Life cycle arrest

Feeding directly or indirectly from their hosts, parasites set themselves apart from commensals as their growth and/or development is arrested in the absence of a suitable host through lack of nutrition more usually, parasitic species in the phase of their life cycle requiring a host will die if one is not available and without a host they are unable to complete their life cycle. Commensals, whilst often found in association with their hosts, are not so dependent on them their nutrition may be facilitated by their hosts but they do not necessarily die in the absence of a host. There is obviously a continuum between the terms free-living and parasitic, with commensal somewhere between the two where one draws the line between commensal and... 

Cheng YL, Chang WL, Lee SC, Liu YG, Chen CJ, Lin SZ, Tsai NM, Yu DS, Yen CY, Harn HJ. Acetone extract of Angelica sinensis inhibits proliferation of human cancer cells via inducing cell cycle arrest and apoptosis. Life Sci 2004 75(13) 1579-94. 

The utilization of metabolic probes is a key strategy for the decryption of intracellular life processes. Luedtke and co-workers developed a vinyl-decorated deoxyuridine ll(VdU) that was able to be incorporated by endogenous enzymes into DNA synthesis and visualized by fluorescent tetrazine conjugates [55]. Additionally, VdU displayed lowered cytotoxicity and caused less DNA damage and cell cycle arrest compared to other clickable metabolic nucleic probes such as 5-ethynyl-2 -deoxyuridine (Fig. 3). 

Hsu YL, Kuo PL, Lin CC (2005) Isoliquiritigenin induces apoptosis and cell cycle arrest through p53-dependent pathway in Hep G2 cells. Life Sci 77 279... 

Telomeres play an important role in defining the replicative life span of cells, i.e., the maximal number of cell divisions or the so-called Hayflick limit. Normal human somatic cells, such as fibroblasts, after isolation ftom the body are only able to undergo a limited number of cell divisions, dependent on the age of the donor, before they stop cycling and go into the senescent state , which becomes manifest in phenotypic charges like cellular (lattenii and expression of a senescence-associated. alactosidase. Such cells ate arrested in G, which is different from quiescent cells, which arrest in Gq. After acquirir the senescent phenotype cells are still viable and can be maintained in culture for up to several months. The telomeres in fibroblasts shorten with each di ion due to the end-replication problem , because conventional DNA polymerases need a free 3 -hydroxyl toup lor DNA synthesis. This is usually provided by the activity of the polymerase o/ptimase complex, which synthesizes an initial RNA o%onucleotide primer. Durit strand synthesis, the most distally located primer... 

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