Racial and Socioeconomic Disparities Exist in Patients Pursuing Peanut Oral Immunotherapy.

BACKGROUND: Oral immunotherapy (OIT) is a promising treatment for food allergy. Prior studies demonstrate significant differences among food-allergic individuals across race, ethnicity, and socioeconomic groups. Disparities in OIT have not been evaluated. OBJECTIVE: We assessed disparities in the use of OIT in patients with peanut allergy based on race, ethnicity, and socioeconomic status at a single academic medical center. METHODS: We identified 1028 peanut-allergic patients younger than 18 years receiving care in the University of Michigan food allergy clinics. Of these, 148 patients who underwent peanut OIT (treatment group) were compared with the 880 patients who avoided peanut (control group). Pertinent demographic and socioeconomic characteristics were compared. RESULTS: There were no differences in gender or ethnicity between the OIT and control groups. However, Black patients comprised 18% of the control group but only 4.1% of the OIT treatment group (P < .0001). The proportion of patients with private insurance was significantly higher in the treatment group compared with the control group (93.2% vs 82.2%, P = .0004). Finally, the neighborhood affluence index, a census-based measure of the relative socioeconomic prosperity of a neighborhood, was significantly higher in the OIT group than the control group (0.51 ± 0.18 vs 0.47 ± 0.19, P = .015), whereas the neighborhood disadvantage index, a census-based measure of the relative socioeconomic disadvantage of a neighborhood, was significantly lower (0.082 ± 0.062 vs 0.10 ± 0.093, P = .020). CONCLUSIONS: Significant racial and economic disparities exist at our institution between peanut-allergic individuals who receive OIT and those who do not. Efforts to understand the basis for these disparities are important to ensure that patients have equitable access to OIT.

The effect of a novel AQP4 facilitator, TGN-073, on glymphatic transport captured by diffusion MRI and DCE-MRI.

The glymphatic system is a low resistance pathway, by which cerebrospinal fluid enters the brain parenchyma along perivascular spaces via AQP4 channels. It is hypothesised that the resulting convective flow of the interstitial fluid provides an efficient mechanism for the removal of waste toxins from the brain. Therefore, enhancing AQP4 function might protect against neurodegenerative diseases such as Alzheimer's disease (AD), in which the accumulation of harmful proteins and solutes is a hallmark feature. Here, we test the effect of a putative AQP4 facilitator, TGN-073, on glymphatic transport in a normal rat brain by employing different MRI techniques. Surgical procedures were undertaken to catheterise the cisterna magna, thereby enabling infusion of the MRI tracer. Followed by the intraperitoneal injection of either TGN-073, or the vehicle. Using a paramagnetic contrast agent (Gd-DTPA) as the MRI tracer, dynamic 3D T1 weighted imaging of the glymphatic system was undertaken over two hours. Further, the apparent diffusion coefficient was measured in different brain regions using diffusion-weighted imaging (DWI). While physiological parameters and arterial blood gas analysis were monitored continuously. We found that rats treated with TGN-073 showed the distribution of Gd-DTPA was more extensive and parenchymal uptake was higher compared with the vehicle group. Water diffusivity was increased in the brain of TGN-073 treated group, which indicates greater water flux. Also, MRI showed the glymphatic transport and distribution in the brain is naturally heterogeneous, which is consistent with previous studies. Our results indicate that compounds such as TGN-073 can improve glymphatic function in the brain. Since glymphatic impairment due to AQP4 dysfunction is potentially associated with several neurological disorders such as AD, dementia and traumatic brain injury, enhancing AQP4 functionality might be a promising therapeutic target.

Exploring the failing right ventricle in pulmonary hypertension by cardiac magnetic resonance: An in vivo study utilizing Macitentan.

Cardiac magnetic resonance (CMR) imaging is used to assess the right ventricle (RV) of pulmonary hypertensive (PH) patients and more recently to track changes in response to therapy. We wished to investigate if repeat CMRs could be used to assess ventricular changes in the Sugen 5416 hypoxic (Su/Hx) rat model of PH treated with the dual endothelin receptor antagonist Macitentan. Male Sprague Dawley Su/Hx rats were dosed for 3 weeks with either vehicle or Macitentan (30 mg/kg) daily, control rats received only vehicle. All rats underwent three CMR scans; before treatment, 2 weeks into treatment, and end of the study. A separate group of Su/Hx and control rats, treated as above, underwent terminal hemodynamic measurements. Using terminal and CMR measurements, Macitentan was found to lower RV systolic pressure pulmonary artery remodeling and increase RV ejection fraction but not change RV hypertrophy (RVH). Repeat CMRs determined that Su/Hx rats treated with Macitentan had significantly reversed RVH via reducing RV mass as well as reducing elevated left ventricular eccentricity index; reductions in RV mass were also observed in Su/Hx vehicle rats exposed to normoxic conditions. We have demonstrated that repeat CMRs can be used to assess the volume and structural changes in the ventricles of the Su/Hx rat model. Using repeat CMRs has allowed us to build a more complete picture of the response of the RV and the left ventricle to treatment. It is unknown if these effects are a consequence of direct action on the RV or secondary to improvements in the lung vasculature.

Direct imaging of glymphatic transport using H217O MRI.

The recently proposed glymphatic pathway for solute transport and waste clearance from the brain has been the focus of intense debate. By exploiting an isotopically enriched MRI tracer, H217O, we directly imaged glymphatic water transport in the rat brain in vivo. Our results reveal glymphatic transport that is dramatically faster and more extensive than previously thought and unlikely to be explained by diffusion alone. Moreover, we confirm the critical role of aquaporin-4 channels in glymphatic transport.

Understanding longitudinal biventricular structural and functional changes in a pulmonary hypertension Sugen-hypoxia rat model by cardiac magnetic resonance imaging.

Cardiac magnetic resonance-derived ventricular variables are predictive of mortality in pulmonary arterial hypertension. Rodent models which emphasize ventricular function, allowing serial monitoring, are needed to identify pathophysiological features and novel therapies for pulmonary arterial hypertension. We investigated longitudinal changes in the Sugen-hypoxia model during disease progression. Sprague Dawley rats (n = 32) were divided into two groups. (1) Sugen-hypoxia: a dose of subcutaneous Sugen-5416 and placed in hypobaric hypoxia for two weeks followed by normoxia for three weeks. (2) Normoxia: maintained at normal pressure for five weeks. Rats were examined at five or eight weeks with right-heart catheter, cardiac magnetic resonance, and autopsy. Compared to normoxic controls (23.9 ± 4.1 mmHg), right ventricular systolic pressure was elevated in Sugen-hypoxia rats at five and eight weeks (40.9 ± 15.5 mmHg, p = 0.026; 48.9 ± 9.6 mmHg, p = 0.002). Right ventricular end-systolic volume index was increased in eight weeks Sugen-hypoxia (0.28 ± 0.04 µlcm-2, p = 0.003) compared to normoxic controls (0.18 ±0.03 mlcm-2). There was progressive dilatation of the right ventricular at eight weeks Sugen-hypoxia compared to normoxic controls (0.75 ± 0.13 µlcm-2 vs 0.56 ± 0.1 µlcm-2 p = 0.02). Ventricle mass index by cardiac magnetic resonance at five weeks (0.34 ± 0.06, p = 0.003) and eight weeks Sugen-hypoxia (0.34 ± 0.06, p = 0.002) were higher than normoxic controls (0.21 ± 0.04). Stroke volume, right ventricular ejection fraction, and left ventricular variables were preserved in Sugen-hypoxia. Ventricular changes during the course of illness in a pulmonary arterial hypertension rodent model can be examined by cardiac magnetic resonance. These changes including right ventricular hypertrophy and subsequent dilatation are similar to those seen in pulmonary arterial hypertension patients. Despite the persisting pulmonary hypertension, there are features of adaptive cardiac remodeling through the study duration.

Change in CSF Dynamics Responsible for ICP Elevation After Ischemic Stroke in Rats: a New Mechanism for Unexplained END?

It has been proposed that intracranial pressure (ICP) elevation and collateral failure are responsible for unexplained early neurological deterioration (END) in stroke. The study's aims were to investigate whether cerebral spinal fluid (CSF) dynamics, rather than edema, are responsible for elevation of ICP after ischemic stroke. Permanent middle cerebral artery occlusion (pMCAO) was induced with an intraluminal filament. At 24 h after stroke, baseline ICP was measured and CSF dynamics were probed via a steady-state infusion method. Diffusion-weighted imaging (DWI) and T2-weighted magnetic resonance imaging were performed to define cerebral ischemic damage and the volume of brain swelling. We found that the pMCAO group exhibited a significant increase in CSF outflow resistance (2.27 ± 0.15 mmHg µL-1 min) compared with the sham group (0.93 ± 0.06 mmHg µL-1 min, p = 0.002). There was no correlation between mean ICP at 24 h post-pMCAO and edema (r2 = - 0.03, p = 0.5) or infarct volumes (r2 = 0.09, p = 0.5). However, for the first time, we found a significant correlation between the baseline ICP at 24 h post-stroke and the value of CSF outflow resistance. Results show that CSF outflow resistance, rather than edema, was the mechanism responsible for ICP elevation following ischemic stroke. This challenges current concepts and suggests the possibility that intracranial hypertension may be occurring undetected in a much wider range of stroke patients than is currently considered to be the case. In addition, this further supports the hypothesis that unexplained early neurological deterioration is the result of elevated ICP, leading to reduced collateral flow and cerebral perfusion.

The IMPROVE Guidelines (Ischaemia Models: Procedural Refinements Of in Vivo Experiments).

Most in vivo models of ischaemic stroke target the middle cerebral artery and a spectrum of stroke severities, from mild to substantial, can be achieved. This review describes opportunities to improve the in vivo modelling of ischaemic stroke and animal welfare. It provides a number of recommendations to minimise the level of severity in the most common rodent models of middle cerebral artery occlusion, while sustaining or improving the scientific outcomes. The recommendations cover basic requirements pre-surgery, selecting the most appropriate anaesthetic and analgesic regimen, as well as intraoperative and post-operative care. The aim is to provide support for researchers and animal care staff to refine their procedures and practices, and implement small incremental changes to improve the welfare of the animals used and to answer the scientific question under investigation. All recommendations are recapitulated in a summary poster (see supplementary information).

Rapid and recoverable in vivo magnetic resonance imaging of the adult zebrafish at 7T.

Increasing scientific interest in the zebrafish as a model organism across a range of biomedical and biological research areas raises the need for the development of in vivo imaging tools appropriate to this subject. Development of the embryonic and early stage forms of the subject can currently be assessed using optical based techniques due to the transparent nature of the species at these early stages. However this is not an option during the juvenile and adult stages when the subjects become opaque. Magnetic resonance imaging (MRI) techniques would allow for the longitudinal and non-invasive assessment of development and health in these later life stages. However, the small size of the zebrafish and its aquatic environment represent considerable challenges for the technique. We have developed a suitable flow cell system that incorporates a dedicated MRI imaging coil to solve these challenges. The system maintains and monitors a zebrafish during a scan and allows for it to be fully recovered. The imaging properties of this system compare well with those of other preclinical MRI coils used in rodent models. This enables the rapid acquisition of MRI data which are comparable in terms of quality and acquisition time. This would allow the many unique opportunities of the zebrafish as a model organism to be combined with the benefits of non-invasive MRI.

Sodium-23 magnetic resonance imaging has potential for improving penumbra detection but not for estimating stroke onset time.

Tissue sodium concentration increases in irreversibly damaged (core) tissue following ischemic stroke and can potentially help to differentiate the core from the adjacent hypoperfused but viable penumbra. To test this, multinuclear hydrogen-1/sodium-23 magnetic resonance imaging (MRI) was used to measure the changing sodium signal and hydrogen-apparent diffusion coefficient (ADC) in the ischemic core and penumbra after rat middle cerebral artery occlusion (MCAO). Penumbra and core were defined from perfusion imaging and histologically defined irreversibly damaged tissue. The sodium signal in the core increased linearly with time, whereas the ADC rapidly decreased by >30% within 20 minutes of stroke onset, with very little change thereafter (0.5-6 hours after MCAO). Previous reports suggest that the time point at which tissue sodium signal starts to rise above normal (onset of elevated tissue sodium, OETS) represents stroke onset time (SOT). However, extrapolating core data back in time resulted in a delay of 72 ± 24 minutes in OETS compared with actual SOT. At the OETS in the core, penumbra sodium signal was significantly decreased (88 ± 6%, P=0.0008), whereas penumbra ADC was not significantly different (92 ± 18%, P=0.2) from contralateral tissue. In conclusion, reduced sodium-MRI signal may serve as a viability marker for penumbra detection and can complement hydrogen ADC and perfusion MRI in the time-independent assessment of tissue fate in acute stroke patients.

The design of a double-tuned two-port surface resonator and its application to in vivo hydrogen- and sodium-MRI.

The design and construction of a two-port surface transceiver resonator for both (1)H-and (23)Na-MRI in the rodent brain at 7 T is described. Double-tuned resonators are required for accurately co-registering multi-nuclei data sets, especially when the time courses of (1)H and (23)Na signals are of interest as, for instance, when investigating the pathological progression of ischaemic stroke tissue in vivo. In the current study, a single-element two-port surface resonator was developed wherein both frequency components were measured with the same detector element but with each frequency signal routed along different output channels. This was achieved by using the null spot technique, allowing for optimal variable tuning and matching of each channel in situ within the MRI scanner. The (23)Na signal to noise ratio, measured in the ventricles of the rat brain, was increased by a factor of four compared to recent state-of-the-art rat brain studies reported in the literature. The resonator's performance was demonstrated in an in vivo rodent stroke model, where regional variations in (1)H apparent diffusion coefficient maps and the (23)Na signal were recorded in an interleaved fashion as a function of time in the acute phase of the stroke without having to exchange, re-adjust, or re-connect resonators between scans. Using the practical construction steps described in this paper, this coil design can be easily adapted for MRI of other X-nuclei, such as (17)O, (13)C, (39)K, and (43)Ca at various field strengths.

Regional and temporal variations in tissue sodium concentration during the acute stroke phase.

A technique for noninvasively quantifying the concentration of sodium ((23) Na) ions was applied to the study of ischemic stroke. (23) Na-magnetic resonance imaging techniques have shown considerable potential for measuring subtle changes in ischemic tissue, although studies to date have suffered primarily from poor signal/noise ratio. In this study, accurate quantification of tissue sodium concentration (TSC) was achieved in (23) Na images with voxel sizes of 1.2 µL acquired in 10 min. The evolution of TSC was investigated from 0.5 to 8 h in focal cortical and subcortical ischemic tissue following permanent middle cerebral artery occlusion in the rat (n = 5). Infarct volumes determined from TSC measurements correlated significantly with histology (P = 0.0006). A delayed linear model was fitted to the TSC time course data in each voxel, which revealed that the TSC increase was more immediate (0.2 ± 0.1 h delay time) in subcortical ischemic tissue, whereas it was delayed by 1.6 ± 0.5 h in ischemic cortex (P = 0.0002). No significant differences (P = 0.5) were measured between TSC slope rates in cortical (10.2 ± 1.1 mM/h) and subcortical (9.7 ± 1.1 mM/h) ischemic tissue. The data suggest that any TSC increase measured in ischemic tissue indicates infarction (core) and regions exhibiting a delay to TSC increase indicate potentially salvageable tissue (penumbra).

Novel MRI detection of the ischemic penumbra: direct assessment of metabolic integrity.

We describe a novel magnetic resonance imaging technique to directly assess the metabolic integrity of penumbral tissue following stroke. For ischemically stressed tissue to be salvageable, it has to be capable of recovering aerobic metabolism (in place of anaerobic metabolism) on reperfusion. We probed ischemic brain tissue by altering the rate of oxygen delivery using a challenge of 100% oxygen ventilation. Any change from anaerobic to aerobic metabolism should alter the rate of lactate production and hence, levels of tissue lactate. Stroke was induced by permanent middle cerebral artery occlusion in rats. In Series 1 (n = 6), changes in tissue lactate during and following 100% oxygen challenge were monitored using (1)H magnetic resonance spectroscopy (MRS). Diffusion weighted imaging (DWI) and perfusion weighted imaging (PWI) were used to locate MRS voxels within the ischemic core, the homotopic contralateral striatum and within PWI/DWI mismatch (i.e. presumed penumbra). After 20 min of oxygen, lactate signal change was -16.1 ± 8.8% (mean ± SD) in PWI/DWI mismatch, +2.8 ± 5.1% in the ischemic core, and -0.6 ± 7.6% in the contralateral striatum. Return to air ventilation for 20 min resulted in a reversal, with lactate increasing by 46 ± 25.3% in the PWI/DWI mismatch, 6.6 ± 6.2% in the ischemic core, and -5 ± 11.4% in the contralateral striatum. In Series 2 (n = 6), a novel form of spectroscopic imaging was used to acquire lactate change maps to spatially identify regions of lactate change within the ischemic brain. This technique has potential clinical utility by identifying tissue that displays anaerobic metabolism capable of recovering aerobic metabolism when oxygen delivery is increased, which could provide a more precise assessment of penumbra.

Stroke penumbra defined by an MRI-based oxygen challenge technique: 2. Validation based on the consequences of reperfusion.

Magnetic resonance imaging (MRI) with oxygen challenge (T(2)(*) OC) uses oxygen as a metabolic biotracer to define penumbral tissue based on CMRO(2) and oxygen extraction fraction. Penumbra displays a greater T(2)(*) signal change during OC than surrounding tissue. Since timely restoration of cerebral blood flow (CBF) should salvage penumbra, T(2)(*) OC was tested by examining the consequences of reperfusion on T(2)(*) OC-defined penumbra. Transient ischemia (109 ± 20 minutes) was induced in male Sprague-Dawley rats (n=8). Penumbra was identified on T(2)(*)-weighted MRI during OC. Ischemia and ischemic injury were identified on CBF and apparent diffusion coefficient maps, respectively. Reperfusion was induced and scans repeated. T(2) for final infarct and T(2)(*) OC were run on day 7. T(2)(*) signal increase to OC was 3.4% in contralateral cortex and caudate nucleus and was unaffected by reperfusion. In OC-defined penumbra, T(2)(*) signal increased by 8.4% ± 4.1% during ischemia and returned to 3.25% ± 0.8% following reperfusion. Ischemic core T(2)(*) signal increase was 0.39% ± 0.47% during ischemia and 0.84% ± 1.8% on reperfusion. Penumbral CBF increased from 41.94 ± 13 to 116.5 ± 25 mL per 100 g per minute on reperfusion. On day 7, OC-defined penumbra gave a normal OC response and was located outside the infarct. T(2)(*) OC-defined penumbra recovered when CBF was restored, providing further validation of the utility of T(2)(*) OC for acute stroke management.

Stroke penumbra defined by an MRI-based oxygen challenge technique: 1. Validation using [14C]2-deoxyglucose autoradiography.

Accurate identification of ischemic penumbra will improve stroke patient selection for reperfusion therapies and clinical trials. Current magnetic resonance imaging (MRI) techniques have limitations and lack validation. Oxygen challenge T(2)(*) MRI (T(2)(*) OC) uses oxygen as a biotracer to detect tissue metabolism, with penumbra displaying the greatest T(2)(*) signal change during OC. [(14)C]2-deoxyglucose (2-DG) autoradiography was combined with T(2)(*) OC to determine metabolic status of T(2)(*)-defined penumbra. Permanent middle cerebral artery occlusion was induced in anesthetized male Sprague-Dawley rats (n=6). Ischemic injury and perfusion deficit were determined by diffusion- and perfusion-weighted imaging, respectively. At 147 ± 32 minutes after stroke, T(2)(*) signal change was measured during a 5-minute 100% OC, immediately followed by 125 µCi/kg 2-DG, intravenously. Magnetic resonance images were coregistered with the corresponding autoradiograms. Regions of interest were located within ischemic core, T(2)(*)-defined penumbra, equivalent contralateral structures, and a region of hyperglycolysis. A T(2)(*) signal increase of 9.22% ± 3.9% (mean ± s.d.) was recorded in presumed penumbra, which displayed local cerebral glucose utilization values equivalent to contralateral cortex. T(2)(*) signal change was negligible in ischemic core, 3.2% ± 0.78% in contralateral regions, and 1.41% ± 0.62% in hyperglycolytic tissue, located outside OC-defined penumbra and within the diffusion abnormality. The results support the utility of OC-MRI to detect viable penumbral tissue following stroke.

A double-tuned (1)H/(23)Na dual resonator system for tissue sodium concentration measurements in the rat brain via Na-MRI.

A method for quantifying the tissue sodium concentration (TSC) in the rat brain from ²³Na-MR images was developed. TSC is known to change in a variety of common human diseases and holds considerable potential to contribute to their study; however, its accurate measurement in small laboratory animals has been hindered by the extremely low signal to noise ratio (SNR) in ²³Na images. To address this, the design, construction and characterization of a double-tuned ¹H/²³Na dual resonator system for ¹H-guided quantitative ²³Na-MRI are described. This system comprises an SNR-optimized surface detector coil for ²³Na image acquisition, and a volume resonator producing a highly homogeneous B1 field (<5% inhomogeneity) for the Na channel across the rat head. The resonators incorporated channel-independent balanced matching and tuning capabilities with active decoupling circuitry at the ²³Na resonance frequency. A quantification accuracy of TSC of <10 mM was achieved in Na-images with 1.2 µl voxel resolution acquired in 10 min. The potential of the quantification technique was demonstrated in an in vivo experiment of a rat model of cerebral stroke, where the evolution of the TSC was successfully monitored for 8 h after the stroke was induced.

mRNA and micro-RNA expression analysis in laser-capture microdissected prostate biopsies: valuable tool for risk assessment and prevention trials.

Diagnosis of prostate cancer (PCa) typically relies on needle biopsies, which are routinely archived in paraffin after formalin fixation and may contain valuable risk or prognostic information. The objective of this study was to determine the feasibility of mRNA and miRNA expression analysis in laser-capture microdissected (LCM) formalin-fixed paraffin-embedded archived prostate biopsies compared to the gold standard of frozen tissue. We analyzed the expression of compartment-specific and PCa-related genes in epithelial and stromal tissues collected from paired sets of archived prostate biopsies and frozen radical prostatectomy specimens from three patients. Our results showed appropriate compartment-specific and PCa-related expression with good within patient agreement between the FFPE biopsies and the frozen tissue. The potential for both mRNA and micro-RNA expression profiling in the biopsies was also demonstrated using PCR arrays which showed high correlation between the biopsy and frozen tissue, notwithstanding sensitivity limitations for mRNA detection in the FFPE specimen. This is the first study to compare RNA expression from biopsy and frozen tissues from the same patient and to examine miRNA expression in LCM-collected tissue from prostate biopsies. With careful technique and use of appropriate controls, RNA profiling from archived biopsy material is quite feasible showing high correlation to frozen tissue.

Differences in the evolution of the ischemic penumbra in stroke-prone spontaneously hypertensive and Wistar-Kyoto rats.

BACKGROUND AND PURPOSE: Stroke-prone spontaneously hypertensive rats (SHRSP) are a highly pertinent stroke model with increased sensitivity to focal ischemia compared with the normotensive reference strain (Wistar-Kyoto rats; WKY). Study aims were to investigate temporal changes in the ischemic penumbra in SHRSP compared with WKY. METHODS: Permanent middle cerebral artery occlusion was induced with an intraluminal filament. Diffusion- (DWI) and perfusion- (PWI) weighted magnetic resonance imaging was performed from 1 to 6 hours after stroke, with the PWI-DWI mismatch used to define the penumbra and thresholded apparent diffusion coefficient (ADC) maps used to define ischemic damage. RESULTS: There was significantly more ischemic damage in SHRSP than in WKY from 1 to 6 hours after stroke. The perfusion deficit remained unchanged in WKY (39.9+/-6 mm(2) at 1 hour, 39.6+/-5.3 mm(2) at 6 hours) but surprisingly increased in SHRSP (43.9+/-9.2 mm(2) at 1 hour, 48.5+/-7.4 mm(2) at 6 hours; P=0.01). One hour after stroke, SHRSP had a significantly smaller penumbra (3.4+/-5.8 mm(2)) than did WKY (9.7+/-3.8, P=0.03). In WKY, 56% of the 1-hour penumbra area was incorporated into the ADC lesion by 6 hours, whereas in SHRSP, the small penumbra remained static owing to the temporal increase in both ADC lesion size and perfusion deficit. CONCLUSIONS: First, SHRSP have significantly more ischemic damage and a smaller penumbra than do WKY within 1 hour of stroke; second, the penumbra is recruited into the ADC abnormality over time in both strains; and third, the expanding perfusion deficit in SHRSP predicts more tissue at risk of infarction. These results have important implications for management of stroke patients with preexisting hypertension and suggest ischemic damage could progress at a faster rate and over a longer time frame in the presence of hypertension.

c-Jun N-terminal kinase 1 interacts with and negatively regulates Wnt/beta-catenin signaling through GSK3beta pathway.

Increasing evidence shows that there is an interaction between mitogen-activated protein kinase and Wnt signaling and that their interaction plays important roles in a variety of cellular processes. However, how the two signaling interacts is not clear. In this study, we found that beta-catenin expression was strikingly increased in the intestinal normal mucosa and tumors of c-Jun N-terminal kinase (JNK) 1-deficient mice by immunohistochemical staining and that both beta-catenin expression and transcriptional activity were significantly upregulated in JNK1-deficient mouse embryonic fibroblasts. However, active JNK1 significantly inhibited beta-catenin expression and suppressed beta-catenin-mediated transcriptional activity by enhancing glycogen synthase kinase 3beta (GSK3beta) activity. But beta-catenin inhibition was significantly reduced by GSK3beta RNA interference or GSK3beta inhibitor lithium chloride and proteasome inhibitor MG132. Further, mutant beta-catenin at the phosphorylation sites of Ser33 and Ser37 by GSK3beta was resistant to activated JNK1-induced beta-catenin degradation. Moreover, the physical interaction between JNK1 and beta-catenin was detected by immunoprecipitation, and their colocalization was seen in cellular nuclei and cytoplasm. Taken together, our data provide direct evidence that JNK1 interacts with and negatively regulates beta-catenin signaling through GSK3beta pathway and that the beta-catenin alteration is probably responsible for the intestinal tumor formation in JNK1-deficient mice.

Potential use of oxygen as a metabolic biosensor in combination with T2*-weighted MRI to define the ischemic penumbra.

We describe a novel magnetic resonance imaging technique for detecting metabolism indirectly through changes in oxyhemoglobin:deoxyhemoglobin ratios and T2(*) signal change during 'oxygen challenge' (OC, 5 mins 100% O(2)). During OC, T2(*) increase reflects O(2) binding to deoxyhemoglobin, which is formed when metabolizing tissues take up oxygen. Here OC has been applied to identify tissue metabolism within the ischemic brain. Permanent middle cerebral artery occlusion was induced in rats. In series 1 scanning (n=5), diffusion-weighted imaging (DWI) was performed, followed by echo-planar T2(*) acquired during OC and perfusion-weighted imaging (PWI, arterial spin labeling). Oxygen challenge induced a T2(*) signal increase of 1.8%, 3.7%, and 0.24% in the contralateral cortex, ipsilateral cortex within the PWI/DWI mismatch zone, and ischemic core, respectively. T2(*) and apparent diffusion coefficient (ADC) map coregistration revealed that the T2(*) signal increase extended into the ADC lesion (3.4%). In series 2 (n=5), FLASH T2(*) and ADC maps coregistered with histology revealed a T2(*) signal increase of 4.9% in the histologically defined border zone (55% normal neuronal morphology, located within the ADC lesion boundary) compared with a 0.7% increase in the cortical ischemic core (92% neuronal ischemic cell change, core ADC lesion). Oxygen challenge has potential clinical utility and, by distinguishing metabolically active and inactive tissues within hypoperfused regions, could provide a more precise assessment of penumbra.