To: ageing at net.bio.net
From: rick at sjubiol.stjohns.edu (Richard A. Lockshin)
Subject: APOPTOSIS - Programmed cell death (Information needed)--reply
Answers to:
uunet!brunel.ac.uk!md93mgk (Michael G Karras)
1. Apoptosis is a specific morphology in the general category of
physiological cell deaths. It includes movement of the chromatin to
the margin of the nucleus, coalescence of the chromatin, usually but
not always degradation of the DNA to characteristic small fragments termed
a nucleosomal ladder, and shrinkage and fragmentation of the cell. If
one can further establish that the cell follows a specific sequence to
its death, including synthesis of new messages and proteins, the death
is called programmed. The terms are frequently interchanged, though
they are slightly different. You may wish to consult "Apoptosis.
The Molecular Basis of Cell Death", edited by L. D. Tomei and F. O. Cope,
Cold Spring Harbor Laboratory Press, 1991, or several lead articles in
Cell Biology International for 1993, notably those by Bowen and his
colleagues. Both of these should be available to you.
2. Dead cells have severed their connections with other cells, but
the causal and temporal connections between severing and death are not
known. Ced-9 is a gene that in the nematode Caenorhabditis elegans
prevents known programmed deaths. It is slightly similar to a mammalian
gene, bcl-2, but it has not been identified elsewhere. It is a gene
of enormous interest. There was a review in Annual Reviews of Cell
Biology in, I believe, 1991, by (Ellis and?) H. R. Horvitz on this
subject.
3. We (workers in the field) tend to feel that most cells are capable
of killing themselves (programmed cell death or apoptosis), including
probably unfertilized eggs. A lot of work is going into the question,
because it has many ramifications in cancer, aging, neurobiology, and
immunology including AIDS. There are a few thousand publications now,
with the number increasing logarithmically. Stay tuned.
4. Obviously, as you correctly observed, many cells, including blood
cells and eggs, do not need to maintain cell-to-cell contact and in
fact abandon it. Given the proper nutritional background, most cells
can survive, albeit wanly, out of contact with others. (The dependent
clause there is a big "if".)
