POSSIBLE FUNCTIONS of the CIRCADIAN CLOCK
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Transcript of POSSIBLE FUNCTIONS of the CIRCADIAN CLOCK
POSSIBLE FUNCTIONS of the CIRCADIAN CLOCK
IS IT IMPORTANT AT ALL? YES!
POSSIBLE FUNCTIONS DAILY PROGRAMING of PHYSIOLOGY
PHOTOPERIODIC REPRODUCTION
ANIMAL MIGRATION
MCB 186 December 5, 2007
IS THE CIRCADIAN CLOCK IMPORTANT ?
DOES THE CLOCK CONFER SELECTIVE ADVANTAGE?
MAYBE NOT: NULL MUTANTS are VIABLE in ALL STUDIES
TWO KINDS of STUDIES
MEASURE LIFESPAN IN ANIMALS SUBJECTED TO NON-24 hr CYCLES
RESONANCE EXPERIMENTS IN CYANOBACTERIA USING PERIOD MUTANTS
SURVIVIAL CURVES for FLIES in LIGHT/DARK CYCLES with PERIODS of 20, 24 AND 28 HOURS
FIVE HOUR LD PHASE SHIFTS EACH CYCLE
CYANOBACTERIA MUTANTS V.S. WILD TYPE IN DIFFERENT LD CYCLES
C.H. Johnson lab
CYANOBACTERIA MUTANT Tau-28 V.S. WILD TYPE Tau-25
C.H.Johnson lab
Two independent experiments
SOME FUNCTIONS OF THE CIRCADIAN CLOCK
TIMED PHYSIOLOGY: SPECIFIC TIMES OF DAY/NIGHTSynthesis of specific proteins at specific times of day
Insect eclosion acrophase is at time of daily temperature minimum.
The internal bee clock; Visitations timed to time of flower openingsCyanobacteria, photosynthesis by day, nitrogen fixation by night.
PHOTOPERIODIC REPRODUCTION: MEASURE DURATION OF DAY AND NIGHT-Plants: seasonal flowering, spring, summer or fall.-Animal seasonal reproduction; hamster only once per year.
ANIMAL MIGRATION-Celestial navigation for migration (birds, butterflies, arthropods, fish, reptiles); knowledge of time of day required.
TIME of DAY PROGRAMS
• Different activities at different times of day involve different genes and proteins
• In circadian systems, different proteins are synthesized at different times of day
• Cyanobacteria carry out photosynthesis with oxygen production and nitrogen fixation at different times of day. Oxygen inhibits nitrogenase.
BEAN (top) and CANAVALIA CIRCADIAN LEAF MOVEMENTS
DROSOPHILA ENTRAINMENT TO FULL LD CYCLES PITTENDRIGH
ACROPHASE DEPENDS ON PHOTO-FRACTION
TEMPORAL SEPARATION OF CELL BIOCHEMICAL ACTIVITIES IN CYANOBACTERIA (OXYGEN, NITROGENASE ETC) MITSUI ET AL 1986
PATTERNS of CLOCK-CONTROLLED PROTEIN SYNTHESIS in Gony
Markovic et al., 1996J. Biol. Rhythms 11
p21 unknown p32 PCPp33 OEE1p45 GAPDHp55 Rubisco IIp75 Luciferin binding
protein
PHOTOPERIODISM
DISCOVERY: Garner & Allard, 1920
TOBACCO FLOWERING ONLY IN FALL WITH SHORT DAYS OTHER PLANTS SHOWN TO FLOWER WITH LONG DAYS. STILL OTHERS DAY LENGTH NEUTRAL
TERMINOLOGY CORRECTED: Hamner & Bonner, 1938
LENGTH OF THE NIGHT, NOT THE DAY, IS CRITICAL LIGHT INTERRUPTIONS OF NIGHT BLOCK RESPONSE, DARK INTERRUPTIONS OF DAY DO NOT BLOCK
INCORRECT TERMINOLOGY STILL IN USE:
DAY LENGTH AT DIFFERENT LATITUDES & SEASONS
HAMSTER TESTIS WEIGHT IN DIFFERENTFULL PHOTOPERIODS Elliott, 1976
PHOTOPERIODIC INDUCTION OF CYSTS IN GONYAULAX
SOY BEAN (SHORT DAY PLANT) 0.5 hr LIGHT INTERRUPTION of LONG DARK PERIOD WARING, 1954
H. NIGER (LONG-DAY PLANT) 2 hr LIGHT INTERRUPTION OF LONG DARK PERIOD
SOYBEAN (short day) FLOWERING IN DIFFERENT LD CYCLES
MODELS FOR PHOTOPERIODISM
HOUR GLASS: Substance X builds up during dark
Explains night interruption by brief light exposure
Does not explain oscillation of long dark periods.
ENDOGENOUS OSCILLATION
Explains circadian recurrence of susceptibility to brief light exposure during prolonged DD
External Coincidence model:
Night interruption causes delays & advances
EXTERNAL COINCIDENCE: POSTULATED PHOTOPERIODIC EFFECTS ON AN ORGANISM WITH A CIRCADIAN tau OF 24.5 hr
ENTRAINED T of HAMSTER ACTIVITY RHYTHM DEPENDS on PERIOD of SINGLE PULSE T CYCLE and PULSE is
POSITIONED DIFFERENTLY Elliott 1976
Tau for hamster is very close to 24 hBoth T cycles cause phase shifts, + & -
ADVANCES DELAYS
HAMSTER TESTICULAR RESPONSES to T CYCLE PERIOD LENGTH
DROSOPHILA ENTRAINMENT TO FULL LD CYCLES PITTENDRIGH
PHASE ANGLES WITH DIFFERENT TWO PULSE SKELETONS Pittendrigh
BISTABILITY IN HAMSTER ENTRAINMENT SKELETON PHOTOPERIOD 13.5:0.25:10:0.25 hrs
ANIMAL C15 ACTIVE in SHORT NIGHT TESTES MAINTAINED; ANIMAL C16 ACTIVE in LONG NIGHT; TESTES REGRESSED
SKELETON PHOTOPERIOD PHASING GIVES DIFFERENT RESPONSES
ARE HUMANS AFFECTED by PHOTOPERIOD?
It appears so!
• ANNUAL CYCLES
• DAILY ENTRAINMENT PHASE
1824 1947
HUMAN ANNUAL CONCEPTION RHYTHMS
SOCIAL INFLUENCES on the ANNUAL CONCEPTION RHYTHM
SOCIAL INFLUENCES on the ANNUAL CONCEPTION RHYTHM
Effect of Residence Locations on Sleep Acrophase (n=21,600)
Germany
Roenneberg, 2006
DEPENDENCE of TIME of MID-SLEEP on LONGITUDE 8.5O=34min and RELATION to POPULATION DENSITY
Rural and towns less than 300,000 persons
300,000 - 500,000
> 500,000
Roenneberg, 2006
DAYLIGHT SAVING TIME RELATED to SLEEP PHASE and DURATION
CIRCANNUAL RHYTHMS IN SQUIRRELS & GONYAULAX
FUNCTIONS of the CIRCADIAN CLOCK
CELESTIAL NAVIGATION
-Animal migration (birds, butterflies, arthropods, fish, reptiles); knowledge of time of day required.
DIRECTION OF STARLING MIGRATORY ACTIVITYKramer,1950 a) clear sky b)overcast c),d) direction of incident light deflected by mirrors
DIRECTION OF DEPARTURE IN PIGEONS ALTERED AFTER EXPOSURE TO LD CYCLE ALTERED BY 6 hr Schmidt-Koenig,1961
SHIFTING THE DIRECTIONAL RESPONSE OF PIGEONS
DELAYED SLEEP PHASE INSOMMNIA THERAPY
Deficiency in advance phase shifts
Treatment: Impose repeated delaysuntil patient is back in phase.