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NEURO4850_ContemporaryTopics > Nikes and Neurons > Flashcards

Nikes and Neurons Flashcards

1
Q

ITS BETTER FOR YOUR BRAIN to Walk or bike to class

A

In town, it usually faster to get somewhere by bike if you are traveling

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2
Q

PHYSICAL ACTIVITY

at least 30MIN / DAY

A

Decreases risk of Cancer, Diabetes, Heart disease

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3
Q

DOES PHYSICAL ACTIVITY AFFECT THE CNS?

YES

A

Enhances cognition

Counteracts age-relate memory decline

Delays neurodegenerative disease onset

Reduces depression & anxiety

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4
Q

PHYSICAL ACTIVITY AFFECTS THE CNS

Enhances cognition

A

Farmers in Indiana, Percept Mot Skills. 1986 Feb;62(1):71-7.

It was hypothesized that increased physical fitness would lead to improved information processing, decision making, and psycho-motor performance.

Two groups with a pre and post test with 8 months in between to allow an improvement in physical fitness

• Control = no exercise
• Experimental = participated in physical fitness program of 3
1h sessions each week
• 25min of jogging
• 35min of stretching/calisthenics

Recorded measures of physical fitness:
O2, CO2, blood pressure, heart rate, body weight, skin fold measurement of fat vs muscle

Examined performance on a variety of cognitive tests

RESULTS:
Control groups fitness did not change.
Experimental group increased fitness by ~17%.
Cognitive performance increased.
Hypothesis testing: correct responses increased by 68%.

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5
Q

PHYSICAL ACTIVITY AFFECTS THE CNS

Counteracts age-relate memory decline

A

Longitudinal study of Cardio Fitness & Cognitive Function in Healthy Elderly Adults

Prior to this study, results were mixed; some studies found exercise improved cognitive function in older adults, maintained, or found no effect.

They were short-term studies (12 weeks to a year)

The authors hypothesized that baseline cardio-respiratory fitness would be positively associated with maintenance of cognitive function

Rationale:
Cardiorespiratory fitness is largely determined by habitual physical activity.
Wanted to specifically test if a person with sustained increased cardiorespiratory health had better cognitive function.

2092 OLDER ADULTS IN SONOMA, CALIFORNIA
• Longitudinal study
• gathered info approx. every 2 years
• in-home interviews to obtain data on subjects medical, physical, social, mental, emotional health
• Treadmill tests to obtain data on cardiorespiratory health (N=998)
• After 6 years, subjects underwent a detailed cognitive battery
• Random, sex-stratified subsample

Participants with lower VO2 max had:
• 4.6 fewer connections on the Trails B
• Named 8.4 fewer ink colors in 1 min
• Filled in 6.3 fewer squares per minute on the Digit Symbol
• Remembered 1.6 fewer words in immediate recall tests
• Produced 1.7 fewer words beginning with the letter ‘s’
• Named 1.8 fewer animals

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6
Q

VO2 max

A

aka, maximal oxygen uptake, maximal oxygen consumption, maxial oxygen uptake, peak oxygen uptake or maximal aerobic capacity

VO2 max is the maximum rate of oxygen consumption as measured during incremental exercise, most typically on a motorized treadmill.

VO2max is ultimately a measure of cardiorespiratory fitness.

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7
Q

PHYSICAL ACTIVITY AFFECTS THE CNS

Delays neurodegenerative disease onset

A

The Oldest Old and the 90+ Study

*Watch the video on this

Evaluated a short physical performance battery
• 4min walk
• 5 timed chair stands
• Standing balance
• Feet side-by-side
• One foot in front of the other in a stride
• One foot in front of the other in tandem

Evaluated dementia with Mini-Mental State Examine (MMSE)

Published in 2008

Correlated the incidence of dementia to many variables:
• Physical performance
• Vitamins
• Estrogen therapy
• BMI
• Alcohol consumption
• Physical activity
• Nonphysical activity (playing cards, reading the paper, etc…)
• Presynaptic marker expression & brain weight

Lower odds of dementia was associated with:

  1. High blood oxygen.
  2. Distance walked in in 4 minutes.
  3. Number of chair stands.
  4. Good balance.
  5. Strong grip

Cognitive function correlates strongly with presynaptic protein expression and brain weight

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8
Q

OR

A

Odds Ratio is strength of association between the risk factor and outcome

(odds of disease in exposed individuals)
÷
(odds of disease in unexposed individuals)

OR=1 Exposure does not affect odds of outcome
OR>1 Exposure associated with higher odds of outcome
OR

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9
Q

Lower odds of dementia was associated with

A
  1. High blood oxygen.
  2. Distance walked in in 4 minutes.
  3. Number of chair stands.
  4. Good balance.
  5. Strong grip
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10
Q

Cognitive function correlates strongly with….

A

presynaptic protein expression and brain weight

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11
Q

PHYSICAL ACTIVITY AFFECTS THE CNS

Reduces depression & anxiety

A

EFFECTS OF EXERCISE ON THE OLD & DEPRESSED:

156 men & women aged 50 and older

Randomly assigned to one of 3 groups:
• Medicated
• Exercise
(3x’s per week: 5 min warm up, 30 minutes of walk/jog to reach a target heart rate, 70-80% of heart rate reserve (max-resting).
• Combination of exercise (as above) + medication

VO2 Max & Treadmill test were given to evaluate cardiorespiratory
improvements

HAM-D and BDI tests were given to evaluate depression

Mean aerobic capacity and exercise tolerance for each treatment group, adjusting for pretreatment levels of depression.
I.E., VO2Max and length of time walking/running near max.
–> Compared with patients in the medication group, those in the exercise & combination groups showed significantly higher aerobic capacity (V̇O2) and longer treadmill test duration after 16 weeks of treatment.

Observed mean depression scores before and after treatment. All changes from pretreatment to posttreatment were statistically significant (P18 = moderately to severely depressed

Evaluated by two physicians
Self report questionnaire
Scale: 0 – 63
Higher the score = more depressed

Fitted values for HAM-D & BDI across 16 weeks of treatment.
–> Values represent the fitted scores in each treatment group for 2 selected values of baseline depression treatment (22 for moderate-severe, 16 for mild). Week 0 values represent the baseline starting points selected for this illustration and were not generated by the model. Depression ratings of mild and moderate-severe are at baseline.

Medicine improved depression symptoms more rapidly, but exercise was as effective as medication by 16 weeks

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12
Q

HAM-D indicates Hamilton Rating Scale for Depression;

BDI, Beck Depression Inventory.

A

HAM-D score and BDI Score are usually highly correlated

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13
Q

PHYSICAL ACTIVITY AFFECTS THE CNS

Improves recovery after CNS injury

A

Exercise helps cognition, aging, and depression in people.
This is supported by experiments in animal models.

The mechanism?

EXERCISE INDUCED IGF1 CAN CROSS THE BBB AND AFFECT NEURONAL FUNCTION

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14
Q

INSULIN GROWTH FACTOR-1

A 
IGF-1
• Hormone
• Peripherally derived from
the liver
• Stimulated by growth hormone
• Can cross the BBB
• Linked to exercise induced effects in the brain

Its effects are nonsuppressible insulin-like activity

Factors that are known to cause variation in the levels of growth hormone (GH) and IGF-1 in the circulation include: insulin levels, genetic make-up, time of day, age, sex, exercise status, stress levels, nutrition levels, body mass index (BMI), disease state, race, estrogen status, and xenobiotic intake.

IGF-1 binds to IGF receptors within the cells, which ultimately causes a stimulation of cell growth (both causing new tissue formation and existing tissue growth) and an inhibition of cell death. It is a highly anabolic and anti-catabolic compound. For the athlete or bodybuilder, this had many positive effects: increased nitrogen retention and protein synthesis because it is highly anabolic. IGF-1 (in the presence of sufficient protein) actually promotes growth of new muscle cells, which increases the overall number of cells in the muscle.

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15
Q

3 CNS NEURODEGENERATION MODELS

A

Domic acid = kills hippocampal neurons

Neurotoxin-3-acetylpyridine = damages inferior olive (IO) neurons

PCD mouse = degeneration of Purkinje cells in the cerebellum

Examined outcomes in mice

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16
Q

antibody

A

a large, Y-shape protein produced by plasma cells that is used by the immune system to identify and neutralize pathogens, such as bacteria & viruses.

The antibody recognizes a unique molecule of the harmful agent, called an antigen, via the variable region.

Using its binding mechanism, an antibody can tag a microbe or an infected cell for attack by other parts of the immune system, or it can neutralize its target directly (for example, by blocking a part of a microbe that is essential for its invasion & survival).

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17
Q

EXERCISE INDUCED IGF1 CAN CROSS THE BBB AND AFFECT NEURONAL FUNCTION

A

Striatum
Cerebral cortex
Red nucleus (midbrain, involved in motor coordination)

HOW DO THEY KNOW IGF1 CROSSES THE BBB?
Digoxigenin (DIG)-labeled IGF1

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18
Q

Digoxigenin (DIG)

A

Digoxigenin is thus an all-purpose immuno-tag, and in particular a standard immunohistochemical marker for in situ hybridization.

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19
Q

IGF1 IS TAKEN UP BY NEURONS

Purkinje neurons

A

ANTI-IGF1 ANTIBODY INFUSION INTO THE CSF BLOCKS IGF1 PERMEABILITY INTO THE BRAIN

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20
Q

EXERCISED ANIMALS PERFORM BETTER ON BEHAVIORAL ASSAYS THAN SEDENTARY ANIMALS REGARDLESS OF BRAIN LESION

A

EXERCISE RESCUES NEURONAL DEATH!!!

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21
Q

WHAT DOES EXERCISE DO TO THE CNS?

A

Changes neurotransmitters, neurotrophins, and vasculature

Induces neurogenesis.

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22
Q

EXERCISE INCREASES THE AVAILABILITY OF TROPHIC SUPPORT

A

In situ hybridization to measure brain derived neurotrophic factor messenger RNA expression

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23
Q

What is in situ hybridization?

A

a type of hybridization that uses a labeled complementary DNA, RNA, or modified nucleic acids strand (i.e., probe) to localize a specific DNA or RNA sequence in a portion of tissue (in situ), or, if the tissue is small enough (e.g., plant seeds, Drosophila embryos), in the entire tissue (whole mount ISH), in cells, and in circulating tumor cells (CTCs).

This is distinct from immunohistochemistry, which usually localizes proteins in tissue sections.

In situ hybridization is a powerful technique for identifying specific mRNA species within individual cells in tissue sections, providing insights into physiological processes and disease pathogenesis.
However, in situ hybridization requires that many steps be taken with precise optimization for each tissue examined and for each probe used.
In order to preserve the target mRNA within tissues, it is often required that crosslinking fixatives (such as formaldehyde) be used.

In situ hybridization is used to reveal the location of specific nucleic acid sequences on chromosomes or in tissues, a crucial step for understanding the organization, regulation, and function of genes.
The key techniques currently in use include: in situ hybridization to mRNA with oligonucleotide and RNA probes (both radio-labelled and hapten-labelled); analysis with light and electron microscopes; whole mount in situ hybridization; double detection of RNAs and RNA plus protein; and fluorescent in situ hybridization to detect chromosomal sequences. DNA ISH can be used to determine the structure of chromosomes. Fluorescent DNA ISH (FISH) can, for example, be used in medical diagnostics to assess chromosomal integrity. RNA ISH (RNA in situ hybridization) is used to measure and localize RNAs (mRNAs, lncRNAs, and miRNAs) within tissue sections, cells, whole mounts, and circulating tumor cells (CTCs).

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24
Q

TROPHIC

A

(of a hormone or its effect) stimulating the activity of another endocrine gland.

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25
Q

IN SITU HYBRIDIZATION

Summary

A

…..

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26
Q

IN SITU HYBRIDIZATION TO MEASURE BRAIN DERIVED NEUROTROPHIC FACTOR MESSENGER RNA EXPRESSION

A

control rat brain
vs.
rats that exercised for 7 days

CA1, DG

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27
Q

EXERCISE Induces neurogenesis

A

The process of generating functional neurons from progenitor cells

Progenitor cells proliferate and mature into functional neurons – integrate into neural circuits

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28
Q

HOW DO WE STUDY NEUROGENESIS?

A

Mark proliferating cells

Bromodeoxyuridine (BrdU)
• Synthetic thymidine analogue

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29
Q

STUDY:

Running increases cell proliferation & neurogenesis in the adult mouse dentate gyrys.

A

Exposure to a rich environment induces structural & functional changes in the rodent brain and significantly increases hippocampal neurogenesis

THEY TESTED
the contribution of learning (via water maze) and physical activity (running wheel) on the generation of new dentate granule cells

WHAT THEY DID:
Divided the mice into 4 living conditions:
1. Enriched-environment (aka: enriched)
2. Hidden-platform water-maze learning (aka: swimmer &
forced exercise)
3. Voluntary exercise (aka: runners)
4. Standard living (aka: control)

Injected with BrdU for the first 12 days & examined the number of BrdU+ cells in the dentate gyrus

ASSESSMENT OF SUBGRANULAR PROGENITOR CELL PROLIFERATION

30
Q

‘Enrichment’ is a combination of inanimate and social

stimulation

A

Larger housing area
More friends to interact with
Greater opportunity for physical activity
Greater opportunity for learning

31
Q

MORRIS WATER MAZE:

THE MICE ARE LEARNING

A

IS LEARNING IN THE MORRIS WATER MAZE ASSOCIATED WITH CELL PROLIFERATION?

ASSESSED PROLIFERATION BY MEASURING BRDU INCORPORATION

32
Q

12 days of BrdU injections followed by immunohistochemistry 1 day after the last injection

A

Runners were the only ones to be significantly better

33
Q

12 days of BrdU injections followed by immunohistochemistry 4 weeks after the last injection

A

Runners were significantly the best.

Enriched Environment mice were also significantly affected.

Everybody else was not much different than the controls.

34
Q

THERE ARE MORE NEURONS, SO WHAT

A

Are they functional?
YES!

Running enhances neurogenesis, learning, and long-term potentiation

35
Q

Physical activity:
Facilitates recovery from injury
Improves cognitive function
Increases trophic factors associated with increased (Progenitor cell differentiation & survival, Long-term potentiation, Memory)

A

….This was known… but

Does physical activity affect synaptic plasticity & learning?

36
Q

Does physical activity affect synaptic plasticity & learning?

A

THEY TESTED
If exercise will increase synaptic plasticity, learning, and neurogenesis

WHAT THEY DID:
Running wheel vs. controls with no wheel for excursive

37
Q

ENTERTAINING ASIDE

A

Remember how I said reviewers can be Pains?
• “Scientists, researchers and animal rights advocates have argued over the years about the nature of mice running
on wheels in their cages. Rights activists claim the running is a form or neurotic behavior brought about by living in the confines of a small cage. Some researchers, on the other hand, have suggested that the mice seemed to like, or enjoy running on the wheel, and even exhibited unhappy behavior if a wheel was removed.”

“To learn more, Meijer & Robbers decided to carry out a very simple experiment—they set up a running wheel in their backyard, then used an infrared camera to capture on tape how animals in the wild would respond.”

38
Q

WHEEL RUNNING IS REALLY ENRICHMENT

A

And, to personify mice, maybe even enjoyed by mice

39
Q

MORRIS WATER MAZE

PROTOCOL

A 
Training
• 2 or 4 trails / day
• 6 days
• Subject placed in pool near edge
• Entry point varied
• Each trial last 40s or until the mouse found the platform

Testing was done between day 30 and 49

Length of swim path (path) & time to reach the platform
(latency) were recorded

TWO TRIAL/DAY
Slight, but significant improvements in
• Path length (runner

40
Q

RUNNING INCREASED LTP IN THE DENTATE GYRUS

A

Running does not affect
initial EPSP amplitude
BUT
Running increased EPSP amplitude at a greater rate

41
Q

RUNNING DID NOT CHANGE LTP INDUCTION IN THE CA1 SCHAFFER COLLATERAL PATHWAY

A

LTP IN THE DG AND THE CA1 SCHAFFER COLLATERAL IS USUALLY MEDIATED BY NMDA RECEPTORS

42
Q

To test NMDA receptor dependence of enhanced LTP with running, they
blocked NMDA receptors by apply AP1 (NMDA receptor
antagonist) to the slices

A

LTP induction was completely blocked.

Suggests that NMDA receptors mediate running induced
increases in LTP

43
Q

SUMMARY #2

A

BDNF is an exercise-induced trophic factor

Wheel running increased LTP in the dentate gyrus

Even slugs will use a running wheel

44
Q

Motor skill learning requires active central myelination

A

THIS PAPER IS NOT LOOKING
AT THE EFFECT OF EXERCISE FOR THE SAKE OF EXERCISE…

its not neurons, its about oligodendrocytes…

45
Q

OLIGODENDROCYTES

A

WRAP NEURONAL
PROCESSES IN MYELIN

a glial cell concerned with the production of myelin in the central nervous system.

46
Q

WHAT IS MYELIN ?

A

protein and phospholipids that form an insulating sheath
around axons

increases the speed of electrical communication between
neurons

white matter (myelin tracts) vs grey matter (neurons)

in the CNS, myelin is made by oligodendrocytes

47
Q

WHAT ABOUT

OLIGODENDROCYTES?

A

majority are born and develop in the first 6 weeks (in rodents)

there is some oligo proliferation in the adult mice

oligo precursor cells are called NG2+ glia
• NG2 is marker (a protein that can be immunostained and observed)

NG2+ glia are found in the adult brain

48
Q

DOES MYELIN CHANGE

IN THE ADULT?

A

YES

MRI studies on piano players (or other people who learn complex motor tasks) show structural changes in white matter

If you train rodents in new
motor learning tasks, you can find changes to the structure of their white matter

UR: unskilled reaching
SR: skilled reaching

49
Q

PRIMARY RESEARCH
QUESTION?

What is the role of adult
oligodendrogenesis?

A

HOW DO THEY ANSWER
THIS QUESTION?

Use Cre-LoxP conditional deletion techniques, they target a gene (myelin regulatory factor, Myrf) that when lost, blocks the maturation of oligodendrocytes and thus myelinating capability of new oligos

  • Majority of oligos are already formed
  • This approach only inhibiting the ability of new oligos to myelinate
  • Use the Pdfra promoter (active in NG2+ oligo precursor cells) to drive Cre-ERt2 expression
  • ER-T2 = estrogen receptor – treat with tamoxifen and Cre translocates from membrane to the nucleus where it can act on LoxP sites
  • Spatial control conferred by the Pdfra promoter
  • Temporal control conferred by ER-T2 (no deletion until tamoxifen treatment)
50
Q

Does deleting oligo precursors cause major deficits in myelin or function?

A
  1. Deleted Myrf
  2. Waited 5 weeks
  3. Then asked: does loss of
    oligo precursor cells cause demyelination?
  4. Stained for myelin (dark
    blue/purple)
  5. Found no difference in
    gross myelin characteristics
  6. Looked a myelin wrapping by EM and found no difference
51
Q

LOSS OF MYELINATION FROM
NEWLY DIFFERENTIATED/FORMED
OLIGOS DOES NOT CHANGE MOTOR FUNCTION

A

…rotarod

52
Q

LOSS OF MYELINATION FROM
MATURE OLIGOS IMPAIRS
FUNCTION

A

Deletes Myrf from both
oligo and oligo precursors

Sox10 – drives Cre expression in oligo precursor & mature
oligodendrocytes
–> lose myelinating ability in
both

53
Q

ESTABLISHED THE ANIMAL MODEL TO BLOCK THE MYELINATION ABILITY IN NEWLY FORMED OLIGOS

A

Now, what about the motor learning task?

Complex Wheel Running (CW)
• This running wheel has missing rungs
• Mice love running, so missing rungs will not stop them, they will ‘learn’ to deal with the missing rungs

THE EXPERIMENT...
Cre active = Myrf loss of
function in oligo precursor cells
3 weeks after Myrf Loss-Of-Function in OPs introduced to complex wheel

MYRF-/- MICE RUN
SLOWER

54
Q

REMEMBER THOSE REVIEWER
QUESTIONS I SAID TO LOOK
OUT FOR?

A

Someone was not convinced…
Repeated the experiment a total of 5Xs
N=36 Myrf+/-
N=32 Myrf-/-

So do mice need active remyelination to remember how to use the complex wheel?
No!!

55
Q

CW RUNNING STIMULATES OLIGO PRECURSOR PROLIFERATION & OLIGO PRODUCTION

A

CC1 = marks mature
oligos

EdU = marks proliferating cells
• similar to BrdU but
easier to use

56
Q

Bromodeoxyuridine (BrdU)

A

a synthetic nucleoside that is an analog of thymidine.

BrdU is commonly used in the detection of proliferating cells in living tissues.

BrdU can be incorporated into the newly synthesized DNA of replicating cells (during the cell cycle in which DNA is replicated), substituting for thymidine during DNA replication.

Antibodies specific for BrdU can then be used to detect the incorporated chemical (see immunohistochemistry), thus indicating cells that were actively replicating their DNA.

Binding of the antibody requires denaturation of the DNA, usually by exposing the cells to acid or heat.

BrdU can be passed to daughter cells upon replication.

BrdU has been demonstrated to be detectable over two years post-infusion.

57
Q

CW RUNNING STIMULATES OLIGO PRECURSOR PROLIFERATION & OLIGO PRODUCTION

A

Spike in precursors

2 days later spike in oligos

58
Q

OLIGO PRECURSOR CELLS DO NOT PROLIFERATE WHEN MICE ‘REMEMBER’ HOW TO RUN ON THE COMPLEX WHEEL

A

Novelty of learning how to run on the CW is what triggered oligogenesis and myelination

59
Q

OLIGO DIFFERENTIATION OCCURS AROUND THE SAME TIME THEIR RUNNING IMPROVES

A

Suggests new oligos are important for motor skill
learning/acquisition of new tasks

• How?
• New connections are formed and/or existing connections are strengthened which stimulates
myelination or myelin remodeling

Is there other evidence for this?
• Learn a new language = new myelination

60
Q

TAKE HOME POINTS

A

New myelination / new oligos are necessary for motor learning

Existing myelination is sufficient to maintain previously learned motor tasks

61
Q

Myelin-forming oligodendrocytes (OLs) are formed continuously in the healthy adult brain.

A

Learning a new motor skill (such as juggling) alters the structure of the brain’s white
matter, which contains many OLs, suggesting that late-born OLs might contribute to motor
learning.

Consistent with this idea, we show that production of newly formed OLs is briefly
accelerated in mice that learn a new skill (running on a “complex wheel” with irregularly spaced rungs).

62
Q

By genetically manipulating the transcription factor myelin regulatory factor in OL precursors, they blocked production of new OLs during adulthood without affecting preexisting OLs or myelin.

A

This prevented the mice from mastering the complex
wheel.

Thus, generation of new OLs and myelin is important for learning motor skills.

63
Q

Myelin greatly increases the speed of electrical communication among neurons and, hence, the brain’s computational power

A

….

64
Q

What is the function of adult-born OLs and myelin?

A

(MRI) has detected changes in the structure of white matter in people trained in complex sensorimotor tasks such as playing the piano, juggling, or abacus use.

65
Q

Active myelination during adulthood is required for motor skill learning and that motor learning increases OL production.

A

….

66
Q

Preventing adult myelination by conditional deletion of myelin regulatory factor

A

Preventing new OL production does not trigger demyelination

67
Q

Myelin regulatory factor (MyRF)

A

a transcription factor required in OLs to initiate & maintain their myelination program

It is not expressed in OL precursors, in other CNS cells, or in Schwann cells, which myelinate PNS axons

68
Q

Administering tamoxifen induces Cre-mediated
recombination, inactivating one or both alleles of Myrf in Pdgfra-expressing precursors while simultaneously labeling the precursors with yellow fluorescent protein (YFP)

A

We refer to the tamoxifen-treated mice as P-Myrf (+/−) and P-Myrf (−/−).

Recombination at the Myrf locus was confirmed by reverse transcription polymerase chain reaction.

69
Q

We inactivated Myrf in OPs by tamoxifen administration

on postnatal day 60 (P60) or P90.

A

our strategy prevents the formation of new OLs without affecting preexisting OLs

70
Q

Consistent with the myelin histology, P-Myrf (–/–) mice showed no outward signs of demyelination (e.g., tremors) and were indistinguishable from their P-Myrf (+/−) littermates on an accelerating rotarod, a test for motor coordination & balance.

A

In contrast, S10-Myrf (−/−) mice
developed severe tremors around 1 month posttamoxifen, and their performance on the rotarod was seriously impaired, similar to when Myrf deletion was targeted to mature OLs using Plp-CreER.

71
Q

Active myelination is required for motor skill learning.

A

Active myelination is not required to recall a prelearned skill

NEURO4850_ContemporaryTopics (4 decks)

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