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J B Clegg

Publications and source records attributed to J B Clegg.

At least 163 records · Page 9Linked to original sources
PubMed1980

The genetic basis of Hb Q-H disease.

A Chinese family has been studied in which two siblings have haemoglobin Q-H disease. Using a combination of haematological and haemoglobin analysis, globin chain synthesis, analysis of alpha/beta globin messenger RNA ratios and restriction endonuclease mapping, it has been shown that each of these siblings has received one chromosome on which both alpha chain genes have been deleted and another on which there is only a single alpha chain locus which carries the alpha Q mutation. Their genotype is thus --/-alpha Q. Despite the fact that the haemoglobin Q mutation in this family is carried on a chromosome with a single alpha chain locus, heterozygous carriers for the variant have only 25% or less haemoglobin Q. Our observations indicate that the molecular basis for haemoglobin Q-alpha thalassaemia is similar to that for the common form of haemoglobin H disease in Orientals. Furthermore, they provide clear evidence that the level of an alpha chain variant in heterozygous carriers is not a reliable reflection of the number of alpha globin genes.

Aged↗
PubMed1980

alpha thalassemia in black populations.

The different alpha thalassemia genotypes in American and Jamaican black populations have been defined by hematologic and globin-chain synthesis studies, alpha/beta globin messenger RNA ratios and restriction endonuclease mapping of DNA. The results indicate that the common form of alpha thalassemia in these populations is the deletion type of alpha-thalassemia 2 (- alpha/alpha alpha). The homozygous state (- alpha/alpha- alpha) is expressed at birth by the presence of more than 2--3% hemoglobin Bart's; in adult life it has the same phenotype as the heterozygous state for the deletion form of alpha-thalassemia 1 (--/alpha alpha). The heterozygous state is not always associated with detectable amounts of hemoglobin Bart's at birth or with recognizable hematologic changes in adults.

Black People↗
PubMed1979

Negro alpha-thalassaemia is caused by deletion of a single alpha-globin gene.

Studies in two Jamaican Negro families, including haematological and haemoglobin analysis, haemoglobin synthesis, and globin messenger-RNA assay, have defined two alpha-thalassaemia phenotypes which resemble the severe (alpha-thalassaemia 1) and mild (alpha-thalassaemia 2) forms of the disorder described in Orientals. Genetic analysis suggests that subjects with the alpha-thalassaemia-1 phenotype are homozygous for the alpha-thalassaemia-2 determinant. Restriction-endonuclease mapping shows that alpha-thalassaemia-2 results from the deletion of one of the linked pair of alpha-chain genes. Hence the genotypes of the alpha-thalassaemia heterozygotes and homozygotes in these families are -alpha/alpha alpha and -alpha/-alpha respectively. If these are the usual alpha-thalassaemia genotypes in Negroes, these findings explain the difference in clinical expression of the disorder between Orientals and Negroes--in particular, the absence of haemoglobin Bart's hydrops and the rarity of haemoglobin-H disease in Negroes.

Black People↗
PubMed1979

Hemoglobin polymorphism in Equus przewalskii and E. caballus analyzed by isoelectric focusing.

1. Through the use of isoelectric focusing and peptide analysis, the hemoglobins of Przewalski's horse. Equus przewalskii and the domestic horse, E. caballus have been compared. 2. Przewalski's horses have two separate alpha-globin chain polymorphisms similar to domestic horses. Each hemoglobin phenotype could be accurately determined by isoelectric focusing. 3. Confirmation of the electrofocusing hemoglobin determinations was made by comparison to amino acid composition analyses of purified tryptic peptides and by analysis of the rare hemoglobins phenotypes observed in a family of Norwegian trotting horses. 4. Hemoglobin genotypes of fifteen Przewalski's horses were determined and inheritance of hemoglobin haplotypes has been observed.

Amino Acids↗
PubMed1979

Occurrence of G gamma Hb F in Greek HPFH: analysis of heterozygotes and compound heterozygotes with beta thalassaemia.

Haemoglobin F has been isolated from the red cells of individuals with the Greek form of hereditary persistence of fetal haemoglobin (HPFH), and the glycine/alanine composition of the gamma CB3 peptides determined. In contrast to previous reports we have shown that the Hb F of the Greek HPFH heterozygotes contains significant amounts of G gamma chains and circumstantial evidence indicates that these are the products of the same chromosome that carries the Greek HPFH determinant. Hence this chromosome must be directing the synthesis of G gamma, A gamma and (probably) beta and delta chains, thus implying that the Greek form of HPFH does not result from a deletion involving the globin chain structural genes. Analysis of the levels and structure of Hb F from the Greek HPFH heterozygotes and from separated cell populations from the Greek HPFH/beta thalassaemia compound heterozygotes indicate that the Greek HPFH determinant, while allowing an overall increase in gamma chain synthesis, is not the sole factor determining the absolute amount of Hb F production on a cellular basis.

Adult↗
PubMed1979

A comparison of the homozygous states for G gamma and G gamma A gamma delta beta thalassaemia.

One Arabic and two Indian patients with thalassaemia intermedia produce only Hb F for the G gamma type. Haemoglobin synthesis studies and genetic analysis indicate that they are homozygous for G gamma delta beta thalassaemia. The findings in these patients and their heterozygous relatives are compared with those in an individual homozygous for G gamma A gamma delta beta thalassaemia. From this analysis, and from previously reported data on G gamma A gamma delta beta thalassaemia, the phenotypic expression of the two varieties of delta beta thalassaemia is defined. The relationship between the clinical expression and molecular pathology of these forms of delta beta thalassaemia is discussed.

Adolescent↗
PubMed1979

G gamma beta + type of hereditary persistence of fetal haemoglobin in association with Hb C.

This report describes a Negro family with the G gamma beta + type of hereditary persistence of fetal haemoglobin. Family members with levels of haemoglobin F of 17 to 23% had normal red cell indices, balanced globin chain synthesis, and a pancellular distribution of the fetal haemoglobin, showing that these subjects have a form of HPFH. The production of Hb A and C in addition to the large amount of Hb F in one family member showed that there was an active beta A gene in cis to the HPFH determinant, while structural analysis of the Hb F revealed the presence of only G gamma chains. The criteria for the diagnosis of G gamma beta + HPFH, and the relevance of such conditions to the control of globin gene expression, are discussed.

Adult↗
PubMed1979

Genetic control of F cells in human adults.

Hb F levels were determined on samples from 750 normal blood donors. Six individuals (0.8%) had Hb F levels in excess of 1.1%, the upper end of the continuous distribution. Eight individuals at the upper end and 7 individuals at the lower end of the range were selected for family studies. These studies revealed that the control of Hb F levels in adults, as judged by the more sensitive F-cell technique, has a major genetic component. Structural analysis of the Hb F in several cases demonstrated that both G gamma and A gamma chains were present, but in variable proportions. These results are discussed in light of current concepts of adult F-cell production.

Adolescent↗
PubMed1978

Antenatal diagnosis of thalassaemia major.

Haemoglobin synthesis was studied in fetal blood samples obtained at 17 to 20 weeks' gestation in 22 women at risk of carrying a fetus with homozygous beta-thalassaemia. A presumptive diagnosis of homozygous beta-thalassaemia was made in four cases, and the pregnancy was terminated. An inconclusive answer was obtained in one case, and the patient also chose to have her pregnancy terminated. Two fetuses were lost as a result of the procedure. Of the remaining 15 pregnancies, 13 proceeded to term and two to 36 weeks; in each case a normal infant or one heterozygous for beta-thalassaemia was delivered. Current efforts should be directed towards improving the blood sampling technology so that fetal blood sampling can be used widely in those countries where thalassaemia is a major problem.

Abortion, Eugenic↗