Detecting peritoneal dissemination of ovarian cancer in mice by DWIBS.

Diffusion-weighted whole-body imaging with background body signal suppression (DWIBS) is a relatively new diffusion-based pulse sequence that produces positron emission tomography (PET) with 2-[fluorine-18]-fluoro-2-deoxy-D-glucose ((18)F-FDG)-like images. We tested the feasibility of DWIBS in detecting peritoneal ovarian cancer in a syngeneic mouse model. Female C57BL/6 mice were injected intraperitoneally with ID8 murine ovarian carcinoma cells. After 11 weeks, the abdomen was imaged by DWIBS. A respiratory gating diffusion-weighted spin-echo echo-planar imaging in abdomen was used (imaging parameters of field of view of 47×47 mm(2), matrix size of 64×64 zero-filled to 256×256 and b-value of 1500 s/mm(2)). We also performed FDG microPET as the reference standard. For comparison of the correlating surface areas of tumor foci on both DWIBS and FDG microPET imaging, two-dimensional region-of-interest (ROI) analysis was performed, and correlation between the two modalities was determined. Mice were also subjected to macroscopic examination for tumor location and pathology after imaging. DWIBS in all mice depicted the tumors as abnormal high signal intensity. The results show that the ROI analysis of correlating lesions reveals relatively high correlation (r²=0.7296) and significant difference (P=.021) between DWIBS and FDG microPET. These results demonstrate that DWIBS has the potential for detecting peritoneal dissemination of ovarian cancer. Nonetheless, due to low ratios of image signal-to-noise and motion artifacts, DWIBS can be limited for lesions near the liver.

Effect of oxygen concentration on viability and metabolism in a fluidized-bed bioartificial liver using ³¹P and ¹³C NMR spectroscopy.

Many oxygen mass-transfer modeling studies have been performed for various bioartificial liver (BAL) encapsulation types; yet, to our knowledge, there is no experimental study that directly and noninvasively measures viability and metabolism as a function of time and oxygen concentration. We report the effect of oxygen concentration on viability and metabolism in a fluidized-bed NMR-compatible BAL using in vivo ³¹P and ¹³C NMR spectroscopy, respectively, by monitoring nucleotide triphosphate (NTP) and ¹³C-labeled nutrient metabolites, respectively. Fluidized-bed bioreactors eliminate the potential channeling that occurs with packed-bed bioreactors and serve as an ideal experimental model for homogeneous oxygen distribution. Hepatocytes were electrostatically encapsulated in alginate (avg. diameter, 500 µm; 3.5×107 cells/mL) and perfused at 3 mL/min in a 9-cm (inner diameter) cylindrical glass NMR tube. Four oxygen treatments were tested and validated by an in-line oxygen electrode: (1) 95:5 oxygen:carbon dioxide (carbogen), (2) 75:20:5 nitrogen:oxygen:carbon dioxide, (3) 60:35:5 nitrogen:oxygen:carbon dioxide, and (4) 45:50:5 nitrogen:oxygen:carbon dioxide. With 20% oxygen, ß-NTP steadily decreased until it was no longer detected at 11 h. The 35%, 50%, and 95% oxygen treatments resulted in steady ß-NTP levels throughout the 28-h experimental period. For the 50% and 95% oxygen treatment, a ¹³C NMR time course (∼5 h) revealed 2-¹³C-glycine and 2-¹³C-glucose to be incorporated into [2-¹³C-glycyl]glutathione (GSH) and 2-¹³C-lactate, respectively, with 95% having a lower rate of lactate formation. ³¹P and ¹³C NMR spectroscopy is a noninvasive method for determining viability and metabolic rates. Modifying tissue-engineered devices to be NMR compatible is a relatively easy and inexpensive process depending on the bioreactor shape.

¹³C magnetic resonance spectroscopy detection of changes in serine isotopomers reflects changes in mitochondrial redox status.

The glycine cleavage system (GCS), the major pathway of glycine catabolism in liver, is found only in the mitochondria matrix and is regulated by the oxidized nicotinamide adenine dinucleotide (NAD(+) )/reduced nicotinamide adenine dinucleotide (NADH) ratio. In conjunction with serine hydroxymethyltransferase, glycine forms the 1 and 2 positions of serine, while the 3 position is formed exclusively by GCS. Therefore, we sought to exploit this pathway to show that quantitative measurements of serine isotopomers in liver can be used to monitor the NAD(+) /NADH ratio using (13) C NMR spectroscopy. Rat hepatocytes were treated with modulators of GCS activity followed by addition of 2-(13) C-glycine, and the changes in the proportions of newly synthesized serine isotopomers were compared to controls. Cysteamine, a competitive inhibitor of GCS, prevented formation of mitochondrial 3-(13) C-serine and 2,3-(13) C-serine isotopomers while reducing 2-(13) C-serine by 55%, demonstrating that ca. 20% of glycine-derived serine is produced in the cytosol. Glucagon, which activates GCS activity, and the mitochondrial uncoupler carbonyl cyanide-3-chlorophenylhydrazone both increased serine isotopomers, whereas rotenone, an inhibitor of complex I, had the opposite effect. These results demonstrate that (13) C magnetic resonance spectroscopy monitoring of the formation of serine isotopomers in isolated rat hepatocytes given 2-(13) C-glycine reflects the changes of mitochondrial redox status.

Metabolomic investigations of American oysters using H-NMR spectroscopy.

The Eastern oyster (Crassostrea virginica) is a useful, robust model marine organism for tissue metabolism studies. Its relatively few organs are easily delineated and there is sufficient understanding of their functions based on classical assays to support interpretation of advanced spectroscopic approaches. Here we apply high-resolution proton nuclear magnetic resonance ((1)H NMR)-based metabolomic analysis to C. virginica to investigate the differences in the metabolic profile of different organ groups, and magnetic resonance imaging (MRI) to non-invasively identify the well separated organs. Metabolites were identified in perchloric acid extracts of three portions of the oyster containing: (1) adductor muscle, (2) stomach and digestive gland, and (3) mantle and gills. Osmolytes dominated the metabolome in all three organ blocks with decreasing concentration as follows: betaine > taurine > proline > glycine > ß-alanine > hypotaurine. Mitochondrial metabolism appeared most pronounced in the adductor muscle with elevated levels of carnitine facilitating ß-oxidation, and ATP, and phosphoarginine synthesis, while glycogen was elevated in the mantle/gills and stomach/digestive gland. A biochemical schematic is presented that relates metabolites to biochemical pathways correlated with physiological organ functions. This study identifies metabolites and corresponding (1)H NMR peak assignments for future NMR-based metabolomic studies in oysters.

Applications of chemical shift imaging to marine sciences.

The successful applications of magnetic resonance imaging (MRI) in medicine are mostly due to the non-invasive and non-destructive nature of MRI techniques. Longitudinal studies of humans and animals are easily accomplished, taking advantage of the fact that MRI does not use harmful radiation that would be needed for plain film radiographic, computerized tomography (CT) or positron emission (PET) scans. Routine anatomic and functional studies using the strong signal from the most abundant magnetic nucleus, the proton, can also provide metabolic information when combined with in vivo magnetic resonance spectroscopy (MRS). MRS can be performed using either protons or hetero-nuclei (meaning any magnetic nuclei other than protons or ¹H) including carbon (¹³C) or phosphorus (³¹P). In vivo MR spectra can be obtained from single region of interest (ROI or voxel) or multiple ROIs simultaneously using the technique typically called chemical shift imaging (CSI). Here we report applications of CSI to marine samples and describe a technique to study in vivo glycine metabolism in oysters using ¹³C MRS 12 h after immersion in a sea water chamber dosed with [2-¹³C]-glycine. This is the first report of ¹³C CSI in a marine organism.

Modeling brain tissue volumes over the lifespan: quantitative analysis of postmortem weights and in vivo MR images.

Normative measurements of brain gray matter and white matter tissue volumes across the lifespan have not yet been established. The purpose of this article was to use mathematical modeling and analytical functions to demonstrate the growth trajectory of gray matter and white matter from age 0 to age 90. For each gender, brain weight functions were generated by utilizing existing autopsy data from 4400 subjects. Brain gray matter, white matter and lateral ventricular volumes were measured from 39 MR volumes of normal individuals. These were converted to weight by multiplying the tissue volumes by the specific gravity of that tissue. White matter volumes were described by a saturating exponential function, and the gray matter volume function was calculated by subtracting the white matter weight function from the brain weight function. For each gender, equations were generated for white matter and gray matter volumes as a function of age over the lifespan.

Noninvasive assessment of tumor vasculature response to radiation-mediated, vasculature-targeted therapy using quantified power Doppler sonography: implications for improvement of therapy schedules.

OBJECTIVE: Stereotactic radiotherapy (ablative radiation) is a modality that holds considerable promise for effective treatment of intracranial and extracranial malignancies. Although tumor vasculature is relatively resistant to small fractionated doses of ionizing radiation, large ablative doses of ionizing radiation lead to effective demise of the tumor vasculature. The purpose of this study was (1) to noninvasively monitor and compare tumor physiologic parameters in response to ablative radiation treatments and (2) to use these noninvasive parameters to optimize the schedule of administration of radiation therapy. METHODS: Lewis lung carcinoma tumors were implanted into C57BL/6 mice and treated with ablative radiation. The kinetics of change in physiologic parameters of a response to single-dose 20-Gy treatments was measured. Parameters studied included tumor blood flow, apoptosis, and proliferation rates. Serial tumor sections were stained to correlate noninvasive Doppler assessment of tumor blood flow with microvasculature histologic findings. RESULTS: A single administration of 20 Gy led to an incomplete tumor vascular response, with subsequent recovery of tumor blood flow within 4 days after treatment. Sustained reduction of tumor blood flow by administering the successive ablative radiation treatment before tumor blood flow recovery led to a 3-fold tumor growth delay. The difference in tumor volumes at each measurement time point (every 2 days) was statistically significant (P=.016). CONCLUSIONS: This study suggests a rational design of schedule optimization for radiation-mediated, vasculature-directed treatments guided by noninvasive assessment of tumor blood flow levels to ultimately improve the tumor response.

Targeted molecular imaging agents for cellular-scale bimodal imaging.

Molecular imaging is a powerful tool that has the ability to elucidate biochemical mechanisms and signal the early onset of disease. Overexpression of the peripheral benzodiazepine receptor (PBR) has been observed in a variety disease states, including glioblastoma, breast cancer, and Alzheimer's disease. Thus, the PBR could be an attractive target for molecular imaging. In this paper, the authors report cellular uptake and multimodal (MRI and fluorescence) imaging of PBR-overexpressing C6 glioblastoma (brain cancer) cells using a cocktail administration approach and a new PBR targeted lanthanide chelate molecular imaging agent.

Enhanced tumor formation in cyclin D1 x transforming growth factor beta1 double transgenic mice with characterization by magnetic resonance imaging.

Transgenic mice that overexpress cyclin D1 protein in the liver develop liver carcinomas with high penetrance. Transforming growth factor beta (TGF-beta) serves as either an epithelial cell growth inhibitor or a tumor promoter, depending on the cellular context. We interbred LFABP-cyclin D1 and Alb-TGF-beta1 transgenic mice to produce cyclin D1/TGF-beta1 double transgenic mice and followed the development of liver tumors over time, characterizing cellular and molecular changes, tumor incidence, tumor burden, and tumor physiology noninvasively by magnetic resonance imaging. Compared with age-matched LFABP-cyclin D1 single transgenic littermates, cyclin D1/TGF-beta1 mice exhibited a significant increase in tumor incidence. Tumor multiplicity, tumor burden, and tumor heterogeneity were higher in cyclin D1/TGF-beta1 mice compared with single transgenic littermates. Characteristics of cyclin D1/TGF-beta1 livers correlated with a marked induction of the peripheral periductal oval cell/stem cell compartment of the liver. A number of cancerous lesions from cyclin D1/TGF-beta1 mice exhibited unique features such as ductal plate malformations and hemorrhagic nodules. Some lesions were contiguous with the severely diseased background liver and, in some cases, replaced the normal architecture of the entire organ. Cyclin D1/TGF-beta1 lesions, in particular, were associated with malignant features such as areas of vascular invasion by hepatocytes and heterogeneous hyperintensity of signal on T2-weighted magnetic resonance imaging. These findings demonstrate that TGF-beta1 promotes stem cell activation and tumor progression in the context of cyclin D1 overexpression in the liver.

Proton MR spectroscopic studies of chronic alcohol exposure on the rat brain.

PURPOSE: To better understand the long-term pathophysiologic mechanisms of alcoholism-related organic brain damage by serially assessing brain metabolites in chronically exposed rats using both in vivo magnetic resonance spectroscopy (MRS) and high-resolution nuclear magnetic resonance (NMR) from brain extracts. MATERIALS AND METHODS: The alcoholic regimen was continued up to 60 weeks. In vivo proton MRS studies were performed at 200 MHz using a small animal imaging/spectrometer. In vitro rat brain extracts were also examined using a 500 MHz vertical bore magnet. Comparison measurements were also obtained in an age-matched control group. RESULTS: In vivo results showed that there is a significant increase in the Cho/NAA ratio in the chronic alcohol-exposed group that reached a maximum around 16 weeks. After 44 weeks of alcohol exposure, Cho/NAA in the alcohol group decreased significantly from its maximum value to a value that was significantly lower than those from the control groups. Brain extract studies demonstrated that PC and GPC were the main components responsible for the observed in vivo spectral changes after 16 and 60 weeks of alcohol consumption, respectively. CONCLUSION: The fluctuation of choline-containing metabolites during alcohol intoxication could explain sometimes seemingly conflicting and confusing results from MRS studies in human and animal studies in which the duration of alcohol consumption and amount are varied widely.

Experimental model for functional magnetic resonance imaging of somatic sensory cortex in the unanesthetized rat.

Functional magnetic resonance imaging (fMRI) has evolved into a method widely used to map neural activation in the human brain. fMRI is a method for recording blood oxygen level-dependent (BOLD) signals. These signals change with local cerebral blood flow coupled to neural activity. However, the relationship between BOLD signals and neural function is poorly understood and requires the development of animal models. Here we use an unanesthetized rat preparation to study BOLD responses to whisker stimulation in somatic sensory barrel cortex. Five rats were trained to tolerate restraint in a holder and fMRI noise with positive reinforcement. For maximal immobilization, the head was fastened to the holder with nuts screwed on threaded bolts attached to the head. On scanning day, residual stress was alleviated with injections of diazepam, and the rats were restrained in the holder and transferred into the scanner. After >75 min to allow the tranquilization to abate, structural images were acquired from three coronal brain slices. Subsequently, functional images were taken utilizing 4-min epochs without stimulation alternated with equivalent epochs during which the right caudal whiskers were stimulated with three air puffs/s. After 4 weeks, fMRI could be repeated in four rats. In seven of the nine functional runs, head motion was minimal and whisker stimulation resulted in a statistically significant (P