Short-range order and dynamics in crystalline α-TeO2

The short-range order and dynamics in crystalline α-TeO2 have been investigated by neutron and X-ray total scattering and by Rietveld refinement of neutron diffraction data. The true lengths of the two bonds in a Te–O–Te bridge are 1.882(1) and 2.117(1) Å, and the high valence, 1.293, of the strong, short bond is balanced by the low valence, 0.686, of the weak, long bond. The root-mean-square (rms) thermal variation, 0.083(1) Å, in the long bond length is nearly twice the rms thermal variation, 0.048(1) Å, in the short bond length because the largest motion of both Te and O atoms is perpendicular to the short bonds. A bond-valence model for the thermal variation in bond lengths, in which both the average and the instantaneous positions of the atoms conform to bond-valence requirements, accounts closely for the observed distribution of Te–O distances in α-TeO2. This has important implications for the interpretation of diffraction experiments on tellurite glasses

Relevance of nitric oxide for myocardial remodeling.

Endogenous myocardial nitric oxide (NO) may modulate the transition from adaptive to maladaptive remodeling leading to heart failure. In rodent models of pressure overload or myocardial infarction, the three NO synthase (NOS) isoforms were shown to play a neutral, protective, or even adverse role in myocardial remodeling, depending on the quantity of NO produced, the location of each NOS and their regulators, the prevailing oxidant stress and resultant NO/oxidant balance, as well as NOS coupling/dimerization. Beside neuronal NOS and--in specific conditions--inducible NOS isoforms, endothelial NOS (eNOS) exerts cardioprotective effects on pressure-overload, ischemia/reperfusion, and myocardial infarction-induced myocardial remodeling, provided the enzyme remains in a coupled state. Besides its effects on excitation-contraction coupling in response to stretch, eNOS acts as an "endogenous beta-blocker" by restoring the sympathovagal balance, opposing excessive hypertrophy as well as promoting vasodilatation and neoangiogenesis, thereby contributing to tissue repair. As eNOS was also shown to mediate the beneficial effects of cardiovascular drugs commonly used in patients with heart failure, strategies to increase its expression and/or coupled catalytic activity in the myocardium offer new therapeutic avenues for the treatment of this disease