Levy exchange mechanism

Finally, it should be noted that the phonon part in eq. (14) also leads to an effective quadrupolar interaction between 4f ions if the phonon coordinates are eliminated in second-order perturbation theory. This virtual phonon exchange mechanism is important in insulators, see Orbach and Tachiki (1967). In R intermetallics such as TmZn and TmCd, however, the electronic origin of effective interactions is now established, Levy et al. (1979). 

Silver RB, Mackins CJ, Smith NCE, Koritchneva IL, Lefkowitz K, Lovenberg TW> Levi R Coupling of histamine H3 receptors to neuronal Na+/H+ exchange a novel protective mechanism in myocardial ischemia, Proc Natl Acad Sci USA 2001 98 2855. Silver RB, Poonwasi KS, Seyedi N, Wilson SJ, Lovenberg TW, Levi R Decreased intracellular calcium mediates the histamine H3-receptor-induced attenuation of norepinephrine exocytosis from cardiac sympathetic nerve endings. Proc Natl Acad Sci USA 2002 99 501. 

In myocardial ischemia, several of the mechanisms presented above come into play. First, neuropeptides such as CGRP are released from cardiac sensory C fibers and subsequently release histamine from mast cells as just mentioned. Histamine then can act at least at two presynaptic H3 heteroreceptors on the C fibers to attenuate further neuropeptide release (Section 3.9), and on postganglionic sympathetic fibers to attenuate exocytotic as well as carrier-mediated noradrenaline release (Section 3.3). Both presynaptic effects are potentially beneficial. The H3 receptors are unique in this pattern of effects. Presynaptic adenosine Ai receptors, when activated, also inhibit both exocytotic and carrier-mediated noradrenaline release, but cardiac Ai receptors in addition mediate negative chronotropic and dro-motropic effects. Presynaptic 0C2-adrenoceptors, when activated, reduce exocytotic noradrenaline release but enhance carrier-mediated noradrenaline release (due to stimulation of the Na+/H+ exchanger, Imamura et al. 1996b), which is the major mode of noradrenaline release and the major arrhythmogenic risk in protracted myocardial ischemia (see Levi and Smith 2000 Koyama et al. 2003). 

G. Zundel, Hydrate structures, intermolecular interactions and proton conducting mechanism in polyelectrolyte membranes - infrared results, J. Membr. Sci., 1982, 11, 249-274 C. Heitner-Wirguin, Infra-red spectra of perfluorinated cation-exchange membranes, Polym., 1979, 20, 371-374 L.Y. Levy, A. Jenard and H.D. Hurwitz, Infrared investigation of ionic hydration in ion-exchange membranes. Part 1. Alkaline salts of grafted polystyrene sulphonic acid membranes, J. Chem. Soc., Faraday Trans. 

Lipid removal may be a critical factor in plaque formation and the location of lecithin-cholesterol trans-acylase in the arterial wall could play an important role since cholesterol is rapidly exchanged" with the blood while cholesterol ester is not. Kuo in an editorial cites the evidence for the theory that a dlsturbemce in carbohydrate metabolism can be responsible for atherosclerosis and should be included as one of the primary risk factors in coronary heart disease. In this regard, Clements and coworkers have shown the presence in aorta of aldose reductase, an enzyme which they feel provides a mechanism for the alteration of arterial metabolism by hyperglycemia. Another approach to molecular interactions was described by Levy and Day who concluded from their results that the low density lipoproteins are uniquely polycationic at the surface and that these ions react with the internal arterial macromolecular polyanions. 

---