Osmolality expression

Culture medium osmolality has a large influence on animal cell culture. Hyperosmotic conditions, achieved by using salts, CO2, or concentrated media, has been shown as a low-cost method to increase specific productivity of cells. Hybridoma cultures, for instance, show improved productivity with an increase in osmolality (Oh et al., 1993). However, this method is not very popular due to the negative effects on cell growth. The drop in cell growth under hyperosmotic conditions occurs, probably, due to cell death by apoptosis. Thus, expression of anti-apoptotic genes, such as Bcl-2, could allow the use of hyperosmotic conditions to simultaneously limit cell death and increase cell productivity (Kim and Lee, 2002). 

Arricau, N., Hermant, D., Waxin, H., Ecobichon, C., Duffey, P., Popoff, M. The RcsB-RcsC regulatory system of Salmonella typhi differentially modulates the expression of invasion proteins, flagellin and Vi antigen in response to osmolality. Mol Microbiol 29 (1998) 835-850. 

Physiologists studying osmotic relationships of organisms, however, are often concerned with the total concentration of all dissolved substances, not just the concentrations of specific solutes. For expressing the total number of osmotically active particles in a solution, the concept of osmolality is commonly employed to refer to the osmotic pressure characteristic of a solution. One osmole is defined as the osmotic pressure of a 1.0 molal solution of an ideal solute. Because conditions of ideality do not pertain to the case of biological fluids, it is not possible to extrapolate precisely from chemical determinations of moles of solute per kilogram (or liter) of fluid to the osmolality of that fluid. Rather, this value must be determined empirically. 

Figure 6.18. The three common elements in the osmosensory signal transduction cascade of cells (1) osmosensors that monitor osmolality (2) signal transduction pathways that transmit the information provided by the primary osmosensors to (3) osmotic response elements that regulate gene expression and activities of proteins (enzymes and transporters) that are essential for osmotic adaptation.

The compactness of nucleosomes has been found to depend on osmolality (Bednar et al., 1995), albeit the impacts of this effect on gene expression remain to be established. Changes in chromatin structure induced by osmotic stress could be offset by alterations in histone proteins. Certain histones of mammalian cells are... 

Enzyme activity is expressed either per unit of time or per unit of creatinine. Normalization of enzyme activity per unit of volume or osmolality is not recommended because of the high degree of variability of these parameters (Price 1982 Plummer et al. 1986). 

The defining equation applies to ideal dilute solutions. The entities B are individually moving solute molecules, ions, etc. regardless of their nature. Their amount is sometimes expressed in osmoles (meaning a mole of osmotically active entities), but this use is discouraged. 

Osmolarity Where molarity is the term used to express the concentration of a solution based on the number of moles per litre, osmolarity is the term used to express the concentration of a solution based on the number of osmotically active moles per litre. The unit of osmolarity is expressed as osmoles per litre. 

Osmolality Where molality is the term used to express the concentration based on number of moles of a solute per mass of solvent, osmolality is the term used to express the number of moles of osmotically active solute particles per mass of solvent. The unit of osmolality is osmoles per kilograms. 

This non-SI expression is used to describe the number of moles of osmotically active solute particles per litre of solution (osmolL )- The need for such a term arises because some molecules dissociate to give more than one osmotically active particle in aqueous solution. 

This is based on the concept of a membrane permeable to water, but not to solute molecules. For example, if a sucrose solution is placed on one side and pure water on the other, then a passive driving force will be created and water will diffuse across the membrane into the sucrose solution, since the effective water concentration in the sucrose solution wiU be lower. The tendency for water to diffuse into the sucrose solution could be counteracted by applying a hydrostatic pressure equivalent to the passive driving force. Thus, the osmotic pressure of a solution is the excess hydrostatic pressure required to prevent the net flow of water into a vessel containing the solution. The SI unit of osmotic pressure is the pascal. Pa (=kgm s ). Older sources may use atmospheres, or bars, and conversion factors are given in Box 9.1 (p. 72). Osmotic pressure and osmolality can be interconverted using the expression 1 osmol kg = 2.479 MPa at 25 °C. 

Based on the theory of colligative properties and the principles of osmometry, it is understood that osmometer will read osmolalities and not osmolarities because colligative properties are directly proportional to the total solute concentration expressed in molality [see Eqs. (1)-(16)]. The relationship between osmolality and osmolarity and its significance can be found in the Remington s Pharmaceutical Sciences and in a review article by Deardorff. However, it is more convenient to use osmolarity because it is based on weight/volume rather than on weight/weight as in... 

Water, salt, and blood pressure are related. The blood volume is closely related to the blood pressure. A loss in blood volume can occur with water deficiency or because of extensive bleeding. The lack of enough blood to fill up the vessels of the circulatory system leads to a drop in blood pressure. A severe drop in blood pressure results in the inability of the heart to pump vital nutrients to the brain and other tissues. A loss in blood volume can also result from sodium deficiency. The concentrations of sodium and its counterion chloride must be maintained to maintain the osmotic strength of the blood plasma. Osmotic strength is expressed by the term osmolality. Osmolality is equal to the sum of the molarities of the separate particles (ions or molecules) in a liquid. For example, a solution of 1 mole of NaCl in 1 liter has an osmolality of 2.0 osmol/liter. Na and Cl ions dissociate completely in solution. Osmotic pressure develops when two solutions of differing osmolalities are placed in contact with each other but separated by a semiperme-able membrane. The walls of capillaries are semipermeable membranes. The renal... 

The experimentally derived osmotic pressure is frequently expressed as the osmolality which is the mass of solute which, when dissolved in 1 kg of water, will exert an osmotic pressure, H, equal to that exerted by 1 mole of an ideal unionised substance dissolved in 1 kg of water. The unit of osmolality is the osmole (abbreviated as osmol), which is the amount of substance that dissociates in solution to form one mole of osmotically active particles, thus 1 mole of glucose (not ionised) forms 1 osmole of solute, whereas 1 mole of NaCl forms 2 osmoles (1 mole of Na+ and 1 mole of... 

Osmotic pressure is expressed as osmolarity or osmolality. Osmolality is the concentration of body fluids. Tonicity is the effect bodily fluid has on cellular volume and is used to measure the concentration of intravenous solutions. Serum osmolality instead of tonicity is used to indicate the concentration of solutes in body fluids. 

Osmotic pressure is expressed as osmolarity or osmolality. Osmolality is the concentration of body fluids. 

The osmolality of stool "water wiU normally be that of serum (i.e., 290mosm/kg), but the contribution of electrolytes and of nonelectrolytes to the total osmolality will vary depending on the cause of the diarrhea. Fecal osmotic (osmolal) gap (FOG) expresses the difference between the theoretical normal osmolality (290 mosm/kg) and the contribution of Na and as follows ... 

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