Structure and bonding in WCn (n = 2–5) clusters

Stochastic explorations of the configurational spaces for WC n (n = 2–5) clusters lead to densely populated spin states at each molecularity. We found 8, 16, 42, and 68 well-defined minima for n = 2, 3, 4, 5, respectively, in spin states ranging from singlets to quintuplets. The lowest energy isomers are triplets in all cases, except for n = 2 where there is competition between a quintuplet and a triplet state for the global minimum. The transition from planar to 3D structural preferences occurs between n = 4 and n = 5. For the global minima, the structures may be considered as the result of the interaction between two fragments: a tungsten cation and a covalently bonded anionic carbon chain. We found that spin–orbit (SO) effects reduce energy differences among isomers. Likewise, SO effects diminish as a function of the carbon content in the clusters to the point that for n = 5 they become negligible

Receptor-Induced Dilatation in the Systemic and Intrarenal Adaptation to Pregnancy in Rats

Normal pregnancy is associated with systemic and intrarenal vasodilatation resulting in an increased glomerular filtration rate. This adaptive response occurs in spite of elevated circulating levels of angiotensin II (Ang II). In the present study, we evaluated the potential mechanisms responsible for this adaptation. The reactivity of the mesangial cells (MCs) cultured from 14-day-pregnant rats to Ang II was measured through changes in the intracellular calcium concentration ([Cai]). The expression levels of inducible nitric oxide synthase (iNOS), the Ang II-induced vasodilatation receptor AT2, and the relaxin (LGR7) receptor were evaluated in cultured MCs and in the aorta, renal artery and kidney cortex by real time-PCR. The intrarenal distribution of LGR7 was further analyzed by immunohistochemistry. The MCs displayed a relative insensitivity to Ang II, which was paralleled by an impressive increase in the expression level of iNOS, AT2 and LGR7. These results suggest that the MCs also adapt to the pregnancy, thereby contributing to the maintenance of the glomerular surface area even in the presence of high levels of Ang II. The mRNA expression levels of AT2 and LGR7 also increased in the aorta, renal artery and kidney of the pregnant animals, whereas the expression of the AT1 did not significantly change. This further suggests a role of these vasodilatation-induced receptors in the systemic and intrarenal adaptation during pregnancy. LGR7 was localized in the glomeruli and on the apical membrane of the tubular cells, with stronger labeling in the kidneys of pregnant rats. These results suggest a role of iNOS, AT2, and LGR7 in the systemic vasodilatation and intrarenal adaptation to pregnancy and also suggest a pivotal role for relaxin in the tubular function during gestation

ICAR: endoscopic skull‐base surgery

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Wound healing after radiation therapy: Review of the literature

Radiation therapy is an established modality in the treatment of head and neck cancer patients. Compromised wound healing in irradiated tissues is a common and challenging clinical problem. The pathophysiology and underlying cellular mechanisms including the complex interaction of cytokines and growth factors are still not understood completely. In this review, the current state of research regarding the pathomechanisms of compromised wound healing in irradiated tissues is presented. Current and possible future treatment strategies are critically reviewed