Single- and multifrequency models for bioelectrical impedance analysis of body water compartments.

The 1994 National Institutes of Health Technology Conference on bioelectrical impedance analysis (BIA) did not support the use of BIA under conditions that alter the normal relationship between the extracellular (ECW) and intracellular water (ICW) compartments. To extend applications of BIA to these populations, we investigated the accuracy and precision of seven previously published BIA models for the measurement of change in body water compartmentalization among individuals infused with lactated Ringer solution or administered a diuretic agent. Results were compared with dilution by using deuterium oxide and bromide combined with short-term changes of body weight. BIA, with use of proximal, tetrapolar electrodes, was measured from 5 to 500 kHz, including 50 kHz. Single-frequency, 50-kHz models did not accurately predict change in total body water, but the 50-kHz parallel model did accurately measure changes in ICW. The only model that accurately predicted change in ECW, ICW, and total body water was the 0/infinity-kHz parallel (Cole-Cole) multifrequency model. Use of the Hanai correction for mixing was less accurate. We conclude that the multifrequency Cole-Cole model is superior under conditions in which body water compartmentalization is altered from the normal state.     

Validation of tetrapolar bioelectrical impedance method to assess human body composition

This study was conducted to validate the relationship between bioelectrical conductance (ht2/R) and densitometrically determined fat-free mass, and to compare the prediction errors of body fatness derived from the tetrapolar impedance method and skinfold thicknesses, relative to hydrodensitometry. One-hundred and fourteen male and female subjects, aged 18-50 yr, with a wide range of fat-free mass (34-96 kg) and percent body fat (4-41%), participated. For males, densitometrically determined fat-free mass was correlated highly (r = 0.979), with fat-free mass predicted from tetrapolar conductance measures using an equation developed for males in a previous study. For females, the correlation between measured fat-free mass and values predicted from the combined (previous and present male data) equation for men also was strong (r = 0.954). The regression coefficients in the male and female regression equations were not significantly different. Relative to hydrodensitometry, the impedance method had a lower predictive error or standard error of the estimates of estimating body fatness than did a standard anthropometric technique (2.7 vs. 3.9%). Therefore this study establishes the validity and reliability of the tetrapolar impedance method for use in assessment of body composition in healthy humans.     

Sensitivity of bioelectrical impedance to detect changes in human body composition

The purpose of this study was to compare the estimates of lean body mass (LBM) and percent body fat (%BF), as predicted by bioelectrical impedance (BIA) and sum of skinfolds (SF), with those derived by hydrostatic weighing (HW) obtained before and after a 10-wk diet and exercise regimen. The experimental (E) group consisted of 17 healthy male subjects; 20 healthy males served as the control (C) group. Post hoc Scheffé contrasts computed on E group data indicated that, for both LBM and %BF, the Lukaski and Segal BIA equations, as well as the Durnin SF equation, derived mean values that were not significantly different (0.05 significance level) from HW in both pre- and postregimen conditions. For LBM, the same equations derived the following significant (P less than 0.01) correlation coefficients for both pre- and postregimen data: Lukaski, 0.87 and 0.85; Segal, 0.89 and 0.87; and Durnin, 0.90 and 0.88. For %BF, the correlation coefficients were slightly lower but remained statistically significant (P less than 0.01). The findings of this study suggest that the BIA method, by use of either the Lukaski or Segal prediction equations, is a valid means of predicting changes in human body composition as measured by the Siri transformation of body density.     

A phylogenetic approach to assessing the targets of microbial warfare

Bacteriocins are the most abundant and diverse defense systems in bacteria. As a result of the specific mechanisms of bacteriocin recognition and translocation into the target cell it is assumed that these toxins mediate intra-specific or population-level interactions. However, no published studies specifically address this question. We present here a survey of bacteriocin production in a collection of enteric bacteria isolated from wild mammals in Australia. A subset of the bacteriocin-producing strains was assayed for the ability to kill a broad range of enteric bacteria from the same bacterial collection. A novel method of estimating killing breadth was developed and used to compare the surveyed bacteriocins in terms of the phylogenetic range over which they kill. The most striking result is that although bacteriocin-producers kill members of their own species most frequently, some kill phylogenetically distant taxa more frequently than they kill closer relatives. This study calls into question the role these toxins play in natural populations. A significant number of bacteriocins are highly effective in killing inter-specific strains and thus bacteriocins may serve to mediate bacterial community interactions.     

A prediction equation for total body water from bioelectrical impedance in Japanese children

Total body water (TBW) measured by isotope dilution techniques can be used to assess body composition safely and accurately in children. Unfortunately, this method is not readily available for most research projects, particularly when working with large groups of people, because the equipment is complicated and highly specialized. Bioelectrical impedance (BI) method is a simple, quick, and inexpensive method for the assessment of total body water (TBW). In Japanese child population, however, a lack of prediction equations is a problem to determine TBW. The purpose of this study was to determine the prediction equation for TBW determination in Japanese children using the isotope dilution technique as the reference method. Seventy Japanese children (39 boys, 31 girls) with ages ranging between 3 and 6 years participated in this study. They were randomly divided into the validation group (26 boys, 20 girls) and cross-validation group (13 boys, 11 girls). In a forward stepwise regression analysis, 96% of the variability in TBW measured by deuterium oxide (D(2)O) dilution could be predicted by the following equation: TBW(kg)=0.149 x Resistance Index (Stature(2)/resistance, cm(2)/Omega)+0.244 x Weight(kg)+0.460 x Age(y)+0.501 x Sex (boy=1, girl=0)+1.628, with a root mean square error (RMSE) of 0.440 kg in the validation group. This equation predicted TBW in the cross-validation group with R(2)=0.946 and a pure error (PE)=0.400 kg TBW. Hence, this equation should be applicable for predicting TBW in Japanese children aged 3-6 y.     

Total body water and ECFV measured using bioelectrical impedance analysis and indicator dilution in horses.

The purposes of this study were 1) to determine the compartmentation of body water in horses by using indicator dilution techniques and 2) to simultaneously measure bioelectrical impedance to current flow at impulse current frequencies of 5 and 200 kHz to formulate predictive equations that could be used to estimate total body water (TBW), extracellular fluid volume (ECFV), and intracellular fluid volume (ICFV). Eight horses and ponies weighing from 214 to 636 kg had catheters placed into the left and right jugular veins. Deuterium oxide, sodium thiocyanate, and Evans blue were infused for the measurement of TBW, ECFV, and plasma volume (PV), respectively. Bioelectrical impedance was measured by using a tetrapolar electrode configuration, with electrode pairs secured above the knee and hock. Measured TBW, ECFV, and PV were 0.677 +/- 0.022, 0.253 +/- 0.006, and 0.040 +/- 0.002 l/kg body mass, respectively. Strong linear correlations were determined among measured variables that allowed for the prediction of TBW, ECFV, ICFV, and PV from measures of horse length or height and impedance. It is concluded that bioelectrical impedance analysis (BIA) can be used to improve the predictive accuracy of noninvasive estimates of ECFV and PV in euhydrated horses at rest.     

Use of bioelectrical impedance to assess body composition changes at high altitude.

This study determined the feasibility of using bioelectrical impedance analysis (BIA) to assess body composition alterations associated with body weight (BW) loss at high altitude. The BIA method was also evaluated relative to anthropometric assessments. Height, BW, BIA, skinfold (SF, 6 sites), and circumference (CIR, 5 sites) measurements were obtained from 16 males (23-35 yr) before, during, and after 16 days of residence at 3,700-4,300 m. Hydrostatic weighings (HW) were performed pre- and postaltitude. Results of 13 previously derived prediction equations using various combinations of height, BW, age, BIA, SF, or CIR measurements as independent variables to predict fat-free mass (FFM), fat mass (FM), and percent body fat (%Fat) were compared with HW. Mean BW decreased from 84.74 to 78.84 kg (P less than 0.01). As determined by HW, FFM decreased by 2.44 kg (P less than 0.01), FM by 3.46 kg (P less than 0.01), and %Fat by 3.02% (P less than 0.01). The BIA and SF methods overestimated the loss in FFM and underestimated the losses in FM and %Fat (P less than 0.01). Only the equations utilizing the CIR measurements did not differ from HW values for changes in FFM, FM, and %Fat. It was concluded that the BIA and SF methods were not acceptable for assessing body composition changes at altitude.     

A new approach using the Pierce two-node model for different body parts

This paper presents a new approach, in applying the Pierce two-node model, to predict local skin temperatures of individual body parts with good accuracy. In this study, local skin temperature measurements at 24 sites on the bodies of 11 human subjects were carried out in a controlled environment under three different indoor conditions (i.e. neutral, warm and cold). The neutral condition measurements were used to adjust the local skin set-points in the model for each body part. Additional modifications to the calculation algorithm were introduced corresponding to different body parts. The local core set-points were then calculated, using a line search method, as the input values that allow the model to predict the skin temperatures with maximum deviation of ±0.1°C for the neutral condition. The model predictability was verified for the other two indoor conditions, and the results show that the modified model predicts local skin temperatures with average deviation of ±0.3°C.     

A novel approach for assessing the susceptibility of Escherichia coli to antibiotics

The dynamic growth process of Escherichia coli CVCC249 under different concentrations of antibiotics was analyzed. The results suggested that the main reason that definitive results cannot be obtained by antibiotic susceptibility testing (AST) is that the ratio of drug concentration to the population of bacteria and the combined effect of drug concentration and action time cannot be completely determined with the methods used. Based on the analysis of the growth process with a series of concentrations of gentamicin acting for a certain time, and according to the forward difference method, a novel method for AST was proposed. The net increase in turbidity of the bacterial population was used to eliminate the existing effects of resting cells, and then the recurrent coefficient for a growing sequence was used to characterize the effect of antibiotics on bacterial division, and the contour plot was used to display and analyze the combined effect of drug concentration and action time. The inhibition rate of the antibiotics can be characterized as the dynamic change in the composite function of the antibiotic concentration and action time, which indicated that the inhibition rate was dependent on the combined effect of time and concentration of antibiotics. The effectiveness of this new method has been verified with different kinds of antibiotics, such as enrofloxacin, levofloxacin, and ceftriaxone, having different antibacterial mechanisms.     

A general-purpose framework to simulate musculoskeletal system of human body: using a motion tracking approach*

Computation of muscle force patterns that produce specified movements of muscle-actuated dynamic models is an important and challenging problem. This problem is an undetermined one, and then a proper optimization is required to calculate muscle forces. The purpose of this paper is to develop a general model for calculating all muscle activation and force patterns in an arbitrary human body movement. For this aim, the equations of a multibody system forward dynamics, which is considered for skeletal system of the human body model, is derived using Lagrange–Euler formulation. Next, muscle contraction dynamics is added to this model and forward dynamics of an arbitrary musculoskeletal system is obtained. For optimization purpose, the obtained model is used in computed muscle control algorithm, and a closed-loop system for tracking desired motions is derived. Finally, a popular sport exercise, biceps curl, is simulated by using this algorithm and the validity of the obtained results is evaluated via EMG signals.     

A metabolomics approach to assessing phytotoxic effects on the green alga Scenedesmus vacuolatus

The potential of metabolomics for toxicity analysis with synchronized algal populations during growth was explored in a proof of principle study. Low molecular weight compounds from hydrophilic and lipophilic extracts of algal populations of the unicellular green alga Scenedesmus vacuolatus were analyzed using gas chromatography-mass spectrometry (GC-MS) and subsequent multivariate analysis to identify time-related patterns. Algal metabolite responses were studied under control and exposure conditions for the photosystem II-inhibiting herbicide prometryn. To define the typical metabolic profile of control S. vacuolatus cultures seven time points over a growth period of 14 h were evaluated. The results show a clear time-related trend in metabolite levels and a distinct separation of exposed and reference algal populations. The results suggest an impairment of the energy metabolism associated with an activation of catabolic processes and a retardation of carbohydrate biosynthesis in treated algae. Metabolite results were compared to observation parameters, currently used in phytotoxicity assessment, showing that metabolites respond faster to exposure than algal growth. The potential of metabolomics for toxicity evaluation, especially to identify physiological markers and to detect effects at an early state of exposure, are discussed. Therefore, we suggest a metabolomics approach utilizing synchronous algal cultures to be a suitable future tool in ecotoxicology.     

A new approach to assessing the validity of indels in algorithmic pair alignments

Analysis of the structure of indels in algorithmic versus evolutionary alignments based on a set of inequalities confirms the conclusions from numerical modeling. For the more divergent sequences (PAM > 60), the tested aligning algorithm (SW) tends to increase the mean length of indels and decrease their number.     

A complementary approach to identifying and assessing the remediation potential of hydrocarbonoclastic bacteria

The isolation and assessment of hydrocarbonoclastic bacteria often represents a key strategy in the bioremediation of hydrocarbon-contaminated sites. However the isolation and assessment of such bacteria is often a lengthy and expensive procedure. The aim of this study was to identify potential isolates for use in the remediation of hydrocarbon contaminated sites using a combination of selective isolation plating, the Biolog system and subsequent multivariate analyses. The use of weathered oil as the main C source restricted the number of isolates growing to 5×10(2)CFUg soil(-1). Isolates (n=96) were then assessed individually using Biolog MT2 plates with seven different hydrocarbons (dodecane, tridecane, hexadecane, octadecane, eicosane, naphthalene and phenanthrene). The results indicated that all isolates were able to grow on at least one hydrocarbon from the seven chosen. This confirmed that the isolation media developed was selective in isolating hydrocarbonoclastic bacteria only. Cluster analysis of Biolog data separated the isolates into two discrete clusters with cluster 2 identifying hydrocarbonoclastic bacteria that are effective in degrading a variety of contaminants. Further study on the isolates from cluster 2 was carried out based on their phylogenetic analysis. Phylogenetic analysis of 28 bacterial isolates from cluster 2 based on the 1500bp sequences from 16S rDNA genes using MRBAYES confirmed all isolates as being hydrocarbonoclastic, providing supportive evidence that isolates from cluster 2 have a potential use in bioremediation. This approach could improve both the speed and efficiency of the commercial bioremediation process.     

Immunological approach to assessing the health of the environment

The article sums up 10 years of experience in assessing the quality of the environment based on the parameters of the immune system. The studies were conducted on rodents caught in areas with different levels of radioactive or chemical contamination, under the influence of electromagnetic fields of the radio range, and also in laboratory conditions. The most revealing results were obtained when evaluating the proliferative activity of lymphoid cells. A formula has been proposed that allows one to evaluate the degree of anthropogenic impact on the state of an organism in points based on an analysis of the level of spontaneous and mito-gen-induced proliferation of lymphocytes.     

A graph theoretical approach for assessing bio-macromolecular complex structural stability

Fast and proper assessment of bio macro-molecular complex structural rigidity as a measure of structural stability can be useful in systematic studies to predict molecular function, and can also enable the design of rapid scoring functions to rank automatically generated bio-molecular complexes. Based on the graph theoretical approach of Jacobs et al. [Jacobs DJ, Rader AJ, Kuhn LA, Thorpe MF (2001) Protein flexibility predictions using graph theory. Proteins: Struct Funct Genet 44:150–165] for expressing molecular flexibility, we propose a new scheme to analyze the structural stability of bio-molecular complexes. This analysis is performed in terms of the identification in interacting subunits of clusters of flappy amino acids (those constituting regions of potential internal motion) that undergo an increase in rigidity at complex formation. Gains in structural rigidity of the interacting subunits upon bio-molecular complex formation can be evaluated by expansion of the network of intra-molecular inter-atomic interactions to include inter-molecular inter-atomic interaction terms. We propose two indices for quantifying this change: one local, which can express localized (at the amino acid level) structural rigidity, the other global to express overall structural stability for the complex. The new system is validated with a series of protein complex structures reported in the protein data bank. Finally, the indices are used as scoring coefficients to rank automatically generated protein complex decoys.