Nuclear fission processes can provide a lot of energy but can also have safety concerns. What if Congress decided to outlaw all processes that involve fission? How would that change our society?
PNB 3260 Exam 2 material Anna Ciara Mason Lec 10: Adult stem cells and adult stem cell niches Adult stem cell niche adult stem cells are quiescent (periods stopped in one spot in cell cycle/division) o increased division can increase mutation potential o divide infrequently to generate one stem cell copy and a rapidly cycling cell Microenvironment is both proliferation-limiting and differentiation-limiting o type of cells made, extent of differentiation etc. Niche is unique for each organ and tissue type o there are many overlapping systems Required for day to day physiological replacement and injury related replacement in an organ Rapidly cycling cells (transit-amplifying cells) undergo a limited number of cell divisions before terminally differentiating to functional cells of tissue symmetric division- cancer treatments may lower amount of stem cells. quiescent stem cell that wasn't targeted in the chemotherapy can start dividing stem cell can generate 2 transindental cells - lose cell line o stem cell might only be able to undergo a certain amount of divisions Stem cell niches A) A germination of the ovary o organization is important in the ovary and testes stem cells attach to somatic cells to anchor themselves B) the apex of the testes o only stem cells that are attached to hub will remain as stem cells - limits number of stem cells possible C) The subventricular zone (SVZ) of the brain o 2 stem cell niches in the brain subventricular zone - rodents humans - pretty much limited at 2 years old epithelial cells that line the ventricle - stem cells attach here and also help to circulate cerebral spinal fluid stem cells generate these epithelial cells D) Hair follicle as a niche o Regeneration of hair follicles in skin ~1 - 1.5 months E) The crypt of an intestinal villus o Protected region where stem cells are located because so much is coming through F) The bone marrow o Hemaptopoetic also attached to stromal cells in bone marrow o can go on to make multipotent o can make lymphoid or myloid lineages Asymmetric vs Symmetric cell division only a certain number of stem cells can go around a hub- way of restricting the stem cells committed cell is trans and amplifying cell Adherens junctions help maintain stem cells in niche via somatic cell contact Adult stem cells divide relatively infrequectly depending on organ system generate one stem cell copy and rapidly cycling cell (transit-amplifying cell) transit-amplifying cell: limited number ** Intestine Lining made up of villi to increase the surface area Complete cell turn over: 2-3 days Each villi has a crypt area and each contribute to the cells that line the villa Intestinal stem cells (ISCs) o secrete antimicrobials o red are molecular signals from crypt o 2 kinds of stem cells +4 markers label retention cell takes up marker in division if cell is quicent - keeps marker if division continues then marker will be diluted CBC markers not label retaining - means they are more actively proliferating o localized in intestinal crypt o regenerate entire villus every 3-5 days o Generate paneth, enteroendocrine o cells at top of villus are constantly shedding Stomach lining of stomach is highly regenerative pyloric region is most studied stem cells are found throughout but we're talking about pyloric adult stem cell-driven epithelial renewal in the pyloric stomach o pit mucus cell, parietal (oxyntic) cell, gland mucus cell, endocrine cell o took out LGR5 positive stem cell and cultured it to form an organoid similar to stomach Hair follicle stem cells (HFSCs) budge surrounds entire follicle Skin transplantation assays o different skin stem cell classes are capable of generating all epidermal lineages in skin transplantation assays o stem cells mixed with neonatal dermal fibroblasts and implants onto back of immuno- compromised nude mice o niche defines the differential potential of otherwise equivalent stem cell populations Cre-recombinase-based lineage tracing system No tamoxifen vs tamoxifen tamoxifen activates CRE enzymes which cuts 2/25/2016 12:59:00 PM 2/25/2016 12:59:00 PM