Water, body composition

Equalizing basin A holding basin in which variations in flow and composition of liquid are averaged. Such basins are used to provide a flow of reasonably uniform volume and composition to a treatment unit. Also called a balancing reservoir. Estuaries Bodies of water which are located at the lower end of a river and are subject to tidal fluctuations. 

B. Friss-Hansen, Body water compartments in children during growth and related changes in body composition, Pediatrics, 28, 169 (1961). 

The volume of distribution of many drugs is significantly increased or decreased in patients with CKD. Changes result from altered protein or tissue binding, or pathophysiologic alterations in body composition (e.g., fractional contribution of total body water to total body weight). 

Body composition 1 Total body water 1 Lean body mass T Body fat or i Serum albumin <-> or T -Acid glycoprotein (T by several disease states)... 

During development, marked changes in body composition occur. Alterations in the total body water (TBW), extracellular water (ECW) and body fat pools are illustrated in Fig. 1. The most dynamic changes occur in the first year of life with the exception of total body fat which in males is reduced by approximately 50% between 10 and 20 years of life. 

It is possible to predict what happens to Vd when fu or fur changes as a result of physiological or disease processes in the body that change plasma and/or tissue protein concentrations. For example, Vd can increase with increased unbound toxicant in plasma or with a decrease in unbound toxicant tissue concentrations. The preceding equation explains why because of both plasma and tissue binding, some Vd values rarely correspond to a real volume such as plasma volume, extracellular space, or total body water. Finally interspecies differences in Vd values can be due to differences in body composition of body fat and protein, organ size, and blood flow as alluded to earlier in this section. The reader should also be aware that in addition to Vd, there are volumes of distribution that can be obtained from pharmacokinetic analysis of a given data set. These include the volume of distribution at steady state (Vd]SS), volume of the central compartment (Vc), and the volume of distribution that is operative over the elimination phase (Vd ea). The reader is advised to consult other relevant texts for a more detailed description of these parameters and when it is appropriate to use these parameters. 

FGETS is parameterized for a particular fish species by means of two morphological/ physiological databases that delineate the fish s gill morphometry, feeding and metabolic demands, and body composition. Presently, joint water and food exposure is parameterized for salmonids, centrarchids, cyprinids, percids, and ictalurids. The copy of the model can be obtained from the USEPA at web site ftp //ftp.epa.gov/epa ceam/ wwwhtml/ software.htm. 

Woo, N.Y.S., Bern, H.A. and Nishioka, R.S. (1978). Changes in body composition associated with smoltification and premature transfer to sea water in coho salmon and ring salmon. Journal of Fish Biology 13,421-428. 

Two imaging systems, dual energy X-ray absorptiometry scanning (DEXA) and magnetic resonance imaging (MRI), allow for longitudinal studies of whole body composition. DEXA measures bone mineral density and content, fat content, and lean content in anesthetized mice. Echo MRI from Echo Medical System, Houston, TX, is used to measure whole body composition parameters such as total body fat, lean mass, body fluids, and total body water in live mice without the need for anesthesia or sedation (15). The MRI technology is more rapid, less than a minute to scan one mouse, than DEXA which takes about 5 min per mouse. 

Several methods are available to evaluate a patient s actual body composition rather than total body mass. Skin-fold measurement may be of value in evaluating subcutaneous adiposity (adipose tissue accumulation) proper technique is required for reliable results. Other anthropomorphic measurements such as bioelectrical impedance, dual-energy x-ray absorptiometry, and total body water immersion are also available.These last techniques are often of value in research studies, but it is clinically impractical to use them routinely (Elberg et al., 2004). 

The action of winds mixes the atmosphere so that the composition of the dry atmosphere is fairly constant over the entire Earth. Water vapour, though an important component of the atmosphere, is not listed in the table. The quantity of water vapour in the air, or humidity, is variable. In desert climates, the quantity of water vapour will be very small (low humidity). In tropical areas, or near large bodies of water, the quantity of water vapour in the air can be quite substantial (high humidity). 

Measurements of body composition consist of direct and indirect methods. Direct methods include measures of body protein, water, fat, and ash (minerals). An alternative direct approach is measurement of individual tissue weights. While these methods are unambiguous and preferred, they are generally limited to studies with animals. In non-sacrificial beings, direct determinations of tissue weights are impossible, and determinations of body composition are restricted to use of indirect, noninvasive methods. 

Anderson, E. C. (1963) Three-component body composition analysis based on potassium and water determinations. Ann. 

Body composition, especially water and fat content, are also highly age dependent (Figure 23.2) (24). Total body water accounts for a larger fraction of body weight in newborns than in older children and adults. There is also a larger fraction of extracellular water at birth. As a result of this change and... 

Sheng, H--P and Huggins, R. A. (1979). A review of body composition studies with emphasis on total body water and fat. Am.. Clin. Nutr. 32, 630-647. 

Body composition 1 lean body mass 1 body fat 1 body water... 

To better understand changes in drug disposition, the pediatric population needs to be categorized into various groups (Table 1) because children vary markedly in their absorption, distribution, metabolism, and elimination of medications. This occurs because neonates, infants, children, adolescents, and adults have different body compositions (i.e., as to their percentages of body water and fat) and have their body organs in different stages of development. 

Chemical Composition of Bacteria.—The quantitative chemical composition of bacteria is subject to wide variations, dependent upon the nutritive materials furnished them. About 80 to 85 per cent, of the bacterial body is water proteid substances constitute about 50 to 80 per cent, of the dry residue. When these are extracted, there remain fats, in some cases wax, in some bacteria traces of cellulose appear, and the remainder consists of i to 2 per cent. ash. 

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