Extracellular Water Compartment Research Articles

Body Composition, Sarcopenia, and Serum Myokines in Acromegaly: A Narrative Review.

Patients with active acromegaly have a higher percentage of lean body mass, a lower percentage of fat body mass, and an increase in their extracellular water compartment compared to healthy individuals. However, muscle function appears to be compromised in patients with acromegaly, with some experiencing worsened physical performance and sarcopenia. Myokine alterations, insulin resistance, dysregulation of protein metabolism, muscle oxidative stress, neuromuscular junction impairment, and increased ectopic intramuscular fat deposits may play roles in muscle dysfunction in patients with acromegaly.

Bioelectrical, Anthropometric, and Hematological Analysis to Assess Body Fluids and Muscle Changes in Elite Cyclists during the Giro d'Italia.

This study aimed to characterize and monitor the body fluid and muscle changes during the Giro d'Italia in nine elite cyclists via bioelectrical (whole-body and muscle-localized) anthropometric and hematological analysis. There were three checkpoint assessments: at the beginning, middle, and end of the race. The Wilcoxon signed-rank test was used to compare the data at baseline and follow up. The Spearman correlation was used to explore relationships between variables. Hotelling's T2 test was used to determine bioelectrical differences in the complex vector. Bodyweight did not change during the competition, despite bioelectrical and hematological data indicating that at the first half of the race, there was a fluid gain, and in the second half a fluid loss occurred, reaching baseline values. These changes were especially prevalent in the extracellular water compartment. Significant correlations between whole-body bioelectrical vector changes and red blood cell parameter changes were reported. The muscle group most sensitive to changes were the calves. Quadriceps, hamstrings, and calves reported a PhA decrease trend during the first half of the race, and an increase during the second half. Bioelectrical impedance vector analysis appears to be sensitive enough to detect hydration and cellular integrity adaptions induced by competitions as demanding as the Giro d'Italia.

Low-field 1H NMR parameterization of model cell suspensions. A diffusion and relaxation study.

Nuclear magnetic resonance (NMR) is a powerful method for the non-invasive study of a wide range of objects. Among its many characteristics, molecular diffusion can be examined without the need for any chemical or isotopic tracers by applying magnetic field gradients within the NMR sequence. In our study, model cell suspensions were characterized by means of low-field (LF) (0.05 T) 1H NMR relaxometry. The proposed multi-parametric characterization based on independent 2D T1-T2 and D-T2 measurements was implemented to obtain a set of MR parameters as a specific signature for model cells. The D-T2 and T1-T2 correlation measurements were conducted on yeast samples with different amounts of added water. Signals from intracellular and extracellular water compartments and free water were identified on D-T2 maps and their diffusion coefficients were extracted. Mean D_IC was equal to 8.4 × 10-11 m2/s and mean D_EC ranged from 1.0 × 10-9 m2/s to 1.65 × 10-9 m2/s. T1/T2 ratio was calculated and for IC space values in the range of 4.2-5.3 were observed. Finally, we demonstrated the possibility of detecting signals from cells for the samples with a low concentration of cell suspensions or a small amount of the sample. These findings are promising for more complex cell investigations in vitro and in vivo, without any contrast agents, applying solely biomarkers.

Стан водних секторів у жінок із прееклампсією в перипартальному періоді

Актуальність. Прееклампсія у вагітних є загрозливим станом, що зумовлює значні порушення водного балансу, формує гіпергідратацію позаклітинного сектора. Це обумовлено основними патогенетичними ланками — ендотеліальною дисфункцією та подальшим розвитком гіпопротеїнемії. Підтвердити дані зміни можливо методом визначення показників об’ємів водних секторів організму. Мета: дослідити вплив стандартної інтенсивної терапії на показники водних секторів організму в породіль із прееклампсією середнього та тяжкого ступенів. Матеріали та методи. Обстежені 90 жінок, включених у три групи: здорові невагітні жінки, вагітні жінки з неускладненим перебігом вагітності та жінки з прееклампсією середнього та тяжкого ступенів. Методом неінвазивної біоімпедансометрії визначали показники водних секторів організму. Результати. Вагітність, ускладнена прееклампсією, у терміні 34–40 тижнів супроводжується зростанням загального об’єму рідини за рахунок збільшення як позаклітинного, так і внутрішньоклітинного водних секторів організму, але з перевагою позаклітинного сектора. До 7-ї доби післяпологового періоду формується тенденція до зниження загального об’єму рідини, але зберігаються набряк інтерстицію та внутрішньоклітинний набряк. Висновки. Результати біоімпедансного аналізу водних секторів свідчать про необхідність залучення додаткових методів лікування для корекції водних секторів організму в породіль із прееклампсією.

Resistance Training Improves a Cellular Health Parameter in Obese Older Women: A Randomized Controlled Trial.

Ribeiro, AS, Schoenfeld, BJ, dos Santos, L, Nunes, JP, Tomeleri, CM, Cunha, PM, Sardinha, LB, and Cyrino, ES. Resistance training improves a cellular health parameter in obese older women: a randomized controlled trial. J Strength Cond Res 34(10): 2996-3002, 2020-Phase angle (PhA) is a viable indicator of cellular health, with higher values reflecting better cellularity, cell membrane integrity, and cell function. Adaptive responses to resistance training (RT) on PhA may be important in obese older people. The main purpose of the present study was to investigate the effects of 8 weeks of RT on PhA in obese older women. Thirty-three obese older women (68.1 ± 5.7 years, 71.6 ± 10.1 kg, 154.5 ± 6.7 cm, 30.0 ± 4.1 kg·m, and 45.0 ± 6.0% body fat) were randomly allocated into 1 of 2 groups: a training group that performed the RT program (TG, n = 18) or a nonexercise control group (CG, n = 15). The whole-body RT consisted of an 8-week RT program involving 8 exercises performed for 3 sets of 8-12 repetitions 3 times a week. Anthropometric, body fat and fat-free mass, PhA, total body water (TBW), intracellular water (ICW), and extracellular water compartments were performed at before and after training. After the intervention period, the TG presented greater increases (p < 0.05) than CG for fat-free mass (TG = +1.3% and CG = -0.3%), TBW (TG = +2.0% and CG = -1.7%), ICW (TG = +3.1% and CG = -1.9%), and PhA (TG = +3.4% and CG = -1.4%), and lower values for percentage of body fat (TG = -1.3% and CG = +0.9%) and bioimpedance resistance (TG = -4.6% and CG = +2.3%). Our results suggest that 8 weeks of RT improves PhA-a cellular health parameter-in obese older women.

Probing Tissue Microarchitecture of the Baby Brain via Spherical Mean Spectrum Imaging.

During the first years of life, the human brain undergoes dynamic spatially-heterogeneous changes, invo- lving differentiation of neuronal types, dendritic arbori- zation, axonal ingrowth, outgrowth and retraction, synaptogenesis, and myelination. To better quantify these changes, this article presents a method for probing tissue microarchitecture by characterizing water diffusion in a spectrum of length scales, factoring out the effects of intra-voxel orientation heterogeneity. Our method is based on the spherical means of the diffusion signal, computed over gradient directions for a set of diffusion weightings (i.e., b -values). We decompose the spherical mean profile at each voxel into a spherical mean spectrum (SMS), which essentially encodes the fractions of spin packets undergoing fine- to coarse-scale diffusion proce- sses, characterizing restricted and hindered diffusion stemming respectively from intra- and extra-cellular water compartments. From the SMS, multiple orientation distribution invariant indices can be computed, allowing for example the quantification of neurite density, microscopic fractional anisotropy ( μ FA), per-axon axial/radial diffusivity, and free/restricted isotropic diffusivity. We show that these indices can be computed for the developing brain for greater sensitivity and specificity to development related changes in tissue microstructure. Also, we demonstrate that our method, called spherical mean spectrum imaging (SMSI), is fast, accurate, and can overcome the biases associated with other state-of-the-art microstructure models.

Measuring Water Distribution in the Heart: Preventing Edema Reduces Ischemia-Reperfusion Injury.

BackgroundEdema is present in many heart diseases, and differentiation between intracellular (ICW) and extracellular (ECW) myocardial water compartments would be clinically relevant. In this work we developed a magnetic resonance imaging–based method to differentiate ICW and ECW and applied it to analyze ischemia–reperfusion–induced edema.Methods and ResultsIsolated rat hearts were perfused with gadolinium chelates as a marker of extracellular space. Total water content was measured by desiccation. Gadolinium quantification provided ECW, and ICW was calculated by subtraction of ECW from total water content. In separate experiments, T1, T2, diffusion‐weighted imaging and proton‐density parameters were measured in isolated saline‐perfused hearts. In in‐situ rat hearts, ECW and ICW were 79±10 mL and 257±8 mL of water per 100 g of dry tissue, respectively. After perfusion for 40 minutes, ECW increased by 92.4±3% without modifying ICW (−1±3%). Hyposmotic buffer (248 mOsm/L) increased ICW by 16.7±2%, while hyperosmotic perfusion (409 mOsm/L) reduced ICW by 26.5±3%. Preclinical imaging showed good correlation between T2 and diffusion‐weighted imaging with ECW, and proton‐density correlated with total water content. Ischemia–reperfusion resulted in marked myocardial edema at the expense of ECW, because of cellular membrane rupture. When cell death was prevented by blebbistatin, water content and distribution were similar to normoxic perfused hearts. Furthermore, attenuation of intracellular edema with hyperosmotic buffer reduced cell death.ConclusionsWe devised a method to determine edema and tissue water distribution. This method allowed us to demonstrate a role of edema in reperfusion‐induced cell death and could serve as a basis for the study of myocardial water distribution using magnetic resonance imaging.

Hypertrophy-type Resistance Training Improves Phase Angle in Young Adult Men and Women.

The main purpose of the present study was to investigate the effect of a hypertrophy-type resistance training protocol on phase angle, an indicator of cellular integrity, in young adult men and women. 28 men (22.2±4.3 years, 67.8±9.0 kg and 174.2±6.8 cm) and 31 women (23.2±4.1 years, 58.7±12.1 kg and 162.7±6.4 cm) underwent a progressive RT for 16 weeks (2 phases, 8 weeks each), 3 times per week, consisting of 10 to 12 whole body exercises with 3 sets of 8-12 repetitions maximum. Phase angle, resistance, reactance and total body water (intra and extracellular water compartments) were assessed by bioimpedance spectroscopy (Xitron 4200 Bioimpedance Spectrum Analyzer). Total body water, intracellular water and phase angle increased significantly (P<0.05) in men (7.8, 8.3, and 4.3%, respectively) and women (7.6, 11.7, and 5.8% respectively), with no significant difference between sexes (P>0.05). Bioimpedance resistance decreased (P<0.05) similarly in both sex (men=-4.8%, women=-3.8%). The results suggest that regardless of sex, progressive RT induces an increase in phase angle and a rise in cellular hydration.

Healthy overweight/obese youth: early osteosarcopenic obesity features

Osteosarcopenic obesity was recently described as a variant phenotype of obesity, mainly observed in old age. This nested case-control study was performed to detect the differences in body composition between young, healthy overweight/obese and healthy lean populations of both genders. Our null hypothesis was that except for the fat mass, there would be absence of body composition differences, namely skeletal muscle and bone masses, between the groups. We used an advanced bio-impedance device to determine the body composition and measured circulating CRP (hsCRP) and diurnal salivary cortisol concentrations, as indices of inflammation and chronic stress, respectively. Overall, 2551 subjects aged 18-21 years participated in the study. The healthy lean group included 1072 participants [900 males (84%) and 172 females (16%)], and the healthy overweight/obese group included 1479 participants [74 males (5%) and 1405 females (95%)]. Healthy overweight/obese participants presented with an increased fat mass (P < 0·001), as expected, but lower muscle (P < 0·001) and bone (P < 0·001) masses than lean controls. These findings were accompanied by increased extracellular water compartments, circulating hsCRP levels and evening salivary cortisol concentrations in the healthy overweight/obese group. Our study suggests that 'osteosarcopenic' elements exist even in very young populations. These may represent a 'precursor' or forme fruste of the osteosarcopenic obesity phenotype in young healthy overweight/obese subjects, who may progressively develop osteosarcopenia in its full form at an older age. Our study highlights the significance of body composition analysis in medical practice, improving prevention and alleviating later health-related economic burden.

R1correction in amide proton transfer imaging: indication of the influence of transcytolemmal water exchange on CEST measurements

Amide proton transfer (APT) imaging may potentially detect mobile proteins/peptides non-invasively in vivo, but its specificity may be reduced by contamination from other confounding effects such as asymmetry of non-specific magnetization transfer (MT) effects and spin-lattice relaxation with rate R1 (=1/T1). Previously reported spillover, MT and R1 correction methods were based on a two-pool model, in which the existence of multiple water compartments with heterogeneous relaxation properties in real tissues was ignored. Such simple models may not adequately represent real tissues, and thus such corrections may be unreliable. The current study investigated the effectiveness and accuracy of correcting for R1 in APT imaging via simulations and in vivo experiments using tumor-bearing rats subjected to serial injections of Gd-DTPA that produced different tissue R1 values in regions of blood-brain-barrier breakdown. The results suggest that conventional measurements of APT contrast (such as APT* and MTRasym ) may be significantly contaminated by R1 variations, while the R1 -corrected metric AREX* was found to be relatively unaffected by R1 changes over a broad range (0.4-1 Hz). Our results confirm the importance of correcting for spin-lattice relaxation effects in quantitative APT imaging, and demonstrate the reliability of using the observed tissue R1 for corrections to obtain more specific and accurate measurements of APT contrast in vivo. The results also indicate that, due to relatively fast transcytolemmal water exchange, the influence of intra- and extracellular water compartments on CEST measurements with seconds long saturation time may be ignored in tumors.

Differences In Body Water Compartment Ratios By Gender, Age, And Fat-free Mass

INTRODUCTION: The extracellular water (ECW) compartment is used to signify disease states via edema or the expansion of interstitial water. The ratio of ECW to total body water (TBW) is an indication of normal fluid distributions. A ratio greater than 0.39 indicates malnutrition, aging, and obesity, while ratios less than 0.36 are seen in athletes or individuals with increased muscle mass. Additionally, the ratio of ECW to intracellular water (ICW) is used indicate fluid shifts in body water as it relates to increased adipose tissue. PURPOSE: To investigate the effects of gender, age, fat-free mass/weight (%FFM), BMI, and fitness level (FIT) on ECW/TBW and ECW/ICW ratios in healthy individuals. METHODS: Fifty healthy volunteers (36±15 yrs, 170.0±9.1 cm, 69.1±10.9 kg, 21 men, 29 women) followed standard pretest guidelines for body composition assessment. ECW (L) and ICW (L) were measured supine with a Xitron 4200 multifrequency BIA at the 5th minute according to Xitron recommendations. We investigated five independent variables (IV) (gender, age, BMI, FIT, and %FFM) and two dependent variables (DV) (ECW/TBW and ECW/ICW). Each IV was categorized into two groups by the median of the variable. Independent t-tests analyzed the differences of IV and DV (p<.05). RESULTS: Significant differences were found for gender, age, and %FFM. However, there were no significant differences based on BMI and FIT. Males displayed lower ECW/TBW (0.398±0.024) and ECW/ICW (0.664±0.068) compared to females (0.442±0.026 and 0.796±0.084, respectively). Younger participants (≤30.5 yrs) displayed lower ECW/TBW (0.412±0.033) and ECW/ICW (0.706±0.097) than older participants (>30.5 yrs) (0.436±0.030 and 0.776±0.094, respectively). Participants who had higher %FFM (>70.2%) displayed lower ECW/TBW (0.402±0.027) and ECW/ICW (0.677±0.077) than participants who had lower %FFM (≤70.2%) (0.445±0.024 and 0.805±0.080, respectively). CONCLUSION: Male gender, age ≤ 30.5 yrs, and %FFM >70.2% resulted in lower ECW/TBW and ECW/ICW ratios in our sample. Conversely, mean measurements of ECW/TBW were all seen to be higher than the upper limit for normal ECW/TBW (0.39) suggested for this population. This may suggest a need for re-evaluation of this limit. In our sample, BMI or FIT did not have significant differences in ECW/TBW or ECW/ICW ratios.

Dual X-ray absorptiometry model for characterizing water in the human forearm using multiple frequency bioimpedance analysis

The purpose of this study was to develop a method for measuring intracellular (ICW) and extracellular water (ECW) in the human forearm using multiple frequency bioimpedance analysis (MFBIA). The approach was (i) to measure whole-body and forearm fat-free mass using dual X-ray absorptiometry (DXA); (ii) to use these measurements to estimate the fat-free mass (FFM) resistivity in both the forearm and in the whole body; and (iii) to use the ratio of these FFM resistivities to estimate the resistivity in the ICW and ECW compartments of the forearm. To first demonstrate the accuracy of the DXA software in differentiating lean body mass from fat and bone within a volume of tissue, ex-vivo bovine muscle tissue samples (n = 3) were used to approximate the physical properties of the human forearm. It was found that although the human whole-body software overestimates FFM, it was slightly underestimated by the small animal software. Using this technique, DXA measures of FFM were obtained from human volunteers (n = 11; age = 20 +/- 5 years; height = 170 +/- 12 cm; mass = 64 +/- 16 kg). These measures were used in conjunction with MFBIA measures of impedance of the whole body and of the forearm to determine the resistivities of the ICW and ECW compartments of the forearm, namely 375.8 +/- 25.2 ohms cm and 55.6 +/- 3.7 ohms cm, respectively. These were used in MFBIA equations to calculate the ICW, ECW, and total arm water (TAW) volumes of the human forearm. The calculated TAW and the ECW (+/- SD) volume fraction (667.29 +/- 200.15 mL and 0.169 +/- 0.039 mL, respectively) were in agreement with literature values. MFBIA results were compared with those obtained using nuclear magnetic resonance relaxometry (NMRR). MFBIA was performed on 15 subjects before and after an intense maximal handgrip exercise to estimate changes in water volume in muscle. Following exercise, the total and intracellular water of the forearm increased on average by 8% +/- 3% and 10% +/- 4% (mean +/- SD), respectively. In 5 healthy volunteers, MFBIA and NMRR were performed before and after a similar exercise of the forearm muscle. The changes with exercise of intracellular and total arm water volumes as measured by MFBIA were estimated. The percent increases in total water were found to be 9.4% +/- 4.2% and 9.4% +/- 2.6% and in intracellular water were found to be 10.6% +/- 4.6% and 12.0% +/- 2.8% (mean +/- SD) for NMRR and MFBIA, respectively. The results show that the exercise-induced changes in ICW and TAW determined with the MFBIA model are consistent with those observed with NMRR and radiotracer literature.

Body water compartments in patients with obstructive jaundice

To elucidate the pathogenesis of renal dysfunction associated with obstructive jaundice, body water compartments were measured using a multi-isotope dilution technique in ten patients with biliary tract obstruction and in ten control subjects matched for age, sex, weight, height and body surface area. Expressed as a fraction of body-weight, total body water was reduced in jaundiced patients (41.8 versus 46.2 per cent, P less than 0.02). Extracellular water volume was also reduced in patients with jaundice (20.3 versus 24.3 per cent, P less than 0.003) owing to a reduction of the interstitial space (16.1 versus 19.5 per cent, P less than 0.004) and, to a lesser degree, of the plasma volume (4.2 versus 4.8 per cent, P = 0.1). There was a close correlation in jaundiced patients between plasma volume and the creatinine clearance rate (r2 = 0.56, P less than 0.02) and between plasma volume and extracellular volume (r2 = 0.77, P less than 0.0001). Extracellular volume in such patients also correlated with the percentage weight loss (r2 = 0.42, P = 0.04). Obstructive jaundice is associated with a contracted extracellular water compartment, although extracellular water, as a percentage of body-weight, increased in proportion to the body-weight lost. Reduction of the interstitial volume and a marginally reduced plasma volume may be determinant factors in the pathogenesis of the renal and haemodynamic disturbances observed in patients with biliary tract obstruction.

Reduced water and sodium intakes associated with high levels of natriuretic factor following common bile duct ligation in the rabbit

Renal failure complicating obstructive jaundice (OJ) is probably linked to reduction of the extracellular water compartment. To elucidate the mechanism by which OJ leads to isotonic water depletion we studied a group of rabbits with OJ after common bile duct ligation (n = 17) and another group of sham operated rabbits (n = 14) for 10 days. Water intake and balance for two study periods (1-4 and 7-10 days after operation) were calculated. Renal function, sodium balance and plasma atrial natriuretic factor were determined on the fourth and tenth days after operation. Water intake and balance were lower in the OJ group both in the first study period (230 versus 519 ml/days 1-4, P less than 0.001; and -2.4 versus 219 ml/days 1-4, P less than 0.0001 respectively) and in the second study period (260 versus 865 ml/days 7-10, P less than 0.0001; and 11 versus 379 ml/days 7-10, P less than 0.0001 respectively). Sodium intake was negligible in the OJ group both on day four (0.73 versus 7.15 mM/24 h, P less than 0.0001) and on day 10 (0.78 versus 15.78 mM/24 h, P less than 0.0001). As a result plasma osmolality did not change. Day 10 urine osmolality and osmolar clearance were reduced in the OJ group (653 versus 1103 mOsm/kg, P less than 0.0001 and 0.09 versus 0.25 ml/min, P less than 0.0001 respectively) together with a decreased creatinine clearance (3 versus 11 ml/min, P less than 0.0001). Atrial natriuretic factor was increased in jaundiced rabbits (day 4, 22.7 versus 7.5 fmol/ml, P less than 0.0001; and day 10, 26.5 versus 11.2 fmol/ml, P less than 0.02). These findings suggest that OJ leads to an isotonic volume depletion resulting from abnormalities of the extracellular volume regulating mechanisms. These appear to be secondary to an inappropriate elevation of the atrial natriuretic factor plasma concentration.

Biexponential parameterization of diffusion and T2 relaxation decay curves in a rat muscle edema model: Decay curve components and water compartments

Quantitative T2 relaxation and diffusion imaging studies of a rat muscle edema model were performed in order to determine the effects of intra- and extracellular water compartmentation on the respective decay curves. The right hind paw of rats was injected with a carrageenan solution to generate edematous muscle. A Carr-Purcell-Meiboom-Gill (CPMG) imaging sequence was used to acquire T2 relaxation decay curves from both paws. A line scan diffusion imaging (LSDI) sequence was then used to acquire diffusion decay curves from the same paws over a wide b-factor range. Measurements were made from both edematous muscle (EM) and control muscle (CM). The EM and CM T2 relaxation decay curves were best fit with biexponential functions. The fraction of the fast T2 component dropped dramatically from approximately 0.95 in CM to 0.45 in EM, consistent with a water compartmentation model in which the fast and slow T2 components reflect intra- and extracellular water, respectively. Both CM and EM diffusion decay curves required biexponential fitting functions, and the diffusion coefficients of the fast and slow components were substantially larger in EM than CM. The fraction of the fast diffusion component, however, was not radically altered between CM and EM conditions (0.84 versus 0.89 for CM versus EM). Assuming a model in which intra- and extracellular water compartments are responsible for the fast and slow T2-decay components and for the slow and fast diffusion decay components, respectively, leads to fractional sizes of the diffusion components that are not supported by experiment. We conclude that intra- and extracellular water compartmentation is a reasonable interpretation for the two T2-decay components in both CM and EM but that other factors, such as restricted diffusion and/or alternate forms of water compartmentation like surface versus volume water, most probably have profound influences on the precise shapes of the diffusion decay curves, a complete understanding of which will require significant theoretical work.

Multivariate analysis of factors associated with renal dysfunction in patients with obstructive jaundice

The aim was to evaluate the factors determining preoperative renal dysfunction in patients with obstructive jaundice. In a prospective cross-sectional observational study, 63 patients, 27 with benign and 36 with malignant obstructive jaundice, were investigated at admission and compared with 25 healthy control subjects. Variables analysed included extracellular body water (ECW) compartment, plasma levels of aldosterone, renin, atrial natriuretic peptide, vasopressin, nitric oxide, endothelin (ET) 1 and prostaglandin E2 (PGE2), urinary nitric oxide and PGE2, serum albumin and renal function. The metabolic profile of obstructive jaundice was characterized by a depletion of the ECW (P = 0.004), and increased plasma levels of atrial natriuretic peptide (P < 0.001), ET-1 (P = 0.044), vasopressin (P = 0.017), aldosterone (P = 0.005) and renin (P = 0.001). Increased plasma (P < 0.001) and urinary (P = 0.001) PGE2 levels were also found. Fifty-four per cent of patients had a creatinine clearance of less than 70 ml/min. In multivariate analysis, serum bilirubin, renin, ET-1, PGE2, decreased urinary sodium excretion and age were identified as predictors of renal dysfunction. Renal dysfunction in patients with obstructive jaundice was associated with the degree of biliary obstruction, age of the patient and reduced urinary sodium excretion. These alterations were closely related to derangements in sodium- and water-regulating hormones.

Kinetic Modeling of Plasma Leucine Levels during Continuous Venovenous Extracorporeal Removal Therapy in Neonates with Maple Syrup Urine Disease

A kinetic modeling of leucine plasma concentration changes is proposed to describe the plasma leucine reduction rate during continuous extracorporeal removal therapy (CECRT) in neonates with maple syrup urine disease. Data were obtained from seven neonates using a bicompartmental model for the best fitted curve of plasma leucine decrease during CECRT. During the first 3 h, leucine plasma levels decreased according to an exponential curve: [Leu](t) = [Leu](i) x 0.95 x 10(-0.09t) where [Leu](t) is the leucine plasma level (mumol/L) at time t (h) during CECRT and [Leu](I) is the initial plasma level. From h 4 to the end of CECRT, a second exponential curve was observed: [Leu](t) = [Leu](i) x 0.74 x 10(-0.05t). Plasma leucine levels obtained from three other neonates were similar to those predicted by the model. The apparent distribution volumes for leucine that correspond to the two exponential equations obtained were calculated from the leucine mass removal collected in the spent dialysate and ultrafiltrate. The distribution volume was 34 +/- 3% of body weight during the first 3 h of CECRT and 72 +/- 7% from h 4 to the end of CECRT. These figures are similar to known values for the extracellular water compartment and for total body water in the newborn. The findings suggest that leucine handling during CECRT is similar to that of nonprotein-bound small-molecular-weight solutes such as urea.

Extracellular water: greater expansion with age in African Americans

Aging is associated with the onset of chronic diseases that lead to pathological expansion of the extracellular water (ECW) compartment. Healthy aging, in the absence of disease, is also reportedly accompanied by a relative expansion of the ECW compartment, although the studies on which this observation is based are few in number, applied different ECW measurement methods, included small ethnically homogeneous subject samples, and failed to adjust ECW for non-age-related influencing factors. The aim of the current study was to examine, in a large (n = 1,538) ethnically diverse [African American (AA), Asian, Caucasian, Hispanic] subject group the cross-sectional relationships between ECW and age after controlling first for other potential factors that may influence fluid distribution. ECW and intracellular water (ICW) were derived from measured total body water (isotope dilution) and potassium (40K whole body counting). The cross-sectional relationships between ECW, ICW, and ECW/ICW (E/I), and age were developed using multiple regression modelling methods. Body weight, weight squared, height, age, sex, race, and interactions were all significant ECW predictors. The slope of the observed race x age interaction was significantly greater in AA (beta = 0.0005, P = 0.005) than in the three other race groups. Race, sex, and age differences in fluid distribution persisted after adjusting for body composition in a subgroup (n = 994) with dual-energy X-ray absorptiometry lean soft tissue and fat measurements. A relative ECW expansion (i.e., E/I) was present with greater age in most sex-race groups, although the effect was not significantly larger in AA males (P > 0.05) compared with the other race groups, except Asians (P < 0.05). For females, a larger E/I-age effect was found in AA compared with the other race groups, but only the comparison against Hispanics was significant (P < 0.05). The ECW compartment and E/I are thus variably larger, according to race, in healthy older subjects independent of sex, lean soft tissue, and fat mass.

Assessment of body composition in long-term hemodialysis patients: Rationale and methodology

Protein-energy malnutrition is seen in patients with advanced stages of chronic kidney disease (CKD) and is even more pronounced in patients receiving long-term hemodialysis treatment. Both entities have great impact on patient morbidity and mortality. Analysis of body composition is an integral part of nutritional assessment and includes the estimation of muscle, fat, and fat-free mass, as well as the extracellular water compartment. Clinical assessment of these compartments is difficult, and gold-standard methods such as tracer dilution, magnetic resonance imaging, and dual-energy x-ray absorptiometry are expensive, cumbersome, and rarely available. We report an ongoing study of body composition in hemodialysis patients involving deuterium and sodium bromide dilution, total body potassium counting, magnetic resonance imaging, whole-body and segmental bioimpedance spectroscopy, and anthropometry. The goals of the study are (1) to validate bioimpedance technology against gold-standard methods for assessment of the various body compartments, (2) to directly quantify visceral adipose tissue mass, a potential source of cytokine production (adipokines) promoting chronic inflammation, and to study its relation to inflammatory markers, and (3) to directly quantify visceral organ mass and to study its relation to uremia toxin generation as assessed by protein catabolic rate and resting energy expenditure. Preliminary results based on up to 40 hemodialysis patients are reported.

Body Water in Children During Recovery from Severe Burn Injury Using a Combined Tracer Dilution Method

Useful information about hydration and the size of the body cell mass (BCM) can be obtained by monitoring changes in the amount of total body water (TBW) and its components, extracellular water (ECW) and intracellular water (ICW). A combined tracer dilution method with deuterium to measure TBW and bromide to measure ECW was used to assess changes in ICW (as a proxy for the BCM) and in the ECW/ICW ratio (an indicator of water distribution) over the course of recovery in nine severely burned children. During the acute phase of recovery, ICW losses averaged (mean +/- SD) 2.2 +/- 2.0 liters (P = .02) or 18.5 +/- 0.4%. During the rehabilitative phase, mean ICW increased by 3.4 +/- 3.7 liters or 31.9 +/- 14%. The ECW/ICW ratio varied widely both between patients and during the course of the study. During the acute phase of recovery, the mean ECW/ICW ratio increased from 1.06 +/- 0.15 liters to 1.20 +/- 0.14 liters because the ECW compartment had expanded relative to the ICW compartment. During rehabilitation, the ECW/ICW ratio decreased from 1.20 +/- 0.14 liters to 0.86 +/- 0.20 liters, with a recoup of ICW and continued ECW losses. Tracking ICW and the ECW/ICW ratio using the combined tracer dilution method is practical for monitoring BCM and water distribution in severely burned children. Taken together, the indices provide useful information about hydration and nutritional status in individuals recovering from severe burn injury.