High-frequency oscillations in a pulse wave signal and their relation to differential blood count leucocytes

High-frequency oscillations in a pulse wave signal in the range of 1-50 Hz and their relation to differential blood count leucocytes have been investigated. It is shown that the correlation coefficients grow in the frequency range of 1-12.5 Hz between high-frequency oscillations in a pulse wave signal and stab neutrophils, monocytes and segmented granulocytes. The procedure of smoothing the coefficients of harmonic variation has been proposed.     

High-frequency oscillations in a pulse wave signal and their relation to adaptation responses

High-frequency oscillations in a pulse wave signal in the range of 1-50 Hz and their relation to heart rhythms have been investigated. Informative parameters to estimate the adaptation reactions have been determined using the Kohonen maps, the results of simulating the pulse wave signal (single rheocycles), and the experimental data. The coefficient of harmonic variation was used as an informative parameter. It was shown that the space of signs in the frequency range of 1-12.5 Hz, formed on the basis of the coefficient of harmonic variation, possesses a significant degree of structuring relative to the distribution of data for different types of adaptation reactions.     

Frequency sensitivity in Hodgkin–Huxley systems

 The frequency sensitivity of weak periodic signal detection has been studied via numerical simulations for both a single neuron and a neuronal network. The dependence of the critical amplitude of the signal upon its frequency and a resonance between the intrinsic oscillations of a neuron and the signal could account for the frequency sensitivity. In the presence of both a subthreshold periodic signal and noise, the signal-to-noise ratio (SNR) of the output of either a single neuron or a neuronal network present the typical characteristics of stochastic resonance. In particular, there exists a frequency-sensitive range of 30–100 Hz, and for signals with frequencies within this range the SNRs have large values. This implies that the system under consideration (a single neuron or a neuronal network) is more sensitive to the detection of periodic signals, and the frequency sensitivity may be of a functional significance to signal processing. Received: 26 October 1999 / Accepted in revised form: 25 July 2000     

The response of a classical Hodgkin–Huxley neuron to an inhibitory input pulse

A population of uncoupled neurons can often be brought close to synchrony by a single strong inhibitory input pulse affecting all neurons equally. This mechanism is thought to underlie some brain rhythms, in particular gamma frequency (30–80 Hz) oscillations in the hippocampus and neocortex. Here we show that synchronization by an inhibitory input pulse often fails for populations of classical Hodgkin–Huxley neurons. Our reasoning suggests that in general, synchronization by inhibitory input pulses can fail when the transition of the target neurons from rest to spiking involves a Hopf bifurcation, especially when inhibition is shunting, not hyperpolarizing. Surprisingly, synchronization is more likely to fail when the inhibitory pulse is stronger or longer-lasting. These findings have potential implications for the question which neurons participate in brain rhythms, in particular in gamma oscillations.     

Modest increase in temperature affects ODC activity in L929 cells: low-level radiofrequency radiation does not

The effects of low-level radiofrequency (RF) radiation and elevated temperature on ornithine decarboxylase (ODC) activity were investigated in murine L929 fibroblasts. The cells were exposed at 900 MHz either to a pulse-modulated (pulse frequency 217 Hz; GSM-type modulation) or a continuous wave signal at specific absorption rate (SAR) levels of 0.2 W kg⁻¹ (0.1–0.3 W kg⁻¹) and 0.4 W kg⁻¹ (0.3–0.5 W kg⁻¹) for 2, 8, or 24 h. RF radiation did not affect cellular ODC activity. However, a slight increase in temperature (0.8–0.9°C) in the exposure system lead to decreased ODC activity in cell cultures. This was verified by tests in which cells were exposed to different temperatures in incubators. The results show that ODC activity is sensitive to small temperature differences in cell cultures. Hence, a precise temperature control in cellular ODC activity studies is needed.     

Peculiarities of myocardial electrogenesis in laboratory rats under conditions of acute nitrite intoxication

In anesthetized male rats the arterial blood pressure in femoral artery and electrocardiogram in standard leads were recorded uninterruptedly for 1–1.5 h under conditions of acute nitrite intoxication produced by a subcutaneous injection of water solution of sodium nitrite (donor of nitric oxide) at concentrations of 10, 30, and 50 mg/kg body mass. Results of the study have shown dose-dependent changes of arterial pressure as well as of time and amplitude characteristics of electrocardiogram under effect of NaNO₂. At the threshold hypoxic dose, an increase of amplitude of R and S waves was observed by the 30–45th min, while at the maximal NaNO₂ dose, amplitude of all waves rose by the 15th min of intoxication. High nitrite doses often caused an elevation of the ST segment above the isoelectric line and a rise of the amplitude of the T wave, on which a notch appeared in some cases. The change of the ECG time parameters was expressed in the dose-dependent development of bradycardia for the first 4–7 min; its level correlated with the progressively decreasing arterial pressure in the beginning (the 2–4th min) of nitrite intoxication. Variation analysis of the heart rate spectral characteristics by Baevskii’s method has revealed a rise of the total spectral power of pulse oscillations. Under effect of nitrite, in the specter of cardiointervals, the slower oscillations have been revealed with frequency of 0.15–0.2 Hz in the LF diapason with subsequent recovery of the normal ECG specter at the end of the experimental period. The maximal nitrite dose produced more pronounced shifts of the heart rate specter towards the LF and VLF diapasons that were not restored for 1 h of experiment. Transitory processes of readjustment of the cardiac rhythm had discrete character. The nitrite dose of 100 mg/kg body mass increased the RR-interval after 4–7 min with amplitude steps of 3–5 imp/s and the time constant of 20–40 s. The revealed ECG changes had the reflex (enhancement of parasympathetic tonus) and metabolic (the hypoxic and histotoxic damage of myocardium) nature.     

The effects of extra-low-frequency atmospheric pressure oscillations on human mental activity

 Slight atmospheric pressure oscillations (APO) in the extra-low-frequency range below 0.1 Hz, which frequently occur naturally, can influence human mental activity. This phenomenon has been observed in experiments with a group of 12 healthy volunteers exposed to experimentally created APO with amplitudes 30–50 Pa in the frequency band 0.011–0.17 Hz. Exposure of the subjects to APO for 15–30 min caused significant changes in attention and short-term memory functions, performance rate, and mental processing flexibility. The character of the response depended on the APO frequency and coherence. Periodic APO promoted purposeful mental activity, accompanied by an increase in breath-holding duration and a slower heart rate. On the other hand, quasi-chaotic APO, similar to the natural perturbations of atmospheric pressure, disrupted mental activity. These observations suggest that APO could be partly responsible for meteorosensitivity in humans. Received: 22 August 1997/Revised: 3 December 1998/Accepted: 25 February 1999     

Modifications of EEG Related to Directed Perception and Analysis of Olfactory Information in Humans

We recorded EEG in adult volunteers in the course of perception of smells of plant essential oils under conditions of directed attention. It was found that perception of olfactory information, even in the case of mild intensity of the smells inducing no aversive effects, correlates with noticeable changes in the EEG characteristics mostly typical of the reaction of nonspecific EEG activation induced by sensory stimulation and manifested in a decrease in the spectral power, SP, of low-frequency EEG components (6–10 Hz)). In addition, the SP of relatively high-frequency EEG components (11–25 Hz) increased; this effect was most pronounced in the occipital regions of the neocortex. Perception of the smells of essential oils was also accompanied by increases in the coherence of EEG oscillations, most intense in the β2 range (20–25 Hz). Such modifications were maximum in the left temporal/parietal region; this is interpreted as an indication of the special role of these cortical areas in the processes of interaction between the neocortical part of the olfactory analyzer and the respective structures of other analyzer systems. It is hypothesized that such interaction is necessary for the formation of a semantic image of the analyzed stimuli. Neirofiziologiya/Neurophysiology, Vol. 41, No. 1, pp. 70–78, January–February, 2009.     

Frequency-intensity characteristics of cricket cercal interneurons: units with high-pass functions

Interneurons in the cercal sensory system of crickets respond in a cell-specific manner if the cercal hair sensilla are stimulated by air-particle oscillations at frequencies below about 2000 Hz. We investigated the filter properties of several of these interneurons, and tested the effect of stimulus intensity (typically 0.3–50 mm s⁻¹ peak-to-peak air-particle velocity) on the frequency response in the range 5–600 Hz. We focus on three interneurons (the lateral and medial giant interneurons and interneuron 9-3a) of Acheta domesticus which are characterized by a relatively high sensitivity above ca. 50–200 Hz. The responses of the medial giant interneuron usually increase monotonically with frequency and intensity. Interneuron 9-3a and the lateral giant interneuron exhibit saturation or response decrement at high frequencies and intensities. The lateral giant interneuron has an additional peak of sensitivity below about 40 Hz. Small individual variations in the relative locations of the two response areas of this interneuron within the frequency-intensity field are responsible for a large variability obtained if frequency-response curves are determined for particular intensities. Stimulus frequency does not affect the principal directional preferences of the three interneurons. Nevertheless, if tested individually, the lateral giant interneuron and interneuron 9-3a exhibit small changes of directional tuning. Accepted: 12 November 1997     

Effect of pulse electromagnetic radiation on erythrocyte ghosts

The pulse microwave radiation has been shown to increase the fluorescence intensity of 2-toluidinonaphthanene-6-sulfonate (2,6-TNS) and 1-anilinonaphthalene-8-sulfonate (1,8-ANS) built-in membranes of erythrocyte ghosts. In experiments with 2,6-TNS a frequency dependence of the effect of microwave radiation with maximum within the frequency range of 55-65 Hz has been found. It is suggested that the changes registered with fluorescent probes are induced by mechanical oscillations generated by the pulse microwave radiation.     

Time-frequency analysis of the electrocortical activity during maturation using wavelet transform

In this study, we introduce the wavelet transform (WT) as a method for characterizing the maturational changes in electrocortical activity in 24 fetal lambs ranging from 110–144 days gestation (term 145 days). The WT, based on multiresolution signal decomposition, is free of assumptions regarding the characteristics of the signal. The approximation of the electrocortical activity at resolutions varying from 2^j+1 to 2^j can be extracted by decomposing the signal on a wavelet orthonormal basis of L ²(R). We performed multiresolution decomposition for four sets of parameters D _2j, where −1<j<−4. The four series WT represent the detail signal bandwidths: (1) 16–32 Hz, (2) 8–16 Hz, (3) 4–8 Hz, (4) 2–4 Hz. The data were divided into three groups according to gestational age: 110–122 days (early), 123–135 days (middle), and 136–144 days (late). In the early group, the power was highest in the fourth signal bandwidth, with relatively low power in the other bands. Increase in gestational age was characterized by increased power in all four bandwidths. Comparison of the cumulative distribution function of the power in the four wavelet bands confirmed the presence of two statistically different patterns in all three age groups. These two patterns correspond to the visually identified patterns of HVSA (high-voltage slow activity) and LVFA (low-voltage fast activity). The earliest development change occurred in HVSA, with progressive increase in power in the 2–8 Hz band. Later changes occurred in LVFA, with a significant increase in power in the 16–32 Hz band. The same database was also analyzed by the short-term Fourier transform (STFT) method, the most common time-frequency analysis method. Comparison of the results clearly show that the WT provided much better time-frequency resolution than the STFT method and was superior in demonstrating maturational changes in electrocortical activity. Received: 7 July 1993/Accepted in revised form: 15 November 1993     

Ripple-associated high-firing interneurons in the hippocampal CA1 region

By simultaneously recording the activity of individual neurons and field potentials in freely behaving mice, we found two types of interneurons firing at high frequency in the hippocampal CA1 region, which had high correlations with characteristic sharp wave-associated ripple oscillations (100–250 Hz) during slow-wave sleep. The firing of these two types of interneurons highly synchronized with ripple oscillations during slow-wave sleep, with strongly increased firing rates corresponding to individual ripple episodes. Interneuron type I had at most one spike in each sub-ripple cycle of ripple episodes and the peak firing rate was 310±33.17 Hz. Interneuron type II had one or two spikes in each sub-ripple cycle and the peak firing rate was 410±47.61 Hz. During active exploration, their firing was phase locked to theta oscillations with the highest probability at the trough of theta wave. Both two types of interneurons increased transiently their firing rates responding to the startling shake stimuli. The results showed that these two types of high-frequency interneurons in the hippocampal CA1 region were involved in the modulation of the hippocampal neural network during different states.     

Frequency-intensity characteristics of cricket cercal interneurons: low-frequency-sensitive units

Three identified interneurons of the cercal system were investigated electrophysiologically; these interneurons are sensitive only to stimulation of cercal filiform-hair sensilla by low-frequency sound. Measurement of the frequency ranges revealed cut-off frequencies between ca. 20 and 70 Hz. Analysis of the responses near threshold and at higher intensities in the frequency range 5–500 Hz shows that one of them (Interneuron 9-1b) exhibits a sensitivity maximum at the frequency-intensity combination necessary for the perception of an intraspecific signal at 30 Hz. This band-pass behavior disappears at higher stimulus intensities. In order to investigate the mechanism of the low-frequency selectivity of the interneurons, two-tone stimulation experiments were performed. When stimuli in the best-frequency range were superimposed by a 100-Hz tone, the spiking activity was suppressed in an intensity-dependent manner. Accepted: 22 July 1998     

Impact of gamma-oscillatory inhibition on the signal transmission of a cortical pyramidal neuron

Networks of synchronized fast-spiking interneurons are thought to be key elements in the generation of gamma (γ) oscillations (30–80 Hz) in the brain. We examined how such γ-oscillatory inhibition regulates the output of a cortical pyramidal cell. Specifically, we modeled a situation where a pyramidal cell receives inputs from γ-synchronized fast-spiking inhibitory interneurons. This model successfully reproduced several important aspects of a recent experimental result regarding the γ-inhibitory regulation of pyramidal cellular firing that is presumably associated with the sensation of whisker stimuli. Through an in-depth analysis of this model system, we show that there is an obvious rhythmic gating effect of the γ-oscillated interneuron networks on the pyramidal neuron’s signal transmission. This effect is further illustrated by the interactions of this interneuron network and the pyramidal neuron. Prominent power in the γ frequency range can emerge provided that there are appropriate delays on the excitatory connections and inhibitory synaptic conductance between interneurons. These results indicate that interactions between excitation and inhibition are critical for the modulation of coherence and oscillation frequency of network activities.     

Pheromone-evoked potentials and oscillations in the antennal lobes of the sphinx moth Manduca sexta

Using intra- and extracellular recording methods, we studied the activity of pheromone-responsive projection neurons in the antennal lobe of the moth Manduca sexta. Intracellularly recorded responses of neurons to antennal stimulation with the pheromone blend characteristically included both inhibitory and excitatory stages of various strengths. To observe the activity of larger groups of neurons, we recorded responses extracellularly in the macroglomerular complex of the antennal lobe. The macroglomerular complex is part of a specialized olfactory subsystem and the site of first-order central processing of sex-pheromonal information. Odors such as the pheromone blend and host-plant (tobacco) volatiles gave rise to evoked potentials that were reproducible upon repeated antennal stimulation. Evoked potentials showed overriding high-frequency oscillations when the antenna was stimulated with the pheromone blend or with either one of the two key pheromone components. The frequency of the oscillations was in the range of 30–50 Hz. Amplitude and frequency of the oscillations varied during the response to pheromonal stimulation. Recording intracellular and extracellular activity simultaneously revealed phase-locking of action potentials to potential oscillations. The results suggest that the activity of neurons of the macroglomerular complex was temporally synchronized, potentially to strengthen the pheromone signal and to improve olfactory perception. Accepted: 19 December 1997     

Physical and physiological aspects of gear efficiency in North Sea brown shrimp fisheries

In search of means to reduce the by-catch of juvenile flatfish in the shrimp fishery, vibrations and changes in current velocity caused by shrimp trawls were investigated in the field and in the laboratory. Buried as well as emerged shrimps (Crangon crangon) exhibit tailflips 5–10 cm before being touched by the rollers of a shrimp gear approaching them at a speed of 0.5 m·sec⁻¹, as was revealed by slow motion video recordings in aquaria under artificial light. Hence, the signal effective in triggering escape must be attenuated strongly with increasing distance. Sediment vibration, commonly assumed to be an important signal in triggering escape of shrimps, was found to decrease by a factor 100·m⁻¹. Signals from the rollers of a commercial shrimp gear in operation (towing speed 1 m·sec⁻¹) were directly recorded with an accelerometer. Their frequency ranged from 50 to 500 Hz and reached an acceleration of 40 m·sec⁻² on soft bottom or up to 100 m·sec⁻² on hard substrate. Accelerometers, which had been buried right at the surface of a tidal sand flat during low tide, produced only one sharp signal of 100 Hz with an acceleration of 24 m·sec⁻², when a shrimp gear swept them on the submerged tidal flats. However, in aquaria short sinusoidal signals (<5 m·sec⁻²; 20 to 300 Hz) made buried shrimps and flatfish (Pleuronectes platessa, Solea solea, Microstomus kitt) hide rather than flee. The vibrations recorded directly at the rollers and the underlying jolting movements of the rollers induce corresponding pulses in the water surrounding the rollers in a layer of approximately 10–15 cm. Similar water displacement of high acceleration was experimentally produced by a spring loaded transparent lucite piston (7 cm in diameter) fitted to an accelerometer. Accelerating this piston (12–116 m·sec⁻², 50–200 Hz range) from 5 cm above towards the shrimp produced escape responses in up to 94% of the tests. Arthropods are known to perceive medium displacement rather than pressure. Hence, strong and rapidly rising water currents caused by the rollers rather than sediment vibration are assumed to mainly trigger the escape reaction, which makesCrangon accessible to the gear.     

Coherent phenomena of charge separation in reaction centers of LL131H and LL131H/LM160H/FM197H mutants of <Emphasis Type="Italic">Rhodobacter sphaeroides</Emphasis>

Primary stage of charge separation and transfer of charges was studied in reaction centers (RCs) of point mutants LL131H and LL131H/LM160H/FM197H of the purple bacterium Rhodobacter sphaeroides by differential absorption spectroscopy with temporal resolution of 18 fsec at 90 K. Difference absorption spectra measured at 0–4 psec delays after excitation of dimer P at 870 nm with 30 fsec step were obtained in the spectral range of 935–1060 nm. It was found that a decay of P* due to charge separation is considerably slower in the mutant RCs in comparison with native RCs of Rba. sphaeroides. Coherent oscillations were found in the kinetics of stimulated emission of the P* state at 940 nm. Fourier analysis of the oscillations revealed a set of characteristic bands in the frequency range of 20–500 cm⁻¹. The most intense band has the frequency of −30 cm⁻¹ in RCs of mutant LL131H and in native RCs and the frequency of ∼100 cm⁻¹ in RCs of the triple mutant. It was found that an absorption band of bacteriochlorophyll anion B_A⁻ which is registered in the difference absorption spectra of native RCs at 1020 nm is absent in the analogous spectra of the mutants. The results are analyzed in terms of the participation of the B_A molecule in the primary electron transfer in the presence of a nuclear wave packet moving along the inharmonic surface of P* potential energy.     

Photosynthetic oscillation in individual cells of the marine diatom <Emphasis Type="Italic">Coscinodiscus wailesii</Emphasis> (Bacillariophyceae) revealed by microsensor measurements

Oscillations with a period of 1–2 min in the rate of photosynthesis have been found in leaves of C₃ and C₄ land plants under invariant, saturating, light and carbon dioxide. This article reports the occurrence of similar oscillations with a period of 2–2.5 min in individual cells of the marine diatom Coscinodiscus wailesii. These oscillations were determined by measurements of both oxygen (oxygen microelectrode) and carbon dioxide (pH microelectrode) just outside the plasmalemma. These oscillations were found in less than 1% of the cells examined. The occurrence of oscillations in unicelluar diatoms rules out for these organisms hypotheses as to the origin of oscillations in land plant leaves that are based on cell–cell interactions.     

Ripple-associated high-firing interneurons in the hippocampal CA1 region

By simultaneously recording the activity of individual neurons and field potentials in freely behaving mice, we found two types of interneurons firing at high frequency in the hippocampal CA1 region, which had high correlations with characteristic sharp wave-associated ripple oscillations (100―250 Hz) during slow-wave sleep. The firing of these two types of interneurons highly synchronized with ripple oscillations during slow-wave sleep, with strongly increased firing rates corresponding to individual ripple episodes. Interneuron type I had at most one spike in each sub-ripple cycle of ripple episodes and the peak firing rate was 310±33.17 Hz. Interneuron type II had one or two spikes in each sub-ripple cycle and the peak firing rate was 410±47.61 Hz. During active exploration, their firing was phase locked to theta oscillations with the highest probability at the trough of theta wave. Both two types of interneurons increased transiently their firing rates responding to the startling shake stimuli. The results showed that these two types of high-frequency interneurons in the hippocampal CA1 region were involved in the modulation of the hippocampal neural network during different states.     

Desynchronization and synchronization of EEG related to stimuli triggering or forbidding sensory-motor reaction in adolescents: II. The peculiarities in case of the attention deficit and hyperactivity syndrome

Evoked desynchronization and synchronization of EEG in θ (4–7.5 Hz), α (7.5–14 Hz) and β (14–20 Hz) ranges were recorded by 19 electrodes in healthy volunteer adolescents and those with attention deficit hyperactivity syndrome in the modified GO/NO-GO test. Two stimuli (high and low tone) were presented in pairs with 1 s intervals inside the pair and 1.5 s intervals between the pairs. Test subjects had to push the button in response to presentation of a pair of high tones and to ignore other stimulus combinations. The components of evoked EEG synchronization in α-θ range that were revealed in the frontocentral and temporoparietal brain regions in connection with inhibition of action (inhibition of movements and making a decision to cancel sensory-motor task performance) were statistically significantly lower in subjects with attention deficit hyperactivity disorder compared with that in healthy subjects.