Two programs have been written which permit analysis of multiple continuous-rate enzyme-cascade assays conducted with the use of an ELISA spectrophotometer and a synthetic chromogenic substrate. Because the product of the first reaction functions as the enzyme in the second reaction, production of chromophore continuously accelerates and it is the rate of acceleration which serves to measure the rate of the initial reaction in the system. The first program determines the rate of acceleration using linear regression to analyze the reaction curves as a function of the square of time. The second program, using a Simplex algorithm, determines the parameters which establish the assay standard curve by fitting the rate data to the Hill equation. Used together, these programs facilitate the analysis of many kinetic experiments conducted simultaneously.
A computer program package has been constructed for use in patient survival analyses for chronic diseases based on aggregated data. The central concept of the analyses--the relative survival rate--is the ratio of the observed survival rate of the patients to the survival rate expected in a group in the general population similar to the group of patients at the beginning of the follow-up (interval), with respect to age, sex and calendar time. This quantity is used to measure patient survival adjusted for the effect of mortality attributable to the competing risks of death without employing information on causes of death of individual patients. The package contains three alternative methods of estimating the relative survival rates, two different ways of estimating the expectation of life for the patients, and five methods of testing the relative survival patterns using information on the whole follow-up period. Conventional survival and competing risk analysis can also be performed with the package. It is hoped that the package will facilitate standardization of statistical methodology and terminology in long-term survival studies for chronic diseases.
The glomerular capillary wall of the kidney behaves as an electronegatively charged structure consisting of three layers, the lamina densa and the two laminae rarae, which are differently chrrged. Thus, a three layer model is proposed to analyse the transport of charged macromolecules across this wall.
A program has been written to determine T-score profile patterns, thus allowing the immediate assessment of morphological similarities and differences between taxa. For a given data set, the program will produce T-scores, T-score correlation coefficients and associated significance statistics, weighted means and standard deviations for all input variables, and a graphic display of the T-score profile pattern(s). This program should prove to be of great interest to physical anthropologists, zoologists and other researchers in the life sciences with an interest in taxonomy, systematics and phylogeny.
A microcomputer program has been developed to aid field and laboratory anthropologists and demographers estimate biological dynamics of human populations.
A computer program has been developed that can be used for analysing a binary outcome variable and a set of regressors of type interval with a logistic (i.e. nonlinear) model.
Writing programs for use by others is not easy. Above all, one must know the group the program is written for, and try to relate the program to this group.
A pharmacokinetic program that allows individualization of drug dosage regimens through the Bayesian method is described. The program, which is designed for the Hewlett-Packard HP-41 CV calculator, is based upon the one-compartment open model with either instantaneous or zero-order absorption. Individualized estimation of the patient's kinetic parameters (clearance and volume of distribution) is performed by analyzing the plasma levels measured in the patient as well as considering the population data of the drug. After estimating the individual kinetic parameters by the Bayesian method, the program predicts the dosage regimen that will elicit the desired peak and trough plasma levels at steady state. For comparison purposes, the least-squares estimates for clearance and volume of distribution are calculated, and dosage prediction can also be made on the basis of the least-squares estimates. The least-squares estimates can be used to calculate population pharmacokinetic parameters according to the Standard Two-Stage method. Several examples of clinical use of the program are presented. The examples refer to patients with classic hemophilia who were treated with Factor VIII concentrates. In these patients, the Bayesian kinetic parameters of Factor VIII have been estimated through the calculator program. The Bayesian parameter estimates generated by the HP-41 have been compared with those determined by a Bayesian program (ADVISE) designed for microcomputers.
The program described analyses DNA histograms obtained in flow cytometry using the Gaussians method. The program is written in BASIC to run on a low-cost microcomputer. It utilizes a simple strategy to obtain good estimates of the parameters required for reducing the problem to a task solvable with linear least-squares methods. Features of the program are flexibility, since it is possible to choose different options for parametrization and spacing of Gaussians, and the fact that the operator is not required to provide interactive inspection or inputting parameter values. The capability and velocity of the program, in all its options, are tested and compared on a series of different (not computer-simulated) histograms obtained in our flow cytometry laboratory. Our results suggest that a fresh approach to parametrization may be useful.
The Kappa statistic is used to measure the interobserver similarity based on categorical scales. The cases of two or more observers with two or more rating categories are considered. Allowance is made for the attachment of disagreement weights, based on rational or clinical grounds, to different rating categories. Tests of hypotheses about the conditions Kappa = 0 and Kappa greater than 0 are conducted.
A computer system is presented which provides off-line computation of cycle-triggered histograms (CTH) of respiration-related neuronal activity. Binwidths of the histograms are freely selectable by software from 10 ms to 100 ms. For special evaluation purposes, CTHs can be standardized in different ways concerning cycle duration as well as amplitude. Time incidence of maximum frequency, center of gravity and expiration-to-inspiration phase transition within the respiratory cycle are computed. The system employs special hardware interfaces to an 8-bit microcomputer which are briefly described. Data acquisition, data manipulation and output handling of the results are performed by chaining 3 compiled BASIC programs. Some comments on peculiarities of the BASIC language concerning combined application of a BASIC interpreter and a BASIC compiler are brought up. The usefulness of the method is demonstrated by examples of CTHs computed from the activity of medullary respiration-related neurons as well as of the corresponding phrenic nerve mass activity.
A noniterative procedure based upon the minimum modified X2 approach is employed to test the model of homogeneity of one-dimensional margins in square tables. Such tables may arise from matched pairs with k outcomes. The special case of double dichotomy (i.e. matched pairs with two outcomes) reduces to the McNemar test statistic. The case of multiple matched controls is also dealt with. The Cochran's Q test is used to test the marginal homogeneity in cases comparing m distinct matched samples in addition to testing trends in proportions. Reference is made to the equivalence between these tests and the approach of hierarchical log-linear models for testing marginal homogeneity of square tables.
A FORTRAN program is provided for testing linear trend and homogeneity in proportions. Trend is evaluated by the Cochran-Armitage method and homogeneity is tested by an overall X2 test as well by multiple pairwise comparisons by the Fisher-Irwin exact method. The program should be easy to implement on any size of computer with a FORTRAN compiler.
A microprocessor-based system was developed for the measurement and on-line calculation of values and derivatives of expiratory variables and their response to exercise. The system accepts analog signals from gas analysers, ECG electrodes and flow transducer, digitizes these signals, calculates values of required parameters and presents results on a video display. The system offers the user various options of logging and data processing. Plots of the values of calculated parameters versus exercise time and correlation between variables can be easily produced by the system. A mass storage unit was available with the system to enable the storage of calculated variables for off-line analysis. Hardcopy of displayed results and plots can be provided by the system.
This paper presents two programs implemented on a microcomputer for analog-to-digital (A-to-D) conversion of neurophysiological signals. The first program, TIMET, sets flexible pulse trains for the timing of the A-to-D conversions, executed by the second program, ADC8. TIMET contains options for a continuous or a triggered pulse train with variable onset delay. ADC8 allows sampling rates up to 30 kHz for one channel and 9 kHz for the maximum of 7 channels, with about 8 μs lag between channels. The digitized data are displayed with interactive gain control from keyboard input, and selected sweeps can be stored on disk files.
Four parameters of a two-pool model are evaluated by an iterative method using the explicit solutions of the linear differential equations. For this it was presumed that the residual renal clearance is sufficiently small. Five data pairs of measured plasma concentrations ci for the time points ti (i = 0 to 4), as well as the dialyzer and residual renal clearances (KD and KR), must be given and put in the calculator. A sample run is shown for urea kinetics. The parameter estimation takes about 10 min. The program is suitable to assist in the individualization of dialysis therapy.
An attempt was made to simulate in a mathematical model one of the two major effects of glucose upon 45Ca fractional outflow rate from prelabelled pancreatic islets, namely the increase in effluent radioactivity which is currently ascribed to the displacement of 45Ca from intracellular sites, as resulting from a facilitated influx of unlabelled 40Ca into the islet cells. The occurrence of such a rise in effluent radioactivity and its suppression in the absence of extracellular Ca2+ could only be simulated if the release of Ca by the vacuolar system was assumed to be stimulated by a rise in the cytosolic Ca concentration. It is proposed therefore that, in islets like in muscle, a process of Ca-stimulated Ca release may participate in the regulation of intracellular Ca distribution.
A calculator program that performs a nonlinear least-squares fit to data conforming to the one-compartment model with zero-order input is described. The program, which is designed for the Hewlett-Packard HP-41 CV calculator, is based on the Gauss-Newton iterative algorithm as modified by Hartley. A subroutine for calculation of initial parameter estimates is incorporated into the program. Plasma concentration data relative to a single oral dose of a sustained-release theophylline formulation are used to demonstrate the practical application of the program.
