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Biomedical subjects

S L Ng

Publications and source records attributed to S L Ng.

16 recordsLinked to original sources
PubMed2001

Magnetic properties and heavy-metal contents of contaminated seabed sediments of Penny's Bay, Hong Kong.

Magnetic properties and heavy-metal concentrations of vibrocore samples were found to be potential indicators of shipping contamination in seabed sediments in Hong Kong Harbour. Geochemical results of 74 vibrocores located off Penny's Bay on Lantau Island revealed an enrichment of heavy metals in the upper 1-2 m of the cores within the eastern part of the study site. Whole-core magnetic susceptibility measurements also showed a greater concentration of magnetic particles in the surficial layer of these cores. A significant correlation exists between the magnetic susceptibility and the concentrations of Pb, Zn and Cu, as well as the Tomlinson pollution load index (PLI). The proximity of these cores to a major navigation fairway and an anchorage site suggests probable contamination of the surficial seabed sediments by shipping-related wastes. A study of the magnetic properties of one of the cores, VT60, revealed a difference in the magnetic properties between the contaminated and the uncontaminated sediments. Samples from the contaminated zone exhibited relatively stronger magnetic remanence and susceptibility. The two groups of samples also formed distinct trends on the hysteresis ratios plot. A level of unusually high magnetic susceptibility within the contaminated zone was attributable to the presence of strongly magnetized granules, which were probably refuse from shipping-related activities. Geochemical and magnetic results were also conducted on samples of different size-fractions from this core. The < 63 microns fraction was found to contain a relatively higher magnetic susceptibility and greater heavy-metal content.

Environmental Monitoring↗
PubMed2001

Respiratory suspended particulate (RSP) concentration and its implications to roadside workers: a case study of Hong Kong.

Respiratory Suspended Particulates (RSPs) have attracted increasing interest in recent years because of the potential risk of RSPs to human health. In Hong Kong, a large population of roadside workers is believed to be continuously exposed to high levels of RSPs. In this study, the roadside RSP concentrations at 72 locations in 6 urban districts of different land use types in Hong Kong are examined. Results show that the RSP pollution in Hong Kong's roadside environment is quite serious. The average RSP concentration at 61.11% of sampling sites is over 180 microg m(-3), the highest 24 h RSP mean concentration recommended by the Environmental Protection Department of Hong Kong. Analyses of RSP concentration data with reference to the local environmental conditions indicate that, among various environmental factors, land use, population density and traffic flow are important determinants of the RSP level. Because many roadside workers are exposed to high levels of RSP for prolonged periods, it is necessary to increase the public awareness of the health hazard of roadside workers.

Air Pollutants↗
PubMed2000

Green up-conversion emission in Er3+:BaTiO3 sol-gel powders.

Bright green emissions at 549 and 526 nm have been observed from sol-gel derived Er3+:BaTiO3 powders upon excitations at two near infrared (NIR) wavelengths of 973 and 816 nm. The decay characteristics were measured and studied. It was found that the predominant emission at 549 nm has very different lifetimes upon excitation at 973 and 816 nm, which was explained by the mechanisms of excited state absorption (ESA) of individual Er3+ ion and cooperative energy transfer (CET) between two near Er3+ ions for the up-conversion emission. Analysis also showed that 973-nm excitation is more effective for the green up-conversion emission.

Barium Compounds↗
PubMed1998

In vivo Doppler shift measurements using multimode fiber-optic catheters.

A new fiber-optic catheter for in vivo blood-flow measurements has been developed. The catheter is designed to measure blood flow in both the forward (toward the catheter tip) and reverse (away from the catheter tip) flow directions. It consists of two multimode optical fibers with core diameter of 50 microns and cladding diameter of 125 microns. One fiber transmits the laser beam into blood and the other receives the backscattered light from the erythrocytes within the probe volume. In the flow experiment, it was found that the flow within the boundary layer is indeed laminar and, hence, the relationship between the Doppler shift frequencies and the flow velocities is linear, thereby making the linear calibration possible for predicting the free stream flow velocity. Plots of the maximum shift frequency (frequency at which the Doppler spectrum disappeared into the noise spectrum) against the flow velocities are found to be more linear in both the forward and reverse flow directions than that of the dominant shift frequency (frequency with the highest amplitude). These results were reaffirmed by the numerical flow simulation along the catheter side wall.

Catheterization↗
PubMed1996

X-ray and NMR structure of human Bcl-xL, an inhibitor of programmed cell death.

THE Bcl-2 family of proteins regulate programmed cell death by an unknown mechanism. Here we describe the crystal and solution structures of a Bcl-2 family member, Bcl-xL (ref. 2). The structures consist of two central, primarily hydrophobic alpha-helices, which are surrounded by amphipathic helices. A 60-residue loop connecting helices alpha1 and alpha2 was found to be flexible and non-essential for anti-apoptotic activity. The three functionally important Bcl-2 homology regions (BH1, BH2 and BH3) are in close spatial proximity and form an elongated hydrophobic cleft that may represent the binding site for other Bcl-2 family members. The arrangement of the alpha-helices in Bcl-xL is reminiscent of the membrane translocation domain of bacterial toxins, in particular diphtheria toxin and the colicins. The structural similarity may provide a clue to the mechanism of action of the Bcl-2 family of proteins.

Amino Acid Sequence↗
PubMed1995

A community's attitudes towards the mentally ill.

AIM: To assess the general community's knowledge of mental illness and personal experience of people with mental illness. METHOD: Three hundred randomly selected Dunedin residents were surveyed by a postal questionnaire. The instruments used to measure attitudes were a shortened form of the Californian attitudes towards mental illness scale (CAMI scale) and a social distance scale. In addition, questions were asked about the respondent's age, gender, marital status, level of education, their main source of opinion, their experience with the mentally ill, and their beliefs about the causes and types of mental illness. RESULTS: Having known a person with mental illness facilitates more intimate relationships with people with a mental illness. Sociodemographic variables did not predict attitudes on the CAMI scale. Most respondents who had been in contact with the mentally ill held informed and enlightened views. CONCLUSION: The community needs and welcomes information on the subject of mental illness and has a positive outlook for the future planning of the rehabilitation of people with mental illness.

Adult↗
PubMed1992

Interaction of natriuretic peptides and cGMP production via the same receptor in mouse astrocytes.

Atrial and brain natriuretic peptides have been found previously to bind to specific receptors on cultured mouse astrocytes and to stimulate cyclic guanosine 5-monophosphate (cGMP) production with similar dose dependency although brain natriuretic peptide (BNP) shows a greater maximal stimulatory effect. The present study provides evidence that both peptides work through the same pathway. No additive or synergistic effect was observed when astrocytes were exposed to both peptides. However, human ANF(99-126) at high concentrations partially inhibited porcine BNP induced cGMP production to the level seen with ANF alone. ANF could be viewed as a partial agonist of pBNP competing for the same effector sites. Differences in structure between human ANF(99-126) and porcine BNP may account for the difference in cGMP response. The interaction between the two peptides and the cGMP response does not reflect receptor binding affinities and is likely to be a post-binding event.

Animals↗
PubMed1992

Automated detection and classification of breast tumors.

This paper presents a new method for the mammographic detection and classification of two types of breast tumors, stellate lesions and circumscribed lesions. The method assumes that both types of tumors appear as approximately circular, bright masses with a fuzzy boundary and that stellate lesions are in addition surrounded by a radiating structure of sharp, fine lines. Experimental results for a set of 27 mammograms are presented and the method is shown to have a high detection rate and an extremely low false positive rate.

Automation↗
PubMed1990

Beta-endorphin-like and adrenocorticotropin-like materials in heart tissues of the rat, gerbil, hamster and guinea pig.

1. Heart tissues of several rodent species including the rat, gerbil (Meriones unguiculatus), hamster (Mesocricetus auratus) and guinea pig (Cavia porcellus) were extracted with an acetone-water-HCl mixture. An acid acetone powder was obtained by adding a copious volume of acetone to the extract. 2. Rat heart acid acetone powder was subjected to ion exchange chromatography on CM-cellulose. Gerbil heart acid acetone powder was subjected to salt fractionation, gel filtration on Sephadex G-10 and then ion exchange chromatography on CM-cellulose. Hamster and guinea pig heart acid acetone powders were subjected to gel filtration on Sephadex G-25. 3. The fractions were assayed for the ability to stimulate corticosterone production in isolated rat adrenal decapsular (zona fasciculata, zona reticularis and medulla) cells, to displace D-ala2-D-leu5-(tyrosyl-3,5-3H) enkephalin from binding to rat brain membranes, and to inhibit 125I-human beta-endorphin from binding to its antibodies. 4. The widespread occurrence of beta-endorphin-like immunoreactivity among the rat heart CM-cellulose fractions may reflect different species of beta-endorphin. The fraction with the highest beta-endorphin-like immunoreactivity and opiate receptor binding activity was strongly adsorbed on CM-cellulose. 5. In hamster and guinea pig hearts, beta-endorphin-like immunoreactivity and opiate receptor binding activity were distributed among high molecular weight and low molecular weight fractions. 6. In gerbil hearts, opiate receptor binding activity was present in fractions unretarded on Sephadex G-10 (i.e. with a molecular weight greater than 700) as well as in the retarded fractions (i.e. with a molecular weight smaller than 700).(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenocorticotropic Hormone↗
PubMed1987

Corticotropin-like material in pigeon brains.

1. Pigeon brain acetone powder was extracted with a mixture of acetone, water and hydrochloric acid (40:21:1 v/v/v). The extract was added to a large volume of chilled acetone. 2. The resultant precipitate was washed with cold acetone and then chromatographed on Sephadex G-25. The void volume peak constituted fraction A. The trailing peak immediately following fraction A was divided into two fractions designated B and C. 3. Fraction B (mol. wt less than 5,000) stimulated corticosterone production in isolated rat adrenal cells while the other fractions were devoid of similar ACTH-like bioactivity. 4. None of the fractions showed activity in the opiate radioreceptor assay or hot plate test, implying the absence or presence of only trace amounts of opiate-like materials. Other possibilities that cannot be ruled out include the presence of molecules with substitutions in the sequence by amino acids that result in little or no activity.

Adrenocorticotropic Hormone↗
PubMed1987

Materials with opiate receptor binding activity in bovine testis and ovine pancreas.

Two groups of opiate-like materials, one with a molecular weight equal to or greater than 5000 daltons and another with a molecular weight smaller than 5000 daltons as judged by gel filtration on Sephadex G-25, were detected in bovine testes. The existence of opiate-like materials with a molecular weight smaller than 5000 daltons was demonstrated in ovine pancreas. The pancreatic fraction most strongly adsorbed on CM-cellulose possessed the highest opiate receptor binding activity. Bovine testis contained corticotropin-like material(s) which stimulated corticosterone production by isolated rat adrenal cells.

Animals↗
PubMed1982

Loss of concanavalin A induced suppressor T-lymphocyte function in patients with mesangial IgA nephritis.

Using the method of concanavalin A (Con a) inducible suppressor activity the peripheral mononuclear cells (PMC) of 17 patients with Mesangial IgA nephritis, 13 patients with idiopathic mesangial proliferative glomerulonephritis but with no IgA deposits on immunofluorescence (Non-IgA nephritis) and 18 healthy subjects were studied. DNA synthesis was measured by incorporation of 3H Thymidine. The mean suppression index (S.I.) of 0.94 +/- 0.08 (SEM) in the IgA nephritic patients was significantly different from that of the non-IgA nephritic patients (0.67 +/- 0.05) (P less than 0.01) as well as the group of normal healthy controls (0.64 +/- 0.05) (P less than 0.0025). The data show that patients with IgA nephritis have abnormal suppressor cell function and suggest an autoimmune basis in the pathogenesis of IgA nephritis.

Adult↗
PubMedDate not supplied

Outcome measure for paediatric rehabilitation: use of the Functional Independence Measure for children (WeeFIM). A pilot study in Chinese children with neurodevelopmental disabilities.

PURPOSE: To study the use of Functional Independence Measure for children (WeeFIM) in monitoring neurorehabilitation programmes for children with neurodevelopmental disabilities. METHODS: The neurorehabilitation team of the Children's Habilitation Institute of the Duchess of Kent Children's Hospital were trained to administer the WeeFIM. The WeeFIM was administered to children with various neuro-developmental impairment groups undergoing neurorehabilitation programmes in the hospital inpatient and also outpatient setting. The WeeFIM was scored on hospital admission and prior to discharge for those admitted for the rehabilitation programme. The WeeFIM profile was then monitored half yearly. The pilot study used WeeFIM in assessing 104 children with different medical disease categories. The disease or impairment categories included very low birth weight babies (n = 44), cerebral palsy (n = 19), Down's syndrome (n = 9), pervasive developmental disorder (n = 11), Duchenne Muscular Dystrophy (n = 18), and others (n = 3). RESULTS: WeeFim could be used to measure disability, monitor progress, enhance communication, measure the effectiveness of treatment, and document the benefits of rehabilitation intervention. It also served as a networking of neurorehabilitation programmes for different impairment categories in a continuum of settings: hospital, community, school and at home. WeeFIM was found to be a quick and reliable functional assessment instrument in this rehabilitation facility. CONCLUSIONS: WeeFIM could be used to assist neurorehabilitation clinicians in the selection of short term realistic goals and long term rehabilitation strategies for children with various neurodevelopmental disabilities, and the subsequent progress of the children could be monitored objectively.

China↗