Irreversible sickle cells

Decreased formation of irreversibly sickled cells in vitro 405,406... 

Zinc is known to compete with cadmium, lead, copper, iron, and calcium for similar binding sites (109). In the future, a potential use of zinc may be to alleviate toxic effects of cadmium and lead in human subjects. Use of zinc as an antisickling agent is an example of its antagonistic effect on calcium, which is known to produce irreversible sickle cells by its action on red-cell membrane. 

The zinc content of human blood is 8.8 /Ug/mL, of which 80-90% is within erythrocytes, mostly in carbonic an-hydrase. Zinc binds to hemoglobin, increasing its oxygen affinity. By binding to erythrocyte membranes, it increases the flexibility of irreversibly sickled cells in vitro but plasma levels high enough to be therapeutic cannot be achieved. Leukocytes and platelets also contain an appreciable amount of zinc. 

HbS 8+-thal, HbS 8°-thal hemoglobin sickle /3 -thalassemia and hemoglobin sickle 8 -thalassemia HbSC sickle-hemoglobin C HbSS homozygous sickle hemoglobin HbS sickle hemoglobin HSCT hematopoietic stem cell transplantation ISC irreversibly sickled cell... 

The prion protein, therefore, exhibits a phase transition from a monomeric protein to an aggregated protein that bears analogy in fundamental respects to the phase transition exhibited by the model proteins discussed in Chapter 5. For the phase transition of our model proteins, association is relatively fast and dissociation or dissolution is quite slow. The difference with the prion phase transition is only qualitative in that the association step of the phase transition of prion protein is extremely slow, and dissociation is so slow as to be irreversible. The slow relentless growth of insoluble prion protein fibers continues until it destroys the cell or tissue with which it may be associated. This calls to mind sickle cell anemia due to an inverse temperature transition of hemoglobin S wherein intracellular fiber growth distorts and sickles red blood cells and leads to their destruction (see Figure 7.22). 

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