Medicina: Ematologia: Talassemie e trapianto del midollo osseo
| English |
| precipitation |
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| Attestation |
3
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| Part of speech |
Noun
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| Grammatical label |
Countable
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| Definition |
The lack of b-globin chain components in b-thalassemia trait is usually sufficiently compensated for by increased b-globin chain expression of the normal allele and by an increase in red cell production. The short b gene products and free a-chains, remaining in excess after formation of the hemoglobin tetramers, are usually efficiently eliminated by proteolytic cleavage and are only responsible for a minor degree of ineffective erythropoiesis, which is usually well tolerated and not associated with hemolysis. However, chain precipitation and cell membrane damage, leading to ineffective erythropoiesis and hemolysis, may be present in patients heterozygous for b-thalassemia, when the trait is induced by mutations located on the third exon of the gene.
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| Definition source |
Giordano, PC., et al. (1998). ‘Phenotype variability of the dominant beta-thalassemia induced in four Dutch families by the rare cd121 (G-->T) mutation’. Annals of Hematology 77(6):249-55. (RISCEN92)
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| Context |
The precipitation starts already in the poly-chromatophilic erythroblasts and is maximal in the most mature cells. Precipitation of unbound a-chains occurs in the cytoplasm, but apparently takes place also within the nuclei. The latter event is probably connected with the disturbed erythroblast cycle in thalassemia, namely their arrest in phase Gl and the accumulation of glycogen. - The a-chain precipitation is followed by severe impairment of the electrolyte balance and by abundant release of free radicals which attack all cellular constituents (membranes, hemoglobin, enzymes etc.) and lead to premature death of the cell.
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| Context source |
Loukopoulos, D. (1991). ‘Thalassemia: genotypes and phenotypes’. Annals of Hematology 62(4):85-94. Review. (RISCEN96)
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| Subject field |
Haemopoiesis
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| Sub-field (level 1) |
Thalassemias
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| Related concept |
Globin synthesis imbalance
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| it |
Precipitazione
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| Reliability code |
3
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