Depolarisation concepts

Polarisation. In the event that e.e.m. takes place then the emission from the trap, excimer in the case of pure polymers, should be completely depolarised. Some time ago data was published on the emission of excimer for both polystyrene and poly(a-methyl styrene) indicating polarised emission (8) and therefore little e.e.m. More recently Phillips questioned the validity of the data and reported mesurements which suggest the excimer emission is depolarised (9 ). An experimental difference between the two sets of data is apparent - Phillips solutions were more dilute than these used in ref. 8. The range of concentrations has subsequently been extended with the results shown in Figure 1. A possible explanation for the effect of concentrations and molecular weights on the extent of polarisation of excimer emission is that the rate of rotational relaxation of this bulky entity becomes slower than the emission life-time as these two parameters increase. It is difficult to reconcile the concept of e.e.m. with polarised excimer emission. 

The direct measurement of the time course of the influx of Na during a depolarising rectangular voltage-clamp pulse, and during an action potential discussed in Section 3b, resolved the question of specificity of the voltage-clamp measurements, and the concept of two independent kinetic components in the membrane currents, each representing an ionic pathway with different ionic selectivity, was established without doubt. 

The peroxynitrite generator SIN-1 (0.5 mM) induced apoptosis both in src oncogene-transformed and non-transformed rat fibroblasts 208 F, indicating that peroxynitrite is no selective apoptosis inducer per se, but that selective apoptosis induction in transformed cells by NO is achieved through selective peroxynitrite generation (Heigold et al. 2002). The interaction of NO with target cell derived superoxide anions represents a novel concept for selective apoptosis induction in transformed cells. Apoptosis induction mediated by NO involves mitochondrial depolarisation and is blocked by Bcl-2 overexpression. 

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