- A congenital haemolytic anaemia with thermal sensitivity of the erythrocyte membrane. [Journal Article]
- BJBr J Haematol 1975; 29(4):537-43
- Microspherocytes, measuring 2-3 mum in diameter, and cells with blunted projections or triangular in shape characterized the erythrocoyte morphology in three children with congenital haemolytic anaem…
Microspherocytes, measuring 2-3 mum in diameter, and cells with blunted projections or triangular in shape characterized the erythrocoyte morphology in three children with congenital haemolytic anaemia. Since the erythrocyte morphology resembled that associated with thermal injury, heat-induced changes in erythrocyte morphology and membrane composition were studied. Erythrocytes developed filaments and spheroid bodies which fragmented, resulting in microspherocyte transformation. Normal cells required exposure to 49 degrees C, whereas the patients' cells fragmented at 45 degrees C. Fragmentation was also observed during incubation of patients' cells at 37 degrees C for 17h. The heat-induced transformation of the patients' cells was associated with an increase in the membrane cholesterol:phospholipid and cholesterol:protein ratios. The phospholipid:protein ratio was unchanged. This suggests that fragmentation produces a selective loss of membrane components. Splenectomy ameliorated the haemolytic process. We propose that the patients' red-cell morphology is the result of in vivo fragmentation, and that the spleen is the major site of microspherocyte and poikilocyte destruction.
- Molecular mechanism of hemolytic anemia in homozygous hemoglobin C disease. Electron microscopic study by the freeze-etching technique. [Journal Article]
- JEJ Exp Med 1969 Sep 01; 130(3):443-66
- Erythrocytes from a patient with homozygous hemoglobin C disease were subjected to gradual osmotic dehydration by incubation in hypertonic saline. Serial observations of these cells before and after …
Erythrocytes from a patient with homozygous hemoglobin C disease were subjected to gradual osmotic dehydration by incubation in hypertonic saline. Serial observations of these cells before and after 4 and 12 hr incubation were carried out by means of interference, Soret absorption, polarization microscopy, and the electron microscope employing the freeze-etching technique. Light microscopic studies showed a progressive contraction of cellular contents into central masses which, after 12 hr dehydration, formed birefringent intracellular hemoglobin crystals in 50-75% of the cells. Electron microscopic study of freeze-etched replicas of these cells at 0, 4, and 12 hr of dehydration reveals progressive aggregation, alignment, and crystallization of hemoglobin molecules. Molecular aggregation found in C-C cells prior to osmotic dehydration was not seen in normal erythrocytes. Aggregation and packing varied from cell to cell. Reticulocytes showed a loosely packed aggregate mesh-work; older cells showed variation of molecular packing, which appeared tightest in cells corresponding to microspherocytes. With further loss of intracellular water, aggregates coalesced into patterns of tighter molecular packing with small regions of alignment, and, finally, crystallization occurred. Hemoglobin molecules measuring 70 A in diameter were readily identified within the period patterns of intracellular crystals. These findings suggest that the hemoglobin C molecules within C-C erythrocytes exist in an aggregated state. As the cell ages, intracellular water is lost and intermolecular distance decreases, hemoglobin C molecules polymerize into intracellular crystals. This pathological behavior of hemoglobin C is associated with a charge alteration conferred by the substitution of beta-6-lysine for glutamic acid on the external surface in the A-helix region of the beta-chain of the molecule, possibly increasing intermolecular attraction. Molecular aggregation accounts for the increased rigidity of C-C cells which leads to accelerated membrane and water loss with resultant microspherocyte formation. The microspherocyte, with highest intracellular hemoglobin concentration, rapidly undergoes intracellular crystallization, and is sequestered and destroyed by reticuloendothelial elements.