Cellular fluid, compartments

The whole of a multi-cellular organism is contained by outer cell layers, which are described in biology texts, and maintained by connective tissue. Connective tissue is a novel, external biopolymer structure of multi-cellular organisms found within their new extracellular, circulating fluid compartments (see Section 8.9). As mentioned there, the main connective tissues, covalently cross-linked structures, are (1) those of plants, celluloses (polysaccharides), often cross-linked by lignin (2) those of lower animals and insects, mixed cross-linked polysaccharides and... 

The cytosol is the fluid compartment of the cell and contains the enzymes responsible for cellular metabolism together with free ribosomes concerned with local protein synthesis. In addition to these structures which are common to all cell types, the neuron also contains specific organelles which are unique to the nervous system. For example, the neuronal skeleton is responsible for monitoring the shape of the neuron. This is composed of several fibrous proteins that strengthen the axonal process and provide a structure for the location of specific membrane proteins. The axonal cytoskeleton has been divided into the internal cytoskeleton, which consists of microtubules linked to filaments along the length of the axon, which provides a track for the movement of vesicular material by fast axonal transport, and the cortical cytoskeleton. 

Except for respiratory and dermal insensible water-vapor losses, all remaining water lost by the body contains electrolytes, mainly sodium and chloride. The normal cation and anion constituent composition of the fluid spaces is given in Table IV. In the extracellular fluid space, sodium is the major cation and chloride the major anion. Those two ions constitute 95 of the extracellular fluid osmolality. Changes in plasma sodium concentration reflect changes in extracellular fluid volume. Potassium is the major cellular cation and phosphates and proteins comprise the major anions. The total cellular osmolality (175 + 135 = 310 mosraol/kg H2O) is equal to the total extracellular osmolality (155 + 155 = 310 mosmol/kg HaO) therefore, equal total osmotic concentrations are maintained between two fluid compartments of widely different ionic contents (Table IV). 

Figure 1. Cellular and extracellular (plasma and interstitial) fluid compartments.

The cytotoxic hypoxia of acute CN intoxication affects the energy-dependent processes controlling cellular ionic homeostasis and the ionic disequilibrium normally maintained between the intracellular and extracellular fluid compartments (Maduh et al., 1993). In isolated cell preparations, the cellular ionic disruption results in marked cellular acidosis and accumulation of cytosolic Ca++ (Bondy and Komu-lainen, 1988 Li and White, 1977 Nieminen et al., 1988). This may result in disturbances of Ca++-activated lipolytic enzyme activity, peroxidation of membrane phospholipids, changes in transmitter release and metabolism and effects on other Ca++-modulating cell signaling systems. Johnson etal. (1986) found that CN significantly... 

When a drug is administered, it does not achieve an equal concentration throughout the body. Unless a drug is injected directly into the blood stream it will be absorbed from its site of administration, then enter the systemic circulation and be transported to the tissues in plasma. The body can be considered to be made up of aqueous and lipid compartments. Lipid compartments include all cell membranes and adipose tissue. Aqueous compartments include tissue fluid, cellular fluid, blood plasma and fluid in places like the central nervous system, the lymphatic system, joints and the gastrointestinal tract. The distribution of a drug into these different compartments depends on many factors. 

Water distributes between the different fluid compartments according to the concentration of solutes, or osmolality, of each compartment. The osmolality of a fluid is proportionate to the total concentration of all dissolved molecules, including ions, organic metabolites, and proteins (usually expressed as milliosmoles (mOsm)/kg water). The semipermeable cellular membrane that separates the extracellular and intracellular compartments contains a number of ion channels through which water can freely move, but other molecules cannot. Likewise, water can freely move through the capillaries separating the interstitial fluid and the plasma. As a result, water will move from a compartment with a low concentration of solutes (lower osmolality) to one with a higher concentration to achieve an equal osmolality on both sides of the membrane. The force it would take to keep the same amount of water on both sides of the membrane is called the osmotic pressure. 

Osmotic effects are very important from a physiological standpoint. This is because biological membranes including the membrane of red blood cells behave like semipermeable membranes. Consequently, when red blood cells are immersed in a hypertonic solution (e.g., D5 A NS or D5NS), they shrink as water leaves the blood cells in an attempt to dilute and establish a concentration equilibrium across the blood cell membrane. Thus, when hypertonic solutions are administered into the blood stream, the fluid moves from interstitial and cellular space into the intravascular space. Conversely, when cells are placed in hypotonic environment (e.g., V2 NS), they swell because of the entry of fluid from the intravascular compartment, and may eventually undergo lysis. 

Although it has been known from the mid-19th century that cations were not distributed equally between the intra and extra cellular compartments of animal cells—the cytoplasm of which contained much more potassium and less sodium than extracellular fluid—for more than 100 years the possibility that this was a... 

Vanadate transport in the erythrocyte was shown to occur via facilitated diffusion in erythrocyte membranes and was inhibited by 4,4 -diisothiocyanostilbene-2,2 -disulfonic acid (DIDS), a specific inhibitor of the band 3 anion transport protein [23], Vanadium is also believed to enter cells as the vanadyl ion, presumably through cationic facilitated diffusion systems. The divalent metal transporter 1 protein (called DMT1, and also known as Nramp2), which carries iron into cells in the gastrointestinal system and out of endosomes in the transferrin cycle [24], has been proposed to also transport the vanadyl cation. In animal systems, specific transport protein systems facilitate the transport of vanadium across membranes into the cell and between cellular compartments, whereas the transport of vanadium through fluids in the organism occurs via binding to proteins that may not be specific to vanadium. 

To deal with the array of choices just outlined, samples have been subdivided into three groups. In group I (see Fig. S.l) are samples that contain both a cellular and an extracellular compartment. The extracellular compartment can contain low molecular weight compounds such as the nutrients found in a fermentation broth, as well as macromolecular materials such as collagen or proteoglycans found in tissues. Also included in this extracellular compartment are fluids, such as tears, saliva, and urine. 

In group I, we considered the question of obtaining an activity from a tissue or organ, from a biological fluid, or from cultured cells. The primary task in all these samples was the separation of the extracellular and cellular compartments. Next, the problem of separation of the different cell types within the cellular compartment was considered. In the section that follows, we will open the cell for a look inside. However, let us first consider briefly the surface of the intact cell and the problems associated with the assay of any activities that might be located there. 

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