Effects of hypotonic stress and ouabain on the apparent diffusion coefficient of water at cellular and tissue levels in Aplysia.

There is evidence that physiological or pathological cell swelling is associated with a decrease of the apparent diffusion coefficient (ADC) of water in tissues, as measured with MRI. However the mechanism remains unclear. Magnetic resonance microscopy, performed on small tissue samples, has the potential to distinguish effects occurring at cellular and tissue levels. A three-dimensional diffusion prepared fast imaging with steady-state free precession sequence for MR microscopy was implemented on a 17.2 T imaging system and used to investigate the effect of two biological challenges known to cause cell swelling, exposure to a hypotonic solution or to ouabain, on Aplysia nervous tissue. The ADC was measured inside isolated neuronal soma and in the region of cell bodies of the buccal ganglia. Both challenges resulted in an ADC increase inside isolated neuronal soma (+31 ± 24% and +30 ± 11%, respectively) and an ADC decrease at tissue level in the buccal ganglia (-12 ± 5% and -18 ± 8%, respectively). A scenario involving a layer of water molecules bound to the inflating cell membrane surface is proposed to reconcile this apparent discrepancy.

High precision vibration sectioning for 3D imaging of the whole central nervous system.

BACKGROUND: Imaging and reconstruction of the morphology of neurons within the entire central nervous system (CNS) is important for deciphering the neural circuitry and related brain functions. With combination of tissue clearing and light sheet microscopy, previous studies have imaged the mouse CNS at cellular resolution, while remaining single axons unresolvable due to the tradeoff between sample size and imaging resolution. This could be improved by sectioning the sample into thick slices and imaged with high resolution light sheet microscopy as described in our previous study. However, the achievable quality for 3D imaging of serial thick slices is often hindered by surface undulation and other artifacts introduced by sectioning and handling limitations. NEW METHODS: In order to improve the imaging quality for mouse CNS, we develop a high-performance vibratome system for sample sectioning and handling automation. The sectioning mechanism of the system was modeled theoretically and verified experimentally. The effects of process parameters and sample properties on sectioning accuracy were studied to optimize the sectioning outcome. The resultant imaging outcome was demonstrated on mouse samples. RESULTS: Our theoretical model of vibratome effectively depicts the relationship between the sample surface undulation errors and the sectioning parameters. With the guidance of the theoretical model, the vibratome is able to achieve a local surface undulation error of ±0.5 µm and a surface arithmetic mean deviation (Sa) of 220 nm for 300-µm-thick tissue slices. Imaging results of mouse CNS show the continuous sectioning capability of the vibratome. COMPARISON WITH EXISTING METHOD: Our automatic sectioning and handling system is able to process serial thick slices for 3D imaging of the whole CNS at a single-axon resolution, superior to the commercially available vibratome devices. CONCLUSION: Our automatic sectioning and handling system can be optimized to prepare thick sample slices with minimal surface undulation and manual manipulation in support of 3D brain mapping with high-throughput and high-accuracy.

Cranial MRI Abnormalities and Long-term Follow-up of the Lesions in 770 Girls With Central Precocious Puberty.

CONTEXT: Central precocious puberty (CPP) may arise from central nervous system (CNS) lesions in a few affected girls. Recently, the incidence of girls with CPP has increased mostly in 6-8 year olds, in whom the necessity of magnetic resonance imaging (MRI) is debated. OBJECTIVE: To investigate the frequency, long-term outcome and potential predictors of CNS lesions in a large cohort of girls with CPP. METHODS: A multicenter cohort of 770 Turkish girls with CPP who had systematic cranial MRI between 2005 and 2017. Age at puberty onset was <6 years in 116 and 6-8 years in 654. CNS lesions were followed until final decision(6.2 ± 3.1 years). Potential predictors of CNS lesions were evaluated by univariate analyses. RESULTS: A total of 104/770 (13.5%) girls had abnormal brain MRI. Of these, 2.8% were previously known CNS lesions, 3.8% had newly detected and causally related CNS lesions, 3.1 % were possibly, related and 3.8% were incidental. Only 2 (0.25%) neoplastic lesions (1 low grade glioma and 1 meningioma) were identified; neither required intervention over follow-up of 6 and 3.5 years respectively. Age at breast development <6 years (odds ratio [OR] 2.38; 95% CI 1.08-5.21) and the peak luteinizing hormone/follicle-stimulating hormone (LH/FSH) ratio >0.6 (OR 3.13; 95% CI 1.02-9.68) were significantly associated with CNS lesions. However, both patients with neoplastic lesions were >6 years old. CONCLUSION: Although age and LH/FSH ratio are significant predictors of CNS lesions, their predictive power is weak. Thus, systematic MRI seems to be the most efficient current approach to avoid missing an occult CNS lesion in girls with CPP, despite the low likelihood of finding a lesion requiring intervention.

Manganese-Enhanced Magnetic Resonance Imaging: Overview and Central Nervous System Applications With a Focus on Neurodegeneration.

Manganese-enhanced magnetic resonance imaging (MEMRI) rose to prominence in the 1990s as a sensitive approach to high contrast imaging. Following the discovery of manganese conductance through calcium-permeable channels, MEMRI applications expanded to include functional imaging in the central nervous system (CNS) and other body systems. MEMRI has since been employed in the investigation of physiology in many animal models and in humans. Here, we review historical perspectives that follow the evolution of applied MRI research into MEMRI with particular focus on its potential toxicity. Furthermore, we discuss the more current in vivo investigative uses of MEMRI in CNS investigations and the brief but decorated clinical usage of chelated manganese compound mangafodipir in humans.

Comparison of intravital thinned skull and cranial window approaches to study CNS immunobiology in the mouse cortex.

Fluorescent imaging coupled with high-resolution femto-second pulsed infrared lasers allows for interrogation of cellular interactions deeper in living tissues than ever imagined. Intra-vital imaging of the central nervous system (CNS) has provided insights into neuronal development, synaptic transmission, and even immune interactions. In this review we will discuss the two most common intravital approaches for studying the cerebral cortex in the live mouse brain for pre-clinical studies, the thinned skull and cranial window techniques, and focus on the advantages and drawbacks of each approach. In addition, we will discuss the use of neuronal physiologic parameters as determinants of successful surgical and imaging preparation.

Synthesis and biological evaluation of carbon-11 and fluorine-18 labeled tracers for in vivo visualization of PDE10A.

INTRODUCTION: In vivo visualization of PDE10A using PET provides a tool to evaluate the role of PDE10A in various neuropsychiatric diseases and can also be useful in the clinical evaluation of PDE10A inhibitor drug candidates. We evaluated several carbon-11 and fluorine-18 labeled PDE10A inhibitors as potential PDE10A PET radioligands. MATERIALS & METHODS: [(11)C]MP10, [(11)C]JNJ42071965 and four other tracers were developed. Their biodistribution was evaluated in rats. Rat plasma and brain radiometabolites were quantified. Baseline microPET imaging was performed in normal rats and PDE10A knockout (KO) and wild-type (WT) mice. Blocking and displacement studies were conducted. The selectivity of the tracer binding was further studied in an ex vivo autoradiography experiment in PDE10A KO and WT mice. RESULTS: Biodistribution showed brain uptake for all tracers in the striatum and wash-out from the cerebellum. [(11)C]1 ((11)C-MP10) had the highest specific uptake index (striatum (S) vs. cerebellum (C) ratios (S/C)-1) at 60 min (7.4). [(11)C]5 ([(11)C]JNJ42071965) had a high index at the early time points (1.0 and 3.7 at 2 and 30 min p.i., respectively). The affinity of [(11)C]4, [(18)F]3 and [(18)F]6 was too low to visualize PDE10A using microPET. [(11)C] 2 showed a specific binding, while kinetics of [(11)C]1 were too slow. [(11)C]5 reached equilibrium after 10 min (uptake index=1.2). Blocking and displacement experiments in rats and baseline imaging in PDE10A KO mice showed specific and reversible binding of [(11)C]5 to PDE10A. CONCLUSIONS: We successfully radiolabeled and evaluated six radiotracers for their potential to visualize PDE10A in vivo. While [(11)C]1 had the highest striatal specific uptake index, its slow kinetics likely compromise clinical use of this tracer. [(11)C]5 has a relatively high striatum-to-background ratio and fast kinetic profile, which makes it a valuable carbon-11 alternative.