Arrested states

If dividing mammalian cells are exposed to higher concentrations of H2O2 than those that cause temporary growth-arrest and transient adaptation, they can be forced into a permanently growth-arrested state (Scheme 2). Thus, cells exposed to H2O2 concentrations of 250-400 pM,or 9-14 pmol 10 cells, will never divide again [15]. 

Findings with ingestion of tryptophan-deficient diets are of special interest because tryptophan is an obligatory dietary precursor of brain amines that regulate hormonal function in the central nervous system. Early studies have revealed that tryptophan-deficient rats have low brain levels of serotonin55 and appear to remain in an arrested state of growth and maturation.65... 

As discussed in section 10.6, the increase in Ca at fertilization appears to induce some phosphorylation event(s) via calmodulin-activated protein kinase (Lorca et al., 1993). One result of this is the activation of the cyclin degradation pathway, which releases the oocyte from metaphase arrest. A recent study in rabbit oocytes (Collas et at, 1995) was aimed at measuring MPF-associated kinase activity as a function of the number of Ca pulses applied to the oocytes. The results suggest that, whereas a single Ca pulse elicits only a transient decrease in MPF activity, a prolonged series of Ca spikes is needed to sustain the MPF inactivation associated with exit from the metaphase arrested state. 

In summary, the observed state diagram for large q is sketched in Fig. 4.19. Across the three-phase region a narrow concentration regime was found of equilibrium fluid-crystal phase behaviour [16,17], see also the discussion near Fig. 4.3. The only difference with Fig. 4.15 is that an arrested state (a gel) is found at high polymer concentrations (j)p (or large depletion attraction) [19] (P.A. Smith, S.U. 

Dawson KA (2002) The glass paradigm for coQoidal glasses, gels, and other arrested states driven by attractive interactions. Curr Opin CoQoid Interface Sci 7 218... 

When looking into polyelectrolyte complex formation, it is important to consider non-ideal thermod mamics. This is so since at least one of the components in the complex will typically have a large molecular weight which may lead to slow kinetics, especially in concentrated regimes. Systems where the two major components have a reasonable amount of charge will be strongly coupled and may additionally lead to kinetically arrested states which can be studied at the single-molecule level. 

Colloid Dynamics and Transitions to Dynamically Arrested States 5... 

Thus, for a given system one first determines 5 p(A ), as well as the matrices c, h, and X needed in these equations, and then numerically solve the v equations for the v parameters to classify the resulting state. For a binary mixture, for example, the solution Yi = Y2 = corresponds to a fully ergodic state, whereas a finite solution for both of these parameters corresponds to a fully arrested state. Under some conditions we also expect mixed states in which the particles of one species are arrested (e.g., finite Y2). while the other particles remain mobile (Yi = >) In this manner one may scan the state space to determine the regions where these different dynamic states occur, and the boundaries between them. Of course, mixtures with more than two components will present richer dynamic arrest phase diagrams. 

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