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2012.03.19 - Bio 1202 Lecture Review Notes.docx

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Biology 1202B
Gardiner/ Murphy

Biology Lecture Review Notes Lecture 9 Stem Cells  Stem cells – unspecialized cells o Capable of self renewal (mitosis division) even after long periods of inactivity o Under certain physiological or experimental conditions, can differentiate/specialize o Totipotent – ability to give rise to all cells of body (the fetus) and the embryonic tissue o Pluripotent – ability to give rise to all cells of body (the fetus) except the embryonic tissue o Multipotent - ability to give rise to a number of closely related family of cells o Oligopotent - ability to give rise to only a few cells (i.e. lymphoid or myleoid stem cells) o Unipotent - ability to produce only one cell type, their own o Can manipulate some of these cells and possibly go from specialized cells, back to general totipotent cells o They don’t undergo identical division because their daughter cells have the ability of self renewal o They can differentiate into all the cells in our body:  Ectoderm = nervous system & skin  Endoderm = gut tube & lungs  Mesoderm = muscle, bone & blood o There must be some kind of internal repair system in stem cells  Example: can remove a huge chunk of your liver and it grows back very quickly  Embryonic stem cells (ESC) o Most research have been going on with these stem cells o Mouse and human stem cells are not the same – so it is not easy to correlate o Since 1998 have been able to derive stem cells from human embryos o In vitro fertilization has a low success rate, so they typically put 2-3 fertilized eggs back into the mother o The leftovers that would have been discarded as waste are donated to this research o Development of the fetus:  Fluid enters the morula (big group of cells) and pushes the cells to the outside  The inner cell mass forms the fetus (it is pluripotent)  These inner mass cells are the ones that are being researched o Removing inner cell mass cells, destroys the zygote/fetus/embryo o Identification of embryonic stem cells:  Stem cell lines can grow & subculture for many months  After 40-50 divisions, normal cells typically die (telomerase)  But stem cells can stay alive for much longer periods of time  Presence of transcription factors & cell surface antigens  These transcription factors bind to promoter factors in genes and are important in turning on/off genes  Cytogenetic assessment (looking at the chromosomes) to confirm absence of numerical & structural changes to the chromosomes  Tissue culture to confirm that cultures frozen, thawed & replated will grow & subculture o Confirm cells are pluripotent by:  Allowing spontaneous differentiation in cell culture  Inducing differentiation  In vivo introduction of stem cells into an immunodepressed mouse & observe how they grow & differentiate  Immunodepressed – can’t reject foreign material o They look for many markers and absence of others to determine if it is a stem cell  First clinical trial of human embryonic stem cells (hESC) o Previous experiments had shown an improvement in locomotor recovery in spinal cord- injured rats after a 7-day delayed transplantation of hESC injected into an oligodendrocytic lineage (myelin producing cells in CNS)  The stem cells differentiated into myelin producing cells in CNS – on the neurons to send signals quickly o Busch administration had strict restrictions on hESC o Obama administration loosened restrictions on hESC o Jan 2009 – FDA approved trial for spinal cord injured humans o Oct 2010 – company Geron Corporation finally started the study on 8-10 paraplegics who had only had their injury for less than 2 weeks  hESC must be injected before scar tissue can form o Oct 2011 - Geron Corp (south of San Francisco) spent $170 million on developing a stem cell treatment for spinal cord injury and 4 patients each had 2 million cells injected into them with no complications o Nov 14, 2011 – announced Geron Corp will discontinue further development of its stem cell programs and that data from these trials will be available in 2013  Not exactly sure why  Somatic or adult stem cells o Rare, undifferentiated cells found among differentiated cells in a tissue or organ o Testing with these cells is not as ethically controversial o Identification of adult stem cells:  Remove cells from
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