Impacts of Microgravity Analogs to Spaceflight on Cerebral Autoregulation.

It is well known that exposure to microgravity in astronauts leads to a plethora physiological responses such as headward fluid shift, body unloading, and cardiovascular deconditioning. When astronauts return to Earth, some encounter problems related to orthostatic intolerance. An impaired cerebral autoregulation (CA), which could be compromised by the effects of microgravity, has been proposed as one of the mechanisms responsible for orthostatic intolerance. CA is a homeostatic mechanism that maintains cerebral blood flow for any variations in cerebral perfusion pressure by adapting the vascular tone and cerebral vessel diameter. The ground-based models of microgravity are useful tools for determining the gravitational impact of spaceflight on human body. The head-down tilt bed rest (HDTBR), where the subject remains in supine position at -6 degrees for periods ranging from few days to several weeks is the most commonly used ground-based model of microgravity for cardiovascular deconditioning. head-down bed rest (HDBR) is able to replicate cephalic fluid shift, immobilization, confinement, and inactivity. Dry immersion (DI) model is another approach where the subject remains immersed in thermoneutral water covered with an elastic waterproof fabric separating the subject from the water. Regarding DI, this analog imitates absence of any supporting structure for the body, centralization of body fluids, immobilization and hypokinesia observed during spaceflight. However, little is known about the impact of microgravity on CA. Here, we review the fundamental principles and the different mechanisms involved in CA. We also consider the different approaches in order to assess CA. Finally, we focus on the effects of short- and long-term spaceflight on CA and compare these findings with two specific analogs to microgravity: HDBR and DI

Increased origin activity in transformed versus normal cells: identification of novel protein players involved in DNA replication and cellular transformation

Using libraries of replication origins generated previously, we identified three clones that supported the autonomous replication of their respective plasmids in transformed, but not in normal cells. Assessment of their in vivo replication activity by in situ chromosomal DNA replication assays revealed that the chromosomal loci corresponding to these clones coincided with chromosomal replication origins in all cell lines, which were more active by 2–3-fold in the transformed by comparison to the normal cells. Evaluation of pre-replication complex (pre-RC) protein abundance at these origins in transformed and normal cells by chromatin immunoprecipitation assays, using anti-ORC2, -cdc6 and -cdt1 antibodies, showed that they were bound by these pre-RC proteins in all cell lines, but a 2–3-fold higher abundance was observed in the transformed by comparison to the normal cells. Electrophoretic mobility shift assays (EMSAs) performed on the most efficiently replicating clone, using nuclear extracts from the transformed and normal cells, revealed the presence of a DNA replication complex in transformed cells, which was barely detectable in normal cells. Subsequent supershift EMSAs suggested the presence of transformation-specific complexes. Mass spectrometric analysis of these complexes revealed potential new protein players involved in DNA replication that appear to correlate with cellular transformation

Resiniferatoxin hampers the nocifensive response of Caenorhabditis elegans to noxious heat, and pathway analysis revealed that the Wnt signaling pathway is involved

Resiniferatoxin (RTX) is a metabolite extracted from Euphorbia resinifera. RTX is a potent capsaicin analog with specific biological activities resulting from its agonist activity with the transient receptor potential channel vanilloid subfamily member 1 (TRPV1). RTX has been examined as a pain reliever, and more recently, investigated for its ability to desensitize cardiac sensory fibers expressing TRPV1 to improve chronic heart failure (CHF) outcomes using validated animal models. Caenorhabditis elegans (C. elegans) expresses orthologs of vanilloid receptors activated by capsaicin, producing antinociceptive effects. Thus, we used C. elegans to characterize the antinociceptive properties and performed proteomic profiling to uncover specific signaling networks. After exposure to RTX, wild-type (N2) and mutant C. elegans were placed on petri dishes divided into quadrants for heat stimulation. The thermal avoidance index was used to phenotype each tested C. elegans experimental group. The data revealed for the first time that RTX can hamper the nocifensive response of C. elegans to noxious heat (32 – 35 °C). The effect was reversed 6 h after RTX exposure. Additionally, we identified the RTX target, the C. elegans transient receptor potential channel OCR-3. The proteomics and pathway enrichment analysis results suggest that Wnt signaling is triggered by the agonistic effects of RTX on C. elegans vanilloid receptors

Cortical abnormalities and non-spatial learning deficits in a mouse model of CranioFrontoNasal syndrome.

Eph receptors and their ephrin ligands play critical roles in the development of the nervous system, however, less is known about their functions in the adult brain. Here, we investigated the function of ephrinB1, an ephrinB family member that is mutated in CranioFrontoNasal Syndrome. We show that ephrinB1 deficient mice (EfnB1(Y/-)) demonstrate spared spatial learning and memory but exhibit exclusive impairment in non-spatial learning and memory tasks. We established that ephrinB1 does not control learning and memory through direct modulation of synaptic plasticity in adults, since it is not expressed in the adult brain. Rather we show that the cortex of EfnB1(Y/-) mice displayed supernumerary neurons, with a particular increase in calretinin-positive interneurons. Further, the increased neuron number in EfnB1(Y/-) mutants correlated with shorter dendritic arborization and decreased spine densities of cortical pyramidal neurons. Our findings indicate that ephrinB1 plays an important role in cortical maturation and that its loss has deleterious consequences on selective cognitive functions in the adult

Proteomics reveals long-term alterations in signaling and metabolic pathways following both myocardial infarction and chemically induced denervation

Myocardial infraction (MI) is the principal risk factor for the onset of heart failure (HF). Investigations regarding the physiopathology of MI progression to HF have revealed the concerted engagement of other tissues, such as the autonomic nervous system and the medulla oblongata (MO), giving rise to systemic effects, important in the regulation of heart function. Cardiac sympathetic afferent denervation following application of resiniferatoxin (RTX) attenuates cardiac remodelling and restores cardiac function following MI. While the physiological responses are well documented in numerous species, the underlying molecular responses during the initiation and progression from MI to HF remains unclear. We obtained multi-tissue time course proteomics with a murine model of HF induced by MI in conjunction with RTX application. We isolated tissue sections from the left ventricle (LV), MO, cervical spinal cord and cervical vagal nerves at four time points over a 12-week study. Bioinformatic analyses consistently revealed a high statistical enrichment for metabolic pathways in all tissues and treatments, implicating a central role of mitochondria in the tissue-cellular response to both MI and RTX. In fact, the additional functional pathways found to be enriched in these tissues, involving the cytoskeleton, vesicles and signal transduction, could be downstream of responses initiated by mitochondria due to changes in neuronal pulse frequency after a shock such as MI or the modification of such frequency communication from the heart to the brain after RTX application. Development of future experiments, based on our proteomic results, should enable the dissection of more precise mechanisms whereby metabolic changes in neuronal and cardiac tissues can effectively ameliorate the negative physiological effects of MI via RTX application

Scalable Batch Fabrication of Ultrathin Flexible Neural Probes using Bioresorbable Silk Layer

International audienceFlexible deep brain probes have been the focus of many research works and aims at achieving better compliance with the surrounding brain tissue while maintaining minimal rejection. Strategies have been explored to find the best way to implant a flexible probe in the brain, while maintaining its flexibility once positioned in the cortex. Here, we present a novel and versatile scalable batch fabrication approach to deliver ultra-thin and flexible penetrating neural probe consisting of a silk-parylene bilayer. The biodegradable silk layer provides a temporary and programmable stiffener to ensure ease of insertion of the ultrathin parylene-based flexible devices. The innovative and yet robust batch fabrication technology allows complete design freedom of the neural probe in terms of materials, size, shape and thickness. These results provide a novel technological solution for implanting ultra-flexible and ultrathin devices, which possesses great potential for brain research

Changes in cell number in <i>EfnB1</i> mutant cortices.

<p><i>A, B.</i> Representative images of cortical sections from <i>EfnB1^Y/+</i> (WT; <i>A</i>) and <i>EfnB1^Y/−</i> (<i>B</i>) mice at P150 stained for NeuN. Shown are areas of the frontal cortex. <i>C.</i> Quantification of NeuN stained cells demonstrating an increase in NeuN-positive cells in P150 <i>EfnB1^Y/−</i> mice, P10 <i>EfnB1^Y/−</i> mice and not at P0 stages. * p<0.05. <i>D.</i> Ratio of cortical thickness in <i>EfnB1^Y</i>^{<b><i>/−</i></b>} mice as compared to controls. <i>E.</i> Quantification of NeuN positive cells in the CA3 and CA1 region of the hippocampus, and in the striatum and amygdala in P150 <i>EfnB1^Y/+</i> and <i>EfnB1^Y/−</i> mice.</p

Increased interneuron number in adult <i>EfnB1^Y/−</i> mutants.

<p><i>A–F.</i> Representative immunofluorescent images of <i>EfnB1^Y/+</i> (<i>A, C, E</i>) and <i>EfnB1^Y/−</i> (<i>B, D, F</i>) mutant somatosensory S2 cortices stained for PV (<i>A, B</i>), CR (<i>C, D</i>) and NPY (<i>E, F</i>) The percent of interneuron numbers per 100 micro(µ)m² is shown for the S2 region of <i>EfnB1^Y/+</i> versus <i>EfnB1^Y/−</i> samples. <i>G.</i> We observed an overall increase in PV+, CR+ and NPY+ neurons in <i>EfnB1^Y/−</i> mutants as compared to <i>EfnB1^Y/+</i> in all cortical regions studied. A significant increase was detected for CR+ neurons in the <i>EfnB1^Y/−</i> S2 cortical region. * p<0.05.</p

General behaviour and spatial memory are preserved in <i>EfnB1</i> mutant mice.

<p><i>A.</i> Locomotor activity and anxiety levels in <i>EfnB1</i> mutant (<i>EfnB1^Y/−</i>) mice as compared to control (WT) mice. <i>B.</i> Graph presenting swim path length as a function of individual training sessions (S1–S4). Throughout the training sessions, <i>EfnB1^Y/−</i> mice learned equally well to locate the hidden platform and exhibited decreasing swim distances over blocks of trials (F_3,45 = 12.58, <i>p</i><0.001). <i>C.</i> Number of annulus crossings during probe tests. All groups of mice showed similar preference for the target zone where the platform was located during training sessions as compared to the adjacent (Adj1 and Adj2) and opposite zones (target <i>vs</i> others, **<i>p</i><0.01; ***<i>p</i><0.001). <i>D.</i> Performances in the object location task are expressed as the group mean (± SEM) preference index. The horizontal line represents equal exploration of the two objects. <i>EfnB1^Y/−</i> and WT mice presented the same level of reaction to the object displacement (F_1,17 = 0.139, <i>p</i> = 0.714) and spent significantly more time exploring the displaced object than the non-displaced one (^###p<0.001; index <i>vs</i> chance level (50%)). NS: not significant.</p

EphrinB1 is not expressed in the adult cortex.

<p><i>A, B.</i> Representative coronal section of the brain from wild type (<i>A</i>) and <i>EfnB1</i> mutant (<i>B</i>) adult mice showing normal gross morphology of the brain. Both mutant and wild type brains have similar sizes. A slight enlargement of the ventricles was observed in some of the mutant brains (<i>B</i>, asterisks). <i>C–D’’’.</i> Immunohistochemistry for EphrinB1 at noted postnatal (P) dates in <i>EfnB1^Y/+</i> and <i>EfnB1^Y/−</i> cortices. EphrinB1 is not detected in <i>EfnB1^Y/+</i> adult cortices (<i>C</i>), rather strong, positive signals are observed at P5 (<i>C”’</i>) and decline by P15 (<i>C’</i>) in <i>EfnB1^Y/+</i> samples. <i>E</i>. Quantitative RT-PCR of P30–150 whole brain (WB) extracts and cortical extracts were analysed for <i>EfnB1</i> expression and compared to control embryonic (E) day 16.5 cortical extracts that express <i>EfnB1.</i> n = 3/age. <i>F–G’.</i> Immunohistochemistry for ephrinB1 in <i>EfnB1^Y/+</i> and <i>EfnB1^Y/−</i> hippocampi at P5 and P150. EphrinB1 is not detected in <i>EfnB1^Y/+</i> adult hippocampi (<i>F</i>), but observed in the CA1 region at P5 (F’; inlet).</p