Yoshinori Ikebe

Characterization of Experimental Ischemic Brain Edema Utilizing Proton Nuclear Magnetic Resonance Imaging

Correlations between T1 and T2 relaxation times and water and electrolyte content in the normal and ischemic rat and gerbil brains were studied by means of both nuclear magnetic resonance (NMR) spectroscopic and imaging methods. In the spectroscopic experiment on excised rat brains, T1 was linearly dependent on tissue water content and T2 was prolonged in edematous tissue to a greater extent than expected by an increase in water content, showing that T2 possesses a greater sensitivity for edema identification and localization. Changes in Na+ and K+ content of the tissue mattered little in the prolongation of relaxation times. Serial NMR imaging of gerbil brains insulted with permanent hemispheric ischemia offered early lesion detection in T1- and especially T2-weighted images (detection as soon as 30 min after insult). The progressive nature of lesions was also imaged. Calculated T1 and T2 relaxation times in regions of interest correlated excellently with tissue water content (r = 0.892 and 0.744 for T1 and T2, respectively). As a result, detection of cerebral ischemia utilizing NMR imaging was strongly dependent on a change in tissue water content. The different nature of T1 and T2 relaxation times was also observed.

On carbon-13 spectra of thio- and dithiocarboxylic acids triorgano group 14 metal esters

Abstract The thiocarbonyl carbon chemical shifts of thio- and dithiocarboxyl acid triorgano group 14 metal esters have been studied in comparison with the carbonyl chemical shifts of the corresponding carboxylic and thiocarboxylic acid derivatives. Triorgano group 14 metal groups cause remarkable downfield shifts of the carbonyl and thiocarbonyl carbon chemical shifts in the esters. The thiocarbonyl carbon chemical shifts of the dithio esters (i-C3H7CS2EMe3, E = group 14 element) are correlated linearly with the Allred-Rochow electronegativity of the metals, and with their ππ* transition energies except for the silyl esters. The 13CO chemical shifts of trimethyltin isobutyrate appear at the lowest field in the carboxylic acid triorgano group 14 metal esters (RCOOER′3, E = group 14 metal). The unusual downfield shifts reflect the polymetric structure of the tin esters. The empirical equation (δ(CS) = 1.45 δ(CO)−46.5 ppm) predicting 13CO and 13CS chemical shifts, which has been proposed by Kolinowski and Kessler, can not be applied for these triorgano group 14 metal esters and ortho substituted benzoates and thio- and dithiobenzoates.