Recently, we reported a SOMAmer-based, highly multiplexed assay for the purpose of biomarker identification. To enable seamless transition from highly multiplexed biomarker discovery assays to a ...format suitable and convenient for diagnostic and life-science applications, we developed a streamlined, plate-based version of the assay. The plate-based version of the assay is robust, sensitive (sub-picomolar), rapid, can be highly multiplexed (upwards of 60 analytes), and fully automated. We demonstrate that quantification by microarray-based hybridization, Luminex bead-based methods, and qPCR are each compatible with our platform, further expanding the breadth of proteomic applications for a wide user community.
The cerebral cortex of humans and macaques has specialized regions for processing faces and other visual stimulus categories. It is unknown whether a similar functional organization exists in New ...World monkeys, such as the common marmoset (Callithrix jacchus), a species of growing interest as a primate model in neuroscience. To address this question, we measured selective neural responses in the brain of four awake marmosets trained to fix their gaze upon images of faces, bodies, objects, and control patterns. In two of the subjects, we measured high gamma-range field potentials from electrocorticography arrays implanted over a large portion of the occipital and inferotemporal cortex. In the other two subjects, we measured BOLD fMRI responses across the entire brain. Both techniques revealed robust, regionally specific patterns of category-selective neural responses. We report that at least six face-selective patches mark the occipitotemporal pathway of the marmoset, with the most anterior patches showing the strongest preference for faces over other stimuli. The similar appearance of these patches to previous findings in macaques and humans, including their apparent arrangement in two parallel pathways, suggests that core elements of the face processing network were present in the common anthropoid primate ancestor living ∼35 million years ago. The findings also identify the marmoset as a viable animal model system for studying specialized neural mechanisms related to high-level social visual perception in humans.
T1-weighted divided by T2-weighted (T1w/T2w) myelin maps were initially developed for neuroanatomical analyses such as identifying cortical areas, but they are increasingly used in statistical ...comparisons across individuals and groups with other variables of interest. Existing T1w/T2w myelin maps contain radiofrequency transmit field (B1+) biases, which may be correlated with these variables of interest, leading to potentially spurious results. Here we propose two empirical methods for correcting these transmit field biases using either explicit measures of the transmit field or alternatively a ‘pseudo-transmit’ approach that is highly correlated with the transmit field at 3T. We find that the resulting corrected T1w/T2w myelin maps are both better neuroanatomical measures (e.g., for use in cross-species comparisons), and more appropriate for statistical comparisons of relative T1w/T2w differences across individuals and groups (e.g., sex, age, or body-mass-index) within a consistently acquired study at 3T. We recommend that investigators who use the T1w/T2w approach for mapping cortical myelin use these B1+ transmit field corrected myelin maps going forward.
While algal phago-mixotrophs play a major role in aquatic microbial food webs, their diversity remains poorly understood. Recent studies have indicated several species of prasinophytes, early ...diverging green algae, to be able to consume bacteria for nutrition. To further explore the occurrence of phago-mixotrophy in green algae, we conducted feeding experiments with live fluorescently labeled bacteria stained with CellTracker Green CMFDA, heat-killed bacteria stained with 5-(4,6-dichlorotriazin-2-yl) aminofluorescein (DTAF), and magnetic beads. Feeding was detected via microscopy and/or flow cytometry in five strains of prasinophytes when provided with live bacteria: Pterosperma cristatum NIES626, Pyramimonas parkeae CCMP726, Pyramimonas parkeae NIES254, Nephroselmis pyriformis RCC618, and Dolichomastix tenuilepis CCMP3274. No feeding was detected when heat-killed bacteria or magnetic beads were provided, suggesting a strong preference for live prey in the strains tested. In parallel to experimental assays, green algal bacterivory was investigated using a gene-based prediction model. The predictions agreed with the experimental results and suggested bacterivory potential in additional green algae. Our observations underline the likelihood of widespread occurrence of phago-mixotrophy among green algae, while additionally highlighting potential biases introduced when using prey proxy to evaluate bacterial ingestion by algal cells.
The visual brain is composed of interconnected subcortical and cortical structures that receive and process image information originating in the retina. The visual system of nonhuman primates, in ...particular macaques, has been studied in great detail in order to elucidate principles of human sensation and perception. The common marmoset (Callithrix jacchus) is a small New World monkey of growing interest as a primate model for neuroscience. Marmosets have advantages over macaques because of their small size, lissencephalic cortex, and growing potential for viral and genetic manipulations. Previous anatomical studies and electrophysiological recordings in anesthetized marmosets have shown that this species’ cortical visual hierarchy closely resembles that of other primates, including humans. Until now, however, there have been no attempts to systematically study visual responses throughout the marmoset brain using fMRI. Here we show that awake marmosets readily learn to carry out a simple visual task inside the bore of an MRI scanner during functional mapping experiments. Functional scanning at 500μm in-plane resolution in a 30cm horizontal bore at 7T revealed robust positive blood oxygenation level-dependent (BOLD) fMRI responses to visual stimuli throughout visual cortex and associated subcortical areas. Nonvisual sensory areas showed negative contrasts to visual stimuli compared to the fixation dot only baseline. Structured images of objects and faces led to stronger responses than scrambled control images at stages beyond early visual cortex. Our study establishes fMRI mapping of visual responses in awake, behaving marmosets as a straightforward and valuable tool for assessing the functional organization of the primate brain at high resolution.
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•Awake, behaving marmosets were trained to perform visual tasks in an MRI scanner.•Anatomical regions of interest were registered to an MRI template.•Robust fMRI responses in both cortical and subcortical visual areas were obtained.•Higher visual areas responded better to structured than to scrambled visual stimuli.
The metal manganese is a potent magnetic resonance imaging (MRI) contrast agent that is essential in cell biology. Manganese-enhanced magnetic resonance imaging (MEMRI) is providing unique ...information in an ever-growing number of applications aimed at understanding the anatomy, the integration, and the function of neural circuits both in normal brain physiology as well as in translational models of brain disease. A major drawback to the use of manganese as a contrast agent, however, is its cellular toxicity. Therefore, paramount to the successful application of MEMRI is the ability to deliver Mn2+ to the site of interest using as low a dose as possible while preserving detectability by MRI. In the present work, the different approaches to MEMRI in translational neuroimaging are reviewed and challenges for future identified from a practical standpoint.
Imaging and postmortem studies into the severe mental illnesses of major depressive disorder (MDD), bipolar disorder (BD), and schizophrenia (SZ) have revealed deficiencies in the myelination of deep ...white matter tracts of the brain. Recent studies have further suggested that deficits could extend to myelinated fibers running through the cortex in those illnesses. Disruptions in this intracortical myelin may underlie functional symptomology in MDD, BD, and SZ; thus, in this study, we hypothesized that individuals with these illnesses may have reduced myelin staining relative to controls in the cerebral cortex. We stained 60 sections of dorsolateral prefrontal cortex for myelin with Luxol
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fast blue in four groups: 15 BD, 15 MDD, 15 SZ, and 15 controls with no psychiatric illness. We digitally measured optical tissue attenuation reflecting the amount of myelin staining across six cortical depths in the middle frontal gyrus (MFG), in superficial white matter in the crown of the MFG, and in deep white matter. We found that a diagnosis of MDD or SZ meant that optical tissue attenuation was significantly reduced in the shallowest depths of the cortex. Furthermore, there was a trend toward reduced optical tissue attenuation in all illnesses across all myelinated regions we studied. These results encourage future studies into potential reductions in intracortical myelin in severe mental illness.
Abstract
Age-related changes of intracortical myelin in bipolar disorder (BD) have been observed to deviate from the quadratic age curve observed in healthy controls (HC), but it is unclear if this ...holds at varying cortical depths. From BD (n = 44; age range = 17.6–45.5 years) and HC (n = 60; age range = 17.1–45.8 years) participants, we collected 3T T1-weighted (T1w) images with strong intracortical contrast. Signal values were sampled from 3 equivolume cortical depths. Linear mixed models were used to compare age-related changes in the T1w signal between depths and between groups at each depth. In HC, the age-related changes were significantly different between the superficial one-fourth depth and the deeper depths in the right ventral somatosensory (t = −4.63; FDRp = 0.00025), left dorsomedial somatosensory (t = −3.16; FDRp = 0.028), left rostral ventral premotor (t = −3.16; FDRp = 0.028), and right ventral inferior parietal cortex (t = −3.29; FDRp = 0.028). BD participants exhibited no differences in the age-related T1w signal between depths. Illness duration was negatively correlated with the T1w signal at the one-fourth depth in the right anterior cingulate cortex (rACC; rho = −0.50; FDRp = 0.029). Physiological age-related and depth-specific variation in the T1w signal were not observed in BD. The T1w signal in the rACC may reflect lifetime disease burden in the disorder.
Myeloarchitecture, the pattern of myelin density across the cerebral cortex, has long been visualized in histological sections to identify distinct anatomical areas of the cortex. In humans, ...two-dimensional (2D) magnetic resonance imaging (MRI) has been used to visualize myeloarchitecture in select areas of the cortex, such as the stripe of Gennari in the primary visual cortex and Heschl's gyrus in the primary auditory cortex. Here, we investigated the use of MRI contrast based on longitudinal relaxation time (T1) to visualize myeloarchitecture in vivo over the entire cortex of the common marmoset (Callithrix jacchus), a small non-human primate that is becoming increasingly important in neuroscience and neurobiology research. Using quantitative T1 mapping, we found that T1 at 7T in a cortical region with a high myelin content was 15% shorter than T1 in a region with a low myelin content. To maximize this T1 contrast for imaging cortical myelination patterns, we optimized a magnetization-prepared rapidly acquired gradient echo (MP-RAGE) sequence. In whole-brain, 3D T1-weighted images made in vivo with the sequence, we identified six major cortical areas with high myelination and confirmed the results with histological sections stained for myelin. We also identified several subtle features of myeloarchitecture, showing the sensitivity of our technique. The ability to image myeloarchitecture over the entire cortex may prove useful in studies of longitudinal changes of the topography of the cortex associated with development and neuronal plasticity, as well as for guiding and confirming the location of functional measurements.
Alterations in the myelination of the cerebral cortex may underlie abnormal cortical function in a variety of brain diseases. Here, we describe a technique for investigating changes in intracortical ...myelin in clinical populations on the basis of cortical thickness measurements with magnetic resonance imaging (MRI) at 3 Tesla. For this, we separately compute the thickness of the shallower, lightly myelinated portion of the cortex and its deeper, heavily myelinated portion (referred to herein as unmyelinated and myelinated cortex, respectively). Our expectation is that the thickness of the myelinated cortex will be a specific biomarker for disruptions in myeloarchitecture. We show representative atlases of total cortical thickness, T, unmyelinated cortical thickness, G, and myelinated cortical thickness, M, for a healthy group of 20 female subjects. We further demonstrate myelinated cortical thickness measurements in a preliminary clinical study of 10 bipolar disorder type-I subjects and 10 healthy controls, and report significant decreases in the middle frontal gyrus in T, G, and M in the disorder, with the largest percentage change occurring in M. This study highlights the potential of myelinated cortical thickness measurements for investigating intracortical myelin involvement in brain disease at clinically relevant field strengths and resolutions.
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