Effects of hydroxyl radicals on purified angiotensin I converting enzyme

Somatic angiotensin-converting enzyme (ACE) is a protein which contains two similar domains (N and C), each possessing a functional active site. The relationship between ACE, its natural substrates and oxygen free radicals is starting to be explored. On one hand, superoxide anions production is induced by angiotensin II and on the other hand, activated polynuclear neutrophils, through free radicals generation, alter endothelial ACE activity. In this study, we examined the impact of hydroxyl radicals (.OH) on purified ACE. .OH were produced using a generator: 2,2'-azo-bis 2-amidinopropane (GRH) provided by Lara-Spiral (Fr). GRH (3 mM), in a time-dependent fashion, inhibited ACE activity. When ACE was co-incubated for 4 h with GRH, its activity decreased by 70%. Addition of dimethylthiourea (DMTU: 0.03 to 1 mM) or mannitol + methionine (20/10 mM), two sets of .OH scavengers, produced a dose-dependent protection on ACE activity. To examine whether oxidation of thiol groups in the ACE molecule could be involved in the action of GRH, the effects of thiol reducing agents: mercaptoethanol and dithiotreitol (DTT) were investigated. These compounds produced a dose-dependent and significant protection; with 100% protection at 0.2 and 0.3 mM for mercaptoethanol and at 0.1 mM for DTT. The hydrolysis of two natural and domain-specific substrates were also explored. The hydrolysis of angiotensin I preferentially cleaved by the C domain was significantly (p < 0.01) inhibited by 57, 58 and 69% in contact with 0.3, 1 and 3 mM GRH [in nmol angio II formed/min/nmol of ACE, n = 4; 35.9 +/- 0.6 (control), 15.5 +/- 2.8 (GRH : 0.3 mM), 15.1 +/- 0.5 (1), 10.9 +/- 0.6 (3)]. The hydrolysis of the hemoregulatory peptide (hp), preferential substrate for the N domain was not affected by GRH at 0.3 mM and inhibited by 28% (not significant) by 1 mM GRH [in nmol ph hydrolized/min/nmol ACE, n = 4; 12.6 +/- 1.9 (control), 14.9 (GRH : 0.3 mM), 8.3 +/- 4.0 (1). These results demonstrated that .OH affect ACE activity and could suggest a privileged impact of GRH on the C domain. The precise sites of action of .OH remain unknown. The Cys residues near the active centers, by forming disulphide bridges during the oxidation could be of critical importance. Further studies will be needed to determine whether oxidative stress again ACE can be involved in the genesis of inflammatory vascular pathologies.     

Local penalty methods for flows interacting with moving solids at high Reynolds numbers

An original numerical modelling of multiphase flows interacting with solids in unsteady regimes is presented. Based on the generalized Navier-Stokes equations for multiphase flows and Volume of Fluid (VOF) formulations, an Uzawa minimization algorithm is implemented for the treatment of incompressibility and solid constraints. Augmented Lagrangian terms are added in the momentum equations to speed the convergence of the iterative solver. Defining a priori the penalty parameters which are dedicated to incompressibility and solid constraints is difficult, or impossible, as soon as the flow involves more than one phase and inertia becomes predominant compared to viscous and gravity forces. The Lagrangian penalty terms are calculated automatically according to an original local estimate of the various physical contributions. Numerical validations have been carried out for single particle settling in confined media and viscous flow through a fixed Cubic Faced Centered array. A very good agreement is obtained between experimental, theoretical and numerical results. Extension to unsteady free surface flow interacting with particles is illustrated with the simulation of a dam break flow over moving obstacles.     

Alkaloids in the Mite <Emphasis Type="Italic">Scheloribates laevigatus</Emphasis>: Further Alkaloids Common to Oribatid Mites and Poison Frogs

Poison frogs are chemically defended from predators by diverse alkaloids, almost all of which are sequestered unchanged from alkaloid-containing arthropods in the frog diet. Oribatid mites recently have been proposed as a major dietary source of poison frog alkaloids. Here, we report on alkaloids common to an oribatid mite and poison frogs. Gas chromatographic-mass spectrometric analysis of methanol extracts of adult Scheloribates laevigatus (Oribatida: Scheloribatidae) revealed nine alkaloids. Five of these have been detected previously in the skin glands of poison frogs: two isomers of the pumiliotoxin 291G, two isomers of the 5,6,8-trisubstituted indolizidine 209C, and the 5,6,8-trisubstituted indolizidine 195G. The other four alkaloids, a pumiliotoxin, a tricyclic (coccinelline-like), and two isomers of an izidine, were not previously known, but are similar in structure to alkaloids found in poison frogs. Alkaloids were not detected in immature S. laevigatus, suggesting that they are adult-specific and possibly the result of mite biosynthesis. Although most of the alkaloids detected in S. laevigatus are common to poison frogs, the geographic distributions of these organisms are not sympatric. The findings of this study indicate that oribatid mites, and in particular, members of the genus Scheloribates, represent a relatively unexplored arthropod repository for alkaloids and a significant dietary source of alkaloids in poison frogs.     

High deposition efficiency and delamination issues during high-pressure cold spraying metallization of PEEK using spherical copper powders

The International Journal of Advanced Manufacturing Technology - Achieving high deposition efficiency (DE) is a current challenge of cold spraying metallization of polymers for developing surface...     

An adaptative augmented Lagrangian method for three-dimensional multimaterial flows

The direct numerical simulation of incompressible multimaterial flows, based on predictor/corrector and volume of fluid (VOF) approaches is presented. An original adaptative augmented Lagrangian method is proposed to solve the predictor solution, satisfying at the same time the conservation equations as well as the incompressibility constraint. This algorithm is based on an Uzawa optimisation technique. The corrector solution is obtained with a projection method on a divergence free subspace. Several examples of two- and three-dimensional flows are proposed to illustrate the ability of the method to deal with unsteady, multimaterial problems.     

Accelerated fractionation in esophageal cancers: a multivariate analysis on 88 patients

PURPOSE: Accelerated fractionation was used to shorten overall treatment time to increase locoregional control and cause-specific survival. METHODS AND MATERIALS: Eighty-eight patients with cancer of the esophagus ineligible for surgery were entered in the study between 1986 and 1993. Neoadjuvant chemotherapy was given to 64% of patients. Accelerated radiotherapy using the concomitant boost technique delivered a median dose of 65 Gy in a median overall treatment time of 32 days. RESULTS: The 3-year actuarial local control rate in patients with T1, T2, and T3 tumors was 71%, 42%, and 33%, respectively. The 3-year cause-specific survival rates were 40%, 22%, and 6%, respectively. Sixteen percent of patients experienced Grade 3 esophagitis. Late toxicity included esophageal stenosis and pulmonary fibrosis in 8% and 9% of the patients, respectively. Multivariate analysis demonstrated that T stage and overall treatment time were prognostic factors for cause-specific survival. T stage and neoadjuvant chemotherapy were independent prognostic factors for locoregional control. CONCLUSION: These findings suggest that accelerated fractionation given in an overall treatment time of <35 days might be beneficial for early-stage cancer of the esophagus. Neoadjuvant chemotherapy is not recommended, as it was a significant adverse prognostic factor in the multivariate analysis for local control. Accelerated fractionation can be carried out with moderate acute and late toxicity.     

Composition and antimicrobial activity of essential oils of Cinnamosma fragrans

Essential oil samples of Cinnamosma fragrans from two regions in Madagascar, Tsaramandroso (38 samples) and Mariarano (30 samples), were analysed by GC/MS. Fifty-seven components were identified, accounting from 88.3% to 99.4% of the oils’ composition. The major components were linalool (72.5 ± 23.3%) in Tsaramandroso and 1,8-cineole (47.3 ± 10.2%) in Mariarano.     

Intratumoral oxygen tension in metastatic melanoma

Tumour hypoxia can lead to a decrease in the biological effectiveness of radiation and alkylating agents. Few data are available on oxygen tension (PO2) in melanoma. In 20 patients with past history of melanoma, PO2 was evaluated in normal tissues and suspected metastatic lesions (nodes and skin metastases). Oxygen tension was measured using a needle probe technique (KIMOC-6650 histograph, Eppendorf, Germany), the day before the surgical removal of the suspected metastatic lesion. Histological confirmation of the malignant origin of the removed lesion was obtained in 18 cases. In two cases invasion by the known melanoma was not seen histologically. The median PO2 for normal tissues was 40.5 mmHg. For tumours, the median PO2 was 11.6 mmHg, and it was 17.1 mmHg in nodes and 6.7 mmHg in skin metastases. Very low values (< 2 mmHg) accounted for 20% of the recorded values in nodes and 15% in skin metastases. When analysed according to the node size (< or > or = 3 cm in diameter), the median PO2 was 10.4 mmHg in large nodes (six patients) and 53.3 mmHg in small nodes (six patients). For the two non-tumoral lesions, the median PO2 values were 20.9 and 25.1 mmHg, with no values below 10 mmHg. Thus a decrease in PO2 values, probably corresponding to tumour hypoxia, was found in most of the metastatic tumours when compared with normal tissues. The prognostic value of these PO2 measurements in melanoma remains to be demonstrated in the tumour response to radiotherapy or alkylating agents. However, tumour hypoxia can already be investigated as a target for new treatment modalities in metastatic melanoma.     

Structural behavior of laser-irradiated γ-Fe2O3 nanocrystals dispersed in porous silica matrix : γ-Fe2O3 to α-Fe2O3 phase transition and formation of ε-Fe2O3

The effects of laser irradiation on γ-Fe₂O₃ 4 ± 1 nm diameter maghemite nanocrystals synthesized by co-precipitation and dispersed into an amorphous silica matrix by sol-gel methods have been investigated as function of iron oxide mass fraction. The structural properties of γ-Fe₂O₃ phase were carefully examined by X-ray diffraction and transmission electron microscopy. It has been shown that γ-Fe₂O₃ nanocrystals are isolated from each other and uniformly dispersed in silica matrix. The phase stability of maghemite nanocrystals was examined in situ under laser irradiation by Raman spectroscopy and compared with that resulting from heat treatment by X-ray diffraction. It was concluded that ε-Fe₂O₃ is an intermediate phase between γ-Fe₂O₃ and α-Fe₂O₃ and a series of distinct Raman vibrational bands were identified with the ε-Fe₂O₃ phase. The structural transformation of γ-Fe₂O₃ into α-Fe₂O₃ occurs either directly or via ε-Fe₂O₃, depending on the rate of nanocrystal agglomeration, the concentration of iron oxide in the nanocomposite and the properties of silica matrix. A phase diagram is established as a function of laser power density and concentration.