Midterm 2 Flashcards
Understand Concept and content for the second midterm
_____ and _____ are dependant on the relationship between cell proliferation (process that results in an increase in the number of cells), differentiation and death
Tissue turnover, homeostasis
In cell proliferation, extracellular signals such as _____ and _____, play an essential role
growth factors, hormones
Penetrate the cell membrane and bind to specific receptors that directly effect genomic regulatory mechanisms
Steroids (e.g. testosterone, estrogen, cortisol)
Act on membrane receptors to activate kinases as a result of inability to pass cell membrane
Polypeptide growth factors (e.g. IGF-I, IF-2)
True or False: Growth factors both enable the cell to enter the cell cycle and are required to inhibit the cell from dying, to some extent.
True
The phases of the cell cycle are…
G0, G1, S, G2, and M
cdks and cdk Inhibitors refer to…
Cyclin-Dependant Kinases and Cyclin-Dependant Kinase Inhibitors
When a cell is not in the cell cycle and receives the appropriate growth stimulation it leaves _____ phase.
G0
Regulates progress in the cell cycle
cyclins and cdks
What must be present to activate a cdk?
Cyclins
Cyclin-cdk complexes phosphorylate _____ to stimulate expression of important cell cycle genes
proteins
True or False: cdk inhibitors regulate the amount of proteins that a ribosome can translate
False… cdk inhibitors regulate the activity of cyclin-cdk complexes alongside tumor surpressors
p53 is a…
tumour suppressor gene
Promote cell cycle
Growth factors, cyclins, oncogenes and cdks
Halt cell cycle
Tumour suppressor genes and cdk inhibitors
Cyclin and cdk associated with G1
Cyclin D and cdk 4/6
Cyclin and cdk associated with transitioning from G1 to S phase
Cyclin E and cdk 2
Cyclin and cdk associated with transitioning from S to G2 phase
Cyclin A and cdk 2
Cyclin and cdk associated with transitioning from G2 to M phase
Cyclin B and cdk 1
Finite number of cellular divisions possible, regardless of expression levels of protein and factors that promote proliferation
Hayflick Limit
The Hayflick Limit is a result of the replication of DNA for the chromosomes of the sister cells resulting from the cell division. Why does the DNA strand shorten every time a cell divides?
DNA polymerase cannot add nucleotides to the new 5’ end
Internal mechanism to deal with DNA strand shortening during cell proliferation
Telomeres
Telomeres consist of approximately 1,000 to 1,700 _____ and a _____ overhang from the 3’ end
base pairs, single strand
A reverse transcriptase that is responsible for adding base pairs to the telomere
Telomerase (Telomere terminal transferase)
A chromosome telomere shortens by _____ base pairs every replication
50
True or False: Telomeric length is equivalent throughout an organism, but varies between species
False… Telomeric length varies between cell types and from one chromosome to another (e.g. faster replicating cells like leukocytes > slower replicating cells like skin fibroblasts)
Is telomerase activity greater or lesser in adult cells
Lesser or even absent
An indicator of cellular senescence and aging is…
The halt of cell proliferation
Rank in order of a greatest telomere length maintenance during cell division to least telomere length maintenance during cell division:
Normal Cells
Germ Cells
Stem Cells
Germ Cells > Stem Cells > Normal Cells
Can skeletal muscle fibers proliferate?
No, it is terminally differentiated or post-mitotic tissue
Addition of _____ allows for repair and adaptation of muscle fibers.
nuclei
Adult mammalian skeletal muscle is very stable; no more than _____ of the _____ are replaced on a weekly basis.
1-2%, myonuclei
The two types of cells that provide a sufficient source of new myonuclei for muscle regeneration
Satellite cells and myogenic stem cells
Undifferentiated mononuclear cells first identified by Alexander Mauro in 1961 (from a frog)
Muscle satellite cells
Satellite cells are termed “satellite” due to their _____ position in relation to the fiber.
peripheral
Satellite cells are located between which two membranes?
The plasma membrane (proximal) and the basement membrane (distal)
Do satellite cells or myonuclei have both decreased organelle content and a smaller nuclear size?
Satellite cells
Pax7
A marker for satellite cells as it can only be found on satellite cells. It is required for satellite cell development.
Molecular markers for identifying quiescent, activated and proliferating satellite cells
MNF, Pax7, c-Met, M-cadherin, NCAM, VCAM-1
Molecular markers for identifying activated and proliferating satellite cells
Desmin, myf5, MyoD
At _____ days after the primary muscle fiber has been formed, satellite cells are present in limb muscle
18
The percentage of satellite cells in all muscle falls rapidly following _____
birth
The number of satellite cells is much greater in _____ fibers than _____ fibers
slow, fast
Why might satellite cells be more abundant in slow fibers than fast fibers?
Because slow fibers are used to greater extent and receive a greater amount of “wear and tear” and thus need more myonuclei to repair the fiber. And with greater levels of myofibers there needs to be greater satellite cell levels to replace the nuclei
Satellite cells are quiescent until activated in response to _____, _____ and _____
disease, damage, excercise
When injury or damage occurs, satellite cells are activated, enter the _____ _____ and _____
cell cycle, proliferate
Muscle precursor cells must do what before fusing to the myofiber?
Terminally differentiate
When can new myofibers form as a result of two satellite cells fusing together?
During severe disease states such as muscular dystrophy
Transplantation of one myofiber containing 7 satellite cells can give rise to _____ new myofibers
> 100
The quality of being able to divide many times is to have a high _____ _____
proliferative potential
What are the two types of cellular division that satellite cells can undergo?
Planar division and apical-basal division
Division on a horizontal plain that results in one cell maintaining contact with the basal lamina and the other losing contact
Apical-basal division
Typically generates two identical daughter cells (symmetric division)
Planar division
Division on a vertical plain that results in both cells maintaining contact with the basal lamina and the sarcolemma
Planar division
Typically generates one cell committed to becoming a myotube and another cell with proliferative potential (asymmetric division)
Apical-basal division
True or False: The majority of satellite cells that divide will differentiate and form myotubes or incorporate into existing fibers
True
Is the regenerative capacity of satellite cells limited?
Yes
Growth factors that stimulate muscle regeneration and satellite cell expansion can be produced by _____, _____ and _____ sources
autocrine, paracrine, endocrine
_____ cells typically become activated _____ hours after tissue damage
Satellite, 6
Satellite cells’ main growth factors
IGF-I & IGF-II, HGF (hepatocyte growth factor), FGF (fibroblast growth factor) and LIF (leukemia inhibitory factor)
Other factors that play a role in satellite cell activation
NO, testosterone, IL-6 (interleukin-6), PDGF (platelet-derived growth factor), and EDGF (endothelial-derived growth factor)
What are some things that can be modulated by satellite cell growth factors?
Activation, chemotaxis, proliferation and differentiation