L8 - Stem Cells and the Future Flashcards
What are stem cells?
Cells that can differentiate into other types of cells and can divide to produce more of the same stem cells.
They are functionally unspecialised.
What was the early dogma on neurogenesis?
Once early childhood was reached, the number of neurons in the brain only decreases.
Idea that the central nerve system just doesn’t regenerate at all.
What forms of neural replacement occurs aside from neurogenesis?
Synapses are very dynamic systems that repeatedly appear and disappear, as they are replaced and regenerate.
Scaffolding proteins that form large molecular complexes in synapses have a very high rate of turnover and are highly mobile.
What are the timescales of turnover of synapses?
Minutes/hours, whole synapse taking in the order of months to replace.
What are the timescales that it takes spines to turnover?
Hours, the whole structure taking in the order of months/years to fully replace.
What is neurogenesis?
The growth and development of nervous tissue
In most regions of the brain, new neurons are not produced once you are born. What are the exceptions, and why?
New neurons are made throughout life in the olfactory bulb (OB), and dentate gyrus (DG) of the hippocampus.
This is likely because olfactory stimuli are constantly stressing the cells, so a mechanism is developed to replace them.
In the DG/hippocampus it is thought to be related to the acquisition of new memories.
What did Spalding et al., (2013) find about the regrowth of neurons in the hippocampus using radioactive elements?
In the 1950s, nuclear bomb testing began, causing the levels of radioactive Carbon 14 (14C) to increase.
Presence of 14C in a neuron would indicate that it had been created since nuclear testing began.
Found that 1/3 of hippocampal cells are in a renewing state - estimated that an adult creates 700 new neurons per day (2% of annual turnover rate)
Indicates neurogenesis in adults.
What are the two types of stem cells, and what are the differences?
Adult stem cells - organ-specific and are restricted in their developmental potential (i.e. can only be new nerve cells, or skeletal muscle cells)
Embryonic stem cells - appear unrestricted in their developmental potential
What is self-renewal?
The ability to go through numerous cycles of cell division while maintaining the undifferentiated state.
What is potency?
The capacity to differentiate into specialised cell types - to be able o give rise to any mature cell type.
What are the 5 levels of potency?
Totipotent (/omnipotent) Pluripotent Multipotent Oligopotent Unipotent
What are totipotent (/omnipotent) stem cells?
Stem cells which can construct a complete, viable organism. Found/produced when a sperm and egg fuse.
What are pluripotent stem cells?
Descendants of totipotent cells, and can differentiate into nearly all cells.
What are multipotent stem cells?
Can differentiate into a number of cell types, but only those of a closely related family of cells.
What are oligopotent stem cells?
Can differentiate into only a few cell types, such as lymphoid or myeloid (bone marrow) stem cells.
What are unipotent stem cells?
Can produce only one cell type, their own - they have the property of self-renewal.
What are progenitor cells?
Can differentiate into a specific type of cell, but is more specific than a stem cell and can only differentiate into its target cell. Cannot self-replicate/perform self-renewal like a stem cell can.
