碩士 / 國立彰化師範大學 / 生物學系 / 91 / In crustaceans, circulating hemocytes assume various immune functions. The present study determined the presence and biochemical characteristics of nitric oxide synthase (NOS) and investigated the immune roles of nitric oxide (NO) in the hemocytes of the crayfish Procambarus clarkii. Morphological analysis identified three types of hemocytes, namely, hyaline, semigranular, and granular cells. Biochemical analysis indicated the presence of a Ca2+-independent NOS in the homogenates of the hemocytes. When bacteria and hemocytes were co-incubated in vitro, adhesion of bacteria around intact and lysed hemocytes was observed. Addition of sodium nitroprusside (SNP; a NO releaser) to the incubation led to a significant increase in the numbers of intact or lysed hemocytes that bacteria adhered to. Similar to SNP, lipopolysaccharide (LPS; a NO inductor) also elicited bacterial adhesion, but this LPS-induced adhesion is prevented by the addition of NG-monomethyl-L-arginine (L-NMMA; a NOS inhibitor). Furthermore, when induced by either SNP or LPS, significant increase in the numbers of bacteria-adhered intact hemocytes occurred prior to that of bacteria-adhered lysed hemocytes, implying bacterial association promotes hemolysis. Finally, standard plate count assay demonstrated that addition of LPS to the hemocyte/bacterium co-incubation resulted in a significant decrease in bacterial colony forming unit (CFU) and that L-NMMA reversed this LPS-induced decrease in bacterial CFU, suggesting that LPS induces NOS expression that ultimately leads to a higher bactericidal activity. In summary, the combined results indicated the presence of Ca2+- independent inducible NOS in the hemocytes of the crayfish Procambarus clarkii. NO, generated by induced NOS, is presumably involved in defending against invading pathogens via promoting bacterial adhesion and hemolysis that subsequently elevate cellular cytotoxicity.
| Identifer | oai:union.ndltd.org:TW/091NCUE0112007 |
| Date | January 2003 |
| Creators | 葉鳳枝 |
| Contributors | 李奇英 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 52 |
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