Early detection of cerebrovascular pathology and protective antiviral immunity by MRI.

Central nervous system (CNS) infections are a major cause of human morbidity and mortality worldwide. Even patients that survive, CNS infections can have lasting neurological dysfunction resulting from immune and pathogen induced pathology. Developing approaches to noninvasively track pathology and immunity in the infected CNS is crucial for patient management and development of new therapeutics. Here, we develop novel MRI-based approaches to monitor virus-specific CD8+ T cells and their relationship to cerebrovascular pathology in the living brain. We studied a relevant murine model in which a neurotropic virus (vesicular stomatitis virus) was introduced intranasally and then entered the brain via olfactory sensory neurons - a route exploited by many pathogens in humans. Using T2*-weighted high-resolution MRI, we identified small cerebral microbleeds as an early form of pathology associated with viral entry into the brain. Mechanistically, these microbleeds occurred in the absence of peripheral immune cells and were associated with infection of vascular endothelial cells. We monitored the adaptive response to this infection by developing methods to iron label and track individual virus specific CD8+ T cells by MRI. Transferred antiviral T cells were detected in the brain within a day of infection and were able to reduce cerebral microbleeds. These data demonstrate the utility of MRI in detecting the earliest pathological events in the virally infected CNS as well as the therapeutic potential of antiviral T cells in mitigating this pathology.

The Peer Education Project to improve mental health literacy in secondary school students in England: a qualitative realist evaluation.

BACKGROUND: Worsening of adolescent mental health and exacerbated health inequalities after the COVID-19 pandemic calls for universal preventative strategies. The Mental Health Foundation's school-based Peer Education Project seeks to improve students' mental health literacy through peer educators (aged 14-18 years) teaching peer learners (aged 11-13 years) to recognise good and bad mental health, identify risk and protective factors, and seek help accordingly. Although previous before and after quantitative assessments have found the intervention to be effective, this realist evaluation aimed to qualitatively develop the theory of change, exploring how the mechanisms played out in different contexts to achieve the desired outcomes. METHODS: Our initial programme theory was developed following expert stakeholder consultation and reviewing the literature. We divided mechanisms into resources and reasoning to explain how the intervention components (ie, resources), experienced within specific contexts, engendered responses in the participants (ie, reasoning), to produce observable outcomes. Data collected from six purposively recruited schools in England comprised staff interviews (n=11), student focus groups (n=15), and observations (n=5). Deductive and inductive analysis was undertaken, using NVivo-informed multiple causal statements represented as context-mechanism-outcome configurations (CMOcs), to test and refine the programme theory. FINDINGS: We created several distinct CMOcs. For example, in learners accustomed to didactic teaching methods (context), conversing with educators having similar life experience (mechanism resource) endorsed and destigmatised help-seeking behaviour (mechanism reasoning) and facilitated a realisation that seeking help was appropriate and acceptable (outcome). Other mechanisms included the following: learners perceiving the information as tailored and relevant, educators feeling empowered, and a cultural shift percolating across the school. INTERPRETATION: Our findings show how peer education can work to improve mental health literacy, which will inform changes to the intervention to maximise its effectiveness in different operational contexts. Future research could test our theory of change in a randomised controlled trial, and examine impacts on inequalities in a more diverse sample. FUNDING: National Institute for Health and Care Research School for Public Health Research.

A process evaluation of a peer education project to improve mental health literacy in secondary school students: study protocol.

BACKGROUND: Emotional disorders in young people are increasing but studies have found that this age group do not always recognise the signs and symptoms of mental health problems in themselves or others. The Mental Health Foundation's school-based Peer Education Project (PEP) has the potential to improve young people's understanding of their own mental health at a critical developmental stage (early adolescence) using a peer teaching method. This study is a process evaluation to understand: the mechanisms through which PEP might improve young people's mental health literacy, any challenges with delivery, how the project can be embedded within wider school life and how it can be improved to be of most benefit to the widest number of young people. We will also validate a bespoke mental health literacy questionnaire, and test the feasibility of using it to measure outcomes in preparation for a future study evaluating effectiveness. METHODS: All schools recruited to the study will receive the PEP intervention. The process evaluation will be informed by realist evaluation approaches to build understanding regarding key mechanisms of change and the impact of different school contexts. The evaluation will test and revise an existing intervention logic model which has been developed in partnership with the Mental Health Foundation. Process evaluation data will be collected from newly recruited schools (n = 4) as well as current PEP user schools (n = 2) including training and lesson delivery observations, staff interviews and student focus groups. Baseline and follow-up data will be collected in all newly recruited intervention schools (n = 4) from all students in Year 7/8 (who receive the PEP) and recruited peer educators in Year 12 via a self-report survey. DISCUSSION: This study will enable us to refine the logic model underpinning the peer education project and identify areas of the intervention that can be improved. Findings will also inform the design of a future effectiveness study which will test out the extent to which PEP improves mental health literacy.

A hierarchy of manganese competition and entry in organotypic hippocampal slice cultures.

Contrast agents improve clinical and basic research MRI. The manganese ion (Mn2+ ) is an essential, endogenous metal found in cells and it enhances MRI contrast because of its paramagnetic properties. Manganese-enhanced MRI (MEMRI) has been widely used to image healthy and diseased states of the body and the brain in a variety of animal models. There has also been some work in translating the useful properties of MEMRI to humans. Mn2+ accumulates in brain regions with high neural activity and enters cells via voltage-dependent channels that flux calcium (Ca2+ ). In addition, metal transporters for zinc (Zn2+ ) and iron (Fe2+ ) can also transport Mn2+ . There is also transfer through channels specific for Mn2+ . Although Mn2+ accumulates in many tissues including brain, the mechanisms and preferences of its mode of entry into cells are not well characterized. The current study used MRI on living organotypic hippocampal slice cultures to detect which transport mechanisms are preferentially used by Mn2+ to enter cells. The use of slice culture overcomes the presence of the blood brain barrier, which limits inferences made with studies of the intact brain in vivo. A range of Mn2+ concentrations were used and their effects on neural activity were assessed to avoid using interfering doses of Mn2+ . Zn2+ and Fe2+ were the most efficient competitors for Mn2+ uptake into the cultured slices, while the presence of Ca2+ or Ca2+ channel antagonists had a more moderate effect. Reducing slice activity via excitatory receptor antagonists was also effective at lowering Mn2+ uptake. In conclusion, a hierarchy of those agents which influence Mn2+ uptake was established to enhance understanding of how Mn2+ enters cells in a cultured slice preparation.

From seeds to plasma: Confirmed exposure of multiple farmland bird species to clothianidin during sowing of winter cereals.

Neonicotinoids are the largest group of systemic insecticides worldwide and are most commonly applied as agricultural seed treatments. However, little is known about the extent to which farmland birds are exposed to these compounds during standard agricultural practices. This study uses winter cereal, treated with the neonicotinoid clothianidin, as a test system to examine patterns of exposure in farmland birds during a typical sowing period. The availability of neonicotinoid-treated seed was recorded post-sowing at 39 fields (25 farms), and camera traps were used to monitor seed consumption by wild birds in situ. The concentration of clothianidin in treated seeds and crop seedlings was measured via liquid chromatography-tandem mass spectrometry, and avian blood samples were collected from 11 species of farmland bird from a further six capture sites to quantify the prevalence and level of clothianidin exposure associated with seed treatments. Neonicotinoid-treated seeds were found on the soil surface at all but one of the fields surveyed at an average density of 2.8 seeds/m2. The concentration of clothianidin in seeds varied around the target application rate, whilst crop seedlings contained on average 5.9% of the clothianidin measured in seeds. Exposure was confirmed in 32% of bird species observed in treated fields and 50% of individual birds post-sowing; the median concentration recorded in positive samples was 12 ng/mL. Results here provide clear evidence that a variety of farmland birds are subject to neonicotinoid exposure following normal agricultural sowing of neonicotinoid-treated cereal seed. Furthermore, the widespread availability of seeds at the soil surface was identified as a primary source of exposure. Overall, these data are likely to have global implications for bird species and current agricultural policies where neonicotinoids are in use, and may be pertinent to any future risk assessments for systemic insecticide seed treatments.

Interhemispheric plasticity is mediated by maximal potentiation of callosal inputs.

Central or peripheral injury causes reorganization of the brain's connections and functions. A striking change observed after unilateral stroke or amputation is a recruitment of bilateral cortical responses to sensation or movement of the unaffected peripheral area. The mechanisms underlying this phenomenon are described in a mouse model of unilateral whisker deprivation. Stimulation of intact whiskers yields a bilateral blood-oxygen-level-dependent fMRI response in somatosensory barrel cortex. Whole-cell electrophysiology demonstrated that the intact barrel cortex selectively strengthens callosal synapses to layer 5 neurons in the deprived cortex. These synapses have larger AMPA receptor- and NMDA receptor-mediated events. These factors contribute to a maximally potentiated callosal synapse. This potentiation occludes long-term potentiation, which could be rescued, to some extent, with prior long-term depression induction. Excitability and excitation/inhibition balance were altered in a manner consistent with cell-specific callosal changes and support a shift in the overall state of the cortex. This is a demonstration of a cell-specific, synaptic mechanism underlying interhemispheric cortical reorganization.

Sensitivity Enhancement of an Inductively Coupled Local Detector Using a HEMT-Based Current Amplifier.

PURPOSE: To improve the signal transmission efficiency and sensitivity of a local detection coil that is weakly inductively coupled to a larger receive coil. METHODS: The resonant detection coil is connected in parallel with the gate of a high electron mobility transistor (HEMT) transistor without impedance matching. When the drain of the transistor is capacitively shunted to ground, current amplification occurs in the resonator by feedback that transforms a capacitive impedance on the transistor's source to a negative resistance on its gate. RESULTS: High resolution images were obtained from a mouse brain using a small, 11 mm diameter surface coil that was inductively coupled to a commercial, phased array chest coil. Although the power consumption of the amplifier was only 88 µW, 14 dB gain was obtained with excellent noise performance. CONCLUSION: An integrated current amplifier based on a HEMT can enhance the sensitivity of inductively coupled local detectors when weakly coupled. This amplifier enables efficient signal transmission between customized user coils and commercial clinical coils, without the need for a specialized signal interface. Magn Reson Med 75:2573-2578, 2016. Published 2015. This article is a U.S. Government work and is in the public domain in the USA.

Tracking the effects of crusher gradients on gradient-echo BOLD signal in space and time during rat sensory stimulation.

A unique method to map the effect of crusher gradients in space and time on the gradient echo blood oxygen level dependent (BOLD) signal is introduced. Using the Radial Correlation Contrast (RCC) analysis method, amplitude-RCC maps at different time segments and different gradient strengths were obtained. The ratio of amplitude-RCC cluster volumes, with and without crusher gradients, showed a temporal dependency with stronger volume reduction for stimulation-onset versus stimulation-decline. Aside from signal-to-noise ratio reduction in diffusion weighted images, the average temporal patterns were equal. Comparison of the data with and without crushers showed a stronger reduction in local coherence for stimulation-onset times. We hypothesize that the stimulation decline was weighted by extravascular effects originating in expanded veins due to their larger volume and long range susceptibility which couples neighboring voxels. The ratio of amplitude-RCC with and without crushers calculated for each voxel at each time segment yielded a spatial-temporal mapping of the crusher effect. These maps suggest that early stimulation-onset ( approximately 9 s) is weighted by flow; later a dynamic steady-state between intra- and extravascular effects is obtained. Stimulation-decline was dominated by extravascular effects, and at late stimulation decline as well as at early stimulation onset, clusters were small and localized to expected site of neuronal activity.

Observation of two distinct spatial-temporal BOLD clusters during sensory stimulation in rats.

Neuronal activity evokes changes in local CBF and CBV, whose spatial differences are not fully known. We use the Radial Correlation Contrast (RCC) analysis method with high spatial resolution 100 x 100 x 1000 microm3 data collected with an 11.7 T magnet to differentiate two spatial-temporal BOLD clusters during sensory rat forepaw stimulation and hypothesize that each corresponds to either the CBF or the CBV processes. One cluster, obtained during the time segment of stimulation onset, is characterized by a high positive BOLD signal whereas the other, obtained during the simulation decline time segment, is characterized by a lower positive signal and strong post stimulus undershoot. The average volume of stimulation onset clusters is embedded in the stimulation decline clusters with the latter significantly larger and shifted towards deeper cortical layers. Comparison of amplitude-RCC and cross-correlation analyses performed on equivalent time segments (30 s, 40 images) revealed no differences in cluster size or location, demonstrating that temporal locality is more important than spatial locality in distinguishing between stimulation onset and stimulation decline clusters. We hypothesize that clusters characterized by stimulation onset are highly weighted by local changes in CBF whereas clusters characterized by stimulation decline are more CBV weighted. Moreover, the data suggest that the locations of the highest CBF changes are distinct from the locations of the highest CBV changes. While the former located within stimulation decline clusters and its weight is gradually reduced towards cluster's periphery (mainly ventrally), the highest changes in CBV occur in the cluster's periphery with only modest changes towards its center.