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PubMed2006

Multiplexed and microparticle-based analyses: quantitative tools for the large-scale analysis of biological systems.

While the term flow cytometry refers to the measurement of cells, the approach of making sensitive multiparameter optical measurements in a flowing sample stream is a very general analytical approach. The past few years have seen an explosion in the application of flow cytometry technology for molecular analysis and measurements using microparticles as solid supports. While microsphere-based molecular analyses using flow cytometry date back three decades, the need for highly parallel quantitative molecular measurements that has arisen from various genomic and proteomic advances has driven the development in particle encoding technology to enable highly multiplexed assays. Multiplexed particle-based immunoassays are now common place, and new assays to study genes, protein function, and molecular assembly. Numerous efforts are underway to extend the multiplexing capabilities of microparticle-based assays through new approaches to particle encoding and analyte reporting. The impact of these developments will be seen in the basic research and clinical laboratories, as well as in drug development.

Coloring Agents↗
PubMed1987

Methods for determination of lipid peroxidation in biological samples.

Interest in the pathological consequences of lipid peroxidation has led to the development of a number of analytical approaches to the quantitation of products. However, the various analytical methodologies employed often do not measure the same chemical classes of products, and apparent discrepencies have been observed, particularly in studies of lipid peroxidation in biological systems. This review provides a brief discussion of some of the strengths and weakness of methods currently used for the determination of lipid peroxidation in biological tissues.

Animals↗
PubMed1997

Real-time neural network based camera localization and its extension to mobile robot control.

The feasibility of using neural networks for camera localization and mobile robot control is investigated here. This approach has the advantages of eliminating the laborious and error-prone process of imaging system modeling and calibration procedures. Basically, two different approaches of using neural networks are introduced of which one is a hybrid approach combining neural networks and the pinhole-based analytic solution while the other is purely neural network based. These techniques have been tested and compared through both simulation and real-time experiments and are shown to yield more precise localization than analytic approaches. Furthermore, this neural localization method is also shown to be directly applicable to the navigation control of an experimental mobile robot along the hallway purely guided by a dark wall strip. It also facilitates multi-sensor fusion through the use of multiple sensors of different types for control due to the network's capability of learning without models.

Algorithms↗
PubMed2006

Microarray data on gene modulation by HIV-1 in immune cells: 2000-2006.

Here, we review 34 HIV microarray studies in human immune cells over the period of 2000-March 2006 with emphasis on analytical approaches used and conceptual advances on HIV modulation of target cells (CD4 T cell, macrophage) and nontargets such as NK cell, B cell, and dendritic cell subsets. Results to date address advances on gene modulation associated with immune dysregulation, susceptibility to apoptosis, virus replication, and viral persistence following in vitro or in vivo infection/exposure to HIV-1 virus or HIV-1 accessory proteins. In addition to gene modulation associated with known functional correlates of HIV infection and replication (e.g., T cell apoptosis), microarray data have yielded novel, potential mechanisms of HIV-mediated pathogenesis such as modulation of cholesterol biosynthetic genes in CD4 T cells (relevant to virus replication and infectivity) and modulation of proteasomes and histone deacetylases in chronically infected cell lines (relevant to virus latency). Intrinsic challenges in summarizing gene modulation studies remain in development of sound approaches for comparing data obtained using different platforms and analytical tools, deriving unifying concepts to distil the large volumes of data collected, and the necessity to impose a focus for validation on a small fraction of genes. Notwithstanding these challenges, the field overall continues to demonstrate progress in expanding the pool of target genes validated to date in in vitro and in vivo datasets and understanding the functional correlates of gene modulation to HIV-1 pathogenesis in vivo.

Apoptosis↗
PubMed2006

Revisiting inhibitory control across the life span: insights from the ex-Gaussian distribution.

Changes in inhibitory control occur across the life span and have been associated with alterations in prefrontal function. In this study, ex-Gaussian analysis was used to reexamine data from an inhibitory control task. Participants (ages 6 to 82 years) composed three groups: children, young adults, and older adults. In fitting the ex-Gaussian distribution to reaction time data, estimates of three parameters were obtained: mu (mu), reflecting average performance; sigma (sigma), reflecting variability in performance; and tau (tau), reflecting extremes in performance. Older adults differed from young adults in terms of mu, sigma, and tau. For children, mu and tau values were comparable to those of young adults; sigma, however, was different. Thus, inhibitory changes in older adults were due to slower, more variable, and more extreme responding. Inhibitory changes in children were due only to more variable responding. These findings suggest that different mechanisms underlie age-related changes in inhibitory control during different epochs of the life span. This study demonstrates that the ex-Gaussian approach provides a finer level of analysis than data analytic approaches typically used in neuropsychological research.

Adolescent↗
PubMed1985

Sexuality in the older individual.

Approximately 12% of the population of the United States is over 65 and almost one quarter is over the age of 50. It is obvious from these numbers, that our older citizens constitute an ever expanding segment of our society. As a consequence of this, we as analysts and therapists must re-examine our clinical approaches to such people. A review of the sparse analytic literature dealing with the sexuality of older people is presented, as are a number of clinical examples of analytic approaches toward the sexual problems of older people. Special emphasis is given to certain transference and counter-transference phenomena encountered in such treatments.

Aged↗
PubMed2001

Quantitative determination of vapor-phase compound A in sevoflurane anesthesia using gas chromatography-mass spectrometry.

BACKGROUND: During low-flow or closed-circuit anesthesia with the fluorinated inhalation anesthetic sevoflurane, compound A, an olefinic degradation product with known nephrotoxicity in rats, is generated on contact with alkaline CO(2) adsorbents. To evaluate compound A formation and thus potential sevoflurane toxicity, a reliable and reproducible assay for quantitative vapor-phase compound A determination was developed. METHODS: Compound A concentrations were measured by fully automated capillary gas chromatography-mass spectrometry with cryofocusing. Calibrators of compound A in the vapor phase were prepared from liquid volumetric dilutions of stock solutions of compound A and sevoflurane in ethyl acetate. 1,1,1-Trifluoro-2-iodoethane was chosen as an internal standard. The resulting quantitative method was fully validated. RESULTS: A linear response over a clinically useful concentration interval (0.3-75 microL/L) was obtained. Specificity, sensitivity, and accuracy conformed with current analytical requirements. The CVs were 4.1-10%, the limit of detection was 0.1 microL/L, and the limit of quantification was 0.3 microL/L. Analytical recoveries were 100.6% +/- 10.1%, 102.5% +/- 7.3%, and 99.0% +/- 4.1% at 0.5, 10, and 75 microL/L, respectively. The method described was used to determine compound A concentrations during simulated closed-circuit conditions. Some of the resulting data are included, illustrating the practical applicability of the proposed analytical approach. CONCLUSIONS: A simple, fully automated, and reliable quantitative analytical method for determination of compound A in air was developed. A solution was established for sampling, calibration, and chromatographic separation of volatiles in an area complicated by limited availability of sample volume and low concentrations of the analyte.

Air↗
PubMed1994

Substance use clusters in a college sample: a multitheoretical approach.

Substance use factors were examined and cross-validated in a cluster analytic approach in two independent samples of college students: N = 291 and N = 602. Reported frequency, intensity, and amount of substance use were examined for beer, hard liquor, marijuana, amphetamines, barbiturates, psychedelics, cocaine, and heroin. Variables were reduced using Principal Components Analysis (PCA) to form four substance use composites. Composite scores were entered into two different methods of cluster analysis that each identified four distinct clusters of substance use groups. External validity was obtained by showing that these four groups differed on a set of relevant variables. The four groups served as levels of the independent variable, substance use type, in four MANOVAs examining group differences on peer and family influence, psychosocial functioning, habit acquisition, and self-efficacy. Findings indicate that as frequency and intensity of substance use increased, individuals reported more problems in living, although a causal direction cannot be established. The findings are of potential value in early identification, prevention, and education regarding substance use among college populations.

Adaptation, Psychological↗
PubMed2003

A review of approaches to the analysis of 3-nitrotyrosine.

Our understanding of in vivo tyrosine nitration has been confounded by problems associated with the analytical approaches that have been employed to quantify 3-nitroyrosine (3-NT). Trace analysis is a demanding task under the best of circumstances, but 3-NT offers some special concerns. This review examines some of these concerns and discusses approaches to ensuring that carefully validated analytical data are generated.

Animals↗
PubMed1983

The general toxicology unknown. I. The systematic approach.

The general toxicology unknown often presents challenges and interests to toxicologists. A systematic analytical approach to search for drugs or poisons is presented here. The preliminary screening analyses were as follows: alcohol by gas chromatography (GC), ethchlorvynol colorimetric analysis, enzyme multiplied immunoassay technique (EMIT), basic drug screening by GC, and neutral and weakly acidic drug screening by GC. Other additional analyses were performed depending on the special circumstance of each individual case and the results of these preliminary analyses. Positive findings were confirmed by computerized gas chromatography/mass spectrometry when practical. Quantitation was performed by GC whenever possible.

Alcohols↗
PubMed1997

Sinistrin clearance for determination of glomerular filtration rate: a reappraisal of various approaches using a new analytical method.

Several approaches are available to estimate the glomerular filtration rate (GFR) from the sinistrin clearance. To compare such approaches, GFR was estimated in six healthy volunteers, both after a bolus injection and a bolus dose followed by a 6-hour infusion. A recently developed high-performance liquid chromatography method was used for the determination of sinistrin levels, enabling precise measurements in plasma and urine samples with high sensitivity. Blood and urine were sampled up to 6 hours. Four calculation methods for estimating GFR were applied: 1) classical ratio of urinary excretion rate over plasma concentration (UV/P); 2) two-point (log-linear regression slope times monocompartmental volume of distribution) after bolus; 3) ratio of dose over area under the curve (D/AUC) after bolus; and 4) ratio of infusion rate over steady-state concentration during infusion (Rinf/P). The results obtained by fitting a pharmacokinetic model to all the plasma and urine data served as the standard against which the performance of the respective calculation methods were examined. The UV/P method performed poorly on bolus data, mainly by underestimating GFR at late times; on both bolus and infusion data, it suffered from important imprecisions on the urinary volume. The two-point method appeared applicable only between 2 and 4 hours after the bolus dose. The D/AUC method with extrapolation to infinity was highly reliable when integrating the concentrations up to 3 hours or more after the bolus dose. The Rinf/P method was satisfactory if applied later than 2 to 3 hours after the loading dose. The advantages and drawbacks of each method have to be evaluated in relation to the particular clinical setting in which GFR is to be estimated.

Adult↗
PubMed2004

Stability in legged locomotion.

Stability is a key element in a gait synthesis. Static stability margins are widely adopted in crawlers, while no similar approach has been developed for dynamically stable systems. Utilizing an analytical approach, we developed a set of easy-to-calculate stability indices to describe instantaneous static and dynamic (In)stability for a certain group of walking systems. The analysis is based on a thorough analysis of the interaction between ground reaction forces and the walking system. The indices are applicable to walking systems regardless of the number of legs or mechanical/biological design. We show that static and dynamic stability are independent of each other. We suggest a possible categorization of gait modes based on stability. Stability characteristics are analyzed in a healthy and highly pathological human gait. Finally, we discuss the applicability of the proposed methods.

Gait↗
PubMed2006

WDS versus silicon drift detector EDS: a case report for the comparison of quantitative chemical analyses of natural silicate minerals.

Electron probe microanalysis (EPMA) is an essential analytical approach to determine elemental concentrations of various solid specimens quantitatively in mineralogical, petrological and materials research. Either wavelength dispersive X-ray (WDS) or energy dispersive X-ray (EDS) spectrometric techniques can collect the characteristic X-rays generated from each element in the specimen by an incident electron beam in order to define chemical constituents. Although WDS has been the preferred technique because of its higher spectral resolution and ability to detect trace elements, new generation EDS systems with silicon drift detectors (SDD), equipped with thin windows and integrated digital processing electronics, are claimed to approach the WDS throughput. In this study, we compared the analytical capability of a SDD EDS system with respect to WDS equipped systems on natural silicate minerals. For this purpose, natural rock samples, in which the silicate minerals present had already been analysed by various WDS systems, were chosen to compare these results with the ones acquired with a SDD EDS system. SDD EDS yielded satisfactory results for major elements (Na, Mg, Al, Si, K, Ca, Ti, Mn and Fe) compared with the results of the same minerals obtained by various WDS systems.

Journal Article↗
PubMed2005

Endocrine disruption of water and sediment extracts in a non-radioactive dot blot/RNAse protection-assay using isolated hepatocytes of rainbow trout.

GOAL, SCOPE AND BACKGROUND: In order to evaluate the estrogenic activity of sediments and XAD water extracts of selected sites of the catchment area of the River Neckar, a river system in Southern Germany, an integrative assessment approach was used to assess the ecological hazard potential of endocrine-disrupting compounds in sediment and water. METHODS: The approach is based on estrogen receptor-mediated vitellogenin synthesis induced in isolated hepatocytes of rainbow trout and quantified in a non-radioactive dot blot/RNAse protection-assay in parallel to comprehensive chemical analyses of estrogenic substances. RESULTS AND DISCUSSION: Numerous investigated extracts revealed an estrogen activity comparable to that of the positive control (1 nM 17beta-estradiol corresponding to 270 ng/L in the test medium). Based on a concentration factor of 30 in the extracts and a recovery of XAD resins of approximately 80%, 17beta-estradiol equivalent concentrations between 20 and 26.7 ng/L could be calculated downstream of a sewage treatment plant (< 0.1 ng/L for a reference site). A comparison of the bioassay-derived Bio-TEQs (toxicity equivalents) and the Chem-TEQs revealed a high correlation with a Pearson coefficient of 0.85, indicating that the same ranking of the samples could be obtained with respect to the endocrine disrupting potential with both chemical and bioanalytical analysis. However, the TEQ concentrations computed from chemical analyses were significantly lower than the bioassay-derived TEQ concentrations. In fact, in none of the samples, more than 14% of the vitellogenin-inducing potency could be attributed to the substances (steroids, alkylphenols, bisphenol A, diethylstilbestrol) analyzed. A comparison of the endocrine disrupting potential of sediments extracted by the solvents acetone and methanol revealed lower biological effects for acetone-extracted samples. Possible reasons may be a masking of endocrine effects in acetone extracts by cytotoxicity, a low extraction efficiency of the solvent acetone, or anti- estrogen potencies of some extracted sediment compounds. Using a mass balance approach, the contribution of the compounds analyzed chemically (Chem-TEQs) to the total endocrine activity (Bio-TEQs) was calculated. Based on the very low detection limits, particularly of the steroids with their high TEF factors, results revealed that a calculation of the Chem-TEQs is associated with considerable scale inaccuracy: Whereas only 7-15% of the biological effectiveness (Bio-TEQs) could be explained by endocrine substances identified above the detection limits, the assumption of concentrations slightly below the given detection limits would result in a significant over estimation (137-197%) of the Bio-TEQs. Even the interassay variation of the dot blot assay with different fish donors for primary hepatocyte (factor 2-2.5) is relatively low, when compared to the large range of the Chem-TEQ concentrations (factor 20) obtained when applying different modes of calculation. CONCLUSIONS AND OUTLOOK: Overall, only a minor portion of the endocrine activity detected by bioassays could be linked to compounds identified by chemical analysis. In vitro assays for assessment of endocrine activities are useful as sensitive integrating methods that provide quantitative estimates of the total activity of particular receptor-mediated responses. Although discrepancies may also result from different bioanalytical approaches, it is overall likely that bioanalytical and not chemical analytical approaches give the correct estimate of endocrine disrupting potencies in environmental samples. As a conclusion, assessment of endocrine disruption based on chemical analysis alone does not appear sufficient and further research into the spectrum of substances with potential endocrine activity as well as into additive or even synergistic effects in complex environmental samples is urgently needed.

Acrylic Resins↗
PubMed2003

Effects of an automated telephone support system on caregiver burden and anxiety: findings from the REACH for TLC intervention study.

PURPOSE: We determine the main outcome effects of a 12-month computer-mediated automated interactive voice response (IVR) intervention designed to assist family caregivers managing persons with disruptive behaviors related to Alzheimer's disease (AD). DESIGN AND METHODS: We conducted a randomized controlled study of 100 caregivers, 51 in the usual care control group and 49 in the technology intervention group, who received yearlong access to an IVR-mediated system. The system provided caregiver stress monitoring and counseling information, personal voice-mail linkage to AD experts, a voice-mail telephone support group, and a distraction call for care recipients. We conducted analyses by using a repeated measures approach for longitudinal data and an intention-to-treat analytic approach. Outcomes included the caregiver's appraisal of the bothersome nature of caregiving, anxiety, depression, and mastery at baseline, 6, 12, and 18 months. RESULTS: There was a significant intervention effect as hypothesized for participants with lower mastery at baseline on all three outcomes: bother (p =.04), anxiety (p =.01), and depression (p =.007). Additionally, wives exhibited a significant intervention effect in the reduction of the bothersome nature of caregiving (p =.02). IMPLICATIONS: Wives who exhibited low mastery and high anxiety benefited the most from the automated telecare intervention. Findings suggest that, to optimize outcome effects, similar interventions should be tailored to match the users' characteristics and preferences.

Aged↗
PubMed2005

Proteomic analysis of supernatants of stored red blood cell products.

BACKGROUND: The development of the red blood cell (RBC) storage lesion remains incompletely understood. To gain a greater insight into the mechanisms involved, a proteomics analysis was used to identify proteins that accumulate in supernatants of standard nonleukoreduced RBC products (S-RBCs) and prestorage leukofiltered RBC products (LF-RBCs) during storage. STUDY DESIGN AND METHODS: S-RBCs and LF-RBCs were collected and stored in accordance with standard blood bank procedures. Supernatant samples were collected at fortnightly intervals until product expiry (at Day 42). Maps of supernatant proteins were generated by two-dimensional (2D)-gel electrophoresis and selected proteins were identified by mass spectrometry. RESULTS: 2D-gel mapping revealed that greater numbers of proteins accumulated in supernatants of S-RBCs compared to LF-RBCs. Abundant plasma proteins were strongly represented in both products. Several potentially bioactive proteins were found to predominantly accumulate in supernatant of S-RBCs. Among these, a promoter of neutrophil adhesion and an acute-phase scavenger protein were identified. In contrast, proteins found to accumulate predominantly in supernatant of LF-RBCs were RBC-regulatory proteins. CONCLUSION: Proteomics provides a valuable approach to examine storage-related effects on RBCs. Such analytical approaches may help to elucidate the mechanisms involved in the RBC storage lesion and provide insights into the biologic consequences of transfusion of stored RBC products.

Acute-Phase Proteins↗
PubMed2001

Statistical power for nonequivalent pretest-posttest designs. The impact of change-score versus ANCOVA models.

Nonequivalent controlled pretest-posttest designs are central to evaluation science, yet no practical and unified approach for estimating power in the two most widely used analytic approaches to these designs exists. This article fills the gap by presenting and comparing useful, unified power formulas for ANCOVA and change-score analyses, indicating the implications of each on sample-size requirements. The authors close with practical recommendations for evaluators. Mathematical details and a simple spreadsheet approach are included in appendices.

Analysis of Variance↗
PubMed2003

Analytic expressions for the fourth- and the fifth-order dispersions of crossed prisms pairs.

In case of tunable ultrashort-pulse lasers, besides the prism material, separation, and insertion, one may choose the central wavelength providing a better high-order dispersion compensation. Because of errors that accumulate in numerical iterations, the analytic approach may be preferable for high-order dispersion examination. Analytic expressions for the fourth- and the fifth-order dispersions of crossed prisms pairs, both at arbitrary and Brewster-angle incidences are presented. Examples are given for e-sapphire slabs and for one or two pairs of fused-silica prisms. Results are shown providing compensation of both the second- and the third-order dispersions, by keeping as low as possible the higher-order ones.

Journal Article↗