Forging a head: A tail of new frontiers
LE3 .A278 2005
Gibson, Glenys D.
Bachelor of Science
The marine polychaete Pygospio elegans has the capability to regenerate a new head in just 8 days with amazing consistency and faithfulness to the original body plan. Previous studies, based on histological observations describing morphogenesis at various stages of anterior regeneration, have suggested that mesodermally derived structures have an interesting mode of regeneration. The present study attempted to study the cell origin, migration and fate of the regenerating tissue, with emphasis on mesodermally derived cells. I microinjected specimens with the fluorescent vital dye DiI to track cells during formation of the blastema (i.e., regenerating tissue), then induced fission between the abdomen and the thorax. Specimens at 3 and 6 days of regeneration were observed using confocal laser scanning microscopy. I also observed cell proliferation using BrdU, which labels actively dividing cells. Only specimens injected into the first abdominal segment showed any fluorescence in the blastema, suggesting that only the adjacent segment contributed cells to the regenerating regions. However, not all regions of the adjacent segment contributed to the blastema. The fluorescence within the blastema was always localized to certain areas or organs within the blastema. Within mesodermal structures, there appear to be different modes of regeneration. For example, the blood vessels appear to regenerate by growing into the blastema from the original blood vessels, whereas the muscles seem to differentiate from the small mesenchyme-like cells which fill the blastema before organogenesis begins. BrdU labeling was not successful in penetrating into the mesoderm, but revealed a lot of epidermal cell proliferation, which was not previously thought to occur. These results suggest that mesodermal tissues regenerate from different source populations.
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