Biology 3602A/B Lecture Notes - Lecture 30: Myocyte, Lipid Droplet, Vo2 Max

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5 Aug 2016
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Review: proportion of diff types of muscle fibres differs among species, within
individuals, and within muscles fibres in individuals
E.g. sprinter and marathon runner have very diff macromuscles which carries down to
the micro level as well
Scientists were interested in athletic ability of animals within a species, but they
wondered how can there be a more athletic animal that can evolve?
What determines the ability to run?
Desire/behavioural tendency to run?
Or having the physiological machinery that allows you to run far and fast
Testing the behaviour vs physiology
How they did it: measured both behaviour and physiology, and then they selected
animals that liked to run and bred them together
Measured behaviour, and measured the physiological ability to run using the VO2max
Mice were not trained to run on wheel; some liked to run, and some didn’t
High runners were bred together and measured wheel running in offspring
Other control group were of 2 randomly bred mice
Continued this for many generations; for each generation, they took animals that have
never seen a wheel before, exposed it to them, and measured their tendency to run,
and measured the VO2max
Compared high runners to random control groups
#s of generations on x axis
Revolutions per day on y axis (for mice that have never seen a wheel before)
If you breed high running dads with high running moms, you get babies that like to run
Mice that like to run have the physiology to be able to run
After 20 gens, they bred them like this, and there were 4 groups that they compared
1st group was the control mice that never saw a wheel until they were tested for their
tendency to run (sedentary)
2nd group that was randomly bred but those mice had access to wheels so they could
train on the wheels and get some exercise (trained)
3rd group: parents like to run but the babies didn’t have access to wheel; genes to like
to run but weren’t trained to run (sedentary)
4th group: liked to run and could get on a wheel (trained)
So now we have ability to test the behavioural tendency to run and compare it to the
ability to train to run
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These are data for maximal O2 cons in each of those 4 groups
Does selection for tendency to run (behaviour) correspond in change in VO2max? I.e., If
you like to run, does that go along with giving you more machinery to run
So choose 1 and 3 (sedentary), and 2 and 4 (trained)
1 & 3: Compare sedentary control to sedentary selected: significant increase in
VO2max with selection (WITHOUT training); just because parents liked to run, more
likely to have better machinery to allow you to run
2 & 4: If parents didn’t like to run, but you were allowed to train, VO2max also went up a
bit
How does training affect VO2max?
1 and 2: goes up
3 and 4: goes up
Both selection for wanting to run and the ability for access to train increases the ability
to run; is there an interaction between selection for running and being allowed to train?
Yes
If you compare 1 (control, sedentary) and 4 (selected, trained): much bigger response
So both evolution and training/acclimitization helps the mice get a higher VO2max
Long term selection and short term acclimitization will increase VO2max
Here we have VO2 (O2 consumption) on Y axis, and treadmill speed on x axis
Sooner or later, as speed gets higher and higher, you get a maximal rate of O2
consumption (VO2max)
In pink line, it is VO2max consumption for horses that weren’t trained
If you take the SAME animals and train them for 6 weeks, the VO2max does go up
This is another example of how training can increase the rate of maximum O2
consumption
It affects the whole animal O2 consumption, but what effect does it have on muscles?
Mostly locomotory muscles are consuming the O2; heart and diaphragm also has to
work a bit more too but mostly skeletal muscles
To increase VO2max in muscles, could do a # of things:
1. make more muscle cells and allow them to work; making more cells is called
hyperplasia
But skeletal muscles are what we call post-mitotic – the # of muscle cells you’ve got is
the # you’re going to have; if you kill them you won’t grow more daughter cells
So not an option for skeletal muscle cells
2. make bigger muscle cells: hypertrophy
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