Feasibility of simultaneous intracranial EEG-fMRI in humans: a safety study

In epilepsy patients who have electrodes implanted in their brains as part of their pre-surgical assessment, simultaneous intracranial EEG and fMRI (icEEG-fMRI) may provide important localising information and improve understanding of the underlying neuropathology. However, patient safety during icEEG-fMRI has not been addressed. Here the potential health hazards associated with icEEG-fMRI were evaluated theoretically and the main risks identified as: mechanical forces on electrodes from transient magnetic effects, tissue heating due to interaction with the pulsed RF fields and tissue stimulation due to interactions with the switched magnetic gradient fields. These potential hazards were examined experimentally in vitro on a Siemens 3 T Trio, 1.5 T Avanto and a GE 3 T Signa Excite scanner using a Brain Products MR compatible EEG system. No electrode flexion was observed. Temperature measurements demonstrated that heating well above guideline limits can occur. However heating could be kept within safe limits (< 1.0 °C) by using a head transmit RF coil, ensuring EEG cable placement to exit the RF coil along its central z-axis, using specific EEG cable lengths and limiting MRI sequence specific absorption rates (SARs). We found that the risk of tissue damage due to RF-induced heating is low provided implant and scanner specific SAR limits are observed with a safety margin used to account for uncertainties (e.g. in scanner-reported SAR). The observed scanner gradient switching induced current (0.08 mA) and charge density (0.2 μC/cm2) were well within safety limits (0.5 mA and 30 μC/cm2, respectively). Site-specific testing and a conservative approach to safety are required to avoid the risk of adverse events

Hyperthermia treatment of tumors by mesenchymal stem cell-delivered superparamagnetic iron oxide nanoparticles.

Magnetic hyperthermia - a potential cancer treatment in which superparamagnetic iron oxide nanoparticles (SPIONs) are made to resonantly respond to an alternating magnetic field (AMF) and thereby produce heat - is of significant current interest. We have previously shown that mesenchymal stem cells (MSCs) can be labeled with SPIONs with no effect on cell proliferation or survival and that within an hour of systemic administration, they migrate to and integrate into tumors in vivo. Here, we report on some longer term (up to 3 weeks) post-integration characteristics of magnetically labeled human MSCs in an immunocompromized mouse model. We initially assessed how the size and coating of SPIONs dictated the loading capacity and cellular heating of MSCs. Ferucarbotran(®) was the best of those tested, having the best like-for-like heating capability and being the only one to retain that capability after cell internalization. A mouse model was created by subcutaneous flank injection of a combination of 0.5 million Ferucarbotran-loaded MSCs and 1.0 million OVCAR-3 ovarian tumor cells. After 2 weeks, the tumors reached ~100 µL in volume and then entered a rapid growth phase over the third week to reach ~300 µL. In the control mice that received no AMF treatment, magnetic resonance imaging (MRI) data showed that the labeled MSCs were both incorporated into and retained within the tumors over the entire 3-week period. In the AMF-treated mice, heat increases of ~4°C were observed during the first application, after which MRI indicated a loss of negative contrast, suggesting that the MSCs had died and been cleared from the tumor. This post-AMF removal of cells was confirmed by histological examination and also by a reduced level of subsequent magnetic heating effect. Despite this evidence for an AMF-elicited response in the SPION-loaded MSCs, and in contrast to previous reports on tumor remission in immunocompetent mouse models, in this case, no significant differences were measured regarding the overall tumor size or growth characteristics. We discuss the implications of these results on the clinical delivery of hyperthermia therapy to tumors and on the possibility that a preferred therapeutic route may involve AMF as an adjuvant to an autologous immune response

Rapid microscale evaluation of the impact of fermentation conditions on inclusion body formation, solubilisation and protein refolding yields

Heterologous protein expression in E. coli can lead to the formation of dense insoluble aggregates named inclusion bodies (IB). The refolding of protein derived from IB is often characterised by low yields of active product. Process optimisation is often achieved empirically and requires significant resource and time efforts. Microscale experimentation may provide a valuable alternative by enabling representative process studies to be conducted early on in process development, using minimal quantities of product, parallel experimentation and automated liquid handling procedures. An automated robotic platform has been used to develop a dilution refold microscale process-screening tool with a set of hierarchical assays to rapidly determine optimal refolding conditions. The hierarchical orthogonal assays enable the simplest, cheapest and most generic high-throughput assays to first screen for a smaller subset of potentially high-yielding conditions. Absorbance can be used as an initial filter to measure particulate formation and fluorescence boundaries can then be used to select the conditions with the most native-like tertiary structure. The subset can then be analysed for native protein yield by slower, more expensive or protein specific assays, thus saving resources whilst maximising information output, alleviating the analytical bottleneck. This approach has been demonstrated in this work using lysozyme, with fluorescence boundaries to select 30% of highest yielding samples, and also with DHFR. An automated whole bioprocess sequence comprising fermentation, cell harvest and lysis, inclusion body harvest, denaturation and refolding has been developed at the microscale to study the effect of fermentation conditions on inclusion body yield and quality. The approach has been applied to dihydrofolate reductase (DHFR) and insulin, allowing a more thorough understanding of the effect of fermentation feeding, media and induction strategies on protein refolding yield and purity. This approach allowed yields of active insulin of increased from 10% to 68%. The results obtained from this approach have been compared to larger scales of operation, illustrating the challenges of scale-up. The process sequence, integrated with rapid analytical assays, provides a powerful tool for understanding the interaction between fermentation conditions and downstream processing yields, allowing a whole process approach to optimisation

In vivo assessment of a novel dual cell cancer therapy using conventional and novel cell tracking methods

Adoptive immunotherapy for cancer is a rapidly expanding field. Along with new techniques and technologies for cell engineering comes a pressing clinical need to discover the location of these cells after injection and to quantify the number of cells in a particular location. The use of agents to enhance tissue contrast is crucial to improve the ability of imaging techniques to distinguish cells from background signal, in order to track cells in vivo. Human donor T cells were transduced to express a tumour antigen specific T cell receptor. Transduced T cells were labeled with novel and conventional radiolabels for in vivo tracking using a combined single photon emission computed tomography and computed tomography (SPECT/CT) scanner. Transduced T cells were used in combination with TRAIL-expressing MSCs to produce a novel dual cell anti-cancer therapy in an in vivo lung metastases cancer model. The data in this thesis demonstrates that a novel tri-functional probe designed for long-term cell tracking, whilst resulting in superior cell labeling and retained activity over time compared with conventional methods, causes significant cell toxicity. It also demonstrates, for the first time, that a tumour antigen specific T cell therapy can be effective against lung metastases, leading to a significant reduction in tumour burden. These engineered T cells combined with MSC TRAIL also significantly reduce metastatic tumour burden, although there was no significant benefit to using the dual cell therapy

Magnetization transfer effects on the efficiency of flow-driven adiabatic fast passage inversion of arterial blood

Continuous arterial spin labeling experiments typically use flow-driven adiabatic fast passage inversion of the arterial blood water protons. In this article, we measure the effect of magnetization transfer in blood and how it affects the inversion label. We use modified Bloch equations to model flow-driven adiabatic inversion in the presence of magnetization transfer in blood flowing at velocities from 1 to 30 cm/s in order to explain our findings. Magnetization transfer results in a reduction of the inversion efficiency at the inversion plane of up to 3.65% in the range of velocities examined, as well as faster relaxation of the arterial label in continuous labeling experiments. The two effects combined can result in inversion efficiency reduction of up to 8.91% in the simulated range of velocities. These effects are strongly dependent on the velocity of the flowing blood, with 10 cm/s yielding the largest loss in efficiency due to magnetization transfer effects. Flowing blood phantom experiments confirmed faster relaxation of the inversion label than that predicted by T 1 decay alone. Copyright © 2007 John Wiley & Sons, Ltd.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/57383/1/1137_ftp.pd

ECPGR recommended simple sequence repeat loci for analyses of European plum (Prunus domestica) collections

A set of nine Simple Sequence Repeat (SSR) loci, approved by the ECPGR Prunus working group, are proposed as a standard set for genotyping European plum accessions. These loci show sufficient reliability in spite of problems caused by hexaploidy. Polymorphism in the loci is high and enables differentiation between unique plum accessions as well as analyses of genetic grouping and overall genetic structure. A set of seven reference accessions are described. A compiled dataset with allelic information for 165 accessions is presented. Genetic structure reveals three different K-values (2, 4 and 9) demonstrating a major dichotomy between Prunus insititia-related accessions and cultivars belonging to Prunus domestica sensu stricto, as well as differentiation among minor subgroups defined by pomological traits and geographical origin

Hyperthermia treatment of tumors by mesenchymal stem cell-delivered superparamagnetic iron oxide nanoparticles

Magnetic hyperthermia – a potential cancer treatment in which superparamagnetic iron oxide nanoparticles (SPIONs) are made to resonantly respond to an alternating magnetic field (AMF) and thereby produce heat – is of significant current interest. We have previously shown that mesenchymal stem cells (MSCs) can be labeled with SPIONs with no effect on cell proliferation or survival and that within an hour of systemic administration, they migrate to and integrate into tumors in vivo. Here, we report on some longer term (up to 3 weeks) post-integration characteristics of magnetically labeled human MSCs in an immunocompromized mouse model. We initially assessed how the size and coating of SPIONs dictated the loading capacity and cellular heating of MSCs. Ferucarbotran® was the best of those tested, having the best like-for-like heating capability and being the only one to retain that capability after cell internalization. A mouse model was created by subcutaneous flank injection of a combination of 0.5 million Ferucarbotran-loaded MSCs and 1.0 million OVCAR-3 ovarian tumor cells. After 2 weeks, the tumors reached ~100 µL in volume and then entered a rapid growth phase over the third week to reach ~300 µL. In the control mice that received no AMF treatment, magnetic resonance imaging (MRI) data showed that the labeled MSCs were both incorporated into and retained within the tumors over the entire 3-week period. In the AMF-treated mice, heat increases of ~4°C were observed during the first application, after which MRI indicated a loss of negative contrast, suggesting that the MSCs had died and been cleared from the tumor. This post-AMF removal of cells was confirmed by histological examination and also by a reduced level of subsequent magnetic heating effect. Despite this evidence for an AMF-elicited response in the SPION-loaded MSCs, and in contrast to previous reports on tumor remission in immunocompetent mouse models, in this case, no significant differences were measured regarding the overall tumor size or growth characteristics. We discuss the implications of these results on the clinical delivery of hyperthermia therapy to tumors and on the possibility that a preferred therapeutic route may involve AMF as an adjuvant to an autologous immune response

Pseudorandom Selective Excitation in NMR

In this work, average Hamiltonian theory is used to study selective excitation in a spin-1/2 system evolving under a series of small flip-angle $\theta-$pulses $(\theta\ll 1)$ that are applied either periodically [which corresponds to the DANTE pulse sequence] or aperiodically. First, an average Hamiltonian description of the DANTE pulse sequence is developed; such a description is determined to be valid either at or very far from the DANTE resonance frequencies, which are simply integer multiples of the inverse of the interpulse delay. For aperiodic excitation schemes where the interpulse delays are chosen pseudorandomly, a single resonance can be selectively excited if the $\theta$-pulses' phases are modulated in concert with the time delays. Such a selective pulse is termed a pseudorandom-DANTE or p-DANTE sequence, and the conditions in which an average Hamiltonian description of p-DANTE is found to be similar to that found for the DANTE sequence. It is also shown that averaging over different p-DANTE sequences that are selective for the same resonance can help reduce excitations at frequencies away from the resonance frequency, thereby improving the apparent selectivity of the p-DANTE sequences. Finally, experimental demonstrations of p-DANTE sequences and comparisons with theory are presented.Comment: 23 pages, 8 figure