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PubMed1987

Data-reduction methods for immunoradiometric assays of thyrotropin compared.

In an attempt to optimize curve fitting for immunoradiometric assays, we investigated eight data-reduction methods with two commercially available assays of thyrotropin. In four of these methods linear data-reduction models are used: logit-log programs of Iso-Data, Micromedic, and Hewlitt-Packard, and probit-log of Hewlitt-Packard. The other four were nonlinear data-reduction models: Iso-Data's "French curve" (modified spline), four-parameter logistic function, and point-to-point methods, as well as a nonlinear least squares method. In using the eight data-reduction methods on data from analyses of 78 patients' samples, we found clinically relevant differences between models. In fact, differences found by changing data-reduction models were greater than the difference between the two commercial kits.

Humans↗

PubMed1980

A simple method for fitting multi-exponential curves of the decay type in a hand calculator.

The method of curve fitting here described is simple, dependable and can be programmed in a hand calculator. It consists in a log linear regression "peeling" that uses the maximization of the correlation coefficient for determining the number of exponential terms. It was experimentally verified and found to give satisfactory answers when compared to weighted least square iterative techniques.

Animals↗

PubMed1993

Overhead and forward reach capability during exposure to +1 to +6 Gx loads.

The lack of reach performance data obtained under space-flight conditions has led to questions regarding the operational impact of higher G loads on crew performance. This investigation studied the effect of increasing G loads on reach capability. Ten subjects were exposed in a stepwise fashion to increasing accelerations resulting in G loads of from +1 to +6 Gx in the Brooks AFB centrifuge. Four subjects wore the pre-Challenger Launch Entry Helmet (LEH) ensemble and six the current Launch Entry Suit (LES). The subjects performed standardized reach sweeps at each G level. These sweeps were recorded on videotape and subsequently analyzed using a 3-dimensional motion analysis system. Significant differences in forward and overhead reach were determined using the General Linear Models (GLM) procedure of the Statistical Analysis System (SAS) program. The results from this study suggest that purposeful movement can be realistically performed in the LEH at the 5 G level and in the LES up to the 4 G level.

Gravitation↗

PubMed1996

[Adaptation of the measurement of plasma and erythrocyte glutathione peroxidase activity on Hitachi 911].

The aim was to automate the assay of plasma and erythrocyte glutathione peroxidase (GSH-Px) activity using the Hitachi 911 (Boehringer Mannheim). There is a need for a reliable and rapid technique for the determination of GSH-Px activity to evaluate 'the oxidative stress'. The technique used was that proposed by the Randox laboratories (Randox Laboratories Ltd, Ransel test, reference: RS-505). The Hitachi 911 was programmed by adapting the manual Randox technique. Repeatability, reproducibility and linearity were satisfactory, and usual values for plasma and erythrocyte GSH-Px activity were determined. Automation of the Ransel test for determination of GSH-Px activity was very useful for serial assays. In addition, the technique is practical and has good interlaboratory reproducibility.

Blood Chemical Analysis↗

PubMed1989

A computer program in BASIC for estimation of ED50 and LD50.

A BASIC computer program for calculating ED50 and LD50 values and their confidence limits by probit analysis and weighted linear regression is presented. It also includes the Chi square procedure for testing the mathematical model and allows on-screen high resolution graphic display. The portable program can easily be modified for use in different models of microcomputers.

Animals↗

PubMedDate not supplied

Implementing the Fisher's discriminant ratio in a k-means clustering algorithm for feature selection and data set trimming.

The Fisher's discriminant ratio has been used as a class separability criterion and implemented in a k-means clustering algorithm for performing simultaneous feature selection and data set trimming on a set of 221 HIV-1 protease inhibitors. The total number of molecular descriptors computed for each inhibitor is 43, and they are scaled to lie between 1 and 0 before being subjected to the feature selection process. Since the purpose is to select some of the most class sensitive descriptors, several feature evaluation indices such as the Shannon entropy, the linear regression of selected descriptors on the pKi of selected inhibitors, and a stepwise variable selection program are used to filter them. While the Shannon entropy provides the information content for each descriptor computed, more class sensitive descriptors are searched by both the linear regression and stepwise variable selection procedures. The inhibitors are divided into several different numbers of classes. They are subsequently divided into five classes due to the fact that the best feature selection result is obtained by the division. Most of the good features selected are the topological descriptors, and they are correlated well with the pKi values. The outliers or the inhibitors with less class-sensitive descriptor values computed for each selected descriptor are identified and gathered by the k-means clustering algorithm. These are the trimmed inhibitors, while the remaining ones are retained or selected. We find that 44% or 98 inhibitors can be retained when the number of good descriptors selected for clustering is three. The descriptor values of these selected inhibitors are far more class sensitive than the original ones as evidenced by substantial increasing in statistical significance when they are subjected to both the SYBYL CoMFA PLS and Cerius2 PLS regression analyses.

Journal Article↗

PubMedDate not supplied

Parametrization strategy for the MolFESD concept: quantitative surface representation of local hydrophobicity.

We derive a new model for the established concept of the molecular free energy surface density (MolFESD) yielding a more rigorous representation of local surface contributions to the overall hydrophobicity of a molecule. The model parametrization makes efficient use of both local and global information about solvation thermodynamics, as formulated earlier for the problem of predicting free energies of hydration. The free energy of transfer is separated into an interaction contribution and a term related to the cavity formation. Interaction and cavity components are obtained from the statistical three-dimensional (3D) free energy density and a linear combination of surface and volume terms, respectively. An appropriate molecular interaction field generated by the program Grid is used as an approximate representation of the interaction part of the 3D free energy density. We further compress the 3D density by means of a linear combination of localized surface functions allowing for the derivation of local hydrophobic contributions in the form of a free energy surface density. For a set of 400 compounds our model yields significant correlation (R(2) = 0.95, sigma = 0.57) between experimental and calculated log P values. The final model is applied to establish a correlation between partial free energies of transfer for a series of sucrose derivatives and their relative sweetness, as studied earlier in the group of the authors. We find considerable improvement regarding the rms error of the regression thus validating the presented approach.

Journal Article↗

PubMed2000

A new in vitro/in vivo kinetic correlation method for nitrofurantoin matrix tablet formulations.

The kinetic distributions of in vitro percentage release and in vivo percentage urinary excretion rates of nitrofurantoin from matrix tablets were plotted using a kinetic program. In vitro release rates were determined using the USP paddle and half-change methods. Urinary excretion curves of the drug were characterized by means of the statistical moments. The individual linear correlations between each in vitro and in vivo kinetic distribution were established, and regression equations were calculated. The application results of the best correlations obtained were evaluated according to in vivo results. A reversed kinetic procedure was applied for transformation of the correlated kinetic values to the drug percentage release rates. The modified Langenbucher kinetic showed excellent linear correlation (r = .9985). The method that is proposed in this study, the kinetic correlation program, is simple, independent of time, and suggests that it is possible to use kinetic distributions in the in vitro/in vivo correlation. This study also suggests using kinetic correlation to investigate the suitability of the in vitro dissolution methods with the in vivo drug dissolution.

Anti-Infective Agents, Urinary↗

PubMed1984

Identification of genes and gene products necessary for bacterial bioluminescence.

Expression of luminescence in Escherichia coli was recently achieved by cloning genes from the marine bacterium Vibrio fischeri. One DNA fragment on a hybrid plasmid encoded regulatory functions and enzymatic activities necessary for light production. We report the results of a genetic analysis to identify the luminescence genes (lux) that reside on this recombinant plasmid. lux gene mutations were generated by hydroxylamine treatment, and these mutations were ordered on a linear map by complementation in trans with a series of polar transposon insertions on other plasmids. lux genes were defined by complementation of lux gene defects on pairs of plasmids in trans in E. coli. Hybrid plasmids were also used to direct the synthesis of polypeptides in the E. coli minicell system. Seven lux genes and the corresponding gene products were identified from the complementation analysis and the minicell programing experiments. These genes, in the order of their position on a linear map, and the apparent molecular weights of the gene products are luxR (27,000), luxI (25,000), luxC (53,000), luxD (33,000), luxA (40,000), luxB (38,000), and luxE (42,000). From the luminescence phenotypes of E. coli containing mutant plasmids, functions were assigned to these genes: luxA, luxB, luxC, luxD, and luxE encode enzymes for light production and luxR and luxI encode regulatory functions.

Cloning, Molecular↗

PubMed1998

Effects of readiness for drug abuse treatment on client retention and assessment of process.

AIMS: This study examined client motivation as a predictor of retention and therapeutic engagement across the major types of treatment settings represented in the third national drug abuse treatment outcome study (DATOS) conducted in the United States. DESIGN: Sequential admissions during 1991-93 to 37 programs provided representative samples of community-based treatment populations. Based on this naturalistic non-experimental evaluation design, hierarchical linear model (HLM) analysis for nested data was used to control for systematic variations in retention rates and client attributes among programs within modalities. SETTING: The data were collected from long-term residential (LTR), outpatient methadone (OMT) and outpatient drug-free (ODF) programs located in 11 large cities. PARTICIPANTS: A total of 2265 clients in 18 LTR, 981 clients in 13 OMT and 1791 clients in 16 ODF programs were studied. MEASUREMENTS: Pre-treatment variables included problem recognition and treatment readiness (two stages of motivation), socio-demographic indicators, drug use history and dependence, criminality, co-morbid psychiatric diagnosis and previous treatment. Retention and engagement (based on ratings of client and counselor relationships) served as outcome criteria. FINDINGS: Pre-treatment motivation was related to retention in all three modalities, and the treatment readiness scale was the strongest predictor in LTR and OMT. Higher treatment readiness also was significantly related to early therapeutic engagement in each modality. CONCLUSIONS: Indicators of intrinsic motivation--especially readiness for treatment--were not only significant predictors of engagement and retention, but were more important than socio-demographic, drug use and other background variables. Improved assessments and planning of interventions that focus on stages of readiness for change and recovery should help improve treatment systems.

Adult↗

PubMed1982

Cyclic nucleotide-induced maturation of human promyelocytic leukemia cells.

Myeloid differentiation in vitro is characterized by the sequential appearance of morphological, functional, and biochemical markers of maturation. We examined the effect of agents that increased the intracellular concentration of adenosine 3'5'-cyclic monophosphate on the expression of these markers by human promyelocytic leukemia cells (HL60). Cells treated with 500 muM N(6),O(2)-dibutyryl adenosine 3'5'-cyclic monophosphate expressed formyl peptide and complement receptors, reduced nitroblue tetrazolium, adhered to substrate, demonstrated chemotaxis and stimulated lysosomal enzyme release, rapidly ceased proliferation, and assumed the morphology of myelocytes and metamyelocytes. Prostaglandin E(2) (100 nM) and theophyllin (500 muM) induced similar functional changes but the cells did not mature beyond the myelocyte stage. Cholera toxin (1 or 50 nM) induced formyl-peptide receptor expression and adherence, but the cells did not reduce nitroblue tetrazolium, continued to proliferate, and were unchanged morphologically. Formyl-peptide receptor expression was the earliest marker of these modified programs of maturation. The receptor appeared within 2 h after treatment and increased linearly for 72 h. Receptor expression was dependent on new protein synthesis. At 48 h, Scatchard analysis demonstrated 2.4 x 10(5) receptors/ cell with a K(D) of 1.3 nM. In contrast to induction of HL60 differentiation by dimethyl sulfoxide, retinoic acid, or phorbol myristate acetate, the developmental programs initiated by agents that raised intracellular adenosine 3'5'-cyclic monophosphate shared several unique features: (a) plasma membrane maturation was dissociated from morphological maturation; (b) no latent period was evident following induction-the earliest membrane marker was expressed within 2 h; (c) commitment to terminal differentiation was delayed.

Binding, Competitive↗

PubMed2004

Computer program for determining fluorescence resonance energy transfer efficiency from flow cytometric data on a cell-by-cell basis.

The determination of fluorescence resonance energy transfer (FRET) with flow cytometry (FCET) is one of the most efficient tools to study the proximity relationships of cell membrane components in cell populations on a cell-by-cell basis. Because of the high amount of data and the relatively tedious calculations, this procedure should be assisted by powerful data processing software. The currently available programs are not able to fulfill this requirement. We developed a Windows-based program to calculate fluorescence resonance energy transfer efficiency values from list mode flow cytometry standard (FCS) files. This program displays the measured data in standard plots by generating one- and two-parameter histograms on linear or logarithmic scales. A graphical gating tool allows the user to select the desired cell population according to any combination of the parameter values. The program performs several statistical calculations, including mean, S.D., percent of the gated data. We have implemented two types of data sheet for FRET calculations to aid and guide the user during the analysis: one with population-mean-based autofluorescence correction and the other with spectrum-based cell-by-cell autofluorescence correction. In this paper, we describe the gating algorithms, the file opening procedure and the rules of gating. The structure of the program and a short description of the graphical user-interface (GUI) are also presented in this article.

Algorithms↗

PubMed2000

Deprived areas and attendance to screening of cervix uteri cancer in a French region.

OBJECTIVES: To examine the relationship between deprivation and attendance to cervical cancer screening. METHODS: Three deprivation indices (Carstairs, UnderPrivileged Area, Department of Environment) were calculated for women aged 25-65 attending a 1993-95 cervical cancer screening program (Doubs "département", France), with 594 municipalities as statistical units. Weighted multivariate linear regressions were performed, with attendance rate as the dependent variable, and the three deprivation indices in turn as independent variables along with women's mean age, average net income, density of (para)medical amenities, density of population and proportion of women. RESULTS: Per municipality women were numbered 1-29,822 (mean 210). In multivariate models, the three deprivation indices were negatively linked to attendance rate, and so were mean age of women and density of population. Average net income, proportion of women, and density of (para)medical amenities (nurses, laboratories, ambulances, physicians, dentists) were positively associated with attendance rate. CONCLUSIONS: In early stages, cervical cancer screening programs should account for populations living in deprived areas, through focused health promotion efforts and easier access to screening facilities.

Adult↗

PubMed2004

Reliability of calculating the cepstral peak without linear regression analysis.

Measures of cepstral peak prominence, using the smoothing algorithm and linear regression analysis software developed by Hillenbrand, have been shown to be reliable predictors of dysphonia in voice samples.(1-4) Recently, the Computerized Speech Laboratory [(CSL) Kay Elemetrics, Pinebrook, New Jersey] has introduced cepstral analysis as a component of that software package. The cepstral peak, in this instance, is calculated by the voice clinician analyzing the phonatory sample by subtracting the value of the peak from the apparent baseline signal. This study compares the ability of cepstral peak values calculated from the CSL software to predict dysphonia reliably with that of the values produced by the smoothing algorithm and linear regression analysis of Hillenbrand. The results of this study show that linear regression analysis is an important step in calculating the cepstral peak prominence, thus limiting the usefulness of software programs that do not employ this step.

Algorithms↗

PubMed2004

A review of medical school records to investigate the effectiveness of enrichment programs for "at risk" students.

BACKGROUND: Although considerable attention has been given to the establishment of enrichment programs, almost none has focused on evaluating their effectiveness. PURPOSE: To assess whether or not skills acquired during enrichment programs contributed to students' academic success in medical school. METHODS: Success in medical school, as characterized by lack of delaying events (DE), student status, and United States Medical Licensing Examination-Step I scores were analyzed using a general linear model procedure to determine the effect of participation in 1 or more enrichment programs. Proportional program participation was analyzed using a chi-square test of equal proportion. RESULTS: Participants from the "serious research" enrichment programs experienced significantly fewer DE (p <.01), which contributed to student success. Some enrichment programs had disproportionately higher attendance. CONCLUSIONS: Participation in research-based enrichment programs for matriculating students who are "at risk" may develop critical thinking and problem-solving skills that help students to minimize DE.

Educational Measurement↗

PubMed1997

The extent of military medicine topics taught in military family practice residency programs: Part II, A survey of residency graduates from 1987-1990.

The Military Unique Curricula (MUC) was published in 1988 as a guideline for instruction at military residencies in military-specific topics. Questionnaires were sent to 464 military family practice residency graduates from 1987-1990 to evaluate the degree of implementation of the MUC and attitudes and logistical factors relevant to military medicine instruction in military family practice residencies. Analysis reveals a range of opinions regarding the importance of military medicine and the amount of instruction on military medicine topics offered among programs. The total number of topics offered for instruction was positively correlated (p < 0.05) with the time available to teach the material, a perception that the material would not be best learned at the Combat Casualty Care Course, and the presence of a specific military medicine curriculum within the residency. This survey provides baseline information for future evaluation of the influence of MUC on military medicine instruction in residency programs. Suggestions are offered to improve instruction on military medicine topics in military family practice residencies.

Attitude of Health Personnel↗

PubMed2005

Local-MP2 electron correlation method for nonconducting crystals.

Rigorous methods for the post-HF (HF-Hartree-Fock) determination of correlation corrections for crystalline solids are currently being developed following different strategies. The CRYSTAL program developed in Torino and Daresbury provides accurate HF solutions for periodic systems in a basis set of Gaussian type functions; for insulators, the occupied HF manifold can be represented as an antisymmetrized product of well localized Wannier functions. This makes possible the extension to nonconducting crystals of local correlation linear scaling On techniques as successfully and efficiently implemented in Stuttgart's MOLPRO program. These methods exploit the fact that dynamic electron correlation effects between remote parts of a molecule (manifesting as dispersive interactions in intermolecular perturbation theory) decay as an inverse sixth power of the distance R between these fragments, that is, much more quickly than the Coulomb interactions that are treated already at the HF level. Translational symmetry then permits the crystalline problem to be reduced to one concerning a cluster around the reference zero cell. A periodic local correlation program (CRYSCOR) has been prepared along these lines, limited for the moment to the solution of second-order Moller-Plesset equations. Exploitation of point group symmetry is shown to be more important and useful than in the molecular case. The computational strategy adopted and preliminary results concerning five semiconductors with tetrahedral structure (C, Si, SiC, BN, and BeS) are presented and discussed.

Journal Article↗

PubMed1992

An image analysis and statistical evaluation program for the assessment of tumour cell invasion in vitro.

Tumour cell invasion is a complex process, which is essential for the formation of metastasis and is therefore of critical clinical importance. For detailed investigations of the invasive process, quantifiable in vitro models of invasion are necessary. In this study we describe an image analysis procedure and a statistical program which facilitate an objective analysis of experiments carried out using the embryonic chick heart invasion model of Mareel. Tumour multicellular spheroids are confronted with embryonic chick heart fragments in culture and are sampled after different time intervals for up to 7 days. Immunohistological sections are then evaluated by an image analysis procedure which provides 9 parameters indicating invasion, proliferation and destruction taking place in the confrontation cultures. The data obtained by image analysis are further evaluated by a statistical program which describes the change with time of each parameter by means of linear regression analysis. Thus the data obtained at various time intervals serve as the source data for a single statistic, namely the slope of the regression line. Confidence intervals and statistical differences between various experiments can be calculated. In order to make the procedure more comprehensible in biological terms, the program provides a full text interpretation of the experimental results. The image analysis procedure in conjunction with statistical evaluation and text interpretation provides a comprehensive tool for the quantitative assessment of experimental invasion in vitro.

Animals↗