Thrombosis risk with haemoglobin C trait and haemoglobin C disease: A systematic review

The thrombotic risk with haemoglobin C trait (HbAC) or haemoglobin C disease (HbCC) is unclear. However, individuals with HbCC have demonstrated chronic haemolysis, higher blood viscosity and altered rheology when compared to individuals with wild-type haemoglobin (HbAA). These physiological alterations may theoretically translate to increased risk of thrombosis; therefore, a systematic literature review was performed to investigate the possible association between HbAC and/or HbCC and thrombosis. Twenty-two studies met inclusion criteria representing 782 individuals with HbAC (n = 694) or HbCC (n = 88). Fifteen studies described the presence/absence of venous thromboembolism (VTE) in patients with HbAC (n = 685) or HbCC (n = 79), while seven studies described patients with HbAC (n = 9) or HbCC (n = 9) and arterial thrombosis. Most (n = 20) studies were case reports or case series; however, two studies suggested a potential increased VTE risk with HbAC compared to HbAA in (i) all patients (OR 2.2, 95% CI: 0.9-5.5) and in (ii) pregnant individuals (RR 3.7, 95% CI 0.9-16). This review is the largest assessment of patients with HbC trait or disease and thrombosis to date; despite its limitations, the findings suggest HbC may be a predisposing risk factor to thrombosis. Prospective cohort studies are warranted to definitively elucidate the risk of thrombosis in this population.

Tractional Retinal Detachment Related to Hemoglobin C Trait Retinopathy: A Case Report

Hemoglobin C (HbC) disease is an uncommon disease that is generally considered benign, causing only occasionally painless hematuria, osteomyelitis, and dental abnormalities. Ocular manifestations have rarely been described in these patients. Here we report a novel ophthalmological manifestation of the disease. A 20-year-old woman presented with progressive visual loss in her right eye due to tractional retinal detachment. The left eye was apparently normal, but wide-field fluorescence angiography showed mild peripheral ischemia with multiple vascular abnormalities. Vitrectomy was performed and the systemic workup revealed the presence of hemoglobinopathy C in heterozygous form. HbC disease can be sight-threating due to retinal proliferation, similar to sickle cell retinopathy. Patients affected with this disease should undergo regular surveillance. Ultra-wide angiography is a helpful examination to detect peripheral ischemia in the earlier stages.

Evaluation of interference from hemoglobin C, D, E and S traits on measurements of hemoglobin A1c by fifteen methods

BACKGROUND

Hemoglobin C, D Punjab, E or S trait can interfere with hemoglobin A1c (HbA1c) results. We assessed whether they affect results obtained with 15 current assay methods.

METHODS

Hemoglobin AA (HbAA), HbAC, HbAD Punjab, HbAE and HbAS samples were analyzed on 2 enzymatic, 4 ion-exchange HPLC and 9 immunoassay methods. Trinity Premier Hb9210 boronate affinity HPLC was the comparative method. An overall test of coincidence of least-squared linear regression lines was performed to determine if HbA1c results were statistically significantly different from those of HbAA samples. Clinically significant interference was defined as >6% difference from HbAA at 6 or 9% HbA1c compared to Premier Hb9210 using Deming regression.

RESULTS

All methods showed statistically significant effects for one or more variants. Clinically significant effects were observed for the Tosoh G11 variant mode (HbAD), Roche b 101 (HbAC and HbAE) and Siemens DCA Vantage (HbAE and HbAS). All other methods (Beckman Coulter B93009 and B00389 on DxC700AU, and Unicel DxC, Ortho Clinical Vitros 5.1, Roche cobas c 513, Siemens Dimension RxL and Vista, and Enzymatic on Advia and Atellica, Tosoh G8 5.24 and 5.28, and GX) showed no clinically significant differences.

CONCLUSIONS

A few methods showed interference from one or more variants. Laboratories need to be aware of potential HbA1c assay interferences.

alpha-Thalassemia 2, 3.7 kb deletion and hemoglobin AC heterozygosity in pregnancy: a molecular and hematological analysis

alpha-Thalassemia is a synthesis hemoglobinopathy with a worldwide distribution. alpha-thalassemia-23.7kb (alpha-Thal23.7kb) was investigated by PCR and standard hematologic analysis techniques in 106 pregnant women - 53 heterozygous for hemoglobin (Hb) A and C (AC) and 53 homozygous for the normal Hb A (AA) with similar ages and race ancestry. Eleven (21%) of AC women were alpha-Thal23.7kb heterozygous and 1 (2%) was homozygous, while 12 AA women (23%) were heterozygous. In the AA group, the MCV differed among those with normal alpha genes and those with alpha-Thal23.7kb (P = 0.031). Statistical analysis of AC group patients with normal alpha genes and alpha-Thal23.7kb carriers showed differences in MCV (P = 0.001); MCH (P = 0.003) and Hb C concentrations (P = 0.011). Analysis of AA and AC group patients with normal alpha genes showed differences in RBC (P = 0.033), Hb concentration (P = 0.003) and MCHC (P < 0.0001). There were no statistically significant differences for any hematologic parameters between AC and AA group patients with the alpha-Thal23.7kb genotype. The AC alpha-Thal23.7kb homozygous women had low hematologic parameters. Serum ferritin levels were normal among the groups studied. These results emphasize the importance of diagnosis and follow-up of patients with hemoglobinopathy carriers during pregnancy in order to administer adequate therapy and avoid further complications for mothers and newborns.

Hemoglobin patterns in American Indians

Two populations of North Carolina have been analyzed for hemoglobin patterns by paper electrophoresis. Of 534 Cherokee Indians, both mixed and full bloods, all showed normal hemoglobin. Lumbee Indians of less certain ethnic status had 1.7 percent of hemoglobin S, an equal amount of hemoglobin C, and one possible hemoglobin D trait among 1332 bloods studied.

Serum transferrin receptor levels are increased in asymptomatic and mild Plasmodium falciparum-infection

BACKGROUND AND OBJECTIVE

The serum transferrin receptor (sTfR) concentration in an individual reflects the extent of erythropoietic activity and is considered a useful marker of iron deficiency independent of concurrent inflammation or infection. However, data on the impact of malaria on this parameter are ambiguous. We have examined potential associations of asymptomatic and mild Plasmodium falciparum-infections and of several erythrocyte variants with sTfR values in South West Nigeria.

DESIGN AND METHODS

In a cross-sectional study among 161 non-hospitalized children, sTfR concentrations and P. falciparum parasitemia were assessed. In addition, hemoglobin (Hb) and serum ferritin values, Hb-types, glucose-6-phosphate dehydrogenase (G6PD)deficiency and a-globin genotypes were determined and the effects of these factors on sTfR levels were analyzed by univariate and multivariate statistical methods.

RESULTS

P. falciparum-infection was present in 77% of the children. Mean sTfR levels were higher in infected than in non-infected children (geometric mean, 3.68, 95% confidence interval [3.5-3.9] vs. 2.99 [2.7-3.3] mg/L; p = 0.0009). There was a significant trend for higher sTfR values with increasing parasite density. sTfR values decreased continuously with age. Hb-types, G6PD-, and a-globin genotypes did not correlate with sTfR levels. In the multivariate analysis, age, Hb and log ferritin values, and parasite density of P. falciparum were independently associated with log sTfR values.

INTERPRETATION AND CONCLUSIONS

sTfR concentrations are increased in asymptomatic and mild P. falciparum-infections suggesting adequate bone marrow response in this condition. The diagnostic value of sTfR levels for iron deficiency may be impaired in areas where stable malaria occurs.

[Rheumatic diseases and hemoglobinopathies in Lomé (Togo)]

This prospective cross-sectional study was designed to determine the frequency and impact of hemoglobinopathies in rheumatology clinic patients in Lomé (Togo). Among the 405 study patients, 142 (35%) had an abnormal hemoglobin, 22% had hemoglobin S, and 16.8% had hemoglobin C. Sickle cell anemia and sickle cell-hemoglobin C disease (2% and 4.2% of patients respectively) were associated with vasoocclusive crises and necrosis of the femoral head. Presence of AS or AC (heterozygotic forms of hemoglobins S and C) was found in 15.8% and 12.1% of patients, respectively. These proportions were similar to those reported in the population at large. Presence of AS or AC had no detectable influence on degenerative spinal disease, osteoarthritis of the knee, tendinitis or inflammatory joint diseases. Our data suggest that presence of AS or AC has no adverse significance and should be disregarded when evaluating patients with musculoskeletal symptoms.

[Hemoglobin O Arab in Ivory Coast and western Africa]

The authors report 44 cases of hemoglobin O Arab share out in 3 phenotypes (A O Arab, C O Arab and S O Arab). The study of this abnormal hemoglobin has allowed the following conclusions: The Hb O Arab is a rare mutant of hemoglobin. The heterozygote form A O Arab and the association Hb C--Hb O Arab do not present any clinical and hematological manifestations. The associations Hb S--Hb O Arab brings about a serious hemoglobinopathy which has clinical and hematological features like the sickle-cell disease (SSFA2).

Proton nuclear magnetic resonance and electron paramagnetic resonance investigation of alpha-alpha cross-linked Fe-Co hybrid hemoglobins

The following asymmetric alpha 1 99 Lys-alpha 2 99 Lys cross-linked Fe(II)-Co(II) hybrid hemoglobins (Hbs) were first prepared from derivatives of hemoglobin C (beta 6 Glu-Lys) and human normal HbA: [alpha(Co)beta(Fe)]A[alpha(Co)beta(Co)]cXL, [alpha(Fe)beta(Co)]A[alpha(Co)beta(Co)]cXL, etc. Their 500 MHz 1H NMR and EPR spectra were measured in order to study the change in their tertiary and quaternary structure under atmosphere of deoxy, oxy and carbon monoxide (with or without IHP). From the change of T and R marks in 1H NMR hydrogen bonding region, it is proved that oxygen molecules are first bonded to alpha(Fe) subunits rather than to beta(Fe). The experimental phenomena provided further evidence that intermediate states of ligation are present in addition to T and R state during process of binding of oxygen to Hb. IHP facilitates transformation of T state to R state. The same conclusion can also be drawn from the results of EPR spectra at 77 K.

The inhibition of hemoglobin C crystallization by hemoglobin F

We have reported that circulating CC erythrocytes containing HbO2 C crystals exhibit little or no Hb F suggesting that Hb F may inhibit the crystallization of Hb C. We report now that Hb F inhibits in vitro crystallization of HbO2 and HbCO C when compared to the effect of Hb A in a wide range of mixture proportions. For example, while HbCO C solutions form tetragonal C crystals within 25 min, no crystals form within 2 h with 30% Hb F, whereas 550 crystals/mm3 form with 30% Hb A. Furthermore, an increase in the percent of Hb A is correlated with a greater number of orthorhombic crystal formation rather than the tetragonal morphology observed with 100% Hb C. We also report that Hb A2 (containing delta chains that exhibit 10 sequence differences with beta chains) and Hb Lepore Boston-Washington (a fusion mutant of delta and beta chains that contains only six of these differences) both inhibit Hb C crystallization. By comparing the sequences of the three inhibitory hemoglobins, we conclude that position Gln-87 in the gamma chains is, at least partially, the cause of the inhibitory effect of Hb F on the crystallization of Hb C.

Effect of the beta 73 amino acid on the hydrophobicity, solubility, and the kinetics of polymerization of deoxyhemoglobin S

The role of Asp-beta 73 on the surface hydrophobicity and solubility of hemoglobin was studied using Hb A, Hb S, Hb C Harlem (alpha 2 beta 2Val-6,Asn-73), and Hb Korle Bu (alpha 2 beta 2Asn-73). The surface hydrophobicity of the oxy form of these hemoglobins increased in the order of Hb A, Hb Korle Bu, Hb S, and Hb C Harlem, coinciding with the change in solubility. The same is not true for deoxyhemoglobins. The solubilities of deoxy-Hb S and deoxy-Hb C Harlem were much lower than that expected from their surface hydrophobicity. Although the hydrophobicity of deoxy-Hb C Harlem is greater than that of deoxy-Hb S, the solubility of deoxy-Hb S is only one-third that of deoxy-Hb C Harlem. This deviation must be caused by the substitution of Asn for Asp at the beta 73 position and its inhibitory effect on hydrogen bonding in Hb S polymers. The kinetics of the polymerization of 1:1 mixtures of the deoxy form of S-C Harlem, A-C Harlem, Korle Bu-S, and Korle Bu-C Harlem were studied in comparison with that of deoxy-Hb S and deoxy-Hb C Harlem alone. All of these binary mixtures polymerized with a distinct delay time prior to polymerization. Based on the results of kinetic studies, the probability factors for nucleation of S-C Harlem, A-S, A-C Harlem, S-Korle Bu, and Korle Bu-C Harlem hybrid hemoglobins were calculated as 0.65, 0.5, 0.5, 0.15, and 0.17, respectively, in comparison with that of Hb S (1.0). The probability factor for Hb C Harlem alone was 0.3. These data suggest that the Asp-beta 73 is directly involved in nucleation during Hb S polymerization and that the beta 73 is always trans to the active Val-beta 6 in the formation of nuclei.

[A case of association of Hb C Ziguinchor (alpha A2 beta 6-2 (A3) Glu replaced by Val beta 58 (E2) Pro replaced by Arg) with a hereditary persistence of fetal hemoglobin (HPFH). Clinical and biological results]

The authors report on one case of association between Hb C Ziguinchor and an hereditary persistence of Hb foetal. Despite an high rate of Hb F estimated at 37,2% painful manifestations due to Hb S (beta 6 Glu-Val) mutation are present.

Electrostatic attraction governs the dimer assembly of human hemoglobin

We have investigated the effect of surface charge on the rate of assembly of alpha beta dimers of human hemoglobin A: alpha + beta k a----alpha beta. Heme intact beta A subunits were compared with four mutant subunits which differ by integral units of charge: beta N(Lys-95----Glu) (2-); beta J(Gly-16----Asp) (1-); beta S(Glu-6----Val) (1+); beta C(Glu-6----Lys) (2+). Subunit competition experiments were performed as follows. Varying amounts of 3H-labeled alpha A subunits were added to a mixture containing equal amounts of beta A and beta X subunits so that alpha/(beta A + beta X) ranged from 0.05-1.0. The reconstituted 3H-labeled Hbs A and X were analyzed by ion-exchange high pressure liquid chromatography as well as by gel electrofocusing and fluorography. Under the solvent conditions employed (10 mM PO4(Na), pH 7.0, 0 degrees C) a predominant proportion of the beta subunits was monomeric. Therefore, the ratio of Hb X to Hb A formed from subunit reconstitution when alpha/(beta X + beta A) approached zero provides a direct measure of the relative rates of monomer combination: kXa/kAa. The experimental values of this ratio decreased monotonically with the overall charge of the variant beta subunit: beta N = 2.6; beta J = 1.5; beta S = 0.41; beta C = 0.13. In contrast surface charge had no significant effect on the rate of dissociation of the alpha beta dimer: alpha beta kd----alpha + beta. At pH 8.0, where the alpha chains lack a net surface charge, they combined equally well to beta A and beta C chains. These experiments are consistent with a two-step mechanism, alpha + beta in equilibrium (alpha...beta) in equilibrium alpha beta, where the oppositely charged monomers diffuse together under the influence of their mutual electrostatic interaction to form a nonspecifically bound encounter complex [alpha...beta] that undergoes a surface charge-independent rearrangement to form the stable dimer.

Interaction of human hemoglobin and its variants with agar

In citrate agar electrophoresis hemoglobin appears to bind reversibly to the sulfated polysaccharide agaropectin, a natural component of Difco Bacto-Agar. This complex migrates anodally, since the hemoglobin is only weakly positively charged at pH 6.2 whereas the carbohydrate carries a net negative charge. Electroendosmosis, on the other hand, proceeds in the cathodal direction. These opposing fluxes separate the hemoglobins in the order of their affinity for agaropectin. An agaropectin binding site was identified on hemoglobin by computer-assisted modeling, and the relation of the site to hemoglobin variants that exhibit abnormal citrate agar mobility was established. The citrate anion is postulated to function as a "counter ion." Preliminary evidence indicates that agaropectin has antigelling properties with respect to hemoglobin S.

Cell sorter immunofluorescence detection of human erythrocytes labelled in suspension with antibodies specific for hemoglobin S and C

We have developed an immunochemical method for labeling human red blood cells in suspension with hemoglobin-specific antibodies. A membrane permeable cross-linking reagent, dimethyl suberimidate, is used to covalently bind, in situ, a fraction of the intracellular hemoglobin to integral membrane proteins. Hypotonic lysis and washing of the cells removes the unbound hemoglobin resulting in red blood cell ghosts which are permeable to macromolecules. Fluorescein-labeled antibodies for the hemoglobin variants S and C bind specifically to hemoglobin AS and AC ghosts, respectively, and not to normal hemoglobin AA ghosts. This technique can be used to prepare ghost suspensions for cell sorter analysis in which large numbers (10(9)--10(10)) of normal ghosts can be rapidly screened for the presence of rare anti-hemoglobin S and anti-hemoglobin C binding ghosts. In reconstruction experiments using mixtures of AS and AA cells and anti-hemoglobin S, AS ghosts as rare as 3 X 10(-5) were quantitatively recovered. Fluorescence artifacts prevented direct enumeration of AS ghosts at lower frequencies, but a two-step flow sorting-fluorescence microscope visual scanning procedure allows semiquantitative detection of anti-hemoglobin S-labeled ghosts as low as 10(--7). This method can be used for rapidly screening blood samples from individuals of normal hemoglobin A genotype for the presence of rare anti-hemoglobin S and anti-hemoglobin C binding ghosts.

Isoelectric focusing of hemoglobins on thin-layer agarose

Isoelectric focusing on thin layers of agarose was used to separate several human hemoglobin variants in narrow pH range (pH 6-9). Problems with gel flooding and distortions due to electroendosmotic flow were solved by altering the casting and processing of the gel, by modifying the focusing apparatus, and by utilizing commercial agarose that had been chemically modified to reduce electroendomosis. Hemoglobins C, O-ARAB, A2, and E were distinguished from one another, as were hemoglobins S, D-LOS ANGELES, G-PHILADELPHIA, F. A, I, and J. The technic is rapid, simple, and relatively inexpensive. The agarose is nontoxic, has excellent gelling properties, and possesses large pores, yet gives resolution equivalent or superior to that obtained on thin layers of polyacrylamide gel, making it preferable to polyacrylamide for thin-layer isoelectric focusing.

Aggregation and crystallization of hemoglobins A, S, and C. Probable formation of different nuclei for gelation and crystallization

The oxy and carbonmonoxy forms of Hb A and Hb S formed aggregates or gels when dissolved in phosphate buffers at concentrations above their solubility and warmed rapidly to 30 degrees C from 0 degrees C. Kinetic studies showed that although deoxy-Hb A and deoxy-Hb S aggregated with a clear exhibition of a delay time, the oxy and carbonmonoxy forms of Hb A and Hb S did not show a delay time. These results suggest that the deoxy forms of Hb A and Hb S aggregate according to the nucleation-controlled mechanism, while oxy- and carbonmonoxyhemoglobins aggregate by the simple linear aggregation mechanism. It was also found that the gels or aggregates of deoxy-Hb A and carbonmonoxy-Hb S could be converted to crystals by further incubation. The rate of crystallization depended upon the concentration of hemoglobin in the supernatant, with faster crystallization at higher concentrations. Similar experiments with deoxy-Hb C (beta 6 Glu leads to Lys) showed that this hemoglobin also crystallized after aggregation, with both reactions accompanied by a delay time. The activation energy for the crystallization reaction of deoxy-Hb C (100 approximately 150 kcal/mol) was much higher than that for the aggregation reaction (20 kcal/mol). These results suggest that deoxy-Hb A, deoxy-Hb S, and deoxy-Hb C form two types of nuclei that are specific to the formation of gels (or aggregates) or crystals. The concentration of hemoglobin measured after completion of crystallization was much lower than that measured after gelation (or aggregation) and was independent of the initial hemoglobin concentration. This concentration is assumed to be the real solubility of hemoglobin.

Immunochemical properties of abnormal hemoglobins C-Harlem (beta 6 Glu replaced by Val, beta 73 Asp replaced by Asn), S (beta 6 Glu replaced by Val), Korle Bu (beta 73 Asp replaced by Asn), Vancouver (beta 73 Asp replaced by Tyr), and Mobile (beta 73 Asp replaced by Val)

Antibodies were made to three mutant hemoglobins, each containing different single amino acid substitutions at beta 73:Hb Korle Bu (Asp replaced by Asn), Hb Mobile (Asp leads to Val), Hb Vancouver (Asp replaced by Tyr); and to one mutant hemoglobin, Hb C-Harlem, containing two substitutions in the beta chain (beta 6 Glu replaced by Val, as in Hb S, and beta 73 Asp replaced by Asn, as in Hb Korle Bu). The antiserum to Hb C-Harlem contained two antibody populations, each specific for one mutant amino acid residue. The antiserum to Hb Vancouver was completely specific for this mutant and did not cross-react with Hb Mobile and Hb Korle Bu; however, antiserum to Hb Korle Bu partially cross-reacted with Hb Mobile and to a smaller degree with Hb Vancouver. Antiserum to Hb Mobile exhibited even less cross-reactivity with Hb Korle Bu and C-Harlem and none with Hb Vancouver. These and previous studies indicate the involvement of at least three independent areas in the beta chain as antigenic determinant sites. It appears that the three mutants at beta 73 elicit the formation of antibodies which have a gradation in their specificity due to the nature of the amino acid sidechain.

Erythropoietic stress, macrocytosis, and hemoglobin switching in HbAA sheep

Hemoglobin switching and macrocytosis were studied in homozygous hemoglobinAA sheep. An abrupt initiation of erythropoietic stress, accompanied by a pulsed elevation of circulating erythropoietin levels, was induced by phlebotomy. Sequential blood samples were separated according to density on Stractan gradients to isolate cells newly entering the circulation from the marrow each day. Analysis of hemoglobin phenotype and cell volume distribution in these young reticulocytes revealed a distinct temporal separation in the appearance of hemoglobin C and increased cell volume. The appearance of macrocytes within 24 hr of erythropoietin elevation suggests that macrocytosis could be the result of the action of erythropoietin during the late stages of erythroid maturation. The 72-hr delay in the appearance of hemoglobin C indicates that commitment to a particular hemoglobin phenotype occurs at an early stage of differentiation and involves immature erythroid stem cells. The results of this study show that these consequences of erythropoietic stress are initiated at two different developmental stages, resulting in the production of macrocytosis and hemoglobin switching.

Hybrid formation for liganded hemoglobins A and C at subzero temperatures

The kinetics of formation of the asymmetric carbonmonoxyhemoglobin hybrid (alpha beta)A(alpha beta)C from the parent molecules alpha 2 beta 2A and alpha 2 beta 2C have been studied by electrophoresis at subzero temperatures (down to -40 degrees C) using as supporting media gels of acrylamide/methylacrylate in dimethyl sulfoxide/water mixtures. It has been found that in these media the rate of hybrid formation is markedly affected by pH and decreases by an order of magnitude between pH 7.3 and 8.3. At pH greater than 10, t = -40 degrees C, the hybrid between alpha 2 beta 2A and alpha 2 beta 2C is stable for several hours. A rapid thermal quenching of a mixture of alpha 2 beta 2A and alpha 2 beta 2C prevented hybrid formation during the time required to separate the 2 molecules.

Structure of human hemoglobin C: a disease with intraerythrocytic crystals

Crystals of human cyanomethemoglobin C (beta 6A3 glu leads to Lys) crystallized in the orthorhombic space group P212121, A = 158(1), B = 65.5(4), C = 54.9(5) A with Z =4. Single crystal electron micrographs show filaments parallel to the b direction. The molecules are unusually densely packed compared to other hemoglobin crystals, and this may be related to the ease of intraerythrocytic crystallization.

Demonstration of a delay time during aggregation of diluted solutions of deoxyhemoglobin S and hemoglobin CHarlem in concentrated phosphate buffer

Diluted solutions (less than 100 mg/dl) of deoxygenated sickle hemoglobin (Hb S) and Hb CHarlem were found to aggregate with a clear demonstration of a delay time when dissolved in concentrated phosphate buffer. The delay time could be shortened by increasing the concentration of either hemoglobin or phosphate. Upon cooling or bubbling with carbon monoxide, the aggregates melted quickly. The logarithmic plot of reciprocal delay time versus hemoglobin or phosphate concentration shows a linear line with a slope of 2.7 for hemoglobin and 44 for phosphate. This suggests that diluted solutions of Hb S aggregate by the nucleation mechanism which is similar to that reported in the gelation of concentrated Hb S solution.

Duffy blood group and hemoglobin variants

Data on a sample of 809 Afro-Americans indicated that there is no association between Duffy null (a-,b-) blood type and sickle cell trait. The results further rule out close linkage as an alternative hypothesis to explain the reported association between these loci in areas where falciparum and vivax malaria are endemic and indicate that, even if the two loci are independent or loosely linked, direct evidence of the selection favoring AS Fy-Fy- individuals must come from populations where mixed malaria infections occur. Stratification, as an explanation for the reported association, is also discussed.

Detection of sickle alpha- or beta0-thalassemia by studies of globin biosynthesis

Globin synthesis studies are useful in the analysis of thalassemia syndromes. We have applied globin synthesis and free alpha-chain pool studies of peripheral blood to characterize hematologic disorders where alpha- or beta-thalassemia was present in combination with HbS or HbC. In 60 non-thalassemic controls, the beta/alpha specific activity ratio was 1.01 +/- 0.06 (SD). In three patients with HbS-beta0-thalassemia, the (betas + gamma)/alpha ratios were 0.48-.067. In four patients with HbSS-alpha-thalassemia, the (BETAS/ALPHA RATIO was 1.26 +/- 0.18 (1.13-1.53). The radioactive free alpha-chain pool in three patients with HbS-beta0-thalassemia was elevated (35.1%-53.0%), while three patients with HbSS-alpha-thalassemia had decreased free radioactive alpha-chain pools (3.2%-6.4%); both were significantly different from the mean (15.1% +/- 2.6%) of the 17 iron-sufficient controls. Simultaneous studies of the fraction of newly synthesized alpha chain contained in the free alpha-chain pool in peripheral blood and bone marrow demonstrated that this fraction was larger in peripheral blood than in marrow, and that the differences between thalassemia patients and controls previously found in bone marrow using these methods were also present in peripheral blood. The results indicate that even when family studies are not possible, patients with HbS in combination with alpha- or beta0-thalassemia can be differentiated from those with homozygous sickle cell disease by globin synthesis and free alpha-chain pool studies using peripheral blood.

Rheological evaluation of hemoglobin S and hemoglobin C hemoglobinopathies

The concept of optimum hematocrit was used to compare the rheology of bloods from patients with various hemoglobin S and hemoglobin C hemoglobinopathies. The technique involved the utilization of cone and plate viscometric data to predict average flow rates under representative physiological-fluid mechanical conditions. The shape of the curve relating optimum hematocrit to oxygen tension, rather than the absolute magnitude of the optimum hematocrit at fixed oxygen tension, is shown to give an indication of clinical severity of the disease.

Properties of the double substituted hemoglobin C Ziguinchor alpha2A beta 2 6 Glu replaced by Val 58 Pro replaced by Arg

We have previously described the structural identification of the sickle hemoglobin variant Hb C Ziguinchor (alpha2A beta2 6 Glu replaced by Val, 58 Pro replaced by Arg). This hemoglobin was found in two generations (three members) of an African family. In two family members, the clinical picture resembled that typical of a sickle cell trait, while the third member showed a more extreme clinical condition due to complication by an iron deficiency anemia. The functional properties of Hb C Zig. in red blood cells or in dilute solutions were identical to those of Hb S. The gelling behaviour of deoxy Hb C Zig. was also indistinguishable from that of Hb S. These findings suggest that, in contrast to the case of Hb C Harlem, the second substitution in position beta58 in Hb C Zig. does not interfere with the intermolecular interactions determined by the sickle substitution.