21 research outputs found
Diffusion MRI and Q-Space Diffusion MRI: From Cerebral Ischemia to Multiple Sclerosis and Beyond
No full textStructural changes in glutamate cell swelling followed by multiparametric q-space diffusion MR of excised rat spinal cord
No full textDiffusion in the extracellular and intracellular spaces (ECS and ICS, respectively) was evaluated in excised spinal cords, before and after cell swelling induced by glutamate, by high b-value q-space diffusion MR of specific markers and water. The signal decays of deuterated tetramethylammonium (TMA-d12) chloride, an exogenous marker of the ECS, and N-acetyl aspartate (NAA), an endogenous marker of the ICS, were found to be non-mono-exponential at all diffusion times. The signal decays of these markers were found to depend on the diffusion time and the cell swelling induced by the glutamate. It was found, for example, that the mean displacements of the apparent fast and slow diffusion components of TMA-d12 are 7.21 ± 0.11 and 1.16 ± 0.05 μm, respectively at a diffusion time of 496 ms. After exposure of the spinal cords to 10 mM of glutamate, these values decreased to 6.62 ± 0.13 and 1.01 ± 0.05 μm, respectively. The mean displacement of NAA, however, showed a less pronounced opposite trend and increased after cell swelling induced by exposure to glutamate. q-Space diffusion MR of water was found to be sensitive to exposure to glutamate, and q-space diffusion MRI showed that a more pronounced decrease in the apparent diffusion coefficient and the mean displacement of water is observed in the gray matter (GM) of the spinal cord. All these changes demonstrate that diffusion MR is indeed sensitive to structural changes caused by cell swelling induced by glutamate. Multiparametric high b-value q-space diffusion MR is useful for obtaining microstructural information in neuronal tissues
Cerebellar learning properties are modulated by the CRF receptor in granular cells
No full textCorticotropin-releasing factor (CRF) and its type 1 receptor (CRFR1) play an important role in the responses to stressful challenges. Despite the well-established expression of CRFR1 in granular cells (GrCs), its role in procedural motor performance and memory formation remains elusive. To investigate the role of CRFR1 expression in cerebellar GrCs, we used a mouse model depleted of CRFR1 in these cells. We detected changes in the cellular learning mechanisms in GrCs depleted of CRFR1 in that they showed changes in intrinsic excitability and long-term synaptic plasticity. Moreover, male mice depleted of CRFR1 specifically in GrCs showed accelerated Pavlovian associative eye-blink conditioning, but no differences in baseline motor performance, locomotion or fear and anxiety-related behaviors. Last, we analyzed cerebella transcriptome of KO and control mice and detected prominent alterations in the expression of calcium signaling pathways components. Our findings shed light on the interplay between stress-related central mechanisms and cerebellar motor conditioning, highlighting the role of the CRF system in regulating particular forms of cerebellar learning.SIGNIFICANCE STATEMENTAlthough it is known that CRFR1 is highly expressed in the cerebellum, little attention has been given to its role in cerebellar functions in the behaving animal. Moreover, most of the attention was directed to the effect of CRF on Purkinje cells at the cellular level, and to this date, almost no data exist on the role of this stress-related receptor in other cerebellar structures. Here, we explored the behavioral and cellular effect of GrCs specific ablation of CRFR1 We found a profound effect on learning, both at the cellular and behavioral levels, without affecting baseline motor skills
Assessing mucosal inflammation in a DSS-induced colitis mouse model by MR colonography
No full textInflammatory bowel disease (IBD) is characterized by a chronic flaring inflammation of the gastrointestinal tract. To determine disease activity, the inflammatory state of the colon should be assessed. Endoscopy in patients with IBD aids visualization of mucosal inflammation. However, because the mucosa is fragile, there is a significant risk of perforation. In addition, the technique is based on grading of the entire colon, which is highly operator-dependent. An improved, noninvasive, objective magnetic resonance imaging (MRI) technique will effectively assess pathologies in the small intestinal mucosa, more specifically, along the colon, and the bowel wall and surrounding structures. Here, dextran sodium sulfate polymer induced acute colitis in mice that was subsequently characterized by multisection magnetic resonance colonography. This study aimed to develop a noninvasive, objective, quantitative MRI technique for detecting mucosal inflammation in a dextran sodium sulfate–induced colitis mouse model. MRI results were correlated with endoscopic and histopathological evaluations.</jats:p
Improved detectability of experimental allergic encephalomyelitis in excised swine spinal cords by high b-value q-space DWI
No full textExperimental allergic encephalomyelitis (EAE) is the primary experimental model of multiple sclerosis (MS), which involves both inflammation and demyelination and is known to be species-dependent. Spinal cord abnormalities were found in more than 80% of postmortem specimens of MS patients. In the present study, T1, T2 and high b-value q-space diffusion-weighted magnetic resonance imaging (MRI) were used, for the first time, to characterize the EAE model in excised swine spinal cords. The MR images were compared with histological staining and clinical scoring. Although all spinal cords were excised from swine with severe or very severe (clinical score between 3 to 5 on a scale of 5) motor impairments, T1- and T2-weighted MRI revealed white matter (WM) abnormalities in only five of the ten EAE diseased spinal cords studied, while high b-value q-space diffusion weighted MRI (q-space DWI) detected WM abnormalities in all diseased spinal cords studied. Interestingly, high b-value q-space DWI was able to detect abnormalities in the normal appearing white matter (NAWM) even in spinal cords where no plaques were identified by the T1- and T2-weighted MR images. Good anatomical correlation was observed between the high b-value q-space MR images and histology. The extent of DWI abnormalities paralleled the clinical scoring and correlated with histology. In addition, areas classified as NAWM by the T1- and T2-weighted MR images that showed abnormalities in the q-space DWI were also found to have abnormal histology. This improved detection level of the EAE model by high b-value q-space DWI over conventional T1-, and T2-weighted MRI is briefly discussed
Neurodegeneration in thiamine deficient rats? A longitudinal MRI study
No full textSelective neurodegeneration accompanied by mitochondrial dysfunction characterizes neurodegenerative disorders such as Alzheimer's and Parkinson's diseases. Thiamine deficiency (TD) in rats is a model for the study of cellular and molecular mechanisms that lead to selective neuronal loss caused by chronic oxidative deficits. Neurodegeneration in TD-rats develops over a period of 12 to 14 days and can be partially reversed by thiamine administration. The aim of this study was to characterize the in-vivo progression of neurodegeneration and the neuronal rescue processes in TD using T2 magnetic resonance mapping and diffusion tensor imaging (DTI). Each rat was scanned prior to TD induction (day 0), before the appearance of neurological symptoms (day 10), during the symptomatic stage (days 12 and 14) and during the recuperation period (days 31 and 87). Time-dependent lesions were revealed mainly in the thalamus and the inferior colliculi. Early decrease in the fractional anisotropy (FA) was found on day 10 in the inferior colliculi and to a lesser degree in the thalamus, while the earliest detectable changes in the T2 parameter occurred only on day 12. FA values in the thalamus remained significantly low after thiamine restoration, suggesting irreversible disarrangement and replacement of neuronal structures. While T2 values in the frontal cortex demonstrated no lesions, FA values significantly increased on days 14 and 31. An enlargement of the lateral ventricles was observed and persevered during the recovery period. This longitudinal MRI study demonstrated that in TD MRI can detect neurodegeneration and neuronal recovery. DTI is more sensitive than T2 mapping in the early detection of TD lesions
Unique in utero identification of fetuses in multifetal mouse pregnancies by placental bidirectional arterial spin labeling MRI
No full textCooperative Doping in Ultrasmall BaF<sub>2</sub> Nanocrystals for Multimodal <sup>19</sup>F‑MRI and CT Applications
No full textNanostructured metal fluorides (nanofluorides) are an
emerging
type of inorganic nanocrystals (NCs) with unique physiochemical properties
for advanced applications. One recent demonstration used water-dispersed
ultrasmall CaF2 nanofluorides as imaging agents that combined
the advantages of inorganic NCs with the benefit of background-free 19F-magnetic resonance imaging (19F-MRI). Nevertheless,
obtaining small nanofluorides with a face-centered cubic crystal structure,
where all fluorides are magnetically equivalent to result in a single 19F NMR signal, is challenging for other types of nanofluorides,
preventing their use in 19F-MRI. Here, we show the development
of ultrasmall, water-dispersed, barium fluoride (BaF2)
NCs for bioimaging applications. By doping BaF2 with two
types of lanthanides, diamagnetic-La3+ and paramagnetic-Sm3+, we were able to control the morphology and 19F-MR properties of the final La,Sm:BaF2 (termed LaSamBa) formulation. The fine-tuning of the La3+ content enabled us to obtain monodispersed 4.5 nm NCs, and control
over the Sm3+ content provided LaSamBa with very short T1 relaxation properties (ca. 100 ms) needed for enhanced 19F-MRI sensitivity. This
type of nanofluorides was examined in two different imaging modalities
(i.e., 19F-MRI and CT), benefiting from
their single 19F-NMR signal and the high atomic number
of barium atoms, respectively. As their 19F chemical shift
significantly differs from that of other nanofluorides (e.g., CaF2 and SrF2), LaSamBa expanded the nanofluoride
library for future multitarget 19F-MRI studies
