More about apoptosis
rick at sjubiol.stjohns.edu
Tue Apr 12 22:40:18 EST 1994
To: ageing at net.bio.net
Subject: More about Apoptosis
>In normal intestinal cell lines, I can detect DNA fragmentation.
>I call it spontaneous cell death and it is somehow cell density
>dependent. I can see very few trypan blue stained cells even
>though I can identify and then purify detergent-insoulbe envelope
(apoptotic bodies). I assumed apoptotic cells were engulfed by
>neigboring cells before they lost their membrane intergrity.
intestinal cells are normally discarded into the lumen rather than
being phagocytosed. I assume that you are seeing an (interesting)
reflection of this in vitro. Also, cultured cells are not normally
phagocytosed. This may be an artifact of the culture system.
>In some transformed cell lines, such as HT-29, most dead cells
>detach from the monolayer. Detached cells can be judged as
>apoptotic by acridine organe staining and are all stained well >
with trypan blue, even the cells maintaining good morphology
>(I assume they are in the early stage of cell death) . I got
>beautiful DNA ladder from those cells.
that's nice to hear!
>Is it possible that apoptotic cells, when not engulfed by other
>cells, can not maintain their membrane intergrity?
That would appear to be reasonable. At some point they must not
be able to keep up their function. We have no reason to feel that
apoptotic bodies are like spores or other dormant cells, and we
know of no reversal from the collapsed state.
>Also, what do you think is the function of apoptotic bodies?
I don't know what you mean by the question. The evolutionary sig-
nificance of apoptosis appears to be controlled, non-inflammatory
elimination of injured cells, especially in the sense that they
are potentially dangerous (carriers of viruses or toxins, or
lytic enzymes). The apoptotic body appears to be an encapsulated
form of the cell.
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