Mechanism indirect

We are not concerned here with the mechanism of nitrosation, but with the anticatalytic effect of nitrous acid upon nitration, and with the way in which this is superseded with very reactive compounds by an indirect mechanism for nitration. The term nitrous acid indicates all the species in a solution which, after dilution with water, can be estimated as nitrous acid. 

Prostacyclin (epoprostanol) is one of the few drugs effective for the treatment of Primary Pulmonary Hypertension (PPH) a rare but frequently fatal illness of young adults. Increased blood pressure in the pulmonary circulation leads to right-heart failure. Continuous infusion of epoprostanol leads to a decrease in blood pressure however, it is unclear whether this is due to direct dilator activity of the IP receptor acting on smooth muscle, or a more indirect mechanism. 

A change in the agitation intensity or gas flow rate will change 0. As a result, b, c0, and the total mass-transfer rate are affected. Thus, the effect of mixing in the vessel is considered by indirect mechanisms. 

The mechanisms of HIV-associated DSP are incompletely understood. Over the years, various hypotheses have been put forward, but recent data suggest that multiple mechanisms are likely to play a role in neuronal or axonal injury in DSP. These processes may be mediated by direct neurotoxicity of HIV or secreted viral proteins such as the envelope glycoprotein gpl20, or by indirect mechanisms... 

The mu, delta and kappa opioid receptors are coupled to G° and G proteins and the inhibitory actions of the opioids occur from the closing of calcium channels (in the case of the K receptor) and the opening of potassium channels (for /i, d and ORL-1). These actions result in either reductions in transmitter release or depression of neuronal excitability depending on the pre- or postsynaptic location of the receptors. Excitatory effects can also occur via indirect mechanisms such as disinhibition, which have been reported in the substantia gelatinosa and the hippocampus. Flere, the activation of opioid receptors on GABA neurons results in removal of GABA-mediated inhibition and so leads to facilitation. 

Cell suspensions of Geobacter sulfurreducens can conple the oxidation of hydrogen to the reduction of Tc(VII) to insolnble Tc(IV). An indirect mechanism involving Fe(II) was also observed, and was snbstantially increased in the presence of the redox mediator AQDS (Lloyd et al. 2000). 

Oxytocin is well established as an inducer of labour and is frequently used clinically for this purpose. Oxytocin acts by both direct and indirect mechanisms to stimulate uterine contraction. Firstly, it acts directly on the myometrium to cause uterine contractions and secondly, oxytocin acts to stimulate the production of other mediators of uterine contractions, most notably prostaglandins [8]. 

SCHEME 9.12 The QM3 adduct attached to the 6-amino of dA may form through direct and indirect mechanisms. 

Hartwig A. Schlepegrell R. Beyersmann D. 1990. Indirect mechanism of lead-induced genotoxicity in cultured mammalian cells. Mutat Res 241 75-82. 

Despite the existence of direct and indirect mechanisms for pharmaceutical price regulation in most countries, some authors put forward reasons for a growing opposition to the need to regulate prices.2,3 The discussion on the possible lack of justification for drug price regulation policies to improve welfare can be built on three types of argument, which it is important to understand. 

There are two kinds of damping that are considered within the strong anharmonic coupling theory the direct and the indirect. In the direct mechanism the excited state of the high-frequency mode relaxes directly toward the medium, whereas in the indirect mechanism it relaxes toward the slow mode to which it is anharmonically coupled, which relaxes in turn toward the medium. 

Observe that all the mechanisms—that is, the classical indirect mechanism and the two quantum ones—predict a satisfactory isotope effect when the proton of the H bond is substituted by deuterium All the damping mechanisms induce approximately a l/y/2 low-frequency shift of the first moment and a 1 / y/2 narrowing of the breadth, which is roughly in agreement with experiment. As a consequence, the isotope effect does not allow us to distinguish between the two damping mechanisms. 

Indirect mechanism, high-concentration limiting conditions ... 

These observations, combined with experimental data concerning the activation energy in solution experiments (see below), led to the consideration of the indirect mechanism. As will be seen below, this mechanism does account for the observed reactivity with H2, and indeed with other species also, either on its own or in combination with the direct mechanism (24). In the context of this review, it is interesting to expend a few words regarding why this mechanism was not considered in the earlier work on this topic (23,26). There are in fact several reasons for this oversight... 

We now consider the results obtained for the indirect mechanism (for a reminder of this mechanism, see Scheme 4). The overall rate law for this mechanism is given by Eq. (1) ... 

Ammonia has deleterious effects on brain function by direct and indirect mechanisms. Concentrations of ammonia in the 1-2 mmol/1 range, equivalent to those reported in the brain in liver failure, impair postsynaptic inhibition in cerebral cortex and brainstem by a direct effect on Cl extrusion from the postsynaptic neuron. Millimolar concentrations of ammonia also inhibit excitatory neurotransmission. Synaptic transmission from Schaffer collaterals to CA1 hippocampal neurons is reversibly depressed by 1 mmol/1 ammonia, and the firing of CA1 neurons by iontophoretic application of glutamate is inhibited by 2 mmol/1 ammonia [10],... 

Animal cells are separated from each other by lipid membranes. During signal transduction this barrier has to be passed, which can be realized by permanently or temporarily opened channels or by an indirect mechanism without material flux between the extra- and intracellular lumen (Fig. 1). 

These indirect mechanisms may be energetically preferable to a direct exchange of atoms. 

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