Thrombophilia in sickle cell disease: the red cell connection.

Complex pertubations of hemostasis occur in sickle cell disease (SCD). Although the procoagulant property of sickle erythrocytes in vitro is tied to exposure of phosphatidylserine (PS), no study has directly linked this PS positivity to in vivo thrombin generation. This study was designed to determine if thrombin generation in SCD correlates with erythrocyte PS, or whether platelets play a significant role. PS was quantified on erythrocytes and platelets from 40 patients with SCD (SS genotype = 25; SC genotype = 15) and 11 controls. Markers of thrombin generation (prothrombin fragment F1.2; thrombin-antithrombin or TAT complexes) and fibrin dissolution (D-dimer; plasmin-antiplasmin or PAP complexes) were also evaluated. Thrombin generation and activation of fibrinolysis occurred with elevations in F1.2, TAT, and D-dimer. Although numbers of both PS-positive erythrocytes and platelets were elevated, there was no correlation between PS-positive platelets and any hemostatic markers. In contrast, correlations were noted between PS-positive erythrocytes and F1.2 (P <.0002), D-dimer (P <.000002), and PAP (P <.01). Correlations between F1.2 and D-dimer (P <.0001) demonstrated that fibrinolysis was secondary to thrombin generation. In patients with the SC genotype, abnormalities in coagulation, although present, were of a lesser magnitude than in SS disease. This study suggests that the sickle erythrocyte is the cell responsible for the thrombophilic state in SCD because associations between erythrocyte PS and thrombin generation were observed. No such relationship with platelet PS was noted. The use of erythrocyte PS as a surrogate marker in trials testing new therapeutic modalities may provide insights into the vascular complications of SCD.     

Key endothelial cell angiogenic mechanisms are stimulated by the circulating milieu in sickle cell disease and attenuated by hydroxyurea

As hypoxia-induced inflammatory angiogenesis may contribute to the manifestations of sickle cell disease, we compared the angiogenic molecular profiles of plasma from sickle cell disease individuals and correlated these with in vitro endothelial cell-mediated angiogenesis-stimulating activity and in vivo neovascularization. Bioplex demonstrated that plasma from patients with steady-state sickle cell anemia contained elevated concentrations of pro-angiogenic factors (angiopoietin-1, basic fibroblast growth factor, vascular endothelial growth factor, vascular endothelial growth factor-D and placental growth factor) and displayed potent pro-angiogenic activity, significantly increasing endothelial cell proliferation, migration and capillary-like structure formation. In vivo neovascularization of Matrigel plugs was significantly greater in sickle cell disease mice than in non-sickle cell disease mice, consistent with an up-regulation of angiogenesis in the disease. In plasma from patients with hemoglobin SC disease without proliferative retinopathy, anti-angiogenic endostatin and thrombospondin-2 were significantly elevated. In contrast, plasma from hemoglobin SC individuals with proliferative retinopathy had a pro-angiogenic profile and more significant effects on endothelial cell proliferation and capillary formation than plasma from patients without retinopathy. Hydroxyurea therapy was associated with significant reductions in plasma angiogenic factors and inhibition of endothelial cell-mediated angiogenic mechanisms and neovascularization. Thus, individuals with sickle cell anemia or hemoglobin SC disease with retinopathy present a highly angiogenic circulating milieu, capable of stimulating key endothelial cell-mediated angiogenic mechanisms. Combination anti-angiogenic therapy to prevent the progression of unregulated neovascularization and associated manifestations in sickle cell disease, such as pulmonary hypertension, may be indicated; furthermore, the benefits and drawbacks of the potent anti-angiogenic effects of hydroxyurea should be clarified.     

Systemic lupus erythematosus in patients with sickle cell disease

Sickle cell disease (SCD) is a prevalent genetic disorder that includes sickle cell anemia (hemoglobin SS), hemoglobin SC, and hemoglobin Sb-thalassemia. Patients with SCD present with a defective activation of the alternate pathway of the complement system that increases the risk of capsulate bacteria infection and failure to eliminate antigens, predisposing these patients to autoimmune diseases. The authors describe three patients with SCD that developed systemic lupus erythematosus (SLE). In all patients, SLE diagnosis was delayed because symptoms were initially attributable to SCD. Physicians should be alerted to the possible development of SLE in patients with SCD to not delay the diagnosis and start appropriate treatment.     

Hypercoagulability in sickle cell disease: a curious paradox

There is evidence of activation of both blood coagulation and platelets in sickle cell disease. For example, plasma samples obtained in the steady state and during painful crisis demonstrate high levels of thrombin generation, depletion of anticoagulant proteins, and abnormal activation of the fibrinolytic system. Similarly, exposure of surface markers such as CD62P and CD40L, along with increased circulating levels of thrombospondin, signal platelet activation. In addition to its effects on the cleavage of fibrinogen and its ability to activate platelets, the increase in circulating thrombin levels, with its wide-ranging effects on endothelial cells and blood vessels, may be important in the pathophysiology of sickle cell disease. Therefore, treatments that could decrease thrombin generation or platelet activation may be beneficial in both the treatment of sickle cell disease and the prevention of complications that characterize this genetic disorder. This review discusses hypercoagulability in the various forms of sickle cell disease, including homozygous sickle cell anemia, hemoglobin SC disease, hemoglobin SD disease, and sickle cell-beta-thalassemia.     

Hemorheological risk factors of acute chest syndrome and painful vaso-occlusive crisis in children with sickle cell disease

Background

Little is known about the effects of blood rheology on the occurrence of acute chest syndrome and painful vaso-occlusive crises in children with sickle cell anemia and hemoglobin SC disease.

Design and Methods

To address this issue, steady-state hemorheological profiles (blood viscosity, red blood cell deformability, aggregation properties) and hematologic parameters were assessed in 44 children with sickle cell anemia and 49 children with hemoglobin SC disease (8-16 years old) followed since birth. Clinical charts were retrospectively reviewed to determine prior acute chest syndrome or vaso-occlusive episodes, and rates of these complications were calculated.

Results

Multivariate analysis revealed that: 1) a higher steady-state blood viscosity was associated with a higher rate of vaso-occlusive crises in children with sickle cell anemia, but not in children with hemoglobin SC disease; 2) a higher steady-state red blood cell disaggregation threshold was associated with previous history of acute chest syndrome in children with hemoglobin SC disease and boys with sickle cell anemia.

Conclusions

Our results indicate for the first time that the red blood cell aggregation properties may play a role in the pathophysiology of acute chest syndrome in children with hemoglobin SC disease and boys with sickle cell anemia. In addition, whereas greater blood viscosity is associated with a higher rate of vaso-occlusive crises in children with sickle cell anemia, no association was found in children with hemoglobin SC disease, underscoring differences in the etiology of vaso-occlusive crises between sickle cell anemia and hemoglobin SC disease.Key words: sickle cell anemia, hemoglobin SC disease, red blood aggregation, blood viscosity, red blood cell deformability     

Hematologic and hemorheological determinants of resting and exercise-induced hemoglobin oxygen desaturation in children with sickle cell disease

The aim of the study was to determine the factors associated with resting and exercise-induced hemoglobin oxygen desaturation. The well-established six-minute walk test was conducted in 107 sickle cell children (50 with sickle hemoglobin C disease and 57 with sickle cell anemia) at steady state. Hemoglobin oxygen saturation was measured before and immediately after the six-minute walk test. Blood samples were obtained on the same day to measure hematologic and hemorheological parameters. Exercise-induced hemoglobin oxygen desaturation was defined as a drop in hemoglobin oxygen saturation of 3% or more at the end of the six-minute walk test compared to resting levels. No children with sickle hemoglobin C disease, but approximately 50% of children with sickle cell anemia showed mild or moderate oxygen desaturation at rest, which was independently associated with the percentage of reticulocytes. Exercise-induced hemoglobin oxygen desaturation was observed in 18% of children with sickle hemoglobin C disease and 34% of children with sickle cell anemia, and was independently associated with the six-minute walk test, acute chest syndrome rate and the strength of red blood cell aggregates in children with sickle cell anemia. No association was found in children with sickle hemoglobin C disease between exercise-induced hemoglobin oxygen desaturation and the measured parameters. Hemoglobin oxygen desaturation at rest was common in children with sickle cell anemia but not in children with sickle hemoglobin C disease, and was mainly associated with greater hemolysis. Physiological strain during exercise and red blood cell aggregation properties may predict the occurrence of exercise-induced hemoglobin oxygen desaturation in children with sickle cell anemia.     

Plasma Hemoglobin-Binding Capacity in Sickle Cell Disease

Studies of the capacity of plasma proteins to bind hemoglobin were madein patients with sickle cell anemia (SS), sickle cell trait (SA), hemoglobinC disease and in patients with hemolytic anemias. Hemoglobin binding wasquantitatively normal in sickle cell trait, but was greatly reduced or absentin sickle cell anemia, hemoglobin C disease and in other hemolytic disorders.These alterations have been attributed to a reduction in the level of hemoglobin-binding proteins in circulating plasma. The mechanism of this reduction was not established, but the observed changes were correlated with thepresence of increased hemolytic activity.

The binding of hemoglobin C and hemoglobin S by normal plasma wasquantitatively normal.

Submitted on October 25, 1958 Accepted on December 12, 1958     

Clinical,hematological, and biochemical features of Hb SC disease

Twenty-seven patients were seen and followed at our Sickle Cell Center over a period of seven years. Their clinical, hematological, and biochemical features were determined and compared to those of patients with sickle cell anemia who were concurrently investigated. The data indicate that the mild anemia of hemoglobin (Hb) SC disease is slightly microcytic and hyperchromatic. Parameters of hemolysis and the complications of chronic hemolytic anemia (cholelithiasis, leg ulcers, hepatomegaly, and cardiomegaly) are milder in Hb SC disease than in sickle cell anemia. Asplenia and its sequelae (increased platelet count and reduced serum IgM levels) are less frequent in Hb SC disease. Cerebrovascular accidents and the decreased leukocyte alkaline phosphatase scores are similar in both diseases. Thromboembolic complications, retinopathy, and renal papillary necrosis are more frequent in Hb SC disease.     

Coagulation changes in individuals with sickle cell trait

Sickle cell disorders, such as Hb SS and Hb SC, are associated with a hypercoagulable state that may contribute to the vaso-occlusive episodes observed in the disorders. To what extent increased coagulation activity occurs in individuals with sickle cell trait has had limited study. Because such information may help clarify clinical and pathologic findings that may occur in these individuals and may be useful in clarifying the hypercoagulable state in sickle cell disease, we have examined individuals with Hb AS to determine the extent that increased coagulation activity does occur. We measured d-dimers, thrombin-antithrombin (TAT) complexes, prothrombin fragment 1.2 (F1.2), absolute blood monocyte levels, proteins C and S, and isotypes of antiphospholipid antibodies in individuals with Hb AS and in matched controls (Hb AA). Results showed that d-dimers, TAT, and F1.2 were increased significantly above normal levels. Absolute blood monocyte levels were increased. The d-dimers, TAT, F1.2, and monocyte counts showed significant increasing trends through groups of increasing severity (Hb AA, Hb AS, Hb SC, and Hb SS). Our study shows that individuals with Hb AS have increased coagulation activity, with d-dimers, TAT, and F1.2 being consistent indicators. The measures of coagulation activity in Hb AS are lower than in patients with Hb SC and Hb SS disease. These results extend our previous observation that the degree of coagulation activation parallels the degree of disease severity among sickle cell genotypes. The findings suggest that monocytosis, with the possible expression of monocyte-derived tissue factor, and the associated hypercoagulable state are driven by disease severity.     

Sickle cell trait and the risk of venous thromboembolism among blacks

People with sickle cell disease have a chronically activated coagulation system and display hemostatic perturbations, but it is unknown whether they experience an increased risk of venous thromboembolism. We conducted a case-control study of venous thromboembolism that included 515 hospitalized black patients and 555 black controls obtained from medical clinics. All subjects were assayed for hemoglobin S and hemoglobin C genotypes. The prevalence of the S allele was 0.070 and 0.032 for case patients and controls, respectively (P < .001). The odds that a patient had sickle cell trait were approximately twice that of a control, indicating that the risk of venous thromboembolism is increased approximately 2-fold among blacks with sickle cell trait compared with those with the wild-type genotype (odds ratio = 1.8 with 95% confidence interval, 1.2-2.9). The odds ratio for pulmonary embolism and sickle cell trait was higher, 3.9 (2.2-6.9). The prevalence of sickle cell disease was also increased among case patients compared with controls. We conclude that sickle cell trait is a risk factor for venous thromboembolism and that the proportion of venous thromboembolism among blacks attributable to the mutation is approximately 7%.     

Left ventricular systolic and diastolic functions in patients with sickle cell anemia

BACKGROUND: Sickle cell anemia is a formidable problem in India, and is more prevalent in Maharashtra. Cardiovascular involvement in this condition has not been well studied. The present study therefore sought to investigate the systolic and diastolic left ventricular function of children with sickle cell anemia. METHODS AND RESULTS: This prospective controlled study comprised of 25 cases of sickle cell anemia, 25 cases of anemia (hemoglobin <11 gm/dl) with 'AA' types of hemoglobin electrophoresis and 25 non-anemic controls (hemoglobin >11 gm/dl) with normal hemoglobin electrophoresis pattern. M-mode, 2-dimensional and Doppler echcardiographic measurements of patients and controls were performed according to criteria of the American Echocardiography Society. In the study cases, age ranged from 5 years to 15 years with the mean age of 9.91 years. There were 14 males and 11 females in the study cases. Patients with sickle cell anemia had significantly larger left atrial (23.26 +/- 3.6 mm, 22.9 +/- 2.56 mm, 20.72 +/- 2.79 mm; p < 0.05), left ventricular (34.88 +/- 4.53, 33.28 +/- 3.28, 30.72 +/- 3.68: p < 0.05) and aortic root (19 +/- 2.7, 18.91 +/- 2.24, 17.56 +/- 1.44; p < 0.05) dimensions. They also had higher indexed end-diastolic left ventricular volumes (101.84 +/- 22.74 ml/m2 v. 65.05 +/- 10.81 ml/m2; p < 0.001), and higher stroke volume (29.32 +/- 11.32 ml, 27.12 +/- 7.82 ml, 22.4 +/- 6.67 ml; p < 0.05). Left ventricular mass (62.24+/- 18.44 gm, 52.53 +/- 16.23 gm, 50.2 +/- 15.68 gm; p < 0.05) was greater in sickle cell anemia patients than in controls. No statistically significant differences were detected in the Doppler finding of patients with or without anemia. No statistically significant correlation was found between echocardiographic parameters (M-mode and Doppler) and the hemoglobin in the sickle cell patients. CONCLUSIONS: Echocardiography is a useful non-invasive technique to study the changes in cardiac structure and function. In spite of left ventricular volume load and dilation in sickle cell anemic patients, left ventricular contraction was good and systolic function was normal, and there was no correlation between the echocardiographic findings and hemoglobin level.     

Glycosylated hemoglobin levels in Sudanese sickle cell anemia patients

Glycosylated hemoglobin was measured, by a colorimetric method, in 49 patients with sickle cell anemia attending Khartoum Teaching Hospital. The level obtained (4.9%, SD 1.3) was significantly lower than the control value (5.6%, SD 0.2; p less than 0.0025). Expressed as percentage of the control value, the glycosylated hemoglobin level in these patients was 81%. This falls midway between the 90% reported in a benign form of sickle cell anemia in Saudi Arabia and the 58% reported in a severe form in an American Black group, which gives support to the observed heterogeneity of sickle cell anemia. Alternatively, glycosylated hemoglobin level in 27 subjects with sickle cell trait (5.6%, SD 0.2) was identical to that of the controls. The state of hemolysis in the sickle cell anemia patients, as indicated by bilirubin levels, did not correlate with the glycosylated hemoglobin values. Although glycosylated hemoglobin measurement is affected by red cell survival, it does not reflect the state of ongoing hemolysis.     

Abnormal platelet von willebrand factor (vWF) as a marker of abnormal function in megakaryocytic dysplasia

Recent progress in the measurements of the hemostatic markers enables us to assess the detailed profiles of hemostatic activation in various diseases. To evaluate the degree of hemostatic system activation in patients with cerebral thrombosis, detailed coagulation studies were performed in 28 patients with acute-phase cerebral thrombosis and in 36 with chronic-phase cerebral thrombosis, together with 6 with chronic-phase cerebral hemorrhage and 37 age-matched healthy volunteers. In both acute-phase and chronic-phase cerebral thrombosis, plasma levels of thrombin-antithrombin III complex, plasmin-α₂-plasmin inhibitor complex and D-dimer were significantly higher, and antithrombin III and protein C were significantly lower than those in the normal group. Plasma fibrinogen concentration was significantly higher in chronic-phase cerebral thrombosis than that in chronic-phase cerebral hemorrhage. No significant difference was found in these variables between acute-phase and chronic-phase cerebral thrombosis. In addition, there was no difference in these parameters between chronic phase cerebral hemorrhage and normal subjects. These findings indicate that a sustained activation of coagulation and fibrinolysis is present in cerebral thrombosis, and it might contribute to the pathogenesis of cerebral thrombosis.     

Plasma factor VII and thrombin–antithrombin III levels indicate increased tissue factor activity in sickle cell patients

Although the mechanisms involved in the persistent clinical complications of sickle cell disease have not yet been fully delineated, previous studies suggest that sickle cell (HbSS) patients have a disposition to generate more thrombin and plasma in vivo than normal subjects. The reasons for the impaired regulation of haemostasis in HbSS patients is poorly understood. We report studies evaluating the extent to which in vivo coagulation and fibrinolysis are altered in HbSS patients in steady state. The concentrations of total factor VII (F(VII)t), factor VII zymogen (F(VII)z), thrombin-antithrombin III (TAT), fibrinopeptide A(FPA), and fibrin D-dimer in plasmas of 50 normal controls (HbAA) and 45 HbSS steady state patients, were measured using sensitive and specific enzyme-linked immunoassays. The average plasma concentration of F(VII)t, in sickle cell plasma was significantly lower than that of the control subjects (0.70 +/- 0.19 U/ml versus 1.16 +/- 0.41 U/ml), whereas F(VII)z in the patients and controls were 0.47 +/- 0.15 U/ml and 1.15 +/- 0.33 U/ml respectively, P < 0.001. Both measures of factor VII suggest a higher factor VII turnover in sickle cell disease. The mean concentration of TAT in the plasma of HbSS patients were significantly higher than those of HbAA controls (371 +/- 44 pM versus 42 +/- 2 pM) (P < 0.001), a difference that is strongly indicative of higher rates of in vivo thrombin generation by HbSS patients. Plasmas of HbSS patients had significantly higher concentrations of FPA compared to those of the control subjects (12.85 +/- 1.96 ng/ml versus 4.22 +/- 0.37 ng/ml) (P < 0.001). The D-dimer levels were also higher in the HbSS than control plasmas (1029.6 +/- 58.6 ng/ml versus 224.3 +/- 27.6 g/ml) (P < 0.001), with the patients' values being indicative of enhanced fibrinolysis. These results strongly suggest accelerated in vivo coagulation and fibrinolysis in HbSS patients even during steady state. They are consistent with the hypothesis that haemostasis is less tightly regulated in the HbSS patients than in HbAA controls. The altered regulation of haemostasis may contribute to the initiation of vaso-occlusive processes associated with sickle cell painful episodes.     

Tissue factor-positive monocytes in children with sickle cell disease: correlation with biomarkers of haemolysis

Tissue Factor (TF) initiates thrombin generation, and whole blood TF (WBTF) is elevated in sickle cell disease (SCD). We sought to identify the presence of TF-positive monocytes in SCD and their relationship with the other coagulation markers including WBTF, microparticle-associated TF, thrombin-antithrombin (TAT) complexes and D-dimer. Whether major SCD-related pathobiological processes, including haemolysis, inflammation and endothelial activation, contribute to the coagulation abnormalities was also studied. The cohort comprised children with SCD (18 HbSS, 12 HbSC, mean age 3·6 years). We demonstrated elevated levels of TF-positive monocytes in HbSS, which correlated with WBTF, TAT and D-dimer (P = 0·02 to P = 0·0003). While TF-positive monocytes, WBTF, TAT and D-dimer correlated with several biomarkers of haemolysis, inflammation and endothelial activation in univariate analyses, in multiple regression models the haemolytic markers (reticulocytes and lactate dehydrogenase) contributed exclusively to the association with all four coagulant markers evaluated. The demonstration that haemolysis is the predominant operative pathology in the associated perturbations of coagulation in HbSS at a young age provides additional evidence for the early use of therapeutic agents, such as hydroxycarbamide to reduce the haemolytic component of this disease.     

Staged single-ventricle palliation in an infant with hemoglobin SC disease

Staged single-ventricle palliation is used to treat many cyanotic congenital heart diseases. Hemoglobin sickle cell disease is associated with anemia and significant vascular sickling sequelae, which increase the risk associated with single-ventricle palliation. To our knowledge, there are no reports in the English-language medical literature of single-ventricle palliation having been performed on a patient who had either sickle cell anemia or sickle cell-hemoglobin C disease. Herein, we discuss our clinical and surgical management of an infant with tricuspid atresia type IA and hemoglobin sickle cell disease who survived single-ventricle palliative procedures through the 2nd stage of a bidirectional Glenn anastomosis.     

Prognostic significance of hemostatic parameters in patients with lung cancer

There is a subclinical activation of coagulation and fibrinolysis system in lung cancer. Alterations in hemostatic system are seen frequently in lung cancer correlated with the prognosis of disease. In this prospective study, our purpose was to investigate the prognostic significance of hemostatic markers in patients with lung cancer. The study comprised 58 patients (22 squamous cell carcinoma, 16 adenocarcinoma, 20 small cell carcinoma). There were 55 men (95%)and 3 women (5%) with a mean age of 61 years range (36-74). Plasma level of platelets (PLT), prothrombin time (PT), active partial thromboplastin time (aPTT), antithrombin III (AT III), fibrinogen (F) and D-dimer level were measured before the initiation of any therapy. Patients were followed up for 17 (12-20) months. The median survival was determined as 6.4 months. Three histopathologic groups; squamous cell carcinoma, adenocarcinoma and small cell carcinoma were compared for the hemostatic parameters. There were no statistically significant differences among the histopathologic types for any of the parameters (P > 0.05). Patients were divided into two groups as patients without distant metastasis (stages I,II,III) and with distant metastasis (stage IV). The group with distant metastasis had higher level of D-dimer than the other group (P < 0.05). However, there were no statistically significant differences for D-dimer level between stages IIIB and IV (P > 0.05). Patients having high D-dimer and low AT III level had poor survival in our study. Thus, high level of D-dimer and low AT III level were determined as correlated with short survival (P < 0.05). These results suggest that elevated plasma level of D-dimer and low AT III level might be a sign of poor prognosis in patients with lung cancer.     

Relation of serum sialic acid to blood coagulation activity in type 2 diabetes.

The level of serum sialic acid, which is known to reflect atherosclerotic progress and to be related to the incidence of cardiovascular diseases, is increased in patients with diabetes. To elucidate the mechanism of the relation of serum sialic acid to fibrinogen, the relationship between serum sialic acid and markers of blood coagulation activity was investigated in type 2 diabetic patients. The concentration of serum sialic acid showed significant positive correlations with blood platelet count and with plasma concentrations of fibrinogen, D-dimer, thrombin-antithrombin III complex and plasmin-alpha2 plasmin inhibitor complex. These relationships were still significant after adjustment for age, sex, smoking history, body mass index, hemoglobin A, mean arterial pressure and low-density lipoprotein cholesterol. The correlation coefficient of blood fibrinogen with serum sialic acid was still significant after adjustment for D-dimer, thrombin-antithrombin III complex or plasmin-alpha2 plasmin inhibitor complex. On the contrary, blood fibrinogen showed no significant correlation with D-dimer, thrombin-antithrombin III complex or plasmin-alpha2 plasmin inhibitor complex, although an increase in blood fibrinogen is known to be an atherosclerotic risk factor. These results suggest that the serum sialic acid level reflects blood coagulation activity in type 2 diabetic patients and is related to blood fibrinogen level independently of blood coagulation activity.     

Regulation of Fetal and Adult Hemoglobin Formation in Patients with Sickle Cell Disease Transfused to Normal Hematocrits

Two patients with sickle cell anemia and one patient with sickle thalassemiawere acutely transfused to normal hemoglobin levels. The synthesis of fetaland adult (in this instance, Hb S) hemoglobins was assessed in cohorts ofreticulocytes emerging during the period of erythroid suppression which followed. In two patients observations were also made during the period of recovery from the suppression. Hemoglobin synthesis in the reticulocytes wasassessed by means of in vitro incorporation of C¹⁴-labeled leucine into the separate hemoglobins. The results in all three patients suggested that both fetaland adult hemoglobin synthesis are under similar physiologic control mechanisms during short-term alterations in the state of erythropoiesis; the formationof both was almost completely stopped soon after transfusion, and both werealmost simultaneously reactivated as the patients returned to the anemic state.

Submitted on April 7, 1966 Accepted on July 18, 1966     

Abnormal Human Hemoglobins. I. Biosynthesis in Vitro of Fe59-Labeled Human Hemoglobin A and Hemoglobin S

The synthesis of Fe⁵⁹ labeled-hemoglobin during incubation of bone marrow from normal and sickle cell anemia (crisis and non-crisis) patients hasbeen investigated. The in vitro synthesis of hemoglobin S in the steadystate (noncrisis) sickle cell anemia individual was found to proceed ata much faster rate than the synthesis of hemoglobin A from normal individuals. In the crisis of sickle cell anemia, the uptake of Fe⁵⁹ and synthesis ofhemogobin S was approximately at the same level as synthesis of hemoglobin A from the normal individual. The results of this study indicatethat one of the mechanisms involved in sickle cell anemia crisis is a decrease in synthesis of hemoglobin S as compared to the synthesis of hemoglobin S during the steady state of noncrisis.

Submitted on November 20, 1958 Accepted on March 10, 1959