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 +5  (nbme21#28)

I think it has something to do with glycine (due to its small size it can fit in many places where other amino acids can not and hence it provides “structural compactness” to the collagen, i.e. put a kink in the alpha helix). If glycine is misplaced by something else, I don’t think pro-collagen can form its correct secondary structure.

jotajota94  True! also, glycine is 1/3 of collagen alfa chains, so it makes sense that substitution with alanine (which is much bigger) would lead to disruption in the alpha helix formation.
jotajota94  True! also, glycine is 1/3 of collagen alfa chains, so it makes sense that substitution with alanine (which is much bigger) would lead to disruption in the alpha helix formation.
thepacksurvives  Glycine is small and bendy, which allows it to form the fibrils for the triple helix

 +5  (nbme21#39)

This is what I thought but not sure if it’s correct. There is a UWorld q where it describes co-administration of cortisol and epinephrine. Cortisol significantly enhances the effect of epi because cortisol has a permissive effect on maintaining the adrenergic receptors.

194orbust  per UWorld, "cortisol exerts a permissive effect on many hormones to help improve the response to a variety of stressors. For example, cortisol increases vascular and bronchial smooth muscle reactivity to catecholamines". FA also uses the effect of cortisol on catecholamine responsiveness as the lone example for a permissive drug interaction (FA2018 pg 229). The difference here is that we're talking about exogenous glucocorticoid and adrenergic agonist. I guess it was expected for us to assume that the mechanism is analogous for the analogous drugs
maxillarythirdmolar  I'm sure it's related to the activating effect of Cortisol on phenylethanolamine-N-methyltransferase, converting NE to Epi. Sounds like a synergistic thing to me. (FA.83)

 +5  (nbme21#2)

Syphilis pathogenesis is the inflammation and obliteration of the vasa vasorum (small blood vessels) that feeds bigger blood vessels like aorta, arteries, arterioles. It does not matter what the stage is, T. pallidum infects the vasa vasorum and, in the process, obliterates the nerves and blood vessels. This kills blood supply to those areas = ischemia but no pain (painless chancre). More localized in earlier stages, and in later stage, the spirochetes disseminate, so you have the aorta and spinal cord involvement but same pathogenesis. (Edit: Goljan explained this somewhere.)

privatejoker  So is the heavily implied step-wise formation of Syphilis symptoms as presented in FA complete BS then? Why break it down into stages and have us learn it as such if this is not the case in real practice?
lilmonkey  Exactly, Goljan mentioned this in one of his audio lectures. All kinds of lesions in syphilis caused by vasculitis.

 +4  (nbme21#3)

I think they want you to think about how conjugate vaccine is made: polysaccharide + protein fragment (to induce T dependent immune response). Only flagellin is a protein (or at least sounds like one) in the option list.

vi_capsule  Flagellum is protein. Pilli/Fimbriae - GLycoprotein




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