Official Step 1 High Yield Concepts Thread

[Transposony]

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Let's discuss our doubts/offer clarifications about mechanisms/concepts for Step 1

ASK ANY QUESTIONS here.

To kick start the thread here is something I didn't know:

1. Penicillin-binding proteins (PBPs) are actually enzymes (transpeptidases & carboxypeptidases) which cross-link peptidoglycan. Penicillins binds to these enzymes and inactivating them thereby preventing cross-linkiing of peptidoglycan.

2. Periplasmic space (Gram -ve) contain proteins which functions in cellular processes (transport, degradation, and motility). One of the enzyme is β-lactamase which degrades penicillins before they get into the cell cytoplasm.
It is also the place where toxins harmful to bacteria e.g. antibiotics are processed, before being pumped out of cells by efflux transporters (mechanism of resistance).

There are three excellent threads which you may find useful:

List of Stereotypes

Complicated Concepts Thread

USMLE images

 

[dfib slim]

otherwise known as HNPCC!

Does coxiella require a vector for transmission to humans? If yes, what is the vector? If no, why not?

Nope. You just inhale that aborted animal fetus vapor. It makes a spore-like structure or something.

 

[seminoma]

How many days post-MI?

 

[Transposony]

How many days post-MI?

3 days--Lots of Neurophils.

 

[dfib slim]

Monoclonal antibody that "turns on" rather than "turns off" the immune system?

 

[Transposony]

Monoclonal antibody that "turns on" rather than "turns off" the immune system?

Multiple myeloma

 

[dfib slim]

Multiple myeloma

I was thinking of a certain pharmacological agent. Not in FA and don't know if HY but thought it was interesting as having a unique mechanism that activates the immune system.

 

[Transposony]

I was thinking of a certain pharmacological agent. Not in FA and don't know if HY but thought it was interesting as having a unique mechanism that activates the immune system.

No idea at all.

 

[dfib slim]

No idea at all.

Ipilimumab. It targets CTLA4 on the T cell allowing for increased proliferation of CTLs. Used for melanoma.

 

[seminoma]

Ipilimumab. It targets CTLA4 on the T cell allowing for increased proliferation of CTLs. Used for melanoma.

Nice. I was (wrongly) thinking abatacept or belatacept, which are both CTLA4s.. but they are Tcell inhibitors and aren't mabs like you asked for.

 

[Transposony]

Nice. I was (wrongly) thinking abatacept or belatacept, which are both CTLA4s.. but they are Tcell inhibitors and aren't mabs like you asked for.

So, basically abatacept/belatacept work like a condom i.e. the APCs and T cells can have sex but can't make babies.

 

[dfib slim]

So, basically abatacept/belatacept work like a condom i.e. the APCs and T cells can have sex but can't make babies.

And ipilimumab would be the sildenafil.

 

[Transposony]

What is the the purpose behind HIV viral genome being diploid ?

 

[Transposony]

In HIV which viral gene mutation slows down the progression of disease?

 

[Transposony]

Antibiotic which is also a 5-lipoxygenase inhibitor ?

 

[seminoma]

I was thinking of a certain pharmacological agent. Not in FA and don't know if HY but thought it was interesting as having a unique mechanism that activates the immune system.

Phloston has said that the mabs aren't super HY (except the obvious ones in FA), but my school really hammers them.. I guess they're becoming more popular clinically, but since USMLE questions are a few years behind that might be why they aren't tested often?

Antibiotic which is also a 5-lipoxygenase inhibitor ?

Minocycline. Btw, can anyone confirm or deny that zileuton is no longer available in the US? Our pharm teacher told us there are "currently no 5-lox inhibitors available in the US", but I didn't find anything online saying that zileuton had been completely discontinued.. I know one formulation of zileuton is gone, but according to wiki the other formulation is still available.

 

[seminoma]

Robertsonian translocation occurs in what chromosomes? (5 total)

 

[Mr. Mojo Risin]

@seminoma Maybe your pharm professor knows something the rest of us don't, but as far as I know, Zileuton immediate release was removed from the US market in 2008. Zileuton CR is still available.

http://www.ncbi.nlm.nih.gov/pubmedhealth/PMHT0012704/

 

[dfib slim]

Mechanism for megaloblastic anemia from phenytoin use?

 

[Mr. Mojo Risin]

Mechanism for megaloblastic anemia from phenytoin use?

Conjugase turns dietary polyglutamate form of folate into monoglutamate form. Phenytoin inhibits conjugase, thus causing folate deficiency.

 

[dfib slim]

Reason behind kidney stones with Crohn's disease?

 

[mcloaf]

Reason behind kidney stones with Crohn's disease?

Fat malabsorption leads to increased free oxalate which is taken up by the gut and leads to oxalate stones.

 

[Transposony]

Reason behind kidney stones with Crohn's disease?

Normally Calcium binds oxalate in the gut. In Crohn's fat binds this Calcium leaving oxalate free to be absorbed.

 

[Pisiform]

Reason behind kidney stones with Crohn's disease?

Malabsorption causing fat to bind to calcium leaving oxalate to be absorbed and deposit in kidney

 

[dfib slim]

Fat malabsorption leads to increased free oxalate which is taken up by the gut and leads to oxalate stones.

Normally Calcium binds oxalate in the gut. In Crohn's fat binds this Calcium leaving oxalate free to be absorbed.

Malabsorption causing fat to bind to calcium leaving oxalate to be absorbed and deposit in kidney

It's actually fat malabsorbtion, decreased calcium in the gut with increased oxalate absorption and resulting kidney stone formation. I'm disappointed in all of you.

 

[Pisiform]

It's actually fat malabsorbtion, decreased calcium in the gut with increased oxalate absorption and resulting kidney stone formation. I'm disappointed in all of you.

My mom is disappointed in me too. No worries

 

[mcloaf]

It's actually fat malabsorbtion, decreased calcium in the gut with increased oxalate absorption and resulting kidney stone formation. I'm disappointed in all of you.

****. Brb delaying my exam.

 

[seminoma]

Urine pH in early type 2 RTA?

 

[seminoma]

In HIV which viral gene mutation slows down the progression of disease?

What's the answer to this?

 

[dfib slim]

What's the answer to this?

Maybe nef?

 

[Mr. Mojo Risin]

What's the answer to this?

I would say heterozygous CCR5 mutation, because homozygous CCR5 mutation leads to immunity.

 

[seminoma]

Maybe nef?

Just read about it on wiki and it seems likely. We didn't learn about nef in micro though... maybe I need to look into HIV more.

I would say heterozygous CCR5 mutation, because homozygous CCR5 mutation leads to immunity.

Yeah that's true, but he was asking about a viral gene mutation. CCR5 is a host gene.

 

[dfib slim]

I would say heterozygous CCR5 mutation, because homozygous CCR5 mutation leads to immunity.

Wouldn't a CCR5 mutation be in the human genome instead of the viral?

 

[Mr. Mojo Risin]

Just read about it on wiki and it seems likely. We didn't learn about nef in micro though... maybe I need to look into HIV more.


Yeah that's true, but he was asking about a viral gene mutation. CCR5 is a host gene.

Wouldn't a CCR5 mutation be in the human genome instead of the viral?

Derp. My bad guys. My vote would be for nef since that confers virulence.

I guess I'll add to the discussion with the following question: what's the effect of the nef protein on host immunity? (I'm thinking of two).

 

[dfib slim]

Derp. My bad guys. My vote would be for nef since that confers virulence.

I guess I'll add to the discussion with the following question: what's the effect of the nef protein on host immunity? (I'm thinking of two).

Downregulation of CD4 and IL2?

 

[seminoma]

Which drug sometimes used to treat hypertension also inhibits 17-20-desmolase?

 

[Transposony]

what's the effect of the nef protein on host immunity? (I'm thinking of two).

Down-regulation of CD4 & MHC 1 expression.

 

[Transposony]

Just read about it on wiki and it seems likely. We didn't learn about nef in micro though... maybe I need to look into HIV more.
Yeah that's true, but he was asking about a viral gene mutation. CCR5 is a host gene.

Yes, that was the reason for posting this Qs.

 

[Transposony]

Which drug sometimes used to treat hypertension also inhibits 17-20-desmolase?

Spironolactone.
But it's antiandrogenic effect is mostly due to it's partial agonism of androgen receptors.

 

[Mr. Mojo Risin]

Down-regulation of CD4 & MHC 1 expression.

Yep!

 

[Transposony]

What's responsible for Genetic drift & Genetic shift in HIV ?

 

[dfib slim]

What's responsible for Genetic drift & Genetic shift in HIV ?

Gene mutation for drift and recombination during superinfection with shift?

 

[dfib slim]

Reason for metabolic acidosis in INH overdose?

 

[Transposony]

Gene mutation for drift and recombination during superinfection with shift?

Let me put it this way-Which components of HIV are responsible for Genetic drift & Genetic shift ?

 

[Mr. Mojo Risin]

Since newly approved drugs are fair game, I'll post this here as well as the HY Pharm thread: http://www.centerwatch.com/drug-information/fda-approved-drugs/

 

[seminoma]

What are struvite stones made of? What 3 organisms are a/w struvite stones and why?

 

[dfib slim]

What are struvite stones made of? What 3 organisms are a/w struvite stones and why?

Mag ammonium phos. Proteus, ureaplasma, and kleb. They all have urease activity.

 

[dfib slim]

Let me put it this way-Which components of HIV are responsible for Genetic drift & Genetic shift ?

Gp120/41 for drift and genomic RNA for shift?

 

[dfib slim]

What is a gardos channel and what condition may an inhibitor be used for?

 

[aspiringmd1015]

with the ca oxalate, isnt it that normally oxalate just simply doesnt get reabsorbed normally in the gut, but with crohns ileal trasmural damage, allows oxalate to be reabsorbed, which normally isnt suppose to, and gets into the bloodstream in abnormal amounts, and in the kidney it precipitates out? (this is what sattar said i think)

 

[Transposony]

What is a gardos channel and what condition may an inhibitor be used for?

Had no idea so looked it up.

The Gardos channel aka KCNN4 is a protein "pump" that expels intracellular potassium when activated by calcium. The red cells loose water along with calcium. The result is a higher intracellular Hb concentration. This promotes polymerization of deoxygenated HbS.

Senicapoc for SCD.