Multi-parametric MRI can detect enhanced myelination in the Gli1 -/- mouse brain.

Purpose: The ability of MRI-based markers to detect myelin in the brain is limited. This study investigated the potential of combining multiple MRI markers, each targeting distinct myelin properties, to improve myelin characterization. Methods: We acquired ex vivo multiparametric MRI data at 7 Tesla from control and Gli1 -/- mouse brains at postnatal day 10 (P10), which exhibits enhanced myelination in the corpus callosum, followed by myelin basic protein (MBP) stained immunohistochemistry. Results: Although most MRI markers included in this study showed significant differences in the corpus callosum between control and Gli1 -/- , only fractional anisotropy (FA), mean diffusivity (MD), and T 2 had strong correlations with MBP signals. Partial least square regression (PSLR) based on MRI and MBP values from white matter regions suggested that T 2 had the highest contributions to myelin estimation. When both white and gray matter regions were included, inhomogeneous MT ratio and FA showed strong contributions. Conclusion: This study demonstrates the efficacy of multi-parametric MRI in detecting enhanced myelination in the Gli1 -/- mouse brain. T 2 and diffusion MRI parameters showed strong correlation with MBP signals in the genu of the corpus callosum at P10. The contribution of individual MRI parameter for detecting myelin can be evaluated using PLSR.

Using mesoscopic tract-tracing data to guide the estimation of fiber orientation distributions in the mouse brain from diffusion MRI.

Diffusion MRI (dMRI) tractography is the only tool for non-invasive mapping of macroscopic structural connectivity over the entire brain. Although it has been successfully used to reconstruct large white matter tracts in the human and animal brains, the sensitivity and specificity of dMRI tractography remained limited. In particular, the fiber orientation distributions (FODs) estimated from dMRI signals, key to tractography, may deviate from histologically measured fiber orientation in crossing fibers and gray matter regions. In this study, we demonstrated that a deep learning network, trained using mesoscopic tract-tracing data from the Allen Mouse Brain Connectivity Atlas, was able to improve the estimation of FODs from mouse brain dMRI data. Tractography results based on the network generated FODs showed improved specificity while maintaining sensitivity comparable to results based on FOD estimated using a conventional spherical deconvolution method. Our result is a proof-of-concept of how mesoscale tract-tracing data can guide dMRI tractography and enhance our ability to characterize brain connectivity.

Virtual mouse brain histology from multi-contrast MRI via deep learning.

1H MRI maps brain structure and function non-invasively through versatile contrasts that exploit inhomogeneity in tissue micro-environments. Inferring histopathological information from magnetic resonance imaging (MRI) findings, however, remains challenging due to absence of direct links between MRI signals and cellular structures. Here, we show that deep convolutional neural networks, developed using co-registered multi-contrast MRI and histological data of the mouse brain, can estimate histological staining intensity directly from MRI signals at each voxel. The results provide three-dimensional maps of axons and myelin with tissue contrasts that closely mimic target histology and enhanced sensitivity and specificity compared to conventional MRI markers. Furthermore, the relative contribution of each MRI contrast within the networks can be used to optimize multi-contrast MRI acquisition. We anticipate our method to be a starting point for translation of MRI results into easy-to-understand virtual histology for neurobiologists and provide resources for validating novel MRI techniques.

Nanostructure-specific X-ray tomography reveals myelin levels, integrity and axon orientations in mouse and human nervous tissue.

Myelin insulates neuronal axons and enables fast signal transmission, constituting a key component of brain development, aging and disease. Yet, myelin-specific imaging of macroscopic samples remains a challenge. Here, we exploit myelin's nanostructural periodicity, and use small-angle X-ray scattering tensor tomography (SAXS-TT) to simultaneously quantify myelin levels, nanostructural integrity and axon orientations in nervous tissue. Proof-of-principle is demonstrated in whole mouse brain, mouse spinal cord and human white and gray matter samples. Outcomes are validated by 2D/3D histology and compared to MRI measurements sensitive to myelin and axon orientations. Specificity to nanostructure is exemplified by concomitantly imaging different myelin types with distinct periodicities. Finally, we illustrate the method's sensitivity towards myelin-related diseases by quantifying myelin alterations in dysmyelinated mouse brain. This non-destructive, stain-free molecular imaging approach enables quantitative studies of myelination within and across samples during development, aging, disease and treatment, and is applicable to other ordered biomolecules or nanostructures.

Early life stress causes sex-specific changes in adult fronto-limbic connectivity that differentially drive learning.

It is currently unclear whether early life stress (ELS) affects males and females differently. However, a growing body of work has shown that sex moderates responses to stress and injury, with important insights into sex-specific mechanisms provided by work in rodents. Unfortunately, most of the ELS studies in rodents were conducted only in males, a bias that is particularly notable in translational work that has used human imaging. Here we examine the effects of unpredictable postnatal stress (UPS), a mouse model of complex ELS, using high resolution diffusion magnetic resonance imaging. We show that UPS induces several neuroanatomical alterations that were seen in both sexes and resemble those reported in humans. In contrast, exposure to UPS induced fronto-limbic hyper-connectivity in males, but either no change or hypoconnectivity in females. Moderated-mediation analysis found that these sex-specific changes are likely to alter contextual freezing behavior in males but not in females.

On the Origins of Diffusion MRI Signal Changes in Stroke.

Magnetic resonance imaging (MRI) is a leading diagnostic technique especially for neurological studies. However, the physical origin of the hyperintense signal seen in MR images of stroke immediately after ischemic onset in the brain has been a matter of debate since it was first demonstrated in 1990. In this article, we hypothesize and provide evidence that changes in the glial cells, comprising roughly one-half of the brain's cells and therefore a significant share of its volume, accompanying ischemia, are the root cause of the MRI signal change. Indeed, a primary function of the glial cells is osmoregulation in order to maintain homeostasis in the neurons and nerve fibers for accurate and consistent function. This realization also impacts our understanding of signal changes in other tissues following ischemia. We anticipate that this paradigm shift will facilitate new and improved models of MRI signals in tissues, which will, in turn, impact clinical utility.

A Growth-Promoting Bacteria, Paenibacillus yonginensis DCY84T Enhanced Salt Stress Tolerance by Activating Defense-Related Systems in Panax ginseng.

Panax ginseng (C.A. Mayer) is a well-known medicinal plant used in traditional medicine in Korea that experiences serious salinity stress related to weather changes or incorrect fertilizer application. In ginseng, the use of Paenibacillus yonginensis DCY84T to improve salt stress tolerance has not been thoroughly explored. Therefore, we studied the role of P. yonginensis DCY84T under short-term and long-term salinity stress conditions in a controlled environment. In vitro testing of DCY84T revealed high indole acetic acid (IAA) production, siderophore formation, phosphate solubilization and anti-bacterial activity. We determined that 10-min dip in 1010 CFU/ml DCY84T was sufficient to protect ginseng against short-term salinity stress (osmotic stress) upon exposure to 300 mM NaCl treatment by enhancing nutrient availability, synthesizing hydrolyzing enzymes and inducing osmolyte production. Upon exposure to salinity stress (oxidative and ionic stress), strain DCY84T-primed ginseng seedlings were protected by the induction of defense-related systems such as ion transport, ROS scavenging enzymes, proline content, total sugars, and ABA biosynthetic genes, as well as genes involved in root hair formation. Additionally, ginseng primed with DCY84T and exposed to 300 mM NaCl showed the same metabolite profile as control ginseng plants, suggesting that DCY84T effectively reduced salt stress. These results indicated that DCY84T can be widely used as a microbial inoculant to protect ginseng plants against salinity stress conditions.

Comprehensive Secondary Metabolite Profiling Toward Delineating the Solid and Submerged-State Fermentation of Aspergillus oryzae KCCM 12698.

Aspergillus oryzae has been commonly used to make koji, meju, and soy sauce in traditional food fermentation industries. However, the metabolic behaviors of A. oryzae during fermentation in various culture environments are largely uncharacterized. Thus, we performed time resolved (0, 4, 8, 12, 16 day) secondary metabolite profiling for A. oryzae KCCM 12698 cultivated on malt extract agar and broth (MEA and MEB) under solid-state fermentation (SSF) and submerged fermentation (SmF) conditions using the ultrahigh performance liquid chromatography-linear trap quadrupole-ion trap-mass spectrometry (UHPLC-LTQ-IT-MS/MS) followed by multivariate analyses. We observed the relatively higher proportions of coumarins and oxylipins in SSF, whereas the terpenoids were abundant in SmF. Moreover, we investigated the antimicrobial efficacy of metabolites that were extracted from SSF and SmF. The SSF extracts showed higher antimicrobial activities as compared to SmF, with higher production rates of bioactive secondary metabolites viz., ketone-citreoisocoumarin, pentahydroxy-anthraquinone, hexylitaconic acid, oxylipins, and saturated fatty acids. The current study provides the underpinnings of a metabolomic framework regarding the growth and bioactive compound production for A. oryzae under the primarily employed industrial cultivation states. Furthermore, the study holds the potentials for rapid screening and MS-characterization of metabolites helpful in determining the consumer safety implications of fermented foods involving Koji mold.

Volatiles Mediated Interactions Between Aspergillus oryzae Strains Modulate Morphological Transition and Exometabolomes.

Notwithstanding its mitosporic nature, an improbable morpho-transformation state i. e., sclerotial development (SD), is vaguely known in Aspergillus oryzae. Nevertheless an intriguing phenomenon governing mold's development and stress response, the effects of exogenous factors engendering SD, especially the volatile organic compounds (VOCs) mediated interactions (VMI) pervasive in microbial niches have largely remained unexplored. Herein, we examined the effects of intra-species VMI on SD in A. oryzae RIB 40, followed by comprehensive analyses of associated growth rates, pH alterations, biochemical phenotypes, and exometabolomes. We cultivated A. oryzae RIB 40 (S1VMI: KACC 44967) opposite a non-SD partner strain, A. oryzae (S2: KCCM 60345), conditioning VMI in a specially designed "twin plate assembly." Notably, SD in S1VMI was delayed relative to its non-conditioned control (S1) cultivated without partner strain (S2) in twin plate. Selectively evaluating A. oryzae RIB 40 (S1VMI vs. S1) for altered phenotypes concomitant to SD, we observed a marked disparity for corresponding growth rates (S1VMI < S1)7days, media pH (S1VMI > S1)7days, and biochemical characteristics viz., protease (S1VMI > S1)7days, amylase (S1VMI > nS1)3-7days , and antioxidants (S1VMI > S1)7days levels. The partial least squares-discriminant analysis (PLS-DA) of gas chromatography-time of flight-mass spectrometry (GC-TOF-MS) datasets for primary metabolites exhibited a clustered pattern (PLS1, 22.04%; PLS2, 11.36%), with 7 days incubated S1VMI extracts showed higher abundance of amino acids, sugars, and sugar alcohols with lower organic acids and fatty acids levels, relative to S1. Intriguingly, the higher amino acid and sugar alcohol levels were positively correlated with antioxidant activity, likely impeding SD in S1VMI. Further, the PLS-DA (PLS1, 18.11%; PLS2, 15.02%) based on liquid chromatography-mass spectrometry (LC-MS) datasets exhibited a notable disparity for post-SD (9-11 days) sample extracts with higher oxylipins and 13-desoxypaxilline levels in S1VMI relative to S1, intertwining Aspergillus morphogenesis and secondary metabolism. The analysis of VOCs for the 7 days incubated samples displayed considerably higher accumulation of C-8 compounds in the headspace of twin-plate experimental sets (S1VMI:S2) compared to those in non-conditioned controls (S1 and S2-without respective partner strains), potentially triggering altered morpho-transformation and concurring biochemical as well as metabolic states in molds.

Magnetic Resonance Microscopy (MRM) of Single Mammalian Myofibers and Myonuclei.

Recently, the first magnetic resonance microscopy (MRM) images at the cellular level in isolated mammalian brain tissues were obtained using microsurface coils. These methods can elucidate the cellular origins of MR signals and describe how these signals change over the course of disease progression and therapy. In this work, we explore the capability of these microimaging techniques to visualize mouse muscle fibers and their nuclei. Isolated myofibers expressing lacZ were imaged with and without a stain for ß-galactosidase activity (S-Gal + ferric ammonium citrate) that produces both optical and MR contrast. We found that MRM can be used to image single myofibers with 6-µm resolution. The ability to image single myofibers will serve as a valuable tool to study MR properties attributed to healthy and myopathic cells. The ability to image nuclei tagged with MR/Optical gene markers may also find wide use in cell lineage MRI studies.

Perplexing Metabolomes in Fungal-Insect Trophic Interactions: A Terra Incognita of Mycobiocontrol Mechanisms.

The trophic interactions of entomopathogenic fungi in different ecological niches viz., soil, plants, or insect themselves are effectively regulated by their maneuvered metabolomes and the plethora of metabotypes. In this article, we discuss a holistic framework of co-evolutionary metabolomes and metabotypes to model the interactions of biocontrol fungi especially with mycosed insects. Conventionally, the studies involving fungal biocontrol mechanisms are reported in the context of much aggrandized fungal entomotoxins while the adaptive response mechanisms of host insects are relatively overlooked. The present review asserts that the selective pressure exerted among the competing or interacting species drives alterations in their overall metabolomes which ultimately implicates in corresponding metabotypes. Quintessentially, metabolomics offers a most generic and tractable model to assess the fungal-insect antagonism in terms of interaction biomarkers, biosynthetic pathway plasticity, and their co-evolutionary defense. The fungi chiefly rely on a battery of entomotoxins viz., secondary metabolites falling in the categories of NRP's (non-ribosomal peptides), PK's (polyketides), lysine derive alkaloids, and terpenoids. On the contrary, insects overcome mycosis through employing different layers of immunity manifested as altered metabotypes (phenoloxidase activity) and overall metabolomes viz., carbohydrates, lipids, fatty acids, amino acids, and eicosanoids. Here, we discuss the recent findings within conventional premise of fungal entomotoxicity and the evolution of truculent immune response among host insect. The metabolomic frameworks for fungal-insect interaction can potentially transmogrify our current comprehensions of biocontrol mechanisms to develop the hypervirulent biocontrol strains with least environmental concerns. Moreover, the interaction metabolomics (interactome) in complementation with other -omics cascades could further be applied to address the fundamental bottlenecks of adaptive co-evolution among biological species.

Outcome after cementless total hip arthroplasty for arthritic hip in patients with residual poliomyelitis: a case series.

PURPOSE: In this case series, we investigated the outcome of cementless total hip arthroplasty (THA) for advanced hip osteoarthritis in patients with residual poliomyelitis to evaluate its clinical usefulness for these patients. METHODS: 11 unilateral cementless primary THA were performed to arthritic hips in patients with residual poliomyelitis. 7 were in paralytic and 4 were in nonparalytic limbs. The mean follow-up duration was 79.9 months. Retrospective clinical evaluations with various scores and radiological evaluations were made. RESULTS: Harris Hip Score, Western Ontario and McMaster Universities Arthritis Index (WOMAC) and Short-form (SF)-36 physical scales were significantly improved after the surgery. However, UCLA activity score and SF-36 mental scale were not. Because of remaining leg length discrepancies, all but 1 noted a residual limp. In nonparalytic hip, functional acetabular cup inclination during weight bearing significantly increased from installed inclination. Other than 1 case of posterior dislocation, no complications were observed. CONCLUSIONS: Although the overall result itself is excellent, THA for these patients cannot improve limp, physical activity and mental status. Surgeons should be aware of the change of the inclination of acetabular cup during mobilisation, especially for THA in contralateral hip.

Magnetic resonance microscopy of renal and biliary abnormalities in excised tissues from a mouse model of autosomal recessive polycystic kidney disease.

Polycystic kidney disease (PKD) is transmitted as either an autosomal dominant or recessive trait and is a major cause of renal failure and liver fibrosis. The cpk mouse model of autosomal recessive PKD (ARPKD) has been extensively characterized using standard histopathological techniques after euthanasia. In the current study, we sought to validate magnetic resonance microscopy (MRM) as a robust tool for assessing the ARPKD phenotype. We used MRM to evaluate the liver and kidney of wild-type and cpk animals at resolutions <100 µm and generated three-dimensional (3D) renderings for pathological evaluation. Our study demonstrates that MRM is an excellent method for evaluating the complex, 3D structural defects in this ARPKD mouse model. We found that MRM was equivalent to water displacement in assessing kidney volume. Additionally, using MRM we demonstrated for the first time that the cpk liver exhibits less extensive ductal arborization, that it was reduced in volume, and that the ductal volume was disproportionately smaller. Histopathology indicates that this is a consequence of bile duct malformation. With its reduced processing time, volumetric information, and 3D capabilities, MRM will be a useful tool for future in vivo and longitudinal studies of disease progression in ARPKD. In addition, MRM will provide a unique tool to determine whether the human disease shares the newly appreciated features of the murine biliary phenotype.

Investigation of the subcellular architecture of L7 neurons of Aplysia californica using magnetic resonance microscopy (MRM) at 7.8 microns.

Magnetic resonance microscopy (MRM) is a non-invasive diagnostic tool which is well-suited to directly resolve cellular structures in ex vivo and in vitro tissues without use of exogenous contrast agents. Recent advances in its capability to visualize mammalian cellular structure in intact tissues have reinvigorated analytical interest in aquatic cell models whose previous findings warrant up-to-date validation of subcellular components. Even if the sensitivity of MRM is less than other microscopic technologies, its strength lies in that it relies on the same image contrast mechanisms as clinical MRI which make it a unique tool for improving our ability to interpret human diagnostic imaging through high resolution studies of well-controlled biological model systems. Here, we investigate the subcellular MR signal characteristics of isolated cells of Aplysia californica at an in-plane resolution of 7.8 µm. In addition, direct correlation and positive identification of subcellular architecture in the cells is achieved through well-established histology. We hope this methodology will serve as the groundwork for studying pathophysiological changes through perturbation studies and allow for development of disease-specific cellular modeling tools. Such an approach promises to reveal the MR contrast changes underlying cellular mechanisms in various human diseases, for example in ischemic stroke.

Visualization of synaptic domains in the Drosophila brain by magnetic resonance microscopy at 10 micron isotropic resolution.

Understanding the complex architecture, connectivity, and pathology of the human brain is a major application of magnetic resonance imaging (MRI). However, the cellular basis of MR signal is still poorly understood. The advent of MR microscopy (MRM) enables imaging biological samples at cellular resolution, helping to interpret the nature of MR signal at the cellular level. In this regard, the small Drosophila brain can reveal key aspects of MR signal through the visualization of complex, intact neuronal structures in their native spatial arrangement. Applying state-of-the-art MR technology, we imaged fixed Drosophila heads at 10 µm isotropic resolution by two endogenously contrasted MRM sequences. The improved MRM sensitivity described here delivered the highest 3D resolution of an intact animal head reported so far. 3D fast low angle shot (FLASH) revealed strong signal in most internal tissues, particularly in the brain cortex, which contains the cell bodies of neurons and glia. Remarkably, 3D diffusion weighted imaging (DWI) delivered unprecedented contrast within the modular brain neuropil, revealing hyperintense signal in synapse-rich microdomains. Thus, the complex Drosophila brain revealed unknown features of FLASH and DWI with potential applications in characterizing the structure and pathology of the mammalian brain.

Magnetic resonance microscopy of mammalian neurons.

Magnetic resonance imaging (MRI) is now a leading diagnostic technique. As technology has improved, so has the spatial resolution achievable. In 1986 MR microscopy (MRM) was demonstrated with resolutions in the tens of micrometers, and is now an established subset of MRI with broad utility in biological and non-biological applications. To date, only large cells from plants or aquatic animals have been imaged with MRM limiting its applicability. Using newly developed microsurface coils and an improved slice preparation technique for correlative histology, we report here for the first time direct visualization of single neurons in the mammalian central nervous system (CNS) using native MR signal at a resolution of 4-8 microm. Thus MRM has matured into a viable complementary cellular imaging technique in mammalian tissues.