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PubMedDate not supplied

A simple, effective system for assessing viability in split-thickness skin with the use of oxygen consumption.

To address the recognized need for better viability-assessment techniques in the banking of allograft skin, we have developed a simple, effective, and easily constructed system for measuring the aerobic activity in small skin samples. The system consists of a microcomputer interfaced to a Clark-type polarographic oxygen electrode to measure oxygen concentrations in discs (5 mm diameter) of split-thickness skin. The system allows simultaneous data acquisition and an on-screen display of oxygen readings on a linear or logarithmic scale. The computer program quantifies the rate of oxygen consumption by calculating a linear regression of oxygen measurements between 100 and 600 seconds. Data are stored in a standard format for easy transfer to commercial software packages for further analysis. The kinetics of oxygen consumption by porcine split-thickness skin stored at 4 degrees C for up to 21 days was assessed with this technique and showed a gradual decline in rate as function of storage time, reaching 50% recovery after 6 days. This assay is a simple and inexpensive method to establish and perform, thus making it suitable as a routine assay for use in the banking of skin and other tissues.

Animals↗
PubMed2003

New speech tests reveal benefit of wide-dynamic-range, fast-acting compression for consonant discrimination in children with moderate-to-profound hearing loss.

Fast-acting, wide-dynamic-range compression (WDRC) has been shown to give better discrimination of soft speech and shouted speech than linear amplification for moderately hearing-impaired young adults. For severe and profound hearing losses, higher compression ratios are needed. The resultant distortion of the temporal envelope and reduced modulation depth may offset improvements in audibility offered by WDRC. This study compares the effectiveness of WDRC and linear amplification for children with different degrees of hearing loss. Pre-recorded tests of closed-set consonant confusions and open-set word recognition were developed to assess performance. Three groups of subjects (aged 4-14 years) with moderate (51-70 dB), severe (71-90 dB) and profound (91-115 dB) hearing loss were fitted with hearing aids programmed with WDRC or linear amplification. The frequency response was adjusted to match each child's own hearing aid prescription. For each group, stimuli were presented both in quiet and in noise at levels chosen to avoid floor and ceiling effects. Consonant confusion scores for the profound and severe groups combined and for the moderate group were significantly better with WDRC than with linear amplification. Open-set test results showed greater variability. Although mean scores were higher for WDRC than for linear processing, the effects were of marginal statistical significance.

Adolescent↗
PubMed2006

Using LinLog and FACETS to model item components in the LLTM.

The current study investigates the performance of two Rasch measurement programs and their parameter estimations on the linear logistic test model (LLTM; Fischer, 1973). These two programs, LinLog (Whitely & Nieh, 1981) and FACETS (Linacre, 2002), are used to investigate within-item complexity factors in a spatial memory measure tool. LinLog uses conditional maximum likelihood to estimate person and item parameters and is an LLTM specific program. FACETS is usually reserved for the many-facet Rasch model (MFRM; Linacre, 1989), however in the case of specifically designed within-item solution processes, a multifaceted approach makes good sense. It is possible to consider each dimension within the item as a separate facet, just as if there were multiple raters for each item. Simulations of 500 and 1000 persons expand the original data set (114 persons) to better examine each estimation technique. LinLog and FACETS analyses show strikingly similar results in both the simulation and original data conditions, indicating that the FACETS program produces accurate LLTM parameter estimates.

Humans↗
PubMed1999

Pharmacokinetic-pharmacodynamic modeling of risperidone effects on electroencephalography in healthy volunteers.

RATIONALE: CNS-active drugs produce specific electroencephalographic changes and the concentration-effect relationship of antipsychotics may be elucidated by adopting electroencephalography (EEG) as an effect measurement tool. OBJECTIVE: The purpose of the present study was to determine the concentration-effect relationship of risperidone by assessing the EEG effect after oral administrations of single dose risperidone in healthy young males. METHODS: Nine healthy male volunteers received a 1 mg single oral dose of risperidone according to a placebo controlled crossover design. Plasma levels of risperidone and its active metabolite 9-hydroxyrisperidone were measured by radioimmunoassay. Quantitative EEG parameters were obtained for each of four frequency bands through spectral EEG analysis. The difference in the absolute power in the delta frequency band for the F3 lead between risperidone and placebo was used as a drug effect parameter. For pharmacokinetic-pharmacodynamic modeling, the hypothetical effect compartment kinetically linked to plasma by a first-order process was postulated. All curve fittings were done with the non-linear curve-fitting program NONLIN. RESULTS: Our results showed that absolute powers in delta and theta frequency bands were higher for risperidone administration than for placebo at all EEG leads, and the maximum effects were detected at about 3 h after administration of the drug. The hysteresis loop was observed in the plot of plasma concentration of risperidone or sum of risperidone and 9-hydroxyrisperidone (Cp) versus EEG effect for each subject. A linear model adequately described the relationship between the effect compartment concentrations (Ce) and EEG effects, and the two limbs of hysteresis in the Cp-effect plot were collapsed in the Ce-effect plot for risperidone or risperidone plus 9-hydroxyrisperidone. CONCLUSION: The increases of absolute power for delta and theta frequency bands of EEG were induced by single oral administration of risperidone. The linear PK-PD model fit well with the relationship between effect compartment concentrations (Ce) and EEG effects of risperidone.

Administration, Oral↗
PubMed2000

[Determination of chlorzoxazone and paracetamol in co-chlorzoxazone tablet by multi-wavelength linear regression method].

This paper reports that the contents of chlorzoxazone and paracetamol in the co-chlorzoxazone tablet may be determined by the multi-wavelength linear regression method. The program was edited by BASIC. The average recovery and RSD of chlorzoxazone and paracetamol were 98.67%, 0.34% and 100.05%, 0.31% (n = 5), respectively. This method is simple and rapid with satisfactory results.

Acetaminophen↗
PubMed1990

Use of a Lotus 1-2-3 spreadsheet to plot the confidence and the prediction intervals in linear regression analysis.

Computer-derived spreadsheet programs such as Lotus 1-2-3 are being used by many investigators for individualized statistical calculations. Spreadsheet templates have been described for the performance of simple statistical tests by non-statisticians with relatively limited computer experience. This paper describes a template for use with Lotus 1-2-3 for automatic graphic display of confidence and prediction intervals of simple linear regression analysis. The graph can be printed using the Lotus printgraph program. The program also allows comparison of the slope and the intercept of two regression lines.

Computer Graphics↗
PubMed1975

Steroid-receptor quantitation and characterization by electrophoresis in highly cross-linked polyacrylamide gels.

Conditions for discontinuous polyacrylamide gel electrophoresis have been defined in which progesterone receptors of chick oviduct cytosol and a variety of steroid-binding proteins from other sources are stable and amenable to quantitative analysis. The essential modifications from standard procedures include the use of (1) separation gels in which the cross-linking agent/acrylamide monomer = 15:85, (2) glycerol (10% v/v) in all phases of the Trisglycine-HCl buffer system (pH 10.2 in the separation phase during electrophoresis at 0 degrees), and (3) a layer of a charged reducing agent, thioglycolate, beneath the sample layer. Electrophoresis of untreated oviduct cytosol labeled with [3H]progesterone +/- competing steroids revealed a heterodisperse slow peak and a sharp fast peak. Both peaks displayed the steroid-binding specificity and saturability that are characteristic of intracellular receptors. Recovery of steroid from both the slow and fast components increased linearly with sample load up to 60 mul of cytosol (1.2 mg of protein)/gel (6 mm diameter). The specific progesterone binding detected by this technique was comparable to that detected by charcoal-dextran treatment or ion exchange filtration. Relative electrophoretic mobilities (Rf) of globular protein standards and steroid-protein complexes in cytosol and chick serum were measured in separation gels with total gel concentrations (T) systematically varied from 5 to 15% (w/v). Data were processed by computer programs to obtain weighted linear regressions of log Rf on T (Ferguson plots) and the joint 95% confidence limits of the slopes (-KR) and intercepts of these plots. Molecular radii (R) of the binding components and apparent molecular weights (M) were calculated from the linear correlation of R with KR 1/2 for the standards. The value of M is approximately 158,000 obtained for the cytosol fast component was independent of the length of the separation gel, the presence of a stacking gel or prior exposure of the cytosol to KCl. It was higher than expected from the sedimentation coefficient of 4.2 S in the same pH 10.2 buffer. Electrophoresis in 170-mm separation gels without stacking gels revealed that KCl extracts of protamine-precipitated cytosol contain a different receptor form, of lower net negative charge than the cytosol fast form. The results demonstrate the utility of electrophoresis in highly cross-linked gels of several concentrations to discriminate between various receptor forms and steroid-binding components of serum. This method may lead to overestimates of M for highly asymmetric receptor forms.

Animals↗
PubMed1986

Compartment modelling in nuclear medicine: a new program for the determination of transfer coefficients.

In many investigations concerning transport/exchange of matter in a natural system, e.g. functional studies in nuclear medicine, it is advantageous to relate experimental results to a model of the system. This paper presents a new computer program for the determination of linear transfer coefficients in a compartment model from experimentally observed time-compartment content curves. The program performs a least-square fit with the specified precision of the observed values as weight factors. The resulting uncertainty in the calculated transfer coefficients may also be assessed. The application of the program in nuclear medicine is demonstrated and discussed.

Animals↗
PubMed2002

Psychobehavioral response and weight loss prediction in a hospital-based weight reduction program.

BACKGROUND AND PURPOSE: Depression and binge eating are common adverse psychologic responses associated with weight loss in overweight and obese adults. This study aimed to assess the effects of different degrees of weight loss on psychologic functioning and the relationship between mood change and weight reduction, and to identify predictors of short-term weight loss among subjects in a hospital-based weight reduction program. METHODS: A total of 189 obese subjects who participated in a hospital-based weight-reduction program during a 12-week interval were enrolled in this study. They ranged in age from 18 to 67 years (mean, 40.5 +/- 12.3 yr) with female predominance (87.8%). Mean body weight was 79.3 +/- 13.9 kg and mean body mass index was 31.1 +/- 3.8 kg/m2 on entry into the program. Body weight was periodically measured and subjects were asked to complete two self-administered questionnaires including the Brief Symptom Rating Scale (BSRS) and the Bulimic Investigatory Test, Edinburgh (BITE), pre- and post-treatment. RESULTS: Using the last observation carried forward method of analysis, the average weight loss for all participants was 5.6 +/- 3.7 kg. For subjects who completed the 12-week program, weight loss was 6.6 +/- 3.6 kg. Subjects who completed the program (n = 115, 60.8%) had significantly reduced BITE as well as all BSRS subscale scores at the end of the program. There was no linear relationship between mood change and weight loss by correlation analysis, but subjects with higher degrees of weight loss had improvement in more dimensions of psychologic functioning. Initial mood and binge-eating status predicted neither compliance nor weight reduction. Two biologic factors (initial weight loss, initial body weight) and one behavioral factor (attendance rate) were identified as significant predictors of short-term weight loss for all subjects. CONCLUSIONS: There was no evidence that weight loss made mood or eating pathology worse among those who completed the weight loss program. Beneficial effects on general psychologic functioning and eating pathology were demonstrated for subjects with a minimal weight loss of 5% of initial weight and who completed the program. Psychologic assessments at the start of the program did not predict weight loss at the end of participation in this hospital-based weight loss program.

Adolescent↗
PubMedDate not supplied

Clinical implementation of stereotaxic brain implant optimization.

This optimization method for stereotaxic brain implants is based on seed/strand configurations of the basic type developed for the National Cancer Institute (NCI) atlas of regular brain implants. Irregular target volume shapes are determined from delineation in a stack of contrast enhanced computed tomography scans. The neurosurgeon may then select up to ten directions, or entry points, of surgical approach of which the program finds the optimal one under the criterion of smallest target volume diameter. Target volume cross sections are then reconstructed in 5-mm-spaced planes perpendicular to the implantation direction defined by the entry point and the target volume center. This information is used to define a closed line in an implant cross section along which peripheral seed strands are positioned and which has now an irregular shape. Optimization points are defined opposite peripheral seeds on the target volume surface to which the treatment dose rate is prescribed. Three different optimization algorithms are available: linear least-squares programming, quadratic programming with constraints, and a simplex method. The optimization routine is implemented into a commercial treatment planning system. It generates coordinate and source strength information of the optimized seed configurations for further dose rate distribution calculation with the treatment planning system, and also the coordinate settings for the stereotaxic Brown-Roberts-Wells (BRW) implantation device.

Algorithms↗
PubMedDate not supplied

Computer generation of high-energy x-ray dose distributions.

A computer program for the generation of high-energy x-ray dose distributions has been developed. The program takes account of the fact that the x-ray beam profile, as affected by penumbra, wedges, beam blocks, or flattening filters, is one of the prime determinants of the dose distribution. Doses from primary and scattered radiation are calculated separately by using published tissue-air ratio (TAR) and scatter-air ratio (SAR) data. The dose from scattered radiation is determined by dividing the x-ray field into a series of scattered strips and summing the contribution from each. Wedges or beam blocks are taken into account simply by earning their actual coordinates and linear attenuation coefficients. The program may be used to design wedges, beam blocks, or flattening filters prior to fabrication. Complete libraries of dose distribution for 60Co, 2-, 4-, and 6-MV x rays have been generated.

Computers↗
PubMed1996

[Study clinical application to determine heparin requirements during hemodialysis].

A de nove Weighted Stepwise Linear Model based on Gotch's heparin pharmacokinetic model has been designed to determine the heparin elimination rate constant during hemodialysis (HD). 100 times of HD in 26 patients with unstable dosage requirements of heparin were performed according to the computing method and the new heparin pharmacokinetic Weighted Stepwise Linear Model monitored be program of pocket calculator. The results showed not only stable anticoagulation but also successful prevention of patients's bleeding and avoidance of coagulation in hemodialyzer and blood tubing. The computer diagram presented in this paper is useful for propramming with different computer languages to calculate the heparin dosage requirements of patients undergoing HD.

Computers↗
PubMed1989

A BASIC program for the estimation of Michaelis-Menten parameters by the direct linear plot.

The use of manual graphical methods for the estimation of Michaelis-Menten kinetic parameters as recommended by Eisenthal and Cornish-Bowden (Biochem. J. 139 (1974) 715-720) was found to be impractical for large (n greater than 5) sample numbers. A BASIC program providing the rank ordered coordinates of intersections, which correspond to estimates of Km and Vmax in the direct linear plot method, is described.

Cytochrome P-450 Enzyme System↗
PubMed2004

On stochastic optimal control of partially observable nonlinear quasi Hamiltonian systems.

A stochastic optimal control strategy for partially observable nonlinear quasi Hamiltonian systems is proposed. The optimal control forces consist of two parts. The first part is determined by the conditions under which the stochastic optimal control problem of a partially observable nonlinear system is converted into that of a completely observable linear system. The second part is determined by solving the dynamical programming equation derived by applying the stochastic averaging method and stochastic dynamical programming principle to the completely observable linear control system. The response of the optimally controlled quasi Hamiltonian system is predicted by solving the averaged Fokker-Planck-Kolmogorov equation associated with the optimally controlled completely observable linear system and solving the Riccati equation for the estimated error of system states. An example is given to illustrate the procedure and effectiveness of the proposed control strategy.

Algorithms↗
PubMedDate not supplied

[Effect of linear, impact and vibration accelerations on the accuracy of performance of force load programs by an operator].

The factors that influence the accuracy with which motor commands are actualized were investigated. The study concentrated on linear acceleration of different sign (produced by rocking a heavy metal platform), vibration at a frequency of about 23 Hz, and impact acceleration resulting from the platform or the rotating chair being suddenly stopped. The force applied to hand sticks or foot levers was recorded by means of electromechanical sensors. It was demonstrated that smoothly varying and in particular impact acceleration caused normal men to subjectively underestimate their own muscle efforts. As a rule, this led to a greater than prescribed strength applied. It is very important to note that acceleration acting from right to left or from left to right (in the frontal plane) produced nonsymmetric pressure by the right and left limbs.

Acceleration↗
PubMed2005

Compartmental pharmacokinetics and tissue distribution of the antifungal triazole ravuconazole following intravenous administration of its di-lysine phosphoester prodrug (BMS-379224) in rabbits.

OBJECTIVES: Ravuconazole is a broad-spectrum antifungal triazole in clinical development. We investigated the compartmental plasma pharmacokinetics and tissue distribution of ravuconazole following administration of its novel intravenous (i.v.) di-lysine phosphoester prodrug, BMS-379224. METHODS: Normal catheterized rabbits received the prodrug at 1.25, 2.5, 5, 10, 20 and 40 mg/kg once daily as 5 min i.v. bolus for 8 days. Serial plasma levels were collected at days 1 and 7, and tissues were obtained 30 min after the eighth dose. Concentrations of ravuconazole were determined by a validated HPLC method. Plasma concentration data were fitted to a three-compartment pharmacokinetic model. Pharmacokinetic parameters were estimated by weighted non-linear least squares regression analysis using the WinNonlin computer program. RESULTS: Following single dosing, ravuconazole demonstrated linear plasma pharmacokinetics across the investigated dosage range. Cmax, AUC(0-infinity), V(ss), CL and terminal half-life (means +/- SEM) ranged from 2.03 to 58.82 mg/L, 5.80 to 234.21 mg x h/L, 5.16 to 6.43 L/kg, 0.25 to 0.18 L/h/kg and 20.55 to 26.34 h, respectively. Plasma data after multiple dosing revealed non-linear disposition at the 20 and 40 mg/kg dosage levels as evidenced by a dose-dependent decrease in CL (from 0.104-0.147 to 0.030 and 0.022 L/h/kg; P = 0.1053) and an increase in the dose-normalized AUC(0-infinity) (from 2.40-3.01 up to 11.90 and 14.56 mg x h/L; P = 0.0382). Tissue concentrations 30 min after the last dose were highest in the liver (12.91-562.68 microg/g), adipose tissue (10.57-938.55 microg/g), lung (5.46-219.12 microg/g), kidney (3.95-252.44 microg/g) and brain tissue (2.37-144.85 microg/g). CONCLUSIONS: The pharmacokinetics of ravuconazole fitted best to a three-compartment pharmacokinetic model. The compound revealed non-linear pharmacokinetics at higher dosages, indicating saturable clearance and/or protein binding. Ravuconazole displayed a long elimination half-life and achieved substantial plasma and tissue concentrations including in the brain.

Adipose Tissue↗
PubMed1984

An economic analysis of psychosocial rehabilitation.

The author examines three studies of the major monetary costs and benefits of psychosocial rehabilitation of the mentally ill; he focuses on hospitalization costs, costs of community treatment, and earnings from competitive employment. In the first study, which compared the effects of psychosocial rehabilitation with those of a support group over a nine-month period, an estimated savings of +1,880 per client was found among the clients receiving psychosocial rehabilitation. In the second study of treatment costs for 40 chronic psychiatric recidivists who were involved in an aggressive home outreach program, an estimated annual savings of +5,000 per client was found. In the third study 101 clients were interviewed six months after they had left a psychosocial rehabilitation program. Their earnings from competitive employment were linearly related to their length of participation in the program. The author concludes that these studies offer substantial evidence for the economic advantages of psychosocial rehabilitation.

Community Mental Health Services↗
PubMed1991

Algorithms for the derivation of Flux and Concentration Control Coefficients.

A computer program is described that derives the Flux and Concentration Control Coefficients for linear and branched metabolic pathways. The program prompts the user to enter a concise description of the metabolic pathway. From this description, the program constructs the appropriate equations in matrix form. The algorithm employed to obtain the symbolic determinants is described, and this algorithm also provides a convenient method for manual derivation of the Control Coefficients. The computer-based method will accommodate unlimited feed-forward and feed-backward loops and a maximum of two branches from each metabolite on the main pathway. The utility of the method is illustrated with a linear path with feed-forward and feed-backward loops, and with a substrate cycle as an example of a path with two branches.

Algorithms↗