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768 results on '"Clegg, J. B."'

201. High frequencies of α-thalassaemia are the result of natural selection by malaria

Author

Flint, J., Hill, A. V. S., Bowden, D. K., Oppenheimer, S. J., Sill, P. R., Serjeantson, S. W., Bana-Koiri, J., Bhatia, K., Alpers, M. P., Boyce, A. J., Weatherall, D. J., and Clegg, J. B.

Abstract

The frequency of α+-thalassaemia, but not other unlinked DNA polymorphisms, exhibits an altitude- and latitude-dependent correlation with malaria endemicity throughout Melanesia, supporting the hypothesis that protection against this parasitic disease is the major factor responsible for the high frequencies of haemoglobinopathies in many parts of the world.

Published
1986
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202. Haemoglobin Constant Spring—A Chain Termination Mutant ?

Author

CLEGG, J. B., WEATHERALL, D. J., and MILNER, P. F.

Abstract

Haemoglobin Constant Spring is an unusual variant which comprises only 1–2% of the total haemoglobin in heterozygotes. It has α-chains which are 172 residues long instead of the normal 141, and when it is inherited together with an α-thalassaemia gene it gives rise to haemoglobin H disease.

Published
1971
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203. Immunoglobulin λ-chains. The complete amino acid sequence of a Bence-Jones protein

Author

Milstein, C., Clegg, J. B., and Jarvis, J. M.

Abstract

The total amino acid sequence of a λ Bence-Jones protein has been established. The protein contains 211 residues, which include two methionine residues. Splitting with cyanogen bromide gave three fragments, the largest of which included the C-terminal half, which is common to other Bence-Jones proteins of the same type. The peptides obtained by tryptic, chymotryptic and peptic digestion were isolated and purified by paper-electrophoretic and chromatographic techniques. Reduction followed by carboxymethylation of the cysteine residues with radioactive iodoacetate was found to be a powerful tool in the isolation of some insoluble peptides. Unusual features of the molecule are the fact that it contains six cysteine residues and not five as observed in both κ and λ Bence-Jones proteins studied previously, and its size, which seems two residues smaller than the smallest Bence-Jones protein studied hitherto. The similarities and differences between this and other Bence-Jones proteins are discussed.

Published
1968
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204. Association of two DNA polymorphisms in the alpha-globin gene cluster: implications for genetic analysis

Author

Wainscoat, J S, Higgs, D R, Kanavakis, E, Cao, A, Georgiou, D, Clegg, J B, and Weatherall, D J

Subjects
Polymorphism, Genetic, Greece, Homozygote, Chromosome Mapping, DNA, DNA Restriction Enzymes, Globins, Genes, Italy, Cyprus, Humans, Deoxyribonucleases, Type II Site-Specific, Research Article, Chromosomes, Human, 16-18
Abstract

A new polymorphic BgI II restriction endonuclease site in the alpha-globin gene complex has been found in Cypriot, Sardinian, and Greek populations. In all cases, this polymorphism is linked to a particular hypervariable region between the zeta 2 and zeta 1 genes. This suggests that these hypervariable regions are stable and will be useful for genetic analysis.

Published
1983

205. The Depth Resolution of Secondary Ion Mass Spectrometers: A Critical Evaluation

Author

McPhail, D. S., Clark, E. A., Clegg, J. B., Dowsett, M. G., Gold, J. P., Spiller, G. D. T., and Sykes, D.

Subjects
Depth Resolution, Diffusion, Silicon Molecular Beam Epitaxy, Topography, Secondary Ion Mass Spectrometry, Etching, Ion Beam Lithography, Low Dimensional Structures, Life Sciences, Bevelling, Imaging
Abstract

The ability of five Secondary Ion Mass Spectrometry (SIMS) instruments to resolve thin layer and modulated dopant structures by depth profiling has been assessed. Three magnetic sector instruments (two Cameca IMS 3f's and one 4f), which use optical gating and a high extraction field, were used, together with two different quadrupole based instruments (EVA 2000 and Atomika) , which use electronic gating and a low extraction field. The test structure, a thirty-one peak boron-in-silicon modulating dopant structure, was grown by Molecular Beam Epitaxy (MBE). In all the depth profiles the near surface peaks appeared narrow and asymmetric, being broadened only by fundamental processes (e.g., atomic mixing and recoil implantation). As the profiles proceeded, however, further broadening was observed. This phenomena varied markedly both from one instrument to another and from one experiment to another on the same instrument. In some cases the loss of depth resolution with depth was manifested by broadening mainly in the leading edge, in others the trailing edge, of successive boron peaks. The 'order of merit' of the instruments thus depended on the parameter used to define depth resolution. The loss of peak (depth) resolution with depth was due to variations in primary ion beam density across the gated area of the crater, which led to uneven etching. The changes in peak shape with depth can be explained by a numerical model of the etching process. These observations dictate that the depth resolution of a SIMS instrument should not be measured in terms of a single interface width, such as the leading or trailing edge.

Published
1988

222. Why are hemoglobin F levels increased in HbE/β thalassemia?

Author

Rees, D. C., John Porter, Clegg, J. B., and Weatherall, D. J.

Subjects
congenital, hereditary, and neonatal diseases and abnormalities, hemic and lymphatic diseases, Immunology, Cell Biology, Hematology, Biochemistry
Abstract

To try to further define the mechanisms that increase the levels of hemoglobin F (HbF) in the blood of patients with severe forms of β thalassemia, we have studied two comparable populations of hemoglobin E (HbE)/β thalassemics, one regularly transfused and one receiving only occasional blood transfusions. Regular transfusion was associated with a significant decrease in soluble transferrin receptor and erythropoietin levels. Globin chain synthesis studies also show a highly significant decrease in HbF synthesis relative to HbE in the transfused patients. This effect was confirmed by sequential data on one patient, studied before and after the commencement of regular blood transfusion; blood transfusion was followed by a marked increase in the /γ, βE/γ, and HbE/HbF ratios. These data suggest that the high HbF levels in HbE/β thalassemia, and other β thalassemia syndromes, result from increased erythropoietin levels leading to bone marrow expansion, and possibly increased F-cell production, combined with ineffective erythropoiesis giving a survival advantage to F cells. This study also suggests that alteration in blood transfusion regimes must be taken into account when interpreting changes in HbF levels seen in trials of HbF-promoting drugs.

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