An experiment was conducted to evaluate the effects of dietary corn oil (CO) and commercial free fatty acids on the fatty acid composition of blood plasma and egg yolk lipids and on the reproductive performance of Japanese quail. When quail were fed a semi-purified low-fat basal mix, the substitution of 3% of CO for corn starch (CS) improved egg weight (11.2 versus 10.8 g), reduced late embryonic mortality (16.7 versus 28.4%), and improved hatchability (75.7 versus 64.1%). Diets in which palmitic acid or oleic acid were substituted on a weight basis for 3% of CS performed as well as those in which CO was used. When linoleic acid replaced 3% of CS, late embryonic mortality was reduced (13.7 versus 28.4%) and hatchability was improved (80.1 versus 64.1%), but fertility was depressed (85.8 versus 93.6%). The substitution of linolenic acid for 3% of CS depressed feed consumption, body weight, and egg weight relative to the low-fat CS diet and did not improve the low 18-day embryonic livability and low hatchability. The fatty acid compositions of plasma and yolk were influenced by the lipid composition of the diets. Quail fed 3% of CO deposited more linoleic acid in the egg than those fed 3% of linoleic acid (15.2 versus 11.7%). Thus, quail fed a simplified basal breeder diet containing .6% of linoleic acid showed decreased embryonic livability and hatchability and these parameters achieved normal levels in response to the substitution of 3% of either CO, palmitic acid, oleic acid, or linoleic acid for CS.

Animals↗

PubMed1989

Fiberoptic endoscopic examination and biopsy in determining the extent of nasopharyngeal carcinoma.

This is a prospective study on the use of flexible endoscope and multiple biopsies in the assessment of nasopharyngeal carcinoma in 72 patients. This study confirmed the presence of submucosal growth pattern in nasopharyngeal carcinoma in 72 patients. This study confirmed the presence of submucosal growth pattern in nasopharyngeal carcinoma and this occurred in 13.8% of patients. Occult microscopic extension of tumor not detectable by fiberoptic endoscopy occurred in another 51.4% of patients. It has also been shown that multiple biopsy is superior to clinical examination in evaluating the extent of disease in nasopharyngeal carcinoma. Multiple biopsies are suggested for the early detection of nasopharyngeal carcinoma in high-risk cases. Although the better-defined tumor extent do not currently influence the treatment policy of nasopharyngeal carcinoma, and it is too early to assess its prognostic significance, it betters our understanding of the behavior of this tumor. Future analysis in correlation with long-term follow-up data may help to improve the stage classification systems and treatment strategy.

Biopsy↗

PubMed1989

Colorectal carcinoma in Hong Kong Chinese. A pathological survey of 1,117 cases, 1972-1981.

Hong Kong Chinese, when compared with the world population, have an intermediate incidence rate for colorectal carcinoma. The purpose of this retrospective analysis of a large number of colorectal carcinomas (1,117 cases) was to explore possible differences between this series and others, and to re-examine the divergent features reported in a smaller series. The present study revealed a distribution by age, sex, site and Dukes' stage, as well as histopathological features, which were analogous to those reported from other countries. Thus, while the incidence is lower in this group, the other manifestations of the disease are very similar to those seen elsewhere. The implication is that, apart from varying incidence, there is a global similarity among colorectal tumours.

Adult↗

PubMed1989

Subjective pain sensation is linearly correlated with the flexion reflex in man.

In an attempt to define the relationship between physiological and psychological correlates of pain during low-level voluntary contraction, electrical stimuli between threshold and maximally tolerable intensities were delivered to the sole of the foot in 7 normal subjects. The two measures used to assess the response magnitude are: (1) the flexion reflex (FR) in the ipsilateral biceps femoris (BF), and (2) the estimate of perceived intensity reported on a visual analog scale (VAS). Our results showed that both BF FR area and VAS ratings bore a direct linear relationship with stimulus intensity and with each other, suggesting that at least under our paradigm, the sensory component of a nociceptive stimulus may already be largely set at the spinal interneuronal level.

Adult↗