L312/Spring 2003Lecture 22Drummond April 7

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L312/Spring 2003 Lecture 22 Drummond April 7
For today Start Chapter 21 tissue structure
and connections today (skip plant
tissues) Last time Anaphase initiation by
APC (anaphase promoting complex) triggers
inhibitor degradation active protease
degrades cohesins, metaphase progresses to
anaphase MAPs and catastrophins in
maintaining a steady state involving
microtubules failure to degrade long
strings/hair failure to stabilize short,
unconnected Critically compare features
of microtubules and MAPs in mitosis XKCM-1
(catastrophin) and XMAP-215 (X xenopus, a
favored frog) Finish Steps in
anaphase anaphase A kinetochore
microtubules shorten anaphase B interpolar
microtubles lengthen and slide
centrosomes move apart The steps in
mammalian cytokinesis The role of actin and
myosin This time Tissues (connective,
epithelial, etc.) and the extracellular
matrix What holds cells together? What
gives tissues strength?
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MAPs bind microtubules and modulate stability and
function
XMAP215
Antibody depleted
Antibody depleted
XKCM1
Antibody depleted
Implications MT? GTP?
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Actin and myosin are central to cell resolution
into two cells
What are possible roles for the interpolar
microtubules at this late stage?
Initiated in anaphase
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What happens to the integrins during cytokinesis?
what is the key molecular event That mediates
integrin release?
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Stepping back cells in the context of structure
Tendons Bone Cartilage Eye matrix
What and where is the extracellular matrix? Who
makes it? What role does each cell type
serve? Where do you think tumors arise?
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What is the primary protein structure that
provides ECM strength?
(elastin, keratin, And others)
What are the dots?
Tendons Bone Cartilage Eye matrix
Compare to cell Dimensions!
Collagen A 1000 aa long
1/4th of your protein
What distinguishes these from IFs?
Secretion and assembly? Fibroblasts?
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How are collagen Fibers crosslinked?
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Vitamin C is essential for crosslinking
collagen (deficiencies result in weakened
skin, teeth, bones)


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James Morris couldnt cross-link his collagen
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Packing of collagen fibers leads to a banding
pattern
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Stripped ECM reveals collagen and fibroblasts
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Perpendicular layering of collagen fibrils in
skin (and elsewhere)
How do you make Collagen fibers into A strong
skin Network?
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Bone cells (osteoblasts)/osteoclasts in a
connective matrix
Where is the bone? Where is the collagen?
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Integrins mediate transmembrane interactions
What else?
The shallow lake analogy
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Glycosaminoglycans (GAGs) are long, negatively
charged polymers
(polymer hyaluronan)
What role do these ECM components play? Why are
they sulfated?
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Proteoglycan structure in the ECM