The effect of EDTA, cations, and various buffers on the morphology of erythrocyte membranes: an electron-microscopic study

Membranes of human erythrocytes were prepared by stepwise osmotic hemolysis in Ca2+-free solutions. Examination with the electron microscope after negative staining showed some short, conelike protuberances on the surface of about 20 percent of the ghosts, while 80 percent were round, intact spheres. After Ca2+ treatment, all membranes were round and intact. After exposure to ethylenediaminetetraacetic acid (EDTA) (1.0 mM, pH 7.4), the entire ghost surface was covered with long, thin extrusions called stromalytic forms (about 460 per cell). Their sizes, shapes, and fine structure are described. Exposure to ionic calcium (1.4 times 10-minus 4M) abolished the EDTA-induced stromalytic forms. A second exposure to EDTA reversed this Ca2+ effect. ATP, like EDTA, produced stromalytic forms. EDTA- induced stromalytic forms were also abolished by Zn2+, La3+, and Nd3+ at concentrations of 1-5 times 10-minus 4 M. Mg2+ at 10-minus 2 M was ineffective. Ghosts were prepared by graded lysis in various buffers. Those prepared in phosphate were the most stable and provided consistent EDTA effects and Ca2+ reversal. Ghosts in Tris-HCl showed breakdown unless salt was added. Moderately satisfactory ghosts were also obtained in Hepes-NaOH buffer and salt.     

Upper Neck Forces and Moments and Cranial Angular Accelerations in Lateral Impact

Biomechanical studies using postmortem human subjects (PMHS) in lateral impact have focused primarily on chest and pelvis injuries, mechanisms, tolerances, and comparison with side impact dummies. A paucity of data exists on the head–neck junction, i.e., forces and moments, and cranial angular accelerations. The objective of this study was to determine lateral impact-induced three-dimensional temporal forces and moments at the head–neck junction and cranial linear and angular accelerations from sled tests using PMHS and compare with responses obtained from an anthropomorphic test device (dummy) designed for lateral impact. Following initial evaluations, PMHS were seated on a sled, restrained using belts, and lateral acceleration was applied. Specimens were instrumented with a pyramid-shaped nine-accelerometer package to record cranial accelerations. A sled accelerometer was used to record the input acceleration. Radiographs and computed tomography scans were obtained to identify pathology. A similar testing protocol was adopted for dummy tests. Results indicated that profiles of forces and moments at the head–neck junction and cranial accelerations were similar between the two models. However, peak forces and moments at the head–neck junction were lower in the dummy than PMHS. Peak cranial linear and angular accelerations were also lower in the dummy than in the PMHS. Fractures to the head–neck complex were not identified in PMHS tests. Peak cranial angular accelerations were suggestive of mild traumatic brain injury with potential for loss of consciousness. Findings from this study with a limited dataset are valuable in establishing response corridors for side impacts and evaluating side impact dummies used in crashworthiness and safety-engineering studies.