An innovative and automated method for the at-line monitoring of secreted protein was developed by harnessing a Surface Plasmon Resonance-based biosensor to a bioreactor. The proof of concept was ...performed by following at-line the relative concentration of a secreted protein produced by transient transfection of mammalian cells in a bioreactor. Our results suggest that our approach can be readily applied to the at-line determination of both protein concentration and bioactivity. Our experimental setup and strategy can thus satisfy the needs related to the development of novel bioprocess control protocols in the context of the new process analytical technology that arises in the biopharmaceutical industry. Biotechnol. Bioeng. 2008;100: 184-188.
We used functional magnetic resonance imaging (fMRI) to precisely measure both the localization and size of the cortical projections of artificial scotomas in healthy subjects as well as the size of ...a reversible retinal scotoma in a patient with central serous chorioretinopathy (CSCR).
Using a 3T MRI scanner, anatomical and functional data were acquired on two healthy subjects and a patient with CSCR. Retinotopic maps were first reconstructed using phase mapping techniques. Next, a block paradigm consisting of a grey background alternating with a full-field, flickering checkerboard was used to stimulate the complete central (19.5 degrees) visual field. A condition with artificial peri-foveal scotomas of different sizes and eccentricities was interleaved in healthy subjects. Differential maps were computed to obtain the cortical representation (size and location) of artificial scotomas. Full-field functional data were also acquired in the CSRC patient, at the acute stage and after recovery.
Cortical projections of each scotoma were identified using differential maps and carefully characterized with quantitative analysis: the measured cortical positions of the inactivated cortical zones were compared with the known radius and eccentricity values in the scotomas in the visual field. We also compared the size of the inactivated cortical zones to the known size of scotomas. However, we found a consistent relationship between the size of the scotomas and their cortical projections, albeit with the absolute size smaller than expected from known cortical magnification factors. The cortical deactivation zone was also observed in the CRSC patient, which disappeared at recovery stage.
Cortical retinotopic mapping can be performed successfully for both artificial and retinal scotomas. This study can serve as a basis for the future investigation of cortical plasticity in the visual cortex.
INTRODUCTION. We used high-field (3T) functional magnetic resonance imaging (fMRI) to map the retinotopic organization of human cortical areas.
Retinotopic maps were reconstructed using existing ...mapping techniques. Stimuli were made of a rotating wedge stimulus, which provided angular coordinate maps, and an expanding or contracting ring, which provided eccentricity coordinate maps. Stimuli consisted of a grey background alternating with a flickering checkerboard. A Brucker 3T scanner equipped with a head coil and a custom optical system was used to acquire sets of echoplanar images of 20 occipital coronal slices within a RT of 2.111 ms and an 8 mm3 voxel resolution. Surface models of each subject's occipital lobes were constructed using the Brainvisa software from a sagittal T1-weighted image with a 1 mm3 voxel resolution. The cortical models were then inflated to obtain unfolded surfaces. Statistical analyses of the functional data were made under SPM99, and the response amplitudes were finally assigned to the cortical reconstructed surfaces.
We identified boundaries between different early visual areas (V1, V2, V3) using eccentricity and polar angle retinotopic maps and detection of reversals in the representation of the polar angle. Both complete maps and reversals corresponding to the V1/V2 borders were clearly visible with a single recording session. Also, we were able to compare data from subjects across various fMRI acquisitions and found that there was a strong correlation between maps acquired at different sessions for the same subject.
We developed a quick (<40 min) retinotopic cortical area mapping method at 3T, which makes it possible to study the cortical remapping in patients with retinal scotomas.
L’origine temporelle et spatiale détermine de façon critique la diversité des neurones corticaux. Nous nous sommes intéressés au gyrus denté (GD) qui est la principale porte d’entrée des afférences ...du cortex entorhinal sur l’hippocampe. Il a été rapporté que le GD (hors hile) comprenait deux sous-catégories morpho-physiologiques de cellules glutamatergiques, les cellules granulaires (CG) et les cellules granulaires semilunaires (CGS). Bien qu'elles ne représentent qu’une faible proportion des neurones glutamatergiques du GD, avec une morphologie dendritique et une localisation de leur soma particulière, elles ont été dernièrement identifiées comme étant un composant majeur du traitement de l’information à travers le circuit du GD. Étant donné que les neurones GABAergiques et glutamatergiques pionniers de CA3 ont été montrés comme se développant en neurones supportant les fonctions majeures de réseau, nous nous sommes demandé si une origine temporelle précoce pourrait également spécifier le devenir des CGS. Nous avons alors montré que les CGS sont générées bien avant la population générale des CG et qu'elles présentent des caractéristiques électrophysiologiques particulières contribuant à une excitabilité moindre, qu’elles partagent avec les CG pionnières. De plus, nous avons mis en évidence que les cellules moussues (CM) du hile du GD, faisaient également partie d’une population de neurones générés tôt. Nous avons montré l’existence de contacts entre les axones des CG et CGS et les dendrites des CM générées tôt du hile. Cela mettrait donc en exergue un réseau pionnier au sein du GD entre des populations de neurones générés tôt de différentes sous-structures.
Spatial and temporal origin critically determines the cortical neurons diversity. We were interested in the dentate gyrus (DG), which is the main entry point for afference of the entorhinal cortex on the hippocampus.It has been reported that the DG comprise two morpho-physiological subcategories of glutamatergic cells, granule cell (GC) and semilunar granule cell (SGC). The latter represent only a very small minority of GD glutamatergic neurons, characterized by a particular dendritic morphology and localization of their soma, they have recently been identified as a major component of information processing across DG circuit. Since both early born GABAergic and glutamatergic neurons in CA3 were shown to develop into neurons supporting major network functions, we wondered whether an early temporal origin could similarly specify the semilunar cell fate. We then showed that SGC, are generated earlier than the general population of GCs. Besides morphology, adult SGC display characteristic electrophysiological features contributing to a lower excitability shared with pioneer GC. In addition, our observations to fate map GC and SGC showed that mossy cells (MC), the main glutamatergic neurons of the DG hilus, were also part of an early born neuronal population. Taking into account this observation, we have shown the existence of contacts between the mossy fibers (GC and SGC axons) and the dendrites of the early born MC of the hilus. This would highlight a pioneer network within the GD between early born neuron populations of different substructures.
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