EGFR Kinase Regulates Volume-sensitive Chloride Current Elicited by Integrin Stretch via PI-3K and NADPH Oxidase in Ventricular Myocytes

Stretch of β1 integrins activates an outwardly rectifying, tamoxifen-sensitive Cl− current (Cl− SAC) via AT1 receptors, NADPH oxidase, and reactive oxygen species, and Cl− SAC resembles the volume-sensitive Cl− current (ICl,swell). Epidermal growth factor receptor (EGFR) kinase undergoes transactivation upon stretch, integrin engagement, and AT1 receptor activation and, in turn, stimulates NADPH oxidase. Therefore, we tested whether Cl− SAC is regulated by EGFR kinase signaling and is volume sensitive. Paramagnetic beads coated with mAb for β1 integrin were attached to myocytes and pulled with an electromagnet. Stretch activated a Cl− SAC that was 1.13 ± 0.10 pA/pF at +40 mV. AG1478 (10 μM), an EGFR kinase blocker, inhibited 93 ± 13% of Cl− SAC, and intracellular pretreatment with 1 μM AG1478 markedly suppressed Cl− SAC activation. EGF (3.3 nM) directly activated an outwardly rectifying Cl− current (0.81 ± 0.05 pA/pF at +40 mV) that was fully blocked by 10 μM tamoxifen, an ICl,swell blocker. Phosphatidylinositol 3-kinase (PI-3K) is downstream of EGFR kinase. Wortmannin (500 nM) and LY294002 (100 μM), blockers of PI-3K, inhibited Cl− SAC by 67 ± 6% and 91 ± 25% respectively, and the EGF-induced Cl− current also was fully blocked by LY294002. Furthermore, gp91ds-tat (500 nM), a cell-permeable, chimeric peptide that specifically blocks NADPH oxidase assembly, profoundly inhibited the EGF-induced Cl− current. Inactive permeant and active impermeant control peptides had no effect. Myocyte shrinkage with hyperosmotic bathing media inhibited the Cl− SAC and EGF-induced Cl− current by 88 ± 9% and 127 ± 11%, respectively. These results suggest that β1 integrin stretch activates Cl− SAC via EGFR, PI-3K, and NADPH oxidase, and that both the Cl− SAC and the EGF-induced Cl− currents are likely to be the volume-sensitive Cl− current, ICl,swell

Angiotensin II (AT1) Receptors and NADPH Oxidase Regulate Cl− Current Elicited by β1 Integrin Stretch in Rabbit Ventricular Myocytes

Direct stretch of β1 integrin activates an outwardly rectifying, tamoxifen-sensitive Cl− current (Cl− SAC) via focal adhesion kinase (FAK) and/or Src. The characteristics of Cl− SAC resemble those of the volume-sensitive Cl− current, ICl,swell. Because myocyte stretch releases angiotensin II (AngII), which binds AT1 receptors (AT1R) and stimulates FAK and Src in an autocrine-paracrine loop, we tested whether AT1R and their downstream signaling cascade participate in mechanotransduction. Paramagnetic beads coated with mAb for β1-integrin were applied to myocytes and pulled upward with an electromagnet while recording whole-cell anion current. Losartan (5 μM), an AT1R competitive antagonist, blocked Cl− SAC but did not significantly alter the background Cl− current in the absence of integrin stretch. AT1R signaling is mediated largely by H2O2 produced from superoxide generated by sarcolemmal NADPH oxidase. Diphenyleneiodonium (DPI, 60 μM), a potent NADPH oxidase inhibitor, rapidly and completely blocked both Cl− SAC elicited by stretch and the background Cl− current. A structurally unrelated NADPH oxidase inhibitor, 4-(2-aminoethyl) benzenesulfonyl fluoride (AEBSF, 0.5 and 2 mM), also rapidly and completely blocked Cl− SAC as well as a large fraction of the background Cl− current. With continuing integrin stretch, Cl− SAC recovered upon washout of AEBSF (2 mM). In the absence of stretch, exogenous AngII (5 nM) activated an outwardly rectifying Cl− current that was rapidly and completely blocked by DPI (60 μM). Moreover, exogenous H2O2 (10, 100, and 500 μM), the eventual product of NADPH oxidase activity, also activated Cl− SAC in the absence of stretch, whereas catalase (1,000 U/ml), an H2O2 scavenger, attenuated the response to stretch. Application of H2O2 during NADPH oxidase inhibition by either DPI (60 μM) or AEBSF (0.5 mM) did not fully reactivate Cl− SAC, however. These results suggest that stretch of β1-integrin in cardiac myocytes elicits Cl− SAC by activating AT1R and NADPH oxidase and, thereby, producing reactive oxygen species. In addition, NADPH oxidase may be intimately coupled to the channel responsible for Cl− SAC, providing a second regulatory pathway

Stretch of β1 Integrin Activates an Outwardly Rectifying Chloride Current via FAK and Src in Rabbit Ventricular Myocytes

Osmotic swelling of cardiac myocytes and other types of cells activates an outwardly rectifying, tamoxifen-sensitive Cl− current, ICl,swell, but it is unclear whether Cl− currents also are activated by direct mechanical stretch. We tested whether specific stretch of β1-integrin activates a Cl− current in rabbit left ventricular myocytes. Paramagnetic beads (4.5-μm diameter) coated with mAb to β1-integrin were applied to the surface of myocytes and pulled upward with an electromagnet while recording whole-cell current. In solutions designed to isolate anion currents, β1-integrin stretch elicited an outwardly rectifying Cl− current with biophysical and pharmacological properties similar to those of ICl,swell. Stretch-activated Cl− current activated slowly (t1/2 = 3.5 ± 0.1 min), partially inactivated at positive voltages, reversed near ECl, and was blocked by 10 μM tamoxifen. When stretch was terminated, 64 ± 8% of the stretch-induced current reversed within 10 min. Mechanotransduction involved protein tyrosine kinase. Genistein (100 μM), a protein tyrosine kinase inhibitor previously shown to suppress ICl,swell in myocytes, inhibited stretch-activated Cl− current by 62 ± 6% during continued stretch. Because focal adhesion kinase and Src are known to be activated by cell swelling, mechanical stretch, and clustering of integrins, we tested whether these tyrosine kinases mediated the response to β1-integrin stretch. PP2 (10 μM), a selective blocker of focal adhesion kinase and Src, fully inhibited the stretch-activated Cl− current as well as part of the background Cl− current, whereas its inactive analogue PP3 (10 μM) had no significant effect. In addition to activating Cl− current, stretch of β1-integrin also appeared to activate a nonselective cation current and to suppress IK1. Integrins are the primary mechanical link between the extracellular matrix and cytoskeleton. The present results suggest that integrin stretch may contribute to mechano-electric feedback in heart, modulate electrical activity, and influence the propensity for arrhythmogenesis

Locations of marine animals revealed by carbon isotopes

Knowing the distribution of marine animals is central to understanding climatic and other environmental influences on population ecology. This information has proven difficult to gain through capture-based methods biased by capture location. Here we show that marine location can be inferred from animal tissues. As the carbon isotope composition of animal tissues varies with sea surface temperature, marine location can be identified by matching time series of carbon isotopes measured in tissues to sea surface temperature records. Applying this technique to populations of Atlantic salmon (Salmo salar L.) produces isotopically-derived maps of oceanic feeding grounds, consistent with the current understanding of salmon migrations, that additionally reveal geographic segregation in feeding grounds between individual philopatric populations and age-classes. Carbon isotope ratios can be used to identify the location of open ocean feeding grounds for any pelagic animals for which tissue archives and matching records of sea surface temperature are available

Boom‐bust dynamics in biological invasions: towards an improved application of the concept

Boom‐bust dynamics – the rise of a population to outbreak levels, followed by a dramatic decline – have been associated with biological invasions and offered as a reason not to manage troublesome invaders. However, boom‐bust dynamics rarely have been critically defined, analyzed, or interpreted. Here, we define boom‐bust dynamics and provide specific suggestions for improving the application of the boom‐bust concept. Boom‐bust dynamics can arise from many causes, some closely associated with invasions, but others occurring across a wide range of ecological settings, especially when environmental conditions are changing rapidly. As a result, it is difficult to infer cause or predict future trajectories merely by observing the dynamic. We use tests with simulated data to show that a common metric for detecting and describing boom‐bust dynamics, decline from an observed peak to a subsequent trough, tends to severely overestimate the frequency and severity of busts, and should be used cautiously if at all. We review and test other metrics that are better suited to describe boom‐bust dynamics. Understanding the frequency and importance of boom‐bust dynamics requires empirical studies of large, representative, long‐term data sets that use clear definitions of boom‐bust, appropriate analytical methods, and careful interpretations

Detecting attitudinal changes about death and dying as a result of end-of-life care curricula for medical undergraduates

BACKGROUND: There is heightened emphasis on teaching end-of-life (EOL) care in the medical school curriculum, but a relative paucity of tools focused on assessing key attitudinal changes due to curricula. OBJECTIVE: We sought to evaluate the responsiveness of two validated measures of relevant attitudes to changes caused by two EOL curricula: a year-long Elective and a day-long Inter-Clerkship for medical undergraduates. DESIGN: A case control design (n = 100) and a one group pretest-posttest design (n = 98) were used to ask: (1) Are these two attitudinal measures responsive to changes induced by two undergraduate EOL curricula? (2) Do these two curricula have an additive effect (i.e., taking both yields a stronger attitudinal change than taking only one)? (3) Are there attitudinal and sociodemographic differences between students who took the year-long elective EOL course and those who did not? SUBJECTS: Undergraduate medical students. MEASUREMENTS: Two self-report measures: Concept of a Good Death and Concerns about Dying. RESULTS: Compared to nonelective participants, Elective participants reported less concern about working with dying patients at the end of the course and increased their valuation of clinical criteria in thinking about a good death. There were trends suggesting decreased general concern about dying and increased valuation of closure, and an interaction suggesting a larger impact on those with higher precourse concern scores. There were no differences between elective and nonelective participants at baseline. The Interclerkship increased students\u27 valuation of personal control aspects of death, and there was a trend in reducing concerns about working with dying patients. We did not find an additive effect of taking both curricula. CONCLUSIONS: We conclude that both measures were responsive to the relatively large effects this study would have been able to detect, and may be useful in future research to substantiate the effectiveness of EOL curricula in influencing attitudes and level of comfort with death and dying

Dominant Nuclear Outflow Driving Mechanisms in Powerful Radio Galaxies

In order to identify the dominant nuclear outflow mechanisms in Active Galactic Nuclei, we have undertaken deep, high resolution observations of two compact radio sources (PKS 1549-79 and PKS 1345+12) with the Advanced Camera for Surveys (ACS) aboard the Hubble Space Telescope. Not only are these targets known to have powerful emission line outflows, but they also contain all the potential drivers for the outflows: relativistic jets, quasar nuclei and starbursts. ACS allows the compact nature (<0.15") of these radio sources to be optically resolved for the first time. Through comparison with existing radio maps we have seen consistency in the nuclear position angles of both the optical emission line and radio data. There is no evidence for bi-conical emission line features on the large-scale and there is a divergance in the relative position angles of the optical and radio structure. This enables us to exclude starburst driven outflows. However, we are unable to clearly distinguish between radiative AGN wind driven outflows and outflows powered by relativistic radio jets. The small scale bi-conical features, indicative of such mechanisms could be below the resolution limit of ACS, especially if aligned close to the line of sight. In addition, there may be offsets between the radio and optical nuclei induced by heavy dust obscuration, nebular continuum or scattered light from the AGN.Comment: 9 pages, 8 figures, emulateapj, ApJ Accepte

Summer 1982

Registration of Isofenphos (page 3) Managing Annual Bluegrass (4) Helminthosporium Leaf Spot Fungicide Control Trial--1981 (8) Cultivar Trials--1981 (9) Dollar Spot (Sclerotinia Homeocarpa Sp.) Fungicide Control Trial--1981 (14) Living with the Gypsy Moth (15