Uptake and Release

Werner complexes can be used to form clathrates with the Cg aromatic isomers (35—42). The aromatic compounds are released upon heating. Since the uptake and release characteristics of the four Cg aromatic isomers are each different, this method has been suggested as a means of separating the isomers. 

Parent substances and metaboHtes may be stored in tissues, such as fat, from which they continue to be released following cessation of exposure to the parent material. In this way, potentially toxic levels of a material or metaboHte may be maintained in the body. However, the relationship between uptake and release, and the quantitative aspects of partitioning, may be complex and vary between different materials. For example, volatile lipophilic materials are generally more rapidly cleared than nonvolatile substances, and the half-Hves may differ by orders of magnitude. This is exemplified by comparing halothane and DDT (see Anesthetics Insectcontholtechnology). 

Another model, first introduced by Moore, et al. (2i), was used to examine the role of terrestrial vegetation and the global carbon cycle, but did not include an ocean component. This model depended on estimates of carbon pool size and rates of CO2 uptake and release. This model has been used to project the effect of forest clearing and land-use change on the global carbon cycle (22, 23, 24). 

Aggradation or degradation of biomass or soil reservoirs may also produce effects that appear to be fractionation. This is because the elemental ratios in vegetation or soil reservoirs can be very different from those of bedrock. Sufficiently large and rapid changes in these reservoirs are sometimes evident in river chemistry. For example, the uptake and release of potassium in association with the seasonal growth and loss of leaves can affect the composition of streams that drain temperate deciduous forests (Likens et al, 1977 Vitousek, 1977). 

As reactive P is transported through the terrestrial system, it is assimilated into plants and subsequently into the rest of the biosphere (2). Although many elements are required for plant life, in many ecosystems P is the least available and, therefore, limits overall primary production (Schindler, 1977 Smith et al., 1986). Thus, in many instances the availability of P influences or controls the cycling of other bioactive elements. When organisms die, the organic P compounds decompose and the P is released back into the soil-water system. This cycle of uptake and release may be repeated numerous times as P makes its way to the oceans. 

GLUT 2 Liver, pancreatic B cell, small intestine, kidney Rapid uptake and release of glucose... 

Poddar, M.K. and Dewey, W.L., Effects of cannabinoids on catecholamine uptake and release in hypothalamic and striatal synaptosomes, J. Pharmacol. Exp. Ther., 214, 63, 1980. 

Hetey, L. and Quirling, K., Synaptosomal uptake and release of dopamine and 5-hydroxytryptamine in the nucleus accumbens in vitro following in vivo administration of lysergic acid diethlamide in rats, Acta Biol. Med. Ger., 39, 889, 1980. 

Fig. 7.4. Vesicle uptake and release mechanisms V, vesicle, V, vesicle coalesced with membrane.

Calmodulin, a calcium binding protein, is involved in Ca2+-dependent regulation of several synaptic functions of the brain synthesis, uptake and release of neurotransmitters, protein phosphorylation and Ca+2 transport. It reacts with TET, TMT and TBT which then inactivates enzymes like Ca+2-ATPase and phosphodiesterase. In vitro studies indicated TBT was greater at inhibiting calmodulin activity than TET and TMT, whereas in vivo the order was TET > TMT > TBT. This may be due to the greater detoxification of TBT (66%) in the liver before moving to other organs30,31. 

Vighi, M. 1981. Lead uptake and release in an experimental trophic chain. Ecotoxicol. Environ. Safety 5 177-193. 

Sunderman, F.W., Jr., B.L. Mongillo, M.C. Plowman, and S.M. Brennan. 1990. Uptake and release of 63Ni2+ by Xenopus embryos during early cleavage stages. Biol. Metals 2 214-218. 

Crecelius, E. and D. Phillips. 1995. Uptake and release of silver from marine sediment, in A.W. Andren and T.W. Bober (organizers). Transport, Fate and Effects of Silver in the Environment. 3rd International Conference. August 6-9, 1995, Washington, D.C. Univ. Wisconsin Sea Grant Inst., Madison, WI. 

Conesa373 modeled the surfaces and defects on ceria, and based on computer simulations, determined the relative stabilities of surfaces (111) > (110) > (211) > (100). Although the formation of anion vacancy defects was suggested to be more difficult to form on the more stable (111) surface, he indicated that anion vacancy pairs, important for 02 uptake and release processes, were easiest to form on the ceria (111) surface. 

Figure 7.4 Copper uptake and release in E. hirae. The extracellular reductase CorA reduces Cu2+ to Cu+ for uptake by CopA. In conditions of copper excess CopB functions as a copper exporter. (From Solioz and Stoyanov, 2003. Reproduced with permission from Blackwell Publishing Ltd.)...

Argyle RL, Williams GC, Dupree HK. 1973. Endrin uptake and release by fingering channel (Ictalurus punctatus). J Fish Res Board Can 30 1743-1744. 

Poddar MK, Dewey WL. 1983. Kepone induced changes in the synaptosomal uptake and release of dopamine in corpus striatum and norepinephrine in hypothalamus. IRCS Medical Science Library Compendium 11 (7) 632-633. 

Uptake and release of protons can be described by the acidity constants (assuming a solution of constant ionic strength, we imply that the activity coefficients of the surface species are equal) ... 

Girvin et al. [358] evaluated the release of PCBs from electrical substation soils contaminated with transformer fluids. They observed that there are two phases to the uptake and release of PCBs with these soils. The initial phase is a rapid, labile phase that is followed by a slower, nonlabile phase. The labile phase occurs at a scale of hours to days while the nonlabile phase releases over weeks and months. Girvin et al. [422] also reviewed the effects of adsorption on the mobility of PCBs and their transport. In an example presented for a hexa-chlorobiphenyl, these authors noted that the PCB isomer would have a retardation factor Rf of 1400 for the particular case given. This means that the ground-... 

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