SPLINT: a cubic spline interpolation program for the analysis of fragment sizes in one-dimensional electrophoresis gels.

SPLINT (SPLine INTerpolation) is a BASIC microcomputer program that uses electrophoretic data on the migration distances of DNA fragments of known size to approximate the relationship between distance moved and DNA fragment size by a piecewise cubic spline function. This function places all standards exactly on the calibration curve and then determines from it the sizes of other fragments in the gel. Special advantages of this program include the use of a digitizer to enter the fragment positions directly from a gel photograph and the optional generation of a graph of the approximating function plus the placement on it of points from any specified gel lanes.     

Comparing polynomial and cubic spline interpolation of segment angles for estimating L5/S1 net moment during symmetric lifting tasks

Simple video-based methods previously proposed for field research to estimate L5/S1 net moments during real-world manual materials handling rely on polynomial interpolation on the joint angles from key frames extracted from video recordings; however, polynomial interpolations may not converge as the number of interpolation points increases. Therefore, we compared L5/S1 net moments calculated from continuous kinematic measurements to those calculated from both polynomial and cubic spline interpolation on body segments angles during lifting tasks. For small number of interpolation points (<6) the error in the predicted moment from both the spline and polynomial fits decreased with the increase in the number of interpolation points; however, above 6 interpolation points error for the polynomial fits started to increase while the error from the spline fit continued to decrease. These results suggest that cubic spline interpolation on body segments angles provides a more robust basis for calculating L5/S1 net moment from a few key video frames.     

A computer program for the analysis of dental arch form using the cubic spline function.

This paper presents the details and logic of a FORTRAN computer program which fits a cubic interpolatory spline to a set of data points digitized from an exact size photographic reproduction of a dental model. It also measures the length of the arc and computes a set of normals to the curve to be used in evaluating the error in the fit of the spline. The program is used in studies of dental arch form and is useful in evaluating changes in the form of the arches due to orthodontic treatment. The measurement of the arc length provides an adequate assessment of space available in the dental arch, which is of importance to the orthodontist.     

Measuring the accuracies of motor unit firing times and action potential waveforms derived from surface electromyographic decomposition

This study included spike trigger averaging (STA) procedures to examine the acceptability of the Precision Decomposition (PD) III derived motor unit action potential (MUAP) trains that met the >90% accuracy criteria from the reconstruct-and-test. MUs met the >90% accuracy criteria from the reconstruct-and-test with STA procedures then applied. Y-intercepts and slopes were calculated for the firing rate- and MUAP amplitude-recruitment threshold relationships. Gaussian noise (1% of the SD of the mean interspike interval) was added to the firing times with the changes in MUAPs quantified. A total of 455 MUs were decomposed with 155 MUs removed as a result of the reconstruct-and-test. Five additional MUs were excluded via the STA criteria. The MUAP waveforms deteriorated with the inclusion of Gaussian noise. There were differences in the derived action potentials amplitudes of higher-threshold MUs between the PD III algorithm and the STA procedure. There was excellent agreement among the slopes and y-intercepts between the relationships that included or excluded MUs that did not meet the STA criteria. There was good agreement between the MUAP amplitude-recruitment threshold relationships derived from the PD III and STA procedure. The addition of the STA procedures did not alter the MU-derived relationships.     

用单相动作电位研究触发性心律失常

触发性心律失常(triggered arrhythmia)以冲动起源异常机制为特征受到临床的普通重视。近年来,接触电极或接触电极导管记录人或动物心内、外膜单相动作电位新技术的出现,为在整体动物或人心脏上获得触发性活动提供了前提。目前,单相动作电位(mono-phasic action Potential,MAP)已用于冠状动脉搭桥术中的局部心肌缺血、心肌电生理     

High-resolution structure determination of the CylR2 homodimer using paramagnetic relaxation enhancement and structure-based prediction of molecular alignment

Structure determination of homooligomeric proteins by NMR spectroscopy is difficult due to the lack of chemical shift perturbation data, which is very effective in restricting the binding interface in heterooligomeric systems, and the difficulty of obtaining a sufficient number of intermonomer distance restraints. Here we solved the high-resolution solution structure of the 15.4 kDa homodimer CylR2, the regulator of cytolysin production from Enterococcus faecalis, which deviates by 1.1 angstroms from the previously determined X-ray structure. We studied the influence of different experimental information such as long-range distances derived from paramagnetic relaxation enhancement, residual dipolar couplings, symmetry restraints and intermonomer Nuclear Overhauser Effect restraints on the accuracy of the derived structure. In addition, we show that it is useful to combine experimental information with methods of ab initio docking when the available experimental data are not sufficient to obtain convergence to the correct homodimeric structure. In particular, intermonomer distances may not be required when residual dipolar couplings are compared to values predicted on the basis of the charge distribution and the shape of ab initio docking solutions.     

Consideration of sample motion in cryo-tomography based on alignment residual interpolation

Recently, it has been shown that the resolution in cryo-tomography could be improved by considering the sample motion in tilt-series alignment and reconstruction, where a set of quadratic polynomials were used to model this motion. One requirement of this polynomial method is the optimization of a large number of parameters, which may limit its practical applicability. In this work, we propose an alternative method for modeling the sample motion. Starting from the standard fiducial-based tilt-series alignment, the method uses the alignment residual as local estimates of the sample motion at the 3D fiducial positions. Then, a scattered data interpolation technique characterized by its smoothness and a closed-form solution is applied to model the sample motion. The motion model is then integrated in the tomographic reconstruction. The new method improves the tomogram quality similar to the polynomial one, with the important advantage that the determination of the motion model is greatly simplified, thereby overcoming one of the major limitations of the polynomial model. Therefore, the new method is expected to make the beam-induced motion correction methodology more accessible to the cryoET community.     

Low back muscle action potential conduction velocity estimated using high-density electromyography

While a decreasing spectral content of surface electromyography reflects low back muscle fatigue development, reliability of these decreases may be insufficient. Decreasing frequency content is largely determined by decreasing average motor unit action potential conduction velocities (CV), which is considered a more direct measure of muscle fatigue development. However, for the low back muscles it has been proven difficult to identify propagating potentials and consequently estimate the CV. The aim of this study was to estimate the low back muscle CV from high-density multi-channel electromyography by using peak-delay and cross-correlation methods. Fourteen healthy male participants without a history of low-back pain performed a 30 degrees lumbar flexion trial until exhaustion while standing. For 10 out of the 14 participants (118 out of 560 sites) realistic CV estimates were obtained using both methods, the majority likely over the iliocostalis lumborum muscle. Between-method CV differences appeared to be small. Close to the spine a considerable number of sites (79) yielded systematically overestimated low back muscle CV values. Estimating low back muscle CV may allow additional insight into low back muscle fatigue development and potentially improve its monitoring using (high-density) surface electromyography.     

Study of the restitution of action potential duration using the artificial neural network

It is widely accepted that the APD (action potential duration) restitution plays a key role in the initializing and maintaining of the reentry arrhythmias. The Luo-Rudy II models paced with different protocols showed that the current APD had a complex relation with the previous APDs and diastole intervals (DIs). This relation could not be accurately described by a single exponential function. We used an artificial neural network to formularize this relation. The results suggested that back-propagation (BP) network could predict the current APD from the information of the first three previous beats. This would help provide a target for potential anti-arrhythmic therapies.     

High-resolution alignment of a 1-megabase-long genome region of three strains of Rhodobacter capsulatus.

A detailed restriction map of the genome of Rhodobacter capsulatus SB1003 was constructed recently by using an ordered set of overlapping cosmids. Pulsed-field gel electrophoresis-generated restriction patterns of the chromosomes of 14 other R. capsulatus strains were compared. Two of them, St. Louis and 2.3.1, were chosen for high-resolution alignment of their genomes with that of SB1003. A 1-Mb segment of the R. capsulatus SB1003 cosmid set was used as a source of ordered probes to group cosmids from the other strains. Selected cosmids were linked into one 800-kb contig and two smaller contigs of 100 kb each. EcoRV and BamHI restriction maps of the newly ordered cosmids were constructed by using lambda terminase. Long-range gene order in the new strains was mainly conserved for the regions studied. However, one large genome rearrangement inverted a 470-kb DNA fragment of the St. Louis strain between the rrnA and rrnB operons. A 50-kb deletion covering three SB1003 probes was found in strain 2.3.1 near rrnB. Conservation of about 50% of the positions of restriction sites in all these strains and nearly 80% for the pair 2.3.1- St. Louis made it possible to produce high-resolution alignment of the contiguous 800-kb genome segment. Ten deletions of 2 to 27 kb, one 30-kb inversion, and three translocations were found in this region. Strong clustering of the positions of polymorphic restriction sites was observed. For a 50-kb size interval, two patterns of the distribution of restriction sites were found, one with about 90% and the other with 5 to 30% conservation of sites. This structure may be explained by independent acquisition of these divergent regions from other Rhodobacter strains.     

Analysis of exposure-time-response relationships using a spline weight function

To examine the time-dependent effects of exposure histories on disease, we estimate a weight function within a generalized linear model. The shape of the weight function, which is modeled as a cubic B-spline, gives information about the impact of exposure increments at different times on disease risk. The method is evaluated in a simulation study and is applied to data on smoking histories and lung cancer from a recent case-control study in Germany.     

动作电位形成的机制

动作电位是短暂、快速的膜电位的变化(100 mV),在此期间,细胞膜内外的极性发生反转,即细胞膜由静息状态时的膜内为负、膜外为正转变为膜内为正而膜外为负的状态。一个单个动作电位仅包括全部兴奋细胞膜的一小部分。与分级动作电位不同的是,动作     

Estimates of genetic parameters for Holstein cows for test-day yield traits with a random regression cubic spline model

Genetic parameters were estimated with restricted maximum likelihood for individual test-day milk, fat, and protein yields and somatic cell scores with a random regression cubic spline model. Test-day records of Holstein cows that calved from 1994 through early 1999 were obtained from Dairy Records Management Systems in Raleigh, North Carolina, for the analysis. Estimates of heritability for individual test-days and estimates of genetic and phenotypic correlations between test-days were obtained from estimates of variances and covariances from the cubic spline analysis. Estimates were calculated of genetic parameters for the averages of the test days within each of the ten 30-day test intervals. The model included herd test-day, age at first calving, and bovine somatropin treatment as fixed factors. Cubic splines were fitted for the overall lactation curve and for random additive genetic and permanent environmental effects, with five predetermined knots or four intervals between days 0, 50, 135, 220, and 305. Estimates of heritability for lactation one ranged from 0.10 to 0.15, 0.06 to 0.10, 0.09 to 0.15, and 0.02 to 0.06 for test-day one to test-day 10 for milk, fat, and protein yields and somatic cell scores, respectively. Estimates of heritability were greater in lactations two and three. Estimates of heritability increased over the course of the lactation. Estimates of genetic and phenotypic correlations were smaller for test-days further apart.     

Analysis of photoacoustic waveforms using the nonlinear least squares method.

Pulsed-laser photoacoustics is a technique which measures photoinduced enthalpic and volumetric changes on the nano- and microsecond timescales. Analysis of photoacoustic data generally requires deconvolution for a sum of exponentials, a procedure which has been developed extensively in the field of time-resolved fluorescence decay. Initial efforts to adapt an iterative nonlinear least squares computer program, utilizing the Marquardt algorithm, from the fluorescence field to photoacoustics indicated that significant modifications were needed. The major problem arises from the wide range of transient decay times which must be addressed by the photoacoustic technique. We describe an alternative approach to numerical convolution with exponential decays, developed to overcome the problems. Instead of using an approximation method (Simpson's rule) for evaluating the convolution integral, we construct a continuous instrumental response function by quadratic fitting of the discrete data and evaluate the convolution integral directly, without approximations. The success and limitations of this quadratic-fit convolution program are then demonstrated using simulated data. Finally, the program is applied to the analysis of experimental data to compare the resolution capabilities of two commercially available transducers. The advantages of a broadband, heavily damped transducer are shown for a standard organic photochemical system, the quenching of the triplet state of benzophenone by 2,5-dimethyl-2,4-hexadiene.     

Resting membrane potential and action potential of Nitella expansa protoplasts

Inside negative membrane potentials were observed for protoplastsobtained from Nitella expansa leaf internodal cells in mediacontaining 1 to 100 mM CaCl₂ using the microelectrode technique.The potential values were less negative than the membrane potentialof intact N. expansa leaf internodal cells. In addition, anaction potential consisting of two components—a fast componentand a slow component—was induced by electrical stimulationfor the protoplasts as well as the intact cells. (Received December 18, 1979; )     

Direct action of estradiol-17β on the atrial action potential

The effect of the two C-17 isomers of estradiol on the shape of the action potential of rat atrial tissue was studied by means of classical glass electrodes for different concentrations of estradiol. Resting potential and upstroke were not affected by estradiol, but the duration of the action potential was reduced. Only estradiol-17β exhibits an effect in a concentration dependent way, while estradiol-17α has no effect at all. The ionic mechanism was studied by adding specific ionic blockers to the perfusate. Since the effect was much less pronounced when a slow inward current blocker was added, it was concluded that estradiol-17β acts mainly via the slow inward current channel. Only a small part of the interaction takes place via the potassium outward channel.     

Energetic aspects of propagation of action potential

On the basis of the electrical analogue of an action potential suggested previously, the distribution of electrical field outside and inside the membrane was obtained. The energy released upon the propagation of a single action potential along the nerve fibre was calculated. A comparison of the results with the available data showed the correctness of the calculations performed.     

Dynamics of chloride and potassium currents during the action potential in Chara studied with action potential clamp

TheCl^– and K⁺ currents underlying the action potential (AP) in the giant alga Chara were directly recorded with the action potential clamp method. An electrically triggered action potential was recorded and repetitively replayed as command voltage to the same cell under voltage clamp. The resulting clamp current was close to zero. Only the initial rectangular current used for stimulation was approximately reproduced by the clamp circuit. Inhibition of Cl^– channels with niflumic acid or ethacrynic acid and of K⁺ channels with Ba²⁺ evoked characteristic compensation currents because the amplifier had to add the selectively inhibited currents. Integration of the compensation currents revealed a mean flux through Cl^– and K⁺ channels of 3.3 10^–6 and 2.1 10^–6 mole M^–2 AP^–1 respectively. The dynamics of CI^– and K⁺ channel activation/inactivation were obtained by converting the relevant clamp currents to ionic permeabilities using the Goldman-Hodgkin-Katz current equation. During the AP the Cl^– permeability reaches a peak 370 ms, on average, after termination of the stimulating pulse. The following inactivation proceeds 3.6 times slower than the activation. The increase in K⁺ permeability lags behind the rise in Cl^– permeability, reaching a peak approximately 2 s after the latter.