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Biomedical subjects

M Hui

Publications and source records attributed to M Hui.

At least 19 recordsLinked to original sources
PubMed2006

An in vitro study on the compatibility and concentrations of combinations of vancomycin, amikacin, and dexamethasone in human vitreous.

PURPOSE: To investigate the precipitation process of a mixture of vancomycin, amikacin, and dexamethasone by equilibrium dialysis and its subsequent effect on the levels of available-free antibiotics and steroid. METHODS: Concentrations of amikacin, vancomycin, and dexamethasone in an equilibrium dialysis chamber were measured during the equilibrium process by high-performance liquid chromatography and fluorescence polarisation immunoassay. Vitreous were used as the medium of dialysis, with the three medications prepared in normal saline (NS) and balanced salt solution plus (BSS Plus) separately. RESULTS: Amikacin showed no measurable loss in NS or BSS Plus, either alone or when mixed with vancomycin or dexamethasone. Vancomycin showed minimal loss in BSS Plus, either alone or when mixed with amikacin or dexamethasone. Dexamethasone showed a median loss of 16 and 15% when incubated alone in NS and BSS Plus, respectively, at 48 h. When mixed with vancomycin or amikacin in BSS Plus, it showed a median loss of 13 and 12%, respectively, at 48 h. There was no statistically significant difference in the loss of dexamethasone under various conditions. In equilibrium dialysis in vitreous, amikacin, vancomycin, and dexamethasone reached equilibrium within 24 h and with no loss up to 192 h. There was no difference observed when the medications were prepared in NS or BSS Plus. CONCLUSIONS: Both amikacin and vancomycin did not show precipitation or decrease in concentration in NS or BSS Plus. Dexamethasone showed relatively small percentage loss. As a result, treatment of endophthalmitis with vancomycin and amikacin combination is preferred.

Amikacin↗
PubMed2006

Pneumocystis carinii pneumonia in Hong Kong: a 10 year retrospective study.

A retrospective review was performed of patients diagnosed with Pneumocystis carinii pneumonia (PCP) from 1994 to 2003 at the Prince of Wales Hospital in Hong Kong. Eighteen patients were identified. Six (33.3%) were co-infected with human immunodeficiency virus (HIV). The remaining 12 non-HIV-infected patients had underlying diseases: three post-renal transplant recipients, three with haematological malignancies, two with auto-immune diseases, two with renal diseases, one with hepatocellular carcinoma and one with congenital cytomegalovirus disease. Cytomegalovirus co-infection was observed in four patients. All patients received cotrimoxazole therapy, with intolerance observed in four of them, including one with glucose-6-phosphate dehydrogenase deficiency, two with repeated vomiting and one with renal impairment. Overall crude mortality was 33.3%. The results suggested that, apart from being a common infection for patients with HIV infection, PCP can occur during the course of many immunosuppressive diseases and therapies. The mortality of PCP was high despite appropriate treatment. Chemoprophylaxis should be considered in populations at risk.

AIDS-Related Opportunistic Infections↗
PubMed2006

Fatal septicaemia from Chromobacterium violaceum: case reports and review of the literature.

Chromobacterium violaceum rarely causes infection in humans and its mechanism of pathogenicity is not well understood. Human infection carries a high mortality rate with a fulminating clinical progression. A high index of suspicion is required for diagnosis, and is based on recovering the organisms from blood cultures or other appropriate specimens. We present three cases of human infection managed in a tertiary referral hospital in Hong Kong with a review of the literature.

Adult↗
PubMed2004

An in vitro study on the compatibility and precipitation of a combination of ciprofloxacin and vancomycin in human vitreous.

AIMS: To investigate the precipitation process of a mixture of vancomycin and ciprofloxacin by equilibrium dialysis and its subsequent effect on the level of available free antibiotics. METHODS: Concentrations of vancomycin and ciprofloxacin in an equilibrium dialysis chamber were measured during the equilibrium process by high performance liquid chromatography and fluorescence polarisation immunoassay. Normal saline (NS), balanced salt solution plus (BSS Plus), and vitreous were used separately as the medium of dialysis. RESULTS: Precipitation of ciprofloxacin occurred on incubation at 37 degrees C. It formed precipitate on its own or when mixed with vancomycin in all the three media of NS, BSS Plus, and vitreous. There was more precipitation at higher initial ciprofloxacin concentrations; at 25.0 mg/l about 75% free drug in BSS Plus was lost after 72 hours. The extent of precipitation was similar in both NS and BSS Plus. In the dialysis chambers, 20 mg/l ciprofloxacin dialysed against 125 mg/l vancomycin was reduced to a concentration about 5.0 mg/l after 168 hours. Precipitation of vancomycin was negligible. Ciprofloxacin precipitated in vitreous at body temperature, irrespective of the presence of vancomycin. Even after precipitation, the resultant concentration of ciprofloxacin was still higher than the MIC(90) of the drug against most Gram negative organisms. CONCLUSIONS: Based on this in vitro study, ciprofloxacin precipitated in vitreous at body temperature, irrespective of the presence of vancomycin or the medium for intravitreal injection. The resultant amount of ciprofloxacin was still higher than the MIC(90) of the drug against most Gram negative organisms after precipitation. The authors suggest ciprofloxacin in place of ceftazidime when used in combination with vancomycin for treatment of infective endophthalmitis.

Aged↗
PubMed2001

Prevalence and distribution of human herpesvirus 6 variants A and B in adult human brain.

The presence of human herpesvirus 6 (HHV-6) in brain tissues of 40 consecutive post-mortem cases was examined. For each case, autopsy samples were collected from the cerebellum, frontal, temporal, parietal and occipital lobes of both sides of the brain. HHV-6 DNA was detected by nested polymerase chain reaction and characterised into variants A and B. Overall, 97/400 (24.3%) samples were positive for HHV-6 DNA with 16 being variant A and 81 being variant B, but none of the samples harboured both variants. When analysed by patient, 34/40 (85%) had HHV-6 DNA detected in the brain. The viral DNA positivity did not show significant variation with gender and age. Four patients harboured variant A, 23 harboured variant B, and seven had both variants at different positions. The results indicate that both HHV-6A and HHV-6B are neurotropic and human brain may be another site for latency. HHV-6B was detected in brain tissues of a majority (75%) of the studied population and with a widespread distribution within the brain. Although the observed prevalence of HHV-6A in brain is lower (27.5%), in view of its lower seroprevalence, the neuroinvasive potential of variant A may be comparable to that of variant B. Although both variants are potential pathogens for the nervous system, the fact that they can exist, probably for most of the time, as commensals in human brain needs to be considered when interpreting their roles in neuropathology.

Adult↗
PubMed2001

Clearance of TT virus after allogeneic bone marrow transplantation.

A 10-year-old girl with thalassemia underwent bone marrow transplantation. Before transplantation, she had persistent TT virus (TTV) DNAemia for at least 18 months. Interestingly, the viral DNAemia was cleared soon after transplant and remained undetectable at the latest follow-up at 28 months. The early clearance of TTV that had occurred before engraftment or initiation of any antiviral therapy, together with the absence of TTV DNA from the results of the liver biopsy performed before transplantation, led us to hypothesize that the hematologic compartment could have been the site for viral persistence. Thus, the conditioning regimen may have depleted the hemic cells and the hematologically compartmentalized TTV. The potential of hemic tropism of TTV and its role in hematologic diseases need to be considered.

Biopsy↗
PubMed2001

Postantibiotic effects of antituberculosis agents alone and in combination.

The postantibiotic effects (PAEs) of seven antimycobacterial agents, tested at their respective peak concentrations in serum alone and in different combinations, against Mycobacterium tuberculosis ATCC 27294 were studied with a radiometric culture system in parallel with the viable count method. Rifampin gave the longest PAE (67.8 h) among the drugs used alone, and combinations of first-line drugs generally gave PAEs longer than 120 h. The data obtained might help provide a better understanding of the scientific basis of intermittently administered antituberculosis chemotherapy.

Antitubercular Agents↗
PubMed2001

Rapid identification of mycobacterium tuberculosis complex from Bactec 12B broth cultures originating from non-respiratory secretion specimens: comparison between Accuprobe and in-house polymerase chain reaction.

The rapid identification of Mycobacterium tuberculosis complex from 161 consecutive positive Bactec 12B cultures originated from non-respiratory secretion specimens was evaluated by comparing Accuprobe and an in-house polymerase chain reaction method. Using conventional biochemical method as the gold standard, 85.7% of the isolates (n = 138) were identified as Mycobacterium tuberculosis. The sensitivities of Accuprobe and the in-house-polymerase chain reaction method in identifying Mycobacterium tuberculosis complex were 92.0% (127/138) and 93.5% (129/138), respectively. Specificities of both methods being 87.0% (20/23 for both tests). Using a batch system of performing identification once weekly, the average turnaround time for Accuprobe, from the time of primary inoculation, was 27 days, which was comparable with that of in-house polymerase chain reaction, which was 29 days. The average time required for a confirmatory result based on conventional biochemical identification method was 84 days. The estimated reagent cost of in-house polymerase chain reaction was only one-fifth of that of Accuprobe. Therefore, the choice of methodology will depend on the individual laboratory's availability of resources and clinical demand. In the event of discrepant results between rapid identification methods and conventional methods, histological examination and clinical assessment can provide guidance as to the nature of the infection.

Bacteriological Techniques↗
PubMed2000

Rapid identification of medically important Candida to species level by polymerase chain reaction and single-strand conformational polymorphism.

Invasive fungal disease has taken a great toll on immunocompromised patients. With the emergence of fluconazole and amphotericin B resistance, the rapid identification of fungi to species level is of clinical relevance in guiding appropriate antifungal therapy. Among these opportunistic fungi, Candida species are the most commonly encountered. We had developed a molecular method utilizing single-strand conformational polymorphism (SSCP) to delineate different patterns on a 260-bp amplicon from the 28S rRNA gene from six medically important Candida species. The SSCP banding patterns obtained from a total of 52 isolates were sufficiently unique to allow distinction between the species, thus indicated a high level of specificity. This method of PCR-SSCP can provide a simple and specific method for the rapid identification of medically important Candida to species level.

Candida↗
PubMed1999

Determination of ginsenoside Rg3 in plasma by solid-phase extraction and high-performance liquid chromatography for pharmacokinetic study.

A method using high-performance liquid chromatography (HPLC) and solid-phase extraction (SPE) is described for the determination of ginsenoside Rg3 in human plasma. A 2.5-ml volume of plasma was mixed with 2.5 ml 60% methanol aqueous solution, and centrifuged at 1100 g for 10 min, the supernatant fluid was further purified by SPE with 200 mg/5 ml 40 microns octadecyl silica and separation was obtained using a reversed-phase column under isocratic conditions with ultraviolet absorbance detection. The intra- and inter-day precision, determined as relative standard deviations, were less than 5.0%, and method recovery was more than 97%. The lower limit of quantitation, based on standards with acceptable RSDs, was 2.5 ng/ml. No endogenous compounds were found to interfere with analyte. A good linear relationship with a regression coefficient of 0.9999 in the range of 2.5 to 200 ng/ml was observed. This method has been demonstrated to be suitable for pharmacokinetic studies in humans. Method development for determination of drug with low UV absorption by SPE and HPLC is also discussed.

Calibration↗
PubMed1999

Presence of human herpesviruses 6, 7, and 8 DNA sequences in normal brain tissue.

The three novel human herpesviruses (HHV) 6, 7, and 8 are predominantly, but not exclusively, lymphotropic. In an attempt to elucidate their neurotropism in vivo, viral DNA sequences present in fresh autopsy cortical brain tissues obtained from 84 consecutive Chinese subjects (mean age, 66.9 years; range, 21-98 years) were detected by a nested polymerase chain reaction. These patients were apparently immunocompetent and free of clinical signs of viral diseases. HHV-6 DNA was detected in 36 of 84 (42.9%) patients, and the DNA-positive and -negative groups did not show a significant difference in age or sex distribution. Of the 36 HHV-6 DNA-positive cases, 9 (25%) were variant A and 27 (75%) were variant B. In view of the lower prevalence of variant A than variant B in the adult population, the two variants may share a comparable neuroinvasive potential. HHV-7 and HHV-8 DNA were detected respectively in three and two patients. The low positive rates of HHV-7 and HHV-8 may represent a relatively lower neuroinvasive potential of the viruses. Alternatively, the localization of HHV-7 and HHV-8 may be more restricted and the sampled cortical tissues may not represent the most abundant site of persistence in the nervous system. The results provide molecular evidence of the presence of the three newly identified herpesviruses in brain tissue. The pathogenic role for HHV-7 and HHV-8, as with HHV-6, in neurological diseases should not be overlooked.

Adult↗
PubMed1999

Epidemiology of respiratory syncytial virus infection among paediatric patients in Hong Kong: seasonality and disease impact.

In a 5-year retrospective survey of respiratory syncytial virus (RSV) infections among hospitalized children, 1340 cases were identified of which, 98.4% were children < 5 years old with a male:female ratio of 1.5: 1. Most cases occurred from April to September showing a significant positive correlation with temperature and relative humidity. Community-acquired infections accounted for 92.5% of the cases with a mean hospital stay of 5 days. The estimated annual incidence of RSV infection requiring hospitalization was 2.5/1000 children < 5 years old with a mortality of 0.15% among hospitalized cases. On average, 248 children were admitted each year to the 1400-bed acute regional hospital accounting for an expenditure of HK S1.94 ((approximately US +/-0.25) million for hospitalization costs which equates to an annual cost in excess of HK $6.67 (approximately US $0.86) million for the whole of Hong Kong. An RSV vaccine should be a priority.

Child, Preschool↗
PubMed1999

Improved recovery of Mycobacterium tuberculosis from pleural aspirates: bedside inoculation, heparinized containers and liquid culture media.

The effects of bedside inoculation, heparinized containers and liquid culture media on the recovery of Mycobacterium tuberculosis from pleural aspirates were evaluated in this study. Of 155 patients, 63 were diagnosed to have pleural effusion tuberculous in origin. The overall recovery of M. tuberculosis was 57.1%. Bedside inoculation of the specimens produced a significantly higher yield than laboratory inoculation using non-heparinized specimens. When the pleural aspirates were transported in heparinized containers, the recovery rate was comparable to that from bedside inoculation, but lower when non-heparinized containers were used. No significant difference was found in recovery rate between the two liquid media, but the rate was significantly higher with the use of liquid media than conventional solid media. Thus, bedside inoculation of pleural aspirates, use of heparinized containers for transport for delayed inoculation in the laboratory and use of liquid culture media are recommended.

Anticoagulants↗
PubMed1998

A novel neuron-specific aminopeptidase in rat brain synaptosomes. Its identification, purification, and characterization.

A specific aminopeptidase localized exclusively in neurons of the central nervous system was identified with an automated continuous-flow aminopeptidase analyzer developed recently in this laboratory. The enzyme was purified from rat brain 4933-fold to homogeneity with 9.3% recovery by ammonium sulfate fractionation, followed by column chromatography successively on phenyl-Sepharose, Sephadex G-200, and twice on Mono Q FPLC. The purified single-chain enzyme was estimated to be 110 kDa in molecular mass. It has a pI of 5.25 and a pH optimum of 7.0. Only Mg(II) restores the activity of the apoenzyme. The neutral aminopeptidase hydrolyzes beta-naphthylamides of amino acids with aliphatic, polar uncharged, positively charged, or aromatic side chains. It has a Km of 95 microM and a kcat of 7.8 s-1 on methionine-enkephalin, releasing only the N-terminal tyrosine. The thiol-dependent metallo-enzyme is most sensitive to amastatin inhibition with a Ki of 0.04 microM, and is the aminopeptidase most sensitive to puromycin. Its properties are different from those of the ubiquitous puromycin-sensitive aminopeptidase obtained from the same enzyme preparation. The blocked N terminus, substrate and inhibitor specificity, hydrolytic coefficiency, metal effects, pI, molecular weight, and catalytic site show that this enzyme is distinct from all other known aminopeptidases. Its enrichment in the synaptosomes suggests that this first reported neuron-specific peptidase plays a role in neurotransmission and synaptic differentiation.

Amino Acid Sequence↗
PubMed1998

New face of an old enzyme: alkaline phosphatase may contribute to human tissue aging by inducing tissue hardening and calcification.

Tissue nonspecific alkaline phosphatase (AP) plays a well-known role in bone mineralization. This role was first suggested by a human AP deficiency disease, hypophosphatasia. Further studies with AP gene knockout mice have also suggested a role for AP in mineralization. However, AP is also expressed in other human tissues besides bone and cartilage, and this raises a question as to whether AP may also play a role in pathological mineralization such as dystrophic and vascular calcification. In vitro studies carried out in our laboratory indicate that a variety of cell types stably expressing membrane-bound AP can affect extracellular mineralization regardless of the tissue from which the cell lines originated (e.g. fibroblasts, vascular endothelial cells, or renal epithelial cells). This AP-mediated extracellular mineralization is both substrate/dependent and culture environment/dependent and may be consistent with a putative role for AP in pathological mineralization in tissues other than bone and cartilage. In this regard, it is interesting to note that high levels of AP are observed in vascular endothelia of small arterioles in brain and heart. It is probable that expression of AP in small arterioles of brain and heart may also contribute to the vascular hardening and calcification observed in humans. This in turn could be related to vascular aging, vascular disease, and the resultant weakening of and/or rupture of vessel walls.

Aging↗
PubMed1997

Stable transfection of nonosteogenic cell lines with tissue nonspecific alkaline phosphatase enhances mineral deposition both in the presence and absence of beta-glycerophosphate: possible role for alkaline phosphatase in pathological mineralization.

It is documented that alkaline phosphatase (AP) plays an important role in bone mineralization. Considering that TN-AP is expressed in periodontal ligament fibroblasts, renal epithelial cells, and vascular endothelial cells, and that TN-AP is both a calcium-/phosphate-binding protein and a phosphohydrolytic enzyme, we hypothesize that membrane-bound AP also plays an important role in the initiation of physiological and pathological mineralizations in tissues other than bone and cartilage. To test this hypothesis, nonosteoblast cell lines, including a fibroblast line, a renal epithelial line, and a capillary endothelial line, were stably transfected to express high levels of rat bone AP on their cell surfaces. These rat bone AP-expressing cells were then cultured on filter membranes in the presence or absence of beta-glycerol phosphate. von Kossa staining for calcium phosphate and transmission electron microscopy with electron diffraction analysis for minerals were employed to investigate the effect of membrane AP on extracellular calcium phosphate mineralization. Our results indicated that AP expression on these nonosteoblast-like cell surfaces have induced extracellular hydroxyapatite (HAP) mineralization. Our findings support the concept that membrane-bound AP contributes to extracellular apatitic mineralization by mechanisms that do not necessarily involve its hydrolase activity. They also suggest that AP might be important for the initiation of pathological mineralization in nonosteogenic tissues.

Alkaline Phosphatase↗