Ca2+-activated K+(BK) channel inactivation contributes to spike broadening during repetitive firing in the rat lateral amygdala

In many neurons, trains of action potentials show frequency-dependent broadening. This broadening results from the voltage-dependent inactivation of K+ currents that contribute to action potential repolarisation. In different neuronal cell types these K+ currents have been shown to be either slowly inactivating delayed rectifier type currents or rapidly inactivating A-type voltage-gated K+ currents. Recent findings show that inactivation of a Ca2+-dependent K+ current, mediated by large conductance BK-type channels, also contributes to spike broadening. Here, using whole-cell recordings in acute slices, we examine spike broadening in lateral amygdala projection neurons. Spike broadening is frequency dependent and is reversed by brief hyperpolarisations. This broadening is reduced by blockade of voltage-gated Ca2+ channels and BK channels. In contrast, broadening is not blocked by high concentrations of 4-aminopyridine (4-AP) or alpha-dendrotoxin. We conclude that while inactivation of BK-type Ca2+-activated K+ channels contributes to spike broadening in lateral amygdala neurons, inactivation of another as yet unidentified outward current also plays a role.

APPL proteins link Rab5 to nuclear signal transduction via an endosomal compartment

Signals generated in response to extracellular stimuli at the plasma membrane are transmitted through cytoplasmic transduction cascades to the nucleus. We report the identification of a pathway directly linking the small GTPase Rab5, a key regulator of endocytosis, to signal transduction and mitogenesis. This pathway operates via APPL1 and APPL2, two Rab5 effectors, which reside on a subpopulation of endosomes. In response to extracellular stimuli such as EGF and oxidative stress, APPL1 translocates from the membranes to the nucleus where it interacts with the nucleosome remodeling and histone deacetylase multiprotein complex NuRD/MeCP1, an established regulator of chromatin structure and gene expression. Both APPL1 and APPL2 are essential for cell proliferation and their function requires Rab5 binding. Our findings identify an endosomal compartment bearing Rab5 and APPL proteins as an intermediate in signaling between the plasma membrane and the nucleus.

An Analytical Solution for the Elastic Lateral-Distortional Buckling of I-section Beams

Lateral-distortional buckling may occur in I-section beams with slender webs and stocky flanges. A computationally efficient method is presented in this paper to study this phenomenon. Previous studies on distortional buckling have been on the use of 3(rd) and 5(th) order polynomials to model the displacements. The present study provides an alternative way, using Fourier Series, to model the behaviour. Beams of different cross-sectional dimensions, load cases and restraint conditions are examined and compared. The accuracy and versatility of the method are verified by calibrating against the results of other published studies. The present method is believed to be a simple and efficient way of determining the buckling load and mode shapes of I-section beams that are susceptible to lateral-distortional buckling modes.

Opioids Inhibit Lateral Amygdala Pyramidal Neurons by Enhancing A Dendritic Potassium Current

Pyramidal neurons in the lateral amygdala discharge trains of action potentials that show marked spike frequency adaptation, which is primarily mediated by activation of a slow calcium-activated potassium current. We show here that these neurons also express an alpha-dendrotoxin- and tityustoxin-Kalpha-sensitive voltage-dependent potassium current that plays a key role in the control of spike discharge frequency. This current is selectively targeted to the primary apical dendrite of these neurons. Activation of mu-opioid receptors by application of morphine or D-Ala(2)-N-Me-Phe(4)-Glycol(5)-enkephalin (DAMGO) potentiates spike frequency adaptation by enhancing the alpha-dendrotoxin-sensitive potassium current. The effects of mu-opioid agonists on spike frequency adaptation were blocked by inhibiting G-proteins with N-ethylmaleimide (NEM) and by blocking phospholipase A(2). Application of arachidonic acid mimicked the actions of DAMGO or morphine. These results show that mu-opioid receptor activation enhances spike frequency adaptation in lateral amygdala neurons by modulating a voltage-dependent potassium channel containing Kv1.2 subunits, through activation of the phospholipase A(2)-arachidonic acid-lipoxygenases cascade.

A systematic review and meta-analysis of clinical trials on physical interventions for lateral epicondylalgia

A systematic review of the literature on the effectiveness of physical interventions for lateral epicondylalgia ( tennis elbow) was carried out. Seventy six randomised controlled trials were identified, 28 of which satisfied the minimum criteria for meta-analysis. The evidence suggests that extracorporeal shock wave therapy is not beneficial in the treatment of tennis elbow. There is a lack of evidence for the long term benefit of physical interventions in general. However, further research with long term follow up into manipulation and exercise as treatments is indicated.

Independent roles of calcium and voltage-dependent potassium currents in controlling spike frequency adaptation in lateral amygdala pyramidal neurons

The calcium-dependent afterhyperpolarization (AHP) that follows trains of action potentials is responsible for controlling action potential firing patterns in many neuronal cell types. We have previously shown that the slow AHP contributes to spike frequency adaptation in pyramidal neurons in the rat lateral amygdala. In addition, a dendritic voltage-gated potassium current mediated by Kv1.2-containing channels also suppresses action potential firing in these neurons. In this paper we show that this voltage-gated potassium current and the slow AHP act together to control spike frequency adaptation in lateral amygdala pyramidal neurons. The two currents have similar effects on action potential number when firing is evoked either by depolarizing current injections or by synaptic stimulation. However, they differ in their control of firing frequency, with the voltage-gated potassium current but not the slow AHP determining the initial frequency of action potential firing. This dual mechanism of controlling firing patterns is unique to lateral amygdala neurons and is likely to contribute to the very low levels of firing seen in lateral amygdala neurons in vivo.

Estimating percolation and lateral water flow on sloping land in rainfed lowland rice ecosystem

Quantifying water losses in paddy fields assists estimation of water availability in rainfed lowland rice ecosystem. Little information is available on water balance in different toposequence positions of sloped rainfed lowland. Therefore, the aim of this work was to quantify percolation and the lateral water flow with special reference to the toposequential variation. Data used for the analysis was collected in Laos and northeast Thailand. Percolation and water tables were measured on a daily basis using a steel cylindrical tube with a lid and perforated PVC tubes, respectively. Percolation rate was determined using linear regression analysis of cumulative percolation. Assuming that the total amount of evaporation and transpiration was equivalent to potential evapotranspiration, the lateral water flow was estimated using the water balance equation. Separate perched water and groundwater tables were observed in paddy fields on coarse-textured soils. The percolation rate varied between 0 and 3 mm/day across locations, and the maximum water loss by lateral movement was more than 20 mm/day. Our results are in agreement with the previously reported findings, and the methodology of estimating water balance components appears reasonably acceptable. With regard to the toposequential variation, the higher the position in the topoesquence, the greater potential for water loss because of higher percolation and lateral flow rates.

Motor unit synchronization between medial and lateral vasti muscles

Objective: Accurate neuromuscular control of the patellofemoral joint is important in knee joint mechanics. Strategies to coordinate the vasti muscles, such as motor unit synchronization, may simplify control of patellar tracking. This study investigated motor unit synchronization between vastus medialis (VM) and lateralis (VL). Methods: Electromyographic (EMG) recordings of single motor unit action potentials (MUAPs) were made from VM and single- and multi-unit recordings were made from VL. Synchronization was quantified from peaks in the cross-correlogram generated from single MUAP pairs in VL and VM. The proportion of motor units in VM with synchronized firing in VL was also quantified from peaks in averages of multiunit VL EMG triggered from the VM MUAP. Results: A high degree of synchronization of motor unit firing between VM and VL was identified. Results were similar for cross-correlation (similar to 45% of cases) and triggered averages (similar to 41% of cases). Conclusions: The data suggest that synchronization between VM and VL is higher than expected. Agreement between traditional cross-correlation and triggered averaging methods suggest that this new technique may provide a more clinically viable method to quantify synchronization. Significance: High synchronization between VM and VL may provide a solution to simplify control of the mechanically unstable patellofemoral joint. (c) 2005 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.

Study of the calcification of PHEMA hydrogels using a two compartment permeation cell

To simulate the process of calcification in hydrogel implants, particularly calcification inside hydrogels, in vitro experiments using two compartment permeation cells have been performed. PHEMA hydrogel membranes were synthesized by free radical polymerization in bulk. The permeability and diffusion coefficient for Ca2+ ions at 37 ° C were determined using Fick's laws of diffusion. It was evident that Ca2+ ions either from CaCl2 or SBF solutions may diffuse through PHEMA hydrogel membranes. The fort-nation of calcium phosphate deposits inside the hydrogel was observed and attributed to a heterogeneous nucleation from diffusing calcium and phosphate ions. The morphology of the deposits both on the surface and inside the hydrogels was found to be similar, i.e. spherical aggregates with a diameter of less than one micron. © 2005 Elsevier B.V. All rights reserved.

Rab11 in recycling endosomes regulates the sorting and basolateral transport of E-cadherin

E-cadherin plays an essential role in cell polarity and cell-cell adhesion; however, the pathway for delivery of E-cadherin to the basolateral membrane of epithelial cells has not been fully characterized. We first traced the post-Golgi, exocytic transport of GFP-tagged E-cadherin (Ecad-GFP) in unpolarized cells. In live cells, Ecad-GFP was found to exit the Golgi complex in pleiomorphic tubulovesicular carriers, which, instead of moving directly to the cell surface, most frequently fused with an intermediate compartment, subsequently identified as a Rab11-positive recycling endosome. In MDCK cells, basolateral targeting of E-cadherin relies on a dileucine motif. Both E-cadherin and a targeting mutant, Delta S1-E-cadherin, colocalized with Rab11 and fused with the recycling endosome before diverging to basolateral or apical membranes, respectively. In polarized and unpolarized cells, coexpression of Rab11 mutants disrupted the cell surface delivery of E-cadherin and caused its mistargeting to the apical membrane, whereas apical Delta S1-E-cadherin was unaffected. We thus demonstrate a novel pathway for Rab11 dependent, dileucine-mediated, mu 1B-independent sorting and basolateral trafficking, exemplified by E-cadherin. The recycling endosome is identified as an intermediate compartment for the post-Golgi trafficking and exocytosis of E-cadherin, with a potentially important role in establishing and maintaining cadherin-based adhesion.

Development of an oligonucleotide-based SNP detection method on lateral flow strips using hexapet tages

Detection of point mutations or single nucleotide polymorphisms (SNPs) is important in relation to disease susceptibility or detection in pathogens of mutations determining drug resistance or host range. There is an emergent need for rapid detection methods amenable to point-of-care applications. The purpose of this study was to reduce to practice a novel method for SNP detection and to demonstrate that this technology can be used downstream of nucleic acid amplification. The authors used a model system to develop an oligonucleotide-based SNP detection system on nitrocellulose lateral flow strips. To optimize the assay they used cloned sequences of the herpes simplex virus-1 (HSV-1) DNA polymerase gene into which they introduced a point mutation. The assay system uses chimeric polymerase chain reaction (PCR) primers that incorporate hexameric repeat tags ("hexapet tags"). The chimeric sequences allow capture of amplified products to predefined positions on a lateral flow strip. These "hexapet" sequences have minimal cross-reactivity and allow specific hybridization-based capture of the PCR products at room temperature onto lateral flow strips that have been striped with complementary hexapet tags. The allele-specific amplification was carried out with both mutant and wild-type primer sets present in the PCR mix ("competitive" format). The resulting PCR products carried a hexapet tag that corresponded with either a wild-type or mutant sequence. The lateral flow strips are dropped into the PCR reaction tube, and mutant sequence and wild-type sequences diffuse along the strip and are captured at the corresponding position on the strip. A red line indicative of a positive reaction is visible after 1 minute. Unlike other systems that require separate reactions and strips for each target sequence, this system allows multiplex PCR reactions and multiplex detection on a single strip or other suitable substrates. Unambiguous visual discrimination of a point mutation under room temperature hybridization conditions was achieved with this model system in 10 minutes after PCR. The authors have developed a capture-based hybridization method for the detection and discrimination of HSV-1 DNA polymerase genes that contain a single nucleotide change. It has been demonstrated that the hexapet oligonucleotides can be adapted for hybridization on the lateral flow strip platform for discrimination of SNPs. This is the first step in demonstrating SNP detection on lateral flow using the hexapet oligonucleotide capture system. It is anticipated that this novel system can be widely used in point-of-care settings.