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Multiple sclerosis (MS) is an autoimmune disease involving demyelination and axonal damage in the central nervous system (CNS). In this study, we investigated pathological changes in the lumbar spinal cord of C57BL/6 mice induced with progressive experimental autoimmune encephalomyelitis (EAE) disease using 9.4-T magnetic resonance imaging (MRI). Multiparametric MRI measurements including MR spectroscopy, diffusion tensor imaging (DTI) and volumetric analyses were applied to detect metabolic changes in the CNS of EAE mice. Compared with healthy mice, EAE mice showed a significant reduction in N-acetyl aspartate and increases in choline, glycine, taurine and lactate. DTI revealed a significant reduction in fractional anisotropy and axial diffusivity and an increase in radial diffusivity in the lumbar spinal cord white matter (WM), while in the grey matter (GM), fractional anisotropy increased. High-resolution structural imaging also revealed lumbar spinal cord WM hypertrophy and GM atrophy. Importantly, these MRI changes were strongly correlated with EAE disease scoring and pathological changes in the lumbar (L2-L6), particularly WM demyelination lesions and aggregation of immune cells (microglia/macrophages and astrocytes) in this region. This study identified changes in MRI biomarker signatures that can be useful for evaluating the efficacy of novel drugs using EAE models in vivo., (© 2023 The Authors. NMR in Biomedicine published by John Wiley & Sons Ltd.)

Several classes of cannabinoid receptor type 2 radioligands have been evaluated for imaging of neuroinflammation, with successful clinical translation yet to take place. Here we describe the synthesis of fluorinated 5-azaindoles and pharmacological characterization and in vivo evaluation of 18 F-radiolabeled analogues. [ 18 F] 2 (hCB2 K i = 96.5 nM) and [ 18 F] 9 (hCB2 K i = 7.7 nM) were prepared using Cu-mediated 18 F-fluorination with non-decay-corrected radiochemical yields of 15 ± 6% and 18 ± 2% over 85 and 80 min, respectively, with high radiochemical purities (>97%) and molar activities (140-416 GBq/μmol). In PET imaging studies in rats, both [ 18 F] 2 and [ 18 F] 9 demonstrated specific binding in CB2-rich spleen after pretreatment with CB2-specific GW405833. Moreover, [ 18 F] 9 exhibited higher brain uptake at later time points in a murine model of neuroinflammation compared with a healthy control group. The results suggest further evaluation of azaindole based CB2 radioligands is warranted in other neuroinflammation models.

Background: Descriptions of the radiological appearance of the craniovertebral ligaments often lack detail. This study aimed to provide an accurate description of the morphology and radiological appearance of the alar and cruciform ligaments with confirmation of findings by fine dissection., Materials and Methods: Six embalmed human cadaveric specimens were reduced to an osseoligamentous arrangement spanning the C2/3 disc to the occiput. Specimens were imaged on a 4.6T Bruker magnetic resonance (MR) system using a 3D RARE multiple SE sequence with acquisition time 18 h 24 min. Acquired images were viewed in three planes, and detailed descriptions and morphometric measurement of the ligaments were obtained. Specimens were then examined and described using fine dissection. Direct comparison of the descriptions of each method was undertaken., Results: From imaging, detailed features of all alar ligaments could be identified in all specimens. Consistency in shape, orientation, and attachments is described. Attachment to the medial aspect of the atlantooccipital joints was evident in all specimens. Five of six alar ligament pairs contained fibers that traversed the dens without attachment. Ascending cruciform ligaments could be clearly identified in four of six specimens. No descending cruciform ligaments could be clearly delineated. Detailed features of the transverse ligaments could be identified and described in all planes. Dissection findings were mostly consistent with descriptions obtained from MR images., Conclusion: 4.6T MR images provide accurate detail of the structure, dimensions, and attachments of the craniovertebral ligaments. The morphology of the craniovertebral ligaments assessed radiologically was consistent with findings on gross dissection., Competing Interests: There are no conflicts of interest., (Copyright: © 2022 Journal of Craniovertebral Junction and Spine.)

The developing brain is particularly vulnerable to foetal growth restriction (FGR) and abnormal neurodevelopment is common in the FGR infant ranging from behavioural and learning disorders to cerebral palsy. No treatment exists to protect the FGR newborn brain. Recent evidence suggests inflammation may play a key role in the mechanism responsible for the progression of brain impairment in the FGR newborn, including disruption to the neurovascular unit (NVU). We explored whether ibuprofen, an anti-inflammatory drug, could reduce NVU disruption and brain impairment in the FGR newborn. Using a preclinical FGR piglet model, ibuprofen was orally administered for 3 days from birth. FGR brains demonstrated a proinflammatory state, with changes to glial morphology (astrocytes and microglia), and blood-brain barrier disruption, assessed by IgG and albumin leakage into the brain parenchyma and a decrease in blood vessel density. Loss of interaction between astrocytic end-feet and blood vessels was evident where plasma protein leakage was present, suggestive of structural deficits to the NVU. T-cell infiltration was also evident in the parenchyma of FGR piglet brains. Ibuprofen treatment reduced the pro-inflammatory response in FGR piglets, reducing the number of activated microglia and enhancing astrocyte interaction with blood vessels. Ibuprofen also attenuated plasma protein leakage, regained astrocytic end-feet interaction around vessels, and decreased T-cell infiltration into the FGR brain. These findings suggest postnatal administration of ibuprofen modulates the inflammatory state, allowing for stronger interaction between vasculature and astrocytic end-feet to restore NVU integrity. Modulation of the NVU improves the FGR brain microenvironment and may be key to neuroprotection., (© 2021. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

Objectives: Pathophysiologic mechanisms underpinning ongoing pain in whiplash-associated disorder (WAD) are not well understood, however, alterations in brain morphology and function have been observed in this population and in other chronic pain conditions. This study investigated metabolite profiles of brain regions in people with chronic WAD compared with controls., Materials and Methods: Thirty-eight individuals with chronic WAD (mean [SD] age, 39.5 [11.3] years, 23 female individuals) and 16 pain-free controls (38.9 [12.7] years, 11 female individuals) underwent multivoxel brain magnetic resonance spectroscopy. At the anterior cingulate cortex (ACC), primary motor cortex (1MC), and somatosensory cortex (SSC), ratios of metabolite concentrations were calculated for N-acetylaspartate (NAA), creatine (Cr), choline (Cho), myo-inositol (Ins), and glutamate/glutamine (Glx). Chronic WAD group participants completed clinical questionnaires and cold and pressure pain threshold assessment. Data were analyzed with hypothesis testing and Spearman correlations (P≥0.05), with Benjamini-Hochberg corrections (5% false discovery rate)., Results: No group differences were observed for NAA:Cr, NAA:Cho, Cr:Cho, Glx:NAA, Glx:Cr, Glx:Cho, Ins:NAA, Ins:Cr, Ins:Cho or Ins:Glx for left or right ACC, 1MC, or SSC following correction for multiple comparisons. No significant correlations were observed between metabolite ratios and any clinical variable., Discussion: These results suggest that ongoing pain and disability in this population may not be underpinned by metabolite aberrations in the brain regions examined. Further research is required to progress our understanding of cortical contributions to neurophysiologic mechanisms in chronic WAD.

Purpose: The aim of this work was to identify whether biochemical and physiological sources of mAb pharmacokinetic sex-effects could be identified in the rat model where target-mediated disposition is avoided., Methods: Plasma and lymphatic pharmacokinetics of the humanised anti-EGFR antibody cetuximab, along with potential physiological and biochemical drivers of pharmacokinetic sex differences, were examined in male and female rats. Cetuximab was used as a model mAb since plasma clearance is slower in female patients., Results: When plasma concentrations were normalised to dose, female rats displayed slower plasma clearance than males, but no significant differences were observed in liver and spleen biodistribution. Sex differences in apparent plasma clearance, however, were abolished after normalisation to body weight, surface area or fat-free mass. Significant sex differences were observed in plasma testosterone, endogenous IgG and fat free mass, but did not correlate with apparent clearance. Females did, however, show two-fold higher lymphatic exposure compared to males., Conclusions: These data suggested that mAbs more efficiently access lymph in females, but this does not affect plasma pharmacokinetics or biodistribution. Further, the data suggest that sex differences observed in humans could be a function of antigen density.

A water-soluble fluorine magnetic resonance spectroscopy host-guest probe, P(HPA- co -AdamCF 3 A), was successfully constructed from the facile synthesis of a bifunctional monomer via a quantitative Passerini reaction. Supramolecular complexation with (2-hydroxypropyl)- β -cyclodextrin promoted a change in the chemical environment, leading to modulation of both the relaxation properties as well as chemical shift of the fluorine moieties. This change was used to probe the supramolecular interaction by 19 F MRI spectroscopy and give insight into fluorine probe formulation. This work provides a fundamental basis for an 19 F MR imaging tracer capable of assessing host-guest inclusion and a potential model to follow the fate of a drug delivery system in vivo .

The neural interface is a critical factor in governing efficient and safe charge transfer between a stimulating electrode and biological tissue. The interface plays a crucial role in the efficacy of electric stimulation in chronic implants and both electromechanical properties and biological properties shape this. In the case of cochlear implants, it has long been recognized that neurotrophins can stimulate growth of the target auditory nerve fibers into a favorable apposition with the electrode array, and recently such arrays have been re-purposed to enable electrotransfer (electroporation)-based neurotrophin gene augmentation to improve the "bionic ear." For both this acute bionic array-directed electroporation and for chronic conventional cochlear implant arrays, the electric fields generated in target tissue during pulse delivery are central to efficacy, but are challenging to map. We present a computational model for predicting electric fields generated by array-driven DNA electrotransfer in the cochlea. The anatomically realistic model geometry was reconstructed from magnetic resonance images of the guinea pig cochlea and an eight-channel electrode array embedded within this geometry. The model incorporates a description of both Faradaic and non-Faradaic mechanisms occurring at the electrode-electrolyte interface with frequency dependency optimized to match experimental impedance spectrometry measurements. Our simulations predict that a tandem electrode configuration with four ganged cathodes and four ganged anodes produces three to fourfold larger area in target tissue where the electric field is within the range for successful gene transfer compared to an alternate paired anode-cathode electrode configuration. These findings matched in vivo transfection efficacy of a green fluorescent protein (GFP) reporter following array-driven electrotransfer of the reporter-encoding plasmid DNA. This confirms utility of the developed model as a tool to optimize the safety and efficacy of electrotransfer protocols for delivery of neurotrophin growth factors, with the ultimate aim of using gene augmentation approaches to improve the characteristics of the electrode-neural interfaces in chronically implanted neurostimulation devices.

We present a computational model for predicting electric field distributions following array-based closed-loop electroporation in the cochlea. The model geometry was reconstructed from magnetic resonance images of the guinea pig cochlea and an eight-channel electrode array embedded within this geometry. The model's electrode voltage output waveform was obtained from electric potential mapping conducted in physiological solution following constant-current stimulation using the electrode array. Our simulations predict that a tandem electrode configuration with four ganged cathodes and four ganged anodes produces a larger area in target tissue where the electric field is within the range for successful gene transfer compared to an alternate paired anode-cathode electrode configuration. These findings corroborate published in vivo evidence comparing the two configurations and support the utility of the developed model as a tool to optimize the efficacy of electroporation electrodes.

Objective: This work describes a phantom containing regions of controlled R2* (1/T2*) values to provide a stable reference object for testing implementations of R2* relaxometry commonly used for liver and heart iron assessments., Materials and Methods: A carrageenan-strengthened gadolinium DTPA doped agarose gel was used to enclose nine gels additionally doped with ultra-small superparamagnetic iron oxide. R2* values were determined at 1.5 T using multi-echo GRE sequences and exponential regression of pixel values from a region of interest against echo time using non-linear regression algorithms. We measured R2*, R2 and R1 values and the inter-scan and inter-operator reproducibility., Results: The phantom reliably demonstrated R2* values in seven steps between 22.4 s -1 (SE 1.98) and 441.9 s -1 (SE 6.76), with an R2* relaxivity (r2*) of 792 (SE 5.6) mM -1  s -1 . The doped gels displayed a concentration-dependent R2' component of R2* phantom, indicating superparamagnetic enhancement effects. We observed no significant change in relaxivity (r2*) over 12 months, and estimate a useful life of 3 years. Detailed descriptions of the production process and calculators are been provided as Online Resources., Conclusion: The phantom provides a durable test object with controlled R2* relaxation behaviour, useful for a range of R2* relaxometry reference work.

Aim: To evaluate the potential of newly-developed, biocompatible iron oxide magnetic nanoparticles (MNPs) conjugated with J591, an antibody to an extracellular epitope of PSMA, to enhance MRI of prostate cancer., Materials & Methods: Specific binding to PSMA by J591-MNP was investigated in vitro. MRI studies were performed on orthotopic tumor-bearing NOD.SCID mice 2 h and 24 h after intravenous injection of J591-MNPs, or non-targeting MNPs., Results & Conclusion: In vitro, MNPs did not affect prostate cancer cell viability, and conjugation to J591 did not compromise antibody specificity and enhanced cellular iron uptake. Magnetic resonance contrast of tumors was increased in vivo using PSMA-targeting MNPs, but not by non-targeting MNPs. This provides proof-of-concept that PSMA-targeting MNPs have potential to enhance magnetic resonance detection/localization of prostate cancer.

The Rar-related orphan receptor-α (Rorα) is a nuclear receptor that regulates adiposity and is a potential regulator of energy homeostasis. We have demonstrated that the Rorα-deficient staggerer (sg/sg) mice display a lean and obesity-resistant phenotype. Adaptive Ucp1-dependent thermogenesis in beige/brite and brown adipose tissue serves as a mechanism to increase energy expenditure and resist obesity. DEXA and MRI analysis demonstrated significantly decreased total fat mass and fat/lean mass tissue ratio in male chow-fed sg/sg mice relative to wt mice. In addition, we observed increased Ucp1 expression in brown adipose and subcutaneous white adipose tissue but not in visceral adipose tissue from Rorα-deficient mice. Moreover, this was associated with significant increases in the expression of the mRNAs encoding the thermogenic genes (i.e., markers of brown and beige adipose) Pparα, Errα, Dio2, Acot11/Bfit, Cpt1β, and Cidea in the subcutaneous adipose in the sg/sg relative to WT mice. These changes in thermogenic gene expression involved the significantly increased expression of the (cell-fate controlling) histone-lysine N-methyltransferase 1 (Ehmt1), which stabilizes the Prdm16 transcriptional complex. Moreover, primary brown adipocytes from sg/sg mice displayed a higher metabolic rate, and further analysis was consistent with increased uncoupling. Finally, core body temperature analysis and infrared thermography demonstrated that the sg/sg mice maintained greater thermal control and cold tolerance relative to the WT littermates. We suggest that enhanced Ucp1 and thermogenic gene expression/activity may be an important contributor to the lean, obesity-resistant phenotype in Rorα-deficient mice., (Copyright © 2015 the American Physiological Society.)

Noninvasive imaging is a critical technology for diagnosis, classification, and subsequent treatment planning for patients with glioblastoma. It has been shown that the EphA2 receptor tyrosine kinase (RTK) is overexpressed in a number of tumors, including glioblastoma. Expression levels of Eph RTKs have been linked to tumor progression, metastatic spread, and poor patient prognosis. As EphA2 is expressed at low levels in normal neural tissues, this protein represents an attractive imaging target for delineation of tumor infiltration, providing an improved platform for image-guided therapy. In this study, EphA2-4B3, a monoclonal antibody specific to human EphA2, was labeled with 64Cu through conjugation to the chelator 1,4,7-triazacyclononane-1,4,7-triacetic acid (NOTA). The resulting complex was used as a positron emission tomography (PET) tracer for the acquisition of high-resolution longitudinal PET/magnetic resonance images. EphA2-4B3-NOTA-64Cu images were qualitatively and quantitatively compared to the current clinical standards of [18F]FDOPA and gadolinium (Gd) contrast-enhanced MRI. We show that EphA2-4B3-NOTA-64Cu effectively delineates tumor boundaries in three different mouse models of glioblastoma. Tumor to brain contrast is significantly higher in EphA2-4B3-NOTA-64Cu images than in [18F]FDOPA images and Gd contrast-enhanced MRI. Furthermore, we show that nonspecific uptake in the liver and spleen can be effectively blocked by a dose of nonspecific (isotype control) IgG.

Background & Aims: Nonalcoholic fatty liver disease (NAFLD), characterized by accumulation of hepatic triglycerides (steatosis), is associated with abdominal obesity, insulin resistance, and inflammation. Although weight loss via calorie restriction reduces features of NAFLD, there is no pharmacologic therapy. Resveratrol is a polyphenol that prevents high-energy diet-induced steatosis and insulin resistance in animals by up-regulating pathways that regulate energy metabolism. We performed a placebo-controlled trial to assess the effects of resveratrol in patients with NAFLD., Methods: Overweight or obese men diagnosed with NAFLD were recruited from hepatology outpatient clinics in Brisbane, Australia from 2011 through 2012. They were randomly assigned to groups given 3000 mg resveratrol (n = 10) or placebo (n = 10) daily for 8 weeks. Outcomes included insulin resistance (assessed by the euglycemic-hyperinsulinemic clamp), hepatic steatosis, and abdominal fat distribution (assessed by magnetic resonance spectroscopy and imaging). Plasma markers of inflammation, as well as metabolic, hepatic, and antioxidant function, were measured; transcription of target genes was measured in peripheral blood mononuclear cells. Resveratrol pharmacokinetics and safety were assessed., Results: Eight-week administration of resveratrol did not reduce insulin resistance, steatosis, or abdominal fat distribution when compared with baseline. No change was observed in plasma lipids or antioxidant activity. Levels of alanine and aspartate aminotransferases increased significantly among patients in the resveratrol group until week 6 when compared with the placebo group. Resveratrol did not significantly alter transcription of NQO1, PTP1B, IL6, or HO1 in peripheral blood mononuclear cells. Resveratrol was well-tolerated., Conclusions: Eight weeks administration of resveratrol did not significantly improve any features of NAFLD, compared with placebo, but it increased hepatic stress, based on observed increases in levels of liver enzymes. Further studies are needed to determine whether agents that are purported to mimic calorie restriction, such as resveratrol, are safe and effective for complications of obesity. Clinical trials registration no: ACTRN12612001135808., (Copyright © 2014 AGA Institute. Published by Elsevier Inc. All rights reserved.)

This study examined the sensitivity of ultra-high field (16.4 T) diffusion tensor imaging (DTI; 70 μm in-plane resolution, 1mm slice thickness) to evaluate the spatiotemporal development of severe mid-thoracic contusive spinal cord injury (SCI) in mice. In vivo imaging was performed prior to SCI, then again at 2h, 1 day, 3 days, 7 days, and 30 days post-SCI using a Bruker 16.4 T small animal nuclear magnetic resonance spectrometer. Cross-sectional spinal cord areas were measured in axial slices and various DTI parameters, i.e. fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (λ||) and radial diffusivity (λ⊥), were calculated for the total spared white matter (WM), ventral funiculi (VF), lateral funiculi (LF) and dorsal columns (DCs) and then correlated with histopathology. Cross-sectional area measurements revealed significant atrophy (32% reduction) of the injured spinal cord at the lesion epicentre in the chronic phase of injury. Analysis of diffusion tensor parameters further showed that tissue integrity was most severely affected in the DCs, i.e. the site of immediate impact, which demonstrated a rapid and permanent decrease in FA and λ||. In contrast, DTI parameters for the ventrolateral white matter changed more gradually with time, suggesting that these regions are undergoing more delayed degeneration in a manner that may be amenable to therapeutic intervention. Of all the DTI parameters, λ⊥ was most closely correlated to myelin content whereas changes in FA and λ|| appeared more indicative of axonal integrity, Wallerian degeneration and associated presence of macrophages. We conclude that longitudinal DTI at 16.4T provides a clinically relevant, objective measure for assessing white matter pathology following contusive SCI in mice that may aid the translation of putative neuroprotective strategies into the clinic., (Copyright © 2013 Elsevier Inc. All rights reserved.)

The mRNA encoding Nor-1/NR4A3 is rapidly and strikingly induced by β2-adrenergic signaling in glycolytic and oxidative skeletal muscle. In skeletal muscle cells, Nor-1 expression is important for the regulation of oxidative metabolism. Transgenic skeletal muscle-specific expression of activated Nor-1 resulted in the acquisition of an endurance phenotype, an increase in type IIA/X oxidative muscle fibers, and increased numbers of mitochondria. In the current study, we used dual-energy x-ray absorptiometry and magnetic resonance imaging analysis to demonstrate decreased adiposity in transgenic (Tg) Nor-1 mice relative to that in wild-type littermates. Furthermore, the Tg-Nor-1 mice were resistant to diet-induced weight gain and maintained fasting glucose at normoglycemic levels. Expression profiling and RT-quantitative PCR analysis revealed significant increases in genes involved in glycolysis, the tricarboxylic acid cycle, oxidative phosphorylation, fatty acid oxidation, and glycogen synthesis, in concordance with the lean phenotype. Moreover, expression profiling identified several Z-disc and sarcomeric binding proteins that modulate fiber type phenotype and endurance, eg, α-actinin-3. In addition, we demonstrated that the Tg-Nor-1 mouse line has significantly higher glycogen content in skeletal muscle relative to that in wild-type littermates. Finally, we identified a decreased NAD(+)/NADH ratio with a concordant increase in peroxisome proliferator-activated receptor γ coactivator-1α1 protein/mRNA expression. Increased NADH was associated with an induction of the genes involved in the malate-aspartate shuttle and a decrease in the glycerol 3-phosphate shuttle, which maximizes aerobic ATP production. In conclusion, skeletal muscle-specific Nor-1 expression regulates genes and pathways that regulate adiposity, muscle fiber type metabolic capacity, and endurance.

The main aim of this study was to employ high-resolution MRI to investigate the spatiotemporal development of pathological features associated with contusive spinal cord injury (SCI) in mice. Experimental mice were subjected to either sham surgery or moderate contusive SCI. A 16.4-T small-animal MR system was employed for nondestructive imaging of post-mortem, fixed spinal cord specimens at the subacute (7 days) and more chronic (28-35 days) stages post-injury. Routine histological techniques were used for subsequent investigation of the observed neuropathology at the microscopic level. The central core of the lesion appeared as a dark hypo-intense area on MR images at all time points investigated. Small focal hypo-intense spots were also observed spreading through the dorsal funiculi proximal and distal to the site of impact, an area that is known to undergo gliosis and Wallerian degeneration in response to injury. Histological examination revealed these hypo-intense spots to be high in iron content as determined by Prussian blue staining. Quantitative image analysis confirmed the increased presence of iron deposits at all post-injury time points investigated (p<0.05). Distant iron deposits were also detectable through live imaging without the use of contrast-enhancing agents, enabling the longitudinal investigation of this pathology in individual animals. Further immunohistochemical evaluation showed that intracellular iron deposits localised to macrophages/microglia, astrocytes and oligodendrocytes in the subacute phase of SCI, but predominantly to glial fibrillary acidic protein-positive, CC-1-positive astrocytes at later stages of recovery. Progressive, widespread intracellular iron accumulation is thus a normal feature of SCI in mice, and high-resolution MRI can be effectively used to detect and monitor these neuropathological changes with time., (Copyright © 2012 John Wiley & Sons, Ltd.)

Because sucrose stored in mature stalks (in excess of 40% of stalk dry weight) can be wholly mobilized to supply carbon for the growth of heterotrophic tissues, we propose that sucrose mobilization requires a net sink-to-source transition that acts in toto within sett internode storage parenchyma. Based on our data we propose that mobilization of sucrose from culm storage parenchyma requires minimal investment of metabolic resources, and that the mechanism of sucrose mobilization is metabolically neutral. By magnetic resonance spectroscopy and phloem-specific tracer dyes, strong evidence was found that sucrose is mobilized from sett storage parenchyma via phloem to the growing shoot tissue. An analysis of the enzyme activities involved in sucrose metabolism and glycolysis suggested that sucrose synthase activity is downregulated due to the effects of sucrose mobilization. Overall, metabolism in storage parenchyma shifts from futile cycling to a more quiescent state during sucrose mobilization.

Transgenic mice overexpressing chicken Ski (c-Ski) have marked decrease in adipose mass with skeletal muscle hypertrophy. Recent evidence indicates a role for c-Ski in lipogenesis and energy expenditure. In the present study, wild type (WT) and c-Ski mice were challenged on a high-fat (HF) diet to determine whether c-Ski mice were resistant to diet-induced obesity. During the HF feeding WT mice gained significantly more weight than chow-fed animals, while c-Ski mice were partially resistant to the effects of the HF diet on weight. Body composition analysis confirmed the decreased adipose mass in c-Ski mice compared to WT mice. c-Ski mice possess a similar metabolic rate and level of food consumption to WT littermates, despite lower activity levels and on chow diet show mild glucose intolerance relative to WT littermates. On HF diet, glucose tolerance surprisingly remained unchanged in c-Ski mice, while it became worse in WT mice. Skeletal muscle of c-Ski mice exhibit impaired insulin-stimulated Akt phosphorylation and glucose uptake. In concordance, gene expression profiling of skeletal muscle of chow and HF-fed mice indicated that Ski suppresses gene expression associated with insulin signaling and glucose uptake and alters gene pathways involved in myogenesis and adipogenesis. In conclusion, c-Ski mice are partially resistant to diet-induced obesity and display aberrant insulin signaling and glucose homeostasis which is associated with alterations in gene expression that inhibit lipogenesis and insulin signaling. These results suggest Ski plays a major role in skeletal muscle metabolism and adipogenesis and hence influences risk of obesity and diabetes.

High-resolution magnetic resonance imaging using dedicated high-field radiofrequency micro-coils at 16.4 T (700 MHz) was investigated. Specific solenoid coils primarily using silver and copper as conductors with enamel and polyurethane coatings were built to establish which coil configuration produces the best image. Image quality was quantified using signal-to-noise ratio and signal variation over regions of interest. Benchmarking was conducted using 5-mm diameter coils, as this size is comparable to an established coil of the same size. Our 1.4-mm-diameter coils were compared directly to each other, from which we deduce performance as a function of conductor material and coating. A variety of materials and conductor coatings allowed us to choose an optimal design, which we used to image a kidney section at 10-micron resolution. We applied zero-fill extrapolation to achieve 5-micron resolution., (Copyright © 2012 Elsevier Inc. All rights reserved.)

Background: Hyperpolarised helium MRI (He3 MRI) is a new technique that enables imaging of the air distribution within the lungs. This allows accurate determination of the ventilation distribution in vivo. The technique has the disadvantages of requiring an expensive helium isotope, complex apparatus and moving the patient to a compatible MRI scanner. Electrical impedance tomography (EIT) a non-invasive bedside technique that allows constant monitoring of lung impedance, which is dependent on changes in air space capacity in the lung. We have used He3MRI measurements of ventilation distribution as the gold standard for assessment of EIT., Methods: Seven rats were ventilated in supine, prone, left and right lateral position with 70% helium/30% oxygen for EIT measurements and pure helium for He3 MRI. The same ventilator and settings were used for both measurements. Image dimensions, geometric centre and global in homogeneity index were calculated., Results: EIT images were smaller and of lower resolution and contained less anatomical detail than those from He3 MRI. However, both methods could measure positional induced changes in lung ventilation, as assessed by the geometric centre. The global in homogeneity index were comparable between the techniques., Conclusion: EIT is a suitable technique for monitoring ventilation distribution and inhomgeneity as assessed by comparison with He3 MRI.

Unlabelled: The measurement of ventilation distribution is currently performed using inhaled tracer gases for multiple breath inhalation studies or imaging techniques to quantify spatial gas distribution. Most tracer gases used for these studies have properties different from that of air. The effect of gas density on regional ventilation distribution has not been studied. This study aimed to measure the effect of gas density on regional ventilation distribution., Methods: Ventilation distribution was measured in seven rats using electrical impedance tomography (EIT) in supine, prone, left and right lateral positions while being mechanically ventilated with either air, heliox (30% oxygen, 70% helium) or sulfur hexafluoride (20% SF6, 20% oxygen, 60% air). The effect of gas density on regional ventilation distribution was assessed., Results: Gas density did not impact on regional ventilation distribution. The non-dependent lung was better ventilated in all four body positions. Gas density had no further impact on regional filling characteristics. The filling characteristics followed an anatomical pattern with the anterior and left lung showing a greater impedance change during the initial phase of the inspiration., Conclusion: It was shown that gas density did not impact on convection dependent ventilation distribution in rats measured with EIT.

Prostate cancer detection using diffusion-weighted imaging is highly affected by the accuracy of the apparent diffusion coefficient (ADC) values in an image. Echo planar imaging (EPI) is a fast sequence commonly used for diffusion imaging but has inherent magnetic susceptibility and chemical shift artefacts associated. A diffusion sequence that is less affected by these artefacts is therefore advantageous. The half-Fourier acquisition single-shot turbo spin-echo (HASTE) sequence was chosen. The diffusion sequences were compared in image quality, repeatability of the ADC value and the effect on the ADC value with varied b values. Eight volunteers underwent three scans of each sequence, on a 1.5-T Siemens system, using b values of 0, 150, 300, 450, 600, 750, 900 and 1000 s/mm(2). ADC maps were created to address the reproducibility of the ADC value when using two b values compared to eight b values. The ADC value using all b values with the HASTE sequence gave the best performance in all tested categories. Both sequences gave significantly different ADC mean values for two b values compared to when using eight b values (P<.05) suggesting larger error is present when using two b values. HASTE was shown to be an improvement over EPI in terms of repeatability, signal variation within a region of interest and standard deviation over the volunteer set. The improved accuracy of the ADC value in the HASTE sequence makes it potentially a more sensitive tumor detection technique., (Copyright © 2012 Elsevier Inc. All rights reserved.)

Determining the information content of vocal signals and understanding morphological modifications of vocal anatomy are key steps towards revealing the selection pressures acting on a given species' vocal communication system. Here, we used a combination of acoustic and anatomical data to investigate whether male koala bellows provide reliable information on the caller's body size, and to confirm whether male koalas have a permanently descended larynx. Our results indicate that the spectral prominences of male koala bellows are formants (vocal tract resonances), and show that larger males have lower formant spacing. In contrast, no relationship between body size and the fundamental frequency was found. Anatomical investigations revealed that male koalas have a permanently descended larynx: the first example of this in a marsupial. Furthermore, we found a deeply anchored sternothyroid muscle that could allow male koalas to retract their larynx into the thorax. While this would explain the low formant spacing of the exhalation and initial inhalation phases of male bellows, further research will be required to reveal the anatomical basis for the formant spacing of the later inhalation phases, which is predictive of vocal tract lengths of around 50 cm (nearly the length of an adult koala's body). Taken together, these findings show that the formant spacing of male koala bellows has the potential to provide receivers with reliable information on the caller's body size, and reveal that vocal adaptations allowing callers to exaggerate (or maximise) the acoustic impression of their size have evolved independently in marsupials and placental mammals.

Amyotrophic lateral sclerosis (ALS) is characterized by selective degeneration of motor neurons. Current imaging studies have concentrated on areas of the brain and spinal cord that contain mixed populations of sensory and motor neurons. In this study, ex vivo magnetic resonance microimaging (MRM) was used to separate motor and sensory components by visualizing individual dorsal and ventral roots in fixed spinal cords. MRM at 15μm in plane resolution enabled the axons of pure populations of sensory and motor neurons to be measured in the lumbar region of the SOD1 mouse model of ALS. MRM signal intensity increased by 38.3% (p<0.05) exclusively in the ventral motor nerve roots of the lumbar spinal cord of ALS-affected SOD1 mice compared to wildtype littermates. The hyperintensity was therefore limited to white matter tracts arising from the motor neurons, whereas sensory white matter fibers were unchanged. Significant decreases in ventral nerve root volume were also detected in the SOD1 mice, which correlated with the axonal degeneration observed by microscopy. These results demonstrate the usefulness of MRM in visualizing the ultrastructure of the mouse spinal cord. The detailed 3D anatomy allowed the processes of pure populations of sensory and motor neurons to be compared., (Copyright © 2011 Elsevier Inc. All rights reserved.)

Amyotrophic lateral sclerosis (ALS) is characterized by selective degeneration of motor neurons. Here we examine the ability of magnetic resonance imaging (MRI) to measure axonal degeneration in the lumbar spinal cord of the SOD1 mouse model of ALS. Diffusion tensor imaging (DTI) was successful in detecting axonal spinal cord damage in vivo. Fractional anisotropy (FA) values were reduced exclusively in the ventral white matter tracts of the lumbar spinal cord of ALS-affected SOD1 mice compared to wild-type littermates, with this effect becoming more pronounced with disease progression. The reduced FA values were therefore limited to white matter tracts arising from the motor neurons, whereas sensory white matter fibers were preserved. Significant decreases in water diffusion parallel to the white matter fibers or axial diffusivity were observed in the SOD1 mice, which can be attributed to the axonal degeneration observed by electron microscopy. At the same time, radial diffusivity perpendicular to the spinal column increased in the SOD1 mice, reflecting reduced myelination. These results demonstrate the usefulness of MRI in tracking disease progression in live animals and will aid in the assessment of treatment efficacy. This method could also potentially be adapted to aid the diagnosis and assessment of ALS progression in humans., (Copyright © 2010 Elsevier Inc. All rights reserved.)

Super-resolution reconstruction is a process by which a set of different low resolution images of the same object are used to create an enhanced, higher resolution image of that object. Recently there has been debate amongst researchers whether it is possible to obtain in-plane image enhancement using a set of low resolution magnetic resonance images, acquired by making small, independent changes to the demodulation frequency. We show that shifted low-resolution images contain different information that can be used to obtain denser sampling, leading to image enhancement. We conclude this from specific phantom experiments, applying signal processing sampling theory and taking into consideration the relative sampling of the point spread function with respect to the location of signal sources. Furthermore, the maximum achievable resolution for Fourier encoded MRI data at a boundary or object feature is governed by the effective width of the point spread function or the Fourier pixel size determined by the extent of k-space; this is verified experimentally., (Copyright © 2010 Wiley-Liss, Inc.)

Background/aims: Currently the diagnosis and severity of hepatic steatosis can be established accurately only by liver biopsy. Previous small studies found that steatosis measured by magnetic resonance spectroscopy (MRS) and imaging (MRI) correlated with histological assessment of liver triglyceride content. However, the accuracy of MRS/MRI for grading the severity of steatosis has not been addressed. The aims of this study were (1) to determine whether MRS and MRI can discriminate grades of steatosis in a large cohort of consecutive patients with a wide spectrum of liver disease aetiology and severity (2) to evaluate the effect of hepatic fibrosis, inflammation and iron on quantitation of intrahepatocellular lipid (IHCL) by these techniques., Methods: Ninety-four sequential patients who underwent percutaneous liver biopsy or liver resection had MRS and MRI (Dixon in phase/out of phase (Dixon IP/OP) and with/without fat saturation (+/-FS) images) to determine IHCL. Histology was used as the reference standard., Results: Close relationships were observed between the percentage of steatosis estimated by histology and MRS/MRI (r(s)=0.88 p<0.001 for all techniques). However, separate equations were required for the percentage of steatosis to avoid underestimation by imaging for patients with moderate or advanced fibrosis. All techniques had good diagnostic accuracy for mild steatosis (AUROC > or =0.87) as well as moderate/severe steatosis (AUROC > or =0.89). Hepatic inflammation and mild iron deposition (Perls' grade 1 and 2) did not interfere with estimation of steatosis by imaging., Conclusions: MRS and MRI had good accuracy for grading the severity of steatosis in subjects with liver disease, provided that stage of fibrosis was considered.

Purpose: To compare noninvasive MRI and magnetic resonance spectroscopy (MRS) methods with liver biopsy to quantify liver fat content., Materials and Methods: Quantification of liver fat was compared by liver biopsy, proton MRS, and MRI using in-phase/out-of-phase (IP/OP) and plus/minus fat saturation (+/-FS) techniques. The reproducibility of each MR measure was also determined. An additional group of overweight patients with steatosis underwent hepatic MRI and MRS before and after a six-month weight-loss program., Results: A close correlation was demonstrated between histological assessment of steatosis and measurement of intrahepatocellular lipid (IHCL) by MRS (r(s) = 0.928, P < 0.0001) and MRI (IP/OP r(s) = 0.942, P < 0.0001; FS r(s) = 0.935, P < 0.0001). Following weight reduction, four of five patients with >5% weight loss had a decrease in IHCL of >or=50%., Conclusion: These findings suggest that standard MRI protocols provide a rapid, safe, and quantitative assessment of hepatic steatosis. This is important because MRS is not available on all clinical MRI systems. This will enable noninvasive monitoring of the effects of interventions such as weight loss or pharmacotherapy in patients with fatty liver diseases., ((c) 2008 Wiley-Liss, Inc.)

Intrauterine growth restriction (IUGR) can increase susceptibility to perinatal hypoxic brain injury for reasons that are unknown. Previous studies of the neonatal IUGR brain have suggested that the cerebral mitochondrial capacity is reduced but the glycolytic capacity increased relative to normal weight (NW) neonates. In view of these two factors, we hypothesized that the generation of brain lactate during a mild hypoxic insult would be greater in neonatal IUGR piglets compared to NW piglets. Brain lactate/N-acetylaspartate (NAA) ratios and apparent diffusion coefficients (ADCs) were determined by proton magnetic resonance spectroscopy and imaging of the brain before, during and after hypoxia in seven neonatal piglets with asymmetric IUGR and six NW piglets. During hypoxia, IUGR piglets had significantly higher brain lactate/NAA ratios than NW piglets (P=0.046). The lactate response in the IUGR piglets correlated inversely with apoptosis in the thalamus and frontal cortex of the brain measured 4 h post hypoxia (Pearson's r=0.86, P<0.05). Apoptosis in IUGR piglets with high brain lactate was similar to that in the NW piglets whereas IUGR piglets with low brain lactate had significantly higher apoptosis than NW piglets (P=0.019). ADCs in the high lactate IUGR piglets were significantly lower during hypoxia than in all the other piglets. This signifies increased diffusion of water into brain cells during hypoxia, possibly in response to increased intracellular osmolality caused by high intracellular lactate concentrations. These findings support previous studies showing increased susceptibility to hypoxic brain injury in IUGR neonates but suggest that increased glycolysis during hypoxia confers neuroprotection in some IUGR piglets.

Spatial encoding in MR techniques is achieved by sampling the signal as a function of time in the presence of a magnetic field gradient. The gradients are assumed to generate a linear magnetic field gradient, and typical image reconstruction relies upon this approximation. However, high-speed gradients in the current generation of MRI scanners often sacrifice linearity for improvements in speed. Such nonlinearity results in distorted images. The problem is presented in terms of first principles, and a correction method based on a gradient field spherical harmonic expansion is proposed. In our case, the amount of distortion measured within a typical field of view (FOV) required for head imaging is sufficiently large that without the use of some distortion correction technique, the images would be of limited use for stereotaxy or longitudinal studies, where precise volumetric information is required., (Copyright 2004 Wiley-Liss, Inc.)

Objective: To investigate the effects of rosiglitazone (RSG) on insulin sensitivity and regional adiposity (including intrahepatic fat) in patients with type 2 diabetes., Research Methods and Procedures: We examined the effect of RSG (8 mg/day, 2 divided doses) compared with placebo on insulin sensitivity and body composition in 33 type 2 diabetic patients. Measurements of insulin sensitivity (euglycemic hyperinsulinemic clamp), body fat (abdominal magnetic resonance imaging and DXA), and liver fat (magnetic resonance spectroscopy) were taken at baseline and repeated after 16 weeks of treatment., Results: There was a significant improvement in glycemic control (glycosylated hemoglobin -0.7 +/- 0.7%, p < or = 0.05) and an 86% increase in insulin sensitivity in the RSG group (glucose-disposal rate change from baseline: 17.5 +/- 14.5 micro mol glucose/min/kg free fat mass, p < 0.05), but no significant change in the placebo group compared with baseline. Total body weight and fat mass increased (p < or = 0.05) with RSG (2.1 +/- 2.0 kg and 1.4 +/- 1.6 kg, respectively) with 95% of the increase in adiposity occurring in nonabdominal regions. In the abdominal region, RSG increased subcutaneous fat area by 8% (25.0 +/- 28.7 cm(2), p = 0.02), did not alter intra-abdominal fat area, and reduced intrahepatic fat levels by 45% (-6.7 +/- 9.7%, concentration relative to water)., Discussion: Our data indicate that RSG greatly improves insulin sensitivity in patients with type 2 diabetes and is associated with an increase in adiposity in subcutaneous but not visceral body regions.

Renal osmolyte concentrations are reduced during reflow following ischemia. Osmolyte decreases may follow oxygen depletion or loss of extracellular osmolality in the medulla. Image-guided volume-localized magnetic resonance (MR) microspectroscopy was used to monitor regional osmolytes during hyposmotic shock and hypoxia in the intact rat kidney. Alternate spectra were acquired from 24-microl voxels in cortex and medulla of the isolated perfused kidney. There was a progressive decrease in the combined betaine-glycerophosphorylcholine (GPC) peak intensity of 21% in cortex and 35% in medulla of normoxic kidneys between 60 and 160 min after commencing perfusion. Hypoxia had no significant effect on the betaine-GPC peak intensity in cortex or medulla, despite a dramatic reduction in tubular sodium, potassium, and water reabsorption. The results suggest that cortical and medullary intracellular osmolyte concentrations depend on osmotically regulated channels that are insensitive to oxygen and dissociated from the oxygen-dependent parameters of renal function, the fractional excretion of sodium, the fractional excretion of potassium, and urine-to-plasma inulin concentration ratio.

Volume-localized proton nuclear magnetic resonance spectroscopy was used as an assay of regional biochemistry in the isolated perfused rat kidney. This model eliminated artifacts caused by respiratory and cardiac motion experienced in vivo. Immersion of the kidney under its venous effluent reduced the susceptibility artifacts evoked by tissue-air interfaces. The rapid acquisition with relaxation enhancement imaging sequence was used for scout imaging. This gave excellent spatial resolution of the cortex, outer medulla, and inner medulla. Spectra were then acquired in 10 minutes using the volume-selective multipulse spectroscopy sequence from voxels with a volume of approximately 24 microL located within the cortical or medullary regions. Spectral peaks were assigned by the addition of known compounds to the perfusion medium and by comparison with spectra of protein-free extracts of cortex and medulla. The medullary region spectra were characterized by signals from the osmolytes betaine, glycerophosphorylcholine, and inositol. The spectra from the cortex were more complex and contained lesser contributions from osmolytes.

[2-(13)C]glycine metabolism was studied in freshly isolated rat renal proximal tubules. Mitochondrial coupling of the glycine cleavage complex (GC) and serine hydroxymethyltransferase (SHMT) was confirmed by the formation of three serine isotopomers, [2-(13)C]-, [3-(13)C]- and [2,3-(13)C]serine, detected by 13C-NMR. Incubation with different fractions of 13C-labelled glycine altered the labelling pattern of the serine isotopomers predictably and allowed calculation of the 13C-labelled fractions of total glycine and methylene in N5,N10-methylenetetrahydrofolate (m-THF) available for serine metabolism. Within 20 min there was a fall in labelled glycine (to 42 +/- 3, 68 +/- 3 and 93 +/- 2%, (n = 4, mean +/- S.D.) from 50%, 75% and 100% 13C-labelled added glycine respectively), followed by a slow rate of endogenous glycine formation for up to 80 min incubation. The C2 of glycine was the source of more than 90% of the methylene group of m-THF formed. Gas chromatography-mass spectroscopy (GC-MS) showed that greater than 50% of serine formed was unlabelled. GC and SHMT proceeded in the direction of serine formation. Serine isotopomer analysis by NMR and GC-MS allowed the actions of GC and SHMT and de novo contributions to glycine, serine and m-THF to be monitored in situ in fresh renal proximal tubules.

Glycine-serine interconversion is important to numerous metabolic processes and serine release by the kidney. Incubation of freshly isolated rat renal proximal tubules with 5 mM glycine 75% 13C-labelled in the 2-position resulted in 13C-labelled incorporation into serine of 69 micromol.g protein(-1) (+/- 14, n = 16) at 20 min. Addition of 5 mM glucose, 4 mM lactate, 1 mM alanine, 1 mM butyrate and 1 mM glutamate increased 13C-label incorporation into serine to 173 micromol.g protein(-1) (+/- 32, n = 4) at 60 min, 50% greater than tubules incubated with 5 mM glycine alone (P < 0.05). The increase was prevented by hypoxia. Reoxygenation for 20 min restored the rate of incorporation of 13C-label into serine. The fraction of unlabelled serine remained approximately 47% at 20, 40 and 60 min in each group. The results indicate that in the presence of oxygen, TCA and glycolytic intermediates stimulate serine synthesis via the glycine cleavage complex and serine hydroxymethyltransferase pathways and not the phosphorylated pathway. In addition, significant serine production occurs from an unidentified source, which is also tightly coupled to glycine metabolism. Both in the presence and absence of added TCA and glycolytic intermediates, glycine was the principle source of the methylene group in methylene tetrahydrofolate.

Protection against hypoxic injury by supraphysiological glycine and alanine concentrations was investigated in the isolated perfused rat kidney (IPRK). 23Na NMR detects consistent increases in total renal Na in IPRK during hypoxic perfusion. Increasing the concentration of glycine and alanine to 5 mM each produced a 34% (p < 0.001) reduction in the increase in total renal Na following 30 minutes of hypoxia compared to a matched control group supplemented with 5 mM each of serine and glutamine. There was also a trend (p = 0.067) to improvement in the fractional excretion of sodium (FENa) in the glycine plus alanine treated group. Hypoxic alterations of other physiological parameters were not prevented by supraphysiological glycine plus alanine. This suggests that monitoring total renal Na is a more sensitive method of defining renal injury and protection than monitoring changes in FENa, fractional excretion of potassium (FEK) and inulin clearance.

Hypoxic injury in the isolated perfused rat kidney (IPRK) was monitored using 23Na-NMR in the presence or absence of 1.5 and 15 mM dimethylthiourea (DMTU) or 15 mM dimethylsulphoxide (DMSO) before and after inducing hypoxia. Hypoxia induced a prompt exponential increase in total renal 23Na+, renal vascular resistance, and sodium excretion and decreased inulin clearance and adenine nucleotides and reduced glutathione concentrations. Lipid peroxide metabolites were unaltered. The increase in 23Na+ was significantly reduced (P < 0.001) by both DMTU and DMSO although hypoxic perturbations of function and biochemical parameters were not. Posthypoxic increases in renal 23Na+ include approximately 10% from the intratubular compartment, but principally reflect the intracellular and interstitial compartments. The results demonstrate that 23Na-NMR is a sensitive indicator of hypoxic renal injury in intact kidney and suggest that DMTU and DMSO protect against hypoxic injury by a mechanism independent of free radical-binding.