Section 3.5.<\/strong> Elucidating the causes for starting or stopping of the cell Causes for Starting or Stopping of the Cell Division Section 3.5. Elucidating the causes for starting or stopping of the celldivision is one of the basic problems of cell biology. The presence of certainfactors is necessary to stimulate the cell to divide. Some authors (Gurwitsch,1926; Wasserman, 1929; Swann, 1957) divide these factors in two groups: […]<\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"site-sidebar-layout":"default","site-content-layout":"","ast-site-content-layout":"default","site-content-style":"default","site-sidebar-style":"default","ast-global-header-display":"","ast-banner-title-visibility":"","ast-main-header-display":"","ast-hfb-above-header-display":"","ast-hfb-below-header-display":"","ast-hfb-mobile-header-display":"","site-post-title":"","ast-breadcrumbs-content":"","ast-featured-img":"","footer-sml-layout":"","theme-transparent-header-meta":"","adv-header-id-meta":"","stick-header-meta":"","header-above-stick-meta":"","header-main-stick-meta":"","header-below-stick-meta":"","astra-migrate-meta-layouts":"set","ast-page-background-enabled":"default","ast-page-background-meta":{"desktop":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"tablet":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"mobile":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""}},"ast-content-background-meta":{"desktop":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"tablet":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"mobile":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""}},"footnotes":""},"categories":[6],"tags":[],"class_list":["post-854","post","type-post","status-publish","format-standard","hentry","category-book"],"_links":{"self":[{"href":"https:\/\/cellandcelldivision.com\/index.php?rest_route=\/wp\/v2\/posts\/854","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/cellandcelldivision.com\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/cellandcelldivision.com\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/cellandcelldivision.com\/index.php?rest_route=\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/cellandcelldivision.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=854"}],"version-history":[{"count":1,"href":"https:\/\/cellandcelldivision.com\/index.php?rest_route=\/wp\/v2\/posts\/854\/revisions"}],"predecessor-version":[{"id":859,"href":"https:\/\/cellandcelldivision.com\/index.php?rest_route=\/wp\/v2\/posts\/854\/revisions\/859"}],"wp:attachment":[{"href":"https:\/\/cellandcelldivision.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=854"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/cellandcelldivision.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=854"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/cellandcelldivision.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=854"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}
division is one of the basic problems of cell biology. The presence of certain
factors is necessary to stimulate the cell to divide. Some authors (Gurwitsch,
1926; Wasserman, 1929; Swann, 1957) divide these factors in two groups: a)
factors determining the readiness of the cell to divide; b) factors realizing the
entry of cell into division, being prepared for that.
To the first group Swann (1957) refers: increasing the mass of cell;
synthesis of precursors necessary for the division (including DNA and
proteins); creating certain level of energetic reserve; accumulation of SH-
containing compounds (mainly glutathione); synthesis of nuclear RNA; the
mechanisms controlling the sensitivity to temperature and irradiation. A
great importance is attached to various other substances \u2014 hormones,
active components of embryonic extracts, etc.
Undoubtedly, these factors play an important role in the processes
proceeding during the preparation of cell for division. There are close
connections and interactions among them. The absence of only one of
them leads to retention or stopping the cell division. Besides, these factors
possess certain independence. Cell growth can proceed in absence of
DNA-synthesis and vice versa<\/em>, blocking the systems responsible for
sensitivity to the temperature do not terminate cell growth and DNA\u0002synthesis, etc.
Much more unclear is the role of the factors realizing the entry of cell
into division. In this respect also various suppositions are expressed:
alterations in nuclear-plasmatic proportions (Hertwig, 1903, 1908; Popoff,
1908); the necrohormones (Harberlandt, 1921); mitogenic irradiations
(Gurwitsch, Gurwitsch, 1948); activation and reactivation of specific genes
(Epifanova 1965), etc.
The complexity of the cell mechanisms is most clearly expressed in the
processes related with the realization of cell division. Every living cell has to
divide and \u201cprolong its existence\u201d through the subsequent generations or to
die. This is its life, i.e. cell cycle. Its duration varies within a great limits.
To a great extent the differences in the duration of cell cycle are
determined by the period, when the cells are in G1-phase. Some cells
divide very slowly, staying in G1 for days or years. After passing this phase
and in the beginning of S-phase up to the completion of mitosis the
processes are realized an equal same speed, not corresponding to the
previous one. At the end of G1-phase there is a moment after which their
retention is not possible any more. This moment has been termed
restriction point<\/strong> (R-point). After R-point the cells inevitably acomplish their
cycle, irrespective of the influence of surroundings, of course if it is not fatal
(Pardee, 1974).<\/p>\n","protected":false},"excerpt":{"rendered":"