Adaptive Significance

Question 1

Organizational adaptive uses of biological rhythms

Answer 1

• Rhythm mutations and competition
• Learning impairments and reduced longevity
• SCN transplants that improve rhythms result in increased longevity in hamsters
• Internal desynchrony and disease

Question 2

Anticipatory uses of biological rhythms

Answer 2

• Optimal uses of biochemical processes
• Increased predation w/ SCN lesions or decreased lifespan
• Preparation for nutrient availability
• Avoidance of danger

Question 3

(Growth and competition for resources significance)
Cyanobacteria had changed periods:
- SP22 (Short period @ 22 h)
- P28
- P28R (Reverted from 28 h back to 24)
- Wild type (24 h)

What happened to growth rate when there’s no competition (LL), normal conditions (LD 12:12), and 30 h light cycle
Conclusion?

Answer 3

1) Growth rate mot affected when there’s no selection
2) Mutant bacteria (P28, SP22) dropped growth rate
3) Wild type and P28R dropped growth rate

Conclusion: When matched to Zeitgeber, promotes competition for resources

Question 4

(Survival and anticipation significance)
Flying squirrels given SCN lesions, sham, or just wild type
Conclusion?

Answer 4

Lesion ended up dying more often due to predation
Sham had same rate as lesion during first 10 days before levelling off

Conclusion: Biological clocks promote survival; SCN lesions increase predation and decrease lifespan

Question 5

(Organization and survival significance)
Tau mutant hamster longevity was measured
- What happened to heterozygous mutation hamsters?

Conclusion?

Answer 5

Rhythm was disturbed and longevity decreased
- Fragmented activity that started 4 hrs earlier than usual

Conclusion: When matched to Zeitgeber, health is promoted

Question 6

Hypothesis of circadian systems for organization and disorganization

Answer 6

Circadian systems provide organization that is essential to health, and that disorganization leads to disease

Question 7

(Organization and survival significance)
Old tau mutant hamster -> Some left to die naturally and others transplanted w/ young SCN

Conclusion?

Answer 7

Younger SCN increased activity of intact SCN
- Transplant recovered rhythmicity and increased lifespan

Conclusion: SCN transplants improve rhythms and produce an increase in longevity in hamsters

Question 8

Pressure overload hypertrophy in mice (Had heterozygous tau mutant that caused heart disease on 24 h LD cycles)
- What happened to the heart?
- When did the disease become present?
- What did the tau mutation result in?
- Conlusion

Answer 8

Heart:
- Had loss of fibrosis and flexibility
- Higher heart rate
- Larger and heavier heart
- Heart weight to body weight ratio was larger

Disease only appeared after 17 months

Tau mutation caused:
- Hypotension (reduced blood pressure)
- Cardiac hypertrophy, collagen deposition, and fibrosis
- Impaired cardiac hemodynamics
- Impaired cardiac function

Conclusion: Abnormal circadian entrainment is associated w/ extensive cardiovascular and renal disease

Question 9

Homozygous tau mutant hamster
- 24 hr and 20 hr going thru LD, DD, then LL
- Which one is more likely to get heart disease?
- What happened in LL?

Answer 9

20 hr cycle prevents heart disease
- Less freerunning during DD and LL

Less running compared to DD in LL

Question 10

Hamster heterozygous tau at 14:10 (24 hr) vs 12:10 (22 hr)
- Which one is more likely to get heart disease?

Answer 10

24 hr more likely to get heart disease

22 hr shows results closer to wild type

Question 11

True or False?
1) There are no diffs among genotypes at 4 months of age
2) Heterozygous tau mutants don’t develop significant symptoms of disease
3) Tau mutant heterozgotes develop disease symptoms when held on 22 hr LD cycles
4) Poor entrainment leads to disorganization

Answer 11

1) True
2) False - Homozgous
3) False - 24 hr
4) True

Question 12

Aortic banding

Answer 12

• Created pressure overload (back pressure in aorta)
• Stimulates a blockage

Question 13

(Organized circadian system important for preventing disease)
Aortic banding on animals running on 24 hr and 20 hr cycles
What happened to 20 hr with:
- Long dimension of heart was contracted
- Long dimension of heart was relaxed
- Fractional shortening (Movements to pump same amount of blood as usual)
- Change in blood pressure
- Fibrosis
- Wall thickness

Answer 13

Long dimensions: Much larger than 24 hrs

Fractional shortening: Had smaller movements

Blood pressure: Higher blood pressure and hypertension

Fibrosis: More fibrosis on 20 hr

Wall thickness: Thin wall, making it harder to sustain high pressure

Question 14

What is the most important zeitgeber?

Answer 14

The LD cycle

Question 15

Temporal program
List 4 potential zeitgebers

Answer 15

System that can be synced

Sleep-Wake (+ Body temp)
Rest-Work
Fast-Feed
Light-Dark

Question 16

2 ways energy is stored in body

What happens when you eat a lot late at night?

Answer 16

Lipage (long term)
Glycogen (Short term)

Since body is get optimized for next day, food eaten late will get piled up and not get used or stored as lipage

Question 17

Tricarboxylic cycle
What is necessary to move energy?

Answer 17

Cycle that provides energy for the cell

NAD, FAD, ATP

Question 18

___ converts NAD+ to ___

Clock and BMAL1 interact w/ ___ to produce metabolic cycle

Answer 18

SIRT1, nicotinamide

SIRT1

Question 19

Fragmented old hamsters vs healthy old hamsters
Paired w/ cage w/ running wheel
Do they prefer cage w/ running wheel?

(Shows importance of bio rhythms on cognitive processing)

Answer 19

Fragmented did not show preference (No learning of pairing)
Healthy preferred cage w/ running wheel

Question 20

Fragmented vs non-fragmented rats on water maze task
- One group of tats also phase shifted by 3 hrs everyday (3 h advance), causing fragmentation

(show show aging affects cognitive ability and rhythmicity)

Answer 20

Non-fragmented learned and retained memory for at least 10 days
Fragmented did not retain memory
Phase advance learned but didn’t retain memory next day (Possibly caused by not yet syncing to light cycle of next day)

Question 21

Circadian amplitudes in the liver and lung
- Looked at what sites in the genome are modified (which get turned off or on as you age)
- Findings (2)

Answer 21

Locations in DNA become rhythmically modified permanently the higher the circadian amplitude
Older animals have higher circadian amplitude and more cytosine rhythmically modified

Question 22

1) Intraspective competitive: Organisms w/ what kind of clock periods are favoured? This is important for what?

2) Interspecies competition: Organisms w/ what are favoured? This is important for what?

3) Longevity: ___ is associated w/ reduced longevity/fecundity?

4) Learning: ___ and/or ___ linked to reduced memory retention, sleep disturbances, and cog impairment

5) Mental health: ___ and ___ disturbance is linked to depression, schizophrenia, ADHD, etc.

6) Physical health: Rhythm/sleep disturbance is linked to ___, diabetes, ___, ___, etc. This overall leads to ___

Answer 22

1) Clock periods matching period of the enviro; Important for health, survival

2) Functional clocks; Competition, growth, survival

3) Rhythm disorganization

4) Disturbed rhythms; Circadian misalignment (e.g. chronic jet lag)

5) Rhythm; Sleep

6) Obesity; Metabolic syndrome; Heart disease; Reduced lifespan

Question 23

All cryptochromes (CRY) are sensitive to what?
What kind of CRY is most diff?
What does the C terminus do?
What does the flavin dinucleotide molecule do?

Answer 23

Light
Mammal CRY (uses melanopsin to signal)
Allows interaction w/ other proteins (like PER)
Associates w/ CRY to produce changes in CRY, creating its activity to interact w/ circadian system

Question 24

Drosphila and human cryptochromes (CRY) are most sensitive to what wavelength of light

Answer 24

440 nm

Question 25

Why do we not pay attention to chronobiology?
What does lack of attention cause?

Answer 25

Because we think it’s reasonable
Causes reduction in performance

Question 26

What 2 systems cause memory of past images?
What causes sense of time?

Answer 26

Ascending arousal systems (involved in getting us to places)
Dopamine system, which feeds back into basal ganglia (start of arousal system)

Sense of time created from images that are gradually changing