The mechanism by which the mammalian kidney generates a concentration gradient of sodium from cortex to papilla is still not entirely understood. Studies of how the kidney as an organ generates this gradient have been hampered by the lack of a noninvasive method for monitoring the intrarenal sodium distribution. Herein, we demonstrate the value of sodium-23 nuclear magnetic resonance (23Na-NMR) imaging to nondestructively assess the intrarenal sodium distribution. 23Na-NMR images were obtained from a surgically exposed kidney preparation that showed the two-dimensional distribution of sodium in the rabbit kidney. In the antidiuretic kidney this gradient resulted in papillary sodium concentrations that were approximately threefold higher than cortical values. Serial 23Na-NMR images obtained during saline infusion demonstrated the kinetics by which the sodium gradient increases with diuresis. The half-time for 23Na washout of the medulla of the kidney was approximately 6 min with this protocol. In addition, a three-dimensional data set of the sodium distribution of the kidney was obtained with voxel dimensions of 1.5 mm3 by use of a three-dimensional 23Na-NMR imaging technique. Without surgical exposure, 23Na-NMR images of the rabbit kidney were collected under completely noninvasive conditions by use of a surface coil. The 23Na-NMR signal from the kidney was easily detected; however, to obtain images of comparable signal-to-noise ratio to the surgically exposed kidney, spatial and temporal resolution were significantly reduced.
Cellular immunity was studied in three homogeneous groups of patients with cancer to determine whether the pattern of depression of immune competence varied between solid tumours with different patterns of clinical behaviour. Delayed hypersensitivity skin responses were measured in patients with carcinoma of the breast, stomach, and colon and matched controls. Response to 2,4-dinitrochlorobenzene (DNCB) was used as an indication of primary responses and the Mantoux reaction as an index of recall responses. Responses were diminished in all three cancer groups, but there were significant differences between each type of cancer and even between different control groups. Cellular immunity was lost earliest and to the greatest extent in patients with colonic cancers and tended to be retained until a late stage in breast cancer, with gastric cancer occupying an intermediate position. Thus, while there was some degree of correlation between depressed immunity and prognosis our results gave no evidence that general host immune competence could explain the worse prognosis of gastric than colonic cancer. Paradoxical findings in patients with breast cancer suggested a great complexity in the host tumour interaction. Assessments of immune competence in cancer patients must be related to specific types of neoplasms with appropriate control groups if the results are to be meaningful.
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