Water balance, regulation

Cells exposed to excessive levels of salinity have to acquire essential nutrients from a milieu with a preponderance of ions that are potentially toxic and non-essential. In this ionic environment the success of a plant cell will require intracellular tolerance and/or specific acquisition of nutrients essential for normal metabolic functioning. The cell is also exposed to an unfavourable water balance with an absolute requirement to maintain an internal osmotic regulation that favours uptake of water into the cell (Stavarek Rains, 1984 ). 

Regulation of water balance through the effects of blood on the exchange of water between the circulating fluid and the tissue fluid... 

Sodium and water balance are primarily regulated by the kidney Reductions in nephron mass decrease glomerular filtration and subsequent reabsorption of sodium and water, leading to edema. 

Regulation of volume and water balance is of critical importance to survival in sepsis therefore it is not surprising that multiple mechanisms exist to maintain normovolemia and adequate blood pressure. 

Regulation of the osmolarity of extracellular fluid, including that of the plasma, is necessary in order to avoid osmotically induced changes in intracellular fluid volume. If the extracellular fluid were to become hypertonic (too concentrated), water would be pulled out of the cells if it were to become hypotonic (too dilute), water would enter the cells. The osmolarity of extracellular fluid is maintained at 290 mOsm/1 by way of the physiological regulation of water excretion. As with sodium, water balance in the body is achieved when water intake is equal to water output. Sources of water input include ... 

Strange, K. Regulation of solute and water balance and cell volume in the central nervous system (editorial). /. Am. Soc. Nephrol. 3 12-27,1992. 

Mineralocorticoids regulate salt and water balance in the human body. 

It has also become more evident that the loop of Henle is of major importance in the regulation of sodium and water balance, and in agreement with this, both frusemide (furosemide, fursemide, Lasilix, Lasix) and ethacrynic acid (XXIII... 

Quantitatively, proteins are the most important part of the soluble components of the blood plasma. With concentrations of between 60 and 80 g L they constitute approximately 4% of the body s total protein. Their tasks include transport, regulation of the water balance, hemostasis, and defense against pathogens. 

A similar system may operate in brain, best characterized in the rat 1 Ibeta-hydroxysteroid dehydrogenase type 2 is expressed along with mineralocorti-coid receptor (MR) in a few select areas involved in central regulation of salt, water balance, and blood pressure. There are however areas of the brain where MR is likely unprotected and may be exposed to cortisol. 

It has become Increasingly obvious to us that regulation of water balance In Insects Is one of the keys to the success of these animals In their adaptation to such a wide variety of habitats. The complexities Involved In undertaking studies of such systems may require expansion of our Interdisciplinary approach so as to Include such diverse fields as biophysics, ecology, and cell biology. The subject Is a fascinating one, perhaps all the more so due to Its complexity, and promises to open up new areas In which Interdisciplinary research will play a role. 

Insect growth regulation involving such processes as water balance or ecdysis (moulting) are processes that are insect specific but are also fundamental to insect survival. Another is chitin biosynthesis, as chitin is a major component of the insect cuticle. 

The hypothalamus, a four gram portion of the brain, receives a great deal of biochemical attention because of its function in the autonomic nervous system, in homeostasis, and in endocrine secretion. Its liberation of neurohormones that stimulate the hypophysis has already been considered in Section A,3. The hypothalamus is also involved in the regulation of the body temperature, of water balance, and possibly of glucose concentration. 

Regulates general adaptation syndrome, water balance, blood pressure, and hormone release. 

Regulates water balance Stimulates contraction of smooth muscles Increases renal tubular water reubsorption Releases anterior pituitary hormones... 

Jung J S, Bhat R V, Preston G M, Guggino W B, Baraban J M, Agre P. 1994. Molecular chracterization of an aquaporin cDNA from brain candidate osmoreceptor and regulator of water balance. Proc Natl Acad Sci USA 91 13052-13056. 

Long-term control of arterial pressure has been attributed to the kidney by virtue of its ability to couple the regulation of blood volume to the maintenance of sodium and water balance by the mechanisms of pressure natriuresis and dieresis [31]. In the presence of a... 

Angiotensin II is an octapeptide, which was initially described as a potent vasoconstrictor agent. However, its functions have since been expanded to include regulation of cell growth, inflammation, electrolyte and water balance, hormone secretion, sympathetic nervous system activity, differentiation, and apoptosis. The discovery that it is produced both systemically and locally was instrumental in establishing a pivotal role for the peptide in several disease states, including hypertension, coronary heart disease, myocarditis, congestive heart failure, atherosclerosis, and nephrosclerosis. 

Additional evidence supporting a role for melanization in water conservation comes from a study of D. polymorpha populations in Brazil (Brisson et al., 2005). Dark flies were most abundant in open, dry environments, despite the fact that these were warmer than more humid forest habitats, where light flies predominated. In this case, melanization patterns were opposite to those expected for thermal regulation, but consistent with a role in water conservation. Thus, in combination with studies by Parkash and colleagues, there is increasing evidence that melanization significantly affects water balance, at least in Drosophila. The fact that transitions in water-loss can be observed in solvent-extracted animals (Yoder and Tank, 2006) also supports a role for non-lipid layers in determining... 

Hyaluronan, despite the simplicity of its structure, has a surprisingly wide range of functions. In high concentrations, as found in the ECM of the dermis, it regulates water balance, osmotic pressure, functions as an ion exchange resin, and regulates ion flow. It functions as a sieve, to exclude certain molecules, to enhance the extracellular domain of cell surfaces, particularly the luminal surface of endothelial cells.28 It can also function as a lubricant and as a shock absorber. Hyaluronan can also act as a structural molecule, as in the vitreous of the eye, in joint fluid, and in Wharton s jelly. 

An analysis of the water balance of the Sea of Azov over the years cited shows that the components of the balance changed in the period before the regulation of the riverine runoff inl952 and after it. On average, the riverine runoff to the sea reduced by 5.7 km3/year, the supply of the Black Sea waters increased by 1.5 km3/year, and the outflow of the waters of the Sea of Azov to the Black Sea increased by 1.9 km3/year. Meanwhile, on the whole, the water balance remained almost the same. 

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