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Sickle

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mjl1717
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04/30/04 - 02:54 PM

What actually causes the sickling in Sickle cell anemia and how do you treat it?

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rida
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04/30/04 - 06:25 PM

Sickle cell is due to a mutation in the Hemoglobin Beta chain, where a Val is changed to Glu. The RBC's have a rigid structure because of this change, and exposure to infection, low oxygen, or dehydration, these cells form crescent shapes, and can block arteries resulting in infarcts of organs, causing massive pain. I know normally the treatment is geared towards the symptoms, however, bone marrow transplants are effective.

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mjl1717
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04/30/04 - 08:45 PM

I know there is a substitution of amino acids. but since you mention it what is that called. Again what is the Most important factor that induces that sickling?

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rida
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04/30/04 - 09:18 PM

I believe the substitution is called missense mutation, as far as the Most important factor, my guess is hypoxia????

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mash
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04/30/04 - 10:46 PM

yeah hypoxia is d cause
--increased deoxy Hb causes polymerization of HbS molecules n they bcm sickle cells.
--they revert back to normal on oxygenation
--But continued sickling causes cell mem damage leading to loss of K n H2O & inc in Ca. This produces irreversible sickling n t1/2 of cell reduces frm 120 to 20 days...
Tx(not v sure)
inc HbF decreases sickling
hydroxyurea increases synthesis of HbF.....
it prevents crisis

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Malaysian
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05/01/04 - 09:25 AM

In sickle cell there is abnormal HbS which is due to replacement of Leucine with Valine on the 9th Amino acid of the Beta chain.
During hypoxia(low O2 conc.)these HbS polemerize and form long chains which stretch the RBC(hence the sickle cell shaped....which is like an elongated RBC).....this abnormal shape of the cell clogs the capillaries and other narrow spaces.

To revert it back one needs to re-oxidize the cells mash has mentioned some points which are valid and also need to rehydrate the patient

Idiopathic
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05/01/04 - 09:30 AM

decreased O2-tension causes sickling (i.e. renal medulla)

rida
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05/01/04 - 12:42 PM

"Malaysian" wrote:
In sickle cell there is abnormal HbS which is due to replacement of Leucine with Valine on the 9th Amino acid of the Beta chain.

Malaysian are you sure about the change from val to leucine, cuz apparently even my post has it backwards, according to lippincott biochem, the amino acid substitution is at position six, where a glutamate has been replaced with valine. Correct me if i am wrong please!!!

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Sakaki-
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05/01/04 - 12:50 PM

I agree with Rida, as I'm quite positive that a valine replaces glutamate (at the 6th position of the beta chain of hemoglobin).

Malaysian
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05/01/04 - 12:51 PM

#10

yes you're correct rida,my apologies

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