Src mediates TGF-ß-induced intraocular pressure elevation in glaucoma.

Glaucoma, a progressive and irreversible optic neuropathy, is one of the leading causes of vision impairment worldwide. Elevation of intraocular pressure (IOP) due to transforming growth factor-ß (TGF-ß)-induced dysfunction of the trabecular meshwork is a risk factor for glaucoma, but the underlying molecular mechanisms remain elusive. Here, we show that Src kinase is involved in TGF-ß-induced IOP elevation. We observed that dasatinib, a potent Src inhibitor, suppressed TGF-ß2-induced IOP in rat eyes. Mechanistic analyses in human trabecular meshwork cells showed that TGF-ß2 activated Src signaling and concomitantly increased cytoskeletal remodeling, cell adhesion, and extracellular matrix (ECM) accumulation. Src was activated via TGF-ß2-induced upregulation of the Src scaffolding protein CasL, which mediates the assembly of focal adhesions, cytoskeletal remodeling, and ECM deposition. Activation of Src suppressed the expression of tissue plasminogen activator, thereby attenuating ECM degradation. Furthermore, the Src inhibitor ameliorated TGF-ß2-induced changes in the contractile and adhesive characteristics of trabecular meshwork cells, and ECM deposition. These findings underscore the crucial role of Src activity in TGF-ß-induced IOP elevation and identify Src signaling as a potential therapeutic target in glaucoma.

Clinical utility of arterial spin labeling imaging in disorders of the nervous system.

Neuroimaging is an indispensable tool in the workup and management of patients with neurological disorders. Arterial spin labeling (ASL) is an imaging modality that permits the examination of blood flow and perfusion without the need for contrast injection. Noninvasive in nature, ASL provides a feasible alternative to existing vascular imaging techniques, including angiography and perfusion imaging. While promising, ASL has yet to be fully incorporated into the diagnosis and management of neurological disorders. This article presents a review of the most recent literature on ASL, with a special focus on its use in moyamoya disease, brain neoplasms, seizures, and migraines and a commentary on recent advances in ASL that make the imaging technique more attractive as a clinically useful tool.

Neural correlates of experimentally induced flow experiences.

Flow refers to a positive, activity-associated, subjective experience under conditions of a perceived fit between skills and task demands. Using functional magnetic resonance perfusion imaging, we investigated the neural correlates of flow in a sample of 27 human subjects. Experimentally, in the flow condition participants worked on mental arithmetic tasks at challenging task difficulty which was automatically and continuously adjusted to individuals' skill level. Experimental settings of "boredom" and "overload" served as comparison conditions. The experience of flow was associated with relative increases in neural activity in the left anterior inferior frontal gyrus (IFG) and the left putamen. Relative decreases in neural activity were observed in the medial prefrontal cortex (MPFC) and the amygdala (AMY). Subjective ratings of the flow experience were significantly associated with changes in neural activity in the IFG, AMY, and, with trend towards significance, in the MPFC. We conclude that neural activity changes in these brain regions reflect psychological processes that map on the characteristic features of flow: coding of increased outcome probability (putamen), deeper sense of cognitive control (IFG), decreased self-referential processing (MPFC), and decreased negative arousal (AMY).

Mapping of arterial transit time by intravascular signal selection.

The arterial transit time (δa ) is a potentially important physiological parameter which may provide valuable information for the characterization of cerebrovascular diseases. The present study shows that δa can be measured by arterial spin labeling (ASL) applied quasi-continuously in an amplitude-modulated fashion at the human neck. Imaging was performed using short repetition times and excitation flip angles of 90°, which resulted in the selection of an ASL signal of mostly intravascular origin. Model-independent estimates of δa were obtained directly from the temporal shift of the ASL time series. An extended two-compartment perfusion model was developed in order to simulate the basic features of the proposed method and to validate the evaluation procedure. Vascular structures found in human δa maps, such as the circle of Willis or cerebral border zones, hint at the sensitivity of the method to most sizes of arterial vessels. Group-averaged values of δa measured from the carotid bifurcation to the tissue of interest in selected regions of the human brain ranged from 925 ms in the insular cortex to 2000 ms in the thalamic region.

In vivo visualization of the PICA perfusion territory with super-selective pseudo-continuous arterial spin labeling MRI.

In this work a method is described to discern the perfusion territories in the cerebellum that are exclusively supplied by either or both vertebral arteries. In normal vascular anatomy the posterior inferior cerebellar artery (PICA) is supplied exclusively by its ipsilateral vertebral artery. The perfusion territories of the vertebral arteries were determined in 14 healthy subjects by means of a super-selective pseudo-continuous ASL sequence on a 3T MRI scanner. Data is presented to show the feasibility of determining the PICA perfusion territory. In 10 subjects it was possible to accurately determine both PICA perfusion territories. In two subjects it was possible to determine the perfusion territory of one PICA. Examples in which it was not possible to accurately determine the PICA territory are also given. Additionally, the high variability of the extent of the PICA territory is illustrated using a statistical map. The posterior surface of the cerebellum is entirely supplied by the PICA in six subjects. The most posterior part of the superior surface is supplied by the PICA in eight subjects, and the inferior half of the anterior surface in six subjects. The inferior part of the vermis is supplied by the PICA in all subjects. Two subjects were found with interhemispheric blood flow to both tonsils from one PICA without contribution from the contralateral PICA. With the method as presented, clinicians may in the future accurately classify cerebellar infarcts according to affected perfusion territories, which might be helpful in the decision whether a stenosis should be considered symptomatic.

PlexinA1-deficient mice exhibit decreased cell density and augmented oxidative stress in parvalbumin-expressing interneurons in the medial prefrontal cortex.

PlexinA1 (PlxnA1) is a transmembrane receptor for semaphorins (Semas), a large family of axonal guidance cues vital during neural development. PlxnA1 is expressed in embryonic interneurons, and PlxnA1 deletion in mice leads to less interneurons in the developing cortex. In addition, PlxnA1 has been identified as a schizophrenia susceptibility gene. In our previous study, PlxnA1 knockout (KO) mice under a BALB/cAJ genetic background exhibited significantly increased self-grooming and reduced prepulse inhibition, a reliable phenotype for investigating the neurobiology of schizophrenia. However, the mechanism underlying the abnormal behavior of PlxnA1 KO mice remains unclear. We first confirmed PlxnA1 mRNA expression in parvalbumin-expressing interneurons (PV cells) in the medial prefrontal cortex (mPFC) of adult mice. Immunohistochemical analysis (IHC) showed significantly decreased densities of both GABAergic neurons and PV cells in the mPFC of PlxnA1 KO mice compared with wild type mice (WT). PV cells were found to express molecule interacting with CasL 1 (MICAL1), an effector involved in Sema-Plxn signaling for axon guidance, suggesting MICAL1 and PlxnA1 co-expression in PV cells. Furthermore, IHC analysis of 8-oxo-dG, an oxidative stress marker, revealed significantly increased oxidative stress in PlxnA1-deficient PV cells compared with WT. Thus, increased oxidative stress and decreased PV cell density in the mPFC may determine the onset of PlxnA1 KO mice's abnormal behavior. Accordingly, deficient PlxnA1-mediated signaling may increase oxidative stress in PV cells, thereby disrupting PV-cell networks in the mPFC and causing abnormal behavior related to neuropsychiatric diseases.

An update from the Canadian Association for the Study of the Liver on the management of liver disease during the COVID-19 pandemic.

Coronavirus disease 2019 (COVID-19) has challenged how care is delivered to patients with chronic liver disease (CLD). In an attempt to update Canadian health care practitioners taking care of individuals with CLD, the Canadian Association for the Study of the Liver (CASL) hosted a webinar on May 7, 2020, with more than 120 participants. The resultant article is a partnership between members of CASL's executive and education committees to provide best practice management principles on liver disease during COVID-19 to the broader hepatology community.

Characterization of paralogous uncx transcription factor encoding genes in zebrafish.

The paired-type homeodomain transcription factor Uncx is involved in multiple processes of embryogenesis in vertebrates. Reasoning that zebrafish genes uncx4.1 and uncx are orthologs of mouse Uncx, we studied their genomic environment and developmental expression. Evolutionary analyses indicate the zebrafish uncx genes as being paralogs deriving from teleost-specific whole-genome duplication. Whole-mount in situ mRNA hybridization of uncx transcripts in zebrafish embryos reveals novel expression domains, confirms those previously known, and suggests sub-functionalization of paralogs. Using genetic mutants and pharmacological inhibitors, we investigate the role of signaling pathways on the expression of zebrafish uncx genes in developing somites. In identifying putative functional role(s) of zebrafish uncx genes, we hypothesized that they encode transcription factors that coordinate growth and innervation of somitic muscles.

Management of Hepatitis B Virus Infection: 2018 Guidelines from the Canadian Association for the Study of Liver Disease and Association of Medical Microbiology and Infectious Disease Canada.

Hepatitis B virus (HBV) infection is an important public health problem in Canada. In keeping with evolving evidence and understanding of HBV pathogenesis, the Canadian Association for the Study of Liver Disease periodically publishes HBV management guidelines. The goals of the 2018 guidelines are to (1) highlight the public health impact of HBV infection in Canada and the need to improve diagnosis and linkage to care, (2) recommend current best-practice guidelines for treatment of HBV, (3) summarize the key HBV laboratory diagnostic tests, and (4) review evidence on HBV management in special patient populations and include more detail on management of HBV in pediatric populations. An overview of novel HBV tests and therapies for HBV in development is provided to highlight the recent advances in HBV clinical research. The aim and scope of these guidelines are to serve as an up-to-date, comprehensive resource for Canadian health care providers in the management of HBV infection.

A comparison study between the saturation-recovery-T1 and CASL MRI methods for quantitative CBF imaging.

The saturation-recovery (SR)-T1 MRI method for quantitatively imaging cerebral blood flow (CBF) change (ΔCBF) concurrently with the blood oxygenation level dependence (BOLD) alteration has been recently developed and validated by simultaneous measurement of relative CBF change using laser Doppler flowmetry (LDF) in rats at 9.4T. In this study, ΔCBF induced by mildly transient hypercapnia and measured by the SR-T1 MRI method was rigorously compared with an established perfusion MRI method-continuous arterial spin labeling (CASL) approach in normal and preclinical middle cerebral artery occlusion (MCAo) rat models. The results show an excellent agreement between ΔCBF values measured with these two imaging methods. Moreover, the intrinsic longitudinal relaxation rate (R1int) was experimentally determined in vivo in normal rat brains at 9.4T by comparing two independent measures of the apparent longitudinal relaxation rate (R1app) and CBF measured by the CSAL approach across a wide range of perfusion. In turn, the R1int constant can be employed to calculate the CBF value based on the R1app measurement in healthy brain. This comparison study validates the fundamental relationship for linking brain tissue water R1app and cerebral perfusion, demonstrates the feasibility of imaging and quantifying both CBF and its change using the SR-T1 MRI method in vivo.

Effect of intranasally administered insulin on cerebral blood flow and perfusion; a randomized experiment in young and older adults.

Insulin, a vasoactive modulator regulating peripheral and cerebral blood flow, has been consistently linked to aging and longevity. In this proof of principle study, using a randomized, double-blinded, placebo-controlled crossover design, we explored the effects of intranasally administered insulin (40IU) on cerebral blood flow (CBF) and perfusion in older (60-69 years, n=11) and younger (20-26 years, n=8) adults. Changes in CBF through the major cerebropetal arteries were assessed via phase contrast MR-angiography, and regional cortical tissue perfusion via pseudo-continuous arterial spin labelling. Total flow through the major cerebropetal arteries was unchanged in both young and old. In the older participants, intranasal insulin compared to placebo increased perfusion through the occipital gray matter (65.2±11.0 mL/100g/min vs 61.2±10.1 mL/100g/min, P=0.001), and in the thalamus (68.28±6.75 mL/100g/min versus 63.31±6.84 mL/100g/min, P=0.003). Thus, intranasal insulin improved tissue perfusion of the occipital cortical brain region and the thalamus in older adults.

Arterial spin labeling perfusion magnetic resonance imaging of non-human primates.

Non-human primates (NHPs) resemble most aspects of humans in brain physiology and anatomy and are excellent animal models for translational research in neuroscience, biomedical research and pharmaceutical development. Cerebral blood flow (CBF) offers essential physiological information of the brain to examine the abnormal functionality in NHP models with cerebral vascular diseases and neurological disorders or dementia. Arterial spin labeling (ASL) perfusion MRI techniques allow for high temporal and spatial CBF measurement and are intensively used in studies of animals and humans. In this article, current high-resolution ASL perfusion MRI techniques for quantitative evaluation of brain physiology and function in NHPs are described and their applications and limitation are discussed as well.

Preclinical and clinical studies of the NEDD9 scaffold protein in cancer and other diseases.

Cancer progression requires a significant reprogramming of cellular signaling to support the essential tumor-specific processes that include hyperproliferation, invasion (for solid tumors) and survival of metastatic colonies. NEDD9 (also known as CasL and HEF1) encodes a multi-domain scaffolding protein that assembles signaling complexes regulating multiple cellular processes relevant to cancer. These include responsiveness to signals emanating from the T and B cell receptors, integrins, chemokine receptors, and receptor tyrosine kinases, as well as cytoplasmic oncogenes such as BCR-ABL and FAK- and SRC-family kinases. Downstream, NEDD9 regulation of partners including CRKL, WAVE, PI3K/AKT, ERK, E-cadherin, Aurora-A (AURKA), HDAC6, and others allow NEDD9 to influence functions as pleiotropic as migration, invasion, survival, ciliary resorption, and mitosis. In this review, we summarize a growing body of preclinical and clinical data that indicate that while NEDD9 is itself non-oncogenic, changes in expression of NEDD9 (most commonly elevation of expression) are common features of tumors, and directly impact tumor aggressiveness, metastasis, and response to at least some targeted agents inhibiting NEDD9-interacting proteins. These data strongly support the relevance of further development of NEDD9 as a biomarker for therapeutic resistance. Finally, we briefly discuss emerging evidence supporting involvement of NEDD9 in additional pathological conditions, including stroke and polycystic kidney disease.

Characterizing the white matter hyperintensity penumbra with cerebral blood flow measures.

OBJECTIVE: White matter hyperintensities (WMHs) are common with age, grow over time, and are associated with cognitive and motor impairments. Mechanisms underlying WMH growth are unclear. We aimed to determine the presence and extent of decreased normal appearing white matter (NAWM) cerebral blood flow (CBF) surrounding WMHs to identify 'WM at risk', or the WMH CBF penumbra. We aimed to further validate cross-sectional finding by determining whether the baseline WMH penumbra CBF predicts the development of new WMHs at follow-up. METHODS: Sixty-one cognitively intact elderly subjects received 3 T MPRAGE, FLAIR, and pulsed arterial spin labeling (PASL). Twenty-four subjects returned for follow-up MRI. The inter-scan interval was 18 months. A NAWM layer mask, comprised of fifteen layers, 1 mm thick each surrounding WMHs, was generated for periventricular (PVWMH) and deep (DWMH) WMHs. Mean CBF for each layer was computed. New WMH and persistent NAWM voxels for each penumbra layer were defined from follow-up MRI. RESULTS: CBF in the area surrounding WMHs was significantly lower than the total brain NAWM, extending approximately 12 mm from both the established PVWMH and DWMH. Voxels with new WMH at follow-up had significantly lower baseline CBF than voxels that maintained NAWM, suggesting that baseline CBF can predict the development of new WMHs over time. CONCLUSIONS: A CBF penumbra exists surrounding WMHs, which is associated with future WMH expansion. ASL MRI can be used to monitor interventions to increase white matter blood flow for the prevention of further WM damage and its cognitive and motor consequences.

A fast multiparameter MRI approach for acute stroke assessment on a 3T clinical scanner: preliminary results in a non-human primate model with transient ischemic occlusion.

Many MRI parameters have been explored and demonstrated the capability or potential to evaluate acute stroke injury, providing anatomical, microstructural, functional, or neurochemical information for diagnostic purposes and therapeutic development. However, the application of multiparameter MRI approach is hindered in clinic due to the very limited time window after stroke insult. Parallel imaging technique can accelerate MRI data acquisition dramatically and has been incorporated in modern clinical scanners and increasingly applied for various diagnostic purposes. In the present study, a fast multiparameter MRI approach including structural T1-weighted imaging (T1W), T2-weighted imaging (T2W), diffusion tensor imaging (DTI), T2-mapping, proton magnetic resonance spectroscopy, cerebral blood flow (CBF), and magnetization transfer (MT) imaging, was implemented and optimized for assessing acute stroke injury on a 3T clinical scanner. A macaque model of transient ischemic stroke induced by a minimal interventional approach was utilized for evaluating the multiparameter MRI approach. The preliminary results indicate the surgical procedure successfully induced ischemic occlusion in the cortex and/or subcortex in adult macaque monkeys (n=4). Application of parallel imaging technique substantially reduced the scanning duration of most MRI data acquisitions, allowing for fast and repeated evaluation of acute stroke injury. Hence, the use of the multiparameter MRI approach with up to five quantitative measures can provide significant advantages in preclinical or clinical studies of stroke disease.