MINI MED SCHOOL QUESTIONS &
ANSWERS
Session 1: Anatomy and Physiology
Q: How do your ears adapt to pressure changes, like
when diving? What happens when you purposely pop your ears, i.e., yawning?
A: It’s all about the
Eustachian tubes, that connect the back of the throat with the middle ear. When
pressure changes in the mouth (as it will when environmental pressure changes),
that should be communicated to the inner ear. Usually there is a bit of saliva
in the passage, and when it “gives” you hear a pop. If there is inflammation,
it may be too narrow to give easily, and the pressure difference across the
eardrum makes it bulge in or out, which can be painful. Yawning pulls on the
muscles around the Eustachian tube, opening it.
Q: Even Lance couldn’t expend 3500 kCal in 2 hours.
A: Right. That should have
been 3 hours.
Q: Why cannot some bodies digest simple sugars like
sucrose?
A: Sucrose is a
disaccharide, composed of glucose and fructose. You need an enzyme to break it
down. Disaccharide Intolerance Type I (Mendelian Inheritance in Man database:
*222900) is a rare inborn error of
metabolism resulting from mutation in sucrase-isomaltase (Enzyme Catalog
3.2.1.48). Usually, infants with SI deficiency come to attention because of chronic
diarrhea and nutritional evidence of malabsorption.
Q: How do macrophages dispose of the garbage they
collect?
A: They are very efficient
digesters and have lots of the appropriate enzymes. What they can’t digest they
either secrete to be disposed of by kidneys or liver. Or compact into little
undigested balls within them.
Q: I’d like all the slides—can we get them?
A: Unfortunately not, as
most of them are subject to copyright. We can “fair use” them in the lectures but
are not licensed to distribute them. To get permission would be very expensive.
Q: What is a “photographic memory”?
A: No one is quite sure..
The greatest book on the subject is “The Mind of a Mnemonist: A Little Book
About a Vast Memory” by Aleksandr
Luria; it is available from Amazon or the Tattered Cover and is a wonderful
read for anyone.
Q: What is a heart
murmur?
A:
A murmur is caused by turbulence in the blood flow through the heart or the
great vessels near it. They mean the valves may have some roughness or not
close fully. There are “regurgitation” murmurs, where the valve allows some
backflow; and “ejection” murmurs where the valve is rough and blood rumbles as
it passes through. Many murmurs are “benign” in that there is a sound, but it isn’t
associated with serious damage or risk.
Q: Do you think too much
phosphate in cells leads to the pain of fibromyalgia?
A:
I (JJC) don’t. I think the best evidence for fibromyalgia is that it is the
complex result of not enough sleep leading to fatigue leading to decreased
exercise leading to unbalanced muscle pulls leading to anxiety leading to
depression leading to not enough sleep. You can enter this vicious circle
anywhere, and not all parts need to be present. Notably, in an experiment,
healthy young males were waken up each night as soon as they reached REM
(dreaming) sleep. After a week all experienced symptoms characteristic of
fibromyalgia.
Q: How does
hypno-anaesthesia work? How does meditation and guided imagery ease dis-ease?
A:
We don’t know. But the mind has very strong powers over the body. People with
positive TB skin tests can be hypnotized and told they are negative; when
tested, they are. That’s pretty impressive. But we don’t know the exact
mechanism in the brain. We don’t even know how the placebo effect works; but
the same parts of the brain “light up” with placebo as do with the real drug.
More research needed here.
Q: Diabetes = Insulin
resistance?
A:
Sometimes, especially in Type II (adult) diabetes. In Type I, there simply isn’t
enough insulin as the cells making it are reduced, probably by an autoimmune
process.
Q: How do I treat severe
reactive hypoglycemia?
A:
Talk to your doctor. If you really have it, don’t fool around with
self-medication.
Q: Comment, please on:
“Skin, your largest organ, which is replaced once a week.”
A:
Apparently if you carefully peel all the skin off someone, it would weigh more
than his liver (I assume this information comes from Dr. Hannibal Lechter, I
can’t find it in the regular literature). At the base of the skin are basal
cells, the skin stem cells. When one divides, on daughter remains a basal cell,
and the other starts differentiating into a squamous cell—flat, tough,
waterproof. It is gradually pushed up; as it nears the surface it dies and is
sloughed off. That process takes about a week.
Q: What is
immuno-anesthesia? How does it work
physiologically?
A: I’ve heard a lot of things about immunology, but
not this one. Can whoever asked it elaborate?
Q: Recently I read a story where this man lost all
but 3 feet of his small intestine, and I know it is near impossible to
transplant small intestine, but if that is to happen what food should one eat
to receive full nutrients?
A: I can’t answer
specifically but this does sometimes happen, and that’s the sort of thing
research nutritionists study. My guess is they monitor the patient carefully
and when they see a nutritional deficiency developing, they add a supplement,
by mouth or injection as necessary.
Session 2: Cell Biology
Q: Is there
any thinking that if malaria were eradicated that sickle cell anemia would also
die out?
A: That's a good
question. Presumably, if the selective
advantage conferred by the sickle cell trait (malaria resistance) disappeared,
then the selective disadvantage conferred because of the disease would
dominate, and the trait would tend to vanish from the population.
Q: If a
person is low on calcium or potassium and body limbs can't move or bend, is
this because the ions aren't sending electrical impulses?
A: Imbalances in calcium and
potassium affect the ability of nerve cells to transmit electrical impulses,
especially those that control muscle activity.
Low calcium (a condition called hypocalcemia) tends to actually INCREASE
the activity of nerves and muscles, giving rise to tingling sensations and
spontaneous writhing motions of the limbs.
Low potassium makes it harder for nerves cells to fire.
Session 3: Microbiology/Virology
Q: Is it true that if you have been exposed to West
Nile you will not get it again?
A: If you were infected once
(proven by antibody test in your blood), then you will not get it again.
However, even in areas where the virus has been circulating heavily(i.e.
Colorado in 2003 had the highest number of cases in the country), only about
1-3% of the population are actually infected (so that leaves about 97-99%
of the population that are still susceptible, even after a year with
lots of infections).
Q: Can you give me some basic information about Ebola?
Ebola Virus is an
RNA virus which causes severe, often-fatal disease in humans and
nonhuman primates (monkeys, gorillas, and chimpanzees) that has appeared
sporadically (mostly in Africa) since its initial recognition in
1976. Illness is characterized by fever, headache, joint and muscle aches,
sore throat, and weakness, followed by diarrhea, vomiting, and stomach pain. A
rash, red eyes, and internal and external bleeding is seen in many
patients. there is no effective treatment, and it is still a mystery as
to what the natural reservoir of Ebola virus is, why it
sporadically breaks out and then goes back into hiding, and how the virus
is spread Here is a great reference from the CDC website for
more reading: http://www.cdc.gov/ncidod/dvrd/spb/mnpages/dispages/ebola.htm
Q: Why does there seem to be more flu virus pandemics coming from Asia?
Most likely because the
population density is much higher in Asia in other parts of the world,
and it is much more common for humans to live in very close proximity to
poultry and/or pigs, providing a great chance for recombination of avian, swine
and human influenza strains (thus setting up the perfect condition for
a "shift", leading to a pandemic).
Q: Are prions the next evolutionary stage of viruses?
A: Probably not, but we really
have a lot more to learn about prions before that could be stated with
certainty (they were really just discovered and accepted as being a true entity
in the last 10-15 years). Since prions are actually SIMPLER than viruses,
consisting of only a misshapen protein, not even any nucleic acid, if you
believe in evolution, prions would likely be even EARLIER in evolution than a
virus - but that is just a guess. They may be completely unrelated to one
another or evolved simultaneously.
Q: What are common "triggers" which prompt latent or chronic viral
infections to begin active production and disease activity?
A: Usually it is something
which decreases the effectiveness of the infected person's immune system (i.e.
cancer, immunosuppressive medications such as chemotherapy or steroids).
However, for something as simple as a Herpes Simplex recurrent cold sore
on you lip, it can be something as simple as stress, cold weather,
sunlight....But HOW the virus actually figures out how to start revving up
again and DOES it, is a huge area of active research.
Q: Since viruses are not alive and have no
metabolism, why is it their
spread is temperature dependent? (i.e. - they won't grow if it is too
warm)
A: Temperature affects how
well viruses are internalized by the cell that they are trying to infect and
temperature also affects the efficiency with which the host cell
transcriptional and translational machinery works (which the virus relies
upon to propagate itself). Some viruses have adapted to grow in very warm
environments, and some viruses have adapted to grow in colder
environments (temperature sensitive mutants).
Q: If you were vaccinated against smallpox in the 70s are you still
immune?
A: Past experience indicates
that the first dose of the vaccine offers protection from smallpox for 3 to 5
years, with decreasing immunity thereafter. If a person is vaccinated again
later, immunity lasts longer. Vaccination within 3 days of exposure will
completely prevent or significantly modify smallpox in the vast majority of
persons. Vaccination 4 to 7 days after exposure likely offers some protection
from disease or may modify the severity of disease. Here is a great link
to the CDC website on smallpox:nnnnhttp://www.bt.cdc.gov/agent/smallpox/index.asp
Q: Is leprosy a viral disease?
A: No, it is a
mycobacteria: Mycobacterium Leprae. Does it still
exist? It does still exist. In 2002, the number of new cases detected
worldwide was 763,917. In 2002, 96 cases occurring in the United States were
reported to CDC. In 2002, WHO listed Brazil, Madagascar, Mozambique, Tanzania,
and Nepal as having 90% of cases. Here is a great link to the CDC
website http://www.cdc.gov/ncidod/dbmd/diseaseinfo/hansens_t.htm
Q: Can you speak a little about prions? How do they spread? Do they have
a
dormancy?
A: Prions are recently
described infectious pathogens consisting only of protein, without
any nucleic acid at all, that cause a group of invariably fatal
neurodegenerative diseases. The normally shaped prion protein is present
in normal mammalian cells, but when the normal prion protein is converted to
the abnormal shape, there are big changes in the chemical properties of the
protein which lead to disease. They "spread" by an abnormally
shaped prion coming into contact with a normally shaped prion protein, which
leads to a conversion to the abnormally shaped form. (conformational
change). So for instance, if a human (with normal prion proteins)
eats a cow with mad cow disease (containing abnormal shaped prion proteins),
there is the potential for one of those abnormal shaped cow prion proteins to
convert the normal shaped human proteins into an abnormal one, and
then the abnormally shaped human proteins can contact more and
more previously normal proteins within that person's brain, over and over
again over a long period of time (for instance, a decade), with the
potential (not ALWAYS) to cause neurodegenerative disease. A couple
of great references, written by Dr. Stanley Prusiner (who is the discoverer of
prions and won the Nobel Prize for doing so) can be found in Scientific
American, 1995 January ; Volume 272, Number 1: Pagers 48-51 and 54-7
and also in Proceedings of the National Academy of Sconces, USA, 1998,
November, volume 95, pages 13363-83 (which is an abbreviated version of his
Nobel Prize acceptance lecture).
Q: Why is the mosquito still around? Do these viruses not affect
mosquitoes?
A: Mosquitoes are vectors
(transmitters) of many viral diseases because they are not affected by the
virus - just us unlucky humans who happen to get bitten.
Q: In one of my Popular Science magazines they had an article about the
study of changing goat's milk to a substance like spider silk. How does
that work and is it basically like a virus in cell change?
A: This is not an infectious
question or related to viruses at all, but this was reported in January 2002 in
Science magazine: A team of scientists took the genes responsible for
creating spider silk and transferred them into the cells of mammals, such
as goats. Using those genes, the re-engineered goats were then able to produce
in their milk the same protein that makes up spider's silk. The scientists
then isolated those proteins from the goats' milk, they were then able to
"spin" a thread remarkably similar to natural spider silk.
Q: Please explain how Hep C Causes cancer, and how Epstein Barr causes
Burkitt's Lymphoma.
A: It is very complicated,
but basically the viruses set up a chronic infection in our cells at a low
level and have the ability to send signals to the infected cell (either
removal of important signals which tell the cell to stop growing and rest, or
addition/stimulation of signals which tell the cell to divide), leading to a
tip in the balance toward uncontrolled growth, or cancer.
Q: What is homology?
A: Homology of a
gene refers to how similar the genetic code or protein amino acid
sequence is between two differ rent things you are comparing. For example
if you have two different viral strains and you look at the genetic code for
each of them, nucleic acid, by nucleic acid, you can determine what the
differences are and the calculate the percent homology (or similarity) between
those two strains. When things are VERY homologous, it means they are
probably derived evolutionarily very close to each other, whereas if they are
NOT very homologous, they are probably not very closely evolutionarily
related.
Q: It is my understanding that we cannot cure/eradicate HIV because it
mutates/evolves so quickly with RNA transcription errors. Is it possible
to
make an antivirus that mutates at the same frequency or rate as the mutating
HIV virus?
A: Not yet, but I assure
you, scientists are trying all sorts of things to outsmart this virus, to no
avail yet. It sounds like a great idea to me!
Q: Are there studies that show how often people get sick due to
immunization?
A: There are many many
studies in both animals and humans before a vaccine is ever released
and then after a vaccine is released. The most powerful data after a
vaccine is released comes from the Vaccine Adverse Event
Reporting System. . A great reference that will link you
to all kinds of information that you may be interested in with regard to
adverse events from vaccines is on the CDC
website: http://www.cdc.gov/node.do/id/0900f3ec8000ea1e