Home About us Contact
|
Home About us Contact | ||
|
|
||
Fluid Compartments (fluid + compartment)
Selected AbstractsImproved EEG source analysis using low-resolution conductivity estimation in a four-compartment finite element head modelHUMAN BRAIN MAPPING, Issue 9 2009Seok Lew Abstract Bioelectric source analysis in the human brain from scalp electroencephalography (EEG) signals is sensitive to geometry and conductivity properties of the different head tissues. We propose a low-resolution conductivity estimation (LRCE) method using simulated annealing optimization on high-resolution finite element models that individually optimizes a realistically shaped four-layer volume conductor with regard to the brain and skull compartment conductivities. As input data, the method needs T1- and PD-weighted magnetic resonance images for an improved modeling of the skull and the cerebrospinal fluid compartment and evoked potential data with high signal-to-noise ratio (SNR). Our simulation studies showed that for EEG data with realistic SNR, the LRCE method was able to simultaneously reconstruct both the brain and the skull conductivity together with the underlying dipole source and provided an improved source analysis result. We have also demonstrated the feasibility and applicability of the new method to simultaneously estimate brain and skull conductivity and a somatosensory source from measured tactile somatosensory-evoked potentials of a human subject. Our results show the viability of an approach that computes its own conductivity values and thus reduces the dependence on assigning values from the literature and likely produces a more robust estimate of current sources. Using the LRCE method, the individually optimized four-compartment volume conductor model can, in a second step, be used for the analysis of clinical or cognitive data acquired from the same subject. Hum Brain Mapp, 2009. © 2008 Wiley-Liss, Inc. [source] Effects of immersion water temperature on whole-body fluid distribution in humansACTA PHYSIOLOGICA, Issue 1 2004J. M. Stocks Abstract Aim:, In this study, we quantified acute changes in the intracellular and extracellular fluid compartments during upright neutral- and cold-water immersion. We hypothesized that, during short-term cold immersion, fluid shifts would be wholly restricted to the extracellular space. Methods:, Seven males were immersed 30 days apart: control (33.3 ° SD 0.6 °C); and cold (18.1 ° SD 0.3 °C). Posture was controlled for 4 h prior to a 60-min seated immersion. Results:, Significant reductions in terminal oesophageal (36.9 ° ± 0.1 °,36.3 ° ± 0.1 °C) and mean skin temperatures (30.3 ° ± 0.3 °,23.0 ° ± 0.3 °C) were observed during the cold, but not the control immersion. Both immersions elicited a reduction in intracellular fluid [20.17 ± 6.02 mL kg,1 (control) vs. 22.72 ± 9.90 mL kg,1], while total body water (TBW) remained stable. However, significant plasma volume (PV) divergence was apparent between the trials at 60 min [12.5 ± 1.0% (control) vs. 6.1 ± 3.1%; P < 0.05], along with a significant haemodilution in the control state (P < 0.05). Plasma atrial natriuretic peptide concentration increased from 18.0 ± 1.6 to 58.7 ± 15.1 ng L,1 (P < 0.05) during cold immersion, consistent with its role in PV regulation. We observed that, regardless of the direction of the PV change, both upright immersions elicited reductions in intracellular fluid. Conclusion:, These observations have two implications. First, one cannot assume that PV changes reflect those of the entire extracellular compartment. Second, since immersion also increases interstitial fluid pressure, fluid leaving the interstitium must have been rapidly replaced by intracellular water. [source] Hydration of exercised Standardbred racehorses assessed noninvasively using multi-frequency bioelectrical impedance analysisEQUINE VETERINARY JOURNAL, Issue S36 2006A. WALLER Summary Reasons for performing study: In human and animal clinical practice, multi-frequency bioelectrical impedance analysis (MF-BIA) is increasingly used as a diagnostic tool to assess hydration of intra-and extracellular fluid compartments. Accurate determination of changes in hydration status within individuals over time has remained problematic due to the requirement for complete impedance-frequency relationships at the time points of interest. Objectives: To use MF-BIA in 13 Standardbred racehorses and 7 ,endurance' research horses to determine if MF-BIA could be used to track changes in total body water (TBW), intracellular fluid volume (ICFV) and extracellular fluid volume (ECFV) resulting from exercise. Methods: Jugular venous blood was sampled at rest and for 2,13 h following exercise. TBW, ECFV and plasma volume (PV) were measured at rest using indicator dilution techniques (D2O, thiocyanate and Evans Blue, respectively). TBW, ECFV, ICFV and PV were correlated to impedance measures and predictive equations used to determine hydration status from MF-BIA measures. Results: TBW loss continued throughout the recovery period, and was primarily borne by the ECF compartment at 90 min of recovery. Conclusions: MF-BIA predictions of compartmental hydration status were significantly correlated to measured/calculated decreases in these compartments. Potential relevance: Practical applications for MF-BIA in horses include monitoring of hydration status during transport and competition, assessment of body compostion, clinical health assessment and critical care management. [source] Vitamin D and calcium deficits predispose for multiple chronic diseasesEUROPEAN JOURNAL OF CLINICAL INVESTIGATION, Issue 5 2005M. Peterlik Abstract There is evidence from both observational studies and clinical trials that calcium malnutrition and hypovitaminosis D are predisposing conditions for various common chronic diseases. In addition to skeletal disorders, calcium and vitamin D deficits increase the risk of malignancies, particularly of colon, breast and prostate gland, of chronic inflammatory and autoimmune diseases (e.g. insulin-dependent diabetes mellitus, inflammatory bowel disease, multiple sclerosis), as well as of metabolic disorders (metabolic syndrome, hypertension). The aim of the present review was to provide improved understanding of the molecular and cellular processes by which deficits in calcium and vitamin D cause specific changes in cell and organ functions and thereby increase the risk for chronic diseases of different aetiology. 1,25-dihydroxyvitamin D3 and extracellular Ca++ are both key regulators of proliferation, differentiation and function at the cellular level. However, the efficiency of vitamin D receptor-mediated intracellular signalling is limited by the negative effects of hypovitaminosis D on extrarenal 25-hydroxyvitamin D-1,-hydroxylase activity and thus on the production of 1,25-dihydroxyvitamin D3. Calcium malnutrition eventually causes a decrease in calcium concentration in extracellular fluid compartments, resulting in organ-specific modulation of calcium-sensing receptor activity. Hence, attenuation of signal transduction from the ligand-activated vitamin D receptor and calcium-sensing receptor seems to be the prime mechanism by which calcium and vitamin D insufficiencies cause perturbation of cellular functions in bone, kidney, intestine, mammary and prostate glands, endocrine pancreas, vascular endothelium, and, importantly, in the immune system. The wide range of diseases associated with deficits in calcium and vitamin D in combination with the high prevalence of these conditions represents a special challenge for preventive medicine. [source] Hemodynamic and Volume Changes during HemodialysisHEMODIALYSIS INTERNATIONAL, Issue 3 2003Robert M. Lindsay Background:,Volume overload is a factor in the hypertension of hemodialysis (HD) patients. Fluid removal is therefore integral to the hemodialysis treatment. Fluid removal by hemodialysis ultrafiltration (UF) may cause intradialytic hypotension and leg cramps. Understanding blood pressure (BP) and volume changes during UF may eliminate intradialytic hypotension and cramps. Studies (S1, S2, and S3) were carried out to determine the amount and direction of changes in body fluid compartments following UF and to determine the relationships between BP, changes in blood volume (,BV), central blood volume (CBV), cardiac output (CO), peripheral vascular resistance (PVR) plus total body water (TBW), and intra- and extracellular fluid volumes (ICF, ECF) in both the whole body and body segments (arms, legs, trunk). Methods:,Indicator dilution technology (Transonic) was used for CBV, CO, and PVR; hematocrit monitoring (Crit-Line) was used for ,BV segmental bioimpedance (Xitron) for TBW, ICF, and ECF. Results:,S1 (n = 21) showed UF sufficient to cause ,BV of ,7% and lead to minor changes (same direction) in CBV and CO, and with cessation of UF, vascular refilling was preferential to CBV. S2 (n = 20) showed that predialysis HD patients are ECF-expanded (ECF/ICF ratio = 0.96, controls = 0.74 [P < 0.0001]) and BP correlates with ECF (r = 0.47, P = 0.35). UF to cause ,BV of ,7% was associated with a decrease in ECF (P < 0.0001) and BP directly (r = 0.46, P = 0.04) plus ,BV indirectly (r = ,0.5, P = 0.024) correlated with PVR, while CBV and CO were maintained. S3 (n = 11) showed that following UF, total-body ECF changes were correlated with leg ECF (r = 0.94) and arm ECF (r = 0.72) but not trunk ECF. Absolute ECF reduction was greatest from the legs. Conclusions:,Predialysis ECF influences BP and UF reduces ,BV and ECF, but CBV and BP are conserved by increasing PVR. ECF reduction is mainly from the legs, hence may cause cramps. Intradialytic hypotension is caused by failure of PVR response. [source] Physiological distribution of placental growth factor and soluble Flt-1 in early pregnancyPRENATAL DIAGNOSIS, Issue 3 2008George Makrydimas Abstract Objective To examine the distribution of placental growth factor (PlGF), vascular endothelial growth factor (VEGF) and soluble VEGF receptor-1 (sFlt-1) in maternal and embryonic fluid compartments in early pregnancy. Method The concentrations of PlGF, VEGF and sFlt-1 were measured in coelomic fluid and maternal serum from 16 singleton pregnancies at 7.0,9.3 weeks. In six cases, amniotic fluid was also examined. Results The median concentration of PlGF was 14.1 (range 8.9,27.6) pg/mL in maternal serum, 13.9 (range 9.5,31.4) pg/mL in coelomic fluid and 8.9 (range 3.9,15.3) pg/mL in amniotic fluid. The concentration of PlGF increased between 7.0 and 9.3 weeks in maternal serum (p = 0.001) and decreased in coelomic and amniotic fluid (p = 0.001). The median concentration of sFlt-1 was 8561 (range 6724-10 673) pg/mL in coelomic fluid, 523 (range 244,986) pg/mL in maternal serum, 30 (range 12,83) pg/mL in amniotic fluid (p = 0.0001), and it did not change significantly with gestation. VEGF was undetectable in most of the samples, and therefore, no further analysis was performed. Conclusion PlGF and sFlt-1 are present in the maternal and fetal fluid compartments in very early pregnancy, and their distribution is consistent with their site of production and the local conditions of transport. Copyright © 2008 John Wiley & Sons, Ltd. [source] ADAM12-s in coelomic fluid and maternal serum in early pregnancyPRENATAL DIAGNOSIS, Issue 13 2006George Makrydimas Abstract Objectives ADAM12-s is a placental protein. In early pregnancy, reduced maternal levels of ADAM12-s have been reported in association with foetal trisomy 21 or 18 and in cases that subsequently develop pre-eclampsia and foetal growth restriction. The aim of this study is to investigate the distribution of ADAM12-s in early pregnancy by comparing its concentration in maternal serum, amniotic fluid and coelomic fluid. Methods Coelomic fluid was obtained by coelocentesis from 13 singleton pregnancies with live foetuses at 6.9,9.3 weeks of gestation. Maternal serum was also obtained in all cases and in six cases amniotic fluid was also obtained. The concentration of ADAM12-s was measured by dissociation enhanced lanthanide fluoro-immunoassay. Results The median concentration of ADAM12-s in maternal serum was 132.7 (range 33.8,254.5) ng/mL and in coelomic fluid it was 10.5 (range 1.3,15.8) ng/mL; there were no detectable levels in five of the six amniotic fluid samples. The concentration of maternal serum ADAM12-s increased significantly with gestation (r = 0.862, p < 0.0001). There was no significant association between coelomic fluid ADAM12-s and either gestation (r = 0.255, p = 0.401) or maternal serum ADAM12-s (r = 0.302, p = 0.316). Conclusion The distribution of ADAM12-s in maternal serum and the early embryonic fluid compartments is consistent with its syncytiotrophoblastic origin. Copyright © 2006 John Wiley & Sons, Ltd. [source] Geochemistry of Heavy Oil in the T Block, Oriente Basin and its Origin MechanismACTA GEOLOGICA SINICA (ENGLISH EDITION), Issue 2 2010Ying HU Abstract: Exploration and development experience show that there is obvious oil gravity difference between the southern part and northern part of the "M1" reservoir in the Fanny oil field in the slope of the Oriente Basin, Ecuador. The American Petroleum Institute Gravity (API) values of oils in the northern part are higher than the one in the southern part of the Fanny oil field, with the values of 20° and 10.0°,13.0°, respectively. So the primary purpose of this study was to analyze the heavy oil characteristics of biodegradation and the oil,oil correlation according to the biomarker data and the ,13C signature of oil samples from T block. The results of the hydrocarbon gas chromatography fingermark and the inversion attribute characteristics indicated that there are fluid compartments between the "M1" reservoir of Fanny south. Finally, the models of oil,gas accumulation under the control of multiple-activities of complicated fault systems, as well as the origin of heavy oil, are contended. The early stage oils from the western part of the basin were biodegraded heavily in varying degrees in the whole basin, and the later stage oils were derived from the southern part in a large scale and were mature and lighter. Generally, oil mixing is the primary control of net oil properties, such as API gravity in Oriente Basin. We therefore predicted that the API gravity variation of oil pools radically depends on the injection amount of the later stage oil. Because of the shale barrier in the "M1" reservoir of Fanny south, the later stage hydrocarbon could not pass through and contribute to increase the oil API value. [source] | |||||||||||||