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Extraction of morphological features from biological models and cells by Fourier analysis of static light scatter measurements.

Models of biological cells of varying geometric complexity were used to generate data to test a method of extracting geometric features from light scatter distributions. Measurements of the dynamic range and angular distribution of intensity and light scatter from these models was compared to the distributions predicted by a complete theory of light scatter (Mie) and by diffraction theory (Fraunhofer). An approximation to the Fraunhofer theory provides a means of obtaining size and shape features from the data by a spectrum analysis. Experimental verification using nucleated erythrocytes as the biological material show the potential application of this method for the extraction of important size and shape parameters from light scatter data.

Animals↗

[High-frequency sonographic analysis of postoperative blood flow properties after microvascular anastomoses].

Examination of blood flow characteristics using high frequency ultrasonic waves, has shown that in the region of the microvascular anastomosis, even in successfully replanted digits, there is turbulent flow. If this turbulence increases in the first 30 minutes following release of the clamps, vascular occlusion may be expected. In order to monitor the blood flow characteristics during the post-operative period, a high frequency ultrasonic measuring device has been developed which assisted by computer detects the spectrum analysis of the shift frequency delta f proportional to the erythrocyte velocity. This data is presented instantaneously on a monitor and shows fine changes in the flow characteristics permitting early intervention.

Fingers↗

Surface EMG frequency dependence on force in the masseter and the anterior temporal muscles.

Myoelectric power spectrum analysis was used to study isometric contractions, 10-15 s long, of the masseter muscles and the anterior temporal muscles. Surface EMG activity was recorded from these muscles for nine females while biting on a bite force transducer up to maximal effort (100% maximal voluntary contraction; MVC). The mean frequency (MF) was calculated as a single estimate of the myoelectric power spectrum. Regression analyses were made of MF versus bite force (0-100% MVC). The mean MF values of all females' masseter muscles increased up to 55-60% MVC. For the anterior temporal muscles no increase in mean MF was found above 20-25% MVC. The increase in MF was possibly dependent on recruitment of type I fibers and low-pass tissue filtering effects. The slope of regression for the force level 0-60% MVC was intraindividually steeper for the masseter muscles than for the anterior temporal muscles. A similar decrease in mean MF was found for the masseter muscles and the anterior temporal muscles for the force level 60-100% MVC. The possibility of muscular fatigue was discussed.

Adult↗

A comparison of coarctation resection and subclavian flap angioplasty using ultrasonographically monitored postocclusive reactive hyperemia.

The reported relatively high incidence of early restenosis at the coarctation repair site with subclavian flap angioplasty, especially in infants less than 3 months of age, prompted a physiologically oriented analysis of relief of obstruction from coarctation after subclavian flap angioplasty versus resection and end-to-end anastomosis in infancy. Twenty-one patients who had undergone repair of coarctation in infancy by either subclavian flap angioplasty (nine patients) (median age 8 years) or resection and end-to-end anastomosis (12 patients) (median age 8 years) were evaluated by Doppler spectrum analysis of the blood flow velocities in the femoral artery at rest and during reactive hyperemia. The median resting right upper to lower limb systolic pressure difference (with interquartile range) was similar in the angioplasty, resection and anastomosis, and control groups: -5 mm Hg (18 mm Hg), 0 mm Hg (12 mm Hg), and -2.5 mm Hg (10 mm Hg), respectively. Also, similar resting values for the maximum frequency of the advancing curve and the pulsatility and resistance indices were measured in the three groups. During reactive hyperemia of the leg, however, a significant hemodynamic obstruction across the repair site became clinically manifest in the angioplasty group only, as documented by a lower pulsatility index in comparison with the control group (p = 0.01, Mann-Whitney U test). Comparison of the hemodynamic results between the angioplasty and resection and anastomosis groups in subdivisions of infants operated on at an age of less or greater than 3 months, both at rest and during reactive hyperemia, showed, already at rest, a significantly lower value for the pulsatility index in the former angioplasty subdivision (p = 0.05, Student's t test), indicating a significant resistance at the coarctation repair site in the angioplasty patients operated on before the third month of life. A disadvantage of angioplasty (compared with resection and anastomosis) was noted when angioplasty was performed before the third month of life, and an unequivocal lack of advantage was noted when performed beyond that period regarding relief of obstruction from coarctation. In addition, a definite potential for adverse long-term effects on the hemodynamics of the left upper limb after subclavian flap angioplasty in infancy has been documented. For these reasons we prefer to perform resection and end-to-end anastomosis for repair of coarctation in infancy.

Adolescent↗

Dynamic autoregulation testing in the posterior cerebral artery.

BACKGROUND AND PURPOSE: Dynamic autoregulation has been studied predominantly in the middle cerebral artery (MCA). Because certain clinical conditions, ie, presyncopal symptoms or hypertensive encephalopathy, suggest a higher vulnerability of autoregulation within posterior parts of the brain, we investigated whether the cerebral blood flow velocity (CBFV) is modulated differently within the posterior cerebral artery (PCA). METHODS: Spontaneous oscillations of CBFV and arterial blood pressure (ABP) in the frequency range of 0.5 to 20 cycles per minute were studied in 30 volunteers (supine and tilted positions). Analysis was based on the "high-pass filter model," which predicts a specific frequency-dependent phase and amplitude relationship between oscillations in CBFV to ABP. These parameters, characterized as phase shift angles and transfer function gains, were calculated from simultaneously recorded beat-to-beat blood pressure and transcranial Doppler signals of the PCA and MCA by means of cross-spectrum analysis. RESULTS: In the MCA and PCA, phase shift angles were decreased, and gains were elevated with increasing oscillation frequency. The PCA gain values in supine and tilted positions were significantly higher than in the MCA. CONCLUSIONS: The phase and amplitude relationship between CBFV and ABP showed a frequency dependence in the PCA similar to that in the MCA. The study therefore suggests that the high-pass filter model of dynamic cerebral autoregulation can be applied to the PCA. In this model the generally higher gain values in the PCA indicate a lower damping of ABP oscillations, which are transmitted to the posterior part of cerebral circulation.

Aged↗

Effects of surrounding tissue on the sound spectrum of arterial bruits in vivo.

Turbulent flow distal to arterial stenoses producers bruits with a characteristic sound spectrum, analysis of which has permitted accurate non-invasive assessment of the residual lumen diameter of the stenosis in the case of the human carotid artery. In contrast, investigators working with in vitro elastic models of arteries or with excised vessels have reported finding mainly resonant spectra of bruits recorded distal to stenoses. We have studied the effects of turbulent flow on the sound spectrum produced at the arterial wall and the influence of surrounding tissue on this spectrum. Aortic, carotid, and femoral stenoses were produced in dogs by external banding of the arteries with 5mm wide Teflon bands. Recordings of bruits made directly on the vessel wall had a sound spectrum made up of 2 components, one due to turbulent flow, and the second to a superimposed resonant spectrum from arterial wall vibration. This was true of 3 kinds of vessels studied. The effects of surrounding tissue on the sound spectrum of arterial bruits was shown by comparing the spectra o bruits recorded directly on the vessel wall, on the freshly closed wound and on the healed wound. The sound properties of the artery in situ are very different from those of exposed or excised vessels or elastic tubes. Although intravascular turbulence may be accurately appreciated at the skin surface, arterial wall resonance in the intact animal is extensively damped by the normal coupling of the artery to its surrounding tissue.

Animals↗

Spectral electromyographic fatigue analysis of back muscles in healthy adult women compared with men.

OBJECTIVE AND DESIGN: To investigate the difference in back muscle endurance between normal adult women and men using surface electromyographic (EMG) power spectral analyses. METHODS: Forty-five healthy subjects (22 men and 23 women) were studied during an unsupported trunk holding test for 120 seconds. Recording surface electrodes were placed over each erector spinae muscle at L1 level. OUTCOME MEASURES: Median frequency (MF), mean power frequency (MPF), and zero crossing rate (ZCR) were evaluated using the ME3000P Fast Fourier Transform spectrum analysis program. The rate of change was determined for each parameter during the test, and correlation was examined by Pearson's correlation. RESULTS: The negative slopes of all indices of back muscle fatigue were significantly steeper in men than in women. CONCLUSION: Our results indicated that the trunk holding test combined with EMG power spectral analysis of lumbosacral muscles is useful for the evaluation of fatigue performance of these muscles. Our results also showed a higher muscle endurance in healthy adult women than in men.

Adult↗

[An application of genetic algorithms to the analysis of EXAFS spectrum].

Extended X-ray absorption fine structure (EXAFS) has been extensively used in the structural study in recent years. But the current methods of analysis EXAFS spectrum is difficult and tedious,demanding either very similar standard samples or the initial parameters near the solution. In this paper, a new technique Genetic Algorithms (GAs), was applied to the analyzing of the EXAFS spectrum,and two spectra of CU samples were investigated by the method. It was found that reasonable results can be obtained by the method only with limiting the initial parameters to a broad range. Comparing the results with those obtained by EXCURVE88, the fitting is superior, and the parameters are reasonable. Therefore, it is proved that the GAs may be a high performance method for the analyzing of the EXAFS spectra.

Algorithms↗

Longitudinal intrafascicular electrodes in collection and analysis of sensory signals of the peripheral nerve in a feline model.

The purpose of this study was to evaluate the value of utilizing longitudinal intrafascicular electrodes (LIFEs) in collecting and analyzing sensory signals from the peripheral nerve. The longitudinal intrafascicular electrodes were made of 25-microm Teflon-insulated Pt/Ir wire and implanted into the fascicle of the superficial peroneal nerves in a feline model. The sensory signals at rest status and induced with various stimulations were recorded. The action potential area, frequency, coefficient of variation (CV) of the peak, and functional spectrum were then analyzed by the MF Lab version 3.01 software package. The results showed that the sensory nerve action potentials (SNAPs) were 0-2 spikes per second at rest state; the count was increased when stimulation was administered. SNAPs were 16-24 spikes per second when scraping stimulation was applied. The pulse intervals and the waveform remained consistent. SNAPs burst and were clustered when stress stimulation was given. The comparison of area, frequency, and CV of the peak showed statistically significant differences between these parameters receiving different stimulations. The functional spectrum analysis showed that the frequency of action potential increased when the stress stimulation was applied. In conclusion, LIFEs can sensitively collect sensory signals and provide a good interface to analyze sensory information from peripheral fasciculi. These data provide useful information for further study of control of electronic prostheses.

Action Potentials↗

Paradoxical phenomenon of physiological tremor in prolonged tapping load.

Cumulative fatigue caused by a tapping load is investigated by power spectrum analysis of both physiological tremor of the finger and surface electromyogram (EMG) of the forearm muscle controlling the finger. A load for two hours at a rate of 200 taps/minute is performed on ten male subjects. The physiological tremor and the EMG are measured before and during the load. The measurement is performed under the isometric contraction at 10% maximum voluntary contraction in the m. flexor digitorum superficialis. The total power and the slow wave ratio of the power spectrum are evaluated. During the load, both spectra of the physiological tremor and the EMG show the maximum total power at 30 minutes after the load. The total powers of both spectra, however, decrease in the period after 60 minutes. Namely, the results of the physiological tremor and the EMG for prolonged load show the "paradox of fatigue." In order to elucidate the cause of the paradox of fatigue, the slow wave ratio of the EMG spectrum is studied. The ratio increases during the load. The muscle loaded indicates the state close to exhaustion, and the change of the function of the muscle contraction affects the amplitude of the physiological tremor. Therefore, the criterion judging muscular fatigue is denoted due to the change of the amplitude of the physiological tremor.

Adult↗

[A quantitative analysis of the phrenic nerve activities during the cough reflex].

The phrenic nerve activity is an appropriate indicator for the output of the respiratory center as a whole, although a quantitative analysis of each of the frequency band components that constitute the neural activities during the respiratory reflex has not yet been made by other investigators. In the present study, we have made a quantitative analysis of each of the frequency band components of phrenic nerve activity during the cough reflex in anesthetized dogs. The efferent activities of the phrenic nerve were recorded from the central cut end of the phrenic nerve. Each fraction of phrenic nerve activity was separated into bands spanning a range of 100 Hz each by a variable filter and analyzed using a program for the power spectrum. The cough reflex was induced by mechanical stimulation of the tracheal mucosa. In the power spectrum analysis of each frequency band, increase in the power of each of the frequency band components was observed during the cough reflex. Particularly, the power of the 2 approximately 100 Hz band components increased significant as compared with the other frequency band components. Such as increase in the power of the 2 approximately 100 Hz band components toward the other frequency band components during the cough reflex was not observed after an i.v. administration of DMPP and lobeline, but the power increased extended over every frequency band. These findings suggest that the process for integrating the cough reflex was different from that of the other respiratory reflexes and that the present method is useful for investigating the central mechanisms of the cough reflex.

Action Potentials↗

A study on the optimum order of autoregressive models for heart rate variability.

Heart rate variability (HRV) has been used as a non-invasive marker of the activity of the autonomic nervous system and its spectrum analysis gives a measure of the sympatho-vagal balance. If short segments are used in an attempt to improve temporal resolution, autoregressive spectral estimation, where the mode] order must be estimated, is preferred. In this paper we compare four criteria for the estimation of the 'optimum' model order for an autoregressive (AR) process applied to short segments of tachograms used for HRV analysis. The criteria used were Akaike's final prediction error, Akaike's information criterion, Parzen's criterion of autoregressive transfer function and Rissanen's minimum description length method, and they were first applied to tachograms to verify (i) the range and distribution of model orders obtained and (ii) if the different techniques suggest the same model order for the same frames. The four techniques were then tested using a true AR process of known order p = 6; this verified the ability of the criteria to estimate the correct order of a true AR process and the effect, on the spectrum, of choosing a wrong model order was also investigated. It was found that all the four criteria underestimate the true AR order; specifying a fixed model order was then looked at and it is recommended that an AR order not less than p = 16, should be used for spectral analysis of short segments of tachograms.

Adult↗

Mass spectral and electrophoretic characterization of acidic peptides bound to chromatin of pea bud.

Structural features of a class of chromatin peptides are studied in the aim of understanding their mechanism of action. They have been reported as a family of small acidic peptides that can affect cell proliferation and RNA transcription. Mass spectrometry analysis has suggested some molecular models of possible sequences that might be present in this group of peptides. These sequences have been synthesised and their chromatographic and electrophoretic behaviour is compared with that obtained from peptides extracted from pea bud chromatin. In this way electric charge and hydrophilic properties of the native peptides are evaluated. On the basis of these data and those obtained from further mass spectrum analysis new models for native peptides are proposed.

Chromatin↗

The fluctuations of accommodation and ageing.

OBJECTIVE: The aim of this study was to investigate the influence of age on the fluctuations of accommodation. METHOD: Fluctuations of accommodation were measured on six 'young' (16-25 years, mean age 22 years) observers and six 'older' (35-48 years, mean age 42 years) observers. Accommodation was continuously recorded using a SRI optometer whilst the observers steadily viewed a high contrast target at stimulus levels 0.25 D, 1.00 D and 2.00 D. Fluctuations were quantified using power spectrum analysis, and frequencies were grouped into bands: low (LFC 0.3-0.6 Hz and 0.3-0.9 Hz) and high (HFC 1.1-2.2 Hz). RESULTS: Accommodation response levels for these stimuli for both groups of observers were quite similar. Fourier analysis was used to generate power spectra so that the fluctuations of accommodation for each observer group could be compared. In general power increased for increasing response levels for both groups of observers, although less power was evident for the older observers in both LFC and HFC bands. Differences in power were not significant at these frequency bands for the two observer groups. When the whole power spectrum is compared these differences became significant with more power evident in the younger cohort. CONCLUSION: Reductions in both amplitude and speed of accommodation with age are well known, and the decline in magnitude of the fluctuations found here is consistent with a general diminution in accommodation dynamics as the accommodation mechanism ages. For the older group, some of who were near absolute presbyopia, there may be little contribution to power from changes in lens shape and it is possible that small changes in lens position in the eye contribute to the power spectrum.

Accommodation, Ocular↗

Automated analysis of electromyographic (EMG) recordings during botulinum injections.

PURPOSE: Botulinum toxin is injected into extraocular muscles using electromyographic (EMG) guidance to confirm needle location prior to injection. The purpose of this study was to develop and test an automated, objective method of storing and grading EMG signal quality obtained during botulinum injection. A reliable, nonsubjective estimate of signal quality will enhance future studies of the complications or effectiveness of botulinum toxin injections into extraocular muscle. METHODS: Injections were administered using a standard procedure. The EMG was digitized, recorded, and analyzed using discrete Fourier transform and power spectrum analysis. Audible signal quality was also graded subjectively by the surgeon. Patients were followed to determine the clinical response to the injection. RESULTS: Eighteen patients (24 injections) were studied. Each sample was collected and analyzed in less than one second. The EMG contained signals over a range of frequencies from 50 to 500 Hz, with an average peak near 90 Hz. Substantial variability of the signal was observed between patients. Contracting muscle had a higher total power and peak frequency in most, but not all, cases. Total signal power correlated moderately with subjective estimates of signal quality. Neither subjective nor computer-derived signal quality estimates correlated with the response to injection or complications. CONCLUSIONS: Computerized signal analysis can automatically characterize EMG signal power and frequency distribution. Although this technique has the potential to identify needle location at the time of botulinum injection accurately, signal variability limited the clinical and research utility of the present protocol.

Botulinum Toxins↗

Expression, purification, and in vitro refolding of soluble tumor necrosis factor-related apoptosis-inducing ligand (TRAIL).

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is a new member of the TNF superfamily. Here, a recombinant form of the extracellular domain of the TRAIL (sTRAIL) was expressed in Escherichia coli BL21(DE3) under the control of a T7 promoter. The resulting insoluble bodies were separated from cellular debris by centrifugation and solubilized with 8 M urea. A rapid and simple on-column refolding procedure was developed. It was applied and then the refolded sTRAIL was purified by anion-exchange chromatography. The purified final product was >98% pure by SDS-PAGE stained with Coomassie brilliant blue R-250. Mass spectroscopic analysis indicated the protein to be 19.2 kDa, which equalled the theoretically expected mass. N-terminal sequencing of refolding sTRAIL showed the sequence which corresponded to the designed protein. The renatured protein displayed its immunoreactivity with the antibodies to TRAIL protein by Western blotting. The purified sTRAIL had a strong cytotoxic activity against human cervical cancer HeLa cells with ED50 about 1.5 mg/L. Circular dichroism and fluorescence spectrum analysis showed that the refolded sTRAIL had a structure similar to that of native protein with beta-sheet secondary structure. This efficient procedure of sTRAIL renaturation may be useful for the mass production of this therapeutically important protein.

Amino Acid Sequence↗

Fourier transform infrared attenuated total reflection and transmission spectra studied by dispersion analysis.

Fourier transform infrared transmission (FT-IR) and attenuated total reflection (ATR) spectra of water-ethanol mixtures are recorded and reconstructed thanks to a causal dispersion analysis technique. As expected, the Beer's law technique is an empirical approximate method that cannot account for complex spectral features. On the other hand, a rigorous analysis performed by using the theoretical optical paths for both experimental techniques and Gaussian dispersion analysis (GDA) allows the dielectric functions of the pure liquids to be calculated. Simulations of the whole mid-infrared spectra in the range 500-4000 cm(-1) match the experimental data very well, whatever the water-ethanol mixtures. This method is a powerful tool to quantify such model mixtures and more generally could be the first step toward software for assistance to the FT-IR spectrum analysis.

Algorithms↗

[Clinical study of 83 cases with spinal muscular atrophy in children].

OBJECTIVE: Spinal muscular atrophy (SMA) is a common autosomal recessive disorder and represents one of the most common genetic causes of death in childhood. The last 10 years have seen major advances in the field of SMA, but no curative treatment is available so far. This study aimed to analyze the clinical characteristics of SMA, improve the clinical diagnosis of SMA, and explore the importance of gene diagnosis and prenatal diagnosis of SMA by gene deletion analysis. METHODS: Totally 83 cases with SMA including 55 males and 28 females were enrolled in this study. The age was between 1 day and 14 years (average 23.7 months). The clinical characteristics and changes of electromyography were assessed in all cases. The muscular biopsy was performed in 2 of 83 cases. The deletion of survival of motor neuron gene (SMN) was detected by PCR and restriction endonuclease spectrum analysis in 13 of 83 cases. RESULTS: The 83 cases were subdivided into three clinical groups based on age of onset of symptom, age at death and achievement of certain motor milestone, 60 cases with type I, 19 cases with type II and 4 cases with type III. They were all characterized by symmetric muscle weakness (more proximal than distal) associated with atrophy, absence or marked decrease of deep tendon reflexes. Electromyographic studies showed a pattern of denervation with neither sensory involvement nor marked decrease of motor nerve conduction velocities in all cases. Muscle biopsy provided evidence of skeletal muscle denervation with groups of atrophy in 2 cases. The SMN detection revealed deletion of exon 7 and exon 8 in 11 of 13 cases, only lacking exon 7 in 1 of 13 cases and lacking exon 8 in 1 of 13 cases. CONCLUSION: SMA is characterized by degeneration of lower motor neuron associated with muscle paralysis and atrophy. The definite diagnosis of SMA will rely on the typical clinical characteristics, changes of electromyogram and muscle biopsy and gene deletion analysis. Gene diagnosis of SMA can provide a basis for prenatal diagnosis which is of great importance in preventing SMA.

Adolescent↗