Glymphatic fluid transport is suppressed by the aquaporin-4 inhibitor AER-271.

The glymphatic system transports cerebrospinal fluid (CSF) into the brain via arterial perivascular spaces and removes interstitial fluid from the brain along perivenous spaces and white matter tracts. This directional fluid flow supports the clearance of metabolic wastes produced by the brain. Glymphatic fluid transport is facilitated by aquaporin-4 (AQP4) water channels, which are enriched in the astrocytic vascular endfeet comprising the outer boundary of the perivascular space. Yet, prior studies of AQP4 function have relied on genetic models, or correlated altered AQP4 expression with glymphatic flow in disease states. Herein, we sought to pharmacologically manipulate AQP4 function with the inhibitor AER-271 to assess the contribution of AQP4 to glymphatic fluid transport in mouse brain. Administration of AER-271 inhibited glymphatic influx as measured by CSF tracer infused into the cisterna magna and inhibited increases in the interstitial fluid volume as measured by diffusion-weighted MRI. Furthermore, AER-271 inhibited glymphatic efflux as assessed by an in vivo clearance assay. Importantly, AER-271 did not affect AQP4 localization to the astrocytic endfeet, nor have any effect in AQP4 deficient mice. Since acute pharmacological inhibition of AQP4 directly decreased glymphatic flow in wild-type but not in AQP4 deficient mice, we foresee AER-271 as a new tool for manipulation of the glymphatic system in rodent brain.

Human brain clearance imaging: Pathways taken by magnetic resonance imaging contrast agents after administration in cerebrospinal fluid and blood.

Over the last decade, it has become evident that cerebrospinal fluid (CSF) plays a pivotal role in brain solute clearance through perivascular pathways and interactions between the brain and meningeal lymphatic vessels. Whereas most of this fundamental knowledge was gained from rodent models, human brain clearance imaging has provided important insights into the human system and highlighted the existence of important interspecies differences. Current gold standard techniques for human brain clearance imaging involve the injection of gadolinium-based contrast agents and monitoring their distribution and clearance over a period from a few hours up to 2 days. With both intrathecal and intravenous injections being used, which each have their own specific routes of distribution and thus clearance of contrast agent, a clear understanding of the kinetics associated with both approaches, and especially the differences between them, is needed to properly interpret the results. Because it is known that intrathecally injected contrast agent reaches the blood, albeit in small concentrations, and that similarly some of the intravenously injected agent can be detected in CSF, both pathways are connected and will, in theory, reach the same compartments. However, because of clear differences in relative enhancement patterns, both injection approaches will result in varying sensitivities for assessment of different subparts of the brain clearance system. In this opinion review article, the "EU Joint Programme - Neurodegenerative Disease Research (JPND)" consortium on human brain clearance imaging provides an overview of contrast agent pharmacokinetics in vivo following intrathecal and intravenous injections and what typical concentrations and concentration-time curves should be expected. This can be the basis for optimizing and interpreting contrast-enhanced MRI for brain clearance imaging. Furthermore, this can shed light on how molecules may exchange between blood, brain, and CSF.

Mapping of CSF transport using high spatiotemporal resolution dynamic contrast-enhanced MRI in mice: Effect of anesthesia.

PURPOSE: Dynamic contrast-enhanced MRI (DCE-MRI) represents the only available approach for glymphatic cerebrospinal fluid (CSF) flow 3D mapping in the brain of living animals and humans. The purpose of this study was to develop a novel DCE-MRI protocol for mapping of the glymphatic system transport with improved spatiotemporal resolution, and to validate the new protocol by comparing the transport in mice anesthetized with either isoflurane or ketamine/xylazine. METHODS: The contrast agent, gadobutrol, was administered into the CSF of the cisterna magna and its transport visualized continuously on a 9.4T preclinical scanner using 3D fast-imaging with a steady-state free-precession sequence (3D-FISP), which has a spatial resolution of 0.001 mm3 and a temporal resolution of 30 s. The MR signals were measured dynamically for 60 min in multiple volumes of interest covering the entire CSF space and brain parenchyma. RESULTS: The results confirm earlier findings that glymphatic CSF influx is higher under ketamine/xylazine than with isoflurane anesthesia. This was extended to account for new details about the distinct CSF efflux pathways under the two anesthetic regimens. Dynamic contrast MR shows that CSF clearance occurs mainly along the vagus nerve near the jugular vein under isoflurane and via the olfactory bulb under ketamine/xylazine. CONCLUSION: The improved spatial and temporal sampling rates afforded by 3D-FISP shed new light on the pharmacological modulation of CSF efflux paths. The present observations may have the potential to set a new standard for future experimental DCE-MRI studies of the glymphatic system.

23 Na-T1 quantification with saturation recovery TrueFISP and variable flip angle GRE at 3T: A phantom study.

PURPOSE: The aim of the current study was to compare the reproducibility of sodium (23 Na)-T1 estimation using a centric-reordered saturation recovery (SR) true fast imaging with steady-state precession (TrueFISP) and a variable flip angle (VFA) spoiled gradient echo (GRE). Additionally, we evaluated the effect of spatial averaging on 23 Na-T1 estimation by the two methods. METHODS: Measurements were performed in the phantom, consisting of 10 dm3 volume rectangular polyethylene container filled with distilled water solution of 0.6% NaCl + 0.004% CuSO4 , using a dual-tunable 23 Na/1 H coil at 3 Tesla. 23 Na images were acquired for FOV = 384 × 384 mm2 and voxel size = 6 × 6 × 6 mm3 using: (1) TrueFISP: TR/TE = 900/1.5 ms, flip angle = 90°, bandwidth = 450 Hz/px, and (2) GRE: TR/TE = 30/1.5 ms, bandwidth = 350 Hz/px. 23 Na-T1 weightings were obtained with nonselective saturation prepulses delayed from the center of the k-space acquisition by 25/40/60/130/280 ms (SR-TrueFISP) and by applying different nominal flip angles: 10°/30°/50°/70°/90° (VFA-GRE). Both sequences were acquired twice, applying 20 and 30 spatial averages. The resulting images were B1 -corrected with a double-angle GRE method. RESULTS: Image acquisition varied from 5:41 to 9:37 for TrueFISP and from 12:48 to 19:12 min for GRE using 20 and 30 spatial averages, respectively. Higher averaging increased the acquisition time by 53% and mean SNR at scan < 10%, without an effect on 23 Na-T1 estimations with both methods (SR-Truefisp |Δ| = 1.58 ms, VFA-GRE |Δ| = 0.53 ms; for SNR P < .001). Overall, mean ± SD of 23 Na-T1 was found as 51 ± 3 ms with SR-TrueFISP and 53 ± 2 ms with VFA-GRE. CONCLUSION: Both SR-TrueFISP and VFA-GRE provided similar 23 Na-T1 estimates based on the phantom measurements with isotropic resolution.

Quantification of sodium T1 in abdominal tissues at 3 T.

INTRODUCTION: Although relevant for assessment of sodium in multiple endocrine pathways, 23Na-T1 quantification is challenging due to technical limitations (SAR, B1 inhomogeneity) or influence of tissue's local molecular dynamics. Hereby, we propose T1 quantification of 23Na-MRI signal acquired over the abdomen using a centric-reordered saturation-recovery (SR) true fast imaging with steady state precession (TrueFISP) sequence. MATERIALS AND METHODS: Measurements were performed at 3T using a dual-tunable 23Na/1H coil in 7 healthy volunteers (TR/TE = 858-928/1.57 ms; flip angle = 90°; bandwidth = 450 Hz/px; voxel size = 5 × 5 × 10 mm3). Variable T1-weighting was achieved applying non-selective saturation pre-pulses delayed from the centre of the k-space acquisition by 25, 40, 60, 120 and 250 ms. T1-curve fitting was performed slice-wise, separately for average intensity values from the manually segmented areas of the renal parenchyma and spinal canal, over the increasing SR times- assuming monoexponential signal pattern. RESULTS: Mean ± standard deviation of 23Na-T1 was found as 29 ± 10 ms and 35 ± 8 ms for the renal parenchyma and the spinal canal, respectively. DISCUSSION: 23Na-T1 quantification using a SR-TrueFISP is feasible in clinical settings, in the images constrained by clinically applicable acquisition time of reduced spatial resolution or averages.

Homozygous Loss of Autism-Risk Gene CNTNAP2 Results in Reduced Local and Long-Range Prefrontal Functional Connectivity.

Functional connectivity aberrancies, as measured with resting-state functional magnetic resonance imaging (rsfMRI), have been consistently observed in the brain of autism spectrum disorders (ASD) patients. However, the genetic and neurobiological underpinnings of these findings remain unclear. Homozygous mutations in contactin associated protein-like 2 (CNTNAP2), a neurexin-related cell-adhesion protein, are strongly linked to autism and epilepsy. Here we used rsfMRI to show that homozygous mice lacking Cntnap2 exhibit reduced long-range and local functional connectivity in prefrontal and midline brain "connectivity hubs." Long-range rsfMRI connectivity impairments affected heteromodal cortical regions and were prominent between fronto-posterior components of the mouse default-mode network, an effect that was associated with reduced social investigation, a core "autism trait" in mice. Notably, viral tracing revealed reduced frequency of prefrontal-projecting neural clusters in the cingulate cortex of Cntnap2-/- mutants, suggesting a possible contribution of defective mesoscale axonal wiring to the observed functional impairments. Macroscale cortico-cortical white-matter organization appeared to be otherwise preserved in these animals. These findings reveal a key contribution of ASD-associated gene CNTNAP2 in modulating macroscale functional connectivity, and suggest that homozygous loss-of-function mutations in this gene may predispose to neurodevelopmental disorders and autism through a selective dysregulation of connectivity in integrative prefrontal areas.

The role of apelin in central cardiovascular regulation in rats with post-infarct heart failure maintained on a normal fat or high fat diet.

Based on the available literature, it can be assumed that in cases of post-infarct heart failure (HF) and obesity, a significant change in the central regulation of the cardiovascular system takes place with, among others, the involvement of the apelinergic system. The main objective of the present study was to clarify the role of apelin-13 in the central regulation of the cardiovascular system in Sprague Dawley rats with HF or sham operated (SO) and fed on a normal fat (NFD) or a high fat diet (HFD). The study was divided into two parts: Part I, hemodynamic studies; and Part II, biochemical and molecular studies. The animals were subjected to the following research procedures. Part I and II: feeding NFD or HFD; experimental induction of HF or SO; Part I: intracerebroventricular (ICV) infusion of the examined substances, monitoring of mean arterial blood pressure (MABP) and heart rate (HR); Part II: venous blood and tissue samples collected. ICV infusion of apelin-13 caused significantly higher changes in ΔMABP in the SO NFD group. No changes were noted in ΔHR in any of the studied groups. Apelin and apelin receptor (APJ) mRNA expression in the brain and adipose tissues was higher in the HF rats. HFD causes significant increase in expression of apelin and APJ mRNA in the left ventricle. In conclusion, HF and HFD appear to play an important role in modifying the activity of the central apelinergic system and significant changes in mRNA expression of apelin and APJ receptor.

High-fat diet and chronic stress reduce central pressor and tachycardic effects of apelin in Sprague-Dawley rats.

Central application of apelin elevates blood pressure and influences neuroendocrine responses to stress and food consumption. However, it is not known whether the central cardiovascular effects of apelin depend also on caloric intake or chronic stress. The purpose of the present study was to determine the effects of intracerebroventricular administration of apelin on blood pressure (mean arterial blood pressure) and heart rate in conscious Sprague-Dawley rats consuming either a normal-fat diet (NFD) or high-fat diet (HFD) for 12 weeks. During the last 4 weeks of the food regime, the rats were exposed (NFDS and HFDS groups) or not exposed (NFDNS and HFDNS groups) to chronic stress. Each group was divided into two subgroups receiving intracerebroventricular infusions of either vehicle or apelin. Apelin elicited significant increase of mean arterial blood pressure and heart rate in the NFDNS rats. This effect was abolished in the HFDNS, HFDS and NFDS groups. HFD resulted in a significant elevation of blood concentrations of total cholesterol, triglycerides glucose and insulin. Chronic stress reduced plasma concentration of total and high-density lipoprotein cholesterol, and increased plasma corticosterone concentration and APJ receptor mRNA expression in the hypothalamus, whereas a combination of a HFD with chronic stress resulted in the elevation of plasma triglycerides, total cholesterol and low-density lipoprotein cholesterol, and in increased plasma corticosterone concentration, apelin concentration and APJ receptor mRNA expression in the hypothalamus. It is concluded that a HFD and chronic stress result in significant suppression of the central pressor action of apelin, and cause significant though not unidirectional changes of metabolic and endocrine parameters.

Transient but not chronic hyperglycemia accelerates ocular glymphatic transport.

Glymphatic transport is vital for the physiological homeostasis of the retina and optic nerve. Pathological alterations of ocular glymphatic fluid transport and enlarged perivascular spaces have been described in glaucomatous mice. It remains to be established how diabetic retinopathy, which impairs vision in about 50% of diabetes patients, impacts ocular glymphatic fluid transport. Here, we examined ocular glymphatic transport in chronic hyperglycemic diabetic mice as well as in healthy mice experiencing a daily transient increase in blood glucose. Mice suffering from severe diabetes for two and four months, induced by streptozotocin, exhibited no alterations in ocular glymphatic fluid transport in the optic nerve compared to age-matched, non-diabetic controls. In contrast, transient increases in blood glucose induced by repeated daily glucose injections in healthy, awake, non-diabetic mice accelerated antero- and retrograde ocular glymphatic transport. Structural analysis showed enlarged perivascular spaces in the optic nerves of glucose-treated mice, which were absent in diabetic mice. Thus, transient repeated hyperglycemic events, but not constant hyperglycemia, ultimately enlarge perivascular spaces in the murine optic nerve. These findings indicate that fluid transport in the mouse eye is vulnerable to fluctuating glycemic levels rather than constant hyperglycemia, suggesting that poor glycemic control drives glymphatic malfunction and perivascular enlargement in the optic nerve.

A mesothelium divides the subarachnoid space into functional compartments.

The central nervous system is lined by meninges, classically known as dura, arachnoid, and pia mater. We show the existence of a fourth meningeal layer that compartmentalizes the subarachnoid space in the mouse and human brain, designated the subarachnoid lymphatic-like membrane (SLYM). SLYM is morpho- and immunophenotypically similar to the mesothelial membrane lining of peripheral organs and body cavities, and it encases blood vessels and harbors immune cells. Functionally, the close apposition of SLYM with the endothelial lining of the meningeal venous sinus permits direct exchange of small solutes between cerebrospinal fluid and venous blood, thus representing the mouse equivalent of the arachnoid granulations. The functional characterization of SLYM provides fundamental insights into brain immune barriers and fluid transport.

Loss of aquaporin-4 results in glymphatic system dysfunction via brain-wide interstitial fluid stagnation.

The glymphatic system is a fluid transport network of cerebrospinal fluid (CSF) entering the brain along arterial perivascular spaces, exchanging with interstitial fluid (ISF), ultimately establishing directional clearance of interstitial solutes. CSF transport is facilitated by the expression of aquaporin-4 (AQP4) water channels on the perivascular endfeet of astrocytes. Mice with genetic deletion of AQP4 (AQP4 KO) exhibit abnormalities in the brain structure and molecular water transport. Yet, no studies have systematically examined how these abnormalities in structure and water transport correlate with glymphatic function. Here, we used high-resolution 3D magnetic resonance (MR) non-contrast cisternography, diffusion-weighted MR imaging (MR-DWI) along with intravoxel-incoherent motion (IVIM) DWI, while evaluating glymphatic function using a standard dynamic contrast-enhanced MR imaging to better understand how water transport and glymphatic function is disrupted after genetic deletion of AQP4. AQP4 KO mice had larger interstitial spaces and total brain volumes resulting in higher water content and reduced CSF space volumes, despite similar CSF production rates and vascular density compared to wildtype mice. The larger interstitial fluid volume likely resulted in increased slow but not fast MR diffusion measures and coincided with reduced glymphatic influx. This markedly altered brain fluid transport in AQP4 KO mice may result from a reduction in glymphatic clearance, leading to enlargement and stagnation of fluid in the interstitial space. Overall, diffusion MR is a useful tool to evaluate glymphatic function and may serve as valuable translational biomarker to study glymphatics in human disease.

Delivery of gene therapy through a cerebrospinal fluid conduit to rescue hearing in adult mice.

Inner ear gene therapy has recently effectively restored hearing in neonatal mice, but it is complicated in adulthood by the structural inaccessibility of the cochlea, which is embedded within the temporal bone. Alternative delivery routes may advance auditory research and also prove useful when translated to humans with progressive genetic-mediated hearing loss. Cerebrospinal fluid flow via the glymphatic system is emerging as a new approach for brain-wide drug delivery in rodents as well as humans. The cerebrospinal fluid and the fluid of the inner ear are connected via a bony channel called the cochlear aqueduct, but previous studies have not explored the possibility of delivering gene therapy via the cerebrospinal fluid to restore hearing in adult deaf mice. Here, we showed that the cochlear aqueduct in mice exhibits lymphatic-like characteristics. In vivo time-lapse magnetic resonance imaging, computed tomography, and optical fluorescence microscopy showed that large-particle tracers injected into the cerebrospinal fluid reached the inner ear by dispersive transport via the cochlear aqueduct in adult mice. A single intracisternal injection of adeno-associated virus carrying solute carrier family 17, member 8 (Slc17A8), which encodes vesicular glutamate transporter-3 (VGLUT3), rescued hearing in adult deaf Slc17A8-/- mice by restoring VGLUT3 protein expression in inner hair cells, with minimal ectopic expression in the brain and none in the liver. Our findings demonstrate that cerebrospinal fluid transport comprises an accessible route for gene delivery to the adult inner ear and may represent an important step toward using gene therapy to restore hearing in humans.

Advanced diffusion imaging of abdominal organs in different hydration states of the human body: stability of biomarkers.

BACKGROUND: MR diffusion weighted imaging (DWI) may provide important information regarding the pathophysiology of parenchymal abdominal organs. The purpose of our study was to investigate the stability of imaging biomarkers of diffusion weighted imaging (DWI), intravoxel incoherent motion (IVIM) and diffusion kurtosis imaging (DKI) in abdominal parenchymal organs regarding two body hydration states. METHODS: Ten healthy volunteers twice underwent DWI of abdominal organs using a double-refocused spin-echo echo-planar imaging sequences with 11 different b-values (ranging from 0 to 1,500 s/mm2): after 4 h of fluid deprivation; 45 min following 1000 ml of water intake. Four different diffusion models were evaluated and compared: standard DWI, DKI with mono-exponential fitting, multistep algorithm with variable b-value threshold for IVIM, combined IVIM-Kurtosis; in four abdominal organs: kidneys, liver, spleen and psoas muscle. RESULTS: Diffusion parameters from all four models remained similar for the renal parenchyma before and after the water challenge. Significant differences were found for the liver, spleen, and psoas muscle. The largest effects were seen for: the liver parenchyma after the water challenge by means of IVIM model's true diffusion (p < 0.02); the spleen, for IVIM's perfusion fraction (p < 0.03), the psoas muscle for the ADC value (p < 0.02). CONCLUSIONS: Herein, we showed that diffusion parameters of the kidney remain remarkably stable regarding the hydration status. This may be attributed to the kidney-specific compensatory mechanisms. For the liver, spleen and psoas muscle the diffusion parameters were sensitive to changes of the hydration. This phenomenon needs to be considered when evaluating diffusion data of these organs.

Brain vasopressin V(1) receptors contribute to enhanced cardiovascular responses to acute stress in chronically stressed rats and rats with myocardial infarcton.

The present study was designed to determine the role of central vasopressin 1 receptors (V(1)R) in the regulation of cardiovascular parameters in chronically stressed infarcted rats and sham-operated rats under resting conditions and during exposure to acute alarming stress. The experiments were performed on four groups of conscious sham-operated and four groups of infarcted rats subjected to intraventricular infusion of either vehicle or a V(1)R antagonist (V(1)RANT). Two groups of infarcted and two groups of sham-operated rats were subjected to mild chronic stressing. Mean arterial blood pressure (MABP) and heart rate (HR) were determined under resting conditions and after exposure to acute stress (air jet). During vehicle infusion, MABP and HR increases in response to acute stress in the infarcted rats not subjected to chronic stress, and in the infarcted and sham-operated chronically stressed rats, were significantly greater than in the sham-operated rats not exposed to chronic stress. However, MABP and HR responses to acute stress in the chronically stressed infarcted rats and chronically stressed sham-operated rats did not differ. V(1)RANT abolished differences in cardiovascular responses to acute stress between the experimental groups. Resting cardiovascular parameters were not affected by any of the experimental treatments. It is concluded that chronic stressing enhances the pressor and tachycardic responses to acute stress in the sham-operated rats but does not further intensify these responses in infarcted rats.The results provide evidence that central V(1)Rs are involved in potentiation of cardiovascular responses to acute stress in chronically stressed rats, infarcted rats, and chronically stressed infarcted rats.

Evaluation of Urinary Sphincter Function by Rapid Magnetic Resonance Diffusion Tensor Imaging.

PURPOSE: This study aimed to assess the feasibility of a rapid diffusion tensor imaging (DTI) for evaluation of the female urinary sphincter function based on differentiation between rest and muscle contraction. METHODS: Magnetic resonance imaging (MRI) of the lower pelvis was performed at 3 Tesla in 10 healthy female volunteers (21-36 years; body mass index, 20.8±3.6 kg/m2) between June and July 2019. High-resolution T1- and T2-weighted images were acquired for anatomical reference, and following DTI performed in 4 experiment phases: twice during rest (denoted rest-1, rest-2) and contraction (contraction-1, contraction-2). Manual segmentation of the urinary sphincter and the levator ani muscles were performed by 2 independent readers. Mean diffusivity (MD) and fractional anisotropy (FA) values derived from DTI volumes were compared in search for significant differences between the experiment phases. Interreader agreement was assessed by intraclass correlation coefficient (ICC). RESULTS: Kruskal-Wallis test showed significant differences between MD values among all the experiment phases, by both independent readers (1st: X2 [3,76]=17.16, P<0.001 and 2nd: X2 [3,76]=15.88, P<0.01). Post hoc analysis revealed differences in MD values by both readers between: rest-1 vs. contraction-1 (least P<0.05), rest-1 vs. contraction-2 (P<0.01), rest-2 vs. contraction-1 (P<0.03), rest-2 vs. contraction-2 (P=0.02) with overall mean 'rest' to 'contraction' ΔMD=20.6%. No MD or FA differences were found between rest-1 vs. rest-2 and contraction-1 vs. contraction-2 among all the experiment phases, and interreader agreement was ICC=0.85 (MD) and ICC=0.79 (FA). CONCLUSION: Rapid DTI might prospectively act as a supporting tool for the evaluation of female pelvic floor muscle function, and incontinence assessment.

Computer analysis of histopathological images for tumor grading.

OBJECTIVE: We developed a new method that enables automatic and rapid assessment of a tumor's proliferation index from immunohistochemically (IHC) stained microscopic images. APPROACH: The method is based on computer-aided analysis of images - color filtration pixel-by-pixel (CFPP method) of the whole histopathological virtual slides. MAIN RESULTS: The method is simple, rapid, and does not require the time consuming step of selecting manually areas of interest nor the need for computationally complicated detection of hot-spots, both of which attempt to emulate a pathologist's way of estimating a proliferation index. We apply our method to a set of diffuse large B-cell lymphoma (DLBCL) slide images. SIGNIFICANCE: By appropriate changes in the color filtration thresholds, our method may be adapted to the analysis of other types of tumors. It may also be adapted for analysis of microscopic images in neuropathology, like biopsies of dystrophic muscles. Because of its simplicity and rapidity it may also be applied for analysis of series of images to assess dynamics of image complexity in network physiology.

Higuchi Fractal Dimension of Heart Rate Variability During Percutaneous Auricular Vagus Nerve Stimulation in Healthy and Diabetic Subjects.

Analysis of heart rate variability (HRV) can be applied to assess the autonomic nervous system (ANS) sympathetic and parasympathetic activity. Since living systems are non-linear, evaluation of ANS activity is difficult by means of linear methods. We propose to apply the Higuchi fractal dimension (HFD) method for assessment of ANS activity. HFD measures complexity of the HRV signal. We analyzed 45 RR time series of 84 min duration each from nine healthy and five diabetic subjects with clinically confirmed long-term diabetes mellitus type II and with diabetic foot ulcer lasting more than 6 weeks. Based on HRV time series complexity analysis we have shown that HFD: (1) discriminates healthy subjects from patients with diabetes mellitus type II; (2) assesses the impact of percutaneous auricular vagus nerve stimulation (pVNS) on ANS activity in normal and diabetic conditions. Thus, HFD may be used during pVNS treatment, to provide stimulation feedback for on-line regulation of therapy in a fast and robust way.

A Quantitative Method Using Head Noncontrast CT Scans to Detect Hyperacute Nonvisible Ischemic Changes in Patients With Stroke.

PURPOSE: Because clinical evaluation of noncontrast computed tomography (CT) has a poor sensitivity in the evaluation of acute ischemic stroke, computer-aided diagnosis may be able to facilitate the performance. Recently, we introduced a computational method for the detection and localization of visible infarcts. Herein, we aimed to evaluate and extend a previous method, the Stroke Imaging Marker (SIM), to localize nonvisible hyperacute ischemia. MATERIALS AND METHODS: On the basis of the SIM and its components-the ratio of percentile differences in subranges of Hounsfield Unit (HU) distribution (P-ratio), ratio of voxels count in ranges of brain CT intensity, median HU attenuation value-the infarct localization was performed in 140 early and follow-up scans of 70 patients. In none of the early scans was the infarct visible to a radiologist or an experienced stroke neuroradiologist. The infarcted hemisphere detection rate (HDR) and sensitivity of infarct localization were measured by overlapping the region of detected tissue in the initial scan, with the gold standard set for the fully visible stroke in the follow-up scan. RESULTS: The best performance of the algorithm was found for the P-ratio including seven percentile subranges within the range of 35th-75th percentile. The modified SIM provided a 76% ischemic HDR and 54% sensitivity in spatial localization of hyperacute ischemia (68% among properly detected infarct sides). CONCLUSION: The improved SIM is a dedicated and potentially useful tool for hyperacute nonvisible brain infarct detection from CT scans and may contribute to reduction of image-to-needle time in patients eligible for revascularization therapy.

Reduction of pressor response to stress by centrally acting apelin in spontaneously hypertensive rats.

BACKGROUND: Numerous studies suggest that apelin plays a significant role in cardiovascular regulation and in the pathogenesis of hypertension. The purpose of the present study was to determine whether apelin-13 (AP-13) is involved in the regulation of cardiovascular responses to acute stress in spontaneous hypertension. METHODS: The effects of intracerebroventricular (ICV) administration of AP-13 on changes in mean arterial blood pressure (MABP) and heart rate evoked by an alarming stress (air jet stress) were compared in awake normotensive Wistar-Kyoto (WKY) rats and spontaneously hypertensive rats (SHR). The rats were divided into four groups: Groups 1 (WKY) and 3 (SHR) received ICV infusion of 0.9% sodium chloride (vehicle), whereas Groups 2 (WKY) and 4 (SHR) were ICV infused with AP-13. All animals were exposed to the alarming stress. RESULTS: During the ICV administration of the vehicle, the pressor response to stress was significantly greater in SHR than in WKY. The ICV infusion of AP-13 reduced the pressor response evoked by the application of the stressor in SHR but not in WKY. It also abolished the difference in stress-induced MABP increases between WKY and SHR. CONCLUSIONS: The results show that centrally acting apelin may play an essential role in the regulation of blood pressure responses to an alarming stress in SHR rats.

Characterization of intraventricular and intracerebral hematomas in non-contrast CT.

Characterization of hematomas is essential in scan reading, manual delineation, and designing automatic segmentation algorithms. Our purpose is to characterize the distribution of intraventricular (IVH) and intracerebral hematomas (ICH) in NCCT scans, study their relationship to gray matter (GM), and to introduce a new tool for quantitative hematoma delineation. We used 289 serial retrospective scans of 51 patients. Hematomas were manually delineated in a two-stage process. Hematoma contours generated in the first stage were quantified and enhanced in the second stage. Delineation was based on new quantitative rules and hematoma profiling, and assisted by a dedicated tool superimposing quantitative information on scans with 3D hematoma display. The tool provides: density maps (40-85HU), contrast maps (8/15HU), mean horizontal/vertical contrasts for hematoma contours, and hematoma contours below a specified mean contrast (8HU). White matter (WM) and GM were segmented automatically. IVH/ICH on serial NCCT is characterized by 59.0HU mean, 60.0HU median, 11.6HU standard deviation, 23.9HU mean contrast, -0.99HU/day slope, and -0.24 skewness (changing over time from negative to positive). Its 0.1(st)-99.9(th) percentile range corresponds to 25-88HU range. WM and GM are highly correlated (R (2)=0.88; p<10(-10)) whereas the GM-GS correlation is weak (R (2)=0.14; p<10(-10)). The intersection point of mean GM-hematoma density distributions is at 55.6±5.8HU with the corresponding GM/hematoma percentiles of 88(th)/40(th). Objective characterization of IVH/ICH and stating the rules quantitatively will aid raters to delineate hematomas more robustly and facilitate designing algorithms for automatic hematoma segmentation. Our two-stage process is general and potentially applicable to delineate other pathologies on various modalities more robustly and quantitatively.