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Biomedical subjects

C L Wong

Publications and source records attributed to C L Wong.

At least 19 recordsLinked to original sources
PubMed2006

Application of two-dimensional spectral surface plasmon resonance to imaging of pressure distribution in elastohydrodynamic lubricant films.

What we believe to be a novel two-dimensional spectral surface plasmon resonance imaging technique determining pressure distribution in elastohydrodynamic lubricant films is presented. This technique makes use of the spectral characteristics associated with the surface plasmon resonance (SPR) effect, and it provides more spectral information in refractive index mapping than conventional contrast SPR imaging. Two-dimensional imaging is demonstrated and applied to a highly pressurized liquid lubricant trapped inside an elastohydrodynamic lubrication (EHL) dimple. The hydrostatic pressure inside the EHL dimple causes a localized change of the refractive index of the lubrication oil. This also results in a shift in the spectral SPR absorption dip. By monitoring the color changes within the SPR image and calibrating with lubricants of known refractive index profiles, we can obtain a direct measurement of the refractive index distribution within the EHL dimple. PB 2400 lubricant dimples were studied in our experiments. The proposed SPR imaging approach is irrespective of the absolute lubricant film thickness h, therefore overcoming the major limitations of a conventional optical interference technique. With further development of the two-dimensional refractive index mapping technique, widespread applications in various fields are possible, including high-throughput sensors and the detection of bioaffinity interactions.

Journal Article↗
PubMed2003

Hirschsprung's disease: the Australian Paediatric Surveillance Unit's experience.

Hirschsprung's disease (HD) was introduced into the Australian Paediatric Surveillance Unit (APSU) system in 1996 with the objective to collect data on demographics, incidence, family history, associated anomalies, clinical features, investigation, and surgical treatment in Australia. Children under 15 years of age with HD (confirmed by biopsy) were entered into a database maintained at The Children's Hospital at Westmead in Sydney. Nationwide, 127 children with HD were reported from January 1997 to December 2000, and near-complete information was available on 126. Neonatal presentation was seen in 114 cases (90%), whereas 12 (10%) presented post-neonatally. There was a history of delayed passage of meconium (more than 24 h) in 65 of the 114 patients (57%) who presented in the neonatal period. In those presenting post-neonatally there was no history of delayed passage of meconium. Primary pull-through was performed in 42 of the 82 patients (51%) operated upon. The Soave procedure was performed in 53 of the total 82 (65%) operations and 29 of 42(69%) primary pull-through operations. Pre-operative enterocolitis was seen in 15 of 126 (12%) and postoperative enterocolitis in 17 of 82 (21%) children. The majority of children with HD are diagnosed in the neonatal period (90%). Primary pull-through is becoming more popular (51%). The Soave procedure is the most commonly performed operation (65%) in Australia. Pre- and post-operative enterocolitis is still a significant problem.

Abnormalities, Multiple↗
PubMed2003

Papuloerythroderma of Ofuji associated with acute myeloid leukaemia.

Papuloerythroderma of Ofuji (PEO) is an uncommon skin condition most commonly described in Japan. The aetiology of PEO is unknown and treatment may be difficult. There are several reports of an association between PEO and malignancy, most particularly with T-and B-cell lymphomas. We describe PEO complicated by acute myeloid leukaemia occurring in a 62-year-old man. This association has not been reported previously.

Dermatitis, Exfoliative↗
PubMed2002

Industrial wastewater minimization using water pinch analysis: a case study on an old textile plant.

Industrial wastewater minimization can be conducted using four main strategies: (i) reuse; (ii) regeneration-reuse; (iii) regeneration-recycling; and (iv) process changes. This study is concerned with (i) and (ii) to investigate the most suitable approach to wastewater minimization for an old textile industry plant. A systematic water networks design using water pinch analysis (WPA) was developed to minimize the water usage and wastewater generation for the textile plant. COD was chosen as the main parameter. An integrated design method has been applied, which brings the engineering insight using WPA that can determine the minimum flowrate of the water usage and then minimize the water consumption and wastewater generation as well. The overall result of this study shows that WPA has been effectively applied using both reuse and regeneration-reuse strategies for the old textile industry plant, and reduced the operating cost by 16% and 50% respectively.

Conservation of Natural Resources↗
PubMed2001

A case series of six children with primary pulmonary hypertension.

INTRODUCTION: Primary pulmonary hypertension is an uncommon but serious disease in children. Management is difficult despite recent advances in pharmacotherapy. CLINICAL PICTURE: We reviewed patients with this condition with respect to their presenting symptoms, investigations, treatment and outcome. TREATMENT: These children were treated with individualised combinations of oxygen, diuretics and calcium antagonists. OUTCOME: In our follow-up of 5 children, 4 had died. CONCLUSION: This condition is irreversible and progressive with a high mortality rate. A better understanding of, and research into, the pathogenesis would hopefully lead to the formulation of improved therapeutic strategies for this condition.

Adolescent↗
PubMed2000

Population dynamics of the feral macaques in the Kowloon Hills of Hong Kong.

Hong Kong's feral monkey population is controversial. Many people complain about the aggressiveness of the monkeys, while some conservationists urge the government to deal with the problem in a way that will not harm the monkeys. The population dynamics of the macaques in the Kowloon Hills were studied in 1992 and 1993. Vital statistics are provided from this study as a first step in resolving the problems of human provisioning and wildlife management. It is unlikely that these macaques are indigenous to the area. They are the descendents of macaques that were released in the early twentieth century to control the spread of a local poisonous plant, the strychnos, which contains alkaloids poisonous to livestock and humans but which is a favorite food of the macaques. The macaque population expanded dramatically during the 1980s. The census method employed in this study is direct head count and photo-identification. At the end of 1993, the estimated abundance was 690 (+/-6) in eight social groups in the Kowloon Hills. Species found were rhesus (Macaca mulatta) 65.3%, longtailed (M. fascicularis) 2.2%, Tibetan (M. thibetana) 0.2%, and hybrids 32.3%. The overall home ranges occupied 2.15 km2, resulting in a very high macaque density of 326 per km2. The birth rates were 56.9% and 69.4% in 1992 and 1993, respectively. Mean adult sex ratio (M:F) was 1:2.2 for social groups and 1:1.6 including all peripheral males. The main mortality factor was road accidents and these contributed to the "missing rate" of 9.8% and 10.6% in 1992 and 1993, respectively. Population growth was 5.6% in 1992 and 7.8% in 1993. The estimated macaque population in the year 2000 will be around 1,100 if conditions remain favorable. Management strategies are recommended.

Animals↗
PubMed2000

Trabeculated embryonic myocardium shows rapid stress relaxation and non-quasi-linear viscoelastic behavior.

Passive viscoelastic behavior is important in embryonic cardiovascular function, influencing the rate and magnitude of contraction and relaxation. We hypothesized that if viscoelastic behavior is influenced by interstitial fluid flow, then the stage-21 (312d) and stage-24 (4d) chick myocardium with large intertrabecular spaces will exhibit much different viscoelastic behavior than stage-16 (212d) and stage-18 (3d) compact myocardium and a non-quasi-linear response. Excised left ventricular sections were tested with ramp-and-hold stress relaxation tests at axial stretch ratios of 1.05:1.1:1.2:1.3. The measured stress relaxation was much more rapid than previously observed in the compact, non-trabeculated myocardium. The reduced relaxation curves depended significantly on the stretch level. A continuous-spectrum quasi-linear relaxation function described their shape well but the model-fit parameters also depended on the stretch level. Sinusoidal stretching of ventricular sections at rates from 0.2 to 25Hz showed that the steepening of stress-strain curves with increasing strain rate was half as much as predicted by a quasi-linear model. Hysteresis ranged from 25-35%, varied little with loading rate from 0.2 to 8Hz, and was twice that predicted from a quasi-linear model. Doubling the viscosity of the perfusate in stress-relaxation tests produced increased stiffness and decreased relaxation rate. These results demonstrate that the passive viscoelastic behavior of the trabeculated embryonic myocardium is markedly different from that of younger, compact myocardium and is not quasi-linear.

Animals↗
PubMed1995

Effects of a histamine H2 receptor agonist and antagonist on restraint-induced antinociception in female mice.

Restraint for 1 h induced significant antinociceptive activity, as assessed by the hot plate test, in female mice. The antinociceptive activity was significant throughout the 1 h period of observation starting immediately after restraint. Prior administration of the histamine H2 receptor agonist dimaprit (1.5-6.0 mg/kg s.c.) 15 min before restraint further enhanced the restraint-induced antinociceptive activity. Furthermore, the induction of antinociceptive activity by restraint was antagonised by prior administration of histamine H2 receptor antagonists, cimetidine (2.5-10.0 mg/kg s.c.) or zolantidine (2.5-10.0 mg/kg s.c.). However, when these drugs were administered immediately after restraint for 1 h, the antinociceptive activity observed was similar to those restrained animals receiving saline injection. The histamine receptor agonist and antagonists, at the doses used in the present study, did not affect the response of unrestrained animals to the hot plate test. These results demonstrate that the effect of a histamine H2 receptor agonist and antagonists on restraint-induced antinociception is dependent upon their time of administration and may act by altering the intensity of stress, thus affecting the antinociceptive activity induced.

Animals↗
PubMed1994

The involvement of opioid delta receptor in restraint-induced antinociception in mice.

Restraint for 1 h induced significant antinociceptive activity in both male and female mice. The restraint animals all showed an increase in response time to the hot plate test at 55 degrees C. The antinociceptive activity decreased with time after restraint but was still apparent at 1 h post restraint. In the male animals, prior administration of opioid delta receptor antagonist naltrindole (0.5-2.0 mg/kg s.c.) 15 min before restraint for 1 h did not affect the degree of antinociceptive activity induced by restraint. In addition, the same doses of naltrindole administered s.c. immediately after restraint for 1 h also did not affect the degree of antinociceptive activity in male mice. However, for female mice the same doses of naltrindole administered s.c. before restraint dose-dependently suppressed the antinociceptive activity induced by restraint. When administered immediately after restraint for 1 h, naltrindole also reversed the antinociceptive activity in female mice. The response times measured 10 min after restraint were significantly reduced when compared with the saline restraint controls. It is concluded that restraint can induce antinociceptive activity in mice; however, different mechanisms may be involved in the antinociception observed. In male mice the endogenous opioid systems did not seem to play a significant role in restraint-induced antinociception, whereas for female animals blockade of opioid delta receptors greatly diminished the antinociception observed after restraint.

Animals↗
PubMed1992

Reconstituted thiopentone retains its alkalinity without bacterial contamination for up to four weeks.

The manufacturers of thiopentone recommend that after reconstitution, it should be kept only for 24 hr to reduce the risk of contamination. However, there are no studies to support this practice and compliance with this recommendation has economic implications. The reasons for discarding a reconstituted bottle of thiopentone are related to concerns about chemical and physical (pH) stability, contamination with infectious agents, and contamination with cellular material. We studied the incidence of bacterial contamination and pH stability of thiopentone in clinical use, as well as the pH stability of thiopentone not in clinical use, and surveyed the eight hospitals affiliated with the University of British Columbia to determine their protocols for thiopental preparation and storage. Cost comparisons were made between our current practice of discarding thiopentone when depleted and the practice of routinely discarding it 24 hr after reconstitution. Samples of thiopentone in clinical use were cultured daily and the pH was measured. The bottles had been in clinical use from 1 to 25 days (mean 4.23 +/- 4.32 SD). Of 106 samples there were no positive bacteriological cultures and there were only minor changes in pH. The telephone survey of the eight hospitals revealed that only one had a policy to discard thiopentone after 24 hr. Cost comparisons indicate that discarding thiopentone 24 hr after reconstitution would result in increased cost. In conclusion, reconstituted thiopentone retains its alkalinity for up to four weeks, and has an acceptably low risk of bacterial contamination for periods beyond 24 hr, therefore thiopentone need not be discarded after 24 hr.

Alkalies↗
PubMed1992

Dispositional study of opioids in mice pretreated with sympathomimetic agents.

Brain and plasma levels of morphine and codeine were determined by an assay method involving solid-phase extraction and ion-pair reversed phase HPLC. Detection was by a variable wavelength UV-detector (for codeine) and an amperometric electro-chemical detector (for morphine) coupled in series. Ephedrine or phenylpropanolamine pretreatment did not interfere with the plasma disposition of morphine, evidenced by overlapping plasma concentration-time profiles. Brain opioid levels were equally unaffected by sympathomimetic pretreatment. The relative ratios of brain to plasma concentrations at the time corresponding to the respective peak anti-nociceptive activity for morphine and codeine revealed no significant differences. It is concluded that single doses of ephedrine and phenylpropanolamine do not affect the disposition of morphine and codeine in mice.

Animals↗
PubMed1992

The effect of naloxone on restraint-induced antinociception in mice.

Restraint for a period from 15-60 min induced significant antinociceptive effect in both male and female mice. The restraint animals all showed an increase in response time to the hot plate test at 55 degrees C. The antinociceptive activity was still apparent one hour after restraint. In the male animals, prior administration of naloxone s.c. 15 min before restraint for 60 min did not affect the degree of antinociceptive activity induced by restraint. In addition, naloxone administered s.c. immediately after restraint for 60 min also did not affect the degree of antinociceptive activity in male mice. These findings indicate that in male animals the endogenous opioid mechanism is most likely not involved in the restraint-induced antinociception. However, for the female mice naloxone administered s.c. either before or immediately after restraint for 60 min dose-dependently suppressed the antinociceptive activity induced by restraint. It is concluded that restraint can induce antinociceptive activity in mice; however, different mechanisms may be involved in the antinociception observed. In male mice the endogenous opioid systems do not seem to play a significant role in restraint-induced antinociception, while for female animals blockade of opioid receptors would greatly diminish the antinociception observed after restraint.

Animals↗
PubMed1992

Further metabolic studies of codeine and morphine in mice pretreated with sympathomimetics.

The effects of ephedrine and phenylpropanolamine (PPA) on the 24 h urinary excretion of morphine, codeine and their metabolites, and on the plasma and brain disposition of morphine and codeine at steady state in mice were studied. Morphine-3-glucuronide was the major urinary metabolite in morphine treated animals, while for codeine treated animals norcodeine and morphine-3-glucuronide were the major metabolites. In all cases percentage of drug excreted unchanged was 10-15% of the administered dose. Ephedrine or PPA pretreatment had no apparent effect on these parameters. The metabolic ratios for the different pathways were comparable in all treatment groups. Steady-state plasma and brain concentration-time profiles of codeine and morphine also showed marked similarity in all treatment groups. Apparently, ephedrine or PPA pretreatment has no effect on the disposition of morphine and codeine in mice. The results are discussed from the perspective of our earlier findings of dependence on cough mixtures containing opioids and sympathomimetics.

Animals↗
PubMed1991

Simultaneous assay for isoniazid and hydrazine metabolite in plasma and cerebrospinal fluid in the rabbit.

A simple procedure for the simultaneous determination of isoniazid and hydrazine metabolite in plasma and cerebrospinal fluid in the rabbit is described. The assay involves organic extraction before and after derivatization of the two compounds and the internal standard, phenelzine. The extract of the derivatized compounds was evaporated to dryness at 40 degrees C and the residue redissolved in the mobile phase (50 microliters). A 25-microliters aliquot was injected into the liquid chromatograph and eluted with acetonitrile-water-triethylamine (70:30:0.4, v/v) containing 5 mM heptanesulphonic acid on a 30-microns C8 precolumn linked to a 10-microns C18 microBondapak column at ambient temperature (25 +/- 1 degree C). The eluate was detected by ultraviolet detection at 320 nm.

Animals↗
PubMed1991

Role of adrenoceptors in the potentiation of opioid antinociception by ephedrine and phenylpropanolamine in mice.

Ephedrine and phenylpropanolamine (PPA) (10 mg/kg) pretreatment intraperitoneally (IP) potentiated the antinociceptive effects of subcutaneous (SC) morphine (5 mg/kg) and codeine (60 mg/kg) in mice using the tail-flick method. Prior administration of propranolol (6 mg/kg, SC) 10 min before the sympathomimetics had no effect on this action. Phentolamine (2 mg/kg, SC), on the other hand, abolished the enhancing effects of ephedrine and PPA on opioid antinociception. Prazosin (2 mg/kg, SC) pretreatment did not significantly affect the potentiation of opioid antinociception by ephedrine and PPA, while yohimbine (4 mg/kg, SC) effectively antagonised this enhancing effect. None of the adrenoceptor antagonists had any effect on the tail-flick reaction time on their own in the doses used, and neither did they affect opioid antinociceptive responses. It is concluded that ephedrine and PPA potentiate the antinociceptive effects of morphine and codeine, most probably through an action on alpha 2-adrenoceptors.

Analgesics, Opioid↗
PubMed1991

An overview of the use of anti-tuberculous drugs in Uganda and Hong Kong.

Anti-tuberculous (Anti-TB) chemotherapy in Uganda is outlined. Its pattern of use and the subsequent shortcomings have prompted the need for the present review. A collateral comparison to that of Hong Kong was run to emphasize the correlation of anti-TB chemotherapy with economic development and regional variation in the population of the two areas. Tuberculosis of the central nervous system (CNS) has a high fatality rate. In the search for a more comprehensive anti-TB dosage regimen, the difficulty in treating tuberculosis of the CNS has attracted special attention with emphasis on the fate of anti-TB drugs across the meninges. The choice of a method for drug analysis in routine therapeutic drug monitoring for a country is likewise determined by factors similar to those for the anti-TB regimen. Uganda needs an inexpensive, precise and selective method for TB treatment tailored to its financial and manpower resources.

Child↗
PubMed1991

[Tolosa-Hunt syndrome--case report].

This is a case of a 38-year-old male who developed painful ophthalmoplegia two years after head injury. Under the impression of Tolosa-Hunt syndrome, the patient received long term unsustained oral steroid therapy for two years. Persistent growth of the parasellar lesion was confirmed by computed tomography. Due to the aggravation of the symptoms, craniotomy and partial parasellar granulation tissue extirpation were performed. Symptoms were then gradually subsided. The pathological study confirmed the presence of granulation tissue with marked acute and chronic inflammatory cells. No evidence of malignancy was noted. No further steroid treatment was rendered to the patient and he was well in the following 18 months after the operation.

Adult↗