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).     

Differential bronchial and pulmonary vascular responses to vagal stimulation in the pig.

The pulmonary and bronchial vascular responses and changes in bronchial tone upon vagal stimulation (240 impulses at 2 Hz or 10 Hz) were studied in anaesthetized pigs paralyzed with pancuronium. The acetylcholine-evoked vasodilatation in the tracheobronchial circulation had the same magnitude when using pancuronium or succinylcholine as skeletal muscle relaxants. Atropine-sensitive bradycardia, hypotension and bronchoconstriction were observed upon vagal stimulation. A vasoconstrictor response in the pulmonary vascular bed and clear-cut vasodilatation in the bronchial circulation supplied by the bronchial artery also occurred upon vagal stimulation. The vagally-evoked increase in pulmonary vascular resistance was markedly reduced after atropine while the bronchial vasodilatation was unchanged. This suggests that the vagally-induced increase in bronchial blood flow was not secondary to changes in the pulmonary circulation. Furthermore, the pulmonary vasoconstrictor response caused by vagal stimulation under control conditions is probably explained by reflex sympathetic activation due to the fall in systemic blood pressure. These data indicate selective vagal non-cholinergic influence of blood flow in the bronchial vascular bed compared to the pulmonary circulation.