Transmyocardial laser revascularization remodels the intrinsic cardiac nervous system in a chronic setting. (41/497)

BACKGROUND: Prospective trials have demonstrated that transmyocardial laser revascularization (TMLR) imparts symptomatic relief to patients with refractory angina. Because peak clinical effectiveness of TMLR is usually delayed by several months, it has been proposed that ventricular denervation is one mechanism whereby TMLR imparts symptomatic relief. We have demonstrated that TMLR does not denervate the heart in the acute setting, nor does it modify the intrinsic cardiac nervous system (ICNS) in the acute setting. However, the long-term effects of TMLR on the ICNS remain unknown. METHODS AND RESULTS: A holmium:yttrium-aluminum-garnet laser created 20 channels through the anterolateral left ventricular free wall of 10 dogs. Four weeks later, the function of cardiac sensory inputs to the ICNS was studied by applying veratridine (7.5 micromol/L) to ventricular sensory fields. Chronotropic and inotropic responses elicited by cardiac sympathetic or parasympathetic efferent neurons stimulated electrically (10 Hz, 4 V, 4 ms) or chemically (nicotine 5 to 20 microgram/kg IV) were also assessed. Chemical activation of epicardial sensory neurites with veratridine elicited expected ICNS excitatory responses. Electrical stimulation of sympathetic and parasympathetic efferent neurons induced expected altered cardiac responses. In contrast, the responsiveness of the ICNS to systemically administered nicotine was obtunded. CONCLUSIONS: Although chronic TMLR does not affect cardiac afferent or extracardiac efferent neuronal function, it does "remodel" the ICNS so that its responsiveness to a known potent chemical agonist (ie, nicotine) becomes obtunded. Remodeling of the ICNS may account in part for the delayed symptomatic relief that TMLR imparts to patients with refractory angina.  (+info)

Group-specific monitoring of phenol hydroxylase genes for a functional assessment of phenol-stimulated trichloroethylene bioremediation. (42/497)

The sequences of the largest subunit of bacterial multicomponent phenol hydroxylases (LmPHs) were compared. It was found that LmPHs formed three phylogenetic groups, I, II, and III, corresponding to three previously reported kinetic groups, low-K(s) (the half-saturation constant in Haldane's equation for trichloroethylene [TCE]), moderate-K(s), and high-K(s) groups. Consensus sequences and specific amino acid residues for each group of LmPH were found, which facilitated the design of universal and group-specific PCR primers. PCR-mediated approaches using these primers were applied to analyze phenol/TCE-degrading populations in TCE-contaminated aquifer soil. It was found that the aquifer soil harbored diverse genotypes of LmPH, and the group-specific primers successfully amplified LmPH fragments affiliated with each of the three groups. Analyses of phenol-degrading bacteria isolated from the aquifer soil confirmed the correlation between genotype and phenotype. Competitive PCR assays were used to quantify LmPHs belonging to each group during the enrichment of phenol/TCE-degrading bacteria from the aquifer soil. We found that an enrichment culture established by batch phenol feeding expressed low TCE-degrading activity at a TCE concentration relevant to the contaminated aquifer (e.g., 0.5 mg liter(-1)); group II and III LmPHs were predominant in this batch enrichment. In contrast, group I LmPHs overgrew an enrichment culture when phenol was fed continuously. This enrichment expressed unexpectedly high TCE-degrading activity that was comparable to the activity expressed by a pure culture of Methylosinus trichosporium OB3b. These results demonstrate the utility of the group-specific monitoring of LmPH genes in phenol-stimulated TCE bioremediation. It is also suggested that phenol biostimulation could become a powerful TCE bioremediation strategy when bacteria possessing group I LmPHs are selectively stimulated.  (+info)

Involvement of the flavin si-face tyrosine on the structure and function of ferredoxin-NADP+ reductases. (43/497)

In ferredoxin-NADP(+) reductase (FNR), FAD is bound outside of an anti-parallel beta-barrel with the isoalloxazine lying in a two-tyrosine pocket. To elucidate the function of the flavin si-face tyrosine (Tyr-89 in pea FNR) on the enzyme structure and catalysis, we performed ab initio molecular orbital calculations and site-directed mutagenesis. Our results indicate that the position of Tyr-89 in pea FNR is mainly governed by the energetic minimum of the pairwise interaction between the phenol ring and the flavin. Moreover, most of FNR-like proteins displayed geometries for the si-face tyrosine phenol and the flavin, which correspond to the more negative free energy theoretical value. FNR mutants were obtained replacing Tyr-89 by Phe, Trp, Ser, or Gly. Structural and functional features of purified FNR mutants indicate that aromaticity on residue 89 is essential for FAD binding and proper folding of the protein. Moreover, hydrogen bonding through the Tyr-89 hydroxyl group may be responsible of the correct positioning of FAD and the substrate NADP(+)  (+info)

Chemoprotection by phenolic antioxidants. Inhibition of tumor necrosis factor alpha induction in macrophages. (44/497)

Phenolic antioxidants exhibit anti-inflammatory activity in protection against chemical toxicity and cancer. To investigate the molecular mechanism of anti-inflammation, we analyzed the regulation of tumor necrosis factor alpha (TNF-alpha) expression in macrophages, a key step in inflammation, by the antioxidants. Whereas lipopolysaccharide (LPS), an inflammatory inducer, stimulates rapid synthesis of TNF-alpha protein, phenolic antioxidants, exemplified by tert-butyl hydroquinone and 1,4-dihydroquinone, block LPS-induced production of TNF-alpha protein in a time- and dose-dependent manner. Inhibition of TNF-alpha induction correlates with the capacity of the antioxidants to undergo oxidation-reduction cycling, implicating oxidative signaling in the inhibition. The antioxidants blocked LPS-induced increase of the steady-state mRNA of TNF-alpha but did not affect the half-life of the mRNA. Electrophoretic mobility shift assay reveals a total inhibition of LPS-induced formation of nuclear factor kappaB.DNA binding complexes by phenolic antioxidants. Finally, 1,4-dihydroquinone blocks the induction of TNF-alpha target genes interleukin 1beta and interleukin 6 at both mRNA and protein levels. Our findings demonstrate that phenolic antioxidants potently inhibit signal-induced TNF-alpha transcription and suggest a mechanism of anti-inflammation by the antioxidants through control of cytokine induction during inflammation.  (+info)

Mechanism of anaerobic ether cleavage: conversion of 2-phenoxyethanol to phenol and acetaldehyde by Acetobacterium sp. (45/497)

2-Phenoxyethanol is converted into phenol and acetate by a strictly anaerobic Gram-positive bacterium, Acetobacterium strain LuPhet1. Acetate results from oxidation of acetaldehyde that is the early product of the biodegradation process (Frings, J., and Schink, B. (1994) Arch. Microbiol. 162, 199-204). Feeding experiments with resting cell suspensions and 2-phenoxyethanol bearing two deuterium atoms at either carbon of the glycolic moiety as substrate demonstrated that the carbonyl group of the acetate derives from the alcoholic function and the methyl group derives from the adjacent carbon. A concomitant migration of a deuterium atom from C-1 to C-2 was observed. These findings were confirmed by NMR analysis of the acetate obtained by fermentation of 2-phenoxy-[2-(13)C,1-(2)H(2)]ethanol, 2-phenoxy-[1-(13)C,1-(2)H(2)]ethanol, and 2-phenoxy-[1,2-(13)C(2),1-(2)H(2)]ethanol. During the course of the biotransformation process, the molecular integrity of the glycolic unit was completely retained, no loss of the migrating deuterium occurred by exchange with the medium, and the 1,2-deuterium shift was intramolecular. A diol dehydratase-like mechanism could explain the enzymatic cleavage of the ether bond of 2-phenoxyethanol, provided that an intramolecular H/OC(6)H(5) exchange is assumed, giving rise to the hemiacetal precursor of acetaldehyde. However, an alternative mechanism is proposed that is supported by the well recognized propensity of alpha-hydroxyradical and of its conjugate base (ketyl anion) to eliminate a beta-positioned leaving group.  (+info)

Probing alkali metal-pi interactions with the side chain residue of tryptophan. (46/497)

Feeble forces play a significant role in the organization of proteins. These include hydrogen bonding, hydrophobic interactions, salt bridge formation, and steric interactions. The alkali metal cation-pi interaction is a force of potentially profound importance but its consideration in biology has been limited by the lack of experimental evidence. Our previous studies of cation-pi interactions with Na(+) and K(+) involved the side arms of tryptophan (indole), tyrosine (phenol), and phenylalanine (benzene) as the arene donors. The receptor system possesses limiting steric constraints. In this report, we show that direct interactions between alkali metals and arenes occur at or within the van der Waals contact distance.  (+info)

Intestinal metabolism: the role of enzyme localization in phenol metabolite kinetics. (47/497)

The influence of enzyme localization and blood flow on intestinal elimination was evaluated in rats. Phenol was administered vascularly (approximately 1400 and 2500 microg) and luminally (intrajejunal bolus doses of approximately 100 and 1000 microg) to the recirculating in situ perfused intestine. The portal effluent and the reservoir were sampled. The intestinal extraction ratios for phenol at the low and high vascular doses were (mean +/- S.D., n = 3) 0.09 +/- 0.02 and 0.11 +/- 0.01, respectively. The perfusion flow rate was also varied from 5 to 12 ml/min at a vascular dose of approximately 2500 microg of phenol. The organ clearance at the lowest flow rate significantly exceeded those at the higher flow rates. The presence of a diffusional barrier at the mucosa-serosa interface was suggested. The calculated mean diffusional clearance of phenol was 1.11 ml/min. Sulfation was the predominant metabolic pathway after vascular administration of phenol. After luminal dosing, the intestinal intrinsic clearances of phenol at the low and high doses were 7.29 +/- 1.39 (n = 4) and 3.55 +/- 1.16 ml/min (n = 3), respectively, indicating saturation at the higher dose. Moreover, there was a decrease in the area under the curve ratio (metabolite/phenol) at the high luminal dose. Luminal administration, in general, produced greater glucuronidation. These data and STELLA simulations suggest that enzyme localization at both the cellular and tissue levels has a significant influence on intestinal metabolism.  (+info)

Biomimetic macrocyclic receptors for carboxylate anion recognition based on C-linked peptidocalix[4]arenes. (48/497)

Two neutral macrobicyclic anion receptors 4 and 6, containing a calix[4]arene in the cone conformation, two l-alanine units, and a 2,6-diacylpyridine or a phthaloyl bridge, are described. The x-ray crystal structure of the acetone complexes of the pyridine containing macrocycle 6 shows the four amide NH groups to be in close proximity to the chiral pocket delimited by the pyridine and one aromatic nucleus of the calix[4]arene. This conformation is also the most stable in acetone-d6 solution, as proven by one- and two-dimensional NMR spectral measurements. Electrospray ionization-MS and (1)H NMR experiments reveal that the two ligands strongly bind carboxylate anions in acetone solution. H-bonding interactions between the carboxylate anions and the amide NH groups, together with pi/pi stacking, are invoked to explain the efficiency and the selectivity of these anion receptors.  (+info)