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D J Weatherall

Publications and source records attributed to D J Weatherall.

At least 361 records · Page 20Linked to original sources
PubMed1976

A direct estimate of the number of human gamma-globin genes.

The number of genes specifying human gamma-globin has been determined directly by hybridization of complementary DNA to total human DNA. The complementary DNA was enriched in sequences specific for gamma-globin genes by transcribing globin mRNA isolated from fetal reticulocytes with viral reverse transcriptase, and collecting the material which does not back-hybridize to adult globin mRNA. When hybridized in cDNA excess to DNA, very similar values are found for gamma-gene number as for beta-gene number, suggesting two or at most three gamma-globin genes per haploid human genome. This indicates that the non-Mendelian ratios of gamma-chain mutants found in heterozygotes are due to transcriptional or post-transcriptional regulation rather than to gene dosage. The number of each major human globin gene has now been determined directly by molecular methods.

Genes↗
PubMed1976

Assay of thalassaemic messenger RNA in the wheat germ system.

Messenger RNA(mRNA) has been prepared from reticulocytes obtained from patients with different types of thalassaemia and assayed in the wheat germ system. Since normal human reticulocyte mRNA directs the synthesis of equal numbers of alpha- and beta-globin chains in this system it offers a rapid and simple technique for assaying mRNA in the thalassaemic disorders. In mRNA from beta+ thalassaemics the deficiency of beta-globin synthesis mirrored that observed in intact reticulocytes while that prepared from patients wiht haemoglobin H disease gave alpha/beta globin chain production ratios which showed consistently greater imbalance than was found in reticulocytes. Messenger RNA prepared from haemoglobin E-beta0 thalassaemics from Thailand directed no detectable beta-chain synthesis while that prepared from a betaO thalassaemic from Ferrara synthesized a fraction with the chromatographic characteristics of beta-globin chains.

Globins↗
PubMed1976

The patterns of fetal haemoglobin production in leukaemia.

Elevated levels of haemoglobin F (Hb F) have been foudn in a wide range of haematological malignancies, but very high levels were found only in juvenile chronic myeloid leukaemia (JCML), and erythroleukaemia occurring in infancy. In both these disorders a reversion to a fetal form of erythropoiesis may occur, as judged by both the structure of the Hb F and by the disappearance of Hb A2 and the carbnoic-anhydrase isozymes during the course of the illness. The clinical picture of JCML is not always associated with a reversion to fetal erythropoiesis; there appears to be a heterogeneity of conditions with this clinical label. Thus the reversion to a completely fetal pattern of erythropoiesis seems to occur in a variety of leukaemias which start in early life. This change is associated with a uniformly bad prognosis. Of a group of 17 patients with acute myeloid leukaemia 15 developed an increase in the level of Hb F about 60 days after the commencement of treatment; significantly greater increases were observed in those achieving a clinical remission. The level of Hb F usually declined during remission but high levels persisted in a few cases. Increased levels of Hb F were found also in patients with other haematological malignancies who had undergone periods of marrow aplasia during treatment. In all cases the Hb F was heterogeneously distributed throughout the red cells. Analysis of gamma15 or gammaCB3 peptides of Hb F from a variety of leukaemias gave glycine compositions ranging from 0.20 to 0.85 residues with many values in the fetal range; all cases with a reversion to fetal erythropoiesis had values in the fetal range. Attempts to confirm the 'fetal' origin of the cells containing Hb F by means of other markers was possible only in the cases of JCML and in one child with erythroleukaemia. These studies indicate that in some forms of leukaemia there may be a genuine reversion to fetal erythropoiesis while in others the emergence of cells containing Hb F appears to be part of a rapid regeneration process occurring after a period of marrow aplasia. The diagnostic and prognostic value of these observations is discussed.

Adult↗
PubMed1976

The Negro variety of hereditary persistence of fetal haemoglobin is a mild form of thalassaemia.

Further studies have been carried out on blood of the 15-year-old Negro male from Baltimore who was the first reported case of the homozygous state for hereditary persistence of fetal haemoglobin. His red cells contain only Hb F; Hbs A and A2 have never been detected. Over a 15-year period of follow up the red cells of this individual have shown persistent microcytosis with reduced MCH and MCV values. His whole-blood p50 value is decreased, probably because of lack of interaction between Hb F and 2,3-diphosphoglycerate. However, his haemoglobin level at the age of 15 years is lower than would be predicted from the degree of increased oxygen affinity. Globin-chain synthesis studies suggest that this is because he has a mild thalassaemia disorder with an alpha/gamma-chain production ratio of about 1.5, similar to that found in beta-thalassemia heterozygotes. Thus Negro HPFH appears to be a well-compensated form of delta beta thalassaemia.

Adolescent↗
PubMed1976

Globin synthesis in normal human bone marrow.

Globin synthesis has been studied by in vitro labelling with radioactive amino acids in 60 normal human bone-marrow samples. Under the conditions routinely used to fractionate alpha and beta chains by chromatography alpha/beta production ratios ranging from 0.5 to 1.0 were obtained, depending on the method of sample treatment. This variation was due entirely to the presence of non-haem proteins derived from white cells which chromagraphy with globin on CM-cellulose. Purification of globin on Sephadex G100 and fractionation of alpha and beta globin chains by a modified chromatographic system resulted in alpha/beta ratios of unity. The relevance of these findings to the study of marrows in which there is unbalanced globin chain production is discussed.

Blood Proteins↗
PubMed1976

Linkage relationships between beta- and delta-structural loci and African forms of beta thalassaemia.

Five families are described in which there have been matings between individuals doubly heterozygous for beta thalassaemia and the delta-chain variant haemoglobin A2' to normal persons. In all there were 24 informative offspring. There were no crossovers between the beta-thalassaemia and delta-chain loci; in three of the families the genes were linked in cis and in two families the genes were found in trans. Together with previously reported families there have now been 58 opportunities for crossing over between the beta-thalassaemia and delta-chain loci and there have been two possible and one highly probable crossovers. Of the total of 9 families reported to date 4 have had the genes for beta thalassaemia and Hb A2' in cis and 5 in trans. These findings are contrasted with the findings in families where a beta-chain structural variant and Hb A2' have been observed together and these genes have always been found in trans and never in cis. The reasons for linkage disequilibrium of this type are discussed. It is concluded tentatively that the distance between the delta-structural and beta-thalassaemia loci is greater than that between the delta-structural and beta-structural loci. To date this conclusion can only be applied to the beta+ -thalassaemia and beta-thalassaemia genes as found in the African population, since this is the only population with a high incidence of delta-chain mutants which allow linkage analysis of this type to be carried out.

Africa↗
PubMed1975

The alpha-chain-termination mutants and their relation to the alpha-thalassaemias.

The structure, synthesis, genetic transmission, clinical associations and distribution of the elongated alpha-chain haemoglobin variants has been described. The data indicate that the most likely molecular basis for these common abnormal haemoglobins is a single base substitution in the alpha-chain termination codon. Because these variants are produced inefficiently they give rise to the clinical picture of alpha-thalassaemia. When these findings are taken together with recent work regarding the molecular basis for other forms of alpha-thalassaemia it is possible to build up a fairly complete picture of the molecular pathology of the alpha-thalassaemias.

Amino Acids↗
PubMed1975

Imbalanced globin chain synthesis in heterozygous beta-thalassemic bone marrow.

Globin synthesis was studied in the bone marrow of seven heterozygous beta-thalassemic subjects. We found evidence of significant imbalance of alpha- and beta-chain production particularly at short times of incubation. There was a progressive decrease in alpha/beta-chain production ratio with increasing incubation time which was due to a decreased rate of net alpha-chain production, indicating that a large proportion of the newly synthesized alpha chains are degraded, particularly in bone marrow, within a few minutes of synthesis, leading to relatively low alpha/beta ratios if these are measured solely at incubation times greater than 10 min. The significant degradation of excess alpha chains explains why inclusion body formation and ineffective erythropoiesis, notable in beta-thalassemia homozygotes where there is gross chain imbalance, are not observed to any marked degree in heterozygotes.

Bone Marrow↗
PubMed1975

Human globin gene analysis for a patient with beta-o/delta beta-thalassemia.

Complementary DNA (cDNA) was prepared with RNA-dependent DNA polymerase from human globin messenger RNA (mRNA). Annealing and translation experimenta with total mRNA from circulating cells from a patient with heterozygous beta/heterozygous beta-delta-o thalassemia (beta-o/delta beta-o-thalassemia) demonstrated no detectable mRNA for beta-globin. cDNA enriched in sequences homologous to beta-globin mRNA was prepared by hydroxylapatite fractionation of hybrids formed between beta-o/delta beta-o-thalassemic mRNA and cDNA made from mRNA from a patient with alpha-thalassemia (hemoglobin H disease). The rate of annealing of this beta-enriched cDNA to normal human nuclear DNA was that of a sequence present as only a single copy per haploid genome. The beta-enriched cDNA annealed to the beta-o-delta beta-o-thalassemia total DNA with approximately the same kinetics as to normal DNA, indicating that no total gene deletion of beta-globin genes from the diploid genome has occurred, although the accuracy of the technique could not exclude with certainty a partial deletion or a deletion of a beta-globin gene from only one of the haploid genomes. This demonstrates that at least one of the beta-o- or the delta beta-o-thalassemia haploid genomes in this case contains a substantially intact beta-globin gene.

Adolescent↗
PubMed1975

Haemoglobin synthesis in human fetal liver maintained in short-term tissue culture.

Human fetal liver maintained in tissue culture has been examined as a model system for studying the factors involved in the switch from fetal to adult haemoglobin production. In erythropoietin-treated cultures alpha-, beta- and gamma-chain synthesis remains active for up to 12 days. Globin-chain synthesis is balanced and the alpha/beta + gamma-chain production ratio remains constant up to about 8 days; in longer cultures gamma-chain production declines before that of beta chains. It is concluded that the system may be useful for examining factors involved in the switch from gamma- to beta-chain production provided that these are acting on cells already committed to the erythroid compartment.

Dose-Response Relationship, Drug↗