Uptake dietary

Thompson, E. M., Nafpakdtis, B. G., and Tsuji, F. I. (1988). Dietary uptake and blood transport of Vargula (crustacean) luciferin in the bioluminescent fish, Porichthys notatus. Comp. Biochem. Physiol., A comp. Physiol. 89A 203-209. 

Bohm, F, R Edge, M Burke, and TG Truscott. 2001. Dietary uptake of lycopene protects human cells from singlet oxygen and ntirogen dioxide—ROS components from cigarette smoke. J Photochem Photobiol B 64 176-178. 

Yamada, H., M. Tateishi, and K. Takayanagi. 1994. Bioaccumulation of organotin compounds in the red sea bream (Pagrus major) by two uptake pathways dietary uptake and direct uptake from water. Environ. Toxicol. Chem. 13 1415-1422. 

Clark, K.E. and D. Mackay. 1991. Dietary uptake and biomagnihcation of four chlorinated hydrocarbons by guppies. Environ. Toxicol. Chem. 10 1205-1217. 

Some introductory comments on the conceptual basis of SPMD uptake (ku) and release (ke) rate constants and the associated sampling rates (i.e., Rs) are in order. The can be conceptualized as the volume of air or water cleared of chemical per unit sampler mass or volume per unit time (e.g., mL g d or mL mL d ) and Rs is the volume of air or water cleared per unit time (e.g., L d ). Thus, the only difference between ku and Rs is that Rs is not normalized to a unit mass or unit volume of sampler. In the context of organism exposure (see Section l.L), the SPMD is equivalent to the encounter volume times the fractional bioavailability of the chemical (which excludes dietary uptake). The release rate constant (d ) is equal to kuK J. 

The primary role of SPMDs and other passive samplers is to provide convenient, powerful analytical tools for determining dissolved and vapor phase HOC concentrations in environmental systems. This chapter has shown that they are also useful as biomimetic screening tools for estimating exposure of organisms to bioconcentratable compounds and for deriving BCFs based on EP theory. Even for those chemicals that are present at vanishingly small amounts in the dissolved phase and are primarily accumulated via the dietary uptake, SPMDs generally extract sufficient amounts of residues for analysis. 

Up to now, the TTC concept has only been developed and used for systemic effects following oral exposure (dietary uptake). For industrial chemicals, the predominant exposure is to workers and consumers via inhalation and/or by skin contact. Toxic endpoints of concern for industrial chemicals such as irritation and sensitization relevant for skin and lung are therefore not covered by the TTC concepts developed up to now. 

Johnson JR, Lamothe ES. 1989. A review of the dietary uptake of Th. Health Phys 56 165-168. 

Loftus, N.J., Woolen, B.H., Steel, G.T., Wilks, M.F. Castle, L. (1994) An assessment of the dietary uptake of di-2-(ethylhexyl) adipate (DEHA) in a limited population study. Food chem. Toxicol, 32, 1-5... 

Barber, M.C. (2008) Dietary uptake models used for modeling the bioaccumulation of organic contaminants in fish. Environ. Toxicol. Chem., 23 (4), 755-777. 

Burreau S, Axelman J, Brogman D, et al. 1997. Dietary uptake in pike Esox incius) of some polychlorinated biphenyls, polychlorinated naphthalenes and polybrominated diphenyl ethers administered in natural diets. Environ Toxicol Chem 16 2508-2513. 

Kierkegaard A, Balk L, Tiamlund U, et al. 1999. Dietary uptake and biological effects on... 

FIGURE 21-44 Regulation of cholesterol formation balances synthesis with dietary uptake. Glucagon promotes phosphorylation (inactivation) of HMG-CoA reductase insulin promotes dephosphorylation (activation). X represents unidentified metabolites of cholesterol that stimulate proteolysis of HMG-CoA reductase. 

Cholesterol is both absorbed from the intestinal tract and synthesized from acetate via squalene, principally in the liver. The quantities produced are substantial. Daily biosynthesis is 600 mg, and dietary uptake may supply another 300 mg.182 Not only is there a large amount of cholesterol in the brain and... 

Dietary Uptake Efficiency or Chemical Assimilation Efficiency... 

To enable a comparison of hazards from chemicals a Hazard Index (HI) can be calculated as the ratio to the ADI. In addition to dietary uptake the possible pathways of entry of POPs for humans are... 

Wagman, N., Strandberg, B., Tysklind, M. (2001) Dietary uptake and elimination of selected polychlorinated biphenyl congeners and hexachlorobenzene in earthworms. Environ. Toxicol. Chem. 20, 1778-1784. 

In the absence of inadequate endogenous synthesis, vitamin D must be obtained from dietary sources or from supplements. Few foods contain vitamin D except for the flesh of fatty fish (salmon, mackerel, sardines), fish liver oils, and eggs from hens fed feed enriched with vitamin D. In the United States, all commercially produced milk is fortified with vitamin D2 at a level of 400 IU/L (1 IU = 0.025 fig of vitamin D3). Therefore, in the United States (and other economically advanced countries) most dietary vitamin D is obtained from milk and other vitamin D2-fortified foods. Both vitamin D2 and vitamin D3 are converted at the same rate to 25-hydroxyvitamin D by a hydroxylase in the liver and are equally active as a prohormone. Because dietary uptake of vitamin D is dependent on normal fat absorption, conditions in which fat malabsorption is present can result in vitamin D deficiency. Because breast milk contains little vitamin D, vitamin D deficiency can occur in infants who are solely breastfed, are not exposed to adequate sunlight, and are not receiving vitamin D supplements. The adequate intake of vitamin D for children is 5 pg/day (200 IU/day) (Table 30-2). 

Nichols JW, Fitzsimmons PN, Whiteman FW. 2004a. A physiologically based toxicokinetic model for dietary uptake of hydrophobic organic compounds by fish. II. Simulation of chronic exposure scenarios. Toxicol Sci 77 219-229. 

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