Intracellular fluid compound

Striated muscle is composed of multinucleated muscle fiber cells surrounded by an electrically excitable plasma membrane, the sarcolemma. An individual muscle fiber cell, which may extend the entire length of the muscle, contains a bundle of many myofibrils arranged in parallel, embedded in intracellular fluid termed sarcoplasm. Within this fluid is contained glycogen, the high-energy compounds ATP and phosphocreatine, and the enzymes of glycolysis. 

Cells have substantial chemical defenses against the UV photoproducts produced in seawater and intracellular fluids. Many organisms have antioxidants (e.g., carotenoids, ascorbate, tocopherols, anthocyanins, and tridentatols) that quench photo-oxidative reactions.64-67 Cells also have enzymes (e.g., catalase and superoxide dismutase) that can counteract the oxidative nature of peroxides and other radicals.26 Some compounds, such as the UV-absorbing pigment melanin, can act as both optical filter and antioxidant.68 The MAA mycosporine-glycine (Figure 15.3) functions in a similar dual capacity.69 The role of UV-mediated reactions in seawater relative to biological effects is an important current area of study. 

Distribution describes the movement of a compound from its site of absorption to other areas of the body. When a compound is absorbed it passes through absorptive cells into the interstitial fluid of the organ these body fluids (interstitial fluid, intracellular fluid, and blood plasma) are not isolated and separate, but represent one continuous pool. In contrast to fast-moving blood that allows mechanical transport to occur, interstitial- and intracellular fluids remain in place with a slow movement of components such as water and electrolytes into and out of cells. Any compound can leave the interstitial fluid by entering local tissue cells, the circulating blood, or the lymphatic system. After entry into... 

What is the principal type of organic compound found in intracellular fluid ... 

To allow for this effect, the physicist substitutes an effective concentration which is called the activity of a chemical in place of real concentration determined chemically. For dilute solutions such as extracellular fluid which are of primary concern in this book, concentrations and activities are sufficiently close for little error to be introduced by use of concentration. For intracellular fluid, however, the concentrations of organic compounds are relatively high and errors become significant in this situation activities should be used for accurate analysis. 

ECF, respectively). The ECF comprises interstitial fluid (15%) and plasma (5%). The total blood volume (TBV) is 8% of body water, the 3% of the body water associated with red cells being counted as part of the intracellular fluid volume. The localisation of a drug into blood cells is often studied since it provides a measure of how the compound will distribute into other tissues. Apart from water, the overall body composition is made up (approximately ) as follows water G0%, protein 18%, fat 15% and minerals 7%. 

Didanosine (ddl) is a synthetic analog of deoxyadenosine (Figure 49-2). Oral bioavailability is approximately 40% dosing on an empty stomach is optimal, but buffered formulations are necessary to prevent inactivation by gastric acid (Table 49-3). Cerebrospinal fluid concentrations of the drug are approximately 20% of seram concentrations. Serum half-life is 1.5 hours, but the intracellular half-life of the activated compound is as long as 20-24 hours. The drug is eliminated by both cellular metabolism and renal excretion. 

Oral bioavailability exceeds 80% and is not food-dependent. In children, the mean cerebrospinal fluid plasma ratio of lamivudine was 0.2. Serum half-life is 2.5 hours, whereas the intracellular half-life of the triphosphorylated compound is 11-14 hours. Most of lamivudine is eliminated unchanged in the urine (Table 49-3). 

Although it is primarily an intracellular compound, glutathione is secreted by epithelial and other cells. It may regulate the redox state of proteins in plasma and other extracellular fluids as well as within cells. In addition, glutathione released from the liver may be an important source of cysteine for other tissues. In the endoplasmic reticulum and the periplasm of bacteria glutathione functions in crosslinking thiol groups in newly formed proteins (Eq. 10-9). 

Table 10.3 lists the approximate concentrations of various inorganic nutrients in the biological fluids. In most cases, the data refer to the total concentration of the ion, including free ion and ion complexed with organic compounds. The data for intracellular calcimn and magnesiiun refer to the approximate concentration of the free, uncomplexed ions. A vital relationship revealed by the table is that Na levels are high in the plasma, and low in the cells, while K levels are low in plasma, and high in cells. 

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