Water, doubly labeled

A third aspect concerns heat loss mechanisms. Most animals lose heat either by sweating or by panting. Doubly labeled water studies in humans (Schoeller 1988 Wong et al. 1988) indicate that respiratory waters (mouth and nasal) have 5 0 values that can be 10%o to 20%o lower than sweat. Thus, animals that pant could be expected to increase their body water 5 0 compared to animals that sweat. 

Schoeller, D.A. 1988 Measurement of energy expenditure in free-living humans by using doubly labeled water. Journo/of Nutrition 118 1278-1289. 

The energy intake by an organism plus or minus any change in body mass or composition. Lifson and McClin-tock introduced the use of doubly labeled water ( H20 and H2 0) to estimate energy expenditure. In this strategy, is lost from the body as labeled water and carbon... 

Trabulsi, J. and Schoeller, D. A. (2001). Evaluation of dietary assessment instruments against doubly labeled water, a biomarker of habitual energy intake. Am. J. Physiol. Endocrinol. Metab. 281, E891-E899. 

Fig. 31.2. Agarose gel electrophoresis of doubly labeled PCR product (lane 2) obtained from Salmonella enterica serovar Typhimurium ATCC 14028 with the doubly labeled primer set IS200. Lane 3 Molecular weight marker (OX174-Hinf I genome). No band was obtained with sterile water used as a negative PCR control (lane 1).

If D20 is used instead of water, this method provides a straightforward access to doubly labeled products. The reaction mechanism seems to proceed via hydrogen transfer from 42 to the late-transition metal complex. This results in the formation of a hydrido metal complex that hydrogenates the alkene or alkyne substrate. Theoretical calculations strongly support this mechanistic proposal by suggesting an activation energy of only 17.3 kcal mol-1 for the HAT [83]. 

The tetrahedral intermediate T can eliminate any one of the three -OH groups to reform either the original carboxylic acid or labeled caiboxylic acid. Further reaction of water with mono-labeled carboxylic acid leads to the doubly labeled product. 

Further biosynthetic studies by Cane et have shown that the conversion of farnesyl pyrophosphate (15) into nerolidyl pyrophosphate (16) proceeds by a net syn (suprafacial) process and that the subsequent cyclization to cyclonerodiol (17) occurs in a trans manner (Scheme 4). This careful piece of work was achieved by incorporation studies with doubly labelled nerolidol and mevalonate precursors and then by ascertaining the chirality of the acetate derived by Kuhn-Roth oxidation through enzymatic conversion (malate synthase/fumarase incubation) into labelled malate. In a subsequent series of experiments with labelled precursors, Cane et have confirmed that (i) only the C-7 hydroxy-group in cyclonerodiol is derived from water whereas the C-3 hydroxy-group is derived... 

Doubly Labeled Water Technique for Determining Energy Expenditure Issues in Energy Nutiiticn Refetences Bibliography... 

DOUBLY LABELED WATER TECHNIQUE FOR DETERMINING ENERGY EXPENDITURE... 

The use of direct calorimetry is not a convenient technique, since it requires a specially constructed room and the confinement of human subjects for a day or longer in the room. The doubly labeled water technique offers a convenient alternative, providing that one has a machine to perform isotope ratio mass spectrometry. The doubly labeled water technique is used to measure the rate of total CO2 production in the body. This number alone is not sufficient to allow one to calculate the total energy expenditure. But the value for COj production (moles COi/day), along with the RQ, allows one to calculate the oxygen consumption using the following formula ... 

The doubly labeled water method is used to determine the moles of COi produced as follows. The human subject drinLs a known quantity of deuterated water ( HjOj and oxygen-18 labeled water Hydrogen-2 is deuterium. 

The doubly labeled water technique measures CO production, and not O production. Because the heal created per mole of expired CO differs between the three major fuels (carbohydrate, fat, protein), the calculation of energy expenditure requires a knowledge of the Lntemal fuel being oxidized. Thus, the doubly labeled water technique, coupled with infomnatior from RQ measurements, may be used instead of the method of indirect calorimetry (using an insulated chamber to measure heat production) to determine total energy production over the course of several days. 

Since the doubly labeled water technique can be used to determine total body water, the method can be used to estimate the fat-free naass, as defined in the Obesity chapter. In brief, with a knowledge of the amount of total body water, and the assumption that normal subjects have a fat-free mass that is about 73% water, one can calculate the amount of fat-free mass. Further details are in the Obesity chapter... 

Coran, M., Poehlman, E., and Danforth, E. (1994). Experiinental reliability of the doubly labeled water technique. Am. J. Ph-pioi 29, E510-E5I5. 

Calazel, C. M., Young, V., Evans, W., and Roberts, S. (J993). Effect of fasting and feeding on measurement of carbon dioxide production using doubly labeled water. ]. Appl. Physiol. 74, 1824-J829. 

Roberts, S- 0., Coward, W Schlingenseipen, K., Nohiia, V, and Lucas, A. (1986). Comparison of the doubly labeled water ( H2 0) method with indirect calorimetry and a nutrient balance study for simultaneous determination of energy expenditure, water intake, and metabolisable energy intake in preterm infants. Am.. Clin. Natr. 44,315-322. 

Schocller, , A- (1983). Energy expenditure from doubly labeled water Some fundamental considerations in humans. Am.. Clin. Wjdr. 3B, 999-1005. 

Schoeller, D. A., and Hnilicka, J. M. (1996). Reliability of the doubly labeled water method for the measurement of total daily enei v expenditure in frce living humans. /.. NFulr. 126, 348S-354S. 

SchoeKer, D. A., and Santen, E. (1982). Measurement of energy expenditure in humans by doubly labeled water method. /. Appl Physiol 53, 955-959. 

Dot blot lest, 218-219, 220, 290, 935 Double-isotope technique, calcium absorption by, 769 Double-stranded DNA,sffdsDNA Doubly labeled water technique, 303-305 DPA, see Docopentaenoicr acid Dnig nesislanee, in molecular clonittg, 946 Dry beriberi, 604, 606 dsDNA (double-stranded DNA), 13,34, 591,937,938... 

ATP calculation, 278-285 calculating energy expenditures, 297-299 bomb calorimeter 297-299 direct calarimefay, 300-301 doubly labeled water technique, 303-305 indirect calorimetiy, 299 energy nutrition, 305-306 metabolic rate, 301 -333 qbrsity and, 295,297 luspiratoty quotient, 274-305 units of, 274-276... 

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