Modifying the magnetic response of magnetotactic bacteria: incorporation of Gd and Tb ions into the magnetosome structure.

Magnetotactic bacteria Magnetospirillum gryphiswaldense MSR-1 biosynthesise chains of cube-octahedral magnetosomes, which are 40 nm magnetite high quality (Fe3O4) nanoparticles. The magnetic properties of these crystalline magnetite nanoparticles, which can be modified by the addition of other elements into the magnetosome structure (doping), are of prime interest in a plethora of applications, those related to cancer therapy being some of the most promising ones. Although previous studies have focused on transition metal elements, rare earth (RE) elements are very interesting as doping agents, both from a fundamental point of view (e.g. significant differences in ionic sizes) and for the potential applications, especially in biomedicine (e.g. magnetic resonance imaging and luminescence). In this work, we have investigated the impact of Gd and Tb on the magnetic properties of magnetosomes by using different complementary techniques. X-ray diffraction, transmission electron microscopy, and X-ray absorption near edge spectroscopy analyses have revealed that a small amount of RE ions, ∼3-4%, incorporate into the Fe3O4 structure as Gd3+ and Tb3+ ions. The experimental magnetic characterisation has shown a clear Verwey transition for the RE-doped bacteria, located at T ∼ 100 K, which is slightly below the one corresponding to the undoped ones (106 K). However, we report a decrease in the coercivity and remanence of the RE-doped bacteria. Simulations based on the Stoner-Wohlfarth model have allowed us to associate these changes in the magnetic response with a reduction of the magnetocrystalline (K C) and, especially, the uniaxial (K uni) anisotropies below the Verwey transition. In this way, K uni reaches a value of 23 and 26 kJ m-3 for the Gd- and Tb-doped bacteria, respectively, whilst a value of 37 kJ m-3 is obtained for the undoped bacteria.

Correction: Modifying the magnetic response of magnetotactic bacteria: incorporation of Gd and Tb ions into the magnetosome structure.

[This corrects the article DOI: 10.1039/D2NA00094F.].

New Aluminum Syntactic Foam: Synthesis and Mechanical Characterization.

Metal matrix syntactic foams (MMSF) are advanced cellular materials constituted by a system of a minimum of two phases, in which a dispersion of hollow particles is embedded by a continuous metal matrix. The incorporation of porous fillers favors the development of low-density materials with exceptional behavior for damping vibrations, impacts, and blast effects, shielding acoustic, thermal, and electromagnetic energies. There are three main techniques to produce them: infiltration casting technique (ICT), stir casting technique (SCT), and powder metallurgy technique (P/M). The first two techniques are used for embedding filler into lower melting point metallic matrices than fillers, in contrast to P/M. The present study demonstrates the feasibility of producing MMSF with components of similar melting points by ICT. The fillers were synthesized in-situ with aluminum and a natural foaming agent from wastes of Spanish white marble quarries. These novel aluminum syntactic foams (ASF) were mechanically characterized following the ISO-13314 and exhibited a porosity, plateau stress, and energy absorption capacity of 41%, 37.65 MPa, 8.62 MJ/m3 (at 35% of densification), respectively. These properties are slightly superior to equal porosity LECA ASF, making these novel ASF suitable for the same applications as LECA-ASF.

Problematic use or addiction? A scoping review on conceptual and operational definitions of negative social networking sites use in adolescents.

The aim of this study was to assess the conceptual and operational descriptions of negative social networking site (SNS) use in adolescents. A search was conducted among four databases, following the guidelines set forth in the PRISMA-ScR. The search resulted in 1503 articles, of which 112 met the inclusion criteria. The results showed that the negative use of SNS has been conceptualised from two approaches: (1) the component model of addiction and (2) a cognitive-behavioural problematic use paradigm. Thirty-seven instruments assessing this problem were found, with the Bergen Facebook Addiction Scale and its adaptations being the most widely used ones. These instruments dimensions were vaguely defined and often overlapped with one another. In conclusion, no standardised theoretical framework exists to assess negative SNS use in adolescents. This lack of a theoretical definition makes it difficult to compare results among studies and determine the true extent of the problem.

Magnetosomes could be protective shields against metal stress in magnetotactic bacteria.

Magnetotactic bacteria are aquatic microorganisms with the ability to biomineralise membrane-enclosed magnetic nanoparticles, called magnetosomes. These magnetosomes are arranged into a chain that behaves as a magnetic compass, allowing the bacteria to align in and navigate along the Earth's magnetic field lines. According to the magneto-aerotactic hypothesis, the purpose of producing magnetosomes is to provide the bacteria with a more efficient movement within the stratified water column, in search of the optimal positions that satisfy their nutritional requirements. However, magnetosomes could have other physiological roles, as proposed in this work. Here we analyse the role of magnetosomes in the tolerance of Magnetospirillum gryphiswaldense MSR-1 to transition metals (Co, Mn, Ni, Zn, Cu). By exposing bacterial populations with and without magnetosomes to increasing concentrations of metals in the growth medium, we observe that the tolerance is significantly higher when bacteria have magnetosomes. The resistance mechanisms triggered in magnetosome-bearing bacteria under metal stress have been investigated by means of x-ray absorption near edge spectroscopy (XANES). XANES experiments were performed both on magnetosomes isolated from the bacteria and on the whole bacteria, aimed to assess whether bacteria use magnetosomes as metal storages, or whether they incorporate the excess metal in other cell compartments. Our findings reveal that the tolerance mechanisms are metal-specific: Mn, Zn and Cu are incorporated in both the magnetosomes and other cell compartments; Co is only incorporated in the magnetosomes, and Ni is incorporated in other cell compartments. In the case of Co, Zn and Mn, the metal is integrated in the magnetosome magnetite mineral core.

Configuration of the magnetosome chain: a natural magnetic nanoarchitecture.

Magnetospirillum gryphiswaldense is a microorganism with the ability to biomineralize magnetite nanoparticles, called magnetosomes, and arrange them into a chain that behaves like a magnetic compass. Rather than straight lines, magnetosome chains are slightly bent, as evidenced by electron cryotomography. Our experimental and theoretical results suggest that due to the competition between the magnetocrystalline and shape anisotropies, the effective magnetic moment of individual magnetosomes is tilted out of the [111] crystallographic easy axis of magnetite. This tilt does not affect the direction of the chain net magnetic moment, which remains along the [111] axis, but explains the arrangement of magnetosomes in helical-like shaped chains. Indeed, we demonstrate that the chain shape can be reproduced by considering an interplay between the magnetic dipolar interactions between magnetosomes, ruled by the orientation of the magnetosome magnetic moment, and a lipid/protein-based mechanism, modeled as an elastic recovery force exerted on the magnetosomes.

Influence of the bacterial growth phase on the magnetic properties of magnetosomes synthesized by Magnetospirillum gryphiswaldense.

BACKGROUND: The magnetosome biosynthesis is a genetically controlled process but the physical properties of the magnetosomes can be slightly tuned by modifying the bacterial growth conditions. METHODS: We designed two time-resolved experiments in which iron-starved bacteria at the mid-logarithmic phase are transferred to Fe-supplemented medium to induce the magnetosomes biogenesis along the exponential growth or at the stationary phase. We used flow cytometry to determine the cell concentration, transmission electron microscopy to image the magnetosomes, DC and AC magnetometry methods for the magnetic characterization, and X-ray absorption spectroscopy to analyze the magnetosome structure. RESULTS: When the magnetosomes synthesis occurs during the exponential growth phase, they reach larger sizes and higher monodispersity, displaying a stoichiometric magnetite structure, as fingerprinted by the well defined Verwey temperature. On the contrary, the magnetosomes synthesized at the stationary phase reach smaller sizes and display a smeared Verwey transition, that suggests that these magnetosomes may deviate slightly from the perfect stoichiometry. CONCLUSIONS: Magnetosomes magnetically closer to stoichiometric magnetite are obtained when bacteria start synthesizing them at the exponential growth phase rather than at the stationary phase. GENERAL SIGNIFICANCE: The growth conditions influence the final properties of the biosynthesized magnetosomes. This article is part of a Special Issue entitled "Recent Advances in Bionanomaterials" Guest Editors: Dr. Marie-Louise Saboungi and Dr. Samuel D. Bader.

Studying nanoparticles' 3D shape by aspect maps: Determination of the morphology of bacterial magnetic nanoparticles.

Magnetic nanoparticles (MNPs) are widely investigated due to their potential use in various applications, ranging from electronics to biomedical devices. The magnetic properties of MNPs are strongly dependent on their size and shape (i.e., morphology), thus appropriate tools to investigate their morphology are fundamental to understand the physics of these systems. Recently a new approach to study nanoparticle morphology by Transmission Electron Microscopy (TEM) analysis has been proposed, introducing the so-called Aspect Maps (AMs). In this paper, a further evolution of the AM method is presented, allowing determination of the nanoparticles' 3D shape by TEM image. As a case study, this paper will focus on magnetite nanoparticles (Fe3O4), with a mean size of ∼45 nm extracted from Magnetospirillum gryphiswaldense magnetostatic bacteria (MTB). The proposed approach gives a complete description of the nanoparticles' morphology, allowing estimation of an average geometrical size and shape. In addition, preliminary investigation of the magnetic properties of MTB nanoparticles was performed, giving some insight into interparticle interactions and on the reversal mechanism of the magnetization.

On the mineral core of ferritin-like proteins: structural and magnetic characterization.

It is generally accepted that the mineral core synthesized by ferritin-like proteins consists of a ferric oxy-hydroxide mineral similar to ferrihydrite in the case of horse spleen ferritin (HoSF) and an oxy-hydroxide-phosphate phase in plant and prokaryotic ferritins. The structure reflects a dynamic process of deposition and dissolution, influenced by different biological, chemical and physical variables. In this work we shed light on this matter by combining a structural (High Resolution Transmission Electron Microscopy (HRTEM) and Fe K-edge X-ray Absorption Spectroscopy (XAS)) and a magnetic study of the mineral core biomineralized by horse spleen ferritin (HoSF) and three prokaryotic ferritin-like proteins: bacterial ferritin (FtnA) and bacterioferritin (Bfr) from Escherichia coli and archaeal ferritin (PfFtn) from Pyrococcus furiosus. The prokaryotic ferritin-like proteins have been studied under native conditions and inside the cells for the sake of preserving their natural attributes. They share with HoSF a nanocrystalline structure rather than an amorphous one as has been frequently reported. However, the presence of phosphorus changes drastically the short-range order and magnetic response of the prokaryotic cores with respect to HoSF. The superparamagnetism observed in HoSF is absent in the prokaryotic proteins, which show a pure atomic-like paramagnetic behaviour attributed to phosphorus breaking the Fe-Fe exchange interaction.

Función renal en pacientes con insuficiencia cardiaca: valor pronóstico / Renal function in patients with heart failure: prognostic value

Antecedentes y objetivo. La insuficiencia renal es un factor pronóstico adverso en pacientes con insuficiencia cardiaca (IC). Hemos evaluado la prevalencia de insuficiencia renal en una cohorte de pacientes ingresados por IC y su valor pronóstico. Métodos. Entre marzo de 2008 y septiembre de 2009 y a partir del Registro RICA (estudio de cohortes multicéntrico y prospectivo) analizamos los pacientes admitidos por IC en los Servicios de Medicina Interna de 52 hospitales españoles. Los pacientes se clasificaron según su función renal filtrado glomerular estimado (FGe) utilizando la fórmula Modification of Diet in Renal Disease (MDRD). Resultados. Se incluyeron 714 pacientes con una edad media de 77,3+8,7 años (54% mujeres). El 84% presentaban antecedentes de hipertensión arterial. La cardiopatía hipertensiva fue la causa más frecuente de IC (39,2%). El 64,7% presentaron una fracción de eyección del ventrículo izquierdo (FEVI) conservada. Un 59,5% de los enfermos presentó un FGe<60mL/min/1,73m2. De ellos, un 11,2% tenía un FGe<30mL/min/1,73m2). Se observó una menor prescripción de fármacos antialdosterónicos en los pacientes con disfunción renal severa (24%) con respecto a los que tenían un FGe>60mL/min/1,73m2 (35%; p=0,025). El deterioro de la función renal se asoció de manera independiente y significativa con un aumento de mortalidad (RR: 2,05; IC del 95%: 1,13-3,71; p=0,018). Conclusiones. Cerca del 60% de los enfermos que ingresan en Medicina Interna con IC presentan insuficiencia renal. Esta comorbilidad se asocia a un incremento medio del doble en la mortalidad global(AU)

Introduction. Impaired renal function can lead to a poor prognosis in patients with heart failure (HF). This study analyses the prevalence and prognostic value of impaired renal function in a cohort of patients with HF. Methods. We analysed patients who were included in the RICA study (multicentre, prospective cohort study) who were admitted for decompensated HF in 52 Spanish Internal Medicine Departments between March 2008 and September 2009. The patients were grouped according to their renal function, evaluated by eGF, using the MDRD formula. Results. A total of 714 patients (54% women) with a mean age of 77.3+8.7 years were included. Of these, 84% had hypertension, and hypertensive heart disease was the most common aetiology of HF (39.2%). Ejection fraction was normal in 64.7% of patients, and 59.5% had an eGF less than 60mL/min per 1.73m2, and 11.2% with an eGF less than 30mL/min per 1.73m2. Less spironolactone was prescribed in patients with advanced stages of renal dysfunction (24%), compared with patients with an eGF>60mL/min/1.73m2 (35%; P=.025). Worsening renal function was independently associated with an increased mortality risk (RR: 2.05; 95% CI: 1.13-3.71; P=.018). Conclusions. About 60% of patients admitted to Internal Medicine with HF have impaired renal function. This comorbidity is associated with a two-fold increase in all-cause mortality(AU)

[Renal function in patients with heart failure: prognostic value]. / Función renal en pacientes con insuficiencia cardiaca: valor pronóstico.

INTRODUCTION: Impaired renal function can lead to a poor prognosis in patients with heart failure (HF). This study analyses the prevalence and prognostic value of impaired renal function in a cohort of patients with HF. METHODS: We analysed patients who were included in the RICA study (multicentre, prospective cohort study) who were admitted for decompensated HF in 52 Spanish Internal Medicine Departments between March 2008 and September 2009. The patients were grouped according to their renal function, evaluated by eGF, using the MDRD formula. RESULTS: A total of 714 patients (54% women) with a mean age of 77.3+8.7 years were included. Of these, 84% had hypertension, and hypertensive heart disease was the most common aetiology of HF (39.2%). Ejection fraction was normal in 64.7% of patients, and 59.5% had an eGF less than 60 mL/min per 1.73 m(2), and 11.2% with an eGF less than 30 mL/min per 1.73 m(2). Less spironolactone was prescribed in patients with advanced stages of renal dysfunction (24%), compared with patients with an eGF>60 mL/min/1.73 m(2) (35%; P=.025). Worsening renal function was independently associated with an increased mortality risk (RR: 2.05; 95% CI: 1.13-3.71; P=.018). CONCLUSIONS: About 60% of patients admitted to Internal Medicine with HF have impaired renal function. This comorbidity is associated with a two-fold increase in all-cause mortality.

Mercury biomethylation assessment in the estuary of Bilbao (North of Spain).

The relationship between the microbial methylation of mercury and the microbial activities in sediments and water collected from the estuary of Bilbao (North of Spain) was studied in three different sampling points and in two different seasons. Three different cultures were prepared with a sediment slurry to distinguish between biotic and abiotic methylation pathways and the variations of the methylmercury concentration and the variations of the population of total number of bacteria (TDC), anaerobic heterotrophic bacteria (AHB), sulphate-reducing bacteria (SRB) and Desulfovibrio were measured. From this work, it can be concluded that the variation of MeHg concentrations is a result of the methylation/demethylation processes in the sediments, and that the abiotic processes have a negligible contribution to those processes. According to the statistical analysis of the results (partial least squares analysis) a significant statistical correlation was established between methylmercury and the SRB counts.

Hominin lower second premolar morphology: evolutionary inferences through geometric morphometric analysis.

Mandibular premolars are increasingly used in taxon-specific diagnostic analyses of hominins. Among the principal difficulties in these evaluations is the absence of discrete, discernible, and comparable anatomical structures for rigorous quantitative assessment. Previous research has addressed either internal crown surface features (such as cusps and fossae) or the morphology of the crown outline. In the present paper, we integrate both types of information in the examination of morphological variation of lower P4s (n = 96) among various fossil hominin species with an emphasis on genus Homo. We use a set of 34 2D landmarks combining coordinate data from four classical dental landmarks on the occlusal surface and 30 sliding semilandmarks of the crown outline. Our results indicate that external shape variation is closely related to the configuration of the occlusal morphological features and influenced by dental size. The external and internal shapes of P4 are polymorphic but still useful in depicting a primitive-derived gradient. The primitive pattern seems to have been an asymmetrical contour with a mesially displaced metaconid, development of a bulging talonid, and a broad occlusal polygon. The trend toward dental reduction during the Pleistocene produced different morphological variants with a reduced occlusal polygon and decreased lingual occlusal surface in later Homo species. Homo heidelbergensis/neanderthalensis have fixed plesiomorphic traits in high percentages, whereas in modern humans a symmetrical outline with a centered metaconid and talonid reduction evolved.

[Diagnostic value of gated-SPECT for each coronary artery in patients clinically diagnosed of coronary heart disease]. / Valor diagnóstico del gated-SPECT para cada arteria coronaria en pacientes con el diagnóstico clínico de cardiopatía isquémica.

UNLABELLED: This study aimed to evaluate the diagnostic value of gated-SPECT for each coronary artery in patients with clinical diagnosis or suspicion of coronary heart disease. PATIENTS AND METHODS: The study population is made up of 43 patients (64 9 years, 88% male gender) with prior clinical diagnosis or suspicion of coronary heart disease who had undergone gated-SPECT (99mTc-tetrofosmin) and cardiac catheterization. Scintigraphic study after exercise treadmill test and rest study were performed on the same day. RESULTS: Gated-SPECT showed perfusion defects in 86% of patients, the mean number of territories with perfusion defects being 1.58 +/- 0.79. A total of 39 (91%) of the 43 patients had significant coronary heart disease. Single, two- and three-vessel disease was demonstrated in 12 (28%), 15 (35%) and 12 (28%) patients, respectively. Sensitivity and specificity were 81% and 91%, respectively, for left anterior descending artery, 88% and 65% for right coronary artery, and 55% and 81% for circumflex one. CONCLUSIONS: Myocardial scintigraphy with gated-SPECT offers high sensitivity and specificity for the diagnosis of left anterior descending artery disease. However, sensitivity for circumflex artery and specificity for right coronary artery were low in our series.

[Clinical predictors of the presence of perfusion defects in more than than one territory in myocardial scintigraphy with GATED-SPECT]. / Predictores clínicos de la existencia de defectos de perfusión de más de un territorio en la gammagrafía de perfusión miocárdica con GATED-SPECT.

BACKGROUND AND OBJECTIVE: Extension of perfusion defects is associated with outcome in patients undergoing myocardial scintigraphy. The study aimed to identify the clinical characteristics that can predict the existence of perfusion defects in more than one territory in patients referred for myocardial scintigraphy with GATED-SPECT. PATIENTS AND METHODS: A total of 193 patients undergoing myocardial scintigraphy with GATED-SPECT (99mTc-tetrofosmine) were studied. Clinical variables and scintigraphy results were studied to determine what clinical variables are associated with perfusion defects in more than one territory. RESULTS: The number of territories with perfusion defects per patient was 1.1 0.8 and 29% had perfusion defects in > 1 territory. Patients with greater probability of having perfusion defects in > 1 territory were those with previous myocardial infarction (44% vs 21%, p = 0.030) and males (33% vs 10%, p = 0.006). In addition, patients with > 2 coronary risk factors had a statistical tendency to have defects in > 1 territory (47% vs 20%, p = 0.057). Only 15% of the patients with one of these three characteristics had perfusion defects in > 1 territory in comparison with 45% and 83% in those with 2 or 3 factors, respectively. CONCLUSION: Considering 3 simple clinical characteristics (male gender, previous infarction and existence of > 2 coronary risk factors), it is possible to predict which patients are more likely to show perfusion defects in > 1 territory during GATED-SPECT myocardial scintigraphy.

Predictores clínicos de la existencia de defectos de perfusión de más de un territorio en la gammagrafía de perfusión miocárdica con GATED-SPECT / Clinical predictors of the presence of perfusion defects in more than one territory in myocardial scintigraphy with gated spect

Introducción y objetivo: La extensión de los defectos de perfusión es un marcador pronóstico en los pacientes a los que se realiza gammagrafía de perfusión miocárdica. El objetivo fue determinar qué variables clínicas pueden predecir la existencia de defectos de perfusión en más de un territorio en pacientes a los que se realiza gammagrafía de perfusión miocárdica mediante GATED-SPECT. Pacientes y métodos: Se estudiaron 193 pacientes a los que se realizó estudio de perfusión miocárdica mediante GATEDSPECT con 99mTc-tetrofosmina. Se analizaron las variables clínicas y el resultado del estudio isotópico, con objeto de determinar las características asociadas a la existencia de defectos de perfusión en > 1 territorio. Resultados: El número de territorios con defectos de perfusión por paciente fue 1,1 ñ 0,8 y el 29 per cent presentaron defectos de perfusión en > 1 territorio. Los pacientes con mayor probabilidad de tener defectos de perfusión en > 1 territorio fueron aquellos con infarto de miocardio previo (44 per cent vs 21 per cent, p = 0,030) y los varones (33 per cent vs 10 per cent, p = 0,006). Además, los pacientes con > 2 factores de riesgo coronario presentaron una tendencia estadística a tener más frecuentemente defectos de perfusión en > 1 territorio (47 per cent vs 20 per cent, p = 0,057).Sólo el 15 per cent de los pacientes con una de estas tres características tuvieron defectos de perfusión en > 1 territorio, en comparación con el 45 per cent y el 83 per cent de los que presentaron dos o tres factores, respectivamente. Conclusiones: Teniendo en cuenta tres variables clínicas sencillas (sexo masculino, infarto previo y existencia de > 2 factores de riesgo), podemos conocer qué pacientes tienen mayor probabilidad de presentar defectos de perfusión en más de un territorio en el estudio mediante GATED-SPECT (AU)

Valor diagnóstico del GATED-SPECT para cada arteria coronaria en pacientes con el diagnóstico clínico de cardiopatía isquémica / Diagnostic value of gated-spect for each coronary artery in patients clinically diagnosed of coronary heart disease

El objetivo de este estudio fue evaluar el valor diagnóstico del gated-SPECT para cada una de las arterias coronarias en pacientes con diagnóstico previo o sospecha de enfermedad coronaria. Pacientes y métodos: La población de estudio esta formada por 43 pacientes (64 ñ 9 años, 88 per cent varones) con diagnóstico previo o sospecha de cardiopatía isquémica a los que se les había realizado estudio gated-SPECT y coronariografía. El radiofármaco empleado fue 99mTc-tetrofosmina, realizándose en el mismo día el estudio tras ejercicio físico en tapiz rodante y el estudio de reposo. Resultados: El estudio gated-SPECT mostró defectos de perfusión en el 86 per cent de los pacientes, siendo el número de territorios con defecto de perfusión por paciente 1,58 ñ 0,79.De los 43 pacientes, 39 (91 per cent) tenían enfermedad coronaria significativa. La enfermedad fue de 1, 2 y 3 vasos en 12 (28 per cent), 15 (35 per cent) y 12 (28 per cent) pacientes, respectivamente. La sensibilidad y especificidad fueron, respectivamente, 81 per cent y 91 per cent para la descendente anterior, 88 per cent y 65 per cent para la coronaria derecha y 55 per cent y 81 per cent para la circunfleja. Conclusiones: En pacientes con diagnóstico previo o sospecha de cardiopatía isquémica, la gammagrafía mediante gated-SPECT posee una elevada sensibilidad y especificidad en el diagnóstico de enfermedad de la arteria descendente anterior. Sin embargo, la sensibilidad para la circunfleja y la especificidad para la coronaria derecha fueron bajas en nuestra serie. (AU)

gfp-Tagged cells as a useful tool to study the survival of Escherichia coli in the presence of the river microbial community.

We have used an Escherichia coli strain DH5a containing pGreenTIR to study the survival of this bacterium in river water. As green fluorescence was maintained throughout survival both in dark and illuminated conditions, gfp-tagged E. coli cells were clearly distinguished from the microbial community of the river Butrón. gfp-tagged E. coli cells were monitored to estimate total density as well as the density of the culturable and viable (active electron transport system, CTC+) cells. Our results indicate that autochthonous bacteria and introduced E. coli are predated by flagellates. The autochthonous bacterial community behaves as predation-escaping prey, showing a tendency to cellular miniaturization and so maintaining the density of the population. In contrast, introduced E. coli behaves as predation-non-escaping prey, so E. coli was eliminated from the system. When comparing the elimination by predation of heat-treated and non-heated gfp-tagged E. coli cells we deduce that the flagellates do not discriminate between live and heat-treated cells. Finally, in the presence of the river microbial community, the E. coli cells appeared to be ingested before cellular deterioration could occur. Thus predation reduces the quantitative importance of the viable but nonculturable (VBNC) population of E. coli in the aquatic systems.

Participation of oxygen and role of exogenous and endogenous sensitizers in the photoinactivation of Escherichia coli by photosynthetically active radiation, UV-A and UV-B.

We studied the mechanisms by which photosynthetically active radiation (PAR) and ultraviolet (UV-A and UV-B) radiation damage Escherichia coli suspended in water. The roles played by oxygen and exogenous and endogenous sensitizers were analyzed by monitoring changes in the physiological state of irradiated cells. Impairment of the cellular functions was more severe in the case of UV radiations. Radiation caused cellular damage in the absence of oxygen. PAR, UV-A, and UV-B radiation induced photobiological and photodynamic reactions mediated by endogenous sensitizers, which significantly shortened the T90 (time needed to reduce a cellular parameter by 90%) based on the growth ability of the cells. In addition, when exogenous sensitizers were present, the photodynamic reactions also had a negative effect on the operation of the electron transport chains. The presence of oxygen might enhance photoinactivation, affecting both the growth ability and the electron transport chains. Endogenous sensitizers were responsible for the noxious action of oxygen. The presence of dissolved organic material played a protective role against the oxygen by absorbing the incident radiation, thereby reducing the energy that reached the endogenous sensitizers.

Serum basic fibroblast growth factor levels in exercise-induced myocardial ischemia more likely a marker of endothelial dysfunction than a marker of ischemia?

Increased levels and activity of fibroblast growth factor (FGF) have been documented in a variety of diseases, including ischemia. Both acute coronary syndromes and exercise are situations that stimulate FGF release. Since experimental studies have demonstrated that FGFs are involved in myocardial preconditioning, it has been suggested that cardiac and circulating FGFs may play a cardioprotective role in ischemic diseases. However, the profile of basic FGF (bFGF) release during transient myocardial ischemia remains uncertain. We sought to determine whether circulating bFGF might be changed in patients with demonstrated coronary artery disease and evidence of ischemia in exercise scintigraphy (Isch +; n = 21). Serum from 22 age-matched patients with no coronary artery disease and no isotopic ischemia (Isch-) were used as controls. Three blood samples were obtained to determine bFGF at different times: baseline (bFGF-A); maximal exercise (bFGF-B), and isotopic redistribution (bFGF-C). An enzyme-linked immunoassay specific for bFGF was used (limit of detection, 1.0 pg/ml). Circulating bFGF was increased at maximal exercise in both Isch + and control patients. However, serum levels of bFGF were elevated up to more than two-fold in Isch-patients compared to Isch+ patients (8.67 +/- 2.10 pg/ml in Isch+ vs 17.83 +/- 2.97 pg/ml in Isch- patients; p<0.01). According to previous data, these findings suggest that bFGF serum levels could be considered more likely a marker of endothelial dysfunction occurring in patients with coronary artery disease, rather than a marker of acute ischemia. This situation could be different in the clinical setting of chronic myocardial ischemia.