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  #1  
Old 04-02-2013
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Default NBME 7 question

A pharmacologist discovers a new fungal metabolite with unusual antimicrobial properties. It naturally concentrates in the endosomes, lysosomes, and phagolysosomes of cells and directly kills microorganisms (eg, Mycobacterium tuberculosis) that are normally resistant to degradation in the phagolysosomes. The metabolite has the undesirable effect of increasing the pH within phagolysosomes. Which of the following processes will be primarily affected?

A)Class I MHC molecule peptide loading

B)Class II MHC molecule peptide loading

C)Peptide binding to T-lymphocyte receptor αβ

D) Peptide binding to T-lymphocyte receptor γδ

What is the answer and why? FYI ppl reading this...I'm going to post like 30 questions online today These are the questions that I simply do not understand. I would really appreciate your help. I need a 15 point increase by the end of the month. Hopefully this helps everyone.
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  #2  
Old 04-02-2013
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Default The answer is B

MHC II
Expressed only on antigen-presenting cells (APCs).
Antigen is loaded following release of invariant chain in an acidified endosome
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  #3  
Old 04-02-2013
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Default Explanation please

A 7 yr old boy drinks cocoa and watches TV while petting his cat. He watches while his mother bakes fragrant cinnamon rolls while the stereo plays Mozart's string quartet in the background. Which of the following sensory modalities goes directly to the cortex without going into the thalamus.

1. Hearing
2 Taste
3. Touch
4. Vision
5. Smell
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  #4  
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During an experiment 500mg of both drug X and Y are simultaneously administered IV, the serum concentration of both drugs after bolus administration is 5 mg and 2.5mg respectively. Assuming no drug interactions. Which of the finding regarding the drug Y is compared with drug X?

A. decreased clearance
B. decreased half life
C. decreased volume of distribution
D. increased clearance
E. increased half life
F. increased volume of distribution

I googled and found out that the answer. BUT I don't understand it. Can someone please explain? Thanks
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  #5  
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Default It's b

increase in the pH interfere with the peptide protein (presented by the antigen presenting cells) binding to the MHC-II molecules which is expressed on the APCs
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25) a healthy 54 year old woman undergoes an exercise stress test. During the moderate phase of the exercise, her pulse is 140/min, respirations are 25/min, & bp is 130/90 mmHg. Which of the following is the relative proportion of coronary oxygen delivery during the rest & during the exercise times?

Rest moderate exercise
a) systolic > diastolic systolic > diastolic
b) systolic > diastolic systolic < dia
c) systolic < diastolic systolic > diastolic
d) sys < dia sys < dia
e) sys = dia sys > dia
f) sys = diastolic sys < dia

I thought that coronary arteries always fill during diastole...therefore oxygen delivery is highest during diastole. I'm obviously incorrect. Explanation please.
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  #7  
Old 04-02-2013
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Default Smell

Hearing-----> MGN (Medial geniculate nucleus) in the thalamus
Taste------> VPM (Ventral posteromedial n.)
Touch------> VPL (Ventral posterolateral n.)
Vision------> LGN (Lateral geniculate n.)
SMELL goes straight to the cortex without relaying in the thalamus
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  #8  
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Default

Quote:
Originally Posted by OMGStep View Post
During an experiment 500mg of both drug X and Y are simultaneously administered IV, the serum concentration of both drugs after bolus administration is 5 mg and 2.5mg respectively. Assuming no drug interactions. Which of the finding regarding the drug Y is compared with drug X?

A. decreased clearance
B. decreased half life
C. decreased volume of distribution
D. increased clearance
E. increased half life
F. increased volume of distribution

I googled and found out that the answer. BUT I don't understand it. Can someone please explain? Thanks
LD was 500mg
LD=CpxVd/F
F=1
Cp=LD/Vd

Larger volume of distribution contributed to decreased plasma concentration
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Everything is possible for him who believes (MARK 9:23)
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Default

Volume of distribution = loading dose/plasma concentration
Vd (drug x)= 500/5=100
Vd (drug Y)=500/2.5)=200
So there is an increase of the Vd of drug Y
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  #10  
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Default 25-d

DD
coronaries fill more during diastole regardless of resting or excercising muscle
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  #11  
Old 04-15-2014
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Default nbme 7

a 68 yr old woman with left homony hemianop for 2 wks, and to find the lesion on the c t...

its supposed to be on the right side, that i know. i put choice E, which seemed like the optic tract.
but it was wrong.

can anyone pls pls pls explain?????/
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