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Lecture

Lecture 21.docx

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Department
Biology
Course Code
Biology 1202B
Professor
Brenda Murphy

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1 Stem Cells (Page 781) Stem Cells (Useful for cancers, blood disorders, immune disorders, metabolic disorders)  Unspecialized Cells  Has not yet became heart tissue, lung tissue, etc. therefore it is capable of many things o Self-Renewal – Capable of self renewal (mitosis) even after long periods of inactivity o Potency – Under certain physiologic or experimental conditions can differentiate/specialize Different Levels of Potency  Totipotent – Ability to give rise to all the cell types of the body plus all the cell types that make up the extra-embryonic tissues such as the placenta  Pluripotent – Ability to give tissue to all of the various cell types of the body but can not make extra- embryonic tissues such as amnion, chorion, and other components of the placenta o Already differentiated and therefore cannot make placenta  Multipotent – Ability to give rise to a number of closely related family of cells  Oligopotent – Ability to give rise to only a few cells (i.e. lymphoid or myeloid stem cells)  Unipotent – Ability to produce only one cell type; their own Function of Stem Cells  Development o Differentiate into all the cells of our body  Ectoderm – Nervous system & skin  Endoderm – Gut tube & lungs  Mesoderm – Muscle, bone, blood  Internal Repair o Regenerate organs (blood, skin, intestinal tissue, etc.) Two Types of Stem Cells Based on their Site of Origination & Degree of Specialization  Embryonic Stem Cells (ESC) o Most research on mouse & human embryonic stem cells, but in vitro mESC are not identical to hESC 2 o Since 1998 able to derive stem cells from human embryos (where you get them from— discarded waste of in-vitro fertilization donated to research) o hESC are isolated from the inner cell mass of the blastocyst o Embryonic Stem cells from a 4-5 day old embryo  Pluripotent so they cannot make placenta  Instead, they can make the circulatory system, nervous system, immune system  Somatic or Adult Stem Cells o Rare, undifferentiated cell found among differentiated cells in a tissue or organ o Since 2006, unable to reprogram differentiated/specialized cells to a stem-cell-like state o Testing with these cells is not as ethnically controversial  No destruction of embryo  Obtained from the intended recipient o Location: skeletal muscle, heart, bone marrow, blood vessels, umbilical cord, skin, teeth rd (developing tooth bud of the mandibular 3 molar…8-10 years of age before calcification), gut, liver, ovarial epithelium testis, brain o 1990’s agreed that adult brain contains stem cells able to generate the three major cell types  Non-neuronal cells  Astrocytes & Eligodendrocytes  Neurons o Most adult stem cells are lineage restricted hESC Research is Ethnically Very Controversial  Removing inner cell mass cells, which destroys the zygote/embryo/fetus  However, these embryos have been donated/recycled as they were intended to be disposed of (incinerated) Identification of Embryonic Stem Cells  Stem cell lines can grow & subculture for months  Presence of transcription factors (NANOG, Oct-4 & Sox2) & cell surface antigens (glycolipids stage specific antigen 3 & 4, and the keratin sulfate antigens Tra-1-60 & Tra-1-81)  Cytogenetic assessment to confirm absence of numerical & structural changes to the chromosomes  Tissue culture to confirm that cultures frozen, thawed & replicated will grow & subculture  Confirm cells are pluripotent by: o Allowing spontaneous differentiation in cell culture o Inducing differentiation 3 o In vivo introduction of stem cells into an immune-depressed mouse & observe how they grow & differentiate (immune-depressed – will not reject any cell) Transcription Factors that are Marker for Undifferentiated hESC  Why Oct-4, NANOG & Sox2? o Suppression of genes that
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