Intracellular volume

FIGURE 10-2. Distribution of body fluids showing the extracellular fluid volume, intracellular body fluid volume, and total body fluids in a 70 kg adult. Extracellular volume (ECV) comprises 14 liters of total body fluid (42 liters). Plasma volume makes up approximately 3 liters of the 14 liters of ECV. Intracellular volume accounts for the remaining 28 liters of total body fluids with roughly 2 liters being located within the red blood cells. Blood volume (approximately 5 liters) is also depicted and is made up of primarily red blood cells and plasma. (Reprinted from Guyton AC, Hall JE. Textbook of Medical Physiology. 8th ed. Philadelphia Saunders, 1991 275, with permission.)... 

Adding an isotonic solution to the extracellular fluid (ECF) does not change intracellular volume. Adding a hypertonic solution to the ECF decreases cell volume, whereas adding a hypotonic solution increases it (Table 78-1). 

Le Maguer and Yao (1995) presented a physical model of a plant storage tissue based on its cellular structure. The mathematical equivalent of this model was solved using a finite element-based computer method and incorporated shrinkage and different boundary conditions. The concept of volume average was used to express the concentration and absolute pressure in the intracellular volume, which is discontinuous in the tissue, as a... 

Thiazide diuretics are effective antihypertensive agents in black hypertensive patients and studies suggest that they cause a greater decrease in blood pressure in black patients than in whites. The better hypotensive response in black hypertensive patients is probably due to the fact that, in comparison with whites, more black patients have an expanded intracellular volume and low plasma renin activity. In developing countries, in which the majority of black people live, the cost of therapy is important. Thiazide diuretics are because of their low cost important baseline drugs in the treatment of hypertension. 

Osmotic diuretics alter Starling forces so that water leaves cells and reduces intracellular volume. This effect is used to reduce intracranial pressure in neurologic conditions and to reduce intraocular pressure before ophthalmologic procedures. A dose of 1-2 g/kg mannitol is administered intravenously. Intracranial pressure, which must be monitored, should fall in 60-90 minutes. 

Hereditary spherocytosis (HS) comprises a group of inherited hemolytic anemias characterized by chronic hemolysis with a broad spectrum of severity (Hassoun et al, 1997). The principal cellular defect is the loss of erythrocyte surface area relative to the intracellular volume, although increased osmotic frailty is also a factor. A distinctive spherical red blood cell (RBC) morphology is observed in sufferers of HS and splenic destruction of these abnormal erythrocytes is the primary cause of the hemolysis experienced (Delaunay, 1995 Palek and Jarolim, 1993). 

The intravenous administration of isotonic saline (0.9% NaCl) should be used to restore ECF and intracellular fluid volumes. Infusion of isotonic saline restores the extracellular volume deficit. Isotonic saline also restore intracellular volume deficits in patients with DKA and hypotonicity. Aggressive hydration itself... 

The influx of vanadate is a rapid (t1/2 = 57 s at 0°C), monophasic process85, but the rate of vanadate influx approaches a saturation limit at high concentrations of exogenous vanadate. Influx experiments with added EDTA (ethylenediamminetetraacetic acid) were carried out to eliminate exchange or adhesion of vanadate to the cell surface to account for the reduction of radiovanadium in the extracellular medium. The amount of vanadium accumulated in a typical influx experiment was independent of added EDTA, and raised the intracellular concentration by 2.5 mM. Therefore, there is a net uptake of vanadium into the intracellular volume of the vanadocytes in these experiments. 

Membrane-impermeant drugs will be excluded from the intracellular volume (Example Lithium, which largely resembles sodium in its distribution)... 

The X-ray microanalytical studies suggest that accumulated vanadium is not found in aqueous intracellular volumes such as vacuoles but occurs mainly in hydrophobic granules and membranes. Chelation by a mixture of ligands including water, sulfate, and tunichrome could have two effects on the lower oxidation states of vanadium, namely, to decrease the reduction potential and increase the stabilization at physiological pH. The EPR line-width studies (145), carried out on whole blood samples and based on aqua vanadyl models, may simply be inappropriate or applicable to only a fraction of the acciunulated vanadium. 

There are many specific methods available that are suitable for a certain set of conditions or for a particular experimental aim (Patterson, 1979 Griffiths, 1985). These include radiochromium labelling (radiochromium binds to viable protein and is released on cell damage/death), cellular ATP, intracellular volume (by ratios of radiochemicals), specific stains (e.g. MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide), triphenyltetrazolium chloride, neutral red), redox potential, turbidity, calorimetry (Griffiths, 1985) and biomass monitors. 

In tissues, the extracellular volume is small compared to the intracellular volume-completely the opposite of the situation when performing in vitro electroporation where the suspension medium volume by far exceeds the intracellular volume. This means that the threshold for electroporation is lowered [5]. It also means that the cell may tolerate permeabilization better, for example, since loss of ionic homeostasis may be less pronounced [6]. 

Primarily extensions of pharmacologic actions (e.g., fluid overload dilutional coagulopathy intracellular volume depletion)... 

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. 

Devreotes, 1980a), and for the hydrolysis of extracellular cAMP by phosphodiesterase finally, /i is a dilution factor equal to the ratio of extracellular to total intracellular volume. 

The assumption that R and j remain constant holds in first approximation, given that the time scale for the variation of these parameters is much longer than the time scale for relay and oscillations. The conservation relations (A2) take into account the fact that the receptor and adenylate cyclase concentrations are defined with respect to the extracellular and intracellular volumes, respectively. Equations (A2) yield the following expressions for y and cs, which supplement eqns (Al) ... 

Keys et al. (2000) explored five approaches to modeling the pharmacokinetics of di- -butyl phthalate and mono- -butyl phthalate. In a flow-limited version of the model, transfers between blood and tissues are simulated as functions of blood flow, tissue concentrations of di- -butyl phthalate or mono-n-butyl phthalate, and tissue blood partition coefficients, assuming instantaneous partitioning of the compounds between tissue and blood (Ramsey and Anderson 1984). In an enterohepatic circulation version of the model, the transfer of mono-n-butyl phthalate from the liver to the small intestine is represented with a first order rate constant (diffusion-limited) and a time delay constant for the subsequent reabsorption of mono- -butyl phthalate from the small intestine. In a diffusion-limited version of the model, the tissue transfers include a first order rate term (referred to as the permeation constant) that relates the intracellular-to-extracellular concentration gradient to the rates of transfer. This model requires estimates of extracellular tissue volume (ECV) and intracellular volume (ICV) ECV is assumed to be equal to tissue blood volume and ICV is assumed to be equal to the difference between tissue blood volume and... 

In modeling spatial dynamics, it is sometimes necessary to consider situations where the interacting species reside on different compartments. For example binding can occur when one reactant resides on the cell membrane (a binding site) and the other in an extra- or intracellular volume (e.g., the cytosol). In this case, the product is on the membrane. 

FIGURE 19.10 Extracellular stimulus currents, concept drawing. A stimulus is applied between and extracellular anode, at z = 10, and an extracellular cathode, at z = 0. Most current will flow in the extracellular volume (thick line). Some current will enter the intracellular volume (thin line). Current entering or leaving the membrane causes that portion of the membrane to become hyperpolarized (high z region) or depolarized (low z region). 

When the electric field is applied perpendicular to the fiber direction, a suspension of fibers is similar to the suspension of cells described above (in Figure 21. la, we must now imagine that the circles represent cross sections of cylindrical fibers, rather than spherical cells). The expression for the effective transverse conductivity of a suspension of cylindrical cells, of radius a and intracellular conductivity cr , placed in a solution of conductivity a, with intracellular volume fraction/, is [Cole, 1968]... 

When a small molecule is introduced into the circulation, it may attain either an intravascular, extracellular or intracellular volume of distribution( 1). The capillary walls are porous and are generally freely permeable to small molecules. Almost all compounds used as drugs are small enough to pass freely through pores in the capillary membrane, thus, in the absence of protein binding (which will be discussed below) small molecules should attain at least an extracellular volume of distribution. 

Extraction and assay of PP1 and ATP At the time of sampling 14 ml of the culture was taken for protein and cell density determination and 14 ml 1 M KOH was rapidly mixed with the rest of the culture under continuous shaking. After 30 min at room temperature the sample was put on Ice, 14 ml Ice-cold 20% tri chloroacetic acid (TCA) was rapidly mixed with It and, after standing 5-10 min at 0°C, the cell debris was separated from the medium by centrifugation at 6000 rpm for a period of 10 min. The supernatant was diluted ten times with 0.1 M glycylgly-clne, 2 mM EDTA (pH 7.75) and 10 y1 was taken for PP1 and ATP determination as described by Nyren et al. (3). For estimation of intracellular concentrations of PPi and ATP an Intracellular volume of 1.5 yl/mg protein was used according to Ref. 4. 

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