PAMELA results on the cosmic-ray antiproton flux from 60 MeV to 180 GeV in kinetic energy

The satellite-borne experiment PAMELA has been used to make a new measurement of the cosmic-ray antiproton flux and the antiproton-to-proton flux ratio which extends previously published measurements down to 60 MeV and up to 180 GeV in kinetic energy. During 850 days of data acquisition approximately 1500 antiprotons were observed. The measurements are consistent with purely secondary production of antiprotons in the galaxy. More precise secondary production models are required for a complete interpretation of the results.Comment: 11 pages, 3 figures, 1 table. Accepted for publication in Physical Review Letter

Deficiency of C-C Chemokine Receptor 5 Suppresses Tumor Development via Inactivation of NF-κB and Upregulation of IL-1Ra in Melanoma Model

To evaluate the relevance of C-C chemokine receptor type 5 (CCR5) expression and tumor development, we compared melanoma growth in CCR5 knockout (CCR5−/−) mice and wild type (CCR5+/+) mice. CCR5−/− mice showed reduced tumor volume, tumor weight, and increased survival rate when compared to CCR5+/+ mice. We investigated the activation of NF-κB since it is an implicated transcription factor in the regulation of genes involving cell growth, apoptosis, and tumor growth. Significant inhibition of DNA binding activity of NF-κB, and translocation of p50 and p65 into the nucleus through the inhibition of phosphorylation of IκB was found in the melanoma tissues of CCR5−/− mice compared to melanoma tissues of CCR5+/+ mice. NF-κB target apoptotic protein expression, such as cleaved caspase-3, cleaved PARP, and Bax, was elevated, whereas the survival protein expression levels, such as Bcl-2, C-IAP1, was decreased in the melanoma tissues of CCR5−/− mice. Interestingly, we found that the level of IL-1Ra, a tumor growth suppressive cytokine, was significantly elevated in tumor tissue and spleen of CCR5−/− mice compared to the level in CCR5+/+ mice. Moreover, infiltration of CD8+ cytotoxic T cell and CD57+ natural killer cells was significantly increased in melanoma tumor and spleen tissue of CCR5−/− mice compared to that of CCR5+/+ mice. Therefore, these results showed that CCR5 deficiency caused apoptotic cell death of melanoma through inhibition of NF-κB and upregulation of IL-1Ra

Biomechanical evaluation of DTRAX® posterior cervical cage stabilization with and without lateral mass fixation

Leonard I Voronov,1,2 Krzysztof B Siemionow,3 Robert M Havey,1,2 Gerard Carandang,2 Avinash G Patwardhan1,2 1Department of Orthopaedic Surgery and Rehabilitation, Loyola University Chicago, Maywood, 2Musculoskeletal Biomechanics Laboratory, Edward Hines Jr. VA Hospital, Hines, 3Department of Orthopaedics, University of Illinois College of Medicine at Chicago, Chicago, IL, USA Introduction: Lateral mass screw (LMS) fixation with plates or rods is the current standard procedure for posterior cervical fusion. Recently, implants placed between the facet joints have become available as an alternative to LMS or transfacet screws for patients with cervical spondylotic radiculopathy. The purpose of this study was to evaluate the biomechanical stability of the DTRAX® cervical cage for single- and two-level fusion and compare this to the stability achieved with LMS fixation with rods in a two-level construct.Methods: Seven cadaveric cervical spine (C3–C7) specimens were tested in flexion–extension, lateral bending, and axial rotation to ±1.5 Nm moment without preload (0 N) in the following conditions: 1) intact (C3–C7), 2) LMS and rods at C4–C5 and C5–C6, 3) removal of all rods (LMS retained) and placement of bilateral posterior cages at C5–C6, 4) bilateral posterior cages at C4–C5 and C5–C6 (without LMS and rods), and 5) C4–C5 and C5–C6 bilateral posterior cages at C4–C5 and C5–C6 with rods reinserted.Results: Bilateral posterior cervical cages significantly reduced range of motion in all tested directions in both single- and multilevel constructs (P<0.05). Similar stability was achieved with bilateral posterior cages and LMS in a two-level construct: 0.6°±0.3° vs 1.2°±0.4° in flexion–­extension (P=0.001), (5.0°±2.6° vs 3.1°±1.3°) in lateral bending (P=0.053), (1.3°±1.0° vs 2.2°±0.9°) in axial rotation (P=0.091) for posterior cages and LMS, respectively. Posterior cages, when placed as an adjunct to LMS, further reduced range of motion in a multilevel construct (P<0.05).Conclusion: Bilateral posterior cages provide similar cervical segmental stability compared with a LMS and rod construct and may be an alternative surgical option for select patients. Furthermore, supplementation of a lateral mass construct with posterior cages increases cervical spine stability in single- and multilevel conditions. Keywords: cervical spine, posterior fusion, biomechanics, cervical facets, DTRAX cervical cage, lateral mass scre

Bilateral posterior cervical cages provide biomechanical stability: assessment of stand-alone and supplemental fixation for anterior cervical discectomy and fusion

Leonard I Voronov,1,2 Krzysztof B Siemionow,3 Robert M Havey,1,2 Gerard Carandang,1,2 Frank M Phillips,4 Avinash G Patwardhan1,2 1Musculoskeletal Biomechanics Laboratory, Department of Research, Edward Hines Jr VA Hospital, Hines, IL, USA; 2Department of Orthopaedic Surgery and Rehabilitation, Loyola University Chicago, Maywood, IL, USA; 3College of Medicine at Chicago, University of Illinois, Chicago, IL, USA; 4Midwest Orthopedics at Rush, Rush University Medical Center, Chicago, IL, USA Introduction: Supplemental posterior instrumentation has been widely used to enhance stability and improve fusion rates in higher risk patients undergoing anterior cervical discectomy and fusion (ACDF). These typically involve posterior lateral mass or pedicle screw fixation with significant inherent risks and morbidities. More recently, cervical cages placed bilaterally between the facet joints (posterior cervical cages) have been used as a less disruptive alternative for posterior fixation. The purpose of this study was to compare the stability achieved by both posterior cages and ACDF at a single motion segment and determine the stability achieved with posterior cervical cages used as an adjunct to single- and multilevel ACDF.Methods: Seven cadaveric cervical spine (C2–T1) specimens were tested in the following sequence: intact, C5–C6 bilateral posterior cages, C6–C7 plated ACDF with and without posterior cages, and C3–C5 plated ACDF with and without posterior cages. Range of motion in flexion–extension, lateral bending, and axial rotation was measured for each condition under moment loading up to ±1.5 Nm.Results: All fusion constructs significantly reduced the range of motion compared to intact in flexion–extension, lateral bending, and axial rotation (P<0.05). Similar stability was achieved with bilateral posterior cages and plated ACDF at a single level. Posterior cages, when placed as an adjunct to ACDF, further reduced range of motion in both single- and multilevel constructs (P<0.05).Conclusion: The biomechanical effectiveness of bilateral posterior cages in limiting cervical segmental motion is comparable to single-level plated ACDF. Furthermore, supplementation of single- and multilevel ACDF with posterior cervical cages provided a significant increase in stability and therefore may be a potential, minimally disruptive option for supplemental fixation for improving ACDF fusion rates. Keywords: cervical spine, posterior fusion, biomechanics, cervical facets, DTRAX Posterior Cervical Cag

Time Dependence of the electron and positron components of the cosmic radiation measured by the PAMELA experiment between July 2006 and December 2015

Cosmic-ray electrons and positrons are a unique probe of the propagation of cosmic rays as well as of the nature and distribution of particle sources in our Galaxy. Recent measurements of these particles are challenging our basic understanding of the mechanisms of production, acceleration, and propagation of cosmic rays. Particularly striking are the differences between the low energy results collected by the space-borne PAMELA and AMS-02 experiments and older measurements pointing to sign-charge dependence of the solar modulation of cosmic-ray spectra. The PAMELA experiment has been measuring the time variation of the positron and electron intensity at Earth from July 2006 to December 2015 covering the period for the minimum of solar cycle 23 (2006-2009) until the middle of the maximum of solar cycle 24, through the polarity reversal of the heliospheric magnetic field which took place between 2013 and 2014. The positron to electron ratio measured in this time period clearly shows a sign-charge dependence of the solar modulation introduced by particle drifts. These results provide the first clear and continuous observation of how drift effects on solar modulation have unfolded with time from solar minimum to solar maximum and their dependence on the particle rigidity and the cyclic polarity of the solar magnetic field