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Biomedical subjects

W Köckenberger

Publications and source records attributed to W Köckenberger.

9 recordsLinked to original sources
PubMed2004

High resolution NMR microscopy of plants and fungi.

Nuclear magnetic resonance (NMR) microscopy is a completely noninvasive technique that can be used to acquire images with high spatial resolution through opaque objects such as plant organs and tissue parts. The image contrast can be chosen to represent the anatomical details or to visualize the spatial distribution of a range of physico-chemical parameters such as the apparent diffusion constant of water or the velocity of water flow within plants in vivo. In addition, images can be generated which show the spatial distribution of metabolites. Furthermore, it is possible to detect chemical compounds labelled with the stable isotope (13)C and to generate images showing the spatial distribution of the (13)C label in the intact plant. The ability to monitor water flow and transport of (13)C-labelled tracer in intact plants with NMR microscopy favours the use of this technique in the investigation of long-distance transport processes in plants. A short introduction into the technical principles of NMR microscopy is provided and the problems associated with applications to plants are summarized. The potential of the technique is explained with applications to Zinnia elegans plants, wheat grains and Brassica napus siliques.

Carbon Isotopes↗
PubMed2003

Magnetic resonance imaging in entomology: a critical review.

Magnetic resonance imaging (MRI) enables in vivo imaging of organisms. The recent development of the magnetic resonance microscope (MRM) has enabled organisms within the size range of many insects to be imaged. Here, we introduce the principles of MRI and MRM and review their use in entomology. We show that MRM has been successfully applied in studies of parasitology, development, metabolism, biomagnetism and morphology, and the advantages and disadvantages relative to other imaging techniques are discussed. In addition, we illustrate the images that can be obtained using MRM. We conclude that although MRM has significant potential, further improvements to the technique are still desirable if it is to become a mainstream imaging technology in entomology.

Animals↗
PubMed2001

Functional imaging of plants by magnetic resonance experiments.

Microimaging based on magnetic resonance is an experimental technique that can provide a unique view of a variety of plant physiological processes. Particularly interesting applications include investigations of water movement and spatially resolved studies of the transport and accumulation of labelled molecules in intact plant tissue. Some of the fundamental principles of nuclear and electron magnetic resonance microimaging are explained here and the potential of these techniques is shown using several representative examples.

Carbon Isotopes↗
PubMed2001

Nuclear magnetic resonance micro-imaging in the investigation of plant cell metabolism.

Micro-imaging based on nuclear magnetic resonance offers the possibility to map metabolites in plant tissues non-invasively. Major metabolites such as sucrose and amino acids can be observed with high spatial resolution. Stable isotope tracers, such as (13)C-labelled metabolites can be used to measure the in vivo conversion rates in a metabolic network. This review summarizes the different nuclear magnetic resonance micro-imaging techniques that are available to obtain spatially resolved information on metabolites in plants. A short general introduction into NMR imaging techniques is provided. Particular emphasis is given to the difficulties encountered when NMR micro-imaging is applied to plant systems.

Amino Acids↗
PubMed2000

Open access birdcage coils for microscopic imaging of plants at 11.7 T.

The use of a U-shaped high-pass birdcage coil for microscopic imaging at 11.7 T has been investigated. The study was motivated by the requirement for a side access coil, permitting higher filling factors for the in-vivo imaging of plant petioles and stems. The performance of a U-shaped coil (with a cross section consisting of a 16 mm diameter semi-circle plus two 12 mm length straight sections) has been experimentally assessed, and compared both in terms of homogeneity and sensitivity to a 16 mm diameter conventional (linear) birdcage and a saddle coil of the same diameter. The U-shaped coil, which offers 12 mm width side access, has a significantly better performance than the saddle coil, whilst providing 57% of the B(1) sensitivity of the bird-cage.

Biophysical Phenomena↗
PubMed2000

Dual resonant birdcage coils for 1H detected 13C microscopic imaging at 11.7 T.

Liquid state, rotating frame cross polarisation experiments are very sensitive to RF field inhomogeneity. In this work, we present an easily fabricated, co-resident high- and low-pass linear birdcage resonator, optimised to perform liquid state rotating frame polarisation transfer at 1H and 13C frequencies. Both the RF fields have been experimentally mapped, and used to validate the spatial signal dependence of a proton detected, 13C image. The predicted performance was then confirmed using PRAWN-based, cyclic J-cross polarisation (CYCLCROP) imaging. A novel variant of a B(1)-field mapping approach is also presented, using the signal enhancement of the CYCLCROP sequence to generate proton detected, 13C field maps.

Biophysical Phenomena↗
PubMed1996

Correlation-peak imaging.

Identification and quantitation in conventional 1H spectroscopic imaging in vivo is often hampered by the small chemical-shift range. To improve the spectral resolution of spectroscopic imaging, homonuclear two-dimensional correlation spectroscopy has been combined with phase encoding of the spatial dimensions. From the theoretical description of the coherence-transfer signal in the Fourier-transform domain, a comprehensive acquisition and processing strategy is presented that includes optimization of the width and the position of the acquisition windows, matched filtering of the signal envelope, and graphical presentation of the cross peak of interest. The procedure has been applied to image the spatial distribution of the correlation peaks from specific spin systems in the hypocotyl of castor bean (Ricinus communis) seedlings. Despite the overlap of many resonances, correlation-peak imaging made it possible to observe a number of proton resonances, such as those of sucrose, beta-glucose, glutamine/glutamate, lysine, and arginine.

Ricinus communis↗
PubMed1995

Plant histochemistry by correlation peak imaging.

Using a new NMR correlation-peak imaging technique, we were able to investigate noninvasively the spatial distribution of carbohydrates and amino acids in the hypocotyl of castor bean seedlings. In addition to the expected high sucrose concentration in the phloem area of the vascular bundles, we could also observe high levels of sucrose in the cortex parenchyma, but low levels in the pith parenchyma. In contrast, the glucose concentration was found to be lower in the cortex parenchyma than in the pith parenchyma. Glutamine and/or glutamate was detected in the cortex parenchyma and in the vascular bundles. Lysine and arginine were mainly visible in the vascular bundles, whereas valine was observed in the cortex parenchyma, but not in the vascular bundles. Although the physiological significance of these metabolite distribution patterns is not known, they demonstrate the potential of spectroscopic NMR imaging to study noninvasively the physiology and spatial metabolic heterogeneity of living plants.

Journal Article↗