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At least 937 records · Page 52Linked to original sources
PubMed2001

Intraoperative microvascular Doppler monitoring of blood flow within a spinal dural arteriovenous fistula: a precious surgical tool. Case report.

The authors describe a case of spinal arteriovenous fistula (AVF) treated by a microvascular Doppler-assisted surgical interruption of the arterialized vein. Microvascular Doppler monitoring represents a valid, widely available, noninvasive tool that enables identification, through flow spectrum analysis, of components of this type of vascular malformation. In this case because the location of the fistula was identified prior to opening the dura only minimally invasive surgery was required. Direct recordings of the arterialized draining vein and the nidus of the fistula demonstrated a pathological spectrum caused by the arterial supply and the disturbed venous outflow in which a high-resistance flow pattern and low diastolic flow resembling an arterial-like flow velocity were observed. The fistula was obliterated by interruption of the draining vein, and Doppler measurements provided information on flow velocity changes in the medullary veins from an arterial to a venous pattern. The absence of any residual flow in the AVF confirmed successful hemodynamic treatment. Intraoperative microvascular Doppler recording during surgical closure of spinal AVF is a widely available and reliable monitoring modality that helps to produce excellent clinical results.

Central Nervous System Vascular Malformations↗
PubMed1998

In vitro investigation of lymph node metastasis of colorectal cancer using ultrasonic spectral parameters.

Lymph node involvement is one of the major factors affecting the prognosis of colorectal cancer. Various imaging methods, including ultrasound and computed tomography, are not sufficiently sensitive or specific for reliably determining lymph node involvement. We investigated the feasibility of using ultrasonic tissue characterization (UTC) based on spectrum analysis of backscattered echo signals for diagnosing lymph node metastasis of colorectal cancer in vitro. Forty lymph nodes, including 17 metastatic and 23 nonmetastatic nodes, from 11 colorectal cancer operations were investigated. Lymph nodes were scanned using a clinical instrument; B-mode imaging was performed for each lymph node, and radiofrequency (RF) data were acquired. The UTC parameters, slope and intercept, were calculated from the normalized power spectrum of the backscattered echo signals from each lymph node. The mean values of UTC parameters of metastatic and nonmetastatic lymph nodes were compared. The accuracy of UTC in distinguishing metastatic from nonmetastatic lymph nodes was calculated using discriminant analysis. Receiver operating characteristic (ROC) analysis was performed to compare the classification efficacy of UTC and B-mode ultrasound. UTC parameters demonstrated a significant difference in parameter values between metastatic and nonmetastatic lymph nodes. The overall accuracy in diagnosing the lymph node metastasis was 87.5% for UTC and 77.5% for B-mode ultrasound. ROC analysis produced an ROC curve area of 0.92 or 0.89 for UTC (depending on the performance-assessment algorithm) and 0.84 for B-mode ultrasound, which indicated that UTC performed markedly better than B-mode ultrasound in diagnosing metastatic lymph nodes. The advantages of UTC over conventional B-mode ultrasound in discriminating metastatic lymph nodes from nonmetastatic lymph nodes are extremely encouraging, and warrant an in vivo UTC study.

Aged↗
PubMed2005

Maternal cigarette-smoking during pregnancy disrupts rhythms in fetal heart rate.

OBJECTIVE: To examine the effects of maternal cigarette smoking during pregnancy on the developing infant's autonomic regulation before the possible effects of parturition and neonatal withdrawal could alter outcome measures. METHODS: Heart rate variability (HRV) was assessed for 10 min during late gestation for 21 cigarette-exposed (CE) and 22 nonexposed (NE) fetuses. RESULTS: HRV was significantly lower in fetuses whose mothers smoked cigarettes during pregnancy. Spectrum analysis of that variability showed temporally organized rhythms at a frequency similar to rhythms previously found in fetal cyclic motility (approximately .3 cycles per min). Lower powered rhythms--associated with poorer development--at the first, second, and dominant rhythms, as well as lower overall power of the power spectrum, were found for CE fetuses. Pearson correlations showed significant negative correlations between the amount of maternal cigarette smoking during the first trimester of pregnancy and measures of fetal HRV and power of spectral peaks. CONCLUSIONS: Results show that CE fetuses have lower HRV and disrupted temporal organization of autonomic regulation before effects of parturition, postnatal adaptation, and possible nicotine withdrawal contributes to differences in infant neurobehavioral function.

Adult↗
PubMed2006

Impairment of instantaneous autonomic regulation relates to blood pressure fall immediately after standing in the elderly and hypertensives.

The relation between changes in blood pressure and changes in autonomic activity over a very short period of time has not been reported thus far. To examine this relation, we here introduced a new method of power spectrum analysis with wavelet transformation, which has very fine time resolution and is able to assess changes in autonomic activity quantitatively even during movement. Our subjects were 15 hypertensive and 17 normotensive subjects. A head-up tilt test was performed in all subjects, and during the test, electrocardiogram and blood pressure were recorded continuously. The power spectrums for both parameters were calculated simultaneously every 5 s using wavelet transformation. The high frequency of the RR interval of the electrocardiogram (RR-HF) and low frequency of systolic blood pressure (SBP-LF) were defined and calculated as markers of parasympathetic and alpha-1 receptor blocker, bunazosin-sensitive sympathetic activity, respectively. Focusing on the changes for 2 min immediately after head-up tilting, it was found that the changes in SBP-LF and RR-HF were significantly delayed, by at least 40 s, in hypertensives compared with normotensives and also in elderly compared with non-elderly subjects. Multiple regression analysis demonstrated that the instantaneous change in RR-HF was the most important confounding factor for a fall in blood pressure immediately after head-up tilting. In conclusion, real-time changes in autonomic activity calculated by wavelet transformation may provide sensitive and useful information about acute changes in cardiovascular regulation, such as delayed reaction of the autonomic regulation after head-up tilting, that may be major causes of the blood pressure fall in hypertensive and elderly subjects.

Adult↗
PubMed1990

Spectral analysis of heart rate variability signal and respiration in diabetic subjects.

The paper deals with methods of processing ECG and respiration signals which aim at detecting parameters whose values may be correlated to normal and diabetic subjects with or without cardiovascular autonomic neuropathy (CAN). Beat-to-beat R-R duration values of the ECG and discrete series of respiration are obtained from original signals using a recognition algorithm. Power spectrum analysis (autospectra, cross-spectra and coherence via autoregressive modelling) is carried out on segments of about 200 consecutive cardiac cycles. Spectral parameters of the R-R variability signal are obtained as follows: total power, powers of low-frequency (LF) and high-frequency (HF) components, power of the signal which is (or is not) coherent with respiration, in absolute or in percentage values. The experimental protocol considers 40 diabetic patients (21 of whom have diabetic neuropathy) and 14 normals in three different conditions: resting, standing and controlled respiration. The developed spectral parameters seem sensitive enough to differentiate between normal and pathological subjects. These parameters may constitute a quantitative means to be added to the classical diabetic tests for the diagnosis of cardiovascular autonomic neuropathy.

Adult↗
PubMed1977

New technique for movement analysis: application to biological systems.

A new system for motion analysis is described. Modulation of light intensity of an organism's movement over an opaque and transparent checkerboard grid is monitored by a photocell. The photocell's output is proportional to the organism's amplitude and frequency of movement. This output is analyzed by a continuous interval dot display and spectrum analysis. The system was tested by analyzing the activity of 4 Drosophila strains which are known to differ in their activity. General applicability of the system is discussed.

Animals↗
PubMed1977

[Periodic variations in motor endplate potentials].

The amplitudes of motor end-plate potentials in the Frog have been measured during repetitive stimulations of the motor nerve at frequencies between 0,5 and 30 Hz. A serial analysis showed that cyclic variations of these amplitudes were superimposed on the random fluctuation of epp due to the quantal nature of transmitter release. The period of these cyclic variations varied between 3 and 10 stimulations. This period was not significantly related to the frequency of the stimulation. The frequency spectrum analysis of the epp amplitudes showed similar values for the period of the cyclic variation of epp. The same kind of analysis applied to a binomial series of random numbers did not significantly present periodic fluctuations. The same analysis was applied to mean amplitudes of groups of 5 to 120 successive epps at the same end-plate. Periodic fluctuations were identified with periods of about 10 to 180 sec. It is suggested that periodic failures of nerve spike propagation in nerve terminals at sites of low safety factor, as at branchings, are responsible for the observed cyclic variation of epp.

Animals↗
PubMed1996

p53 mutations in lung cancer following radiation therapy for Hodgkin's disease.

High risks of lung cancer occur after successful treatment of Hodgkin's disease. In addition to tobacco smoking, other risk factors include radiotherapy, chemotherapy, and immunosuppression, although the relative contributions of each are unknown. We conducted p53 mutational spectrum analysis in second lung cancers after radiation therapy for Hodgkin's disease in the Netherlands and in Ontario, Canada. Lung cancer tissues from 11 patients were analyzed by p53 immunohistochemistry and DNA sequence analysis. All were male cigarette smokers, all received radiation therapy, and six also received chemotherapy. The lung cancers occurred 9.8 years (mean) after treatment. Radiation doses to lung lobes that developed the tumors averaged 5.7 Gy (range, 3.7-11.7 Gy). Sequence analysis showed four missense and two silent p53 point mutations in five patients. There were four G:C-->A:T transitions; three of four mutated deoxyguanines occurred on the coding strand, and one was a CpG site. There were two transversions: one G:C-->C:G and one A:T-->C:G. Despite moderate or heavy smoking histories in all patients, the mutational spectrum appears to differ from usual smoking-related lung cancers in which G:C-->T:A transversions predominate. The absence of G:C-->T:A mutations and the prominence of G:C-->A:T transitions, which are characteristic of radiation and oxidative damage, suggest that radiotherapy might have caused some of the p53 mutations. These data illustrate the potential of mutation analysis to determine causes of human cancer. If confirmed in a larger series, these results imply that some radiation-induced cancers can be distinguished from those caused by other factors.

Adult↗
PubMed1996

Mutagenicity of the fullerene C60-generated singlet oxygen dependent formation of lipid peroxides.

Fullerene C60 dissolved in polyvinylpyrrolidone was mutagenic for Salmonella strains TA102, TA104 and YG3003 in the presence of rat liver microsomes when it was irradiated by visible light. The mutagenicity was elevated in strain YG3003, a repair enzyme-deficient mutant of TA102. The mutation was reduced in the presence of beta-carotene and parabromophenacyl bromide, a scavenger and an inhibitor, respectively, of phospholipase. The results suggest that singlet oxygen was generated by irradiating the C60 by visible light and that the mutagenicity was due to oxidized phospholipids in rat liver microsomes. Of the phospholipids in rat liver microsomes, the linoleate fraction isolated by high performance liquid chromatography was a major component, and played an important role in mutagenicity. Methyl linoleate, which was prepared for gas chromatographic analysis, was readily oxidized to hydroperoxymethyl linoleate, and associated with both 10- and 12-hydroxyl derivatives with a double bond in chemical structure by singlet oxygen: radicals to the hydroxyl function were probably generated. Because of the instability of the hydroxymethyl linoleate radicals, guanine residues generated radicals. The results of ESR spectrum analysis suggested generation of radicals at the guanine base but not thymine, cytosine and adenine bases as estimated with the g value of 2.0150. On the other hand, the singlet oxygen-generating C60 formed 8-hydroxydeoxyguanosine (8-OH-dG) upon treatment with 2' deoxyguanosine and microsomes or linoleate. The formation of 8-OH-dG was highly elevated in the presence of microsomes and linoleate. The level of 8-OH-dG formed with and without the microsome fraction was 47 and 9.6 units, respectively, per 10(4) deoxyguanosine. It was considered that the mechanism is indirect action of singlet oxygen due to lipid peroxidation of linoleate that causes oxidative DNA damage.

8-Hydroxy-2'-Deoxyguanosine↗
PubMed2005

Low-frequency Fourier spectrum for predicting membrane protein types.

Cell membranes are vitally important to living cells. Although the infrastructure of biological membrane is provided by the lipid bilayer, membrane proteins perform most of the specific functions. Knowledge of membrane protein types often provides crucial hints toward determining the function of an uncharacterized membrane protein. With the avalanche of new protein sequences generated in the post-genomic era, it is highly demanded to develop a high throughput tool in identifying the type of newly found membrane proteins according to their primary sequences, so as to timely annotate them for reference usage in both basic research and drug discovery. To realize this, the key is to establish a powerful identifier that can catch their characteristic sequence patterns for different membrane protein types. However, it is not easy because they are buried in a pile of long and complicated sequences. In this paper, based on the concept of the pseudo-amino acid composition [K.C. Chou, PROTEINS: Struct., Funct., Genet. 43 (2001) 246-255], the low-frequency Fourier spectrum analysis is introduced. The merits by doing so are that the sequence pattern information can be more effectively incorporated into a set of discrete components, and that all the existing prediction algorithms can be straightforwardly used on such a formulation for protein samples. High success rates were observed by the re-substitution test, jackknife test, and independent dataset test, indicating that the low-frequency Fourier spectrum approach may become a very useful tool for membrane protein type prediction. The novel approach also holds a high potential for predicting many other attributes of proteins.

Fourier Analysis↗
PubMed2002

Assessment of autonomic nervous system with analysis of heart rate variability in children with spastic cerebral palsy.

The purpose of this study was to investigate the function of the autonomic nervous system in children with spastic cerebral palsy (CP) through an analysis of heart rate variability (HRV) occurring with orthostatic stress. Twelve children with spastic CP and twelve normal children participated in this study. The echocardiogram (ECG) signals were recorded for 3 minutes in both the supine and 70 degrees C head-up tilt positions, and then the HRV signals underwent power spectrum analysis at each position. Two components were measured; a low- frequency (LF) component (0.05 - 0.15 Hz) primarily reflecting sympathetic activity during orthostatic stress and a high-frequency (HF) component (0.15 - 0.4 Hz) reflecting parasympathetic activity. In the supine position, there was no significant difference between any of the HRV components of the two groups. In the head-up tilt position, absolute and normalized LF were significantly increased and absolute HF was significantly decreased in the normal children (p < 0.05), but not in the children with spastic CP. The results of this study suggest that cardiac autonomic functions, such as vagal withdrawal and sympathetic activation which occur during head-up tilt position, are not sufficient to overcome the orthostatic stress arising in spastic CP children.

Autonomic Nervous System↗
PubMed1985

[The activating effect of MCI-2016 (bifemelane hydrochloride) on EEG in cats].

In order to make clear the activating effect of MCI-2016 on EEG, power spectrum analysis was performed and the interaction in EEG between MCI-2016 and some drugs were studied in succinylcholine-immobilized cats. MCI-2016 at doses of 5 and 10 mg/kg iv produced apparent arousal pattern in cortical EEG characterized by low amplitude fast wave, and evoked the right-shift in power spectrum. In the case of meclofenoxate at doses of 20 and 40 mg/kg iv, the shifts in power spectra were similar to that of MCI-2016, very slight changes were observed by Ca-hopantenate at a dose of 200 mg/kg iv and typical left-shift was introduced by imipramine at a dose of 2 mg/kg iv. MCI-2016 tended to suppress the SWS state induced by alpha-methyl-p-tyrosine and scopolamine at a dose of 350 mg/kg ip and 0.015 mg/kg iv, respectively. Subsequently, the duration of arousal state in EEG induced by physostigmine at a dose of 0.01 mg/kg iv was enhanced by MCI-2016 at a dose of 1.5 mg/kg iv whose injection does not produce any arousal pattern in EEG. The activating effect of MIC-2016 on EEG was indicated quantitatively and it is suggested that the cholinergic mechanism and the catecholaminergic mechanism would be involved in the EEG activating effect of MCI-2016.

Animals↗
PubMed1999

Diurnal variation of autonomic nervous activity in the rat: investigation by power spectral analysis of heart rate variability.

We studied the diurnal variations of autonomic nervous function in rats. For this purpose, a long-term electrocardiogram (ECG) was recorded from conscious and unrestrained rats using a telemetry system, and the autonomic nervous function was investigated by the power spectral analysis of heart rate variability. No arrhythmias were observed in the ECG of any of the rats. Nocturnal patterns, in which the values of heart rate in the dark phase (2000-0600) were higher than those in the light phase (0600-2000), were observed. All normal rats shared a characteristic pattern in their power spectrum analysis. Both low-frequency and high-frequency power in the light phase were higher than those in the dark phase. However, these differences were not statistically significant (P > .05). The low frequency to high frequency ratio also showed a nocturnal pattern. The value in the dark phase was significantly higher (P < .05) than that in the light phase. These results suggest that the sympathetic nervous activity is predominant in the dark phase in rats. Therefore, we believe that this information may be useful for future biobehavioral studies.

Animals↗
PubMed1999

Effects of unilateral stellate ganglion block on the spectral characteristics of heart rate variability.

The effect of unilateral stellate ganglion block on cardiovascular regulation remains controversial, so the present study used power spectral analysis of heart rate variability to investigate its effect on the autonomic neural control of the heart. In 20 young healthy volunteers (mean age: 25 years), heart rate variability was determined before and after unilateral stellate ganglion block (right side 11, left side 9) using 8 ml of 1% mepivacaine during supine rest. Using autoregressive spectrum analysis, power spectra were quantified by measuring the area in 3 frequency bands: high-frequency power (lnHF, parasympathetic influence) from 0.15 to 0.40 Hz, low-frequency power (lnLF, predominantly sympathetic influence) from 0.04 to 0.15 Hz, and total-frequency power (lnTF) less than 0.40 Hz. Right stellate ganglion block decreased not only the lnLF component from 6.55+/-0.84 to 5.77+/-0.47 but also the lnHF component from 4.40+/-0.95 to 3.42+/-1.12 (p<0.05). In contrast, left stellate ganglion block changed neither the lnLF nor the lnHF component. The lnTF component was also decreased significantly by right stellate ganglion block from 7.80+/-0.95 to 7.01+/-0.36 (p<0.05), but was unchanged following left stellate ganglion block. Neither right nor left stellate ganglion block induced any significant change in both the RR and corrected QT intervals. However, changes in the RR interval induced by right stellate ganglion block showed significant positive correlation with changes in lnHF (p<0.005) and lnTF (p<0.05). These results suggest that (1) autonomic innervation to the sinus node is mainly through the right-sided stellate ganglion, (2) pharmacological right-sided stellate ganglion block may attenuate not only sympathetic but also parasympathetic activity and (3) following right stellate ganglion block the decrease in both the sympathetic and parasympathetic influence on the sinus node may inconsistently counterbalance and change the RR interval.

Adult↗
PubMed1992

Autonomic mechanisms in heart rate variability after isoproterenol-induced myocardial damage in rats.

The effect of isoproterenol-induced myocardial damage on heart rate variability was examined in conscious, unrestrained, male, Sprague-Dawley rats. We used power spectrum analysis of beat-to-beat heart rate to study the levels and interaction of sympathetic and parasympathetic neural influences on the heart. One day after isoproterenol (80 mg/kg s.c.), mean heart rate was significantly elevated when compared to controls (isoproterenol 413.9 b.p.m. +/- 7.7 S.E.M.; saline 368.8 b.p.m. +/- 12.8 S.E.M.; P less than 0.05), even though the low frequency and respiratory components of the power spectrum were not different between the two groups. By contrast, a week after isoproterenol administration, heart rate was normal; however, variability in low frequency and respiratory areas of the power spectrum was significantly increased suggesting an abnormal sympathovagal balance. An imbalance in autonomic regulation of cardiac automaticity could account for the 27% incidence of arrhythmias in rats given isoproterenol. These results indicate that autonomic responses associated with isoproterenol-induced myocardial ischemia differ from those in human and in animal models of myocardial infarction.

Animals↗
PubMed1984

Quantitation of rhythmic diameter changes in arterial microcirculation.

The diameter of the arterial and arteriolar blood vessels was measured as a function of time in the hamster skin fold window preparation. When the animals recovered from the surgical implantation, the diameters of the arterial microvessels exhibited a continuous rhythmic activity throughout the preparation for a period of 2 wk while the chamber was intact. The amplitude of the diameter changes was directly proportional to the mean vessel size. The frequency of this phenomenon was determined by power spectrum analysis implemented with a Fourier transform method and was found to decrease from a maximum of 9-15 cycles/min in 8- to 15-micron A4 arterioles to 1-3 cycles/min in 70- to 100-micron A1 small arteries. A1 and A4 vessels had relatively well-defined characteristic fundamental frequencies, whereas A2 and A3 vessels showed a power spectrum that included the frequencies present in A1 and A4 vessels. The activity was not synchronized throughout the microvasculature, and frequencies and amplitudes of diameter variations changed at branching points. Anesthesia induced by the intravenous injections of pentobarbital and chloralose-urethan invariably stopped this activity throughout the preparation. The distribution of this time-dependent activity and the nature of the effect of the anesthetics suggests that this phenomenon is due to local pacemaker activity of groups of unitary smooth muscle cells.

Animals↗
PubMed2001

Electromyography of male rat perineal musculature during copulatory behavior.

Electromyogram (EMG) recordings were made from the bulbospongiosus (BS) and ischiocavernosus (IC) muscles of the awake male rat in order to evaluate the roles played by these muscles in the implementation of penile intromission during a copulatory encounter. Male rats with bipolar wire electrodes implanted chronically in the BS and IC muscles were mated with sexually receptive females. Concurrent videotape recordings established a relationship between EMG and components of male rat copulatory behavior, i.e. mount, intromission and ejaculation. On EMGs recorded from the IC muscle, the initial low-amplitude phase at the initiation of each behavioral component was distinguished from the late high-amplitude phase whenever the male accomplished mounting or intromission. In the BS muscle, the late high-amplitude phase was observed only when the male accomplished intromission. Power spectrum analysis by fast Fourier transformation revealed that in the IC muscle the two phases differed at an overall range of 100-1,000 Hz. In the BS muscle, however, the spectra of the two phases differed at a specific range of 400-600 Hz. Recruitment of additional motor units would culminate in such a characteristic rise in the power spectrum. The results suggest that somatosensory inputs contingent on the intromission cause such recruitment in the BS to regulate penile cups and other movements.

Animals↗
PubMed1996

Purification and partial characterization of a novel antibacterial agent (Bac1829) Produced by Staphylococcus aureus KSI1829.

A novel antimicrobial agent from Staphylococcus aureus KSI1829, designated Bac1829, was purified by sequential steps of ammonium sulfate precipitation, Sephadex G-50 gel filtration chromatography, and hydrophobic interaction chromatography. Purified Bac1829 has a molecular mass of 6,418 +/- 2 Da. The peptide in heat stable, since full biological activity is retained after heating at 95 degrees C for 15 min, and it is destroyed by digestion with proteases. Amino acid sequence analysis revealed a high concentration of Ala and Gly residues, which respectively comprised 24 and 19% of the total amino acid content. Additionally, high levels of hydrophobic amino acids were present, accounting for the hydrophobic nature of Bac1829. Purified Bac1829 killed exponentially growing Corynebacterium renale in a dose-dependent manner by a bactericidal mode of action. A partial inhibitory spectrum analysis revealed that the following organisms were sensitive to the inhibitory activity of Bac1829: S. aureus RN4220, Streptococcus suis, Corynebacterium pseudotuberculosis, C. renale, Corynebacterium diptheriae, Haemophilus parasuis, Bordetella pertussis, Bordetella bronchoseptica, Moraxella bovis, and Pasteurella multocida.

Bacteria↗