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Biomedical subjects

W K Seow

Publications and source records attributed to W K Seow.

At least 73 records · Page 4Linked to original sources
PubMed1989

Direct activation of human polymorphonuclear leukocytes by Pseudomonas aeruginosa.

Brief exposure of polymorphonuclear leukocytes (PMNs) to unopsonized Pseudomonas aeruginosa resulted in significant enhancement of PMN adherence and 3H-deoxyglucose uptake, two important indicators of PMN activation. Dose-response and time-course experiments show that maximal stimulation of PMNs occurred at a PMN: bacteria ratio of 10:1 and exposure time of 10 min. The PMN-stimulatory capacity of P. aeruginosa was completely or partially abolished by treatment with formalin, heat, ultrasonication and ultraviolet (UV) irradiation, all of which affect the integrity of ligands on the bacteria surface. The putative glycoprotein ligand(s) contains galactose rather than glucose as shown by the ability of galactose in the medium to abrogate PMN-stimulatory activity. This PMN-stimulatory activity was not mediated by soluble factor(s) released from either P. aeruginosa or PMNs as shown by experiments with appropriate supernatants. Finally, PMN-stimulating activity was also observed with P. maltophilia and P. pseudomallei, but not by the other Pseudomonas spp. such as P. cepacia and P. fluorescens. These results suggest that P. aeruginosa and other Pseudomonas spp. may have little capacity to circumvent PMN host defences. This may account in part for their limited pathogenic role as opportunistic micro-organisms, for the severe inflammatory lesions seen in Pseudomonas infections when they do occur, and is consistent with the fact that infection with these organisms is commonly associated with impaired quantity or function of PMNs.

Antigens, Bacterial↗
PubMed1989

Palmoplantar hyperkeratosis with short stature, facial dysmorphism, and hypodontia--a new syndrome?: case report.

In this study, a possible new syndrome affecting 18 members of a family spanning 4 generations is described. The main features include palmoplantar hyperkeratosis, proportionate short stature, facial dysmorphism, clinodactyly, epilepsy, deafness, and hypodontia. This syndrome is inherited in an autosomal dominant manner with a high degree of penetrance but variable expressivity. This syndrome differs markedly from the autosomal recessive types of palmoplantar hyperkeratosis such as Papillon-Lefèvre syndrome which shows premature loss of both dentitions. It is also distinct from other previously described cases of autosomal dominant forms of palmoplantar hyperkeratosis such as the Unna-Thost syndrome in that it presents short stature, facial dysmorphism, and hypodontia. These features which previously have not been associated with palmoplantar hyperkeratosis suggest that this may be a new syndrome.

Adult↗
PubMed1989

Suppression of human monocyte interleukin 1 production by the plant alkaloid tetrandrine.

The bisbenzylisoquinoline alkaloid, tetrandrine, was shown to affect some important human monocyte functions. The drug caused significant inhibition of random movement, chemotaxis, superoxide anion generation and interleukin 1 (IL-1) production. By contrast, degranulation and hexose-monophosphate shunt activity were unaffected. Tetrandrine may be of value in the treatment of chronic inflammatory diseases where IL-1 has a major role as an inflammatory mediator.

Alkaloids↗
PubMed1989

Micromorphologic features of dentin in vitamin D-resistant rickets: correlation with clinical grading of severity.

This study was a histological analysis of 20 primary teeth from 5 patients with 3 clinical grades of vitamin D-resistant rickets (VDRR). The results showed that the degree of globular dentin formation in the histological sections may be graded into Grades I-III in increasing order of severity. In Grade I, the amount of globular dentin was less than 50% of the total dentin thickness, and the interglobular spaces were small. By contrast, in Grade III severity, globular dentin extended throughout the entire thickness of dentin, and the interglobular spaces were large. In Grade II severity, the amount of globular dentin was more than half but did not involve the entire dentin thickness. These histologic grades of severity correlated directly with the clinical grades of the patients. In addition, the study found that lack of medical treatment in affected mothers might lead to globular dentin formation in the fetus in-utero. Conversely, adequate phosphate supplementation in a hypophosphatemic mother might prevent the formation of globular dentin in the fetus.

Adolescent↗
PubMed1989

Sequelae of trauma to the primary dentition.

A total of 69 traumatized maxillary primary incisors were followed to determine the sequelae of trauma. At initial presentation, discoloration was the most common presenting sign of trauma (30.4%), followed by crown fractures (21.8%) and displacement of the teeth (15.9%). The affected teeth were treated by routine clinical procedures. In the 11 teeth showing crown fractures, over 90% were normal at the first follow-up visit with a mean of approximately 27 weeks, but 2 more became necrotic at later recall periods. In contrast, displacement injuries were associated with greater incidence of pulpal necrosis with nearly half of the affected teeth showing periapical radiolucencies after a mean follow-up period of 44 weeks. Similarly, nearly half of the teeth affected by discoloration showed radiographic evidence of pulpal pathology after a mean recall period of 44 weeks. This study shows that a high proportion of traumatized primary incisor teeth eventually become necrotic and the need for continual supervision of all injured primary teeth is stressed.

Dental Pulp Necrosis↗
PubMed1989

The prevalence of furcation foramina in primary molars.

Accessory canals in the furcation region of primary molars provide pulpal-periodontal communications which have important clinical implications. This study of 75 extracted primary molars using dye penetration under vacuum suction showed that 42.7% have foramina located within the furcation region. There were no significant differences in the prevalence between the first and second primary molars. However, in the second primary molar series most of these foramina were located on the root surfaces within the furcation region, rather than in the immediate area of root division. The high prevalence of accessory canals in the furcation region of primary teeth indicates the need for greater clinical consideration during endodontic and periodontal management.

Dental Pulp Cavity↗
PubMed1989

Association of taurodontism with hypodontia: a controlled study.

Although taurodontism has been reported in many syndromes which also feature hypodontia, there have been no previous investigations on the prevalence of taurodontism in patients with hypodontia. Using a novel biometric method for the assessment of taurodontism, we found that 34.8% of 66 patients with hypodontia had at least one mandibular first permanent molar which showed taurodontism compared to only 7.5% of a control group without hypodontia. The trait may be seen both unilaterally and bilaterally and is most frequently seen in patients with multiple missing teeth. The results indicate that clinicians should be alerted to the possibility of taurodontism with its accompanying clinical difficulties in patients with hypodontia.

Anodontia↗
PubMed1989

A controlled study of the association of various dental anomalies with hypodontia of permanent teeth.

Although hypodontia, or oligodontia, is one of the most common human dental anomalies observed, there have been few studies on the association of other anomalies occurring with it. The present investigation of 1032 patient records found that 65.7% of patients with hypodontia showed ankylosis of primary molars compared to only 1.5% of control children (P less than 0.001). In addition, taurodontism of the mandibular first permanent molar was observed in 34.3% of hypodontia cases compared to 7.1% in the controls (P less than 0.001). Other dental anomalies significantly associated with hypodontia include enamel hypoplasia (11.9%, P less than 0.01) and conical incisors (8.9%, P less than 0.01). In contrast, there were significantly more impacted teeth in control children compared to the hypodontia group. The results indicate that for patients with missing permanent teeth, clinicians should be alert to the possibility of these associated anomalies and their accompanying clinical implications.

Adolescent↗
PubMed1989

Mineral deficiency in the pathogenesis of enamel hypoplasia in prematurely born, very low birthweight children.

Although it is well known that enamel hypoplasia commonly is observed in prematurely born, very low birthweight (VLBW) children, its pathogenesis is not understood clearly. One likely mechanism may be related to mineral deficiency, which may be diagnosed as radiological demineralization of the long bones. In this study, we compared the cortical area of the humerus as measured from neonatal radiographs in 31 VLBW children with enamel hypoplasia and 14 VLBW children without enamel hypoplasia. The results showed that children with enamel hypoplasia had a lower mean cortical area of 10.1 +/- 1.9 mm2 compared with 13.9 +/- 1.4 mm2 in children without enamel hypoplasia (P less than 0.001). It was also found that intubated children with a lower cortical mass may be more predisposed to develop localized enamel hypoplasia caused by the laryngoscope (P less than 0.001).

Bone and Bones↗
PubMed1988

Inhibition of adherence of Candida albicans by conventional and experimental antifungal drugs.

We tested the effects of antifungal drugs on adherence of Candida albicans in vitro. Significant reduction of adherence occurred after 2 h incubation with amphotericin B, nystatin, miconazole, econazole, ketoconazole, chlorohexidine and ICI 195,739. Significant inhibition of candida adherence by 5-fluorocytosine and amorolfin required 18 h incubation. Combinations of amphotericin B with 5-fluorocytosine, miconazole, ICI 195,739 and amorolfin resulted in synergistic inhibition of adherence. Adherence is an important pathogenic mechanism in candida infections and interference with this process may represent a major component of the mode of action of antifungal drugs.

Adhesiveness↗
PubMed1988

Lymphocyte-neutrophil interactions: opposite effects of interleukin-2 and tumour necrosis factor-beta (lymphotoxin) on human neutrophil adherence.

Human neutrophil adherence was enhanced by recombinant human tumour necrosis factor-beta (TNF beta) but suppressed by recombinant human interleukin-2 (IL-2). The opposite effects of these two lymphokines were observed over a range of concentrations consistent with their other biological activities, occurred within 15 min of incubation, and were still evident after 60 min. Pretreatment of neutrophils with both IL-2 and TNF beta resulted in adherence values intermediate between the values obtained with the individual lymphokines. IL-2 suppressed the stimulatory effects of both the chemotactic peptide formyl-methionyl-leucyl-phenyl-alanine (FMLP) and the phorbol ester phorbol myristate acetate (PMA). The combination of TNF beta with either FMLP or PMA produced enhancement of neutrophil adherence which exceeded that of either agent alone. These effects of the lymphokines were not due to endotoxin contamination since their effects were sensitive to heating and insensitive to polymyxin B treatment. These experiments provide further evidence for the critical role of these lymphokines in the regulation of acute and chronic inflammatory processes.

Cell Adhesion↗
PubMed1988

Antiphagocytic and antioxidant properties of plant alkaloid tetrandrine.

The effects of tetrandrine, a benzylisoquinoline alkaloid useful in the treatment of silicosis, on a broad range of human neutrophil activities was examined in vitro. Random movement, chemotaxis and phagocytosis were significantly suppressed. There was minimal but significant inhibition of lysosomal enzyme secretion from specific (secondary) but not azurophil (primary) granules. The same concentration of tetrandrine (10 micrograms/ml) caused marked depression of hexose-monophosphate shunt activity and hydrogen peroxide production, but inhibition of superoxide anion generation was observed even at a concentration of 0.1 microgram/ml. This discrepancy was attributed to the capacity of tetrandrine to scavenge oxygen radicals, as shown by experiments using hypoxanthine-xanthine oxidase to generate superoxide. These potent antiphagocytic and antioxidant properties of tetrandrine may account for some of its remarkable anti-inflammatory effects.

Alkaloids↗
PubMed1988

In vitro immunosuppressive properties of the plant alkaloid tetrandrine.

Tetrandrine is an extract of the creeper Stephania tetrandra used in traditional Chinese medicine for the treatment of rheumatic diseases. It has recently been shown to retard and even reverse the lesions of silicosis in humans and rats. Data presented in this report indicate that tetrandrine has potent immunosuppressive properties. Mitogen-induced lymphoproliferative responses were markedly reduced even when tetrandrine was added after the initiation of cultures. In vitro antibody synthesis by B cells was also suppressed by tetrandrine, as was the natural killer cell-mediated lysis of K562 cells. It does not interfere with receptor-ligand binding, but does affect the inositol triphosphate second messenger system. These effects of tetrandrine were observed at nontoxic concentrations as shown by lymphocyte viability studies. These results indicate that tetrandrine possesses potent immunosuppressive properties, and may warrant further study in animal models of chronic inflammatory conditions, autoimmune diseases and transplant rejection.

Alkaloids↗
PubMed1988

Inhibition of histamine release from rat mast cells by the plant alkaloid tetrandrine.

The plant alkaloid tetrandrine was shown to have significant inhibitory effects on receptor-ligand-mediated histamine release from rat mast cells at concentrations similar to or lower than that observed with theophylline and sodium cromoglycate. Inhibition of histamine release did not occur when non-specific stimulants such as aspirin, A23187 or adenosine triphosphate were used. Inhibition of ovalbumin-IgE and concanavalin A-mediated histamine release was reversible by washing the cells, showing that tetrandrine does not bind tightly to the cell membrane or cytoplasmic components. These results, taken together with previous reports of its anti-phagocytic, anti-oxidant and immunosuppressive properties, suggest that tetrandrine may be a broad spectrum non-steroidal drug of potential value in the treatment of allergic diseases.

Alkaloids↗
PubMed1988

Isolation of a chemotactic protein for neutrophils from human ovarian follicular fluid.

Human follicular fluid was found to contain a factor chemotactic for human neutrophils. This chemotactic activity was shown to be heat labile and trypsin sensitive. Gel permeation chromatography experiments indicate that the chemotactic protein has an approximate molecular weight of 100 kd. Isoelectric focussing suggests an isoelectric point for this protein of around 5.8. The biologic and clinical significance of this apparently unique chemotactic protein remains to be determined.

Body Fluids↗
PubMed1987

Uptake of 3H-deoxyglucose as a microassay of human neutrophil and monocyte activation.

The accumulation of 2-deoxy-D-[1-3H]glucose, a non-metabolised analogue of glucose provides a quantitative measurement of the state of activation of phagocytic cells. A microassay for 3H-deoxyglucose uptake by human neutrophils and monocytes is described. Optimal conditions for the assay include the use of 5 X 10(5) cells and 0.78 microCi/ml of deoxyglucose in a final volume of 0.2 ml per microtitre well, and an incubation time of 30 min at 37 degrees C. This simple, rapid and reproducible technique may find application in experimental immunology.

Cell Count↗
PubMed1987

Bacteria-phagocyte interactions: Fusobacterium-induced secretion of a neutrophil self-regulatory factor.

Direct interaction between Fusobacterium nucleatum and human neutrophils resulted in the secretion of a neutrophil self-regulatory factor(s). The secretion of this factor was bacteria specific, and depended on the integrity of the bacteria cell surface. Factor secretion occurred within 15 min of bacteria--neutrophil interaction. Pre-treatment of neutrophils with cytochalasin B but not sodium fluoride inhibited factor secretion. The factor was sensitive to trypsin and heat treatment. Ultrafiltration experiments showed that it has a molecular weight between 10,000 and 30,000 daltons. Its biologic role may be that of a molecular mediator for the recruitment of resting neutrophils so as to amplify the immunological and inflammatory response.

Antigens, Bacterial↗