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Properties Consistent (property + consistent)
Selected AbstractsHeterogeneity of Kir4.1 channel expression in glia revealed by mouse transgenesisGLIA, Issue 16 2009Xiaofang Tang Abstract The weakly inwardly rectifying K+ channel Kir4.1 is found in many glial cells including astrocytes. However, questions remain regarding the relative contribution of Kir4.1 to the resting K+ conductance of mature astrocytes in situ. We employed a bacterial artificial chromosome transgenic approach in mice to visualize Kir4.1 expression in vivo. These mice (Kir4.1-EGFP) express enhanced green fluorescent protein (EGFP) under the transcriptional control of the Kir4.1 promoter. The brains of adult Kir4.1-EGFP transgenic mice showed co-expression of EGFP and Kir4.1 in astrocytes. In addition, weaker expression of EGFP was detected in NG2+ glial cells when compared with EGFP expression in GFAP+ glial cells. Whole-cell voltage clamp recordings of EGFP+ glial cells in the CA1 area of the adult mouse hippocampus indicated astrocytes displaying properties consistent with both the "passive" and "complex" subpopulations. EGFP+ cells with bright fluorescence had the linear current,voltage (I,V) relationships and extensive gap junctional coupling characteristic of passive astrocytes. However, EGFP+ glia with weaker fluorescence displayed properties associated with complex astrocytes including nonlinear I,V relationships and lack of intercellular gap junctional coupling. Pharmacological blockade of inward currents implied that Kir4.1 channels constitute the dominant resting K+ conductance in both glial cell types and are more highly expressed in passive astrocytes. These results suggest differential expression of Kir4.1 in glia and that this channel likely underlies the resting K+ conductance in passive and complex astrocytes. © 2009 Wiley-Liss, Inc. [source] Dental plaque: biological significance of a biofilm and community life-styleJOURNAL OF CLINICAL PERIODONTOLOGY, Issue 2005P. D. Marsh Abstract Background: Most microorganisms in nature attach to surfaces and form matrix-embedded biofilms. Biofilms are highly structured and spatially organized, and are often composed of consortia of interacting microorganisms, termed microbial communities, the properties of which are more than the sum of the component species. Microbial gene expression alters markedly in biofilms; organisms communicate by gene transfer and by secretion of diffusible signalling molecules. Cells in biofilms are less susceptible to antimicrobial agents. Aim and Materials & Methods: To comprehensively review the literature to determine whether dental plaque displays properties consistent with those of a typical biofilm and microbial community. Results: Novel microscopic and molecular techniques have demonstrated that plaque has a structured architecture with an extracellular matrix, and a diverse composition (around 50% of cells are unculturable). The constituent species communicate by gene transfer, by secreted peptides (Gram-positive bacteria) and autoinducer-2 (Gram-positive and Gram-negative bacteria). These organisms are functionally organized for increased metabolic efficiency, greater resistance to stress and for enhanced virulence. Plaque formation has direct and indirect effects on gene expression. Conclusion: Dental plaque displays properties that are typical of biofilms and microbial communities in general, a clinical consequence of which is a reduced susceptibility to antimicrobial agents as well as pathogenic synergism. [source] Human and mouse microglia express connexin36, and functional gap junctions are formed between rodent microglia and neuronsJOURNAL OF NEUROSCIENCE RESEARCH, Issue 3 2005K. Dobrenis Abstract Microglia, the tissue macrophages of the central nervous system (CNS), intimately interact with neurons physically and through soluble factors that can affect microglial activation state and neuronal survival and physiology. We report here a new mechanism of interaction between these cells, provided by the formation of gap junctions composed of connexin (Cx) 36. Among eight Cxs tested, expression of Cx36 mRNA and protein was found in microglial cultures prepared from human and mouse, and Cx45 mRNA was found in mouse microglial cultures. Electrophysiological measurements found coupling between one-third of human or mouse microglial pairs that averaged below 30 pico-Siemens and displayed electrical properties consistent with Cx36 gap junctions. Importantly, similar frequency of low-strength electrical coupling was also obtained between microglia and neurons in cocultures prepared from neocortical or hippocampal rodent tissue. Lucifer yellow dye coupling between neurons and microglia was observed in 4% of pairs tested, consistent with the low strength and incidence of electrical coupling. Cx36 expression level and/or the degree of coupling between microglia did not significantly change in the presence of activating agents, including lipopolysaccharide, granulocyte-macrophage colony-stimulating factor, interferon-,, and tumor necrosis factor-,, except for some reduction of Cx36 protein when exposed to the latter two agents. Our findings that intercellular coupling occurs between neuronal and microglial populations through Cx36 gap junctions have potentially important implications for normal neural physiology and microglial responses in neuronopathology in the mammalian CNS. © 2005 Wiley-Liss, Inc. [source] Development and content validity of a gastroparesis cardinal symptom index daily diaryALIMENTARY PHARMACOLOGY & THERAPEUTICS, Issue 6 2009D. A. REVICKI Summary Background, The Gastroparesis Cardinal Symptom Index (GCSI) is a patient-reported outcome for gastroparesis using a two-week recall period. To minimize potential patient recall effects, a daily diary version of the GCSI (GCSI-DD) was developed. Aims, To evaluate the content validity of GCSI-DD for the symptoms in patients with documented gastroparesis, to capture symptom variability over time and to compare responses of this GCSI-DD to the original GCSI. Methods, In gastroparesis adults with delayed gastric emptying, cognitive debriefing interviews were conducted to elicit their perspective on relevant symptoms of gastroparesis and relevant recall periods and to evaluate patient understanding of GCSI-DD. Patients completed the GCSI-DD daily over a 2-week period and completed the GCSI at baseline and the 2-week follow-up visit. Results, Twelve gastroparesis patients, of whom five were diabetic and nine women, reported nausea (100%), vomiting (100%), stomach fullness (75%), bloating (58%) and loss of appetite (50%) were important symptoms. All patients understood diary instructions and item content and reported that the diary captured their gastroparesis symptom experience; 83% considered response scales adequate. There was significant daily variability in GCSI-DD scores. Mean GCSI-DD subscale and total scores over 2 weeks correlated strongly (all r > 0.90) with GCSI scores at 2-week follow-up. Conclusions, The GCSI-DD includes symptoms relevant to patients with gastroparesis, captures daily variability of those symptoms and has psychometric properties consistent with a good patient-reported outcome endpoint for gastroparesis clinical trials. [source] Recent advances in enteric neurobiology: mechanosensitive interneuronsNEUROGASTROENTEROLOGY & MOTILITY, Issue 11 2007T. K. Smith Abstract, Until recently, it was generally assumed that the only intrinsic sensory neuron, or primary afferent neuron, in the gut was the after-hyperpolarizing AH/Type II neuron. AH neurons excited by local chemical and mechanical stimulation of the mucosa appear to be necessary for activating the peristaltic reflex (oral excitation and anal inhibition of the muscle layers) and anally propagating ring like contractions (peristaltic waves) that depend upon smooth muscle tone. However, our recent findings in the guinea-pig distal colon suggest that different neurochemical classes of interneuron in the colon are also mechanosensitive in that they respond directly to changes in muscle length, rather than muscle tone or tension. These interneurons have electrophysiological properties consistent with myenteric S-neurons. Ascending and descending interneurons respond directly to circumferential stretch by generating an ongoing polarized peristaltic reflex activity (oral excitatory and anal inhibitory junction potentials) in the muscle for as long as the stimulus is maintained. Some descending (nitric oxide synthase +ve) interneurons, on the other hand, appear to respond directly to longitudinal stretch and are involved in accommodation and slow transit of faecal pellets down the colon. This review will present recent evidence that suggests some myenteric S interneurons, in addition to AH neurons, behave as intrinsic sensory neurons. [source] Characteristics and physiological role of hyperpolarization activated currents in mouse cold thermoreceptorsTHE JOURNAL OF PHYSIOLOGY, Issue 9 2009Patricio Orio Hyperpolarization-activated currents (Ih) are mediated by the expression of combinations of hyperpolarization-activated, cyclic nucleotide-gated (HCN) channel subunits (HCN1,4). These cation currents are key regulators of cellular excitability in the heart and many neurons in the nervous system. Subunit composition determines the gating properties and cAMP sensitivity of native Ih currents. We investigated the functional properties of Ih in adult mouse cold thermoreceptor neurons from the trigeminal ganglion, identified by their high sensitivity to moderate cooling and responsiveness to menthol. All cultured cold-sensitive (CS) neurons expressed a fast activating Ih, which was fully blocked by extracellular Cs+ or ZD7288 and had biophysical properties consistent with those of heteromeric HCN1,HCN2 channels. In CS neurons from HCN1(,/,) animals, Ih was greatly reduced but not abolished. We find that Ih activity is not essential for the transduction of cold stimuli in CS neurons. Nevertheless, Ih has the potential to shape the excitability of CS neurons. First, Ih blockade caused a membrane hyperpolarization in CS neurons of about 5 mV. Furthermore, impedance power analysis showed that all CS neurons had a prominent subthreshold membrane resonance in the 5,7 Hz range, completely abolished upon blockade of Ih and absent in HCN1 null mice. This frequency range matches the spontaneous firing frequency of cold thermoreceptor terminals in vivo. Behavioural responses to cooling were reduced in HCN1 null mice and after peripheral pharmacological blockade of Ih with ZD7288, suggesting that Ih plays an important role in peripheral sensitivity to cold. [source] Kinetic and functional analysis of transient, persistent and resurgent sodium currents in rat cerebellar granule cells in situ: an electrophysiological and modelling studyTHE JOURNAL OF PHYSIOLOGY, Issue 1 2006Jacopo Magistretti Cerebellar neurones show complex and differentiated mechanisms of action potential generation that have been proposed to depend on peculiar properties of their voltage-dependent Na+ currents. In this study we analysed voltage-dependent Na+ currents of rat cerebellar granule cells (GCs) by performing whole-cell, patch-clamp experiments in acute rat cerebellar slices. A transient Na+ current (INaT) was always present and had the properties of a typical fast-activating/inactivating Na+ current. In addition to INaT, robust persistent (INaP) and resurgent (INaR) Na+ currents were observed. INaP peaked at ,,40 mV, showed half-maximal activation at ,,55 mV, and its maximal amplitude was about 1.5% of that of INaT. INaR was elicited by repolarizing pulses applied following step depolarizations able to activate/inactivate INaT, and showed voltage- and time-dependent activation and voltage-dependent decay kinetics. The conductance underlying INaR showed a bell-shaped voltage dependence, with peak at ,35 mV. A significant correlation was found between GC INaR and INaT peak amplitudes; however, GCs expressing INaT of similar size showed marked variability in terms of INaR amplitude, and in a fraction of cells INaR was undetectable. INaT, INaP and INaR could be accounted for by a 13-state kinetic scheme comprising closed, open, inactivated and blocked states. Current-clamp experiments carried out to identify possible functional correlates of INaP and/or INaR revealed that in GCs single action potentials were followed by depolarizing afterpotentials (DAPs). In a majority of cells, DAPs showed properties consistent with INaR playing a role in their generation. Computer modelling showed that INaR promotes DAP generation and enhances high-frequency firing, whereas INaP boosts near-threshold firing activity. Our findings suggest that special properties of voltage-dependent Na+ currents provides GCs with mechanisms suitable for shaping activity patterns, with potentially important consequences for cerebellar information transfer and computation. [source] | |||||||||||||