That is not surprising in itself, but it means that the virus must have become endogenous fairly recently, otherwise it would not look so similar to its free-living counterpart.
While the functional role of electrophysiology in stem cell biology is poorly understood, it has become clear that endogenous ion flows represent a powerful set of signals by means of which cell proliferation, differentiation, and migration can be controlled in regeneration and embryonic morphogenesis.
Furthermore, it has become clear that endogenous damage or danger signals [ 45] also lead to inflammation [ 46] and evidence now supports their role in the response to pathogens [ 47].
Although CSCs (cardiac cells proven to have stem and/or progenitor characteristics) can be isolated and amplified in vitro or stimulated to differentiate in situ, it has become reasonable to exploit this endogenous regenerative potential to replace the lost muscle with autologous functional myocardium.
Over the past 20 years, major advances have been made toward understanding the role of nitric oxide (NO) in the ischemic biology of the heart and it has become clear that NO, either endogenous or exogenous, represents one of the most important defenses against myocardial ischemia and reperfusion injury.
Use of tissue-specific promoters has become a powerful tool for studies on endogenous gene expression [ 22] and to analyse the function of promoters [ 9, 23- 25] and transgenic fish have become an established technique in developmental analyses.
The targeting of them to tumour cells has become an interesting new concept to augment endogenous anti-tumour reactivity but little is known so far about the mechanisms involved (Choi et al, 1996).
To address this question we turned to Drosophila eye development, which has become a powerful tool for analyzing the effects of both endogenous and exogenous gene function (Thomas and Wassarman, 1999).
The trouble lies however in that, to deal with the monotonicity constraints that typically intervene in the analysis, it has become customary the adoption of strong differentiability assumptions with regards to variables that are endogenous to the problem.
The host defense system has become very efficient by acting at both transcriptional and post-transcriptional levels, in both exogenous and endogenous sequences, and through ping-pong mechanisms or systemy (in plants and nematodes) [ 146].
