Mitochondrial differentiation, introgression and phylogeny of species in the Tegenaria atrica group (Araneae, Agelenidae)

The relationships between the three members of the Tegenaria atrica group (T. atrica, T. saeva and T. gigantea) were examined with DNA sequence data from mitochondrial CO1, 16S rRNA, tRNAleu(CUN) and ND1 genes. Members of this group of large house spiders have overlapping distributions in western Europe and hybridize with each other to a variable degree. The close relatedness of all three species was supported by all analyses. T. saeva and T. gigantea are more closely affiliated than either is to T. atrica. Haplotypes clearly assignable to T. gigantea were also present in many specimens of T. saeva suggesting asymmetrical introgression of mtDNA from T. gigantea into T. saeva. Molecular clock calibrations (CO1) suggest that deeper divisions within the genus Tegenaria may be in excess of 10 million years old, and that the evolutionary history of the T. atrica group has been moulded by Quaternary glacial-interglacial cycles

Interaction of internal anions with potassium channels of the squid giant axon

The interaction of internal anions with the delayed rectifier potassium channel was studied in perfused squid axons. Changing the internal potassium salt from K+ glutamate- to KF produced a reversible decline of outward K currents and a marked slowing of the activation of K channels at all voltages. Fluoride ions exert a differential effect upon K channel gating kinetics whereby activation of IK during depolarizing steps is slowed dramatically, but the rate of closing after the step is not much altered. These effects develop with a slow time course (30-60 min) and are specific for K channels over Na channels. Both the amplitude and activation rate of IK were restored within seconds upon return to internal glutamate solutions. The fluoride effect is independent of the external K+ concentration and test membrane potential, and does not recover with repetitive application of depolarizing voltage steps. Of 11 different anions tested, all inorganic species induced similar decreases and slowing of IK, while K currents were maintained during extended perfusion with several organic anions. Anions do not alter the reversal potential or shape of the instantaneous current-voltage relation of open K channels. The effect of prolonged exposure to internal fluoride could be partially reversed by the addition of cationic K channel blocking agents such as TEA+, 4-AP+, and Cs+. The competitive antagonism between inorganic anions and internal cationic K channel blockers suggests that they may interact at a related site(s). These results indicate that inorganic anions modify part of the K channel gating mechanism (activation) at a locus near the inner channel surface

Evolution of crystalline orientations in the production of ferritic stainless steel

Ferritic stainless steel EN 1.4016 is used in a wide range of applications, the most common ones related to sheet forming. Several problems in the post-processing of these steels relates to their texture and anisotropy. Therefore, it is necessary to know the mechanisms of texture formation in the subsequent stages of metal manufacturing processes. EBSD has been demonstrated as a successful characterisation technique for this purpose. It is known that during re-crystallisation of Fe-Cr steels, deviations from the desired.-fibre texture promote a decrease of deep drawability. Additionally, a-fibre damages formability. Subsequent cold rolling and annealing can enhance the deep drawing properties of the steel sheet. In this research, a standard sample and a modified one with optimised settings as regard to chemical composition and manufacturing process, to improve the formability properties, are characterised. To analyse the preferred orientation and the type of main fibre present in the material, ODF and Aztec Reclassify Phase, to calculate the content of martensite, were used

Modulation of aminopyridine block of potassium currents in squid axon

Aminopyridines are known to block potassium (K) currents in excitable membranes in a manner dependent upon membrane potential, such that the block is relieved by depolarization and restored upon repolarization. In the present study, the effects of aminopyridines on voltage-dependent potassium (K) channels were examined in internally perfused, voltage-clamped squid giant axons. The time course of block restoration after conditioning depolarization was found to be modulated by membrane electric field, K-channel gating, and external cations. Depolarized holding potentials accelerated block restoration without altering steady-state block levels, suggesting that the voltage dependence of block restoration may be related to K channel gating rather than drug binding per se. In support of this notion, low external calcium concentration, which shifts the voltage dependence of K-channel gating to more negative potentials, also accelerated block restoration. Conversely, the relationship between the rate of block restoration and membrane holding potential was shifted in the depolarizing direction by phloretin, an agent that shifts the dependence of K-channel opening on membrane potential in a similar manner. Modification of K-channel gating also was found to alter the rate of block restoration. Addition of internal zinc or internal treatment with glutaraldehyde slowed the time course of both K-channel activation and aminopyridine block restoration. Aminopyridines also were found to interact in the K channel with external Cs+, NH4+, and Rb+, each of which slowed aminopyridine block restoration. Our results suggest that aminopyridines enter and occlude K channels, and that the availability of the binding site may be modulated by channel gating such that access is limited by the probability of the channel reaching an intermediate closed state at the resting potential

Recovery of Stem Cell Proliferation by Low Intensity Vibration Under Simulated Microgravity Requires LINC Complex

Mesenchymal stem cells (MSC) rely on their ability to integrate physical and spatial signals at load bearing sites to replace and renew musculoskeletal tissues. Designed to mimic unloading experienced during spaceflight, preclinical unloading and simulated microgravity models show that alteration of gravitational loading limits proliferative activity of stem cells. Emerging evidence indicates that this loss of proliferation may be linked to loss of cellular cytoskeleton and contractility. Low intensity vibration (LIV) is an exercise mimetic that promotes proliferation and differentiation of MSCs by enhancing cell structure. Here, we asked whether application of LIV could restore the reduced proliferative capacity seen in MSCs that are subjected to simulated microgravity. We found that simulated microgravity (sMG) decreased cell proliferation and simultaneously compromised cell structure. These changes included increased nuclear height, disorganized apical F-actin structure, reduced expression, and protein levels of nuclear lamina elements LaminA/C LaminB1 as well as linker of nucleoskeleton and cytoskeleton (LINC) complex elements Sun-2 and Nesprin-2. Application of LIV restored cell proliferation and nuclear proteins LaminA/C and Sun-2. An intact LINC function was required for LIV effect; disabling LINC functionality via co-depletion of Sun-1, and Sun-2 prevented rescue of cell proliferation by LIV. Our findings show that sMG alters nuclear structure and leads to decreased cell proliferation, but does not diminish LINC complex mediated mechanosensitivity, suggesting LIV as a potential candidate to combat sMG-induced proliferation loss

D2 dopamine receptor activation of potassium channels in identified rat lactotrophs: whole-cell and single-channel recording

Dopamine (DA) is the major physiological regulator of prolactin secretion from the anterior pituitary, exerting a tonic inhibitory control that is mediated by D2 DA receptors. D2 receptors in both the anterior pituitary and CNS are thought to produce some of their inhibitory effects via a coupling to potassium (K+) channels to increase K+ conductance. Utilizing the reverse hemolytic plaque assay and patch-clamp techniques, we characterize the actions of DA on membrane potential and associated DA-activated whole-cell current, as well as the single K+ channels that underlie the response in primary rat lactotrophs. We demonstrate that DA (5 nM to 1 microM) or D2- selective agonists (RU24213 and quinpirole) evoke a hyperpolarization of membrane potential that was blocked by D2 antagonists and associated with an increased K+ conductance. Whole-cell current responses to ramp voltage commands revealed a DA-activated current whose reversal potential was near the calculated Nernst potential for K+, varied as a function of K+ concentration, exhibited some inward rectification, and was Ca2+ independent. The current was insensitive to tetraethylammonium (TEA; 10 mM), partially blocked by 4-aminopyridine (4-AP; 5 mM), and almost completely inhibited by quinine (100 microM). Cell-attached recordings in the presence of DA or a D2 agonist revealed the opening of a K+ channel that was not present in the absence of DA or when a D2 receptor antagonist was included with DA. Analysis of the single- channel current showed the current-voltage relationship to be linear at negative patch potentials and yielded a unitary conductance of 40.2 pS in the presence of 150 mM KCl. The channels were not blocked by TEA (10 mM), were slightly suppressed by 4-AP (5 mM), and were almost completely inhibited by quinine (100 microM). These experiments establish that in primary rat lactotrophs, DA acts at D2 receptors to activate the opening of single K+ channels, which results in an increase in K+ conductance and associated membrane hyperpolarization. This is the first characterization of single DA-activated K+ channels in an endocrine cell

Designing and Piloting a Tool for the Measurement of the Use of Pronunciation Learning Strategies

What appears to be indispensable to drive the field forward and ensure that research findings will be comparable across studies and provide a sound basis for feasible pedagogic proposals is to draw up a classification of PLS and design on that basis a valid and reliable data collection tool which could be employed to measure the use of these strategies in different groups of learners, correlate it with individual and contextual variables, and appraise the effects of training programs. In accordance with this rationale, the present paper represents an attempt to propose a tentative categorization of pronunciation learning strategies, adopting as a point of reference the existing taxonomies of strategic devices (i.e. O'Malley and Chamot 1990; Oxford 1990) and the instructional options teachers have at their disposal when dealing with elements of this language subsystem (e.g. Kelly 2000; Goodwin 2001). It also introduces a research instrument designed on the basis of the classification that shares a number of characteristics with Oxford's (1990) Strategy Inventory for Language Learning but, in contrast to it, includes both Likert-scale and open-ended items. The findings of a pilot study which involved 80 English Department students demonstrate that although the tool requires considerable refinement, it provides a useful point of departure for future research into PLS

Single crystal of superconducting SmFeAsO1-xFy grown at high pressure

Single crystals of SmFeAsO1-xFy of a size up to 120 micrometers have been grown from NaCl/KCl flux at a pressure of 30 kbar and temperature of 1350-1450 C using the cubic anvil high-pressure technique. The superconducting transition temperature of the obtained single crystals varies between 45 and 53 K.Obtained crystals are characterized by a full diamagnetic response in low magnetic fields and by a high critical current density in high magnetic fields. Structural refinement has been performed on single crystal. Differential thermal analysis investigations at 1 bar Ar pressure show decomposition of SmFeAsO1-xFy at 1302 C.Comment: 12 pages, 3 tables, 6 figure

Emerging Gene-Editing Modalities for Osteoarthritis

Osteoarthritis (OA) is a pathological degenerative condition of the joints that is widely prevalent worldwide, resulting in significant pain, disability, and impaired quality of life. The diverse etiology and pathogenesis of OA can explain the paucity of viable preventive and disease-modifying strategies to counter it. Advances in genome-editing techniques may improve disease-modifying solutions by addressing inherited predisposing risk factors and the activity of inflammatory modulators. Recent progress on technologies such as CRISPR/Cas9 and cell-based genome-editing therapies targeting the genetic and epigenetic alternations in OA offer promising avenues for early diagnosis and the development of personalized therapies. The purpose of this literature review was to concisely summarize the genome-editing options against chronic degenerative joint conditions such as OA with a focus on the more recently emerging modalities, especially CRISPR/Cas9. Future advancements in novel genome-editing therapies may improve the efficacy of such targeted treatments