Chronobiology Dr storch Flashcards
animals located where in the world have the strongest circannual clock? why?
close to equator because not much changes in photoperiod
why do species living farther from the equator have a weak circannual clock?
because the photoperiod changes a lot and they can rely on that to know the time of the year
what does it mean that the circannual clock exhibits limit of entrainment?
it will resist the decrease in photoperiod if the change is too big
why do hamsters and sheep have opposit testis size in the seasons?
because they have very different gestation time
in what season do hamsters and sheeps have high prolactin?
summer when the days are long
what regulates animal’s reproductive status?
the sensing of day length via pineal gland melatonin production
what brain region is thought to be the decoder of photoperiodic information?
pars tuberalis PT in which melatonin receptor 1 are expressed
what hormones are very differently expressed in the PT in summer vs winter?
TSH, DIO2, KISS1
what hormone is inversely expressed in PT in hamster vs sheep?
KISS1
do receptors expression change in PT in summer vs winter?
no; TSH-R expression doesn’t change, but TSH expression does
what happens to TSH levels in PT of mice? why is it unexpected?
higher TSH levels in the summer, even if mice reproductive activity is not season-dependent
what circadian genes were found to regulate TSH transcriptional activity?
Eya3 MAINLY.
also Tef and Six1
what is Eya3 transcriptionally controlled by?
E boxes and D elements
what are E and D boxes?
promoter elements that are specifically engaged by the circadian system
when does Eya3 peak?
always 12 hours after lights off, unless it is still dark out.
this is how reproduction period is regulated.
what happens to Eya3 levels after day-long melatonin implant? what does it show?
Eya3 levels decrease, showing that melatonin causes depression of Eya3 expression
what do we hypothesize to be the regulator of Eya3 promoter?
cAMP
where must the season-specific switch be encoded?
downstream of DIO2 (translates T3 and T4)
how was it proved that TSH and DIO2 levels are under circannual clock?
subjects still had higher TSH and DIO2 levels during the summer, even when kept under constant L:D cycle for the whole year (no photoperiodic changes)
what is Cre/crept?
crept gets activated by light information in retina and binds per promoter to drive transcription;
independent of E/D boxes
where is the circannual clock?
we don’t know
how long do we think that babies’ rhythm is?
4 hours (ultradian cycle)
why is it good that Svalbard reindeer loose their circadian rhythm when it is only light / dark?
because they probably had all different lengths of circadian rhythm so they would become out of phase with the other animals; have their own schedule
why do some hamsters develop a 12h circadian cycle when under constant light conditions?
each SCN hemisphere goes in anti-phase
