Effective osmoles

Excess effective osmoles in the extracellular fluid ° Hyperglycemic state or use of mannitol... 

An alternative is a solution of 2.5% dextrose and 0.45% sodium chloride (85Kcal/L), which, once the dextrose has been metabolized, has an effective osmolality one-half of that of plasma. It is retained better in e circulation (20% after 30 min compared with 10% for D5W) (Spalding Goodwin 1999) and can be used in the treatment of moderate plasma hypertonicity or when plasma glucose concentration is a concern. It should be noted that a rapid reduction in plasma tonicity has been associated with the development of cerebral edema, resulting in coma, seizures and death in other species (Adrogue Madias 2000a). This has not been documented in the horse. 

Since many molecules in plasma interact, the measured osmolality of a sample is an effective osmolality and is lower than the value calculated from the concentrations... 

Solutes that cannot freely cross cell membranes, such as sodium, are referred to as effective osmoles. The concentration of effective os-moles in the ECF determines the tonicity of the ECF, which directly affects the distribution of water between the extra- and intracellular compartments. Addition of an isotonic solution to the ECF will result in no change in intracellular volume because there will be no change in the effective osmolality of the ECF. Addition of a hypertonic solution to the ECF, however, will result in a decrease in cell volume, whereas addition of a hypotonic solution to the ECF will result in an increase in cell volume. Table 49-1 summarizes the composition of commonly used intravenous solutions and their respective distribution into extracellular and intracellular compartments following infusion. 

The effective osmolality of cell lysate was fit to a Langmuir expression, where OSM is the maximum stabilizing effect and K is the equilibrium constant for interaction of the stabilizers with the protoplasts. The resulting equation,... 

Maximum effective osmolality of released lysis products... 

CTC, and CTC fluorescence (excitation 400 nm, emission 430 nm) was monitored versus time at 37°C. Addition of 10 H FMLP at the arrow resulted in an abrupt decrease in CTC fluorescence. Lower panel Increasing medium osmolality by addition of either sodium sulfate (middle trace) or sodium HEPES (right trace) had little effect on the FMLP induced decrease in CTC fluorescence when compared to that seen in medium of normal osmolality (left trace). ... 

The mechanisms of the allergy-like reactions to RCM are still a matter of speculation (table 2). Anaphylaxis to RCM has been discussed to be due to a direct membrane effect possibly related to the osmolality of the RCM solution or the chemical structure of the RCM molecule (pseudo-allergy) [2], an activation of the complement system [27], a direct bradykinin formation [28], or an IgE-mediated mechanism [3]. 

In situ perfusion studies assess absorption as lumenal clearance or membrane permeability and provide for isolation of solute transport at the level of the intestinal tissue. Controlled input of drug concentration, perfusion pH, osmolality, composition, and flow rate combined with intestinal region selection allow for separation of aqueous resistance and water transport effects on solute tissue permeation. This system provides for solute sampling from GI lumenal and plasma (mesenteric and systemic) compartments. A sensitive assay can separate metabolic from transport contributions. 

Billich, C. O., Levitan, R., Effects of sodium concentration and osmolality on water and electrolyte absorption form the intact human colon, J. Clin. Invest. 1969, 48, 1336-1347. 

Sugatt, R.H. 1980a. Effects of sublethal sodium dichromate exposure in freshwater on the salinity tolerance and serum osmolality of juvenile coho salmon Oncorhynchus kisutch, in seawater. Arch. Environ. Contam. Toxicol. 9 41-52. 

FIGURE 78-1. Diagnostic algorithm for the evaluation of hyponatremia. (CHF, congestive heart failure EABV, effective arterial blood volume SIADH, syndrome of inappropriate antidiuretic hormone UNa, urine sodium concentration Uosm, urine osmolality.)... 

Preliminary Cytotoxicity Testing. An essential first step is to carry out a preliminary study to evaluate the toxicity of the test material to the indicator cells, under the conditions of the main mutagenicity test. When selecting dose levels, the solubility of the test compound, the resulting pH of the media, and the osmolality of the test solutions all need to be considered. The latter two parameters have been known to induce false positive effects in in vitro mammalian tests (Brusick, 1986). The experimental procedure is carried out as follows. 

Prepare treatment medium containing various concentrations of test compound 19.7 ml of Eagle s medium (without serum) plus 300 pi of stock concentration of compound in a preferred solvent (e.g., water, ethanol, DMSO, etc.). The final concentration of solvent other than water should not exceed 1% v/v. Normally a range of 0-5000 pg ml-1 (final concentration) is covered. For a sparingly soluble compound, the highest concentration will be the lowest at which visible precipitation occurs. Similarly, if a compound has a marked effect on osmolality, concentrations should not be used that exceed 500 milliosmoles (mosm) per kg. In addition, a pH range of 6.5-7.5 should be maintained. 

In the absence of precipitation or effects on pH or osmolality, the maximum concentration of the main mutagenicity study is a concentration that reduces survival to approximately 20% of the control value. 

Vist GE, Maughan RJ. The effect of osmolality and carbohydrate content on the rate of gastric emptying of liquids in man. J Physiol 1995 486(21 523-531. 

Angiotensin II has two effects first, as a vasoconstrictor acting via receptors on vascular smooth muscle cells, and second, it stimulates the adrenal cortex gland to produce aldosterone (a mineralocorticoid steroid hormone, see Chapter 4). Aldosterone promotes the reabsorption of sodium from the renal tubule into the bloodstream and the resulting increase in osmolality (osmotic potential) of the blood causes water reabsorption in the nephrons. The outcome is an increase in blood volume and, therefore, pressure which inhibits (by negative feedback) further renin secretion from the JGA. 

The ICH S7A states that the effects of the NCE on renal parameters should be assessed for example, urinary volume, specific gravity, osmolality, pH value, fluid/electrolyte balance, proteins, cytology, and blood chemistry determinations such as blood urea... 

Renal Effects. Urinary parameters (blood urea nitrogen, pH, osmolality, voliune, protein, sugar, and sediment) were normal in female dogs exposed to 3,3 -dichlorobenzidine (10.4 mg/kg/day) throughout a 7-year study in which female dogs were exposed to 10.4 mg/kg/day 3,3 -dichlorobenzidine. At necropsy, no histological effects to the kidneys were reported in any of the dogs (Stula et al. 1978). 

High osmolality is directly related to certain types of side-effects such as pain at the injection site, cardiovascular effects (heart rate, blood pressure) and... 

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