Calcium-activated potassium channels: Multiple contributions to neuronal function

Calcium-activated potassium channels are a large family of potassium channels that are found throughout the central nervous system and in many other cell types. These channels are activated by rises in cytosolic calcium largely in response to calcium influx via voltage-gated calcium channels that open during action potentials. Activation of these potassium channels is involved in the control of a number of physiological processes from the firing properties of neurons to the control of transmitter release. These channels form the target for modulation for a range of neurotransmitters and have been implicated in the pathogenesis of neurological and psychiatric disorders. Here the authors summarize the varieties of calcium-activated potassium channels present in central neurons and their defining molecular and biophysical properties.

Public opinion of a proposed wind farm situated close to a populated area in New Zealand: Results from a cross-sectional study

In accordance with New Zealand’s Resource Management Act 1991, in 2003, electricity generating company Genesis Energy made public its intention to apply for consent to build the Awhitu wind farm. Several community groups claiming to represent the majority opposed this application and in September 2004 consent was declined. The aim was to investigate the attitudes of local community members to the proposed wind farm. A survey was mailed to 500 Franklin residents, systematically selected from the local 2004/2005 telephone directory. Forty questionnaires were returned undelivered. Of the remaining 460, completed questionnaires were returned from 46% (211). Most, 70% (145), residents supported a wind farm being built in their area, with 17% (35) neutral, and only 13% (28) against the farm. There was no statistical difference in respondents’ attitudes between sex, age, or residential proximity to the farm. Respondents listed renewable resource (83%), suitability (78%), and environmental friendliness (76%) as main advantages. Visual unsightliness (24%) and noise pollution (21%) were listed as main perceived disadvantages. Contrary to the assertions of several lobby groups, the majority of local residents support the construction of the Awhitu wind farm. Scientifically robust methods are essential to measure appropriately community attitudes, particularly on contentious issues.

The Las Campanas/AAT Rich Cluster Survey - II. The environmental dependence of galaxy colours in clusters at z similar to 0.1

We present a photometric investigation of the variation in galaxy colour with environment in 11 X-ray-luminous clusters at 0.07 less than or equal to z less than or equal to 0.16 taken from the Las Campanas/AAT Rich Cluster Survey. We study the properties of the galaxy populations in individual clusters, and take advantage of the homogeneity of the sample to combine the clusters together to investigate weaker trends in the composite sample. We find that modal colours of galaxies lying on the colour-magnitude relation in the clusters become bluer by d(B - R)/dr(p) = -0.022 +/- 0.004 from the cluster core out to a projected radius of r(p) = 6 Mpc, further out in radius than any previous study. We also examine the variation in modal galaxy colour with local galaxy density, 2, for galaxies lying close to the colour-magnitude relation, and find that the median colour shifts bluewards by d(B - R)/d log(10)(Sigma) = -0.076 +/- 0.009 with decreasing local density across three orders of magnitude. We show that the position of the red envelope of galaxies in the colour-magnitude relation does not vary as a function of projected radius or density within the clusters, suggesting that the change in the modal colour results from an increasing fraction of bluer galaxies within the colour-magnitude relation, rather than a change in the colours of the whole population. We show that this shift in the colour-magnitude relations with projected radius and local density is greater than that expected from the changing morphological mix based on the local morphology-density relation. We therefore conclude that we are seeing a real change in the properties of galaxies on the colour-magnitude relation in the outskirts of clusters. The simplest interpretation of this result (and similar constraints in local clusters) is that an increasing fraction of galaxies in the lower density regions at large radii within clusters exhibit signatures of star formation in the recent past, signatures which are not seen in the evolved galaxies in the highest density regions.

Expression and function of neuronal nicotinic ACh receptors in rat microvascular endothelial cells

The expression and function of nicotinic ACh receptors (nAChRs) in rat coronary microvascular endothelial cells (CMECs) were examined using RT-PCR and whole cell patch-clamp recording methods. RT-PCR revealed expression of mRNA encoding for the subunits alpha(2), alpha(3), alpha(4), alpha(5), alpha(7), beta(2), and beta(4) but not beta(3). Focal application of ACh evoked an inward current in isolated CMECs voltage clamped at negative membrane potentials. The current-voltage relationship of the ACh-induced current exhibited marked inward rectification and a reversal potential (E-rev) close to 0 mV. The cholinergic agonists nicotine, epibatidine, and cytisine activated membrane currents similar to those evoked by ACh. The nicotine-induced current was abolished by the neuronal nAChR antagonist mecamylamine. The direction and magnitude of the shift in E-rev of nicotine-induced current as a function of extracellular Na+ concentration indicate that the nAChR channel is cation selective and follows that predicted by the Goldman-Hodgkin-Katz equation assuming K+/Na+ permeability ratio of 1.11. In fura-2-loaded CMECs, application of ACh, but not of nicotine, elicited a transient increase in intracellular free Ca2+ concentration. Taken together, these results demonstrate that neuronal nAChR activation by cholinergic agonists evokes an inward current in CMECs carried primarily by Na+, which may contribute to the plasma nicotine-induced changes in microvascular permeability and reactivity induced by elevations in plasma nicotine.

Effects of a change in abundance of elephants on willingness to pay for their conservation

This paper explores the way in which the stated willingness to pay for the conservation of Asian elephants in Sri Lanka varies with hypothetical variations in their abundance. To do that, it relies on results from a sample of residents of Colombo. The willingness to pay function is found to be unusual. It increases at an increasing rate for hypothetical reductions in the elephant population compared to its current level (a level that makes the Asian elephant endangered) and also increases at a decreasing rate for increases in this population from its current level. Rational explanations are given for this relationship. The relationship is, however, at odds with relationships suggested in some of the literature for total economic value as a function of the abundance of a wildlife species. It is suggested that willingness to pay for conservation of a species rationally includes a strategic element and may not always measure the total economic value of a species. Nevertheless, willingness to pay is still policy relevant in such cases.

A hybrid, inverse approach to the design of magnetic resonance imaging magnets

This paper describes a hybrid numerical method of an inverse approach to the design of compact magnetic resonance imaging magnets. The problem is formulated as a field synthesis and the desired current density on the surface of a cylinder is first calculated by solving a Fredholm equation of the first, kind. Nonlinear optimization methods are then invoked to fit practical magnet coils to the desired current density. The field calculations are performed using a semi-analytical method. The emphasis of this work is on the optimal design of short MRI magnets. Details of the hybrid numerical model are presented, and the model is used to investigate compact, symmetric MRI magnets as well as asymmetric magnets. The results highlight that the method can be used to obtain a compact MRI magnet structure and a very homogeneous magnetic field over the central imaging volume in clinical systems of approximately 1 m in length, significantly shorter than current designs. Viable asymmetric magnet designs, in which the edge of the homogeneous region is very close to one end of the magnet system are also presented. Unshielded designs are the focus of this work. This method is flexible and may be applied to magnets of other geometries. (C) 2000 American Association of Physicists in Medicine. [S0094-2405(00)00303-5].

Mechanical loading modulates glutamate receptor subunit expression in bone

The cellular mechanisms coupling mechanical loading with bone remodeling remain unclear. In the CNS, the excitatory amino acid glutamate (Glu) serves as a potent neurotransmitter exerting its effects via various membrane Glu receptors (GluR). Nerves containing Glu exist close to bone cells expressing functional GluRs. Demonstration of a mechanically sensitive glutamate/aspartate transporter protein and the ability of glutamate to stimulate bone resorption in vitro suggest a role for glutamate linking mechanical load and bone remodeling. We used immunohistochemical techniques to identify the expression of N-methyl-D-aspartate acid (NMDA) and non-NMDA (AMPA or kainate) ionotropic GluR subunits on bone cells in vivo. In bone sections from young adult rats, osteoclasts expressed numerous GluR subunits including AMPA (GluR2/3 and GluR4), kainic acid (GluR567) and NMDA (NMDAR2A, NMDAR2B and NMDAR2C) receptor subtypes. Bone lining cells demonstrated immunoexpression for NMDAR2A, NMDAR2B, NMDAR2C, GluR567, GluR23, GuR2 and GluR4 subunits. Immunoexpression was not evident on osteocytes, chondrocytes or vascular channels. To investigate the effects of mechanical loading on GluR expression, we used a Materials Testing System (MTS) to apply 10 N sinusoidal axial compressive loads percutaneously to the right limbs (radius/ulna, tibia/fibula) of rats. Each limb underwent 300-load cycles/day (cycle rate, 1 Hz) for 4 consecutive days. Contralateral, non-loaded limbs served as controls. Mechanically loaded limbs revealed a load-induced loss of immunoexpression for GluR2/3, GluR4, GluR567 and NMDAR2A on osteoclasts and NMDAR2A, NMDAR2B, GluR2/3 and GluR4 on bone lining cells. Both neonatal rabbit and rat osteoclasts were cultured on bone slices to investigate the effect of the NMDA receptor antagonist, MK801, and the AMPA/kainic acid receptor antagonist, NBQX, on osteoclast resorptive activity in vitro. The inhibition of resorptive function seen suggested that both NMDAR and kainic acid receptor function are required for normal osteoclast function. While the exact role of ionotropic GluRs in skeletal tissue remains unclear, the modulation of GluR subunit expression by mechanical loading lends further support for participation of Glu as a mechanical loading effector. These ionotropic receptors appear to be functionally relevant to normal osteoclast resorptive activity. (C) 2005 Elsevier Inc. All rights reserved.

Axial Young's modulus prediction of single-walled carbon nanotube arrays with diameters from nanometer to meter scales

Based on a self-similar array model, we systematically investigated the axial Young's modulus (Y-axis) of single-walled carbon nanotube (SWNT) arrays with diameters from nanometer to meter scales by an analytical approach. The results show that the Y-axis of SWNT arrays decreases dramatically with the increases of their hierarchy number (s) and is not sensitive to the specific size and constitution when s is the same, and the specific Young's modulus Y-axis(s) is independent of the packing configuration of SWNTs. Our calculations also show that the Y-axis of SWNT arrays with diameters of several micrometers is close to that of commercial high performance carbon fibers (CFs), but the Y-axis(s) of SWNT arrays is much better than that of high performance CFs. (C) 2005 American Institute of Physics.

The status of the Diplosentidae (Acanthocephala : Palaeacanthocephala) and a new family of acanthocephalans from Australian wrasses (Pisces : Labridae)

The status and composition of the Diplosentidae Tubangui et Masilungan, 1937 are reviewed. The type species of the type genus, Diplosentis amphacanthi Tubangui et Masilungan, 1937 from Siganus canaliculatus (Park, 1797) in the Philippines, is concluded to have been described inaccurately,in supposedly possessing, only two cement glands and lemnisci enclosed in a membranous sac. The species is almost certainly very close to species of Neorhadinorhynchus yamaguti, 1939 and Sclerocollum Schmidt of Paperna, 1978 which have also been reported from siganids from the tropical Indo-Pacific. Species of these genera have four cement glands and unexceptional lemnisci. As a result, Diplosentis Tubangui et Masilungan, 1937 is best considered to have affinities with the Cavisomidae Meyer, 1932. The Cavisomidae has priority over the Diplosentidae; thus the Diplosentidae becomes a synonym of the Cavisomidae. Neorhadinorhynchus and Sclerocollum are considered synonyms of Diplosentis. The affinities of the other species and genera formerly included in the Diplosentidae (other species of Diplosentis, Allorhadinorhynchus Yamaguti, 1959, Amapacanthus Salgado-Maldonado et Santos, 2000, Pararhadinorhynchus Johnston et Edmonds, 1947, Golvanorhynchus Noronha, do Fabio et Pinto, 1978 and Slendrorhynchus Amin et Soy, 1996) are discussed. It is concluded that all but Pararhadinorhynchus, two species of Diplosentis and Amapacanthus can be accommodated elsewhere satisfactorily. A new family, Transvenidae, is proposed for a small group of acanthocephalans that genuinely possess only two cement glands. Transvena annulospinosa gen. n., sp. n. is described from the labrids Anampses neoguinaicus Bleeker, 1878 (type host), A. geographicus Valenciennes, 1840, A. caeruleopunctatus Ruppell, 1829, Hemigymnus fasciatus (Bloch, 1792), and H. melapterus (Bloch, 1791) from the Great Barrier Reef, Queensland, Australia. Transvena gen. n. is distinguished from all other acanthocephalan genera by having a combination of a single ring of small spines on its trunk near or at the junction between the neck and trunk, two cement glands, a double-walled proboscis receptacle and hooks which decrease in length from the apex to the base of the proboscis. A second new genus within the Transvenidae, Trajectura, is proposed for T. perinsolens sp. n. from Anampses neoguinaicus, also from the Great Barrier Reef. Trajectura gen. n. is distinguished by the possession of only two cement glands and an anterior conical projection (function unknown) on the females. Diplosentis ikedai Machida, 1992 shares these characters and is recombined as Trajectura ikedai comb. n. Pararhadinorhynchus is transferred to the Transvenidae and Diplosentis manteri Gupta et Fatma, 1979 is recombined as Pararhadinorhynchus manteri comb. n.

Assessment of regional long-axis function during dobutamine echocardiography

Echocardiographic analysis of regional left ventricular function is based upon the assessment of radial motion. Long-axis motion is an important contributor to overall function. but has been difficult to evaluate clinically until the recent development of tissue Doppler techniques. We sought to compare the standard visual assessment of radial motion with quantitative tissue Doppler measurement of peak systolic velocity. timing and strain rate (SRI) in 104 patients with known or suspected coronary artery disease undergoing dobutamine stress echocardiography (DbE). A standard DbE protocol was used with colour tissue Doppler images acquired in digital cine-loop format. peak systolic velocity (PSV), time to peak velocity (TPV) and SRI were assessed off-line by an independent operator. Wall motion was assessed by an experienced reader. Mean PSV, TPV and SRI values were compared with wall motion and the presence of coronary artery disease by angiography. A further analysis included assessing the extent of jeopardized myocardium by comparing average values of PSV, TPV and SRI against the previously validated angiographic score. Segments identified as having normal and abnormal radial wall motion showed significant differences in mean PSV (7.9 +/- 3.8 and 5.9 +/- 3.3 cm/s respectively; P < 0.001), TPV (84 40 and 95 +/- 48 ms respectively; P = 0.005) and SRI (- 1.45 +/- 0.5 and - 1.1 +/- 0.9 s(-1) respectively; P < 0.001). The presence of a stenosed subtending coronary artery was also associated with significant differences from normally perfused segments for mean PSV (8.1 3.4 compared with 5.7 +/- 3.7 cm/s; P < 0.001), TPV (78 50 compared with 92 +/- 45 ms; P < 0.001) and SRI (- 1.35 0.5 compared with - 1.20 +/- 0.4 s(-1); P = 0.05). PSV, TPV and SRI also varied significantly according to the extent of jeopardized myocardium within a vascular territory. These results suggest that peak systolic velocity, timing of contraction and SRI reflect the underlying physiological characteristics of the regional myocardium during DbE, and may potentially allow objective analysis of wall motion.

An ATP-sensitive K+ conductance in dissociated neurones from adult rat intracardiac ganglia

1. An ATP-sensitive K+ (K-ATP) conductance has been identified using the perforated patch recording configuration in a population (52%) of dissociated neurones from adult rat intracardiac ganglia. The presence of the sulphonylurea receptor in approximately half of the intracardiac neurones was confirmed by labelling with fluorescent glibenclamide-BODIPY. 2. Under current clamp conditions in physiological solutions, leveromakalim (10 muM) evoked a hyperpolarization, which was inhibited by the sulphonylurea drugs glibenclamide and tolbutamide. 3. Under voltage clamp conditions in symmetrical (140 mM) K+ solutions, hath application of levcromakalim evoked an inward current with a density of similar to8 pA pF(-1) at -50 mV and a slope conductance of similar to9 nS, which reversed close to the potassium equilibrium potential (E-K). Cell dialysis with an ATP-free intracellular solution also evoked an inward current, which was inhibited by tolbutamide. 4. Bath application of either glibenclamide (10 muM) or tolbutamide (100 muM) depolarized adult intracardiac neurones by 3-5 mV, suggesting that a K-ATP conductance is activated under resting conditions and contributes to the resting membrane potential. 5. Activation of a membrane current by levcromakalim leas concentration dependent, with an EC50 of 1.6 muM. Inhibition of the levcromakalim-activated current by glibenclamide leas also concentration dependent, with an IC50 of 55 nM. 6. Metabolic inhibition with 2,4-dinitrophenol and iodoacetic acid or superfusion with hypoxic solution (P-O2 similar to 16 mmHg) also activated a membrane current. These currents exhibited similar I-P characteristics to the levcroinakalim-induced current and were inhibited by glibenclamide. 7. Activation of K-ATP channels in mammalian intracardiac neurones may contribute to changes in neural regulation of the mature heart and. cardiac function during ischaemia-reperfusion.

Do female rainbowfish (Melanotaenia spp.) prefer to shoal with familiar individuals under predation pressure?

Shoaling with familiar individuals may have many benefits including enhanced escape responses or increased foraging efficiency. This study describes the results of two complimentary experiments. The first utilised a simple binary choice experiment to determine if rainbowfish (Melanotaenia spp.) preferred to shoal with familiar individuals or with strangers. The second experiment used a free range situation where familiar and unfamiliar individuals were free to intermingle and were then exposed to a predator threat. Like many other small species of fish, rainbowfish were capable of identifying and distinguishing between individuals and choose to preferentially associate with familiar individuals as opposed to strangers. Contrary to expectations. however. rainbowrish did not significantly increase their preference for familiar individuals in the presence of a stationary predator model. Griffiths [J Fish Biol (1997) 51:489-4951 conducted similar studies under semi-natural conditions examining, the shoaling preferences of European minnows and showed similar results. Both the current study and that of Griffiths were conducted using predator wary populations of fish. It is suggested that, in predator sympatric populations, the benefits of shoaling with familiar individuals are such that it always pays to stay close to familiar individuals even when the probability If predator attack is remote.