Jackofknives
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In the determination of serum insulin levels by radioimmunoassay, which one of the following is NOT needed?
A) Isotope-labeled insulin
B) Anti-insulin antibody made in goats
C) Anti-goat gamma globulin made in rabbits
D) Isotope-labeled anti-insulin antibody made in goats
Explain your answer for Pete's sake!
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| new_n_lost
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| silver
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C
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| new_n_lost
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silver wrote:
C
For Pete's Sake Explain ???  
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| mytime
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For Pete's Sake Explain ???
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| me007
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i would say A.
bcs you going to find out serum insulin level
based on antigen- antibody complex formation,
so radiolabeled antibody will show this
and anti-goat rabbit Ig - to precipitate those complexes
and that serum insulin we a re interested in - we can't put label directly on them
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| po
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 me007;expln too.
who is pete?
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| keepgoing
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good discussion on pete's sake....lol
yes agree with me007's explanation i also go for a...b/c dont think target is directly labeled but in some cases it can take up but less likely so might be D is the answer
b/c in RIA--
its either ag+flurocent conjugated(ab),or
ag+ab=an-ab +flusocent conjuagated antiglobulin serum
d also seem swrong b/c we dont make antibody serum istope labbeled inside the goat but in lab
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| Jackofknives
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Radioimmunoassay (RIA) is a scientific method used to test antigens (for example, hormone levels in the blood) without the need to use a bioassay. It involves mixing known quantities of radioactive antigen (JOK: isotope labeled known quantity of insulin) (frequently labeled with gamma-radioactive isotopes of iodine attached to tyrosine) with antibody to that antigen, then adding unlabeled or "cold" antigen (JOK: that is the serum insulin we are going to quantify) and measuring the amount of labeled antigen displaced.
For the rest of the article see http://en.wikipedia.org/wiki/Radioimmunoassay.
This is how I understood it. So thats why A is needed.
The second AB is needed for precipitation and thus doesnt have to be radio labeled.
So D! God bless Pete!
Edited by Jackofknives on 06/27/07 - 04:05 AM
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| silver
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JOK,
once we have anti-insulin Ab made in goats, then why do we need the ones made in rabbits?
yeah you're right, choice A we definitely need, that was the first one i ruled out.
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| unique1
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Why not C ?
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| GoodGirl
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 This is surely above my knowledge.
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| unique1
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Eureka !!!!! I got it.
RIA ( RadioImmunoAssay ) is used to detect the presence of hormones,drugs,antibiotics, serum proteins, infectious disease agents and tumor markers . Following are the steps to perform this test :
1 : Microtiter plates are coated with antigen to be tested ( In this question Insulin )
2 : Antibodies to this particular antigen are added next ( In this question Anti-insulin antibodies )
3 : Gammaglobulins against these antibodies are added ( In this question Anti-goat gammaglobulin )
So the thingy that is not needed is D .
Hope I got it right  .
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| silver
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can you cite your source unique1?
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| unique1
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Our good old Kaplan Immunology .
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| silver
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ok thanks!
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| sfk
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radiolabelled and unlabelled antibodies binding to the antigen (which is insulin in this case) the rabbit antibodies are not needed.
ans is c
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| usmletopper1
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1.we get the insulin ag from the patient ( it would not be isotope labelled)
2.to that we add anti insulin antibodies obtained from the goat
3.to that we add isotope labelled anti goat insulin ab,
i think ans would be both a and c
am i right
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| spinal shock
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its C
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| macintosh
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I beg to differ.
After reviewing the diagram under RIA topic in Kaplan Immunology, I am sure that "A" is the correct answer choice. This is because in RIA the antigen is used in an unlabelled form. As the antigen (in this case insulin) is already radiolabelled with a radioactive isotope it can not be used in the RIA test.
Furthermore I do not see any point in doing the RIA if the antigen is alredy radiolabelled.
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