Search results for "HYPERPOLARIZATION"
showing 10 items of 64 documents
Presynaptic nitric oxide/cGMP facilitates glutamate release via hyperpolarization-activated cyclic nucleotide-gated channels in the hippocampus
2011
In hippocampal neurons, synaptic transmission is affected by a variety of modulators, including nitric oxide (NO), which was proposed as a retrograde messenger as long as two decades ago. NO signals via two NO-sensitive guanylyl cyclases (NO-GCs) (NO-GC1 and NO-GC2) and the subsequent increase in cGMP. Lack of long-term potentiation in mice deficient in either one of the two NO-GCs demonstrates the involvement of both NO-GCs in synaptic transmission. However, the physiological consequences of NO/cGMP and the cellular mechanisms involved are unknown. Here, we analyzed glutamatergic synaptic transmission, most likely reflecting glutamate release, in the hippocampal CA1 region of NO-GC knockou…
Singlet‐Contrast Magnetic Resonance Imaging: Unlocking Hyperpolarization with Metabolism
2020
Abstract Hyperpolarization‐enhanced magnetic resonance imaging can be used to study biomolecular processes in the body, but typically requires nuclei such as 13C, 15N, or 129Xe due to their long spin‐polarization lifetimes and the absence of a proton‐background signal from water and fat in the images. Here we present a novel type of 1H imaging, in which hyperpolarized spin order is locked in a nonmagnetic long‐lived correlated (singlet) state, and is only liberated for imaging by a specific biochemical reaction. In this work we produce hyperpolarized fumarate via chemical reaction of a precursor molecule with para‐enriched hydrogen gas, and the proton singlet order in fumarate is released a…
Towards Large-Scale Steady-State Enhanced Nuclear Magnetization with In Situ Detection
2021
Signal Amplification By Reversible Exchange (SABRE) boosts NMR signals of various nuclei enabling new applications spanning from magnetic resonance imaging to analytical chemistry and fundamental physics. SABRE is especially well positioned for continuous generation of enhanced magnetization on a large scale, however, several challenges need to be addressed for accomplishing this goal. Specifically, SABRE requires (i) a specialized catalyst capable of reversible H2 activation and (ii) physical transfer of the sample from the point of magnetization generation to the point of detection (e.g., a high-field or a benchtop NMR spectrometer). Moreover, (iii) continuous parahydrogen bubbling accele…
MRI using hyperpolarized noble gases.
1998
The aim of this study was to review the physical basis of MRI using hyperpolarized noble gases as well as the present status of preclinical and clinical applications. Non-radioactive noble gases with a nuclear spin 1/2 (He-3, Xe-129) can be hyperpolarized by optical pumping. Polarization is transferred from circularly polarized laser light to the noble-gas atoms via alkali-metal vapors (spin exchange) or metastable atoms (metastability exchange). Hyperpolarization results in a non-equilibrium polarization five orders of magnitude higher than the Boltzmann equilibrium compensating for the several 1000 times lower density of noble gases as compared with liquid state hydrogen concentrations in…
Helium-3 imaging of pulmonary ventilation.
1998
In the first studies in humans, the 3He gas was Helium is an inert, non-radioactive, noble gas. directly inhaled from the glass cell or via a mouth 3He is a rare isotope with a nuclear spin c. As it tip or plastic bag [2, 3]. The estimated inhaled is derived from tritium decay, it is quite expensive. volume in our studies was 400–500 ml. Recently, Non-polarized 3He costs 100–150 US$. Advanwe developed a computer-assisted application tages for applications in humans are: negligible system which is compatible with spontaneous solubility in water or blood, no adverse effects — breathing, assisted or mechanical ventilation. The widely used in deep-sea diving (80% He, 20% lungs can be flushed wi…
Elucidation of structure-function relationships in the lung: contributions from hyperpolarized 3 helium MRI
2002
Magnetic resonance imaging (MRI) using hyperpolarized 3helium (He) gas as the source of signal provides new physiological insights into the structure-function relationships of the lung. Traditionally, lung morphology has been visualized by chest radiography and computed tomography, whereas lung function was assessed by using nuclear medicine. As all these techniques rely on ionizing radiation, MRI has some inherent advantages. 3He MRI is based on 'optical pumping' of the 3He gas which increases the nuclear spin polarization by four to five orders of magnitude translating into a massive gain in signal. Hyperpolarized 3He gas is administered as an inhaled 'contrast agent' and allows for selec…
Spontaneous Cingulate High-Current Spikes Signal Normal and Pathological Pain States
2019
Prominent 7–12 Hz oscillations in frontal cortical networks in rats have been reported. However, the mechanism of generation and the physiological function of this brain rhythm have not yet been clarified. Multichannel extracellular field potentials of the ACC were recorded and analyzed using the current source density method in halothane-anesthetized rats. Spontaneous high-current spikes (HCSs) were localized in the deep part of layer II/III and upper part of layer V of the ACC. The frequency of HCSs in the ACC was 7–12 Hz, with an amplitude of 6.5 ± 0.76 mV/mm(2) and duration of 55.24 ± 2.43 ms. The power density significantly decreased (84.56 ± 6.93%, p < 0.05, t test) after pinching the…
Neurotransmitters involved in the fast inhibitory junction potentials in mouse distal colon
2003
We investigated, in murine colon circular muscle, the role of adenosine 5′-triphosphate (ATP) and pituitary adenylate cyclase activating peptide (PACAP) as inhibitory neurotransmitters of the fast component of nerve-evoked inhibitory junction potential (fast IJP). Fast IJP was antagonised by apamin or suramin, abolished by desensitisation with the P2Y receptor agonist, adenosine 5′-O-2-thiodiphosphate (ADPβS), unaffected by desensitisation with P2X receptor agonist, α,β-methylene ATP (α,β-meATP), and reduced by PACAP-(6-38), a PACAP receptor antagonist. ATP induced membrane hyperpolarization resistant to tetrodotoxin, Nω-nitro-L-arginine methyl ester (L-NAME) or PACAP-(6-38), but antagonise…
Altered electrical activity in colonic smooth muscle cells from dystrophic (mdx) mice
2001
Because the colon from dystrophic (mdx) mice shows an altered motor pattern, probably due to neural disorders, our aim was to examine the electrophysiological properties of muscle cells and the functionality of nitrergic transmission in circular muscle from normal and mdx colon. Normal colonic cells (resting membrane potential [RMP] about -50 mV) showed spontaneous hyperpolarizations (inhibitory junction potentials; IJPs) and cyclic slow depolarizations were sometimes recorded. Mdx colon had a depolarized RMP (about -36 mV) and spontaneous IJPs, but the cyclic activity was never observed. In the normal colon, Nomega-nitro-L-arginine methyl ester (L-NAME) induced depolarization and abolished…
Inhibitory purinergic transmission in mouse caecum: Role for P2Y1 receptors as prejunctional modulators of ATP release
2007
Using conventional microelectrode recording techniques, we investigated, in the circular muscle of the mouse caecum, the neurotransmitter(s) involved in the neurally-evoked inhibitory junction potentials (IJPs) and the existence of possible prejunctional mechanisms controlling neurotransmitter release. Electrical field stimulation with single pulses elicited IJPs, consisting only of a "fast" hyperpolarization, while using train stimuli (30-50 Hz) the initial fast hyperpolarization was followed by a slower hyperpolarization. The fast and the slow component were selectively antagonized by apamin, a blocker of calcium-activated potassium channels, and N(omega)-nitro-l-arginine methyl ester (l-…