Metabotropic glutamate receptors as targets of neuromodulatory influence of nitric oxide.

A possible effect of nitric oxide (NO) on metabotropic glutamate receptor (mGluR) function in the amino acid afferent synapse was investigated in the isolated labyrinth of the frog Rana temporaria. The modification of the amplitude of responses of metabotropic glutamate receptor agonist trans-ACPD was analyzed during bath applied NO donor S-nitroso-N-acetyl-DL-penicillamine SNAP (0.1-100 µM) or nitric oxide synthase inhibitor L-NAME. It was shown that NO donor SNAP (1 µM) inhibited mGluR induced responses, and the inhibitor of NO-synthase L-NAME (100 µM) increased the amplitude of trans-ACPD evoked answers. The results suggest that NO can depress mGluR function due to modulation of functions of the endoplasmic reticulum channels.

[Noise affect to the fragmented contour image recognition].

We performed a comparison of the results of recognition of fragmented outline images in the presence of noise and without it. Contour images and visual noise were synthesized form Gabor elements. Distances between the Gabor elements in contour and in noise were changed and image sizes varied too. The percentage of correct responses was not dependent on the size of the stimuli, but differed for the same objects in the noise and without noise. The percentage of recognition was higher for images with lots of turns in case without noise. The recognition in noise was better for contour images having lines with slightly varying curvature. Identification in noise depended on the ration of the distances between the elements in noise and in contour.

[Estimates of the size of inhibitory areas in crowding effects in periphery].

In psychophysical experiments we studied how surround influences recognition of test objects. The tests were low-contrast Landolt rings of the size 1.1, 1.5 and 2.3 deg. Their centers were located at 13.2 deg from the fixation point. The additional objects were similar Landolt rings or rings without gaps. The distance between the centers of the test and the additional objects varied from 2.2 to 13.2 deg. Inone experiment, the task of the observer was to identify both the test objects and the surrounding objects. In the second experiment the stimulus layout was the same, but'identification of only the test stimulus was required. In both experiments, deterioration of performance was found at all distances between the test objects and the surround, but the deterioration was more significant when the observer carried out the dual task. The data showed that the size of the inhibitory areas in our case does not comply with the Bouma low which states that the size of the interaction areas are equal to half of the eccentricity where the test is presented. Further deterioration of performance in the dual task reveals the contribution of attention into peripheral crowding effects.

Foveal crowding for large and small Landolt Cs: Similarity and Attention.

We compare the recognition of foveal crowded Landolt Cs of two sizes: brief (40 ms), large, low-contrast Cs and high-contrast (1 sec) tests at the resolution limit of the visual system. In different series, the test Landolt C was surrounded by two identical distractors located symmetrically along the horizontal or by a single distractor. The distractors were Landolt Cs or rings. At the resolution limit, the critical spacing was similar in the two series and did not depend on the type of distractor. The result supports the hypothesis that crowding at the resolution limit occurs when both the test and the distractors fall into the same smallest receptive field responsible for the target recognition. For large stimuli, at almost all separations distractors of the same shape caused greater impairment than did rings, and recognition errors were non-random. The critical spacing was equal to 0.5 test diameters only in the presence of one distracting Landolt C. This result suggests that attention is involved: When one distractor is added, involuntary attention, which is directed to the centre of gravity of the stimulus, can lead to confusion of features that are present in both tests and distractors and thus to non-random errors.

[Interdependent changes of the axon and Schwann cell in the process of reactive remodeling of a myelinated nerve fiber].

Using the inverted phase-contrast microscope, the living undamaged frog sciatic nerve fibers and the fibers mechanically injured to varying degrees, were studied. It was found that the swelling of myelin incisures (MI) (of Schmidt-Lanterman) occured according to the principles similar to those controlling the changes of the myelin gap (node of Ranvier) and depended on the swelling of a Schwann cell (SC) perikaryon. It was detected that this was a single process, which which could be united in a complex of nonspecific changes of a myelinated nerve fiber. It was also demonstrated that under the action of mechanical injury and hypotonic solution, swelling of MI, nodes of Ranvier and SC perikaryon occurred without modifications of outer fiber diameter, due to the pronounced local axon thinning. Electron microscopic study of the cytoskeletal axonal structures showed that there was not a simple local contraction of an axon, but a significant local increase in the density of cytoskeletal components of the axoplasm (by 200-275%). Reactive reversible remodeling of a myelinated fiber suggests a new type of interaction between the axon and SC, the mechanism of reversible translocation of liquid axoplasmic fraction to the glial cell cytoplasm.

[Crowding-effect and attention].

We studied the influence of additional objects on recognition of the test visual objects. The test objects were stylized low-contrast letters having size 1.1, 2.1 or 4.3 ang. deg. The additional objects after 30 ms were followed by the test objects which were presented in the middle of the screen. The additional objects were digits 1-9 having size 1.3 ang. deg. The digits were presented at various distances from the centre of the screen. The observers' task was to identify both the test objects and the digits. Recognition of the test objects deteriorated when the digits were at small distances to the tests (crowding-effect). Recognition of digits deteriorated with the increasing distances from the centre of the screen; the effect was more pronounced when the tests were large. The contribution of laterals masking and attention into crowding-effect is discussed.

[Age related size invariance in perception of illusory and fragmented contours].

We investigated invariant perception to sizes of images. Observers were schoolmates of 7-17 years and adults. Two types of stimuli were used: fragmented line drawing of common objects and discs with deleted sectors, which represented illusory Kanizsa contours when discs were in particular positions. In experiments with fragmented images, we found an improvement in image recognition with observers' age, increasing up to 13-14 years. The probability of recognition of fragmented line drawings increased significantly with decreasing stimulus size for children of 7-12 years, indicating that size invariance at recognition for fragmented line drawings was absent in these children. However, size invariance was found for observers of 13-17 years and for adults in this task. At Kanizsa illusion appearance, the ratio of the separation between discs and disc diameter was smaller when we used larger disc diameters. This ratio increased with increasing age of observers. Obtained results provide evidence for the absence of size invariance when perceiving the Kanizsa illusion in our experimental conditions.

The threshold signal:noise ratio in the perception of fragmented figures.

Perception thresholds were measured for fragmented outline figures (the Gollin test). A new approach to the question of the perception of incomplete images was developed. In this approach, figure fragmentation consisted of masking with multiplicative texture-like noise--this interference was termed "invisible" masking. The first series of studies established that the "similarity" between the amplitude-frequency spectra of test figures and "invisible" masks, expressed as a linear correlation coefficient, had significant effects on the recognition thresholds of these figures. The second series of experiments showed that progressing formation of the figures was accompanied by increases in the correlation between their spatial-frequency characteristics and the corresponding characteristics of the incomplete figure, while the correlation with the "invisible" mask decreased. It is suggested that the ratio of the correlation coefficients, characterizing the "similarity" of the fragmented figure with the intact figure and the "invisible" mask, corresponds to the signal:noise ratio. The psychophysical recognition threshold for figures for naive subjects not familiar with the test image alphabet was reached after the particular level of fragmentation at which this ratio was unity.

The optical-geometrical characteristics and thresholds of perception of fragmented outline figures.

Measurements were made of the threshold of recognition of cumulatively forming line figures. The threshold value of the outline, expressed in pixels, depended on the length of the outline of the whole unfragmented figure. Relative threshold values were constant, and for the measures of figure fragments used in the present study, averaged 12.5%. A spatial frequency analysis of the test images was performed. Variation of the amplitude-frequency parameters of the spectra of the images of various figures with threshold fragmentation was minimal as compared with the variation of these parameters in figures with subthreshold or suprathreshold levels of fragmentation.

Effect of electrode dimensions on motor unit potentials.

Different effects of longitudinal and transversal electrode dimensions on nerve or muscle single fibre action potentials detected monopolarly, were reported in the literature. The results were contradictory. We studied motor unit potentials (MUPs) detected at a large distance (typical of surface recording) on the basis of a mathematical model without source simplification. The MUPs were calculated as a single convolution of the first temporal derivative of a realistic intracellular action potential and MU impulse response. The spatial averaging of the MUPs by rectangular plate electrodes was performed through analytical integration of the MU impulse response over the electrode area. The effects of longitudinal dimension of the electrode were stronger than those of a transversal one. The effects were distance dependent. The longitudinal dimension of the electrode influenced the main phases (that reflected the excitation origin and propagation) more than the terminal phases (that reflected the excitation extinction at the muscle fibers' ends). This was due to differences in the character of the potential fields (quadrupole or dipole) during generation of individual MUP phases. It was shown that the relative weight of the individual MUP phases could be stressed or suppressed by a proper choice of electrode dimensions, position and orientation.

Comparison of the postural and movement components during learning by dogs of an operant defensive reflex.

Chronic experiments on six dogs using a model of an operant defensive reflex associated with maintenance of flexion of the hindlimb of specified amplitude were performed to compare the characteristics of the postural and movement components during the learning process. Dogs were placed standing on four tension platforms. Signals were activated and data were recorded and stored using original PC programs. Original programs running on another PC were used to analyze the data. All dogs showed a series of characteristics for the appearance of a diagonal pattern of conditioned reflex posture rearrangement. During the period of complete formation of the "coordinated" program of the operant reflex (indicated by high performance criteria for execution of the operant task), the diagonal pattern of posture rearrangement was seen extremely rarely, in only occasional performances in calm dogs. It was only during the period of complete automatization of the movement habit that the diagonal pattern of postural rearrangement was seen consistently in all performances. By this time, there was a sharp increase in the tensogram amplitudes for all four limbs, which sharp increases in the correlation coefficients between individual tensogram performances. These results suggest that in the experimental conditions used here, the diagonal pattern of postural rearrangement appeared significantly later than the movement pattern needed for resolving the operant task. These data also lead to the conclusion that dogs can complete operant defensive limb movements associated with maintaining a specified flexor posture in the absence of preliminary rearrangement of the posture having the diagonal pattern.

Computerized morphometric analysis of the dendrites of Dogiel type II neurons.

Silver nitrate impregnation by the Bil'shovskii-Gros method was used to study the dendrites of Dogiel type II cells in the cat large intestine (local receptors) by computerized morphometric analysis. The following parameters were measured: the areas of the receptive field of the dendrite, the total area of all receptor elements, the total length of all branches of the receptor. There was significant individual variation in all these measures: the ratios of maximum to minimum values were 41, 29, and 45 respectively. There were no correlations between these three measures. It is suggested that this morphological heterogeneity of dendrites may underlie functional differences in Dogiel type II cells.

The effects of corticoliberin at different concentrations on long-term potentiation in slices of rat olfactory cortex.

Experiments were performed to investigate evoked focal potentials in slices of rat olfactory cortex. The results showed that 1 microM corticotropin-releasing factor (CRF; corticoliberin) increases the frequency of posttetanic potentiation, which had a shorter delay phase than in control experiments. Posttetanic potentiation during perfusion with 0.1 microM corticoliberin had a longer delay phase than in control experiments.

Operant behavior in conditions of activation and blockade of neostriatal muscarinic receptors.

Chronic experiments were performed on four dogs using a model of an operant defensive reflex associated with maintaining a flexion posture to study the effects of bilateral intraneostriatal microinjection of the non-selective muscarinic receptor agonist carbachol, the selective D2 dopamine receptor blocker raclopride, and the selective M1 muscarinic receptor blocker pirenzipine on the performance of the operant defensive reflex and differentiation of signals. The results show that microinjection of carbachol induced increases in the tonic component and inhibition of the phasic component of the reflex, an ordering rearrangement of the posture, and increases in the amplitudes of its components. Raclopride microinjection gave similar but less marked results. The greatest effects with both substances were seen using differential stimuli. There were sharp increases in the process of differentiation of sound signals. Pirenzipine microinjections gave the opposite result. These data are assessed on the basis of concepts of the existence of two efferent outputs from the neostriatum with opposite effects on their targets and the roles of muscarinic and dopamine receptors in triggering and blocking these effects.

A model of adaptive visual processes of primary image processing.

A computer model of adaptive segmentation of two-dimensional visual objects was developed, based on neurophysiological and psychophysiological principles. The model imitates several stages of visual information processing. At the first stage, a preliminary assessment of the image is performed using a brightness pattern analyzer. At the second stage, control parameters are formed on the bases of the initial assessment. A defined control vector is synthesized for each type of starting image, which allows adaptive processing; this initiates two parallel mechanisms of primary image description: one contains the outlines of images and the sharp boundaries between their fragments, and the second contains areas of uniform intensity. The control parameter vector is applied to these two descriptions to analyze their brightnesses and spatial characteristics, and this is used as the basis for forming the regime for subsequent processing, which includes a set of processing operators whose parameters are tuned for each fragment of the image. The primary phasic and tonic descriptions are then used to extract individual fragments of the image (i.e., discrimination of figures from the background) and to form the final presentation. The resulting descriptions complement each other, creating a basis for quantitative measurements of image characteristics and allowing various signs needed for image classification to be formed. The computer program for adaptive image segmentation was tested using a large number of different two-dimensional half-tone objects, the purposes of these exercises including segmentation and measurement of objects in morphometric and cytometric studies.

[The structure of the white pulp of the spleen and the peripheral blood indices in rats under increased muscle activity]. / Struktura beloi pulpy selezenki i pokazateli perifericheskoi krovi u krys v usloviiakh povyshennoi myshechnoi deiatel'nosti.

The white pulp structure was studied in rat spleen white pulp in conditions of increased muscle activity as well as certain parameters of peripheral blood. 36 male outbred albino rats were involved. Experimental rats were subjected to the increased physical load (everyday swimming seances lasting from 10 to 40 hrs during 4 weeks). The number of erythrocytes, leukocytes and level of hemoglobin were determined in peripheral blood. Perimeter squares and density of lymphoid nodules (LN) and marginal zone (MZ) as well as LN minimal and maximal diameter and MZ minimal and maximal width were determined in histological sections prepared at the level of the organ portae using TV-computer set. Besides, marginal sinuses width were measured in nine sites in every LN as well as the capsule thickness in three sites and at the level of portae. The data obtained indicate that increased muscle activity causes reorganization of red and white pulp in the direction of growth of the red pulp square which is associated with the increase of erythropoietic function. The appearance of lymphoid nodules with germination centres indicates lymphocytopoietic function intensification while the significant increase of marginal zone morphometric parameters witnesses its participant in primary immune response. High correlation between certain blood indexes and the parameters of lymphoid nodules and marginal zones supports these data.

[Computer morphometric analysis of dendrites of the type II Dogiel neurons]. / Komp'iuternyi morfometricheskii analiz dendritov neironov Gogelia II tipa.

Dendrites of type II Dogiel neurons (the local receptors) stained with silver nitrate impregnation by Bilschovsky-Gross method, were analyzed with computer morphometry in cat large intestine. The following parameters have been measured: an area of dendritic receptor field, total area of all receptor elements and total length of all receptor branches. Significant individual variability was noted in the values of these parameters: the maximum value exceeded the minimum one by a factor of 41, 29 and 45, respectively. No correlation between these three parameters has been found. It is suggested that the morphological diversity of dendrites found in this study may serve as a basis of the functional variability of type II Dogiel neurons.

[Quantitative analysis of morphogenesis of local nerve plexuses forming in tissue culture]. / Kolicherstvennyi analiz morfogeneza lokal'nykh nervnykh spletenii, formiruiushchikhsia v kul'ture tkanei.

Discrete stages of formation of nervous plexuses in the culture of isolated neurons of a mollusc were analyzed autonomically. Area of plexus expansion (S1) and area, occupied by nerve structures (neurites and neuron bodies) were determined. It was demonstrated that despite intensive radial growth of peripheral neurites and S1 growth the density of plexus (S2/S1) was not changed. Relative acceleration of plexus expansion (as compared to S2 growth) registered on 40th and 50th hrs of cultivation indicates the absence of necessary cells in the plexus and development of contacts with adjacent local plexuses. Scanning of lamellar structures revealed submembranous aggregation of cytoskeleton apart from longitudinally directed cytoskeletal bands, which prevents one of the ways of neurite ramification. Elimination of lamellae between cytoskeletal bundles leads to formation of several neurites.

[Innervation of the humerus metaepiphysis in newborn and one year old children]. / Innervatsiia metaépifiza plechevoi kosti novorozhdennykh i detei pervogo goda zhizni.

Analysis of home and foreign literature on metaepiphyseal cartilage innervation and blood supply was presented, data on these organ diseases substantiate theoretical and clinical significance of the study was performed. Using macro-microscopic preparation, histological study, automatic image analyzer branches of humerus proximal metaepiphysis were shown to originate from axillary and subscapulary nerves. Nerves and vessels penetrating in the cartilaginous canals form neurovascular complexes. Cartilaginous canals are located unevenly. Nervous structures were found in the canals and their characteristics was given.

[Principles of temporal processing of spectral information during vowel perception]. / Printsipy vremennói obrabotki spektral'noi informatsii pri vospriiatii glasnykh.

Pairs of "one-formant pulses" with 10 ms onset-to-onset interval and highly different F values for the first and the second pulse (LH and HL pairs) were used in vowel identification experiment. Response distributions corresponding to these stimuli and to "stationary" two-formant and one-formant pulse pairs were compared to calculate the phonetic distance between stimuli. The results are in favour of low-pass filtering of excitation pattern with sampling at the stimulus offset.