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Biomedical subjects

M N Zhadin

Publications and source records attributed to M N Zhadin.

At least 19 recordsLinked to original sources
PubMed2001

Review of russian literature on biological action of DC and low-frequency AC magnetic fields.

This review considers the Russian scientific literature on the influence of weak static and of low-frequency alternating magnetic fields on biological systems. The review covers the most interesting works and the main lines of investigation during the period 1900 to the present. Shown here are the historical roots, beginning with the ideas of V. Vernadsky and A. Chizhevsky, which led in the field of Russian biology to an increasing interest in magnetic fields, based on an intimate connection between solar activity and life on the Earth, and which determined the peculiar development of Russian magnetobiology. The variety of studies on the effects of magnetic storms and extremely low-frequency, periodic variations of the geomagnetic field on human beings and animals as well as on social phenomena are described. The diverse experiments involving artificial laboratory magnetic fields acting on different biological entities under different conditions are also considered. A series of theoretical advances are reviewed that have paved the way for a step-by-step understanding of the mechanisms of magnetic field effects on biological systems. The predominantly unfavorable influence of magnetic fields on living beings is shown, but the cases of favorable influence of magnetic fields on human beings and lower animals are demonstrated as well. The majority of Russian investigations in this area of science has been unknown among the non-Russian speaking audience for many reasons, primarily because of a language barrier. Therefore, it is hoped that this review may be of interest to the international scientific community.

Animals↗
PubMed1999

Influence of combined DC and AC magnetic fields on rat behavior.

The action of combined parallel static (DC) and alternating (AC) magnetic fields at the cyclotron frequencies for different biologically active ions, specifically, calcium, sodium, potassium, chlorine, magnesium and lithium, on rat behavior in the "open field" were investigated. It was shown that the DC and AC fields at the calcium cyclotron frequency lower the locomotor and exploratory activity of the rats, whereas action of the fields at the magnesium cyclotron frequency enhances these forms of behavioral activity. The effects were qualitatively alike at the weak (50 microT) and relatively strong (500 microT) DC fields with proportional changes in the frequencies and amplitudes of the AC fields. Statistically significant effects of cyclotron frequencies for other ions studied were not observed.

Animals↗
PubMed1998

Combined action of static and alternating magnetic fields on ionic current in aqueous glutamic acid solution.

Combined parallel static and alternating magnetic fields cause a rapid change in the ionic current flowing through an aqueous glutamic acid solution when the alternating field frequency is equal to the cyclotron frequency. The current peak is 20-30% of the background direct current. The peak is observed with slow sweep in the alternating magnetic field frequency from 1 Hz-10 Hz. Only one resonance peak in the current is observed in this frequency range. The frequency corresponding to the peak is directly proportional to the static magnetic field. The above effect only arises at very small alternating field amplitude in the range from 0.02 microT-0.08 microT.

Cyclotrons↗
PubMed1998

Combined action of static and alternating magnetic fields on ion motion in a macromolecule: theoretical aspects.

This is an attempt to solve the energetic problem of the primary detection of weak parallel static (DC) and alternating (AC) extremely low frequency (ELF) magnetic fields. We studied the equations of motion for an ion situated inside a macromolecule under the influence of these fields. The main concern is with the magnetic field influence on thermal motion of the ion in the macromolecule. The resonance effects are revealed at discrete frequencies of the ion thermal oscillations determined by the DC field magnitude and the AC field frequency. These phenomena result from the Larmor precession of the ion thermal motion. When the DC field or, to a greater extent, the combined DC and AC fields with the specific frequencies are turned on or cut off, changes occur in the energy of the ion thermal motion. If, inside the macromolecule, the ion is sufficiently protected against immediate impacts of particles of the medium surrounding the macromolecule, these changes may be enough to trigger alteration in the quantum state of the macromolecule.

Cyclotrons↗
PubMed1990

Ionic cyclotron resonance in biomolecules.

The possible mechanism of action of weak electric and magnetic fields of extremely low frequency on biomolecules is discussed in terms of the resonance effects on the precession of the ion orbits in a static magnetic field. The proposed model retains the principal merits of the familiar model of Liboff, but is free from the basic shortcomings of the latter.

Biophysical Phenomena↗
PubMed1985

[Structure of the background neuronal activity in thin slices of guinea pig neocortex].

Background neuronal discharges were recorded extracellularly in guinea-pig cerebral cortex slices maintained in vitro. Six types of activity were classified: 1--regular single discharges (38.5%), 2--irregular spikes (6.5%), 3--bursts (6.5%), 4--burst-single discharge (mixed) activity (26.5%), 5--group discharges (2.5%), 6--multineuronal volleys (18.5%). Characteristic distributions of interspike intervals and autocorrelograms corresponded to each of these types of activity. Regular pacemaker-type discharges were most peculiar under conditions of small volumes of the grey matter and lack of afferentation. Such regular activity was never observed in normal or isolated neocortex.

Action Potentials↗
PubMed1984

Rhythmic processes in the cerebral cortex.

A differential equation describing the electroencephalogram (EEG) is deduced based on the data on the structure of the brain cortex and the conceptions about a recurrent inhibition. This equation allows the study of a number of essential electrophysiological phenomena: the philogenetic differences in the frequency composition of the EEG, the shift of the EEG spectrum to higher frequencies upon excitation of the cortex, the lowering of the EEG rhythms and changes in cell reaction on deafferentation of the cortex, the identity in the spectra of a spontaneous EEG and evoked responses. A possible mechanism for the onset of epileptic activity is proposed.

Afferent Pathways↗
PubMed1977

[Correlation spectral analysis of the spontaneous impulse activity of cerebral cortex neurons].

Spontaneous unit activity in alert unrestrained rabbits was recorded simultaneously with two microelectrodes from the visual and sensorimotor cortex. The correlation analysis revealed that activity of majority of the neurons had no regular rhythm. But spectral analysis of the average correlograms showed existence of oscillations in the delta- and theta-ranges. The synergic type of interaction between cortical neurons was prevalent. Analysis of structure of the distant interaction showed the reduced probability of synergic spikes with periods 150-200 msec and less and the increased one with periods within 200-500 msec.

Animals↗
PubMedDate not supplied

Effect of repetitive stimulation on cortical single unit activity.

Activity of single units in the visual and sensomotor cortex of an uncurarized, unanesthetized rabbit was recorded by means of two independent microelectrodes during photic stimulation at different frequencies. Trace effects characterized by repetition of the temporal structure of afferent stimulation and by an increase in the level of intercellular correlation were discovered mainly on analysis of distant interneuronal relations after stimulation with frequencies of 2 and Hz. Stimulation at a frequency of 8 Hz did not evoke trace effects.

Animals↗
PubMedDate not supplied

Electrophysiological manifestations of the monoaminergic systems' effects on the cerebral cortex.

Consideration is given to a possible mechanism of reinforcement during training mediated through the monoaminergic systems in the brain that modulate the effectiveness of intracortical synapses. Various forms of electroencephalographic manifestations of the effect of these systems on the cerebral cortex are discussed. A comparison of the theoretical and experimental results favors the modulating role of the serotoninergic and noradrenergic systems.

Animals↗