54 research outputs found
The He(e, ed)p Reaction in q-constant Kinematics
The cross section for the He(e, ed)p reaction has been measured as a
function of the missing momentum in q -constant kinematics at
beam energies of 370 and 576 MeV for values of the three-momentum transfer
of 412, 504 and 604 \mevc. The L(+TT), T and LT structure functions have been
separated for = 412 and 504 \mevc. The data are compared to three-body
Faddeev calculations, including meson-exchange currents (MEC), and to
calculations based on a covariant diagrammatic expansion. The influence of
final-state interactions and meson-exchange currents is discussed. The
-dependence of the data is reasonably well described by all calculations.
However, the most advanced Faddeev calculations, which employ the AV18
nucleon-nucleon interaction and include MEC, overestimate the measured cross
sections, especially the longitudinal part, and at the larger values of .
The diagrammatic approach gives a fair description of the cross section, but
under(over)estimates the longitudinal (transverse) structure function.Comment: 17 pages, 7 figure
Doxorubicin upregulates CXCR4 via miR-200c/ZEB1-dependent mechanism in human cardiac mesenchymal progenitor cells.
Doxorubicin (DOXO) treatment is limited by its cardiotoxicity, since it causes cardiac-progenitor-cell depletion. Although the cardioprotective role of the stromal cell-derived factor-1/C-X-C chemokine receptor type 4 (SDF1/CXCR4) axis is well established, its involvement during DOXO-induced cardiotoxicity has never been investigated. We showed that in a mouse model of DOXO-induced cardiomyopathy, CXCR4 <sup>+</sup> cells were increased in response to DOXO, mainly in human cardiac mesenchymal progenitor cells (CmPC), a subpopulation with regenerative potential. Our in vitro results showed a CXCR4 induction after 24 h of DOXO exposure in CmPC. SDF1 administration protected from DOXO-induced cell death and promoted CmPC migration. CXCR4 promoter analysis revealed zinc finger E-box binding homeobox 1 (ZEB1) binding sites. Upon DOXO treatment, ZEB1 binding decreased and RNA-polymerase-II increased, suggesting a DOXO-mediated transcriptional increase in CXCR4. Indeed, DOXO induced the upregulation of miR-200c, that directly targets ZEB1. SDF1 administration in DOXO-treated mice partially reverted the adverse remodeling, decreasing left ventricular (LV) end diastolic volume, LV ejection fraction and LV anterior wall thickness in diastole, recovering LV end systolic pressure and reducing±dP/dt. Moreover, in vivo administration of SDF1 partially reverted DOXO-induced miR-200c and p53 protein upregulation in mouse hearts. In addition, downmodulation of ZEB1 mRNA and protein by DOXO was significantly increased by SDF1. In keeping, p21 mRNA, that is induced by p53 and inhibited by ZEB1, is induced by DOXO treatment and is decreased by SDF1 administration. This study showed new players of the DOXO-induced cardiotoxicity, that can be exploited to ameliorate DOXO-associated cardiomyopathy
Chronic viral infections persistently alter marrow stroma and impair hematopoietic stem cell fitness
Chronic viral infections are associated with hematopoietic suppression, bone marrow (BM) failure, and hematopoietic stem cell (HSC) exhaustion. However, how persistent viral challenge and inflammatory responses target BM tissues and perturb hematopoietic competence remains poorly understood. Here, we combine functional analyses with advanced 3D microscopy to demonstrate that chronic infection with lymphocytic choriomeningitis virus leads to (1) long-lasting decimation of the BM stromal network of mesenchymal CXCL12-abundant reticular cells, (2) proinflammatory transcriptional remodeling of remaining components of this key niche subset, and (3) durable functional defects and decreased competitive fitness in HSCs. Mechanistically, BM immunopathology is elicited by virus-specific, activated CD8 T cells, which accumulate in the BM via interferon-dependent mechanisms. Combined antibody-mediated inhibition of type I and II IFN pathways completely preempts degeneration of CARc and protects HSCs from chronic dysfunction. Hence, viral infections and ensuing immune reactions durably impact BM homeostasis by persistently decreasing the competitive fitness of HSCs and disrupting essential stromal-derived, hematopoietic-supporting cues
Investigation of the Exclusive 3He(e,e'pp)n Reaction
Cross sections for the 3He(e,e'pp)n reaction were measured over a wide range
of energy and three- momentum transfer. At a momentum transfer q=375 MeV/c,
data were taken at transferred energies omega ranging from 170 to 290 MeV. At
omega=220 MeV, measurements were performed at three q values (305, 375, and 445
MeV/c). The results are presented as a function of the neutron momentum in the
final-state, as a function of the energy and momentum transfer, and as a
function of the relative momentum of the two-proton system. The data at neutron
momenta below 100 MeV/c, obtained for two values of the momentum transfer at
omega=220 MeV, are well described by the results of continuum-Faddeev
calculations. These calculations indicate that the cross section in this domain
is dominated by direct two-proton emission induced by a one-body hadronic
current. Cross section distributions determined as a function of the relative
momentum of the two protons are fairly well reproduced by continuum-Faddeev
calculations based on various realistic nucleon-nucleon potential models. At
higher neutron momentum and at higher energy transfer, deviations between data
and calculations are observed that may be due to contributions of isobar
currents.Comment: 14 pages, 1 table, 17 figure
Quaiselastic scattering from relativistic bound nucleons: Transverse-Longitudinal response
Predictions for electron induced proton knockout from the and
shells in O are presented using various approximations for the
relativistic nucleonic current. Results for the differential cross section,
transverse-longitudinal response () and left-right asymmetry
are compared at (GeV/c) corresponding to TJNAF experiment
89-003. We show that there are important dynamical and kinematical relativistic
effects which can be tested by experiment.Comment: 10 pages, including 2 figures. Removed preliminary experimental data
from the figure
A Measurement of the Interference Structure Function, R_LT, for the 12C(e,e'p) reaction in the Quasielastic Region
The coincidence cross-section and the interference structure function, R_LT,
were measured for the 12C(e,e'p) 11B reaction at quasielastic kinematics and
central momentum transfer of q=400 MeV/c. The measurement was at an opening
angle of theta_pq=11 degrees, covering a range in missing energy of E_m = 0 to
65 MeV. The R_LT structure function is found to be consistent with zero for E_m
> 50 MeV, confirming an earlier study which indicated that R_L vanishes in this
region. The integrated strengths of the p- and s-shell are compared with a
Distorted Wave Impulse Approximation calculation. The s-shell strength and
shape are compared with a Hartree Fock-Random Phase Approximation calculation.
The DWIA calculation overestimates the cross sections for p- and s-shell proton
knockout as expected, but surprisingly agrees with the extracted R_LT value for
both shells. The HF-RPA calculation describes the data more consistently, which
may be due to the inclusion of 2-body currents in this calculation.Comment: 8 Pages LaTex, 5 postscript figures. Submitted to Phys. Rev.
Relativistic mean field approximation to the analysis of 16O(e,e'p)15N data at |Q^2|\leq 0.4 (GeV/c)^2
We use the relativistic distorted wave impulse approximation to analyze data
on 16O(e,e'p)15N at |Q^2|\leq 0.4 (GeV/c)^2 that were obtained by different
groups and seemed controversial. Results for differential cross-sections,
response functions and A_TL asymmetry are discussed and compared to different
sets of experimental data for proton knockout from p_{1/2} and p_{3/2} shells
in 16O. We compare with a nonrelativistic approach to better identify
relativistic effects. The present relativistic approach is found to accommodate
most of the discrepancy between data from different groups, smoothing a long
standing controversy.Comment: 28 pages, 7 figures (eps). Major revision made. New figures added. To
be published in Phys. Rev.
Analysis of Meson Exchange and Isobar Currents in (e,e'p) Reactions from O-16
An analysis of the effects of meson exchange and isobar currents in exclusive
(e,e'p) processes from O-16 under quasi-free kinematics is presented. A model
that has probed its feasibility for inclusive quasi-elastic (e,e') processes is
considered. Sensitivity to final state interactions between the outgoing proton
and the residual nucleus is discussed by comparing the results obtained with
phenomenological optical potentials and a continuum nuclear shell-model
calculation. The contribution of the meson-exchange and isobar currents to the
response functions is evaluated and compared to previous calculations, which
differ notably from our results. These two-body contributions cannot solve the
puzzle of the simultaneous description of the different responses
experimentally separated. Copyright 1999 by The American Physical SocietyComment: 5 pages, plus 3 PS figures. To be published in Phys. Rev. C Updated
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