Passive leg raising (PLR) represents an endogenous volume challenge that can be used to predict fluid responsiveness.
In contrast to a mechanical breath that normally reduces CO, passive leg-raising causes an endogenous fluid challenge that will increase CO in responders.
In such problematic cases, PLR, by acting as an endogenous volume challenge, represents a helpful tool for predicting fluid responsiveness [ 2].
Increasing the dose of NE significantly augments cardiac output by 11 to 17% [ 21], suggesting NE might recruit some blood from the large venous unstressed volume as another method of "endogenous fluid challenge".
Macrophages are capable of assuming numerous phenotypes in order to adapt to endogenous and exogenous challenges but many of the factors that regulate this process are still unknown.
When stimulated by endogenous and exogenous challenges, the paraventricular nucleus of the hypothalamus increases its production of corticotropin-releasing hormone (CRH), which in turn promotes the release of adrenocorticotropin (ACTH) by the anterior pituitary, leading to an increase in the secretion of glucocorticoids, including cortisol, by the adrenal cortex.
The effective use of therapeutic peptides derived from endogenous proteins is challenged by the lack of optimal delivery strategies.
Whenever an endogenous or exogenous challenge is perceived as unpleasant, aversive or threatening, a series of systems and processes is activated that generates a coordinated response to that particular challenge, or stressor.
In this study, therefore, we looked for relative stable endogenous reference gene challenging a 17,000 cDNA clone data base against approximately 400 specimens that included a broad variety of normal and neoplastic tissues as well as cell lines.
Unfortunately, the climatic conditions in Sub-Saharan Africa make the extraction of endogenous DNA still challenging but new methods developed in the last few years are promising as recently showed (Morris et al. 2014; Sirak et al. 2015).
