reply and query on cell death

[Richard Lockshin]

To: ageing at net.bio.net
Reply to: uunet!reed.edu!tkim (Tae Hoon Kim)
Subject: STUDENT QUESTION: relationship between senescence and 
apoptosis
From:  richard a. lockshin
 
-->incidentally, I might as well ask here.  Is there much 
interest in trying to organize a cell death discussion group?
 
->be careful to distinguish, in the animal world, cell senescence 
(limited lifespan of cells in culture), programmed cell death 
(developmental, usually requiring gene activity), and apoptosis 
(a particular type of morphology and non-lysosomal death seen in 
many types of cells.
-->for aging and cell death, see Lockshin R. A. and Zakeri Z. F., 
Physiology and protein synthesis in programmed cell death.  Early 
synthesis and DNA degradation. in Franceschi C, Crepaldi G, 
Cristofalo V. J., and Vijg, J, eds, Aging and Cellular Defense 
Mechanisms, Annals N.Y. Acad. Sciences  663: 234-249, 1992.
 
1. Are there evidences that may implicate PKC in the pathwway of 
cell ageing?
 
-->not that I know of.  There are some papers coming out on 
metabolism of dying cells.
 
2. Are ultrastructural, morphological, behavior changes in ageing 
cells
similar to apoptotic cells?
 
-->in senescing cells, most people feel that the changes are not 
like apoptosis. A few feel that they are.  Cristofalo is working 
on this now, and there will be a book out at the end of 94 in 
which both subjects are treated.  My understanding is that dying 
plant cells do not have the morphology of apoptosis.  I solicit 
references.
 
3. How is senescence regulated? Or is it regulated at all?
 
-->wow.  Do you want a course, a Ph.D., or a Nobel prize?
 
4. How are ageing cells affected by environment?
 
-->again, senescence:  nutrients, glucocorticoids, growth factors 
play a large role.  The environment in general (e.g., ecological 
concerns) ??
 
5. How much evidence are there to suggest that senescence is a 
genetic
process?
 
-->Please see C. Finchs book.  Researchers primarily interested 
in the genetics of senescence include George Martin (U Wash), Tom 
Johnson (Boulder), Michael Rose (Irvine)
 
6. What is the relationship between senescence and cell cycle?
 
-->see articles by Judith Campisi, Eugenia Wang, James Smith and 
Olivia Pereira-Smith, Tom Norwood.  You can find these by a 
literature search.  The field is extensive.
 
7. Can this generalization hold?:
        Senescence occurs in a terminally differentiated cells, 
while
        apoptosis occurs in relatively more neoplastic tissues.
 
-->no.  The concepts at present are incommensurable.  Interesting 
thought though.  Do you mean instead of  neoplastic--a 
cancerous lesion--mitotic?
 
Can I view apoptosis as a suicide and senescence as a natural 
death? This
distinction seems to helpful in conceptualizing these ideas.
 
-->dont confuse cells and organisms.  also, dont confuse 
continuing mitosis and failure of same with cell death.  phase 
III cells in culture survive a very long time, without undergoing 
mitosis.  Unless you insist on a precise definition of cell 
senescence, usually considered to refer to limited lifespan of 
cells in culture, you will end up with total confusion.
 
--richard a. lockshin (rick at sjubiol.stjohns.edu)