exactly the opposite: its regulation by sudden protein destruction, or
proteolysis, triggered by a molecule named uliquitin”.
For obvious reasons cell is an object of numerous investigations. In the
literature there are given still a number of factors having certain influence
over cell development and division. Nevertheless, the problem connected
with the causes for beginning or stopping of cell division remains far from
elucidation. That is why, it is reasonable to be referred to the “white spots”
of cell biology.
Depending on the structural organization of cells and their place in
evolutionary hierarchy, they can divide continuously (non-stop), to
differentiate and again to dedifferentiate. Thorough review on these
problem is given by Hay (1962). All that argues for the presence of complex
genetic mechanisms determining their broad capabilities for adaptation,
acquired in ontogenesis and phylogenesis. Some of these questions are
related with the biological aging and neoplasms, which will be considered in
the next Section 3. 6.
Biological Aging and Neoplasms
Section 3.6. Biological aging and neoplasms are key problems of biology,
which affect man directly. In recent several decades they attract the
attention of the investigators. Numerous investigations are carried out, but
the causes and mechanisms connected with their appearance and
development as biological processes are not elucidated.
There are different opinions, hypotheses and theories on the nature
and causes for the biological aging and the emergence of neoplasms.
Except mistakes in synthesis of macromolecules, damages of the genetic
material, effect of carcinogenic factors of the surroundings and oncoviruses
(Watson, 1976, and others), recently some authors direct the attention to
the cell cycle, the differentiation and proliferation of the cells (see Goldstein,
1990; Cohen, Ellwien, 1990; North, 1991).
Biological Aging
As a phenomenon the biological aging (senescence) is observed in both
the animal and plant world. The time duration preceding biological death
varies for the different species. The age limit of human life-span is
considered to be about 115—120 years, while for some plants —
bristlecone pine (Pinus aristata) and sequoia (Sequoiadendron giganteum)
— it is of the order of 4—5 millennia.
These data, however, refer to the studying of the problem at multicellular
organism level. Firmly believing that its essence is encoded in the cells which
build the organisms, our attention will be mainly focused on that.