Role of ionotropic GABA,glutamate and glycine receptors in the tonic and reflex control of cardiac vagal outflow in the rat

Background  

Cardiac vagal preganglionic neurons (CVPN) are responsible for the tonic, reflex and respiratory modulation of heart rate (HR). Although CVPN receive GABAergic and glutamatergic inputs, likely involved in respiratory and reflex modulation of HR respectively, little else is known regarding the functions controlled by ionotropic inputs. Activation of g-protein coupled receptors (GPCR) alters these inputs, but the functional consequence is largely unknown. The present study aimed to delineate how ionotropic GABAergic, glycinergic and glutamatergic inputs contribute to the tonic and reflex control of HR and in particular determine which receptor subtypes were involved. Furthermore, we wished to establish how activation of the 5-HT_1A GPCR affects tonic and reflex control of HR and what ionotropic interactions this might involve.     

On the interpretation of sensitivity analyses of neural responses

Responses of auditory neurons vary with many dimensions of acoustical stimuli. As a consequence, there is a difference between sensitivity to a particular dimension (e.g., ITD or level), which is assessed when only that dimension is varied while other dimensions are fixed (yielding tuning curves), and information about that dimension, which requires that all natural variability be considered. In particular, the rate of a neuron can be very sensitive to a dimension while poorly informative about it, if it is also sensitive to other dimensions. One implication is that in a multi-dimensional world, stimulus properties such as ITD are optimally coded with heterogeneous neural populations.     

Mechanism of the differentiation of neural responses to excitatory input signals

A dynamical mechanism of the generation of qualitatively different neural responses to typical excitatory stimuli such as an applied current or AMPA and NMDA synaptic currents has been presented. The mechanism is based on a nonlinearity simulating the calcium-dependent potassium current. It has been shown with the FitzHugh-Nagumo equation that, in the presence of such a nonlinearity, only the NMDA synaptic current can strongly increase the frequency of self-sustained oscillations, whereas other stimuli suppress neural activity.     

Semaphorins and their receptors: Novel features of neural guidance molecules

Semaphorins were originally identified as axon guidance cues involved in the development of the nervous system. In recent years, it is emerging that they also participate in various biological systems, including physiological and pathological processes. In this review, we primarily focus on our cumulative findings for the role of semaphorins and their receptors in the regulation of the immune system, while also summarizing recent progress in the context of cardiovascular system.     

Modulatory effects of nitric oxide-active drugs on the anticonvulsant activity of lamotrigine in an experimental model of partial complex epilepsy in the rat

Background  

The effects induced by administering the anticonvulsant lamotrigine, the preferential inhibitor of neuronal nitric oxide synthase 7-nitroindazole and the precursor of NO synthesis L-arginine, alone or in combination, on an experimental model of partial complex seizures (maximal dentate gyrus activation) were studied in urethane anaesthetized rats. The epileptic activity of the dentate gyrus was obtained through the repetitive stimulation of the angular bundle and maximal dentate gyrus activation latency, duration and post-stimulus afterdischarge duration were evaluated.     

Exploration of chalcones and related heterocycle compounds as ligands of adenosine receptors: therapeutics development

Molecular Diversity - Adenosine receptors (ARs) are ubiquitously distributed throughout the mammalian body where they are involved in an extensive list of physiological and pathological processes...     

Size-dependent effect on thermo-electro-mechanical responses of heated nano-sized piezoelectric plate

The booming development of nanotechnology motivates the widespread applications of piezoelectric nanomaterials (e.g. ZnO, ZnS, GaN) and their nanostructures (e.g. nanobelts, nanorings nanowires). It is noted that the coupled field analysis of nano-sized piezoelectric structure under non-uniform temperature in-service environment is of great importance for the fabrication and exploitation of nanoelectromechanical devices. In such situation, spatial size effect of heat conduction is necessary to be taken into account due to its important significance in characterizing the nonlocal feature of heat transport in nanosystems. In this study, thermal nonlocal effect is introduced into the thermo-electro-mechanical model based on nonlocal elasticity theory to further shed light on the size-dependent coupling behavior of thermal, electric, and elastic fields. The coupled field equations involving size-dependent parameters are derived. The solutions can be obtained using Laplace transformation methods. Parametric studies are conducted to evaluate the influences of thermal as well as elastic nonlocal parameters on the transient responses. The results indicate that the piezoelectric performance of the nanoplate is greatly improved in the presence of thermal nonlocal effect.     

Correction to: Exploration of chalcones and related heterocycle compounds as ligands of adenosine receptors: therapeutics development

Molecular Diversity -     

The effect of cell size distribution on predicted osmotic responses of cells

An understanding of the kinetics of the osmotic response of cells is important in understanding permeability properties of cell membranes and predicting cell responses during exposure to anisotonic conditions. Traditionally, a mathematical model of cell osmotic response is obtained by applying mass transport and Boyle-vant Hoff equations using numerical methods. In the usual application of these equations, it is assumed that all cells are the same size equal to the mean or mode of the population. However, biological cells (even if they had identical membranes and hence identical permeability characteristics--which they do not) have a distribution in cell size and will therefore shrink or swell at different rates when exposed to anisotonic conditions. A population of cells may therefore exhibit a different average osmotic response than that of a single cell. In this study, a mathematical model using mass transport and Boyle-van't Hoff equations was applied to measured size distributions of cells. Chinese hamster fibroblast cells (V-79W) and Madin-Darby canine kidney cells (MDCK), were placed in hypertonic solutions and the kinetics of cell shrinkage were monitored. Consistent with the theoretical predictions, the size distributions of these cells were found to change over time, therefore the selection of the measure of central tendency for the population may affect the calculated osmotic parameters. After examining three different average volumes (mean, median, and mode) using four different theoretical cell size distributions, it was determined that, for the assumptions used in this study, the mean or median were the best measures of central tendency to describe osmotic volume changes in cell suspensions.     

Symbiotic bacteria and the structural specializations in the ileum of Cephalotes ants

Light, scanning, and transmission electron microscopy were used to examine the ultramorphology and ultrastructure of the ileum of Cephalotes atratus, Cephalotes clypeatus, and Cephalotes pusillus. Sections along the ileum revealed differences among the three main regions: proximal (or pylorus), medial, and distal. The structural specializations present in the ileum of these three ants have implications especially to the symbiotic bacteria harbored in this region of the digestive tract. The structural similarities are conspicuous for the three species examined, suggesting that this is the pattern adopted by the genus Cephalotes.     

Influence of acute hyperglycemia on otoacoustic emissions and the medial olivocochlear reflex

Stimulus-frequency (SF) otoacoustic emission (OAE) amplitude and the amplitude of medial olivocochlear (MOC) inhibition of SF OAEs for ipsilateral, contralateral and bilateral MOC reflex elicitors were recorded in six subjects with type 2 diabetes during a glucose tolerance test (GTT). Five of the six subjects were tested twice for a total of 11 trials and three subjects were tested in a control experiment. During the GTT experiment, the subjects' blood glucose was elevated from a euglycemic level below 150 mg/dL to a hyperglycemic level above 160 mg/dL following the consumption of a bolus of 80 g of sugar. A subset of three subjects were tested in a control experiment during which SF OAE and MOC reflex measurements were made while blood sugar levels remained constant within the euglycemic region. Mean SF OAE amplitudes were elevated following glucose consumption. A statistically significant increase in MOC inhibition amplitude was observed during elevated sugar levels for the 11 GTT trials. Maximum inhibition occurred about an hour after glucose consumption when blood glucose levels peaked. Results indicate that acute hyperglycemia influences efferent control of the cochlea in people with type 2 diabetes.     

The effects of aging on the stapedius reflex thresholds.

The acoustic reflex thresholds for broadband noise and 500-, 1000-, and 2000-Hz activating signals were measured in a group of young normal hearing adults and a group of elderly normal hearing subjects. The results indicated that the acoustic reflex thresholds for tonal activating signals in the young subjects were similar to those in the elderly subjects. However, the acoustic stapedius reflex thresholds for broadband noise activating signals is significantly higher in the elderly subjects than in the young. These differences were explained in light of Bredburg's findings [Acta Otolaryngol. Suppl. 236, 1--135 (1968)] regarding degeneration of outer hair cells as a function of aging.     

Correlation of neural responses in the cochlear nucleus with low-frequency noise amplitude modulation of a tonal signal

The responses of single neurons of the cochlear nucleus of a grass frog to long tonal signals amplitude-modulated by repeat intervals of low-frequency noise have been studied. The carrier frequency always corresponded to the characteristic frequency of the studied cell (a range of 0.2 kHz–2 kHz); the modulated signal was noise in the ranges 0–15 Hz, 0–50 Hz, or 0–150 Hz. We obtained the correlation functions of the cyclic histogram reflecting the change in probability of a neuron pulse discharge (spike) during the modulation period with the shape of the signal envelope in the same period. The form of the obtained correlation functions usually does not change qualitatively with a change in carrier level or modulation depth; however, this could essentially depend of the frequency component of the modulating function. In the majority of cases, comparison of the cyclic histogram of the reaction with only the current amplitude value does not adequately reveal the signal’s time features that determine the reaction of a neuron. The response is also determined by the other sound features, primarily by the rate of the change in amplitude. The studied neurons differed among themselves, both in preference toward a certain range of modulated frequencies and in the features of the envelope that caused the cell’s response.     

Effects of perturbation magnitude and voice F0 level on the pitch-shift reflex

The purpose of the present study was to investigate the responsiveness of the pitch-shift reflex to small magnitude stimuli and voice fundamental frequency (F(0)) level. English speakers received pitch-shifted voice feedback (+/-10, 20, 30, 40, and 50 cents, 200 ms duration) during vowel phonations at a high and a low F(0) level. Mean pitch-shift response magnitude increased as a function of pitch-shift stimulus magnitude, but when expressed as a percent of stimulus magnitude, declined from 100% with +/-10 cents to 37% with +/-50 cents stimuli. Response magnitudes were larger and latencies were shorter with a high F(0) level (16 cents;130 ms) compared to a low F(0) level (13 cents;152 ms). Data from the present study demonstrate that vocal response magnitudes are equal to small perturbation magnitudes, and they are larger and faster with a high F(0) voice. These results suggest that the audio-vocal system is optimally suited for compensating for small pitch rather than larger perturbations. Data also suggest the sensitivity of the audio-vocal system to voice perturbation may vary with F(0) level.     

Effects of hypothermia on ischaemic depolarisation in brain : a comparison of responses in rat and gerbil

The latency of development of ischaemic depolarization (LID) has been used to compare the relative effects of different levels of hypothermia on ischaemic responses in brains of rat and gerbil, using a model with imposed complete cessation of cerebral blood flow (CBF=0). At temperatures reducing from 37 degrees C to 20 degrees C, the LIDs were consistently shorter in the gerbil than in the rat. For example, at 37 degrees C the LID in the gerbil was 0.71+/- 01.2 min, and in the rat, 1.37 +/- 0.02 min respectively (P<0.01), whilst at 20 degrees C, the values were 5.48 +/- 0.25 min and 7.30 +/- 0.76 min (P<0.01). However, the relative effects of hypothermia on each species were similar (by linear regression with slopes of -0.29 and -0.35 min/degree C in the two species). There may be underlying differences in brain biophysics or structure between species, but in spite of this, applied hypothermia still imposes a similar depression on the development of ischaemic damage. Both models may thus be used in studies of brain hypothermia as long as the intrinsic differences are appreciated.     

Differential orientation effect in the neural response to interacting biological motion of two agents

Background  

A recent behavioral study demonstrated that the meaningful interaction of two agents enhances the detection sensitivity of biological motion (BM), however, it remains unclear when and how the 'interaction' information of two agents is represented in our neural system. To clarify this point, we used magnetoencephalography and introduced a novel experimental technique to extract a neuromagnetic response relating to two-agent BM perception. We then investigated how this response was modulated by the interaction of two agents. In the present experiment, we presented two kinds of visual stimuli (interacting and non-interacting BM) with two orientations (upright and inverted).     

Impulsive effect on exponential synchronization of neural networks with leakage delay under sampled-data feedback control

We consider the impulsive effect on the exponential synchronization of neural networks with leakage delay under the sampled-data feedback control. We use an appropriate Lyapunov–Krasovskii functional combined with the input delay approach and some inequality techniques to derive sufficient conditions that ensure the exponential synchronization of the delayed neural network. The conditions are formulated in terms of the leakage delay, the sampling period, and the exponential convergence rate. Numerical examples are given to demonstrate the usefulness and the effectiveness of the results.     

Protein expression differs between neural progenitor cells from the adult rat brain subventricular zone and olfactory bulb

Background  

Neural progenitor cells can be isolated from various regions of the adult mammalian brain, including the forebrain structures of the subventricular zone and the olfactory bulb. Currently it is unknown whether functional differences in these progenitor cell populations can already be found on the molecular level. Therefore, we compared protein expression profiles between progenitor cells isolated from the subventricular zone and the olfactory bulb using a proteomic approach based on two-dimensional gel electrophoresis and mass spectrometry. The subventricular zone and the olfactory bulb are connected by the Rostral Migratory Stream (RMS), in which glial fibrillary acidic protein (GFAP)-positive cells guide neuroblasts. Recent literature suggested that these GFAP-positive cells possess neurogenic potential themselves. In the current study, we therefore compared the cultured neurospheres for the fraction of GFAP-positive cells and their morphology of over a prolonged period of time.