La Deriva Natural (en l'obra) de Natalie Jeremijenko

Punta de llança de l'art digital i electrònic, el Bioart o A-Life Art, Natalie Jeremijenko juga amb la intel.ligència artificial i la biotecnologia i duu al terreny del hightech unes pràctiques socials d'art activista que tenen les seves arrels en els moviments socials lligats als nous mitjans (nous media). Els seus exponents conjuguen el coneixement científic amb la teoria crítica i la reflexió interdisciplinària al voltant de la relació entre tecnologia, natura i cultura

La Deriva Natural (en la obra) de Natalie Jeremijenko

Punta de lanza del arte digital y electrónico, el Bioart o A-Life Art, Natalie Jeremijenko juega con la inteligencia artificial y la biotecnología llevando al terreno del hightech unas prácticas sociales de arte activista que tienen sus raíces en los movimientos sociales ligados a los nuevos media. Sus exponentes conjugan el conocimiento científico con la teoría crítica y la reflexión interdisciplinaria alrededor de la relación entre tecnología, naturaleza y cultura

A novel mechanism of contrast in MRI: pseudo super-diffusion of water molecules unveils microstructural details in biological tissues

The goal of this work is to investigate the properties of the contrast provided by Anomalous Diffusion (AD) γ-imaging technique and to test its potential in detecting tissue microstructure. The collateral purpose is to implement this technique by optimizing data acquisition and data processing, with the long term perspective of adoption in massive in vitro, in vivo and clinical studies. The AD γ-imaging technique is a particular kind of Diffusion Weighted- Magnetic Resonance Imaging (DW-MRI). It represents a refinement of conventionally used DW-MRI methods, sharing with them the advantage of being non invasive, since it uses water as an endogenous contrast agent. Besides, it is more suitable to the study of complex tissues, because it is based on a theoretical model that overcomes the simplistic Gaussian assumption. While the Gaussian assumption predicates the linearity between the average molecular displacement of water and the diffusing time, as in case of diffusion in isotropic, homogeneous and infinite environments, a number of experiments performed in vitro and in vivo on both animals and humans showed an anomalous behavior of water molecules, with a non linear relation between the distance travelled and the elapsed time. In particular, the γ-parameter quantifies water pseudo super-diffusion, a peculiarity due to the fact that water diffusion occurs in multi-compartments and it is probed by means of MRI. In fact, a restricted diffusion is rather predicted for water diffusing in biological tissues. Recently, the trick that allows to make the traditional DW-MRI acquisition sequence suitable for pseudo super-diffusion quantification has been unveiled, and in short it consists in performing DW experiments varying the diffusion gradient strengths, at a constant diffusive time. The γ-parameter is extracted by fitting DW-data to a stretched-exponential function. Finally, probing water diffusion in different directions allows to reconstruct a γ-tensor, with scalar invariants that quantify the entity of AD and its anisotropy in a given volume element. In vitro results on inert materials revealed that γ correlates with internal gradients arising from magnetic susceptibility differences (Δ) between neighboring compartments, and that it reflects the multi-compartmentalization of the space explored by diffusing molecules. Furthermore, values of γ compatible with a description of super-diffusive motion were found. This anomaly can be explained considering that the presence of Δ induce an additional attenuation to the signal, simulating a pseudo super-diffusion. Finally, In vivo results on human brain showed that γ is more effective in discriminating among different brain regions compared to conventional DWMRI parameters. These studies suggest that the contrast provided by AD γ-imaging is influenced by an interplay of two factors, Δ -effects on one hand, multicompartmentalization on the other hand, through which γ could reflect tissue microstructure. With the aim to shed some light on this issue I performed AD γ-imaging in excised mouse spinal cord (MSC) at 9.4 T and healthy human brain at 3.0 T. The adoption of MSC was motivated by its current use in studies of demyelination due to an induced pathology that mimics Multiple Sclerosis alterations, and by its simplified geometry. I acquired DW-data with parameters optimized for the particular system chosen: the MSC was scanned along 3 orthogonal directions, thus an apparent γ was derived; for the in vivo studies I used more directions and I extracted a γ-tensor. I found that γ and its anisotropy reflected the microstructure of spinal cord tracts (such as the axon diameters and the axonal density). I investigated both in MSC and human brain the relation between γ and the rate of relaxation (R2*), a parameter well-known to reflect Δ, and found significant linear correlations. Because of this γ was able to differentiate white matter regions on the basis of their spatial orientation, and gray matter regions on the basis of their intrinsic iron content in human brain imaged at 3.0 T. These results suggest that AD γ-imaging could be an alternative or complementary technique to DW-MRI in the field of neuroscience. Indeed it could be useful for the assessment of the bulk susceptibility inhomogeneity, which reflects iron deposition, the hallmark of several neurodegenerative diseases. The part of this thesis work concerning the in vivo experiment in human brain gave rise to a paper published on NeuroImage, a relevant scientific journal in the field of MRI applied to brain investigation

Acquisition Parameters Influence Diffusion Metrics Effectiveness in Probing Prostate Tumor and Age-Related Microstructure

: This study aimed to investigate the Diffusion-Tensor-Imaging (DTI) potential in the detection of microstructural changes in prostate cancer (PCa) in relation to the diffusion weight (b-value) and the associated diffusion length lD. Thirty-two patients (age range = 50-87 years) with biopsy-proven PCa underwent Diffusion-Weighted-Imaging (DWI) at 3T, using single non-zero b-value or groups of b-values up to b = 2500 s/mm2. The DTI maps (mean-diffusivity, MD; fractional-anisotropy, FA; axial and radial diffusivity, D// and D┴), visual quality, and the association between DTI-metrics and Gleason Score (GS) and DTI-metrics and age were discussed in relation to diffusion compartments probed by water molecules at different b-values. DTI-metrics differentiated benign from PCa tissue (p ≤ 0.0005), with the best discriminative power versus GS at b-values ≥ 1500 s/mm2, and for b-values range 0-2000 s/mm2, when the lD is comparable to the size of the epithelial compartment. The strongest linear correlations between MD, D//, D┴, and GS were found at b = 2000 s/mm2 and for the range 0-2000 s/mm2. A positive correlation between DTI parameters and age was found in benign tissue. In conclusion, the use of the b-value range 0-2000 s/mm2 and b-value = 2000 s/mm2 improves the contrast and discriminative power of DTI with respect to PCa. The sensitivity of DTI parameters to age-related microstructural changes is worth consideration

Changes of statistical structural fluctuations unveils an early compacted degraded stage of PNS myelin

Degradation of the myelin sheath is a common pathology underlying demyelinating neurological diseases from Multiple Sclerosis to Leukodistrophies. Although large malformations of myelin ultrastructure in the advanced stages of Wallerian degradation is known, its subtle structural variations at early stages of demyelination remains poorly characterized. This is partly due to the lack of suitable and non-invasive experimental probes possessing sufficient resolution to detect the degradation. Here we report the feasibility of the application of an innovative non-invasive local structure experimental approach for imaging the changes of statistical structural fluctuations in the first stage of myelin degeneration. Scanning micro X-ray diffraction, using advances in synchrotron x-ray beam focusing, fast data collection, paired with spatial statistical analysis, has been used to unveil temporal changes in the myelin structure of dissected nerves following extraction of the Xenopus laevis sciatic nerve. The early myelin degeneration is a specific ordered compacted phase preceding the swollen myelin phase of Wallerian degradation. Our demonstration of the feasibility of the statistical analysis of SmXRD measurements using biological tissue paves the way for further structural investigations of degradation and death of neurons and other cells and tissues in diverse pathological states where nanoscale structural changes may be uncovered.Comment: 16 pages, 6 figure

Transient Anomalous Diffusion MRI in Excised Mouse Spinal Cord: Comparison Among Different Diffusion Metrics and Validation With Histology

Neural tissue is a hierarchical multiscale system with intracellular and extracellular diffusion compartments at different length scales. The normal diffusion of bulk water in tissues is not able to detect the specific features of a complex system, providing nonlocal, diffusion measurement averaged on a 10-20 mm length scale. Being able to probe tissues with sub-micrometric diffusion length and quantify new local parameters, transient anomalous diffusion (tAD) would dramatically increase the diagnostic potential of diffusion MRI (DMRI) in detecting collective and sub-micro architectural changes of human tissues due to pathological damage. In DMRI, the use of tAD parameters quantified using specific DMRI acquisition protocols and their interpretation has often aroused skepticism. Although the derived formulas may accurately fit experimental diffusion-weighted data, the relationships between the postulated dynamical feature and the underlying geometrical structure remains elusive, or at most only suggestive. This work aimed to elucidate and validate the image contrast and information that can be obtained using the tAD model in white matter (WM) through a direct comparison between different diffusion metrics and histology. Towards this goal, we compared tAD metrics extracted from pure subdiffusion (a-imaging) and superpseudodiffusion (g-imaging) in excised mouse spinal cord WM, together with T2 and T2  relaxometry, conventional (normal diffusion-based) diffusion tensor imaging (DTI) and q-space imaging (QSI), with morphologic measures obtained by optical microscopy, to determine which structural and topological characteristics of myelinated axons influenced tAD contrast. Axon diameter (AxDiam), the standard deviation of diameters (SDax:diam), axonal density (AxDens) and effective local density (ELD) were extracted from optical images in several WM tracts. Among all the diffusion parameters obtained at 9.4 T, g-metrics confirmed a strong dependence on magnetic in-homogeneities quantified by R2  = 1/T2  and showed the strongest associations with AxDiam and ELD. On the other hand, a-metrics showed strong associations with SDax:diam and was significantly related to AxDens, suggesting its ability to quantify local heterogeneity degree in neural tissue. These results elucidate the biophysical mechanism underpinning tAD parameters and show the clinical potential of tAD-imaging, considering that both physiologic and pathologic neurodegeneration translate into alterations of WM morphometry and topology

Design, Optimization, and Structural Characterization of an Apoptosis-Inducing Factor Peptide Targeting Human Cyclophilin A to Inhibit Apoptosis Inducing Factor-Mediated Cell Death

Blocking the interaction between the apoptosis-inducing factor (AIF) and cyclophilin A (CypA) by the AIF fragment AIF(370-394) is protective against glutamate-induced neuronal cell death and brain injury in mice. Starting from AIF(370-394), we report the generation of the disulfide-bridged and shorter variant AIF(381-389) and its structural characterization by nuclear magnetic resonance (NMR) in the free and CypA-bound state. AIF(381-389) in both the free and bound states assumes a β-hairpin conformation similar to that of the fragment in the AIF protein and shows a highly reduced conformational flexibility. This peptide displays a similar in vitro affinity for CypA, an improved antiapoptotic activity in cells and an enhanced proteolytic stability compared to the parent peptide. The NMR-based 3D model of the AIF(381-389)/CypA complex provides a better understanding of the binding hot spots on both the peptide and the protein and can be exploited to design AIF/CypA inhibitors with improved pharmacokinetic and pharmacodynamics features

La praxis de la movilización: voces colectivas

Este capítulo expone las voces colectivas de divers@s activistas que formaron parte de la movilización del 15M en sus inicios. Estas voces se recogieron através de tres grupos de discusión que se realizaron en Sevilla, Madrid y Barcelona a principios del 2012. Nuestro interés inicial era analizar el proceso de construcción de la movilización con la pretensión de acercarnos al porqué se inicia el 15M y al porqué adquiere la potencialidad y fuerza que tuvo en sus primeros momentos. En otras palabras, ¿porqué ahora y porqué así? Para ello consideramos necesario atender a lo que sería la micro-política, en la que ocurre el proceso de socialización movimentista por parte de sus personas integrantes. Queríamos observar aquí la percepción subjetiva de las personas que participaron en el 15M acerca de los motivos, mecanismos y situaciones que causaron su participación y acerca de las opciones tomadas sobre los modos de participación política. La socialización de la indignación, el enfado o la decepción, sus principales reivindicaciones, sus modos de protesta, su identificación colectiva eran todos ellos elementos a tener en cuenta para este rastreo de la micro-política, del mismo modo que lo fueron las ideas fuerza de arranque de este movimiento (centradas en el modelo democrático y financiero actual) y la percepción y argumentación de las personas implicadas acerca deestas problemáticas iniciales. Con este objetivo, planteamos la realización de tres grupos, los cuales se hicieron en tres grandes ciudades del territorio del Estado español, donde la actividad de la movilización fue intensa. Concretamente, se optó por llevar acabo dos grupos (Sevilla y Barcelona) con personas que previamente al 15M no habían participado en otras movilizaciones, y otro grupo (Madrid) con personas que ya tenían una larga trayectoria previa de participación en movimientos sociales. Esta distinción, nos permitía ver de forma añadida cómo se produjo la confluencia entre estas dos corrientes y su posible peso como factor clave o no del éxito del devenir de la movilización en los primeros días. A su vez, la selección de las personas integrantes en los dos grupos de “nuevosactivistas” se guió por la paridad en términos de sexo, por la diversidad en la edad -que osciló entre los 20 y los 50 años de edad-, y por su espacio principal de participación, ya fuera temático como por barrios. En cuanto al nivel educativo, este fue alto –con estudios universitarios- tanto en Sevilla y enMadrid, mientras que en Barcelona se incluyó una mayor disparidad. En el grupo de Madrid además, primó la selección en base a la trayectoria previa y su vinculación con espacios de movilización como Jóvenes sin futuro, DRY, Izquierda anticapitalista, Traficantes de sueños y el movimiento feminista. Los grupos fueron dinamizados a partir de unos bloques temáticos generales establecidos a priori por nuestra parte, y sin apenas participación de sus moderadores para dejar fluir así los discursos y debates entre los y las participantes. Estos bloques fueron: a) el porqué de la entrada en la movilización, b) cómo se entra y despliega la participación, c) procesos de identificación con las propuestas, temas y discursos, d) el papel de las redes virtuales y físicas y e) el devenir y futuro de la movilización. En adelante, nuestra propuesta es exponer las voces colectivas que surgieron de este proceso de observación como material en bruto. Es decir que por nuestra parte, más que redactar este capítulo poniendo en primer termino la mirada analítica de quien quiere interpretar los factores clave que explican el porqué ahora y así del 15M a través de estas voces, las mostraremos de forma directa para que cada lector pueda extraer sus propias aproximaciones a dichas preguntas. Nuestra posición aquí, se limita entonces a organizar y exponer una muestra de los debates surgidos. Concretamente, hemos organizado esta muestra a partir de algunos temas generales que han aparecido de forma reiterada, los cuales se detectaron al hacer una primera lectura de las transcripciones. Creemos que a través de estos temas generales podemos ofrecer una muestra, que aunque pequeña en comparación con las más de 100 páginas transcritas de los grupos, puede ofrecer una visión rica para el lector de aquello que surgió en las conversaciones. Antes de dejar paso a estas voces2, queremos agradecer enormemente a todas y todos los que participaron en los grupos por el relato valioso que nos exponen y las posibilidades de interpretación que nos brindan

Cerebrovascular reactivity in multiple sclerosis is restored with reduced inflammation during immunomodulation

Cerebrovascular reactivity (CVR) reflects the capacity of the brain’s vasculature to increase blood flow following a vasodilatory stimulus. Reactivity is an essential property of the brain’s blood vessels that maintains nutrient supplies in the face of changing demand. In Multiple Sclerosis (MS), CVR may be diminished with brain inflammation and this may contribute to neurodegeneration. We test the hypothesis that CVR is altered with MS neuroinflammation and that it is restored when inflammation is reduced. Using a breath-hold task during functional Magnetic Resonance Imaging (MRI), we mapped grey matter and white matter CVRs (CVRGM and CVRWM, respectively) in 23 young MS patients, eligible for disease modifying therapy, before and during Interferon beta treatment. Inflammatory activity was inferred from the presence of Gadolinium enhancing lesions at MRI. Eighteen age and gender-matched healthy controls (HC) were also assessed. Enhancing lesions were observed in 12 patients at the start of the study and in 3 patients during treatment. Patients had lower pre-treatment CVRGM (p = 0.04) and CVRWM (p = 0.02) compared to HC. In patients, a lower pre-treatment CVRGM was associated with a lower GM volume (r = 0.60, p = 0.003). On-treatment, there was an increase in CVRGM (p = 0.02) and CVRWM (p = 0.03) that negatively correlated with pre-treatment CVR (GM: r = − 0.58, p = 0.005; WM: r = − 0.60, p = 0.003). CVR increased when enhancing lesions reduced in number (GM: r = − 0.48, p = 0.02, WM: r = − 0.62, p = 0.003). Resolution of inflammation may restore altered cerebrovascular function limiting neurodegeneration in MS. Imaging of cerebrovascular function may thereby inform tissue physiology and improve treatment monitoring