15,619 research outputs found
A proposal for a coordinated effort for the determination of brainwide neuroanatomical connectivity in model organisms at a mesoscopic scale
In this era of complete genomes, our knowledge of neuroanatomical circuitry
remains surprisingly sparse. Such knowledge is however critical both for basic
and clinical research into brain function. Here we advocate for a concerted
effort to fill this gap, through systematic, experimental mapping of neural
circuits at a mesoscopic scale of resolution suitable for comprehensive,
brain-wide coverage, using injections of tracers or viral vectors. We detail
the scientific and medical rationale and briefly review existing knowledge and
experimental techniques. We define a set of desiderata, including brain-wide
coverage; validated and extensible experimental techniques suitable for
standardization and automation; centralized, open access data repository;
compatibility with existing resources, and tractability with current
informatics technology. We discuss a hypothetical but tractable plan for mouse,
additional efforts for the macaque, and technique development for human. We
estimate that the mouse connectivity project could be completed within five
years with a comparatively modest budget.Comment: 41 page
Optical coherence tomography:age estimation of <i>Calliphora vicina</i> pupae <i>in vivo</i>?
Necrophagous blowfly pupae are valuable contributors to the estimation of post-mortem interval, should an accurate age estimate be obtained. At present, this is reliant on a combination of rearing and destructive methods conducted on preserved samples, including morphological observation and gene expression analyses. This study demonstrates the use of optical coherence tomography (OCT) as a tool for in vivo morphological observation and pupal age estimation. Using a Michelson OCT microscope, alive and preserved four and ten-day old Calliphora vicina pupae were scanned in different orientations. Two and three-dimensional images were created. Morphological characteristics such as the brain, mouthparts and legs were identifiable in both living and preserved samples, with distinct differences noted between the two ages. Absorption of light by the puparium results in a vertical resolution of 1-2 mm, preventing observation of deeper tissues. The use of contrast agents or a longer wavelength laser would improve the images obtainable. At present, the data suggests OCT provides a primary view of external and internal morphology, which can be used to distinguish younger and older pupae for further analysis of age and PMI estimation
Nanodiamonds-induced effects on neuronal firing of mouse hippocampal microcircuits
Fluorescent nanodiamonds (FND) are carbon-based nanomaterials that can
efficiently incorporate optically active photoluminescent centers such as the
nitrogen-vacancy complex, thus making them promising candidates as optical
biolabels and drug-delivery agents. FNDs exhibit bright fluorescence without
photobleaching combined with high uptake rate and low cytotoxicity. Focusing on
FNDs interference with neuronal function, here we examined their effect on
cultured hippocampal neurons, monitoring the whole network development as well
as the electrophysiological properties of single neurons. We observed that FNDs
drastically decreased the frequency of inhibitory (from 1.81 Hz to 0.86 Hz) and
excitatory (from 1.61 Hz to 0.68 Hz) miniature postsynaptic currents, and
consistently reduced action potential (AP) firing frequency (by 36%), as
measured by microelectrode arrays. On the contrary, bursts synchronization was
preserved, as well as the amplitude of spontaneous inhibitory and excitatory
events. Current-clamp recordings revealed that the ratio of neurons responding
with AP trains of high-frequency (fast-spiking) versus neurons responding with
trains of low-frequency (slow-spiking) was unaltered, suggesting that FNDs
exerted a comparable action on neuronal subpopulations. At the single cell
level, rapid onset of the somatic AP ("kink") was drastically reduced in
FND-treated neurons, suggesting a reduced contribution of axonal and dendritic
components while preserving neuronal excitability.Comment: 34 pages, 9 figure
Quantum diamond microscopy with sub-ms temporal resolution
Quantum diamond magnetometers using lock-in detection have successfully
detected weak bio-magnetic fields from neurons, a live mammalian muscle, and a
live mouse heart. This opens up the possibility of quantum diamond
magnetometers visualizing microscopic distributions of the bio-magnetic fields.
Here, we demonstrate a lock-in-based wide-field quantum diamond microscopy,
achieving a mean volume-normalized per pixel sensitivity of 43.9
. We obtain the sensitivity by
implementing a double resonance with hyperfine driving and magnetic field
alignment along the orientation of the diamond. Additionally, we have
demonstrated that sub-ms temporal resolution ( 0.4 ms) can be achieved at
a micrometer scale with tens of nanotesla per-pixel sensitivity using quantum
diamond microscopy. This lock-in-based diamond quantum microscopy could be a
step forward in mapping functional activity in neuronal networks in micrometer
spatial resolution
Mechanism of age-dependent susceptibility and novel treatment strategy in glutaric acidemia type I
Glutaric acidemia type I (GA-I) is an inherited disorder of lysine and tryptophan metabolism presenting with striatal lesions anatomically and symptomatically similar to Huntington disease. Affected children commonly suffer acute brain injury in the context of a catabolic state associated with nonspecific illness. The mechanisms underlying injury and age-dependent susceptibility have been unknown, and lack of a diagnostic marker heralding brain injury has impeded intervention efforts. Using a mouse model of GA-I, we show that pathologic events began in the neuronal compartment while enhanced lysine accumulation in the immature brain allowed increased glutaric acid production resulting in age-dependent injury. Glutamate and GABA depletion correlated with brain glutaric acid accumulation and could be monitored in vivo by proton nuclear magnetic resonance (1H NMR) spectroscopy as a diagnostic marker. Blocking brain lysine uptake reduced glutaric acid levels and brain injury. These findings provide what we believe are new monitoring and treatment strategies that may translate for use in human GA-I
Tumour cell labelling by magnetic nanoparticles with determination of intracellular iron content and spatial distribution of the intracellular iron
Abstract: Magnetically labelled cells are used for in vivo cell tracking by MRI, used for the clinical translation of cell-base therapies. Studies involving magnetic labelled cells may include separation of labelled cells, targeted delivery and controlled release of drugs, contrast enhanced MRI and magnetic hyperthermia for the in situ ablation of tumours. Dextran-coated super-paramagnetic iron oxide (SPIO) ferumoxides are used clinically as an MR contrast agents primarily for hepatic imaging. The material is also widely used for in vitro cell labelling, as are other SPIO-based particles. Our results on the uptake by human cancer cell lines of ferumoxides indicate that electroporation in the presence of protamine sulphate (PS) results in rapid high uptake of SPIO nanoparticles (SPIONs) by parenchymal tumour cells without significant impairment of cell viability. Quantitative determination of cellular iron uptake performed by colorimetric assay is in agreement with data from the literature. These results on intracellular iron content together with the intracellular distribution of SPIONs by magnetic force microscopy (MFM) following in vitro uptake by parenchymal tumour cells confirm the potential of this technique for clinical tumour cell detection and destruction
In Vivo Monitoring of Adult Neurogenesis in Health and Disease
Adult neurogenesis, i.e., the generation of new neurons in the adult brain, presents an enormous potential for regenerative therapies of the central nervous system. While 5-bromo-2′-deoxyuridine labeling and subsequent histology or immunohistochemistry for cell-type-specific markers is still the gold standard in studies of neurogenesis, novel techniques, and tools for in vivo imaging of neurogenesis have been recently developed and successfully applied. Here, we review the latest progress on these developments, in particular in the area of magnetic resonance imaging (MRI) and optical imaging. In vivo in situ labeling of neural progenitor cells (NPCs) with micron-sized iron oxide particles enables longitudinal visualization of endogenous progenitor cell migration by MRI. The possibility of genetic labeling for cellular MRI was demonstrated by using the iron storage protein ferritin as the MR reporter-gene. However, reliable and consistent results using ferritin imaging for monitoring endogenous progenitor cell migration have not yet been reported. In contrast, genetic labeling of NPCs with a fluorescent or bioluminescent reporter has led to the development of some powerful tools for in vivo imaging of neurogenesis. Here, two strategies, i.e., viral labeling of stem/progenitor cells and transgenic approaches, have been used. In addition, the use of specific promoters for neuronal progenitor cells such as doublecortin increases the neurogenesis-specificity of the labeling. Naturally, the ultimate challenge will be to develop neurogenesis imaging methods applicable in humans. Therefore, we certainly need to consider other modalities such as positron emission tomography and proton magnetic resonance spectroscopy (1H-MRS), which have already been implemented for both animals and humans. Further improvements of sensitivity and neurogenesis-specificity are nevertheless required for all imaging techniques currently available
Neuronal growth on high-aspect-ratio diamond nanopillar arrays for biosensing applications
Monitoring neuronal activity with simultaneously high spatial and temporal resolution in living cell cultures is crucial to advance understanding of the development and functioning of our brain, and to gain further insights in the origin of brain disorders. While it has been demonstrated that the quantum sensing capabilities of nitrogen-vacancy (NV) centers in diamond allow real time detection of action potentials from large neurons in marine invertebrates, quantum monitoring of mammalian neurons (presenting much smaller dimensions and thus producing much lower signal and requiring higher spatial resolution) has hitherto remained elusive. In this context, diamond nanostructuring can offer the opportunity to boost the diamond platform sensitivity to the required level. However, a comprehensive analysis of the impact of a nanostructured diamond surface on the neuronal viability and growth was lacking. Here, we pattern a single crystal diamond surface with large-scale nanopillar arrays and we successfully demonstrate growth of a network of living and functional primary mouse hippocampal neurons on it. Our study on geometrical parameters reveals preferential growth along the nanopillar grid axes with excellent physical contact between cell membrane and nanopillar apex. Our results suggest that neuron growth can be tailored on diamond nanopillars to realize a nanophotonic quantum sensing platform for wide-field and label-free neuronal activity recording with sub-cellular resolution
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