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Biomedical subjects

T Wong

Publications and source records attributed to T Wong.

At least 19 recordsLinked to original sources
PubMed2006

In vivo protective performance of N95 respirator and surgical facemask.

BACKGROUND: The SARS outbreak in 2003 has spawned a major controversy concerning protective performance facemasks for healthcare workers. This study reports a study on in-vivo protective performance of surgical masks and N95 respirators. METHODS: Typical surgical masks and N95 respirators used in Hong Kong hospitals were tested in comparison with those treated with nano-functional materials (called nano-masks) on various physical properties and in-vivo wear filtration efficiency, as well as usability test in hospitals for surgical masks. RESULTS: Tests on physical properties showed that N95 respirators had significantly lower air permeability and water vapor permeability than surgical masks. The in-vivo filtration tests illustrated that N95 respirators filtered out 97% of potassium chloride (KCl) solution, while surgical masks filtered out 95% of KCl solution. Nano-masks show stronger water repellency and antibacterial activities, but no difference in usability, comparing with normal N95 and surgical masks. CONCLUSIONS: Surgical masks can provide in-vivo filtration protection of 95% filtration efficiency. N95 respirators provide higher in-vivo filtration efficiency of 97% with significant reduction of air permeability and water vapor permeability. Compared to normal surgical masks/respirators, the nano-masks can provide additional protective functions in stopping capillary diffusion and antibacterial activities.

Aerosols↗
PubMed2006

Target proteins in inherited and acquired blistering skin disorders.

Maintenance of an intact epidermis depends on secure adhesion between adjacent keratinocytes, and between basal keratinocytes and the underlying epidermal basement membrane. The major adhesion units that achieve this are the hemidesmosomes and desmosomes, but when these structures are disrupted, e.g., by gene mutations or autoantibodies, the resilience of the epidermis is lost and blisters develop. Recently, there have been considerable advances in our knowledge of the proteins and glycoproteins that contribute to maintaining keratinocyte adhesion via hemidesmosomes and desmosomes, as well as new insights into the molecular pathogenesis of several inherited and autoimmune blistering skin diseases. These new basic scientific data are clinically relevant, helping to improve patient management and to provide a rationale for developing better and more specific treatments for patients with inherited or acquired blistering skin diseases. In addition, there have also been improvements in our understanding of the organization and assembly of these adhesion structures, and their involvement in signalling pathways, intricately linked to skin development, wound healing and tumour invasion. This review provides an update on the structure and organization of hemidesmosomes and desmosomes, and on the molecular pathology of their various components that result in bullous skin diseases.

Autoimmune Diseases↗
PubMed2005

Effects of wearing N95 and surgical facemasks on heart rate, thermal stress and subjective sensations.

AIM: The study was aimed at investigating the effects of wearing N95 and surgical facemasks with and without nano-functional treatments on thermophysiological responses and the subjective perception of discomfort. METHOD: Five healthy male and five healthy female participants performed intermittent exercise on a treadmill while wearing the protective facemasks in a climate chamber controlled at an air temperature of 25 degrees C and a relative humidity of 70%. Four types of facemasks, including N95 (3M 8210) and surgical facemasks, which were treated with nano-functional materials, were used in the study. RESULTS: (1) The subjects had significantly lower average heart rates when wearing nano-treated and untreated surgical facemasks than when wearing nano-treated and untreated N95 facemasks. (2) The outer surface temperature of both surgical facemasks was significantly higher than that of both N95 facemasks. On the other hand, the microclimate and skin temperatures inside the facemask were significantly lower than those in both N95 facemasks. (3) Both surgical facemasks had significantly higher absolute humidity outside the surface than both N95 facemasks. The absolute humidity inside the surgical facemask was significantly lower than that inside both N95 facemasks. (4) Both surgical facemasks were rated significantly lower for perception of humidity, heat, breath resistance and overall discomfort than both N95 facemasks. The ratings for other sensations, including feeling unfit, tight, itchy, fatigued, odorous and salty, that were obtained while the subjects were wearing the surgical facemasks were significantly lower than when the subjects were wearing the N95 facemasks. (5) Subjective preference for the nano-treated surgical facemasks was the highest. There was significant differences in preference between the nano-treated and untreated surgical facemasks and between the surgical and N95 facemasks. DISCUSSION: We discuss how N95 and surgical facemasks induce significantly different temperature and humidity in the microclimates of the facemasks, which have profound influences on heart rate and thermal stress and subjective perception of discomfort.

Blood Pressure↗
PubMed2005

Postnatal development of intrinsic GABAergic rhythms in mouse hippocampus.

The local circuitry of the mammalian limbic cortices, including the hippocampus, is capable of generating spontaneous rhythmic activities of 0.5-4 Hz when isolated in vitro. These rhythmic activities are mediated by synchronous inhibitory postsynaptic potentials in pyramidal neurons as the result of repeated discharges of inhibitory interneurons. As such, they are thought to represent an intrinsic inhibitory rhythm. It is unknown at present whether such a rhythm occurs in the immature rodent hippocampus and, if so, the postnatal time window in which it develops. We explored these issues using our recently developed whole mouse hippocampal isolate preparation in vitro. We found that spontaneous rhythmic field potentials started to emerge in mouse hippocampal isolates around postnatal day 10, stabilized after postnatal day 15 and persisted into adulthood. In postnatal days 11-14 mouse hippocampi, the properties of these rhythmic potentials were in keeping with a CA3-driven, IPSP-based intrinsic network activity. The lack of spontaneous field rhythm in neonatal (postnatal days 2-7) hippocampi cannot be attributed to the excitatory activities mediated by gamma-aminobutyric acid type A (GABA-A) receptors, as chloride-dependent hyperpolarizing inhibitory postsynaptic potentials were detectable in neonatal pyramidal neurons at voltages near resting potentials and pharmacological antagonisms of GABA-A receptors produced robust epileptiform discharges in neonatal hippocampi. High frequency afferent stimulation or applications of 4-aminopyridine at low micromolar concentrations failed to induce persistent field rhythm in neonatal hippocampi, suggesting that an overall weak glutamatergic drive is not the sole causing factor. We suggest that the inhibitory postsynaptic potential-based spontaneous rhythmic field potentials develop in a discrete time window during the second postnatal week in the mouse hippocampus due to a fine-tuning in the structure and function of CA3 recurrent circuitry and associated GABAergic inhibitory interneurons.

2-Amino-5-phosphonovalerate↗
PubMed2005

Familial multiple cutaneous and uterine leiomyomas associated with papillary renal cell cancer.

Multiple cutaneous and uterine leiomyomas is an autosomal dominant condition that results in benign smooth muscle tumours of the skin and, in females, uterine fibroids. This syndrome overlaps with hereditary leiomyomatosis and renal cell cancer syndrome in which affected individuals may develop the rare type II papillary renal cell cancer, in addition to skin leiomyomas. Recently, heterozygous mutations in the gene encoding fumarate hydratase have been found to underlie both conditions. Fumarate hydratase is an enzyme that catalyses the conversion of fumarate to malate in the Kreb's cycle and may also function as a tumour suppressor gene. We report a family with multiple leiomyomas, uterine fibroids and papillary renal cell cancer. The proband is a 77-year-old Polish woman who developed multiple cutaneous leiomyomas on her right upper arm in her thirties and subsequently underwent a hysterectomy for uterine fibroids in her forties. She has four offspring: her eldest daughter also has skin and uterine leiomyomas with a similar onset; her son has multiple skin leiomyomas and in addition was diagnosed with metastatic papillary renal cell cancer at the age of 50 years; the two youngest daughters are unaffected. DNA sequencing in all the affected individuals disclosed a heterozygous G-->C substitution at nucleotide 173 of the fumarate hydratase gene, that converts an arginine residue (CGA) to proline (CCA). This missense mutation has not been reported previously and is designated R58P. Interestingly, the clinically asymptomatic 20-year-old son of the individual with renal cancer was also found to be heterozygous for R58P. It is likely that he will develop skin leiomyomas in the future but the risk of renal cancer is difficult to predict. Nevertheless, detection of this mutation has important implications for screening and genetic counselling in this and other family members.

Aged↗
PubMed2004

Feasibility of optimizing the dose distribution in lung tumors using fluorine-18-fluorodeoxyglucose positron emission tomography and single photon emission computed tomography guided dose prescriptions.

The information provided by functional images may be used to guide radiotherapy planning by identifying regions that require higher radiation dose. In this work we investigate the dosimetric feasibility of delivering dose to lung tumors in proportion to the fluorine-18-fluorodeoxyglucose activity distribution from positron emission tomography (FDG-PET). The rationale for delivering dose in proportion to the tumor FDG-PET activity distribution is based on studies showing that FDG uptake is correlated to tumor cell proliferation rate, which is shown to imply that this dose delivery strategy is theoretically capable of providing the same duration of local control at all voxels in tumor. Target dose delivery was constrained by single photon emission computed tomography (SPECT) maps of normal lung perfusion, which restricted irradiation of highly perfused lung and imposed dose-function constraints. Dose-volume constraints were imposed on all other critical structures. All dose-volume/function constraints were considered to be soft, i.e., critical structure doses corresponding to volume/function constraint levels were minimized while satisfying the target prescription, thus permitting critical structure doses to minimally exceed dose constraint levels. An intensity modulation optimization methodology was developed to deliver this radiation, and applied to two lung cancer patients. Dosimetric feasibility was assessed by comparing spatially normalized dose-volume histograms from the nonuniform dose prescription (FDG-PET proportional) to those from a uniform dose prescription with equivalent tumor integral dose. In both patients, the optimization was capable of delivering the nonuniform target prescription with the same ease as the uniform target prescription, despite SPECT restrictions that effectively diverted dose from high to low perfused normal lung. In one patient, both prescriptions incurred similar critical structure dosages, below dose-volume/function limits. However, in the other patient, critical structure dosage from the nonuniform dose prescription exceeded dose-volume/function limits, and greatly exceeded that from the uniform dose prescription. Strict compliance to dose-volume/ function limits would entail reducing dose proportionality to the FDG-PET activity distribution, thereby theoretically reducing the duration of local control. Thus, even though it appears feasible to tailor lung tumor dose to the FDG-PET activity distribution, despite SPECT restrictions, strict adherence to dose-volume/function limits could compromise the effectiveness of functional image guided radiotherapy.

Algorithms↗
PubMed2004

The Auckland Cataract Study: 2 year postoperative assessment of aspects of clinical, visual, corneal topographic and satisfaction outcomes.

AIM: To assess clinical, visual, computerised corneal topographic, and subjective satisfaction with visual acuity, in a cohort of subjects 2 years after phacoemulsification surgery in a public hospital in New Zealand. METHODS: Prospective study of a representative sample of 97 subjects (20%) randomly selected from 480 subjects in the original Auckland Cataract Study (ACS) cohort. The clinical assessment protocol was identical to the ACS and included an extensive questionnaire to enable direct comparisons to be made between the two groups. RESULTS: The study population was predominantly female (66%) with a mean age of 76.3 (SD 9.9) years. New systemic and ocular disease affected 18.4% and 10.3% of subjects respectively, and 10.3% required referral to either a general practitioner (2.1%) or ophthalmologist (8.2%). Mean best spectacle corrected visual acuity (BSCVA) was 0.2 (0.2) logMAR units (6/9 Snellen equivalent), with mean spherical equivalent -0.37 (1.01) dioptres (D) and astigmatism -1.07 (0.70) D 2 years postoperatively, compared to mean BSCVA 0.1 (0.2) logMAR units (6/7.5 Snellen equivalent), spherical equivalent -0.59 (1.07) D, and astigmatism -1.14 (0.77) D 4 weeks after surgery. 94.9% of subjects retained a BSCVA of 6/12 or better, irrespective of pre-existing ocular disease. The overall posterior capsule opacification (PCO) rate was 20.4% and this was visually insignificant in all but 3.1% of eyes that had already undergone Nd:YAG posterior capsulotomy. Orbscan II elevation technology demonstrated corneal stability 2 years after uncomplicated phacoemulsification. Although corneal astigmatism was eliminated in approximately half of the subjects 1 month postoperatively, astigmatism showed a tendency to regress towards the preoperative level with local corneal thickening at the site of incision 2 years after cataract surgery. Of fellow eyes, 61.2% had undergone cataract surgery. Overall, 75.3% of subjects were moderately to very satisfied with their current level of visual acuity. CONCLUSION: Two years after cataract surgery subjects are generally satisfied with their current level of vision and distance BSCVA is 6/12 or better in the majority of eyes. Although only a minority of eyes develop sufficient PCO to require capsulotomy 10.3% of eyes develop new vision threatening ocular pathology.

Adult↗
PubMed2004

Sexual network analysis of a gonorrhoea outbreak.

OBJECTIVES: Sexual partnerships can be viewed as networks in order to study disease transmission. We examined the transmission of Neisseria gonorrhoeae in a localised outbreak in Alberta, Canada, using measures of network centrality to determine the association between risk of infection of network members and their position within the sexual network. We also compared risk in smaller disconnected components with a large network centred on a social venue. METHODS: During the investigation of the outbreak, epidemiological data were collected on gonorrhoea cases and their sexual contacts from STI surveillance records. In addition to traditional contact tracing information, subjects were interviewed about social venues they attended in the past year where casual sexual partnering may have occurred. Sexual networks were constructed by linking together named partners. Univariate comparisons of individual network member characteristics and algebraic measures of network centrality were completed. RESULTS: The sexual networks consisted of 182 individuals, of whom 107 were index cases with laboratory confirmed gonorrhoea and 75 partners of index cases. People who had significantly higher information centrality within each of their local networks were found to have patronised a popular motel bar in the main town in the region (p = 0.05). When the social interaction through the bar was considered, a large network of 89 individuals was constructed that joined all eight of the largest local networks. Moreover, several networks from different communities were linked by individuals who served as bridge populations as a result of their sexual partnering. CONCLUSION: Asking clients about particular social venues emphasised the importance of location in disease transmission. Network measures of centrality, particularly information centrality, allowed the identification of key individuals through whom infection could be channelled into local networks. Such individuals would be ideal targets for increased interventions.

Adolescent↗
PubMed2004

Delayed neuropsychiatric impairment after carbon monoxide poisoning from burning charcoal.

Poisoning by carbon monoxide from burning charcoal has become one of the popular and lethal ways of attempting suicide in Hong Kong. Survivors of the carbon monoxide poisoning often face acute and delayed adverse problems in both their physical and mental health. We report two cases of delayed onset neuropsychiatric complications caused by carbon monoxide poisoning from burning charcoal. These symptoms were characterised by a latent period, followed by an abrupt and profound deterioration in the neurocognitive function with a seemingly reversible course. The literature is reviewed regarding the aetiology, pathophysiology, and management of this condition. Regular monitoring of their neurocognitive function and forewarning of this potential complication to the survivors of carbon monoxide poisoning and their families should be essential.

Adult↗
PubMed2003

Severe infective keratitis leading to hospital admission in New Zealand.

AIM: To identify key risk factors and the management and outcome of severe infective keratitis leading to public hospital admission in New Zealand. METHODS: Over a 2 year period, all admissions of presumed infective keratitis to Auckland Hospital were identified. The clinical records of all 103 cases were retrospectively reviewed with respect to clinical features, risk factors, management, and outcomes. RESULTS: The mean time from first symptoms or signs and presentation to hospital was 8.9 (SD 15.5) days. The majority of subjects, 88%, had at least one of the risk factors commonly associated with infective keratitis including previous ocular surgery (30%), contact lens wear (26%), topical corticosteroid use (25%), and ocular trauma (24%). Corneal scraping was performed in 92% and of a total of 105 scrapes, 71% were positive. Bacteria were isolated in all these cases, the majority being Gram positive organisms (72%). The most common isolates identified were coagulase negative Staphylococcus (16%), Propionibacterium acnes (14%), Staphylococcus epidermidis (11%), and Streptococcus pneumoniae (9%). In addition, yeasts were isolated in 5%, fungi in 4%, virus in 2%, and chlamydia in 1%. Importantly, polymicrobial infection accounted for 33% of culture positive cases. Antimicrobial treatment was changed on the basis of culture results in 17 cases (16.5%). Median initial visual and final best corrected visual acuity was 6/36-6/48 (logMAR 0.86) (IQR 0.39-2.00) and 6/12-6/15 (logMAR 0.360) (IQR 0.15-1.70), respectively. Previous ocular surgery and topical corticosteroid use were significantly associated with poorer visual acuity. The mean hospital stay was 5.8 days and the median 4.0 (IQR 2.0-8.0) days. Longer duration of stay was associated with the presence of hypopyon, larger ulcers, previous ocular surgery, and poor visual acuity. CONCLUSIONS: Infectious keratitis is an important cause of ocular morbidity. A significant proportion of cases have potentially modifiable risk factors. Previous ocular surgery and topical corticosteroid use, in particular, were associated with poorer visual outcomes. Many cases of severe keratitis might be avoided, or their severity reduced, by appropriate education of patients and ophthalmologists.

Administration, Topical↗
PubMed2003

Management of gallbladder polyps.

Polypoid lesions of the gallbladder (PLG) are a common finding on trans-abdominal ultrasound scan (USS). Once discovered the exact nature of the PLG must be elucidated to avoid unnecessary removal of benign lesions. This is particularly difficult for the intermediate sized PLG (5-15 mm). Recent developments, however, such as the higher resolution of USS and the availability of endoscopic ultrasound (EUS), mean that the management of PLG can be refined. In this review we outline methods for differentiating malignant from benign lesions and discuss their appropriate management.

Journal Article↗
PubMed2002

Larvae of Contracaecum sp. among inshore fish species of southwestern Australia.

Larval nematode infections were investigated in 236 fish from 17 estuarine and near-shore species in southwestern Australia. Larvae of the genus Contracaecum were found in 4 species of fish (Acanthopagrus butcheri, Sillaginodes punctata, Mugil cephalus and Aldrichetta forsteri). The prevalence and intensity of infection was highest in the 2 species of mullet: 81% infected and 9.8 +/- 1.5 larvae fish(-1) for M. cephalus; 100% and 12.7 +/- 3.7 larvae fish(-1) for A. forsteri. There was no evidence of post-mortem migration of worms from the visceral organs to the musculature of the fish.

Animals↗
PubMed2002

Drug release properties of pectinate microspheres prepared by emulsification method.

This study explored the potential of pectin for use in making microspheres for sustained-release of drugs. The pectin microspheres were prepared by external gelation using an emulsification technique with calcium chloride as the crosslinking agent. The influences of drug core (sulphanilamide, sulphaguanidine and sulphathiazole) and dissolution media (distilled water, USP HCl and phosphate buffers) on the drug release properties of the pectinate microspheres were examined. The morphology and drug content of the microspheres, and the solubility and solution pH of the drugs were also determined. Pectinate microspheres were successfully prepared by the emulsification technique. The rate of drug released from microspheres was highest in USP HCl buffer, followed by USP phosphate buffer and distilled water. Interestingly, the lowest percentage of drug released was produced by microspheres which were smallest in size and therefore largest in specific surface area, and consisting of sulphanilamide, the most water soluble drug. Further investigation showed that the microspheres consisted of both bound and unbound drugs. The percentage of drug released was predominantly determined by the relative contents of bound and unbound drugs embedded in the pectinate matrix.

Anti-Infective Agents↗