Atomistic simulations of calcium aluminosilicate interfaced with liquid water.

The dissolution behavior of calcium aluminosilicate based glass fibers, such as stone wool fibers, is an important consideration in mineral wool applications for both the longevity of the mineral wool products in humid environments and limiting the health impacts of released and inhaled fibers from the mineral wool product. Balancing these factors requires a molecular-level understanding of calcium aluminosilicate glass dissolution mechanisms, details that are challenging to resolve with experiment alone. Molecular dynamics simulations are a powerful tool capable of providing complementary atomistic insights regarding dissolution; however, they require force fields capable of describing not-only the calcium aluminosilicate surface structure but also the interactions relevant to dissolution phenomena. Here, a new force field capable of describing amorphous calcium aluminosilicate surfaces interfaced with liquid water is developed by fitting parameters to experimental and first principles simulation data of the relevant oxide-water interfaces, including ab initio molecular dynamics simulations performed for this work for the wüstite and periclase interfaces. Simulations of a calcium aluminosilicate surface interfaced with liquid water were used to test this new force field, suggesting moderate ingress of water into the porous glass interface. This design of the force field opens a new avenue for the further study of calcium and network-modifier dissolution phenomena in calcium aluminosilicate glasses and stone wool fibers at liquid water interfaces.

Propuesta teórica para el cambio de conducta en el consumo excesivo de alcohol en adolescentes / Theory-based proposal for changing the behavior of adolescents consuming alcohol in excess / Proposta teórica para mudança de comportamento no consumo excessivo de álcool em adolescentes

RESUMEN Introducción El consumo de alcohol en los adolescentes es un problema cada vez más frecuente y va en aumento debido a que el consumo episódico excesivo es una tendencia cada vez más común en esta población. Para el profesional de enfermería de primer nivel de atención, se vuelve necesario implementar herramientas sustentadas en evidencia científica como una alternativa factible que responda a las necesidades actuales. Objetivo Desarrollar una propuesta de aplicación a partir de la Teoría de Situación Específica del Modelo de Intención de Cambio (I-Change) enfocada al cambio de conducta del consumo excesivo de bebidas alcohólicas en adolescentes. Desarrollo Se utilizó la metodología de tres pasos propuesta por Fawcett. Para la revisión de literatura sobre consumo excesivo de bebidas alcohólicas, se emplearon términos en inglés y español, así como los operadores booleanos AND y OR en diversas bases de datos, posteriormente se construyó una estructura conceptual teórico-empírica de la propuesta de la Teoría de Situación Específica para el consumo excesivo de bebidas alcohólicas. Conclusiones La presente propuesta supone una alternativa para lograr el cambio de conducta del consumo excesivo de bebidas alcohólicas a través de un proceso motivacional de tres fases (premotivacional, motivacional y postmotivacional). Implementar esta propuesta, busca dar solución a una problemática que genera una carga importante de salud en una población vulnerable. Los hallazgos derivados de su aplicación pueden aportar evidencia para la labor del profesional de enfermería en el campo de la prevención del consumo de alcohol.

ABSTRACT Introduction Alcohol consumption among adolescents is a growing and frequent problem. Moreover, the episodic but excessive consumption of alcohol is becoming more common among the population. This situation makes it necessary for the nursing professional practicing in primary care to implement strategies and tools based on scientific evidence to address this problem. Objective Based on the Change Intention Model Specific Situation Theory (I-Change), to develop a proposal aimed at changing the behaviors of adolescents who binge drinking. Development The three steps methodology proposed by Fawcett was used. Using both English and Spanish terms, as well as the boolean operators AND and OR, diverse databases, were consulted regarding the literature on binge drinking. The conceptual theoretical- empirical structure of the proposal based on the Specific Situation Theory (binge drinking) was then constituted. Conclusions The present proposal offers an alternative to achieve a behavior change regarding binge drinking through a motivational process of three phases: pre-motivational, motivational, and post-motivational. This proposal can be implemented in order to address the problem of binge drinking among adolescents. The findings derived from this application can further provide evidence to the nursing professionals practicing alcohol consumption prevention.

RESUMO Introdução O consumo de álcool em adolescentes é um problema cada vez mais frequente e está aumentando, pois o consumo episódico excessivo é uma tendência cada vez mais comum nessa população. Para o profissional de enfermagem de atenção básica, torna-se necessária a implementação de ferramentas baseadas em evidências científicas como uma alternativa viável que responda às necessidades atuais. Objetivo Desenvolver uma proposta de aplicação baseada na Teoria da Situação Específica do Modelo de Intenção de Mudança (I-Change) focada na mudança comportamental no consumo excessivo episódico de álcool em adolescentes. Desenvolvimento Foi utilizada a metodologia de três etapas proposta por Fawcett. Para a revisão da literatura sobre o consumo episódico excessivo de álcool, foram utilizados termos em inglês e espanhol, bem como os operadores booleanos AND e OR em diversas bases de dados, posteriormente foi construída uma estrutura conceitual teórico-empírica da Teoria proposta. para o consumo episódico excessivo de álcool. Conclusões A presente proposta supõe uma alternativa para alcançar a mudança de comportamento do consumo episódico excessivo de álcool através de um processo motivacional de três fases (pré-motivacional, motivacional e pós-motivacional). A implementação desta proposta busca responder a um problema que gera uma carga significativa de saúde em uma população vulnerável. Os achados derivados de sua aplicação podem fornecer evidências para a atuação do profissional de enfermagem no campo da prevenção do consumo de álcool.

Sentido de coherencia asociado al bienestar psicológico y social en adultos mayores / Sense of coherence associated with psychological and social well-being in elderly

Introducción: La población mundial enfrenta el incremento de adultos mayores (AM) que crece de forma acelerada. Esto plantea oportunidades y desafíos dado que aumentará la demanda de atención médica y cuidados a largo plazo por la presencia de las enfermedades crónicas degenerativas y los síndromes geriátricos; además el AM experimenta eventos que pueden ser críticos y estresantes que pueden afectar su bienestar psicológico y social. Un factor que ha demostrado apoyar al individuo a enfrentar el estrés y se ha asociado con el bienestar es el sentido de coherencia. Objetivo: Conocer la relación y el efecto entre el sentido de coherencia y el bienestar psicológico y social en los AM del norte de México. Metodología:Estudio descriptivo correlacional con muestreo probabilístico proporcional al tamaño del estrato. Resul-tados: con una muestra integrada en un 77’3% por mujeres, el sentido de coherencia fue predictor positivo del bienestar psicológico (β = 0’45, p = 0’001) y social (β = 0’38, p = 0’001) en los AM. Conclusiones: El sentido de coherencia puede ayudar al AM a comprender, manejar y dar significado a los eventos que experimenta, a percibir su entorno como menos amenazador y alcanzar o mantener el bienestar psicológico y socia (AU)

Introduction: The world’s population faces an unprecedented phenomenon the proportional increase of elderly is growing fast. This phenomenon poses opportunities and challenges as the demand for medical attention and long-term care that will increase due to the presence of chronic degenerative diseases and geriatric syndromes; It is also common for the elderly to experience a series of events that can be critical and stressful and as a result affect their psychologi-cal and social well-being. Objective: To know the relationship and the effect between the sense of coherence and the psychological and social well-being in elderly of northern Mexico. Methodology: A descriptive correlational study was carried out with probabilistic sampling proportional to the size of each stratum. Results: in a sample of 77.3% of women, the Simple Linear Regression Model revealed that the sense of coherence was a positive predictor of psychological (β = .45, p = .001) and social (β = .38, p =. 001) in Elderly. Conclusions: The sense of coherence can help elderly to understand, manage and give meaning to the events they experience, to perceive their environment as less threatening and to achieve or maintain psychological and social well-being (AU)

Incertidumbre y afrontamiento en familiares de personas dependientes del alcohol: apoyo social y espiritualidad / Uncertainty and coping among relatives of alcohol dependent persons: social support and spirituality / Incerteza e enfrentamento em parentes de pessoas dependentes de álcool: apoio social e espiritualidade

Resumen Introducción: La dependencia al alcohol, considerada como una enfermedad crónica, es un detonante de incertidumbre para el familiar de la persona con dependencia, lo cual genera trastornos emocionales negativos. El apoyo social y la espiritualidad son mecanismos de afrontamiento que podrían disminuir la incertidumbre y favorecer el bienestar tanto físico, como psicológico. Objetivos: Determinar la relación y el efecto del apoyo social y la espiritualidad sobre la incertidumbre del familiar de la persona dependiente del alcohol. Métodos: Estudio descriptivo y correlacional, muestra de 135 mujeres pertenecientes a grupos Al-Anon, se utilizaron la Escala de Percepción de Incertidumbre en Padres y Miembros de la Familia (PPUS-FM) de Mishel, el cuestionario MOS-SSS de Sherbourne y Stewart y la Escala de Perspectiva Espiritual elaborada por Reed. Resultados: Se identificó un coeficiente de correlación negativo y significativo de la incertidumbre con el apoyo social (r s= -.356, p <.01) y la espiritualidad (r s= -.216, p <.05). Mediante un modelo de regresión lineal general univariado se determinó que únicamente el apoyo social influye en la disminución de la incertidumbre (β= -.280, t= -3.62, p= .001) con un coeficiente de determinación o varianza explicada del 11.5%, mientras que la espiritualidad no mostró efecto (β= -.041, t= .218, p >.05) sobre la incertidumbre. Conclusiones: El apoyo social es identificado como un mecanismo de afrontamiento efectivo que permitirá al personal de enfermería desarrollar intervenciones dirigidas a reducir la incertidumbre en familiares de personas con algún tipo de dependencia.

Abstract Introduction: Alcohol dependency is a chronic illness which generates uncertainty and other emotional problems among the relatives of persons who suffer alcoholism. Social support and spirituality are some coping mechanisms which could reduce uncertainty and favor the physical and psychological wellbeing. Objective: To determine the relationship and the effect of social support and spirituality on the uncertainty experienced by relatives of alcohol dependent persons. Methods: This is a descriptive and correlational study. The sample was constituted by 135 women members of Al-Anon. The Mishel Scale of Perception of Uncertainty among Parents and Family Members (PPUS-FM), the Sherbourne and Stewart Questionnaire, and the Reed Spiritual Perspective Scale were all used. Results: Significant negative correlation coefficients between uncertainty and social support (r s= -.356, p .05). and spirituality (r s= -.216, p .05). were identified. Using a univariate general linear regression model, it was determined that only social supports reduced uncertainty (β= -.280, t= -3.62, p= .001) with 11.5% of variance explained; while spirituality did not produce any effect (β = -.041, t= .218, p >.05). Conclusions: Social support is identified as a coping mechanism which can be used by nursing staff to develop interventions aimed at reducing uncertainty among relatives of alcohol dependent persons.

Resumo Introdução: A dependência do álcool, considerada como uma doença crónica, é um gatilho de incerteza para o familiar da pessoa com dependência, o qual gera transtornos emocionais negativos. O suporte social e a espiritualidade são mecanismos de enfrentamento que poderiam diminuir a incerteza e favorecer o bem-estar tanto físico, quanto psicológico. Objetivos: Determinar a relação e o efeito do suporte social e a espiritualidade sobre a incerteza do familiar da pessoa dependente de álcool. Métodos: Estudo descritivo e correlacional, amostra de 135 mulheres pertencentes aos grupos Al-Anon, utilizaram-se a Escala de Percepção de Incerteza em Pais e Membros da Família (PPUS-FM) de Mishel, o questionário MOS-SSS de Sherbourne e Stewart e a Escala de Perspectiva Espiritual elaborada por Reed. Resultados: Identificou-se um coeficiente de correlação negativo e significativo da incerteza com o apoio social (r s= -.356, p <.01) e a espiritualidade (r s= -.216, p <.05). Mediante um modelo de regressão linear geral univariado determinou-se que unicamente o apoio social influencia a diminuição da incerteza (β= -.280, t= -3.62, p= .001) com um coeficiente de determinação ou variância explicada do 11.5%, enquanto a espiritualidade não mostrou efeito (β= -.041, t= .218, p >.05) sobre a incerteza. Conclusões: O suporte social é identificado como um mecanismo de enfrentamento eficaz que permitirá ao pessoal de enfermagem desenvolver intervenções dirigidas a reduzir a incerteza em familiares de pessoas com algum tipo de dependência.

Circulating exosomes deliver free fatty acids from the bloodstream to cardiac cells: Possible role of CD36.

Regulation of circulating free fatty acid (FFA) levels and delivery is crucial to maintain tissue homeostasis. Exosomes are nanomembranous vesicles that are released from diverse cell types and mediate intercellular communication by delivering bioactive molecules. Here, we sought to investigate the uptake of FFAs by circulating exosomes, the delivery of FFA-loaded exosomes to cardiac cells and the possible role of the FFA transporter CD36 in these processes. Circulating exosomes were purified from the serum of healthy donors after an overnight fast (F) or 20 minutes after a high caloric breakfast (postprandial, PP). Western blotting, Immunogold Electron Microscopy and FACS analysis of circulating exosomes showed that CD36 was expressed under both states, but was higher in postprandial-derived exosomes. Flow cytometry analysis showed that circulating exosomes were able to take-up FFA directly from serum. Importantly, preincubation of exosomes with a blocking CD36 antibody significantly impeded uptake of the FFA analogue BODIPY, pointing to the role of CD36 in FFA exosomal uptake. Finally, we found that circulating exosomes could delivery FFA analogue BODIPY into cardiac cells ex vivo and in vivo in a mice model. Overall, our results suggest a novel mechanism in which circulating exosomes can delivery FFAs from the bloodstream to cardiac tissue. Further studies will be necessary to understand this mechanism and, in particular, its potential involvement in metabolic pathologies such as obesity, diabetes and atherosclerosis.

Analysing the natural population growth of a large marine mammal after a depletive harvest.

An understanding of the underlying processes and comprehensive history of population growth after a harvest-driven depletion is necessary when assessing the long-term effectiveness of management and conservation strategies. The South American sea lion (SASL), Otaria flavescens, is the most conspicuous marine mammal along the South American coasts, where it has been heavily exploited. As a consequence of this exploitation, many of its populations were decimated during the early 20th century but currently show a clear recovery. The aim of this study was to assess SASL population recovery by applying a Bayesian state-space modelling framework. We were particularly interested in understanding how the population responds at low densities, how human-induced mortality interplays with natural mechanisms, and how density-dependence may regulate population growth. The observed population trajectory of SASL shows a non-linear relationship with density, recovering with a maximum increase rate of 0.055. However, 50 years after hunting cessation, the population still represents only 40% of its pre-exploitation abundance. Considering that the SASL population in this region represents approximately 72% of the species abundance within the Atlantic Ocean, the present analysis provides insights into the potential mechanisms regulating the dynamics of SASL populations across the global distributional range of the species.

Interaction between Human Serum Albumin and antidiabetic compounds and its influence on the O2((1)Δg)-mediated degradation of the protein.

The complexity depicted by disease scenarios as diabetes mellitus, constitutes a very interesting field of study when drugs and biologically relevant components may be affected by such environments. In this report, the interaction between the protein Human Serum Albumin (HSA) and two antidiabetics (Andb), Gliclazide (Gli) and Glipizide (Glip) was studied through fluorescence and docking assays, in order to characterize these systems. On the basis that HSA and Andb can be exposed in vivo at high Reactive Oxygen Species (ROS) concentrations in diabetic patients, the degradative process of the protein free and bound to Andb, in presence of the species singlet molecular oxygen (O2((1)Δg)), was evaluated. Fluorescence and docking assays indicated that Gli, as well as Glip bind to HSA on two sites, with binding constants values in the order of 10(4)-10(5)M(-1). Likewise, docking assays revealed that the location of Gli or Glip on the protein may be the HSA binding sites II and III. Thermodynamic parameters showed that the interaction between HSA and Glip is a favored, enthalpically-controlled process. Oxygen uptake experiments indicated that Glip is less photooxidizable than Gli through a O2((1)Δg)-mediated process. Besides, the protein-Andb binding produced a decrease in the overall rate constant for O2((1)Δg) quenching as compared to the value for the free protein. This fact could be interpreted in terms of a reduction in the availability of Tyrosine residues in the bonded protein, with a concomitant decrease in the physical quenching deactivation of the oxidative species.

Star polymers rupture induced by constant forces.

In this work, we study the breakage process of an unknotted three-arm star-shaped polymer when it is pulled from its free ends by a constant force. The star polymer configuration is described through an array of monomers coupled by anharmonic bonds, while the rupture process is tracked in three-dimensional space by means of Langevin Molecular Dynamics simulations. The interaction between monomers is described by a Morse potential, while a Weeks-Chandler-Anderson energetic contribution accounts for the excluded volume interaction. We explore the effect of the molecular architecture on the distributions of rupture times over a broad interval of pulling forces and star configurations. It was found that the rupture time distribution of the individual star arms is strongly affected by the star configuration imposed by the pulling forces and the length of the arms. We also observed that for large pulling forces the rupture time distributions resemble the dominant features observed for linear polymer chains. The model introduced here provides the basic ingredients to describe the effects of tensile forces on stress-induced degradation of branched macromolecules and polymer networks.

Intestinal helminth fauna of the South American sea lion Otaria flavescens and fur seal Arctocephalus australis from northern Patagonia, Argentina.

We report on the intestinal helminth fauna of 56 South American sea lions, Otaria flavescens, and 5 South American fur seals, Arctocephalus australis, from northern Patagonia, Argentina. A total of 97,325 helminth specimens were collected from sea lions. Gravid individuals were represented by 6 species of parasites: 1 digenean (Ascocotyle (Ascocotyle) patagoniensis), 1 cestode (Diphyllobothrium spp.), 3 nematodes (Uncinaria hamiltoni, Contracaecum ogmorhini s.s., Pseudoterranova cattani) and 1 acanthocephalan (Corynosoma australe). In addition, third-stage larvae of 2 nematodes (Contracaecum sp. and Anisakis sp. type I) and 3 juvenile acanthocephalans (Andracantha sp., Profilicollis chasmagnathi and Corynosoma cetaceum) were also collected. Andracantha sp., C. ogmorhini s.s. and P. chasmagnathi represent new host records. A total of 1516 helminth specimens were collected from fur seals. Gravid individuals were represented by three species of parasites, namely, Diphyllobothrium spp., C. ogmorhini s.s. and C. australe. In addition, larvae of Contracaecum sp. and P. cattani, juveniles of C. cetaceum and immature cestodes (Tetrabothriidae gen. sp.) were also collected. Corynosoma australe was the most prevalent and abundant parasite in both hosts, accounting for >90% of all specimens. Sea lions and furs seals from northern Patagonia harbour the intestinal helminth communities that could be predicted for otariids, i.e. the combination of species of the genera Corynosoma, Diphyllobothrium, Pseudoterranova, Contracaecum and, in pups, Uncinaria. Additionally, both species of otariid are apparently unsuitable hosts (i.e. non-hosts) for as many as five parasite taxa. The inclusion or exclusion of these species affects estimation of species richness at both component community (11 versus 6 species in sea lions; 7 versus 3 species in fur seals) and infracommunity (mean: 3.1 versus 2.6 in sea lions; 2.2 versus 1.7 species) levels. Information about the reproductive status of helminth species is often lacking in parasitological surveys on otariids and other marine vertebrates, but it is of significance to improve precision in parascript studies or ecological meta-analyses.

Aporocotyle mariachristinae n. sp., and A. ymakara Villalba & Fernández, 1986 (Digenea: Aporocotylidae) of the pink cusk-eel, Genypterus blacodes (Ophidiiformes: Ophidiidae) from Patagonia, Argentina.

Aporocotyle mariachristinae n. sp. and A. ymakara Villalba & Fernández, 1986 were collected from the bulbus arteriosus and ventral aorta of pink cusk-eels, Genypterus blacodes (Forster, 1801) from Patagonia, Argentina. A. mariachristinae n. sp. can be distinguished from all the species of Aporocotyle by the asymmetrical extension of posterior caeca (right posterior caecum longer, terminating at the area between mid-level of ovary and posterior body end; left posterior caecum shorter, terminating at the area between mid-level of cirrus sac and posterior to reproductive organs), the distribution of spines along the ventro-lateral body margins and the number of testes. The new species clearly differs from A. ymakara, from the same host species, in the esophagus / body length ratio, the absence of distal loops at caeca, the anterior caeca / posterior caeca length ratio, and the number of testes. Additionally, in A. ymakara the left posterior caecum may be longer than right posterior caecum, while in the new species left posterior caecum is always shorter. The specimen of A. ymakara collected from Argentina is also described. We also provide observations of the distribution of spines in different species of Aporocotyle, including new specimens of A. argentinensis Smith, 1969 from Merluccius hubbsi Marini, 1933. Molecular sequence data obtained from partial 18S and 28S rDNA regions were compared between the new species and other two species of Aporocotyle (A. argentinensis and A. spinosicanalis Williams, 1958). This is a new locality record for A. ymakara, extending the known geographical distribution for this species from Chile to Argentina, and the first report of two species of Aporocotyle in the same host species and locality.

Prevalence of accessory pudendal artery.

This study investigated the frequency of an accessory pudendal artery in 15 adult cadavers fixed with formaldehyde solution. The prevalence of accessory pudendal artery varies between 7 and 75% according to the method of identification (imaging studies, microstereoscopic cadaveric dissection, and open and laparoscopic surgeries). Currently, under discussion is the role of this artery in postprostatectomy erectile dysfunction. Accordingly, it is important to know the true prevalence to appreciate its clinical significance. The internal pudendal system was examined through direct dissection, and findings were compared with the different methods of identification published.

Organochlorine residues in South American sea lions, Otaria flavescens (Shaw, 1800): bioaccumulation and time trends.

Blubber from stranded South American sea lions (Otaria flavescens) was sampled between 1991 and 2005 on the Peninsula Valdés in Argentina and analyzed for organochlorine (OC) pollutants. Mean blubber concentrations, expressed on an extractable basis, were 686 (SD = 1,060) ng g(-1) for dichlorodiphenyl trichloroethane (tDDT) and 735 (SD = 787) ng g(-1) for polychlorinated byphenils (PCB). The OC levels were well below those associated with adverse sublethal effects and lethality in mammals. OC concentrations showed statistically significant associations with age that were positive in males and negative in females. These trends are consistent with the majority of marine mammal populations studied. There were no trends in the levels of tDDT or PCB over time. In spite of the low levels detected, OC contamination was present consistently over the 14-year period, suggesting continuous inputs from geographic redistribution.

Kinetics of the photosensitized oxidation of chymotrypsin in different media.

The kinetic aspects of the Perinaphthenone-sensitized photooxidation (singlet molecular oxygen [O2 ((1)Delta(g))]-mediated) of alpha-chymotrypsin (alpha-Chymo) have been studied at pH 8 and pH 11 as well in reverse micelles (RMs) of sodium 1, 4 bis (2-ethylhexyl) sulfosuccinate (AOT) in n-heptane. The rate constant values for both overall (k(t)) and chemical (k(r)) quenching of O2 ((1)Delta(g)) by alpha-Chymo in homogeneous media were higher at pH = 11 than at pH = 8, indicating that the OH-ionized tyrosine (Tyr) residues, clearly dominate the quenching process. Besides, the rate constants in water were higher than those determined in RMs, demonstrating that the organized medium protects the protein against photooxidation, probably due to a diminution in both, the accessibility towards oxidizable amino acid residues and the polarity inside the aggregate, as compared to water. The protection effect of alpha-Chymo against the attack by the oxidative species O2 ((1)Delta(g)) in RMs of AOT seems to be due to the increase of protein stability by the encapsulation within the micellar structure. The effect of both, surfactant concentration and variation of the ratio ([H2O]/[AOT]) = W on the reactive rate constant was also investigated. The process does not depend significantly on micelles concentration while the k(r) values increase as W increases. Furthermore, at W = 30, the highest W studied, k(r) tends to the value obtained in aqueous medium.

Singlet molecular oxygen [O2(1Deltag)]-mediated photodegradation of tyrosine derivatives in the presence of cationic and neutral micellar systems.

The kinetics of rose bengal-sensitized photooxidation of tyrosine and several tyrosine-derivatives (tyr-D) named tyrosine methyl ester, tyrosine ethyl ester and tyrosine benzyl ester was studied in buffered pH 11 water, and buffered pH 11 micellar aqueous solutions of 0.01 M cetyltrimethylammonium chloride (CTAC) and 0.01 M-octylphenoxypolyethoxyethanol [triton X100 (TX100)]. Through time-resolved phosphorescence detection of singlet molecular oxygen (O(2)((1)Delta(g))) and polarographic determination of oxygen consumption, the respective bimolecular rate constants for reactive (k(r)) and overall (k(t)) quenching of the oxidative species by tyr-D were evaluated. Both rate constants behave in different fashion depending on the particular reaction medium. k(r)/k(t) values, increase in the sense CTAC<

On the antioxidant properties of three synthetic flavonols.

The antioxidant properties of a series of synthetic and natural flavonoids towards the oxygenated species superoxide radical anion (*O2-) enzimatically generated, were evaluated. 7-Hydroxyflavonol, 7,3'-dihydroxyflavonol and 3'-hydroxyflavonol were synthesised, with a systematic variation of the OH substitution on positions C3, C7, C3'and C4', and their respective antioxidative abilities compared to those of the already characterised natural flavonoids quercetin, kaempferol and rutin. The efficiency of *O2- deactivation by the flavonoids does not correlate with their respective determined oxidation potentials, suggesting that the pure one-electron-transfer-mechanism of *O2 quenching could not be the main scavenging process involved. Experimental evidence demonstrated that the possible inhibition of the *O2(-)-generator enzymatic system by the flavonoids must be disregarded as a possible indirect cause for the inhibition of the oxidative species. One possible mechanism for the inhibition of *O2-, highly dependent on the substitution pattern of the flavonoid, may be the generation of hydroperoxides or dioxetanes as oxidation products, as already postulated for other biologically relevant compounds. The simultaneous OH-substitution on positions C3 and C7 of the flavonoid skeleton plays a definitive role in the enhancement of the *O2- inhibitory effect. The replacement of OH by a O-rutinosyl group on position C7 suppresses at all that effect, whereas the absence of an OH group in position 7 significantly reduces the antioxidative power. Finally, the presence of OH groups on positions 3'and 4' does not produce any determinant effect in the antioxidative behaviour of the flavonoids.

Photoproducts and proposed degradation pathway in the riboflavin-sensitised photooxidation of isoproterenol.

Products of the aerobic visible-light-promoted riboflavin-sensitised photooxidation of the sympathomimetic drug isoproterenol were identified by means of HPLC and spectrophotometric techniques. The oxidative process, mediated by superoxide radical anion, generates N-isopropylaminochrome as a main photoproduct with a quantum yield of 0.15. In parallel, the photodecomposition of riboflavin is prevented in the presence of isoproterenol. A reaction scheme for the photooxidation pathway of isoproterenol is proposed in analogy to former reports for related compounds.

Photodegradation of the herbicide Norflurazon sensitised by Riboflavin. A kinetic and mechanistic study.

The kinetics and mechanism of the Riboflavin (Rf)-promoted photochemical degradation with visible light of the herbicide Norflurazon (NF) has been studied by time-resolved and stationary techniques. Using light of wavelength higher than 400 nm--a region where NF is totally transparent--and with concentrations of Rf and NF of ca. 0.02 and 1 mM, respectively, only the excited triplet state of Rf ((3)Rf*) is quenched by NF, in competition with dissolved ground state triplet oxygen, O(2)((3)Sigma(g)(-)). NF degradation mainly occurs by reaction with superoxide radical anion O(2)(-) formed through two electron transfer steps: from NF to (3)Rf*, yielding Rf radical anion, and from this anion to O(2)((3)Sigma(g)(-)), regenerating ground state Rf. Although singlet molecular oxygen is also produced, NF only quenches this oxidative species in a physical mode. The global result is the photoprotection of the sensitiser and the photodegradation of NF.

Corynebacterium striatum peritoneal dialysis catheter exit site infection.

BACKGROUND: Regarded as normal flora of the human skin and mucus membranes, non-diphtheria corynebacteria are frequently dismissed as contaminants or harmless colonizers. Recently, the pathogenic potential of C. striatum has been realized in immunocompromised patients with indwelling medical devices and previous antibiotic exposure. OBJECTIVE: We report here the diagnosis, treatment and clinical outcome of a peritoneal dialysis patient with a C. striatum infection of the catheter exit site. The aim is to present important features to assist in identifying clinically significant infections and provide guidelines for treatment. RESULTS: An immunocompromised patient with previous antimicrobial exposure developed an acute dialysis catheter exit site infection. C. striatum was isolated in pure growth. After initial treatment failure with oral antibiotics and intensified wound care, a satisfactory outcome was ultimately achieved without relapse or loss of the catheter with a 1-month course of vancomycin, 1 g intravenously, administered at 5-day intervals. CONCLUSIONS: The virulent capacity of Corynebacterium species should not be underestimated, particularly in high-risk patients. The presence of clinical signs of infection with isolation of the organism in pure culture and the presence of Gram-positive rods on direct Gram stain, especially in association with a leukocyte reaction, supports a cause and effect relationship. Because corynebacteria may be multiresistant, susceptibility testing should be performed on clinically significant isolates. Initial antibiotic selection is influenced by the severity of the infection, however, current experience favors vancomycin in significant infections.

A comparative kinetic study on the singlet molecular oxygen-mediated photoxidation of alpha- and beta-chymotrypsins.

Kinetic aspects of the sensitized photooxidation of alpha- and beta-chymotrypsins have been studied at pH 6 and 8. The sensitization, employing classical O2(1Deltag)-photogenerators, such as xanthene dyes, is a kinetically intricate process because of the presence of ground state dye-protein associations and to the simultaneous participation of superoxide ion and singlet molecular oxygen [O2(1Deltag)]. Both proteins, that possess the same distribution pattern of photooxidizable amino acids, suffer a pure O2(1Deltag)-mediated photodynamic attack, using the carbonylic sensitizer Perinaphthenone. Overall and reactive rate constants for the O2(1Deltag)-quenching (in the order of 108 and 107/M/s, respectively), and rates of oxygen consumption determined by time-resolved, spectroscopic and polarographic methods indicate that alpha- and beta-chymotrypsins are less photooxidizable at pH 6, as a result of an enhancement of the O2(1Deltag)-physical quenching component. In general terms, beta-chymotrypsin exhibits the greater overall proclivity to interact with O2(1Deltag), whereas structural factors, possibly evidenced by a higher exposure of the reactive tryptophan residues, impart an increased photooxidation degree to the proteins at pH 8, specially to the alpha-chymotrypsin.

Kinetic study of the riboflavin-sensitised photooxygenation of two hydroxyquinolines of biological interest.

4-Hydroxyquinoline (4-OHQ) and 8-hydroxyquinoline (8-OHQ), two compounds of interest because of their bioactivity and their structural relation with bioactive products, are effectively photooxygenated when irradiated with visible light in the presence of riboflavin (Rf) (vitamin B2) in solution in air-saturated water-methanol (9:1). Rf behaves as a dye-sensitiser, since both quinolines are transparent to visible light. 8-OHQ degrades about five times faster than 4-OHQ. Kinetic data obtained through time-resolved and stationary detection of Rf-electronically excited states indicate that a superoxide radical anion-mediated mechanism exclusively operates for 4-OHQ, whereas singlet molecular oxygen--mainly--plus superoxide radical anion is the species that reacts with 8-OHQ. The sensitiser Rf, which is known to photodegrade under visible-light aerobic irradiation, is regenerated in the presence of any of the quinolines through an electron transfer process that produces superoxide radical anion. The overall picture indicates that both quinolines act as sacrificial scavengers of the photogenerated oxygen species, thus preventing the photodegradation of Rf.