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  • 1
    ISSN: 1432-1203
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract We have identified a minor hemoglobin component (∼5%) in the blood of a healthy Costa Rican female, but not in her mother and two brothers (father not studied), that has an His→Arg replacement at position β77 (Hb Costa Rica). No other amino acid replacements were observed and no β- or γ-chain-like peptides were present. Hb Costa Rica has a normal stability. Sequence analyses of numerous polymerase chain reaction (PCR)-amplified segments of DNA that contain exon 2 of the β gene failed to identify a CAC→CGC (His→Arg) mutation. The same was the case when cDNA was sequenced, indicating that a β-Costa Rica-mRNA could not be detected with this procedure. Gene mapping of genomic DNA with BglII, BamHI, and HindIII gave normal fragments only and with the same intensity as observed for the fragments of a normal control. The quantities of the β chain variants Hb J-Iran and Hb Fukuyama with related mutations at β77 vary between 30% and 45% in heterozygotes, whereas that of Hb F-Kennestone with the same His→Arg mutation but in the Gγ-globin gene, is a high 40%–45% (as percentage of total Gγ) in a heterozygous newborn. These different observations exclude a heterozygosity of the A→G mutation at codon β77, as well as a deletion comparable to that of Hbs Lepore or Kenya, or a β-globin gene duplication, and point to a nontraditional inheritance of Hb Costa Rica. Allele-specific amplification of cDNA with appropriate primers identified the presence of a low level of mutated mRNA in the reticulocytes of the patient, which was confirmed by dotblot analysis of the same material with 32P-labeled probes. Comparable amplification products were not observed in genomic DNA. The A→G mutation apparently occurred in a somatic cell at a relatively early stage in the development of the hematopoietic cell system, and Hb Costa Rica accumulated through rapid cell divisions in patchy areas in the bone marrow (somatic mosaicism). An unequal distribution of Hb Costa Rica over the red cells supports this possibility.
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  • 2
    ISSN: 1432-1203
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract We have identified a minor hemoglobin component (∼5%) in the blood of a healthy Costa Rican female, but not in her mother and two brothers (father not studied), that has an His→Arg replacement at position β77 (Hb Costa Rica). No other amino acid replacements were observed and no β- or γ-chain-like peptides were present. Hb Costa Rica has a normal stability. Sequence analyses of numerous polymerase chain reaction (PCR)-amplified segments of DNA that contain exon 2 of the β gene failed to identify a CAC→WGC (His→Arg) mutation. The same was the case when cDNA was sequenced, indicating that a β-Costa Rica-mRNA could not be detected with this procedure. Gene mapping of genomic DNA withBglII,BamHI, andHindIII gave normal fragments only and with the same intensity as observed for the fragments of a normal control. The quantities of the β chain variants Hb JIran and Hb Fukuyama with related mutations at (β77 vary between 30% and 45% in heterozygotes, whereas that of Hb F-Kennestone with the same His→Arg mutation but in theGyγ-globin gene, is a high 40%–45% (as percentage of totalGγ) in a heterozygous newborn. These different observations exclude a heterozygosity of the A→G mutation at codon β77, as well as a deletion comparable to that of Hbs Lepore or Kenya, or a β-globin gene duplication, and point to a nontraditional inheritance of Hb Costa Rica. Allele-specific amplification of cDNA with appropriate primers identified the presence of a low level of mutated mRNA in the reticulocytes of the patient, which was confirmed by dotblot analysis of the same material with32p-labeled probes. Comparable amplification products were not observed in genomic DNA. The A→G mutation apparently occurred in a somatic cell at a relatively early stage in the development of the hematopoietic cell system, and Hb Costa Rica accumulated through rapid cell divisions in patchy areas in the bone marrow (somatic mosaicism). An unequal distribution of Hb Costa Rica over the red cells supports this possibility.
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  • 3
    ISSN: 1432-1203
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Hb Lepore is one of the most common abnormal haemoglobins in Caucasians in Central Portugal and in the Spanish Alta Extremadura (0.28% in a survey of school children). A group of 19 Portuguese and 14 Spanish Hb Lepore carriers (all unrelated) was characterised at the molecular level by the polymerase chain reaction, sequencing and restriction enzyme analysis. The Portuguese and one Spanish carrier were heterozygous for Hb Lepore-Baltimore, whereas all other Spanish subjects were Hb Lepore-Washington-Boston carriers. Sequencing of the Hb Lepore-Baltimore gene further established the crossover at δ68-β84, a region two codons (CDs) shorter than that previously described and easily confirmed by digestion with MaeI and BanI. Data from haplotype analysis suggest that this crossover occurred as an independent event on the lberian Peninsula. The haematological data were similar in both groups except for the levels of Hb F and the Gγ chain, which were significantly higher in the Hb Lepore-Baltimore heterozygotes. Quantification of the globin chains and the mRNA transcripts showed that the δβ gene is transcribed at a higher level than the δ gene with levels of translation giving rise to 10%–15% of Hb Lepore. The different levels of Hb F observed in the two groups are the results of the higher transcription rate of the γ genes in Hb Lepore-Baltimore heterozygotes and an apparently less efficient translation of Gγ genes in Hb Lepore-Washington-Boston heterozygotes.
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