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lsmarshall  Rectal prolapse through posterior vagina ("rectocele"). https://www.drugs.com/cg/images/en2362586.jpg +5  
famylife  "When a rectocele becomes large, stool can become trapped within it, making it difficult to have a bowel movement or creating a sensation of incomplete evacuation. Symptoms are usually due to stool trapping, difficulty passing stool, and protrusion of the back of the vagina through the vaginal opening. During bowel movements, women with large, symptomatic rectoceles may describe the need to put their fingers into their vagina and push back toward the rectum to allow the stool to pass (“splinting”). Rectoceles are more common in women who have delivered children vaginally." https://www.fascrs.org/patients/disease-condition/pelvic-floor-dysfunction-expanded-version +9  
usmleuser007  really like the pubic hair.... +  
nnp  why not spasm of external anal sphincter? +  
vulcania  After looking it up I think that external anal sphincter spasm would be more associated with rectal pain and maybe fecal incontinence. I chose the same answer because I figured if there was a problem with the rectovaginal septum it would have been noted on physical exam... +1  
ajss  I did the same, put sphincter spasm because I thought a rectocele would be found on a physical exam. +  

submitted by lsmarshall(314),

An experimental design or experimental study must have an intervention, by definition. Case-control studies are observational studies, not experimental. This question is technically incorrect. They wanted to amke a point that case-control studies are time and cost efficient since they don't require following patients over time or any resources besides reviewing/gathering information. Case series could not test this hypothesis.

Also, the wording "associated wit an increased risk" somewhat alludes to case-control studies only having the ability to find odds of an associations between exposure and outcome, but not establish causal relationship.

bigjimbo  classic nbme +1  
poisonivy  totally agree, I dont understand why the right answer is Case control since that is not experimental +  
howdywhat  am I subject to this kind of poor wording for the day of the exam? +  
ajss  I bieleve so +  

Mast cells degranulate, producing histamine which attracts eosinophils. The early stage of an allergic reaction is mast cell mediated, but the late stage (including mucus production) is mediated by eosinophils.

atstillisafraud  Thanks for a good answer. This question made me feel like I was taking T21 pills +10  
medguru2295  Thank you- I was really thinking this question had 2 correct answers... of course my dumbass picked Mast cells. +2  
ajss  where do i find this info?? +  
paperbackwriter  @ajss pg 112 of first aid 2019, under type I hypersensitivity. Immediate --> mast cells releasing histamine and tryptase, late--> eosinophils and leukotrienes recruited via chemokines +2  
graciewacie9  Wow, i missed the fact that the question is asking for the RESULT of the reaction, NOT the cause of the reaction. Mast cells cause the initial reaction, eosinophils would be the result of the eosinophils. *facepalm +  

submitted by bubbles(51),

Can someone explain properly how we know that this trait follows Mendelian genetics and is autosomal recessive and furthermore how the parents were heterozygous?

I guessed a lot on this question and got lucky :(

niboonsh  Autosomal Dominant disorders usually present as defects in structural genes, where as Autosomal Recessive disorders usually present as enzyme deficiencies. P450 is an enzyme, so we are probably dealing with an autosomal recessive disorder. furthermore, the question states there was a "homozygous presence of p450.....". In autosomal recessive problemos, parents are usually heterozygous, meaning that 1/4 of their kiddos will be affected (aka homozygous), 1/2 of the kids will be carriers, and 1/4 of their kids will be unaffected. +14  
nwinkelmann  Is this how we should attack this probelm?: First clue stating endoxifen is active metabolite of Tamoxifen should make us recognize this undering first pass hepatic CYP450 metabolism? Once we know that, the fact that the metabolite is decrease suggests an enzyme defect, which is supported by patient's homozygous enzyme alleles. Then use the general rule that enzyme defects are AR whereas structural protein defects are AD inheritance patters. Once we know the pattern, think that most common transmission of AR comes from two carrier parents. So offspring alleles = 25% homozygous normal, 50% heterozygous carrier, and 25% homozygous affected, thus sister has a 25% of having the same alleles as patient (i.e. homozygous CYP450 2D6*4)? +6  
impostersyndromel1000  we had the exact same thought process, so i too am hoping this is the correct way to approach it get reasoning friend +  
ajss  thanks for this explanation, I totally forgot about AR patterns are most likely enzymes deficiencies, this kind of make the question easier if you approach it that way, thanks +  

Warfarin inhibits Vit K dependent synthesis of factors & proteins.

Vit K is necessary for the maturation of clotting factors II, VII, IX, X and protein C & S

So a drug that can inhibit the carboxylation of precursor proteins or in other words inhibit the maturation of the clotting factors will decrease the risk of thrombosis in this patient.

ajss  this is why warfarin is given as prophylaxis after this type of surgeries +  

submitted by sacredazn(59),

The concept is a convoluted way of asking if you knew how VDJ recombination works, which is that it is actually an example of altering the DNA of the B/T lymphocyte.

Southern blot technique: So when they use a probe against some region, and outputting a size of 1.5 kb or 6 kb, this is telling you the size of the DNA fragment in each cell (doesn’t matter if they say J probe or constant region probe, they’re just saying they’re targeting some nucleotide sequence found in the Ig locus/TCR beta chain locus respectively for B/T cells).

I think the confusing part could be wondering how you know whether you’re partly through rearrangement (answer choices B thru D) or if it hasn’t occurred at all yet (correct answer). Here, the concept is that B cells undergo V(D)J rearrangement in the bone marrow, while T cells do it in the thymus, and it all happens at once. So a plasma cell in the blood like in Multiple Myeloma would have fully undergone recombination, while a T cell in the blood could either be fully educated (and have finished VDJ recombination) or immature (hasn’t started VDJ).

Since the T cell gene was 6 kb and definitely bigger than the 1.5 kb gene, the T cell hasn’t undergone recombination yet.

trichotillomaniac  very nice explanation! +7  
nwinkelmann  This was awesome! Made so much sense and hopefully I will be able to think that critically about questions in the future (because I NEVER would have come up with this on my own, hah). +4  
eacv  OMG! THANK YOU. I DIDNT KNOW ANYTHING about this!! Hope this is not testesd on real examen :p +3  
ribosome01  I would like to meet you personally and say thank you I wish I had a teacher like you +  
ajss  wow! this explanation was awesome! thanks! +  
mrglass  Also the T-cell V-D-J segments are not the same as the B-cell V-D-J segments. Therefore a B-cell J segment southern blot would look for whether the B-cell site VDJ segment in a T-cell, which would always non-rearranged. +4  
mynamejeff  Thank you! So is this because multiple myeloma produces excessive monoclonal light chain Ig? Is this the 1.5 kb gene? Whereas, T-cells that have not gone through differentiation yet and their J region includes everything (VDJ) vs. just VJ in the light chain? (FA 2020 pg 104) +  
peridot  This explanation is amazing! However, to fully understand another step of what the question is getting at, please take a look at @highyieldboardswards's and/or @mrglass' explanation as well - a very important addition!! +  

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