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  #1  
Old 02-20-2012
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Arrow NBME 1 Block 3 discussion

Question 4:

The answer is E. VIP is important for the relaxation of sphincters. In this case it is not present which is the defect in the Sphincter of Oddi. It cannot relax therefore causes obstruction of bile flow leading to biliary colic.


Question 48:

Is Plasmin considered an enzyme??? I was thinking it was just a regular protein.



Surprisingly this block was pretty straight forward without many twist and turns!!
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  #2  
Old 02-21-2012
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For Q 4

Now i am confused mate i marked it C Which is right according to key.But then yes VIP causes relaxation of sphincter.The rationale of marking it C was that may be during sphinterectomy it may had parasympathetic ganglia ( which is also a source of VIP)around the bladder causing Loss of PARASYMPATHETIC stimulation to the sphincters.

I am really confused lets post it on the forum.

Yes its an enzyme degrading the Fibrin hence used in fibrinous pericarditis.


Can you help me with Q 42 although i guessed it right but i am unable to figure out what the question exactly says.
Also what does slip-stranded DNA errors mean ?

Last edited by jinni; 02-21-2012 at 02:32 AM.
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Old 02-21-2012
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Quote:
Originally Posted by jinni View Post
For Q 4

Now i am confused mate i marked it C Which is right according to key.But then yes VIP causes relaxation of sphincter.The rationale of marking it C was that may be during sphinterectomy it may had parasympathetic ganglia ( which is also a source of VIP)around the bladder causing Loss of PARASYMPATHETIC stimulation to the sphincters.

I am really confused lets post it on the forum.
I'm pretty sure its E. See as answer C says, if it was a loss of enteric inhibitory motor innervation then there would be nothing obstructing the flow of bile. It would constantly keep moving, hence no colic. VIP is secreted by all sphincters after cholinergic stimulation to relax them. A decreased in VIP secretion is also the case for increased LES tone in achalasia.

Only way to fix it is to do surgery, take out the sphincter and get the bile flowing again.



Quote:
Originally Posted by jinni View Post
Can you help me with Q 42 although i guessed it right but i am unable to figure out what the question exactly says.
Also what does slip-stranded DNA errors mean ?
The right answer is D as in the key.

Basically they are just trying to see if you know the difference between Conjugation and Transduction (Bacterial genetics), but they ask it in a difficult way.

In Conjugation there is exchange of plasmids. Plasmids is the main mechanism of gaining drug tolerance as has happened here. Transposition is the way in which segments of DNA that can move can transfer themselves to plasmids and can bring along with themselves new chromosome from the bacterial DNA. The only way a plasmid can get bigger is if incorporates a Transposon. This will obviously change the function of the plasmid as it changes the genes it carries.

Once you know this then you can picutre it in your head. Plasmid transferred to a bacteria that has transposons. These transposons incorporate themselves into the plasmid, increasing its size and altering its function where it no longer passes along drug tolerance genes.


As for slip-stranded DNA Replication errors...I looked it up and it turned out to be something important. A process which occurs during DNA replication. It involves denaturation and displacement of the DNA strands, resulting in mispairing of the complementary bases. Slipped strand mispairing is one explanation for the origin and evolution of repetitive DNA sequences. The disease-associated expansion of (CTG)(CAG) repeats is likely to involve slipped-strand DNAs. This is the mechanism of action for diseases characterized by triplet repeat especially Myotonic dystrophy (CTG) and Huntington's (CAG).


I didn't know that, will be adding it to my notes. It doesn't apply to this question though.
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Old 02-21-2012
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For Q 4 yes got it dear thanks

For Q 42 awesome explanation...........
So much to learn so near the exam seems i will be learning even while i am doing the real exam....

Thanks
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Old 02-24-2012
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Default nbme 12 block 3 q 30

please somebody explain me the answer for q40 in block 3 of nbme 12
seq of human beta globin chain...where is the mutation?
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Old 06-04-2012
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Quote:
Originally Posted by haga View Post
I'm pretty sure its E.
I just want to further explain why E is the correct answer and no C....

"Innervation of the bile duct does not appear to be essential as sphincter function has been reported to be preserved following liver transplantation. Cholecystokinin and secretin appear to be most important in causing sphincter relaxation. Nonadrenergic, noncholinergic neurons which in part transmit vasoactive intestinal peptide (VIP) and nitric oxide also relax the sphincter."

JOP. J. Pancreas (Online) 2001; 2(6):382-400.
Sphincter of Oddi Dysfunction: Diagnosis and Treatment
Stuart Sherman, Glen A Lehman

https://docs.google.com/viewer?a=v&q...QtJ0vasQ&pli=1
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