Transmission effect

To achieve their different effects NTs are not only released from different neurons to act on different receptors but their biochemistry is different. While the mechanism of their release may be similar (Chapter 4) their turnover varies. Most NTs are synthesised from precursors in the axon terminals, stored in vesicles and released by arriving action potentials. Some are subsequently broken down extracellularly, e.g. acetylcholine by cholinesterase, but many, like the amino acids, are taken back into the nerve where they are incorporated into biochemical pathways that may modify their structure initially but ultimately ensure a maintained NT level. Such processes are ideally suited to the fast transmission effected by the amino acids and acetylcholine in some cases (nicotinic), and complements the anatomical features of their neurons and the recepter mechanisms they activate. Further, to ensure the maintenance of function in vital pathways, glutamate and GABA are stored in very high concentrations (10 pmol/mg) just as ACh is at the neuromuscular junction. 

Table 6-5 Steps in Autonomic Transmission Effects of Drugs. ...

Compounds 28 and 29 are pentacoordinated models of the activated state of 3, 5 -cyclic adenosine monophosphate (cAMP), which plays a dominant role as second messenger in cell metabolism regulation69. A conformational transmission effect found by dynamic H and 13C NMR70 results in 51% of trans position for the Oa) and 0(2) atoms, but only when... 

Although transmission effects can be accounted for more readily by scanning the analyzer electric field while allowing the electrons to enter on a field free path, this mode of operation is not usually convenient since it results in a changing energy resolution (AE/E is constant rather than A ) over the spectrum. An alternative procedure to minimize differences in... 

The source of this webi-transmission effect and the nature of the 7r-7r excitation process is made apparent by inspection of Figure 3 which schematically gives the electron distribution of the seven molecular orbitals of the benzyl species these seven orbitals are dissected energetically and would, of course, he superimposed on the same sigma framework of the molecule. The electron density per electron at each atom in a particular MO is given adjacent to that atom in Figure 3. 

Collins JS, Go RC. Disease classification and transmission effects on linkage analyses in the NIMH1 bipolar disorder pedigrees. Genet Epidemiol 1997 14(6) 587-592. 

When the agitated reactors are used for gas-liquid systems, several correlations have been proposed to evaluate the effective attenuation coefficient. Otake et al. (1981) proposed a simple empirical expression that accounts for the absorption effects produced by the liquid phase and the reflection, refraction, and transmission effects provoked by the gaseous phase. Considering that the latter are proportional to the specific surface area (aj.), /jeff v may be represented by the correlation... 

The PMR spectra of certain related titanocene derivatives have been similarly studied and analyzed for transmission effects. For the para-substituted diaryltitanocenes (VIII), 21% of the effect from the substituent was estimated to be transmitted through the metal atom to the cyclo-pentadienyl ring (3, 11). It is interesting that this value is higher than that obtained for the arylferrocenes (14%). This is not, however, unexpected since the aryl group of titanocene is directly bonded to the metal. 

It is evident from this description that calculation of this interactive processes entails a complicated mathematical operation. The diffuse reflection, the transmission effects and the specular reflection of the light must be taken into account. In 1953, Williams and Clapper developed an equation that enables calculation of the concentration of an analyte from a sample the reflection of which had been determined as described above ... 

The non-bonded, through-space transmission of spin information, known as the Barfield transmission effect, has been investigated theoretically for five-membered rings by the FPT-INDO-SCF-MO method.50 An early observation of this effect was the non-equivalence of /endo-endo and exo-exo in norbomanes,51,52 which was also... 

The approach is based on a theoretical model for the transmission of the polar effect but its further extension is beyond the scope of this book. Future models of the polar transmission effect will undoubtedly be firmly based in MO theory.24-25,26... 

The Ojy, values for the substituents are in the series CH3- < CH3O- < H- < Cl- CH3CO- CH3OCO- < NC- < O2N-. Note that these are inductive effects and do not include resonance interactions. A slightly different order would be obtained if Op were used, owing to the possible incursion of resonance transmission effects. 

Steroid Properties and Reactions (Chapter 1).— The application of modem computing techniques to valence-force calculations marks a new phase in the conformational analysis of steroids. This approach brings within reach the accurate specification of preferred conformations, and the evaluation of conformational energies and conformational transmission effects and thus promises to complement the chemical and physical techniques used hitherto. The introduction of lanthanide shift reagents in n.m.r. spectroscopy promises to be particularly valuable in the analysis of steroids since it overcomes to a large extent a major limitation, namely the near-equivalence of many protons attached to the steroid nucleus. Further useful advances in applying solvent shifts... 

The alternative explanation of zwitterionic hexaco-ordinated intermediates (or transition states) to account for the faster pseudorotation rates with X=0, appears to be negated by studies of pseudorotational barriers in (16ab). In these molecules, no conformational transmission effect is possible but the presence of the tetrahydrofuran oxygen atoms would permit a zwitterionic T.S. to accelerate ligand reorganization. In fact the pseudorotational barriers for (16a) and (16b) at 55.2 and 71.9 kjmol respectively, are in excellent agreement with those found for (11a) and (11c) where no hexaco-ordinate species are possible along the isomerisation pathway. 

Although interest in pn-bonded compounds continues at a high level the pace of advance seems to be slackening, perhaps reflecting that the most interesting chemistry in this area has now been revealed. The year has seen a further consolidation of knowledge in the area of hypervalent phosphorus chemistry and the principles established in this area have expanded further into the chemistry of As, Sb, Bi and Si. Notable contributions have appeared on the importance of the conformational transmissions effect to ligand... 

Hammett a values are adequate for reactions and equilibria involving separation of substituent and reaction centre by a phenylene grouping. Examination of aliphatic species necessitates a more sophisticated set of o values as transmission effects are now markedly different from the model. Resonance and inductive effects may be separated if we can use as models reactions with no resonance interactions so that a° type values may be defined. Entirely new approaches have led to the definition of an inductive scale of a parameters (O]). Although some of these parameters are now only of historic value we shall include a brief discussion of early attempts to define the a, scale. 

The relative rates of basic methanolysis of the stereoisomers of 631 was attributed to the participation of pentacoordinate intermediates in which the six-membered ring takes up the equatorial-equatorial position and in which that from the equatorial isomer would have an electronic interaction between ring oxygen and oxygen of the exocyclic P—OPh bond implied by structure 632. A conformational transmission effect was proposed to account for the hydrolyses of the diphenylphosphinic esters 633 (X, Y = O or... 

Table 6-5. Steps in autonomic transmission Effects of drugs. ...

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