Determinants of haemoglobin level in sickle cell-haemoglobin C disease

The determinants of steady state haemoglobin levels in sickle cell-haemoglobin C (SC) disease were investigated by measuring routine haematological and biochemical indices, red cell survival, oxygen affinity, pitted erythrocytes, and red cell and plasma volumes in 31 adult patients (15 male; 16 female). Red cell survival was shortened in all subjects, and was positively correlated with haemoglobin level. However, many haemoglobin values were within the normal range, especially in male subjects. Palpable splenomegaly, which occurred in 53 percent of patients, did not appear to effect haemoglobin levels, red cell survival, plasma volume, but was associated with lower platelet counts and decreased pitted red cells. Sex related differences were found in total haemoglobin, packed cell volume, conductivity cell volume, red cell count, and in the blood volume measurements. Red cell, plasma and total blood volumes in patients varied with weight and cube of height in manner observed in normal subjects, although red cell volumes were lower and plasma volumes were greater than in normal subjects of given height and weight. Anaemia in SC disease is related to the haemolytic rate but the major determinant appears to be an inappropriate increase in plasma volume (Summary)

Beta-chain variants in Jamaica newborns

In an electrophoretic study of 15,661 Jamaican cord bloods, 8 rare beta-chain variants were found in 18 subjects in addition to the common beta-chain variants, Hb S and Hb C. The heterozygote frequencies for Hb S and Hb C were 10.1 percent and 3.7 percent respectively. The most frequent of the rare beta-chain variants were Hb Korle Bu (beta 73 Asp leads to Asn) (7 cases) and Hb O su-Christiansborg (beta 52 Asp leads to Asn) (3 cases). One new beta-chain variant, Hb Caribbean (beta 91 Leu leads to Arg) was found. (AU)

Beta-thalassaemia of clinical significance in adult Jamaican negroes

Over a 9-year period, three adult Negro patients with á-thalassaemia of clinical significance were recognized out of approximately 185,000 new adult patients attending the University Hospital. These patients, ages 15-58 years, have clinical and haematological characteristics within the spectrum of á-thalassaemia intermedia; which in this paper refers to phenotypes resulting from defects in á-chain synthesis clinically intermediate between classical Cooley's anaemia and á-thalassaemia trait, genetic classification being dependent on family study. Family studies established the presence of two á-thalassaemia genes conclusively in one case (proposita, family A); presumptively in another(propositus, family C); while in the remaining subject (proposita, famaily B), who has two similarly affected siblings, homozygosity is suspected, but not proven by family study. In simultaneous Fe and Cr studies, estimates of effective erythropoiesis are in reasonable agreement with measurements of red cell destruction.(Summary)

Erythrocyte Hb-S concentration: an important factor in the low oxygen affinity of blood in sickle cell anemia

The blood in sickle cell anemia has a very low oxygen affinity and, although 2,3-diphosphoglycerate (2,3-DPG) is increased, there is doubt as to whether this is the only factor responsible. In this study of 15 patients with sickle cell anemia (Hb SS) no correlation was found between oxygen affinity (P 50 at pH 7.13) and 2,3-DPG in fresh venous blood. Whole populations of Hb SS erythrocytes were therefore separated, by an ultracentrifuge technique, into fractions of varying density. The packed red cell column was divided into three fractions; a bottom fraction rich in deformed cells or irreversibly sickled cells (ISC), with a very high mean corpuscular hemoglobin concentration (MCHC); a middle fraction containing cells but free of deformed cells. Oxygen affinity was shifted to the right in all layers (mean P 50 (pH 7.13)ñ1SD: top 46.3ñ2.9 mm Hg; middle 49.8ñ4.9 mm Hg; bottom 61.0ñ5.8mm Hg) compared with normal blood (top 32.1ñ0.7 mm Hg; bottom 30.1ñ0.5 mm Hg). 2,3-DPG was increased in the top fraction, but was low or normal in the bottom fraction (top 21.8ñ3.4 æmol/g Hb; middle 17.7ñ2.2 æmol/g Hb; bottom 13.8ñ3.1 æmol/g Hb; normal whole blood 14.3ñ1.2 æmol/g Hb). The level of 2,3-DPG in top fractions could not account for the degree of right shift of P 50, and in the middle and bottom fractions the even greater right shifts were associated with lower levels of 2,3-DPG had a higher, but still abnormally low, oxygen affinity. A strong relationship was found between oxygen affinity and MCHc. The fractions with the greatest right shift in P 50 had the highest MCHC (top 32.4ñ2.0; middle 36.2ñ3.1; bottom 44.6ñ3.2 g/100 ml, respectively) and the plot of P 50 vs. MCHC showed a positive corelation (r=0.90,P<0.001). The red cell popualtion in sickle cell anemia is not homogeneous but contains cells of widely varying HB F content, 2,3-DPG, but they also have the highest concentration of Hb S. The dense, deformed cell called the ISC is but the end stage in a process of membrane loss and consequent increase in hemoglobin concentration. The P 50 of Hb SS blood is, to a large extent, determined by the presence of these cells (r=0.85, P<0.001). Increased concentration of Hb S in the cell favors deoxygenation and crystallization even at relatively high Poý. Lowered affinity for oxygen appears to be closely associated with Hb S concentration and not with 2,3-DPG content (AU)

Hemoglobin O Arab in four negro families and its interaction with Hemoglobin S and Hemoglobin C

Hemoglobin O Arab was found in 25 members of four apparently unrelated negro families in the West Indies of Jamaica. In each family the propositus had Hb SO disease. Two cases had been mistakenly diagnosed as Hb SC disease. Two persons heterozygous for both Hb C and Hb O Arab were found in these families, and Hb O Arab áthalassemia in one other relative. The clinical course and symptomatology of Hb SO disease is incomparable to that in Hb SD (O2á2121 Glu-> GluNH2) disease and more severe than Hb S2C2 disease. In vitro mixtures of Hb O Arab and Hb S change from a liquid to a gel phase at total hemoglobin concentrations weaker than those required to gel pure Hb S, whereas mixtures of Hb S with Hb A or Hb C require a stronger total hemoglobin concentration before gelling will occur. Oxygen dissociation studies on red cells containing Hb SO show a lowered oxygen affinity comparable to that found in homozygous sickle-cell anemia and outside the range for subjects with sickle-cell Hb C disease.(AU)

Hemoglobin O Arab in four negro families and its interaction with hemoglobin S and hemoglobin C

Hemoglobin O Arab (O2á2 121 Glu leads to Lys) was found in 25 members of four apparently unrelated Negro families in the West Indian island of Jamaica. In each family the propositus had Hb SO disease. Two cases had been mistakenly diagnosed as Hb SC disease. Two persons heterozygous for both Hb C and Hb O Arab were found in these families, and Hb O Arab á thalassemia in one other relative. The clinical course and symptomatology of Hb SO disease is comparable to that in Hb SD(O2á2 121 Glu leads to GluNH2) disease and more severe than Hb SC disease. In vitro mixtures of Hb O Arab and Hb S change from a liquid to a gel phase at total hemoglobin concentrations weaker than those required to gel pure Hb S, whereas mixtures of Hb C require a stronger total hemoglobin concentration before gelling will occur. Oxygen dissociation studies on red cells containing Hb SO show a homozygous sickle-cell anemia and outside the range for subjects with sickle-cell Hb C disease.(AU)

Sickle cell Hb oarab disease - abstract

An infant presented with megaloblastic anaemia of folate deficiency complicating a haemolytic anaemia with hepatosplenomegaly. At first, the laboratory investigations indicated Hb SC disease but, as it is very unusual to see such severe clinical effects in this haemoglobinopathy, especially in infancy, further investigations were carried out which demonstrated a haemoglobin electrophoretically similar to Hb C but having certain distinguishing characteristics. This Hb was compared with Hb C and Hb E on various electrophoretic media. The tryptic peptide maps (prepared at the Institute for Anthropology, Leiden, Netherlands, by W. de Jong) showed an abnormality in beta Tp XIII and amino acid analysis further revealed that lysine had replaced the normal glutamic acid at the 121st residue in the beta chain. This substitution has been previously described for Hb O Arab. In the helical notation of Perutz this position, in the peptide chain, lies between the G and H helices, GH4. The glutamyl residue is invariant at this site in all human haemoglobin chains. Four mutations have been described at this site. One in the gamma chain, one in the alpha chain and two in the beta chain. The other one in the B chain is Hb D Punjab, and this also causes a more severe type of haemoglobinopathy when inherited together with Hb S. Another infant, presenting in a similar way, was found to have the same defect, Hb S with Hb O Arab. The mother of this second case has Hb O-Thalassaemia. A search was then carried out in patients who had previously been diagnosed as SC disease. Two further cases of Hb SO disease were found, making four families in all. The clinical features of Hb SO disease appear to be more like those of homozygous sickle cell desease than SC disease. There are more sickled cells in the blood, a lower haematocrit and haemoglobin level, a greater shift in oxygen dissociation curve and a shorter red cell survival. Hb O Arab is apparently not uncommon in Jamaica and all cases of suspected Hb SC disease who have a clinical course more like SS disease should be further investigated (AU)

Glucose-6-phosphate dehydrogenase deficiency and methaemoglobin reduction in sickle cell anaemia - abstract only

Red cell glucose-6-phosphate dehydrogenase (G6PD) deficiency is inherited as an X-linked condition with full expression in males and homozygous females, who can be detected by assay of their red cell enzyme activity and by various simple tests. G6PD converts glucose-6-phosphate (GSP) to 6-phosphogluconate (6PG), thereby making hydrogen available for the reduction of the nucleotide nicotine-adenine dinucleotide phosphate (here referred to as TPN) to its reduced form (TPNH), which may be measured by its absorbance at 340 millimicrons. The TPNH formed as a result of G6PD activity is available for the reduction of oxidised glutathione (GSSG) and methaemoglobin and thus protects the red cell from the effects of oxidants and oxidant drugs. In erythrocytes with normal G6PD levels the pathway is strongly stimulated by the presence of small quantities of methylene blue. Brewer's test, which takes advantage of this stimulation, has been widely used to detect G6PD deficiency. It was reported recently from West Africa that there is an association between sickling and G6PD deficiency; Brewer's test indicates that, in that area, some 28 percentof sickle cell traits (Hb AS) and 48 percentof sickle cell anaemias (Hb SS) are deficient, whilst only 14 percentof controls (Hb AA) are deficient. Such an association requires the existence of strong forces of natural selection in favour of the double genetic defect and the workers in West Africa suggest that G6PD-deficient sickle cell anaemia patients have such an advantage. In Jamaica, 13 percentof males are G6PD-deficient and, as sickle cell anaemia is common, it was decided to investigate the incidence of the deficiency in sickle cell patients. Three methods for detecting G6PD deficiency were employed, viz.(1) Sass' method, involving the reduction of methylene blue, (2) the G6PD assay by TPN reduction, (3) the nitrite-free reduction of methaemoglobin in the presence of methylene blue (modified Brewer's test). The deficiency in males and homozygous females was detected by the first two methods. As expected, faster methaemoglobin reduction rates and higher G6PD assay levels were found for sickle cell anaemia blood than for normal blood. With the modified Brewer's test, the initial methaemoglobin reduction rate was found to be independent of the haemoglobin type, but dependent on the G6PD assay levels. The reaction showed approximately zero-order kinetics when sufficient G6PD was present but tended to first-order behaviour when G6PD was low. Blood from some females had methaemoglobin reduction behaviour with a tendency towards first-order kinetics but a rate and G6PD level within the normal range. These are probably heterozygous, with uneven distribution of the enzyme in their red cell. They can be detected with the Sass m ethylene blue test if the dividing line between normal and deficient blood is lowered to allow for the effect of increased G6PD in sickle cell anaemia generally. By these tests, 7 1/2 per cent of males and 12 per cent of females with sickle cell anemia are relatively G6PD deficient, which is a lower incidence than expected and does not support the hypothesis that there is a natural selection of these two mutant genes. (AU)