Small RNAs have a big impact on regeneration.
A number of lower vertebrates including urodele amphibians and teleost fish are remarkably adept at repairing and regenerating damaged tissues and organs. Freshwater planarians are even more amazing, capable of regenerating entire body plans from small amputated fragments. In contrast, mammalian regenerative capacity is quite limited but of intense interest, especially related to human health and disease. For those organisms capable of robust regeneration, a common theme is the use of stem cells to replace complex tissues. Key questions remain as to the origin of these cells, whether there are pools of such cells that migrate to injured regions or whether they are generated on site. Beyond their origin, how are the genetic pathways that enable differentiation into multiple cell types and tissues regulated? microRNAs (miRNAs) are small noncoding RNAs that have recently been shown to play important roles in controlling stem cell self-renewal, proliferation and differentiation. Some of these are thought to be required to maintain "stemness". Here, we summarize recent work on the role of miRNAs in stem cells and their roles during regeneration. (+info)
Pathological study on the scuticociliatosis affecting farmed Japanese flounder (Paralichthys olivaceus) in Japan.
Pathological findings associated with scuticociliatosis in farmed Japanese flounder in Japan are described. Ten moribund fishes, farmed in Tottori Prefectural Fisheries Experimental Station, showed cutaneous ulcers, darkened skin, fin and tail rot, exophthalmia and alterations in swimming behaviour. Histopathologically, severe epidermal degeneration and necrosis, hyperplasia of branchial epithelium, myositis, myelitis, encephalitis associated with heavy accumulation of scuticociliates in the periorbital cavity and optic nerve fiber were observed. Moreover, masses of ciliates were found to feed on the host tissues such as skeletal muscles, gills and brain, causing severe degenerative changes associated with abundant neutrophilic and lymphocytic infiltration. These findings suggest that the present scuticociliate, Miamiensis avidus, is a highly invasive and destructive pathogen infecting Japanese flounder and capable of developing systemic fatal infection. (+info)
Zebrafish sp7:EGFP: a transgenic for studying otic vesicle formation, skeletogenesis, and bone regeneration.