No description available.

Background: Many COPD patients have recurrent exacerbations due to infection, but there are no valid predictors of this phenotype. Previously an observational study showed that higher iron content in sputum macrophages was associated with infectious exacerbations. Objectives: The thesis aimed to assess the mechanisms of pulmonary macrophage iron sequestration, test the effect of macrophage iron-loading on bacterial uptake and killing, and prospectively determine if sputum hemosiderin index can predict infectious exacerbations of COPD. Methods: Intracellular iron was measured directly and indirectly in cell-line-derived and isolated sputum macrophages after treatment with exogenous IL-6, hepcidin or heat-inactivated H.influenzae. Bacterial uptake and killing were compared in both types of macrophages, in the presence or absence of iron-loading. A prospective cohort of COPD patients had their sputum hemosiderin index measured at baseline and were monitored for 1-year for infectious exacerbations requiring admission to hospital. Results: For pulmonary iron sequestration, IL-6 appears important, but the role of hepcidin is not clear. Iron-loading reduced the uptake of COPD-relevant organisms by almost one-third in cell-line-derived macrophage, and there was a near-significant linear relationship between sputum hemosiderin index and killing of H.influenzae (p=0.075). In terms of infective exacerbations, FEV1 had predictive utility (beta=-0.051, p=0.017) while a positive trend for sputum hemosiderin index (beta=0.035, p=0.051) suggests that this biomarker has clinical promise. Conclusion: Through in vitro experiments and cohort data, we have established a framework suggesting that excess iron in pulmonary macrophage may contribute to recurrent bacterial airway infection in COPD. IL-6 appears to contribute to sputum macrophage iron sequestration, which subsequently may lead to immune cell dysfunction and ultimately result in an increased frequency of infective exacerbation. / Thesis / Master of Science (MSc) / COPD patients often require hospitalization due to respiratory infections (bacterial or viral) that result in worsening of their breathing. It is difficult to predict who is at high risk for this to occur, which makes it harder to prevent. Many species of bacteria depend on iron as a nutrient. We wanted to see if iron being present in certain immune cells (macrophages) in the sputum could predict these flares by: testing how iron enters these cells, seeing if bacterial growth is altered by putting iron into these cells, and following a group of COPD patients and seeing if those with higher iron in their sputum had higher risk of infectious flares. Though more testing is needed, we found that a protein often present with chronic inflammation may be associated with higher sputum macrophage iron, and that there is evidence that killing of bacteria in COPD sputum macrophages is lower with high iron, and that patients with higher sputum iron are at greater risk of having infectious flares.

No description available.

No description available.

Thesis (M.D.)--Boston University

No description available.

Chronic iron overload (CIO) in patients leads to a cardiomyopathy characterized by conduction defects, including bradyarrhythmias. Using a murine model of CIO, we explored the effects of iron loading on the electrophyisology of the heart. Telemetric heart rate was reduced in conscious CIO mice compared to controls. Similarly, heart rates were depressed in both isolated CIO hearts and CIO mice following autonomic blockade, suggesting an intrinsic impairment of the SA node (SAN). Indeed, spontaneous action potential frequency was reduced in CIO SAN myocytes. The depressed pacing rate in CIO SAN myocytes was linked to reduced L-type Ca2+ current (ICa,L) density and a rightward shift in ICa,L activation, suggesting a selective reduction in α1D-mediated ICa,L. Western blot analysis demonstrates that the α1D isoform was reduced by ~ 89% in CIO atrial tissue. Therefore, the conduction defects under conditions of CIO are due to reductions in Cav1.3 channel expression in atrial tissue.

Chronic iron overload (CIO) in patients leads to a cardiomyopathy characterized by conduction defects, including bradyarrhythmias. Using a murine model of CIO, we explored the effects of iron loading on the electrophyisology of the heart. Telemetric heart rate was reduced in conscious CIO mice compared to controls. Similarly, heart rates were depressed in both isolated CIO hearts and CIO mice following autonomic blockade, suggesting an intrinsic impairment of the SA node (SAN). Indeed, spontaneous action potential frequency was reduced in CIO SAN myocytes. The depressed pacing rate in CIO SAN myocytes was linked to reduced L-type Ca2+ current (ICa,L) density and a rightward shift in ICa,L activation, suggesting a selective reduction in α1D-mediated ICa,L. Western blot analysis demonstrates that the α1D isoform was reduced by ~ 89% in CIO atrial tissue. Therefore, the conduction defects under conditions of CIO are due to reductions in Cav1.3 channel expression in atrial tissue.

Presented for the degree of Doctor of Science of University of the Uiituatersrand. October, 1964. / ffiy interest in iron metabolism was initially aroused in 1948 by a young patient with idiopathic haemochromatosis who was admitted to Professor Elliott*© ward while I was serving my medical internship, With the support of the Council for Scientific and Industrial Research it was possible to carry out radioisotopic studies on this patient and over the next four years a number of other subjects with the same disease ware investigated. As the study continued, attention was also directed to the siderosis which is so common in adult Bantu, and to the Iron overload which results from the administration of repeated blood transfusions to subjects with refractory anaemias. / IT2018

The Congenital Dyserythropoietic Anemias (CDA) are rare hereditary hemolytic disorders with large bi- to multi-nucleated erythroblasts in the bone marrow. Hemolysis is negative in a direct antiglobulin test (DAT). Based on morphology and clinical picture, three major forms of CDAs, type I, II, and III have been defined. CDA III, dominantly inherited, constitutes the rarest type with a majority of cases belonging to a family in Västerbotten, Sweden. The genetic background of CDA I and CDA II has been linked to mutations in CDAN1 and SEC23B respectively. The mutation of CDA III has been linked to 15q22 in earlier studies. In this project we have defined the causative genetic lesion in two families with CDA III. The novel mutation KIF23 c.2747C>G (p.P916R) was shown to segregate with CDA III in the Swedish and American CDA III families and was absent in 356 healthy controls. KIF23 encodes mitotic kinesin-like protein 1 (MKLP1), which plays a central role in the last step of cytokinesis. RNAi-based knock-down and rescue experiments demonstrated that the p.P916R mutation causes cytokinesis failure in HeLa cells, resulting in increasing number of bi-nuclear cells, consistent with appearance of large multinucleated erythroblasts in CDA III patients. We conclude that CDA III is caused by a mutation in KIF23, encoding MKLP1, a conserved mitotic kinesin crucial for cytokinesis. Flow cytometry with eosin-5´-maleimide (EMA), anti-CD55 and anti-CD59 is commonly used when investigating non-autoimmune hemolytic anemias. Reduced fluorescence of EMA, typically detected in hereditary spherocytosis, is also seen in CDA II, while reduction of CD55 and CD59 characterizes paroxysmal nocturnal hemoglobinuria (PNH). We studied the flow cytometric profile of EMA, CD55, and CD59 on erythrocytes in CDA III. We found no abnormality of the erythrocyte membrane in CDA III and concluded that standard flow cytometry cannot be used to discriminate between CDA III and normal controls. In CDA I and CDA II a majority of patients, including those who are not transfusion dependent, suffer from iron overload, which, according to earlier studies, is not the case in CDA III. We found that individuals of the Västerbotten CDA III family carry mutations in the hemochromatosis (HFE) gene. Three CDA III patients with heterozygous or compound HFE mutations need treatment with phlebotomy due to iron overload. One of them carries heterozygous H63D mutation, which is not reported to lead to iron overload by itself in otherwise healthy individuals. We propose that molecular genetic testing of the HFE gene is indicated in all patients with CDA, including CDA III.