Hemispheric participation in the shaping of spatial-motor asymmetry in visual recognition in rats

Asymmetry of movement direction was found in Wistar rats at establishing of motor alimentary conditioned reflex to simultaneously presented visual stimuli. In the course of learning the asymmetry weakened on the whole, but some individuals retained right- or left side preference. The analysis of asymmetry change before and after unilateral cortical inactivation revealed a special role of right hemisphere influences for the formation of right-side preference and of the left hemisphere--for the choice of the left direction. The lack of asymmetry was observed at the presence of the influences from the left hemisphere cortex depressing ipsilateral nigro-striate system and activating the contralateral one. Influences of the cortex of both hemispheres reduce the absolute value of the asymmetry coefficient; the left hemisphere has a special significance for manifestation of temporal asymmetry parameters. Photic interference is a factor modulating the asymmetry. It reduces the right hemisphere activity more than that of the left one; it intensifies right hemisphere influences, contributes to the involvement of the transcallosal conduction channel in the formation of spatial-motor asymmetry.     

The dependence of lipid asymmetry upon phosphatidylcholine acyl chain structure

Lipid asymmetry, the difference in inner and outer leaflet lipid composition, is an important feature of biomembranes. By utilizing our recently developed MβCD-catalyzed exchange method, the effect of lipid acyl chain structure upon the ability to form asymmetric membranes was investigated. Using this approach, SM was efficiently introduced into the outer leaflet of vesicles containing various phosphatidylcholines (PC), but whether the resulting vesicles were asymmetric (SM outside/PC inside) depended upon PC acyl chain structure. Vesicles exhibited asymmetry using PC with two monounsaturated chains of >14 carbons; PC with one saturated and one unsaturated chain; and PC with phytanoyl chains. Vesicles were most weakly asymmetric using PC with two 14 carbon monounsaturated chains or with two polyunsaturated chains. To define the origin of this behavior, transverse diffusion (flip-flop) of lipids in vesicles containing various PCs was compared. A correlation between asymmetry and transverse diffusion was observed, with slower transverse diffusion in vesicles containing PCs that supported lipid asymmetry. Thus, asymmetric vesicles can be prepared using a wide range of acyl chain structures, but fast transverse diffusion destroys lipid asymmetry. These properties may constrain acyl chain structure in asymmetric natural membranes to avoid short or overly polyunsaturated acyl chains.     

The nature of pacemaker activity]

A general equation of the membrane resting potential (RP) has been derived for closed cell membrane (CM) model. It is shown that Na,K-ATPase of cardiomyocytes is in the antielectrogenic phase. A hypothesis is proposed: a pacemaker cell is an excitable cell, which has RP corresponding to the given activity of Na,K-ATPase and non-activated cationic conductivities of CM higher than the activation threshold of Na-channels. The equation of the equipotential levels of the membrane RP on the surface of the cationic conductivities has been derived. It is shown that the substances (e. g. neuromediator) that change the membrane cation permeability are able to depolarize or to hyperpolarize CM. The direction of polarization is dependent on the state of the cell electrogenic system. The following factors promote the hyperpolarizing effect of the magnifying cation permeability substances: 1) high activity of Na,K-ATPase, 2) low background cation permeability of CM (among their number the integrity of CM) and 3) high ratio of the potassium permeability alteration in respect to that of sodium which is evoked by the substance (delta gK/delta gNa).     

The functional asymmetry of the limbic structures of the brain]

The recent evidence from literature testify to functional asymmetry of the structures belonging to the limbic system: hippocampus, amygdala, and hypothalamus. Predominant activation of the right hippocampus and right amygdala during perception and memorizing of visual picturesque images and solving the tasks provoking emotional stress, apparently, concerns the functional specialization of the right hemisphere in general. The leading role of the left hypothalamus in provocation of food, sexual, and defensive responses was experimentally verified. This finding is in line with the functional role of the left hemisphere in genesis of motivational states.     

The dependence of hippocampal electrical activity on the probability of the reinforcement of a conditioned food stimulus

In three dogs the dynamics was studied of changes in the number of instrumental motor reactions, the heart rate and the hippocampus theta rhythm was studied at the change of constant reinforcement to various regimes of probable reinforcement of alimentary conditioned stimulus. At 70 and 50% levels of the reinforcement the instrumental reflex appeared in response to all presentations of the signal stimulus. The greatest decrease in the number of reactions took place at 5% probability. The heart rate both in the intersignal period and at getting of empty feeder depended on the used probability of reinforcement and individual characteristics of animals. The frequency of the theta rhythm in all dogs was the highest at the 30% level and the lowest values were found at the 5% level of reinforcement. The obtained facts testify once more to complex genesis of emotional excitation, the value of which depends both on informational (uncertainty) and motivational (significance of reinforcement) factors.     

The characteristics of motor asymmetry in the ontogeny of calves]

The side of preference (first turn of head) was recorded in calves in situation of free equal probability two-sides choice, and rate of reconstruction of conditioned reflex to food presented from the left or from the right was determined. Initially the calves preferred the left turn, i.e. manifested motor asymmetry. Preference to the left turn changed depending on the calves age with the period of 22-23 days. The rate of conditioned reflexes reconstruction was higher in calves with the left-side preference. Correlation of the motor asymmetry and rate of conditioned reflex reconstruction in calves of different age changed in analogy with age changes of asymmetry. Probably the observed periodical changes of asymmetry and its correlation with the rate of reconstruction reflect formation of interhemispheric interactions in regulation of the organism functions in animals ontogenesis.     

The topography of functional interhemispheric asymmetry in the visual cortex]

Functional interhemispheric asymmetry was investigated by evoked potentials method in experiments on ten cats under ethaminal anaesthesia at 200 points of the visual cortex during the action of binocular and monocular photic flashes of submaximal intensity. Topographic maps have been plotted of the functional interhemispheric asymmetry. In most of the animals a hemisphere dominant and non-dominant at the given moment can be singled out. Section of the callosal body leads to reduction of the functional interhemispheric asymmetry due to a decrease of the focus of maximum activity in the dominant hemisphere and its increase in the non-dominant one. A mozaic pattern of functional interhemispheric asymmetry has been demonstrated, as expressed in the existence of zones of inverse dominance along with prevailing zones of direct dominance. Section of the callosal body produced a decrease in the area of direct dominance and an increase in that of inverse dominance. Absolute interhemispheric asymmetry was most pronounced in the central part of the visual cortex (field 18 and its medial boundary) and the relative one, on the periphery of the visual area (fields 17 and 19).     

The mechanistic nature of the membrane potential dependence of sodium-sugar cotransport in small intestine

Summary Methods are described which demonstrate the use of unidirectional influx of¹⁴C-tetraphenylphosphonium (¹⁴C-TPP⁺) into isolated intestinal epithelial cells as a quantitative sensor of the magnitude of membrane potentials created by experimentally imposed ion gradients. Using this technique the quantitative relationship between membrane potential () and Na⁺-dependent sugar influx was determined for these cells at various Na⁺ and -methylglucoside (-MG) concentrations. The results show a high degree of dependence for the transport Michaelis constant but a maximum velocity for transport which is independent of . No transinhibition by intracellular sugar (40mm) can be detected. Sugar influx in the absence of Na⁺ is insensitive to 1.3mm phlorizin and independent of . The mechanistic implications of these results were evaluated using the quality of fit between calculated and experimentally observed kinetic constants for rate equations derived from several transport models. The analysis shows that for models in which translocation is the potential-dependent step the free carrier cannot be neutral. If it is anionic, the transporter must be functionally asymmetric. A model in which Na⁺ binding is the potential-dependent step (Na⁺ well concept) also provides an appropriate kinetic fit to the experimental data, and must be considered as a possible mechanistic basis for function of the system.     

The nature of differences in beta-adrenergic receptors]

Results of investigation of the affinity between teranol (practalol), alpheprol (alprenolol), propranolol to beta-adrenoreceptors of various organs confirmed the division of these receptors into two subtypes. The action of isadrin on beta1-adrenoreceptors of the myocardium and smooth muscles of the gastrointestinal tract was accompanied by changes in Ca2+ entrance into the cells. With the action of isadrin on beta2-adrenoreceptors of the trachea and the vessels there was seen an intensification of the Ca2+ ions from the cells and a reduction of the smooth muscle tone.     

Surgical correction of facial asymmetry]

It is not possible to group the facial asymmetries in one single nosological entity. However, whatever the origin of these malformations, their surgical treatment is governed by the same principles. In this article, the author attempts to define certain aetiologies:genetic, congenital and developmental, of the minor assymmetries of the face. He then reviews the different techniques in current use, in plastic and reconstructive surgery:autogenic or homogenic tissue grafts (bone, cartilage, derm, fascia, etc.), implants of plastic material, osteotomies. He stresses the use of simple techniques which cause little mutilation, as well as the simultaneous correction of the profile which greatly enhances the aesthetic appearance and the psychological well-being of these patients.     

The interhemispheric asymmetry of the spatial-temporal organization of cortical potentials in the rabbit]

In experiments on freely moving rabbits the existence of interhemispheric asymmetry of spatial-temporal organization of the cortical potentials in the state of calm alertness was shown. Episodes were revealed of interhemispheric discordance of spatial reconstructions of momentary reliefs of the cortical potentials topograms 1/64-1/3-1/5 s in duration, i.e. periods of the theta- or delta-rhythms. Total duration of time of interhemispheric asymmetry (according to significant divergences in dynamics of resemblance coefficients of consequent reliefs of the cortical potentials topograms) in most cases was not less than 10% and not more than 30% of time of analysis epoch and consisted of discordance episodes both of different global reconstructions of spatial correlations of the left and right hemisphere potentials and of interhemispheric local shifts in spatial organization of the cortex potentials.     

The possible effect of parameters of the gravitational field on indicators of functional asymmetry of the brain]

Correlation of the brain functional asymmetry (BFA) in 2400 humans born in 1930-1984 and numbers of the joining of planets, moon and the Sun was investigated in corresponding years of conception and birth. A significant correlation with BFA was found in men, while there was no such correlation in women.     

The choice of reinforcement quality depending on the delay time of the instrumental reaction in cats]

In experiments on seven cats instrumental delayed reflexes with different quality reinforcement were elaborated by method of "active choice", where the time of delay of the motor reaction served as a signal of quality of the reinforcement. Five cats used a strategy with long delay high-quality reinforcement (meat), and two cats preferred short delay and low-quality reinforcement (bread-meat mixture). In special experiments with the change of alimentary motivation (24-hour alimentary deprivation and saturation of animals) it was established that the level of alimentary motivation within the studied limits did not change the strategy of behaviour preferred by the given animal. Individually varying ability to choice of reaction determining more valuable reinforcement it is possible to consider as an experimental analogue of the mechanisms of will. The question is discussed about the role of typological properties of cats in choice of behaviour strategy.     

The dynamics of neocortical modifications: the dependence on motivational and emotiogenic systems]

A concept is advanced according to which for complete and successive development of membrane and synaptic modifications in the neocortex during the conditioned reflex (CR) elaboration the differentiated changes in impulse flow structure of the motivation and emotion systems of the hypothalamus and reciprocal character of excitatory and inhibitory interactions between them are necessary. Motivation excitation coordinated with repeated activation of synaptic inputs by pairing stimuli contributes to temporary (lasting about hour) increase in somatodendritic electroexcitability of neocortical neurons. It is necessary for maintaining cells in the state of readiness for summation of polymodal excitations during the CR generalization stage. Emotion excitation contributes to long-lasting (about twenty-four hours) increase in synaptic efficacy of excitatory and inhibitory connections which determine a conditioned act during the stage of specialization. Hetero- and homosynaptic facilitation of synaptic transmission lead to global and local character of spatial synchronization of slow activity during these stages. These processes are mainly determined cooperative interaction glutamatergic system with modulator cholin- and monoaminergic (noradren- and serotonin-) systems activating during motivational and emotional behavior components, respectively.     

The nature of the dependence of the rate of development on temperature determines the greatest efficiency of metabolism at optimal temperatures

Metabolism intensity and development rate have different pattern of dependence on temperature. Oxygen intake and several other metabolic processes bear an exponential relationship to temperature. The pattern of this relationship is similar in different poikilothermal species. On the contrary, the relationship between the rate of development and temperature is species-specific and more complex. Hence, the curves obtained by plotting oxygen intake per developmental stage against temperature resemble parabola and the minimum values of oxygen intake correspond to optimal temperatures. Such a correspondence is almost solely determined by parameters of the relationship between the rate of development and temperature. Therefore, the efficiency of metabolism does not determine the range of optimal temperatures. It is suggested that adaptive alterations of this range during evolution proceed via changes of the parameters of relationship between the rate of development and temperature dependence. Relatively small number of mutations is required to produce such changes.     

The nature of stability of yeast cells to drying]

The residual water and dry matter condition in the lyophilized biomass of the yeast Saccharomyces cerevisiae was studied by NMR-relaxation technique. It was shown that the slow component of the transverse magnetization NMR signal spectrum corresponding to the so-called "isolated mobile water" was caused in fact by the interaction of the disaccharide trehalose with the cell biopolymers. The big amount of hydrogen bonds formed by trehalose and their three-dimensional orientation closed to the orientation in water clusters assure the valuable functioning of this disaccharide during the process of removing water out of cells. When stationary phase yeast biomass containing a lot of trehalose was dried the cell organelles condition remained practically unchanged what led to the high resistance of such cells to dehydration.