Browsing by Subject "brain"

Now showing 1 - 3 of 3

Open Access
Effect of patient sex on white matter alterations in unilateral medial temporal lobe epilepsy with hippocampal sclerosis assessed by diffusion tensor imaging
(2013) Oguz, K.K.; Tezer I.; Sanverdi, E.; Has, A.C.; Bilginer, B.; Dolgun, A.; Saygi, S.
BACKGROUND AND PURPOSE: Studies shows ictal behavior and symptoms are affected by patient sex in temporal lobe epilepsy. The purpose of our study was to determine whether alterations in the WM as assessed by DTI display different patterns in male and female patients with unilateral HS. MATERIALS AND METHODS: Patients with unilateral HS were categorized as women with right HS ( n=12), men with right HS ( n=10), women with left HS ( n=12), and men with left HS ( n=10). DTI of the brain along 64 noncollinear directions was obtained from 44 patients and 37 sex-matched control participants. We used TBSS to analyze whole-brain WM. Regions with significant changes of FA and MD, and their mean FA, MD, total number of significant voxels, and asymmetry indices were determined for each group. RESULTS: All groups showed bilateral and extensive reductions of FA and elevated MD in the WM, more prominent ipsilateral to the affected hippocampus. The total number of voxels with decreased FA in patients compared with that of control participants was higher in women with right HS (24,727 vs 5,459) and in men with left HS (27,332 vs 14,013) than in their counterparts. Changes in MD associated with right HS were more extensive in both men and women (right vs left HS, women: 16,926 vs 5,458; men: 5,389 vs 4,764) than in those with left HS. In patients with right HS, the ipsilateral cingulum, uncinate fasciculus, internal and external capsules, and right acoustic radiation were involved extensively in women. CONCLUSIONS: Women and men showed different patterns in extent of WM alterations associated with HS.
Open Access
Modes of shear wave in magnetic resonance elastography
(2014) Arıyürek, Cemre
Manual palpation is used for diagnosing change in stiffness of tissues, due to a pathological state. Unfortunately, this diagnosis tool is limited with organs close to the surface of the body. Magnetic resonance elastography (MRE), also known as palpation by magnetic resonance imaging (MRI), can be used in detecting changes in material properties of the heart, liver, muscle, breast and brain. Alteration in stiffness of tissues can be detected by MRE, by simply measuring the wavelength of the induced shear wave by the actuator, from the phase difference images obtained by MR scanner. In addition to wavelength information, dependence of shear wave displacement amplitude to the frequency and excitation direction carry important information about material properties of the tissue. Modes of shear waves in MRE have not been studied previously. Change in material properties of the tissue, may affect modes of shear waves in MRE. Hence, a shift in natural frequencies may indicate a pathological state in the tissue. We propose a novel method to detect change in stiffness of tissues, by analyzing modes of shear waves and detecting frequency shift in peak displacement of shear waves in MRE. Eigenfrequency simulations are computed for a simple geometric object whose eigenfrequencies are known analytically. Validating simulation results with theoretical values, we are encouraged to continue with eigenfrequency analysis of the brain model. For different directions of motions of head, it is demonstrated by eigenfrequency analysis that brain has modes at certain frequencies. Results of frequency domain analysis indicates that modes of shear waves can be observed in brain by exciting head at its eigenfrequencies with correct excitation in that frequency. Results of frequency domain analysis repeated for neurodegenerative brain model are compared with the findings in healthy brain model. Comparing frequencies of peak displacements in neurodegenerative and healthy model, a constant frequency shift is observed in all frequencies of peak displacements. Preliminary results of modes of shear waves in brain MRE are presented, by sweeping mechanical excitation frequency. This method can be used in detecting change in stiffness of tissues for diagnosing diseases by observing shift in frequency of peak displacement and be beneficial for patient follow-up.
Open Access
Systematic discovery of Rab GTPases with synaptic functions in Drosophila
(2011) Chan, C.-C.; Scoggin, S.; Wang, D.; Cherry, S.; Dembo, T.; Greenberg, B.; Jin, E.J.; Kuey, C.; Lopez, A.; Mehta, S.Q.; Perkins, T.J.; Brankatschk, M.; Rothenfluh, A.; Buszczak, M.; Hiesinger P.R.
Background: Neurons require highly specialized intracellular membrane trafficking, especially at synapses. Rab GTPases are considered master regulators of membrane trafficking in all cells, and only very few Rabs have known neuron-specific functions. Here, we present the first systematic characterization of neuronal expression, subcellular localization, and function of Rab GTPases in an organism with a brain. Results: We report the surprising discovery that half of all Drosophila Rabs function specifically or predominantly in distinct subsets of neurons in the brain. Furthermore, functional profiling of the GTP/GDP-bound states reveals that these neuronal Rabs are almost exclusively active at synapses and the majority of these synaptic Rabs specifically mark synaptic recycling endosomal compartments. Our profiling strategy is based on Gal4 knockins in large genomic fragments that are additionally designed to generate mutants by ends-out homologous recombination. We generated 36 large genomic targeting vectors and transgenic rab-Gal4 fly strains for 25 rab genes. Proof-of-principle knockout of the synaptic rab27 reveals a sleep phenotype that matches its cell-specific expression. Conclusions: Our findings suggest that up to half of all Drosophila Rabs exert specialized synaptic functions. The tools presented here allow systematic functional studies of these Rabs and provide a method that is applicable to any large gene family in Drosophila. © 2011 Elsevier Ltd. All rights reserved.