Application of P-31 nuclear magnetic resonance spectroscopy to a new experimental kidney perfusion model using cadaveric porcine kidneys from slaughterhouse.

Larger NMR magnets with relatively high field strengths have become available recently, allowing the application of magnetic resonance spectroscopy (MRS) in larger mammalian organs. The aim of this study was to develop and test a new and simple kidney perfusion model from slaughterhouse swine using a new 4.7-tesla/40-cm diameter system, with the intention behind to provide a human-like mammalian experimental kidney perfusion model, and to avoid sensitive in vivo animal experiments on higher-developed mammalians, 35 pig kidneys obtained 10-15 min post mortem were studied to evaluate and define conditions for optimum metabolic preservation with the following perfusion protocols: (1) immediate plegia with cold Collins solution, 1-3 h cold storage, P-31 MRS; (2) immediate plegia, 1-3 h cold storage, blood reperfusion, P-31 MRS; (3) immediate blood reperfusion, plegia, 1-3 h cold storage, blood reperfusion, P-31 MRS; (4) immediate blood reperfusion, plegia, 24 h cold storage, blood reperfusion, P-31 MRS, P-31 MRS at 81 MHz with a double-tuned surface coil yielded the following results: [table: see text] Blood flow showed a weak correlation with beta-ATP/inorganic phosphate in protocols 3 and 4 of r = 0.64. Repeated reperfusion and ischemia experiments of this model allowed the on-line observation of the metabolic response of the energy phosphate pattern for several hours. In conclusion, slaughterhouse-harvested swine kidneys lend themselves to a simple, low-cost in vitro perfusion model, provided they are reperfused with arterial blood immediately after harvesting.(ABSTRACT TRUNCATED AT 250 WORDS)

Hydrogen/fluorine retuning tomography. Applications to 1H image-guided volume-selective 19F spectroscopy and relaxometry of perfluorocarbon emulsions in tissue.

A hardware modification which permits the record of 19F images, spectra, and relaxation times with a 1H tomography bird-cager resonator is described. Changing the spectrometer frequency from 1H to 19F resonance and vice versa is possible without removing the object to be investigated. This hydrogen/fluorine retuning tomography (HYFY) technique permits studies of identical slices or volume elements with 1H as well as with 19F resonance. In particular, it is possible to localize volume elements on the basis of multislice proton images and then to investigate these volume elements with fluorine magnetic resonance by the aid of volume selection methods. For this purpose, pulse sequences for the localized and spectroscopically resolved determination of spin-lattice and transverse relaxation times have been developed. The applicability of the techniques has been demonstrated by the aid of phantom samples as well as with excised porcine organs which have been perfused with perfluorocarbon emulsions.

Fluctuations, exchange processes, and water diffusion in aqueous protein systems: A study of bovine serum albumin by diverse NMR techniques.

Experimental frequency, concentration, and temperature dependences of the deuteron relaxation times T(1) and T(2) of D(2)O solutions of bovine serum albumin are reported and theoretically described in a closed form without formal parameters. Crucial processes of the theoretical concept are material exchange, translational diffusion of water molecules on the rugged surfaces of proteins, and tumbling of the macromolecules. It is also concluded that, apart from averaging of the relaxation rates in the diverse deuteron phases, material exchange contributes to transverse relaxation by exchange modulation of the Larmor frequency. The rate limiting factor of macromolecular tumbling is determined by the free water content. In a certain analogy to the classical free-volume theory, a "free-water-volume theory" is presented. There are two characteristic water mass fractions indicating the saturation of the hydration shells (C(s) approximately 0.3) and the onset of protein tumbling (C(0) approximately 0.6). The existence of the translational degrees of freedom of water molecules in the hydration shells has been verified by direct measurement of the diffusion coefficient using an NMR field-gradient technique. The concentration and temperature dependences show phenomena indicating a percolation transition of clusters of free water. The threshold water content was found to be C(c) (w) approximately 0.43.

[Studies of myocardial metabolism using P-31-NMR spectroscopy and a simple heart perfusion model of slaughtered animals--an approach to avoiding in vivo animal experiments]. / Myokard-Stoffwechseluntersuchungen mit der P-31-NMR-Spektroskopie und einem einfachen Herz-Perfusionsmodell von Schlachttieren--ein Ansatz zur Vermeidung von In-vivo-Tierexperimenten.

In research cardiology large numbers of in vivo animal experiments, mostly with dogs or pigs, are necessary. It was the aim of this study to test a simple in vitro perfusion heart model from swine harvested in the slaughterhouse as a potential substitute for in vivo animal studies. 32 unselected hearts of slaughterhouse swine after 10 to 15 min of warm ischemia were subjected to reperfusion with warm oxygenized blood and were examined for mechanical recovery, which occurred in 56%, increasing to 95% if primarily using only hearts that were in relaxation. In 21 of selected relaxed heart models the energy phosphate pattern as an index of viability was measured by P-31 MRS on a 4.7 Tesla NMR tomograph in 37 experimental runs with the following perfusion protocols: 1) immediate cardioplegia with cold Bretschneider or Collins solution, transportation under cooling, MRS after approximately 1 h; 2) immediate cardioplegia, transportation, reperfusion with oxygenated warm blood, MRS; 3) immediate blood perfusion with genuine fresh arterial blood from the slaughterhouse, cold plegia perfusion, transportation, MRS; 4) immediate blood perfusion with transportation MRS; 4) immediate blood perfusion with genuinefresh arterial blood, cold plegia perfusion, transportation, reperfusion with oxygenated warm blood, MRS during reperfusion; 5) An experimental pig heart was made plegic in vivo and reperfused with oxygenated warm blood during MRS as reference.(ABSTRACT TRUNCATED AT 250 WORDS)

Volume-selective multi-pulse spin-echo spectroscopy and selective suppression of spectral lines.

A method is described allowing the recording of in vivo NMR spectra in sharply bound volume elements preselected on the basis of slice images. Experiments with phantom samples, as well as with a test person in a whole-body instrument, have been carried out to demonstrate the applicability of the technique. In the case of proton spectroscopy, suppression of the water and/or or of the lipid line is often desirable. A corresponding pulse sequence has been implemented and successfully tested with a phantom sample.

Phase II trial of N-methylformamide in advanced head and neck cancer.

Eighteen patients with advanced epidermoid carcinoma of the head and neck were entered into a phase II trial of N-Methylformamide (NMF), 800 mg/M2 IV daily for 5 days every 4 weeks. Seventeen patients had received prior radiation therapy and 11 were previously treated with chemotherapy. No complete or partial responses were observed. The major toxicity was gastrointestinal. Fifty percent of patients experienced nausea and vomiting or reversible hepatotoxicity with greater than a 3-fold elevation of liver enzymes. Mild reversible myelosuppression occurred in 2 patients. NMF in this dose and schedule was not a useful agent to treat recurrent epidermoid carcinoma of the head and neck.