Automated oxyhemoglobin dissociation curve construction to assess sickle cell anemia therapy.

Oxyhemoglobin dissociation curves measure the most important function of red blood cells - the affinity for oxygen and its delivery to the tissues. This function may be deranged in sickle cell anemia and some other hemoglobinopathies. An automated oxyhemoglobin dissociation curve analyzer constructed dissociation curves in 55 patients with hemoglobinopathies and in 24 control subjects while maintaining constant temperature and pH. Sigmoid curves were converted to rectilinear ones using the Hill equation. Oxygen affinity of red cells was assessed by calculation of P50 (the PO2 at which hemoglobin is half saturated). Results revealed separation of oxyhemoglobin dissociation Hill plots according to phenotype but with wide variability. Mean oxygen affinity of fetal hemoglobin was greatest, whereas that of sickle hemoglobin was least. Other hemoglobins were intermediate. A positive correlation between decreased oxygen affinity and carboxyhemoglobin confirmed the decreased oxygen affinity of sickle hemoglobin and decreased oxygen affinity and increased diphosphoglycerate in red cells. Hill plots are less sensitive discriminators of oxygen affinity than traditional sigmoid dissociation curves and offer no particular advantage. Serial studies in a subset of three sickle cell anemia patients treated conservatively suggest automated oxyhemoglobin dissociation curves may be useful in assessment of effectiveness of newer therapies of sickle cell anemia after refinement of the method and studies of larger populations.

Folate deficiency delays the onset but increases the incidence of leukemia in Friend virus-infected mice.

Clinical studies have indicated that folate deficiency may enhance the development of various malignancies. In animal studies that examined the effect of folate deficiency on malignancies, conflicting results have been reported. In some studies, folate deficiency increased the development and growth of malignant tumors; in others, it decreased the development and growth of malignancies. We examined the effect of transient folate deficiency on the development of leukemia in mice infected with the anemia-inducing strain of Friend leukemia virus. Friend virus disease can be considered as a model for human acute leukemias that are preceded by a preleukemic period. These include leukemias that develop in patients who received previous chemotherapy and/or radiation therapy, as well as patients with chronic granulocytic leukemia or myelodysplasia. Folate deficiency around the time of Friend virus-infection delayed the onset but increased the incidence of leukemia. The rates of rearrangement of the Spi-1 (PU.1 ) oncogene by provirus integration and alteration of the p53 tumor-suppressor gene were the same in leukemia cell lines derived from folate-deficient mice as they were in cell lines from control mice. These results indicate that folate deficiency did not exert its enhancement of leukemogenesis through changes in either Spi-1 or p53, even though these two genes have been found to be the most frequently altered ones in Friend virus-induced leukemias. Our results suggest that folate deficiency may enhance the development of acute leukemia in patients who are at high risk for this disease.