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At least 343 records · Page 19Linked to original sources
PubMed1997

Power spectrum analysis of human femoral rotations during gait.

Femoral rotational waveforms sampled at 15 Hz for a duration 20 s satisfy the sampling rate and frequency resolution requirements of such waveforms during walking. Spectral analysis provides a unique signature of the frequency composition of such signals. This identity may prove useful in characterising human gait and could be of value in future studies of walking in health and disease.

Biomedical Engineering↗
PubMed1995

Awareness detection during caesarean section under general anaesthesia using EEG spectrum analysis.

This study examined the relationship between the EEG (spectral edge frequency 90-SEF90) and the occurrence of awareness defined for the purpose of this study as responsiveness to verbal commands. Fifty women undergoing general anaesthesia for elective Caesarean section were examined. Responsiveness to verbal commands was detected every minute in the period from the induction of anaesthesia to the delivery of the newborn using the Tunstall isolated forearm technique and correlated with the SEF90 value. The patients were assigned by a randomized code to receive either thiopentone (4 mg.kg-1) or ketamine (1 mg.kg-1) for induction of anaesthesia. Before the administration of succinylcholine a tourniquet was applied to the free arm, and inflated to 200 mmHg, to maintain motor function to one arm. The EEG recordings started five minutes before induction and were recorded throughout anaesthesia. The incidence of responsiveness to verbal commands was lower in the ketamine group (24%) where the average SEF90 was 12.0 +/- 3 Hz, than in the thiopentone group (52%), where the average SEF90 was 18.09 +/- 3 Hz (P = 0.01). The results suggest that SEF values of < or = 8.6 Hz were sufficient to avoid responsiveness to verbal commands.

Adult↗
PubMed2001

[Possibilities of broad spectrum analysis of gene expression patterns with cDNA arrays].

BACKGROUND: Our knowledge about the molecular and genomic background of diseases has expanded dramatically in the recent past and cDNA microarrays now provide the opportunity to simultaneously analyse the expression of thousands of genes. This could pave the way towards a systematic exploration of the pathogenetic principle of ophthalmological diseases which could lead to the identification of key disease-specific molecules that will be useful as diagnostic marker or serve as therapeutic targets. MATERIALS AND METHODS: Various strategies for cDNA microarray analysis are reviewed, including different commercially available arrays (microarrays on glass and arrays on nylon filters) as well as methods for analysing the unprecedented large amounts of data from a single experiment. Possible applications for research and clinical applications in ophthalmology are discussed. RESULTS: The cDNA microarray-based technology allows the rapid and cost-effective screening of gene expression without a priori knowledge about which gene might be of interest. Here, we discuss how the analysis of gene expression as whole profiles instead of the conventional focus on an individual gene may offer new insights into the fundamental nature of the pathogenesis of complex diseases using the example of early diabetic retinopathy. CONCLUSION: To date, the gene-array technology is still largely a laboratory procedure and has not yet been used in the clinical setting. However, in clinically oriented basic research, it will allow a more encompassing analysis of disease processes and thus lead to the identification of important diagnostic tools and potential drug targets in ophthalmological diseases.

Diabetic Retinopathy↗
PubMed1998

Differentiation of autonomic nervous activity in different stages of coma displayed by power spectrum analysis of heart rate variability.

The analysis of heart rate (HR) variability offers a noninvasive method to investigate autonomic nervous system activity in comatose patients. We analyzed three components of the HR variability in a group of comatose patients: the low-frequency band (LF), representing mainly sympathetic influence, the mid-frequency band (MF), representing sympathetic and parasympathetic influence, and the high-frequency band (HF), representing the parasympathetic influence. A value for sympathovagal balance was defined as LF/HF and MF/HF ratio. Moreover, the skin conductance level (SCL) and the skin conductance resistance (SCR) variability were recorded. The patient group consisted of 22 patients with traumatic brain injuries. Coma depth was assessed by the Glacow Coma Scale and artifact-free HR, SCL, and SCR were measured 75 times in the patient group. The results documented a significant gain in sympathetic nervous system activity corresponding with the state of emerging from coma. This gain was most pronounced in the HF component of the HR and in the sympathovagal balance between LF/HF. The findings in SCL and SCR variability endorsed this result. It is concluded that emerging from coma is accompanied by an increasing influence of the sympathetic nervous system on HR control. This leads to a change in the sympathovagal balance, i.e., a reintegration of parasympathetic and sympathetic activity.

Adolescent↗
PubMed2002

Prediction of endurance capacity of quadriceps muscles in humans using surface electromyogram spectrum analysis during submaximal voluntary isometric contractions.

The measurement of endurance time ( t(lim)) is the procedure commonly used to quantify the ability of a muscle to maintain force. The relationship between surface electromyographic (sEMG) manifestations of localised muscle fatigue and t(lim) during an effort at 50% of maximal voluntary isometric torque of the knee extensors (vastus lateralis and vastus medialis) until exhaustion was studied in 14 healthy volunteers. It was carried out to test whether changes in sEMG computed over shorter periods than expected t(lim) could be used to predict t(lim). Changes in mean muscle fibre conduction velocity, mean power frequency, median frequency, root mean square ), in the relative power in the 6-30 Hz and 30-60 Hz frequency bands were monitored using linear slope and area ratio index as statistical indicators. These indicators were computed over fixed periods shorter than t(lim). The subjects were able to maintain the required force level for [mean (SD)] 78.8 (9.5) s. During the fatigue trial, it was the greatest of the increases in the 6-30 Hz frequency band, recorded for either of the two muscles investigated, that was the only variable which correlated with t(lim). Significant relationships between t(lim) and changes in this low frequency band were observed as early as the first 15-30 s of the contraction. These results suggest that sEMG frequency banding may predict mechanical endurance without the need to maintain the contraction until exhaustion. From a clinical perspective, this could be an advantage for patients who might not be able to tolerate contractions to exhaustion.

Adult↗
PubMed1989

Mutational spectrum analysis of umuC-independent and umuC-dependent gamma-radiation mutagenesis in Escherichia coli.

gamma-Radiation mutagenesis (oxic versus anoxic) was examined in wild-type, umuC and recA strains of Escherichia coli K-12. Mutagenesis [argE3(Oc)----Arg+] was blocked in a delta (recA-srlR)306 strain at the same doses that induced mutations in umuC122::Tn5 and wild-type strains, indicating that both umuC-independent and umuC-dependent mechanisms function within recA-dependent misrepair. Analyses of various suppressor and back mutations that result in argE3 and hisG4 ochre reversion and an analysis of trpE9777 (+1 frameshift) reversion were performed on umuC and wild-type cells irradiated in the presence and absence of oxygen. While the umuC strain showed the gamma-radiation induction of base substitution and frameshifts when irradiated in the absence of oxygen, the umuC mutation blocked all oxygen-dependent base-substitution mutagenesis, but not all oxygen-dependent frameshift mutagenesis. For anoxically irradiated cells, the yields of GC----AT [i.e., at the supB and supE (Oc) loci] and AT----GC transitions (i.e., at the argE3 and hisG4 loci) were essentially umuC independent, while the yields of (AT or GC)----TA transversions (i.e., at the supC, supL, supM, supN and supX loci) were heavily umuC dependent. These data suggest new concepts about the nature of the DNA lesions and the mutagenic mechanisms that lead to gamma-radiation mutagenesis.

Aerobiosis↗
PubMed1987

Spectrum analysis in carotid sonography.

Numerous Doppler spectral parameters for measurement of carotid obstructive lesions have been developed in recent years. This proliferation of parameters has caused sonologists to wonder which are valid and should be used routinely. This review article surveys the most commonly used Doppler spectral parameters. The physiological basis for each parameter is considered along with clinical applications and limitations. The use of spectral parameters for measuring carotid stenoses is summarized by means of an algorithm.

Arterial Occlusive Diseases↗
PubMed2006

Power spectrum analysis and cardiovascular morbidity in anxiety disorders.

Spectral analysis of heart rate variability (HRV) and related measures has been shown to be a reliable noninvasive technique enabling quantitative assessment of cardiovascular autonomic regulatory responses to autonomic regulatory mechanisms; it provides a dynamic probe of sympathetic and parasympathetic tone, reflecting the interactions between the two. Over 20 studies reported abnormalities of HRV in anxiety, and patients with heart disease and anxiety are at increased risk for morbidity and mortality. Psychiatric drugs partly correct abnormalities of HRV and, recently, autonomic drugs (beta-blockers) have been studied in anxiety disorders. The authors call for further studies, especially in patients with co-existing anxiety disorders and heart disease, incorporating assessment of HRV.

Adrenergic beta-Antagonists↗
PubMed2006

Whole spectrum analysis of ligand efficacy at constitutively active human wild-type and S267K 5-HT6 receptors in HEK-293F cells.

INTRODUCTION: Modulation of constitutive activity by the recombinant wild-type human 5-HT6 receptor was investigated with a series of 5-HT6 receptor ligands by monitoring the cAMP signalling pathway. The impact of the mutation S267K near the B(261)BXXB(265) CIII-loop motif was analyzed on the magnitude of constitutive receptor activity as previously conflicting results have been reported. METHODS: The wild-type 5-HT6 receptor plasmid was obtained by PCR and the mutant S267K5-HT6 receptor was constructed by site-directed mutagenesis and stably transfected in HEK-293F cells by electroporation. The cAMP signalling pathway was monitored as a functional read-out to investigate ligands' responses using homogeneous time resolved fluorescence. RESULTS: Constitutive activity was present both at wild-type and mutant S267K 5-HT6 receptors. Negative efficacy (E(max), % versus basal) as observed at nanomolar concentrations with SB-271046 was larger for mutant (-92+/-1%) than wild-type 5-HT6 receptor (-45+/-1%). Ro 04-6790 also demonstrated negative efficacy at the wild-type 5-HT6 receptor with a magnitude similar to SB-271046 but with a 36-fold lower potency. MS-245 demonstrated at nanomolar concentrations intermediate negative efficacy; -48+/-3% and -16+/-2% at mutant and wild-type 5-HT6 receptor, respectively. The 5-HT-mediated cAMP response was blocked by SB-271046, MS-245 and Ro 04-6790 to their respective level of negative efficacy with pKB values fitting with their binding pK(i) values. E-6801 was a highly potent (pEC50: 10.17 to 10.19) and efficacious agonist (+98 to +102% versus 5-HT) at both wild-type and mutant 5-HT6 receptors. DISCUSSION: The recombinant wild-type human 5-HT6 receptor is constitutively active in HEK-293F cells and displays a high resolution to monitor efficacy properties of 5-HT6 receptor ligands. The resolution capacity to differentiate between efficacy properties of 5-HT6 receptor ligands, in particular for negative efficacy, can be further enhanced by monitoring the mutant S267K 5-HT6 receptor.

Cyclic AMP↗
PubMed1997

The electrical activity is impaired in the red nucleus of dt(sz) mutant hamsters with paroxysmal dystonia: an EEG power spectrum analysis of depth electrode recordings.

The genetically dystonic (dt(sz)) hamster is an animal model of paroxysmal dystonia that displays attacks of sustained abnormal movements and postures in response to mild stress. Dysfunctions within the basal ganglia may be critically involved in the pathophysiology of dystonia in mutant hamsters. Furthermore, previous observations from autoradiographic studies pointed to an altered neural activity in the red nucleus (RN). In the present study, computerized EEG spectral analysis of depth electrode recordings from the RN was performed before and after dystonic attacks in freely moving dt(sz) hamsters and compared to age-matched non-dystonic controls. No epileptic activity was seen in any of the recordings, substantiating previous notions that paroxysmal dystonia in these mutants has no epileptogenic basis. The predominant EEG changes in RN of dystonic hamsters were a decrease in total power over the range of 1.25-42.00 Hz, a decrease in maximum power and a shift of frequency at maximum power to lower frequencies. With regard to selected frequency bands, there was a decrease in the alpha, beta and gamma band. Although the observed changes of neural activity in the RN are probably based on a primary dysfunction in related structures, the present data demonstrate its importance in the expression of dystonic movements.

Animals↗
PubMed2002

The reproducibility of power spectrum analysis of heart rate variability before and after a standardized meal.

We tested the reproducibility of the heart rate variability (HRV) measurements before and after a standardized meal. Heart rate recordings were obtained in 14 healthy subjects tested in a reclining position before and after a standardized meal on two separated occasions, apart by a 1-2-week interval. We measured three components of HRV: sympathetic activity (SYMP), parasympathetic activity (PSYMP) and the ratio of SYMP/PSYMP under controlled breathing and noncontrolled breathing conditions. We observed that all components were reproducible during noncontrolled breathing condition, whereas only PSYMP was reproducible during controlled breathing condition. Our results thus indicate that HRV measurements could be a useful, noninvasive and nonexpensive method to provide SYMP and SYMP/PSYMP in feeding behavior studies when measured under noncontrolled breathing conditions. Nonetheless, using a controlled breathing condition may be relevant when assessing the effect of various interventions or drugs on parasympathetic activity.

Adult↗
PubMed2000

Autonomic dysregulation in panic disorder and in post-traumatic stress disorder: application of power spectrum analysis of heart rate variability at rest and in response to recollection of trauma or panic attacks.

Power spectral analysis (PSA) of heart rate variability (HRV) offers reliable assessment of cardiovascular autonomic responses, providing a 'window' onto the interaction of peripheral sympathetic and parasympathetic tone. Alterations in HRV are associated with various physiological and pathophysiological processes, and may contribute to morbidity and mortality. Previous studies of posttraumatic stress disorder (PTSD) found lower resting HRV in patients compared to controls, suggesting increased sympathetic and decreased parasympathetic tone. This article describes the analysis of HRV at rest and after psychological stress in panic disorder (PD) patients, in an enlarged sample of PTSD patients, and in healthy control subjects. Standardized heart rate (HR) analysis was carried out in 14 PTSD patients, 11 PD patients and 25 matched controls. ECG recordings were made while subjects were resting ('rest 1'), while recalling the trauma implicated in PTSD, or the circumstances of a severe panic attack, as appropriate ('recall'), and again while resting ('rest 2'). Controls were asked to recall a stressful life event during recall. While both patient groups had elevated HR and low frequency (LF) components of HRV at baseline (suggesting increased sympathetic activity), PTSD patients, unlike PD patients and controls, failed to respond to the recall stress with increases in HR and LF. HRV analysis demonstrates significant differences in autonomic regulation of PTSD and PD patients compared to each other and to control subjects. HRV analysis may augment biochemical studies of peripheral measures in these disorders.

Adult↗
PubMed1987

Quantitative assessment of vasospasm by Doppler spectrum analysis in patients with primary Raynaud's phenomenon.

The aim of the study was to investigate whether increased peripheral resistance which is supposed to exist in patients with primary Raynaud's phenomenon, can be quantified by using parameters of Doppler spectra of flow in the ulnar and radial arteries. A group of 24 patients with this abnormality were compared with a matched group of 24 normal subjects. Doppler spectra were analysed according to the methods of Fronek, Gosling and by Fast Fourier Transform analysis. The Doppler spectra obtained from patients at room temperature were very different from those in normal subjects, showing characteristic wave-forms with multiple oscillations in 92% of the patients. All three analysing techniques demonstrated significant differences between the two groups, which can be attributed to increased peripheral vascular resistance in the patient group. The results of this study emphasize the value of analysis of Doppler spectra obtained from ulnar and radial arteries in the assessment of peripheral vascular resistance in vasospastic disease.

Adolescent↗