Date of Award
Master of Science
The tendency of normal calves to have crenated RBCs impaired the usefulness of the image analysis procedure and a single shape factor equation. The second study examined the direct effects of STX on human RBCs in vitro and found no significant differences in osmotic fragility or RBC membrane proteins as evaluated with polyacrylamide gel electrophoresis. The effects of STX on RBC adhesion to confluent layers of cultured endothelial cells was studied using a gravity adherence assay. STX was incubated with human microvascular endothelial cells and uptake of the toxin by the endothelial cells was confirmed by immunofluorescence. RBCs were added to the chamber and incubated at 37ÃÂ°C for 30 minutes. No increase in RBC adherence to endothelial cells was observed after incubation with STX. The mechanism of human RBC fragmentation is likely an indirect effect of STX. Combinations of E. coli toxins, including lipopolysaccharide, may also be involved in the pathogenesis of RBC fragmentation.The hemolytic uremic syndrome (HUS) of children was originally described as a triad of acute renal failure, fragmented red blood cells (RBCS) and thrombocytopenia. This syndrome is most often associated with infection with Escherichia coli O157:H7 and the shiga-like toxin (STX) it produces. One of the proposed pathogenic mechanisms of RBC fragmentation was damage to RBCs as they were forced through fibrin thrombi that occur in the renal microvasculature. However, direct damage to RBC by E. coli toxins may also be involved. In order to better understand the mechanistic basis of RBC fragmentation during HUS, two studies were carried out. The first examined the utility of computerized image analysis and a single shape factor equation ([Crofton perimeterÃÂ²][division symbol] [4*[Pi]*Area]) to quantify the degree of poikilocytosis in calves infected with E. coli O157:H7. The percentage of cells with different shape factor scores were compared in calves prior to and after infection with E. coli O157:H7. Cell shape was also manually scored by two investigators. No significant increases in poikilocytosis were detected using either image analysis or manual scoring in calves after infection with E. coli. Crenation of calf RBCs caused the greatest discordance between image analysis and manual scores.
Denise Stephanie Wunn
Wunn, Denise Stephanie, "Hematologic effects of Esherichia coli O157:H7 and Shiga-like toxin 1" (2000). Retrospective Theses and Dissertations. 17702.