The first measurements of the absorption coefficient of materials via surface electromagnetic wave (SEW) techniques are reported. By simply laying samples on a metal sheet on which SEW were passing, the transmittances and absorption coefficients of the sample have been determined. These measurements were made at microwave frequencies, but the general techniques are applicable over the entire frequency range from microwaves into the near ir. Solid samples were used in these measurements, but liquid or gases could also be studied by this new easy-to-use technique. Comments about the applicability of the technique to very thin samples are made. Another result reported is the existence of different propagating SEW modes as a function of the height of a sample (film thickness) measured from the metal-sample interface to the top of the sample at the sample-vacuum interface above.

Angiotensin II (Ang II) is a pleuripotential hormone that is important in the pathophysiology of multiple conditions including ageing, cardiovascular and renal diseases and insulin resistance. Reactive oxygen species (ROS) are important mediators of Ang II-induced signaling generally and have a well defined role in vascular hypertrophy, which is inhibited by overexpression of catalase, inferring a specific role of H(2)O(2). Molecular mechanisms are understood incompletely. The transcriptional coactivator peroxisome proliferator-activated receptor gamma coactivator-1alpha (PGC-1alpha) is a key regulator of energy metabolism and ROS-scavenging enzymes including catalase. We show that Ang II stimulates Akt-dependent PGC-1alpha serine570 phosphorylation, which is required for the binding of the histone acetyltransferase general control nonderepressible 5 (GCN5) to PGC-1alpha and for its lysine acetylation. These sequential posttranslational modifications suppress PGC-1alpha activity and prevent its binding to the catalase promoter, thus decreasing catalase expression. We demonstrate that overexpression of the phosphorylation defective mutant PGC-1alpha (S570A) prevents Ang II-induced increases in H(2)O(2) levels and hypertrophy ([(3)H] leucine incorporation). Knock-down of PGC-1alpha by siRNA promotes basal and Ang II-stimulated ROS and hypertrophy, which is reversed by PEG-catalase. Thus, endogenous PGC-1alpha is a negative regulator of vascular hypertrophy by upregulating catalase expression and thus reducing ROS levels. We provide novel mechanistic insights by which Ang II may mediate its ROS-dependent pathophysiologic effects on multiple cardiometabolic diseases.

As the molecular representation of the genetic code, tRNA plays a central role in the translational machinery where it interacts with several proteins and other RNAs during the course of protein synthesis. These interactions exploit the dynamic flexibility of tRNA. In this minireview, we discuss the effects of modified bases, ions, and proteins on tRNA structure and dynamics and the challenges of observing its motions over the cycle of translation.

To establish guidelines for more effectively incorporating part-time faculty into departments of internal medicine, a task force was convened in early 2007 by the Association of Specialty Professors. The task force used informal surveys, current literature, and consensus building among members of the Alliance for Academic Internal Medicine to produce a consensus statement and a series of recommendations. The task force agreed that part-time faculty could enrich a department of medicine, enhance workforce flexibility, and provide high-quality research, patient care, and education in a cost-effective manner. The task force provided a series of detailed steps for operationalizing part-time practice; to do so, key issues were addressed, such as fixed costs, malpractice insurance, space, cross-coverage, mentoring, career development, productivity targets, and flexible scheduling. Recommendations included (1) increasing respect for work-family balance,(2) allowing flexible time as well as part-time employment,(3) directly addressing negative perceptions about part-time faculty,(4) developing policies to allow flexibility in academic advancement,(5) considering part-time faculty as candidates for leadership positions,(6) encouraging granting agencies, including the National Institutes of Health and Veterans Administration, to consider part-time faculty as eligible for research career development awards, and (7) supporting future research in "best practices" for incorporating part-time faculty into academic departments of medicine.

Enzymes regulated by allostery undergo conformational rearrangement upon binding effector molecules. For modular proteins, a flexible interface may mediate reorientation of the protein domains and transmit binding events to activate catalysis at a distance. Aminoacyl-tRNA synthetases (aaRSs) that use tRNA anticodons as identity elements can be considered allosteric enzymes in which aminoacylation of the tRNA acceptor stem is enhanced upon anticodon binding. We reasoned that anticodon-triggered conformational change might be restricted upon introduction of a disulfide linkage near the core of an aaRS. Here we show that a double cysteine mutation engineered at the E. coli MetRS domain interface spontaneously generates a disulfide linkage. This disulfide clamp has no effect on methionyl-adenylate formation but reduces tRNAMet aminoacylation about two-fold. Activity is restored upon chemical reduction of the disulfide, demonstrating that E. coli MetRS requires a flexible interface domain for full catalytic efficiency.

BACKGROUND: We hypothesized that granulocyte macrophage colony-stimulating factor (GM-CSF) administration will be safe and will improve endothelial dysfunction and exercise capacity by mobilizing progenitor cells in patients with peripheral arterial disease (PAD). METHODS: Forty-five patients with PAD received thrice-weekly injections for 2 weeks of 3, 6, or 10 mug/kg per day of GM-CSF or placebo in successive cohorts of 15 subjects randomized 2:1 to drug or placebo. CD34(+) mononuclear cell subsets and colony formation assay, endothelial function, ankle-brachial index, and walking capacity were measured. RESULTS: Granulocyte macrophage colony-stimulating factor administration was safe. After pooling data from GM-CSF cohorts, at 2 weeks, there was a significant increase in total leukocytes (43%, P <.0001), CD34(+) cells (46%, P =.035), and colony-forming units (31%, P =.026, week 1). At 12 weeks, endothelial function improved with GM-CSF (flow-mediated vasodilation increased by 59%, P <.01) as did pain-free treadmill walking time (38 seconds, P =.008) and total treadmill walking time (55 seconds, P =.016). Corresponding changes were not observed in the placebo group. CONCLUSIONS: Granulocyte macrophage colony-stimulating factor therapy in patients with PAD was associated with mobilization of progenitor cells, improvement of endothelial dysfunction, and exercise capacity. The efficacy of strategies designed to mobilize bone marrow progenitors warrants further study in patients with PAD.

Proton nuclear magnetic resonance ((1)H-NMR) spectroscopy of plasma provides a global metabolic profiling method which shows promise for clinical diagnostics. However, cross-sectional studies are complicated by a lack of understanding of intra-individual variation, and this limits experimental design and interpretation of data. The present study determined the diurnal variation detected by (1)H NMR spectroscopy of human plasma. Data reduction methods revealed 3 time-of-day metabolic patterns, which were associated with morning, afternoon and night. Major discriminatory regions for these time-of-day patterns included the various kinds of lipid signals (-CH2- and -CH2OCOR) and the region between 3-4 ppm heavily overlapped with amino acids which had alpha-CH and alpha-CH2. The phasing and duration of time-of-day patterns were variable among individuals, apparently due to individual difference in food processing/digestion and absorption and clearance of macronutrient energy sources (fat, protein, carbohydrate). The times of day which were most consistent among individuals, and therefore most useful for cross-sectional studies, were fasting morning (8:30-9:30), post-prandial afternoon (14:30-16:30) and nighttime samples (4:30-5:30). Importantly, the integrated picture of metabolism provided by (1)H-NMR spectroscopy of plasma suggests that this approach is suitable to study complex regulatory processes including eating patterns/eating disorders, upper gastrointestinal functions (gastric emptying, pancreatic, biliary functions) and absorption/clearance of macronutrients. Hence,(1)H-NMR spectroscopy of plasma could provide a global metabolic tolerance test to assess complex processes involved in disease, including eating disorders and the range of physiologic processes causing dysregulation of energy homeostasis. Key words: metabolomics, diurnal variation, eating disorders, gastrointestinal regulation.

Endothelial dysfunction is known to precede the development of atherosclerosis and results primarily from increased oxidative degradation of NO. We hypothesized that assessment of oxidative stress in the bloodstream will reliably predict endothelial function in healthy adults. A total of 124 healthy nonsmokers had endothelial function assessed using ultrasound measurement of brachial artery flow-mediated vasodilation. Plasma oxidative stress was estimated by measuring the levels of the reduced and oxidized forms of thiols, including glutathione (reduced glutathione and oxidized glutathione) and cysteine (cysteine and cystine), respectively, and the mixed disulfide. Among the traditional risk factors, there were significant and independent correlations between flow-mediated vasodilation and high-density lipoprotein level, body mass index, gender, and the Framingham risk score. Among the thiol markers, plasma cystine (r=-0.23; P=0.009) and the mixed disulfide (r=-0.23; P=0.01) levels correlated with endothelium-dependent but not endothelium-independent vasodilation, even after adjusting for the Framingham risk score and high-sensitivity C-reactive protein level. A higher level of oxidized metabolites was associated with worse endothelial function. In conclusion, the oxidative stress markers, cystine, and the mixed disulfide are independent predictors of endothelial function. These markers, in combination with the Framingham risk score, may help in the early identification of asymptomatic subjects with endothelial dysfunction who are at potentially increased risk for future atherosclerotic disease progression.

The assignment of AUG codons to methionine remains a central question of the evolution of the genetic code. We have unveiled a strategy for the discrimination among tRNAs containing CAU (AUG-decoding) anticodons. Mycoplasma penetrans methionyl-tRNA synthetase can directly differentiate between tRNA(Ile)(CAU) and tRNA(Met)(CAU) transcripts (a recognition normally achieved through the modification of anticodon bases). This discrimination mechanism is based only on interactions with the acceptor stems of tRNA(Ile)(CAU) and tRNA(Met)(CAU). Thus, in certain species, the fidelity of translation of methionine codons requires a discrimination mechanism that is independent of the information contained in the anticodon.

Long-range functional communication is a hallmark of many enzymes that display allostery, or action-at-a-distance. Many aminoacyl-tRNA synthetases can be considered allosteric, in that their trinucleotide anticodons bind the enzyme at a site removed from their catalytic domains. Such is the case with E. coli methionyl-tRNA synthase (MetRS), which recognizes its cognate anticodon using a conserved tryptophan residue 50 A away from the site of tRNA aminoacylation. The lack of details regarding how MetRS and tRNA(Met) interact has limited efforts to deconvolute the long-range communication that occurs in this system. We have used molecular dynamics simulations to evaluate the mobility of wild-type MetRS and a Trp-461 variant shown previously by experiment to be deficient in tRNA aminoacylation. The simulations reveal that MetRS has significant mobility, particularly at structural motifs known to be involved in catalysis. Correlated motions are observed between residues in distant structural motifs, including the active site, zinc binding motif, and anticodon binding domain. Both mobility and correlated motions decrease significantly but not uniformly upon substitution at Trp-461. Mobility of some residues is essentially abolished upon removal of Trp-461, despite being tens of Angstroms away from the site of mutation and solvent exposed. This conserved residue does not simply participate in anticodon binding, as demonstrated experimentally, but appears to mediate the protein's distribution of structural ensembles. Finally, simulations of MetRS indicate that the ligand-free protein samples conformations similar to those observed in crystal structures with substrates and substrate analogs bound. Thus, there are low energetic barriers for MetRS to achieve the substrate-bound conformations previously determined by structural methods. Proteins 2007.(c) 2007 Wiley-Liss, Inc.