A study was made of the renal and cardiovascular responses of rats to the chronic intravenous administration of bacterial endotoxin. Endotoxin (E coli; 026: B6) was infused intravenously at the rate of 10 μg/h for a period of 4-6 days by means of subcutaneously implanted osmotic mini-pumps. The chronic endotoxemia resulted in a large fall in the renal output of sodium, a decrease in urine osmolality and an increase in potassium output. Aldosterone concentration in plasma was not changed. The renal retention of sodium was associated with an increased plasma volume, sodium space and total body exchangeable sodium. A study of renal function using clearance methods showed that the above changes occurred in the absence of statistically significant changes in glomerular filtration rate, renal plasma flow or filtration fraction. Measurements of renal medullary plasma flow by means of an isotope accumulation method indicated that no significant redistribution of intrarenal blood flow had occurred which might account for either the retention of sodium or the impaired renal concentrating ability. An investigation of cardiovascular function showed that rats with chronic endotoxemia had a significantly increased cardiac output as measured by the reference sample technique using radio-labelled plastic microspheres. These animals also had an increased stroke volume, bradycardia, hypotension and a decreased total peripheral resistance. The renal fraction of the cardiac output was significantly reduced but total renal blood flow was unchanged. The fractional distribution of nutritional blood flow to the kidney, as measured with ⁸⁶RbCl, was not significantly changed. Because of theoretical, but possible, sources of error inherent in the use of microspheres to measure cardiac output an attempt was made to confirm the above data using an alternative method. Measurement of cardiac output using the direct Fick method did not disclose a significant difference in cardiac output. Measurements were also made of the circulating half-life of endotoxin in plasma using ⁵¹Cr-labelled endotoxin. There was a very large increase in the rate of plasma clearance of endotoxin in rats subjected to chronic endotoxemia but no change in the fractional uptake of endotoxin by selected organs. It is suggested that the observed changes in renal function were secondary to the hemodynamic effects of endotoxin rather than to direct nephrotoxic effects. / Medicine, Faculty of / Cellular and Physiological Sciences, Department of / Graduate

No description available.

No description available.

published_or_final_version / abstract / Dentistry / Doctoral / Doctor of Philosophy

No description available.

PhD, Faculty of Health Sciences, University of the Witwatersrand / Background: Dental procedures associated with dental unit waterlines (DUWLs) in dental health care settings generate aerosolised droplets that have the potential to cause adverse health effects in exposed workers. Aim: The aim of this study was to evaluate the risk of work-related asthma associated with endotoxin exposure in dental health care workers. Materials and methods: The study population included dental personnel (n = 454) from 5 academic dental institutions in South Africa. Personal air samples (n = 413) in various dental jobs as well as airborne area and water samples from dental handpieces and basin taps were collected. A self-administered modified European Community Respiratory Health Survey questionnaire was used to obtain information on respiratory symptoms and the occupational history. Serum samples were collected to determine atopic status, specific IgE to composite latex (k82) extract and 8 recombinant latex proteins, myeloperoxidase (MPO), eosinophilic cationic protein (ECP), inflammatory cytokines, and endotoxin levels. Spirometry including pre- and post-bronchodilator testing was conducted according to ATS/ERS guidelines. Multivariate linear and logistic regression and factor analysis was used in the data analysis. Results: Airborne endotoxin levels were variable across departments with administration having the lowest and laboratories the highest mean exposures (geometric mean: 2.38 versus 5.63 EU/m3). Job status as a student (compared to staff member) and dental unit characteristics (age, model type, number of units) were important predictors of airborne endotoxin. The most common asthma phenotypes were atopic asthma (6.9%), non-atopic asthma (5.9%) and work-aggravated asthma (4%). Four inflammatory groups related to eosinophilic versus neutrophilic inflammation and chronicity of the response were identified. Acute neutrophilic response was associated with work-related chest symptoms (OR = 4.99, 95% CI: 1.32 - 18.92). Cumulative endotoxin exposures (>51.12 EU/m3-year) was an important predictor of work-related ocular-nasal symptoms (OR = 3.82, 95% CI: 1.01 – 14.41) in non-atopic workers. Borderline significant associations were also observed between current airborne endotoxin concentrations (>5.83 EU/m3) and asthma-related symptoms (OR = 2.24, 95% CI: 0.97 – 5.17) as well as suboptimal lung function (FEV1<80% predicted) (OR = 8.02, 95% CI: 0.94 – 68.35) in non-atopic workers. Dental workers using latex gloves and concurrently exposed to low-grade (> 5.83 EU/m3) elevated endotoxin levels were at increased risk (OR = 2.59, 95% CI: 1.20 – 5.60) of presenting with latex sensitisation. Conclusion: This study demonstrated that endotoxin exposures from DUWLs play an important role in the manifestation of non-atopic asthma through the neutrophilic-response mechanism. Neutrophilic inflammatory cell asthma phenotypes coexist with eosinophilic inflammatory cell asthma phenotypes in this group of workers. Furthermore, low-grade elevated endotoxin levels increase the risk of sensitisation to latex among dental workers using latex gloves. This is the first study to demonstrate airway effects associated with low-grade elevated endotoxin exposures in dental settings.

Sepsis affects hundreds of thousands each year in the United States alone, with an estimated 20-30% mortality rate in spite of current treatment regimens. Sepsis mortality was originally understood to be the caused by overproduction of inflammatory cytokines in response to pathogen detection by the host. However, recent studies suggest that with modern treatments, secondary infection, rather than inflammatory shock, may be of greater concern. In either case, the failure of a large number of anti-inflammatory agents to produce beneficial outcomes in sepsis treatment during clinical trial suggests that the development of a new class of immunomodulatory agents may be required for effective treatment. In experimental models, pre-treatment with sub-lethal doses of lipopolysaccharide (LPS, previously referred to as endotoxin) induces a state of "LPS tolerance" that reduces septic shock lethality. Paradoxically, LPS tolerance also results in increased antimicrobial gene expression and resistance to secondary infection in some models. Further exploration of this process may provide drug targets capable of limiting inflammation without dampening antimicrobial immunity, which could be of great benefit in the treatment of sepsis and chronic inflammatory disease. Many groups have studied signaling changes that occur during LPS tolerance. However, mediators of tolerance that can account for the changes in LPS-induced gene expression that result in increased microbial resistance are not well described. This has prevented proper testing of the physiological effects of tolerance on disease, and it remains unclear if this process could be artificially induced or is of any benefit to sepsis patients. Recent in vitro work suggests that tolerant gene expression patterns are the result of large scale changes in chromatin organization that occur in macrophages after prolonged LPS stimulation. Because microRNAs (miRNAs), a new class of gene regulator, have been found to regulate chromatin modifying complexes in other systems, LPS-induced miRNAs were screened to identify potential mediators of tolerance that could cause changes in gene expression patterns without necessarily impacting LPS signaling itself. Several tolerance-associated miRNAs were identified. One miRNA in particular, miR-222, was found to repress tumor necrosis factor (Tnf) and Brahma-related gene one (Brg1) expression. This attenuates expression of genes dependent on nucleosome remodeling, primarily affecting inflammatory genes. Consequently, miR-222 expression effectively limits septic shock lethality. However, low-level responses, as well as NF-κB signaling and the expression of a subset of antimicrobial and antiviral genes, are left intact. Thus, although miR-222 does not entirely recapitulate the tolerance response, by directing the LPS response into a less damaging expression profile, miR-222 may accelerate the onset of tolerance and be a promising target for therapeutics aiming to treat inflammatory disease without compromising host immunity.

Thesis (Ph. D.)--University of Missouri-Columbia, 2003. / Typescript. Vita. Includes bibliographical references (leaves 94-101). Also available on the Internet.

Thesis (Ph. D.)--University of Missouri-Columbia, 2003. / Typescript. Vita. Includes bibliographical references (leaves 94-101). Also available on the Internet.

Chronic obstructive pulmonary disease (COPD) is a highly prevalent disease in the elderly. It is currently the fourth leading cause of death and will become the third by 2030. Cigarette smoke is the major cause of COPD pathogenesis, resulting from the burden of oxidants, which stimulates the production of inflammatory chemokines, leading to the influx of inflammatory cells into the airways and causing chronic inflammation. Due to lung infection by bacteria, such as Pseudomonas Aeruginosa during acute exacerbation in COPD, cigarette smoking might induce an immunosuppressive effect, which leads to bacteria colonization in the airways and further contributes to the chronic inflammation in the airway of COPD. Furthermore, cigarette smoke-induced production of reactive oxygen species (ROS) also plays an important role in the pathogenesis of COPD, however, N-acetyl-L-cysteine (NAC), which has been administered for the treatment of COPD as a mucolytic agent, also showed antioxidant and anti-inflammatory effect. The exact mechanism or cellular pathway through which cigarette smoke suppresses bacteria-induced inflammatory response and how NAC acts as an anti-inflammatory agent still remains uncertain. This study aims to investigate the effect of cigarette smoke and lipopolysaccharide (LPS) alone or in combination on the release of pro-inflammatory chemokines and to elucidate cigarette smoke-induced chemokines release in the presence and absence of NAC. Both cigarette smoke and LPS alone induced the release of interleukin-8 (IL-8) and monocyte chemoattractant protein-1 (MCP-1).Cigarette smoke suppressed the LPS-induced IL-8 and MCP-1release. NAC reduced both basal and cigarette smoke-induced secretion of these inflammatory chemokines. Moreover, Western blot demonstrated that cigarette smoke activated AMPKα phosphorylation, which was suppressed with NAC pretreatment, suggesting that NAC might have inhibitory effect on the release of chemokine release via the AMPK pathway. Our current data suggests that there may be a link between ROS generation to AMPK activation and chemokine release in BEAS-2B cells. / published_or_final_version / Pharmacology and Pharmacy / Master / Master of Medical Sciences