Neuromedin U is regulated by the metastasis suppressor RhoGDI2 and is a novel promoter of tumor formation, lung metastasis and cancer cachexia.

Most deaths from urinary bladder cancer are owing to metastatic disease. A reduction in Rho GDP Dissociation Inhibitor 2 (RhoGDI2) protein has been associated with increased risk of metastasis in patients with locally advanced bladder cancer, whereas in animal models, RhoGDI2 reconstitution in cells without expression results in lung metastasis suppression. Recently, we noted an inverse correlation between tumor RhoGDI2 and Neuromedin U (NMU) expression, suggesting that NMU might be a target of the lung metastasis suppressor effect of RhoGDI2. Here we evaluated whether NMU is regulated by RhoGDI2 and is functionally important in tumor progression. We used small interfering RNA knockdown of endogenous RhoGDI2 in poorly tumorigenic and non-metastatic human bladder cancer T24 cells and observed increased NMU RNA expression. Although NMU overexpression did not increase the monolayer growth of T24 or related T24T poorly metastatic human bladder cancer cells, it did augment anchorage-independent growth for the latter. Overexpression of NMU in T24 and T24T cells significantly promoted tumor formation of both cell lines in nude mice, but did not alter the growth rate of established tumors. Furthermore, NMU-overexpressing xenografts were associated with lower animal body weight than control tumors, indicating a possible role of NMU in cancer cachexia. NMU overexpression in T24T cells significantly enhanced their lung metastatic ability. Bioluminescent in vivo imaging revealed that lung metastases in T24T grew faster than the same tumors in the subcutaneous microenvironment. In conclusion, NMU is a RhoGDI2-regulated gene that appears important for tumorigenicity, lung metastasis and cancer cachexia, and thus a promising therapeutic target in cancer.

Contrast-enhanced MR angiography at 1.5 T after implantation of platinum stents: in vitro and in vivo comparison with conventional stent designs.

OBJECTIVE: The objective of our study was to evaluate the in vitro and in vivo 3D contrast-enhanced MR angiography characteristics of a new platinum-based balloon-expandable stent system and compare this system with a variety of competing metallic stents. MATERIALS AND METHODS: All experiments were performed on 1.5-T scanners. In vitro experiments were performed using 10 stents implanted into a custom-built phantom. Different orientations of the stents along the magnetic field and multiple flip angles were examined. In addition, 19 patients underwent contrast-enhanced MR angiography after the implantation of 36 stents, including four patients with six platinum stents. Angiographic correlation was available for all 19 patients, and luminal patency and stent-induced artifacts were assessed quantitatively. RESULTS: Of the tested balloon-expandable stents, only the platinum-based stents created artifact causing luminal narrowing of 30% or less. All other balloon-expandable stents induced larger artifacts that resulted in higher degrees of narrowing. Thus, if patent, the platinum-based stents allow significant in-stent stenosis to be ruled out reliably. Selected nitinol- or tantalum-based self-expandable stents also are suitable in this regard. CONCLUSION: Of the tested devices, platinum-based stents are the only type of currently available balloon-expandable stent that creates 30% or less artifact-induced apparent stenosis and thus are suitable for MR angiography.

Gravity-dependent perfusion of the lung demonstrated with the FAIRER arterial spin tagging method.

Magnetic resonance imaging of lung perfusion using an arterial spin tagging (AST) sequence called flow sensitive alternating inversion recovery with an extra RF pulse (FAIRER) was performed in the left and right lateral positions in five volunteers. Coronal slices were obtained and the average intensity of each lung was measured. In both positions, an increase in the intensity of the dependent lung was found (229% for left lateral, 40% for right lateral). No change was seen along an isogravitational plane. Lung volumes were measured in each position to account for the compression of the lungs by the heart. This effect was found to be symmetric and did not contribute to the perfusion gradient. This demonstrates that AST is sensitive to gravity-dependent perfusion gradients in the lung.

Theoretical analysis of the effect of imperfect slice profiles on tagging schemes for pulsed arterial spin labeling MRI.

Pulsed arterial spin labeling (ASL) techniques provide a noninvasive method of obtaining qualitative and quantitative perfusion images with MRI. ASL techniques employ inversion recovery and/or saturation recovery to induce perfusion weighting, and thus the performance of these techniques is dependent on the slice profiles of the inversion or saturation pulses. This article systematically examines through simulations the effects of slice profile imperfections on the perfusion signal for nine labeling schemes, including FAIR, FAIRER, and EST (UNFAIR). Each sequence is evaluated for quantitative accuracy, suppression of stationary signal, and magnitude of perfusion signal. Perfusion effects are modeled from a modified Bloch equation and experimentally determined slice profiles. The results show that FAIR, FAIRER, and EST have excellent tissue suppression. The magnitude of the perfusion signal is comparable for FAIR and FAIRER, with EST providing a slightly weaker signal. For quantitative measurements, all three methods underestimate the perfusion signal by more than 20%. Of the additional six ASL techniques examined, only one performed well in this model. This method, which combines inversion and saturation recovery, yields improved signal accuracy (<15% difference from the theoretical value) and tissue suppression similar to that of FAIR and its variants, but has only half the signal. Magn Reson Med 46:141-148, 2001.

Effect of lung inflation on arterial spin labeling signal in MR perfusion imaging of human lung.

The effect of lung inflation on arterial spin-labeling signal in lung perfusion is investigated. Arterial spin-labeling schemes, called alternation of selective inversion pulse (ASI) and its hybrid (HASI), which uses blood water as an endogenous, freely diffusible tracer, were applied to magnetic resonance (MR) perfusion imaging of the lung. Perfusion-weighted images of the lung from nine healthy volunteers were obtained at different time delays. There was a significant signal difference in ASI images acquired at different respiratory phases. Greater signal enhancement has been observed when the volunteers performed breath holding on end expiration than on end inspiration. This is in agreement with the normal physiologic effect of lung inflation on the pressure-flow relationship of pulmonary vasculature. ASI and HASI perfusion-weighted images show similar lung features and image quality. Preliminary results from pulmonary embolism patients indicate that arterial spin labeling is sensitive for the detection of areas of perfusion deficit. J. Magn. Reson. Imaging 2001;13:954-959.

Uterine fibroid embolization: assessment of treatment response using perfusion-weighted extraslice spin tagging (EST) magnetic resonance imaging.

In this pilot study, we demonstrate the feasibility of using an arterial spin tagging technique, Extraslice Spin Tagging (EST), to assess tumor perfusion before and after uterine fibroid embolization (UFE) and correlate the changes in perfusion with fibroid size reduction. We followed two patient volunteers over a six-month period. The perfusion-weighted image intensity decreased immediately after UFE. The size of the tumor decreased by 14% immediately after UFE and continued to decrease over a six-month period to 84%. The imaging methods presented allow for rapid measurement of tumor volume and the evaluation of perfusion of the tumor without the need for intravenous administration of gadolinium compounds. J. Magn. Reson. Imaging 2001;13:982-986.

Noninvasive in vivo magnetic resonance imaging of injury-induced neointima formation in the carotid artery of the apolipoprotein-E null mouse.

Mice deficient in apolipoprotein-E (apoE) experience severe hypercholesterolemia, are prone to atherosclerosis, and recently have emerged as a powerful tool in the study of plaque formation. In this study, we developed magnetic resonance (MR) imaging methods to detect the progression of atherosclerosis noninvasively in a mouse model of arterial injury. Four 14-week-old apoE-deficient mice were imaged 5 weeks after beginning an atherogenic Western diet and 4 weeks after wire denudation injury of the left common carotid artery (LCCA). Information from several images was combined into high-information content images using methods previously developed. The image resolution was 47 x 47 x 750 microm(3). We acquired T1-, T2-, and proton density (PD)-weighted images (TR/TE 650/14, 2000/60, and 2000/14 msec, respectively). Each 8-bit image was placed in a separate color channel to produce a 24-bit color image (red = T1, green = PD, and blue = T2). The composite image created contrast between different tissue types that was superior to that of any single image and revealed significant luminal narrowing of the LCCA, but not the uninjured RCCA. MR images were compared with corresponding histopathology cross sections and luminal area measurements from each method correlated(r2= 0.61). Atherosclerotic luminal narrowing was successfully detected through MR imaging in a mouse model of arterial injury that is small, reproduces quickly, and lends itself to genetic analysis and manipulation.

1H magnetic resonance imaging of human lung using inversion recovery turbo spin echo.

Evaluation of lung pathologies using magnetic resonance imaging remains limited, primarily due to the lung's low proton density and high density of magnetic field susceptibility gradients. It is hypothesized that visualization of the lung is possible if signal intensity from muscle and/or fat is suppressed or reduced. Using the inversion recovery and frequency selective saturation pulse with a half-Fourier single-shot turbo spin-echo (HASTE) or a segmented, centric reordered turbo spin-echo (TSE) readout, signal intensity and contrast of tissues can be manipulated to enhance the visibility of the lung. Multislice images of the lung from 10 healthy volunteers were acquired with negligible motion artifacts. Peripheral pulmonary vessels appear well delineated. T(1) maps of the lung are also presented; the overall average was 1335 +/- 85 msec and 1245 +/- 93 msec with the volunteers performing breath-holding on end-expiration and end-inspiration, respectively. This difference is statistically significant, at P < 0.01.

Imaging pulmonary blood flow and perfusion using phase-sensitive selective inversion recovery.

A technique is described for imaging pulmonary blood flow using a phase-sensitive selective inversion recovery (PS-SIR) sequence. PS-SIR image reconstruction provides excellent contrast, differentiating fully relaxed inflowing blood from inverted blood and lung tissue. The magnetization of the inverted tissues remains negative at any inversion delay less than that at which the magnetization of the lung tissue is nulled, whereas that of the fully relaxed inflowing blood is always positive. Pulmonary blood flow can be observed by tracking the propagation of the pixels with positive values. Five healthy volunteers were imaged. The normal pattern of blood flow advancing from the central arteries toward the peripheries and into the lung parenchyma with return toward the center via draining veins was depicted. The method offers promise for evaluating pulmonary blood flow without the need for image subtraction or contrast administration. Magn Reson Med 43:793-795, 2000.

Detection of regional pulmonary perfusion deficit of the occluded lung using arterial spin labeling in magnetic resonance imaging.

Detection of regional perfusion deficit in the lung has been demonstrated using an arterial spin labeling technique called flow-sensitive alternating inversion recovery with an extra radiofrequency pulse (FAIRER). A pulmonary artery was occluded using a nondetachable balloon catheter to simulate an acute pulmonary embolism in 3 of 10 rabbits. Inflating the balloon occludes the artery, and deflating the balloon allows for reperfusion. Perfusion imaging was performed pre-occlusion, during occlusion, and after reperfusion. Signal enhancement due to perfusion of the pulmonary parenchyma was observed in the perfusion images with negligible artifacts. The perfusion deficit of the pulmonary parenchyma was detected distal to the site of occlusion in all three rabbits. Return of the pulmonary parenchymal perfusion was observed after reperfusion. Magnetic resonance imaging using FAIRER can detect signal loss due to absence of perfusion caused by pulmonary embolism.

Determination of intracranial tumor volumes in a rodent brain using magnetic resonance imaging, Evans blue, and histology: a comparative study.

The measurement of tumor volumes is a practical and objective method of assessing the efficacy of a therapeutic agent. However, the relative accuracy of different methods of assessing tumor volume has been unclear. Using T1-weighted, gadolinium-enhanced magnetic resonance Imaging (T1-MRI), Evans Blue infusion and histology we measured intracranial tumor volumes in a rodent brain tumor model (RT2) at days 10, 16 and 18 after implantation of cells in the caudate putamen. There is a good correlation between tumor volumes comparing T1-MRI and Evans Blue (r2 = 0.99), T1-MRI and Histology (r2 = 0.98) and histology and Evans Blue (r2 = 0.93). Each of these methods is reliable in estimating tumor volumes in laboratory animals. There was significant uptake of gadolinium and Evans Blue in the tumor suggesting a wide disruption of the blood-brain barrier.

Perfusion of the kidney using extraslice spin tagging (EST) magnetic resonance imaging.

This study was undertaken to determine whether extraslice spin tagging (EST) perfusion-weighted magnetic resonance imaging is suitable for screening persons for renal perfusion deficits. Six normal and seven patient volunteers with suspected decreased renal perfusion due to renal vascular disease were imaged. X-ray angiograms were also obtained on all patients. The normalized EST signal intensity showed a linear correlation with respect to the percent stenosis measured from the X-ray angiograms. This demonstrates the potential utility of using EST for the evaluation of kidney perfusion, which was done without the need for exogenous MR contrast agents. EST is fast and less expensive than contrast-based methods. These features make EST a candidate for routine screening of patients for renal vascular disease and for the assessment of angiographically equivocal renal artery stenoses. J. Magn. Reson. Imaging 1999;10:886-891.

Consequences of (129)Xe-(1)H cross relaxation in aqueous solutions.

We have investigated the transfer of polarization from (129)Xe to solute protons in aqueous solutions to determine the feasibility of using hyperpolarized xenon to enhance (1)H sensitivity in aqueous systems at or near room temperatures. Several solutes, each of different molecular weight, were dissolved in deuterium oxide and although large xenon polarizations were created, no significant proton signal enhancement was detected in l-tyrosine, alpha-cyclodextrin, beta-cyclodextrin, apomyoglobin, or myoglobin. Solute-induced enhancement of the (129)Xe spin-lattice relaxation rate was observed and depended on the size and structure of the solute molecule. The significant increase of the apparent spin-lattice relaxation rate of the solution phase (129)Xe by alpha-cyclodextrin and apomyoglobin indicates efficient cross relaxation. The slow relaxation of xenon in beta-cyclodextrin and l-tyrosine indicates weak coupling and inefficient cross relaxation. Despite the apparent cross-relaxation effects, all attempts to detect the proton enhancement directly were unsuccessful. Spin-lattice relaxation rates were also measured for Boltzmann (129)Xe in myoglobin. The cross-relaxation rates were determined from changes in (129)Xe relaxation rates in the alpha-cyclodextrin and myoglobin solutions. These cross-relaxation rates were then used to model (1)H signal gains for a range of (129)Xe to (1)H spin population ratios. These models suggest that in spite of very large (129)Xe polarizations, the (1)H gains will be less than 10% and often substantially smaller. In particular, dramatic (1)H signal enhancements in lung tissue signals are unlikely.

Improved visualization of the human lung in 1H MRI using multiple inversion recovery for simultaneous suppression of signal contributions from fat and muscle.

1H magnetic resonance imaging of the lung is hampered by the low contrast between lung parenchyma, and muscle and fat in the thorax. We show that it is possible to improve contrast greatly and thereby enhance the visibility of the lung, by suppression of signal of surrounding muscle and fat based on differences in T1 relaxation times using a double inversion recovery preparation pulses (TI1 800 msec, and TI2 150 msec) and a half-Fourier acquisition single-shot turbo spin-echo (HASTE) sequence. The measured T1 values for the right and left lungs at 1.5 T were 1.37 +/- 0.18 and 1.41 +/- 0.21 sec, respectively.

MR perfusion imaging of pulmonary parenchyma using pulsed arterial spin labeling techniques: FAIRER and FAIR.

Magnetic resonance imaging of pulmonary parenchyma perfusion using pulsed arterial spin labeling (ASL) techniques is presented. ASL uses magnetically labeled water as an endogenous, freely diffusible tracer. Presented are comparative results of ASL methods called Flow sensitive Alternating Inversion Recovery (FAIR), and FAIR with an Extra Radiofrequency pulse (FAIRER). Six healthy human volunteers were imaged. Perfusion-weighted images at different time delays, TI, were calculated from the subtraction of the control and tag images, which were acquired within a single breathhold. Detailed pulmonary structures can be visualized with negligible cardiac or respiratory motion artifacts. Different patterns of signal enhancement between the pulmonary vessels and parenchyma are shown in the perfusion images acquired at different TIs.

Perfusion imaging of the human lung using flow-sensitive alternating inversion recovery with an extra radiofrequency pulse (FAIRER).

Pulmonary perfusion is an important parameter in the evaluation of lung diseases such as pulmonary embolism. A noninvasive MR perfusion imaging technique of the lung is presented in which magnetically labeled blood water is used as an endogenous, freely diffusible tracer. The perfusion imaging technique is an arterial spin tagging method called Flow sensitive Alternating Inversion Recovery with an Extra Radiofrequency pulse (FAIRER). Seven healthy human volunteers were studied. High-resolution perfusion-weighted images with negligible artifacts were acquired within a single breathhold. Different patterns of signal enhancement were observed between the pulmonary vessels and parenchyma, which persists up to TI = 1400 ms. The T1s of blood and lung parenchyma were determined to be 1.46s and 1.35 s, respectively.

Extraslice spin tagging (EST) magnetic resonance imaging for the determination of perfusion.

A new magnetic resonance technique to measure perfusion is described in detail. The means by which this is done is to invert all the spins in the radiofrequency RF coil with a non-spatially selective pulse and immediately re-invert the spins in the imaging plane. The net effect is that the spins in the imaging plane experience minimal perturbation of their magnetization while the spins outside the plane (extraslice) are inverted, or tagged. Tagged spins that flow into the imaging plane before image data are acquired decrease the signal intensity in the imaging plane when compared with an image in which the inflowing spins are not tagged. This decrease in signal can be used to calculate the number of spins that have flowed into the imaging plane, i.e., can be used to calculate the perfusion in mL x 100 g(tissue)(- 1)x min(-1). The extraslice spin tagging (EST) magnetization preparation period was coupled with a fast imaging sequence to obtain perfusion maps for normal volunteers.

Gender differences in leptin levels during puberty are related to the subcutaneous fat depot and sex steroids.

Little is known about the influence of adiposity and hormone release on leptin levels in children and adolescents. We utilized criterion methods to examine the relationships among sex steroids, body composition (4 compartment), abdominal visceral and subcutaneous fat (magnetic resonance imagery), total subcutaneous fat (sum of 9 skinfolds), energy expenditure (doubly labeled water), aerobic fitness, and serum leptin levels in prepubertal and pubertal boys (n = 16; n = 13) and girls (n = 12; n = 15). The sum of skinfolds accounted for more variance in leptin levels of all girls [coefficient of determination (R2) = 0.70, P < 0.001] and all boys (R2 = 0.60, P < 0.001) than the total fat mass (girls, R2 = 0.52, P < 0.001; boys, R2 = 0.23, P < 0.001). Total energy expenditure, corrected for the influence of fat-free mass, correlated inversely with leptin (R2 = 0.18, P = 0.02). Gender differences in leptin disappeared when corrected for sex steroid levels or the combination of adiposity and energy expenditure. In multiple regression, the sum of skinfolds and free testosterone and estrogen levels accounted for 74% of the variance in leptin levels. We conclude that serum leptin levels are positively related to subcutaneous adiposity but negatively related to androgen levels. Energy expenditure may be negatively related to leptin levels by reduction of the adiposity, or a common genetic factor may influence both the activity and serum leptin levels.