Home About us Contact
|
Home About us Contact | ||
|
|
||
Extracellular Water (extracellular + water)
Selected AbstractsFluid Volumes Determination by Impedance Spectroscopy and Hematocrit Monitoring: Application to Pediatric HemodialysisARTIFICIAL ORGANS, Issue 2 2001Marianne Fenech Abstract: A method for extracting fluid volumes from multifrequency bioimpedance, which takes into account the body geometry and the presence of nonconducting elements, was tested on 12 young dialyzed patients against correlations for total body water volumes (TBW) from Watson et al. and Humes et al. Our calculations of TBW from impedance were found to overestimate Humes' values by 0.25 L (0.8%) postdialysis and by 2.08 L (6.5%) predialysis. Extracellular water (ECW) was found to contribute an average of 93% of ultrafiltered volume. Intracellular water volume (ICW) determination from impedance was found to be too imprecise to predict its variation during dialysis; therefore, ICW variations were calculated as the difference between ultrafiltration and ECW changes. The continuous recording of hematocrit by an optical device monitored changes in plasma and interstitial volumes. In most cases, ultrafiltration was compensated mainly by a contribution from interstitial fluid, and the drop in plasma volume was generally moderate. [source] Drug metabolism and disposition in childrenFUNDAMENTAL & CLINICAL PHARMACOLOGY, Issue 3 2003M. Strolin Benedetti Abstract Key factors undergoing maturational changes accounting for differences in drug metabolism and disposition in the pediatric population compared with adults are reviewed. Gastric and duodenal pH, gastric emptying time, intestinal transit time, bacterial colonization and probably P-glycoprotein are important factors for drug absorption, whereas key factors explaining differences in drug distribution between the pediatric population and adults are membrane permeability, plasma protein concentration and plasma protein characteristics, endogenous substances in plasma, total body and extracellular water, fat content, regional blood flow and probably P-glycoprotein, mainly that present in the gut, liver and brain. As far as drug metabolism is concerned, important differences have been found in the pediatric population compared with adults both for phase I enzymes [oxidative (e.g. cytochrome CYP3A7 vs. CYP3A4 and CYP1A2), reductive and hydrolytic enzymes] and phase II enzymes (e.g. N -methyltransferases and glucuronosyltransferases). Finally, key factors undergoing maturational changes accounting for differences in renal excretion in the pediatric population compared with adults are glomerular filtration and tubular secretion. It would be important to generate information on the developmental aspects of renal P-glycoprotein and of other renal transporters as done and still being done with the different isozymes involved in drug metabolism. [source] Distribution, metabolism, and excretion of a novel surface-active agent, purified poloxamer 188, in rats, dogs, and humansJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 9 2002J. Michael Grindel Abstract Purified poloxamer 188 (PP188) is a nonionic, block copolymer surfactant with hemorheologic, antithrombotic, and anti-adhesive properties. PP188 is being studied in phase III clinical trials in sickle cell disease and has been found to be well tolerated and has demonstrated benefit in ameliorating the effects of acute painful vasoocclusive crisis. The disposition of PP188 was studied in rats, dogs, and humans to establish a basis for understanding the safety parameters in support of clinical trials. PP188 was primarily distributed in extracellular water with little or no uptake by red blood cells, and had its highest concentrations in highly perfused tissues such as the kidney, liver, spleen, lymph nodes, and gastrointestinal tract. PP188 had no apparent effect on P450 isozymes in vitro. Metabolism was limited (<,5% of dose) with a higher molecular weight copolymer being the only other material detected in plasma or urine. Renal clearance was the controlling route of clearance for PP188 from the body. The 48-h intravenous infusion doses of PP188 were cleared in all species by approximately 1 week after the cessation of dose administration. PP188's disposition is a model for other nonionic block copolymers with similar physical and chemical properties. © 2002 Wiley-Liss Inc. and the American Pharmaceutical Association J Pharm Sci 91:1936,1947, 2002 [source] Compartmental relaxation and diffusion tensor imaging measurements in vivo in ,-carrageenan-induced edema in rat skeletal muscle,NMR IN BIOMEDICINE, Issue 6 2008Reuben H. Fan Abstract Integrated diffusion tensor T2 measurements were made on normal and edematous rat muscle, and the data were fitted with one- and two-compartment models, respectively. Edematous muscle exhibited a short-lived component (T2,=,28,±,6,ms), with diffusion characteristics similar to that of normal muscle, and a long-lived component (T2,=,96,±,27,ms), with greater mean apparent diffusion coefficient (ADC) and lower fractional anisotropy (FA). With this two-component description of diffusion and relaxation, values of ADC and FA estimated with a conventional pulsed-gradient spin-echo sequence will depend on the echo time, relative fraction of short-lived and long-lived water signals, and the intrinsic ADC and FA values within the tissue. On the basis of the relative differences in water diffusion properties between long-lived and short-lived water signals, as well as the similarities between the short-lived component and normal tissue, it is postulated that these two signal components largely reflect intracellular and extracellular water. Copyright © 2007 John Wiley & Sons, Ltd. [source] | ||||||||||