Physiology, question water

Our questions broadened to consider how the transport and metabolic capabilities of these aquatic species compare with those of mammalian species. One reason for asking such a question is to assess whether the presence or absence of these capabilities alters the ability of fish to survive in toxic environments. Survival mechanisms fall into two catagories - behavioral and physiologic. An example of a behavioral mechanism could be as simple as a fish avoiding that area of a stream which contains toxic quantitites of phenol. When external perturbations caused by pollutants are small, homeostatic mechanisms such as those of the liver and kidney, allow fish to adapt to the body of water in which they exist. The problem then is related to defining the limits to which homeostatic phenomena can be stressed in aquatic species. An important reason to establish such information in fish is that bodies of water are the "ultimate sink" for a number of pollutants (12). Thus, while a behavioral response such as removing itself from a toxic environment is invariably available to a mammalian species, this type of response is impossible for a fish if a toxic xenobiotic occurs uniformly throughout an entire body of water. 

In addition, the reversibility of phase transition in lipid-water systems has been studied [30]. It was observed that the relaxation times in the transition region and the lifetimes of the metastable phases are similar, and sometimes significantly longer than the times characteristic of the biomembrane processes. The question arises as to the physiological significance of the equilibration that occurs a long time after lipid phase transition. 

Our treatment of basic principles of water-solute relationships involves a bottom-up approach that begins with a basic physical-chemical analysis of how fundamental water solute interactions have set many of the boundary conditions for the evolution of life. We discuss how the properties of macromolecules and micromolecules alike reflect selection based on such fundamental criteria as the differential solubilities of different organic and inorganic solutes in water, and the effects that these solutes in turn have on water structure these are two closely related issues of vast importance in cellular evolution. With these basic features of water-solute interactions established, we will then be in a position to appreciate more fully why regulation of cellular volume and the composition of the internal milieu demands such precision. We then can move upwards on the reductionist ladder to consider the physiological mechanisms that have evolved to enable cells to defend the appropriate solutions conditions that are fit for the functions of macromolecular systems. This multitiered analysis is intended to help provide answers to three primary questions about the evolution and regulation of the internal milieu ... 

An initial answer to this question is given by data found in the four panels of figure 6.3. Each data set illustrates the effects of one or more inorganic ions on the activity of a physiological process. In sum, these data provide a strong case for the lack of fitness of inorganic ions as osmolytes whose concentrations are varied under water stress. 

One of the major questions in this area is how the same active site and catalytic machinery can be so specific for its physiological substrate but yet still be promiscuous. The authors outline five scenarios to address this question including conformational plasticity, the same but suboptimal interactions, different protonation states, different subsites, alternative cofactors, and the assistance of water. Various models are also discussed to explain how low-level catalytic activities can spawn new activities. 

We conclude that a chain of hydrogen-bonded water molecules is able to translocate protons at a rate sufficient for measured ATP synthesis if the proton supply from the bulk phase is adequate. In the physiological pH range, the question of proton supply to a putative proton channel becomes... 

The Tractatus Quinque concerned itself with other scientific questions beyond the medical, physiological, and chemical. For example, Mayow discussed the origins of water spouts as due to air turbulence (see Figures 151 and 152 see also Benjamin Franklin s studies of these phenomena and Figure 119 later in this book). Mayow s explanation of lightning and thunder are reminiscent of those of Paracelsus and imagine explosions between nitro-aerial spirit and sulphureous matter in the atmosphere. 

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