Spontaneous Release

The semilogarithmic plot is resolved into components by the method of subtraction, and the half-time (fi/2) of each component is determined graphically. The rate of efflux of labeled solute (k, %/min) is calculated from k = 0.693/fi/2 x 100 (Cutler et al., 1971). This method reveals a fast component for amino acids, as well as other compounds of different molecular weight. It has a ty2 of 2-3 mm in tissue slices for all components studied and probably represents the washout of adherent medium. The slow component is the loss of isotope from the tissue as a whole it is different for different substances and is sensitive to temperature changes The apparent first order kinetics of the slow component does not preclude the possibility that the amino acids are lost from different tissue compartments at different rates. This does, however, suggest that the loss from one major compartment to another may be rate-limiting for clearance from the whole tissue (Cutler et al., 1971). In brain slices, the slow exponential loss of amino acids is linear throughout 40 min of superfusion, and at the end of this time, 60-70% of the labeled amino acids are recovered in the effluent (Cutler et al., 1971) 

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Giesbrecht, H., K. Hess, W. Leuckel, and B. Maurer, 1981. Analysis of explosion hazards on spontaneous release of inflammable gases into the atmosphere. Part 1 Propagation and deflagration of vapor clouds on the basis of bursting tests on model vessels. Ger. Chem. Eng. 4 305-314. 

Bio Hi4 + O2 B2 O3 + H2 O (unbalanced) The two starting materials are stored in separate containers. When mixed, they ignite spontaneously, releasing large amounts of energy. Both fuel materials should run out at the same time because this minimizes the excess mass that the rocket must carry. If the total mass of both components is to be 12.0 X 10 kg, what mass of liquid oxygen and what mass of decaborane should be used ... 

Optical emission is a result of electron impact excitation or dissociation, or ion impact. As an example, the SiH radical is formed by electron impact on silane, which yields an excited or superexcited silane molecule (e + SiHa SiH -t-e ). The excess energy in SiH is released into the fragments SiH SiH -I-H2 + H. The excited SiH fragments spontaneously release their excess energy by emitting a photon at a wavelength around 414 nm. the bluish color of the silane discharge. In addition, the emission lines from Si. H, and H have also been observed at 288, 656, and 602 nm, respectively. 

Curie P, Laborde A (1903) On the heat spontaneously released by the salts of radium. Comptes Rendus de Seances de I academie de Sciences 86 673... 

A drum containing distillation wastes of ethyl carbonate, ethyl bromoacetate and another bromoester (not intelligibly named) burst spontaneously, releasing a cloud which caused considerable lachrymation and respiratory irritation in nearby housing. Carbon dioxide was doubtless generated, but whether by water contamination or a previously unknown catalytic reaction of the known contents is unclear to the editor. 

Stimulation of the motoneuron releases acetylcholine onto the muscle endplate and results in contraction of the muscle fiber. Contraction and associated electrical events can be produced by intra-arterial injection of ACh close to the muscle. Since skeletal muscle does not possess inherent myogenic tone, the tone of apparently resting muscle is maintained by spontaneous and intermittent release of ACh. The consequences of spontaneous release at the motor endplate of skeletal muscle are small depolarizations from the quantized release of ACh, termed miniature endplate potentials (MEPPs) [15] (seeCh. 10). Decay times for the MEPPs range between l and 2 ms, a duration similar to the mean channel open time seen with ACh stimulation of individual receptor molecules. Stimulation of the motoneuron results in the release of several hundred quanta of ACh. The summation of MEPPs gives rise to a postsynaptic excitatory potential (PSEP),... 

Pacifici R, Rifas L, Teitelbaum S, Slatopolsky E, McCracken R, Bergfeld M, Lee W, Avioli LV, Peck WA (1987) Spontaneous release of interleukin 1 from human blood monocytes refiects bone formation in idiopathic osteoporosis. Proc Nad Acad Sci USA 84 4616-4620... 

There have been no reports of sparks occurring in uterine cells. Ca2+ sparks are considered to be due to spontaneous releases of Ca2+ from RyR. 

Brading Fabiato showed years ago in the heart that quite a lot of Ca2+ is needed in the SR before there were these spontaneous releases of Ca2+. 

Brading Do your expression cells generate sparks Do you get spontaneous release from the SR in these cells You showed some of these cells where the SR was overloaded with Ca2+, and I wondered whether there is a difference in the behaviour of the SR depending on the amount of intracellular Ca2+. This is going back to this business of stretch-activated channels and whether if you stretch the SR by superfilling it with Ca2+ and getting some osmotic expansion it changes its behaviour. 

SN P spontaneously releases N O both thermally and photochemically [61-65], but is quite stable in the dark and in aqueous in vitro physiological media [66]. This implies that absorption of heat and light energy induces electron transfer from the Fe2+ center to the N 0+ ligand, resulting in weakening of the Fe-N O bond and subsequent release of NO [65]. SNP also decomposes in an aqueous environment in the presence of biological reductants [65, 66] and some transition metal ions to produce nitric oxide. 

SIN-1 spontaneously releases NO and superoxide under physiological conditions thereby stimulating cGMP production. SIN-1 significantly decreased expression of P-selectin and both total and activated GP Ilb/IIIa and also promoted reversal of activated GP Ilb/IIIa complex in platelets stimulated with thrombin [61]. However, in rats SIN-1 could only partially reduce the degree of platelet activation [62]. SIN-1 stimulated VASP Ser157 phosphorylation and inhibited GP Ilb/IIIa activation. Threshold... 

Non-heteroatom-substituted carbene complexes can also be generated by treatment of electrophilic transition metal complexes with ylides (e.g. diazoalkanes, phosphorus ylides, nucleophilic carbene complexes, etc. Section 3.1.3). Alkyl complexes with a leaving group in the a-position are formed as intermediates. These alkyl complexes can undergo spontaneous release of the leaving group to yield a carbene complex (Figure 3.2). 

Important functional interactions of the dopaminergic and other key neurochemical systems have also been demonstrated. Durkin et al., (1986) reported that dopamine in the septum inhibits acetylcholine release in the hippocampus, whilst destruction of the A-10 septal dopaminergic pathways in mice results in increased choline acetyltransferase (Yanai et al., 1993). Pharmacological reduction of nigral dopamine levels to 5% of normal in guinea pigs results in a marked increase (over 70%) in the spontaneous release of acetyl-... 

Based on the stereospecific transketolase-catalyzed ketol transfer from hydroxy-pyruvate (20) to D-glyceraldehyde 3-phosphate (18), we have thus developed a practical and efficient one-pot procedure for the preparation of the valuable keto-sugar 19 on a gram scale in 82% overall yield [29]. Retro-aldolization of D-fructose 1,6-bisphosphate (2) in the presence of FruA with enzymatic equilibration of the C3 fragments is used as a convenient in-situ source of the triose phosphate 18 (Scheme 2.2.5.8). Spontaneous release of CO2 from the ketol donor 20 renders the overall synthetic reaction irreversible [29]. 

The transmitter is present throughout the cholinergic neurones and exists within the axon terminals in vesicles. About 1% of the vesicles are the readily releasable store that maintains transmitter release but more than 80% is in motor nerve endings in the releasable store, which is released in response to a nerve impulse. The remainder of ACh is in the so-called stationary store. The release of ACh may be spontaneous or in response to nerve impulses. Spontaneous release of ACh results in the production of random miniature endplate potentials. It is, however, in response to a nerve impulse that we see a large release of ACh provided there is adequate calcium present in the extracellular fluid. Evoked release of ACh usually results in the production of an endplate potential due to depolarisation of the motor endplate. 

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