The reactivity of the hypophyseal-adrenal system in rats with different forms of adaptive behavioral pathology]

The dexamethasone suppression test (DST) was applied to male Wistar rats with different models of depression: group with the learned helplessness, group with informational neurosis provided by time-deficit conditioned avoidance training, as well as groups of rats of two strains selected for low (KLA)--and high (KHA) avoidance learning. The pre-dexamethasone basal and stress-induced corticosterone levels were similar in intact rats and those exposed to inescapable shock. The dexamethasone administration (5 mkg/kg) failed to decrease the serum corticosterone level in rats with learned helplessness. The informational neurosis increased significantly the basal corticosterone level and decreased the stress response. Serum corticosterone levels were similar in KLA and KHA rats. These results give evidence that two stress-induced rat models of depression with similar behavioural disturbances (reduction of escape/avoidance reactions) exhibit marked differences in the activity of hypothalamo-pituitary-adrenal (HPA) axis.     

The spatial organization of the cortical potentials in exposure to different forms of photic stimuli]

Reactive changes of spatial-temporal organization of cerebral cortex potentials of rabbits under the action of light stimuli of various shapes (circle, square, triangle, cross and weaker diffusive light presented prior to and after the application of structural stimuli) were studied on the basis of multi-channel EEG recording data (24 leads). The data were evaluated of spectral-correlative analysis of the electrical activity and the results of comparison of successive momentary topograms of cortical potentials (EEG) on two-second segments prior to and during the action of the applied light stimulus. The obtained results showed that localization of interconnected changes of the cortical potentials were more sensitive to the perception of the form of light stimuli than the change of frequency characteristics of the EEG rhythms.     

Characteristics of the motor potentials in disorders of the subcortical motor structures of the human brain

Properties of motor potentials (MPs) were studied in patients with disturbance of function of subcortical motor structures--disturbance causing parkinsonism manifestations. MPs components are singled out preceding movement--"readiness potential" (N1), "motor potential" (N2) and MP components which are electrophysiological correlates of realization processes (component P2) and movement completion (component N3). It is revealed that MPs in patients with parkinsonism are changed in comparison with the norm; the most significant differences are observed in components N1, P2, N3, what is expressed in prolongation and a certain amplitude decrease of these components. Amplitude-temporal parameters most similar to the norm belong to the component N2, which is considered as an electrophysiological correlate of movement triggering. A hypothesis is suggested on its cortical origin.     

Modeling of movement-related potentials using a fractal approach

In bio-signal applications, classification performance depends greatly on feature extraction, which is also the case for electroencephalogram (EEG) based applications. Feature extraction, and consequently classification of EEG signals is not an easy task due to their inherent low signal-to-noise ratios and artifacts. EEG signals can be treated as the output of a non-linear dynamical (chaotic) system in the human brain and therefore they can be modeled by their dimension values. In this study, the variance fractal dimension technique is suggested for the modeling of movement-related potentials (MRPs). Experimental data sets consist of EEG signals recorded during the movements of right foot up, lip pursing and a simultaneous execution of these two tasks. The experimental results and performance tests show that the proposed modeling method can efficiently be applied to MRPs especially in the binary approached brain computer interface applications aiming to assist severely disabled people such as amyotrophic lateral sclerosis patients in communication and/or controlling devices.     

Pain perception and its genesis in the human brain

In the past two decades, pain perception in the human brain has been studied with EEG/MEG brain topography and PET/ fMRI neuroimaging techniques. A host of cortical and subeortical loci can be activated by various nociceptive conditions. The activation in pain perception can be induced by physical (electrical, thermal, mechanical), chemical (capsacin, ascoric acid), psychological (anxiety, stress, nocebo) means, and pathological (e.g. migraine, neuropathic) diseases. This article deals mainly on the activation, but not modulation, of human pain in the brain. The brain areas identified are named pain representation, matrix, neuraxis, or signature. The sites are not uniformly isolated across various studies, but largely include a set of cores sites: thalamus and primary somatic area (SI), second somatic area (SII), insular cortex (IC), prefrontal cortex (PFC), cingnlate, and parietal cortices. Other areas less reported and considered important in pain perception include brainstem, hippocampus, amygdala and supplementary motor area (SMA). The issues of pain perception basically encompass both the site and the mode of brain function. Although the site issue is delineared to a large degree, the mode issue has been much less explored. From the temporal dynamics, IC can be considered as the initial stage in genesis of pain perception as conscious suffering, the unique aversion in the human brain.     

Event-related potentials of human brain in spatial hearing

The review presents the data concerning auditory event-related potentials and their "mismatch negativity" component under conditions of stationary and moving sound source localization. Both free-field and dichotic experimental conditions are considered. The interhemispheric asymmetry of the brain responses elicited by the sound sources of various spatial properties is also discussed.     

The relationship between different forms of human alpha-mannosidase.

The tissue distribution and some properties of human alpha-mannosidase (alpha-D-mannoside mannohydrolase EC 3.2.1.24) have been studied. The acidic forms of the enzyme were fairly stable, whereas the neutral forms easily lost enzymic activity. The acidic forms were sensitive to neuraminidase but the neutral forms were unaffected. The experiments indicate that the acidic components are closely related to each other, differing only in sialic acid content and possibly conformation. The neutral forms of the enzyme are probably quite different from the acidic forms both in structure and cellular function.     

The role of the genotype in the variability of human evoked potentials at different stages of ontogeny]

The determinants of individual differences in visual EPs to stimuli of different type depending on the age of subjects were studied. EPs to flash, checkerboard pattern and some other stimuli with semantic aspect were recorded in three groups of MZ, DZ twins aged 8-9, 10-12, 18-25 years. The heritability of EPs parameters is not ontogenetically stable characteristic. It changes from one age group to another in different way for separate EPs components and parameters depending on their nature, type of stimulus, area of recording. Most of all genotypical influences are manifested in EPs parameters of 10-12 years old subjects, especially the middle latency components from vertex area and latent periods of EPs in comparison with their amplitudes.     

Changes in the dimensions of motor neurons and their components with different forms of nerve center activation]

Experiments in frogs have shown that a prolonged orthodromic rhythmical activation of motoneurons induce changes in their size and staining. Under these conditions the size of all components of motoneurons (cytoplasm, nucleus, nucleolus) is changed. The cytoplasm size changes are more pronounced than those of the nucleus. Under prolongation of the low frequency stimulation (1 per sec.) of the dorsal roots the changes are of phasic character: an initial enlargement (10 minute-long stimulation) and a subsequent decrease of all the above spinal cord motoneuron components (25 minute stimulation). After the 10 minute high frequency stimulation (50 impulses per second) of nerve centers there occur a sharp decrease of the size of the cytoplasm and the nucleus.     

Myocyte polyploidy in human cardiac pathology]

With general atherosclerosis, the ploidy of left ventricle myocytes in the hearts of patients that underwent infarction corresponds to the norm variation irrespective of the ventricle and heart weights. At heart diseases the myocyte nucleus ploidy is often much higher than the norm variability both in hypertrophied ventricles and in those with normal weight. An additional polyploidization is suggested that may occur at some natural ontogenetic periods of human development (in the childhood) during heart diseases both innate or spontaneously appearing at the particular time. Unlike, the myocardial hypertrophy in adults does not stimulate myocyte polyploidy.     

The genesis and transmission of epidermal potentials in an amphibian embryo

The genesis and transmission of action potentials in epidermal cells of the newt (Cynops pyrrhogaster) embryo were investigated with special reference to cellular differentiation during development. Typical action potentials can be recorded from any of the epidermal cells at Stage 31. These potentials consist of a fast spike (18 msec) followed by a slow component (164 msec). The potential is graded with current intensity, and only the slow component initiates action potentials in adjacent cells and induces a transmission to other cells. The fast spike was found in all epidermal cells throughout the embryonic stages examined (Stages 26–47). The slow potential, however, appears at Stage 28, persists until Stage $\text{36}\text{37}$ just before hatching and then disappears at Stage $\text{38}\text{42}$. Electrical recordings from traumatic embryos (embryos without neural crest cells) or from cultured epidermal cell masses isolated from the pregastrula or the ventral region of the neurula, were compared with the intact embryo. No differences were observed in either the form of the action potential or its transmission. Thus these action potentials appear to be derived from epidermal cells, and are not of nervous origin. Evidence suggests that the transient establishment of excitable membranes in epidermal cells during differentiation is closely related to neural cell differentiation.     

The effect of motor training on evoked sensorimotor cortex potentials in rats during ontogenesis]

Investigation into the influence of motor training on the functional activity of the rat sensorimotor cortex in ontogenesis has shown that three to four-month training, starting at the age of four weeks, leads to a statistically significant enhancement of sensorimotor cortex activity both by latencies and recovery cycles durations. A similar six to seven-month locomotor training produces the same statistically significant results. The differences in the shifts of functional activity after motor training observed between two age groups are not statistically significant. The probability of changes in the average definitive electrophysiological parameters of functional activity after motor training observed between two age groups are not statistically significant. The probability of changes in the average definitive electrophysiological parameters of functional activity of the sensorimotor cortex is suggested in rats aged more than a month, as a result of individual experience.     

Antiherpetic activity of l-lysine-alpha-oxidase in different dosage forms]

The antiviral effect of different medicinal forms on base of L-lysin-alpha-oxidase (LO) in treatment of experimental keratits and skin diseases induced by herpes simplex virus type 1 (HSV-1) at the rabbits was examined. Treatment with gel form of LO was more effective in comparison with water solution form of LO. This effect was tested by morphological, histological and immunoblotting methods in dynamics of viral disease.     

Dipole tracing of visual evoked potentials in human brain

3D tracing of equivalent current dipoles (ECDs) of averaged human visual evoked potentials (VEP) by their distribution across a 34-electrode array was obtained under short presentation of pattern-onset stimuli (sets of 45 horizontal, vertical bars or crosses). Using a 2-dipole spherical three-layer model, we dynamically (step of 1 ms) localized dipoles in four healthy subjects. Dipole locations were matched to anatomical brain regions visualized in structural MRI. Best-fitting source parameters were superimposed on MR images of each subject to identify the anatomical structures giving rise to the surface patterns. It was found that during 50-300 ms following the onset of the stimuli, the ECDs in all subjects were localized in the occipital cortex and demonstrated reliable systematic shift in localization. Two local (1-2 cm3) zones of the preferable dipole attendance were found at 5-6 cm behind zero line: the first one was localized near the midline of the brain, whereas the other zone was situated in the right hemisphere at a distance of 6-7 cm from the first zone. Their localization and strength of activation were reliably different for crosses and lines and changed during VEP generation. Zones of relatively rare dipole attendance were found also. The data are discussed in relation to localization of initial and endpoint of ECDs trajectories, as well as with sensitivity of the visual cortex to line crossing and branching.