Search results for "Asymmetric"
showing 10 items of 241 documents
Combining organocatalysis and lanthanide catalysis: a sequential one-pot quadruple reaction sequence/hetero-Diels-Alder asymmetric synthesis of funct…
2016
A stereoselective one-pot synthesis of functionalized complex tricyclic polyethers has been achieved using the combination of secondary amine and lanthanide catalysis. This one-pot quadruple reaction/Hetero-Diels–Alder sequence gave good yields (per step) as well as excellent diastereo- and enantioselectivities. Furthermore, the particular combination of lanthanide complexes with organocatalysis is one of the first examples described for sequential catalysis.
Optically Active Titanium Complexes Containing Linked Amido‐cyclopentadienyl Ligands: Their Use as Asymmetric Hydrogenation Catalysts
1996
Optically active titanium complexes of the formula Ti(η5:η1−C5R4SiMe2NCHMePh)Cl2 (R = H, Me), containing the cyclopentadienyl ligand linked to a chiral 1-phenylethylamido moiety, were synthesized and characterized in both enantiomerically pure forms. A single-crystal X-ray structural analysis of (S)()Ti(η5:η1−C5H4SiMe2NCHMePh)Cl2 shows a conformation in which the phenyl group is turned away from the metal center. NOE measurements suggest that a related structure is retained in solution. Upon activation with n-butyllithium, these complexes show hydrogenation activity toward imines with slight enantioselectivity.
On the roles of Notch, Delta, kuzbanian, and inscuteable during the development of Drosophila embryonic neuroblast lineages
2009
AbstractThe generation of cellular diversity in the nervous system involves the mechanism of asymmetric cell division. Besides an array of molecules, including the Par protein cassette, a heterotrimeric G protein signalling complex, Inscuteable plays a major role in controlling asymmetric cell division, which ultimately leads to differential activation of the Notch signalling pathway and correct specification of the two daughter cells. In this context, Notch is required to be active in one sibling and inactive in the other. Here, we investigated the requirement of genes previously known to play key roles in sibling cell fate specification such as members of the Notch signalling pathway, e.g…
Effects of asymmetric dimethylarginine on renal arteries in portal hypertension and cirrhosis
2016
AIM. To evaluate the effects of asymmetric dimethylarginine (ADMA) in renal arteries from portal hypertensive and cirrhotic rats. METHODS. Rat renal arteries from Sham (n = 15), pre-hepatic portal hypertension (PPVL; n = 15) and bile duct ligation and excision-induced cirrhosis (BDL; n = 15) were precontracted with norepinephrine, and additional contractions were induced with ADMA (10-6-10-3 mol/L), an endogenous inhibitor of nitric oxide (NO) synthase. Concentration-response curves to acetylcholine (1 × 10-9-3 × 10-6 mol/L) were determined in precontracted renal artery segments with norepinephrine in the absence and in the presence of ADMA. Kidneys were collected to determine the protein e…
Accumulation of Symmetric Dimethylarginine in Hepatorenal Syndrome
2005
In patients with cirrhosis, nitric oxide (NO), asymmetric dimethylarginine (ADMA), and possibly symmetric dimethylarginine (SDMA) have been linked to the severity of the disease. We investigated whether plasma levels of dimethylarginines and NO are elevated in patients with hepatorenal syndrome (HRS), compared with patients with cirrhosis without renal failure (no-HRS). Plasma levels of NO, ADMA, SDMA, and l-arginine were measured in 11 patients with HRS, seven patients with no-HRS, and six healthy volunteers. SDMA concentration in HRS was higher than in no-HRS and healthy subjects (1.47 ± 0.25 vs. 0.38 ± 0.06 and 0.29 ± 0.04 μM, respectively; P < 0.05). ADMA and NOx concentrations were…
Inbreeding removes sex differences in lifespan in a population of Drosophila melanogaster
2016
Sex differences in ageing rates and lifespan are common in nature, and an enduring puzzle for evolutionary biology. One possibility is that sex-specific mortality rates may result from recessive deleterious alleles in ‘unguarded’ heterogametic X or Z sex chromosomes (the unguarded X hypothesis). Empirical evidence for this is, however, limited. Here, we test a fundamental prediction of the unguarded X hypothesis in Drosophila melanogaster, namely that inbreeding shortens lifespan more in females (the homogametic sex in Drosophila) than in males. To test for additional sex-specific social effects, we studied the lifespan of males and females kept in isolation, in related same-sex groups, and…
High Levels of Asymmetric Dimethylarginine Are Strongly Associated with Low HDL in Patients with Acute Myocardial Infarction
2013
International audience; Objectives: Low levels of high-density lipoprotein (HDL) cholesterol are associated with an increased risk of acute myocardial infarction possibly through impaired endothelial atheroprotection and decreased nitric oxide (NO) bioavailability. Asymmetric dimethylarginine (ADMA) mediates endothelial function by inhibiting nitric oxide synthase activity. In patients with acute myocardial infarction, we investigated the relationship between serum levels of HDL and ADMA. Approach and Results: Blood samples from 612 consecutive patients hospitalized for acute MI ,24 hours after symptom onset were taken on admission. Serum levels of ADMA, its stereoisomer, symmetric dimethyl…
Incentive and Selection Effects of Medigap Insurance on Inpatient Care
2012
The Medicare program, which provides insurance coverage to the elderly in the United States, does not protect them fully against high out-of-pocket costs. For this reason private supplementary insurance, named Medigap, has been available to cover Medicare gaps. This paper studies how Medigap affects the utilization of inpatient care, separating the incentive and selection effects of supplementary insurance. For this purpose, we use two alternative estimation methods: a standard recursive bivariate probit and a discrete multivariate finite mixture model. We find that estimated incentive effects are modest and quite similar across models. On the other hand, there seems to be very significant …
Extensive characterization of the human DDAH1 transgenic mice
2009
Abstract Purpose of the research Overexpression of the human dimethylarginine dimethylaminohydrolase type 1 (hDDAH1) gene was reported to have beneficial cardiovascular effects in mice. To date, it is unclear whether these effects are related to enhanced metabolic clearance of asymmetric dimethylarginine (ADMA) and l - N G -mono-methyl- l -arginine ( l -NMMA) or increased DDAH1 expression and activity in cardiovascular tissues of hDDAH1 transgenic mice. Principal results DDAH activity (DDAH1 + DDAH2) was found to be markedly increased in aortic and heart tissues but unaltered in liver and kidney tissues of hDDAH1 transgenic as compared to wild-type (WT) mice. In WT mice, DDAH activity was m…
Effects of a quercetin-rich onion skin extract on 24 h ambulatory blood pressure and endothelial function in overweight-to-obese patients with (pre-)…
2015
AbstractThe polyphenol quercetin may prevent CVD due to its antihypertensive and vasorelaxant properties. We investigated the effects of quercetin after regular intake on blood pressure (BP) in overweight-to-obese patients with pre-hypertension and stage I hypertension. In addition, the potential mechanisms responsible for the hypothesised effect of quercetin on BP were explored. Subjects (n 70) were randomised to receive 162 mg/d quercetin from onion skin extract powder or placebo in a double-blinded, placebo-controlled cross-over trial with 6-week treatment periods separated by a 6-week washout period. Before and after the intervention, ambulatory blood pressure (ABP) and office BP were m…