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Biomedical subjects

T Ooi

Publications and source records attributed to T Ooi.

At least 19 recordsLinked to original sources
PubMed2006

Imiquimod-induced regression of actinic keratosis is associated with infiltration by T lymphocytes and dendritic cells: a randomized controlled trial.

BACKGROUND: Imiquimod 5% cream is a topically applied immune response modifier that has been shown to give effective treatment of actinic keratosis (AK). The therapeutic effects of imiquimod are likely to involve the provocation of a cutaneous immune response against abnormal cells, an assumption based on a strong correlation between complete clearance rates and the severity of the local skin reactions (erythema, oedema, erosion/ulceration, weeping/exudation and scabbing/crusting); however, no clinical studies have conclusively proved this mechanism. OBJECTIVES: To determine the nature of cellular infiltrates induced by the application of imiquimod to AK lesions and to study cells involved in the cutaneous immune response. METHODS: Eighteen patients participated in this phase I, randomized, double-blind, parallel group, vehicle-controlled study. Enrolled patients were randomized in a 2 : 1 ratio to receive imiquimod cream or vehicle cream and applied study cream to five lesions on the scalp, forearm or upper trunk once daily, three days per week for up to 16 weeks. Each patient had punch biopsies of two distinct AK lesions: a lesion was biopsied before treatment to obtain baseline biomarker levels, and a different lesion was biopsied after 2 weeks of treatment. Biopsy specimens were examined using routine and immunohistochemical staining. RESULTS: The imiquimod group showed statistically significant increases from baseline to week 2 in tissue biomarker levels for CD3, CD4, CD8, CD11c, CD86/CD11c, CD68, HLA-DR and TUNEL. No significant differences were seen for the vehicle group. Complete clearance of all treated AK lesions was achieved in five of 11 (45%) imiquimod patients and in none of six vehicle patients. CONCLUSIONS: Imiquimod stimulates a cutaneous immune response characterized by increases in activated dendritic cells and CD4+ and CD8+ T cells.

Aged↗
PubMed2004

Are sleep problems under-recognised in general practice?

AIMS: To evaluate the frequency of sleep problems in Australian children aged 4.5-16.5 years, and to determine whether the frequency of sleep problems on questionnaire predicts the reporting of sleep problems at consultation. METHODS: Parents of 361 children (aged 4.5-16.5 years) attending their general practitioner for "sick" visits were asked to assess their child's sleep over the previous six months using the Sleep Disturbance Scale for Children, from which six sleep "disorder" factors and a total sleep problem score were obtained. RESULTS: The percentage of children with a total sleep problem score indicative of clinical significance (T score >70 or >95th centile) was 24.6% (89/361). Despite this high frequency, parents only addressed sleep problems in 4.1% (13/317) of cases and reported that GPs discussed sleep problems in 7.9% (25/317) of cases. Of the 79 children who reported total sleep problem T scores in the clinical range, only 13.9% (11/79) discussed sleep with their general practitioner within the previous 12 months. Regression analyses revealed an age related decrease in problems with sleep-wake transition and sleep related obstructive breathing; sleep hyperhydrosis, initiating and maintaining sleep, and excessive daytime sleepiness did not significantly decrease with age. No significant gender differences were observed. CONCLUSIONS: Results suggest that chronic sleep problems in Australian children are significantly under-reported by parents during general practice consultations despite a relatively high frequency across all age groups. Given the impact on children and families, there is a need for increased awareness of children's sleep problems in the community and for these to be more actively addressed at consultation.

Adolescent↗
PubMed2001

Distinct advantage of the in situ generation of quaternary ammonium fluorides under phase-transfer conditions toward catalytic asymmetric synthesis.

[structure in text] Quaternary ammonium fluorides were found to be efficiently generated in situ from the corresponding ammonium hydrogensulfates by treatment with commercially available potassium fluoride dihydrate (KF.2H(2)O) in THF and directly used as a fluoride source for the generation of carbon nucleophiles from organosilicon compounds. This method can be successfully applied to the preparation of structurally well-defined, C(2)-symmetric chiral quaternary ammonium fluorides of type 1 (X = F), thereby allowing catalytic enantioselective Mukaiyama-type aldol reactions under mild conditions.

Journal Article↗
PubMed2000

Unique synthetic utility of BF(3).OEt(2) in the highly diastereoselective reduction of hydroxy carbonyl and dicarbonyl substrates

A new aspect of commonly used BF(3).OEt(2) has been illuminated by successfully demonstrating the unique but highly stereoselective reactions of hydroxy carbonyl and dicarbonyl substrates. For example, treatment of gamma-hydroxy ketone 1c with BF(3).OEt(2)/Bu(3)SnH in CH(2)Cl(2) at -78 to -40 degrees C afforded the corresponding 1, 4-diol 2c with virtually complete diastereoselection, while use of TiCl(4) as a Lewis acid under similar reaction conditions caused a total lack of diol yield and selectivity (17%; 2c/3c = 1.2:1), accompanied by a significant formation of 2,3-disubstituted tetrahydrofuran 4 (44%).

Journal Article↗
PubMed2000

Integration of an immunosorbent assay system: analysis of secretory human immunoglobulin A on polystyrene beads in a microchip.

An immunosorbent assay system was integrated into a glass microchip. Polystyrene beads were introduced into a microchannel, and then human secretory immunoglobulin A (s-IgA) adsorbed on the bead surface was reacted with colloidal gold conjugated anti-s-IgA antibody and detected by a thermal lens microscope. The scale merits of liquid microspace on the molecular behavior remarkably contributed to reduced assay time. The integration cut the time necessary for the antigen-antibody reaction by 1/90, thus shortening the overall analysis time from 24 h to less than 1 h. Moreover, troublesome operations required for conventional immunosorbent assays could be replaced by simple operations.

Antigen-Antibody Reactions↗
PubMed2000

New terpenoid components from the volatile oils of the soft corals Clavularia viridis and Sarcophyton acutangulum.

A new tetracyclic terpenoid hydrocarbon, cyclosinularane (1), and (+)-alloaromadendrene (2), the enantiomer of terrestrial (-)-alloaromadendrene, have been isolated from the volatile oil of the soft corals Clavularia viridis and Sarcophyton acutangulum, respectively. Their structures have been determined on the basis of NMR spectral analysis and their chiroptical properties.

Animals↗
PubMed2000

Differential scanning calorimetry of light meromyosin fragments having various lengths of carp fast skeletal muscle isoforms.

Various recombinant light meromyosin (LMM) fragments were prepared from cDNAs encoding the 10 degrees C and 30 degrees C types of myosin heavy chain isoforms predominantly expressed in fast skeletal muscles of the 10 degrees C- and 30 degrees C-acclimated carp, respectively. These included three kinds of quarter fragments, 1/4-, 2/4-, and 4/4-quarter, composed of residues 1-130, 131-270, and 401-563 from the N-terminus, respectively, as well as three halves, N-, M-, and C-half fragments, containing residues 1-301, 131-400, and 302-563, respectively, and 69K fragments of residues 1-525. Unfortunately, in spite of extensive efforts, the 3/4-quarter fragment was not expressed for both 10 degrees C and 30 degrees C types in our expression system using Escherichia coli. All the LMM fragments except for the 10- and 30-2/4 quarters for the 10 degrees C and 30 degrees C types, respectively, exhibited a typical pattern of a-helix in CD spectrometry. When these were subjected to differential scanning calorimetry (DSC), 30 degrees C-type LMM fragments were all found to be more thermostable than the 10 degrees C-type counterparts. To identify amino acid substitutions responsible for different thermostabilities between the 10 degrees C- and 30 degrees C-type LMMs, six mutant proteins were prepared, mainly focusing on substitutions in the C-terminal half of LMM, and subjected to DSC and CD analyses. For three mutants in which two residues of the 10 degrees C type were replaced by those of the 30 degrees C type, 10-S355T/T361A, 10-M415L/L417V, and 10-S535A/H536Q, the endothermic peaks in DSC increased by 1.4-2.0 degrees C from that of the original 10 degrees C type. The T(m) values for two single-residue substitutions, 10-H449R and 10-T491I, shifted 0.8 and 1.3 degrees C higher than that for the 10 degrees C-type LMM, respectively, whereas the last mutant, 10-G61V, showed no change in thermostability. The finding that the difference in T(m) values for major endothermic peaks from the 10-69K and 30-69K fragments was 4.6 degrees C, which roughly corresponds to that between the original 10 degrees C and 30 degrees C types, suggested that the eight substitutions located in the C-terminal region of the 69K fragments (residues 302-525) are major candidates for the residues responsible for the difference in thermostability between the 10 degrees C- and 30 degrees C-type LMMs.

Amino Acid Sequence↗
PubMed2000

"Amphiphilic" Cleavage of gamma-Stannyl Ketones with ATPH/RLi: Application to Enone Fragmentation by the Conjugate Addition - Cleavage Sequence.

The use of a combined Lewis acid/base system consisting of aluminum tris(2,6-diphenylphenoxide) (ATPH) and MeLi has allowed the electrophilically activated nucleophilic ("amphiphilic") cleavage of C(alpha)-C(beta) bonds in gamma-stannyl ketones. Through combination with the conjugate addition of alpha-stannyl carbanion to enone, this approach constitutes a novel two-step conjugate addition - cleavage sequence that leads to functionalized ketones (see reaction).

Journal Article↗
PubMed1999

Sesterterpenoids and diterpenoids of the wax excreted by a scale insect, Ceroplastes pseudoceriferus.

A new sesterterpene, (2Z,6Z,10E)-cericerene-15,24-diol (1), and its 30-hydroxytriacontanoate (2) were isolated from the wax exuded by the scale insect Ceroplastes pseudoceriferus, together with the acetates and 30-hydroxytriacontanoates of 3,15-dihydroxy- and 15, 20-dihydroxylabda-7,13-diene (3-6). The absolute configurations of the labdadiene alcohols were antipodal to the ordinary labdanes isolated from terrestrial plants.

Animals↗
PubMed1999

Analysis of a catalytic acidic pair in the active center of cellulase from Aspergillus aculeatus.

Four acidic amino acid residues, Asp97, Asp101, Glu118, and Glu202, were located in the cleft from the X-ray crystallographic analysis of FI-CMCase, endo-1,4-beta-glucanase (EC: 3.2.1.4) of Aspergillus aculeatus No. F-50. To identify the catalytic residues of the FI-CMCase, these residues were mutated to Glu or Ser from Asp97 and Asp101, and to Asp or Ser from Glu118 and Glu202 by site-directed mutagenesis, and totally 8 single mutant enzymes expressed in Escherichia coli were prepared: D97E, D97S, D101E, D101S, E118D, E118S, E202D, and E202S. Mutant enzymes E118S and E202S were not shown to have any detectable activity. Kinetic parameters of other mutant enzymes were measured after purification. The Km of mutant enzymes were not much different from that of wild type FI-CMCase, while the Vmax of mutant enzymes D97E, D97S, D101E, D101S, E118D, and D202E were much decreased to 1/50, 1/20, 1/4000, 1/2000, 1/800, and 1/1600 of the wild type FI-CMCase, respectively. From these results we concluded that Glu118 and Glu202 were most probable candidates for a catalytic pair of acidic amino acids in FI-CMCase.

Amino Acid Sequence↗
PubMed1998

Genes from nine genomes are separated into their organisms in the dinucleotide composition space.

A set of 16 kinds of dinucleotide compositions was used to analyze the protein-encoding nucleotide sequences in nine complete genomes: Escherichia coli, Haemophilus influenzae, Helicobacter pylori, Mycoplasma genitalium, Mycoplasma pneumoniae, Synechocystis sp., Methanococcus jannaschii, Archaeoglobus fulgidus, and Saccharomyces cerevisiae. The dinucleotide composition was significantly different between the organisms. The distribution of genes from an organism was clustered around its center in the dinucleotide composition space. The genes from closely related organisms such as Gram-negative bacteria, mycoplasma species and eukaryotes showed some overlap in the space. The genes from nine complete genomes together with those from human were discriminated into respective clusters with 80% accuracy using the dinucleotide composition alone. The composition data estimated from a whole genome was close to that obtained from genes, indicating that the characteristic feature of dinucleotides holds not only for protein coding regions but also noncoding regions. When a dendrogram was constructed from the disposition of the clusters in the dinucleotide space, it resembled the real phylogenetic tree. Thus, the distinct feature observed in the dinucleotide composition may reflect the phylogenetic relationship of organisms.

Amino Acids↗
PubMed1998

Thermal unfolding of three acclimation temperature-associated isoforms of carp light meromyosin expressed by recombinant DNAs.

Differential scanning calorimetry (DSC) was performed to investigate thermodynamic properties of three carp fast skeletal light meromyosin (LMM) isoforms expressed in Escherichia coli by recombinant DNAs. Three isoforms were the 10 degreesC-, intermediate-, and 30 degreesC-type LMM predominantly expressed in carp acclimated to 10, 20, and 30 degreesC. The isoforms expressed in E. coli by recombinant DNAs exhibited a typical pattern of alpha-helix in CD spectroscopy with two minima at 222 and 208 nm. Moreover, the three isoforms formed paracrystals typical of LMM, suggesting that expressed proteins retained intact structural properties. When the LMM isoforms were subjected to DSC analysis, the 10 degreesC and 30 degreesC types showed endotherms having transition temperatures (Tm) at 35.1 and 39.5 degreesC, respectively, which are responsible for thermal unfolding of alpha-helix. The intermediate type exhibited two comparable endotherms with Tm values at 34.9 and 40.6 degreesC, implying that it has intermediate thermodynamic properties between those of 10 degreesC and 30 degreesC types. However, a chimeric LMM having the 10 degreesC and 30 degreesC type as N- and C-terminal halves, respectively, showed the DSC pattern typical of the whole 30 degreesC-type molecule. On the other hand, another chimeric LMM composed of the N-terminal 30 degreesC type and C-terminal 10 degreesC type gave the pattern of the full 10 degreesC type. These results suggest that thermodynamic properties of the C-terminal half largely account for thermal unfolding of the whole molecule.

Acclimatization↗
PubMed1997

Differential scanning calorimetry and CD spectrometry of acclimation temperature-associated types of carp light meromyosin.

Differential scanning calorimetry and CD spectrometry were employed to study the thermal unfolding of light meromyosin (LMM) prepared from carp acclimated to different temperatures. The transition temperatures given by the major peaks at pH 8.0 in 0.6 M KCl for LMM from carp acclimated to 10 degrees C were 32.5 and 39.5 degrees C with the calorimetric enthalpies (DeltaHcal) of 269 and 52 kcal/mol, respectively. LMM from carp acclimated to 20 degrees C exhibited three peaks of transition temperatures at 34.5, 40.2, and 46.9 with DeltaHcal of 152, 20, and 10 kcal/mol, respectively. On the other hand, LMM from carp acclimated to 30 degrees C showed two different patterns. The first experiment gave two transition temperatures at 39.2 and 47.3 degrees C with DeltaHcal of 231 and 39 kcal/mol, respectively. The second series of experiments resulted in showing three peaks of 34.4, 39.5, and 47.5 degrees C with DeltaHcal of 117, 123, and 28 kcal/mol, respectively. N-terminal amino acid sequence analysis revealed that LMM at the second series of experiments with the 30 degrees C-acclimated carp contained component(s) predominant in the 20 degrees C-acclimated carp. Thermal unfolding responsible for these transition temperatures was well explained by melting of alpha-helices which could be determined by far-ultraviolet CD spectroscopy. These results clearly demonstrate that the 30 degrees C-acclimated carp contained the most thermostable LMM.

Acclimatization↗
PubMed1997

Differences in dinucleotide frequencies of human, yeast, and Escherichia coli genes.

Nucleotide sequences coding proteins in human, yeast and Escherichia coli genes were analyzed in terms of dinucleotide occurrences. Every gene is plotted as a point in the dinucleotide space, which is spanned by 16 axes corresponding to the 16 components of the dinucleotide. The metric unit in the space is defined using the log-odds ratio of dinucleotide occurrences in a gene. The distribution of points showed that genes from the same organism are clustered in the space. The clusters of human and E. coli are completely separated, and the yeast cluster sits between, implying that individual genes are classified into the three sources from their location. In fact, they could be identified with accuracy of 90%, using the DNA data alone. Even genes encoding homologous proteins belonging to the same protein superfamily were discriminated by the DNA data, and were correctly identified into their sources with the same accuracy as above. DNA sequences of non-coding regions, including human introns, as well as human genes of GC-rich and GC-poor types, were also analyzed in the same manner. The most significant finding is that human genomic DNA sequences, including genes and introns together, exhibit the largest deviation of dinucleotide occurrence from the random expectation. Possible origins for this phenomenon are discussed.

Dinucleotide Repeats↗
PubMed1997

Characterization of L-glutamine:D-fructose-6-phosphate amidotransferase from an extreme thermophile Thermus thermophilus HB8.

Glucosamine-6-phosphate synthase from the extremophile Thermus thermophilus (GlmSth) was purified to homogeneity from an Escherichia coli overproducer. The homodimeric enzyme exhibits an optimum activity at 70 degrees C with a half-life of 90 min at 80 degrees C. Dissociation experiments in guanidinium chloride and urea are consistent with the absence of catalytic activity of the monomer. Differential scanning microcalorimetry analysis of GlmSth revealed an irreversible denaturation process with a delta(H)cal = 257 kcal x mol(-1) and Tm = 82.6 degrees C. Antigenic cross-reaction with GlmSth was observed with the E. coli enzyme using monoclonal antibodies (mAbs) specific for linear epitopes of the glutamine binding domain. However, no cross-reactivity was observed with an mAb specific for a native conformation of the E. coli enzyme. The inhibition constants of 6-diazo-5-oxo-L-norleucine and methoxyfumaroyl-L-2,3-diaminopropionic acid, potent glutamine site-directed affinity labels of the E. coli enzyme, were reduced by 2 to 3 orders of magnitude when tested on GlmSth, whereas the properties of 2-amino-2-deoxyglucitol-6P, a potent competitive inhibitor of the fructose-6P site, remained unaffected. These data, combined with its unexpected resistance to limited proteolysis, are consistent with an increase in the structural constraint of the thermophile enzyme vs its mesophilic counterpart.

Catalysis↗
PubMed1997

Cloning and sequence analysis of the gene (alyII) coding for an alginate lyase of Pseudomonas sp. OS-ALG-9.

Pseudomonas sp. OS-ALG-9 produces several kinds of alginate-degrading enzymes both intra- and extracellularly. As a second alginate lyase of this bacterium, the gene encoding alyII has been cloned in Escherichia coli JM109 by shotgun techniques and then sequenced. The alyII gene has an open reading frame of 2141 bp encoding 713 amino acid residues with a calculated molecular mass of 79,803 Da. The deduced amino acid sequence did not show any extensive similarity with those of other known alginate lyases, however, hydrophobic cluster analysis showed that alyII belonged to class 3 of alginate lyases. The alginate lyase from E. coli harboring the alyII gene showed a single active band, which coincided with one of four major alginate lyases from the crude cell extracts of Pseudomonas sp. OS-ALG-9 on a zymogram.

Amino Acid Sequence↗
PubMed1996

Cloning and sequencing of the cDNA encoding beta-glucosidase 1 from Aspergillus aculeatus.

A cDNA was isolated from an Aspergillus aculeatus cDNA library using synthetic oligodeoxyribonucleotide mixtures that corresponded to the internal amino acid (aa) sequence of mature beta-glucosidase 1 (BGL1). Analysis of the nucleotide sequence of the cloned cDNA insert revealed a 2580-bp open reading frame (ORF) that encoded a 860-aa protein. The deduced aa sequence of the ORF shared sequence similarity with several BGL from other microorganisms.

Amino Acid Sequence↗