Magnetic resonance imaging: a tool to monitor and optimize enzyme distribution during porcine pancreas distention for islet isolation.

Porcine islet xenotransplantation is emerging as a potential alternative for allogeneic clinical islet transplantation. Optimization of porcine islet isolation in terms of yield and quality is critical for the success and cost-effectiveness of this approach. Incomplete pancreas distention and inhomogeneous enzyme distribution have been identified as key factors for limiting viable islet yield per porcine pancreas. The aim of this study was to explore the utility of magnetic resonance imaging (MRI) as a tool to investigate the homogeneity of enzyme delivery in porcine pancreata. Traditional and novel methods for enzyme delivery aimed at optimizing enzyme distribution were examined. Pancreata were procured from Landrace pigs via en bloc viscerectomy. The main pancreatic duct was then cannulated with an 18-g winged catheter and MRI performed at 1.5-T. Images were collected before and after ductal infusion of chilled MRI contrast agent (gadolinium) in physiological saline. Regions of the distal aspect of the splenic lobe and portions of the connecting lobe and bridge exhibited reduced delivery of solution when traditional methods of distention were utilized. Use of alternative methods of delivery (such as selective re-cannulation and distention of identified problem regions) resolved these issues, and MRI was successfully utilized as a guide and assessment tool for improved delivery. Current methods of porcine pancreas distention do not consistently deliver enzyme uniformly or adequately to all regions of the pancreas. Novel methods of enzyme delivery should be investigated and implemented for improved enzyme distribution. MRI serves as a valuable tool to visualize and evaluate the efficacy of current and prospective methods of pancreas distention and enzyme delivery.

Magnetic deposition of aerosols composed of aggregated superparamagnetic nanoparticles.

PURPOSE: The deposition of magnetic particles was examined for the possibility of further enhancing the selectivity of inhalation drug administration for the treatment of lung cancer. METHODS: Superparamagnetic magnetite nanoparticles were prepared and ultrasonically atomized, dried, and passed through glass tubes in the presence and absence of a wedge-shaped permanent magnet. The change in the outlet aerosol size distribution due to magnetic deposition under various well-defined aerodynamic conditions and a measured magnetic field was determined by an aerodynamic particle sizer. In addition, computational fluid dynamics (CFD) simulations of magnetic aerosol transport and deposition were conducted. RESULTS: The deposition fraction increased nearly linearly with particle diameter and was greater with lower air flow rates. The effect of tube diameter was complicated but well described by CFD simulations, as was the effect of particle size and air flow rate. CONCLUSIONS: The descriptive power of CFD simulations was demonstrated in the in vitro deposition of magnetic aerosol particles. This suggests that CFD simulations can potentially be used in future studies to design systems for selective drug delivery in vivo as a function of magnetic properties, aerosol characteristics, and respiratory physiology.

Magnetic Levitation of MC3T3 Osteoblast Cells as a Ground-Based Simulation of Microgravity.

Diamagnetic samples placed in a strong magnetic field and a magnetic field gradient experience a magnetic force. Stable magnetic levitation occurs when the magnetic force exactly counter balances the gravitational force. Under this condition, a diamagnetic sample is in a simulated microgravity environment. The purpose of this study is to explore if MC3T3-E1 osteoblastic cells can be grown in magnetically simulated hypo-g and hyper-g environments and determine if gene expression is differentially expressed under these conditions. The murine calvarial osteoblastic cell line, MC3T3-E1, grown on Cytodex-3 beads, were subjected to a net gravitational force of 0, 1 and 2 g in a 17 T superconducting magnet for 2 days. Microarray analysis of these cells indicated that gravitational stress leads to up and down regulation of hundreds of genes. The methodology of sustaining long-term magnetic levitation of biological systems are discussed.

Ferrous-Ferric Ion exchange dosemeter.

In this work a three-dimensional ferrous-ferric ion exchange dosemeter is proposed and the dose response measured. The dosemeter consists of strong acid cation exchange resin beads in the H form in water. Amberlyst 15 Wet beads with a harmonic mean diameter of 0.600-0.850 mm were prepared by soaking them in an aqueous solution of ferrous ammonium sulphate to exchange ferrous ions for H(+) ions. The beads were rinsed with distilled water and packed in glass vials. Sets of samples with ferrous ion concentrations of 0.5 and 1.0 mM were dosed with 6 MV X rays from a Varian 2100C linac. The spin-lattice relaxation time constants (T1) for the samples were measured using an Apollo spectrometer (Tecmag, Houston, TX) interfaced to a 1.5 T magnet (Magnex, Abingdon, UK). Each sample had two T1 values; a long T1 at 1200 ms that did not significantly change with dose and a short T1 that ranged from 56 ms at 0 Gy to 36 ms at 100 Gy. The R1 vs. dose responses were linear with slopes of 0.066 and 0.079 s(-1) Gy(-1).

Ringer's ethyl pyruvate in hemorrhagic shock and resuscitation does not improve early hemodynamics or tissue energetics.

Reactive oxygen species (ROS) have been implicated in the pathogenesis of hemorrhagic shock. Ethyl pyruvate, a derivative of pyruvate and a proposed oxygen radical scavenger, is attractive as a possible resuscitation fluid. We investigated whether resuscitation with lactated Ringer's (LR) containing ethyl pyruvate (REP) had any hemodynamic or tissue energetic benefits compared with LR alone for hemorrhagic shock. Hemorrhagic shock was induced in splenectomized pigs via inferior vena cava cannula. After 90 min of shock, animals were resuscitated in a stepwise fashion with LR or REP (30 mg/kg/dose, given as 1.5 mg/mL in LR) at 20 cc/kg/step for four steps. Data collected during this experiment included physiologic and hemodynamic parameters, near-infrared reflectance spectroscopy measurements of tissue hemoglobin oxygen (StO(2)) of the stomach, liver, and hind limb, and nuclear magnetic resonance phosphorus spectra of the liver and hind limb at each time point. In both resuscitative groups, heart rate, and lactate and pyruvate values increased during shock and began to drop toward baseline values during resuscitation. Mean arterial pressure, oxygen delivery, and oxygen consumption decreased during shock and increased toward baseline levels during the resuscitative process. There were no significant changes in physiologic parameters between the LR- and REP-resuscitated animals. There was a significantly lower stomach StO(2) and hind limb cellular cytoplasmic pH during later resuscitative endpoints in REP-resuscitated animals. The clinical significance of these findings are unclear. There is no short-term hemodynamic or tissue energetic advantage to using REP as a resuscitation fluid when compared with LR. Long-term outcome studies are needed to further evaluate any potential benefits of use of REP in hemorrhagic shock.

Tissue energetics as measured by nuclear magnetic resonance spectroscopy during hemorrhagic shock.

The defect in energy production in an organism during shock states may be related to the impairment of mitochondrial respiration early in shock. The aim of this study was to investigate the timing and degree of cellular energetic changes during hemorrhagic shock in real time. Instrumented, splenectomized swine were randomized to undergo hemorrhagic shock, induced by a 35% blood volume bleed, for 90 min with (n = 10) or without (n = 9) subsequent resuscitation. Resuscitated animals received shed blood in two increments followed by two normal saline boluses (20 mL/kg/bolus). Throughout experimentation, tissue phosphoenergetics of liver and skeletal muscle were monitored using 31P nuclear magnetic resonance (NMR) spectroscopy via NMR coils on the liver and hindlimb. Near-infrared spectroscopy probes were used to measure liver, stomach, and skeletal muscle oxyhemoglobin saturation (StO2). Hemorrhagic shock induced an increase in phosphomonoesters in skeletal muscle (baseline: 7.09%, 90 min: 9.94% (P < 0.05); expressed as percent total phosphorus). This increase resolved in animals receiving resuscitation (n = 10) but remained elevated in those in unresuscitated shock (n = 9). Inorganic phosphate levels increased and betaATP levels decreased significantly in the liver of animals in shock as compared with baseline. StO2 in skeletal muscle, stomach, and liver correlated with whole organism oxygen delivery (r2 = 0.356, 0.368, and 0.432, respectively). We conclude that hemorrhagic shock induces early elevation of phosphomonoesters in skeletal muscle, which correlates with the severity of shock. This implies an early transition to anaerobic glycolysis during hemorrhagic shock, which may be indicative of early mitochondrial dysfunction.

Image-guided drug delivery in lung cancer.

Lung cancer continues to be the number one cause of cancer-related deaths in the USA. Early identification of the disease, availability of more effective drugs, and improved delivery of such drugs specifically to cancer cells are needed to decrease lung cancer-associated morbidity and mortality. The concept of image-guided drug delivery (IGDD), which envisions the utilization of imaging techniques for quantitative assessments of tumor-targeted drug delivery and therapeutic response, has the potential to make a significant impact in lung cancer. While the anatomic and physiological features of the lung pose distinct problems for imaging drug delivery, several new techniques are emerging that have the potential to overcome these problems. X-ray is a routinely used technique for diagnosing lung cancer; however, positron emission tomography (PET) and magnetic resonance imaging (MRI) are complementary approaches. PET- and MRI-based techniques (such as functional MRI) offer the possibility of imaging the delivery of specific molecules to cancer tissues in the lung. This paper reviews fundamentals of imaging with an emphasis on MRI and to some extent PET, since it will be argued that these techniques are the most promising for development in IGDD for lung cancer. Finally, key literature contributions will be highlighted, which exemplify the current successes in this area.

Phosphomonoesters predict early mortality in porcine hemorrhagic shock.

BACKGROUND: Hemodynamic, laboratory, and tissue energetics were measured in a porcine model of hemorrhagic shock to evaluate variables as predictors of early mortality from shock. We hypothesized that elevated phosphomonoesters would predict early mortality in hemorrhagic shock. METHODS: Pigs (n = 36) were subjected to 35% hemorrhage for 90 minutes in a 1.5-T nuclear magnetic resonance (NMR) magnet. Measurements included base deficit (BD); lactate; oxygen consumption/delivery; near-infrared spectroscopy of liver, stomach, and skeletal muscle tissue oxyhemoglobin saturation; and NMR spectroscopic measurements of high-energy phosphates of liver and skeletal muscle. Variables were compared between nonsurvivors and survivors to resuscitation after 90-minute measurements. RESULTS: Ninety-minute mortality was 25%. Muscle phosphomonoesters (PMEs) and oxygen consumption differed significantly between survivors and nonsurvivors at baseline. Regression analysis identified baseline muscle PME levels, baseline BD, and 30-minute BD as early predictors of mortality before resuscitation (r2 = 0.304). CONCLUSION: Baseline elevation in muscle PME levels predicts mortality in an animal model of severe hemorrhagic shock.