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1.
Contemp Clin Trials ; 142: 107564, 2024 Jul.
Article in English | MEDLINE | ID: mdl-38704119

ABSTRACT

INTRODUCTION: Women with atypical hyperplasia (AH) or lobular carcinoma in situ (LCIS) have a significantly increased risk of breast cancer, which can be substantially reduced with antiestrogen therapy for chemoprevention. However, antiestrogen therapy for breast cancer risk reduction remains underutilized. Improving knowledge about breast cancer risk and chemoprevention among high-risk patients and their healthcare providers may enhance informed decision-making about this critical breast cancer risk reduction strategy. METHODS/DESIGN: We are conducting a cluster randomized controlled trial to evaluate the effectiveness and implementation of patient and provider decision support tools to improve informed choice about chemoprevention among women with AH or LCIS. We have cluster randomized 26 sites across the U.S. through the SWOG Cancer Research Network. A total of 415 patients and 200 healthcare providers are being recruited. They are assigned to standard educational materials alone or combined with the web-based decision support tools. Patient-reported and clinical outcomes are assessed at baseline, after a follow-up visit at 6 months, and yearly for 5 years. The primary outcome is chemoprevention informed choice after the follow-up visit. Secondary endpoints include other patient-reported outcomes, such as chemoprevention knowledge, decision conflict and regret, and self-reported chemoprevention usage. Barriers and facilitators to implementing decision support into clinic workflow are assessed through patient and provider interviews at baseline and mid-implementation. RESULTS/DISCUSSION: With this hybrid effectiveness/implementation study, we seek to evaluate if a multi-level intervention effectively promotes informed decision-making about chemoprevention and provide valuable insights on how the intervention is implemented in U.S. TRIAL REGISTRATION: NCT04496739.


Subject(s)
Breast Neoplasms , Chemoprevention , Humans , Female , Breast Neoplasms/prevention & control , Chemoprevention/methods , Patient Education as Topic/methods , Decision Support Techniques , Middle Aged , Adult , Decision Making , Health Knowledge, Attitudes, Practice , Risk Reduction Behavior , Research Design , Estrogen Antagonists/therapeutic use , Estrogen Antagonists/administration & dosage , Patient Reported Outcome Measures
2.
ESMO Open ; 7(4): 100526, 2022 08.
Article in English | MEDLINE | ID: mdl-35780590

ABSTRACT

BACKGROUND: Tumor genomic profiling (TGP) often incidentally identifies germline pathogenic variants (PVs) associated with cancer predisposition syndromes. Methods used by somatic testing laboratories, including germline analysis, differ from designated germline laboratories that have optimized the identification of germline PVs. This study evaluated discrepancies between somatic and germline testing results, and their impact on patients. PATIENTS AND METHODS: Chart reviews were carried out at a single institution for patients who had both somatic and designated germline genetic testing. Cases with discrepant results in which germline PVs were not detected by the somatic laboratory or in which variant classification differed are summarized. RESULTS: TGP was carried out on 2811 cancer patients, 600 of whom also underwent designated germline genetic testing. Germline PVs were identified for 109 individuals. Discrepancies between germline genetic testing and tumor profiling reports were identified in 20 cases, including 14 PVs identified by designated germline genetic testing laboratories that were not reported by somatic testing laboratories and six variants with discrepant classifications between the designated germline and somatic testing laboratories. Three PVs identified by designated germline laboratories are targets for poly adenosine diphosphate-ribose polymerase (PARP) inhibitors and resulted in different treatment options. Of the PVs identified by designated germline laboratories, 60% (n = 12) were in genes with established associations to the patients' cancer, and 40% of the PVs were incidental. The majority (90%) of all discrepant findings, both contributory and incidental, changed management recommendations for these patients, highlighting the importance of comprehensive germline assessment. CONCLUSIONS: Methods used by somatic laboratories, regardless of the inclusion of germline analysis, differ from those of designated germline laboratories for identifying germline PVs. Unrecognized germline PVs may harm patients by missing hereditary syndromes and targeted therapy opportunities (e.g. anti-programmed cell death protein 1 immunotherapy, PARP inhibitors). Clinicians should refer patients who meet the criteria for genetic evaluation regardless of somatic testing outcomes.


Subject(s)
Germ-Line Mutation , Neoplasms , Genetic Predisposition to Disease , Genetic Testing , Genomics , Germ Cells , Humans
3.
Nanotechnology ; 32(15): 152001, 2021 Apr 09.
Article in English | MEDLINE | ID: mdl-33412522

ABSTRACT

Silicene, the 2D silicon allotrope analogue of graphene, was theoretically predicted in 1994 as a metastable buckled honeycomb silicon monolayer. Similarly to its carbon counterpart it was predicted to present an electronic structure hosting Dirac cones. In the last decade a great deal of work has been done to synthesize silicene and exploit its properties. In this paper we will review our research group activity in the field, dealing in particular with silicon-substrate interaction upon silicon deposition, and discuss the still debated silicene formation starting from the chemistry of silicon unsaturated compounds.

4.
Sci Rep ; 10(1): 14619, 2020 Sep 03.
Article in English | MEDLINE | ID: mdl-32884112

ABSTRACT

Topological surface states usually emerge at the boundary between a topological and a conventional insulator. Their precise physical character and spatial localization depend on the complex interplay between the chemical, structural and electronic properties of the two insulators in contact. Using a lattice-matched heterointerface of single and double bilayers of ß-antimonene and bismuth selenide, we perform a comprehensive experimental and theoretical study of the chiral surface states by means of microscopy and spectroscopic measurements complemented by first-principles calculations. We demonstrate that, although ß-antimonene is a trivial insulator in its free-standing form, it inherits the unique symmetry-protected spin texture from the substrate via a proximity effect that induces outward migration of the topological state. This "topologization" of ß-antimonene is found to be driven by the hybridization of the bands from either side of the interface.

5.
Nanotechnology ; 29(6): 065704, 2018 02 09.
Article in English | MEDLINE | ID: mdl-29320369

ABSTRACT

We report a study of the interface between antimony and the prototypical topological insulator Bi2Se3. Scanning tunnelling microscopy measurements show the presence of ordered domains displaying a perfect lattice match with bismuth selenide. Density functional theory calculations of the most stable atomic configurations demonstrate that the ordered domains can be attributed to stacks of ß-antimonene.

6.
J Phys Condens Matter ; 29(21): 215001, 2017 Jun 01.
Article in English | MEDLINE | ID: mdl-28362270

ABSTRACT

The surface electronic structure of Si(1 1 1)-[Formula: see text] has been studied by angle-resolved photo electron spectroscopy. Replicas of the S 1 surface state are found in correspondence with several [Formula: see text] unit cells in the reciprocal space. This observation resolves in a direct way the long-standing dichotomy between the structural and electronic properties of the system previously discussed on the basis of the [Formula: see text] or [Formula: see text] R30° surface models.

7.
J Phys Condens Matter ; 25(31): 315301, 2013 Aug 07.
Article in English | MEDLINE | ID: mdl-23835457

ABSTRACT

Interest in the Si/Ag(110) system, which forms highly ordered linear nanostructures coined 'silicon nanoribbons', was recently boosted by the claim that such nanoribbons may be formed by silicon atoms arranged in a 2D honeycomb structure as in graphene, i.e. silicene. Despite such a revived interest, many discrepancies still exist in the recently reported results. This paper reports on a systematic investigation by scanning tunneling microscopy and low-energy electron diffraction of the Si/Ag(110) system as a function of the amount of deposited silicon and the deposition temperature. This reveals a complex interplay between these two factors, resulting in a rich array of possible self-assembled nanostructures and surface reconstructions. Several novel findings and clarification of the contradictory results reported in the literature are discussed in this work. In particular, the deposition temperature is demonstrated to be a key parameter to control the width of the Si nanoribbons produced. Recently, massive linear nanostructures were reported to be 'multilayer silicene', forming once the deposited silicon amount exceeds full coverage. However, we show that such nanostructures are also observed at low silicon coverage, demonstrating that their formation is exclusively determined by a deposition temperature higher than 460 K. On the other hand, for Si amounts higher than one monolayer the surface presents a novel c(8 × 4) reconstruction, which is responsible for the ×4 periodicity detected by LEED measurements, previously attributed to the 1.6 nm-wide nanoribbons overlayer or to 'multilayer silicene'. Finally, the large collection of acquired data also allowed us to single out image artifacts that may explain the contradictory results appearing in previous papers.

8.
Langmuir ; 27(12): 7410-8, 2011 Jun 21.
Article in English | MEDLINE | ID: mdl-21604683

ABSTRACT

The formation of 2D chiral monolayers obtained by self-assembly of chiral molecules on surfaces has been widely reported in the literature. Control of chirality transfer from a single molecule to surface superstructures is a challenging and important aspect for tailoring the properties of 2D nanostructures. However, despite the wealth of investigations performed in recent years, how chiral transfer takes place on a large scale still remains an open question. In this paper we report a coupling of scanning tunneling microscopy and low energy electron diffraction measurements with an original theoretical approach, combining molecular dynamics and essential dynamics with density functional theory, to investigate self-assembled chiral structures formed when alaninol adsorbs on Cu(100). The peculiarity of this system is related to the formation of tetrameric molecular structures which constitute the building blocks of the self-assembled chiral monolayer. Such characteristics make alaninol/Cu(100) a good candidate to reveal chiral expression changes. We find that the deposition of alaninol enantiomers results in the formation of isolated tetramers that are aligned along the directions of the substrate at low coverage or when geometrical confinement prevents long-range order. Conversely, a rotation of 14° with respect to the Cu(100) unit vectors is observed when small clusters of tetramers are formed. An insight to the process leading to a 2D globally chiral surface has been obtained by monitoring molecular assemblies as they grow from the early stages of adsorption, suggesting that the distinctive orientation of the self-assembled monolayer originates from a balance of cooperating forces which start acting only when tetramers pack together to form small clusters.

9.
Minerva Pediatr ; 62(2): 217-21, 2010 Apr.
Article in Italian | MEDLINE | ID: mdl-20440241

ABSTRACT

Infantile subglottic hemangioma is a pediatric tumor of endothelial cells characterized by an initial phase of rapid proliferation (around 6 months), followed by slow involution, often leading to complete regression following the first year of life. It is most frequently found in females and it usually it occurs also in the skin. From its position it can cause a progressive airway obstruction, so early diagnosis and treatment are very important. Many treatments have been described in the literature, including systemic steroids, intralesional steroid injection, carbon dioxide laser therapy, submucous resection, interferon alfa-2 and also tracheostomy as last approach. This case report discusses a 6-month old infant, that arrived to our attention for an acute two-way stridor. Laringoscopy under general anesthesia showed a subocclusive subglottic haemangioma that closed 70% of the laryngeal airway. In agreement with our ENT specialist it was decided to begin systemic steroid therapy, first by i.v. ingection during intensive therapy with rinotracheal intubation and mechanic ventilation; after the canula removal and the hemangioma reduction, the patient took oral steroids with a gradual reduction of the dose. This case evidences the importance of laryngoscopy in the diagnosis of subglottic haemangioma; it also proves the importance of multi-disciplinary collaboration with ENT specialist and dermatologist for the diagnosis and treatment of this kind of patient. It also shows that systemic steroids are an effective alternative in the management of obstructive pediatric subglottic hemangiomas.


Subject(s)
Glottis , Hemangioma/diagnosis , Laryngeal Neoplasms/diagnosis , Acute Disease , Female , Hemangioma/complications , Humans , Infant , Laryngeal Neoplasms/complications , Respiratory Sounds/etiology
10.
Phys Rev Lett ; 96(10): 106106, 2006 Mar 17.
Article in English | MEDLINE | ID: mdl-16605767

ABSTRACT

In order to provide a structural basis for a physical understanding of exchange bias in metal/magnetic-oxide interfaces, we have determined the structure of the Fe/NiO(001) interface by means of x-ray absorption spectroscopy and ab initio density functional theory calculations. A Fe-Ni alloyed phase on top of an interfacial FeO planar layer is formed. The FeO layer exhibits a 7% expanded interlayer distance and a 0.3 A buckling; its presence is predicted to increase the spin magnetic moment of the interface Fe atoms by 0.6 mu(B), compared to the ideally abrupt interface.

11.
Biotechnol Bioeng ; 78(5): 489-96, 2002 Jun 05.
Article in English | MEDLINE | ID: mdl-12115117

ABSTRACT

The performance, in Baeyer-Villiger and heteroatom oxidations, of a partially purified preparation of cyclohexanone monooxygenase obtained from an Escherichia coli strain in which the gene of the enzyme was cloned and overexpressed was investigated. As model reactions, the oxidations of racemic bicyclo[3.2.0]hept-2-en-6-one into two regioisomeric lactones and of methyl phenyl sulphide into the corresponding (R)-sulphoxide were used. Enzyme stability and reuse, substrate and product inhibition, product removal, and cofactor recycling were evaluated. Of the various NADPH regeneration systems tested, 2-propanol/alcohol dehydrogenase from Thermoanerobium brockii appeared the most suitable because of the low cost of the second substrate and the high regeneration rate. Concerning enzyme stability, kosmotropic salts were the only additives able to improve it (e.g., half-life from 1 day in diluted buffer to 1 week in 1 M sodium sulphate) but only under storage conditions. Instead, significant stabilization under working conditions was obtained by immobilization on Eupergit C (half-life approximately 2.5 days), a procedure that made it possible to reuse the catalyst up to 16 times with complete substrate (5 g x L(-1)) conversion at each cycle. Reuse of free enzyme was also achieved in a membrane reactor but with lower efficiency. Water-organic solvent biphasic systems, which would overcome substrate inhibition and remove from the aqueous phase, where reaction takes place, the formed product, were unsuccessful because of their destabilizing effect on cyclohexanone monooxygenase. More satisfactory was continuous substrate feeding, which shortened reaction times and, very importantly, yielded in the case of bicyclo[3.2.0]hept-2-en-6-one (10 g x L(-1)) both lactone products with high optical purity (enantiomeric excess > or = 96%), which was not the case when all of the substrate was added in a single batch.


Subject(s)
Alcohol Dehydrogenase/chemistry , Bridged Bicyclo Compounds, Heterocyclic/chemistry , Escherichia coli/metabolism , Oxygenases/chemistry , Oxygenases/isolation & purification , Sulfides/chemistry , Catalysis , Enzyme Stability , Enzymes, Immobilized , Escherichia coli/genetics , Gene Expression Regulation, Bacterial , Oxidation-Reduction , Oxygenases/biosynthesis , Oxygenases/genetics , Polymers , Recombinant Proteins/biosynthesis , Recombinant Proteins/chemistry , Recombinant Proteins/genetics , Recombinant Proteins/isolation & purification , Sensitivity and Specificity
12.
Minerva Cardioangiol ; 50(4): 383-8, 2002 Aug.
Article in English | MEDLINE | ID: mdl-12147971

ABSTRACT

The first case of combined procedure of catheter-based balloon pulmonary valvuloplasty and atrial septal defect closure using Amplatzer Septal Occluder, in a patient with Noonan syndrome, is reported. The literature regarding prevalence, genetics, pattern of involvement, symptoms, diagnosis, and treatment of this syndrome is reviewed.


Subject(s)
Angioplasty, Balloon , Cardiac Catheterization , Heart Septal Defects, Atrial/therapy , Noonan Syndrome/therapy , Pulmonary Valve Stenosis/therapy , Female , Humans , Middle Aged
13.
J Clin Endocrinol Metab ; 87(1): 322-8, 2002 Jan.
Article in English | MEDLINE | ID: mdl-11788669

ABSTRACT

Endothelin (ET)-1[1-21] stimulates steroid secretion and zona glomerulosa growth and is expressed in the human and rat adrenal cortex together with its receptor subtypes A and B (ETA and ETB). Although ET-1[1-21] is generated from bigET-1 by an ET-converting enzyme (ECE-1), there is evidence of an alternative chymase-mediated biosynthetic pathway leading to the production of an ET-1[1-31] peptide, the role of which in adrenal pathophysiology is largely unknown. Gene expression and immunohistochemical studies allowed localization of chymase in the normal human adrenal cortex. Sizable amounts, not only of ET-1[1-21] but also of ET-1[1-31], were found in the adrenal vein plasma of three patients. ET-1[1-21] and ET-1[1-31] elicited a clear-cut secretory response by dispersed human adrenocortical cells, ET-1[1-31] being significantly less potent than ET-1[1-21]. The secretagogue effect of ET-1[1-31] was abolished by the ETA receptor antagonist BQ-123 and was unaffected by the ETB receptor antagonist BQ-788. Because, in humans, the secretagogue effect of ET-1[1-21] involves both ETA and ETB receptors, the weaker action of ET-1[1-31] could be attributable to a selective ETA receptor activation. Two lines of evidence support this contention: 1) ET-1[1-31] was more effective than ET-1[1-21] in stimulating ETA-mediated cell proliferation of human adrenocortical cells cultured in vitro; and 2) autoradiography showed that a) ET-1[1-31] displaced in vitro [(125)I]ET-1[1-21] binding to the ETA, but not ETB receptors, in human internal thoracic artery rings; and b) BQ-123, but not BQ-788, eliminated [(125)I]ET-1[1-31] binding in the rat adrenal cortex.


Subject(s)
Adrenal Cortex/drug effects , Endothelins/pharmacology , Peptide Fragments/pharmacology , Adrenal Cortex/metabolism , Adrenal Cortex/physiology , Aldosterone/metabolism , Autoradiography , Cell Division/drug effects , Cells, Cultured , Chymases , Endothelin-1/analogs & derivatives , Glycopeptides/pharmacology , Humans , Hydrocortisone/metabolism , Immunohistochemistry , In Vitro Techniques , Muscle, Smooth, Vascular/drug effects , Oligopeptides/pharmacology , Peptides, Cyclic/pharmacology , Piperidines/pharmacology , RNA, Messenger/analysis , Reverse Transcriptase Polymerase Chain Reaction , Serine Endopeptidases/analysis , Serine Endopeptidases/genetics , Serine Endopeptidases/metabolism
14.
Phys Med Biol ; 46(4): 967-74, 2001 Apr.
Article in English | MEDLINE | ID: mdl-11324971

ABSTRACT

Conventional radiographic techniques have strong limitations when low-absorption contrast samples are imaged. Phase contrast radiography has been shown to produce high-quality images of soft tissues. In this technique the recorded intensity patterns are related to gradients in the refractive index of the sample. A critical point of this new technique is the need to employ crystal analysers, which results in an appreciable reduction in the beam intensity and consequently in rather long exposure times. In this paper the use of focused beams is suggested to overcome this aspect. Biological samples with small structures and low absorption variations were imaged using both flat and curved monochromator crystals, demonstrating that the use of curved optics leads to a decrease in the exposure time with only a limited degradation of the spatial resolution. This opens up the possibility of using the phase contrast technique with laboratory sources.


Subject(s)
Diagnostic Imaging/instrumentation , Diagnostic Imaging/methods , Synchrotrons , Tomography, X-Ray Computed/methods , Animals , Butterflies , Microscopy, Phase-Contrast/methods , Time Factors , X-Rays
15.
Chirality ; 13(1): 40-2, 2001 Jan.
Article in English | MEDLINE | ID: mdl-11135413

ABSTRACT

Cyclohexanone monooxygenase from Acinetobacter calcoaceticus catalyzes the asymmetric oxidation of tert-butyl disulfide to enantiomerically pure (R)-tert-butyl tert-butanethiosulfinate. Lower enantioselectivities and conversions were observed in the oxidation of i-propyl, n-butyl, p-tolyl tert-butyl disulfides and alkylthiophosphonates.


Subject(s)
Oxygenases/chemistry , Sulfonic Acids/chemical synthesis , Acinetobacter calcoaceticus/enzymology , Catalysis , Stereoisomerism
16.
J Psycholinguist Res ; 30(6): 569-99, 2001 Nov.
Article in English | MEDLINE | ID: mdl-11913847

ABSTRACT

The four eye-tracking experiments reported examined the way in which Adjunct Predicates (APs) located at the beginning of French sentences of the type "Tired (feminine/masculine) of calling the woman (s/he) left the room" are interpreted and interact with syntactic parsing strategies. The results suggest that the first NP (the woman) was initially interpreted as the potential AP gender controller. Moreover, in the case of gender agreement (the woman is the one who is tired) the syntactic status of the first NP (either the object of the preceding verb or the subject of the main verb) apparently remained ambiguous until the main verb was reached. The implications of these results for Frazier and Clifton's (1996) Construal Theory are discussed.


Subject(s)
Cognition , Language , Speech Perception , Humans
17.
Trends Biotechnol ; 17(4): 163-8, 1999 Apr.
Article in English | MEDLINE | ID: mdl-10203775

ABSTRACT

Peroxidases are ubiquitous oxidoreductases that use hydrogen peroxide or alkyl peroxides as oxidants. Advances have recently been made in using them to prepare, under mild and controlled conditions, chiral organic molecules that are valuable for the chemoenzymatic synthesis of a wide range of useful compounds. Horseradish peroxidase can be converted into a peroxygenative enzyme by molecular engineering. Chloroperoxidase, the most versatile peroxidase, behaves like a 'true' monooxygenase in sulfoxidations with molecular oxygen and an external reductant, with substantial increases in enantioselectivity and enzyme stability.


Subject(s)
Biotechnology/methods , Peroxidases/metabolism , Alcohols/chemistry , Alcohols/metabolism , Catalysis , Enzyme Stability , Hydroxylation , Indoles/chemistry , Indoles/metabolism , Nitrogen/chemistry , Nitrogen/metabolism , Oxidation-Reduction , Peroxidases/chemistry , Sulfur/chemistry , Sulfur/metabolism
18.
Biotechnol Bioeng ; 62(4): 489-493, 1999 Feb.
Article in English | MEDLINE | ID: mdl-10099556

ABSTRACT

The chloroperoxidase catalyzed oxidation of methyl phenyl sulfide to (R)-methyl phenyl sulfoxide was investigated, both in batch and membrane reactors, using as oxidant H2O2, or O2 in the presence of either dihydroxyfumaric acid or ascorbic acid. The effects of pH and nature and concentration of the oxidants on the selectivity, stability, and productivity of the enzyme were evaluated. The highest selectivity was displayed by ascorbic acid/O2, even though the activity of chloroperoxidase with this system was lower than that obtained with the others. When the reaction was carried out in a membrane reactor, it was possible to reuse the enzyme for several conversion cycles. The results obtained with ascorbic acid/O2 and dihydroxyfumaric acid/O2 as oxidants do not seem to be compatible with either a mechanism involving hydroxyl radicals as the active species or with the hypothesis that oxidation occurs through the initial formation of H2O2. Copyright 1999 John Wiley & Sons, Inc.

19.
Circulation ; 99(9): 1147-55, 1999 Mar 09.
Article in English | MEDLINE | ID: mdl-10069781

ABSTRACT

BACKGROUND: The participation of endothelin-1 (ET-1) in the control of vascular tone in humans has been questioned, on the basis of the finding of subthreshold immunoreactive (ir) ET-1 plasma levels. However, because most ET-1 is secreted abluminally, it might attain a higher concentration in the tunica media than in plasma. Furthermore, evidence indicates that vascular smooth muscle cells (VSMCs) can synthesize ET-1 on stimulation in vitro. We therefore looked for irET-1 in the different layers of the wall of human arteries, including renal, gastric, and internal thoracic artery wall, obtained ex vivo from consenting patients with coronary artery disease and/or high blood pressure undergoing surgery, as well as from young organ donors. METHODS AND RESULTS: We performed immunohistochemistry with specific anti-ET-1 and anti-vWF antibodies followed by detection with an avidin-biotin complex ultrasensitive kit. The presence of preproET-1 and human endothelin-converting enzyme-1 (hECE-1) mRNA was also investigated by reverse transcription-polymerase chain reaction in homogenates of vessel wall, including preparations deprived of both endothelium and adventitia, and in isolated VSMCs. We detected irET-1 in the endothelium of all arteries and in the tunica media of internal thoracic artery from most patients with coronary artery disease. PreproET-1 and hECE-1 mRNA was also detected in VSMCs isolated from these vessels. irET-1 and irvWF staining in endothelium and tunica media was measured by use of microscope-coupled computer-assisted technology. Significant correlations between the amount of irET-1 in the tunica media and mean blood pressure (P<0.05), total serum cholesterol (P<0.05), and number of atherosclerotic sites (P<0.001) were found. Thus, in organ donors, irET-1 was detectable almost exclusively in endothelial cells, whereas in patients with coronary artery disease and/or arterial hypertension, sizable amounts of irET-1 were detectable in the tunica media of different types of arteries. In addition, VSMCs isolated from these vessels coexpressed the preproET-1 and hECE-1 genes. CONCLUSIONS: Collectively, these findings are consistent with the contention that endothelial damage occurs in most patients with atherosclerosis and/or hypertension and that ET-1 is synthesized in VSMCs of these patients.


Subject(s)
Arteries/metabolism , Endothelin-1/genetics , Endothelin-1/metabolism , RNA, Messenger/metabolism , Adult , Aged , Aged, 80 and over , Arteries/chemistry , Aspartic Acid Endopeptidases/analysis , Aspartic Acid Endopeptidases/genetics , Child , Coronary Disease/metabolism , Coronary Disease/pathology , Endothelin-1/biosynthesis , Endothelin-Converting Enzymes , Endothelins/analysis , Endothelins/genetics , Endothelium, Vascular/chemistry , Endothelium, Vascular/metabolism , Endothelium, Vascular/pathology , Female , Fluorescent Antibody Technique , Gene Expression , Humans , Hypertension/metabolism , Immunohistochemistry , Male , Metalloendopeptidases , Middle Aged , Muscle, Smooth, Vascular/metabolism , Muscle, Smooth, Vascular/pathology , Protein Precursors/analysis , Protein Precursors/genetics , Tunica Media/metabolism , Tunica Media/pathology
20.
Biochem J ; 335 ( Pt 1): 27-33, 1998 Oct 01.
Article in English | MEDLINE | ID: mdl-9742209

ABSTRACT

The oxidation of alkyl aryl sulphides by myeloperoxidase (MPO) at the expense of hydrogen peroxide was investigated under steady-state conditions. The sulphide concentration effect was studied under saturating H2O2 concentrations at pH 5.0 and 20 degreesC. The kinetic constants, kcat and Km, of the different substrates were determined and the values were in the 1-10 s-1 range and around 43+/-26 microM respectively, whatever the sulphide considered. In the case of p-substituted thioanisoles, the oxidation rate was dependent upon the substituent effect. The correlation of log(kcat) with the substituent constants (sigma+ values) (Hammett equation) could be explained by a reaction mechanism involving the enzyme compound II and a sulphenium radical cation. This conclusion was also supported by spectrophotometric analysis of catalytic intermediates of the enzyme, showing the accumulation of compound II. Moreover, chiral HPLC analyses showed that MPO oxidation of alkyl aryl sulphides produced the corresponding (R)-sulphoxides with a low enantioselectivity (4-8%). Chloride ion effects on the MPO-catalysed oxygenation of sulphides were also studied. Chloride acted as a substrate for MPO and as an activator in MPO-catalysed sulphoxidation. Inhibition occurred at chloride concentrations above 120 mM, whereas below 120 mM, chloride increased the reaction rate when using p-tolyl methyl sulphide as the substrate. In the presence of 100 mM chloride the catalytic efficiency (kcat/Km) of MPO increased 3-4-fold, whatever the sulphide considered, but racemic products were obtained. These data have been interpreted in the light of known structural information on the accessibility of the distal haem cavity.


Subject(s)
Neutrophils/enzymology , Peroxidase/metabolism , Sulfuric Acid Esters/metabolism , Catalysis , Chlorides/metabolism , Humans , Hydrogen Peroxide/metabolism , Kinetics , Oxidation-Reduction , Stereoisomerism , Sulfides/metabolism
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