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Search Results: 1 - 10 of 3199 matches for " Roland Dosch "
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Souffle/Spastizin Controls Secretory Vesicle Maturation during Zebrafish Oogenesis
Palsamy Kanagaraj equal contributor,Amandine Gautier-Stein equal contributor,Dietmar Riedel,Christoph Schomburg,Joan Cerdà,Nadine Vollack,Roland Dosch
PLOS Genetics , 2014, DOI: doi/10.1371/journal.pgen.1004449
Abstract: During oogenesis, the egg prepares for fertilization and early embryogenesis. As a consequence, vesicle transport is very active during vitellogenesis, and oocytes are an outstanding system to study regulators of membrane trafficking. Here, we combine zebrafish genetics and the oocyte model to identify the molecular lesion underlying the zebrafish souffle (suf) mutation. We demonstrate that suf encodes the homolog of the Hereditary Spastic Paraplegia (HSP) gene SPASTIZIN (SPG15). We show that in zebrafish oocytes suf mutants accumulate Rab11b-positive vesicles, but trafficking of recycling endosomes is not affected. Instead, we detect Suf/Spastizin on cortical granules, which undergo regulated secretion. We demonstrate genetically that Suf is essential for granule maturation into secretion competent dense-core vesicles describing a novel role for Suf in vesicle maturation. Interestingly, in suf mutants immature, secretory precursors accumulate, because they fail to pinch-off Clathrin-coated buds. Moreover, pharmacological inhibition of the abscission regulator Dynamin leads to an accumulation of immature secretory granules and mimics the suf phenotype. Our results identify a novel regulator of secretory vesicle formation in the zebrafish oocyte. In addition, we describe an uncharacterized cellular mechanism for Suf/Spastizin activity during secretion, which raises the possibility of novel therapeutic avenues for HSP research.
Reconciling Trade and Environmental Protection in ASEAN-China Relations: More than Political Window Dressing?
Joern Dosch
Journal of Current Southeast Asian Affairs , 2011,
Abstract: Has the growing pro-environment rhetoric in ASEAN-China relations resulted in the effective mainstreaming of environmental issue into trade agreements and multilateral cooperation frameworks? The article discusses the cases of the ASEAN China Free Trade Area (ACFTA) and the Greater Mekong Subregion (GMS) and argues that there is no shortage of national and regional policy agendas that visibly link trade growth and environmental considerations. However, this nexus is still a weak one in terms of implementation and effectiveness. The most promising initiatives towards an effective reconciliation of trade growth and environmental sustainability are promoted and often driven by foreign donors, most prominently the European Union (EU).
Few-body aspects of non-perturbative QCD
H. G. Dosch
Physics , 1997, DOI: 10.1016/S0375-9474(98)00030-X
Abstract: After some general remarks on non-perturbative QCD I present shortly models which lead to a color-electric flux tube formation. The implications of such a flux tube formation especially on high energy scattering are discussed.
Two-photon reactions at high energies
H. G. Dosch
Physics , 2000, DOI: 10.1016/S0920-5632(01)01119-7
Abstract: We present a short overview over the different contributions to high energy photon photon scattering and explore the possibilities of tuning the sizes of the scattered objects by changing the virtuality of the photons. We compare the experimental data with model calculations. The difficulties with inclusive charm production are discussed.
A Novel Role for MAPKAPK2 in Morphogenesis during Zebrafish Development
Beth A. Holloway,Sol Gomez de la Torre Canny equal contributor,Ying Ye equal contributor,Diane C. Slusarski,Christina M. Freisinger,Roland Dosch,Margaret M. Chou,Daniel S. Wagner ,Mary C. Mullins
PLOS Genetics , 2009, DOI: 10.1371/journal.pgen.1000413
Abstract: One of the earliest morphogenetic processes in the development of many animals is epiboly. In the zebrafish, epiboly ensues when the animally localized blastoderm cells spread, thin over, and enclose the vegetally localized yolk. Only a few factors are known to function in this fundamental process. We identified a maternal-effect mutant, betty boop (bbp), which displays a novel defect in epiboly, wherein the blastoderm margin constricts dramatically, precisely when half of the yolk cell is covered by the blastoderm, causing the yolk cell to burst. Whole-blastoderm transplants and mRNA microinjection rescue demonstrate that Bbp functions in the yolk cell to regulate epiboly. We positionally cloned the maternal-effect bbp mutant gene and identified it as the zebrafish homolog of the serine-threonine kinase Mitogen Activated Protein Kinase Activated Protein Kinase 2, or MAPKAPK2, which was not previously known to function in embryonic development. We show that the regulation of MAPKAPK2 is conserved and p38 MAP kinase functions upstream of MAPKAPK2 in regulating epiboly in the zebrafish embryo. Dramatic alterations in calcium dynamics, together with the massive marginal constrictive force observed in bbp mutants, indicate precocious constriction of an F-actin network within the yolk cell, which first forms at 50% epiboly and regulates epiboly progression. We show that MAPKAPK2 activity and its regulator p38 MAPK function in the yolk cell to regulate the process of epiboly, identifying a new pathway regulating this cell movement process. We postulate that a p38 MAPKAPK2 kinase cascade modulates the activity of F-actin at the yolk cell margin circumference allowing the gradual closure of the blastopore as epiboly progresses.
Nucleon Structure and High Energy Scattering
Michael Rueter,H. G. Dosch
Physics , 1996, DOI: 10.1016/0370-2693(96)00490-X
Abstract: If the pomeron is generated by a two gluon exchange there is no a priori reason for a drastic suppression of three gluon exchange with negative parity and charge parity. This would lead to an unacceptably large difference between $p\,p$ and $p\, \bar{p}$ scattering. It is shown that a natural suppression of the $C$=$P$=--1 contribution to high energy scattering is given by a cluster structure of the nucleon.
Direct extraction of the chiral quark condensate and bounds on the light quark masses
H. G. Dosch,S. Narison
Physics , 1997, DOI: 10.1016/S0370-2693(97)01370-1
Abstract: We select sum rules from which one can extract directly reliable limits on the size of the chiral symmetry breaking light quark condensate $<\bar\psi\psi>$. Combined results from the nucleon and $B^*-B$ mass-splitting sum rules give a result compatible with the standard value: $<\bar\psi\psi> (1 GeV) \simeq (-229 MeV)^3$, through the determinations of the quark-gluon mixed condensate. The vector form factor of the $D\rar K^*l\nu$ semi-leptonic decay leads to the range $0.6\leq <\bar\psi\psi> (-229 MeV)^3 \leq 1.5$. The upper limit combined with the Gell-Mann-Oakes-Renner (GMOR) relation implies the interesting lower bound on the sum of light quark masses:$(m_u+m_d) (1 GeV) \geq$ 9.4 MeV, which combined with the ratio of light quark masses from chiral perturbation theory leads to $m_s (1 GeV) \geq (121\pm 12)$ MeV. The lower limit combined with the positivity of the $m_q^2$ contribution to the GMOR relation leads to the upper bound : $(m_u+m_d) (1 GeV) \leq$ 15.7 MeV, which is independent on the nature of chiral symmetry breaking.
SU(3) Flux Tubes in a Model of the stochastic Vacuum
M. Rueter H. G. Dosch
Physics , 1994, DOI: 10.1007/BF01496598
Abstract: We calculate the squared gluon field strengths of a heavy q-$\rm \bar{q}$-pair in the model of the stochastic vacuum. We observe that with increasing separation a chromoelectric flux tube is built. The properties of the emerging flux tube are investigated.
$B^*Bπ(γ)$ couplings and $D^*\rar Dπ(γ) $-decays within a $1/M$-expansion in $full$ QCD
H. G Dosch,S. Narison
Physics , 1995, DOI: 10.1016/0370-2693(95)01417-9
Abstract: To leading order in $\alpha_s$, we evaluate the leading and non-leading $1/M_b$ corrections to the $B^*B\pi$ and $B^*B\gamma$ couplings using QCD spectral moment sum rules in the full theory. We find that, for large $M_b$ and contrary to the heavy-to-light $B\rar \pi(\rho) l\bar \nu$ form factors, which are dominated by the $soft$ light quark vacuum condensate, these couplings are governed by the $hard$ perturbative graph, like other heavy-to-heavy transitions. We also find that for the $B^{*}\rar B\gamma$, the $1/M_b$ correction is mainly due to the perturbative and light quark condensate contributions originating from the graphs involving the heavy quark part of the electromagnetic current, which are essential for explaining the large charge dependence in the observed $D^{*-}\rar D^-\gamma$ and $D^{*0}\rar D^0\gamma$ decays. Our $best$ numerical predictions {\it without any free parameters} for the $B^*$-meson are: $g_{B^{*-}B^0\pi^-}\simeq 14\pm 4$, $\Gamma_{B^{*-}\rar B^-\gamma}\simeq (0.10\pm 0.03)$ keV and the large charge dependence of the ratio: ${\Gamma_{B^{*-}\rar B^- \gamma}}/ {\Gamma_{B^{*0}\rar B^0 \gamma}}\simeq 2.5~$. For the $D^*$-meson, we find: $\Gamma_{D^{*-}\rar D^0\pi^-}\simeq 1.54\Gamma_{D^{*0}\rar D^0\pi^0} \simeq (8\pm 5)$ keV, $\Gamma_{D^{*-}\rar D^-\gamma}\simeq (0.09^{+0.40}_{-0.07} )$ keV and $\Gamma_{D^{*0}\rar D^0\gamma}\simeq (3.7\pm 1.2)$ keV, where the branching ratios agree within the errors with the present data, while the total widths $\Gamma_{D^{*0}\rar all} \simeq (11\pm 4)$ keV and $\Gamma_{D^{*-}\rar all}\simeq (12\pm 7)$ keV are much smaller than the present experimental upper limits.
Higher Cumulants in the Cluster Expansion in QCD
W. Kornelis,H. G. Dosch
Physics , 2000, DOI: 10.1016/S0920-5632(01)01162-8
Abstract: In this work an extension of the Gaussian model of the stochastic vacuum is presented. It consists of including higher cumulants than just the second one in the cluster expansion in QCD. The influence of nonabelian fourth cumulants on the potential of a static quark-antiquarkpair is examined and the formation of flux tubes between a static $q\bar{q}$-pair is investigated. It is found that the fourth cumulants can contribute to chromomagnetic flux tubes. Furthermore the contribution of fourth cumulants to the total cross section of soft high energy hadron-hadron scattering is examined and it is found that the fourth cumulants do not change the general picture obtained in the Gaussian model.
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