Enhancement of ATP levels and glucose metabolism during an infection by Chlamydia: NMR studies of living cells

The Chlamydia species are obligate intracellular bacteria that proliferate only within the infected cell. Since the extracellular bacteria are metabolically inert and there are no cell-free systems for characterizingChlamydia metabolism, we studied metabolic changes related to ATP synthesis and glycolysis in HeLa cells infected withChlamydia psittaci during the course of the 2-day infection cycle using noninvasive 31P and 13C NMR methods. We find that the infection stimulates ATP synthesis in the infected cell, with a peak of ATP levels occurring midway through the infection cycle, when most of the metabolically active bacteria are proliferating. The infection also stimulates synthesis of glutamate with a similar time course as for ATP. The stimulation is apparently due to an enhancement in glucose consumption by the infected cell, which also results in an increased rate of lactate production and glutamate synthesis as well as higher glycogen accumulation during the infection. Concurrently, infection leads to an increase in the expression of the glucose transporter, GLUT-1, on HeLa cells, which may account for the enhanced glucose consumption. The chlamydiae are thus able to stimulate glucose transport in the host cell sufficiently to compensate for the extra energy load on the cell represented by the infection

Nested Surface Coils for Multinuclear NMR

This article introduces the design of surface coils for multinuclear applications. The relative sensitivities of several NMR-visible nuclei of biological interest are considered, and the motivations to operate an RF coil at multiple frequencies, both sequentially and simultaneously, are reviewed. The design of nested surface coils is then developed. Magnetic fields generated by planar loop and butterfly coils are first introduced. The benefits of quadrature design are briefly considered, and methods for combining coils to produce a quadrature field are investigated. These designs are then extended to dual-nuclei coils using multiple, geometrically decoupled loops. The insertion of trap circuits into the low-frequency coil, as an alternative to geometric decoupling, is then considered. Finally, the optimum placement of filters is discussed to prevent noise injection from the RF power amplifiers and to prevent the preamplifiers from saturating during J-decoupling

Scale-up of an RF heated micro trickle bed reactor to a kg/day production scale

The scale-up of a radiofrequency (RF) heated micro trickle bed reactor for hydrogenation of 2-methyl-3-butyne-2-ol (MBY) over a Pd/TiO2 catalyst has been performed. The axial and radial temperature profiles were calculated using a 2D convection and conduction heat transfer model. The effect of the reactor length, tube diameter and number of parallel tubes on the temperature non-uniformity parameter has been studied. The axial scale-up was achieved by repeating a single periodic unit consisting of one heating and one catalytic zone along the reactor length. The catalyst loading can be increased by an order of magnitude following this approach. A radial temperature difference of 2 K was developed in a reactor with an inner diameter of 15 mm. The scale-up by numbering up allows the accommodation of seven parallel tubes inside a single RF coil. It creates a 7 K difference in the average temperature between the central and the outer tubes which results in a 5% difference in MBY conversion. An overall scale-up factor of near 700 is achieved which corresponds to a production rate of 0.5 kg of product/day

Whole Body Screening Using High-Temperature Superconducting MR Volume Resonators: Mice Studies

High temperature superconducting (HTS) surface resonators have been used as a low loss RF receiver resonator for improving magnetic resonance imaging image quality. However, the application of HTS surface resonators is significantly limited by their filling factor. To maximize the filling factor, it is desirable to have the RF resonator wrapped around the sample so that more nuclear magnetic dipoles can contribute to the signal. In this study, a whole new Bi2Sr2Ca2Cu2O3 (Bi-2223) superconducting saddle resonator (width of 5 cm and length of 8 cm) was designed for the magnetic resonance image of a mouse's whole body in Bruker 3 T MRI system. The experiment was conducted with a professionally-made copper saddle resonator and a Bi-2223 saddle resonator to show the difference. Signal-to-noise ratio (SNR) with the HTS saddle resonator at 77 K was 2.1 and 2 folds higher than that of the copper saddle resonator at 300 K for a phantom and an in-vivo mice whole body imaging. Testing results were in accordance with predicted ones, and the difference between the predicted SNR gains and measured SNR gains were 2.4%∼2.7%. In summary, with this HTS saddle system, a mouse's whole body can be imaged in one scan and could reach a high SNR due to a 2 folds SNR gain over the professionally-made prototype of copper saddle resonator at 300 K. The use of HTS saddle resonator not only improves SNR but also enables a mouse's whole body screen in one scan

Rapid and Recoverable in vivo Magnetic Resonance Imaging of the Adult Zebrafish at 7 T

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 is 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

Validating layer-specific VASO across species

Cerebral blood volume (CBV) has been shown to be a robust and important physiological parameter for quantitative interpretation of functional (f)MRI, capable of delivering highly localized mapping of neural activity. Indeed, with recent advances in ultra-high-field (≥7T) MRI hardware and associated sequence libraries, it has become possible to capture non-invasive CBV weighted fMRI signals across cortical layers. One of the most widely used approaches to achieve this (in humans) is through vascular-space-occupancy (VASO) fMRI. Unfortunately, the exact contrast mechanisms of layer-dependent VASO fMRI have not been validated for human fMRI and thus interpretation of such data is confounded. Here we validate the signal source of layer-dependent SS-SI VASO fMRI using multi-modal imaging in a rat model in response to neuronal activation (somatosensory cortex) and respiratory challenge (hypercapnia). In particular VASO derived CBV measures are directly compared to concurrent measures of total haemoglobin changes from high resolution intrinsic optical imaging spectroscopy (OIS). Quantified cortical layer profiling is demonstrated to be in agreement between VASO and contrast enhanced fMRI (using monocrystalline iron oxide nanoparticles, MION). Responses show high spatial localisation to layers of cortical processing independent of confounding large draining veins which can hamper BOLD fMRI studies, (depending on slice positioning). Thus, a cross species comparison is enabled using VASO as a common measure. We find increased VASO based CBV reactivity (3.1 ± 1.2 fold increase) in humans compared to rats. Together, our findings confirm that the VASO contrast is indeed a reliable estimate of layer-specific CBV changes. This validation study increases the neuronal interpretability of human layer-dependent VASO fMRI as an appropriate method in neuroscience application studies, in which the presence of large draining intracortical and pial veins limits neuroscientific inference with BOLD fMRI