An early PEEP/FIO2 trial identifies different degrees of lung injury in patients with acute respiratory distress syndrome

RATIONALE: Current American-European Consensus Conference definitions for acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) are inadequate for inclusion into clinical trials due to the lack of standardization for measuring the oxygenation defect. OBJECTIVES: We questioned whether an early assessment of oxygenation on specific ventilator settings would identify patients with established ARDS (persisting over 24 h). METHODS: At the time of meeting ARDS criteria (Day 0) and 24 hours later (Day 1), arterial blood gases were obtained on standard ventilator settings, Vt 7 ml/kg predicted body weight plus the following positive end-expiratory pressure (PEEP) and Fi(O(2)) settings in sequence: (1) PEEP >or= 5 cm H(2)O and Fi(O(2)) >or= 0.5, (2) PEEP >or= 5 cm H(2)O and Fi(O(2)) 1.0, (3) PEEP >or= 10 cm H(2)O and Fi(O(2))>or=0.5, and (4) PEEP >or= 10 cm H(2)O and Fi(O(2)) 1.0. Measurements and Main Results: One hundred seventy patients meeting ARDS criteria (Pa(O(2))/Fi(O(2)) 128 +/- 33 mm Hg) were enrolled. Overall hospital mortality was 34.1%. The standard ventilator settings that best identified patients with established ARDS and predicted differences in intensive care unit (ICU) mortality were PEEP >or= 10 cm H(2)O and Fi(O(2)) >or= 0.5 at Day 1 (P = 0.0001). Only 99 (58.2%) patients continued to meet ARDS criteria (Pa(O(2))/Fi(O(2)), 155.8 +/- 29.8 mm Hg; ICU mortality, 45.5%), whereas 55 patients were reclassified as having ALI (Pa(O(2))/Fi(O(2)), 246.5 +/- 25.6 mm Hg; ICU mortality, 20%) and 16 patients as having acute respiratory failure (Pa(O(2))/Fi(O(2)), 370 +/- 54 mm Hg; ICU mortality, 6.3%) (P = 0.0001) on these settings. CONCLUSIONS: Patients meeting current American-European Consensus Conference ARDS criteria may have highly variable levels of lung injury and outcomes. A systematic method of assessing severity of lung injury is required for enrollment of patients with ARDS into randomized controlled trials. Clinical trial registered with www.clinicaltrials.gov (NCT 00435110).     

An FeIV=O complex of a tetradentate tripodal nonheme ligand

The reaction of [Fe(II)(tris(2-pyridylmethyl)amine, TPA)(NCCH(3))(2)](2+) with 1 equiv. peracetic acid in CH(3)CN at -40 degrees C results in the nearly quantitative formation of a pale green intermediate with lambda(max) at 724 nm ( epsilon approximately 300 M(-1).cm(-1)) formulated as [Fe(IV)(O)(TPA)](2+) by a combination of spectroscopic techniques. Its electrospray mass spectrum shows a prominent feature at mz 461, corresponding to the [Fe(IV)(O)(TPA)(ClO(4))](+) ion. The M?ssbauer spectra recorded in zero field reveal a doublet with DeltaE(Q) = 0.92(2) mms and delta = 0.01(2) mms; analysis of spectra obtained in strong magnetic fields yields parameters characteristic of S = 1 Fe(IV)O complexes. The presence of an Fe(IV)O unit is also indicated in its Fe K-edge x-ray absorption spectrum by an intense 1-s --> 3-d transition and the requirement for an ON scatterer at 1.67 A to fit the extended x-ray absorption fine structure region. The [Fe(IV)(O)(TPA)](2+) intermediate is stable at -40 degrees C for several days but decays quantitatively on warming to [Fe(2)(mu-O)(mu-OAc)(TPA)(2)](3+). Addition of thioanisole or cyclooctene at -40 degrees C results in the formation of thioanisole oxide (100% yield) or cyclooctene oxide (30% yield), respectively; thus [Fe(IV)(O)(TPA)](2+) is an effective oxygen-atom transfer agent. It is proposed that the Fe(IV)O species derives from OO bond heterolysis of an unobserved Fe(II)(TPA)-acyl peroxide complex. The characterization of [Fe(IV)(O)(TPA)](2+) as having a reactive terminal Fe(IV)O unit in a nonheme ligand environment lends credence to the proposed participation of analogous species in the oxygen activation mechanisms of many mononuclear nonheme iron enzymes.     

Oxide Formation during Transpassive Material Removal of Martensitic 42CrMo4 Steel by Electrochemical Machining

The efficiency of material removal by electrochemical machining (ECM) and rim zone modifications is highly dependent on material composition, the chemical surface condition at the break through potential, the electrolyte, the machining parameters and the resulting current densities and local current density distribution at the surfaces. The ECM process is mechanistically determined by transpassive anodic metal dissolution and layer formation at high voltages and specific electrolytic compositions. The mechanisms of transpassive anodic metal dissolution and oxide formation are not fully understood yet for steels such as 42CrMo4. Therefore, martensitic 42CrMo4 was subjected to ECM in sodium nitrate solution with two different current densities and compared to the native oxide of ground 42CrMo4. The material removal rate as well as anodic dissolution and transpassive oxide formation were investigated by mass spectroscopic analysis (ICP-MS) and (angle-resolved) X-ray photoelectron spectroscopy ((AR)XPS) after ECM. The results revealed the formation of a Fe_3−xO₄ mixed oxide and a change of the oxidation state for iron, chromium and molybdenum, e.g., 25% Fe (II) was present in the oxide at 20.6 A/cm² and was substituted by Fe (III) at 34.0 A/cm² to an amount of 10% Fe (II). Furthermore, ECM processing of 42CrMo4 in sodium nitrate solution was strongly determined by a stationary process with two parallel running steps: 1. Transpassive Fe_3−xO₄ mixed oxide formation/repassivation; as well as 2. dissolution of the transpassive oxide at the metal surface.     

Pulsatile stretch induces release of angiotensin II and oxidative stress in human endothelial cells: effects of ACE inhibition and AT1 receptor antagonism

Mechanical forces and the activation of the renin-angiotensin system (RAS) may alter the NO/O2(*-) balance, imparing endothelial nitric oxide (NO) availability. This study investigates the link between RAS and NO/O2(*-) balance in human aortic endothelial cells (HAEC) exposed to pulsatile stretch with and without ACE inhibitor quinaprilat or angiotensin II type 1 (AT(1)) receptor antagonist losartan. Pulsatile stretch increased Ang II levels and O2(*-) production, reducing NO release. RAS blockade with quinaprilat or losartan restored the balance between NO and O2(*-). These results provide a molecular basis for understanding the vascular protective effects of ACE inhibition and AT(1) receptor antagonism.     

Superoxo,mu-peroxo,and mu-oxo complexes from heme/O2 and heme-Cu/O2 reactivity: copper ligand influences in cytochrome c oxidase models

The O(2)-reaction chemistry of 1:1 mixtures of (F(8))Fe(II) (1; F(8) = tetrakis(2,6-diflurorophenyl)porphyrinate) and [(L(Me(2))N)Cu(I)](+) (2; L(Me(2))N = N,N-bis(2-[2-(N',N'-4-dimethylamino)pyridyl]ethyl)methylamine) is described, to model aspects of the chemistry occurring in cytochrome c oxidase. Spectroscopic investigations, along with stopped-flow kinetics, reveal that low-temperature oxygenation of 1/2 leads to rapid formation of a heme-superoxo species (F(8))Fe(III)-(O(2)(-)) (3), whether or not 2 is present. Complex 3 subsequently reacts with 2 to form [(F(8))Fe(III)-(O(2)(2-))-Cu(II)(L(Me(2))N)](+) (4), which thermally converts to [(F(8))Fe(III)-(O)-Cu(II)(L(Me(2))N)](+) (5), which has an unusually bent (Fe-O-Cu) bond moiety. Tridentate chelation, compared with tetradentate, is shown to dramatically lower the nu(O-O) values observed in 4 and give rise to the novel structural features in 5.     

Deuterium isotope effect on the intramolecular electron transfer in Pseudomonas aeruginosa azurin

Intramolecular electron transfer in azurin in water and deuterium oxide has been studied over a broad temperature range. The kinetic deuterium isotope effect, k(H)/k(D), is smaller than unity (0.7 at 298 K), primarily caused by the different activation entropies in water (-56.5 J K(-1) mol(-1)) and in deuterium oxide (-35.7 J K(-1) mol(-1)). This difference suggests a role for distinct protein solvation in the two media, which is supported by the results of voltammetric measurements: the reduction potential (E(0')) of Cu(2+/+) at 298 K is 10 mV more positive in D(2)O than in H(2)O. The temperature dependence of E(0') is also different, yielding entropy changes of -57 J K(-1) mol(-1) in water and -84 J K(-1) mol(-1) in deuterium oxide. The driving force difference of 10 mV is in keeping with the kinetic isotope effect, but the contribution to DeltaS from the temperature dependence of E(0') is positive rather than negative. Isotope effects are, however, also inherent in the nuclear reorganization Gibbs free energy and in the tunneling factor for the electron transfer process. A slightly larger thermal protein expansion in H(2)O than in D(2)O (0.001 nm K(-1)) is sufficient both to account for the activation entropy difference and to compensate for the different temperature dependencies of E(0'). Thus, differences in driving force and thermal expansion appear as the most straightforward rationale for the observed isotope effect.     

Nerve sprouting induced by radiofrequency catheter ablation in dogs

OBJECTIVES: The purpose of this study was to test the hypothesis that radiofrequency (RF) catheter ablation results in cardiac nerve sprouting. BACKGROUND: Nerve sprouting plays a role in cardiac arrhythmogenesis. Whether or not nerve sprouting occurs after RF catheter ablation is unclear. METHODS: We performed RF catheter ablation in the right atrium (RA) and right ventricle (RV) in 10 dogs, which then were sacrificed in 2 hours (acute group, n = 5) or 1 month (chronic group, n = 5). Seven normal dogs were used as control. Immunohistochemical staining for growth-associated protein 43 (GAP-43) was performed to measure growing (sprouting) nerves. RESULTS: A significant increase of GAP-43 immunoreactive nerve fiber density was observed at the RA ablation sites in 2 hours (4,410 +/- 1,379 microm(2)/mm(2)) and in 1 month (2,948 +/- 666 microm(2)/mm(2)) after ablation compared to controls (1,377 +/- 471 microm(2)/mm(2), P = .0001). At remote sites (>2 cm away from ablation sites) of RA, RF ablation also resulted in robust nerve sprouting in both the acute group (5,846 +/- 3241 microm(2)/mm(2)) and the chronic group (6,030 +/- 2226 microm(2)/mm(2)). RF ablation in the RV did not increase nerve density at the ablation sites, but nerve density was increased at remote sites in 2 hours (1,345 +/- 451 microm(2)/mm(2), P = .0136) that was reduced down to the normal control level (722 +/- 337 microm(2)/mm(2)) in 1 month. CONCLUSIONS: Nerve sprouting occurred within 2 hours after RF ablation in both the RA and RV and persisted for at least 1 month in the RA but not the RV. The increased GAP-43(+) nerve densities developed at both the ablation and the remote sites.     

A Novel Mechanism for the NIH-Shift

Kinetics of aromatization of 1,4-dimethylbenzene oxide (I) to 2,5-dimethylphenol (II) and 2,4-dimethylphenol (III), the latter arising by an NIH-Shift of a methyl group, as measured in the pH range 1-12, follow the equation -d[I]/dt = [I][k(0) + (k[unk] + k[unk])aH], where k(0) = 4.8 x 10(-3) sec(-1), k[unk] = 7.3 x 10(2) M(-1) sec(-1), and k[unk] = 5.3 x 10(2) M(-1) sec(-1). The ratio of products II to III at pH >/= 6 in the spontaneous rearrangement (k(0)) is 13 to 87, and changes to 54 to 46 in the acid-catalyzed rearrangement (k[unk] and k[unk]). While no intermediate is detectable in the acid-catalyzed rearrangement of the arene oxide by pathway k[unk], simultaneous addition of water (and other nucleophiles) by pathway k[unk] leads, via the intermediate 1,4-dimethyl-2,5-cyclohexadiene-1,4-diol (IV), to the phenols II and III. This new mechanism for the NIH-Shift serves as a model for the ease of nucleophilic addition to other arene oxides, such as those of the polycyclic aromatic hydrocarbons recently implicated in mechanisms of carcinogenesis.     

Angiotensin II induces angiogenesis in the hypoxic adult mouse heart in vitro through an AT2-B2 receptor pathway

Angiotensin II is a vasoactive peptide that may affect vascularization of the ischemic heart via angiogenesis. In this study we aimed at studying the mechanisms underlying the angiogenic effects of angiotensin II under hypoxia in the mouse heart in vitro. Endothelial sprout formation from pieces of mouse hearts was assessed under normoxia (21% O(2)) and hypoxia (1% O(2)) during a 7-day period of in vitro culture. Only under hypoxia did angiotensin II dose-dependently induce endothelial sprout formation, peaking at 10(-7) mol/L of angiotensin II. Angiotensin II type 1 (AT(1)) receptor blockade by losartan did not affect angiotensin II-induced sprouting in wild-type mice. Conversely, the angiotensin II type 2 (AT(2)) receptor antagonist PD 123319 blocked this response. In hearts from AT(1)(-/-) mice, angiotensin II-elicited sprouting was preserved but blocked again by AT(2) receptor antagonism. In contrast, no angiotensin II-induced sprouting was found in preparations from hearts of AT(2)(-/-) mice. Angiotensin II-mediated angiogenesis was also abolished by a specific inhibitor of the B2 kinin receptor in both wild-type and AT(1)(-/-) mice. Furthermore, angiotensin II failed to induce endothelial sprout formation in hearts from B2(-/-) mice. Finally, NO inhibition completely blunted sprouting in hearts from wild-type mice, whereas NO donors could restore sprouting in AT(2)(-/-) and B2(-/-) hearts. This in vitro study suggests the obligatory role of hypoxia in the angiogenic effect of angiotensin II in the mouse heart via the AT(2) receptor through a mechanism that involves bradykinin, its B2 receptor, and NO as a downstream effector.     

Using diastereopeptides to control metal ion coordination in proteins

Here, we report a previously undescribed approach for controlling metal ion coordination geometry in biomolecules by reorientating amino acid side chains through substitution of L- to D-amino acids. These diastereopeptides allow us to manipulate the spatial orientation of amino acid side chains to alter the sterics of metal binding pockets. We have used this approach to design the de novo metallopeptide, Cd(TRIL12L(D)L16C)(3)(-), which is an example of Cd(II) bound to 3 L-Cys as exclusively trigonal CdS(3), as characterized by a combination of (113)Cd NMR and (111m)Cd PAC spectroscopy. We subsequently show that the physical properties of such a site, such as the high pK(a2) for Cd(II) binding of 15.1, is due to the nature of the coordination number and not the ligating group. Further more this approach allowed for the design of a construct, GRANDL12L(D)L16CL26AL30C, capable of independently binding 2 equivalents of Cd(II) to 2 very similar Cys sites as exclusively 3- and 4-, CdS(3) and CdS(3)O, respectively. Demonstrating that we are capable of controlling the Cd(II) coordination number in these 2 sites solely by varying the nature of a noncoordinating second coordination sphere amino acid, with D-leucine and L-alanine resulting in exclusively 3- and 4-coordinate structures, respectively. Cd(II) was found to selectively bind to the 4-coordinate CdS(3)O site, demonstrating that a protein can be designed that displays metal-binding selectivity based solely on coordination number control and not on the chemical identity of coordinating ligands.     

Iron uptake in ferritin is blocked by binding of [Cr(TREN)(H(2)O)(OH)](2+), a slow dissociating model for [Fe(H(2)O)(6)](2+)

Ferritin concentrates iron as a hydrous ferric oxide in a protein cavity (8 nm in diameter) by using eight pores along the threefold symmetry axes of the octahedral supramolecular structure. The role of ligand exchange in the entry of Fe(II) hexahydrate into ferritin protein has been studied with [Cr(TREN)(H(2)O)(OH)](2+) [TREN = N(CH(2)CH(2)NH(2))(3)], a model for Fe(H(2)O)(6)2+ with only two exchangeable ligands. The results show that five different ferritin proteins, varying in pore structure, oxidation sites, and nucleation sites, bind Cr(TREN) at functional protein sites, based on inhibition of iron mineralization and oxidation. Properties of Cr(TREN)-ferritin adducts include an increased isoelectric point, a shift in the Cr(TREN) UV/vis spectrum consistent with exchange of water for protein carboxylate or thiolate ligands, binding affinities of 50-250 microM, and a slow rate of dissociation (k = 4 x 10(-6) sec(-1)). The relationship of Cr(TREN) inhibition of iron oxidation and mineralization by Cr(TREN) to the known structures of the various ferritins tested suggests that Cr(TREN) plugs the ferritin pores, obstructing Fe(II) entry in folded and unfolded pores. Because only two exchangeable waters are sufficient for pore binding of Cr(TREN), the physiological Fe(II) donor must bind to the pore with few exchangeable ligands. These results show the advantage of using stable model complexes to explore properties of transient Fe-protein complexes during Fe mineralization in ferritin.     

Investigation into the sources of superoxide in human blood vessels: angiotensin II increases superoxide production in human internal mammary arteries

BACKGROUND: Increased vascular superoxide anion (.O(2)(-)) production contributes to endothelial dysfunction and hypertension in animal models of cardiovascular disease. Observations in experimental animals suggest that angiotensin II (Ang II) increases.O(2)(-) production by activation of vascular NAD(P)H oxidase. We studied the sources of.O(2)(-) production in human blood vessels and investigated whether, and by what mechanism, Ang II might alter vascular.O(2)(-) production. METHODS AND RESULTS: Internal mammary arteries (IMAs) and saphenous veins (SVs) were collected at the time of cardiac surgery. Vessels were incubated in Krebs buffer at 37 degrees C.O(2)(-) was measured by lucigenin chemiluminescence. Basal. O(2)(-) concentrations were greater in IMAs than SVs. Inhibitors of NAD(P)H oxidase (10 micromol/L to 200 micromol/L diphenyleneiodonium) and xanthine oxidase (1 mmol/L allopurinol) caused reductions in.O(2)(-) concentrations in both IMAs and SVs. Western blotting of superoxide dismutase proteins demonstrated similar expression in IMAs and SVs. Vessels were also incubated in the presence or absence of Ang II (1 pmol/L to 1 micromol/L). Ang II increased.O(2)(-) production in IMAs at 4 hours of incubation (control, 978+/-117 pmol. min(-1). mg(-1); 1 micromol/L of Ang II, 1690+/-213 pmol. min(-1). mg(-1); n=27, P=0.0001, 95% CI 336, 925) but not in SVs. This effect was completely inhibited by coincubation of IMAs with DPI (100 micromol/L), a nonspecific Ang II antagonist ([sar(1), thre(8)]-Ang II, 1 micromol/L) and a specific Ang II type 1 (AT(1)) receptor antagonist (losartan, 1 micromol/L). Conclusions-. O(2)(-) production is greater in human IMAs than in SVs. NAD(P)H oxidase and xanthine oxidase are sources of.O(2)(-) production in these vessels. The vasoactive peptide Ang II increases.O(2)(-) production in human arteries by an AT(1) receptor-dependent mechanism.     

P(O(2))-P(CO(2)) stimulus interaction in [Ca(2+)](i) and CSN activity in the adult rat carotid body

Since glomus cell intracellular calcium ([Ca(2+)](i)) plays a key role in generating carotid sinus nerve (CSN) discharge, we hypothesized that glomus cell [Ca(2+)](i) would correspond to CSN discharge rates during P(O(2))-P(CO(2)) stimulus interaction in adult rat carotid body (CB). Accordingly, we measured steady state P(O(2))-P(CO(2)) interaction in CSN discharge rates during hypocapnia (P(CO(2))=8-10 Torr), normocapnia (P(CO(2))=33-35 Torr) and hypercapnia (P(CO(2))=68-70 Torr) in normoxia (P(O(2)) approximately 130 Torr) and hypoxia (P(O(2)) approximately 36 Torr). The results showed P(O(2))-P(CO(2)) stimulus interaction in CSN responses. [Ca(2+)](i) levels were measured in isolated type I cells (2-3 cells/field), using Ca(2+) sensitive fluoroprobe indo-1AM. The [Ca(2+)](i) responses increased with increasing P(CO(2)) in normoxia. In hypoxia, [Ca(2+)](i) did not increase during hypocapnia but increased during normocapnia, showing P(O(2))-P(CO(2)) interaction. However, CSN response during hypoxia was far greater than that for [Ca(2+)](i) response, particularly during hypocapnic hypoxia. Thus, the [Ca(2+)](i) interaction cannot account for the whole CSN interaction. The origin of this CSN P(O(2)-)P(CO(2)) interaction must have occurred in part beyond cellular [Ca(2+)](i) interaction. Interactions at both sites (glomus cell membrane and sinus nerve endings) are reminiscent of reversible O(2)-heme protein reaction with a Bohr effect.     

Metal-coordinating substrate analogs as inhibitors of metalloenzymes.

A group of active-site metal coordinating inhibitors of zinc proteases (carboxypeptidase A, thermolysin, Bacillus cereus neutral protease, and angiotensin-converting enzyme) have been synthesized and their properties investigated. Their general structures are R-SH and R-NH-PO2(O phi)H, where-S- or -O- serve as metal ligands and R refers to an amino acid or peptide group designed to interact with substrate recognition sites. These inhibitors can be extremely potent; thus, N-(2-mercaptoacetyl)-D-phenylalanine, e.g., inhibits carboxypeptidase A with a Kiapp of 2.2 x 10(-7) M. The spectral response of cobalt(II)-substituted thermolysin or carboxypeptidase A to the sulfur-containing inhibitors signals the direct interaction of the mercaptan with the metal. An S leads to Co(II) charge transfer band is generated near 340 nm and is detected by absorption, circular dichroism, and magnetic circular dichroism. The cobalt(II) spectra indicate both inner sphere coordination with sulfur and 4-coordination in the enzyme-inhibitor complex. Thus, the metal undergoes a simple substitution reaction, the inhibitor most likely displacing water at the fourth coordination site.     

Neuronal nitric oxide synthase negatively regulates xanthine oxidoreductase inhibition of cardiac excitation-contraction coupling

Although interactions between superoxide (O(2)(.-)) and nitric oxide underlie many physiologic and pathophysiologic processes, regulation of this crosstalk at the enzymatic level is poorly understood. Here, we demonstrate that xanthine oxidoreductase (XOR), a prototypic superoxide O(2)(.-) -producing enzyme, and neuronal nitric oxide synthase (NOS1) coimmunoprecipitate and colocalize in the sarcoplasmic reticulum of cardiac myocytes. Deficiency of NOS1 (but not endothelial NOS, NOS3) leads to profound increases in XOR-mediated O(2)(.-) production, which in turn depresses myocardial excitation-contraction coupling in a manner reversible by XOR inhibition with allopurinol. These data demonstrate a unique interaction between a nitric oxide and an O(2)(.-) -generating enzyme that accounts for crosstalk between these signaling pathways; these findings demonstrate a direct antioxidant mechanism for NOS1 and have pathophysiologic implications for the growing number of disease states in which increased XOR activity plays a role.     

Shewanella secretes flavins that mediate extracellular electron transfer

Bacteria able to transfer electrons to metals are key agents in biogeochemical metal cycling, subsurface bioremediation, and corrosion processes. More recently, these bacteria have gained attention as the transfer of electrons from the cell surface to conductive materials can be used in multiple applications. In this work, we adapted electrochemical techniques to probe intact biofilms of Shewanella oneidensis MR-1 and Shewanella sp. MR-4 grown by using a poised electrode as an electron acceptor. This approach detected redox-active molecules within biofilms, which were involved in electron transfer to the electrode. A combination of methods identified a mixture of riboflavin and riboflavin-5'-phosphate in supernatants from biofilm reactors, with riboflavin representing the dominant component during sustained incubations (>72 h). Removal of riboflavin from biofilms reduced the rate of electron transfer to electrodes by >70%, consistent with a role as a soluble redox shuttle carrying electrons from the cell surface to external acceptors. Differential pulse voltammetry and cyclic voltammetry revealed a layer of flavins adsorbed to electrodes, even after soluble components were removed, especially in older biofilms. Riboflavin adsorbed quickly to other surfaces of geochemical interest, such as Fe(III) and Mn(IV) oxy(hydr)oxides. This in situ demonstration of flavin production, and sequestration at surfaces, requires the paradigm of soluble redox shuttles in geochemistry to be adjusted to include binding and modification of surfaces. Moreover, the known ability of isoalloxazine rings to act as metal chelators, along with their electron shuttling capacity, suggests that extracellular respiration of minerals by Shewanella is more complex than originally conceived.     

Superoxide dismutase improves gas exchange and pulmonary hemodynamics in premature lambs

RATIONALE: Oxidant stress may increase the severity of respiratory distress syndrome (RDS) after premature birth by altering vasoreactivity and increasing lung edema, but the acute effects of superoxide dismutase (SOD) treatment on gas exchange, lung compliance (CL), and pulmonary vascular resistance in premature animals with RDS are unknown. OBJECTIVE: We studied the effects of intratracheal recombinant human SOD treatment (rhSOD) on gas exchange, CL, and pulmonary hemodynamics in 46 premature lambs with RDS. Methods: After C-section delivery, lambs were randomly assigned to treatment with SOD (2.5-10 mg/kg) with or without inhaled nitric oxide (iNO, 5 ppm), and mechanically ventilated for 4 hours. At the end of the study, pressure-volume curves and wet-dry lung weights were measured to assess CL and edema, respectively. MAIN RESULTS: Despite an initial rise in Pa(O(2)), Pa(O(2)) in control animals progressively declined over the 4-hour treatment period (Pa(O(2)) = 25.0 +/- 7.5 mm Hg at 4 hours). In comparison with control animals, early treatment with SOD at 5 and 10 mg/kg improved Pa(O(2)) at 4 hours (167 +/- 44 and 269 +/- 33 mm Hg, respectively; p < 0.05 vs. control), but did not decrease lung edema or improve CL. In contrast, late treatment with SOD did not improve Pa(O(2)). Treatment with iNO increased Pa(O(2)) (196 +/- 22 vs. 25 +/- 8 mm Hg, control animals; p < 0.01), but the response to iNO was not augmented by combined therapy (SOD + iNO). After 4 hours of ventilation with FI(O(2)) = 1.00, rhSOD treatment lowered pulmonary vascular resistance compared with control animals. CONCLUSIONS: Early intratracheal rhSOD treatment improves oxygenation in premature lambs with RDS and prevents the development of pulmonary hypertension.     

In salt-sensitive hypertension,increased superoxide production is linked to functional upregulation of angiotensin II

The balance between endothelial nitric oxide (NO) and angiotensin II (Ang II) maintains the homeostasis of the cardiovascular and renal systems. We tested the hypothesis that increased oxidant stress linked to a functional imbalance between NO and Ang II might play a central pathogenetic role in salt-sensitive (SS) hypertension. We studied Dahl SS (DS) rats during the prehypertensive (5 days) and hypertensive (12 weeks) phases of a high-salt (4% NaCl) diet. Control rats received a normal-salt (0.5% NaCl, [NS]) diet. Prehypertensive DS rats (systolic blood pressure [SBP] 138+/-2 mm Hg) manifested a 35% increase (P<0.05) in aortic superoxide (O2-) production without evidence of end-organ damage. Hypertensive DS rats (SBP 214+/-11 mm Hg) had impaired endothelium-dependent relaxation (EDR) and increased aortic O2- production (320%), urinary isoprostane excretion (83%), aortic (20%) and left ventricular (LVH, 21%) hypertrophy, and proteinuria (124%). In prehypertensive DS rats, candesartan (10 mg x kg(-1) x d(-1)) an Ang II type 1 receptor blocker (ARB), normalized O2- production. In hypertensive DS rats, the ARB decreased aortic O2- production by 71% and normalized EDR without affecting SBP (212+/-8 mm Hg), aortic hypertrophy, LVH, or proteinuria. Switching hypertensive DS rats to an NS diet did not affect SBP (208+/-8 mm Hg), LVH, aortic hypertrophy, or proteinuria and had minimal effects on O2- and EDR. Concomitant ARB administration plus a switch to an NS diet normalized SBP (138+/-8 mm Hg) as well as end-organ damage. Dahl salt-resistant rats fed an HS diet for 12 weeks did not show hypertension or increased O2- production. Thus, SS hypertension might represent a specific vascular diathesis linked to functional upregulation of Ang II action (increased O2- synthesis) accompanied by insufficient NO bioavailability, which promotes severe endothelial dysfunction.     

Work-rate affects cardiopulmonary exercise test results in heart failure

AIMS: Cardiopulmonary exercise test (CPET) is used to evaluate patients with chronic heart failure (HF) usually by means of a personalized ramp exercise protocol. Our aim was to evaluate if exercise duration or ramp rate influences the results. METHODS AND RESULTS: Ninety HF patients were studied (peak V (O(2)): >20 ml/min/kg, n=28, 15-20 ml/min/kg, n=39 and <15 ml/min/kg, n=23). Each patient did four CPET studies. The initial study was used to separate the subjects into three groups, according to their exercise capacity. In the remaining studies, work-rate was increased at three different rates designed to have the subjects reach peak exercise in 5, 10 and 15 min from the start of the ramp increase in work-rate, respectively. The order was randomized. The work-rate applied for the total population averaged 22.7+/-8.0, 11.6+/-3.7, 7.5+/-2.9 W/min with effective loaded exercise duration of 5 min and 16 s+/-29 s, 9 min and 43 s+/-49 s and 14 min and 32 s+/-1 min and 12 s for the 5-, 10- and 15-min tests, respectively. Peak V (O(2)) averaged 16.9+/-4.3*, 18.0+/-4.4 and 18.0+/-5.4 ml/min/kg for the 5-, 10- and 15-min tests, (*=p<0.001 vs. 10 min). The shortest test had the lowest peak heart rate and ventilation and highest peak work-rate. Peak V (O(2)) and heart rate were lowest in 5-min tests regardless of HF severity. The DeltaV (O(2))/Deltawork-rate was lowest in 5-min tests and highest in 15-min tests. At all ramp rates, DeltaV (O(2))/Deltawork-rate was lower for the subjects with the lower peak V (O(2)). The V (e)/V (CO(2)) slope and V (O(2)) at anaerobic threshold were not affected by the protocol for any grade of HF. CONCLUSIONS: In chronic HF, exercise protocol has a small effect on peak V (O(2)) and DeltaV (O(2))/Deltawork but does not affect V (O(2)) at anaerobic threshold and V (e)/V (CO(2)) slope.     

O2 activation by binuclear Cu sites: noncoupled versus exchange coupled reaction mechanisms

Binuclear Cu proteins play vital roles in O(2) binding and activation in biology and can be classified into coupled and noncoupled binuclear sites based on the magnetic interaction between the two Cu centers. Coupled binuclear Cu proteins include hemocyanin, tyrosinase, and catechol oxidase. These proteins have two Cu centers strongly magnetically coupled through direct bridging ligands that provide a mechanism for the 2-electron reduction of O(2) to a mu-eta(2):eta(2) side-on peroxide bridged Cu(II)(2)(O(2)(2-)) species. This side-on bridged peroxo-Cu(II)(2) species is activated for electrophilic attack on the phenolic ring of substrates. Noncoupled binuclear Cu proteins include peptidylglycine alpha-hydroxylating monooxygenase and dopamine beta-monooxygenase. These proteins have binuclear Cu active sites that are distant, that exhibit no exchange interaction, and that activate O(2) at a single Cu center to generate a reactive Cu(II)/O(2) species for H-atom abstraction from the C-H bond of substrates. O(2) intermediates in the coupled binuclear Cu enzymes can be trapped and studied spectroscopically. Possible intermediates in noncoupled binuclear Cu proteins can be defined through correlation to mononuclear Cu(II)/O(2) model complexes. The different intermediates in these two classes of binuclear Cu proteins exhibit different reactivities that correlate with their different electronic structures and exchange coupling interactions between the binuclear Cu centers. These studies provide insight into the role of exchange coupling between the Cu centers in their reaction mechanisms.