Our study explores the potential of conventional and advanced diffusion MRI techniques including diffusion tensor imaging (DTI), and single-shell 3-tissue constrained spherical deconvolution ...(SS3T-CSD) to investigate complex microstructural changes following severe traumatic brain injury in rats at a chronic phase. Rat brains after sham-operation or lateral fluid percussion (LFP) injury were scanned ex vivo in a 9.4 T scanner. Our region-of-interest-based approach of tensor-, and SS3T-CSD derived fixel-, 3-tissue signal fraction maps were sensitive to changes in both white matter (WM) and grey matter (GM) areas. Tensor-based measures, such as fractional anisotropy (FA) and radial diffusivity (RD), detected more changes in WM and GM areas as compared to fixel-based measures including apparent fiber density (AFD), peak FOD amplitude and primary fiber bundle density, while 3-tissue signal fraction maps revealed distinct changes in WM, GM, and phosphate-buffered saline (PBS) fractions highlighting the complex tissue microstructural alterations post-trauma. Track-weighted imaging demonstrated changes in track morphology including reduced curvature and average pathlength distal from the primary lesion in severe TBI rats. In histological analysis, changes in the diffusion MRI measures could be associated to decreased myelin density, loss of myelinated axons, and increased cellularity, revealing progressive microstructural alterations in these brain areas five months after injury. Overall, this study highlights the use of combined conventional and advanced diffusion MRI measures to obtain more precise insights into the complex tissue microstructural alterations in chronic phase of severe brain injury.
Summary
Objective
Status epilepticus (SE) is an abnormally prolonged epileptic seizure that if associated with convulsive motor symptoms is potentially life threatening for a patient. However, ...20%‐40% of patients with SE lack convulsive events and instead present with more subtle semiology such as altered consciousness and less motor activity. Today, there is no general consensus regarding to what extent nonconvulsive SE (NCSE) is harmful to the brain, which adds uncertainty to stringent treatment regimes.
Methods
Here, we evaluated brain pathology in an experimental rat and mouse model of complex partial NCSE originating in the temporal lobes with Western blot analysis, immunohistochemistry, and ex vivo diffusion tensor imaging (DTI). The NCSE was induced by electrical stimulation with intrahippocampal electrodes and terminated with pentobarbital anesthesia. Video‐electroencephalographic recordings were performed throughout the experiment.
Results
DTI of mice 7 weeks post‐NCSE showed no robust long‐lasting changes in fractional anisotropy within the hippocampal epileptic focus. Instead, we found pathophysiological changes developing over time when measuring protein levels and cell counts in extracted brain tissue. At 6 and 24 hours post‐NCSE in rats, few changes were observed within the hippocampus and cortical or subcortical structures in Western blot analyses of key components of the cellular immune response and synaptic protein expression, while neurodegeneration had started. However, 1 week post‐NCSE, both excitatory and inhibitory synaptic protein levels were decreased in hippocampus, concomitant with an excessive microglial and astrocytic activation. At 4 weeks, a continuous immune response in the hippocampus was accompanied with neuronal loss. Levels of the excitatory synaptic adhesion molecule N‐cadherin were decreased specifically in rats that developed unprovoked spontaneous seizures (epileptogenesis) within 1 month following NCSE, compared to rats only exhibiting acute symptomatic seizures within 1 week post‐NCSE.
Significance
These findings provide evidence for a significant brain pathology following NCSE in an experimental rodent model.
Abstract
Laterite soils are highly permeable and make the foundation unsuitable construction. Foundation is a significant structural element which play a key role in safety and stability of structure ...and it has to be strong enough to support the overlying and underlying structures. This research focuses on stabilizing the laterite soil adding coconut coirs fibres at varying percentages viz., 0.25%, 0.5%, 0.75%, and 1%, which are extracted from coconuts serving as natural fibre for stabilization of soil. The tests such as liquid limit, plastic limit, plasticity index, optimum moisture content, maximum dry density, unconfined compressive strength, and soaked & unsoaked California Bearing Ratio tests were conducted on soil specimens made with varying percentages of coconut coir. It was noted that at 0% addition of coconut coir fibre maximum liquid and plastic limits were obtained and with every increase in the coir content the plasticity index, unconfined compressive strength and California Bearing Ratio strengths were increased. On the other hand, the dry density of all the specimens showed almost equal range of density content and the moisture content was decreased with increase in the coconut coir content. Overall, it was found that stabilization of laterite soil using coconut coir as natural fibres is a cost-effective and eco-friendly approach to improve the properties of soil.
Our study investigates the potential of diffusion MRI (dMRI), including diffusion tensor imaging (DTI), fixel-based analysis (FBA) and neurite orientation dispersion and density imaging (NODDI), to ...detect microstructural tissue abnormalities in rats after mild traumatic brain injury (mTBI). The brains of sham-operated and mTBI rats 35 days after lateral fluid percussion injury were imaged
in a 11.7-T scanner. Voxel-based analyses of DTI-, fixel- and NODDI-based metrics detected extensive tissue changes in directly affected brain areas close to the primary injury, and more importantly, also in distal areas connected to primary injury and indirectly affected by the secondary injury mechanisms. Histology revealed ongoing axonal abnormalities and inflammation, 35 days after the injury, in the brain areas highlighted in the group analyses. Fractional anisotropy (FA), fiber density (FD) and fiber density and fiber bundle cross-section (FDC) showed similar pattern of significant areas throughout the brain; however, FA showed more significant voxels in gray matter areas, while FD and FDC in white matter areas, and orientation dispersion index (ODI) in areas most damage based on histology. Region-of-interest (ROI)-based analyses on dMRI maps and histology in selected brain regions revealed that the changes in MRI parameters could be attributed to both alterations in myelinated fiber bundles and increased cellularity. This study demonstrates that the combination of dMRI methods can provide a more complete insight into the microstructural alterations in white and gray matter after mTBI, which may aid diagnosis and prognosis following a mild brain injury.
It is necessary to develop reliable biomarkers for epileptogenesis and cognitive impairment after traumatic brain injury when searching for novel antiepileptogenic and cognition-enhancing treatments. ...We hypothesized that a multiparametric magnetic resonance imaging (MRI) analysis along the septotemporal hippocampal axis could predict the development of post-traumatic epilepsy and cognitive impairment. We performed quantitative T2 and T2* MRIs at 2, 7 and 21 days, and diffusion tensor imaging at 7 and 21 days after lateral fluid-percussion injury in male rats. Morris water maze tests conducted between 35–39 days post-injury were used to diagnose cognitive impairment. One-month-long continuous video-electroencephalography monitoring during the 6th post-injury month was used to diagnose epilepsy. Single-parameter and regularized multiple linear regression models were able to differentiate between sham-operated and brain-injured rats. In the ipsilateral hippocampus, differentiation between the groups was achieved at most septotemporal locations (cross-validated area under the receiver operating characteristic curve (AUC) 1.0, 95% confidence interval 1.0–1.0). In the contralateral hippocampus, the highest differentiation was evident in the septal pole (AUC 0.92, 95% confidence interval 0.82–0.97). Logistic regression analysis of parameters imaged at 3.4 mm from the contralateral hippocampus’s temporal end differentiated between the cognitively impaired rats and normal rats (AUC 0.72, 95% confidence interval 0.55–0.84). Neither single nor multiparametric approaches could identify the rats that would develop post-traumatic epilepsy. Multiparametric MRI analysis of the hippocampus can be used to identify cognitive impairment after an experimental traumatic brain injury. This information can be used to select subjects for preclinical trials of cognition-improving interventions.
A premature termination codon in the human histidine decarboxylase (Hdc) gene has been identified in a family suffering from Guilles de la Tourette syndrome (GTS). In the current study we ...investigated if mice lacking the histamine producing enzyme HDC share the morphological and cytological phenotype with GTS patients by using magnetic resonance (MRI) and diffusion tensor imaging (DTI), unbiased stereology and immunohistochemistry. Behavior of Hdc knock‐out (Hdc KO) mice was assessed in an open field test. The results of stereological, volumetric and DTI analysis measurements showed no significant differences between control and Hdc KO mice. The numbers and distribution of GABAergic parvalbumin or nitric oxide‐expressing and cholinergic interneurons were normal in Hdc KO mice. Cortical morphology and layering in adult Hdc KO mice were also preserved. In open field test Hdc KO mice showed impaired exploratory activity and habituation when introduced to novel environment. Our results indicate that Hdc deficiency in mice does not disturb the development of striatal and cortical interneurons and does not lead to the morphological and cytological phenotypes characterized by humans with GTS. Nevertheless, histamine deficiency leads to behavioral alterations probably due to neurotransmitter dysbalance on the level of the striatum.
A mutation in Hdc gene has been found in Tourette syndrome patients. MRI, DTI and stereological analyses of Hdc knock‐out mice showed normal morphology and cytoarchitecture in the cortex and striatum. Thus, these mice lack “Tourette syndrome‐like” phenotype found previously in human imaging and post‐mortem studies.
Objective
To identify magnetic resonance imaging (MRI) biomarkers for post‐traumatic epilepsy.
Methods
The EPITARGET (Targets and biomarkers for antiepileptogenesis, epitarget.eu) animal cohort ...completing T2 relaxation and diffusion tensor MRI follow‐up and 1‐month‐long video‐electroencephalography monitoring included 98 male Sprague‐Dawley rats with traumatic brain injury and 18 controls. T2 imaging was performed on day (D) 2, D7, and D21 and diffusion tensor imaging (DTI) on D7 and D21 using a 7‐Tesla Bruker PharmaScan MRI scanner. The mean and standard deviation (SD) of the T2 relaxation rate, multiple diffusivity measures, and diffusion anisotropy at each time‐point within the ventroposterolateral and ventroposteromedial thalamus were used as predictor variables in multi‐variable logistic regression models to distinguish rats with and without epilepsy.
Results
Twenty‐nine percent (28/98) of the rats with traumatic brain injury (TBI) developed epilepsy. The best‐performing logistic regression model utilized the D2 and D7 T2 relaxation time as well as the D7 diffusion tensor data. The model distinguished rats with and without epilepsy (Bonferroni‐corrected p‐value < .001) with a cross‐validated concordance statistic of 0.74 (95% confidence interval CI 0.60–0.84). In a cross‐validated classification test, the model exhibited 54% sensitivity and 91% specificity, enriching the epilepsy rate within the study population from the expected 29% to 71%. A model using the D2 T2 data only resulted in a 73% enriched epilepsy rate (regression p‐value .007, cross‐validated concordance 0.70, 95% CI 0.56–0.80, sensitivity 29%, specificity 96%).
Significance
An MRI parameter set reporting on acute and subacute neuropathologic changes common to experimental and human TBI presents a diagnostic biomarker for post‐traumatic epileptogenesis. Significant enrichment of the study population was achieved even when using a single time‐point measurement, producing an expected epilepsy rate of 73%.
In this research, an attempt has been made to enhance the heat transfer for a plate-fin heat exchanger with the new arrangement of classic delta winglets used for vortex generators and compared the ...same with the existing literature. The computational domains are developed by dislocating delta winglets from their original position, so there is no additional pressure loss with flow geometry. All the flow domains are analyzed by computing the 3D Reynolds averaged Navier-Stokes equations using ANSYS Fluent. Two different working fluids are considered one is water and nanofluids (water with Aluminum oxide). Heat transfer characteristics are analyzed for different placements of winglets for both water and nanofluids. The plate-fin heat exchanger's performance has been optimized with the optimum location of winglets and nanofluids from the analysis of numerical results. For the case of 0% nanofluids at 300 Reynolds number, Case 3 Nusselt number has been increased by 23.2% with a decrease in pressure drop of 17.7% with the dislocation of one winglet. It represents the enhancement of heat transfer.
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