Noninvasive quantification of axon radii using diffusion MRI

Axon caliber plays a crucial role in determining conduction velocity and, consequently, in the timing and synchronization of neural activation. Noninvasive measurement of axon radii could have significant impact on the understanding of healthy and diseased neural processes. Until now, accurate axon radius mapping has eluded in vivo neuroimaging, mainly due to a lack of sensitivity of the MRI signal to micron-sized axons. Here, we show how – when confounding factors such as extra-axonal water and axonal orientation dispersion are eliminated – heavily diffusion-weighted MRI signals become sensitive to axon radii. However, diffusion MRI is only capable of estimating a single metric, the effective radius, representing the entire axon radius distribution within a voxel that emphasizes the larger axons. Our findings, both in rodents and humans, enable noninvasive mapping of critical information on axon radii, as well as resolve the long-standing debate on whether axon radii can be quantified.

Download Full-text

Imaging Microglia and Astrocytes non-invasively using Diffusion MRI

10.1101/2020.02.07.938910 ◽

2020 ◽

Author(s):

Raquel Garcia-Hernandez ◽

Alejandro Trouve Carpena ◽

Mark Drakesmith ◽

Kristen Koller ◽

Derek K. Jones ◽

...

Keyword(s):

Clinical Research ◽

Diffusion Mri ◽

Grey Matter ◽

Diffusion Weighted Mri ◽

Healthy Humans ◽

Diffusion Weighted

AbstractWe present a strategy to image neuroinflammation in grey matter using diffusion-weighted MRI. We demonstrate that the MRI signal carries the fingerprint of microglia and astrocytes activation, and that specific signatures from each glia population can be extracted in vivo. In addition, we prove the translational value of the approach in a cohort of healthy humans. This framework will aid basic and clinical research to clarify the role of inflammation during lifespan.

Download Full-text

Diffusion MRI microstructure models with in vivo human brain Connectome data: results from a multi-group comparison

NMR in Biomedicine ◽

10.1002/nbm.3734 ◽

2017 ◽

Vol 30 (9) ◽

pp. e3734 ◽

Cited By ~ 14

Author(s):

Uran Ferizi ◽

Benoit Scherrer ◽

Torben Schneider ◽

Mohammad Alipoor ◽

Odin Eufracio ◽

...

Keyword(s):

Human Brain ◽

Diffusion Mri ◽

Group Comparison ◽

Brain Connectome

Download Full-text

EBV-LMP1 promotes radioresistance by inducing protective autophagy through BNIP3 in nasopharyngeal carcinoma

Cell Death and Disease ◽

10.1038/s41419-021-03639-2 ◽

2021 ◽

Vol 12 (4) ◽

Author(s):

San Xu ◽

Zhuan Zhou ◽

Xingzhi Peng ◽

Xuxiu Tao ◽

Peijun Zhou ◽

...

Keyword(s):

Nasopharyngeal Carcinoma ◽

Crucial Role ◽

Epstein Barr Virus ◽

Interacting Protein ◽

Multiple Tumors ◽

Barr Virus ◽

Signaling Axis ◽

Epstein Barr ◽

Adenovirus E1b

AbstractStudies have indicated that dysfunction of autophagy is involved in the initiation and progression of multiple tumors and their chemoradiotherapy. Epstein–Barr virus (EBV) is a lymphotropic human gamma herpes virus that has been implicated in the pathogenesis of nasopharyngeal carcinoma (NPC). EBV encoded latent membrane protein1 (LMP1) exhibits the properties of a classical oncoprotein. In previous studies, we experimentally demonstrated that LMP1 could increase the radioresistance of NPC. However, how LMP1 contributes to the radioresistance in NPC is still not clear. In the present study, we found that LMP1 could enhance autophagy by upregulating the expression of BCL2/adenovirus E1B 19 kDa protein-interacting protein 3 (BNIP3). Knockdown of BNIP3 could increase the apoptosis and decrease the radioresistance mediated by protective autophagy in LMP1-positive NPC cells. The data showed that increased BNIP3 expression is mediated by LMP1 through the ERK/HIF1α signaling axis, and LMP1 promotes the binding of BNIP3 to Beclin1 and competitively reduces the binding of Bcl-2 to Beclin1, thus upregulating autophagy. Furthermore, knockdown of BNIP3 can reduce the radioresistance promoted by protective autophagy in vivo. These data clearly indicated that, through BNIP3, LMP1 induced autophagy, which has a crucial role in the protection of LMP1-positive NPC cells against irradiation. It provides a new basis and potential target for elucidating LMP1-mediated radioresistance.

Download Full-text

Diffusion-weighted MRI of hepatic tumor in rats: Comparison between in vivo and postmortem imaging acquisitions

Journal of Magnetic Resonance Imaging ◽

10.1002/jmri.21675 ◽

2009 ◽

Vol 29 (3) ◽

pp. 621-628 ◽

Cited By ~ 21

Author(s):

Xihe Sun ◽

Huaijun Wang ◽

Feng Chen ◽

Frederik De Keyzer ◽

Jie Yu ◽

...

Keyword(s):

Hepatic Tumor ◽

Diffusion Weighted Mri ◽

Postmortem Imaging ◽

Diffusion Weighted

Download Full-text

In vivo lung morphometry with hyperpolarized 3 He diffusion MRI: Reproducibility and the role of diffusion-sensitizing gradient direction

Magnetic Resonance in Medicine ◽

10.1002/mrm.25241 ◽

2014 ◽

Vol 73 (3) ◽

pp. 1252-1257 ◽

Cited By ~ 17

Author(s):

James D. Quirk ◽

Yulin V. Chang ◽

Dmitriy A. Yablonskiy

Keyword(s):

Diffusion Mri ◽

Gradient Direction ◽

Lung Morphometry

Download Full-text

A Novel Noninvasive Technique for Pulse-Wave Imaging and Characterization of Clinically-Significant Vascular Mechanical Properties In Vivo

Ultrasonic Imaging ◽

10.1177/016173460702900301 ◽

2007 ◽

Vol 29 (3) ◽

pp. 137-154 ◽

Cited By ~ 73

Author(s):

Kana Fujikura ◽

Jianwen Luo ◽

Viktor Gamarnik ◽

Mathieu Pernot ◽

Royd Fukumoto ◽

...

Keyword(s):

Aortic Wall ◽

Pulse Wave ◽

Distal Region ◽

Noninvasive Technique ◽

Abdominal Aortic ◽

Wave Imaging ◽

Risk Patients ◽

Noninvasive Mapping ◽

Clinically Significant

The pulse-wave velocity (PWV) has been used as an indicator of vascular stiffness, which can be an early predictor of cardiovascular mortality. A noninvasive, easily applicable method for detecting the regional pulse wave (PW) may contribute as a future modality for risk assessment. The purpose of this study was to demonstrate the feasibility and reproducibility of PW imaging (PWI) during propagation along the abdominal aortic wall by acquiring electrocardiography-gated (ECG-gated) radiofrequency (rf) signals noninvasively. An abdominal aortic aneurysm (AAA) was induced using a CaCl2 model in order to investigate the utility of this novel method for detecting disease. The abdominal aortas of twelve normal and five CaCl2, mice were scanned at 30 MHz and electrocardiography (ECG) was acquired simultaneously. The radial wall velocities were mapped with 8000 frames/s. Propagation of the PW was demonstrated in a color-coded ciné-loop format in all cases. In the normal mice, the wave propagated in linear fashion from a proximal to a distal region. However, in CaCl2 mice, multiple waves were initiated from several regions (i.e., most likely initiated from various calcified regions within the aortic wall). The regional PWV in normal aortas was 2.70 ± 0.54 m/s ( r2 = 0.85 ± 0.06, n = 12), which was in agreement with previous reports using conventional techniques. Although there was no statistical difference in the regional PWV between the normal and CaCl2-treated aortas (2.95 ± 0.90 m/s ( r2 = 0.51 ± 0.22, n = 5)), the correlation coefficient was found to be significantly lower in the CaCl2-treated aortas ( p<0.01). This state-of-the-art technique allows noninvasive mapping of vascular disease in vivo. In future clinical applications, it may contribute to the detection of early stages of cardiovascular disease, which may decrease mortality among high-risk patients.

Download Full-text

Crucial role of lysosomal iron in the formation of dinitrosyl iron complexes in vivo

JBIC Journal of Biological Inorganic Chemistry ◽

10.1007/s00775-006-0192-8 ◽

2006 ◽

Vol 12 (3) ◽

pp. 345-352 ◽

Cited By ~ 19

Author(s):

Hanna Lewandowska ◽

Sylwia Męczyńska ◽

Barbara Sochanowicz ◽

Jarosław Sadło ◽

Marcin Kruszewski

Keyword(s):

Crucial Role ◽

Iron Complexes ◽

Dinitrosyl Iron Complexes ◽

Dinitrosyl Iron

Download Full-text

High-Sugar, but Not High-Fat, Food Activates Supraoptic Nucleus Neurons in the Male Rat

Endocrinology ◽

10.1210/en.2016-1640 ◽

2017 ◽

Vol 158 (7) ◽

pp. 2200-2211 ◽

Cited By ~ 13

Author(s):

Catherine Hume ◽

Nancy Sabatier ◽

John Menzies

Keyword(s):

Firing Rate ◽

Supraoptic Nucleus ◽

Male Rat ◽

Plasma Sodium ◽

Neural Activation ◽

High Fat ◽

Gastric Distention ◽

High Sugar ◽

Anesthetized Rats

Abstract Oxytocin is a potent anorexigen and is believed to have a role in satiety signaling. We developed rat models to study the activity of oxytocin neurons in response to voluntary consumption or oral gavage of foods using c-Fos immunohistochemistry and in vivo electrophysiology. Using c-Fos expression as an indirect marker of neural activation, we showed that the percentage of magnocellular oxytocin neurons expressing c-Fos increased with voluntary consumption of sweetened condensed milk (SCM). To model the effect of food in the stomach, we gavaged anesthetized rats with SCM. The percentage of supraoptic nucleus and paraventricular nucleus magnocellular oxytocin-immunoreactive neurons expressing c-Fos increased with SCM gavage but not with gastric distention. To further examine the activity of the supraoptic nucleus, we made in vivo electrophysiological recordings from SON neurons, where anesthetized rats were gavaged with SCM or single cream. Pharmacologically identified oxytocin neurons responded to SCM gavage with a linear, proportional, and sustained increase in firing rate, but cream gavage resulted in a transient reduction in firing rate. Blood glucose increased after SCM gavage but not cream gavage. Plasma osmolarity and plasma sodium were unchanged throughout. We show that in response to high-sugar, but not high-fat, food in the stomach, there is an increase in the activity of oxytocin neurons. This does not appear to be a consequence of stomach distention or changes in osmotic pressure. Our data suggest that the presence of specific foods with different macronutrient profiles in the stomach differentially regulates the activity of oxytocin neurons.

Download Full-text