Medium osmolarity

The effect of medium osmolarity on the growth of GS-NSO cells was investigated by Bibila et al. [17]. Gell growth was reduced when the osmolarity was increased to 400 mOsm and completely inhibited above 500 mOsm. The specific production rate increased as the osmolarity was increased from the baseline of 270 mOsm to 300 and 400mOsm. However, as a direct result of reduced growth, the cultures at 400 mOsm reached a lower product concentration than the controls. Zhou et al. [2] noted that increases in osmolarity below 450 mOsm had little impact upon productivity, but above this level there was a rapid increase in the specific production rate. However, growth cessation occurred at this elevated osmolarity. 

Hyperosmolar medium is known to be advantageous for the production of proteins such as antibodies in animal cell cultures [70, 71]. Likewise, raising the osmolarity of MS medium using mannitol was found to improve the accumulation of foreign pro-... 

PercoU is a polyvinylpyrrolidone-coated silica sol with very low osmolarity. For cell separations therefore the osmolarity is adjusted to isotonic conditions by mixing 9 vol. Percoll stock suspension with 1vol. of 2.5 M sucrose, 1.5 M sodium chloride, or tenfold concentrated cell culture medium (e.g., 10 x RPMl). 

In experiments in which we have used medium supply for cell cultures with 800 mOsmol/kg, we have found the cellular resistance, needed to keep cellular integrity without exploding cells, to be acutely above 280 mOsmol/kg [41]. Lower osmolarities resulted in lysis of cells. The rinsing concept of Diphoterine with an osmolarity of 820 mOsmol/kg reflects a stepwise reduction of the osmolar constitution of the tissues [42]. 

In a setup of cell culture, we have found that tissue culture medium salts (Earls salts) can be replaced by NaOH or HCl and water within a range of pH 2-11.3 without changing the 350 mOsmol/kg osmolarity of the medium. Therefore, the experimental setup does not interfere by means of semipermeable membranes with the water content of the cells. 

L929 cells were exposed to osmolar stable solutions with variation of pH from 11.3 to 9.5 for 64 min. After this time, the medium was changed to normal MEM and the surviving cells were counted 24 h later. For pH over 10.75, a significant loss of cells can be detected after 1 h 24 h later, no regrowth occurs on these cells. 

Several mechanisms have evolved to prevent this catastrophe. In bacteria and plants, the plasma membrane is surrounded by a nonexpandable cell wall of sufficient rigidity and strength to resist osmotic pressure and prevent osmotic lysis. Certain freshwater protists that live in a highly hypotonic medium have an organelle (contractile vacuole) that pumps water out of the cell. In multicellular animals, blood plasma and interstitial fluid (the extracellular fluid of tissues) are maintained at an osmolarity close to that of the cytosol. The high concentration of albumin and other proteins in blood plasma contributes to its osmolarity. Cells also actively pump out ions such as Na+ into the interstitial fluid to stay in osmotic balance with their surroundings. 

FIGURE 2-13 Effect of extracellular osmolarity on water movement across a plasma membrane. When a cell in osmotic balance with its surrounding medium (that is, in an isotonic medium) (a) is transferred into a hypertonic solution (b) or hypotonic solution (c), water moves across the plasma membrane in the direction that tends to equalize osmolarity outside and inside the cell. 

Cells of E. coli can adapt to at least 100-fold changes in osmolarity. Because of the porosity of the bacterial outer membrane the osmolarity of the periplasmic space is normally the same as that of the external medium. However, the inner membrane is freely permeable only to water and a few solutes such as glycerol.b The bacterial cells avoid loss of water when the external osmolarity is high by accumulating K+ together with anions such as... 

Functioning in a somewhat different way in E. coli are 6- to 12-residue periplasmic membrane-derived oligosaccharides. These are p-1,2- and P 1,6-linked glucans covalently linked to sn-l-phospho-glycerol, phosphoethanolamine, or succinate (see Fig. 8-28).b e/f They accumulate in the periplasm when cells are placed in a medium of low osmolarity. 

Iso-osmolar or low-osmolar contrast medium is recommended, and it appears to be associated with a lower renal complication rate. Serum creatinine level should be measured 24 to 48 hours after the administration of the contrast medium. Nonsteroidal anti-inflammatory drugs and... 

Polyhedra bioactivity can be compromised due to nutrient limitations, causing abnormalities in virion development and occlusion within polyhedra (Rollinson et al., 1965 Slavicek et al., 1995 Belloncik et al., 1997). The most important aspects of culture medium selection are pH, osmolar-ity, and organic salt components. Components such as amino acids, vitamins, and carbon source (glucose for example), are typically found in the basal culture medium formulation. However, these simple formulations cannot promote cell growth themselves, unless supplemented with animal serum, normally 5-20% (v/v) fetal bovine serum (FBS) (Schlaeger, 1996). 

FIGURE 9 Effect of (a) concentrations, (b) osmolarity, and (c) medium of chitosan solution on mean serum glucose concentrations after nasal administration of lOIU/kg insulin to rats. Bars represent the standard deviation (SD) of five experiment. (Reproduced from ref. 73 with permission of Elsevier.)... 

Delayed reactions are generally benign, but not always. In a Japanese study, the incidence of delayed reactions was investigated in 6764 patients who received the low-osmolar non-ionic contrast medium iohexol intravenously (33). Delayed reactions (rash, pruritus, nausea, vomiting, fever, headache, and others) occurred in 192 patients (2.8%). There were no severe delayed reactions. A history of allergy and hay fever were risk factors for delayed adverse reactions. 

A 69-year-old man with idiopathic nasal bleeding underwent contrast-enhanced CT examination of the head with an intravenous non-ionic low-osmolar contrast medium (96). Convulsions and tremor developed 1 hour after the examination and lasted for 50 minutes. 

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