Effects of radio-frequency fields on bacterial cell membranes and nematode temperature-sensitive mutants

Membrane-related bioeffects have been reported in response to both radio-frequency (RF) and extremely low-frequency (ELF) electromagnetic fields (EMFs), particularly in neural cells. We have tested whether RF fields might cause inner membrane leakage in ML35 E. coli cells, which express β-galactosidase (lacZ) constitutively, but lack the lacY permease required for substrate entry. The activity of lacZ (indicating substrate leakage through the inner cell membrane) was increased only slightly by RF exposure (1 GHz, 0.5 W) over 45 min. Since lacZ activity showed no further increase with a longer exposure time of 90 min, this suggests that membrane permeability per se is not significantly affected by RF fields, and that slight heating (≤ 0.1°C) could account for this small difference. Temperature-sensitive (ts) mutants of the nematode, Caenorhabditis elegans, are wild-type at 15°C but develop the mutant phenotype at 25°C; an intermediate temperature of 21°C results in a reproducible mixture of both phenotypes. For two ts mutants affecting transmembrane receptors (TRA-2 and GLP-1), RF exposure for 24 h during the thermocritical phase strongly shifts the phenotype mix at 21°C towards the mutant end of the spectrum. For ts mutants affecting nuclear proteins, such phenotype shifts appear smaller (PHA-1) or non-significant (LIN-39), apparently confirming suggestions that RF power is dissipated mainly in the plasma membrane of cells. However, these phenotype shifts are no longer seen when microwave treatment is applied at 21°C in a modified exposure apparatus that minimises the temperature difference between sham and exposed conditions. Like other biological effects attributed to microwaves in the C. elegans system, phenotype shifts in ts mutants appear to be an artefact caused by very slight heating

Resonant Raman scattering by collective modes of the one-dimensional electron gas

We show that the low-energy peak in the polarized resonant Raman spectra of quantum wires, which is commonly associated with ``single particle excitations'', can be interpreted as signature of intra-band collective spin excitations. A broad maximum in the resonant depolarized spectra is predicted to exist above the frequency of the spin density excitation, due to simultaneous but independent propagation of spin- and charge-density modes.Comment: 4 pages, accepted for publication in Phys. Rev. Let

Practical recommendations for measuring rates of visual field change in glaucoma

To date, there has been a lack of evidence-based guidance on the frequency of visual field examinations required to identify clinically meaningful rates of change in glaucoma. The objective of this perspective is to provide practical recommendations for this purpose. The primary emphasis is on the period of time and number of examinations required to measure various rates of change in mean deviation (MD) with adequate statistical power. Empirical data were used to obtain variability estimates of MD while statistical modelling techniques derived the required time periods to detect change with various degrees of visual field variability. We provide the frequency of examinations per year required to detect different amounts of change in 2, 3 and 5 years. For instance, three examinations per year are required to identify an overall change in MD of 4 dB over 2 years in a patient with average visual field variability. Recommendations on other issues such as examination type, strategy and quality are also made

Far-infrared absorption in parallel quantum wires with weak tunneling

We study collective and single-particle intersubband excitations in a system of quantum wires coupled via weak tunneling. For an isolated wire with parabolic confinement, the Kohn's theorem guarantees that the absorption spectrum represents a single sharp peak centered at the frequency given by the bare confining potential. We show that the effect of weak tunneling between two parabolic quantum wires is twofold: (i) additional peaks corresponding to single-particle excitations appear in the absorption spectrum, and (ii) the main absorption peak acquires a depolarization shift. We also show that the interplay between tunneling and weak perpendicular magnetic field drastically enhances the dispersion of single-particle excitations. The latter leads to a strong damping of the intersubband plasmon for magnetic fields exceeding a critical value.Comment: 18 pages + 6 postcript figure

Enhanced suppresion of localization in a continuous Random-Dimer Model

We consider a one-dimensional continuous (Kronig-Penney) extension of the (tight-binding) Random Dimer model of Dunlap et al. [Phys. Rev. Lett. 65, 88 (1990)]. We predict that the continuous model has infinitely many resonances (zeroes of the reflection coefficient) giving rise to extended states instead of the one resonance arising in the discrete version. We present exact, transfer-matrix numerical calculations supporting, both realizationwise and on the average, the conclusion that the model has a very large number of extended states.Comment: 10 pages, 3 Figures available on request, REVTeX 3.0, MA/UC3M/1/9

Control mechanisms of primary productivity revealed by Calcareous Nannoplankton from marine isotope stages 12 to 9 at the Shackleton Site (IODP Site U1385)

Nowadays, primary productivity variations at the SW Iberian Margin (IbM) are primarily controlled by wind-driven upwelling. Thus, major changes in atmospheric circulation and wind regimes between the Marine Isotope Stages (MIS) 12 and 9 could have driven substantial changes in phytoplankton productivity which remains poorly understood. We present a high-resolution calcareous nannofossil record from the Shackleton Site Integrated Ocean Discovery Program Site U1385 that allow the assessment of primary productivity and changing surface conditions on orbital and suborbital timescales over the SW IbM. These records are directly compared and integrated with terrestrial – Mediterranean forest pollen – and marine – benthic and planktic oxygen stable isotopes (δ18O), alkenone concentration [C37], Uk´37-Sea Surface Temperature and % C37:4 – proxy records from Site U1385. Our results indicate intra-interglacial increase in primary productivity together with intensification of the Azores anticyclonic high-pressure cell beyond the summer that suggests a two-phase upwelling behavior during the full interglacial MIS 11c (420–397ka), potentially drived by atmospheric NAO-like variability. Primary productivity is largely enhanced during the inception of glacial MIS 10 and the early MIS 10 (392–356ka), linked to intensified upwelling and associated processes during a period of strengthened atmospheric circulation. In agreement with the conditions observed during Heinrich events of the last glacial cycle, primary productivity reductions during abrupt cold episodes, including the Heinrich-type (Ht) events 4 to 1 (436, 392, 384 and 339ka) and the Terminations V and IV, seems to be the result of halocline formation induced by meltwater arrival, reducing the regional upward nutrient transferenceFPU17/03349, PTDC/CTA-GEO/29897/2017, UIDB/04326/2020, UIDB/04326/2020, CEECIND/02208/2017info:eu-repo/semantics/publishedVersio

Fractal dimension analysis of grey matter in multiple sclerosis

The fractal dimension (FD) is a quantitative parameter that characterizes the morphometric variability of a complex object. Among other applications, FD has been used to identify abnormalities of the human brain in conventional magnetic resonance imaging (MRI), including white matter abnormalities in patients with Multiple Sclerosis (MS). Extensive grey matter (GM) pathology has been recently identified in MS and it appears to be a key factor in long-term disability. The aim of the present work was to assess whether FD measurement of GM in T1 MRI sequences can identify GM abnormalities in patients with MS in the early phase of the disease. A voxel-based morphometry approach optimized for MS was used to obtain the segmented brain, where we later calculated the three-dimensional FD of the GM in MS patients and healthy controls.We found that patients with MS had a significant increase in the FD of the GM compared to controls. Such differences were present even in patients with short disease durations, including patients with first attacks of MS. In addition, the FD of the GM correlated with T1 and T2 lesion load, but not with GM atrophy or disability. The FD abnormalities of the GM here detected differed from the previously published FD of the white matter in MS, suggesting that different pathological processes were taking place in each structure. These results indicate that GM morphology is abnormal in patients with MS and that this alteration appears early in the course of the disease

Effect of Finite Impurity Mass on the Anderson Orthogonality Catastrophe in One Dimension

A one-dimensional tight-binding Hamiltonian describes the evolution of a single impurity interacting locally with $N$ electrons. The impurity spectral function has a power-law singularity $A(\omega)\propto\mid\omega-\omega_0\mid^{-1+\beta}$ with the same exponent $\beta$ that characterizes the logarithmic decay of the quasiparticle weight $Z$ with the number of electrons $N$, $Z\propto N^{-\beta}$. The exponent $\beta$ is computed by (1) perturbation theory in the interaction strength and (2) numerical evaluations with exact results for small systems and variational results for larger systems. A nonanalytical behavior of $\beta$ is observed in the limit of infinite impurity mass. For large interaction strength, the exponent depends strongly on the mass of the impurity in contrast to the perturbative result.Comment: 26 pages, RevTeX, 7 figures included, to be published in Phys. Rev.

Complement proteins regulating macrophage polarisation on biomaterials

[EN] One of the events occurring when a biomaterial is implanted in an host is the protein deposition onto its surface, which might regulate cell responses. When a biomaterial displays a compromised biocompatibility, distinct complement pathways can be activated to produce a foreign body reaction. In this article, we have designed different types of biomaterial surfaces to study the inflammation process. Here, we used different concentrations of (3-glycidoxypropyl)-trimethoxysilane (GPTMS), an organically-modified alkoxysilane as a precursor for the synthesis of various types of sol-gel materials functionalizing coatings for titanium implants to regulate biological responses. Our results showed that greater GPTMS surface concentrations induced greater secretion of TNF-alpha and IL-10 on RAW 264.7 macrophages. When implanted into rabbit tibia, osseointegration decreased with higher GPTMS concentrations. Interestingly, higher deposition of complement-related proteins C-reactive protein (CRP) and ficolin-2 (FCN2), two main activators of distinct complement pathways, was observed. Taking all together, inflammatory potential increase seems to be GPTMS concentration-dependent. Our results show that a greater adsorption of complement proteins can condition macrophage polarization.This work was supported by MINECO [MAT2017-86043-R]; Universitat Jaume I [Predoc/2014/25, UJI-B2017-37]; Basque Government [IT611-13, Predoc/2016/1/0141]; University of the Basque Country [UFI11/56]; CIC bioGUNE is supported by Basque Department of Industry, Tourism and Trade (Etortek and Elkartek programs), ProteoRed-ISCIII [PRB3 IPT17/0019]; CIBERehd Network and Severo Ochoa Grant [SEV-2016-0644]. Authors would like to thank Antonio Coso and Jaime Franco (GMI-Ilerimplant) for their inestimable contribution to this study, and Raquel Oliver, Jose Ortega (UJI), René van Rheden, Vicent Cuijpers (Radboudumc) and Iraide Escobes (CIC bioGUNE) for their valuable technical assistance.Araújo-Gomes, N.; Romero-Gavilán, F.; Zhang, Y.; Martínez-Ramos, C.; Elortza, F.; Azkargorta, M.; Martín De Llano, JJ.... (2019). Complement proteins regulating macrophage polarisation on biomaterials. Colloids and Surfaces B Biointerfaces. 181:125-133. https://doi.org/10.1016/j.colsurfb.2019.05.039S12513318

The effect of strontium incorporation into sol-gel biomaterials on their protein adsorption and cell interactions

[EN] It is known strontium can both inhibit the osteoclast formation and stimulate the osteoblast maturation, so biomaterials containing this element can favour bone structure stabilisation. The addition of Sr to biomaterials could affect their interactions with proteins and cells. Here, a silica-hybrid sol-gel network doped with different amounts of SrCl2 and applied as coatings on titanium discs was examined. in vitro analysis was performed to determine the potential effect of Sr in the coatings, showing enhanced gene expression of osteogenic markers (alkaline phosphatase and transforming growth factor-beta) in MC3T3-E1 incubated with Sr-doped biomaterials. The examination of inflammatory markers (tumour necrosis factor-alpha and interleukin 10) in RAW 264.7 macrophages revealed an anti-inflammatory potential of these materials. Proteins adsorbed onto the coatings incubated with human serum (3 h at 37 degrees C) were also analysed; mass spectrometry was used to characterise the proteins adhering to materials with different Sr content. Adding Sr to the coatings increased their affinity to APOE and VTNC proteins (associated with anti-inflammatory and osteogenic functions). Moreover, the proteins involved in coagulation processes, such as prothrombin, were more abundant on the coatings containing Sr than on the base sol-gel surfaces. Correlations between gene expression and proteomic results were also examined.This work was supported by MINECO (MAT2017-86043-R); Universitat Jaume I (grant numbers Predoc/2014/25, UJI-B2017-37); Basque Government (grant numbers IT611-13, Predoc/2016/1/0141), and University of the Basque Country (UFI11/56). Authors would like to thank Antonio Coso and Jaime Franco (GMI-Ilerimplant) for their inestimable contribution to this study, and Raquel Oliver, Jose Ortega (UJI), and Iraide Escobes (CIC bioGUNE) for their valuable technical assistance.Romero-Gavilán, F.; Araújo-Gomes, N.; García-Arnáez, I.; Martínez-Ramos, C.; Elortza, F.; Azkargorta, M.; Iloro, I.... (2019). The effect of strontium incorporation into sol-gel biomaterials on their protein adsorption and cell interactions. Colloids and Surfaces B Biointerfaces. 174:9-16. https://doi.org/10.1016/j.colsurfb.2018.10.075S91617