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Biomedical subjects

W K Seow

Publications and source records attributed to W K Seow.

At least 91 records · Page 5Linked to original sources
PubMed1987

Modulatory effects of Streptococcus mutans on human neutrophil adherence and deoxyglucose uptake.

Suppression of human neutrophil adherence and deoxyglucose uptake was observed after direct interaction between neutrophils and serotype c of Streptococcus mutans, but not other serotypes. Since neutrophils comprise more than 95% of leukocytes in gingival crevicular fluid and constitute one of the first lines of defense in the oral cavity, the capacity of S. mutans serotype c to suppress neutrophil activation may explain its predominance over other serotypes, and its greater propensity for colonization of the oral cavity.

Cell Adhesion↗
PubMed1987

Direct modulation of human neutrophil adherence by coaggregating periodontopathic bacteria.

Direct interaction between Fusobacterium nucleatum and PMNs produced consistent enhancement of PMN adherence. In contrast, consistent suppression of PMN adherence was observed after direct interactions between PMNs and Bacteroides gingivalis or Actinomyces viscosus. The modulatory effects of these periodontopathic bacteria on PMN function could be seen as early as 2 min after interaction. The effects were abrogated by alterations of bacterial structural integrity with heat, formalin or ultrasonic disruption. Carbohydrate or glycoprotein receptors on PMNs may be involved because the effects were blocked by monosaccharides in the medium. Coaggregation experiments showed that permutations involving F. nucleatum always resulted in enhancement of PMN adherence, and that this can be blocked by D-galactose. These findings may have implications in the initiation and sustenance of chronic inflammatory tissue damage in periodontitis.

Actinomyces↗
PubMed1987

Macrophage-neutrophil interactions: contrasting effects of the monokines interleukin-1 and tumour necrosis factor (cachectin) on human neutrophil adherence.

Incubation of human neutrophils with recombinant human interleukin-1 alpha (IL-1 alpha) resulted in the suppression of neutrophil adherence. In contrast, similar treatment with recombinant human tumour necrosis factor-alpha (TNF alpha, cachectin) resulted in the enhancement of neutrophil adherence. These contrasting effects were noted as early as 5 min after incubation, and persisted for at least 60 min. Simultaneous addition of these two monokines resulted in intermediate values between suppression by IL-1 and enhancement by TNF alpha. The stimulatory effects of the chemotactic peptide FMLP and the phorbol ester PMA were ameliorated by IL-1 but augmented by TNF alpha. The effects of these monokines on neutrophil adherence were abolished by heating but not by polymyxin B treatment, showing that their modulatory properties were not mediated by endotoxin.

Dose-Response Relationship, Immunologic↗
PubMed1986

Effect of twenty-three chemotherapeutic agents on the adherence and growth of Giardia lamblia in vitro.

The sensitivity of Giardia lamblia to 23 chemotherapeutic agents was evaluated in vitro with a Growth Inhibition Assay and a recently developed Adherence Inhibition Assay. Of the four established anti-giardia drugs, tinidazole, metronidazole, and furazolidone were found to have strong inhibitory effects on both growth and adherence, while mepacrine had a strong effect on growth only. Three drugs (mefloquine, doxycycline and rifampin) not previously used in giardiasis were found to have significant activity in vitro and may deserve consideration for clinical evaluation of efficacy. Also, the concurrent use of these two in vitro methods provided significant insights into the modes of action of some of these drugs on G. lamblia.

Animals↗
PubMed1986

Inhibitory effects of tetrandrine on human neutrophil and monocyte adherence.

Tetrandrine is a plant alkaloid useful in the treatment of silicosis. Its mode of action is unknown, but results of the present study show dose-dependent inhibition of human neutrophil and monocyte adherence at concentrations (0.1-10 micrograms/ml) easily achieved in plasma during drug therapy. Monocytes were shown to be more sensitive to tetrandrine than neutrophils. Dye-exclusion experiments indicate that tetrandrine is non-toxic to these cells at 10 micrograms/ml concentrations. Suppression of adherence was reversible by washing, suggesting that the drug does not bind tightly to membrane components. Enhancement of adherence by the tumour promoter, phorbol myristate acetate, was abolished by tetrandrine. The uptake of deoxyglucose by neutrophils and monocytes was suppressed by tetrandrine. These results indicate that tetrandrine may act by interfering with the recruitment of these cells into silicotic lesions.

Alkaloids↗
PubMed1986

Augmentation of human polymorphonuclear leukocyte adherence by interferon.

Augmentation of human polymorphonuclear leucocyte adherence by alpha and gamma interferons occurred as early as 2 min after incubation. Enhancement of adherence occurred at optimal concentrations of 100-1,000 IU/ml. There was synergism between alpha and gamma interferons, but not between two subtypes of alpha interferon, on augmentation of adherence, indicating that alpha and gamma interferons act on different receptors on the polymorphonuclear leucocyte. Heat treatment at 65 degrees C for 30 min abolished the effect of interferon on adherence.

Cell Adhesion↗
PubMed1986

Depression of human polymorphonuclear leucocyte function by anti-malarial drugs.

The effect of the anti-malarial drugs quinine, chloroquine, pyrimethamine, mefloquine and quinacrine on human polymorphonuclear leucocyte (PMN) function was examined in vitro. In general, all drugs had their greatest effect on PMN iodination reaction and locomotion, intermediate effects on PMN hexose-monophosphate shunt activity, and least effect on PMN adherence. The most potent of these were pyrimethamine and mefloquine. The PMN iodination reaction and locomotion were inhibited between 0.5-1 microgram/ml (congruent to 2-4 X 10(-6) M) pyrimethamine and 1-4 micrograms/ml (congruent to 0.25-1 X 10(-5) M) mefloquine. The study demonstrates that anti-malarial drugs depress PMN functions associated with antimicrobial activity of the cell.

Antimalarials↗
PubMed1985

The adherence of Giardia lamblia trophozoites to nylon fibre microcolumns: effect of temperature, fluoride, cyanide and metronidazole.

A simple rapid method for the measurement of adherence of Giardia lamblia trophozoites is described. Microcolumns are prepared from 10 mg amounts of nylon fibre packed into 100 microliter size disposable pipette tips. The kinetics show that 30 min is the optimum contact time for the experiments. Maximum adherence occurred at 37 degrees C, minimal at 4 degrees C, and intermediate at 25 degrees C, suggesting that adherence is an energy-dependent process. Adherence was fluoride-sensitive but cyanide-insensitive, suggesting that this parasite derives its energy from the glycolytic pathway, and not the oxidative pathway. Metronidazole, one of the mainstays for chemotherapy of giardiasis, produced significant inhibition of adherence at 10 micrograms/ml and 100 micrograms/ml concentrations after one hour pre-incubation.

Adhesiveness↗
PubMed1985

Effect of 24 antimicrobial drugs on polymorphonuclear leukocyte adherence.

The effects of 24 antimicrobial agents on the adherence of human neutrophils to nylon fibre microcolumns were studied. Neutrophil adherence was found to be remarkably resistant to antimicrobial agents. No effect was observed with penicillin G, nafcillin, cephalothin, vancomycin, bacitracin, tetracycline, minocycline, doxycycline, chloramphenicol, erythromycin, lincomycin, neomycin, streptomycin, acetylspiramycin, 5-fluorocytosine, sulfisoxazole, tinidazole and primaquine. Only 2 enhanced adherence - oxytetracycline and rifampicin - and only 4 suppressed adherence - colistin, polymyxin B, quinine, chloroquine - and then only at high concentrations.

Anti-Bacterial Agents↗