Functional studies with mammals

All of the above discussion on the functional properties of metabolic pathways has focused on short-term responses. The question arises of the effects of adjustments over acclimation or intermediate time courses because studies with humans and mammals dominate this field, we will refer to these as training effects rather than acclimations (the term that is used elsewhere throughout this book). 

Several classes of molecules are involved in metal homeostasis. Metallothioneins (MTs) are a family of cysteine-rich metal-binding proteins that in mammals appear to function in Zn homeostasis and protect against heavy metal toxicity and oxidative stress60. Glutathione (GSH) is a sulfhydryl-rich tripeptide that is generally involved in the protection of cells against toxicants and in the metabolism of xenobiotics71. MTs and GSH are found in fish, and their expression and functions have been conveniently studied with piscine cell lines. 

Aside from providing the targets for HIV-1-induced neuropathogenesis, researchers have also studied the normal functions served by chemokines in the nervous system. One answer to this question can be obtained by considering the evolution of chemokines and their receptors. There are a large number of chemokines that have been identified to date, more than 50 in most mammals. As far as we know, all the actions of chemokines are transduced through stimulation of a family of related, G protein-coupled receptors (Tran and Miller 2003). Research into the pattern of evolution of chemokines and their receptors has revealed that a large expansion of the chemokine family occurred in parallel with the development of a sophisticated... 

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