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1.
West Indian med. j ; 20(4): 266, Dec. 1971.
Artigo em Inglês | MedCarib | ID: med-6324

RESUMO

Of the 120 or so variants of human haemoglobin polypeptide chains so far described, nearly all are the result of the substitution of a single amino acid residue for another, or a deletion of one or more residues in the chain, caused by a point mutation in the codens of the chromosomal DNA. Hb H disease is also a genetically determined haemolytic anaemia, common in Orientals, but is caused by a reduced rate of synthesis of the O-chain of normal haemoglobin, resulting in an excess of á-chains (Hb H). A study of a Chinese family in Jamaica has revealed a slow moving haemoglobin in three children who have clinical haemoglobin H disease and in their fathers and siblings who have no haematological abnormality. The mothers have classical O-thalassaemia trait, as do some of the other siblings. Detailed biochemical analysis of this variant has shown that the O-chain is abnormal and is elongated by the addition of 31 residues to the 141 of the normal OA-chain. The extra residues are continuous with the normal C-terminal (O-141 Arg.) Biosynthetic studies, incorporating H(to 3rd power) leucine have indicated a low rate of synthesis for this abnormal chain. Interest lies in the nature of the genetic defect which could produce this abnormalty. While considering several hypotheses, the authors favour the theory that the genetic codon for 'end of chain' is the site of a mutation. This hypothesis is strengthened by finding Glutamine to be the next residue after the C-terminal Arginine. This extra piece of chain bears no resemblance to any known human globin chain sequence, so that it is unlikely that it has resulted from an unequal crossing over in a similar way to the Lepore haemoglobins. It may be that the messenge RNA for the normal OA-chain is longer than is required to direct synthesis of the chain. Further studies are in progress to try and define the nature of this genetic defect (AU)


Assuntos
Humanos , Talassemia alfa , Hemoglobinas Anormais , Jamaica
2.
Lancet ; 1(7702): 729-32, Apr. 10, 1971.
Artigo em Inglês | MedCarib | ID: med-867

RESUMO

The clinical and genetic properties of an unusual O-chain variant of human haemoglobin are described. It constitutes less than 1 percent of the total haemoglobin in heterozygotes and, when inherited together with an O-thalassaemia gene, produces the clinical picture of haemoglobin-H disease. Preliminary structural studies indicatge that, in addition to the 141 aminoacid residues which constitute the normal O-chain, this variant has about 31 extra residues attached to the C-terminal end.(SUMMARY)


Assuntos
Criança , Feminino , Humanos , Relatos de Casos , Talassemia alfa/etiologia , Cadeias alfa de Imunoglobulina/sangue , Jamaica , Eletroforese em Gel de Amido/métodos
3.
West Indian med. j ; 17(4): 250, Dec. 1968.
Artigo em Inglês | MedCarib | ID: med-7550

RESUMO

The effects of deficient alpha chain synthesis at the clinical and subclinical level are illustrated by observations on 17 members of a family of mixed Chinese-Scottish-Negro origins. The presence of beta thalassaemia and its variants and the haemoglobin structural mutants have been excluded by presently available methods. The family includes 5 cases of Hb H disease, 3 cases of classical alpha thalassaemia trait and two adult subjects presumed to carry "silent" alpha thalassaemia gene. Clinical and laboratory aspects are presented (AU)


Assuntos
Humanos , Feminino , Masculino , Talassemia alfa/genética
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