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  #1  
Old 07-03-2014
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Default NBME 11: Cell Biology

In a study,Radiobeled Lactose is given to two women.One is a 35 yr old healthy women and other is a 35 yr old women with Crohns disease.Their urine is monitored over the next 24hrs.Urinary excretion of radioactivity is higher in women with crohns disease than the normal women.This is observed due to the inflammation associated changes in integrity of which of the following structures?

1.Gap junctions
2.Tight junctions
3.Desmosomes
4.Basement membrane
5.Adherens junctions


Can someone explain How Tight junctions is the answer for this question??
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Old 07-07-2014
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Tight junctions prevent movement of substances between cells. Others are for structure and integrity of the tissue. Since it's lost in this case the lactulose can pass between cells and enter the body. Acc to research tight junctions are lost in crohns
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Old 07-07-2014
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that's the first thing you need to break in order to get into the tissue.
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thank you...I just have a doubt...Gap junctions transmits electrical activity and chemical substance with neighbouring cells right...how does gap junction differ from tight junction could you explain please???
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Old 07-08-2014
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Gap junctions(connexion with central channel) permit substance/ electric impulse movement, eg. in heart tissue, or in the case of osteocytes. Tight junctions (composed of claudins and occluding)prevent the moment of water and substances, eg. blood brain barrier and testes blood barrier.

They're pretty much opposite in function
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