Mediators frequently used

Corticosteroids a chronic painless myopathy associated with the long-term use of corticosteroids is a particularly common example of drug-induced muscle disorder. It is almost certain that mild cases are overlooked because steroids are so frequently used to treat inflammatory myopathies such as polymyositis. Fluorinated steroids are particularly frequently implicated, and the incidence of drug-induced muscle disease is dose and time-related. The presence of muscle weakness can even complicate topical steroid therapy. Corticosteroid-induced myopathy is mediated via intramuscular cytosolic steroid receptors. The steroid-receptor complexes inhibit protein synthesis and interfere with oxidative phosphorylation. The myopathy is associated with vacuolar changes in muscle, and the accumulation of cytoplasmic glycogen and mitochondrial aggregations. 

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]. 

The carbocupration of alkynes occurs in a cis fashion to afford the synthetically useful cis alkenyl products. Recently, copper-mediated introduction of heteroatoms such as stannyl and silyl groups has become frequently used in place of introduction of carbon units as an efficient strategy to build important precursors in syn-... 

Flowever, some associated materials might be perceived as toxic. For example, complexes of osmium find frequent use as electron mediators, because of their rich chemistry, stability, and redox activity. Osmium metal and most compounds are considered nontoxic, but the neat tetroxide of osmium is a strong oxidizer and is considered highly toxic in the U.S. and very toxic by the European Union. On the other hand, the aqueous solution, osmic acid, has been injected at 1% concentration in several European clinical trials, starting in the 1970s, for treatment of arthritis and hemophilia. - No toxic effects were observed. Thus, osmium toxicity might be a question not of in vivo chemistry, but of manufacture, where a concentrated form of the oxide might need to be handled. ... 

The indirect sympathomimetic drugs can be used clinically for systemic or local vasoconstriction. Since the mechanism is an increase in the noradrenaline concentration there are always jSi-adrenoceptor-mediated effects like tachycardia and extrasystoles. Since the re-uptake of noradrenaline is necessary to sufficiently refill the axonal vesicles, a frequent use of indirect sympathetic drugs results in a loss of efficacy by transmitter exhaustion. This phenomenon of use-dependent loss of effect is called tachyphylaxis. 

Whereas the thermal ring-opening reaction of oxrranes and aziridines is frequently used for generation of carbonyl ylides and azomethine ylides, the analogous procedure starting with thiiranes does not produce the expected thiocarbonyl ylides (8). However, in the case of tetraaryl-substituted thiiranes, the photolytically mediated reaction with tetracyanoethylene (TCNE) is believed to occur via a single electron transfer (SET) mechanism, also involving a thiocarbonyl ylide as a likely intermediate (75,76) (Scheme 5.14). 

Inorganic and Organometallic Complexes Frequently used as Mediators in Aqueous Medium at 25 °C... 

Radical anions and dianions of a large number of compounds, mostly aromatics, have been tested as mediators for reductions. Table 8 lists the potentials of frequently used mediator systems. 

In conclusion, the IBTFA-mediated Hofmann rearrangement is the most convenient method for the synthesis of the N-acylated gem-diaminoalkyl derivatives and is certainly the most frequently used procedure for the generation of peptidyl gem-diaminoalkyl derivatives. However, as mentioned above, this method has limitations with regards to the choice of protecting groups and therefore requires careful consideration when applied to amino acids with reactive side chains. 

Agents which block responses of effector cells to sympatho-adrenal stimuli may be termed adrenergic blocking agents. It is only at these effector cells that adrenergic mediators are involved in transmission of the nerve impulse. For a number of reasons, the frequently used terms adrenolytic and sympatholytic agents are ambiguous and undesirable (see 70). 

Motion Sickness. Antimuscarinics (scopolamine in particular) are frequently used in the treatment of motion sickness.22 Scopolamine appears to block cholinergic transmission from areas of the brain and brainstem that mediate motion-related nausea and vomiting (i.e., the vestibular system and reticular formation).8 These drugs are often administered trans-dermally via small patches that adhere to the skin.18... 

Beta antagonists are generally administered for their effect on the beta-1 receptors that are located on the heart.31 When stimulated, these receptors mediate an increase in cardiac contractility and rate of contraction. By blocking these receptors, beta antagonists reduce the rate and force of myocardial contractions. Consequently, beta antagonists are frequently used to decrease cardiac workload in conditions such as hypertension and certain types of angina pectoris. Beta blockers may also be used to normalize heart rate in certain forms of cardiac arrhythmias. Specific clinical applications of individual beta blockers are summarized in Table 20-2. 

Nevertheless, in addition to this general understanding of the term, bond activation has acquired specific meaning in various subdisciplines. Most notably, C-H bond activation is frequently used as an organometallic term to describe certain metal-mediated processes ( organometallic definition ). Before we address this inconsistency, let us first elucidate the origin and historical context of C-H bond activation as an organometallic term. 

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