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Genetic epidemiology of the three predominant abnormal hemoglobins in India.

Hemoglobinopathies in India are Important public health problems. Of the several abnormal of hemoglobin molecules, there are three variants, viz. Sickle cell, hemoglobin E and hemoglobin D which are predominantly prevalent in India. The cumulative gene frequencies of these hemoglobins have been found to be 5.35% in India. The average gene frequency of sickle cell and hemoglobin D in India has been observed to be 4.3% and 0.86%, respectively. In the North Eastern region of India, the gene frequency of hemoglobin E is 10.9%. Gene frequencies and spatial distribution of the predominant abnormal hemoglobins in India have been discussed in variance with the previous generalisations.

Adult↗

Abnormal hemoglobins in Northwestern Mexico.

Blood samples from 9,929 individuals in Northwestern Mexico were assayed for abnormal hemoglobins (Hbs). alpha-thal, beta-thal, beta s and beta c traits, as well as rare abnormal Hbs were observed with variable low frequencies (0 to 0.45%). Eight out of eleven rare abnormal Hbs detected so far have been characterized: Three Hb Riyadh, one Hb J Georgia, one Hb Fannin-Lubbock, one Hb Chiapas and two Hb Tarrant. These results suggest that abnormal Hbs do not constitute a regional public health problem and reflect a wide ethnologic heterogeneity.

Female↗

Standardization on laboratory diagnosis of thalassemia and abnormal hemoglobin.

Thalassemia is one of the most common single gene disorders. The geographic distribution of thalassemia and abnormal hemoglobin has been known for many years. A worldwide significant spread of these abnormal genes, especially from Southeast Asia, occurred in the last two decades. This has resulted in a dramatic increase of Hb E disorders and various Southeast Asian thalassemia genotypes, which means that requests for hemoglobinopathy investigations are likely to increase in many laboratories worldwide. Hemoglobinopathy screening and diagnosis may need to be undertaken antenatally, neonatally and in certain hematological situations. The introduction of automation for hemoglobinopathy screening, including the automated cell counting and HPLC system, is an important advance in technology for hematology laboratories. The instruments need to be calibrated and standardized to get an accurate data for interpretation. Internal and external control samples are also needed. Combination of test results is usually required to achieve a proper diagnosis, which in turn, provide a self-check for each laboratory test.

Adult↗

A new alpha chain variant, Hb Turriff [alpha 99(G6)Lys----Glu]: the interference of abnormal hemoglobins in Hb A1c determination.

Hb Turriff is a new hemoglobin variant which we have identified in a diabetic individual. During the determination of Hb A1c by high performance liquid chromatography, an inappropriately elevated result was found to be due to the abnormal hemoglobin chromatographing with the Hb A1c fraction. This new hemoglobin variant, Hb Turriff [alpha 99(G6)Lys----Glu], is not associated with any hematological disturbance, and family investigations indicate that it has arisen as a de novo mutation.

Adult↗

A test for abnormal hemoglobins in umbilical cord blood.

This article describes a rapid, simple, and inexpensive method for testing the cord blood of infants for the common hemoglobinopathies by electrophoresis using cellulose polyacetate strips. In a study of 7,500 umbilical cord blood specimens, 11% were found to contain an abnormal hemoglobin. While the importance of evaluating cord blood in a screening program for hemoglobinopathies is evident, the procedure must be accurate, verified, and followed by proper counseling.

Black or African American↗

Hemoglobin stability: observations on the denaturation of normal and abnormal hemoglobins by oxidant dyes, heat, and alkali.

Several unstable mutant hemoglobins have alterations which affect areas of the molecule involved in the attachment of heme to globin. Loss of heme from globin has been demonstrated during the denaturation of some of these unstable mutants. The importance of heme ligands for the stability of hemoglobin was illustrated in the present experiments on the denaturation of several hemoglobins and hemoglobin derivatives by heat, oxidative dyes, and alkali. Heating of normal hemolysates diluted to 4 g of hemoglobin per 100 ml at 50 degrees C for 20 hr in 0.05 M sodium phosphate, pH 7.4, caused precipitation of 23-54% of the hemoglobin. Dialysis against water or dilution of the sample decreased denaturation to 12-20%. Precipitation was decreased to less than 3.5% by the presence of 0.015 M potassium cyanide. Increasing the ionic strength of the medium increased precipitation. Cyanide prevented the formation of inclusion bodies when red cells containing unstable hemoglobin Philly, beta35 tyr --> phe, were incubated with the redox dye new methylene blue. Conversion to methemoglobin increased the rate of alkali denaturation of hemoglobin but the presence of potassium cyanide returned the denaturation rate to that of ferrohemoglobin. The ability of cyanide to decrease heat precipitation of hemoglobin may depend on a dimeric or tetrameric state of the hemoglobin molecule. Purified beta-chains, which exist as tetramers, were stabilized but purified monomeric alpha-chains were not rendered more heat resistant by the ligand. Stabilization of hemoglobin by cyanide required binding of the ligand to only one heme of an alphabeta-dimer. Hemoglobin Gun Hill, an unstable molecule with heme groups present only on the alpha-chains was quite heat stable in the presence of cyanide. The binding of cyanide to the iron atom in methemoglobin is thought to be associated with increased planarity of the heme group and increased stability of the heme-globin complex. The stabilizing effect of cyanide in the above experiments suggests that Heinz body formation, heat precipitation of hemoglobin, and the increased alkali denaturation of methemoglobin depend on changes of heme-globin binding.

Alkalies↗

Percentages of abnormal hemoglobins in adults with a heterozygosity for an alpha-chain and/or a beta-chain variant.

The author reviews quantitative data from blood samples involving more than 700 simple and compound heterozygotes for one of 21 types of alpha-chain and 36 types of beta-chain variants. All samples were analyzed during the past few years by the same analytical procedure. Various factors influencing the percentages of the different abnormal hemoglobins are discussed; these include the variability of the method, the number of active alpha-chain genes, the location of the substitution, the type of substitution, the effect of the loss of a critical amino acid residue, and the introduction of a new residue on the physiochemical and/or functional properties of the protein. The use of a single accurate method is promoted; it may well be that high-pressure liquid chromatographic procedures will be the recommended methods for future analyses.

Chromatography, DEAE-Cellulose↗

[An abnormal hemoglobin which was found by chance at a health checkup].

A 68-year-old female visited our hospital because of low hemoglobin A1c content, which was found by chance at a health checkup. She did not have any symptom or sign except hypertension and low HbA1c. To determine the reason why HbA1c was so low in usual laboratory test, we carried out isoelectrofocusing (IEF) of the hemolysate, Hb instability test, and detection and isolation of the abnormal globin chain by urea CM-cellulose column chromatography. The abnormal beta-globin chain was digested with TPCK-trypsin, and the tryptic peptides were separated by HPLC on a reversed phase column. Finally the determination of amino acid composition and amino acid sequence of the abnormal peptide were performed. The Hb variant was identified as Hb Riyadh (beta 120Lys-->Asn). The detection and analysis of abnormal hemoglobin will be expected to increase in accordance with the increased opportunity of public health checkup.

Aged↗

[The distribution of abnormal hemoglobins in the silk road region of China].

215,785 individuals living in the Silk Road region of China were surveyed for abnormal hemoglobins (Hbs). Among them, 695 carriers were detected. The average incidence of abnormal Hbs was 3/22 and the frequencies of abnormal Hbs among 12 nationalities reached 0.15/1000-12.17/1000. The primary structural analyses were made in 271 persons, and 24 variants [13 alpha-chain variants and 11 beta-chain variants] were identified. HbJ Tashikuergan and Hb Tianshui were discovered the first time in the world. HbS, Hb Bunbury, Hb Setif and HbI Philadelphia were not found previously in the Chinese population. Three variants, i.e. HbD Punjab, HbG Taipei and HbG Coushatta occurred at the highest frequencies and showed a gradient distribution along the Silk Road, suggesting that they may originate from Caucasians in Central Asia, Han in the Yellow River valley, and the ancient nomadic minorities of China in Mongolia Plateau respectively. The frequencies of other variants were quite low. Some were probably imported from other countries and areas, and some arose from independent mutations. The data from many variants support the movements of various populations in this area, as reported in numerous historical documents. It is indicated that the Silk Road promoted the national fusion among the Chinese nationalities, Mongolian and Caucasian races.

Adolescent↗

The effects of inositol hexaphosphate on the allosteric properties of two beta-99-substituted abnormal hemoglobins, hemoglobin Yakima and hemoglobin Kempsey.

Hemoglobins (Hb) Yakima and Kempsey were purified from patients' blood with diethylaminoethyl cellulose column chromatography. The oxygen equilibrium curves of the two hemoglobins and the effects of organic phosphates on the function were investigated. In 0.1 M phosphate buffer, Hill's constants n for Hb Yakima and Hb Kempsey were 1.0 to 1.1 at the pH range for 6.5 to 8.0 and the oxygen affinities of both the mutant hemoglobins were about 15 to 20 times that of Hb A at pH 7.0. The Bohr effect was normal in Hb Yakima and one-fourth normal in Hb Kempsey. In the presence of inositol hexaphosphate, the oxygen affinities to Hb Yakima and Hb Kempsey were greatly decreased, and an interesting result revealed that these hemoglobins showed clear cooperativity in oxygen binding. Hill's constant n in the presence of inositol hexaphosphate was 1.9 for Hb Kempsey and 2.3 for Hb Yakima at pH 7.0. The cooperativities of these mutant hemoglobins were pH-dependent, and Hb Kempsey showed high cooperativity at low pH (n equal 2.1 at pH 6.6) and low cooperativity at high pH (n equal 1.0 at pH 8.0). Hb Yakima showed similar pH dependence in cooperativity. In the presence of inositol hexaphosphate, Hb A showed a pH-dependent cooperativity different from those of Hb Yakima and Hb Kempsey, namely, Hill's n was the highest in alkaline pH (n equal 3.0 at pH 8.0) and decreased at lower pH (n equal 1.5 at pH 6.5). 2,3Diphosphoglycerate bound with the deoxygenated Hb Yakima and Hb Kempsey, however, had no effect on the oxygen binding of these abnormal hemoglobin. The pH-dependent cooperativity of alpha1beta2 contact anomalous hemoglobin and normal hemoglobin was explained by the shifts in the equilibrium between the high and low ligand affinity forms.

Allosteric Regulation↗

Abnormal hemoglobins found in Hunan.

OBJECTIVE: To summarize the results of general survey, primary structure analysis and related functional studies of abnormal hemoglobins (Hbs) found in Hunan Province. DATA SOURCES: International Hb journals, Chinese biochemical and biomedical journals and other articles relevant to hematology. STUDY SELECTION: All Hb variants found in Hunan and identified by primary structure analysis during 1980 - 1991 were included. DATA EXTRACTION: Data concerning 11 types of Hb variants found in 3 districts and 7 counties in Hunan Province were briefly documented. Their frequencies of occurrence were calculated and their distributions among Han, Yao, Tujia and Dong ethnic groups were listed. RESULTS: Thirty-six cases with abnormal Hb were identified out of 7412 individuals screened in Hunan. 11 different types of Hb variants were recognized by primary structure analysis in 19 propositi along with their family members, including 5 alpha-chain variants, 4 beta-chain variants, 1 delta-chain variant and 1 delta-beta chain fusion variant. Oxygen equilibrium characteristics, reaction dynamics, the rate of globin chain synthesis (RGCS), morphology observation by electron microscopy and DNA analysis were all used in the functional studies of hemoglobinopathies. CONCLUSIONS: The average incidence of abnormal Hbs in Hunan is 0.486%. In Jianghua County, whose inhabitants are mostly of the Yao ethnic group, the incidence is significantly higher (1.09%). Hb Jianghua [beta120(GH3) Lys-->lle] and Hb Shuangfeng (SF) [alpha27(B8) Glu-->Lys] were two new variants first reported in international literature; whereas Hb Lille [alpha74(EF3) Asp-->Ala], HbA(2) Flatbush [delta22(B4) Ala-->Glu] and Hb Lepore-Boston [delta87(F3)-beta116(G18)] were the first three instances to be found in China. Hb SF displayed an oxygen affinity 1.5-fold higher than that of HbA at pH 7.4 and 25 degrees C with its oxygen equilibrium curve shifted to the left. Reticulocytes of Hb SF heterozygote showed unbalanced RGCS, quite similar to that found in beta-thalassemia minor. Erythrocytes of Hb SF heterozygote were changed to spherocytes and began to lyse after incubation with sodium salicylate or sulfadiazine (pH 7.4, 37 degrees C) for 2 - 4 h. These findings explained the sudden attack of hemolytic anemia provoked by two drugs in Hb SF propositus. The genotype of a patient with Hb Q-H disease is identified as -,-/-,alpha(Q) by DNA restriction mapping.

Erythrocytes↗

Detection of two abnormal hemoglobins, Hb Manitoba and Hb G-Coushatta, during analysis of glycohemoglobin (A1c) by high-performance liquid chromatography.

This report concerns the detection of two abnormal hemoglobins (Hb), Hb Manitoba and Hb G Coushatta, during analysis for glycohemoglobin (Hb A1c). Blood samples from two diabetic patients, analyzed for Hb A1c by HPLC, were found to contain additional Hb peaks. The presence of an abnormal Hb was confirmed in both instances by hemoglobinopathy studies. Structural studies determined the two Hb variants to be Hb Manitoba (alpha 2 102 Ser----Arg beta 2) and Hb G-Coushatta (alpha 2 beta 2 22 Glu----Ala). The significance of the presence of an abnormal Hb in Hb A1c analysis is discussed.

Amino Acid Sequence↗

Abnormal hemoglobins in a quarter million people.

Hemolysates of erythrocytes from more than a quarter million people in Alabama were electrophoresed on cellulose acetate, pH 8.4, and those samples exhibiting an abnormality were also electrophoresed in citrate agar, pH 6.0. The globin chains of mutants other than Hb S and C were electrophoresed in urea-mercaptoethanol buffers at both pH 8.9 and pH 6.0, and 60 of them were also analyzed structurally. Of about 6000 samples from whites, only three contained abnormal hemoglobins--Hb D Los Angeles, Hb J Baltimore, and one unidentified. Of 249,000 samples from blacks, about 29,000 contained electrophoretically detectable abnormalities, most of them associated with Hb S or C, present in a frequency of about 9% and 3%, respectively. About 1000 samples resolved into patterns of potential clinical significance. Twenty other mutant hemoglobins were detected, in various genetic combinations in 164 kindreds; four of these-Hb Alabama, Montgomery, Titusville, and Mobile--were previously unknown. The methods used are rapid, economical, and well suited for large scale surveys. They provide highly specific characterizations of many mutant hemoglobins, and no discrepancies were found between the presumptive identifications based on these characterizations and the definitive identifications obtained from structural analyses.

Alabama↗

Structural characterization of abnormal hemoglobins from dried blood specimens in a neonatal screening program.

Blood specimens dried on filter paper are now widely used for neonatal screening of hemoglobinopathies. These samples are perfectly suited for electrophoresis studies and HPLC analysis. They may also be used for DNA analysis. The structural characterization of a hemoglobin variant is also possible using protein chemistry methods. After elution of the hemoglobin from the paper, the different components are fractionated by a microscale preparative isoelectric focusing. The structural modification of the abnormal hemoglobin is then determined through a series of techniques including chain separation, aminoethylation, trypsin digestion, analysis of the peptides and determination of their aminoacid composition. The efficiency of this strategy is demonstrated by the study of an alpha-chain variant (Hb Hasharon) and three beta-chain variants (Hb S, Hb D Punjab, Hb E). Unambiguous identification of the structural abnormality was obtained with samples stored for up to 18 months and with abnormal fractions amounting to only approximately 10% of the total lysate.

Chromatography, High Pressure Liquid↗

Hemoglobin Ohio (beta 142 Ala replaced by): a new abnormal hemoglobin with high oxygen affinity and erythrocytosis.

Hemoglobin Ohio [beta 142 (H20) Ala replaced by Asp] was found in three members of a white family, all of whom showed erythrocytosis. The variant hemoglobin has a high oxygen affinity, a reduced Bohr effect, and diminished cooperativity. The functional abnormalities of Hb Ohio are explained by the proximity of the substituent beta 142 residue, both to beta 143 His, which is involved in the DPG binding site of hemoglobin, and to the critical C terminal region of the beta chain, which participates in the stabilization of the deoxy (T) conformation.

Adult↗