Circadian Biology Background quantitative analysis and present research

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Circadian Biology Background, quantitative analysis, and present research

Circadian Biology Background, quantitative analysis, and present research

Circadian rhythms “circa” = approximately n “dies” = day n n Rhythms with an

Circadian rhythms “circa” = approximately n “dies” = day n n Rhythms with an approximately 24 -hr cycle length that are endogenous in origin

First demonstartion Jean Jacques d’Ortous de Mairan n 1729 n Leaf movements of a

First demonstartion Jean Jacques d’Ortous de Mairan n 1729 n Leaf movements of a heliotrope plant n Persistence of circadian rhythms in absence of external cues n

Zeitgeber = “time giver” n Signals from the environment that keep non-24 hour clocks

Zeitgeber = “time giver” n Signals from the environment that keep non-24 hour clocks in synch with the 24 hour day

Retinal hypothalamic tract Direct input from the retinal photoreceptors to the hypothalamus n Involved

Retinal hypothalamic tract Direct input from the retinal photoreceptors to the hypothalamus n Involved in circadian system n

Where is this clock? Optic chiasm n SCN n Anterior hypothalamus n Above optic

Where is this clock? Optic chiasm n SCN n Anterior hypothalamus n Above optic chiasm

Activity records

Activity records

Circadian System Light/dark inputs output system photoreceptor rhythm pacemaker

Circadian System Light/dark inputs output system photoreceptor rhythm pacemaker

Entrainment

Entrainment

Phase response curves

Phase response curves

Different quantitative analyses

Different quantitative analyses

Circadian pacemakers are limit cycle oscillators n Oscillators have a standard waveform that they

Circadian pacemakers are limit cycle oscillators n Oscillators have a standard waveform that they return to after a perturbation n Limit cycle models give better appreciation for reactions of circadian pacemakers to stimuli

Limit cycle

Limit cycle

Simple oscillator: 2 state variables n Oscillating components are called “state variables” n Graphically

Simple oscillator: 2 state variables n Oscillating components are called “state variables” n Graphically portray changes in state variable in “phase space” – an abstract space whose coordinates describe the state of the system

Example: frictionless pendulum 2 state variables: 1. Position [x(t)] 2. Rate of change ofposition

Example: frictionless pendulum 2 state variables: 1. Position [x(t)] 2. Rate of change ofposition [x’(t)] Differs from limit cycle oscillators in 2 ways: 1. Limit cycle osc. do not damp 2. State variables return to same trajectory

Fourier analysis of circadian amplitude Wild-type Clock/+ Frequency (cycles/day) Clock/Clock

Fourier analysis of circadian amplitude Wild-type Clock/+ Frequency (cycles/day) Clock/Clock

Principle components analysis

Principle components analysis

Cluster analysis

Cluster analysis

3 -Dimensional Visualization

3 -Dimensional Visualization

Davis lab research (Fred Davis Ph. D)

Davis lab research (Fred Davis Ph. D)

TGF-alpha…the story begins n SCN transplant studies in lesioned animals n Encapsulated graph n

TGF-alpha…the story begins n SCN transplant studies in lesioned animals n Encapsulated graph n No axonal projections n Allowed for diffusion of secreted factors n Locomotor activity rhythms still persist n “locomotor activating/inhibiting factors”

…. and continues…. n n n A screen was preformed, using previously documented SCN

…. and continues…. n n n A screen was preformed, using previously documented SCN factors Constant infusion of each factor took place over a period of 2 -3 weeks TGF-alpha acted as expected for a locomotor inhibitory factor Completely blocked running wheel activity for the duration of the infusion Activity came back with its expected phase and period

Activity records for hamsters infused with different secretory factors: reversible inhibition of locomotor activity

Activity records for hamsters infused with different secretory factors: reversible inhibition of locomotor activity by TGF

Vehicle TGF-a

Vehicle TGF-a

a. CSF TGF-alpha The data: in constant darkness, measured EEG, EMG, body movement, and

a. CSF TGF-alpha The data: in constant darkness, measured EEG, EMG, body movement, and body temperature

Behavior Analysis Vehicle TGF-a Pre - Rx- Post - CT 6. 5 -8. 5

Behavior Analysis Vehicle TGF-a Pre - Rx- Post - CT 6. 5 -8. 5 CT 11 -12

TGF-a Effects on Feeding CSF (n=5) TGF a (n=4) Effects of TGF-a on Feeding

TGF-a Effects on Feeding CSF (n=5) TGF a (n=4) Effects of TGF-a on Feeding Average Food Consumption (grams) Average Change in Body Weight (grams) Effects of TGF-a on Body Weight CSF (n=5) TGF a (n=4) 100 20 10 0 -10 80 60 40 20 -20 Infusion Post-Infusion 7 Day Intervals

Acute injections What effect would an acute injection have versus slow infusion? n How

Acute injections What effect would an acute injection have versus slow infusion? n How do we test this? n Any results yet? n

Testing methods n Cannulation into the third ventricle: steriotaxic surgery n Obtain good activity

Testing methods n Cannulation into the third ventricle: steriotaxic surgery n Obtain good activity records n Injections of TGF-alpha at time of activity onset n Control injections of vehicle/CSF n Obtain activity results

Channel 8: hamster #2 CSF (2/3) TGF (2/7)

Channel 8: hamster #2 CSF (2/3) TGF (2/7)

Channel 11: hamster #1 CSF (2/3) TGF (2/7)

Channel 11: hamster #1 CSF (2/3) TGF (2/7)

In the process….

In the process….

Recent Data CSF TGF-alpha

Recent Data CSF TGF-alpha

In summary… n The study of circadian rhythms is a very broad and open

In summary… n The study of circadian rhythms is a very broad and open area n It is a multi-disciplinary science, can study anything from whole animal behavior to in situ hybridization. n As shown, there are numerous opportunities for quantitative analysis

Sources n Czeisler, C. A. (figures) n Davis, F. (PI) n Johnson, C. (figures)

Sources n Czeisler, C. A. (figures) n Davis, F. (PI) n Johnson, C. (figures) n Kramer, A. (TGF-alpha, and figures) n Low-Zeddies, S. (statistic figures) n Snodgrass-Belt, P. (unpublished data)