Ein einkerniger Cobalt‐Komplex mit einem neuartigen fünfzähnigen Liganden (siehe Bild) katalysiert die Entwicklung von Wasserstoff in ausschließlich wässriger Lösung. Der Komplex könnte als Elektro‐ sowie als Photokatalysator zur effizienten Bildung von Wasserstoff verwendet werden.

Neointimal lesions are characterized by accumulation of cells within the arterial wall and are a prelude to atherosclerotic disease. Here we report that a brief exposure to either alkyl ether analogs of the growth factor–like phospholipid lysophosphatidic acid (LPA), products generated during the oxidative modification of low density lipoprotein, or to unsaturated acyl forms of LPA induce progressive formation of neointima in vivo in a rat carotid artery model. This effect is completely inhibited by the peroxisome proliferator-activated receptor (PPAR)γ antagonist GW9662 and mimicked by PPARγ agonists Rosiglitazone and 1-O-hexadecyl-2-azeleoyl-phosphatidylcholine. In contrast, stearoyl-oxovaleryl phosphatidylcholine, a PPARα agonist and polypeptide epidermal growth factor, platelet-derived growth factor, and vascular endothelial growth factor failed to elicit neointima. The structure-activity relationship for neointima induction by LPA analogs in vivo is identical to that of PPARγ activation in vitro and disparate from that of LPA G protein–coupled receptor activation. Neointima-inducing LPA analogs up-regulated the CD36 scavenger receptor in vitro and in vivo and elicited dedifferentiation of cultured vascular smooth muscle cells that was prevented by GW9662. These results suggest that selected LPA analogs are important novel endogenous PPARγ ligands capable of mediating vascular remodeling and that activation of the nuclear transcription factor PPARγ is both necessary and sufficient for neointima formation by components of oxidized low density lipoprotein.

In eukaryotes and archaea, uridines in various RNAs. The RNA-guided RNA modification system alters the primary sequence and modulates the function of target RNAs that include rRNAs, snRNAs, tRNAs, and perhaps mRNAs (Yu et al. 1998(Yu et al. , 2005Cavaille et al. 2000;King et al. 2003;Omer et al. 2003). In humans it is currently estimated that >200 2Ј-O-methylations and pseudouridylations are introduced into rRNA and other RNAs by this system (Maden 1990;Bachellerie and Cavaille 1998;Ofengand and Fournier 1998;Vitali et al. 2003).There are two large families of modification guide RNAs found in both eukaryotes and archaea: C/D RNAs that guide 2Ј-O-ribose methylation (Kiss-Laszlo et al. 1996;Omer et al. 2000) and H/ACA RNAs that guide pseudouridylation (Balakin et al. 1996; Ganot et al. 1997a,b;Tang et al. 2002). Both families of guide RNAs function in the context of RNA-protein complexes (RNPs) that include the enzyme responsible for modification (Filipowicz and Pogacic 2002;Terns and Terns 2002). The functional organization of modification guide RNPs, including the mechanism by which the enzyme associates with a guide RNA and the roles of the other essential proteins in the complex, is a subject of great interest. In C/D RNPs the 2Ј-O-methyltransferase, fibrillarin, associates with a guide RNA primarily via a bridge formed by the other proteins in the complex, Nop56/58 and L7Ae (or Nop56, Nop58, and p15.5 in eukaryotes).

Lysophosphatidic acid (LPA) and sphingosine 1-phosphate (Sph1P) production was examined in vitro under conditions that simulated blood clotting. Several approaches were utilized to elucidate the metabolic pathways. 1) Platelet phospholipids were labeled using [ 32 P]orthophosphate, and the production of [ 32 P]Sph1P and LPA was examined. Thrombin stimulation of platelets resulted in rapid secretion of Sph1P stored within the platelet. In contrast, LPA was neither stored within nor secreted from platelets. Nonetheless, extracellular levels of LPA gradually increased following stimulation. 2) Stable-isotope dilution mass spectrometry was used to quantify the molecular species of LPA generated from platelets in vitro. Only 10% of the LPA generated following thrombin stimulation was associated with platelets, the remaining 90% was contained within the extracellular medium. The acyl composition of LPA produced by platelets differed depending on the presence or absence of plasma in the incubation. 3) The fate of exogenously added fluorescent phospholipid analogs was determined. Incubation of [(7-nitro-2-1,3-benzoxadiazol-4-yl)amino]dodecanoyl-(NBD)-labeled phosphatidylcholine, phosphatidylethanolamine, and phosphatidylserine with the supernatant fractions from thrombin-stimulated platelets yielded no LPA production. However, these lipids were converted to the corresponding lysolipids by released PLA 1 and PLA 2 activities. When incubated with plasma or serum the NBD-labeled lysophospholipids were readily converted to LPA. Inhibitors of lysophospholipase D and the biological activity of LPA were detected in plasma. These results suggest that the bulk of LPA produced through platelet activation results from the sequential cleavage of phospholipids to lysophospholipids by released phospholipases A 1 and A 2 and then to LPA by plasma lysophospholipase D.Lysophosphatidic acid (LPA) 1 and sphingosine 1-phosphate (Sph1P) are phospholipid mediators with pleiotropic growth factor properties that elicit their actions via the activation of G protein-coupled receptors encoded by the endothelial differentiation gene family (1, 2). Several investigators have identified platelets as the source of Sph1P and LPA. However, contradictions exist in the literature concerning the mechanisms by which these mediators are generated. Although some investigators found no Sph1P generation in thrombin-activated platelets (3), others reported as much as 0.5 M Sph1P in human serum (4). Although it is generally agreed that LPA is generated in thrombin-activated platelets (3, 5, 6), the rate of production found at 0.02 nmol/min/10 9 platelet cannot account for the 5-10 M concentration detected in human serum (7). During the first hour of blood clotting the concentration of LPA increases ϳ300 nM; however, its production continues and an additional 5 M is added to serum during the first 24 h, a time course that is hard to reconcile with that of platelet activation and consequently of platelet only origin. Gerrard and Robinson (6) quantified the molecul...