Biomedical subjects

Y Lim

Publications and source records attributed to Y Lim.

28 records · Page 2Linked to original sources

PubMed1997

Audit of waste collected over one week from ten dental practices. A pilot study.

An audit of the waste practices of ten general dental surgeries identified problems that have occurred due to the lack of specific dental guidelines or codes of practice in this area. Occupational health and safety requirements for types and locations of sharps containers, and lack of consensus on what constitutes a sharp, were identified as areas needing attention. Cross-infection control items, such as gloves, masks, single-use cups, and protective coverings, were found to constitute up to 91 per cent of total waste. When infectious waste was reclassified by the audit team as 'that waste which was visibly blood stained,' a reduction in waste in this category was made, during the audit, at each practice. The practice of disposing of radiographic fixer and developer into the sewerage system occurred in three out of the ten practices, even though the Australian Dental Association Inc. has discouraged this practice.

Blood↗

PubMed1997

Vibriocidal antibody responses in North American volunteers exposed to wild-type or vaccine Vibrio cholerae O139: specificity and relevance to immunity.

The emergence of a new agent of cholera, Vibrio cholerae O139, has prompted a reevaluation of the vibriocidal antibody assay. This assay, primarily directed to lipopolysaccharide, is an important correlate of O1 immunity. V. cholerae O139 strains are encapsulated, rendering them relatively resistant to killing by serum. Recent reports suggest that there is strain-to-strain variability in the sensitivity of the vibriocidal assay to fully encapsulated O139 strains. We have assessed a modified vibriocidal assay for fully encapsulated O139 strain AI-1837 and its unencapsulated mutant 2L in sera from 53 volunteers given wild-type AI-1837 or its attenuated derivative CVD 112 and from 48 controls challenged with V. cholerae O1 or strains of the family Enterobacteriaceae. Vibriocidal responses to the AI-1837 and 2L strains were seen in 67 and 89% of volunteers, respectively, following a single exposure to the wild-type strain. However, >50% of all controls had low-level vibriocidal responses to both strains. These nonspecific responses were transient and of the immunoglobulin G isotype. No binding activity against purified O139 lipopolysaccharide (LPS) by immunoblotting was seen in control sera. In contrast, vibriocidal assay and strain 2L LPS responses by immunoblotting were detectable in 91% of tested volunteers following a single exposure to O139. The presence of vibriocidal antibody to AI-1837 or 2L was not associated with protection in rechallenge studies with O139 strain AI-1837. The vibriocidal assay with unencapsulated strain 2L may be used to detect exposure to O139 strain AI-1837 in controlled research trials. However, its lack of specificity does not make it useful for determining exposure to V. cholerae O139 in the field.

Antibodies, Bacterial↗

PubMed1997

Involvement of protein kinase C, phospholipase C, and protein tyrosine kinase pathways in oxygen radical generation by asbestos-stimulated alveolar macrophage.

Although asbestos stimulates oxygen radical generation in alveolar macrophages, the exact mechanism is still not clear. The purpose of this study was to compare the ability of three asbestos fibers (amosite, chrysotile, and crocidolite) to generate oxygen radicals in macrophages and examine the mechanism of this action. All asbestos fibers were able to induce chemiluminescence but chrysotile induced maximal chemiluminescence at higher concentrations than amosite and crocidolite. Protein kinase C (PKC) inhibitors (sphingosine and staurosporine) suppressed the ability of asbestos to induce oxygen radical generation. Phospholipase C (PLC) inhibitors (U73122 and neomycin) and protein tyrosine kinase (PTK) inhibitors (erbstatin and genistein) decreased oxygen radical generation of asbestos-stimulated alveolar macrophages. Oxygen radical generation was not suppressed by an adenylate cyclase activator (forskolin), a protein kinase A inhibitor (H-8), and a protein serine-threonine phosphatase inhibitor (okadaic acid). PLC and PTK inhibitors suppressed the increment of phosphoinositide turnover by amosite. These results suggest that asbestos fibers induce the generation of oxygen radicals through PTK, PLC, and PKC pathways in a dose-response pattern.

Animals↗

PubMed1997

Silica-induced oxygen radical generation in alveolar macrophage.

Silica is a well-known occupational fibrogenic agent and its primary target cell is alveolar macrophage. Particle-stimulated macrophages are believed to release various mediator which can regulate the inflammation as well as pulmonary fibrosis. Even though oxygen radicals play the major role among these mediators, the mechanisms concerning the stimulation of alveolar macrophages are not clear yet. The present study was carried out to investigate the signal transduction pathway on oxygen radical generation in silica-stimulated alveolar macrophages. Silica induced oxygen radical generation in a dose-response pattern. Extracellular calcium depletion, calcium channel blockers, and calcium release blocker decreased the effect of silica on oxygen radical generation. Silica increased intracellular calcium through the influx of calcium through the calcium channel and the calcium release from the intracellular calcium store. To know the role of protein kinase C (PKC), phospholipase C (PLC), and protein tyrosine kinase (PTK) in silica-induced oxygen radical generation, we pretreated alveolar macrophages with inhibitors of these enzymes. Inhibitors of PKC (sphingosine and staurosporine), PLC (neomycin and U-73122), and PTK (genistein and erbstatin) suppressed the silica-induced oxygen radical generation. Silica increased the PLC activity at the concentration of 5 mg/ml. The inhibitors of PTK and PLC suppressed the action of silica on the PLC activity. From these results, we suggest that silica induces oxygen radical generation through PTK, PLC, and PKC in alveolar macrophages.

Animals↗

PubMed1996

The intratracheal administration of endotoxin: X. Dexamethasone downregulates neutrophil emigration and cytokine expression in vivo.

Intratracheal instillation of endotoxin (LPS) causes acute pulmonary inflammation characterized by the accumulation of plasma proteins and leukocytes within the pulmonary airways. The synthetic glucocorticoid dexamethasone 1) inhibits the LPS-initiated vascular leak of plasma proteins into the airspace, 2) inhibits the LPS-initiated emigration of neutrophils and lymphocytes into the airspace in a dose-dependent fashion, and 3) inhibits LPS-initiated mRNA and/or bronchoalveolar lavage protein expression of cytokines (TNF, IL-1 and IL-6) and chemokines (MIP-1 alpha, MIP-2 and MCP-1). In conclusion, dexamethasone inhibits both the vascular and cellular aspects of acute inflammation by downregulation of a broad spectrum of inflammatory cytokines and chemokines.

Animals↗

PubMed1995

AL072, a novel anti-Legionella antibiotic produced by Streptomyces sp.

AL072 is a potent anti-Legionella antibiotic produced by Streptomyces strain AL91. The compound was isolated from the fermentation broth with 1 volume of isopropyl alcohol, followed by an ethyl acetate extraction and subsequent concentration under reduced pressure. Purification was performed on an octadecyl silica gel column followed by preparative HPLC. AL072 purified as mentioned above showed extremely specific activity only towards Legionella pneumophila. No antibacterial activity against any other bacteria tested was demonstrable. Its molecular weight was determined by FAB-MS (m/z 648) and the compound was identified as a novel 1,3-diacyl glycerol with the molecular formula C41H76O5. One of the two acyl groups is linoleyl and the other is 3,5-dimethyl octadecanoyl.

Anti-Bacterial Agents↗

PubMed1994

Cepacidine A, a novel antifungal antibiotic produced by Pseudomonas cepacia. I. Taxonomy, production, isolation and biological activity.

Cepacidine A is a potent antifungal antibiotic produced by Pseudomonas cepacia AF 2001. The compound was isolated from the fermentation broth with 1 vol isopropyl alcohol, followed by the collection of the precipitation formed upon concentration of the extract. Purification was effected by chromatography on Diaion HP-20, alumina and reversed phase C18 followed by TLC on silica gel. These techniques afforded the two closely related compounds, cepacidine A1 and cepacidine A2. A mixture of these two compounds called capacidine A, showed high in vitro antifungal activity against the various animal and plant pathogenic fungi. The activity was diminished by the presence of serum. No antibacterial activity was demonstrable.

Anti-Bacterial Agents↗

PubMed1994

Cepacidine A, a novel antifungal antibiotic produced by Pseudomonas cepacia. II. Physico-chemical properties and structure elucidation.

Cepacidine A is a novel glycopeptide with a potent antifungal activity, which is produced by Pseudomonas cepacia AF 2001. Its molecular weight was determined by FAB-MS (m/z 1215). The compound is comprised of glycine (1), serine (2), 2,4-diaminobutyric acid (1), aspartic acid (1), beta-hydroxy tyrosine (1), beta-hydroxy asparagine (1), xylose (1) and 5,7-dihydroxy-3,9-diamino-octadecanoic acid (1). Unfortunately, cepacidine A is a mixture of A1 and A2, either of which is barely distinguishable. Cepacidine A2 includes asparagine (1) instead of beta-hydroxy asparagine (1) of cepacidine A1. The MS data and the NOESY, TOCSY and HMBC spectra show that cepacidine A is a cyclic peptide and xylose is connected to 5,7-dihydroxy-3,9-diaminooctadecanoic acid.

Anti-Bacterial Agents↗

PubMed1988

Systemic and mucosal immune responses to rhesus rotavirus vaccine MMU 18006.

Thirty-four children 3 to 20 months of age ingested either 10(5), 10(4) or 10(3) plaque-forming units of rhesus rotavirus vaccine, MMU 18006, which possesses human rotavirus serotype 3 neutralization antigen. Immune responses were evaluated by a plaque reduction neutralization (PRN) assay to rotavirus serotypes 1, 2 and 3 and by a serum IgG, IgM and IgA and fecal IgA class-specific enzyme-linked immunosorbent assay. Homotypic PRN antibody seroconversions to serotype 3 rotavirus were detected in 31 of 34 children (91%), whereas rises in heterotypic PRN antibody to human rotavirus serotypes 1 or 2 were found in only 3 of 21 (14%) (p less than 0.00000001). Thirty of the 34 vaccinated children (88%) had at least one class of rotavirus-specific serum antibody detected by enzyme-linked immunosorbent assay. A rotavirus-specific IgA coproantibody response was seen in 11 of 16 children (69%) following vaccination. Two children who had no evidence of PRN antibody to serotype 3 after vaccination had evidence of both a fecal and a serum rotavirus-specific IgA response, suggesting that in these children the response to the vaccine was primarily mucosal. These data show that orally administered rhesus rotavirus vaccine MMU 18006 elicits local intestinal immunity but produces primarily a homotypic serum neutralization response as measured by plaque reduction neutralization assays.

Antibodies, Viral↗

PubMed1985

Urinary beta 2-microglobulin in full-term newborns: evidence for proximal tubular dysfunction in infants with meconium-stained amniotic fluid.

Urinary concentrations of beta 2-microglobulin (beta 2M) and creatinine were measured in normal term infants and in those born with meconium-stained amniotic fluid. None of the infants or their mothers had conditions known to modify beta 2M excretion. Measurements of beta 2M were made on urines collected by bagging; urines obtained from diapers were not satisfactory. Urinary beta 2M concentrations increased significantly (P less than .02) in the normal infants from the first day (0.36 +/- 0.29 mg/L: n = 29) to the third day (0.60 +/- 0.43 mg/L: n = 21) postpartum. Compared with the normal infants, values for the infants with meconium-stained amniotic fluid were increased significantly on days 1 (1.64 +/- 2.16 mg/L: n = 25: P less than .005) and 3 (2.12 +/- 2.04 mg/L: n = 23: P less than .005). Levels exceeded two standard deviations above the normal mean in 12 of the 26 infants with meconium-stained amniotic fluid on postpartum day 1, and 12 of the 23 infants with meconium-stained amniotic fluid on day 3. Urinary creatinine levels were similar in both the normal infants and those with meconium-stained amniotic fluid. All infants with meconium-stained amniotic fluid with a one-minute Apgar score of 6 or less had an elevated urinary beta 2M concentration. The elevated levels of urinary beta 2M in infants with meconium-stained amniotic fluid indicate the existence of tubular dysfunction, probably mild acute tubular necrosis secondary to hypoxia.

Amniotic Fluid↗