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Solar system constraints on the Dvali-Gabadadze-Porrati braneworld theory of gravity

A number of proposals have been put forward to account for the observed accelerating expansion of the Universe through modifications of gravity. One specific scenario, Dvali-Gabadadze-Porrati (DGP) gravity, gives rise to a potentially observable anomaly in the solar system: all planets would exhibit a common anomalous precession, dw/dt, in excess of the prediction of General Relativity. We have used the Planetary Ephemeris Program (PEP) along with planetary radar and radio tracking data to set a constraint of |dw/dt| < 0.02 arcseconds per century on the presence of any such common precession. This sensitivity falls short of that needed to detect the estimated universal precession of |dw/dt| = 5e-4 arcseconds per century expected in the DGP scenario. We discuss the fact that ranging data between objects that orbit in a common plane cannot constrain the DGP scenario. It is only through the relative inclinations of the planetary orbital planes that solar system ranging data have sensitivity to the DGP-like effect of universal precession. In addition, we illustrate the importance of performing a numerical evaluation of the sensitivity of the data set and model to any perturbative precession.Comment: 9 pages, 2 figures, accepted for publication in Phys. Rev.

An absolute calibration system for millimeter-accuracy APOLLO measurements

Lunar laser ranging provides a number of leading experimental tests of gravitation -- important in our quest to unify General Relativity and the Standard Model of physics. The Apache Point Observatory Lunar Laser-ranging Operation (APOLLO) has for years achieved median range precision at the ~2 mm level. Yet residuals in model-measurement comparisons are an order-of-magnitude larger, raising the question of whether the ranging data are not nearly as accurate as they are precise, or if the models are incomplete or ill-conditioned. This paper describes a new absolute calibration system (ACS) intended both as a tool for exposing and eliminating sources of systematic error, and also as a means to directly calibrate ranging data in-situ. The system consists of a high-repetition-rate (80 MHz) laser emitting short (< 10 ps) pulses that are locked to a cesium clock. In essence, the ACS delivers photons to the APOLLO detector at exquisitely well-defined time intervals as a "truth" input against which APOLLO's timing performance may be judged and corrected. Preliminary analysis indicates no inaccuracies in APOLLO data beyond the ~3 mm level, suggesting that historical APOLLO data are of high quality and motivating continued work on model capabilities. The ACS provides the means to deliver APOLLO data both accurate and precise below the 2 mm level.Comment: 21 pages, 10 figures, submitted to Classical and Quantum Gravit

APOLLO: the Apache Point Observatory Lunar Laser-ranging Operation: Instrument Description and First Detections

A next-generation lunar laser ranging apparatus using the 3.5 m telescope at the Apache Point Observatory in southern New Mexico has begun science operation. APOLLO (the Apache Point Observatory Lunar Laser-ranging Operation) has achieved one-millimeter range precision to the moon which should lead to approximately one-order-of-magnitude improvements in the precision of several tests of fundamental properties of gravity. We briefly motivate the scientific goals, and then give a detailed discussion of the APOLLO instrumentation.Comment: 37 pages; 10 figures; 1 table: accepted for publication in PAS

Transforming Growth Factor-b2 Induces Synthesis and Secretion of Endothelin-1 in Human Trabecular Meshwork Cells

PURPOSE. Analysis of aqueous humor from patients with primary open-angle glaucoma (POAG) revealed marked increases in the content of endothelin-1 (ET-1) and transforming growth factor-beta (TGF-b). We determined the consequences of TGF-b signaling on ET-1 expression and secretion by human trabecular meshwork (TM) cells. METHODS. Primary or transformed (NTM5 and GTM3) human TM cells conditioned in serum-free media were incubated in the absence or presence of TGF-b1 or -b2. Relative changes in preproendothelin (ppET)-1 mRNA content and secreted ET-1 peptide were quantified by real-time PCR and ELISA, respectively. In some experiments, TGF-b or ET-1 receptor antagonists, or Rho G-protein inhibitors, were evaluated for effects on TGF-b signaling. Filamentous actin organization was visualized by phalloidin. RESULTS. Primary or transformed human TM cells cultured in the presence of TGF-b1 or -b2 exhibit a marked (&gt;8-fold) increase in ppET-1 mRNA content compared to vehicle controls. Coincubation with SB-505124, an inhibitor of TGFbRI/ALK-5 signaling, prevented TGF-b-mediated ppET-1 mRNA expression. In contrast, coincubation with ET A or ET B (BQ-788) receptor antagonists had no effect on TGF-b-mediated ppET-1 mRNA expression. TGF-b1 and -b2 each elicited a robust (&gt;7-fold) secretion of ET-1 while enhancing stress fiber organization. Inhibition of Rho signaling attenuated TGF-b-mediated increases in ppET-1 mRNA content, ET-1 secretion, and stress fiber organization. CONCLUSIONS. TGF-b, signaling through the TGFbRI/ALK-5 receptor, elicits marked increases in ET-1 mRNA content and ET-1 secretion from cultured primary or transformed human TM cells. Elevated levels of TGF-b2 present in AH of POAG patients may elevate intraocular pressure, in part, by eliciting aberrant Rho G-protein dependent cell contraction, and increasing ET-1 synthesis and secretion, in human TM cells. (Invest Ophthalmol Vis Sci. 2012;53:5279-5286) DOI:10.1167/iovs.11-9289 P rimary open-angle glaucoma (POAG) is one of the most common causes of blindness worldwide, affecting over 2 million individuals 45 years or older in the United States. 1 In POAG patients, irreversible loss of peripheral vision frequently is associated with a pathologic elevation of intraocular pressure (IOP). 2 Clinically, elevated IOP remains a poorly understood hallmark of POAG. In healthy eyes, normal IOP is maintained through a balance between production and outflow of aqueous humor (AH). In adults, the majority (&gt;50%) of AH exits the eye by a conventional outflow pathway involving the trabecular meshwork (TM) at the iridocorneal angle. 3 TM cells regulate AH outflow facility partly through contraction and relaxation of their actin cytoskeleton. Under pathologic conditions, chronic aberrant contraction of TM cells increases resistance to AH outflow, leading to abnormal and sustained elevation of IOP. The mechanism that promotes harmful chronic aberrant TM cell contraction in POAG remains unknown, but may involve dysregulation of small monomeric Rho G-protein mediated organization of the actin cytoskeleton. 23-26 Levels of transforming growth factor (TGF)-b2, a cytokine known to promote synthesis and release of ECM components, similarly are increased aberrantly in AH from POAG patients. 41 Emerging evidence strongly supports a pathologic association between either ET-1 or TGF-b2 with elevated IOP in the 5279 Downloaded from iovs.arvojournals.org on 06/29/2019 pathogenesis of POAG. Mechanisms responsible for regulating endogenous synthesis and secretion of ET-1 and TGF-b2 within the eye currently remain unknown. A role for TGF-b in promoting transcription and release of ET-1 has been suggested. MATERIALS AND METHODS Human Trabecular Meshwork Cell Culture The use of human cadaver material in our study was approved by the Edward Hines Jr. VA and Loyola University Chicago institutional review boards in compliance with the tenets of the Declaration of Helsinki. Fresh cadaver corneoscleral rims were obtained (Illinois Eye Bank, Chicago, IL) at the time of corneal transplant and primary human TM cells were prepared using a collagenase-free procedure as described previously. Treatment Subconfluent primary or transformed human TM cells were cultured for 24 hours in serum-free media before treatment. Recombinant human TGF-b1 or TGF-b2 (Cell Signaling Technology, Danvers, MA) was reconstituted as a stock solution in 4 mM HCl containing 0.1% BSA for 30 minutes at 238C before use. Serum-starved cultures were treated (24 hours) in the absence (vehicle, 200 nM HCl) or presence (5 ng/mL) of TGF-b1 or TGF-b2 in fresh serum-free media. TM cell viability was routinely determined by Trypan Blue dye exclusion and was consistently &gt;90%. To determine mechanism of action, GTM3 cells were co-treated (24 hours) with TGF-b2 (5 ng/mL) in the absence or presence of SB-505124 (1 lM), a TGF-b type I receptor (TGFbRI)/ activin receptor-like kinase 5 (ALK-5) inhibitor; BQ-123 (1 lM), an ET A antagonist; or BQ-788 (1 lM), an ET B antagonist. To determine the role of Rho G-proteins, TM cells were pretreated (1 hour) with chemicallyactivated lovastatin (10 lM) 3,48,50 ; GGTI-298 (10 lM, a geranylgeranyl transferase-I inhibitor) or with cell-permeable exoenzyme C3 transferase (10 lg /mL, a selective Rho G-protein subfamily inhibitor; Cytoskeleton, Denver, CO). Unless otherwise indicated, all reagents were purchased from Sigma-Aldrich. Real Time RT-PCR Total RNA was extracted from primary or transformed human TM cells using TRIzol reagent, and 5 lg were reverse-transcribed using Super Script III First Strand Synthesis system (Life Technologies) as described previously. Endothelin-1 ELISA The content of ET-1 in cell culture media was assessed using a commercially-available ELISA kit (R&amp;D Systems, Minneapolis, MN) according to manufacturer&apos;s instructions. The working range for this human-specific ET-1 ELISA kit is 0.39-25 pg/ml. Media from primary or transformed human TM cells cultured in 12-well cell culture plates were harvested, centrifuged (700g 3 5 minutes) to remove particulate, and aliquots (75 lL) were added to microtiter wells precoated with a monoclonal antibody against human ET-1. Samples were read at 450 nm with a 540 nm correction, and results expressed as pg of ET-1. Filamentous Actin Staining NTM5 or GTM3 cells were cultured on Nunc Lab-Tek II chambered slides overnight (24 hours) in serum-free DMEM and treated 3 24 hours without (vehicle, 200 nM HCl) or with 5 ng/mL TGF-b1 or TGF-b2. Some cultures were pretreated (1 hour) with chemically-activated lovastatin (10 lM) or GGTI-298 (10 lM) before TGF-b2 treatment. Treated cells were fixed 315 minutes at 238C by immersion in phosphate buffered (pH 7.4) 4% paraformaldehyde. Filamentous actin stress fiber organization was visualized using AlexaFluor488-conjugated phalloidin. Stained slides were mounted using Fluoroshield containing DAPI (Sigma), and visualized by confocal microscopy. Statistical Analysis Results are expressed as mean 6 SD of duplicate (primary) or triplicate (transformed) cultures, repeated at least one additional time unless otherwise specified. Parametric data were analyzed by Student&apos;s t-test or by one-way ANOVA followed by either a Dunnett&apos;s or Bonferroni&apos;s multiple comparison post-hoc analysis, as indicated. In all cases, P &lt; 0.05 was considered statistically significant. RESULTS TGF-b2 Increases ppET-1 mRNA Content Transformed human TM cells (NTM5) conditioned overnight in serum-free media and incubated subsequently for 24 hours in the presence of TGF-b2 (5 ng/mL) exhibited a &gt;8-fold increase in ppET-1 mRNA content compared to vehicle-treated controls The effect of TGF-b2 on relative changes in ppET-1 mRNA content was dose-and time-dependent 39,51-53 GTM3 cells also responded to 5 ng/mL TGF-b2 stimulation in a time-dependent 5280 Von Zee et al. IOVS, August 2012, Vol. 53, No. 9 Downloaded from iovs.arvojournals.org on 06/29/2019 manner, exhibiting significant and sustained changes in ppET-1 mRNA content at 6-12 hours of incubation 44 Pretreating TM cells with SIS3, a specific inhibitor of the canonical TGF-b effector Smad3, however, did not reduce TGFb2 enhanced ppET-1 mRNA expression (data not shown), suggesting the involvement a non-canonical TGF-b signaling pathway. Previously, a role for small monomeric G-proteins in the regulation of ppET-1 expression has been suggested. One mechanism by which statins indirectly inhibit small Gprotein signaling in TM cells is by limiting the availability of isoprenoid intermediates required for post-translational modification and activation of Rho G-proteins

The action of β-hydroxybutyrate on the growth, metabolism and global histone H3 acetylation of spontaneous mouse mammary tumours: evidence of a β-hydroxybutyrate paradox

Background Ketone bodies have both metabolic and epigenetic roles in cancer. In several studies, they showed an anti-cancer effect via inhibition of histone deacetylases; however, other studies observed faster tumour growth. The related molecule butyrate also inhibits growth of some cancer cells and accelerates it in others. This “butyrate paradox” is thought to be due to butyrate mediating histone acetylation and thus inhibiting cell proliferation in cancers that preferentially utilise glucose (the Warburg effect); whereas in cells that oxidise butyrate as a fuel, it fails to reach inhibitory concentrations and can stimulate growth. Methods We treated transgenic mice bearing spontaneous MMTV-NEU-NT mammary tumours with the ketone body β-hydroxybutyrate (β-OHB) and monitored tumour growth, metabolite concentrations and histone acetylation. In a cell line derived from these tumours, we also measured uptake of β-OHB and glucose, and lactate production, in the absence and presence of β-OHB. Results β-OHB administration accelerated growth of MMTV-NEU-NT tumours, and their metabolic profile showed significant increases in ATP, glutamine, serine and choline-related metabolites. The β-OHB concentration within the treated tumours, 0.46 ± 0.05 μmol/g, had no effect on histone acetylation as shown by western blots. Cultured tumour cells incubated with 0.5 mM β-OHB showed β-OHB uptake that would be equivalent to 54% of glycolytic ATP phosphorylation and no significant change in glucose consumption or lactate production. Conclusions These results suggest that a β-OHB paradox may occur in these mammary tumours in a manner analogous to the butyrate paradox. At low β-OHB concentrations (<1 mM, as observed in our tumour model post-treatment), and in the absence of a Warburg effect, β-OHB is consumed and thus acts as an oxidative energy source and not as an epigenetic factor. This would explain the increase in tumour growth after treatment, the metabolic profiles and the absence of an effect on histone H3 acetylation.We acknowledge the support of the University of Cambridge, Cancer Research UK (C14303/A17197) and Hutchison Whampoa Limited

Th17 Cell Response in SOD1G93A Mice following Motor Nerve Injury

An increased risk of ALS has been reported for veterans, varsity athletes, and professional football players. The mechanism underlying the increased risk in these populations has not been identified; however, it has been proposed that motor nerve injury may trigger immune responses which, in turn, can accelerate the progression of ALS. Accumulating evidence indicates that abnormal immune reactions and inflammation are involved in the pathogenesis of ALS, but the specific immune cells involved have not been clearly defined. To understand how nerve injury and immune responses may contribute to ALS development, we investigated responses of CD4(+) T cell after facial motor nerve axotomy (FNA) at a presymptomatic stage in a transgenic mouse model of ALS (B6SJL SOD1(G93A)). SOD1(G93A) mice, compared with WT mice, displayed an increase in the basal activation state of CD4(+) T cells and higher frequency of Th17 cells, which were further enhanced by FNA. In conclusion, SOD1(G93A) mice exhibit abnormal CD4(+) T cell activation with increased levels of Th17 cells prior to the onset of neurological symptoms. Motor nerve injury exacerbates Th17 cell responses and may contribute to the development of ALS, especially in those who carry genetic susceptibility to this disease