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Biomedical subjects

J A Lohman

Publications and source records attributed to J A Lohman.

8 recordsLinked to original sources
PubMed2001

NMR studies of Ru(3)(CO)(10)(PMe(2)Ph)(2) and Ru(3)(CO)(10)(PPh(3))(2) and their H(2) addition products: detection of new isomers with complex dynamic behavior.

The clusters Ru(3)(CO)(10)L(2), where L = PMe(2)Ph or PPh(3), are shown by NMR spectroscopy to exist in solution in at least three isomeric forms, one with both phosphines in the equatorial plane on the same ruthenium center and the others with phosphines in the equatorial plane on different ruthenium centers. Isomer interconversion for Ru(3)(CO)(10)(PMe(2)Ph)(2) is highly solvent dependent, with DeltaH decreasing and DeltaS becoming more negative as the polarity of the solvent increases. The stabilities of the isomers and their rates of interconversion depend on the phosphine ligand. A mechanism that accounts for isomer interchange involving Ru-Ru bond heterolysis is suggested. The products of the reaction of Ru(3)(CO)(10)L(2) with hydrogen have been monitored by NMR spectroscopy via normal and para hydrogen-enhanced methods. Two hydrogen addition products are observed with each containing one bridging and one terminal hydride ligand. EXSY spectroscopy reveals that both intra- and interisomer hydride exchange occurs on the NMR time scale. On the basis of the evidence available, mechanisms for hydride interchange involving Ru-Ru bond heterolysis and CO loss are proposed.

Journal Article↗
PubMed2001

A medical center's experience with managing specialty bed usage.

The focus of this case study was the escalating use of specialty beds at a large military medical center. Members of a multidisciplinary task force looked at current use of specialty beds, clinical appropriateness of past decisions regarding use of these beds, and education of staff members. They concluded that specialty beds were being ordered randomly from multiple vendors without the benefit of sound clinical decision making. The task force narrowed the types of beds used from 16 to only 7, limited the number of primary bed vendors to two and placed them under contract, educated staff regarding proper selection of specialty beds, and established a protocol specifying WOC nurses and physicians as responsible personnel for ordering specialty beds. These efforts resulted in a marked decline in the use of specialty beds, better patient clinical outcomes, and a sizable cost reduction.

Beds↗
PubMed1988

Prospects for NMR imaging in the study of biological morphogenesis.

Small objects can be visualised with a spatial resolution that approaches microscopic dimensions using the technique of high resolution nuclear magnetic resonance (NMR) imaging. Some important features of the method are described and the prospects for using the technique to study morphogenesis are discussed. It is concluded that NMR imaging, in conjunction with the related method of localised spectroscopy, is capable of producing novel structural information.

Animals↗
PubMed1988

Surface coil localization of 31P NMR signals from orthotopic human kidney and liver.

By incorporating the hyperbolic secant inversion pulses with the image-selected in vivo spectroscopy localization technique and by applying a gradient-echo imaging method, we have selected only the 31P NMR signals from orthotopic human kidney and liver, using a single concentric 1H/31P surface coil. Corresponding to the experimental results on animal studies, the phosphocreatine signal is dramatically reduced in the localized spectra. Our localization strategy also allows us to shim easily on the well-defined volume of interest and leads to high-resolution spectra that exhibit multiplet structure. Our results indicate that we can obtain localized signals from deep small organs and point the way for other human metabolism studies.

Humans↗
PubMed1987

Spin echo imaging of multiple chemical shifts.

A method to obtain separate cross-sectional NMR images of chemically different species on the basis of their difference in chemical shift is presented. The total experiment time is no longer than that required for a conventional image and the method retains the full sensitivity of a spin-echo 2DFT imaging experiment. Simple addition of the chemical-shift selective images produces an image free from chemical-shift artifacts. Results of an in vivo experiment on a human subject are presented.

Body Water↗
PubMed1987

Natural abundance 13C NMR spectrum of glycogen in humans.

In vivo NMR has focused on using 31P and 1H to study metabolism in humans. Comparable 13C NMR studies have not been undertaken, presumably, because of its insensitivity. We report herein that the natural abundance 13C signal from C1 glycogen is observable. The ability to observe the signal opens new opportunities to noninvasively study glycogen metabolism in man.

Humans↗
PubMed1987

Combined proton NMR imaging and spectral analysis of locust embryonic development.

Images and spectra of desert locust [Schistocerca gregaria (Forskal)] embryos were collected in vivo using a 4.7-tesla proton ((1)H) NMR imaging spectrometer. The 100 x 100 x 500 mum image resolution and 125-nl localized spectral volumes were obtained within minutes of each other. The dynamics of embryonic development were slow enough that the time delay between imaging and spectral measurements is negligible. Thus, image and spectral data correspond closely and approximate real-time observations of embryonic changes. The above procedure was applied every 12 hr during the entire course of development. This analytical approach demonstrates that imaging and localized spectroscopy can be used to visualize and assess changes in embryonic water and lipid content in concert with the development of a living embryo.

Journal Article↗