Cytoplasmic Accumulation and Permeability of Antibiotics in Gram Positive and Gram Negative Bacteria Visualized in Real-Time via a Fluorogenic Tagging Strategy.

In this study, we describe the first real-time live cell assay for compound accumulation and permeability in both Gram positive and Gram negative bacteria. The assay utilizes a novel fluorogenic tagging strategy that permits direct visualization of compound accumulation dynamics in the cytoplasm of live cells, unobscured by washing or other processing steps. Quantitative differences could be reproducibly measured by flow cytometry at compound concentrations below the limit of detection for MS-based approaches. We establish the fluorogenic assay in E. coli and B. subtilis and compare the intracellular accumulation of two antibiotics, ciprofloxacin and ampicillin, with related pharmacophores in these bacteria.

Free-breathing gradient recalled echo-based CMR in a swine heart failure model.

In swine models, there are well-established protocols for creating a closed-chest myocardial infarction (MI) as well as protocols for characterization of cardiac function with cardiac magnetic resonance (CMR). This methods manuscript outlines a novel technique in CMR data acquisition utilizing smart-signal gradient recalled echo (GRE)-based array sequences in a free-breathing swine heart failure model allowing for both high spatial and temporal resolution imaging. Nine male Yucatan mini swine weighing 48.7 ± 1.6 kg at 58.2 ± 3.1 weeks old underwent the outlined imaging protocol before and 1-month after undergoing closed chest left anterior descending coronary artery (LAD) occlusion/reperfusion. The left ventricular ejection fraction (LVEF) at baseline was 59.3 ± 2.4% and decreased to 48.1 ± 3.7% 1-month post MI (P = 0.029). The average end-diastolic volume (EDV) at baseline was 55.2 ± 1.7 ml and increased to 74.2 ± 4.2 ml at 1-month post MI (P = 0.001). The resulting images from this novel technique and post-imaging analysis are presented and discussed. In a Yucatan swine model of heart failure via closed chest left anterior descending coronary artery (LAD) occlusion/reperfusion, we found that CMR with GRE-based array sequences produced clinical-grade images with high spatial and temporal resolution in the free-breathing setting.

Meningeal Lymphatic Vessel Flow Runs Countercurrent to Venous Flow in the Superior Sagittal Sinus of the Human Brain.

The recent report of the existence of meningeal lymphatic vessels (MLVs) in human and nonhuman primates used both histology and magnetic resonance imaging (MRI). Many questions about the physiology and function of these lymphatic vessels remain unanswered. Through the combination of appropriately positioned saturation bands and time-of-flight angiography sequences, MRI can resolve direction of flow within vessels without the use of exogenous contrast agent. Six healthy volunteers underwent high-resolution MRI of the MLVs running alongside the superior sagittal sinus to determine the direction of the lymphatic flow. In all subjects, the lymphatic flow was posterior to anterior, countercurrent to the direction of venous flow in the superior sagittal sinus and alongside the superior sagittal sinus. This flow strongly supports that a large proportion of the CNS lymphatic flow in humans is directed to the cribriform plate. The countercurrent direction of flow in the MLVs relative to venous flow in the superior sagittal sinus has implications for modeling flow of fluid and solutes across the various compartments of the CNS. A hypothetical compartmental model incorporating countercurrent flow is presented here.

Formation of Chiral Allylic Ethers via an Enantioselective Palladium-Catalyzed Alkenylation of Acyclic Enol Ethers.

This report details a palladium-catalyzed process to access highly functionalized, optically active allylic aryl ethers. A number of electron-deficient alkenyl triflates underwent enantioselective and site-selective coupling with acyclic aryl enol ethers in the presence of a chiral palladium catalyst. This transform provides chiral allylic ether products in high yields and excellent enantiomeric ratios, furnishing a unique disconnection to incorporate heteroatoms at a stereocenter. Finally, the applicability of the products to target synthesis was demonstrated through the formation of a chiral allylic alcohol and the generation of a flavone-inspired product.

Diffusion MRI with Semi-Automated Segmentation Can Serve as a Restricted Predictive Biomarker of the Therapeutic Response of Liver Metastasis.

PURPOSE: To assess the value of semi-automated segmentation applied to diffusion MRI for predicting the therapeutic response of liver metastasis. METHODS: Conventional diffusion weighted magnetic resonance imaging (MRI) was performed using b-values of 0, 150, 300 and 450s/mm(2) at baseline and days 4, 11 and 39 following initiation of a new chemotherapy regimen in a pilot study with 18 women with 37 liver metastases from primary breast cancer. A semi-automated segmentation approach was used to identify liver metastases. Linear regression analysis was used to assess the relationship between baseline values of the apparent diffusion coefficient (ADC) and change in tumor size by day 39. RESULTS: A semi-automated segmentation scheme was critical for obtaining the most reliable ADC measurements. A statistically significant relationship between baseline ADC values and change in tumor size at day 39 was observed for minimally treated patients with metastatic liver lesions measuring 2-5cm in size (p=0.002), but not for heavily treated patients with the same tumor size range (p=0.29), or for tumors of smaller or larger sizes. ROC analysis identified a baseline threshold ADC value of 1.33µm(2)/ms as 75% sensitive and 83% specific for identifying non-responding metastases in minimally treated patients with 2-5cm liver lesions. CONCLUSION: Quantitative imaging can substantially benefit from a semi-automated segmentation scheme. Quantitative diffusion MRI results can be predictive of therapeutic outcome in selected patients with liver metastases, but not for all liver metastases, and therefore should be considered to be a restricted biomarker.

T2 mapping of the heart with a double-inversion radial fast spin-echo method with indirect echo compensation.

BACKGROUND: The abnormal signal intensity in cardiac T2-weighted images is associated with various pathologies including myocardial edema. However, the assessment of pathologies based on signal intensity is affected by the acquisition parameters and the sensitivities of the receiver coils. T2 mapping has been proposed to overcome limitations of T2-weighted imaging, but most methods are limited in spatial and/or temporal resolution. Here we present and evaluate a double inversion recovery radial fast spin-echo (DIR-RADFSE) technique that yields data with high spatiotemporal resolution for cardiac T2 mapping. METHODS: DIR-RADFSE data were collected at 1.5 T on phantoms and subjects with echo train length (ETL) = 16, receiver bandwidth (BW) = ±32 kHz, TR = 1RR, matrix size = 256 × 256. Since only 16 views per echo time (TE) are collected, two algorithms designed to reconstruct highly undersampled radial data were used to generate images for 16 time points: the Echo-Sharing (ES) and the CUrve Reconstruction via pca-based Linearization with Indirect Echo compensation (CURLIE) algorithm. T2 maps were generated via least-squares fitting or the Slice-resolved Extended Phase Graph (SEPG) model fitting. The CURLIE-SEPG algorithm accounts for the effect of indirect echoes. The algorithms were compared based on reproducibility, using Bland-Altman analysis on data from 7 healthy volunteers, and T2 accuracy (against a single-echo spin-echo technique) using phantoms. RESULTS: Both reconstruction algorithms generated in vivo images with high spatiotemporal resolution and showed good reproducibility. Mean T2 difference between repeated measures and the coefficient of repeatability were 0.58 ms and 2.97 for ES and 0.09 ms and 4.85 for CURLIE-SEPG. In vivo T2 estimates from ES were higher than those from CURLIE-SEPG. In phantoms, CURLIE-SEPG yielded more accurate T2s compared to reference values (error was 7.5-13.9% for ES and 0.6-2.1% for CURLIE-SEPG), consistent with the fact that CURLIE-SEPG compensates for the effects of indirect echoes. The potential of T2 mapping with CURLIE-SEPG is demonstrated in two subjects with known heart disease. Elevated T2 values were observed in areas of suspected pathology. CONCLUSIONS: DIR-RADFSE yielded TE images with high spatiotemporal resolution. Two algorithms for generating T2 maps from highly undersampled data were evaluated in terms of accuracy and reproducibility. Results showed that CURLIE-SEPG yields T2 estimates that are reproducible and more accurate than ES.

Rapid water and lipid imaging with T2 mapping using a radial IDEAL-GRASE technique.

Three-point Dixon methods have been investigated as a means to generate water and fat images without the effects of field inhomogeneities. Recently, an iterative algorithm (IDEAL, iterative decomposition of water and fat with echo asymmetry and least squares estimation) was combined with a gradient and spin-echo acquisition strategy (IDEAL-GRASE) to provide a time-efficient method for lipid-water imaging with correction for the effects of field inhomogeneities. The method presented in this work combines IDEAL-GRASE with radial data acquisition. Radial data sampling offers robustness to motion over Cartesian trajectories as well as the possibility of generating high-resolution T(2) maps in addition to the water and fat images. The radial IDEAL-GRASE technique is demonstrated in phantoms and in vivo for various applications including abdominal, pelvic, and cardiac imaging.

Predicting functional gains in a stroke trial.

BACKGROUND AND PURPOSE: A number of therapies in development for patients with central nervous system injury aim to reduce disability by improving function of surviving brain elements rather than by salvaging tissue. The current study tested the hypothesis that, after adjusting for a number of clinical assessments, a measure of brain function at baseline would improve prediction of behavioral gains after treatment. METHODS: Twenty-four patients with chronic stroke underwent baseline clinical and functional MRI assessments, received 6 weeks of rehabilitation therapy with or without investigational motor cortex stimulation, and then had repeat assessments. Thirteen baseline clinical/radiological measures were evaluated for ability to predict subsequent trial-related gains. RESULTS: Across all patients, bivariate analyses found that greater trial-related functional gains were predicted by (1) smaller infarct volume, (2) greater baseline clinical status, and (3) lower degree of activation in stroke-affected motor cortex on baseline functional MRI. When these 3 variables were further assessed using multivariate linear regression modeling, only lower motor cortex activation and greater clinical status at baseline remained significant predictors. Note that lower baseline motor cortex activation was also associated with larger increases in motor cortex activation after treatment. CONCLUSIONS: Lower motor cortex activity at baseline predicted greater behavioral gains after therapy, even after controlling for a number of clinical assessments. The boosts in cortical activity that paralleled behavioral gains suggest that in some patients, low baseline cortical activity represents underuse of surviving cortical resources. A measure of brain function might be important for optimal clinical decision-making in the context of a restorative intervention.

Cardiac MRI is complementary to echocardiography in the assessment of cardiac masses.

Despite the fact that the incidence of cardiac tumors is low, the prompt evaluation and adequate intervention of these is highly important. Although most tumors of the heart are considered histologically benign, there are significant risks associated with these "benign" tumors. These are associated with significant morbidity and mortality due to obstruction of blood flow, alterations of conduction, propagation of arrhythmias, and thromboembolism, depending on their size, location, and nature. With the advent of noninvasive imaging modalities--traditionally echocardiography; but more recently using cross-sectional imaging with cardiac computed tomography and magnetic resonance imaging--cardiac tumors can be optimally assessed providing a greater opportunity for curative treatments by cardiothoracic surgery.

Cardiac MRI is an important complementary tool to Doppler echocardiography in the management of patients with pulmonary regurgitation.

Cardiac MRI (CMR) is a noninvasive diagnostic tool with comprehensive capabilities similar to that of two-dimensional echocardiography with Doppler. In addition to the ability to evaluate the etiology and severity of pulmonary valve regurgitation (PR), CMR is well designed to serially monitor the impact of the PR on the right ventricle (RV). Importantly, RV dilation and dysfunction is a critical determinate to time surgical intervention. CMR gives the silent RV, suffering from PR, a voice.

Cardiac magnetic resonance imaging investigation of sustained ventricular fibrillation in a swine model--with a focus on the electrical phase.

OBJECTIVES: We sought to develop a method to evaluate the rapidly changing cardiac dimensions during sustained ventricular fibrillation (VF). We also present details of our CPR research imaging program to facilitate this avenue of clinically important research. BACKGROUND: The changes in cardiac dimensions occurring during the initial critical electrical phase of sustained VF are not entirely known. Conventional cardiac magnetic resonance imaging (CMR) functional imaging lacks the temporal resolution necessary to capture the dynamic changes within this early time period of sustained VF. We hypothesized that changes in the middle short axis slice of the ventricles will reflect changes in ventricular volumes accurately. METHODS: Ventricular dimensions were determined from CMR for 30 min of untreated VF in a closed chest, closed pericardium model in seven swine. Ungated steady-state free precession images (SSFP) from the cardiac base to the apex were acquired, taking care to align the anatomical short axis (SAX) imaging planes maximally. The middle slice of the ventricles was determined as the mathematical center of the stack of SAX slices. We then compared the relative changes of right ventricle (RV) and left ventricle (LV) volumes to relative changes in mid-ventricular single slice area. RESULTS: During 30 min of sustained VF, there was an excellent correlation between the changes in exact mid-slice area and the quantitative changes in ventricular volumes (r(2)>0.95). CONCLUSIONS: Mid-slice area data can be used as a surrogate marker of prompt ventricular volume changes during VF. By imaging the heart 10 times faster, the rapid anatomical changes occurring during the initial few minutes of sustained VF can be understood better.