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Biomedical subjects

C T Burt

Publications and source records attributed to C T Burt.

At least 55 records · Page 3Linked to original sources
PubMed1982

NMR imaging of forearms in healthy volunteers and patients with giant-cell tumor of bone.

Serial proton nuclear magnetic resonance (NMR) images of distal upper extremities were obtained in four healthy volunteers and four patients with giant cell tumor of the distal radius. The steady-state-free-precession (SSFP) data collection technique and an 8-cm bore superconducting magnet (1.44 tesla) were used. All images demonstrated high spatial resolution and excellent soft-tissue contrast. In patients with giant cell tumor, the NMR images revealed bone marrow replacement by tumor, cortical bone thinning, and cortical bone destruction. The extent of tumor involvement was clearly delineated by the NMR images and corresponded to radiographic and surgical findings. NMR signal intensity was lower in tumors, suggesting altered relaxation times. These findings demonstrate that proton NMR imaging can provide high-resolution images of extremities and detect tumors by changes in both anatomic structure and relaxation times.

Adult↗
PubMed1982

Quantification of experimental myocardial infarction using nuclear magnetic resonance imaging and paramagnetic ion contrast enhancement in excised canine hearts.

Determination of myocardial infarct size is important for clinical management of patients with ischemic heart disease and for research on limiting infarct size. Nuclear magnetic resonance (NMR) imaging permits tomographic depiction of the distribution of mobile tissue protons. NMR images have demonstrated high spatial resolution and contrast. To evaluate the potential of this technique in measuring myocardial infarct size, NMR imaging was performed in six canine hearts excised 24 hours after circumflex coronary artery ligation. Before sacrifice, the dogs received i.v. manganous chloride (0.05 mmol/kg). After NMR imaging, the heart were sectioned and the myocardial slices were stained with triphenyl tetrazolium chloride. The pathologically determined infarct size was compared with the infarct size measured by NMR imaging. The correlation was good (regression line slope 1.06; r = 0.94). We conclude that NMR imaging with paramagnetic contrast agents can be used to determine infarct size in excised hearts.

Animals↗
PubMed1979

Phosphodiesters in muscular dystrophies.

Phosphorus nuclear magnetic resonance studies of various normal and dystrophic muscles have demonstrated differences in phosphodiester contents. Dystrophic chicken pectoralis muscle contains elevated levels of the diester SEP, and Duchenne dystrophic human leg muscle lacks the diester GPC. It is shown that SEP may be characteristic of slow fiber types, indicating imcomplete maturation of the dystrophic pectoralis muscle. The activities of SEP-metabolizing enzymes have been determined in microsomes of pectoralis muscle, kidney, and intestinal mucosa of normal and dystrophic chickens. There was little difference between normal and dystrophic values of SEP phosphodiesterase and SEP synthase in kidney and mucosa. Dystrophic pectoralis muscle microsomes possessed significantly elevated levels of both enzymes. The increase in SEP synthase activity of dystrophic muscle may explain the increase in the SEP level if the phosphodiesterase is regulated in vivo. It is shown that human muscle disease processes may raise, leave unchanged, or lower GPC levels. In certain diseases when GPC is markedly elevated, such as Werdnig-Hoffmann, or depressed, such as Duchenne muscular dystrophy, it may serve as a marker.

Animals↗
PubMed1978

Serine ethanolamine phosphodiester: a major component in chicken semen.

The phosphodiester, serine ethanolamine phosphodiester, has been found by 31P NMR to be present in chicken semen and the structure was confirmed by chromatographic and spectroscopic techniques. The presence of serine ethanolamine phosphodiester in chicken semen completes the analogy between the distribution of this compound in the tissues of the chicken and that of glycerol 3-phosphorylcholine in mammals.

Animals↗
PubMed1977

Analysis of living tissue by phosphorus-31 magnetic resonance.

Nuclear magnetic resonance is a new method for assaying the content of phosphate metabolites in intact tissues. Its nondestructive nature allows simultaneous and repeated determinations of these compounds with a minimum perturbation of tissue. Changes in the concentrations of the phosphates as a function of time characterize the metabolic machinery of the tissue and reveal alterations in enzymic activity that result from drug treatment or disease. The entire phosphate profile shows differences between normal and diseased muscle which should be of diagnostic value. Further, by examining phosphate profiles we detected a family of chemical compounds that were not previously known to exist as major constituents in muscle. Of these, two have been isolated and one has been identified as glycerol 3-phosphorylcholine. Finally, shifts in the positions of resonances monitor the internal environment of the living system, its hydrogen ion concentration, the complexing of alkaline earth metals with ATP, and compartmentalization within the cell.

Adenosine Triphosphate↗
PubMed1977

31P nuclear magnetic relaxation studies of phosphocreatine in intact muscle: determination of intracellular free magnesium.

31P nuclear magnetic relaxation rates for phosphocreatine in intact frog gastrocnemius were compared with those observed in model solutions at 4 degrees, a temperature at which muscle maintains its physiological state for at least 5 hr. Both nuclear Overhauser effect and spin-lattice relaxation rate (1/T1) experiments indicate that dipole-dipole interactions from the dominant relaxation path for 31P in intact muscle and model solutions, independent of phosphocreatine and Mg concentrations. Spin-spin relaxation rates (1/T2) measured by modified Carr-Purcell-Melboom-Gill spin-echo experiments suggest the importance of scalar coupling modulated by chemical exchange with free Mg. From these results, we estimate the free intracellular Mg in intact muscle as 4.4 mM and demonstrate that 31P T2 experiments can be used as a tool for studying free Mg levels with minimum disturbance of the intact cell.

Animals↗
PubMed1976

Phosphorus-31 nuclear magnetic resonance detection of unexpected phosphodiesters in muscle.

In the examination of intact muscles by 31P nuclear magnetic resonance spectroscopy, a number of signals have been detected in the phosphodiester region (-0.5 to 0.5 ppm) of the spectrum which could not be correlated with the known common phosphates of muscle tissue. These signals arise from perchloric acid extractable compounds with several common chemical properties, one of which is a ready solubility in nearly anhydrous ethanol solutions. A component contributing to the major resonance has been identified as glycerol-3-phosphorylcholine. This characterization is based on both 31P nuclear magnetic resonance and chromatographic data.

Animals↗
PubMed1976

Analysis of phosphate metabolites, the intracellular pH, and the state of adenosine triphosphate in intact muscle by phosphorus nuclear magnetic resonance.

31P nuclear magnetic resonance spectra recorded from intact muophosphate, and the sugar phosphates. Quantitation of these metabolites by 31P nuclear magnetic resonance was in good agreement with values obtained by chemical analyses. The spectra obtained from various muscles showed considerable variation in their phosphorus profile. Thus, differences could be detected between (a) normal and diseased muscle; (b) vertebrates and invertebrates; (c) different species of the same animal. The time course of change in phosphate metabolites in frog muscle showed that ATP level remains unchanged until phosphocreatine is nearly depleted. Comparative studies revealed that under anaerobic conditions the Northern frog maintains its ATP content for 7 hours, while other types of amphibian, bird, and mammalian muscles begin to show an appreciable decay in ATP after 2 hours. Several lines of evidence indicated that ATP forms a complex with magnesium in the muscle water: (a) the phosphate resonances of ATP in the muscle were shifted downfield as compared to those in the alkaline earth metal-free perchloric acid extract of the muscle; (b) the coupling constants of ATP measured in various live muscles closely corresponded to those for MgATP in a solution resembling the composition of the muscle water; (c) in the muscle the gamma-phosphate group of ATP exhibited no shift change over a period of 10 hours under conditions where resonances of other phosphate compounds could be titrated. This behavior is similar to that of MgATP in model solutions in the physiological pH range, and it is different from that of CaATP. The chemical shifts of the phosphate metabolites were determined in several relevant solutions as a function of pH. Under all conditions only inorganic orthophosphate showed an invariant titration curve. From the chemical shift of inorganic phosphate observed during aging of intact muscle the intracellular pH of frog muscle was estimated to be 7.2.

Adenosine Triphosphate↗
PubMed1975

Structural changes in myosin during contraction and the state of ATP in the intact frog muscle.

The reactivity of myosin to [14C]-labeled N-ethylmaleimide ([14C]NEM) or to tritium was determined in functionally different frog muscles. The incorporation of [14C]NEM into myosin decreased during isotonic or isometric contractions, as compared to resting muscle. The cysteine residues which were protected during contraction were not involved in the ATPase activity or the actin-binding ability of myosin. Peptide mapping revealed that several residues were protected simultaneously. The incorporation of tritium into the peptide N-H groups of myosin was also decreased during muscle activity. These data support the idea that activation and subsequent contraction of muscle are correlated with structural changes in the myosin molecule. The reactivity of myosin to [14C]NEM was increased when the muscle was stretched to 140% rest length and treated with iodoacetate to deplete ATP. Based on in vitro experiments and on literature data, it is suggested that in the resting muscle myosin contains bound MgATP which decreases the rate of incorporation of [14C]NEM into myosin and that upon the irreversible loss of ATP the rate increases. 31P nuclear magnetic resonance signals from a number of phosphates were detected in the intact frog muscle. The data indicated that the minimum concentration of ATP in the muscle is 3 mM, a value which agrees with that of chemical determination. The characteristic chemical shifts, coupling constants, and line widths of ATP in the muscle were considerably altered from that of either free ATP in aqueous solutions or ATP in perchloric acid extracts of muscle.

Actins↗
PubMedDate not supplied

In vivo 19F NMR studies of hyperthermia: hydrophobic environments probed by halothane.

The steady-state distribution of the general anesthetic halothane in different rat tissues, including a renal adenocarcinoma with and without hyperthermia treatment, has been evaluated by in vivo 19F NMR spectroscopy. The 19F spectra of halothane (which is a hydrophobic probe) from within tissue show differences in the partitioning between normal rat tissues and adenocarcinoma. Muscle, as a control tissue, exhibits a single large resonance around 0 ppm. However, the adenocarcinoma exhibits two slow-exchanging resonances separated by 0.3 ppm with the one at the more hydrophobic chemical shift being more sensitive to hyperthermia treatment. The results from this tumor model suggest that 19F NMR spectroscopy may be useful first in detecting a change in hydrophobic environments using a lipophilic probe such as halothane, and secondly in monitoring the effects of hyperthermia, a treatment whose effectiveness may involve changes at the level of the plasma membrane. Under conditions of continuous delivery, a resonance which is not detected in the spectra of halothane in excised tissue appears 5 ppm downfield from the resonance for halothane localized in tissues. A rotating frame experiment is used to show that this resonance is derived from anesthetic absorbed on the tissue surface.

Animals↗