The role of rib infarcts in the acute chest syndrome of sickle cell diseases

The acute chest syndrome is a generic term for pulmonary complications of sickle cell diseases with heterogeneous etiologies that include pneumonia, vaso-occlusion of pulmonary arterioles, rib infarction, and fat embolism syndrome. My review summarizes these etiologies, the evidence, and pathophysiology supporting the hypothesis that infarction of segments of ribs by the same vaso-occlusive process responsible for the acute episodes of pain (characteristic of the sickle cell diseases) is often involved in the acute chest structure. Inflammation associated with the infarct then causes splinting, hypoventilation, and hypoxia and further vaso-occlusion. The relationship with adult respiratory distress syndrome and fat embolism is also discussed. Use of the incentive spirometer combined with effective analgesia when chest pain is present is advocated for prevention of the pulmonary infiltrates. Newer understanding of the role of nitric oxide in regulating oxygen transport and its relationship to blood transfusions used in therapy of the acute chest syndrome are discussed.

The survival characteristics of dense sickle cells

Sickle red blood cells (RBCs) become depleted of potassium, leading to dehydration and abnormally elevated cellular density. The increased sickling that results is important for both hemolysis and vasocclusion. In this study, sickle cells were subjected to high-speed centrifugation, and the bottom 15% were isolated. This procedure removed light cells and to a variable degree enriched cells that were denser than normal to produce a high-density-enriched (HDE) population of sickle cells. Autologous HDE cells from 3 subjects were labeled with biotin and re-infused. The following determinations were performed: (1) the survival and density changes of HDE cells; (2) the amount of fetal hemoglobin (HbF) in labeled cells after magnetic isolation; (3) the percentage of labeled F cells; (4) the percentage of labeled cells displaying external phosphatidylserine (PS). For patients with 3.5%, 4.5%, and 24% HbF in the HDE RBCs, the circulation half-time was 40, 80, and 180 hours, respectively. The percentage of HbF (measured in all 3 subjects) and of F cells (measured in 2 subjects) in labeled RBCs increased with time after re-infusion, indicating that HDE F cells have longer in vivo survival than HDE non-F cells. The percentage of PS(+), biotin-labeled HDE cells showed no consistent increase or decrease with time after re-infusion. These data provide evidence that HDE sickle cells, especially those that do not contain HbF, have a very short in vivo survival, and that the percentage of PS(+) cells in a re-infused HDE population does not change in a consistent manner as these cells age in the circulation.

Time-dependent changes in the density and hemoglobin F content of biotin-labeled sickle cells

Sickle red blood cells (RBC) are subject to a number of important cellular changes and selection pressures. In this study, we validated a biotin RBC label by comparison to the standard 51Cr label, and used it to study changes that occur in sickle cells as they age. Sickle RBC had a much shorter lifespan than normal RBC, but the two labels gave equivalent results for each cell type. A variable number of sickle, but not normal, RBC disappeared from the circulation during the first few hours after reinfusion. The number of biotinylated sickle reticulocytes was decreased by 50% after 24 h and 75% after 48 h, with a gradual decrease in the amount of reticulum per cell. The labeled sickle cells exhibited major density increases during the first 4-6 d after reinfusion, with smaller changes thereafter. A small population of very light, labeled sickle RBC was essentially constant in number after the first few days. Fetal hemoglobin (HbF) content was determined in isolated biotinylated sickle RBC after reinfusion, allowing an estimate of lifespan for RBC containing HbF (F cells) and non-F cells. The lifespan of sickle biotinylated RBC lacking HbF was estimated to be approximately 2 wk, whereas F cells survived 6-8 wk.

Dehydration of transferrin receptor-positive sickle reticulocytes during continuous or cyclic deoxygenation: role of KCl cotransport and extracellular calcium

The K+ efflux that mediates sickle-cell dehydration may occur through several pathways, including two with a high capacity for mediating rapid K+ loss, KCl cotransport and the Ca(2+)-dependent K+ channel [K(Ca2+)]. The rate and pathway of red blood cell (RBC) dehydration most likely depends on cell age and hemoglobin (Hb) composition, with the presence of HbF playing an important role. Oxygenated sickle RBCs have relatively stable cell volume during incubation in vitro, whereas deoxygenated cells become dehydrated, and therefore more dense, due to activation of one or more K+ efflux pathways. In this investigation, sickle RBCs were deoxygenated either continuously or in 15-minute cycles for 4 hours, and the density increases of very young, transferrin receptor-positive (TfR+) cells and the remaining TfR- cells were determined. The contribution of KCl cotransport was estimated by replacing Cl- with NO3-. K(Ca2+) was inhibited by removal of Ca2+ or addition of charybdotoxin (ChTX). For both continuous and cyclic deoxygenation, TfR+ cells had a greater density increase when compared with TfR- cells. The lower percentage of HbF found in the TfR+ population may contribute to this difference. With continuous deoxygenation, the density shift was decreased by inhibition of K(Ca2+), but not by inhibition of KCl cotransport. With cyclic deoxygenation, the density shift was decreased in an independent, additive manner by inhibition of both pathways. Thus, cyclic deoxygenation of sickle cells under these conditions appears to activate both K(Ca2+) and the KCl cotransporter.

Incentive spirometry to prevent acute pulmonary complications in sickle cell diseases

BACKGROUND

This study was designed to determine the incidence of thoracic bone infarction in patients with sickle cell diseases who were hospitalized with acute chest or back pain above the diaphragm and to test the hypothesis that incentive spirometry can decrease the incidence of atelectasis and pulmonary infiltrates.

METHODS

We conducted a prospective, randomized trial in 29 patients between 8 and 21 years of age with sickle cell diseases who had 38 episodes of acute chest or back pain above the diaphragm and were hospitalized. Each episode of pain was considered to be an independent event. At each hospitalization, patients with normal or unchanged chest radiographs on admission were randomly assigned to treatment with spirometry or to a control nonspirometry group. Each patient in the spirometry group took 10 maximal inspirations using an incentive spirometer every two hours between 8 a.m. and 10 p.m. and while awake during the night until the chest pain subsided. A second radiograph was obtained three or more days after admission, or sooner if clinically necessary, to determine the incidence of pulmonary complications. Bone scanning was performed no sooner than two days after hospital admission to determine the incidence of thoracic bone infarction.

RESULTS

The incidence of thoracic bone infarction was 39.5 percent (15 of 38 hospitalizations). Pulmonary complications (atelectasis or infiltrates) developed during only 1 of 19 hospitalizations of patients assigned to the spirometry group, as compared with 8 of 19 hospitalizations of patients in the nonspirometry group (P = 0.019). Among patients with thoracic bone infarction, no pulmonary complications developed in those assigned to the spirometry group during a total of seven hospitalizations, whereas they developed during five of eight hospitalizations in the nonspirometry group (P = 0.025).

CONCLUSIONS

Thoracic bone infarction is common in patients with sickle cell diseases who are hospitalized with acute chest pain. Incentive spirometry can prevent the pulmonary complications (atelectasis and infiltrates) associated with the acute chest syndrome in patients with sickle cell diseases who are hospitalized with chest or back pain above the diaphragm.

Hemoglobin F-Cincinnati, alpha 2G gamma 2 41(C7) Phe-->Ser in a newborn with cyanosis

A term infant presented with mild cyanosis without evidence of hypoxia. Cardiopulmonary disease, polycythemia, and methemoglobinemia were excluded. Standard hemoglobin electrophoresis, including isoelectric focusing, were normal. However, by reverse-phase C4 HPLC, an abnormal globin chain was detected. Analysis of tryptic peptides and amino acid sequence showed that the patient had an amino acid substitution Phe-->Ser at residue 41(C7) in the G gamma chain. This was confirmed by DNA sequencing that demonstrated a point mutation at the expected site in exon 2 of the G gamma gene, accounting for the appropriate change in the codon. This substitution, hemoglobin F-Cincinnati, alpha 2 gamma 2 41(C7) Phe-->Ser, not previously described, presumably decreased oxygen affinity of the hemoglobin. This substitution is very near the heme group and the alpha 1 beta 2 interface and, hence, in a crucial area of the globin chain. Abnormalities of gamma globin chains tend to be overlooked due to their transient presence and trivial clinical symptomatology, or due to "in utero" selection when physiologically abnormal. Mutant hemoglobins with altered oxygen affinity should be included in the differential diagnosis of newborns presenting with cyanosis, in whom all common causes have been excluded.

X-linked sideroblastic anemia: identification of the mutation in the erythroid-specific delta-aminolevulinate synthase gene (ALAS2) in the original family described by Cooley

In 1945, Thomas Cooley described the first cases of X-linked sideroblastic anemia (XLSA) in two brothers from a large family in which the inheritance of the disease was documented through six generations. Almost 40 years later the enzymatic defect in XLSA was identified as the deficient activity of the erythroid-specific form of delta-aminolevulinate synthase (ALAS2), the first enzyme in the heme biosynthetic pathway. To determine the nature of the mutation in the ALAS2 gene causing XLSA in Cooley's original family, genomic DNAs were isolated from two affected hemizygotes, and each ALAS2 exon was PCR amplified and sequenced. A single transversion (A to C) was identified in exon 5. The mutation predicted the substitution of leucine for phenylalanine at residue 165 (F165L) in the first highly conserved domain of the ALAS2 catalytic core shared by all species. No other nucleotide changes were found by sequencing each of the 11 exons, including intron/exon boundaries, 1 kb of 5'-flanking and 350 nucleotides of 3'-flanking sequence. The mutation introduced an Mse I site and restriction analysis of PCR-amplified genomic DNA confirmed the presence of the lesion in the two affected brothers and in three obligate heterozygotes from three generations of this family. Carrier diagnosis of additional family members identified the mutation in one of the proband's sisters. After prokaryotic expression and affinity purification of both mutant and normal ALAS2 fusion proteins, the specific activity of the F165L mutant enzyme was about 26% of normal. The cofactor, pyridoxal 5'-phosphate, activated and/or stabilized the purified mutant recombinant enzyme in vitro, consistent with the pyridoxine-responsive anemia in affected hemizygotes from this family.

Fetal hemoglobin and potassium in isolated transferrin receptor-positive dense sickle reticulocytes

A subset of sickle cells have an increased density at the reticulocyte stage of development, indicating that they are either abnormally dense upon release from the bone marrow or become dense quickly in the circulation. These cells are of interest because they most likely have severely disrupted cation regulation and a short lifespan. Based on the distribution of fetal hemoglobin (HbF) in the density fractions of sickle red blood cells (RBCs) and in vitro studies of cellular K+ loss, it seems likely that HbF content is an important in vivo determinant of dense cell formation. In this study, we tested the hypothesis that young, dense cells have low HbF content. Sickle RBCs were first separated into light and dense fractions. Reticulocytes were isolated from unfractionated cells and from each density fraction with an immunomagnetic technique directed against transferrin receptors (TfR) and assayed for the percentage of HbF and K+/Hb ratio. TfR+ reticulocytes isolated from unfractionated cells had a much lower HbF content when compared with all the unfractionated RBCs. This is most likely caused by enrichment of F cells because of a longer circulation life span. Heavy TfR+ reticulocytes had a K+/Hb ratio similar to that measured in the entire dense population and contained very low levels of HbF, averaging 2.5% of the level in all RBCs, 11.7% of the level in all TfR+ reticulocytes, and 4.0% of the level in all dense RBCs. These findings suggest that TfR+ dense cells derive predominantly from non-F cells. Furthermore, the amount of HbF in the circulating dense cells suggests that many of these cells do not derive from the TfR+ dense cells.

Fat embolism syndrome associated with asthma and sickle cell-beta(+)-thalassemia

A 25-year-old African-American man with sickle cell-beta(+)-thalassemia presented with acute asthma of 2 days' duration. The asthma was well controlled by 48 hr, and parenteral medications were changed to oral bronchodilators and steroids. Sixty hours after presentation, he developed pain similar to that of sickle cell vaso-occlusion, for which he received small amounts of analgesics. He died approximately 84 hours after presentation. Autopsy showed extensive marrow necrosis and massive fat embolism. This is the first reported case of fat embolism syndrome associated with this genotype, the mildest of the clinically significant sickle cell hemoglobinopathies. The relationship between these etiologic factors and indications for transfusions are discussed.

Deoxygenation-induced changes in sickle cell-sickle cell adhesion

The tendency for sickle cells to adhere to each other is increased in oxygenated sickle blood in parallel with cell density. The increased adherence of these cells occurred despite their reduced deformability and diminished ability to form rouleaux. Using a method developed in our laboratory, we measured the yield stress: a sensitive index of cell-cell adhesion of deoxygenated suspensions of sickle cells. Deoxygenation of whole sickle blood to 30 to 50 mm Hg caused a significant increase in yield stress of all sickle blood samples. Deoxygenation caused a significant increase in yield stress of both dense and light sickle cells. Deoxygenation-induced increases in yield stress occurred at higher oxygen tensions for dense (> 55 mm Hg) than for light sickle cells (< 45 mm Hg). The increase in yield stress on deoxygenation was correlated with hemoglobin polymerization as assessed morphologically by sickling or by changes in relative viscosity. Thus, deoxygenation-induced cell sticking must involve small areas of strong membrane adhesion because the changes in yield stress occurred despite a reduction in rouleaux formation and surface area of membrane contact. Sickle trait red blood cells also exhibited increased yield stress on deoxygenation but only under hypertonic conditions where sickling occurred. Thus, deoxygenation-induced cell adhesion did not require prior membrane damage because it occurred in sickle trait cells. No change in yield stress was seen when deoxygenated sickle cells were suspended in buffer, but the addition of physiologic amounts of fibrinogen to buffer restored the deoxygenation-induced increase in cell adhesion. We speculate that the increase in sticking among sickle cells on deoxygenation results from spicule formation and may involve interaction of fibrinogen and possibly other plasma proteins with the cell membrane.

Simultaneous occurrence of rib infarction and pulmonary infiltrates in sickle cell disease patients with acute chest syndrome

In order to determine if a relationship exists between rib infarction and the acute chest syndrome (ACS) in sickle cell disease patients, bone scans were reviewed in 55 episodes in 38 patients with pain of suspected osseous origin. A bone scan was positive for thoracic bone infarction if abnormally increased or decreased uptake was present in ribs, sternum or thoracic spine. Radiographs were considered to be positive for ACS if there was pulmonary infiltrate or pleural effusion in the absence of laboratory or clinical evidence of bacterial pneumonia. ACS by chest x-ray was present in 22 episodes, 21 of which showed evidence of infarction of the bony thorax on bone scan. Thoracic bone infarction occurred in the absence of chest x-ray changes in only 11 episodes. This association between bone infarction and radiographic ACS was statistically significant (p < 0.001, Fisher's exact test). A strong association exists between ACS and infarction of the bony thorax. It is possible that bone infarction leads to pain, hypoventilation and the clinical picture of ACS.

Mutagenic dissection of hemoglobin cooperativity: effects of amino acid alteration on subunit assembly of oxy and deoxy tetramers

Free energies of oxygen-linked subunit assembly and cooperative interaction have been determined for 34 molecular species of human hemoglobin, which differ by amino acid alterations as a result of mutation or chemical modification at specific sites. These studies required the development of extensions to our earlier methodology. In combination with previous results they comprise a data base of 60 hemoglobin species, characterized under the same conditions. The data base was analyzed in terms of the five following issues. (1) Range and sensitivity to site modifications. Deoxy tetramers showed greater average energetic response to structural modifications than the oxy species, but the ranges are similar for the two ligation forms. (2) Structural localization of cooperative free energy. Difference free energies of dimer-tetramer assembly (oxy minus deoxy) yielded delta Gc for each hemoglobin, i.e., the free energy used for modulation of oxygen affinity over all four binding steps. A structure-energy map constructed from these results shows that the alpha 1 beta 2 interface is a unique structural location of the noncovalent bonding interactions that are energetically coupled to cooperativity. (3) Relationship of cooperativity to intrinsic binding. Oxygen binding energetics for dissociated dimers of mutants strongly indicates that cooperativity and intrinsic binding are completely decoupled by tetramer to dimer dissociation. (4) Additivity, site-site coupling and adventitious perturbations. All these are exhibited by individual-site modifications of this study. Large nonadditivity may be correlated with global (quaternary) structure change. (5) Residue position vs. chemical nature. Functional response is solely dictated by structural location for a subset of the sites, but varies with side-chain type at other sites. The current data base provides a unique framework for further analyses and modeling of fundamental issues in the structural chemistry of proteins and allosteric mechanisms.

Influence of plasma and red cell factors on the rheologic properties of oxygenated sickle blood during clinical steady state

Yield stress is a sensitive index of blood fluidity at low shear stress. Using a method that measured the stress required to cause motion of a thin sedimenting layer of red cells, we found significant elevations of yield stress in patients with homozygous sickle cell anemia during clinical steady state. Mixing studies of sickle cells in normal plasma and buffered saline and of normal red cells in sickle plasma showed (1) that the increased yield stress of sickle blood was not due to differences between sickle and normal plasma factors and (2) that yield stress of sickle cells was not increased in the absence of plasma proteins. Multivariate regression analysis was performed to determine the dependence of sickle blood yield stress on several red cell and plasma factors. The yield stress measurements were normalized for differences in plasma fibrinogen concentration. Other factors studied included cell density, fetal hemoglobin concentration, alpha globin genotype, cell deformability as measured by high shear viscosity, and fibronectin and von Willebrand factor concentrations. Cell density was the primary determinant of yield stress. Measurements of yield stress on density fractionated sickle cells confirmed that the increased yield stress of sickle blood was due to the dense sickle erythrocyte. We conclude that the increased yield stress of sickle blood during clinical steady state was due to an abnormal interaction between the dense sickle cell membrane and plasma protein(s).

Rib infarcts and acute chest syndrome in sickle cell diseases

In the absence of evidence for pneumonia or pulmonary embolus, primary pulmonary infarction has been assumed to be the cause of the syndrome of chest pain, fever, and pulmonary infiltrate on chest X-ray that commonly complicates sickle cell anaemia. To find out whether the syndrome might be due to rib infarction, 99mTc-diphosphonate bone scans were done. In the eleven episodes thus investigated (10 patients) the scans showed segmental areas of increased radionuclide uptake in ribs, indicative of bone infarction. A possible sequence of events is that the rib infarcts are primary and cause bone pain, followed by soft tissue reaction, pleuritis, and splinting. The resultant hypoventilation leads to atelectasis and subsequent development of the radiographic changes of the acute chest syndrome. Prevention of hypoventilation and treatment of bone pain are important therapeutic goals.

Hb Port Huron [alpha 56 (E5)Lys----ARG]: a new alpha chain variant

We have determined the structural abnormality of a putative Hb E detected in an African-American family with no apparent Asian ancestry. The tryptic peptide map performed by high performance liquid chromatography showed that the electrophoretic variant was indeed Hb E [beta 26 (B8)Glu----Lys]. In addition, the tryptic map showed an abnormal peptide adjacent to the alpha T-6 peptide. The amino acid analysis and confirmatory restriction analysis of the DNA showed that a second mutation was also present, characterized by a substitution of arginine for lysine at residue 56 of the alpha chain. The variant is clinically silent and has been named Hb Port Huron for the city in Michigan where the family resides.

Evaluation of the yield stress of normal blood as a function of fibrinogen concentration and hematocrit

The yield stress is a sensitive index of blood fluidity at low shear. Seven healthy adults were studied at hematocrits varying between 40 and 80% and fibrinogen concentrations from 0.0 to 0.935 g/dl. Multivariable analysis was used to determine the functional dependence of yield stress on hematocrit and fibrinogen level. The major findings from this analysis include a decreasing effect of fibrinogen at high concentrations (saturation effect), a relative insensitivity of yield stress to fibrinogen at low concentration (threshold effect), and a strong interaction between the effects of hematocrit and fibrinogen concentration on yield stress. Our results give the normal range of yield stress for a given value of fibrinogen and hematocrit and can be used to predict the effect of reductions in hematocrit or fibrinogen on the yield stress of normal blood.

The relationship between fetal hemoglobin and disease severity in children with sickle cell anemia

A study was conducted in a sample of 140 children with sickle cell anemia to evaluate the relationship between hematological variables (%HbF, %HbA2, %Hb, and mean cell volume) and disease severity. A patient's severity status was determined by whether he/she was hospitalized, had a transfusion, and/or had a pain crisis at 2 evaluation periods; the first was based on a patient's history taken at the initial assessment visit to the Wayne State Comprehensive Sickle Cell Center, and the second was based on a 1-3 year follow-up at the center. Fetal hemoglobin was a strong predictor of a patient's hospitalization and transfusion status. A decrease in %HbF of 4.76% (one SD of %HbF) was associated with a 3.58 fold (95% confidence interval, 1.18-7.28) greater odds of being hospitalized both prior to initial assessment and on follow-up, compared to not being hospitalized at either evaluation. Similarly, a decrease in %HbF of 4.76% was associated with a 5.56 fold (95% confidence interval, 1.67-18.96) greater odds of having a transfusion both prior to initial assessment and on follow-up compared to not having a transfusion at either evaluation. Patients who were both hospitalized and transfused at initial assessment and on follow-up (n = 12) had a mean %HbF of 7.59%, while patients who were not hospitalized or transfused at either evaluation (n = 19) had a mean %HbF of 13.61%. Fetal hemoglobin was not a significant predictor of pain crises in this sample of patients. None of the other hematological variables were significant predictors of disease severity in this study. The strong relationship between %HbF and disease severity identified in this study suggests that a single %HbF measurement may be useful in predicting important aspects of the clinical course of children with sickle cell anemia.

Evaluation of glycosylated hemoglobin in the management of young patients with insulin-dependent diabetes mellitus

Serial glycosylated hemoglobin (HbA1) concentrations were measured in 146 children and young adults with insulin-dependent diabetes mellitus. Patients were randomly divided into two groups. The HbA1 results were made available to the physicians and patients of group A but they were withheld from group B for 12-16 months. The groups were then alternated for an equal time period, with group A being blinded and group B unblinded. When the patients were further subdivided into those with initial HbA1 levels above or below the group mean (12.7%), it was found that the metabolic control of subjects with high HbA1 concentrations tended to improve when the values were made available and to remain unchanged when the results were withheld. Knowledge of HbA1 concentrations by physician and patient/parent appears to be beneficial in patients with relatively poor control. In contrast, no improvement was noted in patients with initial HbA1 less than 12.7% whether or not the results were available to the physician and patient/parent.

Density ultracentrifugation of sickle cells during and after pain crisis: increased dense echinocytes in crisis

An increase in the number of irreversibly sickled cells (ISCs) in pain crisis has been found by some investigators but not others. We have used the technique of discontinuous arabinogalactan density-gradient ultracentrifugation of whole blood to study ISCs from patients with sickle cell anemia (SCA) during pain crisis and again when pain free (5-331 days after crisis). Nine patients have been studied through ten episodes of pain crisis. Five layers with densities from 1.128 g/mL to 1.158 g/mL have been used. Careful classification of the cells using Nomarsky optics demonstrated highly significant changes occurring in the layers of the gradient. The changes involve the appearance of an increased percentage of echinocytic ISCs and echinocytic cells that were not ISCs, especially in the denser gradient layers, during crisis, and their replacement by normal-appearing discocytes in the pain-free state. There was no change in ISCs that were not echinocytic. Data collected previously demonstrated that reduced glutathione activity correlated with increased echinocytosis in our gradient layers. This indicates that the echinocytic change may occur as a result of oxidant stress. Hemoglobin F levels and the percentage of hemoglobin F from reticulocytes showed no consistent change to coincide with the rise in normal-appearing discocytes in the lightest layers after crisis. Our data indicate that pain crisis occurs in association with an echinocytic change, which may be induced by oxidant injury. The rise in normal-appearing cells after crisis may reflect increased hemoglobin F production in some patients but mainly relates to the disappearance of these echinocytic erythrocytes.

Highly sensitive and rapid gene mapping using miniaturized blot hybridization: application to prenatal diagnosis

We have developed a protocol for the preparation and analysis of amniocyte DNA which permits more sensitive and more rapid antenatal detection of sickle-cell anemia (SCA) than previously has been possible. After rapid extraction of DNA from amniotic cells, only 50 ng of MstII-digested DNA need be analyzed by mini-gel electrophoresis and hybridization detection to determine reliably the fetal genotype. Under these conditions, the entire gene-mapping procedure can be performed within 5 days. When larger amounts of DNA (greater than 500 ng) are analyzed, the minimal diagnosis time is reduced to 2 days. The resolution of restriction fragments on mini-gels is comparable to that obtained with larger gels. The 1.15-kb betaA and 1.35-kb betaS MstII fragments are well separated. The technique is useful whenever rapid and sensitive analysis of genomic DNA is desired.

The occurrence of the alpha G-Philadelphia-globin allele on a double-locus chromosome

Hb G-Philadelphia, an alpha-globin allele, is expressed as either 20%, 30%, or 40% of the total hemoglobin. Restriction analyses published thus far have shown that among persons with 30% and 40% hemoglobin (Hb) G the alpha G allele is seen only in a single-locus haplotype. We now report the identification of a second haplotype in which the alpha G allele is found in tandem with an alpha A allele. This haplotype has been found present in DNA from the members of one family in which Hb G is expressed as 20% of the total hemoglobin, determined by both cellulose acetate electrophoresis and high-performance liquid chromatography (HPLC). Synthesis was balanced in all individuals. The identification of a variant alpha-globin allele in two distinct haplotypes presents the possibility of independent mutation. However, an alternative explanation cannot be ruled out; namely, that the original allele may have become distributed among the two haplotypes by unequal crossing-over.

Heterogeneity of sickle-cell anemia based on a profile of hematological variables

Factors that influence the heterogeneity of the disease expression of sickle-cell anemia are not well understood. This study examines the ability of a profile of six hematological variables (HB, HCT, RBC, %Hb F, MCV, and %HBA2) to predict the severity of disease measured on 225 patients ranging from 0.2 to 18 years of age. Four subgroups of patients were identified separately in each sex using cluster analysis techniques. In each sex, mean hemoglobin concentration and percent Hb F increased across the four clusters from 7 to 10 gm/dl and from 7% to 16%, respectively. Mean cell volumes were approximately 90, 80, 90, and 75 in groups 1, 2, 3, and 4, respectively; thus MCV did not increase in an orderly progression along with HB and %Hb F. We studied the distribution of four anthropometric, five physical examination, and seven clinical measures of disease severity among clusters. In each sex, subgroups differed significantly (P less than .05) for percent ever hospitalized for sickle-cell anemia, percent ever transfused, and percent with bone-age delays greater than 1 year. In addition, male clusters differed significantly for percent ever having had pneumonia, priapism, or dactylitis, and females differed significantly for height and weight. %Hb F and its inverse relationship with %HBA2 was more highly associated with the measures of severity than the degree of anemia or MCV. This study establishes the utility of a vector of hematological variables as a predictor of heterogeneity of measures of clinical manifestations among young patients with sickle-cell anemia. The role of alpha-thalassemia and genetic factors that affect Hb F levels were considered as possible explanations for the observed heterogeneity.

Transfer of small plasmid DNA fragments from polyacrylamide gels onto nitrocellulose paper

The incorporation into a 7% polyacrylamide gel of a nucleic acid-specific photochemical reagent 4,5',8-trimethylpsoralen at a concentration of 1 mg/dl of acrylamide solution improves both the sensitivity and the efficiency of the transfer of plasmid DNA fragments from the gel onto nitrocellulose filters. This improvement allows detection by blot hybridization of DNA fragments as small as 57 bp long.

Phenazopyridine induced methaemoglobinaemia associated with decreased activity of erythrocyte cytochrome b5 reductase

A 25-year-old woman taking usual doses of phenazopyridine developed her third clinically significant episode of cyanosis. Life threatening methaemoglobinaemia was documented and was treated with methylene blue. The patient and several members of her family showed decreased activities of erythrocyte NADH-cytochrome b5 reductase, predisposing them to the development of clinically significant methaemoglobinaemia when challenged with oxidant drugs.

Hemoglobin SO Arab and hemoglobin CO Arab diseases. Clinical and laboratory study

A nine-year-old black female who had been considered to have Hb SC disease was admitted with pain of the leg, neck, and upper chest. She had also been hospitalized approximately 20 times for treatment of recurrent pain. Further investigation by citrate agar gel electrophoresis and peptide mapping disclosed that the child had Hb SO Arab disease. She had mild hepatosplenomegaly and the hemoglobin concentration was 10.2 gm/dl. The clinical presentation of Hb SO Arab disease of our patient resembled that of Hb SD disease and was more severe than is Hb SC disease. The mother was found to have Hb O Arab trait. Two of the patient's siblings from a different father were found to have Hb CO Arab disease, an extremely rare condition. These children, 8 and 12 years old, are clinically asymptomatic. Clinical and laboratory data are presented.

A decade of screening in the hemoglobinopathies: is a national program to prevent sickle cell anemia possible?

The increased attention given to sickle cell anemia for the past decade has enhanced public and professional understanding of the disease. The need to counsel a large segment of the general public has resulted in the production of a large amount of informative educational material on the subject. Despite the large amount of effort expended in population screening and counseling, very few studies of the counseling process have been done. It is still not known whether people use the knowledge gained for decisions regarding their reproduction. The development of direct antenatal diagnosis of sickle cell anemia by restriction endonuclease analysis of DNA from amniocytes now makes it possible to make the diagnosis as early as 17 weeks of gestation; use of chorionic villi as a source of DNA may advance the age of allowable diagnosis to 8 weeks. A model program being initiated in Michigan in which screening and counseling is being incorporated into the delivery of obstetrical care is described. Neutral counseling free of coercion will be given. Widespread acceptance of prenatal diagnosis may make general population and newborn sickle cell screening obsolete. Although many women seek obstetrical care too late in pregnancy to avail themselves of the procedure, its availability may have the effect of inducing them to seek care earlier in gestation, thereby improving other aspects of prenatal care. Although many women may currently reject prenatal diagnosis, in time it promises to blunt significantly the effect of sickle cell anemia on public health as well as assure that no couple at risk need have an affected child.

Long survival in sickle cell anemia

Ten patients with sickle cell anemia surviving beyond the age of 40 were compared to 11 subjects with sickle cell anemia who died before that age. Hematologic and biochemical data as well as clinical and physical parameters of the two groups were compared. There was no statistically significant difference between the two groups with respect to the degree of anemia, severity of hemolysis, or hemoglobin A2 levels. A statistically significant difference was found between the two groups with respect to fetal hemoglobin, red cell zinc, and secondary sexual characteristics. Although the long survivors had fewer crises per year than the short survivors, the long-term complications such as leg ulcer, congestive heart failure, and aseptic necrosis of the hip were more common in the older patients. Cerebrovascular accidents were the cause of death in 9/11 short survivors and are absent in the long survivors. The alpha/beta chain synthesis ratio was normal in the long-survivor group and alpha gene mapping in five subject in that group revealed the genotype alpha alpha/alpha alpha in four and -alpha/alpha alpha in one. The older patients as a group had higher red cell zinc values. The secondary sexual characteristics were also better developed in the older subjects. The overall significance of zinc status and of a higher HbF on longevity of sickle cell anemia patients remains unknown.

The proportion of Hb A2 is higher in sickle cell trait than in normal homozygotes

The proportion of Hb A2 was 3.53 +/- 0.94 per cent in the blood of 69 persons with sickle cell trait (A/S) and 2.88 +/- 0.69 per cent in a like number with a normal (A/A) genotype using a radial immunodiffusion assay. This differs significantly at the 0.1% level by the paired comparison technique. It is proposed that this effect is due to the impaired association of beta S with alphaA chains allowing more of the latter to combine with delta-chains. A similar phenomenon may account for the increased proportion of Hb A2 observed in beta-thalassemia. The proportion of Hb F did not differ in the two genotypes.

Clinical implications of recent advances in hemoglobin disorders

The greater availability of sophisticated diagnostic procedures has led to the discovery of more than 350 abnormal human hemoglobins. Whereas most are clinically silent, in a sizeable number of variants, function anomalies and disease states. Their more clinically relevant aspects are discussed.

Duplication 8p syndrome: studies in a family with a reciprocal translocation between chromosomes 8 and 12

We report a family in which six individuals were carriers of a translocation between chromosomes 8 and 12. The balanced carriers had a chromosomes constitution: 46,XX or 46,XY,t(8;12)(021;p13). Six individuals in five generations were mentally retarded. Three of them were examined; their chromosome constitution was 46,XX or 46,XYder(12),t(8;12)(p21;p13); thus they had a duplication of 8pter leads to 8p21 and possible deficiency of 12pter leads to 12p13. The activities of the enzymes that are coded by genes on 8p (glutathione reductase, GSR, E.C. 1.6.4.2.) and 12p (triosephosphate isomerase, TPI, E.C. 5.3.1.1.; lactate dehydrogenase-B, LDH-B, E.C. 1.1.1.27.; and glyceraldehyde-3-phosphate dehydrogenase, G3PD, E.C. 1.2.1.12.) were normal in these individuals. These findings helped in interpreting the position of the break points in the respective chromosomes. The phenotypic findings in our patients are discussed. Segregation analysis indicates no significant variation from a 25% recurrence risk for each of the possible genotypes in the offspring of balanced carriers.

Primary amyloidosis associated with Gaucher's disease

Elevations in serum immunoglobulins, frequently monoclonal in nature, are known to occur in patients with the adult form of Gaucher's disease. We describe amyloidosis in a 46-year-old woman of Italian ancestry with Gaucher's disease, who also had 3100 mg/dl of monoclonal IgA. She died of restrictive cardiac disease. A 50-year-old sister, also with Gaucher's disease, had 1300 mg/dl of polyclonal IgM but no evidence of amyloidosis. A glucosyl sphingosine-Sepharose affinity column provided no evidence that the large amount of immunoglobulin present has specific affinity for glucosyl ceramide. This, to our knowledge, is the first report of amyloidosis complicating Gaucher's disease.

Proteolytic activity in erythrocyte precursors

Thalassemia is characterized by unequal rates of synthesis of the alpha and beta globin chains that are part of the hemoglobin tetramer. In the type of thalassemia due to a defect in beta-chain synthesis (beta-thalassemia), this imbalance results in a relative exoess of alpha-chains. We have studied the susceptibility of excess free alpha-chains to proteolysis. Incubation of isotopically labeled peripheral blood lysates from individuals with beta-thalassemia trait in the presence of bone marrow or normoblast lysates from thalassemic or hematologically normal individuals resulted in a decrease in the alpha/beta ratio and a loss of free alpha-chain radioactivity. Neither contamination with leukocytes nor higher ATP contents in young erythrocytes appeared to be responsible for this activity in normoblasts and bone marrow. We propose that erythroid precursor cells possess proteolytic activity that is markedly diminished in mature cells. This activity serves an important control function in the regulation of hemoglobin synthesis. It accounts at least in part for the more balanced synthesis of alpha- and beta-chains observed in bone marrow than in peripheral blood in heterozygous beta-thalassemia. It also plays a fine-tuning role in maintaining balanced synthesis in non-thalassemic erythrocytes.

Increased bone marrow blood flow in sickle cell anemia demonstrated by thallium-201 and Tc-99m human albumin microspheres

Lower extremity vascularity in nine patients with sickle cell anemia was studied by intra-arterial Tc-99m human albumin microspheres or intravenous thallium 201. In eight patients, the normal pattern of greater muscle than bone activity was reversed with marked tracer localization in skeletal parts usually not visualized. In four cases, there were distinct focal abnormalities in the femurs and tibias which correlated with defects on Tc-99m sulfur colloid marrow scans. Tc-99m pyrophosphate bone scans demonstrated normal uptake in the same areas. The scintigraphic findings indicate a markedly increased relative bone marrow blood flow.

Fetal hemoglobin and alpha-fetoprotein in various malignancies

Fetal hemoglobin (HbF) concentrations were measured by a radial immunodiffusion assay in 233 patients with various malignancies. In 96 of these, alpha-fetoprotein (AFP) was also measured by radioimmunoassay. The concentration of HbF exceeded 2 SDs above the normal mean in 39 of 233 patients, most notably in patients with leukemia, lymphomas, multiple myeloma and testicular tumors. The proportion of HbF was not correlated with the total hemoglobin concentration or with serum AFP concentration.

Trimodality in the proportion of hemoglobin G Philadelphia in heterozygotes: evidence for heterogeneity in the number of human alpha chain loci

The extent of variability in the number of human hemoglobin (Hb) alpha chain loci has not yet been conclusively determined. There is evidence that in some populations individuals may possess two alpha-chain loci, while in other populations only one locus is present. Electrophoresis of peripheral blood from 53 heterozygotes for Hb G Philadelphia (alpha 68 Asn leads to Lys) revealed that the proportion of Hb G is trimodally distributed, with modes at approximately 20, 30, and 40% Hb G. Familial, hematologic, and statistical studies suggest that hte proportion of Hb G is not random but is genetically controlled and inversely correlated with mean cell volume. Two alternative genetic models are proposed to explain these findings: one assums alpha-thalassemia, while the other postulates variability in the number of alpha-chain loci in the American Black population. Biosynthetic studies of blood from 15 subjects revealed balanced synthesis of alpha and beta globin chains in heterozygotes from all three classes, strongly supporting variable gene dosage rather than alpha-thalassemia as the mechanism underlying the observed trimodality in the proportion of Hb G. Incompatibilities between out results and current concepts of alpha-thalassemia are discussed in the context of differences between Black compared with Oriental and Italian forms of Hb H disease.

Hemoglobin Wayne: a frameshift mutation detected in human hemoglobin alpha chains

Hemoglobin Wayne is an alpha chain variant which manifests itself as two minor hemoglobin (Hb) components that migrate more rapidly than Hb A on electrophoresis at pH 8.6. It has been found in a child with Fanconi's anemia and in three generations of the child's family. Each of the minor components yields an alpha chain in which the carboxyl-terminal tripeptide sequence, Lys-Tyr-Arg, has been replaced by the octapeptide sequence Asx-Thr-Val-Lys-Leu-Glu-Pro-Arg. In alpha Wayne I, the slower of the pair, Asx is asparagine, whereas in alpha Wayne II it is aspartic acid. Comparison of the alpha Wayne sequences with the amino-acid sequences of alpha A and alpha Constant Spring leads to the conclusion that Hb Wayne I is the result of a -1 frameshift mutation in the alpha chain and that Hb Wayne II is formed secondarily by spontaneous deamidation of the new asparagine residue. A frameshift is consistent with a single mRNA base sequence for the last eight codons involved and supports the view of Clegg, Weatherall, and Milner [Nature (1971) 234, 337-341] that Hb Constant Spring is the result of a terminator mutation leading to translation of 31 codons not normally translated.

The interaction of alpha-thalassaemia and haemoglobin G Philadelphia

An American Negro woman was found to have HbH disease in association with HbG Philadelphia (alpha68-asn leads to lys). Starch gel electrophoresis failed to reveal the presence of any HbA or HbA2 and studies of globin chain synthesis indicated absence of alphaA production. The alphaG/beta synthesis ratio was 0.63. The woman's son and her two half-sibs had alpha-thalassaemia trait with no HbH and alpha/beta synthesis ratios of 0.84, 0.84 and 0.76. The data indicate that there is no functioning alphaA gene linked to the alphaG gene. The absence of alphaA synthesis by the propositus also indicates that the alpha-thalssaemia gene trans to the alphaG gene completely suppresses alpha chain production, the first evidence for such a gene in Negroes.

Comparison of methodologies for thalassemia screening by Hb A2 quantitation

An efficient, reliable, inexpensive screening test for beta-thalassemia triat is required before the National Cooley's Anemia Control Act can be carried out. Densitometry of hemoglobin samples separated by cellulose acetate has become a routine procedure to quantitate Hb A2 and thereby indicate beta-thalassemia trait carriers. To determine the utility of densitometry in quantitation of Hb A2, we evaluated three densitometers marketed in the United States. Individuals with genetically proved beta-thalassemia trait and normal Hb AA controls were studied. Two analytic procedures (elution and column chromatography) for Hb A2 quantitation were used as reference methods. Densitometry was shown to be unsatisfactory for detecting beta-thalassemia-trait carriers. We recommend that a unified approach to the detection of anemia, which would include thalassemia trait, be developed in the United States rather than free-standing thalassemia screening centers and clinics.

A heterozygote for Hb S beta, Hb C beta and Hb G Philadelphia beta in a family presenting evidence for heterogeneity of hemoglobin alpha chain loci

A child heterozygous for the genes for hemoglobins S, C and G alpha Philadelphia presented with a clinical picture similar to sickle cell anemia. Her hemoglobin electrophoretic pattern contained three components with the mobilities of hemoglobins S (35 per cent), C (47 per cent) and a more slowly migrating hybrid G/C molecule (15 per cent). Seven relatives were heterozygous for Hb G beta and Hb S beta and five were heterozygous only for Hb G alpha. Among the latter, three had approximately 30 per cent and two had 40 per cent of Hb G. These proportions are consistent with the hypothesis that the American Negro genome contains two types of chromosomes bearing structural loci for alpha chains, some possessing one Hb alpha locus, others having two loci. Hb G alpha-Philadelphia presumably arose as a mutation on a chromosome with a single locus. Those heterozygotes having 30 per cent and 40 per cent Hb G presumably have two loci and only one locus, respectively, on the homologous chromosome.