mani
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myelin figure is a sign of reversible or irreversible injury?
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| piter
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myelin figures and cell blebs still reversible
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| rida
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What are the signs for irreversible?
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| mani
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in robins pathology it is given as sign of irreversible injury buy brs says it is reversible
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| piter
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what says Goljan?
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| mani
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i havent read goljan. my test book is robins. anybody please help.
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| mingle
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i thought it is irreversible....after all it contains nuclear fragments after disintegration of the nucleus...hmmm don;t think we can reassemble a nucleus easy )) :P
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| rida
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According to path BRS, myelin figures which are structures originiating from cell membranes and cell blebs are sings of last stage of ischemic cell injury but reversible. The first point at which one knows that the cell cannot return and hence makes it an irreversible damage is damage to the mitochondria and cell membranes resulting in calcium influx.
Hope this helps!
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| mingle
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is this correct? from memory p53 activates bax = cytochrome c release from mitochondrion = initiation of cell death. sooo does it mean nuclear dissociation occurs after mito has released the cyto c? thanks
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| mani
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rida, according to robin's, point of no return that the point where irreversible damage has taken place is yet controvercial, there is no final criteria for it. i believe robin's a text book and we have to appricate its point that myelin figures are irre versible
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| mash
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i think rida is right
REVERSIBLE changes are known to occur when the duration of the ischaemic is short . Myelin figures from plasma and organellar membranes are seen within or outside the cell (disassociation of lipoproteins). Usually at this stage the mitochondria are also swollen. Should oxygen be restored, most of these changes could revert totally to normal.
IRREVERSIBLE changes occur if hypoxia persists. the true biochemical point of no return is not truly defined. Morphologically, however, this is associated with severe vacuolization of mitochondria, damage to plasma membranes, swelling of lysosomes, and massive Ca++ influx into the cell. The intracellular acidosis produce injury to lysosomal cell membranes, leakage of their powerful enzymes into cytoplasm and cell digestion including nuclear changes and cell death. It is believed that the critical changes that make injury irreversible and lethal in hypoxia have to do with the inability of the mitochondria to recover from injury (after re-oxygenation) producing permanent damage on cell membrane function and integrity. The biochemical pathways involved in such cell membrane dysfunction include:
Loss of phospholipids (decreased synthesis and increased degradation).
Cytoskeletal alterations (damage to cytoskeletal-membrane connections, effects of cell swelling, activation of proteases)
Effects of free radicals (toxic oxygen radicals or toxic oxygen species, produced by PMN's)
Lipid breakdown products (free fatty acids and other with a detergent effect on cell membrane).
Once re-oxygenation takes place in a cell so structurally damaged, there is an influx of Ca++ into the cell and mitochondria with inhibition of cellular enzymes, denaturation of proteins and coagulation of cells (coagulative necrosis). After cell death, cell components are degraded by inflammatory processes, with associated further enzyme leakages and release of inflammatory mediators. Final breakdown product of dead cells include free fatty acids which attract Ca++ with formation of soaps.
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| rida
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Mani i agree with you about the point robbins makes, its a very good book, i think what mash also points out though is that even tho its controversial, the bottomline point is that once mitochondria is damaged or involved in the pathologic process, the process becomes irreversible.
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| rida
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I just went back and reread the section in robbins, it says that once myelin figures develop, if oxygen is provided to this ischemic cell, the injury is reversible, however, if the cell continues to be ischmic and without oxygen, then the mitochondria will eventually be damaged and this is the point of no return, hence, myelin figures are seen in both reversible and irreversible, depending on the presence or absence of oxygen. Mash makes this point as well with the hypoxic changes. Hope this helps!
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| mani
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yep, thanx as lot
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