In vivo measurements

Toxic equivalency factors (TEFs) are estimated relative to 2,3,7,8-TCDD, which is assigned a value of 1. They are measures of the toxicity of individual compounds relative to that of 2,3,7,8-TCDD. A variety of toxic indices, measured in vivo or in vitro, have been used to estimate TEFs, including reproductive effects (e.g., embryo toxicity in birds), immunotoxicity, and effects on organ weights. The degree of induction of P450 lAl is another measure from which estimations of TEF values have been made. The usual approach is to compare a dose-response curve for a test compound with that of the reference compound, 2,3,7,8-TCDD, and thereby establish the concentrations (or doses) that are required to elicit a standard response. The ratio of concentration of 2,3,7,8-TCDD to concentration of test chemical when both compounds produce the same degree of response is the TEF. Once determined, a TEF can be used to convert a concentration of a dioxin-like chemical found in an environmental sample to a toxic equivalent (TEQ). 

Hu H Department of Environmental Health, Boston, MA Measure in vivo bone lead level in a National Institute of new longitudinal study of lead exposure Environmental Health and reproduction among married Sciences women and men ... 

Bioavailability is an important parameter in drug screening cascades. It gives a good indication of the efficiency of the delivery of the compound to the systemic circulation by the chosen route. It can only be measured in vivo but, as will be described below, it can be predicted for man using a number of methods. 

In contrast to other analytical methods, ion-selective electrodes respond to an ion activity, not concentration, which makes them especially attractive for clinical applications as health disorders are usually correlated to ion activity. While most ISEs are used in vitro, the possibility to perform measurements in vivo and continuously with implanted sensors could arm a physician with a valuable diagnostic tool. In-vivo detection is still a challenge, as sensors must meet two strict requirements first, minimally perturb the in-vivo environment, which could be problematic due to injuries and inflammation often created by an implanted sensor and also due to leaching of sensing materials second, the sensor must not be susceptible to this environment, and effects of protein adsorption, cell adhesion, and extraction of lipophilic species on a sensor response must be diminished [13], Nevertheless, direct electrolyte measurements in situ in rabbit muscles and in a porcine beating heart were successfully performed with microfabricated sensor arrays [18],... 

Pfister M, Boix L, Huston JP, Schwarting RK. 1994. Different effects of scopolamine on extracellular acetylcholine levels in neostriatum and nucleus accumbens measured in vivo possible interaction with aversive stimulation. J Neural Transm Gen Sect 97(1) 13-25. 

The major tissues that use glutamine are kidney, small intestine, colon, immune cells and bone marrow cells. Rates of utilisation by these last four tissues cannot be measured in vivo. Rates of utilisation by isolated cells have been measured in vitro (Chapters 17 and 21). 

The oxygen uptake of a maximally working individual muscle in adult humans has been measured in vivo, enabling the calculation of the flux through the Krebs cycle in that muscle to be made (Appendix 9.10). It is compared with the capacity that is calculated from the maximal in vitro activity of oxoglutarate dehydrogenase, in an extract... 

The need of designing probes for measuring in vivo temperature is primarily dictated by therapeutical purposes. In fact, useful therapies against tumors like hypertermia or thermal ablation are based on localized heating which selectively kills tumor cells. Such therapies require the achievement of well-defined temperatures that, moreover, have to be maintained constant for a given time. Therefore, a continuous temperature monitoring is essential for the success of the therapy 136). 

C. Schiepers, J. Nuyts, G. Bormans, J. Dequeker, R. Bouillon, L. Mortelmans, A. Verbruggen, R.M. De, Fluoride kinetics of the axial skeleton measured in vivo with fluorine-18-fluoride PET, J. Nucl. Med. 38(12) (1997) 1970-1976. 

C.J. Koch, S.M. Flahn, K.J. Rockwell, J.M. Covey, W.G. McKenna, S.M. Evans, Pharmacokinetics of EF5 [2-(2-nitro-1-FI-imidazol-1-yl)-N-(2,2,3,3,3-pentafluoro-propyl) acetamide] in human patients Implications for hypoxia measurements in vivo by 2-nitroimidazoles, Cancer Chemother. Pharmacol. 48 (2001) 177-187. 

Wood AJ, Elphick M, Aronson JK, et al The effect of lithium on cation transport measured in vivo in patients suffering from bipolar affective illness. Br J Psychiatry 155 504-510, 1989... 

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