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1.
Micromachines (Basel) ; 13(10)2022 Oct 14.
Artículo en Inglés | MEDLINE | ID: mdl-36296092

RESUMEN

In contrast to austenitic and martensitic stainless steels, ferritic stainless steels have a lower hardness and wear resistance but exhibit excellent corrosion resistance. Due to this fact, their use in the aerospace, automobile, and house construction industries is restricted. Several methods have been utilized to enhance the tribological characteristics of ferritic stainless steels. In this work, titanium nitride coating has been carried out by using a cathodic cage of titanium material, and later on, the titanium cathodic cage is replaced by an AISI-304 cathodic cage in a CCPN chamber to form iron nitride coating on AISI-430 ferritic stainless steel coupons through a plasma nitriding process for 4 h at a fixed temperature of 400 °C. The microstructures and mechanical traits of all processed and control coupons were analyzed using scanning electron microscopy, X-ray diffraction, ball-on-disc wear tester, and microhardness tester techniques. The results showed that hardness increased up to 1489 HV with the titanium cage, which is much higher than the hardness of the base material (270 HV). The titanium cage-treated coupons have high layer thickness, smooth surface morphology, and a minimum crystallite size of 2.2 nm. The wear rate was reduced up to 50% over the base material after the titanium cage plasma treatment. The base coupon exhibited severe abrasive wear, whereas nitrided coupons exhibited dominant adhesive wear. In the iron nitride coatings, this effect is also important, owing to the more influential cleaning process in a glow discharge, and the better adhesion with enhanced interlayer thickness is attributed to the fact that the compliance of the interlayer minimizes shear stresses at the coating-substrate interface. The use of a graded interface improves adhesion compared with the case where no interlayer is used but a titanium interlayer of comparable thickness provides a significant increase in measured adhesion. For both titanium and iron nitride films, there is a reduction in wear volume which is a function of interlayer thickness; this will have a substantial effect on wear lifetime. Thus by careful control of the interlayer thickness and composition, it should be possible to improve coating performance in tribological applications.

2.
J Oral Maxillofac Surg ; 78(12): 2289-2295, 2020 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-32814031

RESUMEN

Silent sinus syndrome is a rare disorder characterized by ipsilateral enophthalmos and hypoglobus caused by collapse of the orbital floor in the presence of asymptomatic long-term maxillary sinusitis. The basic principles in the management are to address the diseased sinus and reconstruct the orbit concurrently or separately. Failure to accurately restore the orbit volume can have significant consequences on the patient. In this article, we provide an update on current practices and highlight our experience of using computer-assisted planning and patient-specific implant in managing this syndrome.


Asunto(s)
Enoftalmia , Sinusitis Maxilar , Enfermedades de los Senos Paranasales , Enoftalmia/etiología , Enoftalmia/cirugía , Humanos , Seno Maxilar/diagnóstico por imagen , Seno Maxilar/cirugía , Sinusitis Maxilar/diagnóstico por imagen , Sinusitis Maxilar/cirugía , Órbita/diagnóstico por imagen , Órbita/cirugía
3.
Occup Med (Lond) ; 70(6): 439-441, 2020 Sep 09.
Artículo en Inglés | MEDLINE | ID: mdl-32566940

RESUMEN

BACKGROUND: The UK government has prioritized reducing the harmful effects of excessive alcohol consumption on mental and physical well-being. AIMS: To assess self-reported alcohol consumption amongst doctors at an acute London Trust. METHODS: An opportunistic, anonymous, survey was conducted by Postgraduate Education Fellows over 2 weeks in December 2018. This included all grades of doctors from Foundation Year One to Consultant. The survey consisted of nine questions, modified from the alcohol use disorders identification test (AUDIT) and CAGE questionnaire. RESULTS: Of 446 doctors within our institution, 109 completed the survey (24%). Fourteen per cent of those surveyed abstained from alcohol, 21% drank monthly or less, 31% drank between two to four times per month, 25% drank two to three times per week and 9% drank greater than four times per week. In the preceding 2 years, 9% reported being unable to do what was expected of them on at least one occasion due to alcohol. Five per cent were concerned about alcohol affecting their performance. Two per cent were annoyed by criticism of their drinking, 9% felt guilty about drinking and 4% needed an eye-opener. Eighteen per cent wanted to reduce their alcohol consumption; however, 43% of the 109 doctors surveyed were uncertain where to seek help. CONCLUSIONS: Twenty per cent of surveyed doctors reported consuming potentially hazardous levels of alcohol and 18% of respondents wanted to cut down. Forty-three per cent were unaware of sources of support. Our findings suggest a role for collaboration between Occupational Health departments and Postgraduate Education teams to support doctors misusing alcohol.


Asunto(s)
Consumo de Bebidas Alcohólicas/epidemiología , Médicos/estadística & datos numéricos , Trastornos Relacionados con Alcohol/epidemiología , Trastornos Relacionados con Alcohol/terapia , Humanos , Londres/epidemiología , Inhabilitación Médica , Médicos/psicología , Autoinforme , Encuestas y Cuestionarios
4.
Microvasc Res ; 123: 58-61, 2019 05.
Artículo en Inglés | MEDLINE | ID: mdl-30590061

RESUMEN

Fluorescence-mediated photoplethysmography (FM-PPG) is the first routine clinical methodology by which to quantifiably measure tissue blood perfusion in absolute terms (mL blood/sec ∗ mm2 tissue). The FM-PPG methodology has been described in detail previously in this journal (MVR 114, 2017, 92-100), along with initial proof-of-concept measurements of blood perfusion in both ocular and forearm skin tissues. The motivation for the current study was to investigate whether FM-PPG can be used readily and routinely under realistic clinical conditions. The vehicle for doing this was to measure medial foot capillary blood flow, i.e., tissue perfusion, in 7 normal subjects, mean = 6.76 ±â€¯2.29 E-005 mL/(sec ∙ mm2), and lesion-free areas of 8 type-2 diabetic patients with skin ulceration, mean = 4.67 + 3.15 E-005 mL/(sec ∙ mm2). Thus, perfusion in the diabetics was found to be moderately lower than that in the normal control subjects. Earlier skin perfusion measurements in medial forearms of 4 normal subjects, mean = 2.64 + 0.22 E-005 mL/(sec ∙ mm2), were lower than both the normal and diabetic foot perfusion measurements. Variability in the heartbeat-to-heartbeat blood perfusion pulses in the skin capillaries, defined as the ratio of the standard deviation among beat-to-beat pulses divided by the mean perfusion of those pulses, was determined for each subject. Average variability in foot skin was 21% in the diabetic population, versus 16% for normal subjects; and it was 18% in forearm skin. We conclude that absolute quantitative FM-PPG measurement of skin blood perfusion at the level of nutritive capillaries is feasible routinely under clinical conditions, allowing for quantitative measurement of skin tissue blood perfusion in absolute terms.


Asunto(s)
Capilares/diagnóstico por imagen , Pie Diabético/diagnóstico por imagen , Colorantes Fluorescentes/administración & dosificación , Verde de Indocianina/administración & dosificación , Microcirculación , Imagen de Perfusión/métodos , Fotopletismografía/métodos , Piel/irrigación sanguínea , Velocidad del Flujo Sanguíneo , Capilares/fisiopatología , Estudios de Casos y Controles , Pie Diabético/fisiopatología , Estudios de Factibilidad , Antebrazo , Humanos , Procesamiento de Imagen Asistido por Computador , Valor Predictivo de las Pruebas , Flujo Sanguíneo Regional , Reproducibilidad de los Resultados , Factores de Tiempo
5.
Mol Biol (Mosk) ; 51(2): 334-341, 2017.
Artículo en Ruso | MEDLINE | ID: mdl-28537240

RESUMEN

TP53 mutations play a significant role in glioma tumorigenesis. When located in in the DNA binding domain, these mutations can perturb p53 protein conformation and its function, often culminating in altered downstream signaling. Here we describe prevalent pattern of TP53 point mutations in a cohort of 40 glioma patients and show their relevance to gliomagenesis. Point mutations in exon 5-9 of TP53 gene were detected by DNA sequencing. Possible influence of identified mutations at the function of p53 was studied computationally and correlated with the survival. Point mutations in TP53 were detected in 10 glioma samples (25%), out of which 70% were from high grade glioma. A total of 19 TP53 point mutations were identified, out of which 42% were found to be in the DNA binding region of p53. Computational analysis predicted 87.5% of these mutations to be "probably damaging". In three patients with tumors possessing point mutations R273H, R248Q, Y163H and R175H and poor survival times, structural analysis revealed the nature of these mutations to be disruptive and associated with high risk for cancer progression. In high grade glioma, recurrent TP53 point mutations may be the key to tumor progression, thus, emphasizing their significance in gliomagenesis.


Asunto(s)
Glioma/genética , Glioma/mortalidad , Mutación Puntual , Proteína p53 Supresora de Tumor/genética , Adolescente , Adulto , Sustitución de Aminoácidos , Neoplasias Encefálicas , Niño , Preescolar , Supervivencia sin Enfermedad , Femenino , Glioma/diagnóstico , Humanos , Masculino , Dominios Proteicos , Tasa de Supervivencia
7.
J Pharm Policy Pract ; 10: 7, 2017.
Artículo en Inglés | MEDLINE | ID: mdl-28116107

RESUMEN

BACKGROUND: To assess the effect of policies supporting local medicine production to improve access to medicines. METHODS: We adapted the WHO/HAI instruments measuring medicines availability and prices to differentiate local from imported products, then pilot tested in Ethiopia and Tanzania. In each outlet, prices were recorded for all products in stock for medicines on a country-specific list. Government procurement prices were also collected. Prices were compared to an international reference and expressed as median price ratios (MPR). RESULTS: The Ethiopian government paid more for local products (median MPR = 1.20) than for imports (median MPR = 0.84). Eight of nine medicines procured as both local and imported products were cheaper when imported. Availability was better for local products compared to imports, in the public (48% vs. 19%, respectively) and private (54% vs. 35%, respectively) sectors. Patient prices were lower for imports in the public sector (median MPR = 1.18[imported] vs. 1.44[local]) and higher in the private sector (median MPR = 5.42[imported] vs. 1.85[local]). In the public sector, patients paid 17% and 53% more than the government procurement price for local and imported products, respectively. The Tanzanian government paid less for local products (median MPR = 0.69) than imports (median MPR = 1.34). In the public sector, availability of local and imported products was 21% and 32% respectively, with patients paying slightly more for local products (median MPR = 1.35[imported] vs. 1.44[local]). In the private sector, local products were less available (21%) than imports (70%) but prices were similar (median MPR = 2.29[imported] vs. 2.27[local]). In the public sector, patients paid 135% and 65% more than the government procurement price for local and imported products, respectively. CONCLUSIONS: Our results show how local production can affect availability and prices, and how it can be influenced by preferential purchasing and mark-ups in the public sector. Governments need to evaluate the impact of local production policies, and adjust policies to protect patients from paying more for local products.

8.
East Mediterr Health J ; 22(10): 711-712, 2017 Jan 23.
Artículo en Inglés | MEDLINE | ID: mdl-30387098

RESUMEN

Never before has the flight of human imagination made calls for universal development that are so loud and audacious. The all-encompassing Sustainable Development Agenda 2030 (SD Agenda 2030) has evolved over 67 years since the adoption of the Universal Declaration of Human Rights by the United Nations in 1948. Although based on the same principle of universality, the scope of the Agenda is much broader. It is a melting-pot of human rights, environmental movements and the fight against poverty; hence, it is a plan of action for people, the planet and prosperity. Moreover, it also seeks peace as a necessary condition for development.

11.
Ann R Coll Surg Engl ; 87(5): 353-7, 2005 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-16176695

RESUMEN

INTRODUCTION: The objectives of this work were to assess the clinical knowledge of clinicians in the accident and emergency (A&E) departments in England & Wales and evaluate the current trend for the acute management of radiologically normal, but clinically suspected, fractures of the scaphoid. SUBJECTS AND METHODS: We conducted a telephone survey on 146 A&E senior house officers (SHOs) in 50 different hospitals. This survey assessed the clinicians' experience, their clinical and radiological diagnostic methods, and their initial treatment of suspected scaphoid fractures. RESULTS: The majority (55.8%) of SHOs performed only one clinical test to diagnose suspected scaphoid fractures. Overall, 41% were unable to cite the number of the radiographic views taken and only 10% of departments have direct access to further radiological investigation. There is wide variation in the early treatment of this injury, with the scaphoid cast used most commonly (46%). The majority of SHOs (89%) were unable to describe the features of immobilisation. The mean follow-up period was 10 days, and 53% of cases were followed-up by the senior staff in A&E. Of SHOs, 54% were not aware of any local guidelines for the management of suspected scaphoid fractures in their departments, and 92% were not aware of the existence of the 1992 British Association for Accident and Emergency Medicine (BAEM) guidelines. CONCLUSIONS: The clinical knowledge and the management of suspected scaphoid fractures in A&E are unsatisfactory. We, therefore, suggest that the dissemination of up-to-date guidelines could help to educate clinicians to provide better care to the patients.


Asunto(s)
Servicio de Urgencia en Hospital/estadística & datos numéricos , Fracturas Óseas/terapia , Hueso Escafoides/lesiones , Competencia Clínica , Inglaterra , Femenino , Fracturas Óseas/diagnóstico , Humanos , Tiempo de Internación , Masculino , Cuerpo Médico de Hospitales/normas , Examen Físico , Guías de Práctica Clínica como Asunto , Práctica Profesional , Servicio de Radiología en Hospital/estadística & datos numéricos , Derivación y Consulta/estadística & datos numéricos , Gales
12.
Emerg Med J ; 22(9): 676-7, 2005 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-16113204

RESUMEN

Volatile solvent abuse (VSA) is defined at the "intentional inhalation of a volatile substance for the purpose of achieving a euphoric state". The lifetime prevalence of VSA in the UK remains steady at around 15%, the fourth highest rate in Europe, and VSA is the most common form of drug abuse in the 11-15 year age group in England and Wales. A 13 year old girl presented to the accident and emergency unit following inhalation of butane based deodorant, which resulted in a prolonged semiconscious state with encephalopathic symptoms.


Asunto(s)
Encefalopatías/inducido químicamente , Butanos/envenenamiento , Solventes/envenenamiento , Trastornos Relacionados con Sustancias/complicaciones , Adolescente , Desodorantes/química , Femenino , Humanos , Obesidad/psicología , Trastornos Relacionados con Sustancias/diagnóstico
13.
J Pak Med Assoc ; 54(4): 187-91, 2004 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-15241995

RESUMEN

OBJECTIVES: To gather information on existing prescription practices, dispensing practices and patient satisfaction in government health services of the NWFP, Baluchistan and Punjab province. METHODS: A cross sectional study design was used for this purpose. Ten health care facilities were selected from each province keeping appropriate representation from first level health facilities, district health facilities and tertiary care hospital. Analysis of selected indicators was carried out on the basis of provinces, health facilities, gender and different age groups. RESULTS: Documentation of 914 responses was completed from three provinces. Almost equal distribution of encounters was maintained representing different health facilities. Forty seven percent of encounters involved children under 15 years of age. Female patients comprised of 56% and the mean age of the entire sample was 26 years. The mean dispensing time was only 38 seconds, the mean consultation time was 1.79 minutes and the average number of drugs per prescription turned out to be 2.7 out of which only 1.6 drugs were being dispensed from the facility. More than half of the prescriptions contained antibiotics and 15% of patients were prescribed with injectables. Only half of the patients expressed satisfaction with their visit to health facility. CONCLUSIONS: Like many other developing countries, prescription and dispensing practices are not satisfactory in public sector health facilities of Pakistan. Appropriate and workable solutions need to be developed and implemented in the country to improve systems. Regular audits and qualitative studies should become part of the effort.


Asunto(s)
Centros Comunitarios de Salud/normas , Utilización de Medicamentos/estadística & datos numéricos , Hospitales de Distrito/normas , Administración en Salud Pública/normas , Servicios de Salud Rural/normas , Adolescente , Adulto , Estudios Transversales , Prescripciones de Medicamentos/estadística & datos numéricos , Femenino , Encuestas de Atención de la Salud , Humanos , Masculino , Pakistán , Satisfacción del Paciente
14.
Gut ; 52(6): 807-12, 2003 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-12740335

RESUMEN

BACKGROUND: Some forms of gastric intestinal metaplasia (GIM) may be precancerous but the cellular phenotype that predisposes to gastric carcinogenesis is not well characterised. Mucin staining, as a means of differentiating GIM, is difficult. A monoclonal antibody, mAb Das-1 (initially called 7E(12)H(12)), whose staining is phenotypically specific to colon epithelium, was used to investigate this issue. METHODS: Using mAb Das-1, by a sensitive immunoperoxidase assay, we examined histologically confirmed GIM specimens from two countries, the USA and Japan. A total of 150 patients comprised three groups: group A, GIM (fields away from the cancer area) from patients with gastric carcinoma (n=60); group B, GIM with chronic gastritis (without gastric carcinoma) (n=72); and group C, chronic gastritis without GIM (n=18). RESULTS: Fifty six of 60 (93%) patients with GIM (both goblet and non-goblet metaplastic cells) from group A reacted intensely with mAb Das-1. Cancer areas from the same 56 patients also reacted. In contrast, 25/72 (35%) samples of GIM from patients in group B reacted with mAb Das-1 (group A v B, p<0.0001). None of the samples from group C reacted with the mAb. CONCLUSIONS: Reactivity of mAb Das-1 is clinically useful to simplify and differentiate the phenotypes of GIM. The colonic phenotype of GIM, as identified by mAb Das-1, is strongly associated with gastric carcinoma.


Asunto(s)
Adenocarcinoma/diagnóstico , Anticuerpos , Mucosa Gástrica/patología , Lesiones Precancerosas/diagnóstico , Neoplasias Gástricas/diagnóstico , Adolescente , Adulto , Anciano , Progresión de la Enfermedad , Femenino , Humanos , Técnicas para Inmunoenzimas , Masculino , Metaplasia/diagnóstico , Persona de Mediana Edad
17.
J Accid Emerg Med ; 15(3): 187-9, 1998 May.
Artículo en Inglés | MEDLINE | ID: mdl-9639183

RESUMEN

Two cases are reported in which the diagnosis of a serious condition was delayed as the symptoms had been attributed to migraine. Spontaneous carotid artery dissection is a serious but treatable cause of headache that may be misdiagnosed as recent onset migraine. The importance of correctly identifying this condition is emphasised.


Asunto(s)
Disección Aórtica/diagnóstico , Enfermedades de las Arterias Carótidas/diagnóstico , Trastornos Migrañosos/diagnóstico , Adulto , Disección Aórtica/complicaciones , Angiografía , Enfermedades de las Arterias Carótidas/complicaciones , Diagnóstico Diferencial , Femenino , Estudios de Seguimiento , Humanos , Imagen por Resonancia Magnética , Masculino , Trastornos Migrañosos/etiología
18.
Clin Exp Allergy ; 28(5): 644-52, 1998 May.
Artículo en Inglés | MEDLINE | ID: mdl-9645602

RESUMEN

BACKGROUND: Beta2-adrenoceptor agonists (beta2-agonists) are shown to inhibit airway microvascular leakage in experimental animals. This effect may change in animals with chronic airway inflammation. OBJECTIVE: We examined whether inhaled beta2-agonists inhibit microvascular leakage in guinea-pig airways with chronic allergic inflammation. METHODS: Three weeks after the sensitization with ovalbumin (OA; 6 mg/mL), each guinea pig was challenged with inhaled OA once a day for 1 or 3 weeks. Control animals without sensitization with OA also inhaled vehicle for OA (saline) for 3 weeks. One day after the last challenge, different doses of inhaled procaterol (1, 3 or 10 microg/mL) or vehicle was given to animals for 10 min after an anaesthesia. Fifteen minutes after the end of inhalation, the animals were given i.v. Evans blue dye (EB dye; 20 mg/kg), a marker of microvascular leakage, and then i.v. histamine (3 or 30 microg/kg) or vehicle. Lung resistance, a parameter of airflow obstruction, was measured for 6 min and the lungs were removed to calculate the amount of extravasated EB dye into the airways. RESULTS: A significant increase in eosinophil infiltration into the airways was seen in sensitized and challenged animals compared with control animals without sensitization. Among animals receiving antigenic exposure for either 0 (control), 1 or 3 weeks, 10 microg/mL procaterol significantly inhibited 30 microg/kg histamine-induced increase in EB dye extravasation to a similar degree (ranged from 28.7 to 69.8% inhibition) as well as that in lung resistance (more than 90% inhibition in all groups). The minimal dose of procaterol to inhibit 3 microg/kg histamine-induced microvascular leakage was not different between nonsensitized control animals and those sensitized and challenged for 3 weeks at all airway levels. CONCLUSION: Inhaled beta2-adrenoceptor agonists may be also potent in attenuating microvascular leakage even in the airways with chronic allergic inflammation.


Asunto(s)
Agonistas Adrenérgicos beta/farmacología , Resistencia de las Vías Respiratorias/efectos de los fármacos , Asma/fisiopatología , Permeabilidad Capilar/efectos de los fármacos , Procaterol/farmacología , Sistema Respiratorio/irrigación sanguínea , Administración por Inhalación , Animales , Asma/tratamiento farmacológico , Asma/patología , Bronquios/irrigación sanguínea , Bronquios/patología , Azul de Evans , Cobayas , Histamina/farmacología , Masculino , Ovalbúmina/inmunología , Tráquea/irrigación sanguínea , Tráquea/patología
19.
Am J Physiol ; 269(3 Pt 1): C757-65, 1995 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-7573407

RESUMEN

Vascular endothelium responds to Ca(2+)-mobilizing agonists by producing nitric oxide (NO), a potent vasodilator and inhibitor of platelet aggregation. Regulation of constitutively expressed endothelial NO synthase (eNOS) in intact cells is not well understood. We investigated the kinetics of NO formation in response to Ca(2+)-mobilizing agonists, the requirement for extracellular L-arginine, and the role of NO in regulating eNOS activity. When endothelial cells were stimulated with bradykinin and ATP in the presence of 100 microM L-arginine, we observed a rapid and transient rise in intracellular Ca2+ concentration ([Ca2+]i) from 50 +/- 8 nM to 698 +/- 74 and 637 +/- 53 nM, respectively, and a rapid and transient rise in NO production from a basal level of 37 pmol.min-1.mg protein-1 to 256 and 275 pmol.min-1.mg protein-1, respectively. When cells were stimulated with A-23187 or thapsigargin in the presence of 100 microM L-arginine, we observed a sustained increase in [Ca2+]i and a sustained increase in NO production. The rate of NO synthesis was linear over 30 min, rising above control levels of 7 pmol/min to 53 pmol/min for A-23187 and 62 pmol/min for thapsigargin. Thapsigargin stimulated NO production and [Ca2+]i with 50% effective concentration values of 0.01 and 0.05 microM, respectively. Ca(2+)-stimulated NO production was attenuated by the NO synthase inhibitor NG-monomethyl-L-arginine, the removal of extracellular L-arginine, and the Ca(2+)-chelator ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid. When we exposed cells to NO gas (3.1 mM for 15 min) and S-nitrosoglutathione (10 mM for 1 h) thapsigargin-stimulated NO production was decreased by 50%.(ABSTRACT TRUNCATED AT 250 WORDS)


Asunto(s)
Aorta/metabolismo , Calcio/fisiología , Endotelio Vascular/metabolismo , Óxido Nítrico Sintasa/metabolismo , Animales , Aorta/citología , Arginina/antagonistas & inhibidores , Arginina/farmacología , Transporte Biológico , Calcio/agonistas , Bovinos , Células Cultivadas , Endotelio Vascular/citología , Membranas Intracelulares/metabolismo , Óxido Nítrico/biosíntesis
20.
Am J Respir Cell Mol Biol ; 9(6): 603-9, 1993 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-8257592

RESUMEN

We have investigated factors that regulate hydrogen peroxide (H2O2) release from vascular endothelial cells. Endothelial cells produce H2O2 at an intracellular site in the vicinity of peroxisomes and at a second site near the cell surface that is inaccessible to intracellular catalase or glutathione peroxidase. Regulation of H2O2 generation at the intracellular site was studied using aminotriazole, which inactivates catalase in the presence of H2O2. Regulation of H2O2 generation at the second site was studied by measuring H2O2 release into the medium. The rate of H2O2 release was constant over 2 h when cells were incubated in room air. Changing O2 levels in the atmosphere from 0% to 10% O2 resulted in a threefold increase in the rate of H2O2 release. Elevation of O2 levels from 10% to 95% O2 produced no further enhancement in the rate of release. Preincubation of cells under hypoxic conditions did not lead to an exaggerated rate of H2O2 release when cells were returned to room air. Pretreatment of cells with exogenous H2O2 inhibited subsequent H2O2 release while pretreatment with catalase enhanced H2O2 release. Although arachidonic acid transiently enhanced the rate of H2O2 release through a mechanism dependent on PGH synthase, basal H2O2 release was independent of this enzyme. Neither hypoxia, hyperoxia, or hypoxia followed by reoxygenation altered H2O2 generation at the intracellular site accessible to peroxisomal catalase. These data demonstrate that H2O2 release from endothelial cells is responsive to changes in O2 concentrations over a narrow range. The mechanisms involved are subject to product inhibition and appear to be saturated at 10% O2 in the atmosphere.


Asunto(s)
Endotelio Vascular/metabolismo , Peróxido de Hidrógeno/metabolismo , Oxígeno/farmacología , Animales , Bovinos , Células Cultivadas , Endotelio Vascular/efectos de los fármacos
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