Selective uptake

The selective uptake of iodide ion by the thyroid gland is the basis of radioiodine treatment in hyperthyroidism, mainly with although various other radioactive isotopes ate also used (40,41). With a half-life of eight days, the decay of this isotope produces high energy P-particles which cause selective destmction within a 2 mm sphere of their origin. The y-rays also emitted are not absorbed by the thyroid tissue and are employed for external scanning. 

VMATs are not inhibited by drugs such as cocaine, tricyclic antidqnessants and selective serotonin reuptake inhibitors that affect plasma membrane monoamine transport. Amphetamines have relatively selective effects on monoaminergic cells due to selective uptake by plasma membrane monoamine transporters, but their effect appears to be mediated by their ability as weak bases to reduce ApH, the driving force for vesicular monoamine transport that leads to efflux of the vesicular contents into the cytoplasm. 

Warenycia MW, Goodwin LR, Benishin CG, et al. 1989a. Acute hydrogen sulfide poisoning Demonstration of selective uptake of sulfide by the brainstem by measurement of brain sulfide levels. Biochem Pharmacol 38 973-981. 

RPE plays numerous functions essential for proper structure and function of retinal photoreceptors. They include the maintenance of the blood-retina barrier, selective uptake and transport of nutrients from the blood to the retina and removal of waste products to the blood, enzymatic cleavage of P-carotene into vitamin A, storage of vitamin A and its metabolic transformations, phagocytosis and molecular renewal of POS, expression and secretion of growth factors and immunomodulatory cytokines (Aizman et al., 2007 Aleman et al., 2001 Crane et al., 2000a,b Elner et al., 2006 Holtkamp et al., 2001 Leuenberger et al., 2001 Lindqvist and Andersson, 2002 Maminishkis et al., 2006 Momma et al., 2003 Strauss, 2005). 

The greatest concentration of the macular pigment is present in the avascular part of the retina. This suggests that the RPE may play the predominant role in uptake and transport of xanthophylls to the photoreceptors. Moreover, about 25% of the total retinal xanthophylls are present in the POS (Rapp et al., 2000 Sommerburg et al., 1999), which, under normal conditions, are intimately associated with the RPE. This proximity lends further support to the hypothesis of a role for the RPE in the selective uptake of carotenoids into the retina. 

Selective Uptake of All-trans P-C versus Its cis Isomers by Intestinal Cells...372... 

Hawthorne and co-workers have reported the selective uptake of homogeneous flourescein-labeled nzYfo-carboranyl oligomeric phosphate diesters nido-OPDs) by cell nuclei within 2h after microinjection. The location in the cell of nido-OPDs uptake was found to depend on the location of the carboranyl moiety in the nido-OPDs. When the carborane cage was located on a side chain attached to the oligomeric... 

Yamazaki, M., Tokui, T., Ishigami, M., Sugiyama, Y., Tissue-selective uptake of pravastatin in rats contribution of a specific carrier-mediated uptake system, Biopharm. Drug Dispos. 1996, 17, 775-789. 

Chitosan-clay bio-nanocomposites are very stable materials without significant desorption of the biopolymer when they are treated with aqueous salt solutions for long periods of time. In this way, they act as active phases of electrochemical sensors for detection of ions (Figure 1.8). The particular nanostructuration of the biopolymer in the interlayer region drives the selective uptake of monovalent versus polyvalent anions, which has been applied in electrode arrays of electronic tongues [132]. 

Y. Tani, H. Eun, and Y. Umezawa, A cation selective electrode based on copper(II) and nickel(II) hexacyanoferrates dual response mechanisms, selective uptake or adsorption of analyte cations. Electrochim, Acta 43, 3431-3441 (1998). 

Figure 4. Gamma camera image of a patient with medullary thyroid carcinoma showing selective uptake of Re-186-DMSA in a tumor at the base of the neck (taken 24 h after injection).

Despite the quantitative variability of salts and silicate dust particles in the plants of Arid ecosystems, we can easily discern a trend towards the selective uptake of trace elements. The calculation of coefficient of biogeochemical uptake (Cb) shows the rates of exposure to heavy metals in biogeochemical food webs. One can see that the elements contained in the plant species of both Steppe and Desert ecosystems are in equal measure susceptible to the influence of environmental factors. The most extensively absorbed are Sr, Cu, Mo, and Zn. Their values of Cb are more than unit. The group of other elements, like Ti, Zr, and V, are poorly taken up, with their values of Cb often dropping below 0.1 (see Figures 4 and 5). 

Higuchi, K., Saitoh, T. and Hiraide, M. (2002). Selective uptake of copper (II) ions in water by chelating agent-impregnated liposomes, Bunseki Kagaku, 51, 745-749. 

Photodynamic therapy for the treatment of tumours involves the selective uptake and retention of a highly-coloured porphyrin sensitiser (Figure 6.17) in the tumour. Irradiation by a laser with a wavelength corresponding to the absorption maximum of the porphyrin (D) causes excitation of the porphyrin to the excited singlet state. 

The cis-Pt compound showed some selective uptake into -SH abundant tissues such as kidney, muscle and rectal gland (data not shown) but not RBC s. Most other tissues showed no remarkable concentration and/or increased percentage of dose retained over those expected from uniform distribution. There was moderate CNS penetrance of cis-Pt. Neither the Hg nor Pt compound appeared in... 

Plate number, 3,4,7, 27, 52, S3 Plates per second, 30-33 PLB, see Porous layer beads Polar group selectivity, 181-183 Polar solvent, selective uptake from eluent by polar adsorbent, 8S Polarizability, 206... 

C. Transporters within the membranes allow for selective uptake of specific molecules or classes of molecules and mediate two major types of transpott—passive and active. 

The HDL lipids are removed from the circulation by a selective uptake and by an indirect pathway. The selective uptake of cholesterol esters from HDL into he-patocytes and steroidogenic cells is mediated by the binding of HDL to scavenger receptor B1 (SR-BI). This selective uptake by SR-BI may depend on the presence of cofactors such as HL, which hydrolyses phospholipids on the surface of both HDL and plasma membranes and thereby enables the flux of cholesteryl esters from the lipoprotein core into the plasma membrane [42]. The indirect pathway involves the enzyme CETP, which exchanges cholesteryl esters of a-HDL with triglycerides of chylomicrons, VLDL, IDL, and LDL. The a-HDL derived cholesteryl esters are therefore removed via the LDL-receptor pathway. The removal of excess cholesterol from the periphery and the delivery to the liver for excretion in the bile is termed reverse cholesterol transport. 

Schultz, M.M., Furlong, E.T., Kolpin, D.W., Werner, S.L., Schoenfuss, H.L., Barber, L.B., Blazer, V.S., Norris, D.O. and Vajda, A.M. (2010) Antidepressant pharmaceuticals in two U.S. effluent-impacted streams occurrence and fate in water and sediment, and selective uptake in fish neural tissue. Environ Sci Technol, 44, 1918-1925. 

The selective uptake of paraquat is another excellent example of the importance of size and shape in the disposition and toxicity of foreign compounds (see chap. 3, pages 40-1, and chap. 7). Similarly, the chemical similarities between carbon monoxide and oxygen are important in the toxic effects caused as are discussed in detail in chapter 7. 

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