Unbalanced Globin Chain Synthesis in Erythroid Precursor Cells of Heterozygous αThalassaemia

SUMMARY Globin biosynthesis was studied in both erythroid precursors and reticulocytes of three individuals with heterozygous αthalassaemia. In contrast to the finding of equal or nearly equal α and β chain synthesis in the marrow of patients with heterozygous β-thalassaemia previously examined, our studies showed equal degrees of unbalanced globin synthesis in both reticulocytes and nucleated erythroid cells of αthalassaemia heterozygotes. Greater stability and less susceptibility to proteolysis of the excess β-chain formed in αthalassaemia may explain our findings.     

Alpha Thalassaemia in Sicily: Haematological and Biosynthetic Studies

Eight Sicilian patients with Hb H disease and their families have been studied. The standard haematological tests and the alpha/beta chain synthesis ratios showed significantly different results in the patients with Hb H disease as compared with alpha thalassaemia carriers, except for Hb A2 values. There was no significant difference in the mean RBC, MCV, Hb A2, Hb A1 and Hb F of alpha thalassaemia carriers compared with normal controls. On the contrary significant difference was found between the mean alpha/beta chain synthesis ratio of alpha thalassaemia carriers and that of the normal controls; however, the extensive overlapping of alpha/beta values between these two conditions make this parameter insufficiently discriminant. No correlation was found between MCV, MCH, RBC and alpha/beta chain synthesis ratio in patients with alpha thalassaemia trait, suggesting that the ratio cannot be used to distinguish between carriers of a mild gene ('silent' carrier) and carriers of the more severe alpha thalassaemia gene. A possible genetic model for alpha thalassaemia in Sicily is presented.     

Haematological Aspects of Antenatal Diagnosis for Thalassaemia in Britain

The results are described of 200 antenatal diagnostic tests for haemoglobinopathies performed on samples of fetal blood obtained during the second trimester of pregnancy. Haemoglobin A synthesis in the fetus was measured by incorporation of tritiated leucine in vitro and separation of the globin chains on CM23 columns. The range of HbA synthesis detected was 3.5–8.0% in normal fetuses, 2.0–5.0% in fetuses with thalassaemia trait, and less than 1.6% in fetuses with thalassaemia major. There were eight cases in which other haemoglobinopathies were diagnosed. 29% of the pregnancies were terminated because thalassaemia major was diagnosed, and 9.5% of the remaining healthy fetuses were lost for obstetric reasons. Follow up has been possible for 96% of the 124 surviving babies and three misdiagnoses have come to light; one false positive (0.5%) and two false negatives (1%). These figures represent a first effort at antenatal diagnosis for haemoglobinopathies and it is likely that they will improve with the passage of time.     

The Clinical Features of Sickle-Cell/β Thalassaemia in Jamaica

The clinical and haematological features of 56 Jamaican patients with sickle-cell /β-thalassaemia (S/Thal) are reviewed. The two types of S/Thal (with and without Hb A) had distinctive haematological and clinical characteristics. In general, the non-Hb-A type had evidence of lower haemoglobin levels, a more rapid haemolytic rate, and a more severe clinical course than the Hb-A type.     

The Haematological and Histological Findings in 18 Patients with Clinical Features Resembling those of Myelofibrosis

S ummary . The presentation and haematological abnormalities in 18 patients with splenic and hepatic enlargement and a leukaemoid or leucoerythroblastic blood picture have been reviewed. The clinical features in each case were consistent with a diagnosis of myelofibrosis. Histological examination of the bone marrow showed myeloid proliferation of various types for which no underlying cause was apparent. On the basis of the bone marrow histology, it was possible to divide the 18 patients in this study into two groups.
The first group of four patients presented with a splenomegaly and a marked leucocytosis. Bone marrow aspirate and biopsy specimens showed marked granulocytic proliferation akin to chronic myeloid leukaemia, from which these cases were separated by the findings of a normal or raised leucocyte alkaline phosphatase score. Other distinguishing features these patients had in common were that they were all elderly and their illness appeared to follow a prolonged course, with little need of active treatment.
The second larger group of 14 patients were less uniform. The histological and haematological appearances were variable. Excess bone marrow reticulin was present in each case, and marrow fibrosis was noted in eight. Prominent aggregations of large primitive stem cells were a histological feature in all 14 instances. Correlation between the clinical, haematological and histological features was poor and in particular the marrow aspirate gave little indication of the marrow morphology as found in the bone marrow sections.     

Red Cell Size and the Clinical and Haematological Features of Homozygous Sickle Cell Disease

The contribution of red cell size (mean cell volume) to the clinical and haematological manifestations of homozygous sickle cell (SS) disease has been investigated by comparing the features of two groups of patients with low (less than or equal to 80 fl) and high (greater than 95 fl) MCV values after matching for age, sex and fetal haemoglobin level. The microcytic group manifested significantly higher Hb, PCV, RBC and HbA2 levels and significantly lower reticulocyte and irreversibly sickled-cell counts. Clinical features were not less severe in the microcytic group, splenomegaly persisting for longer and painful crises were more common although the latter difference did not reach significance. The milder haematological picture associated with decreased intravascular sickling was not reflected in a more mild clinical course. It is postulated that the higher viscosity accompanying the higher haemoglobin levels in microcytic patients may offset the rheological advantages of decreased intravascular sickling.     

Globin Biosynthesis in Erythroid Bursts of Heterozygous α or β Thalassaemia

S ummary . We examined globin chain synthesis in erythroid bursts (BFU-E) of patients with heterozygous α or β thalassaemia. BFU-E were cloned from circulating mononuclear cells, labelled with [H]leucine and globin chains purified by gel filtration and column chromatography. In six patients heterozygous for β thalassaemia, globin synthesis in BFU-E was nearly balanced, with an α/non α ratio of 1.05 0α12. These BFU-E produced 33.8 12.7%γ globin chain, an amount similar ( P >1 0.05) to that found in 10 controls with sickle cell anaemia (25.6 6.7) but greater ( P <0.05) than that of five normal controls (17.2 2.2). The balanced globin synthesis appeared due to the large amounts of γ chain made by BFU-E. In two α thalassaemia carriers, who also had sickle cell trait, the BFU-E α/non-α ratio was 0.67 and 0.79. These BFU-E produced 15% and 20%γ chain and 39% and 45%β^S globin. The synthesis of β^S globin in BFU-E exceeded the erythrocyte levels of 20% and 29% HbS and indicated nearly equal expression of β^A and β^B globin genes in these proliferating erythroid precursors. This provides further evidence that the low levels of HbS in sickle cell carriers with α thalassaemia are due to post-translational events resulting from the differing affinity of β^S and β^A globin for α chain and the destruction of excessive β^S chain.     

The Synthesis of Globin Peptide Chains in Sickle-Cell Disease

S ummary . The relative rates of synthesis of the globin chains (α, β^s and γ) have been measured in vitro in the reticulocytes of eight patients homozygous for Hb S. The results indicate that the synthesis of the β^s chain and its association with α chains are normal in the majority of homozygous patients. In two patients an excess synthesis of α chains was detected. The cause for this has not been determined, but it appears to be a transient phenomenon.
The explanation is discussed for the normal synthesis of the β^s globin in home zygotes and the fact that in sickle heterozygotes the specific activities of α- and β-chains have usually been unity, i.e. that they are being produced at the same rate as they appear in the peripheral blood is discussed.     

Lymphoid Cell Sets and Serum Immunoglobulins in Patients with Thalassaemia Intermedia: Relationship to Serum Iron and Splenectomy

S ummary Peripheral blood lymphocyte sets and serum immunoglobulins were examined in 15 patients with thalassaemia intermedia, aged between 5 and 30 years. They were divided in three clinical groups: Group I, non-splenectomized, with serum iron (SI) lower than 200 μg/dl; Group II, splenectomized with serum iron lower than 200 μg/dl; and Group III, splenectomized with serum iron levels greater than 200 μg/dl. High absolute lymphocyte counts were observed in the majority of patients, whether splenectomized or not. Following splenectomy, marked increases were observed in absolute number of lymphocytes and percentages of circulating surface immunoglobulin (SIg) bearing B lymphocytes, mouse rosette forming cells (MRFC) and 'null' cells. The increases in circulating B lymphocytes following splenectomy were due exclusively to cells bearing SIgM and/or SIgD. No changes were observed in numbers and proportions of circulating SIgA or SIgG bearing cells. Serum IgA levels were high in the majority of patients studied whether splenectomized or not. Following splenectomy increases in serum IgA and serum IgG were observed which seemed to relate to increasing SI levels. No significant changes occurred in serum IgM levels.
Absolute numbers of circulating T lymphocytes were unaffected by splenectomy or SI levels. Changes were observed, however, in distribution of T lymphocyte subsets with decreases in number of Tμ cells and concomitant increases in numbers of non-Tμ, non-Tγ cells. Tγ cells were the least affected by splenectomy and increasing SI. The results are compatible with the proposition that iron participates in the regulation of lymphoid cell migration and in the modulation of expression of cell surface markers. The findings also illustrate the role of the spleen in the control of lymphocyte migration and immunoglobulin production.     

Globin Synthesis in the Jamaican Negro with Beta-Thalassaemia

S ummary . Globin synthesis was studied in three Jamaican Negro families with 18 heterozygotes and five homozygotes for β-thalassaemia. Synthesis of the β-chain of Hb A in the peripheral blood of heterozygotes was equal to that of α-chain in 10 patients and was decreased in the remainder. In one patient with Hb C β-thalassaemia, the β/α ratio was normal. These findings were similar to those in American Negroes, but differed from those in Caucasians with β-thalassaemia trait, in each of whom the β/α ratio was decreased. Globin synthesis was balanced in the bone marrows of Negro and Caucasian heterozygotes. Despite the milder clinical disease in Negro homozygotes as compared to Caucasian patients, the β/α synthesis ratios were similar in both groups.
The presence of α-thalassaemia combined with β-thalassaemia in Negro heterezygotes is not a likely explanation for the high incidence of balanced globin synthesis ratios. The expression of relative β- to α-chain synthesis in Negro heterozygotes appears to be modified by a factor which is not linked to the δ-chain locus. The nature of this factor is not known at present.     

急性白血病珠蛋白链合成速率比分析

本文应用￣３Ｈ－亮氨酸体外掺入示踪，Ｐｅｒｃｏｌｌ梯度离心富集网织红细胞和聚丙稀酰胺凝胶电泳微量分析等技术，分别对１０例正常人，１４例ＡＮＬＬ及９例ＡＬＬ患者网织红细胞中α／β珠蛋白链合成速率比进行检测及分析，同时测定了ＨｂＦ和ＨｂＡ＿２以及血红蛋白电泳。１０例正常人α／β合成比为１．０４±０．０８，１４例ＡＮＬＬ为１．５５±０．５（Ｐ＜０．００１），９例ＡＬＬ为０．７６±０．１３（Ｐ＜０．００１）。本文对不同类型急性白血病珠蛋白基因表达调控异常的规律作了初步的分析，并对可能的机制进行了讨论。     

The Haematological Effects of Glucose-6-Phosphate Dehydrogenase Deficiency and Thalassaemia Trait: Interaction between the Two Genes at the Phenotype Level

The haematological effects of glucose-6-phosphate dehydrogenase (G6PD) deficiency and thalassaemia trait were evaluated in a field study of 317 individuals in an isolated Sardinian village, where both traits were present at high frequency. G6PD deficiency was diagnosed with rigid genetic criteria. Thalassaemia trait was diagnosed on the basis of abnormal osmotic fragility.
Complete G6PD deficiency resulted in mild anaemia with macrocytosis, a consequence of mild chronic haemolysis. Partial G6PD deficiency had a similar, but less marked effect. Thalassaemia trait resulted in mild anaemia, with marked microcytosis and moderate hypochromia.
The haematological effects of the combination of both traits were equal to the sum of the independent effect of each. The G6PD activity of the individual red cells was similar in thalassaemic and normal individuals. Because of the microcytosis, the G6PD activity per gram of haemoglobin per unit volume of red cells or of whole blood appeared to be elevated in thalassaemia trait.     

Comparison of Haematological Features of the β0 and β+ Thalassaemia Traits in Jamaican Negroes

Haematological characteristics have been compared in 29 subjects with heterozygous β⁰ thalassaemia and in 33 subjects with heterozygous β⁺ thalassaemia, identified by the type of sickle cell-β thalassaemia among close relatives, in a Jamaican Negro population. Total haemoglobin, MCV and MCH were significantly lower in the β⁰ type but the level of Hb A₂ was not significantly different. Individual values for MCV, MCH and Hb A₂ in the β⁺ type occasionally overlapped those in the normal population casting doubt on the adequacy of these criteria in identifying all cases of heterozygous β⁺ thalassaemia. The haematological differences are those which would be expected on theoretical grounds. The inability to confidently differentiate the two types of heterozygous β thalassaemia has implications for genetic counselling. The inability to distinguish heterozygous β⁺ thalassaemia from normals on any single haematological index suggests that surveys depending on estimations of Hb A₂ or on MCV alone may have underestimated the prevalence of the β⁺ thalassaemia gene.     

Determining the Risk Factors and Clinical Features Associated With Severe Gastrointestinal Dysmotility in Systemic Sclerosis

Objective

A subset of patients with systemic sclerosis (SSc) develop severe gastrointestinal (GI) dysmotility. We sought to determine predictors of severe SSc GI dysmotility and to identify distinct features associated with this phenotype.

Methods

Patients with SSc who required supplemental nutrition (enteral or parenteral tube feeding) were compared to SSc patients with mild GI symptoms in a cross‐sectional analysis. The association between severe GI dysmotility and clinical and serologic features was examined using logistic regression. Baseline data were examined to determine predictors of developing severe GI dysfunction using Cox regression.

Results

SSc patients with severe GI dysmotility (n = 66) were more likely than those patients with mild GI symptoms (n = 1,736) to be male (odds ratio [OR] 2.47 [95% confidence interval (95% CI) 1.34–4.56]; P = 0.004), and to have myopathy (OR 5.53 [95% CI 2.82–10.82]; P < 0.001), and sicca symptoms (OR 2.40 [95% CI 1.30–4.42]; P = 0.005), even after adjustment for potential confounders. Baseline features that were associated with the future development of severe GI dysfunction included male sex (hazard ratio [HR] 2.99 [95% CI 1.53–5.84]; P = 0.001) and myopathy (HR 5.08 [95% CI 2.21–11.67]; P < 0.001).

Conclusion

Distinct clinical features are present in SSc patients who are at risk of developing severe GI dysmotility. This finding is not only important clinically but also suggests that a unique pathologic process is at work in these patients.

     

A Genetically Determined Disorder with Features both of Thalassaemia and Congenital Dyserythropoietic Anaemia

S ummary . What appears to be a hitherto unreported type of congenital anaemia has been found in six members of an Irish family. It is inherited in an autosomal dominant manner and is characterized by moderate anaemia, lifelong jaundice, cholelithiasis and splenomegaly, marked morphological abnormalities of the red cells (which are, however, well haemoglobinized), erythroid hyperplasia of the bone marrow with increased numbers of multinucleate red cell precursors, and the presence of large inclusion bodies in the normoblasts, both in the marrow, and in the peripheral blood after splenectomy. Potassium flux across the red cell membranes is increased and there is imbalanced globin chain synthesis with α-chain production exceeding that of β-chains by a factor of 2/1. Excess α-chains in the bone marrow form a pool of similar magnitude to that observed in β-thalassaemia heterozygotcs but the latter do not have red cell precursor inclusion bodies or the degree of ineffective erythropoiesis seen in the present cases. The most likely molecular mechanisms for this disorder are either an 'overproduction abnormality' of α-chain synthesis, or a defect in cell division leading to increased amounts of genetic material per cell, a mechanism postulated recently as a basis for the unusual distribution of red cell enzyme levels in congenital dyserythropoietic anaemia.     

Variations in Globin Chain Synthesis in Hereditary Persistence of Fetal Haemoglobin

Globin synthesis was studied in four Negro families including 10 members with Hb A-HPFH and four with Hb S-HPFH. The beta/alpha specific activity ratios in 10 of these HPFH heterozygotes were similar to those of the control group. In two patients with Hb A-HPFH, the beta/alpha ratio was slightly decreased in one (0.84) and clearly decreased in another (0.78). In two of the patients with Hb S-HPFH the ratios were clearly decreased (0.71 and 0.75). The extended range of beta/alpha ratios in these 14 patients is similar to that of Negro patients with beta-thalassaemia trait. These studies indicate that a decreased beta/alpha ratio may be found in HPFH, as well as in beta-thalassaemia. Bone marrow globin synthesis was measured in two patients with Hb S-HPFH and decreased peripheral blood beta/alpha ratios, and in one with Hb A-HPFH and a normal peripheral blood beta/alpha ratio. In each patient the (beta+gamma)/alpha ratio of radioactivities as well as the beta/alpha specific activity ratio was close to 1 and therefore balanced, indicating more rapid decay of beta-chain synthesis relative to alpha-chain during red cell maturation or extremely rapid destruction of newly synthesized excess alpha-chains in the bone marrow.