Release of soluble transferrin receptor from the surface of human leukemic HL60 cells

Information regarding transferrin (Tf) receptor degradation is largely incomplete. HL60 cells were shown to release to their growth medium a Tf-binding protein which could be immunoprecipitated by anti-Tf receptor monoclonal antibodies (MoAbs) B3/25 and OKT9. Soluble Tf receptor was detected in the medium within one hour of replating of cells, and its release was inhibited at 4 degrees C. The affinity of Tf for the soluble receptor released by cells (kd = 2.3 x 10(-10) mol/L) was slightly lower than its affinity for the detergent-solubilized cellular receptor (kd = 1.2 x 10(-10) mol/L). 125I-Tf internalized and released by cells subsequently bound to Tf receptor released by the same cells, and soluble Tf receptor in the conditioned medium (CM) inhibited 125I-Tf binding to intact cells. The soluble Tf receptor isolated from the CM was smaller (78,000 daltons) than the cell surface receptor (94,000 daltons) when analyzed by gel electrophoresis under reducing conditions. Isolated cell membranes readily released soluble receptor; however, this release could be blocked by protease inhibitors. The soluble Tf receptor may represent the extracytoplasmic domain of the cellular Tf receptor released from the surface of HL60 cells through proteolytic cleavage by a membrane-based protease.     

Pneumothorax and other lung diseases: effect of altered resolution and edge enhancement on diagnosis with digitized radiographs

Prior studies have shown that pneumothorax is one of the more difficult entities to diagnose with digitized radiography. This study was designed to test whether increasing resolution from 1.25 to 2.5 line pairs per millimeter (lp/mm) and image processing (edge enhancement from unsharp masking) would increase accuracy and confidence in the diagnosis of pneumothorax, as well as normal cases and other forms of lung disease. Conventional radiographs were digitized with use of a laser reader and then reformatted as film hard copy. Eleven observers read 35 cases reformatted in three different ways (1.25 lp/mm, 2.5 lp/mm, 1.25 lp/mm unsharp mask). The images with finer resolution (2.5 lp/mm) and unsharp mask images were superior to those with coarser resolution (1.25 lp/mm) for the diagnosis of pneumothorax. There was no difference in diagnostic accuracy for normal patients. For abnormalities other than pneumothorax, the unsharp mask images were significantly worse. Confidence in the diagnosis of pneumothorax and other abnormalities was highest with the finest resolution (2.5 lp/mm).     

Sinusoidal lining cell damage: the critical injury in cold preservation of liver allografts in the rat

We have previously defined viability limits in a rat transplantation model. All liver allografts stored in a simple preservation solution (NaCl 0.9%, CaCl2 2 mM) at 4 degrees C for 4 hr or at 37 degrees C for 1 hr were viable upon transplantation, but all those stored at 4 degrees C for 8 hr or at 37 degrees C for 2 hr were nonviable. Only cold-preserved, nonviable livers showed increased vascular resistance, platelet trapping and an initially low, but then high, rise in aspartate transaminase (AST) upon reperfusion, all suggesting injury to the microcirculation, with secondary injury to the hepatocyte. In the present study, we investigated the morphological changes that occur in livers stored for the defined critical times, using light and electron microscopy after perfusion-fixation. Accurate and reproducible identification of specimens as belonging to viable or nonviable and warm- or cold-preserved could be made in this way. Preservation in the cold first resulted in reversible changes consisting of cellular swelling, alterations of intracellular organelles, and partial denudation of the sinusoidal lining (cold-preserved viable group). Later, under conditions of nonviable cold preservation, detachment of cell bodies of sinusoidal lining cells with nuclear changes and almost complete denudation of the sinusoidal lining was observed. Endothelial cells of larger vessels were only injured mildly. In contrast, under conditions of warm preservation, changes involving mitochondria and later nuclei were found in hepatocytes, and blebbing was more extensive. Endothelial cells were spared relatively. We also examined livers stored in isotonic citrate solution at 4 degrees C for 8 hr and 16 hr, the critical times determined for this solution in another model of rat liver transplantation. The findings were very similar to storage in saline with respect to the changes in the sinusoidal lining cells after cold preservation for the two critical times. The results provide convincing evidence of a qualitative difference between warm and cold preservation injury, with relatively selective damage to hepatocytes or sinusoidal lining cells, respectively. Endothelial damage represents the primary event, resulting in the loss of organ viability following hypothermic storage. Thus morphology may serve as a useful viability marker after preservation.     

Assessment of different methods to detect increased autochthonous production of immunoglobulin G and oligoclonal immunoglobulins in multiple sclerosis.

The formulae for immunoglobulin G (IgG) synthesis rate, IgG(loc), IgG index, and IgG extended index in determining increased autochthonous production (intra-blood-brain barrier synthesis) of IgG was assessed in 50 chronic progressive multiple sclerosis patients. The results of all four formulae clearly show elevated intra-blood-brain barrier IgG synthesis in 35 patients, 94% of whom had oligoclonal immunoglobulins detected by the method of isoelectric focusing with immunofixation and silver staining (IEF-IS). The results from the four formulae are all normal in seven patients (none have oligoclonal immunoglobulins by IEF-IS) and are discordant in eight patients (five have oligoclonal immunoglobulins by IEF-IS). Whenever intra-blood-brain barrier synthesis of IgG is suspected, IEF-IS should be used to assay for oligoclonal immunoglobulins because this method is more sensitive than agarose electrophoresis with either Coomassie blue dye or silver stain (94% vs. 74% vs. 54%).