Showing papers by "David C. Reutens published in 2012"

Intravenous immunoglobulin protects neurons against amyloid beta-peptide toxicity and ischemic stroke by attenuating multiple cell death pathways.

Abstract: Intravenous immunoglobulin (IVIg) preparations obtained by fractionating blood plasma, are increasingly being used increasingly as an effective therapeutic agent in treatment of several inflammatory diseases. Its use as a potential therapeutic agent for treatment of stroke and Alzheimer's disease has been proposed, but little is known about the neuroprotective mechanisms of IVIg. In this study, we investigated the effect of IVIg on downstream signaling pathways that are involved in neuronal cell death in experimental models of stroke and Alzheimer's disease. Treatment of cultured neurons with IVIg reduced simulated ischemia- and amyloid βpeptide (Aβ)-induced caspase 3 cleavage, and phosphorylation of the cell death-associated kinases p38MAPK, c-Jun NH2 -terminal kinase and p65, in vitro. Additionally, Aβ-induced accumulation of the lipid peroxidation product 4-hydroxynonenal was attenuated in neurons treated with IVIg. IVIg treatment also up-regulated the anti-apoptotic protein, Bcl2 in cortical neurons under ischemia-like conditions and exposure to Aβ. Treatment of mice with IVIg reduced neuronal cell loss, apoptosis and infarct size, and improved functional outcome in a model of focal ischemic stroke. Together, these results indicate that IVIg acts directly on neurons to protect them against ischemic stroke and Aβ-induced neuronal apoptosis by inhibiting cell death pathways and by elevating levels of the anti-apoptotic protein Bcl2.

Neurobehavioral Consequences of Prenatal Antiepileptic Drug Exposure

Abstract: Despite elevated rates of birth defects associated with prenatal antiepileptic drug exposure, pharmacotherapy is typically continued throughout pregnancy because of the risks posed to mother and child by recurrent seizures. Emerging data suggest that prenatal exposure to valproate or polytherapy may also be associated with increased risk of cognitive impairment. However, our understanding of the longer-term sequelae of prenatal antiepileptic drug exposure remains incomplete. Improved understanding of the neurobehavioral consequences of prenatal antiepileptic drug exposure is essential to ensure accurate information is available for women with epilepsy planning a pregnancy, and to achieve optimal outcomes for mothers and children.

Stereotaxic localisation of the dorsolateral prefrontal cortex for transcranial magnetic stimulation is superior to the standard reference position

Abstract: Objective: To determine whether the standard method of localisation of the dorsolateral prefrontal cortex for repetitive transcranial magnetic stimulation is accurate and reliable, and to develop an empirically based method for operational localisation of the dorsolateral prefrontal cortex with reference to the motor hand area. Method: We compared stereotaxic localisation of the dorsolateral prefrontal cortex with the commonly used operational definition of 6 cm anterior to the site of the abductor pollicis brevis muscle in healthy participants (n = 18). We also report the average translational distance from the site of the abductor pollicis brevis to the stereotaxically defined dorsolateral prefrontal cortex. Results: The stereotaxic method was less variable than the operational method of localisation and more frequently targeted the middle frontal gyrus. The average translational distance from the site of the abductor pollicis brevis to the stereotaxically targeted dorsolateral prefrontal cortex was x = −5 mm, y = 53 mm and z = −31 mm. Conclusions: Operational localisation of the dorsolateral prefrontal cortex for repetitive transcranial magnetic stimulation with reference to the motor hand area is more variable than stereotaxic localisation. If future studies choose to use an operational definition of the left dorsolateral prefrontal cortex, we suggest it should be 5 mm lateral, 53 mm anterior and 31 mm inferior to the site of the abductor pollicis brevis.

The Laminar Cortex Model: A New Continuum Cortex Model Incorporating Laminar Architecture

Abstract: Local field potentials (LFPs) are widely used to study the function of local networks in the brain. They are also closely correlated with the blood-oxygen-level-dependent signal, the predominant contrast mechanism in functional magnetic resonance imaging. We developed a new laminar cortex model (LCM) to simulate the amplitude and frequency of LFPs. Our model combines the laminar architecture of the cerebral cortex and multiple continuum models to simulate the collective activity of cortical neurons. The five cortical layers (layer I, II/III, IV, V, and VI) are simulated as separate continuum models between which there are synaptic connections. The LCM was used to simulate the dynamics of the visual cortex under different conditions of visual stimulation. LFPs are reported for two kinds of visual stimulation: general visual stimulation and intermittent light stimulation. The power spectra of LFPs were calculated and compared with existing empirical data. The LCM was able to produce spontaneous LFPs exhibiting frequency-inverse (1/ƒ) power spectrum behaviour. Laminar profiles of current source density showed similarities to experimental data. General stimulation enhanced the oscillation of LFPs corresponding to gamma frequencies. During simulated intermittent light stimulation, the LCM captured the fundamental as well as high order harmonics as previously reported. The power spectrum expected with a reduction in layer IV neurons, often observed with focal cortical dysplasias associated with epilepsy was also simulated.

A Solid State Study of Keto-enol Tautomerismin Three Naphthaledene Schiff Bases

Abstract: Three naphthaledene Schiff bases were synthesized and a detailed analysis by variable temperature X-ray crystallography and solid state electronic spectra was undertaken to assess the tautomeric composition. The crystal structures showed no significant changes despite the compounds changing colour with temperature. Solid state UV spectra were acquired at low temperature and showed that the major absorption band broadened as the temperature was increased. In one compound absorptions were observed that increased in intensity as the temperature increased. For these compounds, the major contribution to the colour change is the broadening of the absorption band as a function of temperature and not the change in enol-keto tautomeric composition.

A fast multi-resolution differential evolution method for multimodal image registration

Abstract: A new method of finding optimal variables using self-adaptive differential evolution derived multi-modal image registration is proposed. The method features multi-resolution images achieved through down-sampling at different stages of the transformation model variable optimization process. The performance of the method is illustrated by registering magnetic resonance images to histological sections. We provide an investigation of the impact of the down-sampling factor and convergence criteria. Our findings show that given appropriately down-sampled images, and by using the proposed approach, it is possible to find optimal registration transformation model variables faster than if appropriate down-sampling is not used.

Magnetic susceptibility derived from T2 and T 2*‐weighted magnetic resonance magnitude images

Abstract: A method of measuring absolute magnetic susceptibility using T2 and T-weighted magnetic resonance images is described. We used magnitude images derived from spin echo and gradient echo acquisitions, without the use of phase information. The findings are validated analytically and also using experimental phantoms. We show that a combination of magnetic resonance images can provide information needed to deduce the absolute susceptibility of the sample. Careful consideration of sample relaxation times and image acquisition parameters is required to ensure that calculations are accurate. We conducted an investigation of optimal imaging parameters and validated our results. © 2012 Wiley Periodicals, Inc. Concepts Magn Reson Part B (Magn Reson Engineering) 41B: 28–36, 2012

HSQC spectral based similarity matching of compounds using nearest neighbours and a fast discrete genetic algorithm

Abstract: HSQC spectra are routinely acquired for chemical structure analysis based on hydrogen and carbon chemical environments. Two fast HSQC peak matching algorithms have been developed; a nearest neighbour approach and a probabilistic method based on an existing discrete genetic algorithm. Both of these techniques are intended to find HSQC spectra matches that supplement information generated by established molecular fingerprint methods. Our results are compared to those calculated using a specific implementation of molecular fingerprints. The nearest neighbour and genetic algorithm-based methods ranked highly particular structures missed by molecular fingerprints. Our analysis shows that by complementing molecular fingerprint matches with our findings, a comprehensive list of matches can be identified. The refined list of compounds could be used to improve the quality of compounds used in screening libraries in the pharmaceutical industry.

An adaptable mri radiofrequency breast coil: Evaluation of size, coil diameter, and uniformity

Abstract: Three quadrature transmit/receive radiofrequency magnetic resonance imaging breast coils were designed and built. The coils are geometrically equivalent but were scaled for different breast sizes. The coils were tested using a 4-T Bruker/Siemens whole-body scanner. We used different coil sizes to establish whether it is necessary to match coil size to load size. Moreover, our work investigated how the coil configuration can be changed to improve signal uniformity in the acquired images. We found that improvements can be gained by carefully matching the coil to the sample. In addition, we propose a coil layout that allows images quality to be improved, as measured by the signal-to-noise ratio and field uniformity of the coil.

The Use of Inverse Phase Fourier Image to Accommodate Intensity Inhomogeneities in Medical Image Registration

Abstract: Medical image registration is generally faced with the confounding effect of spatially dependent intensity variations. This can be the case when images have been acquired using the same imaging modality, for example, in magnetic resonance imaging and also when using various histology and staining processes. We propose the application of an intensity-invariant dense feature extraction method through the use of phase Fourier transforms. The approach allows medical images containing intensity in homogeneities to be aligned and warped as part of a feature-based registration technique. Registration performance was evaluated on mono-modality and multi-modality data, namely magnetic resonance and histology images. Qualitative and quantitative validation was conducted with respect to two established image intensity correction methods.

Probabilistic atlas of the C57BL/6J mouse cerebellum

Abstract: Jeremy F P Ullmann, Andrew L Janke, Charles Watson, Nyoman D Kurniawan, George Paxinos, Marianne D Keller, Zhengyi Yang, Kay Richards, Gary F Egan, Steve Petrou, Graham J Galloway, and David C Reutens Centre for Advanced Imaging, University of Queensland, Brisbane, QLD, Australia, Curtin University, Perth, WA, Australia, Prince of Wales Medical Research Institute, Sydney, NSW, Australia, Florey Neuroscience Institute, Parkville, VIC, Australia, Monash University, Clayton, VIC, Australia, Centre for Neuroscience, University of Melbourne, Parkville, VIC, Australia

Application of Weber's Law to Medical Image Registration to Accommodate Intensity Inhomogeneities

Abstract: Medical image registration is often confronted by the presence of image intensity inhomogeneity, even when the images are acquired of the same subject using mono-modality techniques. An intensity- invariant dense feature extraction method as inspired by the Weber's Law is proposed as a tool to align and warp medical images containing intensity inhomogeneity issues through a feature-based registration method. Registration performance was evaluated using magnetic resonance and histology images and the results were compared to two established intensity correction methods. Our findings show that the proposed method performs comparably in the case of affine registration, and outperforms the other two methods when non-linear warping is used as part of the registration process.