Application of MR spectroscopy to the study of tumor biology

Hepatic encephalopathy: a neurochemical, neuroanatomical, and neuropsychological study

Hepatic encephalopathy (HE) is normally diagnosed by neuropsychological (NP) tests, which are not very specific and do not reveal the underlying pathology. Magnetic resonance imaging (MRI) and spectroscopy (MRS) of the brain offer alternative and possibly more specific markers for HE. These methods were applied in conjunction with NP testing in order to determine their usefulness in the identification of HE and to understand the pathogenesis of HE more clearly. MR imaging and spectroscopy examinations, in addition to a battery of 15 NP tests, were administered to investigate 31 patients awaiting liver transplantation and 23 healthy controls. MR image intensities from the globus pallidus region were calculated and normalized to those of the thalamus. Absolute concentrations and ratios with respect to creatine (Cr) of several metabolites were computed from MR spectra. The MR data were correlated with the results of NP tests. The patients showed impairment in NP tests of attention and visuospatial and verbal fluency. In T1-weighted MRI, the relative intensity of the globus pallidus with respect to that of the thalamus region was significantly elevated in patients and correlated(negatively) with three NP tests (Hooper, FAS, and Trails B). The absolute concentrations of myo-inositol (mI) and choline (Ch) were significantly reduced in three brain regions. In addition, the absolute concentrations of glutamine (Gln) and combined glutamate and glutamine (Glx) were increased in all three locations, with Gln increase being significant in all areas while that of Glx only in the occipital white matter. In summary, this study partially confirms a hypothesized mechanism of HE pathogenesis, an increased synthesis of glutamine by brain glutamate in astrocytes due to excessive blood ammonia, followed by a compensatory loss of myo-inositol to maintain astrocyte volume homeostasis. It also indicates that the hyperintensity observed in globus pallidus could be used as complementary to the NP test scores in evaluating the mental health of HE patients.

Metabolism of breast cancer cells as revealed by non-invasive magnetic resonance spectroscopy studies

The basis for the use of nuclear magnetic resonance (NMR) spectroscopy as a tool to study the metabolism of breast cancer cells is described. The differences between proton (1H), carbon (13C), and phosphorus (31P) NMR methods is explained, and the techniques of cell extracts, cell suspensions and perfusion methods for cells are detailed. In order to perfuse cells they are preferably trapped in a gel matrix, either in the form of a thread or a bead. The gel must have appropriate properties that enables efficient oxygenation and availability of nutrients and drugs. The metabolic effects of perfusion of breast cancer cells with nutrients, drugs, and hormones are reported, and the clinical relevance of these results and methods are outlined.

In vivo 31P NMR spectroscopic changes during liver regeneration

Liver regeneration following partial hepatectomy involves rapid cell division 24 to 72 hr postresection. This cell division would necessarily involve changes in intracellular energy stores and cell membrane phospholipid precursors. In tumor models 31P nuclear magnetic resonance (NMR) has been shown to identify intracellular substrate changes associated with cell growth. The ability to monitor early changes in adenosine triphosphate (ATP), inorganic orthophosphate (Pi), phosphomonoesters (PME), or phosphodiesters (PDE) after liver resection could indicate the intracellular changes necessary for hepatocellular regeneration. In vivo 31P NMR scans of the liver were performed in both normal rats and in rats at 24, 48, 72, and 120 hr after 70% hepatectomy. At 48 hr, total ATP fell to 18.9% (P less than 0.05) and both Pi/beta-ATP and PME/beta-ATP were significantly elevated (P less than 0.01) from controls. These changes correlate with the known mitotic peak in the rat following hepatectomy. We conclude that in vivo 31P NMR is a potentially valuable tool for studying hepatic regeneration. The data also suggest that hepatocellular regeneration may be critically dependent on cellular ATP stores.