Mast cells promote homeostasis by limiting endothelin-1-induced toxicity

Endothelin-1 (ET-1) is a 21-amino-acid peptide, derived from vascular endothelial cells, with potent vasoconstrictor activity. ET-1 has been implicated in diverse physiological or pathological processes, including the vascular changes associated with sepsis. However, the factors that regulate ET-1-associated toxicity during bacterial infections, or in other settings, are not fully understood. Both the pathology associated with certain allergic and autoimmune disorders, and optimal host defence against bacterial and parasitic infections are mediated by mast cells. In vitro, mast cells can produce ET-1 (ref. 11), undergo ET-1-dependent and endothelin-A receptor (ET(A))-dependent activation, and release proteases that degrade ET-1 (ref. 14). Although the potential relationships between mast cells and the ET-1 system thus may be complex, the importance of interactions between ET-1 and mast cells in vivo is obscure. Here we show that ET(A)-dependent mast-cell activation can diminish both ET-1 levels and ET-1-induced pathology in vivo, and also can contribute to optimal survival during acute bacterial peritonitis. These findings identify a new biological function for mast cells: promotion of homeostasis by limiting the toxicity associated with an endogenous mediator.     

The evolution of müllerian mimicry in multispecies communities

Prey species that are unprofitable to attack often share conspicuous colours and patterns with other coexisting defended species. This phenomenon, termed müllerian mimicry, has long been explained as a consequence of selection on defended prey to adopt a common way of advertising their unprofitability. However, studies using two unpalatable prey types have not always supported this theory. Here we show, using a system of humans hunting for computer-generated prey, that predators do not always generate strong selection for mimicry when there are two unprofitable prey types. By contrast, we demonstrate that when predators are faced with a range of different prey species, selection on unprofitable prey to resemble one another can be intense. Here the primary selective force is not one in which predators evaluate the profitabilities of distinct prey types independently, but one in which predators learn better to avoid unprofitable phenotypes that share traits distinguishing them from profitable prey. This need to simplify decision making readily facilitates the spread of imperfect mimetic forms from rarity, and suggests that müllerian mimicry is more likely to arise in multispecies communities.     

Decline of surface temperature and salinity in the western tropical Pacific Ocean in the Holocene epoch

In the present-day climate, surface water salinities are low in the western tropical Pacific Ocean and increase towards the eastern part of the basin. The salinity of surface waters in the tropical Pacific Ocean is thought to be controlled by a combination of atmospheric convection, precipitation, evaporation and ocean dynamics, and on interannual timescales significant variability is associated with the El Ni?o/Southern Oscillation cycles. However, little is known about the variability of the coupled ocean-atmosphere system on timescales of centuries to millennia. Here we combine oxygen isotope and Mg/Ca data from foraminifers retrieved from three sediment cores in the western tropical Pacific Ocean to reconstruct Holocene sea surface temperatures and salinities in the region. We find a decrease in sea surface temperatures of approximately 0.5 degrees C over the past 10,000 yr, whereas sea surface salinities decreased by approximately 1.5 practical salinity units. Our data imply either that the Pacific basin as a whole has become progressively less salty or that the present salinity gradient along the Equator has developed relatively recently.     

短寿命β-放射性核12B磁矩精确测量

通过对核反应¹¹B(d, p) ¹²B的入射束流能量和¹²B反冲核的反冲角度的选择产生极化的β放射性核¹²B(I^π=1⁺, T_1/2=20.18 ms). 在中国第一台β-NMR和β-NQR谱仪上, 我们利用β-NMR技术测量了短寿命核¹²B的磁矩. 通过精确的奈特位移修正后, 得到¹²B的核磁矩μ ＝(0.99993 ± 0.00048) nm, g因子g =(0.99993 ± 0.00048).     

Large eddy simulation of a particle—laden turbulent plane jet

Gas-solid two-phase turbulent plane jet is applied to many natural situations and in engineering systems.To predict the particle dispersion in the gas jet is of great importance in industrial applications and in the designing of engineering systems.A large eddy simulation of the two-phase plane jet eas conducted to in-vestigate the particle dispersion patterns.The particles with Stokes numbers equal to 0.0028,0.3,2.5,28(corresponding to particle diamster 1μm,10μm,30μm,100μm,respectively)in Re=11300 gas flow were strudied.The simulation results of gas phase motion agreed well with previous experimental results.And the simulation results of the solid particles motion showed that particles with different Stokes number have dif-ferent spatial dispersion;and that particles with intermediate Stokes number have the largest dispersion ratio.     

Role of plasminogen activator-plasmin system in tumor angiogenesis

New blood formation or angiogenesis has become a key target in therapeutic strategies aimed at inhibiting tumor growth and other diseases associated with neovascularization. Angiogenesis is associated with important extracellular remodeling involving different proteolytic systems among which the plasminogen system plays an essential role. It belongs to the large serine proteinase family and can act directly or indirectly by activating matrix metalloproteinases or by liberating growth factors and cytokines sequestered within the extracellular matrix. Migration of endothelial cells is associated with significant upregulation of proteolysis and, conversely, immunoneutralization or chemical inhibition of the system reduces angiogenesis in vitro. On the other hand, genetically altered mice developed normally without overt vascular anomalies indicating the possibility of compensation by other proteases in vivo. Nevertheless, they have in some experimental settings revealed unanticipated roles for previously characterized proteinases or their inhibitors. In this review, the complex mechanisms of action of the serine proteases in pathological angiogenesis are summarized alongside possible therapeutic applications.     

Cellular and molecular action of the putative GABA-mimetic,gabapentin

Gabapentin was originally designed as an anti-convulsant gamma-aminobutyric acid (GABA) mimetic capable of crossing the blood-brain barrier. In the present review we show that although gabapentin is not a GABA mimetic, it has great utility as an add-on therapy for epilepsy and as a first-line treatment for neuropathic pain. We summarise the studies that have been performed which demonstrate that gabapentin appears to interact with a novel binding site expressed at high density within the central nervous system (CNS), namely the alpha2delta voltage-dependent calcium channel subunit. The review continues by examining the effects of gabapentin on calcium channel function and neurotransmitter release before, in the latter part of the review, summarising the more recently discovered actions of gabapentin in relation to intracellular signalling.