Nano-assemblies of cationic mPEG brush block copolymers with gadolinium polyoxotungstate [Gd(W5O18)2]9− form stable, high relaxivity MRI contrast agents

Polyoxometalates (POMs) incorporating paramagnetic ions, such as gadolinium, show promise as contrast agents for application in magnetic resonance imaging (MRI). Specifically, [Gd(W5O18)2]9− (denoted as GdWO) has been reported to have a higher relaxivity than commercially available contrast agents, but it's clinical utility has been limited by the intrinsic instability of POMs at physiological pH (7.4). In the current report we present a stability study on neat GdWO and nano-assemblies of block copolymers with GdWO in the pH range 5.0–7.4 to assess their suitability as MRI contrast agents. Neat GdWO only maintained structural stability between pH 5.4 and 6.4, and demonstrated poor MRI contrast at pH 7.4. To address this pH instability, GdWO was self-assembled with cationic mPEG brush block copolymers containing 20 or 40 units derived from the cationic monomer, 2-dimethylaminoethyl methacrylate (DMAEMA). Nano-assemblies with different charge ratios were synthesised and characterised according to their size, stability, contrasting properties and toxicity. The longitudinal relaxivity (r1) of the nano-assemblies was found to be dependent on the charge ratio, but not on the length of the cationic polymer block. Further investigation of PDMAEMA20 nano-assemblies demonstrated that they were stable over the pH range 5.0–7.4, exhibiting a higher r1 than either neat GdWO (2.77 s−1 mM−1) or clinical MRI contrast agent Gd-DTPA (4.1 s−1 mM−1) at pH 7.4. Importantly, the nano-assembly with the lowest charge ratio (0.2), showed the highest r1 (12.1 s−1 mM−1) whilst, stabilising GdWO over the pH range studied, eliciting low toxicity with MDA-MB231 cells

xQSM: Quantitative Susceptibility Mapping with Octave Convolutional and Noise Regularized Neural Networks

Quantitative susceptibility mapping (QSM) is a valuable magnetic resonance imaging (MRI) contrast mechanism that has demonstrated broad clinical applications. However, the image reconstruction of QSM is challenging due to its ill-posed dipole inversion process. In this study, a new deep learning method for QSM reconstruction, namely xQSM, was designed by introducing modified state-of-the-art octave convolutional layers into the U-net backbone. The xQSM method was compared with recentlyproposed U-net-based and conventional regularizationbased methods, using peak signal to noise ratio (PSNR), structural similarity (SSIM), and region-of-interest measurements. The results from a numerical phantom, a simulated human brain, four in vivo healthy human subjects, a multiple sclerosis patient, a glioblastoma patient, as well as a healthy mouse brain showed that the xQSM led to suppressed artifacts than the conventional methods, and enhanced susceptibility contrast, particularly in the ironrich deep grey matter region, than the original U-net, consistently. The xQSM method also substantially shortened the reconstruction time from minutes using conventional iterative methods to only a few seconds.Comment: 37 pages, 10 figures, 3 tabl

Neural mediators of subjective and autonomic responding during threat learning and regulation

Threat learning elicits robust changes across multiple affective domains, including changes in autonomic indices and subjective reports of fear and anxiety. It has been argued that the underlying causes of such changes may be dissociable at a neural level, but there is currently limited evidence to support this notion. To address this, we examined the neural mediators of trial-by-trial skin conductance responses (SCR), and subjective reports of anxious arousal and valence in participants (n = 27; 17 females) performing a threat reversal task during ultra-high field functional magnetic resonance imaging. This allowed us to identify brain mediators during initial threat learning and subsequent threat reversal. Significant neural mediators of anxious arousal during threat learning included the dorsal anterior cingulate, anterior insula cortex (AIC), and ventromedial prefrontal cortex (vmPFC), subcortical regions including the amygdala, ventral striatum, caudate and putamen, and brain-stem regions including the pons and midbrain. By comparison, autonomic changes (SCR) were mediated by a subset of regions embedded within this broader circuitry that included the caudate, putamen and thalamus, and two distinct clusters within the vmPFC. The neural mediators of subjective negative valence showed prominent effects in posterior cortical regions and, with the exception of the AIC, did not overlap with threat learning task effects. During threat reversal, positive mediators of both subjective anxious arousal and valence mapped to the default mode network; this included the vmPFC, posterior cingulate, temporoparietal junction, and angular gyrus. Decreased SCR during threat reversal was positively mediated by regions including the mid cingulate, AIC, two sub-regions of vmPFC, the thalamus, and the hippocampus. Our findings add novel evidence to support distinct underlying neural processes facilitating autonomic and subjective responding during threat learning and threat reversal. The results suggest that the brain systems engaged in threat learning mostly capture the subjective (anxious arousal) nature of the learning process, and that appropriate responding during threat reversal is facilitated by participants engaging self- and valence-based processes. Autonomic changes (SCR) appear to involve distinct facilitatory and regulatory contributions of vmPFC sub-regions

Intratumoral injection of BCNU in ethanol (DTI-015) results in enhanced delivery to tumor – a pharmacokinetic study

Solvent facilitated perfusion (SFP) has been proposed as a technique to increase the delivery of chemotherapeutic agents to tumors. SFP entails direct injection of the agent into the tumor in a water-miscible organic solvent, and because the solvent moves easily through both aqueous solutions and cellular membranes it drives the penetration of the solubilized anticancer agent throughout the tumor. To test this hypothesis, we compared the pharmacokinetics (PK) of 14 C-labeled 1,3-bis-chlorethyl-1-nitrosourea (BCNU) in intra-cerebral 9L rat gliomas after intravenous (IV) infusion in 90% saline –10% ethanol or direct intratumoral (IT) injection of 14 C-BCNU in 100% ethanol (DTI-015). Treatment with DTI-015 yielded a peak radioactive count (Cmax) for the 14 C label that was 100–1000 fold higher in the tumor than in all other tissues in addition to a concentration in the tumor that was 100-fold higher than that achieved following IV infusion of 14 C-BCNU. Pathologic and auto-radiographic analysis of tissue sections following IT injection of 14 C-BCNU in ethanol into either tumor or normal rat brain revealed both an enhanced local volume of distribution and an increased concentration of BCNU delivered to tumor compared to non-tumor bearing brain. To investigate the mechanism behind the SFP of BCNU to the tumor both dynamic contrast and perfusion MRI were performed on 9L tumors before and after treatment and demonstrated a decrease in tumor perfusion following IT injection of DTI-015. Finally, initial PK of patient blood samples following administration of DTI-015 into relapsed high-grade glioma indicated a 20-fold decrease in systemic exposure to BCNU compared to IV infusion of BCNU providing further evidence for the enhanced therapeutic ratio observed for DTI-015.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/45396/1/11060_2004_Article_5675.pd

Alterations in dorsal and ventral posterior cingulate connectivity in APOE ε4 carriers at risk of Alzheimer's disease

Background Recent evidence suggests that exercise plays a role in cognition and that the posterior cingulate cortex (PCC) can be divided into dorsal and ventral subregions based on distinct connectivity patterns. Aims To examine the effect of physical activity and division of the PCC on brain functional connectivity measures in subjective memory complainers (SMC) carrying the epsilon 4 allele of apolipoprotein E (APOE 4) allele. Method Participants were 22 SMC carrying the APOE ɛ4 allele (ɛ4+; mean age 72.18 years) and 58 SMC non-carriers (ɛ4–; mean age 72.79 years). Connectivity of four dorsal and ventral seeds was examined. Relationships between PCC connectivity and physical activity measures were explored. Results ɛ4+ individuals showed increased connectivity between the dorsal PCC and dorsolateral prefrontal cortex, and the ventral PCC and supplementary motor area (SMA). Greater levels of physical activity correlated with the magnitude of ventral PCC–SMA connectivity. Conclusions The results provide the first evidence that ɛ4+ individuals at increased risk of cognitive decline show distinct alterations in dorsal and ventral PCC functional connectivity

Train Smart Study: protocol for a randomised trial investigating the role of exercise training dose on markers of brain health in sedentary middle-aged adults

Introduction Regular aerobic exercise is associated with improved cognitive function, implicating it as a strategy to reduce dementia risk. This is reinforced by the association between greater cardiorespiratory fitness and larger brain volume, superior cognitive performance and lower dementia risk. However, the optimal aerobic exercise dose, namely the intensity and mode of delivery, to improve brain health and lower dementia risk has received less attention. We aim to determine the effect of different doses of aerobic exercise training on markers of brain health in sedentary middle-aged adults, hypothesising that high-intensity interval training (HIIT) will be more beneficial than moderate-intensity continuous training (MICT). Methods and analysis In this two-group parallel, open-label blinded endpoint randomised trial, 70 sedentary middle-aged (45-65 years) adults will be randomly allocated to one of two 12-week aerobic exercise training interventions matched for total exercise training volume: (1) MICT (n=35) or HIIT (n=35). Participants will perform ∼50 min exercise training sessions, 3 days per week, for 12 weeks. The primary outcome will be measured as between-group difference in cardiorespiratory fitness (peak oxygen uptake) change from baseline to the end of training. Secondary outcomes include between-group differences in cognitive function and ultra-high field MRI (7T) measured markers of brain health (brain blood flow, cerebrovascular function, brain volume, white matter microstructural integrity and resting state functional brain activity) changes from baseline to the end of training. Ethics and dissemination The Victoria University Human Research Ethics Committee (VUHREC) has approved this study (HRE20178), and all protocol modifications will be communicated to the relevant parties (eg, VUHREC, trial registry). Findings from this study will be disseminated via peer-review publications, conference presentations, clinical communications and both mainstream and social media. Trial registration number ANZCTR12621000144819

Non-Opsonic Phagocytosis of Legionella pneumophila by Macrophages Is Mediated by Phosphatidylinositol 3-Kinase

Background: Legionella pneumophila, is an intracellular pathogen that causes Legionnaires ’ disease in humans, a potentially lethal pneumonia. L. pneumophila has the ability to enter and replicate in the host and is essential for pathogenesis. Methodology/Principal Findings: Phagocytosis was measured by cell invasion assays. Construction of PI3K mutant by PCR cloning and expression of dominant negative mutant was detected by Western blot. PI3K activity was measured by 32 P labeling and detection of phospholipids products by thin layer chromatography. Infection of macrophages with virulent L. pneumophila stimulated the formation of phosphatidylinositol 3-phosphate (PIP3), a phosphorylated lipid product of PI3K whereas two structurally distinct phosphatidylinositol 3 kinase (PI3K) inhibitors, wortmannin and LY294002, reduced L. pneumophila entry into macrophages in a dose-dependent fashion. Furthermore, PI3K activation led to Akt stimulation, a serine/threonine kinase, which was also inhibited by wortmannin and LY294002. In contrast, PI3K and protein kinase B (PKB/Akt) activities were lower in macrophages infected with an avirulent bacterial strain. Only virulent L. pneumophila increased lipid kinase activity present in immunoprecipitates of the p85a subunit of class I PI3K and tyrosine phosphorylated proteins. In addition, macrophages expressing a specific dominant negative mutant of PI3K reduced L. pneumophila entry into these cells. Conclusion/Significance: Entry of L. pneumophila is mediated by PI3K/Akt signaling pathway. These results suggest an important role for PI3K and Akt in the L. pneumophila infection process. They point to possible novel strategies fo

Nano-assemblies of cationic mPEG brush block copolymers with gadolinium polyoxotungstate [Gd(W5O18)2]9− form stable, high relaxivity MRI contrast agents

Polyoxometalates (POMs) incorporating paramagnetic ions, such as gadolinium, show promise as contrast agents for application in magnetic resonance imaging (MRI). Specifically, [Gd(W5O18)2]9− (denoted as GdWO) has been reported to have a higher relaxivity than commercially available contrast agents, but it's clinical utility has been limited by the intrinsic instability of POMs at physiological pH (7.4). In the current report we present a stability study on neat GdWO and nano-assemblies of block copolymers with GdWO in the pH range 5.0–7.4 to assess their suitability as MRI contrast agents. Neat GdWO only maintained structural stability between pH 5.4 and 6.4, and demonstrated poor MRI contrast at pH 7.4. To address this pH instability, GdWO was self-assembled with cationic mPEG brush block copolymers containing 20 or 40 units derived from the cationic monomer, 2-dimethylaminoethyl methacrylate (DMAEMA). Nano-assemblies with different charge ratios were synthesised and characterised according to their size, stability, contrasting properties and toxicity. The longitudinal relaxivity (r1) of the nano-assemblies was found to be dependent on the charge ratio, but not on the length of the cationic polymer block. Further investigation of PDMAEMA20 nano-assemblies demonstrated that they were stable over the pH range 5.0–7.4, exhibiting a higher r1 than either neat GdWO (2.77 s−1 mM−1) or clinical MRI contrast agent Gd-DTPA (4.1 s−1 mM−1) at pH 7.4. Importantly, the nano-assembly with the lowest charge ratio (0.2), showed the highest r1 (12.1 s−1 mM−1) whilst, stabilising GdWO over the pH range studied, eliciting low toxicity with MDA-MB231 cells

Diffusion Magnetic Resonance Imaging: An Imaging Treatment Response Biomarker to Chemoradiotherapy in a Mouse Model of Squamous Cell Cancer of the Head and Neck1

For the treatment of squamous cell cancer of the head and neck (SCCHN), the assessment of treatment response is traditionally accomplished by volumetric measurements and has been suggested to be prognostic for an eventual response to treatment. An early evaluation response during the course of radiation therapy could provide an opportunity to tailor treatment to individual patients. Diffusion magnetic resonance imaging (MRI) allows for the quantification of tissue water diffusion values, thus treatment-induced loss of tumor cells will result in the increase in water mobility at the microscopic level, which can be detected as an increase in tumor diffusion values before any volumetric changes occur. We evaluated the use of diffusion MRI as an imaging biomarker of treatment response in an orthotopic mouse model of SCCHN. Mice with murine squamous cells expressing the yeast transgene cytosine deaminase were treated with 5-fluorocytosine (5FC), ionizing radiation, and combined therapy and were compared with control animals both during and after treatment for changes in tumor volumes, diffusion values, and survival. Radiation therapy had minimal effect on volumetric growth rate, diffusion, or survival. Although 5FC and combination treatment resulted in similar reductions in tumor volumes, the combination treatment elicited a much greater increase in tumor diffusion values, which correlated with improved survival. Thus, diffusion MRI as an imaging biomarker has a potential for early evaluation of the response to chemoradiation treatment in SCCHN