scholarly journals Depolarization-Induced Ca2+ Entry Preferentially Evokes Release of Large Quanta in the Developing Xenopus Neuromuscular Junction

2010 ◽  
Vol 104 (5) ◽  
pp. 2730-2740 ◽  
Author(s):  
Xiao-Ping Sun ◽  
Bo-Ming Chen ◽  
Olav Sand ◽  
Yoshi Kidokoro ◽  
Alan D. Grinnell
Keyword(s):  
Synaptic Vesicles ◽  
Channel Blocker ◽  
Direct Injection ◽  
External Solution ◽  
Neuromuscular Synapses ◽  
Quantal Size ◽  
Amplitude Histogram ◽  
Wide Range ◽  
Patch Pipette ◽  
Second Peak

The amplitude histogram of spontaneously occurring miniature synaptic currents (mSCs) is skewed positively at developing Xenopus neuromuscular synapses formed in culture. To test whether the quantal size of nerve-evoked quanta (eSCs) distributes similarly, we compared the amplitude histogram of single quantum eSCs in low external Ca2+ with that of mSCs and found that nerve stimulation preferentially released large quanta. Depolarization of presynaptic terminals by elevating [K+] in the external solution or by direct injection of current through a patch pipette increased the mSC frequency and preferentially, but not exclusively, evoked the release of large quanta, resulting in a second broad peak in the amplitude histogram. Formation of the second peak under these conditions was blocked by the N-type Ca2+ channel blocker, ω-conotoxin GVIA. In contrast, when the mSC frequency was elevated by thapsigargin- or caffeine-induced mobilization of internal Ca2+, formation of the second peak did not occur. We conclude that the second peak in the amplitude histogram is generated by Ca2+ influx through N-type Ca2+ channels, causing a local elevation of internal Ca2+. The mSC amplitude in the positively skewed portion of the histogram varied over a wide range. A competitive blocker of acetylcholine (ACh) receptors, d-tubocurarine, reduced the amplitude of smaller mSCs in this range relatively more than that of larger mSCs, suggesting that this variation in the mSC amplitude is due to variable amounts of ACh released from synaptic vesicles. We suggest that Ca2+ influx through N-type Ca2+ channels preferentially induces release of vesicles with large ACh content.

scholarly journals An essential role of acetylcholine-glutamate synergy at habenular synapses in nicotine dependence

eLife ◽  
2015 ◽  
Vol 4 ◽  
Author(s):  
Silke Frahm ◽  
Beatriz Antolin-Fontes ◽  
Andreas Görlich ◽  
Johannes-Friedrich Zander ◽  
Gudrun Ahnert-Hilger ◽  
...  
Keyword(s):  
Synaptic Vesicles ◽  
Critical Role ◽  
Conditioned Reward ◽  
Quantal Size ◽  
Medial Habenula ◽  
Vesicular Transporters ◽  
Circuit Function ◽  
And Behavior ◽  
Presynaptic Facilitation

A great deal of interest has been focused recently on the habenula and its critical role in aversion, negative-reward and drug dependence. Using a conditional mouse model of the ACh-synthesizing enzyme choline acetyltransferase (Chat), we report that local elimination of acetylcholine (ACh) in medial habenula (MHb) neurons alters glutamate corelease and presynaptic facilitation. Electron microscopy and immuno-isolation analyses revealed colocalization of ACh and glutamate vesicular transporters in synaptic vesicles (SVs) in the central IPN. Glutamate reuptake in SVs prepared from the IPN was increased by ACh, indicating vesicular synergy. Mice lacking CHAT in habenular neurons were insensitive to nicotine-conditioned reward and withdrawal. These data demonstrate that ACh controls the quantal size and release frequency of glutamate at habenular synapses, and suggest that the synergistic functions of ACh and glutamate may be generally important for modulation of cholinergic circuit function and behavior.

scholarly journals The nature of the radius valley

2020 ◽  
Vol 643 ◽  
pp. L1 ◽  
Author(s):  
Julia Venturini ◽  
Octavio M. Guilera ◽  
Jonas Haldemann ◽  
María P. Ronco ◽  
Christoph Mordasini
Keyword(s):  
Mass Loss ◽  
Size Distribution ◽  
Point Of View ◽  
Parameter Study ◽  
Type I ◽  
Water Ice ◽  
Wide Range ◽  
Orbital Periods ◽  
Gas Accretion ◽  
Second Peak

The existence of a radius valley in the Kepler size distribution stands as one of the most important observational constraints to understand the origin and composition of exoplanets with radii between those of Earth and Neptune. In this work we provide insights into the existence of the radius valley, first from a pure formation point of view and then from a combined formation-evolution model. We run global planet formation simulations including the evolution of dust by coagulation, drift, and fragmentation, and the evolution of the gaseous disc by viscous accretion and photoevaporation. A planet grows from a moon-mass embryo by either silicate or icy pebble accretion, depending on its position with respect to the water ice line. We include gas accretion, type I–II migration, and photoevaporation driven mass-loss after formation. We perform an extensive parameter study evaluating a wide range of disc properties and initial locations of the embryo. We find that due to the change in dust properties at the water ice line, rocky cores form typically with ∼3 M⊕ and have a maximum mass of ∼5 M⊕, while icy cores peak at ∼10 M⊕, with masses lower than 5 M⊕ being scarce. When neglecting the gaseous envelope, the formed rocky and icy cores account naturally for the two peaks of the Kepler size distribution. The presence of massive envelopes yields planets more massive than ∼10 M⊕ with radii above 4 R⊕. While the first peak of the Kepler size distribution is undoubtedly populated by bare rocky cores, as shown extensively in the past, the second peak can host half-rock–half-water planets with thin or non-existent H-He atmospheres, as suggested by a few previous studies. Some additional mechanisms inhibiting gas accretion or promoting envelope mass-loss should operate at short orbital periods to explain the presence of ∼10–40 M⊕ planets falling in the second peak of the size distribution.

Pharmacological Properties of Excitatory Neuromuscular Synapses in the Locust

1968 ◽  
Vol 49 (2) ◽  
pp. 341-361
Author(s):  
P. N. R. USHERWOOD ◽  
P. MACHILI
Keyword(s):  
Muscle Fibres ◽  
Amino Group ◽  
Mechanical Responses ◽  
Neuromuscular Synapses ◽  
Level Of Activity ◽  
Excitatory Activity ◽  
Wide Range ◽  
Nerve Muscle ◽  
Related Compounds ◽  
Stimulation Of

1. The effects of a wide range of amino acids and related compounds on retractor unguis nerve-muscle preparations from the locust, grasshopper and cockroach have been investigated. 2. L-glutamate is the most active excitatory substance. The presence of two acidic groups and one amino group is essential for excitatory activity while the position of the amino group is of some importance in determining the level of activity. 3. When L-glutamate is applied iontophoretically to the muscle fibres, ‘glutamate’ depolarizations are recorded only at the synaptic sites. Other evidence that the action of glutamate is restricted to the synaptic sites is presented. 4. Perfusion of isolated locust retractor unguis nerve-muscle preparations with locust haemolymph does not markedly affect the neurally evoked mechanical responses. It appears that locust haemolymph contains little ‘free’ L-glutamate. 5. Four acidic amino aids have been identified in the perfusate from isolated retractor unguis preparations namely, glycine, alanine, aspartate and L-glutamate. However, only L-glutamate increases in concentration during stimulation of the retractor unguis nerve.

A qualitative evaluation of the role of simulation in policy development for service improvement

2017 ◽  
Vol 4 (1) ◽  
pp. 19-22 ◽  
Author(s):  
Thomas Blanks ◽  
Nicholas Woodier ◽  
Bryn Baxendale ◽  
Mark Fores ◽  
Lynn Fullerton
Keyword(s):  
Drug Administration ◽  
Policy Development ◽  
Direct Injection ◽  
Qualitative Evaluation ◽  
Service Improvement ◽  
Semistructured Interview ◽  
Training Requirements ◽  
Wide Range ◽  
Simulation Based ◽  
New Policies

ObjectiveTo evaluate the efficacy of simulation-based techniques to prospectively assess developing polices prior to implementation.MethodsA self-selected sample of nursing staff from a local, acute hospital reviewed a draft intravenous drug administration policy before simulating drug administration of either an infusion or direct injection. The participants completed a postsimulation questionnaire regarding the new policy and simulation, took part in a semistructured interview and were observed during the simulation with their consent.Results10 staff attended the simulation. The emergent themes identified a wide range of factors relating to the everyday usability and practicalities of the policy. There were issues surrounding inconsistent language between different clinical teams and training requirements for the new policy.ConclusionSimulation, using simple scenarios, allows the safe evaluation of new policies before publication to ensure they are appropriate for front-line use. It engages staff in user-centred design in their own healthcare system.

Effect of Fuel Injection Timing Relative to Ignition Timing on the Natural-Gas Direct-Injection Combustion

2001 ◽  
Author(s):  
Zuohua Huang ◽  
Seiichi Shiga ◽  
Takamasa Ueda ◽  
Nobuhisa Jingu ◽  
Hisao Nakamura ◽  
...  
Keyword(s):  
Heat Release ◽  
Late Stage ◽  
Equivalence Ratio ◽  
Fuel Injection ◽  
Direct Injection ◽  
Injection Timing ◽  
Ignition Timing ◽  
Fuel Injection Timing ◽  
Initial Stage ◽  
Wide Range

Abstract Effect of fuel injection timing relative to ignition timing on natural gas direct-injection combustion was studied by using a rapid compression machine. The ignition timing was fixed at 80 ms from the compression start. When the injection timing was relatively earlier (injection start at 60 ms), the heat release pattern showed slower burn in the initial stage and faster burn in the late stage, which is similar to that of flame propagation of a premixed gas. In contrast to this, when the injection timing was relatively later (injection start at 75 ms), the heat release rate showed faster burn in the initial stage and slower burn in the late stage, which is similar to that of diesel combustion. The shortest duration was realized at the injection end timing of 80 ms (the same timing as the ignition timing) over the wide range of equivalence ratio. The degree of charge stratification and the intensity of turbulence generated by the fuel jet is considered to cause these behaviors. Earlier injection leads to longer duration of the initial combustion, whereas the later injection does longer duration of the late combustion. Earlier injection showed relatively lower CO emission while later injection produces relatively lower NOx emission. It was suggested that earlier injection leads to lower mixture stratification combustion and later injection leads to higher mixture stratification combustion. Combustion efficiency maintained high value over the wide range of equivalence ratio.

scholarly journals Investigation on Blending Effects of Gasoline Fuel with N-Butanol, DMF, and Ethanol on the Fuel Consumption and Harmful Emissions in a GDI Vehicle

Energies ◽  
2019 ◽  
Vol 12 (10) ◽  
pp. 1845 ◽  
Author(s):  
Haifeng Liu ◽  
Xichang Wang ◽  
Diping Zhang ◽  
Fang Dong ◽  
Xinlu Liu ◽  
...  
Keyword(s):  
Steady State ◽  
Fuel Consumption ◽  
Large Fraction ◽  
Direct Injection ◽  
Transient State ◽  
Gasoline Direct Injection ◽  
Nox Emissions ◽  
Fuel Blends ◽  
Wide Range ◽  
Oxygenated Fuel

The effects of three kinds of oxygenated fuel blends—i.e., ethanol-gasoline, n-butanol-gasoline, and 2,5-dimethylfuran (DMF)-gasoline-on fuel consumption, emissions, and acceleration performance were investigated in a passenger car with a chassis dynamometer. The engine mounted in the vehicle was a four-cylinder, four-stroke, turbocharging gasoline direct injection (GDI) engine with a displacement of 1.395 L. The test fuels include ethanol-gasoline, n-butanol-gasoline, and DMF-gasoline with four blending ratios of 20%, 50%, 75%, and 100%, and pure gasoline was also tested for comparison. The original contribution of this article is to systemically study the steady-state, transient-state, cold-start, and acceleration performance of the tested fuels under a wide range of blending ratios, especially at high blending ratios. It provides new insight and knowledge of the emission alleviation technique in terms of tailoring the biofuels in GDI turbocharged engines. The results of our works showed that operation with ethanol–gasoline, n-butanol–gasoline, and DMF–gasoline at high blending ratios could be realized in the GDI vehicle without any modification to its engine and the control system at the steady state. At steady-state operation, as compared with pure gasoline, the results indicated that blending n-butanol could reduce CO2, CO, total hydrocarbon (THC), and NOX emissions, which were also decreased by employing a higher blending ratio of n-butanol. However, a high fraction of n-butanol increased the volumetric fuel consumption, and so did the DMF–gasoline and ethanol–gasoline blends. A large fraction of DMF reduced THC emissions, but increased CO2 and NOX emissions. Blending n-butanol can improve the equivalent fuel consumption. Moreover, the particle number (PN) emissions were significantly decreased when using the high blending ratios of the three kinds of oxygenated fuels. According to the results of the New European Drive Cycle (NEDC) cycle, blending 20% of n-butanol with gasoline decreased CO2 emissions by 5.7% compared with pure gasoline and simultaneously reduced CO, THC, NOX emissions, while blending ethanol only reduced NOX emissions. PN and particulate matter (PM) emissions decreased significantly in all stages of the NEDC cycle with the oxygenated fuel blends; the highest reduction ratio in PN was 72.87% upon blending 20% ethanol at the NEDC cycle. The high proportion of n-butanol and DMF improved the acceleration performance of the vehicle.

scholarly journals Effect of Sr-P Interaction on the Microstructure and Tensile Properties of A413.0 Type Alloys

2016 ◽  
Vol 2016 ◽  
pp. 1-11 ◽  
Author(s):  
A. M. Samuel ◽  
H. W. Doty ◽  
S. Valtierra ◽  
F. H. Samuel
Keyword(s):  
Heat Treatment ◽  
Tensile Properties ◽  
Solution Heat Treatment ◽  
Eutectic Silicon ◽  
Low Magnesium ◽  
The Third ◽  
Wide Range ◽  
Eutectic Si ◽  
Second Peak ◽  
Silicon Particles

The present study was performed on low magnesium A413.0 type alloys. The results show that strontium (Sr) is mainly concentrated in the silicon particles. Overmodification occurs when Sr precipitates in the form of Al2SrSi2, which takes place over a wide range of temperatures. The first peak occurs following the precipitation ofα-Al, the second peak is merged with the precipitation of eutectic silicon (Si), and the third peak is a posteutectic reaction. Introduction of phosphorus (P) to Sr-modified alloys leads to the formation of (Al,P,Sr)2O5compound, which reduces the modification effectiveness of Sr. Therefore, in the presence of P, the amount of added Sr should exceed 200 ppm. For the same levels of P, the tensile parameters of well modified alloys (233 ppm Sr) are relatively higher than those partially modified with Sr (about 60 ppm Sr) containing the same amount of P. During solution heat treatment, coarsening of the eutectic Si particles occurs by the growth of some particles at the expense of the dissolution of the smaller ones, as well as by the collision of nearby particles.

Numerical Simulation of Direct Injection Engine With Using Porous Medium

2012 ◽  
Author(s):  
Arash Mohammadi ◽  
Ali Jazayeri ◽  
Masoud Ziabasharhagh
Keyword(s):  
Porous Medium ◽  
Direct Injection ◽  
Combustion Process ◽  
Packed Bed ◽  
Published Data ◽  
Mixture Formation ◽  
Flammability Limits ◽  
Ic Engine ◽  
Engine Simulation ◽  
Wide Range

Porous media (PM) has interesting advantages in compared with free flame combustion due to the higher burning rates, the increased power range, the extension of the lean flammability limits, and the low emissions of pollutants. Future clean internal combustion (IC) engines should have had minimum emissions level (for both gaseous and particulate matter) under possible lowest fuel consumption permitted in a wide range of speed, loads and having good transient response. These parameters strongly depend on mixture formation and combustion processes which are difficult to be controlled in a conventional engine. This may be achieved by realization of homogeneous combustion process in engine. This paper deals with the simulation of direct injection IC engine equipped with a chemically inert PM, with cylindrical geometry to homogenize and stabilize the combustion of engine. A 3D numerical model for PM engine is presented in this study based on a modified version of the KIVA-3V code. Due to lack of any published data for PM engines, numerical results of thermal and combustion wave propagation in a porous medium are compared with experimental data of lean methane-air mixture under filtration in packed bed and very good agreement is seen. For PM engine simulation methane as a fuel is injected directly inside hot PM that is assumed, mounted in cylinder head. Lean mixture is formed and volumetric combustion occurs in PM and in-cylinder. Mixture formation, pressure and temperature distribution in both phases of PM and in-cylinder fluid with the production of pollutants CO and NO and also effects of injection time in the closed part of the cycle are studied.

Studies on lipopolysaccharides of Proteus

1971 ◽  
Vol 17 (11) ◽  
pp. 1385-1394 ◽  
Author(s):  
B. A. Dmitriev ◽  
N. A. Hinton ◽  
R. W. Lowe ◽  
J. K. N. Jones
Keyword(s):  
Molecular Weight ◽  
Acetic Acid ◽  
Weight Fraction ◽  
Low Molecular Weight ◽  
The Core ◽  
Wide Range ◽  
Homologous Antiserum ◽  
Main Components ◽  
Different Strains ◽  
Second Peak

The polysaccharide moieties of the lipopolysaccharides of serotyped strains of Proteus have been examined. The strains were selected to provide a wide range of serotypes. The primary acetic acid extracts of different strains of Proteus were fractionated on Sephadex G-50 and yielded three main components: a peak (I), which was composed mainly of polysaccharide; a second peak (II), the core polysaccharide, which contained heptose and phosphate; and a third component (III), which corresponded to a low molecular weight fraction and contained KDO and phosphate as well as other components. Peak I was not encountered in rough strains of Proteus. The chemical composition of the peaks obtained for S, SR, and R strains is discussed in relation to their agglutinating ability to homologous antiserum.

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