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D K Chan

Publications and source records attributed to D K Chan.

At least 19 recordsLinked to original sources
PubMed2003

A palliative care approach to end-stage neurodegenerative conditions.

INTRODUCTION: Neurodegenerative conditions, such as Alzheimer's disease, Parkinson's disease and motor neurone disease, are progressive and incurable conditions that ultimately lead to a state of total functional incapacitation and death. These conditions are "terminal" and, therefore, should be managed with a palliative care approach. This article highlights some of the issues in caring for patients with end-stage neurodegenerative conditions from a palliative perspective. METHODS: This review is based on evidence from pre-existing medical literature on the above subject and the authors' personal experiences and observations. CONCLUSION: Patients with end-stage neurodegenerative conditions have needs similar to that of advanced cancer patients. Therefore, the principles and practice of palliative care should be applied to such patients. This may also mean that palliative care training should be undertaken in nursing homes, where a large number of such patients are located.

Aged↗
PubMed2001

Pilot study of prevalence of Parkinson's disease in Australia.

Parkinson's disease is a common neurological disease and its prevalence increases with age. Because of an ageing population and changing environment compared to the last epidemiological study done in Australia over 30 years ago, we have conducted a door-to-door pilot survey which looked at the latest prevalence as well as putative risk factors in a random population. We used a two-phase investigation method (screening followed by detailed examination) in a random community sample of 2,820 households (with 527 individuals aged 55 and over) along with 203 residents in aged care facilities (single-phase examination for residents aged 55 and above) in the Randwick area of Sydney, New South Wales. We had a 75% participation rate in the community and a 94% in the aged care facilities. The results of the survey in this sample of 730 subjects indicated that the crude prevalence of Parkinson's disease was between 3.6 and 4.9% (higher in the aged care facilities). The putative risk factors positively identified using chi-square method were 'family history' (p < 0.01) and 'exposure to chemicals at work or in surrounding environment' (p < 0.05). The age-adjusted prevalence rate of Parkinson's disease revealed at least a 42.5% increase in the disease compared to 1966. We conclude that there may be an increase in the disease in Australia due to ageing and other risk factors.

Aged↗
PubMed2001

Effects of cortisol on chloride cells in the gill epithelium of Japanese eel, Anguilla japonica.

The purpose of the present study was to determine the effects of cortisol on the development of the freshwater chloride cell (CC), using flow cytometry. Scanning electron microscopy was used to determine the corresponding modifications in CC apical structure. Simultaneously, biochemical analyses were conducted to determine the activities of transport ATPases, mitochondrial enzymes (succinate dehydrogenase (SDH) and Mg(2+)-ATPase) and lactate dehydrogenase (Ldh). The effects of daily i.m. injection of 2 microg/g cortisol were compared with sham-injected freshwater-, control freshwater- and seawater-adapted fish. The hormone did not affect the activities of Ca(2+)-ATPases in CCs. However, it stimulated the proliferation and differentiation of the two freshwater CC subtypes (F1, 66+/-2.18% (s.e.m. ) and F2, 34+/-2.18%), in which the relative proportion of F1 CCs was transiently reduced in the first 5 days of treatment (F1, 53+/-1.83%; F2, 47+/-1.83%) but was then restored to a higher relative percentage on day 10 (F1, 70+/-1.42%; F2, 30+/-1.42%). Biochemically, it induced the activities of Na(+)/K(+)-ATPase, Mg(2+)-ATPase, SDH and Ldh, suggesting an increase in ion pumping and its associated metabolic activities. CCs from cortisoltreated fish demonstrated recessed apical morphology, accompanied by an increase in cell density (2012 to 2413/mm(2)). Nevertheless, the extent of cell proliferation and differentiation and the biochemical changes were significantly lower than those of seawater fish. Our results indicate that cortisol alone cannot stimulate a complete differentiation of freshwater CCs to seawater CCs. However, the respective roles of the two CC subtypes in freshwater and seawater environments are indicated.

Analysis of Variance↗
PubMed2001

Enteral nutrition of the very low birth weight (VLBW) infant.

INTRODUCTION: Optimal nutrition is critical in the management of the very low birth weight (VLBW) infant. METHODS: The type of feeding, initiation, route and schedule of feeding, and the rate of increase in feeding volume were reviewed. RESULTS: Human milk from the preterm infant's mother is the feeding of choice. When full enteral feeding is established, supplementation of human milk with a multi-nutrient fortifier is required. In VLBW infants having poor weight gain when exclusively fed human milk, feeding of hindmilk is encouraged if the mother expresses large quantities of breast milk. Lactation support is vital for the mother, including appropriate methods of milk collection, storage and transport to the nursery. In mothers who produce no or insufficient human milk, preterm formulas are an alternative feeding, used either alone or in conjunction with human milk. Minimal enteral nutrition using sub-nutritional feedings in the first week of life is advantageous. Intragastric intermittent ("bolus") tube feeding is the route of choice for the infant born at < 32 to 34 weeks gestational age. Feeding volume must be advanced cautiously at < 20 mL/kg/day. CONCLUSION: Future goals of nutrition research in the VLBW infant must include determining the role and optimal composition of the various nutrients and duration of use.

Enteral Nutrition↗
PubMed2001

Parkinson disease and its differentials. Diagnoses made easy.

BACKGROUND: Parkinson disease is a common neurological disorder that is both underdiagnosed and inaccurately diagnosed. There is no reliable biological marker or test that can differentiate between causes of parkinsonism. Even for experienced clinicians, the clinical diagnostic accuracy compared to post mortem findings is about 80%. OBJECTIVE: To discuss the clinical features that differentiate Parkinson disease from other important causes of parkinsonism. DISCUSSION: Although Parkinson disease is a common cause of parkinsonism, other candidates such as drug reactions, benign essential tremor, vascular disease and Lewy body dementia need to be differentiated. Incorrect diagnosis can result in complications related particularly to the use of levodopa and antipsychotic agents. Diagnostic accuracy is important to ensure appropriate management, to avoid complications and to assist patients to have realistic expectations and prognostic information about their condition.

Adult↗
PubMed2000

The alpha-synuclein gene and Parkinson disease in a Chinese population.

OBJECTIVE: To study the Ala53Thr and Ala30Pro mutations of the alpha-synuclein gene in a large number of Chinese patients with Parkinson disease (PD) as well as controls. METHODS: We recruited 183 Chinese patients with sporadic PD, 17 with younger-onset PD (onset age <50 years), and 7 with PD and a positive family history as well as 227 unaffected Chinese control subjects from the outpatient departments of 2 major hospitals in Hong Kong. All subjects were assessed for the the diagnosis of PD by a consultant neurologist or geriatrician. Subjects were interviewed with a standard questionnaire that also questioned for family history. Venous blood samples were obtained from the subjects and genomic DNA was extracted and studied for the presence of Ala53Thr mutation in exon 4 and Ala30Pro mutation in exon 3 of the alpha-synuclein gene using a polymerase chain reaction restriction fragment length polymorphism method. RESULTS: None of the Chinese PD patients or controls had either the Ala53Thr (exon 4) or Ala30Pro (exon 3) mutation of the alpha-synuclein gene. CONCLUSION: We failed to discover Ala53Thr or Ala30Pro mutations in a large number of Chinese patients with PD and control subjects, adding to the emerging consensus that variations in the alpha-synuclein gene are associated with PD in few families worldwide.

Alleles↗
PubMed2000

The monoamine oxidase B gene GT repeat polymorphism and Parkinson's disease in a Chinese population.

Monoamine oxidase B (MAOB) metabolises dopamine and activates neurotoxins known to induce parkinsonism in humans and primates. Therefore the MAOB gene (MAOB; Xp15.21-4) is a candidate gene for Parkinson's disease (PD). Longer length dinucleotide repeat sequences in a highly polymorphic GT repeat region of intron 2 of this gene showed an association with PD in an Australian cohort. We repeated this allele-association study in a population of 176 Chinese PD patients (90 men, 86 women) and 203 agematched controls (99 men, 104 women). Genomic DNA was extracted from venous blood and the polymerase chain reaction was used to amplify the appropriate regions of the MAOB gene. The length of each (GT) repeat sequence was determined by 5% polyacrylamide denaturing gel electrophoresis. There was no significant difference in allele frequencies of the (GT) repeat allelic variation between patients and controls (chi2 = 2.48; df = 5, P<0.75). Therefore the longer length GT repeat alleles are not associated with PD in this Chinese population. Possible reasons for the discrepancy between Chinese and Australian populations include a different interaction between this genetic factor and environmental factors in the two populations and the possibility that the long length GT repeat alleles may represent a marker mutation, genetically linked to another susceptibility allele in whites but not in Chinese. Methodological differences in the ascertainment of cases and controls in this cohort could also explain the observed differences. Further study is required to determine whether the longer length GT repeat alleles are true susceptibility alleles in PD.

Aged↗
PubMed2000

Intention and responsibility in double effect cases.

I argue that the moral distinction in double effect cases rests on a difference not in intention as traditionally stated in the Doctrine of Double Effect (DDE), but in desire. The traditional DDE has difficulty ensuring that an agent intends the bad effect just in those cases where what he does is morally objectionable. I show firstly that the mental state of a rational agent who is certain that a side-effect will occur satisfies Bratman's criteria for intending that effect. I then clarify the nature of the moral distinction in double effect cases and how it can be used to evaluate the moral blameworthiness of agents rather than the moral status of the acts. The agent's blameworthiness is reduced not by his lack of intention but by his desire not to bring about the side-effect, and the 'counterfactual test' can be used to determine whether he desires the effect in acting. In my version, the DDE has its rationale in virtue ethics; it is not liable to abuse as the traditional version is; and it makes more plausible distinctions when applied to standard examples.

Abortion, Therapeutic↗
PubMed2000

A comparison of polymorphism in the 3'-untranslated region of the prothrombin gene between Chinese and Caucasians in Australia.

The 20210G-->A mutation in the 3'-untranslated (UT) region of the prothrombin gene is extremely rare or absent in the Chinese population (0 in 449 subjects, 140 with a history of thromboembolism). This is in contrast to the results from 302 Caucasians from Australia in our study (4.6% in 153 patients with a thromboembolic history and 1.3% in 149 patients with no history). This rarity implies that the variant of the prothrombin gene is probably not the main cause of venous thromboembolism in the Chinese population. Even among Caucasians this mutation accounts for only a minor percentage of all patients with thromboembolism. The relatively low incidence of venous thromboembolism in the Chinese population compared with Caucasians is probably as a result of the low prevalence of factor V Leiden or other environmental or genetic factors.

3' Untranslated Regions↗
PubMed2000

Validating a screening questionnaire for parkinsonism in Australia.

Parkinson's disease is a common neurodegenerative disorder in elderly people. Epidemiological studies of the disease can be labour intensive. A two phase design including a screening questionnaire as the first phase has become a popular method in prevalence studies of Parkinson's disease. Such a design has many advantages including less work for assessing physicians and enhanced recruitment of people to be screened. However, its wider application may be questioned because validation has been limited to samples that are drawn from hospitals (or clinics) and may be inappropriate for a community setting. This study assesses whether validating screening questionnaire by using a hospital sample yields the same result as a community based sample. Furthermore, it seeks to establish whether the screening instrument can be simplified to involve less questions. The findings show that some of the questions used in the screening phase yield different responses when comparing a hospital group with a community group. This study also provides a simplified model of questions that may be relevant for screening in the community setting.

Aged↗
PubMed1999

The potential impact of home telecare on clinical practice.

Home telecare, in which the health status of patients at home is monitored remotely, has the potential to improve care and reduce costs. Its widespread implementation would require fundamental changes in the healthcare system.

Activities of Daily Living↗
PubMed1999

Isolation of viable cell types from the gill epithelium of Japanese eel Anguilla japonica.

High-purity viable cells with low mitochondria (pavement cells) and mitochondria-rich content (chloride cells) were successfully isolated from the gill epithelium of Japanese eels, using three-step Percoll gradient low-speed centrifugation. Cytochemistry (silver staining for chloride, rhodamine-123, and Mitotracker for mitochondria and actin/spectrin immunofluorescence) and scanning electron microscope images were used to identify the cell types in the gill epithelium of the eel. Pavement cells were isolated at 97 and 98% purity for freshwater- and seawater-adapted eels, respectively, and chloride cells were obtained at 89 and 92% purity. The enzymatic activities of the isolated cells were determined. Na+-K+-ATPase, Mg2+-ATPase, and succinate dehydrogenase were found mainly in the chloride cell. Alkaline Ca2+-ATPase and low- and high-affinity Ca2+-ATPase were about twice as high in the chloride cell compared with the pavement cell. Transfer of eels to seawater resulted in enlargement of chloride cell sizes and significant increases in Na+-K+-ATPase, Mg2+-ATPase, and succinate dehydrogenase activities, while all Ca2+-ATPases declined by approximately 60-80%. This is the first report demonstrating the successful isolation of freshwater chloride cells and also an exclusive method of getting high-purity seawater chloride cells. The isolated cells are viable and suitable for further cytological and molecular studies to elucidate the mechanisms of ionic transport.

Anguilla↗
PubMed1999

Chloride cell subtypes in the gill epithelium of Japanese eel Anguilla japonica.

The purpose of the present study was to characterize chloride cell subtypes in the fish gill and to monitor the kinetic change of cell division in the gill epithelia during seawater adaptation. Employing a three-step Percoll gradient method, the gill chloride cells and nonchloride cell population were isolated. The isolated cells were studied using multiparameter flow cytometry, recording the changes in 1) cell size, 2) cellular granularity, and 3) cell autofluorescence. Two chloride cell subtypes were identified in the freshwater eels. Within 2-4 days after entering seawater, new subtypes of transitory chloride cell, with bigger cell size and more intense mitochondria autofluorescence, appeared. After full adaptation, two major seawater chloride cell subtypes were again discerned; their sizes were the largest and their mitochondria autofluorescence was the highest. In the second part of the experiment, cell cycle analysis demonstrated a progressive increase in the percentage of gill cells entering the DNA synthesis phase during seawater adaptation, where a small population of mitotic cells was identified in the nonchloride cell population but not in chloride cells. We hypothesize that the mitotic cells identified are stem cells, which will ultimately differentiate into seawater chloride cells. Our results confirm the existence of heterogeneity of chloride cells. Individual subtypes could be isolated in high purity for further studies to elucidate their respective function in mediating ion transport.

Anguilla↗
PubMed1999

Vitamin E status of infants at birth.

Preterm infants may be susceptible to chronic lung disease and retinopathy of prematurity because of deficient antioxidant mechanisms including deficiency of vitamin E. The aim of this study was to evaluate the status of the antioxidant vitamin E among preterm and term livebirths. Umbilical cord blood samples collected from 40 preterm and 180 term babies were analyzed for vitamin E levels using high performance liquid chromatography. Linear regression analysis was used to examine the relationship of vitamin E with gestational age, birth weight and appropriateness of weight for gestational age. The median vitamin E level of preterm babies (2.61 mg/L) was not significantly different from that of term babies (2.77 mg/L), p = 0.2. Linear regression analysis demonstrated a weak but statistically significant correlation between cord blood vitamin E levels and gestational age (r = 0.14, p = 0.046). Vitamin E levels did not correlate with birth weight or weight for gestational age. Preterm babies had a higher incidence of vitamin E deficiency compared to term babies (38% v 19%, p = 0.02). Our findings lead us to conclude that vitamin E accumulates in the fetus throughout the third trimester so that preterm infants are likely to have vitamin E deficiency.

Birth Weight↗
PubMed1998

Genetic and environmental risk factors for Parkinson's disease in a Chinese population.

An epidemiological study of the environmental and genetic factors as well as the possible interplay between them was conducted among 215 patients with Parkinson's disease and 313 controls in a Chinese population in Hong Kong. In univariate analysis, a regular tea drinking habit was found to be a protective factor, which had not been reported before. Smoking (a protective factor), family history, duration of pesticide exposure (in years) in farming and pesticide exposure during farming in women (both risk factors) have been reported previously. In multivariate analysis, current smoking reached borderline significance at the 5% level and the variables, years exposed to pesticides and family history were significant at the 10% level. By contrast with the common occurrence of polymorphism of the CYP2D6 gene (a gene involved with xenobiotic metabolism) in white people, it is very rare in China and is not thought to be a significant factor contributing to Parkinson's disease in Chinese people.

Aged↗
PubMed1998

Congenital sodium diarrhoea in an Indian girl.

We report the case of a newborn Indian girl with congenital sodium diarrhoea (CSD) who presented typically in utero, in whom diagnosis was made from markedly raised stool sodium in the presence of an alkaline stool. Treatment with sodium citrate normalised her metabolic and electrolyte status but resulted in transient uremia necessitating supplementation with sodium bicarbonate instead. She died at 11 weeks old following re-admission in a moribund state with grossly increased abdominal distension. Her fatal outcome in infancy suggests that CSD has a wide spectrum of clinical severity.

Citrates↗
PubMed1997

Mortality among infants with high-risk congenital diaphragmatic hernia in Singapore.

Several factors suggested to predict mortality in congenital diaphragmatic hernia (CDH) have not always been applicable in different centers. A retrospective review was conducted of 19 consecutive neonates in Singapore in whom CDH was diagnosed within 12 hours of birth to identify factors associated with mortality. Of the 19 cases, 15 (79%) were diagnosed using antenatal ultrasonography. Eight (42%) underwent primary repair at a median age of 23 hours (range, 12 to 50 hours). Of the 19 infants, 15 died (mortality rate, 79%). Survivors until hospital discharge were compared with nonsurvivors. Antenatal diagnosis and stomach position in left-sided defects had no effect on outcome, although polyhydramnios tended to be associated with nonsurvival. Significant postnatal factors associated with mortality included a low arterial pH level, low initial arterial-alveolar oxygen ratio, high initial alveolar-arterial oxygen gradient, as well as high oxygenation and ventilation indices. These results reflect difficulty in oxygenation because of pulmonary hypoplasia despite evidence of adequate ventilation. There was no difference between survivors and nonsurvivors in either their initial or best postductal blood gases. The "Bohn quadrants" did not aid in predicting survival of infants who underwent repair because all eight such infants had best postductal carbon dioxide values of less than 40 mm Hg and ventilation indices of less than 1,000. Yet only four (50%) survived until hospital discharge. Large-scale evaluation of these factors may be required in the future to demonstrate their validity and reliability because of changing management strategies for CDH.

Carbon Dioxide↗