Channels underlying neuronal calcium-activated potassium currents

In many cell types rises in cytosolic calcium, either due to influx from the extracellular space, or by release from an intracellular store activates calcium dependent potassium currents on the plasmalemma. In neurons, these currents are largely activated following calcium influx via voltage gated calcium channels active during the action potentials. Three types of these currents are known: I-c. I-AHP and I-sAHP. These currents can be distinguished by clear differences in their pharmacology and kinetics. Activation of these potassium currents modulates action potential time course and the repetitive firing properties of neurons. Single channel studies have identified two types of calcium-activated potassium channel which can also be separated on biophysical and pharmacological grounds and have been named BK and SK channels. It is now clear that BK channels underlie Ic whereas SK channels underlie I-AHP. The identity of the channels underlying I-sAHP are not known. In this review, we discuss the properties of the different types of calcium-activated potassium channels and the relationship between these channels and the macroscopic currents present in neurons. (C) 2002 Elsevier Science Ltd. All rights reserved.

Causes of communication problems at work: A qualitative analysis of supervisor-subordinate differences

This study provided information about how individual workers perceive, describe and interpret episodes of problematic communication. Sixteen full-time workers (5 males, 11 females) were interviewed in depth about specific incidents of problematic communication within their workplace. Their descriptions of the attributed causes of the incidents were coded using a categorisation scheme developed from Coupland, Wieman, and Giles' (1991) model of sources of problematic communication. Communication problems were most commonly attributed to individual deficiency and group membership, although there were differences depending on the direction of communication. The most negative attributions (to personality flaws, to lack of skills, and to negative stereotypes of the outgroup) were most commonly applied by individuals to their supervisors, whilst attributions applied to co-workers and subordinates tended to be less negative, or even positive in some instances (where individuals attributed the fault to themselves). Overall, results highlighted distinctions between the perceptions of communication problems with supervisors and with subordinates, and are interpreted with reference to social identity theory.

To fix or not to fix: The role of 2-phenoxyethanol in rabbit, Oryctolagus cuniculus, chin gland secretion

The European rabbit (Oryctolagus cuniculus) uses the secretion of the chin gland to maintain dominance hierarchies in the wild. Recent work has investigated changes in the secretion when social status is manipulated in the rabbit. When a rabbit becomes dominant, a new compound appears in his secretion, 2-phenoxyethanol. This compound is used as a fixative in the perfume industry. This study investigates whether the compound performs a similar function in the secretion of the rabbit. 2-Phenoxyethanol is not detected olfactorially by rabbits, and slows the release rate of some of the compounds that occur naturally in rabbit chin gland secretion. We suggest that when a rabbit becomes dominant, he adds a fixative to his secretion so that his scent will persist in the environment and not dissipate. He will thus come to dominate the olfactory environment, in much the same way as he does the physical environment.

Ca2+-activated K+ channels in rat otic ganglion cells: Role of Ca2+ entry via Ca2+ channels and nicotinic receptors

1. Intracellular recordings were made from neurones in the rat otic ganglion in vitro in order to investigate their morphological, physiological and synaptic properties. We took advantage of the simple structure of these cells to test for a possible role of calcium influx via nicotinic acetylcholine receptors during synaptic transmission. 2. Cells filled with biocytin comprised a homogeneous population with ovoid somata and sparse dendritic trees. Neurones had resting membrane potentials of -53 +/- 0.7 mV (n = 69), input resistances of 112 + 7 M Omega, and membrane time constants of 14 +/- 0.9 ms (n = 60). Upon depolarization, all cells fired overshooting action potentials which mere followed by an apamin-sensitive after-hyperpolarization (AHP). In response to a prolonged current injection, all neurones fired tonically. 3. The repolarization phase of action potentials had a calcium component which was mediated by N-type calcium channels. Application of omega-conotoxin abolished both the repolarizing hump and the after-hgrperpolarization suggesting that calcium influx via N-type channels activates SK-type calcium-activated potassium channels which underlie the AHP. 4. The majority (70%) of neurones received innervation from a single preganglionic fibre which generated a suprathreshold excitatory postsynaptic potential mediated by nicotinic acetylcholine receptors. The other 30% of neurones also had one or more subthreshold nicotinic inputs. 5. Calcium influx via synaptic nicotinic receptors contributed to the AHP current, indicating that this calcium has access to the calcium-activated potassium channels and therefore plays a role in regulating cell excitability.

Concentration dependence of sodium permeation and sodium ion interactions in the cyclic AMP-gated channels of mammalian olfactory receptor neurons

The dependence of currents through the cyclic nucleotide-gated (CNG) channels of mammalian olfactory receptor neurons (ORNs) on the concentration of NaCl was studied in excised inside-out patches from their dendritic knobs using the patch-clamp technique. With a saturating concentration (100 mu M) of adenosine 3', 5'-cyclic monophosphate (cAMP), the changes in the reversal potential of macroscopic currents were studied at NaCl concentrations from 25 to 300 mM. In symmetrical NaCl solutions without the addition of divalent cations, the current-voltage relations were almost linear, reversing close to O mV. When the external NaCl concentration was maintained at 150 mM and the internal concentrations were varied, the reversal potentials of the cAMP-activated currents closely followed the Na+ equilibrium potential indicating that P-Cl/P-Na approximate to 0. However, at low external NaCl concentrations (less than or equal to 100 mM) there was some significant chloride permeability. Our results further indicated that Na+ currents through these channels: (i) did not obey the independence principle; (ii) showed saturation kinetics with K(m)s in the range of 100-150 mM and (iii) displayed a lack of voltage dependence of conductance in asymmetric solutions that suggested that ion-binding sites were situated midway along the channel. Together, these characteristics indicate that the permeation properties of the olfactory CNG channels are significantly different from those of photoreceptor CNG channels.

Mechanisms of the inhibition of epithelial Na+ channels by CFTR and purinergic stimulation

The epithelial Na+ channel ENaC is inhibited when the cystic fibrosis transmembrane conductance regulator (CFTR) coexpressed in the same cell is activated by the cyclic adenosine monophosphate (cAMP)-dependent pathway. Regulation of ENaC by CFTR has been studied in detail in epithelial tissues from intestine and trachea and is also detected in renal cells. In the kidney, regulation of other membrane conductances might be the predominant function of CFTR. A similar inhibition of ENaC takes place when luminal purinergic receptors a re activated by 5 ' -adenosine triphosphate (ATP) or uridine triphosphate (UTP). Because both stimulation of purinergic receptors and activation of CFTR induce a Cl- conductance, it is likely that Cl- ions control ENaC activity.

A Ku-band active transmit-array module with a horn or patch array as a signal launching/receiving device

This paper is concerned with the design of a Ku-band active transmit-array module of transistor amplifiers excited by either a pyramidal horn or a patch array Optimal distances between the active transmit array and the signal-launching:receiving device, which is either a passive corporate-fed array or a horn, are determined to maximise the power gain at a design frequency: Having established these conditions, the complete structure is investigated in terms of operational bandwidth and near-field and far-field distributions measured at the output side of the transmit array, The experimental results show that the use of a corporate-fed array as an illuminating/receiving device gives higher gain and significantly larger operational bandwidth, An explanation for this behavior is sought.

Credibility and staff conduct make or break bank customer service quality

Service quality is assessed by customers along the dimensions of staff conduct, credibility, communication, and access to teller services. Credibility and staff conduct emerge as the highest loading first-order factors. This highlights the significance of rectifying mistakes while keeping customers informed, and employing branch staff that are responsive and civilized in their conduct. Discovery of a valid second-order factor, namely, overall customer service quality, underscores the importance of providing quality service across all its dimensions. For example, if the bank fails to rectify mistakes and keep customers informed but excels in all other dimensions, its overall customer service quality can still be rated poorly.

Ionic selectivity of native ATP-activated (P2X) receptor channels in dissociated neurones from rat parasympathetic ganglia

1. The relative permeability of the native P2X receptor channel to monovalent and divalent inorganic and organic cations was determined from reversal potential measurements of ATP-evoked currents in parasympathetic neurones dissociated from rat submandibular ganglia using the dialysed whole-cell patch clamp technique. 2. The P2X receptor-channel exhibited weak selectivity among the alkali metals with a selectivity sequence of Na+ > Li+ > Cs+ > Rb+ > K+, and permeability ratios relative to Cs+ (P-X/P-Cs) ranging from 1. 11 to 0.86. 3. The selectivity for the divalent alkaline earth cations was also weak with the sequence Ca2+ > Sr2+ > Ba2+ > Mn2+ > Mg2+. ATP-evoked currents were strongly inhibited when the extracellular divalent cation concentration was increased. 4, The calculated permeability ratios of different ammonium cations are higher than those of the alkali metal cations. The permeability sequence obtained for the saturated organic cations is inversely correlated with the size of the cation. The unsaturated organic cations have a higher permeability than that predicted by molecular size. 5. Acidification to pH 6.2 increased the ATP-induced current amplitude twofold, whereas alkalization to 8.2 and 9.2 markedly reduced current amplitude. Cell dialysis with either anti-P2X(2) and/or anti-P2X(4) but not anti-P2X(1) antibodies attenuated the ATP-evoked current amplitude. Taken together, these data are consistent with homomeric and/or heteromeric P2X(2) and P2X(4) receptor subtypes expressed in rat submandibular neurones. 6. The permeability ratios for the series of monovalent organic cations, with the exception of unsaturated cations, were approximately related to the ionic size. The relative permeabilities of the monovalent inoganic and organic cations tested are similar to those reported previously for cloned rat P2X2 receptors expressed in mammalian cells.

Beyond hearing aid fitting: improving communication for older adults

Many older adults with hearing impairment continue to have substantial communication difficulties after being fitted with hearing aids, and many do not choose to wear hearing aids. Two group communication education programs aimed at such older people are described. The 'Keep on Talking' program has a health promotion focus, and is aimed at maintaining communication for older adults living in the community. An experimental group (n=120) attended the program, and a control group (n=130) received a communication assessment but no intervention. Significant improvements were found in the experimental participants in terms of knowledge about communication changes with age and about strategies to maintain communication skills. At the follow-up evaluation at 1 year, 45% of the experimental group, compared to 10% of the control group, had acted to improve their communication skills. The 'Active Communication Education' program focuses on the development of problem-solving strategies to improve communication in everyday life situations. Preliminary outcomes have been assessed on a small scale (n=14) to date. It is concluded that communication programs represent an important adjunct to, or supplement for, the traditional approach that focuses on hearing aid fitting.

ATP-dependent K+ channels in renal ischemia reperfusion injury

ATP-dependent K+ channels (K-ATP) account for most of the recycling of K+ which enters the proximal tubules cell via Na, K-ATPase. In the mitochondrial membrane, opening of these channels preserves mitochondrial viability and matrix volume during ischemia. We examined KATP channel modulation in renal ischemia-reperfusion injury (IRI), using an isolated perfused rat kidney (IPRK) model, in control, IRI, IRI + 200 muM diazoxide (a K-ATP opener), IRI + 10 muM glibenclamide (a K-ATP blocker) and IRI + 200 muM diazoxide + 10 muM glibenclamide groups. IRI was induced by 2 periods of warm ischemia, followed by 45 min of reperfusion. IRI significantly decreased glomerular filtration rate (GFR) and increased fractional excretion of sodium (FENa) (p < 0.01). Neither diazoxide nor glibenclamide had an effect on control kidney function other than an increase in renal vascular resistance produced by glibenclamide. Pretreatment with 200 muM diazoxide reduced the postischemic increase in FENa (p < 0.05). Adding 10 muM glibenclamide inhibited the diazoxide effect on postischemic FENa (p < 0.01). Histology showed that kidneys pretreated with glibenclamide demonstrated an increase in injure in the thick ascending limb of outer medulla (p < 0.05). Glibenclamide significantly decreased post ischemic renal vascular resistance (p < 0.05). but had no significant effect on other renal function parameters. Our results suggest that sodium reabsorption is improved by K-ATP activation and blockade of K-ATP channels during IRI has an injury enhancing effect on renal epithelial function and histology. This may be mediated through K-ATP modulation in cell and or mitochondrial inner membrane.

Majority versus minority influence: When, not whether, source status instigates heuristic or systematic processing

Two experiments investigated the extent of message processing of a persuasive communication proposed by either a numerical majority or minority. Both experiments crossed source status (majority versus minority) with message quality (strong versus weak arguments) to determine which source condition is associated with systematic processing. The first experiment showed a reliable difference between strong and weak messages, indicating systematic processing had occurred, for a minority irrespective of message direction (pro- versus counter-attitudinal), but not for a majority. The second experiment showed that message outcome moderates when a majority or a minority leads to systematic processing. When the message argued for a negative personal outcome, there was systematic processing only for the majority source; but when the message did not argue for a negative personal outcome, there was systematic processing only for the minority source. Thus one key moderator of whether a majority or minority source leads to message processing is whether the topic induces defensive processing motivated by self-interest. Copyright (C) 2002 John Wiley Sons, Ltd.

Meeting in the middle: Improving communication in primary health care consultations with people with an intellectual disability

The increased presence and participation in Australian society of people with an intellectual disability provides challenges for the provision of primary health care. General practitioners (GPs) identify themselves as ill equipped to provide for this heterogeneous population. A major obstacle to the provision of appropriate health care is seen as inadequate communication between the GP and the person with an intellectual disability, who may or may not be accompanied by a carer or advocate. This qualitative study in which five GPs, three people with intellectual disability, seven carers and two advocates (parent and friend) were interviewed was conducted in Brisbane, Australia. The aim was to better understand the factors that have an impact upon the success of communication in a medical consultation. Findings suggested that GPs were concerned with the aspects of communication difficulties which influenced their ability to adequately diagnose, manage and inform patients. Implications for practice management were also identified. People with intellectual disability reported frustration when they felt that they could not communicate adequately with the GP and annoyance when they were not included in the communication exchange. Carers were strong advocates for the person with intellectual disability, but indicated insufficient skill and knowledge to provide the level of assistance required in the consultation. The outcome was a model of cooperation that outlined the responsibilities of all players in the medical encounter, prior to, during and after the event.

Evaluating parent use of functional communication training to replace and enhance prelinguistic behaviours in six children with developmental and physical disabilities

Purpose: To evaluate parent use of functional communication training (FCT) to replace and enhance prelinguistic behaviours in six young children with developmental and physical disabilities. Method: Initially, the communicative functions of the children's prelinguistic behaviours were assessed by parent interviews. Three communication functions were identified for each child and intervention goals to replace or enhance the child's existing prelinguistic behaviours were developed in consultation with parents. After a baseline phase, parents received training on implementation of FCT. Intervention was staggered across the three communicative functions in a multiple-probe design. Results: Intervention was associated with increases in the replacement communication behaviour. Treatment gains were generally maintained at the monthly follow-ups. Conclusion: The results suggest that parents can use FCT to enhance communication skills in children with developmental and physical disabilities.