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Chronoengineering
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Exam of 27 pages for the course Body systems at Body systems (Chronoengineering)
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ChronoengineeringA clinician researcher studying a new treatment for pain relief in arthritis patients. Two
sets of volunteers are randomly assigned to treatment and non-treatment groups. The
treatment group is given a small white pill containing the new pharmaceutical agent at
10 am every day for a week. How should the non-treatment group be treated and why. -
ANS-They should serve as a negative control (a group from which no response is
expected); the non-treatment group should be given an identical pill without the
pharmaceutical agent at 10 am every day for a week as well. This is to control the
placebo effect - when people believe that they are getting an effective treatment, even
when they are not, they often report improvement in the condition being treated. The
negative control in this instance is to determine if the new drug is effective over and
beyond any such placebo effect.
A constant level of stimulation provided to the endocrine model described in class (and
considering the example of real data involving glucose and insulin) resulted in: -
ANS-continuous oscillations as long as the stimulus was applied
It was an interesting observation using the model that a continuous moderate level of
stimulation generated an oscillatory output. Such results appear to be mimicked by
actual data from living organisms, such as enteral feeding resulting in oscillatory
glucose and insulin levels.
A new chemical toxin is uncovered which prevents the CLOCK/BMAL1 heterodimer
from interacting with any genes outside of version of PER, CRY, and Rev-erb alpha
(second feedback loop). What would be the results in terms of cellular and organismal
physiology? - ANS-CLOCK/BMAL1 is a positive transcription factor for multiple clock
controlled genes which couple the molecular circadian clock to cellular metabolism and
processes which, in turn, link the clock to the output rhythms in physiology. Loss of the
ability of CLOCK/BMAL 1 to control those genes would eliminate the coupling
mechanism between the circadian clock and the rest of the body, generating a loss of
circadian rhythms.
A new heart medication has a maximum biological half-life of five hours - in other words,
the effectiveness of the medication drops by 50% within five hours and by 75% within
10 hours. Knowing this, when would you suggest patients take this medication? -
ANS-early morning
,Given the date indicating the maximum risk for heart attack being in the morning around
9 AM to 10 AM, taking the medication in the early morning would ensure maximum
availability of drug at the time when the patient is most susceptible to cardiovascular
issues.
A new mutation is discovered in doubletime (DBT) which increases the rate of
phosphorylation of the PER protein but has no effect on the ability of the protein to form
a dimer with TIM or any other activities of the PER protein. What kind of effect on the
Drosophila biological clock might you expect this mutation to have? - ANS-parametric
effect
In order for PER to form a timer with TIM, the amount of PER translated from mRNA for
PER must reach a certain concentration. If this new doubletime mutation
phosphorylates PER more efficiently or effectively than the original doubletime protein, it
is likely to take longer time for sufficient concentrations of PER to build up in the
cytoplasm. This would mean that the section of the biological rhythm which occurs
during the PER buildup will be longer than it would be in a normal Drosophila. Under
those circumstances, the angular velocity of the clock would be slower during that
section of the rhythm and this would generate a parametric effect.
A new species is discovered in the Southern hemisphere in Chile with circadian activity
rhythms. When placed in constant conditions and subjected to different light intensities,
the period of the activity rhythm lengthens when the light intensity is reduced and
shortens when the light intensity increases. Based upon this information, you expect the
peak of activity to be ___________________ in the summer relative to the winter
months. - ANS-phase advanced
This a T/tau ratio question: when the ratio decreases (T is shorter or tau is longer), there
are phase delays in entrained rhythms while when the ratio increases (T is longer or tau
is shorter), there are phase advances in entrained rhythms. In this case, increasing light
intensity leads to shorter period in the circadian clock (tau) and thus phase advances.
Summer is a time of increased light intensity and therefore the new species should
display a phase advance in activity rhythms compared to the winter.
A new species of nocturnal mammal is discovered in New Guinea. When examining the
animal in your laboratory, you discover that the animal only eats in darkness during a
LD 12/12 cycle when supplied constant access to food. You leave the food container
half full and leave for the weekend, confident that there is enough food based upon
observed eating habits. However, when you return on Monday, you find the animal is
, active and trying to get more food from the empty food containing during the light phase
of the LD cycle. From this, you conclude: - ANS-feeding is controlled by an interval timer
The observation that the animal only eats normally during the dark phase of the LD
cycle indicates that there is a rhythm to feeding. The observation that the animal was
eating during the light phase after the weekend indicates that the feeding rhythm is not
simply a response to a light and dark. The same observation suggests that feedings
cannot be simply controlled by an oscillator because the animal is active in the light
phase of the cycle. Therefore, the most likely conclusion is that feeding is controlled by
an interval timer.
A new species of rodent is found in the Siberian wilderness which displays seasonal
rhythms synchronized by changes in the photoperiod. Scientists wish to ascertain the
effect of changing the amplitude of this Zeitgeber. To do so they should: - ANS-change
the difference in lighting during the duration between the longest and shortest
photoperiod.
The difference that is being measured annual clock in synchronizing to photoperiodic
changes is the difference in the duration of light within the different photoperiods, with
winter having a very short photoperiod and summer a very long one. Changing the light
intensity uniformly across all photoperiods or making night uniformly lit with red light
across all photo periods would not change the amplitude. The only way to
experimentally change the amplitude would be to change the amount of difference
between the longest and shortest photoperiods.
A Nobel prize winning researcher claims to have observed cold fusion - a fusion
reaction which worked at room temperature. No other information is provided. The
researcher's claim would be considered as ________________ evidence. -
ANS-anecdotal
The fact that the claimant is a Nobel prize winner is not relevant to the level of evidence
being provided. Since no data other than a personal claim is provided, the evidence
would have to be classified as anecdotal.
A recent paper was published on a 7-day pattern in infection and deaths caused by the
SARS-CoV-2 virus (causing the COVID-19 pandemic). The paper was based upon data
collected by the Centers for Disease Control (CDC) in Atlanta, GA. This type of study is
________________. - ANS-observational
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