[Clinical functional assessment of electric cardiac instability in diastolic dysfunction of the left ventricle in patients with coronary heart disease]

AIM

To study parameters characterizing electric myocardial unstability in coronary heart disease (CHD) patients with different variants of diastolic dysfunction (DD) of the left ventricle (LV).

MATERIAL AND METHODS

The study included 86 outpatients (26 females, 60 males, mean age 57.3 +/- 5.6 years) who had myocardial infarction (MI) more than 1 year before the trial with stable course of CHD during a previous month, LV ejection fraction more than 45% and with a stable sinus rhythm. Group 1 consisted of 36 patients with abnormal LV relaxation, group 2--of 28 patients with pseudo-normal LV DD, group 3--22 patients with a restrictive type of LV DD. The following examinations were made: Holter ECG monitoring, echocardiography, signal-average ECG with isolation of late ventricular potentials (LVP), estimation of heart rate variability, ventricular repolarization (Q-T interval dispersion, corrected interval Q-T).

RESULTS

The following variants of LV DD were detected: type 1--42%, type 2--32.5%, type 3--25.5%. LV DD progression was accompanied with enhancing vegetative imbalance and sympathetic activity: in the group with abnormal relaxation--in 52.5% patients, in the group with a restrictive type--in 93.3%. CHD patients with restrictive DD had more frequent LVP (chi-square = 4.1; p < 0.05) and visualization of anomalous contractility zones (60%), ventricular extrasystole (VE) was registered in 100% cases (VE of grade IV-V in 43.3%), QT(c) and QT(d) were higher than threshold--450.2 +/- 5.4 and 71.2 +/- 6.5 ms.

CONCLUSION

Because of multifactorial genesis of electric unstability, perfection of diagnosis and prognosis of risk in CHD patients with aggravation of LV DD demands a complex analysis of parameters respecting functional condition of the myocardium, relations between electric and structural-geometric remodeling of the heart.

Clinical application of magnetic mapping

Noninvasive screening technique to identify cardiac disease in its early phase is developed. Magnetic imaging of cardiac action currents is a new and an ideally suited technology for testing the level of local electric heterogeneities of myocardium. Magnetocardiography has the potential to make a valuable contribution in basic examination and analysis of biosignals of a heart. in particular whilst all vector components are used, vast spatial coverage and excellent signal quality.

The sense of water in the blowfly Protophormia terraenovae

The gustatory system of the blowfly, Protophormia terraenovae, is a relatively simple biological model for studies on chemosensory input and behavioral output. It appears to have renewed interest as a model for studies on the role of water channels, namely aquaporins or aquaglyceroporins, in water detection. To this end, we investigated the presence of water channels, their role in "water" and "salt" cell responsiveness and the transduction mechanism involved. For the first time our electrophysiological results point to the presence of an aquaglyceroporin in the chemoreceptor membrane of the "water" cell in the blowfly taste chemosensilla whose transduction mechanism ultimately involves an intracellular calcium increase and consequently cell depolarization. This hypothesis is also supported by calcium imaging data following proper stimulation. This mechanism is triggered by "water" cell stimulation with hypotonic solutions and/or solutes such as glycerol which crosses the membrane by way of aquaglyceroporins. Behavioral output indicates that the "sense" of water in blowflies is definitely not dependent on the "water" cell only, but also on the "salt" cell sensitivity. These findings also hypothesize a new role for aquaglyceroporin in spiking cell excitability.

Reward guides vision when it's your thing: trait reward-seeking in reward-mediated visual priming

Reward-related mesolimbic dopamine is thought to play an important role in guiding animal behaviour, biasing approach towards potentially beneficial environmental stimuli and away from objects unlikely to garner positive outcome. This is considered to result in part from an impact on perceptual and attentional processes: dopamine initiates a series of cognitive events that result in the priming of reward-associated perceptual features. We have provided behavioural and electrophysiological evidence that this mechanism guides human vision in search, an effect we refer to as reward priming. We have also demonstrated that there is substantial individual variability in this effect. Here we show that behavioural differences in reward priming are predicted remarkably well by a personality index that captures the degree to which a person's behaviour is driven by reward outcome. Participants with reward-seeking personalities are found to be those who allocate visual resources to objects characterized by reward-associated visual features. These results add to a rapidly developing literature demonstrating the crucial role reward plays in attentional control. They additionally illustrate the striking impact personality traits can have on low-level cognitive processes like perception and selective attention.

Development of a variational scheme for model inversion of multi-area model of brain. Part I: simulation evaluation

We previously developed an integrated model of the brain within a single cortical area for functional Magnetic Resonance Imaging (fMRI), electroencephalography (EEG), and magnetoencephalography (MEG) using an extended neural mass model (ENMM). We then extended ENMM from a single-area to a multi-area model to develop a neural mass model of the entire brain. To this end, we derived a nonlinear state-space representation of the multi-area model. In Parts I and II of these two companion papers (henceforth called Part I and Part II), we develop and evaluate a variational Bayesian expectation maximization (VBEM) method to estimate parameters of multi-area ENMM (MEN) using E/MEG data. In Part I, we derive a state-space representation of MEN and use VBEM method for model inversion (parameter estimation). We evaluate and validate performance of VBEM method for model inversion of MEN using simulation studies in various signal-to-noise ratios. Details of VBEM method are presented in Part II. The proposed approach provides a useful technique for analyzing effective connectivity using non-invasive EEG and MEG methods.

See the light: electrophysiological characterization of the Bolwig organ's light response of Calliphora vicina 3rd instar larvae

The anatomy and development of the larval cyclorraphous Diptera visual system is well established. It consists of the internal Bolwig organ (BO), and the associated nerve connecting it to the brain. The BO contributes to various larval behaviors but was never electrophysiologically characterized. We recorded extracellulary from the Bolwig nerve of 3rd instar Calliphora vicina larvae to quantify the sensory response caused by BO stimulation with light stimuli of different wavelengths, intensities and directions. Consistent with previous behavioral experiments we found the BO most sensitive to white and green, followed by blue, yellow, violet and red light. The BO showed a phasic-tonic response curve. Increasing light intensity produced a sigmoid response curve with an approximate threshold of 0.0105 nW/cm(2) and a dynamic range from 0.105 nW/cm(2) to 52.5 nW/cm(2). No differences exist between feeding and wandering larvae which display opposed phototaxis. This excludes reduced BO sensitivity from causing the switch in behavior. Correlating to the morphology of the BO frontal light evoked the maximal reaction, while lateral light reduced the neural response asymmetrically: Light applied ipsilaterally to the recorded BO always produced a stronger response than when applied from the contralateral side. This implies that phototacic behavior is based on a tropotactic mechanism.

Electrophysiological identification of hygroreceptor neurons from the antennal dome-shaped sensilla in the ground beetle Pterostichus oblongopunctatus

This study gives the first electrophysiological evidence of hygroreceptors in carabids. Extracellular recordings from the antennal dome-shaped sensilla of the carabid beetle Pterostichus oblolongopunctatus (Coleoptera, Carabidae) clearly show the presence of moist and dry neuron antagonistically responding to humidity changes. The cold neuron of the same sensillum did not respond to changes in humidity. For the first time, we demonstrate that the binary system of two antagonistic hygroreceptor neurons discriminates differences between steady-state humidity levels more sensitively than either neuron separately. Another advantage of the binary system is that it guarantees immediate and strong phasic-tonic response to rapid humidity changes in either direction. In the hygrosensing system of carabids, this would allow detection of subtle step-changes in humidity with greater sensitivity than differences in steady-state values of humidity. Thus, construction of the hygrosensing system with opposing receptor neurons may allow insects to detect environmental humidity differences critical for their habitat and microhabitat selection, and survival with great precision.

Experience-based behavioral and chemosensory changes in the generalist insect herbivore Helicoverpa armigera exposed to two deterrent plant chemicals

Behavioral and electrophysiological responses of larvae of the polyphagous moth species Helicoverpa armigera to two plant-derived allelochemicals were studied, both in larvae that had been reared on a diet devoid of these compounds and in larvae previously exposed to these compounds. In dual-choice cotton leaf disk and pepper fruit disk arena assays, caterpillars reared on a normal artificial diet were strongly deterred by strychnine and strophanthin-K. However, caterpillars reared on an artificial diet containing strychnine were insensitive to strychnine and strophanthin-K. Similarly, caterpillars reared on an artificial diet containing strophanthin-K were also desensitized to both deterrent chemicals. Electrophysiological tests revealed that the deterrent-sensitive neurons in taste sensilla on the maxillae of caterpillars reared on each deterrent-containing diet displayed reduced sensitivity to the two chemicals compared with the caterpillars reared on normal diets. We conclude that the experience-dependent behavioral plasticity was partly based on the reduced sensitivity of taste receptor neurons and that the desensitization of taste receptor neurons contributed to the cross-habituation to the two chemicals.

[Effect of acetylcholine on coordination of spontaneous activities registered from different areas of uterus in rats]

Spontaneous electrical activities of uterine corpus, periuterine part of horn and uterine cervix in response to intravenous injections of different concentrations of acetylcholine were observed. The changes of frequency and amplitude characteristics of rhythmogenesis in these conditions, both separately and with their co-active state were analysed. Acetylcholine in concentration of 10(-3) M in the blood of the animal creates the optimal conditions for synchronization and coordination of electrical activities in the above areas of the uterus.

Distribution of electromechanical delay in the heart: insights from a three-dimensional electromechanical model

In the intact heart, the distribution of electromechanical delay (EMD), the time interval between local depolarization and myocyte shortening onset, depends on the loading conditions. The distribution of EMD throughout the heart remains, however, unknown because current experimental techniques are unable to evaluate three-dimensional cardiac electromechanical behavior. The goal of this study was to determine the three-dimensional EMD distributions in the intact ventricles for sinus rhythm (SR) and epicardial pacing (EP) by using a new, to our knowledge, electromechanical model of the rabbit ventricles that incorporates a biophysical representation of myofilament dynamics. Furthermore, we aimed to ascertain the mechanisms that underlie the specific three-dimensional EMD distributions. The results revealed that under both conditions, the three-dimensional EMD distribution is nonuniform. During SR, EMD is longer at the epicardium than at the endocardium, and is greater near the base than at the apex. After EP, the three-dimensional EMD distribution is markedly different; it also changes with the pacing rate. For both SR and EP, late-depolarized regions were characterized with significant myofiber prestretch caused by the contraction of the early-depolarized regions. This prestretch delays myofiber-shortening onset, and results in a longer EMD, giving rise to heterogeneous three-dimensional EMD distributions.

[Multiform wave organization of neurophysiological processes--universal "language" of human brain in realization of informational-controlling functions]

There are summarized literature data and results of many-year Laboratory studies disclosing principles of multiform spatial-temporal organization of different by rates neurophysiologic brain processes as the universal "language" of its informational-controlling functions. Current concepts of electrogenesis and physiological significance of ratios of gradual changes of biopotentials and impulse activity of neurons are considered in studies of cerebral mechanisms of regulation of normal and pathological states, organization of human psychic activity. Proposed and argumented is the concept of probability principle of hierarchical organization of different by rates neurophysiologic processes of the brain zones, structures, and areas in formation of the brain systems participating in provision of the higher psychic functions and states. It is proposed to discuss the concept of the brain as the "swimming", many-contour, neurodynamic informational-controlling suprasystem with universal, hierarchically organized neurodynamic structures--"functional organs" after A. A. Ukhtomskii (1978), of which formation provides an extensive informational brain capacity and a large specter of adaptive possibilities of the human organism.

[Exploring spatiotemporal patterns of epileptiform discharge in hippocampal slice using multi-electrode arrays]

To investigate the spatiotemporal properties of epileptiform activity in vitro, 400 microm-thick transverse hippocampal slices were prepared from juvenile rat and planar multi-electrode array (MEA) containing 60 electrodes was used to record the electrical activity induced by bath application of high potassium artificial cerebrospinal fluid (ACSF) on slices. Following successful induction of epileptiform bursts, phenobarbital sodium was applied to test for its inhibitory effects on bursting activity in different regions of slice. Region-specific characteristics of epileptiform activity and anticonvulsant actions of phenobarbital sodium in the hippocampal network were determined by comparing the population activity obtained from MEA. The results showed that: (1) 15 min after high-K+ ACSF application, rhythmic and synchronous epileptiform bursts could be detected from all CA sub-regions. Quantitative analysis indicates that the firing patterns of different CA sub-regions were not statistically different (P>0.05). However, no bursting activity was recorded from granular cells in dentate gyrus, only sparse spikes were observed, with frequency significantly lower than that in CA regions (P<0.05). (2) The high-K+-induced bursting activity could last for more than 40 min with stable bursting activities. (3) Bath application of 60 micromol/L phenobarbital sodium inhibited the bursting activities on hippocampal slice. Bursting activities in CA3c and CA1 were firstly suppressed. 10 min after the phenobarbital sodium application, strong bursting activities persisted only in some of pyramidal cells in CA3a and CA3b. These results show that MEA could be applied for studying the spatial and temporal properties of epileptiform activity in vitro, as well as the region-specific effects of anti-epileptic drugs.

Connexins and gap junctions in the EDHF phenomenon and conducted vasomotor responses

It is becoming increasingly evident that electrical signaling via gap junctions plays a central role in the physiological control of vascular tone via two related mechanisms (1) the endothelium-derived hyperpolarizing factor (EDHF) phenomenon, in which radial transmission of hyperpolarization from the endothelium to subjacent smooth muscle promotes relaxation, and (2) responses that propagate longitudinally, in which electrical signaling within the intimal and medial layers of the arteriolar wall orchestrates mechanical behavior over biologically large distances. In the EDHF phenomenon, the transmitted endothelial hyperpolarization is initiated by the activation of Ca(2+)-activated K(+) channels channels by InsP(3)-induced Ca(2+) release from the endoplasmic reticulum and/or store-operated Ca(2+) entry triggered by the depletion of such stores. Pharmacological inhibitors of direct cell-cell coupling may thus attenuate EDHF-type smooth muscle hyperpolarizations and relaxations, confirming the participation of electrotonic signaling via myoendothelial and homocellular smooth muscle gap junctions. In contrast to isolated vessels, surprisingly little experimental evidence argues in favor of myoendothelial coupling acting as the EDHF mechanism in arterioles in vivo. However, it now seems established that the endothelium plays the leading role in the spatial propagation of arteriolar responses and that these involve poorly understood regenerative mechanisms. The present review will focus on the complex interactions between the diverse cellular signaling mechanisms that contribute to these phenomena.

Differential protein abundance and function of UT-B urea transporters in human colon

Facilitative UT-B urea transporters enable the passage of urea across cell membranes. Gastrointestinal urea transporters are thought to play a significant role in the urea nitrogen salvaging process that occurs between mammalian hosts and their gut bacteria. This study investigated the expression of UT-B urea transporters in different segments of human colon. Immunoblot analysis showed that human colon expressed a 35-kDa glycosylated UT-B protein in the colonic mucosa. The 35-kDa UT-B transporter was predominantly located in plasma membrane-enriched samples (P < 0.001; n = 6), and its expression was greater in the ascending colon compared with the descending colon (P < 0.01; n = 3). At the cellular level, UT-B transporters were located throughout colonocytes situated in the upper portion of the colonic crypts. Bidirectional trans-epithelial urea transport was significantly greater in the ascending colon than the descending colon (P < 0.05; n = 6). In addition, the facilitative urea transporter inhibitor 1,3,dimethylurea significantly reduced urea transport in the ascending colon (P < 0.05; n = 6) but had no effect in the descending colon (NS; n = 6). These results illustrate differential protein abundance of functional UT-B protein in different sections of the human colon, strongly correlating to regions that contain the largest populations of intestinal bacteria. This study suggests an important role for UT-B urea transporters in maintaining the symbiotic relationship between humans and their gut bacteria.

Electrophysiological properties of isthmic neurons in frogs revealed by in vitro and in vivo studies

The frog nucleus isthmi (parabigeminal nucleus in mammals) is a visually responsive, cholinergic and anatomically well-defined group of neurons in the midbrain. It shares reciprocal topographic projections with the ipsilateral optic tectum (superior colliculus in mammals) and strongly influences visual processing. Anatomical and biochemical information indicates the existence of distinct neural populations within the frog nucleus isthmi, which raises the question: are there electrophysiological distinctions between neurons that are putatively classified by their anatomical and biochemical properties? To address this question, we measured frog nucleus isthmi neuron cellular properties in vitro and visual response properties in vivo. No evidence for distinct electrophysiological classes of neurons was found. We thus conclude that, despite the anatomical and biochemical differences, the cells of the frog nucleus isthmi respond homogeneously to both current injections and simple visual stimuli.

Clinical and electrophysiological parameters distinguishing acute-onset chronic inflammatory demyelinating polyneuropathy from acute inflammatory demyelinating polyneuropathy

Up to 16% of chronic inflammatory demyelinating polyneuropathy (CIDP) patients may present acutely. We performed a retrospective chart review on 30 acute inflammatory demyelinating polyneuropathy (AIDP) and 15 acute-onset CIDP (A-CIDP) patients looking for any clinical or electrophysiological parameters that might differentiate AIDP from acutely presenting CIDP. A-CIDP patients were significantly more likely to have prominent sensory signs. They were significantly less likely to have autonomic nervous system involvement, facial weakness, a preceding infectious illness, or need for mechanical ventilation. With regard to electrophysiological features, neither sural-sparing pattern, sensory ratio >1, nor the presence of A-waves was different between the two groups. This study suggests that patients presenting acutely with a demyelinating polyneuropathy and the aforementioned clinical features should be closely monitored as they may be more likely to have CIDP at follow-up.

[Speech recognition in the norm and pathology]

The purpose of this paper was to study theoretically and experimentally clinical and electrophysiological correlates of the human abilities to recognize emotions in speech. It was shown that the disorder of the recognition of emotions in speech occurred following the lesion of the right temporal region, however the most serious defect of recognition manifested itself at the frontal temporal localization of the lesion. The comparison of the EEG characteristics between two groups of subjects with high and low indices of recognition of emotions in speech revealed a higher level of activation in the posterior temporal regions of the right hemisphere and in the frontal regions of the left hemisphere in the group with the low index of recognition. Clinical data and findings obtained in electrophysiological studies permitted us to make a conclusion that the recognition of emotions in speech involved not only temporal regions of the right hemisphere, but also speech centers in the left hemisphere.

[Effects of hypokinesia and hypoxia on the bone static electrogenesis]

It was studied the conformities to law of quasistatic electric potential (QSEP) distribution on the periosteal surface of 64 adult Vistar rats-males fresh exited femur and their changes after dosed hypokinesia and hypoxia influences. The maximal negative sizes of QSEP were incorporated in epiphyseal-metaphyseal departments and minimal--in the central part of bone diaphysis. Conformities to law of QSEP distribution on the periosteal surface fresh exited bone represented the physiology unevenness of metabolic processes intensity in the different bone departments. Reparative regeneration was accompanied with strengthening of electro-negativity of reparations and adjacent parts and changing of physiology character of QSEP distribution on the periosteal surface of the damaged bone. Hypokinesia disturbed of bone static electrogenesis. It was accompanied with diminishing of QSEP size especially in bone parts which had hight level of metabolism. Dosed an intermittent normobarical and hypobarical hypoxia activated of bone static electrogenesis. More considerably increasing of QSEP in old rats was obtained after the intermittent hypobarical hypoxia influences.

[Effect of oxytocin on activation of spontaneous electrical activities registered from uterine corpus and uterine tubes in rats]

The effects if different concentrations of oxytocin (10(-2), 10(-1), 1 and 10 microg/kg) on burst duration and spikes frequency of spontaneous electrical activity in various parts of uterine horns and uterine corpus in non-pregnant rats have been shown. The changes in given parameters for ovarian parts of horns had similar characters unlike cervical parts of horns and middle part of uterine corpus under these conditions, so the last mentioned areas could be grouped together by the reason of similar changes in their parameters. Oxytocin in a concentration of 10(-1) microg/kg promoted the longest duration of spike electrical activity genesis in ovarian parts of horns. Morphological experiments showed that ovarian parts of horns had a great amount of atypical cells with strongly expressed functional activities.

The time course of temporal discrimination: An ERP study

OBJECTIVE

The question of how temporal information is processed by the brain is still a matter of debate. This study aimed to elucidate the brain electrical activity associated with a visual temporal discrimination task.

METHODS

For this purpose, 44 participants were required to compare pairs of sequentially presented time intervals: a fixed standard interval (1000ms), and an equal-to-standard, longer (1200ms) or shorter (800ms) comparison interval. Behavioural data and event-related potentials (ERPs) were analyzed.

RESULTS

Long intervals were more rapidly identified than short intervals. The amplitude of the contingent negative variation (CNV) found at frontocentral sites before the end of the comparison interval was significantly affected by the difference between its duration and the standard one. The amplitude and the scalp distribution of ERPs registered after the offset of the comparison interval were linearly modulated by its absolute duration.

CONCLUSIONS

ERP components associated with the offset of the comparison intervals clarified the involvement of working memory processes and different brain structures in temporal discrimination.

SIGNIFICANCE

This study further improves our understanding of the cognitive processes and neural substrates underlying temporal discrimination in healthy subjects and lays the ground for the investigation of clinical samples with time processing deficits.

Comparison of cardiac and gastric responses to vagal stimulation in hypertensive women

BACKGROUND

The aim was to evaluate the interactions between the effects of vagal stimulation by sham feeding (nonbaroreflex) and deep breathing (baroreflex) on heart rate variability (HRV) and gastric myoelectrical activity (GMA) in pre- and postmenopausal women with essential hypertension.

MATERIAL/METHODS

One hundred five post- and premenopausal women with hypertension and 60 premenopausal normotensive women were observed. The study protocol consisted of 5 min of resting HRV followed by 5 min of deep breathing (DB), then 6 min of sham feeding (SF) with 30-min electrogastrography (EGG) before and after SF. The fasting plasma level of noradrenalin was measured.

RESULTS

The HRV parameter values at rest in the hypertensive group were half those in the control group (p<0.05). There were notably higher HRV parameter values in the premenopausal women. Plasma noradrenalin level was higher in the postmenopausal women (p=0.0009). The effect of DB was similar before and after menopause; however, HRV parameters in response to DB were lower in the hypertensive women than in the controls (p<0.05). In the controls there was a marked increase in the main HRV parameters in response to DB. In fasting electrogastrography the lowest normogastria percentage was observed in the postmenopausal women. EGG showed that only SF significantly affected the period dominant power (PDP) in all groups and the bradygastria percentage in the postmenopausal women.

CONCLUSIONS

This study suggests that the interactions that occur between the effects of non-baroreflex and baroreflex vagal stimulation in hypertensive women may contribute to gastric motility disorders and dyspeptic symptoms.

Towards a computational method for imaging the extracellular potassium concentration during regional ischemia

We investigate the possibility of using body surface potential maps to image the extracellular potassium concentration during regional ischemia. The problem is formulated as an inverse problem based on a linear approximation of the bidomain model, where we minimize the difference between the results of the model and observations of body surface potentials. The minimization problem is solved by a one-shot technique, where the original PDE system, an adjoint problem, and the relation describing the minimum, are solved simultaneously. This formulation of the problem requires the solution of a 5 x 5 system of linear partial differential equations. The performance of the model is investigated by performing tests based on synthetic data. We find that the model will in many cases detect the correct position and approximate size of the ischemic regions, while some cases are more difficult to locate. It is observed that a simple post-processing of the results produces images that are qualitatively very similar to the true solution.

Deriving macroscopic myocardial conductivities by homogenization of microscopic models

We derive the values for the intracellular and extracellular conductivities needed for bidomain simulations of cardiac electrophysiology using homogenization of partial differential equations. In our model, cardiac myocytes are rectangular prisms and gap junctions appear in a distributed manner as flux boundary conditions for Laplace's equation. Using directly measurable microproperties such as cellular dimensions and end-to-end and side-to-side gap junction coupling strengths, we inexpensively obtain effective conductivities close to those given by simulations with a detailed cyto-architecture (Stinstra et al. in Ann. Biomed. Eng. 33:1743-1751, 2005). This model provides a convenient framework for studying the effect on conductivities of aligned vs. brick-like arrangements of cells and the effect of different distributions of gap junctions along the myocyte membranes.