bluuebunny/crossref_metadata_2025_split huggingface dataset:
Formation and detectability of Earth-like planets around Alpha-Centauri B
Authors: Davis Erica 
Published: May 2008

AbstractWe simulate the late stages of planet formation around Alpha Centauri B and analyze the detectability of the resulting terrestrial planet systems. The N-body accretionary evolution of a Σ ∝ r−-1 disk populated with 400–900 lunar-mass oligarchs is followed for 200 Myr for each simulation. All of eight runs result in the formation of multiple-planet systems with at least one planet in the 1–2 M⊕ mass range at 0.5–1.5 AU. We examine the detectability of our simulated planetary systems by generating synthetic radial velocity observations including noise based on the radial velocity residuals to the recently published three planet fit to the nearby K0V star HD 69830. Using these synthetic observations, we find that we can reliably detect a 1.8 M⊕ planet in the habitable zone of α Centauri B after only three years of high cadence observations. We also find that the planet is detectable even if the radial velocity precision is 3 ms−1, as long as the noise spectrum is white.
On the formation age of the first planetary system
Authors: Hara T. , Kunitomo S. , Shigeyasu M. , Kajiura D. 
Published: May 2008

AbstractRecently, it has been observed the extreme metal-poor stars in the Galactic halo, which must be formed just after Pop III objects. On the other hand, the first gas clouds of mass ∼ 106 M⊙ are supposed to be formed at z ∼ 10, 20, and 30 for the 1σ, 2σ and 3σ, where the density perturbations are assumed of the standard ΛCDM cosmology. Usually it is approximated that the distribution of the density perturbation amplitudes is gaussian where σ means the standard deviation. If we could apply this gaussian distribution to the extreme small probability, the gas clouds would be formed at z ∼40, 60, and 80 for the 4σ, 6σ, and 8σ where the probabilities are approximately 3 × 10−5, 10−9, and 10−15. Within our universe, there are almost ∼ 1016 (∼ 1022M⊙/106M⊙) clouds of mass 106M⊙. Then the first gas clouds must be formed around z ∼ 80, where the time is ∼ 20 Myr (∼ 13.7/(1 + z)3/2 Gyr). Even within our galaxy, there are ∼ 105 (∼ 1011M⊙/106M⊙) clouds, then the first gas clouds within our galaxy must be formed around z ∼ 40, where the time is ∼ 54 Myr (∼ 13.7/(1+z)3/2Gyr).The evolution time for massive star (∼ 102M⊙) is ∼ 3 Myr and the explosion of the massive supernova distributes the metal within a cloud. The damping time of the supernova shock wave in the adiabatic and isothermal era is several Myr and stars of the second generation (Pop II) are formed within a free fall time ∼ 20 Myr. Even if the gas cloud is metal poor, there is a lot of possibility to form the planets around such stars. The first planetary systems could be formed within ∼ 6 × 107 years after the Big Bang in the universe. Even in our galaxies, the first planetary systems could be formed within ∼ 1.7 × 108 years. If the abundance of heavy elements such as Fe is small compared to the elements of C, N, O, the planets must be the one where the rock fraction is small. It is interesting to wait the observations of planets around metal-poor stars. For the panspermia theory, the origin of life could be expected in such systems.
Origin of debris disks and the supply of metals in DZ white dwarfs
Authors: Wang Y. , Dong R. B. , Lin D. N. C. , Liu X. W. 
Published: May 2008

AbstractWe discuss the dynamical evolution of minor planetary bodies in the outer regions of planetary systems around the progenitors of DZ white dwarfs. We show that during the planetary-nebula phase of these stars, mass loss can lead to the expansion of all planetary bodies. The orbital eccentricity of the minor bodies, as relics of planetesimals, may be largely excited by the perturbation due to both gas drag effects and nearby gas giant planets. Some of these bodies migrate toward the host star, while others are scattered out of the planetary system. The former have modest probability of being captured by the sweeping secular resonances of giant planets, and induced to migrate toward the host star. When they venture close to their host stars, their orbits are tidally circularized so that they form compact disks where they may undergo further collisionally driven evolution. During the subsequent post main sequence evolution of their host stars, this process may provide an avenue which continually channels heavy elements onto the surface of the white dwarfs. We suggest that this scenario provides an explanation for the recently discovered Calcium line variation in G29-38.
Dynamics and instabilities in exoplanetary systems
Authors: Ford Eric B. 
Published: May 2008

AbstractExtrasolar planet surveys have discovered over two dozen multiple planet systems. As radial velocity searches push towards higher precisions and longer survey durations, they can be expected to discover an even higher fraction of multiple planet systems. Combined with radial velocity data, dynamical studies of these systems can constrain planet masses and inclinations, measure the significance of resonant and secular interactions, and provide insights into the formation and evolution of these systems. Here, we review the dynamical properties of known extrasolar multiple planet systems and their implications for planet formation theory. We conclude by outlining pressing questions to be addressed by a combination of future observations and theoretical research.
Analysis of near-separatrix motion in planetary systems
Authors: Wang Su , Zhou Ji-Lin 
Published: May 2008

AbstractNear-separatrix motion is a kind of motion of two planets with their relative apsidal longitude near the boundary between libration and circulation. Observed multiple planetary systems seem to favor near-separatrix motions between neighboring planets. In this report, we study the probability that near-separatrix motion occurs with both the linear secular system and full three-body systems. We find that generally the ratio of near-separatrix motion is small unless the eccentricities of the two planets differ from each other by an order of magintude, or they are in mean motion resonance. To explore the dynamical procedures causing the near-separatrix motion, we suppose a modification to scattering model by adding a mass-accretion process during the protoplanet growth. Statistics on the modified scattering model indicate that the probability of the final planet pairs in near-separatrix motion is high (∼ 85%), which may explain the high occurrence of near-separatrix motions in observed planetary systems.
Retrograde resonances in compact multi-planetary systems: a feasible stabilizing mechanism
Authors: Gayon Julie , Bois Eric 
Published: May 2008

AbstractMulti-planet systems detected until now are in most cases characterized by hot-Jupiters close to their central star as well as high eccentricities. As a consequence, from a dynamical point of view, compact multi-planetary systems form a variety of the general N-body problem (with N ≥ 3), whose solutions are not necessarily known. Extrasolar planets are up to now found in prograde (i.e. direct) orbital motions about their host star and often in mean-motion resonances (MMR). In the present paper, we investigate a theoretical alternative suitable for the stability of compact multi-planetary systems. When the outer planet moves on a retrograde orbit in MMR with respect to the inner planet, we find that the so-called retrograde resonances present fine and characteristic structures particularly relevant for dynamical stability. We show that retrograde resonances and their resources open a family of stabilizing mechanisms involving specific behaviors of apsidal precessions. We also point up that for particular orbital data, retrograde MMRs may provide more robust stability compared to the corresponding prograde MMRs.
Persistent downregulation of hippocampal CREB mRNA parallels a Y‐maze deficit in adolescent rats following semi‐chronic amphetamine administration
Authors: Featherby T , Van Den Buuse M , Lubman D I , Lawrence A J 
Published: May 2008

Background and purpose:We investigated possible differences in the impact of chronic amphetamine administration during adolescence and adulthood on aspects of behaviour and brain chemistry.Experimental approach:Adult (n=32) and adolescent (n=32) male Sprague–Dawley rats were given either D‐amphetamine sulphate (10 mg kg−1 daily, i.p.) or saline (1 mL kg−1, i.p.) for 10 days. Rats were subsequently tested for anxiety‐like behaviour, learning and memory, and sensorimotor gating. Nine weeks later, rats received saline (1 mL kg−1) or acute amphetamine challenge (1.5 mg kg−1) and the expression levels of mRNA for tyrosine kinase B (TrkB) or cAMP response element‐binding protein (CREB) were measured in the hippocampus.Key results:The adolescent amphetamine pretreated group revealed a deficit in exploration on the Y‐maze during a 6 h retention test. The frequency of visits to the novel arm was 35% lower for the amphetamine group compared with controls. In parallel, a 43% decrease in hippocampal CREB mRNA, but not TrkB mRNA, was observed in periadolescent rats treated chronically with amphetamine 9 weeks earlier. None of the effects were detected in the adult treated cohort.Conclusions and implications:Chronic amphetamine treatment during periadolescence resulted in altered behaviour on the Y‐maze and persistent downregulation of hippocampal CREB mRNA expression. Given that this group had intact spatial learning and reference memory, it would appear that the deficits observed on the Y‐maze reflect a dysfunction in response to novelty. Because no effects of amphetamine treatment were observed in the adult cohort, these data suggest idiosyncratic sensitivity of periadolescence to the long‐term effects of psychostimulants.British Journal of Pharmacology (2008) 154, 417–428; doi:10.1038/bjp.2008.126
From ultrasocial to antisocial: a role for oxytocin in the acute reinforcing effects and long‐term adverse consequences of drug use?
Authors: McGregor I S , Callaghan P D , Hunt G E 
Published: May 2008

Addictive drugs can profoundly affect social behaviour both acutely and in the long‐term. Effects range from the artificial sociability imbued by various intoxicating agents to the depressed and socially withdrawn state frequently observed in chronic drug users. Understanding such effects is of great potential significance in addiction neurobiology. In this review we focus on the ‘social neuropeptide’ oxytocin and its possible role in acute and long‐term effects of commonly used drugs. Oxytocin regulates social affiliation and social recognition in many species and modulates anxiety, mood and aggression. Recent evidence suggests that popular party drugs such as MDMA and gamma‐hydroxybutyrate (GHB) may preferentially activate brain oxytocin systems to produce their characteristic prosocial and prosexual effects. Oxytocin interacts with the mesolimbic dopamine system to facilitate sexual and social behaviour, and this oxytocin‐dopamine interaction may also influence the acquisition and expression of drug‐seeking behaviour. An increasing body of evidence from animal models suggests that even brief exposure to drugs such as MDMA, cannabinoids, methamphetamine and phencyclidine can cause long lasting deficits in social behaviour. We discuss preliminary evidence that these adverse effects may reflect long‐term neuroadaptations in brain oxytocin systems. Laboratory studies and preliminary clinical studies also indicate that raising brain oxytocin levels may ameliorate acute drug withdrawal symptoms. It is concluded that oxytocin may play an important, yet largely unexplored, role in drug addiction. Greater understanding of this role may ultimately lead to novel therapeutics for addiction that can improve mood and facilitate the recovery of persons with drug use disorders.British Journal of Pharmacology (2008) 154, 358–368; doi:fn1
Crocetin improves the insulin resistance induced by high‐fat diet in rats
Authors: Sheng L , Qian Z , Shi Y , Yang L , Xi L , Zhao B , Xu X , Ji H 
Published: May 2008

Background and purpose:The amelioration of insulin resistance by treatment with crocetin is closely related to the hypolipidaemic effect. The present study is designed to clarify the insulin‐sensitizing mechanism of crocetin by elucidating the mechanism of regulation of lipid metabolism by crocetin.Experimental approach:Rats given a high‐fat diet were treated with crocetin for 6 weeks before hyperinsulinaemic–euglycaemic clamp. 14C‐palmitate was used as tracer to track the fate of non‐esterified fatty acids or as substrate to measure β‐oxidation rate. Triglyceride clearance in plasma and lipoprotein lipase activity in tissues were tested. Content of lipids in plasma and tissues was determined. Real‐time PCR was used to assay the level of mRNA from genes involved in non‐esterified fatty acid and triglyceride uptake and oxidation.Key results:Crocetin prevented high‐fat‐diet induced insulin resistance (increased clamp glucose infusion rate), raised hepatic non‐esterified fatty acid uptake and oxidation, accelerated triglyceride clearance in plasma, enhanced lipoprotein lipase activity in liver, and reduced the accumulation of detrimental lipids (DAG and long‐chain acyl CoA) in liver and muscle. Genes involved in hepatic lipid metabolism which are regulated by peroxisome proliferator‐activated receptor‐α, were modulated to accelerate lipid uptake and oxidation.Conclusions and implications:Through regulating genes involved in lipid metabolism, crocetin accelerated hepatic uptake and oxidation of non‐esterified fatty acid and triglyceride, and reduced lipid availability to muscle, thus decreasing lipid accumulation in muscle and liver, and consequently improving sensitivity to insulin.British Journal of Pharmacology (2008) 154, 1016–1024; doi:10.1038/bjp.2008.160; published online 12 May 2008
In vivopharmacological evaluation of compound 48/80‐induced airways oedema by MRI
Authors: Karmouty‐Quintana H , Blé F‐X , Cannet C , Zurbruegg S , Fozard J R , Page C P , Beckmann N 
Published: May 2008

Background and purpose:Allergen‐induced airways oedema in actively sensitized rats has been studied earlier by magnetic resonance imaging (MRI). We used MRI to follow the consequences of non‐immunological mast cell activation induced by compound 48/80 in the rat lungsin vivo.Experimental approach:Male naïve rats were scanned by MRI prior to and at several time points following intratracheal administration of the mast cell secretagogue, compound 48/80. The effects of a range of drugs on the response induced by compound 48/80 were studied.Key results:Strong fluid signals were detected by MRI in the lungs at 24 h after compound 48/80, correlating with increased protein concentration and inflammatory cell infiltration in bronchoalveolar lavage, and with perivascular oedema observed histologically. Pharmacological intervention demonstrated that the increase in MRI signal volume induced by compound 48/80 24 h after challenge was blocked by disodium cromoglycate and the glucocorticoid, budesonide. Pretreatment with wortmannin, capsazepine, DNK333 (a dual neurokinin (NK) 1 and NK2 antagonist) or the anti‐allergy drug CGS8515, but not indomethacin, resulted in partial inhibition.Conclusions and implications:Compound 48/80 induced a complex inflammatory reaction which did not solely involve mast cell degranulation but also activation of sensory nerves and was qualitatively similar to allergen challenge. Changes observed by MRI correlated with decreases in protein concentration in BAL fluid. However, the magnitude of the changes detected was greater using MRI. Our results demonstrate that MRI is a sensitive and efficient tool to assess the effects of drugs on lung inflammation.British Journal of Pharmacology(2008)154, 1063–1072; doi:10.1038/bjp.2008.174; published online 12 May 2008
Brain oxytocin receptors mediate ejaculation elicited by 7‐hydroxy‐2‐(di‐N‐propylamino) tetralin (7‐OH‐DPAT) in anaesthetized rats
Authors: Clément P , Peeters M , Bernabé J , Denys P , Alexandre L , Giuliano F 
Published: May 2008

Background and purpose:The involvement of the neuropeptide oxytocin in the control of male sexual responses is documented although its exact mechanisms of action, and especially the site(s) of action, are not fully delineated. In order to clarify this issue, we tested the effects of a peptide oxytocin antagonist delivered through different routes on sexual responses elicited, in anaesthetized male rats, by i.c.v. 7‐hydroxy‐2‐(di‐N‐propylamino) tetralin (7‐OH‐DPAT), a dopamine agonist, preferentially active on D3receptors.Experimental approach:Seminal vesicle pressure (SVP) and bulbospongiosus muscle (BS) electromyograms were recorded as physiological markers of emission and expulsion phases of ejaculation respectively and intracavernosal pressure (ICP) was monitored as a physiological marker of erection.Key results:When injected i.v., the oxytocin antagonist did not impair 7‐OH‐DPAT‐induced SVP and ICP responses while BS burst frequency was diminished. When delivered i.c.v., the oxytocin antagonist dose‐dependently inhibited occurrence of 7‐OH‐DPAT‐induced sexual responses. When delivered intrathecally (i.t.) at the level of the 6thlumbar (L6) segment, but not the 13ththoracic (T13) segment, the oxytocin antagonist reduced the duration of BS responses and the occurrence of ejaculation without impairing ICP responses.Conclusions and implications:Brain oxytocin receptors mediate male sexual responses elicited by i.c.v. 7‐OH‐DPAT in anaesthetized rats whereas L6 spinal oxytocin receptors only impair the occurrence of ejaculation. Peripheral oxytocin receptors are marginally involved in 7‐OH‐DPAT‐induced sexual responses. These findings should be considered for the development of potential pharmacological treatment of premature ejaculation in man.British Journal of Pharmacology(2008)154, 1150–1159; doi:10.1038/bjp.2008.176; published online 12 May 2008
Endothelial nitric oxide attenuates Na+/Ca2+exchanger‐mediated vasoconstriction in rat aorta
Authors: Zhao J , Majewski H 
Published: May 2008

Background and purpose:The Na+/Ca2+exchanger (NCX) may be an important modulator of Ca2+entry and exit. The present study investigated whether NCX was affected by prostacyclin and nitric oxide (NO) released from the vascular endothelium, as NCX contains phosphorylation sites for PKA and PKG.Experimental approach:Rat aortic rings were set up in organ baths. Tension was measured across the ring with a force transducer.Key results:Lowering extracellular [Na+] ([Na+]o) to 1.18 mMinduced vasoconstriction in rat endothelium‐denuded aortic rings. This effect was blocked by the NCX inhibitor KB‐R7943 (2‐2‐[4‐(4‐nitrobenzyloxy)phenyl] ethyl isothiourea methanesulphonate; 1 μM). In endothelium‐intact aortic rings, decreasing [Na+]odid not constrict the aortic rings significantly, but after treatment with the guanylate cyclase inhibitor ODQ (1H‐[1,2,4]oxadiazolo[4,3‐a]quinoxalin‐1‐one; 1 μM) or the NOS inhibitorL‐NAME (Nω‐nitro‐L‐arginine methyl ester; 50 μM), a vasoconstriction that was similar in size to that in endothelium‐denuded preparations was evident. The vasorelaxation induced by the NO donor sodium nitroprusside sodium nitroprusside dihydrate (30 nM) was the same in the endothelium‐denuded aortic rings preconstricted with either low Na+(1.18 mM), the thromboxane A2 agonist U46619 (9,11‐dideoxy‐9α, 11α‐methanoepoxy prostaglandin F2α; 0.1 μM) or high K+(80 mM).Conclusions and implications:The results suggest that the endothelium inhibits NCX operation via guanylate cyclase/NO. This is stronger than for other constrictors such as phenylephrine and may relate to concomitant NCX‐stimulated NO release from the endothelium. This finding may be important where NCX operates in reverse mode, such as during ischaemia, and highlights a new mechanism whereby the endothelium modulates Ca2+homoeostasis in vascular smooth muscle.British Journal of Pharmacology(2008)154, 982–990; doi:10.1038/bjp.2008.178; published online 12 May 2008
Interactions between cell death induced by statins and 7‐ketocholesterol in rabbit aorta smooth muscle cells
Authors: Martinet W , Schrijvers D M , Timmermans J‐P , Bult H 
Published: May 2008

Background and purpose:7‐Ketocholesterol, an oxysterol present in atherosclerotic lesions, induces smooth muscle cell (SMC) death, thereby destabilizing plaques. Statins protect patients from myocardial infarction, though they induce SMC apoptosis. We investigated whether statins and 7‐ketocholesterol exerted additive cell death effects.Experimental approach:Cultured rabbit aorta SMCs (passage 2–6) were exposed to 7‐ketocholesterol with or without fluvastatin, simvastatin or pravastatin. Uptake of neutral red (NR), monolayer protein, cleavage of the pan‐caspase substrate Asp‐Glu‐Val‐Asp‐rhodamine110, cell morphology (light and electron microscopy) and processing of microtubule‐associated protein 1 light chain 3 (LC3, immunoblot) were determined.Key results:NR uptake declined upon 18 h exposure to 25 μM 7‐ketocholesterol (−41±3%, n=13), 100 μM fluvastatin (−59%) or 30–100 μM simvastatin (−28 to −74%). Oxysterol and high statin concentrations exerted additive effects, but lower concentrations (fluvastatin 10–30 μM, simvastatin 1–10 μM) partly reversed viability loss. 7‐Ketocholesterol caused intense cytoplasmic vacuolization, processing of LC3‐I to LC3‐II, but little caspase activation (increase 29.5%). Fluvastatin (10–100 μM, 70–545% increase) and simvastatin (3–100 μM 43–322% increase) induced caspase activation without LC3 processing, but failed to activate caspases in 7‐ketocholesterol‐treated SMCs. Pravastatin up to 100 μM was always inactive.Conclusions and implications:7‐Ketocholesterol caused SMC death, mainly via autophagic vesicle formation with LC3 processing, whereas lipophilic statins evoked SMC apoptosis. Cell death following 7‐ketocholesterol and low statin concentrations were not additive, presumably because the autophagic process interfered with statin‐induced caspase activation. This further illustrates that drug effects in normal SMCs are not necessarily predictive for activities in atherosclerotic settings.British Journal of Pharmacology (2008) 154, 1236–1246; doi:10.1038/bjp.2008.181; published online 12 May 2008
Molecular control of the glucan synthase-like protein NaGSL1 and callose synthesis during growth of Nicotiana alata pollen tubes
Authors: Brownfield Lynette , Wilson Sarah , Newbigin Ed , Bacic Antony , Read Steve 
Published: May 2008

The protein NaGSL1 (Nicotiana alata glucan synthase-like 1) is implicated in the synthesis of callose, the 1,3-β-glucan that is the major polysaccharide in the walls of N. alata (flowering tobacco) pollen tubes. Here we examine the production, intracellular location and post-translational processing of NaGSL1, and relate each of these to the control of pollen-tube callose synthase (CalS). The 220 kDa NaGSL1 polypeptide is produced after pollen-tube germination and accumulates during pollen-tube growth, as does CalS. A combination of membrane fractionation and immunoelectron microscopy revealed that NaGSL1 was present predominantly in the endoplasmic reticulum and Golgi membranes in younger pollen tubes when CalS was mostly in an inactive (latent) form. In later stages of pollen-tube growth, when CalS was present in both latent and active forms, a greater proportion of NaGSL1 was in intracellular vesicles and the plasma membrane, the latter location being consistent with direct deposition of callose into the wall. N. alata CalS is activated in vitro by the proteolytic enzyme trypsin and the detergent CHAPS, but in neither case was activation associated with a detectable change in the molecular mass of the NaGSL1 polypeptide. NaGSL1 may thus either be activated by the removal of a few amino acids or by the removal of another protein that inhibits NaGSL1. These findings are discussed in relation to the control of callose biosynthesis during pollen germination and pollen-tube growth.