Absolute oxygen tension (pO₂) in murine fatty and muscle tissue as determined by EPR

Abstract

The absolute partial pressure of oxygen (pO 2 ) in the mammary gland pad and femoral muscle of female mice was measured using EPR oximetry at 700 MHz. A small quantity of lithium phthalocyanine (LiPc) crystals was implanted in both mammary and femoral muscle tissue of female C3H mice. Subsequent EPR measurements were carried out 1-30 days after implantation with or without control of core body temperature. The pO 2 values in the tissue became stable 2 weeks after implantation of LiPc crystals. The pO 2 level was found to be higher in the femoral muscle than in the mammary tissue. However, the pO 2 values showed a strong dependence on the core body temperature of the mice. The pO 2 values were responsive to carbogen (95% O 2 , 5% CO 2 ) breathing even 44 -58 days after the implantation of LiPc. The LiPc linewidth was also sensitive to changes in the blood supply even 60 days after implantation of the crystals. This study further validates the use of LiPc crystals and EPR oximetry for long-term non-invasive assessment of pO 2 levels in tissues, underscores the importance of maintaining normal body core temperature during the measurements, and demonstrates that mammary tissue functions at a lower pO 2 level than muscle in female C3H mice.

A parametric approach to spectral–spatial EPR imaging

“…In contrast, in tomographic processing with magnetic field modulation, numerical integration to obtain projection data introduces strong noise correlation, and backprojection disregards the high variability in PSNR that is due to the cos 2 α scaling shown in Eq. [7].…”

“…The technique has evolved over two decades to become an important tool for studying free radicals in many branches of science [3][4][5] and has potential for the study of living biological systems [6][7][8][9]. Despite progress, high-quality EPR imaging has been limited by several technical factors including resolution, sensitivity, and acquisition time [10,11].…”

Spatially uniform sampling in 4-D EPR spectral-spatial imaging

“…Electron paramagnetic resonance imaging (EPRI) has been successfully applied to biological systems to quantify physiologic parameters, most importantly tissue oxygenation based on spectral linewidth imaging [1][2][3][4][5][6]. One can extract information about the local fluid environment from the EPR spectrum, which is obtained for each spatial voxel in a 4-D spectral-spatial image [2,7].…”

Enhanced resolution for EPR imaging by two-step deblurring

“…It has a distinct advantage in many medical applications [3][4][5] where it can be used for the direct measurement of both endogenous and introduced free radicals. In the past few years, the potential applications of EPRI to studies of living biological systems have been recognized [6][7][8][9]. Despite all the progress made in the last two decades, the acquisition of high quality images of biological samples has been limited by several technical factors including resolution, sensitivity, and speed of data acquisition [10,11].…”