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Biomedical subjects

S M Wong

Publications and source records attributed to S M Wong.

At least 37 records · Page 2Linked to original sources
PubMed2002

Genetic variability in the coat protein genes of two orchid viruses: Cymbidium mosaic virus and Odontoglossum ringspot virus.

The variability in coat protein gene sequences of Cymbidium mosaic virus (CymMV) and Odontoglossum ringspot virus (ORSV) that naturally infect orchids worldwide was investigated. Samples were collected from Korea, Singapore and Taiwan. The sequence data were compared with available published coat protein gene sequences of CymMV and ORSV, including those from Japan and Thailand. Among CymMV isolates, the homology was 89.1%-99.7% and 93.2%-100% at the nucleotide and amino acid levels, respectively. Among the ORSV isolates, the homology was 95.5%-100% and 93%-100% at the nucleotide and amino acid levels, respectively. No particular region of variability could be defined in either of the viruses. In deduced amino acid sequence, the N-terminal was more conserved than the C-terminal in both CymMV and ORSV. By comparing all sequences determined in this study and those that are published in the GenBank databases, we did not find clustering based on geographical distribution or sequence identity. Such high sequence conservation suggests that both CymMV and ORSV coat protein genes are suitable candidates to provide resistance to orchids cultivated in different geographical locations.

Amino Acid Sequence↗
PubMed2001

Local vs systemic corticosteroids in the treatment of carpal tunnel syndrome.

The authors compared the effectiveness of low-dose, short-term oral prednisolone vs local methylprednisolone injection in a prospective, double-blinded, parallel treatment study of carpal tunnel syndrome (CTS). A single injection of 15 mg methylprednisolone resulted in significant improvement in global symptom scores over a 12-week period. This study demonstrated the superiority of local steroid injection to oral steroid in the treatment of CTS.

Administration, Oral↗
PubMed2001

Is anomalous production of omega and omega; evidence for disoriented chiral condensates?

No conventional picture of nucleus-nucleus collisions has yet been able to explain the abundance of Omega and Omega; hadrons in central collisions between Pb nuclei at 158A GeV at the CERN SPS. We argue that this is evidence that they are produced as topological defects arising from the formation of disoriented chiral condensates with an average domain size of about 2 fm.

Journal Article↗
PubMed2001

15-deoxy-delta12,14-prostaglandin J2, a specific ligand for peroxisome proliferator-activated receptor-gamma, induces neuronal apoptosis.

Although considerable research has shown a role for peroxisome proliferator-activated receptors (PPAR) in adipose differentiation and in the regulation of inflammation, little is known about its possible functions in neurons. We investigated the role of PPARgamma in primary cultures of cortical neurons and human neuroblastoma SH-SYSY cells. Incubation of cortical neurons with the specific PPARgamma ligand 15-Deoxy-delta12,14-prostaglandin J2 (15d-PGJ2) induced morphological changes including neurite degeneration and nuclear condensation that were consistent with neurons dying by apoptosis. The morphological changes associated with incubation of cortical neurons with 15d-PGJ2 were prevented following pretreatment of neurons with the general caspase inhibitor, Z-VAD. These results highlight a novel role for PPARgamma in neurons and suggest that unwarranted activation of PPARgamma may contribute to the neuronal apoptosis associated with certain neurodegenerative disorders including Alzheimer's disease (AD).

Animals↗
PubMed2001

Complete sequences and phylogenetic analyses of a Singapore isolate of broad bean wilt fabavirus.

The complete nucleotide (nt) sequence of a Singapore isolate of broad bean wilt fabavirus from Megakepasma erythrochlamys L., designated BBWV-ME, was determined. Its bipartite genome consisted of two positive-sense single-stranded ribonucleic acids (RNA). RNA1 (5951 nt in length) encoded a putative protease cofactor, nucleotide triphosphate (NTP)-binding domain (helicase), viral genome-linked protein (VPg), protease and RNA-dependent RNA polymerase (RdRp). RNA2 (3607 nt in length) encoded a putative movement protein (MP) and coat proteins (CP). Genome organization of BBWV-ME was similar to other viruses in the Comoviridae family. Phylogenetic analyses showed that fabaviruses were more closely related to the comoviruses than the nepoviruses.

Base Sequence↗
PubMed2001

Cucurbit protoplast isolation for the study of plant virus replication.

A cucurbit protoplast isolation protocol was established for the study of plant virus replication in vivo. This protocol is applicable to both cucumber and squash leaf tissue with significant increases in yields of viable protoplasts suitable for electroporation, compared to other published methods. A combination of Cellulase RS, Macerozyme R10 and mannitol was used as digestion enzymes and osmoticum. An average of 1.7x10(7) protoplasts per gram of fresh leaf tissue were obtained from cucumber cultivar Bet-alpha. Both cucumber cultivar Shimson and squash cultivar First Taste produced an average yield of 6.0x10(6) protoplasts per g of fresh leaf tissue. Electroporation of 10 microg of Zucchini yellow mosaic potyvirus (ZYMV-S) RNA into the protoplasts resulted in virus replication and synthesis of coat protein (CP). SDS-PAGE and immunoblotting were used to detect the CP 48 h post-electroporation. This protocol is highly reproducible and will assist researchers who require cucurbit protoplasts to study virus replication.

Cell Separation↗
PubMed2001

Enflurane actions on spinal cords from mice that lack the beta3 subunit of the GABA(A) receptor.

BACKGROUND: Gamma-aminobutyric acid type A (GABA(A)) receptors are considered important in mediating anesthetic actions. Mice lacking the beta3 subunit of this receptor (beta3-/-) have a higher enflurane minimum alveolar concentration (MAC) than wild types (+/+). MAC is predominantly determined in spinal cord. METHODS: The authors measured three population-evoked responses in whole spinal cords, namely, the excitatory postsynaptic potential (pEPSP), the slow ventral root potential (sVRP), and the dorsal root potential. Synaptic and glutamate-evoked currents from motor neurons in spinal cord slices were also measured. RESULTS: Sensitivity of evoked responses to enflurane did not differ between +/+ and -/- cords. The GABA(A) receptor antagonist bicuculline significantly (P < 0.05) attenuated the depressant effects of enflurane on pEPSP, sVRP and glutamate-evoked currents in +/+ but not -/- cords. The glycine antagonist strychnine elevated the pEPSP to a significantly greater extent in -/- than in +/+ cords, but the interactions between strychnine and enflurane did not differ between -/- and +/+ cords. CONCLUSIONS: Similar enflurane sensitivity in spinal cords from -/- and +/+ mice was coupled with a decreased role for GABA(A) receptors in mediating the actions of enflurane in the former. This finding implies that other anesthetic targets substitute for GABA(A) receptors. Increase in glycine receptor-mediated inhibition was found in -/- cords, but the glycine receptor does not appear to be a substitute anesthetic target. This mutation thus led to a quantitative change in the molecular basis for anesthetic depression of spinal neurotransmission in a fashion not predicted by the mutation itself. The results argue against an immutable dominant role for GABA(A) receptors in mediating spinal contributions to MAC.

Anesthetics, Inhalation↗
PubMed2001

Redox signal transduction by the ArcB sensor kinase of Haemophilus influenzae lacking the PAS domain.

The Arc (anoxic redox control) two-component signal transduction system of Escherichia coli, which comprises the tripartite ArcB sensor kinase and the ArcA response regulator, modulates the expression of numerous operons in response to redox conditions of growth. We demonstrate that the arcA and arcB genes of Haemophilus influenzae specify a two-component system. The Arc proteins of the two bacterial species sufficiently resemble each other that they can participate in heterologous transphosphorylation in vitro. Moreover, the Arc system of H. influenzae mediates transcriptional control according to the redox condition of growth both autologously in its own host and homologously in E. coli, indicating a high degree of functional conservation of the signal transduction system. The H. influenzae ArcB, however, lacks the PAS domain present in the region of E. coli ArcB linking the transmembrane to the cytosolic catalytic domains. Because the PAS domain participates in signal reception in a variety of sensory proteins, including sensors of molecular oxygen and redox state, a similar role was previously ascribed to it in ArcB. Our results demonstrate that the ArcB protein of H. influenzae mediates signal transduction in response to redox conditions of growth despite the absence of the PAS domain.

Amino Acid Sequence↗
PubMed2000

Genetic footprinting with mariner-based transposition in Pseudomonas aeruginosa.

The complete DNA sequence of Pseudomonas aeruginosa provides an opportunity to apply functional genomics to a major human pathogen. A comparative genomics approach combined with genetic footprinting was used as a strategy to identify genes required for viability in P. aeruginosa. Use of a highly efficient in vivo mariner transposition system in P. aeruginosa facilitated the analysis of candidate genes of this class. We have developed a rapid and efficient allelic exchange system by using the I-SceI homing endonuclease in conjunction with in vitro mariner mutagenesis to generate mutants within targeted regions of the P. aeruginosa chromosome for genetic footprinting analyses. This technique for generating transposon insertion mutants should be widely applicable to other organisms that are not naturally transformable or may lack well developed in vivo transposition systems. We tested this system with three genes in P. aeruginosa that have putative essential homologs in Haemophilus influenzae. We show that one of three H. influenzae essential gene homologs is needed for growth in P. aeruginosa, validating the practicality of this comparative genomics strategy to identify essential genes in P. aeruginosa.

Alleles↗
PubMed2000

A unique virus complex causes Ageratum yellow vein disease.

Ageratum conyzoides L., a weed species widely distributed throughout southeast Asia, frequently exhibits striking yellow vein symptoms associated with infection by Ageratum yellow vein virus (AYVV), a member of the Geminiviridae (genus Begomovirus). Most begomoviruses have bipartite genomes (DNAs A and B), but only a DNA A has been identified for AYVV. We demonstrate that yellow vein disease of A. conyzoides results from co-infection by AYVV DNA A (2,741 nt) and a circular DNA that is approximately half its size (1,347 nt) that we designate DNA beta. Apart from the sequence TAATATTAC, common to all geminiviruses and containing the initiation site of rolling circle replication, DNA beta shows negligible sequence homology either to AYVV DNA A or to DNA B associated with bipartite begomoviruses. DNA beta depends on DNA A for replication and is encapsidated by DNA A-encoded coat protein and so has characteristics of a DNA satellite. However, systemic infection of A. conyzoides by DNA A alone is sporadic and asymptomatic, and DNA A accumulation is reduced to 5% or less of its accumulation in the presence of DNA beta. Therefore, DNA A and DNA beta together form a previously unrecognized disease-inducing complex. Our data also demonstrate that the nanovirus-like DNA 1 component associated with infected A. conyzoides plays no essential role in the disease and represents a satellite-like DNA. Furthermore, the satellite DNA previously found associated with tomato leaf curl virus is probably a defective DNA beta homologue.

Base Sequence↗
PubMed2000

Rapid simultaneous detection of two orchid viruses using LC- and/or MALDI-mass spectrometry.

Liquid chromatography/mass spectrometry (LC/MS) and matrix-assisted laser desorption-ionization (MALDI) mass spectrometry are capable of providing molecular mass information on biological samples with high speed, accuracy and sensitivity. With mass spectrometry, identifying a virus based on the molecular weight of its coat protein is relatively simple and accurate. The technique can be applied to all viruses with known coat protein molecular weights. Using the LC/MS and/or MALDI, this paper describes rapid simultaneous detection of the two most prevalent orchid viruses, namely cymbidium mosaic potexvirus (CymMV) and odontoglossum ringspot tobamovirus (ORSV). The coat protein molecular weights of CymMV and ORSV were detected accurately using an extract from 1 g of virus-infected Oncidium orchid flower. Because LC/MS and MALDI allow automated analyses of multiple samples with simple preparation steps, both techniques are ideal for rapid identification of viruses from a large number of samples. This is the first report on the application of LC/MS and/or MALDI for simultaneous detection of two plant viruses from an infected plant extract.

Chromatography, Liquid↗