Research Article - Cardiomyocyte FGF signaling is required for Cx43 phosphorylation and cardiac gap junction maintenance
Contributors: Takashi Sakurai, Mariko Tsuchida, Paul D. Lampe, Masahiro Murakami
... Cardiac remodeling resulting from impairment of myocardial integrity leads to heart failure, through still incompletely understood mechanisms. The fibroblast growth factor (FGF) system has been implicated in tissue maintenance, but its role in the adult heart is not well defined. We hypothesized that the FGF system plays a role in the maintenance of cardiac homeostasis, and the impairment of cardiomyocyte FGF signaling leads to pathological cardiac remodeling.
Contributors: Spyridon Gerontas, Michael S. Shapiro, Daniel G. Bracewell
... Chromatographic modelling can be used to describe and further understand the behaviour of biological species during their chromatography separation on adsorption resins. Current modelling approaches assume uniform rate parameters throughout the column. Software and hardware advances now allow us to consider what can be learnt from modelling at bead level, enabling simulation of heterogeneity in bead and packed bed structure due to design or due to changes during operation. In this paper, a model has been developed to simulate at bead level protein loading in 1.5μl microfluidic columns. This model takes into account the heterogeneity in bead sizes and the spatial variations of the characteristics of a packed bed, such as bed void fraction and dispersion, thus offering a detailed description of the flow field and mass transfer phenomena. Simulations were shown to be in good agreement with published experimental data.
Case Report - Pathological laughter associated with paroxysmal kinesigenic dyskinesia: A rare presentation of acute disseminated encephalomyelitis
Contributors: Neera Chaudhry, Vinod Puri, Yogesh Patidar, Geeta A. Khwaja
... A 13-year-old boy presented with recurrent episodes of sudden brief posturing of the right upper and lower limbs accompanied by transient inability to speak and a tendency to smile which would sometimes break into laughter. Awareness was retained during the attack, and there was no associated emotional abnormality. The events were precipitated by walking and occurred several times in a day. The laughter was pathological in nature, and the abnormal posturing was akin to ‘paroxysmal kinesigenic dyskinesia’ (PKD). ‘Pathological laughter or crying’ is defined as an involuntary, inappropriate, unmotivated laughter, crying or both, without any associated mood change. It can occur as a result of cerebral lesions like tumors, trauma, vascular insults, multiple sclerosis and/or degenerative disorders. It can also be a component of gelastic epilepsy which is characterized by stereotyped recurrences, presence of interictal and ictal epileptiform discharges and absence of external precipitants. In our patient, however, there was no ictal or interictal EEG correlate. Paroxysmal kinesigenic dyskinesia is characterized by intermittent, involuntary movements triggered by kinesigenic stimuli and is usually familial but can also be secondary to metabolic and structural brain disorders. Magnetic Resonance Imaging (MRI), in our case, revealed multiple T2 and FLAIR hyperintense, non-enhancing lesions in the periaqueductal gray matter, pontine and midbrain tegmentum, bilateral thalami and left lentiform nucleus suggesting a diagnosis of ‘acute disseminated encephalomyelitis’, in which this unique combination of pathological laughter and PKD has not been described so far. Magnetic Resonance Spectroscopy (MRS) confirmed a demyelinating pathology, and the patient responded well to steroids.
Influenza A virus progeny vRNP trafficking in live infected cells studied with the virus-encoded fluorescently tagged PB2 protein
Contributors: Sergiy V. Avilov, Dorothée Moisy, Nadia Naffakh, Stephen Cusack
... Dynamic studies of influenza virus infection in the live cells are limited because of the lack of appropriate methods for non-invasive detection of the viral components. Using the split-GFP strategy, we have recently developed and characterized an unimpaired recombinant influenza A virus encoding a tagged PB2 subunit of RNA-dependent RNA polymerase, which enabled continuous real-time visualization of the viral ribonucleoproteins (vRNPs) in living cells (Avilov, Moisy, Munier, Schraidt, Naffakh and Cusack ). Here, using this virus, we studied vRNP trafficking and interaction with Rab11 in the context of quasi-wild type infection. In agreement with recent reports, we observed that upon nuclear export, progeny vRNPs accumulate in the particles containing Rab11, a multifunctional protein involved in vesicle trafficking which resides at recycling endosomes. Fluorescence resonance energy transfer microscopy indicated a distance <10nm between PB2 and Rab11, suggesting that a direct interaction occurs. Single particle tracking analysis showed that most of the motions of vRNP-positive particles in infected cells are slow, while rapid directional motions intermittently occur. Analysis focused on these intermittent motions indicated that depolymerization of either microtubules or actin filaments moderately reduced their occurrence, while disruption of both cytoskeleton components in combination suppressed the rapid motions entirely. Thus, the split-GFP based virus enabled us to obtain a live-cell based confirmation for the model of vRNP trafficking which assumes accumulation of vRNP in recycling endosomes through a direct interaction of PB2 with Rab11, and subsequent transport across the cytoplasm involving microtubules and actin filaments.
Store-independent pathways for cytosolic STIM1 clustering in the regulation of store-operated Ca2+ influx
Contributors: Bo Zeng, Gui-Lan Chen, Shang-Zhong Xu
... STIM1 is a Ca2+ sensing molecule. Once the Ca2+ stores are depleted, STIM1 moves towards the plasma membrane (PM) (translocation), forms puncta (clustering), and triggers store-operated Ca2+ entry (SOCE). Although this process has been regarded as a main mechanism for store-operated Ca2+ channel activation, the STIM1 clustering is still unclear. Here we discovered a new phenomenon of STIM1 clustering, which is not triggered by endoplasmic reticulum (ER) Ca2+ depletion.
Contributors: Robert Hall
... The heterogeneous Sundaland region was assembled by closure of Tethyan oceans and addition of continental fragments. Its Mesozoic and Cenozoic history is illustrated by a new plate tectonic reconstruction. A continental block (Luconia–Dangerous Grounds) rifted from east Asia was added to eastern Sundaland north of Borneo in the Cretaceous. Continental blocks that originated in western Australia from the Late Jurassic are now in Borneo, Java and Sulawesi. West Burma was not rifted from western Australia in the Jurassic. The Banda (SW Borneo) and Argo (East Java–West Sulawesi) blocks separated from western Australia and collided with the SE Asian margin between 110 and 90Ma, and at 90Ma the Woyla intra-oceanic arc collided with the Sumatra margin. Subduction beneath Sundaland terminated at this time. A marked change in deep mantle structure at about 110°E reflects different subduction histories north of India and Australia since 90Ma. India and Australia were separated by a transform boundary that was leaky from 90 to 75Ma and slightly convergent from 75 to 55Ma. From 80Ma, India moved rapidly north with north-directed subduction within Tethys and at the Asian margin. It collided with an intra-oceanic arc at about 55Ma, west of Sumatra, and continued north to collide with Asia in the Eocene. Between 90 and 45Ma Australia remained close to Antarctica and there was no significant subduction beneath Sumatra and Java. During this interval Sundaland was largely surrounded by inactive margins with some strike-slip deformation and extension, except for subduction beneath Sumba–West Sulawesi between 63 and 50Ma. At 45Ma Australia began to move north; subduction resumed beneath Indonesia and has continued to the present. There was never an active or recently active ridge subducted in the Late Cretaceous or Cenozoic beneath Sumatra and Java. The slab subducted between Sumatra and east Indonesia in the Cenozoic was Cretaceous or older, except at the very western end of the Sunda Arc where Cenozoic lithosphere has been subducted in the last 20million years. Cenozoic deformation of the region was influenced by the deep structure of Australian fragments added to the Sundaland core, the shape of the Australian margin formed during Jurassic rifting, and the age of now-subducted ocean lithosphere within the Australian margin.
Contributors: Chloé Mauroy, Thomas Portet, Martin Winterhalder, Elisabeth Bellard, Marie-Claire Blache, Justin Teissié, Andreas Zumbusch, Marie-Pierre Rols
... We present experimental results regarding the effects of electric pulses on giant unilamellar vesicles (GUVs). We have used phase contrast and coherent anti-Stokes Raman scattering (CARS) microscopy as relevant optical approaches to gain insight into membrane changes under electropermeabilization. No addition of exogenous molecules (lipid analogue, fluorescent dye) was needed. Therefore, experiments were performed on pure lipid systems avoiding possible artefacts linked to their use. Structural membrane changes were assessed by loss of contrast inside the GUVs due to sucrose and glucose mixing. Our observations, performed at the single vesicle level, indicate these changes are under the control of the number of pulses and field intensity. Larger number of pulses enhances membrane alterations. A threshold value of the field intensity must be applied to allow exchange of molecules between GUVs and the external medium. This threshold depends on the size of the vesicles, the larger GUVs being affected at lower electric field strengths than the smaller ones. Our experimental data are well described by a simple model in which molecule entry is driven by direct exchange. The CARS microscopic study of the effect of pulse duration confirms that pulses, in the ms time range, induce loss of lipids and membrane deformations facing the electrodes.
Adrenergic deficiency leads to impaired electrical conduction and increased arrhythmic potential in the embryonic mouse heart
Contributors: Candice Baker, David G. Taylor, Kingsley Osuala, Anupama Natarajan, Peter J. Molnar, James Hickman, Sabikha Alam, Brittany Moscato, David Weinshenker, Steven N. Ebert
... To determine if adrenergic hormones play a critical role in the functional development of the cardiac pacemaking and conduction system, we employed a mouse model where adrenergic hormone production was blocked due to targeted disruption of the dopamine β-hydroxylase (Dbh) gene. Immunofluorescent histochemical evaluation of the major gap junction protein, connexin 43, revealed that its expression was substantially decreased in adrenergic-deficient (Dbh−/−) relative to adrenergic-competent (Dbh+/+ and Dbh+/−) mouse hearts at embryonic day 10.5 (E10.5), whereas pacemaker and structural protein staining appeared similar. To evaluate cardiac electrical conduction in these hearts, we cultured them on microelectrode arrays (8×8, 200μm apart). Our results show a significant slowing of atrioventricular conduction in adrenergic-deficient hearts compared to controls (31.4±6.4 vs. 15.4±1.7ms, respectively, p<0.05). To determine if the absence of adrenergic hormones affected heart rate and rhythm, mouse hearts from adrenergic-competent and deficient embryos were cultured ex vivo at E10.5, and heart rates were measured before and after challenge with the β-adrenergic receptor agonist, isoproterenol (0.5μM). On average, all hearts showed increased heart rate responses following isoproterenol challenge, but a significant (p<0.05) 225% increase in the arrhythmic index (AI) was observed only in adrenergic-deficient hearts. These results show that adrenergic hormones may influence heart development by stimulating connexin 43 expression, facilitating atrioventricular conduction, and helping to maintain cardiac rhythm during a critical phase of embryonic development.
Contributors: Kris Kemper, Allissa Lee, Betty J. Simkins
... Many investment companies hold diversified asset portfolios and frequently try to mirror or outperform a market index for each asset class such as stocks and bonds. As Wibaut and Wilford (2009) show, often the same issuers appear in each of those indices and this may lead to undesirable results such as during a crisis period. Our research further explores the topic of diversification with a special focus on the financial crisis period of 2007 through 2009. Our results indicate that there is benefit in terms of correlations from holding bond and stock portfolios. Interestingly, these findings show the benefit is most pronounced during times of market stress.
Two-photon excitation with pico-second fluorescence lifetime imaging to detect nuclear association of flavanols
Contributors: Irene Mueller-Harvey, Walter Feucht, Juergen Polster, Lucie Trnková, Pierre Burgos, Anthony W. Parker, Stanley W. Botchway
... Two-photon excitation enabled for the first time the observation and measurement of excited state fluorescence lifetimes from three flavanols in solution, which were ∼1.0ns for catechin and epicatechin, but <45ps for epigallocatechin gallate (EGCG). The shorter lifetime for EGCG is in line with a lower fluorescence quantum yield of 0.003 compared to catechin (0.015) and epicatechin (0.018).