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Neurophysiology    Follow    
  Hybrid Journal Hybrid journal (It can contain Open Access articles)
     ISSN (Print) 1573-9007 - ISSN (Online) 0090-2977
     Published by Springer-Verlag Homepage  [2187 journals]   [SJR: 0.136]   [H-I: 7]
  • Anatomy and Evolution of the Nervous System
    • PubDate: 2013-12-20
       
  • Dynamics of Functioning of Voltage-Operated Ion Channels in the Dendrite
           Plasma Membrane
    • Abstract: Dendrites provide the analysis and transmission of numerous and variable synaptic signals to the soma and axon hillock of nerve cells. According to generally accepted concepts, generation of action potentials (APs) is initiated precisely in the latter cell compartment. The problem of the dynamics of functioning of voltage-operated ion channels, whose properties are extremely variable, is closely related to the integrative functions of the dendrites. These channels are involved in information transmission and its translation to other domains of the neuron. The biophysical properties of dendrite ion channels and the density of their distribution in many cases differ significantly from the analogous indices in other compartments of the neuron. Moreover, the expression of ion channels and their properties in different branches of the dendrite tree of one and the same neuron can be considerably dissimilar. Such phenomena as back-propagation of APs via the dendrites and the possible initiation of local APs in some branches of the dendrite tree are significantly involved in the induction of synaptic plasticity; these processes may result in either augmentation of synaptic potentials or their suppression. Local synthesis of definite proteins is also realized in the dendrites; this process is controlled by synaptic inputs and postsynaptic activity. The possibility of performance of a few integrative functions by separate dendrites of a single neuron is at present intensely discussed; earlier, such functions were postulated to be a prerogative of complex neuronal networks.
      PubDate: 2013-12-20
       
  • Functional Convergence of Thalamic and Intrinsic Projections to Cortical
           Layers 4 and 6
    • Abstract: Ascending sensory information is conveyed from the thalamus to layers 4 and 6 of the sensory cortical areas. Interestingly, receptive field properties of cortical layer-6 neurons differ from those in layer 4. Do such differences reflect distinct inheritance patterns from the thalamus, or are they derived instead from local cortical circuits' To distinguish between these possibilities, we utilized in vitro slice preparations containing the thalamo-cortical pathways of the auditory and somatosensory systems. Responses from neurons in layers 4 and 6 that resided in the same column were recorded using whole-cell patch clamp. Laser-scanning photostimulation via uncaging of glutamate in the thalamus and cortex was used to map the functional topography of thalamo-cortical and intracortical inputs to each layer. In addition, we assessed the functional divergence of thalamo-cortical inputs by optical imaging of flavoprotein autofluorescence. We found that the thalamo-cortical inputs to layers 4 and 6 originated from the same thalamic domain, but the intracortical projections to the same neurons differed dramatically. Our results suggest that the intracortical projections, rather than the thalamic inputs, to each layer contribute more to the differences in their receptive field properties.
      PubDate: 2013-12-18
       
  • Mathematical Model of the Calcium-Dependent Chloride Current in a Smooth
           Muscle Cell
    • Abstract: Employing the Hodgkin-Huxley formalism, we have developed a mathematical model of the calcium-dependent chloride current on the basis of published experimental data concerning the kinetics of such current in cells of different types. The obtained results are destined for further use in a currently developed model of a smooth muscle cell of the bladder detrusor. A feature of the simulated current is the presence of two components with common kinetics of calcium-dependent activation and different (fast and slow) kinetics of voltage-dependent activation. In computational experiments performed with the use of a protocol of stepwise clamp of the membrane potential or the intracellular calcium concentration ([Са2+]i), static and dynamic dependences of the current on the membrane potential and [Са2+]i (the current-voltage and current-concentration relations, IVs and ICs, respectively) were obtained; analogous dependences of the kinetic variables of calcium- and voltage-dependent activation of the current were also plotted. The obtained characteristics of the simulated current were close to those of the prototype currents. The following properties were typical of the current: (i) the outward rectification, (ii) enhancement of the rectification effect with increase in the [Са2+]i, and (iii) a higher sensitivity to [Са2+]i deviations from the basal level (manifested in greater ratios of the current/concentration increments) within the range <1 μM, as compared to that within the range of higher concentrations.
      PubDate: 2013-12-18
       
  • Does Sight Predominate Sound' Electrophysiological Evidence for
           Multisensory Mismatch Negativity Correlation
    • Abstract: When being presented with consistent and repetitive sensory stimuli, the human brain creates a predictive “memory trace” against which subsequent stimuli are compared. When later stimuli do not match this predictive model, a highly localized negative shift in the brain polarity occurs. This response, known as the mismatch negativity (MMN), is believed to represent a pre-attentive deviance-detection mechanism that serves to provide direct attention toward unanticipated events. At present, there are conflicting data as to whether visually generated and auditorily generated MMNs interact, or whether they are mediated by independent sensory-specific networks. We present compelling evidence that visual and auditory MMNs are strongly correlated, and that, upon presentation of dual-sensory “audiovisual” deviants, this synergy is heavily dictated by an individual’s unique visual response. This finding is suggestive of inhibitory interaction between the visual and auditory MMN networks. The characterization of this correlation helps one to explain (and explain away) much conflicting data published to date and opens the door to many questions regarding individual perception.
      PubDate: 2013-12-18
       
  • Features of GABAergic Cardiovascular Control Provided by Medullary Neurons
           in Rats
    • Abstract: In acute experiments on rats anesthetized with urethane, features of the involvement of GABA in medullary cardiovascular control were studied. It was found that microinjections of GABA (10–8 or 10–10 M) into the medullary nuclei (paramedian reticular nucleus, PMn, lateral reticular nucleus, LRN, and nucl. ambiguous, AMB) were accompanied by the development of either hypo- or hypertensive responses in a dose-dependent manner. There were some differences in the structure of GABA-induced hemodynamic responses. In particular, the cardiac and vascular components contributed about equally to the development of the hypotensive responses caused by GABA injections into the PMn (with significant inhibition of the heart’s chronotropic function). However, GABA-induced hypotensive responses evoked from the LRN were mainly based on the vascular component, with the a less pronounced cardiac component. GABA injections into the AMB resulted in significant decreases in the diastolic blood pressure and the heart rate. As for GABA-induced hypertensive responses originated from PMn and LRN neurons, the vascular component was predominant in their development, and chronotropic effects on the cardiac function were less pronounced. Injections of bicuculline (10–7 M), a competitive antagonist of GABAA receptors, into the medullary nuclei under investigation were accompanied by increases in both the systolic and diastolic blood pressure and heart rate. Therefore, bicuculline-sensitive GABAA receptors are involved in GABA-induced hypotensive effects. After inhibition of neuronal NO synthase, injections of GABA into the medullary nuclei did not cause the development of hypotensive responses, and GABA-induced hypertensive responses were weakened, indicating the possibility for GABA interaction with nitric oxide in nervous control of the cardiovascular system. It was also found that the effects of GABA injected into the medullary nuclei depended on the activity of Na+,K+-ATPase, the enzyme of the plasma membrane of cardiovascular neurons.
      PubDate: 2013-12-18
       
  • Prospects of the Use of Mesenchymal and Neuromesenchymal Stem Cells
    • Abstract: Mesenchymal stem cells, MSCs, were identified in the 1960s. Recently, these cells have attracted great attention from researchers because their clinical applications look rather promising. At present, MSCs are most frequently interpreted as multipotent cells characterized by fibroblast-like morphology and capable of proliferating. These are non-differentiated cells possessing a great potential for differentiation and formation of tissues of different types, including the bone, cartilage, and muscle tissues, and also of the bone marrow stroma. In accessible publications, there is information that extremely wide plasticity is typical of MSCs obtained from the bone marrow; these cells can serve as originating units for the nerve tissue, hepatocytes, cardiomyocytes, and epithelial cells of the lungs. In this review, we describe results of recent studies in the field of fundamental biology of MSCs separated from different sources, their identification, potential for differentiation, and possibilities for therapeutic use.
      PubDate: 2013-12-18
       
  • Stimulation of CB1 Cannabinoid and NMDA Receptors Increases
           Neuroprotective Effect against Diazinon-Induced Neurotoxicity
    • Abstract: Cannabinoids have been shown to exert a neuroprotective influence in organophosphorus-induced toxicity. In our study, we examined the effects of the cannabinoid receptor agonist WIN55,212-2 and NMDA receptor agonist NMDA on cell death in the pheochromocytoma cell line PC12 subjected to the action of an organophosphorus compound, diazinon. Diazinon decreased cell viability in a concentration-dependent manner. Following the exposure of PC12 cells to 200 μM diazinon for 48 h, reductions in cell survival and protein level of CB1 receptors were observed. Treatment of the cells with 0.1 μM WIN55,212-2 and 100 μM NMDA prior to diazinon exposure significantly elevated the cell survival level and protein level of CB1 receptors. The cannabinoid antagonist AM251 (1 μM) did not inhibit the neuroprotection effect induced by WIN55,212-2, indicating that the neuroprotective effect of this agonist was cannabinoid receptor-independent. The NMDA receptor antagonist MK-801 (1 μM) enhanced diazinon-mediated neurotoxicity suggesting that precisely NMDA receptors may play a protective role.
      PubDate: 2013-12-18
       
  • Coherent Relations in Ongoing Encephalograms of Preschool Boys with
           Neurosis-Like Stammering
    • Abstract: We studied coherence of EEG oscillations of different frequency ranges in preschool boys with neurosislike stammering and healthy boys of analogous age; EEG was recorded in the resting state. It was found that the activity of deep cerebral structures in boys suffering from neurosis-like stammering is probably excessively intense, since the normalized number of significant- and high-level coherence relations between low-frequency EEG oscillations (delta waves) in these boys exceeded the analogous indices in healthy preschool children. In boys with stammering, we also found certain specificity of the pattern of coherent relations of theta oscillations and greater coherence of oscillations in symmetrical loci of the left and right hemispheres.
      PubDate: 2013-12-18
       
  • Morphofunctional Modifications of Cells of the Preoptic Hypothalamic
           Nucleus of Prepubescent Rats under Conditions of Stimulation and Blocking
           of the α-Adrenergic and Kisspeptinergic Systems
    • Abstract: In experiments on prepubescent (one-month-old) male albino rats, we studied the effects of pharmacological blockade and activation of kisspeptinergic and α-adrenergic systems on neurocytes and astrocytes of the preoptic hypothalamic nucleus. Intracerebroventricular injection of kisspeptin induced activation of the processes of synthesis of proteins in neurons and astrocytes of this nucleus, which was manifested in significantly greater mean values of cross-section areas of the nuclei of these cell units. Injections of a blocker of kisspeptin receptors, Р-234, inhibited synthetic activity in neurons but not in astrocytes. Mezaton intensely activated the above-mentioned activity in cells of both types; such activation could not be eliminated completely by simultaneous injection of the kisspeptin antagonist Р-234. Prazosin suppressed synthetic processes in neurons but not in astrocytes. In the case of combined introduction of prazosin and kisspeptin, the effect of inhibition of protein synthesis in neurons was significantly weakened but could not be eliminated completely; in astrocytes, the functional activity increased. We discuss the mechanisms of action of the α-adrenergic and kisspeptinergic systems on production of gonadotropin-releasing hormone (gonadoliberin) by cells of the preoptic hypothalamic nucleus and the actions of these events on the functioning of the reproductive system.
      PubDate: 2013-12-18
       
  • Antioxidant Activity-Mediated Neuroprotective Effects of an Antagonist of
           AT1 Receptors, Candesartan, against Cerebral Ischemia and Edema in Rats
    • Abstract: We examined the effects of post-ischemic blockade of angiotensin AT1 receptors by candesartan on cerebral infarction and formation of edema. Male Sprague–Dawley rats were divided into three groups, sham, control ischemic, and candesartan-treated (0.3 mg/kg) ischemic. Transient focal cerebral ischemia was induced by 90-min-long occlusion of the left middle cerebral artery followed by 24-h-long reperfusion. Neurological deficit score was evaluated at the end of the reperfusion period. Thereafter, the animals were randomly selected and used for three projects: (i) Measurement of the infarct volumes, (ii) investigation of ischemic brain edema formation using a wet/dry method, and (iii) assessment of the malondialdehyde (MDA) and reduced glutathione (GSH) concentrations using a HPLC technique. Induction of cerebral ischemia in the control group produced considerable infarctions in the cortex and striatum in conjunction with severely impaired motor functions. Candesartan treatment significantly reduced the infarct volumes and improved the above functions. The water content in the left (lesioned) hemisphere was considerably elevated in the control ischemic group. Candesartan treatment significantly lowered the water content in the ischemic lesioned hemisphere, retained tissue GSH level, and led to a lower MDA production. AT1 receptor blockade by candesartan treatment can noticeably decrease ischemic brain injury and attenuate edema formation, likely via increasing the antioxidant activity.
      PubDate: 2013-12-18
       
  • Effect of Valinomycin-Induced Potassium Influx on the Formation of
           Reactive Oxygen Species in the Rat Brain Mitochondria
    • Abstract: We studied the effect of valinomycin-induced voltage-dependent potassium influx on the formation of reactive oxygen species (ROs) in preparations of isolated rat brain mitochondria. In the presence of valinomycin, the stationary rate of formation of ROSs decreased with increase in the K+ concentration in the medium. We conclude that the drop in ROS production in the brain mitochondria is due to the depolarizing effect of voltage-dependent K+ influx. Our experiments show that the mechanism underlying the control of ROS formation in the brain mitochondria under conditions of potassiuminduced valinomycin-related depolarization of the membrane is voltage-dependent.
      PubDate: 2013-12-18
       
  • Analgesic Effects of 3-Substituted Derivatives of 1,4-Benzodiazepines and
           their Possible Mechanisms
    • Abstract: In experiments on mice, we studied the analgesic activity of some 3-substituted derivatives of 1,4-benzodiazepines, including 3-propoxy-7-bromo-5-(2’-chloro)phenyl-1,2-dihydro-3Н-1,4-benzodiazepin-2-one (compound 6). This compound demonstrated clearly pronounced anti-inflammatory and antinociceptive properties in the acetic acid-induced writhing test (induction of visceral pain) in mice, test with carrageenan-induced paw edema in rats, and formalin test in mice. On multicellular preparations of circular smooth muscles from the fundal part of the rat stomach, we estimated the value of affinity of compound 6 (рKВ = 6.41). We hypothesize that the mechanism underlying inhibition of bradykinin (BK) receptors by compound 6 is mostly competitive. Therefore, compound 6 can be considered a promising basis for the development and synthesis of antagonists of BK receptors, which can be applied in clinical practice.
      PubDate: 2013-12-18
       
  • Effects of Oxytocin on the Formation of a Food-Procuring Reflex in Rats
    • Abstract: In experiments on albino rats, we studied the process of formation of a food-procuring conditioned reflex (receipt of the food reward from one of two feedboxes designated by the visual conditioning signal) and characteristics of behavior in the open field test. It was found that course injections of oxytocin (4 μg daily, 15 min prior to the test for 12 days) relatively slightly influenced the process of development of the food-procuring conditioned reaction (animals reached the 80% critical level of correct differentiations practically simultaneously), but rats injected with oxytocin demonstrated smaller manifestations of anxiety, more rapid food-procuring activity, and higher intensity of motor/research activities in the open field. In general, food-procuring behavior under the action of oxytocin develops more effectively at the expense of formation of a more favorable emotional/autonomic background.
      PubDate: 2013-12-18
       
  • Hypoalgesia Induced by Preliminary Microwave Irradiation of an Acupuncture
           Point: Effects on Somatic Pain in Mice
    • Abstract: We studied the effects of preliminary irradiation of the acupuncture point (AP) E36 by low-intensity microwaves on experimentally evoked somatic pain in mice. Irradiation preceded induction of somatic pain in the formalin test, FT (subcutaneous injection of 25 μl 5% formalin solution into the dorsal surface of the foot).The FT was carried out in different groups of animals immediately, 10 min, and 20 min after termination of a period of microwave irradiation of the AP. Analgesic effects were observed in all examined animal groups within both acute and tonic pain phases. Normalized decreases in the duration of behavioral manifestations of the acute pain phase were equal to 57.7, 50.4, and 28.8% in the cases where the FT was realized immediately, 10 min, and 20 min after irradiation of the AP. For the tonic phase of the pain reaction, the respective figures were 49.6, 60.5, and 56.2%, respectively. Thus, irradiation of the AP E36 by low-intensity microwaves performed before the development of somatic pain exerts noticeably stronger hypoalgesic effects with respect to tonic somatic pain.
      PubDate: 2013-12-18
       
  • Peculiarities of the Tail-Withdrawal Reflex Circuit in        class="a-plus-plus">Aplysia: a Model Study
    • Abstract: The circuit of the tail-withdrawal reflex in Aplysia opens up possibilities to construct model systems allowing researchers to effectively investigate simple forms of learning and memory. Using the Python interface of the NEURON software, we simulated this reflex circuit and studied various characteristics of the latter. The phenomenon of spike frequency adaptation (SFA) and the period-adding bifurcation of the minimum were found in sensory neurons, when the latter were stimulated by square-wave stimuli. In all neurons of the circuit, variation of the stimulus strength first increased and then decreased the number of spikes in a burst. In addition, with decreases in the number of stimulated sensory neurons, a subliminal firing other than that in an intact burst appeared at the outputs of interneurons and motor neuron. Moreover, the potentials produced in the motor neuron induced corresponding oscillations of the muscle fiber force, which was indicative of a procedure of excitement-contraction coupling in the tail part of Aplysia. Finally, upon alteration of the conductance of synapses between interneurons and motoneuron, the duration of long-lasting responses increased regularly, implying synaptic plasticity.
      PubDate: 2013-12-18
       
  • Antinociceptive Effects of        class="a-plus-plus">Valeriana Extract in Mice:
           Involvement of the Dopaminergic and Serotonergic Systems
    • Abstract: Valeriana officinalis has been extensively used as a herbal remedy in traditional medicine. However, there is no clear evidence on the antinociceptive effects of this plant. The aim of our study was to evaluate the effect of Valeriana officinalis hydroalcoholic extract on pain modulation and its possible mechanism in mice. Adult male Balb/c mice were randomly divided into nine experimental groups. They received i.p. injections of saline, hydroalcoholic root extract of Valeriana officinalis (800, 200, or 50 mg/kg), and morphine; four groups received Valeriana (800 mg/kg) + antagonists of the systems involved in antinociception effects, naloxone, ondansetron, metoclopramide, or scopolamine. Tail-flick and writhing tests were used for estimation of possible modulation of pain. The tail-flick latencies in the Valeriana 800 and 200 mg/kg, but not 50 mg/kg, morphine, and combined Valeriana 800 + + naloxone, ondansetron, metoclopramide, or scopolamine-treated groups were significantly longer than that in the control group. However, the tail-flick latencies in the Valeriana 800 mg/kg + ondansetronand metoclopramide-treated groups were significantly shorter than that upon single action of the extract (800 mg/kg). The numbers of writhings in the extract-treated groups were smaller than in the control one. The numbers of writhings in the Valeriana (800 mg/kg) + ondansetron- and metoclopramidetreated groups were significantly greater than in the extract (800 mg/kg) group. It is concluded that Valeriana officinalis extract possesses a clear analgesic effect and works through the serotonergic and dopaminergic systems.
      PubDate: 2013-12-18
       
  • Maintenance of the Upright Posture in Humans upon Disturbance of Stability
           of the Visually Perceived Environment: Effect of an Instruction for
           Controlling Body Sway
    • Abstract: We examined the maintenance of the upright posture under conditions of immersion of the tested subject in a 3D virtual visual environment, VVE. The latter consisted of two plans, the foreground looked like a window of the room, while the background was a fragment of the urban landscape. The software used allowed us to correlate body sway within the sagittal plane with shifts of the VVE foreground doing the latter mobile. The linkage in the course of testing could be either antiphase (APh) or synphase (SPh); the background always remained immobile. Each experiment was conventionally divided into two parts. In the first part, the subjects were not informed that body sways in some trials can be linked with shifts of the visual environment and were proposed to look at some object within the stable background. In the second part, the subjects were preliminarily informed of the existence of such a linkage and proposed to minimize body sways within the sagittal plane by tracking shifts of the foreground with respect to some, selected preliminarily, object within the background. Trials with a linkage between body sways and VVE shifts were altered by trials with standing of the subject facing an absolutely immobile visual pattern (IVP) and trials with the eyes closed (EC). The impact of visual control on the postural maintenance was estimated according to changes in the amplitude and frequency characteristics of two variables; i) shifts of the vertical projection of the center of gravity (CG) of the body and ii) difference between the position of the center of feet pressure (CFP) and CG projection. Changes in the latter were considered the main controlled variable in the postural maintenance, while the CFP-CG was interpreted as a variable containing information on changes in the resulting muscle/joint stiffness in the ankle joints related to activation of the shin muscles. The analysis of CG and CFP-CG oscillations demonstrated clear dependence of their spectra on the direction of linkage between body sways and oscillations of the foreground and on the instruction obtained by the subjects. In the first group of tests, RMSs of the spectra of oscillations of both variables at the SPh linkage were found to be within the same range as in standing with the EC, while at the APh linkage these oscillations were closer to the range typical of IVP conditions. In the second group of tests, the RMS of the spectra calculated for both variables were qualitatively different. In the case of APh relations between body sways and foreground shifts, these values were smaller than values in standing at IVP, while under SPh conditions they were smaller than those typical of standing with the EC. Introduction of the instruction of the second test group was also reflected in changes of the parameters of the CFP-CG variable. At the APh relation, the RMSs of the spectra for this variable decreased somewhat, and their median frequency increased significantly. The data obtained allow us to hypothesize that the improvement of stability standing after introduction of the instruction specifying visual control and concentrating the latter on one direction of body sway results from more active using of visual feedback under conditions of perception of the VVE unstable foreground. This should be considered additional proof in favor of effective involvement of vision in postural control upon disturbances in stability of the external environment.
      PubDate: 2013-09-11
       
  • Morphological Effects of Combined Systemic Administration of Fluoxetine
           and Sildenafil in the Murine Hippocampus
    • Abstract: We examined the effects of fluoxetine, a selective serotonin re-uptake inhibitor, of sildenafil, a phosphodiesterase-5 (PDE5) inhibitor, and of combined administration of these agents on morphometric characteristics of principal cells of the murine hippocampus. Fluoxetine (5 mg/kg), sildenafil (2 mg/kg), or a combination of these drugs in the above doses were administered i.p. daily for 2 weeks to male mice. Hippocampal sections (5 mm thick) were stained with hematoxylin/eosin. Both drugs and their combination evoked no considerable changes in the dimensions of pyramidal cells in the CA1 and CA2 areas and in the dentate gyrus (DG), except for a trend toward some decrease of this parameter after fluoxetine injections in the CA1 area. Combined administration of fluoxetine and sildenafil provided significant decreases in the density of pyramidal neurons (their mean number per 10 mm of the slice) in the CA1 area and DG. Isolated administration of fluoxetine resulted in significant but less intense decreases in the density of principal cells in the CA2 area and DG. Possible mechanisms of the effects of the mentioned drugs are discussed. Further studies of interaction between fluoxetine and sildenafil in their effects on morphological and physiological properties of cells in different subregions of the hippocampus are recommended.
      PubDate: 2013-09-11
       
  • Vascular Cognitive Impairment with No Dementia: Neuropsychology, Brain
           Imaging, and Event-Related Potentials
    • Abstract: We investigated the neuropsychological characteristics, cranial MRI, and P300 ERPs in patients suffering from vascular cognitive impairment with no dementia (VCIND). A study was performed on 68 cases of VCIND after stroke. The cranial MRI patterns and P300 waves of the patients were compared with those of 56 stroke patients without cognitive impairment and 52 healthy subjects. The MoCA (Montreal Cognitive Assessment) was also used to assess their mental status. The proportion of patients with frontotemporal lesions, multiple lesions, and leukoaraiosis (LA) in the VCIND group was greater than that in the stroke group. The cognitive impairment in patients with the former deficiencies was more significant. The MoCA scores in the VCIND group were significantly lower, and the P300 latency was significantly longer, as compared with other two groups. The P300 latency inversely correlated with the MoCA score. Patients with frontotemporal lesions, multiple lesions, and LA are susceptible to cognitive impairment. The MoCA score and the P300 test are helpful for the early diagnosis of VCIND.
      PubDate: 2013-09-11
       
 
 
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